Automatic recognition of seismic intensity based on RS and GIS: a case study in Wenchuan Ms8.0 earthquake of China.

PubMed

Zhang, Qiuwen; Zhang, Yan; Yang, Xiaohong; Su, Bin

2014-01-01

In recent years, earthquakes have frequently occurred all over the world, which caused huge casualties and economic losses. It is very necessary and urgent to obtain the seismic intensity map timely so as to master the distribution of the disaster and provide supports for quick earthquake relief. Compared with traditional methods of drawing seismic intensity map, which require many investigations in the field of earthquake area or are too dependent on the empirical formulas, spatial information technologies such as Remote Sensing (RS) and Geographical Information System (GIS) can provide fast and economical way to automatically recognize the seismic intensity. With the integrated application of RS and GIS, this paper proposes a RS/GIS-based approach for automatic recognition of seismic intensity, in which RS is used to retrieve and extract the information on damages caused by earthquake, and GIS is applied to manage and display the data of seismic intensity. The case study in Wenchuan Ms8.0 earthquake in China shows that the information on seismic intensity can be automatically extracted from remotely sensed images as quickly as possible after earthquake occurrence, and the Digital Intensity Model (DIM) can be used to visually query and display the distribution of seismic intensity.

Japan Meteorological Agency/Meteorological Research Institute-Coupled Prediction System version 2 (JMA/MRI-CPS2): atmosphere-land-ocean-sea ice coupled prediction system for operational seasonal forecasting

NASA Astrophysics Data System (ADS)

Takaya, Yuhei; Hirahara, Shoji; Yasuda, Tamaki; Matsueda, Satoko; Toyoda, Takahiro; Fujii, Yosuke; Sugimoto, Hiroyuki; Matsukawa, Chihiro; Ishikawa, Ichiro; Mori, Hirotoshi; Nagasawa, Ryoji; Kubo, Yutaro; Adachi, Noriyuki; Yamanaka, Goro; Kuragano, Tsurane; Shimpo, Akihiko; Maeda, Shuhei; Ose, Tomoaki

2018-02-01

This paper describes the Japan Meteorological Agency/Meteorological Research Institute-Coupled Prediction System version 2 (JMA/MRI-CPS2), which was put into operation in June 2015 for the purpose of performing seasonal predictions. JMA/MRI-CPS2 has various upgrades from its predecessor, JMA/MRI-CPS1, including improved resolution and physics in its atmospheric and oceanic components, introduction of an interactive sea-ice model and realistic initialization of its land component. Verification of extensive re-forecasts covering a 30-year period (1981-2010) demonstrates that JMA/MRI-CPS2 possesses improved seasonal predictive skills for both atmospheric and oceanic interannual variability as well as key coupled variability such as the El Niño-Southern Oscillation (ENSO). For ENSO prediction, the new system better represents the forecast uncertainty and transition/duration of ENSO phases. Our analysis suggests that the enhanced predictive skills are attributable to incremental improvements resulting from all of the changes, as is apparent in the beneficial effects of sea-ice coupling and land initialization on 2-m temperature predictions. JMA/MRI-CPS2 is capable of reasonably representing the seasonal cycle and secular trends of sea ice. The sea-ice coupling remarkably enhances the predictive capability for the Arctic 2-m temperature, indicating the importance of this factor, particularly for seasonal predictions in the Arctic region.

Do French macroseismic intensity observations agree with expectations from the European Seismic Hazard Model 2013?

NASA Astrophysics Data System (ADS)

Rey, Julien; Beauval, Céline; Douglas, John

2018-02-01

Probabilistic seismic hazard assessments are the basis of modern seismic design codes. To test fully a seismic hazard curve at the return periods of interest for engineering would require many thousands of years' worth of ground-motion recordings. Because strong-motion networks are often only a few decades old (e.g. in mainland France the first accelerometric network dates from the mid-1990s), data from such sensors can be used to test hazard estimates only at very short return periods. In this article, several hundreds of years of macroseismic intensity observations for mainland France are interpolated using a robust kriging-with-a-trend technique to establish the earthquake history of every French mainland municipality. At 24 selected cities representative of the French seismic context, the number of exceedances of intensities IV, V and VI is determined over time windows considered complete. After converting these intensities to peak ground accelerations using the global conversion equation of Caprio et al. (Ground motion to intensity conversion equations (GMICEs): a global relationship and evaluation of regional dependency, Bulletin of the Seismological Society of America 105:1476-1490, 2015), these exceedances are compared with those predicted by the European Seismic Hazard Model 2013 (ESHM13). In half of the cities, the number of observed exceedances for low intensities (IV and V) is within the range of predictions of ESHM13. In the other half of the cities, the number of observed exceedances is higher than the predictions of ESHM13. For intensity VI, the match is closer, but the comparison is less meaningful due to a scarcity of data. According to this study, the ESHM13 underestimates hazard in roughly half of France, even when taking into account the uncertainty in the conversion from intensity to acceleration. However, these results are valid only for the acceleration range tested in this study (0.01 to 0.09 g).

Do French macroseismic intensity observations agree with expectations from the European Seismic Hazard Model 2013?

NASA Astrophysics Data System (ADS)

Rey, Julien; Beauval, Céline; Douglas, John

2018-05-01

Probabilistic seismic hazard assessments are the basis of modern seismic design codes. To test fully a seismic hazard curve at the return periods of interest for engineering would require many thousands of years' worth of ground-motion recordings. Because strong-motion networks are often only a few decades old (e.g. in mainland France the first accelerometric network dates from the mid-1990s), data from such sensors can be used to test hazard estimates only at very short return periods. In this article, several hundreds of years of macroseismic intensity observations for mainland France are interpolated using a robust kriging-with-a-trend technique to establish the earthquake history of every French mainland municipality. At 24 selected cities representative of the French seismic context, the number of exceedances of intensities IV, V and VI is determined over time windows considered complete. After converting these intensities to peak ground accelerations using the global conversion equation of Caprio et al. (Ground motion to intensity conversion equations (GMICEs): a global relationship and evaluation of regional dependency, Bulletin of the Seismological Society of America 105:1476-1490, 2015), these exceedances are compared with those predicted by the European Seismic Hazard Model 2013 (ESHM13). In half of the cities, the number of observed exceedances for low intensities (IV and V) is within the range of predictions of ESHM13. In the other half of the cities, the number of observed exceedances is higher than the predictions of ESHM13. For intensity VI, the match is closer, but the comparison is less meaningful due to a scarcity of data. According to this study, the ESHM13 underestimates hazard in roughly half of France, even when taking into account the uncertainty in the conversion from intensity to acceleration. However, these results are valid only for the acceleration range tested in this study (0.01 to 0.09 g).

Development of Spaceborne Radar Simulator by NICT and JAXA using JMA Cloud-resolving Model

NASA Astrophysics Data System (ADS)

Kubota, T.; Eito, H.; Aonashi, K.; Hashimoto, A.; Iguchi, T.; Hanado, H.; Shimizu, S.; Yoshida, N.; Oki, R.

2009-12-01

We are developing synthetic spaceborne radar data toward a simulation of the Dual-frequency Precipitation Radar (DPR) aboard the Global Precipitation Measurement (GPM) core-satellite. Our purposes are a production of test-bed data for higher level DPR algorithm developers, in addition to a diagnosis of a cloud resolving model (CRM). To make the synthetic data, we utilize the CRM by the Japan Meteorological Agency (JMA-NHM) (Ikawa and Saito 1991, Saito et al. 2006, 2007), and the spaceborne radar simulation algorithm by the National Institute of Information and Communications Technology (NICT) and the Japan Aerospace Exploration Agency (JAXA) named as the Integrated Satellite Observation Simulator for Radar (ISOSIM-Radar). The ISOSIM-Radar simulates received power data in a field of view of the spaceborne radar with consideration to a scan angle of the radar (Oouchi et al. 2002, Kubota et al. 2009). The received power data are computed with gaseous and hydrometeor attenuations taken into account. The backscattering and extinction coefficients are calculated assuming the Mie approximation for all species. The dielectric constants for solid particles are computed by the Maxwell-Garnett model (Bohren and Battan 1982). Drop size distributions are treated in accordance with those of the JMA-NHM. We assume a spherical sea surface, a Gaussian antenna pattern, and 49 antenna beam directions for scan angles from -17 to 17 deg. in the PR. In this study, we report the diagnosis of the JMA-NHM with reference to the TRMM Precipitation Radar (PR) and CloudSat Cloud Profiling Radar (CPR) using the ISOSIM-Radar from the view of comparisons in cloud microphysics schemes of the JMA-NHM. We tested three kinds of explicit bulk microphysics schemes based on Lin et al. (1983), that is, three-ice 1-moment scheme, three-ice 2-moment scheme (Eito and Aonashi 2009), and newly developed four-ice full 2-moment scheme (Hashimoto 2008). The hydrometeor species considered here are rain, graupel

Seismic belt in the upper plane of the double seismic zone extending in the along-arc direction at depths of 70-100km beneath NE Japan, and its relation with the dehydration embrittlement hypothesis

NASA Astrophysics Data System (ADS)

Kita, S.; Okada, T.; Nakajima, J.; Matsuzawa, T.; Hasegawa, A.

2006-12-01

1. Introduction Dehydration embrittlement or CO2¨Cbearing devolatization embrittlement hypothesis has been proposed as a possible cause of intraslab earthquakes in several studies [e.g., Peacock, 2001; Kirby et al., 1996; Meade and Jeanloz, 1991]. Precise location of intraslab seismicity is needed to discuss its cause in these studies. Recently, a very dense nationwide seismic network (Hi-net) has been constructed by NIED in Japan. In this study, we relocate microearthquakes more precisely by using data obtained by this dense seismic network to detect the characteristic distribution of the seismicity within the Pacific slab beneath Hokkaido and Tohoku, NE Japan. 2. Data and method In the present study, we relocated events at depths of 20¨C300 km for the period from January 2002 to August 2005 from the JMA earthquake catalog. Hypocenter locations and arrival time data in the JMA catalog were used as the initial hypocenters and data for relocations. We applied the double-difference hypocenter location method (DDLM) by Waldhauser and Ellsworth (2000) to the arrival time data of the events. We also checked spatial distribution of the focal mechanisms of the events in the seismic belts and the surrounding upper seismic plane. We used focal mechanism solutions determined by Igarashi et al. (2001). 3. Results and discussion 1) There exist earthquakes occurring in the area between the upper and lower seismic planes (interplane earthquakes), and their focal mechanisms tend to be the down-dip compressional (DC-) type like those of upper plane events. 2) We found a seismic "belt" which is parallel to the iso-depth contour of the plate interface beneath the forearc area at depths of 80¨C100 km. The location of the seismic belt seems to correspond to one phase boundary (from jadeite lawsonite blueschist (H2O content: 5.4 wt% ) to lawsonite amphibole eclogite (3.0wt %) (Hacker et al., 2003)) with dehydration reaction. 3) The location of the deeper limit of seismicity of the

Data-Intensive Discovery Methods for Seismic Monitoring

NASA Astrophysics Data System (ADS)

Richards, P. G.; Schaff, D. P.; Ammon, C. J.; Cleveland, M.; Young, C. J.; Slinkard, M.; Heck, S.

2012-12-01

Seismic events are still mostly located one-at-a-time by Geiger's method of 1909, which uses phase picks and minimizes differences between observed and modeled travel times. But methods that recognize and use seismogram archives as a major resource have been successfully demonstrated---especially for California, China, and for the mid-ocean ridge-transform system---where they enable new insights into earthquake physics and Earth structure, and have raised seismic monitoring to new levels. We report progress on a series of collaborative projects to evaluate such data-intensive methods on ever-larger scales. We use cross correlation (CC): (1) to improve estimates of the relative size of neighboring seismic events in regions of high seismicity; and (2) as a detector, to find new events in current data streams that are similar to events already in the archive, to add to the number of detections of an already known event, or to place a threshold on the size of undetected events occurring near a template event. Elsewhere at this meeting Schaff and Richards report on uses of non-normalized CC measurements to estimate relative event size---a procedure that may be as important as widely-used CC methods to improve the precision of relative location estimates. They have successfully modeled the degradation in CC value that is due to the spatial separation of similar events and can prevent this bias from seriously influencing estimates of relative event size for non-collocated events. Cleveland and Ammon report in more detail on cross-correlation used to measure Rayleigh-wave time shifts, and on improved epicentroid locations and relative origin-time shifts in remote oceanic transform regions. They seek to extend the correlation of R1 waveforms from vertical strike-slip transform-fault earthquakes with waveforms from normal faulting events at nearby ridges, to improve the locations of events offshore from the Pacific northwest and southwestern China. Finally our collaborating

Renewal of K-NET (National Strong-motion Observation Network of Japan)

NASA Astrophysics Data System (ADS)

Kunugi, T.; Fujiwara, H.; Aoi, S.; Adachi, S.

2004-12-01

The National Research Institute for Earth Science and Disaster Prevention (NIED) operates K-NET (Kyoshin Network), the national strong-motion observation network, which evenly covers the whole of Japan at intervals of 25 km on average. K-NET was constructed after the Hyogoken-Nambu (Kobe) earthquake in January 1995, and began operation in June 1996. Thus, eight years have passed since K-NET started, and large amounts of strong-motion records have been obtained. As technology has progressed and new technologies have become available, NIED has developed a new K-NET with improved functionality. New seismographs have been installed at 443 observatories mainly in southwestern Japan where there is a risk of strong-motion due to the Nankai and Tonankai earthquakes. The new system went into operation in June 2004, although seismographs have still to be replaced in other areas. The new seismograph (K-NET02) consists of a sensor module, a measurement module and a communication module. A UPS, a GPS antenna and a dial-up router are also installed together with a K-NET02. A triaxial accelerometer, FBA-ES-DECK (Kinemetrics Inc.) is built into the sensor module. The measurement module functions as a conventional strong-motion seismograph for high-precision observation. The communication module can perform sophisticated processes, such as calculation of the Japan Meteorological Agency (JMA) seismic intensity, continuous recording of data and near real-time data transmission. It connects to the Data Management Center (DMC) using an ISDN line. In case of a power failure, the measurement module can control the power supply to the router and the communication module to conserve battery power. One of the main features of K-NET02 is a function for processing JMA seismic intensity. K-NET02 functions as a proper seismic intensity meter that complies with the official requirements of JMA, although the old strong-motion seismograph (K-NET95) does not calculate seismic intensity. Another

Seismic intensity monitoring: from mature basins in the North Sea to sample-scale porosity measurements.

NASA Astrophysics Data System (ADS)

De Siena, Luca; Sketsiou, Panayiota

2017-04-01

We plan the application of a joint velocity, attenuation, and scattering tomography to the North Sea basins. By using seismic phases and intensities from previous passive and active surveys our aim is to image and monitor fluids under the subsurface. Seismic intensities provide unique solutions to the problem of locating/tracking gas/fluid movements in the volcanoes and depicting sub-basalt and sub-intrusives in volcanic reservoirs. The proposed techniques have been tested in volcanic Islands (Deception Island), continental calderas (Campi Flegrei) and Quaternary Volcanoes (Mount. St. Helens) and have been proved effective at monitoring fracture opening, imaging buried fluid-filled bodies, and tracking water/gas interfaces. These novel seismic attributes are modelled in space and time and connected with the lithology of the sampled medium, specifically density and permeability, with as key output a novel computational code with strong commercial potential. Data are readily available in the framework of the NERC CDT Oil & Gas project.

Probabilistic seismic demand analysis using advanced ground motion intensity measures

USGS Publications Warehouse

Tothong, P.; Luco, N.

2007-01-01

One of the objectives in performance-based earthquake engineering is to quantify the seismic reliability of a structure at a site. For that purpose, probabilistic seismic demand analysis (PSDA) is used as a tool to estimate the mean annual frequency of exceeding a specified value of a structural demand parameter (e.g. interstorey drift). This paper compares and contrasts the use, in PSDA, of certain advanced scalar versus vector and conventional scalar ground motion intensity measures (IMs). One of the benefits of using a well-chosen IM is that more accurate evaluations of seismic performance are achieved without the need to perform detailed ground motion record selection for the nonlinear dynamic structural analyses involved in PSDA (e.g. record selection with respect to seismic parameters such as earthquake magnitude, source-to-site distance, and ground motion epsilon). For structural demands that are dominated by a first mode of vibration, using inelastic spectral displacement (Sdi) can be advantageous relative to the conventionally used elastic spectral acceleration (Sa) and the vector IM consisting of Sa and epsilon (??). This paper demonstrates that this is true for ordinary and for near-source pulse-like earthquake records. The latter ground motions cannot be adequately characterized by either Sa alone or the vector of Sa and ??. For structural demands with significant higher-mode contributions (under either of the two types of ground motions), even Sdi (alone) is not sufficient, so an advanced scalar IM that additionally incorporates higher modes is used.

Forecasting probabilistic seismic shaking for greater Tokyo from 400 years of intensity observations

USGS Publications Warehouse

Bozkurt, S.B.; Stein, R.S.; Toda, S.

2007-01-01

The long recorded history of earthquakes in Japan affords an opportunity to forecast seismic shaking exclusively from past shaking. We calculate the time-averaged (Poisson) probability of severe shaking by using more than 10,000 intensity observations recorded since AD 1600 in a 350 km-wide box centered on Tokyo. Unlike other hazard-assessment methods, source and site effects are included without modeling, and we do not need to know the size or location of any earthquake nor the location and slip rate of any fault. The two key assumptions are that the slope of the observed frequency-intensity relation at every site is the same, and that the 400-year record is long enough to encompass the full range of seismic behavior. Tests we conduct here suggest that both assumptions are sound. The resulting 30-year probability of IJMA ??? 6 shaking (??? PGA ??? 0.4 g or MMI ??? IX) is 30%-40% in Tokyo, Kawasaki, and Yokohama, and 10% 15% in Chiba and Tsukuba. This result means that there is a 30% chance that 4 million people will be subjected to IJMA ??? 6 shaking during an average 30-year period. We also produce exceedance maps of PGA for building-code regulations, and calculate short-term hazard associated with a hypothetical catastrophe bond. Our results resemble an independent assessment developed from conventional seismic hazard analysis for greater Tokyo. ?? 2007, Earthquake Engineering Research Institute.

Examination of the site amplification factor of OBS and their application to magnitude estimation and ground-motion prediction for EEW

NASA Astrophysics Data System (ADS)

Hayashimoto, N.; Hoshiba, M.

2013-12-01

1. Introduction Ocean bottom seismograph (OBS) is useful for making Earthquake Early Warning (EEW) earlier. However, careful handling of these data is required because the installation environment of OBSs may be different from that of land stations. Site amplification factor is an important factor to estimate the magnitudes, and to predict ground motions (e.g. seismic intensity) in EEW. In this presentation, we discuss the site amplification factor of OBS in the Tonankai area of Japan from these two points of view. 2. Examination of magnitude correction of OBS In the EEW of JMA, the magnitude is estimated from the maximum amplitude of the displacement in real time. To provide the fast magnitude estimation, the magnitude-estimation algorithm switches from the P to S formula (Meew(P) to Meew(S)) depending on the expected S-phase arrival (Kamigaichi,2004). To estimate the magnitude correction for OBS, we determine Meew(P) and Meew(S) at OBSs and compare them with JMA magnitude (Mjma). We find Meew(S) at OBS is generally larger than Mjma by approximately 0.6. The slight differences of spatial distribution of Meew(S) amplification are also found among other OBSs. From the numerical simulations, Nakamura et al. (MGR,submitted) pointed out that the oceanic layer and the low-velocity sediment layers causes the large amplifications in low frequency range (0.1-0.2Hz) at OBSs. We conclude that the site effect of OBS characterized by such a low velocity sediment layers causes those amplification of Magnitude. 3. The frequency-dependent site factor of OBS estimated from Fourier spectrum ratio and their application for prediction of seismic intensity of land station We compare Fourier spectra of S-wave portion on OBSs with those on adjacent land stations. Station pair whose distance is smaller than 50 km is analyzed, and we obtain that spectral ratio of land station (MIEH05 of the KiK-net/NIED) to OBS (KMA01 of the DONET/JAMSTEC) is 5-20 for frequencies 10-20Hz for both

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.

Performance of Real-time Earthquake Information System in Japan

NASA Astrophysics Data System (ADS)

Nakamura, H.; Horiuchi, S.; Wu, C.; Yamamoto, S.

2008-12-01

on regions and tends to increase when earthquakes occurred outward the network. Depth differences for 70 percent of events are less than 20km and original time differences for 48 percent within one second. In addition to JMA magnitude (MJMA), which is estimated from moment magnitude, REIS estimates a new scaling parameter called intensity magnitude (MI), which is defined from observed P wave seismic intensity (Yamamoto et al., 2008). Our statistical results show that these two kinds of magnitudes are reasonably determined. Either MJMA or MI by REIS for 94 percent of events has differences less than 1.0 compared with reported JMA catalog. However, the difference increases with values of the magnitude. There is an apparent underestimation of MJMA for large earthquakes because the first report is issued when the rupture is still undergoing. Moreover, there are cases when most of Hi-net seismograms close to epicenter are clipped, but still these data are used for the determination of the lower limit of magnitude. We are making an EEWS using real-time strong motion network data for the better estimate of earthquake magnitude and seismic intensity.

On the use of remote infrasound and seismic stations to constrain the eruptive sequence and intensity for the 2014 Kelud eruption

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

Caudron, Corentin; Taisne, Benoit; Garces, Milton

The February 2014 eruption of Kelud volcano (Indonesia) destroyed most of the instruments near it. We use remote seismic and infrasound sensors to reconstruct the eruptive sequence. The first explosions were relatively weak seismic and infrasound events. A major stratospheric ash injection occurred a few minutes later and produced long-lasting atmospheric and ground-coupled acoustic waves that were detected as far as 11,000 km by infrasound sensors and up to 2300 km away on seismometers. A seismic event followed ~12 minutes later and was recorded 7000 km away by seismometers. We estimate a volcanic intensity around 10.9, placing the 2014 Keludmore » eruption between the 1980 Mount St. Helens and 1991 Pinatubo eruptions intensities. As a result, we demonstrate how remote infrasound and seismic sensors are critical for the early detection of volcanic explosions, and how they can help to constrain and understand eruptive sequences.« less

On the use of remote infrasound and seismic stations to constrain the eruptive sequence and intensity for the 2014 Kelud eruption

DOE PAGES

Caudron, Corentin; Taisne, Benoit; Garces, Milton; ...

2015-07-14

The February 2014 eruption of Kelud volcano (Indonesia) destroyed most of the instruments near it. We use remote seismic and infrasound sensors to reconstruct the eruptive sequence. The first explosions were relatively weak seismic and infrasound events. A major stratospheric ash injection occurred a few minutes later and produced long-lasting atmospheric and ground-coupled acoustic waves that were detected as far as 11,000 km by infrasound sensors and up to 2300 km away on seismometers. A seismic event followed ~12 minutes later and was recorded 7000 km away by seismometers. We estimate a volcanic intensity around 10.9, placing the 2014 Keludmore » eruption between the 1980 Mount St. Helens and 1991 Pinatubo eruptions intensities. As a result, we demonstrate how remote infrasound and seismic sensors are critical for the early detection of volcanic explosions, and how they can help to constrain and understand eruptive sequences.« less

JMA's regional atmospheric transport model calculations for the WMO technical task team on meteorological analyses for Fukushima Daiichi Nuclear Power Plant accident.

PubMed

Saito, Kazuo; Shimbori, Toshiki; Draxler, Roland

2015-01-01

The World Meteorological Organization (WMO) convened a small technical task team of experts to produce a set of meteorological analyses to drive atmospheric transport, dispersion and deposition models (ATDMs) for the United Nations Scientific Committee on the Effects of Atomic Radiation's assessment of the Fukushima Daiichi Nuclear Power Plant (DNPP) accident. The Japan Meteorological Agency (JMA) collaborated with the WMO task team as the regional specialized meteorological center of the country where the accident occurred, and provided its operational 5-km resolution mesoscale (MESO) analysis and its 1-km resolution radar/rain gauge-analyzed precipitation (RAP) data. The JMA's mesoscale tracer transport model was modified to a regional ATDM for radionuclides (RATM), which included newly implemented algorithms for dry deposition, wet scavenging, and gravitational settling of radionuclide aerosol particles. Preliminary and revised calculations of the JMA-RATM were conducted according to the task team's protocol. Verification against Cesium 137 ((137)Cs) deposition measurements and observed air concentration time series showed that the performance of RATM with MESO data was significantly improved by the revisions to the model. The use of RAP data improved the (137)Cs deposition pattern but not the time series of air concentrations at Tokai-mura compared with calculations just using the MESO data. Sensitivity tests of some of the more uncertain parameters were conducted to determine their impacts on ATDM calculations, and the dispersion and deposition of radionuclides on 15 March 2011, the period of some of the largest emissions and deposition to the land areas of Japan. The area with high deposition in the northwest of Fukushima DNPP and the hotspot in the central part of Fukushima prefecture were primarily formed by wet scavenging influenced by the orographic effect of the mountainous area in the west of the Fukushima prefecture. Copyright © 2014 The Authors

Development of an event search and download system for analyzing waveform data observed at seafloor seismic network, DONET

NASA Astrophysics Data System (ADS)

Takaesu, M.; Horikawa, H.; Sueki, K.; Kamiya, S.; Nakamura, T.; Nakano, M.; Takahashi, N.; Sonoda, A.; Tsuboi, S.

2014-12-01

Mega-thrust earthquakes are anticipated to occur in the Nankai Trough in southwest Japan. In the source areas, we installed seafloor seismic network, DONET (Dense Ocean-floor Network System for Earthquake and Tsunamis), in 2010 in order to monitor seismicity, crustal deformations, and tsunamis. DONET system consists of totally 20 stations, which is composed of six kinds of sensors; strong-motion and broadband seismometers, quartz and differential pressure gauges, hydrophone, and thermometer. The stations are densely distributed with an average spatial interval of 15-20 km and cover near coastal areas to the trench axis. Observed data are transferred to a land station through a fiber-optical cable and then to JAMSTEC (Japan Agency for Marine-Earth Science and Technology) data management center through a private network in real time. The data are based on WIN32 format in the private network and finally archived in SEED format in the management center to combine waveform data with related metadata. We are developing a web-based application system to easily download seismic waveform data of DONET. In this system, users can select 20 Hz broadband (BH type) and 200 Hz strong-motion (EH type) data and download them in SEED. Users can also search events from the options of time periods, magnitude, source area and depth in a GUI platform. Event data are produced referring to event catalogues from USGS and JMA (Japan Meteorological Agency). The thresholds of magnitudes for the production are M6 for far-field and M4 for local events using the USGS and JMA lists, respectively. Available data lengths depend on magnitudes and epicentral distances. In this presentation, we briefly introduce DONET stations and then show our developed application system. We open DONET data through the system and want them to be widely recognized so that many users analyze. We also discuss next plans for further developments of the system.

Pole tide triggering of seismicity

NASA Astrophysics Data System (ADS)

Gorshkov, V.

2015-08-01

The influence of the pole tide (PT) on intensity of seismic process is searched on base of Harvard Centroid-moment tensors catalogue (CMT). The normal and shear stresses excited by PT were calculated for each earthquake (EQ) from CMT (32.3 thousands of EQ events after for- and aftershock declustering). There was revealed that there are two maxima of PT influence on weak (less 5.5 magnitudes) thrust-slip EQ near the both extrema (min and max) of shear stress. This influence has 95 % level of statistical significance by Schuster and χ^2 criteria and could explain the 0.6-year periodicity in seismic intensity spectrum. The PT influence on seismicity becomes negligible when PT variations decrease up to 100~mas. This could explain 6-7 years periodicity in seismic intensity spectrum.

Extending the life of mature basins in the North Sea and imaging sub-basalt and sub-intrusive structures using seismic intensity monitoring.

NASA Astrophysics Data System (ADS)

De Siena, Luca; Rawlinson, Nicholas

2016-04-01

Non-standard seismic imaging (velocity, attenuation, and scattering tomography) of the North Sea basins by using unexploited seismic intensities from previous passive and active surveys are key for better imaging and monitoring fluid under the subsurface. These intensities provide unique solutions to the problem of locating/tracking gas/fluid movements in the crust and depicting sub-basalt and sub-intrusives in volcanic reservoirs. The proposed techniques have been tested in volcanic Islands (Deception Island) and have been proved effective at monitoring fracture opening, imaging buried fluid-filled bodies, and tracking water/gas interfaces. These novel seismic attributes are modelled in space and time and connected with the lithology of the sampled medium, specifically density and permeability with as key output a novel computational code with strong commercial potential.

New Intensity Attenuation in Georgia

NASA Astrophysics Data System (ADS)

Tsereteli, N. S.; Varazanashvili, O.; Tibaldi, A.; Bonali, F.; Gogoladze, Z.; Kvavadze, N.; Kvedelidze, I.

2016-12-01

In seismic-prone zones, increase of urbanization and infrastructures in turn produces increase of seismic risk that is mainly related to: the level of seismic hazard itself, the seismic resistance of dwelling houses, and many other factors. The relevant objectives of the present work is to improve the regional seismic hazard maps of Georgia, by implementing state-of-the art probabilistic seismic hazard assessment techniques and outputs from recent national and international collaborations. Seismic zoning is the identification of zones of similar levels of earthquake hazard. With reference to seismic zoning by ground motion assessment, the shaking intensity essentially depends on i) regional seismicity, ii) attenuation of ground motion with distance, iii) local site effects on ground motion. In the last decade, seismic hazard assessment is presented in terms of Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), or other recorded parameters. But there are very limited strong motion dataset in Georgia. Furthermore, vulnerability of buildings still is estimated for intensity, and there are no information about correlation between the distribution of ground motion recorded parameters and damage. So, macroseimic Intensity is still a very important parameter for strong ground motion evaluation. In the present work, we calibrated intensity prediction equations (IPE) for the Georgian dataset based on about 78 reviewed earthquakes. Metadata for Intensity (MSK 64 scale) were constrained and predictionequations for various types of distance (epicentral and hypocentral distance, Joyner-Boore distance, closest distance to the fault rupture plane) were calibrated. Relations between intensity and PGA values were derived. For this we used hybrid-empirical ground motion equation derived for Georgia and run scenario earthquakes for events with macroseismic data.

Modelling and forecasting 3D-hypocentre seismicity in the Kanto region

NASA Astrophysics Data System (ADS)

Guo, Yicun; Zhuang, Jiancang; Hirata, Naoshi

2018-04-01

This study analyses the seismicity in the Kanto region by fitting the 2D-epicentre and 3D-hypocentre ETAS models to the JMA catalogue for events above magnitude M4.0. In the 3D ETAS model, the focal depth is assumed to follow the beta distribution. Compared with results from the 2D-epicentre ETAS model, the 3D ETAS model greatly improves the data fitting. In addition, the stochastic reconstruction method is used when validating the results of the 3D ETAS model, with results indicating that the shallow events are more productive and their aftershocks decay slightly faster in the time and epicentre dimensions. We also study the changes of seismicity patterns before and after the 2011 Tohoku earthquake. The direct aftershocks of events from the post-Tohoku period are more diffusive in time and epicentre but more concentrated in depth. The seismicity rate increases significantly following the Tohoku earthquake, especially along the interface of the subducting Pacific plate. The curve of cumulative background probabilities for events above M4.0 implies that the background rate decays back to the pre-Tohoku level in about 5 years after the Tohoku earthquake. However, the occurrence rates of smaller events (from M2.0 to M4.0) indicate that the adjustments of local stress field continue at finer scales. Finally, we verify that the 3D model can reproduce the focal depths better than the 2D model and improve the forecasting performance.

Angola Seismicity MAP

NASA Astrophysics Data System (ADS)

Neto, F. A. P.; Franca, G.

2014-12-01

The purpose of this job was to study and document the Angola natural seismicity, establishment of the first database seismic data to facilitate consultation and search for information on seismic activity in the country. The study was conducted based on query reports produced by National Institute of Meteorology and Geophysics (INAMET) 1968 to 2014 with emphasis to the work presented by Moreira (1968), that defined six seismogenic zones from macro seismic data, with highlighting is Zone of Sá da Bandeira (Lubango)-Chibemba-Oncócua-Iona. This is the most important of Angola seismic zone, covering the epicentral Quihita and Iona regions, geologically characterized by transcontinental structure tectono-magmatic activation of the Mesozoic with the installation of a wide variety of intrusive rocks of ultrabasic-alkaline composition, basic and alkaline, kimberlites and carbonatites, strongly marked by intense tectonism, presenting with several faults and fractures (locally called corredor de Lucapa). The earthquake of May 9, 1948 reached intensity VI on the Mercalli-Sieberg scale (MCS) in the locality of Quihita, and seismic active of Iona January 15, 1964, the main shock hit the grade VI-VII. Although not having significant seismicity rate can not be neglected, the other five zone are: Cassongue-Ganda-Massano de Amorim; Lola-Quilengues-Caluquembe; Gago Coutinho-zone; Cuima-Cachingues-Cambândua; The Upper Zambezi zone. We also analyzed technical reports on the seismicity of the middle Kwanza produced by Hidroproekt (GAMEK) region as well as international seismic bulletins of the International Seismological Centre (ISC), United States Geological Survey (USGS), and these data served for instrumental location of the epicenters. All compiled information made possible the creation of the First datbase of seismic data for Angola, preparing the map of seismicity with the reconfirmation of the main seismic zones defined by Moreira (1968) and the identification of a new seismic

The Sidebar Computer Program, a seismic-shaking intensity meter: users' manual and software description

USGS Publications Warehouse

Evans, John R.

2003-01-01

The SideBar computer program provides a visual display of seismic shaking intensity as recorded at one specific seismograph. This software allows a user to tap into the seismic data recorded on that specific seismograph and to display the overall level of shaking at the single location where that seismograph resides (usually the same place the user is). From this shaking level, SideBar also estimates the potential for damage nearby. SideBar cannot tell you the “Richter magnitude” of the earthquake (see box), only how hard the ground shook locally and this estimate of how much damage is likely in the neighborhood. This combination of local effects is called the “seismic intensity”. SideBar runs on a standard desktop or laptop PC, and is intended for the media, schools, emergency responders, and any other group hosting a seismograph and who want to know immediately after an earthquake the levels of shaking measured by that instrument. These local values can be used to inform the public and help initiate appropriate local emergency response activities in the minutes between the earthquake and availability of the broader coverage provided by the USGS over the Web, notably by ShakeMap. For example, for instruments installed in schools, the level of shaking and likely damage at the school could immediately be Web broadcast and parents could quickly determine the likely safety of their children—their biggest postearthquake concern. Also, in the event of a Web outage, SideBar may be a continuing primary source of local emergency response information for some additional minutes. Specifically, SideBar interprets the peak level of acceleration (that is, the force of shaking, as a percentage of the force of gravity) as well as the peak velocity, or highest speed, at which the ground moves. Using these two basic measurements, SideBar computes what is called Instrumental Intensity—a close approximation of the Modified Mercalli Intensity scale, or “MMI” (using the

The Detection of Very Low Frequency Earthquake using Broadband Seismic Array Data in South-Western Japan

NASA Astrophysics Data System (ADS)

Ishihara, Y.; Yamanaka, Y.; Kikuchi, M.

2002-12-01

The existences of variety of low-frequency seismic sources are obvious by the dense and equalized equipment_fs seismic network. Kikuchi(2000) and Kumagai et.al. (2001) analyzed about 50sec period ground motion excited by the volcanic activities Miyake-jima, Izu Islands. JMA is listing the low frequency earthquakes routinely in their hypocenter determination. Obara (2002) detected the low frequency, 2-4 Hz, tremor that occurred along subducting Philippine Sea plate by envelope analysis of high dense and short period seismic network (Hi-net). The monitoring of continuos long period waveform show us the existence of many unknown sources. Recently, the broadband seismic network of Japan (F-net, previous name is FREESIA) is developed and extends to linear array about 3,000 km. We reviewed the long period seismic data and earthquake catalogues. Many candidates, which are excited by unknown sources, are picked up manually. The candidates are reconfirmed in detail by the original seismograms and their rough frequency characteristics are evaluated. Most events have the very low frequency seismograms that is dominated period of 20 _E30 sec and smaller amplitude than ground noise level in shorter period range. We developed the hypocenter determination technique applied the grid search method. Moreover for the major events moment tensor inversion was performed. The most source locates at subducting plate and their depth is greater than 30km. However the location don_ft overlap the low frequency tremor source region. Major event_fs moment magnitude is 4 or greater and estimated source time is around 20 sec. We concluded that low frequency seismic event series exist in wide period range in subduction area. The very low frequency earthquakes occurred along Nankai and Ryukyu trough at southwestern Japan. We are planing to survey the very low frequency event systematically in wider western Pacific region.

Real-time Seismic Alert System of NIED

NASA Astrophysics Data System (ADS)

Horiuchi, S.; Fujinawa, Y.; Negishi, H.; Matsumoto, T.; Fujiwara, H.; Kunugi, T.; Hayashi, Y.

2001-12-01

An extensive seismic network has been constructed nationwide composed of hi-sensitivity seismographic network, broadband seismographic network and strong motion seismographic network. All these data from some 3,000 sites belonging to NIED, JMA and universities are to be accumulated and distributed through NIED to any scientists and engineering through INTERNET under the coordination of the National Seismic Research Committee of MEXT. As a practical application of those data we are now developing a real-time seismic alert information system for the purpose of providing short-term warning of imminent strong grounds motions from major earthquakes from several seconds to a few days. The contents of information are seismic focal parameters (several seconds), seismic fault plane solutions (some 10 seconds), after-shock activities (several minutes-a few days ). The fundamental fault parameters are used to build specific information at sites for particular users for use of triggering automated and /or half-automated responses. The most important application is an immediate estimate of expected shaking distribution and damages in a district using synthetic database and site effects for local governments to initial proper measures of hazard mitigation. Another application is estimation of arrival time and shaking strength at any individual site for human lives to be safeguarded. The system could also start an automatic electrical isolation and protection of computer systems, protection of hazardous chronic systems, transportation systems and so on. The information are corrected successively as seismic ground motion are received at a larger number of sites in time with the result that more accurate and more sophisticated earthquake information is transmitted to any user. Besides the rapid determination of seismic parameters, one of essential items in this alert system is the data transmission means. The data transmission is chosen to assure negligibly small delay of data

Geometry and spatial variations of seismic reflection intensity of the upper surface of the Philippine Sea plate off the Boso Peninsula, Japan

NASA Astrophysics Data System (ADS)

Kono, Akihiro; Sato, Toshinori; Shinohara, Masanao; Mochizuki, Kimihiro; Yamada, Tomoaki; Uehira, Kenji; Shinbo, Takashi; Machida, Yuya; Hino, Ryota; Azuma, Ryousuke

2017-07-01

In the region off the Boso Peninsula, Japan, the Pacific plate is subducting westward beneath both the Honshu island arc and Philippine Sea plate, while the Philippine Sea plate is subducting northwestward beneath the Honshu island arc. These complex tectonic interactions have caused numerous seismic events occurred in the past. To better understand these seismic events, it is important to determine the geometry of the plate boundary, in particular the upper surface of the Philippine Sea plate. We conducted an active-source seismic refraction survey in July and August 2009 from which we obtained a 2-D P-wave velocity structure model along a 216-km profile. We used the velocity model and previously published data that indicate a P-wave velocity of 5.0 km/s for the upper surface of the subducting Philippine Sea plate to delineate its boundary with the overriding Honshu island arc. Our isodepth contours of the upper surface of the Philippine Sea plate show that its dip is shallow at depths of 10 to 15 km, far off the Boso Peninsula. This shallow dip may be a result of interference from the Pacific plate slab, which is subducting westward under the Philippine Sea plate. Within our survey data, we recognized numerous seismic reflections of variable intensity, some of which came from the upper surface of the Philippine Sea plate. An area of high seismic reflection intensity corresponds with the main slip area of the Boso slow slip events. Our modeling indicates that those reflections can be explained by an inhomogeneous layer close to the upper surface of the Philippine Sea plate.

Spatiotemporal seismic velocity change in the Earth's subsurface associated with large earthquake: contribution of strong ground motion and crustal deformation

NASA Astrophysics Data System (ADS)

Sawazaki, K.

2016-12-01

It is well known that seismic velocity of the subsurface medium changes after a large earthquake. The cause of the velocity change is roughly attributed to strong ground motion (dynamic strain change), crustal deformation (static strain change), and fracturing around the fault zone. Several studies have revealed that the velocity reduction down to several percent concentrates at the depths shallower than several hundred meters. The amount of velocity reduction correlates well with the intensity of strong ground motion, which indicates that the strong motion is the primary cause of the velocity reduction. Although some studies have proposed contributions of coseismic static strain change and fracturing around fault zone to the velocity change, separation of their contributions from the site-related velocity change is usually difficult. Velocity recovery after a large earthquake is also widely observed. The recovery process is generally proportional to logarithm of the lapse time, which is similar to the behavior of "slow dynamics" recognized in laboratory experiments. The time scale of the recovery is usually months to years in field observations, while it is several hours in laboratory experiments. Although the factor that controls the recovery speed is not well understood, cumulative strain change due to post-seismic deformation, migration of underground water, mechanical and chemical reactions on the crack surface could be the candidate. In this study, I summarize several observations that revealed spatiotemporal distribution of seismic velocity change due to large earthquakes; especially I focus on the case of the M9.0 2011 Tohoku earthquake. Combining seismograms of Hi-net (high-sensitivity) and KiK-net (strong motion), geodetic records of GEONET and the seafloor GPS/Acoustic ranging, I investigate contribution of the strong ground motion and crustal deformation to the velocity change associated with the Tohoku earthquake, and propose a gross view of

Seismic activity preceding the 2016 Kumamoto earthquakes: Multiple approaches to recognizing possible precursors

NASA Astrophysics Data System (ADS)

Nanjo, K.; Izutsu, J.; Orihara, Y.; Furuse, N.; Togo, S.; Nitta, H.; Okada, T.; Tanaka, R.; Kamogawa, M.; Nagao, T.

2016-12-01

We show the first results of recognizing seismic patterns as possible precursory episodes to the 2016 Kumamoto earthquakes, using existing four different methods: b-value method (e.g., Schorlemmer and Wiemer, 2005; Nanjo et al., 2012), two kinds of seismic quiescence evaluation methods (RTM-algorithm, Nagao et al., 2011; Z-value method, Wiemer and Wyss, 1994), and foreshock seismic density analysis based on Lippiello et al. (2012). We used the earthquake catalog maintained by the Japan Meteorological Agency (JMA). To ensure data quality, we performed catalog completeness check as a pre-processing step of individual analyses. Our finding indicates the methods we adopted do not allow the Kumamoto earthquakes to be predicted exactly. However, we found that the spatial extent of possible precursory patterns differs from one method to the other and ranges from local scales (typically asperity size), to regional scales (e.g., 2° × 3° around the source zone). The earthquakes are preceded by periods of pronounced anomalies, which lasted decade scales (e.g., 20 years or longer) to yearly scales (e.g., 1 2 years). Our results demonstrate that combination of multiple methods detects different signals prior to the Kumamoto earthquakes with more considerable reliability than if measured by single method. This strongly suggests great potential to reduce the possible future sites of earthquakes relative to long-term seismic hazard assessment. This study was partly supported by MEXT under its Earthquake and Volcano Hazards Observation and Research Program and Grant-in-Aid for Scientific Research (C), No. 26350483, 2014-2017, by Chubu University under the Collaboration Research Program of IDEAS, IDEAS201614, and by Tokai University under Project Resarch of IORD. A part of this presentation is given in Nanjo et al. (2016, submitted).

Detailed Analysis of the Interoccurrence Time Statistics in Seismic Activity

NASA Astrophysics Data System (ADS)

Tanaka, Hiroki; Aizawa, Yoji

2017-02-01

The interoccurrence time statistics of seismiciry is studied theoretically as well as numerically by taking into account the conditional probability and the correlations among many earthquakes in different magnitude levels. It is known so far that the interoccurrence time statistics is well approximated by the Weibull distribution, but the more detailed information about the interoccurrence times can be obtained from the analysis of the conditional probability. Firstly, we propose the Embedding Equation Theory (EET), where the conditional probability is described by two kinds of correlation coefficients; one is the magnitude correlation and the other is the inter-event time correlation. Furthermore, the scaling law of each correlation coefficient is clearly determined from the numerical data-analysis carrying out with the Preliminary Determination of Epicenter (PDE) Catalog and the Japan Meteorological Agency (JMA) Catalog. Secondly, the EET is examined to derive the magnitude dependence of the interoccurrence time statistics and the multi-fractal relation is successfully formulated. Theoretically we cannot prove the universality of the multi-fractal relation in seismic activity; nevertheless, the theoretical results well reproduce all numerical data in our analysis, where several common features or the invariant aspects are clearly observed. Especially in the case of stationary ensembles the multi-fractal relation seems to obey an invariant curve, furthermore in the case of non-stationary (moving time) ensembles for the aftershock regime the multi-fractal relation seems to satisfy a certain invariant curve at any moving times. It is emphasized that the multi-fractal relation plays an important role to unify the statistical laws of seismicity: actually the Gutenberg-Richter law and the Weibull distribution are unified in the multi-fractal relation, and some universality conjectures regarding the seismicity are briefly discussed.

Seismic Hazard and Risk Assessments for Beijing-Tianjin-Tangshan, China, Area

USGS Publications Warehouse

Xie, F.; Wang, Z.; Liu, J.

2011-01-01

Seismic hazard and risk in the Beijing-Tianjin-Tangshan, China, area were estimated from 500-year intensity observations. First, we digitized the intensity observations (maps) using ArcGIS with a cell size of 0.1 ?? 0.1??. Second, we performed a statistical analysis on the digitized intensity data, determined an average b value (0.39), and derived the intensity-frequency relationship (hazard curve) for each cell. Finally, based on a Poisson model for earthquake occurrence, we calculated seismic risk in terms of a probability of I ??? 7, 8, or 9 in 50 years. We also calculated the corresponding 10 percent probability of exceedance of these intensities in 50 years. The advantages of assessing seismic hazard and risk from intensity records are that (1) fewer assumptions (i. e., earthquake source and ground motion attenuation) are made, and (2) site-effect is included. Our study shows that the area has high seismic hazard and risk. Our study also suggests that current design peak ground acceleration or intensity for the area may not be adequate. ?? 2010 Birkh??user / Springer Basel AG.

Assessment of macroseismic intensity in the Nile basin, Egypt

NASA Astrophysics Data System (ADS)

Fergany, Elsayed

2018-01-01

This work intends to assess deterministic seismic hazard and risk analysis in terms of the maximum expected intensity map of the Egyptian Nile basin sector. Seismic source zone model of Egypt was delineated based on updated compatible earthquake catalog in 2015, focal mechanisms, and the common tectonic elements. Four effective seismic source zones were identified along the Nile basin. The observed macroseismic intensity data along the basin was used to develop intensity prediction equation defined in terms of moment magnitude. Expected maximum intensity map was proven based on the developed intensity prediction equation, identified effective seismic source zones, and maximum expected magnitude for each zone along the basin. The earthquake hazard and risk analysis was discussed and analyzed in view of the maximum expected moment magnitude and the maximum expected intensity values for each effective source zone. Moderate expected magnitudes are expected to put high risk at Cairo and Aswan regions. The results of this study could be a recommendation for the planners in charge to mitigate the seismic risk at these strategic zones of Egypt.

The effect of different intensity measures and earthquake directions on the seismic assessment of skewed highway bridges

NASA Astrophysics Data System (ADS)

Bayat, M.; Daneshjoo, F.; Nisticò, N.

2017-01-01

In this study the probable seismic behavior of skewed bridges with continuous decks under earthquake excitations from different directions is investigated. A 45° skewed bridge is studied. A suite of 20 records is used to perform an Incremental Dynamic Analysis (IDA) for fragility curves. Four different earthquake directions have been considered: -45°, 0°, 22.5°, 45°. A sensitivity analysis on different spectral intensity meas ures is presented; efficiency and practicality of different intensity measures have been studied. The fragility curves obtained indicate that the critical direction for skewed bridges is the skew direction as well as the longitudinal direction. The study shows the importance of finding the most critical earthquake in understanding and predicting the behavior of skewed bridges.

Imaging inhomogeneous seismic velocity structure in and around the fault plane of the 2008 Iwate-Miyagi, Japan, Nairiku Earthquake (M7.2) - spatial variation in depth of seismic-aseismic transition and possible high-T/overpressurized fluid distribution

NASA Astrophysics Data System (ADS)

Okada, T.; Umino, N.; Hasegawa, A.; 2008 Iwate-Miyagi Nairiku Earthquake, G. O.

2008-12-01

A large shallow earthquake (named the 2008 Iwate-Miyagi Nairiku Earthquake) with a JMA magnitude of 7.2 occurred in the central part of NE Japan on June 14, 2008. Focal area of the present earthquake is located in the Tohoku backbone range strain concentration zone (Miura et al., 2004) along the volcanic front. Just after the occurrence of this earthquake, Japanese universities (Hokkaido, Hirosaki, Tohoku, Tokyo, Nagoya, Kyoto, Kochi, Kyusyu, Kagoshima) and NIED deployed a dense aftershock observation network in and around the focal area. Total number of temporal stations is 128. Using data from this dense aftershock observation and other temporary and routinely operated stations, we estimate hypocenter distribution and seismic velocity structure of the crust in and around the focal area of the present earthquake. We determined three-dimensional seismic velocity structure and relocated hypocenters simultaneously using the double- difference tomography method (Zhang and Thurber, 2003). Spatial extent of the aftershock area is about 45 km (NNE-SSW) by 15 km (WNW-ESE). Most of aftershocks are aligned in westward dipping. Shallower extensions of aftershock alignments seem to be located nearly at the coseismic surface deformations, which are along a geological fault, and the surface trace of the active fault (Detana fault). Note that some aftershocks seem to occur off the fault plane of the mainshock. The focal area of the present earthquake is located at a high Vs area. In the lower crust, we found some distinct low-Vs areas. These low velocity zones are located just beneath the strain concentration zones / seismic belts along the backbone range and in the northern Miyagi region. Focal area of the present earthquake is also located just above the low velocity zone in the lower crust. Beneath active volcanoes, these low velocity zones become more distinct and shallower, and aftershocks tend to occur shallower and not occur within such low-velocity zones. These low

The seismic traffic footprint: Tracking trains, aircraft, and cars seismically

NASA Astrophysics Data System (ADS)

Riahi, Nima; Gerstoft, Peter

2015-04-01

Although naturally occurring vibrations have proven useful to probe the subsurface, the vibrations caused by traffic have not been explored much. Such data, however, are less sensitive to weather and low visibility compared to some common out-of-road traffic sensing systems. We study traffic-generated seismic noise measured by an array of 5200 geophones that covered a 7 × 10 km area in Long Beach (California, USA) with a receiver spacing of 100 m. This allows us to look into urban vibrations below the resolution of a typical city block. The spatiotemporal structure of the anthropogenic seismic noise intensity reveals the Blue Line Metro train activity, departing and landing aircraft in Long Beach Airport and their acceleration, and gives clues about traffic movement along the I-405 highway at night. As low-cost, stand-alone seismic sensors are becoming more common, these findings indicate that seismic data may be useful for traffic monitoring.

Maximum Historical Seismic Intensity Map of S. Miguel Island (azores)

NASA Astrophysics Data System (ADS)

Silveira, D.; Gaspar, J. L.; Ferreira, T.; Queiroz, G.

The Azores archipelago is situated in the Atlantic Ocean where the American, African and Eurasian lithospheric plates meet. The so-called Azores Triple Junction located in the area where the Terceira Rift, a NW-SE to WNW-ESE fault system with a dextral component, intersects the Mid-Atlantic Ridge, with an approximate N-S direction, dominates its geological setting. S. Miguel Island is located in the eastern segment of the Terceira Rift, showing a high diversity of volcanic and tectonic structures. It is the largest Azorean island and includes three active trachytic central volcanoes with caldera (Sete Cidades, Fogo and Furnas) placed in the intersection of the NW-SE Ter- ceira Rift regional faults with an E-W deep fault system thought to be a relic of a Mid-Atlantic Ridge transform fault. N-S and NE-SW faults also occur in this con- text. Basaltic cinder cones emplaced along NW-SE fractures link that major volcanic structures. The easternmost part of the island comprises an inactive trachytic central volcano (Povoação) and an old basaltic volcanic complex (Nordeste). Since the settle- ment of the island, early in the XV century, several destructive earthquakes occurred in the Azores region. At least 11 events hit S. Miguel Island with high intensity, some of which caused several deaths and significant damages. The analysis of historical documents allowed reconstructing the history and the impact of all those earthquakes and new intensity maps using the 1998 European Macrosseismic Scale were produced for each event. The data was then integrated in order to obtain the maximum historical seismic intensity map of S. Miguel. This tool is regarded as an important document for hazard assessment and risk mitigation taking in account that indicates the location of dangerous seismogenic zones and provides a comprehensive set of data to be applied in land-use planning, emergency planning and building construction.

Seismic Hazard Assessment of the Sheki-Ismayilli Region, Azerbaijan

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

Ayyubova, Leyla J.

2006-03-23

Seismic hazard assessment is an important factor in disaster management of Azerbaijan Republic. The Shaki-Ismayilli region is one of the earthquake-prone areas in Azerbaijan. According to the seismic zoning map, the region is located in intensity IX zone. Large earthquakes in the region take place along the active faults. The seismic activity of the Shaki-Ismayilli region is studied using macroseismic and instrumental data, which cover the period between 1250 and 2003. Several principal parameters of earthquakes are analyzed: maximal magnitude, energetic class, intensity, depth of earthquake hypocenter, and occurrence. The geological structures prone to large earthquakes are determined, and themore » dependence of magnitude on the fault length is shown. The large earthquakes take place mainly along the active faults. A map of earthquake intensity has been developed for the region, and the potential seismic activity of the Shaki-Ismayilli region has been estimated.« less

Angola seismicity

NASA Astrophysics Data System (ADS)

Neto, Francisco António Pereira; França, George Sand; Condori, Cristobal; Sant'Anna Marotta, Giuliano; Chimpliganond, Cristiano Naibert

2018-05-01

This work describes the development of the Angolan earthquake catalog and seismicity distribution in the Southwestern African Plate, in Angola. This region is one of the least seismically active, even for stable continental regions (SCRs) in the world. The maximum known earthquake had a magnitude of 6.0 Ms, while events with magnitudes of 4.5 have return period of about 10 years. Events with magnitude 5 and above occur with return period of about 20 years. Five seismic zones can be confirmed in Angola, within and along craton edges and in the sedimentary basins including offshore. Overall, the exposed cratonic regions tend to have more earthquakes compared to other regions such as sedimentary basins. Earthquakes tend to occur in Archaic rocks, especially inside preexisting weakness zones and in tectonic-magmatic reactivation zones of Mesozoic and Meso-Cenozoic, associated with the installation of a wide variety of intrusive rocks, strongly marked by intense tectonism. This fact can be explained by the models of preexisting weakness zones and stress concentration near intersecting structures. The Angolan passive margin is also a new region where seismic activity occurs. Although clear differences are found between different areas along the passive margin, in the middle near Porto Amboim city, seismic activity is more frequent compared with northwestern and southwestern regions.

Semi-automatic mapping for identifying complex geobodies in seismic images

NASA Astrophysics Data System (ADS)

Domínguez-C, Raymundo; Romero-Salcedo, Manuel; Velasquillo-Martínez, Luis G.; Shemeretov, Leonid

2017-03-01

Seismic images are composed of positive and negative seismic wave traces with different amplitudes (Robein 2010 Seismic Imaging: A Review of the Techniques, their Principles, Merits and Limitations (Houten: EAGE)). The association of these amplitudes together with a color palette forms complex visual patterns. The color intensity of such patterns is directly related to impedance contrasts: the higher the contrast, the higher the color intensity. Generally speaking, low impedance contrasts are depicted with low tone colors, creating zones with different patterns whose features are not evident for a 3D automated mapping option available on commercial software. In this work, a workflow for a semi-automatic mapping of seismic images focused on those areas with low-intensity colored zones that may be associated with geobodies of petroleum interest is proposed. The CIE L*A*B* color space was used to perform the seismic image processing, which helped find small but significant differences between pixel tones. This process generated binary masks that bound color regions to low-intensity colors. The three-dimensional-mask projection allowed the construction of 3D structures for such zones (geobodies). The proposed method was applied to a set of digital images from a seismic cube and tested on four representative study cases. The obtained results are encouraging because interesting geobodies are obtained with a minimum of information.

Updated Colombian Seismic Hazard Map

NASA Astrophysics Data System (ADS)

Eraso, J.; Arcila, M.; Romero, J.; Dimate, C.; Bermúdez, M. L.; Alvarado, C.

2013-05-01

possible to determinate environments and scenarios where the seismic hazard is a function of distance and magnitude and also the principal seismic sources that contribute to the seismic hazard at each site (dissagregation). This project was conducted by the Servicio Geológico Colombiano (Colombian Geological Survey) and the Universidad Nacional de Colombia (National University of Colombia), with the collaboration of national and foreign experts and the National System of Prevention and Attention of Disaster (SNPAD). It is important to stand out that this new seismic hazard map was used in the updated national building code (NSR-10). A new process is ongoing in order to improve and present the Seismic Hazard Map in terms of intensity. This require new knowledge in site effects, in both local and regional scales, checking the existing and develop new acceleration to intensity relationships, in order to obtain results more understandable and useful for a wider range of users, not only in the engineering field, but also all the risk assessment and management institutions, research and general community.

Using H/V Spectral Ratio Analysis to Map Sediment Thickness and to Explain Macroseismic Intensity Variation of a Low-Magnitude Seismic Swarm in Central Belgium

NASA Astrophysics Data System (ADS)

Van Noten, K.; Lecocq, T.; Camelbeeck, T.

2013-12-01

Between 2008 and 2010, the Royal Observatory of Belgium received numerous ';Did You Feel It'-reports related to a 2-year lasting earthquake swarm at Court-Saint-Etienne, a small town in a hilly area 20 km SE of Brussels, Belgium. These small-magnitude events (-0.7 ≤ ML ≤ 3.2, n = c. 300 events) were recorded both by the permanent seismometer network in Belgium and by a locally installed temporary seismic network deployed in the epicentral area. Relocation of the hypocenters revealed that the seismic swarm can be related to the reactivation of a NW-SE strike-slip fault at 3 to 6 km depth in the basement rocks of the Lower Palaeozoic London-Brabant Massif. This sequence caused a lot of emotion in the region because more than 60 events were felt by the local population. Given the small magnitudes of the seismic swarm, most events were more often heard than felt by the respondents, which is indicative of a local high-frequency earthquake source. At places where the bedrock is at the surface or where it is covered by thin alluvial sediments (<10 m), such as in incised river valleys and on hill slopes, reported macroseismic intensities are higher than those on hill tops where respondents live on a thicker Quaternary and Cenozoic sedimentary cover (> 30 m). In those river valleys that have a considerable alluvial sedimentary cover, macroseismic intensities are again lower. To explain this variation in macroseismic intensity we present a macroseismic analysis of all DYFI-reports related to the 2008-2010 seismic swarm and a pervasive H/V spectral ratio (HVSR) analysis of ambient noise measurements to model the thickness of sediments covering the London-Brabant Massif. The HVSR method is a very powerful tool to map the basement morphology, particularly in regions of unknown subsurface structure. By calculating the soil's fundamental frequency above boreholes, we calibrated the power-law relationship between the fundamental frequency, shear wave velocity and the thickness

Microzonation of Seismic Hazard Potential in Taipei, Taiwan

NASA Astrophysics Data System (ADS)

Liu, K. S.; Lin, Y. P.

2017-12-01

The island of Taiwan lies at the boundary between the Philippine Sea plate and the Eurasia plate. Accordingly, the majority of seismic energy release near Taiwan originates from the two subduction zones. It is therefore not surprising that Taiwan has repeatedly been struck by large earthquakes such as 1986 Hualien earthquake, 1999 Chi Chi and 2002 Hualien earthquake. Microzonation of seismic hazard potential becomes necessary in Taipei City for the Central Geological Survey announced the Sanchiao active fault as Category II. In this study, a catalog of more than 2000 shallow earthquakes occurred from 1900 to 2015 with Mw magnitudes ranging from 5.0 to 8.2, and 11 disastrous earthquakes occurred from 1683-1899, as well as Sanchiao active fault in the vicinity are used to estimate the seismic hazard potential in Taipei City for seismic microzonation. Furthermore, the probabilities of seismic intensity exceeding CWB intensity 5, 6, 7 and MMI VI, VII, VIII in 10, 30, and 50-year periods in the above areas are also analyzed for the seismic microzonation. Finally, by comparing with the seismic zoning map of Taiwan in current building code that was revised after 921 earthquakes, Results of this study will show which areas with higher earthquake hazard potential in Taipei City. They provide a valuable database for the seismic design of critical facilities. It will help mitigate Taipei City earthquake disaster loss in the future, as well as provide critical information for emergency response plans.

Seismicity map of the state of Georgia

USGS Publications Warehouse

Reagor, B. Glen; Stover, C.W.; Algermissen, S.T.; Long, L.T.

1991-01-01

This map is one of a series of seismicity maps produced by the U.S. Geological Survey that show earthquake data of individual states or groups of states at the scale of 1:1,000,000. This maps shows only those earthquakes with epicenters located within the boundaries of Georgia, even though earthquakes in nearby states or countries may have been felt or may have cause damage in Georgia. The data in table 1 were used to compile the seismicity map; these data are a corrected, expanded, and updated (through 1987) version of the data used by Algermissen (1969) for a study of seismic risk in the United States. The locations and intensities of some earthquakes were revised and intensities were assigned where none had been before. Many earthquakes were added to the original list from new data sources as well as from some old data sources that has not been previously used. The data in table 1 represent best estimates of the location of the epicenter, magnitude, and intensity of each earthquake on the basis of historical and current information. Some of the aftershocks from large earthquakes are listed, but not all, especially for earthquakes that occurred before seismic instruments were universally used. The latitude and longitude coordinates of each epicenter were rounded to the nearest tenth of a degree and sorted so that all identical locations were grouped and counted. These locations are represented on the map by a triangle. The number of earthquakes at each location is shown on the map by the Arabic number to the right of the triangle. A Roman numeral to the left of a triangle is the maximum Modified Mercoili intensity (Wood and Neumann, 1931) of all earthquakes at that geographic location, The absence of an intensity value indicates that no intensities have been assigned to earthquakes at that location. The year shown below each triangle is the latest year for which the maximum intensity was recorded.

Seismicity map of the State of Louisiana

USGS Publications Warehouse

Stover, C.W.; Reagor, B.G.; Algermissen, S.T.

1979-01-01

This map is one of a series of seismicity maps produced by the U. S. Geological Survey that show earthquake data of individual states or groups of states at the scale of 1:1,000,000. This map shows only those earthquakes with epicenters located within the boundaries of Louisiana, even though earthquakes in nearby states or countries may have been felt or may have caused damage in Louisiana.The data in table 1 were used to compile the seismicity map; these data are a corrected, expanded, and updated (through 1983) version of the data used by Algermissen (1969) for a study of seismic risk in the United States. The locations and intensities of some earthquakes were revised and intensities were assigned where none had been before. Many earthquakes were added to the original list from new data sources as well as from some old data sources that had not been previously used. The data in table 1 represent best estimates of the location of the epicenter, magnitude, and intensity of each earthquake on the basis of historical and current information. Some of the aftershocks from large earthquakes are listed, but not all, especially for earthquakes that occurred before seismic instruments were universally used.The latitude and longitude coordinates of each epicenter were rounded to the nearest tenth of a degree and sorted so that all identical locations were grouped and counted. These locations are represented on the map by a triangle. The number of earthquakes at each location is shown on the map by the arabic number to the right of the triangle. A Roman numeral to the 1eft of a triangle is the maximum Modified Mercalli intensity (Wood and Neumann, 1931) of all earthquakes at that geographic location. The absence of an intensity value indicates that no intensities have been assigned to earthquakes at that location. The year shown below each triangle is the latest year for which the maximum intensity was recorded.

Seismicity map of the state of Pennsylvania

USGS Publications Warehouse

Stover, C.W.; Reagor, B.G.; Algermissen, S.T.

1987-01-01

This map is one of a series of seismicity maps produced by the U. S. Geological Survey that show earthquake data of individual states or groups of states at the scale of 1:1,000,000. This map shows only those earthquakes with epicenters located within the boundaries of Pennsylvania, even though earthquakes in nearby states may have been felt or may have caused damage in Pennsylvania.The data in table 1 were used to compile the seismicity map; these data are a corrected, expanded, and updated (through 1983) version of the data used by Algermissen (1969) for a study of seismic risk in the United States. The locations and intensities of some earthquakes were revised and intensities were assigned where none had been before. Many earthquakes were added to the original list from new data sources as well as from some old data sources that had not been previously used. The data in table 1 represent best estimates of the location of the epicenter, magnitude, and intensity of each earthquake on the basis of historical and current information. Some of the aftershocks from large earthquakes are listed, but not all, especially for earthquakes that occurred before seismic instruments were universally used.The latitude and longitude coordinates of each epicenter were rounded to the nearest tenth of a degree and sorted so that all identical locations were grouped and counted. These locations are represented on the map by a triangle. The number of earthquakes at each location is shown on the map by the arabic number to the right of the triangle. A Roman numeral to the left of a triangle is the maximum Modified Mercalli intensity (Wood and Neumann, 1931) of a11 earthquakes at that geographic location. The absence of an intensity value indicates that no intensities have been assigned to earthquakes at that location. The year shown below each triangle is the latest year for which the maximum intensity was recorded.

The intensity signature of induced seismicity

USGS Publications Warehouse

Atkinson, Gail M.; Wald, David J.; Worden, Charles; Quitoriano, Vince

2018-01-01

We analyze a comprehensive database of ∼63,000">∼63,000 geocoded community intensity observations from >400">>400 earthquakes of moment magnitude M≥3.5">M≥3.5 in Oklahoma from 2010 to 2016 to define the intensity signature of induced events. We show that natural and induced events have similar average intensities within 10 km of the epicenter. At greater distances, induced events have low‐average intensities compared with deeper natural events. These trends are predictable based on ground‐motion prediction equations. They are a consequence of two focal‐depth effects that have offsetting impacts on the strength of ground motion: (1) the epicenter is near the source for shallow events, and (2) the stress parameter scales with focal depth.

Seismicity map of the State of Georgia

USGS Publications Warehouse

Stover, C.W.; Reagor, B.G.; Algermissen, S.T.; Long, L.T.

1979-01-01

The earthquake data shown on this map and listed in table 1 are a list of earthquakes that were originally used in preparing the Seismic Risk Studies in the United States (Algermissen, 1969) which have been recompiled and updated through 1977. The data have been reexamined and intensities assigned where none had been assigned before, on the basis of available data. Other intensity values were updated from new and additional data sources that were not available at the time of original compilation. Some epicenters were relocated on the basis of new information. The data shown in table 1 are estimates of the most accurate hypocenter, magnitude, and intensity of each earthquake, on the basis of historical and current information. Known or suspected explosions are listed in table 1 but are not plotted on the seismicity map.The data in table 1 were used to compile the seismicity map. The latitude and longitude were rounded to the nearest tenth of a degree and sorted so that all identical locations were grouped together and counted. A triangle represents the epicenter plotted to a tenth of a degree. The number of earthquakes at each location is shown on the map by the number to the right of the triangle. A Roman numeral to the left of a triangle is the maximum Modified Mercalli intensity (Wood and Neumann, 1931) of all earthquakes located at that geographic position. The absence of an intensity value indicates that no intensities have been assigned to earthquakes at that location. A year shown below a triangle is the latest year for which the maximum intensity was recorded.

