Time-Lapse Monitoring with 4D Seismic Coda Waves in Active, Passive and Ambient Noise Data

NASA Astrophysics Data System (ADS)

Lumley, D. E.; Kamei, R.; Saygin, E.; Shragge, J. C.

2017-12-01

The Earth's subsurface is continuously changing, due to temporal variations in fluid flow, stress, temperature, geomechanics and geochemistry, for example. These physical changes occur at broad tectonic and earthquake scales, and also at very detailed near-surface and reservoir scales. Changes in the physical states of the earth cause time-varying changes in the physical properties of rocks and fluids, which can be monitored with natural or manmade seismic waves. Time-lapse (4D) seismic monitoring is important for applications related to natural and induced seismicity, hydrocarbon and groundwater reservoir depletion, CO2 sequestration etc. An exciting new research area involves moving beyond traditional methods in order to use the full complex time-lapse scattered wavefield (4D coda waves) for both manmade active-source 3D/4D seismic data, and also to use continuous recordings of natural-source passive seismic data, especially (micro) earthquakes and ocean ambient noise. This research involves full wave-equation approaches including waveform inversion (FWI), interferometry, Large N sensor arrays, "big data" information theory, and high performance supercomputing (HPC). I will present high-level concepts and recent data results that are quite spectacular and highly encouraging.

Observation and modeling of source effects in coda wave interferometry at Pavlof volcano

USGS Publications Warehouse

Haney, M.M.; van, Wijik K.; Preston, L.A.; Aldridge, D.F.

2009-01-01

Sorting out source and path effects for seismic waves at volcanoes is critical for the proper interpretation of underlying volcanic processes. Source or path effects imply that seismic waves interact strongly with the volcanic subsurface, either through partial resonance in a conduit (Garces et al., 2000; Sturton and Neuberg, 2006) or by random scattering in the heterogeneous volcanic edifice (Wegler and Luhr, 2001). As a result, both source and path effects can cause seismic waves to repeatedly sample parts of the volcano, leading to enhanced sensitivity to small changes in material properties at those locations. The challenge for volcano seismologists is to detect and reliably interpret these subtle changes for the purpose of monitoring eruptions. ?? 2009 Society of Exploration Geophysicists.

Temporal change in shallow subsurface P- and S-wave velocities and S-wave anisotropy inferred from coda wave interferometry

NASA Astrophysics Data System (ADS)

Yamamoto, M.; Nishida, K.; Takeda, T.

2012-12-01

Recent progresses in theoretical and observational researches on seismic interferometry reveal the possibility to detect subtle change in subsurface seismic structure. This high sensitivity of seismic interferometry to the medium properties may thus one of the most important ways to directly observe the time-lapse behavior of shallow crustal structure. Here, using the coda wave interferometry, we show the co-seismic and post-seismic changes in P- and S-wave velocities and S-wave anisotropy associated with the 2011 off the Pacific coast of Tohoku earthquake (M9.0). In this study, we use the acceleration data recorded at KiK-net stations operated by NIED, Japan. Each KiK-net station has a borehole whose typical depth is about 100m, and two three-component accelerometers are installed at the top and bottom of the borehole. To estimate the shallow subsurface P- and S-wave velocities and S-wave anisotropy between two sensors and their temporal change, we select about 1000 earthquakes that occurred between 2004 and 2012, and extract body waves propagating between borehole sensors by computing the cross-correlation functions (CCFs) of 3 x 3 component pairs. We use frequency bands of 2-4, 4-8, 8-16 Hz in our analysis. Each averaged CCF shows clear wave packets traveling between borehole sensors, and their travel times are almost consistent with those of P- and S-waves calculated from the borehole log data. Until the occurrence of the 2011 Tohoku earthquake, the estimated travel time at each station is rather stable with time except for weak seasonal/annual variation. On the other hand, the 2011 Tohoku earthquake and its aftershocks cause sudden decrease in the S-wave velocity at most of the KiK-net stations in eastern Japan. The typical value of S-wave velocity changes, which are measured by the time-stretching method, is about 5-15%. After this co-seismic change, the S-wave velocity gradually recovers with time, and the recovery continues for over one year following the logarithm of the lapse time. At some stations, the estimated P-wave velocity also shows co-seismic velocity decrease and subsequent gradual recovery. However, the magnitude of estimated P-wave velocity change is much smaller than that of S-wave, and at the other stations, the magnitude of P-wave velocity change is smaller than the resolution of our analysis. Using the CCFs computed from horizontal components, we also determine the seismic anisotropy in subsurface structure, and examine its temporal change. The estimated strength of anisotropy strength shows co-seismic increase at most of stations where co-seismic velocity change is detected. Nevertheless, the direction of anisotropy after the 2011 Tohoku earthquake stays about the same as before. These results suggest that, in addition to the change in pore pressure and corresponding decrease in the rigidity, the change in the aspect ratio of pre-existing subsurface fractures/micro-crack may be another key mechanism causing the co-seismic velocity change in shallow subsurface structures.

High-resolution probing of inner core structure with seismic interferometry

NASA Astrophysics Data System (ADS)

Huang, Hsin-Hua; Lin, Fan-Chi; Tsai, Victor C.; Koper, Keith D.

2015-12-01

Increasing complexity of Earth's inner core has been revealed in recent decades as the global distribution of seismic stations has improved. The uneven distribution of earthquakes, however, still causes a biased geographical sampling of the inner core. Recent developments in seismic interferometry, which allow for the retrieval of core-sensitive body waves propagating between two receivers, can significantly improve ray path coverage of the inner core. In this study, we apply such earthquake coda interferometry to 1846 USArray stations deployed across the U.S. from 2004 through 2013. Clear inner core phases PKIKP2 and PKIIKP2 are observed across the entire array. Spatial analysis of the differential travel time residuals between the two phases reveals significant short-wavelength variation and implies the existence of strong structural variability in the deep Earth. A linear N-S trending anomaly across the middle of the U.S. may reflect an asymmetric quasi-hemispherical structure deep within the inner core with boundaries of 99°W and 88°E.

A continuous record of intereruption velocity change at Mount St. Helens from coda wave interferometry

USGS Publications Warehouse

Hotovec-Ellis, Alicia J.; Gomberg, Joan S.; Vidale, John; Creager, Ken C.

2014-01-01

In September 2004, Mount St. Helens volcano erupted after nearly 18 years of quiescence. However, it is unclear from the limited geophysical observations when or if the magma chamber replenished following the 1980–1986 eruptions in the years before the 2004–2008 extrusive eruption. We use coda wave interferometry with repeating earthquakes to measure small changes in the velocity structure of Mount St. Helens volcano that might indicate magmatic intrusion. By combining observations of relative velocity changes from many closely located earthquake sources, we solve for a continuous function of velocity changes with time. We find that seasonal effects dominate the relative velocity changes. Seismicity rates and repeating earthquake occurrence also vary seasonally; therefore, velocity changes and seismicity are likely modulated by snow loading, fluid saturation, and/or changes in groundwater level. We estimate hydrologic effects impart stress changes on the order of tens of kilopascals within the upper 4 km, resulting in annual velocity variations of 0.5 to 1%. The largest nonseasonal change is a decrease in velocity at the time of the deep Mw = 6.8 Nisqually earthquake. We find no systematic velocity changes during the most likely times of intrusions, consistent with a lack of observable surface deformation. We conclude that if replenishing intrusions occurred, they did not alter seismic velocities where this technique is sensitive due to either their small size or the finite compressibility of the magma chamber. We interpret the observed velocity changes and shallow seasonal seismicity as a response to small stress changes in a shallow, pressurized system.

Mechanical Strain Measurement from Coda Wave Interferometry

NASA Astrophysics Data System (ADS)

Azzola, J.; Schmittbuhl, J.; Zigone, D.; Masson, F.; Magnenet, V.

2017-12-01

Coda Wave Interferometry (CWI) aims at tracking small changes in solid materials like rocks where elastic waves are diffusing. They are intensively sampling the medium, making the technique much more sensitive than those relying on direct wave arrivals. Application of CWI to ambient seismic noise has found a large range of applications over the past years like for multiscale imaging but also for monitoring complex structures such as regional faults or reservoirs (Lehujeur et al., 2015). Physically, observed changes are typically interpreted as small variations of seismic velocities. However, this interpretation remains questionable. Here, a specific focus is put on the influence of the elastic deformation of the medium on CWI measurements. The goal of the present work is to show from a direct numerical and experimental modeling that deformation signal also exists in CWI measurements which might provide new outcomes for the technique.For this purpose, we model seismic wave propagation within a diffusive medium using a spectral element approach (SPECFEM2D) during an elastic deformation of the medium. The mechanical behavior is obtained from a finite element approach (Code ASTER) keeping the mesh grid of the sample constant during the whole procedure to limit numerical artifacts. The CWI of the late wave arrivals in the synthetic seismograms is performed using both a stretching technique in the time domain and a frequency cross-correlation method. Both show that the elastic deformation of the scatters is fully correlated with time shifts of the CWI differently from an acoustoelastic effect. As an illustration, the modeled sample is chosen as an effective medium aiming to mechanically and acoustically reproduce a typical granitic reservoir rock.Our numerical approach is compared to experimental results where multi-scattering of an acoustic wave through a perforated loaded Au4G (Dural) plate is performed at laboratory scale. Experimental and numerical results of the strain influence on CWI are shown to be consistent.Lehujeur, M., J. Vergne, J. Schmittbuhl, and A. Maggi. Characterization of ambient seismic noise near a deep geothermal reservoir and implications for interferometric methods: a case study in northern alsace, france. Geothermal Energy, 3(1):1-17, 2015.

Can repeating glacial seismic events be used to monitor stress changes within the underlying volcano? -Case study from the glacier overlain Katla volcano, Iceland

NASA Astrophysics Data System (ADS)

Jonsdottir, K.; Vogfjord, K. S.; Bean, C. J.; Martini, F.

2013-12-01

The glacier overlain Katla volcano in South Iceland, is one of the most active and hazardous volcano in Europe. Katla eruptions result in hazardous glacial floods and intense tephra fall. On average there are eruptions every 50 years but the volcano is long overdue and we are now witnessing the longest quiescence period in 1000 years or since the settlement. Because of the hazard the volcano poses, it is under constant surveillance and gets a good share of the seismic stations from the national seismic network. Every year the seismic network records thousands of seismic events at Katla with magnitudes seldom exceeding M3. The bulk of the seismicity is however not due to volcano tectonics but seems to be caused mainly by shallow processes involving glacial deformation. Katla's ice filled caldera forms a glacier plateau of several hundred meters thick ice. The 9x14 km oval caldera is surrounded by higher rims where the glacier in some places gently and in others abruptly falls off tens and up to hundred meters to the surrounding lowland. The glacier surface is marked with dozen depressions or cauldrons which manifest geothermal activity below, probably coinciding with circular faults around the caldera. Our current understanding is that there are several glacial processes which cause seismicity; these include dry calving, where steep valley glaciers fall off cliffs and movements of glacier ice as the cauldrons deform due to hydraulic changes and geothermal activity at the glacier/bedrock boundary. These glacial events share a common feature of containing low frequency (2-4 hz) and long coda. Because of their shallow origin, surface waves are prominent. In our analysis we use waveforms from all of Katla's seismic events between years 2003-2013, with the criteria M>1 and minimum 4 p-wave picks. We correlate the waveforms of these events with each other and group them into families of highly similar events. Looking at the occurrence of these families we find that individual families are usually clustered in time over several months, and sometimes families may reappear even up to several years later. Using families including many events and covering long periods (10-20 months) we compare the coda (the tail) of individual events within a family. This is repeated for all the surrounding stations. The analysis, coda wave interferometry (cwi) is a correlation method that builds on the fact that changes in stress in the edifice lead to changes in seismic velocities. The coda waves are highly sensitive to small stress changes. By using a repeating source, implying we have the same source mechanism and the same path, we can track temporal stress changes in the medium between the source and the receiver. Preliminary results from Katla suggest that by using the repeating glacial events and the coda wave interferometry technique we observe annual seismic velocity changes around the volcano of ca. 0.7%. We find that seismic velocities increase from January through July and decrease in August to December. These changes can be explained by pore-water pressure changes and/or loading and de-loading of the overlain glacier. We do not find immediate precursors for an impending eruption at Katla; however we now have a better understanding of its background seismicity.

Scattered surface wave energy in the seismic coda

USGS Publications Warehouse

Zeng, Y.

2006-01-01

One of the many important contributions that Aki has made to seismology pertains to the origin of coda waves (Aki, 1969; Aki and Chouet, 1975). In this paper, I revisit Aki's original idea of the role of scattered surface waves in the seismic coda. Based on the radiative transfer theory, I developed a new set of scattered wave energy equations by including scattered surface waves and body wave to surface wave scattering conversions. The work is an extended study of Zeng et al. (1991), Zeng (1993) and Sato (1994a) on multiple isotropic-scattering, and may shed new insight into the seismic coda wave interpretation. The scattering equations are solved numerically by first discretizing the model at regular grids and then solving the linear integral equations iteratively. The results show that scattered wave energy can be well approximated by body-wave to body wave scattering at earlier arrival times and short distances. At long distances from the source, scattered surface waves dominate scattered body waves at surface stations. Since surface waves are 2-D propagating waves, their scattered energies should in theory follow a common decay curve. The observed common decay trends on seismic coda of local earthquake recordings particular at long lapse times suggest that perhaps later seismic codas are dominated by scattered surface waves. When efficient body wave to surface wave conversion mechanisms are present in the shallow crustal layers, such as soft sediment layers, the scattered surface waves dominate the seismic coda at even early arrival times for shallow sources and at later arrival times for deeper events.

Coda Wave Analysis in Central-Western North America Using Earthscope Transportable Array Data

NASA Astrophysics Data System (ADS)

Escudero, C. R.; Doser, D. I.

2011-12-01

We determined seismic wave attenuation in the western and central United States (e.g. Washington, Oregon, California, Idaho, Nevada, Montana, Wyoming, Colorado, New Mexico, North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, and Texas) using coda waves. We selected approximately twenty moderate earthquakes (magnitude between 5.5 and 6.5) located along the Mexican subduction zone, Gulf of California, southern and northern California, and off the coast of Oregon for the analysis. These events were recorded by the EarthScope transportable array (TA) network from 2008 to 2011. In this study we implemented a method based on the assumption that coda waves are single backscattered waves from randomly distributed heterogeneities to calculate the coda Q. The frequencies studied lie between 1 and 15 Hz. The scattering attenuation is calculated for frequency bands centered at 1.5, 3, 5, 7.5, 10.5, and 13.5 Hz. In this work, we present coda Q resolution maps along with a correlation analysis between coda Q and seismicity, tectonic and geology setting. We observed higher attenuation (low coda Q values) in regions of sedimentary cover, and lower attenuation (high coda Q values) in hard rock regions. Using the 4-6 Hz frequency band, we found the best general correlation between coda Q and central-western North America bedrock geology.

In-situ changes in the elastic wave velocity of rock with increasing temperature using high-resolution coda wave interferometry

NASA Astrophysics Data System (ADS)

Griffiths, Luke; Heap, Michael; Lengliné, Olivier; Schmittbuhl, Jean; Baud, Patrick

2017-04-01

Rock undergoes fluctuations in temperature in various settings in Earth's crust, including areas of volcanic or geothermal activity, or industrial environments such as hydrocarbon or geothermal reservoirs. Changes in temperature can cause thermal stresses that can result in the formation of microcracks, which affect the mechanical, physical, and transport properties of rocks. Of the affected physical properties, the elastic wave velocity of rock is particularly sensitive to microcracking. Monitoring the evolution of elastic wave velocity during the thermal stressing of rock therefore provides valuable insight into thermal cracking processes. One monitoring technique is Coda Wave Interferometry (CWI), which infers high-resolution changes in the medium from changes in multiple-scattered elastic waves. We have designed a new experimental setup to perform CWI whilst cyclically heating and cooling samples of granite (cylinders of 20 mm diameter and 40 mm length). In our setup, the samples are held between two pistons within a tube furnace and are heated and cooled at a rate of 1 °C/min to temperatures of up to 300 °C. Two high temperature piezo-transducers are each in contact with an opposing face of the rock sample. The servo-controlled uniaxial press compensates for the thermal expansion and contraction of the pistons and the sample, keeping the coupling between the transducers and the sample, and the axial force acting on the sample, constant throughout. Our setup is designed for simultaneous acoustic emission monitoring (AE is commonly used as a proxy for microcracking), and so we can follow thermal microcracking precisely by combining the AE and CWI techniques. We find that during the first heating/cooling cycle, the onset of thermal microcracking occurs at a relatively low temperature of around 65 °C. The CWI shows that elastic wave velocity decreases with increasing temperature and increases during cooling. Upon cooling, back to room temperature, there is an irreversible relative decrease in velocity of several percent associated with the presence of new thermal microcracks. Our data suggest that few new microcracks were formed when the same sample was subject to subsequent identical heating/cooling cycles as changes in the elastic wave velocity are near-reversible. Our results shed light on the temperature conditions required for thermal microcracking and the influence of temperature on elastic wave velocity with applications to a wide variety of geoscientific disciplines.

Studies of the seismic coda using an earthquake cluster as a deeply buried seismograph array

NASA Astrophysics Data System (ADS)

Spudich, Paul; Bostwick, Todd

1987-09-01

Loosely speaking, the principle of Green's function reciprocity means that the source and receiver positions in a seismic experiment can be exchanged without affecting the observed seismograms. Consequently, the seismograms observed at a single observation location o and caused by a cluster of microearthquakes at locations {ei} are identical to the time series that would be measured by an array of stress meters emplaced at positions {ei}, recording waves generated by a source acting at o. By applying array analysis techniques like slant stacking and frequency-wave number analysis to these seismograms, we can determine the directions and velocities of the component waves as they travel in the earthquake focal region rather than at the surface. We have developed a computationally rapid plane-wave decomposition which we have applied to single-station recordings of aftershocks of the 1984 Morgan Hill, California, earthquake. The analysis is applied to data from three seismic stations having considerably different site geologies. One is a relatively hard rock station situated on Franciscan metamorphics, one is within the Calaveras fault zone, and one is on semiconsolidated sand and gravels. We define the early coda to be the part of the coda initiating immediately after the direct S wave and ending at twice the S wave lapse time. The character of the S wave and early coda varies from being impulsive at the first station to highly reverberative at the last. We examine waves in sequential time windows starting at the S wave and continuing through the early part of the coda. At all seismic stations the early coda is dominated by a persistent signal that must be caused by multiple scattering, probably within 2 km of each seismic station. Despite clear station-to-station differences in the character of the early coda, coda Q values measured in the late coda (greater than twice the S lapse time) agree well among stations, implying that the mechanisms causing the varying behavior of the early coda do not control the coda decay rate at the stations we have considered. Coda Q values measured on horizontal components of motion agree within a factor of 2 with those measured on vertical components. We have not been able to determine the composition of the late coda because of a low signal-to-noise ratio. Our analysis technique, however, is quite appropriate for such a task.

Teleseismic P wave coda from oceanic trench and other bathymetric features

NASA Astrophysics Data System (ADS)

Wu, W.; Ni, S.

2012-12-01

Teleseismic P waves are essential for studying rupture processes of great earthquakes, either in the back projection method or in finite fault inversion method involving of quantitative waveform modeling. In these studies, P waves are assumed to be direct P waves generated by localized patches of the ruptured fault. However, for some oceanic earthquakes happening near the subductiontrenches or mid-ocean ridges, we observed strong signals between P and PP are often observed on theat telseseismic networkdistances. These P wave coda signals show strong coherence and their amplitudes are sometimes comparable with those of the direct P wave or even higher for some special frequenciesfrequency band. With array analysis, we find that the coda's slowness is very close to that of the direct P wave, suggesting that they are generated near the source region. As the earthquakes occur near the trenches or mid-ocean ridges which are both featured by rapid variation of bathymetry, the coda waves are very probably generated by the scattered surface wave or S wave at the irregular bathymetry. Then, we apply the realistic bathymetry data to calculate the 3D synthetics and the coda can be well predicted by the synthetics. So the topography/bathymetry is confirmed to be the main source of the coda. The coda waves are so strong that it may affect the imaging rupture processes of ocean earthquakes, so the topography/bathymetry effect should be taken into account. However, these strong coda waves can also be used utilized to locate the oceanic earthquakes. The 3D synthetics demonstrate that the coda waves are dependent on both the specific bathymetry and the location of the earthquake. Given the determined bathymetry, the earthquake location can be constrained by the coda, e.g. the distance between trench and the earthquake can be determine from the relative arrival between the P wave and its coda which is generated by the trench. In order to locate the earthquakes using the bathymetry, it is indispensible to get all the 3D synthetics with possible different horizontal locations and depths of the earthquakes. However, the computation will be very expensive if using the numerical simulation in the whole medium. Considering that the complicated structure is only near the source region, we apply ray theory to interface full wave field from spectral-element simulation to get the teleseismic P waves. With this approach, computation efficiency is greatly improved and the relocation of the earthquake can be completed more efficiently. As for the relocation accuracy, it can be as high as 10km for the earthquakes near the trench. So it provides us another, sometimes most favorable, method to locate the ocean earthquakes with ground-truth accuracy.

Quantitative ultrasonic coda wave (diffuse field) NDE of carbon-fiber reinforced polymer plates

NASA Astrophysics Data System (ADS)

Livings, Richard A.

The increasing presence and applications of composite materials in aerospace structures precipitates the need for improved Nondestructive Evaluation (NDE) techniques to move from simple damage detection to damage diagnosis and structural prognosis. Structural Health Monitoring (SHM) with advanced ultrasonic (UT) inspection methods can potentially address these issues. Ultrasonic coda wave NDE is one of the advanced methods currently under investigation. Coda wave NDE has been applied to concrete and metallic specimens to assess damage with some success, but currently the method is not fully mature or ready to be applied for SHM. Additionally, the damage diagnosis capabilities and limitations of coda wave NDE applied to fibrous composite materials have not been widely addressed in literature. The central objective of this work, therefore, is to develop a quantitative foundation for the use of coda wave NDE for the inspection and evaluation of fibrous composite materials. Coda waves are defined as the superposition of late arriving wave modes that have been scattered or reflected multiple times. This results in long, complex signals where individual wave modes cannot be discriminated. One method of interpreting the changes in such signals caused by the introduction or growth of damage is to isolate and quantify the difference between baseline and damage signals. Several differential signal features are used in this work to quantify changes in the coda waves which can then be correlated to damage size and growth. Experimental results show that coda wave differential features are effective in detecting drilled through-holes as small as 0.4 mm in a 50x100x6 mm plate and discriminating between increasing hole diameter and increasing number of holes. The differential features are also shown to have an underlying basis function that is dependent on the hole volume and can be scaled by a material dependent coefficient to estimate the feature amplitude and size holes. The fundamental capabilities of the coda wave measurements, such as error, repeatability, and reproducibility, are also examined. Damage detection was found to be repeatable, reproducible, and relatively insensitive to noise. The measurements are found to be sensitive to thermal changes and absorbing boundaries. Several propagation models are also presented and discussed along with a brief analysis of coda wave signals and spectra.

Envelope of coda waves for a double couple source due to non-linear elasticity

NASA Astrophysics Data System (ADS)

Calisto, Ignacia; Bataille, Klaus

2014-10-01

Non-linear elasticity has recently been considered as a source of scattering, therefore contributing to the coda of seismic waves, in particular for the case of explosive sources. This idea is analysed further here, theoretically solving the expression for the envelope of coda waves generated by a point moment tensor in order to compare with earthquake data. For weak non-linearities, one can consider each point of the non-linear medium as a source of scattering within a homogeneous and linear medium, for which Green's functions can be used to compute the total displacement of scattered waves. These sources of scattering have specific radiation patterns depending on the incident and scattered P or S waves, respectively. In this approach, the coda envelope depends on three scalar parameters related to the specific non-linearity of the medium; however these parameters only change the scale of the coda envelope. The shape of the coda envelope is sensitive to both the source time function and the intrinsic attenuation. We compare simulations using this model with data from earthquakes in Taiwan, with a good fit.

Correlation of Coseismic Velocity and Static Volumetric Strain Changes Induced by the 2010 Mw6.3 Jiasian Earthquake under the Southern Taiwan Orogenic Belt

NASA Astrophysics Data System (ADS)

Wu, S. M.; Hung, S. H.

2015-12-01

Earthquake-induced temporal changes in seismic velocity of the earth's crust have been demonstrated to be monitored effectively by the time-lapse shifts of coda waves recently. Velocity drop during the coseismic rupture has been explicitly observed in proximity to the epicenters of large earthquakes with different styles of faulting. The origin of such sudden perturbation in crustal properties is closely related to the damage and/or volumetric strain change influenced by seismic slip distribution. In this study, we apply a coda wave interferometry method to investigate potential velocity change in both space and time related to the moderate-sized (Mw6.3) 2010 Jiasian earthquake, which nucleated deeply in the crust (~23 km), ruptured and terminated around the depth of 10 km along a previously unidentified blind thrust fault near the lithotectonic boundary of the southern Taiwan orogenic belt. To decipher the surface and crustal response to this relatively deep rupture, we first measure relative time-lapse changes of coda between different short-term time frames spanning one year covering the pre- and post-seismic stages by using the Moving Window Cross Spectral Method. Rather than determining temporal velocity variations based on a long-term reference stack, we conduct a Bayesian least-squares inversion to obtain the optimal estimates by minimizing the inconsistency between the relative time-lapse shifts of individual short-term stacks. The results show the statistically significant velocity reduction immediately after the mainshock, which is most pronounced at the pairs with the interstation paths traversing through the hanging-wall block of the ruptured fault. The sensitivity of surface wave coda arrivals mainly in the periods of 3-5 s to shear wave speed perturbation is confined within the depth of 10 km, where the crust mostly experienced extensional strain changes induced by the slip distribution from the finite-fault model. Compared with coseismic slip distribution from GPS data and finite-fault inversion, peak ground velocity, and static volumetric strain field following the earthquake, the velocity decrease observed in the hanging wall side of the shallow crust is most likely attributed to pervasive dilatational strain changes induced by the slip rupture on the underlying blind thrust.

Micro-crack detection in CFRP laminates using coda wave NDE

NASA Astrophysics Data System (ADS)

Dayal, Vinay; Barnard, Dan; Livings, Richard

2018-04-01

Coda Waves or diffuse field has been touted to be an NDE method that does not require the damage to be in the path of the ultrasound. The object is insonified with ultrasound and instead of catching the first or second arrival, the waves are allowed to bounce multiple times. This aspect is very important in structural health monitoring (SHM) where the potential damage development location is unknown. Researchers have used Coda waves in the interrogation of seismic damage and metallic materials. In this work we have applied the technique to composite material, and present the results herein. The coda wave and acoustic emission signals are recorded simultaneously and corroborated. Development of small incipient damage in the form of micro-crack and their detection is the objective of this work.

Attenuation of seismic waves obtained by coda waves analysis in the West Bohemia earthquake swarm region

NASA Astrophysics Data System (ADS)

Bachura, Martin; Fischer, Tomas

2014-05-01

Seismic waves are attenuated by number of factors, including geometrical spreading, scattering on heterogeneities and intrinsic loss due the anelasticity of medium. Contribution of the latter two processes can be derived from the tail part of the seismogram - coda (strictly speaking S-wave coda), as these factors influence the shape and amplitudes of coda. Numerous methods have been developed for estimation of attenuation properties from the decay rate of coda amplitudes. Most of them work with the S-wave coda, some are designed for the P-wave coda (only on teleseismic distances) or for the whole waveforms. We used methods to estimate the 1/Qc - attenuation of coda waves, methods to separate scattering and intrinsic loss - 1/Qsc, Qi and methods to estimate attenuation of direct P and S wave - 1/Qp, 1/Qs. In this study, we analyzed the S-wave coda of local earthquake data recorded in the West Bohemia/Vogtland area. This region is well known thanks to the repeated occurrence of earthquake swarms. We worked with data from the 2011 earthquake swarm, which started late August and lasted with decreasing intensity for another 4 months. During the first week of swarm thousands of events were detected with maximum magnitudes ML = 3.6. Amount of high quality data (including continuous datasets and catalogues with an abundance of well-located events) is available due to installation of WEBNET seismic network (13 permanent and 9 temporary stations) monitoring seismic activity in the area. Results of the single-scattering model show seismic attenuations decreasing with frequency, what is in agreement with observations worldwide. We also found decrease of attenuation with increasing hypocentral distance and increasing lapse time, which was interpreted as a decrease of attenuation with depth (coda waves on later lapse times are generated in bigger depths - in our case in upper lithosphere, where attenuations are small). We also noticed a decrease of frequency dependence of 1/Qc with depth, where 1/Qc seems to be frequency independent in depth range of upper lithosphere. Lateral changes of 1/Qc were also reported - it decreases in the south-west direction from the Novy Kostel focal zone, where the attenuation is the highest. Results from more advanced methods that allow for separation of scattering and intrinsic loss show that intrinsic loss is a dominant factor for attenuating of seismic waves in the region. Determination of attenuation due to scattering appears ambiguous due to small hypocentral distances available for the analysis, where the effects of scattering in frequency range from 1 to 24 Hz are not significant.

2-D Path Corrections for Local and Regional Coda Waves: A Test of Transportability

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

Mayeda, K M; Malagnini, L; Phillips, W S

2005-07-13

Reliable estimates of the seismic source spectrum are necessary for accurate magnitude, yield, and energy estimation. In particular, how seismic radiated energy scales with increasing earthquake size has been the focus of recent debate within the community and has direct implications on earthquake source physics studies as well as hazard mitigation. The 1-D coda methodology of Mayeda et al. [2003] has provided the lowest variance estimate of the source spectrum when compared against traditional approaches that use direct S-waves, thus making it ideal for networks that have sparse station distribution. The 1-D coda methodology has been mostly confined to regionsmore » of approximately uniform complexity. For larger, more geophysically complicated regions, 2-D path corrections may be required. We will compare performance of 1-D versus 2-D path corrections in a variety of regions. First, the complicated tectonics of the northern California region coupled with high quality broadband seismic data provides for an ideal ''apples-to-apples'' test of 1-D and 2-D path assumptions on direct waves and their coda. Next, we will compare results for the Italian Alps using high frequency data from the University of Genoa. For Northern California, we used the same station and event distribution and compared 1-D and 2-D path corrections and observed the following results: (1) 1-D coda results reduced the amplitude variance relative to direct S-waves by roughly a factor of 8 (800%); (2) Applying a 2-D correction to the coda resulted in up to 40% variance reduction from the 1-D coda results; (3) 2-D direct S-wave results, though better than 1-D direct waves, were significantly worse than the 1-D coda. We found that coda-based moment-rate source spectra derived from the 2-D approach were essentially identical to those from the 1-D approach for frequencies less than {approx}0.7-Hz, however for the high frequencies (0.7 {le} f {le} 8.0-Hz), the 2-D approach resulted in inter-station scatter that was generally 10-30% smaller. For complex regions where data are plentiful, a 2-D approach can significantly improve upon the simple 1-D assumption. In regions where only 1-D coda correction is available it is still preferable over 2-D direct wave-based measures.« less

Spatial variation of crustal coda Q in California

USGS Publications Warehouse

Philips, W.S.; Lee, W.H.K.; Newberry, J.T.

1988-01-01

Coda wave data from California microearthquakes were studied in order to delineate regional fluctuations of apparent crustal attenuation in the band 1.5 to 24 Hz. Apparent attenuation was estimated using a single back scattering model of coda waves. The coda wave data were restricted to ???30 s following the origin time; this insures that crustal effects dominate the results as the backscattered shear waves thought to form the coda would not have had time to penetrate much deeper. Results indicate a strong variation in apparent crustal attenuation at high frequencies between the Franciscan and Salinian regions of central California and the Long Valley area of the Sierra Nevada. Although the coda Q measurements coincide at 1.5 Hz (Qc=100), at 24 Hz there is a factor of four difference between the measurements made in Franciscan (Qc=525) and Long Valley (Qc=2100) with the Salinian midway between (Qc=900). These are extremely large variations compared to measures of seismic velocities of comparable resolution, demonstrating the exceptional sensitivity of the high frequency coda Q measurement to regional geology. In addition, the frequency trend of the results is opposite to that seen in a compilation of coda Q measurements made worldwide by other authors which tend to converge at high and diverge at low frequencies, however, the worldwide results generally were obtained without limiting the coda lengths and probably reflect upper mantle rather than crustal properties. Our results match those expected due to scattering in random media represented by Von Karman autocorrelation functions of orders 1/2 to 1/3. The Von Karman medium of order 1/3 corresponding to the Franciscan coda Q measurement contains greater amounts of high wavenumber fluctuations. This indicates relatively large medium fluctuations with wavelengths on the order of 100 m in the highly deformed crust associated with the Franciscan, however, the influence of scattering on the coda Q measurement is currently a matter of controversy. ?? 1988 Birkha??user Verlag.

Constraining the depth of the time-lapse changes of P- and S-wave velocities in the first year after the 2011 Tohoku earthquake, Japan

NASA Astrophysics Data System (ADS)

Sawazaki, K.; Kimura, H.; Uchida, N.; Takagi, R.; Snieder, R.

2012-12-01

Using deconvolutions of vertical array of KiK-net (nationwide strong-motion seismograph digital network in Japan) records and applying coda wave interferometry (CWI) to Hi-net (high-sensitivity seismograph network in Japan; collocated with a borehole receiver of KiK-net) borehole records, we constrain the responsible depth of the medium changes associated with the 2011 Tohoku earthquake (MW9.0). There is a systematic reduction in VS up to 6% in the shallow subsurface which experienced strong dynamic strain by the Tohoku earthquake. In contrast, both positive and negative changes are observed for VP, which are less than 2% for both directions. We propose that this discrepancy between the changes of VS and VP is explained by the behavior of shear and bulk moduli of a porous medium exposed to an increase of excess pore fluid pressure. At many stations, VS recovers proportional to logarithm of the lapse time after the mainshock, and mostly recovers to the reference value obtained before the mainshock in one year. However, some stations that have been exposed by additional strong motions of aftershocks and/or other earthquakes take much longer time for the recovery. The CWI technique applied to horizontal components of S-coda reveals a velocity reduction up to 0.2% widely along the coastline of northeastern Japan. For the vertical component of P-coda, however, the velocity change is mostly less than 0.1% at the same region. From single scattering model including P-S and S-P conversion scatterings, we verify that both components are sensitive to VS change around the source, but the vertical component of P-coda is sensitive to VP change around the receiver. Consequently, the difference in velocity changes revealed from the horizontal and vertical components represents the difference of VS and VP changes near the receiver. As the conclusion, VS reduction ratio in the deep lithosphere is smaller than that at the shallow ground by 1 to 2 orders.

2-D or not 2-D, that is the question: A Northern California test

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

Mayeda, K; Malagnini, L; Phillips, W S

2005-06-06

Reliable estimates of the seismic source spectrum are necessary for accurate magnitude, yield, and energy estimation. In particular, how seismic radiated energy scales with increasing earthquake size has been the focus of recent debate within the community and has direct implications on earthquake source physics studies as well as hazard mitigation. The 1-D coda methodology of Mayeda et al. has provided the lowest variance estimate of the source spectrum when compared against traditional approaches that use direct S-waves, thus making it ideal for networks that have sparse station distribution. The 1-D coda methodology has been mostly confined to regions ofmore » approximately uniform complexity. For larger, more geophysically complicated regions, 2-D path corrections may be required. The complicated tectonics of the northern California region coupled with high quality broadband seismic data provides for an ideal ''apples-to-apples'' test of 1-D and 2-D path assumptions on direct waves and their coda. Using the same station and event distribution, we compared 1-D and 2-D path corrections and observed the following results: (1) 1-D coda results reduced the amplitude variance relative to direct S-waves by roughly a factor of 8 (800%); (2) Applying a 2-D correction to the coda resulted in up to 40% variance reduction from the 1-D coda results; (3) 2-D direct S-wave results, though better than 1-D direct waves, were significantly worse than the 1-D coda. We found that coda-based moment-rate source spectra derived from the 2-D approach were essentially identical to those from the 1-D approach for frequencies less than {approx}0.7-Hz, however for the high frequencies (0.7{le} f {le} 8.0-Hz), the 2-D approach resulted in inter-station scatter that was generally 10-30% smaller. For complex regions where data are plentiful, a 2-D approach can significantly improve upon the simple 1-D assumption. In regions where only 1-D coda correction is available it is still preferable over 2-D direct wave-based measures.« less

Comparison of techniques that use the single scattering model to compute the quality factor Q from coda waves

USGS Publications Warehouse

Novelo-Casanova, D. A.; Lee, W.H.K.

1991-01-01

Using simulated coda waves, the resolution of the single-scattering model to extract coda Q (Qc) and its power law frequency dependence was tested. The back-scattering model of Aki and Chouet (1975) and the single isotropic-scattering model of Sato (1977) were examined. The results indicate that: (1) The input Qc models are reasonably well approximated by the two methods; (2) almost equal Qc values are recovered when the techniques sample the same coda windows; (3) low Qc models are well estimated in the frequency domain from the early and late part of the coda; and (4) models with high Qc values are more accurately extracted from late code measurements. ?? 1991 Birkha??user Verlag.

Neutral axis determination of full size concrete structures using coda wave measurements

NASA Astrophysics Data System (ADS)

Jiang, Hanwan; Zhan, Hanyu; Zhuang, Chenxu; Jiang, Ruinian

2018-03-01

Coda waves experiencing multiple scattering behaviors are sensitive to weak changes occurring in media. In this paper, a typical four-point bending test with varied external loads is conducted on a 30-meter T-beam that is removed from a bridge after being in service for 15 years, and the coda wave signals are collected with a couple of sources-receivers pairs. Then the observed coda waves at different loads are compared to calculate their relative velocity variations, which are utilized as the parameter to distinct the compression and tensile zones as well as determine the neutral axis position. Without any prior knowledge of the concrete beam, the estimated axis position agrees well with the associated strain gage measurement results, and the zones bearing stress and tension behaviors are indicated. The presented work offers significant potential for Non-Destructive Testing and Evaluation of full-size concrete structures in future work.

A surface wave reflector in Southwestern Japan

NASA Astrophysics Data System (ADS)

Mak, S.; Koketsu, K.; Miyake, H.; Obara, K.; Sekine, S.

2009-12-01

Surface waves at short periods (<35s) are affected severely by heterogeneities in the crust and the uppermost mantle. When the scale of heterogeneity is sufficiently large, its effect can be studied in a deterministic way using conventional concepts of reflection and refraction. A well-known example is surface wave refraction at continental margin. We present a case study to investigate the composition of surface wave coda in a deterministic approach. A long duration of surface wave coda with a predominant period of 20s is observed during various strong earthquakes around Japan. The coda shows an unambiguous propagation direction, implying a deterministic nature. Beamforming and particle motion analysis suggest that the surface wave later arrivals could be explained by Love wave reflections by a point reflector located at offshore southeast to Kyushu. The reflection demonstrates a seemingly incidence-independent favorable azimuth in emitting strength. In additional to beamforming, we use a new regional crustal velocity model to perform a grid-search ray-tracing with the assumption of point reflector to further constrain to location of coda generation. Because strong velocity anomalies exist near the zone of interest, we decide to use a network shortest-path ray-tracing method, instead of analytical methods like shooting and bending, to avoid the problems like convergence, shadow zone, and smooth model assumption. Two geological features are found to be related to the formation of the coda. The primary one is the intersection between the Kyushu-Palau Ridge and the Nankai Trough at offshore southeast to Kyushu (hereafter referred as "KPR-NT"), which may act as a point reflector. There is a strong Love wave phase velocity anomaly at KPR-NT but not other parts of the ridge, implying that topography is irrelevant. Rayleigh wave phase velocity does not experience a strong anomaly there, which is consistent to the absence of Rayleigh wave reflections implied by the observed particle motions. The secondary one is a low phase velocity (<2km/s for T=20s) at the accretionary wedge of the Nankai Trough due to the thick sediment. Such a long and narrow low velocity zone, with its southwest tip at KPR-NT, is a potential wave-guide to channel waves towards KPR-NT. The longer duration of deterministic later arrivals than the direct arrival is partially explained by multi-pathing due to the wave-guide. The surface wave coda is observable for earthquakes whose propagation path does not include the accretionary wedge, implying that the wedge is an enhancer but not indispensable of the formation of the observed coda.

Regional Body-Wave Attenuation Using a Coda Source Normalization Method: Application to MEDNET Records of Earthquakes in Italy

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

Walter, W R; Mayeda, K; Malagnini, L

2007-02-01

We develop a new methodology to determine apparent attenuation for the regional seismic phases Pn, Pg, Sn, and Lg using coda-derived source spectra. The local-to-regional coda methodology (Mayeda, 1993; Mayeda and Walter, 1996; Mayeda et al., 2003) is a very stable way to obtain source spectra from sparse networks using as few as one station, even if direct waves are clipped. We develop a two-step process to isolate the frequency-dependent Q. First, we correct the observed direct wave amplitudes for an assumed geometrical spreading. Next, an apparent Q, combining path and site attenuation, is determined from the difference between themore » spreading-corrected amplitude and the independently determined source spectra derived from the coda methodology. We apply the technique to 50 earthquakes with magnitudes greater than 4.0 in central Italy as recorded by MEDNET broadband stations around the Mediterranean at local-to-regional distances. This is an ideal test region due to its high attenuation, complex propagation, and availability of many moderate sized earthquakes. We find that a power law attenuation of the form Q(f) = Q{sub 0}f{sup Y} fit all the phases quite well over the 0.5 to 8 Hz band. At most stations, the measured apparent Q values are quite repeatable from event to event. Finding the attenuation function in this manner guarantees a close match between inferred source spectra from direct waves and coda techniques. This is important if coda and direct wave amplitudes are to produce consistent seismic results.« less

Medium change based image estimation from application of inverse algorithms to coda wave measurements

NASA Astrophysics Data System (ADS)

Zhan, Hanyu; Jiang, Hanwan; Jiang, Ruinian

2018-03-01

Perturbations worked as extra scatters will cause coda waveform distortions; thus, coda wave with long propagation time and traveling path are sensitive to micro-defects in strongly heterogeneous media such as concretes. In this paper, we conduct varied external loads on a life-size concrete slab which contains multiple existing micro-cracks, and a couple of sources and receivers are installed to collect coda wave signals. The waveform decorrelation coefficients (DC) at different loads are calculated for all available source-receiver pair measurements. Then inversions of the DC results are applied to estimate the associated distribution density values in three-dimensional regions through kernel sensitivity model and least-square algorithms, which leads to the images indicating the micro-cracks positions. This work provides an efficiently non-destructive approach to detect internal defects and damages of large-size concrete structures.

P and S wave Coda Calibration in Central Asia and South Korea

NASA Astrophysics Data System (ADS)

Kim, D.; Mayeda, K.; Gok, R.; Barno, J.; Roman-Nieves, J. I.

2017-12-01

Empirically derived coda source spectra provide unbiased, absolute moment magnitude (Mw) estimates for events that are normally too small for accurate long-period waveform modeling. In this study, we obtain coda-derived source spectra using data from Central Asia (Kyrgyzstan networks - KN and KR, and Tajikistan - TJ) and South Korea (Korea Meteorological Administration, KMA). We used a recently developed coda calibration module of Seismic WaveForm Tool (SWFT). Seismic activities during this recording period include the recent Gyeongju earthquake of Mw=5.3 and its aftershocks, two nuclear explosions from 2009 and 2013 in North Korea, and a small number of construction and mining-related explosions. For calibration, we calculated synthetic coda envelopes for both P and S waves based on a simple analytic expression that fits the observed narrowband filtered envelopes using the method outlined in Mayeda et al. (2003). To provide an absolute scale of the resulting source spectra, path and site corrections are applied using independent spectral constraints (e.g., Mw and stress drop) from three Kyrgyzstan events and the largest events of the Gyeongju sequence in Central Asia and South Korea, respectively. In spite of major tectonic differences, stable source spectra were obtained in both regions. We validated the resulting spectra by comparing the ratio of raw envelopes and source spectra from calibrated envelopes. Spectral shapes of earthquakes and explosions show different patterns in both regions. We also find (1) the source spectra derived from S-coda is more robust than that from the P-coda at low frequencies; (2) unlike earthquake events, the source spectra of explosions have a large disagreement between P and S waves; and (3) similarity is observed between 2016 Gyeongju and 2011 Virginia earthquake sequence in the eastern U.S.

Evidence for small-scale heterogeneity in Earth's inner core from a global study of PKiKP coda waves

NASA Astrophysics Data System (ADS)

Koper, Keith D.; Franks, Jill M.; Dombrovskaya, Marina

2004-12-01

Recent seismic observations have provided evidence that the inner core contains strong heterogeneity at a scale-length of tens of kilometers. The corresponding lateral variations in elastic properties could be caused by pockets of partial melt, alignment of iron crystals, or variations in chemistry. However, the relevant seismic observations (precritical PKiKP coda waves) were subtle and were made using historic seismic data. Furthermore, it has been suggested that the seismic data might be explainable by scatterers in the lower mantle or by a complex inner core boundary. To address these issues, we investigate a preexisting global database of precritical PKiKP waveforms at distances of 10°-50°, and a second, newly generated global data base of PKiKP waveforms at distances of 50°-90°. We analyze the data using standard array processing techniques and identify PKiKP coda waves based on travel time, ray parameter, amplitude, and coherence. Although it remains unclear whether the scattered energy is being created within the inner core or along its boundary, we find three lines of evidence which support the idea that it is in fact related to the inner core: at smaller distances the decay rate of PKiKP coda is significantly lower than the decay rates of the corresponding PcP and ScP codas; at larger distances, we find examples of emergent, spindle-shaped PKiKP coda waves that exist without the parent PKiKP phase; and at larger distances, we infer a PKiKP coda decay rate similar to that determined from the data at the smaller distances. It is likely that many more PKiKP coda observations can be made with existing data sets, and hence seismologists possess a new, extraordinarily fine probe for inferring inner core structure.

Active doublet method for measuring small changes in physical properties

DOEpatents

Roberts, Peter M.; Fehler, Michael C.; Johnson, Paul A.; Phillips, W. Scott

1994-01-01

Small changes in material properties of a work piece are detected by measuring small changes in elastic wave velocity and attenuation within a work piece. Active, repeatable source generate coda wave responses from a work piece, where the coda wave responses are temporally displaced. By analyzing progressive relative phase and amplitude changes between the coda wave responses as a function of elapsed time, accurate determinations of velocity and attenuation changes are made. Thus, a small change in velocity occurring within a sample region during the time periods between excitation origin times (herein called "doublets") will produce a relative delay that changes with elapsed time over some portion of the scattered waves. This trend of changing delay is easier to detect than an isolated delay based on a single arrival and provides a direct measure of elastic wave velocity changes arising from changed material properties of the work piece.

