New strong motion network in Georgia: basis for specifying seismic hazard

NASA Astrophysics Data System (ADS)

Kvavadze, N.; Tsereteli, N. S.

2017-12-01

Risk created by hazardous natural events is closely related to sustainable development of the society. Global observations have confirmed tendency of growing losses resulting from natural disasters, one of the most dangerous and destructive if which are earthquakes. Georgia is located in seismically active region. So, it is imperative to evaluate probabilistic seismic hazard and seismic risk with proper accuracy. National network of Georgia includes 35 station all of which are seismometers. There are significant gaps in strong motion recordings, which essential for seismic hazard assessment. To gather more accelerometer recordings, we have built a strong motion network distributed on the territory of Georgia. The network includes 6 stations for now, with Basalt 4x datalogger and strong motion sensor Episensor ES-T. For each site, Vs30 and soil resonance frequencies have been measured. Since all but one station (Tabakhmelam near Tbilisi), are located far from power and internet lines special system was created for instrument operation. Solar power is used to supply the system with electricity and GSM/LTE modems for internet access. VPN tunnel was set up using Raspberry pi, for two-way communication with stations. Tabakhmela station is located on grounds of Ionosphere Observatory, TSU and is used as a hub for the network. This location also includes a broadband seismometer and VLF electromagnetic waves observation antenna, for possible earthquake precursor studies. On server, located in Tabakhmela, the continues data is collected from all the stations, for later use. The recordings later will be used in different seismological and engineering problems, namely selecting and creating GMPE model for Caucasus, for probabilistic seismic hazard and seismic risk evaluation. These stations are a start and in the future expansion of strong motion network is planned. Along with this, electromagnetic wave observations will continue and additional antennas will be implemented with strong motion sensors and possible earthquake precursors will be studied using complex methods of observation and data analysis.

Benefits of rotational ground motions for planetary seismology

NASA Astrophysics Data System (ADS)

Donner, S.; Joshi, R.; Hadziioannou, C.; Nunn, C.; van Driel, M.; Schmelzbach, C.; Wassermann, J. M.; Igel, H.

2017-12-01

Exploring the internal structure of planetary objects is fundamental to understand the evolution of our solar system. In contrast to Earth, planetary seismology is hampered by the limited number of stations available, often just a single one. Classic seismology is based on the measurement of three components of translational ground motion. Its methods are mainly developed for a larger number of available stations. Therefore, the application of classical seismological methods to other planets is very limited. Here, we show that the additional measurement of three components of rotational ground motion could substantially improve the situation. From sparse or single station networks measuring translational and rotational ground motions it is possible to obtain additional information on structure and source. This includes direct information on local subsurface seismic velocities, separation of seismic phases, propagation direction of seismic energy, crustal scattering properties, as well as moment tensor source parameters for regional sources. The potential of this methodology will be highlighted through synthetic forward and inverse modeling experiments.

Direct determination of geocenter motion by combining SLR, VLBI, GNSS, and DORIS time series

NASA Astrophysics Data System (ADS)

Wu, X.; Abbondanza, C.; Altamimi, Z.; Chin, T. M.; Collilieux, X.; Gross, R. S.; Heflin, M. B.; Jiang, Y.; Parker, J. W.

2013-12-01

The longest-wavelength surface mass transport includes three degree-one spherical harmonic components involving hemispherical mass exchanges. The mass load causes geocenter motion between the center-of-mass of the total Earth system (CM) and the center-of-figure of the solid Earth surface (CF), and deforms the solid Earth. Estimation of the degree-1 surface mass changes through CM-CF and degree-1 deformation signatures from space geodetic techniques can thus complement GRACE's time-variable gravity data to form a complete change spectrum up to a high resolution. Currently, SLR is considered the most accurate technique for direct geocenter motion determination. By tracking satellite motion from ground stations, SLR determines the motion between CM and the geometric center of its ground network (CN). This motion is then used to approximate CM-CF and subsequently for deriving degree-1 mass changes. However, the SLR network is very sparse and uneven in global distribution. The average number of operational tracking stations is about 20 in recent years. The poor network geometry can have a large CN-CF motion and is not ideal for the determination of CM-CF motion and degree-1 mass changes. We recently realized an experimental Terrestrial Reference Frame (TRF) through station time series using the Kalman filter and the RTS smoother. The TRF has its origin defined at nearly instantaneous CM using weekly SLR measurement time series. VLBI, GNSS and DORIS time series are combined weekly with those of SLR and tied to the geocentric (CM) reference frame through local tie measurements and co-motion constraints on co-located geodetic stations. The unified geocentric time series of the four geodetic techniques provide a much better network geometry for direct geodetic determination of geocenter motion. Results from this direct approach using a 90-station network compares favorably with those obtained from joint inversions of GPS/GRACE data and ocean bottom pressure models. We will also show that a previously identified discrepancy in X-component between direct SLR orbit-tracking and inverse determined geocenter motions is largely reconciled with the new unified network.

Significant motions between GPS sites in the New Madrid region: implications for seismic hazard

USGS Publications Warehouse

Frankel, Arthur; Smalley, Robert; Paul, J.

2012-01-01

Position time series from Global Positioning System (GPS) stations in the New Madrid region were differenced to determine the relative motions between stations. Uncertainties in rates were estimated using a three‐component noise model consisting of white, flicker, and random walk noise, following the methodology of Langbein, 2004. Significant motions of 0.37±0.07 (one standard error) mm/yr were found between sites PTGV and STLE, for which the baseline crosses the inferred deep portion of the Reelfoot fault. Baselines between STLE and three other sites also show significant motion. Site MCTY (adjacent to STLE) also exhibits significant motion with respect to PTGV. These motions are consistent with a model of interseismic slip of about 4  mm/yr on the Reelfoot fault at depths between 12 and 20 km. If constant over time, this rate of slip produces sufficient slip for an M 7.3 earthquake on the shallow portion of the Reelfoot fault, using the geologically derived recurrence time of 500 years. This model assumes that the shallow portion of the fault has been previously loaded by the intraplate stress. A GPS site near Little Rock, Arkansas, shows significant southward motion of 0.3–0.4  mm/yr (±0.08  mm/yr) relative to three sites to the north, indicating strain consistent with focal mechanisms of earthquake swarms in northern Arkansas.

Impact of seasonal and postglacial surface displacement on global reference frames

NASA Astrophysics Data System (ADS)

Krásná, Hana; Böhm, Johannes; King, Matt; Memin, Anthony; Shabala, Stanislav; Watson, Christopher

2014-05-01

The calculation of actual station positions requires several corrections which are partly recommended by the International Earth Rotation and Reference Systems Service (IERS) Conventions (e.g., solid Earth tides and ocean tidal loading) as well as other corrections, e.g. accounting for hydrology and atmospheric loading. To investigate the pattern of omitted non-linear seasonal motion we estimated empirical harmonic models for selected stations within a global solution of suitable Very Long Baseline Interferometry (VLBI) sessions as well as mean annual models by stacking yearly time series of station positions. To validate these models we compare them to displacement series obtained from the Gravity Recovery and Climate Experiment (GRACE) data and to hydrology corrections determined from global models. Furthermore, we assess the impact of the seasonal station motions on the celestial reference frame as well as on Earth orientation parameters derived from real and also artificial VLBI observations. In the second part of the presentation we apply vertical rates of the ICE-5G_VM2_2012 vertical land movement grid on vertical station velocities. We assess the impact of postglacial uplift on the variability in the scale given different sampling of the postglacial signal in time and hence on the uncertainty in the scale rate of the estimated terrestrial reference frame.

Kinematic Source Rupture Process of the 2008 Iwate-Miyagi Nairiku Earthquake, a MW6.9 thrust earthquake in northeast Japan, using Strong Motion Data

NASA Astrophysics Data System (ADS)

Asano, K.; Iwata, T.

2008-12-01

The 2008 Iwate-Miyagi Nairiku earthquake (MJMA7.2) on June 14, 2008, is a thrust type inland crustal earthquake, which occurred in northeastern Honshu, Japan. In order to see strong motion generation process of this event, the source rupture process is estimated by the kinematic waveform inversion using strong motion data. Strong motion data of the K-NET and KiK-net stations and Aratozawa Dam are used. These stations are located 3-94 km from the epicenter. Original acceleration time histories are integrated into velocity and band- pass filtered between 0.05 and 1 Hz. For obtaining the detailed source rupture process, appropriate velocity structure model for Green's functions should be used. We estimated one dimensional velocity structure model for each strong motion station by waveform modeling of aftershock records. The elastic wave velocity, density, and Q-values for four sedimentary layers are assumed following previous studies. The thickness of each sedimentary layer depends on the station, which is estimated to fit the observed aftershock's waveforms by the optimization using the genetic algorithm. A uniform layered structure model is assumed for crust and upper mantle below the seismic bedrock. We succeeded to get a reasonable velocity structure model for each station to give a good fit of the main S-wave part in the observation of aftershocks. The source rupture process of the mainshock is estimated by the linear kinematic waveform inversion using multiple time windows (Hartzell and Heaton, 1983). A fault plane model is assumed following the moment tensor solution by F-net, NIED. The strike and dip angle is 209° and 51°, respectively. The rupture starting point is fixed at the hypocenter located by the JMA. The obtained source model shows a large slip area in the shallow portion of the fault plane approximately 6 km southwest of the hypocenter. The rupture of the asperity finishes within about 9 s. This large slip area corresponds to the area with surface break reported by the field survey group (e.g., AIST/GSJ, 2008), which supports the existence of the large slip close to the ground surface. But, most of surface offset found by the field survey are less than 0.5 m whereas the slip amount of the shallow asperity of the source inversion result is 3-4 m. In north of the hypocenter, the estimated slip amount is small. Slip direction is almost pure dip-slip for the entire fault (Northwest side goes up against southeast side). Total seismic moment is 2.6× 1019 Nm (MW 6.9). Acknowledgments: Strong motion data of K-NET and KiK-net operated by the National Research Institute for Earth Science and Disaster Prevention are used. Strong motion data of Aratozawa Dam obtained by Miyagi prefecture government is also used in the study.

Exploration of S-wave velocity profiles at strong motion stations in Eskisehir, Turkey, using microtremor phase velocity and S-wave amplification

NASA Astrophysics Data System (ADS)

Yamanaka, Hiroaki; Özmen, Ögur Tuna; Chimoto, Kosuke; Alkan, Mehmet Akif; Tün, Muammer; Pekkan, Emrah; Özel, Oguz; Polat, Derya; Nurlu, Murat

2018-05-01

We have explored 1D S-wave velocity profiles of shallow and deep soil layers over a basement at strong motion stations in Eskisehir Province, Turkey. Microtremor array explorations were conducted at eight strong motion stations in the area to know shallow 1D S-wave velocity models. Rayleigh wave phase velocity at a frequency range from 3 to 30 Hz was estimated with the spatial autocorrelation analysis of array records of vertical microtremors at each station. Individual phase velocity was inverted to a shallow S-wave velocity profile. Low-velocity layers were identified at the stations in the basin. Site amplification factors from S-wave parts of earthquake records that had been estimated at the strong motion stations by Yamanaka et al. (2017) were inverted to the S-wave velocities and Q-values of the sedimentary layers. The depths to the basement with an S-wave velocity of 2.2 km/s are about 1 km in the central part of the basin, while the basement becomes shallow as 0.3 km in the marginal part of the basin. We finally discussed the effects of the shallow and deep sedimentary layers on the 1D S-wave amplification characteristics using the revealed profiles. It is found that the shallow soil layers have no significant effects in the amplification at a frequency range lower than 3 Hz in the area.

Field and modeling framework and case study of truck weigh station operations

DOT National Transportation Integrated Search

2002-01-01

Weigh-in-Motion (WIM) systems improve the capacity of weigh station operations significantly by screening trucks while traveling at high speeds and only requiring trucks within a threshold of a maximum permissible gross of axle weight to be weighed o...

Source effects on the simulation of the strong groud motion of the 2011 Lorca earthquake

NASA Astrophysics Data System (ADS)

Saraò, Angela; Moratto, Luca; Vuan, Alessandro; Mucciarelli, Marco; Jimenez, Maria Jose; Garcia Fernandez, Mariano

2016-04-01

On May 11, 2011 a moderate seismic event (Mw=5.2) struck the city of Lorca (South-East Spain) causing nine casualties, a large number of injured people and damages at the civil buildings. The largest PGA value (360 cm/s2) ever recorded so far in Spain, was observed at the accelerometric station located in Lorca (LOR), and it was explained as due to the source directivity, rather than to local site effects. During the last years different source models, retrieved from the inversions of geodetic or seismological data, or a combination of the two, have been published. To investigate the variability that equivalent source models of an average earthquake can introduce in the computation of strong motion, we calculated seismograms (up to 1 Hz), using an approach based on the wavenumber integration and, as input, four different source models taken from the literature. The source models differ mainly for the slip distribution on the fault. Our results show that, as effect of the different sources, the ground motion variability, in terms of pseudo-spectral velocity (1s), can reach one order of magnitude for near source receivers or for sites influenced by the forward-directivity effect. Finally, we compute the strong motion at frequencies higher than 1 Hz using the Empirical Green Functions and the source model parameters that better reproduce the recorded shaking up to 1 Hz: the computed seismograms fit satisfactorily the signals recorded at LOR station as well as at the other stations close to the source.

New algorithms for motion error detection of numerical control machine tool by laser tracking measurement on the basis of GPS principle.

PubMed

Wang, Jindong; Chen, Peng; Deng, Yufen; Guo, Junjie

2018-01-01

As a three-dimensional measuring instrument, the laser tracker is widely used in industrial measurement. To avoid the influence of angle measurement error on the overall measurement accuracy, the multi-station and time-sharing measurement with a laser tracker is introduced on the basis of the global positioning system (GPS) principle in this paper. For the proposed method, how to accurately determine the coordinates of each measuring point by using a large amount of measured data is a critical issue. Taking detecting motion error of a numerical control machine tool, for example, the corresponding measurement algorithms are investigated thoroughly. By establishing the mathematical model of detecting motion error of a machine tool with this method, the analytical algorithm concerning on base station calibration and measuring point determination is deduced without selecting the initial iterative value in calculation. However, when the motion area of the machine tool is in a 2D plane, the coefficient matrix of base station calibration is singular, which generates a distortion result. In order to overcome the limitation of the original algorithm, an improved analytical algorithm is also derived. Meanwhile, the calibration accuracy of the base station with the improved algorithm is compared with that with the original analytical algorithm and some iterative algorithms, such as the Gauss-Newton algorithm and Levenberg-Marquardt algorithm. The experiment further verifies the feasibility and effectiveness of the improved algorithm. In addition, the different motion areas of the machine tool have certain influence on the calibration accuracy of the base station, and the corresponding influence of measurement error on the calibration result of the base station depending on the condition number of coefficient matrix are analyzed.

New algorithms for motion error detection of numerical control machine tool by laser tracking measurement on the basis of GPS principle

NASA Astrophysics Data System (ADS)

Wang, Jindong; Chen, Peng; Deng, Yufen; Guo, Junjie

2018-01-01

As a three-dimensional measuring instrument, the laser tracker is widely used in industrial measurement. To avoid the influence of angle measurement error on the overall measurement accuracy, the multi-station and time-sharing measurement with a laser tracker is introduced on the basis of the global positioning system (GPS) principle in this paper. For the proposed method, how to accurately determine the coordinates of each measuring point by using a large amount of measured data is a critical issue. Taking detecting motion error of a numerical control machine tool, for example, the corresponding measurement algorithms are investigated thoroughly. By establishing the mathematical model of detecting motion error of a machine tool with this method, the analytical algorithm concerning on base station calibration and measuring point determination is deduced without selecting the initial iterative value in calculation. However, when the motion area of the machine tool is in a 2D plane, the coefficient matrix of base station calibration is singular, which generates a distortion result. In order to overcome the limitation of the original algorithm, an improved analytical algorithm is also derived. Meanwhile, the calibration accuracy of the base station with the improved algorithm is compared with that with the original analytical algorithm and some iterative algorithms, such as the Gauss-Newton algorithm and Levenberg-Marquardt algorithm. The experiment further verifies the feasibility and effectiveness of the improved algorithm. In addition, the different motion areas of the machine tool have certain influence on the calibration accuracy of the base station, and the corresponding influence of measurement error on the calibration result of the base station depending on the condition number of coefficient matrix are analyzed.

Strong ground motion simulation of the 2016 Kumamoto earthquake of April 16 using multiple point sources

NASA Astrophysics Data System (ADS)

Nagasaka, Yosuke; Nozu, Atsushi

2017-02-01

The pseudo point-source model approximates the rupture process on faults with multiple point sources for simulating strong ground motions. A simulation with this point-source model is conducted by combining a simple source spectrum following the omega-square model with a path spectrum, an empirical site amplification factor, and phase characteristics. Realistic waveforms can be synthesized using the empirical site amplification factor and phase models even though the source model is simple. The Kumamoto earthquake occurred on April 16, 2016, with M JMA 7.3. Many strong motions were recorded at stations around the source region. Some records were considered to be affected by the rupture directivity effect. This earthquake was suitable for investigating the applicability of the pseudo point-source model, the current version of which does not consider the rupture directivity effect. Three subevents (point sources) were located on the fault plane, and the parameters of the simulation were determined. The simulated results were compared with the observed records at K-NET and KiK-net stations. It was found that the synthetic Fourier spectra and velocity waveforms generally explained the characteristics of the observed records, except for underestimation in the low frequency range. Troughs in the observed Fourier spectra were also well reproduced by placing multiple subevents near the hypocenter. The underestimation is presumably due to the following two reasons. The first is that the pseudo point-source model targets subevents that generate strong ground motions and does not consider the shallow large slip. The second reason is that the current version of the pseudo point-source model does not consider the rupture directivity effect. Consequently, strong pulses were not reproduced enough at stations northeast of Subevent 3 such as KMM004, where the effect of rupture directivity was significant, while the amplitude was well reproduced at most of the other stations. This result indicates the necessity for improving the pseudo point-source model, by introducing azimuth-dependent corner frequency for example, so that it can incorporate the effect of rupture directivity.[Figure not available: see fulltext.

Atypical soil hardening during the Tohoku earthquake of March 11, 2011 ( M w = 9.0)

NASA Astrophysics Data System (ADS)

Pavlenko, O. V.

2017-10-01

Based on the records of KiK-net vertical arrays, models of soil behavior down to depths of 100-200 m in the near-fault zones during the Tohoku earthquake are examined. In contrast to the regular pattern observed during strong earthquakes, soft soils have not broadly demonstrated nonlinear behavior, or a reduction (with the onset of strong motions) and recovery (after strong motions finished) of the shear modulus in soil layers. At the stations where anomalously high peak ground accelerations were recorded (PGA > 1g), the values of the shear modulus in soil layers increased with the onset of strong motions and reached a maximum when motions were the most intensive, which indicated hardening of soils. Soil behavior was close to linear, here. The values of the shear moduli decrease along with a decrease in intensity of strong ground motions, and at soft soil stations, this was accompanied by a stepwise decrease in the frequency of motion.

Rotational motions for teleseismic surface waves

NASA Astrophysics Data System (ADS)

Lin, Chin-Jen; Huang, Han-Pang; Pham, Nguyen Dinh; Liu, Chun-Chi; Chi, Wu-Cheng; Lee, William H. K.

2011-08-01

We report the findings for the first teleseismic six degree-of-freedom (6-DOF) measurements including three components of rotational motions recorded by a sensitive rotation-rate sensor (model R-1, made by eentec) and three components of translational motions recorded by a traditional seismometer (STS-2) at the NACB station in Taiwan. The consistent observations in waveforms of rotational motions and translational motions in sections of Rayleigh and Love waves are presented in reference to the analytical solution for these waves in a half space of Poisson solid. We show that additional information (e.g., Rayleigh wave phase velocity, shear wave velocity of the surface layer) might be exploited from six degree-of-freedom recordings of teleseismic events at only one station. We also find significant errors in the translational records of these teleseismic surface waves due to the sensitivity of inertial translation sensors (seismometers) to rotational motions. The result suggests that the effects of such errors need to be counted in surface wave inversions commonly used to derive earthquake source parameters and Earth structure.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, K; Yu, Z; Chen, H

Purpose: To implement VMAT in RayStation with the Elekta Synergy linac with the new Agility MLC, and to utilize the same vendor softwares to determine the optimum Elekta VMAT machine parameters in RayStation for accurate modeling and robust delivery. Methods: iCOMCat is utilized to create various beam patterns with user defined dose rate, gantry, MLC and jaw speed for each control point. The accuracy and stability of the output and beam profile are qualified for each isolated functional component of VMAT delivery using ion chamber and Profiler2 with isocentric mounting fixture. Service graphing on linac console is used to verifymore » the mechanical motion accuracy. The determined optimum Elekta VMAT machine parameters were configured in RayStation v4.5.1. To evaluate the system overall performance, TG-119 test cases and nine retrospective VMAT patients were planned on RayStation, and validated using both ArcCHECK (with plug and ion chamber) and MapCHECK2. Results: Machine output and profile varies <0.3% when only variable is dose rate (35MU/min-600MU/min). <0.9% output and <0.3% profile variation are observed with additional gantry motion (0.53deg/s–5.8deg/s both directions). The output and profile variation are still <1% with additional slow leaf motion (<1.5cm/s both direction). However, the profile becomes less symmetric, and >1.5% output and 7% profile deviation is seen with >2.5cm/s leaf motion. All clinical cases achieved comparable plan quality as treated IMRT plans. The gamma passing rate is 99.5±0.5% on ArcCheck (<3% iso center dose deviation) and 99.1±0.8% on MapCheck2 using 3%/3mm gamma (10% lower threshold). Mechanical motion accuracy in all VMAT deliveries is <1°/1mm. Conclusion: Accurate RayStation modeling and robust VMAT delivery is achievable on Elekta Agility for <2.5cm/s leaf motion and full range of dose rate and gantry speed determined by the same vendor softwares. Our TG-119 and patient results have provided us with the confidence to use VMAT clinically.« less

Uncertainty in Vs30-based site response

USGS Publications Warehouse

Thompson, Eric M.; Wald, David J.

2016-01-01

Methods that account for site response range in complexity from simple linear categorical adjustment factors to sophisticated nonlinear constitutive models. Seismic‐hazard analysis usually relies on ground‐motion prediction equations (GMPEs); within this framework site response is modeled statistically with simplified site parameters that include the time‐averaged shear‐wave velocity to 30 m (VS30) and basin depth parameters. Because VS30 is not known in most locations, it must be interpolated or inferred through secondary information such as geology or topography. In this article, we analyze a subset of stations for which VS30 has been measured to address effects of VS30 proxies on the uncertainty in the ground motions as modeled by GMPEs. The stations we analyze also include multiple recordings, which allow us to compute the repeatable site effects (or empirical amplification factors [EAFs]) from the ground motions. Although all methods exhibit similar bias, the proxy methods only reduce the ground‐motion standard deviations at long periods when compared to GMPEs without a site term, whereas measured VS30 values reduce the standard deviations at all periods. The standard deviation of the ground motions are much lower when the EAFs are used, indicating that future refinements of the site term in GMPEs have the potential to substantially reduce the overall uncertainty in the prediction of ground motions by GMPEs.

Postseismic deformation following the 2015 Gorkha earthquake and implications for rheology

NASA Astrophysics Data System (ADS)

Rollins, C.; Gualandi, A.; Avouac, J. P.; Liu, J.; Zhang, Z.

2017-12-01

The 2015 Mw 7.9 Gorkha earthquake ruptured the lower, northern edge of the interseismically locked section of the Main Himalayan Thrust (MHT). Independent Component Analysis of location timeseries at GPS stations in Nepal and Tibet reveals significant transient postseismic motion following the mainshock. In order to probe the frictional properties of the MHT and the viscoelastic properties of the crust and upper mantle, we compare the extracted postseismic motions to those predicted by forward models of afterslip and viscoelastic relaxation. Postseismic displacements are minimal south of the coseismic rupture, suggesting that minimal afterslip occurred there and that the upper MHT remains mostly locked. North of the rupture, postseismic displacements feature south-southwest horizontal motion and uplift, each on the order of a few cm in the first postseismic year. A model of stress-driven afterslip extending 100 km north of the coseismic rupture reproduces the horizontal postseismic timeseries and the general pattern of uplift and subsidence; however, this model significantly overpredicts the uplift at stations overlying the rupture, and the down-dip extent of afterslip may be unrealistic. Viscoelastic relaxation in the high-temperature Tibetan crust reproduces the observed SSW motion without overpredicting the uplift; viscoelastic relaxation in the downgoing Indian mantle, however, produces northward motion and subsidence north of the rupture, i.e. opposite to the observed motions. We argue that models of coupled afterslip (confined close to the rupture) and viscoelastic relaxation can reproduce the postseismic timeseries with physically plausible parameters.

The SCEC Broadband Platform: Open-Source Software for Strong Ground Motion Simulation and Validation

NASA Astrophysics Data System (ADS)

Silva, F.; Goulet, C. A.; Maechling, P. J.; Callaghan, S.; Jordan, T. H.

2016-12-01

The Southern California Earthquake Center (SCEC) Broadband Platform (BBP) is a carefully integrated collection of open-source scientific software programs that can simulate broadband (0-100 Hz) ground motions for earthquakes at regional scales. The BBP can run earthquake rupture and wave propagation modeling software to simulate ground motions for well-observed historical earthquakes and to quantify how well the simulated broadband seismograms match the observed seismograms. The BBP can also run simulations for hypothetical earthquakes. In this case, users input an earthquake location and magnitude description, a list of station locations, and a 1D velocity model for the region of interest, and the BBP software then calculates ground motions for the specified stations. The BBP scientific software modules implement kinematic rupture generation, low- and high-frequency seismogram synthesis using wave propagation through 1D layered velocity structures, several ground motion intensity measure calculations, and various ground motion goodness-of-fit tools. These modules are integrated into a software system that provides user-defined, repeatable, calculation of ground-motion seismograms, using multiple alternative ground motion simulation methods, and software utilities to generate tables, plots, and maps. The BBP has been developed over the last five years in a collaborative project involving geoscientists, earthquake engineers, graduate students, and SCEC scientific software developers. The SCEC BBP software released in 2016 can be compiled and run on recent Linux and Mac OS X systems with GNU compilers. It includes five simulation methods, seven simulation regions covering California, Japan, and Eastern North America, and the ability to compare simulation results against empirical ground motion models (aka GMPEs). The latest version includes updated ground motion simulation methods, a suite of new validation metrics and a simplified command line user interface.

A multiple fault rupture model of the November 13 2016, M 7.8 Kaikoura earthquake, New Zealand

NASA Astrophysics Data System (ADS)

Benites, R. A.; Francois-Holden, C.; Langridge, R. M.; Kaneko, Y.; Fry, B.; Kaiser, A. E.; Caldwell, T. G.

2017-12-01

The rupture-history of the November 13 2016 MW7.8 Kaikoura earthquake recorded by near- and intermediate-field strong-motion seismometers and 2 high-rate GPS stations reveals a complex cascade of multiple crustal fault rupture. In spite of such complexity, we show that the rupture history of each fault is well approximated by simple kinematic model with uniform slip and rupture velocity. Using 9 faults embedded in a crustal layer 19 km thick, each with a prescribed slip vector and rupture velocity, this model accurately reproduces the displacement waveforms recorded at the near-field strong-motion and GPS stations. This model includes the `Papatea Fault' with a mixed thrust and strike-slip mechanism based on in-situ geological observations with up to 8 m of uplift observed. Although the kinematic model fits the ground-motion at the nearest strong station, it doesn not reproduce the one sided nature of the static deformation field observed geodetically. This suggests a dislocation based approach does not completely capture the mechanical response of the Papatea Fault. The fault system as a whole extends for approximately 150 km along the eastern side of the Marlborough fault system in the South Island of New Zealand. The total duration of the rupture was 74 seconds. The timing and location of each fault's rupture suggests fault interaction and triggering resulting in a northward cascade crustal ruptures. Our model does not require rupture of the underlying subduction interface to explain the data.

KALREF—A Kalman filter and time series approach to the International Terrestrial Reference Frame realization

NASA Astrophysics Data System (ADS)

Wu, Xiaoping; Abbondanza, Claudio; Altamimi, Zuheir; Chin, T. Mike; Collilieux, Xavier; Gross, Richard S.; Heflin, Michael B.; Jiang, Yan; Parker, Jay W.

2015-05-01

The current International Terrestrial Reference Frame is based on a piecewise linear site motion model and realized by reference epoch coordinates and velocities for a global set of stations. Although linear motions due to tectonic plates and glacial isostatic adjustment dominate geodetic signals, at today's millimeter precisions, nonlinear motions due to earthquakes, volcanic activities, ice mass losses, sea level rise, hydrological changes, and other processes become significant. Monitoring these (sometimes rapid) changes desires consistent and precise realization of the terrestrial reference frame (TRF) quasi-instantaneously. Here, we use a Kalman filter and smoother approach to combine time series from four space geodetic techniques to realize an experimental TRF through weekly time series of geocentric coordinates. In addition to secular, periodic, and stochastic components for station coordinates, the Kalman filter state variables also include daily Earth orientation parameters and transformation parameters from input data frames to the combined TRF. Local tie measurements among colocated stations are used at their known or nominal epochs of observation, with comotion constraints applied to almost all colocated stations. The filter/smoother approach unifies different geodetic time series in a single geocentric frame. Fragmented and multitechnique tracking records at colocation sites are bridged together to form longer and coherent motion time series. While the time series approach to TRF reflects the reality of a changing Earth more closely than the linear approximation model, the filter/smoother is computationally powerful and flexible to facilitate incorporation of other data types and more advanced characterization of stochastic behavior of geodetic time series.

Probabilistic reconstruction of GPS vertical ground motion and comparison with GIA models

NASA Astrophysics Data System (ADS)

Husson, Laurent; Bodin, Thomas; Choblet, Gael; Kreemer, Corné

2017-04-01

The vertical position time-series of GPS stations have become long enough for many parts of the world to infer modern rates of vertical ground motion. We use the worldwide compilation of GPS trend velocities of the Nevada Geodetic Laboratory. Those rates are inferred by applying the MIDAS algorithm (Blewitt et al., 2016) to time-series obtained from publicly available data from permanent stations. Because MIDAS filters out seasonality and discontinuities, regardless of their causes, it gives robust long-term rates of vertical ground motion (except where there is significant postseismic deformation). As the stations are unevenly distributed, and because data errors are also highly variable, sometimes to an unknown degree, we use a Bayesian inference method to reconstruct 2D maps of vertical ground motion. Our models are based on a Voronoi tessellation and self-adapt to the spatially variable level of information provided by the data. Instead of providing a unique interpolated surface, each point of the reconstructed surface is defined through a probability density function. We apply our method to a series of vast regions covering entire continents. Not surprisingly, the reconstructed surface at a long wavelength is dominated by the GIA. This result can be exploited to evaluate whether forward models of GIA reproduce geodetic rates within the uncertainties derived from our interpolation, not only at high latitudes where postglacial rebound is fast, but also in more temperate latitudes where, for instance, such rates may compete with modern sea level rise. At shorter wavelengths, the reconstructed surface of vertical ground motion features a variety of identifiable patterns, whose geometries and rates can be mapped. Examples are transient dynamic topography over the convecting mantle, actively deforming domains (mountain belts and active margins), volcanic areas, or anthropogenic contributions.

Very long baseline interferometry applied to polar motion, relativity, and geodesy. Ph. D. thesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, C.

1978-01-01

The causes and effects of diurnal polar motion are described. An algorithm was developed for modeling the effects on very long baseline interferometry observables. A selection was made between two three-station networks for monitoring polar motion. The effects of scheduling and the number of sources observed on estimated baseline errors are discussed. New hardware and software techniques in very long baseline interferometry are described.

Crew activity and motion effects on the space station

NASA Technical Reports Server (NTRS)

Rochon, Brian V.; Scheer, Steven A.

1987-01-01

Among the significant sources of internal disturbances that must be considered in the design of space station vibration control systems are the loads induced on the structure from various crew activities. Flight experiment T013, flown on the second manned mission of Skylab, measured force and moment time histories for a range of preplanned crew motions and activities. This experiment has proved itself invaluable as a source of on-orbit crew induced loads that has allowed a space station forcing function data base to be built. This will enable forced response such as acceleration and deflections, attributable to crew activity, to be calculated. The flight experiment, resultant database and structural model pre-processor, analysis examples and areas of combined research shall be described.

The Orbit of Water Droplets around Charged Rod

ERIC Educational Resources Information Center

Ferstl, Andrew; Burns, Andrew

2013-01-01

The motion of charges around a centrally charged object is often compared to gravitational orbits (such as satellites around planets). Recently, a video taken by astronaut Don Pettit onboard the International Space Station shows water droplets orbiting a charged knitting needle. Here we attempt to model this motion and estimate the charges on the…

Toward Improving Seismic Hazard Estimates for Northwest Coastal British Columbia

NASA Astrophysics Data System (ADS)

Nykolaishen, L.; Dragert, H.; Wang, K.; James, T. S.

2016-12-01

Planned development for energy and shipping infrastructure in the Prince Rupert/Kitimat area of northern coastal British Columbia precipitated a more detailed study of natural hazards in this region. Over a two-year span beginning in the summer of 2014, an eight-station continuous GNSS network was established in order to measure crustal strain rates which could reveal the likelihood of infrequent but large (M>6) crustal earthquakes along the inner coast. However, the determination of representative regional elastic strain rates is confounded not only by the brevity of the monitoring period but also by the occurrence of the Haida Gwaii M7.8 earthquake which struck the outer coast of Haida Gwaii on Oct. 28, 2012. Significant regional postseismic motions have been observed at GNSS sites on Haida Gwaii (Nykolaishen et al., 2015) and still continue. It is clear that the motions of the Haida Gwaii GNSS stations have not recovered their long-term trends and consequently, the velocities of the newly established stations are also likely affected by postseismic motions. For these new sites, the clear resolution of any exponential decay, characteristic for postseismic motion, is further masked by seasonal effects which are difficult to estimate from the current two-year time series. In addition, the linear signals may also include the effect of inter-annual surface loading, which needs to be modelled and removed to recover the tectonic signal. The similarity of time series for the new stations to the more recent trends at the Haida Gwaii stations underlines the facts that the effects of postseismic motions are wide-spread and regional elastic deformation trends are not likely to be recovered for another 5 years.

Stochastic ground-motion simulations for the 2016 Kumamoto, Japan, earthquake

NASA Astrophysics Data System (ADS)

Zhang, Long; Chen, Guangqi; Wu, Yanqiang; Jiang, Han

2016-11-01

On April 15, 2016, Kumamoto, Japan, was struck by a large earthquake sequence, leading to severe casualty and building damage. The stochastic finite-fault method based on a dynamic corner frequency has been applied to perform ground-motion simulations for the 2016 Kumamoto earthquake. There are 53 high-quality KiK-net stations available in the Kyushu region, and we employed records from all stations to determine region-specific source, path and site parameters. The calculated S-wave attenuation for the Kyushu region beneath the volcanic and non-volcanic areas can be expressed in the form of Q s = (85.5 ± 1.5) f 0.68±0.01 and Q s = (120 ± 5) f 0.64±0.05, respectively. The effects of lateral S-wave velocity and attenuation heterogeneities on the ground-motion simulations were investigated. Site amplifications were estimated using the corrected cross-spectral ratios technique. Zero-distance kappa filter was obtained to be the value of 0.0514 ± 0.0055 s, using the spectral decay method. The stress drop of the mainshock based on the USGS slip model was estimated optimally to have a value of 64 bars. Our finite-fault model with optimized parameters was validated through the good agreement of observations and simulations at all stations. The attenuation characteristics of the simulated peak ground accelerations were also successfully captured by the ground-motion prediction equations. Finally, the ground motions at two destructively damaged regions, Kumamoto Castle and Minami Aso village, were simulated. We conclude that the stochastic finite-fault method with well-determined parameters can reproduce the ground-motion characteristics of the 2016 Kumamoto earthquake in both the time and frequency domains. This work is necessary for seismic hazard assessment and mitigation.[Figure not available: see fulltext.

Electrostatic Model Applied to ISS Charged Water Droplet Experiment

NASA Technical Reports Server (NTRS)

Stevenson, Daan; Schaub, Hanspeter; Pettit, Donald R.

2015-01-01

The electrostatic force can be used to create novel relative motion between charged bodies if it can be isolated from the stronger gravitational and dissipative forces. Recently, Coulomb orbital motion was demonstrated on the International Space Station by releasing charged water droplets in the vicinity of a charged knitting needle. In this investigation, the Multi-Sphere Method, an electrostatic model developed to study active spacecraft position control by Coulomb charging, is used to simulate the complex orbital motion of the droplets. When atmospheric drag is introduced, the simulated motion closely mimics that seen in the video footage of the experiment. The electrostatic force's inverse dependency on separation distance near the center of the needle lends itself to analytic predictions of the radial motion.

Geodetic Constraints on Fault Slip Rates and Seismic Hazard in the Greater Las Vegas Area

NASA Astrophysics Data System (ADS)

Hammond, W. C.; Kreemer, C.; Blewitt, G.; Broermann, J.; Bennett, R. A.

2014-12-01

We address fundamental questions about how contemporary tectonic deformation of the crust in the southern Great Basin occurs in the region around Las Vegas (LV) Nevada, western Arizona and eastern California. This area lies in the intersection of the eastern Walker Lane Belt, southern Great Basin and western Colorado Plateau (CP), sharing features of transtensional and extensional deformation associated with Pacific/North America relative motion. We use GPS data collected from 48 stations of the MAGNET semi-continuous network and 77 stations from continuous networks including BARGEN and EarthScope Plate Boundary Observatory. MAGNET stations have been observed for a minimum of 7 years, while most continuous stations have longer records. From these data we estimate the velocity of crustal motion for all stations with respect to the stable North America reference frame NA12. To correct for transients from recent large earthquakes including the 1999 Hector Mine and 2010 El Mayor-Cucapah events we use models of co- and post-seismic deformation, subtracting the predicted motions from the time series before estimating interseismic stain rates. We find approximately 2 mm/yr of relative motion distributed over 200 km centered on Las Vegas, with a mean strain accumulation rate of 10 × 10-9 yr-1, with lower rates of predominantly extensional strain to the east and higher rates of predominantly shear deformation to the west. The mean strain rate is lower than that of the western Walker Lane but about twice that of eastern Nevada where e.g., the Wells, NV MW 6.0 earthquake occurred in 2008. From this new velocity field we generated a horizontal tensor strain rate map and a crustal block motion model to portray the transition of active strain from the CP into the Walker Lane. For faults in the Las Vegas Valley, including the Eglington Fault and Frenchman Mountain Fault, the observed velocity gradients and model results are consistent with normal slip rates of 0.2 mm/yr, which are typical for the region. The Stateline Fault system experiences dextral slip of at least 0.4 mm/yr while normal faults south of LV collectively accommodate 0.9 mm/yr of east-west extension across a zone ~150 km wide. We see no evidence for concentrations of deformation or isolated rigid microplates within this zone.

Large Subduction Earthquake Simulations using Finite Source Modeling and the Offshore-Onshore Ambient Seismic Field

NASA Astrophysics Data System (ADS)

Viens, L.; Miyake, H.; Koketsu, K.

2016-12-01

Large subduction earthquakes have the potential to generate strong long-period ground motions. The ambient seismic field, also called seismic noise, contains information about the elastic response of the Earth between two seismic stations that can be retrieved using seismic interferometry. The DONET1 network, which is composed of 20 offshore stations, has been deployed atop the Nankai subduction zone, Japan, to continuously monitor the seismotectonic activity in this highly seismically active region. The surrounding onshore area is covered by hundreds of seismic stations, which are operated the National Research Institute for Earth Science and Disaster Prevention (NIED) and the Japan Meteorological Agency (JMA), with a spacing of 15-20 km. We retrieve offshore-onshore Green's functions from the ambient seismic field using the deconvolution technique and use them to simulate the long-period ground motions of moderate subduction earthquakes that occurred at shallow depth. We extend the point source method, which is appropriate for moderate events, to finite source modeling to simulate the long-period ground motions of large Mw 7 class earthquake scenarios. The source models are constructed using scaling relations between moderate and large earthquakes to discretize the fault plane of the large hypothetical events into subfaults. Offshore-onshore Green's functions are spatially interpolated over the fault plane to obtain one Green's function for each subfault. The interpolated Green's functions are finally summed up considering different rupture velocities. Results show that this technique can provide additional information about earthquake ground motions that can be used with the existing physics-based simulations to improve seismic hazard assessment.

Application of constrained k-means clustering in ground motion simulation validation

NASA Astrophysics Data System (ADS)

Khoshnevis, N.; Taborda, R.

2017-12-01

The validation of ground motion synthetics has received increased attention over the last few years due to the advances in physics-based deterministic and hybrid simulation methods. Unlike for low frequency simulations (f ≤ 0.5 Hz), for which it has become reasonable to expect a good match between synthetics and data, in the case of high-frequency simulations (f ≥ 1 Hz) it is not possible to match results on a wiggle-by-wiggle basis. This is mostly due to the various complexities and uncertainties involved in earthquake ground motion modeling. Therefore, in order to compare synthetics with data we turn to different time series metrics, which are used as a means to characterize how the synthetics match the data on qualitative and statistical sense. In general, these metrics provide GOF scores that measure the level of similarity in the time and frequency domains. It is common for these scores to be scaled from 0 to 10, with 10 representing a perfect match. Although using individual metrics for particular applications is considered more adequate, there is no consensus or a unified method to classify the comparison between a set of synthetic and recorded seismograms when the various metrics offer different scores. We study the relationship among these metrics through a constrained k-means clustering approach. We define 4 hypothetical stations with scores 3, 5, 7, and 9 for all metrics. We put these stations in the category of cannot-link constraints. We generate the dataset through the validation of the results from a deterministic (physics-based) ground motion simulation for a moderate magnitude earthquake in the greater Los Angeles basin using three velocity models. The maximum frequency of the simulation is 4 Hz. The dataset involves over 300 stations and 11 metrics, or features, as they are understood in the clustering process, where the metrics form a multi-dimensional space. We address the high-dimensional feature effects with a subspace-clustering analysis, generate a final labeled dataset of stations, and discuss the within-class statistical characteristics of each metric. Labeling these stations is the first step towards developing a unified metric to evaluate ground motion simulations in an application-independent manner.

Estimated SLR station position and network frame sensitivity to time-varying gravity

NASA Astrophysics Data System (ADS)

Zelensky, Nikita P.; Lemoine, Frank G.; Chinn, Douglas S.; Melachroinos, Stavros; Beckley, Brian D.; Beall, Jennifer Wiser; Bordyugov, Oleg

2014-06-01

This paper evaluates the sensitivity of ITRF2008-based satellite laser ranging (SLR) station positions estimated weekly using LAGEOS-1/2 data from 1993 to 2012 to non-tidal time-varying gravity (TVG). Two primary methods for modeling TVG from degree-2 are employed. The operational approach applies an annual GRACE-derived field, and IERS recommended linear rates for five coefficients. The experimental approach uses low-order/degree coefficients estimated weekly from SLR and DORIS processing of up to 11 satellites (tvg4x4). This study shows that the LAGEOS-1/2 orbits and the weekly station solutions are sensitive to more detailed modeling of TVG than prescribed in the current IERS standards. Over 1993-2012 tvg4x4 improves SLR residuals by 18 % and shows 10 % RMS improvement in station stability. Tests suggest that the improved stability of the tvg4x4 POD solution frame may help clarify geophysical signals present in the estimated station position time series. The signals include linear and seasonal station motion, and motion of the TRF origin, particularly in Z. The effect on both POD and the station solutions becomes increasingly evident starting in 2006. Over 2008-2012, the tvg4x4 series improves SLR residuals by 29 %. Use of the GRGS RL02 series shows similar improvement in POD. Using tvg4x4, secular changes in the TRF origin Z component double over the last decade and although not conclusive, it is consistent with increased geocenter rate expected due to continental ice melt. The test results indicate that accurate modeling of TVG is necessary for improvement of station position estimation using SLR data.

Empirical Ground Motion Characterization of Induced Seismicity in Alberta and Oklahoma

NASA Astrophysics Data System (ADS)

Novakovic, M.; Atkinson, G. M.; Assatourians, K.

2017-12-01

We develop empirical ground-motion prediction equations (GMPEs) for ground motions from induced earthquakes in Alberta and Oklahoma following the stochastic-model-based method of Atkinson et al. (2015 BSSA). The Oklahoma ground-motion database is compiled from over 13,000 small to moderate seismic events (M 1 to 5.8) recorded at 1600 seismic stations, at distances from 1 to 750 km. The Alberta database is compiled from over 200 small to moderate seismic events (M 1 to 4.2) recorded at 50 regional stations, at distances from 30 to 500 km. A generalized inversion is used to solve for regional source, attenuation and site parameters. The obtained parameters describe the regional attenuation, stress parameter and site amplification. Resolving these parameters allows for the derivation of regionally-calibrated GMPEs that can be used to compare ground motion observations between waste water injection (Oklahoma) and hydraulic fracture induced events (Alberta), and further compare induced observations with ground motions resulting from natural sources (California, NGAWest2). The derived GMPEs have applications for the evaluation of hazards from induced seismicity and can be used to track amplitudes across the regions in real time, which is useful for ground-motion-based alerting systems and traffic light protocols.

Stochastic finite-fault simulation of ground motion from the August 11, 2012, M w 6.4 Ahar earthquake, northwestern Iran

NASA Astrophysics Data System (ADS)

Heidari, Reza

2016-04-01

In this study, the 11 August 2012 M w 6.4 Ahar earthquake is investigated using the ground motion simulation based on the stochastic finite-fault model. The earthquake occurred in northwestern Iran and causing extensive damage in the city of Ahar and surrounding areas. A network consisting of 58 acceleration stations recorded the earthquake within 8-217 km of the epicenter. Strong ground motion records from six significant well-recorded stations close to the epicenter have been simulated. These stations are installed in areas which experienced significant structural damage and humanity loss during the earthquake. The simulation is carried out using the dynamic corner frequency model of rupture propagation by extended fault simulation program (EXSIM). For this purpose, the propagation features of shear-wave including {Q}_s value, kappa value {k}_0 , and soil amplification coefficients at each site are required. The kappa values are obtained from the slope of smoothed amplitude of Fourier spectra of acceleration at higher frequencies. The determined kappa values for vertical and horizontal components are 0.02 and 0.05 s, respectively. Furthermore, an anelastic attenuation parameter is derived from energy decay of a seismic wave by using continuous wavelet transform (CWT) for each station. The average frequency-dependent relation estimated for the region is Q=(122± 38){f}^{(1.40± 0.16)}. Moreover, the horizontal to vertical spectral ratio H/V is applied to estimate the site effects at stations. Spectral analysis of the data indicates that the best match between the observed and simulated spectra occurs for an average stress drop of 70 bars. Finally, the simulated and observed results are compared with pseudo acceleration spectra and peak ground motions. The comparison of time series spectra shows good agreement between the observed and the simulated waveforms at frequencies of engineering interest.

Equations of motion of a space station with emphasis on the effects of the gravity gradient

NASA Technical Reports Server (NTRS)

Tuell, L. P.

1987-01-01

The derivation of the equations of motion is based upon the principle of virtual work. As developed, these equations apply only to a space vehicle whose physical model consists of a rigid central carrier supporting several flexible appendages (not interconnected), smaller rigid bodies, and point masses. Clearly evident in the equations is the respect paid to the influence of the Earth's gravity field, considerably more than has been the custom in simulating vehicle motion. The effect of unpredictable crew motion is ignored.

Very Long Baseline Interferometry Applied to Polar Motion, Relativity and Geodesy. Ph.D. Thesis - Maryland Univ.

NASA Technical Reports Server (NTRS)

Ma, C.

1978-01-01

The causes and effects of diurnal polar motion are described. An algorithm is developed for modeling the effects on very long baseline interferometry observables. Five years of radio-frequency very long baseline interferometry data from stations in Massachusetts, California, and Sweden are analyzed for diurnal polar motion. It is found that the effect is larger than predicted by McClure. Corrections to the standard nutation series caused by the deformability of the earth have a significant effect on the estimated diurnal polar motion scaling factor and the post-fit residual scatter. Simulations of high precision very long baseline interferometry experiments taking into account both measurement uncertainty and modeled errors are described.

A New Unified Approach to Determine Geocenter Motion Using Space Geodesy and GRACE Gravity Data

NASA Astrophysics Data System (ADS)

Wu, X.; Kusche, J.; Landerer, F. W.

2016-12-01

Spherical harmonic expansions of Earth's surface mass variations start from three degree-1 terms. These longest-wavelength terms induce geocenter motion between the center-of-mass of the total Earth system (CM) and the center-of-figure of the solid Earth surface (CF), and a degree-1 surface deformation field. For complete spectral coverage and robust assessment of geographic mass budget using GRACE data, very accurate knowledge of geocenter motion between CM and CF is required with precision goals of 0.2 mm in annual amplitude and 0.2 mm/yr leading to equivalent degree-1 coefficients. However, GRACE's K-band ranging data system is not sensitive to these variation modes. Although satellite laser ranging (SLR) system is thought to have the most reliable sensitivity to CM, its surface network is very sparse and can only deliver motion between CM and the center of a changing network (CN) of roughly 20 unevenly distributed stations. Recently, the network has been extended to include 82 stations with their geocentric displacements derived by transferring SLR's CM sensitivity to other technique networks through local tie and co-motion constraints. The CM-CN motion of this network has a better agreement with the geocenter motion result from a global inversion of relative GPS, GRACE, and the ECCO ocean bottom pressure (OBP) model. Still, there is no guarantee that such a CM-CN motion is the same as the CM-CF motion. Also, the global inversion result is subject to the impact of unknown errors in the OBP model. To improve reliability of geocenter motion determination, we use a new unified approach to geocenter motion determination by combining geocentric displacements of ground stations with GRACE gravity data. Both translational and deformational signatures will be exploited for retrieval of the degree-1 surface mass variation coefficients. Higher degree terms are estimated simultaneously using GRACE gravity data, which further improves CF knowledge and reduces aliasing effects. Such a data combination also uses full covariance matrices of all data types to facilitate a reliable variance component estimation. High-precision results for non-linear geocenter motion have been achieved and will be reported. We will also discuss challenges and strategies for improving geocenter velocity determination.

Stress Drop and Depth Controls on Ground Motion From Induced Earthquakes

NASA Astrophysics Data System (ADS)

Baltay, A.; Rubinstein, J. L.; Terra, F. M.; Hanks, T. C.; Herrmann, R. B.

2015-12-01

Induced earthquakes in the central United States pose a risk to local populations, but there is not yet agreement on how to portray their hazard. A large source of uncertainty in the hazard arises from ground motion prediction, which depends on the magnitude and distance of the causative earthquake. However, ground motion models for induced earthquakes may be very different than models previously developed for either the eastern or western United States. A key question is whether ground motions from induced earthquakes are similar to those from natural earthquakes, yet there is little history of natural events in the same region with which to compare the induced ground motions. To address these problems, we explore how earthquake source properties, such as stress drop or depth, affect the recorded ground motion of induced earthquakes. Typically, due to stress drop increasing with depth, ground motion prediction equations model shallower events to have smaller ground motions, when considering the same absolute hypocentral distance to the station. Induced earthquakes tend to occur at shallower depths, with respect to natural eastern US earthquakes, and may also exhibit lower stress drops, which begs the question of how these two parameters interact to control ground motion. Can the ground motions of induced earthquakes simply be understood by scaling our known source-ground motion relations to account for the shallow depth or potentially smaller stress drops of these induced earthquakes, or is there an inherently different mechanism in play for these induced earthquakes? We study peak ground-motion velocity (PGV) and acceleration (PGA) from induced earthquakes in Oklahoma and Kansas, recorded by USGS networks at source-station distances of less than 20 km, in order to model the source effects. We compare these records to those in both the NGA-West2 database (primarily from California) as well as NGA-East, which covers the central and eastern United States and Canada. Preliminary analysis indicates that the induced ground motions appear similar to those from the NGA-West2 database. However, upon consideration of their shallower depths, ground motion behavior from induced events seems to fall in between the West data and that of NGA-East, so we explore the control of stress drop and depth on ground motion in more detail.

Contact dynamics math model

NASA Technical Reports Server (NTRS)

Glaese, John R.; Tobbe, Patrick A.

1986-01-01

The Space Station Mechanism Test Bed consists of a hydraulically driven, computer controlled six degree of freedom (DOF) motion system with which docking, berthing, and other mechanisms can be evaluated. Measured contact forces and moments are provided to the simulation host computer to enable representation of orbital contact dynamics. This report describes the development of a generalized math model which represents the relative motion between two rigid orbiting vehicles. The model allows motion in six DOF for each body, with no vehicle size limitation. The rotational and translational equations of motion are derived. The method used to transform the forces and moments from the sensor location to the vehicles' centers of mass is also explained. Two math models of docking mechanisms, a simple translational spring and the Remote Manipulator System end effector, are presented along with simulation results. The translational spring model is used in an attempt to verify the simulation with compensated hardware in the loop results.

Strong ground motion in the Taipei basin from the 1999 Chi-Chi, Taiwan, earthquake

USGS Publications Warehouse

Fletcher, Joe B.; Wen, K.-L.

2005-01-01

The Taipei basin, located in northwest Taiwan about 160 km from the epicenter of the Chi-Chi earthquake, is a shallow, triangular-shaped basin filled with low-velocity fluvial deposits. There is a strong velocity contrast across the basement interface of about 600 m/sec at a depth of about 600-700 m in the deeper section of the basin, suggesting that ground motion should be amplified at sites in the basin. In this article, the ground-motion recordings are analyzed to determine the effect of the basin both in terms of amplifications expected from a 1D model of the sediments in the basin and in terms of the 3D structure of the basin. Residuals determined for peak acceleration from attenuation curves are more positive (amplified) in the basin (average of 5.3 cm/ sec2 compared to - 24.2 cm/sec2 for those stations outside the basin and between 75 and 110 km from the surface projection of the faulted area, a 40% increase in peak ground acceleration). Residuals for peak velocity are also significantly more positive at stations in the basin (31.8 cm/sec compared to 20.0 cm/sec out). The correlation of peak motion with depth to basement, while minor in peak acceleration, is stronger in the peak velocities. Record sections of ground motion from stations in and around the Taipei basin show that the largest long-period arrival, which is coherent across the region, is strongest on the vertical component and has a period of about 10-12 sec. This phase appears to be a Rayleigh wave, probably associated with rupture at the north end of the Chelungpu fault. Records of strong motion from stations in and near the basin have an additional, higher frequency signal: nearest the deepest point in the basin, the signal is characterized by frequencies of about 0.3 - 0.4 Hz. These frequencies are close to simple predictions using horizontal layers and the velocity structure of the basin. Polarizations of the S wave are mostly coherent across the array, although there are significant differences along the northwest edge that may indicate large strains across that edge of the basin. The length of each record after the main S wave are all longer at basin stations compared to those outside. This increase in duration of ground shaking is probably caused by amplification of ground motion at basin stations, although coda Q (0.67 - 1.30 Hz) is slightly larger inside the basin compared to those at local stations outside the basin. Durations correlate with depth to basement. These motions are in the range that can induce damage in buildings and may have contributed to the structural collapse of multistory buildings in the Taipei basin.

Source Rupture Process for the February 21, 2011, Mw6.1, New Zealand Earthquake and the Characteristics of Near-field Strong Ground Motion

NASA Astrophysics Data System (ADS)

Meng, L.; Shi, B.

2011-12-01

The New Zealand Earthquake of February 21, 2011, Mw 6.1 occurred in the South Island, New Zealand with the epicenter at longitude 172.70°E and latitude 43.58°S, and with depth of 5 km. The Mw 6.1 earthquake occurred on an unknown blind fault involving oblique-thrust faulting, which is 9 km away from southern of the Christchurch, the third largest city of New Zealand, with a striking direction from east toward west (United State Geology Survey, USGS, 2011). The earthquake killed at least 163 people and caused a lot of construction damages in Christchurch city. The Peak Ground Acceleration (PGA) observed at station Heathcote Valley Primary School (HVSC), which is 1 km away from the epicenter, is up to almost 2.0g. The ground-motion observation suggests that the buried earthquake source generates much higher near-fault ground motion. In this study, we have analyzed the earthquake source spectral parameters based on the strong motion observations, and estimated the near-fault ground motion based on the Brune's circular fault model. The results indicate that the larger ground motion may be caused by a higher dynamic stress drop,Δσd , or effect stress drop named by Brune, in the major source rupture region. In addition, a dynamical composite source model (DCSM) has been developed to simulate the near-fault strong ground motion with associated fault rupture properties from the kinematic point of view. For comparison purpose, we also conducted the broadband ground motion predictions for the station of HVSC; the synthetic seismogram of time histories produced for this station has good agreement with the observations in the waveforms, peak values and frequency contents, which clearly indicate that the higher dynamic stress drop during the fault rupture may play an important role to the anomalous ground-motion amplification. The preliminary simulated result illustrated in at Station HVSC is that the synthetics seismograms have a realistic appearance in the waveform and time duration to the observations, especially for the vertical component. Synthetics Fourier spectra are reasonably similar to the recordings. The simulated PGA values of vertical and S26W components are consistent with the recorded, and for the S64E component, the PGA derived from our simulation is smaller than that from observation. The resultant Fourier spectra both for the synthetic and observation is much similar with each other for three components of acceleration time histories, except for the vertical component, where the derived spectra from synthetic data is smaller than that resultant from observation when the frequency is above 10 Hz. Both theoretical study and numerical simulation indicate that, for the 2011 Mw 6.1, New Zealand Earthquake, the higher dynamic stress drop during the source rupture process could play an important role to the anomalous ground-motion amplification beside to the other site-related seismic effects. The composite source modeling based on the simple Brune's pulse model could approximately provide us a good insight into earthquake source related rupture processes for a moderate-sized earthquake.

Peak ground motion predictions with empirical site factors using Taiwan Strong Motion Network recordings

NASA Astrophysics Data System (ADS)

Chung, Jen-Kuang

2013-09-01

A stochastic method called the random vibration theory (Boore, 1983) has been used to estimate the peak ground motions caused by shallow moderate-to-large earthquakes in the Taiwan area. Adopting Brune's ω-square source spectrum, attenuation models for PGA and PGV were derived from path-dependent parameters which were empirically modeled from about one thousand accelerograms recorded at reference sites mostly located in a mountain area and which have been recognized as rock sites without soil amplification. Consequently, the predicted horizontal peak ground motions at the reference sites, are generally comparable to these observed. A total number of 11,915 accelerograms recorded from 735 free-field stations of the Taiwan Strong Motion Network (TSMN) were used to estimate the site factors by taking the motions from the predictive models as references. Results from soil sites reveal site amplification factors of approximately 2.0 ~ 3.5 for PGA and about 1.3 ~ 2.6 for PGV. Finally, as a result of amplitude corrections with those empirical site factors, about 75% of analyzed earthquakes are well constrained in ground motion predictions, having average misfits ranging from 0.30 to 0.50. In addition, two simple indices, R 0.57 and R 0.38, are proposed in this study to evaluate the validity of intensity map prediction for public information reports. The average percentages of qualified stations for peak acceleration residuals less than R 0.57 and R 0.38 can reach 75% and 54%, respectively, for most earthquakes. Such a performance would be good enough to produce a faithful intensity map for a moderate scenario event in the Taiwan region.

Site effects in the city of Port au Prince (Haiti) : A combined use of spectral ratio methods and empirical Greens functions simulations

NASA Astrophysics Data System (ADS)

St Fleur, S.; Courboulex, F.; Bertrand, E.; Deschamps, A.; Mercier de Lepinay, B.; Prepetit, C.; Hough, S. E.

2013-12-01

Haiti was struck in January 2010 by a strong Mw=7 earthquake that caused extensive damages in the city of Port au Prince. At this time, very few seismological stations were working in Haiti and the only one that recorded the mainshock in Port au Prince was saturated. Thus, there were no direct measurements of the ground motion produced by this large event. Quickly after the 2010 event, several permanent accelerometric stations were installed by the USGS (U.S. Geological Survey) and the BME (Bureau des Mines et de l'Energie d'Haiti) as well as broad-band stations by the GSC (Geological Survey of Canada). Since their installation, these stations recorded several tens of aftershocks. The aim of our work is to take advantage of this new dataset to better understand the ground motions generated by earthquakes in the city of Port au Prince. We have used first spectral ratio methods to obtain the transfer function of each station, and then an empirical Green's Function simulation approach to combine source and site effects. In order to estimate site effects under each station, we have used classical spectral ratio methods. In a first step, the H/V (Horizontal/Vertical) method was used to select a reference station (in Port au Prince) that should be ideally a station without any site effects. We selected two stations, HCEA and PAPH, as reference stations, as even if the shape of their H/V curves is not always equal to 1 in the entire frequency band. In a second step, we computed the transfer function at each station by a ratio between the spectra of each earthquake at each station and the spectra obtained at the reference station (we use successively HCEA, PAPH and a combination of both). The results were kept only for the frequencies where the signal to noise was larger than 3. In the frequency range 1 to 20 Hz, we found site/reference ratios that reach values from 3 to 8 and a large variability from one station to another one. In the low frequency band 0.5 to 1 Hz a peak is present at almost all the stations in Port au Prince, which may indicate an amplification due to a deep interface. However, these values have a large variability from one earthquake recording to the other. This may indicate that the observed amplification depends not only on the effect of local site, but also on the source or the propagation direction. We then used the recordings of two earthquakes (Mw 4.3 and Mw 4.4) that occurred on the Leogane fault as Empirical Green's Functions (EGF) in order to simulate the ground motions generated by a virtual Mw 6.8 earthquake. For this simulation a stochastic EGF summation method was used. The results obtained using the two events are surprisingly very different. Using the first EGF, nearly the same ground motion was obtained at each station in Port-au-Prince, whereas with the second EGF, the results highlight large differences. Finally, the estimated site response (site/reference) was used in combination with a direct estimation of the rock site motion (HCEA simulation) in order to reproduce the ground motions which were compared to the EGF simulation method. The comparison confirms the large variability in the modeled ground shaking which can be due to both site and source effects and the low frequency amplification on the plain of Port-au-Prince.

Comparisons of ground motions from the 1999 Chi-Chi, earthquake with empirical predictions largely based on data from California

USGS Publications Warehouse

Boore, D.M.

2001-01-01

This article has the modest goal of comparing the ground motions recorded during the 1999 Chi-Chi, Taiwan, mainshock with predictions from four empirical-based equations commonly used for western North America; these empirical predictions are largely based on data from California. Comparisons are made for peak acceleration and 5%-damped response spectra at periods between 0.1 and 4 sec. The general finding is that the Chi-Chi ground motions are smaller than those predicted from the empirically based equations for periods less than about 1 sec by factors averaging about 0.4 but as small as 0.26 (depending on period, on which equation is used, and on whether the sites are assumed to be rock or soil). There is a trend for the observed motions to approach or even exceed the predicted motions for longer periods. Motions at similar distances (30-60 km) to the east and to the west of the fault differ dramatically at periods between about 2 and 20 sec: Long-duration wave trains are present on the motions to the west, and when normalized to similar amplitudes at short periods, the response spectra of the motions at the western stations are as much as five times larger than those of motions from eastern stations. The explanation for the difference is probably related to site and propagation effects; the western stations are on the Coastal Plain, whereas the eastern stations are at the foot of young and steep mountains, either in the relatively narrow Longitudinal Valley or along the eastern coast-the sediments underlying the eastern stations are probably shallower and have higher velocity than those under the western stations.

A refined gravity model from Lageos /GEM-L2/

NASA Technical Reports Server (NTRS)

Lerch, F. J.; Klosko, S. M.; Patel, G. B.

1982-01-01

Lageos satellite laser ranging (SLR) data taken over a 2.5 yr period were employed to develop the Goddard Earth Model GEM-L2, a refined gravity field model. Additional data was gathered with 30 other satellites, resulting in spherical harmonics through degree and order 20, based on over 600,000 measurements. The Lageos data was accurate down to 10 cm, after which the GEM 9 data were used to make adjustments past order 7. The resolution of long wavelength activity, through degree and order 4, was made possible by the Lageos data. The GEM-L2 model features a 20 x 20 geopotential, tracking station coordinates (20), 5-day polar motion and A1-UT1 values, and a GM value of 398,600.607 cu km/sq sec. The accuracy of station positioning has been raised to within 6 cm total position globally and within 1.8 cm in baselines. It is concluded that SLR is useful for measuring tectonic plate motions and inter-plate deformations.

Geocenter Motion Derived from the JTRF2014 Combination

NASA Astrophysics Data System (ADS)

Abbondanza, C.; Chin, T. M.; Gross, R. S.; Heflin, M. B.; Parker, J. W.; van Dam, T. M.; Wu, X.

2016-12-01

JTRF2014 represents the JPL Terrestrial Reference Frame (TRF) recently obtained as a result of the combination of the space-geodetic reprocessed inputs to the ITRF2014. Based upon a Kalman filter and smoother approach, JTRF2014 assimilates station positions and Earth-Orientation Parameters (EOPs) from GNSS, VLBI, SLR and DORIS and combine them through local tie measurements. JTRF is in its essence a time-series based TRF. In the JTRF2014 the dynamical evolution of the station positions is formulated by introducing linear and seasonal terms (annual and semi-annual periodic modes). Non-secular and non-seasonal motions of the geodetic sites are included in the smoothed time series by properly defining the station position process noise whose variance is characterized by analyzing station displacements induced by temporal changes of planetary fluid masses (atmosphere, oceans and continental surface water). With its station position time series output at a weekly resolution, JTRF2014 materializes a sub-secular frame whose origin is at the quasi-instantaneous Center of Mass (CM) as sensed by SLR. Both SLR and VLBI contribute to the scale of the combined frame. The sub-secular nature of the frame allows the users to directly access the quasi-instantaneous geocenter and scale information. Unlike standard combined TRF products which only give access to the secular component of the CM-CN motions, JTRF2014 is able to preserve -in addition to the long-term- the seasonal, non-seasonal and non-secular components of the geocenter motion. In the JTRF2014 assimilation scheme, local tie measurements are used to transfer the geocenter information from SLR to the space-geodetic techniques which are either insensitive to CM (VLBI) or whose geocenter motion is poorly determined (GNSS and DORIS). Properly tied to the CM frame through local ties and co-motion constraints, GNSS, VLBI and DORIS contribute to improve the SLR network geometry. In this paper, the determination of the weekly (CM-CN) time series as inferred from the JTRF2014 combination will be presented. Comparisons with geocenter time series derived from global inversions of GPS, GRACE and ocean bottom pressure models show the JTRF2014-derived geocenter favourably compares to the results of the inversion.

Determining parameters of Moon's orbital and rotational motion from LLR observations using GRAIL and IERS-recommended models

NASA Astrophysics Data System (ADS)

Pavlov, Dmitry A.; Williams, James G.; Suvorkin, Vladimir V.

2016-11-01

The aim of this work is to combine the model of orbital and rotational motion of the Moon developed for DE430 with up-to-date astronomical, geodynamical, and geo- and selenophysical models. The parameters of the orbit and physical libration are determined in this work from lunar laser ranging (LLR) observations made at different observatories in 1970-2013. Parameters of other models are taken from solutions that were obtained independently from LLR. A new implementation of the DE430 lunar model, including the liquid core equations, was done within the EPM ephemeris. The postfit residuals of LLR observations make evident that the terrestrial models and solutions recommended by the IERS Conventions are compatible with the lunar theory. That includes: EGM2008 gravitational potential with conventional corrections and variations from solid and ocean tides; displacement of stations due to solid and ocean loading tides; and precession-nutation model. Usage of these models in the solution for LLR observations has allowed us to reduce the number of parameters to be fit. The fixed model of tidal variations of the geopotential has resulted in a lesser value of Moon's extra eccentricity rate, as compared to the original DE430 model with two fit parameters. A mixed model of lunar gravitational potential was used, with some coefficients determined from LLR observations, and other taken from the GL660b solution obtained from the GRAIL spacecraft mission. Solutions obtain accurate positions for the ranging stations and the five retroreflectors. Station motion is derived for sites with long data spans. Dissipation is detected at the lunar fluid core-solid mantle boundary demonstrating that a fluid core is present. Tidal dissipation is strong at both Earth and Moon. Consequently, the lunar semimajor axis is expanding by 38.20 mm/yr, the tidal acceleration in mean longitude is -25.90 {{}^' ' }}/cy^2, and the eccentricity is increasing by 1.48× 10^{-11} each year.

The three dimensional motion and stability of a rotating space station: Cable-counterweight configuration

NASA Technical Reports Server (NTRS)

Bainum, P. M.; Evans, K. S.

1974-01-01

The three dimensional equations of motion for a cable connected space station--counterweight system are developed using a Lagrangian formulation. The system model employed allows for cable and end body damping and restoring effects. The equations are then linearized about the equilibrium motion and nondimensionalized. To first degree, the out-of-plane equations uncouple from the inplane equations. Therefore, the characteristic polynomials for the in-plane and out-of-plane equations are developed and treated separately. From the general in-plane characteristic equation, necessary conditions for stability are obtained. The Routh-Hurwitz necessary and sufficient conditions for stability are derived for the general out-of-plane characteristic equation. Special cases of the in-plane and out-of-plane equations (such as identical end masses, and when the cable is attached to the centers of mass of the two end bodies) are then examined for stability criteria.

The SCEC Broadband Platform: Open-Source Software for Strong Ground Motion Simulation and Validation

NASA Astrophysics Data System (ADS)

Goulet, C.; Silva, F.; Maechling, P. J.; Callaghan, S.; Jordan, T. H.

2015-12-01

The Southern California Earthquake Center (SCEC) Broadband Platform (BBP) is a carefully integrated collection of open-source scientific software programs that can simulate broadband (0-100Hz) ground motions for earthquakes at regional scales. The BBP scientific software modules implement kinematic rupture generation, low and high-frequency seismogram synthesis using wave propagation through 1D layered velocity structures, seismogram ground motion amplitude calculations, and goodness of fit measurements. These modules are integrated into a software system that provides user-defined, repeatable, calculation of ground motion seismograms, using multiple alternative ground motion simulation methods, and software utilities that can generate plots, charts, and maps. The BBP has been developed over the last five years in a collaborative scientific, engineering, and software development project involving geoscientists, earthquake engineers, graduate students, and SCEC scientific software developers. The BBP can run earthquake rupture and wave propagation modeling software to simulate ground motions for well-observed historical earthquakes and to quantify how well the simulated broadband seismograms match the observed seismograms. The BBP can also run simulations for hypothetical earthquakes. In this case, users input an earthquake location and magnitude description, a list of station locations, and a 1D velocity model for the region of interest, and the BBP software then calculates ground motions for the specified stations. The SCEC BBP software released in 2015 can be compiled and run on recent Linux systems with GNU compilers. It includes 5 simulation methods, 7 simulation regions covering California, Japan, and Eastern North America, the ability to compare simulation results against GMPEs, updated ground motion simulation methods, and a simplified command line user interface.

Applicability of the site fundamental frequency as a VS30 proxy for Central and Eastern North America

NASA Astrophysics Data System (ADS)

Hassani, B.; Atkinson, G. M.

2015-12-01

One of the most important issues in developing accurate ground-motion prediction equations (GMPEs) is the effective use of limited regional site information in developing a site effects model. In modern empirical GMPE models site effects are usually characterized by simplified parameters that describe the overall near-surface effects on input ground-motion shaking. The most common site effects parameter is the time-averaged shear-wave velocity in the upper 30 m (VS30), which has been used in the Next Generation Attenuation-West (NGA-West) and NGA-East GMPEs, and is widely used in building code applications. For the NGA-East GMPE database, only 6% of the stations have measured VS30 values, while the rest have proxy-based VS30 values. Proxy-based VS30 values are derived from a weighted average of different proxies' estimates such as topographic slope and surface geology proxies. For the proxy-based approaches, the uncertainty in the estimation of Vs30 is significantly higher (~0.25, log10 units) than that for stations with measured VS30(0.04, log10 units); this translates into error in site amplification and hence increased ground motion variability. We introduce a new VS30 proxy as a function of the site fundamental frequency (fpeak) using the NGA-East database, and show that fpeak is a particularly effective proxy for sites in central and eastern North America We first use horizontal to vertical spectra ratios (H/V) of 5%-damped pseudo spectral acceleration (PSA) to find the fpeak values for the recording stations. We develop an fpeak-based VS30 proxy by correlating the measured VS30 values with the corresponding fpeak value. The uncertainty of the VS30 estimate using the fpeak-based model is much lower (0.14, log10 units) than that for the proxy-based methods used in the NGA-East database (0.25 log10 units). The results of this study can be used to recalculate the VS30 values more accurately for stations with known fpeak values (23% of the stations), and potentially reduce the overall variability of the developed NGA-East GMPE models.

Sea level rise within the west of Arabian Gulf using tide gauge and continuous GPS measurements

NASA Astrophysics Data System (ADS)

Ayhan, M. E.; Alothman, A.

2009-04-01

Arabian Gulf is connected to Indian Ocean and located in the south-west of the Zagros Trust Belt. To investigate sea level variations within the west of Arabian Gulf, monthly means of sea level at 13 tide gauges along the coast of Saudi Arabia and Bahrain, available in the database of the Permanent Service for Mean Sea Level (PSMSL), are studied. We analyzed individually the monthly means at each station, and estimated secular sea level rate by a robust linear trend fitting. We computed the average relative sea level rise rate of 1.96 ± 0.21 mm/yr within the west of Arabian Gulf based on 4 stations spanning longer than 19 years. Vertical land motions are included into the relative sea level measurements at the tide gauges. Therefore sea level rates at the stations are corrected for vertical land motions using the ICE-5G v1.2 VM4 Glacial Isostatic Adjustment (GIA) model then we found the average sea level rise rate of 2.27 mm/yr. Bahrain International GPS Service (IGS) GPS station, which is close to the Mina Sulman tide gauge station in Bahrain, is the only continuous GPS station accessible in the region. The weekly GPS time series of vertical component at Bahrain IGS-GPS station referring to the ITRF97 from 1999.2 to 2008.6 are downloaded from http://www-gps.mit.edu/~tah/. We fitted a linear trend with an annual signal and one break to the GPS vertical time series and found a vertical land motion rate of 0.48 ± 0.11 mm/yr. Assuming the vertical rate at Bahrain IGS-GPS station represents the vertical rate at each of the other tide gauge stations studied here in the region, we computed average sea level rise rate of 2.44 ± 0.21 mm/yr within the west of Arabian Gulf.

Space station rotational equations of motion

NASA Technical Reports Server (NTRS)

Rheinfurth, M. H.; Carroll, S. N.

1985-01-01

Dynamic equations of motion are developed which describe the rotational motion for a large space structure having rotating appendages. The presence of the appendages produce torque coupling terms which are dependent on the inertia properties of the appendages and the rotational rates for both the space structure and the appendages. These equations were formulated to incorporate into the Space Station Attitude Control and Stabilization Test Bed to accurately describe the influence rotating solar arrays and thermal radiators have on the dynamic behavior of the Space Station.

Long-period Ground Motion Characteristics Inside and Outside of the Osaka Basin during the 2011 Great Tohoku Earthquake and Its Largest Aftershock

NASA Astrophysics Data System (ADS)

Sato, K.; Iwata, T.; Asano, K.; Kubo, H.; Aoi, S.

2013-12-01

The 2011 great Tohoku earthquake (Mw 9.0) occurred on March 11, 2011, and the largest aftershock (Mw 7.7) at the region adjacent to south boundary of the mainshock's source region. Long-period ground motions (1-10s) of large amplitude were observed in the Osaka sedimentary basin about 550-800km away from the source regions during both events. We studied propagation and site characteristics of these ground motions, and found some common features between these two events in the Osaka basin. (1) The amplitude of horizontal components of the ground motion at the site-specific period is amplified at each sedimentary station. The predominant period is around 7s in the bayside area where the largest pSv were observed. (2) The velocity Fourier spectra have their peak values around 7s at the bedrock sites surrounding the Osaka basin. (3) Two remarkable wave packets separated by 30s propagating from stations around the Nobi plain to the bedrock sites near the Osaka basin were seen in the pasted-up velocity waveforms from the source regions to the Osaka basin for both events (Sato et al., 2012). Therefore, large long-period ground motions in the Osaka basin are generated by the combination of propagation-path and basin effects. Firstly, we simulate ground motions due to the largest aftershock using three-dimensional FDM (GMS; Aoi and Fujiwara, 1999). The reason we focus on the largest aftershock is that this event has a relatively small rupture area and simple rupture process compared to the mainshock. The source model is based on the model estimated by Kubo et al. (2013). The velocity structure model is a three-dimensional velocity structure based on the Japan Integrated Velocity Structure Model (Koketsu et al., 2012) and the layer of Vs 350m/s in this model is replaced with one of Vs 500m/s. The minimum effective period in this computation is 3s. Then, we compare synthetic waveforms with observed ones. At CHBH14, the nearest station to the source and 60km away from the epicenter, the synthetic waveforms of the period-band 5-50s, where Kubo et al. (2013) studied, fit well to the observed ones. However, in our target period-band 5-8s, the earlier portion of the synthetic waveform of the main packet has smaller amplitude than the observation. At the bedrock sites near the Osaka basin, two wave packets which are appeared in the observation are qualitatively reproduced in the synthetics. However, the amplitudes are not well reproduced. Moreover, the amplitude ratio of horizontal components of synthetics between the rock and the bayside stations is underestimated compared to the observed one. Improvements of the source and velocity structure models for propagation-path and basin are needed. For that sake, we will analyze the characteristics of the synthetic waveforms, study how those wave packets are generated, and discuss the discrepancy between the synthetic and observed waveforms. We will also simulate the ground motion for the mainshock to study propagation characteristics of the mainshock. ACKNOWLEDGEMENTS We used strong motion data recorded by K-NET, KiK-net and F-net of NIED, CEORKA, BRI, JMA, and Osaka prefecture. GMS provided by NIED is used for the computation.

Source Model of the MJMA 6.5 Plate-Boundary Earthquake at the Nankai Trough, Southwest Japan, on April 1, 2016, Based on Strong Motion Waveform Modeling

NASA Astrophysics Data System (ADS)

Asano, K.

2017-12-01

An MJMA 6.5 earthquake occurred offshore the Kii peninsula, southwest Japan on April 1, 2016. This event was interpreted as a thrust-event on the plate-boundary along the Nankai trough where (Wallace et al., 2016). This event is the largest plate-boundary earthquake in the source region of the 1944 Tonankai earthquake (MW 8.0) after that event. The significant point of this event regarding to seismic observation is that this event occurred beneath an ocean-bottom seismic network called DONET1, which is jointly operated by NIED and JAMSTEC. Since moderate-to-large earthquake of this focal type is very rare in this region in the last half century, it is a good opportunity to investigate the source characteristics relating to strong motion generation of subduction-zone plate-boundary earthquakes along the Nankai trough. Knowledge obtained from the study of this earthquake would contribute to ground motion prediction and seismic hazard assessment for future megathrust earthquakes expected in the Nankai trough. In this study, the source model of the 2016 offshore the Kii peninsula earthquake was estimated by broadband strong motion waveform modeling using the empirical Green's function method (Irikura, 1986). The source model is characterized by strong motion generation area (SMGA) (Miyake et al., 2003), which is defined as a rectangular area with high-stress drop or high slip-velocity. SMGA source model based on the empirical Green's function method has great potential to reproduce ground motion time history in broadband frequency range. We used strong motion data from offshore stations (DONET1 and LTBMS) and onshore stations (NIED F-net and DPRI). The records of an MJMA 3.2 aftershock at 13:04 on April 1, 2016 were selected for the empirical Green's functions. The source parameters of SMGA are optimized by the waveform modeling in the frequency range 0.4-10 Hz. The best estimate of SMGA size is 19.4 km2, and SMGA of this event does not follow the source scaling relationship for past plate-boundary earthquakes along the Japan trench, northeast Japan. This finding implies that the source characteristics of plate-boundary events in the Nankai trough are different from those in the Japan Trench, and it could be important information to consider regional variation in ground motion prediction.

Ambient Noise Tomography In The Great Valley, California Near The Sacramento/San Joaquin Delta

NASA Astrophysics Data System (ADS)

Fletcher, J. B.; Seats, K.; Lawrence, J. F.; Erdem, J.

2013-12-01

We use ambient noise tomography to develop a shear-wave velocity model of the Great Valley centered on the Sacramento/San Joaquin Delta, which is located just west of Stockton, CA. The 3-D model is needed for ground motion simulations resulting from Delta and Bay area earthquakes to better estimate the seismic hazard for sites in the Delta. We analyze ground motion data from a 24-station network consisting of up to 14 USGS stations, 5 Berkeley Digital Seismic Net (BDSN) stations, and 5 Transportable Array (TA) stations that were deployed in 2006 and 2007. Ground motions are measured using broadband seismometers with a broad frequency response from about 0.016 to 20 Hz or greater. Seismograms are Fourier transformed in 1 hour overlapping segments and coherencies (normalized cross correlations) between stations are computed. Coherencies are stacked for a minimum of 8 months in 2006 to over 17 months starting in January 2012. Time series, transformed from coherencies that are filtered in narrow bands centered at periods from about 4.5s to 20s are used to determine the group velocity dispersion curves between pairs of stations. A velocity model is imaged for each period. Smoothing is applied. We considered block sizes ranging from 0.05° to 0.10° and obtained the best resolution at 0.08° (8.9 km). Checkerboard tests show that the full set of stations yields adequate resolution throughout the Delta. We image an irregular low-velocity structure (-0.1 to -0.2 km/s below average of 1.55 km/s at 5.5s period) that is roughly coincident with the Delta, but extends about 40 km to the north at short periods (4s to 10s). At longer periods, the low-velocity structure shrinks in area as the periods increase (up to 18.5s) and the center shifts about 20 km to the north. Also, at longer periods, higher velocities form a 130 km wide band on the eastern margin of the study area presumably indicating basement velocities of the western edge of the Sierra Nevada Mountains and the asymmetry of the Great Valley. The low-velocity structure roughly corresponds to the Delta depocenter that formed in the Tertiary with the partial uplift of the Coast Ranges.

Single-station 6C beamforming

NASA Astrophysics Data System (ADS)

Nakata, N.; Hadziioannou, C.; Igel, H.

2017-12-01

Six-component measurements of seismic ground motion provide a unique opportunity to identify and decompose seismic wavefields into different wave types and incoming azimuths, as well as estimate structural information (e.g., phase velocity). By using the relationship between the transverse component and vertical rotational motion for Love waves, we can find the incident azimuth of the wave and the phase velocity. Therefore, when we scan the entire range of azimuth and slownesses, we can process the seismic waves in a similar way to conventional beamforming processing, without using a station array. To further improve the beam resolution, we use the distribution of amplitude ratio between translational and rotational motions at each time sample. With this beamforming, we decompose multiple incoming waves by azimuth and phase velocity using only one station. We demonstrate this technique using the data observed at Wettzell (vertical rotational motion and 3C translational motions). The beamforming results are encouraging to extract phase velocity at the location of the station, apply to oceanic microseism, and to identify complicated SH wave arrivals. We also discuss single-station beamforming using other components (vertical translational and horizontal rotational components). For future work, we need to understand the resolution limit of this technique, suitable length of time windows, and sensitivity to weak motion.

Estimate of procession and polar motion errors from planetary encounter station location solutions

NASA Technical Reports Server (NTRS)

Pease, G. E.

1978-01-01

Jet Propulsion Laboratory Deep Space Station (DSS) location solutions based on two JPL planetary ephemerides, DE 84 and DE 96, at eight planetary encounters were used to obtain weighted least squares estimates of precession and polar motion errors. The solution for precession error in right ascension yields a value of 0.3 X 10 to the minus 5 power plus or minus 0.8 X 10 to the minus 6 power deg/year. This maps to a right ascension error of 1.3 X 10 to the minus 5 power plus or minus 0.4 X 10 to the minus 5 power deg at the first Voyager 1979 Jupiter encounter if the current JPL DSS location set is used. Solutions for precession and polar motion using station locations based on DE 84 agree well with the solution using station locations referenced to DE 96. The precession solution removes the apparent drift in station longitude and spin axis distance estimates, while the encounter polar motion solutions consistently decrease the scatter in station spin axis distance estimates.

Modelling and simulation of Space Station Freedom berthing dynamics and control

NASA Technical Reports Server (NTRS)

Cooper, Paul A.; Garrison, James L., Jr.; Montgomery, Raymond C.; Wu, Shih-Chin; Stockwell, Alan E.; Demeo, Martha E.

1994-01-01

A large-angle, flexible, multibody, dynamic modeling capability has been developed to help validate numerical simulations of the dynamic motion and control forces which occur during berthing of Space Station Freedom to the Shuttle Orbiter in the early assembly flights. This paper outlines the dynamics and control of the station, the attached Shuttle Remote Manipulator System, and the orbiter. The simulation tool developed for the analysis is described and the results of two simulations are presented. The first is a simulated maneuver from a gravity-gradient attitude to a torque equilibrium attitude using the station reaction control jets. The second simulation is the berthing of the station to the orbiter with the station control moment gyros actively maintaining an estimated torque equilibrium attitude. The influence of the elastic dynamic behavior of the station and of the Remote Manipulator System on the attitude control of the station/orbiter system during each maneuver was investigated. The flexibility of the station and the arm were found to have only a minor influence on the attitude control of the system during the maneuvers.

Monitoring of the orbital position of geostationary satellite by spatially separated reception of signals of digital satellite television

NASA Astrophysics Data System (ADS)

Kaliuzhnyi, M. P.; Bushuev, F. I.; Sibiriakova, Ye. S.; Shulga, O. V.; Shakun, L. S.; Bezrukovs, V.; Kulishenko, V. F.; Moskalenko, S. S.; Malynovsky, Ye. V.; Balagura, O. A.

2017-02-01

The results of the determination of the geostationary satellite "Eutelsat-13B" orbital position obtained during 2015-2016 years using European stations' network for reception of DVB-S signals from the satellite are presented. The network consists of five stations located in Ukraine and Latvia. The stations are equipped with a radio engineering complex developed by the RI "MAO". The measured parameter is a time difference of arrival (TDOA) of the DVB-S signals to the stations of the network. The errors of TDOA determination and satellite coordinates, obtained using a numerical model of satellite motion, are equal ±2.6 m and ±35 m respectively. Software implementation of the numerical model is taken from the free space dynamics library OREKIT.

Stabilizing a spinning Skylab

NASA Technical Reports Server (NTRS)

Seltzer, S. M.; Patel, J. S.; Justice, D. W.; Schweitzer, G. E.

1972-01-01

The results are presented of a study of the dynamics of a spinning Skylab space station. The stability of motion of several simplified models with flexible appendages was investigated. A digital simulation model that more accurately portrays the complex Skylab vehicle is described, and simulation results are compared with analytically derived results.

Satellite-tracking and earth-dynamics research programs. [NASA Programs on satellite orbits and satellite ground tracks of geodetic satellites

NASA Technical Reports Server (NTRS)

1974-01-01

Observations and research progress of the Smithsonian Astrophysical Observatory are reported. Satellite tracking networks (ground stations) are discussed and equipment (Baker-Nunn cameras) used to observe the satellites is described. The improvement of the accuracy of a laser ranging system of the ground stations is discussed. Also, research efforts in satellite geodesy (tides, gravity anomalies, plate tectonics) is discussed. The use of data processing for geophysical data is examined, and a data base for the Earth and Ocean Physics Applications Program is proposed. Analytical models of the earth's motion (computerized simulation) are described and the computation (numerical integration and algorithms) of satellite orbits affected by the earth's albedo, using computer techniques, is also considered. Research efforts in the study of the atmosphere are examined (the effect of drag on satellite motion), and models of the atmosphere based on satellite data are described.

Tossing on a Rotating Space Station

NASA Astrophysics Data System (ADS)

Paetkau, Mark

2004-10-01

The following analysis was inspired by a question posed by a listener of a radio science show. The listener asked the question: "If an astronaut in a space station that was rotating to simulate gravity threw a ball up, where would the ball go?" The physicist answered, "The ball would travel straight across the space station (assuming an open structure). "The main point is that to an outside observer the ball would not "fall" back down as on Earth. As I pondered this it occurred to me that while the answer is correct, it is a special case with a more general solution. Below is an analysis of the motions a thrown object can undergo on a rotating space station. The first part of the discussion is aimed at lower-level undergraduates who have a basic understanding of vectors and circular motion, and the motion is described from the point of view of an external reference frame. Further analysis of the motion by an observer on the space station is appropriate for upper-level students.

Improved earthquake monitoring in the central and eastern United States in support of seismic assessments for critical facilities

USGS Publications Warehouse

Leith, William S.; Benz, Harley M.; Herrmann, Robert B.

2011-01-01

Evaluation of seismic monitoring capabilities in the central and eastern United States for critical facilities - including nuclear powerplants - focused on specific improvements to understand better the seismic hazards in the region. The report is not an assessment of seismic safety at nuclear plants. To accomplish the evaluation and to provide suggestions for improvements using funding from the American Recovery and Reinvestment Act of 2009, the U.S. Geological Survey examined addition of new strong-motion seismic stations in areas of seismic activity and addition of new seismic stations near nuclear power-plant locations, along with integration of data from the Transportable Array of some 400 mobile seismic stations. Some 38 and 68 stations, respectively, were suggested for addition in active seismic zones and near-power-plant locations. Expansion of databases for strong-motion and other earthquake source-characterization data also was evaluated. Recognizing pragmatic limitations of station deployment, augmentation of existing deployments provides improvements in source characterization by quantification of near-source attenuation in regions where larger earthquakes are expected. That augmentation also supports systematic data collection from existing networks. The report further utilizes the application of modeling procedures and processing algorithms, with the additional stations and the improved seismic databases, to leverage the capabilities of existing and expanded seismic arrays.

Simulation of a flexible spinning vehicle

NASA Technical Reports Server (NTRS)

Baudry, W. A.

1972-01-01

Results are presented of experimental investigation of the controlled and uncontrolled dynamical behavior of a rotating or artificial gravity space station including flexible body effects. A dynamically scaled model was supported by a spherical air bearing which provided a nearly moment free environment. Reaction jet system were provided for spin-up and spin-down and for damping of wobble motion. Two single-gimbal gyros were arranged as a control moment gyro wobble damping system. Remotely controllable movable masses were provided to simulate mass shift disturbances such as arise from crew motions. An active mass balance wobble damping system which acted to minimize the wobble motions induced by crew motions was also installed. Flexible body effects were provided by a pair of inertia augmentation booms. Inertia augmentation booms are contemplated for use on rotating space stations to cause the spin axis moment of inertia to be the largest of the three moments of inertia as is necessary to assure gyroscopic stability. Test runs were made with each of the control systems with the booms locked (rigid body) and unlocked (flexible body).

An investigation of a movable mass-attitude stabilization system for artificial-G space

NASA Technical Reports Server (NTRS)

Childs, D. W.