The Pollino Seismic Sequence: Activated Graben Structures in a Seismic Gap

NASA Astrophysics Data System (ADS)

Rößler, Dirk; Passarelli, Luigi; Govoni, Aladino; Bindi, Dino; Cesca, Simone; Hainzl, Sebatian; Maccaferri, Francesco; Rivalta, Eleonora; Woith, Heiko; Dahm, Torsten

2015-04-01

The Mercure Basin (MB) and the Castrovillari Fault (CF) in the Pollino range (Southern Apennines, Italy) represent one of the most prominent seismic gaps in the Italian seismic catalogue, with no M>5.5 earthquakes during the last centuries. In historical times several swarm-like seismic sequences occurred in the area including two intense swarms within the past two decades. The most energetic one started in 2010 and has been still active in 2014. The seismicity culminated in autumn 2012 with a M=5 event on 25 October. The range hosts a number of opposing normal faults forming a graben-like structure. Their rheology and their interactions are unclear. Current debates include the potential of the MB and the CF to host large earthquakes and the style of deformation. Understanding the seismicity and the behaviour of the faults is necessary to assess the tectonics and the seismic hazard. The GFZ German Research Centre for Geosciences and INGV, Italy, have jointly monitored the ongoing seismicity using a small-aperture seismic array, integrated in a temporary seismic network. Based on this installation, we located more than 16,000 local earthquakes that occurred between November 2012 and September 2014. Here we investigate quantitatively all the phases of the seismic sequence starting from January 2010. Event locations along with moment tensor inversion constrain spatially the structures activated by the swarm and the migration pattern of the seismicity. The seismicity forms clusters concentrated within the southern part of the MB and along the Pollino Fault linking MB and CF. Most earthquakes are confined to the upper 10 km of the crust in an area of ~15x15 km2. However, sparse seismicity at depths between 15 and 20 km and moderate seismicity further north with deepening hypocenters also exist. In contrast, the CF appears aseismic; only the northern part has experienced micro-seismicity. The spatial distribution is however more complex than the major tectonic structures

Long Period Seismic Waves

DTIC Science & Technology

1976-08-01

Geoffsica, TPHM. No. 5 , p. 161. Vargas, Freddy (To he published in 1976) 1 .-DTSCRP1TNACTON DE EVENTO«; NATHDALE«; Y ARTTFTCT ALES. 2.- CALCULO DEL...seismic risk, bv de - fininn relative weiqht of maximum MM intensity at a pivon distance ponulation density, area feolupy and attenuation of intensity wit...Population densitv, area peolopv and attenuation of intensitv with distance, is presented topether with a map anplvinp theorv to Bo- livia. ^«^a

Seismic Hazard and risk assessment for Romania -Bulgaria cross-border region

NASA Astrophysics Data System (ADS)

Simeonova, Stela; Solakov, Dimcho; Alexandrova, Irena; Vaseva, Elena; Trifonova, Petya; Raykova, Plamena

2016-04-01

Among the many kinds of natural and man-made disasters, earthquakes dominate with regard to their social and economical impact on the urban environment. Global seismic hazard and vulnerability to earthquakes are steadily increasing as urbanization and development occupy more areas that are prone to effects of strong earthquakes. The assessment of the seismic hazard and risk is particularly important, because it provides valuable information for seismic safety and disaster mitigation, and it supports decision making for the benefit of society. Romania and Bulgaria, situated in the Balkan Region as a part of the Alpine-Himalayan seismic belt, are characterized by high seismicity, and are exposed to a high seismic risk. Over the centuries, both countries have experienced strong earthquakes. The cross-border region encompassing the northern Bulgaria and southern Romania is a territory prone to effects of strong earthquakes. The area is significantly affected by earthquakes occurred in both countries, on the one hand the events generated by the Vrancea intermediate-depth seismic source in Romania, and on the other hand by the crustal seismicity originated in the seismic sources: Shabla (SHB), Dulovo, Gorna Orjahovitza (GO) in Bulgaria. The Vrancea seismogenic zone of Romania is a very peculiar seismic source, often described as unique in the world, and it represents a major concern for most of the northern part of Bulgaria as well. In the present study the seismic hazard for Romania-Bulgaria cross-border region on the basis of integrated basic geo-datasets is assessed. The hazard results are obtained by applying two alternative approaches - probabilistic and deterministic. The MSK64 intensity (MSK64 scale is practically equal to the new EMS98) is used as output parameter for the hazard maps. We prefer to use here the macroseismic intensity instead of PGA, because it is directly related to the degree of damages and, moreover, the epicentral intensity is the original

Seismic Hazard Assessment for the Baku City and Absheron Peninsula, Azerbaijan

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

Babayev, Gulam R.

2006-03-23

This paper deals with the seismic hazard assessment for Baku and the Absheron peninsula. The assessment is based on the information on the features of earthquake ground motion excitation, seismic wave propagation (attenuation), and site effect. I analyze active faults, seismicity, soil and rock properties, geological cross-sections, the borehole data of measured shear-wave velocity, lithology, amplification factor of each geological unit, geomorphology, topography, and basic rock and surface ground motions. To estimate peak ground acceleration (PGA) at the surface, PGA at the basic rock is multiplied by the amplification parameter of each surface layers. Quaternary soft deposits, representing a highmore » risk due to increasing PGA values at surface, are studied in detail. For a near-zone target earthquake PGA values are compared to intensity at MSK-64 scale for the Absheron peninsula. The amplification factor for the Baku city is assessed and provides estimations for a level of a seismic motion and seismic intensity of the studied area.« less

Fault specific GIS based seismic hazard maps for the Attica region, Greece

NASA Astrophysics Data System (ADS)

Deligiannakis, G.; Papanikolaou, I. D.; Roberts, G.

2018-04-01

Traditional seismic hazard assessment methods are based on the historical seismic records for the calculation of an annual probability of exceedance for a particular ground motion level. A new fault-specific seismic hazard assessment method is presented, in order to address problems related to the incompleteness and the inhomogeneity of the historical records and to obtain higher spatial resolution of hazard. This method is applied to the region of Attica, which is the most densely populated area in Greece, as nearly half of the country's population lives in Athens and its surrounding suburbs, in the Greater Athens area. The methodology is based on a database of 24 active faults that could cause damage to Attica in case of seismic rupture. This database provides information about the faults slip rates, lengths and expected magnitudes. The final output of the method is four fault-specific seismic hazard maps, showing the recurrence of expected intensities for each locality. These maps offer a high spatial resolution, as they consider the surface geology. Despite the fact that almost half of the Attica region lies on the lowest seismic risk zone according to the official seismic hazard zonation of Greece, different localities have repeatedly experienced strong ground motions during the last 15 kyrs. Moreover, the maximum recurrence for each intensity occurs in different localities across Attica. Highest recurrence for intensity VII (151-156 times over 15 kyrs, or up to a 96 year return period) is observed in the central part of the Athens basin. The maximum intensity VIII recurrence (115 times over 15 kyrs, or up to a 130 year return period) is observed in the western part of Attica, while the maximum intensity IX (73-77/15 kyrs, or a 195 year return period) and X (25-29/15 kyrs, or a 517 year return period) recurrences are observed near the South Alkyonides fault system, which dominates the strong ground motions hazard in the western part of the Attica mainland.

Seismic structure of subducted Philippine Sea plate beneath the southern Ryukyu arc by receiver function and local earthquakes tomography

NASA Astrophysics Data System (ADS)

Nakamura, M.

2012-12-01

Seismic coupling of the Ryukyu subduction zone is assumed to be weak from the lack of historical interplate large earthquakes. However, recent investigation of repeating slow slip events (Heki & Kataoka, 2008), shallow low frequency earthquakes (Ando et al., 2012), and source of 1771 Yaeyama mega-tsunami (Nakamura, 2009), showed that the interplate coupling is not weak in the south of Ryukyu Trench. The biannually repeating SSEs (Mw=6.5) occur at the depth of 20-40 km on the upper interface of the subducted Philippine Sea plate beneath Yaeyama region, where earthquake swarm occurred on 1991 and 1992. To reveal the relation among the crustal structure, earthquake swarms, and occurrence of slow slip events (SSE), local earthquake tomography and receiver function (RF) analysis was computed in the southwestern Ryukyu arc. A tomographic inversion was used to determine P and S wave structures beneath Iriomote Island in the southwestern Ryukyu region for comparison with the locations of the SSE. The seismic tomography (Thurber & Eberhart-Phillips, 1999) was employed. The P- and S- wave arrival time data picked manually by Japan Meteorological Agency (JMA) are used. The 6750 earthquakes from January 2000 to July 2012 were used. For the calculation of the receiver function, the 212 earthquakes whose magnitudes are over 6.0 and epicentral distances are between 30 and 90 degrees were selected. The teleseicmic waveforms observed at two short-period seismometers of the JMA, and one broadband seismometer of F-net of National Research Institute for Earth Science and Disaster Prevention were used. The water level method (the water level is 0.01) is applied to original waveforms. Assuming that each later phase in a RF is the wave converted from P to S at a depth, I transformed the time domain RF into the depth domain one along each ray path in a reference velocity model. The JMA2001 velocity model is used in this study. The results of tomography show that the low Vp and high Vp

Georgia-Armenia Transboarder seismicity studies

NASA Astrophysics Data System (ADS)

Godoladze, T.; Tvaradze, N.; Javakishvili, Z.; Elashvili, M.; Durgaryan, R.; Arakelyan, A.; Gevorgyan, M.

2012-12-01

In the presented study we performed Comprehensive seismic analyses for the Armenian-Georgian transboarder active seismic fault starting on Armenian territory, cutting the state boarder and having possibly northern termination on Adjara-Triealeti frontal structure in Georgia. In the scope of International projects: ISTC A-1418 "Open network of scientific Centers for mitigation risk of natural hazards in the Southern Caucasus and Central Asia" and NATO SfP- 983284 Project "Caucasus Seismic Emergency Response" in Akhalkalaki (Georgia) seismic center, Regional Summer school trainings and intensive filed investigations were conducted. Main goal was multidisciplinary study of the Javakheti fault structure and better understanding seismicity of the area. Young scientists from Turkey, Armenia, Azerbaijan and Georgia were participated in the deployment of temporal seismic network in order to monitor seisimity on the Javakheti highland and particularly delineate fault scarf and identify active seismic structures. In the scope of international collaboration the common seismic database has been created in the southern Caucasus and collected data from the field works is available now online. Javakheti highland, which is located in the central part of the Caucasus, belongs to the structure of the lesser Caucasus and represents a history of neotectonic volcanism existed in the area. Jasvakheti highland is seismicalu active region devastating from several severe earthquakes(1088, 1283, 1899…). Hypocenters located during analogue network were highly scattered and did not describe real pattern of seismicity of the highland. We relocated hypocenters of the region and improved local velocity model. The hypocenters derived from recently deployed local seismic network in the Javakheti highland, clearly identified seismically active structures. Fault plane solutions of analogue data of the Soviet times have been carefully analyzed and examined. Moment tensor inversion were preformed

Korea Integrated Seismic System tool(KISStool) for seismic monitoring and data sharing at the local data center

NASA Astrophysics Data System (ADS)

Park, J.; Chi, H. C.; Lim, I.; Jeong, B.

2011-12-01

The Korea Integrated Seismic System(KISS) is a back-bone seismic network which distributes seismic data to different organizations in near-real time at Korea. The association of earthquake monitoring institutes has shared their seismic data through the KISS from 2003. Local data centers operating remote several stations need to send their free field seismic data to NEMA(National Emergency Management Agency) by the law of countermeasure against earthquake hazard in Korea. It is very important the efficient tool for local data centers which want to rapidly detect local seismic intensity and to transfer seismic event information toward national wide data center including PGA, PGV, dominant frequency of P-wave, raw data, and etc. We developed the KISStool(Korea Integrated Seismic System tool) for easy and convenient operation seismic network in local data center. The KISStool has the function of monitoring real time waveforms by clicking station icon on the Google map and real time variation of PGA, PGV, and other data by opening the bar type monitoring section. If they use the KISStool, any local data center can transfer event information to NEMA(National Emergency Management Agency), KMA(Korea Meteorological Agency) or other institutes through the KISS using UDP or TCP/IP protocols. The KISStool is one of the most efficient methods to monitor and transfer earthquake event at local data center in Korea. KIGAM will support this KISStool not only to the member of the monitoring association but also local governments.

Earthquake Intensity and Strong Motion Analysis Within SEISCOMP3

NASA Astrophysics Data System (ADS)

Becker, J.; Weber, B.; Ghasemi, H.; Cummins, P. R.; Murjaya, J.; Rudyanto, A.; Rößler, D.

2017-12-01

Measuring and predicting ground motion parameters including seismic intensities for earthquakes is crucial and subject to recent research in engineering seismology.gempa has developed the new SIGMA module for Seismic Intensity and Ground Motion Analysis. The module is based on the SeisComP3 framework extending it in the field of seismic hazard assessment and engineering seismology. SIGMA may work with or independently of SeisComP3 by supporting FDSN Web services for importing earthquake or station information and waveforms. It provides a user-friendly and modern graphical interface for semi-automatic and interactive strong motion data processing. SIGMA provides intensity and (P)SA maps based on GMPE's or recorded data. It calculates the most common strong motion parameters, e.g. PGA/PGV/PGD, Arias intensity and duration, Tp, Tm, CAV, SED and Fourier-, power- and response spectra. GMPE's are configurable. Supporting C++ and Python plug-ins, standard and customized GMPE's including the OpenQuake Hazard Library can be easily integrated and compared. Originally tailored to specifications by Geoscience Australia and BMKG (Indonesia) SIGMA has become a popular tool among SeisComP3 users concerned with seismic hazard and strong motion seismology.

Seismicity map of the State of Illinois

USGS Publications Warehouse

Stover, C.W.; Reagor, B.G.; Algermissen, S.T.

1979-01-01

The earthquake data shown on this map and listed in table 1 are a list of earthquakes that were originally used in preparing the Seismic Risk Studies in the United States (Algermissen, 1969) which have been recompiled and updated through 1977. The data have been reexamined and intensities assigned where none had been assigned before, on the basis of available data. Other intensity values were updated from new and additional data sources that were not available at the time of original compilation. Some epicenters were relocated on the basis of new information. The data shown in table 1 are estimates of the most accurate epicenter, magnitude, and intensity of teach earthquake, on the basis of historical and current information. Some of the aftershocks from large earthquakes are listed but are incomplete in many instances, especially for the ones that occurred before seismic instruments were in universal usage. 

Lunar seismicity and tectonics

NASA Technical Reports Server (NTRS)

Lammlein, D. R.

1977-01-01

Results are presented for an analysis of all moonquake data obtained by the Apollo seismic stations during the period from November 1969 to May 1974 and a preliminary analysis of critical data obtained in the interval from May 1974 to May 1975. More accurate locations are found for previously located moonquakes, and additional sources are located. Consideration is given to the sources of natural seismic signals, lunar seismic activity, moonquake periodicities, tidal periodicities in moonquake activity, hypocentral locations and occurrence characteristics of deep and shallow moonquakes, lunar tidal control over moonquakes, lunar tectonism, the locations of moonquake belts, and the dynamics of the lunar interior. It is concluded that: (1) moonquakes are distributed in several major belts of global extent that coincide with regions of the youngest and most intense volcanic and tectonic activity; (2) lunar tides control both the small quakes occurring at great depth and the larger quakes occurring near the surface; (3) the moon has a much thicker lithosphere than earth; (4) a single tectonic mechanism may account for all lunar seismic activity; and (5) lunar tidal stresses are an efficient triggering mechanism for moonquakes.

The ESI scale, an ethical approach to the evaluation of seismic hazards

NASA Astrophysics Data System (ADS)

Porfido, Sabina; Nappi, Rosa; De Lucia, Maddalena; Gaudiosi, Germana; Alessio, Giuliana; Guerrieri, Luca

2015-04-01

The dissemination of correct information about seismic hazard is an ethical duty of scientific community worldwide. A proper assessment of a earthquake severity and impact should not ignore the evaluation of its intensity, taking into account both the effects on humans, man-made structures, as well as on the natural evironment. We illustrate the new macroseismic scale that measures the intensity taking into account the effects of earthquakes on the environment: the ESI 2007 (Environmental Seismic Intensity) scale (Michetti et al., 2007), ratified by the INQUA (International Union for Quaternary Research) during the XVII Congress in Cairns (Australia). The ESI scale integrates and completes the traditional macroseismic scales, of which it represents the evolution, allowing to assess the intensity parameter also where buildings are absent or damage-based diagnostic elements saturate. Each degree reflects the corresponding strength of an earthquake and the role of ground effects, evaluating the Intensity on the basis of the characteristics and size of primary (e.g. surface faulting and tectonic uplift/subsidence) and secondary effects (e.g. ground cracks, slope movements, liquefaction phenomena, hydrological changes, anomalous waves, tsunamis, trees shaking, dust clouds and jumping stones). This approach can be considered "ethical" because helps to define the real scenario of an earthquake, regardless of the country's socio-economic conditions and level of development. Here lies the value and the relevance of macroseismic scales even today, one hundred years after the death of Giuseppe Mercalli, who conceived the homonymous scale for the evaluation of earthquake intensity. For an appropriate mitigation strategy in seismic areas, it is fundamental to consider the role played by seismically induced effects on ground, such as active faults (size in length and displacement) and secondary effects (the total area affecting). With these perspectives two different cases

South-Central Tibetan Seismicity from HiCLIMB Seismic Array Data

NASA Astrophysics Data System (ADS)

Carpenter, S.; Nabelek, J.; Braunmiller, J.

2010-12-01

The HiCLIMB broadband passive seismic experiment (2002-2005) operated 233 sites along a 800-km long north-south array extending from the Himalayan foreland into the Central Tibetan Plateau and a flanking 350x350 km lateral array in southern Tibet and eastern Nepal. We use data from the experiment’s second phase (June 2004 to August 2005), when stations operated in Tibet, to locate earthquakes in south-central Tibet, a region with no permanent seismic network where little is known about its seismicity. We used the Antelope software for automatic detection and arrival time picking, event-arrival association and event location. Requiring a low detection and event association threshold initially resulted in ~110,000 declared events. The large database size rendered manual inspection unfeasible and we developed automated post-processing modules to weed out spurious detections and erroneous phase and event associations, which stemmed, e.g., from multiple coincident earthquakes within the array or misplaced seismicity from the great 2004 Sumatra earthquake. The resulting database contains ~32,000 events within 5° distance from the closest station. We consider ~7,600 events defined by more than 30 P and S arrivals well located and discuss them here. Seismicity in the subset correlates well with mapped faults and structures seen on satellite imagery attesting to high location quality. This is confirmed by non-systematic, kilometer-scale differences between automatic and manual locations for selected events. Seismicity in south-central Tibet is intense north of the Yarlung-Tsangpo Suture. Almost 90% of events occurred in the Lhasa Terrane mainly along north-south trending rifts. Vigorous activity (>4,800 events) accompanied two M>6 earthquakes in the Payang Basin (84°E), ~100 km west of the linear array. The Tangra-Yum Co (86.5°E) and Pumqu-Xianza (88°E) rifts were very active (~1,000 events) without dominant main shocks indicating swarm like-behavior possibly related

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

Seismic activity in northeastern Brazill-new perspectives

NASA Astrophysics Data System (ADS)

Ferreira, J. M.; Do Nascimento, A. F.; Vilar, C. S.; Bezerra, F. H.; Assumpcao, M.; Berrocal, J.; Fuck, R. A.

2007-05-01

Northeastern Brazil is the most seismic active region in the country. Some earthquakes with magnitude above 5.0 and intensity VII MM associated with swam-like seismic activity lasting for many years are a serious social concern. Since the 1980's macroseismic and instrumental surveys have been carried out in this region and they are an important data archive which allows the composition of a reliable catalogue of seismic activity for this region. Among the many scientific results it was possible to identify the main seismogenic areas, obtain reliable hypocentres and focal mechanisms. As a consequence, it was possible also to analyse the relationship between seismicity and geological features. It was also possible to determined maximum horizontal stress direction for the region. An important induced seismic activity case has also been reported in the area as being a classical example of pore pressure diffusion triggering mechanism. The majority of the results were obtained using analogic data. Recently, a new research project is being conducted and will allow us to provide a regional scale monitoring with 6 broad-band stations and a new portable six station digital seismic network equipped with short- period sensors. Thus, with the continuous seismic activity in the area we trust that the results of this project will increase the present knowledge of seismic activity in northeastern Brazil.

Towards Improved Considerations of Risk in Seismic Design (Plinius Medal Lecture)

NASA Astrophysics Data System (ADS)

Sullivan, T. J.

2012-04-01

The aftermath of recent earthquakes is a reminder that seismic risk is a very relevant issue for our communities. Implicit within the seismic design standards currently in place around the world is that minimum acceptable levels of seismic risk will be ensured through design in accordance with the codes. All the same, none of the design standards specify what the minimum acceptable level of seismic risk actually is. Instead, a series of deterministic limit states are set which engineers then demonstrate are satisfied for their structure, typically through the use of elastic dynamic analyses adjusted to account for non-linear response using a set of empirical correction factors. From the early nineties the seismic engineering community has begun to recognise numerous fundamental shortcomings with such seismic design procedures in modern codes. Deficiencies include the use of elastic dynamic analysis for the prediction of inelastic force distributions, the assignment of uniform behaviour factors for structural typologies irrespective of the structural proportions and expected deformation demands, and the assumption that hysteretic properties of a structure do not affect the seismic displacement demands, amongst other things. In light of this a number of possibilities have emerged for improved control of risk through seismic design, with several innovative displacement-based seismic design methods now well developed. For a specific seismic design intensity, such methods provide a more rational means of controlling the response of a structure to satisfy performance limit states. While the development of such methodologies does mark a significant step forward for the control of seismic risk, they do not, on their own, identify the seismic risk of a newly designed structure. In the U.S. a rather elaborate performance-based earthquake engineering (PBEE) framework is under development, with the aim of providing seismic loss estimates for new buildings. The PBEE framework

Seismic velocity structure and spatial distribution of reflection intensity off the Boso Peninsula, Central Japan, revealed by an ocean bottom seismographic experiment

NASA Astrophysics Data System (ADS)

Kono, Akihiro; Sato, Toshinori; Shinohara, Masanao; Mochizuki, Kimihiro; Yamada, Tomoaki; Uehira, Kenji; Shinbo, Takashi; Machida, Yuuya; Hino, Ryota; Azuma, Ryosuke

2016-04-01

Off the Boso Peninsula, central Japan, where the Sagami Trough is in the south and the Japan Trench is in the east, there is a triple junction where the Pacific plate (PAC), the Philippine Sea plate (PHS) and the Honshu island arc (HIA) meet each other. In this region, the PAC subducts beneath the PHS and the HIA, and the PHS subducts beneath the HIA. Due to the subduction of 2 oceanic plates, numerous seismic events took place in the past. In order to understand these events, it is important to image structure of these plates. Hence, many researchers attempted to reveal the substructure from natural earthquakes and seismic experiments. Because most of the seismometers are placed inland area and the regular seismicity off Boso is inactive, it is difficult to reveal the precise substructure off Boso area using only natural earthquakes. Although several marine seismic experiments using active sources were conducted, vast area remains unclear off Boso Peninsula. In order to improve the situation, a marine seismic experiment, using airgun as an active source, was conducted from 30th July to 4th of August, 2009. The survey line has 216 km length and 20 Ocean Bottom Seismometers (OBSs) were placed on it. We estimated 2-D P-wave velocity structure from the airgun data using the PMDM (Progressive Model Development Method; Sato and Kenett, 2000) and the FAST (First Arrival Seismic Tomography ; Zelt and Barton, 1998). Furthermore, we identified the probable reflection phases from the data and estimated the location of reflectors using Travel time mapping method (Fujie et al. 2006). We found some reflection phases from the data, and the reflectors are located near the region where P-wave velocity is 5.0 km/s. We interpret that the reflectors indicate the plate boundary between the PHS and the HIA. The variation of the intensity of reflection along the upper surface of PHS seems to be consistent with the result from previous reflection seismic experiment conducted by Kimura et

Seismicity map of the state of Arizona

USGS Publications Warehouse

Stover, C.W.; Reagor, B.G.; Algermissen, S.T.

1986-01-01

This map is one of a series of seismicity maps produced by the U. S. Geological Survey that show earthquake data of individual states or groups of states at the scale of 1:1,000,000. This map shows only those earthquakes with epicenters located within the boundaries of Arizona, even though earthquakes in nearby states or countries may have been felt or may have caused damage in Arizona.The data in table 1 were used to compile the seismicity map; these data are a corrected, expanded, and updated (through 1982) version of the data used by Algermissen (1969) for a study of seismic risk in the United States. The locations and intensities of some earthquakes were revised and intensities were assigned where none had been before. Many earthquakes were added to the original list from new data sources as well as from some old data sources that had not been previously used. The data in table 1 represent best estimates of the location of the epicenter, magnitude, and intensity of each earthquake on the basis of historical and current information. Some of the aftershocks from large earthquakes are listed, but not all, especially for earthquakes that occurred before seismic instruments were universally used.Table 1 includes earthquakes reported felt in Yuma, Arizona that had no corroborating reports from other areas. These events are listed with coordinates (32.7°N., 114.6° W.) near Yuma even though it is suspected that they may have actually occurred in the Imperial Valley, California or Baja California, Mexico. Very few earthquakes have been instrumentally located near Yuma and it is believed that most historical felt reports correspond to earthquakes that occurred in the seismic zone extending from the Gulf of California northward into California. It is known that some earthquakes located graphically from phase data prior to epicenter determinations by electronic computer were erroneously located in southern Arizona and actually had locations in the Gulf of California or

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.

Exposure to seismic survey alters blue whale acoustic communication

PubMed Central

Di Iorio, Lucia; Clark, Christopher W.

2010-01-01

The ability to perceive biologically important sounds is critical to marine mammals, and acoustic disturbance through human-generated noise can interfere with their natural functions. Sounds from seismic surveys are intense and have peak frequency bands overlapping those used by baleen whales, but evidence of interference with baleen whale acoustic communication is sparse. Here we investigated whether blue whales (Balaenoptera musculus) changed their vocal behaviour during a seismic survey that deployed a low-medium power technology (sparker). We found that blue whales called consistently more on seismic exploration days than on non-exploration days as well as during periods within a seismic survey day when the sparker was operating. This increase was observed for the discrete, audible calls that are emitted during social encounters and feeding. This response presumably represents a compensatory behaviour to the elevated ambient noise from seismic survey operations. PMID:19776059

The Wenchuan, China M8.0 Earthquake: A Lesson and Implication for Seismic Hazard Mitigation

NASA Astrophysics Data System (ADS)

Wang, Z.

2008-12-01

The Wenchuan, China M8.0 earthquake caused great damage and huge casualty. 69,197 people were killed, 374,176 people were injured, and 18,341 people are still missing. The estimated direct economic loss is about 126 billion U.S. dollar. The Wenchuan earthquake again demonstrated that earthquake does not kill people, but the built environments and induced hazards, landslides in particular, do. Therefore, it is critical to strengthen the built environments, such buildings and bridges, and to mitigate the induced hazards in order to avoid such disaster. As a part of the so-called North-South Seismic Zone in China, the Wenchuan earthquake occurred along the Longmen Shan thrust belt which forms a boundary between the Qinghai-Tibet Plateau and the Sichuan basin, and there is a long history (~4,000 years) of seismicity in the area. The historical records show that the area experienced high intensity (i.e., greater than IX) in the past several thousand years. In other words, the area is well-known to have high seismic hazard because of its tectonic setting and seismicity. However, only intensity VII (0.1 to 0.15g PGA) has been considered for seismic design for the built environments in the area. This was one of the main reasons that so many building collapses, particularly the school buildings, during the Wenchuan earthquake. It is clear that the seismic design (i.e., the design ground motion or intensity) is not adequate in the Wenchuan earthquake stricken area. A lesson can be learned from the Wenchuan earthquake on the seismic hazard and risk assessment. A lesson can also be learned from this earthquake on seismic hazard mitigation and/or seismic risk reduction.

Seismic Intensity, PGA and PGV for the South Napa Earthquake, August 24, 2014

NASA Astrophysics Data System (ADS)

Chen, S.; Pickering, A.; Mooney, W. D.; Crewdson, E.

2014-12-01

Numerous studies have investigated the statistical relationship between Modified Mercalli Intensity (MMI) and peak ground acceleration (PGA) and peak ground velocity (PGV). The Mw 6.0 South Napa (California) earthquake of August 24, 2014 provides valuable data to examine these relationships for both urban and rural environments within northern California. The finite fault model (D. Dreger, 2014) indicates that the fault rupture propagated predominantly NNW and up-dip from a 11-km-deep hypocenter. The epicentral location was 8 km SSW of downtown Napa. Recorded PGA north of the epicenter is as high as 600 cm/s2 and PGV locally reaches 80 cm/s. Field studies by two teams of investigators were conducted on August 24-26 and September 8-11, 2014 to assign MMI values at 108 sites. The highest MMI values are strongly localized along the NNW-SSE rupture trend north of the epicenter. Parts of the city of Napa and some communities several km farther north on Dry Creek Road were found to have experienced shaking intensities of MMI VII to VIII. The observed effects include houses moved off their foundations, chimney collapse or damage, cracked foundations and/or interior walls, broken windows, and the lateral displacement of heavy furniture. Communities to the east and west of this zone of high seismic intensity reported significantly lower values of MMI, typically IV and V even at distances as close as 10 km from the mapped surface rupture. In comparison with previous estimates by Wald et al. (1999) and Dangkua and Cramer (2011), we find that MMI III-VIII uniformly correspond to significantly larger (>150%) PGA and PGV values, as reported by the Center for Engineering Strong Motion Data (2014). We attribute this observation to two primary factors: (1) improved earthquake engineering in the post-Loma Prieta earthquake era that has led to building construction, both new and retrofitted, that is more resistant to earthquake strong ground motions; and (2) a frequency band relevant

Preliminary consideration on the seismic actions recorded during the 2016 Central Italy seismic sequence

NASA Astrophysics Data System (ADS)

Carlo Ponzo, Felice; Ditommaso, Rocco; Nigro, Antonella; Nigro, Domenico S.; Iacovino, Chiara

2017-04-01

After the Mw 6.0 mainshock of August 24, 2016 at 03.36 a.m. (local time), with the epicenter located between the towns of Accumoli (province of Rieti), Amatrice (province of Rieti) and Arquata del Tronto (province of Ascoli Piceno), several activities were started in order to perform some preliminary evaluations on the characteristics of the recent seismic sequence in the areas affected by the earthquake. Ambient vibration acquisitions have been performed using two three-directional velocimetric synchronized stations, with a natural frequency equal to 0.5Hz and a digitizer resolution of equal to 24bit. The activities are continuing after the events of the seismic sequence of October 26 and October 30, 2016. In this paper, in order to compare recorded and code provision values in terms of peak (PGA, PGV and PGD), spectral and integral (Housner Intensity) seismic parameters, several preliminary analyses have been performed on accelerometric time-histories acquired by three near fault station of the RAN (Italian Accelerometric Network): Amatrice station (station code AMT), Norcia station (station code NRC) and Castelsantangelo sul Nera station (station code CNE). Several comparisons between the elastic response spectra derived from accelerometric recordings and the elastic demand spectra provided by the Italian seismic code (NTC 2008) have been performed. Preliminary results retrieved from these analyses highlight several apparent difference between experimental data and conventional code provision. Then, the ongoing seismic sequence appears compatible with the historical seismicity in terms of integral parameters, but not in terms of peak and spectral values. It seems appropriate to reconsider the necessity to revise the simplified design approach based on the conventional spectral values. Acknowledgements This study was partially funded by the Italian Department of Civil Protection within the project DPC-RELUIS 2016 - RS4 ''Seismic observatory of structures and

Seismic Symphonies

NASA Astrophysics Data System (ADS)

Strinna, Elisa; Ferrari, Graziano

2015-04-01

The project started in 2008 as a sound installation, a collaboration between an artist, a barrel organ builder and a seismologist. The work differs from other attempts of sound transposition of seismic records. In this case seismic frequencies are not converted automatically into the "sound of the earthquake." However, it has been studied a musical translation system that, based on the organ tonal scale, generates a totally unexpected sequence of sounds which is intended to evoke the emotions aroused by the earthquake. The symphonies proposed in the project have somewhat peculiar origins: they in fact come to life from the translation of graphic tracks into a sound track. The graphic tracks in question are made up by copies of seismograms recorded during some earthquakes that have taken place around the world. Seismograms are translated into music by a sculpture-instrument, half a seismograph and half a barrel organ. The organ plays through holes practiced on paper. Adapting the documents to the instrument score, holes have been drilled on the waves' peaks. The organ covers about three tonal scales, starting from heavy and deep sounds it reaches up to high and jarring notes. The translation of the seismic records is based on a criterion that does match the highest sounds to larger amplitudes with lower ones to minors. Translating the seismogram in the organ score, the larger the amplitude of recorded waves, the more the seismogram covers the full tonal scale played by the barrel organ and the notes arouse an intense emotional response in the listener. Elisa Strinna's Seismic Symphonies installation becomes an unprecedented tool for emotional involvement, through which can be revived the memory of the greatest disasters of over a century of seismic history of the Earth. A bridge between art and science. Seismic Symphonies is also a symbolic inversion: the instrument of the organ is most commonly used in churches, and its sounds are derived from the heavens and

Spatial heterogeneity of the structure and stress field in Hyuga-nada region, southwest Japan, deduced from onshore and offshore seismic observations

NASA Astrophysics Data System (ADS)

Uehira, K.; Yakiwara, H.; Yamada, T.; Umakoshi, K.; Nakao, S.; Kobayashi, R.; Goto, K.; Miyamachi, H.; Mochizuki, K.; Nakahigashi, K.; Shinohara, M.; Kanazawa, T.; Hino, R.; Goda, M.; Shimizu, H.

2010-12-01

In Hyuga-nada region, the Philippine Sea (PHS) plate is subducting beneath the Eurasian (EU) plate (the southwest Japan arc) along the Nankai trough at a rate of about 5 cm per year. The seismic activity in the boundary between the PHS and the Eurasian (EU) plates varies spatially along the Nankai trough. Especially the region from off coast of Shikoku to the Bungo channel and Hyuga-nada has large variation of seismicity. Although usual microearthquake activity is active in Hyuga-nada, it is inactive near Shikoku. On the other hand, although the great earthquake (M>8) has occurred repeatedly in near Shikoku at intervals of about 100 years, in Hyuga-nada, smaller earthquakes (M7 class) has occurred at intervals of about dozens of years, and so plate coupling varies dozens of kilometers specially. Big earthquakes (M7 class) have occurred in the north region from latitude 31.6 degrees north, but it has not occurred in the south region from latitude 31.6 degrees north. The largest earthquake ever recorded in Hyuga-nada region is the 1968 Hyuga-nada earthquake (Mw 7.5). And microseismicity varies spatially. It is important to understand seismic activity, stress field, and structure in such region in order to understand seismic cycle. We performed extraordinary seismic observation in and around Hyuga-nada region. More than 20 pop-up type OBSs were deployed above hypocentral region of Hyuga-nada using Nagasaki-maru and several data loggers were deployed in order to compensate a regular seismic network on land. We detected earthquakes more than 2 times of JMA. Seismic activity in source region of the 1961 Hyuga-nada Earthquake (M7.0) is low, but around its source region, seismic activity is very high. In order to obtain a 3D seismic velocity structure and precise hypocenter distribution and focal mechanisms around the Hyuga-nada region, we used Double-Difference (DD) Tomography method developed by Zhang and Thurber (2003). We could detect the structure of subduction of

Effects of seismic intensity and socioeconomic status on injury and displacement after the 2007 Peru earthquake.

PubMed

Milch, Karen; Gorokhovich, Yuri; Doocy, Shannon

2010-10-01

Earthquakes are a major cause of displacement, particularly in developing countries. Models of injury and displacement can be applied to assist governments and aid organisations in effectively targeting preparedness and relief efforts. A stratified cluster survey was conducted in January 2008 to evaluate risk factors for injury and displacement following the 15 August 2007 earthquake in southern Peru. In statistical modelling, seismic intensity, distance to rupture, living conditions, and educational attainment collectively explained 54.9 per cent of the variability in displacement rates across clusters. Living conditions was a particularly significant predictor of injury and displacement, indicating a strong relationship between risk and socioeconomic status. Contrary to expectations, urban, periurban, and rural clusters did not exhibit significantly different injury and displacement rates. Proxies of socioeconomic status, particularly the living conditions index score, proved relevant in explaining displacement, likely due to unmeasured aspects of housing construction practices and building materials. © 2010 The Author(s). Journal compilation © Overseas Development Institute, 2010.

Fault Specific Seismic Hazard Maps as Input to Loss Reserves Calculation for Attica Buildings

NASA Astrophysics Data System (ADS)

Deligiannakis, Georgios; Papanikolaou, Ioannis; Zimbidis, Alexandros; Roberts, Gerald

2014-05-01

Greece is prone to various natural disasters, such as wildfires, floods, landslides and earthquakes, due to the special environmental and geological conditions dominating in tectonic plate boundaries. Seismic is the predominant risk, in terms of damages and casualties in the Greek territory. The historical record of earthquakes in Greece has been published from various researchers, providing useful data in seismic hazard assessment of Greece. However, the completeness of the historical record in Greece, despite being one of the longest worldwide, reaches only 500 years for M ≥ 7.3 and less than 200 years for M ≥ 6.5. Considering that active faults in the area have recurrence intervals of a few hundred to several thousands of years, it is clear that many active faults have not been activated during the completeness period covered by the historical records. New Seismic Hazard Assessment methodologies tend to follow fault specific approaches where seismic sources are geologically constrained active faults, in order to address problems related to the historical records incompleteness, obtain higher spatial resolution and calculate realistic source locality distances, since seismic sources are very accurately located. Fault specific approaches provide quantitative assessments as they measure fault slip rates from geological data, providing a more reliable estimate of seismic hazard. We used a fault specific seismic hazard assessment approach for the region of Attica. The method of seismic hazard mapping from geological fault throw-rate data combined three major factors: Empirical data which combine fault rupture lengths, earthquake magnitudes and coseismic slip relationships. The radiuses of VI, VII, VIII and IX isoseismals on the Modified Mercalli (MM) intensity scale. Attenuation - amplification functions for seismic shaking on bedrock compared to basin filling sediments. We explicitly modeled 22 active faults that could affect the region of Attica, including

Revised seismic hazard map for the Kyrgyz Republic

NASA Astrophysics Data System (ADS)

Fleming, Kevin; Ullah, Shahid; Parolai, Stefano; Walker, Richard; Pittore, Massimiliano; Free, Matthew; Fourniadis, Yannis; Villiani, Manuela; Sousa, Luis; Ormukov, Cholponbek; Moldobekov, Bolot; Takeuchi, Ko

2017-04-01

As part of a seismic risk study sponsored by the World Bank, a revised seismic hazard map for the Kyrgyz Republic has been produced, using the OpenQuake-engine developed by the Global Earthquake Model Foundation (GEM). In this project, an earthquake catalogue spanning a period from 250 BCE to 2014 was compiled and processed through spatial and temporal declustering tools. The territory of the Kyrgyz Republic was divided into 31 area sources defined based on local seismicity, including a total area covering 200 km from the border. The results are presented in terms of Peak Ground Acceleration (PGA). In addition, macroseismic intensity estimates, making use of recent intensity prediction equations, were also provided, given that this measure is still widely used in Central Asia. In order to accommodate the associated epistemic uncertainty, three ground motion prediction equations were used in a logic tree structure. A set of representative earthquake scenarios were further identified based on historical data and the nature of the considered faults. The resulting hazard map, as expected, follows the country's seismicity, with the highest levels of hazard in the northeast, south and southwest of the country, with an elevated part around the centre. When considering PGA, the hazard is slightly greater for major urban centres than in previous works (e.g., Abdrakhmatov et al., 2003), although the macroseismic intensity estimates are less than previous studies, e.g., Ulomov (1999). For the scenario assessments, the examples that most affect the urban centres assessed are the Issyk Ata fault (in particular for Bishkek), the Chilik and Kemin faults (in particular Balykchy and Karakol), the Ferghana Valley fault system (in particular Osh, Jalah-Abad and Uzgen), the Oinik Djar fault (Naryn) and the central and western Talas-Ferghanafaukt (Talas). Finally, while site effects (in particular, those dependent on the upper-most geological structure) have an obvious effect on the

Man-caused seismicity of Kuzbass

NASA Astrophysics Data System (ADS)

Emanov, Alexandr; Emanov, Alexey; Leskova, Ekaterina; Fateyev, Alexandr

2010-05-01

A natural seismicity of Kuznetsk Basin is confined in the main to mountain frame of Kuznetsk hollow. In this paper materials of experimental work with local station networks within sediment basin are presented. Two types of seismicity display within Kuznetsk hollow have been understood: first, man-caused seismic processes, confined to mine working and concentrated on depths up to one and a half of km; secondly, seismic activations on depths of 2-56 km, not coordinated in plan with coal mines. Every of studied seismic activations consists of large quantity of earthquakes of small powers (Ms=1-3). From one to first tens of earthquakes were recorded in a day. The earthquakes near mine working shift in space along with mine working, and seismic process become stronger at the instant a coal-plough machine is operated, and slacken at the instant the preventive works are executed. The seismic processes near three lavas in Kuznetsk Basin have been studied in detail. Uplift is the most typical focal mechanism. Activated zone near mine working reach in diameter 1-1,5 km. Seismic activations not linked with mine working testify that the subsoil of Kuznetsk hollow remain in stress state in whole. The most probable causes of man-caused action on hollow are processes, coupled with change of physical state of rocks at loss of methane from large volume or change by mine working of rock watering in large volume. In this case condensed rocks, lost gas and water, can press out upwards, realizing the reverse fault mechanism of earthquakes. A combination of stress state of hollow with man-caused action at deep mining may account for incipient activations in Kuznetsk Basin. Today earthquakes happen mainly under mine workings, though damages of workings themselves do not happen, but intensive shaking on surface calls for intent study of so dangerous phenomena. In 2009 replicates of the experiment on research of seismic activations in area of before investigated lavas have been conducted

Seismic hazard assessment based on the Unified Scaling Law for Earthquakes: the Greater Caucasus

NASA Astrophysics Data System (ADS)

Nekrasova, A.; Kossobokov, V. G.

2015-12-01

Losses from natural disasters continue to increase mainly due to poor understanding by majority of scientific community, decision makers and public, the three components of Risk, i.e., Hazard, Exposure, and Vulnerability. Contemporary Science is responsible for not coping with challenging changes of Exposures and their Vulnerability inflicted by growing population, its concentration, etc., which result in a steady increase of Losses from Natural Hazards. Scientists owe to Society for lack of knowledge, education, and communication. In fact, Contemporary Science can do a better job in disclosing Natural Hazards, assessing Risks, and delivering such knowledge in advance catastrophic events. We continue applying the general concept of seismic risk analysis in a number of seismic regions worldwide by constructing regional seismic hazard maps based on the Unified Scaling Law for Earthquakes (USLE), i.e. log N(M,L) = A - B•(M-6) + C•log L, where N(M,L) is the expected annual number of earthquakes of a certain magnitude M within an seismically prone area of linear dimension L. The parameters A, B, and C of USLE are used to estimate, first, the expected maximum magnitude in a time interval at a seismically prone cell of a uniform grid that cover the region of interest, and then the corresponding expected ground shaking parameters including macro-seismic intensity. After a rigorous testing against the available seismic evidences in the past (e.g., the historically reported macro-seismic intensity), such a seismic hazard map is used to generate maps of specific earthquake risks (e.g., those based on the density of exposed population). The methodology of seismic hazard and risks assessment based on USLE is illustrated by application to the seismic region of Greater Caucasus.

The persistent signature of tropical cyclones in ambient seismic noise

NASA Astrophysics Data System (ADS)

Gualtieri, Lucia; Camargo, Suzana J.; Pascale, Salvatore; Pons, Flavio M. E.; Ekström, Göran

2018-02-01

The spectrum of ambient seismic noise shows strong signals associated with tropical cyclones, yet a detailed understanding of these signals and the relationship between them and the storms is currently lacking. Through the analysis of more than a decade of seismic data recorded at several stations located in and adjacent to the northwest Pacific Ocean, here we show that there is a persistent and frequency-dependent signature of tropical cyclones in ambient seismic noise that depends on characteristics of the storm and on the detailed location of the station relative to the storm. An adaptive statistical model shows that the spectral amplitude of ambient seismic noise, and notably of the short-period secondary microseisms, has a strong relationship with tropical cyclone intensity and can be employed to extract information on the tropical cyclones.

Post-processing of seismic parameter data based on valid seismic event determination

DOEpatents

McEvilly, Thomas V.

1985-01-01

An automated seismic processing system and method are disclosed, including an array of CMOS microprocessors for unattended battery-powered processing of a multi-station network. According to a characterizing feature of the invention, each channel of the network is independently operable to automatically detect, measure times and amplitudes, and compute and fit Fast Fourier transforms (FFT's) for both P- and S- waves on analog seismic data after it has been sampled at a given rate. The measured parameter data from each channel are then reviewed for event validity by a central controlling microprocessor and if determined by preset criteria to constitute a valid event, the parameter data are passed to an analysis computer for calculation of hypocenter location, running b-values, source parameters, event count, P- wave polarities, moment-tensor inversion, and Vp/Vs ratios. The in-field real-time analysis of data maximizes the efficiency of microearthquake surveys allowing flexibility in experimental procedures, with a minimum of traditional labor-intensive postprocessing. A unique consequence of the system is that none of the original data (i.e., the sensor analog output signals) are necessarily saved after computation, but rather, the numerical parameters generated by the automatic analysis are the sole output of the automated seismic processor.

Modeling the Excitation of Seismic Waves by the Joplin Tornado

NASA Astrophysics Data System (ADS)

Valovcin, Anne; Tanimoto, Toshiro

2017-10-01

Tornadoes generate seismic signals when they contact the ground. Here we examine the signals excited by the Joplin tornado, which passed within 2 km of a station in the Earthscope Transportable Array. We model the tornado-generated vertical seismic signal at low frequencies (0.01-0.03 Hz) and solve for the strength of the seismic source. The resulting source amplitude is largest when the tornado was reported to be strongest (EF 4-5), and the amplitude is smallest when the tornado was weak (EF 0-2). A further understanding of the relationship between source amplitude and tornado intensity could open up new ways to study tornadoes from the ground.

Mapping seismic intensity using twitter data; A Case study: The February 26th, 2014 M5.9 Kefallinia (Greece) earthquake

NASA Astrophysics Data System (ADS)

Arapostathis, Stathis; Parcharidis, Isaak; Kalogeras, Ioannis; Drakatos, George

2015-04-01

In this paper we present an innovative approach for the development of seismic intensity maps in minimum time frame. As case study, a recent earthquake that occurred in Western Greece (Kefallinia Island, on February 26, 2014) is used. The magnitude of the earthquake was M=5.9 (Institute of Geodynamics - National Observatory of Athens). Earthquake's effects comprising damages in property and changes of the physical environment in the area. The innovative part of this research is that we use crowdsourcing as a source to assess macroseismic intensity information, coming out from twitter content. Twitter as a social media service with micro-blogging characteristics, a semantic structure which allows the storage of spatial content, and a high volume production of user generated content is a suitable source to obtain and extract knowledge related to macroseismic intensity in different geographic areas and in short time periods. Moreover the speed in which twitter content is generated affects us to have accurate results only a few hours after the occurrence of the earthquake. The method used in order to extract, evaluate and map the intensity related information is described in brief in this paper. At first, we pick out all the tweets that have been posted within the first 48 hours, including information related to intensity and refer to a geographic location. The geo-referencing of these tweets and their association with an intensity grade according to the European Macroseismic Scale (EMS98) based on the information they contain in text followed. Finally, we apply various spatial statistics and GIS methods, and we interpolate the values to cover all the appropriate geographic areas. The final output contains macroseismic intensity maps for the Lixouri area (Kefallinia Island), produced from twitter data that have been posted in the first six, twelve, twenty four and forty eight hours after the earthquake occurrence. Results are compared with other intensity maps for same

Preliminary map of peak horizontal ground acceleration for the Hanshin-Awaji earthquake of January 17, 1995, Japan - Description of Mapped Data Sets

USGS Publications Warehouse

Borcherdt, R.D.; Mark, R.K.

1995-01-01

The Hanshin-Awaji earthquake (also known as the Hyogo-ken Nanbu and the Great Hanshin earthquake) provided an unprecedented set of measurements of strong ground shaking. The measurements constitute the most comprehensive set of strong- motion recordings yet obtained for sites underlain by soft soil deposits of Holocene age within a few kilometers of the crustal rupture zone. The recordings, obtained on or near many important structures, provide an important new empirical data set for evaluating input ground motion levels and site amplification factors for codes and site-specific design procedures world wide. This report describes the data used to prepare a preliminary map summarizing the strong motion data in relation to seismicity and underlying geology (Wentworth, Borcherdt, and Mark., 1995; Figure 1, hereafter referred to as Figure 1/I). The map shows station locations, peak acceleration values, and generalized acceleration contours superimposed on pertinent seismicity and the geologic map of Japan. The map (Figure 1/I) indicates a zone of high acceleration with ground motions throughout the zone greater than 400 gal and locally greater than 800 gal. This zone encompasses the area of most intense damage mapped as JMA intensity level 7, which extends through Kobe City. The zone of most intense damage is parallel, but displaced slightly from the surface projection of the crustal rupture zone implied by aftershock locations. The zone is underlain by soft-soil deposits of Holocene age.

Instrumental shaking thresholds for seismically induced landslides and preliminary report on landslides triggered by the October 17, 1989, Loma Prieta, California earthquake

USGS Publications Warehouse

Harp, E.L.

1993-01-01

The generation of seismically induced landslide depends on the characteristics of shaking as well as mechanical properties of geologic materials. A very important parameter in the study of seismically induced landslide is the intensity based on a strong-motion accelerogram: it is defined as Arias intensity and is proportional to the duration of the shaking record as well as the amplitude. Having a theoretical relationship between Arias intensity, magnitude and distance it is possible to predict how far away from the seismic source landslides are likely to occur for a given magnitude earthquake. Field investigations have established that the threshold level of Arias intensity depends also on site effects, particularly the fracture characteristics of the outcrops present. -from Author

Intense Seismic Activity at Chiles and Cerro Negro Volcanoes on the Colombia-Ecuador Border

NASA Astrophysics Data System (ADS)

Torres, R. A.; Cadena, O.; Gomez, D.; Ruiz, M. C.; Prejean, S. G.; Lyons, J. J.; White, R. A.

2015-12-01

The region of Chiles and Cerro Negro volcanoes, located on the Colombian-Ecuadorian border, has experienced an ongoing seismic swarm beginning in Aug. 2013. Based on concern for local residents and authorities, a cooperative broadband monitoring network was installed by the Servicio Geológico Colombiano in Colombia and the Instituto Geofísico of the Escuela Politécnica Nacional in Ecuador. Since November 2013 more than 538,000 earthquakes were recorded; although since May 2015 the seismicity has decreased significantly to an average of 70 events per day. Three large earthquake swarms with increasing energy occurred in Aug.-Oct. 2013, March-May 2014, and Sept.-Dec. 2014. By the end of 2014, roughly 400 earthquakes greater than M 3 had occurred with a maximum rate of 8000 earthquakes per day. The largest earthquake was a 5.6 ML on Oct. 20, 2014. This event produced an InSAR coseismic deformation of ~23 cm (S. Ebmeier, personal communication). Most events are typical brittle failure volcano-tectonic (VT) earthquakes that are located in a cluster beneath the southern flank of Chiles volcano, with depths between 1.5 and 10 km. Although the great majority of earthquakes are VT, some low-frequency (LF, ~0.5 Hz) and very-low-frequency (VLF) events have occurred. Particle motion analysis suggests that the VLF source migrated with time. While a VLF on Oct. 15, 2014 was located south of Chiles volcano, near the InSAR source, the VLF registered on Feb. 14, 2015 was likely located very close to Chiles Volcano. We infer that magma intrusion and resulting fluid exsolution at depths greater than 5 km are driving seismicity in the Chiles-Cerro Negro region. However earthquakes are failing in a manner consistent with regional tectonics. Relative relocations reveal a structure consistent with mapped regional faults. Thus seismicity is likely controlled by an interaction of magmatic and tectonic processes. Because the regional stress field is highly compressional and the volcanoes

Some new methods and results in examination of distribution of rare strongest events

NASA Astrophysics Data System (ADS)

Pisarenko, Vladilen; Rodkin, Mikhail

2016-04-01

In the study of disaster statistics the examination of the distribution tail - the range of rare strongest events - appears to be the mostly difficult and the mostly important problem. We discuss here this problem using two different approaches. In the first one we use the limit distributions of the theory of extreme values for parameterization of behavior of the distribution tail. Our method consists in estimation of the maximum size Mmax(T) (e.g. magnitude, earthquake energy, PGA value, victims or economic losses from catastrophe, etc.) that will occur in a prescribed future time interval T. In this particular case we combine the historical earthquake catalogs with instrumental ones since historical catalogs cover much longer time periods and thus can essentially improve seismic statistics in the higher magnitude domain. We apply here this technique to two historical Japan catalogs (the Usami earthquake catalog 599-1884, and the Utsu catalog, 1885-1925) and to the instrumental JMA catalog (1926-2014). We have compared the parameters of historical catalogs with ones derived from the instrumental JMA catalog and have found that the Usami catalog is incompatible with the instrumental one, whereas the Utsu catalog is statistically compatible in the higher magnitude domain with the JMA catalog. In all examined cases the effect of the "bending down" of the graph of strong earthquake recurrence was found as the typical of the seismic regime. Another method is connected with the use of the multiplicative cascade model (that in some aspects is an analogue of the ETAS model). It is known that the ordinary Gutenberg-Richter law of earthquake recurrence can be imitated within the scheme of multiplicative cascade in which the seismic regime is treated as a sequence of a large number of episodes of avalanche-like relaxation, randomly occurring on the set of metastable subsystems. This model simulates such well known regularity of the seismic regime as a decrease in b-value in

Seismicity in South Carolina

USGS Publications Warehouse

Shedlock, K.M.

1988-01-01

The largest historical earthquake in South Carolina, and in the southeastern US, occurred in the Coastal Plain province, probably northwest of Charleston, in 1886. Locations for aftershocks associated with this earthquake, estimated using intensities based on newspaper accounts, defined a northwest trending zone about 250 km long that was at least 100 km wide in the Coastal Plain but widened to a northeast trending zone in the Piedmont. The subsequent historical and instrumentally recorded seismicity in South Carolina images the 1886 aftershock zone. Instrumentally recorded seismicity in the Coastal Plain province occurs in 3 seismic zones or clusters: Middleton Place-Summervile (MPSSZ), Adams Run (ARC), and Bowman (BSZ). Approximately 68% of the Coastal Plain earthquakes occur in the MPSSZ, a north trending zone about 22 km long and 12 km wide, lying about 20 km northwest of Charleston. The hypocenters of MPSSZ earthquakes range in depth from near the surface to almost 12 km. Thrust, strike-slip, and some normal faulting are indicated by the fault plane solutions for Coastal Plain earthquakes. The maximum horizontal compressive stress, inferred from the P-axes of the fault plane solutions, is oriented NE-SW in the shallow crust (<9 km deep) but appears to be diffusely E-W between 9 to 12 km deep. -from Author

Bayesian identification of multiple seismic change points and varying seismic rates caused by induced seismicity

NASA Astrophysics Data System (ADS)

Montoya-Noguera, Silvana; Wang, Yu

2017-04-01

The Central and Eastern United States (CEUS) has experienced an abnormal increase in seismic activity, which is believed to be related to anthropogenic activities. The U.S. Geological Survey has acknowledged this situation and developed the CEUS 2016 1 year seismic hazard model using the catalog of 2015 by assuming stationary seismicity in that period. However, due to the nonstationary nature of induced seismicity, it is essential to identify change points for accurate probabilistic seismic hazard analysis (PSHA). We present a Bayesian procedure to identify the most probable change points in seismicity and define their respective seismic rates. It uses prior distributions in agreement with conventional PSHA and updates them with recent data to identify seismicity changes. It can determine the change points in a regional scale and may incorporate different types of information in an objective manner. It is first successfully tested with simulated data, and then it is used to evaluate Oklahoma's regional seismicity.

Evaluation of Cloud Microphysics in JMA-NHM Simulations Using Bin or Bulk Microphysical Schemes through Comparison with Cloud Radar Observations

NASA Technical Reports Server (NTRS)

Iguchi, Takamichi; Nakajima, Teruyuki; Khain, Alexander P.; Saito, Kazuo; Takemura, Toshihiko; Okamoto, Hajime; Nishizawa, Tomoaki; Tao, Wei-Kuo

2012-01-01

Numerical weather prediction (NWP) simulations using the Japan Meteorological Agency NonhydrostaticModel (JMA-NHM) are conducted for three precipitation events observed by shipborne or spaceborneW-band cloud radars. Spectral bin and single-moment bulk cloud microphysics schemes are employed separatelyfor an intercomparative study. A radar product simulator that is compatible with both microphysicsschemes is developed to enable a direct comparison between simulation and observation with respect to theequivalent radar reflectivity factor Ze, Doppler velocity (DV), and path-integrated attenuation (PIA). Ingeneral, the bin model simulation shows better agreement with the observed data than the bulk modelsimulation. The correction of the terminal fall velocities of snowflakes using those of hail further improves theresult of the bin model simulation. The results indicate that there are substantial uncertainties in the masssizeand sizeterminal fall velocity relations of snowflakes or in the calculation of terminal fall velocity of snowaloft. For the bulk microphysics, the overestimation of Ze is observed as a result of a significant predominanceof snow over cloud ice due to substantial deposition growth directly to snow. The DV comparison shows thata correction for the fall velocity of hydrometeors considering a change of particle size should be introducedeven in single-moment bulk cloud microphysics.

Source area of the 1858 earthquake swarm in the central Ryukyu Islands revealed by the observations of Father Louis Furet

NASA Astrophysics Data System (ADS)

Oda, Takuma; Nakamura, Mamoru

2017-09-01

We estimated the location and magnitude of earthquakes constituting the 1858 earthquake swarm in the central Ryukyu Islands using the felt earthquakes recorded by Father Louis Furet who lived in Naha, Okinawa Island, in the middle of the nineteenth century. First, we estimated the JMA seismic intensity of the earthquakes by interpreting the words used to describe the shaking. Next, using the seismic intensity and shaking duration of the felt earthquakes, we estimated the epicentral distance and magnitude range of three earthquakes in the swarm. The results showed that the epicentral distances of the earthquakes were 20-250 km and that magnitudes ranged between 4.5 and 6.5, with a strong correlation between epicentral distance and magnitude. Since the rumblings accompanying some earthquakes in the swarm were heard from a northward direction, the swarm probably occurred to the north of Naha. The most likely source area for the 1858 swarm is the central Okinawa Trough, where a similar swarm event occurred in 1980. If the 1858 swarm occurred in the central Okinawa Trough, the estimated maximum magnitude would have reached 6-7. In contrast, if the 1858 swarm occurred in the vicinity of Amami Island, which is the second most likely candidate area, it would have produced a cluster of magnitude 7-8 earthquakes.[Figure not available: see fulltext.

Significant earthquakes on the Enriquillo fault system, Hispaniola, 1500-2010: Implications for seismic hazard

USGS Publications Warehouse

Bakun, William H.; Flores, Claudia H.; ten Brink, Uri S.

2012-01-01

Historical records indicate frequent seismic activity along the north-east Caribbean plate boundary over the past 500 years, particularly on the island of Hispaniola. We use accounts of historical earthquakes to assign intensities and the intensity assignments for the 2010 Haiti earthquakes to derive an intensity attenuation relation for Hispaniola. The intensity assignments and the attenuation relation are used in a grid search to find source locations and magnitudes that best fit the intensity assignments. Here we describe a sequence of devastating earthquakes on the Enriquillo fault system in the eighteenth century. An intensity magnitude MI 6.6 earthquake in 1701 occurred near the location of the 2010 Haiti earthquake, and the accounts of the shaking in the 1701 earthquake are similar to those of the 2010 earthquake. A series of large earthquakes migrating from east to west started with the 18 October 1751 MI 7.4–7.5 earthquake, probably located near the eastern end of the fault in the Dominican Republic, followed by the 21 November 1751 MI 6.6 earthquake near Port-au-Prince, Haiti, and the 3 June 1770 MI 7.5 earthquake west of the 2010 earthquake rupture. The 2010 Haiti earthquake may mark the beginning of a new cycle of large earthquakes on the Enriquillo fault system after 240 years of seismic quiescence. The entire Enriquillo fault system appears to be seismically active; Haiti and the Dominican Republic should prepare for future devastating earthquakes.

A probabilistic seismic risk assessment procedure for nuclear power plants: (II) Application

USGS Publications Warehouse

Huang, Y.-N.; Whittaker, A.S.; Luco, N.

2011-01-01

This paper presents the procedures and results of intensity- and time-based seismic risk assessments of a sample nuclear power plant (NPP) to demonstrate the risk-assessment methodology proposed in its companion paper. The intensity-based assessments include three sets of sensitivity studies to identify the impact of the following factors on the seismic vulnerability of the sample NPP, namely: (1) the description of fragility curves for primary and secondary components of NPPs, (2) the number of simulations of NPP response required for risk assessment, and (3) the correlation in responses between NPP components. The time-based assessment is performed as a series of intensity-based assessments. The studies illustrate the utility of the response-based fragility curves and the inclusion of the correlation in the responses of NPP components directly in the risk computation. ?? 2011 Published by Elsevier B.V.

An interdisciplinary perspective on social and physical determinants of seismic risk

NASA Astrophysics Data System (ADS)

Lin, K.-H.; Chang, Y.-C.; Liu, G.-Y.; Chan, C.-H.; Lin, T.-H.; Yeh, C.-H.

2015-01-01

While disaster studies researchers usually view risk as a function of hazard, exposure, and vulnerability, few studies have systematically examined the relationships among the various physical and socioeconomic determinants underlying disasters, and fewer have done so through seismic risk analysis. In the context of the 1999 Chi-Chi earthquake in Taiwan, this study constructs five hypothetical models to test different determinants that affect disaster fatality at the village level, namely seismic hazard intensity, population, building fragility, demographics and socioeconomics. The Poisson Regression Model is used to estimate the impact of natural hazards and social factors on fatality. Results indicate that although all of the determinants have an impact on the specific dimension of seismic fatality, some indicators of social inequality, such as gender ratio, dependency ratio, income and its SD, are the driving determinants deteriorating vulnerability to seismic risk. These findings have strong social implications for policy interventions to mitigate such disasters. This study presents an interdisciplinary investigation into social and physical determinants in seismic risk.

Fractal analysis of earthquake swarms of Vogtland/NW-Bohemia intraplate seismicity

NASA Astrophysics Data System (ADS)

Mittag, Reinhard J.

2003-03-01

The special type of intraplate microseismicity with swarm-like occurrence of earthquakes within the Vogtland/NW-Bohemian Region is analysed to reveal the nature and the origin of the seismogenic regime. The long-term data set of continuous seismic monitoring since 1962, including more than 26000 events within a range of about 5 units of local magnitude, provides an unique database for statistical investigations. Most earthquakes occur in narrow hypocentral volumes (clusters) within the lower part of the upper crust, but also single event occurrence outside of spatial clusters is observed. Temporal distribution of events is concentrated in clusters (swarms), which last some days until few month in dependence of intensity. Since 1962 three strong swarms occurred (1962, 1985/86, 2000), including two seismic cycles. Spatial clusters are distributed along a fault system of regional extension (Leipzig-Regensburger Störung), which is supposed to act as the joint tectonic fracture zone for the whole seismogenic region. Seismicity is analysed by fractal analysis, suggesting a unifractal behaviour of seismicity and uniform character of seismotectonic regime for the whole region. A tendency of decreasing fractal dimension values is observed for temporal distribution of earthquakes, indicating an increasing degree of temporal clustering from swarm to swarm. Following the idea of earthquake triggering by magma intrusions and related fluid and gas release into the tectonically pre-stressed parts of the crust, a steady increased intensity of intrusion and/or fluid and gas release might account for that observation. Additionally, seismic parameters for Vogtland/NW-Bohemia intraplate seismicity are compared with an adequate data set of mining-induced seismicity in a nearby mine of Lubin/Poland and with synthetic data sets to evaluate parameter estimation. Due to different seismogenic regime of tectonic and induced seismicity, significant differences between b-values and temporal

Towards Coupling of Macroseismic Intensity with Structural Damage Indicators

NASA Astrophysics Data System (ADS)

Kouteva, Mihaela; Boshnakov, Krasimir

2016-04-01

Knowledge on basic data of ground motion acceleration time histories during earthquakes is essential to understanding the earthquake resistant behaviour of structures. Peak and integral ground motion parameters such as peak ground motion values (acceleration, velocity and displacement), measures of the frequency content of ground motion, duration of strong shaking and various intensity measures play important roles in seismic evaluation of existing facilities and design of new systems. Macroseismic intensity is an earthquake measure related to seismic hazard and seismic risk description. Having detailed ideas on the correlations between the earthquake damage potential and macroseismic intensity is an important issue in engineering seismology and earthquake engineering. Reliable earthquake hazard estimation is the major prerequisite to successful disaster risk management. The usage of advanced earthquake engineering approaches for structural response modelling is essential for reliable evaluation of the accumulated damages in the existing buildings and structures due to the history of seismic actions, occurred during their lifetime. Full nonlinear analysis taking into account single event or series of earthquakes and the large set of elaborated damage indices are suitable contemporary tools to cope with this responsible task. This paper presents some results on the correlation between observational damage states, ground motion parameters and selected analytical damage indices. Damage indices are computed on the base of nonlinear time history analysis of test reinforced structure, characterising the building stock of the Mediterranean region designed according the earthquake resistant requirements in mid XX-th century.

The improved broadband Real-Time Seismic Network in Romania

NASA Astrophysics Data System (ADS)

Neagoe, C.; Ionescu, C.

2009-04-01

Starting with 2002 the National Institute for Earth Physics (NIEP) has developed its real-time digital seismic network. This network consists of 96 seismic stations of which 48 broad band and short period stations and two seismic arrays are transmitted in real-time. The real time seismic stations are equipped with Quanterra Q330 and K2 digitizers, broadband seismometers (STS2, CMG40T, CMG 3ESP, CMG3T) and strong motions sensors Kinemetrics episensors (+/- 2g). SeedLink and AntelopeTM (installed on MARMOT) program packages are used for real-time (RT) data acquisition and exchange. The communication from digital seismic stations to the National Data Center in Bucharest is assured by 5 providers (GPRS, VPN, satellite communication, radio lease line and internet), which will assure the back-up communications lines. The processing centre runs BRTT's AntelopeTM 4.10 data acquisition and processing software on 2 workstations for real-time processing and post processing. The Antelope Real-Time System is also providing automatic event detection, arrival picking, event location and magnitude calculation. It provides graphical display and reporting within near-real-time after a local or regional event occurred. Also at the data center was implemented a system to collect macroseismic information using the internet on which macro seismic intensity maps are generated. In the near future at the data center will be install Seiscomp 3 data acquisition processing software on a workstation. The software will run in parallel with Antelope software as a back-up. The present network will be expanded in the near future. In the first half of 2009 NIEP will install 8 additional broad band stations in Romanian territory, which also will be transmitted to the data center in real time. The Romanian Seismic Network is permanently exchanging real -time waveform data with IRIS, ORFEUS and different European countries through internet. In Romania, magnitude and location of an earthquake are now

Seismicity and eruptive activity at Fuego Volcano, Guatemala: February 1975 -January 1977

USGS Publications Warehouse

Yuan, A.T.E.; McNutt, S.R.; Harlow, D.H.