Changes in Seismic Velocity During the 2004 - 2008 Eruption of Mount St. Helens Volcano

NASA Astrophysics Data System (ADS)

Hotovec-Ellis, A. J.; Vidale, J. E.; Gomberg, J. S.; Moran, S. C.; Thelen, W. A.

2013-12-01

Mount St. Helens (MSH) effusively erupted in late 2004, following an 18-year quiescence. Many swarms of repeating earthquakes accompanied the extrusion and in some cases the waveforms from these earthquakes evolved slowly, possibly reflecting changes in the properties of the volcano that affect seismic wave propagation. We use coda-wave interferometry to quantify these changes in terms of small (usually <1%) changes in seismic velocity structure by determining how relatively condensed or stretched the coda is between two similar earthquakes. We then utilize several hundred distinct families of repeating earthquakes at once to create a continuous function of velocity change observed at any station in the seismic network. The rate of earthquakes allows us to track these changes on a daily or even hourly time scale. Following years of no seismic velocity changes larger than those due to climatic processes (tenths of a percent), we observed decreases in seismic velocity of >1% coincident with the onset of increased earthquake activity beginning September 23, 2004. These changes are largest near the summit of the volcano, and likely related to shallow deformation as magma first worked its way to the surface. Changes in velocity are often attributed to deformation, especially volumetric strain and the opening or closing of cracks, but also with nonlinear responses to ground shaking and fluid intrusion. We compare velocity changes across the eruption with other available observations, such as deformation (e.g., GPS, tilt, photogrammetry), to better constrain the relationships between velocity change and its possible causes.

Seismic Attenuation, Event Discrimination, Magnitude and Yield Estimation, and Capability Analysis

DTIC Science & Technology

2011-09-01

waves are subject to path-dependent variations in amplitudes. We see geographic similarities between the crustal shear-wave attenuation and the...either Sn or Lg depending on tectonic region, distance, and frequency. Over the past year, we have made great progress on the calibration of surface...between the crustal shear-wave attenuation and the results from the coda attenuation. Calibration of coda in the Middle East and other areas is

Attenuation of Lg waves in the New Madrid seismic zone of the central United States using the coda normalization method

NASA Astrophysics Data System (ADS)

Nazemi, Nima; Pezeshk, Shahram; Sedaghati, Farhad

2017-08-01

Unique properties of coda waves are employed to evaluate the frequency dependent quality factor of Lg waves using the coda normalization method in the New Madrid seismic zone of the central United States. Instrument and site responses are eliminated and source functions are isolated to construct the inversion problem. For this purpose, we used 121 seismograms from 37 events with moment magnitudes, M, ranging from 2.5 to 5.2 and hypocentral distances from 120 to 440 km recorded by 11 broadband stations. A singular value decomposition (SVD) algorithm is used to extract Q values from the data, while the geometric spreading exponent is assumed to be a constant. Inversion results are then fitted with a power law equation from 3 to 12 Hz to derive the frequency dependent quality factor function. The final results of the analysis are QVLg (f) = (410 ± 38) f0.49 ± 0.05 for the vertical component and QHLg (f) = (390 ± 26) f0.56 ± 0.04 for the horizontal component, where the term after ± sign represents one standard error. For stations within the Mississippi embayment with an average sediment depth of 1 km around the Memphis metropolitan area, estimation of quality factor using the coda normalization method is not well-constrained at low frequencies (f < 3 Hz). There may be several reasons contributing to this issue, such as low frequency surface wave contamination, site effects, or even a change in coda wave scattering regime which can exacerbate the scatter of the data.

Using seismic coda waves to resolve intrinsic and scattering attenuation

NASA Astrophysics Data System (ADS)

Wang, W.; Shearer, P. M.

2016-12-01

Seismic attenuation is caused by two factors, scattering and intrinsic absorption. Characterizing scattering and absorbing properties and the power spectrum of crustal heterogeneity is a fundamental problem for informing strong ground motion estimates at high frequencies, where scattering and attenuation effects are critical. Determining the relative amount of attenuation caused by scattering and intrinsic absorption has been a long-standing problem in seismology. The wavetrain following the direct body wave phases is called the coda, which is caused by scattered energy. Many studies have analyzed the coda of local events to constrain crustal and upper-mantle scattering strength and intrinsic attenuation. Here we examine two popular attenuation inversion methods, the Multiple Lapse Time Window Method (MLTWM) and the Coda Qc Method. First, based on our previous work on California attenuation structure, we apply an efficient and accurate method, the Monte Carlo Approach, to synthesize seismic envelope functions. We use this code to generate a series of synthetic data based on several complex and realistic forward models. Although the MLTWM assumes a uniform whole space, we use the MLTWM to invert for both scattering and intrinsic attenuation from the synthetic data to test how accurately it can recover the attenuation models. Results for the coda Qc method depend on choices for the length and starting time of the coda-wave time window. Here we explore the relation between the inversion results for Qc, the windowing parameters, and the intrinsic and scattering Q structure of our synthetic model. These results should help assess the practicality and accuracy of the Multiple Lapse Time Window Method and Coda Qc Method when applied to realistic crustal velocity and attenuation models.

Diffusion approximation with polarization and resonance effects for the modelling of seismic waves in strongly scattering small-scale media

NASA Astrophysics Data System (ADS)

Margerin, Ludovic

2013-01-01

This paper presents an analytical study of the multiple scattering of seismic waves by a collection of randomly distributed point scatterers. The theory assumes that the energy envelopes are smooth, but does not require perturbations to be small, thereby allowing the modelling of strong, resonant scattering. The correlation tensor of seismic coda waves recorded at a three-component sensor is decomposed into a sum of eigenmodes of the elastodynamic multiple scattering (Bethe-Salpeter) equation. For a general moment tensor excitation, a total number of four modes is necessary to describe the transport of seismic waves polarization. Their spatio-temporal dependence is given in closed analytical form. Two additional modes transporting exclusively shear polarizations may be excited by antisymmetric moment tensor sources only. The general solution converges towards an equipartition mixture of diffusing P and S waves which allows the retrieval of the local Green's function from coda waves. The equipartition time is obtained analytically and the impact of absorption on Green's function reconstruction is discussed. The process of depolarization of multiply scattered waves and the resulting loss of information is illustrated for various seismic sources. It is shown that coda waves may be used to characterize the source mechanism up to lapse times of the order of a few mean free times only. In the case of resonant scatterers, a formula for the diffusivity of seismic waves incorporating the effect of energy entrapment inside the scatterers is obtained. Application of the theory to high-contrast media demonstrates that coda waves are more sensitive to slow rather than fast velocity anomalies by several orders of magnitude. Resonant scattering appears as an attractive physical phenomenon to explain the small values of the diffusion constant of seismic waves reported in volcanic areas.

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

Eken Tuna, Kevin Mayeda, Abraham Hofstetter, Rengin Gok, Gonca Orgulu, Niyazi Turkelli

A recently developed coda magnitude methodology was applied to selected broadband stations in Turkey for the purpose of testing the coda method in a large, laterally complex region. As found in other, albeit smaller regions, coda envelope amplitude measurements are significantly less variable than distance-corrected direct wave measurements (i.e., L{sub g} and surface waves) by roughly a factor 3-to-4. Despite strong lateral crustal heterogeneity in Turkey, they found that the region could be adequately modeled assuming a simple 1-D, radially symmetric path correction. After calibrating the stations ISP, ISKB and MALT for local and regional distances, single-station moment-magnitude estimates (M{submore » W}) derived from the coda spectra were in excellent agreement with those determined from multistation waveform modeling inversions, exhibiting a data standard deviation of 0.17. Though the calibration was validated using large events, the results of the calibration will extend M{sub W} estimates to significantly smaller events which could not otherwise be waveform modeled. The successful application of the method is remarkable considering the significant lateral complexity in Turkey and the simple assumptions used in the coda method.« less

Lapse-time-dependent coda-wave depth sensitivity to local velocity perturbations in 3-D heterogeneous elastic media

NASA Astrophysics Data System (ADS)

Obermann, Anne; Planès, Thomas; Hadziioannou, Céline; Campillo, Michel

2016-10-01

In the context of seismic monitoring, recent studies made successful use of seismic coda waves to locate medium changes on the horizontal plane. Locating the depth of the changes, however, remains a challenge. In this paper, we use 3-D wavefield simulations to address two problems: first, we evaluate the contribution of surface- and body-wave sensitivity to a change at depth. We introduce a thin layer with a perturbed velocity at different depths and measure the apparent relative velocity changes due to this layer at different times in the coda and for different degrees of heterogeneity of the model. We show that the depth sensitivity can be modelled as a linear combination of body- and surface-wave sensitivity. The lapse-time-dependent sensitivity ratio of body waves and surface waves can be used to build 3-D sensitivity kernels for imaging purposes. Second, we compare the lapse-time behaviour in the presence of a perturbation in horizontal and vertical slabs to address, for instance, the origin of the velocity changes detected after large earthquakes.

Coda Calibration Tool

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

Addair, Travis; Barno, Justin; Dodge, Doug

CCT is a Java based application for calibrating 10 shear wave coda measurement models to observed data using a much smaller set of reference moment magnitudes (MWs) calculated from other means (waveform modeling, etc.). These calibrated measurement models can then be used in other tools to generate coda moment magnitude measurements, source spectra, estimated stress drop, and other useful measurements for any additional events and any new data collected in the calibrated region.

Numerical modeling of time-lapse monitoring of CO2 sequestration in a layered basalt reservoir

USGS Publications Warehouse

Khatiwada, M.; Van Wijk, K.; Clement, W.P.; Haney, M.

2008-01-01

As part of preparations in plans by The Big Sky Carbon Sequestration Partnership (BSCSP) to inject CO2 in layered basalt, we numerically investigate seismic methods as a noninvasive monitoring technique. Basalt seems to have geochemical advantages as a reservoir for CO2 storage (CO2 mineralizes quite rapidly while exposed to basalt), but poses a considerable challenge in term of seismic monitoring: strong scattering from the layering of the basalt complicates surface seismic imaging. We perform numerical tests using the Spectral Element Method (SEM) to identify possibilities and limitations of seismic monitoring of CO2 sequestration in a basalt reservoir. While surface seismic is unlikely to detect small physical changes in the reservoir due to the injection of CO2, the results from Vertical Seismic Profiling (VSP) simulations are encouraging. As a perturbation, we make a 5%; change in wave velocity, which produces significant changes in VSP images of pre-injection and post-injection conditions. Finally, we perform an analysis using Coda Wave Interferometry (CWI), to quantify these changes in the reservoir properties due to CO2 injection.

Relative Seismic Velocity Variations Correlate with Deformation at Kīlauea Volcano.

NASA Astrophysics Data System (ADS)

Donaldson, C.; Caudron, C.; Green, R. G.; White, R. S.

2016-12-01

Passive interferometry using ambient seismic noise is an appealing monitoring tool at volcanoes. The continuous nature of seismic noise provides better temporal resolution than earthquake interferometry and ambient noise may be sensitive to changes at depths that do not deform the volcano surface. Despite this, to our knowledge, no studies have yet comprehensively compared deformation and velocity at a volcano over a significant length of time. We use a volcanic tremor source (approximately 0.3 - 1.0 Hz) at Kīlauea volcano as a source for interferometry to measure relative velocity changes with time. The tremor source that dominates the cross correlations is located under the Halema'uma'u caldera at Kīlauea summit. By cross-correlating the vertical component of day-long seismic records between 200 pairs of stations, we extract coherent and temporally consistent coda wave signals with time lags of up to 70 seconds. Our resulting time series of relative velocity shows a remarkable correlation with the tilt record measured at Kīlauea summit. Kīlauea summit is continually inflating and deflating as the level of the lava lake rises and falls. During these deflation-inflation (DI) events the tilt increases (inflation), as the velocity increases, on the scale of days to weeks. In contrast, we also detect a longer-term velocity decrease between 2011-2015 as the volcano slowly inflates. We suggest that variations in velocity result from opening and closing cracks and pores due to changes in magma pressurization. Early modeling results indicate that pressurizing magma reservoirs at different depths can result in opposite changes in compression/extension at the surface. The consistent correlation of relative velocity and deformation in this study provides an opportunity to better understand the mechanism causing velocity changes, which currently limits the scope of passive interferometry as a monitoring tool.

Broadband bearing-time records of three-component seismic array data and their application to the study of local earthquake coda

NASA Astrophysics Data System (ADS)

Wagner, Gregory S.; Owens, Thomas J.

1993-09-01

High-frequency three-component array d, are used to study the P and S coda produced by* cal earthquakes. The data are displayed as broadba bearing-time records which allow us to examine a compl, time history of the propagation directions and arrival tin of direct and scattered phases crossing the array. This ~ sualization technique is used to examine the wavefield ~ two scale lengths using two sub-arrays~of sensors. Resu suggest that P coda is dominated by P energy propag, ing sub-parallel to the direct P arrival. The S coda pro agates in all directions and appears to be composed p~ dominantly of S and/or surface wave energy. Significant more 0e coda appears on the smaller scale length sub-art relative to the larger scale array suggesting that much, the ~, coda remains coherent for only very short distanc

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

NASA Astrophysics Data System (ADS)

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

2016-12-01

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

SEISMIC SOURCE SCALING AND DISCRIMINATION IN DIVERSE TECTONIC ENVIRONMENTS

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

Abercrombie, R E; Mayeda, K; Walter, W R

2007-07-10

The objectives of this study are to improve low-magnitude regional seismic discrimination by performing a thorough investigation of earthquake source scaling using diverse, high-quality datasets from varied tectonic regions. Local-to-regional high-frequency discrimination requires an estimate of how earthquakes scale with size. Walter and Taylor (2002) developed the MDAC (Magnitude and Distance Amplitude Corrections) method to empirically account for these effects through regional calibration. The accuracy of these corrections has a direct impact on our ability to identify clandestine explosions in the broad regional areas characterized by low seismicity. Unfortunately our knowledge of source scaling at small magnitudes (i.e., m{sub b}more » < {approx}4.0) is poorly resolved. It is not clear whether different studies obtain contradictory results because they analyze different earthquakes, or because they use different methods. Even in regions that are well studied, such as test sites or areas of high seismicity, we still rely on empirical scaling relations derived from studies taken from half-way around the world at inter-plate regions. We investigate earthquake sources and scaling from different tectonic settings, comparing direct and coda wave analysis methods. We begin by developing and improving the two different methods, and then in future years we will apply them both to each set of earthquakes. Analysis of locally recorded, direct waves from events is intuitively the simplest way of obtaining accurate source parameters, as these waves have been least affected by travel through the earth. But there are only a limited number of earthquakes that are recorded locally, by sufficient stations to give good azimuthal coverage, and have very closely located smaller earthquakes that can be used as an empirical Green's function (EGF) to remove path effects. In contrast, coda waves average radiation from all directions so single-station records should be adequate, and previous work suggests that the requirements for the EGF event are much less stringent. We can study more earthquakes using the coda-wave methods, while using direct wave methods for the best recorded subset of events so as to investigate any differences between the results of the two approaches. Finding 'perfect' EGF events for direct wave analysis is difficult, as is ascertaining the quality of a particular EGF event. We develop a multi-taper method to obtain time-domain source-time-functions by frequency division. If an earthquake and EGF event pair are able to produce a clear, time-domain source pulse then we accept the EGF event. We then model the spectral (amplitude) ratio to determine source parameters from both direct P and S waves. We use the well-recorded sequence of aftershocks of the M5 Au Sable Forks, NY, earthquake to test the method and also to obtain some of the first accurate source parameters for small earthquakes in eastern North America. We find that the stress drops are high, confirming previous work suggesting that intraplate continental earthquakes have higher stress drops than events at plate boundaries. We simplify and improve the coda wave analysis method by calculating spectral ratios between different sized earthquakes. We first compare spectral ratio performance between local and near-regional S and coda waves in the San Francisco Bay region for moderate-sized events. The average spectral ratio standard deviations using coda are {approx}0.05 to 0.12, roughly a factor of 3 smaller than direct S-waves for 0.2 < f < 15.0 Hz. Also, direct wave analysis requires collocated pairs of earthquakes whereas the event-pairs (Green's function and target events) can be separated by {approx}25 km for coda amplitudes without any appreciable degradation. We then apply coda spectral ratio method to the 1999 Hector Mine mainshock (M{sub w} 7.0, Mojave Desert) and its larger aftershocks. We observe a clear departure from self-similarity, consistent with previous studies using similar regional datasets.« less

Monitoring transmitted waves across a fault with a high potential for mining induced earthquakes -the Ezulwini gold mine in South Africa

NASA Astrophysics Data System (ADS)

Kawakata, H.; Yoshimitsu, N.; Nakatani, M.; Philipp, J.; Doi, I.; Naoi, M. M.; Ward, T.; Visser, V.; Morema, G.; Khambule, S.; Masakale, T.; Milev, A.; Durrheim, R. J.; Ribeiro, L.; Ward, M.; Ogasawara, H.

2011-12-01

It gives us important information about earthquake processes to monitor transmitted waves across a fault with a high potential for earthquake generation. In laboratory experiments, the decreases in elastic wave speed (e.g., Yoshimitsu et al., 2009) and attenuation parameter Q (Yoshimitsu and Kawakata, 2011) have been found prior to the faulting. In South African gold mines, we can specify a fault with a high potential for mining induced earthquakes of relatively large magnitude based on mining plans. In addition, the seismic line can be set at the depth of a few kilometers, so that the transmitted waves propagate through only hard rock. Hence, we started to monitor transmitted waves across a fault that has a high potential for an M˜2 earthquake at about 1 km deep in the Ezulwini gold mine. We installed a piezoelectric transmitter as a wave source about 20 m away from the fault in the hanging wall. Three accelerometers of 3-component were also installed in alignment with the transmitter; one is about 7 m away from the fault in the hanging wall, and the other two are about 7 m and 13 m away from the fault in the footwall, respectively. Then, the total length of our seismic line is ˜ 33 m long. The frequency response of accelerometers is within ±3 dB from 1 Hz to 10 kHz. For 10 minutes from midnight everyday, when there is no blasting, the elastic waves are transmitted every 0.05 seconds, and the received waves are recorded at 400 ksps on 14bit. Transmitted signals can be clearly recognized in stacked waveforms of all channels, although signal-to-noise ratios are high enough only in a frequency range from 3 kHz up to 10 kHz. The waveforms of three components are rotated so that one component (radial component) is parallel to the seismic line. Then, P waves are dominant in radial components for two sites in the footwall. On the other hand, at the nearest site in the hanging wall, near field term and/or intermediate term seem to be included. In addition to the transmission monitoring, ambient noise recording at 200 ksps for 50 minutes is carried out every day after the 10-minute transmission for the analysis of seismic noise interferometry. Further, from 1 AM to the next midnight everyday, earthquake trigger recording at 200 ksps is held for the analysis of coda-wave interferometry. These enable us not only to monitor the fault properties but to compare active imaging using transmission signals with passive imaging with seismic interferometry.

Analysis of P and Pdiff Coda Arrivals for Water Reverberations to Evaluate Shallow Slip Extent in Large Megathrust Earthquakes

NASA Astrophysics Data System (ADS)

Rhode, A.; Lay, T.

2017-12-01

Determining the up-dip rupture extent of large megathrust ruptures is important for understanding their tsunami excitation, frictional properties of the shallow megathrust, and potential for separate tsunami earthquake occurrence. On land geodetic data have almost no resolution of the up-dip extent of faulting and teleseismic observations have limited resolution that is strongly influenced by typically poorly known shallow seismic velocity structure near the toe of the accretionary prism. The increase in ocean depth as slip on the megathrust approaches the trench has significant influence on the strength and azimuthal distribution of water reverberations in the far-field P wave coda. For broadband P waves from large earthquakes with dominant signal periods of about 10 s, water reverberations generated by shallow fault slip under deep water may persist for over a minute after the direct P phases have passed, giving a clear signal of slip near the trench. As the coda waves can be quickly evaluated following the P signal, recognition of slip extending to the trench and associated enhanced tsunamigenic potential could be achieved within a few minutes after the P arrival, potentially contributing to rapid tsunami hazard assessment. We examine the broadband P wave coda at distances from 80 to 120° for a large number of recent major and great earthquakes with independently determined slip distributions and known tsunami excitation to evaluate the prospect for rapidly constraining up-dip rupture extent of large megathrust earthquakes. Events known to have significant shallow slip, at least locally extending to the trench (e.g., 2016 Illapel, Chile; 2010 Maule, 2010 Mentawai) do have relatively enhanced coda levels at all azimuths, whereas events that do not rupture the shallow megathrust (e.g., 2007 Sumatra, 2014 Iquique, 2003 Hokkaido) do not. Some events with slip models lacking shallow slip show strong coda generation, raising questions about the up-dip resolution of slip of their finite-fault models, and others show strong azimuthal patterns in coda strength that suggest propagation from the slip zone to the deep near-trench environments is involved rather than slip near the trench. The various behaviors will be integrated into an assessment of this approach.

Relative seismic velocity variations correlate with deformation at Kīlauea volcano.

PubMed

Donaldson, Clare; Caudron, Corentin; Green, Robert G; Thelen, Weston A; White, Robert S

2017-06-01

Seismic noise interferometry allows the continuous and real-time measurement of relative seismic velocity through a volcanic edifice. Because seismic velocity is sensitive to the pressurization state of the system, this method is an exciting new monitoring tool at active volcanoes. Despite the potential of this tool, no studies have yet comprehensively compared velocity to other geophysical observables on a short-term time scale at a volcano over a significant length of time. We use volcanic tremor (~0.3 to 1.0 Hz) at Kīlauea as a passive source for interferometry to measure relative velocity changes with time. By cross-correlating the vertical component of day-long seismic records between ~230 station pairs, we extract coherent and temporally consistent coda wave signals with time lags of up to 120 s. Our resulting time series of relative velocity shows a remarkable correlation between relative velocity and the radial tilt record measured at Kīlauea summit, consistently correlating on a time scale of days to weeks for almost the entire study period (June 2011 to November 2015). As the summit continually deforms in deflation-inflation events, the velocity decreases and increases, respectively. Modeling of strain at Kīlauea suggests that, during inflation of the shallow magma reservoir (1 to 2 km below the surface), most of the edifice is dominated by compression-hence closing cracks and producing faster velocities-and vice versa. The excellent correlation between relative velocity and deformation in this study provides an opportunity to understand better the mechanisms causing seismic velocity changes at volcanoes, and therefore realize the potential of passive interferometry as a monitoring tool.

Tracking changes in volcanic systems with seismic Interferometry

USGS Publications Warehouse

Haney, Matt; Alicia J. Hotovec-Ellis,; Bennington, Ninfa L.; Silvio De Angelis,; Clifford Thurber,

2014-01-01

The detection and evaluation of time-dependent changes at volcanoes form the foundation upon which successful volcano monitoring is built. Temporal changes at volcanoes occur over all time scales and may be obvious (e.g., earthquake swarms) or subtle (e.g., a slow, steady increase in the level of tremor). Some of the most challenging types of time-dependent change to detect are subtle variations in material properties beneath active volcanoes. Although difficult to measure, such changes carry important information about stresses and fluids present within hydrothermal and magmatic systems. These changes are imprinted on seismic waves that propagate through volcanoes. In recent years, there has been a quantum leap in the ability to detect subtle structural changes systematically at volcanoes with seismic waves. The new methodology is based on the idea that useful seismic signals can be generated “at will” from seismic noise. This means signals can be measured any time, in contrast to the often irregular and unpredictable times of earthquakes. With seismic noise in the frequency band 0.1–1 Hz arising from the interaction of the ocean with the solid Earth known as microseisms, researchers have demonstrated that cross-correlations of passive seismic recordings between pairs of seismometers yield coherent signals (Campillo and Paul 2003; Shapiro and Campillo 2004). Based on this principle, coherent signals have been reconstructed from noise recordings in such diverse fields as helioseismology (Rickett and Claerbout 2000), ultrasound (Weaver and Lobkis 2001), ocean acoustic waves (Roux and Kuperman 2004), regional (Shapiro et al. 2005; Sabra et al. 2005; Bensen et al. 2007) and exploration (Draganov et al. 2007) seismology, atmospheric infrasound (Haney 2009), and studies of the cryosphere (Marsan et al. 2012). Initial applications of ambient seismic noise were to regional surface wave tomography (Shapiro et al. 2005). Brenguier et al. (2007) were the first to use ambient noise tomography (ANT) to map the 3D structure of a volcanic interior (at Piton de la Fournaise). Subsequent studies have imaged volcanoes with ANT at Okmok (Masterlark et al. 2010), Toba (Stankiewicz et al. 2010), Katmai (Thurber et al. 2012), Asama (Nagaoka et al. 2012), Uturuncu (Jay et al. 2012), and Kilauea (Ballmer et al. 2013b). In addition, Ma et al. (2013) have imaged a scatterer in the volcanic region of southern Peru by applying array techniques to ambient noise correlations. Prior to and in tandem with the development of ANT, researchers discovered that repeating earthquakes, which often occur at volcanoes, could be used to monitor subtle time-dependent changes with a technique known as the doublet method or coda wave interferometry (CWI) (Poupinet et al. 1984; Roberts et al. 1992; Ratdomopurbo and Poupinet 1995; Snieder et al. 2002; Pandolfi et al. 2006; Wegler et al. 2006; Martini et al. 2009; Haney et al. 2009; De Angelis 2009; Nagaoka et al. 2010; Battaglia et al. 2012; Erdem and Waite 2005; Hotovec-Ellis et al. 2014). Chaput et al. (2012) have also used scattered waves from Strombolian eruption coda at Erebus volcano to image the reflectivity of the volcanic interior with body wave interferometry. However, CWI in its original form was limited in that repeating earthquakes, or doublets, were not always guaranteed to occur. With the widespread use of noise correlations in seismology following the groundbreaking work by Campillo and Paul (2003) and Shapiro et al. (2005), it became evident that the nature of the ambient seismic field, due to its oceanic origin, enabled the continuous monitoring of subtle, time-dependent changes at both fault zones (Wegler and Sens-Schönfelder 2007; Brenguier et al. 2008b; Wegler et al. 2009; Sawazaki et al. 2009; Tatagi et al. 2012) and volcanoes (Sens-Schönfelder and Wegler 2006; Brenguier et al. 2008a) without the need for repeating earthquakes. Seismic precursors to eruptions based on ambient noise we

Fine Structure of the Outermost Solid Core from Analysis of PKiKP Coda Waves

NASA Astrophysics Data System (ADS)

Krasnoshchekov, D.; Kaazik, P.; Ovtchinnikov, V.

2006-05-01

Near surface heterogeneities in the Earth's inner core have recently been confirmed to exist, and pods of partial melt or variations in seismic anisotropy either due to orientation of iron crystals or changes in strength were indicated as possible sources for such peculiarities. In the same time, analysis of the phase reflected from the inner core boundary (PKiKP) predicts complex character of the reflecting discontinuity in the form of local thin transition layers resulting in mosaic structure of the Earth's inner core's surface. Precritical PKiKP waveforms and coda waves provide necessary seismological constraints to investigate fine structure of the upper part of the Earth's inner core and its boundary, and rank high among researches that detected the described specifics of the solid core. PKiKP coda studies have to do with weak amplitudes and subtle effects, which frequently requires using a reference core related seismic phase and array data processing, as well as eliminating max number of factors biasing the resulting estimates (for example, source related inaccuracies typical for earthquake analysis). In this work we report new observations of PKiKP coda waves detected on records of a group of Underground Nuclear Explosions (UNEs) carried out in USSR and recorded at distances from 6 to 95 degrees by stations of the world seismological network. Our dataset benefits from using accurate ground truth information on source parameters (locations, origin times, depths, etc.), requires no accounting for different source radiation patterns and contains records corresponding to the whole range of precritical reflection including so called transparent zone where amplitudes of direct PKiKP phase are negligible. The processed dataset incorporates records of the array of sources consisted of the same magnitude explosions closely carried out at Semipalatinsk Test Site and recorded by stations located in Eurasia, Africa and North America. We detect PKiKP coda waves on records of all stations that registered this array. The performed frequency-wavenumber analysis and stacking of the array data reveal both scattering mechanism tracked in the form of slight dependence of PKiKP coda's frequency content on epicentral distance, and reflective mechanism evidenced by detection of distinct arrivals of waves reflected from isotropic or anisotropic discontinuities below the inner core boundary. We infer, that PKiKP coda is built by both volumetric scattering and reverberations on reflectors in the upper portion of the inner core. We also find no significant evidence for the presence of a constant depth global isotropic reflector all through 300 km below the ICB and attribute different types of the observed PKiKP coda patterns to variability in properties of the outermost portion of the Earth's inner core either due to its anisotropy or local specifics. The research described was made possible in part by contribution from grant RUG1-2675-MO-05 of the US Civilian Research & Development Foundation for the Independent States of the Former Soviet Union (CRDF) and the President Grant MK-1600.2005.5.

Diffuse ultrasound monitoring of stress and damage development on a 15-ton concrete beam.

PubMed

Zhang, Yuxiang; Planès, Thomas; Larose, Eric; Obermann, Anne; Rospars, Claude; Moreau, Gautier

2016-04-01

This paper describes the use of an ultrasonic imaging technique (Locadiff) for the Non-Destructive Testing & Evaluation of a concrete structure. By combining coda wave interferometry and a sensitivity kernel for diffuse waves, Locadiff can monitor the elastic and structural properties of a heterogeneous material with a high sensitivity, and can map changes of these properties over time when a perturbation occurs in the bulk of the material. The applicability of the technique to life-size concrete structures is demonstrated through the monitoring of a 15-ton reinforced concrete beam subject to a four-point bending test causing cracking. The experimental results show that Locadiff achieved to (1) detect and locate the cracking zones in the core of the concrete beam at an early stage by mapping the changes in the concrete's micro-structure; (2) monitor the internal stress level in both temporal and spatial domains by mapping the variation in velocity caused by the acousto-elastic effect. The mechanical behavior of the concrete structure is also studied using conventional techniques such as acoustic emission, vibrating wire extensometers, and digital image correlation. The performances of the Locadiff technique in the detection of early stage cracking are assessed and discussed.

Lateral Variations of Lg Coda Q in Southern Mexico

NASA Astrophysics Data System (ADS)

Yamamoto, J.; Quintanar, L.; Herrmann, R. B.; Fuentes, C.

Broad band digital three-component data recorded at UNM, a GEOSCOPE station, were used to estimate Lg coda Q for 34 medium size (3.9 <=mb<= 6.3) earthquakes with travel paths laying in different geological provinces of southern Mexico in an effort to establish the possible existence of geological structures acting as wave guides and/or travel paths of low attenuation between the Pacific coast and the Valley of Mexico. The stacked spectral ratio method proposed by XIE and NUTTLI (1988) was chosen for computing the coda Q. The variation range of Q0 (Q at 1Hz) and the frequency dependence parameter η estimates averaged on the frequency interval of 0.5 to 2Hz for the regions and the three components considered are: i) Guerrero region 173 <=Q0<= 182 and 0.6 <=Q0<= 0.7, ii) Oaxaca region 183 <=Q0<= 198 and 0.6 <=Q0<= 0.8, iii) Michoacan-Jalisco region 187 <=Q0<= 204 and 0.7 <=Q0<= 0.8 and iv) eastern portion of the Transmexican Volcanic Belt (TMVB) 313 <=Q0<= 335 and η = 0.9. The results show a very high coda Q for the TMVB as compared to other regions of southern Mexico. This unexpected result is difficult to reconcile with the geophysical characteristics of the TMVB, e.g., low seismicity, high volcanic activity and high heat flow typical of a highly attenuating (low Q) region. Visual inspection of seismograms indicates that for earthquakes with seismic waves traveling along the TMVB, the amplitude decay of Lg coda is anomalously slow as compared to other earthquakes in southern Mexico. Thus, it seems that the high Q value found does not entirely reflect the attenuation characteristics of the TMVB but it is probably contaminated by a wave-guide effect. This phenomenon produces an enhancement in the time duration of the Lg wave trains travelling along this geological structure. This result is important to establish the role played by the transmission medium in the extremely long duration of ground motion observed during the September 19, 1985 Michoacan earthquake. The overall spatial distribution of coda Q values indicates that events with focus in the Michoacan-Jalisco and Oaxaca regions yield slightly higher values than those from Guerrero. This feature is more pronounced for the horizontal component of coda Q. A slight dependence of average coda Q-1 on earthquake focal depth is observed in the frequency range of 0.2 to 1.0Hz approximately on the horizontal component. Deeper (h > 50km) events yield lower values of Q-1 than shallower events. For frequencies higher than 1.0Hz no clear dependence of Q-1 on focal depth is observed. However, due to the estimates uncertainties this result is not clearly established.

Site Effects on Regional Seismograms Recorded in the Vicinity of Weston Observatory

DTIC Science & Technology

1993-09-30

flanks of the active volcanoes of Mauna Loa and Kilauea . The distances between the sites ranged from a few km to over 100 km. Although there is little...on the island of Hawaii using S-wave coda spectral ratios for frequencies between 1.5 and 15-Hz. They used 40 vertical I-Hz seismometers, and recorded...for the island of Hawaii , Bull. Seis Soc. Am-, 12 No- 3 1151-1185. Mayeda, K., S. Koyanagi, and K. Aki (1991). Site amplification from S-wave coda in

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

Eken, T; Mayeda, K; Hofstetter, A

A recently developed coda magnitude methodology was applied to selected broadband stations in Turkey for the purpose of testing the coda method in a large, laterally complex region. As found in other, albeit smaller regions, coda envelope amplitude measurements are significantly less variable than distance-corrected direct wave measurements (i.e., L{sub g} and surface waves) by roughly a factor 3-to-4. Despite strong lateral crustal heterogeneity in Turkey, we found that the region could be adequately modeled assuming a simple 1-D, radially symmetric path correction for 10 narrow frequency bands ranging between 0.02 to 2.0 Hz. For higher frequencies however, 2-D pathmore » corrections will be necessary and will be the subject of a future study. After calibrating the stations ISP, ISKB, and MALT for local and regional distances, single-station moment-magnitude estimates (M{sub w}) derived from the coda spectra were in excellent agreement with those determined from multi-station waveform modeling inversions of long-period data, exhibiting a data standard deviation of 0.17. Though the calibration was validated using large events, the results of the calibration will extend M{sub w} estimates to significantly smaller events which could not otherwise be waveform modeled due to poor signal-to-noise ratio at long periods and sparse station coverage. The successful application of the method is remarkable considering the significant lateral complexity in Turkey and the simple assumptions used in the coda method.« less

High-resolution lithospheric imaging with seismic interferometry

NASA Astrophysics Data System (ADS)

Ruigrok, Elmer; Campman, Xander; Draganov, Deyan; Wapenaar, Kees

2010-10-01

In recent years, there has been an increase in the deployment of relatively dense arrays of seismic stations. The availability of spatially densely sampled global and regional seismic data has stimulated the adoption of industry-style imaging algorithms applied to converted- and scattered-wave energy from distant earthquakes, leading to relatively high-resolution images of the lower crust and upper mantle. We use seismic interferometry to extract reflection responses from the coda of transmitted energy from distant earthquakes. In theory, higher-resolution images can be obtained when migrating reflections obtained with seismic interferometry rather than with conversions, traditionally used in lithospheric imaging methods. Moreover, reflection data allow the straightforward application of algorithms previously developed in exploration seismology. In particular, the availability of reflection data allows us to extract from it a velocity model using standard multichannel data-processing methods. However, the success of our approach relies mainly on a favourable distribution of earthquakes. In this paper, we investigate how the quality of the reflection response obtained with interferometry is influenced by the distribution of earthquakes and the complexity of the transmitted wavefields. Our analysis shows that a reasonable reflection response could be extracted if (1) the array is approximately aligned with an active zone of earthquakes, (2) different phase responses are used to gather adequate angular illumination of the array and (3) the illumination directions are properly accounted for during processing. We illustrate our analysis using a synthetic data set with similar illumination and source-side reverberation characteristics as field data recorded during the 2000-2001 Laramie broad-band experiment. Finally, we apply our method to the Laramie data, retrieving reflection data. We extract a 2-D velocity model from the reflections and use this model to migrate the data. On the final reflectivity image, we observe a discontinuity in the reflections. We interpret this discontinuity as the Cheyenne Belt, a suture zone between Archean and Proterozoic terranes.

Relative seismic velocity variations correlate with deformation at Kīlauea volcano

PubMed Central

Donaldson, Clare; Caudron, Corentin; Green, Robert G.; Thelen, Weston A.; White, Robert S.

2017-01-01

Seismic noise interferometry allows the continuous and real-time measurement of relative seismic velocity through a volcanic edifice. Because seismic velocity is sensitive to the pressurization state of the system, this method is an exciting new monitoring tool at active volcanoes. Despite the potential of this tool, no studies have yet comprehensively compared velocity to other geophysical observables on a short-term time scale at a volcano over a significant length of time. We use volcanic tremor (~0.3 to 1.0 Hz) at Kīlauea as a passive source for interferometry to measure relative velocity changes with time. By cross-correlating the vertical component of day-long seismic records between ~230 station pairs, we extract coherent and temporally consistent coda wave signals with time lags of up to 120 s. Our resulting time series of relative velocity shows a remarkable correlation between relative velocity and the radial tilt record measured at Kīlauea summit, consistently correlating on a time scale of days to weeks for almost the entire study period (June 2011 to November 2015). As the summit continually deforms in deflation-inflation events, the velocity decreases and increases, respectively. Modeling of strain at Kīlauea suggests that, during inflation of the shallow magma reservoir (1 to 2 km below the surface), most of the edifice is dominated by compression—hence closing cracks and producing faster velocities—and vice versa. The excellent correlation between relative velocity and deformation in this study provides an opportunity to understand better the mechanisms causing seismic velocity changes at volcanoes, and therefore realize the potential of passive interferometry as a monitoring tool. PMID:28782009

Seismic Interferometry at a Large, Dense Array: Capturing the Wavefield at the Source Physics Experiment

NASA Astrophysics Data System (ADS)

Matzel, E.; Mellors, R. J.; Magana-Zook, S. A.

2016-12-01

Seismic interferometry is based on the observation that the Earth's background wavefield includes coherent energy, which can be recovered by observing over long time periods, allowing the incoherent energy to cancel out. The cross correlation of the energy recorded at a pair of stations results in an estimate of the Green's Function (GF) and is equivalent to the record of a simple source located at one of the stations as recorded by the other. This allows high resolution imagery beneath dense seismic networks even in areas of low seismicity. The power of these inter-station techniques increases rapidly as the number of seismometers in a network increases. For large networks the number of correlations computed can run into the millions and this becomes a "big-data" problem where data-management dominates the efficiency of the computations. In this study, we use several methods of seismic interferometry to obtain highly detailed images at the site of the Source Physics Experiment (SPE). The objective of SPE is to obtain a physics-based understanding of how seismic waves are created at and scattered near the source. In 2015, a temporary deployment of 1,000 closely spaced geophones was added to the main network of instruments at the site. We focus on three interferometric techniques: Shot interferometry (SI) uses the SPE shots as rich sources of high frequency, high signal energy. Coda interferometry (CI) isolates the energy from the scattered wavefield of distant earthquakes. Ambient noise correlation (ANC) uses the energy of the ambient background field. In each case, the data recorded at one seismometer are correlated with the data recorded at another to obtain an estimate of the GF between the two. The large network of mixed geophone and broadband instruments at the SPE allows us to calculate over 500,000 GFs, which we use to characterize the site and measure the localized wavefield. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344

Estimation of Coda Wave Attenuation in Northern Morocco

NASA Astrophysics Data System (ADS)

Boulanouar, Abderrahim; Moudnib, Lahcen El; Padhy, Simanchal; Harnafi, Mimoun; Villaseñor, Antonio; Gallart, Josep; Pazos, Antonio; Rahmouni, Abdelaali; Boukalouch, Mohamed; Sebbani, Jamal

2018-03-01

We studied the attenuation of coda waves and its frequency and lapse-time dependence in northern Morocco. We analysed coda waves of 66 earthquakes recorded in this region during 2008 for four lapse time windows of length 30, 40, 50, and 60 s, and at five frequency bands with central frequency in the range of 0.75-12 Hz. We determined the frequency dependent Q c relation for the horizontal (NS and EW) and vertical (Z) component seismograms. We analyzed three-component broadband seismograms of 66 local earthquakes for determining coda-Q based on the single back-scattering model. The Q c values show strong frequency dependence in 1.5-12 Hz that is related to high degree of heterogeneity of the medium. The lapse time dependence of Q c shows that Q 0 ( Q c at 1 Hz) significantly increases with lapse time that is related to the depth dependence of attenuation and hence of the level of heterogeneity of the medium. The average frequency-dependent Q c( f) values are Qc = (143.75 ± 1.09)f^{(0.864 ± 0.006)}, Qc = (149.12 ± 1.08)f^{(0.85 ± 0.005)} and Qc = (140.42 ± 1.81)f^{(0.902 ± 0.004)} for the vertical, north-south and east-west components of motion, respectively. The frequency-dependent Q c(f) relations are useful for evaluating source parameters (Singh et al. 2001), which are the key inputs for seismic hazard assessment of the region.

Estimation of the intrinsic absorption and scattering attenuation in Northeastern Venezuela (Southeastern Caribbean) using coda waves

USGS Publications Warehouse

Ugalde, A.; Pujades, L.G.; Canas, J.A.; Villasenor, A.

1998-01-01

Northeastern Venezuela has been studied in terms of coda wave attenuation using seismograms from local earthquakes recorded by a temporary short-period seismic network. The studied area has been separated into two subregions in order to investigate lateral variations in the attenuation parameters. Coda-Q-1 (Q(c)-1) has been obtained using the single-scattering theory. The contribution of the intrinsic absorption (Q(i)-1) and scattering (Q(s)-1) to total attenuation (Q(t)-1) has been estimated by means of a multiple lapse time window method, based on the hypothesis of multiple isotropic scattering with uniform distribution of scatterers. Results show significant spatial variations of attenuation: the estimates for intermediate depth events and for shallow events present major differences. This fact may be related to different tectonic characteristics that may be due to the presence of the Lesser Antilles subduction zone, because the intermediate depth seismic zone may be coincident with the southern continuation of the subducting slab under the arc.

Temporal evolution of the Green's function reconstruction in the seismic coda

NASA Astrophysics Data System (ADS)

Clerc, V.; Roux, P.; Campillo, M.

2013-12-01

In presence of multiple scattering, the wavefield evolves towards an equipartitioned state, equivalent to ambient noise. CAMPILLO and PAUL (2003) reconstructed the surface wave part of the Green's function between three pairs of stations in Mexico. The data indicate that the time asymmetry between causal and acausal part of the Green's function is less pronounced when the correlation is performed in the later windows of the coda. These results on the correlation of diffuse waves provide another perspective on the reconstruction of Green function which is independent of the source distribution and which suggests that if the time of observation is long enough, a single source could be sufficient. The paper by ROUX et al. (2005) provides a theoretical frame for the reconstruction of the Green's function in a homogeneous middle. In a multiple scattering medium with a single source, scatterers behave as secondary sources according to the Huygens principle. Coda waves are relevant to multiple scattering, a regime which can be approximated by diffusion for long lapse times. We express the temporal evolution of the correlation function between two receivers as a function of the secondary sources. We are able to predict the effect of the persistence of the net flux of energy observed by CAMPILLO and PAUL (2003) in numerical simulations. This method is also effective in order to retrieve the scattering mean free path. We perform a partial reconstruction of the Green's function in a strongly scattering medium in numerical simulations. The prediction of the flux asymmetry allows defining the parts of the coda providing the same information as ambient noise cross correlation.

Improvements to a Major Digital Archive of Seismic Waveforms from Nuclear Explosions: Borovoye Seismogram Archive

DTIC Science & Technology

2008-09-30

coda) meet expectations. We are also interpreting absolute amplitudes, for those underground nuclear explosions at the Semipalatinsk Test Site (STS...waves, coda) meet expectations. We are also interpreting absolute amplitudes, for those underground nuclear explosions at the Semipalatinsk Test Site ...Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies 4.0- Balapan Subregion Semipalatinsk Test Site n- 3.5 - (U CIO ’-3.0 ES UI

Auto Correlation Analysis of Coda Waves from Local Earthquakes for Detecting Temporal Changes in Shallow Subsurface Structures: the 2011 Tohoku-Oki, Japan Earthquake

NASA Astrophysics Data System (ADS)

Nakahara, Hisashi

2015-02-01

For monitoring temporal changes in subsurface structures I propose to use auto correlation functions of coda waves from local earthquakes recorded at surface receivers, which probably contain more body waves than surface waves. Use of coda waves requires earthquakes resulting in decreased time resolution for monitoring. Nonetheless, it may be possible to monitor subsurface structures in sufficient time resolutions in regions with high seismicity. In studying the 2011 Tohoku-Oki, Japan earthquake (Mw 9.0), for which velocity changes have been previously reported, I try to validate the method. KiK-net stations in northern Honshu are used in this analysis. For each moderate earthquake normalized auto correlation functions of surface records are stacked with respect to time windows in the S-wave coda. Aligning the stacked, normalized auto correlation functions with time, I search for changes in phases arrival times. The phases at lag times of <1 s are studied because changes at shallow depths are focused. Temporal variations in the arrival times are measured at the stations based on the stretching method. Clear phase delays are found to be associated with the mainshock and to gradually recover with time. The amounts of the phase delays are 10 % on average with the maximum of about 50 % at some stations. The deconvolution analysis using surface and subsurface records at the same stations is conducted for validation. The results show the phase delays from the deconvolution analysis are slightly smaller than those from the auto correlation analysis, which implies that the phases on the auto correlations are caused by larger velocity changes at shallower depths. The auto correlation analysis seems to have an accuracy of about several percent, which is much larger than methods using earthquake doublets and borehole array data. So this analysis might be applicable in detecting larger changes. In spite of these disadvantages, this analysis is still attractive because it can be applied to many records on the surface in regions where no boreholes are available.

Long codas of coupled wave systems in seismic basins

NASA Astrophysics Data System (ADS)

Seligman, Thomas H.