1972-01-01

The application of a single movable mass to generate control torques for the attitude control of space vehicles is discussed. The feasibility of a movable mass control in stabilizing a cable-connected, artificial gravity configuration is proposed. A dynamic model for cable-connected configurations to account for the aggregate motion of the space station and relative torsional motion between the crew quarters and counter weight is developed.

Upper mantle anisotropy from long-period P polarization

NASA Astrophysics Data System (ADS)

Schulte-Pelkum, Vera; Masters, Guy; Shearer, Peter M.

2001-10-01

We introduce a method to infer upper mantle azimuthal anisotropy from the polarization, i.e., the direction of particle motion, of teleseismic long-period P onsets. The horizontal polarization of the initial P particle motion can deviate by >10° from the great circle azimuth from station to source despite a high degree of linearity of motion. Recent global isotropic three-dimensional mantle models predict effects that are an order of magnitude smaller than our observations. Stations within regional distances of each other show consistent azimuthal deviation patterns, while the deviations seem to be independent of source depth and near-source structure. We demonstrate that despite this receiver-side spatial coherence, our polarization data cannot be fit by a large-scale joint inversion for whole mantle structure. However, they can be reproduced by azimuthal anisotropy in the upper mantle and crust. Modeling with an anisotropic reflectivity code provides bounds on the magnitude and depth range of the anisotropy manifested in our data. Our method senses anisotropy within one wavelength (250 km) under the receiver. We compare our inferred fast directions of anisotropy to those obtained from Pn travel times and SKS splitting. The results of the comparison are consistent with azimuthal anisotropy situated in the uppermost mantle, with SKS results deviating from Pn and Ppol in some regions with probable additional deeper anisotropy. Generally, our fast directions are consistent with anisotropic alignment due to lithospheric deformation in tectonically active regions and to absolute plate motion in shield areas. Our data provide valuable additional constraints in regions where discrepancies between results from different methods exist since the effect we observe is local rather than cumulative as in the case of travel time anisotropy and shear wave splitting. Additionally, our measurements allow us to identify stations with incorrectly oriented horizontal components.

Puerto Rico Strong Motion Seismic Network

NASA Astrophysics Data System (ADS)

Huerta-Lopez, C. I.; Martínez-Cruzado, J. A.; Martínez-Pagan, J.; Santana-Torres, E. X.; Torres-O, D. M.

2014-12-01

The Puerto Rico Strong Motion Seismic Network is currently in charge of the operation of: (i) free-field (ff) strong motion stations, (ii) instrumented structures (STR) (Dams, Bridges, Buildings), and (iii) the data acquisition/monitoring and analysis of earthquakes considered strong from the point of view of their intensity and magnitude. All these instruments are deployed in the Puerto Rico Island (PRI), US-, and British-Virgin Islands (BVI), and Dominican Republic (DR). The Puerto Rico Island and the Caribbean region have high potential to be affected by earthquakes that could be catastrophic for the area. The Puerto Rico Strong Motion Seismic Network (actually Puerto Rico Strong Motion Program, PRSMP) has grown since 1970's from 7 ff strong motion stations and one instrumented building with analog accelerographs to 111 ff strong motion stations and 16 instrumented buildings with digital accelerographs: PRI: 88 ff, 16 STR., DR: 13 ff, BVI: 5 ff, 2 STR collecting data via IP (internet), DU (telephone), and stand alone stations The current stage of the PRSMP seismic network, the analysis of moderate earthquakes that were recorded and/or occurred on the island, results of the intensity distribution of selected earthquakes, as well as results of dynamic parameter identification of some of the instrumented structures are here presented.

Strong Motion Recording in the United States

NASA Astrophysics Data System (ADS)

Archuleta, R. J.; Fletcher, J. B.; Shakal, A. F.

2014-12-01

The United States strong motion program began in 1932 when the Coast and Geodetic Survey (C&GS) installed eight strong motion accelerographs in California. During the March 1933 Long Beach earthquake, three of these produced the first strong motion records. With this success the C&GS expanded the number of accelerographs to 71 by 1964. With development of less expensive, mass-produced accelerographs the number of strong motion accelerographs expanded to ~575 by 1972. Responsibilities for operating the network and disseminating data were transferred to the National Oceanic and Atmospheric Administration in 1970 and then to the U.S. Geological Survey in 1973. In 1972 the California Legislature established the California Strong Motion Instrumentation Program (CSMIP). CSMIP operates accelerographs at 812 ground stations, with multi-channel accelerographs in 228 buildings, 125 lifelines and 37 geotechnical arrays, in California. The USGS and the ANSS effort operate accelerographs at 1584 ground stations, 96 buildings, 14 bridges, 70 dams, and 15 multi-channel geotechnical arrays. The USC Los Angeles array has 78 ground stations; UCSB operates 5 geotechnical arrays; other government and private institutions also operate accelerographs. Almost all accelerographs are now digital with a sampling rate of 200 Hz. Most of the strong motion data can be downloaded from the Center for Engineering Strong Motion Data (http://strongmotioncenter.org). As accelerographs have become more sophisticated, the concept of what constitutes strong motion has blurred because small earthquakes (M ~3) are well recorded on accelerometers as well as seismometers. However, when accelerations are over ~10%g and velocities over ~1 cm/s, the accelerometers remain on scale, providing the unclipped data necessary to analyze the ground motion and its consequences. Strong motion data are essential to the development of ground motion prediction equations, understanding structural response, performance based engineering, soil response, and inversions for earthquake rupture parameters. While an important number of stations have been installed, many areas of the US are significantly deficient, e.g., recordings were obtained from only 2 stations within 60 km of the Mineral earthquake that damaged the nation's capital and other areas.

Geodetic Constraints on the Rigidity and Eastern Boundary of the Sierra Nevada Micro-Plate, from Mohawk Valley to Southern Walker Lane

NASA Astrophysics Data System (ADS)

Kreemer, C. W.; Hammond, W. C.; Blewitt, G.

2009-12-01

The Sierra Nevada - Great Valley (SNGV) micro-plate has long been recognized as a tectonically rigid, though mobile, entity within the Pacific - North America plate boundary zone. The motion of the SNGV relative to stable North America (and the Colorado Plateau) provides the kinematic boundary condition for, and perhaps drives, the deformation in the Basin and Range Province (BRP) and Walker Lane. In the north the motion of the SNGV is aligned with the Mohawk Valley fault zone, which could have a slip rate of over a few mm/yr. The crest of the Sierras marks the SNGV’s eastern edge, but the obliquity between orientation of this boundary and the block’s motion implies an expected increase in rangefront-normal extension from the northern to southern Walker Lane. We use new GPS data from the EarthScope Plate Boundary Observatory (PBO) and our own semi-continuous MAGNET network to revisit the following questions: 1) Do the data still support rigidity of the SNGV?; 2) How far east does the rigidity extend and how does this relate to SNGV lithology?; 3) How does the direction of SNGV motion relate to the strike of its eastern margin and observed strain partitioning (and its along strike variation) in the Walker Lane?; and 4) How is SNGV-BRP motion accommodated between the Walker Lane and the Cascadia forearc? We analyze data from all the available continuous GPS sites in the greater SNGV region, including new data from PBO, as well as data from MAGNET. All data are processed with the GIPSY-OASIS II precise point positioning software using recently reprocessed orbits from JPL's IGS Analysis Center. The processing includes satellite and station antenna calibrations and all data have the phase ambiguities fixed using the Ambizap algorithm. Positions are estimated in our custom-made North America reference frame in which continental-scale common-mode errors are removed. Velocities and uncertainties are estimated using the CATS software in which we assuming an error model with flicker plus white noise. Many stations in the Great Valley show anomalous horizontal motions compared to the most stable stations in the Sierra Nevada Mountains. These motions are likely due to hydrological effects in the Great Valley, which can be seen in the significant subsidence that occurs at these stations. Consequently, there are a relatively small number of stations that should be used to constrain the SNGV rigid body rotation. We find that stations in the southernmost Sierra Nevada Mountains have a northward motion of >1 mm/yr relative to the central and northern Sierras. This could partly be explained in terms of regional post-seismic viscoelastic relaxation from recent earthquakes (e.g. Kern County 1952, Landers, 1992, Hector Mine1999), but may also reflect the region’s anomalous mantle dynamics.

S-velocity structure in Cimandiri fault zone derived from neighbourhood inversion of teleseismic receiver functions

NASA Astrophysics Data System (ADS)

Syuhada; Anggono, T.; Febriani, F.; Ramdhan, M.

2018-03-01

The availability information about realistic velocity earth model in the fault zone is crucial in order to quantify seismic hazard analysis, such as ground motion modelling, determination of earthquake locations and focal mechanism. In this report, we use teleseismic receiver function to invert the S-velocity model beneath a seismic station located in the Cimandiri fault zone using neighbourhood algorithm inversion method. The result suggests the crustal thickness beneath the station is about 32-38 km. Furthermore, low velocity layers with high Vp/Vs exists in the lower crust, which may indicate the presence of hot material ascending from the subducted slab.

Horizontal and Vertical Velocities Derived from the IDS Contribution to ITRF2014, and Comparisons with Geophysical Models

NASA Technical Reports Server (NTRS)

Moreaux, G.; Lemoine, F. G.; Argus, D. F.; Santamaria-Gomez, A.; Willis, P.; Soudarin, L.; Gravelle, M.; Ferrage, P.

2016-01-01

In the context of the 2014 realization of the International Terrestrial Reference Frame (ITRF2014), the International DORIS Service (IDS) has delivered to the IERS a set of 1140 weekly SINEX files including station coordinates and Earth orientation parameters, covering the time period from 1993.0 to 2015.0. From this set of weekly SINEX files, the IDS Combination Center estimated a cumulative DORIS position and velocity solution to obtain mean horizontal and vertical motion of 160 stations at 71 DORIS sites. The main objective of this study is to validate the velocities of the DORIS sites by comparison with external models or time series. Horizontal velocities are compared with two recent global plate models (GEODVEL 2010 and NNR-MORVEL56). Prior to the comparisons, DORIS horizontal velocities were corrected for Global Isostatic Adjustment (GIA) from the ICE-6G (VM5a) model. For more than half of the sites, the DORIS horizontal velocities differ from the global plate models by less than 2-3 mm/yr. For five of the sites (Arequipa, Dionysos/Gavdos, Manila, Santiago) with horizontal velocity differences wrt these models larger than 10 mm/yr, comparisons with GNSS estimates show the veracity of the DORIS motions. Vertical motions from the DORIS cumulative solution are compared with the vertical velocities derived from the latest GPS cumulative solution over the time span 1995.0-2014.0 from the University of La Rochelle (ULR6) solution at 31 co-located DORIS-GPS sites. These two sets of vertical velocities show a correlation coefficient of 0.83. Vertical differences are larger than 2 mm/yr at 23 percent of the sites. At Thule the disagreement is explained by fine-tuned DORIS discontinuities in line with the mass variations of outlet glaciers. Furthermore, the time evolution of the vertical time series from the DORIS station in Thule show similar trends to the GRACE equivalent water height.

Joint Inversion of 1-Hz GPS Data and Strong Motion Records for the Rupture Process of the 2008 Iwate-Miyagi Nairiku Earthquake: Objectively Determining Relative Weighting

NASA Astrophysics Data System (ADS)

Wang, Z.; Kato, T.; Wang, Y.

2015-12-01

The spatiotemporal fault slip history of the 2008 Iwate-Miyagi Nairiku earthquake, Japan, is obtained by the joint inversion of 1-Hz GPS waveforms and near-field strong motion records. 1-Hz GPS data from GEONET is processed by GAMIT/GLOBK and then a low-pass filter of 0.05 Hz is applied. The ground surface strong motion records from stations of K-NET and Kik-Net are band-pass filtered for the range of 0.05 ~ 0.3 Hz and integrated once to obtain velocity. The joint inversion exploits a broader frequency band for near-field ground motions, which provides excellent constraints for both the detailed slip history and slip distribution. A fully Bayesian inversion method is performed to simultaneously and objectively determine the rupture model, the unknown relative weighting of multiple data sets and the unknown smoothing hyperparameters. The preferred rupture model is stable for different choices of velocity structure model and station distribution, with maximum slip of ~ 8.0 m and seismic moment of 2.9 × 1019 Nm (Mw 6.9). By comparison with the single inversion of strong motion records, the cumulative slip distribution of joint inversion shows sparser slip distribution with two slip asperities. One common slip asperity extends from the hypocenter southeastward to the ground surface of breakage; another slip asperity, which is unique for joint inversion contributed by 1-Hz GPS waveforms, appears in the deep part of fault where very few aftershocks are occurring. The differential moment rate function of joint and single inversions obviously indicates that rich high frequency waves are radiated in the first three seconds but few low frequency waves.

Using Google Earth to Explore Multiple Data Sets and Plate Tectonic Concepts

NASA Astrophysics Data System (ADS)

Goodell, L. P.

2015-12-01

Google Earth (GE) offers an engaging and dynamic environment for exploration of earth science data. While GIS software offers higher-level analytical capability, it comes with a steep learning curve and complex interface that is not easy for the novice, and in many cases the instructor, to negotiate. In contrast, the intuitive interface of GE makes it easy for students to quickly become proficient in manipulating the globe and independently exploring relationships between multiple data sets at a wide range of scales. Inquiry-based, data-rich exercises have been developed for both introductory and upper-level activities including: exploration of plate boundary characteristics and relative motion across plate boundaries; determination and comparison of short-term and long-term average plate velocities; crustal strain analysis (modeled after the UNAVCO activity); and determining earthquake epicenters, body-wave magnitudes, and focal plane solutions. Used successfully in undergraduate course settings, for TA training and for professional development programs for middle and high school teachers, the exercises use the following GE data sets (with sources) that have been collected/compiled by the author and are freely available for non-commercial use: 1) tectonic plate boundaries and plate names (Bird, 2003 model); 2) real-time earthquakes (USGS); 3) 30 years of M>=5.0 earthquakes, plotted by depth (USGS); 4) seafloor age (Mueller et al., 1997, 2008); 5) location and age data for hot spot tracks (published literature); 6) Holocene volcanoes (Smithsonian Global Volcanism Program); 7) GPS station locations with links to times series (JPL, NASA, UNAVCO); 8) short-term motion vectors derived from GPS times series; 9) long-term average motion vectors derived from plate motion models (UNAVCO plate motion calculator); 10) earthquake data sets consisting of seismic station locations and links to relevant seismograms (Rapid Earthquake Viewer, USC/IRIS/DELESE).

A combined source and site-effect study of ground motions generated by an earthquake in Port au Prince (Haiti)

NASA Astrophysics Data System (ADS)

St Fleur, Sadrac; Courboulex, Francoise; Bertrand, Etienne; Deschamps, Anne; Mercier de Lepinay, Bernard; Prepetit, Claude; Hough, Suzan

2013-04-01

We present the preliminary results of a study with the aim of understanding how some combinations of source and site effects can generate extreme ground motions in the city of Port au Prince. For this study, we have used the recordings of several tens of earthquakes with magnitude larger than 3.0 at 3 to 14 stations from three networks: 3 stations of the Canadian Broad-band network (RNCan), 2 stations of the educational French network (SaE) and 9 stations of the accelerometric network (Bureau des Mines et de l'Energie of Port au Prince and US Geological survey). In order to estimate site effects under each station, we have applied classical spectral ratio methods: The H/V (Horizontal/Vertical) method was first used to select a reference station, which was itself used in a site/reference method. Because a true reference station was not available, we have used successively stations HCEA, then station PAPH, then an average value of 3 stations. In the frequency range studied (0.5 - 20 Hz), we found a site-to-reference ratio up to 3 to 8. However, these values present a large variability, depending on the earthquake recordings. This may indicate that the observed amplification from one station to the other depends not only from the local site effect but also from the source. We then used the same earthquake recordings as Empirical Green's Functions (EGF) in order to simulate the ground motions generated by a virtual earthquake. For this simulation, we have used a stochastic EGF summation method. We have worked on the simulation of a magnitude Mw=6.8 using successively 2 smaller events that occurred on the Leogane fault as EGF. The results obtained using the two events are surprisingly very different. Using the first EGF, we obtained almost the same ground motion values at each station in Port au Prince, whereas with the second EGF, the results highlight large differences. The large variability obtained in the results indicates that a particular combination of site and source effects may be responsible of large ground motions, especially at some given sites.

Improved source inversion from joint measurements of translational and rotational ground motions

NASA Astrophysics Data System (ADS)

Donner, S.; Bernauer, M.; Reinwald, M.; Hadziioannou, C.; Igel, H.

2017-12-01

Waveform inversion for seismic point (moment tensor) and kinematic sources is a standard procedure. However, especially in the local and regional distances a lack of appropriate velocity models, the sparsity of station networks, or a low signal-to-noise ratio combined with more complex waveforms hamper the successful retrieval of reliable source solutions. We assess the potential of rotational ground motion recordings to increase the resolution power and reduce non-uniquenesses for point and kinematic source solutions. Based on synthetic waveform data, we perform a Bayesian (i.e. probabilistic) inversion. Thus, we avoid the subjective selection of the most reliable solution according the lowest misfit or other constructed criterion. In addition, we obtain unbiased measures of resolution and possible trade-offs. Testing different earthquake mechanisms and scenarios, we can show that the resolution of the source solutions can be improved significantly. Especially depth dependent components show significant improvement. Next to synthetic data of station networks, we also tested sparse-network and single station cases.

Human Factors Research Under Ground-Based and Space Conditions. Part 2

NASA Technical Reports Server (NTRS)

1997-01-01

In this session, Session WP2, the discussion focuses on the following topics: Training Astronauts Using Three-Dimensional Visualizations of the International Space Station; Measurement and Validation of Bidirectional Reflectance of Shuttle and Space Station Materials for Computerized Lighting Models; Effects of Environmental Color on Mood and Performance of Astronauts in ISS; Psychophysical Measures of Motion and Orientation, Implications for Human Interface Design; and the Sopite Syndrome Revisited, Drowsiness and Mood Changes in Student Aviators.

LAGEOS geodetic analysis-SL7.1

NASA Technical Reports Server (NTRS)

Smith, D. E.; Kolenkiewicz, R.; Dunn, P. J.; Klosko, S. M.; Robbins, J. W.; Torrence, M. H.; Williamson, R. G.; Pavlis, E. C.; Douglas, N. B.; Fricke, S. K.

1991-01-01

Laser ranging measurements to the LAGEOS satellite from 1976 through 1989 are related via geodetic and orbital theories to a variety of geodetic and geodynamic parameters. The SL7.1 analyses are explained of this data set including the estimation process for geodetic parameters such as Earth's gravitational constant (GM), those describing the Earth's elasticity properties (Love numbers), and the temporally varying geodetic parameters such as Earth's orientation (polar motion and Delta UT1) and tracking site horizontal tectonic motions. Descriptions of the reference systems, tectonic models, and adopted geodetic constants are provided; these are the framework within which the SL7.1 solution takes place. Estimates of temporal variations in non-conservative force parameters are included in these SL7.1 analyses as well as parameters describing the orbital states at monthly epochs. This information is useful in further refining models used to describe close-Earth satellite behavior. Estimates of intersite motions and individual tracking site motions computed through the network adjustment scheme are given. Tabulations of tracking site eccentricities, data summaries, estimated monthly orbital and force model parameters, polar motion, Earth rotation, and tracking station coordinate results are also provided.

(In)sensitivity of GNSS techniques to geocenter motion

NASA Astrophysics Data System (ADS)

Rebischung, Paul; Altamimi, Zuheir; Springer, Tim

2013-04-01

As a satellite-based technique, GNSS should be sensitive to motions of the Earth's center of mass (CM) with respect to the Earth's crust. In theory, the weekly solutions of the IGS Analysis Centers (ACs) should indeed have the "instantaneous" CM as their origin, and the net translations between the weekly AC frames and a secular frame such as ITRF2008 should thus approximate the non-linear motion of CM with respect to the Earth's center of figure. However, the comparison of the AC translation time series with each other, with SLR geocenter estimates or with geophysical models reveals that this way of observing geocenter motion with GNSS currently gives unreliable results. The fact that the origin of the weekly AC solutions shoud be CM stems from the satellite equations of motion, in which no degree-1 Stokes coefficients are included. It is therefore reasonable to think that any mis-modeling or uncertainty about the forces acting on GNSS satellites can potentially offset the network origin from CM. That is why defects in radiation pressure modeling have long been assumed to be the main origin of the GNSS geocenter errors. In particular, Meindl et al. (2012) incriminate the correlation between the Z component of the origin and the direct radiation pressure parameters D0. We review here the sensitivity of GNSS techniques to geocenter motion from a different perspective. Our approach consists in determining the signature of a geocenter error on GNSS observations, and seeing how and how well such an error can be compensated by all other usual GNSS parameters. (In other words, we look for the linear combinations of parameters which have the maximal partial correlations with each of the 3 components of the origin, and evaluate these maximal partial correlations.) Without setting up any empirical radiation pressure parameter, we obtain maximal partial correlations of 99.98 % for all 3 components of the origin: a geocenter error can almost perfectly be absorbed by the other GNSS parameters. Satellite clock offsets, if estimated epoch-wise, especially devastate the sensitivity of GNSS to geocenter motion. The numerous station-related parameters (station positions, station clock offsets, ZWDs and horizontal tropospheric gradients) do the rest of the job. The maximal partial correlations increase a bit more when the classic "ECOM" set of 5 radiation pressure parameters is set up for each satellite. But this increase is almost fully attributable to the once-per-revolution parameters BC & BS. In particular, we do not find the direct radiation pressure parameters D0 to play a predominant role in the GNSS geocenter determination problem.

Real-time GPS integration for prototype earthquake early warning and near-field imaging of the earthquake rupture process

NASA Astrophysics Data System (ADS)

Hudnut, K. W.; Given, D.; King, N. E.; Lisowski, M.; Langbein, J. O.; Murray-Moraleda, J. R.; Gomberg, J. S.

2011-12-01

Over the past several years, USGS has developed the infrastructure for integrating real-time GPS with seismic data in order to improve our ability to respond to earthquakes and volcanic activity. As part of this effort, we have tested real-time GPS processing software components , and identified the most robust and scalable options. Simultaneously, additional near-field monitoring stations have been built using a new station design that combines dual-frequency GPS with high quality strong-motion sensors and dataloggers. Several existing stations have been upgraded in this way, using USGS Multi-Hazards Demonstration Project and American Recovery and Reinvestment Act funds in southern California. In particular, existing seismic stations have been augmented by the addition of GPS and vice versa. The focus of new instrumentation as well as datalogger and telemetry upgrades to date has been along the southern San Andreas fault in hopes of 1) capturing a large and potentially damaging rupture in progress and augmenting inputs to earthquake early warning systems, and 2) recovering high quality recordings on scale of large dynamic displacement waveforms, static displacements and immediate and long-term post-seismic transient deformation. Obtaining definitive records of large ground motions close to a large San Andreas or Cascadia rupture (or volcanic activity) would be a fundamentally important contribution to understanding near-source large ground motions and the physics of earthquakes, including the rupture process and friction associated with crack propagation and healing. Soon, telemetry upgrades will be completed in Cascadia and throughout the Plate Boundary Observatory as well. By collaborating with other groups on open-source automation system development, we will be ready to process the newly available real-time GPS data streams and to fold these data in with existing strong-motion and other seismic data. Data from these same stations will also serve the very practical purpose of enabling earthquake early warning and greatly improving rapid finite-fault source modeling. Multiple uses of the effectively very broad-band data obtained by these stations, for operational and research purposes, are bound to occur especially because all data will be freely, openly and instantly available.

Dtection of Sea Level Rise within the Arabian Gulf Using Space Based GNSS Measurements and Insitu Tide Gauge data

NASA Astrophysics Data System (ADS)

Alothman, Abdulaziz; Ayhan, Mehmet

In the 21st century, sea level rise is expected to be about 30 cm or even more (up to 60 cm). Saudi Arabia has very long coasts of about 3400 km and hundreds of islands. Therefore, sea level monitoring may be important in particular along coastal low lands on Red Sea and Arabian Gulf coasts. Arabian Gulf is connected to Indian Ocean and lying along a parallel course in the south-west of the Zagros Trust Belt. We expect vertical land motion within the area due to both tectonic structures of the Arabian Peninsula and oil production activities. Global Navigation Satellite System (GNSS) Continues observations were used to estimate the vertical crustal motion. Bahrain International GPS Service (IGS-GPS) station is the only continuous GPS station accessible in the region, and it is close to the Mina Sulman tide gauge station in Bahrain. The weekly GPS time series of vertical component at Bahrain IGS-GPS station referring to the ITRF97 from 1999.2 to 2008.6 are used in the computation. We fitted a linear trend with an annual signal and a break to the GPS vertical time series and found a vertical land motion rate of 0.46 0.11 mm/yr. To investigate sea level variation within the west of Arabian Gulf, monthly means of sea level at 13 tide gauges along the coast of Saudi Arabia and Bahrain, available in the database of the Permanent Service for Mean Sea Level (PSMSL), are studied. We analyzed separately the monthly mean sea level measurements at each station, and estimated secular sea level rate by a robust linear trend fitting. We computed the average relative sea level rise rate of 1.96 0.21 mm/yr within the west of Arabian Gulf based on 4 stations spanning longer than 19 years. Sea level rates at the stations are first corrected for vertical land motion contamination using the ICE-5G v1.2 VM4 Glacial Isostatic Adjustment (GIA) model, and the average sea level rate is found 2.27 0.21 mm/yr. Assuming the vertical rate at Bahrain IGS-GPS station represents the vertical rate at each of the other tide gauge stations studied here in the region, we computed average sea level rise rate of 2.42 0.21 mm/yr within the west of Arabian Gulf.

Coastal Vertical Land motion in the German Bight

NASA Astrophysics Data System (ADS)

Becker, Matthias; Fenoglio, Luciana; Reckeweg, Florian

2017-04-01

In the framework of the ESA Sea Level Climate Change Initiative (CCI) we analyse a set of GNSS equipped tide gauges at the German Bight. Main goals are the determination of tropospheric zenith delay corrections for altimetric observations, precise coordinates in ITRF2008 and vertical land motion (VLM) rates of the tide gauge stations. These are to be used for georeferencing the tide gauges and the correction of tide gauge observations for VLM. The set of stations includes 38 GNSS stations. 19 stations are in the German Bight, where 15 of them belong to the Bundesanstalt für Gewässerkunde, 3 to EUREF and 1 to GREF. These stations are collocated with tide gauges (TGs). The other 19 GNSS stations in the network belong to EUREF, IGS and GREF. We analyse data in the time span from 2008 till the end of 2016 with the Bernese PPP processing approach. Data are partly rather noisy and disturbed by offsets and data gaps at the coastal TG sites. Special effort is therefore put into a proper estimation of the VLM. We use FODITS (Ostini2012), HECTOR (Bos et al, 2013), CATS (Williams, 2003) and the MIDAS approach of Blewitt (2016) to robustly derive rates and realistic error estimates. The results are compared to those published by the European Permanent Network (EPN), ITRF and the Système d'Observation du Niveau des Eaux Littorales (SONEL) for common stations. Vertical motion is small in general, at the -1 to -2 mm/yr level for most coastal stations. A comparison of the standard deviations of the velocity differences to EPN with the mean values of the estimated velocity standard deviations for our solution shows a very good agreement of the estimated velocities and their standard deviations with the reference solution from EPN. In the comparison with results by SONEL the standard deviation of the differences is slightly higher. The discrepancies may arise from differences in the time span analyzed and gaps, offsets and data preprocessing. The combined estimation of functional and stochastic parameters is rather sensitive to the characteristics of the time series and thus the estimated velocity also depends on the applied stochastic model and on the selected parameters. The GPS vertical land motion rates are finally compared to the difference between sea level rates measured by co-located altimetry and by tide gauge station data, which gives another estimation of VLM.

Estimating network effect in geocenter motion: Theory

NASA Astrophysics Data System (ADS)

Zannat, Umma Jamila; Tregoning, Paul

2017-10-01

Geophysical models and their interpretations of several processes of interest, such as sea level rise, postseismic relaxation, and glacial isostatic adjustment, are intertwined with the need to realize the International Terrestrial Reference Frame. However, this realization needs to take into account the geocenter motion, that is, the motion of the center of figure of the Earth surface, due to, for example, deformation of the surface by earthquakes or hydrological loading effects. Usually, there is also a discrepancy, known as the network effect, between the theoretically convenient center of figure and the physically accessible center of network frames, because of unavoidable factors such as uneven station distribution, lack of stations in the oceans, disparity in the coverage between the two hemispheres, and the existence of tectonically deforming zones. Here we develop a method to estimate the magnitude of the network effect, that is, the error introduced by the incomplete sampling of the Earth surface, in measuring the geocenter motion, for a network of space geodetic stations of a fixed size N. For this purpose, we use, as our proposed estimate, the standard deviations of the changes in Helmert parameters measured by a random network of the same size N. We show that our estimate scales as 1/√N and give an explicit formula for it in terms of the vector spherical harmonics expansion of the displacement field. In a complementary paper we apply this formalism to coseismic displacements and elastic deformations due to surface water movements.

Source Characterization of Underground Explosions from Combined Regional Moment Tensor and First-Motion Analysis

DOE PAGES

Chiang, Andrea; Dreger, Douglas S.; Ford, Sean R.; ...

2014-07-08

Here in this study, we investigate the 14 September 1988 U.S.–Soviet Joint Verification Experiment nuclear test at the Semipalatinsk test site in eastern Kazakhstan and two nuclear explosions conducted less than 10 years later at the Chinese Lop Nor test site. These events were very sparsely recorded by stations located within 1600 km, and in each case only three or four stations were available in the regional distance range. We have utilized a regional distance seismic waveform method fitting long-period, complete, three-component waveforms jointly with first-motion observations from regional stations and teleseismic arrays. The combination of long-period waveforms and first-motionmore » observations provides a unique discrimination of these sparsely recorded events in the context of the Hudson et al. (1989) source-type diagram. We demonstrate through a series of jackknife tests and sensitivity analyses that the source type of the explosions is well constrained. One event, a 1996 Lop Nor shaft explosion, displays large Love waves and possibly reversed Rayleigh waves at one station, indicative of a large F-factor. We show the combination of long-period waveforms and P-wave first motions are able to discriminate this event as explosion-like and distinct from earthquakes and collapses. We further demonstrate the behavior of network sensitivity solutions for models of tectonic release and spall-based tensile damage over a range of F-factors and K-factors.« less

Source Characterization of Underground Explosions from Combined Regional Moment Tensor and First-Motion Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiang, Andrea; Dreger, Douglas S.; Ford, Sean R.

Here in this study, we investigate the 14 September 1988 U.S.–Soviet Joint Verification Experiment nuclear test at the Semipalatinsk test site in eastern Kazakhstan and two nuclear explosions conducted less than 10 years later at the Chinese Lop Nor test site. These events were very sparsely recorded by stations located within 1600 km, and in each case only three or four stations were available in the regional distance range. We have utilized a regional distance seismic waveform method fitting long-period, complete, three-component waveforms jointly with first-motion observations from regional stations and teleseismic arrays. The combination of long-period waveforms and first-motionmore » observations provides a unique discrimination of these sparsely recorded events in the context of the Hudson et al. (1989) source-type diagram. We demonstrate through a series of jackknife tests and sensitivity analyses that the source type of the explosions is well constrained. One event, a 1996 Lop Nor shaft explosion, displays large Love waves and possibly reversed Rayleigh waves at one station, indicative of a large F-factor. We show the combination of long-period waveforms and P-wave first motions are able to discriminate this event as explosion-like and distinct from earthquakes and collapses. We further demonstrate the behavior of network sensitivity solutions for models of tectonic release and spall-based tensile damage over a range of F-factors and K-factors.« less

A computer program for an analysis of the relative motion of a space station and a free flying experiment module

NASA Technical Reports Server (NTRS)

Butler, J. H.

1971-01-01

A preliminary analysis of the relative motion of a free flying experiment module in the vicinity of a space station under the perturbative effects of drag and earth oblateness was made. A listing of a computer program developed for determining the relative motion of a module utilizing the Cowell procedure is presented, as well as instructions for its use.

Research on the technique of large-aperture off-axis parabolic surface processing using tri-station machine and its applicability.

PubMed

Zhang, Xin; Luo, Xiao; Hu, Haixiang; Zhang, Xuejun

2015-09-01

In order to process large-aperture aspherical mirrors, we designed and constructed a tri-station machine processing center with a three station device, which bears vectored feed motion of up to 10 axes. Based on this processing center, an aspherical mirror-processing model is proposed, in which each station implements traversal processing of large-aperture aspherical mirrors using only two axes, while the stations are switchable, thus lowering cost and enhancing processing efficiency. The applicability of the tri-station machine is also analyzed. At the same time, a simple and efficient zero-calibration method for processing is proposed. To validate the processing model, using our processing center, we processed an off-axis parabolic SiC mirror with an aperture diameter of 1450 mm. The experimental results indicate that, with a one-step iterative process, the peak to valley (PV) and root mean square (RMS) of the mirror converged from 3.441 and 0.5203 μm to 2.637 and 0.2962 μm, respectively, where the RMS reduced by 43%. The validity and high accuracy of the model are thereby demonstrated.

Site evaluation for laser satellite-tracking stations

NASA Technical Reports Server (NTRS)

Mao, N. H.; Mohr, P. A.

1976-01-01

Twenty-six locations for potential laser satellite-tracking stations, four of them actually already occupied in this role, are reviewed in terms of their known local and regional geology and geophysics. The sites are also considered briefly in terms of weather and operational factors. Fifteen of the sites qualify as suitable for a stable station whose motions are likely to reflect only gross plate motion. The others, including two of the present laser station sites (Arequipa and Athens), fail to qualify unless extra monitoring schemes can be included, such as precise geodetic surveying of ground deformation.

Single-Station Sigma for the Iranian Strong Motion Stations

NASA Astrophysics Data System (ADS)

Zafarani, H.; Soghrat, M. R.

2017-11-01

In development of ground motion prediction equations (GMPEs), the residuals are assumed to have a log-normal distribution with a zero mean and a standard deviation, designated as sigma. Sigma has significant effect on evaluation of seismic hazard for designing important infrastructures such as nuclear power plants and dams. Both aleatory and epistemic uncertainties are involved in the sigma parameter. However, ground-motion observations over long time periods are not available at specific sites and the GMPEs have been derived using observed data from multiple sites for a small number of well-recorded earthquakes. Therefore, sigma is dominantly related to the statistics of the spatial variability of ground motion instead of temporal variability at a single point (ergodic assumption). The main purpose of this study is to reduce the variability of the residuals so as to handle it as epistemic uncertainty. In this regard, it is tried to partially apply the non-ergodic assumption by removing repeatable site effects from total variability of six GMPEs driven from the local, Europe-Middle East and worldwide data. For this purpose, we used 1837 acceleration time histories from 374 shallow earthquakes with moment magnitudes ranging from M w 4.0 to 7.3 recorded at 370 stations with at least two recordings per station. According to estimated single-station sigma for the Iranian strong motion stations, the ratio of event-corrected single-station standard deviation ( Φ ss) to within-event standard deviation ( Φ) is about 0.75. In other words, removing the ergodic assumption on site response resulted in 25% reduction of the within-event standard deviation that reduced the total standard deviation by about 15%.

Mooring line damping estimation for a floating wind turbine.

PubMed

Qiao, Dongsheng; Ou, Jinping

2014-01-01

The dynamic responses of mooring line serve important functions in the station keeping of a floating wind turbine (FWT). Mooring line damping significantly influences the global motions of a FWT. This study investigates the estimation of mooring line damping on the basis of the National Renewable Energy Laboratory 5 MW offshore wind turbine model that is mounted on the ITI Energy barge. A numerical estimation method is derived from the energy absorption of a mooring line resulting from FWT motion. The method is validated by performing a 1/80 scale model test. Different parameter changes are analyzed for mooring line damping induced by horizontal and vertical motions. These parameters include excitation amplitude, excitation period, and drag coefficient. Results suggest that mooring line damping must be carefully considered in the FWT design.

Mooring Line Damping Estimation for a Floating Wind Turbine

PubMed Central

Qiao, Dongsheng; Ou, Jinping

2014-01-01

The dynamic responses of mooring line serve important functions in the station keeping of a floating wind turbine (FWT). Mooring line damping significantly influences the global motions of a FWT. This study investigates the estimation of mooring line damping on the basis of the National Renewable Energy Laboratory 5 MW offshore wind turbine model that is mounted on the ITI Energy barge. A numerical estimation method is derived from the energy absorption of a mooring line resulting from FWT motion. The method is validated by performing a 1/80 scale model test. Different parameter changes are analyzed for mooring line damping induced by horizontal and vertical motions. These parameters include excitation amplitude, excitation period, and drag coefficient. Results suggest that mooring line damping must be carefully considered in the FWT design. PMID:25243231

Tether Elevator Crawler Systems (TECS)

NASA Technical Reports Server (NTRS)

Swenson, Frank R.

1987-01-01

One of the needs of the experimenters on the space station is access to steady and controlled-variation microgravity environments. A method of providing these environments is to place the experiment on a tether attached to the space station. This provides a high degree of isolation from structural oscillations and vibrations. Crawlers can move these experiments along the tethers to preferred locations, much like an elevator. This report describes the motion control laws developed for these crawlers and the testing of laboratory models of these tether elevator crawlers.

Stability and uncertainty of finite-fault slip inversions: Application to the 2004 Parkfield, California, earthquake

USGS Publications Warehouse

Hartzell, S.; Liu, P.; Mendoza, C.; Ji, C.; Larson, K.M.

2007-01-01

The 2004 Parkfield, California, earthquake is used to investigate stability and uncertainty aspects of the finite-fault slip inversion problem with different a priori model assumptions. We utilize records from 54 strong ground motion stations and 13 continuous, 1-Hz sampled, geodetic instruments. Two inversion procedures are compared: a linear least-squares subfault-based methodology and a nonlinear global search algorithm. These two methods encompass a wide range of the different approaches that have been used to solve the finite-fault slip inversion problem. For the Parkfield earthquake and the inversion of velocity or displacement waveforms, near-surface related site response (top 100 m, frequencies above 1 Hz) is shown to not significantly affect the solution. Results are also insensitive to selection of slip rate functions with similar duration and to subfault size if proper stabilizing constraints are used. The linear and nonlinear formulations yield consistent results when the same limitations in model parameters are in place and the same inversion norm is used. However, the solution is sensitive to the choice of inversion norm, the bounds on model parameters, such as rake and rupture velocity, and the size of the model fault plane. The geodetic data set for Parkfield gives a slip distribution different from that of the strong-motion data, which may be due to the spatial limitation of the geodetic stations and the bandlimited nature of the strong-motion data. Cross validation and the bootstrap method are used to set limits on the upper bound for rupture velocity and to derive mean slip models and standard deviations in model parameters. This analysis shows that slip on the northwestern half of the Parkfield rupture plane from the inversion of strong-motion data is model dependent and has a greater uncertainty than slip near the hypocenter.

A strawman SLR program plan for the 1990s

NASA Technical Reports Server (NTRS)

Degnan, John J.

1994-01-01

A series of programmatic and technical goals for the satellite laser ranging (SLR) network are presented. They are: (1) standardize the performance of the global SLR network; (2) improve the geographic distribution of stations; (3) reduce costs of field operations and data processing; (4) expand the 24 hour temporal coverage to better serve the growing constellation of satellites; (5) improve absolute range accuracy to 2 mm at key stations; (6) improve satellite force, radiative propagation, and station motion models and investigate alternative geodetic analysis techniques; (7) support technical intercomparison and the Terrestrial Reference Frame through global collocations; (8) investigate potential synergisms between GPS and SLR.

Systematic Site Characterization at Seismic Stations combined with Empirical Spectral Modeling: critical data for local hazard analysis

NASA Astrophysics Data System (ADS)

Michel, Clotaire; Hobiger, Manuel; Edwards, Benjamin; Poggi, Valerio; Burjanek, Jan; Cauzzi, Carlo; Kästli, Philipp; Fäh, Donat

2016-04-01

The Swiss Seismological Service operates one of the densest national seismic networks in the world, still rapidly expanding (see http://www.seismo.ethz.ch/monitor/index_EN). Since 2009, every newly instrumented site is characterized following an established procedure to derive realistic 1D VS velocity profiles. In addition, empirical Fourier spectral modeling is performed on the whole network for each recorded event with sufficient signal-to-noise ratio. Besides the source characteristics of the earthquakes, statistical real time analyses of the residuals of the spectral modeling provide a seamlessly updated amplification function w.r. to Swiss rock conditions at every station. Our site characterization procedure is mainly based on the analysis of surface waves from passive experiments and includes cross-checks of the derived amplification functions with those obtained through spectral modeling. The systematic use of three component surface-wave analysis, allowing the derivation of both Rayleigh and Love waves dispersion curves, also contributes to the improved quality of the retrieved profiles. The results of site characterisation activities at recently installed strong-motion stations depict the large variety of possible effects of surface geology on ground motion in the Alpine context. Such effects range from de-amplification at hard-rock sites to amplification up to a factor of 15 in lacustrine sediments with respect to the Swiss reference rock velocity model. The derived velocity profiles are shown to reproduce observed amplification functions from empirical spectral modeling. Although many sites are found to exhibit 1D behavior, our procedure allows the detection and qualification of 2D and 3D effects. All data collected during the site characterization procedures in the last 20 years are gathered in a database, implementing a data model proposed for community use at the European scale through NERA and EPOS (www.epos-eu.org). A web stationbook derived from it can be accessed through the interface www.stations.seismo.ethz.ch.

The dynamics of a space station tethered refueling facility

NASA Technical Reports Server (NTRS)

Abbott, P.; Rudolph, L. K.; Fester, D. A.

1986-01-01

The fluid stored in a tethered orbital refueling facility is settled at the bottom of the storage tanks by gravity-gradient forces. The fluid motions (slosh) induced by outside disturbances must be limited to ensure the tank outlet is not uncovered during a fluid transfer. The dynamics of a LO2/LH2 TORF attached to the space station have been analyzed to identify design parameters necessary to limit fluid motion. Using the worst case disturbance of a shuttle docking at the space station, the fluid motion was found to be a function of tether length and allowable facility swing angle. Acceptable fluid behavior occurs for tether lengths of at least 1000 ft. To ensure motions induced by separate disturbances do not add to unacceptable values, a slosh damping coefficient of 5 percent is recommended.

On the establishment and maintenance of a modern conventional terrestrial reference system

NASA Technical Reports Server (NTRS)

Bock, Y.; Zhu, S. Y.

1982-01-01

The frame of the Conventional Terrestrial Reference System (CTS) is defined by an adopted set of coordinates, at a fundamental epoxh, of a global network of stations which contribute the vertices of a fundamental polyhedron. A method to estimate this set of coordinates using a combination of modern three dimensional geodetic systems is presented. Once established, the function of the CTS is twofold. The first is to monitor the external (or global) motions of the polyhedron with respect to the frame of a Conventional Inertial Reference System, i.e., those motions common to all stations. The second is to monitor the internal motions (or deformations) of the polyhedron, i.e., those motions that are not common to all stations. Two possible estimators for use in earth deformation analysis are given and their statistical and physical properties are described.

Down and Out at Pacaya Volcano: A Glimpse of Magma Storage and Diking as Interpreted From GPS Geodesy

NASA Astrophysics Data System (ADS)

Lechner, H. N.; Waite, G. P.; Wauthier, D. C.; Escobar-Wolf, R. P.; Lopez-Hetland, B.

2017-12-01

Geodetic data from an eight-station GPS network at Pacaya volcano Guatemala allows us to produce a simple analytical model of deformation sources associated with the 2010 eruption and the eruptive period in 2013-2014. Deformation signals for both eruptive time-periods indicate downward vertical and outward horizontal motion at several stations surrounding the volcano. The objective of this research was to better understand the magmatic plumbing system and sources of this deformation. Because this down-and-out displacement is difficult to explain with a single source, we chose a model that includes a combination of a dike and spherical source. Our modelling suggests that deformation is dominated the inflation of a shallow dike seated high within the volcanic edifice and deflation of a deeper, spherical source below the SW flank of the volcano. The source parameters for the dike feature are in good agreement with the observed orientation of recent vent emplacements on the edifice as well the horizontal displacement, while the parameters for a deeper spherical source accommodate the downward vertical motion. This study presents GPS observations at Pacaya dating back to 2009 and provides a glimpse of simple models of possible deformation sources.

Ground-Motion Variability for a Strike-Slip Earthquake from Broadband Ground-Motion Simulations

NASA Astrophysics Data System (ADS)

Iwaki, A.; Maeda, T.; Morikawa, N.; Fujiwara, H.

2016-12-01

One of the important issues in seismic hazard analysis is the evaluation of ground-motion variability due to the epistemic and aleatory uncertainties in various aspects of ground-motion simulations. This study investigates the within-event ground-motion variability in broadband ground-motion simulations for strike-slip events. We conduct ground-motion simulations for a past event (2000 MW6.6 Tottori earthquake) using a set of characterized source models (e.g. Irikura and Miyake, 2011) considering aleatory variability. Broadband ground motion is computed by a hybrid approach that combines a 3D finite-difference method (> 1 s) and the stochastic Green's function method (< 1 s), using the 3D velocity model J-SHIS v2. We consider various locations of the asperities, which are defined as the regions with large slip and stress drop within the fault, and the rupture nucleation point (hypocenter). Ground motion records at 29 K-NET and KiK-net stations are used to validate our simulations. By comparing the simulated and observed ground motion, we found that the performance of the simulations is acceptable under the condition that the source parameters are poorly constrained. In addition to the observation stations, we set 318 virtual receivers with the spatial intervals of 10 km for statistical analysis of the simulated ground motion. The maximum fault-distance is 160 km. Standard deviation (SD) of the simulated acceleration response spectra (Sa, 5% damped) of RotD50 component (Boore, 2010) is investigated at each receiver. SD from 50 different patterns of asperity locations is generally smaller than 0.15 in terms of log10 (0.34 in natural log). It shows dependence on distance at periods shorter than 1 s; SD increases as the distance decreases. On the other hand, SD from 39 different hypocenter locations is again smaller than 0.15 in log10, and showed azimuthal dependence at long periods; it increases as the rupture directivity parameter Xcosθ(Somerville et al. 1997) increases at periods longer than 1 s. The characteristics of ground-motion variability inferred from simulations can provide information on variability in simulation-based seismic hazard assessment for future earthquakes. We will further investigate the variability in other source parameters; rupture velocity and short-period level.

Comprehensive Analysis of Broadband Seismic Data in Las Vegas Valley

NASA Astrophysics Data System (ADS)

Tkalcic, H.; Rodgers, A.; Snelson, C.; McEwan, D.

2003-12-01

The city of Las Vegas is one of the fastest growing metropolitan areas in the world. Its urban area is located in a relatively broad sedimentary basin in the Basin and Range Province. Acknowledging that Las Vegas of 2003 is drastically different from Las Vegas of a decade ago, our objectives are to understand and predict ground motions and evaluate the effects of possible future earthquakes and nuclear tests at Nevada Test Site (NTS) on buildings in Las Vegas. A model of the basin depth was derived from gravity data in an independent study, while a model of compressional velocity structure of the basin was derived from seismic refraction studies. We are using strong motion accelerometers regional data, as well as newly acquired broadband teleseismic data to evaluate these models, and predict ground motions at the surface. Delay times of about a dozen analyzed teleseismic P-waves show variation of up to 0.5 seconds across relatively short distances (15 km or less), providing some valuable information on basin shape and thickness. Teleseismic P-waves have favorable signal-to-noise for low frequencies (0.1 to 1.0 Hz). This provides complementary site response measurements to those obtained from regional earthquakes and explosions. Our results indicate a clear difference in site response between hard-rock and basin stations, with amplification reaching factor 5 for the basin stations. The measured P and S wave energies for the recorded data also corelate well with the existing basin depth model, providing additional constraint in modeling the basin shape and structure. We use time domain deconvolution receiver functions to constrain the position of basin boundaries and main crustal discontinuities. Finally, we simulate low frequency (f < 1 Hz) theoretical ground motion in Las Vegas Valley by an elastic finite difference code. Preliminary results show that we can predict relative amplification, as well as some of the complexity in the waveforms, even without invoking complex (and computationaly expensive) three-dimensional structural models. This work is in progress.

Modeling moving systems with RELAP5-3D

DOE PAGES

Mesina, G. L.; Aumiller, David L.; Buschman, Francis X.; ...

2015-12-04

RELAP5-3D is typically used to model stationary, land-based reactors. However, it can also model reactors in other inertial and accelerating frames of reference. By changing the magnitude of the gravitational vector through user input, RELAP5-3D can model reactors on a space station or the moon. The field equations have also been modified to model reactors in a non-inertial frame, such as occur in land-based reactors during earthquakes or onboard spacecraft. Transient body forces affect fluid flow in thermal-fluid machinery aboard accelerating crafts during rotational and translational accelerations. It is useful to express the equations of fluid motion in the acceleratingmore » frame of reference attached to the moving craft. However, careful treatment of the rotational and translational kinematics is required to accurately capture the physics of the fluid motion. Correlations for flow at angles between horizontal and vertical are generated via interpolation where no experimental studies or data exist. The equations for three-dimensional fluid motion in a non-inertial frame of reference are developed. As a result, two different systems for describing rotational motion are presented, user input is discussed, and an example is given.« less

Preliminary analysis of strong-motion recordings from the 28 September 2004 Parkfield, California earthquake

USGS Publications Warehouse

Shakal, A.; Graizer, V.; Huang, M.; Borcherdt, R.; Haddadi, H.; Lin, K.-W.; Stephens, C.; Roffers, P.

2005-01-01

The Parkfield 2004 earthquake yielded the most extensive set of strong-motion data in the near-source region of a magnitude 6 earthquake yet obtained. The recordings of acceleration and volumetric strain provide an unprecedented document of the near-source seismic radiation for a moderate earthquake. The spatial density of the measurements alon g the fault zone and in the linear arrays perpendicular to the fault is expected to provide an exceptional opportunity to develop improved models of the rupture process. The closely spaced measurements should help infer the temporal and spatial distribution of the rupture process at much higher resolution than previously possible. Preliminary analyses of the peak a cceleration data presented herein shows that the motions vary significantly along the rupture zone, from 0.13 g to more than 2.5 g, with a map of the values showing that the larger values are concentrated in three areas. Particle motions at the near-fault stations are consistent with bilateral rupture. Fault-normal pulses similar to those observed in recent strike-slip earthquakes are apparent at several of the stations. The attenuation of peak ground acceleration with distance is more rapid than that indicated by some standard relationships but adequately fits others. Evidence for directivity in the peak acceleration data is not strong. Several stations very near, or over, the rupturing fault recorded relatively low accelerations. These recordings may provide a quantitative basis to understand observations of low near-fault shaking damage that has been reported in other large strike-slip earthquak.

Intrasite motions and monument instabilities at Medicina ITRF co-location site

NASA Astrophysics Data System (ADS)

Sarti, Pierguido; Abbondanza, Claudio; Legrand, Juliette; Bruyninx, Carine; Vittuari, Luca; Ray, Jim

2013-03-01

We process the total-station surveys performed at the ITRF co-location site Medicina (Northern Italy) over the decade (2001-2010) with the purpose of determining the extent of local intrasite motions and relating them to local geophysical processes, the geological setting and the design of the ground pillars. In addition, continuous observations acquired by two co-located GPS stations (MEDI and MSEL separated by ≈27 m) are analysed and their relative motion is cross-checked with the total-station results. The local ground control network extends over a small area (<100 × 100 m) but the results demonstrate significant anisotropic deformations with rates up to 1.6 mm a-1, primarily horizontal, a value comparable to intraplate tectonic deformations. The results derived from GPS and total-station observations are consistent and point to the presence of horizontal intrasite motions over very short distances possibly associated with varying environmental conditions in a very unfavourable local geological setting and unsuitable monument design, these latter being crucial aspects of the realization and maintenance of global permanent geodetic networks and the global terrestrial reference frame.

A comparison of ITRF2014, DTRF2014 and JTRF2014 polar motion series with geophysical excitation data

NASA Astrophysics Data System (ADS)

Rebischung, Paul; Chen, Wei; Ray, Jim

2017-04-01

Three solutions were generated in response to the 2014 update by the IERS of the International Terrestrial Reference Frame: ITRF2014, the official solution from IGN; DTRF2014, from DGFI; JTRF2014, from JPL. Each incorporates essentially the same time series information of geocentric station positions + Earth rotation parameters + their associated variance-covariances from the four contributing space geodetic techniques (SLR, VLBI, DORIS, GNSS) plus local 3D vector ties (measured by conventional surveying methods) that relate a subset of co-located stations. Given the fact that measurements by all the techniques, as well as the local ties, suffer significant unmodeled systematic errors that are poorly understood, the covariance matrices are not reliable except for their geometrical aspect. So the three combination strategies differ not just in their mathematical procedures, but more importantly in how the systematic errors are handled (or not). Factors include the relative weighting of inputs, modeling of non-linear station motions, detection of time series discontinuities, etc. The final combination results therefore also differ, mostly in rather subtle ways. There are very few ways to make external evaluations of the quality of the various combinations as independent observations are generally not accurate enough. However, one approach has been shown to give useful insight by comparing the daily polar motions with geophysical excitations computed from global circulation models for atmosphere, ocean, and hydrology. J. Kouba (2010) did this for ITRF2008 and DTRF2008 and found an excess of high-frequency rotational scatter in the DGFI solution. After the development of the IGS in the 1990s, the ITRF daily polar motion accuracy has been about 30 uas or 1 mm of surface rotation. The corresponding geophysical models are not nearly so accurate but their independence does provide a valuable reference against which the geodetic results can be compared. Direct inter-comparisons of the three combined polar motion series and the IGS-only series (which predominates since 2000) already reveal interesting features: seasonal amplitudes vary markedly, up to 20 uas for the annual term in one case; differences for periods longer than monthly are greater than found in 2008; and 7-d harmonics are found in one series but not the others. We also apply the refined polar motion excitation theory of W. Chen et al. (2013), which incorporates frequency-dependent effects and updated Earth parameters, to further study the 2014 frame solutions. Results will be presented in the poster.

Rigidity and definition of Caribbean plate motion from COCONet and campaign GPS observations

NASA Astrophysics Data System (ADS)

Mattioli, G. S.; Miller, J. A.; DeMets, C.; Jansma, P. E.

2015-12-01

The kinematic model of the Caribbean plate presented by DeMets et al. (2007) is based on velocities from 6 continuous and 14 campaign GPS sites. COCONet is a multi-hazard GPS-Met observatory, which extends the existing infrastructure of the PBO in North America into the Caribbean basin. In 2010, UNAVCO in collaboration with UCAR, was funded by NSF to design, build, and initially maintain a network of 50 new cGPS/Met sites and include data from another 50 existing sites in the Caribbean region. The COCONet siting plan is for 46 new stations, 21 refurbished stations, and 77 existing stations across 26 nations in the Caribbean region. Data from all COCONet sites flow into the UNAVCO archive and are processed by the PBO analysis centers and are also processed independently by the UTA Geodesy Lab using GIPSY-OASISII (v.6.3) using an APP strategy and final, precise orbits, clocks, and EOP from JPL in the IGS08r frame. We present a refined estimate of Caribbean plate motion by evaluating data from an expanded number of stations with an improved spatial distribution. In order to better constrain the eastern margin of the plate near the Lesser Antilles subduction interface, campaign GPS observations have been collected on the island of Dominica over the last decade. These are combined with additional campaign observations from the western Caribbean, specifically from Honduras and Nicaragua. We have analyzed a total of 117 sites from the Caribbean region, including campaign data and the data from the cGPS stations that comprise COCONet. An updated velocity field for the Caribbean plate is presented and an inversion of the velocities for 24 sites yields a plate angular velocity that differs from previously published models. Our best fitting inversion to GPS velocities from these 24 sites suggests that 2-plate model for the Caribbean is required to fit the GPS observations, which implies that the Caribbean is undergoing modest (1-3 mm/yr) deformation within its interior. Some sites in the western Caribbean included in our analysis may be biased by small, but significant coseismic deformation, which has not been removed from the site velocities used in our inversion to define Caribbean motion and rigidity. Scenarios for possible east-west deformation accommodated across the Lower Nicaraguan Rise and Beata Ridge will be presented.

Seismic switch for strong motion measurement

DOEpatents

Harben, Philip E.; Rodgers, Peter W.; Ewert, Daniel W.

1995-01-01

A seismic switching device that has an input signal from an existing microseismic station seismometer and a signal from a strong motion measuring instrument. The seismic switch monitors the signal level of the strong motion instrument and passes the seismometer signal to the station data telemetry and recording systems. When the strong motion instrument signal level exceeds a user set threshold level, the seismometer signal is switched out and the strong motion signal is passed to the telemetry system. The amount of time the strong motion signal is passed before switching back to the seismometer signal is user controlled between 1 and 15 seconds. If the threshold level is exceeded during a switch time period, the length of time is extended from that instant by one user set time period.

Seismic switch for strong motion measurement

DOEpatents

Harben, P.E.; Rodgers, P.W.; Ewert, D.W.

1995-05-30

A seismic switching device is described that has an input signal from an existing microseismic station seismometer and a signal from a strong motion measuring instrument. The seismic switch monitors the signal level of the strong motion instrument and passes the seismometer signal to the station data telemetry and recording systems. When the strong motion instrument signal level exceeds a user set threshold level, the seismometer signal is switched out and the strong motion signal is passed to the telemetry system. The amount of time the strong motion signal is passed before switching back to the seismometer signal is user controlled between 1 and 15 seconds. If the threshold level is exceeded during a switch time period, the length of time is extended from that instant by one user set time period. 11 figs.

Modeling of Autovariator Operation as Power Components Adjuster in Adaptive Machine Drives

NASA Astrophysics Data System (ADS)

Balakin, P. D.; Belkov, V. N.; Shtripling, L. O.

2018-01-01

Full application of the available power and stationary mode preservation for the power station (engine) operation of the transport machine under the conditions of variable external loading, are topical issues. The issues solution is possible by means of mechanical drives with the autovaried rate transfer function and nonholonomic constraint of the main driving mediums. Additional to the main motion, controlled motion of the driving mediums is formed by a variable part of the transformed power flow and is implemented by the integrated control loop, functioning only on the basis of the laws of motion. The mathematical model of the mechanical autovariator operation is developed using Gibbs function, acceleration energy; the study results are presented; on their basis, the design calculations of the autovariator driving mediums and constraints, including its automatic control loop, are possible.

Broadband Ground Motion Observation and Simulation for the 2016 Kumamoto Earthquake

NASA Astrophysics Data System (ADS)

Miyake, H.; Chimoto, K.; Yamanaka, H.; Tsuno, S.; Korenaga, M.; Yamada, N.; Matsushima, T.; Miyakawa, K.

2016-12-01

During the 2016 Kumamoto earthquake, strong motion data were widely recorded by the permanent dense triggered strong motion network of K-NET/KiK-net and seismic intensity meters installed by local government and JMA. Seismic intensities close to the MMI 9-10 are recorded twice at the Mashiki town, and once at the Nishihara village and KiK-net Mashiki (KMMH16 ground surface). Near-fault records indicate extreme ground motion exceeding 400 cm/s in 5% pSv at a period of 1 s for the Mashiki town and 3-4 s for the Nishihara village. Fault parallel velocity components are larger between the Mashiki town and the Nishihara village, on the other hand, fault normal velocity components are larger inside the caldera of the Aso volcano. The former indicates rupture passed through along-strike stations, and the latter stations located at the forward rupture direction (e.g., Miyatake, 1999). In addition to the permanent observation, temporary continuous strong motion stations were installed just after the earthquake in the Kumamoto city, Mashiki town, Nishihara village, Minami-Aso village, and Aso town, (e.g., Chimoto et al., 2016; Tsuno et al., 2016; Yamanaka et al. 2016). This study performs to estimate strong motion generation areas for the 2016 Kumamoto earthquake sequence using the empirical Green's function method, then to simulate broadband ground motions for both the permanent and temporary strong motion stations. Currently the target period range is between 0.1 s to 5-10 s due to the signal-to-noise ratio of element earthquakes used for the empirical Green's functions. We also care fault dimension parameters N within 4 to 10 to avoid spectral sags and artificial periodicity. The simulated seismic intensities as well as fault normal and parallel velocity components will be discussed.

International Space Station Attitude Motion Associated With Flywheel Energy Storage

NASA Technical Reports Server (NTRS)

Roithmayr, Carlos M.

1999-01-01

Flywheels can exert torque that alters the Station's attitude motion, either intentionally or unintentionally. A design is presented for a once planned experiment to contribute torque for Station attitude control, while storing or discharging energy. Two contingencies are studied: the abrupt stop of one rotor while another rotor continues to spin at high speed, and energy storage performed with one rotor instead of a counter rotating pair. Finally, the possible advantages to attitude control offered by a system of ninety-six flywheels are discussed.

Finite-fault inversion of the Mw 5.9 2012 Emilia-Romagna earthquake (Northern Italy) using aftershocks as near-field Green's function approximations

NASA Astrophysics Data System (ADS)

Causse, Mathieu; Cultrera, Giovanna; Herrero, André; Courboulex, Françoise; Schiappapietra, Erika; Moreau, Ludovic

2017-04-01

On May 29, 2012 occurred a Mw 5.9 earthquake in the Emilia-Romagna region (Po Plain) on a thrust fault system. This shock, as well as hundreds of aftershocks, were recorded by 10 strong motion stations located less than 10 km away from the rupture plane, with 4 stations located within the surface rupture projection. The Po Plain is a very large EW trending syntectonic alluvial basin, delimited by the Alps and Apennines chains to the North and South. The Plio-Quaternary sedimentary sequence filling the Po Plain is characterized by an uneven thickness, ranging from several thousands of meters to a few tens of meters. This particular context results especially in a resonance basin below 1 Hz and strong surface waves, which makes it particularly difficult to model wave propagation and hence to obtain robust images of the rupture propagation. This study proposes to take advantage of the large set of recorded aftershocks, considered as point sources, to model wave propagation. Due to the heterogeneous distribution of the aftershocks on the fault plane, an interpolation technique is proposed to compute an approximation of the Green's function between each fault point and each strong motion station in the frequency range [0.2-1Hz]. We then use a Bayesian inversion technique (Monte Carlo Markov Chain algorithm) to obtain images of the rupture propagation from the strong motion data. We propose to retrieve the slip distribution by inverting the final slip value at some control points, which are allowed to move on the fault plane, and by interpolating the slip value between these points. We show that the use of 5 control points to describe the slip, coupled with the hypothesis of spatially constant rupture velocity and rise-time (that is 18 free source parameters), results in a good level of fit with the data. This indicates that despite their complexity, the strong motion data can be properly modeled up to 1 Hz using a relatively simple rupture. The inversion results also reveal that the rupture propagated slowly, at a speed of about 45% of the shear wave velocity.

Ambient Noise Green's Function Simulation of Long-Period Ground Motions for Reverse Faulting

NASA Astrophysics Data System (ADS)

Miyake, H.; Beroza, G. C.

2009-12-01

Long-time correlation of ambient seismic noise has been demonstrated as a useful tool for strong ground motion prediction [Prieto and Beroza, 2008]. An important advantage of ambient noise Green's functions is that they can be used for ground motion simulation without resorting to either complex 3-D velocity structure to develop theoretical Green’s functions, or aftershock records for empirical Green’s function analysis. The station-to-station approach inherent to ambient noise Green’s functions imposes some limits to its application, since they are band-limited, applied at the surface, and for a single force. We explore the applicability of this method to strong motion prediction using the 2007 Chuetsu-oki, Japan, earthquake (Mw 6.6, depth = 9 km), which excited long-period ground motions in and around the Kanto basin almost 200 km from the epicenter. We test the performance of ambient noise Green's function for long-period ground motion simulation. We use three components of F-net broadband data at KZK station, which is located near the source region, as a virtual source, and three components of six F-net stations in and around the Kanto basin to calculate the response. An advantage to applying this approach in Japan is that ambient-noise sources are active in diverse directions. The dominant period of the ambient noise for the F-net datasets is mostly 7 s over the year, and amplitudes are largest in winter. This period matches the dominant periods of the Kanto and Niigata basins. For the 9 components of the ambient noise Green’s functions, we have confirmed long-period components corresponding to Love wave and Rayleigh waves that can be used for simulation of the 2007 Chuetsu-oki earthquake. The relative amplitudes, phases, and durations of the ambient noise Green’s functions at the F-net stations in and around the Kanto basin respect to F-net KZK station are fairly well matched with those of the observed ground motions for the 2007 Chuetsu-oki earthquake.

Strain Accumulation and Release of the Gorkha, Nepal, Earthquake (M w 7.8, 25 April 2015)

NASA Astrophysics Data System (ADS)

Morsut, Federico; Pivetta, Tommaso; Braitenberg, Carla; Poretti, Giorgio

2017-08-01

The near-fault GNSS records of strong-ground movement are the most sensitive for defining the fault rupture. Here, two unpublished GNSS records are studied, a near-fault-strong-motion station (NAGA) and a distant station in a poorly covered area (PYRA). The station NAGA, located above the Gorkha fault, sensed a southward displacement of almost 1.7 m. The PYRA station that is positioned at a distance of about 150 km from the fault, near the Pyramid station in the Everest, showed static displacements in the order of some millimeters. The observed displacements were compared with the calculated displacements of a finite fault model in an elastic halfspace. We evaluated two slips on fault models derived from seismological and geodetic studies: the comparison of the observed and modelled fields reveals that our displacements are in better accordance with the geodetic derived fault model than the seismologic one. Finally, we evaluate the yearly strain rate of four GNSS stations in the area that were recording continuously the deformation field for at least 5 years. The strain rate is then compared with the strain released by the Gorkha earthquake, leading to an interval of 235 years to store a comparable amount of elastic energy. The three near-fault GNSS stations require a slightly wider fault than published, in the case of an equivalent homogeneous rupture, with an average uniform slip of 3.5 m occurring on an area of 150 km × 60 km.

Laser tracking for vertical control

NASA Technical Reports Server (NTRS)

Dunn, Peter; Torrence, Mark; Pavlis, Erricos; Kolenkiewicz, Ron; Smith, David

1993-01-01

The Global Laser Tracking Network has provided LAGEOS ranging data of high accuracy since the first MERIT campaign in late 1983 and we can now resolve centimeter-level three dimensional positions of participating observatories at monthly intervals. In this analysis, the station height estimates have been considered separately from the horizontal components, and can be determined by the strongest stations with a formal standard error of 2 mm using eight years of continuous observations. The rate of change in the vertical can be resolved to a few mm/year, which is at the expected level of several geophysical effects. In comparing the behavior of the stations to that predicted by recent models of post-glacial rebound, we find no correlation in this very small effect. Particular attention must be applied to data and survey quality control when measuring the vertical component, and the survey observations are critical components of the geodynamic results. Seasonal patterns are observed in the heights of most stations, and the possibility of secular motion at the level of several millimeters per year cannot be excluded. Any such motion must be considered in the interpretation of horizontal inter-site measurements, and can help to identify mechanisms which can cause variations which occur linearly with time, seasonally, or abruptly.

In search of periodic signatures in IGS REPRO1 solution

NASA Astrophysics Data System (ADS)

Mtamakaya, J. D.; Santos, M. C.; Craymer, M. R.

2010-12-01

We have been looking for periodic signatures in the REPRO1 solution recently released by the IGS. At this stage, a selected sub-set of IGS station time series in position and residual domain are under harmonic analysis. We can learn different things from this analysis. From the position domain, we can learn more about actual station motions. From the residual domain, we can learn more about mis-modelled or un-modelled errors. As far as error sources are concerned, we have investigated effects that may be due to tides, atmospheric loading, definition of the position of the figure axis and GPS constellation geometry. This poster presents and discusses our findings and presents insights on errors that need to be modelled or have their models improved.

Free-flying dynamics and control of an astronaut assistant robot based on fuzzy sliding mode algorithm

NASA Astrophysics Data System (ADS)

Gao, Qing; Liu, Jinguo; Tian, Tongtong; Li, Yangmin

2017-09-01

Space robots can perform some tasks in harsh environment as assistants of astronauts or substitutions of astronauts. Taking the limited working time and the arduous task of the astronauts in the space station into account, an astronaut assistant robot (AAR-2) applied in the space station is proposed and designed in this paper. The AAR-2 is achieved with some improvements on the basis of AAR-1 which was designed before. It can exploit its position and attitude sensors and control system to free flight or hover in the space cabin. And it also has a definite environmental awareness and artificial intelligence to complete some specified tasks under the control of astronauts or autonomously. In this paper, it mainly analyzes and controls the 6-DOF motion of the AAR-2. Firstly, the system configuration of AAR-2 is specifically described, and the movement principles are analyzed. Secondly, according to the physical model of the AAR-2, the Newton - Euler equation is applied in the preparation of space dynamics model of 6-DOF motion. Then, according to the mathematical model's characteristics which are nonlinear and strong coupling, a dual closed loop position and attitude controller based on fuzzy sliding mode control is proposed and designed. Finally, simulation experiments are appropriate to provide for AAR-2 control system by using Matlab/Simulink. From the simulation results it can be observed that the designed fuzzy sliding mode controller can control the 6-DOF motion of AAR-2 quickly and precisely.

Dynamical analysis of rendezvous and docking with very large space infrastructures in non-Keplerian orbits

NASA Astrophysics Data System (ADS)

Colagrossi, Andrea; Lavagna, Michèle

2018-03-01

A space station in the vicinity of the Moon can be exploited as a gateway for future human and robotic exploration of the solar system. The natural location for a space system of this kind is about one of the Earth-Moon libration points. The study addresses the dynamics during rendezvous and docking operations with a very large space infrastructure in an EML2 Halo orbit. The model takes into account the coupling effects between the orbital and the attitude motion in a circular restricted three-body problem environment. The flexibility of the system is included, and the interaction between the modes of the structure and those related with the orbital motion is investigated. A lumped parameter technique is used to represents the flexible dynamics. The parameters of the space station are maintained as generic as possible, in a way to delineate a global scenario of the mission. However, the developed model can be tuned and updated according to the information that will be available in the future, when the whole system will be defined with a higher level of precision.

Characterisation of ground motion recording stations in the Groningen gas field

NASA Astrophysics Data System (ADS)

Noorlandt, Rik; Kruiver, Pauline P.; de Kleine, Marco P. E.; Karaoulis, Marios; de Lange, Ger; Di Matteo, Antonio; von Ketelhodt, Julius; Ruigrok, Elmer; Edwards, Benjamin; Rodriguez-Marek, Adrian; Bommer, Julian J.; van Elk, Jan; Doornhof, Dirk

2018-05-01

The seismic hazard and risk analysis for the onshore Groningen gas field requires information about local soil properties, in particular shear-wave velocity ( V S). A fieldwork campaign was conducted at 18 surface accelerograph stations of the monitoring network. The subsurface in the region consists of unconsolidated sediments and is heterogeneous in composition and properties. A range of different methods was applied to acquire in situ V S values to a target depth of at least 30 m. The techniques include seismic cone penetration tests (SCPT) with varying source offsets, multichannel analysis of surface waves (MASW) on Rayleigh waves with different processing approaches, microtremor array, cross-hole tomography and suspension P-S logging. The offset SCPT, cross-hole tomography and common midpoint cross-correlation (CMPcc) processing of MASW data all revealed lateral variations on length scales of several to tens of metres in this geological setting. SCPTs resulted in very detailed V S profiles with depth, but represent point measurements in a heterogeneous environment. The MASW results represent V S information on a larger spatial scale and smooth some of the heterogeneity encountered at the sites. The combination of MASW and SCPT proved to be a powerful and cost-effective approach in determining representative V S profiles at the accelerograph station sites. The measured V S profiles correspond well with the modelled profiles and they significantly enhance the ground motion model derivation. The similarity between the theoretical transfer function from the V S profile and the observed amplification from vertical array stations is also excellent.

Characterisation of ground motion recording stations in the Groningen gas field

NASA Astrophysics Data System (ADS)

Noorlandt, Rik; Kruiver, Pauline P.; de Kleine, Marco P. E.; Karaoulis, Marios; de Lange, Ger; Di Matteo, Antonio; von Ketelhodt, Julius; Ruigrok, Elmer; Edwards, Benjamin; Rodriguez-Marek, Adrian; Bommer, Julian J.; van Elk, Jan; Doornhof, Dirk

2018-01-01

The seismic hazard and risk analysis for the onshore Groningen gas field requires information about local soil properties, in particular shear-wave velocity (V S). A fieldwork campaign was conducted at 18 surface accelerograph stations of the monitoring network. The subsurface in the region consists of unconsolidated sediments and is heterogeneous in composition and properties. A range of different methods was applied to acquire in situ V S values to a target depth of at least 30 m. The techniques include seismic cone penetration tests (SCPT) with varying source offsets, multichannel analysis of surface waves (MASW) on Rayleigh waves with different processing approaches, microtremor array, cross-hole tomography and suspension P-S logging. The offset SCPT, cross-hole tomography and common midpoint cross-correlation (CMPcc) processing of MASW data all revealed lateral variations on length scales of several to tens of metres in this geological setting. SCPTs resulted in very detailed V S profiles with depth, but represent point measurements in a heterogeneous environment. The MASW results represent V S information on a larger spatial scale and smooth some of the heterogeneity encountered at the sites. The combination of MASW and SCPT proved to be a powerful and cost-effective approach in determining representative V S profiles at the accelerograph station sites. The measured V S profiles correspond well with the modelled profiles and they significantly enhance the ground motion model derivation. The similarity between the theoretical transfer function from the V S profile and the observed amplification from vertical array stations is also excellent.

Borehole P- and S-wave velocity at thirteen stations in Southern California

USGS Publications Warehouse

Gibbs, James F.; Boore, David M.; Tinsley, John C.; Mueller, Charles S.

2001-01-01

The U.S. Geological Survey (USGS), as part of a program to acquire seismic velocity data at locations of strong-ground motion in earthquakes (e.g., Gibbs et al., 2000), has investigated thirteen additional sites in the Southern California region. Of the thirteen sites, twelve are in the vicinity of Whittier, California, and one is located in San Bernardino, California. Several deployments of temporary seismographs were made after the Whittier Narrows, California earthquake of 1 October 1987 (Mueller et al., 1988). A deployment, between 2 October and 9 November 1987, was the motivation for selection of six of the drill sites. Temporary portable seismographs at Hoover School (HOO), Lincoln School (LIN), Corps of Engineers Station (NAR), Olive Junior High School (OLV), Santa Anita Golf Course (SAG), and Southwestern Academy (SWA) recorded significant aftershock data. These portable sites, with the exception of Santa Anita Golf Course, were co-sited with strong-motion recorders. Stations at HOO, Lincoln School Whittier (WLB), Saint Paul High School (STP), Alisos Adult School (EXC), Cerritos College Gymnasium (CGM), Cerritos College Physical Science Building (CPS), and Cerritos College Police Building (CPB) were part of an array of digital strong-motion stations deployed from "bedrock" in Whittier to near the deepest part of the Los Angeles basin in Norwalk. Although development and siting of this new array (partially installed at the time of this writing) was generally motivated by the Whittier Narrows earthquake, these new sites (with the exception of HOO) were not part of any Whittier Narrows aftershock deployments. A similar new digital strong-motion site was installed at the San Bernardino Fire Station during the same time frame. Velocity data were obtained to depths of about 90 meters at two sites, 30 meters at seven sites, and 18 to 25 meters at four sites. Lithology data from the analysis of cuttings and samples was obtained from the two 90-meter deep holes and from five of the shallower holes to supplement the velocity interpretation. The two 90-meter boreholes (SB1, CPB) have been instrumented with borehole seismometers for continuous monitoring of earthquake activity (Rogers et al., 1998). No drill samples or cuttings were obtained from the other six sites, but driller's logs were scanned for major changes noted there. The velocity models at those sites were interpreted using only the measured data and major changes in the driller's log as noted above. The sites are shown in Figure 1 and listed in Table 1, which gives references to information regarding the strong-motion data. Several hundred strong-motion records of the main-shock were written by this moderate size earthquake (ML = 5.9), making it important from a scientific and engineering prospective (Brady et al., 1988; Shakal et al., 1988).

Strong motion observations and recordings from the great Wenchuan Earthquake

USGS Publications Warehouse

Li, X.; Zhou, Z.; Yu, H.; Wen, R.; Lu, D.; Huang, M.; Zhou, Y.; Cu, J.

2008-01-01

The National Strong Motion Observation Network System (NSMONS) of China is briefly introduced in this paper. The NSMONS consists of permanent free-field stations, special observation arrays, mobile observatories and a network management system. During the Wenchuan Earthquake, over 1,400 components of acceleration records were obtained from 460 permanent free-field stations and three arrays for topographical effect and structural response observation in the network system from the main shock, and over 20,000 components of acceleration records from strong aftershocks occurred before August 1, 2008 were also obtained by permanent free-field stations of the NSMONS and 59 mobile instruments quickly deployed after the main shock. The strong motion recordings from the main shock and strong aftershocks are summarized in this paper. In the ground motion recordings, there are over 560 components with peak ground acceleration (PGA) over 10 Gal, the largest being 957.7 Gal. The largest PGA recorded during the aftershock exceeds 300 Gal. ?? 2008 Institute of Engineering Mechanics, China Earthquake Administration and Springer-Verlag GmbH.

Tsunami simulation using submarine displacement calculated from simulation of ground motion due to seismic source model

NASA Astrophysics Data System (ADS)

Akiyama, S.; Kawaji, K.; Fujihara, S.

2013-12-01

Since fault fracturing due to an earthquake can simultaneously cause ground motion and tsunami, it is appropriate to evaluate the ground motion and the tsunami by single fault model. However, several source models are used independently in the ground motion simulation or the tsunami simulation, because of difficulty in evaluating both phenomena simultaneously. Many source models for the 2011 off the Pacific coast of Tohoku Earthquake are proposed from the inversion analyses of seismic observations or from those of tsunami observations. Most of these models show the similar features, which large amount of slip is located at the shallower part of fault area near the Japan Trench. This indicates that the ground motion and the tsunami can be evaluated by the single source model. Therefore, we examine the possibility of the tsunami prediction, using the fault model estimated from seismic observation records. In this study, we try to carry out the tsunami simulation using the displacement field of oceanic crustal movements, which is calculated from the ground motion simulation of the 2011 off the Pacific coast of Tohoku Earthquake. We use two fault models by Yoshida et al. (2011), which are based on both the teleseismic body wave and on the strong ground motion records. Although there is the common feature in those fault models, the amount of slip near the Japan trench is lager in the fault model from the strong ground motion records than in that from the teleseismic body wave. First, the large-scale ground motion simulations applying those fault models used by the voxel type finite element method are performed for the whole eastern Japan. The synthetic waveforms computed from the simulations are generally consistent with the observation records of K-NET (Kinoshita (1998)) and KiK-net stations (Aoi et al. (2000)), deployed by the National Research Institute for Earth Science and Disaster Prevention (NIED). Next, the tsunami simulations are performed by the finite difference calculation based on the shallow water theory. The initial wave height for tsunami generation is estimated from the vertical displacement of ocean bottom due to the crustal movements, which is obtained from the ground motion simulation mentioned above. The results of tsunami simulations are compared with the observations of the GPS wave gauges to evaluate the validity for the tsunami prediction using the fault model based on the seismic observation records.

3D Volume and Morphology of Perennial Cave Ice and Related Geomorphological Models at Scăriloara Ice Cave, Romania, from Structure from Motion, Ground Penetrating Radar and Total Station Surveys

NASA Astrophysics Data System (ADS)

Hubbard, J.; Onac, B. P.; Kruse, S.; Forray, F. L.

2017-12-01

Research at Scăriloara Ice Cave has proceeded for over 150 years, primarily driven by the presence and paleoclimatic importance of the large perennial ice block and various ice speleothems located within its galleries. Previous observations of the ice block led to rudimentary volume estimates of 70,000 to 120,000 cubic meters (m3), prospectively placing it as one of the world's largest cave ice deposits. The cave morphology and the surface of the ice block are now recreated in a total station survey-validated 3D model, produced using Structure from Motion (SfM) software. With the total station survey and the novel use of ArcGIS tools, the SfM validation process is drastically simplified to produce a scaled, georeferenced, and photo-texturized 3D model of the cave environment with a root-mean-square error (RMSE) of 0.24 m. Furthermore, ground penetrating radar data was collected and spatially oriented with the total station survey to recreate the ice block basal surface and was combined with the SfM model to create a model of the ice block itself. The resulting ice block model has a volume of over 118,000 m3 with an uncertainty of 9.5%, with additional volumes left un-surveyed. The varying elevation of the ice block basal surface model reflect specific features of the cave roof, such as areas of enlargement, shafts, and potential joints, which offer further validation and inform theories on cave and ice genesis. Specifically, a large depression area was identified as a potential area of initial ice growth. Finally, an ice thickness map was produced that will aid in the designing of future ice coring projects. This methodology presents a powerful means to observe and accurately characterize and measure cave and cave ice morphologies with ease and affordability. Results further establish the significance of Scăriloara's ice block to paleoclimate research, provide insights into cave and ice block genesis, and aid future study design.

Dynamics and control of tethered antennas/reflectors in orbit

NASA Astrophysics Data System (ADS)

Liu, Liangdong; Bainum, Peter M.

The system linear equations for the motion of a tethered shallow spherical shell in orbit with its symmetry axis nominally following the local vertical are developed. The shell roll, yaw, tether out-of-plane swing motion and elastic vibrations are decoupled from the shell and tether in-plane pitch motions and elastic vibrations. The neutral gravity stability conditions for the special case of a constant length rigid tether are given for in-plane motion and out-of-plant motion. It is proved that the in-plane motion of the system could be asymptotically stable based on Rupp's tension control law, for a variable length tether. However, the system simulation results indicate that the transient responses can be improved significantly, especially for the damping of the tether and shell pitch motion, by an optimal feedback control law for the rigid variable length tether model. It is also seen that the system could be unstable when the effect of tether flexibility is included if the control gains are not chosen carefully. The transient responses for three different tension control laws are compared during typical station keeping operations.

A study of possible ground-motion amplification at the Coyote Lake Dam, California

USGS Publications Warehouse

Boore, D.M.; Graizer, V.M.; Tinsley, J.C.; Shakal, A.F.

2004-01-01

The abutment site at the Coyote Lake Dam recorded an unusually large peak acceleration of 1.29g during the 1984 Morgan Hill earthquake. Following this earthquake another strong-motion station was installed about 700 m downstream from the abutment station. We study all events (seven) recorded on these stations, using ratios of peak accelerations, spectral ratios, and particle motion polarization (using holograms) to investigate the relative ground motion at the two sites. We find that in all but one case the motion at the abutment site is larger than the downstream site over a broad frequency band. The polarizations are similar for the two sites for a given event, but can vary from one event to another. This suggests that the dam itself is not strongly influencing the records. Although we can be sure that the relative motion is usually larger at the abutment site, we cannot conclude that there is anomalous site amplification at the abutment site. The downstream site could have lower-than-usual near-surface amplifications. On the other hand, the geology near the abutment site is extremely complex and includes fault slivers, with rapid lateral changes in materials and presumably seismic velocities. For this reason alone, the abutment site should not be considered a normal free-field site.

Characteristics of strong ground motion generation areas by fully dynamic earthquake cycles

NASA Astrophysics Data System (ADS)

Galvez, P.; Somerville, P.; Ampuero, J. P.; Petukhin, A.; Yindi, L.

2016-12-01

During recent subduction zone earthquakes (2010 Mw 8.8 Maule and 2011 Mw 9.0 Tohoku), high frequency ground motion radiation has been detected in deep regions of seismogenic zones. By semblance analysis of wave packets, Kurahashi & Irikura (2013) found strong ground motion generation areas (SMGAs) located in the down dip region of the 2011 Tohoku rupture. To reproduce the rupture sequence of SMGA's and replicate their rupture time and ground motions, we extended previous work on dynamic rupture simulations with slip reactivation (Galvez et al, 2016). We adjusted stresses on the most southern SMGAs of Kurahashi & Irikura (2013) model to reproduce the observed peak ground velocity recorded at seismic stations along Japan for periods up to 5 seconds. To generate higher frequency ground motions we input the rupture time, final slip and slip velocity of the dynamic model into the stochastic ground motion generator of Graves & Pitarka (2010). Our results are in agreement with the ground motions recorded at the KiK-net and K-NET stations.While we reproduced the recorded ground motions of the 2011 Tohoku event, it is unknown whether the characteristics and location of SMGA's will persist in future large earthquakes in this region. Although the SMGA's have large peak slip velocities, the areas of largest final slip are located elsewhere. To elucidate whether this anti-correlation persists in time, we conducted earthquake cycle simulations and analysed the spatial correlation of peak slip velocities, stress drops and final slip of main events. We also investigated whether or not the SMGA's migrate to other regions of the seismic zone.To perform this study, we coupled the quasi-dynamic boundary element solver QDYN (Luo & Ampuero, 2015) and the dynamic spectral element solver SPECFEM3D (Galvez et al., 2014; 2016). The workflow alternates between inter-seismic periods solved with QDYN and coseismic periods solved with SPECFEM3D, with automated switch based on slip rate thersholds (Kaneko et al., 2011). We parallelized QDYN with MPI to enable the simulation of fully dynamic earthquake cycles of Mw 8-9 earthquakes in faults that also produce Mw 7 earthquakes.This study was based on the 2015 research project `Improvement for uncertainty of strong ground motion prediction' by the Nuclear Regulation Authority (NRA), Japan.

A generalization of the double-corner-frequency source spectral model and its use in the SCEC BBP validation exercise

USGS Publications Warehouse

Boore, David M.; Di Alessandro, Carola; Abrahamson, Norman A.

2014-01-01

The stochastic method of simulating ground motions requires the specification of the shape and scaling with magnitude of the source spectrum. The spectral models commonly used are either single-corner-frequency or double-corner-frequency models, but the latter have no flexibility to vary the high-frequency spectral levels for a specified seismic moment. Two generalized double-corner-frequency ω2 source spectral models are introduced, one in which two spectra are multiplied together, and another where they are added. Both models have a low-frequency dependence controlled by the seismic moment, and a high-frequency spectral level controlled by the seismic moment and a stress parameter. A wide range of spectral shapes can be obtained from these generalized spectral models, which makes them suitable for inversions of data to obtain spectral models that can be used in ground-motion simulations in situations where adequate data are not available for purely empirical determinations of ground motions, as in stable continental regions. As an example of the use of the generalized source spectral models, data from up to 40 stations from seven events, plus response spectra at two distances and two magnitudes from recent ground-motion prediction equations, were inverted to obtain the parameters controlling the spectral shapes, as well as a finite-fault factor that is used in point-source, stochastic-method simulations of ground motion. The fits to the data are comparable to or even better than those from finite-fault simulations, even for sites close to large earthquakes.

On the dynamical stability of the space 'monorail'

NASA Astrophysics Data System (ADS)

Bergamaschi, S.; Manni, D.

The dynamical stability of 'monorail' tethered-satellite/elevator configurations being studied for the Space Station is investigated analytically, treating the end platforms and elevator as point masses, neglecting tether elasticity, and taking the Coriolis force and the complex gravitational field into account in analyzing the orbital-plane motion of the system. A mathematical model is constructed; the equations of motion are derived; and results obtained by numerical integration for platform masses 100,000 and 10,000 kg, elevator mass 5000 kg, and a 10-km-long 6-mm-diameter 4070-kg-mass tether are presented in graphs and briefly characterized.

Numerical simulation analysis on Wenchuan seismic strong motion in Hanyuan region

NASA Astrophysics Data System (ADS)

Chen, X.; Gao, M.; Guo, J.; Li, Z.; Li, T.

2015-12-01

69227 deaths, 374643 injured, 17923 people missing, direct economic losses 845.1 billion, and a large number houses collapse were caused by Wenchuan Ms8 earthquake in Sichuan Province on May 12, 2008, how to reproduce characteristics of its strong ground motion and predict its intensity distribution, which have important role to mitigate disaster of similar giant earthquake in the future. Taking Yunnan-Sichuan Province, Wenchuan town, Chengdu city, Chengdu basin and its vicinity as the research area, on the basis of the available three-dimensional velocity structure model and newly topography data results from ChinaArray of Institute of Geophysics, China Earthquake Administration, 2 type complex source rupture process models with the global and local source parameters are established, we simulated the seismic wave propagation of Wenchuan Ms8 earthquake throughout the whole three-dimensional region by the GMS discrete grid finite-difference techniques with Cerjan absorbing boundary conditions, and obtained the seismic intensity distribution in this region through analyzing 50×50 stations data (simulated ground motion output station). The simulated results indicated that: (1)Simulated Wenchuan earthquake ground motion (PGA) response and the main characteristics of the response spectrum are very similar to those of the real Wenchuan earthquake records. (2)Wenchuan earthquake ground motion (PGA) and the response spectra of the Plain are much greater than that of the left Mountain area because of the low velocity of the shallow surface media and the basin effect of the Chengdu basin structure. Simultaneously, (3) the source rupture process (inversion) with far-field P-wave, GPS data and InSAR information and the Longmenshan Front Fault (source rupture process) are taken into consideration in GMS numerical simulation, significantly different waveform and frequency component of the ground motion are obtained, though the strong motion waveform is distinct asymmetric, which should be much more real. It indicated that the Longmenshan Front Fault may be also involved in seismic activity during the long time(several minutes) Wenchuan earthquake process. (4) Simulated earthquake records in Hanyuan region are indeed very strong, which reveals source mechanism is one reason of Hanyuan intensity abnormaly.

Rigidity and definition of Caribbean plate motion from COCONet and campaign GPS observations

NASA Astrophysics Data System (ADS)

Mattioli, Glen; Miller, Jamie; DeMets, Charles; Jansma, Pamela

2014-05-01

The currently accepted kinematic model of the Caribbean plate presented by DeMets et al. (2007) is based on velocities from 6 continuous and 14 campaign GPS sites. COCONet is a multi-hazard GPS-Met observatory, which extends the existing infrastructure of the Plate Boundary Observatory in North America into the Caribbean basin. In 2010, UNAVCO in collaboration with UCAR, was funded by NSF to design, build, and initially maintain a network of 50 new cGPS/Met sites and include data from another 50 existing sites in the Caribbean region. The current COCONet siting plan calls for 46 new stations, 21 refurbished stations, and 77 existing stations across 26 nations in the Caribbean region. Data from all COCONet sites flow into the UNAVCO archive and are processed by the PBO analysis centers and are also processed independently by the UTA Geodesy Lab using GIPSY-OASISII (v.6.2) using an absolute point positioning strategy and final, precise orbits, clocks, and Earth orientation parameters from JPL in the IGS08 frame. We present here our refined estimate of Caribbean plate motion by evaluating data from an expanded number of stations with an improved spatial distribution. In order to better constrain the eastern margin of the plate near the Lesser Antilles subduction interface, campaign GPS observations have been collected on the island of Dominica over the last decade. These are combined with additional campaign observations from the western Caribbean, specifically from Honduras and Nicaragua. We have analyzed a total of 117 sites from the Caribbean region, including campaign data and the data from the cGPS stations that comprise COCONet. An updated velocity field for the Caribbean plate is presented and an inversion of the velocities for 24 sites yields a plate angular velocity that differs from previously published models. Our best fitting inversion to GPS velocities from these 24 sites suggests that 2-plate model for the Caribbean is required to fit the GPS observations, which implies that the Caribbean is undergoing modest (1-3 mm/yr) deformation within its interior. Some sites in the western Caribbean included in our analysis may be biased by small, but significant coseismic deformation, which has not been removed from the site velocities used in our inversion to define Caribbean motion and rigidity. Scenarios for possible east-west deformation accommodated across the Lower Nicaraguan Rise and Beata Ridge will be presented.