1984-01-01

We examine seismic and eruptive activity at Fuego Volcano (14??29???N, 90?? 53???W), a 3800-m-high stratovolcano located in the active volcanic arc of Guatemala. Eruptions at Fuego are typically short-lived vulcanian eruptions producing ash falls and ash flows of high-alumina basalt. From February 1975 to December 1976, five weak ash eruptions occurred, accompanied by small earthquake swarms. Between 0 and 140 (average ??? 10) A-type or high-frequency seismic events per day with M > 0.5 were recorded during this period. Estimated thermal energies for each eruption are greater by a factor of 106 than cumulative seismic energies, a larger ratio than that reported for other volcanoes. Over 4000 A-type events were recorded January 3-7, 1977 (cumulative seismic energy ??? 109 joules), yet no eruption occurred. Five 2-hour-long pulses of intense seismicity separated by 6-hour intervals of quiescence accounted for the majority of events. Maximum likelihood estimates of b-values range from 0.7 ?? 0.2 to 2.1 ?? 0.4 with systematically lower values corresponding to the five intense pulses. The low values suggest higher stress conditions. During the 1977 swarm, a tiltmeter located 6 km southeast of Fuego recorded a 14 ?? 3 microradian tilt event (down to SW). This value is too large to represent a simple change in the elastic strain field due to the earthquake swarm. We speculate that the earthquake swarm and tilt are indicative of subsurface magma movement. ?? 1984.

Extracting physical parameters from marine seismic data: New methods in seismic oceanography and velocity inversion

NASA Astrophysics Data System (ADS)

Fortin, Will F. J.

The utility and meaning of a geophysical dataset is dependent on good interpretation informed by high-quality data, processing, and attribute examination via technical methodologies. Active source marine seismic reflection data contains a great deal of information in the location, phase, and amplitude of both pre- and post-stack seismic reflections. Using pre- and post-stack data, this work has extracted useful information from marine reflection seismic data in novel ways in both the oceanic water column and the sub-seafloor geology. In chapter 1 we develop a new method for estimating oceanic turbulence from a seismic image. This method is tested on synthetic seismic data to show the method's ability to accurately recover both distribution and levels of turbulent diffusivity. Then we apply the method to real data offshore Costa Rica where we observe lee waves. Our results find elevated diffusivities near the seafloor as well as above the lee waves five times greater than surrounding waters and 50 times greater than open ocean diffusivities. Chapter 2 investigates subsurface geology in the Cascadia Subduction Zone and outlines a workflow for using pre-stack waveform inversion to produce highly detailed velocity models and seismic images. Using a newly developed inversion code, we achieve better imaging results as compared to the product of a standard, user-intensive method for building a velocity model. Our results image the subduction interface ~30 km farther landward than previous work and better images faults and sedimentary structures above the oceanic plate as well as in the accretionary prism. The resultant velocity model is highly detailed, inverted every 6.25 m with ~20 m vertical resolution, and will be used to examine the role of fluids in the subduction system. These results help us to better understand the natural hazards risks associated with the Cascadia Subduction Zone. Chapter 3 returns to seismic oceanography and examines the dynamics of nonlinear

Long seismic activity in the Porto dos Gaúchos Seismic Zone(PGSZ) - Amazon Craton Brazil

NASA Astrophysics Data System (ADS)

Barros, L. V.; Bowen, B. M. D.; Schmidt, K.

2017-12-01

The largest earthquake ever observed in the stable continental interior of the South American plate occurred in Serra do Tombador (ST), Mato Grosso state - Brazil, on January 31, 1955 with magnitude 6.2 m b . Since then no other earthquake has been located near the 1955 epicenter. However, in Porto dos Gaúchos (PG), 100 km northeast of ST, a recurrent seismicity has been observed since 1959. Both ST and PG are located in the Phanerozoic Parecis basin whose sediments overlies the crystalline basement of Amazon craton. Two magnitude 5 earthquakes occurred in PG, in 1998 and 2005 with intensities up to VI and V, respectively. These two main shocks were followed by aftershock sequences, studied by local seismic networks, last up today, almost 30 years later, period in which it was detected more than seven thousand of seismic events. Both sequences occurred in the same WSW-ENE oriented fault zone with right-lateral strike-slip mechanisms. The epicentral zone is near the northern border of Parecis basin, where there are buried grabens, generally trending WNW-ESE, such as the deep Mesoproterozoic Caiabis graben which lies partly beneath the Parecis basin. The seismogenic fault is located in a basement high, which is probably related with the same seismogenic feature responsible for the earthquakes in PGSZ. The 1955 earthquake, despite the uncertainty in its epicenter, does not seem to be directly related to any buried graben either. The seismicity in the PGSZ, therefore, is not directly related to rifted crust.Not considering the possibility of miss location in the ST earthquake, its isolated occurrence - from the perspective of new studies on intraplate seismicity - lead us to think that the PGSZ was activated by stresses released by the earthquake of 1955 and that the seismogenic fault of ST would have closed a cycle of activity. This would explain its seismic quiescence. However, other studies are necessary to prove this hypothesis, such as the measurement of the

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.

Present Status of Historical Seismicity Studies in Colombia and Venezuela

NASA Astrophysics Data System (ADS)

Sarabia, A.; Cifuentes, H.; Altez Ortega, R.; Palme, C.; Dimate, C.

2013-05-01

After the publication of the SISRA (CERESIS-1985) regional project, a unified catalog of seismic parameters and intensities for South America, researchers in historical seismicity have continued advancing on different scales in the area of this study of seismic hazard. The most important initiatives carried out in this area in Colombia and Venezuela can be grouped as follows: a) Reviews of destructive earthquakes in national and international historic archives, principally by Altez and FUNVISIS in Venezuela and Espinosa, Salcedo, and Sarabia et al in Colombia, leading to the preparation of seismologic catalogues, scientific and dissemination articles, reports, books, among others. b) Organization and systematization of historic information to develop public domain data bases and information, specifically the Historic Seismologic Teleinformation System in Venezuela, carried out between 2004 and 2008 under the coordination of Christl Palme and accessible on-line: http://sismicidad.ciens.ula.ve. As well, the "Historia Sísmica de Colombia 1550-1830" (Seismic History in Colombia 1550-1830) data base, in CD-ROM, by Espinosa Baquero (2003) and the historic seismicity information system of Colombia (Servicio Geológico Colombiano-Universidad Nacional de Colombia), published on the internet in 2012: http://agata.ingeominas.gov.co:9090/SismicidadHistorica/. c) Macroseismic studies for the development of intensity attenuation equations and the quantification and revaluation of basic historic earthquake parameters using isoseismal maps (Rengifo et al., Palme et al., Salcedo et al., among others) and procedures such as Boxer and Bakun & Wentworth (Palme et al., Dimaté, among others), which have produced significant changes in the parameters of some of the large earthquakes. d) Symposiums of researchers to promote interest and development in the discipline, including Jornadas Venezolanas de Sismología Histórica (Venezuelan Congress of Historical Seismology), held

Avoidance of seismic survey activities by penguins.

PubMed

Pichegru, Lorien; Nyengera, Reason; McInnes, Alistair M; Pistorius, Pierre

2017-11-24

Seismic surveys in search for oil or gas under the seabed, produce the most intense man-made ocean noise with known impacts on invertebrates, fish and marine mammals. No evidence to date exists, however, about potential impacts on seabirds. Penguins may be expected to be particularly affected by loud underwater sounds, due to their largely aquatic existence. This study investigated the behavioural response of breeding endangered African Penguins Spheniscus demersus to seismic surveys within 100 km of their colony in South Africa, using a multi-year GPS tracking dataset. Penguins showed a strong avoidance of their preferred foraging areas during seismic activities, foraging significantly further from the survey vessel when in operation, while increasing their overall foraging effort. The birds reverted to normal behaviour when the operation ceased, although longer-term repercussions on hearing capacities cannot be precluded. The rapid industrialization of the oceans has increased levels of underwater anthropogenic noises globally, a growing concern for a wide range of taxa, now also including seabirds. African penguin numbers have decreased by 70% in the last 10 years, a strong motivation for precautionary management decisions, including the exclusion of seismic exploratory activities within at least 100 km of their breeding colonies.

Evaluating the intensity of U.S. earthquakes

USGS Publications Warehouse

Simon, R.; Stover, C.

1977-01-01

The effects of seismic shaking are objective. All observers can agree these are real occurences and not subjective speculation. Reliable intensity evaluations are based not on a single factor on any scale but on consistent combinations. 

Toward uniform probabilistic seismic hazard assessments for Southeast Asia

NASA Astrophysics Data System (ADS)

Chan, C. H.; Wang, Y.; Shi, X.; Ornthammarath, T.; Warnitchai, P.; Kosuwan, S.; Thant, M.; Nguyen, P. H.; Nguyen, L. M.; Solidum, R., Jr.; Irsyam, M.; Hidayati, S.; Sieh, K.

2017-12-01

Although most Southeast Asian countries have seismic hazard maps, various methodologies and quality result in appreciable mismatches at national boundaries. We aim to conduct a uniform assessment across the region by through standardized earthquake and fault databases, ground-shaking scenarios, and regional hazard maps. Our earthquake database contains earthquake parameters obtained from global and national seismic networks, harmonized by removal of duplicate events and the use of moment magnitude. Our active-fault database includes fault parameters from previous studies and from the databases implemented for national seismic hazard maps. Another crucial input for seismic hazard assessment is proper evaluation of ground-shaking attenuation. Since few ground-motion prediction equations (GMPEs) have used local observations from this region, we evaluated attenuation by comparison of instrumental observations and felt intensities for recent earthquakes with predicted ground shaking from published GMPEs. We then utilize the best-fitting GMPEs and site conditions into our seismic hazard assessments. Based on the database and proper GMPEs, we have constructed regional probabilistic seismic hazard maps. The assessment shows highest seismic hazard levels near those faults with high slip rates, including the Sagaing Fault in central Myanmar, the Sumatran Fault in Sumatra, the Palu-Koro, Matano and Lawanopo Faults in Sulawesi, and the Philippine Fault across several islands of the Philippines. In addition, our assessment demonstrates the important fact that regions with low earthquake probability may well have a higher aggregate probability of future earthquakes, since they encompass much larger areas than the areas of high probability. The significant irony then is that in areas of low to moderate probability, where building codes are usually to provide less seismic resilience, seismic risk is likely to be greater. Infrastructural damage in East Malaysia during the 2015

Seismo-Electromagnetic Emissions Related to Seismic Waves can Trigger TLEs

NASA Astrophysics Data System (ADS)

Sorokin, Leonid V.

2009-04-01

This paper deals with the rare high intensity electromagnetic pulses associated with earthquakes, whose spectrum signature differs from that of atmospherics produced by lightning discharges. On the basis of actual data records, cases of the generation of anomalous seismo-electromagnetic emissions are described. These natural sub-millisecond electromagnetic pulses were associated with the passage of seismic waves from earthquakes to Moscow, the place where the electromagnetic field observations were made. Space-time coupling has been revealed between exact seismic waves from the earthquakes, lightning triggering and Transient Luminous Events triggering.

Characteristics of foreshock activity inferred from the JMA earthquake catalog

NASA Astrophysics Data System (ADS)

Tamaribuchi, Koji; Yagi, Yuji; Enescu, Bogdan; Hirano, Shiro

2018-05-01

We investigated the foreshock activity characteristics using the Japan Meteorological Agency Unified Earthquake Catalog for the last 20 years. Using the nearest-neighbor distance approach, we systematically and objectively classified the earthquakes into clustered and background seismicity. We further categorized the clustered events into foreshocks, mainshocks, and aftershocks and analyzed their statistical features such as the b-value of the frequency-magnitude distribution. We found that the b-values of the foreshocks are lower than those of the aftershocks. This b-value difference suggested that not only the stochastic cascade effect but also the stress changes/aseismic processes may contribute to the mainshock-triggering process. However, forecasting the mainshock based on b-value analysis may be difficult. In addition, the rate of foreshock occurrence in all clusters (with two or more events) was nearly constant (30-40%) over a wide magnitude range. The difference in the magnitude, time, and epicentral distance between the mainshock and largest foreshock followed a power law. We inferred that the distinctive characteristics of foreshocks can be better revealed using the improved catalog, which includes the micro-earthquake information.

Martian seismicity

NASA Technical Reports Server (NTRS)

Phillips, Roger J.; Grimm, Robert E.

1991-01-01

The design and ultimate success of network seismology experiments on Mars depends on the present level of Martian seismicity. Volcanic and tectonic landforms observed from imaging experiments show that Mars must have been a seismically active planet in the past and there is no reason to discount the notion that Mars is seismically active today but at a lower level of activity. Models are explored for present day Mars seismicity. Depending on the sensitivity and geometry of a seismic network and the attenuation and scattering properties of the interior, it appears that a reasonable number of Martian seismic events would be detected over the period of a decade. The thermoelastic cooling mechanism as estimated is surely a lower bound, and a more refined estimate would take into account specifically the regional cooling of Tharsis and lead to a higher frequency of seismic events.

Seismic Ecology

NASA Astrophysics Data System (ADS)

Seleznev, V. S.; Soloviev, V. M.; Emanov, A. F.

The paper is devoted to researches of influence of seismic actions for industrial and civil buildings and people. The seismic actions bring influence directly on the people (vibration actions, force shocks at earthquakes) or indirectly through various build- ings and the constructions and can be strong (be felt by people) and weak (be fixed by sensing devices). The great number of work is devoted to influence of violent seismic actions (first of all of earthquakes) on people and various constructions. This work is devoted to study weak, but long seismic actions on various buildings and people. There is a need to take into account seismic oscillations, acting on the territory, at construction of various buildings on urbanized territories. Essential influence, except for violent earthquakes, man-caused seismic actions: the explosions, seismic noise, emitted by plant facilities and moving transport, radiation from high-rise buildings and constructions under action of a wind, etc. can exert. Materials on increase of man- caused seismicity in a number of regions in Russia, which earlier were not seismic, are presented in the paper. Along with maps of seismic microzoning maps to be built indicating a variation of amplitude spectra of seismic noise within day, months, years. The presence of an information about amplitudes and frequencies of oscillations from possible earthquakes and man-caused oscillations in concrete regions allows carry- ing out soundly designing and construction of industrial and civil housing projects. The construction of buildings even in not seismically dangerous regions, which have one from resonance frequencies coincident on magnitude to frequency of oscillations, emitted in this place by man-caused objects, can end in failure of these buildings and heaviest consequences for the people. The practical examples of detail of engineering- seismological investigation of large industrial and civil housing projects of Siberia territory (hydro power

Ischia Island: Historical Seismicity and Dynamics

NASA Astrophysics Data System (ADS)

Carlino, S.; Cubellis, E.; Iannuzzi, R.; Luongo, G.; Obrizzo, F.

2003-04-01

The seismic energy release in volcanic areas is a complex process and the island of Ischia provides a significant scenario of historical seismicity. This is characterized by the occurence of earthquakes with low energy and high intensity. Information on the seismicity of the island spans about eight centuries, starting from 1228. With regard to effects, the most recent earthquake of 1883 is extensively documented both in the literature and unpublished sources. The earthquake caused 2333 deaths and the destruction of the historical and environmental heritage of some areas of the island. The most severe damage occurred in Casamicciola. This event, which was the first great catastrophe after the unification of Italy in the 1860s (Imax = XI degree MCS), represents an important date in the prevention of natural disasters, in that it was after this earthquake that the first Seismic Safety Act in Italy was passed by which lower risk zones were identified for new settlements. Thanks to such detailed analysis, reliable modelling of the seismic source was also obtained. The historical data onwards makes it possible to identify the area of the epicenter of all known earthquakes as the northern slope of Monte Epomeo, while analysis of the effects of earthquakes and the geological structures allows us to evaluate the stress fields that generate the earthquakes. In a volcanic area, interpretation of the mechanisms of release and propagation of seismic energy is made even more complex as the stress field that acts at a regional level is compounded by that generated from migration of magmatic masses towards the surface, as well as the rheologic properties of the rocks dependent on the high geothermic gradient. Such structural and dynamic conditions make the island of Ischia a seismic area of considerable interest. It would appear necessary to evaluate the expected damage caused by a new event linked to the renewal of dynamics of the island, where high population density and the

Seismic array observations for monitoring phreatic eruptions in Iwojima Island, Japan

NASA Astrophysics Data System (ADS)

Ueda, H.; Kawaguchi, R.; Chiba, K.; Fujita, E.; Tanada, T.

2015-12-01

Iwojima is an active volcanic island located within a 10 km wide submarine caldera about 1250 km to the south of Tokyo, Japan. The volcanic activity is characterized by intensive earthquake activity associated with an island-wide uplift with high uplift rate (30~40 cm/year) and hydrothermal activity. In the last 10 years, phreatic eruptions took place in and near the island in 2012, 2013, and 2015. In such restless volcano, predictions and detections of occurrence points of phreatic eruptions are important for ensuring safety of residents. In the previous studies, we found that the earthquake activity of Iwojima highly correlates with the island wide large uplift, but the precursory activity of the phreatic eruption in 2012 was deviated from the correlation (Ueda et al. 2013 AGU Fall Meeting). For prediction of occurrence points of phreatic eruptions and investigation of the eruption mechanism, we began observation by seismic arrays at two areas in December 2014. The seismic arrays enable to locate epicenters of volcanic tremors, which are not well located by existing seismic stations. In May and June 2015, Japan Maritime Self-Defense Force stayed in Iwojima and a live camera of Japan Meteorological Agency found very small phreatic eruptions occurred at the northern beach. Existing seismic stations could not detect seismic signals related with the eruptions. The seismic array could detect weak seismic signals related with the eruptions. Although the seismic arrays could not detect precursory signals because of too small eruption, we expect the seismic arrays can detect precursory seismic signals suggesting occurrence points of small or medium-sized phreatic eruptions. The seismic arrays also detected epicenters of harmonic and monotonic tremors took place at an active fumarolic field in the north earthen part of Iwojima. The apparent velocity of seismic waves (~1km/s) strongly suggests that the tremors relate with hydrothermal activity near ground surface.

Discriminating Characteristics of Tectonic and Human-Induced Seismicity

NASA Astrophysics Data System (ADS)

Zaliapin, I. V.; Ben-Zion, Y.

2015-12-01

We analyze statistical features of background and clustered subpopulations of earthquakes in different regions in an effort to distinguish between human-induced and natural seismicity. Analysis of "end-member" areas known to be dominated by human-induced earthquakes (the Geyser geothermal field in northern California and TauTona gold mine in South Africa) and regular tectonic activity (the San Jacinto fault zone in southern California and Coso region excluding the Coso geothermal field in eastern central California) reveals several distinguishing characteristics. Induced seismicity is shown to have (i) higher rate of background events (both absolute and relative to the total rate), (ii) faster temporal offspring decay, (iii) higher intensity of repeating events, (iv) larger proportion of small clusters, and (v) larger spatial separation between parent and offspring, compared to regular tectonic activity. These differences also successfully discriminate seismicity within the Coso and Salton Sea geothermal fields in California before and after the expansion of geothermal production during the 1980s.

Vulnerability and seismic damage scenarios for Barcelona (Spain) by using GIS

NASA Astrophysics Data System (ADS)

Lantada, N.; Pujades, L. G.; Barbat, A.

2003-04-01

An integrated GIS-based analysis (using ArcView GIS) is performed in order to estimate damage scenarios for VI, VII and VIII EMS-98 seismic intensities in Barcelona (Spain). The analysis of vulnerability and damage of individual buildings is performed according to a simplified method developed by Giovanazzi and Lagomarsino at the University of Genoa (Italy). An index of average vulnerability is associated to each building typology, which may be refined on the basis of behaviour modifiers. The index allows identification of an analytical relationship between seismic input (intensity) and damage, described by a binomial distribution. This methodology, which is based on the EMS-98 building typologies and preserves the compatibility with preceding methods, is applied to the two main residential building typologies of Barcelona, that is, unreinforced masonry and reinforced concrete buildings. Then, the specific residential buildings of Barcelona are classified in different groups characterized by a similar seismic behaviour. Therefore, all buildings belonging to each typology are cast in the most probable class according to vulnerability. In this way, the average vulnerability index is associated to each building typology of Barcelona and it is refined later on the basis of behaviour modifiers, linked to the number of stories, the year of construction and their state of maintenance. The ability of GIS tools to store, manage, analyse, and display the large amount of spatial and tabular data involved in this study allows to map average vulnerability indexes, and damage for the entire city. That is, vulnerability and damage scenarios. The obtained results show a high vulnerability and high expected seismic damage. For a VI degree of intensity, the maximum expected damage is in the range 15-30 % in the oldest zones of the city, the downtown, while for intensity VII it is in the range 45-60%. The developed GIS tool involves a friendly interface that allows new models and

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

Multiple plates subducting beneath Colombia, as illuminated by seismicity and velocity from the joint inversion of seismic and gravity data

DOE PAGES

Syracuse, Ellen M.; Maceira, Monica; Prieto, German A.; ...

2016-04-12

Subduction beneath the northernmost Andes in Colombia is complex. Based on seismicity distributions, multiple segments of slab appear to be subducting, and arc volcanism ceases north of 5° N. Here, we illuminate the subduction system through hypocentral relocations and Vp and Vs models resulting from the joint inversion of local body wave arrivals, surface wave dispersion measurements, and gravity data. The simultaneous use of multiple data types takes advantage of the differing sensitivities of each data type, resulting in velocity models that have improved resolution at both shallower and deeper depths than would result from traditional travel time tomography alone.more » The relocated earthquake dataset and velocity model clearly indicate a tear in the Nazca slab at 5° N, corresponding to a 250-km shift in slab seismicity and the termination of arc volcanism. North of this tear, the slab is flat, and it comprises slabs of two sources: the Nazca and Caribbean plates. The Bucaramanga nest, a small region of among the most intense intermediate-depth seismicity globally, is associated with the boundary between these two plates and possibly with a zone of melting or elevated water content, based on reduced Vp and increased Vp/Vs. As a result, we also use relocated seismicity to identify two new faults in the South American plate, one related to plate convergence and one highlighted by induced seismicity.« less

Integrating population dynamics into mapping human exposure to seismic hazard

NASA Astrophysics Data System (ADS)

Freire, S.; Aubrecht, C.

2012-11-01

Disaster risk is not fully characterized without taking into account vulnerability and population exposure. Assessment of earthquake risk in urban areas would benefit from considering the variation of population distribution at more detailed spatial and temporal scales, and from a more explicit integration of this improved demographic data with existing seismic hazard maps. In the present work, "intelligent" dasymetric mapping is used to model population dynamics at high spatial resolution in order to benefit the analysis of spatio-temporal exposure to earthquake hazard in a metropolitan area. These night- and daytime-specific population densities are then classified and combined with seismic intensity levels to derive new spatially-explicit four-class-composite maps of human exposure. The presented approach enables a more thorough assessment of population exposure to earthquake hazard. Results show that there are significantly more people potentially at risk in the daytime period, demonstrating the shifting nature of population exposure in the daily cycle and the need to move beyond conventional residence-based demographic data sources to improve risk analyses. The proposed fine-scale maps of human exposure to seismic intensity are mainly aimed at benefiting visualization and communication of earthquake risk, but can be valuable in all phases of the disaster management process where knowledge of population densities is relevant for decision-making.

Seismic Sources for the Territory of Georgia

NASA Astrophysics Data System (ADS)

Tsereteli, N. S.; Varazanashvili, O.

2011-12-01

The southern Caucasus is an earthquake prone region where devastating earthquakes have repeatedly caused significant loss of lives, infrastructure and buildings. High geodynamic activity of the region expressed in both seismic and aseismic deformations, is conditioned by the still-ongoing convergence of lithospheric plates and northward propagation of the Afro-Arabian continental block at a rate of several cm/year. The geometry of tectonic deformations in the region is largely determined by the wedge-shaped rigid Arabian block intensively intended into the relatively mobile Middle East-Caucasian region. Georgia is partner of ongoing regional project EMME. The main objective of EMME is calculation of Earthquake hazard uniformly with heights standards. One approach used in the project is the probabilistic seismic hazard assessment. In this approach the first parameter requirement is the definition of seismic source zones. Seismic sources can be either faults or area sources. Seismoactive structures of Georgia are identified mainly on the basis of the correlation between neotectonic structures of the region and earthquakes. Requirements of modern PSH software to geometry of faults is very high. As our knowledge of active faults geometry is not sufficient, area sources were used. Seismic sources are defined as zones that are characterized with more or less uniform seismicity. Poor knowledge of the processes occurring in deep of the Earth is connected with complexity of direct measurement. From this point of view the reliable data obtained from earthquake fault plane solution is unique for understanding the character of a current tectonic life of investigated area. There are two methods of identification if seismic sources. The first is the seimsotectonic approach, based on identification of extensive homogeneous seismic sources (SS) with the definition of probability of occurrence of maximum earthquake Mmax. In the second method the identification of seismic sources

Reassessment of the Seismicity and seismic hazards of Libya

NASA Astrophysics Data System (ADS)

Ben Suleman, A.; Elmeladi, A.

2009-04-01

The tectonic evolution of Libya, located at the northern extreme of the African continent, has yielded a complex crustal structure that is composed of a series of basins and uplifts. The present day deformation of Libya is the result of the Eurasia-Africa continental collision. At the end of the year 2005, The Libyan National Seismological Network was established to monitor local, regional and teleseismic activities, as well as to provide high quality data for research projects both locally and on the regional and global scale. This study aims to discuss the seismicity of Libya by using the new data from the Libyan national seismological network and to focus on the seismic hazards. At first glance the seismic activity map shows dominant trends of seismicity with most of the seismic activity concentrated along the northern coastal areas. Four major seismic trends were quite noticeable. A first trend is a NW-SE direction coinciding with the eastern boarder of the Hun Graben. A second trend is also a NW-SE direction in the offshore area and might be a continuation of this trend. The other two trends were located in the western Gulf of Sirt and Cyrenaica platform. The rest of seismicity is diffuse either offshore or in land, with no good correlation with well-mapped faults. Detailed investigations of the Libyan seismicity indicates that the Libya has experienced earthquakes of varying magnitudes and that there is definitely a certain amount of seismic risk involved in engineering projects, particularly in the northern regions. Detailed investigation of the distribution of the Libyan earthquakes in space and time along with all other geological considerations suggested the classification of the country into four seismic zones with the Hun graben zone being the most seismically active zone.

Seismogenic zones and attenuation laws for probabilistic seismic hazard assessment in low deformation area =

NASA Astrophysics Data System (ADS)

Le Goff, Boris

Seismic Hazard Analysis (PSHA), rather than the subjective methodologies that are currently used. This study focuses particularly in the definition of the seismic sources, through the seismotectonic zoning, and the determination of historical earthquake location. An important step in the Probabilistic Seismic Hazard Analysis consists in defining the seismic source model. Such a model expresses the association of the seismicity characteristics with the tectonically-active geological structures evidenced by seismotectonic studies. Given that most of the faults, in low seismic regions, are not characterized well enough, the source models are generally defined as areal zones, delimited with finite boundary polygons, within which the seismicity and the geological features are deemed homogeneous (e.g., focal depth, seismicity rate). Besides the lack of data (short period of instrumental seismicity), such a method generates different problems for regions with low seismic activity: 1) a large sensitivity of resulting hazard maps to the location of zone boundaries, while these boundaries are set by expert decisions; 2) the zoning cannot represent any variability or structural complexity in seismic parameters; 3) the seismicity rate is distributed throughout the zone and the location of the determinant information used for its calculation is lost. We investigate an alternative approach to model the seismotectonic zoning, with three main objectives: 1) obtaining a reproducible method that 2) preserves the information on the sources and extent of the uncertainties, so as to allow to propagate them (through Ground Motion Prediction Equations on to the hazard maps), and that 3) redefines the seismic source concept to debrief our knowledge on the seismogenic structures and the clustering. To do so, the Bayesian methods are favored. First, a generative model with two zones, differentiated by two different surface activity rates, was developed, creating synthetic catalogs drawn

Detecting Seismic Infrasound Signals on Balloon Platforms

NASA Astrophysics Data System (ADS)

Krishnamoorthy, S.; Komjathy, A.; Cutts, J. A.; Pauken, M.; Garcia, R.; Mimoun, D.; Jackson, J. M.; Kedar, S.; Smrekar, S. E.; Hall, J. L.

2017-12-01

The determination of the interior structure of a planet requires detailed seismic investigations - a process that entails the detection and characterization of seismic waves due to geological activities (e.g., earthquakes, volcanoes, etc.). For decades, this task has primarily been performed on Earth by an ever-expanding network of terrestrial seismic stations. However, on planets such as Venus, where the surface pressure and temperature can reach as high as 90 atmospheres and 450 degrees Celsius respectively, placing seismometers on the planet's surface poses a vexing technological challenge. However, the upper layers of the Venusian atmosphere are more benign and capable of hosting geophysical payloads for longer mission lifetimes. In order to achieve the aim of performing geophysical experiments from an atmospheric platform, JPL and its partners (ISAE-SUPAERO and California Institute of Technology) are in the process of developing technologies for detection of infrasonic waves generated by earthquakes from a balloon. The coupling of seismic energy into the atmosphere critically depends on the density differential between the surface of the planet and the atmosphere. Therefore, the successful demonstration of this technique on Earth would provide ample reason to expect success on Venus, where the atmospheric impedance is approximately 60 times that of Earth. In this presentation, we will share results from the first set of Earth-based balloon experiments performed in Pahrump, Nevada in June 2017. These tests involved the generation of artificial sources of known intensity using a seismic hammer and their detection using a complex network of sensors, including highly sensitive micro-barometers suspended from balloons, GPS receivers, geophones, microphones, and seismometers. This experiment was the first of its kind and was successful in detecting infrasonic waves from the earthquakes generated by the seismic hammer. We will present the first comprehensive analysis

Estimating earthquake location and magnitude from seismic intensity data

USGS Publications Warehouse

Bakun, W.H.; Wentworth, C.M.

1997-01-01

Analysis of Modified Mercalli intensity (MMI) observations for a training set of 22 California earthquakes suggests a strategy for bounding the epicentral region and moment magnitude M from MMI observations only. We define an intensity magnitude MI that is calibrated to be equal in the mean to M. MI = mean (Mi), where Mi = (MMIi + 3.29 + 0.0206 * ??i)/1.68 and ??i is the epicentral distance (km) of observation MMIi. The epicentral region is bounded by contours of rms [MI] = rms (MI - Mi) - rms0 (MI - Mi-), where rms is the root mean square, rms0 (MI - Mi) is the minimum rms over a grid of assumed epicenters, and empirical site corrections and a distance weighting function are used. Empirical contour values for bounding the epicenter location and empirical bounds for M estimated from MI appropriate for different levels of confidence and different quantities of intensity observations are tabulated. The epicentral region bounds and MI obtained for an independent test set of western California earthquakes are consistent with the instrumental epicenters and moment magnitudes of these earthquakes. The analysis strategy is particularly appropriate for the evaluation of pre-1900 earthquakes for which the only available data are a sparse set of intensity observations.

2016 one-year seismic hazard forecast for the Central and Eastern United States from induced and natural earthquakes

USGS Publications Warehouse

Petersen, Mark D.; Mueller, Charles S.; Moschetti, Morgan P.; Hoover, Susan M.; Llenos, Andrea L.; Ellsworth, William L.; Michael, Andrew J.; Rubinstein, Justin L.; McGarr, Arthur F.; Rukstales, Kenneth S.

2016-03-28

The U.S. Geological Survey (USGS) has produced a 1-year seismic hazard forecast for 2016 for the Central and Eastern United States (CEUS) that includes contributions from both induced and natural earthquakes. The model assumes that earthquake rates calculated from several different time windows will remain relatively stationary and can be used to forecast earthquake hazard and damage intensity for the year 2016. This assessment is the first step in developing an operational earthquake forecast for the CEUS, and the analysis could be revised with updated seismicity and model parameters. Consensus input models consider alternative earthquake catalog durations, smoothing parameters, maximum magnitudes, and ground motion estimates, and represent uncertainties in earthquake occurrence and diversity of opinion in the science community. Ground shaking seismic hazard for 1-percent probability of exceedance in 1 year reaches 0.6 g (as a fraction of standard gravity [g]) in northern Oklahoma and southern Kansas, and about 0.2 g in the Raton Basin of Colorado and New Mexico, in central Arkansas, and in north-central Texas near Dallas. Near some areas of active induced earthquakes, hazard is higher than in the 2014 USGS National Seismic Hazard Model (NHSM) by more than a factor of 3; the 2014 NHSM did not consider induced earthquakes. In some areas, previously observed induced earthquakes have stopped, so the seismic hazard reverts back to the 2014 NSHM. Increased seismic activity, whether defined as induced or natural, produces high hazard. Conversion of ground shaking to seismic intensity indicates that some places in Oklahoma, Kansas, Colorado, New Mexico, Texas, and Arkansas may experience damage if the induced seismicity continues unabated. The chance of having Modified Mercalli Intensity (MMI) VI or greater (damaging earthquake shaking) is 5–12 percent per year in north-central Oklahoma and southern Kansas, similar to the chance of damage caused by natural earthquakes

Probabilistic Seismic Hazard Analysis for Georgia

NASA Astrophysics Data System (ADS)

Tsereteli, N. S.; Varazanashvili, O.; Sharia, T.; Arabidze, V.; Tibaldi, A.; Bonali, F. L. L.; Russo, E.; Pasquaré Mariotto, F.

2017-12-01

Nowadays, seismic hazard studies are developed in terms of the calculation of Peak Ground Acceleration (PGA), Spectral Acceleration (SA), Peak Ground Velocity (PGV) and other recorded parameters. In the frame of EMME project PSH were calculated for Georgia using GMPE based on selection criteria. In the frame of Project N 216758 (supported by Shota Rustaveli National Science Foundation (SRNF)) PSH maps were estimated using hybrid- empirical ground motion prediction equation developed for Georgia. Due to the paucity of seismically recorded information, in this work we focused our research on a more robust dataset related to macroseismic data,and attempted to calculate the probabilistic seismic hazard directly in terms of macroseismicintensity. For this reason, we started calculating new intensity prediction equations (IPEs)for Georgia taking into account different sets, belonging to the same new database, as well as distances from the seismic source.With respect to the seismic source, in order to improve the quality of the results, we have also hypothesized the size of faults from empirical relations, and calculated new IPEs also by considering Joyner-Boore and rupture distances in addition to epicentral and hypocentral distances. Finally, site conditions have been included as variables for IPEs calculation Regarding the database, we used a brand new revised set of macroseismic data and instrumental records for the significant earthquakes that struck Georgia between 1900 and 2002.Particularly, a large amount of research and documents related to macroseismic effects of individual earthquakes, stored in the archives of the Institute of Geophysics, were used as sources for the new macroseismic data. The latter are reported in the Medvedev-Sponheuer-Karnikmacroseismic scale (MSK64). For each earthquake the magnitude, the focal depth and the epicenter location are also reported. An online version of the database, with therelated metadata,has been produced for the 69

Validating induced seismicity forecast models—Induced Seismicity Test Bench

NASA Astrophysics Data System (ADS)

Király-Proag, Eszter; Zechar, J. Douglas; Gischig, Valentin; Wiemer, Stefan; Karvounis, Dimitrios; Doetsch, Joseph

2016-08-01

Induced earthquakes often accompany fluid injection, and the seismic hazard they pose threatens various underground engineering projects. Models to monitor and control induced seismic hazard with traffic light systems should be probabilistic, forward-looking, and updated as new data arrive. In this study, we propose an Induced Seismicity Test Bench to test and rank such models; this test bench can be used for model development, model selection, and ensemble model building. We apply the test bench to data from the Basel 2006 and Soultz-sous-Forêts 2004 geothermal stimulation projects, and we assess forecasts from two models: Shapiro and Smoothed Seismicity (SaSS) and Hydraulics and Seismics (HySei). These models incorporate a different mix of physics-based elements and stochastic representation of the induced sequences. Our results show that neither model is fully superior to the other. Generally, HySei forecasts the seismicity rate better after shut-in but is only mediocre at forecasting the spatial distribution. On the other hand, SaSS forecasts the spatial distribution better and gives better seismicity rate estimates before shut-in. The shut-in phase is a difficult moment for both models in both reservoirs: the models tend to underpredict the seismicity rate around, and shortly after, shut-in.

What can He II 304 Å tell us about transient seismic emission from solar flares?

NASA Astrophysics Data System (ADS)

Lindsey, C.; Donea, A. C.

2017-10-01

After neary 20 years since their discovery by Kosovichev and Zharkova, the mechanics of the release of seismic transients into the solar interior from some flares remain a mystery. Seismically emissive flares invariably show the signatures of intense chromosphere heating consistent with pressure variations sufficient to drive seismic transients commensurate with helioseismic observations-under certain conditions. Magnetic observations show the signatures of apparent magnetic changes, suggesting Lorentz-force transients that could likewise drive seismic transients-similarly subject to certain conditions. But, the diagnostic signatures of both of these prospective drivers are apparent over vast regions from which no significant seismic emission emanates. What distinguishes the source regions of transient seismic emission from the much vaster regions that show the signatures of both transient heating and magnetic variations but are acoustically unproductive? Observations of acoustically active flares in He II 304 Å by the Atomospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) offer a promising new resource with which to address this question.

Seismic hazard estimation of northern Iran using smoothed seismicity

NASA Astrophysics Data System (ADS)

Khoshnevis, Naeem; Taborda, Ricardo; Azizzadeh-Roodpish, Shima; Cramer, Chris H.

2017-07-01

This article presents a seismic hazard assessment for northern Iran, where a smoothed seismicity approach has been used in combination with an updated seismic catalog and a ground motion prediction equation recently found to yield good fit with data. We evaluate the hazard over a geographical area including the seismic zones of Azerbaijan, the Alborz Mountain Range, and Kopeh-Dagh, as well as parts of other neighboring seismic zones that fall within our region of interest. In the chosen approach, seismic events are not assigned to specific faults but assumed to be potential seismogenic sources distributed within regular grid cells. After performing the corresponding magnitude conversions, we decluster both historical and instrumental seismicity catalogs to obtain earthquake rates based on the number of events within each cell, and smooth the results to account for the uncertainty in the spatial distribution of future earthquakes. Seismicity parameters are computed for each seismic zone separately, and for the entire region of interest as a single uniform seismotectonic region. In the analysis, we consider uncertainties in the ground motion prediction equation, the seismicity parameters, and combine the resulting models using a logic tree. The results are presented in terms of expected peak ground acceleration (PGA) maps and hazard curves at selected locations, considering exceedance probabilities of 2 and 10% in 50 years for rock site conditions. According to our results, the highest levels of hazard are observed west of the North Tabriz and east of the North Alborz faults, where expected PGA values are between about 0.5 and 1 g for 10 and 2% probability of exceedance in 50 years, respectively. We analyze our results in light of similar estimates available in the literature and offer our perspective on the differences observed. We find our results to be helpful in understanding seismic hazard for northern Iran, but recognize that additional efforts are necessary to

Advanced Seismic While Drilling System

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

Robert Radtke; John Fontenot; David Glowka

by TII. An APS Turbine Alternator powered the SeismicPULSER{trademark} to produce two Hz frequency peak signals repeated every 20 seconds. Since the ION Geophysical, Inc. (ION) seismic survey surface recording system was designed to detect a minimum downhole signal of three Hz, successful performance was confirmed with a 5.3 Hz recording with the pumps running. The two Hz signal generated by the sparker was modulated with the 3.3 Hz signal produced by the mud pumps to create an intense 5.3 Hz peak frequency signal. The low frequency sparker source is ultimately capable of generating selectable peak frequencies of 1 to 40 Hz with high-frequency spectra content to 10 kHz. The lower frequencies and, perhaps, low-frequency sweeps, are needed to achieve sufficient range and resolution for realtime imaging in deep (15,000 ft+), high-temperature (150 C) wells for (a) geosteering, (b) accurate seismic hole depth, (c) accurate pore pressure determinations ahead of the bit, (d) near wellbore diagnostics with a downhole receiver and wired drill pipe, and (e) reservoir model verification. Furthermore, the pressure of the sparker bubble will disintegrate rock resulting in an increased overall rates of penetration. Other applications for the SeismicPULSER{trademark} technology are to deploy a low-frequency source for greater range on a wireline for Reverse Vertical Seismic Profiling (RVSP) and Cross-Well Tomography. Commercialization of the technology is being undertaken by first contacting stakeholders to define the value proposition for rig site services utilizing SeismicPULSER{trademark} technologies. Stakeholders include national oil companies, independent oil companies, independents, service companies, and commercial investors. Service companies will introduce a new Drill Bit SWD service for deep HTHP wells. Collaboration will be encouraged between stakeholders in the form of joint industry projects to develop prototype tools and initial field trials. No barriers have been

Active seismic experiment

NASA Technical Reports Server (NTRS)

Kovach, R. L.; Watkins, J. S.; Talwani, P.

1972-01-01

The Apollo 16 active seismic experiment (ASE) was designed to generate and monitor seismic waves for the study of the lunar near-surface structure. Several seismic energy sources are used: an astronaut-activated thumper device, a mortar package that contains rocket-launched grenades, and the impulse produced by the lunar module ascent. Analysis of some seismic signals recorded by the ASE has provided data concerning the near-surface structure at the Descartes landing site. Two compressional seismic velocities have so far been recognized in the seismic data. The deployment of the ASE is described, and the significant results obtained are discussed.

New 3D seismicity maps using chromo-stereoscopy with two alternative freewares

NASA Astrophysics Data System (ADS)

Okamoto, Y.

2011-12-01

Seismicity maps play a key role in an introduction of geosciences studies or outreach programs. Various techniques are used in order to show earthquakes in a three dimensional field. To use "chromo-stereoscopy" is our simple and easier-making solution. The Chroma Depth 3D Glasses are employed for this purpose. The glasses consist of two transparent blazed grating films covered with a paper holder and cost a little (1 US$). Looking through these glasses, the colored chart turns into three dimensional perspective due to the mechanism that the color codes make a depth dimension with dispersion. We use two complementary freewares to make maps, the GMT (Generic Mapping Tools, Wessel and Smith.1988) and the POV-Ray (Persistence of Vision Pty. Ltd. 2004). The two softwares have their own advantages; the GMT is specialized for map making with simple scripts, while the POV-Ray produces realistic 3D rendering images with more complicated scripts. The earthquakes are plotted with the rainbow color codes depending on their depths in a black background as printed or PC images. Therefore, the red colored shallow earthquakes are float in front and blue colored ones sink deeper. This effect is so amazing that the students who first wear these glasses are strongly moved and fascinated with this simple mechanism. The data used here are from JMA seismicity catalogue and USGS (ANSS) catalogue. The POV-Ray version needs coastline data, so we got them from the Coastline Extractor (NGDC) web site. Also, the POR-Ray has no function to draw lines in three dimensions, so we had to make some trials for showing them in relief. The main target of our map is "the Wadati-Beniof zone", in which the sub-ducting oceanic plate surface is fringed by deeper earthquakes colored yellow, green to blue. The active volcanic regions such as the Hawaii islands or the active fault regions such as the San Andreas Fault are also effective targets of our method. However, since their shallow complicated seismic

Seismic stability of the survey areas of potential sites for the deep geological repository of the spent nuclear fuel

NASA Astrophysics Data System (ADS)

Kaláb, Zdeněk; Šílený, Jan; Lednická, Markéta

2017-07-01

This paper deals with the seismic stability of the survey areas of potential sites for the deep geological repository of the spent nuclear fuel in the Czech Republic. The basic source of data for historical earthquakes up to 1990 was the seismic website [1-]. The most intense earthquake described occurred on September 15, 1590 in the Niederroesterreich region (Austria) in the historical period; its reported intensity is Io = 8-9. The source of the contemporary seismic data for the period since 1991 to the end of 2014 was the website [11]. It may be stated based on the databases and literature review that in the period from 1900, no earthquake exceeding magnitude 5.1 originated in the territory of the Czech Republic. In order to evaluate seismicity and to assess the impact of seismic effects at depths of hypothetical deep geological repository for the next time period, the neo-deterministic method was selected as an extension of the probabilistic method. Each one out of the seven survey areas were assessed by the neo-deterministic evaluation of the seismic wave-field excited by selected individual events and determining the maximum loading. Results of seismological databases studies and neo-deterministic analysis of Čihadlo locality are presented.

Progressive Seismic Failure, Seismic Gap, and Great Seismic Risk across the Densely Populated North China Basin

NASA Astrophysics Data System (ADS)

Yin, A.; Yu, X.; Shen, Z.

2014-12-01

Although the seismically active North China basin has the most complete written records of pre-instrumentation earthquakes in the world, this information has not been fully utilized for assessing potential earthquake hazards of this densely populated region that hosts ~200 million people. In this study, we use the historical records to document the earthquake migration pattern and the existence of a 180-km seismic gap along the 600-km long right-slip Tangshan-Hejian-Cixian (THC) fault zone that cuts across the North China basin. The newly recognized seismic gap, which is centered at Tianjin with a population of 11 million people and ~120 km from Beijing (22 million people) and Tangshan (7 million people), has not been ruptured in the past 1000 years by M≥6 earthquakes. The seismic migration pattern in the past millennium suggests that the epicenters of major earthquakes have shifted towards this seismic gap along the THC fault, which implies that the 180- km gap could be the site of the next great earthquake with M≈7.6 if it is ruptured by a single event. Alternatively, the seismic gap may be explained by aseismic creeping or seismic strain transfer between active faults.

Time-Independent Annual Seismic Rates, Based on Faults and Smoothed Seismicity, Computed for Seismic Hazard Assessment in Italy

NASA Astrophysics Data System (ADS)

Murru, M.; Falcone, G.; Taroni, M.; Console, R.

2017-12-01

In 2015 the Italian Department of Civil Protection, started a project for upgrading the official Italian seismic hazard map (MPS04) inviting the Italian scientific community to participate in a joint effort for its realization. We participated providing spatially variable time-independent (Poisson) long-term annual occurrence rates of seismic events on the entire Italian territory, considering cells of 0.1°x0.1° from M4.5 up to M8.1 for magnitude bin of 0.1 units. Our final model was composed by two different models, merged in one ensemble model, each one with the same weight: the first one was realized by a smoothed seismicity approach, the second one using the seismogenic faults. The spatial smoothed seismicity was obtained using the smoothing method introduced by Frankel (1995) applied to the historical and instrumental seismicity. In this approach we adopted a tapered Gutenberg-Richter relation with a b-value fixed to 1 and a corner magnitude estimated with the bigger events in the catalogs. For each seismogenic fault provided by the Database of the Individual Seismogenic Sources (DISS), we computed the annual rate (for each cells of 0.1°x0.1°) for magnitude bin of 0.1 units, assuming that the seismic moments of the earthquakes generated by each fault are distributed according to the same tapered Gutenberg-Richter relation of the smoothed seismicity model. The annual rate for the final model was determined in the following way: if the cell falls within one of the seismic sources, we merge the respective value of rate determined by the seismic moments of the earthquakes generated by each fault and the value of the smoothed seismicity model with the same weight; if instead the cells fall outside of any seismic source we considered the rate obtained from the spatial smoothed seismicity. Here we present the final results of our study to be used for the new Italian seismic hazard map.

High temporal resolution mapping of seismic noise sources using heterogeneous supercomputers

NASA Astrophysics Data System (ADS)

Gokhberg, Alexey; Ermert, Laura; Paitz, Patrick; Fichtner, Andreas

2017-04-01

Time- and space-dependent distribution of seismic noise sources is becoming a key ingredient of modern real-time monitoring of various geo-systems. Significant interest in seismic noise source maps with high temporal resolution (days) is expected to come from a number of domains, including natural resources exploration, analysis of active earthquake fault zones and volcanoes, as well as geothermal and hydrocarbon reservoir monitoring. Currently, knowledge of noise sources is insufficient for high-resolution subsurface monitoring applications. Near-real-time seismic data, as well as advanced imaging methods to constrain seismic noise sources have recently become available. These methods are based on the massive cross-correlation of seismic noise records from all available seismic stations in the region of interest and are therefore very computationally intensive. Heterogeneous massively parallel supercomputing systems introduced in the recent years combine conventional multi-core CPU with GPU accelerators and provide an opportunity for manifold increase and computing performance. Therefore, these systems represent an efficient platform for implementation of a noise source mapping solution. We present the first results of an ongoing research project conducted in collaboration with the Swiss National Supercomputing Centre (CSCS). The project aims at building a service that provides seismic noise source maps for Central Europe with high temporal resolution (days to few weeks depending on frequency and data availability). The service is hosted on the CSCS computing infrastructure; all computationally intensive processing is performed on the massively parallel heterogeneous supercomputer "Piz Daint". The solution architecture is based on the Application-as-a-Service concept in order to provide the interested external researchers the regular access to the noise source maps. The solution architecture includes the following sub-systems: (1) data acquisition responsible for

Characteristics of seismic and tsunami fragility of industries, revealed by the 2011 Tohoku-oki earthquake

NASA Astrophysics Data System (ADS)

Kuwahara, Y.; Hasegawa, I.; Yoshimi, M.; Namegaya, Y.; Horikawa, H.; Nakai, M.; Masuda, S.

2013-12-01

We have developed seismic and tsunami fragility curves of industries by using damage data of industrial companies, estimated strong motions and estimated tsunami heights of the 2011 Tohoku-oki earthquake. The damage data were obtained from 7,019 industrial companies, which responded to an inquiry survey to 30,000 companies carried out by the Regional Innovation Research Center of Tohoku University. As a damage level indicator for each company, we introduced a ratio of an economical damage of physical fixed assets excluding lands to previous balance of the physical fixed assets. The estimated strong motions of the 2011 Tohoku-oki earthquake at all the sites of the companies were from the database of the so-called QuiQuake system (Quick estimation system for earthquake maps triggered by observation records) operated by the National Institute of Advanced Industrial Science and Technology (AIST). It is noted that the estimated data were obtained by taking account of seismic local site effects and the actually observed ones. The tsunami height data at each site of the company were obtained by interpolating the confirmed data compiled by the 2011 Tohoku Earthquake Tsunami Joint Survey Group (2013). A frequency-damage level distribution for each seismic intensity is well correlated with a binominal distribution where the only parameter characterizing the distribution is an average value of the damage levels in each seismic intensity. The averaged damage levels of all the data for respective seismic intensity scales are 0.016 for SIj 5 lower, 0.042 for SIj 5 upper, 0.067 for SIj 6 lower, 0.092 for SIj 6 upper, and 0.16 for SIj 7, where SIj stands for the Japanese seismic intensity scale. The data were sorted into several classified industries and fragility curve for each classified industry is found to have a different character from each other. The tsunami fragilities are also obtained as a function of the tsunami height in the same way. The averaged damage levels of all

[Operating room during natural disaster: lessons from the 2011 Tohoku earthquake].

PubMed

Fukuda, Ikuo; Hashimoto, Hiroshi; Suzuki, Yasuyuki; Satomi, Susumu; Unno, Michiaki; Ohuchi, Noriaki; Nakaji, Shigeyuki

2012-03-01

Objective of this study is to clarify damages in operating rooms after the 2011 Tohoku Earthquake. To survey structural and non-structural damage in operating theaters, we sent questionnaires to 155 acute care hospitals in Tohoku area. Questionnaires were sent back from 105 hospitals (70.3%). Total of 280 patients were undergoing any kinds of operations during the earthquake and severe seismic tremor greater than JMA Seismic Intensity 6 hit 49 hospitals. Operating room staffs experienced life-threatening tremor in 41 hospitals. Blackout occurred but emergency electronic supply unit worked immediately in 81 out of 90 hospitals. However, emergency power plant did not work in 9 hospitals. During earthquake some materials fell from shelves in 44 hospitals and medical instruments fell down in 14 hospitals. In 5 hospitals, they experienced collapse of operating room wall or ceiling causing inability to maintain sterile operative field. Damage in electric power and water supply plus damage in logistics made many operating rooms difficult to perform routine surgery for several days. The 2011 Tohoku earthquake affected medical supply in wide area of Tohoku district and induced dysfunction of operating room. Supply-chain management of medical goods should be reconsidered to prepare severe natural disaster.

ON-SITE CAVITY LOCATION-SEISMIC PROFILING AT NEVADA TEST SITE

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

Forbes, C.B.; Peterson, R.A.; Heald, C.L.

1961-10-25

Experimental seismic studies were conducted at the Nevada Test Site for the purpose of designing and evaluating the most promising seismic techniques for on-site inspection. Post-explosion seismic profiling was done in volcanic tuff in the vicinity of the Rainier and Blanca underground explosions. Pre-explosion seismic profiling was done over granitic rock outcrops in the Climax Stock area, and over tuff at proposed location for Linen and Orchid. Near surface velocity profiling techniques based on measurements of seismic time-distance curves gave evidence of disturbances in near surface rock velocities over the Rainier and Refer als0 to abstract 30187. Blanca sites. Thesemore » disturbances appear to be related to near surface fracturing and spallation effects resulting from the reflection of the original intense compression wave pulse at the near surface as a tension pulse. Large tuned seismometer arrays were used for horizontal seismic ranging in an attempt to record back-scattered'' or reflected seismic waves from subsurface cavities or zones of rock fracturing around the underground explosions. Some possible seismic events were recorded from the near vicinities of the Rainier and Blanca sites. However, many more similar events were recorded from numerous other locations, presumably originating from naturally occurring underground geological features. No means was found for discriminating between artificial and natural events recorded by horizontal seismic ranging, and the results were, therefore, not immediately useful for inspection purposes. It is concluded that in some instances near surface velocity profiling methods may provide a useful tool in verifying the presence of spalled zones above underground nuclear explosion sites. In the case of horizontal seismic ranging it appears that successful application would require development of satisfactory means for recognition of and discrimination against seismic responses to naturally occurring geological

Seismic Noise Analysis and Reduction through Utilization of Collocated Seismic and Atmospheric Sensors at the GRO Chile Seismic Network

NASA Astrophysics Data System (ADS)

Farrell, M. E.; Russo, R. M.

2013-12-01

The installation of Earthscope Transportable Array-style geophysical observatories in Chile expands open data seismic recording capabilities in the southern hemisphere by nearly 30%, and has nearly tripled the number of seismic stations providing freely-available data in southern South America. Through the use of collocated seismic and atmospheric sensors at these stations we are able to analyze how local atmospheric conditions generate seismic noise, which can degrade data in seismic frequency bands at stations in the ';roaring forties' (S latitudes). Seismic vaults that are climate-controlled and insulated from the local environment are now employed throughout the world in an attempt to isolate seismometers from as many noise sources as possible. However, this is an expensive solution that is neither practical nor possible for all seismic deployments; and also, the increasing number and scope of temporary seismic deployments has resulted in the collection and archiving of terabytes of seismic data that is affected to some degree by natural seismic noise sources such as wind and atmospheric pressure changes. Changing air pressure can result in a depression and subsequent rebound of Earth's surface - which generates low frequency noise in seismic frequency bands - and even moderate winds can apply enough force to ground-coupled structures or to the surface above the seismometers themselves, resulting in significant noise. The 10 stations of the permanent Geophysical Reporting Observatories (GRO Chile), jointly installed during 2011-12 by IRIS and the Chilean Servicio Sismológico, include instrumentation in addition to the standard three seismic components. These stations, spaced approximately 300 km apart along the length of the country, continuously record a variety of atmospheric data including infrasound, air pressure, wind speed, and wind direction. The collocated seismic and atmospheric sensors at each station allow us to analyze both datasets together, to

Comparing Foreshock Characteristics and Foreshock Forecasting in Observed and Simulated Earthquake Catalogs

NASA Astrophysics Data System (ADS)

Ogata, Y.

2014-12-01

In our previous papers (Ogata et al., 1995, 1996, 2012; GJI), we characterized foreshock activity in Japan, and then presented a model that forecasts the probability that one or more earthquakes form a foreshock sequence; then we tested prospectively foreshock probabilities in the JMA catalog. In this talk, I compare the empirical results with results for synthetic catalogs in order to clarify whether or not these results are consistent with the description of the seismicity by a superposition of background activity and epidemic-type aftershock sequences (ETAS models). This question is important, because it is still controversially discussed whether the nucleation process of large earthquakes is driven by seismically cascading (ETAS-type) or by aseismic accelerating processes. To explore the foreshock characteristics, I firstly applied the same clustering algorithms to real and synthetic catalogs and analyzed the temporal, spatial and magnitude distributions of the selected foreshocks, to find significant differences particularly in the temporal acceleration and magnitude dependence. Finally, I calculated forecast scores based on a single-link cluster algorithm which could be appropriate for real-time applications. I find that the JMA catalog yields higher scores than all synthetic catalogs and that the ETAS models having the same magnitude sequence as the original catalog performs significantly better (more close to the reality) than ETAS-models with randomly picked magnitudes.

Expected Seismicity and the Seismic Noise Environment of Europa

NASA Astrophysics Data System (ADS)

Panning, Mark P.; Stähler, Simon C.; Huang, Hsin-Hua; Vance, Steven D.; Kedar, Sharon; Tsai, Victor C.; Pike, William T.; Lorenz, Ralph D.

2018-01-01

Seismic data will be a vital geophysical constraint on internal structure of Europa if we land instruments on the surface. Quantifying expected seismic activity on Europa both in terms of large, recognizable signals and ambient background noise is important for understanding dynamics of the moon, as well as interpretation of potential future data. Seismic energy sources will likely include cracking in the ice shell and turbulent motion in the oceans. We define a range of models of seismic activity in Europa's ice shell by assuming each model follows a Gutenberg-Richter relationship with varying parameters. A range of cumulative seismic moment release between 1016 and 1018 Nm/yr is defined by scaling tidal dissipation energy to tectonic events on the Earth's moon. Random catalogs are generated and used to create synthetic continuous noise records through numerical wave propagation in thermodynamically self-consistent models of the interior structure of Europa. Spectral characteristics of the noise are calculated by determining probabilistic power spectral densities of the synthetic records. While the range of seismicity models predicts noise levels that vary by 80 dB, we show that most noise estimates are below the self-noise floor of high-frequency geophones but may be recorded by more sensitive instruments. The largest expected signals exceed background noise by ˜50 dB. Noise records may allow for constraints on interior structure through autocorrelation. Models of seismic noise generated by pressure variations at the base of the ice shell due to turbulent motions in the subsurface ocean may also generate observable seismic noise.

Seismic Risk Assessment for the Kyrgyz Republic

NASA Astrophysics Data System (ADS)

Pittore, Massimiliano; Sousa, Luis; Grant, Damian; Fleming, Kevin; Parolai, Stefano; Fourniadis, Yannis; Free, Matthew; Moldobekov, Bolot; Takeuchi, Ko

2017-04-01

The Kyrgyz Republic is one of the most socially and economically dynamic countries in Central Asia, and one of the most endangered by earthquake hazard in the region. In order to support the government of the Kyrgyz Republic in the development of a country-level Disaster Risk Reduction strategy, a comprehensive seismic risk study has been developed with the support of the World Bank. As part of this project, state-of-the-art hazard, exposure and vulnerability models have been developed and combined into the assessment of direct physical and economic risk on residential, educational and transportation infrastructure. The seismic hazard has been modelled with three different approaches, in order to provide a comprehensive overview of the possible consequences. A probabilistic seismic hazard assessment (PSHA) approach has been used to quantitatively evaluate the distribution of expected ground shaking intensity, as constrained by the compiled earthquake catalogue and associated seismic source model. A set of specific seismic scenarios based on events generated from known fault systems have been also considered, in order to provide insight on the expected consequences in case of strong events in proximity of densely inhabited areas. Furthermore, long-span catalogues of events have been generated stochastically and employed in the probabilistic analysis of expected losses over the territory of the Kyrgyz Republic. Damage and risk estimates have been computed by using an exposure model recently developed for the country, combined with the assignment of suitable fragility/vulnerability models. The risk estimation has been carried out with spatial aggregation at the district (rayon) level. The obtained results confirm the high level of seismic risk throughout the country, also pinpointing the location of several risk hotspots, particularly in the southern districts, in correspondence with the Ferghana valley. The outcome of this project will further support the local

Evaluation of induced seismicity forecast models in the Induced Seismicity Test Bench

NASA Astrophysics Data System (ADS)

Király, Eszter; Gischig, Valentin; Zechar, Jeremy; Doetsch, Joseph; Karvounis, Dimitrios; Wiemer, Stefan

2016-04-01

Induced earthquakes often accompany fluid injection, and the seismic hazard they pose threatens various underground engineering projects. Models to monitor and control induced seismic hazard with traffic light systems should be probabilistic, forward-looking, and updated as new data arrive. Here, we propose an Induced Seismicity Test Bench to test and rank such models. We apply the test bench to data from the Basel 2006 and Soultz-sous-Forêts 2004 geothermal stimulation projects, and we assess forecasts from two models that incorporate a different mix of physical understanding and stochastic representation of the induced sequences: Shapiro in Space (SiS) and Hydraulics and Seismics (HySei). SiS is based on three pillars: the seismicity rate is computed with help of the seismogenic index and a simple exponential decay of the seismicity; the magnitude distribution follows the Gutenberg-Richter relation; and seismicity is distributed in space based on smoothing seismicity during the learning period with 3D Gaussian kernels. The HySei model describes seismicity triggered by pressure diffusion with irreversible permeability enhancement. Our results show that neither model is fully superior to the other. HySei forecasts the seismicity rate well, but is only mediocre at forecasting the spatial distribution. On the other hand, SiS forecasts the spatial distribution well but not the seismicity rate. The shut-in phase is a difficult moment for both models in both reservoirs: the models tend to underpredict the seismicity rate around, and shortly after, shut-in. Ensemble models that combine HySei's rate forecast with SiS's spatial forecast outperform each individual model.

Gas and seismicity within the Istanbul seismic gap.

PubMed

Géli, L; Henry, P; Grall, C; Tary, J-B; Lomax, A; Batsi, E; Riboulot, V; Cros, E; Gürbüz, C; Işık, S E; Sengör, A M C; Le Pichon, X; Ruffine, L; Dupré, S; Thomas, Y; Kalafat, D; Bayrakci, G; Coutellier, Q; Regnier, T; Westbrook, G; Saritas, H; Çifçi, G; Çağatay, M N; Özeren, M S; Görür, N; Tryon, M; Bohnhoff, M; Gasperini, L; Klingelhoefer, F; Scalabrin, C; Augustin, J-M; Embriaco, D; Marinaro, G; Frugoni, F; Monna, S; Etiope, G; Favali, P; Bécel, A

2018-05-01

Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the "Istanbul seismic gap") has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25 th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5-5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain.

Seismic Catalogue and Seismic Network in Haiti

NASA Astrophysics Data System (ADS)

Belizaire, D.; Benito, B.; Carreño, E.; Meneses, C.; Huerfano, V.; Polanco, E.; McCormack, D.

2013-05-01

The destructive earthquake occurred on January 10, 2010 in Haiti, highlighted the lack of preparedness of the country to address seismic phenomena. At the moment of the earthquake, there was no seismic network operating in the country, and only a partial control of the past seismicity was possible, due to the absence of a national catalogue. After the 2010 earthquake, some advances began towards the installation of a national network and the elaboration of a seismic catalogue providing the necessary input for seismic Hazard Studies. This paper presents the state of the works carried out covering both aspects. First, a seismic catalogue has been built, compiling data of historical and instrumental events occurred in the Hispaniola Island and surroundings, in the frame of the SISMO-HAITI project, supported by the Technical University of Madrid (UPM) and Developed in cooperation with the Observatoire National de l'Environnement et de la Vulnérabilité of Haiti (ONEV). Data from different agencies all over the world were gathered, being relevant the role of the Dominican Republic and Puerto Rico seismological services which provides local data of their national networks. Almost 30000 events recorded in the area from 1551 till 2011 were compiled in a first catalogue, among them 7700 events with Mw ranges between 4.0 and 8.3. Since different magnitude scale were given by the different agencies (Ms, mb, MD, ML), this first catalogue was affected by important heterogeneity in the size parameter. Then it was homogenized to moment magnitude Mw using the empirical equations developed by Bonzoni et al (2011) for the eastern Caribbean. At present, this is the most exhaustive catalogue of the country, although it is difficult to assess its degree of completeness. Regarding the seismic network, 3 stations were installed just after the 2010 earthquake by the Canadian Government. The data were sent by telemetry thought the Canadian System CARINA. In 2012, the Spanish IGN together

Participation in the Apollo passive seismic experiment

NASA Technical Reports Server (NTRS)

Press, F.; Toksoez, M. N.; Dainty, A.

1972-01-01

Computer programs which were written to read digital tapes containing lunar seismic data were studied. Interpreting very early parts of the lunar seismogram as seismic body-wave phases enabled the determination of the structure of the outer part of the moon in the Fra Mauro region. The crust in the Fra Mauro region is 60 to 65 km-thick, overlaying a high velocity mantle. The crust is further divided into an upper part, 25 km thick, apparently made of material similar to the surficial basalts, and a lower part of seemingly different composition, possibly an anorthositic gabbro. The generation of the exceedingly long reverberating wave-train observed in lunar seismogram was also studied. This is believed to be due to an intense scattering layer with very high quality coefficient overlying a more homogeneous elastic medium. Titles and abstracts of related published papers are included.

Seismic gradiometry using ambient seismic noise in an anisotropic Earth

NASA Astrophysics Data System (ADS)

de Ridder, S. A. L.; Curtis, A.

2017-05-01

We introduce a wavefield gradiometry technique to estimate both isotropic and anisotropic local medium characteristics from short recordings of seismic signals by inverting a wave equation. The method exploits the information in the spatial gradients of a seismic wavefield that are calculated using dense deployments of seismic arrays. The application of the method uses the surface wave energy in the ambient seismic field. To estimate isotropic and anisotropic medium properties we invert an elliptically anisotropic wave equation. The spatial derivatives of the recorded wavefield are evaluated by calculating finite differences over nearby recordings, which introduces a systematic anisotropic error. A two-step approach corrects this error: finite difference stencils are first calibrated, then the output of the wave-equation inversion is corrected using the linearized impulse response to the inverted velocity anomaly. We test the procedure on ambient seismic noise recorded in a large and dense ocean bottom cable array installed over Ekofisk field. The estimated azimuthal anisotropy forms a circular geometry around the production-induced subsidence bowl. This conforms with results from studies employing controlled sources, and with interferometry correlating long records of seismic noise. Yet in this example, the results were obtained using only a few minutes of ambient seismic noise.

Adding seismic broadband analysis to characterize Andean backarc seismicity in Argentina

NASA Astrophysics Data System (ADS)

Alvarado, P.; Giuliano, A.; Beck, S.; Zandt, G.

2007-05-01

Characterization of the highly seismically active Andean backarc is crucial for assessment of earthquake hazards in western Argentina. Moderate-to-large crustal earthquakes have caused several deaths, damage and drastic economic consequences in Argentinean history. We have studied the Andean backarc crust between 30°S and 36°S using seismic broadband data available from a previous ("the CHARGE") IRIS-PASSCAL experiment. We collected more than 12 terabytes of continuous seismic data from 22 broadband instruments deployed across Chile and Argentina during 1.5 years. Using free software we modeled full regional broadband waveforms and obtained seismic moment tensor inversions of crustal earthquakes testing for the best focal depth for each event. We also mapped differences in the Andean backarc crustal structure and found a clear correlation with different types of crustal seismicity (i.e. focal depths, focal mechanisms, magnitudes and frequencies of occurrence) and previously mapped terrane boundaries. We now plan to use the same methodology to study other regions in Argentina using near-real time broadband data available from the national seismic (INPRES) network and global seismic networks operating in the region. We will re-design the national seismic network to optimize short-period and broadband seismic station coverage for different network purposes. This work is an international effort that involves researchers and students from universities and national government agencies with the goal of providing more information about earthquake hazards in western Argentina.

Estimation of earthquake effects associated with a great earthquake in the New Madrid seismic zone

USGS Publications Warehouse

Hopper, Margaret G.; Algermissen, Sylvester Theodore; Dobrovolny, Ernest E.