2002-11-01

Quite some time ago it was pointed out that the damage patterns and Fourier spectra of the 1985 earthquake in Mexico City are only compatible with a resonant effect of horizontal waves with the approximate speed of sound waves in water [see Flores et al., Nature 326, 783 (1987)]. In a more recent paper it was pointed out that this indeed will occur with a very specific frequency selection for a coupled system of Raleigh waves at the interface of the bottom of the ancient lakebed with the more solid deposits, and an evanescent sound wave in the mud above [see J. Flores et al., Bull. Seismol. Soc. Am. 89, 14-21 (1999)]. In the present talk we shall go over these arguments again and show that strong reflection at the edges of the lake must occur to account for the strong magnification entailing necessarily a long coda, and that the mecanism can be understood in the same terms.

Seismic Wave Propagation from Underground Chemical Explosions: Sensitivity to Velocity and Thickness of a Weathered Layer

NASA Astrophysics Data System (ADS)

Hirakawa, E. T.; Ezzedine, S. M.

2017-12-01

Recorded motions from underground chemical explosions are complicated by long duration seismic coda as well as motion in the tangential direction. The inability to distinguish the origins of these complexities as either source or path effects comprises a limitation to effective monitoring of underground chemical explosions. With numerical models, it is possible to conduct rigorous sensitivity analyses for chemical explosive sources and their resulting ground motions under the influence of many attributes, including but not limited to complex velocity structure, topography, and non-linear source characteristics. Previously we found that topography can cause significant scattering in the direct wave but leads to relatively little motion in the coda. Here, we aim to investigate the contribution from the low-velocity weathered layer that exists in the shallow subsurface apart from and in combination with surface topography. We use SW4, an anelastic anisotropic fourth order finite difference code to simulate chemical explosive source in a 1D velocity structure consisting of a single weathered layer over a half space. A range of velocity magnitudes are used for the upper weathered layer with the velocities always being lower than that of the granitic underlaying layer. We find that for lower weathered layer velocities, the wave train is highly dispersed and causes a large percentage of energy to be contained in the coda in relation to the entire time series. The percentage of energy contained in the coda grows with distance from the source but saturates at a certain distance that depends on weathered layer velocity and thickness. The saturation onset distance increases with decreasing layer thickness and increasing velocity of the upper layer. Measurements of relative coda energy and coda saturation onset distance from real recordings can provide an additional constraint on the properties of the weathered layer in remote sites as well as test sites like the Nevada National Security Site (NNSS). The results of this modeling study will aid in distinguishing source effects from path effects to the recorded motions in experiments such as the Source Physics Experiment (SPE). This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

High-resolution imaging of the low velocity layer in Alaskan subduction zone with scattered waves and interferometry

NASA Astrophysics Data System (ADS)

Kim, D.; Keranen, K. M.; Abers, G. A.; Kim, Y.; Li, J.; Shillington, D. J.; Brown, L. D.

2017-12-01

The physical factors that control the rupture process of great earthquakes at convergent plate boundaries remain incompletely understood. While recent developments in imaging using the teleseismic wavefield have led to marked advances at wavelengths of a couple kilometers to tens of kilometers, higher resolution imaging of the rupture zone would improve the resolution of imaging and thus provide improved parameter estimation, as the teleseismic wavefield is fundamentally limited by its low frequency content. This study compares and evaluates two seismic imaging techniques using the high-frequency signals from teleseismic coda versus earthquake scattered waves to image the subducting Yakutat oceanic plateau in the Alaska subduction zone. We use earthquakes recorded by the MOOS PASSCAL broadband deployment in southern Alaska. In our first method, we select local earthquakes that lie directly beneath and laterally near the recording array for imaging, and extract body wave information via a simple autocorrelation and stacking. Profiles analogous to seismic reflection profile are constructed using the near-vertically travelling waves. In our second method, we compute teleseismic receiver functions within the 0.02-1.0 Hz frequency band. Both results image interfaces that we associate with the subducting oceanic plate in Alaska-Aleutian system, with greater resolution than commonly used methods with teleseismic sources. Structural details from our results can further our understanding of the conditions and materials that characterize the subduction megathrusts, and the techniques can be employed in other regions along the Alaska-Aleutian system and at other convergent margins with suitable seismic arrays.

Atom Interferometry for Fundamental Physics and Gravity Measurements in Space

NASA Technical Reports Server (NTRS)

Kohel, James M.

2012-01-01

Laser-cooled atoms are used as freefall test masses. The gravitational acceleration on atoms is measured by atom-wave interferometry. The fundamental concept behind atom interferometry is the quantum mechanical particle-wave duality. One can exploit the wave-like nature of atoms to construct an atom interferometer based on matter waves analogous to laser interferometers.

Using Co-located Rotational and Translational Ground-Motion Sensors to Characterize Seismic Scattering in the P-Wave Coda

NASA Astrophysics Data System (ADS)

Bartrand, J.; Abbott, R. E.

2017-12-01

We present data and analysis of a seismic data collect at the site of a historical underground nuclear explosion at Yucca Flat, a sedimentary basin on the Nevada National Security Site, USA. The data presented here consist of active-source, six degree-of-freedom seismic signals. The translational signals were collected with a Nanometrics Trillium Compact Posthole seismometer and the rotational signals were collected with an ATA Proto-SMHD, a prototype rotational ground motion sensor. The source for the experiment was the Seismic Hammer (a 13,000 kg weight-drop), deployed on two-kilometer, orthogonal arms centered on the site of the nuclear explosion. By leveraging the fact that compressional waves have no rotational component, we generated a map of subsurface scattering and compared the results to known subsurface features. To determine scattering intensity, signals were cut to include only the P-wave and its coda. The ratio of the time-domain signal magnitudes of angular velocity and translational acceleration were sectioned into three time windows within the coda and averaged within each window. Preliminary results indicate an increased rotation/translation ratio in the vicinity of the explosion-generated chimney, suggesting mode conversion of P-wave energy to S-wave energy at that location. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.

A local earthquake coda magnitude and its relation to duration, moment M sub O, and local Richter magnitude M sub L

NASA Technical Reports Server (NTRS)

Suteau, A. M.; Whitcomb, J. H.

1977-01-01

A relationship was found between the seismic moment, M sub O, of shallow local earthquakes and the total duration of the signal, t, in seconds, measured from the earthquakes origin time, assuming that the end of the coda is composed of backscattering surface waves due to lateral heterogenity in the shallow crust following Aki. Using the linear relationship between the logarithm of M sub O and the local Richter magnitude M sub L, a relationship between M sub L and t, was found. This relationship was used to calculate a coda magnitude M sub C which was compared to M sub L for Southern California earthquakes which occurred during the period from 1972 to 1975.

Changes in seismic velocity during the first 14 months of the 2004-2008 eruption of Mount St. Helens, Washington

NASA Astrophysics Data System (ADS)

Hotovec-Ellis, A. J.; Vidale, J. E.; Gomberg, J.; Thelen, W.; Moran, S. C.

2015-09-01

Mount St. Helens began erupting in late 2004 following an 18 year quiescence. Swarms of repeating earthquakes accompanied the extrusion of a mostly solid dacite dome over the next 4 years. In some cases the waveforms from these earthquakes evolved slowly, likely reflecting changes in the properties of the volcano that affect seismic wave propagation. We use coda-wave interferometry to quantify small changes in seismic velocity structure (usually <1%) between two similar earthquakes and employed waveforms from several hundred families of repeating earthquakes together to create a continuous function of velocity change observed at permanent stations operated within 20 km of the volcano. The high rate of earthquakes allowed tracking of velocity changes on an hourly time scale. Changes in velocity were largest near the newly extruding dome and likely related to shallow deformation as magma first worked its way to the surface. We found strong correlation between velocity changes and the inverse of real-time seismic amplitude measurements during the first 3 weeks of activity, suggesting that fluctuations of pressure in the shallow subsurface may have driven both seismicity and velocity changes. Velocity changes during the remainder of the eruption likely result from a complex interplay of multiple effects and are not well explained by any single factor alone, highlighting the need for complementary geophysical data when interpreting velocity changes.

Changes in seismic velocity during the first 14 months of the 2004–2008 eruption of Mount St. Helens, Washington

USGS Publications Warehouse

Hotovec-Ellis, A.J.; Vidale, J.E.; Gomberg, Joan S.; Thelen, Weston A.; Moran, Seth C.

2015-01-01

Mount St. Helens began erupting in late 2004 following an 18 year quiescence. Swarms of repeating earthquakes accompanied the extrusion of a mostly solid dacite dome over the next 4 years. In some cases the waveforms from these earthquakes evolved slowly, likely reflecting changes in the properties of the volcano that affect seismic wave propagation. We use coda-wave interferometry to quantify small changes in seismic velocity structure (usually <1%) between two similar earthquakes and employed waveforms from several hundred families of repeating earthquakes together to create a continuous function of velocity change observed at permanent stations operated within 20 km of the volcano. The high rate of earthquakes allowed tracking of velocity changes on an hourly time scale. Changes in velocity were largest near the newly extruding dome and likely related to shallow deformation as magma first worked its way to the surface. We found strong correlation between velocity changes and the inverse of real-time seismic amplitude measurements during the first 3 weeks of activity, suggesting that fluctuations of pressure in the shallow subsurface may have driven both seismicity and velocity changes. Velocity changes during the remainder of the eruption likely result from a complex interplay of multiple effects and are not well explained by any single factor alone, highlighting the need for complementary geophysical data when interpreting velocity changes.

A comparison of methods to estimate seismic phase delays--Numerical examples for coda wave interferometry

USGS Publications Warehouse

Mikesell, T. Dylan; Malcolm, Alison E.; Yang, Di; Haney, Matthew M.

2015-01-01

Time-shift estimation between arrivals in two seismic traces before and after a velocity perturbation is a crucial step in many seismic methods. The accuracy of the estimated velocity perturbation location and amplitude depend on this time shift. Windowed cross correlation and trace stretching are two techniques commonly used to estimate local time shifts in seismic signals. In the work presented here, we implement Dynamic Time Warping (DTW) to estimate the warping function – a vector of local time shifts that globally minimizes the misfit between two seismic traces. We illustrate the differences of all three methods compared to one another using acoustic numerical experiments. We show that DTW is comparable to or better than the other two methods when the velocity perturbation is homogeneous and the signal-to-noise ratio is high. When the signal-to-noise ratio is low, we find that DTW and windowed cross correlation are more accurate than the stretching method. Finally, we show that the DTW algorithm has better time resolution when identifying small differences in the seismic traces for a model with an isolated velocity perturbation. These results impact current methods that utilize not only time shifts between (multiply) scattered waves, but also amplitude and decoherence measurements. DTW is a new tool that may find new applications in seismology and other geophysical methods (e.g., as a waveform inversion misfit function).

Multiple scattering from icequakes at Erebus volcano, Antarctica: Implications for imaging at glaciated volcanoes

NASA Astrophysics Data System (ADS)

Chaput, J.; Campillo, M.; Aster, R. C.; Roux, P.; Kyle, P. R.; Knox, H.; Czoski, P.

2015-02-01

We examine seismic coda from an unusually dense deployment of over 100 short-period and broadband seismographs in the summit region of Mount Erebus volcano on a network with an aperture of approximately 5 km. We investigate the energy-partitioning properties of the seismic wavefield generated by thousands of small icequake sources originating on the upper volcano and use them to estimate Green's functions via coda cross correlation. Emergent coda seismograms suggest that this locale should be particularly amenable to such methods. Using a small aperture subarray, we find that modal energy partition between S and P wave energy between ˜1 and 4 Hz occurs in just a few seconds after event onset and persists for tens of seconds. Spatially averaged correlograms display clear body and surface waves that span the full aperture of the array. We test for stable bidirectional Green's function recovery and note that good symmetry can be achieved at this site even with a geographically skewed distribution of sources. We estimate scattering and absorption mean free path lengths and find a power law decrease in mean free path between 1.5 and 3.3 Hz that suggests a quasi-Rayleigh or Rayleigh-Gans scattering situation. Finally, we demonstrate the existence of coherent backscattering (weak localization) for this coda wavefield. The remarkable properties of scattered seismic wavefields in the vicinity of active volcanoes suggests that the abundant small icequake sources may be used for illumination where temporal monitoring of such dynamic structures is concerned.

Auto correlation analysis of coda waves from local earthquakes for detecting temporal changes in shallow subsurface structures - The 2011 Tohoku-Oki, Japan, earthquake -

NASA Astrophysics Data System (ADS)

Nakahara, H.

2013-12-01

For monitoring temporal changes in subsurface structures, I propose to use auto correlation functions of coda waves from local earthquakes recorded at surface receivers, which probably contain more body waves than surface waves. Because the use of coda waves requires earthquakes, time resolution for monitoring decreases. But at regions with high seismicity, it may be possible to monitor subsurface structures in sufficient time resolutions. Studying the 2011 Tohoku-Oki (Mw 9.0), Japan, earthquake for which velocity changes have been already reported by previous studies, I try to validate the method. KiK-net stations in northern Honshu are used in the analysis. For each moderate earthquake, normalized auto correlation functions of surface records are stacked with respect to time windows in S-wave coda. Aligning the stacked normalized auto correlation functions with time, I search for changes in arrival times of phases. The phases at lag times of less than 1s are studied because changes at shallow depths are focused. Based on the stretching method, temporal variations in the arrival times are measured at the stations. Clear phase delays are found to be associated with the mainshock and to gradually recover with time. Amounts of the phase delays are in the order of 10% on average with the maximum of about 50% at some stations. For validation, the deconvolution analysis using surface and subsurface records at the same stations are conducted. The results show that the phase delays from the deconvolution analysis are slightly smaller than those from the auto correlation analysis, which implies that the phases on the auto correlations are caused by larger velocity changes at shallower depths. The auto correlation analysis seems to have an accuracy of about several percents, which is much larger than methods using earthquake doublets and borehole array data. So this analysis might be applicable to detect larger changes. In spite of these disadvantages, this analysis is still attractive because it can be applied to many records on the surface in regions where no boreholes are available. Acknowledgements: Seismograms recorded by KiK-net managed by National Research Institute for Earth Science and Disaster Prevention (NIED) were used in this study. This study was partially supported by JST J-RAPID program and JSPS KAKENHI Grant Numbers 24540449 and 23540449.

Analysis of intermediate period correlations of coda from deep earthquakes

NASA Astrophysics Data System (ADS)

Poli, Piero; Campillo, Michel; de Hoop, Maarten

2017-11-01

We aim at assessing quantitatively the nature of the signals that appear in coda wave correlations at periods >20 s. These signals contain transient constituents with arrival times corresponding to deep seismic phases. These (body-wave) constituents can be used for imaging. To evaluate this approach, we calculate the autocorrelations of the vertical component seismograms for the Mw 8.4 sea of Okhotsk earthquake at 400 stations in the Eastern US, using data from 1 h before to 50 h after the earthquake. By using array analysis and modes identification, we discover the dominant role played by high quality factor normal modes in the emergence of strong coherent phases as ScS-like, and P'P'df-like. We then make use of geometrical quantization to derive the constituent rays associated with particular modes, and gain insights about the ballistic reverberation of the rays that contributes to the emergence of body waves. Our study indicates that the signals measured in the spatially averaged autocorrelations have a physical significance, but a direct interpretation of ScS-like and P'P'df-like is not trivial. Indeed, even a single simple measurement of long period late coda in a limited period band could provide valuable information on the deep structure by using the temporal information of its autocorrelation, a procedure that could be also useful for planetary exploration.

Improved mb-Ms Discrimination Using mb(P-coda) and MsU with Application to the Six North Korean Nuclear Tests

NASA Astrophysics Data System (ADS)

Napoli, V.; Yoo, S. H.; Russell, D. R.

2017-12-01

To improve discrimination of small explosions and earthquakes, we developed a new magnitude scale based on the standard Ms:mb discrimination method. In place of 20 second Ms measurements we developed a unified Rayleigh and Love wave magnitude scale (MsU) that is designed to maximize available information from single stations and then combine magnitude estimates into network averages. Additionally, in place of mb(P) measurements we developed an mb(P-Coda) magnitude scale as the properties of the coda make sparse network mb(P-Coda) more robust and less variable than network mb(P) estimates. A previous mb:MsU study conducted in 2013 in the Korean Peninsula shows that the use of MsU in place of standard 20 second Ms, leads to increased population separation and reduced scattering. The goals of a combined mb(P-coda):MsU scale are reducing scatter, ensuring applicability at small magnitudes with sparse networks, and improving the overall distribution for mb:Ms earthquake and explosion populations. To test this method we are calculating mb(P-coda)and MsU for a catalog earthquakes located in and near the Korean Peninsula, for the six North Korean nuclear tests (4.1 < mb < 6.3) and for the 3 aftershocks to date that occurred after the sixth test (2.6 < ML < 4.0). Compared to the previous 2013 study, we expect to see greater separation in the populations and less scattering with the inclusion of mb(P-coda) and with the implementation of additional filters for MsU to improve signal-to-noise levels; this includes S-transform filtering for polarization and off-azimuth signal reduction at regional distances. As we are expanding our database of mb(P-coda):MsU measurements in the Korean Peninsula to determine the earthquake and explosion distribution, this research will address the limitations and potential for discriminating small magnitude events using sparse networks.

Full-Waveform Envelope Templates for Low Magnitude Discrimination and Yield Estimation at Local and Regional Distances with Application to the North Korean Nuclear Tests

NASA Astrophysics Data System (ADS)

Yoo, S. H.

2017-12-01

Monitoring seismologists have successfully used seismic coda for event discrimination and yield estimation for over a decade. In practice seismologists typically analyze long-duration, S-coda signals with high signal-to-noise ratios (SNR) at regional and teleseismic distances, since the single back-scattering model reasonably predicts decay of the late coda. However, seismic monitoring requirements are shifting towards smaller, locally recorded events that exhibit low SNR and short signal lengths. To be successful at characterizing events recorded at local distances, we must utilize the direct-phase arrivals, as well as the earlier part of the coda, which is dominated by multiple forward scattering. To remedy this problem, we have developed a new hybrid method known as full-waveform envelope template matching to improve predicted envelope fits over the entire waveform and account for direct-wave and early coda complexity. We accomplish this by including a multiple forward-scattering approximation in the envelope modeling of the early coda. The new hybrid envelope templates are designed to fit local and regional full waveforms and produce low-variance amplitude estimates, which will improve yield estimation and discrimination between earthquakes and explosions. To demonstrate the new technique, we applied our full-waveform envelope template-matching method to the six known North Korean (DPRK) underground nuclear tests and four aftershock events following the September 2017 test. We successfully discriminated the event types and estimated the yield for all six nuclear tests. We also applied the same technique to the 2015 Tianjin explosions in China, and another suspected low-yield explosion at the DPRK test site on May 12, 2010. Our results show that the new full-waveform envelope template-matching method significantly improves upon longstanding single-scattering coda prediction techniques. More importantly, the new method allows monitoring seismologists to extend coda-based techniques to lower magnitude thresholds and low-yield local explosions.

Monitoring daily and sub-daily variations in crustal strain with seismic arrays

NASA Astrophysics Data System (ADS)

Mao, S.; Campillo, M.; van der Hilst, R. D.; Brenguier, F.; Hillers, G.

2017-12-01

We demonstrate that we can monitor deformation of the shallow crust (with hourly temporal resolution) directly with seismic waves, by measuring relative seismic wave speed changes (dv/v) due to relatively known periodical forcing (tides and changes in atmospheric temperature) at Piton de la Fournaise Volcano (PdF), La Réunion. We use ambient seismic noise recorded (for one month) at VolcArray, an experiment with three arrays of 49 vertical-component geophones deployed on a 7x7 grid of approximately 80 m spacing. Through noise-based coda wave interferometry we infer for each array the average relative changes in propagation speed of seismic waves (dv/v) as a function of time, which relate to temporal changes in medium properties within 100m depth. The variations in dv/v ( 0.05%) on time-scales longer than a day are best explained by effects of precipitation on pore pressure. In contrast, the (weaker) daily and sub-daily fluctuations of dv/v ( 0.01%) are likely to be caused by tidal and thermal effects. We verify that the inferred variations of dv/v are unrelated to spatiotemporal changes of noise wavefields. We further compare the power spectrum of dv/v with spectra of simulated tide-induced volumetric strain, temperature records, very broadband (VBB) seismograms, and borehole tilt records. In all five types of data, dominant peaks are found at around diurnal, semi-diurnal, and ter-diurnal frequencies. A comparison of phase and spectra of the data suggests that the tidal and thermal effects on dv/v are of similar magnitude but vary with frequency. Theoretical modeling of tide- and temperature-induced strain in different frequency bands agrees with the relative magnitude of the two effects on dv/v from passive monitoring.

Attenuation Characteristics of the Armutlu Peninsula (NW Turkey) Using Coda Q

NASA Astrophysics Data System (ADS)

Yavuz, Evrim; Çaka, Deniz; Tunç, Berna; Woith, Heiko; Gottfried Lühr, Birger; Barış, Şerif

2016-04-01

Attenuation characteristic of seismic waves was determined using coda Q in the frame of MARsite (MARsite has received funding from the European Union's Seventh Programme for research, technological development and demonstration under grant agreement No 308417). Data from 82 earthquakes recorded in 2013-2014 in the Armutlu Peninsula and its vicinity by 9 ARNET seismic stations were used for processing. The earthquake magnitudes (Ml) and depths vary from 1.5 to 3.7 and 1.2-16.9 km, respectively. Epicentral distances closer than 90 km were selected to ensure better signal-to-noise ratios. Lapse times between 20 seconds and 40 seconds at intervals of 5 seconds were used for the calculation of the coda wave quality factor. The coda windows were filtered at central frequencies of 1.5, 3, 6, 9 and 12 Hz bandpass filter. To obtain reliable results, only data with signal-to-noise ratios greater than 5 and correlation coefficents higher than 0.7 were used. The SEISAN software and one of its subroutines (CODAQ) were used for data processing and analyses. In the whole study area, Qc=(51±4)f^(0.91±0.04) for 20 seconds, Qc=(77±7)f^(0.80±0.04) for 30 seconds and Qc=(112±13)f^(0.72±0.06) for 40 seconds lapse times are obtained for coda wave quality factor. The observed quality factor is dependent on frequency and lapse time. The results indicate that the upper lithosphere is more heterogeneous and seismically more active than the lower lithosphere as expected in the region which is tectonically complex refering to the effects of the North Anatolian Fault Zone. By considering earthquake clusters and recorded stations, the scattering area was drawn. The intersection of the scattered areas for 20 seconds lapse time is covering all stations. Quality factor in 1 Hz and frequency dependent values were calculated separately and for the intersection of all scattered areas. Calculated Qo and n values of the intersection area are 50 and 0.89, respectively. Hence, the Qo and n values which are calculated using all stations and both values of the intersection area are very close to each other. Additionally, in the detailed review of TRML station which located in Yalova Province Termal District; Qc=(46±3)f^(0.97±0.04) for 20 seconds, Qc=(61±6)f^(1.03±0.06), for 30 seconds and Qc=(74±6)f^(1.06±0.05) for 40 seconds lapse times are obtained for coda wave quality factor. With these results, both the lower Qo values increasing with lapse times demonstrate high tectonic activity. Furthermore, the increasing n value with lapse times is conformable with the geothermal sources, next to the TRML station.

Comparing Laser Interferometry and Atom Interferometry Approaches to Space-Based Gravitational-Wave Measurement

NASA Technical Reports Server (NTRS)

Baker, John; Thorpe, Ira

2012-01-01

Thoroughly studied classic space-based gravitational-wave missions concepts such as the Laser Interferometer Space Antenna (LISA) are based on laser-interferometry techniques. Ongoing developments in atom-interferometry techniques have spurred recently proposed alternative mission concepts. These different approaches can be understood on a common footing. We present an comparative analysis of how each type of instrument responds to some of the noise sources which may limiting gravitational-wave mission concepts. Sensitivity to laser frequency instability is essentially the same for either approach. Spacecraft acceleration reference stability sensitivities are different, allowing smaller spacecraft separations in the atom interferometry approach, but acceleration noise requirements are nonetheless similar. Each approach has distinct additional measurement noise issues.

Wave Propagation in Non-Stationary Statistical Mantle Models at the Global Scale

NASA Astrophysics Data System (ADS)

Meschede, M.; Romanowicz, B. A.

2014-12-01

We study the effect of statistically distributed heterogeneities that are smaller than the resolution of current tomographic models on seismic waves that propagate through the Earth's mantle at teleseismic distances. Current global tomographic models are missing small-scale structure as evidenced by the failure of even accurate numerical synthetics to explain enhanced coda in observed body and surface waveforms. One way to characterize small scale heterogeneity is to construct random models and confront observed coda waveforms with predictions from these models. Statistical studies of the coda typically rely on models with simplified isotropic and stationary correlation functions in Cartesian geometries. We show how to construct more complex random models for the mantle that can account for arbitrary non-stationary and anisotropic correlation functions as well as for complex geometries. Although this method is computationally heavy, model characteristics such as translational, cylindrical or spherical symmetries can be used to greatly reduce the complexity such that this method becomes practical. With this approach, we can create 3D models of the full spherical Earth that can be radially anisotropic, i.e. with different horizontal and radial correlation functions, and radially non-stationary, i.e. with radially varying model power and correlation functions. Both of these features are crucial for a statistical description of the mantle in which structure depends to first order on the spherical geometry of the Earth. We combine different random model realizations of S velocity with current global tomographic models that are robust at long wavelengths (e.g. Meschede and Romanowicz, 2014, GJI submitted), and compute the effects of these hybrid models on the wavefield with a spectral element code (SPECFEM3D_GLOBE). We finally analyze the resulting coda waves for our model selection and compare our computations with observations. Based on these observations, we make predictions about the strength of unresolved small-scale structure and extrinsic attenuation.

Physical and non-physical energy in scattered wave source-receiver interferometry.

PubMed

Meles, Giovanni Angelo; Curtis, Andrew

2013-06-01

Source-receiver interferometry allows Green's functions between sources and receivers to be estimated by means of convolution and cross-correlation of other wavefields. Source-receiver interferometry has been observed to work surprisingly well in practical applications when theoretical requirements (e.g., complete enclosing boundaries of other sources and receivers) are contravened: this paper contributes to explain why this may be true. Commonly used inter-receiver interferometry requires wavefields to be generated around specific stationary points in space which are controlled purely by medium heterogeneity and receiver locations. By contrast, application of source-receiver interferometry constructs at least kinematic information about physically scattered waves between a source and a receiver by cross-convolution of scattered waves propagating from and to any points on the boundary. This reduces the ambiguity in interpreting wavefields generated using source-receiver interferometry with only partial boundaries (as is standard in practical applications), as it allows spurious or non-physical energy in the constructed Green's function to be identified and ignored. Further, source-receiver interferometry (which includes a step of inter-receiver interferometry) turns all types of non-physical or spurious energy deriving from inter-receiver interferometry into what appears to be physical energy. This explains in part why source-receiver interferometry may perform relatively well compared to inter-receiver interferometry when constructing scattered wavefields.

Localized water reverberation phases and its impact on back-projection images

NASA Astrophysics Data System (ADS)

Yue, H.; Castillo, J.; Yu, C.; Meng, L.; Zhan, Z.

2017-12-01

Coherent radiators imaged by back-projections (BP) are commonly interpreted as part of the rupture process. Nevertheless, artifacts introduced by structure related phases are rarely discriminated from the rupture process. In this study, we adopt the logic of empirical Greens' function analysis (EGF) to discriminate between rupture and structure effect. We re-examine the waveforms and BP images of the 2012 Mw 7.2 Indian Ocean earthquake and an EGF event (Mw 6.2). The P wave codas of both events present similar shape with characteristic period of approximately 10 s, which are back-projected as coherent radiators near the trench. S wave BP doesn't image energy radiation near the trench. We interpret those coda waves as localized water reverberation phases excited near the trench. We perform a 2D waveform modeling using realistic bathymetry model, and find that the sharp near-trench bathymetry traps the acoustic water waves forming localized reverberation phases. These waves can be imaged as coherent near-trench radiators with similar features as that in the observations. We present a set of methodology to discriminate between the rupture and propagation effects in BP images, which can serve as a criterion of subevent identification.

Frequency dependent Lg attenuation in south-central Alaska

USGS Publications Warehouse

McNamara, D.E.

2000-01-01

The characteristics of seismic energy attenuation are determined using high frequency Lg waves from 27 crustal earthquakes, in south-central Alaska. Lg time-domain amplitudes are measured in five pass-bands and inverted to determine a frequency-dependent quality factor, Q(f), model for south-central Alaska. The inversion in this study yields the frequency-dependent quality factor, in the form of a power law: Q(f) = Q0fη = 220(±30) f0.66(±0.09) (0.75≤f≤12Hz). The results from this study are remarkably consistent with frequency dependent quality factor estimates, using local S-wave coda, in south-central Alaska. The consistency between S-coda Q(f) and Lg Q(f) enables constraints to be placed on the mechanism of crustal attenuation in south-central Alaska. For the range of frequencies considered in this study both scattering and intrinsic attenuation mechanisms likely play an equal role.

Intrinsic and scattering attenuation of high-frequency S-waves in the central part of the External Dinarides

NASA Astrophysics Data System (ADS)

Majstorović, Josipa; Belinić, Tena; Namjesnik, Dalija; Dasović, Iva; Herak, Davorka; Herak, Marijan

2017-09-01

The central part of the External Dinarides (CED) is a geologically and tectonically complex region formed in the collision between the Adriatic microplate and the European plate. In this study, the contributions of intrinsic and scattering attenuation ( Q i - 1 and Q sc - 1 , respectively) to the total S-wave attenuation were calculated for the first time. The multiple lapse-time window analysis (MLTWA method), based on the assumptions of multiple isotropic scattering in a homogeneous medium with uniformly distributed scatterers, was applied to seismograms of 450 earthquakes recorded at six seismic stations. Selected events have hypocentral distances between 40 and 90 km with local magnitudes between 1.5 and 4.7. The analysis was performed over 11 frequency bands with central frequencies between 1.5 and 16 Hz. Results show that the seismic albedo of the studied area is less than 0.5 and Q i - 1 > Q sc - 1 at all central frequencies and for all stations. These imply that the intrinsic attenuation dominates over scattering attenuation in the whole study area. Calculated total S-wave and expected coda wave attenuation for CED are in a very good agreement with the ones measured in previous studies using the coda normalization and the coda-Q methods. All estimated attenuation factors decrease with increasing frequency. The intrinsic attenuation for CED is among the highest observed elsewhere, which could be due to the highly fractured and fluid-filled carbonates in the upper crust. The scattering and the total S-wave attenuation for CED are close to the average values obtained in other studies performed worldwide. In particular, good agreement of frequency dependence of total attenuation in CED and in the regions that contributed most strong-motion records for ground motion prediction equations used in PSHA in Croatia indicates that those were well chosen and applicable to this area as far as their attenuation properties are concerned.

Waveform anomaly caused by strong attenuation in the crust and upper mantle in the Okinawa Trough region

NASA Astrophysics Data System (ADS)

Padhy, S.; Furumura, T.; Maeda, T.

2017-12-01

The Okinawa Trough is a young continental back-arc basin located behind the Ryukyu subduction zone in southwestern Japan, where the Philippine Sea Plate dives beneath the trough, resulting in localized mantle upwelling and crustal thinning of the overriding Eurasian Plate. The attenuation structure of the plates and surrounding mantle in this region associated with such complex tectonic environment are poorly documented. Here we present seismological evidence for these features based on the high-resolution waveform analyses and 3D finite difference method (FDM) simulation. We analyzed regional broadband waveforms recorded by F-net (NIED) of in-slab events (M>4, H>100 km). Using band-passed (0.5-8 Hz), mean-squared envelopes, we parameterized coda-decay in terms of rise-time (time from P-arrival to maximum amplitude in P-coda), decay-time (time from maximum amplitude to theoretical S-arrival), and energy-ratio defined as the ratio of energy in P-coda to that in direct P wave. The following key features are observed. First, there is a striking difference in S-excitation along paths traversing and not traversing the trough: events from SW Japan not crossing the trough show clear S waves, while those occurring in the trough show very weak S waves at a station close to the volcanic front. Second, some trough events exhibit spindle-shaped seismograms with strong P-coda excitation, obscuring the development of S waves, at back-arc stations; these waveforms are characterized by high decay-time (>10s) and high energy-ratio (>>1.0), suggesting strong forward scattering along ray paths. Third, some trough events show weak S-excitation characterized by low decay-time (<5s) and low energy-ratio (<1.0) at fore-arc stations, suggesting high intrinsic absorption. To investigate the mechanism of the observed anomalies, we will conduct FDM simulation for a suite of models comprising the key subduction features like localized mantle-upwelling and crustal thinning expected in the region. It is expected that simulation results help to resolve rift-induced crust and upper mantle anomalies in the trough showing maximum waveform distortion as we observed in broadband records, and will enhance understanding of tectonic processes related to back-arc rifting in the region.

Analyses of unusual long-period earthquakes with extended coda recorded at Katmai National Park, Alaska, USA

USGS Publications Warehouse

De Angelis, Silvio

2006-01-01

A swarm of six long-period (LP) events with slowly decaying coda wave amplitudes and durations up to 120 s, was recorded by seismic stations located in the proximity of Mt. Griggs, a fumarolically active volcano in the Katmai National Park, Alaska, during December 8–21, 2004. Spectral analyses reveal the quasi-monochromatic character of the waveforms, dominated by a 2.5 Hz mode frequently accompanied by a weaker high-frequency onset (6.0–9.0 Hz). Particle motion azimuths and inclination angles show a dominant WNW-ESE direction of polarization for all the signals, and suggest that seismic energy is radiated by a stable source at shallow depth. Damping coefficients between 0.0014 and 0.0063 are estimated by fitting an exponential decay model to the signal's coda; corresponding quality factors range from 78 to 351. The source of the waveforms is modelled as a resonant cavity filled with a fluid/gas mixture.

Interferometry

NASA Technical Reports Server (NTRS)

Ridgway, Stephen; Wilson, Robert W.; Begelman, Mitchell C.; Bender, Peter; Burke, Bernard F.; Cornwell, Tim; Drever, Ronald; Dyck, H. Melvin; Johnston, Kenneth J.; Kibblewhite, Edward

1991-01-01

The following recommended programs are reviewed: (1) infrared and optical interferometry (a ground-based and space programs); (2) compensation for the atmosphere with adaptive optics (a program for development and implementation of adaptive optics); and (3) gravitational waves (high frequency gravitational wave sources (LIGO), low frequency gravitational wave sources (LAGOS), a gravitational wave observatory program, laser gravitational wave observatory in space, and technology development during the 1990's). Prospects for international collaboration and related issues are also discussed.

Temporal Change of Seismic Earth's Inner Core Phases: Inner Core Differential Rotation Or Temporal Change of Inner Core Surface?

NASA Astrophysics Data System (ADS)

Yao, J.; Tian, D.; Sun, L.; Wen, L.

2017-12-01

Since Song and Richards [1996] first reported seismic evidence for temporal change of PKIKP wave (a compressional wave refracted in the inner core) and proposed inner core differential rotation as its explanation, it has generated enormous interests in the scientific community and the public, and has motivated many studies on the implications of the inner core differential rotation. However, since Wen [2006] reported seismic evidence for temporal change of PKiKP wave (a compressional wave reflected from the inner core boundary) that requires temporal change of inner core surface, both interpretations for the temporal change of inner core phases have existed, i.e., inner core rotation and temporal change of inner core surface. In this study, we discuss the issue of the interpretation of the observed temporal changes of those inner core phases and conclude that inner core differential rotation is not only not required but also in contradiction with three lines of seismic evidence from global repeating earthquakes. Firstly, inner core differential rotation provides an implausible explanation for a disappearing inner core scatterer between a doublet in South Sandwich Islands (SSI), which is located to be beneath northern Brazil based on PKIKP and PKiKP coda waves of the earlier event of the doublet. Secondly, temporal change of PKIKP and its coda waves among a cluster in SSI is inconsistent with the interpretation of inner core differential rotation, with one set of the data requiring inner core rotation and the other requiring non-rotation. Thirdly, it's not reasonable to invoke inner core differential rotation to explain travel time change of PKiKP waves in a very small time scale (several months), which is observed for repeating earthquakes in Middle America subduction zone. On the other hand, temporal change of inner core surface could provide a consistent explanation for all the observed temporal changes of PKIKP and PKiKP and their coda waves. We conclude that the observed temporal changes of the inner core phases are caused by temporal changes of inner core surface. The temporal changes of inner core surface are found to occur in some localized regions within a short time scale (years to months), a phenomenon that should provide important clues to a potentially fundamental change of our understanding of core dynamics.

Parsimonious surface wave interferometry

NASA Astrophysics Data System (ADS)

Li, Jing; Hanafy, Sherif; Schuster, Gerard T.

2018-03-01

To decrease the recording time of a 2-D seismic survey from a few days to one hour or less, we present a parsimonious surface wave interferometry method. Interferometry allows for the creation of a large number of virtual shot gathers from just two reciprocal shot gathers by crosscoherence of trace pairs. Then, the virtual surface waves can be inverted for the S-wave velocity model by wave-equation dispersion inversion (WD). Synthetic and field data tests suggest that parsimonious WD (PWD) gives S-velocity tomograms that are comparable to those obtained from a conventional survey with a shot at each receiver. The limitation of PWD is that the virtual data lose some information so that the resolution of the S-velocity tomogram can be modestly lower than that of the S-velocity tomogram inverted from a conventional survey.

Attention in western Nevada: Preliminary results from earthquake and explosion sources

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

Hough, S.E.; Anderson, J.G.; Patton, H.J.

1989-02-01

We present preliminary results from a study of the attenuation of regional seismic waves at frequencies between 1 and 15 Hz and distances up to 250 km in Western Nevada. Following the methods of Anderson and Hough (1984) and Hough et al. (1988), we parameterize the asymptote of the high frequency acceleration spectrum by the two-parameter model. We relate the model parameters to a two-layer model for Q/sub i/ and Q/sub d/, the freuqency-independent and the frequency dependent components of the quality factor. We compare our results to previously published Q studies in the Basin and Range and find thatmore » our estimate of total Q, Q/sub t/, in the shallow crust is consistent with shear wave Q at close distances with previous estimates of coda Q (Singh and Hermann, 1983) and LgQ (Chavez and Priestley, 1986), suggesting that both coda Q and LgQ are insensitive to near-surface contributions to attenuation.« less

Source spectral variation and yield estimation for small, near-source explosions

NASA Astrophysics Data System (ADS)

Yoo, S.; Mayeda, K. M.

2012-12-01

Significant S-wave generation is always observed from explosion sources which can lead to difficulty in discriminating explosions from natural earthquakes. While there are numerous S-wave generation mechanisms that are currently the topic of significant research, the mechanisms all remain controversial and appear to be dependent upon the near-source emplacement conditions of that particular explosion. To better understand the generation and partitioning of the P and S waves from explosion sources and to enhance the identification and discrimination capability of explosions, we investigate near-source explosion data sets from the 2008 New England Damage Experiment (NEDE), the Humble-Redwood (HR) series of explosions, and a Massachusetts quarry explosion experiment. We estimate source spectra and characteristic source parameters using moment tensor inversions, direct P and S waves multi-taper analysis, and improved coda spectral analysis using high quality waveform records from explosions from a variety of emplacement conditions (e.g., slow/fast burning explosive, fully tamped, partially tamped, single/ripple-fired, and below/above ground explosions). The results from direct and coda waves are compared to theoretical explosion source model predictions. These well-instrumented experiments provide us with excellent data from which to document the characteristic spectral shape, relative partitioning between P and S-waves, and amplitude/yield dependence as a function of HOB/DOB. The final goal of this study is to populate a comprehensive seismic source reference database for small yield explosions based on the results and to improve nuclear explosion monitoring capability.

Effective Algorithm for Detection and Correction of the Wave Reconstruction Errors Caused by the Tilt of Reference Wave in Phase-shifting Interferometry

NASA Astrophysics Data System (ADS)

Xu, Xianfeng; Cai, Luzhong; Li, Dailin; Mao, Jieying

2010-04-01

In phase-shifting interferometry (PSI) the reference wave is usually supposed to be an on-axis plane wave. But in practice a slight tilt of reference wave often occurs, and this tilt will introduce unexpected errors of the reconstructed object wave-front. Usually the least-square method with iterations, which is time consuming, is employed to analyze the phase errors caused by the tilt of reference wave. Here a simple effective algorithm is suggested to detect and then correct this kind of errors. In this method, only some simple mathematic operation is used, avoiding using least-square equations as needed in most methods reported before. It can be used for generalized phase-shifting interferometry with two or more frames for both smooth and diffusing objects, and the excellent performance has been verified by computer simulations. The numerical simulations show that the wave reconstruction errors can be reduced by 2 orders of magnitude.

Lateral and depth variations of coda Q in the Zagros region of Iran

NASA Astrophysics Data System (ADS)

Irandoust, Mohsen Ahmadzadeh; Sobouti, Farhad; Rahimi, Habib

2016-01-01

We have analyzed more than 2800 local earthquakes recorded by the Iranian National Seismic Network (INSN) and the Iranian Seismological Center (IRSC) to estimate coda wave quality factor, Q c , in the Zagros fold and thrust belt and the Sanandaj-Sirjan metamorphic zone in Iran. We used the single backscattering model to investigate lateral and depth variations of Q c in the study region. In the interior of Zagros, no strong lateral variation in attenuation parameters is observed. In SE Zagros (the Bandar-Abbas region) where transition to the Makran subduction setting begins, the medium shows lower attenuation. The average frequency relations for the SSZ, the Bandar-Abbas region, and the Zagros are Q c = (124 ± 11) f 0.82 ± 0.04, Q c = (109 ± 2) f 0.99 ± 0.01, and Q c = (85 ± 5) f 1.06 ± 0.03, respectively. To investigate the depth variation of Q c , 18 time windows between 5 and 90 s and at two epicentral distance ranges of R < 100 km and 100 < R < 200 km were considered. It was observed that with increasing coda lapse time, Q 0 ( Q c at 1 Hz) and n (frequency dependence factor) show increasing and decreasing trends, respectively. Beneath the SSZ and at depths of about 50 to 80 km, there is a correlation between the reported low velocity medium and the observed sharp change in the trend of Q 0 and n curves. In comparison with results obtained in other regions of the Iranian plateau, the Zagros along with the Alborz Mountains in the north show highest attenuation of coda wave and strongest frequency dependence, an observation that reflects the intense seismicity and active faulting in these mountain ranges. We also observe a stronger depth dependence of attenuation in the Zagros and SSZ compared to central Iran, indicating a thicker lithosphere in the Zagros region than in central Iran.

Simultaneous Dual Species Matter Wave Interferometry

NASA Astrophysics Data System (ADS)

Schlippert, Dennis; Albers, Henning; Richardson, Logan; Meiners, Christian; Hartwig, Jonas; Ertmer, Wolfgang; Rasel, Ernst

2014-05-01

We report on the first realization of a simultaneous 39K-87Rb-dual species matter wave interferometer measuring gravitational acceleration with the aim to test Einstein's Equivalence Principle (EEP). Compared to classical tests such as torsion pendulum experiments and Lunar Laser Ranging, chemical elements suitable for performing matter wave interferometry can provide complementary information. We show the performance of our apparatus and discuss current limitations and future improvements towards highly sensitive matter wave tests of EEP.

A model for attenuation and scattering in the Earth's crust

NASA Astrophysics Data System (ADS)

Toksöz, M. Nafi; Dainty, Anton M.; Reiter, Edmund; Wu, Ru-Shan

1988-03-01

The mechanisms contributing to the attenuation of earthquake ground motion in the distance range of 10 to 200 km are studied with the aid of laboratory data, coda waves Rg attenuation, strong motion attenuation measurements in the northeast United States and Canada, and theoretical models. The frequency range 1 10 Hz has been studied. The relative contributions to attenuation of anelasticity of crustal rocks (constant Q), fluid flow and scattering are evaluated. Scattering is found to be strong with an albedo B 0=0.8 0.9 and a scattering extinction length of 17 32 km. The albedo is defined as the ratio of the total extinction length to the scattering extinction length. The Rg results indicate that Q increases with depth in the upper kilometer or two of the crust, at least in New England. Coda Q appears to be equivalent to intrinsic (anelastic) Q and indicates that this Q increases with frequency as Q=Q o f n , where n is in the range of 0.2 0.9. The intrinsic attenuation in the crust can be explained by a high constant Q (500≤ Q o≤2000) and a frequency dependent mechanism most likely due to fluid effects in rocks and cracks. A fluid-flow attenuation model gives a frequency dependence ( Q≃ Q o f 0.5) similar to those determined from the analysis of coda waves of regional seismograms. Q is low near the surface and high in the body of the crust.

Detectability of temporal changes in fine structures near the inner core boundary beneath the eastern hemisphere

NASA Astrophysics Data System (ADS)

Yu, Wen-che

2016-04-01

The inner core boundary (ICB), where melting and solidification of the core occur, plays a crucial role in the dynamics of the Earth's interior. To probe temporal changes near the ICB beneath the eastern hemisphere, I analyze differential times of PKiKP (dt(PKiKP)), double differential times of PKiKP-PKPdf, and PKiKP coda waves from repeating earthquakes in the Southwest Pacific subduction zones. Most PKiKP differential times are within ±30 ms, comparable to inherent travel time uncertainties due to inter-event separations, and suggest no systematic changes as a function of calendar time. Double differential times measured between PKiKP codas and PKiKP main phases show promising temporal changes, with absolute values of time shifts of >50 ms for some observations. However, there are discrepancies among results from different seismographs in the same calendar time window. Negligible changes in PKiKP times, combined with changes in PKiKP coda wave times on 5 year timescales, favor a smooth inner core boundary with fine-scale structures present in the upper inner core. Differential times of PKiKP can be interpreted in the context of either melting based on translational convection, or growth based on thermochemical mantle-inner core coupling. Small dt(PKiKP) values with inherent uncertainties do not have sufficient resolution to distinguish the resultant longitudinal (melting) and latitudinal (growth) dependencies predicted on the basis of the two models on 5 year timescales.

Identification of T-Waves in the Alboran Sea

NASA Astrophysics Data System (ADS)

Carmona, Enrique; Almendros, Javier; Alguacil, Gerardo; Soto, Juan Ignacio; Luzón, Francisco; Ibáñez, Jesús M.