Euler-Vector Clustering of GPS Velocities Defines Microplate Geometry in Southwest Japan

NASA Astrophysics Data System (ADS)

Savage, J. C.

2018-02-01

I have used Euler-vector clustering to assign 469 GEONET stations in southwest Japan to k clusters (k = 2, 3,..., 9) so that, for any k, the velocities of stations within each cluster are most consistent with rigid-block motion on a sphere. That is, I attempt to explain the raw (i.e., uncorrected for strain accumulation), 1996-2006 velocities of those 469 Global Positioning System stations by rigid motion of k clusters on the surface of a spherical Earth. Because block geometry is maintained as strain accumulates, Euler-vector clustering may better approximate the block geometry than the values of the associated Euler vectors. The microplate solution for each k is constructed by merging contiguous clusters that have closely similar Euler vectors. The best solution consists of three microplates arranged along the Nankaido Trough-Ryukyu Trench between the Amurian and Philippine Sea Plates. One of these microplates, the South Kyushu Microplate (an extension of the Ryukyu forearc into the southeast corner of Kyushu), had previously been identified from paleomagnetic rotations. Relative to ITRF2000 the three microplates rotate at different rates about neighboring poles located close to the northwest corner of Shikoku. The microplate model is identical to that proposed in the block model of Wallace et al. (2009, https://doi.org/10.1130/G2522A.1) except in southernmost Kyushu. On Shikoku and Honshu, but not Kyushu, the microplate model is consistent with that proposed in the block models of Nishimura and Hashimoto (2006, https://doi.org/10.1016/j.tecto.2006.04.017) and Loveless and Meade (2010, https://doi.org/10.1029/2008JB006248) without the low-slip-rate boundaries proposed in the latter.

Attitude control/momentum management of the Space Station Freedom for large angle torque-equilibrium-attitude configurations

NASA Technical Reports Server (NTRS)

Parlos, Alexander G.; Sunkel, John W.

1990-01-01

An attitude-control and momentum-management (ACMM) system for the Space Station in a large-angle torque-equilibrium-attitude (TEA) configuration is developed analytically and demonstrated by means of numerical simulations. The equations of motion for a rigid-body Space Station model are outlined; linearized equations for an arbitrary TEA (resulting from misalignment of control and body axes) are derived; the general requirements for an ACMM are summarized; and a pole-placement linear-quadratic regulator solution based on scheduled gains is proposed. Results are presented in graphs for (1) simulations based on configuration MB3 (showing the importance of accounting for the cross-inertia terms in the TEA estimate) and (2) simulations of a stepwise change from configuration MB3 to the 'assembly complete' stage over 130 orbits (indicating that the present ACCM scheme maintains sufficient control over slowly varying Space Station dynamics).

Update on the Center for Engineering Strong Motion Data

NASA Astrophysics Data System (ADS)

Haddadi, H. R.; Shakal, A. F.; Stephens, C. D.; Oppenheimer, D. H.; Huang, M.; Leith, W. S.; Parrish, J. G.; Savage, W. U.

2010-12-01

The U.S. Geological Survey (USGS) and the California Geological Survey (CGS) established the Center for Engineering Strong-Motion Data (CESMD, Center) to provide a single access point for earthquake strong-motion records and station metadata from the U.S. and international strong-motion programs. The Center has operational facilities in Sacramento and Menlo Park, California, to receive, process, and disseminate records through the CESMD web site at www.strongmotioncenter.org. The Center currently is in the process of transitioning the COSMOS Virtual Data Center (VDC) to integrate its functions with those of the CESMD for improved efficiency of operations, and to provide all users with a more convenient one-stop portal to both U.S. and important international strong-motion records. The Center is working with COSMOS and international and U.S. data providers to improve the completeness of site and station information, which are needed to most effectively employ the recorded data. The goal of all these and other new developments is to continually improve access by the earthquake engineering community to strong-motion data and metadata world-wide. The CESMD and its Virtual Data Center (VDC) provide tools to map earthquakes and recording stations, to search raw and processed data, to view time histories and spectral plots, to convert data files formats, and to download data and a variety of information. The VDC is now being upgraded to convert the strong-motion data files from different seismic networks into a common standard tagged format in order to facilitate importing earthquake records and station metadata to the CESMD database. An important new feature being developed is the automatic posting of Internet Quick Reports at the CESMD web site. This feature will allow users, and emergency responders in particular, to view strong-motion waveforms and download records within a few minutes after an earthquake occurs. Currently the CESMD and its Virtual Data Center provide selected strong-motion records from 17 countries. The Center has proved to be significantly useful for providing data to scientists, engineers, policy makers, and emergency response teams around the world.

Variability of site response in the Los Angeles urban area

USGS Publications Warehouse

Hartzell, S.; Cranswick, E.; Frankel, A.; Carver, D.; Meremonte, M.

1997-01-01

This article addresses the variability of site response in the Los Angeles area and possible structural causes for the observations. Aftershock records from 231 sites in the San Fernando and Los Angeles basins and the surrounding mountains are used in this study. Spectral ratios, taken with respect to a low-amplitude reference site, are used to document the variation in site amplification in the frequency range 2 to 6 Hz, both spatially and with backazimuth to the source. At higher frequencies (6 to 10 Hz), spectral ratios are shown to have greater spatial variability. Interstation spectral ratios are used to measure the standard deviation among sources as a function of station separation. An increase in the variation in ground motion is shown to take place at a station separation of 1 km. Relative site-response estimates between nearby stations are used to demonstrate that preferred directions of motion can exist even in areas with no surface topographic effects. Significant variations in site response exist over short baselines (up to a factor of 2 over 200 m) that are not explained by differences in surficial geology or shallow shear-wave velocity. A variety of investigative approaches is used, including spectral ratios, arrival-time variations, 1D and 2D waveform modeling, and comparison with seismic reflection lines, to determine the most likely causes of these observations. A correlation is demonstrated between late arrival times of P and S waves and larger site amplification in Sherman Oaks and Northridge. This observation, in conjunction with waveform modeling and seismic reflection profiles, is used to infer that sedimentary structures in the upper 1 to 2 km and topography on the sediment-basement interface play an important role in determining site amplification. These structures, in the form of folds and buried basins, focus energy in spatially restricted areas at the surface. Comparison of displacement waveforms at nearby stations having disparate site amplifications, complemented by known shallow shear-wave velocities at selected sites, is used to support the argument that these structures, in some cases, can be the dominant factor in the modification of local ground motions.

The Engineering Strong Ground Motion Network of the National Autonomous University of Mexico

NASA Astrophysics Data System (ADS)

Velasco Miranda, J. M.; Ramirez-Guzman, L.; Aguilar Calderon, L. A.; Almora Mata, D.; Ayala Hernandez, M.; Castro Parra, G.; Molina Avila, I.; Mora, A.; Torres Noguez, M.; Vazquez Larquet, R.

2014-12-01

The coverage, design, operation and monitoring capabilities of the strong ground motion program at the Institute of Engineering (IE) of the National Autonomous University of Mexico (UNAM) is presented. Started in 1952, the seismic instrumentation intended initially to bolster earthquake engineering projects in Mexico City has evolved into the largest strong ground motion monitoring system in the region. Today, it provides information not only to engineering projects, but also to the near real-time risk mitigation systems of the country, and enhances the general understanding of the effects and causes of earthquakes in Mexico. The IE network includes more than 100 free-field stations and several buildings, covering the largest urban centers and zones of significant seismicity in Central Mexico. Of those stations, approximately one-fourth send the observed acceleration to a processing center in Mexico City continuously, and the rest require either periodic visits for the manual recovery of the data or remote interrogation, for later processing and cataloging. In this research, we document the procedures and telecommunications systems used systematically to recover information. Additionally, we analyze the spatial distribution of the free-field accelerographs, the quality of the instrumentation, and the recorded ground motions. The evaluation criteria are based on the: 1) uncertainty in the generation of ground motion parameter maps due to the spatial distribution of the stations, 2) potential of the array to provide localization and magnitude estimates for earthquakes with magnitudes greater than Mw 5, and 3) adequacy of the network for the development of Ground Motion Prediction Equations due to intra-plate and intra-slab earthquakes. We conclude that the monitoring system requires a new redistribution, additional stations, and a substantial improvement in the instrumentation and telecommunications. Finally, we present an integral plan to improve the current network's monitoring capabilities.

Near-Fault Ground Motion Velocity Pulses Input and Its Non-Stationary Characteristics from 2015 Gorkha Nepal Mw7.8 Earthquake KATNP Station

NASA Astrophysics Data System (ADS)

Chen, Bo; Wen, Zengping; Wang, Fang

2017-04-01

Using near-fault strong motions from Nepal Mw7.8 earthquake at KATNP station in the city center of Kathmandu, velocity-pulse and non-stationary characteristics of the strong motions are shown, and the reason and potential effect on earthquake damage for intense non-stationary characteristics of near fault velocity-pulse strong motions are mainly studied. The observed strong ground motions of main shock were collected from KATNP station located in 76 kilometers south-east away from epicenter along with forward direction of the rupture fault at an inter-montane basin of the Himalaya. Large velocity pulse show the period of velocity pulse reach up to 6.6s and peak ground velocity of the pulse ground motion is 120 cm/s. Compared with the median spectral acceleration value of NGA prediction equation, significant long-period amplification effect due to velocity pulse is detected at period more than 3.2s. Wavelet analysis shows that the two horizontal component of ground motion is intensely concentration of energy in a short time range of 25-38s and period range of 4-8s. The maximum wavelet-coefficient of horizontal component is 2455, which is about four time of vertical component of strong ground motion. On the perspective of this study, large velocity pulses are identified from two orthogonal components using wavelet method. Intense non-stationary characteristics amplitude and frequency content are mainly caused by site conditions and fault rupture mechanism, which will help to understand the damage evaluation and serve local seismic design.

A GPS and modelling study of deformation in northern Central America

NASA Astrophysics Data System (ADS)

Rodriguez, M.; DeMets, C.; Rogers, R.; Tenorio, C.; Hernandez, D.

2009-09-01

We use GPS measurements at 37 stations in Honduras and El Salvador to describe active deformation of the western end of the Caribbean Plate between the Motagua fault and Central American volcanic arc. All GPS sites located in eastern Honduras move with the Caribbean Plate, in accord with geologic evidence for an absence of neotectonic deformation in this region. Relative to the Caribbean Plate, the other stations in the study area move west to west-northwest at rates that increase gradually from 3.3 +/- 0.6 mm yr-1 in central Honduras to 4.1 +/- 0.6 mm yr-1 in western Honduras to as high as 11-12 mm yr-1 in southern Guatemala. The site motions are consistent with slow westward extension that has been inferred by previous authors from the north-striking grabens and earthquake focal mechanisms in this region. We examine the factors that influence the regional deformation by comparing the new GPS velocity field to velocity fields predicted by finite element models (FEMs) that incorporate the regional plate boundary faults and known plate motions. Our modelling suggests that the obliquely convergent (~20°) direction of Caribbean-North American Plate motion relative to the Motagua fault west of 90°W impedes the ENE-directed motion of the Caribbean Plate in southern Guatemala, giving rise to extension in southern Guatemala and western Honduras. The FEM predictions agree even better with the measured velocities if the plate motion west of the Central American volcanic arc is forced to occur over a broad zone rather than along a single throughgoing plate boundary fault. Our analysis confirms key predictions of a previous numerical model for deformation in this region, and also indicates that the curvature of the Motagua fault causes significant along-strike changes in the orientations of the principal strain-rate axes in the fault borderlands, in accord with earthquake focal mechanisms and conclusions reached in a recent synthesis of the structural and morphologic data from Honduras. Poor fits of our preferred models to the velocities of GPS sites near the Gulf of Fonseca may be an artefact of the still-short GPS time-series in this region or the simplifying assumptions of our FEMs.

A Dramatic Increase in Seismic Observations in the Central and Eastern US

NASA Astrophysics Data System (ADS)

Woodward, R.; Busby, R.; Simpson, D.; Alvarez, M.; Vernon, F.

2009-05-01

The USArray Transportable Array (TA) is a network of 400 seismograph stations that is systematically moving west-to-east across the contiguous United States. The TA is part of the National Science Foundation's multi- disciplinary EarthScope program. The TA has already occupied over 700 stations in the western US, and is continuing its multi-year migration towards the Atlantic coast before heading for Alaska. The stations use a grid-like deployment with 70 km separation between stations. At any given time there are approximately 400 stations operational, occupying a nominal 800 km by 2000 km "footprint." Each station is operated for two years. TA stations consist of three component broadband seismometers, with a few sites in the westernmost United States also including three component strong motion instruments. The instruments are installed about two meters below the surface, in thermally stable vaults. All stations transmit continuous data in near-real-time, and the data are freely distributed through the IRIS Data Management Center. TA stations can be upgraded to incorporate high frequency or strong motion instrument. Organizations can also "adopt" stations after installation by reimbursing the cost of the hardware, so that the stations become permanent. The TA is presently operating in the swath of the country extending from Texas to Montana. From 2010 to 2013 the TA will occupy ~800 sites in the central and eastern US. The array will be centered on the New Madrid, MO region during the bicentennial of the 1811-1812 earthquakes. During the TA deployment every existing or planned nuclear plant in the eastern US will be within 70 km of at least four new seismic stations. Thus, this station deployment in the eastern half of the US presents an unprecedented opportunity for improving source characterization, modeling the regional velocity and attenuation structure, and mapping seismic zones down to low magnitude thresholds. We will provide an overview of TA installation plans, instrumentation, and data so that scientists and decision makers are better prepared to capitalize on the unique opportunity presented by the TA moving through the central and eastern US. We will provide examples of TA station performance, as well as examples of data quality and seismic detection thresholds observed in the western US.

Estimating seismic site response in Christchurch City (New Zealand) from dense low-cost aftershock arrays

USGS Publications Warehouse

Kaiser, Anna E.; Benites, Rafael A.; Chung, Angela I.; Haines, A. John; Cochran, Elizabeth S.; Fry, Bill

2011-01-01

The Mw 7.1 September 2010 Darfield earthquake, New Zealand, produced widespread damage and liquefaction ~40 km from the epicentre in Christchurch city. It was followed by the even more destructive Mw 6.2 February 2011 Christchurch aftershock directly beneath the city’s southern suburbs. Seismic data recorded during the two large events suggest that site effects contributed to the variations in ground motion observed throughout Christchurch city. We use densely-spaced aftershock recordings of the Darfield earthquake to investigate variations in local seismic site response within the Christchurch urban area. Following the Darfield main shock we deployed a temporary array of ~180 low-cost 14-bit MEMS accelerometers linked to the global Quake-Catcher Network (QCN). These instruments provided dense station coverage (spacing ~2 km) to complement existing New Zealand national network strong motion stations (GeoNet) within Christchurch city. Well-constrained standard spectral ratios were derived for GeoNet stations using a reference station on Miocene basalt rock in the south of the city. For noisier QCN stations, the method was adapted to find a maximum likelihood estimate of spectral ratio amplitude taking into account the variance of noise at the respective stations. Spectral ratios for QCN stations are similar to nearby GeoNet stations when the maximum likelihood method is used. Our study suggests dense low-cost accelerometer aftershock arrays can provide useful information on local-scale ground motion properties for use in microzonation. Preliminary results indicate higher amplifications north of the city centre and strong high-frequency amplification in the small, shallower basin of Heathcote Valley.

Ground motion simulation for the 23 August 2011, Mineral, Virginia earthquake using physics-based and stochastic broadband methods

USGS Publications Warehouse

Sun, Xiaodan; Hartzell, Stephen; Rezaeian, Sanaz

2015-01-01

Three broadband simulation methods are used to generate synthetic ground motions for the 2011 Mineral, Virginia, earthquake and compare with observed motions. The methods include a physics‐based model by Hartzell et al. (1999, 2005), a stochastic source‐based model by Boore (2009), and a stochastic site‐based model by Rezaeian and Der Kiureghian (2010, 2012). The ground‐motion dataset consists of 40 stations within 600 km of the epicenter. Several metrics are used to validate the simulations: (1) overall bias of response spectra and Fourier spectra (from 0.1 to 10 Hz); (2) spatial distribution of residuals for GMRotI50 peak ground acceleration (PGA), peak ground velocity, and pseudospectral acceleration (PSA) at various periods; (3) comparison with ground‐motion prediction equations (GMPEs) for the eastern United States. Our results show that (1) the physics‐based model provides satisfactory overall bias from 0.1 to 10 Hz and produces more realistic synthetic waveforms; (2) the stochastic site‐based model also yields more realistic synthetic waveforms and performs superiorly for frequencies greater than about 1 Hz; (3) the stochastic source‐based model has larger bias at lower frequencies (<0.5  Hz) and cannot reproduce the varying frequency content in the time domain. The spatial distribution of GMRotI50 residuals shows that there is no obvious pattern with distance in the simulation bias, but there is some azimuthal variability. The comparison between synthetics and GMPEs shows similar fall‐off with distance for all three models, comparable PGA and PSA amplitudes for the physics‐based and stochastic site‐based models, and systematic lower amplitudes for the stochastic source‐based model at lower frequencies (<0.5  Hz).

Probabilistic and deterministic aspects of linear estimation in geodesy. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Dermanis, A.

1976-01-01

Recent advances in observational techniques related to geodetic work (VLBI, laser ranging) make it imperative that more consideration should be given to modeling problems. Uncertainties in the effect of atmospheric refraction, polar motion and precession-nutation parameters, cannot be dispensed with in the context of centimeter level geodesy. Even physical processes that have generally been previously altogether neglected (station motions) must now be taken into consideration. The problem of modeling functions of time or space, or at least their values at observation points (epochs) is explored. When the nature of the function to be modeled is unknown. The need to include a limited number of terms and to a priori decide upon a specific form may result in a representation which fails to sufficiently approximate the unknown function. An alternative approach of increasing application is the modeling of unknown functions as stochastic processes.

Spin motion determination of the Envisat satellite through laser ranging measurements from a single pass measured by a single station

NASA Astrophysics Data System (ADS)

Pittet, Jean-Noël; Šilha, Jiří; Schildknecht, Thomas

2018-02-01

The Satellite Laser Ranging (SLR) technology is used to accurately determine the position of space objects equipped with so-called retro-reflectors or retro-reflector arrays (RRA). This type of measurement allows to measure the range to the spacecraft with high precision, which leads to determination of very accurate orbits for these targets. Non-active spacecraft, which are not attitude controlled any longer, tend to start to spin or tumble under influence of the external and internal torques and forces. If the return signal is measured for a non-spherical non-active rotating object, the signal in the range residuals with respect to the reference orbit is more complex. For rotating objects the return signal shows an oscillating pattern or patterns caused by the RRA moving around the satellite's centre of mass. This behaviour is projected onto the radial component measured by the SLR. In our work, we demonstrate how the SLR ranging technique from one sensor to a satellite equipped with a RRA can be used to precisely determine its spin motion during one passage. Multiple SLR measurements of one target over time allow to accurately monitor spin motion changes which can be further used for attitude predictions. We show our solutions of the spin motion determined for the non-active ESA satellite Envisat obtained from measurements acquired during years 2013-2015 by the Zimmerwald SLR station, Switzerland. All the necessary parameters are defined for our own so-called point-like model which describes the motion of a point in space around the satellite centre of mass.

Analysis of the Source and Ground Motions from the 2017 M8.2 Tehuantepec and M7.1 Puebla Earthquakes

NASA Astrophysics Data System (ADS)

Melgar, D.; Sahakian, V. J.; Perez-Campos, X.; Quintanar, L.; Ramirez-Guzman, L.; Spica, Z.; Espindola, V. H.; Ruiz-Angulo, A.; Cabral-Cano, E.; Baltay, A.; Geng, J.

2017-12-01

The September 2017 Tehuantepec and Puebla earthquakes were intra-slab earthquakes that together caused significant damage in broad regions of Mexico, including the states of Oaxaca, Chiapas, Morelos, Puebla, Mexico, and Mexico City. Ground motions in Mexico City have approximately the same angle of incidence from both earthquakes and potentially sample similar paths close to the city. We examine site effects and source terms by analysis of residuals between Ground-Motion Prediction Equations (GMPEs) and observed ground motions for both of these events at stations from the Servicio Sismólogico Nacional, Instituto de Ingeniería, and the Instituto de Geofísica Red del Valle de Mexico networks. GMPEs are a basis for seismic design, but also provide median ground motion values to act as a basis for comparison of individual earthquakes and site responses. First, we invert for finite-fault slip inversions for Tehuantepec with high-rate GPS, static GPS, tide gauge and DART buoy data, and for Puebla with high-rate GPS and strong motion data. Using the distance from the stations with ground motion observations to the derived slip models, we use the GMPEs of Garcia et al. (2005), Zhao et al. (2006), and Abrahamson, Silva and Kamai (2014), to compute predicted values of peak ground acceleration and velocity (PGA and PGV) and response spectral accelerations (SA). Residuals between observed and predicted ground motion parameters are then computed for each recording, and are decomposed into event and site components using a mixed effects regression. We analyze these residuals as an adjustment away from median ground motions in the region to glean information about the earthquake source properties, as well as local site response in and outside of the Mexico City basin. The event and site terms are then compared with available values of stress drop for the two earthquakes, and Vs30 values for the sites, respectively. This analysis is useful in determining which GMPE is most appropriate in the central Mexico region, important for future ground motion studies and rapid response products such as ShakeMap.

State Estimation of International Space Station Centrifuge Rotor With Incomplete Knowledge of Disturbance Inputs

NASA Technical Reports Server (NTRS)

Sullivan, Michael J.

2005-01-01

This thesis develops a state estimation algorithm for the Centrifuge Rotor (CR) system where only relative measurements are available with limited knowledge of both rotor imbalance disturbances and International Space Station (ISS) thruster disturbances. A Kalman filter is applied to a plant model augmented with sinusoidal disturbance states used to model both the effect of the rotor imbalance and the 155 thrusters on the CR relative motion measurement. The sinusoidal disturbance states compensate for the lack of the availability of plant inputs for use in the Kalman filter. Testing confirms that complete disturbance modeling is necessary to ensure reliable estimation. Further testing goes on to show that increased estimator operational bandwidth can be achieved through the expansion of the disturbance model within the filter dynamics. In addition, Monte Carlo analysis shows the varying levels of robustness against defined plant/filter uncertainty variations.

Characterization of Non-Linearized Spacecraft Relative Motion using Nonlinear Normal Modes

DTIC Science & Technology

2016-04-20

10 5.1 Results for Four Models with Different Nonlinearities ..................................................11 5.2 Effects of...Force Research Laboratory or the U.S. Government. 1.0 SUMMARY In this report, the effects of incorporating nonlinearities in sequential relative orbit...exactly. Huxel and Bishop [1] discussed the effects of using both inertial range measurements from tracking stations and relative range measurements

Vienna SAC-SOS: Analysis of the European VLBI Sessions

NASA Astrophysics Data System (ADS)

Ros, C. T.; Pavetich, P.; Nilsson, T.; Böhm, J.; Schuh, H.

2012-12-01

The Institute of Geodesy and Geophysics (IGG) of the Vienna University of Technology as an IVS Special Analysis Center for Specific Observing Sessions (SAC-SOS) has analyzed the European VLBI sessions using the software VieVS. Between 1990 and 2011, 115 sessions have been carried out. The analyzed baselines have lengths ranging from approximately 445 to 4580 km, and they show good repeatabilities, apart from the ones containing station Simeiz. The station velocities have also been investigated. The stations situated in the stable part of Europe have not shown significant relative movements w.r.t. Wettzell, whereas the stations located in the northern areas have the largest vertical motions as a result of the post glacial isostatic rebound of the zone. The stations placed in Italy, around the Black Sea, in Siberia, and near the Arctic Circle show the largest relative horizontal motions because they belong to different geodynamical units.

Full Seismic Waveform Tomography of the Japan region using Adjoint Methods

NASA Astrophysics Data System (ADS)

Steptoe, Hamish; Fichtner, Andreas; Rickers, Florian; Trampert, Jeannot

2013-04-01

We present a full-waveform tomographic model of the Japan region based on spectral-element wave propagation, adjoint techniques and seismic data from dense station networks. This model is intended to further our understanding of both the complex regional tectonics and the finite rupture processes of large earthquakes. The shallow Earth structure of the Japan region has been the subject of considerable tomographic investigation. The islands of Japan exist in an area of significant plate complexity: subduction related to the Pacific and Philippine Sea plates is responsible for the majority of seismicity and volcanism of Japan, whilst smaller micro-plates in the region, including the Okhotsk, and Okinawa and Amur, part of the larger North America and Eurasia plates respectively, contribute significant local intricacy. In response to the need to monitor and understand the motion of these plates and their associated faults, numerous seismograph networks have been established, including the 768 station high-sensitivity Hi-net network, 84 station broadband F-net and the strong-motion seismograph networks K-net and KiK-net in Japan. We also include the 55 station BATS network of Taiwan. We use this exceptional coverage to construct a high-resolution model of the Japan region from the full-waveform inversion of over 15,000 individual component seismograms from 53 events that occurred between 1997 and 2012. We model these data using spectral-element simulations of seismic wave propagation at a regional scale over an area from 120°-150°E and 20°-50°N to a depth of around 500 km. We quantify differences between observed and synthetic waveforms using time-frequency misfits allowing us to separate both phase and amplitude measurements whilst exploiting the complete waveform at periods of 15-60 seconds. Fréchet kernels for these misfits are calculated via the adjoint method and subsequently used in an iterative non-linear conjugate-gradient optimization. Finally, we employ custom smoothing algorithms to remove the singularities of the Fréchet kernels and artifacts introduced by the heterogeneous coverage in oceanic regions of the model.

Rupture process and strong ground motions of the 2007 Niigataken Chuetsu-Oki earthquake -Directivity pulses striking the Kashiwazaki-Kariwa Nuclear Power Plant-

NASA Astrophysics Data System (ADS)

Irikura, K.; Kagawa, T.; Miyakoshi, K.; Kurahashi, S.

2007-12-01

The Niigataken Chuetsu-Oki earthquake occurred on July 16, 2007, northwest-off Kashiwazaki in Niigata Prefecture, Japan, causing severe damages of ten people dead, about 1300 injured, about 1000 collapsed houses and major lifelines suspended. In particular, strong ground motions from the earthquake struck the Kashiwazaki-Kariwa nuclear power plant (hereafter KKNPP), triggering a fire at an electric transformer and other problems such as leakage of water containing radioactive materials into air and the sea, although the radioactivity levels of the releases are as low as those of the radiation which normal citizens would receive from the natural environment in a year. The source mechanism of this earthquake is a reverse fault, but whether it is the NE-SW strike and NW dip or the SW-NE strike and SE dip are still controversial from the aftershock distribution and geological surveys near the source. Results of the rupture processes inverted by using the GPS and SAR data, tsunami data and teleseismic data so far did not succeed in determining which fault planes moved. Strong ground motions were recorded at about 390 stations by the K-NET of NIED including the stations very close to the source area. There was the KKNPP which is probably one of buildings and facilities closest to the source area. They have their own strong motion network with 22 three-components' accelerographs locating at ground-surface, underground, buildings and basements of reactors. The PGA attenuation-distance relationships made setting the fault plane estimated from the GPS data generally follow the empirical relations in Japan, for example, Fukushima and Tanaka (1990) and Si and Midorikawa (1999), even if either fault plane, SE dip or NW dip, is assumed. However, the strong ground motions in the site of the KKNPP had very large accelerations and velocities more than those expected from the empirical relations. The surface motions there had the PGA of more than 1200 gals and even underground motions at the basements of the reactors locating five stories below the ground had the PGA of 680 gals. We simulated ground motions using the characterized source model (Kamae and Irikura, 1998) with three asperities and the empirical Green's function method (Irikura, 1986). Then, we found that the source model should be a reverse fault with the NE-SW strike and NW dip to explain the strong motion records obtained near the source area. In particular, strong ground motions in the site of the KKNPP had three significant pulses which are generated as directivity pulses in forward direction of rupture propagation. This is the reason why the strong ground motions in the site of the KKNPP had very large accelerations and velocities. The source model is also verified comparing the observed records at the KKNPP with the numerical simulations by the discrete wavenumber method (Bouchon, 1981).

Toward a Global Horizontal and Vertical Elastic Load Deformation Model Derived from GRACE and GNSS Station Position Time Series

NASA Astrophysics Data System (ADS)

Chanard, Kristel; Fleitout, Luce; Calais, Eric; Rebischung, Paul; Avouac, Jean-Philippe

2018-04-01

We model surface displacements induced by variations in continental water, atmospheric pressure, and nontidal oceanic loading, derived from the Gravity Recovery and Climate Experiment (GRACE) for spherical harmonic degrees two and higher. As they are not observable by GRACE, we use at first the degree-1 spherical harmonic coefficients from Swenson et al. (2008, https://doi.org/10.1029/2007JB005338). We compare the predicted displacements with the position time series of 689 globally distributed continuous Global Navigation Satellite System (GNSS) stations. While GNSS vertical displacements are well explained by the model at a global scale, horizontal displacements are systematically underpredicted and out of phase with GNSS station position time series. We then reestimate the degree 1 deformation field from a comparison between our GRACE-derived model, with no a priori degree 1 loads, and the GNSS observations. We show that this approach reconciles GRACE-derived loading displacements and GNSS station position time series at a global scale, particularly in the horizontal components. Assuming that they reflect surface loading deformation only, our degree-1 estimates can be translated into geocenter motion time series. We also address and assess the impact of systematic errors in GNSS station position time series at the Global Positioning System (GPS) draconitic period and its harmonics on the comparison between GNSS and GRACE-derived annual displacements. Our results confirm that surface mass redistributions observed by GRACE, combined with an elastic spherical and layered Earth model, can be used to provide first-order corrections for loading deformation observed in both horizontal and vertical components of GNSS station position time series.

Site correction of stochastic simulation in southwestern Taiwan

NASA Astrophysics Data System (ADS)

Lun Huang, Cong; Wen, Kuo Liang; Huang, Jyun Yan

2014-05-01

Peak ground acceleration (PGA) of a disastrous earthquake, is concerned both in civil engineering and seismology study. Presently, the ground motion prediction equation is widely used for PGA estimation study by engineers. However, the local site effect is another important factor participates in strong motion prediction. For example, in 1985 the Mexico City, 400km far from the epicenter, suffered massive damage due to the seismic wave amplification from the local alluvial layers. (Anderson et al., 1986) In past studies, the use of stochastic method had been done and showed well performance on the simulation of ground-motion at rock site (Beresnev and Atkinson, 1998a ; Roumelioti and Beresnev, 2003). In this study, the site correction was conducted by the empirical transfer function compared with the rock site response from stochastic point-source (Boore, 2005) and finite-fault (Boore, 2009) methods. The error between the simulated and observed Fourier spectrum and PGA are calculated. Further we compared the estimated PGA to the result calculated from ground motion prediction equation. The earthquake data used in this study is recorded by Taiwan Strong Motion Instrumentation Program (TSMIP) from 1991 to 2012; the study area is located at south-western Taiwan. The empirical transfer function was generated by calculating the spectrum ratio between alluvial site and rock site (Borcheret, 1970). Due to the lack of reference rock site station in this area, the rock site ground motion was generated through stochastic point-source model instead. Several target events were then chosen for stochastic point-source simulating to the halfspace. Then, the empirical transfer function for each station was multiplied to the simulated halfspace response. Finally, we focused on two target events: the 1999 Chi-Chi earthquake (Mw=7.6) and the 2010 Jiashian earthquake (Mw=6.4). Considering the large event may contain with complex rupture mechanism, the asperity and delay time for each sub-fault is to be concerned. Both the stochastic point-source and the finite-fault model were used to check the result of our correction.

Predicted torque equilibrium attitude utilization for Space Station attitude control

NASA Technical Reports Server (NTRS)

Kumar, Renjith R.; Heck, Michael L.; Robertson, Brent P.

1990-01-01

An approximate knowledge of the torque equilibrium attitude (TEA) is shown to improve the performance of a control moment gyroscope (CMG) momentum management/attitude control law for Space Station Freedom. The linearized equations of motion are used in conjunction with a state transformation to obtain a control law which uses full state feedback and the predicted TEA to minimize both attitude excursions and CMG peak and secular momentum. The TEA can be computationally determined either by observing the steady state attitude of a 'controlled' spacecraft using arbitrary initial attitude, or by simulating a fixed attitude spacecraft flying in desired orbit subject to realistic environmental disturbance models.

A fast topographic characterization of seismic station locations in Iran through integrated use of digital elevation models and GIS

NASA Astrophysics Data System (ADS)

Karimzadeh, Sadra; Miyajima, Masakatsu; Kamel, Batoul; Pessina, Vera

2015-10-01

We present topographic slope positions of seismic stations within four independent networks (IGUT, IIEES, GSI, and BHRC) in Iran through integrated use of digital elevation models and GIS. Since topographic amplification factor (TAF) due to ground surface irregularity could be one of the reasons of earthquake wave amplification and unexpected damage of structures located on the top of ridges in many previous studies, the ridge stations in the study area are recognized using topographic position index (TPI) as a spatial-based scale-dependent approach that helps in classification of topographic positions. We also present the correlation between local topographic positions and V {/s 30} along with Voronoi tiles of two networks (IGUT and IIEES). The obtained results can be profitably used in seismology to establish homogeneous subnetworks based on Voronoi tiles with precise feedback and in the formulation of new ground motion prediction equations with respect to topographic position and topographic amplification factor.

New Downhole Strong-Motion Data Recorded at Tarzana Array

NASA Astrophysics Data System (ADS)

Graizer, V.; Shakal, A.; Haddadi, H.

2001-12-01

Significantly amplified ground accelerations at the Tarzana station were recorded during many, but not all, earthquakes (e.g., Shakal et al., 1988). Peak horizontal ground acceleration at the Tarzana station during the M7.1 Hector Mine earthquake was almost twice as large as the accelerations recorded at nearby stations. After the Northridge earthquake the California Strong Motion Instrumentation Program (CSMIP) significantly increased instrumentation at Tarzana to study the unusual site amplification effect. Current instrumentation at Tarzana consists of an accelerograph at the top of Tarzana hill (Tarzana - Cedar Hill B), a downhole instrument at 60 m depth, and an accelerograph at the foot of the hill (Tarzana - Clubhouse), 180 m from the Cedar Hill B station. The original station, Tarzana - Cedar Hill Nursery A, was lost in 1999 due to construction. Thirteen events, including the Hector Mine earthquake, were simultaneously recorded by these instruments at Tarzana. The downhole instrument (A) was used as a reference site to compare the amplification effects at the top of Tarzana hill (B) and at the foot of the hill (C). Spectral amplification from the bottom of the hole to the top of the hill (B/A) and to the foot of the hill (C/A) is similar along the component parallel to the strike of Tarzana hill. But B/A is almost double C/A along the component transverse to the strike of the hill in period range from 0.04 to 0.8 sec (1.2 to 25 Hz). Comparison of the response spectra demonstrates clear directional site response resonance (perpendicular to the strike of the hill) at Tarzana. In contrast to accelerations recorded during the Mw 7.1 Hector Mine earthquake (high frequency part of seismic signal), displacements (relatively low frequency part of seismic signal) demonstrate almost no site amplification from the bottom of the hole to the surface (B/A) at periods greater than 1.5 sec, in either direction. Ground displacements at other CSMIP downhole arrays which recorded the Hector Mine earthquake also demonstrate almost no near-surface site amplification at long periods. Comparison of empirical and theoretical site amplification effects at Tarzana was performed using SHAKE91 modeling motion separately in the longitudinal and transverse directions. The source of the site amplification that produces large motions at Tarzana is still under investigation. The topography, shear-wave velocity profile and three-dimensional structure of the site apparently all contribute to the higher amplification of ground motion at the Tarzana site. The studies of Tarzana were co-funded by CSMIP and by the National Science Foundation (NSF) through the Resolution of Site Response Issues from the Northridge Earthquake Project (ROSRINE).

Progress Towards a Comprehensive Site Database for Taiwan Strong Motion Network

NASA Astrophysics Data System (ADS)

Kuo, C. H.; Lin, C. M.; Chang, S. C.; Wen, K. L.

2016-12-01

Site effect is usually treated as a simple site parameter like Vs30, which is a value of average shear wave velocity for the top 30 m of layers, in Ground Motion Prediction Equations (GMPEs) and engineering seismology. Although debates on usage of Vs30 for its advantage and disadvantage are still an open question, it has become the most widely be used site parameter in ground motion prediction, seismic hazard analysis, and building codes. Depth to the horizons with shear wave velocity of larger than 1.0 km/s (or 1.5 km/s, 2.5 km/s), the so called Z1.0 (or Z1.5, Z2.5), was recently introduced to the GMPEs of the Next Generation of Attenuation Equations (NGA) project in order to make up for the insufficient of Vs30 especially in regions covered by large thickness of sediments. However this kind of data is still rare and quite difficult to be acquired. This parameter is only available in Japan, California, and part region of Turkey at present. The high-frequency attenuation factor, i.e. kappa, is considered a significant parameter controlling attenuation of high-frequency seismic waves. High correlation is believed between kappa and local site conditions. S-wave velocity profiles of the Engineering Geology Database for TSMIP (EGDT) were measured using suspension PS-logging at more than 450 strong ground motion stations throughout Taiwan. Accurate Vs30 is therefore provided by the site database. Although the depths of most stations were only 35 m, Z1.0 still can be derived at dozens of stations near basin edges or piedmont area from EGDT. Several techniques including microtremor array, receiver function, and HVSR inversion have been used to obtain S-wave velocity profiles at strong motion stations and thus the parameter Z1.0 can be derived. A relationship between Vs30 and Z1.0 for Taiwan is consequently evaluated and further compared with those for Japan and California. Kappa at strong motion stations was calculated and a special correlation with Vs30 is found. The achievement in the progress toward a comprehensive site database for a national strong motion network is quite important for engineering seismology and national seismic hazard analysis.

Some Key Features of the Strong-Motion Data from the M 6.0 Parkfield, California, Earthquake of 28 September 2004

USGS Publications Warehouse

Shakal, A.; Haddadi, H.; Graizer, V.; Lin, K.; Huang, M.

2006-01-01

The 2004 Parkfield, California, earthquake was recorded by an extensive set of strong-motion instruments well positioned to record details of the motion in the near-fault region, where there has previously been very little recorded data. The strong-motion measurements obtained are highly varied, with significant variations occurring over only a few kilometers. The peak accelerations in the near fault region range from 0.13g to over 1.8g (one of the highest acceleration recorded to date, exceeding the capacity of the recording instrument The largest accelerations occurred near the northwest end of the inferred rupture zone. These motions are consistent with directivity for a fault rupturing from the hypocenter near Gold Hill toward the northwest. However, accelerations up to 0.8g were also observed in the opposite direction, at the south end of the Cholame Valley near Highway 41, consistent with bilateral rupture, with rupture southeast of the hypocenter. Several stations near and over the rupturing fault recorded relatively weak motions, consistent with seemingly paradoxical observations of low shaking damage near strike-slip faults. This event had more ground-motion observations within 10 km of the fault than many other earthquakes combined. At moderate distances peak horizontal ground acceleration (PGA) values dropped off more rapidly with distance than standard relationships. At close-in distance the wide variation of PGA suggests a distance-dependent sigma may be important to consider. The near-fault ground-motion variation is greater than that assumed in ShakeMap interpolations, based on the existing set of observed data. Higher density of stations near faults may be the only means in the near future to reduce uncertainty in the interpolations. Outside of the near-fault zone the variance is closer to that assumed. This set of data provides the first case where near-fault radiation has been observed at an adequate number of stations around the fault to allow detailed study of the fault-normal and fault-parallel motion and the near-field S-wave radiation. The fault-normal motions are significant, but they are not large at the central part of the fault, away from the ends. The fault-normal and fault-parallel motions drop off quite rapidly with distance from the fault. Analysis of directivity indicates increased values of peak velocity in the rupture direction. No such dependence is observed in the peak acceleration, except for stations close to the strike of the fault near and beyond the ends of the faulting.

Joint inversion of surface wave dispersion and receiver functions for crustal structure in Oklahoma

NASA Astrophysics Data System (ADS)

Guo, Hao

The surge in seismicity in Oklahoma starting in 2008 raises questions about the actual locations of the earthquakes in the upper crust. The key to answering this is an improved crustal model that explains as many observations as possible. Love and Rayleigh wave dispersion, teleseismic P-wave receiver functions and some unique transverse motions observed at distances less than 100 km that are characteristics of rays reverberating in a basin provide data to derive the crustal model. The surface wave dispersion data set consists of over 300,000 Love/Rayleigh phase/group values obtained from ambient noise cross-correlation of BH channels of the 133 Transportable Array (TA) stations of Earthscope to periods as short as 2 seconds. Station coverage is dense enough to perform the tomography on a 25*25 km grid that should be able to image shallow geological structures. In addition, receiver functions were obtained using teleseismic data recorded from 3 US Geological Survey Networks (GS) stations and 6 Oklahoma Seismic Network (OK) stations from 2011 to 2014. The 1-D S-wave velocity models derived by the joint inversion of surface wave dispersion and receiver functions with geological constraints are tested by fitting the independent transverse seismograms. This test also provides constraints on the earthquake depths in relation to the geological structure.

Sea Level Variability in the Mediterranean

NASA Astrophysics Data System (ADS)

Zerbini, S.; Bruni, S.; del Conte, S.; Errico, M.; Petracca, F.; Prati, C.; Raicich, F.; Santi, E.

2015-12-01

Tide gauges measure local sea-level relative to a benchmark on land, therefore the interpretation of these measurements can be limited by the lack of appropriate knowledge of vertical crustal motions. The oldest sea-level records date back to the 18th century; these observations are the only centuries-old data source enabling the estimate of historical sea-level trends/variations. In general, tide gauge benchmarks were not frequently levelled, except in those stations where natural and/or anthropogenic subsidence was a major concern. However, in most cases, it is difficult to retrieve the historical geodetic levelling data. Space geodetic techniques, such as GNSS, Doris and InSAR are now providing measurements on a time and space-continuous basis, giving rise to a large amount of different data sets. The vertical motions resulting from the various analyses need to be compared and best exploited for achieving reliable estimates of sea level variations. In the Mediterranean area, there are a few centennial tide gauge records; our study focuses, in particular, on the Italian time series of Genoa, Marina di Ravenna, Venice and Trieste. Two of these stations, Marina di Ravenna and Venice, are affected by both natural and anthropogenic subsidence, the latter was particularly intense during a few decades of the 20th century because of ground fluids withdrawal. We have retrieved levelling data of benchmarks at and/or close to the tide gauges from the end of 1800 and, for the last couple of decades, also GPS and InSAR height time series in close proximity of the stations. By using an ensemble of these data, modelling of the long-period non-linear behavior of subsidence was successfully accomplished. After removal of the land vertical motions, the linear long period sea-level rates of all stations are in excellent agreement. Over the last two decades, the tide gauge rates were also compared with those obtained by satellite radar altimetry data.

A crack-like rupture model for the 19 September 1985 Michoacan, Mexico, earthquake

NASA Astrophysics Data System (ADS)

Ruppert, Stanley D.; Yomogida, Kiyoshi

1992-09-01

Evidence supporting a smooth crack-like rupture process of the Michoacan earthquake of 1985 is obtained from a major earthquake for the first time. Digital strong motion data from three stations (Caleta de Campos, La Villita, and La Union), recording near-field radiation from the fault, show unusually simple ramped displacements and permanent offsets previously only seen in theoretical models. The recording of low frequency (0 to 1 Hz) near-field waves together with the apparently smooth rupture favors a crack-like model to a step or Haskell-type dislocation model under the constraint of the slip distribution obtained by previous studies. A crack-like rupture, characterized by an approximated dynamic slip function and systematic decrease in slip duration away from the point of rupture nucleation, produces the best fit to the simple ramped displacements observed. Spatially varying rupture duration controls several important aspects of the synthetic seismograms, including the variation in displacement rise times between components of motion observed at Caleta de Campos. Ground motion observed at Caleta de Campos can be explained remarkably well with a smoothly propagating crack model. However, data from La Villita and La Union suggest a more complex rupture process than the simple crack-like model for the south-eastern portion of the fault.

Station coordinates, baselines, and earth rotation from Lageos laser ranging - 1976-1984

NASA Technical Reports Server (NTRS)

Tapley, B. D.; Schultz, B. E.; Eanes, R. J.

1985-01-01

The orbit of the Lageos satellite is well suited as a reference frame for studying the rotation of the earth and the relative motion of points on the earth's crust. The satellite laser measurements can determine the location of a set of tracking stations in an appropriate terrestrial coordinate system. The motion of the earth's rotation axis relative to this system can be studied on the basis of the established tracking station locations. The present investigation is concerned with an analysis of 7.7 years of Lageos laser ranging data. In the first solution considered, the entire data span was used to adjust a single set of station positions simultaneously with orbit and earth rotation parameters. Attention is given to the accuracy of earth rotation parameters which are determined as an inherent part of the solution process.

Stratigraphic Profiles for Selected Hanford Site Seismometer Stations and Other Locations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Last, George V.

2014-02-01

Stratigraphic profiles were constructed for eight selected Hanford Site seismometer stations, five Hanford Site facility reference locations, and seven regional three-component broadband seismometer stations. These profiles provide interpretations of the subsurface layers to support estimation of ground motions from past earthquakes, and the prediction of ground motions from future earthquakes. In most cases these profiles terminated at the top of the Wanapum Basalt, but at selected sites profiles were extended down to the top of the crystalline basement. The composite one-dimensional stratigraphic profiles were based primarily on previous interpretations from nearby boreholes, and in many cases the nearest deep boreholemore » is located kilometers away.« less

System Hazard Analysis of TACOM’s Crew Station/Turret Motion Base Simulator

DTIC Science & Technology

1992-01-01

Safety devices have been located on the equipment where necessary and are described in the Contraves USA Manual No. IM-27751, "INSTRUCTION MANUAL FOR...OF TACOM’s CREW STATION/TURRET MOTION BASE SIMULATOR" and Contraves USA Manual No. IM-27751, "INSTRUCTION MANUAL FOR TACOM" in an attempt to satisfy... Contraves USA and assembled jointly by Contraves USA and TACOM. All control compensation was performed by TACOM. The CS/TMBS is expected to open doors

Coupled orbit-attitude dynamics and relative state estimation of spacecraft near small Solar System bodies

NASA Astrophysics Data System (ADS)

Misra, Gaurav; Izadi, Maziar; Sanyal, Amit; Scheeres, Daniel

2016-04-01

The effects of dynamical coupling between the rotational (attitude) and translational (orbital) motion of spacecraft near small Solar System bodies is investigated. This coupling arises due to the weak gravity of these bodies, as well as solar radiation pressure. The traditional approach assumes a point-mass spacecraft model to describe the translational motion of the spacecraft, while the attitude motion is considered to be completely decoupled from the translational motion. The model used here to describe the rigid-body spacecraft dynamics includes the non-uniform rotating gravity field of the small body up to second degree and order along with the attitude dependent terms, solar tide, and solar radiation pressure. This model shows that the second degree and order gravity terms due to the small body affect the dynamics of the spacecraft to the same extent as the orbit-attitude coupling due to the primary gravity (zeroth order) term. Variational integrators are used to simulate the dynamics of both the rigid spacecraft and the point mass. The small bodies considered here are modeled after Near-Earth Objects (NEO) 101955 Bennu, and 25143 Itokawa, and are assumed to be triaxial ellipsoids with uniform density. Differences in the numerically obtained trajectories of a rigid spacecraft and a point mass are then compared, to illustrate the impact of the orbit-attitude coupling on spacecraft dynamics in proximity of small bodies. Possible implications on the performance of model-based spacecraft control and on the station-keeping budget, if the orbit-attitude coupling is not accounted for in the model of the dynamics, are also discussed. An almost globally asymptotically stable motion estimation scheme based solely on visual/optical feedback that estimates the relative motion of the asteroid with respect to the spacecraft is also obtained. This estimation scheme does not require a model of the dynamics of the asteroid, which makes it perfectly suited for asteroids whose properties are not well known.

Land motion estimates from GPS at tide gauges: a geophysical evaluation

NASA Astrophysics Data System (ADS)

Bouin, M. N.; Wöppelmann, G.

2010-01-01

Space geodesy applications have mainly been limited to horizontal deformations due to a number of restrictions on the vertical component accuracy. Monitoring vertical land motion is nonetheless of crucial interest in observations of long-term sea level change or postglacial rebound measurements. Here, we present a global vertical velocity field obtained with more than 200 permanent GPS stations, most of them colocated with tide gauges (TGs). We used a state of the art, homogeneous processing strategy to ensure that the reference frame was stable throughout the observation period of almost 10 yr. We associate realistic uncertainties to our vertical rates, taking into account the time-correlation noise in the time-series. The results are compared with two independent geophysical vertical velocity fields: (1) vertical velocity estimates using long-term TG records and (2) postglacial model predictions from the ICE-5G (VM2) adjustment. The quantitative agreement of the GPS vertical velocities with the `internal estimates' of vertical displacements using the TG record is very good, with a mean difference of -0.13 +/- 1.64 mm yr-1 on more than 100 sites. For 84 per cent of the GPS stations considered, the vertical velocity is confirmed by the TG estimate to within 2 mm yr-1. The overall agreement with the glacial isostatic adjustment (GIA) model is good, with discrepancy patterns related either to a local misfit of the model or to active tectonics. For 72 per cent of the sites considered, the predictions of the GIA model agree with the GPS results to within two standard deviations. Most of the GPS velocities showing discrepancies with respect to the predictions of the GIA model are, however, consistent with previously published space geodesy results. We, in turn, confirm the value of 1.8 +/- 0.5 mm yr-1 for the 20th century average global sea level rise, and conclude that GPS is now a robust tool for vertical land motion monitoring which is accurate at least at 1 mm yr-1.

The Influence of Sediment Isostatic Adjustment on Sea-Level Change and Land Motion along the US Gulf Coast

NASA Astrophysics Data System (ADS)

Kuchar, J.; Milne, G. A.; Wolstencroft, M.; Love, R.; Tarasov, L.; Hijma, M.

2017-12-01

Sea level rise presents a hazard for coastal populations and the Mississippi Delta (MD) is a region particularly at risk due to the high rates of land subsidence. We apply a gravitationally self-consistent model of glacial and sediment isostatic adjustment (SIA) along with a realistic sediment load reconstruction in this region for the first time to determine isostatic contributions to relative sea level (RSL) and land motion. We determine optimal model parameters (Earth rheology and ice history) using a new high quality compaction-free sea level indicator database and a parameter space of four ice histories and 400 Earth rheologies. Using the optimal model parameters, we show that SIA is capable of lowering predicted RSL in the MD area by several metres over the Holocene and so should be taken into account when modelling these data. We compare modelled contemporary rates of vertical land motion with those inferred using GPS. This comparison indicates that isostatic processes can explain the majority of the observed vertical land motion north of latitude 30.7oN, where subsidence rates average about 1 mm/yr; however, vertical rates south of this latitude shows large data-model discrepancies of greater than 3 mm/yr, indicating the importance of non-isostatic processes controlling the observed subsidence. This discrepancy extends to contemporary RSL change, where we find that the SIA contribution in the Delta is on the order of 10-1 mm per year. We provide estimates of the isostatic contributions to 20th and 21st century sea level rates at Gulf Coast PSMSL tide gauge locations as well as vertical and horizontal land motion at GPS station locations near the Mississippi Delta.

The Influence of Sediment Isostatic Adjustment on Sea Level Change and Land Motion Along the U.S. Gulf Coast

NASA Astrophysics Data System (ADS)

Kuchar, Joseph; Milne, Glenn; Wolstencroft, Martin; Love, Ryan; Tarasov, Lev; Hijma, Marc

2018-01-01

Sea level rise presents a hazard for coastal populations, and the Mississippi Delta (MD) is a region particularly at risk due to the high rates of land subsidence. We apply a gravitationally self-consistent model of glacial and sediment isostatic adjustment (SIA) along with a realistic sediment load reconstruction in this region for the first time to determine isostatic contributions to relative sea level (RSL) and land motion. We determine optimal model parameters (Earth rheology and ice history) using a new high-quality compaction-free sea level indicator database. Using the optimal model parameters, we show that SIA can lower predicted RSL in the MD area by several meters over the Holocene and so should be taken into account when modeling these data. We compare modeled contemporary rates of vertical land motion with those inferred using GPS. This comparison indicates that isostatic processes can explain the majority of the observed vertical land motion north of latitude 30.7°N, where subsidence rates average about 1 mm/yr; however, subsidence south of this latitude shows large data-model discrepancies of greater than 3 mm/yr, indicating the importance of nonisostatic processes. This discrepancy extends to contemporary RSL change, where we find that the SIA contribution in the Delta is on the order of 10-1 mm/yr. We provide estimates of the isostatic contributions to 20th and 21st century sea level rates at Gulf Coast Permanent Service for Mean Sea Level tide gauge locations as well as vertical and horizontal land motion at GPS station locations near the MD.

UT/CSR analysis of earth rotation from Lageos SLR data

NASA Technical Reports Server (NTRS)

Tapley, B. D.; Eanes, R. J.; Schutz, B. E.

1986-01-01

The 1983-1984 data collected by NASA and stations participating in the Crustal Dynamics Project from satellite laser ranging (SLR) systems are used to generate solutions for the earth polar motion. Solutions obtained using the MERIT Lageos standard data set are compared to operational results based on quick-look data and generated in near real-time, and the capability of Lageos SLR for the determination of earth orientation parameters (EOP) with high temporal resolution is investigated. Finally, the sensitivity of the MERIT campaign results to the number of tracking stations and to changes in the MERIT standard model is evaluated. It is concluded that the departures from the IAU/IUGG MERIT standards do not significantly change the solution and that solutions accurate at the 2 milliarcsec level can be maintained with a network of fewer than 10 appropriately selected stations.

GPS coordinate time series measurements in Ontario and Quebec, Canada

NASA Astrophysics Data System (ADS)

Samadi Alinia, Hadis; Tiampo, Kristy F.; James, Thomas S.

2017-06-01

New precise network solutions for continuous GPS (cGPS) stations distributed in eastern Ontario and western Québec provide constraints on the regional three-dimensional crustal velocity field. Five years of continuous observations at fourteen cGPS sites were analyzed using Bernese GPS processing software. Several different sub-networks were chosen from these stations, and the data were processed and compared to in order to select the optimal configuration to accurately estimate the vertical and horizontal station velocities and minimize the associated errors. The coordinate time series were then compared to the crustal motions from global solutions and the optimized solution is presented here. A noise analysis model with power-law and white noise, which best describes the noise characteristics of all three components, was employed for the GPS time series analysis. The linear trend, associated uncertainties, and the spectral index of the power-law noise were calculated using a maximum likelihood estimation approach. The residual horizontal velocities, after removal of rigid plate motion, have a magnitude consistent with expected glacial isostatic adjustment (GIA). The vertical velocities increase from subsidence of almost 1.9 mm/year south of the Great Lakes to uplift near Hudson Bay, where the highest rate is approximately 10.9 mm/year. The residual horizontal velocities range from approximately 0.5 mm/year, oriented south-southeastward, at the Great Lakes to nearly 1.5 mm/year directed toward the interior of Hudson Bay at stations adjacent to its shoreline. Here, the velocity uncertainties are estimated at less than 0.6 mm/year for the horizontal component and 1.1 mm/year for the vertical component. A comparison between the observed velocities and GIA model predictions, for a limited range of Earth models, shows a better fit to the observations for the Earth model with the smallest upper mantle viscosity and the largest lower mantle viscosity. However, the pattern of horizontal deformation is not well explained in the north, along Hudson Bay, suggesting that revisions to the ice thickness history are needed to improve the fit to observations.

Modeling of Wave Propagation in the Osaka Sedimentary Basin during the 2013 Awaji Island Earthquake (Mw5.8)

NASA Astrophysics Data System (ADS)

Asano, K.; Sekiguchi, H.; Iwata, T.; Yoshimi, M.; Hayashida, T.; Saomoto, H.; Horikawa, H.

2013-12-01

The three-dimensional velocity structure model for the Osaka sedimentary basin, southwest Japan is developed and improved based on many kinds of geophysical explorations for decades (e.g., Kagawa et al., 1993; Horikawa et al., 2003; Iwata et al., 2008). Recently, our project (Sekiguchi et al., 2013) developed a new three-dimensional velocity model for strong motion prediction of the Uemachi fault earthquake in the Osaka basin considering both geophysical and geological information by adding newly obtained exploration data such as reflection surveys, microtremor surveys, and receiver function analysis (hereafter we call UMC2013 model) . On April 13, 2013, an inland earthquake of Mw5.8 occurred in Awaji Island, which is close to the southwestern boundary of the aftershock area of the 1995 Kobe earthquake. The strong ground motions are densely observed at more than 100 stations in the basin. The ground motion lasted longer than four minutes in the Osaka urban area where its bedrock depth is about 1-2 km. This long-duration ground motions are mainly due to the surface waves excited in this sedimentary basin whereas the magnitude of this earthquake is moderate and the rupture duration is expected to be less than 5 s. In this study, we modeled long-period (more than 2s) ground motions during this earthquake to check the performance of the present UMC2013 model and to obtain a better constraint on the attenuation factor of sedimentary part of the basin. The seismic wave propagation in the region including the source and the Osaka basin is modeled by the finite difference method using the staggered grid solving the elasto-dynamic equations. The domain of 90km×85km×25.5km is modeled and discretized with a grid spacing of 50 m. Since the minimum S-wave velocity of the UMC2013 model is about 250 m/s, this calculation is valid up to the period of about 1 s. The effect of attenuation is included in the form of Q(f)=Q0(T0/T) proposed by Graves (1996). A PML is implemented in the side and bottom of the domain. It is parallelized by the MPI and OpenMP. We computed for 120000 steps with a time step of 0.0025 s, which equals to 300s from the origin time. The source is represented by a point source having the focal mechanism determined by the F-net, NIED and the duration of its source time function is set to 3.1s referring to the waveform fitting at the rock stations outside the basin. In the previous studies for the Osaka basin (Horikawa et al., 2003; Kawabe and Kamae, 2006; Iwaki and Iwata, 2011), Q0 at a reference period T0 is given by a function of S-wave velocity; Q0=αVs. We fixed T0 at 5s, and tested Q0 value changing α from 0.1 to 1.0. Comparing the envelope of synthetic velocity waveforms with that of observed waveforms in the basin, α of 0.3 fits to the observation well, whereas the difference from 0.2 to 0.5 is not significant. The simulation explains the characteristics of observed seismic waves propagating inside the basin in terms of duration and amplitude at most stations. The response velocity spectra and dominant period would be demonstrated to see the areal performance of present velocity model (UMC2013), and we will discuss how later phases generates and propagates based on the simulated wave field. Acknowledgements: We used strong motion data from K-NET/KiK-net, JMA, Osaka Prefectural Government, BRI, and CEORKA.

Simulation and analysis of a proposed replacement for the McCook port of entry inspection station

DOT National Transportation Integrated Search

1999-04-01

This report describes a study of a proposed replacement for the McCook Port of Entry inspection station at the entry to South Dakota. In order to assess the potential for a low-speed weigh in motion (WIM) scale within the station to pre-screen trucks...

Ground motion attenuation during M 7.1 Darfield and M 6.2 Christchurch, New Zealand, earthquakes and performance of global Ppedictive models

USGS Publications Warehouse

Segou, Margaret; Kalkan, Erol

2011-01-01

The M 7.1 Darfield earthquake occurred 40 km west of Christchurch (New Zealand) on 4 September 2010. Six months after, the city was struck again with an M 6.2 event on 22 February local time (21 February UTC). These events resulted in significant damage to infrastructure in the city and its suburbs. The purpose of this study is to evaluate the performance of global predictive models (GMPEs) using the strong motion data obtained from these two events to improve future seismic hazard assessment and building code provisions for the Canterbury region.The Canterbury region is located on the boundary between the Pacific and Australian plates; its surface expression is the active right lateral Alpine fault (Berryman et al. 1993). Beneath the North Island and the north South Island, the Pacific plate subducts obliquely under the Australian plate, while at the southwestern part of the South Island, a reverse process takes place. Although New Zealand has experienced several major earthquakes in the past as a result of its complex seismotectonic environment (e.g., M 7.1 1888 North Canterbury, M 7.0 1929 Arthur's Pass, and M 6.2 1995 Cass), there was no evidence of prior seismic activity in Christchurch and its surroundings before the September event. The Darfield and Christchurch earthquakes occurred along the previously unmapped Greendale fault in the Canterbury basin, which is covered by Quaternary alluvial deposits (Forsyth et al. 2008). In Figure 1, site conditions of the Canterbury epicentral area are depicted on a VS30 map. This map was determined on the basis of topographic slope calculated from a 1-km grid using the method of Allen and Wald (2007). Also shown are the locations of strong motion stations.The Darfield event was generated as a result of a complex rupture mechanism; the recordings and geodetic data reveal that earthquake consists of three sub-events (Barnhart et al. 2011, page 815 of this issue). The first event was due to rupturing of a blind reverse fault with M 6.2, followed by a second event (M 6.9), releasing the largest portion of the energy on the right-lateral Greendale fault. The third sub-event (M 5.7) is due to a reverse fault with a right-lateral component (Holden et al. 2011). The Christchurch earthquake occurred on an oblique thrust fault. The comparison of spectral acceleration values at stations near Christchurch reveals that the second event produced much larger amplitudes of shaking than the Darfield event due to its proximity to the epicenter. Both events resulted in noticeably large amplitudes of the vertical motion, often exceeding horizontal motion in the near-fault area. The vertical motions, showing asymmetric acceleration traces and pulses, reached 1.26 g during the Darfield earthquake and 2.2 g during the Christchurch event. These events were recorded by more than 100 strong motion stations operated by the Institute of Geological and Nuclear Sciences (http://www.geonet.org.nz/). Using the processed data from these stations, peak ground acceleration (PGA) and 5%-damped spectral acceleration values at 0.3, 1, and 3 s are used for performance evaluation of the global ground motion predictive equations (GMPEs). The selected GMPEs are the Next Generation Attenuation (NGA) models of Abrahamson and Silva (2008), Boore and Atkinson (2008), Campbell and Bozorgnia (2008), and Chiou and Youngs (2008). The Graizer and Kalkan (2007, 2009) model, which is based on the NGA project database, is also included. These GMPEs are abbreviated respectively as AS08, BA08, CB08, CY08, and GK07. Because they have been used widely for seismic hazard analysis for crustal earthquakes, their performance assessment becomes a critical issue especially for immediate response and recovery planning after major events. The occurrence of aftershocks similar to the Christchurch event will most probably control seismic hazard in the broader area, as confirmed by the recent M 6.0 event on June 13, 2011.

On the impact of reducing global geophysical fluid model deformations in SLR data processing

NASA Astrophysics Data System (ADS)

Weigelt, Matthias; Thaller, Daniela

2016-04-01

Mass redistributions in the atmosphere, oceans and the continental hydrology cause elastic loading deformations of the Earth's crust and thus systematically influence Earth-bound observation systems such as VLBI, GNSS or SLR. Causing non-linear station variations, these loading deformations have a direct impact on the estimated station coordinates and an indirect impact on other parameters of global space-geodetic solutions, e.g. Earth orientation parameters, geocenter coordinates, satellite orbits or troposphere parameters. Generally, the impact can be mitigated by co-parameterisation or by reducing deformations derived from global geophysical fluid models. Here, we focus on the latter approach. A number of data sets modelling the (non-tidal) loading deformations are generated by various groups. They show regionally and locally significant differences and consequently the impact on the space-geodetic solutions heavily depends on the available network geometry. We present and discuss the differences between these models and choose SLR as the speace-geodetic technique of interest in order to discuss the impact of atmospheric, oceanic and hydrological loading on the parameters of space-geodetic solutions when correcting for the global geophysical fluid models at the observation level. Special emphasis is given to a consistent usage of models for geometric and gravimetric corrections during the data processing. We quantify the impact of the different deformation models on the station coordinates and discuss the improvement in the Earth orientation parameters and the geocenter motion. We also show that a significant reduction in the RMS of the station coordinates can be achieved depending on the model of choice.

Strong Ground Motion Generation during the 2011 Tohoku-Oki Earthquake

NASA Astrophysics Data System (ADS)

Asano, K.; Iwata, T.

2011-12-01

Strong ground motions during the 2011 Tohoku-Oki earthquake (Mw9.0) were densely observed by the strong motion observation networks all over Japan. Seeing the acceleration and velocity waveforms observed at strong stations in northeast Japan along the source region, those ground motions are characterized by plural wave packets with duration of about twenty seconds. Particularly, two wave packets separated by about fifty seconds could be found on the records in the northern part of the damaged area, whereas only one significant wave packets could be recognized on the records in the southern part of the damaged area. The record section shows four isolated wave packets propagating from different locations to north and south, and it gives us a hint of the strong motion generation process on the source fault which is related to the heterogeneous rupture process in the scale of tens of kilometers. In order to solve it, we assume that each isolated wave packet is contributed by the corresponding strong motion generation area (SMGA). It is a source patch whose slip velocity is larger than off the area (Miyake et al., 2003). That is, the source model of the 2011 Tohoku-Oki earthquake consists of four SMGAs. The SMGA source model has succeeded in reproducing broadband strong ground motions for past subduction-zone events (e.g., Suzuki and Iwata, 2007). The target frequency range is set to be 0.1-10 Hz in this study as this range is significantly related to seismic damage generation to general man-made structures. First, we identified the rupture starting points of each SMGA by picking up the onset of individual packets. The source fault plane is set following the GCMT solution. The first two SMGAs were located approximately 70 km and 30 km west of the hypocenter. The third and forth SMGAs were located approximately 160 km and 230 km southwest of the hypocenter. Then, the model parameters (size, rise time, stress drop, rupture velocity, rupture propagation pattern) of these four SMGAs were determined by waveform modeling using the empirical Green's function method (Irikura, 1986). The first and second SMGAs are located close to each other, and they are partially overlapped though the difference in the rupture time between them is more than 40 s. Those two SMGA appear to be included in the source region of the past repeating Miyagi-Oki subduction-zone event in 1936. The third and fourth SMGAs appear to be located in the source region of the past Fukushima-Oki events in 1938. Each of Those regions has been expected to cause next major earthquakes in the long-term evaluation. The obtained source model explains the acceleration, velocity, and displacement time histories in the target frequency range at most stations well. All of four SMGAs exist apparently outside of the large slip area along the trench east of the hypocenter, which was estimated by the seismic, geodetic, and tsunami inversion analyses, and this large slip zone near the trench does not contribute to strong motion much. At this point, we can conclude that the 2011 Tohoku-Oki earthquake has a possibility to be a complex event rupturing multiple preexisting asperities in terms of strong ground motion generation. It should be helpful to validate and improve the applicability of the strong motion prediction recipe for great subduction-zone earthquakes.

Microseismicity of Blawan hydrothermal complex, Bondowoso, East Java, Indonesia

NASA Astrophysics Data System (ADS)

Maryanto, S.

2018-03-01

Peak Ground Acceleration (PGA), hypocentre, and epicentre of Blawan hydrothermal complex have been analysed in order to investigate its seismicity. PGA has been determined based on Fukushima-Tanaka method and the source location of microseismic estimated using particle motion method. PGA ranged between 0.095-0.323 g and tends to be higher in the formation that containing not compacted rocks. The seismic vulnerability index region indicated that the zone with high PGA also has a high seismic vulnerability index. This was because the rocks making up these zones were inclined soft and low-density rocks. For seismic sources around the area, epicentre and hypocentre, have estimated base on seismic particle motion method of single station. The stations used in this study were mobile stations identified as BL01, BL02, BL03, BL05, BL06, BL07 and BL08. The results of the analysis particle motion obtained 44 points epicentre and the depth of the sources about 15 – 110 meters below ground surface.

Simulation of broadband ground motion including nonlinear soil effects for a magnitude 6.5 earthquake on the Seattle fault, Seattle, Washington

USGS Publications Warehouse

Hartzell, S.; Leeds, A.; Frankel, A.; Williams, R.A.; Odum, J.; Stephenson, W.; Silva, W.

2002-01-01

The Seattle fault poses a significant seismic hazard to the city of Seattle, Washington. A hybrid, low-frequency, high-frequency method is used to calculate broadband (0-20 Hz) ground-motion time histories for a M 6.5 earthquake on the Seattle fault. Low frequencies (1 Hz) are calculated by a stochastic method that uses a fractal subevent size distribution to give an ω-2 displacement spectrum. Time histories are calculated for a grid of stations and then corrected for the local site response using a classification scheme based on the surficial geology. Average shear-wave velocity profiles are developed for six surficial geologic units: artificial fill, modified land, Esperance sand, Lawton clay, till, and Tertiary sandstone. These profiles together with other soil parameters are used to compare linear, equivalent-linear, and nonlinear predictions of ground motion in the frequency band 0-15 Hz. Linear site-response corrections are found to yield unreasonably large ground motions. Equivalent-linear and nonlinear calculations give peak values similar to the 1994 Northridge, California, earthquake and those predicted by regression relationships. Ground-motion variance is estimated for (1) randomization of the velocity profiles, (2) variation in source parameters, and (3) choice of nonlinear model. Within the limits of the models tested, the results are found to be most sensitive to the nonlinear model and soil parameters, notably the over consolidation ratio.

Thermal analysis of HGFQ using FIDAP(trademark): Solidification front motion

NASA Technical Reports Server (NTRS)

Woodbury, Keith A.

1996-01-01

The High Gradient Furnace with Quench (HGFQ) is being designed by NASA/MSFC for flight on the International Space Station. The furnace is being designed specifically for solidification experiments in metal and metallic alloy systems. The HGFQ Product development Team (PDT) has been active since January 1994 and their effort is now in early Phase B. Thermal models have been developed both by NASA and Sverdrup (support contractor) to assist in the HGFQ design effort. Both these models use SINDA as a solution engine, but the NASA model was developed using PATRAN and includes more detail than the Sverdrup model. These models have been used to guide design decisions and have been validated through experimentation on a prototypical 'Breadboard' furnace at MSFC. One facet of the furnace operation of interest to the designers is the sensitivity of the solidification interface location to changes in the furnace setpoint. Specifically of interest is the motion (position and velocity) of the solidification front due to a small perturbation in the furnace temperature. FIDAP(TM) is a commercially available finite element program for analysis of heat transfer and fluid flow processes. Its strength is in solution of the Navier-Stokes equations for incompressible flow, but among its capabilities is the analysis of transient processes involving radiation and solidification. The models presently available from NASA and Sverdrup are steady-state models and are incapable of computing the motion of the solidification front. The objective of this investigation is to use FIDAP(TM) to compute the motion of the solidification interface due to a perturbation in the furnace setpoint.

Observational evidences of viscoelastic behaviour at low strain

NASA Astrophysics Data System (ADS)

Daminelli, Rosastella; Marcellini, Alberto; Tento, Alberto

2014-05-01

Theoretical formulations of inhomogeneous waves in low-loss media have been suggested by a number of researchers due to the important role played by anelasticity in changing the characteristics of seismic waves. The Homogeneous Isotropic Linear Viscoelastic Model (HILV) introduced by Borcherdt (2009) is particularly promising because of its mathematical simplicity and the handiness to test the model in real seismograms. We showed that the seismograms of the explosion of a 2nd World War bomb found in Milan recorded by a seismic station at 2 km epicentral distance, exhibit a clear elliptical prograde P wave particle motion (Marcellini and Tento, 2011) as predicted by HILV. We observed a similar P wave prograde elliptical motion analysing a ML 4.8 earthquake occurred on July 17, 2011 in the Po Valley at a 48 km epicentral distance from a seismic station located at Palazzo Te, Mantova (Daminelli et al., 2013). In both cases the stations were situated on the deep quaternary sediments of the Po Valley. Based on measured Vp and Vs and the amplitude of the recorded motion, the strain at the station sites was estimated to be 10-6, 10-7. In this paper we extend the analysis of the previously mentioned seismograms to check the feasibility of HILV application to other types of waves that are particularly relevant in fields such as the engineering seismology. We focus on the S waves (as it is well known HILV predicts the split of S in S type I and S type II) of the seismograms of the earthquake recorded in Mantova and on the Rayleigh waves of the explosion recorded in Milan. The results show that observational evidences of HILV are not as clear as for P waves, probably because of noise or superposition of converted waves. However, once established the validity of HILV by P waves (that is very simple), the whole seismograms can be interpreted following HILV, confirming the relevancy of anelasticity also at low strain. Borcherdt, R.D. (2009) 'Viscoelastic Waves in Layered Media', Cambridge University Press, 328 pp. Marcellini, A. and A. Tento (2011) 'Explosive Sources Prove the Validity of Homogeneous Isotropic Linear Viscoelastic Models', BSSA, Vol. 101, No. 4, pp. 1576-1583. Daminelli R., A. Tento, A. Marcellini (2013) "A Split of Direction of Propagation and Attenuation of P Waves in the Po Valley". Abstract S31C-2361, AGU Fall Meeting, San Francisco, CA, 9-13 December 2013.

Investigation of Slosh Dynamics on Flight and Ground Platforms

NASA Astrophysics Data System (ADS)

Vergalla, Michael; Zhou, Ran

The slosh dynamics in cryogenic fuel tanks under microgravity is a problem that severely affects the reliability of spacecraft launching. To investigate slosh dynamics and their effects on space vehicle dynamics three levels of testing are presently in progress. Platforms include a 3-DOF ground testing table, parabolic flights, sounding rockets and finally the International Space Station. Ground tests provide an economically viable platform for investigating rotational, translational, and coupled feed-back modes due to repeatable CNC motions. The parabolic flight campaign has conducted four successful flights aboard multiple aircraft using static and tethered slosh packages. Using the PANTHER II student designed rocket, a slosh package was launched as a payload. Finally with collaboration between Florida Institute of Technology and Massachusetts Institute of Technology SPHERES project, two test sessions investigating feedback using partially and fully filled propellant tanks have been completed aboard the In-ternational Space Station. Motion data from all tests will be input to in house Dynamic Mesh Model to further establish confidence in the versatility and accuracy of the method. The results show that it is necessary to construct additional hardware for slosh studies.

A formulation of directivity for earthquake sources using isochrone theory

USGS Publications Warehouse

Spudich, Paul; Chiou, Brian S.J.; Graves, Robert; Collins, Nancy; Somerville, Paul

2004-01-01

A functional form for directivity effects can be derived from isochrone theory, in which the measure of the directivity-induced amplification of an S body wave is c, the isochrone velocity. Ground displacement of the near-, intermediate-, and far-field terms of P and S waves is linear in isochrone velocity for a finite source in a whole space. We have developed an approximation c-tilde-prime of isochrone velocity that can easily be implemented as a predictor of directivity effects in empirical ground motion prediction relations. Typically, for a given fault surface, hypocenter, and site geometry, c-tilde-prime is a simple function of the hypocentral distance, the rupture distance, the crustal shear wave speed in the seismogenic zone, and the rupture velocity. c-tilde-prime typically ranges in the interval 0.44, for rupture away from the station, to about 4, for rupture toward the station. In this version of the theory directivity is independent of period. Additionally, we have created another functional form which is c-tilde-prime modified to include the approximate radiation pattern of a finite fault having a given rake. This functional form can be used to model the spatial variations of fault-parallel and fault-normal horizontal ground motions. The strengths of this formulation are 1) the proposed functional form is based on theory, 2) the predictor is unambiguously defined for all possible site locations and source rakes, and 3) it can easily be implemented for well-studied important previous earthquakes. We compare predictions of our functional form with synthetic ground motions calculated for finite strike-slip and dip-slip faults in the magnitude range 6.5 - 7.5. In general our functional form correlates best with computed fault-normal and fault-parallel motions in the synthetic motions calculated for events with M6.5. Correlation degrades but is still useful for larger events and for the geometric average horizontal motions. We have had limited success applying it to geometrically complicated faults.

Along-Arc and Back-Arc Attenuation, Site Response, and Source Spectrum for the Intermediate-Depth 8 January 2006 M 6.7 Kythera, Greece, Earthquake

USGS Publications Warehouse

Boore, David M.; Skarlatoudis, A.A.; Margaris, B.N.; Costas, B.P.; Ventouzi, C.

2009-01-01

An M 6.7 intermediate-depth (66 km), in-slab earthquake occurring near the island of Kythera in Greece on 8 January 2006 was well recorded on networks of stations equipped with acceleration sensors and with broadband velocity sensors. All data were recorded digitally using recording instruments with resolutions ranging from almost 11 to 24 bits. We use data from these networks to study the distance dependence of the horizontal-component Fourier acceleration spectra (FAS) and horizontal-component pseudoabsolute response spectral acceleration (PSA). For purposes of simulating motions in the future, we parameterize the distance decay using several forms of the geometrical-spreading function, for each of which we derive Q as a function of frequency. By extrapolating the distance decay back to 1 km, we obtain a reference spectrum that can be used in future simulations. This spectrum requires a more complicated spectral shape than the classic single-corner-frequency model; in particular, there appears to be an enhancement of motion around 0.2-0.3 Hz that may be due to the radiation of a 3-5 sec pulse from the source. We infer a ??0 value of about 0.055 sec for rock stations and a stress parameter in the range of 400-600 bars. We also find distinctive differences in the site response of stations on soft soil and soil; both the FAS and the 5% damped PSA amplifications have similar peak amplitudes (about 2 and 4 for soil and soft-soil sites, respectively, relative to the rock sites) at similar frequencies (between about 0.4 and 2.0 Hz, with the soft-soil amplifications peaking at somewhat lower frequencies than the soil amplifications). One of the most distinctive features of the data is the clear difference in the motions for along-arc and back-arc stations, with the former being significantly higher than the latter over a broad range of frequencies at distances beyond about 250 km. The motions from the Kythera earthquake are roughly comparable to those from intermediate-depth earthquakes elsewhere, but they appear to be significantly higher than those from recordings of shallow earthquakes in Greece of comparable magnitude and hypocentral distance.

Microplate model for the present-day deformation of Tibet

USGS Publications Warehouse

Thatcher, W.

2007-01-01

Site velocities from 349 Global Positioning System (GPS) stations are used to construct an 11-element quasi-rigid block model of the Tibetan Plateau and its surroundings. Rigid rotations of five major blocks are well determined, and average translation velocities of six smaller blocks can be constrained. Where data are well distributed the velocity field can be explained well by rigid block motion and fault slip across block boundaries. Residual misfits average 1.6 mm/yr compared to typical one standard deviation velocity uncertainties of 1.3 mm/yr. Any residual internal straining of the blocks is small and heterogeneous. However, residual substructure might well represent currently unresolved motions of smaller blocks. Although any smaller blocks must move at nearly the same rate as the larger blocks within which they lie, undetected relative motions between them could be significant, particularly where there are gaps in GPS coverage. Predicted relative motions between major blocks agree with the observed sense of slip and along-strike partitioning of motion across major faults. However, predicted slip rates across Tibet's major strike-slip faults are low, only 5-12 mm/yr, a factor of 2-3 smaller than most rates estimated from fault offset features dated by radiometric methods as ???2000 to ???100,000 year old. Previous work has suggested that both GPS data and low fault slip rates are incompatible with rigid block motions of Tibet. The results reported here overcome these objections.

Acceleration and volumetric strain generated by the Parkfield 2004 earthquake on the GEOS strong-motion array near Parkfield, California

USGS Publications Warehouse

Borcherdt, Rodger D.; Johnston, Malcolm J.S.; Dietel, Christopher; Glassmoyer, Gary; Myren, Doug; Stephens, Christopher

2004-01-01

An integrated array of 11 General Earthquake Observation System (GEOS) stations installed near Parkfield, CA provided on scale broad-band, wide-dynamic measurements of acceleration and volumetric strain of the Parkfield earthquake (M 6.0) of September 28, 2004. Three component measurements of acceleration were obtained at each of the stations. Measurements of collocated acceleration and volumetric strain were obtained at four of the stations. Measurements of velocity at most sites were on scale only for the initial P-wave arrival. When considered in the context of the extensive set of strong-motion recordings obtained on more than 40 analog stations by the California Strong-Motion Instrumentation Program (Shakal, et al., 2004 http://www.quake.ca.gov/cisn-edc) and those on the dense array of Spudich, et al, (1988), these recordings provide an unprecedented document of the nature of the near source strong motion generated by a M 6.0 earthquake. The data set reported herein provides the most extensive set of near field broad band wide dynamic range measurements of acceleration and volumetric strain for an earthquake as large as M 6 of which the authors are aware. As a result considerable interest has been expressed in these data. This report is intended to describe the data and facilitate its use to resolve a number of scientific and engineering questions concerning earthquake rupture processes and resultant near field motions and strains. This report provides a description of the array, its scientific objectives and the strong-motion recordings obtained of the main shock. The report provides copies of the uncorrected and corrected data. Copies of the inferred velocities, displacements, and Psuedo velocity response spectra are provided. Digital versions of these recordings are accessible with information available through the internet at several locations: the National Strong-Motion Program web site (http://agram.wr.usgs.gov/), the COSMOS Virtual Data Center Web site (http://www.cosmos-eq.org), and the CISN Engineering and Berkeley data centers (http://www.quake.ca.gov/cisn-edc). They are also accessible together with recordings on the GEOS Strong-motion Array near Parkfield, CA since its installation in 1987 through the USGS GEOS web site ( http://nsmp.wr.usgs.gov/GEOS).

Measurement of horizontal motions in Alaska using very long baseline interferometry

NASA Technical Reports Server (NTRS)

Ma, C.; Sauber, J. M.; Clark, T. A.; Ryan, J. W.; Bell, L. J.; Gordon, D.; Himwich, W. E.

1990-01-01

Results are presented on an analysis of VLBI measurements performed between 1984 and 1990 by means of a network of 53 sites in Alaska, the Yukon Territory, and the conterminous United States to determine the extent of horizontal motions in Alaska. Results are presented in two ways, one showing the evolution of individual baselines and the other yielding site velocities; both approaches use VLBI data from other permanent stations in order to define a global reference frame. It was found that VLBI sites within the Alaska-Aleutian subduction boundary zone (Yakataga, Kodiak, and Sand Point) had higher instantaneous velocities relative to eastern North America than the interior sites of Alaska. The results of Yakataga data modeling suggests that the observed motion is the result of elastic straining of the overriding plate due to a locked main thrust zone with a component of oblique slip.

Glacial isostatic crustal uplift in southern Victoria Land, Antarctica, from geologic and geodetic records

NASA Astrophysics Data System (ADS)

Konfal, S.; Wilson, T.; Bevis, M. G.; Kendrick, E. C.; Hall, B. L.

2011-12-01

Geologic records and geodetic measurements of glacial isostatic crustal motions are presented from the southern Victoria Land region of Antarctica. In much of the world, key records used for mapping and modeling glacial isostatic crustal motions come from raised paleoshorelines and beaches of ice-marginal lakes and seas. While such records are scarce in Antarctica, preserved paleoshorelines are present in the southern Victoria Land region of Antarctica. Light detection and ranging (LiDAR) data coverages of these features were acquired during the 2001-2002 austral summer field season by NASA's Airborne Topographic Mapper (ATM) system, resulting in 2 meter horizontal resolution digital elevation models (DEMs). This study utilizes these DEM data to derive crustal tilt values from observed changes in elevation along the length of the shorelines. Radiocarbon age data are correlated with the associated degree of shoreline tilt to derive a rate of crustal deformation since deglaciation. Modern rates of glacial isostatic crustal motion are derived from GPS stations in the same region. Campaign station occupation began in 1996-1997 under the TAMDEF (Transantarctic Mountain DEFormation Network) project, and continuous GPS data collected began in 1999 and continues under the ANET/POLENET (Antarctica Polar Earth Observing Network) project, enabling analysis of decadal scale time series. Integrated gradient curves from paleoshoreline records and GPS crustal velocities show exponential form and indicate tilting down to the east. Eastward tilt may be the result of substantial loss of East Antarctic ice, a collapsing forebulge linked to ice centers in the Ross Sea region or in interior West Antarctica, or differences in earth response due to laterally varying earth structure. Modeling of these new data, along with comparison of tilt directions to centers of ice mass loss, provide tests of these scenarios and yield new insights into earth models and ice history.

Designing an Ergonomically Correct CNC Workstation on a Shoe String Budget.

ERIC Educational Resources Information Center

Lightner, Stan

2001-01-01

Describes research to design and construct ergonomically correct work stations for Computer Numerical Control machine tools. By designing ergonomically correct work stations, industrial technology teachers help protect students from repetitive motion injuries. (Contains 12 references.) (JOW)

Ukrainian network of Optical Stations for man-made space objects observation

NASA Astrophysics Data System (ADS)

Sybiryakova, Yevgeniya

2016-07-01

The Ukrainian Network of Optical Stations (UNOS) for man-made objects research was founded in 2012 as an association of professional astronomers. The main goals of network are: positional and photometric observations of man-made space objects, calculation of orbital elements, research of shape and period of rotation. The network consists of 8 stations: Kiev, Nikolaev, Odesa, Uzhgorod, Lviv, Yevpatoriya, Alchevsk. UNOS has 12 telescopes for observation of man-made space objects. The new original methods of positional observation were developed for optical observation of geosynchronous and low earth orbit satellites. The observational campaigns of LEO satellites held in the network every year. The numerical model of space object motion, developed in UNOS, is using for orbit calculation. The results of orbital elements calculation are represented on the UNOS web-site http://umos.mao.kiev.ua/eng/. The photometric observation of selected objects is also carried out in network.

Space station dynamics, attitude control and momentum management

NASA Technical Reports Server (NTRS)

Sunkel, John W.; Singh, Ramen P.; Vengopal, Ravi

1989-01-01

The Space Station Attitude Control System software test-bed provides a rigorous environment for the design, development and functional verification of GN and C algorithms and software. The approach taken for the simulation of the vehicle dynamics and environmental models using a computationally efficient algorithm is discussed. The simulation includes capabilities for docking/berthing dynamics, prescribed motion dynamics associated with the Mobile Remote Manipulator System (MRMS) and microgravity disturbances. The vehicle dynamics module interfaces with the test-bed through the central Communicator facility which is in turn driven by the Station Control Simulator (SCS) Executive. The Communicator addresses issues such as the interface between the discrete flight software and the continuous vehicle dynamics, and multi-programming aspects such as the complex flow of control in real-time programs. Combined with the flight software and redundancy management modules, the facility provides a flexible, user-oriented simulation platform.

Knowledge-based vision for space station object motion detection, recognition, and tracking

NASA Technical Reports Server (NTRS)

Symosek, P.; Panda, D.; Yalamanchili, S.; Wehner, W., III

1987-01-01

Computer vision, especially color image analysis and understanding, has much to offer in the area of the automation of Space Station tasks such as construction, satellite servicing, rendezvous and proximity operations, inspection, experiment monitoring, data management and training. Knowledge-based techniques improve the performance of vision algorithms for unstructured environments because of their ability to deal with imprecise a priori information or inaccurately estimated feature data and still produce useful results. Conventional techniques using statistical and purely model-based approaches lack flexibility in dealing with the variabilities anticipated in the unstructured viewing environment of space. Algorithms developed under NASA sponsorship for Space Station applications to demonstrate the value of a hypothesized architecture for a Video Image Processor (VIP) are presented. Approaches to the enhancement of the performance of these algorithms with knowledge-based techniques and the potential for deployment of highly-parallel multi-processor systems for these algorithms are discussed.

Strong motions observed by K-NET and KiK-net during the 2016 Kumamoto earthquake sequence

NASA Astrophysics Data System (ADS)

Suzuki, Wataru; Aoi, Shin; Kunugi, Takashi; Kubo, Hisahiko; Morikawa, Nobuyuki; Nakamura, Hiromitsu; Kimura, Takeshi; Fujiwara, Hiroyuki

2017-01-01

The nationwide strong-motion seismograph network of K-NET and KiK-net in Japan successfully recorded the strong ground motions of the 2016 Kumamoto earthquake sequence, which show the several notable characteristics. For the first large earthquake with a JMA magnitude of 6.5 (21:26, April 14, 2016, JST), the large strong motions are concentrated near the epicenter and the strong-motion attenuations are well predicted by the empirical relation for crustal earthquakes with a moment magnitude of 6.1. For the largest earthquake of the sequence with a JMA magnitude of 7.3 (01:25, April 16, 2016, JST), the large peak ground accelerations and velocities extend from the epicentral area to the northeast direction. The attenuation feature of peak ground accelerations generally follows the empirical relation, whereas that for velocities deviates from the empirical relation for stations with the epicentral distance of greater than 200 km, which can be attributed to the large Love wave having a dominant period around 10 s. The large accelerations were observed at stations even in Oita region, more than 70 km northeast from the epicenter. They are attributed to the local induced earthquake in Oita region, whose moment magnitude is estimated to be 5.5 by matching the amplitudes of the corresponding phases with the empirical attenuation relation. The real-time strong-motion observation has a potential for contributing to the mitigation of the ongoing earthquake disasters. We test a methodology to forecast the regions to be exposed to the large shaking in real time, which has been developed based on the fact that the neighboring stations are already shaken, for the largest event of the Kumamoto earthquakes, and demonstrate that it is simple but effective to quickly make warning. We also shows that the interpolation of the strong motions in real time is feasible, which will be utilized for the real-time forecast of ground motions based on the observed shakings.[Figure not available: see fulltext.

Assessment of the Water Levels and Currents at the Mississippi Bight During Hurricane Katrina.

NASA Astrophysics Data System (ADS)

Nwankwo, U. C.; Howden, S. D.; Dodd, D.; Wells, D. E.