1983-01-01

Estimates have been made of the effects of a large Ms = 8.6, Io = XI earthquake hypothesed to occur anywhere in the New Madrid seismic zone. The estimates are based on the distributions of intensities associated with the earthquakes of 1811-12, 1843 and 1895 although the effects of other historical shocks are also considered. The resulting composite type intensity map for a maximum intensity XI is believed to represent the upper level of shaking likely to occur. Specific intensity maps have been developed for six cities near the epicentral region taking into account the most likely distribution of site response in each city. Intensities found are: IX for Carbondale, IL; VIII and IX for Evansville, IN; VI and VIII for Little Rock, AR; IX and X for Memphis, TN; VIII, IX, and X for Paducah, KY; and VIII and X for Poplar Bluff, MO. On a regional scale, intensities are found to attenuate from the New Madrid seismic zone most rapidly to the west and southwest sides of the zone, most slowly to the northwest along the Mississippi River, on the northeast along the Ohio River, and on the southeast toward Georgia and South Carolina. Intensities attenuate toward the north, east, and south in a more normal fashion. Known liquefaction effects are documented but much more research is needed to define the liquefaction potential.

Retrieving both phase and amplitude information of Green's functions by ambient seismic wave field cross-correlation: A case study with a limestone mine induced seismic event

NASA Astrophysics Data System (ADS)

Kwak, S.; Song, S. G.; Kim, G.; Shin, J. S.

2015-12-01

Recently many seismologists have paid attention to ambient seismic field, which is no more referred as noise and called as Earth's hum, but as useful signal to understand subsurface seismic velocity structure. It has also been demonstrated that empirical Green's functions can be constructed by retrieving both phase and amplitude information from ambient seismic field (Prieto and Beroza 2008). The constructed empirical Green's functions can be used to predict strong ground motions after focal depth and double-couple mechanism corrections (Denolle et al. 2013). They do not require detailed subsurface velocity model and intensive computation for ground motion simulation. In this study, we investigate the capability of predicting long period surface waves by the ambient seismic wave field with a seismic event of Mw 4.0, which occurred with a limestone mine collapse in South Korea on January 31, 2015. This limestone-mine event provides an excellent opportunity to test the efficiency of the ambient seismic wave field in retrieving both phase and amplitude information of Green's functions due to the single force mechanism of the collapse event. In other words, both focal depth and double-couple mechanism corrections are not required for this event. A broadband seismic station, which is about 5.4 km away from the mine event, is selected as a source station. Then surface waves retrieved from the ambient seismic wave field cross-correlation are compared with those generated by the event. Our preliminary results show some potential of the ambient seismic wave field in retrieving both phase and amplitude of Green's functions from a single force impulse source at the Earth's surface. More comprehensive analysis by increasing the time length of stacking may improve the results in further studies. We also aim to investigate the efficiency of retrieving the full empirical Green's functions with the 2007 Mw 4.6 Odaesan earthquake, which is one of the strongest earthquakes occurred

The Aftershock Risk Index - quantification of aftershock impacts during ongoing strong-seismic sequences

NASA Astrophysics Data System (ADS)

Schaefer, Andreas; Daniell, James; Khazai, Bijan; Wenzel, Friedemann

2016-04-01

The occurrence and impact of strong earthquakes often triggers the long-lasting impact of a seismic sequence. Strong earthquakes are generally followed by many aftershocks or even strong subsequently triggered ruptures. The Nepal 2015 earthquake sequence is one of the most recent examples where aftershocks significantly contributed to human and economic losses. In addition, rumours about upcoming mega-earthquakes, false predictions and on-going cycles of aftershocks induced a psychological burden on the society, which caused panic, additional casualties and prevented people from returning to normal life. This study shows the current phase of development of an operationalised aftershock intensity index, which will contribute to the mitigation of aftershock hazard. Hereby, various methods of earthquake forecasting and seismic risk assessments are utilised and an integration of the inherent aftershock intensity is performed. A spatio-temporal analysis of past earthquake clustering provides first-hand data about the nature of aftershock occurrence. Epidemic methods can additionally provide time-dependent variation indices of the cascading effects of aftershock generation. The aftershock hazard is often combined with the potential for significant losses through the vulnerability of structural systems and population. A historical database of aftershock socioeconomic effects from CATDAT has been used in order to calibrate the index based on observed impacts of historical events and their aftershocks. In addition, analytical analysis of cyclic behaviour and fragility functions of various building typologies are explored. The integration of many different probabilistic computation methods will provide a combined index parameter which can then be transformed into an easy-to-read spatio-temporal intensity index. The index provides daily updated information about the probability of the inherent seismic risk of aftershocks by providing a scalable scheme fordifferent aftershock

Probabilistic seismic vulnerability and risk assessment of stone masonry structures

NASA Astrophysics Data System (ADS)

Abo El Ezz, Ahmad

Earthquakes represent major natural hazards that regularly impact the built environment in seismic prone areas worldwide and cause considerable social and economic losses. The high losses incurred following the past destructive earthquakes promoted the need for assessment of the seismic vulnerability and risk of the existing buildings. Many historic buildings in the old urban centers in Eastern Canada such as Old Quebec City are built of stone masonry and represent un-measurable architectural and cultural heritage. These buildings were built to resist gravity loads only and generally offer poor resistance to lateral seismic loads. Seismic vulnerability assessment of stone masonry buildings is therefore the first necessary step in developing seismic retrofitting and pre-disaster mitigation plans. The objective of this study is to develop a set of probability-based analytical tools for efficient seismic vulnerability and uncertainty analysis of stone masonry buildings. A simplified probabilistic analytical methodology for vulnerability modelling of stone masonry building with systematic treatment of uncertainties throughout the modelling process is developed in the first part of this study. Building capacity curves are developed using a simplified mechanical model. A displacement based procedure is used to develop damage state fragility functions in terms of spectral displacement response based on drift thresholds of stone masonry walls. A simplified probabilistic seismic demand analysis is proposed to capture the combined uncertainty in capacity and demand on fragility functions. In the second part, a robust analytical procedure for the development of seismic hazard compatible fragility and vulnerability functions is proposed. The results are given by sets of seismic hazard compatible vulnerability functions in terms of structure-independent intensity measure (e.g. spectral acceleration) that can be used for seismic risk analysis. The procedure is very efficient for

Earthquake clustering in modern seismicity and its relationship with strong historical earthquakes around Beijing, China

NASA Astrophysics Data System (ADS)

Wang, Jian; Main, Ian G.; Musson, Roger M. W.

2017-11-01

Beijing, China's capital city, is located in a typical intraplate seismic belt, with relatively high-quality instrumental catalogue data available since 1970. The Chinese historical earthquake catalogue contains six strong historical earthquakes of Ms ≥ 6 around Beijing, the earliest in 294 AD. This poses a significant potential hazard to one of the most densely populated and economically active parts of China. In some intraplate areas, persistent clusters of events associated with historical events can occur over centuries, for example, the ongoing sequence in the New Madrid zone of the eastern US. Here we will examine the evidence for such persistent clusters around Beijing. We introduce a metric known as the `seismic density index' that quantifies the degree of clustering of seismic energy release. For a given map location, this multi-dimensional index depends on the number of events, their magnitudes, and the distances to the locations of the surrounding population of earthquakes. We apply the index to modern instrumental catalogue data between 1970 and 2014, and identify six clear candidate zones. We then compare these locations to earthquake epicentre and seismic intensity data for the six largest historical earthquakes. Each candidate zone contains one of the six historical events, and the location of peak intensity is within 5 km or so of the reported epicentre in five of these cases. In one case—the great Ms 8 earthquake of 1679—the peak is closer to the area of strongest shaking (Intensity XI or more) than the reported epicentre. The present-day event rates are similar to those predicted by the modified Omori law but there is no evidence of ongoing decay in event rates. Accordingly, the index is more likely to be picking out the location of persistent weaknesses in the lithosphere. Our results imply zones of high seismic density index could be used in principle to indicate the location of unrecorded historical of palaeoseismic events, in China and

Seismic Methods

EPA Pesticide Factsheets

Seismic methods are the most commonly conducted geophysical surveys for engineering investigations. Seismic refraction provides engineers and geologists with the most basic of geologic data via simple procedures with common equipment.

Seismic fragility formulations for segmented buried pipeline systems including the impact of differential ground subsidence

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

Pineda Porras, Omar Andrey; Ordaz, Mario

2009-01-01

Though Differential Ground Subsidence (DGS) impacts the seismic response of segmented buried pipelines augmenting their vulnerability, fragility formulations to estimate repair rates under such condition are not available in the literature. Physical models to estimate pipeline seismic damage considering other cases of permanent ground subsidence (e.g. faulting, tectonic uplift, liquefaction, and landslides) have been extensively reported, not being the case of DGS. The refinement of the study of two important phenomena in Mexico City - the 1985 Michoacan earthquake scenario and the sinking of the city due to ground subsidence - has contributed to the analysis of the interrelation ofmore » pipeline damage, ground motion intensity, and DGS; from the analysis of the 48-inch pipeline network of the Mexico City's Water System, fragility formulations for segmented buried pipeline systems for two DGS levels are proposed. The novel parameter PGV{sup 2}/PGA, being PGV peak ground velocity and PGA peak ground acceleration, has been used as seismic parameter in these formulations, since it has shown better correlation to pipeline damage than PGV alone according to previous studies. By comparing the proposed fragilities, it is concluded that a change in the DGS level (from Low-Medium to High) could increase the pipeline repair rates (number of repairs per kilometer) by factors ranging from 1.3 to 2.0; being the higher the seismic intensity the lower the factor.« less

The behavior of seasonal variations in induced seismicity in the Koyna-Warna region, western India

NASA Astrophysics Data System (ADS)

Smirnov, V. B.; Srinagesh, D.; Ponomarev, A. V.; Chadha, R.; Mikhailov, V. O.; Potanina, M. G.; Kartashov, I. M.; Stroganova, S. M.

2017-07-01

Based on the earthquake catalog data for the Koyna-Warna region of induced seismicity in western India, the seasonal variations in seismic activity associated with annual fluctuations in the reservoir water level are analyzed over the time span of the entire history of seismological observations in this region. The regularities in the time changes in the structure of seasonal variations are revealed. The seasonal seismic activity is minimal in May-June when the reservoir level is lowest. During the remaining part of the year, the activity has three peaks: the fall peak in September, winter peak in November-December, and spring peak in February-March. The first mentioned peak, which falls in the phase of the water level reaching its maximal seasonal value is considered as the immediate response of the fluid saturated medium to the additional loading under the weight of reservoir water. The two subsequent maxima concur with the decline phase in the reservoir level and are interpreted as the delayed response associated with the changes in the properties of the medium due to water diffusion. It is shown that the intensities of the immediate and delayed responses to the seasonal water level variations both vary with time as does their ratio. The probable factors affecting the variations in the intensity of the seasonal components of the reservoir-induced seismicity are discussed.

Precise hypocenter distribution and earthquake generating and stress in and around the upper-plane seismic belt in the subducting Pacific slab beneath NE Japan

NASA Astrophysics Data System (ADS)

Kita, S.; Okada, T.; Nakajima, J.; Matsuzawa, T.; Uchida, N.; Hasegawa, A.

2007-12-01

1. Introduction We found an intraslab seismic belt (upper-plane seismic belt) in the upper plane of the double seismic zone within the Pacific slab, running interface at depths of 70-100km beneath the forearc area. The location of the deeper limits of this belt appears to correspond to one of the facies boundaries (from jadeite lawsonite blueschist to lawsonite amphibole eclogite) in the oceanic crust [Kita et al., 2006, GRL]. In this study, we precisely relocated intraslab earthquakes by using travel time differences calculated by the waveform cross-spectrum analysis to obtain more detailed distribution of the upper plane-seismic belt within the Pacific slab beneath NE Japan. We also discuss the stress field in the slab by examining focal mechanisms of the earthquakes. 2. Data and Method We relocated events at depths of 50-00 km for the period from March 2003 to November 2006 from the JMA earthquake catalog. We applied the double-difference hypocenter location method (DDLM) by Waldhauser and Ellsworth (2000) to the arrival time data of the events. We use relative earthquake arrival times determined both by the waveform cross-spectrum analysis and by the catalog-picking data. We also determine focal mechanisms using the P wave polarity. 3. Spatial distribution of relocated hypocenters In the upper portion of the slab crust, seismicity is very active and distributed relatively homogeneously at depths of about 70-100km parallel to the volcanic front, where the upper-plane seismic belt has been found. In the lower portion of slab crust and/or the uppermost portion of the slab mantle, seismicity is spatially very limited to some small areas (each size is about 20 x 20km) at depths around 65km. Two of them correspond to the aftershock area of the 2003 Miyagi (M7.1) intraslab earthquake and that of the 1987 Iwaizumi (M6.6) intraslab earthquake, respectively. Based on the dehydration embrittelment hypothesis, the difference of the spatial distribution of the seismicity in

Intensity attenuation in the Pannonian Basin

NASA Astrophysics Data System (ADS)

Győri, Erzsébet; Gráczer, Zoltán; Szanyi, Gyöngyvér

2015-04-01

Ground motion prediction equations play a key role in seismic hazard assessment. Earthquake hazard has to be expressed in macroseismic intensities in case of seismic risk estimations where a direct relation to the damage associated with ground shaking is needed. It can be also necessary for shake map generation where the map is used for prompt notification to the public, disaster management officers and insurance companies. Although only few instrumental strong motion data are recorded in the Pannonian Basin, there are numerous historical reports of past earthquakes since the 1763 Komárom earthquake. Knowing the intensity attenuation and comparing them with relations of other areas - where instrumental strong motion data also exist - can help us to choose from the existing instrumental ground motion prediction equations. The aim of this work is to determine an intensity attenuation formula for the inner part of the Pannonian Basin, which can be further used to find an adaptable ground motion prediction equation for the area. The crust below the Pannonian Basin is thin and warm and it is overlain by thick sediments. Thus the attenuation of seismic waves here is different from the attenuation in the Alp-Carpathian mountain belt. Therefore we have collected intensity data only from the inner part of the Pannonian Basin and defined the boundaries of the studied area by the crust thickness of 30 km (Windhoffer et al., 2005). 90 earthquakes from 1763 until 2014 have sufficient number of macroseismic data. Magnitude of the events varies from 3.0 to 6.6. We have used individual intensity points to eliminate the subjectivity of drawing isoseismals, the number of available intensity data is more than 3000. Careful quality control has been made on the dataset. The different types of magnitudes of the used earthquake catalogue have been converted to local and momentum magnitudes using relations determined for the Pannonian Basin. We applied the attenuation formula by Sorensen

A seismic hazard uncertainty analysis for the New Madrid seismic zone

USGS Publications Warehouse

Cramer, C.H.

2001-01-01

A review of the scientific issues relevant to characterizing earthquake sources in the New Madrid seismic zone has led to the development of a logic tree of possible alternative parameters. A variability analysis, using Monte Carlo sampling of this consensus logic tree, is presented and discussed. The analysis shows that for 2%-exceedence-in-50-year hazard, the best-estimate seismic hazard map is similar to previously published seismic hazard maps for the area. For peak ground acceleration (PGA) and spectral acceleration at 0.2 and 1.0 s (0.2 and 1.0 s Sa), the coefficient of variation (COV) representing the knowledge-based uncertainty in seismic hazard can exceed 0.6 over the New Madrid seismic zone and diminishes to about 0.1 away from areas of seismic activity. Sensitivity analyses show that the largest contributor to PGA, 0.2 and 1.0 s Sa seismic hazard variability is the uncertainty in the location of future 1811-1812 New Madrid sized earthquakes. This is followed by the variability due to the choice of ground motion attenuation relation, the magnitude for the 1811-1812 New Madrid earthquakes, and the recurrence interval for M>6.5 events. Seismic hazard is not very sensitive to the variability in seismogenic width and length. Published by Elsevier Science B.V.

Intensity of geomorphological processes in NW sector of Pacific rim marginal mountain belts

NASA Astrophysics Data System (ADS)

Lebedeva, Ekaterina; Shvarev, Sergey; Gotvansky, Veniamin

2014-05-01

Continental marginal mountains, including the mountain belts of Russian Far East, are characterized by supreme terrain contrast, mosaic structure of surface and crust, and rich complex of modern endogenous processes - volcanism, seismicity, and vertical movements. Unstable state of geomorphological systems and activity of relief forming processes here is caused also by deep dissected topography and the type and amount of precipitation. Human activities further stimulate natural processes and increase the risk of local disasters. So these territories have high intensity (or tension) of geomorphological processes. Intensity in the authors' understanding is willingness of geomorphological system to be out of balance, risk of disaster under external and internal agent, both natural and human. Mapping with quantitative accounting of intensity of natural and human potential impact is necessary for indication the areal distribution trends of geomorphological processes intensity and zones of potential risk of disasters. Methods of map drowning up are based on several criteria analyzing: 1) total terrain-form processes and their willingness to be a hazard-like, 2) existence, peculiarity and zoning of external agents which could cause extreme character of base processes within the territory, 3) peculiarity of terrain morphology which could cause hazard way of terrain-form processes. Seismic activity is one of the most important factors causing activation of geomorphological processes and contributing to the risk of dangerous situations. Earthquake even small force can provoke many catastrophic processes: landslides, mudslides, avalanches and mudflows, tsunami and others. Seismic gravitational phenomenons of different scale accompany almost all earthquakes of intensity 7-8 points and above, and some processes, such as avalanches, activated by seismic shocks intensity about 1-3 points. In this regard, we consider it important selection of high intensity seismic zones in

Magma migration at the onset of the 2012-13 Tolbachik eruption revealed by Seismic Amplitude Ratio Analysis

NASA Astrophysics Data System (ADS)

Caudron, Corentin; Taisne, Benoit; Kugaenko, Yulia; Saltykov, Vadim

2015-12-01

In contrast of the 1975-76 Tolbachik eruption, the 2012-13 Tolbachik eruption was not preceded by any striking change in seismic activity. By processing the Klyuchevskoy volcano group seismic data with the Seismic Amplitude Ratio Analysis (SARA) method, we gain insights into the dynamics of magma movement prior to this important eruption. A clear seismic migration within the seismic swarm, started 20 hours before the reported eruption onset (05:15 UTC, 26 November 2012). This migration proceeded in different phases and ended when eruptive tremor, corresponding to lava flows, was recorded (at 11:00 UTC, 27 November 2012). In order to get a first order approximation of the magma location, we compare the calculated seismic intensity ratios with the theoretical ones. As expected, the observations suggest that the seismicity migrated toward the eruption location. However, we explain the pre-eruptive observed ratios by a vertical migration under the northern slope of Plosky Tolbachik volcano followed by a lateral migration toward the eruptive vents. Another migration is also captured by this technique and coincides with a seismic swarm that started 16-20 km to the south of Plosky Tolbachik at 20:31 UTC on November 28 and lasted for more than 2 days. This seismic swarm is very similar to the seismicity preceding the 1975-76 Tolbachik eruption and can be considered as a possible aborted eruption.

Causality between expansion of seismic cloud and maximum magnitude of induced seismicity in geothermal field

NASA Astrophysics Data System (ADS)

Mukuhira, Yusuke; Asanuma, Hiroshi; Ito, Takatoshi; Häring, Markus

2016-04-01

Occurrence of induced seismicity with large magnitude is critical environmental issues associated with fluid injection for shale gas/oil extraction, waste water disposal, carbon capture and storage, and engineered geothermal systems (EGS). Studies for prediction of the hazardous seismicity and risk assessment of induced seismicity has been activated recently. Many of these studies are based on the seismological statistics and these models use the information of the occurrence time and event magnitude. We have originally developed physics based model named "possible seismic moment model" to evaluate seismic activity and assess seismic moment which can be ready to release. This model is totally based on microseismic information of occurrence time, hypocenter location and magnitude (seismic moment). This model assumes existence of representative parameter having physical meaning that release-able seismic moment per rock volume (seismic moment density) at given field. Seismic moment density is to be estimated from microseismic distribution and their seismic moment. In addition to this, stimulated rock volume is also inferred by progress of microseismic cloud at given time and this quantity can be interpreted as the rock volume which can release seismic energy due to weakening effect of normal stress by injected fluid. Product of these two parameters (equation (1)) provide possible seismic moment which can be released from current stimulated zone as a model output. Difference between output of this model and observed cumulative seismic moment corresponds the seismic moment which will be released in future, based on current stimulation conditions. This value can be translated into possible maximum magnitude of induced seismicity in future. As this way, possible seismic moment can be used to have feedback to hydraulic stimulation operation in real time as an index which can be interpreted easily and intuitively. Possible seismic moment is defined as equation (1), where D

Micro-seismic earthquakes characteristics at natural and exploited hydrothermal systems in West Java, Indonesia

NASA Astrophysics Data System (ADS)

Jousset, P. G.; Jaya, M. S.; Sule, R.; Diningrat, W.; Gassner, A.; Akbar, F.; Ryannugroho, R.; Hendryana, A.; Kusnadi, Y.; Syahbana, D.; Nugraha, A. D.; Umar, M.; Indrinanto, Y.; Erbas, K.

2013-12-01

The assessment of geothermal resources requires the understanding of the structure and the dynamics of geothermal reservoirs. We deployed a multidisciplinary geophysical network around geothermal areas in the south of Bandung, West Java, Indonesia. The first deployment included a network of 30 broadband and 4 short-period seismic stations with Güralp and Trillium sensors (0.008 - 100 Hz) since October 2012. In a second step, we extended the network in June 2013 with 16 short-period (1 Hz) seismometers. We describe the set-up of the seismic networks and discuss first observations and results. The co-existence of a large variety of intense surface manifestations like geysers, hot-steaming grounds, hot water pools, and active volcanoes suggest an intimate coupling between volcanic, tectonic and hydrothermal processes in this area. Preliminary location of earthquakes is performed using a non-linear algorithm, which allows us to define at least 3 seismic clusters. We discuss this seismic pattern within the geothermal fields.

Using Seismic Interferometry to Investigate Seismic Swarms

NASA Astrophysics Data System (ADS)

Matzel, E.; Morency, C.; Templeton, D. C.

2017-12-01

Seismicity provides a direct means of measuring the physical characteristics of active tectonic features such as fault zones. Hundreds of small earthquakes often occur along a fault during a seismic swarm. This seismicity helps define the tectonically active region. When processed using novel geophysical techniques, we can isolate the energy sensitive to the fault, itself. Here we focus on two methods of seismic interferometry, ambient noise correlation (ANC) and the virtual seismometer method (VSM). ANC is based on the observation that the Earth's background noise includes coherent energy, which can be recovered by observing over long time periods and allowing the incoherent energy to cancel out. The cross correlation of ambient noise between a pair of stations results in a waveform that is identical to the seismogram that would result if an impulsive source located at one of the stations was recorded at the other, the Green function (GF). The calculation of the GF is often stable after a few weeks of continuous data correlation, any perturbations to the GF after that point are directly related to changes in the subsurface and can be used for 4D monitoring.VSM is a style of seismic interferometry that provides fast, precise, high frequency estimates of the Green's function (GF) between earthquakes. VSM illuminates the subsurface precisely where the pressures are changing and has the potential to image the evolution of seismicity over time, including changes in the style of faulting. With hundreds of earthquakes, we can calculate thousands of waveforms. At the same time, VSM collapses the computational domain, often by 2-3 orders of magnitude. This allows us to do high frequency 3D modeling in the fault region. Using data from a swarm of earthquakes near the Salton Sea, we demonstrate the power of these techniques, illustrating our ability to scale from the far field, where sources are well separated, to the near field where their locations fall within each other

Fractal and chaotic laws on seismic dissipated energy in an energy system of engineering structures

NASA Astrophysics Data System (ADS)

Cui, Yu-Hong; Nie, Yong-An; Yan, Zong-Da; Wu, Guo-You

1998-09-01

Fractal and chaotic laws of engineering structures are discussed in this paper, it means that the intrinsic essences and laws on dynamic systems which are made from seismic dissipated energy intensity E d and intensity of seismic dissipated energy moment I e are analyzed. Based on the intrinsic characters of chaotic and fractal dynamic system of E d and I e, three kinds of approximate dynamic models are rebuilt one by one: index autoregressive model, threshold autoregressive model and local-approximate autoregressive model. The innate laws, essences and systematic error of evolutional behavior I e are explained over all, the short-term behavior predictability and long-term behavior probability of which are analyzed in the end. That may be valuable for earthquake-resistant theory and analysis method in practical engineering structures.

Intensity earthquake scenario (scenario event - a damaging earthquake with higher probability of occurrence) for the city of Sofia

NASA Astrophysics Data System (ADS)

Aleksandrova, Irena; Simeonova, Stela; Solakov, Dimcho; Popova, Maria

2014-05-01

Among the many kinds of natural and man-made disasters, earthquakes dominate with regard to their social and economical impact on the urban environment. Global seismic risk to earthquakes are increasing steadily as urbanization and development occupy more areas that a prone to effects of strong earthquakes. Additionally, the uncontrolled growth of mega cities in highly seismic areas around the world is often associated with the construction of seismically unsafe buildings and infrastructures, and undertaken with an insufficient knowledge of the regional seismicity peculiarities and seismic hazard. The assessment of seismic hazard and generation of earthquake scenarios is the first link in the prevention chain and the first step in the evaluation of the seismic risk. The earthquake scenarios are intended as a basic input for developing detailed earthquake damage scenarios for the cities and can be used in earthquake-safe town and infrastructure planning. The city of Sofia is the capital of Bulgaria. It is situated in the centre of the Sofia area that is the most populated (the population is of more than 1.2 mil. inhabitants), industrial and cultural region of Bulgaria that faces considerable earthquake risk. The available historical documents prove the occurrence of destructive earthquakes during the 15th-18th centuries in the Sofia zone. In 19th century the city of Sofia has experienced two strong earthquakes: the 1818 earthquake with epicentral intensity I0=8-9 MSK and the 1858 earthquake with I0=9-10 MSK. During the 20th century the strongest event occurred in the vicinity of the city of Sofia is the 1917 earthquake with MS=5.3 (I0=7-8 MSK). Almost a century later (95 years) an earthquake of moment magnitude 5.6 (I0=7-8 MSK) hit the city of Sofia, on May 22nd, 2012. In the present study as a deterministic scenario event is considered a damaging earthquake with higher probability of occurrence that could affect the city with intensity less than or equal to VIII

Reevaluation of the Seismicity and seismic hazards of Northeastern Libya

NASA Astrophysics Data System (ADS)

Ben Suleman, abdunnur; Aousetta, Fawzi

2014-05-01

Libya, located at the northern margin of the African continent, underwent many episodes of orogenic activities. These episodes of orogenic activities affected and shaped the geological setting of the country. This study represents a detailed investigation that aims to focus on the seismicity and its implications on earthquake hazards of Northeastern Libya. At the end of year 2005 the Libyan National Seismological Network starts functioning with 15 stations. The Seismicity of the area under investigation was reevaluated using data recorded by the recently established network. The Al-Maraj earthquake occurred in May 22nd 2005was analyzed. This earthquake was located in a known seismically active area. This area was the sight of the well known 1963 earthquake that kills over 200 people. Earthquakes were plotted and resulting maps were interpreted and discussed. The level of seismic activity is higher in some areas, such as the city of Al-Maraj. The offshore areas north of Al-Maraj seem to have higher seismic activity. It is highly recommended that the recent earthquake activity is considered in the seismic hazard assessments for the northeastern part of Libya.

Contribution to the study of historical seismicity in the Maghrebian region, Catalogue of historiacal seismicity of the Maghreb region

NASA Astrophysics Data System (ADS)

Elmrabet, T.

2009-04-01

The seismic risk assessment in countries with moderate seismic activity is a very delicate action as well as a high priority one in land use management and urban rehabilitation. The credibility of this assessment is based mainly on the effects of destructive earthquakes whose maximum intensities become a reference for determining the level of protection. This knowledge requires a detailed study of the damage caused by major earthquakes over a long period of time. In this context, a broad scale research about past earthquakes started in the Geophysics Laboratory, now called the National Geophysics Institute (ING) within the National Center for Scientific and Technical Research in Rabat, Morocco. It supported a thorough study which included critical historical texts scattered in various local and foreign archives. The pursuit of this study, under the project called PAMERAR, which was launched in the early 80's aimed at reducing of earthquake risk in the Arab region, led us to investigate the origin of these texts according to various public and private libraries, as in Spain and France. The scientific interest in the historical seismicity in Morocco was highlighted at the beginning of the twentieth century in several reports and catalogs but with several gaps in time and space, further research was thus necessary especially to explore documents in particular from origin sources. This interest in historical archives is within the scope of understanding the natural hazards over long period to evaluate the recurrence of earthquakes. This study leads to significant results covering 11 centuries, from AD 846 to the present. We continued to study the effects of recent earthquakes on humans and buildings heritage, this work has led to a study in the footsteps of local seismic culture. Since earthquakes do not recognize the limits of political geography, since 1993 we have undertaken to extend the research to include the entire Maghreb region. We then used the database

Geomorphology and seismic risk

NASA Astrophysics Data System (ADS)

Panizza, Mario

1991-07-01

The author analyses the contributions provided by geomorphology in studies suited to the assessment of seismic risk: this is defined as function of the seismic hazard, of the seismic susceptibility, and of the vulnerability. The geomorphological studies applicable to seismic risk assessment can be divided into two sectors: (a) morpho-neotectonic investigations conducted to identify active tectonic structures; (b) geomorphological and morphometric analyses aimed at identifying the particular situations that amplify or reduce seismic susceptibility. The morpho-neotectonic studies lead to the identification, selection and classification of the lineaments that can be linked with active tectonic structures. The most important geomorphological situations that can condition seismic susceptibility are: slope angle, debris, morphology, degradational slopes, paleo-landslides and underground cavities.

Map showing seismicity and sandblows in the vicinity of New Madrid, Missouri

USGS Publications Warehouse

Rhea, B. Susan; Tarr, Arthur C.; Wheeler, Russell L.

1994-01-01

This is one of a series of five seismotectic maps of the seismically active New Madrid, Missouri, area (table 1; Wheeler and others, 1992). The map area centers near the sites of three great earthquakes that struck during the winter of 1811-12 (Fuller, 1912; Nuttli, 1973). These earthquakes and continuing subsequent seismicity rank the New Madrid area with Cherlevoix, Quebec, as the two most seismically active areas in North America east of the Rocky Mountains. The threat posed by New Madrid seismicity to the central United States makes the area the focus of many investigations (for examples, Heyl and McKeown, 1978; McKeown and Pakiser, 1982; Algemissen and Hopper, 1984; Hamilton and Johnston, 1990; Applied Technology Council, 1991; Johnston and others, 1992). The map area includes the most intense seismic activity in the New Madrid region. A seismotectic map shows some of the geologic and geophysical information needed to assess seismic hazard (Hadley and Devine, 1974; Pavoni, 1985). A previous seismotectonic map of the central Mississippi River valley (Heyl and McKeown, 1978) has had wide use for planning field surveys, as a base map for plotting data collected during single investigations, and for compiling a range of information. Since 1978 numcrous researchers have greatly advanced our knowledge of the geology and geophysics of the central Mississippi Valley. The New Madrid seismotectonic map folio updates approximately the south-central sixth of the central Mississippi Valley seismotectonic map of Heyl and McKeown (1978).

Seismic hazard, risk, and design for South America

USGS Publications Warehouse

Petersen, Mark D.; Harmsen, Stephen; Jaiswal, Kishor; Rukstales, Kenneth S.; Luco, Nicolas; Haller, Kathleen; Mueller, Charles; Shumway, Allison

2018-01-01

We calculate seismic hazard, risk, and design criteria across South America using the latest data, models, and methods to support public officials, scientists, and engineers in earthquake risk mitigation efforts. Updated continental scale seismic hazard models are based on a new seismicity catalog, seismicity rate models, evaluation of earthquake sizes, fault geometry and rate parameters, and ground‐motion models. Resulting probabilistic seismic hazard maps show peak ground acceleration, modified Mercalli intensity, and spectral accelerations at 0.2 and 1 s periods for 2%, 10%, and 50% probabilities of exceedance in 50 yrs. Ground shaking soil amplification at each site is calculated by considering uniform soil that is applied in modern building codes or by applying site‐specific factors based on VS30">VS30 shear‐wave velocities determined through a simple topographic proxy technique. We use these hazard models in conjunction with the Prompt Assessment of Global Earthquakes for Response (PAGER) model to calculate economic and casualty risk. Risk is computed by incorporating the new hazard values amplified by soil, PAGER fragility/vulnerability equations, and LandScan 2012 estimates of population exposure. We also calculate building design values using the guidelines established in the building code provisions. Resulting hazard and associated risk is high along the northern and western coasts of South America, reaching damaging levels of ground shaking in Chile, western Argentina, western Bolivia, Peru, Ecuador, Colombia, Venezuela, and in localized areas distributed across the rest of the continent where historical earthquakes have occurred. Constructing buildings and other structures to account for strong shaking in these regions of high hazard and risk should mitigate losses and reduce casualties from effects of future earthquake strong ground shaking. National models should be developed by scientists and engineers in each country using the best

Seismic sequences in the Sombrero Seismic Zone

NASA Astrophysics Data System (ADS)

Pulliam, J.; Huerfano, V. A.; ten Brink, U.; von Hillebrandt, C.

2007-05-01

The northeastern Caribbean, in the vicinity of Puerto Rico and the Virgin Islands, has a long and well-documented history of devastating earthquakes and tsunamis, including major events in 1670, 1787, 1867, 1916, 1918, and 1943. Recently, seismicity has been concentrated to the north and west of the British Virgin Islands, in the region referred to as the Sombrero Seismic Zone by the Puerto Rico Seismic Network (PRSN). In the combined seismicity catalog maintained by the PRSN, several hundred small to moderate magnitude events can be found in this region prior to 2006. However, beginning in 2006 and continuing to the present, the rate of seismicity in the Sombrero suddenly increased, and a new locus of activity developed to the east of the previous location. Accurate estimates of seismic hazard, and the tsunamigenic potential of seismic events, depend on an accurate and comprehensive understanding of how strain is being accommodated in this corner region. Are faults locked and accumulating strain for release in a major event? Or is strain being released via slip over a diffuse system of faults? A careful analysis of seismicity patterns in the Sombrero region has the potential to both identify faults and modes of failure, provided the aggregation scheme is tuned to properly identify related events. To this end, we experimented with a scheme to identify seismic sequences based on physical and temporal proximity, under the assumptions that (a) events occur on related fault systems as stress is refocused by immediately previous events and (b) such 'stress waves' die out with time, so that two events that occur on the same system within a relatively short time window can be said to have a similar 'trigger' in ways that two nearby events that occurred years apart cannot. Patterns that emerge from the identification, temporal sequence, and refined locations of such sequences of events carry information about stress accommodation that is obscured by large clouds of

Alaska Seismic Hazards Safety Commission

Science.gov Websites

State Employees ASHSC State of Alaska search Alaska Seismic Hazards Safety Commission View of Anchorage and Commissions Alaska Seismic Hazards Safety Commission (ASHSC) main contant Alaska Seismic Hazards Safety Commission logo Alaska Seismic Hazards Safety Commission (ASHSC) - Mission The Alaska Seismic

First seismic shear wave velocity profile of the lunar crust as extracted from the Apollo 17 active seismic data by wavefield gradient analysis

NASA Astrophysics Data System (ADS)

Sollberger, David; Schmelzbach, Cedric; Robertsson, Johan O. A.; Greenhalgh, Stewart A.; Nakamura, Yosio; Khan, Amir

2016-04-01

We present a new seismic velocity model of the shallow lunar crust, including, for the first time, shear wave velocity information. So far, the shear wave velocity structure of the lunar near-surface was effectively unconstrained due to the complexity of lunar seismograms. Intense scattering and low attenuation in the lunar crust lead to characteristic long-duration reverberations on the seismograms. The reverberations obscure later arriving shear waves and mode conversions, rendering them impossible to identify and analyze. Additionally, only vertical component data were recorded during the Apollo active seismic experiments, which further compromises the identification of shear waves. We applied a novel processing and analysis technique to the data of the Apollo 17 lunar seismic profiling experiment (LSPE), which involved recording seismic energy generated by several explosive packages on a small areal array of four vertical component geophones. Our approach is based on the analysis of the spatial gradients of the seismic wavefield and yields key parameters such as apparent phase velocity and rotational ground motion as a function of time (depth), which cannot be obtained through conventional seismic data analysis. These new observables significantly enhance the data for interpretation of the recorded seismic wavefield and allow, for example, for the identification of S wave arrivals based on their lower apparent phase velocities and distinct higher amount of generated rotational motion relative to compressional (P-) waves. Using our methodology, we successfully identified pure-mode and mode-converted refracted shear wave arrivals in the complex LSPE data and derived a P- and S-wave velocity model of the shallow lunar crust at the Apollo 17 landing site. The extracted elastic-parameter model supports the current understanding of the lunar near-surface structure, suggesting a thin layer of low-velocity lunar regolith overlying a heavily fractured crust of basaltic

Statistical methods for investigating quiescence and other temporal seismicity patterns

USGS Publications Warehouse

Matthews, M.V.; Reasenberg, P.A.

1988-01-01

We propose a statistical model and a technique for objective recognition of one of the most commonly cited seismicity patterns:microearthquake quiescence. We use a Poisson process model for seismicity and define a process with quiescence as one with a particular type of piece-wise constant intensity function. From this model, we derive a statistic for testing stationarity against a 'quiescence' alternative. The large-sample null distribution of this statistic is approximated from simulated distributions of appropriate functionals applied to Brownian bridge processes. We point out the restrictiveness of the particular model we propose and of the quiescence idea in general. The fact that there are many point processes which have neither constant nor quiescent rate functions underscores the need to test for and describe nonuniformity thoroughly. We advocate the use of the quiescence test in conjunction with various other tests for nonuniformity and with graphical methods such as density estimation. ideally these methods may promote accurate description of temporal seismicity distributions and useful characterizations of interesting patterns. ?? 1988 Birkha??user Verlag.

Constraints on Long-Term Seismic Hazard From Vulnerable Stalagmites

NASA Astrophysics Data System (ADS)

Gribovszki, Katalin; Bokelmann, Götz; Mónus, Péter; Kovács, Károly; Konecny, Pavel; Lednicka, Marketa; Bednárik, Martin; Brimich, Ladislav

2015-04-01

Earthquakes hit urban centers in Europe infrequently, but occasionally with disastrous effects. This raises the important issue for society, how to react to the natural hazard: potential damages are huge, but infrastructure costs for addressing these hazards are huge as well. Furthermore, seismic hazard is only one of the many hazards facing society. Societal means need to be distributed in a reasonable manner - to assure that all of these hazards (natural as well as societal) are addressed appropriately. Obtaining an unbiased view of seismic hazard (and risk) is very important therefore. In principle, the best way to test PSHA models is to compare with observations that are entirely independent of the procedure used to produce the PSHA models. Arguably, the most valuable information in this context should be information on long-term hazard, namely maximum intensities (or magnitudes) occuring over time intervals that are at least as long as a seismic cycle - if that exists. Such information would be very valuable, even if it concerned only a single site, namely that of a particularly sensitive infrastructure. Such a request may seem hopeless - but it is not. Long-term information can in principle be gained from intact stalagmites in natural caves. These have survived all earthquakes that have occurred, over thousands of years - depending on the age of the stalagmite. Their "survival" requires that the horizontal ground acceleration has never exceeded a certain critical value within that period. We are focusing here on case studies in Austria, which has moderate seismicity, but a well-documented history of major earthquake-induced damage, e.g., Villach in 1348 and 1690, Vienna in 1590, Leoben in 1794, and Innsbruck in 1551, 1572, and 1589. Seismic intensities have reached levels up to 10. It is clearly important to know which "worst-case" damages to expect. We have identified sets of particularly sensitive stalagmites in the general vicinity of two major cities in

Forecasting volcanic unrest using seismicity: The good, the bad and the time consuming

NASA Astrophysics Data System (ADS)

Salvage, Rebecca; Neuberg, Jurgen W.

2013-04-01

Volcanic eruptions are inherently unpredictable in nature, with scientists struggling to forecast the type and timing of events, in particular in real time scenarios. Current understanding suggests that the use of statistical patterns within precursory datasets of seismicity prior to eruptive events could hold the potential to be used as real time forecasting tools. They allow us to determine times of clear deviation in data, which might be indicative of volcanic unrest. The identification of low frequency seismic swarms and the acceleration of this seismicity prior to observed volcanic unrest may be key in developing forecasting tools. The development of these real time forecasting models which can be implemented at volcano observatories is of particular importance since the identification of early warning signals allows danger to the proximal population to be minimized. We concentrate on understanding the significance and development of these seismic swarms as unrest develops at the volcano. In particular, analysis of accelerations in event rate, amplitude and energy rates released by seismicity prior to eruption suggests that these are important indicators of developing unrest. Real time analysis of these parameters simultaneously allows possible improvements to forecasting models. Although more time and computationally intense, cross correlation techniques applied to continuous seismicity prior to volcanic unrest scenarios allows all significant seismic events to be analysed, rather than only those which can be detected by an automated identification system. This may allow a more accurate forecast since all precursory seismicity can be taken into account. In addition, the classification of seismic events based on spectral characteristics may allow us to isolate individual types of signals which are responsible for certain types of unrest. In this way, we may be able to better forecast the type of eruption that may ensue, or at least some of its prevailing

Catalog of Historical Seismicity in the Central United States

NASA Astrophysics Data System (ADS)

Bakun, W. H.; Hopper, M. G.

2004-05-01

Modified Mercalli intensity assignments were used to estimate source locations and moment magnitude M for eighteen 19th-century and twenty early- 20th-century earthquakes in the central United States (CUS). These solutions, comparable solutions for historical M > 6.0 CUS events (Bakun, Johnston, and Hopper, BSSA, 2003; Bakun and Hopper, BSSA, 2004), and instrumental solutions for late-20th-century events provide a uniform catalog of historical M > 5.0 CUS earthquakes. The 1811-1812 New Madrid, Missouri, (NM) earthquakes apparently dominated CUS seismicity in the first two decades of the 19th century. M5-6 NM earthquakes occurred in 1843 and 1878, but none have occurred since 1878. There has been persistent seismic activity that can be associated with faults in the Illinois Basin in Illinois and Indiana, with M > 5.0 earthquakes in 1895, 1909, 1917, 1968, and 1987. Four other M > 5.0 CUS historical earthquakes have occurred: in Kansas in 1867, in Nebraska in 1877, in Oklahoma in 1882, and in Kentucky in 1980. Ohio has also been seismically active with several 4.5 < M < 5.0 events.

The DTW-based representation space for seismic pattern classification

NASA Astrophysics Data System (ADS)

Orozco-Alzate, Mauricio; Castro-Cabrera, Paola Alexandra; Bicego, Manuele; Londoño-Bonilla, John Makario

2015-12-01

Distinguishing among the different seismic volcanic patterns is still one of the most important and labor-intensive tasks for volcano monitoring. This task could be lightened and made free from subjective bias by using automatic classification techniques. In this context, a core but often overlooked issue is the choice of an appropriate representation of the data to be classified. Recently, it has been suggested that using a relative representation (i.e. proximities, namely dissimilarities on pairs of objects) instead of an absolute one (i.e. features, namely measurements on single objects) is advantageous to exploit the relational information contained in the dissimilarities to derive highly discriminant vector spaces, where any classifier can be used. According to that motivation, this paper investigates the suitability of a dynamic time warping (DTW) dissimilarity-based vector representation for the classification of seismic patterns. Results show the usefulness of such a representation in the seismic pattern classification scenario, including analyses of potential benefits from recent advances in the dissimilarity-based paradigm such as the proper selection of representation sets and the combination of different dissimilarity representations that might be available for the same data.

Seismic hazard assessment in the Catania and Siracusa urban areas (Italy) through different approaches

NASA Astrophysics Data System (ADS)

Panzera, Francesco; Lombardo, Giuseppe; Rigano, Rosaria

2010-05-01

The seismic hazard assessment (SHA) can be performed using either Deterministic or Probabilistic approaches. In present study a probabilistic analysis was carried out for the Catania and Siracusa towns using two different procedures: the 'site' (Albarello and Mucciarelli, 2002) and the 'seismotectonic' (Cornell 1968; Esteva, 1967) methodologies. The SASHA code (D'Amico and Albarello, 2007) was used to calculate seismic hazard through the 'site' approach, whereas the CRISIS2007 code (Ordaz et al., 2007) was adopted in the Esteva-Cornell procedure. According to current international conventions for PSHA (SSHAC, 1997), a logic tree approach was followed to consider and reduce the epistemic uncertainties, for both seismotectonic and site methods. The code SASHA handles the intensity data taking into account the macroseismic information of past earthquakes. CRISIS2007 code needs, as input elements, a seismic catalogue tested for completeness, a seismogenetic zonation and ground motion predicting equations. Data concerning the characterization of regional seismic sources and ground motion attenuation properties were taken from the literature. Special care was devoted to define source zone models, taking into account the most recent studies on regional seismotectonic features and, in particular, the possibility of considering the Malta escarpment as a potential source. The combined use of the above mentioned approaches allowed us to obtain useful elements to define the site seismic hazard in Catania and Siracusa. The results point out that the choice of the probabilistic model plays a fundamental role. It is indeed observed that when the site intensity data are used, the town of Catania shows hazard values higher than the ones found for Siracusa, for each considered return period. On the contrary, when the Esteva-Cornell method is used, Siracusa urban area shows higher hazard than Catania, for return periods greater than one hundred years. The higher hazard observed

Micro-seismicity and seismic moment release within the Coso Geothermal Field, California

USGS Publications Warehouse

Kaven, Joern; Hickman, Stephen H.; Davatzes, Nicholas C.

2014-01-01

We relocate 16 years of seismicity in the Coso Geothermal Field (CGF) using differential travel times and simultaneously invert for seismic velocities to improve our knowledge of the subsurface geologic and hydrologic structure. We expand on our previous results by doubling the number of relocated events from April 1996 through May 2012 using a new field-wide 3-D velocity model. Relocated micro-seismicity sharpens in many portions of the active geothermal reservoir, likely defining large-scale fault zones and fluid pressure compartment boundaries. However, a significant fraction of seismicity remains diffuse and does not cluster into sharply defined structures, suggesting that permeability is maintained within the reservoir through distributed brittle failure. The seismic velocity structure reveals heterogeneous distributions of compressional (Vp) and shear (Vs) wave speed, with Vs generally higher in the Main Field and East Flank and Vp remaining relatively uniform across the CGF, but with significant local variations. The Vp/Vs ratio appears to outline the two main producing compartments of the reservoir at depths below mean ground level of approximately 1 to 2.5 km, with a ridge of relatively high Vp/Vs separating the Main Field from the East Flank. Detailed analyses of spatial and temporal variations in earthquake relocations and cumulative seismic moment release in the East Flank reveal three regions with persistently high rates of seismic activity. Two of these regions exhibit sharp, stationary boundaries at the margins of the East Flank that likely represent barriers to fluid flow and advective heat transport. However, seismicity and moment release in a third region at the northern end of the East Flank spread over time to form an elongated NE to SW structure, roughly parallel both to an elongated cluster of seismicity at the southern end of the East Flank and to regional fault traces mapped at the surface. Our results indicate that high

Induced seismicity and the potential for liability under U.S. law

NASA Astrophysics Data System (ADS)

Cypser, Darlene A.; Davis, Scott D.

1998-04-01

Research by seismologists over the past 30+ years has firmly established that some human activities induce seismicity. Sometimes induced seismicity causes injuries to people or property. The activities which induce seismicity generally involve extraction of energy, or natural resources, or the disposal of wastes. As the human population increases these extraction and disposal activities will increase in number of sites and intensity of effort as the demands become greater and the resources scarcer. With these increases the number and severity of damaging induced earthquakes is likely to increase. Induced seismicity may cause injuries by vibrations or by seismically induced ground failure. In either case compensation for injuries caused by induced seismicity should be paid for by the inducer. In the United States the inducer of damaging seismicity can be made to pay for the harm caused. Liability for damage caused by vibrations can be based on several legal theories: trespass, strict liability, negligence and nuisance. Our research revealed no cases in which an appellate court has upheld or rejected the application of tort liability to an induced earthquake situation. However, there are numerous analogous cases that support the application of these legal theories to induced seismicity. Vibrations or concussions due to blasting or heavy machinery are sometimes viewed as a `trespass' analogous to a physical invasion. In some states activities which induce earthquakes might be considered `abnormally dangerous' activities that require companies engaged in them to pay for injuries the quakes cause regardless of how careful the inducers were. In some circumstances, a court may find that an inducer was negligent in its site selection or in maintenance of the project. If induced seismicity interferes with the use or enjoyment of another's land, then the inducing activity may be a legal nuisance, even if the seismicity causes little physical damage. In most states of the

Variable post-Paleozoic deformation detected by seismic reflection profiling across the northwestern "prong" of New Madrid seismic zone

USGS Publications Warehouse

McBride, J.H.; Pugin, Andre J.M.; Nelson, W.J.; Larson, T.H.; Sargent, S.L.; Devera, J.A.; Denny, F.B.; Woolery, E.W.

2003-01-01

High-resolution shallow seismic reflection profiles across the northwesternmost part of the New Madrid seismic zone (NMSZ) and northwestern margin of the Reelfoot rift, near the confluence of the Ohio and Mississippi Rivers in the northern Mississippi embayment, reveal intense structural deformation that apparently took place during the late Paleozoic and/or Mesozoic up to near the end of the Cretaceous Period. The seismic profiles were sited on both sides of the northeast-trending Olmsted fault, defined by varying elevations of the top of Mississippian (locally base of Cretaceous) bedrock. The trend of this fault is close to and parallel with an unusually straight segment of the Ohio River and is approximately on trend with the westernmost of two groups of northeast-aligned epicenters ("prongs") in the NMSZ. Initially suspected on the basis of pre-existing borehole data, the deformation along the fault has been confirmed by four seismic reflection profiles, combined with some new information from drilling. The new data reveal (1) many high-angle normal and reverse faults expressed as narrow grabens and anticlines (suggesting both extensional and compressional regimes) that involved the largest displacements during the late Cretaceous (McNairy); (2) a different style of deformation involving probably more horizontal displacements (i.e., thrusting) that occurred at the end of this phase near the end of McNairy deposition, with some fault offsets of Paleocene and younger units; (3) zones of steeply dipping faults that bound chaotic blocks similar to that observed previously from the nearby Commerce geophysical lineament (CGL); and (4) complex internal deformation stratigraphically restricted to the McNairy, suggestive of major sediment liquefaction or landsliding. Our results thus confirm the prevalence of complex Cretaceous deformations continuing up into Tertiary strata near the northern terminus of the NMSZ. ?? 2003 Elsevier Science B.V. All rights reserved.

A classification of morphoseismic features in the New Madrid seismic zone

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

Knox, R.; Stewart, D.

1993-03-01

The New Madrid Seismic Zone (NMSZ) contains thousands of surface features distributed over 5,000 square miles in four states. These are attributable to some combination of (1) seismically-induced liquefaction (SIL), (2) secondary deformation, and (3) seismically-induced slope failures. Most of these features were produced by the 1811--12 series of great earthquakes, but some predate and some postdate 1811--12. Subsequent non-seismic factors, such as hydrologically-induced liquefaction (HIL), mechanically-induced liquefaction (MIL), human activities, mass wasting, eolian and fluvial processes have modified all of these features. Morphoseismic features are new landforms produced by earthquakes, or are pre-existing landforms modified by them. Involved aremore » complex interrelationships among several variables, including: (1) intensity and duration of seismic ground motion, (2) surface wave harmonics, (3) depth to water table, (4) depth to basement, (5) particle size, composition, and sorting of sediment making up the liquefied (LZ) and non-liquefied zones (NLZ), (6) topographic parameters, and (7) attitudes of beds and lenses susceptible to liquefaction. Morphoseismic features are depicted as results of a time-flow sequence initiated by primary basement disturbances which produce three major categories of surface response: secondary deformation, liquefaction and slope failure. Nine subcategories incorporate features produced by or resulting in: extruded sand, intruded sand, lateral spreading, faulting, subsidence of large areas, uplift of large areas, altered streams, coherent landslides, and incoherent landslides. The total morphoseismic features identified by this classification are 34 in number.« less

Rescaled Range analysis of Induced Seismicity: rapid classification of clusters in seismic crisis

NASA Astrophysics Data System (ADS)

Bejar-Pizarro, M.; Perez Lopez, R.; Benito-Parejo, M.; Guardiola-Albert, C.; Herraiz, M.

2017-12-01

Different underground fluid operations, mainly gas storing, fracking and water pumping, can trigger Induced Seismicity (IS). This seismicity is normally featured by small-sized earthquakes (M<2.5), although particular cases reach magnitude as great as 5. It has been up for debate whether earthquakes greater than 5 can be triggered by IS or this level of magnitude only corresponds to tectonic earthquakes caused by stress change. Whatever the case, the characterization of IS for seismic clusters and seismic series recorded close but not into the gas storage, is still under discussion. Time-series of earthquakes obey non-linear patterns where the Hurst exponent describes the persistency or anti-persistency of the sequence. Natural seismic sequences have an H-exponent close to 0.7, which combined with the b-value time evolution during the time clusters, give us valuable information about the stationarity of the phenomena. Tectonic earthquakes consist in a main shock with a decay of time-occurrence of seismic shocks obeying the Omori's empirical law. On the contrary, IS does not exhibit a main shock and the time occurrence depends on the injection operations instead of on the tectonic energy released. In this context, the H-exponent can give information about the origin of the sequence. In 2013, a seismic crisis was declared from the Castor underground gas storing located off-shore in the Mediterranean Sea, close to the Northeastern Spanish cost. The greatest induced earthquake was 3.7. However, a 4.2 earthquake, probably of tectonic origin, occurred few days after the operations stopped. In this work, we have compared the H-exponent and the b-value time evolution according to the timeline of gas injection. Moreover, we have divided the seismic sequence into two groups: (1) Induced Seismicity and (2) Triggered Seismicity. The rescaled range analysis allows the differentiation between natural and induced seismicity and gives information about the persistency and long

Seismic response in archaeological areas: the case-histories of Rome

NASA Astrophysics Data System (ADS)

Donati, Stefano; Funiciello, Renato; Rovelli, Antonio

1999-03-01

Rome is affected by earthquakes associated to three different seismogenic districts: the Central Apennines area, the Colli Albani volcanic area and the Roman area. The major effects were exclusively due to Apennine seismicity and reached in some cases felt intensities up to VII-VIII degree (MCS scale). The predominant role in the damage distribution seems to be played by the local geological conditions. The historical centre of the city is characterized by the presence of two geomorphologic domains: the alluvial plain of Tiber river and the topographic relieves of Roman Hills, where tradition indicates the first site of the city foundation. In particular, the right river side is characterized by the outcropping of the regional bedrock along the Monte Mario-Gianicolo ridge, while the eastern relieves are the remnants of the Sabatini and Albani volcanic plateau, deeply eroded by the Tiber river and its tributaries during the last glacial low-stand (Würm). These domains are characterized by a large difference in seismic response, due to the high impedance contrast between Holocene coarse deposits filling the Tiber Valley and sedimentary and volcanic Plio-Pleistocene units. Seismic damage observed in 150 monuments of downtown Rome was indicating a significant concentration on alluvial recent deposits. This result was confirmed by the geographical distribution of conservation and retrofitting activities subsequent to main earthquakes, mostly related to local geological conditions. The cases of Marcus Aurelius' Column and Colosseum confirmed the influence of the Holocene alluvial network in local seismic response. During 2500 years of history, the monuments of Rome have `memorized' the seismic effects of historical earthquakes. In some cases, the integration of historical and geological research and macroseismic observations may provide original and useful indications to seismologists to define the seismic response of the city. Local site effects represent a serious

New comprehensive standard seismic noise models and 3D seismic noise variation for Morocco territory, North Africa, obtained using seismic broadband stations

NASA Astrophysics Data System (ADS)

El Fellah, Younes; El-Aal, Abd El-Aziz Khairy Abd; Harnafi, Mimoun; Villaseñor, Antonio

2017-05-01

In the current work, we constructed new comprehensive standard seismic noise models and 3D temporal-spatial seismic noise level cubes for Morocco in north-west Africa to be used for seismological and engineering purposes. Indeed, the original global standard seismic noise models published by Peterson (1993) and their following updates by Astiz and Creager (1995), Ekström (2001) and Berger et al. (2003) had no contributing seismic stations deployed in North Africa. Consequently, this preliminary study was conducted to shed light on seismic noise levels specific to north-west Africa. For this purpose, 23 broadband seismic stations recently installed in different structural domains throughout Morocco are used to study the nature and characteristics of seismic noise and to create seismic noise models for Morocco. Continuous data recorded during 2009, 2010 and 2011 were processed and analysed to construct these new noise models and 3D noise levels from all stations. We compared the Peterson new high-noise model (NHNM) and low-noise model (NLNM) with the Moroccan high-noise model (MHNM) and low-noise model (MLNM). These new noise models are comparable to the United States Geological Survey (USGS) models in the short period band; however, in the period range 1.2 s to 1000 s for MLNM and 10 s to 1000 s for MHNM display significant variations. This variation is attributed to differences in the nature of seismic noise sources that dominate Morocco in these period bands. The results of this study have a new perception about permanent seismic noise models for this spectacular region and can be considered a significant contribution because it supplements the Peterson models and can also be used to site future permanent seismic stations in Morocco.

Two applications of time reversal mirrors: seismic radio and seismic radar.

PubMed

Hanafy, Sherif M; Schuster, Gerard T

2011-10-01

Two seismic applications of time reversal mirrors (TRMs) are introduced and tested with field experiments. The first one is sending, receiving, and decoding coded messages similar to a radio except seismic waves are used. The second one is, similar to radar surveillance, detecting and tracking a moving object(s) in a remote area, including the determination of the objects speed of movement. Both applications require the prior recording of calibration Green's functions in the area of interest. This reference Green's function will be used as a codebook to decrypt the coded message in the first application and as a moving sensor for the second application. Field tests show that seismic radar can detect the moving coordinates (x(t), y(t), z(t)) of a person running through a calibration site. This information also allows for a calculation of his velocity as a function of location. Results with the seismic radio are successful in seismically detecting and decoding coded pulses produced by a hammer. Both seismic radio and radar are highly robust to signals in high noise environments due to the super-stacking property of TRMs. © 2011 Acoustical Society of America

Earthquakes in Oita triggered by the 2016 M7.3 Kumamoto earthquake

NASA Astrophysics Data System (ADS)

Yoshida, Shingo

2016-11-01

During the passage of the seismic waves from the M7.3 Kumamoto, Kyushu, earthquake on April 16, 2016, a M5.7 [semiofficial value estimated by the Japan Meteorological Agency (JMA)] event occurred in the central part of Oita prefecture, approximately 80 km far away from the mainshock. Although there have been a number of reports that M < 5 earthquakes were remotely triggered during the passage of seismic waves from mainshocks, there has been no evidence for M > 5 triggered events. In this paper, we firstly confirm that this event is a M6-class event by re-estimating the magnitude using the strong-motion records of K-NET and KiK-net, and crustal deformation data at the Yufuin station observed by the Geospatial Information Authority of Japan. Next, by investigating the aftershocks of 45 mainshocks which occurred over the past 20 years based on the JMA earthquake catalog (JMAEC), we found that the delay time of the 2016 M5.7 event in Oita was the shortest. Therefore, the M5.7 event could be regarded as an exceptional M > 5 event that was triggered by passing seismic waves, unlike the usual triggered events and aftershocks. Moreover, a search of the JMAEC shows that in the 2016 Oita aftershock area, swarm earthquake activity was low over the past 30 years compared with neighboring areas. We also found that in the past, probably or possibly triggered events frequently occurred in the 2016 Oita aftershock area. The Oita area readily responds to remote triggering because of high geothermal activity and young volcanism in the area. The M5.7 Oita event was triggered by passing seismic waves, probably because large dynamic stress change was generated by the mainshock at a short distance and because the Oita area was already loaded to a critical stress state without a recent energy release as suggested by the past low swarm activity.[Figure not available: see fulltext.

Seismic intrusion detector system

DOEpatents

Hawk, Hervey L.; Hawley, James G.; Portlock, John M.; Scheibner, James E.

1976-01-01

A system for monitoring man-associated seismic movements within a control area including a geophone for generating an electrical signal in response to seismic movement, a bandpass amplifier and threshold detector for eliminating unwanted signals, pulse counting system for counting and storing the number of seismic movements within the area, and a monitoring system operable on command having a variable frequency oscillator generating an audio frequency signal proportional to the number of said seismic movements.

Seismic Design of a Single Bored Tunnel: Longitudinal Deformations and Seismic Joints

NASA Astrophysics Data System (ADS)

Oh, J.; Moon, T.

2018-03-01

The large diameter bored tunnel passing through rock and alluvial deposits subjected to seismic loading is analyzed for estimating longitudinal deformations and member forces on the segmental tunnel liners. The project site has challenges including high hydrostatic pressure, variable ground profile and high seismic loading. To ensure the safety of segmental tunnel liner from the seismic demands, the performance-based two-level design earthquake approach, Functional Evaluation Earthquake and Safety Evaluation Earthquake, has been adopted. The longitudinal tunnel and ground response seismic analyses are performed using a three-dimensional quasi-static linear elastic and nonlinear elastic discrete beam-spring elements to represent segmental liner and ground spring, respectively. Three components (longitudinal, transverse and vertical) of free-field ground displacement-time histories evaluated from site response analyses considering wave passage effects have been applied at the end support of the strain-compatible ground springs. The result of the longitudinal seismic analyses suggests that seismic joint for the mitigation measure requiring the design deflection capacity of 5-7.5 cm is to be furnished at the transition zone between hard and soft ground condition where the maximum member forces on the segmental liner (i.e., axial, shear forces and bending moments) are induced. The paper illustrates how detailed numerical analyses can be practically applied to evaluate the axial and curvature deformations along the tunnel alignment under difficult ground conditions and to provide the seismic joints at proper locations to effectively reduce the seismic demands below the allowable levels.

Method of migrating seismic records

DOEpatents

Ober, Curtis C.; Romero, Louis A.; Ghiglia, Dennis C.

2000-01-01

The present invention provides a method of migrating seismic records that retains the information in the seismic records and allows migration with significant reductions in computing cost. The present invention comprises phase encoding seismic records and combining the encoded seismic records before migration. Phase encoding can minimize the effect of unwanted cross terms while still allowing significant reductions in the cost to migrate a number of seismic records.

Deep Seismic Reflection Images of the Sumatra Seismic and Aseismic Gaps

NASA Astrophysics Data System (ADS)

Singh, S. C.; Hananto, N. D.; Chauhan, A.; Carton, H. D.; Midenet, S.; Djajadihardja, Y.

2009-12-01

The Sumatra subduction zone is seismically most active region on the Earth, and has been the site of three great earthquakes only in the last four years. The first of the series, the 2004 Boxing Day earthquake, broke 1300 km of the plate boundary and produced the devastating tsunami around the Indian Ocean. The second great earthquake occurred three months later in March 2005, about 150 km SE of the 2004 event. The Earth waited for three years, and then broke again in September 2007 at 1300 km SE of the 2004 event producing a twin earthquake of magnitudes of 8.5 and 7.9 at an interval of 12 hours, leaving a seismic gap of about 600 km between the second and third earthquake, the Sumatra Seismic Gap. Seismological and geodetic studies suggest that this gap is fully locked and may break any time. In order to study the seismic and tsunami risk in this locked region, a deep seismic reflection survey (Tsunami Investigation Deep Evaluation Seismic -TIDES) was carried out in May 2009 using the CGGVeritas vessel Geowave Champion towing a 15 long streamer, the longest ever used during a seismic survey, to image the nature of the subducting plate and associated features, including the seismogenic zone, from seafloor down to 50 km depth. A total of 1700 km of deep seismic reflection data were acquired. Three dip lines traverse the Sumatra subduction zone; one going through the Sumatra Seismic Gap, one crossing the region that broke during the 2007 great earthquake, and one going through the aseismic zone. These three dip profiles should provide insight about the locking mechanism and help us to understand why an earthquake occurs in one zone and not in aseismic zone. A strike-line was shot in the forearc basin connecting the locked zone with broken zone profiles, which should provide insight about barriers that might have stopped propagation of 2007 earthquake rupture further northward.

Change-point detection of induced and natural seismicity

NASA Astrophysics Data System (ADS)

Fiedler, B.; Holschneider, M.; Zoeller, G.; Hainzl, S.

2016-12-01

Earthquake rates are influenced by tectonic stress buildup, earthquake-induced stress changes, and transient aseismic sources. While the first two sources can be well modeled due to the fact that the source is known, transient aseismic processes are more difficult to detect. However, the detection of the associated changes of the earthquake activity is of great interest, because it might help to identify natural aseismic deformation patterns (such as slow slip events) and the occurrence of induced seismicity related to human activities. We develop a Bayesian approach to detect change-points in seismicity data which are modeled by Poisson processes. By means of a Likelihood-Ratio-Test, we proof the significance of the change of the intensity. The model is also extended to spatiotemporal data to detect the area of the transient changes. The method is firstly tested for synthetic data and then applied to observational data from central US and the Bardarbunga volcano in Iceland.

Seismic-wave attenuation associated with crustal faults in the New Madrid seismic zone

USGS Publications Warehouse

Hamilton, R.M.; Mooney, W.D.

1990-01-01

The attenuation of upper crustal seismic waves that are refracted with a velocity of about 6 kilometers per second varies greatly among profiles in the area of the New Madrid seismic zone in the central Mississippi Valley. The waves that have the strongest attenuation pass through the seismic trend along the axis of the Reelfoot rift in the area of the Blytheville arch. Defocusing of the waves in a low-velocity zone and/ or seismic scattering and absorption could cause the attenuation; these effects are most likely associated with the highly deformed rocks along the arch. Consequently, strong seismic-wave attenuation may be a useful criterion for identifying seismogenic fault zones.

GIA induced intraplate seismicity in northern Central Europe

NASA Astrophysics Data System (ADS)

Brandes, Christian; Steffen, Holger; Steffen, Rebekka; Wu, Patrick

2015-04-01

Though northern Central Europe is regarded as a low seismicity area (Leydecker and Kopera, 1999), several historic earthquakes with intensities of up to VII affected the area in the last 1200 years (Leydecker, 2011). The trigger for these seismic events is not sufficiently investigated yet. Based on the combination of historic earthquake epicentres with the most recent fault maps we show that the historic seismicity concentrated at major reverse faults. There is no evidence for significant historic earthquakes along normal faults in northern Central Europe. The spatial and temporal distribution of earthquakes (clusters that shift from time to time) implies that northern Central Europe behaves like a typical intraplate tectonic region as demonstrated for other intraplate settings (Liu et al., 2000) We utilized Finite Element models that describe the process of glacial isostatic adjustment to analyse the fault behaviour. We use the change in Coulomb Failure Stress (dCFS) to represent the minimum stress required to reach faulting. A negative dCFS value indicates that the fault is stable, while a positive value means that GIA stress is potentially available to induce faulting or cause fault instability or failure unless released temporarily by an earthquake. The results imply that many faults in Central Europe are postglacial faults, though they developed outside the glaciated area. This is supported by the characteristics of the dCFS graphs, which indicate the likelihood that an earthquake is related to GIA. Almost all graphs show a change from negative to positive values during the deglaciation phase. This observation sheds new light on the distribution of post-glacial faults in general. Based on field data and the numerical simulations we developed the first consistent model that can explain the occurrence of deglaciation seismicity and more recent historic earthquakes in northern Central Europe. Based on our model, the historic seismicity in northern Central Europe

Seismic hazard assessment: Issues and alternatives

USGS Publications Warehouse

Wang, Z.