2015-11-01

Analyses of seismograms from ~1,100 north-Moroccan earthquakes recorded at stations of the Red Sísmica de Andalucía (Southern Spain) reveal the systematic presence of late phases embedded in the earthquake codas. These phases have distinctive frequency contents, similar to the P and S spectra and quite different to the frequency contents of the earthquake codas. They are best detected at near-shore stations. Their amplitudes decay significantly with distance to the shoreline. The delays with respect to the P-wave onsets of the preceding earthquakes are consistently around 85 s. Late phases are only detected for earthquakes located in a small region of about 100 × 60 km centered at 35.4°N, 4.0°W near the northern coast of Morocco. Several hypotheses could, in principle, explain the presence of these late phases in the seismograms, for example, the occurrence of low-energy aftershocks, efficient wave reflections, or Rayleigh waves generated along the source-station paths. However, we conclude that the most-likely origin of these phases corresponds to the incidence of T-waves (generated by conversion from elastic to acoustic energy in the north-Moroccan coast) in the southern coast of the Iberian Peninsula. T-waves are thought to be generated by energy trapping in low-velocity channels along long oceanic paths; in this case, we demonstrate that they can be produced in much shorter paths as well. Although T-waves have been already documented in other areas of the Mediterranean Sea, this is the first time that they have been identified in the Alboran Sea.

Modeling of Compaction Wave Behavior in Confined Granular Energetic Material

DTIC Science & Technology

1990-08-01

Compacted 65% TMD Aggregate Melamine Compaction Wave Microwave DIAGNOSTICS: Interferometry (a) Microwave Interferometry (b) 3 Wall-Mounted Pressure...involved 65% TMD melamine but was run very recently (Dec 1989) The value of compaction wave speed (from the microwave data) just after impact is...47 B. Simulation of PDC-M34 / 65% TMD Melamine (Inert Material) ........ 54 C. Influence of Energy Release / PDC Experiment

Atom Interferometry for Detection of Gravitational Waves: Progress and Prospects

NASA Astrophysics Data System (ADS)

Hogan, Jason

2015-04-01

Gravitational wave astronomy promises to provide a new window into the universe, collecting information about astrophysical systems and cosmology that is difficult or impossible to acquire by other methods. Detector designs based on atom interferometry offer a number of advantages over traditional approaches, including access to conventionally inaccessible frequency ranges and substantially reduced antenna baselines. Atomic physics techniques also make it possible to build a gravitational wave detector with a single linear baseline, potentially offering advantages in cost and design flexibility. In support of these proposals, recent progress in long baseline atom interferometry has enabled observation of matter wave interference with atomic wavepacket separations exceeding 10 cm and interferometer durations of more than 2 seconds. These results are obtained in a 10-meter drop tower incorporating large momentum transfer atom optics. This approach can provide ground-based proof-of-concept demonstrations of many of the technical requirements of both terrestrial and satellite gravitational wave detectors.

Processing and interpretation of experiments in the microwave interferometry of shock waves in a weakly ionized plasma

NASA Astrophysics Data System (ADS)

Ershov, A. P.; Klishin, S. V.; Kuzovnikov, S. V.; Ponomareva, S. E.; Pyt'ev, Iu. P.

1990-12-01

The reduction method is applied to the microwave interferometry of shock waves in a weakly ionized plasma, making it possible to improve the spatial resolution of the instrument. It is shown experimentally that the structure of the shock wave electron component in a high-frequency discharge plasma in atomic and molecular gases is characterized by the presence of a precursor in the form of a rarefaction wave. The origin of the precursor is examined.

Time patterns of sperm whale codas recorded in the Mediterranean Sea 1985-1996.

PubMed

Pavan, G; Hayward, T J; Borsani, J F; Priano, M; Manghi, M; Fossati, C; Gordon, J

2000-06-01

A distinctive vocalization of the sperm whale, Physeter macrocephalus (=P. catodon), is the coda: a short click sequence with a distinctive stereotyped time pattern [Watkins and Schevill, J. Acoust. Soc. Am. 62, 1485-1490 (1977)]. Coda repertoires have been found to vary both geographically and with group affiliation [Weilgart and Whitehead, Behav. Ecol. Sociobiol. 40, 277-285 (1997)]. In this work, the click timings and repetition patterns of sperm whale codas recorded in the Mediterranean Sea are characterized statistically, and the context in which the codas occurred are also taken into consideration. A total of 138 codas were recorded in the central Mediterranean in the years 1985-1996 by several research groups using a number of different detection instruments, including stationary and towed hydrophones, sonobuoys and passive sonars. Nearly all (134) of the recorded codas share the same "3+1" (/// /) click pattern. Coda durations ranged from 456 to 1280 ms, with an average duration of 908 ms and a standard deviation of 176 ms. Most of the codas (a total of 117) belonged to 20 coda series. Each series was produced by an individual, in most cases by a mature male in a small group, and consisted of between 2 and 16 codas, emitted in one or more "bursts" of 1 to 13 codas spaced fairly regularly in time. The mean number of codas in a burst was 3.46, and the standard deviation was 2.65. The time interval ratios within a coda are parameterized by the coda duration and by the first two interclick intervals normalized by coda duration. These three parameters remained highly stable within each coda series, with coefficients of variation within the series averaging less than 5%. The interval ratios varied somewhat across the data sets, but were highly stable over 8 of the 11 data sets, which span 11 years and widely dispersed geographic locations. Somewhat different interval ratios were observed in the other three data sets; in one of these data sets, the variant codas were produced by a young whale. Two sets of presumed sperm whale codas recorded in 1996 had 5- and 6-click patterns; the observation of these new patterns suggests that sperm whale codas in the Mediterranean may have more variations than previously believed.

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.

Laser Development for Gravitational-Wave Interferometry in Space

NASA Technical Reports Server (NTRS)

Numata, Kenji; Camp, Jordan

2012-01-01

We are reporting on our development work on laser (master oscillator) and optical amplifier systems for gravitational-wave interferometry in space. Our system is based on the mature, wave-guided optics technologies, which have advantages over bulk, crystal-based, free-space optics. We are investing in a new type of compact, low-noise master oscillator, called the planar-waveguide external cavity diode laser. We made measurements, including those of noise, and performed space-qualification tests.

Near-source attenuation of high-frequency body waves beneath the New Madrid Seismic Zone

NASA Astrophysics Data System (ADS)

Pezeshk, Shahram; Sedaghati, Farhad; Nazemi, Nima

2018-03-01

Attenuation characteristics in the New Madrid Seismic Zone (NMSZ) are estimated from 157 local seismograph recordings out of 46 earthquakes of 2.6 ≤ M ≤ 4.1 with hypocentral distances up to 60 km and focal depths down to 25 km. Digital waveform seismograms were obtained from local earthquakes in the NMSZ recorded by the Center for Earthquake Research and Information (CERI) at the University of Memphis. Using the coda normalization method, we tried to determine Q values and geometrical spreading exponents at 13 center frequencies. The scatter of the data and trade-off between the geometrical spreading and the quality factor did not allow us to simultaneously derive both these parameters from inversion. Assuming 1/ R 1.0 as the geometrical spreading function in the NMSZ, the Q P and Q S estimates increase with increasing frequency from 354 and 426 at 4 Hz to 729 and 1091 at 24 Hz, respectively. Fitting a power law equation to the Q estimates, we found the attenuation models for the P waves and S waves in the frequency range of 4 to 24 Hz as Q P = (115.80 ± 1.36) f (0.495 ± 0.129) and Q S = (161.34 ± 1.73) f (0.613 ± 0.067), respectively. We did not consider Q estimates from the coda normalization method for frequencies less than 4 Hz in the regression analysis since the decay of coda amplitude was not observed at most bandpass filtered seismograms for these frequencies. Q S/ Q P > 1, for 4 ≤ f ≤ 24 Hz as well as strong intrinsic attenuation, suggest that the crust beneath the NMSZ is partially fluid-saturated. Further, high scattering attenuation indicates the presence of a high level of small-scale heterogeneities inside the crust in this region.

2016 Summer Series - Mark Kasevich: Quantum Mechanics at Macroscopic Scales

NASA Image and Video Library

2016-06-09

The underpinning of the universe is quantum mechanics. It can be used to explain the observed particle and wave nature of atoms. Atom interferometry uses the wave characteristics of atoms to investigate fundamental physics and advance our understanding of the macroscopic world. NASA is working with Dr. Mark Kasevich to apply this technology to advance astrophysics and improve navigation. In his seminar, Kasevich will delve into the world of atom interferometry, gravitational waves and quantum sensors.

Imaging of acoustic fields using optical feedback interferometry.

PubMed

Bertling, Karl; Perchoux, Julien; Taimre, Thomas; Malkin, Robert; Robert, Daniel; Rakić, Aleksandar D; Bosch, Thierry

2014-12-01

This study introduces optical feedback interferometry as a simple and effective technique for the two-dimensional visualisation of acoustic fields. We present imaging results for several pressure distributions including those for progressive waves, standing waves, as well as the diffraction and interference patterns of the acoustic waves. The proposed solution has the distinct advantage of extreme optical simplicity and robustness thus opening the way to a low cost acoustic field imaging system based on mass produced laser diodes.

Modulation of Polarization for Phase Extraction in Holographic Interferometry with Two References

NASA Astrophysics Data System (ADS)

Rodriguez-Zurita, G.; Vázquez-Castillo, J.-F.; Toto-Arellano, N.-I.; Meneses-Fabian, C.; Jiménez-Montero, L.-E.

2010-04-01

Heterodyne holographic interferometry allows high accuracy for phase-difference extraction between two wave fronts, especially when they are previously recorded in the same recording medium. In part, this is because the wave fronts can be affected by the recording process in a very similar way. The double reconstruction of a double-exposure hologram with two independent references results in a two-beam holographic interferometer with an arm conveying a wave modulated in frequency when using heterodyne techniques. The heterodyne frequency has been usually introduced with a plane mirror attached to a piezo-electric stack driven with a suitable variable power supply. For holographic interferometry, however, less attention has been devoted to alternative phase retrieval variants as, for example, phase-shifting with modulation of polarization or Fourier methods. In this work, we propose and demonstrate the basic capabilities of modulation of polarization performing as a phase-shifting technique for holographic interferometry with two references in a phase-stepping scheme. Experimental results are provided.

Instantaneous phase estimation to measure weak velocity variations: application to noise correlation on seismic data at the exploration scale

NASA Astrophysics Data System (ADS)

Corciulo, M.; Roux, P.; Campillo, M.; Dubucq, D.

2010-12-01

Passive imaging from noise cross-correlation is a consolidated analysis applied at continental and regional scale whereas its use at local scale for seismic exploration purposes is still uncertain. The development of passive imaging by cross-correlation analysis is based on the extraction of the Green’s function from seismic noise data. In a completely random field in time and space, the cross-correlation permits to retrieve the complete Green’s function whatever the complexity of the medium. At the exploration scale and at frequency above 2 Hz, the noise sources are not ideally distributed around the stations which strongly affect the extraction of the direct arrivals from the noise cross-correlation process. In order to overcome this problem, the coda waves extracted from noise correlation could be useful. Coda waves describe long and scattered paths sampling the medium in different ways such that they become sensitive to weak velocity variations without being dependent on the noise source distribution. Indeed, scatters in the medium behave as a set of secondary noise sources which randomize the spatial distribution of noise sources contributing to the coda waves in the correlation process. We developed a new technique to measure weak velocity changes based on the computation of the local phase variations (instantaneous phase variation or IPV) of the cross-correlated signals. This newly-developed technique takes advantage from the doublet and stretching techniques classically used to monitor weak velocity variation from coda waves. We apply IPV to data acquired in Northern America (Canada) on a 1-km side square seismic network laid out by 397 stations. Data used to study temporal variations are cross-correlated signals computed on 10-minutes ambient noise in the frequency band 2-5 Hz. As the data set was acquired over five days, about 660 files are processed to perform a complete temporal analysis for each stations pair. The IPV permits to estimate the phase shift all over the signal length without any assumption on the medium velocity. The instantaneous phase is computed using the Hilbert transform of the signal. For each stations pair, we measure the phase difference between successive correlation functions calculated for 10 minutes of ambient noise. We then fit the instantaneous phase shift using a first-order polynomial function. The measure of the velocity variation corresponds to the slope of this fit. Compared to other techniques, the advantage of IPV is a very fast procedure which efficiently provides the measure of velocity variation on large data sets. Both experimental results and numerical tests on synthetic signals will be presented to assess the reliability of the IPV technique, with comparison to the doublet and stretching methods.

Dense array recordings in the San Bernardino Valley of landers-big bear aftershocks: Basin surface waves, Moho reflections, and three-dimensional simulations

USGS Publications Warehouse

Frankel, Arthur

1994-01-01

Fourteen GEOS seismic recorders were deployed in the San Bernardino Valley to study the propagation of short-period (T ≈ 1 to 3 sec) surface waves and Moho reflections. Three dense arrays were used to determine the direction and speed of propagation of arrivals in the seismograms. The seismograms for a shallow (d ≈ 1 km) M 4.9 aftershock of the Big Bear earthquake exhibit a very long duration (60 sec) of sustained shaking at periods of about 2 sec. Array analysis indicates that these late arrivals are dominated by surface waves traveling in various directions across the Valley. Some energy is arriving from a direction 180° from the epicenter and was apparently reflected from the edge of the Valley opposite the source. A close-in aftershock (Δ = 25 km, depth = 7 km) displays substantial short-period surface waves at deep-soil sites. A three-dimensional (3D) finite difference simulation produces synthetic seismograms with durations similar to those of the observed records for this event, indicating the importance of S-wave to surface-wave conversion near the edge of the basin. Flat-layered models severely underpredict the duration and spectral amplification of this deep-soil site. I show an example where the coda wave amplitude ratio at 1 to 2 Hz between a deep-soil and a rock site does not equal the S-wave amplitude ratio, because of the presence of surface waves in the coda of the deep-soil site. For one of the events studied (Δ ≈ 90 km), there are sizable phases that are critically reflected from the Moho (PmP and SmS). At one of the rock sites, the SmS phase has a more peaked spectrum that the direct S wave.

Measurement of energy contrast of amplified ultrashort pulses using cross-polarized wave generation and spectral interferometry.

PubMed

Iliev, Marin; Meier, Amanda K; Galloway, Benjamin; Adams, Daniel E; Squier, Jeff A; Durfee, Charles G

2014-07-28

We present a method using spectral interferometry (SI) to characterize a pulse in the presence of an incoherent background such as amplified spontaneous emission (ASE). The output of a regenerative amplifier is interfered with a copy of the pulse that has been converted using third-order cross-polarized wave generation (XPW). The ASE shows as a pedestal background in the interference pattern. The energy contrast between the short-pulse component and the ASE is retrieved. The spectra of the interacting beams are obtained through an improvement to the self-referenced spectral interferometry (SRSI) analysis.

Infrasonic interferometry of stratospherically refracted microbaroms--a numerical study.

PubMed

Fricke, Julius T; El Allouche, Nihed; Simons, Dick G; Ruigrok, Elmer N; Wapenaar, Kees; Evers, Läslo G

2013-10-01

The atmospheric wind and temperature can be estimated through the traveltimes of infrasound between pairs of receivers. The traveltimes can be obtained by infrasonic interferometry. In this study, the theory of infrasonic interferometry is verified and applied to modeled stratospherically refracted waves. Synthetic barograms are generated using a raytracing model and taking into account atmospheric attenuation, geometrical spreading, and phase shifts due to caustics. Two types of source wavelets are implemented for the experiments: blast waves and microbaroms. In both numerical experiments, the traveltimes between the receivers are accurately retrieved by applying interferometry to the synthetic barograms. It is shown that microbaroms can be used in practice to obtain the traveltimes of infrasound through the stratosphere, which forms the basis for retrieving the wind and temperature profiles.

Development and applications of optical interferometric micrometrology in the Angstrom and subangstrom range

NASA Technical Reports Server (NTRS)

Lauer, James L.; Abel, Phillip B.

1988-01-01

The characteristics of the scanning tunneling microscope and atomic force microscope (AFM) are briefly reviewed, and optical methods, mainly interferometry, of sufficient resolution to measure AFM deflections are discussed. The methods include optical resonators, laser interferometry, multiple-beam interferometry, and evanescent wave detection. Experimental results using AFM are reviewed.

DEVELOPING AND EXPLOITING A UNIQUE DATASET FROM SOUTH AFRICAN GOLD MINES FOR SOURCE CHARACTERIZATION AND WAVE PROPAGATION

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

Julia, J; Nyblade, A; Gok, R

2009-07-06

In this project, we are developing and exploiting a unique seismic dataset to address the characteristics of small seismic events and the associated seismic signals observed at local (< 200 km) and regional (< 2000 km) distances. The dataset is being developed using mining-induced events from three deep gold mines in South Africa recorded on in-mine networks (< 1 km) composed of tens of high-frequency sensors, a network of four broadband stations installed as part of this project at the surface around the mines (1-10 km), and a network of existing broadband seismic stations at local/regional distances (50-1000 km) frommore » the mines. Data acquisition has now been completed and includes: (1) {approx}2 years (2007 and 2008) of continuous recording by the surface broadband array, and (2) tens of thousands of mine tremors in the -3.4 < ML < 4.4 local magnitude range. Events with positive magnitudes are generally well recorded by the surface-mine stations, while magnitudes of 3.0 and larger are seen at regional distances (up to {approx} 600 km) in high-pass filtered recordings. We have now completed the quality control of the in-mine data gathered at the three gold mines included in this project. The quality control consisted of: (1) identification and analysis of outliers among the P- and S-wave travel-time picks reported by the in-mine network operator and (2) verification of sensor orientations. The outliers have been identified through a 'Wadati filter' that searches for the largest subset of P- and S-wave travel-time picks consistent with a medium of uniform wave-speed. They have observed that outliers are generally picked at a few select stations. They have also detected that trigger times were mistakenly reported as origin times by the in-mine network operator, and corrections have been obtained from the intercept times in the Wadati diagrams. Sensor orientations have been verified through rotations into the local ray-coordinate system and, when possible, corrected by correlating waveforms obtained from theoretical and empirical rotation angles. Full moment tensor solutions have been obtained for selected events within the Savuka network volume, with moment magnitudes in the 0.5 < M{sub W} < 2.6 range. The solutions were obtained by inverting P-, SV-, and SH-spectral amplitudes measured on the theoretically rotated waveforms with visually assigned polarities. Most of the solutions have a non-zero implosive contribution (47 out of 76), while a small percentage is purely deviatoric (10 out of 76). The deviatoric moment tensors range from pure double couple to pure non-double couple mechanisms. We have also calibrated the regional stations for seismic coda-derived source spectra and moment magnitude using the envelope methodology of Mayeda et al. (2003). they tie the coda M{sub w} to independent values from waveform modeling. The resulting coda-based source spectra of shallow mining-related events show significant spectral peaking that is not seen in deeper tectonic earthquakes. This coda peaking may be an independent method of identifying shallow events and is similar to coda peaking with previously observed for Nevada explosions, where the frequency of the observed spectral peak correlates with the depth of burial (Murphy et al., 2009).« less

The Use of Barker Coded Signal on the Measurement of Wave Velocity of Rock

NASA Astrophysics Data System (ADS)

Zhu, W.; Wu, H.

2016-12-01

The wave velocity of the rock is important petro physics parameters; it can be used to calculate the elastic parameters, monitor the variations in the stress suffered by rock; and the velocity anisotropy reflects the rock anisotropy. Furthermore, since the coda wave is more sensitive to the change in rock properties, its velocity variation has been applied to monitor the variations in rock structures caused by varying temperature, stress, water saturation and other factors. However, the measurements of velocities heavily depend on signal-to-noise ratio (SNR) of the signals, because low signal-to-noise ratio would result in the difficulty in the identification of information. Fortunately coded excitation technique, widely used in radar, and medical system, just can solve the problem above. Although this technique can effectively improve the SNR and resolution of received signal, there exits very high sidelobes after traditional matched filter. So a pseudo inverse filter was successfully applied to suppress the side lobes. After comparing different coded signals, Barker coded signal are selected to measure the velocity of P wave of Plexiglas, sandstone, granite, marble with automatic measurement method, which are compared with the measurement results of single pulse; the results showed that the measurement of coded signals is more closely to the manual measurement. Moreover, coda wave measurement of loading granite was also made with Barker coded signal, the results of which also showed that the detection result of coded signals is better than that of the single pulse. In conclusion, the experiments verify the effectiveness and reliability of coded signals used on the measurement of wave velocity of rock.

Modeling of high‐frequency seismic‐wave scattering and propagation using radiative transfer theory

USGS Publications Warehouse

Zeng, Yuehua

2017-01-01

This is a study of the nonisotropic scattering process based on radiative transfer theory and its application to the observation of the M 4.3 aftershock recording of the 2008 Wells earthquake sequence in Nevada. Given a wide range of recording distances from 29 to 320 km, the data provide a unique opportunity to discriminate scattering models based on their distance‐dependent behaviors. First, we develop a stable numerical procedure to simulate nonisotropic scattering waves based on the 3D nonisotropic scattering theory proposed by Sato (1995). By applying the simulation method to the inversion of M 4.3 Wells aftershock recordings, we find that a nonisotropic scattering model, dominated by forward scattering, provides the best fit to the observed high‐frequency direct S waves and S‐wave coda velocity envelopes. The scattering process is governed by a Gaussian autocorrelation function, suggesting a Gaussian random heterogeneous structure for the Nevada crust. The model successfully explains the common decay of seismic coda independent of source–station locations as a result of energy leaking from multiple strong forward scattering, instead of backscattering governed by the diffusion solution at large lapse times. The model also explains the pulse‐broadening effect in the high‐frequency direct and early arriving S waves, as other studies have found, and could be very important to applications of high‐frequency wave simulation in which scattering has a strong effect. We also find that regardless of its physical implications, the isotropic scattering model provides the same effective scattering coefficient and intrinsic attenuation estimates as the forward scattering model, suggesting that the isotropic scattering model is still a viable tool for the study of seismic scattering and intrinsic attenuation coefficients in the Earth.

Denoising in digital speckle pattern interferometry using wave atoms.

PubMed

Federico, Alejandro; Kaufmann, Guillermo H

2007-05-15

We present an effective method for speckle noise removal in digital speckle pattern interferometry, which is based on a wave-atom thresholding technique. Wave atoms are a variant of 2D wavelet packets with a parabolic scaling relation and improve the sparse representation of fringe patterns when compared with traditional expansions. The performance of the denoising method is analyzed by using computer-simulated fringes, and the results are compared with those produced by wavelet and curvelet thresholding techniques. An application of the proposed method to reduce speckle noise in experimental data is also presented.

Advanced wave field sensing using computational shear interferometry

NASA Astrophysics Data System (ADS)

Falldorf, Claas; Agour, Mostafa; Bergmann, Ralf B.

2014-07-01

In this publication we give a brief introduction into the field of Computational Shear Interferometry (CoSI), which allows for determining arbitrary wave fields from a set of shear interferograms. We discuss limitations of the method with respect to the coherence of the underlying wave field and present various numerical methods to recover it from its sheared representations. Finally, we show experimental results on Digital Holography of objects with rough surface using a fiber coupled light emitting diode and quantitative phase contrast imaging as well as numerical refocusing in Differential Interference Contrast (DIC) microscopy.

Velocity changes at Volcán de Colima: Seismic and Experimental observations

NASA Astrophysics Data System (ADS)

Lamb, Oliver; Lavallée, Yan; De Angelis, Silvio; Varley, Nick; Reyes-Dávila, Gabriel; Arámbula-Mendoza, Raúl; Hornby, Adrian; Wall, Richard; Kendrick, Jackie

2016-04-01

Immediately prior to dome-building eruptions, volcano-seismic swarms are a direct consequence of strain localisation in the ascending magma. A deformation mechanism map of magma subjected to strain localisation will help develop accurate numerical models, which, coupled to an understanding of the mechanics driving monitored geophysical signals prior to lava eruption, will enhance forecasts. Here we present how seismic data from Volcán de Colima, Mexico, is combined with experimental work to give insights into fracturing in and around magma. Volcán de Colima is a dome-forming volcano that has been almost-continuously erupting since November 1998. We use coda-wave interferometry to quantify small changes in seismic velocity structure between pairs of similar earthquakes, employing waveforms from clusters of repeating earthquakes. The changes in all pairs of events were then used together to create a continuous function of velocity change at all stations within 7 km of the volcano from October to December 1998. We complement our seismic data with acoustic emission data from tensional experiments using samples collected at Volcán de Colima. Decreases in velocity and frequency reflect changes in the sample properties prior to failure. By comparing experimental and seismic observations, we may place constraints on the conditions of the natural seismogenic processes. Using a combination of field and experimental data promises a greater understanding of the processes affecting the rise of magma during an eruption. This will help with the challenge of forecasting and hazard mitigation during dome-forming eruptions worldwide.

CSDP: The seismology of continental thermal regimes

NASA Astrophysics Data System (ADS)

Aki, K.

1991-05-01

The past year continued to be extremely productive following up two major breakthroughs made in the preceding year. One of the breakthroughs was the derivation of an integral equation for time-dependent power spectra, which unified all the existing theories on seismic scattering including the radiative transfer theory for total energy and single-multiple scattering theories based on the ray approach. We successfully applied the method to the data from the United States Geological Survey (USGS) regional seismic arrays in central California, Long Valley and Island of Hawaii, and obtained convincing results on the scattering Q(sup -1) and intrinsic Q(sup -1) in these areas for the frequency range from 1 Hz to 20 Hz. The frequency dependence of scattering Q(sup -1) is, then, interpreted in terms of random medium with continuous or discrete scatterers. The other breakthrough was the application of T-matrix formulation to the seismic scattering problem. We are currently working on two dimensional inclusions with high and low velocity contrast with the surrounding medium. In addition to the above two main lines of research, we were able to use so-called 'T-phase' observed on the Island of Hawaii to map the Q value with a good spatial resolution. The T-phase is seismic waves converted from acoustic waves propagated through the sofar channel of the ocean. We found that we can eliminate remarkably well the frequency dependent recording site effect from the T-phase amplitude using the amplification factor for coda waves, further confirming the fundamental separability of source, path and site effects for coda waves, and proving the effectiveness of stochastic modeling of high-frequency seismic waves.

Coda: The Slow Fuse of Change--Obama, the Schools, Imagination, and Convergence

ERIC Educational Resources Information Center

Greene, Maxine

2009-01-01

The author began writing this essay the day after waves of euphoria swept over what appeared to be a profoundly altered public space. Americans had seen the most diverse gathering of people coming freely together to affirm a common purpose no one could quite yet define. No one had instructed them to come out in the cold of that inauguration…

Combining deterministic and stochastic velocity fields in the analysis of deep crustal seismic data

NASA Astrophysics Data System (ADS)

Larkin, Steven Paul

Standard crustal seismic modeling obtains deterministic velocity models which ignore the effects of wavelength-scale heterogeneity, known to exist within the Earth's crust. Stochastic velocity models are a means to include wavelength-scale heterogeneity in the modeling. These models are defined by statistical parameters obtained from geologic maps of exposed crystalline rock, and are thus tied to actual geologic structures. Combining both deterministic and stochastic velocity models into a single model allows a realistic full wavefield (2-D) to be computed. By comparing these simulations to recorded seismic data, the effects of wavelength-scale heterogeneity can be investigated. Combined deterministic and stochastic velocity models are created for two datasets, the 1992 RISC seismic experiment in southeastern California and the 1986 PASSCAL seismic experiment in northern Nevada. The RISC experiment was located in the transition zone between the Salton Trough and the southern Basin and Range province. A high-velocity body previously identified beneath the Salton Trough is constrained to pinch out beneath the Chocolate Mountains to the northeast. The lateral extent of this body is evidence for the ephemeral nature of rifting loci as a continent is initially rifted. Stochastic modeling of wavelength-scale structures above this body indicate that little more than 5% mafic intrusion into a more felsic continental crust is responsible for the observed reflectivity. Modeling of the wide-angle RISC data indicates that coda waves following PmP are initially dominated by diffusion of energy out of the near-surface basin as the wavefield reverberates within this low-velocity layer. At later times, this coda consists of scattered body waves and P to S conversions. Surface waves do not play a significant role in this coda. Modeling of the PASSCAL dataset indicates that a high-gradient crust-mantle transition zone or a rough Moho interface is necessary to reduce precritical PmP energy. Possibly related, inconsistencies in published velocity models are rectified by hypothesizing the existence of large, elongate, high-velocity bodies at the base of the crust oriented to and of similar scale as the basins and ranges at the surface. This structure would result in an anisotropic lower crust.

Portable fiber optic coupled Doppler interferometer system for detonation and shock wave diagnostics

NASA Technical Reports Server (NTRS)

Fleming, Kevin J.

1993-01-01

Testing and analysis of shock wave characteristics such as detonators and ground shock propagation frequently require a method of measuring velocity and displacement of the surface of interest. One method of measurement is Doppler interferometry. The VISAR (Velocity Interferometer System for Any Reflector) uses Doppler interferometry and has gained wide acceptance as the preferred tool for shock measurement. An important asset of VISAR is that it measures velocity and displacement nonintrusively.

Seismic interferometry of railroad induced ground motions: body and surface wave imaging

NASA Astrophysics Data System (ADS)

Quiros, Diego A.; Brown, Larry D.; Kim, Doyeon

2016-04-01

Seismic interferometry applied to 120 hr of railroad traffic recorded by an array of vertical component seismographs along a railway within the Rio Grande rift has recovered surface and body waves characteristic of the geology beneath the railway. Linear and hyperbolic arrivals are retrieved that agree with surface (Rayleigh), direct and reflected P waves observed by nearby conventional seismic surveys. Train-generated Rayleigh waves span a range of frequencies significantly higher than those recovered from typical ambient noise interferometry studies. Direct P-wave arrivals have apparent velocities appropriate for the shallow geology of the survey area. Significant reflected P-wave energy is also present at relatively large offsets. A common midpoint stack produces a reflection image consistent with nearby conventional reflection data. We suggest that for sources at the free surface (e.g. trains) increasing the aperture of the array to record wide angle reflections, in addition to longer recording intervals, might allow the recovery of deeper geological structure from railroad traffic. Frequency-wavenumber analyses of these recordings indicate that the train source is symmetrical (i.e. approaching and receding) and that deeper refracted energy is present although not evident in the time-offset domain. These results confirm that train-generated vibrations represent a practical source of high-resolution subsurface information, with particular relevance to geotechnical and environmental applications.

Theoretical Properties of Acoustical Speckle Interferometry.

DTIC Science & Technology

1980-09-01

an obvious one , since it was first performed in the acoustical holography. An acoustical speckle interferometry study has been demonstrated to be a...experiments in which pulses were used to study the propagation of the circumferential waves on aluminum cylinders immersed in water. In 1969, Bunney...destructive Testing SB. ABTRACT aCdo as revers. NW ass a" Id by block numb") Acoustical speckle interferometry is based locally on the elastodynamic response

Peptides and proteins in matter wave interferometry: Challenges and prospects

NASA Astrophysics Data System (ADS)

Sezer, Ugur; Geyer, Philipp; Mairhofer, Lukas; Brand, Christian; Doerre, Nadine; Rodewald, Jonas; Schaetti, Jonas; Koehler, Valentin; Mayor, Marcel; Arndt, Markus

2016-05-01

Recent developments in matter wave physics suggest that quantum interferometry with biologically relevant nanomaterials is becoming feasible for amino acids, peptides, proteins and RNA/DNA strands. Quantum interference of biomolecules is interesting as it can mimic Schrödinger's cat states with molecules of high mass, elevated temperature and biological functionality. Additionally, the high internal complexity can give rise to a rich variety of couplings to the environment and new handles for quantitative tests of quantum decoherence. Finally, matter wave interferometers are highly sensitive force sensors and pave the way for quantum-assisted measurements of biomolecular properties in interaction with tailored or biomimetic environments. Recent interferometer concepts such as the Kapitza-Dirac-Talbot-Lau interferometer (KDTLI) or the Optical Time-domain Matter Wave interferometer (OTIMA) have already proven their potential for quantum optics in the mass range beyond 10000 amu and for metrology. Here we show our advances in quantum interferometry with vitamins and peptides and discuss methods of realizing cold, intense and sufficiently slow beams of synthetically tailored or hydrated polypeptides with promising properties for a new generation of quantum optics.

The critical angle in seismic interferometry

USGS Publications Warehouse

Van Wijk, K.; Calvert, A.; Haney, M.; Mikesell, D.; Snieder, R.

2008-01-01

Limitations with respect to the characteristics and distribution of sources are inherent to any field seismic experiment, but in seismic interferometry these lead to spurious waves. Instead of trying to eliminate, filter or otherwise suppress spurious waves, crosscorrelation of receivers in a refraction experiment indicate we can take advantage of spurious events for near-surface parameter extraction for static corrections or near-surface imaging. We illustrate this with numerical examples and a field experiment from the CSM/Boise State University Geophysics Field Camp.

Equatorial anisotropy in the inner part of Earth's inner core from autocorrelation of earthquake coda

NASA Astrophysics Data System (ADS)

Wang, Tao; Song, Xiaodong; Xia, Han H.

2015-03-01

The Earth's solid inner core exhibits strong anisotropy, with wave velocity dependent on the direction of propagation due to the preferential alignment of iron crystals. Variations in the anisotropic structure, laterally and with depth, provide markers for measuring inner-core rotation and offer clues into the formation and dynamics of the inner core. Previous anisotropy models of the inner core have assumed a cylindrical anisotropy in which the symmetry axis is parallel to the Earth's spin axis. An inner part of the inner core with a distinct form of anisotropy has been suggested, but there is considerable uncertainty regarding its existence and characteristics. Here we analyse the autocorrelation of earthquake coda measured by global broadband seismic arrays between 1992 and 2012, and find that the differential travel times of two types of core-penetrating waves vary at low latitudes by up to 10 s. Our findings are consistent with seismic anisotropy in the innermost inner core that has a fast axis near the equatorial plane through Central America and Southeast Asia, in contrast to the north-south alignment of anisotropy in the outer inner core. The different orientations and forms of anisotropy may represent a shift in the evolution of the inner core.

Comment on "Localized water reverberation phases and its impact on back-projection images" by Yue et al. [2017

NASA Astrophysics Data System (ADS)

Fan, W.; Shearer, P. M.

2017-12-01

Fan and Shearer [2016] analyzed the 2012 Mw 7.2 Sumatra earthquake and reported that the earthquake dynamically triggered early aftershock/aftershocks 150 km away from the mainshock and 50 s later. The early aftershock/aftershocks were detected with teleseismic P-wave back-projection, coincided with passing surface waves, and showed observable seismic waveforms in a wide frequency range (0.02—5 Hz). Recently, however, Yue et al. [2017] interpreted these coda arrivals as water reverberations from the mainshock, based mostly on EGF analysis of a nearby M6 earthquake and a water-phase synthetic test. Here, we show detailed back-projection and waveform analysis of three M6 earthquakes within 100km of the Mw 7.2 earthquake, including the EGF event analyzed in Yue et al. [2017]. In addition, we examine the waveforms of three M5.5 reverse faulting earthquakes close to our detected early aftershock landward of the trench. Our results show that the coda energy in question is more likely caused by a separate earthquake near the trench than by a mainshock water reverberation phase, thus supporting our earlier conclusion that the detected coherent radiators are likely to be dynamically triggered early aftershock/aftershocks.

Application of optical interferometry in focused acoustic field measurement

NASA Astrophysics Data System (ADS)

Wang, Yuebing; Sun, Min; Cao, Yonggang; Zhu, Jiang

2018-07-01

Optical interferometry has been successfully applied in measuring acoustic pressures in plane-wave fields and spherical-wave fields. In this paper, the "effective" refractive index for focused acoustic fields was developed, through numerical simulation and experiments, the feasibility of the optical method in measuring acoustic fields of focused transducers was proved. Compared with the results from a membrane hydrophone, it was concluded that the optical method has good spatial resolution and is suitable for detecting focused fields with fluctuant distributions. The influences of a few factors (the generated lamb wave, laser beam directivity, etc.) were analyzed, and corresponding suggestions were proposed for effective application of this technology.

Studies of earthquakes stress drops, seismic scattering, and dynamic triggering in North America

NASA Astrophysics Data System (ADS)

Escudero Ayala, Christian Rene

I use the Relative Source Time Function (RSTF) method to determine the source properties of earthquakes within southeastern Alaska-northwestern Canada in a first part of the project, and earthquakes within the Denali fault in a second part. I deconvolve a small event P-arrival signal from a larger event by the following method: select arrivals with a tapered cosine window, fast fourier transform to obtain the spectrum, apply water level deconvolution technique, and bandpass filter before inverse transforming the result to obtain the RSTF. I compare the source processes of earthquakes within the area to determine stress drop differences to determine their relation with the tectonic setting of the earthquakes location. Results show an consistency with previous results, stress drop independent of moment implying self-similarity, correlation of stress drop with tectonic regime, stress drop independent of depth, stress drop depends of focal mechanism where strike-slip present larger stress drops, and decreasing stress drop as function of time. I determine seismic wave attenuation in the central western United States using coda waves. I select approximately 40 moderate earthquakes (magnitude between 5.5 and 6.5) located alocated along the California-Baja California, California-Nevada, Eastern Idaho, Gulf of California, Hebgen Lake, Montana, Nevada, New Mexico, off coast of Northern California, off coast of Oregon, southern California, southern Illinois, Vancouver Island, Washington, and Wyoming regions. These events were recorded by the EarthScope transportable array (TA) network from 2005 to 2009. We obtain the data from the Incorporated Research Institutions for Seismology (IRIS). In this study we implement a method based on the assumption that coda waves are single backscattered waves from randomly distributed heterogeneities to calculate the coda Q. The frequencies studied lie between 1 and 15 Hz. The scattering attenuation is calculated for frequency bands centered at 1.5, 3, 5, 7.5, 10.5, and 13.5 Hz. Coda Q present a great correlation with tectonic and geology setting, as well as the crustal thickness. I analyze global and Middle American Subduction Zone (MASZ) seismicity from 1998 to 2008 to quantify the transient stresses effects at teleseismic distances. I use the Bulletin of the International Seismological Centre Catalog (ISCCD) published by the Incorporated Research Institutions for Seismology (IRIS). To identify MASZ seismicity changes due to distant, large (Mw ¿ 7) earthquakes, I first identify local earthquakes that occurred before and after the mainshocks. I then group the local earthquakes within a cluster radius between 75 to 200 km. I obtain statistics based on characteristics of both mainshocks and local earthquakes clusters, such as cluster-mainshock azimuth, mainshock focal mechanism, and local earthquakes clusters within the MASZ. Based on the lateral variations of the dip along the subducted oceanic plate, I divide the Mexican subduction zone into four segments. I then apply the Paired Samples Statistical Test (PSST) to the sorted data to identify increment, decrement or either in the local seismicity associated with distant large earthquakes passage of surface waves. I identify dynamic triggering for all MASZ segments produced by large earthquakes emerging from specific azimuths, as well as, a decrease for some cases. I find no dependence of seismicity changes on mainshock focal mechanism.

Double-path acquisition of pulse wave transit time and heartbeat using self-mixing interferometry

NASA Astrophysics Data System (ADS)

Wei, Yingbin; Huang, Wencai; Wei, Zheng; Zhang, Jie; An, Tong; Wang, Xiulin; Xu, Huizhen

2017-06-01

We present a technique based on self-mixing interferometry for acquiring the pulse wave transit time (PWTT) and heartbeat. A signal processing method based on Continuous Wavelet Transform and Hilbert Transform is applied to extract potentially useful information in the self-mixing interference (SMI) signal, including PWTT and heartbeat. Then, some cardiovascular characteristics of the human body are easily acquired without retrieving the SMI signal by complicated algorithms. Experimentally, the PWTT is measured on the finger and the toe of the human body using double-path self-mixing interferometry. Experimental statistical data show the relation between the PWTT and blood pressure, which can be used to estimate the systolic pressure value by fitting. Moreover, the measured heartbeat shows good agreement with that obtained by a photoplethysmography sensor. The method that we demonstrate, which is based on self-mixing interferometry with significant advantages of simplicity, compactness and non-invasion, effectively illustrates the viability of the SMI technique for measuring other cardiovascular signals.

Coda Q Attenuation and Source Parameters Analysis in North East India Using Local Earthquakes

NASA Astrophysics Data System (ADS)

Mohapatra, A. K.; Mohanty, W. K.; Earthquake Seismology

2010-12-01

Alok Kumar Mohapatra1* and William Kumar Mohanty1 *Corresponding author: alokgpiitkgp@gmail.com 1Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, West Bengal, India. Pin-721302 ABSTRACT In the present study, the quality factor of coda waves (Qc) and the source parameters has been estimated for the Northeastern India, using the digital data of ten local earthquakes from April 2001 to November 2002. Earthquakes with magnitude range from 3.8 to 4.9 have been taken into account. The time domain coda decay method of a single back scattering model is used to calculate frequency dependent values of Coda Q (Qc) where as, the source parameters like seismic moment(Mo), stress drop, source radius(r), radiant energy(Wo),and strain drop are estimated using displacement amplitude spectrum of body wave using Brune's model. The earthquakes with magnitude range 3.8 to 4.9 have been used for estimation Qc at six central frequencies 1.5 Hz, 3.0 Hz, 6.0 Hz, 9.0 Hz, 12.0 Hz, and 18.0 Hz. In the present work, the Qc value of local earthquakes are estimated to understand the attenuation characteristic, source parameters and tectonic activity of the region. Based on a criteria of homogeneity in the geological characteristics and the constrains imposed by the distribution of available events the study region has been classified into three zones such as the Tibetan Plateau Zone (TPZ), Bengal Alluvium and Arakan-Yuma Zone (BAZ), Shillong Plateau Zone (SPZ). It follows the power law Qc= Qo (f/fo)n where, Qo is the quality factor at the reference frequency (1Hz) fo and n is the frequency parameter which varies from region to region. The mean values of Qc reveals a dependence on frequency, varying from 292.9 at 1.5 Hz to 4880.1 at 18 Hz. Average frequency dependent relationship Qc values obtained of the Northeastern India is 198 f 1.035, while this relationship varies from the region to region such as, Tibetan Plateau Zone (TPZ): Qc= 226 f 1.11, Bengal Alluvium and Arakan-Yuma Zone (BAZ) : Qc= 301 f 0.87, Shillong Plateau Zone (SPZ): Qc=126 fo 0.85. It indicates Northeastern India is seismically active but comparing of all zones in the study region the Shillong Plateau Zone (SPZ): Qc= 126 f 0.85 is seismically most active. Where as the Bengal Alluvium and Arakan-Yuma Zone (BAZ) are less active and out of three the Tibetan Plateau Zone (TPZ)is intermediate active. This study may be useful for the seismic hazard assessment. The estimated seismic moments (Mo), range from 5.98×1020 to 3.88×1023 dyne-cm. The source radii(r) are confined between 152 to 1750 meter, the stress drop ranges between 0.0003×103 bar to 1.04×103 bar, the average radiant energy is 82.57×1018 ergs and the strain drop for the earthquake ranges from 0.00602×10-9 to 2.48×10-9 respectively. The estimated stress drop values for NE India depicts scattered nature of the larger seismic moment value whereas, they show a more systematic nature for smaller seismic moment values. The estimated source parameters are in agreement to previous works in this type of tectonic set up. Key words: Coda wave, Seismic source parameters, Lapse time, single back scattering model, Brune's model, Stress drop and North East India.

Attenuation Characteristics of High Frequency Seismic Waves in Southern India

NASA Astrophysics Data System (ADS)

Sivaram, K.; Utpal, Saikia; Kanna, Nagaraju; Kumar, Dinesh

2017-07-01

We present a systematic study of seismic attenuation and its related Q structure derived from the spectral analysis of P-, S-waves in the southern India. The study region is separated into parts of EDC (Eastern Dharwar Craton), Western Dharwar Craton (WDC) and Southern Granulite Terrain (SGT). The study is carried out in the frequency range 1-20 Hz, using a single-station spectral ratio technique. We make use of about 45 earthquakes, recorded in a network of about 32 broadband 3-component seismograph-stations, having magnitudes ( M L) varying from 1.6 to 4.5, to estimate the average seismic body wave attenuation quality factors; Q P and Q S. Their estimated average values are observed to be fitting to the power law form of Q = Q 0 f n . The averaged power law relations for Southern Indian region (as a whole) are obtained as Q P = (95 ± 1.12) f (1.32±0.01); Q S = (128 ± 1.84) f (1.49±0.01). Based on the stations and recorded local earthquakes, for parts of EDC, WDC and SGT, the average power law estimates are obtained as: Q P = (97 ± 5) f (1.40±0.03), Q S = (116 ± 1.5) f (1.48±0.01) for EDC region; Q P = (130 ± 7) f (1.20±0.03), Q S = (103 ± 3) f (1.49±0.02) for WDC region; Q P = (68 ± 2) f (1.4±0.02), Q S = (152 ± 6) f (1.48±0.02) for SGT region. These estimates are weighed against coda Q ( Q C) estimates, using the coda decay technique, which is based on a weak backscattering of S-waves. A major observation in the study of body wave analysis is the low body wave Q ( Q 0 < 200), moderately high value of the frequency-exponent, ` n' (>0.5) and Q S/ Q P ≫ 1, suggesting lateral stretches of dominant scattering mode of seismic wave propagation. This primarily could be attributed to possible thermal anomalies and spread of partially fluid-saturated rock-masses in the crust and upper mantle of the southern Indian region, which, however, needs further laboratory studies. Such physical conditions might partly be correlated to the active seismicity and intraplate tectonism, especially in SGT and EDC regions, as per the observed low- Q P and Q S values. Additionally, the enrichment of coda waves and significance of scattering mechanisms is evidenced in our observation of Q C > Q S estimates. Lapse time study shows Q C values increasing with lapse time. High Q C values at 40 s lapse times in WDC indicate that it may be a relatively stable region. In the absence of detailed body wave attenuation studies in this region, the frequency dependent Q relationships developed here are useful for the estimation of earthquake source parameters of the region. Also, these relations may be used for the simulation of earthquake strong ground motions which are required for the estimation of seismic hazard, geotechnical and retrofitting analysis of critical structures in the region.

Modeling the blockage of Lg waves from 3-D variations in crustal structure

NASA Astrophysics Data System (ADS)

Sanborn, Christopher J.; Cormier, Vernon F.