2017-12-01

In an effort to extend the length of GPS baselines further offshore, the Hydrographic Science Research Center at the University of Southern Mississippi deployed a buoy which had a survey grade GPS receiver, an ADPC and a motion sensor unit in the Mississippi Bight in late 2004. The GPS data were initially processed using the Post Processed Kinematic technique with data from a nearby GPS base station on Horn Island. This processing technique discontinued when the storm (Hurricane Katrina) destroyed the base station in late August of 2005. However, since then a stand-alone positioning technique termed Precise Point Positioning (PPP) matured and allowed for the reprocessing of the buoy GPS data throughout Katrina. The processed GPS data were corrected for buoy angular motions using Tait Bryan transformation model. Tidal datums (Epoch 1983-2001) were transferred from the National Oceanic and Atmospheric Administration (NOAA) National Water Level at Waveland, Mississippi (Station ID 8747766) to the buoy using the Modified Range Ratio method. The maximum water level during the storm was found to be about 3.578m, relative to the transferred Mean Sea Level datum. The storm surge built over more than 24 hours, but fell back to normal levels in less than 3 hours. The maximum speed of the current with respect to the seafloor was recorded to be about 4knots towards the southeast as the storm surge moved back offshore.

GPS and Relative Sea-level Constraints on Glacial Isostatic Adjustment in North America

NASA Astrophysics Data System (ADS)

James, T. S.; Simon, K.; Henton, J. A.; Craymer, M.

2015-12-01

Recently, new GIA models have been developed for the Innuitian Ice Sheet and for the north-central portion of the Laurentide Ice Sheet (Simon, 2014; Simon et al., 2015). This new combined model, herein called Innu-Laur15, was developed from the ICE-5G model and load adjustments were made to improve the fit to relative sea-level observations and to GPS-constrained vertical crustal motion in the Canadian Arctic Archipelago and around Hudson Bay. Here, the predictions of Innu-Laur15 are compared to observations and other GIA models over an extended region comprising much of North America east of the Rocky Mountains. GIA predictions are made using compressible Maxwell Earth models with gravitationally self-consistent ocean loading, changing coastlines, and ocean-water inundation where marine ice retreats or floats. For this study, GPS time series are the NA12 solution (Blewitt et al., 2013) downloaded from http://geodesy.unr.edu/NGLStationPages/GlobalStationList and fit with a linear trend, annual and semi-annual terms, and offsets as indicated by station logs and by inspection of the time series. For example, a comparison of GPS observations of vertical crustal motion from the NA12 solution at 360 sites gives root-mean-square (RMS) residuals of 3.2 mm/yr (null hypothesis), 1.8 mm/yr (Innu-Laur15), and 2.9 mm/yr (ICE-5G) for the VM5a Earth model. Preliminary comparisons with other Earth models give similar patterns where Innu-Laur15 provides a better fit than ICE-5G. Further adjustments to the Innu-Laur15 ice sheet history could improve the fit to GPS rates in other regions of North America.

Microgravity Investigation of Crew Reactions in 0-G (MICRO-G)

NASA Technical Reports Server (NTRS)

Newman, Dava; Coleman, Charles; Metaxas, Dimitri

2004-01-01

There is a need for a human factors, technology-based bioastronautics research effort to develop an integrated system that reduces risk and provides scientific knowledge of astronaut-induced loads and motions during long-duration missions on the International Space Station (ISS), which will lead to appropriate countermeasures. The primary objectives of the Microgravity Investigation of Crew Reactions in 0-G (MICRO-GI research effort are to quantify astronaut adaptation and movement as well as to model motor strategies for differing gravity environments. The overall goal of this research program is to improve astronaut performance and efficiency through the use of rigorous quantitative dynamic analysis, simulation and experimentation. The MICRO-G research effort provides a modular, kinetic and kinematic capability for the ISS. The collection and evaluation of kinematics (whole-body motion) and dynamics (reacting forces and torques) of astronauts within the ISS will allow for quantification of human motion and performance in weightlessness, gathering fundamental human factors information for design, scientific investigation in the field of dynamics and motor control, technological assessment of microgravity disturbances, and the design of miniaturized, real-time space systems. The proposed research effort builds on a strong foundation of successful microgravity experiments, namely, the EDLS (Enhanced Dynamics Load Sensors) flown aboard the Russian Mir space station (19961998) and the DLS (Dynamic Load Sensors) flown on Space Shuttle Mission STS-62. In addition, previously funded NASA ground-based research into sensor technology development and development of algorithms to produce three-dimensional (3-0) kinematics from video images have come to fruition and these efforts culminate in the proposed collaborative MICRO-G flight experiment. The required technology and hardware capitalize on previous sensor design, fabrication, and testing and can be flight qualified for a fraction of the cost of an initial spaceflight experiment. Four dynamic load sensors/restraints are envisioned for measurement of astronaut forces and torques. Two standard ISS video cameras record typical astronaut operations and prescribed IVA motions for 3-D kinematics. Forces and kinematics are combined for dynamic analysis of astronaut motion, exploiting the results of the detailed dynamic modeling effort for the quantitative verification of astronaut IVA performance, induced-loads, and adaptive control strategies for crewmember whole-body motion in microgravity. This comprehensive effort, provides an enhanced human factors approach based on physics-based modeling to identify adaptive performance during long-duration spaceflight, which is critically important for astronaut training as well as providing a spaceflight database to drive countermeasure design.

Enhancement of the national strong-motion network in Turkey

USGS Publications Warehouse

Gulkan, Polat; Ceken, U.; Colakoglu, Z.; Ugras, T.; Kuru, T.; Apak, A.; Anderson, J.G.; Sucuoglu, H.; Celebi, M.; Akkar, D.S.; Yazgan, U.; Denizlioglu, A.Z.

2007-01-01

Two arrays comprising 20 strong-motion sensors were established in western Turkey. The 14 stations of BYTNet follow a N-S trending line about 65 km in length, normal to strands of the North Anatolian fault that runs between the cities of Bursa and Yalova. Here the dominant character of the potential fault movement is a right-lateral transform slip. The DATNet array, comprising a total of eight stations, is arranged along a 110-km-long E-W trending direction along the Menderes River valley between Denizli and Aydin. (Two stations in this array were incorporated from the existing Turkish national strong-motion network.) This is an extensional tectonic environment, and the network mornitors potential large normal-faulting earthquakes on the faults in the valley. The installation of the arrays was supported by the North Atlantic Treaty Organization (NATO) under its Science for Peace Program. Maintenance and calibration is performed by the General Directorate of Disaster Affairs (GDDA) according to a protocol between Middle East Technical University (METU) and GDDA. Many young engineers and scientists have been trained in network operation and evaluation during the course of the project, and an international workshop dealing with strong-motion instrumentation has been organized as part of the project activities.

Radiofrequency identification: exploiting an old technology for measuring nurse time and motion.

PubMed

Jones, Terry L

2012-09-01

A national campaign is underway to increase the amount of time staff nurses spend at the bedside of hospitalized patients through redesign of the work environment. This kind of work redesign requires robust data depicting what nurses do and how they spend their time. Historically, these kinds of data have been difficult, costly, and time consuming to collect. Wireless capture of data on the movement of humans within the work environment (ie, time and motion) is now possible through radiofrequency identification technology. When small tracking devices the size of a quarter are affixed to their clothing, the movement of nurses throughout a patient care unit can be monitored. The duration and frequency of patient interaction are captured along with the duration of time spent in other locations of interest to include nurses' station, supply room, medication room, doctors' station, electronic documentation stations, family waiting rooms, and the hallway. Patterns of nurse movement and time allocation can be efficiently identified, and the effects of staffing practices, workflows, and unit layout evaluated. Integration of radiofrequency identification time and motion data with other databases enables nurse leaders to link nursing time to important cost and quality outcomes. Nurse leaders should explore the usefulness of radiofrequency identification technology in addressing data needs for nurse time and motion.

A simulation of the San Andreas fault experiment

NASA Technical Reports Server (NTRS)

Agreen, R. W.; Smith, D. E.

1973-01-01

The San Andreas Fault Experiment, which employs two laser tracking systems for measuring the relative motion of two points on opposite sides of the fault, was simulated for an eight year observation period. The two tracking stations are located near San Diego on the western side of the fault and near Quincy on the eastern side; they are roughly 900 kilometers apart. Both will simultaneously track laser reflector equipped satellites as they pass near the stations. Tracking of the Beacon Explorer C Spacecraft was simulated for these two stations during August and September for eight consecutive years. An error analysis of the recovery of the relative location of Quincy from the data was made, allowing for model errors in the mass of the earth, the gravity field, solar radiation pressure, atmospheric drag, errors in the position of the San Diego site, and laser systems range biases and noise. The results of this simulation indicate that the distance of Quincy from San Diego will be determined each year with a precision of about 10 centimeters. This figure is based on the accuracy of earth models and other parameters available in 1972.

Graphical interface between the CIRSSE testbed and CimStation software with MCS/CTOS

NASA Technical Reports Server (NTRS)

Hron, Anna B.

1992-01-01

This research is concerned with developing a graphical simulation of the testbed at the Center for Intelligent Robotic Systems for Space Exploration (CIRSSE) and the interface which allows for communication between the two. Such an interface is useful in telerobotic operations, and as a functional interaction tool for testbed users. Creating a simulated model of a real world system, generates inevitable calibration discrepancies between them. This thesis gives a brief overview of the work done to date in the area of workcell representation and communication, describes the development of the CIRSSE interface, and gives a direction for future work in the area of system calibration. The CimStation software used for development of this interface, is a highly versatile robotic workcell simulation package which has been programmed for this application with a scale graphical model of the testbed, and supporting interface menu code. A need for this tool has been identified for the reasons of path previewing, as a window on teleoperation and for calibration of simulated vs. real world models. The interface allows information (i.e., joint angles) generated by CimStation to be sent as motion goal positions to the testbed robots. An option of the interface has been established such that joint angle information generated by supporting testbed algorithms (i.e., TG, collision avoidance) can be piped through CimStation as a visual preview of the path.

Computational Prediction of Muscle Moments During ARED Squat Exercise on the International Space Station.

PubMed

Fregly, Benjamin J; Fregly, Christopher D; Kim, Brandon T

2015-12-01

Prevention of muscle atrophy caused by reduced mechanical loading in microgravity conditions remains a challenge for long-duration spaceflight. To combat leg muscle atrophy, astronauts on the International Space Station (ISS) often perform squat exercise using the Advanced Resistive Exercise Device (ARED). While the ARED is effective at building muscle strength and volume on Earth, NASA researchers do not know how closely ARED squat exercise on the ISS replicates Earth-level squat muscle moments, or how small variations in exercise form affect muscle loading. This study used dynamic simulations of ARED squat exercise on the ISS to address these two questions. A multibody dynamic model of the complete astronaut-ARED system was constructed in OpenSim. With the ARED base locked to ground and gravity set to 9.81 m/s², we validated the model by reproducing muscle moments, ground reaction forces, and foot center of pressure (CoP) positions for ARED squat exercise on Earth. With the ARED base free to move relative to the ISS and gravity set to zero, we then used the validated model to simulate ARED squat exercise on the ISS for a reference squat motion and eight altered squat motions involving changes in anterior-posterior (AP) foot or CoP position on the ARED footplate. The reference squat motion closely reproduced Earth-level muscle moments for all joints except the ankle. For the altered squat motions, changing the foot position was more effective at altering muscle moments than was changing the CoP position. All CoP adjustments introduced an undesirable shear foot reaction force that could cause the feet to slip on the ARED footplate, while some foot and CoP adjustments introduced an undesirable sagittal plane foot reaction moment that would cause the astronaut to rotate off the ARED footplate without the use of some type of foot fixation. Our results provide potentially useful information for achieving desired increases or decreases in specific muscle moments during ARED squat exercise performed on the ISS.

Shuttle mission simulator baseline definition report, volume 2

NASA Technical Reports Server (NTRS)

Dahlberg, A. W.; Small, D. E.

1973-01-01

The baseline definition report for the space shuttle mission simulator is presented. The subjects discussed are: (1) the general configurations, (2) motion base crew station, (3) instructor operator station complex, (4) display devices, (5) electromagnetic compatibility, (6) external interface equipment, (7) data conversion equipment, (8) fixed base crew station equipment, and (9) computer complex. Block diagrams of the supporting subsystems are provided.

Characteristics of strong motions and damage implications of M S6.5 Ludian earthquake on August 3, 2014

NASA Astrophysics Data System (ADS)

Xu, Peibin; Wen, Ruizhi; Wang, Hongwei; Ji, Kun; Ren, Yefei

2015-02-01

The Ludian County of Yunnan Province in southwestern China was struck by an M S6.5 earthquake on August 3, 2014, which was another destructive event following the M S8.0 Wenchuan earthquake in 2008, M S7.1 Yushu earthquake in 2010, and M S7.0 Lushan earthquake in 2013. National Strong-Motion Observation Network System of China collected 74 strong motion recordings, which the maximum peak ground acceleration recorded by the 053LLT station in Longtoushan Town was 949 cm/s2 in E-W component. The observed PGAs and spectral ordinates were compared with ground-motion prediction equation in China and the NGA-West2 developed by Pacific Earthquake Engineering Researcher Center. This earthquake is considered as the first case for testing applicability of NGA-West2 in China. Results indicate that the observed PGAs and the 5 % damped pseudo-response spectral accelerations are significantly lower than the predicted ones. The field survey around some typical strong motion stations verified that the earthquake damage was consistent with the official isoseismal by China Earthquake Administration.

Research Enabled through Eighteen Years of Geodesy Data Sharing by the UNAVCO Data Center

NASA Astrophysics Data System (ADS)

Boler, F. M.; Meertens, C. M.; Kreemer, C. W.; Blewitt, G.

2009-12-01

UNAVCO, the NSF and NASA-funded facility that supports and promotes Earth science by advancing high-precision techniques for the measurement of crustal deformation, has operated a Global Navigation Satellite System (GNSS) data archive since 1992. UNAVCO’s Data Policy includes immediate open access to data from continuous GNSS stations and open access after a 2-year embargo period for campaign data. Presently, the GNSS archive holds 3,500,000 files of data, taken principally at a large and growing globally-distributed set of permanent high precision GNSS stations. Each day on average 2,000 new files are archived and 33,000 files are distributed. The spatial and temporal resolution now available for GNSS data enables quantification of motions of the Earth’s crust at all scales with unprecedented detail and precision, leading to fundamental discoveries in plate boundary processes, continental deformation, earthquake processes, magmatic systems, and global and regional hydrological mass movements. The Plate Boundary Observatory (PBO) is the UNAVCO-operated 1100-station geodesy component of EarthScope that studies the three-dimensional strain field resulting from active plate boundary deformation across the western US. Processing of the entire set of data by the PBO Analysis Centers (MIT, New Mexico Tech and Central Washington U.) has added position time series to the open GNSS data products available from the UNAVCO Data Center. This data set forms the basis for an overarching analysis of various non-tectonic processes, such as the effect of soil moisture on multi-path. With the ultimate goal of understanding tectonic and magmatic motions, the ability to model these signals and remove them to further elucidate the tectonic signal alone is crucial. GNSS data are also leading to global strain-rate maps with unprecedented resolution, which allow an integrated description of the surface kinematics accounting for rigid plates and plate boundary zone deformation [Kreemer et al., 2003]. An important contribution to these analyses for the Great Basin is MAGNET, a 307-station array operated by the University of Nevada with 30-50 active stations per day since 2004 [Blewitt et al., 2004]. The simultaneous increase in GNSS data and analysis expertise now allows for routine global analysis of many thousands of GNSS stations. Such analysis ensures that all phase ambiguities are fixed and that common-mode errors are significantly reduced and thereby allow for increased spatial and temporal resolution for strain-rate models and other solid-earth investigations. These examples highlight two research areas where exciting advances are built upon the GNSS data available from the UNAVCO Data Center. The continued open availability of GNSS data will provide an invaluable resource for refinement of current understanding of geodesy and completely new discoveries into the future. Blewitt, G., C. Kreemer, and W.C. Hammond (2009). Geodetic observation of contemporary deformation in the northern Walker Lane: 1. Semipermanent GPS strategy, p. 1-15, doi: 10.1130/2009.2447(03). Kreemer, C., W.E. Holt, and A.J. Haines, An integrated global model of present-day plate motions and plate boundary deformation, Geophys. J. Int., 154, 8-34, 2003.

Sensitivity analysis of the GNSS derived Victoria plate motion

NASA Astrophysics Data System (ADS)

Apolinário, João; Fernandes, Rui; Bos, Machiel

2014-05-01

Fernandes et al. (2013) estimated the angular velocity of the Victoria tectonic block from geodetic data (GNSS derived velocities) only.. GNSS observations are sparse in this region and it is therefore of the utmost importance to use the available data (5 sites) in the most optimal way. Unfortunately, the existing time-series were/are affected by missing data and offsets. In addition, some time-series were close to the considered minimal threshold value to compute one reliable velocity solution: 2.5-3.0 years. In this research, we focus on the sensitivity of the derived angular velocity to changes in the data (longer data-span for some stations) by extending the used data-span: Fernandes et al. (2013) used data until September 2011. We also investigate the effect of adding other stations to the solution, which is now possible since more stations became available in the region. In addition, we study if the conventional power-law plus white noise model is indeed the best stochastic model. In this respect, we apply different noise models using HECTOR (Bos et al. (2013), which can use different noise models and estimate offsets and seasonal signals simultaneously. The seasonal signal estimation is also other important parameter, since the time-series are rather short or have large data spans at some stations, which implies that the seasonal signals still can have some effect on the estimated trends as shown by Blewitt and Lavellee (2002) and Bos et al. (2010). We also quantify the magnitude of such differences in the estimation of the secular velocity and their effect in the derived angular velocity. Concerning the offsets, we investigate how they can, detected and undetected, influence the estimated plate motion. The time of offsets has been determined by visual inspection of the time-series. The influence of undetected offsets has been done by adding small synthetic random walk signals that are too small to be detected visually but might have an effect on the estimated trend (Williams 2003, Langbein 2012). Finally, our preferable angular velocity estimation is used to evaluate the consequences on the kinematics of the Victoria block, namely the magnitude and azimuth of the relative motions with respect to the Nubia and Somalia plates and their tectonic implications. References Agnew, D. C. (2013). Realistic simulations of geodetic network data: The Fakenet package, Seismol. Res. Lett., 84 , 426-432, doi:10.1785/0220120185. Blewitt, G. & Lavallee, D., (2002). Effect of annual signals on geodetic velocity, J. geophys. Res., 107(B7), doi:10.1029/2001JB000570. Bos, M.S., R.M.S. Fernandes, S. Williams, L. Bastos (2012) Fast Error Analysis of Continuous GNSS Observations with Missing Data, Journal of Geodesy, doi: 10.1007/s00190-012-0605-0. Bos, M.S., L. Bastos, R.M.S. Fernandes, (2009). The influence of seasonal signals on the estimation of the tectonic motion in short continuous GPS time-series, J. of Geodynamics, j.jog.2009.10.005. Fernandes, R.M.S., J. M. Miranda, D. Delvaux, D. S. Stamps and E. Saria (2013). Re-evaluation of the kinematics of Victoria Block using continuous GNSS data, Geophysical Journal International, doi:10.1093/gji/ggs071. Langbein, J. (2012). Estimating rate uncertainty with maximum likelihood: differences between power-law and flicker-random-walk models, Journal of Geodesy, Volume 86, Issue 9, pp 775-783, Williams, S. D. P. (2003). Offsets in Global Positioning System time series, J. Geophys. Res., 108, 2310, doi:10.1029/2002JB002156, B6.

Passive correlation ranging of a geostationary satellite using DVB-S payload signals.

NASA Astrophysics Data System (ADS)

Shakun, Leonid; Shulga, Alexandr; Sybiryakova, Yevgeniya; Bushuev, Felix; Kaliuzhnyi, Mykola; Bezrukovs, Vladislavs; Moskalenko, Sergiy; Kulishenko, Vladislav; Balagura, Oleg

2016-07-01

Passive correlation ranging (PaCoRa) for geostationary satellites is now considered as an alternate to tone-ranging (https://artes.esa.int/search/node/PaCoRa). The PaCoRa method has been employed in the Research Institute "Nikolaev astronomical observatory" since the first experiment in August 2011 with two stations spatially separated on 150 km. The PaCoRa has been considered as an independent method for tracking the future Ukrainian geostationary satellite "Lybid'. Now a radio engineering complex (RC) for passive ranging consists of five spatially separated stations of receiving digital satellite television and a data processing center located in Mykolaiv. The stations are located in Kyiv, Kharkiv, Mukacheve, Mykolaiv (Ukraine) and in Ventspils (Latvia). Each station has identical equipment. The equipment allows making synchronous recording of fragments of the DVB-S signal from the quadrature detector output of a satellite television receiver. The fragments are recorded every second. Synchronization of the stations is performed using GPS receivers. Samples of the complex signal obtained in this way are archived and are sent to the data processing center over the Internet. Here the time differences of arrival (TDOA) for pairs of the stations are determined as a result of correlation processing of received signals. The values of the TDOA that measured every second are used for orbit determination (OD) of the satellite. The results of orbit determination of the geostationary telecommunication satellite "Eutelsat-13B" (13º East) obtained during about four months of observations in 2015 are presented in the report. The TDOA and OD accuracies are also given. Single-measurement error (1 sigma) of the TDOA is equal about 8.7 ns for all pairs of the stations. Standard deviations and average values of the residuals between the observed TDOA and the TDOA computed using the orbit elements obtained from optical measurements are estimated for the pairs Kharkiv-Mykolaiv and Mukacheve-Mykolaiv. The standard deviations do not exceed 10 ns for the both pairs and the average values are equal +10 ns and -106 ns respectively for Kharkiv-Mykolaiv and Mukacheve-Mykolaiv. We discuss the residuals between the observed TDOA and estimates of the TDOA that are calculated by fitted models of satellite motion: the SGP4/SDP4 model and the model based on the numerical integration of the equations of motion taking into account the geopotential, and the perturbation from the Moon and the Sun. We note that residuals from the model SGP4/SDP4 have periodic deviations due to the inaccuracy of the SGP4/SDP4 model. As a result, estimation of the standard deviation of the satellite position is about 60 m for the epoch of the SGP4/SDP4 orbit elements. The residuals for the numerical model in the interval of one day do not show low-frequency deviation. In this case, the estimate of the standard deviation of the satellite position is about 12 m for the epoch of the numerical orbit elements. Keywords. DVB-S, geostationary satellite, orbit determination, passive ranging.

Observing tectonic plate motions and deformations from satellite laser ranging

NASA Technical Reports Server (NTRS)

Christodoulidis, D. C.; Smith, D. E.; Kolenkiewicz, R.; Klosko, S. M.; Torrence, M. H.

1985-01-01

The scope of geodesy has been greatly affected by the advent of artificial near-earth satellites. The present paper provides a description of the results obtained from the reduction of data collected with the aid of satellite laser ranging. It is pointed out that dynamic reduction of satellite laser ranging (SLR) data provides very precise positions in three dimensions for the laser tracking network. The vertical components of the stations, through the tracking geometry provided by the global network and the accurate knowledge of orbital dynamics, are uniquely related to the center of mass of the earth. Attention is given to the observations, the methodologies for reducing satellite observations to estimate station positions, Lageos-observed tectonic plate motions, an improved temporal resolution of SLR plate motions, and the SLR vertical datum.

Geodetic antenna calibration test in the Antarctic environment

USGS Publications Warehouse

Grejner-Brzezinska, A.; Vazquez, E.; Hothem, L.

2006-01-01

TransAntarctic Mountain DEFormation (TAMDEF) Monitoring Network is the NSF-sponsored OSU and USGS project, aimed at measuring crustal motion in the Transantarctic Mountains of Victoria Land using GPS carrier phase measurements. Station monumentation, antenna mounts, antenna types, and data processing strategies were optimized to achieve mm-level estimates for the rates of motion. These data contributes also to regional Antarctic frame definition. Significant amount of data collected over several years allow the investigation of unique aspects of GPS geodesy in Antarctica, to determine how the error spectrum compares to the mid-latitude regions, and to identify the optimum measurement and data processing schemes for Antarctic conditions, in order to test the predicted rates of motion (mm-level w.r.t. time). The data collection for the TAMDEF project was initiated in 1996. The primary antenna used has been the Ashtech L1/L2 Dorne Margolin (D/M) choke ring. A few occupations involved the use of a Trimble D/M choke ring. The data were processed using the antenna calibration data available from the National Geodetic Survey (NGS). The recent developments in new antenna designs that are lighter in weight and lower in cost are being considered as a possible alternative to the bulkier and more expensive D/M choke ring design. In November 2003, in situ testing of three alternative models of L1/L2 antennas was conducted at a site located in the vicinity of McMurdo Station, Antarctica (S77.87, E166.56). The antenna models used in this test were: Ashtech D/M choke ring, Trimble D/M choke ring, Trimble Zephyr, and the NovAtel GPS-702. Two stations, spaced within 30 meters, were used in the test. Both had the characteristics similar to the stations of the TAMDEF network, i.e., the UNAVCO fixed-height, force-centered level mounts with a constant antenna offset were used, ensuring extreme stability of the antenna/ mount/pin set up. During each of the four 3-day test data collection sessions, a reference station was occupied continuously with the Ashtech D/M choke ring antenna, while the second station was occupied by the tested antennas, one 3-day session for each antenna type. The coordinate differences were produced using software optimized for the analysis of data collected over short baselines. Each solution incorporated the NGS antenna calibration data appropriate for each antenna model. Hourly and 24-hour solutions were analyzed for repeatability and compared to the standard baseline coordinate differences. No significant variation was observed when comparing the same type of antennas and when switching antennas at the test site using daily solutions. An mm-level scatter can be observed comparing different antennas over the 1-hour solutions; it is smaller for the horizontal components, as compared to the vertical direction. At this point, it can be concluded that the standard antenna calibration models from NGS used for each antenna involved in this test did not result in any significant variation in the daily results, but with some in the hourly results. Thus, based on this fact, the antenna types tested here could be used in the future TAMDEF campaigns, where 24-hour solutions are normally used for deformation monitoring. These results can serve as good guidance to any future use of GPS equipment in Antarctica.

Broad-band simulation of M7.2 earthquake on the North Tehran fault, considering non-linear soil effects

NASA Astrophysics Data System (ADS)

Majidinejad, A.; Zafarani, H.; Vahdani, S.

2018-05-01

The North Tehran fault (NTF) is known to be one of the most drastic sources of seismic hazard on the city of Tehran. In this study, we provide broad-band (0-10 Hz) ground motions for the city as a consequence of probable M7.2 earthquake on the NTF. Low-frequency motions (0-2 Hz) are provided from spectral element dynamic simulation of 17 scenario models. High-frequency (2-10 Hz) motions are calculated with a physics-based method based on S-to-S backscattering theory. Broad-band ground motions at the bedrock level show amplifications, both at low and high frequencies, due to the existence of deep Tehran basin in the vicinity of the NTF. By employing soil profiles obtained from regional studies, effect of shallow soil layers on broad-band ground motions is investigated by both linear and non-linear analyses. While linear soil response overestimate ground motion prediction equations, non-linear response predicts plausible results within one standard deviation of empirical relationships. Average Peak Ground Accelerations (PGAs) at the northern, central and southern parts of the city are estimated about 0.93, 0.59 and 0.4 g, respectively. Increased damping caused by non-linear soil behaviour, reduces the soil linear responses considerably, in particular at frequencies above 3 Hz. Non-linear deamplification reduces linear spectral accelerations up to 63 per cent at stations above soft thick sediments. By performing more general analyses, which exclude source-to-site effects on stations, a correction function is proposed for typical site classes of Tehran. Parameters for the function which reduces linear soil response in order to take into account non-linear soil deamplification are provided for various frequencies in the range of engineering interest. In addition to fully non-linear analyses, equivalent-linear calculations were also conducted which their comparison revealed appropriateness of the method for large peaks and low frequencies, but its shortage for small to medium peaks and motions with higher than 3 Hz frequencies.

Dynamic fault rupture model of the 2008 Iwate-Miyagi Nairiku earthquake, Japan; Role of rupture velocity changes on extreme ground motions

NASA Astrophysics Data System (ADS)

Pulido Hernandez, N. E.; Dalguer Gudiel, L. A.; Aoi, S.

2009-12-01

The Iwate-Miyagi Nairiku earthquake, a reverse earthquake occurred in the southern Iwate prefecture Japan (2008/6/14), produced the largest peak ground acceleration recorded to date (4g) (Aoi et al. 2008), at the West Ichinoseki (IWTH25), KiK-net strong motion station of NIED. This station which is equipped with surface and borehole accelerometers (GL-260), also recorded very high peak accelerations up to 1g at the borehole level, despite being located in a rock site. From comparison of spectrograms of the observed surface and borehole records at IWTH25, Pulido et. al (2008) identified two high frequency (HF) ground motion events located at 4.5s and 6.3s originating at the source, which likely derived in the extreme observed accelerations of 3.9g and 3.5g at IWTH25. In order to understand the generation mechanism of these HF events we performed a dynamic fault rupture model of the Iwate-Miyagi Nairiku earthquake by using the Support Operator Rupture Dynamics (SORD) code, (Ely et al., 2009). SORD solves the elastodynamic equation using a generalized finite difference method that can utilize meshes of arbitrary structure and is capable of handling geometries appropriate to thrust earthquakes. Our spontaneous dynamic rupture model of the Iwate-Miyagi Nairiku earthquake is governed by the simple slip weakening friction law. The dynamic parameters, stress drop, strength excess and critical slip weakening distance are estimated following the procedure described in Pulido and Dalguer (2009) [PD09]. These parameters develop earthquake rupture consistent with the final slip obtained by kinematic source inversion of near source strong ground motion recordings. The dislocation model of this earthquake is characterized by a patch of large slip located ~7 km south of the hypocenter (Suzuki et al. 2009). Our results for the calculation of stress drop follow a similar pattern. Using the rupture times obtained from the dynamic model of the Iwate-Miyagi Nairiku earthquake we estimated the rupture velocity as well as rupture velocity changes distribution across the fault plane based on the procedure proposed by PD09. Our results show that rupture velocity has strong variations concentrated in small patches within large slip areas (asperities). Using this dynamic model we performed the strong motion simulation at the IWTH25 borehole. We obtained that this model is able to reproduce the two HF events observed in the strong motion data. Our preliminary results suggest that the extreme acceleration pulses were induced by two strong rupture velocity acceleration events at the rupture front. References Aoi, S., T. Kunugi, and H. Fujiwara, 2008, Science, 322, 727-730. Ely, G. P., S. M. Day, and J.-B. Minster (2009), Geophys. J. Int., 177(3), 1140-1150. Pulido, N., S. Aoi, and W. Suzuki (2008), AGU Fall meeting, S33C-02. Pulido, N., and L.A. Dalguer, (2009). Estimation of the high-frequency radiation of the 2000 Tottori (Japan) earthquake based on a dynamic model of fault rupture: Application to the strong ground motion simulation, Bull. Seism. Soc. Am. 99(4), 2305-2322. Suzuki, W., S. Aoi, and H. Sekiguchi, (2009), Bull. Seism. Soc. Am. (Accepted).

A demonstration of an independent-station radio interferometry system with 4-cm precision on a 16-km base line. [for geodesy

NASA Technical Reports Server (NTRS)

Thomas, J. B.; Fanselow, J. L.; Macdoran, P. F.; Skjerve, L. J.; Spitzmesser, D. J.; Fliegel, H. F.

1976-01-01

Radio interferometry promises eventually to measure directly, with accuracies of a few centimeters, both whole earth motions and relative crustal motions with respect to an 'inertial' reference frame. Interferometry measurements of arbitrarily long base lines require, however, the development of new techniques for independent-station observation. In connection with the development of such techniques, a series of short base line demonstration experiments has been conducted between two antennas. The experiments were related to a program involving the design of independent-station instrumentation capable of making three-dimensional earth-fixed base line measurements with an accuracy of a few centimeters. Attention is given to the instrumentation used in the experiments, aspects of data analysis, and the experimental results.

Nonlinear Site Response Validation Studies Using KIK-net Strong Motion Data

NASA Astrophysics Data System (ADS)

Asimaki, D.; Shi, J.

2014-12-01

Earthquake simulations are nowadays producing realistic ground motion time-series in the range of engineering design applications. Of particular significance to engineers are simulations of near-field motions and large magnitude events, for which observations are scarce. With the engineering community slowly adopting the use of simulated ground motions, site response models need to be re-evaluated in terms of their capabilities and limitations to 'translate' the simulated time-series from rock surface output to structural analyses input. In this talk, we evaluate three one-dimensional site response models: linear viscoelastic, equivalent linear and nonlinear. We evaluate the performance of the models by comparing predictions to observations at 30 downhole stations of the Japanese network KIK-Net that have recorded several strong events, including the 2011 Tohoku earthquake. Velocity profiles are used as the only input to all models, while additional parameters such as quality factor, density and nonlinear dynamic soil properties are estimated from empirical correlations. We quantify the differences of ground surface predictions and observations in terms of both seismological and engineering intensity measures, including bias ratios of peak ground response and visual comparisons of elastic spectra, and inelastic to elastic deformation ratio for multiple ductility ratios. We observe that PGV/Vs,30 — as measure of strain— is a better predictor of site nonlinearity than PGA, and that incremental nonlinear analyses are necessary to produce reliable estimates of high-frequency ground motion components at soft sites. We finally discuss the implications of our findings on the parameterization of nonlinear amplification factors in GMPEs, and on the extensive use of equivalent linear analyses in probabilistic seismic hazard procedures.

Infrasonic sounds excited by seismic waves of the 2011 Tohoku-oki earthquake as visualized in ionograms

NASA Astrophysics Data System (ADS)

Maruyama, Takashi; Shinagawa, Hiroyuki

2014-05-01

After the M 9.0 Tohoku-oki earthquake in 2011, strong deformation of ionogram echo traces, forming multiple cusp signatures (MCSs), were observed at three stations 790-1880 km from the epicenter. The vertical structure of the ionospheric disturbances was determined by true height analysis and compared with broadband seismograph records at stations close to the ionosondes. These ionospheric disturbances were caused by vertically propagating acoustic waves excited by the up/down ground motion of seismic waves. Numerical simulations have shown that acoustic waves with a period of 15-40 s and amplitude of order 1 mm/s at the ground level were sufficient to create MCSs as sharp as those observed. These acoustic wave parameters are consistent with the seismic records if the motion of the air mass on the ground level is assumed to be the same as the ground motion. The travel time diagram of the seismic records along the line connecting the epicenter and ionosondes showed that the first MCS ionogram detected at each station was caused by P waves, while the others were caused by Rayleigh waves.

Real time numerical shake prediction incorporating attenuation structure: a case for the 2016 Kumamoto Earthquake

NASA Astrophysics Data System (ADS)

Ogiso, M.; Hoshiba, M.; Shito, A.; Matsumoto, S.

2016-12-01

Needless to say, heterogeneous attenuation structure is important for ground motion prediction, including earthquake early warning, that is, real time ground motion prediction. Hoshiba and Ogiso (2015, AGU Fall meeting) showed that the heterogeneous attenuation and scattering structure will lead to earlier and more accurate ground motion prediction in the numerical shake prediction scheme proposed by Hoshiba and Aoki (2015, BSSA). Hoshiba and Ogiso (2015) used assumed heterogeneous structure, and we discuss the effect of them in the case of 2016 Kumamoto Earthquake, using heterogeneous structure estimated by actual observation data. We conducted Multiple Lapse Time Window Analysis (Hoshiba, 1993, JGR) to the seismic stations located on western part of Japan to estimate heterogeneous attenuation and scattering structure. The characteristics are similar to the previous work of Carcole and Sato (2010, GJI), e.g. strong intrinsic and scattering attenuation around the volcanoes located on the central part of Kyushu, and relatively weak heterogeneities in the other area. Real time ground motion prediction simulation for the 2016 Kumamoto Earthquake was conducted using the numerical shake prediction scheme with 474 strong ground motion stations. Comparing the snapshot of predicted and observed wavefield showed a tendency for underprediction around the volcanic area in spite of the heterogeneous structure. These facts indicate the necessity of improving the heterogeneous structure for the numerical shake prediction scheme.In this study, we used the waveforms of Hi-net, K-NET, KiK-net stations operated by the NIED for estimating structure and conducting ground motion prediction simulation. Part of this study was supported by the Earthquake Research Institute, the University of Tokyo cooperative research program and JSPS KAKENHI Grant Number 25282114.

Status of NASA/Army rotorcraft research and development piloted flight simulation

NASA Technical Reports Server (NTRS)

Condon, Gregory W.; Gossett, Terrence D.

1988-01-01

The status of the major NASA/Army capabilities in piloted rotorcraft flight simulation is reviewed. The requirements for research and development piloted simulation are addressed as well as the capabilities and technologies that are currently available or are being developed by NASA and the Army at Ames. The application of revolutionary advances (in visual scene, electronic cockpits, motion, and modelling of interactive mission environments and/or vehicle systems) to the NASA/Army facilities are also addressed. Particular attention is devoted to the major advances made in integrating these individual capabilities into fully integrated simulation environment that were or are being applied to new rotorcraft mission requirements. The specific simulators discussed are the Vertical Motion Simulator and the Crew Station Research and Development Facility.

Autonomous microsystems for ground observation (AMIGO)

NASA Astrophysics Data System (ADS)

Laou, Philips

2005-05-01

This paper reports the development of a prototype autonomous surveillance microsystem AMIGO that can be used for remote surveillance. Each AMIGO unit is equipped with various sensors and electronics. These include passive infrared motion sensor, acoustic sensor, uncooled IR camera, electronic compass, global positioning system (GPS), and spread spectrum wireless transceiver. The AMIGO unit was configured to multipoint (AMIGO units) to point (base station) communication mode. In addition, field trials were conducted with AMIGO in various scenarios. These scenarios include personnel and vehicle intrusion detection (motion or sound) and target imaging; determination of target GPS position by triangulation; GPS position real time tracking; entrance event counting; indoor surveillance; and aerial surveillance on a radio controlled model plane. The architecture and test results of AMIGO will be presented.

Combining structure-from-motion derived point clouds from satellites and unmanned aircraft systems images with ground-truth data to create high-resolution digital elevation models

NASA Astrophysics Data System (ADS)

Palaseanu, M.; Thatcher, C.; Danielson, J.; Gesch, D. B.; Poppenga, S.; Kottermair, M.; Jalandoni, A.; Carlson, E.

2016-12-01

Coastal topographic and bathymetric (topobathymetric) data with high spatial resolution (1-meter or better) and high vertical accuracy are needed to assess the vulnerability of Pacific Islands to climate change impacts, including sea level rise. According to the Intergovernmental Panel on Climate Change reports, low-lying atolls in the Pacific Ocean are extremely vulnerable to king tide events, storm surge, tsunamis, and sea-level rise. The lack of coastal topobathymetric data has been identified as a critical data gap for climate vulnerability and adaptation efforts in the Republic of the Marshall Islands (RMI). For Majuro Atoll, home to the largest city of RMI, the only elevation dataset currently available is the Shuttle Radar Topography Mission data which has a 30-meter spatial resolution and 16-meter vertical accuracy (expressed as linear error at 90%). To generate high-resolution digital elevation models (DEMs) in the RMI, elevation information and photographic imagery have been collected from field surveys using GNSS/total station and unmanned aerial vehicles for Structure-from-Motion (SfM) point cloud generation. Digital Globe WorldView II imagery was processed to create SfM point clouds to fill in gaps in the point cloud derived from the higher resolution UAS photos. The combined point cloud data is filtered and classified to bare-earth and georeferenced using the GNSS data acquired on roads and along survey transects perpendicular to the coast. A total station was used to collect elevation data under tree canopies where heavy vegetation cover blocked the view of GNSS satellites. A subset of the GPS / total station data was set aside for error assessment of the resulting DEM.

Statistical analysis of heavy truck loads using Wisconsin weigh-in-motion data

DOT National Transportation Integrated Search

2009-09-01

This study involved statistical evaluation of heavy truck loads that were recorded in 2007 using Weigh-In-Motion : stations located throughout the State of Wisconsin. The heaviest 5% of all trucks in each class and axle groupings were : selected for ...

Modeling and dynamic simulation of astronaut's upper limb motions considering counter torques generated by the space suit.

PubMed

Li, Jingwen; Ye, Qing; Ding, Li; Liao, Qianfang

2017-07-01

Extravehicular activity (EVA) is an inevitable task for astronauts to maintain proper functions of both the spacecraft and the space station. Both experimental research in a microgravity simulator (e.g. neutral buoyancy tank, zero-g aircraft or a drop tower/tube) and mathematical modeling were used to study EVA to provide guidance for the training on Earth and task design in space. Modeling has become more and more promising because of its efficiency. Based on the task analysis, almost 90% of EVA activity is accomplished through upper limb motions. Therefore, focusing on upper limb models of the body and space suit is valuable to this effort. In previous modeling studies, some multi-rigid-body systems were developed to simplify the human musculoskeletal system, and the space suit was mostly considered as a part of the astronaut body. With the aim to improve the reality of the models, we developed an astronauts' upper limb model, including a torque model and a muscle-force model, with the counter torques from the space suit being considered as a boundary condition. Inverse kinematics and the Maggi-Kane's method was applied to calculate the joint angles, joint torques and muscle force given that the terminal trajectory of upper limb motion was known. Also, we validated the muscle-force model using electromyogram (EMG) data collected in a validation experiment. Muscle force calculated from our model presented a similar trend with the EMG data, supporting the effectiveness and feasibility of the muscle-force model we established, and also, partially validating the joint model in kinematics aspect.

Estimation of source processes of the 2016 Kumamoto earthquakes from strong motion waveforms

NASA Astrophysics Data System (ADS)

Kubo, H.; Suzuki, W.; Aoi, S.; Sekiguchi, H.

2016-12-01

In this study, we estimated the source processes for two large events of the 2016 Kumamoto earthquakes (the M7.3 event at 1:25 JST on April 16, 2016 and the M6.5 event at 21:26 JST on April 14, 2016) from strong motion waveforms using multiple-time-window linear waveform inversion (Hartzell and Heaton 1983; Sekiguchi et al. 2000). Based on the observations of surface ruptures, the spatial distribution of aftershocks, and the geodetic data, a realistic curved fault model was developed for the source-process analysis of the M7.3 event. The source model obtained for the M7.3 event with a seismic moment of 5.5 × 1019 Nm (Mw 7.1) had two significant ruptures. One rupture propagated toward the northeastern shallow region at 4 s after rupture initiation, and continued with large slips to approximately 16 s. This rupture caused a large slip region with a peak slip of 3.8 m that was located 10-30 km northeast of the hypocenter and reached the caldera of Mt. Aso. The contribution of the large slip region to the seismic waveforms was large at many stations. Another rupture propagated toward the surface from the hypocenter at 2-6 s, and then propagated toward the northeast along the near surface at 6-10 s. This rupture largely contributed to the seismic waveforms at the stations south of the fault and close to the hypocenter. A comparison with the results obtained using a single fault plane model demonstrate that the use of the curved fault model led to improved waveform fit at the stations south of the fault. The extent of the large near-surface slips in this source model for the M7.3 event is roughly consistent with the extent of the observed large surface ruptures. The source model obtained for the M6.5 event with a seismic moment of 1.7 × 1018 Nm (Mw 6.1) had large slips in the region around the hypocenter and in the shallow region north-northeast of the hypocenter, both of which had a maximum slip of 0.7 m. The rupture of the M6.5 event propagated from the former region to the latter region at 1-6 s after rupture initiation, which is expected to have caused the strong ground motions due to the forward directivity effect at KMMH16 and surroundings. The occurrence of the near-surface large slips in this source model for the M6.5 event is consistent with the appearance of small surface cracks, which were observed by some residents.

Earthquake Monitoring: SeisComp3 at the Swiss National Seismic Network

NASA Astrophysics Data System (ADS)

Clinton, J. F.; Diehl, T.; Cauzzi, C.; Kaestli, P.

2011-12-01

The Swiss Seismological Service (SED) has an ongoing responsibility to improve the seismicity monitoring capability for Switzerland. This is a crucial issue for a country with low background seismicity but where a large M6+ earthquake is expected in the next decades. With over 30 stations with spacing of ~25km, the SED operates one of the densest broadband networks in the world, which is complimented by ~ 50 realtime strong motion stations. The strong motion network is expected to grow with an additional ~80 stations over the next few years. Furthermore, the backbone of the network is complemented by broadband data from surrounding countries and temporary sub-networks for local monitoring of microseismicity (e.g. at geothermal sites). The variety of seismic monitoring responsibilities as well as the anticipated densifications of our network demands highly flexible processing software. We are transitioning all software to the SeisComP3 (SC3) framework. SC3 is a fully featured automated real-time earthquake monitoring software developed by GeoForschungZentrum Potsdam in collaboration with commercial partner, gempa GmbH. It is in its core open source, and becoming a community standard software for earthquake detection and waveform processing for regional and global networks across the globe. SC3 was originally developed for regional and global rapid monitoring of potentially tsunamagenic earthquakes. In order to fulfill the requirements of a local network recording moderate seismicity, SED has tuned configurations and added several modules. In this contribution, we present our SC3 implementation strategy, focusing on the detection and identification of seismicity on different scales. We operate several parallel processing "pipelines" to detect and locate local, regional and global seismicity. Additional pipelines with lower detection thresholds can be defined to monitor seismicity within dense subnets of the network. To be consistent with existing processing procedures, the nonlinloc algorithm was implemented for manual and automatic locations using 1D and 3D velocity models; plugins for improved automatic phase picking and Ml computation were developed; and the graphical user interface for manual review was extended (including pick uncertainty definition; first motion focal mechanisms; interactive review of station magnitude waveforms; full inclusion of strong motion data). SC3 locations are fully compatible with those derived from the existing in-house processing tools and are stored in a database derived from the QuakeML data model. The database is shared with the SED alerting software, which merges origins from both SC3 and external sources in realtime and handles the alerting procedure. With the monitoring software being transitioned to SeisComp3, acquisition, archival and dissemination of SED waveform data now conforms to the seedlink and ArcLink protocols and continuous archives can be accessed via SED and all EIDA (European Integrated Data Archives) web-sites. Further, a SC3 module for waveform parameterisation has been developed, allowing rapid computation of peak values of ground motion and other engineering parameters within minutes of a new event. An output of this module is USGS ShakeMap XML. n minutes of a new event. An output of this module is USGS ShakeMap XML.

REDOX-SWITCHABLE CALIX[6]ARENE-BASED ISOMERIC ROTAXANES.

PubMed

Zanichelli, Valeria; Bazzoni, Margherita; Arduini, Arturo; Franchi, Paola; Lucarini, Marco; Ragazzon, Giulio; Secchi, Andrea; Silvi, Serena

2018-04-16

Operating molecular machines are based on switchable systems, whose components can be set in motion in a controllable fashion. The presence of non-symmetric elements is a mandatory requirement to obtain and demonstrate the unidirectionality of motion. Calixarene-based macrocycles have proven very efficient hosts in the design of oriented rotaxanes and of pseudorotaxanes with a strict control on the direction of complexation. We have synthesized and characterized a series of two-station rotaxanes based on bypiridinium-ammonium axles. We have exploited a recently reported supramolecular-assisted strategy for the synthesis of different orientational isomers and we identified the ammonium unit as a proper secondary station for the calixarene. We were able to trigger the displacement of the macrocycle upon electrochemical reduction of the bipyridinium primary station and we demonstrated that the shuttling is influenced both by the length of the chain of the axle component and by the position of the secondary station with respect to the calixarene rims. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Application Number 3: Using Tethers for Attitude Control

NASA Technical Reports Server (NTRS)

Muller, R. M.

1985-01-01

Past application of the gravity gradient concept to satellite attitude control produced attitude stabilities of from 1 to 10 degrees. The satellite members were rigigly interconnected and any motion in one part of the satellite would cause motion in all members. This experience has restricted gravity gradient stabilization to applications that need attitude stability no better than 1 degree. A gravity gradient technique that combines the flexible tether with an active control that will allow control stability much better than 1 degree is proposed. This could give gravity gradient stabilization much broader application. In fact, for a large structure like a space station, it may become the preferred method. Two possible ways of demonstrating the techniques using the Tethered Satellite System (TSS) tether to control the attitude of the shuttle are proposed. Then a possible space station tether configuration is shown that could be used to control the initial station. It is then shown how the technique can be extended to the control of space stations of virtually any size.

Investigation on earthquake ground motions observed along a north-south survey line in the Kumamoto Plain, during the aftershocks of 2016 Kumamoto earthquake

NASA Astrophysics Data System (ADS)

Tsuno, S.; Korenaga, M.; Okamoto, K.; Chimoto, K.; Yamanaka, H.; Yamada, N.; Matsushima, T.

2017-12-01

To evaluate local site effects in the Kumamoto Plain, we installed 15 temporary seismic stations along the north-south survey line, after the 2016 Kumamoto earthquake foreshock (Mj 6.4). In this report, to investigate earthquake ground motions observed along the north-south survey line, we estimated site amplification factors from weak ground motion data and estimated S-wave velocity structures by array microtremor observations at temporary seismic stations. We installed 15 temporary seismic stations at an interval of 300m to 2.5km along the north-south survey line. We estimated site amplification factors, with a station at Mt. Kinbo as a reference. Site amplification factors at the middle part and the southern part along the survey line, located in the alluvial lowland, were dominated in the frequency of 1-2Hz. On the other hand, site amplification factors at the northern part along the survey line were dominated in the frequency of 2-5Hz. It suggests that the ground profiles near the surface are complicate along this north-south survey line in the Kumamoto Plain. Therefore, we performed array microtremor observations at the temporary seismic stations, to estimate S-wave velocity structures along the north-south survey line. We obtained phase velocities of Rayleigh waves by the SPAC method and estimated S-wave velocity structures by applying the Genetic Algorism to those phase velocity. The low velocity layer with a thickness of around 15m was deposited on the surface at sites located in the alluvial lowland. Finally, we compared the distribution of PGAs observed along the north-south survey line to AVs30 estimated by S-wave velocity structures. As a result, PGAs along the survey line were strongly concerned by AVs30. We concluded that earthquake ground motions in the frequency of more than 1Hz observed in this north-south survey line were excited by the low velocity layer near the surface.

Design and Implementation of the National Seismic Monitoring Network in the Kingdom of Bhutan

NASA Astrophysics Data System (ADS)

Ohmi, S.; Inoue, H.; Chophel, J.; Pelgay, P.; Drukpa, D.

2017-12-01

Bhutan-Himalayan district is located along the plate collision zone between Indian and Eurasian plates, which is one of the most seismically active region in the world. Recent earthquakes such as M7.8 Gorkha Nepal earthquake in April 25, 2015 and M6.7 Imphal, India earthquake in January 3, 2016 are examples of felt earthquakes in Bhutan. However, there is no permanent seismic monitoring system ever established in Bhutan, whose territory is in the center of the Bhutan-Himalayan region. We started establishing permanent seismic monitoring network of minimum requirements and intensity meter network over the nation. The former is composed of six (6) observation stations in Bhutan with short period weak motion and strong motion seismometers as well as three (3) broad-band seismometers, and the latter is composed of twenty intensity meters located in every provincial government office. Obtained data are transmitted to the central processing system in the DGM office in Thimphu in real time. In this project, DGM will construct seismic vault with their own budget which is approved as the World Bank project, and Japan team assists the DGM for site survey of observation site, designing the observation vault, and designing the data telemetry system as well as providing instruments for the observation such as seismometers and digitizers. We already started the operation of the six (6) weak motion stations as well as twenty (20) intensity meter stations. Additionally, the RIMES (Regional Integrated Multi-hazard Early Warning System for Africa and Asia) is also providing eight (8) weak motion stations and we are keeping close communication to operate them as one single seismic monitoring network composed of fourteen (14) stations. This network will be definitely utilized for not only for seismic disaster mitigation of the country but also for studying the seismotectonics in the Bhutan-Himalayan region which is not yet precisely revealed due to the lack of observation data in the past.

Coherence of Mach fronts during heterogeneous supershear earthquake rupture propagation: Simulations and comparison with observations

USGS Publications Warehouse

Bizzarri, A.; Dunham, Eric M.; Spudich, P.

2010-01-01

We study how heterogeneous rupture propagation affects the coherence of shear and Rayleigh Mach wavefronts radiated by supershear earthquakes. We address this question using numerical simulations of ruptures on a planar, vertical strike-slip fault embedded in a three-dimensional, homogeneous, linear elastic half-space. Ruptures propagate spontaneously in accordance with a linear slip-weakening friction law through both homogeneous and heterogeneous initial shear stress fields. In the 3-D homogeneous case, rupture fronts are curved owing to interactions with the free surface and the finite fault width; however, this curvature does not greatly diminish the coherence of Mach fronts relative to cases in which the rupture front is constrained to be straight, as studied by Dunham and Bhat (2008a). Introducing heterogeneity in the initial shear stress distribution causes ruptures to propagate at speeds that locally fluctuate above and below the shear wave speed. Calculations of the Fourier amplitude spectra (FAS) of ground velocity time histories corroborate the kinematic results of Bizzarri and Spudich (2008a): (1) The ground motion of a supershear rupture is richer in high frequency with respect to a subshear one. (2) When a Mach pulse is present, its high frequency content overwhelms that arising from stress heterogeneity. Present numerical experiments indicate that a Mach pulse causes approximately an ω−1.7 high frequency falloff in the FAS of ground displacement. Moreover, within the context of the employed representation of heterogeneities and over the range of parameter space that is accessible with current computational resources, our simulations suggest that while heterogeneities reduce peak ground velocity and diminish the coherence of the Mach fronts, ground motion at stations experiencing Mach pulses should be richer in high frequencies compared to stations without Mach pulses. In contrast to the foregoing theoretical results, we find no average elevation of 5%-damped absolute response spectral accelerations (SA) in the period band 0.05–0.4 s observed at stations that presumably experienced Mach pulses during the 1979 Imperial Valley, 1999 Kocaeli, and 2002 Denali Fault earthquakes compared to SA observed at non-Mach pulse stations in the same earthquakes. A 20% amplification of short period SA is seen only at a few of the Imperial Valley stations closest to the fault. This lack of elevated SA suggests that either Mach pulses in real earthquakes are even more incoherent that in our simulations or that Mach pulses are vulnerable to attenuation through nonlinear soil response. In any case, this result might imply that current engineering models of high frequency earthquake ground motions do not need to be modified by more than 20% close to the fault to account for Mach pulses, provided that the existing data are adequately representative of ground motions from supershear earthquakes.

Strong-motion data from the two Pingtung, Taiwan, earthquakes of 26 December 2006

USGS Publications Warehouse

Wu, C.-F.; Lee, W.H.K.; Boore, D.M.

2008-01-01

1016 strong-motion records at 527 free-field stations and 131 records at 42 strong-motion arrays at buildings and bridges were obtained for the Pingtung earthquake doublet from the Taiwan Central Weather Bureau's dense, digital strong-motion network. We carried out standard processing of these strong-motion records at free-field stations. A data set, including the originally recorded files, processed data files, and supporting software and information, is archived online http:// tecdc.earth.sinica.edu.tw/data/EQ2006Pingtung/. We have not yet completed the processing of the strong-motion array data at buildings and bridges. However, some preliminary results and the strong-motion array data recorded at the second nearest instrumented building to the Pingtung earthquake doublet are shown. This paper is intended to document our data processing procedures and the online archived data files, so that researchers can efficiently use the data. We also include two preliminary analyses: (1) a comparison of ground motions recorded by multiple accelerographs at a common site, the TAP 117 station in Taipei, and (2) attenuation of the horizontal ground motions (peak acceleration and response spectra at periods of 0.2, 1.0, and 3.0 s) with respect to distance. Our comparison study of multiple recordings at TAP 117 indicates that waveform coherence among 20- and 24-bit accelerograph records is much higher as compared to records from 16-bit or 12-bit accelerographs, suggesting that the former are of better quality. For the 20- and 24-bit accelerographs, waveform coherence is nearly 1 over the frequency range 1 to 8 Hz for all components, and is greater than about 0.9 from 8 to 20 Hz for the horizontal component, but only from 8 to 12 Hz for the vertical component. Plots of pseudo-acceleration response spectra (PSA) as a function of distance, however, show no clear indication for a difference related to the performance level of the accelerographs. The ground-motions of the first event (Mw = 7.0) are comparable, or even somewhat lower, than those from the smaller second event (Mw = 6.9), consistent with the relative difference of the local magnitudes (ML = 6.96 and 6.99 for the first and second events, respectively). The ground motions from the first event are generally lower than those predicted from equations based on other in-slab subduction earthquakes, whereas the ground motions from the second event are closer to the predictions. Ground-motions for soil sites are generally larger than those from rock sites.

Psycho-Motor and Error Enabled Simulations: Modeling Vulnerable Skills in the Pre-Mastery Phase Medical Practice Initiative Procedural Skill Decay and Maintenance (MPI-PSD)

DTIC Science & Technology

2014-04-01

laparoscopic ventral hernia repair. Additional simulation stations were added to the standards and purchases (including a motion tracking system) were...framework for laparoscopic ventral hernia; Incorporation of error-based simulators into an exit assessment of chief surgical residents; Development of...simulating a laparoscopic ventral hernia (LVH) repair. Based on collected data, the lab worked to finalize the incorporation of error-based simulators

Modeling Nonlinear Site Response Uncertainty in Broadband Ground Motion Simulations for the Los Angeles Basin

NASA Astrophysics Data System (ADS)

Assimaki, D.; Li, W.; Steidl, J. M.; Schmedes, J.

2007-12-01

The assessment of strong motion site response is of great significance, both for mitigating seismic hazard and for performing detailed analyses of earthquake source characteristics. There currently exists, however, large degree of uncertainty concerning the mathematical model to be employed for the computationally efficient evaluation of local site effects, and the site investigation program necessary to evaluate the nonlinear input model parameters and ensure cost-effective predictions; and while site response observations may provide critical constraints on interpretation methods, the lack of a statistically significant number of in-situ strong motion records prohibits statistical analyses to be conducted and uncertainties to be quantified based entirely on field data. In this paper, we combine downhole observations and broadband ground motion synthetics for characteristic site conditions the Los Angeles Basin, and investigate the variability in ground motion estimation introduced by the site response assessment methodology. In particular, site-specific regional velocity and attenuation structures are initially compiled using near-surface geotechnical data collected at downhole geotechnical arrays, inverse low-strain velocity and attenuation profiles at these sites obtained by inversion of weak motion records and the crustal velocity structure at the corresponding locations obtained from the Southern California Earthquake Centre Community Velocity Model. Successively, broadband ground motions are simulated by means of a hybrid low/high-frequency finite source model with correlated random parameters for rupture scenaria of weak, medium and large magnitude events (M =3.5-7.5). Observed estimates of site response at the stations of interest are first compared to the ensemble of approximate and incremental nonlinear site response models. Parametric studies are next conducted for each fixed magnitude (fault geometry) scenario by varying the source-to-site distance and source parameters for the ensemble of site conditions. Elastic, equivalent linear and nonlinear simulations are implemented for the deterministic description of the base-model velocity and attenuation structures and nonlinear soil properties, to examine the variability in ground motion predictions as a function of ground motion amplitude and frequency content, and nonlinear site response methodology. The modeling site response uncertainty introduced in the broadband ground motion predictions is reported by means of the COV of site amplification, defined as the ratio of the predicted peak ground acceleration (PGA) and spectral acceleration (SA) at short and long periods to the corresponding intensity measure on the ground surface of a typical NEHRP BC boundary profile (Vs30=760m/s), for the ensemble of approximate and incremental nonlinear models implemented. A frequency index is developed to describe the frequency content of incident ground motion. In conjunction with the rock-outcrop acceleration level, this index is used to identify the site and ground motion conditions where incremental nonlinear analyses should be employed in lieu of approximate methodologies. Finally, the effects of modeling uncertainty in ground response analysis is evaluated in the estimation of site amplification factors, which are successively compared to recently published factors of the New Generation Attenuation Relations (NGA) and the currently employed Seismic Code Provisions (NEHRP).

Estimated cause of extreme acceleration records at the KiK-net IWTH25 station during the 2008 Iwate-Miyagi Nairiku earthquake, Japan

NASA Astrophysics Data System (ADS)

Ohmachi, Tatsuo; Inoue, Shusaku; Mizuno, Ken-Ichi; Yamada, Masato

During the 2008 Iwate-Miyagi Nairiku earthquake in Japan (MJ =7.2), extremely high accelerations were recorded at the KiK-net IWTH25 (Ichinoseki-nishi) station. The peak acceleration in the vertical component of the surface record was about 4 g where g is acceleration due to gravity, and the upward acceleration in the surface record was much larger than the downward acceleration. Some researchers have suggested that the ground surface was tossed into the air like a body on a trampoline. However, additional features found in the surface record suggest rocking motion accompanied with downward impact of the station with the ground. For example, there are many vertical peaks that can be found to occur at the same time as the horizontal peaks. After obtaining information about the station, in-situ investigations, shake-table experiments, and numerical simulations were conducted to determine the fundamental characteristics of the rocking motion and to reproduce the acceleration time histories of the surface record by using the bore-hole record at a depth of 260 m as the input motion. Prior to the numerical simulation, the wave velocities of subsurface layers were evaluated from Fourier spectra of both records, which showed that the velocities were reduced considerably during the main shock. A 2-D FEM code capable of handling separation and impact between the elements was used for the numerical simulation. Simulation results are shown in Figs. 17 and 18 indicating the impact between the IWTH25 station and the ground at around 4 sec when the acceleration in the vertical direction was about 4 g. Three kinds of acceleration time histories are shown with fairly good agreement between the simulated and observed time histories, suggesting the influence of the station is included in the record. It is also indicated that the vertical acceleration at the free surface without the influence of the IWTH25 station is about 1.6 g.

The SCEC Broadband Platform: A Collaborative Open-Source Software Package for Strong Ground Motion Simulation and Validation

NASA Astrophysics Data System (ADS)

Silva, F.; Maechling, P. J.; Goulet, C. A.; Somerville, P.; Jordan, T. H.

2014-12-01

The Southern California Earthquake Center (SCEC) Broadband Platform is a collaborative software development project involving geoscientists, earthquake engineers, graduate students, and the SCEC Community Modeling Environment. The SCEC Broadband Platform (BBP) is open-source scientific software that can generate broadband (0-100Hz) ground motions for earthquakes, integrating complex scientific modules that implement rupture generation, low and high-frequency seismogram synthesis, non-linear site effects calculation, and visualization into a software system that supports easy on-demand computation of seismograms. The Broadband Platform operates in two primary modes: validation simulations and scenario simulations. In validation mode, the Platform runs earthquake rupture and wave propagation modeling software to calculate seismograms for a well-observed historical earthquake. Then, the BBP calculates a number of goodness of fit measurements that quantify how well the model-based broadband seismograms match the observed seismograms for a certain event. Based on these results, the Platform can be used to tune and validate different numerical modeling techniques. In scenario mode, the Broadband Platform can run simulations for hypothetical (scenario) earthquakes. In this mode, users input an earthquake description, a list of station names and locations, and a 1D velocity model for their region of interest, and the Broadband Platform software then calculates ground motions for the specified stations. Working in close collaboration with scientists and research engineers, the SCEC software development group continues to add new capabilities to the Broadband Platform and to release new versions as open-source scientific software distributions that can be compiled and run on many Linux computer systems. Our latest release includes 5 simulation methods, 7 simulation regions covering California, Japan, and Eastern North America, the ability to compare simulation results against GMPEs, and several new data products, such as map and distance-based goodness of fit plots. As the number and complexity of scenarios simulated using the Broadband Platform increases, we have added batching utilities to substantially improve support for running large-scale simulations on computing clusters.

Seismology in Chile

USGS Publications Warehouse

Kausel, E.

1983-01-01

The Department of Geology and Geophysics, which is under the faculties of Mathematics and Physical Sciences of the University of Chile, is the organization that is responsible for the Seismological Service of Chile and for installing,operating, and maintaining the seismological stations as well as all the strong-motion stations in Chile.

Seismic velocity site characterization of 10 Arizona strong-motion recording stations by spectral analysis of surface wave dispersion

USGS Publications Warehouse

Kayen, Robert E.; Carkin, Brad A.; Corbett, Skye C.

2017-10-19

Vertical one-dimensional shear wave velocity (VS) profiles are presented for strong-motion sites in Arizona for a suite of stations surrounding the Palo Verde Nuclear Generating Station. The purpose of the study is to determine the detailed site velocity profile, the average velocity in the upper 30 meters of the profile (VS30), the average velocity for the entire profile (VSZ), and the National Earthquake Hazards Reduction Program (NEHRP) site classification. The VS profiles are estimated using a non-invasive continuous-sine-wave method for gathering the dispersion characteristics of surface waves. Shear wave velocity profiles were inverted from the averaged dispersion curves using three independent methods for comparison, and the root-mean-square combined coefficient of variation (COV) of the dispersion and inversion calculations are estimated for each site.

Mushy Magma beneath Yellowstone

NASA Astrophysics Data System (ADS)

Chu, R.; Helmberger, D. V.; Sun, D.; Jackson, J. M.; Zhu, L.

2009-12-01

A recent prospective on the Yellowstone Caldera discounts its explosive potential based on inferences from tomographic studies on regional earthquake data which suggests a high degree of crystallization of the underlying magma body. In this study, we analyzed P-wave receiver functions recorded by broadband stations above the caldera from 100 teleseismic earthquakes between January and November 2008. After applying a number of waveform modeling tools, we obtained much lower seismic velocities than previous estimates, 2.3 km/sec (Vp) and 1.1 km/sec (Vs), with a thickness of 3.6 km in the upper crust. This shallow low velocity zone is severe enough to cause difficulties with seismic tool applications. In particular, seismologists expect teleseismic P-waves to arrive with motions up and away or down and back. Many of the observations recorded by the Yellowstone Intermountain Seismic Array, however, violate this assumption. We show that many of the first P-wave arrivals observed at seismic stations on the edge of the caldera do not travel through the magma body but have taken longer but faster paths around the edge or wrap-around phases. Three stations near the trailing edge have reversal radial-component motions, while stations near the leading edge do not. Adding our constraints on geometry, we conclude that this relatively shallow magma body has a volume of over 4,300 km3. We estimate the magma body by assuming a fluid-saturated porous material consisting of granite and a mixture of rhyolite melt and supercritical water and CO2 at temperatures of 800 oC and pressure at 5 km (0.1 GPa).Theoretical calculations of seismic wave speed suggests that the magma body beneath the Yellowstone Caldera has a porosity of 32% filled with 92% rhyolite melt and 8% water-CO2 by volume.

Deformation of the Calabrian accretionary wedge and relative kinematics of the Calabrian and Peloritan backstops: Insights from multibeam bathymetry, high-resolution reflection and wide-angle seismics and analog modeling

NASA Astrophysics Data System (ADS)

Dellong, David; Gutscher, Marc-Andre; Klingelhoefer, Frauke; Graindorge, David; Kopp, Heidrun; Moretti, Milena; Marsset, Bruno; Mercier de Lepinay, Bernard; Dominguez, Stephane; Malavieille, Jacques

2016-04-01

Recently acquired swath bathymetric data in the Ionian Sea document in unprecedented detail the morphostructure and dynamics of the Calabrian accretionary wedge. A boundary zone between the eastern and western lobes of the accretionary wedge is examined here. Relative displacement between the Calabrian and Peloritan backstops is expected to cause dextral strike-slip deformation between the lobes. A wide-angle seismic profile was acquired in Oct. 2014 with the R/V Meteor (DIONYSUS survey) recorded by 25 Ocean-bottom seismometers (Geomar and Ifremer instruments) and 3 land-stations (INGV stations). Inversion and forward modeling of these seismic data reveal a 5-10 km deep asymmetric rift zone between the Malta Escarpment and the SW tip of Calabria. Analog modeling was performed to test if the origin of this rift could be related to the relative kinematics of the Calabrian and Peloritan backstops. Modeling, using two independently moving backstops, produces a zone of dextral transtension and subsidence in the accretionary wedge between two lobes. This corresponds well to the asymmetric rift observed in the southward prolongation of the straits of Messina faults. Paradoxically however, this dextral displacement does not appear to traverse the external Calabrian accretionary wedge, where prominent curved lineaments observed indicate a sinistral sense of motion. One possible explanation is that the dextral kinematic motion is transferred into a region of crisscrossing faults in the internal portion of the Eastern lobe. The bathymetry and high-resolution reflection seismic images indicate ongoing compression at the deformation front of both the western and eastern lobes. Together with the analog modeling results, these observations unambiguously demonstrate that the western lobe remains tectonically active.

Methods and apparatus to produce stick-slip motion of logging tool attached to a wireline drawn upward by a continuously rotating wireline drum

DOEpatents

Vail, III, William Banning; Momii, Steven Thomas

1998-01-01

Methods and apparatus are described to produce stick-slip motion of a logging tool within a cased well attached to a wireline that is drawn upward by a continuously rotating wireline drum. The stick-slip motion results in the periodic upward movement of the tool in the cased well described in terms of a dwell time during which time the tool is stationary, the move time during which time the tool moves, and the stroke that is upward distance that the tool translates during the "slip" portion of the stick-slip motion. This method of measurement is used to log the well at different vertical positions of the tool. Therefore, any typical "station-to-station logging tool" may be modified to be a "continuous logging tool", where "continuous" means that the wireline drum continually rotates while the tool undergoes stick-slip motion downhole and measurements are performed during the dwell times when the tool is momentarily stationary. The stick-slip methods of operation and the related apparatus are particularly described in terms of making measurements of formation resistivity from within a cased well during the dwell times when the tool is momentarily stationary during the periodic stick-slip motion of the logging tool.

Methods and apparatus to produce stick-slip motion of logging tool attached to a wireline drawn upward by a continuously rotating wireline drum

DOEpatents

Vail, W.B. III; Momii, S.T.

1998-02-10

Methods and apparatus are described to produce stick-slip motion of a logging tool within a cased well attached to a wireline that is drawn upward by a continuously rotating wireline drum. The stick-slip motion results in the periodic upward movement of the tool in the cased well described in terms of a dwell time during which time the tool is stationary, the move time during which time the tool moves, and the stroke that is upward distance that the tool translates during the ``slip`` portion of the stick-slip motion. This method of measurement is used to log the well at different vertical positions of the tool. Therefore, any typical ``station-to-station logging tool`` may be modified to be a ``continuous logging tool,`` where ``continuous`` means that the wireline drum continually rotates while the tool undergoes stick-slip motion downhole and measurements are performed during the dwell times when the tool is momentarily stationary. The stick-slip methods of operation and the related apparatus are particularly described in terms of making measurements of formation resistivity from within a cased well during the dwell times when the tool is momentarily stationary during the periodic stick-slip motion of the logging tool. 12 figs.

Seismotectonics of the May 19, 2011 Simav- Kutahya Earthquake Activity

NASA Astrophysics Data System (ADS)

Komec Mutlu, Ahu

2014-05-01

Aftershock sequence of May 19, 2011 Simav earthquake (Mw = 5.8) is relocated with a new 1-D seismic velocity model and focal mechanisms of largest aftershocks are determined. The May 19, 2011 Simav-Kutahya earthquake is occured in the most seismically active region of western Turkey. During six months after the mainshock, more than 5000 earthquakes are recorded and aftershocks followed over a period of almost two years. In this study, more than 7600 aftershocks occured between years 2011 and 2012 with magnitudes greater than 1.8 relocated. Waveform data is collected by 13 three component seismic stations from three different networks (Kandilli Observatory and Earthquake Research Institute (NEMC-National Earthquake Monitoring Center), Prime Ministry Disaster and Emergency Management Presidency, Department of Earthquake and Canakkale Onsekiz Mart University Geophysics Department). These seismic stations are deployed closer than 80 km epicentral distance in the Simav-Kutahya. Average crustal velocity and average crustal thickness for the region are computed as 5.68 km/sn and 37.6 km, respectively. The source mechanism of fifty aftershocks with magnitudes greater than 4.0 are derived from first motion P phases. Analysis of focal mechanisms indicate mainly normal fault motions with oblique slip.

Very-long-period seismic signals at the Tatun Volcano Group, northern Taiwan

NASA Astrophysics Data System (ADS)

Lin, C. H.; Pu, H. C.

2016-12-01

Very-long-period (VLP) seismic events have been detected in the Tatun Volcano Group (TVG), located around the border between Taipei City and New Taipei City in northern Taiwan, in which has 7 million residents. By using both analyses of particle motions and travel-time delay, one VLP volcanic earthquake's source is estimated to be at a shallow depth ( 800 m) beneath Mt. Chihsin, which is the highest and youngest volcano in the TVG. The significant variation of seismic energy at different azimuths provides strong evidence to distinguish a crack source from other kinds of sources, such as a sphere, vertical pipe or even double-couple source. This is further confirmed by synthetic modeling of the seismograms recorded at two stations as well as the compressional first-motion at three seismic stations. Thus, a deeper plumping system with high-pressure fluid is required to generate the VLP signals and other volcanic earthquakes in the TVG. Combining this result with those of previous studies, we conclude that the TVG might not be totally extinct and some further investigations must be carried out to improve understanding of the volcanic characteristics of the TVG.

Geoscience Australia Continuous Global Positioning System (CGPS) Station Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruddick, R.; Twilley, B.

2016-03-01

This station formed part of the Australian Regional GPS Network (ARGN) and South Pacific Regional GPS Network (SPRGN), which is a network of continuous GPS stations operating within Australia and its Territories (including Antarctica) and the Pacific. These networks support a number of different science applications including maintenance of the Geospatial Reference Frame, both national and international, continental and tectonic plate motions, sea level rise, and global warming.

Seismic velocity model of the central United States (Version 1): Description and simulation of the 18 April 2008 Mt. Carmel, Illinois, Earthquake

USGS Publications Warehouse

Ramírez‐Guzmán, Leonardo; Boyd, Oliver S.; Hartzell, Stephen; Williams, Robert A.

2012-01-01

We have developed a new three‐dimensional seismic velocity model of the central United States (CUSVM) that includes the New Madrid Seismic Zone (NMSZ) and covers parts of Arkansas, Mississippi, Alabama, Illinois, Missouri, Kentucky, and Tennessee. The model represents a compilation of decades of crustal research consisting of seismic, aeromagnetic, and gravity profiles; geologic mapping; geophysical and geological borehole logs; and inversions of the regional seismic properties. The density, P‐ and S‐wave velocities are synthesized in a stand‐alone spatial database that can be queried to generate the required input for numerical seismic‐wave propagation simulations. We test and calibrate the CUSVM by simulating ground motions of the 18 April 2008 Mw 5.4 Mt. Carmel, Illinois, earthquake and comparing the results with observed records within the model area. The selected stations in the comparisons reflect different geological site conditions and cover distances ranging from 10 to 430 km from the epicenter. The results, based on a qualitative and quantitative goodness‐of‐fit (GOF) characterization, indicate that both within and outside the Mississippi Embayment the CUSVM reasonably reproduces: (1) the body and surface‐wave arrival times and (2) the observed regional variations in ground‐motion amplitude, cumulative energy, duration, and frequency content up to a frequency of 1.0 Hz. In addition, we discuss the probable structural causes for the ground‐motion patterns in the central United States that we observed in the recorded motions of the 18 April Mt. Carmel earthquake.

Towards the application of seismogeodesy in central Italy: a case study for the 2016 August 24 Mw 6.1 Italy earthquake modelling

NASA Astrophysics Data System (ADS)

Chen, Kejie; Liu, Zhen; Liang, Cunren; Song, Y. Tony

2018-06-01

Dense strong motion and high-rate Global Navigation Satellite Systems (GNSS) networks have been deployed in central Italy for rapid seismic source determination and corresponding hazard mitigation. Different from previous studies for the consistency between two kinds of sensor at collocated stations, here we focus on the combination of high-rate GNSS displacement waveforms with collocated seismic strong motion accelerators, and investigate its application to image rupture history. Taking the 2016 August 24 Mw 6.1 Central Italy earthquake as a case study, we first generate more accurate and longer period seismogeodetic displacement waveforms by a Kalman filter, then model the rupture behaviour through a joint inversion including seismogeodetic waveforms and InSAR observations. Our results reveal that strong motion data alone can overestimate the magnitude and mismatch the GNSS observations, while 1 Hz sampling rate GNSS is insufficient and the displacement is too noisy to depict rupture process. By contrast, seismogeodetic data enhances temporal resolution and maintains the static offsets that provide vital constraint to the reliable estimation of earthquake magnitude. The obtained model is close to the jointly inverted one. Our work demonstrates the unique usefulness of seismogeodesy for fast seismic hazard response.

Oceanic-wave-measurement system

NASA Technical Reports Server (NTRS)

Holmes, J. F.; Miles, R. T.

1980-01-01

Barometer mounted on bouy senses wave heights. As wave motion raises and lowers barometer, pressure differential is proportional to wave height. Monitoring circuit samples barometer output every half cycle of wave motion and adds magnitudes of adjacent positive and negative peaks. Resulting output signals, proportional to wave height, are transmitted to central monitoring station.

Strong-motion observations of the M 7.8 Gorkha, Nepal, earthquake sequence and development of the N-shake strong-motion network

USGS Publications Warehouse

Dixit, Amod; Ringler, Adam; Sumy, Danielle F.; Cochran, Elizabeth S.; Hough, Susan E.; Martin, Stacey; Gibbons, Steven; Luetgert, James H.; Galetzka, John; Shrestha, Surya; Rajaure, Sudhir; McNamara, Daniel E.

2015-01-01

We present and describe strong-motion data observations from the 2015 M 7.8 Gorkha, Nepal, earthquake sequence collected using existing and new Quake-Catcher Network (QCN) and U.S. Geological Survey NetQuakes sensors located in the Kathmandu Valley. A comparison of QCN data with waveforms recorded by a conventional strong-motion (NetQuakes) instrument validates the QCN data. We present preliminary analysis of spectral accelerations, and peak ground acceleration and velocity for earthquakes up to M 7.3 from the QCN stations, as well as preliminary analysis of the mainshock recording from the NetQuakes station. We show that mainshock peak accelerations were lower than expected and conclude the Kathmandu Valley experienced a pervasively nonlinear response during the mainshock. Phase picks from the QCN and NetQuakes data are also used to improve aftershock locations. This study confirms the utility of QCN instruments to contribute to ground-motion investigations and aftershock response in regions where conventional instrumentation and open-access seismic data are limited. Initial pilot installations of QCN instruments in 2014 are now being expanded to create the Nepal–Shaking Hazard Assessment for Kathmandu and its Environment (N-SHAKE) network.

Fault parameter constraints using relocated earthquakes: A validation of first-motion focal-mechanism data

USGS Publications Warehouse

Kilb, Debi; Hardebeck, J.L.

2006-01-01

We estimate the strike and dip of three California fault segments (Calaveras, Sargent, and a portion of the San Andreas near San Jaun Bautistia) based on principle component analysis of accurately located microearthquakes. We compare these fault orientations with two different first-motion focal mechanism catalogs: the Northern California Earthquake Data Center (NCEDC) catalog, calculated using the FPFIT algorithm (Reasenberg and Oppenheimer, 1985), and a catalog created using the HASH algorithm that tests mechanism stability relative to seismic velocity model variations and earthquake location (Hardebeck and Shearer, 2002). We assume any disagreement (misfit >30° in strike, dip, or rake) indicates inaccurate focal mechanisms in the catalogs. With this assumption, we can quantify the parameters that identify the most optimally constrained focal mechanisms. For the NCEDC/FPFIT catalogs, we find that the best quantitative discriminator of quality focal mechanisms is the station distribution ratio (STDR) parameter, an indicator of how the stations are distributed about the focal sphere. Requiring STDR > 0.65 increases the acceptable mechanisms from 34%–37% to 63%–68%. This suggests stations should be uniformly distributed surrounding, rather than aligning, known fault traces. For the HASH catalogs, the fault plane uncertainty (FPU) parameter is the best discriminator, increasing the percent of acceptable mechanisms from 63%–78% to 81%–83% when FPU ≤ 35°. The overall higher percentage of acceptable mechanisms and the usefulness of the formal uncertainty in identifying quality mechanisms validate the HASH approach of testing for mechanism stability.

Study of stability and control moment gyro wobble damping of flexible, spinning space stations

NASA Technical Reports Server (NTRS)

Berman, H.; Markowitz, J.; Holmer, W.

1972-01-01

An executive summary and an analysis of the results are discussed. A user's guide for the digital computer program that simulates the flexible, spinning space station is presented. Control analysis activities and derivation of dynamic equations of motion and the modal analysis are also cited.

Earth Day at Union Station

NASA Image and Video Library

2013-04-22

Students assemble balloon race cars and Alka-Seltzer film canister rockets to demonstrate Newton's third Law of motion at the NASA Science Gallery at Union Station, Monday, April 22, 2013 in Washington. The NASA Science Gallery exhibits are being sponsored by NASA in honor of Earth Day. (Photo Credit: NASA/Carla Cioffi)

Observation model and parameter partials for the JPL geodetic (GPS) modeling software 'GPSOMC'

NASA Technical Reports Server (NTRS)

Sovers, O. J.

1990-01-01

The physical models employed in GPSOMC, the modeling module of the GIPSY software system developed at JPL for analysis of geodetic Global Positioning Satellite (GPS) measurements are described. Details of the various contributions to range and phase observables are given, as well as the partial derivatives of the observed quantities with respect to model parameters. A glossary of parameters is provided to enable persons doing data analysis to identify quantities with their counterparts in the computer programs. The present version is the second revision of the original document which it supersedes. The modeling is expanded to provide the option of using Cartesian station coordinates; parameters for the time rates of change of universal time and polar motion are also introduced.

A fault slip model of the 2016 Meinong, Taiwan, earthquake from near-source strong motion and high-rate GPS waveforms

NASA Astrophysics Data System (ADS)

Rau, Ruey-Juin; Wen, Yi-Ying; Tseng, Po-Ching; Chen, Wei-Cheng; Cheu, Chi-Yu; Hsieh, Min-Che; Ching, Kuo-En

2017-04-01

The 6 February 2016 MW 6.5 Meinong earthquake (03:57:26.1 local time) occurred at about 30 km ESE of the Tainan city with a focal depth of 14.6 km. It is a mid-crust moderate-sized event, however, produced widespread strong shaking in the 30-km-away Tainan city and caused about 10 buildings collapsed and 117 death. Furthermore, the earthquake created a 20 x 10 km2 dome-shaped structure with a maximum uplift of 13 cm in between the epicenter and the Tainan city. We collected 81 50-Hz GPS and 130 strong motion data recorded within 60 km epicentral distances. High-rate GPS data are processed with GIPSY 6.4 and the calculated GPS displacement wavefield record section shows 40-60 cm Peak Ground Displacement (PGD) concentrated at 25-30 km WNW of the epicenter. The large PGDs correspond to 65-85 cm/sec PGV, which are significantly larger than the near-fault ground motion collected from moderate-sized earthquakes occurred worldwide. To investigate the source properties of the causative fault, considering the azimuthal coverage and data quality, we selected waveform data from 10 50-Hz GPS stations and 10 free-field 200-Hz strong motion stations to invert for the finite source parameters using the non-negative least squares approach. A bandpass filter of 0.05-0.5 Hz is applied to both high-rate GPS data and strong motion data, with sampling rate of 0.1 sec. The fault plane parameters (strike 281 degrees, dip 24 degrees) derived from Global Centroid Moment Tensor (CMT) are used in the finite fault inversion. The results of our joint GPS and strong motion data inversion indicates two major slip patches. The first large-slip patch occurred just below the hypocenter propagating westward at a 15-25 km depth range. The second high-slip patch appeared at 5-10 km depth slipping westward under the western side of the erected structure shown by InSAR image. These two large-slip patches appeared to devoid of aftershock seismicity, which concentrated mainly at the low-slip zones.

Magma wagging and whirling in volcanic conduits

NASA Astrophysics Data System (ADS)

Liao, Yang; Bercovici, David; Jellinek, Mark

2018-02-01

Seismic tremor characterized by 0.5-7 Hz ground oscillations commonly occur before and during eruptions at silicic volcanoes with widely ranging vent geometries and edifice structures. The ubiquitous characteristics of this tremor imply that its causes are potentially common to silicic volcanoes. Here we revisit and extend to three dimensions the magma-wagging model for tremor (Jellinek and Bercovici, 2011; Bercovici et al., 2013), wherein a stiff magma column rising in a vertical conduit oscillates against a surrounding foamy annulus of bubbly magma, giving rise to tremor. While prior studies were restricted to two-dimensional lateral oscillations, here we explore three-dimensional motion and additional modes of oscillations. In the absence of viscous damping, the magma column undergoes 'whirling' motion: the center of each horizontal section of the column traces an elliptical trajectory. In the presence of viscous effect we identify new 'coiling' and 'uncoiling' column bending shapes with relatively higher and comparable rates of dissipation to the original two-dimensional magma wagging model. We also calculate the seismic P-wave response of the crustal material around the volcanic conduit to the new whirling motions and propose seismic diagnostics for different wagging patterns using the time-lag between seismic stations. We test our model by analyzing pre-eruptive seismic data from the 2009 eruption of Redoubt Volcano. In addition to suggesting that the occurrence of elliptical whirling motion more than 1 week before the eruption, our analysis of seismic time-lags also implies that the 2009 eruption was accompanied by qualitative changes in the magma wagging behavior including fluctuations in eccentricity and a reversal in the direction of elliptical whirling motion when the eruption was immediately impending.

Prediction of Strong Earthquake Ground Motion for the M=7.4 and M=7.2 1999, Turkey Earthquakes based upon Geological Structure Modeling and Local Earthquake Recordings

NASA Astrophysics Data System (ADS)

Gok, R.; Hutchings, L.

2004-05-01

We test a means to predict strong ground motion using the Mw=7.4 and Mw=7.2 1999 Izmit and Duzce, Turkey earthquakes. We generate 100 rupture scenarios for each earthquake, constrained by a prior knowledge, and use these to synthesize strong ground motion and make the prediction. Ground motion is synthesized with the representation relation using impulsive point source Green's functions and synthetic source models. We synthesize the earthquakes from DC to 25 Hz. We demonstrate how to incorporate this approach into standard probabilistic seismic hazard analyses (PSHA). The synthesis of earthquakes is based upon analysis of over 3,000 aftershocks recorded by several seismic networks. The analysis provides source parameters of the aftershocks; records available for use as empirical Green's functions; and a three-dimensional velocity structure from tomographic inversion. The velocity model is linked to a finite difference wave propagation code (E3D, Larsen 1998) to generate synthetic Green's functions (DC < f < 0.5 Hz). We performed the simultaneous inversion for hypocenter locations and three-dimensional P-wave velocity structure of the Marmara region using SIMULPS14 along with 2,500 events. We also obtained source moment and corner frequency and individual station attenuation parameter estimates for over 500 events by performing a simultaneous inversion to fit these parameters with a Brune source model. We used the results of the source inversion to deconvolve out a Brune model from small to moderate size earthquake (M<4.0) recordings to obtain empirical Green's functions for the higher frequency range of ground motion (0.5 < f < 25.0 Hz). Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-ENG-48.

A short note on ground-motion recordings from the M 7.9 Wenchuan, China, earthquake and ground-motion prediction equations in the Central and Eastern United States

USGS Publications Warehouse

Wang, Z.; Lu, M.

2011-01-01

The 12 May 2008 Wenchuan earthquake (M 7.9) occurred along the western edge of the eastern China SCR and was well recorded by modern strong-motion instruments: 93 strong-motion stations within 1.4 to 300 km rupture distance recorded the main event. Preliminary comparisons show some similarities between ground-motion attenuation in the Wenchuan region and the central and eastern United States, suggesting that ground motions from the Wenchuan earthquake could be used as a database providing constraints for developing GMPEs for large earthquakes in the central and eastern United States.

Process modelling for Space Station experiments

NASA Technical Reports Server (NTRS)

Alexander, J. Iwan D.; Rosenberger, Franz; Nadarajah, Arunan; Ouazzani, Jalil; Amiroudine, Sakir

1990-01-01

Examined here is the sensitivity of a variety of space experiments to residual accelerations. In all the cases discussed the sensitivity is related to the dynamic response of a fluid. In some cases the sensitivity can be defined by the magnitude of the response of the velocity field. This response may involve motion of the fluid associated with internal density gradients, or the motion of a free liquid surface. For fluids with internal density gradients, the type of acceleration to which the experiment is sensitive will depend on whether buoyancy driven convection must be small in comparison to other types of fluid motion, or fluid motion must be suppressed or eliminated. In the latter case, the experiments are sensitive to steady and low frequency accelerations. For experiments such as the directional solidification of melts with two or more components, determination of the velocity response alone is insufficient to assess the sensitivity. The effect of the velocity on the composition and temperature field must be considered, particularly in the vicinity of the melt-crystal interface. As far as the response to transient disturbances is concerned, the sensitivity is determined by both the magnitude and frequency of the acceleration and the characteristic momentum and solute diffusion times. The microgravity environment, a numerical analysis of low gravity tolerance of the Bridgman-Stockbarger technique, and modeling crystal growth by physical vapor transport in closed ampoules are discussed.

Analysis of strong ground motions and site effects at Kantipath, Kathmandu, from 2015 Mw 7.8 Gorkha, Nepal, earthquake and its aftershocks

NASA Astrophysics Data System (ADS)

Dhakal, Yadab P.; Kubo, Hisahiko; Suzuki, Wataru; Kunugi, Takashi; Aoi, Shin; Fujiwara, Hiroyuki

2016-04-01

Strong ground motions from the 2015 Mw 7.8 Gorkha, Nepal, earthquake and its eight aftershocks recorded by a strong-motion seismograph at Kantipath (KATNP), Kathmandu, were analyzed to assess the ground-motion characteristics and site effects at this location. Remarkably large elastic pseudo-velocity responses exceeding 300 cm/s at 5 % critical damping were calculated for the horizontal components of the mainshock recordings at peak periods of 4-5 s. Conversely, the short-period ground motions of the mainshock were relatively weak despite the proximity of the site to the source fault. The horizontal components of all large-magnitude (Mw ≥ 6.3) aftershock recordings showed peak pseudo-velocity responses at periods of 3-4 s. Ground-motion prediction equations (GMPEs) describing the Nepal Himalaya region have not yet been developed. A comparison of the observational data with GMPEs for Japan showed that with the exception of the peak ground acceleration (PGA) of the mainshock, the observed PGAs and peak ground velocities at the KATNP site are generally well described by the GMPEs for crustal and plate interface events. A comparison of the horizontal-to-vertical ( H/ V) spectral ratios for the S-waves of the mainshock and aftershock recordings suggested that the KATNP site experienced a considerable nonlinear site response, which resulted in the reduced amplitudes of short-period ground motions. The GMPEs were found to underestimate the response values at the peak periods (approximately 4-5 s) of the large-magnitude events. The deep subsurface velocity model of the Kathmandu basin has not been well investigated. Therefore, a one-dimensional velocity model was constructed for the deep sediments beneath the recording station based on an analysis of the H/ V spectral ratios for S-wave coda from aftershock recordings, and it was revealed that the basin sediments strongly amplified the long-period components of the ground motions of the mainshock and large-magnitude aftershocks.

32 CFR 705.2 - Chief of Information and the Office of Information (CHINFO).

Code of Federal Regulations, 2010 CFR

2010-07-01

... agencies. (v) Maintain a library of Navy motion picture films for use by local television stations... motion picture and network television offices in the Hollywood area. Naval activities will channel all... reaction teams/resource personnel responsive to the requirements of the CNO and CHINFO, and when feasible...