2011-01-01

Seismic hazard and risk are two very important concepts in engineering design and other policy considerations. Although seismic hazard and risk have often been used inter-changeably, they are fundamentally different. Furthermore, seismic risk is more important in engineering design and other policy considerations. Seismic hazard assessment is an effort by earth scientists to quantify seismic hazard and its associated uncertainty in time and space and to provide seismic hazard estimates for seismic risk assessment and other applications. Although seismic hazard assessment is more a scientific issue, it deserves special attention because of its significant implication to society. Two approaches, probabilistic seismic hazard analysis (PSHA) and deterministic seismic hazard analysis (DSHA), are commonly used for seismic hazard assessment. Although PSHA has been pro-claimed as the best approach for seismic hazard assessment, it is scientifically flawed (i.e., the physics and mathematics that PSHA is based on are not valid). Use of PSHA could lead to either unsafe or overly conservative engineering design or public policy, each of which has dire consequences to society. On the other hand, DSHA is a viable approach for seismic hazard assessment even though it has been labeled as unreliable. The biggest drawback of DSHA is that the temporal characteristics (i.e., earthquake frequency of occurrence and the associated uncertainty) are often neglected. An alternative, seismic hazard analysis (SHA), utilizes earthquake science and statistics directly and provides a seismic hazard estimate that can be readily used for seismic risk assessment and other applications. ?? 2010 Springer Basel AG.

Seismic hazard assessment in the megacity of Blida (Algeria) and its surrounding regions using parametric-historic procedure

NASA Astrophysics Data System (ADS)

Bellalem, Fouzi; Talbi, Abdelhak; Djellit, Hamou; Ymmel, Hayet; Mobarki, Mourad

2018-03-01

The region of Blida is characterized by a relatively high seismic activity, pointed especially during the past two centuries. Indeed, it experienced a significant number of destructive earthquakes such as the earthquakes of March 2, 1825 and January 2, 1867, with intensity of X and IX, respectively. This study aims to investigate potential seismic hazard in Blida city and its surrounding regions. For this purpose, a typical seismic catalog was compiled using historical macroseismic events that occurred over a period of a few hundred years, and the recent instrumental seismicity dating back to 1900. The parametric-historic procedure introduced by Kijko and Graham (1998, 1999) was applied to assess seismic hazard in the study region. It is adapted to deal with incomplete catalogs and does not use any subjective delineation of active seismic zones. Because of the lack of recorded strong motion data, three ground prediction models have been considered, as they seem the most adapted to the seismicity of the study region. Results are presented as peak ground acceleration (PGA) seismic hazard maps, showing expected peak accelerations with 10% probability of exceedance in 50-year period. As the most significant result, hot spot regions with high PGA values are mapped. For example, a PGA of 0.44 g has been found in a small geographical area centered on Blida city.

Very-long-period seismic signals - filling the gap between deformation and seismicity

NASA Astrophysics Data System (ADS)

Neuberg, Jurgen; Smith, Paddy

2013-04-01

Good broadband seismic sensors are capable to record seismic transients with dominant wavelengths of several tens or even hundreds of seconds. This allows us to generate a multi-component record of seismic volcanic events that are located in between the conventional high to low-frequency seismic spectrum and deformation signals. With a much higher temporal resolution and accuracy than e.g. GPS records, these signals fill the gap between seismicity and deformation studies. In this contribution we will review the non-trivial processing steps necessary to retrieve ground deformation from the original velocity seismogram and explore which role the resulting displacement signals have in the analysis of volcanic events. We use examples from Soufriere Hills volcano in Montserrat, West Indies, to discuss the benefits and shortcomings of such methods regarding new insights into volcanic processes.

Seismic and Geodetic Monitoring of the Nicoya, Costa Rica, Seismic Gap

NASA Astrophysics Data System (ADS)

Protti, M.; Gonzalez, V.; Schwartz, S.; Dixon, T.; Kato, T.; Kaneda, Y.; Simila, G.; Sampson, D.

2007-05-01

The Nicoya segment of the Middle America Trench has been recognized as a mature seismic gap with potential to generate a large earthquake in the near future (it ruptured with large earthquakes in 1853, 1900 and 1950). Low level of background seismicity and fast crustal deformation of the forearc are indicatives of strong coupling along the plate interface. Given its high seismic potential, the available data and especially the fact that the Nicoya peninsula extends over large part of the rupture area, this gap was selected as one of the two sites for a MARGINS-SEIZE experiment. With the goal of documenting the evolution of loading and stress release along this seismic gap, an international effort involving several institutions from Costa Rica, the United States and Japan is being carried out for over a decade in the region. This effort involves the installation of temporary and permanent seismic and geodetic networks. The seismic network includes short period, broad band and strong motion instruments. The seismic monitoring has provided valuable information on the geometry and characteristics of the plate interface. The geodetic network includes temporary and permanent GPS stations as well as surface and borehole tiltmeters. The geodetic networks have helped quantify the extend and degree of coupling. A continuously recording, three- station GPS network on the Nicoya Peninsula, Costa Rica, recorded what we believe is the first slow slip event observed along the plate interface of the Costa Rica subduction zone. We will present results from these monitoring networks. Collaborative international efforts are focused on expanding these seismic and geodetic networks to provide improved resolution of future creep events, to enhanced understanding of the mechanical behavior of the Nicoya subduction segment of the Middle American Trench and possibly capture the next large earthquake and its potential precursor deformation.

Seismic Structure of Perth Basin (Australia) and surroundings from Passive Seismic Deployments

NASA Astrophysics Data System (ADS)

Issa, N.; Saygin, E.; Lumley, D. E.; Hoskin, T. E.

2016-12-01

We image the subsurface structure of Perth Basin, Western Australia and surroundings by using ambient seismic noise data from 14 seismic stations recently deployed by University of Western Australia (UWA) and other available permanent stations from Geoscience Australia seismic network and the Australian Seismometers in Schools program. Each of these 14 UWA seismic stations comprises a broadband sensor and a high fidelity 3-component 10 Hz geophone, recording in tandem at 250 Hz and 1000 Hz. The other stations used in this study are equipped with short period and broadband sensors. In addition, one shallow borehole station is operated with eight 3 component geophones at depths of between 2 and 44 m. The network is deployed to characterize natural seismicity in the basin and to try and identify any microseismic activity across Darling Fault Zone (DFZ), bounding the basin to the east. The DFZ stretches to approximately 1000 km north-south in Western Australia, and is one of the longest fault zones on the earth with a limited number of detected earthquakes. We use seismic noise cross- and auto-correlation methods to map seismic velocity perturbations across the basin and the transition from DFZ to the basin. Retrieved Green's functions are stable and show clear dispersed waveforms. Travel times of the surface wave Green's functions from noise cross-correlations are inverted with a two-step probabilistic framework to map the absolute shear wave velocities as a function of depth. The single station auto-correlations from the seismic noise yields P wave reflectivity under each station, marking the major discontinuities. Resulting images show the shear velocity perturbations across the region. We also quantify the variation of ambient seismic noise at different depths in the near surface using the geophones in the shallow borehole array.

Dynamic evaluation of seismic hazard and risks based on the Unified Scaling Law for Earthquakes

NASA Astrophysics Data System (ADS)

Kossobokov, V. G.; Nekrasova, A.

2016-12-01

We continue applying the general concept of seismic risk analysis in a number of seismic regions worldwide by constructing seismic hazard maps based on the Unified Scaling Law for Earthquakes (USLE), i.e. log N(M,L) = A + B•(6 - M) + C•log L, where N(M,L) is the expected annual number of earthquakes of a certain magnitude M within an seismically prone area of linear dimension L, A characterizes the average annual rate of strong (M = 6) earthquakes, B determines the balance between magnitude ranges, and C estimates the fractal dimension of seismic locus in projection to the Earth surface. The parameters A, B, and C of USLE are used to assess, first, the expected maximum magnitude in a time interval at a seismically prone cell of a uniform grid that cover the region of interest, and then the corresponding expected ground shaking parameters. After a rigorous testing against the available seismic evidences in the past (e.g., the historically reported macro-seismic intensity or paleo data), such a seismic hazard map is used to generate maps of specific earthquake risks for population, cities, and infrastructures. The hazard maps for a given territory change dramatically, when the methodology is applied to a certain size moving time window, e.g. about a decade long for an intermediate-term regional assessment or exponentially increasing intervals for a daily local strong aftershock forecasting. The of dynamical seismic hazard and risks assessment is illustrated by applications to the territory of Greater Caucasus and Crimea and the two-year series of aftershocks of the 11 October 2008 Kurchaloy, Chechnya earthquake which case-history appears to be encouraging for further systematic testing as potential short-term forecasting tool.

Communication of Seismic Risk in the Kyrgyz Republic

NASA Astrophysics Data System (ADS)

Fourniadis, Yannis; Free, Matthew; Coates, Katherine; Moldobekov, Bolot; Fleming, Kevin; Parolai, Stefano; Pittore, Massimiliano; Ormukov, Cholponbek; Takeuchi, Ko

2017-04-01

of challenges were addressed when developing and implementing the risk communication strategy, and these will be discussed in this presentation. This includes the need for the engineering seismology community of the Kyrgyz Republic to reconsider some of the measures used to describe seismic, such as the ongoing use of macroseismic intensity instead of such measures as peak ground acceleration (PGA).

The theory and method of variable frequency directional seismic wave under the complex geologic conditions

NASA Astrophysics Data System (ADS)

Jiang, T.; Yue, Y.

2017-12-01

It is well known that the mono-frequency directional seismic wave technology can concentrate seismic waves into a beam. However, little work on the method and effect of variable frequency directional seismic wave under complex geological conditions have been done .We studied the variable frequency directional wave theory in several aspects. Firstly, we studied the relation between directional parameters and the direction of the main beam. Secondly, we analyzed the parameters that affect the beam width of main beam significantly, such as spacing of vibrator, wavelet dominant frequency, and number of vibrator. In addition, we will study different characteristics of variable frequency directional seismic wave in typical velocity models. In order to examine the propagation characteristics of directional seismic wave, we designed appropriate parameters according to the character of direction parameters, which is capable to enhance the energy of the main beam direction. Further study on directional seismic wave was discussed in the viewpoint of power spectral. The results indicate that the energy intensity of main beam direction increased 2 to 6 times for a multi-ore body velocity model. It showed us that the variable frequency directional seismic technology provided an effective way to strengthen the target signals under complex geological conditions. For concave interface model, we introduced complicated directional seismic technology which supports multiple main beams to obtain high quality data. Finally, we applied the 9-element variable frequency directional seismic wave technology to process the raw data acquired in a oil-shale exploration area. The results show that the depth of exploration increased 4 times with directional seismic wave method. Based on the above analysis, we draw the conclusion that the variable frequency directional seismic wave technology can improve the target signals of different geologic conditions and increase exploration depth with little

Improvement of real-time seismic magnitude estimation by combining seismic and geodetic instrumentation

NASA Astrophysics Data System (ADS)

Goldberg, D.; Bock, Y.; Melgar, D.

2017-12-01

Rapid seismic magnitude assessment is a top priority for earthquake and tsunami early warning systems. For the largest earthquakes, seismic instrumentation tends to underestimate the magnitude, leading to an insufficient early warning, particularly in the case of tsunami evacuation orders. GPS instrumentation provides more accurate magnitude estimations using near-field stations, but isn't sensitive enough to detect the first seismic wave arrivals, thereby limiting solution speed. By optimally combining collocated seismic and GPS instruments, we demonstrate improved solution speed of earthquake magnitude for the largest seismic events. We present a real-time implementation of magnitude-scaling relations that adapts to consider the length of the recording, reflecting the observed evolution of ground motion with time.

MSNoise: a Python Package for Monitoring Seismic Velocity Changes using Ambient Seismic Noise

NASA Astrophysics Data System (ADS)

Lecocq, T.; Caudron, C.; Brenguier, F.

2013-12-01

Earthquakes occur every day all around the world and are recorded by thousands of seismic stations. In between earthquakes, stations are recording "noise". In the last 10 years, the understanding of this noise and its potential usage have been increasing rapidly. The method, called "seismic interferometry", uses the principle that seismic waves travel between two recorders and are multiple-scattered in the medium. By cross-correlating the two records, one gets an information on the medium below/between the stations. The cross-correlation function (CCF) is a proxy to the Green Function of the medium. Recent developments of the technique have shown those CCF can be used to image the earth at depth (3D seismic tomography) or study the medium changes with time. We present MSNoise, a complete software suite to compute relative seismic velocity changes under a seismic network, using ambient seismic noise. The whole is written in Python, from the monitoring of data archives, to the production of high quality figures. All steps have been optimized to only compute the necessary steps and to use 'job'-based processing. We present a validation of the software on a dataset acquired during the UnderVolc[1] project on the Piton de la Fournaise Volcano, La Réunion Island, France, for which precursory relative changes of seismic velocity are visible for three eruptions betwee 2009 and 2011.

A critical review of the potential impacts of marine seismic surveys on fish & invertebrates.

PubMed

Carroll, A G; Przeslawski, R; Duncan, A; Gunning, M; Bruce, B

2017-01-15

Marine seismic surveys produce high intensity, low-frequency impulsive sounds at regular intervals, with most sound produced between 10 and 300Hz. Offshore seismic surveys have long been considered to be disruptive to fisheries, but there are few ecological studies that target commercially important species, particularly invertebrates. This review aims to summarise scientific studies investigating the impacts of low-frequency sound on marine fish and invertebrates, as well as to critically evaluate how such studies may apply to field populations exposed to seismic operations. We focus on marine seismic surveys due to their associated unique sound properties (i.e. acute, low-frequency, mobile source locations), as well as fish and invertebrates due to the commercial value of many species in these groups. The main challenges of seismic impact research are the translation of laboratory results to field populations over a range of sound exposure scenarios and the lack of sound exposure standardisation which hinders the identification of response thresholds. An integrated multidisciplinary approach to manipulative and in situ studies is the most effective way to establish impact thresholds in the context of realistic exposure levels, but if that is not practical the limitations of each approach must be carefully considered. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

Seismic Reflection Methods

EPA Pesticide Factsheets

Seismic methods are the most commonly conducted geophysical surveys for engineering investigations. Seismic refraction provides engineers and geologists with the most basic of geologic data via simple procedures with common equipment.

Knowledge of seismic hazard for the preservation of cultural heritage: the case study of Naples (Southern Italy)

NASA Astrophysics Data System (ADS)

Porfido, Sabina; Alessio, Giuliana; Gaudiosi, Germana; Nappi, Rosa; Spiga, Efisio

2017-04-01

The recent seismic sequence that struck central Italy, started the August 24, 2016, is characterized by five events with magnitude Mw> 5.0. The strongest events of the seismic sequence were the August 24, with Mw = 6.0 located between Accumoli and Amatrice towns and the October 30 with Mw = 6.5, located between Norcia and Visso town. These earthquakes shocked not only Central Italy, with the death of about 300 people and the almost complete destruction of historical towns (Amatrice, Arquata del Tronto, Accumoli, Pescara del Tronto, Castelluccio, Norcia, Visso), but also shook the entire Italian country, strongly proposing the issue of the vulnerability of the city historical centers. The knowledge, the conservation and preservation of the natural and urban environment represent issues to be faced urgently for preventing the devastation of our heritage, unique in the world. The historical center of Naples was affected by the 30 event October 2016 with an intensity I = V MCS. In the last millennium more than a hundred earthquakes hit Naples, with intensity I> III MCS, ten of which has exceeded the damage level, sometimes with intensity greater of VII MCS. The historical Neapolitan urban context suffered devastating effects, reaching levels of damage equal to the VIII degree MCS, as a result of the large earthquakes occurred in 1456 (I0=XI MCS), 1688 (I0=XI MCS) and 1805 (I0=X MCS). In the twentieth century the city of Napoli was shaken by the 1930, 1962 and 1980, the three strong earthquakes occurred in southern Apennines, between Irpinia and Basilicata regions. The review of earthquakes with higher energy (M> 6) shows that the metropolitan area of Naples suffered high damage levels with intensity I = VIII MCS, especially in the historical center, with a damage recurring on the same architectonic elements of the historical heritage. The recent past of the seismic history teaches us that the Apennines is highly seismic, consequently in the future we can expected

Seismic databases of The Caucasus

NASA Astrophysics Data System (ADS)

Gunia, I.; Sokhadze, G.; Mikava, D.; Tvaradze, N.; Godoladze, T.

2012-12-01

The Caucasus is one of the active segments of the Alpine-Himalayan collision belt. The region needs continues seismic monitoring systems for better understanding of tectonic processes going in the region. Seismic Monitoring Center of Georgia (Ilia State University) is operating the digital seismic network of the country and is also collecting and exchanging data with neighboring countries. The main focus of our study was to create seismic database which is well organized, easily reachable and is convenient for scientists to use. The seismological database includes the information about more than 100 000 earthquakes from the whole Caucasus. We have to mention that it includes data from analog and digital seismic networks. The first analog seismic station in Georgia was installed in 1899 in the Caucasus in Tbilisi city. The number of analog seismic stations was increasing during next decades and in 1980s about 100 analog stations were operated all over the region. From 1992 due to political and economical situation the number of stations has been decreased and in 2002 just two analog equipments was operated. New digital seismic network was developed in Georgia since 2003. The number of digital seismic stations was increasing and in current days there are more than 25 digital stations operating in the country. The database includes the detailed information about all equipments installed on seismic stations. Database is available online. That will make convenient interface for seismic data exchange data between Caucasus neighboring countries. It also makes easier both the seismic data processing and transferring them to the database and decreases the operator's mistakes during the routine work. The database was created using the followings: php, MySql, Javascript, Ajax, GMT, Gmap, Hypoinverse.

Co-seismic slip, post-seismic slip, and largest aftershock associated with the 1994 Sanriku-haruka-oki, Japan, earthquake

NASA Astrophysics Data System (ADS)

Yagi, Yuji; Kikuchi, Masayuki; Nishimura, Takuya

2003-11-01

We analyzed continuous GPS data to investigate the spatio-temporal distribution of co-seismic slip, post-seismic slip, and largest aftershock associated with the 1994 Sanriku-haruka-oki, Japan, earthquake (Mw = 7.7). To get better resolution for co-seismic and post-seismic slip distribution, we imposed a weak constraint as a priori information of the co-seismic slip determined by seismic wave analyses. We found that the post-seismic slip during 100 days following the main-shock amount to as much moment release as the main-shock, and that the sites of co-seismic slip and post-seismic slip are partitioning on a plate boundary region in complimentary fashion. The major post-seismic slip was triggered by the mainshock in western side of the co-seismic slip, and the extent of the post-seismic slip is almost unchanged with time. It rapidly developed a shear stress concentration ahead of the slip area, and triggered the largest aftershock.

Small aperture seismic arrays for studying planetary interiors and seismicity

NASA Astrophysics Data System (ADS)

Schmerr, N. C.; Lekic, V.; Fouch, M. J.; Panning, M. P.; Siegler, M.; Weber, R. C.

2017-12-01

Seismic arrays are a powerful tool for understanding the interior structure and seismicity across objects in the Solar System. Given the operational constraints of ground-based lander investigations, a small aperture seismic array can provide many of the benefits of a larger-scale network, but does not necessitate a global deployment of instrumentation. Here we define a small aperture array as a deployment of multiple seismometers, with a separation between instruments of 1-1000 meters. For example, small aperture seismic arrays have been deployed on the Moon during the Apollo program, the Active Seismic Experiments of Apollo 14 and 16, and the Lunar Seismic Profiling Experiment deployed by the Apollo 17 astronauts. Both were high frequency geophone arrays with spacing of 50 meters that provided information on the layering and velocity structure of the uppermost kilometer of the lunar crust. Ideally such arrays would consist of instruments that are 3-axis short period or broadband seismometers. The instruments must have a sampling rate and frequency range sensitivity capable of distinguishing between waves arriving at each station in the array. Both terrestrial analogs and the data retrieved from the Apollo arrays demonstrate the efficacy of this approach. Future opportunities exist for deployment of seismic arrays on Europa, asteroids, and other objects throughout the Solar System. Here we will present both observational data and 3-D synthetic modeling results that reveal the sensing requirements and the primary advantages of a small aperture seismic array over single station approach. For example, at the smallest apertures of < 1 m, we constrain that sampling rates must exceed 500 Hz and instrument sensitivity must extend to 100 Hz or greater. Such advantages include the improved ability to resolve the location of the sources near the array through detection of backazimuth and differential timing between stations, determination of the small-scale structure

Probabilistic seismic hazard assessment for northern Southeast Asia

NASA Astrophysics Data System (ADS)

Chan, C. H.; Wang, Y.; Kosuwan, S.; Nguyen, M. L.; Shi, X.; Sieh, K.

2016-12-01

We assess seismic hazard for northern Southeast Asia through constructing an earthquake and fault database, conducting a series of ground-shaking scenarios and proposing regional seismic hazard maps. Our earthquake database contains earthquake parameters from global and local seismic catalogues, including the ISC, ISC-GEM, the global ANSS Comprehensive Catalogues, Seismological Bureau, Thai Meteorological Department, Thailand, and Institute of Geophysics Vietnam Academy of Science and Technology, Vietnam. To harmonize the earthquake parameters from various catalogue sources, we remove duplicate events and unify magnitudes into the same scale. Our active fault database include active fault data from previous studies, e.g. the active fault parameters determined by Wang et al. (2014), Department of Mineral Resources, Thailand, and Institute of Geophysics, Vietnam Academy of Science and Technology, Vietnam. Based on the parameters from analysis of the databases (i.e., the Gutenberg-Richter relationship, slip rate, maximum magnitude and time elapsed of last events), we determined the earthquake recurrence models of seismogenic sources. To evaluate the ground shaking behaviours in different tectonic regimes, we conducted a series of tests by matching the felt intensities of historical earthquakes to the modelled ground motions using ground motion prediction equations (GMPEs). By incorporating the best-fitting GMPEs and site conditions, we utilized site effect and assessed probabilistic seismic hazard. The highest seismic hazard is in the region close to the Sagaing Fault, which cuts through some major cities in central Myanmar. The northern segment of Sunda megathrust, which could potentially cause M8-class earthquake, brings significant hazard along the Western Coast of Myanmar and eastern Bangladesh. Besides, we conclude a notable hazard level in northern Vietnam and the boundary between Myanmar, Thailand and Laos, due to a series of strike-slip faults, which could

The use of vertical seismic profiles in seismic investigations of the earth

USGS Publications Warehouse

Balch, Alfred H.; Lee, M.W.; Miller, J.J.; Ryder, Robert T.

1982-01-01

During the past 8 years, the U.S. Geological Survey has conducted an extensive investigation on the use of vertical seismic profiles (VSP) in a variety of seismic exploration applications. Seismic sources used were surface air guns, vibrators, explosives, marine air guns, and downhole air guns. Source offsets have ranged from 100 to 7800 ft. Well depths have been from 1200 to over 10,000 ft. We have found three specific ways in which VSPs can be applied to seismic exploration. First, seismic events observed at the surface of the ground can be traced, level by level, to their point of origin within the earth. Thus, one can tie a surface profile to a well log with an extraordinarily high degree of confidence. Second, one can establish the detectability of a target horizon, such as a porous zone. One can determine (either before or after surface profiling) whether or not a given horizon or layered sequence returns a detectable reflection to the surface. The amplitude and character of the reflection can also be observed. Third, acoustic properties of a stratigraphic sequence can be measured and sometimes correlated to important exploration parameters. For example, sometimes a relationship between apparent attenuation and sand percentage can be established. The technique shows additional promise of aiding surface exploration indirectly through studies of the evolution of the seismic pulse, studies of ghosts and multiples, and studies of seismic trace inversion techniques. Nearly all current seismic data‐processing techniques are adaptable to the processing of VSP data, such as normal moveout (NMO) corrections, stacking, single‐and multiple‐channel filtering, deconvolution, and wavelet shaping.

Revision of seismic design codes corresponding to building damages in the ``5.12'' Wenchuan earthquake

NASA Astrophysics Data System (ADS)

Wang, Yayong

2010-06-01

A large number of buildings were seriously damaged or collapsed in the “5.12” Wenchuan earthquake. Based on field surveys and studies of damage to different types of buildings, seismic design codes have been updated. This paper briefly summarizes some of the major revisions that have been incorporated into the “Standard for classification of seismic protection of building constructions GB50223-2008” and “Code for Seismic Design of Buildings GB50011-2001.” The definition of seismic fortification class for buildings has been revisited, and as a result, the seismic classifications for schools, hospitals and other buildings that hold large populations such as evacuation shelters and information centers have been upgraded in the GB50223-2008 Code. The main aspects of the revised GB50011-2001 code include: (a) modification of the seismic intensity specified for the Provinces of Sichuan, Shanxi and Gansu; (b) basic conceptual design for retaining walls and building foundations in mountainous areas; (c) regularity of building configuration; (d) integration of masonry structures and pre-cast RC floors; (e) requirements for calculating and detailing stair shafts; and (f) limiting the use of single-bay RC frame structures. Some significant examples of damage in the epicenter areas are provided as a reference in the discussion on the consequences of collapse, the importance of duplicate structural systems, and the integration of RC and masonry structures.

Seismic fragility assessment of low-rise stone masonry buildings

NASA Astrophysics Data System (ADS)

Abo-El-Ezz, Ahmad; Nollet, Marie-José; Nastev, Miroslav

2013-03-01

Many historic buildings in old urban centers in Eastern Canada are made of stone masonry reputed to be highly vulnerable to seismic loads. Seismic risk assessment of stone masonry buildings is therefore the first step in the risk mitigation process to provide adequate planning for retrofit and preservation of historical urban centers. This paper focuses on development of analytical displacement-based fragility curves reflecting the characteristics of existing stone masonry buildings in Eastern Canada. The old historic center of Quebec City has been selected as a typical study area. The standard fragility analysis combines the inelastic spectral displacement, a structure-dependent earthquake intensity measure, and the building damage state correlated to the induced building displacement. The proposed procedure consists of a three-step development process: (1) mechanics-based capacity model, (2) displacement-based damage model and (3) seismic demand model. The damage estimation for a uniform hazard scenario of 2% in 50 years probability of exceedance indicates that slight to moderate damage is the most probable damage experienced by these stone masonry buildings. Comparison is also made with fragility curves implicit in the seismic risk assessment tools Hazus and ELER. Hazus shows the highest probability of the occurrence of no to slight damage, whereas the highest probability of extensive and complete damage is predicted with ELER. This comparison shows the importance of the development of fragility curves specific to the generic construction characteristics in the study area and emphasizes the need for critical use of regional risk assessment tools and generated results.

High-resolution seismic monitoring of rockslide activity in the Illgraben, Switzerland

NASA Astrophysics Data System (ADS)

Burtin, Arnaud; Hovius, Niels; Dietze, Michael; McArdell, Brian

2014-05-01

Rockfalls and rockslides are important geomorphic processes in landscape dynamics. They contribute to the evolution of slopes and supply rock materials to channels, enabling fluvial incision. Hillslope processes are also a natural hazard that we need to quantify and, if possible, predict. For these reasons, it is necessary to determine the triggering conditions and mechanisms involved in rockfalls. Rainfall is a well-known contributor since water, through soil moisture or pore pressure, may lead to the inception and propagation of cracks and can induce slope failure. Water can also affect slope stability through effects of climatic conditions such as the fluctuations of temperature around the freezing point. During the winter of 2012, we have recorded with a seismic array of 8 instruments substantial rockslide activity that affected a gully in the Illgraben catchment in the Swiss Alps. Three stations were positioned directly around the gully with a nearest distance of 400 m. The period of intense activity did not start during a rainstorm as it is common in summer but during a period of oscillation of temperatures around the freezing point. The activity did not occur in a single event but lasted about a week with a decay in time of the event frequency. Many individual events had two distinct seismic signals, with first, a short duration phase of about 10 s at frequencies below 5 Hz that we interpret as a slope failure signature, followed by a second long duration signal of > 60 s at frequencies above 10 Hz that we attribute to the propagation of rock debris down the slope. Thanks to the array of seismic sensors, we can study the fine details of this rockslide sequence by locating the different events, determining their distribution in time, and systematic quantification of seismic metrics (energy, duration, intensity...). These observations are compared to independent meteorological constrains and laser scan data to obtain an estimate of the volume mobilized by the

High Temporal Resolution Mapping of Seismic Noise Sources Using Heterogeneous Supercomputers

NASA Astrophysics Data System (ADS)

Paitz, P.; Gokhberg, A.; Ermert, L. A.; Fichtner, A.

2017-12-01

The time- and space-dependent distribution of seismic noise sources is becoming a key ingredient of modern real-time monitoring of various geo-systems like earthquake fault zones, volcanoes, geothermal and hydrocarbon reservoirs. We present results of an ongoing research project conducted in collaboration with the Swiss National Supercomputing Centre (CSCS). The project aims at building a service providing seismic noise source maps for Central Europe with high temporal resolution. We use source imaging methods based on the cross-correlation of seismic noise records from all seismic stations available in the region of interest. The service is hosted on the CSCS computing infrastructure; all computationally intensive processing is performed on the massively parallel heterogeneous supercomputer "Piz Daint". The solution architecture is based on the Application-as-a-Service concept to provide the interested researchers worldwide with regular access to the noise source maps. The solution architecture includes the following sub-systems: (1) data acquisition responsible for collecting, on a periodic basis, raw seismic records from the European seismic networks, (2) high-performance noise source mapping application responsible for the generation of source maps using cross-correlation of seismic records, (3) back-end infrastructure for the coordination of various tasks and computations, (4) front-end Web interface providing the service to the end-users and (5) data repository. The noise source mapping itself rests on the measurement of logarithmic amplitude ratios in suitably pre-processed noise correlations, and the use of simplified sensitivity kernels. During the implementation we addressed various challenges, in particular, selection of data sources and transfer protocols, automation and monitoring of daily data downloads, ensuring the required data processing performance, design of a general service-oriented architecture for coordination of various sub-systems, and

Seismic imaging of the oil and geothermal reservoirs using the induced seismicity

NASA Astrophysics Data System (ADS)

Zhang, H.; Toksoz, M. N.; Fehler, M.

2011-12-01

It is known that microseismicity can be induced in the oil field due to the stress change caused by oil/gas production. Similarly, injection of high-pressure fluids into the reservoir can also induce microseismicity. Due to the proximity of induced seismicity to the reservoir, in some cases, it may be advantageous to use induced seismicity to image the reservoir. The seismic stations for monitoring the induced seismicity are usually sparse. Conventional travel time tomography using travel times from seismic events to stations may not be applicable because of poor ray coverage outside the source region. In comparison, the double-difference tomography method of Zhang and Thurber (2003) that uses the differential travel times is able to image the reservoir by avoiding determining the velocity structure outside the source region. In this study, we present two case studies of applying double-difference tomography to induced seismicity monitored by borehole stations. In the case of an oil field in Oman, five closely spaced monitoring wells are used to monitor microseismicity induced by gas production. In each well, multiple seismic sensors are positioned from depths 750 m - 1250 m and about 2000 events are selected for tomography. Reservoir imaging shows encouraging results in identifying structures and velocity changes within reservoir layers. Clear velocity contrast was seen across the major northeast-southwest faults. Low Vp, low Vs and low Vp/Vs anomalies are mainly associated with the gas production layer. For the case of the Soultz Enhanced Geothermal System at Soultz-sous-Forets, France, we used travel time data from the September and October 1993 hydraulic stimulations, where only four borehole stations are available. The results showed that the S-wave velocity structure correlated well with seismicity and showed low velocity zones at depths between 2900 and 3300 meters, where fluid was believed to have infiltrated the reservoir. We also attempt time

Seismic evolution of the 1989-1990 eruption sequence of Redoubt Volcano, Alaska

USGS Publications Warehouse

Power, J.A.; Lahr, J.C.; Page, R.A.; Chouet, B.A.; Stephens, C.D.; Harlow, D.H.; Murray, T.L.; Davies, J.N.

1994-01-01

Redoubt Volcano in south-central Alaska erupted between December 1989 and June 1990 in a sequence of events characterized by large tephra eruptions, pyroclastic flows, lahars and debris flows, and episodes of dome growth. The eruption was monitored by a network of five to nine seismic stations located 1 to 22 km from the summit crater. Notable features of the eruption seismicity include : (1) small long-period events beginning in September 1989 which increased slowly in number during November and early December; (2) an intense swarm of long-period events which preceded the initial eruptions on December 14 by 23 hours; (3) shallow swarms (0 to 3 km) of volcano-tectonic events following each eruption on December 15; (4) a persistent cluster of deep (6 to 10 km) volcano-tectonic earthquakes initiated by the eruptions on December 15, which continued throughout and beyond the eruption; (5) an intense swarm of long-period events which preceded the eruptions on January 2; and (6) nine additional intervals of increased long-period seismicity each of which preceded a tephra eruption. Hypocenters of volcano-tectonic earthquakes suggest the presence of a magma source region at 6-10 km depth. Earthquakes at these depths were initiated by the tephra eruptions on December 15 and likely represent the readjustment of stresses in the country rock associated with the removal of magma from these depths. The locations and time-history of these earthquakes coupled with the eruptive behavior of the volcano suggest this region was the source of most of the erupted material during the 1989-1990 eruption. This source region appears to be connected to the surface by a narrow pipe-like conduit as inferred from the hypocenters of volcano-tectonic earthquakes. Concentrations of shallow volcano-tectonic earthquakes followed each of the tephra eruptions on December 15; these shocks may represent stress readjustment in the wall rock related to the removal of magma and volatiles at these depths

5 years of continuous seismic monitoring of a mountain river in the Pyrenees

NASA Astrophysics Data System (ADS)

Diaz, Jordi; Sanchez-Pastor, Pilar S.; Gallart, Josep

2017-04-01

The analysis of background seismic noise variations in the proximity of river channels has revealed as a useful tool to monitor river flow, even for modest discharges. Nevertheless, this monitoring is usually carried on using temporal deployments of seismic stations. The CANF seismic broad-band station, acquiring data continuously since 2010 and located inside an old railway tunnel in the Central Pyrenees, at about 400 m of the Aragón River channel, provides an excellent opportunity to enlarge this view and present a long term monitoring of a mountain river. Seismic signals in the 2-10 Hz band clearly related to river discharges have been identified in the seismic records. Discharge increases due to rainfall, large storms resulting in floods and snowmelt periods can be discriminated from the analysis of the seismic data. Up to now, two large rainfall events resulting in large discharge and damaging floods have been recorded, both sharing similar properties which can be used to implement automatic procedures to identify seismically potentially damaging floods. Another natural process that can be characterized using continuouly acquired seismic data is mountain snowmelt, as this process results in characteristic discharge patterns which can be identified in the seismic data. The time occurrence and intensity of the snowmelt stages for each season can be identified and the 5 seasons available so far compared to detect possible trends The so-called fluvial seismology can also provide important clues to evaluate the beadload transport in rivers, an important parameter to evaluate erosion rates in mountain environments. Analyzing both the amplitude and frequency variations of the seismic data and its hysteresis cycles, it seems possible to estimate the relative contribution of water flow and bedload transport to the seismic signal. The available results suggest that most of the river-generated seismic signal seems related to bed load transportation, while water

Development of Towed Marine Seismic Vibrator as an Alternative Seismic Source

NASA Astrophysics Data System (ADS)

Ozasa, H.; Mikada, H.; Murakami, F.; Jamali Hondori, E.; Takekawa, J.; Asakawa, E.; Sato, F.

2015-12-01

The principal issue with respect to marine impulsive sources to acquire seismic data is if the emission of acoustic energy inflicts harm on marine mammals or not, since the volume of the source signal being released into the marine environment could be so large compared to the sound range of the mammals. We propose a marine seismic vibrator as an alternative to the impulsive sources to mitigate a risk of the impact to the marine environment while satisfying the necessary conditions of seismic surveys. These conditions include the repeatability and the controllability of source signals both in amplitude and phase for high-quality measurements. We, therefore, designed a towed marine seismic vibrator (MSV) as a new type marine vibratory seismic source that employed the hydraulic servo system for the controllability condition in phase and in amplitude that assures the repeatability as well. After fabricating a downsized MSV that requires the power of 30 kVA at a depth of about 250 m in water, several sea trials were conducted to test the source characteristics of the downsized MSV in terms of amplitude, frequency, horizontal and vertical directivities of the generated field. The maximum sound level satisfied the designed specification in the frequencies ranging from 3 to 300 Hz almost omnidirectionally. After checking the source characteristics, we then conducted a trial seismic survey, using both the downsized MSV and an airgun of 480 cubic-inches for comparison, with a streamer cable of 2,000m long right above a cabled earthquake observatory in the Japan Sea. The result showed that the penetration of seismic signals generated by the downsized MSV was comparable to that by the airgun, although there was a slight difference in the signal-to-noise ratio. The MSV could become a versatile source that will not harm living marine mammals as an alternative to the existing impulsive seismic sources such as airgun.

Probabilistic properties of injection induced seismicity - implications for the seismic hazard analysis

NASA Astrophysics Data System (ADS)

Lasocki, Stanislaw; Urban, Pawel; Kwiatek, Grzegorz; Martinez-Garzón, Particia

2017-04-01

Injection induced seismicity (IIS) is an undesired dynamic rockmass response to massive fluid injections. This includes reactions, among others, to hydro-fracturing for shale gas exploitation. Complexity and changeability of technological factors that induce IIS, may result in significant deviations of the observed distributions of seismic process parameters from the models, which perform well in natural, tectonic seismic processes. Classic formulations of probabilistic seismic hazard analysis in natural seismicity assume the seismic marked point process to be a stationary Poisson process, whose marks - magnitudes are governed by a Gutenberg-Richter born exponential distribution. It is well known that the use of an inappropriate earthquake occurrence model and/or an inappropriate of magnitude distribution model leads to significant systematic errors of hazard estimates. It is therefore of paramount importance to check whether the mentioned, commonly used in natural seismicity assumptions on the seismic process, can be safely used in IIS hazard problems or not. Seismicity accompanying shale gas operations is widely studied in the framework of the project "Shale Gas Exploration and Exploitation Induced Risks" (SHEER). Here we present results of SHEER project investigations of such seismicity from Oklahoma and of a proxy of such seismicity - IIS data from The Geysers geothermal field. We attempt to answer to the following questions: • Do IIS earthquakes follow the Gutenberg-Richter distribution law, so that the magnitude distribution can be modelled by an exponential distribution? • Is the occurrence process of IIS earthquakes Poissonian? Is it segmentally Poissonian? If yes, how are these segments linked to cycles of technological operations? Statistical tests indicate that the Gutenberg-Richter relation born exponential distribution model for magnitude is, in general, inappropriate. The magnitude distribution can be complex, multimodal, with no ready

iShake: Mobile Phones as Seismic Sensors (Invited)

NASA Astrophysics Data System (ADS)

Dashti, S.; Reilly, J.; Bray, J. D.; Bayen, A. M.; Glaser, S. D.; Mari, E.

2010-12-01

Emergency responders must “see” the effects of an earthquake clearly and rapidly so that they can respond effectively to the damage it has produced. Great strides have been made recently in developing methodologies that deliver rapid and accurate post-earthquake information. However, shortcomings still exist. The iShake project is an innovative use of cell phones and information technology to bridge the gap between the high quality, but sparse, ground motion instrument data that are used to help develop ShakeMap and the low quality, but large quantity, human observational data collected to construct a “Did You Feel It?” (DYFI)-based map. Rather than using people as measurement “devices” as is being done through DYFI, the iShake project is using their cell phones to measure ground motion intensity parameters and automatically deliver the data to the U.S. Geological Survey (USGS) for processing and dissemination. In this participatory sensing paradigm, quantitative shaking data from numerous cellular phones will enable the USGS to produce shaking intensity maps more accurately than presently possible. The phone sensor, however, is an imperfect device with performance variations among phones of a given model as well as between models. The sensor is the entire phone, not just the micro-machined transducer inside. A series of 1-D and 3-D shaking table tests were performed at UC San Diego and UC Berkeley, respectively, to evaluate the performance of a class of cell phones. In these tests, seven iPhones and iPod Touch devices that were mounted at different orientations were subjected to 124 earthquake ground motions to characterize their response and reliability as seismic sensors. The testing also provided insight into the seismic response of unsecured and falling instruments. The cell phones measured seismic parameters such as peak ground acceleration (PGA), peak ground velocity (PGV), peak ground displacement (PGD), and 5% damped spectral accelerations well

Magma migration at the onset of the 2012-13 Tolbachik eruption revealed by Seismic Amplitude Ratio Analyses

NASA Astrophysics Data System (ADS)

Taisne, B.; Caudron, C.; Kugaenko, Y.; Saltykov, V.

2015-12-01

In contrast of the 1975-76 Tolbachik eruption, the 2012-2013 Tolbachik eruption was not preceded by any striking change in seismic activity. By processing the Klyuchevskoy volcano group seismic data with the Seismic Amplitude Ratio Analysis (SARA) method, we gain insights into the dynamics of magma transfer prior to this important eruption. We highlighted a clear migration of the source of the microseismicity within the seismic swarm, starting 20 hours before the reported eruption onset (05:15 UTC, 26 November 2012). This migration proceeded in different phases and ended when eruptive tremor, corresponding to lava extrusion, was recorded (at ~11:00 UTC, 27 November 2012). In order to get a first order approximation of the location of the magma, we compare the calculated seismic intensity ratios with the theoretical ones. As expected, the observations suggest a migration toward the eruptive vent. However, we explain the pre-eruptive observed ratios by a vertical migration under the northern slope of Plosky Tolbachik volcano that would interact at shallower depth with an intermediate storage region and initiate the lateral migration toward the eruptive vents. Another migration is also captured by this technique and coincides with a seismic swarm that started 16-20 km to the south of Plosky Tolbachik at 20:31 UTC on November 28 and lasted for more than 2 days. This seismic swarm is very similar to the seismicity preceding the 1975-76 Tolbachik eruption and can be considered as a possible aborted eruption.

A new concept in seismic landslide hazard analysis for practical application

NASA Astrophysics Data System (ADS)

Lee, Chyi-Tyi

2017-04-01

A seismic landslide hazard model could be constructed using deterministic approach (Jibson et al., 2000) or statistical approach (Lee, 2014). Both approaches got landslide spatial probability under a certain return-period earthquake. In the statistical approach, our recent study found that there are common patterns among different landslide susceptibility models of the same region. The common susceptibility could reflect relative stability of slopes at a region; higher susceptibility indicates lower stability. Using the common susceptibility together with an earthquake event landslide inventory and a map of topographically corrected Arias intensity, we can build the relationship among probability of failure, Arias intensity and the susceptibility. This relationship can immediately be used to construct a seismic landslide hazard map for the region that the empirical relationship built. If the common susceptibility model is further normalized and the empirical relationship built with normalized susceptibility, then the empirical relationship may be practically applied to different region with similar tectonic environments and climate conditions. This could be feasible, when a region has no existing earthquake-induce landslide data to train the susceptibility model and to build the relationship. It is worth mentioning that a rain-induced landslide susceptibility model has common pattern similar to earthquake-induced landslide susceptibility in the same region, and is usable to build the relationship with an earthquake event landslide inventory and a map of Arias intensity. These will be introduced with examples in the meeting.

Microzonation of seismic risk in a low-rise Latin American city based on the macroseismic evaluation of the vulnerability of residential buildings: Colima city, México

NASA Astrophysics Data System (ADS)

Zobin, V. M.; Cruz-Bravo, A. A.; Ventura-Ramírez, F.

2010-06-01

A macroseismic methodology of seismic risk microzonation in a low-rise city based on the vulnerability of residential buildings is proposed and applied to Colima city, Mexico. The seismic risk microzonation for Colima consists of two elements: the mapping of residential blocks according to their vulnerability level and the calculation of an expert-opinion based damage probability matrix (DPM) for a given level of earthquake intensity and a given type of residential block. A specified exposure time to the seismic risk for this zonation is equal to the interval between two destructive earthquakes. The damage probability matrices were calculated for three types of urban buildings and five types of residential blocks in Colima. It was shown that only 9% of 1409 residential blocks are able to resist to the Modify Mercalli (MM) intensity VII and VIII earthquakes without significant damage. The proposed DPM-2007 is in good accordance with the experimental damage curves based on the macroseismic evaluation of 3332 residential buildings in Colima that was carried out after the 21 January 2003 intensity MM VII earthquake. This methodology and the calculated PDM-2007 curves may be applied also to seismic risk microzonation for many low-rise cities in Latin America, Asia, and Africa.

Detection capability of the IMS seismic network based on ambient seismic noise measurements

NASA Astrophysics Data System (ADS)

Gaebler, Peter J.; Ceranna, Lars

2016-04-01

All nuclear explosions - on the Earth's surface, underground, underwater or in the atmosphere - are banned by the Comprehensive Nuclear-Test-Ban Treaty (CTBT). As part of this treaty, a verification regime was put into place to detect, locate and characterize nuclear explosion testings at any time, by anyone and everywhere on the Earth. The International Monitoring System (IMS) plays a key role in the verification regime of the CTBT. Out of the different monitoring techniques used in the IMS, the seismic waveform approach is the most effective technology for monitoring nuclear underground testing and to identify and characterize potential nuclear events. This study introduces a method of seismic threshold monitoring to assess an upper magnitude limit of a potential seismic event in a certain given geographical region. The method is based on ambient seismic background noise measurements at the individual IMS seismic stations as well as on global distance correction terms for body wave magnitudes, which are calculated using the seismic reflectivity method. From our investigations we conclude that a global detection threshold of around mb 4.0 can be achieved using only stations from the primary seismic network, a clear latitudinal dependence for the detection threshold can be observed between northern and southern hemisphere. Including the seismic stations being part of the auxiliary seismic IMS network results in a slight improvement of global detection capability. However, including wave arrivals from distances greater than 120 degrees, mainly PKP-wave arrivals, leads to a significant improvement in average global detection capability. In special this leads to an improvement of the detection threshold on the southern hemisphere. We further investigate the dependence of the detection capability on spatial (latitude and longitude) and temporal (time) parameters, as well as on parameters such as source type and percentage of operational IMS stations.

Hydrologically-driven crustal stresses and seismicity in the New Madrid Seismic Zone.

PubMed

Craig, Timothy J; Chanard, Kristel; Calais, Eric

2017-12-15

The degree to which short-term non-tectonic processes, either natural and anthropogenic, influence the occurrence of earthquakes in active tectonic settings or 'stable' plate interiors, remains a subject of debate. Recent work in plate-boundary regions demonstrates the capacity for long-wavelength changes in continental water storage to produce observable surface deformation, induce crustal stresses and modulate seismicity rates. Here we show that a significant variation in the rate of microearthquakes in the intraplate New Madrid Seismic Zone at annual and multi-annual timescales coincides with hydrological loading in the upper Mississippi embayment. We demonstrate that this loading, which results in geodetically observed surface deformation, induces stresses within the lithosphere that, although of small amplitude, modulate the ongoing seismicity of the New Madrid region. Correspondence between surface deformation, hydrological loading and seismicity rates at both annual and multi-annual timescales indicates that seismicity variations are the direct result of elastic stresses induced by the water load.

The assessment of seismic hazard for Gori, (Georgia) and preliminary studies of seismic microzonation

NASA Astrophysics Data System (ADS)

Gogoladze, Z.; Moscatelli, M.; Giallini, S.; Avalle, A.; Gventsadze, A.; Kvavadze, N.; Tsereteli, N.

2016-12-01

Seismic risk is a crucial issue for South Caucasus, which is the main gateway between Asia and Europe. The goal of this work is to propose new methods and criteria for defining an overall approach aimed at assessing and mitigating seismic risk in Georgia. In this reguard seismic microzonation represents a highly useful tool for seismic risk assessmentin land management, for design of buildings or structures and for emergency planning.Seismic microzonation assessment of local seismic hazard,which is a component of seismicity resulting from specific local characteristics which cause local amplification and soil instability, through identification of zones with seismically homogeneous behavior. This paper presents the results of preliminary study of seismic microzonation of Gori, Georgia. Gori is and is located in the Shida Kartli region and on both sides of Liachvi and Mtkvari rivers, with area of about 135 km2around the Gori fortress. Gori is located in Achara-Trialeti fold-thrust belt, that is tectonically unstable. Half of all earthquakes in Gori area with magnitude M≥3.5 have happened along this fault zone and on basis of damage caused by previous earthquakes, this territory show the highest level of risk (the maximum value of direct losses) in central part of the town. The seismic microzonation map of level 1 for Gori was carried out using: 1) Already available data (i.e., topographic map and boreholes data), 2) Results of new geological surveys and 3) Geophysical measurements (i.e., MASW and noise measurements processed with HVSR technique). Our preliminary results highlight the presence of both stable zones susceptible to local amplifications and unstable zones susceptible to geological instability. Our results are directed to establish set of actions aimed at risk mitigation before initial onset of emergency, and to management of the emergency once the seismic event has occurred. The products obtained, will contain the basic elements of an integrated system

CyberShake: Running Seismic Hazard Workflows on Distributed HPC Resources

NASA Astrophysics Data System (ADS)

Callaghan, S.; Maechling, P. J.; Graves, R. W.; Gill, D.; Olsen, K. B.; Milner, K. R.; Yu, J.; Jordan, T. H.

2013-12-01

As part of its program of earthquake system science research, the Southern California Earthquake Center (SCEC) has developed a simulation platform, CyberShake, to perform physics-based probabilistic seismic hazard analysis (PSHA) using 3D deterministic wave propagation simulations. CyberShake performs PSHA by simulating a tensor-valued wavefield of Strain Green Tensors, and then using seismic reciprocity to calculate synthetic seismograms for about 415,000 events per site of interest. These seismograms are processed to compute ground motion intensity measures, which are then combined with probabilities from an earthquake rupture forecast to produce a site-specific hazard curve. Seismic hazard curves for hundreds of sites in a region can be used to calculate a seismic hazard map, representing the seismic hazard for a region. We present a recently completed PHSA study in which we calculated four CyberShake seismic hazard maps for the Southern California area to compare how CyberShake hazard results are affected by different SGT computational codes (AWP-ODC and AWP-RWG) and different community velocity models (Community Velocity Model - SCEC (CVM-S4) v11.11 and Community Velocity Model - Harvard (CVM-H) v11.9). We present our approach to running workflow applications on distributed HPC resources, including systems without support for remote job submission. We show how our approach extends the benefits of scientific workflows, such as job and data management, to large-scale applications on Track 1 and Leadership class open-science HPC resources. We used our distributed workflow approach to perform CyberShake Study 13.4 on two new NSF open-science HPC computing resources, Blue Waters and Stampede, executing over 470 million tasks to calculate physics-based hazard curves for 286 locations in the Southern California region. For each location, we calculated seismic hazard curves with two different community velocity models and two different SGT codes, resulting in over

Urban MEMS based seismic network for post-earthquakes rapid disaster assessment

NASA Astrophysics Data System (ADS)

D'Alessandro, Antonino; Luzio, Dario; D'Anna, Giuseppe

2014-05-01

Life losses following disastrous earthquake depends mainly by the building vulnerability, intensity of shaking and timeliness of rescue operations. In recent decades, the increase in population and industrial density has significantly increased the exposure to earthquakes of urban areas. The potential impact of a strong earthquake on a town center can be reduced by timely and correct actions of the emergency management centers. A real time urban seismic network can drastically reduce casualties immediately following a strong earthquake, by timely providing information about the distribution of the ground shaking level. Emergency management centers, with functions in the immediate post-earthquake period, could be use this information to allocate and prioritize resources to minimize loss of human life. However, due to the high charges of the seismological instrumentation, the realization of an urban seismic network, which may allow reducing the rate of fatalities, has not been achieved. Recent technological developments in MEMS (Micro Electro-Mechanical Systems) technology could allow today the realization of a high-density urban seismic network for post-earthquakes rapid disaster assessment, suitable for the earthquake effects mitigation. In the 1990s, MEMS accelerometers revolutionized the automotive-airbag system industry and are today widely used in laptops, games controllers and mobile phones. Due to their great commercial successes, the research into and development of MEMS accelerometers are actively pursued around the world. Nowadays, the sensitivity and dynamics of these sensors are such to allow accurate recording of earthquakes with moderate to strong magnitude. Due to their low cost and small size, the MEMS accelerometers may be employed for the realization of high-density seismic networks. The MEMS accelerometers could be installed inside sensitive places (high vulnerability and exposure), such as schools, hospitals, public buildings and places of

IFEQ, app developed based on the J-SHIS system

NASA Astrophysics Data System (ADS)

Azuma, H.; Hao, K. X.; Fujiwara, H.

2015-12-01

Raise an awareness of earthquake disaster prevention is an important issue in Japan. To do that, we have developed an app IFEQ on smartphone based on the APIs provided by the J-SHIS that is an integrated system of Seismic Hazard Assessment. IFEQ can simulate a real situation of earthquake disaster you might experience at current spot. The hint of the IFEQ came from a question "What should I do IF a big EarthQuake hit now?" An earthquake risk situation is estimated by a location information that is acquired from GPS, the detail comprehensive information of a 250m mesh obtained through J-SHIS APIs by the geomorphological classification and a probability of intensity 6 lower (JMA) within 30 years. A user's photo was displayed with a risk situation surrounded by simply one touch. IFEQ helps oneself to overcome a gap between exist scenes and a horrible disaster by enhancing imagination. The results show people have more ideas to handle with the risk situation after using the App IFEQ. IFEQ App's features are summarized as below: 1. Visualizing an image photo with possible risks from a coming earthquake at present spot. 2. Displaying an exceedance probability within 30-years and a maximum seismic intensity within 10,000-years on present location. 3. User can obtain some advices of how to prepare for possible risks. 4. A risk with five ranks is given, especially for items of Building Collapse, Liquefaction and Landslide. IFEQ can be downloaded freely from http://www.j-shis.bosai.go.jp/app-ifearthquake J-SHIS APIs can be obtained from http://www.j-shis.bosai.go.jp/en/category/opencat/api

3D Modelling of Seismically Active Parts of Underground Faults via Seismic Data Mining

NASA Astrophysics Data System (ADS)

Frantzeskakis, Theofanis; Konstantaras, Anthony

2015-04-01

During the last few years rapid steps have been taken towards drilling for oil in the western Mediterranean sea. Since most of the countries in the region benefit mainly from tourism and considering that the Mediterranean is a closed sea only replenishing its water once every ninety years careful measures are being taken to ensure safe drilling. In that concept this research work attempts to derive a three dimensional model of the seismically active parts of the underlying underground faults in areas of petroleum interest. For that purpose seismic spatio-temporal clustering has been applied to seismic data to identify potential distinct seismic regions in the area of interest. Results have been coalesced with two dimensional maps of underground faults from past surveys and seismic epicentres, having followed careful reallocation processing, have been used to provide information regarding the vertical extent of multiple underground faults in the region of interest. The end product is a three dimensional map of the possible underground location and extent of the seismically active parts of underground faults. Indexing terms: underground faults modelling, seismic data mining, 3D visualisation, active seismic source mapping, seismic hazard evaluation, dangerous phenomena modelling Acknowledgment This research work is supported by the ESPA Operational Programme, Education and Life Long Learning, Students Practical Placement Initiative. References [1] Alves, T.M., Kokinou, E. and Zodiatis, G.: 'A three-step model to assess shoreline and offshore susceptibility to oil spills: The South Aegean (Crete) as an analogue for confined marine basins', Marine Pollution Bulletin, In Press, 2014 [2] Ciappa, A., Costabile, S.: 'Oil spill hazard assessment using a reverse trajectory method for the Egadi marine protected area (Central Mediterranean Sea)', Marine Pollution Bulletin, vol. 84 (1-2), pp. 44-55, 2014 [3] Ganas, A., Karastathis, V., Moshou, A., Valkaniotis, S., Mouzakiotis

Seismic Analysis Capability in NASTRAN

NASA Technical Reports Server (NTRS)

Butler, T. G.; Strang, R. F.

1984-01-01

Seismic analysis is a technique which pertains to loading described in terms of boundary accelerations. Earthquake shocks to buildings is the type of excitation which usually comes to mind when one hears the word seismic, but this technique also applied to a broad class of acceleration excitations which are applied at the base of a structure such as vibration shaker testing or shocks to machinery foundations. Four different solution paths are available in NASTRAN for seismic analysis. They are: Direct Seismic Frequency Response, Direct Seismic Transient Response, Modal Seismic Frequency Response, and Modal Seismic Transient Response. This capability, at present, is invoked not as separate rigid formats, but as pre-packaged ALTER packets to existing RIGID Formats 8, 9, 11, and 12. These ALTER packets are included with the delivery of the NASTRAN program and are stored on the computer as a library of callable utilities. The user calls one of these utilities and merges it into the Executive Control Section of the data deck to perform any of the four options are invoked by setting parameter values in the bulk data.

Histortical seismicity of the offshore Fujian-Guangdong region

NASA Astrophysics Data System (ADS)

Xie, Yushou

1992-08-01

The earthquakes offshore Fujian and Guangdong Provinces concentrated along the two segments near Nan’ao in the south and Quanzhou in the north of the off coast fault, which is very active since the late Pleistocene. In 1918 and 1906, two earthquakes with magnitudes 7.3 and 6.1 respectively occurred in the south and the north regions. With the instrumentally determined seismic parameters of these two earthquakes as standards, the author evaluated the parameters of the historical earthquakes by comparing their macroseismic materials with consideration of the geological background. As a result, chronological tables of historical earthquakes of the south and the north regions were compiled. The seismic activity of the two regions synchronized basically, and their strongest recorded earthquakes were both around M s 7.3. Seismic activity usually intensified before the occurrence of strong events. Aftershocks were frequent, but strong aftershocks usually occurred one to several years after the main shock. Two high tides of seismic activity occurred since the late 15th century. Around 1600, eight earthquakes each with magnitudes over 4.3 occurred in both of the two regions. The magnitude of the strongest shock in the south region is 6.7, that in the north region is 7.5. The second high tide occurred at the early 20th century. Among the 18 earthquakes occurred in the south region, one was of magnitude 7.3; whilst only two earthquakes with magnitudes 6.1 and 5.5 respectively occurred in the north region. Further, medium to strong earthquakes never occurred since 1942. Whether this is the “mitigation effect” of strong shocks, or a big earthquake is brewing in the north region is worth intensive study.

Seismic waveform modeling over cloud

NASA Astrophysics Data System (ADS)

Luo, Cong; Friederich, Wolfgang

2016-04-01

With the fast growing computational technologies, numerical simulation of seismic wave propagation achieved huge successes. Obtaining the synthetic waveforms through numerical simulation receives an increasing amount of attention from seismologists. However, computational seismology is a data-intensive research field, and the numerical packages usually come with a steep learning curve. Users are expected to master considerable amount of computer knowledge and data processing skills. Training users to use the numerical packages, correctly access and utilize the computational resources is a troubled task. In addition to that, accessing to HPC is also a common difficulty for many users. To solve these problems, a cloud based solution dedicated on shallow seismic waveform modeling has been developed with the state-of-the-art web technologies. It is a web platform integrating both software and hardware with multilayer architecture: a well designed SQL database serves as the data layer, HPC and dedicated pipeline for it is the business layer. Through this platform, users will no longer need to compile and manipulate various packages on the local machine within local network to perform a simulation. By providing users professional access to the computational code through its interfaces and delivering our computational resources to the users over cloud, users can customize the simulation at expert-level, submit and run the job through it.

Seismic hazard assessment of Syria using seismicity, DEM, slope, active tectonic and GIS

NASA Astrophysics Data System (ADS)

Ahmad, Raed; Adris, Ahmad; Singh, Ramesh

2016-07-01

In the present work, we discuss the use of an integrated remote sensing and Geographical Information System (GIS) techniques for evaluation of seismic hazard areas in Syria. The present study is the first time effort to create seismic hazard map with the help of GIS. In the proposed approach, we have used Aster satellite data, digital elevation data (30 m resolution), earthquake data, and active tectonic maps. Many important factors for evaluation of seismic hazard were identified and corresponding thematic data layers (past earthquake epicenters, active faults, digital elevation model, and slope) were generated. A numerical rating scheme has been developed for spatial data analysis using GIS to identify ranking of parameters to be included in the evaluation of seismic hazard. The resulting earthquake potential map delineates the area into different relative susceptibility classes: high, moderate, low and very low. The potential earthquake map was validated by correlating the obtained different classes with the local probability that produced using conventional analysis of observed earthquakes. Using earthquake data of Syria and the peak ground acceleration (PGA) data is introduced to the model to develop final seismic hazard map based on Gutenberg-Richter (a and b values) parameters and using the concepts of local probability and recurrence time. The application of the proposed technique in Syrian region indicates that this method provides good estimate of seismic hazard map compared to those developed from traditional techniques (Deterministic (DSHA) and probabilistic seismic hazard (PSHA). For the first time we have used numerous parameters using remote sensing and GIS in preparation of seismic hazard map which is found to be very realistic.

Monitoring and Characterizing the Geysering and Seismic Activity at the Lusi Mud Eruption Site, East Java, Indonesia

NASA Astrophysics Data System (ADS)

Karyono, Karyono; Obermann, Anne; Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Abdurrokhim, Abdurrokhim; Masturyono, Masturyono; Hadi, Soffian

2016-04-01

The Lusi eruption began on May 29, 2006 in the northeast of Java Island, Indonesia, and to date is still active. Lusi is a newborn sedimentary-hosted hydrothermal system characterized by continuous expulsion of liquefied mud and breccias and geysering activity. Lusi is located upon the Watukosek fault system, a left lateral wrench system connecting the volcanic arc and the bakarc basin. This fault system is still periodically reactivated as shown by field data. In the framework of the Lusi Lab project (ERC grant n° 308126) we conducted several types of monitoring. Based on camera observations, we characterized the Lusi erupting activity by four main behaviors occurring cyclically: (1) Regular activity, which consists in the constant emission of water and mud breccias (i.e. viscous mud containing clay, silt, sand and clasts) associated with the constant expulsion of gas (mainly aqueous vapor with minor amounts of CO2 and CH4) (2) Geysering phase with intense bubbling, consisting in reduced vapor emission and more powerful bursting events that do not seem to have a regular pattern. (3) Geysering phase with intense vapor and degassing discharge and a typically dense plume that propagates up to 100 m height. (4) Quiescent phase marking the end of the geysering activity (and the observed cycle) with no gas emissions or bursts observed. To investigate the possible seismic activity beneath Lusi and the mechanisms controlling the Lusi pulsating behaviour, we deployed a network of 5 seismic stations and a HD camera around the Lusi crater. We characterize the observed types of seismic activity as tremor and volcano-tectonic events. Lusi tremor events occur in 5-10 Hz frequency band, while volcano tectonic events are abundant in the high frequencies range from 5 Hz until 25 Hz. We coupled the seismic monitoring with the images collected with the HD camera to study the correlation between the seismic tremor and the different phases of the geysering activity. Key words: Lusi

Seismic Wave Propagation

NASA Astrophysics Data System (ADS)

Wu, Xianyun; Wu, Ru-Shan

A seismic wave is a mechanical disturbance or energy packet that can propagate from point to point in the Earth. Seismic waves can be generated by a sudden release of energy such as an earthquake, volcanic eruption, or chemical explosion. There are several types of seismic waves, often classified as body waves, which propagate through the volume of the Earth, and surface waves, which travel along the surface of the Earth. Compressional and shear waves are the two main types of body wave and Rayleigh and Love waves are the most common forms of surface wave.

Seismic seiches

USGS Publications Warehouse

McGarr, Arthur; Gupta, Harsh K.

2011-01-01

Seismic seiche is a term first used by Kvale (1955) to discuss oscillations of lake levels in Norway and England caused by the Assam earthquake of August 15, 1950. This definition has since been generalized to apply to standing waves set up in closed, or partially closed, bodies of water including rivers, shipping channels, lakes, swimming pools and tanks due to the passage of seismic waves from an earthquake.

Landslide seismic magnitude

NASA Astrophysics Data System (ADS)

Lin, C. H.; Jan, J. C.; Pu, H. C.; Tu, Y.; Chen, C. C.; Wu, Y. M.

2015-11-01

Landslides have become one of the most deadly natural disasters on earth, not only due to a significant increase in extreme climate change caused by global warming, but also rapid economic development in topographic relief areas. How to detect landslides using a real-time system has become an important question for reducing possible landslide impacts on human society. However, traditional detection of landslides, either through direct surveys in the field or remote sensing images obtained via aircraft or satellites, is highly time consuming. Here we analyze very long period seismic signals (20-50 s) generated by large landslides such as Typhoon Morakot, which passed though Taiwan in August 2009. In addition to successfully locating 109 large landslides, we define landslide seismic magnitude based on an empirical formula: Lm = log ⁡ (A) + 0.55 log ⁡ (Δ) + 2.44, where A is the maximum displacement (μm) recorded at one seismic station and Δ is its distance (km) from the landslide. We conclude that both the location and seismic magnitude of large landslides can be rapidly estimated from broadband seismic networks for both academic and applied purposes, similar to earthquake monitoring. We suggest a real-time algorithm be set up for routine monitoring of landslides in places where they pose a frequent threat.

Bighorns Arch Seismic Experiment (BASE): Amplitude Response to Different Seismic Charge Configurations

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

Harder, S. H., Killer, K. C., Worthington, L. L., Snelson, C. M.

2010-09-02

Contrary to popular belief, charge weight is not the most important engineering parameter determining the seismic amplitudes generated by a shot. The scientific literature has long claimed that the relationship, A ~R2L1/2, where A is the seismic amplitude generated by a shot, R is the radius of the seismic charge and L is the length of that charge, holds. Assuming the coupling to the formation and the pressure generated by the explosive are constants, this relationship implies that the one should be able to increase the charge radius while decreasing the charge length and obtain more seismic amplitude with lessmore » charge weight. This has significant implications for the economics of lithospheric seismic shots, because shallower holes and small charge sizes decrease cost. During the Bighorns Array Seismic Experiment (BASE) conducted in the summer of 2010, 24 shots with charge sizes ranging from 110 to 900 kg and drill hole diameters of 300 and 450 mm were detonated and recorded by an array of up to 2000 single-channel Texan seismographs. Maximum source-receiver offset of 300 km. Five of these shots were located within a one-acre square in an effort to eliminate coupling effects due to differing geological formations. We present a quantitative comparison of the data from these five shots to experimentally test the equation above.« less

Continuous Seismic Threshold Monitoring

DTIC Science & Technology

1992-05-31

Continuous threshold monitoring is a technique for using a seismic network to monitor a geographical area continuously in time. The method provides...area. Two approaches are presented. Site-specific monitoring: By focusing a seismic network on a specific target site, continuous threshold monitoring...recorded events at the site. We define the threshold trace for the network as the continuous time trace of computed upper magnitude limits of seismic

Atomoxetine administration combined with intensive speech therapy for post-stroke aphasia: evaluation by a novel SPECT method.

PubMed

Yamada, Naoki; Kakuda, Wataru; Yamamoto, Kazuma; Momosaki, Ryo; Abo, Masahiro

2016-09-01

We clarified the safety, feasibility, and efficacy of atomoxetine administration combined with intensive speech therapy (ST) for patients with post-stroke aphasia. In addition, we investigated the effect of atomoxetine treatment on neural activity of surrounding lesioned brain areas. Four adult patients with motor-dominant aphasia and a history of left hemispheric stroke were studied. We have registered on the clinical trials database (ID: JMA-IIA00215). Daily atomoxetine administration of 40 mg was initiated two weeks before admission and raised to 80 mg 1 week before admission. During the subsequent 13-day hospitalization, administration of atomoxetine was raised to 120 mg and daily intensive ST (120 min/day, one-on-one training) was provided. Language function was assessed using the Japanese version of The Western Aphasia Battery (WAB) and the Token test two weeks prior to admission, on the day of admission, and at discharge. At two weeks prior to admission and at discharge, each patient's cortical blood flow was measured using (123)I-IMP-single photon emission computed tomography (SPECT). This protocol was successfully completed by all patients without any adverse effects. Four patients showed improved language function with the median of the Token Test increasing from 141 to 149, and the repetition score of WAB increasing from 88 to 99. In addition, cortical blood flow surrounding lesioned brain areas was found to increase following intervention in all patients. Atomoxetine administration and intensive ST were safe and feasible for post-stroke aphasia, suggesting their potential usefulness in the treatment of this patient population.