2018-05-01

Comprised of S waves trapped in Earth's crust, the high frequency (2-10 Hz) Lg wave is important to discriminating earthquakes from explosions by comparing its amplitude and waveform to those of Pg and Pn waves. Lateral variations in crustal structure, including variations in crustal thickness, intrinsic attenuation, and scattering, affect the efficiency of Lg propagation and its consistency as a source discriminant at regional (200-1500 km) distances. To investigate the effects of laterally varying Earth structure on the efficiency of propagation of Lg and Pg, we apply a radiative transport algorithm to model complete, high-frequency (2-4 Hz), regional coda envelopes. The algorithm propagates packets of energy with ray theory through large-scale 3-D structure, and includes stochastic effects of multiple-scattering by small-scale heterogeneities within the large-scale structure. Source-radiation patterns are described by moment tensors. Seismograms of explosion and earthquake sources are synthesized in canonical models to predict effects on waveforms of paths crossing regions of crustal thinning (pull-apart basins and ocean/continent transitions) and thickening (collisional mountain belts), For paths crossing crustal thinning regions, Lg is amplified at receivers within the thinned region but strongly disrupted and attenuated at receivers beyond the thinned region. For paths crossing regions of crustal thickening, Lg amplitude is attenuated at receivers within the thickened region, but experiences little or no reduction in amplitude at receivers beyond the thickened region. The length of the Lg propagation within a thickened region and the complexity of over- and under-thrust crustal layers, can produce localized zones of Lg amplification or attenuation. Regions of intense scattering within laterally homogeneous models of the crust increase Lg attenuation but do not disrupt its coda shape.

Features of Radiation and Propagation of Seismic Waves in the Northern Caucasus: Manifestations in Regional Coda

NASA Astrophysics Data System (ADS)

Kromskii, S. D.; Pavlenko, O. V.; Gabsatarova, I. P.

2018-03-01

Based on the Anapa (ANN) seismic station records of 40 earthquakes ( M W > 3.9) that occurred within 300 km of the station since 2002 up to the present time, the source parameters and quality factor of the Earth's crust ( Q( f)) and upper mantle are estimated for the S-waves in the 1-8 Hz frequency band. The regional coda analysis techniques which allow separating the effects associated with seismic source (source effects) and with the propagation path of seismic waves (path effects) are employed. The Q-factor estimates are obtained in the form Q( f) = 90 × f 0.7 for the epicentral distances r < 120 km and in the form Q( f) = 90 × f1.0 for r > 120 km. The established Q( f) and source parameters are close to the estimates for Central Japan, which is probably due to the similar tectonic structure of the regions. The shapes of the source parameters are found to be independent of the magnitude of the earthquakes in the magnitude range 3.9-5.6; however, the radiation of the high-frequency components ( f > 4-5 Hz) is enhanced with the depth of the source (down to h 60 km). The estimates Q( f) of the quality factor determined from the records by the Sochi, Anapa, and Kislovodsk seismic stations allowed a more accurate determination of the seismic moments and magnitudes of the Caucasian earthquakes. The studies will be continued for obtaining the Q( f) estimates, geometrical spreading functions, and frequency-dependent amplification of seismic waves in the Earth's crust in the other regions of the Northern Caucasus.

Lateral variation of seismic attenuation in Sikkim Himalaya

NASA Astrophysics Data System (ADS)

Thirunavukarasu, Ajaay; Kumar, Ajay; Mitra, Supriyo

2017-01-01

We use data from local earthquakes (mb ≥ 3.0) recorded by the Sikkim broad-band seismograph network to study the frequency-dependent attenuation of the crust and uppermost mantle. These events have been relocated using body wave phase data from local and regional seismograms. The decay of coda amplitudes at a range of central frequencies (1 to 12 Hz) has been measured for 74 earthquake-receiver pairs. These measurements are combined to estimate the frequency-dependent coda Q of the form Q( f) = Q0 f η. The estimated Q0 values range from 80 to 200, with an average of 123 ± 29; and η ranges from 0.92 to 1.04, with an average of 0.98 ± 0.04. To study the lateral variation of Q0 and η, we regionalized the measured Q values by combining all the earthquake-receiver path measurements through a back projection algorithm. We consider a single back-scatter model for the coda waves with elliptical sampling and parametrize the sampled area using 0.2° square grids. A nine-point spatial smoothening (similar to spatial Gaussian filter) is applied to stabilize the inversion. This is done at every frequency to observe the spatial variation of Q( f) and subsequently combined to obtain η variations. Results of our study reveal that the Sikkim Himalaya is characterized by low Q0 (80-100) compared to the foreland basin to its south (150-200) and the Nepal Himalaya to its west (140-160). The low Q and high η in Sikkim Himalaya is attributed to extrinsic scattering attenuation from structural heterogeneity and active faults within the crust, and intrinsic attenuation due to anelasticity in the hotter lithosphere beneath the actively deforming mountain belt. Similar low Q and high η values had also been observed in northwest and Garhwal-Kumaun Himalaya.

Distribution of fine-scale mantle heterogeneity from observations of Pdiff coda

USGS Publications Warehouse

Earle, P.S.; Shearer, P.M.

2001-01-01

We present stacked record sections of Global Seismic Network data that image the average amplitude and polarization of the high-frequency Pdiff coda and investigate their implications on the depth extent of fine-scale (~10 km) mantle heterogeneity. The extended 1-Hz coda lasts for at least 150 sec and is observed to a distance of 130??. The coda's polarization angle is about the same as the main Pdiff arrival (4.4 sec/deg) and is nearly constant with time. Previous studies show that multiple scattering from heterogeneity restricted to the lowermost mantle generates an extended Pdiff coda with a constant polarization. Here we present an alternative model that satisfies our Pdiff observations. The model consists of single scattering from weak (~1%) fine-scale (~2 km) structures distributed throughout the mantle. Although this model is nonunique, it demonstrates that Pdiff coda observations do not preclude the existence of scattering contributions from the entire mantle.

Source signature estimation from multimode surface waves via mode-separated virtual real source method

NASA Astrophysics Data System (ADS)

Gao, Lingli; Pan, Yudi

2018-05-01

The correct estimation of the seismic source signature is crucial to exploration geophysics. Based on seismic interferometry, the virtual real source (VRS) method provides a model-independent way for source signature estimation. However, when encountering multimode surface waves, which are commonly seen in the shallow seismic survey, strong spurious events appear in seismic interferometric results. These spurious events introduce errors in the virtual-source recordings and reduce the accuracy of the source signature estimated by the VRS method. In order to estimate a correct source signature from multimode surface waves, we propose a mode-separated VRS method. In this method, multimode surface waves are mode separated before seismic interferometry. Virtual-source recordings are then obtained by applying seismic interferometry to each mode individually. Therefore, artefacts caused by cross-mode correlation are excluded in the virtual-source recordings and the estimated source signatures. A synthetic example showed that a correct source signature can be estimated with the proposed method, while strong spurious oscillation occurs in the estimated source signature if we do not apply mode separation first. We also applied the proposed method to a field example, which verified its validity and effectiveness in estimating seismic source signature from shallow seismic shot gathers containing multimode surface waves.

GLINT. Gravitational-wave laser INterferometry triangle

NASA Astrophysics Data System (ADS)

Aria, Shafa; Azevedo, Rui; Burow, Rick; Cahill, Fiachra; Ducheckova, Lada; Holroyd, Alexa; Huarcaya, Victor; Järvelä, Emilia; Koßagk, Martin; Moeckel, Chris; Rodriguez, Ana; Royer, Fabien; Sypniewski, Richard; Vittori, Edoardo; Yttergren, Madeleine

2017-11-01

When the universe was roughly one billion years old, supermassive black holes (103-106 solar masses) already existed. The occurrence of supermassive black holes on such short time scales are poorly understood in terms of their physical or evolutionary processes. Our current understanding is limited by the lack of observational data due the limits of electromagnetic radiation. Gravitational waves as predicted by the theory of general relativity have provided us with the means to probe deeper into the history of the universe. During the ESA Alpach Summer School of 2015, a group of science and engineering students devised GLINT (Gravitational-wave Laser INterferometry Triangle), a space mission concept capable of measuring gravitational waves emitted by black holes that have formed at the early periods after the big bang. Morespecifically at redshifts of 15 < z < 30(˜ 0.1 - 0.3× 109 years after the big bang) in the frequency range 0.01 - 1 Hz. GLINT design strain sensitivity of 5× 10^{-24} 1/√ { {Hz}} will theoretically allow the study of early black holes formations as well as merging events and collapses. The laser interferometry, the technology used for measuring gravitational waves, monitors the separation of test masses in free-fall, where a change of separation indicates the passage of a gravitational wave. The test masses will be shielded from disturbing forces in a constellation of three geocentric orbiting satellites.

DEVELOPING AND EXPLOITING A UNIQUE SEISMIC DATA SET FROM SOUTH AFRICAN GOLD MINES FOR SOURCE CHARACTERIZATION AND WAVE PROPAGATION

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

Julia, J; Nyblade, A A; Gok, R

2008-07-08

In this project, we are developing and exploiting a unique seismic data set to address the characteristics of small seismic events and the associated seismic signals observed at local (< 200 km) and regional (< 2000 km) distances. The dataset is being developed using mining-induced events from 3 deep gold mines in South Africa recorded on inmine networks (< 1 km) comprised of tens of high-frequency sensors, a network of 4 broadband stations installed as part of this project at the surface around the mines (1-10 km), and a network of existing broadband seismic stations at local/regional distances (50-1000 km)more » from the mines. After 1 year of seismic monitoring of mine activity (2007), over 10,000 events in the range -3.4 < ML < 4.4 have been catalogued and recorded by the in-mine networks. Events with positive magnitudes are generally well recorded by the surface-mine stations, while magnitudes 3.0 and larger are seen at regional distances (up to {approx}600 km) in high-pass filtered recordings. We have analyzed in-mine recordings in detail at one of the South African mines (Savuka) to (i) improve on reported hypocentral locations, (ii) verify sensor orientations, and (iii) determine full moment tensor solutions. Hypocentral relocations on all catalogued events have been obtained from P- and S-wave travel-times reported by the mine network operator through an automated procedure that selects travel-times falling on Wadati lines with slopes in the 0.6-0.7 range; sensor orientations have been verified and, when possible, corrected by correlating P-, SV-, and SH-waveforms obtained from theoretical and empirical (polarization filter) rotation angles; full moment tensor solutions have been obtained by inverting P-, SV-, and SH- spectral amplitudes measured on the theoretically rotated waveforms with visually assigned polarities. The relocation procedure has revealed that origin times often necessitate a negative correction of a few tenths of second and that hypocentral locations may move a few hundreds of meters. The full moment tensor determination has revealed that the most common focal mechanism (47 out of 82 solutions for events in the 0.2 < ML < 4.1 range) consists of a similar percentage of isotropic (implosive) and deviatoric components, with a normal fault-type best double couple. We have also calibrated the regional stations for seismic coda derived source spectra and moment magnitude using the envelope methodology of Mayeda et al (2003). We tie the coda Mw to independent values from waveform modeling. The resulting coda-based source spectra of shallow mining-related events show significant spectral peaking that is not seen in deeper tectonic earthquakes. This coda peaking may be an independent method of identifying shallow events and is similar to coda peaking previously observed for Nevada explosions, where the frequency of the observed spectral peak correlates with depth of burial (Murphy et al., 2008).« less

Swarms of repeating stick-slip icequakes triggered by snow loading at Mount Rainier volcano

NASA Astrophysics Data System (ADS)

Allstadt, Kate; Malone, Stephen D.

2014-05-01

We have detected over 150,000 small (M < 1) low-frequency ( 1-5 Hz) repeating earthquakes over the past decade at Mount Rainier volcano, most of which were previously undetected. They are located high (>3000 m) on the glacier-covered edifice and occur primarily in weeklong to monthlong swarms composed of simultaneous distinct families of events. Each family contains up to thousands of earthquakes repeating at regular intervals as often as every few minutes. Mixed polarity first motions, a linear relationship between recurrence interval and event size, and strong correlation between swarm activity and snowfall suggest the source is stick-slip basal sliding of glaciers. The sudden added weight of snow during winter storms triggers a temporary change from smooth aseismic sliding to seismic stick-slip sliding in locations where basal conditions are favorable to frictional instability. Coda wave interferometry shows that source locations migrate over time at glacial speeds, starting out fast and slowing down over time, indicating a sudden increase in sliding velocity triggers the transition to stick-slip sliding. We propose a hypothesis that this increase is caused by the redistribution of basal fluids rather than direct loading because of a 1-2 day lag between snow loading and earthquake activity. This behavior is specific to winter months because it requires the inefficient drainage of a distributed subglacial drainage system. Identification of the source of these frequent signals offers a view of basal glacier processes, discriminates against alarming volcanic noises, documents short-term effects of weather on the cryosphere, and has implications for repeating earthquakes, in general.

Measuring the effects of pore-pressure changes on seismic amplitude using crosswell continuous active-source seismic monitoring (CASSM)

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

Marchesini, Pierpaolo; Daley, Thomas; Ajo-Franklin, Jonathan

Monitoring of time-varying reservoir properties, such as the state of stress, is a primary goal of geophysical investigations, including for geological sequestration of CO 2, enhanced hydrocarbon recovery (EOR), and other subsurface engineering activities. In this work, we used Continuous Active-Source Seismic Monitoring (CASSM), with cross-well geometry, to measure variation in seismic coda amplitude, as a consequence of effective stress change (in the form of changes in pore fluid pressure). To our knowledge, the presented results are the first in-situ example of such crosswell measurement at reservoir scale and in field conditions. Data compliment the findings of our previous workmore » which investigated the relationship between pore fluid pressure and seismic velocity (velocity-stress sensitivity) using the CASSM system at the same field site (Marchesini et al., 2017, in review). We find that P-wave coda amplitude decreases with decreasing pore pressure (increasing effective stress).« less

Near Source Contributions to Teleseismic P Wave Coda and Regional Phases

DTIC Science & Technology

1991-04-27

Pasadena, CA 91-125 Mr. William J. Best Prof. F. A. Dahlen 907 Westwood Drive Geological and Geophysical Sciences Vienna, VA 22180 Princeton...Station S-CUBED University of California A Division of Maxwell Laboratory Berkeley, CA 94720 P.O.Box 1620 La Jolla, CA 92038-1620 2 Prof. William ...Geosciences- Building #77 University of Arizona Tucson, AZ 85721 Dr. William Wortman Mission Research Corporation 8560 Cinderbed Rd. Suite # 700 Newington

Digital off-axis holographic interferometry with simulated wavefront.

PubMed

Belashov, A V; Petrov, N V; Semenova, I V

2014-11-17

The paper presents a novel algorithm based on digital holographic interferometry and being promising for evaluation of phase variations from highly noisy or modulated by speckle-structures digital holograms. The suggested algorithm simulates an interferogram in finite width fringes, by analogy with classical double exposure holographic interferometry. Thus obtained interferogram is then processed as a digital hologram. The advantages of the suggested approach are demonstrated in numerical experiments on calculations of differences in phase distributions of wave fronts modulated by speckle structure, as well as in a physical experiment on the analysis of laser-induced heating dynamics of an aqueous solution of a photosensitizer. It is shown that owing to the inherent capability of the approach to perform adjustable smoothing of compared wave fronts, the resulting difference undergoes noise filtering. This capability of adjustable smoothing may be used to minimize losses in spatial resolution. Since the method allows to vary an observation angle of compared wave fields, an opportunity to compensate misalignment of optical axes of these wave fronts arises. This feature can be required, for example, when using two different setups in comparative digital holography or for compensation of recording system displacements during a set of exposures in studies of dynamic processes.

Are syllabification and resyllabification strategies phonotactically directed in French children with dyslexia? A preliminary report.

PubMed

Maïonchi-Pino, Norbert; de Cara, Bruno; Ecalle, Jean; Magnan, Annie

2012-04-01

In this study, the authors queried whether French-speaking children with dyslexia were sensitive to consonant sonority and position within syllable boundaries to influence a phonological syllable-based segmentation in silent reading. Participants included 15 French-speaking children with dyslexia, compared with 30 chronological age-matched and reading level-matched controls. Children were tested with an audiovisual recognition task. A target pseudoword (TOLPUDE) was simultaneously presented visually and auditorily and then was compared with a printed test pseudoword that either was identical or differed after the coda deletion (TOPUDE) or the onset deletion (TOLUDE). The intervocalic consonant sequences had either a sonorant coda-sonorant onset (TOR.LADE), sonorant coda-obstruent onset (TOL.PUDE), obstruent coda-sonorant onset (DOT.LIRE), or obstruent coda-obstruent onset (BIC.TADE) sonority profile. All children processed identity better than they processed deletion, especially with the optimal sonorant coda-obstruent onset sonority profile. However, children preserved syllabification (coda deletion; TO.PUDE) rather than resyllabification (onset deletion; TO.LUDE) with intervocalic consonant sequence reductions, especially when sonorant codas were deleted but the optimal intersyllable contact was respected. It was surprising to find that although children with dyslexia generally exhibit phonological and acoustic-phonetic impairments (voicing), they showed sensitivity to the optimal sonority profile and a preference for preserved syllabification. The authors proposed a sonority-modulated explanation to account for phonological syllable-based processing. Educational implications are discussed.

Breakdown of equipartition in diffuse fields caused by energy leakage

NASA Astrophysics Data System (ADS)

Margerin, L.

2017-05-01

Equipartition is a central concept in the analysis of random wavefields which stipulates that in an infinite scattering medium all modes and propagation directions become equally probable at long lapse time in the coda. The objective of this work is to examine quantitatively how this conclusion is affected in an open waveguide geometry, with a particular emphasis on seismological applications. To carry our this task, the problem is recast as a spectral analysis of the radiative transfer equation. Using a discrete ordinate approach, the smallest eigenvalue and associated eigenfunction of the transfer equation, which control the asymptotic intensity distribution in the waveguide, are determined numerically with the aid of a shooting algorithm. The inverse of this eigenvalue may be interpreted as the leakage time of the diffuse waves out of the waveguide. The associated eigenfunction provides the depth and angular distribution of the specific intensity. The effect of boundary conditions and scattering anisotropy is investigated in a series of numerical experiments. Two propagation regimes are identified, depending on the ratio H∗ between the thickness of the waveguide and the transport mean path in the layer. The thick layer regime H∗ > 1 has been thoroughly studied in the literature in the framework of diffusion theory and is briefly considered. In the thin layer regime H∗ < 1, we find that both boundary conditions and scattering anisotropy leave a strong imprint on the leakage effect. A parametric study reveals that in the presence of a flat free surface, the leakage time is essentially controlled by the mean free time of the waves in the layer in the limit H∗ → 0. By contrast, when the free surface is rough, the travel time of ballistic waves propagating through the crust becomes the limiting factor. For fixed H∗, the efficacy of leakage, as quantified by the inverse coda quality factor, increases with scattering anisotropy. For sufficiently thin layers H∗≈ 1/5, the energy flux is predominantly directed parallel to the surface and equipartition breaks down. Qualitatively, the anisotropy of the intensity field is found to increase with the inverse non-dimensional leakage time, with the scattering mean free time as time scale. Because it enhances leakage, a rough free surface may result in stronger anisotropy of the intensity field than a flat surface, for the same bulk scattering properties. Our work identifies leakage as a potential explanation for the large deviation from isotropy observed in the coda of body waves.

Attenuation of coda waves in the Aswan Reservoir area, Egypt

NASA Astrophysics Data System (ADS)

Mohamed, H. H.; Mukhopadhyay, S.; Sharma, J.

2010-09-01

Coda attenuation characteristics of Aswan Reservoir area of Egypt were analyzed using data recorded by a local earthquake network operated around the reservoir. 330 waveforms obtained from 28 earthquakes recorded by a network of 13 stations were used for this analysis. Magnitude of these earthquakes varied between 1.4 and 2.5. The maximum epicentral distance and depth of focus of these earthquakes were 45 km and 16 km respectively. Single back-scattering method was used for estimation of coda Q ( Qc). The Q0 values ( Qc at 1 Hz) vary between 54 and 100 and frequency dependence parameter " n" values vary between 1 and 1.2 for lapse time varying between 15 s and 60 s. It is observed that coda Q ( Qc) and related parameters are similar at similar lapse times to those observed for those for Koyna, India, where reservoir induced seismicity is also observed. For both regions these parameters are also similar to those observed for tectonically active regions of the world, although Aswan is located in a moderately active region and Koyna is located in a tectonically stable region. However, Qc does not increase uniformly with increasing lapse time, as is observed for several parts of the world. Converting lapse time to depth/distance it is observed that Qc becomes lower or remains almost constant at around 70 to 90 km and 120 km depth/distance. This indicates presence of more attenuative material at those depth levels or distances compared to their immediate surroundings. It is proposed that this variation indicates presence of fluid filled fractures and/or partial melts at some depths/distance from the area of study. The Qc values are higher than those obtained for the Gulf of Suez and Al Dabbab region of Egypt at distances greater than 300 km from the study area by other workers. The turbidity decreases with depth in the study area.

3D Coda Attenuation Tomography of Acoustic Emission Data from Laboratory Samples as a tool for imaging pre-failure deformation mechanisms

NASA Astrophysics Data System (ADS)

Vinciguerra, S.; King, T. I.; Benson, P. M.; De Siena, L.

2017-12-01

In recent years, 3D and 4D seismic tomography have unraveled medium changes during the seismic cycle or before eruptive events. As our resolving power increases, however, complex structures increasingly affect images. Being able to interpret and understand these features requires a multi-discipline approach combining different methods, each sensitive to particular properties of the sub-surface. Rock deformation laboratory experiments can relate seismic properties to the evolving medium quantitatively. Here, an array of 1 MHz Piezo-Electric Transducers has recorded high-quality low-noise acoustic emission (AE) data during triaxial compressional experiments. Samples of Carrara Marble, Darley Dale Sandstone and Westerly Granite were deformed in saturated conditions representative of a depth of about 1 km until brittle failure. Using a time window around sample failure, AE data were filtered between 5 and 75 KHz and processed using a 3D P-coda attenuation-tomography method. Ratios of P-direct to P-coda energies calculated for each source-receiver path were inverted using the coda normalisation method for values of Q (P-wave quality factor). The results show Q-variation with respect to an average Q. Q is a combination of the effects of scattering attenuation (Qs) and intrinsic attenuation Q (Qi), which can be correlated to the sample structure. Qs primary controls energy dissipation in the presence at acoustic impedance (AI) surfaces and at fracture tips, independently of rock type, while pore fluid effects dissipate energy (Qi). Damaged zones appear as high-Q and low-Q anomalies in unsaturated and saturated samples, respectively. We have attributed frequency-dependent high-Q to resonance in the presence of AI surfaces. Low Q areas appear behind AI surfaces and are interpreted as energy shadows. These shadows can affect attenuation tomography imaging at field scale.

Transitioning the Coda Methodology to Full 2-D for P and S Codas (Postprint)

DTIC Science & Technology

2011-12-30

had great success at local and near-regional distances for simple regions, for crustal S transitioning to Lg coda types, and at longer distances for...coda. This effect was critical for yield estimation work and will be equally critical in other areas of low crustal Q and Lg blockage, such as Iran...for making a change to the methodology is quite simple. First, regions of monitoring interest are rarely tectonically simple, and in fact, most

Statistical parameters of random heterogeneity estimated by analysing coda waves based on finite difference method

NASA Astrophysics Data System (ADS)

Emoto, K.; Saito, T.; Shiomi, K.

2017-12-01

Short-period (<1 s) seismograms are strongly affected by small-scale (<10 km) heterogeneities in the lithosphere. In general, short-period seismograms are analysed based on the statistical method by considering the interaction between seismic waves and randomly distributed small-scale heterogeneities. Statistical properties of the random heterogeneities have been estimated by analysing short-period seismograms. However, generally, the small-scale random heterogeneity is not taken into account for the modelling of long-period (>2 s) seismograms. We found that the energy of the coda of long-period seismograms shows a spatially flat distribution. This phenomenon is well known in short-period seismograms and results from the scattering by small-scale heterogeneities. We estimate the statistical parameters that characterize the small-scale random heterogeneity by modelling the spatiotemporal energy distribution of long-period seismograms. We analyse three moderate-size earthquakes that occurred in southwest Japan. We calculate the spatial distribution of the energy density recorded by a dense seismograph network in Japan at the period bands of 8-16 s, 4-8 s and 2-4 s and model them by using 3-D finite difference (FD) simulations. Compared to conventional methods based on statistical theories, we can calculate more realistic synthetics by using the FD simulation. It is not necessary to assume a uniform background velocity, body or surface waves and scattering properties considered in general scattering theories. By taking the ratio of the energy of the coda area to that of the entire area, we can separately estimate the scattering and the intrinsic absorption effects. Our result reveals the spectrum of the random inhomogeneity in a wide wavenumber range including the intensity around the corner wavenumber as P(m) = 8πε2a3/(1 + a2m2)2, where ε = 0.05 and a = 3.1 km, even though past studies analysing higher-frequency records could not detect the corner. Finally, we estimate the intrinsic attenuation by modelling the decay rate of the energy. The method proposed in this study is suitable for quantifying the statistical properties of long-wavelength subsurface random inhomogeneity, which leads the way to characterizing a wider wavenumber range of spectra, including the corner wavenumber.

Coda Wave Attenuation Characteristics for North Anatolian Fault Zone, Turkey

NASA Astrophysics Data System (ADS)

Sertcelik, Fadime; Guleroglu, Mehmet

2017-10-01

North Anatolian Fault Zone, on which large earthquakes have occurred in the past, migrates regularly from east to west, and it is one of the most active faults in the world. The purpose of this study is to estimate the coda wave quality factor (Qc) for each of the five sub regionsthat were determined according to the fault rupture of these large earthquakes and along the fault. 978 records have been analyzed for 1.5, 3, 6, 9, 12 and 18 Hz frequencies by Single Backscattering Method. Along the fault, the variations in the Qc with lapse time are determined via, Qc = (136±25)f(0.96±0.027), Qc = (208±22)f(0.85±0.02) Qc = (307±28)f(0.72±0.025) at 20, 30, 40 sec lapse times, respectively. The estimated average frequency-dependence quality factor for all lapse time are; Qc(f) = (189±26)f(0.86±0.02) for Karliova-Tokat region; Qc(f) = (216±19)f(0.76±0.018) for Tokat-Çorum region; Qc(f) = (232±18)f(0.76±0.019) for Çorum-Adapazari region; Qc(f) = (280±28)f(0.79±0.021) for Adapazari-Yalova region; Qc(f) = (252±26)f(0.81±0.022) for Yalova-Gulf of Saros region. The coda wave quality factor at all the lapse times and frequencies is Qc(f) = (206±15)f(0.85±0.012) in the study area. The most change of Qc with lapse time is determined at Yalova-Saros region. The result may be related to heterogeneity degree of rapidly decreases towards the deep crust like compared to the other sub region. Moreover, the highest Qc is calculated between Adapazari - Yalova. It was interpreted as a result of seismic energy released by 1999 Kocaeli Earthquake. Besides, it couldn't be established a causal relationship between the regional variation of Qc with frequency and lapse time associated to migration of the big earthquakes. These results have been interpreted as the attenuation mechanism is affected by both regional heterogeneity and consist of a single or multi strands of the fault structure.

Continent-Wide Maps of Lg Coda Q Variation and Rayleigh-wave Attenuation Variation for Eurasia

DTIC Science & Technology

2007-01-30

lithosphere and crustal strain lead us to infer that fluids, originating by hydrothermal release from subducting lithosphere or other upper mantle heat...relatively low Qo values in the Arabian Peninsula are produced by fluids that have been released in the upper mantle by hydrothermal processes and have...Advection of plumes in mantle flow: Implications for hotspot motion, mantle viscosity and plume distribution, Geophys. J. Int., 132, 412–434. Talebian, M

Scattering - a probe to Earth's small scale structure

NASA Astrophysics Data System (ADS)

Rost, S.; Earle, P.

2009-05-01

Much of the short-period teleseismic wavefield shows strong evidence for scattered waves in extended codas trailing the main arrivals predicted by ray theory. This energy mainly originates from high-frequency body waves interacting with fine-scale volumetric heterogeneities in the Earth. Studies of this energy revealed much of what we know about Earth's structure at scale lengths around 10 km throughout the Earth from crust to core. From these data we can gain important information about the mineral-physical and geochemical constitution of the Earth that is inaccessible to many other seismic imaging techniques. Previous studies used scattered energy related to PKP, PKiKP, and Pdiff to identify and map the small-scale structure of the mantle and core. We will present observations related to the core phases PKKP and P'P' to study fine-scale mantle heterogeneities. These phases are maximum travel-time phases with respect to perturbations at their reflection points. This allows observation of the scattered energy as precursors to the main phase avoiding common problems with traditional coda phases which arrive after the main pulse. The precursory arrival of the scattered energy allows the separation between deep Earth and crustal contributions to the scattered wavefield for certain source-receiver configurations. Using the information from these scattered phases we identify regions of the mantle that shows increased scattering potential likely linked to larger scale mantle structure identified in seismic tomography and geodynamical models.

Testing the effect of computer-generated hologram fabrication error in a cylindrical interferometry system

NASA Astrophysics Data System (ADS)

Wang, Qingquan; Yu, Yingjie; Mou, Kebing

2017-10-01

This paper presents a method of testing the effect of computer-generated hologram (CGH) fabrication error in a cylindrical interferometry system. An experimental system is developed for calibrating the effect of this error. In the calibrating system, a mirror with high surface accuracy is placed at the focal axis of the cylindrical wave. After transmitting through the CGH, the reflected cylindrical wave can be transformed into a plane wave again, and then the plane wave interferes with the reference plane wave. Finally, the double-pass transmitted wavefront of the CGH, representing the effect of the CGH fabrication error in the experimental system, is obtained by analyzing the interferogram. The mathematical model of misalignment aberration removal in the calibration system is described, and the feasibility is demonstrated via the simulation system established in Zemax. With the mathematical polynomial, most of the possible misalignment errors can be estimated with the least-squares fitting algorithm, and then the double-pass transmitted wavefront of the CGH can be obtained by subtracting the misalignment errors from the result extracted from the real experimental system. Compared to the standard double-pass transmitted wavefront given by Diffraction International Ltd., which manufactured the CGH used in the experimental system, the result is desirable. We conclude that the proposed method is effective in calibrating the effect of the CGH error in the cylindrical interferometry system for the measurement of cylindricity error.

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Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-31

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Differences in coda voicing trigger changes in gestural timing: A test case from the American English diphthong /aɪ/

PubMed Central

Dahan, Delphine

2016-01-01

We investigate the hypothesis that duration and spectral differences in vowels before voiceless versus voiced codas originate from a single source, namely the reorganization of articulatory gestures relative to one another in time. As a test case, we examine the American English diphthong /aɪ/, in which the acoustic manifestations of the nucleus /a/ and offglide /ɪ/ gestures are relatively easy to identify, and we use the ratio of nucleus-to-offglide duration as an index of the temporal distance between these gestures. Experiment 1 demonstrates that, in production, the ratio is smaller before voiceless codas than before voiced codas; this effect is consistent across speakers as well as changes in speech rate and phrasal position. Experiment 2 demonstrates that, in perception, diphthongs with contextually incongruent ratios delay listeners’ identification of target words containing voiceless codas, even when the other durational and spectral correlates of voicing remain intact. This, we argue, is evidence that listeners are sensitive to the gestural origins of voicing differences. Both sets of results support the idea that the voicing contrast triggers changes in timing: gestures are close to one another in time before voiceless codas, but separated from one another before voiced codas. PMID:26966337

Near-field interferometry of a free-falling nanoparticle from a point-like source

NASA Astrophysics Data System (ADS)

Bateman, James; Nimmrichter, Stefan; Hornberger, Klaus; Ulbricht, Hendrik

2014-09-01

Matter-wave interferometry performed with massive objects elucidates their wave nature and thus tests the quantum superposition principle at large scales. Whereas standard quantum theory places no limit on particle size, alternative, yet untested theories—conceived to explain the apparent quantum to classical transition—forbid macroscopic superpositions. Here we propose an interferometer with a levitated, optically cooled and then free-falling silicon nanoparticle in the mass range of one million atomic mass units, delocalized over >150 nm. The scheme employs the near-field Talbot effect with a single standing-wave laser pulse as a phase grating. Our analysis, which accounts for all relevant sources of decoherence, indicates that this is a viable route towards macroscopic high-mass superpositions using available technology.

TOMO-ETNA Experiment -Etna volcano, Sicily, investigated with active and passive seismic methods

NASA Astrophysics Data System (ADS)

Luehr, Birger-G.; Ibanez, Jesus M.; Díaz-Moreno, Alejandro; Prudencio, Janire; Patane, Domenico; Zieger, Toni; Cocina, Ornella; Zuccarello, Luciano; Koulakov, Ivan; Roessler, Dirk; Dahm, Torsten

2017-04-01

The TOMO-ETNA experiment, as part of the European Union project "MEDiterranean SUpersite Volcanoes (MED-SUV)", was devised to image the crustal structure beneath Etna by using state of the art passive and active seismic methods. Activities on-land and offshore are aiming to obtain new high-resolution seismic images to improve the knowledge of crustal structures existing beneath the Etna volcano and northeast Sicily up to the Aeolian Islands. In a first phase (June 15 - July 24, 2014) at Etna volcano and surrounding areas two removable seismic networks were installed composed by 80 Short Period and 20 Broadband stations, additionally to the existing network belonging to the "Istituto Nazionale di Geofisica e Vulcanologia" (INGV). So in total air-gun shots could be recorded by 168 stations onshore plus 27 ocean bottom instruments offshore in the Tyrrhenian and Ionian Seas. Offshore activities were performed by Spanish and Italian research vessels. In a second phase the broadband seismic network remained operative until October 28, 2014, as well as offshore surveys during November 19 -27, 2014. Active seismic sources were generated by an array of air-guns mounted in the Spanish Oceanographic vessel "Sarmiento de Gamboa" with a power capacity of up to 5.200 cubic inches. In total more than 26.000 shots were fired and more than 450 local and regional earthquakes could be recorded and will be analyzed. For resolving a volcanic structure the investigation of attenuation and scattering of seismic waves is important. In contrast to existing studies that are almost exclusively based on S-wave signals emitted by local earthquakes, here air-gun signals were investigated by applying a new methodology based on the coda energy ratio defined as the ratio between the energy of the direct P-wave and the energy in a later coda window. It is based on the assumption that scattering caused by heterogeneities removes energy from direct P-waves that constitutes the earliest possible arrival to any part later in the seismic wave train. As an independent proxy of the scattering strength along the ray path, we measure the peak delay time of a direct P-wave, which is well correlated with the coda energy ratio. As a result the distribution of heterogeneities around Etna could be visualized as the projection of the observation in directions of incident rays at the stations. Increased seismic scattering could be detected in the volcano and east of it. The strong heterogeneous zone towards the east coast of Sicily supports earlier observations, and is interpreted as a potential signature of the eastward sliding volcano flank. Beside the investigation of P-wave scattering the new seismic tomography software PARTOS (Passive Active Ray Tomography Software) has been developed based on a joint inversion of active and passive seismic sources. With PARTOS real data inversion has been carried out using three different subsets: i) active data; ii) passive data; and iii) joint dataset, permitting to obtain a new tomographic approach of that region.

Predicting Lg Coda Using Synthetic Seismograms and Media With Stochastic Heterogeneity

NASA Astrophysics Data System (ADS)

Tibuleac, I. M.; Stroujkova, A.; Bonner, J. L.; Mayeda, K.

2005-12-01

Recent examinations of the characteristics of coda-derived Sn and Lg spectra for yield estimation have shown that the spectral peak of Nevada Test Site (NTS) explosion spectra is depth-of-burial dependent, and that this peak is shifted to higher frequencies for Lop Nor explosions at the same depths. To confidently use coda-based yield formulas, we need to understand and predict coda spectral shape variations with depth, source media, velocity structure, topography, and geological heterogeneity. We present results of a coda modeling study to predict Lg coda. During the initial stages of this research, we have acquired and parameterized a deterministic 6 deg. x 6 deg. velocity and attenuation model centered on the Nevada Test Site. Near-source data are used to constrain density and attenuation profiles for the upper five km. The upper crust velocity profiles are quilted into a background velocity profile at depths greater than five km. The model is parameterized for use in a modified version of the Generalized Fourier Method in two dimensions (GFM2D). We modify this model to include stochastic heterogeneities of varying correlation lengths within the crust. Correlation length, Hurst number and fractional velocity perturbation of the heterogeneities are used to construct different realizations of the random media. We use nuclear explosion and earthquake cluster waveform analysis, as well as well log and geological information to constrain the stochastic parameters for a path between the NTS and the seismic stations near Mina, Nevada. Using multiple runs, we quantify the effects of variations in the stochastic parameters, of heterogeneity location in the crust and attenuation on coda amplitude and spectral characteristics. We calibrate these parameters by matching synthetic earthquake Lg coda envelopes to coda envelopes of local earthquakes with well-defined moments and mechanisms. We generate explosion synthetics for these calibrated deterministic and stochastic models. Secondary effects, including a compensated linear vector dipole source, are superposed on the synthetics in order to adequately characterize the Lg generation. We use this technique to characterize the effects of depth of burial on the coda spectral shapes.

Radio interferometry: Techniques for Geodesy. [conference

NASA Technical Reports Server (NTRS)

1980-01-01

Progress in the development and application of radio interferometry as a tool for geophysical research is reported and discussed. Among the topics reviewed are: Surveys of is the Seventies, Movements, Terrestrial and Celestial, Degrees Kelvin and Degrees of Phase, the Mark 3 VLBI System, Waves of the Future and other Emissions, and Adherence and Coherence in Networks, and Plans.

Measurement of spatio-temporal field distribution of THz pulses in electro-optic crystal by interferometry method

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

Chizhov, P A; Ushakov, A A; Bukin, V V

2015-05-31

We propose a scheme for measuring the spatial distribution of the THz pulse electric field strength in an electro-optic crystal using optical interferometry. The resulting images of the field distribution from a test source with a spherical wave front are presented. (extreme light fields and their applications)

The California Oak Disease and Arthropod (CODA) Database

Treesearch

Tedmund J. Swiecki; Elizabeth A. Bernhardt; Richard A. Arnold

1997-01-01

The California Oak Disease and Arthropod (CODA) host index database is a compilation of information on agents that colonize or feed on oaks in California. Agents in the database include plant-feeding insects and mites, nematodes, microorganisms, viruses, and abiotic disease agents. CODA contains summarized information on hosts, agents, information sources, and the...

Support for equatorial anisotropy of Earth's inner-inner core from seismic interferometry at low latitudes

NASA Astrophysics Data System (ADS)

Wang, Tao; Song, Xiaodong

2018-03-01

Anisotropy of Earth's inner core provides a key role to understand its evolution and the Earth's magnetic field. Recently, using autocorrelations from earthquake's coda, we found an equatorial anisotropy of the inner-inner core (IIC), in apparent contrast to the polar anisotropy of the outer-inner core (OIC). To reduce the influence of the polar anisotropy and reduce possible contaminations from the large Fresnel zone of the PKIKP2 and PKIIKP2 phases at low frequencies, we processed coda noise of large earthquakes (10,000-40,000 s after magnitude ≥7.0) from stations at low latitudes (within ±35°) during 1990-2013. Using a number of improved procedures of both autocorrelation and cross-correlation, we extracted 52 array-stacked high-quality empirical Green's functions (EGFs), an increase of over 60% from our previous study. The high-quality data allow us to measure the relative arrival times by automatic waveform cross correlation. The results show large variation (∼10.9 s) in the differential times between the PKIKP2 and PKIIKP2 phases. The estimated influence of the Fresnel zone is insignificant (<1.1 s), compared to the observed data variation and measurement uncertainty. The observed time residuals match very well previous IIC model with a quasi-equatorial fast axis (near Central America and the Southeast Asia) and the spatial pattern from the low-latitude measurements is similar to the previous global dataset, including the fast axis and two low-velocity open rings, thus providing further support for the equatorial anisotropy model of the IIC. Speculations for the shift of the fast axis between the OIC and the IIC include: change of deformation regimes during the inner core history, change of geomagnetic field, and a proto-inner core.

Ultra-sensitive inertial sensors via neutral-atom interferometry

NASA Technical Reports Server (NTRS)

Clauser, John F.

1989-01-01

Upon looking at the various colossal interferometers, etc., discussed at this conference to test gravitational theory, one cannot avoid feeling that easier approaches exist. The use of low velocity, neutral atom matter waves in place of electromagnetic waves in sensitive inertial interferometer configurations is proposed. For applications, spacecraft experiments to sense a drag-free condition, to measure the Lense-Thirring precession, to measure the gravitomagnetic effect and/or the earth's geopotential (depending on altitude), and to detect long period gravitational waves are considered. Also, a terrestrial precision test of the equivalence principle on spin polarized atoms, capable of detecting effects of the 5th force is considered. While the ideas described herein are preliminary, the orders of magnitude are sufficiently tantalizing to warrant further study. Although existing proposed designs may be adequate for some of these experiments, the use of matter-wave interferometry offers reduced complexity and cost, and an absence of cryogenics.

The Spanish of Ponce, Puerto Rico: A Phonetic, Phonological, and Intonational Analysis

ERIC Educational Resources Information Center

Luna, Kenneth Vladimir

2010-01-01

This study investigates four aspects of Puerto Rican Spanish as represented in the Autonomous Municipality of Ponce: the behavior of coda /[alveolar flap]/, the behavior of /r/, the different realizations of coda /s/, and its intonational phonology. Previous studies on Puerto Rican Spanish report that coda /[alveolar flap]/ is normally realized as…

Doppler synthetic aperture radar interferometry: a novel SAR interferometry for height mapping using ultra-narrowband waveforms

NASA Astrophysics Data System (ADS)

Yazıcı, Birsen; Son, Il-Young; Cagri Yanik, H.

2018-05-01

This paper introduces a new and novel radar interferometry based on Doppler synthetic aperture radar (Doppler-SAR) paradigm. Conventional SAR interferometry relies on wideband transmitted waveforms to obtain high range resolution. Topography of a surface is directly related to the range difference between two antennas configured at different positions. Doppler-SAR is a novel imaging modality that uses ultra-narrowband continuous waves (UNCW). It takes advantage of high resolution Doppler information provided by UNCWs to form high resolution SAR images. We introduce the theory of Doppler-SAR interferometry. We derive an interferometric phase model and develop the equations of height mapping. Unlike conventional SAR interferometry, we show that the topography of a scene is related to the difference in Doppler frequency between two antennas configured at different velocities. While the conventional SAR interferometry uses range, Doppler and Doppler due to interferometric phase in height mapping; Doppler-SAR interferometry uses Doppler, Doppler-rate and Doppler-rate due to interferometric phase in height mapping. We demonstrate our theory in numerical simulations. Doppler-SAR interferometry offers the advantages of long-range, robust, environmentally friendly operations; low-power, low-cost, lightweight systems suitable for low-payload platforms, such as micro-satellites; and passive applications using sources of opportunity transmitting UNCW.

Dynamic acousto-elastic testing of concrete with a coda-wave probe: comparison with standard linear and nonlinear ultrasonic techniques.

PubMed

Shokouhi, Parisa; Rivière, Jacques; Lake, Colton R; Le Bas, Pierre-Yves; Ulrich, T J

2017-11-01

The use of nonlinear acoustic techniques in solids consists in measuring wave distortion arising from compliant features such as cracks, soft intergrain bonds and dislocations. As such, they provide very powerful nondestructive tools to monitor the onset of damage within materials. In particular, a recent technique called dynamic acousto-elasticity testing (DAET) gives unprecedented details on the nonlinear elastic response of materials (classical and non-classical nonlinear features including hysteresis, transient elastic softening and slow relaxation). Here, we provide a comprehensive set of linear and nonlinear acoustic responses on two prismatic concrete specimens; one intact and one pre-compressed to about 70% of its ultimate strength. The two linear techniques used are Ultrasonic Pulse Velocity (UPV) and Resonance Ultrasound Spectroscopy (RUS), while the nonlinear ones include DAET (fast and slow dynamics) as well as Nonlinear Resonance Ultrasound Spectroscopy (NRUS). In addition, the DAET results correspond to a configuration where the (incoherent) coda portion of the ultrasonic record is used to probe the samples, as opposed to a (coherent) first arrival wave in standard DAET tests. We find that the two visually identical specimens are indistinguishable based on parameters measured by linear techniques (UPV and RUS). On the contrary, the extracted nonlinear parameters from NRUS and DAET are consistent and orders of magnitude greater for the damaged specimen than those for the intact one. This compiled set of linear and nonlinear ultrasonic testing data including the most advanced technique (DAET) provides a benchmark comparison for their use in the field of material characterization. Copyright © 2017 Elsevier B.V. All rights reserved.

Far infrared diagnostics of electron concentration in combustion MHD plasmas using interferometry and Faraday rotation

NASA Astrophysics Data System (ADS)

Kuzmenko, P. J.

1985-12-01

The plasma electrical conductivity is a key parameter in determining the efficiency of an magnetohydrodynamic (MHD) generator. Electromagnetic waves offer an accurate, non-intrusive probe. The electron concentration and mobility may be deduced from the refractive index and absorption coefficient measured with an interferometer. The first experiment used an HCOOH laser at 393.6 microns feeding a Michelson interferometer mounted around a combustor duct with open ports. Simultaneous measurements of positive ion density and plasma temperature made with a Langmuir probe and line reversal apparatus verified the operation of the interferometer. With a magnetic field present, measurement of the polarization rotation and induced ellipticity in a wave traveling along the field provides information on the plasma conductivity. Compared to interferometry, diagnostic apparatus based on Faraday rotation offers simpler optics and requires far less stringent mechanical stability at a cost of lower sensitivity. An advanced detection scheme, using a polarizing beam splitter improved the sensitivity to be comparable to that of interferometry. Interferometry is the preferred technique for small scale, high accuracy measurements, with Faraday rotation reserved for large systems or measurements within a working generator.