32 CFR 705.2 - Chief of Information and the Office of Information (CHINFO).

Code of Federal Regulations, 2011 CFR

2011-07-01

... agencies. (v) Maintain a library of Navy motion picture films for use by local television stations... motion picture and network television offices in the Hollywood area. Naval activities will channel all... reaction teams/resource personnel responsive to the requirements of the CNO and CHINFO, and when feasible...

Present-day plate motions: Retrieval from the TOPEX/Poseidon orbitography network (DORIS system)

NASA Technical Reports Server (NTRS)

Souriau, Annie; Cazenave, Anny; Biancale, R.; Balmino, G.; Dominh, K.; Mazzega, P.; Lemoine, J.-M.; Boucher, Claude; Willis, P.; Kasser, M.

1991-01-01

The goal of the proposal is to determine the present motion of the main tectonic plates from the Doppler data of the Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) orbitography system, which includes in its final configuration about 50 tracking stations with a world-wide distribution.

Tribology approach to the engineering and study of articular cartilage.

PubMed

Wimmer, Markus A; Grad, Sibylle; Kaup, Thomas; Hänni, Markus; Schneider, Erich; Gogolewski, Sylwester; Alini, Mauro

2004-01-01

This study has been based on the assumption that articular motion is an important aspect of mechanotransduction in synovial joints. For this reason a new bioreactor concept, able to reproduce joint kinematics more closely, has been designed. The prototype consists of a rotating scaffold and/or cartilage pin, which is pressed onto an orthogonally rotating ball. By oscillating pin and ball in phase difference, elliptical displacement trajectories are generated that are similar to the motion paths occurring in vivo. Simultaneously, dynamic compression may be applied with a linear actuator, while two-step-motors generate the rotation of pin and ball. The whole apparatus is placed in an incubator. The control station is located outside. Preliminary investigations at the gene expression level demonstrated promising results. Compared with free-swelling control and/or simply compression-loaded samples, chondrocyte-seeded scaffolds as well as nasal cartilage explants exposed to interface motion both showed elevated levels of cartilage oligomeric matrix protein mRNA. The final design of the bioreactor will include four individual stations in line, which will facilitate the investigation of motion-initiated effects at the contacting surfaces in more detail.

Virtual egocenters as a function of display geometric field of view and eye station point

NASA Technical Reports Server (NTRS)

Psotka, Joseph

1993-01-01

The accurate location of one's virtual egocenter in a geometric space is of critical importance for immersion technologies. This experiment was conducted to investigate the role of field of view (FOV) and observer station points in the perception of the location of one's egocenter (the personal viewpoint) in virtual space. Rivalrous cues to the accurate location of one's egocenter may be one factor involved in simulator sickness. Fourteen subjects viewed an animated 3D model, of the room in which they sat, binocularly, from Eye Station Points (ESP) of either 300 or 800 millimeters. The display was on a 190 by 245 mm monitor, at a resolution of 320 by 200 pixels with 256 colors. They saw four models of the room designed with four geometric field of view (FOVg) conditions of 18, 48, 86, and 140 degrees. They drew the apparent paths of the camera in the room on a bitmap of the room as seen from infinity above. Large differences in the paths of the camera were seen as a function of both FOVg and ESP. Ten of the subjects were then asked to find the position for each display that minimized camera motion. The results fit well with predictions from an equation that took the ratio of human FOV (roughly 180 degrees) to FOVg times the Geometric Eye Point (GEP) of the imager: Zero Station Point = (180/FOVg)*GEP

On the potential of seismic rotational motion measurements for extraterrestrial seismology

NASA Astrophysics Data System (ADS)

Schmelzbach, Cedric; Sollberger, David; Khan, Amir; Greenhalgh, Stewart; Van Renterghem, Cederic; Robertsson, Johan

2017-04-01

Classically, seismological recordings consist of measurements of translational ground motion only. However, in addition to three vector components of translation there are three components of rotation to consider, leading to six degrees of freedom. Of particular interest is thereby the fact that measuring rotational motion means isolating shear (S) waves. Recording the rotational motion requires dedicated rotational sensors. Alternatively, since the rotational motion is given by the curl of the vectorial displacements, the rotational motion around the two horizontal axes can be computed from the horizontal spatial gradients of vertical translational recordings if standard translational seismometers are placed in an areal array at the free surface. This follows from the zero stress free surface condition. Combining rotational and translational motion measurements opens up new ways of analyzing seismic data, such as facilitating much improved arrival identification and wavefield separation (e.g., P-/S-wave separation), and local slowness (arrival direction and velocity) determination. Such combined measurements maximize the seismic information content that a single six-component station or a small station array can provide, and are of particular interest for sparse or single-station measurements such as in extraterrestrial seismology. We demonstrate the value of the analysis of combined translational and rotational recordings by re-evaluating data from the Apollo 17 lunar seismic profiling experiment (LSPE). The LSPE setup consisted of four vertical-component geophones arranged in a star-like geometry. This areal receiver layout enables computing the horizontal spatial gradients by spatial finite differencing of the vertical-component data for two perpendicular directions and, hence, the estimation of rotational motion around two horizontal axes. Specifically, the recorded seismic waveform data originated from eight explosive packages as well as from continuously listening to the natural lunar seismic activity of moonquakes. As an example, the combined analysis of translational and rotational motion from the active-source LSPE data provides, for the first time, the possibility to extract S-wave information from the enigmatic and reverbatory lunar seismic waveform data, which hithertofore had masked later arriving S-waves. The identification of S-waves enables to characterize the shallow lunar crust in a full elastic sense. The resultant Poisson's ratio profile allows discriminating shallow basalt layers of different degree of fracturing. Our successful analysis of the Apollo 17 data highlights the anticipated significant value of rotational measurements for future extraterrestrial seismology missions.

How sensitive is earthquake ground motion to source parameters? Insights from a numerical study in the Mygdonian basin

NASA Astrophysics Data System (ADS)

Chaljub, Emmanuel; Maufroy, Emeline; deMartin, Florent; Hollender, Fabrice; Guyonnet-Benaize, Cédric; Manakou, Maria; Savvaidis, Alexandros; Kiratzi, Anastasia; Roumelioti, Zaferia; Theodoulidis, Nikos

2014-05-01

Understanding the origin of the variability of earthquake ground motion is critical for seismic hazard assessment. Here we present the results of a numerical analysis of the sensitivity of earthquake ground motion to seismic source parameters, focusing on the Mygdonian basin near Thessaloniki (Greece). We use an extended model of the basin (65 km [EW] x 50 km [NS]) which has been elaborated during the Euroseistest Verification and Validation Project. The numerical simulations are performed with two independent codes, both implementing the Spectral Element Method. They rely on a robust, semi-automated, mesh design strategy together with a simple homogenization procedure to define a smooth velocity model of the basin. Our simulations are accurate up to 4 Hz, and include the effects of surface topography and of intrinsic attenuation. Two kinds of simulations are performed: (1) direct simulations of the surface ground motion for real regional events having various back azimuth with respect to the center of the basin; (2) reciprocity-based calculations where the ground motion due to 980 different seismic sources is computed at a few stations in the basin. In the reciprocity-based calculations, we consider epicentral distances varying from 2.5 km to 40 km, source depths from 1 km to 15 km and we span the range of possible back-azimuths with a 10 degree bin. We will present some results showing (1) the sensitivity of ground motion parameters to the location and focal mechanism of the seismic sources; and (2) the variability of the amplification caused by site effects, as measured by standard spectral ratios, to the source characteristics

Connecting in Space: Docking with the International Space Station. Educational Brief.

ERIC Educational Resources Information Center

National Aeronautics and Space Administration, Washington, DC.

This brief discusses the space shuttle and the docking procedures used with the International Space Station (ISS). Using this activity designed for grades 5-12, students demonstrate and identify procedures for determining the best method for completing the docking activity. Students will also study and identify Newton's Laws of Motion. A mockup…

Source-Type Identification Analysis Using Regional Seismic Moment Tensors

NASA Astrophysics Data System (ADS)

Chiang, A.; Dreger, D. S.; Ford, S. R.; Walter, W. R.

2012-12-01

Waveform inversion to determine the seismic moment tensor is a standard approach in determining the source mechanism of natural and manmade seismicity, and may be used to identify, or discriminate different types of seismic sources. The successful applications of the regional moment tensor method at the Nevada Test Site (NTS) and the 2006 and 2009 North Korean nuclear tests (Ford et al., 2009a, 2009b, 2010) show that the method is robust and capable for source-type discrimination at regional distances. The well-separated populations of explosions, earthquakes and collapses on a Hudson et al., (1989) source-type diagram enables source-type discrimination; however the question remains whether or not the separation of events is universal in other regions, where we have limited station coverage and knowledge of Earth structure. Ford et al., (2012) have shown that combining regional waveform data and P-wave first motions removes the CLVD-isotropic tradeoff and uniquely discriminating the 2009 North Korean test as an explosion. Therefore, including additional constraints from regional and teleseismic P-wave first motions enables source-type discrimination at regions with limited station coverage. We present moment tensor analysis of earthquakes and explosions (M6) from Lop Nor and Semipalatinsk test sites for station paths crossing Kazakhstan and Western China. We also present analyses of smaller events from industrial sites. In these sparse coverage situations we combine regional long-period waveforms, and high-frequency P-wave polarity from the same stations, as well as from teleseismic arrays to constrain the source type. Discrimination capability with respect to velocity model and station coverage is examined, and additionally we investigate the velocity model dependence of vanishing free-surface traction effects on seismic moment tensor inversion of shallow sources and recovery of explosive scalar moment. Our synthetic data tests indicate that biases in scalar seismic moment and discrimination for shallow sources are small and can be understood in a systematic manner. We are presently investigating the frequency dependence of vanishing traction of a very shallow (10m depth) M2+ chemical explosion recorded at several kilometer distances, and preliminary results indicate at the typical frequency passband we employ the bias does not affect our ability to retrieve the correct source mechanism but may affect the retrieval of the correct scalar seismic moment. Finally, we assess discrimination capability in a composite P-value statistical framework.

Combining Real-time Seismic and Geodetic Data to Improve Rapid Earthquake Information

NASA Astrophysics Data System (ADS)

Murray, M. H.; Neuhauser, D. S.; Gee, L. S.; Dreger, D. S.; Basset, A.; Romanowicz, B.

2002-12-01

The Berkeley Seismological Laboratory operates seismic and geodetic stations in the San Francisco Bay area and northern California for earthquake and deformation monitoring. The seismic systems, part of the Berkeley Digital Seismic Network (BDSN), include strong motion and broadband sensors, and 24-bit dataloggers. The data from 20 GPS stations, part of the Bay Area Regional Deformation (BARD) network of more than 70 stations in northern California, are acquired in real-time. We have developed methods to acquire GPS data at 12 stations that are collocated with the seismic systems using the seismic dataloggers, which have large on-site data buffer and storage capabilities, merge it with the seismic data stream in MiniSeed format, and continuously stream both data types using reliable frame relay and/or radio modem telemetry. Currently, the seismic data are incorporated into the Rapid Earthquake Data Integration (REDI) project to provide notification of earthquake magnitude, location, moment tensor, and strong motion information for hazard mitigation and emergency response activities. The geodetic measurements can provide complementary constraints on earthquake faulting, including the location and extent of the rupture plane, unambiguous resolution of the nodal plane, and distribution of slip on the fault plane, which can be used, for example, to refine strong motion shake maps. We are developing methods to rapidly process the geodetic data to monitor transient deformation, such as coseismic station displacements, and for combining this information with the seismic observations to improve finite-fault characterization of large earthquakes. The GPS data are currently processed at hourly intervals with 2-cm precision in horizontal position, and we are beginning a pilot project in the Bay Area in collaboration with the California Spatial Reference Center to do epoch-by-epoch processing with greater precision.

Towards Integrated Marmara Strong Motion Network

NASA Astrophysics Data System (ADS)

Durukal, E.; Erdik, M.; Safak, E.; Ansal, A.; Ozel, O.; Alcik, H.; Mert, A.; Kafadar, N.; Korkmaz, A.; Kurtulus, A.

2009-04-01

Istanbul has a 65% chance of having a magnitude 7 or above earthquake within the next 30 years. As part of the preparations for the future earthquake, strong motion networks have been installed in and around Istanbul. The Marmara Strong Motion Network, operated by the Department of Earthquake Engineering of Kandilli Observatory and Earthquake Research Institute, encompasses permanent systems outlined below. It is envisaged that the networks will be run by a single entity responsible for technical management and maintanence, as well as for data management, archiving and dissemination through dedicated web-based interfaces. • Istanbul Earthquake Rapid Response and Early Warning System - IERREWS (one hundred 18-bit accelerometers for rapid response; ten 24-bit accelerometers for early warning) • IGDAŞ Gas Shutoff Network (100 accelerometers to be installed in 2010 and integrated with IERREWS) • Structural Monitoring Arrays - Fatih Sultan Mehmet Suspension Bridge (1200m-long suspension bridge across the Bosphorus, five 3-component accelerometers + GPS sensors) - Hagia Sophia Array (1500-year-old historical edifice, 9 accelerometers) - Süleymaniye Mosque Array (450-year-old historical edifice,9 accelerometers) - Fatih Mosque Array (237-year-old historical edifice, 9 accelerometers) - Kanyon Building Array (high-rise office building, 5 accelerometers) - Isbank Tower Array (high-rise office building, 5 accelerometers) - ENRON Array (power generation facility, 4 acelerometers) - Mihrimah Sultan Mosque Array (450-year-old historical edifice,9 accelerometers + tiltmeters, to be installed in 2009) - Sultanahmet Mosque Array, (390-year-old historical edifice, 9 accelerometers + tiltmeters, to be installed in 2009) • Special Arrays - Atakoy Vertical Array (four 3-component accelerometers at 25, 50, 75, and 150 m depths) - Marmara Tube Tunnel (1400 m long submerged tunnel, 128 ch. accelerometric data, 24 ch. strain data, to be installed in 2010) - Air-Force Academy Array (72 ch. dense accelerometric array to be installed in 2010) - Gemlik Array (a dense basin array of 8 stations, to be installed in 2010) The objectives of these systems and networks are: (1) to produce rapid earthquake intensity, damage and loss assessment information after an earthquake (in the case of IERREWS), (2) to monitor conditions of structural systems, (3) to develop real-time data processing, analysis, and damage detection and location tools (in the case of structural networks) after an extreme event, (4) to assess spatial properties of strong ground motion and ground strain, and to characterise basin response (in the case of special arrays), (5) to investigate site response and wave propagation (in the case of vertical array). Ground motion data obtained from these strong motion networks have and are being used for investigations of attenuation, spatial variation (coherence), simulation benchmarking, source modeling, site response, seismic microzonation, system identification and structural model verification and structural health control. In addition to the systems and networks outlined above there are two temporary networks: KIMNET - a dense urban noise and microtremor network consisting of 50 broadband stations expected to be operational in mid 2009, and SOSEWIN - a 20-station, self-organizing structural integrated array at Ataköy in Istanbul.

Limitation and applicability of microtremor records for site-response estimation

NASA Astrophysics Data System (ADS)

Song, G.; Kang, T.; Park, S.

2010-12-01

Site effects are the modifications of seismic motions which are traveling through near-surface materials. The impedance contrast between the topmost layer and bedrock may significantly amplify ground motions and augment their durations. Inelastic behavior of the geological media such as highly fractured/weathered rocks and unconsolidated sediments may absorb seismic energy, and thus damp the resulting ground motions. It is inherently most desirable to evaluate the site effects using seismic records from large earthquakes. If there are only small events that will be recorded by several seismograph stations, it becomes difficult to evaluate site effects using earthquake data. Recently a number of studies pay attention to microtremor records to assess site effects. The main reason of such efforts is that measurements are relatively easy regardless of site condition and cost-effective without necessity of waiting for earthquakes or of using active sources. Especially microtremor measurements are exclusively a useful option to assess site effects, and thus seismic microzonation, in the urban area and/or region of low to moderate seismicity. Spectral ratios of horizontal components to vertical component (HVSR) of microtremor records have been popular for estimation of site resonant frequency. Although some studies have shown that the amplitude of spectral ratios is an indicator of site amplification relative to bedrock motion, there are still debates on it. This discrepancy may originate from the deficiency of our understanding on the nature of microtremor. Therefore, it is important to understand the limitation and applicability of microtremor records for site-effect assessments. The focus on this problem is how microtremor responses on the subsurface structures and their physical properties, and how parameters deduced from microtremor analyses are related to site responses during earthquake ground motions. In order to investigate how these issues have a practical meaning in real cases, results obtained using the microtremor method were compared with results from a field test, a spectral inversion method, and the reference station method for sites of strong motion stations in the southern Korean Peninsula.

Travel time seismic tomography on Reykjanes, SW Iceland

NASA Astrophysics Data System (ADS)

Jousset, Philippe; Ágústsson, Kristjan; Blanck, Hanna; Metz, Malte; Franke, Steven; Pàll Hersir, Gylfi; Bruhn, David; Flovenz, Ólafur; Friðleifsson, Guðmundur

2017-04-01

We present updated tomographic results obtained using seismic data recorded around geothermal reservoirs located both on-land Reykjanes, SW-Iceland and offshore along Reykjanes Ridge. We gathered records from a network of 234 seismic stations (including 24 Ocean Bottom Seismometers) deployed between April 2014 and August 2015. In order to determine the orientation of the OBS stations, we used Rayleigh waves planar particle motions from large magnitude earthquakes. This method proved suitable using the on-land stations: orientations determined using this method with the orientations measured using a giro-compass agreed. We focus on the 3D velocity images using local earthquakes to perform travel time tomography. The processing includes first arrival picking of P- and S- phases using an automatic detection and picking technique based on Akaike Information Criteria. We locate earthquakes by using a non-linear localization technique, as a priori information for deriving a 1D velocity model. We then computed 3D velocity model by joint inversion of each earthquake's location and velocity lateral anomalies with respect to the 1D model. Our models confirms previous models obtained in the area, with enhanced details. In a second step, we performed inversion of the Vp/Vs ratio. Results indicate a low Vp/Vs ratio anomaly at depth suggesting the absence of large magmatic body under Reykjanes, unlike results obtained at other geothermal field, sucha as Krafla and Hengill. We discuss implications of those results in the light of recent IDDP drilling in Reykjanes.

Investigating source processes of isotropic events

NASA Astrophysics Data System (ADS)

Chiang, Andrea

This dissertation demonstrates the utility of the complete waveform regional moment tensor inversion for nuclear event discrimination. I explore the source processes and associated uncertainties for explosions and earthquakes under the effects of limited station coverage, compound seismic sources, assumptions in velocity models and the corresponding Green's functions, and the effects of shallow source depth and free-surface conditions. The motivation to develop better techniques to obtain reliable source mechanism and assess uncertainties is not limited to nuclear monitoring, but they also provide quantitative information about the characteristics of seismic hazards, local and regional tectonics and in-situ stress fields of the region . This dissertation begins with the analysis of three sparsely recorded events: the 14 September 1988 US-Soviet Joint Verification Experiment (JVE) nuclear test at the Semipalatinsk test site in Eastern Kazakhstan, and two nuclear explosions at the Chinese Lop Nor test site. We utilize a regional distance seismic waveform method fitting long-period, complete, three-component waveforms jointly with first-motion observations from regional stations and teleseismic arrays. The combination of long period waveforms and first motion observations provides unique discrimination of these sparsely recorded events in the context of the Hudson et al. (1989) source-type diagram. We examine the effects of the free surface on the moment tensor via synthetic testing, and apply the moment tensor based discrimination method to well-recorded chemical explosions. These shallow chemical explosions represent rather severe source-station geometry in terms of the vanishing traction issues. We show that the combined waveform and first motion method enables the unique discrimination of these events, even though the data include unmodeled single force components resulting from the collapse and blowout of the quarry face immediately following the initial explosion. In contrast, recovering the announced explosive yield using seismic moment estimates from moment tensor inversion remains challenging but we can begin to put error bounds on our moment estimates using the NSS technique. The estimation of seismic source parameters is dependent upon having a well-calibrated velocity model to compute the Green's functions for the inverse problem. Ideally, seismic velocity models are calibrated through broadband waveform modeling, however in regions of low seismicity velocity models derived from body or surface wave tomography may be employed. Whether a velocity model is 1D or 3D, or based on broadband seismic waveform modeling or the various tomographic techniques, the uncertainty in the velocity model can be the greatest source of error in moment tensor inversion. These errors have not been fully investigated for the nuclear discrimination problem. To study the effects of unmodeled structures on the moment tensor inversion, we set up a synthetic experiment where we produce synthetic seismograms for a 3D model (Moschetti et al., 2010) and invert these data using Green's functions computed with a 1D velocity mode (Song et al., 1996) to evaluate the recoverability of input solutions, paying particular attention to biases in the isotropic component. The synthetic experiment results indicate that the 1D model assumption is valid for moment tensor inversions at periods as short as 10 seconds for the 1D western U.S. model (Song et al., 1996). The correct earthquake mechanisms and source depth are recovered with statistically insignificant isotropic components as determined by the F-test. Shallow explosions are biased by the theoretical ISO-CLVD tradeoff but the tectonic release component remains low, and the tradeoff can be eliminated with constraints from P wave first motion. Path-calibration to the 1D model can reduce non-double-couple components in earthquakes, non-isotropic components in explosions and composite sources and improve the fit to the data. When we apply the 3D model to real data, at long periods (20-50 seconds), we see good agreement in the solutions between the 1D and 3D models and slight improvement in waveform fits when using the 3D velocity model Green's functions. (Abstract shortened by ProQuest.).

Broadening the Quality and Capabilities of the EarthScope Alaska Transportable Array

NASA Astrophysics Data System (ADS)

Busby, R. W.

2016-12-01

In 2016, the EarthScope Transportable Array (TA) program will have 195 broadband seismic stations operating in Alaska and western Canada. This ambitious project will culminate in a network of 268 new or upgraded real-time seismic stations operating through 2019. The challenging environmental conditions and the remoteness of Alaska have motivated a new method for constructing a high-quality, temporary seismic network. The Alaska TA station design builds on experience of the Lower 48 TA deployment and adds design requirements because most stations are accessible only by helicopter. The stations utilize new high-performance posthole sensors, a specially built hammer/auger drill, and lightweight lithium ion batteries to minimize sling loads. A uniform station design enables a modest crew to build the network on a short timeline and operate them through the difficult conditions of rural Alaska. The Alaska TA deployment has increased the quality of seismic data, with some well-sited 2-3 m posthole stations approaching the performance of permanent Global Seismic Network stations emplaced in 100 m boreholes. The real-time data access, power budget, protective enclosure and remote logistics of these TA stations has attracted collaborations with NASA, NOAA, USGS, AVO and other organizations to add auxiliary sensors to the suite of instruments at many TA stations. Strong motion sensors have been added to (18) stations near the subduction trench to complement SM stations operated by AEC, ANSS and GSN. All TA and most upgraded stations have pressure and infrasound sensors, and 150 TA stations are receiving a Vaisala weather sensor, supplied by the National Weather Service Alaska Region and NASA, capable of measuring temperature, pressure, relative humidity, wind speed/direction, and precipitation intensity. We are also installing about (40) autonomous soil temperature profile kits adjacent to northern stations. While the priority continues to be collecting seismic data, these additional strong motion, atmospheric, and soil temperature sensors may motivate the desire extend the operation of certain stations in cooperation with these organizations. The TA has always been amenable to partnerships in the research and education communities that extend the capabilities and reach of the EarthScope Transportable Array.

Improving the resolution of the 2010 Haiti earthquake fault geometry using temporary seismometer deployments

NASA Astrophysics Data System (ADS)

Douilly, R.; Haase, J. S.; Ellsworth, W. L.; Bouin, M.; Calais, E.; Armbruster, J. G.; Mercier De Lepinay, B. F.; Deschamps, A.; Saint Louis, M.; Meremonte, M. E.; Hough, S. E.

2011-12-01

Haiti has several active faults that are capable of producing large earthquakes such as the 2010 Mw 7.0 Haiti earthquake. This earthquake was not unexpected, given geodetic measurements showing strain accumulation on the Enriquillo Plantain Garden Fault Zone, the major fault system in southern Haiti (Manaker et al. 2008). GPS and INSAR data (Calais et al., 2010) show, however, that this rupture occurred on the previously unmapped Léogâne fault, a 60° north dipping oblique blind thrust located immediately north of the Enriquillo Fault. Following the earthquake, several groups installed temporary seismic stations to record aftershocks. Natural Resources Canada installed three broadband seismic stations, Géoazur installed 21 ocean bottom seismometers, L'Institut de Physique du Globe de Paris installed 5 broadband seismometers, and the United States Geological Survey deployed 17 short period and strong motion seismometers in and around Port-au-Prince. We use data from this complete set of stations, along with data from permanent regional stations, to relocate all of the events from March 17 to June 24, to determine the regional one-dimensional crustal structure and determine focal mechanisms. The aftershock locations from the combined data set clearly delineate the Léogâne fault. The strike and dip closely agrees with that of the global centroid moment tensor solution, but appears to be more steeply dipping than the finite fault inversions. The aftershocks also delineate a flat structure on the west side of the rupture zone and may indicate triggered seismicity on the Trois Baies fault, although the depths of these events are not as well constrained. There is no clear evidence for aftershocks on the other rupture segments inferred in the Hayes et al. (2010) mainshock rupture model. There is a cluster of aftershocks in the hanging wall near the western patch of high slip identified by Calais et al. (2010) and Meng et al. (2011), or central patch in the Hayes et al. (2010) model. We use first-motion focal mechanism solutions to clarify the relationship of the fault geometry to the mechanisms of the larger events.

Atypical soil behavior during the 2011 Tohoku earthquake ( Mw = 9)

NASA Astrophysics Data System (ADS)

Pavlenko, Olga V.

2016-07-01

To understand physical mechanisms of generation of abnormally high peak ground acceleration (PGA; >1 g) during the Tohoku earthquake, models of nonlinear soil behavior in the strong motion were constructed for 27 KiK-net stations located in the near-fault zones to the south of FKSH17. The method of data processing used was developed by Pavlenko and Irikura, Pure Appl Geophys 160:2365-2379, 2003 and previously applied for studying soil behavior at vertical array sites during the 1995 Kobe (Mw = 6.8) and 2000 Tottori (Mw = 6.7) earthquakes. During the Tohoku earthquake, we did not observe a widespread nonlinearity of soft soils and reduction at the beginning of strong motion and recovery at the end of strong motion of shear moduli in soil layers, as usually observed during strong earthquakes. Manifestations of soil nonlinearity and reduction of shear moduli during strong motion were observed at sites located close to the source, in coastal areas. At remote sites, where abnormally high PGAs were recorded, shear moduli in soil layers increased and reached their maxima at the moments of the highest intensity of the strong motion, indicating soil hardening. Then, shear moduli reduced with decreasing the intensity of the strong motion. At soft-soil sites, the reduction of shear moduli was accompanied by a step-like decrease of the predominant frequencies of motion. Evidently, the observed soil hardening at the moments of the highest intensity of the strong motion contributed to the occurrence of abnormally high PGA, recorded during the Tohoku earthquake.

Threshold for sand mobility on Mars calibrated from seasonal variations of sand flux.

PubMed

Ayoub, F; Avouac, J-P; Newman, C E; Richardson, M I; Lucas, A; Leprince, S; Bridges, N T

2014-09-30

Coupling between surface winds and saltation is a fundamental factor governing geological activity and climate on Mars. Saltation of sand is crucial for both erosion of the surface and dust lifting into the atmosphere. Wind tunnel experiments along with measurements from surface meteorology stations and modelling of wind speeds suggest that winds should only rarely move sand on Mars. However, evidence for currently active dune migration has recently accumulated. Crucially, the frequency of sand-moving events and the implied threshold wind stresses for saltation have remained unknown. Here we present detailed measurements of Nili Patera dune field based on High Resolution Imaging Science Experiment images, demonstrating that sand motion occurs daily throughout much of the year and that the resulting sand flux is strongly seasonal. Analysis of the seasonal sand flux variation suggests an effective threshold for sand motion for application to large-scale model wind fields (1-100 km scale) of τ(s)=0.01±0.0015 N m(-2).

Slip reactivation model for the 2011 Mw9 Tohoku earthquake: Dynamic rupture, sea floor displacements and tsunami simulations.

NASA Astrophysics Data System (ADS)

Galvez, P.; Dalguer, L. A.; Rahnema, K.; Bader, M.

2014-12-01

The 2011 Mw9 Tohoku earthquake has been recorded with a vast GPS and seismic network given unprecedented chance to seismologists to unveil complex rupture processes in a mega-thrust event. In fact more than one thousand near field strong-motion stations across Japan (K-Net and Kik-Net) revealed complex ground motion patterns attributed to the source effects, allowing to capture detailed information of the rupture process. The seismic stations surrounding the Miyagi regions (MYGH013) show two clear distinct waveforms separated by 40 seconds. This observation is consistent with the kinematic source model obtained from the inversion of strong motion data performed by Lee's et al (2011). In this model two rupture fronts separated by 40 seconds emanate close to the hypocenter and propagate towards the trench. This feature is clearly observed by stacking the slip-rate snapshots on fault points aligned in the EW direction passing through the hypocenter (Gabriel et al, 2012), suggesting slip reactivation during the main event. A repeating slip on large earthquakes may occur due to frictional melting and thermal fluid pressurization effects. Kanamori & Heaton (2002) argued that during faulting of large earthquakes the temperature rises high enough creating melting and further reduction of friction coefficient. We created a 3D dynamic rupture model to reproduce this slip reactivation pattern using SPECFEM3D (Galvez et al, 2014) based on a slip-weakening friction with sudden two sequential stress drops . Our model starts like a M7-8 earthquake breaking dimly the trench, then after 40 seconds a second rupture emerges close to the trench producing additional slip capable to fully break the trench and transforming the earthquake into a megathrust event. The resulting sea floor displacements are in agreement with 1Hz GPS displacements (GEONET). The seismograms agree roughly with seismic records along the coast of Japan.The simulated sea floor displacement reaches 8-10 meters of up-lift close to the trench, which may be the cause of such a devastating tsunami followed by the Tohoku earthquake. To investigate the impact of such a huge up-lift, we ran tsunami simulations with the slip reactivation model using sam(oa)2 (O. Meister et al., 2012), a state-of-the-art Finite-Volume framework to simulate the resulting tsunami waves.

Hydrology in Central Europe - a Comparison Between Data from the GRACE Satellite Mission and Ground Superconducting Gravimeters

NASA Astrophysics Data System (ADS)

Crossley, D.; de Linage, C.; Boy, J.-P.; Hinderer, J.

2009-04-01

The surface gravity field is subject to many influences of mass redistribution within the Earth system, operating at the microgal (10-8 m s-2) level and at timescales from minutes to years. We include deformation within the Earth (tides, polar motion), motions within the atmosphere (local, regional, and global loading; also mass attractions), the oceans (non-tidal currents), and near-surface hydrology derived from rainfall (local, regional, and global contributions). In central Europe a network of 7 superconducting gravimeters (the only instrument with the required resolution for this type of work) has been operating for many years, recording variations at the sub-microgal level. Hydrology is the largest component in the un-modelled residual signal, most of which comes from an area within a few hundred m of the instrument. We use data from 2002-2007 to construct a regionalized ground gravity data set that is analyzed by Principal Component (EOF) analysis to extract the predominantly seasonal signal common to all stations. This we compare with the GRACE-derived field using solutions from GFZ Potsdam, CSR Texas, and GRGS Toulouse. There is very good agreement on the phase of the two different types of data, but the amplitude of the ground signal is complicated by the local hydrology around several of the stations, which is both above and below the instrument. We show our most recent analysis and compare the results with the GLDAS global hydrology model from NASA.

SEISMIC ANISOTROPY ANALYSIS IN THE VICTORIA LAND REGION (ANTARCTICA)

NASA Astrophysics Data System (ADS)

Salimbeni, S.; Pondrelli, S.; Danesi, S.; Morelli, A.

2009-12-01

We present here shear wave splitting results obtained from analysis of core refracted teleseismic phases in the Victoria Land region (Antarctica). We used data belonging to permanent and temporary stations in the area. The temporary stations are located around the David Glaciers and installation is part of two expeditions inside the Italian National Antarctic program (PNRA, Programma Nazionale di Ricerche in Antartide). The network was composed by 8 seismic stations, located on rocky outcrops around the glacier, and has been active from November 2003 to February 2004, and from November 2005 to February 2006. One of this (STAR) became permanent on 2004 and data until 2007 are analyzed. We use eigenvalue technique of Silver and Chan (1991) to linearize the rotated and shifted shear wave particle motions and determine the best splitting parameters. Scattered distribution of single shear-wave measurements is obtained. Null measurements follow the same distribution. Average measurements show clearly that the main anisotropy direction is NE-SW, accordingly with previous measurements obtained around this zone. Only two stations, OHG and STAR, have a different orientation and a N-S and NNW-SSE main directions are obtained respectively. The distribution of single shear-wave splitting measurements evidenced periodicity respect the back-azimuth of the events analyzed, therefore a possible two layers anisotropic structures could be supposed. To test this hypothesis we used the Menke and Levin (2003) code that allow to model waveforms using a cross convolution technique in one and two layer's cases. Significant improvements of the misfit in the double layer case allow choosing this more complex model. The one layer structure is the best for permanent stations TNV and VNDA with directions and delay time accordingly with average measurements. The double layer models fit better the data on stations STAR, located near the coast, and OHG located inland, and show in both cases the same contribution of the anisotropy.

Detailed gravity survey to help seismic microzonation: Mapping the thickness of unconsolidated deposits in Ottawa, Canada

NASA Astrophysics Data System (ADS)

Lamontagne, M.; Thomas, M.; Silliker, J.; Jobin, D.

2011-11-01

In this study, measurements of gravity were made to map and model the thickness of Quaternary deposits (sand and clay) overlying Ordovician limestones in a suburb of Ottawa (Orléans, Ontario). Because ground motion amplification is partly related to the thickness of unconsolidated deposits, this work helps refine the assessment of the earthquake damage potential of the area. It also helps the mapping of clay basins, which can locally exceed 100 m in thickness, where ground motion amplification can occur. Previous work, including well log data and seismic methods, have yielded a wealth of information on near-surface geology in Orléans, thereby providing the necessary constraints to test the applicability of gravity modeling in other locations where other methods cannot always be used. Some 104 gravity stations were occupied in an 8 × 12 km test area in the Orléans. Stations were accurately located with differential GPS that provided centimetric accuracy in elevation. Densities of the unconsolidated Quaternary deposits (Champlain Sea clay) determined on core samples and densities determined on limestone samples from outcrops were used to constrain models of the clay layer overlying the higher density bedrock formations (limestone). The gravity anomaly map delineates areas where clay basins attain > 100 m depth. Assuming a realistic density for the Champlain Sea clays (1.9-2.1 g/cm 3), the thickness over the higher density bedrock formations (Ordovician carbonate rocks) was modeled and compared with well logs and two seismic reflection profiles. The models match quite well with the information determined from well logs and seismic methods. It was found that gravity and the thickness of unconsolidated deposits are correlated but the uncertainties in both data sets preclude the definition of a direct correlation between the two. We propose that gravity measurements at a local scale be used as an inexpensive means of mapping the thickness of unconsolidated deposits in low-density urban areas. To obtain meaningful results, three conditions must exist. Firstly, elevations of gravity stations must be measured accurately using differential GPS; secondly, that the regional gravity field must be well defined, and thirdly, that the local geology be simple enough to be realistically represented with a two-layer model.

Standardization of motion sickness induced by left-right and up-down reversing prisms

NASA Technical Reports Server (NTRS)

Reschke, M. F.; Vanderploeg, J. M.; Brumley, E. A.; Kolafa, J. J.; Wood, S. J.

1990-01-01

Reversing prisms are known to produce symptoms of motion sickness, and have been used to provide a chronic stimulus for training subjects on symptom recognition and regulation. However, testing procedures with reversing prisms have not been standardized. A set of procedures were evaluated which could be standardized using prisms for provocation and to compare the results between Right/Left Reversing Prisms (R/L-RP) and Up/Down Reversing Prisms (U/D-RP). Fifteen subjects were tested with both types of prisms using a self paced walking course throughout the laboratory with work stations established at specified intervals. The work stations provided tasks requiring eye-hand-foot coordination and various head movements. Comparisons were also made between these prism tests and two other standardized susceptibility tests, the KC-135 parabolic static chair test and the Staircase Velocity Motion Test (SVMT). Two different types of subjective symptom reports were compared. The R/L-RP were significantly more provocative than the U/D-RP. The incidence of motion sickness symptoms for the R/L-RP was similar to the KC-135 parabolic static chair test. Poor correlations were found between the prism tests and the other standardized susceptibility tests, which might indicate that different mechanisms are involved in provoking motion sickness for these different tests.

On the Analysis of Wind-Induced Noise in Seismological Recordings

NASA Astrophysics Data System (ADS)

Lott, Friederike F.; Ritter, Joachim R. R.; Al-Qaryouti, Mahmoud; Corsmeier, Ulrich

2017-03-01

Atmospheric processes, ranging from microscale turbulence to severe storms on the synoptic scale, impact the continuous ground motion of the earth and have the potential to induce strong broad-band noise in seismological recordings. We designed a target-oriented experiment to quantify the influence of wind on ground motion velocity in the Dead Sea valley. For the period from March 2014 to February 2015, a seismological array, consisting of 15 three-component short-period and broad-band stations, was operated near Madaba, Jordan, complemented by one meteorological tower providing synchronized, continuous three-component measurements of wind speed. Results reveal a pronounced, predominantly linear increase of the logarithmic power of ground motion velocity with rising mean horizontal wind speed at all recording stations. Measurements in rough, mountainous terrain further identify a strong dependency of wind-induced noise on surface characteristics, such as topography and, therefore, demonstrate the necessity to consider wind direction as well. To assess the noise level of seismological recordings with respect to a dynamically changing wind field, we develop a methodology to account for the dependency of power spectral density of ground motion velocity on wind speed and wind direction for long, statistically significant periods. We further introduce the quantitative measure of the ground motion susceptibility to estimate the vulnerability of seismological recordings to the presence of wind.

User needs, benefits and integration of robotic systems in a space station laboratory

NASA Technical Reports Server (NTRS)

Farnell, K. E.; Richard, J. A.; Ploge, E.; Badgley, M. B.; Konkel, C. R.; Dodd, W. R.

1989-01-01

The methodology, results and conclusions of the User Needs, Benefits, and Integration Study (UNBIS) of Robotic Systems in the Space Station Microgravity and Materials Processing Facility are summarized. Study goals include the determination of user requirements for robotics within the Space Station, United States Laboratory. Three experiments were selected to determine user needs and to allow detailed investigation of microgravity requirements. A NASTRAN analysis of Space Station response to robotic disturbances, and acceleration measurement of a standard industrial robot (Intelledex Model 660) resulted in selection of two ranges of low gravity manipulation: Level 1 (10-3 to 10-5 G at greater than 1 Hz.) and Level 2 (less than = 10-6 G at 0.1 Hz). This included an evaluation of microstepping methods for controlling stepper motors and concluded that an industrial robot actuator can perform milli-G motion without modification. Relative merits of end-effectors and manipulators were studied in order to determine their ability to perform a range of tasks related to the three low gravity experiments. An Effectivity Rating was established for evaluating these robotic system capabilities. Preliminary interface requirements were determined such that definition of requirements for an orbital flight demonstration experiment may be established.

Crustal deformation rates in Central and Eastern U.S. inferred from GPS

USGS Publications Warehouse

Gan, Weijun; Prescott, W.H.

2001-01-01

Analysis of continuous GPS observations between 1996 and 2000 at 62 stations distributed throughout the central and eastern United States suggests that the area is generally stable. Seven of the 62 stations show anomalous velocities, but there is reason to suspect their monument stability. Assuming the remaining 55 stations are stable with respect to interior North America, we have found the North America-ITRF97 Euler vector (-1.88o ± 1.04oN, 77.67o ± 0.39oW, 0.201o ± 0.004o Myr-1) that minimizes the RMS station velocity. Referred to fixed North America, all of these velocities are less than 3.2 mm yr-1. Motion of several stations suggests the Mississippi embayment may be moving southward away from the rest of the continent at a rate of 1.7±0.9 mm yr-1. The motion of the embayment produces a large gradient in velocity which, in turn, implies the highest seismic moment accumulation rate that we found. Although the highest rate is only marginally significant, the fact that it occurs near New Madrid, where earthquake risk is thought to be high, argues that the anomaly may be real. Nevertheless, the identification of the anomaly remains tentative.

Shallow Subsurface Velocity Structure using the Ambient Noise for the Garhwal and Kumaon Himalaya.

NASA Astrophysics Data System (ADS)

LAL, S.; Joshi, A.; S.; P.

2017-12-01

Abstract: In this paper effort has been made to obtain one dimensional subsurface velocity structure using H/V spectral ratio method Nakamura (1989). The complete study shows that ambient noises are reflective of structural properties of underlying strata. Data has been obtained at stations from foothills of Himalaya up to higher Himalaya along road using strong motion accelerograph in the Garhwal and Kumaon Himalaya along the two transects lines. Noise data has been processed using the seismosignal software. The ratio between the Fourier amplitude spectra of the horizontal components to the vertical component of the ambient noise had been used to consider the site effects of the concerned site. The relation given by Lermo and Chavez-Garcia (1993) between the thickness of layer and average S- wave velocity of the sedimentary layer has been utilized to obtain sub surface velocity model. To fit the synthetic H/V curve with the observed H/V curve, technique given by Castellaro and Mulargia (2009) is used in the present study. This model is improved via forward modelling to give final one dimensional velocity structure at a particular station. Velocity structures obtained at all stations are used to obtain continuous velocity models for concerned area using Kringing interpolation, which is correlated with the geology and tectonic of region. Keywords: Ambient noise, H/V spectral ratio, Site characterization, Accelerograph, Velocity ReferencesNakamura Y (1989). A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface. QR RTRI 30(1):25-30. Castellaro S, Mulargia F (2009). The effect of velocity inversions on H/V. PAGEOPH 166:567-592. Lermo, J., & Chavez-Garcia, F. J. (1993). Site effect evaluation using spectral ratios with only one station Bulletin Seismological Society of America, 83, 1574-1594.

Ground Motion Prediction Model Using Adaptive Neuro-Fuzzy Inference Systems: An Example Based on the NGA-West 2 Data

NASA Astrophysics Data System (ADS)

Ameur, Mourad; Derras, Boumédiène; Zendagui, Djawed

2018-03-01

Adaptive neuro-fuzzy inference systems (ANFIS) are used here to obtain the robust ground motion prediction model (GMPM). Avoiding a priori functional form, ANFIS provides fully data-driven predictive models. A large subset of the NGA-West2 database is used, including 2335 records from 580 sites and 137 earthquakes. Only shallow earthquakes and recordings corresponding to stations with measured V s30 properties are selected. Three basics input parameters are chosen: the moment magnitude ( Mw), the Joyner-Boore distance ( R JB) and V s30. ANFIS model output is the peak ground acceleration (PGA), peak ground velocity (PGV) and 5% damped pseudo-spectral acceleration (PSA) at periods from 0.01 to 4 s. A procedure similar to the random-effects approach is developed to provide between- and within-event standard deviations. The total standard deviation (SD) varies between [0.303 and 0.360] (log10 units) depending on the period. The ground motion predictions resulting from such simple three explanatory variables ANFIS models are shown to be comparable to the most recent NGA results (e.g., Boore et al., in Earthquake Spectra 30:1057-1085, 2014; Derras et al., in Earthquake Spectra 32:2027-2056, 2016). The main advantage of ANFIS compared to artificial neuronal network (ANN) is its simple and one-off topology: five layers. Our results exhibit a number of physically sound features: magnitude scaling of the distance dependency, near-fault saturation distance increasing with magnitude and amplification on soft soils. The ability to implement ANFIS model using an analytic equation and Excel is demonstrated.

Ground Motion Prediction Model Using Adaptive Neuro-Fuzzy Inference Systems: An Example Based on the NGA-West 2 Data

NASA Astrophysics Data System (ADS)

Ameur, Mourad; Derras, Boumédiène; Zendagui, Djawed

2017-12-01

Adaptive neuro-fuzzy inference systems (ANFIS) are used here to obtain the robust ground motion prediction model (GMPM). Avoiding a priori functional form, ANFIS provides fully data-driven predictive models. A large subset of the NGA-West2 database is used, including 2335 records from 580 sites and 137 earthquakes. Only shallow earthquakes and recordings corresponding to stations with measured V s30 properties are selected. Three basics input parameters are chosen: the moment magnitude (Mw), the Joyner-Boore distance (R JB) and V s30. ANFIS model output is the peak ground acceleration (PGA), peak ground velocity (PGV) and 5% damped pseudo-spectral acceleration (PSA) at periods from 0.01 to 4 s. A procedure similar to the random-effects approach is developed to provide between- and within-event standard deviations. The total standard deviation (SD) varies between [0.303 and 0.360] (log10 units) depending on the period. The ground motion predictions resulting from such simple three explanatory variables ANFIS models are shown to be comparable to the most recent NGA results (e.g., Boore et al., in Earthquake Spectra 30:1057-1085, 2014; Derras et al., in Earthquake Spectra 32:2027-2056, 2016). The main advantage of ANFIS compared to artificial neuronal network (ANN) is its simple and one-off topology: five layers. Our results exhibit a number of physically sound features: magnitude scaling of the distance dependency, near-fault saturation distance increasing with magnitude and amplification on soft soils. The ability to implement ANFIS model using an analytic equation and Excel is demonstrated.

Estimating network effect in geocenter motion: Applications

NASA Astrophysics Data System (ADS)

Zannat, Umma Jamila; Tregoning, Paul

2017-10-01

The network effect is the error associated with the subsampling of the Earth surface by space geodetic networks. It is an obstacle toward the precise measurement of geocenter motion, that is, the relative motion between the center of mass of the Earth system and the center of figure of the Earth surface. In a complementary paper, we proposed a theoretical approach to estimate the magnitude of this effect from the displacement fields predicted by geophysical models. Here we evaluate the effectiveness of our estimate for two illustrative physical processes: coseismic displacements inducing instantaneous changes in the Helmert parameters and elastic deformation due to surface water movements causing secular drifts in those parameters. For the first, we consider simplified models of the 2004 Sumatra-Andaman and the 2011 Tōhoku-Oki earthquakes, and for the second, we use the observations of the Gravity Recovery and Climate Experiment, complemented by an ocean model. In both case studies, it is found that the magnitude of the network effect, even for a large global network, is often as large as the magnitude of the changes in the Helmert parameters themselves. However, we also show that our proposed modification to the definition of the center of network frame to include weights proportional to the area of the Earth surface that the stations represent can significantly reduce the network effect in most cases.

Computational simulation of extravehicular activity dynamics during a satellite capture attempt.

PubMed

Schaffner, G; Newman, D J; Robinson, S K

2000-01-01

A more quantitative approach to the analysis of astronaut extravehicular activity (EVA) tasks is needed because of their increasing complexity, particularly in preparation for the on-orbit assembly of the International Space Station. Existing useful EVA computer analyses produce either high-resolution three-dimensional computer images based on anthropometric representations or empirically derived predictions of astronaut strength based on lean body mass and the position and velocity of body joints but do not provide multibody dynamic analysis of EVA tasks. Our physics-based methodology helps fill the current gap in quantitative analysis of astronaut EVA by providing a multisegment human model and solving the equations of motion in a high-fidelity simulation of the system dynamics. The simulation work described here improves on the realism of previous efforts by including three-dimensional astronaut motion, incorporating joint stops to account for the physiological limits of range of motion, and incorporating use of constraint forces to model interaction with objects. To demonstrate the utility of this approach, the simulation is modeled on an actual EVA task, namely, the attempted capture of a spinning Intelsat VI satellite during STS-49 in May 1992. Repeated capture attempts by an EVA crewmember were unsuccessful because the capture bar could not be held in contact with the satellite long enough for the capture latches to fire and successfully retrieve the satellite.

Radiofrequency Identification

PubMed Central

Jones, Terry L.

2017-01-01

A national campaign is underway to increase the amount of time staff nurses spend at the bedside of hospitalized patients through redesign of the work environment. This kind of work redesign requires robust data depicting what nurses do and how they spend their time. Historically, these kinds of data have been difficult, costly, and time consuming to collect. Wireless capture of data on the movement of humans within the work environment (ie, time and motion) is now possible through radiofrequency identification technology. When small tracking devices the size of a quarter are affixed to their clothing, the movement of nurses throughout a patient care unit can be monitored. The duration and frequency of patient interaction are captured along with the duration of time spent in other locations of interest to include nurses’ station, supply room, medication room, doctors’ station, electronic documentation stations, family waiting rooms, and the hallway. Patterns of nurse movement and time allocation can be efficiently identified, and the effects of staffing practices, workflows, and unit layout evaluated. Integration of radiofrequency identification time and motion data with other databases enables nurse leaders to link nursing time to important cost and quality outcomes. Nurse leaders should explore the usefulness of radiofrequency identification technology in addressing data needs for nurse time and motion. PMID:22592451

Study of plasma environments for the integrated Space Station electromagnetic analysis system

NASA Technical Reports Server (NTRS)

Singh, Nagendra

1992-01-01

The final report includes an analysis of various plasma effects on the electromagnetic environment of the Space Station Freedom. Effects of arcing are presented. Concerns of control of arcing by a plasma contactor are highlighted. Generation of waves by contaminant ions are studied and amplitude levels of the waves are estimated. Generation of electromagnetic waves by currents in the structure of the space station, driven by motional EMF, is analyzed and the radiation level is estimated.

Numerical estimates of secular effects in the translational-rotational motion of an orbital station with 'Martian' gravity on board

NASA Astrophysics Data System (ADS)

Koenov, D. Z.

Attention is given to an orbital station consisting of two identical cylindrical spacecraft with symmetrical wings (solar arrays); connected by a long tether, the two craft rotate about an axis that passes through their common center of mass. It is assumed that a Martian type of gravity has been created on board. Numerical estimates show that, in the course of a single mean solar day, the station performs more than 15.5 revolutions around the earth.

Global Seismic Monitoring: Past, Present, and Future

NASA Astrophysics Data System (ADS)

Zoback, M.; Benz, H.; Oppenheimer, D.

2007-12-01

Global seismological observations began in April 1889 when an earthquake in Tokyo, Japan was accurately recorded in Germany on two different horizontal pendulum instruments. However, modern global observational seismology really began 46 years ago when the 120-station World Wide Standard Seismograph Network was installed by the US to monitor underground nuclear tests and earthquakes using well-calibrated short- and long- period stations. At the same time rapid advances in computing technology enabled researchers to begin sophisticated analysis of the increasing amount of seismic data, which led to better understanding of earthquake source properties and their use in establishing plate tectonics. Today, global seismic networks are operated by German (Geophon), France (Geoscope), the United States (Global Seismograph Network) and the International Monitoring System. Presently, the Federation of Digital Seismograph Networks registers more than 1,000 broadband stations world-wide, a small percentage of the total number of digital seismic stations around the world. Following the devastating Kobe, Japan and Northridge, California earthquakes, Japan and the US have led the world in the integration of existing seismic sensor systems (weak and strong motion) into development of near-real-time, post-earthquake response products like ShakeMap, detailing the spatial distribution of strong shaking. Future challenges include expanding real-time integration of both seismic and geodetic sensor systems to produce early warning of strong shaking, rapid source determination, as well as near-realtime post- earthquake damage assessment. Seismic network data, hydro-acoustic arrays, deep water tide gauges, and satellite imagery of wave propagation should be integrated in real-time to provide input for hydrodynamic modeling yielding the distribution, timing and size of tsunamis runup--which would then be available instantly on the web, e.g. in a Google Earth format. Dense arrays of strong motion sensors together with deployment of MEMS-type accelerometers in buildings and equipment routinely connected to the Web could potentially provide thousands of measurements of damaging strong ground motion. This technology could ultimately become part of smart building design enabling critical facilities to change their structural response to imminent strong shaking. Looking further forward, it is likely that a continuously observing spaceborne system could image the occurrence of "silent" or "slow" earthquakes as well as the propagation of ground displacement by surface waves at scales of continents.

The examination assessment of technical competence in vascular surgery.

PubMed

Pandey, V A; Wolfe, J H N; Liapis, C D; Bergqvist, D

2006-09-01

The European Board of Surgery Qualification in Vascular Surgery is a pan-European examination for vascular surgeons who have attained a national certificate of completion of specialist training. A 2-year study was conducted before the introduction of a technical skills assessment in the examination. The study included 30 surgeons: 22 candidates and eight examiners. They were tested on dissection (on a synthetic saphenofemoral junction model), anastomosis (on to anterior tibial artery of a synthetic leg model) and dexterity (a knot-tying simulator with electromagnetic motion analysis). Validated rating scales were used by two independent examiners. Composite knot-tying scores were calculated for the computerized station. The stations were weighted 35, 45 and 20 percent, respectively. Examiners performed better than candidates in the dissection (P<0.001), anastomosis (P=0.002) and dexterity (P=0.005) stations. Participants performed consistently in the examination (dissection versus anastomosis: r=0.79, P<0.001; dexterity versus total operative score: r=-0.73, P<0.001). Interobserver reliability was high (alpha=0.91). No correlation was seen between a candidate's technical skill and oral examination performance or logbook-accredited scores. Current surgical examinations do not address technical competence. This model appears to be a valid assessment of technical skills in an examination setting. The standards are set at a level appropriate for a specialist vascular surgeon. Copyright (c) 2006 British Journal of Surgery Society Ltd.

Quantifying and Qualifying USGS ShakeMap Uncertainty

USGS Publications Warehouse

Wald, David J.; Lin, Kuo-Wan; Quitoriano, Vincent

2008-01-01

We describe algorithms for quantifying and qualifying uncertainties associated with USGS ShakeMap ground motions. The uncertainty values computed consist of latitude/longitude grid-based multiplicative factors that scale the standard deviation associated with the ground motion prediction equation (GMPE) used within the ShakeMap algorithm for estimating ground motions. The resulting grid-based 'uncertainty map' is essential for evaluation of losses derived using ShakeMaps as the hazard input. For ShakeMap, ground motion uncertainty at any point is dominated by two main factors: (i) the influence of any proximal ground motion observations, and (ii) the uncertainty of estimating ground motions from the GMPE, most notably, elevated uncertainty due to initial, unconstrained source rupture geometry. The uncertainty is highest for larger magnitude earthquakes when source finiteness is not yet constrained and, hence, the distance to rupture is also uncertain. In addition to a spatially-dependant, quantitative assessment, many users may prefer a simple, qualitative grading for the entire ShakeMap. We developed a grading scale that allows one to quickly gauge the appropriate level of confidence when using rapidly produced ShakeMaps as part of the post-earthquake decision-making process or for qualitative assessments of archived or historical earthquake ShakeMaps. We describe an uncertainty letter grading ('A' through 'F', for high to poor quality, respectively) based on the uncertainty map. A middle-range ('C') grade corresponds to a ShakeMap for a moderate-magnitude earthquake suitably represented with a point-source location. Lower grades 'D' and 'F' are assigned for larger events (M>6) where finite-source dimensions are not yet constrained. The addition of ground motion observations (or observed macroseismic intensities) reduces uncertainties over data-constrained portions of the map. Higher grades ('A' and 'B') correspond to ShakeMaps with constrained fault dimensions and numerous stations, depending on the density of station/data coverage. Due to these dependencies, the letter grade can change with subsequent ShakeMap revisions if more data are added or when finite-faulting dimensions are added. We emphasize that the greatest uncertainties are associated with unconstrained source dimensions for large earthquakes where the distance term in the GMPE is most uncertain; this uncertainty thus scales with magnitude (and consequently rupture dimension). Since this distance uncertainty produces potentially large uncertainties in ShakeMap ground-motion estimates, this factor dominates over compensating constraints for all but the most dense station distributions.

Estimation of 1-D velocity models beneath strong-motion observation sites in the Kathmandu Valley using strong-motion records from moderate-sized earthquakes

NASA Astrophysics Data System (ADS)

Bijukchhen, Subeg M.; Takai, Nobuo; Shigefuji, Michiko; Ichiyanagi, Masayoshi; Sasatani, Tsutomu; Sugimura, Yokito

2017-07-01

The Himalayan collision zone experiences many seismic activities with large earthquakes occurring at certain time intervals. The damming of the proto-Bagmati River as a result of rapid mountain-building processes created a lake in the Kathmandu Valley that eventually dried out, leaving thick unconsolidated lacustrine deposits. Previous studies have shown that the sediments are 600 m thick in the center. A location in a seismically active region, and the possible amplification of seismic waves due to thick sediments, have made Kathmandu Valley seismically vulnerable. It has suffered devastation due to earthquakes several times in the past. The development of the Kathmandu Valley into the largest urban agglomerate in Nepal has exposed a large population to seismic hazards. This vulnerability was apparent during the Gorkha Earthquake (Mw7.8) on April 25, 2015, when the main shock and ensuing aftershocks claimed more than 1700 lives and nearly 13% of buildings inside the valley were completely damaged. Preparing safe and up-to-date building codes to reduce seismic risk requires a thorough study of ground motion amplification. Characterizing subsurface velocity structure is a step toward achieving that goal. We used the records from an array of strong-motion accelerometers installed by Hokkaido University and Tribhuvan University to construct 1-D velocity models of station sites by forward modeling of low-frequency S-waves. Filtered records (0.1-0.5 Hz) from one of the accelerometers installed at a rock site during a moderate-sized (mb4.9) earthquake on August 30, 2013, and three moderate-sized (Mw5.1, Mw5.1, and Mw5.5) aftershocks of the 2015 Gorkha Earthquake were used as input motion for modeling of low-frequency S-waves. We consulted available geological maps, cross-sections, and borehole data as the basis for initial models for the sediment sites. This study shows that the basin has an undulating topography and sediment sites have deposits of varying thicknesses, from 155 to 440 m. These models also show high velocity contrast at the bedrock depth which results in significant wave amplification.[Figure not available: see fulltext.

Application of a net-based baseline correction scheme to strong-motion records of the 2011 Mw 9.0 Tohoku earthquake

NASA Astrophysics Data System (ADS)

Tu, Rui; Wang, Rongjiang; Zhang, Yong; Walter, Thomas R.

2014-06-01

The description of static displacements associated with earthquakes is traditionally achieved using GPS, EDM or InSAR data. In addition, displacement histories can be derived from strong-motion records, allowing an improvement of geodetic networks at a high sampling rate and a better physical understanding of earthquake processes. Strong-motion records require a correction procedure appropriate for baseline shifts that may be caused by rotational motion, tilting and other instrumental effects. Common methods use an empirical bilinear correction on the velocity seismograms integrated from the strong-motion records. In this study, we overcome the weaknesses of an empirically based bilinear baseline correction scheme by using a net-based criterion to select the timing parameters. This idea is based on the physical principle that low-frequency seismic waveforms at neighbouring stations are coherent if the interstation distance is much smaller than the distance to the seismic source. For a dense strong-motion network, it is plausible to select the timing parameters so that the correlation coefficient between the velocity seismograms of two neighbouring stations is maximized after the baseline correction. We applied this new concept to the KiK-Net and K-Net strong-motion data available for the 2011 Mw 9.0 Tohoku earthquake. We compared the derived coseismic static displacement with high-quality GPS data, and with the results obtained using empirical methods. The results show that the proposed net-based approach is feasible and more robust than the individual empirical approaches. The outliers caused by unknown problems in the measurement system can be easily detected and quantified.

A Study on Empirical Site Response at Bodrum Peninsula, Turkey

NASA Astrophysics Data System (ADS)

Alcik, H. A.; Tanircan, G.

2016-12-01

The Bodrum Peninsula with a population of one million in summer season is one of the most populated touristic centers of the southwest coast of Turkey. The region is located at the eastern part of the Volcanic Arc and Hellenic Arc-Trench System at the Aegean Sea. It is also surrounded by several offshore Aegean Graben systems. All of those systems have capability of producing large magnitude (M7+) earthquakes. Such tectonic entities pose a great threat to settlements around the region. Enrichment in ground motion arrays is an indispensable tool to investigate ground motion characteristics as well as behavior of shallow site profiles at such seismically active urban regions. Hence, Boğaziçi University Kandilli Observatory and Earthquake Research Institute (KOERI) Earthquake Engineering Department deployed a strong motion network at the Peninsula in June 2015. Three out of five stations (B1, B2, B3) are on an Alluvium sediment. The rests are on Limestone (B4) and Volcanic rock (B5). Soil profiles of the sites are not currently available. The network recorded more than 100 earthquakes in the last year. In the present study 15 events with magnitudes (Ml) from 3.4-5.4 occurred within 170 km epicentral distances were selected for calculation. PGA variations among stations were compared. B2 and B3 stations show consistently greater PGA values than others. Fundamental resonant frequencies of the sites were estimated by the H/V technique and relative amplifications were calculated by the Standard Spectral Ratio (SSR) technique. Based on fundamental resonant frequencies, B5 station was selected as the reference station for calculation of SSR spectra.Examining the earthquake data it was found out that (1) Predominant frequencies change between 2.0 - 3.7 Hz for soft soils, where it is 6 Hz for the reference site. The lowest frequency was observed at site B2; (2) Relative amplifications are in the range of 3 to 8. Even though B1, B2 and B3 stations rest on similar geological units, B1 gives the lowest relative amplification. It has been known that the building housing B1 station has a pile foundation and station may not be representative of free field conditions. Structural behaviors could be one of the reasons of such effect; (3) Spectral shapes obtained from SSR are similar to those obtained from H/V.

Ground Motion Prediction for M7+ scenarios on the San Andreas Fault using the Virtual Earthquake Approach

NASA Astrophysics Data System (ADS)

Denolle, M.; Dunham, E. M.; Prieto, G.; Beroza, G. C.

2013-05-01

There is no clearer example of the increase in hazard due to prolonged and amplified shaking in sedimentary, than the case of Mexico City in the 1985 Michoacan earthquake. It is critically important to identify what other cities might be susceptible to similar basin amplification effects. Physics-based simulations in 3D crustal structure can be used to model and anticipate those effects, but they rely on our knowledge of the complexity of the medium. We propose a parallel approach to validate ground motion simulations using the ambient seismic field. We compute the Earth's impulse response combining the ambient seismic field and coda-wave enforcing causality and symmetry constraints. We correct the surface impulse responses to account for the source depth, mechanism and duration using a 1D approximation of the local surface-wave excitation. We call the new responses virtual earthquakes. We validate the ground motion predicted from the virtual earthquakes against moderate earthquakes in southern California. We then combine temporary seismic stations on the southern San Andreas Fault and extend the point source approximation of the Virtual Earthquake Approach to model finite kinematic ruptures. We confirm the coupling between source directivity and amplification in downtown Los Angeles seen in simulations.

Ground motion in the presence of complex topography: Earthquake and ambient noise sources

USGS Publications Warehouse

Hartzell, Stephen; Meremonte, Mark; Ramírez-Guzmán, Leonardo; McNamara, Daniel

2014-01-01

To study the influence of topography on ground motion, eight seismic recorders were deployed for a period of one year over Poverty Ridge on the east side of the San Francisco Bay Area, California. This location is desirable because of its proximity to local earthquake sources and the significant topographic relief of the array (439 m). Topographic amplification is evaluated as a function of frequency using a variety of methods, including reference‐site‐based spectral ratios and single‐station horizontal‐to‐vertical spectral ratios using both shear waves from earthquakes and ambient noise. Field observations are compared with the predicted ground motion from an accurate digital model of the topography and a 3D local velocity model. Amplification factors from the theoretical calculations are consistent with observations. The fundamental resonance of the ridge is prominently observed in the spectra of data and synthetics; however, higher‐frequency peaks are also seen primarily for sources in line with the major axis of the ridge, perhaps indicating higher resonant modes. Excitations of lateral ribs off of the main ridge are also seen at frequencies consistent with their dimensions. The favored directions of resonance are shown to be transverse to the major axes of the topographic features.

Geocenter Motion Derived from GNSS and SLR Tracking Data of LEO

NASA Astrophysics Data System (ADS)

Li, Y. S.; Ning, F. S.; Tseng, K. H.; Tseng, T. P.; Wu, J. M.; Chen, K. L.

2017-12-01

Space geodesy techniques can provide the monitoring data of global variations with high precision and large coverage through the satellites. Geocenter motion (GM) describes the difference of CF (Center of Figure) respect to CM (Center of Mass of the Earth System) due to the re-distribution and deformation of the earth system. Because satellite tracking data between ground stations and satellites orbit around the CM, geocenter motion is related to the realization of the ITRF (International Terrestrial Reference Frame) origin. In this study, GPS (Global Positioning System) observation data of IGS (International GNSS Service) and SLR (Satellite Laser Ranging) tracking data are applied to estimate the coordinates of observing sites on Earth's surface. The GPS observing sites are distributed deliberately and globally by 15° ×15° grids. Meanwhile, two different global ocean tide models are applied here. The model used in ITRF comparison and combination is parameter transformation, which is a mathematical formula allowing to transform the different frames between ITRF and CM system. Following the parameter transformation, the results of geocenter motion can be determined. The FORMOSAT-7/COSMIC-2 (F7C2) mission is a constellation of LEO (Low-Earth-Orbit) satellites, which will be launched in 2018. Besides the observing system for Meteorology, Ionosphere, and Climate, the F7C2 will be equipped with LRR (Laser Ranging Retroreflector). This work is a pilot survey to study the application of LEO SLR data in Taiwan.

Theory and Realization of Global Terrestrial Reference Systems

NASA Technical Reports Server (NTRS)

Ma, C.; Bolotin, S.; Gipson, J.; Gordon, D.; Le Bail, K.; MacMillan, D.

2010-01-01

Comparison of realizations of the terrestrial reference frame. IGN and DGFI both generated realizations of the terrestrial reference frame under the auspices of the IERS from combination of the same space geodetic data. We examined both results for VLBI sites using the full geodetic VLBI data set with respect to site positions and velocities and time series of station positions, baselines and Earth orientation parameters. One of the difficulties encountered was matching episodic breaks and periods of non-linear motion of the two realizations with the VLBI models. Our analysis and conclusions will be discussed.

Uniformly Processed Strong Motion Database for Himalaya and Northeast Region of India

NASA Astrophysics Data System (ADS)

Gupta, I. D.

2018-03-01

This paper presents the first uniformly processed comprehensive database on strong motion acceleration records for the extensive regions of western Himalaya, northeast India, and the alluvial plains juxtaposing the Himalaya. This includes 146 three components of old analog records corrected for the instrument response and baseline distortions and 471 three components of recent digital records corrected for baseline errors. The paper first provides a background of the evolution of strong motion data in India and the seismotectonics of the areas of recording, then describes the details of the recording stations and the contributing earthquakes, which is finally followed by the methodology used to obtain baseline corrected data in a uniform and consistent manner. Two different schemes in common use for baseline correction are based on the application of the Ormsby filter without zero pads (Trifunac 1971) and that on the Butterworth filter with zero pads at the start as well as at the end (Converse and Brady 1992). To integrate the advantages of both the schemes, Ormsby filter with zero pads at the start only is used in the present study. A large number of typical example results are presented to illustrate that the methodology adopted is able to provide realistic velocity and displacement records with much smaller number of zero pads. The present strong motion database of corrected acceleration records will be useful for analyzing the ground motion characteristics of engineering importance, developing prediction equations for various strong motion parameters, and calibrating the seismological source model approach for ground motion simulation for seismically active and risk prone areas of India.

Vertical Crustal Motion Derived from Satellite Altimetry and Tide Gauges, and Comparisons with DORIS Measurements

NASA Technical Reports Server (NTRS)

Ray, R. D.; Beckley, B. D.; Lemoine, F. G.

2010-01-01

A somewhat unorthodox method for determining vertical crustal motion at a tide-gauge location is to difference the sea level time series with an equivalent time series determined from satellite altimetry, To the extent that both instruments measure an identical ocean signal, the difference will be dominated by vertical land motion at the gauge. We revisit this technique by analyzing sea level signals at 28 tide gauges that are colocated with DORIS geodetic stations. Comparisons of altimeter-gauge vertical rates with DORIS rates yield a median difference of 1.8 mm/yr and a weighted root-mean-square difference of2.7 mm/yr. The latter suggests that our uncertainty estimates, which are primarily based on an assumed AR(l) noise process in all time series, underestimates the true errors. Several sources of additional error are discussed, including possible scale errors in the terrestrial reference frame to which altimeter-gauge rates are mostly insensitive, One of our stations, Male, Maldives, which has been the subject of some uninformed arguments about sea-level rise, is found to have almost no vertical motion, and thus is vulnerable to rising sea levels. Published by Elsevier Ltd. on behalf of COSPAR.

On safe configurations of a natural-artificial space tether system

NASA Astrophysics Data System (ADS)

Rodnikov, A. V.

2018-05-01

We study the dynamics of a particle moving under gravitation of precessing dynamically symmetric rigid body if the particle motion is restricted by two unilateral (flexible) constraints realized by two weightless unstretchable tethers with ends fixed at body poles, formed as the intersection of the body surface with the axis of its dynamical symmetry. The system under consideration is a simple model of an original natural-artificial space construction consisting of an asteroid and a space station tethered to each other via two cables. We note that the problem is integrable for the system safe configurations, i.e. for motions along the constraints common boundary (both tethers are tensed) if the body gravitational potential is invariant with respect to rotation about the axis of dynamical symmetry. We study these motions depicting phase portraits for possible values of system parameters. We also deduce conditions for the particle coming off the boundary of constraint(s) (if the tether(s) are slackened) and analyze these conditions, eliminating corresponding areas from phase portraits. We also formulate some statements, concerning the particle safety.

Periodic-disturbance accommodating control of the space station for asymptotic momentum management

NASA Technical Reports Server (NTRS)

Warren, Wayne; Wie, Bong

1989-01-01

Periodic maneuvering control is developed for asymptotic momentum management of control gyros used as primary actuating devices for the Space Station. The proposed controller utilizes the concepts of quaternion feedback control and periodic-disturbance accommodation to achieve oscillations about the constant torque equilibrium attitude, while minimizing the control effort required. Three-axis coupled equations of motion, written in terms of quaternions, are derived for roll/yaw controller design and stability analysis. It is shown that the quaternion feedback controller is very robust for a wide range of pitch angles. It is also shown that the proposed controller tunes the open-loop unstable vehicle to a stable oscillatory motion which minimizes the control effort needed for steady-state operations.

Generation of the September 29, 2009 Samoa Tsunami: Examination of a Possible Non-Double Couple Component (Invited)

NASA Astrophysics Data System (ADS)

Geist, E. L.; Kirby, S. H.; Ross, S.; Dartnell, P.

2009-12-01

A non-double couple component associated with the Mw=8.0 September 29, 2009 Samoa earthquake is investigated to explain direct tsunami arrivals at deep-ocean pressure sensors (i.e., DART stations). In particular, we seek a tsunami generation model that correctly predicts the polarity of first motions: negative at the Apia station (#51425) NW of the epicenter and positive at the Tonga (#51426) and Aukland (#54401) stations south of the epicenter. Slip on a single, finite fault corresponding to either nodal plane of the best-fitting double couple fails to predict the positive first-motion polarity observed at the southerly (Tonga and Aukland) DART stations. The Samoa earthquake has a significant non-double component as measured by the compensated linear vector dipole (CLVD) ratio that ranges from |ɛ|=0.15 (USGS CMT) to |ɛ| =0.37 (Global CMT). To test what effect the non-double component has on tsunami generation, the static elastic displacement field at the sea floor is computed from the full moment tensor. This displacement field represents the initial conditions for tsunami propagation computed using a finite-difference approximation to the linear shallow-water wave equations. The tsunami waveforms calculated from the full moment tensor are consistent with the observed polarities at all of the DART stations. The static displacement field is then decomposed into double-couple and non-double couple components to determine the relative contribution of each to the tsunami wavefield. Although a point-source approximation to the tsunami source is typically inadequate at near-field and regional distances, finite-fault inversions of the 2009 Samoa earthquake indicate that peak slip is spatially concentrated near the hypocenter, suggesting that the point-source representation may be acceptable in this case. Generation of the 2009 Samoa tsunami may involve earthquake rupture on multiple faults and/or along curved faults, both of which are observed from multibeam bathymetry in the epicentral region. The exact rupture path of the earthquake is presently unclear. It is evident from seismological and tsunami observations of the 2009 Samoa event, however, that uniform slip on a single, planar fault cannot explain all aspects of the observed tsunami wavefield.

Investigation on the real-time prediction of ground motions using seismic records observed in deep boreholes

NASA Astrophysics Data System (ADS)

Miyakoshi, H.; Tsuno, S.

2013-12-01

The present method of the EEW system installed in the railway field of Japan predicts seismic ground motions based on the estimated earthquake information about epicentral distances and magnitudes using initial P-waves observed on the surface. In the case of local earthquakes beneath the Tokyo Metropolitan Area, however, a method to directly predict seismic ground motions using P-waves observed in deep boreholes could issue EEWs more simply and surely. Besides, a method to predict seismic ground motions, using S-waves observed in deep boreholes and S-wave velocity structures beneath seismic stations, could show planar distributions of ground motions for train operation control areas in the aftermath of earthquakes. This information is available to decide areas in which the emergency inspection of railway structures should be performed. To develop those two methods, we investigated relationships between peak amplitudes on the surface and those in deep boreholes, using seismic records of KiK-net stations in the Kanto Basin. In this study, we used earthquake accelerograms observed in boreholes whose depths are deeper than the top face of Pre-Neogene basement and those on the surface at 12 seismic stations of KiK-net. We selected 243 local earthquakes whose epicenters are located around the Kanto Region. Those JMA magnitudes are in the range from 4.5 to 7.0. We picked the on-set of P-waves and S-waves using a vertical component and two horizontal components, respectively. Peak amplitudes of P-waves and S-waves were obtained using vertical components and vector sums of two horizontal components, respectively. We estimated parameters which represent site amplification factors beneath seismic stations, using peak amplitudes of S-waves observed in the deep borehole and those on the surface, to minimize the residuals between calculations by the theoretical equation and observations. Correlation coefficients between calculations and observations are high values in the range from 0.8 to 0.9. This result suggests that we could predict ground motions with the high accuracy using peak amplitudes of S-waves in deep boreholes and site amplification factors based on S-wave velocity structures. Also, we estimated parameters which represent radiation coefficients and the P/S velocity ratios around hypocentral regions, using peak amplitudes of P-waves and S-waves observed in deep boreholes, to minimize the residuals between calculations and observations. Correlation coefficients between calculations and observations are slightly lower values in the range from 0.7 to 0.9 than those for site amplification factors. This result suggests that the variability of radiation patterns for individual earthquakes affects the accuracy to predict ground motions using P-waves in deep boreholes.

Crustal Structure of Iraq from Receiver Functions and Surface Wave Dispersion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gok, R; Mahdi, H; Al-Shukri, H

2006-08-31

We report the crustal structure of Iraq, located in the northeastern Arabian plate, estimated by joint inversion of P-wave receiver functions and surface wave group velocity dispersion. Receiver functions were computed from teleseismic recordings at two temporary broadband seismic stations in Mosul (MSL) and Baghdad (BHD), separated by approximately 360 km. Group velocity dispersion curves at the sites were derived from continental-scale tomography of Pasyanos (2006). The inversion results show that the crustal thicknesses are 39 km at MSL and 43 km at BHD. Both sites reveal low velocity surface layers consistent with sedimentary thickness of about 3 km atmore » station MSL and 7 km at BHD, agreeing well with the existing models. Ignoring the sediments, the crustal velocities and thicknesses are remarkably similar between the two stations, suggesting that the crustal structure of the proto-Arabian Platform in northern Iraq was uniform before subsidence and deposition of the sediments in the Cenozoic. Deeper low velocity sediments at BHD are expected to result in higher ground motions for earthquakes.« less

Simulative design in macroscale for prospective application to micro-catheters.

PubMed

Ha, Cheol Woo

2018-02-09

In this paper, a motion-transforming element is applied to the development of a new catheter device. The motion-transforming element structure allows a reduction of linear movement and converts linear movement to rotational movement. The simulative design of micro-catheters is based on a proposed structure called the Operating Mini Station (OMS). OMS is operated by movement of a motion-transforming element. A new motion-transforming element is designed using multiple links that are connected by hinged joints based on an elastic design. The design of the links and the hinges are optimized for precise and reliable movement of the motion-transforming element. Because of the elastic design, it is possible to realize a catheter that allows various movements in small spaces like capillaries.

Verification and Improvement of the Three-Dimensional Basin Velocity Structure Model in the Osaka Sedimentary Basin, Japan Using Interstation Green's Functions and H/V Spectral Ratios of Microtremors

NASA Astrophysics Data System (ADS)

Asano, K.; Iwata, T.; Sekiguchi, H.; Somei, K.; Nishimura, T.; Miyakoshi, K.; Aoi, S.; Kunugi, T.

2012-12-01

The Osaka sedimentary basin is filled by the Plio-Pleistocene Osaka group, terrace deposits, and alluvium deposits with thickness of 1 to 2 km over the bedrock, and it is surrounded by active fault systems. The Uemachi active fault system underlies the Osaka urban area. In order to predict the strong ground motions for future events of the Uemachi fault and others, the precise basin velocity structure model is indispensable as well as the detailed source fault model. The velocity structure of the Osaka basin has been extensively investigated by using various techniques such as gravity anomaly measurements, reflection surveys, boring explorations, and microtremor measurements. Based on these surveys and ground motion simulations for observed events, the three-dimensional velocity structure models of the Osaka basin have been developed and improved for decades (e.g., Kagawa et al., 1993; Horikawa et al., 2003; Iwata et al., 2008; Iwaki and Iwata, 2011). Now we are trying to verify the velocity structure model of the Osaka basin and to improve it incorporating new data sets. We have conducted two kinds of observations in the Osaka basin. The first observation is continuous microtremor observation. We have temporarily installed three-component velocity sensors at 15 sites covering the Osaka basin to record microtremors continuously for more than one year. The seismic interferometry technique (e.g. Shapiro and Campillo, 2004) is applied to retrieve interstation Green's function for analyzing the wave propagation characteristics inside the sedimentary basin. Both Rayleigh- and Love-wave type signals are identified in 0.1-0.5 Hz from observed interstation Green's functions. The group velocities of Rayleigh and Love waves propagating between two stations are estimated from them using the multiple filter analysis method, and they are compared with the theoretical group-velocities of the model. For example, estimated Love-wave group velocity along a line inside the basin is as low as 350 m/s in 0.2-0.5 Hz. The second observation is a set of short-time (30~60 min) single-station microtremor observations to obtain H/V spectral ratios at sites. We observed microtremor at 100 strong motion stations of Osaka prefecture government, JMA, K-NET, KiK-net, and other institutes. The peak period of H/V ranges from about 1 to 7 s, and it depends on the bedrock depth at the observation site as previously pointed by Miyakoshi et al. (1997). Though the basin velocity model explains the characteristics of observed H/V spectral ratios at most sites, we found discrepancies between observed and predicted H/V peak periods at north part of Osaka bay area and hill area in southeastern part of the basin. By combining the observed constraints from the group velocities, waveform characteristics of interstation Green's functions, and H/V spectral ratios, we will improve the S-wave velocity structure model inside the Osaka basin.

Soil-Air Interactions during Airblast-Induced Ground Motions.

DTIC Science & Technology

1982-01-01

Calculations , Cases 1 to 4. 67 6 . 7 *. . . . . . . . .% = " [ -.° % . °,’ ’ °" Oo ° . o...OVERiPRESSURiE VS. TIME FOR STATIONS 7 -113 7 . 0 6 . 0 5. 0 4. S / 8 La4.0 V󈧘 Station Depth ( cm ) a-3. 0 / 2.0 50 2. 0. 60 ... 08 0 0.1 0.2 0.3 J..4 0. 5 0.6 TIME...3280 CPSE 2 80 ] S!VELOCITY VS. TIME FOR .STATIONS. 7 -18 - 60 40 Station Depth ( cm )-~ 20 - C N, 6 *60 8 0 -40 -60 -80 p0 0. 1 0.2 0.3 0.4 0. 5

Low-Frequency Amplitudes Observed in a Set of the Strongest Recorded Ground Motions (Invited)

NASA Astrophysics Data System (ADS)

Anderson, J. G.; Koketsu, K.; Miyake, H.

2010-12-01

Anderson (2010) compiled a set of “exceptional” ground motion characterized by peak acceleration that exceeds 500 gal on at least one component or peak velocity that exceeds 50 cm/s on at least one component. With the addition of more recent data, there are now over 280 openly available records that meet these criteria. These data are examined to find to the empirical upper bound of observed pseudo-acceleration (PSA) response spectra and smoothed Fourier amplitude spectra. Statistics of amplitudes of PSA and of low-pass filtered acceleration and velocity have also been determined. Amplitudes recorded at the Kawaguchi-cho station (40 km) at 5-6 second period from the 1964 Niigata earthquake (Mw=8.3) are within ~20% of the current empirical limit of ground motions observed from all earthquakes in the data set including those from the near field. An even more impressive example is that amplitudes recorded at the SCT station (~300 km from the fault) with period of about 2 seconds, during the 1985 Michoacan, Mexico, earthquake (Mw=8.0), are about the same as the current empirical limit of ground motions observed from near field records. These examples support the idea that the hazard caused by long-period ground motions, amplified by basins and site conditions, is not sufficiently appreciated. Reference: Anderson, J. G. (2010), Bull. Seism. Soc. Am. 100, 1-36.

Motion sickness and postural sway in console video games.

PubMed

Stoffregen, Thomas A; Faugloire, Elise; Yoshida, Ken; Flanagan, Moira B; Merhi, Omar

2008-04-01

We tested the hypotheses that (a) participants might develop motion sickness while playing "off-the-shelf" console video games and (b) postural motion would differ between sick and well participants, prior to the onset of motion sickness. There have been many anecdotal reports of motion sickness among people who play console video games (e.g., Xbox, PlayStation). Participants (40 undergraduate students) played a game continuously for up to 50 min while standing or sitting. We varied the distance to the display screen (and, consequently, the visual angle of the display). Across conditions, the incidence of motion sickness ranged from 42% to 56%; incidence did not differ across conditions. During game play, head and torso motion differed between sick and well participants prior to the onset of subjective symptoms of motion sickness. The results indicate that console video games carry a significant risk of motion sickness. Potential applications of this research include changes in the design of console video games and recommendations for how such systems should be used.

Seismic Data for Evaluation of Ground Motion Hazards in Las Vegas in Support of Test Site Readiness Ground Motion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodgers, A

2008-01-16

In this report we describe the data sets used to evaluate ground motion hazards in Las Vegas from nuclear tests at the Nevada Test Site. This analysis is presented in Rodgers et al. (2005, 2006) and includes 13 nuclear explosions recorded at the John Blume and Associates network, the Little Skull Mountain earthquake and a temporary deployment of broadband station in Las Vegas. The data are available in SAC format on CD-ROM as an appendix to this report.

Developing Stochastic Models as Inputs for High-Frequency Ground Motion Simulations

NASA Astrophysics Data System (ADS)

Savran, William Harvey

High-frequency ( 10 Hz) deterministic ground motion simulations are challenged by our understanding of the small-scale structure of the earth's crust and the rupture process during an earthquake. We will likely never obtain deterministic models that can accurately describe these processes down to the meter scale length required for broadband wave propagation. Instead, we can attempt to explain the behavior, in a statistical sense, by including stochastic models defined by correlations observed in the natural earth and through physics based simulations of the earthquake rupture process. Toward this goal, we develop stochastic models to address both of the primary considerations for deterministic ground motion simulations: namely, the description of the material properties in the crust, and broadband earthquake source descriptions. Using borehole sonic log data recorded in Los Angeles basin, we estimate the spatial correlation structure of the small-scale fluctuations in P-wave velocities by determining the best-fitting parameters of a von Karman correlation function. We find that Hurst exponents, nu, between 0.0-0.2, vertical correlation lengths, az, of 15-150m, an standard deviation, sigma of about 5% characterize the variability in the borehole data. Usin these parameters, we generated a stochastic model of velocity and density perturbations and combined with leading seismic velocity models to perform a validation exercise for the 2008, Chino Hills, CA using heterogeneous media. We find that models of velocity and density perturbations can have significant effects on the wavefield at frequencies as low as 0.3 Hz, with ensemble median values of various ground motion metrics varying up to +/-50%, at certain stations, compared to those computed solely from the CVM. Finally, we develop a kinematic rupture generator based on dynamic rupture simulations on geometrically complex faults. We analyze 100 dynamic rupture simulations on strike-slip faults ranging from Mw 6.4-7.2. We find that our dynamic simulations follow empirical scaling relationships for inter-plate strike-slip events, and provide source spectra comparable with an o -2 model. Our rupture generator reproduces GMPE medians and intra-event standard deviations spectral accelerations for an ensemble of 10 Hz fully-deterministic ground motion simulations, as compared to NGA West2 GMPE relationships up to 0.2 seconds.

Recent Improvements to the Finite-Fault Rupture Detector Algorithm: FinDer II

NASA Astrophysics Data System (ADS)

Smith, D.; Boese, M.; Heaton, T. H.

2015-12-01

Constraining the finite-fault rupture extent and azimuth is crucial for accurately estimating ground-motion in large earthquakes. Detecting and modeling finite-fault ruptures in real-time is thus essential to both earthquake early warning (EEW) and rapid emergency response. Following extensive real-time and offline testing, the finite-fault rupture detector algorithm, FinDer (Böse et al., 2012 & 2015), was successfully integrated into the California-wide ShakeAlert EEW demonstration system. Since April 2015, FinDer has been scanning real-time waveform data from approximately 420 strong-motion stations in California for peak ground acceleration (PGA) patterns indicative of earthquakes. FinDer analyzes strong-motion data by comparing spatial images of observed PGA with theoretical templates modeled from empirical ground-motion prediction equations (GMPEs). If the correlation between the observed and theoretical PGA is sufficiently high, a report is sent to ShakeAlert including the estimated centroid position, length, and strike, and their uncertainties, of an ongoing fault rupture. Rupture estimates are continuously updated as new data arrives. As part of a joint effort between USGS Menlo Park, ETH Zurich, and Caltech, we have rewritten FinDer in C++ to obtain a faster and more flexible implementation. One new feature of FinDer II is that multiple contour lines of high-frequency PGA are computed and correlated with templates, allowing the detection of both large earthquakes and much smaller (~ M3.5) events shortly after their nucleation. Unlike previous EEW algorithms, FinDer II thus provides a modeling approach for both small-magnitude point-source and larger-magnitude finite-fault ruptures with consistent error estimates for the entire event magnitude range.

Source parameters and effects of bandwidth and local geology on high- frequency ground motions observed for aftershocks of the northeastern Ohio earthquake of 31 January 1986

USGS Publications Warehouse

Glassmoyer, G.; Borcherdt, R.D.

1990-01-01

A 10-station array (GEOS) yielded recordings of exceptional bandwidth (400 sps) and resolution (up to 96 dB) for the aftershocks of the moderate (mb???4.9) earthquake that occurred on 31 January 1986 near Painesville, Ohio. Nine aftershocks were recorded with seismic moments ranging between 9 ?? 1016 and 3 ?? 1019 dyne-cm (MW: 0.6 to 2.3). The aftershock recordings at a site underlain by ???8m of lakeshore sediments show significant levels of high-frequency soil amplification of vertical motion at frequencies near 8, 20 and 70 Hz. Viscoelastic models for P and SV waves incident at the base of the sediments yield estimates of vertical P-wave response consistent with the observed high-frequency site resonances, but suggest additional detailed shear-wave logs are needed to account for observed S-wave response. -from Authors

Merging analytic and empirical GEO debris synchronization dynamics

NASA Astrophysics Data System (ADS)

Anderson, Paul V.; McKnight, Darren S.; Di Pentino, Frank; Schaub, Hanspeter

2016-09-01

The motion of abandoned satellites near the geostationary (GEO) region has been extensively studied, modeled, and compared to the motion of station-kept, operational satellites, providing insights into the evolution of uncontrolled orbits at GEO. Analytic developments produced a family of curves represented in the ascending node versus inclination space describing the long-term precession of the orbit plane at GEO, and forecasted the clustering of objects at the geopotential wells. However, recent investigations were undertaken to characterize apparent anomalistic behavior of GEO objects and classification of objects into related families. This paper provides a unifying summary of early bottom-up analytical theory with more recent top-down operational observations, highlighting the common linkage between these dimensions of GEO object behavior. This paper also identifies the relevance of these patterns of life tendencies for future operations at and near GEO, and discusses the long-term implications of these patterns of life for space situational awareness activities in this regime.

The development of optimal control laws for orbiting tethered platform systems

NASA Technical Reports Server (NTRS)

Bainum, P. M.; Woodard, S.; Juang, J.-N.

1986-01-01

A mathematical model of the open and closed loop in-orbit plane dynamics of a space platform-tethered-subsatellite system is developed. The system consists of a rigid platform from which an (assumed massless) tether is deploying (retrieving) a subsatellite from an attachment point which is, in general, offset from the platform's mass center. A Lagrangian formulation yields equations describing platform pitch, subsatellite tether-line swing, and varying tether length motions. These equations are linearized about the nominal station keeping motion. Control can be provided by both modulation of the tether tension level and by a momentum type platform-mounted device; system controllability depends on the presence of both control inputs. Stability criteria are developed in terms of the control law gains, the platform inertia ratio, and tether offset parameter. Control law gains are obtained based on linear quadratic regulator techniques. Typical transient responses of both the state and required control effort are presented.

The development of optimal control laws for orbiting tethered platform systems

NASA Technical Reports Server (NTRS)

Bainum, P. M.

1986-01-01

A mathematical model of the open and closed loop in orbit plane dynamics of a space platform-tethered-subsatellite system is developed. The system consists of a rigid platform from which an (assumed massless) tether is deploying (retrieving) a subsatellite from an attachment point which is, in general, offset from the platform's mass center. A Langrangian formulation yields equations describing platform pitch, subsatellite tetherline swing, and varying tether length motions. These equations are linearized about the nominal station keeping motion. Control can be provided by both modulation of the tether tension level and by a momentum type platform-mounted device; system controllability depends on the presence of both control inputs. Stability criteria are developed in terms of the control law gains, the platform inertia ratio, and tether offset parameter. Control law gains are obtained based on linear quadratic regulator techniques. Typical transient responses of both the state and required control effort are presented.