Evaluation Seismicity west of block-lut for Deterministic Seismic Hazard Assessment of Shahdad ,Iran

NASA Astrophysics Data System (ADS)

Ney, B.; Askari, M.

2009-04-01

Evaluation Seismicity west of block-lut for Deterministic Seismic Hazard Assessment of Shahdad ,Iran Behnoosh Neyestani , Mina Askari Students of Science and Research University,Iran. Seismic Hazard Assessment has been done for Shahdad city in this study , and four maps (Kerman-Bam-Nakhil Ab-Allah Abad) has been prepared to indicate the Deterministic estimate of Peak Ground Acceleration (PGA) in this area. Deterministic Seismic Hazard Assessment has been preformed for a region in eastern Iran (Shahdad) based on the available geological, seismological and geophysical information and seismic zoning map of region has been constructed. For this assessment first Seimotectonic map of study region in a radius of 100km is prepared using geological maps, distribution of historical and instrumental earthquake data and focal mechanism solutions it is used as the base map for delineation of potential seismic sources. After that minimum distance, for every seismic sources until site (Shahdad) and maximum magnitude for each source have been determined. In Shahdad ,according to results, peak ground acceleration using the Yoshimitsu Fukushima &Teiji Tanaka'1990 attenuation relationship is estimated to be 0.58 g, that is related to the movement of nayband fault with distance 2.4km of the site and maximum magnitude Ms=7.5.

TexNet seismic network performance and reported seismicity in West Texas

NASA Astrophysics Data System (ADS)

Savvaidis, A.; Lomax, A.; Aiken, C.; Young, B.; Huang, D.; Hennings, P.

2017-12-01

In 2015, the Texas State Legislature began funding the Texas Seismological Network (TexNet). Since then, 22 new permanent broadband three-component seismic stations have been added to 17 existing stations operated by various networks [US, N4, IM]. These stations together with 4 auxiliary stations, i.e. long term deployments of 20 sec portable stations, were deployed to provide a baseline of Texas seismicity. As soon as the deployment of the new permanent stations took place in West Texas, TexNet was able to detect and characterize smaller magnitude events than was possible before, i.e. M < 2.5. As a consequence, additional portable stations were installed in the area in order to better map the current seismicity level. During the different stages of station deployment, we monitored the seismic network performance and its ability to detect earthquake activity. We found that a key limitation to the network performance is industrial noise in West Texas. For example, during daytime, phase picking and event detection rates are much lower than during nighttime at noisy sites. Regarding seismicity, the high density portable station deployment close to the earthquake activity minimizes hypocentral location uncertainties. In addition, we examined the effects of different crustal velocity models in the area of study on hypocentral location using the local network first arrivals. Considerable differences in location were obtained, which shows the importance of local networks and/or reliable crustal velocity models for West Texas. Given the levels of seismicity in West Texas, a plan to continuously monitor the study area is under development.

Historical seismicity, palaeoseismicity and seismic risk in Western Macedonia, Northern Greece

NASA Astrophysics Data System (ADS)

Stiros, Stathis C.

Western Macedonia, Northern Greece, was a seismically quiescent region for one or more centuries, and was regarded as a nearly aseismic, rigid block inside a broad zone of distributed continental deformation and faulting, and a region of minimum seismic risk. Consequently, the May 13, 1995 destructive earthquake ( M = 6.6) which hit this assumed aseismic zone was a surprise for scientists, government and population. However, historical and archaeoseismic evidence, as well as coastal change data indicate that the assumed aseismic region of Western Macedonia has been affected in the last 2,000 years by at least seven, and possibly nine destructive earthquakes. One of these earthquakes occurred in circa 1700, and probably had the same epicentre with, but higher magnitude than the 1995 shock. The earthquake in circa 1700 is deduced from historical data and is modelled on the base of a swarm of church repairs which is explained as post-seismic recovery of the broader Kozani area: except for certain well known cases of towns or areas in which religious privileges were granted, large scale repairs or reconstruction of churches during the Ottoman period were possible only after Sultan's permissions, usually following earthquakes and other calamities. It can hence be concluded that some, at least, of the apparently aseismic regions inside broad zones of distributed seismicity are hit by stronger shocks, but with longer (200 years or more) recurrence intervals than their adjacent zones. Consequently, the seismic risk of the apparently aseismic regions is certainly not low, especially since relatively long periods of seismic quiescence lead to constructions vulnerable to earthquakes.

Investigating the Concept of Using Airglow Measurements to Detect Seismicity on Venus

NASA Astrophysics Data System (ADS)

Kenda, Balthasar; Lognonné, Philippe; Komjathy, Attila; Banerdt, Bruce; Cutts, Jim; Soret, Lauriane; Jackson, Jennifer

2017-04-01

The internal structure and dynamics of Venus are poorly constrained by observations. Seismology is among the best candidates for probing the interior of the planet, and it would also provide indispensable information about the present-day tectonic activity of Venus. However, due to the extreme surface temperatures, a long-duration seismic station seems to be beyond the technical capabilities achievable today. Nonetheless, the thick and dense atmosphere, which strongly couples with the ground, gives rise to the attractive option of detecting seismic waves from quakes within the atmosphere itself (Garcia et al., 2005, Lognonné and Johnson, 2007, 2015) using in-situ or remote-sensing measurements (Cutts et al., 2015). Here, we consider the bright airglow emission of O2 at 1.27 μm on the nightside of Venus and we model the intensity fluctuations induced by Venus quakes. Synthetic seismograms in the airglow layer, at 90-120 km altitude, are computed using normal-mode summation for a fully coupled solid planet-atmosphere system, including the effects of molecular relaxation of CO2 and a radiative boundary condition at the top of the atmosphere (Lognonné et al., 2016). The corresponding variations in the volumetric emission rate, calculated for realistic background intensities of the airglow (Soret et al., 2012), are then vertically integrated to reproduce the signals that would be seen from orbit. The noise level of existing airglow cameras suggests that the Rayleigh waves generated by quakes of magnitude 5 and above occurring on the nightside of the planet may be detectable up to about 60° in epicentral distance. A significant advantage of this technique is that a single orbiting camera may be sufficient to serve the role of a seismic network. By identifying and tracking the waves it is indeed possible to locate the source, estimate the magnitude and measure the horizontal surface-wave propagation velocities on Venus. In particular, it is expected that this would

Apollo 14 and 16 Active Seismic Experiments, and Apollo 17 Lunar Seismic Profiling

NASA Technical Reports Server (NTRS)

1976-01-01

Seismic refraction experiments were conducted on the moon by Apollo astronauts during missions 14, 16, and 17. Seismic velocities of 104, 108, 92, 114 and 100 m/sec were inferred for the lunar regolith at the Apollo 12, 14, 15, 16, and 17 landing sites, respectively. These data indicate that fragmentation and comminution caused by meteoroid impacts has produced a layer of remarkably uniform seismic properties moonwide. Brecciation and high porosity are the probable causes of the very low velocities observed in the lunar regolith. Apollo 17 seismic data revealed that the seismic velocity increases very rapidly with depth to 4.7 km/sec at a depth of 1.4 km. Such a large velocity change is suggestive of compositional and textural changes and is compatible with a model of fractured basaltic flows overlying anorthositic breccias. 'Thermal' moonquakes were also detected at the Apollo 17 site, becoming increasingly frequent after sunrise and reaching a maximum at sunset. The source of these quakes could possibly be landsliding.

Pore fluid pressure and the seismic cycle

NASA Astrophysics Data System (ADS)

French, M. E.; Zhu, W.; Hirth, G.; Belzer, B.

2017-12-01

In the brittle crust, the critical shear stress required for fault slip decreases with increasing pore fluid pressures according to the effective stress criterion. As a result, higher pore fluid pressures are thought to promote fault slip and seismogenesis, consistent with observations that increasing fluid pressure as a result of wastewater injection is correlated with increased seismicity. On the other hand, elevated pore fluid pressure is also proposed to promote slow stable failure rather than seismicity along some fault zones, including during slow slip in subduction zones. Here we review recent experimental evidence for the roles that pore fluid pressure and the effective stress play in controlling fault slip behavior. Using two sets of experiments on serpentine fault gouge, we show that increasing fluid pressure does decrease the shear stress for reactivation under brittle conditions. However, under semi-brittle conditions as expected near the base of the seismogenic zone, high pore fluid pressures are much less effective at reducing the shear stress of reactivation even though deformation is localized and frictional. We use an additional study on serpentinite to show that cohesive fault rocks, potentially the product of healing and cementation, experience an increase in fracture energy during faulting as fluid pressures approach lithostatic, which can lead to more stable failure. Structural observations show that the increased fracture energy is associated with a greater intensity of transgranular fracturing and delocalization of deformation. Experiments on several lithologies indicate that the stabilizing effect of fluid pressure occurs independent of rock composition and hydraulic properties. Thus, high pore fluid pressures have the potential to either enhance seismicity or promote stable faulting depending on pressure, temperature, and fluid pressure conditions. Together, the results of these studies indicate that pore fluid pressure promotes

Investigating the Evolution of Southern California Salt Marshes: A Facies Model to Understand the Influence of Seismic Events on Environmental Resiliency and Sustainability

NASA Astrophysics Data System (ADS)

Aranda, A. N.; Carlin, J. A.; Rhodes, B. P.; Kirby, M.

2016-02-01

Only 10-20% of the US Pacific coast is estimated to be suitable for marsh development. In southern California specifically, marshes are disappearing ecosystems due to high population and urbanization. The future environmental impacts from climate change on these ecosystems are complicated not only by anthropogenic influences, but also by seismic activity in the region. In general, marsh evolution and response to seismic activity has yet to be fully explored in southern California. This study aims to develop a sediment facies model for salt marsh evolution in southern California by utilizing the salt marshes of the Seal Beach Wetlands (SBW). The SBW is an ideal location to develop the facies model because it straddles the active Newport-Inglewood Fault Zone. We collected sediment cores from the SBW that underwent a variety of sedimentological and geochemical analyses including grain size, X-Ray Fluorescence core scanning, magnetic susceptibility, and loss-on-ignition.. The results show a facies model consisting of sequences of marsh accretion punctuated by seismic events. These seismic events caused the marsh to subside, effectively re-setting marsh development from peat generation at a vegetated marsh state, to subtidal to intertidal mud deposition. The model also allowed us to qualify and quantify marsh recovery as inferred from event intensity, where what we perceived as more intense events resulted in more significant ecosystem disturbances and longer recovery times. Understanding this interplay between seismic activity and marsh development highlights the fragile nature of these ecosystems to climate change and sea level rise, as these stresses will only become amplified by seismic events.

Reprocessing Seismic Data - Using Wits Seismic Exploration Data to Image the Karoo Basin

NASA Astrophysics Data System (ADS)

Webb, S. J.; Scheiber-Enslin, S. E.; Manzi, M. S.

2016-12-01

During the heyday of seismic exploration of the Witwatersrand Basin, Anglo American's Gold Division acquired several thousand kilometres of Vibroseis reflection seismic data. These data, acquired from 1983-1994, were collected with the goal of finding extensions to the Witwatersrand Basin. In a prescient move, over 500 line kilometres were collected at 16 s two way travel time (TWT), extending to depths of 50 -70 km and have provided critical insight into the formation of the Kaapvaal Craton. In addition to these deep seismic lines, Anglo American acquired an extensive network of heretofore unpublished seismic lines that were collected at 6 sec TWT extending well beyond the known limits of the Witwatersrand Basin. The South African government as part of the national geophysical program in the late 1980s acquired six research reflection seismic lines in varied geological settings accruing another 700 km of data. Many of these data are now hosted at the University of the Witwatersrand's newly established Seismic Research Centre and represent unprecedented coverage and research opportunities. With recent global interest in shale gas, attention focused on the Karoo Basin in South Africa. Early exploration seismic data acquired by Soekor in the 1970s has been lost; however, digitized paper records indicate clear reflection targets. Here we examine one of the AngloGold seismic lines that was acquired in the middle of the Karoo Basin just south of Trompsburg extending to the southeast towards Molteno. This 150 km long line crosses the edge of the Kaapvaal Craton and shows clear reflectors throughout the Karoo Basin. These include the well-defined base of the Karoo and a number of dolerite sills within it. Nearby gas escape structures have been identified on surface and it is likely that several disruptions along this line are related to these or to dykes associated with the sills.

New insights on the seismic hazard in the Balkans inferred from GPS

NASA Astrophysics Data System (ADS)

D'Agostino, Nicola; Métois, Marianne; Avallone, Antonio; Chamot-Rooke, Nicolas

2014-05-01

The Balkans region sits at the transition between stable Eurasia and highly straining continental Eastern Mediterranean, resulting in a widespread seismicity and high seismic hazard. Because of intensive human and economic development over the last decades, the vulnerability has increased in the region faster than the progress in seismic hazard assessments. Opposite to the relatively good understanding of the seismicity in plate boundaries contexts, the seismic hazard is poorly known in the regions of distributed continental deformation like the Balkan region and is often underestimated (England and Jackson, 2011). Current seismic hazard assessments are based on the historical and instrumental catalogues. However, the completeness interval of the historical data bases may be below the average recurrence of individual seismogenic structures. In addition, relatively sparse seismological networks in the region and limited cross-border seismic data exchanges cast doubts in seismotectonic interpretation and challenge our understanding of seismic and geodynamic processes. This results in a inhomogeneous knowledge of the seismic hazard of the region to date. Geodetic measurements have the capability to contribute to seismic hazard by mapping the field of current active deformation and translating it into estimates of the seismogenic potential. With simple assumptions, measurements of crustal deformation can be translated in estimates of the average frequency and magnitude of the largest events and assessments of the aseismic deformation. GPS networks in the Balkans have been growing during the last few years mainly for civilian application (e.g. Cadastral plan, telecommunications), but opening new opportunities to quantify the present-day rates of crustal deformation. Here we present the initial results of GEOSAB (Geodetic Estimate of Strain Accumulation over Balkans), an AXA-Research-Fund supported project devoted to the estimation of crustal deformation and the

Seismic risk perception in Italy

NASA Astrophysics Data System (ADS)

Crescimbene, Massimo; La Longa, Federica; Camassi, Romano; Pino, Nicola Alessandro; Peruzza, Laura

2014-05-01

Risk perception is a fundamental element in the definition and the adoption of preventive counter-measures. In order to develop effective information and risk communication strategies, the perception of risks and the influencing factors should be known. This paper presents results of a survey on seismic risk perception in Italy conducted from January 2013 to present . The research design combines a psychometric and a cultural theoretic approach. More than 7,000 on-line tests have been compiled. The data collected show that in Italy seismic risk perception is strongly underestimated; 86 on 100 Italian citizens, living in the most dangerous zone (namely Zone 1), do not have a correct perception of seismic hazard. From these observations we deem that extremely urgent measures are required in Italy to reach an effective way to communicate seismic risk. Finally, the research presents a comparison between groups on seismic risk perception: a group involved in campaigns of information and education on seismic risk and a control group.

Seismic data compression speeds exploration projects

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

Galibert, P.Y.

As part of an ongoing commitment to ensure industry-wide distribution of its revolutionary seismic data compression technology, Chevron Petroleum Technology Co. (CPTC) has entered into licensing agreements with Compagnie Generale de Geophysique (CGG) and other seismic contractors for use of its software in oil and gas exploration programs. CPTC expects use of the technology to be far-reaching to all of its industry partners involved in seismic data collection, processing, analysis and storage. Here, CGG--one of the world`s leading seismic acquisition and processing companies--talks about its success in applying the new methodology to replace full on-board seismic processing. Chevron`s technology ismore » already being applied on large off-shore 3-D seismic surveys. Worldwide, CGG has acquired more than 80,000 km of seismic data using the data compression technology.« less

Time-reversibility in seismic sequences: Application to the seismicity of Mexican subduction zone

NASA Astrophysics Data System (ADS)

Telesca, L.; Flores-Márquez, E. L.; Ramírez-Rojas, A.

2018-02-01

In this paper we investigate the time-reversibility of series associated with the seismicity of five seismic areas of the subduction zone beneath the Southwest Pacific Mexican coast, applying the horizontal visibility graph method to the series of earthquake magnitudes, interevent times, interdistances and magnitude increments. We applied the Kullback-Leibler divergence D that is a metric for quantifying the degree of time-irreversibility in time series. Our findings suggest that among the five seismic areas, Jalisco-Colima is characterized by time-reversibility in all the four seismic series. Our results are consistent with the peculiar seismo-tectonic characteristics of Jalisco-Colima, which is the closest to the Middle American Trench and belongs to the Mexican volcanic arc.

The influence of regional geological settings on the seismic hazard level in copper mines in the Legnica-Głogów Copper Belt Area (Poland)

NASA Astrophysics Data System (ADS)

Burtan, Zbigniew

2017-11-01

The current level of rockburst hazard in copper mines of the (LGOM) Legnica- Głogów Copper Belt Area is mostly the consequence of mining-induced seismicity, whilst the majority of rockbursting events registered to date were caused by high-energy tremors. The analysis of seismic readings in recent years reveals that the highest seismic activity among the copper mines in the LGOM is registered in the mine Rudna. This study investigates the seismic activity in the rock strata in the Rudna mine fields over the years 2006-2015. Of particular interest are the key seismicity parameters: the number of registered seismic events, the total energy emissions, the energy index. It appears that varied seismic activity in the area may be the function of several variables: effective mining thickness, the thickness of burst-prone strata and tectonic intensity. The results support and corroborate the view that principal factors influencing the actual seismic hazard level are regional geological conditions in the copper mines within the Legnica-Głogów Copper Belt Area.

Seismic fragility analysis of typical pre-1990 bridges due to near- and far-field ground motions

NASA Astrophysics Data System (ADS)

Mosleh, Araliya; Razzaghi, Mehran S.; Jara, José; Varum, Humberto

2016-03-01

Bridge damages during the past earthquakes caused several physical and economic impacts to transportation systems. Many of the existing bridges in earthquake prone areas are pre-1990 bridges and were designed with out of date regulation codes. The occurrences of strong motions in different parts of the world show every year the vulnerability of these structures. Nonlinear dynamic time history analyses were conducted to assess the seismic vulnerability of typical pre-1990 bridges. A family of existing concrete bridge representative of the most common bridges in the highway system in Iran is studied. The seismic demand consists in a set of far-field and near-field strong motions to evaluate the likelihood of exceeding the seismic capacity of the mentioned bridges. The peak ground accelerations (PGAs) were scaled and applied incrementally to the 3D models to evaluate the seismic performance of the bridges. The superstructure was assumed to remain elastic and the nonlinear behavior in piers was modeled by assigning plastic hinges in columns. In this study the displacement ductility and the PGA are selected as a seismic performance indicator and intensity measure, respectively. The results show that pre-1990 bridges subjected to near-fault ground motions reach minor and moderate damage states.

Seismicity within a propagating ice shelf rift: the relationship between icequake locations and ice shelf structure

USGS Publications Warehouse

Heeszel, David S.; Fricker, Helen A.; Bassis, Jeremy N.; O'Neel, Shad; Walter, Fabian

2014-01-01

Iceberg calving is a dominant mass loss mechanism for Antarctic ice shelves, second only to basal melting. An important known process involved in calving is the initiation and propagation of through-penetrating fractures called rifts; however, the mechanisms controlling rift propagation remain poorly understood. To investigate the mechanics of ice-shelf rifting, we analyzed seismicity associated with a propagating rift tip on the Amery Ice Shelf, using data collected during the Austral summers of 2004-2007. We investigated seismicity associated with fracture propagation using a suite of passive seismological techniques including icequake locations, back projection, and moment tensor inversion. We confirm previous results that show that seismicity is characterized by periods of relative quiescence punctuated by swarms of intense seismicity of one to three hours. However, even during periods of quiescence, we find significant seismic deformation around the rift tip. Moment tensors, calculated for a subset of the largest icequakes (MW > -2.0) located near the rift tip, show steeply dipping fault planes, horizontal or shallowly plunging stress orientations, and often have a significant volumetric component. They also reveal that much of the observed seismicity is limited to the upper 50 m of the ice shelf. This suggests a complex system of deformation that involves the propagating rift, the region behind the rift tip, and a system of rift-transverse crevasses. Small-scale variations in the mechanical structure of the ice shelf, especially rift-transverse crevasses and accreted marine ice, play an important role in modulating the rate and location of seismicity associated with propagating ice shelf rifts.

Application of a time probabilistic approach to seismic landslide hazard estimates in Iran

NASA Astrophysics Data System (ADS)

Rajabi, A. M.; Del Gaudio, V.; Capolongo, D.; Khamehchiyan, M.; Mahdavifar, M. R.

2009-04-01

Iran is a country located in a tectonic active belt and is prone to earthquake and related phenomena. In the recent years, several earthquakes caused many fatalities and damages to facilities, e.g. the Manjil (1990), Avaj (2002), Bam (2003) and Firuzabad-e-Kojur (2004) earthquakes. These earthquakes generated many landslides. For instance, catastrophic landslides triggered by the Manjil Earthquake (Ms = 7.7) in 1990 buried the village of Fatalak, killed more than 130 peoples and cut many important road and other lifelines, resulting in major economic disruption. In general, earthquakes in Iran have been concentrated in two major zones with different seismicity characteristics: one is the region of Alborz and Central Iran and the other is the Zagros Orogenic Belt. Understanding where seismically induced landslides are most likely to occur is crucial in reducing property damage and loss of life in future earthquakes. For this purpose a time probabilistic approach for earthquake-induced landslide hazard at regional scale, proposed by Del Gaudio et al. (2003), has been applied to the whole Iranian territory to provide the basis of hazard estimates. This method consists in evaluating the recurrence of seismically induced slope failure conditions inferred from the Newmark's model. First, by adopting Arias Intensity to quantify seismic shaking and using different Arias attenuation relations for Alborz - Central Iran and Zagros regions, well-established methods of seismic hazard assessment, based on the Cornell (1968) method, were employed to obtain the occurrence probabilities for different levels of seismic shaking in a time interval of interest (50 year). Then, following Jibson (1998), empirical formulae specifically developed for Alborz - Central Iran and Zagros, were used to represent, according to the Newmark's model, the relation linking Newmark's displacement Dn to Arias intensity Ia and to slope critical acceleration ac. These formulae were employed to evaluate

Applying the seismic interferometry method to vertical seismic profile data using tunnel excavation noise as source

NASA Astrophysics Data System (ADS)

Jurado, Maria Jose; Teixido, Teresa; Martin, Elena; Segarra, Miguel; Segura, Carlos

2013-04-01

In the frame of the research conducted to develop efficient strategies for investigation of rock properties and fluids ahead of tunnel excavations the seismic interferometry method was applied to analyze the data acquired in boreholes instrumented with geophone strings. The results obtained confirmed that seismic interferometry provided an improved resolution of petrophysical properties to identify heterogeneities and geological structures ahead of the excavation. These features are beyond the resolution of other conventional geophysical methods but can be the cause severe problems in the excavation of tunnels. Geophone strings were used to record different types of seismic noise generated at the tunnel head during excavation with a tunnelling machine and also during the placement of the rings covering the tunnel excavation. In this study we show how tunnel construction activities have been characterized as source of seismic signal and used in our research as the seismic source signal for generating a 3D reflection seismic survey. The data was recorded in vertical water filled borehole with a borehole seismic string at a distance of 60 m from the tunnel trace. A reference pilot signal was obtained from seismograms acquired close the tunnel face excavation in order to obtain best signal-to-noise ratio to be used in the interferometry processing (Poletto et al., 2010). The seismic interferometry method (Claerbout 1968) was successfully applied to image the subsurface geological structure using the seismic wave field generated by tunneling (tunnelling machine and construction activities) recorded with geophone strings. This technique was applied simulating virtual shot records related to the number of receivers in the borehole with the seismic transmitted events, and processing the data as a reflection seismic survey. The pseudo reflective wave field was obtained by cross-correlation of the transmitted wave data. We applied the relationship between the transmission

Short-Period Seismic Noise in Vorkuta (Russia)

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

Kishkina, S B; Spivak, A A; Sweeney, J J

Cultural development of new subpolar areas of Russia is associated with a need for detailed seismic research, including both mapping of regional seismicity and seismic monitoring of specific mining enterprises. Of special interest are the northern territories of European Russia, including shelves of the Kara and Barents Seas, Yamal Peninsula, and the Timan-Pechora region. Continuous seismic studies of these territories are important now because there is insufficient seismological knowledge of the area and an absence of systematic data on the seismicity of the region. Another task of current interest is the necessity to consider the seismic environment in the design,more » construction, and operation of natural gas extracting enterprises such as the construction of the North European Gas Pipeline. Issues of scientific importance for seismic studies in the region are the complex geodynamical setting, the presence of permafrost, and the complex tectonic structure. In particular, the Uralian Orogene (Fig. 1) strongly affects the propagation of seismic waves. The existing subpolar seismic stations [APA (67,57{sup o}N; 33,40{sup o}E), LVZ (67,90{sup o}N; 34,65{sup o}E), and NRIL (69,50{sup o}N; 88,40{sup o}E)] do not cover the extensive area between the Pechora and Ob Rivers (Fig. 1). Thus seismic observations in the Vorkuta area, which lies within the area of concern, represent a special interest. Continuous recording at a seismic station near the city of Vorkuta (67,50{sup o}N; 64,11{sup o}E) [1] has been conducted since 2005 for the purpose of regional seismic monitoring and, more specifically, detection of seismic signals caused by local mining enterprises. Current surveys of local seismic noise [7,8,9,11], are particularly aimed at a technical survey for the suitability of the site for installation of a small-aperture seismic array, which would include 10-12 recording instruments, with the Vorkuta seismic station as the central element. When constructed, this

Seismic source characterization for the 2014 update of the U.S. National Seismic Hazard Model

USGS Publications Warehouse

Moschetti, Morgan P.; Powers, Peter; Petersen, Mark D.; Boyd, Oliver; Chen, Rui; Field, Edward H.; Frankel, Arthur; Haller, Kathleen; Harmsen, Stephen; Mueller, Charles S.; Wheeler, Russell; Zeng, Yuehua

2015-01-01

We present the updated seismic source characterization (SSC) for the 2014 update of the National Seismic Hazard Model (NSHM) for the conterminous United States. Construction of the seismic source models employs the methodology that was developed for the 1996 NSHM but includes new and updated data, data types, source models, and source parameters that reflect the current state of knowledge of earthquake occurrence and state of practice for seismic hazard analyses. We review the SSC parameterization and describe the methods used to estimate earthquake rates, magnitudes, locations, and geometries for all seismic source models, with an emphasis on new source model components. We highlight the effects that two new model components—incorporation of slip rates from combined geodetic-geologic inversions and the incorporation of adaptively smoothed seismicity models—have on probabilistic ground motions, because these sources span multiple regions of the conterminous United States and provide important additional epistemic uncertainty for the 2014 NSHM.

Seismic signal processing on heterogeneous supercomputers

NASA Astrophysics Data System (ADS)

Gokhberg, Alexey; Ermert, Laura; Fichtner, Andreas

2015-04-01

The processing of seismic signals - including the correlation of massive ambient noise data sets - represents an important part of a wide range of seismological applications. It is characterized by large data volumes as well as high computational input/output intensity. Development of efficient approaches towards seismic signal processing on emerging high performance computing systems is therefore essential. Heterogeneous supercomputing systems introduced in the recent years provide numerous computing nodes interconnected via high throughput networks, every node containing a mix of processing elements of different architectures, like several sequential processor cores and one or a few graphical processing units (GPU) serving as accelerators. A typical representative of such computing systems is "Piz Daint", a supercomputer of the Cray XC 30 family operated by the Swiss National Supercomputing Center (CSCS), which we used in this research. Heterogeneous supercomputers provide an opportunity for manifold application performance increase and are more energy-efficient, however they have much higher hardware complexity and are therefore much more difficult to program. The programming effort may be substantially reduced by the introduction of modular libraries of software components that can be reused for a wide class of seismology applications. The ultimate goal of this research is design of a prototype for such library suitable for implementing various seismic signal processing applications on heterogeneous systems. As a representative use case we have chosen an ambient noise correlation application. Ambient noise interferometry has developed into one of the most powerful tools to image and monitor the Earth's interior. Future applications will require the extraction of increasingly small details from noise recordings. To meet this demand, more advanced correlation techniques combined with very large data volumes are needed. This poses new computational problems that

The Caucasus Seismic Network (CNET): Seismic Structure of the Greater and Lesser Caucasus

NASA Astrophysics Data System (ADS)

Sandvol, E. A.; Mackey, K. G.; Nabelek, J.; Yetermishli, G.; Godoladze, T.; Babayan, H.; Malovichko, A.

2017-12-01

The Greater Caucasus are a portion of the Alpine-Himalayan mountain belt that has undergone rapid uplift in the past 5 million years, thus serving as a unique natural laboratory to study the early stages of orogenesis. Relatively lower resolution seismic velocity models of this region show contradictory lateral variability. Furthermore, recent waveform modeling of seismograms has clearly demonstrated the presence of deep earthquakes (with a maximum hypocentral depth of 175 km) below the Greater Caucasus. The region has been largely unexplored in terms of the detailed uppermost mantle and crustal seismic structure due in part to the disparate data sets that have not yet been merged as well as key portions being sparsely instrumented. We have established collaborative agreements across the region. Building on these agreements we recently deployed a major multi-national seismic array across the Greater Caucasus to address fundamental questions about the nature of continental deformation in this poorly understood region. Our seismic array has two components: (1) a grid of stations spanning the entire Caucasus and (2) two seismic transects consisting of stations spaced at distances of less than 10 km that cross the Greater Caucasus. In addition to the temporary stations, we are working to integrate data from the national networks to produce high resolution images of the seismic structure. Using data from over 106 new seismic stations in Azerbaijan, Armenia, Russia, and Georgia, we hope to gain a better understanding of the recent uplift ( 5 Ma) of the Greater Caucasus and the nature of seismogenic deformation in the region.

Seismic Risk Perception compared with seismic Risk Factors

NASA Astrophysics Data System (ADS)

Crescimbene, Massimo; La Longa, Federica; Pessina, Vera; Pino, Nicola Alessandro; Peruzza, Laura

2016-04-01

The communication of natural hazards and their consequences is one of the more relevant ethical issues faced by scientists. In the last years, social studies have provided evidence that risk communication is strongly influenced by the risk perception of people. In order to develop effective information and risk communication strategies, the perception of risks and the influencing factors should be known. A theory that offers an integrative approach to understanding and explaining risk perception is still missing. To explain risk perception, it is necessary to consider several perspectives: social, psychological and cultural perspectives and their interactions. This paper presents the results of the CATI survey on seismic risk perception in Italy, conducted by INGV researchers on funding by the DPC. We built a questionnaire to assess seismic risk perception, with a particular attention to compare hazard, vulnerability and exposure perception with the real data of the same factors. The Seismic Risk Perception Questionnaire (SRP-Q) is designed by semantic differential method, using opposite terms on a Likert scale to seven points. The questionnaire allows to obtain the scores of five risk indicators: Hazard, Exposure, Vulnerability, People and Community, Earthquake Phenomenon. The questionnaire was administered by telephone interview (C.A.T.I.) on a statistical sample at national level of over 4,000 people, in the period January -February 2015. Results show that risk perception seems be underestimated for all indicators considered. In particular scores of seismic Vulnerability factor are extremely low compared with house information data of the respondents. Other data collected by the questionnaire regard Earthquake information level, Sources of information, Earthquake occurrence with respect to other natural hazards, participation at risk reduction activities and level of involvement. Research on risk perception aims to aid risk analysis and policy-making by

Properties of the seismic nucleation phase

USGS Publications Warehouse

Beroza, G.C.; Ellsworth, W.L.

1996-01-01

Near-source observations show that earthquakes begin abruptly at the P-wave arrival, but that this beginning is weak, with a low moment rate relative to the rest of the main shock. We term this initial phase of low moment rate the seismic nucleation phase. We have observed the seismic nucleation phase for a set of 48 earthquakes ranging in magnitude from 1.1-8.1. The size and duration of the seismic nucleation phase scale with the total seismic moment of the earthquake, suggesting that the process responsible for the seismic nucleation phase carries information about the eventual size of the earthquake. The seismic nucleation phase is characteristically followed by quadratic growth in the moment rate, consistent with self-similar rupture at constant stress drop. In this paper we quantify the properties of the seismic nucleation phase and offer several possible explanations for it.

Decay of Hurricanes Tracked by Dense Seismic Array

NASA Astrophysics Data System (ADS)

Lamontagne, A.; Tanimoto, T.

2014-12-01

Tropical cyclones (hurricanes and typhoons) are mostly atmospheric phenomena but they also generate significant ground motions in the solid earth when they become strong. If a dense seismological array existed along the path of a hurricane, we could learn about some processes near the hurricane eye and the change of its intensity through seismic data. We found a few cases of tropical cyclones that passed through the Transportable Array of Earthscope (TA) in the last four years. They provide some interesting time-evolving characteristics of hurricanes but in most cases seismic signals are too weak to gain any insight into the processes. The only exception we have found so far is Hurricane Isaac in 2012. Hurricane Isaac was mostly a tropical storm during its lifetime but it became a hurricane about 12 hours before the first landfall at the mouth of the Mississippi river at 0000 UTC August 29. The eye then went back over the ocean, but stayed near the coast, and made landfall again at 0800 UTC August 29. After this landfall, it went through the TA. This gave us an opportunity to study the decay of this hurricane based on seismic data. Our basic data are amplitude-distance plots for each 6-hour hurricane location. We confine our analysis to frequencies below 0.02 Hz because in higher frequency bands seismic waves were broader oceans, not necessarily near the hurricane eye. Right after the landfall, we found a sharp peak at about 75 km from the eye. This is most likely the location of the eyewall, where a strong ascending flow is known to exist. Over the next 12 hours, we see this peak deteriorate, which is undoubtedly related to the decay of the hurricane after landfall. The peak remained at the same location for these 12 hours and then in the following 18 hours started to move farther from the eye, to about 250 km. Therefore, we can monitor how the eyewall deteriorated over the 30 hours after landfall. The emphasis of this study will be on Hurricane Isaac but we will

Magnitude and location of historical earthquakes in Japan and implications for the 1855 Ansei Edo earthquake

USGS Publications Warehouse

Bakun, W.H.

2005-01-01

Japan Meteorological Agency (JMA) intensity assignments IJMA are used to derive intensity attenuation models suitable for estimating the location and an intensity magnitude Mjma for historical earthquakes in Japan. The intensity for shallow crustal earthquakes on Honshu is equal to -1.89 + 1.42MJMA - 0.00887?? h - 1.66log??h, where MJMA is the JMA magnitude, ??h = (??2 + h2)1/2, and ?? and h are epicentral distance and focal depth (km), respectively. Four earthquakes located near the Japan Trench were used to develop a subducting plate intensity attenuation model where intensity is equal to -8.33 + 2.19MJMA -0.00550??h - 1.14 log ?? h. The IJMA assignments for the MJMA7.9 great 1923 Kanto earthquake on the Philippine Sea-Eurasian plate interface are consistent with the subducting plate model; Using the subducting plate model and 226 IJMA IV-VI assignments, the location of the intensity center is 25 km north of the epicenter, Mjma is 7.7, and MJMA is 7.3-8.0 at the 1?? confidence level. Intensity assignments and reported aftershock activity for the enigmatic 11 November 1855 Ansei Edo earthquake are consistent with an MJMA 7.2 Philippine Sea-Eurasian interplate source or Philippine Sea intraslab source at about 30 km depth. If the 1855 earthquake was a Philippine Sea-Eurasian interplate event, the intensity center was adjacent to and downdip of the rupture area of the great 1923 Kanto earthquake, suggesting that the 1855 and 1923 events ruptured adjoining sections of the Philippine Sea-Eurasian plate interface.

Induced Seismicity

NASA Astrophysics Data System (ADS)

Keranen, Katie M.; Weingarten, Matthew

2018-05-01

The ability of fluid-generated subsurface stress changes to trigger earthquakes has long been recognized. However, the dramatic rise in the rate of human-induced earthquakes in the past decade has created abundant opportunities to study induced earthquakes and triggering processes. This review briefly summarizes early studies but focuses on results from induced earthquakes during the past 10 years related to fluid injection in petroleum fields. Study of these earthquakes has resulted in insights into physical processes and has identified knowledge gaps and future research directions. Induced earthquakes are challenging to identify using seismological methods, and faults and reefs strongly modulate spatial and temporal patterns of induced seismicity. However, the similarity of induced and natural seismicity provides an effective tool for studying earthquake processes. With continuing development of energy resources, increased interest in carbon sequestration, and construction of large dams, induced seismicity will continue to pose a hazard in coming years.

Improvement of a picking algorithm real-time P-wave detection by kurtosis

NASA Astrophysics Data System (ADS)

Ishida, H.; Yamada, M.

2016-12-01

Earthquake early warning (EEW) requires fast and accurate P-wave detection. The current EEW system in Japan uses the STA/LTAalgorithm (Allen, 1978) to detect P-wave arrival.However, some stations did not trigger during the 2011 Great Tohoku Earthquake due to the emergent onset. In addition, accuracy of the P-wave detection is very important: on August 1, 2016, the EEW issued a false alarm with M9 in Tokyo region due to a thunder noise.To solve these problems, we use a P-wave detection method using kurtosis statistics. It detects the change of statistic distribution of the waveform amplitude. This method was recently developed (Saragiotis et al., 2002) and used for off-line analysis such as making seismic catalogs. To apply this method for EEW, we need to remove an acausal calculation and enable a real-time processing. Here, we propose a real-time P-wave detection method using kurtosis statistics with a noise filter.To avoid false triggering by a noise, we incorporated a simple filter to classify seismic signal and noise. Following Kong et al. (2016), we used the interquartilerange and zero cross rate for the classification. The interquartile range is an amplitude measure that is equal to the middle 50% of amplitude in a certain time window. The zero cross rate is a simple frequency measure that counts the number of times that the signal crosses baseline zero. A discriminant function including these measures was constructed by the linear discriminant analysis.To test this kurtosis method, we used strong motion records for 62 earthquakes between April, 2005 and July, 2015, which recorded the seismic intensity greater equal to 6 lower in the JMA intensity scale. The records with hypocentral distance < 200km were used for the analysis. An attached figure shows the error of P-wave detection speed for STA/LTA and kurtosis methods against manual picks. It shows that the median error is 0.13 sec and 0.035 sec for STA/LTA and kurtosis method. The kurtosis method tends to be

Seismic isolation of nuclear power plants using sliding isolation bearings

NASA Astrophysics Data System (ADS)

Kumar, Manish

eight sites across the United States to show that the factor is equal to 1.0 for seismically isolated NPPs, if the risk is dominated by horizontal earthquake shaking. Response-history analyses using different models of seismically isolated NPPs are performed to understand the importance of the choice of friction model, model complexity and vertical ground motion for calculating horizontal displacement response across a wide range of sites and shaking intensities. A friction model for the single concave FP bearing should address heating. The pressure- and velocity-dependencies were not important for the models and sites studied. Isolation-system displacements can be computed using a macro model comprising a single FP bearing.

Using Network Theory to Understand Seismic Noise in Dense Arrays

NASA Astrophysics Data System (ADS)

Riahi, N.; Gerstoft, P.

2015-12-01

Dense seismic arrays offer an opportunity to study anthropogenic seismic noise sources with unprecedented detail. Man-made sources typically have high frequency, low intensity, and propagate as surface waves. As a result attenuation restricts their measurable footprint to a small subset of sensors. Medium heterogeneities can further introduce wave front perturbations that limit processing based on travel time. We demonstrate a non-parametric technique that can reliably identify very local events within the array as a function of frequency and time without using travel-times. The approach estimates the non-zero support of the array covariance matrix and then uses network analysis tools to identify clusters of sensors that are sensing a common source. We verify the method on simulated data and then apply it to the Long Beach (CA) geophone array. The method exposes a helicopter traversing the array, oil production facilities with different characteristics, and the fact that noise sources near roads tend to be around 10-20 Hz.

DIaaS: Data-Intensive workflows as a service - Enabling easy composition and deployment of data-intensive workflows on Virtual Research Environments

NASA Astrophysics Data System (ADS)

Filgueira, R.; Ferreira da Silva, R.; Deelman, E.; Atkinson, M.

2016-12-01

We present the Data-Intensive workflows as a Service (DIaaS) model for enabling easy data-intensive workflow composition and deployment on clouds using containers. DIaaS model backbone is Asterism, an integrated solution for running data-intensive stream-based applications on heterogeneous systems, which combines the benefits of dispel4py with Pegasus workflow systems. The stream-based executions of an Asterism workflow are managed by dispel4py, while the data movement between different e-Infrastructures, and the coordination of the application execution are automatically managed by Pegasus. DIaaS combines Asterism framework with Docker containers to provide an integrated, complete, easy-to-use, portable approach to run data-intensive workflows on distributed platforms. Three containers integrate the DIaaS model: a Pegasus node, and an MPI and an Apache Storm clusters. Container images are described as Dockerfiles (available online at http://github.com/dispel4py/pegasus_dispel4py), linked to Docker Hub for providing continuous integration (automated image builds), and image storing and sharing. In this model, all required software (workflow systems and execution engines) for running scientific applications are packed into the containers, which significantly reduces the effort (and possible human errors) required by scientists or VRE administrators to build such systems. The most common use of DIaaS will be to act as a backend of VREs or Scientific Gateways to run data-intensive applications, deploying cloud resources upon request. We have demonstrated the feasibility of DIaaS using the data-intensive seismic ambient noise cross-correlation application (Figure 1). The application preprocesses (Phase1) and cross-correlates (Phase2) traces from several seismic stations. The application is submitted via Pegasus (Container1), and Phase1 and Phase2 are executed in the MPI (Container2) and Storm (Container3) clusters respectively. Although both phases could be executed

New Madrid Seismic Zone: a test case for naturally induced seismicity

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

Nava, S.J.

1983-09-01

Induced seismicity caused by man-made events, such as the filling of reservoirs has been well documented. In contrast, naturally induced seismicity has received little attention. It has been shown that a fluctuation of as little as several bars can trigger reservoir induced earthquakes. Naturally occurring phenomena generate similar fluctuations and could trigger earthquakes where the faults in ambient stress field are suitably oriented and close to failure. The New Madrid Seismic Zone (NMSZ) presents an ideal test case for the study of naturally induced seismicity. The ideal data set for a study of triggering effects must contain a statistically significantmore » number of events, a constant accumulated strain, and a limited focal region. New Madrid earthquakes are well documented from 1974 to the present, down to a magnitude approx. 1.8. They lie in a distinct fault pattern and occur as a reaction to the regional stress regime. A statistical correlation was made between the earthquakes and a variety of different types of loads, to see if New Madrid seismicity could be triggered by natural fluctuations. The types of triggers investigated ranged from solid earth tides to variations in barometric pressure, rainfall, and stages of the Mississippi River. This analysis becomes complex because each factor investigated creates individual stresses, as well as having imbedded in it a reaction to other factors.« less

Controllable seismic source

DOEpatents

Gomez, Antonio; DeRego, Paul Jeffrey; Ferrell, Patrick Andrew; Thom, Robert Anthony; Trujillo, Joshua J.; Herridge, Brian

2015-09-29

An apparatus for generating seismic waves includes a housing, a strike surface within the housing, and a hammer movably disposed within the housing. An actuator induces a striking motion in the hammer such that the hammer impacts the strike surface as part of the striking motion. The actuator is selectively adjustable to change characteristics of the striking motion and characteristics of seismic waves generated by the impact. The hammer may be modified to change the physical characteristics of the hammer, thereby changing characteristics of seismic waves generated by the hammer. The hammer may be disposed within a removable shock cavity, and the apparatus may include two hammers and two shock cavities positioned symmetrically about a center of the apparatus.

Controllable seismic source

DOEpatents

Gomez, Antonio; DeRego, Paul Jeffrey; Ferrel, Patrick Andrew; Thom, Robert Anthony; Trujillo, Joshua J.; Herridge, Brian

2014-08-19

An apparatus for generating seismic waves includes a housing, a strike surface within the housing, and a hammer movably disposed within the housing. An actuator induces a striking motion in the hammer such that the hammer impacts the strike surface as part of the striking motion. The actuator is selectively adjustable to change characteristics of the striking motion and characteristics of seismic waves generated by the impact. The hammer may be modified to change the physical characteristics of the hammer, thereby changing characteristics of seismic waves generated by the hammer. The hammer may be disposed within a removable shock cavity, and the apparatus may include two hammers and two shock cavities positioned symmetrically about a center of the apparatus.

The Salton Seismic Imaging Project: Seismic velocity structure of the Brawley Seismic Zone, Salton Buttes and Geothermal Field, Salton Trough, California

NASA Astrophysics Data System (ADS)

Delph, J.; Hole, J. A.; Fuis, G. S.; Stock, J. M.; Rymer, M. J.

2011-12-01

The Salton Trough is an active rift in southern California in a step-over between the plate-bounding Imperial and San Andreas Faults. In March 2011, the Salton Seismic Imaging Project (SSIP) investigated the rift's crustal structure by acquiring several seismic refraction and reflection lines. One of the densely sampled refraction lines crosses the northern-most Imperial Valley, perpendicular to the strike-slip faults and parallel to a line of small Quaternary rhyolitic volcanoes. The line crosses the obliquely extensional Brawley Seismic Zone and goes through one of the most geothermally productive areas in the United States. Well logs indicate the valley is filled by several kilometers of late Pliocene-recent lacustrine, fluvial, and shallow marine sediment. The 42-km long seismic line was comprised of eleven 110-460 kg explosive shots and receivers at a 100 m spacing. First arrival travel times were used to build a tomographic seismic velocity image of the upper crust. Velocity in the valley increases smoothly from <2 km/s to >5 km/s, indicating diagenesis and gradational metamorphism of rift sediments at very shallow depth due to an elevated geotherm. The velocity gradient is much smaller in the relatively low velocity (<6 km/s) crystalline basement comprised of recently metamorphosed sediment reaching greenschist to lower amphibolite facies. The depth of this basement is about 4-km below the aseismic region of the valley west of the Brawley Seismic Zone, but rises sharply to ~2 km depth beneath the seismically, geothermally, and volcanically active area of the Brawley Seismic Zone. The basement deepens to the northeast of the active tectonic zone and then is abruptly offset to shallower depth on the northeast side of the valley. This offset may be the subsurficial expression of a paleofault, most likely an extension of the Sand Hills Fault, which bounds the basin to the east. Basement velocity east of the fault is ~5.7 km/s, consistent with the granitic rocks

Global Seismic Cross-Correlation Results: Characterizing Repeating Seismic Events

NASA Astrophysics Data System (ADS)

Vieceli, R.; Dodge, D. A.; Walter, W. R.

2016-12-01

Increases in seismic instrument quality and coverage have led to increased knowledge of earthquakes, but have also revealed the complex and diverse nature of earthquake ruptures. Nonetheless, some earthquakes are sufficiently similar to each other that they produce correlated waveforms. Such repeating events have been used to investigate interplate coupling of subduction zones [e.g. Igarashi, 2010; Yu, 2013], study spatio-temporal changes in slip rate at plate boundaries [e.g. Igarashi et al., 2003], observe variations in seismic wave propagation velocities in the crust [e.g. Schaff and Beroza, 2004; Sawazaki et al., 2015], and assess inner core rotation [e.g. Yu, 2016]. The characterization of repeating events on a global scale remains a very challenging problem. An initial global seismic cross-correlation study used over 310 million waveforms from nearly 3.8 million events recorded between 1970 and 2013 to determine an initial look at global correlated seismicity [Dodge and Walter, 2015]. In this work, we analyze the spatial and temporal distribution of the most highly correlated event clusters or "multiplets" from the Dodge and Walter [2015] study. We examine how the distributions and characteristics of multiplets are effected by tectonic environment, source-station separation, and frequency band. Preliminary results suggest that the distribution of multiplets does not correspond to the tectonic environment in any obvious way, nor do they always coincide with the occurrence of large earthquakes. Future work will focus on clustering correlated pairs and working to reduce the bias introduced by non-uniform seismic station coverage and data availability. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Water-table and discharge changes associated with the 2016-2017 seismic sequence in central Italy: hydrogeological data and a conceptual model for fractured carbonate aquifers

NASA Astrophysics Data System (ADS)

Petitta, Marco; Mastrorillo, Lucia; Preziosi, Elisabetta; Banzato, Francesca; Barberio, Marino Domenico; Billi, Andrea; Cambi, Costanza; De Luca, Gaetano; Di Carlo, Giuseppe; Di Curzio, Diego; Di Salvo, Cristina; Nanni, Torquato; Palpacelli, Stefano; Rusi, Sergio; Saroli, Michele; Tallini, Marco; Tazioli, Alberto; Valigi, Daniela; Vivalda, Paola; Doglioni, Carlo

2018-01-01

A seismic sequence in central Italy from August 2016 to January 2017 affected groundwater dynamics in fractured carbonate aquifers. Changes in spring discharge, water-table position, and streamflow were recorded for several months following nine Mw 5.0-6.5 seismic events. Data from 22 measurement sites, located within 100 km of the epicentral zones, were analyzed. The intensity of the induced changes were correlated with seismic magnitude and distance to epicenters. The additional post-seismic discharge from rivers and springs was found to be higher than 9 m3/s, totaling more than 0.1 km3 of groundwater release over 6 months. This huge and unexpected contribution increased streamflow in narrow mountainous valleys to previously unmeasured peak values. Analogously to the L'Aquila 2009 post-earthquake phenomenon, these hydrogeological changes might reflect an increase of bulk hydraulic conductivity at the aquifer scale, which would increase hydraulic heads in the discharge zones and lower them in some recharge areas. The observed changes may also be partly due to other mechanisms, such as shaking and/or squeezing effects related to intense subsidence in the core of the affected area, where effects had maximum extent, or breaching of hydraulic barriers.

Water-table and discharge changes associated with the 2016-2017 seismic sequence in central Italy: hydrogeological data and a conceptual model for fractured carbonate aquifers

NASA Astrophysics Data System (ADS)

Petitta, Marco; Mastrorillo, Lucia; Preziosi, Elisabetta; Banzato, Francesca; Barberio, Marino Domenico; Billi, Andrea; Cambi, Costanza; De Luca, Gaetano; Di Carlo, Giuseppe; Di Curzio, Diego; Di Salvo, Cristina; Nanni, Torquato; Palpacelli, Stefano; Rusi, Sergio; Saroli, Michele; Tallini, Marco; Tazioli, Alberto; Valigi, Daniela; Vivalda, Paola; Doglioni, Carlo

2018-06-01

A seismic sequence in central Italy from August 2016 to January 2017 affected groundwater dynamics in fractured carbonate aquifers. Changes in spring discharge, water-table position, and streamflow were recorded for several months following nine Mw 5.0-6.5 seismic events. Data from 22 measurement sites, located within 100 km of the epicentral zones, were analyzed. The intensity of the induced changes were correlated with seismic magnitude and distance to epicenters. The additional post-seismic discharge from rivers and springs was found to be higher than 9 m3/s, totaling more than 0.1 km3 of groundwater release over 6 months. This huge and unexpected contribution increased streamflow in narrow mountainous valleys to previously unmeasured peak values. Analogously to the L'Aquila 2009 post-earthquake phenomenon, these hydrogeological changes might reflect an increase of bulk hydraulic conductivity at the aquifer scale, which would increase hydraulic heads in the discharge zones and lower them in some recharge areas. The observed changes may also be partly due to other mechanisms, such as shaking and/or squeezing effects related to intense subsidence in the core of the affected area, where effects had maximum extent, or breaching of hydraulic barriers.

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

Systematic detection of seismic events at Mount St. Helens with an ultra-dense array

NASA Astrophysics Data System (ADS)

Meng, X.; Hartog, J. R.; Schmandt, B.; Hotovec-Ellis, A. J.; Hansen, S. M.; Vidale, J. E.; Vanderplas, J.

2016-12-01

During the summer of 2014, an ultra-dense array of 900 geophones was deployed around the crater of Mount St. Helens and continuously operated for 15 days. This dataset provides us an unprecedented opportunity to systematically detect seismic events around an active volcano and study their underlying mechanisms. We use a waveform-based matched filter technique to detect seismic events from this dataset. Due to the large volume of continuous data ( 1 TB), we performed the detection on the GPU cluster Stampede (https://www.tacc.utexas.edu/systems/stampede). We build a suite of template events from three catalogs: 1) the standard Pacific Northwest Seismic Network (PNSN) catalog (45 events); 2) the catalog from Hansen&Schmandt (2015) obtained with a reverse-time imaging method (212 events); and 3) the catalog identified with a matched filter technique using the PNSN permanent stations (190 events). By searching for template matches in the ultra-dense array, we find 2237 events. We then calibrate precise relative magnitudes for template and detected events, using a principal component fit to measure waveform amplitude ratios. The magnitude of completeness and b-value of the detected catalog is -0.5 and 1.1, respectively. Our detected catalog shows several intensive swarms, which are likely driven by fluid pressure transients in conduits or slip transients on faults underneath the volcano. We are currently relocating the detected catalog with HypoDD and measuring the seismic velocity changes at Mount St. Helens using the coda wave interferometry of detected repeating earthquakes. The accurate temporal-spatial migration pattern of seismicity and seismic property changes should shed light on the physical processes beneath Mount St. Helens.

Seismicity and seismic hazard in Sabah, East Malaysia from earthquake and geodetic data

NASA Astrophysics Data System (ADS)

Gilligan, A.; Rawlinson, N.; Tongkul, F.; Stephenson, R.

2017-12-01

While the levels of seismicity are low in most of Malaysia, the state of Sabah in northern Borneo has moderate levels of seismicity. Notable earthquakes in the region include the 1976 M6.2 Lahad Datu earthquake and the 2015 M6 Ranau earthquake. The recent Ranau earthquake resulted in the deaths of 18 people on Mt Kinabalu, an estimated 100 million RM ( US$23 million) damage to buildings, roads, and infrastructure from shaking, and flooding, reduced water quality, and damage to farms from landslides. Over the last 40 years the population of Sabah has increased to over four times what it was in 1976, yet seismic hazard in Sabah remains poorly understood. Using seismic and geodetic data we hope to better quantify the hazards posed by earthquakes in Sabah, and thus help to minimize risk. In order to do this we need to know about the locations of earthquakes, types of earthquakes that occur, and faults that are generating them. We use data from 15 MetMalaysia seismic stations currently operating in Sabah to develop a region-specific velocity model from receiver functions and a pre-existing surface wave model. We use this new velocity model to (re)locate earthquakes that occurred in Sabah from 2005-2016, including a large number of aftershocks from the 2015 Ranau earthquake. We use a probabilistic nonlinear earthquake location program to locate the earthquakes and then refine their relative locations using a double difference method. The recorded waveforms are further used to obtain moment tensor solutions for these earthquakes. Earthquake locations and moment tensor solutions are then compared with the locations of faults throughout Sabah. Faults are identified from high-resolution IFSAR images and subsequent fieldwork, with a particular focus on the Lahad Datau and Ranau areas. Used together, these seismic and geodetic data can help us to develop a new seismic hazard model for Sabah, as well as aiding in the delivery of outreach activities regarding seismic hazard

Borehole seismic monitoring of seismic stimulation at OccidentalPermian Ltd's -- South Wason Clear Fork Unit

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

Daley, Tom; Majer, Ernie

2007-04-30

Seismic stimulation is a proposed enhanced oil recovery(EOR) technique which uses seismic energy to increase oil production. Aspart of an integrated research effort (theory, lab and field studies),LBNL has been measuring the seismic amplitude of various stimulationsources in various oil fields (Majer, et al., 2006, Roberts,et al.,2001, Daley et al., 1999). The amplitude of the seismic waves generatedby a stimulation source is an important parameter for increased oilmobility in both theoretical models and laboratory core studies. Theseismic amplitude, typically in units of seismic strain, can be measuredin-situ by use of a borehole seismometer (geophone). Measuring thedistribution of amplitudes within amore » reservoir could allow improved designof stimulation source deployment. In March, 2007, we provided in-fieldmonitoring of two stimulation sources operating in Occidental (Oxy)Permian Ltd's South Wasson Clear Fork (SWCU) unit, located near DenverCity, Tx. The stimulation source is a downhole fluid pulsation devicedeveloped by Applied Seismic Research Corp. (ASR). Our monitoring used aborehole wall-locking 3-component geophone operating in two nearbywells.« less

Seismic Scenario in the Acambay Graben and Possible Affectations in the Miguel Hidalgo Refinery

NASA Astrophysics Data System (ADS)

Valderrama Membrillo, S.; Aguirre, J.

2015-12-01

In this paper we presented synthetic acceleration records in the Miguel Hidalgo refinery, Hidalgo due to a seismic scenario originated in the graben Acambay, such as occurred in 1912 (70 km distance to it). This earthquake had a magnitude of 6.9 and caused extensive damage, according to reports caused 164 deaths and numerous houses collapsing. To simulate the event of M = 6.9 we used the empirical Greeńs function method proposed by Irikura (1986). Due to the low seismic activity we have not any small earthquake record or an "element earthquake" so that we generated a synthetic seismogram of M = 4.1 to be used as empirical Greeńs function. The seismogram was constructed in two parts. For low frequencies we constructed from cross-correlations of seismic noise, while for high frequencies we made a stochastic simulation. Subsequently, we applied a "matched filter" to join the two frequency bands of synthetic earthquake. For the construction of seismic scenario the method of Irikura (1986) was used. We consider a square fault of 47.75 km long, a radial rupture propagation, rupture velocity of 3.06 m/s, and with the following focal mechanism: strike of 280°, dip of 66 ° and rake of -138 °. With these parameters we obtained the synthetic seismograms. Since there was not any observed earthquake to validate the model, the 1912 event was simulated and then from relationships of intensity (obtained Wald et al.,2005; Sandoval et al., 2013; and Arias, 1969), we estimated the Modified Mercalli Intensity (MMI) for the refinery. We compare our result with isoseismal map obtained by Suter et al. (1996) for the earthquake of 1912. In agreement with Suter, our results shown a MMI V-VI for the Miguel Hidalgo refinery. With this qualitative validation we search the seismic scenario with the higher accelerations and from this synthetic seismogram, we obtained parameters that are of interest in engineering to estimate the possible affectations to the Miguel Hidalgo refinery, such as

Seismic source models for very-long period seismic signals on White Island, New Zealand

NASA Astrophysics Data System (ADS)

Jiwani-Brown, Elliot; Neuberg, Jurgen; Jolly, Art

2015-04-01

Very-long-period seismic signals (VLP) from White Island have a duration of only a few tens of seconds and a waveform that indicates an elastic (or viscoelastic) interaction of a source region with the surrounding medium; unlike VLP signals on some other volcanoes that indicate a step function recorded in the near field of the seismic source, White Island VLPs exhibit a Ricker waveform. We explore a set of isotropic, seismic source models based on the interaction between magma and water/brine in direct contact. Seismic amplitude measurements are taken into account to estimate the volume changes at depth that can produce the observed displacement at the surface. Furthermore, the influence of different fluid types are explored.

A detailed study of the Pernik (Bulgaria) seismic sequence of 2012

NASA Astrophysics Data System (ADS)

Raykova, Plamena; Solakov, Dimcho; Simeonova, Stela; Dimitrova, Liliya

2014-05-01

A detailed study of the Pernik (Bulgaria) seismic sequence of 2012 D.Solakov, S.Simeonova ,I. Georgiev, P.Raykova, L.Dimitrova and V.Protopopova National Institute of Geophysics, Geodesy and Geography-BAS, Sofia, Bulgaria The spatial and temporal clustering of aftershocks is the dominant non-random element of seismicity, so that when aftershocks are removed, the remaining activity can be modelled (as first approximation) as a Poisson process. The properties of aftershock sequences (distinct cluster, for example; even aftershocks can have aftershocks) allow time-dependent prediction of aftershock probabilities. Consideration of recent earthquake sequences suggests that aftershocks to large earthquakes although they are still, by definition, smaller events, can be very damaging and should be addressed in emergence planning scenarios. Because of the factors such as location and radiation pattern and the cumulative nature of building damage, aftershocks can cause more damage than the main shock. An earthquake of moment magnitude 5.6 hit Sofia seismic zone, on May 22nd, 2012. The earthquake occurred in the vicinity of Pernik city, at about 25 km south west of the city of Sofia (the capital of Bulgaria). The event was followed by intensive activity. The active area is situated in the central part of western Bulgaria. That is the most populated (more than 1.2 mil. inhabitants), industrial and cultural region of Bulgaria. Seismicity in the zone is related to the marginal neotectonic faults of Sofia graben. The boundaries of the graben are represented by SE-NW fault system with expressive neotectonic activity. This zone is characterized by shallow earthquakes. The strongest known event in the region is the 1858 quake with intensity I0=9-10 MSK. The 1858 earthquake caused heavy destruction in the city of Sofia and the appearance of thermal spring. It is worth mentioning that the seismic sequence of May 2912 occurred in an area characterized by a long quiescence (of 95 years

GeoInt: the first macroseismic intensity database for the Republic of Georgia

NASA Astrophysics Data System (ADS)

Varazanashvili, O.; Tsereteli, N.; Bonali, F. L.; Arabidze, V.; Russo, E.; Pasquaré Mariotto, F.; Gogoladze, Z.; Tibaldi, A.; Kvavadze, N.; Oppizzi, P.

2018-05-01

Our work is intended to present the new macroseismic intensity database for the Republic of Georgia—hereby named GeoInt—which includes earthquakes from the historical (from 1250 B.C. onwards) to the instrumental era. Such database is composed of 111 selected earthquakes and related 3944 intensity data points (IDPs) for 1509 different localities, reported in the Medvedev-Sponheuer-Karnik scale (MSK). Regarding the earthquakes, the M S is in the 3.3-7 range and the depth is in the 2-36 km range. The entire set of IDPs is characterized by intensities ranging from 2-3 to 9-10 and covers an area spanning from 39.508° N to 45.043° N in a N-S direction and from 37.324° E to 48.500° E in an E-W direction, with some of the IDPs located outside the Georgian border, in the (i) Republic of Armenia, (ii) Russian Federation, (iii) Republic of Turkey, and (iv) Republic of Azerbaijan. We have revised each single IDP and have reevaluated and homogenized intensity values to the MSK scale. In particular, regarding the whole set of 3944 IDPs, 348 belong to the Historical era (pre-1900) and 3596 belong to the instrumental era (post-1900). With particular regard to the 3596 IDPs, 105 are brand new (3%), whereas the intensity values for 804 IDPs have been reevaluated (22%); for 2687 IDPs (75%), intensities have been confirmed from previous interpretations. We introduce this database as a key input for further improvements in seismic hazard modeling and seismic risk calculation for this region, based on macroseismic intensity; we report all the 111 earthquakes with available macroseismic information. The GeoInt database is also accessible online at http://www.enguriproject.unimib.it and will be kept updated in the future.

GeoInt: the first macroseismic intensity database for the Republic of Georgia

NASA Astrophysics Data System (ADS)

Varazanashvili, O.; Tsereteli, N.; Bonali, F. L.; Arabidze, V.; Russo, E.; Pasquaré Mariotto, F.; Gogoladze, Z.; Tibaldi, A.; Kvavadze, N.; Oppizzi, P.

2018-01-01

Our work is intended to present the new macroseismic intensity database for the Republic of Georgia—hereby named GeoInt—which includes earthquakes from the historical (from 1250 B.C. onwards) to the instrumental era. Such database is composed of 111 selected earthquakes and related 3944 intensity data points (IDPs) for 1509 different localities, reported in the Medvedev-Sponheuer-Karnik scale (MSK). Regarding the earthquakes, the M S is in the 3.3-7 range and the depth is in the 2-36 km range. The entire set of IDPs is characterized by intensities ranging from 2-3 to 9-10 and covers an area spanning from 39.508° N to 45.043° N in a N-S direction and from 37.324° E to 48.500° E in an E-W direction, with some of the IDPs located outside the Georgian border, in the (i) Republic of Armenia, (ii) Russian Federation, (iii) Republic of Turkey, and (iv) Republic of Azerbaijan. We have revised each single IDP and have reevaluated and homogenized intensity values to the MSK scale. In particular, regarding the whole set of 3944 IDPs, 348 belong to the Historical era (pre-1900) and 3596 belong to the instrumental era (post-1900). With particular regard to the 3596 IDPs, 105 are brand new (3%), whereas the intensity values for 804 IDPs have been reevaluated (22%); for 2687 IDPs (75%), intensities have been confirmed from previous interpretations. We introduce this database as a key input for further improvements in seismic hazard modeling and seismic risk calculation for this region, based on macroseismic intensity; we report all the 111 earthquakes with available macroseismic information. The GeoInt database is also accessible online at http://www.enguriproject.unimib.it and will be kept updated in the future.

Deepwater seismic acquisition technology

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

Caldwell, J.

1996-09-01

Although truly new technology is not required for successful acquisition of seismic data in deep Gulf of Mexico waters, it is helpful to review some basic aspects of these seismic surveys. Additionally, such surveys are likely to see early use of some emerging new technology which can improve data quality. Because such items as depth imaging, borehole seismic, 4-D and marine 3-component recording were mentioned in the May 1996 issue of World Oil, they are not discussed again here. However, these technologies will also play some role in the deepwater seismic activities. What is covered in this paper are somemore » new considerations for: (1) longer data records needed in deeper water, (2) some pros and cons of very long steamer use, and (3) two new commercial systems for quantifying data quality.« less

Classifying elephant behaviour through seismic vibrations.

PubMed

Mortimer, Beth; Rees, William Lake; Koelemeijer, Paula; Nissen-Meyer, Tarje

2018-05-07

Seismic waves - vibrations within and along the Earth's surface - are ubiquitous sources of information. During propagation, physical factors can obscure information transfer via vibrations and influence propagation range [1]. Here, we explore how terrain type and background seismic noise influence the propagation of seismic vibrations generated by African elephants. In Kenya, we recorded the ground-based vibrations of different wild elephant behaviours, such as locomotion and infrasonic vocalisations [2], as well as natural and anthropogenic seismic noise. We employed techniques from seismology to transform the geophone recordings into source functions - the time-varying seismic signature generated at the source. We used computer modelling to constrain the propagation ranges of elephant seismic vibrations for different terrains and noise levels. Behaviours that generate a high force on a sandy terrain with low noise propagate the furthest, over the kilometre scale. Our modelling also predicts that specific elephant behaviours can be distinguished and monitored over a range of propagation distances and noise levels. We conclude that seismic cues have considerable potential for both behavioural classification and remote monitoring of wildlife. In particular, classifying the seismic signatures of specific behaviours of large mammals remotely in real time, such as elephant running, could inform on poaching threats. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

CRUSTAL TECTONICS AND SEISMICITY OF THE MIDDLE EAST

NASA Astrophysics Data System (ADS)

Ghalib, H. A.; Gritto, R.; Sibol, M. S.; Herrmann, R. B.; Aleqabi, G. I.; Caron, P. F.; Wagner, R. A.; Ali, B. S.; Ali, A. A.

2009-12-01

The Arabian plate describes a geological entity and a dynamic system that has been in continuous interaction with the African plate to the west and south and the Eurasian plate to the north and east. The western and southern boundaries are distinguished by see floor spreading along the Gulf of Aden and Red Sea and transform faulting along the Dead Sea, whereas the northern and eastern boundaries are portrayed by compressional suture zones under thrusting the Turkish and Iranian plateaus. Despite this favorable juxtaposition of continental land masses and the plethora of national seismic networks in every country of the Middle East, the majority of published research on the Arabian plate and surrounding tectonic blocks still depends primarily on global seismographic stations and occasional local networks. Since 2005, we deployed a number of seismic stations, and more recently a five elements array, in close proximity to the northeastern boundary of the Arabian plate. The primary objective of the effort is to better understand the regional seismicity and seismotectonics of the Arabian plate and surrounding regions. To date over a terabyte of high quality 100 sps continuous three-component broadband data have been collected and being analyzed to derive models representative of the greater Middle East tectonic setting. This goal is, in part, achieved by estimating local and regional seismic velocity models using receiver function and surface wave dispersion analyses, and by using these models to obtain accurate hypocenter locations and event focal mechanisms. The resulting events distribution reveals a distinct picture of the interaction between the seismicity and tectonics of the region. The highest seismicity rate seems to be confined to the active northern section of the Zagros thrust zone, while it decreases towards the southern end, before the intensity increases again in the Bandar Abbas region. Spatial distribution of the events and stations provide thorough

Demonstration of improved seismic source inversion method of tele-seismic body wave

NASA Astrophysics Data System (ADS)

Yagi, Y.; Okuwaki, R.