SEISMIC SOURCE SCALING AND DISCRIMINATION IN DIVERSE TECTONIC ENVIRONMENTS

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

Abercrombie, R E; Mayeda, K; Walter, W R

2008-07-08

The objectives of this study are to improve low-magnitude (concentrating on M2.5-5) regional seismic discrimination by performing a thorough investigation of earthquake source scaling using diverse, high-quality datasets from varied tectonic regions. Local-to-regional high-frequency discrimination requires an estimate of how earthquakes scale with size. Walter and Taylor (2002) developed the MDAC (Magnitude and Distance Amplitude Corrections) method to empirically account for these effects through regional calibration. The accuracy of these corrections has a direct impact on our ability to identify clandestine explosions in the broad regional areas characterized by low seismicity. Unfortunately our knowledge at small magnitudes (i.e., m{sub b}more » < {approx} 4.0) is poorly resolved, and source scaling remains a subject of on-going debate in the earthquake seismology community. Recently there have been a number of empirical studies suggesting scaling of micro-earthquakes is non-self-similar, yet there are an equal number of compelling studies that would suggest otherwise. It is not clear whether different studies obtain different results because they analyze different earthquakes, or because they use different methods. Even in regions that are well studied, such as test sites or areas of high seismicity, we still rely on empirical scaling relations derived from studies taken from half-way around the world at inter-plate regions. We investigate earthquake sources and scaling from different tectonic settings, comparing direct and coda wave analysis methods that both make use of empirical Green's function (EGF) earthquakes to remove path effects. Analysis of locally recorded, direct waves from events is intuitively the simplest way of obtaining accurate source parameters, as these waves have been least affected by travel through the earth. But finding well recorded earthquakes with 'perfect' EGF events for direct wave analysis is difficult, limits the number of earthquakes that can be studied. We begin with closely-located, well-correlated earthquakes. We use a multi-taper method to obtain time-domain source-time-functions by frequency division. We only accept an earthquake and EGF pair if they are able to produce a clear, time-domain source pulse. We fit the spectral ratios and perform a grid-search about the preferred parameters to ensure the fits are well constrained. We then model the spectral (amplitude) ratio to determine source parameters from both direct P and S waves. We analyze three clusters of aftershocks from the well-recorded sequence following the M5 Au Sable Forks, NY, earthquake to obtain some of the first accurate source parameters for small earthquakes in eastern North America. Each cluster contains a M{approx}2, and two contain M{approx}3, as well as smaller aftershocks. We find that the corner frequencies and stress drops are high (averaging 100 MPa) confirming previous work suggesting that intraplate continental earthquakes have higher stress drops than events at plate boundaries. We also demonstrate that a scaling breakdown suggested by earlier work is simply an artifact of their more band-limited data. We calculate radiated energy, and find that the ratio of Energy to seismic Moment is also high, around 10{sup -4}. We estimate source parameters for the M5 mainshock using similar methods, but our results are more doubtful because we do not have a EGF event that meets our preferred criteria. The stress drop and energy/moment ratio for the mainshock are slightly higher than for the aftershocks. Our improved, and simplified coda wave analysis method uses spectral ratios (as for the direct waves) but relies on the averaging nature of the coda waves to use EGF events that do not meet the strict criteria of similarity required for the direct wave analysis. We have applied the coda wave spectral ratio method to the 1999 Hector Mine mainshock (M{sub w} 7.0, Mojave Desert) and its larger aftershocks, and also to several sequences in Italy with M{approx}6 mainshocks. The Italian earthquakes have higher stress drops than the Hector Mine sequence, but lower than Au Sable Forks. These results show a departure from self-similarity, consistent with previous studies using similar regional datasets. The larger earthquakes have higher stress drops and energy/moment ratios. We perform a preliminary comparison of the two methods using the M5 Au Sable Forks earthquake. Both methods give very consistent results, and we are applying the comparison to further events.« less

Slip Behavior of the Queen Charlotte Plate Boundary Before and After the 2012, MW 7.8 Haida Gwaii Earthquake: Evidence From Repeating Earthquakes

NASA Astrophysics Data System (ADS)

Hayward, Tim W.; Bostock, Michael G.

2017-11-01

The Queen Charlotte plate boundary, near Haida Gwaii, B.C., includes the dextral, strike-slip, Queen Charlotte Fault (QCF) and the subduction interface between the downgoing Pacific and overriding North American plates. In this study, we present a comprehensive repeating earthquake catalog that represents an effective slip meter for both structures. The catalog comprises 712 individual earthquakes (0.3≤MW≤3.5) arranged into 224 repeating earthquake families on the basis of waveform similarity and source separation estimates from coda wave interferometry. We employ and extend existing relationships for repeating earthquake magnitudes and slips to provide cumulative slip histories for the QCF and subduction interface in six adjacent zones within the study area between 52.3°N and 53.8°N. We find evidence for creep on both faults; however, creep rates are significantly less than plate motion rates, which suggests partial locking of both faults. The QCF exhibits the highest degrees of locking south of 52.8°N, which indicates that the seismic hazard for a major strike-slip earthquake is highest in the southern part of the study area. The 28 October 2012, MW 7.8 Haida Gwaii thrust earthquake occurred in our study area and altered the slip dynamics of the plate boundary. The QCF is observed to undergo accelerated, right-lateral slip for 1-2 months following the earthquake. The subduction interface exhibits afterslip thrust motion that persists for the duration of the study period (i.e., 3 years and 2 months after the Haida Gwaii earthquake). Afterslip is greatest (5.7-8.4 cm/yr) on the periphery of the main rupture zone of the Haida Gwaii event.

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.

Ideal-observer detectability in photon-counting differential phase-contrast imaging using a linear-systems approach

PubMed Central

Fredenberg, Erik; Danielsson, Mats; Stayman, J. Webster; Siewerdsen, Jeffrey H.; Åslund, Magnus

2012-01-01

Purpose: To provide a cascaded-systems framework based on the noise-power spectrum (NPS), modulation transfer function (MTF), and noise-equivalent number of quanta (NEQ) for quantitative evaluation of differential phase-contrast imaging (Talbot interferometry) in relation to conventional absorption contrast under equal-dose, equal-geometry, and, to some extent, equal-photon-economy constraints. The focus is a geometry for photon-counting mammography. Methods: Phase-contrast imaging is a promising technology that may emerge as an alternative or adjunct to conventional absorption contrast. In particular, phase contrast may increase the signal-difference-to-noise ratio compared to absorption contrast because the difference in phase shift between soft-tissue structures is often substantially larger than the absorption difference. We have developed a comprehensive cascaded-systems framework to investigate Talbot interferometry, which is a technique for differential phase-contrast imaging. Analytical expressions for the MTF and NPS were derived to calculate the NEQ and a task-specific ideal-observer detectability index under assumptions of linearity and shift invariance. Talbot interferometry was compared to absorption contrast at equal dose, and using either a plane wave or a spherical wave in a conceivable mammography geometry. The impact of source size and spectrum bandwidth was included in the framework, and the trade-off with photon economy was investigated in some detail. Wave-propagation simulations were used to verify the analytical expressions and to generate example images. Results: Talbot interferometry inherently detects the differential of the phase, which led to a maximum in NEQ at high spatial frequencies, whereas the absorption-contrast NEQ decreased monotonically with frequency. Further, phase contrast detects differences in density rather than atomic number, and the optimal imaging energy was found to be a factor of 1.7 higher than for absorption contrast. Talbot interferometry with a plane wave increased detectability for 0.1-mm tumor and glandular structures by a factor of 3–4 at equal dose, whereas absorption contrast was the preferred method for structures larger than ∼0.5 mm. Microcalcifications are small, but differ from soft tissue in atomic number more than density, which is favored by absorption contrast, and Talbot interferometry was barely beneficial at all within the resolution limit of the system. Further, Talbot interferometry favored detection of “sharp” as opposed to “smooth” structures, and discrimination tasks by about 50% compared to detection tasks. The technique was relatively insensitive to spectrum bandwidth, whereas the projected source size was more important. If equal photon economy was added as a restriction, phase-contrast efficiency was reduced so that the benefit for detection tasks almost vanished compared to absorption contrast, but discrimination tasks were still improved close to a factor of 2 at the resolution limit. Conclusions: Cascaded-systems analysis enables comprehensive and intuitive evaluation of phase-contrast efficiency in relation to absorption contrast under requirements of equal dose, equal geometry, and equal photon economy. The benefit of Talbot interferometry was highly dependent on task, in particular detection versus discrimination tasks, and target size, shape, and material. Requiring equal photon economy weakened the benefit of Talbot interferometry in mammography. PMID:22957600

Constraining the source location of the 30 May 2015 (Mw 7.9) Bonin deep-focus earthquake using seismogram envelopes of high-frequency P waveforms: Occurrence of deep-focus earthquake at the bottom of a subducting slab

NASA Astrophysics Data System (ADS)

Takemura, Shunsuke; Maeda, Takuto; Furumura, Takashi; Obara, Kazushige

2016-05-01

In this study, the source location of the 30 May 2015 (Mw 7.9) deep-focus Bonin earthquake was constrained using P wave seismograms recorded across Japan. We focus on propagation characteristics of high-frequency P wave. Deep-focus intraslab earthquakes typically show spindle-shaped seismogram envelopes with peak delays of several seconds and subsequent long-duration coda waves; however, both the main shock and aftershock of the 2015 Bonin event exhibited pulse-like P wave propagations with high apparent velocities (~12.2 km/s). Such P wave propagation features were reproduced by finite-difference method simulations of seismic wave propagation in the case of slab-bottom source. The pulse-like P wave seismogram envelopes observed from the 2015 Bonin earthquake show that its source was located at the bottom of the Pacific slab at a depth of ~680 km, rather than within its middle or upper regions.

Ultrafast dynamic response of single crystal β-HMX

NASA Astrophysics Data System (ADS)

Zaug, Joseph M.; Armstrong, Michael R.; Crowhurst, Jonathan C.; Radousky, Harry B.; Ferranti, Louis; Swan, Raymond; Gross, Rick; Teslich, Nick E.; Wall, Mark A.; Austin, Ryan A.; Fried, Laurence E.

2017-01-01

We report results from ultrafast compression experiments conducted on β-HMX single crystals. Results consist of nominally 12 picosecond time-resolved wave profile data, (ultrafast time domain interferometry -TDI measurements), that were analyzed to determine high-velocity wave speeds as a function of piston velocity. TDI results are used to validate calculations of anisotropic stress-strain behavior of shocked loaded energetic materials. Our previous results derived using a 350 ps duration compression drive revealed anisotropic elastic wave response in single crystal β-HMX from (110) and (010) impact planes. Here we present results using a 1.05 ns duration compression drive with a 950 ps interferometry window to extend knowledge of the anisotropic dynamic response of β-HMX within eight microns of the initial impact plane. We observe two distinct wave profiles from (010) and three wave profiles from (010) impact planes. The (110) impact plane wave speeds typically exceed (010) impact plane wave speeds at the same piston velocities. The development of multiple hydrodynamic wave profiles begins at 20 GPa for the (110) impact plane and 28 GPa for the (10) impact plane. We compare our ultrafast TDI results with previous gun and plate impact results on β-HMX and PBX9501.

Using Earthquake Location and Coda Attenuation Analysis to Explore Shallow Structures Above the Socorro Magma Body, New Mexico

NASA Astrophysics Data System (ADS)

Schmidt, J. P.; Bilek, S. L.; Worthington, L. L.; Schmandt, B.; Aster, R. C.

2017-12-01

The Socorro Magma Body (SMB) is a thin, sill-like intrusion with a top at 19 km depth covering approximately 3400 km2 within the Rio Grande Rift. InSAR studies show crustal uplift patterns linked to SMB inflation with deformation rates of 2.5 mm/yr in the area of maximum uplift with some peripheral subsidence. Our understanding of the emplacement history and shallow structure above the SMB is limited. We use a large seismic deployment to explore seismicity and crustal attenuation in the SMB region, focusing on the area of highest observed uplift to investigate the possible existence of fluid/magma in the upper crust. We would expect to see shallower earthquakes and/or higher attenuation if high heat flow, fluid or magma is present in the upper crust. Over 800 short period vertical component geophones situated above the northern portion of the SMB were deployed for two weeks in 2015. This data is combined with other broadband and short period seismic stations to detect and locate earthquakes as well as to estimate seismic attenuation. We use phase arrivals from the full dataset to relocate a set of 33 local/regional earthquakes recorded during the deployment. We also measure amplitude decay after the S-wave arrival to estimate coda attenuation caused by scattering of seismic waves and anelastic processes. Coda attenuation is estimated using the single backscatter method described by Aki and Chouet (1975), filtering the seismograms at 6, 9 and 12 Hz center frequencies. Earthquakes occurred at 2-13 km depth during the deployment, but no spatial patterns linked with the high uplift region were observed over this short duration. Attenuation results for this deployment suggest Q ranging in values of 130 to 2000, averaging around Q of 290, comparable to Q estimates of other studies of the western US. With our dense station coverage, we explore attenuation over smaller scales, and find higher attenuation for stations in the area of maximum uplift relative to stations outside of the maximum uplift, which could indicate upper crustal heterogeneities with shallow process above the magma body in this area.

Coda Q and its Frequency Dependence in the Eastern Himalayan and Indo-Burman Plate Boundary Systems

NASA Astrophysics Data System (ADS)

Mitra, S.; Kumar, A.

2015-12-01

We use broadband waveform data for 305 local earthquakes from the Eastern Himalayan and Indo-Burman plate boundary systems, to model the seismic attenuation in NE India. We measure the decay in amplitude of coda waves at discreet frequencies (between 1 and 12Hz) to evaluate the quality factor (Qc) as a function of frequency. We combine these measurements to evaluate the frequency dependence of Qc of the form Qc(f)=Qof η, where Qo is the quality factor at 1Hz and η is the frequency dependence. Computed Qo values range from 80-360 and η ranges from 0.85-1.45. To study the lateral variation in Qo and η, we regionalise the Qc by combining all source-receiver measurements using a back-projection algorithm. For a single back scatter model, the coda waves sample an elliptical area with the epicenter and receiver at the two foci. We parameterize the region using square grids. The algorithm calculates the overlap in area and distributes Qc in the sampled grids using the average Qc as the boundary value. This is done in an iterative manner, by minimising the misfit between the observed and computed Qc within each grid. This process is repeated for all frequencies and η is computed for each grid by combining Qc for all frequencies. Our results reveal strong variation in Qo and η across NE India. The highest Qo are in the Bengal Basin (210-280) and the Indo-Burman subduction zone (300-360). The Shillong Plateau and Mikir Hills have intermediate Qo (~160) and the lowest Qo (~80) is observed in the Naga fold thrust belt. This variation in Qo demarcates the boundary between the continental crust beneath the Shillong Plateau and Mikir Hills and the transitional to oceanic crust beneath the Bengal Basin and Indo-Burman subduction zone. Thick pile of sedimentary strata in the Naga fold thrust belt results in the low Qo. Frequency dependence (η) of Qc across NE India is observed to be very high, with regions of high Qo being associated with relatively higher η.

Acquisition of Codas in Spanish as a First Language: The Role of Accuracy, Markedness and Frequency

ERIC Educational Resources Information Center

Polo, Nuria

2018-01-01

Studies on the acquisition of Spanish as a first language do not agree on the patterns and factors relevant for coda development. In order to shed light on the questions involved, a longitudinal study of coda development in Northern European Spanish was carried out to explore the relationship between accuracy, markedness and frequency. The study…

Attenuation Tomography of Northern California and the Yellow Sea / Korean Peninsula from Coda-source Normalized and Direct Lg Amplitudes

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

Ford, S R; Dreger, D S; Phillips, W S

2008-07-16

Inversions for regional attenuation (1/Q) of Lg are performed in two different regions. The path attenuation component of the Lg spectrum is isolated using the coda-source normalization method, which corrects the Lg spectral amplitude for the source using the stable, coda-derived source spectra. Tomographic images of Northern California agree well with one-dimensional (1-D) Lg Q estimated from five different methods. We note there is some tendency for tomographic smoothing to increase Q relative to targeted 1-D methods. For example in the San Francisco Bay Area, which contains high attenuation relative to the rest of it's region, Q is over-estimated bymore » {approx}30. Coda-source normalized attenuation tomography is also carried out for the Yellow Sea/Korean Peninsula (YSKP) where output parameters (site, source, and path terms) are compared with those from the amplitude tomography method of Phillips et al. (2005) as well as a new method that ties the source term to the MDAC formulation (Walter and Taylor, 2001). The source terms show similar scatter between coda-source corrected and MDAC source perturbation methods, whereas the amplitude method has the greatest correlation with estimated true source magnitude. The coda-source better represents the source spectra compared to the estimated magnitude and could be the cause of the scatter. The similarity in the source terms between the coda-source and MDAC-linked methods shows that the latter method may approximate the effect of the former, and therefore could be useful in regions without coda-derived sources. The site terms from the MDAC-linked method correlate slightly with global Vs30 measurements. While the coda-source and amplitude ratio methods do not correlate with Vs30 measurements, they do correlate with one another, which provides confidence that the two methods are consistent. The path Q{sup -1} values are very similar between the coda-source and amplitude ratio methods except for small differences in the Da-xin-anling Mountains, in the northern YSKP. However there is one large difference between the MDAC-linked method and the others in the region near stations TJN and INCN, which point to site-effect as the cause for the difference.« less

New Frontiers at the Interface of General Relativity and Quantum Optics

NASA Astrophysics Data System (ADS)

Feiler, C.; Buser, M.; Kajari, E.; Schleich, W. P.; Rasel, E. M.; O'Connell, R. F.

2009-12-01

In the present paper we follow three major themes: (i) concepts of rotation in general relativity, (ii) effects induced by these generalized rotations, and (iii) their measurement using interferometry. Our journey takes us from the Foucault pendulum via the Sagnac interferometer to manifestations of gravito-magnetism in double binary pulsars and in Gödel’s Universe. Throughout our article we emphasize the emerging role of matter wave interferometry based on cold atoms or Bose-Einstein condensates leading to superior inertial sensors. In particular, we advertise recent activities directed towards the operation of a coherent matter wave interferometer in an extended free fall.

Measurement of fluid properties using rapid-double-exposure and time-average holographic interferometry

NASA Technical Reports Server (NTRS)

Decker, A. J.

1984-01-01

The holographic recording of the time history of a flow feature in three dimensions is discussed. The use of diffuse illumination holographic interferometry or the three dimensional visualization of flow features such as shock waves and turbulent eddies is described. The double-exposure and time-average methods are compared using the characteristic function and the results from a flow simulator. A time history requires a large hologram recording rate. Results of holographic cinematography of the shock waves in a flutter cascade are presented as an example. Future directions of this effort, including the availability and development of suitable lasers, are discussed.

Inner core boundary topography explored with reflected and diffracted P waves

NASA Astrophysics Data System (ADS)

deSilva, Susini; Cormier, Vernon F.; Zheng, Yingcai

2018-03-01

The existence of topography of the inner core boundary (ICB) can affect the amplitude, phase, and coda of body waves incident on the inner core. By applying pseudospectral and boundary element methods to synthesize compressional waves interacting with the ICB, these effects are predicted and compared with waveform observations in pre-critical, critical, post-critical, and diffraction ranges of the PKiKP wave reflected from the ICB. These data sample overlapping regions of the inner core beneath the circum-Pacific belt and the Eurasian, North American, and Australian continents, but exclude large areas beneath the Pacific and Indian Oceans and the poles. In the pre-critical range, PKiKP waveforms require an upper bound of 2 km at 1-20 km wavelength for any ICB topography. Higher topography sharply reduces PKiKP amplitude and produces time-extended coda not observed in PKiKP waveforms. The existence of topography of this scale smooths over minima and zeros in the pre-critical ICB reflection coefficient predicted from standard earth models. In the range surrounding critical incidence (108-130 °), this upper bound of topography does not strongly affect the amplitude and waveform behavior of PKIKP + PKiKP at 1.5 Hz, which is relatively insensitive to 10-20 km wavelength topography height approaching 5 km. These data, however, have a strong overlap in the regions of the ICB sampled by pre-critical PKiKP that require a 2 km upper bound to topography height. In the diffracted range (>152°), topography as high as 5 km attenuates the peak amplitudes of PKIKP and PKPCdiff by similar amounts, leaving the PKPCdiff/PKIKP amplitude ratio unchanged from that predicted by a smooth ICB. The observed decay of PKPCdiff into the inner core shadow and the PKIKP-PKPCdiff differential travel time are consistent with a flattening of the outer core P velocity gradient near the ICB and iron enrichment at the bottom of the outer core.

Time reversal seismic imaging using laterally reflected surface waves in southern California

NASA Astrophysics Data System (ADS)

Tape, C.; Liu, Q.; Tromp, J.; Plesch, A.; Shaw, J. H.

2010-12-01

We use observed post-surface-wave seismic waveforms to image shallow (upper 10 km) lateral reflectors in southern California. Our imaging technique employs the 3D crustal model m16 of Tape et al. (2009), which is accurate for most local earthquakes over the period range 2-30 s. Model m16 captures the resonance of the major sedimentary basins in southern California, as well as some lateral surface wave reflections associated with these basins. We apply a 3D Gaussian smoothing function (12 km horizontal, 2 km vertical) to model m16. This smoothing has the effect of suppressing synthetic waveforms within the period range of interest (3-10 s) that are associated with reflections (single and multiple) from these basins. The smoothed 3D model serves as the background model within which we propagate an ``adjoint wavefield'' comprised of time-reversed windows of post-surface-wave coda waveforms that are initiated at the respective station locations. This adjoint wavefield constructively interferes with the regular wavefield in the locations of potential reflectors. The potential reflectors are revealed in an ``event kernel,'' which is the time-integrated volumetric field for each earthquake. By summing (or ``stacking'') the event kernels from 28 well-recorded earthquakes, we identify several reflectors using this imaging procedure. The most prominent lateral reflectors occur in proximity to: the southernmost San Joaquin basin, the Los Angeles basin, the San Pedro basin, the Ventura basin, the Manix basin, the San Clemente--Santa Cruz--Santa Barbara ridge, and isolated segments of the San Jacinto and San Andreas faults. The correspondence between observed coherent coda waveforms and the imaged reflectors provides a solid basis for interpreting the kernel features as material contrasts. The 3D spatial extent and amplitude of the kernel features provide constraints on the geometry and material contrast of the imaged reflectors.

Monitoring the tidal response of a sea levee with ambient seismic noise

NASA Astrophysics Data System (ADS)

Planès, Thomas; Rittgers, Justin B.; Mooney, Michael A.; Kanning, Wim; Draganov, Deyan

2017-03-01

Internal erosion, a major cause of failure of earthen dams and levees, is often difficult to detect at early stages using traditional visual inspection. The passive seismic-interferometry technique could enable the early detection of internal changes taking place within these structures. We test this technique on a portion of the sea levee of Colijnsplaat, Netherlands, which presents signs of concentrated seepage in the form of sandboils. Applying seismic interferometry to ambient noise collected over a 12-hour period, we retrieve surface waves propagating along the levee. We identify the contribution of two dominant ambient seismic noise sources: the traffic on the Zeeland bridge and a nearby wind turbine. Here, the sea-wave action does not constitute a suitable noise source for seismic interferometry. Using the retrieved surface waves, we compute time-lapse variations of the surface-wave group velocities during the 12-hour tidal cycle for different frequency bands, i.e., for different depth ranges. The estimated group-velocity variations correlate with variations in on-site pore-water pressure measurements that respond to tidal loading. We present lateral profiles of these group-velocity variations along a 180-meter section of the levee, at four different depth ranges (0m-40m). On these profiles, we observe some spatially localized relative group-velocity variations of up to 5% that might be related to concentrated seepage.

Coherent Seismic Arrivals in the P Wave Coda of the 2012 Mw 7.2 Sumatra Earthquake: Water Reverberations or an Early Aftershock?

NASA Astrophysics Data System (ADS)

Fan, Wenyuan; Shearer, Peter M.

2018-04-01

Teleseismic records of the 2012 Mw 7.2 Sumatra earthquake contain prominent phases in the P wave train, arriving about 50 to 100 s after the direct P arrival. Azimuthal variations in these arrivals, together with back-projection analysis, led Fan and Shearer (https://doi.org/10.1002/2016GL067785) to conclude that they originated from early aftershock(s), located ˜150 km northeast of the mainshock and landward of the trench. However, recently, Yue et al. (https://doi.org/10.1002/2017GL073254) argued that the anomalous arrivals are more likely water reverberations from the mainshock, based mostly on empirical Green's function analysis of a M6 earthquake near the mainshock and a water phase synthetic test. Here we present detailed back-projection and waveform analyses of three M6 earthquakes within 100 km of the Mw 7.2 earthquake, including the empirical Green's function event analyzed in Yue et al. (https://doi.org/10.1002/2017GL073254). In addition, we examine the waveforms of three M5.5 reverse-faulting earthquakes close to the inferred early aftershock location in Fan and Shearer (https://doi.org/10.1002/2016GL067785). These results suggest that the reverberatory character of the anomalous arrivals in the mainshock coda is consistent with water reverberations, but the origin of this energy is more likely an early aftershock rather than delayed and displaced water reverberations from the mainshock.

Enhanced Rayleigh waves tomography of Mexico using ambient noise cross-correlations (C1) and correlations of coda of correlations (C3)

NASA Astrophysics Data System (ADS)

Spica, Z. J.; Perton, M.; Calo, M.; Cordoba-Montiel, F.; Legrand, D.; Iglesias, A.

2015-12-01

Standard application of the seismic ambient noise tomography considers the existence of synchronous records at stations for green's functions retrieval. More recent theoretical and experimental observations showed the possibility to apply correlation of coda of noise correlation (C3) to obtain green's functions between stations of asynchronous seismic networks making possible to dramatically increase databases for imagining the Earth's interior. However, this possibility has not been fully exploited yet, and right now the data C3 are not included into tomographic inversions to refine seismic structures. Here we show for the first time how to incorporate the data of C1 and C3 to calculate dispersion maps of Rayleigh waves in the range period of 10-120s, and how the merging of these datasets improves the resolution of the structures imaged. Tomographic images are obtained for an area covering Mexico, the Gulf of Mexico and the southern U.S. We show dispersion maps calculated using both data of C1 and the complete dataset (C1+C3). The latter provide new details of the seismic structure of the region allowing a better understanding of their role on the geodynamics of the study area. The resolving power obtained in our study is several times higher than in previous studies based on ambient noise. This demonstrates the new possibilities for imaging the Earth's crust and upper mantle using this enlarged database.

Seismic interferometry by crosscorrelation and by multidimensional deconvolution: a systematic comparison

NASA Astrophysics Data System (ADS)

Wapenaar, Kees; van der Neut, Joost; Ruigrok, Elmer; Draganov, Deyan; Hunziker, Juerg; Slob, Evert; Thorbecke, Jan; Snieder, Roel

2010-05-01

In recent years, seismic interferometry (or Green's function retrieval) has led to many applications in seismology (exploration, regional and global), underwater acoustics and ultrasonics. One of the explanations for this broad interest lies in the simplicity of the methodology. In passive data applications a simple crosscorrelation of responses at two receivers gives the impulse response (Green's function) at one receiver as if there were a source at the position of the other. In controlled-source applications the procedure is similar, except that it involves in addition a summation along the sources. It has also been recognized that the simple crosscorrelation approach has its limitations. From the various theoretical models it follows that there are a number of underlying assumptions for retrieving the Green's function by crosscorrelation. The most important assumptions are that the medium is lossless and that the waves are equipartitioned. In heuristic terms the latter condition means that the receivers are illuminated isotropically from all directions, which is for example achieved when the sources are regularly distributed along a closed surface, the sources are mutually uncorrelated and their power spectra are identical. Despite the fact that in practical situations these conditions are at most only partly fulfilled, the results of seismic interferometry are generally quite robust, but the retrieved amplitudes are unreliable and the results are often blurred by artifacts. Several researchers have proposed to address some of the shortcomings by replacing the correlation process by deconvolution. In most cases the employed deconvolution procedure is essentially 1-D (i.e., trace-by-trace deconvolution). This compensates the anelastic losses, but it does not account for the anisotropic illumination of the receivers. To obtain more accurate results, seismic interferometry by deconvolution should acknowledge the 3-D nature of the seismic wave field. Hence, from a theoretical point of view, the trace-by-trace process should be replaced by a full 3-D wave field deconvolution process. Interferometry by multidimensional deconvolution is more accurate than the trace-by-trace correlation and deconvolution approaches but the processing is more involved. In the presentation we will give a systematic analysis of seismic interferometry by crosscorrelation versus multi-dimensional deconvolution and discuss applications of both approaches.

A multidisciplinary study of planetary, solar and astrophysical radio emissions

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Calvert, W.; Fielder, R.; Goertz, C.; Grabbe, C.; Kurth, W.; Mutel, R.; Sheerin, J.; Mellott, M.; Spangler, S.

1986-01-01

Combination of the related fields of planetary, solar, and astrophysical radio emissions was attempted in order to more fully understand the radio emission processes. Topics addressed include: remote sensing of astrophysical plasma turbulence; Alfven waves; astrophysical shock waves; surface waves; very long base interferometry results; very large array observations; solar magnetic flux; and magnetohydrodynamic waves as a tool for solar corona diagnostics.

Analysis of standing sound waves using holographic interferometry

NASA Astrophysics Data System (ADS)

Russell, Daniel A.; Parker, David E.; Hughes, Russell S.

2009-08-01

Optical holographic interferometry was used to study standing sound waves in air inside a resonance tube driven by a small loudspeaker at one end. The front face of the resonance tube was constructed with plexiglass, allowing optical interrogation of the tube interior. The object beam of the holographic setup was directed through the plexiglass and reflected off the back wall of the resonator. When driven at resonance, the fluctuations in the air density at the antinodes altered the refractive index of the air in the tube, causing interference patterns in the resulting holographic images. Real-time holography was used to determine resonance frequencies and to measure the wavelengths of the standing waves. Time-average holography was used to observe the effect of increasing the sound pressure level on the resulting fringe pattern. A simple theory was developed to successfully predict the fringe pattern.

Isotope-selective high-order interferometry with large organic molecules in free fall

NASA Astrophysics Data System (ADS)

Rodewald, Jonas; Dörre, Nadine; Grimaldi, Andrea; Geyer, Philipp; Felix, Lukas; Mayor, Marcel; Shayeghi, Armin; Arndt, Markus

2018-03-01

Interferometry in the time domain has proven valuable for matter-wave based measurements. This concept has recently been generalized to cold molecular clusters using short-pulse standing light waves which realized photo-depletion gratings, arranged in a time-domain Talbot–Lau interferometer (OTIMA). Here we extend this idea further to large organic molecules and demonstrate a new scheme to scan the emerging molecular interferogram in position space. The capability of analyzing different isotopes of the same monomer under identical conditions opens perspectives for studying the interference fringe shift as a function of time in gravitational free fall. The universality of OTIMA interferometry allows one to handle a large variety of particles. In our present work, quasi-continuous laser evaporation allows transferring fragile organic molecules into the gas phase, covering more than an order of magnitude in mass between 614 amu and 6509 amu, i.e. 300% more massive than in previous OTIMA experiments. For all masses, we find about 30% fringe visibility.

Local earthquake interferometry of the IRIS Community Wavefield Experiment, Grant County, Oklahoma

NASA Astrophysics Data System (ADS)

Eddy, A. C.; Harder, S. H.

2017-12-01

The IRIS Community Wavefield Experiment was deployed in Grant County, located in north central Oklahoma, from June 21 to July 27, 2016. Data from all nodes were recorded at 250 samples per second between June 21 and July 20 along three lines. The main line was 12.5 km long oriented east-west and consisted of 129 nodes. The other two lines were 5.5 km long north-south oriented with 49 nodes each. During this time, approximately 150 earthquakes of magnitude 1.0 to 4.4 were recorded in the surrounding counties of Oklahoma and Kansas. Ideally, sources for local earthquake interferometry should be near surface events that produce high frequency body waves. Unlike ambient noise seismic interferometry (ANSI), which uses days, weeks, or even months of continuously recorded seismic data, local earthquake interferometry uses only short segments ( 2 min.) of data. Interferometry in this case is based on the cross-correlation of body wave surface multiples where the event source is translated to a reference station in the array, which acts as a virtual source. Multiples recorded between the reference station and all other stations can be cross-correlated to produce a clear seismic trace. This process will be repeated with every node acting as the reference station for all events. The resulting shot gather will then be processed and analyzed for quality and accuracy. Successful application of local earthquake interferometry will produce a crustal image with identifiable sedimentary and basement reflectors and possibly a Moho reflection. Economically, local earthquake interferometry could lower the time and resource cost of active and passive seismic surveys while improving subsurface image quality in urban settings or areas of limited access. The applications of this method can potentially be expanded with the inclusion of seismic events with a magnitude of 1.0 or lower.

Nuclear emulsions for the detection of micrometric-scale fringe patterns: an application to positron interferometry

NASA Astrophysics Data System (ADS)

Aghion, S.; Ariga, A.; Bollani, M.; Ereditato, A.; Ferragut, R.; Giammarchi, M.; Lodari, M.; Pistillo, C.; Sala, S.; Scampoli, P.; Vladymyrov, M.

2018-05-01

Nuclear emulsions are capable of very high position resolution in the detection of ionizing particles. This feature can be exploited to directly resolve the micrometric-scale fringe pattern produced by a matter-wave interferometer for low energy positrons (in the 10–20 keV range). We have tested the performance of emulsion films in this specific scenario. Exploiting silicon nitride diffraction gratings as absorption masks, we produced periodic patterns with features comparable to the expected interferometer signal. Test samples with periodicities of 6, 7 and 20 μ m were exposed to the positron beam, and the patterns clearly reconstructed. Our results support the feasibility of matter-wave interferometry experiments with positrons.

Fringe localization requirements for three-dimensional flow visualization of shock waves in diffuse-illumination double-pulse holographic interferometry

NASA Technical Reports Server (NTRS)

Decker, A. J.

1982-01-01

A theory of fringe localization in rapid-double-exposure, diffuse-illumination holographic interferometry was developed. The theory was then applied to compare holographic measurements with laser anemometer measurements of shock locations in a transonic axial-flow compressor rotor. The computed fringe localization error was found to agree well with the measured localization error. It is shown how the view orientation and the curvature and positional variation of the strength of a shock wave are used to determine the localization error and to minimize it. In particular, it is suggested that the view direction not deviate from tangency at the shock surface by more than 30 degrees.

A scheme for recording a fast process at nanosecond scale by using digital holographic interferometry with continuous wave laser

NASA Astrophysics Data System (ADS)

Wang, Jun; Zhao, Jianlin; Di, Jianglei; Jiang, Biqiang

2015-04-01

A scheme for recording fast process at nanosecond scale by using digital holographic interferometry with continuous wave (CW) laser is described and demonstrated experimentally, which employs delayed-time fibers and angular multiplexing technique and can realize the variable temporal resolution at nanosecond scale and different measured depths of object field at certain temporal resolution. The actual delay-time is controlled by two delayed-time fibers with different lengths. The object field information in two different states can be simultaneously recorded in a composite hologram. This scheme is also suitable for recording fast process at picosecond scale, by using an electro-optic modulator.

Measurement of fluid properties using rapid-double-exposure and time-average holographic interferometry

NASA Technical Reports Server (NTRS)

Decker, A. J.

1984-01-01

The holographic recording of the time history of a flow feature in three dimensions is discussed. The use of diffuse illumination holographic interferometry or the three-dimensional visualization of flow features such as shock waves and turbulent eddies is described. The double-exposure and time-average methods are compared using the characteristic function and the results from a flow simulator. A time history requires a large hologram recording rate. Results of holographic cinematography of the shock waves in a flutter cascade are presented as an example. Future directions of this effort, including the availability and development of suitable lasers, are discussed. Previously announced in STAR as N84-21849

Advanced radiometric and interferometric milimeter-wave scene simulations

NASA Technical Reports Server (NTRS)

Hauss, B. I.; Moffa, P. J.; Steele, W. G.; Agravante, H.; Davidheiser, R.; Samec, T.; Young, S. K.

1993-01-01

Smart munitions and weapons utilize various imaging sensors (including passive IR, active and passive millimeter-wave, and visible wavebands) to detect/identify targets at short standoff ranges and in varied terrain backgrounds. In order to design and evaluate these sensors under a variety of conditions, a high-fidelity scene simulation capability is necessary. Such a capability for passive millimeter-wave scene simulation exists at TRW. TRW's Advanced Radiometric Millimeter-Wave Scene Simulation (ARMSS) code is a rigorous, benchmarked, end-to-end passive millimeter-wave scene simulation code for interpreting millimeter-wave data, establishing scene signatures and evaluating sensor performance. In passive millimeter-wave imaging, resolution is limited due to wavelength and aperture size. Where high resolution is required, the utility of passive millimeter-wave imaging is confined to short ranges. Recent developments in interferometry have made possible high resolution applications on military platforms. Interferometry or synthetic aperture radiometry allows the creation of a high resolution image with a sparsely filled aperture. Borrowing from research work in radio astronomy, we have developed and tested at TRW scene reconstruction algorithms that allow the recovery of the scene from a relatively small number of spatial frequency components. In this paper, the TRW modeling capability is described and numerical results are presented.

Controlled-source seismic interferometry with one way wave fields

NASA Astrophysics Data System (ADS)

van der Neut, J.; Wapenaar, K.; Thorbecke, J. W.

2008-12-01

In Seismic Interferometry we generally cross-correlate registrations at two receiver locations and sum over an array of sources to retrieve a Green's function as if one of the receiver locations hosts a (virtual) source and the other receiver location hosts an actual receiver. One application of this concept is to redatum an area of surface sources to a downhole receiver location, without requiring information about the medium between the sources and receivers, thus providing an effective tool for imaging below complex overburden, which is also known as the Virtual Source method. We demonstrate how elastic wavefield decomposition can be effectively combined with controlled-source Seismic Interferometry to generate virtual sources in a downhole receiver array that radiate only down- or upgoing P- or S-waves with receivers sensing only down- or upgoing P- or S- waves. For this purpose we derive exact Green's matrix representations from a reciprocity theorem for decomposed wavefields. Required is the deployment of multi-component sources at the surface and multi- component receivers in a horizontal borehole. The theory is supported with a synthetic elastic model, where redatumed traces are compared with those of a directly modeled reflection response, generated by placing active sources at the virtual source locations and applying elastic wavefield decomposition on both source and receiver side.

Regional variation of coda Q in Kopili fault zone of northeast India and its implications

NASA Astrophysics Data System (ADS)

Bora, Nilutpal; Biswas, Rajib; Dobrynina, Anna A.

2018-01-01

Kopili fault has been experiencing higher seismic and tectonic activity during the recent years. These kind of active tectonics can be inspected by examining coda-wave attenuation and its dependence with frequency. Exploiting single back-scattering model, we have endeavored to measure coda Q and its associated parameters such as frequency dependent factor (n) and attenuation coefficient (γ) covering seven lapse-time windows spanning from 30 to 90 s and central frequencies 1.5, 3.5, 6, 9 and 12 Hz. The average estimated values of QC increases with frequency and lapse time window from 114 at frequency 1.5 Hz to 1563 at frequency 12 Hz for 30 s window length, and from 305 at frequency 1.5 Hz to 2135 at frequency 12 Hz for 90 s window length. The values of Q0 and n are also estimated for the entire Kopili fault zone. For this study region, the Q0 values vary from 62 to 348 and n varies from 0.57 to 1.51 within the frequency range 1.5 to 12 Hz. Furthermore, depth variation of attenuation of this region reveals that there is velocity anomaly at depth 210-220 km as there arises sharp changes in γ and n which are supported by available data, reported by other researcher for this region. Finally, we have tried to separate the intrinsic and scattering attenuation for this area. It is observed that the entire region is dominated by mainly scattering attenuation, but we can see an increase in intrinsic attenuation with depths in two stations namely TZR and BKD. Furthermore, the obtained results are comparable with the available global data.

Variation of coda wave attenuation in the Alborz region and central Iran

NASA Astrophysics Data System (ADS)

Rahimi, H.; Motaghi, K.; Mukhopadhyay, S.; Hamzehloo, H.

2010-06-01

More than 340 earthquakes recorded by the Institute of Geophysics, University of Tehran (IGUT) short period stations from 1996 to 2004 were analysed to estimate the S-coda attenuation in the Alborz region, the northern part of the Alpine-Himalayan orogen in western Asia, and in central Iran, which is the foreland of this orogen. The coda quality factor, Qc, was estimated using the single backscattering model in frequency bands of 1-25 Hz. In this research, lateral and depth variation of Qc in the Alborz region and central Iran are studied. It is observed that in the Alborz region there is absence of significant lateral variation in Qc. The average frequency relation for this region is Qc = 79 +/- 2f1.07+/-0.08. Two anomalous high-attenuation areas in central Iran are recognized around the stations LAS and RAZ. The average frequency relation for central Iran excluding the values of these two stations is Qc = 94 +/- 2f0.97+/-0.12. To investigate the attenuation variation with depth, Qc value was calculated for 14 lapse times (25, 30, 35,... 90s) for two data sets having epicentral distance range R < 100 km (data set 1) and 100 < R < 200 km (data set 2) in each area. It is observed that Qc increases with depth. However, the rate of increase of Qc with depth is not uniform in our study area. Beneath central Iran the rate of increase of Qc is greater at depths less than 100 km compared to that at larger depths indicating the existence of a high attenuation anomalous structure under the lithosphere of central Iran. In addition, below ~180 km, the Qc value does not vary much with depth under both study areas, indicating the presence of a transparent mantle under them.

Detecting inertial effects with airborne matter-wave interferometry

PubMed Central

Geiger, R.; Ménoret, V.; Stern, G.; Zahzam, N.; Cheinet, P.; Battelier, B.; Villing, A.; Moron, F.; Lours, M.; Bidel, Y.; Bresson, A.; Landragin, A.; Bouyer, P.

2011-01-01

Inertial sensors relying on atom interferometry offer a breakthrough advance in a variety of applications, such as inertial navigation, gravimetry or ground- and space-based tests of fundamental physics. These instruments require a quiet environment to reach their performance and using them outside the laboratory remains a challenge. Here we report the first operation of an airborne matter-wave accelerometer set up aboard a 0g plane and operating during the standard gravity (1g) and microgravity (0g) phases of the flight. At 1g, the sensor can detect inertial effects more than 300 times weaker than the typical acceleration fluctuations of the aircraft. We describe the improvement of the interferometer sensitivity in 0g, which reaches 2 x 10-4 ms-2 / √Hz with our current setup. We finally discuss the extension of our method to airborne and spaceborne tests of the Universality of free fall with matter waves. PMID:21934658

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 response and the reflection response for a 1D multilayer structure, and next 3D approach (Wapenaar 2004). As a result of this seismic interferometry experiment the 3D reflectivity model (frequencies and resolution ranges) was obtained. We proved also that the seismic interferometry approach can be applied in asynchronous seismic auscultation. The reflections detected in the virtual seismic sections are in agreement with the geological features encountered during the excavation of the tunnel and also with the petrophysical properties and parameters measured in previous geophysical borehole logging. References Claerbout J.F., 1968. Synthesis of a layered medium from its acoustic transmision response. Geophysics, 33, 264-269 Flavio Poletto, Piero Corubolo and Paolo Comeli.2010. Drill-bit seismic interferometry whith and whitout pilot signals. Geophysical Prospecting, 2010, 58, 257-265. Wapenaar, K., J. Thorbecke, and D. Draganov, 2004, Relations between reflection and transmission responses of three-dimensional inhomogeneous media: Geophysical Journal International, 156, 179-194.

Waveform complexity caused by near trench structure and its impact on earthquake source study: application to the 2015 Illapel earthquake sequence

NASA Astrophysics Data System (ADS)

Qian, Y.; Wei, S.; Wu, W.; Ni, S.

2017-12-01

Among various types of 3D heterogeneity in the Earth, trench might be the most complex systems, which includes rapidly varying bathymetry and usually thick sediment below water layer. These structure complexities can cause substantial waveform complexities on seismograms, but their corresponding impact on the earthquake source studies has not yet been well understood. Here we explore those effects via studies of two moderate aftershocks (one near the coast while the other close to the Peru-Chile trench axis) in the 2015 Illapel earthquake sequence. The horizontal locations and depths of these two events are poorly constrained and the reported results of various agencies display substantial variations. Thus, we first relocated the epicenters using the P-wave first arrivals and determined other parameters by waveform fitting. In a jackknifing way, we found that the trench event has large differences between regional and teleseismic solutions, in particular for depth, while the coastal event shows consistent results. The teleseismic P/Pdiff waves between these two events also display distinctly different features. More specifically, the trench event has more complex P/Pdiff waves and stronger coda waves, in terms of amplitude and duration (longer than 100s). The coda waves are coherent across stations at different distances and azimuths, indicating a more likely origin of scattering waves due to 3D heterogeneity near trench. To quantitatively model those 3D effects, we adopted a hybrid waveform simulation approach that computes the 3D wavefield in the source region by the Spectral Element Method (SEM) and then propagates the wavefield to teleseismic and shadow zone distances through the Direct Solution Method (DSM). We incorporated the GEBCO bathymetry and water layer into the SEM simulations and assumed the IASP91 1D model for DSM computation. Comparing with the poor 1D synthetics fitting to the data, we do obtain dramatic improvement in 3D waveform fittings across a series of frequency bands. With sensitivity tests of 3D waveform modeling, the centroid longitude and depth for the near trench event are refined. Our study suggests that the complex trench structure must be taken into account for a reliable analysis of shallow earthquake near trench, in particular for the shallowest tsunamigenic earthquakes.

Evaluating the Coda Phase Delay Method for Determining Temperature Ratios in Windy Environments

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

Albert, Sarah; Bowman, Daniel; Rodgers, Arthur

2017-07-01

We evaluate the acoustic coda phase delay method for estimating changes in atmospheric phenomena in realistic environments. Previous studies verifying the method took place in an environment with negligible wind. The equation for effective sound speed, which the method is based upon, shows that the influence of wind is equal to the square of temperature. Under normal conditions, wind is significant and therefore cannot be ignored. Results from this study con rm the previous statement. The acoustic coda phase delay method breaks down in non-ideal environments, namely those where wind speed and direction varies across small distances. We suggest thatmore » future studies make use of gradiometry to better understand the effect of wind on the acoustic coda and subsequent phase delays.« less

Time-Delay Interferometry for Space-based Gravitational Wave Searches

NASA Technical Reports Server (NTRS)

Armstrong, J.; Estabrook, F.; Tinto, M.

1999-01-01

Ground-based, equal-arm-length laser interferometers are being built to measure high-frequency astrophysical graviatational waves. Because of the arm-length equality, laser light experiences the same delay in each arm and thus phase or frequency noise from the laser itself precisely cancels at the photodetector.

Geophysical Signatures to Monitor Fluids and Mineralization for CO2 Sequestration in Basalts

NASA Astrophysics Data System (ADS)

Otheim, L. T.; Adam, L.; Van Wijk, K.; Batzle, M. L.; Mcling, T. L.; Podgorney, R. K.