Tidal atmospheric and ocean loading in VLBI analysis

NASA Astrophysics Data System (ADS)

Girdiuk, Anastasiia; Schindelegger, Michael; Böhm, Johannes

2016-04-01

In VLBI (Very Long Baseline Interferometry) analysis, reductions for tidal atmospheric and ocean loading are commonly used according to the IERS Conventions. In this presentation we examine such loading corrections from contemporary geophysical models within routine VLBI processing and discuss the internal consistency of the applied corrections for various effects. In detail, two gravitational ocean tide models, FES2004 and the recent FES2012 atlas with a much finer horizontal resolution and an improved description of hydrodynamic processes, are employed. Moreover, the contribution of atmospheric tidal loading is also re-considered based on data taken from two providers of station displacements, Goddard Space Flight Center and the TU Wien group. Those two models differ in terms of the underlying meteorological data, which can be a reason for inconsistency of VLBI reductions and may lead to systematics in the VLBI products at tidal frequencies. We validate this assumption in terms of Earth rotation parameters, by a tidal analysis of diurnal and semi-diurnal universal time and semi-diurnal polar motion variations as determined with the Vienna VLBI Software. Applying the loading models in a consistent way still leads to unexplained residuals at about 4-5 μas in the diurnal polar motion band, thus limiting the possibility of assessing geophysical models at this particular frequency.

A motion picture presentation of magnetic pulsations

NASA Technical Reports Server (NTRS)

Suzuki, A.; Kim, J. S.; Sugura, M.; Nagano, H.

1981-01-01

Using the data obtained from the IMS North American magnetometer network stations at high latitudes, a motion picture was made by a computer technique, describing time changes of Pc5 and Pi3 magnetic pulsation vectors. Examples of pulsation characteristics derived from this presentation are regional polarization changes including shifts of polarization demarcation lines, changes in the extent of an active region and its movement with time.

Estimation of current plate motions in Papua New Guinea from Global Positioning System observations

NASA Astrophysics Data System (ADS)

Tregoning, Paul; Lambeck, Kurt; Stolz, Art; Morgan, Peter; McClusky, Simon C.; van der Beek, Peter; McQueen, Herbert; Jackson, Russell J.; Little, Rodney P.; Laing, Alex; Murphy, Brian

1998-06-01

Plate tectonic motions have been estimated in Papua New Guinea from a 20 station network of Global Positioning System sites that has been observed over five campaigns from 1990 to 1996. The present velocities of the sites are consistent with geological models in which the South Bismarck, Woodlark, and Solomon Sea Plates form the principal tectonic elements between the Pacific and Australian Plates in this region. Active spreading is observed on the Woodlark Basin Spreading Centre but at a rate that is about half the rate determined from magnetic reversals. The other major motions observed are subduction on the New Britain Trench, seafloor spreading across the Bismarck Sea Seismic Lineation, convergence across the Ramu-Markham Fault and left-lateral strike slip across the Papuan Peninsula. These motions are consistent with a 8.2° Myr-1 clockwise rotation of the South Bismarck Plate about a pole in the Huon Gulf and a rotation of the Woodlark Plate away from the Australian Plate. Second order deformation may also be occurring; in particular, Manus Island and northern New Ireland may be moving northward relative to the Pacific Plate at ˜5-8 mm yr-1 (significant at the 95% but not at the 99% confidence level) which may suggest the existence of a North Bismarck Plate.

Intense foreshocks and a slow slip event preceded the 2014 Iquique Mw 8.1 earthquake.

PubMed

Ruiz, S; Metois, M; Fuenzalida, A; Ruiz, J; Leyton, F; Grandin, R; Vigny, C; Madariaga, R; Campos, J

2014-09-05

The subduction zone in northern Chile is a well-identified seismic gap that last ruptured in 1877. The moment magnitude (Mw) 8.1 Iquique earthquake of 1 April 2014 broke a highly coupled portion of this gap. To understand the seismicity preceding this event, we studied the location and mechanisms of the foreshocks and computed Global Positioning System (GPS) time series at stations located on shore. Seismicity off the coast of Iquique started to increase in January 2014. After 16 March, several Mw > 6 events occurred near the low-coupled zone. These events migrated northward for ~50 kilometers until the 1 April earthquake occurred. On 16 March, on-shore continuous GPS stations detected a westward motion that we model as a slow slip event situated in the same area where the mainshock occurred. Copyright © 2014, American Association for the Advancement of Science.

Spatial and Temporal Stress Drop Variations of the 2011 Tohoku Earthquake Sequence

NASA Astrophysics Data System (ADS)

Miyake, H.

2013-12-01

The 2011 Tohoku earthquake sequence consists of foreshocks, mainshock, aftershocks, and repeating earthquakes. To quantify spatial and temporal stress drop variations is important for understanding M9-class megathrust earthquakes. Variability and spatial and temporal pattern of stress drop is a basic information for rupture dynamics as well as useful to source modeling. As pointed in the ground motion prediction equations by Campbell and Bozorgnia [2008, Earthquake Spectra], mainshock-aftershock pairs often provide significant decrease of stress drop. We here focus strong motion records before and after the Tohoku earthquake, and analyze source spectral ratios considering azimuth- and distance dependency [Miyake et al., 2001, GRL]. Due to the limitation of station locations on land, spatial and temporal stress drop variations are estimated by adjusting shifts from the omega-squared source spectral model. The adjustment is based on the stochastic Green's function simulations of source spectra considering azimuth- and distance dependency. We assumed the same Green's functions for event pairs for each station, both the propagation path and site amplification effects are cancelled out. Precise studies of spatial and temporal stress drop variations have been performed [e.g., Allmann and Shearer, 2007, JGR], this study targets the relations between stress drop vs. progression of slow slip prior to the Tohoku earthquake by Kato et al. [2012, Science] and plate structures. Acknowledgement: This study is partly supported by ERI Joint Research (2013-B-05). We used the JMA unified earthquake catalogue and K-NET, KiK-net, and F-net data provided by NIED.

Programmable Positioner For Spot Welding

NASA Technical Reports Server (NTRS)

Roden, William A.

1989-01-01

Welding station mechanized by installing preset indexing system and gear drive. Mechanism includes a low-cost, versatile, single-axis motion control and motor drive to provide fully-automatic weld sequencing and spot-to-spot spacing. Welding station relieves operator of some difficult, tedious tasks and increases both productivity and quality of welds. Results in welds of higher quality and greater accuracy, fewer weld defects, and faster welding operation.

Impacts of GNSS position offsets on global frame stability

NASA Astrophysics Data System (ADS)

Griffiths, Jake; Ray, Jim

2015-04-01

Positional offsets appear in Global Navigation Satellite System (GNSS) time series for a variety of reasons. Antenna or radome changes are the most common cause for these discontinuities. Many others are from earthquakes, receiver changes, and different anthropogenic modifications at or near the stations. Some jumps appear for unknown or undocumented reasons. Accurate determination of station velocities, and therefore geophysical parameters and terrestrial reference frames, requires that positional offsets be correctly found and compensated. Williams (2003) found that undetected offsets introduce a random walk error component in individual station time series. The topic of detecting positional offsets has received considerable attention in recent years (e.g., Detection of Offsets in GPS Experiment; DOGEx), and most research groups using GNSS have adopted a mix of manual and automated methods for finding them. The removal of a positional offset from a time series is usually handled by estimating the average station position on both sides of the discontinuity. Except for large earthquake events, the velocity is usually assumed constant and continuous across the positional jump. This approach is sufficient in the absence of time-correlated errors. However, GNSS time series contain periodic and power-law (flicker) errors. In this paper, we evaluate the impact to individual station results and the overall stability of the global reference frame from adding increasing numbers of positional discontinuities. We use the International GNSS Service (IGS) weekly SINEX files, and iteratively insert positional offset parameters. Each iteration includes a restacking of the modified SINEX files using the CATREF software from Institut National de l'Information Géographique et Forestière (IGN). Comparisons of successive stacked solutions are used to assess the impacts on the time series of x-pole and y-pole offsets, along with changes in regularized position and secular velocity for stations with more than 2.5 years of data. Our preliminary results indicate that the change in polar motion scatter is logarithmic with increasing numbers of discontinuities. The best-fit natural logarithm to the changes in scatter for x-pole has R2 = 0.58; the fit for the y-pole series has R2 = 0.99. From these empirical functions, we find that polar motion scatter increases from zero when the total rate of discontinuities exceeds 0.2 (x-pole) and 1.3 (y-pole) per station, on average (the IGS has 0.65 per station). Thus, the presence of position offsets in GNSS station time series is likely already a contributor to IGS polar motion inaccuracy and global frame instability. Impacts to station position and velocity estimates depend on noise features found in that station's positional time series. For instance, larger changes in velocity occur for stations with shorter and noisier data spans. This is because an added discontinuity parameter for an individual station time series can induce changes in average position on both sides of the break. We will expand on these results, and consider remaining questions about the role of velocity discontinuities and the effects caused by non-core reference frame stations.

A unified analysis of crustal motion in Southern California, 1970-2004: The SCEC crustal motion map

NASA Astrophysics Data System (ADS)

Shen, Z.-K.; King, R. W.; Agnew, D. C.; Wang, M.; Herring, T. A.; Dong, D.; Fang, P.

2011-11-01

To determine crustal motions in and around southern California, we have processed and combined trilateration data collected from 1970 to 1992, VLBI data from 1979 to 1992, and GPS data from 1986 to 2004: a long temporal coverage required in part by the occurrence of several large earthquakes in this region. From a series of solutions for station positions, we have estimated interseismic velocities, coseismic displacements, and postseismic motions. Within the region from 31°N to 38°N. and east to 114°W, the final product includes estimated horizontal velocities for 1009 GPS, 190 trilateration, and 16 VLBI points, with ties between some of these used to stabilize the solution. All motions are relative to the Stable North American Reference Frame (SNARF) as realized through the velocities of 20 GPS stations. This provides a relatively dense set of horizontal velocity estimates, with well-tested errors, for the past quarter century over the plate boundary from 31°N to 36.5°N. These velocities agree well with those from the Plate Boundary Observatory, which apply to a later time period. We also estimated vertical velocities, 533 of which have errors below 2 mm/yr. Most of these velocities are less than 1 mm/yr, but they show 2-4 mm/yr subsidence in the Ventura and Los Angeles basins and in the Salton Trough. Our analysis also included estimates of coseismic and postseismic motions related to the 1992 Landers, 1994 Northridge, 1999 Hector Mine, and 2003 San Simeon earthquakes. Postseismic motions increase logarithmically over time with a time constant of about 10 days, and generally mimic the direction and relative amplitude of the coseismic offsets.

Analysis of Earthquake Recordings Obtained from the Seafloor Earthquake Measurement System (SEMS) Instruments Deployed off the Coast of Southern California

USGS Publications Warehouse

Boore, D.M.; Smith, C.E.

1999-01-01

For more than 20 years, a program has been underway to obtain records of earthquake shaking on the seafloor at sites offshore of southern California, near oil platforms. The primary goal of the program is to obtain data that can help determine if ground motions at offshore sites are significantly different than those at onshore sites; if so, caution may be necessary in using onshore motions as the basis for the seismic design of oil platforms. We analyze data from eight earthquakes recorded at six offshore sites; these are the most important data recorded on these stations to date. Seven of the earthquakes were recorded at only one offshore station; the eighth event was recorded at two sites. The earthquakes range in magnitude from 4.7 to 6.1. Because of the scarcity of multiple recordings from any one event, most of the analysis is based on the ratio of spectra from vertical and horizontal components of motion. The results clearly show that the offshore motions have very low vertical motions compared to those from an average onshore site, particularly at short periods. Theoretical calculations find that the water layer has little effect on the horizontal components of motion but that it produces a strong spectral null on the vertical component at the resonant frequency of P waves in the water layer. The vertical-to-horizontal ratios for a few selected onshore sites underlain by relatively low shear-wave velocities are similar to the ratios from offshore sites for frequencies less than about one-half the water layer P-wave resonant frequency, suggesting that the shear-wave velocities beneath a site are more important than the water layer in determining the character of the ground motions at lower frequencies.

Real-time weigh-in-motion measurement using fiber Bragg grating sensors

NASA Astrophysics Data System (ADS)

Huang, Ying; Palek, Leonard; Strommen, Robert; Worel, Ben; Chen, Genda

2014-03-01

Overloading truck loads have long been one of the key reasons for accelerating road damage, especially in rural regions where the design loads are expected to be small and in the cold regions where the wet-and-dry cycle places a significant role. To control the designed traffic loads and further guide the road design in future, periodical weight stations have been implemented for double check of the truck loads. The weight stations give chances for missing measurement of overloaded vehicles, slow down the traffic, and require additional labors. Infrastructure weight-in-motion sensors, on the other hand, keep consistent traffic flow and monitor all types of vehicles on roads. However, traditional electrical weight-in-motion sensors showed high electromagnetic interference (EMI), high dependence on environmental conditions such as moisture, and relatively short life cycle, which are unreliable for long-term weigh-inmotion measurements. Fiber Bragg grating (FBG) sensors, with unique advantages of compactness, immune to EMI and moisture, capability of quasi-distributed sensing, and long life cycle, will be a perfect candidate for long-term weigh-in-motion measurements. However, the FBG sensors also surfer from their frangible nature of glass materials for a good survive rate during sensor installation. In this study, the FBG based weight-in-motion sensors were packaged by fiber reinforced polymer (FRP) materials and further validated at MnROAD facility, Minnesota DOT (MnDOT). The design and layout of the FRP-FBG weight-in-motion sensors, their field test setup, data acquisition, and data analysis will be presented. Upon validation, the FRP-FBG sensors can be applied weigh-in-motion measurement to assistant road managements.

Spaceborne Autonomous and Ground Based Relative Orbit Control for the TerraSAR-X/TanDEM-X Formation

NASA Technical Reports Server (NTRS)

Ardaens, J. S.; D'Amico, S.; Kazeminejad, B.; Montenbruck, O.; Gill, E.

2007-01-01

TerraSAR-X (TSX) and TanDEM-X (TDX) are two advanced synthetic aperture radar (SAR) satellites flying in formation. SAR interferometry allows a high resolution imaging of the Earth by processing SAR images obtained from two slightly different orbits. TSX operates as a repeat-pass interferometer in the first phase of its lifetime and will be supplemented after two years by TDX in order to produce digital elevation models (DEM) with unprecedented accuracy. Such a flying formation makes indeed possible a simultaneous interferometric data acquisition characterized by highly flexible baselines with range of variations between a few hundreds meters and several kilometers [1]. TSX has been successfully launched on the 15th of June, 2007. TDX is expected to be launched on the 31st of May, 2009. A safe and robust maintenance of the formation is based on the concept of relative eccentricity/inclination (e/i) vector separation whose efficiency has already been demonstrated during the Gravity Recovery and Climate Experiment (GRACE) [2]. Here, the satellite relative motion is parameterized by mean of relative orbit elements and the key idea is to align the relative eccentricity and inclination vectors to minimize the hazard of a collision. Previous studies have already shown the pertinence of this concept and have described the way of controlling the formation using an impulsive deterministic control law [3]. Despite the completely different relative orbit control requirements, the same approach can be applied to the TSX/TDX formation. The task of TDX is to maintain the close formation configuration by actively controlling its relative motion with respect to TSX, the leader of the formation. TDX must replicate the absolute orbit keeping maneuvers executed by TSX and also compensate the natural deviation of the relative e/i vectors. In fact the relative orbital elements of the formation tend to drift because of the secular non-keplerian perturbations acting on both satellites. The goal of the ground segment is thus to regularly correct this configuration by performing small orbit correction maneuvers on TDX. The ground station contacts are limited due to the geographic position of the station and the costs for contact time. Only with a polar ground station a contact visibility is possible every orbit for LEO satellites. TSX and TDX use only the Weilheim ground station (in the southern part of Germany) during routine operations. This station allows two scheduled contact per day for the nominal orbit configuration, meaning that the satellite conditions can be checked with an interval of 12 hours. While this limitation is usually not critical for single satellite operations, the visibility constraints drive the achievable orbit control accuracy for a LEO formation if a ground based approach is chosen. Along-track position uncertainties and maneuver execution errors affect the relative motion and can be compensated only after a ground station contact.

A stochastic estimate of ground motion at Oceano, California, for the M 6.5 22 December 2003 San Simeon earthquake, derived from aftershock recordings

USGS Publications Warehouse

Di, Alessandro C.; Boatwright, J.

2006-01-01

The U.S. Geological Survey deployed a digital seismic station in Oceano, California, in February 2004, to investigate the cause of damage and liquefaction from the 22 December 2003 M 6.5 San Simeon earthquake. This station recorded 11 M > 2.8 aftershocks in almost 8 weeks. We analyze these recordings, together with recordings of the mainshock and the same aftershocks obtained from nearby stations in Park Hill and San Luis Obispo, to estimate the mainshock ground motion in Oceano. We estimate the Fourier amplitude spectrum using generalized spectral ratio analysis. We test a set of aftershocks as Green's functions by comparing simulated and recorded acceleration amplitude spectra for the mainshock at San Luis Obispo and Park Hill. We convolve the aftershock accelerograms with a stochastic operator to simulate the duration and phase of the mainshock accelerograms. This approximation allows us to extend the range of aftershocks that can be used as Green's functions to events nearly three magnitude units smaller than the mainshock. Our realizations for the mainshock accelerogram at Oceano yield peak ground accelerations distributed as 28% ?? 4%g. We interpret these realizations as upper bounds for the actual ground motion, because our analysis assumes a linear response, whereas the presence of liquefaction indicates that the ground behaved nonlinearly in Oceano.

Peristalsis

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... series of wave-like muscle contractions that moves food to different processing stations in the digestive tract. ... begins in the esophagus when a bolus of food is swallowed. The strong wave-like motions of ...

Effect of Space Vehicle Structure Vibration on Control Moment Gyroscope Dynamics

NASA Technical Reports Server (NTRS)

Dobrinskaya, Tatiana

2008-01-01

Control Moment Gyroscopes (CMGs) are used for non-propulsive attitude control of satellites and space stations, including the International Space Station (ISS). CMGs could be essential for future long duration space missions due to the fact that they help to save propellant. CMGs were successfully tested on the ground for many years, and have been successfully used on satellites. However, operations have shown that the CMG service life on the ISS is significantly shorter than predicted. Since the dynamic environment of the ISS differs greatly from the nominal environment of satellites, it was important to analyze how operations specific to the station (dockings and undockings, huge solar array motion, crew exercising, robotic operations, etc) can affect the CMG performance. This task became even more important since the first CMG failure onboard the ISS. The CMG failure resulted in the limitation of the attitude control capabilities, more propellant consumption, and additional operational issues. Therefore, the goal of this work was to find out how the vibrations of a space vehicle structure, caused by a variety of onboard operations, can affect the CMG dynamics and performance. The equations of CMG motion were derived and analyzed for the case when the gyro foundation can vibrate in any direction. The analysis was performed for unbalanced CMG gimbals to match the CMG configuration on ISS. The analysis showed that vehicle structure vibrations can amplify and significantly change the CMG motion if the gyro gimbals are unbalanced in flight. The resonance frequencies were found. It was shown that the resonance effect depends on the magnitude of gimbal imbalance, on the direction of a structure vibration, and on gimbal bearing friction. Computer modeling results of CMG dynamics affected by the external vibration are presented. The results can explain some of the CMG vibration telemetry observed on ISS. This work shows that balancing the CMG gimbals decreases the effect of vehicle structure vibration on CMGs. Additionally, the effect of external vibrations may also be decreased by increasing the gimbal bearing friction. With the suggested modifications there may be no need to lower the gimbal rates below the nominal design requirements as it is currently done on ISS. The conclusions of this work

6-C polarization analysis using point measurements of translational and rotational ground-motion: theory and applications

NASA Astrophysics Data System (ADS)

Sollberger, David; Greenhalgh, Stewart A.; Schmelzbach, Cedric; Van Renterghem, Cédéric; Robertsson, Johan O. A.

2018-04-01

We provide a six-component (6-C) polarization model for P-, SV-, SH-, Rayleigh-, and Love-waves both inside an elastic medium as well as at the free surface. It is shown that single-station 6-C data comprised of three components of rotational motion and three components of translational motion provide the opportunity to unambiguously identify the wave type, propagation direction, and local P- and S-wave velocities at the receiver location by use of polarization analysis. To extract such information by conventional processing of three-component (3-C) translational data would require large and dense receiver arrays. The additional rotational components allow the extension of the rank of the coherency matrix used for polarization analysis. This enables us to accurately determine the wave type and wave parameters (propagation direction and velocity) of seismic phases, even if more than one wave is present in the analysis time window. This is not possible with standard, pure-translational 3-C recordings. In order to identify modes of vibration and to extract the accompanying wave parameters, we adapt the multiple signal classification algorithm (MUSIC). Due to the strong nonlinearity of the MUSIC estimator function, it can be used to detect the presence of specific wave types within the analysis time window at very high resolution. We show how the extracted wavefield properties can be used, in a fully automated way, to separate the wavefield into its different wave modes using only a single 6-C recording station. As an example, we apply the method to remove surface wave energy while preserving the underlying reflection signal and to suppress energy originating from undesired directions, such as side-scattered waves.

User Needs, Benefits, and Integration of Robotic Systems in a Space Station Laboratory

NASA Technical Reports Server (NTRS)

Dodd, W. R.; Badgley, M. B.; Konkel, C. R.

1989-01-01

The methodology, results and conclusions of all tasks of the User Needs, Benefits, and Integration Study (UNBIS) of Robotic Systems in a Space Station Laboratory are summarized. Study goals included the determination of user requirements for robotics within the Space Station, United States Laboratory. In Task 1, three experiments were selected to determine user needs and to allow detailed investigation of microgravity requirements. In Task 2, a NASTRAN analysis of Space Station response to robotic disturbances, and acceleration measurement of a standard industrial robot (Intelledex Model 660) resulted in selection of two ranges of microgravity manipulation: Level 1 (10-3 to 10-5 G at greater than 1 Hz) and Level 2 (less than equal 10-6 G at 0.1 Hz). This task included an evaluation of microstepping methods for controlling stepper motors and concluded that an industrial robot actuator can perform milli-G motion without modification. Relative merits of end-effectors and manipulators were studied in Task 3 in order to determine their ability to perform a range of tasks related to the three microgravity experiments. An Effectivity Rating was established for evaluating these robotic system capabilities. Preliminary interface requirements for an orbital flight demonstration were determined in Task 4. Task 5 assessed the impact of robotics.

Seismic anisotropy of northeastern Algeria from shear-wave splitting analysis

NASA Astrophysics Data System (ADS)

Radi, Zohir; Yelles-Chaouche, Abdelkrim; Bokelmann, Götz

2015-11-01

There are few studies of internal deformation under northern Africa; here we present such a study. We analyze teleseismic shear-wave splitting for northeast Algeria, to improve our knowledge of lithospheric and asthenospheric deformation mechanisms in this region. We study waveform data generated by tens of teleseismic events recorded at five recently installed broadband (BB) stations in Algeria. These stations cover an area 2° across, extending from the Tellian geological units in the North to the Saharan Atlas units in the South. Analysis of SKS-wave splitting results insignificant spatial variations in fast polarization orientation, over a scale length of at most 100 km. The seismic anisotropy shows three clear spatial patterns. A general ENE-WSW orientation is observed under the stations in the north. This polarization orientation follows the direction of the Tell Atlas mountain chain, which is perpendicular to the convergence direction between Africa and Eurasia. Delay times vary significantly across the region, between 0.6 and 2.0 s. At several stations there is an indication of a WNW-ESE polarization orientation, which is apparently related to a later geodynamic evolutionary phase in this region. A third pattern of seismic anisotropy emerges in the South, with an orientation of roughly N-S. We discuss these observations in light of geodynamic models and present-day geodetic motion.

Modelling the future Israel EEWS performance using synthetic catalogue

NASA Astrophysics Data System (ADS)

Pinsky, V.

2017-10-01

In 2012 June, Israel government decided about building an Earthquake Early Warning System (EEWS) in the country. The network configuration suggested was to be a staggered line of ˜100 stations along the regional main faults: Dead Sea fault and Carmel fault and additional ˜22 stations spread over the country. The EEWS alarm system should have to utilize two approaches: the P-wave-based algorithm combined with the S-threshold method. The former utilizes first wave arrivals to several closest stations for prompt location and the three initial seconds of the waveform data for magnitude estimation. The latter issues alarm when the surface shaking (velocity or acceleration) exceeds the relatively high threshold corresponding to a magnitude 5 earthquake at a short distance of about 10 km at least for the two neighbouring stations. For each of the approaches and for a reasonable combination of them, we simulate the EEWS performance based on a synthetic catalogue. The input seismicity parameters for the processing are extracted from the real instrumental catalogue. Using a general ground-motion prediction equations for peak ground accelaration, τc and Pd we then evaluate how false and missed alarm rates depend on the corresponding thresholds. Practically, in turn, these dependencies approve choosing initial thresholds for the EEWS providing suitable false and missed alarms rates.

Earthquake Warning Performance in Vallejo for the South Napa Earthquake

NASA Astrophysics Data System (ADS)

Wurman, G.; Price, M.

2014-12-01

In 2002 and 2003, Seismic Warning Systems, Inc. installed first-generation QuakeGuardTM earthquake warning devices at all eight fire stations in Vallejo, CA. These devices are designed to detect the P-wave of an earthquake and initiate predetermined protective actions if the impending shaking is estimated at approximately Modifed Mercalli Intensity V or greater. At the Vallejo fire stations the devices were set up to sound an audio alert over the public address system and to command the equipment bay doors to open. In August 2014, after more than 11 years of operating in the fire stations with no false alarms, the five units that were still in use triggered correctly on the MW 6.0 South Napa earthquake, less than 16 km away. The audio alert sounded in all five stations, providing fire fighters with 1.5 to 2.5 seconds of warning before the arrival of the S-wave, and the equipment bay doors opened in three of the stations. In one station the doors were disconnected from the QuakeGuard device, and another station lost power before the doors opened completely. These problems highlight just a small portion of the complexity associated with realizing actionable earthquake warnings. The issues experienced in this earthquake have already been addressed in subsequent QuakeGuard product generations, with downstream connection monitoring and backup power for critical systems. The fact that the fire fighters in Vallejo were afforded even two seconds of warning at these epicentral distances results from the design of the QuakeGuard devices, which focuses on rapid false positive rejection and ground motion estimates. We discuss the performance of the ground motion estimation algorithms, with an emphasis on the accuracy and timeliness of the estimates at close epicentral distances.

Some observations on colocated and closely spaced strong ground-motion records of the 1999 Chi-Chi, Taiwan, earthquake

USGS Publications Warehouse

Wang, G.-Q.; Boore, D.M.; Igel, H.; Zhou, X.-Y.

2003-01-01

The digital accelerograph network installed in Taiwan produced a rich set of records from the 20 September 1999 Chi-Chi, Taiwan earthquake (Mw 7.6). Teledyne Geotech model A-800 and A-900A* digital accelerographs were colocated at 22 stations that recorded this event. Comparisons of the amplitudes, frequency content, and baseline offsets show that records from several of the A-800 accelerographs are considerably different than those from the colocated A-900A accelerographs. On this basis, and in view of the more thorough predeployment testing of the newer A-900A instruments, we recommend that the records from the A-800 instruments be used with caution in analyses of the mainshock and aftershocks. At the Hualien seismic station two A-900A and one A-800 instruments were colocated, along with a Global Positioning System instrument. Although the records from the two A-900A instruments are much more similar than those from a colocated A-800 instrument, both three-component records contain unpredictable baseline offsets, which produced completely unrealistic ground displacements derived from the accelerations by double integration, as do many of the strong-motion data from this event; the details of the baseline offsets differ considerably on the two three-component records. There are probably numerous sources of the baseline offsets, including sources external to the instruments, such as tilting or rotation of the ground, and sources internal to the instruments, such as electrical or mechanical hysteresis in the sensors. For the two colocated A-900A records at the Hualien seismic station, however, the differences in the baseline offsets suggest that the principal source is some transient disturbance within the instrument. The baseline offsets generally manifest themselves in the acceleration time series as pulses or steps, either singly or in combination. We find a 0.015-Hz low-cut filter can almost completely eliminate the effects of the baseline offsets, but then information regarding the permanent displacements is lost. The causative mechanisms of the baseline offsets are unknown presently. Hence, it is very difficult to recover the permanent displacements from the modern digital records, although for records close to large earthquakes, the signal-to-noise ratio should theoretically be adequate to obtain ground motions with periods of hundreds of seconds. This study reinforces our conclusion from previous studies that the sources of baseline offsets occurring in digital strong-motion records are very complex and often unpredictable, and that, therefore, it is difficult to remove the baseline effects to maximize the information content of the record. The baseline offsets only affect very long period motions (e.g., >20 sec), however, and therefore are of little or no engineering concern.

An integrated framework for detecting suspicious behaviors in video surveillance

NASA Astrophysics Data System (ADS)

Zin, Thi Thi; Tin, Pyke; Hama, Hiromitsu; Toriu, Takashi

2014-03-01

In this paper, we propose an integrated framework for detecting suspicious behaviors in video surveillance systems which are established in public places such as railway stations, airports, shopping malls and etc. Especially, people loitering in suspicion, unattended objects left behind and exchanging suspicious objects between persons are common security concerns in airports and other transit scenarios. These involve understanding scene/event, analyzing human movements, recognizing controllable objects, and observing the effect of the human movement on those objects. In the proposed framework, multiple background modeling technique, high level motion feature extraction method and embedded Markov chain models are integrated for detecting suspicious behaviors in real time video surveillance systems. Specifically, the proposed framework employs probability based multiple backgrounds modeling technique to detect moving objects. Then the velocity and distance measures are computed as the high level motion features of the interests. By using an integration of the computed features and the first passage time probabilities of the embedded Markov chain, the suspicious behaviors in video surveillance are analyzed for detecting loitering persons, objects left behind and human interactions such as fighting. The proposed framework has been tested by using standard public datasets and our own video surveillance scenarios.

Calibration of Subsurface Amplification Factors Using Surface/Borehole Strong-motion Records from the KiK-net

NASA Astrophysics Data System (ADS)

Hayashida, T.; Tajima, F.

2007-12-01

The Real-time Earthquake Information System (REIS, Horiuchi et al., 2005) detects earthquakes and determines event parameters using the Hi-net (High-sensitivity seismograph network Japan) data in Japan. The system also predicts the arrival time and seismic intensity at a given site before ground motions arrive. Here, the seismic intensity is estimated based on the intensity magnitude which is derived from data of the Hi-net. As the Hi-net stations are located in the boreholes, intensity estimation on the ground surface is evaluated using a constant for subsurface amplification. But the estimated intensities based on the conventionally used amplification constants are not always in agreement with those observed at specific sites on the ground surface. The KiK-net (KIBAN Kyoshin network Japan) consists of strong motion instruments. Each station has two sets of accelerometers, one set is installed on the ground surface and the other one is co-located with a Hi-net station in the borehole. We use data recorded at the KiK-net stations to calibrate subsurface site amplification factors between the borehole and the ground surface. We selected data recorded for over 200 events during the period of 1997 to 2006 in Hiroshima prefecture and calculated the ratios of peak velocity amplitudes on the ground surface ( Asurf) to those in the borehole ( Abor). The subsurface amplification varies from station to station showing dependency on the propagation distance as well as on the incident direction of seismic waves. Results suggest that the site amplification factors shall be described as a function of distance and incident direction, and are not constants. Thus, we derived empirical amplification formulas between Asurf and the peak velocity amplitudes on the engineering bedrock ( Abed) as a function of distance in place of the conventionally used amplification constants. Here, the engineering bedrock is defined as the depth where the S- wave velocity is 600 m/s. The estimated intensities show substantial improvement in the accuracy at most stations as compared with those calculated using conventional constants. When the amplification dependence on the incident direction was accounted for, the estimated intensities somewhat improved. This calibration will help an earthquake early warning system such as REIS provide more accurate intensity estimates.

Enhancement of EarthScope Infrastructure with Real Time Seismogeodesy

NASA Astrophysics Data System (ADS)

Bock, Y.; Melgar, D.; Geng, J.; Haase, J. S.; Crowell, B. W.; Squibb, M. B.

2013-12-01

Recent great earthquakes and ensuing tsunamis in Sumatra, Chile and Japan have demonstrated the need for accurate ground displacements that fully characterize the great amplitudes and broad dynamic range of motions associated with these complex ruptures. Our ability to model the source processes of these events and their effects, whether in real-time or after the fact, is limited by the weaknesses of both seismic and geodetic networks. Geodetic instruments provide the static component as well as coarse dynamic motions but are much less precise than seismic instruments, especially in the vertical direction. Seismic instruments provide exceptionally-sensitive dynamic motions but typically have difficulty in recovering unbiased near-field low-frequency absolute displacements. We have shown in several publications that an optimal combination of data from collocated GPS and strong motion accelerometers provides seismogeodetic displacement, velocity and point tilt waveforms spanning the full spectrum of seismic motion, without clipping and magnitude saturation. These observations are suitable for earthquake early warning (EEW) through detection of P wave arrivals, rapid assessment of earthquake magnitude, finite-source centroid moment tensor solutions and fault slip models, and tsunami warning, in particular in the near-source regions of large earthquakes. At present, more than 550 real-time GPS stations are operating in Western North America, a majority as part of the EarthScope/PBO effort with a concentration in the Cascadia region and southern California. Unfortunately, there are few collocations of GPS and accelerometers in this region (the exception being in parts of the BARD network in northern California). We have leveraged the considerable infrastructure already invested in the EarthScope project, and funding through NSF and NASA to create advanced software, hardware, and algorithms that make it possible to utilize EarthScope/PBO as an EEW test bed. We have developed cost-effective hardware and embedded firmware to upgrade existing real-time GPS stations with low-cost MEMS accelerometers. Fifteen PBO and SCIGN stations in southern California have already been upgraded with this technology. We have also developed a software suite to analyze seismogeodetic data in real time using a tightly-coupled precise point positioning (PPP) Kalman filter that supports PPP with ambiguity resolution (PPP-AR) throughout the seismically active regions of the Western U.S. The seismogeodetic system contributes directly to collaborative natural hazards research by providing technology for early warning systems for earthquakes, volcanoes and tsunamis, and for short-term high impact weather forecasting and related flooding hazards (we are also installing MEMS temperature and pressure sensors for GPS meteorology). The systems have also been deployed for earthquake engineering research for large structures (e.g., bridges, buildings, dams). Here we present the components and status of our seismogeodetic earthquake and tsunami monitoring system. Although the analysis techniques are quite advanced, the project lends itself to opportunities for education and outreach, specifically in illustrating concepts in elementary physics of position, velocity, and acceleration. Many of the animations generated in the research are available for development into appealing and accessible educational modules.

Seismic anisotropy beneath South China Sea: using SKS splitting to constrain mantle flow

NASA Astrophysics Data System (ADS)

Xue, M.; Le, K.; Yang, T.

2011-12-01

The evolution of South China Sea is under debate and several hypotheses have been proposed: (1) The collision of India plate and Eurasia plate; (2) the backward movement of the Pacific subduction plate; (3) mantle upwelling; and (4) combinations of above hypotheses. All these causal mechanisms emphasize the contributions of deep structures to the evolution of South China Sea. In this study we use earthquake data recorded by seismic stations surrounding South China Sea to constrain mantle flow beneath. To fill the vacancy of seismic data in Viet Nam, we deployed 4 seismic stations (VT01-VT04) in a roughly north - south orientation in Viet Nam in Nov. 2009. We combine the VT dataset with the AD and MY datasets from IRIS and select 81 events for SKS splitting analysis. Measurements were made at 11 stations using Wolfe and Silver (1998)'s multi-event stacking procedure. Our observed splitting directions in Vietnam are generally consistent with those of Bai et. al. (2009) . In northern Vietnam, the splitting times are around 1 sec and the fast directions are NWW-SEE, parallel to the absolute plate motion as well as the motion of the Earth surface, implying the crust and the mantle are coupled in this region and is moving as a result of the collision of India and China. While in southern Vietnam and Malaya, the fast directions are NE-SW, almost perpendicular to the absolute plate motion as well as the surface motion of Eurasia plate. However, the observed NE-SW is parallel to the subduction direction of the Australian plate, which might be caused by the mantle flow along NE-SW induced by the subduction.

Periodic-disturbance accommodating control of the space station for asymptotic momentum management

NASA Technical Reports Server (NTRS)

Warren, Wayne; Wie, Bong; Geller, David

1989-01-01

Periodic-disturbance accommodating control is investigated for asymptotic momentum management of control moment gyros used as primary actuating devices for the Space Station. The proposed controller utilizes the concepts of quaternion feedback control and periodic-disturbance accommodation to achieve oscillations about the constant torque equilibrium attitude, while minimizing the control effort required. Three-axis coupled equations of motion, written in terms of quaternions, are derived for roll/yaw controller design and stability analysis. The quaternion feedback controller designed using the linear-quadratic regulator synthesis technique is shown to be robust for a wide range of pitch angles. It is also shown that the proposed controller tunes the open-loop unstable vehicle to a stable oscillatory motion which minimizes the control effort needed for steady-state operations.

Ground motion in the presence of complex Topography II: Earthquake sources and 3D simulations

USGS Publications Warehouse

Hartzell, Stephen; Ramirez-Guzman, Leonardo; Meremonte, Mark; Leeds, Alena L.

2017-01-01

Eight seismic stations were placed in a linear array with a topographic relief of 222 m over Mission Peak in the east San Francisco Bay region for a period of one year to study topographic effects. Seventy‐two well‐recorded local earthquakes are used to calculate spectral amplitude ratios relative to a reference site. A well‐defined fundamental resonance peak is observed with individual station amplitudes following the theoretically predicted progression of larger amplitudes in the upslope direction. Favored directions of vibration are also seen that are related to the trapping of shear waves within the primary ridge dimensions. Spectral peaks above the fundamental one are also related to topographic effects but follow a more complex pattern. Theoretical predictions using a 3D velocity model and accurate topography reproduce many of the general frequency and time‐domain features of the data. Shifts in spectral frequencies and amplitude differences, however, are related to deficiencies of the model and point out the importance of contributing factors, including the shear‐wave velocity under the topographic feature, near‐surface velocity gradients, and source parameters.

Calibration of strong motion models for Central America region and its use in seismic hazard assessment

NASA Astrophysics Data System (ADS)

Climent, A.; Benito, M. B.; Piedra, R.; Lindholm, C.; Gaspar-Escribano, J.

2013-05-01

We present the results of a study aimed at choosing the more suitable strong-motion models for seismic hazard analysis in the Central America (CA) Region. After a careful revision of the state of the art, different models developed for subduction and volcanic crustal zones, in tectonic environment similar to those of CA, were selected. These models were calibrated with accelerograms recorded in Costa Rica, Nicaragua and El Salvador. The peak ground acceleration PGA and Spectral Acceleration SA (T) derived from the records were compared with the ones predicted by the models in similar conditions of magnitude, distance and soil. The type of magnitude (Ms, Mb, MW), distance (Rhyp, Rrup, etc) and ground motion parameter (maximum horizontal component, geometrical mean, etc ) was taken into account in the comparison with the real data. As results of the analysis, the models which present a best fit with the local data were identified. These models have been applied for carrying out seismic hazard analysis in the region, in the frame of the RESIS II project financed by the Norwegian Foreign Department and also by the Spanish project SISMOCAES. The methodology followed is based on the direct comparison between PGA and SA 5 % damped response values extracted from actual records with the corresponding acceleration values predicted by the selected ground-motion models for similar magnitude, distance and soil conditions. Residuals between observed and predicted values for PGA, and SA (1sec) are calculated and plotted as a function of distance and magnitude, analyzing their deviation from the mean value. Besides and most important, a statistical analysis of the normalized residuals was carry out using the criteria proposed by Scherbaum et al. (2004), which consists in categorizing ground motion models based in a likelihood parameter that reflects the goodness-of-fit of the median values as well as the shape of the underlying distribution of ground motion residuals. Considering the results of the both analysis the conclusions can be drawn in the following paragraphs. Analyses of residuals show that in some cases the best adjustments of PGA and SA values do not always favor the same equation. Consequently, the following equations that present reasonable adjustments for both parameters are finally selected: Schmidt (2010) and Zhao et al (2006) for shallow crustal sources; Schmidt (2010), Zhao et al (2006), Youngs et al. (1997) and Lin & Lee (2008) for subduction interface and Schmidt (2010), Youngs et al (1997), Zhao et al (2006) and Garcia et al (2005) for inslab subduction sources. Finally, to improve the development of proper models of attenuation of the region, it is recommended to the governmental and private institutions, to support the implementation of permanent strong ground motion networks in all Central America countries, especially in Guatemala, Honduras, Nicaragua and Panama, including free field stations. In case of Costa Rica and El Salvador to strengthen the networks that already they operate.

A Newly Reanalyzed Dataset of GPS-determined Antarctic Vertical Rates

NASA Astrophysics Data System (ADS)

Thomas, I.; King, M.; Clarke, P. J.; Penna, N. T.; Lavallee, D. A.; Whitehouse, P.

2010-12-01

Accurate and precise measurements of vertical crustal motion offer useful constraints on glacial isostatic adjustment (GIA) models. Here we present a newly reprocessed data set of GPS-determined vertical rates for Antarctica. We give details of the global reanalysis of 15-years of GPS data, the overarching aim of which is to achieve homogeneous station coordinate time series, and hence surface velocities, for GPS receivers that are in regions of GIA interest in Antarctica. The means by which the reference frame is realized is crucial to obtaining accurate rates. Considerable effort has been spent on achieving a good global distribution of GPS stations, using data from IGS and other permanently recording stations, as well as a number of episodic campaigns in Antarctica. Additionally, we have focused on minimizing the inevitable imbalance in the number of sites in the northern and southern hemispheres. We align our daily non-fiducial solutions to ITRF2005, i.e. a CM frame. We present the results of investigations into the reference frame realization, and also consider a GPS-derived realization of the frame, and its effect on the vertical velocities. Vertical velocities are obtained for approximately 40 Antarctic locations. We compare our GPS derived Antarctic vertical rates with those predicted by the Ivins and James and ICE-5G models, after converting to a CE frame. We also compare to previously published GPS rates. Our GPS velocities are being used to help tune, and bound errors of, a new GIA model also presented in this session.

Insensitivity of GNSS to geocenter motion through the network shift approach (Invited)

NASA Astrophysics Data System (ADS)

Rebischung, P.; Altamimi, Z.; Springer, T.

2013-12-01

As a satellite-based technique, GNSS should be sensitive to motions of the Earth's center of mass (CM) with respect to the Earth's crust. In theory, the weekly solutions of the Analysis Centers of the International GNSS Service (IGS ACs) should indeed have the "instantaneous" CM as their origin, and the net translations between the weekly AC frames and a secular frame such as ITRF2008 should thus approximate the non-linear motion of CM with respect to the Earth's center of figure. However, the comparison of the AC translation time series with each other, with SLR geocenter estimates or with geophysical models reveals that this way of observing geocenter motion with GNSS currently gives unreliable results. We addressed the problem of observing geocenter motion with GNSS through this network shift approach from the perspective of collinearity (or multicollinearity) among the parameters of a least-squares regression. A collinearity diagnosis, based on the notion of variance inflation factor, was therefore developed and allows handling several peculiarities of the GNSS geocenter determination problem. Its application reveals that the determination of all three components of geocenter motion with GNSS suffers from serious collinearity issues, with a comparable level as in the problem of determining the terrestrial scale simultaneously with the GNSS satellite phase center offsets. We show that the inability of current GNSS, as opposed to Satellite Laser Ranging (SLR), to properly sense geocenter motion is mostly explained by the estimation, in the GNSS case, of epoch-wise station and satellite clock offsets simultaneously with tropospheric parameters. The empirical satellite accelerations, as estimated by most IGS ACs, slightly amplify the collinearity of the Z geocenter coordinate, but their role remains secondary.

Simulation of Local Seismic Ground Motions from the FLASK Underground Nuclear Explosion near the Source Physics Experiment Dry Alluvium Geology Site

NASA Astrophysics Data System (ADS)

Rodgers, A. J.; Pitarka, A.; Wagoner, J. L.; Helmberger, D. V.

2017-12-01

The FLASK underground nuclear explosion (UNE) was conducted in Area 2 of Yucca Flat at the Nevada Test Site on May 26, 1970. The yield was 105 kilotons (DOE/NV-209-Rev 16) and the working point was 529 m below the surface. This test was detonated in faulted Tertiary volcanic rocks of Yucca Flat. Coincidently, the FLASK UNE ground zero (GZ) is close (< 600 m) to the U2ez hole where the Source Physics Experiment will be conducting Phase II of its chemical high explosives test series in the so-called Dry Alluvium Geology (DAG) site. Ground motions from FLASK were recorded by twelve (12) three-component seismic stations in the near-field at ranges 3-4 km. We digitized the paper records and used available metadata on peak particle velocity measurements made at the time to adjust the amplitudes. These waveforms show great variability in amplitudes and waveform complexity with azimuth from the shot, likely due to along propagation path structure such as the geometry of the hard-rock/alluvium contact above the working point. Peak particle velocities at stations in the deeper alluvium to the north, east and south of GZ have larger amplitudes than those to the west where the basement rock is much shallower. Interestingly, the transverse components show a similar trend with azimuth. In fact, the transverse component amplitudes are similar to the other components for many stations overlying deeper basement. In this study, we simulated the seismic response at the available near-field stations using the SW4 three-dimensional (3D) finite difference code. SW4 can simulate seismic wave propagation in 3D inelastic earth structure, including surface topography. SW4 includes vertical mesh refinement which greatly reduces the computational resources needed to run a specific problem. Simulations are performed on high-performance computers with grid spacing as small as 10 meters and resolution to 6 Hz. We are testing various subsurface models to identify the role of 3D structure on path propagation effects from the source. We are also testing 3D models to constrain structure for the upcoming DAG experiments in 2018.

Origin and Evolution of the Yellowstone Hotspot from Seismic-GPS Imaging and Geodynamic Modeling

NASA Astrophysics Data System (ADS)

Smith, R. B.; Jordan, M.; Puskas, C. M.; Farrell, J.; Waite, G. P.

2006-12-01

The Yellowstone hotspot resulted from interaction of a mantle plume with the overriding North America plate. This feature and related processes have influenced a large part of the western U.S., producing the 16 Ma Yellowstone-Snake River Plain-Newberry silicic-basalt volcanic field (YSRPN). We integrate results from a multi-institution experiment that deployed 80 seismic stations and 160 campaign and 21 permanent GPS stations for 1999-2003. Crust and mantle velocity models were derived from inversion of teleseismic and local earthquake data. Kinematic and dynamic models were derived from inversion of GPS velocities constrained by stresses associated the topography and the +15 m geoid anomaly. Tomography revealed a P- and S-wave low-velocity body at depths of 8-16 km beneath the caldera that is interpreted as partial melt of 8-15% that feeds the youthful Yellowstone volcanic field. Volume changes in the magma chamber are responsible for GPS-measured episodes of uplift and subsidence of the caldera at decadal scales with average rates of ~20 mm/yr but much higher short-term rates of up to 80 mm/yr. An upper-mantle low-velocity body was imaged by inverting teleseismic data constrained by the geoid structure, crustal structure, and the upper mantle discontinuities. This low P and S velocity body extends from 80 km to ~250 km directly beneath Yellowstone and then continues to 650 km with unexpected tilt to the west at ~60°. The tilt is consistent with the ascent of the buoyant magma entrained in eastward return-flow of the upper mantle. We estimate this body has an excess temperature from 85K to 120K, depending on the water content and with up to 1.5% melt. Using the inclined plume-geometry and plate motion history, we extrapolate the Yellowstone mantle source southwestward ~800 km as a plume-head in oceanic lithosphere centered beneath the Columbia Plateau basalt field at 16 Ma. Magma ascent was truncated there by the passage of thicker continental lithosphere over the plume beginning at 12 Ma, reducing the rate of large-scale volcanic eruptions in the YSRP. The decapitated plume head beneath Oregon underwent mantle return flow above the subducting Juan de Fuca plate and was responsible for the NW transgressive magmatism of the Newberry system. We then model the overall kinematics of the western U.S. from GPS data as SW motion for the YSRP, ~2 mm/yr, rotating into E-W motion in the Basin-Range, with a cumulative rate of ~4 mm/yr, and rotating to the northwest at rates of up to ~5 mm/yr in the Pacific Northwest, totaling ~10 mm/yr. Geodynamic models employing the GPS data and geometry of the crust-mantle structure suggests that southwest motion of the YSRP is dominated by stresses produced by the high potential energy of the Yellowstone hotspot while westward motion of the Basin-Range is driven by stress differences associated with the high topography of the Rocky Mountains.

Stochastic ground-motion simulation of two Himalayan earthquakes: seismic hazard assessment perspective

NASA Astrophysics Data System (ADS)

Harbindu, Ashish; Sharma, Mukat Lal; Kamal

2012-04-01

The earthquakes in Uttarkashi (October 20, 1991, M w 6.8) and Chamoli (March 8, 1999, M w 6.4) are among the recent well-documented earthquakes that occurred in the Garhwal region of India and that caused extensive damage as well as loss of life. Using strong-motion data of these two earthquakes, we estimate their source, path, and site parameters. The quality factor ( Q β ) as a function of frequency is derived as Q β ( f) = 140 f 1.018. The site amplification functions are evaluated using the horizontal-to-vertical spectral ratio technique. The ground motions of the Uttarkashi and Chamoli earthquakes are simulated using the stochastic method of Boore (Bull Seismol Soc Am 73:1865-1894, 1983). The estimated source, path, and site parameters are used as input for the simulation. The simulated time histories are generated for a few stations and compared with the observed data. The simulated response spectra at 5% damping are in fair agreement with the observed response spectra for most of the stations over a wide range of frequencies. Residual trends closely match the observed and simulated response spectra. The synthetic data are in rough agreement with the ground-motion attenuation equation available for the Himalayas (Sharma, Bull Seismol Soc Am 98:1063-1069, 1998).

Localized damage caused by topographic amplification during the 2010 M7.0 Haiti earthquake

USGS Publications Warehouse

Hough, S.E.; Altidor, J.R.; Anglade, D.; Given, D.; Janvier, M.G.; Maharrey, J.Z.; Meremonte, M.; Mildor, B.S.-L.; Prepetit, C.; Yong, A.

2010-01-01

Local geological conditions, including both near-surface sedimentary layers and topographic features, are known to significantly influence ground motions caused by earthquakes. Microzonation maps use local geological conditions to characterize seismic hazard, but commonly incorporate the effect of only sedimentary layers. Microzonation does not take into account local topography, because significant topographic amplification is assumed to be rare. Here we show that, although the extent of structural damage in the 2010 Haiti earthquake was primarily due to poor construction, topographic amplification contributed significantly to damage in the district of Petionville, south of central Port-au-Prince. A large number of substantial, relatively well-built structures situated along a foothill ridge in this district sustained serious damage or collapse. Using recordings of aftershocks, we calculate the ground motion response at two seismic stations along the topographic ridge and at two stations in the adjacent valley. Ground motions on the ridge are amplified relative to both sites in the valley and a hard-rock reference site, and thus cannot be explained by sediment-induced amplification. Instead, the amplitude and predominant frequencies of ground motion indicate the amplification of seismic waves by a narrow, steep ridge. We suggest that microzonation maps can potentially be significantly improved by incorporation of topographic effects. ?? 2010 Macmillan Publishers Limited. All rights reserved.

Using different ways to determine the focal depth of the 2014 Ludian Ms 6.5 earthquake

NASA Astrophysics Data System (ADS)

Song, X.; Yu, J.; Yang, J.; Cui, X.; Zhu, Y.

2017-12-01

As we all know, focal depth is a very important parameter. And it has remained challenging. The Ludian County of Yunnan Province in southwestern China was struck by an Ms6.5 earthquake on August 3, 2014. The rapid report focal depth of CENC was 12km, and the result of double difference location was 15km (Wang W L, 2014) and 13.3km (Zhang G W, 2014). Because of the great damage, we have studied the focal depth of the Ludian Ms6.5 earthquake with several different methods. The first way is precise location. Due to the significant role of the velocity model in the focal depth determination, we collected the earthquake data which took place in Ludian area in the past few years. A new velocity model was recalculated with these data, which is more suitable for Ludian area. Taking the initial position of the epicenter as center, uniformly distributed stations were chose to improve the accuracy of location. The second way is by seismic phase. We used developed Pn-Pg (A reliable method for the determination of the depth of a hypocenter, Zhu Y Q, 1990) to certify the focal depth. This method aims to determine the depth of a hypocenter in the crust. It requires multiple seismic stations recording simultaneously the initial arrival waves Pg and Pn at each station. And the third way is by the nearest station. One of the main difficulties of the accurate focal depth determination is lack of stations along the direction of depth. A very close station to the epicenter can effectively control the accuracy of depth (Mori, 1999). A strong motion recording of Ludian MS6.5 earthquake was found, which instrument was set nearly perpendicular to the hypocenter. It obviously provides robust evidence. All the results show that the focal depth of Ludian Ms6.5 earthquake is about 7-8km. And we did an error analysis of the result. In the process, it was certified that the velocity model plays a very important role in focal depth calculation as well as the determination method.

Site Amplification Characteristics of the Several Seismic Stations at Jeju Island, in Korea, using S-wave Energy, Background Noise, and Coda waves from the East Japan earthquake (Mar. 11th, 2011) Series.

NASA Astrophysics Data System (ADS)

Seong-hwa, Y.; Wee, S.; Kim, J.

2016-12-01

Observed ground motions are composed of 3 main factors such as seismic source, seismic wave attenuation and site amplification. Among them, site amplification is also important factor and should be considered to estimate soil-structure dynamic interaction with more reliability. Though various estimation methods are suggested, this study used the method by Castro et. al.(1997) for estimating site amplification. This method has been extended to background noise, coda waves and S waves recently for estimating site amplification. This study applied the Castro et. al.(1997)'s method to 3 different seismic waves, that is, S-wave Energy, Background Noise, and Coda waves. This study analysed much more than about 200 ground motions (acceleration type) from the East Japan earthquake (March 11th, 2011) Series of seismic stations at Jeju Island (JJU, SGP, HALB, SSP and GOS; Fig. 1), in Korea. The results showed that most of the seismic stations gave similar results among three types of seismic energies. Each station showed its own characteristics of site amplification property in low, high and specific resonance frequency ranges. Comparison of this study to other studies can give us much information about dynamic amplification of domestic sites characteristics and site classification.

Correlations between ground motion and building damage. Engineering intensity scale applied to the San Fernando earthquake of February 1971

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hafen, D.; Kintzer, F.C.

1977-11-01

The correlation between ground motion and building damage was investigated for the San Fernando earthquake of 1971. A series of iso-intensity maps was compiled to summarize the ground motion in terms of the Blume Engineering Intensity Scale (EIS). This involved the analysis of ground motion records from 62 stations in the Los Angeles area. Damage information for low-rise buildings was obtained in the form of records of loans granted by the Small Business Administration to repair earthquake damage. High-rise damage evaluations were based on direct inquiry and building inspection. Damage factors (ratio of damage repair cost to building value) weremore » calculated and summarized on contour maps. A statistical study was then undertaken to determine relationships between ground motion and damage factor. Several parameters for ground motion were considered and evaluated by means of correlation coefficients.« less

Tsunami magnetic signals in the Northwestern Pacific seafloor magnetic measurements

NASA Astrophysics Data System (ADS)

Schnepf, N. R.; An, C.; Nair, M. C.; Maus, S.

2013-12-01

In the past two decades, underwater cables and seafloor magnetometers have observed motional inductance from ocean tsunamis. This study aimed to characterize the electromagnetic signatures of tsunamis from seafloor stations to assist in the long-term goal of real-time tsunami detection and warning systems. Four ocean seafloor stations (T13, T14, T15, T18) in the Northeastern Philippine Sea collected vector measurements of the electric and magnetic fields every minute during the period of 10/05/2005 to 11/30/2007 (Baba et al., 2010 PEPI). During this time, four major tsunamis occurred as a result of moment magnitude 8.0-8.1 earthquakes. These tsunamis include the 05/03/2006 Tonga event, the 01/13/2007 Kuril Islands event, the 04/01/2007 Solomon Islands event, and the 08/15/2007 Peru event. The Cornell Multi-grid Coupled Tsunami model (COMCOT) was used to predict the arrival time of the tsunamis at each of the seafloor stations. The stations' raw magnetic field signals underwent a high pass filter to then be examined for signals of the tsunami arrival. The high pass filtering showed clear tsunami signals for the Tonga event, but a clear signal was not seen for the other events. This may be due to signals from near Earth space with periods similar to tsunamis. To remove extraneous atmospheric magnetic signals, a cross-wavelet analysis was conducted using the horizontal field components from three INTERMAGNET land stations and the vertical component from the seafloor stations. The cross-wavelet analysis showed that for three of the six stations (two of the four tsunami events) the peak in wavelet amplitude matched the arrival of the tsunami. We discuss implications of our finding in magnetic monitoring of tsunamis.

Seismic Readings from the Deepest Borehole in the New Madrid Seismic Zone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woolery, Edward W; Wang, Zhenming; Sturchio, Neil C

2006-03-01

Since the 1980s, the research associated with the UK network has been primarily strong-motion seismology of engineering interest. Currently the University of Kentucky operates a strong-motion network of nine stations in the New Madrid Seismic Zone. A unique feature of the network is the inclusions of vertical strong-motion arrays, each with one or two downhole accelerometers. The deepest borehole array is 260 m below the surfaces at station VASA in Fulton County, Kentucky. A preliminary surface seismic refraction survey was conducted at the site before drilling the hole at VSAS (Woolery and Wang, 2002). The depth to the Paleozoic bedrockmore » at the site was estimated to be approximately 595 m, and the depth to the first very stiff layer (i.e. Porters Creek Clay) was found to be about 260 m. These depths and stratigraphic interpretation correlated well with a proprietary seismic reflection line and the Ken-Ten Oil Exploration No. 1 Sanger hole (Schwalb, 1969), as well as our experience in the area (Street et al., 1995; Woolery et al., 1999).« less

User Manual for Program SCOMOT Second Part of U.S.C.G. Ship Motion Program.

DTIC Science & Technology

1981-02-01

wave angle, etc. - 52 - Entry 8 - Jl - First Index Number First index for motion calculation using coordinate points or moment and force calculations using...162.4 .6500 .5434 .2942 179.8 .6786 170.0 1.0258 161.8 1.4070 144.3 .7000 .4686 .1774 179.6 .5946 167.1 1.0292 154.8 1.2598 110.5 .7500 .4082 . 0786 ...SHIP MOTION PROGRAM 77.1 02/24/81 05.49.12 PAGE 52 SL-7 - NORMAL FULL LOAD DEPARTURE SPEED = 25.000 KNOTS REGULAR WAVE LATERAL BENDING MOMENT AT STATION

Astronaut-Induced Disturbances to the Microgravity Environment of the Mir Space Station

NASA Technical Reports Server (NTRS)

Newman, Dava J.; Amir, Amir R.; Beck, Sherwin M.

2001-01-01

In preparation for the International Space Station, the Enhanced Dynamic Load Sensors Space Flight Experiment measured the forces and moments astronauts exerted on the Mir Space Station during their daily on-orbit activities to quantify the astronaut-induced disturbances to the microgravity environment during a long-duration space mission. An examination of video recordings of the astronauts moving in the modules and using the instrumented crew restraint and mobility load sensors led to the identification of several typical astronaut motions and the quantification or the associated forces and moments exerted on the spacecraft. For 2806 disturbances recorded by the foot restraints and hand-hold sensor, the highest force magnitude was 137 N. For about 96% of the time, the maximum force magnitude was below 60 N, and for about 99% of the time the maximum force magnitude was below 90 N. For 95% of the astronaut motions, the rms force level was below 9.0 N. It can be concluded that expected astronaut-induced loads from usual intravehicular activity are considerably less than previously thought and will not significantly disturb the microgravity environment.

Site Amplification in the Central U.S.: Towards and understanding of factors influencing the site effect

NASA Astrophysics Data System (ADS)

Yassminh, R.; Sandvol, E. A.

2017-12-01

We have mapped site amplification using a Reverse Two Station (RTS) approach across much of the Central United States. We have found several unexpected results including a lack of amplification in Paleozoic basins such as the Illinois and Michigan basins. In general, we found that the amplification of high frequency regional waves is related to the topography. We also suggest that the HVSR spectra are primarily a function of the shallow velocity structure. The Central United States Seismic Observatory (CUSSO) is a vertical seismic array located adjacent to the central segment of the NMSZ. CUSSO data gives us the opportunity to understand the amplification of the ground motion at different depths within the uppermost crust. Simulating ground motions throughout the CUSSO borehole and examining the factors affecting the ground amplification, such as the velocity and thicknesses of the model layers and the source sizes, is an effective way to understand the role different factors playing in modifying the ground motion for both the local and regional seismic phases. We have used the spectral-element method (SEMs) with a 1D crustal velocity structure derived from logging data taken from CUSSO borehole. This model is comprised of near surface sediment layers and a Paleozoic basement. Utilizing the software package SPECFEM2D with virtual seismometers located on the surface and in the bottom of the different sediment layers, we have computed the true synthetic site amplification for frequencies between 0.01-3 Hz. For the local model, we have tested the sensitivity of the ground motion amplification to the source magnitude. For frequencies>0.6, the ground motions have been amplified with decreasing the magnitudes while for HZ<0.6 the the horizontal amplification increases with increasing the magnitudes. The effect of the velocity of the upper 30m was tested and the result shows that decreasing the Vs30m resulted in amplifying of the ground motion and decreasing of the resonant frequency. The velocity of the lower part of the sediment basin modifies the ground motion amplification and the result shows that increasing the velocity resulted in shifting the horizontal amplification peak frequency toward a lower frequency and increasing the amplification for frequencies >2Hz.

Utah's Regional/Urban ANSS Seismic Network---Strategies and Tools for Quality Performance

NASA Astrophysics Data System (ADS)

Burlacu, R.; Arabasz, W. J.; Pankow, K. L.; Pechmann, J. C.; Drobeck, D. L.; Moeinvaziri, A.; Roberson, P. M.; Rusho, J. A.

2007-05-01

The University of Utah's regional/urban seismic network (224 stations recorded: 39 broadband, 87 strong-motion, 98 short-period) has become a model for locally implementing the Advanced National Seismic System (ANSS) because of successes in integrating weak- and strong-motion recording and in developing an effective real-time earthquake information system. Early achievements included implementing ShakeMap, ShakeCast, point-to- multipoint digital telemetry, and an Earthworm Oracle database, as well as in-situ calibration of all broadband and strong-motion stations and submission of all data and metadata into the IRIS DMC. Regarding quality performance, our experience as a medium-size regional network affirms the fundamental importance of basics such as the following: for data acquisition, deliberate attention to high-quality field installations, signal quality, and computer operations; for operational efficiency, a consistent focus on professional project management and human resources; and for customer service, healthy partnerships---including constant interactions with emergency managers, engineers, public policy-makers, and other stakeholders as part of an effective state earthquake program. (Operational cost efficiencies almost invariably involve trade-offs between personnel costs and the quality of hardware and software.) Software tools that we currently rely on for quality performance include those developed by UUSS (e.g., SAC and shell scripts for estimating local magnitudes) and software developed by other organizations such as: USGS (Earthworm), University of Washington (interactive analysis software), ISTI (SeisNetWatch), and IRIS (PDCC, BUD tools). Although there are many pieces, there is little integration. One of the main challenges we face is the availability of a complete and coherent set of tools for automatic and post-processing to assist in achieving the goals/requirements set forth by ANSS. Taking our own network---and ANSS---to the next level will require standardized, well-designed, and supported software. Other advances in seismic network performance will come from diversified instrumentation. We have recently shown the utility of incorporating strong-motion data (even from soil sites) into the routine analysis of local seismicity, and have also collocated an acoustic array with a broadband seismic station (in collaboration with Southern Methodist University). For the latter experiment, the purpose of collocated seismic and infrasound sensors is to (1) further an understanding of the physics associated with the generation and the propagation of seismic and low-frequency acoustic energy from shallow sources and (2) explore the potential for blast discrimination and improved source location using seismic and infrasonic data in a synergetic way.

Models for the transient stability of conventional power generating stations connected to low inertia systems

NASA Astrophysics Data System (ADS)

Zarifakis, Marios; Coffey, William T.; Kalmykov, Yuri P.; Titov, Sergei V.

2017-06-01

An ever-increasing requirement to integrate greater amounts of electrical energy from renewable sources especially from wind turbines and solar photo-voltaic installations exists and recent experience in the island of Ireland demonstrates that this requirement influences the behaviour of conventional generating stations. One observation is the change in the electrical power output of synchronous generators following a transient disturbance especially their oscillatory behaviour accompanied by similar oscillatory behaviour of the grid frequency, both becoming more pronounced with reducing grid inertia. This behaviour cannot be reproduced with existing mathematical models indicating that an understanding of the behaviour of synchronous generators, subjected to various disturbances especially in a system with low inertia requires a new modelling technique. Thus two models of a generating station based on a double pendulum described by a system of coupled nonlinear differential equations and suitable for analysis of its stability corresponding to infinite or finite grid inertia are presented. Formal analytic solutions of the equations of motion are given and compared with numerical solutions. In particular the new finite grid model will allow one to identify limitations to the operational range of the synchronous generators used in conventional power generation and also to identify limits, such as the allowable Rate of Change of Frequency which is currently set to ± 0.5 Hz/s and is a major factor in describing the volatility of a grid as well as identifying requirements to the total inertia necessary, which is currently provided by conventional power generators only, thus allowing one to maximise the usage of grid connected non-synchronous generators, e.g., wind turbines and solar photo-voltaic installations.

Characterization of site conditions for selected seismic stations in eastern part of Romania

NASA Astrophysics Data System (ADS)

Grecu, B.; Zaharia, B.; Diaconescu, M.; Bala, A.; Nastase, E.; Constantinescu, E.; Tataru, D.

2018-02-01

Strong motion data are essential for seismic hazard assessment. To correctly understand and use this kind of data is necessary to have a good knowledge of local site conditions. Romania has one of the largest strong motion networks in Europe with 134 real-time stations. In this work, we aim to do a comprehensive site characterization for eight of these stations located in the eastern part of Romania. We make use of a various seismological dataset and we perform ambient noise and earthquake-based investigations to estimate the background noise level, the resonance frequencies and amplification of each site. We also derive the Vs30 parameter from the surface shear-wave velocity profiles obtained through the inversion of the Rayleigh waves recorded in active seismic measurements. Our analyses indicate similar results for seven stations: high noise levels for frequencies larger than 1 Hz, well defined fundamental resonance at low frequencies (0.15-0.29 Hz), moderate amplification levels (up to 4 units) for frequencies between 0.15 and 5-7 Hz and same soil class (type C) according to the estimated Vs30 and Eurocode 8. In contrast, the eighth station for which the soil class is evaluated of type B exhibits a very good noise level for a wide range of frequencies (0.01-20 Hz), a broader fundamental resonance at high frequencies ( 8 Hz) and a flat amplification curve between 0.1 and 3-4 Hz.

Magnetic, gravity, radiometric, LiDAR, and seismic data to characterize the region of the M5.8 August 23, 2011 earthquake near Mineral, Virginia

NASA Astrophysics Data System (ADS)

Shah, A. K.; McNamara, D. E.; Odum, J. K.; Stephenson, W. J.; Kayen, R. E.; Emmett, P. F.; Herrmann, R. B.; Snyder, S. L.; Horton, J. W.; Williams, R. A.

2012-12-01

In response to the M5.8 August 23, 2011 Mineral, VA earthquake, the U.S. Geological Survey and partner organizations acquired or sponsored collection of several geophysical datasets to assist characterization of the earthquake region. Goals include the mapping of the main shock causative and aftershock faults as well as associated geologic features which may be buried or difficult to access, estimates of regional ground motion attenuation, and measurements describing local amplification of seismic energy. The deployment of 46 portable seismic stations by several organizations within days following the earthquake, along with public availability of the resulting data, has greatly aided site characterization efforts. The aftershock data recorded by these stations have allowed delineation of the probable causative fault and other faults that were active afterwards. Using the portable seismograph network and regional permanent stations, S and Lg waves were analyzed to estimate crustal attenuation characteristics. Active- and passive-source seismic experiments were also conducted at many of the portable and permanent stations to characterize site conditions and constrain local response models via estimates of Vs30 and bedrock depth. In March 2012, a LiDAR survey with 8pt/m2 resolution was flown over a ~20x35 km area covering the epicenters of the earthquake and most aftershocks. In July 2012, a high-resolution airborne magnetic, gravity, and radiometric survey was flown over a similar but slightly smaller area. Supplementary ground gravity data have been collected inside and outside of the airborne survey areas. The gravity and magnetic data reflect subsurface features in a region where outcropping rocks are sparse, while LiDAR and radiometric data, respectively, delineate subtle features at the land surface and upper few centimeters. Each of these datasets reflects the regional NE-SW striking fabric. Seismic wave analyses show preferential attenuation in a NW-SE direction, perpendicular to major structures and consistent with estimates of motion intensity such as USGS "Did you feel it?" website responses and local damage reports (Virginia DMME). Preliminary analyses of strong ground motions show measurable differences in shaking over scales of kilometers. Magnetic data show numerous NE-SW lineations, some which extend several tens of km to the northeast from near the aftershock plane, suggesting continuity of some features in that direction. Near the earthquake epicenter and primary aftershock plane, small changes in the orientation of major structures (< 20°) are apparent in magnetic, gravity and topographic data. Detailed analyses to understand possible relations are underway.

The ZH ratio method for long-period seismic data: inversion for S-wave velocity structure

NASA Astrophysics Data System (ADS)

Yano, Tomoko; Tanimoto, T.; Rivera, L.

2009-10-01

The particle motion of surface waves, in addition to phase and group velocities, can provide useful information for S-wave velocity structure in the crust and upper mantle. In this study, we applied a new method to retrieve velocity structure using the ZH ratio, the ratio between vertical and horizontal surface amplitudes of Rayleigh waves. Analysing data from the GEOSCOPE network, we measured the ZH ratios for frequencies between 0.004 and 0.05 Hz (period between 20 and 250s) and inverted them for S-wave velocity structure beneath each station. Our analysis showed that the resolving power of the ZH ratio is limited and final solutions display dependence on starting models; in particular, the depth of the Moho in the starting model is important in order to get reliable results. Thus, initial models for the inversion need to be carefully constructed. We chose PREM and CRUST2.0 in this study as a starting model for all but one station (ECH). The eigenvalue analysis of the least-squares problem that arises for each step of the iterative process shows a few dominant eigenvalues which explains the cause of the inversion's initial-model dependence. However, the ZH ratio is unique in having high sensitivity to near-surface structure and thus provides complementary information to phase and group velocities. Application of this method to GEOSCOPE data suggest that low velocity zones may exist beneath some stations near hotspots. Our tests with different starting models show that the models with low-velocity anomalies fit better to the ZH ratio data. Such low velocity zones are seen near Hawaii (station KIP), Crozet Island (CRZF) and Djibuti (ATD) but not near Reunion Island (RER). It is also found near Echery (ECH) which is in a geothermal area. However, this method has a tendency to produce spurious low velocity zones and resolution of the low velocity zones requires further careful study. We also performed simultaneous inversions for volumetric perturbation and discontinuity-depth perturbation. While its formulation and inversion were straightforward, there seemed to be a difficult trade-off problem between volumetric perturbation and discontinuity-depth perturbation.

Application and API for Real-time Visualization of Ground-motions and Tsunami

NASA Astrophysics Data System (ADS)

Aoi, S.; Kunugi, T.; Suzuki, W.; Kubo, T.; Nakamura, H.; Azuma, H.; Fujiwara, H.

2015-12-01

Due to the recent progress of seismograph and communication environment, real-time and continuous ground-motion observation becomes technically and economically feasible. K-NET and KiK-net, which are nationwide strong motion networks operated by NIED, cover all Japan by about 1750 stations in total. More than half of the stations transmit the ground-motion indexes and/or waveform data in every second. Traditionally, strong-motion data were recorded by event-triggering based instruments with non-continues telephone line which is connected only after an earthquake. Though the data from such networks mainly contribute to preparations for future earthquakes, huge amount of real-time data from dense network are expected to directly contribute to the mitigation of ongoing earthquake disasters through, e.g., automatic shutdown plants and helping decision-making for initial response. By generating the distribution map of these indexes and uploading them to the website, we implemented the real-time ground motion monitoring system, Kyoshin (strong-motion in Japanese) monitor. This web service (www.kyoshin.bosai.go.jp) started in 2008 and anyone can grasp the current ground motions of Japan. Though this service provides only ground-motion map in GIF format, to take full advantage of real-time strong-motion data to mitigate the ongoing disasters, digital data are important. We have developed a WebAPI to provide real-time data and related information such as ground motions (5 km-mesh) and arrival times estimated from EEW (earthquake early warning). All response data from this WebAPI are in JSON format and are easy to parse. We also developed Kyoshin monitor application for smartphone, 'Kmoni view' using the API. In this application, ground motions estimated from EEW are overlapped on the map with the observed one-second-interval indexes. The application can playback previous earthquakes for demonstration or disaster drill. In mobile environment, data traffic and battery are limited and it is not practical to regularly visualize all the data. The application has automatic starting (pop-up) function triggered by EEW. Similar WebAPI and application for tsunami are being prepared using the pressure data recorded by dense offshore observation network (S-net), which is under construction along the Japan Trench.

The Los Alamos Seismic Network (LASN): Recent Network Upgrades and Northern New Mexico Earthquake Catalog Updates

NASA Astrophysics Data System (ADS)

Roberts, P. M.; House, L. S.; Greene, M.; Ten Cate, J. A.; Schultz-Fellenz, E. S.; Kelley, R.

2012-12-01

From the first data recorded in the fall of 1973 to now, the Los Alamos Seismograph Network (LASN) has operated for nearly 40 years. LASN data have been used to locate more than 2,500 earthquakes in north-central New Mexico. The network was installed for seismic verification research, as well as to monitor and locate earthquakes near Los Alamos National Laboratory (LANL). LASN stations are the only earthquake monitoring stations in New Mexico north of Albuquerque. In the late 1970s, LASN included 22 stations spread over a geographic area of 150 km (N-S) by 350 km (E-W), of northern New Mexico. In the early 1980s, the available funding limited the stations that could be operated to a set of 7, located within an area of about 15 km (N-S) by 15 km (E-W), centered on Los Alamos. Over the last 3 years, 6 additional stations have been installed, which have considerably expanded the spatial coverage of the network. These new stations take advantage of broadband state-of-the-art sensors as well as digital recording and telemetry technology. Currently, 7 stations have broadband, three-component seismometers with digital telemetry, and the remaining 6 have traditional 1 Hz short-period seismometers with analog telemetry. In addition, a vertical array of accelerometers was installed in a wellbore on LANL property. This borehole station has 3-component digital strong-motion sensors. In addition, four forensic strong-motion accelerometers (SMA) are operated at LANL facilities. With 3 of the new broadband stations in and around the nearby Valles Caldera, LASN is now able to monitor any very small volcano-seismic events that may be associated with the caldera. We will present a complete description of the current LASN station, instrumentation and telemetry configurations, as well as the data acquisition and event-detection software structure used to record events in Earthworm. More than 2,000 earthquakes were detected and located in north-central New Mexico during the first 11 years of LASN's operation (1973 to 1984). With the subsequent downsizing of the network, only 1-2 earthquakes per month were detected and located within about 150 km of Los Alamos. Over 850 of these nearby earthquakes have been located from 1973 to present. We recently updated the LASN earthquake catalog for north-central New Mexico up through 2011 and most of 2012. This involved re-assessing phase picks and ensuring that all locations are derived using updated station locations and the best available velocity model. We are also looking at subsets of the catalog that include earthquake swarms and clusters and applying relative location techniques to obtain high-precision re-locations for these events. Most events that were detected and located by LASN have magnitudes less than 1.5 and do not appear in the catalogs of any other network. We will present a newly updated map of north-central New Mexico seismicity based on these recent efforts.

Istanbul Earthquake Early Warning and Rapid Response System

NASA Astrophysics Data System (ADS)

Erdik, M. O.; Fahjan, Y.; Ozel, O.; Alcik, H.; Aydin, M.; Gul, M.

2003-12-01

As part of the preparations for the future earthquake in Istanbul a Rapid Response and Early Warning system in the metropolitan area is in operation. For the Early Warning system ten strong motion stations were installed as close as possible to the fault zone. Continuous on-line data from these stations via digital radio modem provide early warning for potentially disastrous earthquakes. Considering the complexity of fault rupture and the short fault distances involved, a simple and robust Early Warning algorithm, based on the exceedance of specified threshold time domain amplitude levels is implemented. The band-pass filtered accelerations and the cumulative absolute velocity (CAV) are compared with specified threshold levels. When any acceleration or CAV (on any channel) in a given station exceeds specific threshold values it is considered a vote. Whenever we have 2 station votes within selectable time interval, after the first vote, the first alarm is declared. In order to specify the appropriate threshold levels a data set of near field strong ground motions records form Turkey and the world has been analyzed. Correlations among these thresholds in terms of the epicenter distance the magnitude of the earthquake have been studied. The encrypted early warning signals will be communicated to the respective end users by UHF systems through a "service provider" company. The users of the early warning signal will be power and gas companies, nuclear research facilities, critical chemical factories, subway system and several high-rise buildings. Depending on the location of the earthquake (initiation of fault rupture) and the recipient facility the alarm time can be as high as about 8s. For the rapid response system one hundred 18 bit-resolution strong motion accelerometers were placed in quasi-free field locations (basement of small buildings) in the populated areas of the city, within an area of approximately 50x30km, to constitute a network that will enable early damage assessment and rapid response information after a damaging earthquake. Early response information is achieved through fast acquisition and analysis of processed data obtained from the network. The stations are routinely interrogated on regular basis by the main data center. After triggered by an earthquake, each station processes the streaming strong motion data to yield the spectral accelerations at specific periods, 12Hz filtered PGA and PGV and will send these parameters in the form of SMS messages at every 20s directly to the main data center through a designated GSM network and through a microwave system. A shake map and damage distribution map (using aggregate building inventories and fragility curves) will be automatically generated using the algorithm developed for this purpose. Loss assessment studies are complemented by a large citywide digital database on the topography, geology, soil conditions, building, infrastructure and lifeline inventory. The shake and damage maps will be conveyed to the governor's and mayor's offices, fire, police and army headquarters within 3 minutes using radio modem and GPRS communication. An additional forty strong motion recorders were placed on important structures in several interconnected clusters to monitor the health of these structures after a damaging earthquake.

WHITTIER NARROWS, CALIFORNIA EARTHQUAKE OF OCTOBER 1, 1987-PRELIMINARY ASSESSMENT OF STRONG GROUND MOTION RECORDS.

USGS Publications Warehouse

Brady, A.G.; Etheredge, E.C.; Porcella, R.L.

1988-01-01

More than 250 strong-motion accelerograph stations were triggered by the Whittier Narrows, California earthquake of 1 October 1987. Considering the number of multichannel structural stations in the area of strong shaking, this set of records is one of the more significant in history. Three networks, operated by the U. S. Geological Survey, the California Division of Mines and Geology, and the University of Southern California produced the majority of the records. The excellent performance of the instruments in these and the smaller arrays is attributable to the quality of the maintenance programs. Readiness for a magnitude 8 event is directly related to these maintenance programs. Prior to computer analysis of the analog film records, a number of important structural resonant modes can be identified, and frequencies and simple mode shapes have been scaled.

The determination of interseismic, coseismic and postseismic deformations caused by the Gökçeada-Samothraki earthquake (2014, Mw: 6.9) based on GNSS data

NASA Astrophysics Data System (ADS)

Tiryakioglu, Ibrahim; Yigit, Cemal Ozer; Yavasoglu, Hakan; Saka, Mehmet Halis; Alkan, Reha Metin

2017-09-01

Since the 1990s, seismic deformations have been commonly determined using the Global Navigation Satellite System (GNSS). Recently, the GNSS systems have become even more powerful with the use of new technologies in innovative studies. In this study, the GNSS data was used to investigate interseismic, coseismic and postseismic deformation and velocity of the Gökçeada-Samothraki earthquake (Mw = 6.9) that occurred on May 24, 2014. The data was obtained at 30 s (0.033 Hz) and 1 s (1 Hz) intervals from the GNSS receivers in the network of Continuously Operating Reference Stations, Turkey (CORS-TR). For the interseismic period, the daily coordinate time series of 12 stations located within 90-250 km of the earthquake epicenter was evaluated for the displacement of stations over a period of approximately 2000 days prior to the day of the earthquakes, from October 1, 2008 to May 23, 2014. In order to analyze the ground motion displacement during the Gökçeada-Samothraki earthquake, 1 Hz data from 8 continuous GNSS stations was processed using precise point positioning (PPP) and relative positioning methods to estimate the epoch-by-epoch positions of the stations. During the earthquake, coseismic displacements of approximately 7 and 30 mm were detected in the NW direction at the YENC and CANA stations, respectively. However, at the IPSA station, a coseismic deformation of 20 mm was observed in the NE direction. There were no significant changes at the other stations during the earthquake. For the postseismic period, the daily coordinate time series of the 12 stations were evaluated for station displacements for 570 days after the day of the earthquakes, from May 24, 2014 to January 1, 2016. The results demonstrated that no significant postseismic deformation with the exception of the EDIR station. An abnormal deformation caused by local factors was determined at the EDIR station. In this study, the PPP and the relative solution were also compared in terms of capturing the earthquake wave motion. The results demonstrated that the PPP-based solutions showed good agreement with those of relative positioning in terms of the ability to capture coseismic displacement.

Modelling of Tethered Space-Web Structures

NASA Astrophysics Data System (ADS)

McKenzie, D. J.; Cartnell, M. P.

Large structures in space are an essential milestone in the path of many projects, from solar power collectors to space stations. In space, as on Earth, these large projects may be split up into more manageable sections, dividing the task into multiple replicable parts. Specially constructed spider robots could assemble these structures piece by piece over a membrane or space- web, giving a method for building a structure while on orbit. The modelling and applications of these space-webs are discussed, along with the derivation of the equations of motion of the structure. The presentation of some preliminary results from the solution of these equations will show that space-webs can take a variety of different forms, and give some guidelines for configuring the space-web system.

Ground motions from induced earthquakes in Oklahoma and Kansas and the implications for seismic hazard

NASA Astrophysics Data System (ADS)

Moschetti, M. P.; Rennolet, S.; Thompson, E.; Yeck, W.; McNamara, D. E.; Herrmann, R. B.; Powers, P.; Hoover, S. M.

2016-12-01

Recent efforts to characterize the seismic hazard resulting from increased seismicity rates in Oklahoma and Kansas highlight the need for a regionalized ground motion characterization. To support these efforts, we measure and compile strong ground motions and compare these average ground motions intensity measures (IMs) with existing ground motion prediction equations (GMPEs). IMs are computed for available broadband and strong-motion records from M≥3 earthquakes occurring January 2009-April 2016, using standard strong motion processing guidelines. We verified our methods by comparing results from specific earthquakes to other standard procedures such as the USGS Shakemap system. The large number of records required an automated processing scheme, which was complicated by the extremely high rate of small-magnitude earthquakes 2014-2016. Orientation-independent IMs include peak ground motions (acceleration and velocity) and pseudo-spectral accelerations (5 percent damping, 0.1-10 s period). Metadata for the records included relocated event hypocenters. The database includes more than 160,000 records from about 3200 earthquakes. Estimates of the mean and standard deviation of the IMs are computed by distance binning at intervals of 2 km. Mean IMs exhibit a clear break in geometrical attenuation at epicentral distances of about 50-70 km, which is consistent with previous studies in the CEUS. Comparisons of these ground motions with modern GMPEs provide some insight into the relative IMs of induced earthquakes in Oklahoma and Kansas relative to the western U.S. and the central and eastern U.S. The site response for these stations is uncertain because very little is known about shallow seismic velocity in the region, and we make no attempt to correct observed IMs to a reference site conditions. At close distances, the observed IMs are lower than the predictions of the seed GMPEs of the NGA-East project (and about consistent with NGA-West-2 ground motions). This ground motion database may be used to inform future seismic hazard forecast models and in the development of regionally appropriate GMPEs.

Ground Motion Uncertainty and Variability (single-station sigma): Insights from Euroseistest, Greece

NASA Astrophysics Data System (ADS)

Ktenidou, O. J.; Roumelioti, Z.; Abrahamson, N. A.; Cotton, F.; Pitilakis, K.

2014-12-01

Despite recent improvements in networks and data, the global aleatory uncertainty (sigma) in GMPEs is still large. One reason is the ergodic approach, where we combine data in space to make up for lack of data in time. By estimating the systematic site response, we can make site-specific GMPEs and use a lower, site-specific uncertainty: single-station sigma. In this study we use the EUROSEISTEST database (http://euroseisdb.civil.auth.gr), which has two distinct advantages: good existing knowledge of site conditions at all stations, and careful relocation of the recorded events. Constraining the site and source parameters as best we can, we minimise the within- and between-events components of the global, ergodic sigma. Following that, knowledge of the site response from empirical and theoretical approaches permits us to move on to single-station sigma. The variability per site is not clearly correlated to the site class. We show that in some cases knowledge of Vs30 is not sufficient, and that site-specific data are needed to capture the response, possibly due to 2D/3D effects from complex geometry. Our values of single-station sigma are low compared to the literature. This may be due to the good ray coverage we have in all directions for small, nearby records. Indeed, our single-station sigma values are similar to published single-path values, which means that they may correspond to a fully -rather than partially- non-ergodic approach. We find larger ground motion variability for short distances and small magnitudes. This may be related to the uncertainty in the depth affecting nearby records more, or to stress drop and causing trade-offs between the source and site terms for small magnitudes.

The dynamics and control of large-flexible space structures, part 10

NASA Technical Reports Server (NTRS)

Bainum, Peter M.; Reddy, A. S. S. R.

1988-01-01

A mathematical model is developed to predict the dynamics of the proposed orbiting Spacecraft Control Laboratory Experiment (SCOLE) during the station keeping phase. The equations of motion are derived using a Newton-Euler formulation. The model includes the effects of gravity, flexibility, and orbital dynamics. The control is assumed to be provided to the system through the Shuttle's three torquers, and through six actuators located by pairs at two points on the mast and at the mass center of the reflector. The modal shape functions are derived using the fourth order beam equation. The generic mode equations are derived to account for the effects of the control forces on the modal shape and frequencies. The equations are linearized about a nominal equilibrium position. The linear regulator theory is used to derive control laws for both the linear model of the rigidized SCOLE as well as that of the actual SCOLE including the first four flexible modes. The control strategy previously derived for the linear model of the rigidized SCOLE is applied to the nonlinear model of the same configuration of the system and preliminary single axis slewing maneuvers conducted. The results obtained confirm the applicability of the intuitive and appealing two-stage control strategy which would slew the SCOLE system, as if rigid to its desired position and then concentrate on damping out the residual flexible motions.

Characterizing the Kathmandu Valley sediment response through strong motion recordings of the 2015 Gorkha earthquake sequence

USGS Publications Warehouse

Rajaure, S.; Asimaki, Domniki; Thompson, Eric M.; Hough, Susan E.; Martin, Stacey; Ampuero, J.P.; Dhital, M.R.; Inbal, A; Takai, N; Shigefuji, M.; Bijukchhen, S; Ichiyanagi, M; Sasatani, T; Paudel, L

2017-01-01

We analyze strong motion records and high-rate GPS measurements of the M 7.8 Gorkha mainshock, M 7.3 Dolakha, and two moderate aftershock events recorded at four stations on the Kathmandu basin sediments, and one on rock-outcrop. Recordings on soil from all four events show systematic amplification relative to the rock site at multiple frequencies in the 0.1–2.5 Hz frequency range, and de-amplification of higher frequencies ( >2.5–10 Hz). The soil-to-rock amplification ratios for the M 7.8 and M 7.3 events have lower amplitude and frequency peaks relative to the ratios of the two moderate events, effects that could be suggestive of nonlinear site response. Further, comparisons to ground motion prediction equations show that 1) both soil and rock mainshock recordings were severely depleted of high frequencies, and 2) the depletion at high frequencies is not present in the aftershocks. These observations indicate that the high frequency deamplification is additionally related to characteristics of the source that are not captured by simplified ground motion prediction equations, and allude to seismic hazard analysis models being revised – possibly by treating isolated high frequency radiation sources separately from long period components to capture large magnitude near-source events such as the 2015 Gorkha mainshock.

Near Fault Strong Ground Motion Records in the Kathmandu Valley during the 2015 Gorkha Nepal Earthquake

NASA Astrophysics Data System (ADS)

Takai, N.; Shigefuji, M.; Rajaure, S.; Bijukchhen, S.; Ichiyanagi, M.; Dhital, M. R.; Sasatani, T.

2015-12-01

Kathmandu is the capital of Nepal and is located in the Kathmandu Valley, which is formed by soft lake sediments of Plio-Pleistocene origin. Large earthquakes in the past have caused significant damage as the seismic waves were amplified in the soft sediments. To understand the site effect of the valley structure, we installed continuous recording accelerometers in four different parts of the valley. Four stations were installed along a west-to-east profile of the valley at KTP (Kirtipur; hill top), TVU (Kirtipur; hill side), PTN (Patan) and THM (Thimi). On 25 April 2015, a large interplate earthquake Mw 7.8 occurred in the Himalayan Range of Nepal. The focal area estimated was about 200 km long and 150 km wide, with a large slip area under the Kathmandu Valley where our strong motion observation stations were installed. The strong ground motions were observed during this large damaging earthquake. The maximum horizontal peak ground acceleration at the rock site was 271 cm s-2, and the maximum horizontal peak ground velocity at the sediment sites reached 112 cm s-1. We compared these values with the empirical attenuation formula for strong ground motions. We found the peak accelerations were smaller and the peak velocities were approximately the same as the predicted values. The rock site KTP motions are less affected by site amplification and were analysed further. The horizontal components were rotated to the fault normal (N205E) and fault parallel (N115E) directions using the USGS fault model. The velocity waveforms at KTP showed about 5 s triangular pulses on the N205E and the up-down components; however the N115E component was not a triangular pulse but one cycle sinusoidal wave. The velocity waveforms at KTP were integrated to derive the displacement waveforms. The derived displacements at KTP are characterized by a monotonic step on the N205E normal and up-down components. The displacement waveforms of KTP show permanent displacements of 130 cm in the fault normal direction and 60 cm in the upward direction; the vector sum of these is 143 cm. Inside the Kathmandu Valley, 147 cm deformation and the same moving direction as the USGS fault normal direction were reported using with GPS data. Our results derived from the KTP records are consistent with these observations.

The SCEC Broadband Platform: A Collaborative Open-Source Software Package for Strong Ground Motion Simulation and Validation

NASA Astrophysics Data System (ADS)

Silva, F.; Maechling, P. J.; Goulet, C.; Somerville, P.; Jordan, T. H.