2017-12-01

Seismic rupture inversion of tele-seismic body wave has been widely applied to studies of large earthquakes. In general, tele-seismic body wave contains information of overall rupture process of large earthquake, while the tele-seismic body wave is inappropriate for analyzing a detailed rupture process of M6 7 class earthquake. Recently, the quality and quantity of tele-seismic data and the inversion method has been greatly improved. Improved data and method enable us to study a detailed rupture process of M6 7 class earthquake even if we use only tele-seismic body wave. In this study, we demonstrate the ability of the improved data and method through analyses of the 2016 Rieti, Italy earthquake (Mw 6.2) and the 2016 Kumamoto, Japan earthquake (Mw 7.0) that have been well investigated by using the InSAR data set and the field observations. We assumed the rupture occurring on a single fault plane model inferred from the moment tensor solutions and the aftershock distribution. We constructed spatiotemporal discretized slip-rate functions with patches arranged as closely as possible. We performed inversions using several fault models and found that the spatiotemporal location of large slip-rate area was robust. In the 2016 Kumamoto, Japan earthquake, the slip-rate distribution shows that the rupture propagated to southwest during the first 5 s. At 5 s after the origin time, the main rupture started to propagate toward northeast. First episode and second episode correspond to rupture propagation along the Hinagu fault and the Futagawa fault, respectively. In the 2016 Rieti, Italy earthquake, the slip-rate distribution shows that the rupture propagated to up-dip direction during the first 2 s, and then rupture propagated toward northwest. From both analyses, we propose that the spatiotemporal slip-rate distribution estimated by improved inversion method of tele-seismic body wave has enough information to study a detailed rupture process of M6 7 class earthquake.

The LUSI Seismic Experiment: Deployment of a Seismic Network around LUSI, East Java, Indonesia

NASA Astrophysics Data System (ADS)

Karyono, Karyono; Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Haryanto, Iyan; Masturyono, Masturyono; Hadi, Soffian; Rohadi, Suprianto; Suardi, Iman; Rudiyanto, Ariska; Pranata, Bayu

2015-04-01

The spectacular Lusi eruption started in northeast Java, Indonesia the 29 of May 2006 following a M6.3 earthquake striking the island. Initially, several gas and mud eruption sites appeared along the reactivated strike-slip Watukosek fault system and within weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. Lusi is located few kilometres to the NE of the Arjuno-Welirang volcanic complex. Lusi sits upon the Watukosek fault system. From this volcanic complex originates the Watukosek fault system that was reactivated by the M6.3 earthquake in 2006 and is still periodically reactivated by the frequent seismicity. To date Lusi is still active and erupting gas, water, mud and clasts. Gas and water data show that the Lusi plumbing system is connected with the neighbouring Arjuno-Welirang volcanic complex. This makes the Lusi eruption a "sedimentary hosted geothermal system". To verify and characterise the occurrence of seismic activity and how this perturbs the connected Watukosek fault, the Arjuno-Welirang volcanic system and the ongoing Lusi eruption, we deployed 30 seismic stations (short-period and broadband) in this region of the East Java basin. The seismic stations are more densely distributed around LUSI and the Watukosek fault zone that stretches between Lusi and the Arjuno Welirang (AW) complex. Fewer stations are positioned around the volcanic arc. Our study sheds light on the seismic activity along the Watukosek fault system and describes the waveforms associated to the geysering activity of Lusi. The initial network aims to locate small event that may not be captured by the Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG) seismic network and it will be crucial to design the second phase of the seismic experiment that will consist of a local earthquake tomography of the Lusi-Arjuno Welirang region and temporal variations of vp/vs ratios. Such variations will then be ideally related to

Visualization of volumetric seismic data

NASA Astrophysics Data System (ADS)

Spickermann, Dela; Böttinger, Michael; Ashfaq Ahmed, Khawar; Gajewski, Dirk

2015-04-01

Mostly driven by demands of high quality subsurface imaging, highly specialized tools and methods have been developed to support the processing, visualization and interpretation of seismic data. 3D seismic data acquisition and 4D time-lapse seismic monitoring are well-established techniques in academia and industry, producing large amounts of data to be processed, visualized and interpreted. In this context, interactive 3D visualization methods proved to be valuable for the analysis of 3D seismic data cubes - especially for sedimentary environments with continuous horizons. In crystalline and hard rock environments, where hydraulic stimulation techniques may be applied to produce geothermal energy, interpretation of the seismic data is a more challenging problem. Instead of continuous reflection horizons, the imaging targets are often steep dipping faults, causing a lot of diffractions. Without further preprocessing these geological structures are often hidden behind the noise in the data. In this PICO presentation we will present a workflow consisting of data processing steps, which enhance the signal-to-noise ratio, followed by a visualization step based on the use the commercially available general purpose 3D visualization system Avizo. Specifically, we have used Avizo Earth, an extension to Avizo, which supports the import of seismic data in SEG-Y format and offers easy access to state-of-the-art 3D visualization methods at interactive frame rates, even for large seismic data cubes. In seismic interpretation using visualization, interactivity is a key requirement for understanding complex 3D structures. In order to enable an easy communication of the insights gained during the interactive visualization process, animations of the visualized data were created which support the spatial understanding of the data.

Estimating earthquake magnitudes from reported intensities in the central and eastern United States

USGS Publications Warehouse

Boyd, Oliver; Cramer, Chris H.

2014-01-01

A new macroseismic intensity prediction equation is derived for the central and eastern United States and is used to estimate the magnitudes of the 1811–1812 New Madrid, Missouri, and 1886 Charleston, South Carolina, earthquakes. This work improves upon previous derivations of intensity prediction equations by including additional intensity data, correcting magnitudes in the intensity datasets to moment magnitude, and accounting for the spatial and temporal population distributions. The new relation leads to moment magnitude estimates for the New Madrid earthquakes that are toward the lower range of previous studies. Depending on the intensity dataset to which the new macroseismic intensity prediction equation is applied, mean estimates for the 16 December 1811, 23 January 1812, and 7 February 1812 mainshocks, and 16 December 1811 dawn aftershock range from 6.9 to 7.1, 6.8 to 7.1, 7.3 to 7.6, and 6.3 to 6.5, respectively. One‐sigma uncertainties on any given estimate could be as high as 0.3–0.4 magnitude units. We also estimate a magnitude of 6.9±0.3 for the 1886 Charleston, South Carolina, earthquake. We find a greater range of magnitude estimates when also accounting for multiple macroseismic intensity prediction equations. The inability to accurately and precisely ascertain magnitude from intensities increases the uncertainty of the central United States earthquake hazard by nearly a factor of two. Relative to the 2008 national seismic hazard maps, our range of possible 1811–1812 New Madrid earthquake magnitudes increases the coefficient of variation of seismic hazard estimates for Memphis, Tennessee, by 35%–42% for ground motions expected to be exceeded with a 2% probability in 50 years and by 27%–35% for ground motions expected to be exceeded with a 10% probability in 50 years.

Advances in Rotational Seismic Measurements

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

Pierson, Robert; Laughlin, Darren; Brune, Robert

2016-10-19

Rotational motion is increasingly understood to be a significant part of seismic wave motion. Rotations can be important in earthquake strong motion and in Induced Seismicity Monitoring. Rotational seismic data can also enable shear selectivity and improve wavefield sampling for vertical geophones in 3D surveys, among other applications. However, sensor technology has been a limiting factor to date. The US Department of Energy (DOE) and Applied Technology Associates (ATA) are funding a multi-year project that is now entering Phase 2 to develop and deploy a new generation of rotational sensors for validation of rotational seismic applications. Initial focus is onmore » induced seismicity monitoring, particularly for Enhanced Geothermal Systems (EGS) with fracturing. The sensors employ Magnetohydrodynamic (MHD) principles with broadband response, improved noise floors, robustness, and repeatability. This paper presents a summary of Phase 1 results and Phase 2 status.« less

Two types of seismicity accompanying hydraulic fracturing in Harrison County, Ohio - implications for seismic hazard and seismogenic mechanism

NASA Astrophysics Data System (ADS)

Kozlowska, M.; Brudzinski, M.; Friberg, P. A.; Skoumal, R.; Baxter, N. D.; Currie, B.

2017-12-01

While induced seismicity in the United States has mainly been attributed to wastewater disposal, Eastern Ohio has provided cases of seismicity induced by both hydraulic fracturing (HF) and wastewater disposal. In this study, we investigate five cases of seismicity associated with HF in Harrison County, OH. Because of their temporal and spatial isolation from other injection activities, this provide an ideal setting for studying the relationships between high pressure injection and earthquakes. Our analysis reveals two distinct groups of seismicity. Deeper earthquakes occur in the Precambrian crystalline basement, reach larger magnitudes (M>2), have lower b-values (<1), and continue for weeks following stimulation shut down. Shallower earthquakes, on the other hand, occur in Paleozoic sedimentary rocks 400 m below HF, are limited to smaller magnitudes (M<1), have higher b-values (>1.5), and lack post-stimulation activity. We seek the physical explanation of observed difference in earthquakes character and hypothesize that the maturity of faults is the main factor determining sequences b-values. Based on published results of laboratory experiments and fault modeling, we interpret the deep seismicity as slip on more mature faults in the older crystalline rocks and the shallow seismicity as slip on immature faults in the younger, lower viscosity sedimentary rocks. This suggests that HF inducing seismicity on deeper, more mature faults poses higher seismic hazards. The analysis of water and gas production data from these wells suggests that wells inducing deeper seismicity produced more water than wells with shallow seismicity. This indicates more extensive hydrologic connections outside the target reservoir, which may explain why gas production drops more quickly for wells with deeper seismicity. Despite these indications that hydraulic pressure fluctuations induce seismicity, we also find only 2-3 hours between onset of stimulation of HF wells and seismicity that is

Seismic experiment ross ice shelf 1990/91: Characteristics of the seismic reflection data

USGS Publications Warehouse

1993-01-01

The Transantarctic Mountains, with a length of 3000-3500 km and elevations of up to 4500 m, are one of the major Cenozoic mountain ranges in the world and are by far the most striking example of rift-shoulder mountains. Over the 1990-1991 austral summer Seismic Experiment Ross Ice Shelf (SERIS) was carried out across the Transantarctic Mountain front, between latitudes 82 degrees to 83 degrees S, in order to investigate the transition zone between the rifted area of the Ross Embayment and the uplifted Transantarctic Mountains. This experiment involved a 140 km long seismic reflection profile together with a 96 km long coincident wide-angle reflection/refraction profile. Gravity and relative elevation (using barometric pressure) were also measured along the profile. The primary purpose was to examine the boundary between the rift system and the uplifted rift margin (represented by the Transantarctic Mountains) using modern multi-channel crustal reflection/refraction techniques. The results provide insight into crustal structure across the plate boundary. SERIS also represented one of the first large-scale and modern multi-channel seismic experiments in the remote interior of Antarctica. As such, the project was designed to test different seismic acquisition techniques which will be involved in future seismic exploration of the continent. This report describes the results from the analysis of the acquisition tests as well as detailing some of the characteristics of the reflection seismic data. (auths.)

Continental lithospheric subduction and intermediate-depth seismicity: Constraints from S-wave velocity structures in the Pamir and Hindu Kush

NASA Astrophysics Data System (ADS)

Li, Wei; Chen, Yun; Yuan, Xiaohui; Schurr, Bernd; Mechie, James; Oimahmadov, Ilhomjon; Fu, Bihong

2018-01-01

The Pamir has experienced more intense deformation and shortening than Tibet, although it has a similar history of terrane accretion. Subduction as a primary way to accommodate lithospheric shortening beneath the Pamir has induced the intermediate-depth seismicity, which is rare in Tibet. Here we construct a 3D S-wave velocity model of the lithosphere beneath the Pamir by surface wave tomography using data of the TIPAGE (Tien Shan-Pamir Geodynamic program) and other seismic networks in the area. We imaged a large-scale low velocity anomaly in the crust at 20-50 km depth in the Pamir overlain by a high velocity anomaly at a depth shallower than 15 km. The high velocity anomalies colocate with exposed gneiss domes, which may imply a similar history of crustal deformation, partial melting and exhumation in the hinterland, as has occurred in the Himalaya/Tibet system. At mantle depths, where the intermediate-depth earthquakes are located, a low velocity zone is clearly observed extending to about 180 km and 150 km depth in the Hindu Kush and eastern Pamir, respectively. Moreover, the geometry of the low-velocity anomaly suggests that lower crustal material has been pulled down into the mantle by the subducting Asian and Indian lithospheric mantle beneath the Pamir and Hindu Kush, respectively. Metamorphic processes in the subducting lower crust may cause the intermediate-depth seismicity down to 150-180 km depth beneath the Pamir and Hindu Kush. We inverted focal mechanisms in the seismic zone for the stress field. Differences in the stress field between the upper and lower parts of the Indian slab imply that subduction and detachment of the Indian lithosphere might cause intense seismicity associated with the thermal shear instability in the deep Hindu Kush.

Spots of Seismic Danger Extracted by Properties of Low-Frequency Seismic Noise

NASA Astrophysics Data System (ADS)

Lyubushin, Alexey

2013-04-01

A new method of seismic danger estimate is presented which is based on using properties of low-frequency seismic noise from broadband networks. Two statistics of noise waveforms are considered: multi-fractal singularity spectrum support width D and minimum normalized entropy En of squared orthogonal wavelet coefficients. The maps of D and En are plotted in the moving time window. Let us call the regions extracted by low values of D and high values of En as "spots of seismic danger" - SSD. Mean values of D and En are strongly anti-correlated - that is why statistics D and En extract the same SSD. Nevertheless their mutual considering is expedient because these parameters are based on different approaches. The physical mechanism which underlies the method is consolidation of small blocks of the Earth's crust into the large one before the strong earthquake. This effect has a consequence that seismic noise does not include spikes which are connected with mutual movements of small blocks. The absence of irregular spikes in the noise follows the decreasing of D and increasing of entropy En. The stability in space and size of the SSD provides estimates of the place and energy of the probable future earthquake. The increasing or decreasing of SSD size and minimum or maximum values of D and En within SSD allows estimate the trend of seismic danger. The method is illustrating by the analysis of seismic noise from broadband seismic network F-net in Japan [1-5]. Statistically significant decreasing of D allowed a hypothesis about approaching Japan to a future seismic catastrophe to be formulated at the middle of 2008. The peculiarities of correlation coefficient estimate within 1 year time window between median values of D and generalized Hurst exponent allowed to make a decision that starting from July of 2010 Japan come to the state of waiting strong earthquake [3]. The method extracted a huge SSD near Japan which includes the region of future Tohoku mega-earthquake and the

Induced Seismicity Monitoring System

NASA Astrophysics Data System (ADS)

Taylor, S. R.; Jarpe, S.; Harben, P.

2014-12-01

There are many seismological aspects associated with monitoring of permanent storage of carbon dioxide (CO2) in geologic formations. Many of these include monitoring underground gas migration through detailed tomographic studies of rock properties, integrity of the cap rock and micro seismicity with time. These types of studies require expensive deployments of surface and borehole sensors in the vicinity of the CO2 injection wells. Another problem that may exist in CO2 sequestration fields is the potential for damaging induced seismicity associated with fluid injection into the geologic reservoir. Seismic hazard monitoring in CO2 sequestration fields requires a seismic network over a spatially larger region possibly having stations in remote settings. Expensive observatory-grade seismic systems are not necessary for seismic hazard deployments or small-scale tomographic studies. Hazard monitoring requires accurate location of induced seismicity to magnitude levels only slightly less than that which can be felt at the surface (e.g. magnitude 1), and the frequencies of interest for tomographic analysis are ~1 Hz and greater. We have developed a seismo/acoustic smart sensor system that can achieve the goals necessary for induced seismicity monitoring in CO2 sequestration fields. The unit is inexpensive, lightweight, easy to deploy, can operate remotely under harsh conditions and features 9 channels of recording (currently 3C 4.5 Hz geophone, MEMS accelerometer and microphone). An on-board processor allows for satellite transmission of parameter data to a processing center. Continuous or event-detected data is kept on two removable flash SD cards of up to 64+ Gbytes each. If available, data can be transmitted via cell phone modem or picked up via site visits. Low-power consumption allows for autonomous operation using only a 10 watt solar panel and a gel-cell battery. The system has been successfully tested for long-term (> 6 months) remote operations over a wide range

Incorporating induced seismicity in the 2014 United States National Seismic Hazard Model: results of the 2014 workshop and sensitivity studies

USGS Publications Warehouse

Petersen, Mark D.; Mueller, Charles S.; Moschetti, Morgan P.; Hoover, Susan M.; Rubinstein, Justin L.; Llenos, Andrea L.; Michael, Andrew J.; Ellsworth, William L.; McGarr, Arthur F.; Holland, Austin A.; Anderson, John G.

2015-01-01

The U.S. Geological Survey National Seismic Hazard Model for the conterminous United States was updated in 2014 to account for new methods, input models, and data necessary for assessing the seismic ground shaking hazard from natural (tectonic) earthquakes. The U.S. Geological Survey National Seismic Hazard Model project uses probabilistic seismic hazard analysis to quantify the rate of exceedance for earthquake ground shaking (ground motion). For the 2014 National Seismic Hazard Model assessment, the seismic hazard from potentially induced earthquakes was intentionally not considered because we had not determined how to properly treat these earthquakes for the seismic hazard analysis. The phrases “potentially induced” and “induced” are used interchangeably in this report, however it is acknowledged that this classification is based on circumstantial evidence and scientific judgment. For the 2014 National Seismic Hazard Model update, the potentially induced earthquakes were removed from the NSHM’s earthquake catalog, and the documentation states that we would consider alternative models for including induced seismicity in a future version of the National Seismic Hazard Model. As part of the process of incorporating induced seismicity into the seismic hazard model, we evaluate the sensitivity of the seismic hazard from induced seismicity to five parts of the hazard model: (1) the earthquake catalog, (2) earthquake rates, (3) earthquake locations, (4) earthquake Mmax (maximum magnitude), and (5) earthquake ground motions. We describe alternative input models for each of the five parts that represent differences in scientific opinions on induced seismicity characteristics. In this report, however, we do not weight these input models to come up with a preferred final model. Instead, we present a sensitivity study showing uniform seismic hazard maps obtained by applying the alternative input models for induced seismicity. The final model will be released after

Romanian Complex Data Center for Dense Seismic network

NASA Astrophysics Data System (ADS)

Neagoe, Cristian; Ionescu, Constantin; Marius Manea, Liviu

2010-05-01

Since 2002 the National Institute for Earth Physics (NIEP) developed its own real-time digital seismic network: consisting of 96 seismic stations of which 35 are broadband sensors and 24 stations equipped with short period sensors and two arrays earthquakes that transmit data in real time at the National Data Center (NDC) and Eforie Nord (EFOR) Seismic Observatory. EFOR is the back-up for the NDC and also a monitoring center for Black Sea tsunamis. Seismic stations are equipped with Quanterra Q330 and K2 digitizers, broadband seismometers (STS2, CMG40T, CMG 3ESP, CMG3T) and acceleration sensors Episensor Kinemetrics (+ / - 2G). SeedLink who is a part of Seiscomp2.5 and Antelope are software packages used for acquisition in real time (RT) and for data exchange. Communication of digital seismic stations to the National Data Center in Bucharest and Seismic Observatory Eforie Nord is assured by 5 providers (GPRS, VPN, satellite radio and Internet communication). For acquisition and data processing at the two centers of reception and processing is used AntelopeTM 4.11 running on 2 workstations: one for real-time and other for offline processing and also a Seiscomp 3 server that works as back-up for Antelope 4.11 Both acquisition and analysis of seismic data systems produced information about local and global parameters of earthquakes, in addition Antelope is used for manual processing (association events, the calculation of magnitude, creating a database, sending seismic bulletins, calculation of PGA and PGV , etc.), generating ShakeMap products and interacts with global data centers. In order to make all this information easily available across the Web and also lay the grounds for a more modular and flexible development environment the National Data Center developed tools to enable centralizing of data from software such as Antelope which is using a dedicated database system ( Datascope, a database system based on text files ) to a more general-purpose database, My

Regional Observation of Seismic Activity in Baekdu Mountain

NASA Astrophysics Data System (ADS)

Kim, Geunyoung; Che, Il-Young; Shin, Jin-Soo; Chi, Heon-Cheol

2015-04-01

Seismic unrest in Baekdu Mountain area between North Korea and Northeast China region has called attention to geological research community in Northeast Asia due to her historical and cultural importance. Seismic bulletin shows level of seismic activity in the area is higher than that of Jilin Province of Northeast China. Local volcanic observation shows a symptom of magmatic unrest in period between 2002 and 2006. Regional seismic data have been used to analyze seismic activity of the area. The seismic activity could be differentiated from other seismic phenomena in the region by the analysis.

An analysis of Super typhoon Rammasun's(2014) peak intensity

NASA Astrophysics Data System (ADS)

Cai, Qinbo; Xu, Yinglong

2016-04-01

Super typhoon Rammasun (2014) made landfall over Hainan Island, China, at 0730UTC 18 July 2014. Due to the damage of the anemometers, the Automatic Weather Stations (AWS) and the bouy which by Rammasun passed, failed to obtain its peak wind. Lack of the direct evident, in real-time monitoring, its peak intensities were given by 110kts (.i.e. 60m/s)/910hPa,135kts/922hPa , and 90kts/935hPa based on Dvorak technique , which were made by China Meteorological Administration (CMA),Joint Typhoon Warning Center(JTWC), and Japan Meteorological Agency (JMA) respectively. However, a minimum pressure of 881.2hPa recorded by a barometer which located at Qixhou island (19.982︒N,111.269︒E) while Rammasun approaching, indicates that its intensity was under estimated. By using observation data such as AWS, satellite, Doppler radar and wind tower near the ground, this study performs a detail evaluation to obtain its actual intensity. At 0521UTC, Qizhou Island station recorded 881.2hPa of the minimum station pressure and 899.2hPa of minimum sea level pressure (MSLP) while the anemometer had been destroyed. These are the lowest records in Chinese history and also are ones of the global lowest pressures obtained directly by barometer. It is evident that Rammasun's eyewall did not pass across Qizhou Island directly, so the actual MSLP should be lower than 899.2hPa. By applying wind-pressure relationship, it is reckoned that the reasonable MSLP and peak wind of Rammasun should be 888hPa and 70-76m/s, which makes Rammasun the strongest typhoon ever made landfall in China's history. In order to intuitively investigate the real intensity of Ramasun, eyewall structures are compared with some historical extreme typhoons (hurricanes) such as Saomai(2006), Haiyan(2013) and Katrina(2005). Satellite images show that the dense overcast convection strength of Rammasun is stronger than those when Saomai and Katrina were in their peak intensities and before landing, but weaker than Haiyan. The

The impact of the structural features of the rock mass on seismicity in Polish coal mines

NASA Astrophysics Data System (ADS)

Patyńska, Renata

2017-11-01

The article presents seismic activity induced in the coal mines of the Upper Silesian Coal Basin (GZW) in relation to the locations of the occurrence of rockbursts. The comparison of these measurements with the structural features of the rock mass of coal mines indicates the possibility of estimating the so-called Unitary Energy Expenditure (UEE) in a specific time. The obtained values of UEE were compared with the distribution of seismic activity in GZW mines. The level of seismic activity in the analysed period changed and depended on the intensity of mining works and diverse mining and geological conditions. Five regions, where tremors occurred (Bytom Trough, Main Saddle, Main Trough, Kazimierz Trough, and Jejkowice and Chwałowice Trough) which belong to various structural units of the Upper Silesia were analyzed. It was found out that rock bursts were recorded only in three regions: Main Saddle, Bytom Trough, and Jejkowice and Chwałowice Trough.

Seismic Characterization of EGS Reservoirs

NASA Astrophysics Data System (ADS)

Templeton, D. C.; Pyle, M. L.; Matzel, E.; Myers, S.; Johannesson, G.

2014-12-01

To aid in the seismic characterization of Engineered Geothermal Systems (EGS), we enhance the traditional microearthquake detection and location methodologies at two EGS systems. We apply the Matched Field Processing (MFP) seismic imaging technique to detect new seismic events using known discrete microearthquake sources. Events identified using MFP are typically smaller magnitude events or events that occur within the coda of a larger event. Additionally, we apply a Bayesian multiple-event seismic location algorithm, called MicroBayesLoc, to estimate the 95% probability ellipsoids for events with high signal-to-noise ratios (SNR). Such probability ellipsoid information can provide evidence for determining if a seismic lineation could be real or simply within the anticipated error range. We apply this methodology to the Basel EGS data set and compare it to another EGS dataset. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Real-time Seismic Amplitude Measurement (RSAM): a volcano monitoring and prediction tool

USGS Publications Warehouse

Endo, E.T.; Murray, T.

1991-01-01

Seismicity is one of the most commonly monitored phenomena used to determine the state of a volcano and for the prediction of volcanic eruptions. Although several real-time earthquake-detection and data acquisition systems exist, few continuously measure seismic amplitude in circumstances where individual events are difficult to recognize or where volcanic tremor is prevalent. Analog seismic records provide a quick visual overview of activity; however, continuous rapid quantitative analysis to define the intensity of seismic activity for the purpose of predicing volcanic eruptions is not always possible because of clipping that results from the limited dynamic range of analog recorders. At the Cascades Volcano Observatory, an inexpensive 8-bit analog-to-digital system controlled by a laptop computer is used to provide 1-min average-amplitude information from eight telemetered seismic stations. The absolute voltage level for each station is digitized, averaged, and appended in near real-time to a data file on a multiuser computer system. Raw realtime seismic amplitude measurement (RSAM) data or transformed RSAM data are then plotted on a common time base with other available volcano-monitoring information such as tilt. Changes in earthquake activity associated with dome-building episodes, weather, and instrumental difficulties are recognized as distinct patterns in the RSAM data set. RSAM data for domebuilding episodes gradually develop into exponential increases that terminate just before the time of magma extrusion. Mount St. Helens crater earthquakes show up as isolated spikes on amplitude plots for crater seismic stations but seldom for more distant stations. Weather-related noise shows up as low-level, long-term disturbances on all seismic stations, regardless of distance from the volcano. Implemented in mid-1985, the RSAM system has proved valuable in providing up-to-date information on seismic activity for three Mount St. Helens eruptive episodes from 1985 to

The Virtual Seismic Atlas Project: sharing the interpretation of seismic data

NASA Astrophysics Data System (ADS)

Butler, R.; Mortimer, E.; McCaffrey, B.; Stuart, G.; Sizer, M.; Clayton, S.

2007-12-01

Through the activities of academic research programs, national institutions and corporations, especially oil and gas companies, there is a substantial volume of seismic reflection data. Although the majority is proprietary and confidential, there are significant volumes of data that are potentially within the public domain and available for research. Yet the community is poorly connected to these data and consequently geological and other research using seismic reflection data is limited to very few groups of researchers. This is about to change. The Virtual Seismic Atlas (VSA) is generating an independent, free-to-use, community based internet resource that captures and shares the geological interpretation of seismic data globally. Images and associated documents are explicitly indexed using not only existing survey and geographical data but also on the geology they portray. By using "Guided Navigation" to search, discover and retrieve images, users are exposed to arrays of geological analogues that provide novel insights and opportunities for research and education. The VSA goes live, with evolving content and functionality, through 2008. There are opportunities for designed integration with other global data programs in the earth sciences.

Final Report: Seismic Hazard Assessment at the PGDP

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

Wang, Zhinmeng

2007-06-01

Selecting a level of seismic hazard at the Paducah Gaseous Diffusion Plant for policy considerations and engineering design is not an easy task because it not only depends on seismic hazard, but also on seismic risk and other related environmental, social, and economic issues. Seismic hazard is the main focus. There is no question that there are seismic hazards at the Paducah Gaseous Diffusion Plant because of its proximity to several known seismic zones, particularly the New Madrid Seismic Zone. The issues in estimating seismic hazard are (1) the methods being used and (2) difficulty in characterizing the uncertainties ofmore » seismic sources, earthquake occurrence frequencies, and ground-motion attenuation relationships. This report summarizes how input data were derived, which methodologies were used, and what the hazard estimates at the Paducah Gaseous Diffusion Plant are.« less

The 2012 Emilia seismic sequence (Northern Italy): Imaging the thrust fault system by accurate aftershock location

NASA Astrophysics Data System (ADS)

Govoni, Aladino; Marchetti, Alessandro; De Gori, Pasquale; Di Bona, Massimo; Lucente, Francesco Pio; Improta, Luigi; Chiarabba, Claudio; Nardi, Anna; Margheriti, Lucia; Agostinetti, Nicola Piana; Di Giovambattista, Rita; Latorre, Diana; Anselmi, Mario; Ciaccio, Maria Grazia; Moretti, Milena; Castellano, Corrado; Piccinini, Davide

2014-05-01

Starting from late May 2012, the Emilia region (Northern Italy) was severely shaken by an intense seismic sequence, originated from a ML 5.9 earthquake on May 20th, at a hypocentral depth of 6.3 km, with thrust-type focal mechanism. In the following days, the seismic rate remained high, counting 50 ML ≥ 2.0 earthquakes a day, on average. Seismicity spreads along a 30 km east-west elongated area, in the Po river alluvial plain, in the nearby of the cities Ferrara and Modena. Nine days after the first shock, another destructive thrust-type earthquake (ML 5.8) hit the area to the west, causing further damage and fatalities. Aftershocks following this second destructive event extended along the same east-westerly trend for further 20 km to the west, thus illuminating an area of about 50 km in length, on the whole. After the first shock struck, on May 20th, a dense network of temporary seismic stations, in addition to the permanent ones, was deployed in the meizoseismal area, leading to a sensible improvement of the earthquake monitoring capability there. A combined dataset, including three-component seismic waveforms recorded by both permanent and temporary stations, has been analyzed in order to obtain an appropriate 1-D velocity model for earthquake location in the study area. Here we describe the main seismological characteristics of this seismic sequence and, relying on refined earthquakes location, we make inferences on the geometry of the thrust system responsible for the two strongest shocks.

OGS improvements in 2012 in running the Northeastern Italy Seismic Network: the Ferrara VBB borehole seismic station

NASA Astrophysics Data System (ADS)

Pesaresi, Damiano; Romanelli, Marco; Barnaba, Carla; Bragato, Pier Luigi; Durì, Giorgio

2013-04-01

The Centro di Ricerche Sismologiche (CRS, Seismological Research Center) of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS, Italian National Institute for Oceanography and Experimental Geophysics) in Udine (Italy) after the strong earthquake of magnitude M=6.4 occurred in 1976 in the Italian Friuli-Venezia Giulia region, started to operate the Northeastern Italy Seismic Network: it currently consists of 17 very sensitive broad band and 18 simpler short period seismic stations, all telemetered to and acquired in real time at the OGS-CRS data center in Udine. Real time data exchange agreements in place with other Italian, Slovenian, Austrian and Swiss seismological institutes lead to a total number of about 100 seismic stations acquired in real time, which makes the OGS the reference institute for seismic monitoring of Northeastern Italy. The southwestern edge of the OGS seismic network stands on the Po alluvial basin: earthquake localization and characterization in this area is affected by the presence of soft alluvial deposits. OGS ha already experience in running a local seismic network in high noise conditions making use of borehole installations in the case of the micro-seismicity monitoring of a local gas storage site for a private company. Following the ML=5.9 earthquake that struck the Emilia region around Ferrara in Northern Italy on May 20, 2012 at 02:03:53 UTC, a cooperation of Istituto Nazionale di Geofisica e Vulcanologia, OGS, the Comune di Ferrara and the University of Ferrara lead to the reinstallation of a previously existing very broad band (VBB) borehole seismic station in Ferrara. The aim of the OGS intervention was on one hand to extend its real time seismic monitoring capabilities toward South-West, including Ferrara and its surroundings, and on the other hand to evaluate the seismic response at the site. We will describe improvements in running the Northeastern Italy Seismic Network, including details of the Ferrara VBB

Seismic Attenuation Structure and Intraplate Deformation

NASA Astrophysics Data System (ADS)

Bezada, M.; Kowalke, S.; Smale, J.

2017-12-01

It has been suggested that intraplate deformation and seismicity is localized at weak zones in the lithosphere and at rheological boundaries. Comparisons of intraplate deformation regions with mantle seismic velocity structure suggest a correlation, but are not universally accepted as compelling evidence. We present P-wave attenuation models built from records of teleseismic deep-focus earthquakes in three different regions that show significant correlation between attenuation structure and intraplate seismicity and deformation. In the eastern United States, the New Madrid, Wabash Valley, Eastern Tennessee, Central Virginia, and Carolina seismic zones all occur at or near the edges of high-Q (low attenuation) regions. In Spain, intraplate seismicity is absent from high-Q regions but relatively abundant in surrounding low-Q regions where intraplate orogeny is also observed. In Australia, where our model resolution is relatively poor owing to sparse and uneven station coverage, the Petermann and Alice Springs intraplate orogens occur near the edge of a high-Q feature roughly coinciding with the undeformed Amadeus basin. Our results suggest that lithospheric structure exerts important controls on the localization of intraplate deformation and seismicity and that seismic attenuation is a useful proxy for lithospheric strength.

Seismic Velocity Measurements at Expanded Seismic Network Sites

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

Woolery, Edward W; Wang, Zhenming

2005-01-01

Structures at the Paducah Gaseous Diffusion Plant (PGDP), as well as at other locations in the northern Jackson Purchase of western Kentucky may be subjected to large far-field earthquake ground motions from the New Madrid seismic zone, as well as those from small and moderate-sized local events. The resultant ground motion a particular structure is exposed from such event will be a consequence of the earthquake magnitude, the structures' proximity to the event, and the dynamic and geometrical characteristics of the thick soils upon which they are, of necessity, constructed. This investigation evaluated the latter. Downhole and surface (i.e., refractionmore » and reflection) seismic velocity data were collected at the Kentucky Seismic and Strong-Motion Network expansion sites in the vicinity of the Paducah Gaseous Diffusion Plant (PGDP) to define the dynamic properties of the deep sediment overburden that can produce modifying effects on earthquake waves. These effects are manifested as modifications of the earthquake waves' amplitude, frequency, and duration. Each of these three ground motion manifestations is also fundamental to the assessment of secondary earthquake engineering hazards such as liquefaction.« less

Shallow seismicity patterns in the northwestern section of the Mexico Subduction Zone

NASA Astrophysics Data System (ADS)

Abbott, Elizabeth R.; Brudzinski, Michael R.

2015-11-01

This study characterizes subduction related seismicity with local deployments along the northwestern section of the Mexico Subduction Zone where 4 portions of the plate interface have ruptured in 1973, 1985, 1995, and 2003. It has been proposed that the subducted boundary between the Cocos and Rivera plates occurs beneath this region, as indicated by inland volcanic activity, a gap in tectonic tremor, and the Manzanillo Trough and Colima Graben, which are depressions thought to be associated with the splitting of the two plates after subduction. Data from 50 broadband stations that comprised the MARS seismic array, deployed from January 2006 to June 2007, were processed with the software program Antelope and its generalized source location algorithm, genloc, to detect and locate earthquakes within the network. Slab surface depth contours from the resulting catalog indicate a change in subduction trajectory between the Rivera and Cocos plates. The earthquake locations are spatially anti-correlated with tectonic tremor, supporting the idea that they represent different types of fault slip. Hypocentral patterns also reveal areas of more intense seismic activity (clusters) that appear to be associated with the 2003 and 1973 megathrust rupture regions. Seismicity concentrated inland of the 2003 rupture is consistent with slip on a shallowly dipping trajectory for the Rivera plate interface as opposed to crustal faulting in the overriding North American plate. A prominent cluster of seismicity within the suspected 1973 rupture zone appears to be a commonly active portion of the megathrust as it has been active during three previous deployments. We support these interpretations by determining focal mechanisms and detailed relocations of the largest events within the 1973 and inland 2003 clusters, which indicate primarily thrust mechanisms near the plate interface.

Crustal Fracturing Field and Presence of Fluid as Revealed by Seismic Anisotropy

NASA Astrophysics Data System (ADS)

Pastori, M.; Piccinini, D.; de Gori, P.; Margheriti, L.; Barchi, M. R.; di Bucci, D.

2010-12-01

In the last three years, we developed, tested and improved an automatic analysis code (Anisomat+) to calculate the shear wave splitting parameters, fast polarization direction (φ) and delay time (∂t). The code is a set of MatLab scripts able to retrieve crustal anisotropy parameters from three-component seismic recording of local earthquakes using horizontal component cross-correlation method. The analysis procedure consists in choosing an appropriate frequency range, that better highlights the signal containing the shear waves, and a length of time window on the seismogram centered on the S arrival (the temporal window contains at least one cycle of S wave). The code was compared to other two automatic analysis code (SPY and SHEBA) and tested on three Italian areas (Val d’Agri, Tiber Valley and L’Aquila surrounding) along the Apennine mountains. For each region we used the anisotropic parameters resulting from the automatic computation as a tool to determine the fracture field geometries connected with the active stress field. We compare the temporal variations of anisotropic parameters to the evolution of vp/vs ratio for the same seismicity. The anisotropic fast directions are used to define the active stress field (EDA model), finding a general consistence between fast direction and main stress indicators (focal mechanism and borehole break-out). The magnitude of delay time is used to define the fracture field intensity finding higher value in the volume where micro-seismicity occurs. Furthermore we studied temporal variations of anisotropic parameters and vp/vs ratio in order to explain if fluids play an important role in the earthquake generation process. The close association of anisotropic and vp/vs parameters variations and seismicity rate changes supports the hypothesis that the background seismicity is influenced by the fluctuation of pore fluid pressure in the rocks.

LANL seismic screening method for existing buildings

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

Dickson, S.L.; Feller, K.C.; Fritz de la Orta, G.O.

1997-01-01

The purpose of the Los Alamos National Laboratory (LANL) Seismic Screening Method is to provide a comprehensive, rational, and inexpensive method for evaluating the relative seismic integrity of a large building inventory using substantial life-safety as the minimum goal. The substantial life-safety goal is deemed to be satisfied if the extent of structural damage or nonstructural component damage does not pose a significant risk to human life. The screening is limited to Performance Category (PC) -0, -1, and -2 buildings and structures. Because of their higher performance objectives, PC-3 and PC-4 buildings automatically fail the LANL Seismic Screening Method andmore » will be subject to a more detailed seismic analysis. The Laboratory has also designated that PC-0, PC-1, and PC-2 unreinforced masonry bearing wall and masonry infill shear wall buildings fail the LANL Seismic Screening Method because of their historically poor seismic performance or complex behavior. These building types are also recommended for a more detailed seismic analysis. The results of the LANL Seismic Screening Method are expressed in terms of separate scores for potential configuration or physical hazards (Phase One) and calculated capacity/demand ratios (Phase Two). This two-phase method allows the user to quickly identify buildings that have adequate seismic characteristics and structural capacity and screen them out from further evaluation. The resulting scores also provide a ranking of those buildings found to be inadequate. Thus, buildings not passing the screening can be rationally prioritized for further evaluation. For the purpose of complying with Executive Order 12941, the buildings failing the LANL Seismic Screening Method are deemed to have seismic deficiencies, and cost estimates for mitigation must be prepared. Mitigation techniques and cost-estimate guidelines are not included in the LANL Seismic Screening Method.« less

Multicomponent ensemble models to forecast induced seismicity

NASA Astrophysics Data System (ADS)

Király-Proag, E.; Gischig, V.; Zechar, J. D.; Wiemer, S.

2018-01-01

In recent years, human-induced seismicity has become a more and more relevant topic due to its economic and social implications. Several models and approaches have been developed to explain underlying physical processes or forecast induced seismicity. They range from simple statistical models to coupled numerical models incorporating complex physics. We advocate the need for forecast testing as currently the best method for ascertaining if models are capable to reasonably accounting for key physical governing processes—or not. Moreover, operational forecast models are of great interest to help on-site decision-making in projects entailing induced earthquakes. We previously introduced a standardized framework following the guidelines of the Collaboratory for the Study of Earthquake Predictability, the Induced Seismicity Test Bench, to test, validate, and rank induced seismicity models. In this study, we describe how to construct multicomponent ensemble models based on Bayesian weightings that deliver more accurate forecasts than individual models in the case of Basel 2006 and Soultz-sous-Forêts 2004 enhanced geothermal stimulation projects. For this, we examine five calibrated variants of two significantly different model groups: (1) Shapiro and Smoothed Seismicity based on the seismogenic index, simple modified Omori-law-type seismicity decay, and temporally weighted smoothed seismicity; (2) Hydraulics and Seismicity based on numerically modelled pore pressure evolution that triggers seismicity using the Mohr-Coulomb failure criterion. We also demonstrate how the individual and ensemble models would perform as part of an operational Adaptive Traffic Light System. Investigating seismicity forecasts based on a range of potential injection scenarios, we use forecast periods of different durations to compute the occurrence probabilities of seismic events M ≥ 3. We show that in the case of the Basel 2006 geothermal stimulation the models forecast hazardous levels

The Seismic Alert System of Mexico (SASMEX): Performance and Evolution

NASA Astrophysics Data System (ADS)

Espinosa Aranda, J.

2013-05-01

Originally the Seismic Alert System of Mexico (SASMEX) was proposed to integrate the Seismic Alert System of Mexico City (SAS), operating since 1991, with the Seismic Alert System of Oaxaca City (SASO), in services since 2003. And today, after the intense big earthquake activity observed in our world during 2010 and 2011, local governments of Mexico City, Oaxaca Estate, and the Mexican Ministry of the Interior have been promoting the expansion of this technological EEW development. Until 2012 SASMEX better coverage includes 48 new field seismic sensors (FS) deployed over the seismic region of Jalisco, Colima, Michoacan and Puebla, with someone enhancements over Guerrero and Oaxaca, to reach 97 FS. During 2013, 35 new FS has been proposed to SASMEX enhancements covering the Chiapas and Veracruz seismic regions. The SASMEX, with the support of the Mexico Valley Broadcasters Association (ARVM) since 1993, automatically issue Public and Preventive earthquake early warning signals in the Cities of Mexico, Toluca, Acapulco, Chilpancingo, and Oaxaca. The seismic warning range in each case is seated in accordance with local Civil Protection Authorities: Public Alert, if they expect strong earthquake effects, and Preventive Alert one, the effect could be moderated. Now the SASMEX warning time opportunity could be different to the 60 sec. average typically generated when SAS warned earthquake effects coming from Guerrero to Mexico City valley. Mexican EEW issued today reach: 16 Public and 62 Preventive Alert in Mexico City; 25 Public and 19 Preventive Alerts in Oaxaca City; also 14 Public and 4 Preventive Alerts in Acapulco; 14 Public and 5 Preventive Alerts in Chilpancingo. The earthquakes events registered by SASMEX FS until now reach 3448. With the support of private and Federal telecommunications infrastructure like, TELMEX, Federal Electric Commission, and the Mexican Security Ministry, it was developed a redundant communication system with pads to link the different

Seismic Prediction While Drilling (SPWD): Seismic exploration ahead of the drill bit using phased array sources

NASA Astrophysics Data System (ADS)

Jaksch, Katrin; Giese, Rüdiger; Kopf, Matthias

2010-05-01

In the case of drilling for deep reservoirs previous exploration is indispensable. In recent years the focus shifted more on geological structures like small layers or hydrothermal fault systems. Beside 2D- or 3D-seismics from the surface and seismic measurements like Vertical Seismic Profile (VSP) or Seismic While Drilling (SWD) within a borehole these methods cannot always resolute this structures. The resolution is worsen the deeper and smaller the sought-after structures are. So, potential horizons like small layers in oil exploration or fault zones usable for geothermal energy production could be failed or not identified while drilling. The application of a device to explore the geology with a high resolution ahead of the drill bit in direction of drilling would be of high importance. Such a device would allow adjusting the drilling path according to the real geology and would minimize the risk of discovery and hence the costs for drilling. Within the project SPWD a device for seismic exploration ahead of the drill bit will be developed. This device should allow the seismic exploration to predict areas about 50 to 100 meters ahead of the drill bit with a resolution of one meter. At the GFZ a first prototype consisting of different units for seismic sources, receivers and data loggers has been designed and manufactured. As seismic sources four standard magnetostrictive actuators and as receivers four 3-component-geophones are used. Every unit, actuator or geophone, can be rotated in steps of 15° around the longitudinal axis of the prototype to test different measurement configurations. The SPWD prototype emits signal frequencies of about 500 up to 5000 Hz which are significant higher than in VSP and SWD. An increased radiation of seismic wave energy in the direction of the borehole axis allows the view in areas to be drilled. Therefore, every actuator must be controlled independently of each other regarding to amplitude and phase of the source signal to

Quantifying the seismicity on Taiwan

NASA Astrophysics Data System (ADS)

Wu, Yi-Hsuan; Chen, Chien-Chih; Turcotte, Donald L.; Rundle, John B.

2013-07-01

We quantify the seismicity on the island of Taiwan using the frequency-magnitude statistics of earthquakes since 1900. A break in Gutenberg-Richter scaling for large earthquakes in global seismicity has been observed, this break is also observed in our Taiwan study. The seismic data from the Central Weather Bureau Seismic Network are in good agreement with the Gutenberg-Richter relation taking b ≈ 1 when M < 7. For large earthquakes, M ≥ 7, the seismic data fit Gutenberg-Richter scaling with b ≈ 1.5. If the Gutenberg-Richter scaling for M < 7 earthquakes is extrapolated to larger earthquakes, we would expect a M > 8 earthquake in the study region about every 25 yr. However, our analysis shows a lower frequency of occurrence of large earthquakes so that the expected frequency of M > 8 earthquakes is about 200 yr. The level of seismicity for smaller earthquakes on Taiwan is about 12 times greater than in Southern California and the possibility of a M ≈ 9 earthquake north or south of Taiwan cannot be ruled out. In light of the Fukushima, Japan nuclear disaster, we also discuss the implications of our study for the three operating nuclear power plants on the coast of Taiwan.

Three-component borehole wall-locking seismic detector

DOEpatents

Owen, Thomas E.

1994-01-01

A seismic detector for boreholes is described that has an accelerometer sensor block for sensing vibrations in geologic formations of the earth. The density of the seismic detector is approximately matched to the density of the formations in which the detector is utilized. A simple compass is used to orient the seismic detector. A large surface area shoe having a radius approximately equal to the radius of the borehole in which the seismic detector is located may be pushed against the side of the borehole by actuating cylinders contained in the seismic detector. Hydraulic drive of the cylinders is provided external to the detector. By using the large surface area wall-locking shoe, force holding the seismic detector in place is distributed over a larger area of the borehole wall thereby eliminating concentrated stresses. Borehole wall-locking forces up to ten times the weight of the seismic detector can be applied thereby ensuring maximum detection frequency response up to 2,000 hertz using accelerometer sensors in a triaxial array within the seismic detector.

Fast principal component analysis for stacking seismic data

NASA Astrophysics Data System (ADS)

Wu, Juan; Bai, Min

2018-04-01

Stacking seismic data plays an indispensable role in many steps of the seismic data processing and imaging workflow. Optimal stacking of seismic data can help mitigate seismic noise and enhance the principal components to a great extent. Traditional average-based seismic stacking methods cannot obtain optimal performance when the ambient noise is extremely strong. We propose a principal component analysis (PCA) algorithm for stacking seismic data without being sensitive to noise level. Considering the computational bottleneck of the classic PCA algorithm in processing massive seismic data, we propose an efficient PCA algorithm to make the proposed method readily applicable for industrial applications. Two numerically designed examples and one real seismic data are used to demonstrate the performance of the presented method.

Multivariate Formation Pressure Prediction with Seismic-derived Petrophysical Properties from Prestack AVO inversion and Poststack Seismic Motion Inversion

NASA Astrophysics Data System (ADS)

Yu, H.; Gu, H.

2017-12-01

A novel multivariate seismic formation pressure prediction methodology is presented, which incorporates high-resolution seismic velocity data from prestack AVO inversion, and petrophysical data (porosity and shale volume) derived from poststack seismic motion inversion. In contrast to traditional seismic formation prediction methods, the proposed methodology is based on a multivariate pressure prediction model and utilizes a trace-by-trace multivariate regression analysis on seismic-derived petrophysical properties to calibrate model parameters in order to make accurate predictions with higher resolution in both vertical and lateral directions. With prestack time migration velocity as initial velocity model, an AVO inversion was first applied to prestack dataset to obtain high-resolution seismic velocity with higher frequency that is to be used as the velocity input for seismic pressure prediction, and the density dataset to calculate accurate Overburden Pressure (OBP). Seismic Motion Inversion (SMI) is an inversion technique based on Markov Chain Monte Carlo simulation. Both structural variability and similarity of seismic waveform are used to incorporate well log data to characterize the variability of the property to be obtained. In this research, porosity and shale volume are first interpreted on well logs, and then combined with poststack seismic data using SMI to build porosity and shale volume datasets for seismic pressure prediction. A multivariate effective stress model is used to convert velocity, porosity and shale volume datasets to effective stress. After a thorough study of the regional stratigraphic and sedimentary characteristics, a regional normally compacted interval model is built, and then the coefficients in the multivariate prediction model are determined in a trace-by-trace multivariate regression analysis on the petrophysical data. The coefficients are used to convert velocity, porosity and shale volume datasets to effective stress and then

Seismic Search Engine: A distributed database for mining large scale seismic data

NASA Astrophysics Data System (ADS)

Liu, Y.; Vaidya, S.; Kuzma, H. A.

2009-12-01

The International Monitoring System (IMS) of the CTBTO collects terabytes worth of seismic measurements from many receiver stations situated around the earth with the goal of detecting underground nuclear testing events and distinguishing them from other benign, but more common events such as earthquakes and mine blasts. The International Data Center (IDC) processes and analyzes these measurements, as they are collected by the IMS, to summarize event detections in daily bulletins. Thereafter, the data measurements are archived into a large format database. Our proposed Seismic Search Engine (SSE) will facilitate a framework for data exploration of the seismic database as well as the development of seismic data mining algorithms. Analogous to GenBank, the annotated genetic sequence database maintained by NIH, through SSE, we intend to provide public access to seismic data and a set of processing and analysis tools, along with community-generated annotations and statistical models to help interpret the data. SSE will implement queries as user-defined functions composed from standard tools and models. Each query is compiled and executed over the database internally before reporting results back to the user. Since queries are expressed with standard tools and models, users can easily reproduce published results within this framework for peer-review and making metric comparisons. As an illustration, an example query is “what are the best receiver stations in East Asia for detecting events in the Middle East?” Evaluating this query involves listing all receiver stations in East Asia, characterizing known seismic events in that region, and constructing a profile for each receiver station to determine how effective its measurements are at predicting each event. The results of this query can be used to help prioritize how data is collected, identify defective instruments, and guide future sensor placements.

Comparison of smoothing methods for the development of a smoothed seismicity model for Alaska and the implications for seismic hazard

NASA Astrophysics Data System (ADS)

Moschetti, M. P.; Mueller, C. S.; Boyd, O. S.; Petersen, M. D.

2013-12-01

In anticipation of the update of the Alaska seismic hazard maps (ASHMs) by the U. S. Geological Survey, we report progress on the comparison of smoothed seismicity models developed using fixed and adaptive smoothing algorithms, and investigate the sensitivity of seismic hazard to the models. While fault-based sources, such as those for great earthquakes in the Alaska-Aleutian subduction zone and for the ~10 shallow crustal faults within Alaska, dominate the seismic hazard estimates for locations near to the sources, smoothed seismicity rates make important contributions to seismic hazard away from fault-based sources and where knowledge of recurrence and magnitude is not sufficient for use in hazard studies. Recent developments in adaptive smoothing methods and statistical tests for evaluating and comparing rate models prompt us to investigate the appropriateness of adaptive smoothing for the ASHMs. We develop smoothed seismicity models for Alaska using fixed and adaptive smoothing methods and compare the resulting models by calculating and evaluating the joint likelihood test. We use the earthquake catalog, and associated completeness levels, developed for the 2007 ASHM to produce fixed-bandwidth-smoothed models with smoothing distances varying from 10 to 100 km and adaptively smoothed models. Adaptive smoothing follows the method of Helmstetter et al. and defines a unique smoothing distance for each earthquake epicenter from the distance to the nth nearest neighbor. The consequence of the adaptive smoothing methods is to reduce smoothing distances, causing locally increased seismicity rates, where seismicity rates are high and to increase smoothing distances where seismicity is sparse. We follow guidance from previous studies to optimize the neighbor number (n-value) by comparing model likelihood values, which estimate the likelihood that the observed earthquake epicenters from the recent catalog are derived from the smoothed rate models. We compare likelihood

Comparison of smoothing methods for the development of a smoothed seismicity model for Alaska and the implications for seismic hazard

USGS Publications Warehouse

Moschetti, Morgan P.; Mueller, Charles S.; Boyd, Oliver S.; Petersen, Mark D.

2014-01-01

In anticipation of the update of the Alaska seismic hazard maps (ASHMs) by the U. S. Geological Survey, we report progress on the comparison of smoothed seismicity models developed using fixed and adaptive smoothing algorithms, and investigate the sensitivity of seismic hazard to the models. While fault-based sources, such as those for great earthquakes in the Alaska-Aleutian subduction zone and for the ~10 shallow crustal faults within Alaska, dominate the seismic hazard estimates for locations near to the sources, smoothed seismicity rates make important contributions to seismic hazard away from fault-based sources and where knowledge of recurrence and magnitude is not sufficient for use in hazard studies. Recent developments in adaptive smoothing methods and statistical tests for evaluating and comparing rate models prompt us to investigate the appropriateness of adaptive smoothing for the ASHMs. We develop smoothed seismicity models for Alaska using fixed and adaptive smoothing methods and compare the resulting models by calculating and evaluating the joint likelihood test. We use the earthquake catalog, and associated completeness levels, developed for the 2007 ASHM to produce fixed-bandwidth-smoothed models with smoothing distances varying from 10 to 100 km and adaptively smoothed models. Adaptive smoothing follows the method of Helmstetter et al. and defines a unique smoothing distance for each earthquake epicenter from the distance to the nth nearest neighbor. The consequence of the adaptive smoothing methods is to reduce smoothing distances, causing locally increased seismicity rates, where seismicity rates are high and to increase smoothing distances where seismicity is sparse. We follow guidance from previous studies to optimize the neighbor number (n-value) by comparing model likelihood values, which estimate the likelihood that the observed earthquake epicenters from the recent catalog are derived from the smoothed rate models. We compare likelihood

Dominant seismic sources for the cities in South Sumatra

NASA Astrophysics Data System (ADS)

Sunardi, Bambang; Sakya, Andi Eka; Masturyono, Murjaya, Jaya; Rohadi, Supriyanto; Sulastri, Putra, Ade Surya

2017-07-01

Subduction zone along west of Sumatra and Sumatran fault zone are active seismic sources. Seismotectonically, South Sumatra could be affected by earthquakes triggered by these seismic sources. This paper discussed contribution of each seismic source to earthquake hazards for cities of Palembang, Prabumulih, Banyuasin, OganIlir, Ogan Komering Ilir, South Oku, Musi Rawas and Empat Lawang. These hazards are presented in form of seismic hazard curves. The study was conducted by using Probabilistic Seismic Hazard Analysis (PSHA) of 2% probability of exceedance in 50 years. Seismic sources used in analysis included megathrust zone M2 of Sumatra and South Sumatra, background seismic sources and shallow crustal seismic sources consist of Ketaun, Musi, Manna and Kumering faults. The results of the study showed that for cities relatively far from the seismic sources, subduction / megathrust seismic source with a depth ≤ 50 km greatly contributed to the seismic hazard and the other areas showed deep background seismic sources with a depth of more than 100 km dominate to seismic hazard respectively.

Seismic seiches from the March 1964 Alaska earthquake: Chapter E in The Alaska earthquake, March 27, 1964: effects on hydrologic regimen

USGS Publications Warehouse

McGarr, Arthur; Vorhis, Robert C.

1968-01-01

epicenter had any apparent effect on the distribution of seiches. Where seismic surface waves propagated into an area with thicker sediment, the horizontal acceleration increased about in proportion to the increasing thickness of the sediment. In the Mississippi Embayment however, where the waves emerged from high rigidity crust into the sediment, the horizontal acceleration increased near the edge of the embayment but decreased in the central part and formed a shadow zone. Because both seiches and seismic intensity depend on the horizontal acceleration from surface waves, the distribution of seiches may be used to map the seismic intensity that can be expected from future local earthquakes.

Scanning Seismic Intrusion Detector

NASA Technical Reports Server (NTRS)

Lee, R. D.

1982-01-01

Scanning seismic intrusion detector employs array of automatically or manually scanned sensors to determine approximate location of intruder. Automatic-scanning feature enables one operator to tend system of many sensors. Typical sensors used with new system are moving-coil seismic pickups. Detector finds uses in industrial security systems.

Considering the ranges of uncertainties in the New Probabilistic Seismic Hazard Assessment of Germany - Version 2016

NASA Astrophysics Data System (ADS)

Grunthal, Gottfried; Stromeyer, Dietrich; Bosse, Christian; Cotton, Fabrice; Bindi, Dino

2017-04-01

The seismic load parameters for the upcoming National Annex to the Eurocode 8 result from the reassessment of the seismic hazard supported by the German Institution for Civil Engineering . This 2016 version of hazard assessment for Germany as target area was based on a comprehensive involvement of all accessible uncertainties in models and parameters into the approach and the provision of a rational framework for facilitating the uncertainties in a transparent way. The developed seismic hazard model represents significant improvements; i.e. it is based on updated and extended databases, comprehensive ranges of models, robust methods and a selection of a set of ground motion prediction equations of their latest generation. The output specifications were designed according to the user oriented needs as suggested by two review teams supervising the entire project. In particular, seismic load parameters were calculated for rock conditions with a vS30 of 800 ms-1 for three hazard levels (10%, 5% and 2% probability of occurrence or exceedance within 50 years) in form of, e.g., uniform hazard spectra (UHS) based on 19 sprectral periods in the range of 0.01 - 3s, seismic hazard maps for spectral response accelerations for different spectral periods or for macroseismic intensities. The developed hazard model consists of a logic tree with 4040 end branches and essential innovations employed to capture epistemic uncertainties and aleatory variabilities. The computation scheme enables the sound calculation of the mean and any quantile of required seismic load parameters. Mean, median and 84th percentiles of load parameters were provided together with the full calculation model to clearly illustrate the uncertainties of such a probabilistic assessment for a region of a low-to-moderate level of seismicity. The regional variations of these uncertainties (e.g. ratios between the mean and median hazard estimations) were analyzed and discussed.

Evaluation of seismic design spectrum based on UHS implementing fourth-generation seismic hazard maps of Canada

NASA Astrophysics Data System (ADS)

Ahmed, Ali; Hasan, Rafiq; Pekau, Oscar A.

2016-12-01

Two recent developments have come into the forefront with reference to updating the seismic design provisions for codes: (1) publication of new seismic hazard maps for Canada by the Geological Survey of Canada, and (2) emergence of the concept of new spectral format outdating the conventional standardized spectral format. The fourth -generation seismic hazard maps are based on enriched seismic data, enhanced knowledge of regional seismicity and improved seismic hazard modeling techniques. Therefore, the new maps are more accurate and need to incorporate into the Canadian Highway Bridge Design Code (CHBDC) for its next edition similar to its building counterpart National Building Code of Canada (NBCC). In fact, the code writers expressed similar intentions with comments in the commentary of CHBCD 2006. During the process of updating codes, NBCC, and AASHTO Guide Specifications for LRFD Seismic Bridge Design, American Association of State Highway and Transportation Officials, Washington (2009) lowered the probability level from 10 to 2% and 10 to 5%, respectively. This study has brought five sets of hazard maps corresponding to 2%, 5% and 10% probability of exceedance in 50 years developed by the GSC under investigation. To have a sound statistical inference, 389 Canadian cities are selected. This study shows the implications of the changes of new hazard maps on the design process (i.e., extent of magnification or reduction of the design forces).

Gas and gas hydrate distribution around seafloor seeps in Mississippi Canyon, Northern Gulf of Mexico, using multi-resolution seismic imagery

USGS Publications Warehouse

Wood, W.T.; Hart, P.E.; Hutchinson, D.R.; Dutta, N.; Snyder, F.; Coffin, R.B.; Gettrust, J.F.

2008-01-01

To determine the impact of seeps and focused flow on the occurrence of shallow gas hydrates, several seafloor mounds in the Atwater Valley lease area of the Gulf of Mexico were surveyed with a wide range of seismic frequencies. Seismic data were acquired with a deep-towed, Helmholz resonator source (220-820 Hz); a high-resolution, Generator-Injector air-gun (30-300 Hz); and an industrial air-gun array (10-130 Hz). Each showed a significantly different response in this weakly reflective, highly faulted area. Seismic modeling and observations of reversed-polarity reflections and small scale diffractions are consistent with a model of methane transport dominated regionally by diffusion but punctuated by intense upward advection responsible for the bathymetric mounds, as well as likely advection along pervasive filamentous fractures away from the mounds.

The New Italian Seismic Hazard Model

NASA Astrophysics Data System (ADS)

Marzocchi, W.; Meletti, C.; Albarello, D.; D'Amico, V.; Luzi, L.; Martinelli, F.; Pace, B.; Pignone, M.; Rovida, A.; Visini, F.

2017-12-01

In 2015 the Seismic Hazard Center (Centro Pericolosità Sismica - CPS) of the National Institute of Geophysics and Volcanology was commissioned of coordinating the national scientific community with the aim to elaborate a new reference seismic hazard model, mainly finalized to the update of seismic code. The CPS designed a roadmap for releasing within three years a significantly renewed PSHA model, with regard both to the updated input elements and to the strategies to be followed. The main requirements of the model were discussed in meetings with the experts on earthquake engineering that then will participate to the revision of the building code. The activities were organized in 6 tasks: program coordination, input data, seismicity models, ground motion predictive equations (GMPEs), computation and rendering, testing. The input data task has been selecting the most updated information about seismicity (historical and instrumental), seismogenic faults, and deformation (both from seismicity and geodetic data). The seismicity models have been elaborating in terms of classic source areas, fault sources and gridded seismicity based on different approaches. The GMPEs task has selected the most recent models accounting for their tectonic suitability and forecasting performance. The testing phase has been planned to design statistical procedures to test with the available data the whole seismic hazard models, and single components such as the seismicity models and the GMPEs. In this talk we show some preliminary results, summarize the overall strategy for building the new Italian PSHA model, and discuss in detail important novelties that we put forward. Specifically, we adopt a new formal probabilistic framework to interpret the outcomes of the model and to test it meaningfully; this requires a proper definition and characterization of both aleatory variability and epistemic uncertainty that we accomplish through an ensemble modeling strategy. We use a weighting scheme

Fluid injection and induced seismicity

NASA Astrophysics Data System (ADS)

Kendall, Michael; Verdon, James

2016-04-01

The link between fluid injection, or extraction, and induced seismicity has been observed in reservoirs for many decades. In fact spatial mapping of low magnitude events is routinely used to estimate a stimulated reservoir volume. However, the link between subsurface fluid injection and larger felt seismicity is less clear and has attracted recent interest with a dramatic increase in earthquakes associated with the disposal of oilfield waste fluids. In a few cases, hydraulic fracturing has also been linked to induced seismicity. Much can be learned from past case-studies of induced seismicity so that we can better understand the risks posed. Here we examine 12 case examples and consider in particular controls on maximum event size, lateral event distributions, and event depths. Our results suggest that injection volume is a better control on maximum magnitude than past, natural seismicity in a region. This might, however, simply reflect the lack of baseline monitoring and/or long-term seismic records in certain regions. To address this in the UK, the British Geological Survey is leading the deployment of monitoring arrays in prospective shale gas areas in Lancashire and Yorkshire. In most cases, seismicity is generally located in close vicinity to the injection site. However, in some cases, the nearest events are up to 5km from the injection point. This gives an indication of the minimum radius of influence of such fluid injection projects. The most distant events are never more than 20km from the injection point, perhaps implying a maximum radius of influence. Some events are located in the target reservoir, but most occur below the injection depth. In fact, most events lie in the crystalline basement underlying the sedimentary rocks. This suggests that induced seismicity may not pose a leakage risk for fluid migration back to the surface, as it does not impact caprock integrity. A useful application for microseismic data is to try and forecast induced seismicity

National Seismic Network of Georgia

NASA Astrophysics Data System (ADS)

Tumanova, N.; Kakhoberashvili, S.; Omarashvili, V.; Tserodze, M.; Akubardia, D.

2016-12-01

Georgia, as a part of the Southern Caucasus, is tectonically active and structurally complex region. It is one of the most active segments of the Alpine-Himalayan collision belt. The deformation and the associated seismicity are due to the continent-continent collision between the Arabian and Eurasian plates. Seismic Monitoring of country and the quality of seismic data is the major tool for the rapid response policy, population safety, basic scientific research and in the end for the sustainable development of the country. National Seismic Network of Georgia has been developing since the end of 19th century. Digital era of the network started from 2003. Recently continuous data streams from 25 stations acquired and analyzed in the real time. Data is combined to calculate rapid location and magnitude for the earthquake. Information for the bigger events (Ml>=3.5) is simultaneously transferred to the website of the monitoring center and to the related governmental agencies. To improve rapid earthquake location and magnitude estimation the seismic network was enhanced by installing additional 7 new stations. Each new station is equipped with coupled Broadband and Strong Motion seismometers and permanent GPS system as well. To select the sites for the 7 new base stations, we used standard network optimization techniques. To choose the optimal sites for new stations we've taken into account geometry of the existed seismic network, topographic conditions of the site. For each site we studied local geology (Vs30 was mandatory for each site), local noise level and seismic vault construction parameters. Due to the country elevation, stations were installed in the high mountains, no accessible in winter due to the heavy snow conditions. To secure online data transmission we used satellite data transmission as well as cell data network coverage from the different local companies. As a result we've already have the improved earthquake location and event magnitudes. We

A new approach on seismic mortality estimations based on average population density

NASA Astrophysics Data System (ADS)

Zhu, Xiaoxin; Sun, Baiqing; Jin, Zhanyong

2016-12-01

This study examines a new methodology to predict the final seismic mortality from earthquakes in China. Most studies established the association between mortality estimation and seismic intensity without considering the population density. In China, however, the data are not always available, especially when it comes to the very urgent relief situation in the disaster. And the population density varies greatly from region to region. This motivates the development of empirical models that use historical death data to provide the path to analyze the death tolls for earthquakes. The present paper employs the average population density to predict the final death tolls in earthquakes using a case-based reasoning model from realistic perspective. To validate the forecasting results, historical data from 18 large-scale earthquakes occurred in China are used to estimate the seismic morality of each case. And a typical earthquake case occurred in the northwest of Sichuan Province is employed to demonstrate the estimation of final death toll. The strength of this paper is that it provides scientific methods with overall forecast errors lower than 20 %, and opens the door for conducting final death forecasts with a qualitative and quantitative approach. Limitations and future research are also analyzed and discussed in the conclusion.

Passive seismic imaging based on seismic interferometry: method and its application to image the structure around the 2013 Mw6.6 Lushan earthquake

NASA Astrophysics Data System (ADS)

Gu, N.; Zhang, H.