2011-12-01

Carbon dioxide sequestration in large reservoirs can reduce emissions of this green house gas into the atmosphere. Basalts are promising host rocks due to their volumetric extend, worldwide distribution, and recent observations that CO2-water mixtures react with basalt minerals to precipitate as carbonate minerals, trapping the CO2. The chemical reaction between carbonic acid and minerals rich in calcium, magnesium and iron precipitates carbonates in the pore space. This process would increase the elastic modulus and velocity of the rock. At the same time, the higher compressibility of CO2 over water changes the elastic properties of the rock, decreasing the saturated rock bulk modulus and the P-wave velocity. Reservoirs where the rock properties change as a result of fluid or pressure changes are commonly monitored with seismic methods. Here we present experiments to study the feasibility of monitoring CO2 migration in a reservoir and CO2-rock reactions for a sequestration scenario in basalts. Our goal is to measure the rock's elastic response to mineralization with non-contacting ultrasonic lasers, and the effect of fluid substitution at reservoir conditions at seismic and ultrasonic frequencies. For the fluid substitution experiment we observe changes in the P- and S-wave velocities when saturating the sample with super-critical (sc) CO2, CO2-water mixtures and water alone for different pore and confining pressures. The bulk modulus of the rock is significantly dependent on frequency in the 2~to 106~Hz range, for CO2-water mixtures and pure water saturations. Dry and pure CO2 (sc or gas) do not show a frequency dependence on the modulus. Moreover, the shear wave modulus is not dispersive for either fluid. The frequency dependence of the elastic parameters is related to the attenuation (1/Q) of the rock. We will show the correlation between frequency dependent moduli and attenuation data for the different elastic moduli of the rocks. Three other basalt samples were stored in a pressure chamber with a sc CO2-water solution to study the effect of mineralization on the elastic properties of the rock. The rock elastic properties are recorded with non-contacting ultrasonic lasers at room conditions. After 15 weeks the first post-mineralization scan showed differences in the rock velocities with respect to the pre-mineralization scan. The analysis is done through coda wave interferometry and direct arrivals. The samples were inserted back into the pressure vessel for continuing mineralization and subsequent scans. Finally, we will discuss the applicability of Gassmann's equation and how the combination of mineralization together with CO2-water mixture affects the velocity of waves in basalt rocks.

2D Variations in Coda Amplitudes in the Middle East

DOE PAGES

Pasyanos, Michael E.; Gok, Rengin; Walter, William R.

2016-08-16

Here, coda amplitudes have proven to be a stable feature of seismograms, allowing one to reliably measure magnitudes for moderate to large-sized (M≥3) earthquakes over broad regions. Since smaller (M<3) earthquakes are only recorded at higher frequencies where we find larger interstation scatter, amplitude and magnitude estimates for these events are more variable, regional, and path dependent. In this study, we investigate coda amplitude measurements in the Middle East for 2-D variations in attenuation structure.

Attenuation Tomography of Northern California and the Yellow Sea/Korean Peninsula from Coda-Source Normalized and Direct LG Amplitudes

DTIC Science & Technology

2008-09-01

method correlate slightly with global Vs30 measurements . While the coda-source and amplitude ratio methods do not correlate with Vs30 measurements ...Ford et al., 2008), we compared 1-D methods to measure QLg and attempted to assess the error associated with the results. The assessment showed the...reverse two-station (RTS), source-pair/receiver-pair (SPRP), and the new coda-source normalization (CS) methods to measure Q of the regional phase, Lg

2D Variations in Coda Amplitudes in the Middle East

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

Pasyanos, Michael E.; Gok, Rengin; Walter, William R.

Here, coda amplitudes have proven to be a stable feature of seismograms, allowing one to reliably measure magnitudes for moderate to large-sized (M≥3) earthquakes over broad regions. Since smaller (M<3) earthquakes are only recorded at higher frequencies where we find larger interstation scatter, amplitude and magnitude estimates for these events are more variable, regional, and path dependent. In this study, we investigate coda amplitude measurements in the Middle East for 2-D variations in attenuation structure.

Attenuation characteristics in eastern Himalaya and southern Tibetan Plateau: An understanding of the physical state of the medium

NASA Astrophysics Data System (ADS)

Singh, Sagar; Singh, Chandrani; Biswas, Rahul; Mukhopadhyay, Sagarika; Sahu, Himanshu

2016-08-01

Attenuation characteristics of the crust in the eastern Himalaya and the southern Tibetan Plateau are investigated using high quality data recorded by Himalayan Nepal Tibet Seismic Experiment (HIMNT) during 2001-2003. The present study aims to provide an attenuation model that can address the physical mechanism governing the attenuation characteristics in the underlying medium. We have studied the Coda wave attenuation (Qc) in the single isotropic scattering model hypothesis, S wave attenuation (Qs) by using the coda normalization method and intrinsic (Qi-1) and scattering (Qsc-1) quality factors by the multiple Lapse Time Window Analysis (MLTWA) method under the assumption of multiple isotropic scattering in a 3-D half space within the frequency range 2-12 Hz. All the values of Q exhibit frequency dependent nature for a seismically active area. At all the frequencies intrinsic absorption is predominant compared to scattering attenuation and seismic albedo (B0) are found to be lower than 0.5. The observed discrepancies between the observed and theoretical models can be corroborated by the depth-dependent velocity and attenuation structure as well as the assumption of a uniform distribution of scatterers. Our results correlate well with the existing geo-tectonic model of the area, which may suggest the possible existence of trapped fluids in the crust or its thermal nature. Surprisingly the underlying cause of high attenuation in the crust of eastern Himalaya and southern Tibet makes this region distinct from its adjacent western Himalayan segment. The results are comparable with the other regions reported globally.

Atom Interferometry

ScienceCinema

Kasevich, Mark

2017-12-22

Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton’s constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gryoscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Can atom interference methods be sued to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?

Atom Interferometry

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

Kasevich, Mark

2008-05-07

Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton’s constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gryoscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Canmore » atom interference methods be sued to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?« less

The global short-period wavefield modelled with a Monte Carlo seismic phonon method

USGS Publications Warehouse

Shearer, Peter M.; Earle, Paul

2004-01-01

At high frequencies (∼1 Hz), much of the seismic energy arriving at teleseismic distances is not found in the main phases (e.g. P, PP, S, etc.) but is contained in the extended coda that follows these arrivals. This coda results from scattering off small-scale velocity and density perturbations within the crust and mantle and contains valuable information regarding the depth dependence and strength of this heterogeneity as well as the relative importance of intrinsic versus scattering attenuation. Most analyses of seismic coda to date have concentrated on S-wave coda generated from lithospheric scattering for events recorded at local and regional distances. Here, we examine the globally averaged vertical-component, 1-Hz wavefield (>10° range) for earthquakes recorded in the IRIS FARM archive from 1990 to 1999. We apply an envelope-function stacking technique to image the average time–distance behavior of the wavefield for both shallow (≤50 km) and deep (≥500 km) earthquakes. Unlike regional records, our images are dominated by P and P coda owing to the large effect of attenuation on PPand S at high frequencies. Modelling our results is complicated by the need to include a variety of ray paths, the likely contributions of multiple scattering and the possible importance of P-to-S and S-to-P scattering. We adopt a stochastic, particle-based approach in which millions of seismic phonons are randomly sprayed from the source and tracked through the Earth. Each phonon represents an energy packet that travels along the appropriate ray path until it is affected by a discontinuity or a scatterer. Discontinuities are modelled by treating the energy normalized reflection and transmission coefficients as probabilities. Scattering probabilities and scattering angles are computed in a similar fashion, assuming random velocity and density perturbations characterized by an exponential autocorrelation function. Intrinsic attenuation is included by reducing the energy contained in each particle as an appropriate function of traveltime. We find that most scattering occurs in the lithosphere and upper mantle, as previous results have indicated, but that some lower-mantle scattering is likely also required. A model with 3 to 4 per cent rms velocity heterogeneity at 4-km scale length in the upper mantle and 0.5 per cent rms velocity heterogeneity at 8-km scale length in the lower mantle (with intrinsic attenuation of Qα= 450 above 200 km depth andQα= 2500 below 200 km) provides a reasonable fit to both the shallow- and deep-earthquake observations, although many trade-offs exist between the scale length, depth extent and strength of the heterogeneity.

Evaluation of diffuse-illumination holographic cinematography in a flutter cascade

NASA Technical Reports Server (NTRS)

Decker, A. J.

1986-01-01

Since 1979, the Lewis Research Center has examined holographic cinematography for three-dimensional flow visualization. The Nd:YAG lasers used were Q-switched, double-pulsed, and frequency-doubled, operating at 20 pulses per second. The primary subjects for flow visualization were the shock waves produced in two flutter cascades. Flow visualization was by diffuse-illumination, double-exposure, and holographic interferometry. The performances of the lasers, holography, and diffuse-illumination interferometry are evaluated in single-window wind tunnels. The fringe-contrast factor is used to evaluate the results. The effects of turbulence on shock-wave visualization in a transonic flow are discussed. The depth of field for visualization of a turbulent structure is demonstrated to be a measure of the relative density and scale of that structure. Other items discussed are the holographic emulsion, tests of coherence and polarization, effects of windows and diffusers, hologram bleaching, laser configurations, influence and handling of specular reflections, modes of fringe localization, noise sources, and coherence requirements as a function of the pulse energy. Holography and diffuse illumination interferometry are also reviewed.

Absolute marine gravimetry with matter-wave interferometry.

PubMed

Bidel, Y; Zahzam, N; Blanchard, C; Bonnin, A; Cadoret, M; Bresson, A; Rouxel, D; Lequentrec-Lalancette, M F

2018-02-12

Measuring gravity from an aircraft or a ship is essential in geodesy, geophysics, mineral and hydrocarbon exploration, and navigation. Today, only relative sensors are available for onboard gravimetry. This is a major drawback because of the calibration and drift estimation procedures which lead to important operational constraints. Atom interferometry is a promising technology to obtain onboard absolute gravimeter. But, despite high performances obtained in static condition, no precise measurements were reported in dynamic. Here, we present absolute gravity measurements from a ship with a sensor based on atom interferometry. Despite rough sea conditions, we obtained precision below 10 -5  m s -2 . The atom gravimeter was also compared with a commercial spring gravimeter and showed better performances. This demonstration opens the way to the next generation of inertial sensors (accelerometer, gyroscope) based on atom interferometry which should provide high-precision absolute measurements from a moving platform.

Experimental validation of ultrasonic guided modes in electrical cables by optical interferometry.

PubMed

Mateo, Carlos; de Espinosa, Francisco Montero; Gómez-Ullate, Yago; Talavera, Juan A

2008-03-01

In this work, the dispersion curves of elastic waves propagating in electrical cables and in bare copper wires are obtained theoretically and validated experimentally. The theoretical model, based on Gazis equations formulated according to the global matrix methodology, is resolved numerically. Viscoelasticity and attenuation are modeled theoretically using the Kelvin-Voigt model. Experimental tests are carried out using interferometry. There is good agreement between the simulations and the experiments despite the peculiarities of electrical cables.

Flow visualization of acoustic levitation experiment

NASA Technical Reports Server (NTRS)

Baroth, ED

1987-01-01

Acoustic levitation experiments for space applications were performed. Holographic interferometry is being used to study the heat transfer rates on a heated rod enclosed in a 6 cu in chamber. Acoustic waves at levels up to 150 db increased the heating rates to the rod by factors of three to four. High speed real time holographic interferometry was used to measure the boundary layer on the heated rod. Data reduction and digitization of the interferograms are being implemented.

Comparisons of Source Characteristics between Recent Inland Crustal Earthquake Sequences inside and outside of Niigata-Kobe Tectonic Zone, Japan

NASA Astrophysics Data System (ADS)

Somei, K.; Asano, K.; Iwata, T.; Miyakoshi, K.

2012-12-01

After the 1995 Kobe earthquake, many M7-class inland earthquakes occurred in Japan. Some of those events (e.g., the 2004 Chuetsu earthquake) occurred in a tectonic zone which is characterized as a high strain rate zone by the GPS observation (Sagiya et al., 2000) or dense distribution of active faults. That belt-like zone along the coast in Japan Sea side of Tohoku and Chubu districts, and north of Kinki district, is called as the Niigata-Kobe tectonic zone (NKTZ, Sagiya et al, 2000). We investigate seismic scaling relationship for recent inland crustal earthquake sequences in Japan and compare source characteristics between events occurring inside and outside of NKTZ. We used S-wave coda part for estimating source spectra. Source spectral ratio is obtained by S-wave coda spectral ratio between the records of large and small events occurring close to each other from nation-wide strong motion network (K-NET and KiK-net) and broad-band seismic network (F-net) to remove propagation-path and site effects. We carefully examined the commonality of the decay of coda envelopes between event-pair records and modeled the observed spectral ratio by the source spectral ratio function with assuming omega-square source model for large and small events. We estimated the corner frequencies and seismic moment (ratio) from those modeled spectral ratio function. We determined Brune's stress drops of 356 events (Mw: 3.1-6.9) in ten earthquake sequences occurring in NKTZ and six sequences occurring outside of NKTZ. Most of source spectra obey omega-square source spectra. There is no obvious systematic difference between stress drops of events in NKTZ zone and others. We may conclude that the systematic tendency of seismic source scaling of the events occurred inside and outside of NKTZ does not exist and the average source scaling relationship can be effective for inland crustal earthquakes. Acknowledgements: Waveform data were provided from K-NET, KiK-net and F-net operated by National Research Institute for Earth Science and Disaster Prevention Japan. This study is supported by Multidisciplinary research project for Niigata-Kobe tectonic zone promoted by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

A model of seismic coda arrivals to suppress spurious events.

NASA Astrophysics Data System (ADS)

Arora, N.; Russell, S.

2012-04-01

We describe a model of coda arrivals which has been added to NET-VISA (Network processing Vertically Integrated Seismic Analysis) our probabilistic generative model of seismic events, their transmission, and detection on a global seismic network. The scattered energy that follows a seismic phase arrival tends to deceive typical STA/LTA based arrival picking software into believing that a real seismic phase has been detected. These coda arrivals which tend to follow all seismic phases cause most network processing software including NET-VISA to believe that multiple events have taken place. It is not a simple matter of ignoring closely spaced arrivals since arrivals from multiple events can indeed overlap. The current practice in NET-VISA of pruning events within a small space-time neighborhood of a larger event works reasonably well, but it may mask real events produced in an after-shock sequence. Our new model allows any seismic arrival, even coda arrivals, to trigger a subsequent coda arrival. The probability of such a triggered arrival depends on the amplitude of the triggering arrival. Although real seismic phases are more likely to generate such coda arrivals. Real seismic phases also tend to generate coda arrivals with more strongly correlated parameters, for example azimuth and slowness. However, the SNR (Signal to Noise Ratio) of a coda arrival immediately following a phase arrival tends to be lower because of the nature of the SNR calculation. We have calibrated our model on historical statistics of such triggered arrivals and our inference accounts for them while searching for the best explanation of seismic events their association to the arrivals and the coda arrivals. We have tested our new model on one week of global seismic data spanning March 22, 2009 to March 29, 2009. Our model was trained on two and half months of data from April 5, 2009 to June 20, 2009. We use the LEB bulletin produced by the IDC (International Data Center) as the ground truth and computed the precision (percentage of reported events which are true) and recall (percentage of true events which are reported). The existing model has a precision of 32.2 and recall of 88.6 which changes to a precision of 50.7 and recall of 88.5 after pruning. The new model has a precision of 56.8 and recall of 86.9 without any pruning and the corresponding precision recall curve is dramatically improved. In contrast, the performance of the current automated bulletin at the IDC, SEL3, has a precision of 46.2 and recall of 69.7.

Effects of Word Position on the Acoustic Realization of Vietnamese Final Consonants.

PubMed

Tran, Thi Thuy Hien; Vallée, Nathalie; Granjon, Lionel

2018-05-28

A variety of studies have shown differences between phonetic features of consonants according to their prosodic and/or syllable (onset vs. coda) positions. However, differences are not always found, and interactions between the various factors involved are complex and not well understood. Our study compares acoustical characteristics of coda consonants in Vietnamese taking into account their position within words. Traditionally described as monosyllabic, Vietnamese is partially polysyllabic at the lexical level. In this language, tautosyllabic consonant sequences are prohibited, and adjacent consonants are only found at syllable boundaries either within polysyllabic words (CVC.CVC) or across monosyllabic words (CVC#CVC). This study is designed to examine whether or not syllable boundary types (interword vs. intraword) have an effect on the acoustic realization of codas. The results show significant acoustic differences in consonant realizations according to syllable boundary type, suggesting different coarticulation patterns between nuclei and codas. In addition, as Vietnamese voiceless stops are generally unreleased in coda position, with no burst to carry consonantal information, our results show that a vowel's second half contains acoustic cues which are available to aid in the discrimination of place of articulation of the vowel's following consonant. © 2018 S. Karger AG, Basel.

Perception of English palatal codas by Korean speakers of English

NASA Astrophysics Data System (ADS)

Yeon, Sang-Hee

2003-04-01

This study aimed at looking at perception of English palatal codas by Korean speakers of English to determine if perception problems are the source of production problems. In particular, first, this study looked at the possible first language effect on the perception of English palatal codas. Second, a possible perceptual source of vowel epenthesis after English palatal codas was investigated. In addition, individual factors, such as length of residence, TOEFL score, gender and academic status, were compared to determine if those affected the varying degree of the perception accuracy. Eleven adult Korean speakers of English as well as three native speakers of English participated in the study. Three sets of a perception test including identification of minimally different English pseudo- or real words were carried out. The results showed that, first, the Korean speakers perceived the English codas significantly worse than the Americans. Second, the study supported the idea that Koreans perceived an extra /i/ after the final affricates due to final release. Finally, none of the individual factors explained the varying degree of the perceptional accuracy. In particular, TOEFL scores and the perception test scores did not have any statistically significant association.

Children's Acquisition of English Onset and Coda /l/: Articulatory Evidence

PubMed Central

Demuth, Katherine

2015-01-01

Purpose The goal of this study was to better understand how and when onset /l/ (leap) and coda /l/ (peel) are acquired by children by examining both the articulations involved and adults' perceptions of the produced segments. Method Twenty-five typically developing Australian English–speaking children aged 3;0 (years;months) to 7;11 participated in an elicited imitation task, during which audio, video, and lingual ultrasound images were collected. Transcribers perceptually rated audio, whereas video and ultrasound images were visually examined for the presence of adult-like articulations. Results Data from this study establish that for Australian English–learning children, coda /l/s are acquired later than onset /l/s, and older children produce greater proportions of adultlike /l/s in both onset and coda positions, roughly following established norms for American English–speaking children. However, although perceptibility of coda /l/s was correlated with their articulations, onset /l/s were nearly uniformly perceived as adultlike despite substantial variation in the articulations used to produce them. Conclusions The disparity in the production and perception of children's singleton onset /l/s is linked to both physiological and phonological development. Suggestions are made for future research to tease these factors apart. PMID:25321384

Identifying individual sperm whales acoustically using self-organizing maps

NASA Astrophysics Data System (ADS)

Ioup, Juliette W.; Ioup, George E.

2005-09-01

The Littoral Acoustic Demonstration Center (LADC) is a consortium at Stennis Space Center comprising the University of New Orleans, the University of Southern Mississippi, the Naval Research Laboratory, and the University of Louisiana at Lafayette. LADC deployed three Environmental Acoustic Recording System (EARS) buoys in the northern Gulf of Mexico during the summer of 2001 to study ambient noise and marine mammals. Each LADC EARS was an autonomous, self-recording buoy capable of 36 days of continuous recording of a single channel at an 11.7-kHz sampling rate (bandwidth to 5859 Hz). The hydrophone selected for this analysis was approximately 50 m from the bottom in a water depth of 800 m on the continental slope off the Mississippi River delta. This paper contains recent analysis results for sperm whale codas recorded during a 3-min period. Results are presented for the identification of individual sperm whales from their codas, using the acoustic properties of the clicks within each coda. The recorded time series, the Fourier transform magnitude, and the wavelet transform coefficients are each used separately with a self-organizing map procedure for 43 codas. All show the codas as coming from four or five individual whales. [Research supported by ONR.

Analysis of localized fringes in the holographic optical Schlieren system

NASA Technical Reports Server (NTRS)

Kurtz, R. L.

1980-01-01

The relation between localization of interference fringes in classical and holographic interferometry is reviewed and an application of holographic interferometry is considered for which the object is a transparent medium with nonhomogeneous refractive index. The technique is based on the analysis of the optical path length change of the object wave as it propagates through a transparent medium. Phase shifts due to variations of the speed of light within the medium give rise to an interference pattern. The resulting interferogram can be used to determine the physical properties of the medium or transparent object. Such properties include the mass density of fluids, electron densities of plasmas, the temperature of fluids, the chemical species concentration of fluids, and the state of stress in solids. The optical wave used can be either a simple plane or spherical wave, or it may be a complicated spatial wave scattered by a diffusing screen. The mathematical theory on the formation and analysis of localized fringes, the general theoretical concepts used, and a computer code for analysis are included along with the inversion of fringe order data.

Search for light scalar dark matter with atomic gravitational wave detectors

NASA Astrophysics Data System (ADS)

Arvanitaki, Asimina; Graham, Peter W.; Hogan, Jason M.; Rajendran, Surjeet; Van Tilburg, Ken

2018-04-01

We show that gravitational wave detectors based on a type of atom interferometry are sensitive to ultralight scalar dark matter. Such dark matter can cause temporal oscillations in fundamental constants with a frequency set by the dark matter mass and amplitude determined by the local dark matter density. The result is a modulation of atomic transition energies. We point out a new time-domain signature of this effect in a type of gravitational wave detector that compares two spatially separated atom interferometers referenced by a common laser. Such a detector can improve on current searches for electron-mass or electric-charge modulus dark matter by up to 10 orders of magnitude in coupling, in a frequency band complementary to that of other proposals. It demonstrates that this class of atomic sensors is qualitatively different from other gravitational wave detectors, including those based on laser interferometry. By using atomic-clock-like interferometers, laser noise is mitigated with only a single baseline. These atomic sensors can thus detect scalar signals in addition to tensor signals.

Rotational motions from the 2016, Central Italy seismic sequence, as observed by an underground ring laser gyroscope

NASA Astrophysics Data System (ADS)

Simonelli, A.; Igel, H.; Wassermann, J.; Belfi, J.; Di Virgilio, A.; Beverini, N.; De Luca, G.; Saccorotti, G.

2018-05-01

We present the analysis of rotational and translational ground motions from earthquakes recorded during October/November, 2016, in association with the Central Italy seismic-sequence. We use co-located measurements of the vertical ground rotation rate from a large ring laser gyroscope (RLG), and the three components of ground velocity from a broadband seismometer. Both instruments are positioned in a deep underground environment, within the Gran Sasso National Laboratories (LNGS) of the Istituto Nazionale di Fisica Nucleare (INFN). We collected dozens of events spanning the 3.5-5.9 Magnitude range, and epicentral distances between 30 km and 70 km. This data set constitutes an unprecedented observation of the vertical rotational motions associated with an intense seismic sequence at local distance. Under the plane wave approximation we process the data set in order to get an experimental estimation of the events back azimuth. Peak values of rotation rate (PRR) and horizontal acceleration (PGA) are markedly correlated, according to a scaling constant which is consistent with previous measurements from different earthquake sequences. We used a prediction model in use for Italy to calculate the expected PGA at the recording site, obtaining consequently predictions for PRR. Within the modeling uncertainties, predicted rotations are consistent with the observed ones, suggesting the possibility of establishing specific attenuation models for ground rotations, like the scaling of peak velocity and peak acceleration in empirical ground-motion prediction relationships. In a second step, after identifying the direction of the incoming wave-field, we extract phase velocity data using the spectral ratio of the translational and rotational components.. This analysis is performed over time windows associated with the P-coda, S-coda and Lg phase. Results are consistent with independent estimates of shear-wave velocities in the shallow crust of the Central Apennines.

Rotational motions from the 2016, Central Italy seismic sequence, as observed by an underground ring laser gyroscope

NASA Astrophysics Data System (ADS)

Simonelli, Andreino; Belfi, Jacopo; Beverini, Nicolò; Di Virgilio, Angela; Maccioni, Enrico; De Luca, Gaetano; Saccorotti, Gilberto; Wassermann, Joachim; Igel, Heiner

2017-04-01

We present analyses of rotational and translational ground motions from earthquakes recorded during October-November, 2016, in association with the Central Italy seismic-sequence. We use co-located measurements of the vertical ground rotation rate from a large ring laser gyroscope (RLG), and the three components of ground velocity from a broadband seismometer. Both instruments are positioned in a deep underground environment, within the Gran Sasso National Laboratories (LNGS) of the Istituto Nazionale di Fisica Nucleare (INFN). We collected dozen of events spanning the 3.5-5.9 Magnitude range, and epicentral distances between 40 km and 80 km. This data set constitutes an unprecedented observation of the vertical rotational motions associated with an intense seismic sequence at local distance. In theory - assuming plane wave propagation - the ratio between the vertical rotation rate and the transverse acceleration permits, in a single station approach, the estimation of apparent phase velocity in the case of SH arrivals or real phase velocity in the case of Love surface waves. This is a standard approach for the analysis of earthquakes at teleseismic distances, and the results reported by the literature are compatible with the expected phase velocities from the PREM model. Here we extend the application of the same approach to local events, thus exploring higher frequency ranges and larger rotation rate amplitudes. We use a novel approach to joint rotation/acceleration analysis based on the continuous wavelet transform (CWT). Wavelet coherence (WTC) is used as a filter for identifying those regions of the time-period plane where the rotation rate and transverse acceleration signals exhibit significant coherence. This allows retrieving estimates of phase velocities over the period range spanned by correlated arrivals. Coherency among ground rotation and translation is also observed throughout the coda of the P-wave arrival, an observation which is interpreted in terms of near-receiver P-SH converted energy due to 3D effects. Those particular coda waves, however, do exhibit a large variability in the rotation/acceleration ratio, as a likely consequence of differences in the wavepath and/or source mechanism.

Beyond seismic interferometry: imaging the earth's interior with virtual sources and receivers inside the earth

NASA Astrophysics Data System (ADS)

Wapenaar, C. P. A.; Van der Neut, J.; Thorbecke, J.; Broggini, F.; Slob, E. C.; Snieder, R.

2015-12-01

Imagine one could place seismic sources and receivers at any desired position inside the earth. Since the receivers would record the full wave field (direct waves, up- and downward reflections, multiples, etc.), this would give a wealth of information about the local structures, material properties and processes in the earth's interior. Although in reality one cannot place sources and receivers anywhere inside the earth, it appears to be possible to create virtual sources and receivers at any desired position, which accurately mimics the desired situation. The underlying method involves some major steps beyond standard seismic interferometry. With seismic interferometry, virtual sources can be created at the positions of physical receivers, assuming these receivers are illuminated isotropically. Our proposed method does not need physical receivers at the positions of the virtual sources; moreover, it does not require isotropic illumination. To create virtual sources and receivers anywhere inside the earth, it suffices to record the reflection response with physical sources and receivers at the earth's surface. We do not need detailed information about the medium parameters; it suffices to have an estimate of the direct waves between the virtual-source positions and the acquisition surface. With these prerequisites, our method can create virtual sources and receivers, anywhere inside the earth, which record the full wave field. The up- and downward reflections, multiples, etc. in the virtual responses are extracted directly from the reflection response at the surface. The retrieved virtual responses form an ideal starting point for accurate seismic imaging, characterization and monitoring.

Ambient Vibration and Earthquake-Data Analyses of a 62-STORY Building Using System Identification and Seismic Interferometry

NASA Astrophysics Data System (ADS)

Kalkan, E.; Fletcher, J. B.; Ulusoy, H. S.; Baker, L. A.

2014-12-01

A 62-story residential tower in San Francisco—the tallest all-residential building in California—was recently instrumented by the USGS's National Strong Motion Project in collaboration with the Strong Motion Instrumentation Program of the California Geological Survey to monitor the motion of a tall building built with specifically engineered features (including buckling-restrained braces, outrigger columns and a tuned liquid damper) to reduce its sway from seismic and wind loads. This 641-ft tower has been outfitted with 72 uni-axial accelerometers, spanning through 26 different levels of the building. For damage detection and localization through structural health monitoring, we use local micro-earthquake and ambient monitoring (background noises) to define linear-elastic (undamaged) dynamic properties of the superstructure including its modal parameters (fundamental frequencies, mode shapes and modal damping values) and shear-wave propagation profile and wave attenuation inside the building, which need to be determined in advance of strong shaking. In order to estimate the baseline modal parameters, we applied a frequency domain decomposition method. Using this method, the first three bending modes in the reference east-west direction, the first two bending modes in the reference north-south direction, and the first two torsional modes were identified. The shear-wave propagation and wave attenuation inside the building were computed using deconvolution interferometry. The data used for analyses are from ambient vibrations having 20 minutes duration, and earthquake data from a local M4.5 event located just north east of Geyserville, California. We show that application of deconvolution interferometry to data recorded inside a building is a powerful technique for monitoring structural parameters, such as velocities of traveling waves, frequencies of normal modes, and intrinsic attenuation (i.e., damping). The simplicity and similarity of the deconvolved waveforms from ambient vibrations and a small magnitude event also suggest that a one-dimensional shear velocity model is sufficiently accurate to represent the wave propagation charactersistics inside the building.

Amplitude and phase measurements based on low-coherence interferometry with acousto-optic spectral image filtration

NASA Astrophysics Data System (ADS)

Machikhin, Alexander; Burmak, Ludmila; Pozhar, Vitold

2018-04-01

The manuscript addresses the advantages and possible applications of acousto-optic image spectral filtration in lowcoherence interferometry. In particular, an effective operation of acousto-optical tunable filters in combination with Michelson-type interferometers is shown. The results of original experiments are presented. It is demonstrated that amplitude and phase spatial distributions of light waves reflected from or transmitted through the object can be fast determined in contactless manner for any spectral intervals with use of the presented techniques.

Design of a digital multiradian phase detector and its application in fusion plasma interferometry.

PubMed

Mlynek, A; Schramm, G; Eixenberger, H; Sips, G; McCormick, K; Zilker, M; Behler, K; Eheberg, J

2010-03-01

We discuss the circuit design of a digital multiradian phase detector that measures the phase difference between two 10 kHz square wave TTL signals and provides the result as a binary number. The phase resolution of the circuit is 1/64 period and its dynamic range is 256 periods. This circuit has been developed for fusion plasma interferometry with submillimeter waves on the ASDEX Upgrade tokamak. The results from interferometric density measurement are discussed and compared to those obtained with the previously used phase detectors, especially with respect to the occurrence of phase jumps. It is illustrated that the new phase measurement provides a powerful tool for automatic real-time validation of the measured density, which is important for feedback algorithms that are sensitive to spurious density signals.

One-shot and aberration-tolerable homodyne detection for holographic storage readout through double-frequency grating-based lateral shearing interferometry.

PubMed

Yu, Yeh-Wei; Xiao, Shuai; Cheng, Chih-Yuan; Sun, Ching-Cherng

2016-05-16

A simple method to decode the stored phase signal of volume holographic data storage with adequate wave aberration tolerance is highly demanded. We proposed and demonstrated a one-shot scheme to decode a binary-phase encoding signal through double-frequency-grating based shearing interferometry (DFGSI). The lateral shearing amount is dependent on the focal length of the collimated lens and the frequency difference between the gratings. Diffracted waves with phase encoding were successfully decoded through experimentation. An optical model for the DFGSI was built to analyze phase-error induction and phase-difference control by shifting the double-frequency grating longitudinally and laterally, respectively. The optical model was demonstrated experimentally. Finally, a high aberration tolerance of the DFGSI was demonstrated using the optical model.

A LISA Interferometry Primer

NASA Technical Reports Server (NTRS)

Thorpe, James Ira

2010-01-01

A key challenge for all gravitational wave detectors in the detection of changes in the fractional difference between pairs of test masses with sufficient precision to measure astrophysical strains with amplitudes on the order of approx.10(exp -21). ln the case of the five million km arms of LISA, this equates to distance measurements on the ten picometer level. LISA interferometry utilizes a decentralized topology, in which each of the sciencecraft houses its own light sources, detectors, and electronics. The measurements made at each of the sciencecraft are then telemetered to ground and combined to extract the strain experienced by the constellation as a whole. I will present an overview of LISA interferometry and highlight some of the key components and technologies that make it possible.

A New Optical Bench Concept for Space-Based Laser Interferometric Gravitational Wave Missions

NASA Astrophysics Data System (ADS)

Chilton, Andrew; Apple, Stephen; Ciani, Giacomo; Olatunde, Taiwo; Conklin, John; Mueller, Guido

2015-04-01

Space-based interferometric gravitational wave detectors such as LISA have been proposed to detect low-frequency gravitational wave sources such as the inspirals of compact objects into massive black holes or two massive black holes into each other. The optical components used to perform the high-precision interferometry required to make these measurements have historically been bonded to Zerodur optical benches, which are thermally ultrastable but difficult and time-consuming to manufacture. More modern implementations of LISA-like interferometry have reduced the length stability requirement on these benches from 30fm/√{Hz} to a few pm √{ Hz}. We therefore propose to alter the design of the optical bench in such a way as to no longer require the use of Zerodur; instead, we plan to replace it with more easily-used materials such as titanium or molybdenum. In this presentation, we discuss the current status of and future plans for the construction and testing of such an optical bench.

Imaging of transient surface acoustic waves by full-field photorefractive interferometry.

PubMed

Xiong, Jichuan; Xu, Xiaodong; Glorieux, Christ; Matsuda, Osamu; Cheng, Liping

2015-05-01

A stroboscopic full-field imaging technique based on photorefractive interferometry for the visualization of rapidly changing surface displacement fields by using of a standard charge-coupled device (CCD) camera is presented. The photorefractive buildup of the space charge field during and after probe laser pulses is simulated numerically. The resulting anisotropic diffraction upon the refractive index grating and the interference between the polarization-rotated diffracted reference beam and the transmitted signal beam are modeled theoretically. The method is experimentally demonstrated by full-field imaging of the propagation of photoacoustically generated surface acoustic waves with a temporal resolution of nanoseconds. The surface acoustic wave propagation in a 23 mm × 17 mm area on an aluminum plate was visualized with 520 × 696 pixels of the CCD sensor, yielding a spatial resolution of 33 μm. The short pulse duration (8 ns) of the probe laser yields the capability of imaging SAWs with frequencies up to 60 MHz.

A Study of Regional Wave Source Time Functions of Central Asian Earthquakes

NASA Astrophysics Data System (ADS)

Xie, J.; Perry, M. R.; Schult, F. R.; Wood, J.

2014-12-01

Despite the extensive use of seismic regional waves in seismic event identification and attenuation tomography, very little is known on how seismic sources radiate energy into these waves. For example, whether regional Lg wave has the same source spectrum as that of the local S has been questioned by Harr et al. and Frenkel et al. three decades ago; many current investigators assume source spectra in Lg, Sn, Pg, Pn and Lg coda waves have either the same or very similar corner frequencies, in contrast to local P and S spectra whose corner frequencies differ. The most complete information on how the finite source ruptures radiate energy into regional waves is contained in the time domain source time functions (STFs). To estimate the STFs of regional waves using the empirical Green's function (EGF) method, we have been substantially modifying a semi-automotive computer procedure to cope with the increasingly diverse and inconsistent naming patterns of new data files from the IRIS DMC. We are applying the modified procedure to many earthquakes in central Asia to study the STFs of various regional waves to see whether they have the same durations and pulse shapes, and how frequently source directivity occur. When applicable, we also examine the differences between STFs of local P and S waves and those of regional waves. The result of these analyses will be presented at the meeting.

Chapter 3 – Phenomenology of Tsunamis: Statistical Properties from Generation to Runup

USGS Publications Warehouse

Geist, Eric L.

2015-01-01

Observations related to tsunami generation, propagation, and runup are reviewed and described in a phenomenological framework. In the three coastal regimes considered (near-field broadside, near-field oblique, and far field), the observed maximum wave amplitude is associated with different parts of the tsunami wavefield. The maximum amplitude in the near-field broadside regime is most often associated with the direct arrival from the source, whereas in the near-field oblique regime, the maximum amplitude is most often associated with the propagation of edge waves. In the far field, the maximum amplitude is most often caused by the interaction of the tsunami coda that develops during basin-wide propagation and the nearshore response, including the excitation of edge waves, shelf modes, and resonance. Statistical distributions that describe tsunami observations are also reviewed, both in terms of spatial distributions, such as coseismic slip on the fault plane and near-field runup, and temporal distributions, such as wave amplitudes in the far field. In each case, fundamental theories of tsunami physics are heuristically used to explain the observations.

A resource management tool for public health continuity of operations during disasters.

PubMed

Turner, Anne M; Reeder, Blaine; Wallace, James C

2013-04-01

We developed and validated a user-centered information system to support the local planning of public health continuity of operations for the Community Health Services Division, Public Health - Seattle & King County, Washington. The Continuity of Operations Data Analysis (CODA) system was designed as a prototype developed using requirements identified through participatory design. CODA uses open-source software that links personnel contact and licensing information with needed skills and clinic locations for 821 employees at 14 public health clinics in Seattle and King County. Using a web-based interface, CODA can visualize locations of personnel in relationship to clinics to assist clinic managers in allocating public health personnel and resources under dynamic conditions. Based on user input, the CODA prototype was designed as a low-cost, user-friendly system to inventory and manage public health resources. In emergency conditions, the system can run on a stand-alone battery-powered laptop computer. A formative evaluation by managers of multiple public health centers confirmed the prototype design's usefulness. Emergency management administrators also provided positive feedback about the system during a separate demonstration. Validation of the CODA information design prototype by public health managers and emergency management administrators demonstrates the potential usefulness of building a resource management system using open-source technologies and participatory design principles.

A Resource Management Tool for Public Health Continuity of Operations During Disasters

PubMed Central

Turner, Anne M.; Reeder, Blaine; Wallace, James C.

2014-01-01

Objective We developed and validated a user-centered information system to support the local planning of public health continuity of operations for the Community Health Services Division, Public Health - Seattle & King County, Washington. Methods The Continuity of Operations Data Analysis (CODA) system was designed as a prototype developed using requirements identified through participatory design. CODA uses open-source software that links personnel contact and licensing information with needed skills and clinic locations for 821 employees at 14 public health clinics in Seattle and King County. Using a web-based interface, CODA can visualize locations of personnel in relationship to clinics to assist clinic managers in allocating public health personnel and resources under dynamic conditions. Results Based on user input, the CODA prototype was designed as a low-cost, user-friendly system to inventory and manage public health resources. In emergency conditions, the system can run on a stand-alone battery-powered laptop computer. A formative evaluation by managers of multiple public health centers confirmed the prototype design’s usefulness. Emergency management administrators also provided positive feedback about the system during a separate demonstration. Conclusions Validation of the CODA information design prototype by public health managers and emergency management administrators demonstrates the potential usefulness of building a resource management system using open-source technologies and participatory design principles. PMID:24618165

Survey of Current Clinical and Curriculum Practices of Postgraduate Pediatric Dentistry Programs in Nonintravenous Conscious Sedation in the United States.

PubMed

Morin, Aline; Ocanto, Romer; Drukteinis, Lesbia; Hardigan, Patrick C

2016-10-15

The purposes of this study were to: (1) describe the sedation protocols of postgraduate pediatric dentistry programs (PPDPs) in the U.S.; (2) evaluate how consistent they were with current American Academy of Pediatric Dentistry sedation guidelines and Commission on Dental Accreditation (CODA) sedation curriculum requirements; (3) identify barriers to and tools for implementing these guidelines; and (4) determine the independent association between PPDPs' adherence to guidelines and the program setting. In February 2015, a 40-item questionnaire was e-mailed to all postgraduate pediatric dentistry program directors (PPDPDs) of CODA-accredited programs in the U.S. (n equals 74). Data were analyzed using descriptive statistics and Kruskal-Wallis and pairwise Nemenyi tests. Fifty-two PPDPDs responded (70 percent). Since the 2013 change in CODA sedation requirements, only a limited number of PPDPs (36 percent) were found to be noncompliant with CODA standards. PPDPDs trained at hospital-based programs were found to direct programs that were more compliant with CODA sedation standards (P<.05). A major perceived barrier to increasing the number of sedation cases was the lack of a patient pool (37 percent). Further efforts should be made by teaching institutions for programs to be compliant with American Academy of Pediatric Dentistry and Commission on Dental Accreditation sedation standards.

Full quantum mechanical analysis of atomic three-grating Mach–Zehnder interferometry

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

Sanz, A.S., E-mail: asanz@iff.csic.es; Davidović, M.; Božić, M.

2015-02-15

Atomic three-grating Mach–Zehnder interferometry constitutes an important tool to probe fundamental aspects of the quantum theory. There is, however, a remarkable gap in the literature between the oversimplified models and robust numerical simulations considered to describe the corresponding experiments. Consequently, the former usually lead to paradoxical scenarios, such as the wave–particle dual behavior of atoms, while the latter make difficult the data analysis in simple terms. Here these issues are tackled by means of a simple grating working model consisting of evenly-spaced Gaussian slits. As is shown, this model suffices to explore and explain such experiments both analytically and numerically,more » giving a good account of the full atomic journey inside the interferometer, and hence contributing to make less mystic the physics involved. More specifically, it provides a clear and unambiguous picture of the wavefront splitting that takes place inside the interferometer, illustrating how the momentum along each emerging diffraction order is well defined even though the wave function itself still displays a rather complex shape. To this end, the local transverse momentum is also introduced in this context as a reliable analytical tool. The splitting, apart from being a key issue to understand atomic Mach–Zehnder interferometry, also demonstrates at a fundamental level how wave and particle aspects are always present in the experiment, without incurring in any contradiction or interpretive paradox. On the other hand, at a practical level, the generality and versatility of the model and methodology presented, makes them suitable to attack analogous problems in a simple manner after a convenient tuning. - Highlights: • A simple model is proposed to analyze experiments based on atomic Mach–Zehnder interferometry. • The model can be easily handled both analytically and computationally. • A theoretical analysis based on the combination of the position and momentum representations is considered. • Wave and particle aspects are shown to coexist within the same experiment, thus removing the old wave-corpuscle dichotomy. • A good agreement between numerical simulations and experimental data is found without appealing to best-fit procedures.« less

Elastic properties of transparent nano-polycrystalline diamond measured by GHz-ultrasonic interferometry and resonant sphere methods

NASA Astrophysics Data System (ADS)

Chang, Yun-Yuan; Jacobsen, Steven D.; Kimura, Masaki; Irifune, Tetsuo; Ohno, Ichiro

2014-03-01

The sound velocities and elastic moduli of transparent nano-polycrystalline diamond (NPD) have been determined by GHz-ultrasonic interferometry on three different bulk samples, and by resonant spectroscopy on a spherically fabricated NPD sample. We employ a newly-developed optical contact micrometer to measure the thickness of ultrasonic samples to ±0.05 μm with a spatial resolution of ∼50 μm in the same position of the GHz-ultrasonic measurements, resulting in acoustic-wave sound velocity measurements with uncertainties of 0.005-0.02%. The isotropic and adiabatic bulk and shear moduli of NPD measured by GHz-ultrasonic interferometry are KS0 = 442.5 (±0.5) GPa and G0 = 532.4 (±0.5) GPa. By rotating the shear-wave polarization direction, we observe no transverse anisotropy in this NPD. Using resonant sphere spectroscopy, we obtain KS0 = 440.3 (±0.5) GPa and G0 = 532.7 (±0.4) GPa. For comparison, we also measured by GHz-ultrasonic interferometry the elastic constants of a natural single-crystal type-IA diamond with about one-half the experimental uncertainty of previous measurements. The resulting Voigt-Reuss-Hill averaged bulk and shear moduli of natural diamond are KS0 = 441.8 (±0.8) GPa and G0 = 532.6 (±0.5) GPa, demonstrating that the bulk-elastic properties of transparent NPD are equivalent to natural single-crystal diamond as calculated from polycrystalline averaging of its elastic constants.

Lithospheric structure of the southern French Alps inferred from broadband analysis

NASA Astrophysics Data System (ADS)

Bertrand, E.; Deschamps, A.

2000-11-01

Broadband receiver functions analysis is commonly used to evaluate the fine-scale S-velocity structure of the lithosphere. We analyse teleseismic P-waves and their coda from 30 selected teleseismic events recorded at three seismological stations of to the French TGRS network in the Alpes Maritimes. Receiver functions are computed in the time domain using an SVD matrix inversion method. Dipping Moho and lateral heterogeneities beneath the array are inferred from the amplitude, arrival time and polarity of locally-generated PS phases. We propose that the Moho dips 11° towards 25°±10°N below station CALF, in the outer part of the Alpine belt. At this station, we determine a Moho depth of about 20±2 km; the same depth is suggested below SAOF station also located in the fold-trust belt. Beneath station STET located in the inner part of the Alpine belt, the Moho depth increases to 30 km and dips towards the N-NW. Moreover, 1D-modelling of summed receiver function from STET station constrains a crustal structure significantly different from that observed at stations located in the outer part of the Alps. Indeed, beneath CALF and SAOF stations we need a 2 km thick shallow low velocity layer to fit best the observed receiver functions whereas this layer seems not to be present beneath STET station. Because recent P-coda studies have shown that near-receiver scattering can dominate teleseismic P-wave recordings in tectonically complicated areas, we account for effect of scattering energy in our records from array measurements. As the array aperture is wide relative to the heterogeneity scale length in the area, the array analysis produces only smooth imaging of scatterers beneath the stations.

Local infrasound observations of large ash explosions at Augustine Volcano, Alaska, during January 11–28, 2006

USGS Publications Warehouse

Petersen, Tanja; De Angelis, Silvio; Tytgat, Guy; McNutt, Stephen R.

2006-01-01

We present and interpret acoustic waveforms associated with a sequence of large explosion events that occurred during the initial stages of the 2006 eruption of Augustine Volcano, Alaska. During January 11–28, 2006, 13 large explosion events created ash-rich plumes that reached up to 14 km a.s.l., and generated atmospheric pressure waves that were recorded on scale by a microphone located at a distance of 3.2 km from the active vent. The variety of recorded waveforms included sharp N-shaped waves with durations of a few seconds, impulsive signals followed by complex codas, and extended signals with emergent character and durations up to minutes. Peak amplitudes varied between 14 and 105 Pa; inferred acoustic energies ranged between 2×108 and 4×109 J. A simple N-shaped short-duration signal recorded on January 11, 2006 was associated with the vent-opening blast that marked the beginning of the explosive eruption sequence. During the following days, waveforms with impulsive onsets and extended codas accompanied the eruptive activity, which was characterized by explosion events that generated large ash clouds and pyroclastic flows along the flanks of the volcano. Continuous acoustic waveforms that lacked a clear onset were more common during this period. On January 28, 2006, the occurrence of four large explosion events marked the end of this explosive eruption phase at Augustine Volcano. After a transitional period of about two days, characterized by many small discrete bursts, the eruption changed into a stage of more sustained and less explosive activity accompanied by the renewed growth of a summit lava dome.

Moon meteoritic seismic hum: Steady state prediction

USGS Publications Warehouse

Lognonne, P.; Feuvre, M.L.; Johnson, C.L.; Weber, R.C.