2013-12-01

The Southern California Earthquake Center (SCEC) Broadband Platform is a collaborative software development project involving SCEC researchers, graduate students, and the SCEC Community Modeling Environment. The SCEC Broadband Platform is open-source scientific software that can generate broadband (0-100Hz) ground motions for earthquakes, integrating complex scientific modules that implement rupture generation, low and high-frequency seismogram synthesis, non-linear site effects calculation, and visualization into a software system that supports easy on-demand computation of seismograms. The Broadband Platform operates in two primary modes: validation simulations and scenario simulations. In validation mode, the Broadband Platform runs earthquake rupture and wave propagation modeling software to calculate seismograms of a historical earthquake for which observed strong ground motion data is available. Also in validation mode, the Broadband Platform calculates a number of goodness of fit measurements that quantify how well the model-based broadband seismograms match the observed seismograms for a certain event. Based on these results, the Platform can be used to tune and validate different numerical modeling techniques. During the past year, we have modified the software to enable the addition of a large number of historical events, and we are now adding validation simulation inputs and observational data for 23 historical events covering the Eastern and Western United States, Japan, Taiwan, Turkey, and Italy. In scenario mode, the Broadband Platform can run simulations for hypothetical (scenario) earthquakes. In this mode, users input an earthquake description, a list of station names and locations, and a 1D velocity model for their region of interest, and the Broadband Platform software then calculates ground motions for the specified stations. By establishing an interface between scientific modules with a common set of input and output files, the Broadband Platform facilitates the addition of new scientific methods, which are written by earth scientists in a number of languages such as C, C++, Fortran, and Python. The Broadband Platform's modular design also supports the reuse of existing software modules as building blocks to create new scientific methods. Additionally, the Platform implements a wrapper around each scientific module, converting input and output files to and from the specific formats required (or produced) by individual scientific codes. Working in close collaboration with scientists and research engineers, the SCEC software development group continues to add new capabilities to the Broadband Platform and to release new versions as open-source scientific software distributions that can be compiled and run on many Linux computer systems. Our latest release includes the addition of 3 new simulation methods and several new data products, such as map and distance-based goodness of fit plots. Finally, as the number and complexity of scenarios simulated using the Broadband Platform increase, we have added batching utilities to substantially improve support for running large-scale simulations on computing clusters.

Nonlinear Motion Cueing Algorithm: Filtering at Pilot Station and Development of the Nonlinear Optimal Filters for Pitch and Roll

NASA Technical Reports Server (NTRS)

Zaychik, Kirill B.; Cardullo, Frank M.

2012-01-01

Telban and Cardullo have developed and successfully implemented the non-linear optimal motion cueing algorithm at the Visual Motion Simulator (VMS) at the NASA Langley Research Center in 2005. The latest version of the non-linear algorithm performed filtering of motion cues in all degrees-of-freedom except for pitch and roll. This manuscript describes the development and implementation of the non-linear optimal motion cueing algorithm for the pitch and roll degrees of freedom. Presented results indicate improved cues in the specified channels as compared to the original design. To further advance motion cueing in general, this manuscript describes modifications to the existing algorithm, which allow for filtering at the location of the pilot's head as opposed to the centroid of the motion platform. The rational for such modification to the cueing algorithms is that the location of the pilot's vestibular system must be taken into account as opposed to the off-set of the centroid of the cockpit relative to the center of rotation alone. Results provided in this report suggest improved performance of the motion cueing algorithm.

Modeling of the strong ground motion of 25th April 2015 Nepal earthquake using modified semi-empirical technique

NASA Astrophysics Data System (ADS)

Lal, Sohan; Joshi, A.; Sandeep; Tomer, Monu; Kumar, Parveen; Kuo, Chun-Hsiang; Lin, Che-Min; Wen, Kuo-Liang; Sharma, M. L.

2018-05-01

On 25th April, 2015 a hazardous earthquake of moment magnitude 7.9 occurred in Nepal. Accelerographs were used to record the Nepal earthquake which is installed in the Kumaon region in the Himalayan state of Uttrakhand. The distance of the recorded stations in the Kumaon region from the epicenter of the earthquake is about 420-515 km. Modified semi-empirical technique of modeling finite faults has been used in this paper to simulate strong earthquake at these stations. Source parameters of the Nepal aftershock have been also calculated using the Brune model in the present study which are used in the modeling of the Nepal main shock. The obtained value of the seismic moment and stress drop is 8.26 × 1025 dyn cm and 10.48 bar, respectively, for the aftershock from the Brune model .The simulated earthquake time series were compared with the observed records of the earthquake. The comparison of full waveform and its response spectra has been made to finalize the rupture parameters and its location. The rupture of the earthquake was propagated in the NE-SW direction from the hypocenter with the rupture velocity 3.0 km/s from a distance of 80 km from Kathmandu in NW direction at a depth of 12 km as per compared results.

Strong ground motion of the 2016 Kumamoto earthquake

NASA Astrophysics Data System (ADS)

Aoi, S.; Kunugi, T.; Suzuki, W.; Kubo, H.; Morikawa, N.; Fujiwara, H.

2016-12-01

The 2016 Kumamoto earthquake that is composed of Mw 6.1 and Mw 7.1 earthquakes respectively occurred in the Kumamoto region at 21:26 on April 14 and 28 hours later at 1:25 on April 16, 2016 (JST). These earthquakes are considered to rupture mainly the Hinagu fault zone for the Mw 6.1 event and the Futagawa fault zone for the Mw 7.1 event, respectively, where the Headquarter for Earthquake Research Promotion performed the long-term evaluation as well as seismic hazard assessment prior to the 2016 Kumamoto earthquake. Strong shakings with seismic intensity 7 in the JMA scale were observed at four times in total: Mashiki town for the Mw 6.1 and Mw 7.1 events, Nishihara village for the Mw 7.1 event, and NIED/KiK-net Mashiki (KMMH16) for the Mw 7.1 event. KiK-net Mashiki (KMMH16) recorded peak ground acceleration more than 1000 cm/s/s, and Nishihara village recorded peak ground velocity more than 250 cm/s. Ground motions were observed wider area for the Mw 7.1 event than the Mw 6.1 event. Peak ground accelerations and peak ground velocities of K-NET/KiK-net stations are consistent with the ground motion prediction equations by Si and Midorikawa (1999). Peak ground velocities at longer distance than 200 km attenuate slowly, which can be attributed to the large Love wave with a dominant period around 10 seconds. 5%-damped pseudo spectral velocity of the Mashiki town shows a peak at period of 1-2 s that exceeds ground motion response of JR Takatori of the 1995 Kobe earthquake and the Kawaguchi town of the 2004 Chuetsu earthquake. 5%-damped pseudo spectral velocity of the Nishihara village shows 350 cm/s peak at period of 3-4 s that is similar to the several stations in Kathmandu basin by Takai et al. (2016) during the 2015 Gorkha earthquake in Nepal. Ground motions at several stations in Oita exceed the ground motion prediction equations due to an earthquake induced by the Mw 7.1 event. Peak ground accelerations of K-NET Yufuin (OIT009) records 90 cm/s/s for the Mw 7.1 event and 723 cm/s/s for the near-by induced event.

Secular and annual hydrologic effects from the Plate Boundary Observatory GPS network

NASA Astrophysics Data System (ADS)

Meertens, C. M.; Wahr, J. M.; Borsa, A. A.; Jackson, M. E.; Herring, T.

2009-12-01

The Plate Boundary Observatory (PBO) GPS network is providing accurate and spatially coherent vertical signals that can be interpreted in terms of hydrological loading and poroelastic effects from both natural and anthropogenic changes in water storage. Data used for this analysis are the precise coordinate time series produced on a daily basis by PBO Analysis Centers at New Mexico Institute of Mining and Technology and at Central Washington University and combined by the Analysis Center Coordinator at the Massachusetts Institute of Technology. These products, as well as derived velocity solutions, are made freely available from the UNAVCO Data Center in Boulder. Analysis of secular trends and annual variations in the time series was made using the analysis software of Langbein, 2008. Spatial variations in the amplitude and phase of the annual vertical component of motion allow for identification of anthropogenic effects due to water pumping, irrigation, and reservoir lake variations, and of outliers due to instrumental or other local site effects. Vertical annual signals of 8-10 mm peak-to-peak amplitude are evident at stations in the mountains of northern and central California and the Pacific Northwest. The peak annual uplift is in October and is correlated to hydrological loading effects. Mountainous areas appear to be responding elastically to the load of the water contained in surface soil, fractures, and snow. Vertical signals are highest when the water load is at a minimum. The vertical elastic hydrologic loading signal was modeled using the 0.25 degree community NOAH land-surface model (LSM) and generally fits the observed GPS signal. Addition comparisons will be made using the Mosaic LSM and the NOAA “Leaky Bucket” hydrologic model. In contrast to mountain stations that are installed principally in bedrock, stations in the valleys of California are installed in sediments. Observations from these stations show greater spatial variability ranging from almost no detectable annual signal to very large, 20-30 mm, vertical amplitudes that reach a maximum in March. Vertical signals in the valleys are the result of poroelastic effects induced by groundwater variations caused by pumping for irrigation or other purposes and are highest when groundwater is at maximum recharge level. Secular trends in the vertical time series show 1-3 mm/yr of subsidence across the western U.S. In areas of groundwater pumping the rates are up to several cm/yr showing subsidence as pumping exceeds annual recharge over a multi-year time period. In the mountainous areas where hydrologic loading is evident in the annual signals, secular trends show uplift of 1-3 mm/yr possibly due to regional drought and decreased overall water volumes that result in less load and vertical uplift. Overall, these results illustrate the potential of using GPS data to constrain hydrological models. In return, accurate hydrologic loading models will be needed to better measure and detect vertical tectonic motions at the mm-level.

Path spectra derived from inversion of source and site spectra for earthquakes in Southern California

NASA Astrophysics Data System (ADS)

Klimasewski, A.; Sahakian, V. J.; Baltay, A.; Boatwright, J.; Fletcher, J. B.; Baker, L. M.

2017-12-01

A large source of epistemic uncertainty in Ground Motion Prediction Equations (GMPEs) is derived from the path term, currently represented as a simple geometric spreading and intrinsic attenuation term. Including additional physical relationships between the path properties and predicted ground motions would produce more accurate and precise, region-specific GMPEs by reclassifying some of the random, aleatory uncertainty as epistemic. This study focuses on regions of Southern California, using data from the Anza network and Southern California Seismic network to create a catalog of events magnitude 2.5 and larger from 1998 to 2016. The catalog encompasses regions of varying geology and therefore varying path and site attenuation. Within this catalog of events, we investigate several collections of event region-to-station pairs, each of which share similar origin locations and stations so that all events have similar paths. Compared with a simple regional GMPE, these paths consistently have high or low residuals. By working with events that have the same path, we can isolate source and site effects, and focus on the remaining residual as path effects. We decompose the recordings into source and site spectra for each unique event and site in our greater Southern California regional database using the inversion method of Andrews (1986). This model represents each natural log record spectra as the sum of its natural log event and site spectra, while constraining each record to a reference site or Brune source spectrum. We estimate a regional, path-specific anelastic attenuation (Q) and site attenuation (t*) from the inversion site spectra and corner frequency from the inversion event spectra. We then compute the residuals between the observed record data, and the inversion model prediction (event*site spectra). This residual is representative of path effects, likely anelastic attenuation along the path that varies from the regional median attenuation. We examine the residuals for our different sets independently to see how path terms differ between event-to-station collections. The path-specific information gained from this can inform development of terms for regional GMPEs, through understanding of these seismological phenomena.

Source Process of the 2007 Niigata-ken Chuetsu-oki Earthquake Derived from Near-fault Strong Motion Data

NASA Astrophysics Data System (ADS)

Aoi, S.; Sekiguchi, H.; Morikawa, N.; Ozawa, T.; Kunugi, T.; Shirasaka, M.

2007-12-01

The 2007 Niigata-ken Chuetsu-oki earthquake occurred on July 16th, 2007, 10:13 JST. We performed a multi- time window linear waveform inversion analysis (Hartzell and Heaton, 1983) to estimate the rupture process from the near fault strong motion data of 14 stations from K-NET, KiK-net, F-net, JMA, and Niigata prefecture. The fault plane for the mainshock has not been clearly determined yet from the aftershock distribution, so that we performed two waveform inversions for north-west dipping fault (Model A) and south-east dipping fault (Model B). Their strike, dip, and rake are set to those of the moment tensor solutions by F-net. Fault plane model of 30 km length by 24 km width is set to cover aftershock distribution within 24 hours after the mainshock. Theoretical Green's functions were calculated by the discrete wavenumber method (Bouchon, 1981) and the R/T matrix method (Kennett, 1983) with the different stratified medium for each station based on the velocity structure including the information form the reflection survey and borehole logging data. Convolution of moving dislocation was introduced to represent the rupture propagation in an each subfault (Sekiguchi et al., 2002). The observed acceleration records were integrated into velocity except of F-net velocity data, and bandpass filtered between 0.1 and 1.0 Hz. We solved least-squared equation to obtain slip amount of each time window on each subfault to minimize squared residual of the waveform fitting between observed and synthetic waveforms. Both models provide moment magnitudes of 6.7. Regarding Model A, we obtained large slip in the south-west deeper part of the rupture starting point, which is close to Kashiwazaki-city. The second or third velocity pulses of observed velocity waveforms seem to be composed of slip from the asperity. Regarding Model B, we obtained large slip in the southwest shallower part of the rupture starting point, which is also close to Kashiwazaki-city. In both models, we found small slip near the rupture starting point, and largest slip at about ten kilometer in the south-west of the rupture starting point with the maximum slip of 2.3 and 2.5 m for Models A and B, respectively. The difference of the residual between observed and synthetic waveforms for both models is not significant, therefore it is difficult to conclude which fault plane is appropriate to explain. The estimated large-slip regions in the inverted source models with the Models A and B are located near the cross point of the two fault plane models, which should have similar radiation pattern. This situation may be one of the reasons why judgment of the fault plane orientation is such difficult. We need careful examinations not only strong motion data but also geodetic data to further explore the fault orientation and the source process of this earthquake.

Rapid Earthquake Magnitude Estimation for Early Warning Applications

NASA Astrophysics Data System (ADS)

Goldberg, Dara; Bock, Yehuda; Melgar, Diego

2017-04-01

Earthquake magnitude is a concise metric that provides invaluable information about the destructive potential of a seismic event. Rapid estimation of magnitude for earthquake and tsunami early warning purposes requires reliance on near-field instrumentation. For large magnitude events, ground motions can exceed the dynamic range of near-field broadband seismic instrumentation (clipping). Strong motion accelerometers are designed with low gains to better capture strong shaking. Estimating earthquake magnitude rapidly from near-source strong-motion data requires integration of acceleration waveforms to displacement. However, integration amplifies small errors, creating unphysical drift that must be eliminated with a high pass filter. The loss of the long period information due to filtering is an impediment to magnitude estimation in real-time; the relation between ground motion measured with strong-motion instrumentation and magnitude saturates, leading to underestimation of earthquake magnitude. Using station displacements from Global Navigation Satellite System (GNSS) observations, we can supplement the high frequency information recorded by traditional seismic systems with long-period observations to better inform rapid response. Unlike seismic-only instrumentation, ground motions measured with GNSS scale with magnitude without saturation [Crowell et al., 2013; Melgar et al., 2015]. We refine the current magnitude scaling relations using peak ground displacement (PGD) by adding a large GNSS dataset of earthquakes in Japan. Because it does not suffer from saturation, GNSS alone has significant advantages over seismic-only instrumentation for rapid magnitude estimation of large events. The earthquake's magnitude can be estimated within 2-3 minutes of earthquake onset time [Melgar et al., 2013]. We demonstrate that seismogeodesy, the optimal combination of GNSS and seismic data at collocated stations, provides the added benefit of improving the sensitivity of displacement time series compared to GNSS alone. This not only means that ground motion can be detected at farther stations, but also that smaller seismic arrivals (i.e. P-waves) become visible in the displacement time series. P-wave amplitude (Pd) has been examined as an early indicator of earthquake magnitude. Relations between Pd and magnitude using seismic-only instrumentation appear to suffer from saturation, while the combination of GNSS and seismic data has been demonstrated to eliminate saturation [Meier et al., 2016, Crowell et al., 2013]. We create seismogeodetic displacements by combining the GNSS dataset with Japanese KiK-net and K-net accelerometer data to explore the potential of seismogeodesy for magnitude scaling with several seconds of data using P-wave amplitude.

Low-cost, distributed, sensor-based weigh-in-motion systems.

DOT National Transportation Integrated Search

2009-12-01

Monitoring truck weights is essential for traffic operations, roadway design, traffic safety, and regulations. : Traditional roadside static truck weighing stations have many operational shortcomings, and so there have : been ongoing efforts to devel...

Site classification for National Strong Motion Observation Network System (NSMONS) stations in China using an empirical H/V spectral ratio method

NASA Astrophysics Data System (ADS)

Ji, Kun; Ren, Yefei; Wen, Ruizhi

2017-10-01

Reliable site classification of the stations of the China National Strong Motion Observation Network System (NSMONS) has not yet been assigned because of lacking borehole data. This study used an empirical horizontal-to-vertical (H/V) spectral ratio (hereafter, HVSR) site classification method to overcome this problem. First, according to their borehole data, stations selected from KiK-net in Japan were individually assigned a site class (CL-I, CL-II, or CL-III), which is defined in the Chinese seismic code. Then, the mean HVSR curve for each site class was computed using strong motion recordings captured during the period 1996-2012. These curves were compared with those proposed by Zhao et al. (2006a) for four types of site classes (SC-I, SC-II, SC-III, and SC-IV) defined in the Japanese seismic code (JRA, 1980). It was found that an approximate range of the predominant period Tg could be identified by the predominant peak of the HVSR curve for the CL-I and SC-I sites, CL-II and SC-II sites, and CL-III and SC-III + SC-IV sites. Second, an empirical site classification method was proposed based on comprehensive consideration of peak period, amplitude, and shape of the HVSR curve. The selected stations from KiK-net were classified using the proposed method. The results showed that the success rates of the proposed method in identifying CL-I, CL-II, and CL-III sites were 63%, 64%, and 58% respectively. Finally, the HVSRs of 178 NSMONS stations were computed based on recordings from 2007 to 2015 and the sites classified using the proposed method. The mean HVSR curves were re-calculated for three site classes and compared with those from KiK-net data. It was found that both the peak period and the amplitude were similar for the mean HVSR curves derived from NSMONS classification results and KiK-net borehole data, implying the effectiveness of the proposed method in identifying different site classes. The classification results have good agreement with site classes based on borehole data of 81 stations in China, which indicates that our site classification results are acceptable and that the proposed method is practicable.

The PBO Nucleus: Integration of the Existing Continuous GPS Networks in the Western U.S.

NASA Astrophysics Data System (ADS)

Blume, F.; Anderson, G.; Freymueller, J. T.; Herring, T. A.; Melbourne, T. I.; Murray, M. H.; Prescott, W. H.; Smith, R. B.; Wernicke, B.

2004-12-01

Tectonic and earthquake research in the US has experienced a quiet revolution over the last decade precipitated by the recognition that slow-motion faulting events can both trigger and be triggered by regular earthquakes. Transient motion has now been found in essentially all tectonic environments, and the detection and analysis of such events is the first-order science target of the EarthScope Project. Because of this and a host of other fundamental tectonics questions that can be answered only with long-duration geodetic time series, the incipient 1400-station EarthScope Plate Boundary Observatory (PBO) network has been designed to leverage 432 existing continuous GPS stations whose measurements extend back over a decade. The irreplaceable recording history of these stations will accelerate EarthScope scientific return by providing the highest possible resolution. This resolution will be used to detect and understand transients, to determine the three-dimensional velocity field (particularly vertical motion), and to improve measurement precision by understanding the complex noise sources inherent in GPS. The PBO Nucleus Project is designed operate, maintain and upgrade a subset of six western U.S. geodetic networks: the Alaska Deformation Array (AKDA), Bay Area Regional Deformation network (BARD), the Basin and Range Geodetic Network (BARGEN), the Eastern Basin and Range/Yellowstone network (EBRY), the Pacific Northwest Geodetic Array (PANGA), and the Southern California Integrated Geodetic Network (SCIGN), until they are subsumed by PBO in 2008. Uninterrupted data flow from these stations will effectively double the time-series length of PBO over the expected life of EarthScope, and create, for the first time, a single GPS-based geodetic network in the US. Other existing sites will remain in operation under support from non-NSF sources (e.g. the USGS), and EarthScope will benefit from their continued operation. On the grounds of relevance to EarthScope science goals, geographic distribution and data quality, 209 of the 432 existing stations have been selected as the nucleus upon which to build PBO. We have begun converting these stations to a PBO-compatible mode of operation; data now flow directly to PBO archives and processing centers while maintenance, operations, and meta-data requirements are currently under upgrade to PBO standards.

Observation of the seismic anisotropy effects on free oscillations below 4 mHz

NASA Astrophysics Data System (ADS)

Hu, X.; Liu, L.

2009-12-01

We present observations of significant fundamental spheroidal-toroidal mode coupling at frequencies below 4 mHz in the early part of vertical component records from seismic stations on near-equatorial source-receiver propagation paths and in Antarctica after the 26 December 2004 and 28 March 2005 great Sumatra earthquakes. When seismic surface waves propagate along the equator, the particle motion of Love waves runs parallels to the Earth’s rotation axis, and the particle motion of Rayleigh waves runs perpendicular to it, thus the Coriolis force has no vertical deflection effect on Love waves and no transverse deflection effect on the Rayleigh waves. Coriolis coupling can be naturally minimized at a station on a nearequatorial source-receiver propagation path. In Antarctica, especially near the South Pole, the vertical deflection of toroidial motion is very weak but there are lateral gradients in the anisotropic properties of upper mantle. Therefore, we can find a chance to directly observe seismic anisotropy coupling below 4 mHz without the disturbance of Coriolis coupling at Antarctic station, and at the seismic station locate close to the Earth’s equator when the epicenter also locates close to the equator. Our observations of strong anomalous toroidal-spheroidal coupling at these stations provide direct evidence to confirm the theory that the azimuthal anisotropy has pronounced effects on the quasi-toroidal mode excitations at the frequencies below 4 mHz, which can convince the skeptics that anisotropy really is visible in the low-frequency normal mode data. Strong anisotropic coupling is usually observed at stations having the geometric nodes for the spheroidal fundamentals, giving the association of quasi-toroidal excitation with the geometric effect. The presence of significant anisotropy coupling below 4 mHz depends not only on anisotropic depth, anisotropic identities and orientations but also on radiation nodes for Rayleigh waves and geometry nodes for spheroidal fundamentals. The quasi-toroidal modes below 4 mHz have significant sensitivity throughout most of the mantle, extending into the lower mantle, and therefore, it is likely that the resolution of locating the depth of origin of azimuthal anisotropy in the mantle will be improved by joint inversions that take advantage of the partly complementary depth resolution of anisotropy coupling measurements, quasi-Love surface-wave measurements, body wave splitting measurements and surface-wave dispersion measurements.

The 12 June 2017 Mw 6.3 Lesvos Island (Aegean Sea) earthquake: Slip model and directivity estimated with finite-fault inversion

NASA Astrophysics Data System (ADS)

Kiratzi, Anastasia

2018-01-01

On 12 June 2017 (UTC 12:28:38.26) a magnitude Mw 6.3 earthquake occurred offshore Lesvos Island in SE Aegean Sea, which was widely felt, caused 1 fatality, and partially ruined the village of Vrisa on the south-eastern coast of the island. I invert broad band and strong motion waveforms from regional stations to obtain the source model and the distribution of slip onto the fault plane. The hypocentre is located at a depth of 7 km in the upper crust. The mainshock ruptured a WNW-ESE striking, SW dipping, normal fault, projecting offshore and bounding the Lesvos Basin. The strongest and most aftershocks clustered away from the hypocentre, at the eastern edge of the activated area. This cluster indicates the activation of a different fault segment, exhibiting sinistral strike-slip motions, along a plane striking WNW-ESE. The slip of the mainshock is confined in a single large asperity, WNW from the hypocentre, with dimensions 20 km × 10 km along fault strike and dip, respectively. The average slip of the asperity is 50 cm and the peak slip is 1 m. The rupture propagated unilaterally towards WNW to the coastline of Lesvos island at a relatively high speed ( 3.1 km/s). The imaged slip model and forward modelling was used to calculate peak ground velocities (PGVs) in the near-field. The damage pattern produced by this earthquake, especially in the village of Vrisa is compatible with the combined effect of rupture directivity, proximity to the slip patch and the fault edge, spectral content of motions, and local site conditions.

Properties of Repetitive Long-Period Seismicity at Villarrica Volcano, Chile

NASA Astrophysics Data System (ADS)

Richardson, J.; Waite, G. P.; Palma, J.; Johnson, J. B.

2011-12-01

Villarrica Volcano, Chile hosts a persistent lava lake and is characterized by degassing and long-period seismicity. In order to better understand the relationship between outgassing and seismicity, we recorded broadband seismic and acoustic data along with high-rate SO2 emission data. We used both a densely-spaced linear array deployed on the northern flank of Villarrica, during the austral summer of 2011, and a wider aperture array of stations distributed around the volcano that was active in the austral summer of 2010. Both deployments consisted of three-component broadband stations and were augmented with broadband infrasound sensors. Of particular interests are repetitive, ~1 Hz seismic and coincident infrasound signals that occurred approximately every 2 minutes. Because these events are typically very low amplitude, we used a matched filter approach to identify them. We windowed several high-amplitude records of these events from broadband seismic stations near the vent. The record section of each event served as a template to compare with the entire dataset by cross-correlation. This approach identified ~20,000 nearly identical events during the ~7 day deployment of the linear array, which were otherwise difficult to identify in the raw records. Assuming that all of the events that we identified have identical source mechanisms and depths, we stack the large suite of events to produce low-noise records and particle motions at receivers farther than 5 km from the vent. We find that the records from stations near the edifice are dominated by tangential particle motion, suggesting the influence of near-field components. Correlation of these data with broadband acoustic data collected at the summit suggest that these repeatable seismic processes are linked to acoustic emissions, probably due to gas bubbles bursting at the magma free surface, as no eruptive products besides gas were being emitted by the volcano during the instrument deployment. The acoustic signals affiliated with the repetitive seismic signals do not seem directly related to the continuous, well-correlated acoustic tremor observed both at the vent and at roughly 6 km away from small-aperture acoustic arrays (also reported by other groups in 2009, 2010). We also correlate the acoustic and repetitive seismic signals with high time resolution (~1 Hz sampling rate), sulfur dioxide emissions measured with an ultraviolet camera. Because a subset of stations operated during both 2010 and 2011, we could tie events from both deployments to generate a single stacked event at all 17 stations. We will present results of finite-difference modeling of this event stack using a simple homogeneous velocity structure.

Bringing Hometown Relevance to Introductory Geology Courses

NASA Astrophysics Data System (ADS)

Goodell, L. P.

2008-12-01

An abundance of on-line data and content is increasingly available, especially for the U.S., and can easily bring a "hometown touch" to geoscience courses. This is particularly valuable at the introductory level where student engagement can be a challenge. Students are naturally drawn to material with which they have a personal connection, and this connection can be exploited to instantly engage students in course content. For example, most students have never really thought about the topography of their hometowns and are fascinated to examine topographic maps that cover the areas in which they grew up. The theory of plate tectonics becomes real as students use high-precision GPS data to show near real-time plate motions of where they live (and GPS is something more and more students are familiar with). At Princeton and other institutions drawing students from a wide geographic area, students get the added benefit of being able to compare and contrast characteristics of each other's hometowns. Applications of hometown perspective include: 1) Hometown map exercises: obtain USGS 1:24000 topographic quadrangle maps of students' hometown areas. These can be inexpensively ordered from a variety of sources or printed from downloaded digital scans. 2) Hometown stream projects: students choose streams of personal interest, download NWIS discharge data and discover typical discharge patterns, examine unusual events such as floods or droughts, perform flood frequency analyses, and see changes over time (e.g. due to development or stream exploitation). 3) Hometown plate motions: students can use several independent methods to track both short-term and long-term average plate motions. They can download high-precision GPS data from stations near their hometowns to get near real-time plate motions. These can be compared to independent long-term averages from various "plate motion calculators" that are based on geologic data. 4) Hometown earthquakes: use USGS or IRIS seismic monitors to look at earthquake patterns in hometown regions. 5) Hometown seismic data: analyze remote earthquakes using seismograph data from stations near students' hometowns. 6) Hometown climate change: examine historic temperature and precipitation records from stations or regions near students' hometowns and analyze changes over time.

A study of ground motion attenuation in the Southern Great Basin, Nevada-California, using several techniques for estimates of Qs , log A 0, and coda Q

NASA Astrophysics Data System (ADS)

Rogers, A. M.; Harmsen, S. C.; Herrmann, R. B.; Meremonte, M. E.

1987-04-01

As a first step in the assessment of the earthquake hazard in the southern Great Basin of Nevada-California, this study evaluates the attenuation of peak vertical ground motions using a number of different regression models applied to unfiltered and band-pass-filtered ground motion data. These data are concentrated in the distance range 10-250 km. The regression models include parameters to account for geometric spreading, anelastic attenuation with a power law frequency dependence, source size, and station site effects. We find that the data are most consistent with an essentially frequency-independent Q and a geometric spreading coefficient less than 1.0. Regressions are also performed on vertical component peak amplitudes reexpressed as pseudo-Wood-Anderson peak amplitude estimates (PWA), permitting comparison with earlier work that used Wood-Anderson (WA) data from California. Both of these results show that Q values in this region are high relative to California, having values in the range 700-900 over the frequency band 1-10 Hz. Comparison of ML magnitudes from stations BRK and PAS for earthquakes in the southern Great Basin shows that these two stations report magnitudes with differences that are distance dependent. This bias suggests that the Richter log A0 curve appropriate to California is too steep for earthquakes occurring in southern Nevada, a result implicitly supporting our finding that Q values are higher than those in California. The PWA attenuation functions derived from our data also indicate that local magnitudes reported by California observatories for earthquakes in this region may be overestimated by as much as 0.8 magnitude units in some cases. Both of these results will have an effect on the assessment of the earthquake hazard in this region. The robustness of our regression technique to extract the correct geometric spreading coefficient n and anelastic attenuation Q is tested by applying the technique to simulated data computed with given n and Q values. Using a stochastic modeling technique, we generate suites of seismograms for the distance range 10-200 km and for both WA and short-period vertical component seismometers. Regressions on the peak amplitudes from these records show that our regression model extracts values of n and Q approximately equal to the input values for either low-Q California attenuation or high-Q southern Nevada attenuation. Regressions on stochastically modeled WA and PWA amplitudes also provides a method of evaluating differences in magnitudes from WA and PWA amplitudes due to recording instrument response characteristics alone. These results indicate a difference between MLWA and MLPWA equal to 0.15 magnitude units, which we term the residual instrument correction. In contrast to the peak amplitude results, coda Q determinations using the single scatterer theory indicate that Qc values are dependent on source type and are proportional to ƒp, where p = 0.8 to 1.0. This result suggests that a difference exists between attenuation mechanisms for direct waves and backscattered waves in this region.

ULF/Lower-ELF Electromagnetic Field Measurements in the Polar Caps

DTIC Science & Technology

1980-12-01

motion sensitive and the ice stations are subject to noisy motion from I ordinary ice movements (the bumping, scraping, and so on of ice floes) 56 ,zp and...the earth", Geomag. Aeron. USSR, English Transl., 17, 760-762, 1977. Cagniard, L., "Basic theory of the magneto- telluric method of geo- physical...1967. Nishida, A., Geomagnetic Diagnosis of the Magnetosphere, 256 pp., Springer, New York, 1978. Novysh, V.V., and G.A. Fonarev, " Telluric currents

Characters of Vertical Variability with Geodetic Satellites and Ground-based Continuous GPS in Taiwan

NASA Astrophysics Data System (ADS)

Yang, C.-C.; Wu, Y.-H.; Chao, B. F.; Yu, S.-B.

2009-04-01

Present-day GPS network have been extensively used to monitor crustal deformation due to various geodynamic mechanisms. Situated among the Pacific Ring of Fire on the suture zone of Eurasian and Philippine Sea Plates, the island of Taiwan with a dense continuous GPS network since ~1996 and now over 300 stations sees plenty of geophysical phenomena including particularly prominent crustal motions. We assessed daily solution of each station's coordinate time series, and made the routine corrections, such as orbital, EOP, atmospheric and tidal corrections, using GAMIT/GLOBK software (with ITRF05). We then employ the Quasi-Observation Combination Analysis (QOCA) package to obtain the variability and trend after removing occasional earthquake "disruptions". Preliminary results show strong seasonal variations. We then utilize the numerical method of Empirical Orthogonal Function (EOF) to analysis the geophysical signals from the continuous and dense GPS vertical crustal motion observations. We wish to be able to characterize both the seasonal and non-seasonal variability in the vertical crustal motion, in terms of the EOF modes in the spatial domain over Taiwan (plus a few offshore islets) with time evolution spanning the entire period of time. Corraborating with time-variable gravity data from the geodetic satellite mission GRACE, we can further obtain vertical components of both mass-induced loading with respect to the precipitation minus evaporation and the crustal motion caused by the active tectonic processes on Taiwan.

Noise Configuration and fault zone anisotropy investigation from Taiwan Chelungpu-fault Deep Borehole Array

NASA Astrophysics Data System (ADS)

Hung, R. J.; Ma, K. F.; Song, T. R. A.; Nishida, K.; Lin, Y. Y.

2016-12-01

The Taiwan Chelungpu-fault Drilling Project was operated to understand the fault zone characteristics associated with the 1999 Chichi earthquake. Seven Borehole Seismometers (TCDPBHS) were installed through the identified fault zone to monitor the micro-seismic activities, as well as the fault-zone seismic structure properties. To understand the fault zone anisotropy and its possible temporal variations after the Chichi earthquake, we calculated cross-correlations of the noise at different stations to obtain cross correlation functions (CCFs) of the ambient noise field between every pair of the stations. The result shows that TCDP well site suffers from complex wavefield, and phase traveltime from CCF can't provide explicit result to determine the dominated wavefield. We first analyze the power density spectra and probability density functions of this array. We observe that the spectra show diurnal variation in the frequency band 1-25 Hz, suggesting human-generated sources are dominated in this frequency band. Then, we focus on the particle motion analysis at each CCF. We assume one component at a station plays as a visual source and compute the CCF tensor in other station components. The particle motion traces show high linearity which indicate that the dominated wavefield in our study area is body wave signals with the azimuth approximate to 60° from north. We also analyze the Fourier spectral amplitudes by rotating every 5 degrees in time domain to search for the maximum background energy distribution. The result shows that the spectral amplitudes are stronger at NE-SW direction, with shallow incident angles which are comparable with the CCF particle motion measurement. In order to obtain higher resolution about the dominated wavefield in our study area, we also used beamforming from surface station array to validate our results from CCF analysis. In addition to the CCF analysis to provide the noise configuration at the TCDPBHS site for further analysis on fault zone anisotropy using ambient noise, we also analyze fault zone anisotropy using the events data recorded by TCDPBHS. The identified event clusters through the borehole data enhance the consistency in results to give hints on fault zone anisotropy.

PBO Nucleus Project Status: Integration of 209 Existing GPS Stations into the Plate Boundary Observatory

NASA Astrophysics Data System (ADS)

Blume, F.; Meertens, C.; Anderson, G.; Eriksson, S.; Boyce, E.

2007-12-01

Tectonic and earthquake research in the US has experienced a quiet revolution over the last decade precipitated by the recognition that slow-motion faulting events can both trigger and be triggered by regular earthquakes. Transient motion has now been found in essentially all tectonic environments, and the detection and analysis of such events is the first-order science target of the EarthScope Project. Because of this and a host of other fundamental tectonics questions that can be answered only with long-duration geodetic time series, the incipient 1100-station EarthScope Plate Boundary Observatory (PBO) network has been designed to leverage 445 existing continuous GPS stations whose measurements extend back over a decade. The irreplaceable recording history of these stations will accelerate EarthScope scientific return by providing the highest possible resolution. This resolution will be used to detect and understand transients, to determine the three-dimensional velocity field (particularly vertical motion), and to improve measurement precision by understanding the complex noise sources inherent in GPS. The PBO Nucleus project supports the operation, maintenance and hardware upgrades of a subset of the six western U.S. geodetic networks until they are subsumed by PBO. Uninterrupted data flow from these stations will effectively double the time-series length of PBO over the expected life of EarthScope, and has created, for the first time, a single GPS-based geodetic network in the US. The other existing sites remain in operation under support from non-NSF sources (e.g. the USGS), and EarthScope continues to benefit from their continued operation On the grounds of relevance to EarthScope science goals, geographic distribution and data quality, 209 of the 432 existing stations were selected as the nucleus upon which to build PBO. Conversion of these stations to a PBO-compatible mode of operation was begun under previous funding, and as a result data now flow directly to PBO archives and processing centers while maintenance, operations, and meta-data requirements are continue to be upgraded to PBO standards. At the end of this project all 209 stations will be fully incorporated into PBO, meeting all standards for new PBO construction including data communications and land use permits. Funds for operation of these stations have been included in planned budgets for PBO after the construction phase ends and PBO begins an operational phase in 2008. At this time work on the project is apporixmately 80% complete, with over 90% of the stations having been upgraded. The data from these stations serve a much larger audience than just the few people who work to keep them operating. This project is now collecting the data that will be used by the next generation of solid-earth researchers for at least two decades. Educational modules are being developed by a team of researchers, educators, and curriculum development professionals, and are being disseminated through regional and national workshops. An interactive website provides the newest developments in tectonics research to K-16 classrooms.

Experimental approach for estimating seismic amplification effects at the top of a ridge and their implication on ground motion predictions: the case of Narni (Central Italy).

NASA Astrophysics Data System (ADS)

Lovati, Sara; Bakavoli, Mohammad; Massa, Marco; Ferretti, Gabriele; Pacor, Francesca; Paolucci, Roberto

2010-05-01

From March to September 2009 a dense velocimetric network was installed in correspondence of Narni, a little village in central Italy, built on the top of a massive limestone ridge. The network was planned with the aim to investigate possible local site effects due to the morphology of the ridge, characterized by slopes ranging from 22° to 35° and a maximum difference of quota between top and bottom of 230 m. Three stations were installed at the base of the hill and other 7 monitored the crest. A remarkable dataset was obtained, composed by about 700 earthquakes, the great amount of which occurred after the 06th April 2009, Mw 6.3, L'Aquila earthquake. Site amplifications related to the ridge morphological features were investigated through empirical techniques with and without reference site, computing Spectral Standard Ratio, SSR and Horizontal to Vertical spectral ratio, HVSR. Directional spectral analyses were also performed . The agreement between the results coming from HVSR and SSR techniques allows us to assess with reliability a clear amplification effect for frequencies ranging between 3 and 5 Hz for all stations installed on the crest: in particular, SSR results show an amplification level with respect to the reference station up to 4.5. The highest amplification level (almost double) were observed when the direction perpendicular to the main elongation of the ridge is taken into account. Finally, considering the L'Aquila events with Mw > 4.5 and merging the information coming from the reference and non-reference site techniques, it was possible to recognize further amplification effects, at frequency lower than 1 Hz, probably related not to the morphology of the area but to source and/or polarization effects. Bidimensional numerical simulations were then computed in order to compare the results coming from the experiment with those obtained through numerical modeling. A hybrid finite-boundary element method based on code named HYBRID has been used for modeling. The model has been excited by SV and P Ricker wavelet in order to extract transform functions. The medium assumed to have a linear elastic constitutive behavior. All calculations were performed in time domain using direct boundary element method. The amplification patterns both in time and frequency domain were derived and similarities and discrepancies between the results were discussed. At last, considering only local events (epicentral distance R <= 30 km), empirical ground motion predictive equations, calibrated for maximum horizontal peak ground acceleration, PGA, velocity, PGV, and acceleration response spectra (SA, 5% damping) up to 1s, were carried out with the only aim to estimate topographical corrective coefficients. The results show significant corrective term values (between 0.35 and 0.48 in logarithmic scale) for the spectral ordinates between 0.2 s and 0.3 s. These results, in agreement to those obtained from the spectral analyses, suggest that the introduction of a topographic site class in the calculation of predictive models might probably reduce the inter-station variability for stations installed in correspondence of topographic irregularities, often included in reference-rock classes.

Three-Dimensional Displays In The Future Flight Station

NASA Astrophysics Data System (ADS)

Bridges, Alan L.

1984-10-01

This review paper summarizes the development and applications of computer techniques for the representation of three-dimensional data in the future flight station. It covers the development of the Lockheed-NASA Advanced Concepts Flight Station (ACFS) research simulators. These simulators contain: A Pilot's Desk Flight Station (PDFS) with five 13- inch diagonal, color, cathode ray tubes on the main instrument panel; a computer-generated day and night visual system; a six-degree-of-freedom motion base; and a computer complex. This paper reviews current research, development, and evaluation of easily modifiable display systems and software requirements for three-dimensional displays that may be developed for the PDFS. This includes the analysis and development of a 3-D representation of the entire flight profile. This 3-D flight path, or "Highway-in-the-Sky", will utilize motion and perspective cues to tightly couple the human responses of the pilot to the aircraft control systems. The use of custom logic, e.g., graphics engines, may provide the processing power and architecture required for 3-D computer-generated imagery (CGI) or visual scene simulation (VSS). Diffraction or holographic head-up displays (HUDs) will also be integrated into the ACFS simulator to permit research on the requirements and use of these "out-the-window" projection systems. Future research may include the retrieval of high-resolution, perspective view terrain maps which could then be overlaid with current weather information or other selectable cultural features.

Rapid Modeling of and Response to Large Earthquakes Using Real-Time GPS Networks (Invited)

NASA Astrophysics Data System (ADS)

Crowell, B. W.; Bock, Y.; Squibb, M. B.

2010-12-01

Real-time GPS networks have the advantage of capturing motions throughout the entire earthquake cycle (interseismic, seismic, coseismic, postseismic), and because of this, are ideal for real-time monitoring of fault slip in the region. Real-time GPS networks provide the perfect supplement to seismic networks, which operate with lower noise and higher sampling rates than GPS networks, but only measure accelerations or velocities, putting them at a supreme disadvantage for ascertaining the full extent of slip during a large earthquake in real-time. Here we report on two examples of rapid modeling of recent large earthquakes near large regional real-time GPS networks. The first utilizes Japan’s GEONET consisting of about 1200 stations during the 2003 Mw 8.3 Tokachi-Oki earthquake about 100 km offshore Hokkaido Island and the second investigates the 2010 Mw 7.2 El Mayor-Cucapah earthquake recorded by more than 100 stations in the California Real Time Network. The principal components of strain were computed throughout the networks and utilized as a trigger to initiate earthquake modeling. Total displacement waveforms were then computed in a simulated real-time fashion using a real-time network adjustment algorithm that fixes a station far away from the rupture to obtain a stable reference frame. Initial peak ground displacement measurements can then be used to obtain an initial size through scaling relationships. Finally, a full coseismic model of the event can be run minutes after the event, given predefined fault geometries, allowing emergency first responders and researchers to pinpoint the regions of highest damage. Furthermore, we are also investigating using total displacement waveforms for real-time moment tensor inversions to look at spatiotemporal variations in slip.

GPS Imaging of Global Vertical Land Motion for Sea Level Studies

NASA Astrophysics Data System (ADS)

Hammond, W. C.; Blewitt, G.; Hamlington, B. D.

2015-12-01

Coastal vertical land motion contributes to the signal of local relative sea level change. Moreover, understanding global sea level change requires understanding local sea level rise at many locations around Earth. It is therefore essential to understand the regional secular vertical land motion attributable to mantle flow, tectonic deformation, glacial isostatic adjustment, postseismic viscoelastic relaxation, groundwater basin subsidence, elastic rebound from groundwater unloading or other processes that can change the geocentric height of tide gauges anchored to the land. These changes can affect inferences of global sea level rise and should be taken into account for global projections. We present new results of GPS imaging of vertical land motion across most of Earth's continents including its ice-free coastlines around North and South America, Europe, Australia, Japan, parts of Africa and Indonesia. These images are based on data from many independent open access globally distributed continuously recording GPS networks including over 13,500 stations. The data are processed in our system to obtain solutions aligned to the International Terrestrial Reference Frame (ITRF08). To generate images of vertical rate we apply the Median Interannual Difference Adjusted for Skewness (MIDAS) algorithm to the vertical times series to obtain robust non-parametric estimates with realistic uncertainties. We estimate the vertical land motion at the location of 1420 tide gauges locations using Delaunay-based geographic interpolation with an empirically derived distance weighting function and median spatial filtering. The resulting image is insensitive to outliers and steps in the GPS time series, omits short wavelength features attributable to unstable stations or unrepresentative rates, and emphasizes long-wavelength mantle-driven vertical rates.

The Los Alamos Seismic Network (LASN): Improved Network Instrumentation, Local Earthquake Catalog Updates, and Peculiar Types of Data

NASA Astrophysics Data System (ADS)

Roberts, P. M.; Ten Cate, J. A.; House, L. S.; Greene, M. K.; Morton, E.; Kelley, R. E.

2013-12-01

The Los Alamos Seismic Network (LASN) has operated for 41 years, and provided the data to locate more than 2,500 earthquakes in north-central New Mexico. The network was installed for seismic verification research, as well as to monitor and locate earthquakes near Los Alamos National Laboratory (LANL). LASN stations are the only monitoring stations in New Mexico north of Albuquerque. The original network once included 22 stations in northern Mew Mexico. With limited funding in the early 1980's, the network was downsized to 7 stations within an area of about 15 km (N-S) by 15 km (E-W), centered on Los Alamos. Over the last four years, eight additional stations have been installed, which have considerably expanded the spatial coverage of the network. Currently, 7 stations have broadband, three-component seismometers with digital telemetry, and the remaining 8 have traditional 1 Hz short-period seismometers with either analog telemetry or on-site digital recording. A vertical array of accelerometers was also installed in a wellbore on LANL property. This borehole array has 3-component digital strong-motion sensors. Recently we began upgrading the local strong-motion accelerometer (SMA) network as well, with the addition of high-resolution digitizers and high-sensitivity force-balance accelerometers (FBA). We will present an updated description of the current LASN station, instrumentation and telemetry configurations, as well as the data acquisition and event-detection software structure used to record events in Earthworm. Although more than 2,000 earthquakes were detected and located in north-central New Mexico during the first 11 years of LASN's operation (1973 to 1984), currently only 1-2 earthquakes per month are detected and located within about 150 km of Los Alamos. Over 850 of these nearby earthquakes have been located from 1973 to present. We recently updated the LASN earthquake catalog for north-central New Mexico up through 2012 and most of 2013. Locations for these earthquakes are based on new, consistently picked arrival times, updated station locations, and the best available velocity model. Most have magnitudes less than 1.5 and are not contained in the catalogs of any other network. With 3 of the new broadband stations in and around the nearby Valles Caldera, LASN is now able to monitor even very small volcano-seismic events that may be associated with the caldera. The expanded station coverage and instrument sensitivity has also allowed detection of smaller, more distant events and new types of peculiar, non-earthquake signals we had not previously seen (e.g., train noise). These unusual signals have complicated our event discrimination efforts. We will show an updated map of north-central New Mexico seismicity based on these recent efforts, as well as examples of some the new types of data LASN is now picking up. Although the network and data are generally not accessible to the public, requests for data can be granted on a case-by-case basis.

Rupture History of the 2001 Nisqually Washington Earthquake

NASA Astrophysics Data System (ADS)

Xu, Q.; Creager, K. C.; Crosson, R. S.

2001-12-01

We analyze the temporal-spatial rupture history of the magnitude 6.8 February 28, 2001 Nisqually earthquake using about two dozen 3-component strong-motion records from the Pacific Northwest Seismic Network (PNSN) and the USGS National Strong Motion Program (NSMP) network. We employ a finite-fault inversion scheme similar to Hartzell and Heaton [Bull. Seism. Soc. Am., 1983] to recover the slip history. We assume rupture initiates at the epicenter and origin time determined using PNSN P arrival times and a high-resolution 3-D velocity model. Hypocentral depth is 54 km based on our analysis of teleseismic pP-P times and the regional 3-D model. Using the IASP91 standard Earth model to explain the pP-P times gives a depth of 58 km. Three-component strong motion accelerograms are integrated to obtain velocity, low-pass filtered at 4 s period and windowed to include the direct P- and S- wave arrivals. Theoretical Green's functions are calculated using the Direct Solution Method (DSM) [Cummins, etal, Geophys. Res. Lett., 1994] for each of 169, 4km x 4km, subfaults which lie on one of the two fault plates specified by the Harvard CMT solution. A unique 1-D model that gives an adequate representation of velocity structure for each station is obtained by path averaging the 3-D tomographic model. The S velocity model is generated from the P velocity model. For Vp larger than 4.5 km/s, We use the linear relationship Vs=0.18+0.52Vp obtained from laboratory measurements of local mafic rock samples. For slower velocities, probably associated with sedimentary rocks, we derived Vs=Vp/2.04 which best fits the strong-motion S-arrival times. The resulting source model indicates unilateral rupture along a fault that is elongated in the north-south direction. Inversion for the near vertical (strike 1° , dip 72° ) and horizontal (strike 183° , dip 18° ) fault planes reveal the same source directivity, however, the horizontal fault plane gives a slightly better fit to the data than the vertical one. We will also incorporate teleseismic P pP and sP waves into the waveform modeling to provide additional constraints on vertical source directivity.

Earth Observations taken by Expedition 30 crewmember

NASA Image and Video Library

2012-04-22

ISS030-E-260480 (22 April 2012) --- One of the Expedition 30 crew members aboard the International Space Station photographed this nighttime image featuring a Lyrid meteor, just to the left of center. The space station was over the Gulf of Mexico, and many coastal cities in several states can be seen. Florida is above the center of the image with Cuba to the right. Atlanta is on the left side. A line of thunderstorms had just passed Cuba when the photo was taken. The bright bluish blobs are clouds illuminated by lightning. The reddish streaks are city lights blurred by the motion of the station during the five-second exposure.

A "Kanes's Dynamics" Model for the Active Rack Isolation System

NASA Technical Reports Server (NTRS)

Hampton, R. David; Beech, Geoffrey

1999-01-01

Many microgravity space-science experiments require vibratory acceleration levels unachievable without active isolation. The Boeing Corporation's Active Rack Isolation System (ARIS) employs a novel combination of magnetic actuation and mechanical linkages, to address these isolation requirements on the International Space Station (ISS). ARIS provides isolation at the rack (international Standard Payload Rack, or ISPR) level. Effective model-based vibration isolation requires (1) an appropriate isolation device, (2) an adequate dynamic (i.e., mathematical) model of that isolator, and (3) a suitable, corresponding controller. ARIS provides the ISS response to the first requirement. This paper presents one response to the second, in a state-space framework intended to facilitate an optimal-controls approach to the third. The authors use "Kane's Dynamics" to develop an state-space, analytical (algebraic) set of linearized equations of motion for ARIS.

A "Kane's Dynamics" Model for the Active Rack Isolation System

NASA Technical Reports Server (NTRS)

Hampton, R. D.; Beech, G. S.; Rao, N. N. S.; Rupert, J. K.; Kim, Y. K.

2001-01-01

Many microgravity space science experiments require vibratory acceleration levels unachievable without active isolation. The Boeing Corporation's Active Rack Isolation System (ARIS) employs a novel combination of magnetic actuation and mechanical linkages to address these isolation requirements on the International Space Station (ISS). ARIS provides isolation at the rack (International Standard Payload Rack (ISPR)) level. Effective model-based vibration isolation requires: (1) an appropriate isolation device, (2) an adequate dynamic (i.e., mathematical) model of that isolator, and (3) a suitable, corresponding controller. ARIS provides the ISS response to the first requirement. This paper presents one response to the second, in a state space framework intended to facilitate an optimal-controls approach to the third. The authors use "Kane's Dynamics" to develop a state-space, analytical (algebraic) set of linearized equations of motion for ARIS.

What can we learn from the Wells, NV earthquake sequence about seismic hazard in the intermountain west?

USGS Publications Warehouse

Petersen, M.D.; Pankow, K.L.; Biasi, G.P.; Meremonte, M.

2008-01-01

The February 21, 2008 Wells, NV earthquake (M 6) was felt throughout eastern Nevada, southern Idaho, and western Utah. The town of Wells sustained significant damage to unreinforced masonry buildings. The earthquake occurred in a region of low seismic hazard with little seismicity, low geodetic strain rates, and few mapped faults. The peak horizontal ground acceleration predicted by the USGS National Seismic Hazard Maps is about 0.2 g at 2% probability of exceedance in 50 years, with the contributions coming mostly from the Ruby Mountain fault and background seismicity (M5-7.0). The hazard model predicts that the probability of occurrence of an M>6 event within 50 km of Wells is about 15% in 100 years. Although the earthquake was inside the USArray Transportable Array network, the nearest on-scale recordings of ground motions from the mainshock were too distant to estimate accelerations in town. The University of Nevada Reno, the University of Utah, and the U.S. Geological Survey deployed portable instruments to capture the ground motions from aftershocks of this rare normal-faulting event. Shaking from a M 4.7 aftershock recorded on portable instruments at distances less than 10 km exceeded 0.3 g, and sustained accelerations above 0.1 g lasted for about 5 seconds. For a magnitude 5 earthquake at 10 km distance the NGA equations predict median peak ground accelerations about 0.1 g. Ground motions from normal faulting earthquakes are poorly represented in the ground motion prediction equations. We compare portable and Transportable Array ground-motion recordings with prediction equations. Advanced National Seismic System stations in Utah recorded ground motions 250 km from the mainshock of about 2% g. The maximum ground motion recorded in Salt Lake City was in the center of the basin. We analyze the spatial variability of ground motions (rock vs. soil) and the influence of the Salt Lake Basin in modifying the ground motions. We then compare this data with the September 28, 2004 Parkfield aftershocks to contrast the differences between strike-slip and normal ground motions.

Expected Improvements in VLBI Measurements of the Earth's Orientation

NASA Technical Reports Server (NTRS)

Ma, Chopo

2003-01-01

Measurements of the Earth s orientation since the 1970s using space geodetic techniques have provided a continually expanding and improving data set for studies of the Earth s structure and the distribution of mass and angular momentum. The accuracy of current one-day measurements is better than 100 microarcsec for the motion of the pole with respect to the celestial and terrestrial reference frames and better than 3 microsec for the rotation around the pole. VLBI uniquely provides the three Earth orientation parameters (nutation and UTI) that relate the Earth to the extragalactic celestial reference frame. The accuracy and resolution of the VLBI Earth orientation time series can be expected to improve substantially in the near future because of refinements in the realization of the celestial reference frame, improved modeling of the troposphere and non-linear station motions, larger observing networks, optimized scheduling, deployment of disk-based Mark V recorders, full use of Mark IV capabilities, and e-VLBI. More radical future technical developments will be discussed.

A combined method to calculate co-seismic displacements through strong motion acceleration baseline correction

NASA Astrophysics Data System (ADS)

Zhan, W.; Sun, Y.

2015-12-01

High frequency strong motion data, especially near field acceleration data, have been recorded widely through different observation station systems among the world. Due to tilting and a lot other reasons, recordings from these seismometers usually have baseline drift problems when big earthquake happens. It is hard to obtain a reasonable and precision co-seismic displacement through simply double integration. Here presents a combined method using wavelet transform and several simple liner procedures. Owning to the lack of dense high rate GNSS data in most of region of the world, we did not contain GNSS data in this method first but consider it as an evaluating mark of our results. This semi-automatic method unpacks a raw signal into two portions, a summation of high ranks and a low ranks summation using a cubic B-spline wavelet decomposition procedure. Independent liner treatments are processed against these two summations, which are then composed together to recover useable and reasonable result. We use data of 2008 Wenchuan earthquake and choose stations with a near GPS recording to validate this method. Nearly all of them have compatible co-seismic displacements when compared with GPS stations or field survey. Since seismometer stations and GNSS stations from observation systems in China are sometimes quite far from each other, we also test this method with some other earthquakes (1999 Chi-Chi earthquake and 2011 Tohoku earthquake). And for 2011 Tohoku earthquake, we will introduce GPS recordings to this combined method since the existence of a dense GNSS systems in Japan.

Three Dimensional Viscoelastic Postseismic Deformation of the 2013 Mw8.3 Okhotsk Deep-Focus Earthquake

NASA Astrophysics Data System (ADS)

Hu, Y.; Burgmann, R.; Shestakov, N.; Titkov, N. N.; Serovetnikov, S.; Prytkov, A.; Vasilenko, N. F.; Wang, K.

2016-12-01

The upper mantle rheology at depths within a few hundred kilometers has been well studied through shallow great megathrust earthquakes. However, understanding of the mantle rheology at greater depths, such as in the vicinity of the transition zone, has been limited by the lack of direct or indirect measurements. The largest well-recorded deep earthquake with magnitude Mw 8.3 occurred within the subducting Pacific plate at 600 km depth beneath the Okhotsk Sea on May 24, 2013. Twenty-seven continuous GPS stations in this region recorded coseismic displacements of up to 15 mm in the horizontal direction and up to 20 mm in the vertical direction. Within three years after the earthquake seventeen continuous GPS stations underwent transient westward motion of up to 8 mm/yr and vertical motion of up to 10 mm/yr. The geodetically delineated postseismic crustal deformation thus provides a unique opportunity to study the three dimensional heterogeneity of the mantle rheology and properties of the subducting slab at great depths. We have developed three-dimensional viscoelastic finite element models of the 2013 Okhotsk earthquake to explore these questions. Our initial model includes an elastic lithosphere including the subducting slab, a viscoelastic continental upper mantle and a viscoelastic oceanic upper mantle. We assume that the upper mantle is characterized by a bi-viscous Burgers rheology. For simplicity, we assume that the transient Kelvin viscosity is one order of magnitude lower than that of the steady-state Maxwell viscosity. Our preliminary models indicate that the viscosity of the upper mantle beneath the transition zone has to be at least one order of magnitude lower than that of the upper mantle at shallower depths. A viscoelastic subducting slab at depths >400 km with viscosities of 2-3 orders of magnitude higher than that of the mantle wedge provides a better fit to the observed surface velocities.

Crustal Seismic Vs and Vs anisotropy of Northeast Japan Revealed by Ambient Noise Tomography

NASA Astrophysics Data System (ADS)

Chen, K. X.; Gung, Y.; Kuo, B. Y.; Huang, T. Y.

2017-12-01

We present 3D crustal models of Vs and Vs azimuthal anisotropy of the Tohoku region, Japan. We employ the Welch's method to derive the empirical Green's functions (EGF) of Rayleigh waves from one year of continuous records of 123 short-period stations of the dense high-sensitivity seismograph network (Hi-net). We compute EGFs for about 4000 station pairs with interstation distance less than 300 km. For each qualified EGF, we measure the dispersion in the period range from 3 to 16 seconds. We then construct the models by using a wavelet-based multi-scale inversion technique. In the resulting models, characteristics of Vs variations and Vs azimuthal anisotropy are closely related to surface geology, Quaternary volcano activities, and plate motions. For the Vs variations in the shallow crust (< 12km), the prominent high velocity anomalies are observed in the eastern part of the volcano belt, and they can be attributed to the old (Palaeozoic to Mesozoic) sedimentary and plutonic rocks located in the northeastern and the southeastern Tohoku, respectively. In the middle crust, the distribution of the low velocity anomalies is well correlated to the volcano belt. For the Vs anisotropy, the strength and the patterns of fast polarization directions (FPD) are depth-dependent. In the shallow crust, the anisotropy is strong, and are dominated by the typical orogeny parallel anisotropy, with FPDs parallel to the main strikes of the mountain range. While in the lower crust, the FPDs are generally parallel to the absolute plate motion. Interestingly, the distribution of PFDs is rather chaotic and strength of anisotropy is weak in the middle crust ( 8 - 20 km). We propose that the weak and random anisotropy in this layer is likely related to the presence of magma reservoirs beneath the volcano belt, as the associated active volcanism may cause the destruction of the alignment of crustal fabrics Key words: Tohoku, ambient noise, seismic anisotropy, surface wave tomography, volcano activities

Effects of overweight vehicles on NYSDOT infrastructure.

DOT National Transportation Integrated Search

2015-09-01

This report develops a methodology for estimating the effects of different categories of overweight : trucks on NYSDOT pavements and bridges. A data mining algorithm is used to categorize truck : data collected at several Weigh-In-Motion stations aro...

Is Active Tectonics on Madagascar Consistent with Somalian Plate Kinematics?

NASA Astrophysics Data System (ADS)

Stamps, D. S.; Kreemer, C.; Rajaonarison, T. A.

2017-12-01

The East African Rift System (EARS) actively breaks apart the Nubian and Somalian tectonic plates. Madagascar finds itself at the easternmost boundary of the EARS, between the Rovuma block, Lwandle plate, and the Somalian plate. Earthquake focal mechanisms and N-S oriented fault structures on the continental island suggest that Madagascar is experiencing east-west oriented extension. However, some previous plate kinematic studies indicate minor compressional strains across Madagascar. This inconsistency may be due to uncertainties in Somalian plate rotation. Past estimates of the rotation of the Somalian plate suffered from a poor coverage of GPS stations, but some important new stations are now available for a re-evaluation. In this work, we revise the kinematics of the Somalian plate. We first calculate a new GPS velocity solution and perform block kinematic modeling to evaluate the Somalian plate rotation. We then estimate new Somalia-Rovuma and Somalia-Lwandle relative motions across Madagascar and evaluate whether they are consistent with GPS measurements made on the island itself, as well as with other kinematic indicators.

Graphical explanation in an expert system for Space Station Freedom rack integration

NASA Technical Reports Server (NTRS)

Craig, F. G.; Cutts, D. E.; Fennel, T. R.; Purves, B.

1990-01-01

The rationale and methodology used to incorporate graphics into explanations provided by an expert system for Space Station Freedom rack integration is examined. The rack integration task is typical of a class of constraint satisfaction problems for large programs where expertise from several areas is required. Graphically oriented approaches are used to explain the conclusions made by the system, the knowledge base content, and even at more abstract levels the control strategies employed by the system. The implemented architecture combines hypermedia and inference engine capabilities. The advantages of this architecture include: closer integration of user interface, explanation system, and knowledge base; the ability to embed links to deeper knowledge underlying the compiled knowledge used in the knowledge base; and allowing for more direct control of explanation depth and duration by the user. The graphical techniques employed range from simple statis presentation of schematics to dynamic creation of a series of pictures presented motion picture style. User models control the type, amount, and order of information presented.

Operational EEW Networks in Turkey

NASA Astrophysics Data System (ADS)

Zulfikar, Can; Pinar, Ali

2016-04-01

There are several EEW networks and algorithms under operation in Turkey. The first EEW system was deployed in Istanbul in 2002 after the 1999 Mw7.4 Kocaeli and Mw7.1 Duzce earthquake events. The system consisted of 10 strong motion stations located as close as possible to the main Marmara Fault line. The system was upgraded by 5 OBS (Ocean Bottom Seismometer) in 2012 located in Marmara Sea. The system works in threshold based algorithm. The alert is given according to exceedance of certain threshold levels of amplitude of ground motion acceleration in certain time interval at least in 3 stations. Currently, there are two end-users of EEW system in Istanbul. The critical facilities of Istanbul Gas Distribution Company (IGDAS) and Marmaray Tube tunnel receives the EEW information in order to activate their automatic shut-off mechanisms. The IGDAS has their own strong motion network located at their district regulators. After receiving the EEW signal if the threshold values of ground motion parameters are exceeded the gas-flow is cut automatically at the district regulators. The IGDAS has 750 district regulators distributed in Istanbul. At the moment, the 110 of them are instrumented with strong motion accelerometers. As a 2nd stage of the on-going project, the IGDAS company proposes to install strong motion accelerometers to all remaining district regulators. The Marmaray railway tube tunnel is the world's deepest immersed tube tunnel with 60m undersea depth. The tunnel has 1.4km length with 13 segments. The tunnel is monitored with 2 strong motion accelerometers in each segment, 26 in total. Once the EEW signal is received, the monitoring system is activated and the recording ground motion parameters are calculated in real-time. Depending on the exceedance of threshold levels, further actions are taken such as reducing the train speed, stopping the train before entering the tunnel etc. In Istanbul, there are also on-site EEW system applied in several high-rise buildings. As similar to threshold based algorithm, once the threshold level is exceeded in several strong motion accelerometers installed in the high-rise building, the automated shut-off mechanism is activated in order to prevent secondary damage effects of the earthquakes. In addition to the threshold based EEW system, the regional EEW algorithms Virtual Seismologist (VS) as implemented in SeisComP3 VS(SC3) and PRESTo have been also implemented in Marmara region of Turkey. These applications use the regional seismic networks. The purpose of the regional EEW systems is to determine the magnitude and location of the event from the P-wave information of the closest 3-4 stations and forward this information to interested sites. The regional EEW systems are also important for Istanbul in order to detect far distance earthquake events and provide alert especially for the high-rise buildings for their long duration shaking.

Motion state analysis of space target based on optical cross section

NASA Astrophysics Data System (ADS)

Tian, Qichen; Li, Zhi; Xu, Can; Liu, Chenghao

2017-10-01

In order to solve the problem that the movement state analysis method of the space target based on OCS is not related to the real motion state. This paper proposes a method based on OCS for analyzing the state of space target motion. This paper first establish a three-dimensional model of real STSS satellite, then change the satellite's surface into element, and assign material to each panel according to the actual conditions of the satellite. This paper set up a motion scene according to the orbit parameters of STSS satellite in STK, and the motion states are set to three axis steady state and slowly rotating unstable state respectively. In these two states, the occlusion condition of the surface element is firstly determined, and the effective face element is selected. Then, the coordinates of the observation station and the solar coordinates in the satellite body coordinate system are input into the OCS calculation program, and the OCS variation curves of the three axis steady state and the slow rotating unstable state STSS satellite are obtained. Combining the satellite surface structure and the load situation, the OCS change curve of the three axis stabilized satellite is analyzed, and the conclude that the OCS curve fluctuates up and down when the sunlight is irradiated to the load area; By using Spectral analysis method, autocorrelation analysis and the cross residual method, the rotation speed of OCS satellite in slow rotating unstable state is analyzed, and the rotation speed of satellite is successfully reversed. By comparing the three methods, it is found that the cross residual method is more accurate.

Rotordynamic Instability Problems in High-Performance Turbomachinery - 1982, Proceedings of a Workshop (2nd) Held at College Station, Texas on 10-12 May 1982.

DTIC Science & Technology

1982-01-01

selected from a horse- power-.peed aspect. This method is adequate in most cases because the spacer be- haves as a rigid body with minimal influence on...The theoretical model of this rotor does not include the measured rigid - body eigenmode at 2400 rev/min (figs. 16 and 18). The resonance frequency at...Eigenvectors The equations of motion for the rigid rotor with elastic supports are i 2kl k q L 1 ~1+ L2 ] [2 0 (24)0 Lq 2 -k 2k 22 Lq2 or with the definitions

Production and Uses of Multi-Decade Geodetic Earth Science Data Records

NASA Astrophysics Data System (ADS)

Bock, Y.; Kedar, S.; Moore, A. W.; Fang, P.; Liu, Z.; Sullivan, A.; Argus, D. F.; Jiang, S.; Marshall, S. T.

2017-12-01

The Solid Earth Science ESDR System (SESES) project funded under the NASA MEaSUREs program produces and disseminates mature, long-term, calibrated and validated, GNSS based Earth Science Data Records (ESDRs) that encompass multiple diverse areas of interest in Earth Science, such as tectonic motion, transient slip and earthquake dynamics, as well as meteorology, climate, and hydrology. The ESDRs now span twenty-five years for the earliest stations and today are available for thousands of global and regional stations. Using a unified metadata database and a combination of GNSS solutions generated by two independent analysis centers, the project currently produces four long-term ESDR's: Geodetic Displacement Time Series: Daily, combined, cleaned and filtered, GIPSY and GAMIT long-term time series of continuous GPS station positions (global and regional) in the latest version of ITRF, automatically updated weekly. Geodetic Velocities: Weekly updated velocity field + velocity field histories in various reference frames; compendium of all model parameters including earthquake catalog, coseismic offsets, and postseismic model parameters (exponential or logarithmic). Troposphere Delay Time Series: Long-term time series of troposphere delay (30-min resolution) at geodetic stations, necessarily estimated during position time series production and automatically updated weekly. Seismogeodetic records for historic earthquakes: High-rate broadband displacement and seismic velocity time series combining 1 Hz GPS displacements and 100 Hz accelerometer data for select large earthquakes and collocated cGPS and seismic instruments from regional networks. We present several recent notable examples of the ESDR's usage: A transient slip study that uses the combined position time series to unravel "tremor-less" slow tectonic transient events. Fault geometry determination from geodetic slip rates. Changes in water resources across California's physiographic provinces at a spatial resolution of 75 km. Retrospective study of a southern California summer monsoon event.

The potential of small unmanned aircraft systems and structure-from-motion for topographic surveys: A test of emerging integrated approaches at Cwm Idwal, North Wales

NASA Astrophysics Data System (ADS)

Tonkin, T. N.; Midgley, N. G.; Graham, D. J.; Labadz, J. C.

2014-12-01

Novel topographic survey methods that integrate both structure-from-motion (SfM) photogrammetry and small unmanned aircraft systems (sUAS) are a rapidly evolving investigative technique. Due to the diverse range of survey configurations available and the infancy of these new methods, further research is required. Here, the accuracy, precision and potential applications of this approach are investigated. A total of 543 images of the Cwm Idwal moraine-mound complex were captured from a light (< 5 kg) semi-autonomous multi-rotor unmanned aircraft system using a consumer-grade 18 MP compact digital camera. The images were used to produce a DSM (digital surface model) of the moraines. The DSM is in good agreement with 7761 total station survey points providing a total vertical RMSE value of 0.517 m and vertical RMSE values as low as 0.200 m for less densely vegetated areas of the DSM. High-precision topographic data can be acquired rapidly using this technique with the resulting DSMs and orthorectified aerial imagery at sub-decimetre resolutions. Positional errors on the total station dataset, vegetation and steep terrain are identified as the causes of vertical disagreement. Whilst this aerial survey approach is advocated for use in a range of geomorphological settings, care must be taken to ensure that adequate ground control is applied to give a high degree of accuracy.

Demonstration of a High-Fidelity Predictive/Preview Display Technique for Telerobotic Servicing in Space

NASA Technical Reports Server (NTRS)

Kim, Won S.; Bejczy, Antal K.

1993-01-01

A highly effective predictive/preview display technique for telerobotic servicing in space under several seconds communication time delay has been demonstrated on a large laboratory scale in May 1993, involving the Jet Propulsion Laboratory as the simulated ground control station and, 2500 miles away, the Goddard Space Flight Center as the simulated satellite servicing set-up. The technique is based on a high-fidelity calibration procedure that enables a high-fidelity overlay of 3-D graphics robot arm and object models over given 2-D TV camera images of robot arm and objects. To generate robot arm motions, the operator can confidently interact in real time with the graphics models of the robot arm and objects overlaid on an actual camera view of the remote work site. The technique also enables the operator to generate high-fidelity synthetic TV camera views showing motion events that are hidden in a given TV camera view or for which no TV camera views are available. The positioning accuracy achieved by this technique for a zoomed-in camera setting was about +/-5 mm, well within the allowable +/-12 mm error margin at the insertion of a 45 cm long tool in the servicing task.

The JPL/KSC telerobotic inspection demonstration

NASA Technical Reports Server (NTRS)

Mittman, David; Bon, Bruce; Collins, Carol; Fleischer, Gerry; Litwin, Todd; Morrison, Jack; Omeara, Jacquie; Peters, Stephen; Brogdon, John; Humeniuk, Bob

1990-01-01

An ASEA IRB90 robotic manipulator with attached inspection cameras was moved through a Space Shuttle Payload Assist Module (PAM) Cradle under computer control. The Operator and Operator Control Station, including graphics simulation, gross-motion spatial planning, and machine vision processing, were located at JPL. The Safety and Support personnel, PAM Cradle, IRB90, and image acquisition system, were stationed at the Kennedy Space Center (KSC). Images captured at KSC were used both for processing by a machine vision system at JPL, and for inspection by the JPL Operator. The system found collision-free paths through the PAM Cradle, demonstrated accurate knowledge of the location of both objects of interest and obstacles, and operated with a communication delay of two seconds. Safe operation of the IRB90 near Shuttle flight hardware was obtained both through the use of a gross-motion spatial planner developed at JPL using artificial intelligence techniques, and infrared beams and pressure sensitive strips mounted to the critical surfaces of the flight hardward at KSC. The Demonstration showed that telerobotics is effective for real tasks, safe for personnel and hardware, and highly productive and reliable for Shuttle payload operations and Space Station external operations.

PBO Nucleus Project Summary: The Successful Integration of 209 Existing GPS Sions in the Plate Boundary Observatory

NASA Astrophysics Data System (ADS)

Blume, F.; Miller, M.; Boyce, E.; Borsa, A.; Eriksson, S.

2008-12-01

Tectonic and earthquake research in the US has experienced a quiet revolution over the last decade precipitated by the recognition that slow-motion faulting events can both trigger and be triggered by regular earthquakes. Transient motion has now been found in essentially all tectonic environments, and the detection and analysis of such events is the first-order science target of the EarthScope Project. Because of this and a host of other fundamental tectonics questions that can be answered only with long-duration geodetic time series, the 1100-station EarthScope Plate Boundary Observatory (PBO) network was designed to leverage 445 existing continuous GPS stations whose measurements extend back over a decade. The irreplaceable recording history of these stations will accelerate EarthScope scientific return by providing the highest possible resolution. This resolution will be used to detect and understand transients, to determine the three-dimensional velocity field (particularly vertical motion), and to improve measurement precision by understanding the complex noise sources inherent in GPS. The PBO Nucleus project supports the operation, maintenance and hardware upgrades of a subset of the six western U.S. geodetic networks until they are subsumed by PBO. Uninterrupted data flow from these stations will effectively double the time-series length of PBO over the expected life of EarthScope, and has created, for the first time, a single GPS-based geodetic network in the US. The other existing sites remain in operation under support from non-NSF sources (e.g. the USGS), and EarthScope continues to benefit from their continued operation On the grounds of relevance to EarthScope science goals, geographic distribution and data quality, 209 of the 432 existing stations were selected as the nucleus upon which to build PBO. Conversion of these stations to a PBO-compatible mode of operation was begun under previous funding, and as a result data now flow directly to PBO archives and processing centers while maintenance, operations, and meta-data requirements are continue to be upgraded to PBO standards. At the end of this project all 209 stations have been fully incorporated into PBO, meeting all standards for new PBO construction including data communications and land use permits. Funds for operation of these stations have been included in approved budgets for PBO's Operations and Maintenance phase. The data from these stations serve a much larger audience than just the few people who work to keep them operating. This project is now collecting the data that will be used by the next generation of solid-earth researchers for at least two decades. Educational modules are being developed by a team of researchers, educators, and curriculum development professionals, and are being disseminated through regional and national workshops. An interactive website provides the newest developments in tectonics research to K-16 classrooms. class="ab'>

Field Testing, Installation, and Calibration of a new Data Acquisition System for the USGS-Stanford-Berkley Ultra-Low Frequency Electromagnetic (ULFEM) Array

NASA Astrophysics Data System (ADS)

Creasy, N.; Gardner, J.; Spritzer, J. M.; Keneally, I.; Glen, J. M.; McPhee, D.; Klemperer, S. L.

2013-12-01

Since 2006, Stanford University, USGS, and UC Berkeley collaboratively maintain five permanent stations, to measure electric and magnetic data from 0.01 to 40Hz. Each station consists of three orthogonal coil magnetometers and two orthogonal 100m electrodes. The acquisition of ULFEM data helps study possible correlations between electromagnetic fields and seismic events related to the San Andreas Fault system. The current data acquisition system uses a Quanterra Q330 analog-to-digital converter. In 2010, we began development of a new 24-bit digitizing system known as the ULFEM 2010 digitizer in order to replace the Q330. The design of the new recorder was to be more economical and better tailored to the ULFEM network by providing power, calibration, and improved protection from lightning. However, the prototype had many problems, including a daily phase shift, amplifying error, and a time delay of 15 seconds (Bowden, et al., AGU, 2010). Currently, comparative testing of an improved prototype, ULFEM 2013, and the Q330 is taking place at the Jasper Ridge ULFEM station. The ULFEM 2013 contains eight channels that record input from three coil magnetometers, four electrodes, and temperature. Testing is ongoing and involves comparing the coil magnetometer and electrode signals processed by the Q330 and ULFEM 2013 digitizer. Data from the two systems will be compared in the time and frequency domains, and analyses will include calculating error and cross correlations. The ULFEM 2013 digitizer provides power to the magnetometer sensors as well as a calibration coil system (CCS). Every 24 hours, the CCS sends a calibration signal to calibration induction coils fitted to each of the three orthogonal magnetometers with the aim of testing the sensors' sensitivity and accuracy. The CCS produces a frequency sweep of 0.08, 0.51, 5, and 10Hz, creating a field nearly ten times greater than the Earth's field. The CCS consists of open source hardware and an amplifying frequency generator. Another ongoing effort to calibrate the ULFEM stations uses ground motion produced by distant earthquakes. Because of our stations' relatively close proximity (approximately 70km apart), teleseismic earthquakes at epicentral distances produce near-identical long-period seismic arrivals at each ULFEM station. The ground motion generated by the surface waves of distant earthquakes causes displacement of the induction coils, inducing magnetic anomalies in the recorded data. Because the ground motion has nearly the same characteristics at each station, the magnetic anomalies observed should have similar amplitudes regardless of the station (though modulated by the local conductivity structure at each site). To identify these coseismic signals, magnetic data were compared against seismic data from each station. Magnetic signals are clearly visible due to passage of Love and Rayleigh waves from teleseismic earthquakes of magnitude >7.4 and their relative amplitudes provide additional confirmation of the stability of our coils and recording system prior to the installation of the CCS.

Neurovestibular Effects of Long-Duration Spaceflight: A Summary of Mir-Phase 1 Experiences

NASA Technical Reports Server (NTRS)

Richards, Jason T.; Clark, Jonathan B.; Oman, Charles M.; Marshburn, Thomas H.

2002-01-01

Space motion sickness and associated neurovestibular dysfunction though not completely understood - have been relatively well clinically and operationally characterized on short-duration (1-2 week) Space Shuttle missions (Oman, et al, 1984, 1986; Thornton, et al, 1987; Reschke, et al, 1994). Between March 1995 and June 1998, seven NASA astronauts flew on the Russian Mir space station, as "Phase 1" of the joint effort to build the International Space Station, and provided NASA with invaluable experience on the operational and biomedical problems associated with flights of up to six months in duration. The goal of this paper is to provide a summary of the available information on neurovestibular dysfunction, space motion sickness, and readaptation to Earth's gravity on the NASA Mir flights, based on a set of medical questionnaire data, transcripts, and interviews which are available from the NASA-Mir Phase I program. Records were incomplete and anecdotal. All references to specific crewmembers have been removed, to respect their individual privacy. Material was excerpted from multiple sources of information relating to neurologic function, sensory illusions and motion sickness of NASA-Mir Phase I Program crewmembers. Data were compiled by epoch (in-flight vs landing/postflight) and grouped by neurovestibular topic. The information was recorded either contemporaneously during or within days after landing, or retrospectively weeks to months later. Space motion sickness symptoms are more intense and longer in duration. Sense of spatial orientation takes at least a month to become "natural and instinctive" in space station structures, but mental survey knowledge is apparently not completely developed even after 3 months in some cases. Visual reorientation illusions (VRI) are more easily induced after long exposure to weightlessness. Head movements can cause illusory spinning sensations for up to 7 days postflight. Postural and balance control does not fully recover for at least a month postflight.

Development of a Single Station 6C-Approach for Array Analysis and Microzonation: Using Vertical Rotation Rate to Estimate Love-Wave Disperion Curves and Direction Finding

NASA Astrophysics Data System (ADS)

Wassermann, J. M.; Wietek, A.; Hadziioannou, C.; Igel, H.

2014-12-01

Microzonation, i.e. the estimation of (shear) wave velocity profiles of the upper few 100m in dense 2D surface grids is one of the key methods to understand the variation in seismic hazard caused by ground shaking events. In this presentation we introduce a novel method for estimating the Love-wave phase velocity dispersion by using ambient noise recordings. We use the vertical component of rotational motions inherently present in ambient noise and the well established relation to simultaneous recordings of transverse acceleration. In this relation the frequency dependent phase velocity of a plane SH (or Love)-type wave acts as a proportionality factor between the anti-correlated amplitudes of both measures. In a first step we used synthetic data sets with increasing complexity to evaluate the proposed technique and the developed algorithm to extract the direction and amplitude of the incoming ambient noise wavefield measured at a single site. Since reliable weak rotational motion sensors are not yet readily available, we apply array derived rotation measurements in order to test our method. We next use the technique to analyze different real data sets of ambient noise measurements as well as seismic recordings at active volcanoes and compare these results with findings of the Spatial AutoCorrelation technique which was applied to the same data set. We demonstrate that the newly developed technique shows comparable results to more classical, strictly array based methods. Furthermore, we show that as soon as portable weak motion rotational motion sensors are available, a single 6C-station approach will be feasible, not only for microzonation but also for general array applications, with performance comparable to more classical techniques. An important advantage, especially in urban environments, is that with this approach, the number of seismic stations needed is drastically reduced.

PBO Nucleus Project Status: Integration of 209 Existing GPS Stations into the Plate Boundary Observatory.

NASA Astrophysics Data System (ADS)

Blume, F.; Prescott, W.; Anderson, G.; Eriksson, S.; Feldl, N.

2006-12-01

Tectonic and earthquake research in the US has experienced a quiet revolution over the last decade precipitated by the recognition that slow-motion faulting events can both trigger and be triggered by regular earthquakes. Transient motion has now been found in essentially all tectonic environments, and the detection and analysis of such events is the first-order science target of the EarthScope Project. Because of this and a host of other fundamental tectonics questions that can be answered only with long-duration geodetic time series, the incipient 1400-station EarthScope Plate Boundary Observatory (PBO) network has been designed to leverage 432 existing continuous GPS stations whose measurements extend back over a decade. The irreplaceable recording history of these stations is accelerating EarthScope scientific return by providing the highest possible resolution. This resolution will be used to detect and understand transients, to determine the three-dimensional velocity field (particularly vertical motion), and to improve measurement precision by understanding the complex noise sources inherent in GPS. The PBO Nucleus project supports the operation, maintenance and hardware upgrades of a subset of the six western U.S. geodetic networks until they are subsumed by PBO. Uninterrupted data flow from these stations will effectively double the time-series length of PBO over the expected life of EarthScope, and has created, for the first time, a single GPS-based geodetic network in the US. The other existing sites remain in operation under support from non-NSF sources (e.g. the USGS), and EarthScope continues to benefit from their continued operation. On the grounds of relevance to EarthScope science goals, geographic distribution and data quality, 209 of the 432 existing stations were selected as the nucleus upon which to build PBO. Conversion of these stations to a PBO-compatible mode of operation was begun under previous funding, and as a result data now flow directly to PBO archives and processing centers while maintenance, operations, and meta-data requirements are continuing to be upgraded to PBO standards. At the end of this project all 209 stations will be fully incorporated into PBO, meeting all standards for new PBO construction including data communications and land use permits. Funds for operation of these stations have been included in planned budgets for PBO after the construction phase ends and PBO begins an operational phase in 2008. To date approximately 150 of the 209 stations have been completely upgraded, and data flow from all stations is incorporated into the PBO data analysis flow. The community has only begun to understand the pervasive effects of transient creep, and its societal consequences remained largely unexplored. For example, one open question is whether slow faulting pervasively moderates earthquake nucleation. The existence of slow earthquakes will impact seismic hazards estimation, since these transients are now known to `absorb' a significant component of total slip in some regions and trigger earthquakes in others. The data from these stations serve a much larger audience than just the few people who work to keep them operating. This project is now collecting the data that will be used by the next generation of solid-earth researchers for at least two decades. Educational modules are being developed by a team of researchers, educators, and curriculum development professionals, and are being disseminated through regional and national workshops. An interactive website provides the newest developments in tectonics research to K-16 classrooms.

Uncertainty in geocenter estimates in the context of ITRF2014

NASA Astrophysics Data System (ADS)

Riddell, Anna R.; King, Matt A.; Watson, Christopher S.; Sun, Yu; Riva, Riccardo E. M.; Rietbroek, Roelof

2017-05-01

Uncertainty in the geocenter position and its subsequent motion affects positioning estimates on the surface of the Earth and downstream products such as site velocities, particularly the vertical component. The current version of the International Terrestrial Reference Frame, ITRF2014, derives its origin as the long-term averaged center of mass as sensed by satellite laser ranging (SLR), and by definition, it adopts only linear motion of the origin with uncertainty determined using a white noise process. We compare weekly SLR translations relative to the ITRF2014 origin, with network translations estimated from station displacements from surface mass transport models. We find that the proportion of variance explained in SLR translations by the model-derived translations is on average less than 10%. Time-correlated noise and nonlinear rates, particularly evident in the Y and Z components of the SLR translations with respect to the ITRF2014 origin, are not fully replicated by the model-derived translations. This suggests that translation-related uncertainties are underestimated when a white noise model is adopted and that substantial systematic errors remain in the data defining the ITRF origin. When using a white noise model, we find uncertainties in the rate of SLR X, Y, and Z translations of ±0.03, ±0.03, and ±0.06, respectively, increasing to ±0.13, ±0.17, and ±0.33 (mm/yr, 1 sigma) when a power law and white noise model is adopted.

Polycapillary based μXRF station for 3D colour tomography

NASA Astrophysics Data System (ADS)

Hampai, D.; Cherepennikov, Yu. M.; Liedl, A.; Cappuccio, G.; Capitolo, E.; Iannarelli, M.; Azzutti, C.; Gladkikh, Yu. P.; Marcelli, A.; Dabagov, S. B.

2018-04-01

The "Rainbow X-Ray" (RXR) experimental station at XLab Frascati of the Frascati's National Laboratories (LNF) INFN is a dedicated station for X-ray fluorescence studies based on the use of polycapillary lenses in a confocal geometry. The flexible RXR layout allows investigating specimens of the dimensions ranging from several millimeters up to half meter and weighting up to several tens of kilograms. Compared to similar existing XRF stations, apart of the possibility for investigating large samples, the main advantage of this equipment is the detection system with two spectrometers optimized to work separately at high and at low X-ray energies. The confocal geometry combined with a 3-axes fine motion system makes possible 3D μXRF elemental tomographic acquisitions (colour tomography). At present this station in operation at high XRF energies is used for cultural heritage and geological applications. We present and discuss here the analytical performances of this experimental station pointing out the advantages in different application areas.

Rapid Ice-Sheet Changes and Mechanical Coupling to Solid-Earth/Sea-Level and Space Geodetic Observation

NASA Astrophysics Data System (ADS)

Adhikari, S.; Ivins, E. R.; Larour, E. Y.

2015-12-01

Perturbations in gravitational and rotational potentials caused by climate driven mass redistribution on the earth's surface, such as ice sheet melting and terrestrial water storage, affect the spatiotemporal variability in global and regional sea level. Here we present a numerically accurate, computationally efficient, high-resolution model for sea level. Unlike contemporary models that are based on spherical-harmonic formulation, the model can operate efficiently in a flexible embedded finite-element mesh system, thus capturing the physics operating at km-scale yet capable of simulating geophysical quantities that are inherently of global scale with minimal computational cost. One obvious application is to compute evolution of sea level fingerprints and associated geodetic and astronomical observables (e.g., geoid height, gravity anomaly, solid-earth deformation, polar motion, and geocentric motion) as a companion to a numerical 3-D thermo-mechanical ice sheet simulation, thus capturing global signatures of climate driven mass redistribution. We evaluate some important time-varying signatures of GRACE inferred ice sheet mass balance and continental hydrological budget; for example, we identify dominant sources of ongoing sea-level change at the selected tide gauge stations, and explain the relative contribution of different sources to the observed polar drift. We also report our progress on ice-sheet/solid-earth/sea-level model coupling efforts toward realistic simulation of Pine Island Glacier over the past several hundred years.

Locating Local Earthquakes Using Single 3-Component Broadband Seismological Data

NASA Astrophysics Data System (ADS)

Das, S. B.; Mitra, S.

2015-12-01

We devised a technique to locate local earthquakes using single 3-component broadband seismograph and analyze the factors governing the accuracy of our result. The need for devising such a technique arises in regions of sparse seismic network. In state-of-the-art location algorithms, a minimum of three station recordings are required for obtaining well resolved locations. However, the problem arises when an event is recorded by less than three stations. This may be because of the following reasons: (a) down time of stations in a sparse network; (b) geographically isolated regions with limited logistic support to setup large network; (c) regions of insufficient economy for financing multi-station network and (d) poor signal-to-noise ratio for smaller events at most stations, except the one in its closest vicinity. Our technique provides a workable solution to the above problematic scenarios. However, our methodology is strongly dependent on the velocity model of the region. Our method uses a three step processing: (a) ascertain the back-azimuth of the event from the P-wave particle motion recorded on the horizontal components; (b) estimate the hypocentral distance using the S-P time; and (c) ascertain the emergent angle from the vertical and radial components. Once this is obtained, one can ray-trace through the 1-D velocity model to estimate the hypocentral location. We test our method on synthetic data, which produces results with 99% precision. With observed data, the accuracy of our results are very encouraging. The precision of our results depend on the signal-to-noise ratio (SNR) and choice of the right band-pass filter to isolate the P-wave signal. We used our method on minor aftershocks (3 < mb < 4) of the 2011 Sikkim earthquake using data from the Sikkim Himalayan network. Location of these events highlight the transverse strike-slip structure within the Indian plate, which was observed from source mechanism study of the mainshock and larger aftershocks.

Geological-Seismological Evaluation of Earthquake Hazards at Franklin Falls Damsite, New Hampshire.

DTIC Science & Technology

1986-09-01

8217 the Corps records have been analyzed by Chang (1983) , Toksoz (1982) and Sauber (in press) (Table" 3, Fig. 6). The instrument at Seabrook was just...and others, 1983, Sauber , in press). A strike-slip motion was interpreted from the *. data, although two stations did not fit. The attitudes given by...the two possible solutions given by Sauber (in press) and using her dips are north 230 east, 680 southeast dip, left-lateral motion and north 700 west

Anthropomorphic Robot Hand And Teaching Glove

NASA Technical Reports Server (NTRS)

Engler, Charles D., Jr.

1991-01-01

Robotic forearm-and-hand assembly manipulates objects by performing wrist and hand motions with nearly human grasping ability and dexterity. Imitates hand motions of human operator who controls robot in real time by programming via exoskeletal "teaching glove". Telemanipulator systems based on this robotic-hand concept useful where humanlike dexterity required. Underwater, high-radiation, vacuum, hot, cold, toxic, or inhospitable environments potential application sites. Particularly suited to assisting astronauts on space station in safely executing unexpected tasks requiring greater dexterity than standard gripper.