2017-12-01

Seismic imaging of fault zones generally involves seismic velocity tomography using first arrival times or full waveforms from earthquakes occurring around the fault zones. However, in most cases seismic velocity tomography only gives smooth image of the fault zone structure. To get high-resolution structure of the fault zones, seismic migration using active seismic data needs to be used. But it is generally too expensive to conduct active seismic surveys, even for 2D. Here we propose to apply the passive seismic imaging method based on seismic interferometry to image fault zone detailed structures. Seismic interferometry generally refers to the construction of new seismic records for virtual sources and receivers by cross correlating and stacking the seismic records on physical receivers from physical sources. In this study, we utilize seismic waveforms recorded on surface seismic stations for each earthquake to construct zero-offset seismic record at each earthquake location as if there was a virtual receiver at each earthquake location. We have applied this method to image the fault zone structure around the 2013 Mw6.6 Lushan earthquake. After the occurrence of the mainshock, a 29-station temporary array is installed to monitor aftershocks. In this study, we first select aftershocks along several vertical cross sections approximately normal to the fault strike. Then we create several zero-offset seismic reflection sections by seismic interferometry with seismic waveforms from aftershocks around each section. Finally we migrate these zero-offset sections to create seismic structures around the fault zones. From these migration images, we can clearly identify strong reflectors, which correspond to major reverse fault where the mainshock occurs. This application shows that it is possible to image detailed fault zone structures with passive seismic sources.

Evaluation of seismic performance of reinforced concrete (RC) buildings under near-field earthquakes

NASA Astrophysics Data System (ADS)

Moniri, Hassan

2017-03-01

Near-field ground motions are significantly severely affected on seismic response of structure compared with far-field ground motions, and the reason is that the near-source forward directivity ground motions contain pulse-long periods. Therefore, the cumulative effects of far-fault records are minor. The damage and collapse of engineering structures observed in the last decades' earthquakes show the potential of damage in existing structures under near-field ground motions. One important subject studied by earthquake engineers as part of a performance-based approach is the determination of demand and collapse capacity under near-field earthquake. Different methods for evaluating seismic structural performance have been suggested along with and as part of the development of performance-based earthquake engineering. This study investigated the results of illustrious characteristics of near-fault ground motions on the seismic response of reinforced concrete (RC) structures, by the use of Incremental Nonlinear Dynamic Analysis (IDA) method. Due to the fact that various ground motions result in different intensity-versus-response plots, this analysis is done again under various ground motions in order to achieve significant statistical averages. The OpenSees software was used to conduct nonlinear structural evaluations. Numerical modelling showed that near-source outcomes cause most of the seismic energy from the rupture to arrive in a single coherent long-period pulse of motion and permanent ground displacements. Finally, a vulnerability of RC building can be evaluated against pulse-like near-fault ground motions effects.

Toward a consistent model for strain accrual and release for the New Madrid Seismic Zone, central United States

USGS Publications Warehouse

Hough, S.E.; Page, M.

2011-01-01

At the heart of the conundrum of seismogenesis in the New Madrid Seismic Zone is the apparently substantial discrepancy between low strain rate and high recent seismic moment release. In this study we revisit the magnitudes of the four principal 1811–1812 earthquakes using intensity values determined from individual assessments from four experts. Using these values and the grid search method of Bakun and Wentworth (1997), we estimate magnitudes around 7.0 for all four events, values that are significantly lower than previously published magnitude estimates based on macroseismic intensities. We further show that the strain rate predicted from postglacial rebound is sufficient to produce a sequence with the moment release of one Mmax6.8 every 500 years, a rate that is much lower than previous estimates of late Holocene moment release. However, Mw6.8 is at the low end of the uncertainty range inferred from analysis of intensities for the largest 1811–1812 event. We show that Mw6.8 is also a reasonable value for the largest main shock given a plausible rupture scenario. One can also construct a range of consistent models that permit a somewhat higher Mmax, with a longer average recurrence rate. It is thus possible to reconcile predicted strain and seismic moment release rates with alternative models: one in which 1811–1812 sequences occur every 500 years, with the largest events being Mmax∼6.8, or one in which sequences occur, on average, less frequently, with Mmax of ∼7.0. Both models predict that the late Holocene rate of activity will continue for the next few to 10 thousand years.

Midplate seismicity exterior to former rift-basins

USGS Publications Warehouse

Dewey, J.W.

1988-01-01

Midplate seismicity associated with some former rift-zones is distributed diffusely near, but exterior to, the rift basins. This "basin-exterior' seismicity cannot be attributed to reactivation of major basin-border faults on which uppercrustal extension was concentrated at the time of rifting, because the border faults dip beneath the basins. The seismicity may nonetheless represent reactivation of minor faults that were active at the time of rifting but that were located outside of the principal zones of upper-crustal extension; the occurrence of basin-exterior seismicity in some present-day rift-zones supports the existence of such minor basin-exterior faults. Other hypotheses for seismicity exterior to former rift-basins are that the seismicity reflects lobes of high stress due to lithospheric-bending that is centered on the axis of the rift, that the seismicity is localized on the exteriors of rift-basins by basin-interiors that are less deformable in the current epoch than the basin exteriors, and that seismicity is localized on the basin-exteriors by the concentration of tectonic stress in the highly elastic basin-exterior upper-crust. -from Author

The Canarian Seismic Monitoring Network: design, development and first result

NASA Astrophysics Data System (ADS)

D'Auria, Luca; Barrancos, José; Padilla, Germán D.; García-Hernández, Rubén; Pérez, Aaron; Pérez, Nemesio M.

2017-04-01

Tenerife is an active volcanic island which experienced several eruptions of moderate intensity in historical times, and few explosive eruptions in the Holocene. The increasing population density and the consistent number of tourists are constantly raising the volcanic risk. In June 2016 Instituto Volcanologico de Canarias started the deployment of a seismological volcano monitoring network consisting of 15 broadband seismic stations. The network began its full operativity in November 2016. The aim of the network are both volcano monitoring and scientific research. Currently data are continuously recorded and processed in real-time. Seismograms, hypocentral parameters, statistical informations about the seismicity and other data are published on a web page. We show the technical characteristics of the network and an estimate of its detection threshold and earthquake location performances. Furthermore we present other near-real time procedures on the data: analysis of the ambient noise for determining the shallow velocity model and temporal velocity variations, detection of earthquake multiplets through massive data mining of the seismograms and automatic relocation of events through double-difference location.

From Geodetic Imaging of Seismic and Aseismic Fault Slip to Dynamic Modeling of the Seismic Cycle

NASA Astrophysics Data System (ADS)

Avouac, Jean-Philippe

2015-05-01

Understanding the partitioning of seismic and aseismic fault slip is central to seismotectonics as it ultimately determines the seismic potential of faults. Thanks to advances in tectonic geodesy, it is now possible to develop kinematic models of the spatiotemporal evolution of slip over the seismic cycle and to determine the budget of seismic and aseismic slip. Studies of subduction zones and continental faults have shown that aseismic creep is common and sometimes prevalent within the seismogenic depth range. Interseismic coupling is generally observed to be spatially heterogeneous, defining locked patches of stress accumulation, to be released in future earthquakes or aseismic transients, surrounded by creeping areas. Clay-rich tectonites, high temperature, and elevated pore-fluid pressure seem to be key factors promoting aseismic creep. The generally logarithmic time evolution of afterslip is a distinctive feature of creeping faults that suggests a logarithmic dependency of fault friction on slip rate, as observed in laboratory friction experiments. Most faults can be considered to be paved with interlaced patches where the friction law is either rate-strengthening, inhibiting seismic rupture propagation, or rate-weakening, allowing for earthquake nucleation. The rate-weakening patches act as asperities on which stress builds up in the interseismic period; they might rupture collectively in a variety of ways. The pattern of interseismic coupling can help constrain the return period of the maximum- magnitude earthquake based on the requirement that seismic and aseismic slip sum to match long-term slip. Dynamic models of the seismic cycle based on this conceptual model can be tuned to reproduce geodetic and seismological observations. The promise and pitfalls of using such models to assess seismic hazard are discussed.

Investigations of acoustic-seismic effects at long range - Early-arriving seismic waves from Apollo 16

NASA Technical Reports Server (NTRS)

Dalins, I.; Mccarty, V. M.; Kaschak, G.; Donn, W. L.

1974-01-01

A reasonably comprehensive technical effort is described dealing with the investigations of acoustically generated seismic waves of Apollo 16 and Apollo 17 origin along the eastern seabord of the United States. This expanded effort is a continuation of earlier, rather successful detections of rocket-generated seismic disturbances on Skidaway Island, Georgia. The more recent effort has yielded few positive results other than a recording of an early-arriving seismic wave from Apollo 16 that was detected in Jacksonville. Evaluation of the negative results obtained in the Fort Monmouth area, with earlier studies of infrasound, local weather conditions, and geology, could be advantageous in the process of trying to gain a better insight into the acoustic-seismic resonance mechanism requiring phase-velocity matching at the atmosphere-ground interface.

'Fracking', Induced Seismicity and the Critical Earth

NASA Astrophysics Data System (ADS)

Leary, P.; Malin, P. E.

2012-12-01

Issues of 'fracking' and induced seismicity are reverse-analogous to the equally complex issues of well productivity in hydrocarbon, geothermal and ore reservoirs. In low hazard reservoir economics, poorly producing wells and low grade ore bodies are many while highly producing wells and high grade ores are rare but high pay. With induced seismicity factored in, however, the same distribution physics reverses the high/low pay economics: large fracture-connectivity systems are hazardous hence low pay, while high probability small fracture-connectivity systems are non-hazardous hence high pay. Put differently, an economic risk abatement tactic for well productivity and ore body pay is to encounter large-scale fracture systems, while an economic risk abatement tactic for 'fracking'-induced seismicity is to avoid large-scale fracture systems. Well productivity and ore body grade distributions arise from three empirical rules for fluid flow in crustal rock: (i) power-law scaling of grain-scale fracture density fluctuations; (ii) spatial correlation between spatial fluctuations in well-core porosity and the logarithm of well-core permeability; (iii) frequency distributions of permeability governed by a lognormality skewness parameter. The physical origin of rules (i)-(iii) is the universal existence of a critical-state-percolation grain-scale fracture-density threshold for crustal rock. Crustal fractures are effectively long-range spatially-correlated distributions of grain-scale defects permitting fluid percolation on mm to km scales. The rule is, the larger the fracture system the more intense the percolation throughput. As percolation pathways are spatially erratic and unpredictable on all scales, they are difficult to model with sparsely sampled well data. Phenomena such as well productivity, induced seismicity, and ore body fossil fracture distributions are collectively extremely difficult to predict. Risk associated with unpredictable reservoir well productivity

Modernization of the Slovenian National Seismic Network

NASA Astrophysics Data System (ADS)

Vidrih, R.; Godec, M.; Gosar, A.; Sincic, P.; Tasic, I.; Zivcic, M.

2003-04-01

The Environmental Agency of the Republic of Slovenia, the Seismology Office is responsible for the fast and reliable information about earthquakes, originating in the area of Slovenia and nearby. In the year 2000 the project Modernization of the Slovenian National Seismic Network started. The purpose of a modernized seismic network is to enable fast and accurate automatic location of earthquakes, to determine earthquake parameters and to collect data of local, regional and global earthquakes. The modernized network will be finished in the year 2004 and will consist of 25 Q730 remote broadband data loggers based seismic station subsystems transmitting in real-time data to the Data Center in Ljubljana, where the Seismology Office is located. The remote broadband station subsystems include 16 surface broadband seismometers CMG-40T, 5 broadband seismometers CMG-40T with strong motion accelerographs EpiSensor, 4 borehole broadband seismometers CMG-40T, all with accurate timing provided by GPS receivers. The seismic network will cover the entire Slovenian territory, involving an area of 20,256 km2. The network is planned in this way; more seismic stations will be around bigger urban centres and in regions with greater vulnerability (NW Slovenia, Krsko Brezice region). By the end of the year 2002, three old seismic stations were modernized and ten new seismic stations were built. All seismic stations transmit data to UNIX-based computers running Antelope system software. The data is transmitted in real time using TCP/IP protocols over the Goverment Wide Area Network . Real-time data is also exchanged with seismic networks in the neighbouring countries, where the data are collected from the seismic stations, close to the Slovenian border. A typical seismic station consists of the seismic shaft with the sensor and the data acquisition system and, the service shaft with communication equipment (modem, router) and power supply with a battery box. which provides energy in case

Seismic Hazard Analysis as a Controlling Technique of Induced Seismicity in Geothermal Systems

NASA Astrophysics Data System (ADS)

Convertito, V.; Sharma, N.; Maercklin, N.; Emolo, A.; Zollo, A.

2011-12-01

The effect of induced seismicity of geothermal systems during stimulation and fluid circulation can cover a wide range of values from light and unfelt to severe and damaging. If the design of a modern geothermal system requires the largest efficiency to be obtained from the social point of view it is required that the system could be managed in order to reduce possible impact in advance. In this framework, automatic control of the seismic response of the stimulated reservoir is nowadays mandatory, particularly in proximity of densely populated areas. Recently, techniques have been proposed for this purpose mainly based on the concept of the traffic light. This system provides a tool to decide the level of stimulation rate based on the real-time analysis of the induced seismicity and the ongoing ground motion values. However, in some cases the induced effect can be delayed with respect to the time when the reservoir is stimulated. Thus, a controlling system technique able to estimate the ground motion levels for different time scales can help to better control the geothermal system. Here we present an adaptation of the classical probabilistic seismic hazard analysis to the case where the seismicity rate as well as the propagation medium properties are not constant with time. We use a non-homogeneous seismicity model for modeling purposes, in which the seismicity rate and b-value of the recurrence relationship change with time. Additionally, as a further controlling procedure, we propose a moving time window analysis of the recorded peak ground-motion values aimed at monitoring the changes in the propagation medium. In fact, for the same set of magnitude values recorded at the same stations, we expect that on average peak ground motion values attenuate in same way. As a consequence, the residual differences can be reasonably ascribed to changes in medium properties. These changes can be modeled and directly introduced in the hazard integral. We applied the proposed

Identification of ground motion features for high-tech facility under far field seismic waves using wavelet packet transform

NASA Astrophysics Data System (ADS)

Huang, Shieh-Kung; Loh, Chin-Hsiung; Chen, Chin-Tsun

2016-04-01

Seismic records collected from earthquake with large magnitude and far distance may contain long period seismic waves which have small amplitude but with dominant period up to 10 sec. For a general situation, the long period seismic waves will not endanger the safety of the structural system or cause any uncomfortable for human activity. On the contrary, for those far distant earthquakes, this type of seismic waves may cause a glitch or, furthermore, breakdown to some important equipments/facilities (such as the high-precision facilities in high-tech Fab) and eventually damage the interests of company if the amplitude becomes significant. The previous study showed that the ground motion features such as time-variant dominant frequencies extracted using moving window singular spectrum analysis (MWSSA) and amplitude characteristics of long-period waves identified from slope change of ground motion Arias Intensity can efficiently indicate the damage severity to the high-precision facilities. However, embedding a large hankel matrix to extract long period seismic waves make the MWSSA become a time-consumed process. In this study, the seismic ground motion data collected from broadband seismometer network located in Taiwan were used (with epicenter distance over 1000 km). To monitor the significant long-period waves, the low frequency components of these seismic ground motion data are extracted using wavelet packet transform (WPT) to obtain wavelet coefficients and the wavelet entropy of coefficients are used to identify the amplitude characteristics of long-period waves. The proposed method is a timesaving process compared to MWSSA and can be easily implemented for real-time detection. Comparison and discussion on this method among these different seismic events and the damage severity to the high-precision facilities in high-tech Fab is made.

CPT site characterization for seismic hazards in the New Madrid seismic zone

USGS Publications Warehouse

Liao, T.; Mayne, P.W.; Tuttle, M.P.; Schweig, E.S.; Van Arsdale, R.B.

2002-01-01

A series of cone penetration tests (CPTs) were conducted in the vicinity of the New Madrid seismic zone in central USA for quantifying seismic hazards, obtaining geotechnical soil properties, and conducting studies at liquefaction sites related to the 1811-1812 and prehistoric New Madrid earthquakes. The seismic piezocone provides four independent measurements for delineating the stratigraphy, liquefaction potential, and site amplification parameters. At the same location, two independent assessments of soil liquefaction susceptibility can be made using both the normalized tip resistance (qc1N) and shear wave velocity (Vs1). In lieu of traditional deterministic approaches, the CPT data can be processed using probability curves to assess the level and likelihood of future liquefaction occurrence. ?? 2002 Elsevier Science Ltd. All rights reserved.

NSR&D Program Fiscal Year (FY) 2015 Call for Proposals Mitigation of Seismic Risk at Nuclear Facilities using Seismic Isolation

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

Coleman, Justin

2015-02-01

Seismic isolation (SI) has the potential to drastically reduce seismic response of structures, systems, or components (SSCs) and therefore the risk associated with large seismic events (large seismic event could be defined as the design basis earthquake (DBE) and/or the beyond design basis earthquake (BDBE) depending on the site location). This would correspond to a potential increase in nuclear safety by minimizing the structural response and thus minimizing the risk of material release during large seismic events that have uncertainty associated with their magnitude and frequency. The national consensus standard America Society of Civil Engineers (ASCE) Standard 4, Seismic Analysismore » of Safety Related Nuclear Structures recently incorporated language and commentary for seismically isolating a large light water reactor or similar large nuclear structure. Some potential benefits of SI are: 1) substantially decoupling the SSC from the earthquake hazard thus decreasing risk of material release during large earthquakes, 2) cost savings for the facility and/or equipment, and 3) applicability to both nuclear (current and next generation) and high hazard non-nuclear facilities. Issue: To date no one has evaluated how the benefit of seismic risk reduction reduces cost to construct a nuclear facility. Objective: Use seismic probabilistic risk assessment (SPRA) to evaluate the reduction in seismic risk and estimate potential cost savings of seismic isolation of a generic nuclear facility. This project would leverage ongoing Idaho National Laboratory (INL) activities that are developing advanced (SPRA) methods using Nonlinear Soil-Structure Interaction (NLSSI) analysis. Technical Approach: The proposed study is intended to obtain an estimate on the reduction in seismic risk and construction cost that might be achieved by seismically isolating a nuclear facility. The nuclear facility is a representative pressurized water reactor building nuclear power plant (NPP

OGS improvements in 2012 in running the North-eastern Italy Seismic Network: the Ferrara VBB borehole seismic station

NASA Astrophysics Data System (ADS)

Pesaresi, D.; Romanelli, M.; Barnaba, C.; Bragato, P. L.; Durì, G.

2014-07-01

The Centro di Ricerche Sismologiche (CRS, Seismological Research Centre) of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS, Italian National Institute for Oceanography and Experimental Geophysics) in Udine (Italy) after the strong earthquake of magnitude M=6.4 occurred in 1976 in the Italian Friuli-Venezia Giulia region, started to operate the North-eastern Italy Seismic Network: it currently consists of 17 very sensitive broad band and 18 simpler short period seismic stations, all telemetered to and acquired in real time at the OGS-CRS data centre in Udine. Real time data exchange agreements in place with other Italian, Slovenian, Austrian and Swiss seismological institutes lead to a total number of about 100 seismic stations acquired in real time, which makes the OGS the reference institute for seismic monitoring of North-eastern Italy. The south-western edge of the OGS seismic network (Fig. 1) stands on the Po alluvial basin: earthquake localization and characterization in this area is affected by the presence of soft alluvial deposits. OGS ha already experience in running a local seismic network in high noise conditions making use of borehole installations in the case of the micro-seismicity monitoring of a local gas storage site for a private company. Following the ML = 5.9 earthquake that struck the Emilia region around Ferrara in Northern Italy on 20 May 2012 at 02:03:53 UTC, a cooperation of Istituto Nazionale di Geofisica e Vulcanologia, OGS, the Comune di Ferrara and the University of Ferrara lead to the reinstallation of a previously existing very broad band (VBB) borehole seismic station in Ferrara. The aim of the OGS intervention was on one hand to extend its real time seismic monitoring capabilities toward South-West, including Ferrara and its surroundings, and on the other hand to evaluate the seismic response at the site. We will describe improvements in running the North-eastern Italy Seismic Network, including details of

Seismic Microzonation of Breginjski Kot (NW Slovenia) Based on Detailed Engineering Geological Mapping

PubMed Central

2013-01-01

Breginjski kot is among the most endangered seismic zones in Slovenia with the seismic hazard assessed to intensity IX MSK and the design ground acceleration of 0.250 g, both for 500-year return period. The most destructive was the 1976 Friuli Mw = 6.4 earthquake which had maximum intensity VIII-IX. Since the previous microzonation of the area was based solely on the basic geological map and did not include supplementary field research, we have performed a new soil classification of the area. First, a detailed engineering geological mapping in scale 1 : 5.000 was conducted. Mapped units were described in detail and some of them interpreted anew. Stiff sites are composed of hard to medium-hard rocks which were subjected to erosion mainly evoked by glacial and postglacial age. At that time a prominent topography was formed and different types of sediments were deposited in valleys by mass flows. A distinction between sediments and weathered rocks, their exact position, and thickness are of significant importance for microzonation. On the basis of geological mapping, a soil classification was carried out according to the Medvedev method (intensity increments) and the Eurocode 8 standard (soil factors) and two microzonation maps were prepared. The bulk of the studied area is covered by soft sediments and nine out of ten settlements are situated on them. The microzonation clearly points out the dependence of damage distribution in the case of 1976 Friuli earthquake to local site effects. PMID:24453884

Romanian Educational Seismic Network Project

NASA Astrophysics Data System (ADS)

Tataru, Dragos; Ionescu, Constantin; Zaharia, Bogdan; Grecu, Bogdan; Tibu, Speranta; Popa, Mihaela; Borleanu, Felix; Toma, Dragos; Brisan, Nicoleta; Georgescu, Emil-Sever; Dobre, Daniela; Dragomir, Claudiu-Sorin

2013-04-01

Romania is one of the most active seismic countries in Europe, with more than 500 earthquakes occurring every year. The seismic hazard of Romania is relatively high and thus understanding the earthquake phenomena and their effects at the earth surface represents an important step toward the education of population in earthquake affected regions of the country and aims to raise the awareness about the earthquake risk and possible mitigation actions. In this direction, the first national educational project in the field of seismology has recently started in Romania: the ROmanian EDUcational SEISmic NETwork (ROEDUSEIS-NET) project. It involves four partners: the National Institute for Earth Physics as coordinator, the National Institute for Research and Development in Construction, Urban Planning and Sustainable Spatial Development " URBAN - INCERC" Bucharest, the Babeş-Bolyai University (Faculty of Environmental Sciences and Engineering) and the software firm "BETA Software". The project has many educational, scientific and social goals. The main educational objectives are: training students and teachers in the analysis and interpretation of seismological data, preparing of several comprehensive educational materials, designing and testing didactic activities using informatics and web-oriented tools. The scientific objective is to introduce into schools the use of advanced instruments and experimental methods that are usually restricted to research laboratories, with the main product being the creation of an earthquake waveform archive. Thus a large amount of such data will be used by students and teachers for educational purposes. For the social objectives, the project represents an effective instrument for informing and creating an awareness of the seismic risk, for experimentation into the efficacy of scientific communication, and for an increase in the direct involvement of schools and the general public. A network of nine seismic stations with SEP seismometers

The Global Detection Capability of the IMS Seismic Network in 2013 Inferred from Ambient Seismic Noise Measurements

NASA Astrophysics Data System (ADS)

Gaebler, P. J.; Ceranna, L.

2016-12-01

All nuclear explosions - on the Earth's surface, underground, underwater or in the atmosphere - are banned by the Comprehensive Nuclear-Test-Ban Treaty (CTBT). As part of this treaty, a verification regime was put into place to detect, locate and characterize nuclear explosion testings at any time, by anyone and everywhere on the Earth. The International Monitoring System (IMS) plays a key role in the verification regime of the CTBT. Out of the different monitoring techniques used in the IMS, the seismic waveform approach is the most effective technology for monitoring nuclear underground testing and to identify and characterize potential nuclear events. This study introduces a method of seismic threshold monitoring to assess an upper magnitude limit of a potential seismic event in a certain given geographical region. The method is based on ambient seismic background noise measurements at the individual IMS seismic stations as well as on global distance correction terms for body wave magnitudes, which are calculated using the seismic reflectivity method. From our investigations we conclude that a global detection threshold of around mb 4.0 can be achieved using only stations from the primary seismic network, a clear latitudinal dependence for the detection thresholdcan be observed between northern and southern hemisphere. Including the seismic stations being part of the auxiliary seismic IMS network results in a slight improvement of global detection capability. However, including wave arrivals from distances greater than 120 degrees, mainly PKP-wave arrivals, leads to a significant improvement in average global detection capability. In special this leads to an improvement of the detection threshold on the southern hemisphere. We further investigate the dependence of the detection capability on spatial (latitude and longitude) and temporal (time) parameters, as well as on parameters such as source type and percentage of operational IMS stations.

Planar seismic source characterization models developed for probabilistic seismic hazard assessment of Istanbul

NASA Astrophysics Data System (ADS)

Gülerce, Zeynep; Buğra Soyman, Kadir; Güner, Barış; Kaymakci, Nuretdin

2017-12-01

This contribution provides an updated planar seismic source characterization (SSC) model to be used in the probabilistic seismic hazard assessment (PSHA) for Istanbul. It defines planar rupture systems for the four main segments of the North Anatolian fault zone (NAFZ) that are critical for the PSHA of Istanbul: segments covering the rupture zones of the 1999 Kocaeli and Düzce earthquakes, central Marmara, and Ganos/Saros segments. In each rupture system, the source geometry is defined in terms of fault length, fault width, fault plane attitude, and segmentation points. Activity rates and the magnitude recurrence models for each rupture system are established by considering geological and geodetic constraints and are tested based on the observed seismicity that is associated with the rupture system. Uncertainty in the SSC model parameters (e.g., b value, maximum magnitude, slip rate, weights of the rupture scenarios) is considered, whereas the uncertainty in the fault geometry is not included in the logic tree. To acknowledge the effect of earthquakes that are not associated with the defined rupture systems on the hazard, a background zone is introduced and the seismicity rates in the background zone are calculated using smoothed-seismicity approach. The state-of-the-art SSC model presented here is the first fully documented and ready-to-use fault-based SSC model developed for the PSHA of Istanbul.

Seismic instrumentation plan for the Hawaiian Volcano Observatory

USGS Publications Warehouse

Thelen, Weston A.

2014-01-01

The installation of new seismic stations is only the first part of building a volcanic early warning capability for seismicity in the State of Hawaii. Additional personnel will likely be required to study the volcanic processes at work under each volcano, analyze the current seismic activity at a level sufficient for early warning, build new tools for monitoring, maintain seismic computing resources, and maintain the new seismic stations.

Seismic risk assessment and application in the central United States

USGS Publications Warehouse

Wang, Z.

2011-01-01

Seismic risk is a somewhat subjective, but important, concept in earthquake engineering and other related decision-making. Another important concept that is closely related to seismic risk is seismic hazard. Although seismic hazard and seismic risk have often been used interchangeably, they are fundamentally different: seismic hazard describes the natural phenomenon or physical property of an earthquake, whereas seismic risk describes the probability of loss or damage that could be caused by a seismic hazard. The distinction between seismic hazard and seismic risk is of practical significance because measures for seismic hazard mitigation may differ from those for seismic risk reduction. Seismic risk assessment is a complicated process and starts with seismic hazard assessment. Although probabilistic seismic hazard analysis (PSHA) is the most widely used method for seismic hazard assessment, recent studies have found that PSHA is not scientifically valid. Use of PSHA will lead to (1) artifact estimates of seismic risk, (2) misleading use of the annual probability of exccedance (i.e., the probability of exceedance in one year) as a frequency (per year), and (3) numerical creation of extremely high ground motion. An alternative approach, which is similar to those used for flood and wind hazard assessments, has been proposed. ?? 2011 ASCE.

Evaluation of the Seismic Hazard in Venezuela with a revised seismic catalog that seeks for harmonization along the country borders

NASA Astrophysics Data System (ADS)

Rendon, H.; Alvarado, L.; Paolini, M.; Olbrich, F.; González, J.; Ascanio, W.

2013-05-01

Probabilistic Seismic Hazard Assessment is a complex endeavor that relies on the quality of the information that comes from different sources: the seismic catalog, active faults parameters, strain rates, etc. Having this in mind, during the last several months, the FUNVISIS seismic hazard group has been working on a review and update of the local data base that form the basis for a reliable PSHA calculation. In particular, the seismic catalog, which provides the necessary information that allows the evaluation of the critical b-value, which controls how seismic occurrence distributes with magnitude, has received particular attention. The seismic catalog is the result of the effort of several generations of researchers along the years; therefore, the catalog necessarily suffers from the lack of consistency, homogeneity and completeness for all ranges of magnitude over any seismic study area. Merging the FUNVISIS instrumental catalog with the ones obtained from international agencies, we present the work that we have been doing to produce a consistent seismic catalog that covers Venezuela entirely, with seismic events starting from 1910 until 2012, and report the magnitude of completeness for the different periods. Also, we present preliminary results on the Seismic Hazard evaluation that takes into account such instrumental catalog, the historical catalog, updated known fault geometries and its correspondent parameters, and the new seismic sources that have been defined accordingly. Within the spirit of the Global Earthquake Model (GEM), all these efforts look for possible bridges with neighboring countries to establish consistent hazard maps across the borders.

Ambient seismic wave field

PubMed Central

NISHIDA, Kiwamu

2017-01-01

The ambient seismic wave field, also known as ambient noise, is excited by oceanic gravity waves primarily. This can be categorized as seismic hum (1–20 mHz), primary microseisms (0.02–0.1 Hz), and secondary microseisms (0.1–1 Hz). Below 20 mHz, pressure fluctuations of ocean infragravity waves reach the abyssal floor. Topographic coupling between seismic waves and ocean infragravity waves at the abyssal floor can explain the observed shear traction sources. Below 5 mHz, atmospheric disturbances may also contribute to this excitation. Excitation of primary microseisms can be attributed to topographic coupling between ocean swell and seismic waves on subtle undulation of continental shelves. Excitation of secondary microseisms can be attributed to non-linear forcing by standing ocean swell at the sea surface in both pelagic and coastal regions. Recent developments in source location based on body-wave microseisms enable us to estimate forcing quantitatively. For a comprehensive understanding, we must consider the solid Earth, the ocean, and the atmosphere as a coupled system. PMID:28769015

Seismic retrofit guidelines for Utah highway bridges.

DOT National Transportation Integrated Search

2009-05-01

Much of Utahs population dwells in a seismically active region, and many of the bridges connecting transportation lifelines predate the rigorous seismic design standards that have been developed in the past 10-20 years. Seismic retrofitting method...

Seismic Tomography

NASA Astrophysics Data System (ADS)

Nowack, Robert L.; Li, Cuiping

The inversion of seismic travel-time data for radially varying media was initially investigated by Herglotz, Wiechert, and Bateman (the HWB method) in the early part of the 20th century [1]. Tomographic inversions for laterally varying media began in seismology starting in the 1970’s. This included early work by Aki, Christoffersson, and Husebye who developed an inversion technique for estimating lithospheric structure beneath a seismic array from distant earthquakes (the ACH method) [2]. Also, Alekseev and others in Russia performed early inversions of refraction data for laterally varying upper mantle structure [3]. Aki and Lee [4] developed an inversion technique using travel-time data from local earthquakes.

Research on Seismic Wave Attenuation in Gas Hydrates Layer Using Vertical Cable Seismic Data

NASA Astrophysics Data System (ADS)

Wang, Xiangchun; Liang, Lunhang; Wu, Zhongliang

2018-06-01

Vertical cable seismic (VCS) data are the most suitable seismic data for estimating the quality factor Q values of layers under the sea bottom by now. Here the quality factor Q values are estimated using the high-precision logarithmic spectrum ratio method for VCS data. The estimated Q values are applied to identify the layers with gas hydrates and free gas. From the results it can be seen that the Q value in layer with gas hydrates becomes larger and the Q value in layer with free gas becomes smaller than layers without gas hydrates or free gas. Additionally, the estimated Q values are used for inverse Q filtering processing to compensate the attenuated seismic signal's high-frequency component. From the results it can be seen that the main frequency of seismic signal is improved and the frequency band is broadened, the resolution of the VCS data is improved effectively.

Seismic signal and noise on Europa

NASA Astrophysics Data System (ADS)

Panning, Mark; Stähler, Simon; Bills, Bruce; Castillo Castellanos, Jorge; Huang, Hsin-Hua; Husker, Allen; Kedar, Sharon; Lorenz, Ralph; Pike, William T.; Schmerr, Nicholas; Tsai, Victor; Vance, Steven

2017-10-01

Seismology is one of our best tools for detailing interior structure of planetary bodies, and a seismometer is included in the baseline and threshold mission design for the upcoming Europa Lander mission. Guiding mission design and planning for adequate science return, though, requires modeling of both the anticipated signal and noise. Assuming ice seismicity on Europa behaves according to statistical properties observed in Earth catalogs and scaling cumulative seismic moment release to the moon, we can simulate long seismic records and estimate background noise and peak signal amplitudes (Panning et al., 2017). This suggests a sensitive instrument comparable to many broadband terrestrial instruments or the SP instrument from the InSight mission to Mars will be able to record signals, while high frequency geophones are likely inadequate. We extend this analysis to also begin incorporation of spatial and temporal variation due to the tidal cycle, which can help inform landing site selection. We also begin exploration of how chaotic terrane at the bottom of the ice shell and inter-ice heterogeneities (i.e. internal melt structures) may affect anticipated seismic observations using 2D numerical seismic simulations.M. P. Panning, S. C. Stähler, H.-H. Huang, S. D. Vance, S. Kedar, V. C. Tsai, W. T. Pike, R. D. Lorenz, “Expected seismicity and the seismic noise environment of Europa,” J. Geophys. Res., in revision, 2017.

Seismic efficiency of meteor airbursts

NASA Astrophysics Data System (ADS)

Svetsov, V. V.; Artemieva, N. A.; Shuvalov, V. V.

2017-08-01

We present the results of numerical simulation for impacts of relatively small asteroids and ice bodies of 30-100 m in size, decelerated in the atmosphere and exploding before they reach the surface, but still producing seismic effects due to the impact wave reaching the surface. The calculated magnitudes fall within the range of 4 to 6, and average seismic efficiency of these events is 2.5 × 10-5. The results obtained allow the seismic hazard from impacts of cosmic bodies to be estimated.

Seismic Monitoring for the United Arab Emirates

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

Rodgers, A; Nakanishi, K

2005-04-11

There is potential for earthquakes in the United Arab Emirates and in the Zagros mountains to cause structural damage and pose a threat to safety of people. Damaging effects from earthquakes can be mitigated by knowledge of the location and size of earthquakes, effects on construction, and monitoring these effects over time. Although a general idea of seismicity in the UAE may be determined with data from global seismic networks, these global networks do not have the sensitivity to record smaller seismic events and do not have the necessary accuracy to locate the events. A National Seismic Monitoring Observatory ismore » needed for the UAE that consists of a modern seismic network and a multidisciplinary staff that can analyze and interpret the data from the network. A seismic network is essential to locate earthquakes, determine event magnitudes, identify active faults and measure ground motions from earthquakes. Such a network can provide the data necessary for a reliable seismic hazard assessment in the UAE. The National Seismic Monitoring Observatory would ideally be situated at a university that would provide access to the wide range of disciplines needed in operating the network and providing expertise in analysis and interpretation.« less

Urban seismic risk assessment: statistical repair cost data and probable structural losses based on damage scenario—correlation analysis

NASA Astrophysics Data System (ADS)

Eleftheriadou, Anastasia K.; Baltzopoulou, Aikaterini D.; Karabinis, Athanasios I.

2016-06-01

The current seismic risk assessment is based on two discrete approaches, actual and probable, validating afterwards the produced results. In the first part of this research, the seismic risk is evaluated from the available data regarding the mean statistical repair/strengthening or replacement cost for the total number of damaged structures (180,427 buildings) after the 7/9/1999 Parnitha (Athens) earthquake. The actual evaluated seismic risk is afterwards compared to the estimated probable structural losses, which is presented in the second part of the paper, based on a damage scenario in the referring earthquake. The applied damage scenario is based on recently developed damage probability matrices (DPMs) from Athens (Greece) damage database. The seismic risk estimation refers to 750,085 buildings situated in the extended urban region of Athens. The building exposure is categorized in five typical structural types and represents 18.80 % of the entire building stock in Greece. The last information is provided by the National Statistics Service of Greece (NSSG) according to the 2000-2001 census. The seismic input is characterized by the ratio, a g/ a o, where a g is the regional peak ground acceleration (PGA) which is evaluated from the earlier estimated research macroseismic intensities, and a o is the PGA according to the hazard map of the 2003 Greek Seismic Code. Finally, the collected investigated financial data derived from different National Services responsible for the post-earthquake crisis management concerning the repair/strengthening or replacement costs or other categories of costs for the rehabilitation of earthquake victims (construction and function of settlements for earthquake homeless, rent supports, demolitions, shorings) are used to determine the final total seismic risk factor.

Second Quarter Hanford Seismic Report for Fiscal Year 2009

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

Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.

2009-07-31

The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The HSAP is responsible for locating and identifying sources of seismic activity and monitoring changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, natural phenomena hazards assessments, and engineering design and construction. In addition, the HSAP works with the Hanford Site Emergency Services Organization to provide assistance in the eventmore » of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 44 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. The Hanford Seismic Network recorded over 800 local earthquakes during the second quarter of FY 2009. Nearly all of these earthquakes were detected in the vicinity of Wooded Island, located about eight miles north of Richland just west of the Columbia River. Most of the events were considered minor (magnitude (Mc) less than 1.0) with 19 events in the 2.0-2.9 range. The estimated depths of the Wooded Island events are shallow (averaging less than 1.0 km deep) with a maximum depth estimated at 1.9 km. This places the Wooded Island events within the Columbia River Basalt Group (CRBG). The low magnitude and the shallowness of the Wooded Island events have made them undetectable to most area residents. However, some Hanford employees working within a few miles of the area of highest activity, and individuals living in homes directly across the Columbia River from the swarm center, have reported feeling some movement. The Hanford SMA network was triggered numerous times by the Wooded Island swarm events. The maximum acceleration values recorded by the SMA network

Third Quarter Hanford Seismic Report for Fiscal Year 2009

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

Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.

2009-09-30

The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The HSAP is responsible for locating and identifying sources of seismic activity and monitoring changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, natural phenomena hazards assessments, and engineering design and construction. In addition, the HSAP works with the Hanford Site Emergency Services Organization to provide assistance in the eventmore » of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 44 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. The Hanford Seismic Network recorded 771 local earthquakes during the third quarter of FY 2009. Nearly all of these earthquakes were detected in the vicinity of Wooded Island, located about eight miles north of Richland just west of the Columbia River. The Wooded Island events recorded this quarter is a continuation of the swarm events observed during the January – March 2009 time period and reported in the previous quarterly report (Rohay et al, 2009). The frequency of Wooded Island events has subsided with 16 events recorded during June 2009. Most of the events were considered minor (magnitude (Mc) less than 1.0) with 25 events in the 2.0-3.0 range. The estimated depths of the Wooded Island events are shallow (averaging less than 1.0 km deep) with a maximum depth estimated at 2.2 km. This places the Wooded Island events within the Columbia River Basalt Group (CRBG). The low magnitude of the Wooded Island events has made them undetectable to all but local area residents. However, some Hanford employees working within a few miles of the area of highest

Wing walls for enhancing the seismic performance of reinforced concrete frame structures

NASA Astrophysics Data System (ADS)

Yang, Weisong; Guo, Xun; Xu, Weixiao; Yuan, Xin

2016-06-01

A building retrofitted with wing walls in the bottom story, which was damaged during the 2008 M8.0 Wenchuan earthquake in China, is introduced and a corresponding 1/4 scale wing wall-frame model was subjected to shake table motions to study the seismic behavior of this retrofitted structural system. The results show that wing walls can effectively protect columns from damage by moving areas that bear reciprocating tension and compression to the sections of the wing walls, thus achieving an extra measure of seismic fortification. A `strong column-weak beam' mechanism was realized, the flexural rigidity of the vertical member was strengthened, and a more uniform distribution of deformation among all the stories was measured. In addition, the joint between the wing walls and the beams suffered severe damage during the tests, due to an area of local stress concentration. A longer area of intensive stirrup is suggested in the end of the beams.

The 2012 Ferrara seismic sequence: Regional crustal structure, earthquake sources, and seismic hazard

NASA Astrophysics Data System (ADS)

Malagnini, Luca; Herrmann, Robert B.; Munafò, Irene; Buttinelli, Mauro; Anselmi, Mario; Akinci, Aybige; Boschi, E.

2012-10-01

Inadequate seismic design codes can be dangerous, particularly when they underestimate the true hazard. In this study we use data from a sequence of moderate-sized earthquakes in northeast Italy to validate and test a regional wave propagation model which, in turn, is used to understand some weaknesses of the current design spectra. Our velocity model, while regionalized and somewhat ad hoc, is consistent with geophysical observations and the local geology. In the 0.02-0.1 Hz band, this model is validated by using it to calculate moment tensor solutions of 20 earthquakes (5.6 ≥ MW ≥ 3.2) in the 2012 Ferrara, Italy, seismic sequence. The seismic spectra observed for the relatively small main shock significantly exceeded the design spectra to be used in the area for critical structures. Observations and synthetics reveal that the ground motions are dominated by long-duration surface waves, which, apparently, the design codes do not adequately anticipate. In light of our results, the present seismic hazard assessment in the entire Pianura Padana, including the city of Milan, needs to be re-evaluated.

Newberry Seismic Deployment Fieldwork Report

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

Wang, J; Templeton, D C

2012-03-21

This report summarizes the seismic deployment of Lawrence Livermore National Laboratory (LLNL) Geotech GS-13 short-period seismometers at the Newberry Enhanced Geothermal System (EGS) Demonstration site located in Central Oregon. This Department of Energy (DOE) demonstration project is managed by AltaRock Energy Inc. AltaRock Energy had previously deployed Geospace GS-11D geophones at the Newberry EGS Demonstration site, however the quality of the seismic data was somewhat low. The purpose of the LLNL deployment was to install more sensitive sensors which would record higher quality seismic data for use in future seismic studies, such as ambient noise correlation, matched field processing earthquakemore » detection studies, and general EGS microearthquake studies. For the LLNL deployment, seven three-component seismic stations were installed around the proposed AltaRock Energy stimulation well. The LLNL seismic sensors were connected to AltaRock Energy Gueralp CMG-DM24 digitizers, which are powered by AltaRock Energy solar panels and batteries. The deployment took four days in two phases. In phase I, the sites were identified, a cavity approximately 3 feet deep was dug and a flat concrete pad oriented to true North was made for each site. In phase II, we installed three single component GS-13 seismometers at each site, quality controlled the data to ensure that each station was recording data properly, and filled in each cavity with native soil.« less

In-situ measurements of seismic velocities in the San Francisco Bay Region; part III

USGS Publications Warehouse

Gibbs, James F.; Fumal, Thomas E.; Borcherdt, Roger D.; Roth, Edward F.

1977-01-01

Seismic wave velocities (compressional and shear) are important parameters for estimating the seismic response characteristics of various geologic units when subjected to strong earthquake ground shaking. Seismic velocities of various units often show a strong correlation with the amounts of damage following large earthquakes and have been used as a basis for certain types of seismic zonation studies. In the current program seismic velocities have been measured at 59 locations 1n the San Francisco Bay Region. This report is the third in a series of Open-File Reports and describes the in-situ velocity measurements at locations 35-59. At each location seismic travel times are measured in drill holes, normally at 2.5-m intervals to a depth of 30 m. Geologic logs are determined from drill cuttings, undisturbed (cored) samples, and penetrometer samples. The data provide a detailed comparison of geologic and seismic characteristics and provide parameters for estimating strong earthquake ground motions quantitatively at each of the sites. A major emphasis of this program is to obtain a detailed comparison of geologic and seismic data on a regional scale for use in seismic zonation. There is a variety of geologic and seismic data available in the San Francisco Bay Region for use 1n developing the general zoning techniques which can then be applied to other areas. Shear wave velocities 1n near-surface geologic materials are of especial interest for engineering seismology and seismic zonation studies, yet in general, they are difficult to measure because of contamination by compressional waves. A comparison of various in-situ techniques by Warrick (1974) establishes the reliability of the method utilizing a "horizontal traction" source for sites underlain by bay mud and alluvium. Gibbs, and others (1975a) present data from 12 holes and establishes the reliability of the method for sites underlain by a variety of different rock units and suggest extending the measurements to

Seismicity and Seismic Hazard along the Western part of the Eurasia-Nubia plate boundary

NASA Astrophysics Data System (ADS)

Bezzeghoud, Mourad; Fontiela, João; Ferrão, Celia; Borges, José Fernando; Caldeira, Bento; Dib, Assia; Ousadou, Farida

2016-04-01

,000) make it one of the deadliest earthquakes in history. Measured in lives lost, the 1926, 1980 and 1998 Azores earthquakes (Portugal), the 1954 and 1980 El Asnam earthquakes (North Algeria), the 1994 and 2004 Alhoceima earthquakes (North Morocco), and the 2003 Boumerdes earthquakes (North Algeria) were the worst earthquakes in the past 120 years in the study area. Hence, this region has experienced many large and damaging earthquakes. The city of Cairo (Egypt) was struck in October 1992 by an Mw 5.8 magnitude earthquake, which caused large damage. In 1935, the Syrte region in Libya experienced an M6.9 earthquake with severe damage. Generally, North Africa has experienced moderate earthquakes. However, the region remains vulnerable due to the shallow seismicity, the poor mechanical properties of its soil and local site conditions, and the consequent strength of the ground shaking. Knowing the behaviour of a seismogenic area, particularly the fault zone, will lead us to better assess the hazard and risk in and around large urban areas. In order to mitigate the destructive impact of the earthquakes, the regional seismic hazard in North Africa is assessed using different approaches (ex. deterministic and probabilistic) using historical and instrumental seismicity, earthquake sources, seismotectonic zonation, structural models and attenuation laws. As a result, reliable seismic hazard maps are produced in terms of maximum displacement and in terms of maximum intensity map. This research is funded by the Fundação para a Ciência e a Tecnologia (FCT, Portugal) under the project ICT-UID/GEO/04683/2013. This study also was conducted within the scope of the MEDYNA FP7-PEOPLE-2013-IRSES project, WP-1: Present-day Kinematics and seismic hazards, funded by the Seventh Framework European Programme.

Micro-seismicity in the Gulf of Cadiz: Is there a link between micro-seismicity, high magnitude earthquakes and active faults?

NASA Astrophysics Data System (ADS)

Silva, Sónia; Terrinha, Pedro; Matias, Luis; Duarte, João C.; Roque, Cristina; Ranero, César R.; Geissler, Wolfram H.; Zitellini, Nevio

2017-10-01

The Gulf of Cadiz seismicity is characterized by persistent low to intermediate magnitude earthquakes, occasionally punctuated by high magnitude events such as the M 8.7 1755 Great Lisbon earthquake and the M = 7.9 event of February 28th, 1969. Micro-seismicity was recorded during 11 months by a temporary network of 25 ocean bottom seismometers (OBSs) in an area of high seismic activity, encompassing the potential source areas of the mentioned large magnitude earthquakes. We combined micro-seismicity analysis with processing and interpretation of deep crustal seismic reflection profiles and available refraction data to investigate the possible tectonic control of the seismicity in the Gulf of Cadiz area. Three controlling mechanisms are explored: i) active tectonic structures, ii) transitions between different lithospheric domains and inherited Mesozoic structures, and iii) fault weakening mechanisms. Our results show that micro-seismicity is mostly located in the upper mantle and is associated with tectonic inversion of extensional rift structures and to the transition between different lithospheric/rheological domains. Even though the crustal structure is well imaged in the seismic profiles and in the bathymetry, crustal faults show low to negligible seismic activity. A possible explanation for this is that the crustal thrusts are thin-skinned structures rooting in relatively shallow sub-horizontal décollements associated with (aseismic) serpentinization levels at the top of the lithospheric mantle. Therefore, co-seismic slip along crustal thrusts may only occur during large magnitude events, while for most of the inter-seismic cycle these thrusts remain locked, or slip aseismically. We further speculate that high magnitude earthquake's ruptures may only nucleate in the lithospheric mantle and then propagate into the crust across the serpentinized layers.

Seismic hazard map of the western hemisphere

USGS Publications Warehouse

Shedlock, K.M.; Tanner, J.G.

1999-01-01

Vulnerability to natural disasters increases with urbanization and development of associated support systems (reservoirs, power plants, etc.). Catastrophic earthquakes account for 60% of worldwide casualties associated with natural disasters. Economic damage from earthquakes is increasing, even in technologically advanced countries with some level of seismic zonation, as shown by the 1989 Loma Prieta, CA ($6 billion), 1994 Northridge, CA ($ 25 billion), and 1995 Kobe, Japan (> $ 100 billion) earthquakes. The growth of megacities in seismically active regions around the world often includes the construction of seismically unsafe buildings and infrastructures, due to an insufficient knowledge of existing seismic hazard. Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of seismic hazard. National, state, and local governments, decision makers, engineers, planners, emergency response organizations, builders, universities, and the general public require seismic hazard estimates for land use planning, improved building design and construction (including adoption of building construction codes), emergency response preparedness plans, economic forecasts, housing and employment decisions, and many more types of risk mitigation. The seismic hazard map of the Americas is the concatenation of various national and regional maps, involving a suite of approaches. The combined maps and documentation provide a useful global seismic hazard framework and serve as a resource for any national or regional agency for further detailed studies applicable to their needs. This seismic hazard map depicts Peak Ground Acceleration (PGA) with a 10% chance of exceedance in 50 years for the western hemisphere. PGA, a short-period ground motion parameter that is proportional to force, is the most commonly mapped ground motion parameter because current building codes that include seismic provisions specify the

Correction to "Influence of Dust and Black Carbon on the Snow Albedo in the NASA Goddard Earth Observing System Version 5 Land Surface Model"

NASA Technical Reports Server (NTRS)

Yasunari, Teppei J.; Koster, Randal D.; Kau, K. M.; Aoki, Teruo; Sud, Yogesh C.; Yamazaki, Takeshi; Motoyoshi, Hiroki; Kokdama, Yuji

2012-01-01

The website information describing the forcing meteorological data used for the land surface model (LSM) simulation, which were observed at an Automated Meteorological Station CAWS) at the Sapporo District Meteorological Observatory maintained by the Japan Meteorological Agency (JMA), was missing from the text. The 1-hourly data were obtained from the website of Kisyoutoukeijouhou (Information for available JMA-observed meteorological data in the past) on the website of JMA (in Japanese) (available at: http://www.jma.go.jpijmaimenulreport.html). The measurement height information of 59.5 m for the anemometer at the Sapporo Observatory was also obtained from the website of JMA (in Japanese) (available at: http://www.jma.go.jp/jma/menu/report.html). In addition, the converted 10-m wind speed, based on the AWS/JMA data, was further converted to a 2-m wind speed prior to its use with the land model as a usual treatment of off-line Catchment simulation. Please ignore the ice absorption data on the website mentioned in paragraph [15] which was not used for our calculations (but the data on the website was mostly the same as the estimated ice absorption coefficients by the following method because they partially used the same data by Warren [1984]). We calculated the ice absorption coefficients with the method mentioned in the same paragraph, for which some of the refractive index data by Warren [1984] were used and then interpolated between wavelengths, and also mentioned in paragraph [20] for the visible (VIS) and near-infrared (NIR) ranges. The optical data we used were interpolated between wavelengths as necessary.

Seismic Performance Evaluation of Reinforced Concrete Frames Subjected to Seismic Loads

NASA Astrophysics Data System (ADS)

Zameeruddin, Mohd.; Sangle, Keshav K.

2017-06-01

Ten storied-3 bays reinforced concrete bare frame designed for gravity loads following the guidelines of IS 456 and IS 13920 for ductility is subjected to seismic loads. The seismic demands on this building were calculated by following IS 1893 for response spectra of 5% damping (for hard soil type). Plastic hinges were assigned to the beam and column at both ends to represent the failure mode, when member yields. Non-linear static (pushover) analysis was performed to evaluate the performance of the building in reference to first (ATC 40), second (FEMA 356) and next-generation (FEMA 440) performance based seismic design procedures. Base shear against top displacement curve of structure, known as pushover curve was obtained for two actions of plastic hinge behavior, force-controlled (brittle) and deformation-controlled (ductile) actions. Lateral deformation corresponding to performance point proves the building capability to sustain a certain level of seismic loads. The failure is represented by a sequence of formation of plastic hinges. Deformation-controlled action of hinges showed that building behaves like strong-column-weak-beam mechanism, whereas force-controlled action showed formation of hinges in the column. The study aims to understand the first, second and next generation performance based design procedure in prediction of actual building responses and their conservatism into the acceptance criteria.

Annual Hanford Seismic Report for Fiscal Year 2009

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

Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.

2009-12-31

The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The HSAP is responsible for locating and identifying sources of seismic activity and monitoring changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, natural phenomena hazards assessments, and engineering design and construction. In addition, the HSAP works with the Hanford Site Emergency Services Organization to provide assistance in the eventmore » of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 44 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. During FY 2009, the Hanford Seismic Network recorded nearly 3000 triggers on the seismometer system, which included over 1700 seismic events in the southeast Washington area and an additional 370 regional and teleseismic events. There were 1648 events determined to be local earthquakes relevant to the Hanford Site. Nearly all of these earthquakes were detected in the vicinity of Wooded Island, located about eight miles north of Richland just west of the Columbia River. Recording of the Wooded Island events began in January with over 250 events per month through June 2009. The frequency of events decreased starting in July 2009 to approximately 10-15 events per month through September 2009. Most of the events were considered minor (coda-length magnitude [Mc] less than 1.0) with 47 events in the 2.0-3.0 range. The estimated depths of the Wooded Island events are shallow (averaging less than 1.0 km deep) with a maximum depth estimated at 2.3 km. This places the Wooded Island events within the Columbia River Basalt Group (CRBG). The highest-magnitude event (3

Seismic reflection imaging of shallow oceanographic structures

NASA Astrophysics Data System (ADS)

Piété, Helen; Marié, Louis; Marsset, Bruno; Thomas, Yannick; Gutscher, Marc-André

2013-05-01

Multichannel seismic (MCS) reflection profiling can provide high lateral resolution images of deep ocean thermohaline fine structure. However, the shallowest layers of the water column (z < 150 m) have remained unexplored by this technique until recently. In order to explore the feasibility of shallow seismic oceanography (SO), we reprocessed and analyzed four multichannel seismic reflection sections featuring reflectors at depths between 10 and 150 m. The influence of the acquisition parameters was quantified. Seismic data processing dedicated to SO was also investigated. Conventional seismic acquisition systems were found to be ill-suited to the imaging of shallow oceanographic structures, because of a high antenna filter effect induced by large offsets and seismic trace lengths, and sources that typically cannot provide both a high level of emission and fine vertical resolution. We considered a test case, the imagery of the seasonal thermocline on the western Brittany continental shelf. New oceanographic data acquired in this area allowed simulation of the seismic acquisition. Sea trials of a specifically designed system were performed during the ASPEX survey, conducted in early summer 2012. The seismic device featured: (i) four seismic streamers, each consisting of six traces of 1.80 m; (ii) a 1000 J SIG sparker source, providing a 400 Hz signal with a level of emission of 205 dB re 1 μPa @ 1 m. This survey captured the 15 m thick, 30 m deep seasonal thermocline in unprecedented detail, showing images of vertical displacements most probably induced by internal waves.

Interferometric Seismic Sources on the Core Mantle Boundary Revealed by Seismic Coda Crosscorrelation

NASA Astrophysics Data System (ADS)

Pham, T. S.; Tkalcic, H.; Sambridge, M.

2017-12-01

The crosscorrelation of earthquake coda can be used to extract seismic body waves which are sensitive to deep Earth interior. The retrieved peaks in crosscorrelation of two seismic records are commonly interpreted as seismic phases that originate at a point source collocated with the first recorder (Huygens-Fresnel principle), reflected upward from prominent underground reflectors and reaching the second recorder. From the time shift of these peaks measured at different interstation distances, new travel time curves can be constructed. This study focuses on a previously unexplained interferometric phase (named temporarily a ghost or "G phase") observed in crosscorrelogram stack sections utilizing seismic coda. In particular, we deploy waveforms recorded by two regional seismic networks, one in Australia and another in Alaska. We show that the G phase cannot be explained by as a reflection. Moreover, we demonstrate that the G phase is explained through the principle of energy partitioning, and specifically, conversions from compressional to shear motions at the core-mantle boundary (CMB). This can be thought of in terms of a continuous distribution of Huygens sources across the CMB that are "activated" in long-range wavefield coda following significant earthquakes. The newly explained phase is renamed to cPS, to indicate a CMB origin and the P to S conversion. This mechanism explains a range of newly observed global interferometric phases that can be used in combination with existing phases to constrain Earth structure.

Alternative Energy Sources in Seismic Methods

NASA Astrophysics Data System (ADS)

Tün, Muammer; Pekkan, Emrah; Mutlu, Sunay; Ecevitoğlu, Berkan

2015-04-01

When the suitability of a settlement area is investigated, soil-amplification, liquefaction and fault-related hazards should be defined, and the associated risks should be clarified. For this reason, soil engineering parameters and subsurface geological structure of a new settlement area should be investigated. Especially, faults covered with quaternary alluvium; thicknesses, shear-wave velocities and geometry of subsurface sediments could lead to a soil amplification during an earthquake. Likewise, changes in shear-wave velocities along the basin are also very important. Geophysical methods can be used to determine the local soil properties. In this study, use of alternative seismic energy sources when implementing seismic reflection, seismic refraction and MASW methods in the residential areas of Eskisehir/Turkey, were discussed. Our home developed seismic energy source, EAPSG (Electrically-Fired-PS-Gun), capable to shoot 2x24 magnum shotgun cartridges at once to generate P and S waves; and our home developed WD-500 (500 kg Weight Drop) seismic energy source, mounted on a truck, were developed under a scientific research project of Anadolu University. We were able to reach up to penetration depths of 1200 m for EAPSG, and 800 m for WD-500 in our seismic reflection surveys. WD-500 seismic energy source was also used to perform MASW surveys, using 24-channel, 10 m apart, 4.5 Hz vertical geophone configuration. We were able to reach 100 m of penetration depth in MASW surveys.

Updating the Seismic Hazard Determination in southeastern Brazil

NASA Astrophysics Data System (ADS)

Franca, G. S.; Algarte, K. T.

2012-12-01

This job presents an update of research by Berrocal in 1996 in the determination of seismic hazard for the Southeast of Brazil, based on the earthquake catalog compiled at the Instituto de Astronomia e Geofisica, Universidade de Sao Paulo and bulletin of Seismological Observatory, Universidade de Brasilia, during the period between 1767 until May 2012. The southeastern Brazil has a level of seismic activity is considered low, typical of intraplate regions. Our database has a total of 3726 events, however 1242 events do not have the magnitude estimated, 1638 events are between magnitudes 0.1 to 1.9 and from 2.0 to 3.9 are 819 events. The largest earthquake in the region occurred on February 28, 1955 with magnitude 6.1 mb (Assumpção, 2000), with its epicenter about 400 km from the coast, this was felt in small cities, especially in Espirito Santo State. The intensity VIII-IX MM was estimated by Berrocal et al. (1984). The database also has four events with magnitude above 5.0 mb in the region that occurred during the past 215 years and a little more than a twenty earthquakes with magnitude between 4.0 and 5.0 mb. Instrumental data are available since the 1970s when the station network was installed in Brasilia. Several other short-period vertical stations have been installed in the region. We used data from the same area defined in the previous survey, located between parallels 15S-32S degree and longitudes 35W-52W degree. It contains the most developed area of Brazil, and the major cities and industrial centers of the country (São Paulo, Rio de Janeiro and Belo Horizonte). Major engineering works, hydroelectric and nuclear power plant (Angra dos Reis) are also in this area. Therefore, the results can be applied to the planning and construction of large engineering within that region. With GIS and seismology tools was calculated relative frequency/magnitude for earthquakes mb > 3.0, the value of b with the maximum likelihood method, and so curves of recurrence was

Quantification of source uncertainties in Seismic Probabilistic Tsunami Hazard Analysis (SPTHA)

NASA Astrophysics Data System (ADS)

Selva, J.; Tonini, R.; Molinari, I.; Tiberti, M. M.; Romano, F.; Grezio, A.; Melini, D.; Piatanesi, A.; Basili, R.; Lorito, S.

2016-06-01

We propose a procedure for uncertainty quantification in Probabilistic Tsunami Hazard Analysis (PTHA), with a special emphasis on the uncertainty related to statistical modelling of the earthquake source in Seismic PTHA (SPTHA), and on the separate treatment of subduction and crustal earthquakes (treated as background seismicity). An event tree approach and ensemble modelling are used in spite of more classical approaches, such as the hazard integral and the logic tree. This procedure consists of four steps: (1) exploration of aleatory uncertainty through an event tree, with alternative implementations for exploring epistemic uncertainty; (2) numerical computation of tsunami generation and propagation up to a given offshore isobath; (3) (optional) site-specific quantification of inundation; (4) simultaneous quantification of aleatory and epistemic uncertainty through ensemble modelling. The proposed procedure is general and independent of the kind of tsunami source considered; however, we implement step 1, the event tree, specifically for SPTHA, focusing on seismic source uncertainty. To exemplify the procedure, we develop a case study considering seismic sources in the Ionian Sea (central-eastern Mediterranean Sea), using the coasts of Southern Italy as a target zone. The results show that an efficient and complete quantification of all the uncertainties is feasible even when treating a large number of potential sources and a large set of alternative model formulations. We also find that (i) treating separately subduction and background (crustal) earthquakes allows for optimal use of available information and for avoiding significant biases; (ii) both subduction interface and crustal faults contribute to the SPTHA, with different proportions that depend on source-target position and tsunami intensity; (iii) the proposed framework allows sensitivity and deaggregation analyses, demonstrating the applicability of the method for operational assessments.

Induced Seismicity Potential of Energy Technologies

NASA Astrophysics Data System (ADS)

Hitzman, Murray

2013-03-01

Earthquakes attributable to human activities-``induced seismic events''-have received heightened public attention in the United States over the past several years. Upon request from the U.S. Congress and the Department of Energy, the National Research Council was asked to assemble a committee of experts to examine the scale, scope, and consequences of seismicity induced during fluid injection and withdrawal associated with geothermal energy development, oil and gas development, and carbon capture and storage (CCS). The committee's report, publicly released in June 2012, indicates that induced seismicity associated with fluid injection or withdrawal is caused in most cases by change in pore fluid pressure and/or change in stress in the subsurface in the presence of faults with specific properties and orientations and a critical state of stress in the rocks. The factor that appears to have the most direct consequence in regard to induced seismicity is the net fluid balance (total balance of fluid introduced into or removed from the subsurface). Energy technology projects that are designed to maintain a balance between the amount of fluid being injected and withdrawn, such as most oil and gas development projects, appear to produce fewer seismic events than projects that do not maintain fluid balance. Major findings from the study include: (1) as presently implemented, the process of hydraulic fracturing for shale gas recovery does not pose a high risk for inducing felt seismic events; (2) injection for disposal of waste water derived from energy technologies does pose some risk for induced seismicity, but very few events have been documented over the past several decades relative to the large number of disposal wells in operation; and (3) CCS, due to the large net volumes of injected fluids suggested for future large-scale carbon storage projects, may have potential for inducing larger seismic events.

The Great Maule earthquake: seismicity prior to and after the main shock from amphibious seismic networks

NASA Astrophysics Data System (ADS)

Lieser, K.; Arroyo, I. G.; Grevemeyer, I.; Flueh, E. R.; Lange, D.; Tilmann, F. J.

2013-12-01

The Chilean subduction zone is among the seismically most active plate boundaries in the world and its coastal ranges suffer from a magnitude 8 or larger megathrust earthquake every 10-20 years. The Constitución-Concepción or Maule segment in central Chile between ~35.5°S and 37°S was considered to be a mature seismic gap, rupturing last in 1835 and being seismically quiet without any magnitude 4.5 or larger earthquakes reported in global catalogues. It is located to the north of the nucleation area of the 1960 magnitude 9.5 Valdivia earthquake and to the south of the 1928 magnitude 8 Talca earthquake. On 27 February 2010 this segment ruptured in a Mw=8.8 earthquake, nucleating near 36°S and affecting a 500-600 km long segment of the margin between 34°S and 38.5°S. Aftershocks occurred along a roughly 600 km long portion of the central Chilean margin, most of them offshore. Therefore, a network of 30 ocean-bottom-seismometers was deployed in the northern portion of the rupture area for a three month period, recording local offshore aftershocks between 20 September 2010 and 25 December 2010. In addition, data of a network consisting of 33 landstations of the GeoForschungsZentrum Potsdam were included into the network, providing an ideal coverage of both the rupture plane and areas affected by post-seismic slip as deduced from geodetic data. Aftershock locations are based on automatically detected P wave onsets and a 2.5D velocity model of the combined on- and offshore network. Aftershock seismicity analysis in the northern part of the survey area reveals a well resolved seismically active splay fault in the accretionary prism of the Chilean forearc. Our findings imply that in the northernmost part of the rupture zone, co-seismic slip most likely propagated along the splay fault and not the subduction thrust fault. In addition, the updip limit of aftershocks along the plate interface can be verified to about 40 km landwards from the deformation front. Prior to

A new 1649-1884 catalog of destructive earthquakes near Tokyo and implications for the long-term seismic process

USGS Publications Warehouse

Grunewald, E.D.; Stein, R.S.

2006-01-01

In order to assess the long-term character of seismicity near Tokyo, we construct an intensity-based catalog of damaging earthquakes that struck the greater Tokyo area between 1649 and 1884. Models for 15 historical earthquakes are developed using calibrated intensity attenuation relations that quantitatively convey uncertainties in event location and magnitude, as well as their covariance. The historical catalog is most likely complete for earthquakes M ??? 6.7; the largest earthquake in the catalog is the 1703 M ??? 8.2 Genroku event. Seismicity rates from 80 years of instrumental records, which include the 1923 M = 7.9 Kanto shock, as well as interevent times estimated from the past ???7000 years of paleoseismic data, are combined with the historical catalog to define a frequency-magnitude distribution for 4.5 ??? M ??? 8.2, which is well described by a truncated Gutenberg-Richter relation with a b value of 0.96 and a maximum magnitude of 8.4. Large uncertainties associated with the intensity-based catalog are propagated by a Monte Carlo simulation to estimations of the scalar moment rate. The resulting best estimate of moment rate during 1649-2003 is 1.35 ?? 1026 dyn cm yr-1 with considerable uncertainty at the 1??, level: (-0.11, + 0.20) ?? 1026 dyn cm yr-1. Comparison with geodetic models of the interseismic deformation indicates that the geodetic moment accumulation and likely moment release rate are roughly balanced over the catalog period. This balance suggests that the extended catalog is representative of long-term seismic processes near Tokyo and so can be used to assess earthquake probabilities. The resulting Poisson (or time-averaged) 30-year probability for M ??? 7.9 earthquakes is 7-11%.

New seismic study begins in Puerto Rico

USGS Publications Warehouse

Tarr, A.C.

1974-01-01

A new seismological project is now underway in Puerto Rico to provide information needed for accurate assessment of the island's seismic hazard. The project should also help to increase understanding of the tectonics and geologic evolution of the Caribbean region. The Puerto Rico Seismic Program is being conducted by the Geological Survey with support provided by the Puerto Rico Water Resources Authority, an agency responsible for generation and distribution of electric power throughout the Commonwealth. The Program will include the installation of a network of high quality seismograph stations to monitor seismic activity on and around Puerto Rico. These stations will be distributed across the island to record the seismicity as uniformly as possible. The detection and accurate location of small earthquakes, as well as moderate magnitude shocks, will aid in mapping active seismic zones and in compiling frequency of occurrence statistics which ultimately wil be useful in seismic risk-zoning of hte island.