Non-linear and plastic soil response from strong ground motion detected using the ambient seismic field

NASA Astrophysics Data System (ADS)

Viens, L.; Denolle, M.; Hirata, N.

2017-12-01

Strong ground motion can induce dynamic strains large enough for the shallow subsurface to respond non-linearly and cause permanent velocity changes during earthquakes. We investigate the behavior of the near-surface in the Tokyo metropolitan area during the 2011 Mw 9.0 Tohoku-Oki earthquake using continuous records from 234 seismometers of the Metropolitan Seismic Observation network (MeSO-net). This network, which was deployed in shallow 20-m depth boreholes, recorded horizontal accelerations up to 236 cm/s2 during the mainshock. For each MeSO-net station, we compute the near-surface response using the single-station cross-correlation technique between vertical and horizontal components, every 6 hours for 2.5 months around the main event. Comparing each near-surface response against the pre-event reference, we find seismic velocity drops up to 10% in the near-surface of the Tokyo metropolitan area during the mainshock. The amplitude of the coseismic velocity drop increases with increasing ground shaking and decreasing VS30, which is the S-wave velocity the first 30-m of the ground. Furthermore, the waveforms experience a loss of coherence that recovers exponentially over a time. This recovery rate also increases with the acceleration levels. While most of the velocity changes and waveform coherence recover within a few days, we also find permanent changes at stations that experienced liquefaction and the strongest ground motions. The ambient seismic field captures the coseismic velocity changes in the shallow structure and the following healing process, and may be used to detect permanent damage.

Three-dimensional ground-motion simulations of earthquakes for the Hanford area, Washington

USGS Publications Warehouse

Frankel, Arthur; Thorne, Paul; Rohay, Alan

2014-01-01

This report describes the results of ground-motion simulations of earthquakes using three-dimensional (3D) and one-dimensional (1D) crustal models conducted for the probabilistic seismic hazard assessment (PSHA) of the Hanford facility, Washington, under the Senior Seismic Hazard Analysis Committee (SSHAC) guidelines. The first portion of this report demonstrates that the 3D seismic velocity model for the area produces synthetic seismograms with characteristics (spectral response values, duration) that better match those of the observed recordings of local earthquakes, compared to a 1D model with horizontal layers. The second part of the report compares the response spectra of synthetics from 3D and 1D models for moment magnitude (M) 6.6–6.8 earthquakes on three nearby faults and for a dipping plane wave source meant to approximate regional S-waves from a Cascadia great earthquake. The 1D models are specific to each site used for the PSHA. The use of the 3D model produces spectral response accelerations at periods of 0.5–2.0 seconds as much as a factor of 4.5 greater than those from the 1D models for the crustal fault sources. The spectral accelerations of the 3D synthetics for the Cascadia plane-wave source are as much as a factor of 9 greater than those from the 1D models. The differences between the spectral accelerations for the 3D and 1D models are most pronounced for sites with thicker supra-basalt sediments and for stations with earthquakes on the Rattlesnake Hills fault and for the Cascadia plane-wave source.

Newly discovered geological features and their potential impact on Darlington and Pickering. Report No. INFO-0342

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallach, J.L.

1990-01-01

The design basis seismic ground motion for the nuclear generating stations at Darlington and at Pickering were determined solely through the assessment of previous earthquakes with no geological, or any other geophysical, input. Since then geophysical maps, showing a north-northwest oriented linear feature with some possible associated seismic activity, were examined. This report discusses the impact of these new discoveries on the Darlington and Pickering nuclear generating stations and on the already known geophysical features of the area.

Power optimal single-axis articulating strategies

NASA Technical Reports Server (NTRS)

Kumar, Renjith R.; Heck, Michael L.

1991-01-01

Power optimal single axis articulating PV array motion for Space Station Freedom is investigated. The motivation is to eliminate one of the articular joints to reduce Station costs. Optimal (maximum power) Beta tracking is addressed for local vertical local horizontal (LVLH) and non-LVLH attitudes. Effects of intra-array shadowing are also presented. Maximum power availability while Beta tracking is compared to full sun tracking and optimal alpha tracking. The results are quantified in orbital and yearly minimum, maximum, and average values of power availability.

Attenuation Characteristics of Strong Motions during the 2016 Kumamoto Earthquakes including Near-Field Records

NASA Astrophysics Data System (ADS)

Si, H.; Koketsu, K.; Miyake, H.; Ibrahim, R.

2016-12-01

During the two major earthquakes occurred in Kumamoto prefecture, at 21:26 on 14 April, 2016 (Mw 6.2, GCMT), and at 1:25 on 16 April, 2016 (Mw7.0, GCMT), a large number of strong ground motions were recorded, including those very close to the surface fault. In this study, we will discuss the attenuation characteristics of strong ground motions observed during the earthquakes. The data used in this study are mainly observed by K-NET, KiK-net, Osaka University, JMA and Kumamoto prefecture. The 5% damped acceleration response spectra (GMRotI50) are calculated based on the method proposed by Boore et al. (2006). PGA and PGV is defined as the larger one among the PGAs and PGVs of two horizontal components. The PGA, PGV, and GMRotI50 data were corrected to the bedrock with Vs of 1.5km/s based on the method proposed by Si et al. (2016) using the average shear wave velocity (Vs30) and the thickness of sediments over the bedrock. The thickness is estimated based on the velocity structure model provided by J-SHIS. We use a source model proposed by Koketsu et al. (2016) to calculate the fault distance and the median distance (MED) which defined as the closest distance from a station to the median line of the fault plane (Si et al., 2014). We compared the observed PGAs, PGVs, and GMRotI50 with the GMPEs developed in Japan using MED (Si et al., 2014). The predictions by the GMPEs are generally consistent with the observations during the two Kumamoto earthquakes. The results of the comparison also indicated that, (1) strong motion records from the earthquake on April 14th are generally consistent with the predictions by GMPE, however, at the periods of 0.5 to 2 seconds, several records close to the fault plane show larger amplitudes than the predictions by GMPE, including the KiK-net station Mashiki (KMMH16); (2) for the earthquake on April 16, the PGAs and GMRotI50 at periods from 0.1s to 0.4s with short distance from the fault plane are slightly smaller than the predictions by GMPE. On the other hand, for the PGVs and GMRotI50s at periods longer than 2.5s with MED larger than about 100 km, the observations are generally larger than the prediction by GMPE, showing smaller attenuation.

Analysis of Active Crustal Deformation in Chiayi Area, Southwestern Taiwan by Continues GPS network and numerical modeling

NASA Astrophysics Data System (ADS)

Chung, W. C.; Hu, J. C.

2012-04-01

Locating in the boundary between the Eurasia Plate and the Philippine Sea Plate, the island of Taiwan lies in a complex tectonic area. The fold-and-thrust belt in the southwestern Taiwan provides distinctive morphotectonic features reflecting the initial mountain building stage in Taiwan orogeny. Several devastating earthquakes have occurred in this region since 1900, the famous one is M7.1 Meishan earthquake in 1906. In addition, a seismic concentration zone is observed in Coastal plain in Chiayi counties, which no active faults have been reported in this region. The active deformation in SW Taiwan has been suggested to be related to active growing folding initiated by the blind thrust fault system. How surface deformation related to the subsurface active structures is a crucial topic for seismic hazard assessment in study area. The newly initiated blind fault system increases potential earthquake hazard in the southwestern alluvial plain where is densely populated. Thus we try to characterize the existence of blind fault-folding system beneath the coastal plain area by geodetic method. We derive a velocity field based on data at 55 continuous GPS (CGPS) stations from 2006 to 2010, and data at 97 campaign mode GPS over a time period between 2002 to 2010. The CGPS data used in this study were processed with the GAMIT/GLOBK software version 10.4. The crustal motion in this area shows the horizontal displacement about 30 mm/yr with the directions of 297° in the easternmost part of the Western Foothills, and crossing the main active structures, Chiushiunkeng-Chukou Fault and blind fault systems, the velocities significantly decrease to 3 mm/yr with the directions of 288° in the westernmost part in the coastal plan, with respect to Paisha station, S01R. The compressional strain rate dominates and the larger compressional strain rate is observed at the Foothill region, the east side of Chiushiunkeng- Chukou Fault. In some coordinate time-series of our CGPS sites, the strong periodic signals whether in horizontal component or vertical component is observed. These signals might include the effect of variation of ground water level or tectonic motion. In this study, we try to use the available geological structural profiles from CPC to characterize complex motions in Chiayi region and to assess the fault activity based on 2-D dislocation model. Further, we try to use Poly3D to inverse the fault motion during interseismic period.

Slip model and Synthetic Broad-band Strong Motions for the 2015 Mw 8.3 Illapel (Chile) Earthquake.

NASA Astrophysics Data System (ADS)

Aguirre, P.; Fortuno, C.; de la Llera, J. C.

2017-12-01

The MW 8.3 earthquake that occurred on September 16th 2015 west of Illapel, Chile, ruptured a 200 km section of the plate boundary between 29º S and 33º S. SAR data acquired by the Sentinel 1A satellite was used to obtain the interferogram of the earthquake, and from it, the component of the displacement field of the surface in the line of sight of the satellite. Based on this interferogram, the corresponding coseismic slip distribution for the earthquake was determined based on different plausible finite fault geometries. The model that best fits the data gathered is one whose rupture surface is consistent with the Slab 1.0 model, with a constant strike angle of 4º and variable dip angle ranging from 2.7º near the trench to 24.3º down dip. Using this geometry the maximum slip obtained is 7.52 m and the corresponding seismic moment is 3.78·1021 equivalent to a moment magnitude Mw 8.3. Calculation of the Coulomb failure stress change induced by this slip distribution evidences a strong correlation between regions where stress is increased as consequence of the earthquake, and the occurrence of the most relevant aftershocks, providing a consistency check for the inversion procedure applied and its results.The finite fault model for the Illapel earthquake is used to test a hybrid methodology for generation of synthetic ground motions that combines a deterministic calculation of the low frequency content, with stochastic modelling of the high frequency signal. Strong ground motions are estimated at the location of seismic stations recording the Illapel earthquake. Such simulations include the effect of local soil conditions, which are modelled empirically based on H/V ratios obtained from a large database of historical seismic records. Comparison of observed and synthetic records based on the 5%-damped response spectra yield satisfactory results for locations where the site response function is more robustly estimated.

Estimation and Simulation of Inter-station Green's Functions in the Beppu-Bay Area, Oita Prefecture, Southwest Japan: the Effect of Sedimentary Basin

NASA Astrophysics Data System (ADS)

Hayashida, T.; Yoshimi, M.; Komatsu, M.; Takenaka, H.

2017-12-01

Continuous long-term observations of ambient noise (microseisms) were performed from August 2014 to February 2017 in the Beppu-Bay area, Oita prefecture, to investigate S-wave velocity structure of deep sedimentary basin (Hayashida et al., 2015SSJ; Yoshimi and Hayashida, 2017WCEE). The observation array consists of 12 broadband stations with an average spacing of 12 km. We applied the seismic interferometry technique to the ambient noise data and derived nine-component ambient noise cross-correlation functions (Z-R, Z-T, Z-Z, R-R, R-T, R-Z, T-R, T-T, and T-Z components) between 66 pairs of stations (distance of 6.4 km to 65.2 km). We assumed the stacked cross-correlation functions as "observed Green's functions" between two stations and estimated group velocities of Rayleigh and Love waves in the frequency between 0.2 and 0.5 Hz (Hayashida et al., 2017AGU-JpGU). Theoretical Green's functions for all stations pairs were also calculated using the finite difference method (HOT-FDM, Nakamura et al., 2012BSSA), with an existing three-dimensional basin structure model (J-SHIS V2) with land and seafloor topography and a seawater layer (Okunaka et al., 2016JpGU) and a newly constructed basin structure model of the target area (Yoshimi et al., 2017AGU). The comparisons between observed and simulated Green's functions generally show good agreements in the frequency range between 0.2 and 0.5 Hz. On the other hand, both observed and simulated Green's functions for some station pairs whose traverse lines run across the deeper part of the sedimentary basin (> 2000 m) show prominent later phases that might be generated and propagated inside the basin. This indicates that the understanding of the phase generation and propagation processes can be a key factor to validate the basin structure model and we investigated the characteristics of the later phases, such as its particle motions and arrival times, using observed and simulated Green's functions in detail. Acknowledgements: This work is supported by the Comprehensive Research on the Beppu-Haneyama Fault Zone funded by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan.

Physics-based real time ground motion parameter maps: the Central Mexico example

NASA Astrophysics Data System (ADS)

Ramirez Guzman, L.; Contreras Ruiz Esparza, M. G.; Quiroz Ramirez, A.; Carrillo Lucia, M. A.; Perez Yanez, C.

2013-12-01

We present the use of near real time ground motion simulations in the generation of ground motion parameter maps for Central Mexico. Simple algorithm approaches to predict ground motion parameters of civil protection and risk engineering interest are based on the use of observed instrumental values, reported macroseismic intensities and their correlations, and ground motion prediction equations (GMPEs). A remarkable example of the use of this approach is the worldwide Shakemap generation program of the United States Geological Survey (USGS). Nevertheless, simple approaches rely strongly on the availability of instrumental and macroseismic intensity reports, as well as the accuracy of the GMPEs and the site effect amplification calculation. In regions where information is scarce, the GMPEs, a reference value in a mean sense, provide most of the ground motion information together with site effects amplification using a simple parametric approaches (e.g. the use of Vs30), and have proven to be elusive. Here we propose an approach that includes physics-based ground motion predictions (PBGMP) corrected by instrumental information using a Bayesian Kriging approach (Kitanidis, 1983) and apply it to the central region of Mexico. The method assumes: 1) the availability of a large database of low and high frequency Green's functions developed for the region of interest, using fully three-dimensional and representative one-dimension models, 2) enough real time data to obtain the centroid moment tensor and a slip rate function, and 3) a computational infrastructure that can be used to compute the source parameters and generate broadband synthetics in near real time, which will be combined with recorded instrumental data. By using a recently developed velocity model of Central Mexico and an efficient finite element octree-based implementation we generate a database of source-receiver Green's functions, valid to 0.5 Hz, that covers 160 km x 300 km x 700 km of Mexico, including a large portion of the Pacific Mexican subduction zone. A subset of the velocity and strong ground motion data available in real time is processed to obtain the source parameters to generate broadband ground motions in a dense grid ( 10 km x 10 km cells). These are interpolated later with instrumental values using a Bayesian Kriging method. Peak ground velocity and acceleration, as well as SA (T=0.1, 0.5, 1 and 2s) maps, are generated for a small set of medium to large magnitude Mexican earthquakes (Mw=5 to 7.4). We evaluate each map by comparing against stations not considered in the computation.

Leveraging EarthScope USArray with the Central and Eastern United States Seismic Network

NASA Astrophysics Data System (ADS)

Busby, R.; Sumy, D. F.; Woodward, R.; Frassetto, A.; Brudzinski, M.

2015-12-01

Recent earthquakes, such as the 2011 M5.8 Mineral, Virginia earthquake, raised awareness of the comparative lack of knowledge about seismicity, site response to ground shaking, and the basic geologic underpinnings in this densely populated region. With this in mind, the National Science Foundation, United States Geological Survey, United States Nuclear Regulatory Commission, and Department of Energy supported the creation of the Central and Eastern United States Seismic Network (CEUSN). These agencies, along with the IRIS Consortium who operates the network, recognized the unique opportunity to retain EarthScope Transportable Array (TA) seismic stations in this region beyond the standard deployment duration of two years per site. The CEUSN project supports 159 broadband TA stations, more than 30 with strong motion sensors added, that are scheduled to operate through 2017. Stations were prioritized in regions of elevated seismic hazard that have not been traditionally heavily monitored, such as the Charlevoix and Central Virginia Seismic Zones, and in regions proximal to nuclear power plants and other critical facilities. The stations (network code N4) transmit data in real time, with broadband and strong motion sensors sampling at 100 samples per second. More broadly the CEUSN concept also recognizes the existing backbone coverage of permanently operating seismometers in the CEUS, and forms a network of over 300 broadband stations. This multi-agency collaboration is motivated by the opportunity to use one facility to address multiple missions and needs in a way that is rarely possible, and to produce data that enables both researchers and federal agencies to better understand seismic hazard potential and associated seismic risks. In June 2015, the CEUSN Working Group (www.usarray.org/ceusn_working_group) was formed to review and provide advice to IRIS Management on the performance of the CEUSN as it relates to the target scientific goals and objectives. Map shows the 159 CEUSN stations (yellow) that will be operated and maintained by the IRIS Consortium through 2017. The CEUSN stations were selected for proximity to nuclear power plants (black squares) and other critical infrastructure as well as to more evenly distribute seismic stations across the central and eastern United States.

Moment tensor inversions using strong motion waveforms of Taiwan TSMIP data, 1993–2009

USGS Publications Warehouse

Chang, Kaiwen; Chi, Wu-Cheng; Gung, Yuancheng; Dreger, Douglas; Lee, William H K.; Chiu, Hung-Chie

2011-01-01

Earthquake source parameters are important for earthquake studies and seismic hazard assessment. Moment tensors are among the most important earthquake source parameters, and are now routinely derived using modern broadband seismic networks around the world. Similar waveform inversion techniques can also apply to other available data, including strong-motion seismograms. Strong-motion waveforms are also broadband, and recorded in many regions since the 1980s. Thus, strong-motion data can be used to augment moment tensor catalogs with a much larger dataset than that available from the high-gain, broadband seismic networks. However, a systematic comparison between the moment tensors derived from strong motion waveforms and high-gain broadband waveforms has not been available. In this study, we inverted the source mechanisms of Taiwan earthquakes between 1993 and 2009 by using the regional moment tensor inversion method using digital data from several hundred stations in the Taiwan Strong Motion Instrumentation Program (TSMIP). By testing different velocity models and filter passbands, we were able to successfully derive moment tensor solutions for 107 earthquakes of Mw >= 4.8. The solutions for large events agree well with other available moment tensor catalogs derived from local and global broadband networks. However, for Mw = 5.0 or smaller events, we consistently over estimated the moment magnitudes by 0.5 to 1.0. We have tested accelerograms, and velocity waveforms integrated from accelerograms for the inversions, and found the results are similar. In addition, we used part of the catalogs to study important seismogenic structures in the area near Meishan Taiwan which was the site of a very damaging earthquake a century ago, and found that the structures were dominated by events with complex right-lateral strike-slip faulting during the recent decade. The procedures developed from this study may be applied to other strong-motion datasets to compliment or fill gaps in catalogs from regional broadband networks and teleseismic networks.

Comparison of strong-motion spectra with teleseismic spectra for three magnitude 8 subduction-zone earthquakes

NASA Astrophysics Data System (ADS)

Houston, Heidi; Kanamori, Hiroo

1990-08-01

A comparison of strong-motion spectra and teleseismic spectra was made for three Mw 7.8 to 8.0 earthquakes: the 1985 Michoacan (Mexico) earthquake, the 1985 Valparaiso (Chile) earthquake, and the 1983 Akita-Oki (Japan) earthquake. The decay of spectral amplitude with the distance from the station was determined, considering different measures of distance from a finite fault, and it was found to be different for these three events. The results can be used to establish empirical relations between the observed spectra and the half-space responses depending on the distance and the site condition, making it possible to estimate strong motions from source spectra determined from teleseismic records.

Air motions inside dome room of Big Telescope Alt-azimuth at Special Astrophysical Observatory RAS. Numerical solutions of Navier-Stokes equations

NASA Astrophysics Data System (ADS)

Nosov, V. V.; Lukin, V. P.; Nosov, E. V.; Torgaev, A. V.

2017-11-01

The structure of air turbulent motion inside the closed dome room of Big Telescope Alt-azimuth at Special Astrophysical Observatory of the Russian Academy of Sciences (RAS) has been experimentally and theoretically studied. Theoretical results have been reached by numerical solving of boundary value problem for Navier-Stokes equations. Solitary large vortices (coherent structures, topological solitons) are observed indoors. Coherent breakdown of these vortices leads to the coherent turbulence. In the case of identical boundary conditions the pattern of air motions as a result of the simulation and the pattern, registered experimentally using the compact portable ultrasonic weather station, are practically the same.

Cyberinfrastructure for the Unified Study of Earth Structure and Earthquake Sources in Complex Geologic Environments

NASA Astrophysics Data System (ADS)

Zhao, L.; Chen, P.; Jordan, T. H.; Olsen, K. B.; Maechling, P.; Faerman, M.

2004-12-01

The Southern California Earthquake Center (SCEC) is developing a Community Modeling Environment (CME) to facilitate the computational pathways of physics-based seismic hazard analysis (Maechling et al., this meeting). Major goals are to facilitate the forward modeling of seismic wavefields in complex geologic environments, including the strong ground motions that cause earthquake damage, and the inversion of observed waveform data for improved models of Earth structure and fault rupture. Here we report on a unified approach to these coupled inverse problems that is based on the ability to generate and manipulate wavefields in densely gridded 3D Earth models. A main element of this approach is a database of receiver Green tensors (RGT) for the seismic stations, which comprises all of the spatial-temporal displacement fields produced by the three orthogonal unit impulsive point forces acting at each of the station locations. Once the RGT database is established, synthetic seismograms for any earthquake can be simply calculated by extracting a small, source-centered volume of the RGT from the database and applying the reciprocity principle. The partial derivatives needed for point- and finite-source inversions can be generated in the same way. Moreover, the RGT database can be employed in full-wave tomographic inversions launched from a 3D starting model, because the sensitivity (Fréchet) kernels for travel-time and amplitude anomalies observed at seismic stations in the database can be computed by convolving the earthquake-induced displacement field with the station RGTs. We illustrate all elements of this unified analysis with an RGT database for 33 stations of the California Integrated Seismic Network in and around the Los Angeles Basin, which we computed for the 3D SCEC Community Velocity Model (SCEC CVM3.0) using a fourth-order staggered-grid finite-difference code. For a spatial grid spacing of 200 m and a time resolution of 10 ms, the calculations took ~19,000 node-hours on the Linux cluster at USC's High-Performance Computing Center. The 33-station database with a volume of ~23.5 TB was archived in the SCEC digital library at the San Diego Supercomputer Center using the Storage Resource Broker (SRB). From a laptop, anyone with access to this SRB collection can compute synthetic seismograms for an arbitrary source in the CVM in a matter of minutes. Efficient approaches have been implemented to use this RGT database in the inversions of waveforms for centroid and finite moment tensors and tomographic inversions to improve the CVM. Our experience with these large problems suggests areas where the cyberinfrastructure currently available for geoscience computation needs to be improved.

Strong correlation between stress drop and peak ground acceleration for recent M1–4 earthquakes in the San Francisco Bay Area

DOE PAGES

Trugman, Daniel Taylor; Shearer, Peter M.

2018-03-06

Theoretical and observational studies suggest that between-event variability in the median ground motions of larger ( M≥5 ) earthquakes is controlled primarily by the dynamic properties of the earthquake source, such as Brune-type stress drop. Analogous results remain equivocal for smaller events due to the lack of comprehensive and overlapping ground-motion and source-parameter datasets in this regime. Here in this paper, we investigate the relationship between peak ground acceleration (PGA) and dynamic stress drop for a new dataset of 5297 earthquakes that occurred in the San Francisco Bay area from 2002 through 2016. For each event, we measure PGA onmore » horizontal-component channels of stations within 100 km and estimate stress drop from P-wave spectra recorded on vertical-component channels of the same stations. We then develop a nonparametric ground-motion prediction equation (GMPE) applicable for the moderate (M 1–4) earthquakes in our study region, using a mixed-effects generalization of the Random Forest algorithm. We use the Random Forest GMPE to model the joint influence of magnitude, distance, and near-site effects on observed PGA. We observe a strong correlation between dynamic stress drop and the residual PGA of each event, with the events with higher-than-expected PGA associated with higher values of stress drop. The strength of this correlation increases as a function of magnitude but remains significant even for smaller magnitude events with corner frequencies that approach the observable bandwidth of the acceleration records. Mainshock events are characterized by systematically higher stress drop and PGA than aftershocks of equivalent magnitude. Coherent local variations in the distribution of dynamic stress drop provide observational constraints to support the future development of nonergodic GMPEs that account for variations in median stress drop at different source locations.« less

Strong correlation between stress drop and peak ground acceleration for recent M1–4 earthquakes in the San Francisco Bay Area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trugman, Daniel Taylor; Shearer, Peter M.

Theoretical and observational studies suggest that between-event variability in the median ground motions of larger ( M≥5 ) earthquakes is controlled primarily by the dynamic properties of the earthquake source, such as Brune-type stress drop. Analogous results remain equivocal for smaller events due to the lack of comprehensive and overlapping ground-motion and source-parameter datasets in this regime. Here in this paper, we investigate the relationship between peak ground acceleration (PGA) and dynamic stress drop for a new dataset of 5297 earthquakes that occurred in the San Francisco Bay area from 2002 through 2016. For each event, we measure PGA onmore » horizontal-component channels of stations within 100 km and estimate stress drop from P-wave spectra recorded on vertical-component channels of the same stations. We then develop a nonparametric ground-motion prediction equation (GMPE) applicable for the moderate (M 1–4) earthquakes in our study region, using a mixed-effects generalization of the Random Forest algorithm. We use the Random Forest GMPE to model the joint influence of magnitude, distance, and near-site effects on observed PGA. We observe a strong correlation between dynamic stress drop and the residual PGA of each event, with the events with higher-than-expected PGA associated with higher values of stress drop. The strength of this correlation increases as a function of magnitude but remains significant even for smaller magnitude events with corner frequencies that approach the observable bandwidth of the acceleration records. Mainshock events are characterized by systematically higher stress drop and PGA than aftershocks of equivalent magnitude. Coherent local variations in the distribution of dynamic stress drop provide observational constraints to support the future development of nonergodic GMPEs that account for variations in median stress drop at different source locations.« less

First Indications of Intraplate Deformations in Central Germany from Reprocessed GNSS Time Series and Geological Data

NASA Astrophysics Data System (ADS)

Becker, Matthias; Leinen, Stefan; Läufer, Gwendolyn; Lehné, Rouwen

2013-04-01

Six years of GPS data have been reprocessed in ITRF2008 for a regional SAPOS CORS network in the federal state of Hesse with 25 stations and some anchor sites of IGS and EPN to derive accurate and consistent coordinate time series. Based on daily network solutions coordinate time series parameters like velocities, offsets in case of antenna changes and annual periodic variation have been estimated. The estimation process includes the fitting of a sophisticated stochastic model for the time series which accounts for inherent time correlation. The results are blended with geological data to verify information from geology on potential recent deformations by the geodetic analyses. Besides of some information on the reprocessing of the GNSS the results the stochastics of the derived velocity field will be discussed in detail. Special emphasis will be on the intra-plate deformation: for the horizontal component the residual velocity field after removal of a plate rotation model is presented, while for the vertical velocities the datum-induced systematic effect is removed in order to analyze the remaining vertical motion. The residual velocity field is then matched with the geology for Hesse. Correlation of both vertical and horizontal movements with major geological structures reveals good accordance. SAPOS stations with documented significant subsidence are mainly located in tertiary Graben structures such as the Lower Hessian Basin (station Kassel), the Wetterau (station Kloppenheim) or the Upper Rhine Graben (Station Darmstadt). From the geological point of view these structures are supposed to be subsiding ones. Other major geological features, i.e. the Rhenish Shield as well as the East Hessian Bunter massif are supposed to be affected by recent uplift. SAPOS stations located in these regions match the assumed movement (e.g. Weilburg, Wiesbaden, Bingen, Fulda). Furthermore SAPOS-derived horizontal movements seem to trace tectonic movements in the region, i.e. extension along the tertiary Graben structures, including a sinistral strike slip component. However, a more detailed analysis is needed to confirm the link between detected movement and geodynamic processes.

Amplification Factors for Spectral Acceleration Using Borehole Seismic Array in Taiwan

NASA Astrophysics Data System (ADS)

Lai, T. S.; Yih-Min, W.; Chao, W. A.; Chang, C. H.

2017-12-01

In order to reduce the noise from surface to get the high-quality seismic recordings, there are 54 borehole seismic arrays have been installed in Taiwan deployed by Central Weather Bureau (CWB) until the end of 2016. Each array includes two force balance accelerometers, one at the surface and other inside the borehole, as well as one broadband seismometer inside the borehole. The downhole instruments are placed at a depth between 120 and 400 m. The background noise level are lower at the borehole stations, but the amplitudes recorded by borehole stations are smaller than surface stations for the same earthquake due to the different geology conditions. Therefore, the earthquake magnitude estimated by borehole station is smaller than surface station. So far, CWB only use the surface stations in the magnitude determination due to this situation. In this study, we investigate the site effects between surface and downhole for borehole seismic arrays. Using the spectral ratio derived by the two-station spectral method as the transfer function, simulated the waveform recorded by borehole stations to the surface stations. In the future, through the transfer function, the borehole stations will be included in the estimation of earthquake magnitude and the results of amplification factors can provide the information of near-surface site effects for the ground motion simulation applications.

Crustal seismic structure of Tohoku region, Japan constrained by ambient noises

NASA Astrophysics Data System (ADS)

Chen, K. X.; Gung, Y.; Kuo, B. Y.; Huang, T. Y.

2016-12-01

We present 3D crustal models of Vs and Vs azimuthal anisotropy of Tohoku region, Japan. We construct the models by using short to intermediate periods of Rayleigh waves retreated from noise interferometry and a wavelet-based multi-scale inversion technique. We employ the Welch's method to derive the empirical Green's functions (EGF) of Rayleigh waves from one year of continuous records of 123 short-period stations of the dense high-sensitivity seismograph network (Hi-net), operated by National Research Institute for Earth Science and Disaster Prevention (NIED). We compute EGFs for about 4000 station pairs with interstation distance less than 300 km. For each qualified EGF, we measure the dispersion in the period range from 2 to 18 seconds. While our results are still at the preliminary stage, we have noticed few interesting features in the models: (1) the quasi-N-S trend volcano front seems to be a major boundary for the variations of both velocity and anisotropy, with the eastern part characterized by higher Vs and the western part by low Vs anomalies, consistent with their corresponding surface geology; (2) patterns of the Vs azimuthal anisotropy demonstrate a clear depth-dependent variation, with fast polarization direction (FPD) parallels the strike of the island at the shallow crust; at the larger depths, the FPD gradually rotates to the direction of absolute plate motion in the SW region, and is getting complicated in the NW region, respectively. We present the revealed depth-dependent anisotropy and discuss the tectonic implications of our models. Key words: Tohoku, ambient noise, seismic anisotropy, surface wave tomography We present 3D crustal models of Vs and Vs azimuthal anisotropy of Tohoku region, Japan. We construct the models by using short to intermediate periods of Rayleigh waves retreated from noise interferometry and a wavelet-based multi-scale inversion technique. We employ the Welch's method to derive the empirical Green's functions (EGF) of Rayleigh waves from one year of continuous records of 123 short-period stations of the dense high-sensitivity seismograph network (Hi-net), operated by National Research Institute for Earth Science and Disaster Prevention (NIED). We compute EGFs for about 4000 station pairs with interstation distance less than 300 km. For each qualified EGF, we measure the dispersion in the period range from 2 to 18 seconds. While our results are still at the preliminary stage, we have noticed few interesting features in the models: (1) the quasi-N-S trend volcano front seems to be a major boundary for the variations of both velocity and anisotropy, with the eastern part characterized by higher Vs and the western part by low Vs anomalies, consistent with their corresponding surface geology; (2) patterns of the Vs azimuthal anisotropy demonstrate a clear depth-dependent variation, with fast polarization direction (FPD) parallels the strike of the island at the shallow crust; at the larger depths, the FPD gradually rotates to the direction of absolute plate motion in the SW region, and is getting complicated in the NW region, respectively. We present the revealed depth-dependent anisotropy and discuss the tectonic implications of our models. Key words: Tohoku, ambient noise, seismic anisotropy, surface wave tomography

A New Network-Based Approach for the Earthquake Early Warning

NASA Astrophysics Data System (ADS)

Alessandro, C.; Zollo, A.; Colombelli, S.; Elia, L.

2017-12-01

Here we propose a new method which allows for issuing an early warning based upon the real-time mapping of the Potential Damage Zone (PDZ), e.g. the epicentral area where the peak ground velocity is expected to exceed the damaging or strong shaking levels with no assumption about the earthquake rupture extent and spatial variability of ground motion. The system includes the techniques for a refined estimation of the main source parameters (earthquake location and magnitude) and for an accurate prediction of the expected ground shaking level. The system processes the 3-component, real-time ground acceleration and velocity data streams at each station. For stations providing high quality data, the characteristic P-wave period (τc) and the P-wave displacement, velocity and acceleration amplitudes (Pd, Pv and Pa) are jointly measured on a progressively expanded P-wave time window. The evolutionary estimate of these parameters at stations around the source allow to predict the geometry and extent of PDZ, but also of the lower shaking intensity regions at larger epicentral distances. This is done by correlating the measured P-wave amplitude with the Peak Ground Velocity (PGV) and Instrumental Intensity (IMM) and by interpolating the measured and predicted P-wave amplitude at a dense spatial grid, including the nodes of the accelerometer/velocimeter array deployed in the earthquake source area. Depending of the network density and spatial source coverage, this method naturally accounts for effects related to the earthquake rupture extent (e.g. source directivity) and spatial variability of strong ground motion related to crustal wave propagation and site amplification. We have tested this system by a retrospective analysis of three earthquakes: 2016 Italy 6.5 Mw, 2008 Iwate-Miyagi 6.9 Mw and 2011 Tohoku 9.0 Mw. Source parameters characterization are stable and reliable, also the intensity map shows extended source effects consistent with kinematic fracture models of evets.

Orbit determination based on meteor observations using numerical integration of equations of motion

NASA Astrophysics Data System (ADS)

Dmitriev, V.; Lupovka, V.; Gritsevich, M.

2014-07-01

We review the definitions and approaches to orbital-characteristics analysis applied to photographic or video ground-based observations of meteors. A number of camera networks dedicated to meteors registration were established all over the word, including USA, Canada, Central Europe, Australia, Spain, Finland and Poland. Many of these networks are currently operational. The meteor observations are conducted from different locations hosting the network stations. Each station is equipped with at least one camera for continuous monitoring of the firmament (except possible weather restrictions). For registered multi-station meteors, it is possible to accurately determine the direction and absolute value for the meteor velocity and thus obtain the topocentric radiant. Based on topocentric radiant one further determines the heliocentric meteor orbit. We aim to reduce total uncertainty in our orbit-determination technique, keeping it even less than the accuracy of observations. The additional corrections for the zenith attraction are widely in use and are implemented, for example, here [1]. We propose a technique for meteor-orbit determination with higher accuracy. We transform the topocentric radiant in inertial (J2000) coordinate system using the model recommended by IAU [2]. The main difference if compared to the existing orbit-determination techniques is integration of ordinary differential equations of motion instead of addition correction in visible velocity for zenith attraction. The attraction of the central body (the Sun), the perturbations by Earth, Moon and other planets of the Solar System, the Earth's flattening (important in the initial moment of integration, i.e. at the moment when a meteoroid enters the atmosphere), atmospheric drag may be optionally included in the equations. In addition, reverse integration of the same equations can be performed to analyze orbital evolution preceding to meteoroid's collision with Earth. To demonstrate the developed technique, we provide calculated orbits for several cases, including well-known meteorite-producing fireballs. A comparison of our estimates with previously published ones is also provided.

Automatic spacecraft detumbling by internal mass motion

NASA Technical Reports Server (NTRS)

Edwards, T. L.; Kaplan, M. H.

1974-01-01

In the operation of future manned space vehicles, there will always be a finite probability that an accident will occur which results in uncontrolled tumbling of a craft. Hard docking by a manned rescue vehicle is not acceptable because of the hazardous environment to which rescue crewmen would be exposed and excessive maneuvering accelerations during docking operations. A movable-mass control concept, which is activated upon initiation of tumbling and is autonomous, can convert tumbling motion into simple spin. The complete equations of motion for an asymmetric rigid spacecraft containing a movable mass are presented, and appropriate control law and system parameters are selected to minimize kinetic energy, resulting in simple spin about the major principal axis. Simulations indicate that for a large space station experiencing a collision, which results in tumbling, a 1% movable mass is capable of stabilizing motion in 2 hr.

Recent developments for the Large Binocular Telescope Guiding Control Subsystem

NASA Astrophysics Data System (ADS)

Golota, T.; De La Peña, M. D.; Biddick, C.; Lesser, M.; Leibold, T.; Miller, D.; Meeks, R.; Hahn, T.; Storm, J.; Sargent, T.; Summers, D.; Hill, J.; Kraus, J.; Hooper, S.; Fisher, D.

2014-07-01

The Large Binocular Telescope (LBT) has eight Acquisition, Guiding, and wavefront Sensing Units (AGw units). They provide guiding and wavefront sensing capability at eight different locations at both direct and bent Gregorian focal stations. Recent additions of focal stations for PEPSI and MODS instruments doubled the number of focal stations in use including respective motion, camera controller server computers, and software infrastructure communicating with Guiding Control Subsystem (GCS). This paper describes the improvements made to the LBT GCS and explains how these changes have led to better maintainability and contributed to increased reliability. This paper also discusses the current GCS status and reviews potential upgrades to further improve its performance.

Effects of overweight vehicles on New York State DOT infrastructure.

DOT National Transportation Integrated Search

2015-09-01

This report develops a methodology for estimating the effects of different categories of overweight : trucks on NYSDOT pavements and bridges. A data mining algorithm is used to categorize truck : data collected at several Weigh-In-Motion stations aro...

A Geodetic Strain Rate Model for the Pacific-North American Plate Boundary, western United States

NASA Astrophysics Data System (ADS)

Kreemer, C.; Hammond, W. C.; Blewitt, G.; Holland, A. A.; Bennett, R. A.

2012-04-01

We present a model of crustal strain rates derived from GPS measurements of horizontal station velocities in the Pacific-North American plate boundary in the western United States. The model reflects a best estimate of present-day deformation from the San Andreas fault system in the west to the Basin and Range province in the east. Of the total 2,846 GPS velocities used in the model, 1,197 are derived by ourselves, and 1,649 are taken from (mostly) published results. The velocities derived by ourselves (the "UNR solution") are estimated from GPS position time-series of continuous and semi-continuous stations for which data are publicly available. We estimated ITRF2005 positions from 2002-2011.5 using JPL's GIPSY-OASIS II software with ambiguity resolution applied using our custom Ambizap software. Only stations with time-series that span at least 2.25 years are considered. We removed from the time-series continental-scale common-mode errors using a spatially-varying filtering technique. Velocity uncertainties (typically 0.1-0.3 mm/yr) assume that the time-series contain flicker plus white noise. We used a subset of stations on the stable parts of the Pacific and North American plates to estimate the Pacific-North American pole of rotation. This pole is applied as a boundary condition to the model and the North American - ITRF2005 pole is used to rotate our velocities into a North America fixed reference frame. We do not include parts of the time-series that show curvature due to post-seismic deformation after major earthquakes and we also exclude stations whose time-series display a significant unexplained non-linearity or that are near volcanic centers. Transient effects longer than the observation period (i.e., slow viscoelastic relaxation) are left in the data. We added to the UNR solution velocities from 12 other studies. The velocities are transformed onto the UNR solution's reference frame by estimating and applying a translation and rotation that minimizes the velocities at collocated stations. We removed obvious outliers and velocities in areas that we identified to undergo subsidence likely due to excessive water pumping. For the strain rate calculations we excluded GPS stations with anomalous vertical motion or annual horizontal periodicity, which are indicators of local site instability. First, we used the stations from the UNR solution to create a Delaunay triangulation and estimated the horizontal strain rate components (and rigid body rotation) for each triangle in a linear least-squares inversion using the horizontal velocities as input. Some level of spatial damping was applied to minimize unnecessary spatial variation in the model parameters. The strain rates estimates were then used as a priori strain rate variances in a method that fits continuous bi-cubic Bessel spline functions through the velocity gradient field while minimizing the weighted misfit to all velocities. A minimal level of spatial smoothing of the variances was applied. The strain rate tensor model is shown by contours of the second invariant of the tensor, which is a measure of the amplitude that is coordinate frame independent. We also show a map of the tensor style and of the signal-to-noise ratio of the model.

Keeping up with video game technology: objective analysis of Xbox Kinect™ and PlayStation 3 Move™ for use in burn rehabilitation.

PubMed

Parry, Ingrid; Carbullido, Clarissa; Kawada, Jason; Bagley, Anita; Sen, Soman; Greenhalgh, David; Palmieri, Tina

2014-08-01

Commercially available interactive video games are commonly used in rehabilitation to aide in physical recovery from a variety of conditions and injuries, including burns. Most video games were not originally designed for rehabilitation purposes and although some games have shown therapeutic potential in burn rehabilitation, the physical demands of more recently released video games, such as Microsoft Xbox Kinect™ (Kinect) and Sony PlayStation 3 Move™ (PS Move), have not been objectively evaluated. Video game technology is constantly evolving and demonstrating different immersive qualities and interactive demands that may or may not have therapeutic potential for patients recovering from burns. This study analyzed the upper extremity motion demands of Kinect and PS Move using three-dimensional motion analysis to determine their applicability in burn rehabilitation. Thirty normal children played each video game while real-time movement of their upper extremities was measured to determine maximal excursion and amount of elevation time. Maximal shoulder flexion, shoulder abduction and elbow flexion range of motion were significantly greater while playing Kinect than the PS Move (p≤0.01). Elevation time of the arms above 120° was also significantly longer with Kinect (p<0.05). The physical demands for shoulder and elbow range of motion while playing the Kinect, and to a lesser extent PS Move, are comparable to functional motion needed for daily tasks such as eating with a utensil and hair combing. Therefore, these more recently released commercially available video games show therapeutic potential in burn rehabilitation. Objectively quantifying the physical demands of video games commonly used in rehabilitation aides clinicians in the integration of them into practice and lays the framework for further research on their efficacy. Copyright © 2013 Elsevier Ltd and ISBI. All rights reserved.

Rg excitation by underground explosions: insights from source modelling the 1997 Kazakhstan depth-of-burial experiment

NASA Astrophysics Data System (ADS)

Patton, Howard J.; Bonner, Jessie L.; Gupta, Indra N.

2005-12-01

Near-field seismograms of chemical explosions detonated as part of the 1997 depth-of-burial (DOB) experiment at the former Semipalatinsk nuclear test site provide an excellent opportunity to study the excitation of Rg waves for source effects. Rg waves were identified with particle-motion analysis and isolated from other arrivals using group velocity filtering. Amplitude and phase spectra of Rg waves were corrected for path effects based on observed attenuation in the near-field and path-specific phase velocity models. The path-corrected spectra were inputs to a grid-search method for finding source parameters of an axisymmetric source consisting of a monopole plus a compensated linear vector dipole (CLVD) or a horizontal tensile crack. The suite of observations, including ground-zero accelerograms and geophysical data from borehole logs, are best satisfied by models involving a CLVD with static (zero-frequency) seismic moment Mo. The CLVD source is related to tensile failure occurring at depths above the shotpoint. A static Mo distinguishes this source from classical models of spall, which are usually characterized by horizontal cracks that dynamically open and close with no permanent displacement (i.e. no static Mo). The CLVD source in this study appears to be more closely related to a driven block motion model envisaged by Masse. Rg source amplitudes are consistent with mb(Lg) measurements at station MAK, as would be expected if near-field Rg-to-S scattering plays a role in generating S waves observed at regional distances.

Design, building, and testing of the postlanding systems for the assured crew return vehicle

NASA Technical Reports Server (NTRS)

Hosterman, Kenneth C.; Anderson, Loren A.

1991-01-01

The design, building, and testing of the postlanding support systems for a water-landing Assured Crew Return Vehicle (ACRV) are presented. One ACRV will be permanently docked to Space Station Freedom, fulfilling NASA's commitment to Assured Crew Return Capability in the event of an accident or illness. The configuration of the ACRV is based on an Apollo Command Module (ACM) derivative. The 1990-1991 effort concentrated on the design, building, and testing of a one-fifth scale model of the egress and stabilization systems. The objective was to determine the feasibility of (1) stabilizing the ACM out of the range of motions that cause seasickness and (2) the safe and rapid removal of a sick or injured crew member from the ACRV. The development of the ACRV postlanding systems model was performed at the University of Central Florida with guidance from the Kennedy Space Center ACRV program managers. Emphasis was placed on four major areas. First was design and construction of a one-fifth scale model of the ACM derivative to accommodate the egress and stabilization systems for testing. Second was the identification of a water test facility suitable for testing the model in all possible configurations. Third was the construction of the rapid egress mechanism designed in the previous academic year for incorporation into the ACRV model. The fourth area was construction and motion response testing of the attitude ring and underwater parachute systems.

Crustal Deformation of the Central Walker Lane from GPS velocities: Block Rotations and Slip Rates

NASA Astrophysics Data System (ADS)

Bormann, J. M.; Hammond, W. C.; Kreemer, C. W.; Blewitt, G.; Wesnousky, S. G.

2010-12-01

The Walker Lane is a complex zone of active intracontinental transtension between the Sierra Nevada/Great Valley (SNGV) microplate and the Basin and Range in the western United States. Collectively, this ~100 km wide zone accommodates ~20% of the Pacific-North American relative plate motion. The Central Walker Lane (CWL) extends from the southern boundary of the Mina Deflection (~38.0°N) to the latitude of Lake Tahoe (~39.5°N) and encompasses the transition from Basin and Range style faulting in the east to the stable block motion of the SNGV microplate in the West. We combine GPS data from the Mobile Array of GPS for Nevada Transtension (MAGNET, http://geodesy.unr.edu/networks) with continuous observations from the EarthScope Plate Boundary Observatory to solve for rates of crustal deformation in the CWL through a block modeling approach. The GPS coordinate time series are derived in this region as part of a 7000-station global network solution using the latest JPL reanalysis of GPS orbits, and the latest antenna models for stations and satellites. The data were processed by precise point positioning using JPL's GIPSY OASIS II software followed by our custom Ambizap3 software, to produce a globally-consistent, ambiguity-resolved network solution. GPS time series in the western United States are rotated into a North America-fixed reference frame and are spatially filtered with respect to the secular motions of reference stations that demonstrate long-term secular stability. In the study region, we use 130 GPS velocities that are corrected for viscoelastic postseismic relaxation following 19th and 20th century earthquakes in the Central Nevada Seismic Belt to constrain rates of long-term fault slip and block rotation. The spatial density and precision of our velocity field (average station spacing of ~20 km with uncertainties well below 1 mm/yr) allow us to compare geodetically estimated slip rates with geologic observations as well as address specific questions about how shear is transferred from the Southern Walker Lane through the Mina Deflection and evaluate along-strike variation of the slip rate on the Sierra Nevada range front fault. Preliminary results confirm a pattern of deformation consistent with geological observations. Deformation zones are characterized by 1) left-lateral slip on east-northeast trending faults and clockwise block rotations in the Mina Deflection, 2) right-lateral slip on northwest trending faults along the eastern margin of the CWL, 3) east-west extension along north trending faults in the western portion of the CWL with right lateral slip increasing toward the SNGV microplate boundary, 4) clockwise rotation of blocks in the Carson Domain, and 5) northwest directed extension in the Basin and Range. Estimates of fault slip rates along the eastern boundary of the SNGV block find that slip is oblique with preliminary rates ranging between 0.4-0.8(±0.1) mm/yr horizontal extension and 0.9-1.5(±0.1) mm/yr right lateral.

Basic Operational Robotics Instructional System

NASA Technical Reports Server (NTRS)

Todd, Brian Keith; Fischer, James; Falgout, Jane; Schweers, John

2013-01-01

The Basic Operational Robotics Instructional System (BORIS) is a six-degree-of-freedom rotational robotic manipulator system simulation used for training of fundamental robotics concepts, with in-line shoulder, offset elbow, and offset wrist. BORIS is used to provide generic robotics training to aerospace professionals including flight crews, flight controllers, and robotics instructors. It uses forward kinematic and inverse kinematic algorithms to simulate joint and end-effector motion, combined with a multibody dynamics model, moving-object contact model, and X-Windows based graphical user interfaces, coordinated in the Trick Simulation modeling environment. The motivation for development of BORIS was the need for a generic system for basic robotics training. Before BORIS, introductory robotics training was done with either the SRMS (Shuttle Remote Manipulator System) or SSRMS (Space Station Remote Manipulator System) simulations. The unique construction of each of these systems required some specialized training that distracted students from the ideas and goals of the basic robotics instruction.

Empirical Site Amplification Factors Incorporating Soil Nonlinearity in Taiwan

NASA Astrophysics Data System (ADS)

Kuo, C. H.; Chung, C. H.; Che-Min, L.; Huang, J. Y.; Wen, K. L.

2017-12-01

Characteristics of site amplifications caused by both crustal and subduction earthquakes are important in Taiwan. For example, seismic waves were amplified and led to significant building damages in the Taipei Basin by the 1986 Hualien offshore (subduction interface) and the 1999 Chi-Chi earthquakes (crustal), for which the epicentral distances were about 100 km. To understand local site amplifications in Taiwan, empirical site amplification factors for horizontal ground motions are studied using recently constructed strong motion and site databases for the free-field TSMIP stations in Taiwan. Records of large magnitude earthquakes of ML larger than six from 1994 to 2014 were selected for this study. Site amplification factors at site conditions with Vs30 of 120 m/s to 1500 m/s and base accelerations up to 0.7g were inferred from intensity ratios of station pairs within specific distances. The reference site condition is assumed as Vs30 of 760 m/s (B/C boundary). Preliminary results indicate: 1. Soil nonlinearity is more obviously at short periods (PGA, Sa0.3) than long periods (PGV, Sa1.0). 2. Soil nonlinearity is significant for stations belong to site classes of B, C, D, and E in Taiwan. 3. Effect of station-pair distance is seen at short periods (PGA and Sa0.3). 4. No significant different is found in site amplifications of crustal and subduction earthquakes. The result could be a reference for the Fa and Fv in Taiwan's building code.

Synthesized multi-station tribo-test system for bio-tribological evaluation in vitro

NASA Astrophysics Data System (ADS)

Wu, Tonghai; Du, Ying; Li, Yang; Wang, Shuo; Zhang, Zhinan

2016-07-01

Tribological tests play an important role on the evaluation of long-term bio-tribological performances of prosthetic materials for commercial fabrication. Those tests focus on the motion simulation of a real joint in vitro with only normal loads and constant velocities, which are far from the real friction behavior of human joints characterized with variable loads and multiple directions. In order to accurately obtain the bio-tribological performances of artificial joint materials, a tribological tester with a miniature four-station tribological system is proposed with four distinctive features. Firstly, comparability and repeatability of a test are ensured by four equal stations of the tester. Secondly, cross-linked scratch between tribo-pairs of human joints can be simulated by using a gear-rack meshing mechanism to produce composite motions. With this mechanism, the friction tracks can be designed by varying reciprocating and rotating speeds. Thirdly, variable loading system is realized by using a ball-screw mechanism driven by a stepper motor, by which loads under different gaits during walking are simulated. Fourthly, dynamic friction force and normal load can be measured simultaneously. The verifications of the performances of the developed tester show that the variable frictional tracks can produce different wear debris compared with one-directional tracks, and the accuracy of loading and friction force is within ±5%. Thus the high consistency among different stations can be obtained. Practically, the proposed tester system could provide more comprehensive and accurate bio-tribological evaluations for prosthetic materials.

Salton Trough Post-seismic Afterslip, Viscoelastic Response, and Contribution to Regional Hazard

NASA Astrophysics Data System (ADS)

Parker, J. W.; Donnellan, A.; Lyzenga, G. A.

2012-12-01

The El Mayor-Cucapah M7.2 April 4 2010 earthquake in Baja California may have affected accumulated hazard to Southern California cities due to loading of regional faults including the Elsinore, San Jacinto and southern San Andreas, faults which already have over a century of tectonic loading. We examine changes observed via multiple seismic and geodetic techniques, including micro seismicity and proposed seismicity-based indicators of hazard, high-quality fault models, the Plate Boundary Observatory GNSS array (with 174 stations showing post-seismic transients with greater than 1 mm amplitude), and interferometric radar maps from UAVSAR (aircraft) flights, showing a network of aseismic fault slip events at distances up to 60 km from the end of the surface rupture. Finite element modeling is used to compute the expected coseismic motions at GPS stations with general agreement, including coseismic uplift at sites ~200 km north of the rupture. Postseismic response is also compared, with GNSS and also with the CIG software "RELAX." An initial examination of hazard is made comparing micro seismicity-based metrics, fault models, and changes to coulomb stress on nearby faults using the finite element model. Comparison of seismicity with interferograms and historic earthquakes show aseismic slip occurs on fault segments that have had earthquakes in the last 70 years, while other segments show no slip at the surface but do show high triggered seismicity. UAVSAR-based estimates of fault slip can be incorporated into the finite element model to correct Coloumb stress change.

Illuminating sesmic discontinuities with receiver functions from a dense array in Mexico City

NASA Astrophysics Data System (ADS)

Perez-Campos, X.; Rodríguez-Domínguez, M. Á.; González-López, A.; Espindola, V. H.; Quintanar, L.; Ramirez-Guzman, L.

2017-12-01

Mexico City, with close to 10 million inhabitants, has grown over a sedimentary basin, from an old dried lake. This has been a big factor in amplifying the seismic waves from large subduction earthquakes, located > 300 km away on the Pacific coast, which represents a significant hazard. For this reason, it is of great interest to improve the knowledge of the seismic structure of the city and its details on spatial variations to reduce the uncertainty in ground motion modeling. In May 2017, such array started its way in Mexico City. It consists of 18 broadband stations, that record in place for 3-5 days, moving then to a new location. In total, the city will be covered with 343 recording sites. In this work, we present preliminary results of receiver functions obtained in such array and in permanent stations of the Seismic Network of the Valley of Mexico. Despite the few teleseismic events, the small spacing between stations ( 500 m) allows identification of converted Ps phases from the Moho discontinuity, as well as other converted phases, which might be related to subtle changes in the vertical and lateral seismic structure. This Project was funded by the Secretaria de Ciencia, Tecnología e Innovación (SECITI) of Mexico City. Project SECITI/073/2016.

Present-day crustal motion along the Longitudinal Valley Fault, eastern Taiwan

NASA Astrophysics Data System (ADS)

Yu, Shui-Beih; Kuo, Long-Chen

2001-04-01

The NNE-striking Longitudinal Valley Fault (LVF) in eastern Taiwan is an extremely active high-angle thrust fault. It bounds the Coastal Range and the Longitudinal Valley, which is considered a collision boundary between the Philippine Sea and the Eurasian plates. Repeated GPS data in the Longitudinal Valley area from 1992 to 1999 are utilized to study the spatial variation of crustal motion along the LVF. With respect to Penghu in the Chinese continental margin, velocities for stations on the western side of the LVF (Longitudinal Valley and eastern Central Range) are 18-35 mm/yr in directions 283-311°, whereas those on the eastern side of the LVF, the Coastal Range, are 28-68 mm/yr in directions 303-324°. A major discontinuity of about 30 mm/yr on the rate of crustal motion across the Longitudinal Valley is attributed to the aseismic slip along the LVF as revealed by trilateration data previously. To the south of Fengping, the block motions of the Coastal Range are 31-40 mm/yr in 317-330° relative to the Central Range, while the near-fault motions are 13-33 mm/yr in 309-336°. Various partitions on the left-lateral strike-slip and convergent components along the LVF are found. In the southern Longitudinal Valley crustal motion is mainly accommodated on the LVF and the Luyeh Fault. In contrast, those in the central and northern Longitudinal Valley are partly taken up on the faults to the east of the LVF or result in the elastic deformation of the Coastal Range. The crustal motion in the northern Longitudinal Valley area is likely to be distributed in the several NE-striking thrusts in a horsetail pattern and obliquely cut the northern Coastal Range, with a small portion of fault-slips along the LVF. Data from dense-deployed GPS networks across the LVF can be employed to give better estimates of near-fault motions and delineate the surface traces of the LVF. Repeated GPS and leveling data from two stations on both ends of the Yuli Bridge that are 575 m apart clearly indicate that the surface trace of the LVF passes beneath the bridge with oblique horizontal motion of 23 mm/yr in 306° and uplift rate of 24 mm/yr.

Upper Mantle Seismic Anisotropy Beneath West Antarctica from Shear Wave Splitting Analysis of POLENET/ANET Data

NASA Astrophysics Data System (ADS)

Accardo, N.; Wiens, D. A.; Hernandez, S.; Aster, R. C.; Nyblade, A.; Anandakrishnan, S.; Huerta, A. D.; Wilson, T. J.

2011-12-01

We constrain azimuthal anisotropy in the Antarctic upper mantle using shear wave splitting parameters obtained from teleseismic SKS, SKKS, and PKS phases recorded at 30 broad-band seismometers deployed in West Antarctica, and the Transantarctic Mountains as a part of POLENET/ANET. The first seismometers were deployed in late 2007 and additional seismometers were deployed in 2008 and 2009. The seismometers generally operate year-round using solar power, insulated boxes, and either rechargeable AGM or primary lithium batteries. We used an eigenvalue technique to linearize the rotated and shifted shear wave particle motions and determine the best splitting parameters. Robust windows around the individual phases were chosen using the Teanby cluster-analysis algorithm. We visually inspected all results and assigned a quality rating based on factors including signal-to-noise ratios, particle motions, and error contours. The best results for each station were then stacked to get an average splitting direction and delay time. The delay times range from 0.33 to 1.33 s, but generally average about 1 s. We conclude that the splitting results from anisotropy in the upper mantle, since the large splitting times cannot be accumulated in the relatively thin crust (20-30 km) of the region. Overall, fast directions in West Antarctica are at large angles to the direction of Antarctic absolute plate motion in either hotspot or no-net rotation frameworks, showing that the anisotropic fabric does not result from shear associated with the motion of Antarctica over the mantle. The West Antarctic fast directions are also much different than those found in East Antarctica by previous studies. We suggest that the East Antarctic splitting results from anisotropy frozen into the cold cratonic continental lithosphere, whereas West Antarctic splitting is related to Cenozoic tectonism. Stations within the West Antarctic Rift System (WARS), a region of Cenozoic extension, show fast directions subparallel to the inferred WARS extension direction. Stations located in the Ellsworth-Whitmore Mountains (EWM) show fast directions parallel to those found within WARS. Furthermore, results from WARS and from EWM all show relatively large splitting times of 0.6 - 1.33 s. These results suggest upper mantle anisotropy that results from mantle flow and deformation related to the extensional deformation of the region. Two stations were installed in the Pensacola Mountains which are located grid-north of the EWM. The results from this region deviate from the dominant fast orientation seen in WARS but appear to be approximately perpendicular to the strike of the mountain range. Stations in Marie Byrd Land (MBL) show inconsistent fast directions and a wide range of delay times (0.3 - 0.9 s), perhaps as a result of complex mantle fabric related to a possible MBL hotspot.

Advanced relativistic VLBI model for geodesy

NASA Astrophysics Data System (ADS)

Soffel, Michael; Kopeikin, Sergei; Han, Wen-Biao

2017-07-01

Our present relativistic part of the geodetic VLBI model for Earthbound antennas is a consensus model which is considered as a standard for processing high-precision VLBI observations. It was created as a compromise between a variety of relativistic VLBI models proposed by different authors as documented in the IERS Conventions 2010. The accuracy of the consensus model is in the picosecond range for the group delay but this is not sufficient for current geodetic purposes. This paper provides a fully documented derivation of a new relativistic model having an accuracy substantially higher than one picosecond and based upon a well accepted formalism of relativistic celestial mechanics, astrometry and geodesy. Our new model fully confirms the consensus model at the picosecond level and in several respects goes to a great extent beyond it. More specifically, terms related to the acceleration of the geocenter are considered and kept in the model, the gravitational time-delay due to a massive body (planet, Sun, etc.) with arbitrary mass and spin-multipole moments is derived taking into account the motion of the body, and a new formalism for the time-delay problem of radio sources located at finite distance from VLBI stations is presented. Thus, the paper presents a substantially elaborated theoretical justification of the consensus model and its significant extension that allows researchers to make concrete estimates of the magnitude of residual terms of this model for any conceivable configuration of the source of light, massive bodies, and VLBI stations. The largest terms in the relativistic time delay which can affect the current VLBI observations are from the quadrupole and the angular momentum of the gravitating bodies that are known from the literature. These terms should be included in the new geodetic VLBI model for improving its consistency.

Current Limitations on VLBI Accuracy

NASA Technical Reports Server (NTRS)

Ma, Chopo; Gipson, John; MacMillan, Daniel

1998-01-01

The contribution of VLBI to geophysics and geodesy arises from its ability to measure distances between stations in a network and to determine the orientation of stations in the network as well as the orientation of the network with respect to the external reference frame of extragalactic radio objects. Integrating nearly two decades of observations provides useful information about station positions and velocities and the orientation of the Earth, but the complications of the real world and the limitations of observing, modeling and analysis prevent recovery of all effects. Of the factors that limit the accuracy of seemingly straightforward geodetic parameters, the neutral propagation medium has been subject to the greatest scrutiny, but the treatment of the mapping function, the wet component and spatial/temporal inhomogeneities is still improving. These affect both the terrestrial scale and consistency over time. The modeling of non-secular site motions (tides and loading) has increased in sophistication, but there are some differences between the models and the observations. VLBI antennas are massive objects, so their behavior is quite unlike GPS monuments, but antenna deformations add some (generally) unmodeled signal. Radio sources used in geodetic VLBI observations are selected for strength and (relative) absence of structure, but apparent changes in position can leak into geodetic parameters. A linear rate of change of baseline or site parameters is the simplest model and its error improves with time span. However, in most cases the VLBI data distribution is insufficient to look for real non-linear behavior that might affect the average rate. A few sites have multiple VLBI antennas, and some show small differences in rate. VLBI intrinsically measures relative positions and velocities, but individual site positions and velocities are generally more useful. The creation of the VLBI terrestrial reference frame, which transforms relative information into individual results, is an empirical process that has intrinsic errors. While UT1 is uniquely measured by VLBI, the geographical distribution and availability of VLBI stations, especially in the southern hemisphere, and the consistency of the VLBI terrestrial reference frame may limit the accuracy of Earth orientation measurements. The effects of particular error sources on geodetic and geophysical parameters derived from VLBI data will be illustrated.

Estimation of Source and Attenuation Parameters from Ground Motion Observations for Induced Seismicity in Alberta

NASA Astrophysics Data System (ADS)

Novakovic, M.; Atkinson, G. M.

2015-12-01

We use a generalized inversion to solve for site response, regional source and attenuation parameters, in order to define a region-specific ground-motion prediction equation (GMPE) from ground motion observations in Alberta, following the method of Atkinson et al. (2015 BSSA). The database is compiled from over 200 small to moderate seismic events (M 1 to 4.2) recorded at ~50 regional stations (distances from 30 to 500 km), over the last few years; almost all of the events have been identified as being induced by oil and gas activity. We remove magnitude scaling and geometric spreading functions from observed ground motions and invert for stress parameter, regional attenuation and site amplification. Resolving these parameters allows for the derivation of a regionally-calibrated GMPE that can be used to accurately predict amplitudes across the region in real time, which is useful for ground-motion-based alerting systems and traffic light protocols. The derived GMPE has further applications for the evaluation of hazards from induced seismicity.

Use of Advanced Meteorological Model Output for Coastal Ocean Modeling in Puget Sound

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Zhaoqing; Khangaonkar, Tarang; Wang, Taiping

2011-06-01

It is a great challenge to specify meteorological forcing in estuarine and coastal circulation modeling using observed data because of the lack of complete datasets. As a result of this limitation, water temperature is often not simulated in estuarine and coastal modeling, with the assumption that density-induced currents are generally dominated by salinity gradients. However, in many situations, temperature gradients could be sufficiently large to influence the baroclinic motion. In this paper, we present an approach to simulate water temperature using outputs from advanced meteorological models. This modeling approach was applied to simulate annual variations of water temperatures of Pugetmore » Sound, a fjordal estuary in the Pacific Northwest of USA. Meteorological parameters from North American Region Re-analysis (NARR) model outputs were evaluated with comparisons to observed data at real-time meteorological stations. Model results demonstrated that NARR outputs can be used to drive coastal ocean models for realistic simulations of long-term water-temperature distributions in Puget Sound. Model results indicated that the net flux from NARR can be further improved with the additional information from real-time observations.« less

Shear-wave velocity profile and seismic input derived from ambient vibration array measurements: the case study of downtown L'Aquila

NASA Astrophysics Data System (ADS)

Di Giulio, Giuseppe; Gaudiosi, Iolanda; Cara, Fabrizio; Milana, Giuliano; Tallini, Marco

2014-08-01

Downtown L'Aquila suffered severe damage (VIII-IX EMS98 intensity) during the 2009 April 6 Mw 6.3 earthquake. The city is settled on a top flat hill, with a shear-wave velocity profile characterized by a reversal of velocity at a depth of the order of 50-100 m, corresponding to the contact between calcareous breccia and lacustrine deposits. In the southern sector of downtown, a thin unit of superficial red soils causes a further shallow impedance contrast that may have influenced the damage distribution during the 2009 earthquake. In this paper, the main features of ambient seismic vibrations have been studied in the entire city centre by using array measurements. We deployed six 2-D arrays of seismic stations and 1-D array of vertical geophones. The 2-D arrays recorded ambient noise, whereas the 1-D array recorded signals produced by active sources. Surface-wave dispersion curves have been measured by array methods and have been inverted through a neighbourhood algorithm, jointly with the H/V ambient noise spectral ratios related to Rayleigh waves ellipticity. We obtained shear-wave velocity (Vs) profiles representative of the southern and northern sectors of downtown L'Aquila. The theoretical 1-D transfer functions for the estimated Vs profiles have been compared to the available empirical transfer functions computed from aftershock data analysis, revealing a general good agreement. Then, the Vs profiles have been used as input for a deconvolution analysis aimed at deriving the ground motion at bedrock level. The deconvolution has been performed by means of EERA and STRATA codes, two tools commonly employed in the geotechnical engineering community to perform equivalent-linear site response studies. The waveform at the bedrock level has been obtained deconvolving the 2009 main shock recorded at a strong motion station installed in downtown. Finally, this deconvolved waveform has been used as seismic input for evaluating synthetic time-histories in a strong-motion target site located in the middle Aterno river valley. As a target site, we selected the strong-motion station of AQV 5 km away from downtown L'Aquila. For this site, the record of the 2009 L'Aquila main shock is available and its surface stratigraphy is adequately known making possible to propagate the deconvolved bedrock motion back to the surface, and to compare recorded and synthetic waveforms.

Is Nubia plate rigid? A geodetic study of the relative motion of different cratonic areas within Africa.

NASA Astrophysics Data System (ADS)

Njoroge, M. W.; Malservisi, R.; Hugentobler, U.; Mokhtari, M.; Voytenko, D.

2014-12-01

Plate rigidity is one of the main paradigms of plate tectonics and a fundamental assumption in the definition of a global reference frame as ITRF. Although still far for optimal, the increased GPS instrumentation of the African region can allow us to understand how rigid one of the major plate can be. The presence of diffused band of seismicity, the Cameroon volcanic line, Pan African Kalahari orogenic belt and East Africa Rift suggest the possibility of relative motion among the different regions within the Nubia. The study focuses on the rigidity of Nubia plate. We divide the plate into three regions: Western (West Africa craton plus Nigeria), Central (approximately the region of the Congo craton) and Southern (Kalahari craton plus South Africa) and we utilize Euler Vector formulation to study internal rigidity and eventual relative motion. Developing five different reference frames with different combinations of the 3 regions, we try to understand the presence of the relative motion between the 3 cratons thus the stability of the Nubia plate as a whole. All available GPS stations from the regions are used separately or combined in creation of the reference frames. We utilize continuous stations with at least 2.5 years of data between 1994 and 2014. Given the small relative velocity, it is important to eliminate eventual biases in the analysis and to have a good estimation in the uncertainties of the observed velocities. For this reason we perform our analysis using both Bernese and Gipsy-oasis codes to generate time series for each station. Velocities and relative uncertainties are analyzed using the Allan variance of rate technique, taking in account for colored noise. An analysis of the color of the noise as function of latitude and climatic region is also performed to each time series. Preliminary results indicate a slight counter clockwise motion of West Africa craton with respect to South Africa Kalahari, and South Africa Kalahari-Congo Cratons. In addition, a possible counter clockwise rotation of the South African Kalahari craton with respect to the Nubian plate caused by southward propagation of the East Africa Rift is compatible with the observations. However, the results are at the limit of the statistical significance and within the current velocity uncertainties the Nubia plate appears as single- rigid plate.

Five parameters for the evaluation of the soil nonlinearity during the Ms8.0 Wenchuan Earthquake using the HVSR method

NASA Astrophysics Data System (ADS)

Ren, Yefei; Wen, Ruizhi; Yao, Xinxin; Ji, Kun

2017-08-01

The consideration of soil nonlinearity is important for the accurate estimation of the site response. To evaluate the soil nonlinearity during the 2008 Ms8.0 Wenchuan Earthquake, 33 strong-motion records obtained from the main shock and 890 records from 157 aftershocks were collected for this study. The horizontal-to-vertical spectral ratio (HVSR) method was used to calculate five parameters: the ratio of predominant frequency (RFp), degree of nonlinearity (DNL), absolute degree of nonlinearity (ADNL), frequency of nonlinearity (fNL), and percentage of nonlinearity (PNL). The purpose of this study was to evaluate the soil nonlinearity level of 33 strong-motion stations and to investigate the characteristics, performance, and effective usage of these five parameters. Their correlations with the peak ground acceleration (PGA), peak ground velocity (PGV), average uppermost 30-m shear-wave velocity ( V S30), and maximum amplitude of HVSR ( A max) were investigated. The results showed that all five parameters correlate well with PGA and PGV. The DNL, ADNL, and PNL also show a good correlation with A max, which means that the degree of soil nonlinearity not only depends on the ground-motion amplitude (e.g., PGA and PGV) but also on the site condition. The fNL correlates with PGA and PGV but shows no correlation with either A max or V S30, implying that the frequency width affected by the soil nonlinearity predominantly depends on the ground-motion amplitude rather than the site condition. At 16 of the 33 stations analyzed in this study, the site response showed evident (i.e., strong and medium) nonlinearity during the main shock of the Wenchuan Earthquake, where the ground-motion level was almost beyond the threshold of PGA > 200 cm/s2 or PGV > 15 cm/s. The site response showed weak and no nonlinearity at the other 14 and 3 stations. These results also confirm that RFp, DNL, ADNL, and PNL are effective in identifying the soil nonlinearity behavior. The identification results vary for different parameters because each parameter has individual features. The performance of the PNL was better than that of DNL and ADNL in this case study. The thresholds of ADNL and PNL are proposed to be 2.0 and 7%, respectively.[Figure not available: see fulltext.

High Attenuation Rate for Shallow, Small Earthquakes in Japan

NASA Astrophysics Data System (ADS)

Si, Hongjun; Koketsu, Kazuki; Miyake, Hiroe

2017-09-01

We compared the attenuation characteristics of peak ground accelerations (PGAs) and velocities (PGVs) of strong motion from shallow, small earthquakes that occurred in Japan with those predicted by the equations of Si and Midorikawa (J Struct Constr Eng 523:63-70, 1999). The observed PGAs and PGVs at stations far from the seismic source decayed more rapidly than the predicted ones. The same tendencies have been reported for deep, moderate, and large earthquakes, but not for shallow, moderate, and large earthquakes. This indicates that the peak values of ground motion from shallow, small earthquakes attenuate more steeply than those from shallow, moderate or large earthquakes. To investigate the reason for this difference, we numerically simulated strong ground motion for point sources of M w 4 and 6 earthquakes using a 2D finite difference method. The analyses of the synthetic waveforms suggested that the above differences are caused by surface waves, which are predominant at stations far from the seismic source for shallow, moderate earthquakes but not for shallow, small earthquakes. Thus, although loss due to reflection at the boundaries of the discontinuous Earth structure occurs in all shallow earthquakes, the apparent attenuation rate for a moderate or large earthquake is essentially the same as that of body waves propagating in a homogeneous medium due to the dominance of surface waves.

Earthquake Risk Reduction to Istanbul Natural Gas Distribution Network

NASA Astrophysics Data System (ADS)

Zulfikar, Can; Kariptas, Cagatay; Biyikoglu, Hikmet; Ozarpa, Cevat

2017-04-01

Earthquake Risk Reduction to Istanbul Natural Gas Distribution Network Istanbul Natural Gas Distribution Corporation (IGDAS) is one of the end users of the Istanbul Earthquake Early Warning (EEW) signal. IGDAS, the primary natural gas provider in Istanbul, operates an extensive system 9,867km of gas lines with 750 district regulators and 474,000 service boxes. The natural gas comes to Istanbul city borders with 70bar in 30inch diameter steel pipeline. The gas pressure is reduced to 20bar in RMS stations and distributed to district regulators inside the city. 110 of 750 district regulators are instrumented with strong motion accelerometers in order to cut gas flow during an earthquake event in the case of ground motion parameters exceeds the certain threshold levels. Also, state of-the-art protection systems automatically cut natural gas flow when breaks in the gas pipelines are detected. IGDAS uses a sophisticated SCADA (supervisory control and data acquisition) system to monitor the state-of-health of its pipeline network. This system provides real-time information about quantities related to pipeline monitoring, including input-output pressure, drawing information, positions of station and RTU (remote terminal unit) gates, slum shut mechanism status at 750 district regulator sites. IGDAS Real-time Earthquake Risk Reduction algorithm follows 4 stages as below: 1) Real-time ground motion data transmitted from 110 IGDAS and 110 KOERI (Kandilli Observatory and Earthquake Research Institute) acceleration stations to the IGDAS Scada Center and KOERI data center. 2) During an earthquake event EEW information is sent from IGDAS Scada Center to the IGDAS stations. 3) Automatic Shut-Off is applied at IGDAS district regulators, and calculated parameters are sent from stations to the IGDAS Scada Center and KOERI. 4) Integrated building and gas pipeline damage maps are prepared immediately after the earthquake event. The today's technology allows to rapidly estimate the expected level of shaking when an earthquake starts to occur. However, in Istanbul case for a potential Marmara Sea Earthquake, the time is very limited even to estimate the level of shaking. The robust threshold based EEW system is only algorithm for such a near source event to activate automatic shut-off mechanism in the critical infrastructures before the damaging waves arrive. This safety measure even with a few seconds of early warning time will help to mitigate potential damages and secondary hazards.

Motional Induction by Tsunamis and Ocean Tides: 10 Years of Progress

NASA Astrophysics Data System (ADS)

Minami, Takuto

2017-09-01

Motional induction is the process by which the motion of conductive seawater in the ambient geomagnetic main field generates electromagnetic (EM) variations, which are observable on land, at the seafloor, and sometimes at satellite altitudes. Recent years have seen notable progress in our understanding of motional induction associated with tsunamis and with ocean tides. New studies of tsunami motional induction were triggered by the 2004 Sumatra earthquake tsunami and further promoted by subsequent events, such as the 2010 Chile earthquake and the 2011 Tohoku earthquake. These events yielded observations of tsunami-generated EM variations from land and seafloor stations. Studies of magnetic fields generated by ocean tides attracted interest when the Swarm satellite constellation enabled researchers to monitor tide-generated magnetic variations from low Earth orbit. Both avenues of research benefited from the advent of sophisticated seafloor instruments, by which we may exploit motional induction for novel applications. For example, seafloor EM measurements can serve as detectors of vector properties of tsunamis, and seafloor EM data related to ocean tides have proved useful for sounding Earth's deep interior. This paper reviews and discusses the progress made in motional induction studies associated with tsunamis and ocean tides during the last decade.

Nuclear event time histories and computed site transfer functions for locations in the Los Angeles region

USGS Publications Warehouse

Rogers, A.M.; Covington, P.A.; Park, R.B.; Borcherdt, R.D.; Perkins, D.M.

1980-01-01

This report presents a collection of Nevada Test Site (NTS) nuclear explosion recordings obtained at sites in the greater Los Angeles, Calif., region. The report includes ground velocity time histories, as well as, derived site transfer functions. These data have been collected as part of a study to evaluate the validity of using low-level ground motions to predict the frequency-dependent response of a site during an earthquake. For this study 19 nuclear events were recorded at 98 separate locations. Some of these sites have recorded more than one of the nuclear explosions, and, consequently, there are a total of 159, three-component station records. The location of all the recording sites are shown in figures 1–5, the station coordinates and abbreviations are given in table 1. The station addresses are listed in table 2, and the nuclear explosions that were recorded are listed in table 3. The recording sites were chosen on the basis of three criteria: (1) that the underlying geological conditions were representative of conditions over significant areas of the region, (2) that the site was the location of a strong-motion recording of the 1971 San Fernando earthquake, or (3) that more complete geographical coverage was required in that location.

Source rupture process of the 2016 Kaikoura, New Zealand earthquake estimated from the kinematic waveform inversion of strong-motion data

NASA Astrophysics Data System (ADS)

Zheng, Ao; Wang, Mingfeng; Yu, Xiangwei; Zhang, Wenbo

2018-03-01

On 2016 November 13, an Mw 7.8 earthquake occurred in the northeast of the South Island of New Zealand near Kaikoura. The earthquake caused severe damages and great impacts on local nature and society. Referring to the tectonic environment and defined active faults, the field investigation and geodetic evidence reveal that at least 12 fault sections ruptured in the earthquake, and the focal mechanism is one of the most complicated in historical earthquakes. On account of the complexity of the source rupture, we propose a multisegment fault model based on the distribution of surface ruptures and active tectonics. We derive the source rupture process of the earthquake using the kinematic waveform inversion method with the multisegment fault model from strong-motion data of 21 stations (0.05-0.35 Hz). The inversion result suggests the rupture initiates in the epicentral area near the Humps fault, and then propagates northeastward along several faults, until the offshore Needles fault. The Mw 7.8 event is a mixture of right-lateral strike and reverse slip, and the maximum slip is approximately 19 m. The synthetic waveforms reproduce the characteristics of the observed ones well. In addition, we synthesize the coseismic offsets distribution of the ruptured region from the slips of upper subfaults in the fault model, which is roughly consistent with the surface breaks observed in the field survey.

Vulnerability of Space Station Freedom Modules: A Study of the Effects of Module Perforation on Crew and Equipment. Volume 2; Analytical Modeling of Internal Debris Cloud Effects

NASA Technical Reports Server (NTRS)

Schonberg, William P.; Davenport, Quint

1995-01-01

In this part of the report, a first-principles based model is developed to predict the overpressure and temperature effects of a perforating orbital debris particle impact within a pressurized habitable module. While the effects of a perforating debris particles on crew and equipment can be severe, only a limited number of empirical studies focusing on space vehicles have been performed to date. Traditionally, crew loss or incapacitation due to a perforating impact has primarily been of interest to military organizations and as such have focused on military vehicles and systems. The module wall considered in this study is initially assumed to be a standard Whippletype dual-wall system in which the outer wall protects the module and its inhabitants by disrupting impacting particles. The model is developed in a way such that it sequentially characterizes the phenomena comprising the impact event, including the initial impact, the creation and motion of a debris cloud within the dual-wall system, the impact of the debris cloud on the inner wall, the creation and motion of the debris cloud that enters the module interior, and the effects of the debris cloud within the module on module pressure and temperature levels. This is accomplished through the application of elementary shock physics and thermodynamic theory.

The INGV Real Time Strong Motion Database

NASA Astrophysics Data System (ADS)

Massa, Marco; D'Alema, Ezio; Mascandola, Claudia; Lovati, Sara; Scafidi, Davide; Gomez, Antonio; Carannante, Simona; Franceschina, Gianlorenzo; Mirenna, Santi; Augliera, Paolo

2017-04-01

The INGV real time strong motion data sharing is assured by the INGV Strong Motion Database. ISMD (http://ismd.mi.ingv.it) was designed in the last months of 2011 in cooperation among different INGV departments, with the aim to organize the distribution of the INGV strong-motion data using standard procedures for data acquisition and processing. The first version of the web portal was published soon after the occurrence of the 2012 Emilia (Northern Italy), Mw 6.1, seismic sequence. At that time ISMD was the first European real time web portal devoted to the engineering seismology community. After four years of successfully operation, the thousands of accelerometric waveforms collected in the archive need necessary a technological improvement of the system in order to better organize the new data archiving and to make more efficient the answer to the user requests. ISMD 2.0 was based on PostgreSQL (www.postgresql.org), an open source object- relational database. The main purpose of the web portal is to distribute few minutes after the origin time the accelerometric waveforms and related metadata of the Italian earthquakes with ML≥3.0. Data are provided both in raw SAC (counts) and automatically corrected ASCII (gal) formats. The web portal also provide, for each event, a detailed description of the ground motion parameters (i.e. Peak Ground Acceleration, Velocity and Displacement, Arias and Housner Intensities) data converted in velocity and displacement, response spectra up to 10.0 s and general maps concerning the recent and the historical seismicity of the area together with information about its seismic hazard. The focal parameters of the events are provided by the INGV National Earthquake Center (CNT, http://cnt.rm.ingv.it). Moreover, the database provides a detailed site characterization section for each strong motion station, based on geological, geomorphological and geophysical information. At present (i.e. January 2017), ISMD includes 987 (121.185 waveforms) Italian earthquakes with ML≥3.0, recorded since the 1st January 2012, besides 204 accelerometric stations belonging to the INGV strong motion network and regional partner.

Application of τc*Pd in earthquake early warning

NASA Astrophysics Data System (ADS)

Huang, Po-Lun; Lin, Ting-Li; Wu, Yih-Min

2015-03-01

Rapid assessment of damage potential and size of an earthquake at the station is highly demanded for onsite earthquake early warning. We study the application of τc*Pd for its estimation on the earthquake size using 123 events recorded by the borehole stations of KiK-net in Japan. The new type of earthquake size determined by τc*Pd is more related to the damage potential. We find that τc*Pd provides another parameter to measure the size of earthquake and the threshold to warn strong ground motion.

In-pavement fiber Bragg grating sensors for high-speed weigh-in-motion measurements

NASA Astrophysics Data System (ADS)

Al-Tarawneh, Mu'ath; Huang, Ying

2017-04-01

The demand on high-speed weigh-in-motion (WIM) measurement rises significantly in last decade to collect weight information for traffic managements especially after the introduction of weigh-station bypass programs such as Pre-Pass. In this study, a three-dimension glass fiber-reinforced polymer packaged fiber Bragg grating sensor (3D GFRP-FBG) is introduced to be embedded inside flexible pavements for weigh-in-motion (WIM) measurement at high speed. Sensitivity study showed that the developed sensor is very sensitive to the passing weights at high speed. Field tests also validated that the developed sensor was able to detect weights at a vehicle driving speed up to 55mph, which can be applied for WIM measurements at high speed.

Mantle flow through a tear in the Nazca slab inferred from shear wave splitting

NASA Astrophysics Data System (ADS)

Lynner, Colton; Anderson, Megan L.; Portner, Daniel E.; Beck, Susan L.; Gilbert, Hersh

2017-07-01

A tear in the subducting Nazca slab is located between the end of the Pampean flat slab and normally subducting oceanic lithosphere. Tomographic studies suggest mantle material flows through this opening. The best way to probe this hypothesis is through observations of seismic anisotropy, such as shear wave splitting. We examine patterns of shear wave splitting using data from two seismic deployments in Argentina that lay updip of the slab tear. We observe a simple pattern of plate-motion-parallel fast splitting directions, indicative of plate-motion-parallel mantle flow, beneath the majority of the stations. Our observed splitting contrasts previous observations to the north and south of the flat slab region. Since plate-motion-parallel splitting occurs only coincidentally with the slab tear, we propose mantle material flows through the opening resulting in Nazca plate-motion-parallel flow in both the subslab mantle and mantle wedge.

The Shuttle Mission Simulator computer generated imagery

NASA Technical Reports Server (NTRS)

Henderson, T. H.

1984-01-01

Equipment available in the primary training facility for the Space Transportation System (STS) flight crews includes the Fixed Base Simulator, the Motion Base Simulator, the Spacelab Simulator, and the Guidance and Navigation Simulator. The Shuttle Mission Simulator (SMS) consists of the Fixed Base Simulator and the Motion Base Simulator. The SMS utilizes four visual Computer Generated Image (CGI) systems. The Motion Base Simulator has a forward crew station with six-degrees of freedom motion simulation. Operation of the Spacelab Simulator is planned for the spring of 1983. The Guidance and Navigation Simulator went into operation in 1982. Aspects of orbital visual simulation are discussed, taking into account the earth scene, payload simulation, the generation and display of 1079 stars, the simulation of sun glare, and Reaction Control System jet firing plumes. Attention is also given to landing site visual simulation, and night launch and landing simulation.

Accuracy of velocities from repeated GPS surveys: relative positioning is concerned

NASA Astrophysics Data System (ADS)

Duman, Huseyin; Ugur Sanli, D.

2016-04-01

Over more than a decade, researchers have been interested in studying the accuracy of GPS positioning solutions. Recently, reporting the accuracy of GPS velocities has been added to this. Researchers studying landslide motion, tectonic motion, uplift, sea level rise, and subsidence still report results from GPS experiments in which repeated GPS measurements from short sessions are used. This motivated some other researchers to study the accuracy of GPS deformation rates/velocities from various repeated GPS surveys. In one of the efforts, the velocity accuracy was derived from repeated GPS static surveys using short observation sessions and Precise Point Positioning mode of GPS software. Velocities from short GPS sessions were compared with the velocities from 24 h sessions. The accuracy of velocities was obtained using statistical hypothesis testing and quantifying the accuracy of least squares estimation models. The results reveal that 45-60 % of the horizontal and none of the vertical solutions comply with the results from 24 h solutions. We argue that this case in which the data was evaluated using PPP should also apply to the case in which the data belonging to long GPS base lengths is processed using fundamental relative point positioning. To test this idea we chose the two IGS stations ANKR and NICO and derive their velocities from the reference stations held fixed in the stable EURASIAN plate. The University of Bern's GNSS software BERNESE was used to produce relative positioning solutions, and the results are compared with those of GIPSY/OASIS II PPP results. First impressions indicate that it is worth designing a global experiment and test these ideas in detail.

Using Magnetics and Topography to Model Fault Splays of the Hilton Creek Fault System within the Long Valley Caldera

NASA Astrophysics Data System (ADS)

De Cristofaro, J. L.; Polet, J.

2017-12-01

The Hilton Creek Fault (HCF) is a range-bounding extensional fault that forms the eastern escarpment of California's Sierra Nevada mountain range, near the town of Mammoth Lakes. The fault is well mapped along its main trace to the south of the Long Valley Caldera (LVC), but the location and nature of its northern terminus is poorly constrained. The fault terminates as a series of left-stepping splays within the LVC, an area of active volcanism that most notably erupted 760 ka, and currently experiences continuous geothermal activity and sporadic earthquake swarms. The timing of the most recent motion on these fault splays is debated, as is the threat posed by this section of the Hilton Creek Fault. The Third Uniform California Earthquake Rupture Forecast (UCERF3) model depicts the HCF as a single strand projecting up to 12km into the LVC. However, Bailey (1989) and Hill and Montgomery-Brown (2015) have argued against this model, suggesting that extensional faulting within the Caldera has been accommodated by the ongoing volcanic uplift and thus the intracaldera section of the HCF has not experienced motion since 760ka.We intend to map the intracaldera fault splays and model their subsurface characteristics to better assess their rupture history and potential. This will be accomplished using high-resolution topography and subsurface geophysical methods, including ground-based magnetics. Preliminary work was performed using high-precision Nikon Nivo 5.C total stations to generate elevation profiles and a backpack mounted GEM GS-19 proton precession magnetometer. The initial results reveal a correlation between magnetic anomalies and topography. East-West topographic profiles show terrace-like steps, sub-meter in height, which correlate to changes in the magnetic data. Continued study of the magnetic data using Oasis Montaj 3D modeling software is planned. Additionally, we intend to prepare a high-resolution terrain model using structure-from-motion techniques derived from imagery acquired by an unmanned aerial vehicle and ground control points measured with realtime kinematic GPS receivers. This terrain model will be combined with subsurface geophysical data to form a comprehensive model of the subsurface.

Observations of seismicity and ground motion in the northeast U.S. Atlantic margin from ocean bottom seismometer data

USGS Publications Warehouse

Flores, Claudia; ten Brink, Uri S.; McGuire, Jeffrey J.; Collins, John A.

2017-01-01

Earthquake data from two short-period ocean-bottom seismometer (OBS) networks deployed for over a year on the continental slope off New York and southern New England were used to evaluate seismicity and ground motions along the continental margin. Our OBS networks located only one earthquake of Mc∼1.5 near the shelf edge during six months of recording, suggesting that seismic activity (MLg>3.0) of the margin as far as 150–200 km offshore is probably successfully monitored by land stations without the need for OBS deployments. The spectral acceleration from two local earthquakes recorded by the OBS was found to be generally similar to the acceleration from these earthquakes recorded at several seismic stations on land and to hybrid empirical acceleration relationships for eastern North America. Therefore, the seismic attenuation used for eastern North America can be extended in this region at least to the continental slope. However, additional offshore studies are needed to verify these preliminary conclusions.

Influence of wind turbines on seismic stations in the upper rhine graben, SW Germany

NASA Astrophysics Data System (ADS)

Zieger, Toni; Ritter, Joachim R. R.

2018-01-01

By analysing long- and short-term seismological measurements at wind farms close to the town of Landau, SW Germany, we present new insights into ground motion signals from wind turbines (WTs) at local seismic stations. Because of their need to be located in similar regions with sparsely anthropogenic activities, wind turbines impact seismic stations and their recordings in a way that is not yet fully understood by researchers. To ensure the undisturbed recording tasks of a regional seismic array or a single station by a protected area around those endangered stations, it is very important to investigate the behavior of WTs as a seismic source. For that reason, we calculate averaged one-hour long spectra of the power spectral density (PSD) before and after the installation of a new wind farm within the investigated area. These PSD are ordered according to the rotation speed. We observe a clear increase of the PSD level after the WT installation in a frequency range of 0.5 to 10 Hz up to a distance of 5.5 km away from the WT. By analysing seismic borehole data, we also observe a decrease of the PSD of wind dependent signals with depth. The impact of wind-dependent signals is found to be much more pronounced for the shallower station (150 m depth) than for the deeper one (305 m depth). Using short-term profile measurements, we fit a power-law decay proportional to 1/ r b to the main WT-induced PSD peaks and differentiate between near-field and far-field effects of ground motions. For low frequencies in the range from 1 to 4 Hz, we determine a b value of 0.78 to 0.85 for the far field, which is consistent with surface waves. The b value increases (up to 1.59) with increasing frequencies (up to 5.5 Hz), which is obviously due to attenuating effects like scattering or anelasticity. These results give a better understanding of the seismic wavefield interactions between wind turbines (or wind farms) with nearby seismic stations, including borehole installations, in a sedimentary setting.