2009-01-01

We use three different statistical models describing the frequency of meteoroid impacts on Earth to estimate the seismic background noise due to impacts on the lunar surface. Because of diffraction, seismic events on the Moon are typically characterized by long codas, lasting 1 h or more. We find that the small but frequent impacts generate seismic signals whose codas overlap in time, resulting in a permanent seismic noise that we term the "lunar hum" by analogy with the Earth's continuous seismic background seismic hum. We find that the Apollo era impact detection rates and amplitudes are well explained by a model that parameterizes (1) the net seismic impulse due to the impactor and resulting ejecta and (2) the effects of diffraction and attenuation. The formulation permits the calculation of a composite waveform at any point on the Moon due to simulated impacts at any epicentral distance. The root-mean-square amplitude of this waveform yields a background noise level that is about 100 times lower than the resolution of the Apollo long-period seismometers. At 2 s periods, this noise level is more than 1000 times lower than the low noise model prediction for Earth's microseismic noise. Sufficiently sensitive seismometers will allow the future detection of several impacts per day at body wave frequencies. Copyright 2009 by the American Geophysical Union.

The use of holographic interferometry for measurements of temperature in a rectangular heat pipe. M.S. Thesis

NASA Technical Reports Server (NTRS)

Marn, Jure

1989-01-01

Holographic interferometry is a nonintrusive method and as such possesses considerable advantages such as not disturbing the velocity and temperature field by creating obstacles which would alter the flow field. These optical methods have disadvantages as well. Holography, as one of the interferometry methods, retains the accuracy of older methods, and at the same time eliminates the system error of participating components. The holographic interferometry consists of comparing the objective beam with the reference beam and observing the difference in lengths of optical paths, which can be observed during the propagation of the light through a medium with locally varying refractive index. Thus, change in refractive index can be observed as a family of nonintersecting surfaces in space (wave fronts). The object of the investigation was a rectangular heat pipe. The goal was to measure temperatures in the heat pipe, which yields data for computer code or model assessment. The results were obtained by calculating the temperatures by means of finite fringes.

Evaluation of the wave measurement in a stormy sea by the Along-Track interferometry SAR

NASA Astrophysics Data System (ADS)

Kojima, S.

2015-12-01

NICT developed the along-track interferometry SAR (AT-InSAR) system to detect the running cars and ships and measure sea surface velocity in 2011. The preliminary experiments for the running truck and ship were performed and it confirmed that the system performance was satisfactory to its specifications. In addition, a method to estimate the wave height from the sea surface velocity measured by the AT-InSAR was developed. The preliminary wave height observation was performed in a calm sea, and it was confirmed that the wave height could be estimated from the measured sea surface velocity. The purpose of this study is to check the capability of the ocean waves observation in a stormy sea by the AT-InSAR. Therefore, the ocean wave observation was performed under the low atmospheric pressure. The observation area is the sea surface at 10 km off the coast of Kushiro, south-east to Hokaido, JAPAN on the 4th of March 2015. The wind speed was 8〜10m/s during the observation, and the significant wave height and period were 1.5m and 6.0s. The observation was performed in 2 directions and the accuracy of the estimation results were checked. The significant wave height and period measured by the AT-InSAR agreed with it measured by the wave gage located close to this observation area. In addition, it was confirmed that there were no irregular wave heights in the distribution of the estimated wave height. As a result, it became clear that the AT-InSAR could observe the wave height in a stormy sea.

Towards Simulating a Realistic Planetary Seismic Wavefield: The Contribution of the Megaregolith and Low-Velocity Waveguides

NASA Technical Reports Server (NTRS)

Schmerr, Nicholas C.; Weber, Renee C.; Lin, Pei-Ying Patty; Thorne, Michael Scott; Garnero, Ed J.

2011-01-01

Lunar seismograms are distinctly different from their terrestrial counterparts. The Apollo lunar seismometers recorded moonquakes without distinct P- or S-wave arrivals; instead waves arrive as a diffuse coda that decays over several hours making the identification of body waves difficult. The unusual character of the lunar seismic wavefield is generally tied to properties of the megaregolith: it consists of highly fractured and broken crustal rock, the result of extensive bombardment of the Moon. The megaregolith extends several kilometers into the lunar crust, possibly into the mantle in some regions, and is covered by a thin coating of fine-scale dust. These materials possess very low seismic velocities that strongly scatter the seismic wavefield at high frequencies. Directly modeling the effects of the megaregolith to simulate an accurate lunar seismic wavefield is a challenging computational problem, owing to the inherent 3-D nature of the problem and the high frequencies (greater than 1 Hz) required. Here we focus on modeling the long duration code, studying the effects of the low velocities found in the megaregolith. We produce synthetic seismograms using 1-D slowness integration methodologies, GEMINI and reflectivity, and a 3-D Cartesian finite difference code, Wave Propagation Program, to study the effect of thin layers of low velocity on the surface of a planet. These codes allow us generate seismograms with dominant frequencies of approximately 1 Hz. For background lunar seismic structure we explore several models, including the recent model of Weber et al., Science, 2011. We also investigate variations in megaregolithic thickness, velocity, attenuation, and seismogram frequency content. Our results are compared to the Apollo seismic dataset, using both a cross correlation technique and integrated envelope approach to investigate coda decay. We find our new high frequency results strongly support the hypothesis that the long duration of the lunar seismic codes is generated by the presence of the low velocity megaregolith, and that the diffuse arrivals are a combination of scattered energy and multiple reverberations within this layer. The 3-D modeling indicates the extreme surface topography of the Moon adds only a small contribution to scattering effects, though local geology may play a larger role. We also study the effects of the megaregolith on core reflected and converted phases and other body waves. Our analysis indicates detection of core interacting arrivals with a polarization filter technique is robust and lends the possibility of detecting other body waves from the Moon.

Combining Monte Carlo methods with coherent wave optics for the simulation of phase-sensitive X-ray imaging

PubMed Central

Peter, Silvia; Modregger, Peter; Fix, Michael K.; Volken, Werner; Frei, Daniel; Manser, Peter; Stampanoni, Marco

2014-01-01

Phase-sensitive X-ray imaging shows a high sensitivity towards electron density variations, making it well suited for imaging of soft tissue matter. However, there are still open questions about the details of the image formation process. Here, a framework for numerical simulations of phase-sensitive X-ray imaging is presented, which takes both particle- and wave-like properties of X-rays into consideration. A split approach is presented where we combine a Monte Carlo method (MC) based sample part with a wave optics simulation based propagation part, leading to a framework that takes both particle- and wave-like properties into account. The framework can be adapted to different phase-sensitive imaging methods and has been validated through comparisons with experiments for grating interferometry and propagation-based imaging. The validation of the framework shows that the combination of wave optics and MC has been successfully implemented and yields good agreement between measurements and simulations. This demonstrates that the physical processes relevant for developing a deeper understanding of scattering in the context of phase-sensitive imaging are modelled in a sufficiently accurate manner. The framework can be used for the simulation of phase-sensitive X-ray imaging, for instance for the simulation of grating interferometry or propagation-based imaging. PMID:24763652

Crustal structure of the Alps as seen by attenuation tomography

NASA Astrophysics Data System (ADS)

Mayor, Jessie; Calvet, Marie; Margerin, Ludovic; Vanderhaeghe, Olivier; Traversa, Paola

2016-04-01

We develop a simple tomographic approach exploiting the decay rate of coda waves to map the absorption properties of the crust in a region delimited approximately by the Rhine Graben to the North, the Apennines to the South, the Massif Central to the West and the Dinarides to the East. Our dataset comprises 40 000 coda records of about 2000 weak to moderate crustal earthquakes, with magnitude ranging from 2.8 to 6 and recorded by broad-band, accelerometric and short-period stations. After proper choice of a coda window minimizing the effects of variable epicentral distances, we measure the coda quality factor Qc in five non-overlapping frequency windows covering the 1-32 Hz band for all available source station pairs. These measurements are subsequently converted into maps of absorption quality factor (Qi) using a linearized, approximate relation between Qc and Qi. In practice the following procedure is applied in each frequency band: (1) we divide the target region into 40 × 40 km cells; (2) for each source-station pair, we assign the measured Qc value to each pixel intercepted by the direct ray path; (3) the results are averaged over all paths and subsequently smoothed with a 3 × 3 pixels moving window. Our approach is consistent with the high sensitivity of Qc to the value of Qi between source and station. Our tomographic approach reveals strong lateral variations of absorption with length scales ranging from 100 km to 1000 km. At low frequency (∼ 1 Hz), the correlation with the surface geology is clear, Cenozoic and Mesozoic sedimentary basins (resp. crystalline massifs) being recognized as high (resp. low)-absorption regions. Furthermore the Qi map delineates finer geological features such as the Ivrea Body, the Rhône Valley, or felsic intrusions in the central Alps. At high-frequency (>16 Hz), only the thickest Cenozoic sedimentary deposits show up as high-attenuation regions and a north/south dichotomy is apparent in the absorption structure. The limit between low-attenuation regions to the North and high-attenuation region to the South correlates geographically with the location of the Periadriatic Lineament (PL), a major late-alpine crustal- to lithospheric-scale structure. Furthermore, the attenuation structure seems to prolong the PL to the West along a line marked by large historical earthquakes. The Apennines orogenic belts exhibit a distinct frequency behavior, with high attenuation at low-frequency and low-attenuation at high-frequency. Low-frequency absorption may likely be explained by the relatively thick cover of Cenozoic sedimentary materials, as well as by shallow geothermal activity. We hypothesize that the frequency dependence of the attenuation structure, in particular in the Apennines, is caused by a change of the wavefield composition which accentuates the sensitivity of the coda to the deeper parts of the medium as the frequency increases.

Dual-wavelength, continuous-wave Yb:YAG laser for high-resolution photothermal common-path interferometry.

PubMed

Zhuang, Fengjiang; Jungbluth, Bernd; Gronloh, Bastian; Hoffmann, Hans-Dieter; Zhang, Ge

2013-07-20

We present a continuous-wave (CW) intracavity frequency-doubled Yb:YAG laser providing 1030 and 515 nm output simultaneously. This laser system was designed for photothermal common-path interferometry to measure spatially resolved profiles of the linear absorption in dielectric media and coatings for visible or infrared light as well as of the nonlinear absorption for the combination of both. A Z-shape laser cavity was designed, providing a beam waist in which an LBO crystal was located for effective second-harmonic generation (SHG). Suitable frequency conversion parameters and cavity configurations were discussed to achieve the optimal performance of a diode-pumped CW SHG laser. A 12.4 W 1030 nm laser and 5.4 W 515 nm laser were developed simultaneously in our experiment.

Estimation of seismic attenuation in carbonate rocks using three different methods: Application on VSP data from Abu Dhabi oilfield

NASA Astrophysics Data System (ADS)

Bouchaala, F.; Ali, M. Y.; Matsushima, J.

2016-06-01

In this study a relationship between the seismic wavelength and the scale of heterogeneity in the propagating medium has been examined. The relationship estimates the size of heterogeneity that significantly affects the wave propagation at a specific frequency, and enables a decrease in the calculation time of wave scattering estimation. The relationship was applied in analyzing synthetic and Vertical Seismic Profiling (VSP) data obtained from an onshore oilfield in the Emirate of Abu Dhabi, United Arab Emirates. Prior to estimation of the attenuation, a robust processing workflow was applied to both synthetic and recorded data to increase the Signal-to-Noise Ratio (SNR). Two conventional methods of spectral ratio and centroid frequency shift methods were applied to estimate the attenuation from the extracted seismic waveforms in addition to a new method based on seismic interferometry. The attenuation profiles derived from the three approaches demonstrated similar variation, however the interferometry method resulted in greater depth resolution, differences in attenuation magnitude. Furthermore, the attenuation profiles revealed significant contribution of scattering on seismic wave attenuation. The results obtained from the seismic interferometry method revealed estimated scattering attenuation ranges from 0 to 0.1 and estimated intrinsic attenuation can reach 0.2. The subsurface of the studied zones is known to be highly porous and permeable, which suggest that the mechanism of the intrinsic attenuation is probably the interactions between pore fluids and solids.

Comparison of the results of refractometric measurements in the process of diffusion, obtained by means of the backgroundoriented schlieren method and the holographic interferometry method

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

Kraiskii, A V; Mironova, T V

2015-08-31

The results of the study of interdiffusion of two liquids, obtained using the holographic recording scheme with a nonstationary reference wave with the frequency linearly varying in space and time are compared with the results of correlation processing of digital photographs, made with a random background screen. The spatio-temporal behaviour of the signal in four basic representations ('space – temporal frequency', 'space – time', 'spatial frequency – temporal frequency' and 'spatial frequency – time') is found in the holographic experiment and calculated (in the appropriate coordinates) based on the background-oriented schlieren method. Practical coincidence of the results of the correlationmore » analysis and the holographic double-exposure interferometry is demonstrated. (interferometry)« less

Conduit dynamics and post explosion degassing on Stromboli: A combined UV camera and numerical modeling treatment

PubMed Central

McGonigle, A. J. S.; James, M. R.; Tamburello, G.; Aiuppa, A.; Delle Donne, D.; Ripepe, M.

2016-01-01

Abstract Recent gas flux measurements have shown that Strombolian explosions are often followed by periods of elevated flux, or “gas codas,” with durations of order a minute. Here we present UV camera data from 200 events recorded at Stromboli volcano to constrain the nature of these codas for the first time, providing estimates for combined explosion plus coda SO2 masses of ≈18–225 kg. Numerical simulations of gas slug ascent show that substantial proportions of the initial gas mass can be distributed into a train of “daughter bubbles” released from the base of the slug, which we suggest, generate the codas, on bursting at the surface. This process could also cause transitioning of slugs into cap bubbles, significantly reducing explosivity. This study is the first attempt to combine high temporal resolution gas flux data with numerical simulations of conduit gas flow to investigate volcanic degassing dynamics. PMID:27478285

Upper Crustal Structure of Taiwan Constrained by the Ellipticity of the Noise-derived Rayleigh Waves

NASA Astrophysics Data System (ADS)

Chien, C. C.; Chen, Y. N.; Gung, Y.; Liang, W. T.

2016-12-01

In the last decade, the noise interferometry has been a popular technique, and widely applied to constraint the crust and uppermost mantle structure, bringing in revolutionary resolution in area with dense seismic network, including Taiwan. However, limited by the available frequency band of the noise-derived surface waves, the near surface (<5km) structure is much less resolved as compared to the rest of the crust in Taiwan. Such limitation may be lifted by using the ZH ratio of Rayleigh waves, because, for the same period, the ZH ratio of Rayleigh waves is much more sensitive to the shallower structure than those provided by the corresponding phase or group velocities. In this study, aiming to better constraint the seismic structure of the shallow crust of Taiwan, we measure the ZH ratios of the Rayleigh waves derived by noise interferometry. Continuous records from two major seismic networks in Taiwan are used. In total, data from 63 short period stations and 48 broadband stations are used to derived the four combinations (ZZ, ZR, RZ, RR) of cross-correlation functions (CCF). We then measure the ZH ratios of the derived Rayleigh waves. We present the measured results, invert for the local 1-D structure for sites with stable measurements. We then compare the results with the published tomographic models and discuss their geological implications.

Gravitational wave detection using laser interferometry beyond the standard quantum limit

NASA Astrophysics Data System (ADS)

Heurs, M.

2018-05-01

Interferometric gravitational wave detectors (such as advanced LIGO) employ high-power solid-state lasers to maximize their detection sensitivity and hence their reach into the universe. These sophisticated light sources are ultra-stabilized with regard to output power, emission frequency and beam geometry; this is crucial to obtain low detector noise. However, even when all laser noise is reduced as far as technically possible, unavoidable quantum noise of the laser still remains. This is a consequence of the Heisenberg Uncertainty Principle, the basis of quantum mechanics: in this case, it is fundamentally impossible to simultaneously reduce both the phase noise and the amplitude noise of a laser to arbitrarily low levels. This fact manifests in the detector noise budget as two distinct noise sources-photon shot noise and quantum radiation pressure noise-which together form a lower boundary for current-day gravitational wave detector sensitivities, the standard quantum limit of interferometry. To overcome this limit, various techniques are being proposed, among them different uses of non-classical light and alternative interferometer topologies. This article explains how quantum noise enters and manifests in an interferometric gravitational wave detector, and gives an overview of some of the schemes proposed to overcome this seemingly fundamental limitation, all aimed at the goal of higher gravitational wave event detection rates. This article is part of a discussion meeting issue `The promises of gravitational-wave astronomy'.

Gravitational wave detection using laser interferometry beyond the standard quantum limit.

PubMed

Heurs, M

2018-05-28

Interferometric gravitational wave detectors (such as advanced LIGO) employ high-power solid-state lasers to maximize their detection sensitivity and hence their reach into the universe. These sophisticated light sources are ultra-stabilized with regard to output power, emission frequency and beam geometry; this is crucial to obtain low detector noise. However, even when all laser noise is reduced as far as technically possible, unavoidable quantum noise of the laser still remains. This is a consequence of the Heisenberg Uncertainty Principle, the basis of quantum mechanics: in this case, it is fundamentally impossible to simultaneously reduce both the phase noise and the amplitude noise of a laser to arbitrarily low levels. This fact manifests in the detector noise budget as two distinct noise sources-photon shot noise and quantum radiation pressure noise-which together form a lower boundary for current-day gravitational wave detector sensitivities, the standard quantum limit of interferometry. To overcome this limit, various techniques are being proposed, among them different uses of non-classical light and alternative interferometer topologies. This article explains how quantum noise enters and manifests in an interferometric gravitational wave detector, and gives an overview of some of the schemes proposed to overcome this seemingly fundamental limitation, all aimed at the goal of higher gravitational wave event detection rates.This article is part of a discussion meeting issue 'The promises of gravitational-wave astronomy'. © 2018 The Author(s).

Field observations of seismic velocity changes caused by shaking-induced damage and healing due to mesoscopic nonlinearity

NASA Astrophysics Data System (ADS)

Gassenmeier, M.; Sens-Schönfelder, C.; Eulenfeld, T.; Bartsch, M.; Victor, P.; Tilmann, F.; Korn, M.

2016-03-01

To investigate temporal seismic velocity changes due to earthquake related processes and environmental forcing in Northern Chile, we analyse 8 yr of ambient seismic noise recorded by the Integrated Plate Boundary Observatory Chile (IPOC). By autocorrelating the ambient seismic noise field measured on the vertical components, approximations of the Green's functions are retrieved and velocity changes are measured with Coda Wave Interferometry. At station PATCX, we observe seasonal changes in seismic velocity caused by thermal stress as well as transient velocity reductions in the frequency range of 4-6 Hz. Sudden velocity drops occur at the time of mostly earthquake-induced ground shaking and recover over a variable period of time. We present an empirical model that describes the seismic velocity variations based on continuous observations of the local ground acceleration. The model assumes that not only the shaking of large earthquakes causes velocity drops, but any small vibrations continuously induce minor velocity variations that are immediately compensated by healing in the steady state. We show that the shaking effect is accumulated over time and best described by the integrated envelope of the ground acceleration over the discretization interval of the velocity measurements, which is one day. In our model, the amplitude of the velocity reduction as well as the recovery time are proportional to the size of the excitation. This model with two free scaling parameters fits the data of the shaking induced velocity variation in remarkable detail. Additionally, a linear trend is observed that might be related to a recovery process from one or more earthquakes before our measurement period. A clear relationship between ground shaking and induced velocity reductions is not visible at other stations. We attribute the outstanding sensitivity of PATCX to ground shaking and thermal stress to the special geological setting of the station, where the subsurface material consists of relatively loose conglomerate with high pore volume leading to a stronger nonlinearity compared to the other IPOC stations.

Atom Interferometry in a Warm Vapor

DOE PAGES

Biedermann, G. W.; McGuinness, H. J.; Rakholia, A. V.; ...

2017-04-17

Here, we demonstrate matter-wave interference in a warm vapor of rubidium atoms. Established approaches to light-pulse atom interferometry rely on laser cooling to concentrate a large ensemble of atoms into a velocity class resonant with the atom optical light pulse. In our experiment, we show that clear interference signals may be obtained without laser cooling. This effect relies on the Doppler selectivity of the atom interferometer resonance. Lastly, this interferometer may be configured to measure accelerations, and we demonstrate that multiple interferometers may be operated simultaneously by addressing multiple velocity classes.

Status of the LISA On Table experiment: a electro-optical simulator for LISA

NASA Astrophysics Data System (ADS)

Laporte, M.; Halloin, H.; Bréelle, E.; Buy, C.; Grüning, P.; Prat, P.

2017-05-01

The LISA project is a space mission that aim at detecting gravitational waves in space. An electro-optical simulator called LISA On Table (LOT) is being developed at APC in order to test noise reduction techniques (such as Timed Delayed Interferometry) and instruments that will be used. This document presents its latest results: TimeDelayed Interferometry of 1st generation works in the case of a simulated white noise with static, unequal arms. Future and ongoing developments of the experiment are also addressed.

Monitoring stress related velocity variation in concrete with a 2 x 10(-5) relative resolution using diffuse ultrasound.

PubMed

Larose, Eric; Hall, Stephen

2009-04-01

Ultrasonic waves propagating in solids have stress-dependent velocities. The relation between stress (or strain) and velocity forms the basis of non-linear acoustics. In homogeneous solids, conventional time-of-flight techniques have measured this dependence with spectacular precision. In heterogeneous media such as concrete, the direct (ballistic) wave around 500 kHz is strongly attenuated and conventional techniques are less efficient. In this manuscript, the effect of weak stress changes on the late arrivals constituting the acoustic diffuse coda is tracked. A resolution of 2 x 10(-5) in relative velocity change is attained which corresponds to a sensitivity to stress change of better than 50 kPa. Therefore, the technique described here provides an original way to measure the non-linear parameter with stress variations on the order of tens of kPa.

Reflectometry diagnostics on TCV

NASA Astrophysics Data System (ADS)

Molina Cabrera, Pedro; Coda, Stefano; Porte, Laurie; Offeddu, Nicola; Tcv Team

2017-10-01

Both profile reflectometer and Doppler back-scattering (DBS) diagnostics are being developed for the TCV Tokamak using a steerable quasi-optical launcher and universal polarizers. First results will be presented. A pulse reflectometer is being developed to complement Thomson Scattering measurements of electron density, greatly increasing temporal resolution and also effectively enabling fluctuation measurements. Pulse reflectometry consists of sending short pulses of varying frequency and measuring the roundtrip group-delay with precise chronometers. A fast arbitrary waveform generator is used as a pulse source feeding frequency multipliers that bring the pulses to V-band. A DBS diagnostic is currently operational in TCV. DBS may be used to infer the perpendicular velocity and wave number spectrum of electron density fluctuations in the 3-15 cm-1 wave-number range. Off-the-shelf transceiver modules, originally used for VNA measurements, are being used in a Doppler radar configuration. See author list of S. Coda et al., 2017 Nucl. Fusion 57 102011.

Optical fiber interferometer for the study of ultrasonic waves in composite materials

NASA Technical Reports Server (NTRS)

Claus, R. O.; Zewekh, P. S.; Turner, T. M.; Wade, J. C.; Rogers, R. T.; Garg, A. O.

1981-01-01

The possibility of acoustic emission detection in composites using embedded optical fibers as sensing elements was investigated. Optical fiber interferometry, fiber acoustic sensitivity, fiber interferometer calibration, and acoustic emission detection are reported. Adhesive bond layer dynamical properties using ultrasonic interface waves, the design and construction of an ultrasonic transducer with a two dimensional Gaussian pressure profile, and the development of an optical differential technique for the measurement of surface acoustic wave particle displacements and propagation direction are also examined.

Quantum noise limits to matter-wave interferometry

NASA Technical Reports Server (NTRS)

Scully, Marlan O.; Dowling, Jonathan P.

1994-01-01

We derive the quantum limits for an atomic interferometer in which the atoms obey either Bose-Einstein or Fermi-Dirac statistics. It is found that the limiting quantum noise is due to the uncertainty associated with the particle sorting between the two branches of the interferometer. As an example, the quantum-limited sensitivity of a matter-wave gyroscope is calculated and compared with that of laser gyroscopes.

Phase-sensitive X-ray imager

DOEpatents

Baker, Kevin Louis

2013-01-08

X-ray phase sensitive wave-front sensor techniques are detailed that are capable of measuring the entire two-dimensional x-ray electric field, both the amplitude and phase, with a single measurement. These Hartmann sensing and 2-D Shear interferometry wave-front sensors do not require a temporally coherent source and are therefore compatible with x-ray tubes and also with laser-produced or x-pinch x-ray sources.

Wave packet interferometry and quantum state reconstruction by acousto-optic phase modulation

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

Tekavec, Patrick F.; Dyke, Thomas R.; Marcus, Andrew H.

2006-11-21

Studies of wave packet dynamics often involve phase-selective measurements of coherent optical signals generated from sequences of ultrashort laser pulses. In wave packet interferometry (WPI), the separation between the temporal envelopes of the pulses must be precisely monitored or maintained. Here we introduce a new (and easy to implement) experimental scheme for phase-selective measurements that combines acousto-optic phase modulation with ultrashort laser excitation to produce an intensity-modulated fluorescence signal. Synchronous detection, with respect to an appropriately constructed reference, allows the signal to be simultaneously measured at two phases differing by 90 deg. Our method effectively decouples the relative temporal phasemore » from the pulse envelopes of a collinear train of optical pulse pairs. We thus achieve a robust and high signal-to-noise scheme for WPI applications, such as quantum state reconstruction and electronic spectroscopy. The validity of the method is demonstrated, and state reconstruction is performed, on a model quantum system - atomic Rb vapor. Moreover, we show that our measurements recover the correct separation between the absorptive and dispersive contributions to the system susceptibility.« less

Pixel level optical-transfer-function design based on the surface-wave-interferometry aperture

PubMed Central

Zheng, Guoan; Wang, Yingmin; Yang, Changhuei

2010-01-01

The design of optical transfer function (OTF) is of significant importance for optical information processing in various imaging and vision systems. Typically, OTF design relies on sophisticated bulk optical arrangement in the light path of the optical systems. In this letter, we demonstrate a surface-wave-interferometry aperture (SWIA) that can be directly incorporated onto optical sensors to accomplish OTF design on the pixel level. The whole aperture design is based on the bull’s eye structure. It composes of a central hole (diameter of 300 nm) and periodic groove (period of 560 nm) on a 340 nm thick gold layer. We show, with both simulation and experiment, that different types of optical transfer functions (notch, highpass and lowpass filter) can be achieved by manipulating the interference between the direct transmission of the central hole and the surface wave (SW) component induced from the periodic groove. Pixel level OTF design provides a low-cost, ultra robust, highly compact method for numerous applications such as optofluidic microscopy, wavefront detection, darkfield imaging, and computational photography. PMID:20721038

P and S Velocity Structure in the Groningen Gas Reservoir From Noise Interferometry

NASA Astrophysics Data System (ADS)

Zhou, Wen; Paulssen, Hanneke

2017-12-01

Noise interferometry has proven to be a powerful tool to image seismic structure. In this study we used data from 10 geophones located in a borehole at ˜3 km depth within the Groningen gas reservoir in the Netherlands. The continuous data cross correlations show that noise predominantly comes in from above. The observed daily and weekly variations further indicate that the noise has an anthropogenic origin. The direct P wave emerges from the stacked vertical component cross correlations with frequencies up to 80 Hz and the direct S wave is retrieved from the horizontal components with frequencies up to 50 Hz. The measured intergeophone travel times were used to retrieve the P and S velocity structure along the borehole, and a good agreement was found with well log data. In addition, from the S wave polarizations, we determined azimuthal anisotropy with a fast direction of N65°W±18° and an estimated magnitude of (4±2)%. The fast polarization direction corresponds to the present direction of maximum horizontal stress measured at nearby boreholes but is also similar to the estimated paleostress direction.

Monitoring the Groningen gas field by seismic noise interferometry

NASA Astrophysics Data System (ADS)

Zhou, Wen; Paulssen, Hanneke

2017-04-01

The Groningen gas field in the Netherlands is the world's 7th largest onshore gas field and has been producing from 1963. Since 2013, the year with the highest level of induced seismicity, the reservoir has been monitored by two geophone strings at reservoir level at about 3 km depth. For borehole SDM, 10 geophones with a natural frequency of 15-Hz are positioned from the top to bottom of the reservoir with a geophone spacing of 30 m. We used seismic interferometry to determine, as accurately as possible, the inter-geophone P- and S-wave velocities from ambient noise. We used 1-bit normalization and spectral whitening, together with a bandpass filter from 3 to 400 Hz. After that, for each station pair, the normalized cross-correlation was calculated for 6 seconds segments with 2/3 overlap. These segmented cross-correlations were stacked for every 1 hour, 24(hours)*33(days) segments were obtained for each station pair. The cross-correlations show both day-and-night and weekly variations reflecting fluctuations in cultural noise. The apparent P-wave travel time for each geophone pair is measured from the maximum of the vertical component cross-correlation for each of the hourly stacks. Because the distribution of these (24*33) picked travel times is not Gaussian but skewed, we used Kernel density estimations to obtain probability density functions of the travel times. The maximum likelihood travel times of all the geophone pairs was subsequently used to determine inter-geophone P-wave velocities. A good agreement was found between our estimated P velocity structure and well logging data, with difference less than 5%. The S-velocity structure was obtained from the east-component cross-correlations. They show both the direct P- and S-wave arrivals and, because of the interference, the inferred S-velocity structure is less accurate. From the 9(3x3)-component cross-correlations for all the geophone pairs, not only the direct P and S waves can be identified, but also reflected waves within the reservoir for some of the cross-correlations. It is concluded that noise interferometry can be used to determine the seismic velocity structure from deep borehole data.

Tone-assisted time delay interferometry on GRACE Follow-On

NASA Astrophysics Data System (ADS)

Francis, Samuel P.; Shaddock, Daniel A.; Sutton, Andrew J.; de Vine, Glenn; Ware, Brent; Spero, Robert E.; Klipstein, William M.; McKenzie, Kirk

2015-07-01

We have demonstrated the viability of using the Laser Ranging Interferometer on the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) space mission to test key aspects of the interspacecraft interferometry proposed for detecting gravitational waves. The Laser Ranging Interferometer on GRACE-FO will be the first demonstration of interspacecraft interferometry. GRACE-FO shares many similarities with proposed space-based gravitational wave detectors based on the Laser Interferometer Space Antenna (LISA) concept. Given these similarities, GRACE-FO provides a unique opportunity to test novel interspacecraft interferometry techniques that a LISA-like mission will use. The LISA Experience from GRACE-FO Optical Payload (LEGOP) is a project developing tests of arm locking and time delay interferometry (TDI), two frequency stabilization techniques, that could be performed on GRACE-FO. In the proposed LEGOP TDI demonstration one GRACE-FO spacecraft will have a free-running laser while the laser on the other spacecraft will be locked to a cavity. It is proposed that two one-way interspacecraft phase measurements will be combined with an appropriate delay in order to produce a round-trip, dual one-way ranging (DOWR) measurement independent of the frequency noise of the free-running laser. This paper describes simulated and experimental tests of a tone-assisted TDI ranging (TDIR) technique that uses a least-squares fitting algorithm and fractional-delay interpolation to find and implement the delays needed to form the DOWR TDI combination. The simulation verifies tone-assisted TDIR works under GRACE-FO conditions. Using simulated GRACE-FO signals the tone-assisted TDIR algorithm estimates the time-varying interspacecraft range with a rms error of ±0.2 m , suppressing the free-running laser frequency noise by 8 orders of magnitude. The experimental results demonstrate the practicability of the technique, measuring the delay at the 6 ns level in the presence of a significant displacement signal.

Real-time trichromatic holographic interferometry: preliminary study

NASA Astrophysics Data System (ADS)

Albe, Felix; Bastide, Myriam; Desse, Jean-Michel; Tribillon, Jean-Louis H.

1998-08-01

In this paper we relate our preliminary experiments on real- time trichromatic holographic interferometry. For this purpose a CW `white' laser (argon and krypton of Coherent- Radiation, Spectrum model 70) is used. This laser produces about 10 wavelengths. A system consisting of birefringent plates and polarizers allows to select a trichromatic TEM00 triplet: blue line ((lambda) equals 476 nm, 100 mW), green line ((lambda) equals 514 nm, 100 mW) and red line ((lambda) equals 647 nm, 100 mW). In a first stage we recorded a trichromatic reflection hologram with a separate reference beam on a single-layer silver-halide panchromatic plate (PFG 03C). After processing, the hologram is put back into the original recording set-up, as in classical experiments on real-time monochromatic holographic interferometry. So we observe interference fringes between the 3 reconstructed waves and the 3 actual waves. The interference fringes of the phenomenon are observed on a screen and recorded by a video camera at 25 frames per second. A color video film of about 3 minutes of duration is presented. Some examples related to phase objects are presented (hot airflow from a candle, airflow from a hand). The actual results show the possibility of using this technique to study, in real time, aerodynamic wakes and mechanical deformation.

Children's Acquisition of English Onset and Coda /l/: Articulatory Evidence

ERIC Educational Resources Information Center

Lin, Susan; Demuth, Katherine

2015-01-01

Purpose: The goal of this study was to better understand how and when onset /l/ ("leap") and coda /l/ ("peel") are acquired by children by examining both the articulations involved and adults' perceptions of the produced segments. Method: Twenty-five typically developing Australian English-speaking children aged 3;0…

Coherent properties of a tunable low-energy electron-matter-wave source

NASA Astrophysics Data System (ADS)

Pooch, A.; Seidling, M.; Kerker, N.; Röpke, R.; Rembold, A.; Chang, W. T.; Hwang, I. S.; Stibor, A.

2018-01-01

A general challenge in various quantum experiments and applications is to develop suitable sources for coherent particles. In particular, recent progress in microscopy, interferometry, metrology, decoherence measurements, and chip-based applications rely on intensive, tunable, coherent sources for free low-energy electron-matter waves. In most cases, the electrons get field emitted from a metal nanotip, where its radius and geometry toward a counter electrode determines the field distribution and the emission voltage. A higher emission is often connected to faster electrons with smaller de Broglie wavelengths, requiring larger pattern magnification after matter-wave diffraction or interferometry. This can be prevented with a well-known setup consisting of two counter electrodes that allow independent setting of the beam intensity and velocity. However, it needs to be tested if the coherent properties of such a source are preserved after the acceleration and deceleration of the electrons. Here, we study the coherence of the beam in a biprism interferometer with a single atom tip electron field emitter if the particle velocity and wavelength varies after emission. With a Wien filter measurement and a contrast correlation analysis we demonstrate that the intensity of the source at a certain particle wavelength can be enhanced up to a factor of 6.4 without changing the transverse and longitudinal coherence of the electron beam. In addition, the energy width of the single atom tip emitter was measured to be 377 meV, corresponding to a longitudinal coherence length of 82 nm. The design has potential applications in interferometry, microscopy, and sensor technology.

Inter-station coda wavefield studies using a novel icequake database on Erebus volcano

NASA Astrophysics Data System (ADS)

Chaput, J. A.; Campillo, M.; Roux, P.; Aster, R. C.

2013-12-01

Recent theoretical advances pertaining to the properties of multiply scattered wavefields have yielded a plethora of numerical and controlled source studies aiming to better understand what information may be derived from these otherwise chaotic signals. Practically, multiply scattered wavefields are difficult to compare to numerically derived models due to a combination of source paucity/directionality and array density limitations, particularly in passive seismology scenarios. Furthermore, in situations where data quantities are abundant, such as for ambient noise correlations, it remains very difficult to recover pseudo-Green's function symmetry in the ballistic components of the wavefield, let alone in the coda of the correlations. In this study, we use a large network of short period and broadband instruments on Erebus volcano to show that actual Green's function recovery is indeed possible in some cases. We make use of a large database of small impulsive icequakes distributed randomly on the summit plateau and, using fundamental theoretical properties of equipartitioned wavefields and interstation icequake coda correlations, are able to directly derive notoriously difficult quantities such as the bulk elastic mean free path for the volcano, demonstrations of correlation coda symmetry and its dependence on the number of icequakes used, and a theoretically predicted coherent backscattering amplification factor associated with weak localization. We furthermore show that stable equipartition and H^2/V^2 ratios may be consistently observed for icequake coda, and we perform simple depth inversions of these frequency dependent quantities to compare with known structures.

Bringing mirrors to rest: grating concepts for ultra-precise interferometry

NASA Astrophysics Data System (ADS)

Kroker, Stefanie; Kley, Ernst-Bernhard; Tünnermann, Andreas

2015-02-01

Experiments in the field of high precision metrology such as the detection of gravitational waves are crucially limited by the thermal fluctuations of the optical components. In this contribution we present the current state of knowledge of high contrast gratings (HCGs) as low-noise elements for gravitational wave interferometers. We discuss how the properties of HCGs can be tailored such that beside highly reflective mirrors also diffractive beam splitters can be realized. Further, we show the impact of such gratings on the sensitivity of future gravitational wave detectors which can pave the way for the new field of gravitational wave astronomy.

Three-wave electron vortex lattices for measuring nanofields.

PubMed

Dwyer, C; Boothroyd, C B; Chang, S L Y; Dunin-Borkowski, R E

2015-01-01

It is demonstrated how an electron-optical arrangement consisting of two electron biprisms can be used to generate three-wave vortex lattices with effective lattice spacings between 0.1 and 1 nm. The presence of vortices in these lattices was verified by using a third biprism to perform direct phase measurements via off-axis electron holography. The use of three-wave lattices for nanoscale electromagnetic field measurements via vortex interferometry is discussed, including the accuracy of vortex position measurements and the interpretation of three-wave vortex lattices in the presence of partial spatial coherence. Copyright © 2014 Elsevier B.V. All rights reserved.

Development of phase detection schemes based on surface plasmon resonance using interferometry.

PubMed

Kashif, Muhammad; Bakar, Ahmad Ashrif A; Arsad, Norhana; Shaari, Sahbudin

2014-08-28

Surface plasmon resonance (SPR) is a novel optical sensing technique with a unique ability to monitor molecular binding in real-time for biological and chemical sensor applications. Interferometry is an excellent tool for accurate measurement of SPR changes, the measurement and comparison is made for the sensitivity, dynamic range and resolution of the different analytes using interferometry techniques. SPR interferometry can also employ phase detection in addition to the amplitude of the reflected light wave, and the phase changes more rapidly compared with other approaches, i.e., intensity, angle and wavelength. Therefore, the SPR phase interferometer offers the advantages of spatial phase resolution and high sensitivity. This work discusses the advancements in interferometric SPR methods to measure the phase shifts due to refractive index changes. The main application areas of SPR sensors are demonstrated, i.e., the Fabry-Perot interferometer, Michelson interferometer and Mach-Zehnder interferometer, with different configurations. The three interferometers are discussed in detail, and solutions are suggested to enhance the performance parameters that will aid in future biological and chemical sensors.

Development of Phase Detection Schemes Based on Surface Plasmon Resonance Using Interferometry

PubMed Central

Kashif, Muhammad; Bakar, Ahmad Ashrif A.; Arsad, Norhana; Shaari, Sahbudin

2014-01-01

Surface plasmon resonance (SPR) is a novel optical sensing technique with a unique ability to monitor molecular binding in real-time for biological and chemical sensor applications. Interferometry is an excellent tool for accurate measurement of SPR changes, the measurement and comparison is made for the sensitivity, dynamic range and resolution of the different analytes using interferometry techniques. SPR interferometry can also employ phase detection in addition to the amplitude of the reflected light wave, and the phase changes more rapidly compared with other approaches, i.e., intensity, angle and wavelength. Therefore, the SPR phase interferometer offers the advantages of spatial phase resolution and high sensitivity. This work discusses the advancements in interferometric SPR methods to measure the phase shifts due to refractive index changes. The main application areas of SPR sensors are demonstrated, i.e., the Fabry-Perot interferometer, Michelson interferometer and Mach-Zehnder interferometer, with different configurations. The three interferometers are discussed in detail, and solutions are suggested to enhance the performance parameters that will aid in future biological and chemical sensors. PMID:25171117

Highly sensitive atomic based MW interferometry.

PubMed

Shylla, Dangka; Nyakang'o, Elijah Ogaro; Pandey, Kanhaiya

2018-06-06

We theoretically study a scheme to develop an atomic based micro-wave (MW) interferometry using the Rydberg states in Rb. Unlike the traditional MW interferometry, this scheme is not based upon the electrical circuits, hence the sensitivity of the phase and the amplitude/strength of the MW field is not limited by the Nyquist thermal noise. Further, this system has great advantage due to its much higher frequency range in comparision to the electrical circuit, ranging from radio frequency (RF), MW to terahertz regime. In addition, this is two orders of magnitude more sensitive to field strength as compared to the prior demonstrations on the MW electrometry using the Rydberg atomic states. Further, previously studied atomic systems are only sensitive to the field strength but not to the phase and hence this scheme provides a great opportunity to characterize the MW completely including the propagation direction and the wavefront. The atomic based MW interferometry is based upon a six-level loopy ladder system involving the Rydberg states in which two sub-systems interfere constructively or destructively depending upon the phase between the MW electric fields closing the loop. This work opens up a new field i.e. atomic based MW interferometry replacing the conventional electrical circuit in much superior fashion.

A proposed atom interferometry determination of G at 10-5 using a cold atomic fountain

NASA Astrophysics Data System (ADS)

Rosi, G.

2018-02-01

In precision metrology, the determination of the Newtonian gravity constant G represents a real problem, since its history is plagued by huge unknown discrepancies between a large number of independent experiments. In this paper, we propose a novel experimental setup for measuring G with a relative accuracy of 10-5 , using a standard cold atomic fountain and matter wave interferometry. We discuss in detail the major sources of systematic errors, and provide the expected statistical uncertainty. The feasibility of determining G at the 10-6 level is also discussed.

Amplification of seismic waves by the Seattle basin, Washington State

USGS Publications Warehouse

Pratt, T.L.; Brocher, T.M.; Weaver, C.S.; Creager, K.C.; Snelson, C.M.; Crosson, R.S.; Miller, K.C.; Trehu, A.M.

2003-01-01

Recordings of the 1999 Mw 7.6 Chi-Chi (Taiwan) earthquake, two local earthquakes, and five blasts show seismic-wave amplification over a large sedimentary basin in the U.S. Pacific Northwest. For weak ground motions from the Chi-Chi earthquake, the Seattle basin amplified 0.2- to 0.8-Hz waves by factors of 8 to 16 relative to bedrock sites west of the basin. The amplification and peak frequency change during the Chi-Chi coda: the initial S-wave arrivals (0-30 sec) had maximum amplifications of 12 at 0.5-0.8 Hz, whereas later arrivals (35-65 sec) reached amplifications of 16 at 0.3-0.5 Hz. Analysis of local events in the 1.0- to 10.0-Hz frequency range show fourfold amplifications for 1.0-Hz weak ground motion over the Seattle basin. Amplifications decrease as frequencies increase above 1.0 Hz, with frequencies above 7 Hz showing lower amplitudes over the basin than at bedrock sites. Modeling shows that resonance in low-impedance deposits forming the upper 550 m of the basin beneath our profile could cause most of the observed amplification, and the larger amplification at later arrival times suggests surface waves also play a substantial role. These results emphasize the importance of shallow deposits in determining ground motions over large basins.

Fault zone reverberations from cross-correlations of earthquake waveforms and seismic noise

NASA Astrophysics Data System (ADS)

Hillers, Gregor; Campillo, Michel

2016-03-01

Seismic wavefields interact with low-velocity fault damage zones. Waveforms of ballistic fault zone head waves, trapped waves, reflected waves and signatures of trapped noise can provide important information on structural and mechanical fault zone properties. Here we extend the class of observable fault zone waves and reconstruct in-fault reverberations or multiples in a strike-slip faulting environment. Manifestations of the reverberations are significant, consistent wave fronts in the coda of cross-correlation functions that are obtained from scattered earthquake waveforms and seismic noise recorded by a linear fault zone array. The physical reconstruction of Green's functions is evident from the high similarity between the signals obtained from the two different scattered wavefields. Modal partitioning of the reverberation wavefield can be tuned using different data normalization techniques. The results imply that fault zones create their own ambiance, and that the here reconstructed reverberations are a key seismic signature of wear zones. Using synthetic waveform modelling we show that reverberations can be used for the imaging of structural units by estimating the location, extend and magnitude of lateral velocity contrasts. The robust reconstruction of the reverberations from noise records suggests the possibility to resolve the response of the damage zone material to various external and internal loading mechanisms.

Teleseismic and regional data analysis for estimating depth, mechanism and rupture process of the 3 April 2017 MW 6.5 Botswana earthquake and its aftershock (5 April 2017, MW 4.5)

NASA Astrophysics Data System (ADS)

Letort, J.; Guilhem Trilla, A.; Ford, S. R.; Sèbe, O.; Causse, M.; Cotton, F.; Campillo, M.; Letort, G.

2017-12-01

We constrain the source, depth, and rupture process of the Botswana earthquake of April 3, 2017, as well as its largest aftershock (5 April 2017, Mw 4.5). This earthquake is the largest recorded event (Mw 6.5) in the East African rift system since 1970, making one important case study to better understand source processes in stable continental regions. For the two events an automatic cepstrum analysis (Letort et al., 2015) is first applied on respectively 215 and 219 teleseismic records, in order to detect depth phase arrivals (pP, sP) in the P-coda. Coherent detections of depth phases for different azimuths allow us to estimate the hypocentral depths respectively at 28 and 23 km, suggesting that the events are located in the lower crust. A same cepstrum analysis is conducted on five other earthquakes with mb>4 in this area (from 2002 to 2017), and confirms a deep crustal seismicity cluster (around 20-30 km). The source mechanisms are then characterized using a joint inversion method by fitting both regional long-period surface-waves and teleseismic high-frequency body-waves. Combining regional and teleseismic data (as well as systematic comparisons between theoretical and observed regional surface-waves dispersion curves prior to the inversion) allows us to decrease epistemic uncertainties due to lack of regional data and poor knowledge about the local velocity structure. Focal mechanisms are both constrained as normal faulting with a northwest trending, and hypocentral depths are confirmed at 28 and 24 km. Finally, in order to study the mainshock rupture process, we originally apply a kymograph analysis method (an image processing method, commonly used in the field of cell biology for identifying motions of molecular motors, e.g. Mangeol et al., 2016). Here, the kymograph allows us to better identify high-frequency teleseismic P-arrivals inside the P-coda by tracking both reflected depth phase and direct P-wave arrivals radiated from secondary sources during the faulting process. Secondary P-arrivals are thus identified with a significant azimuthal variation of their arrival times (until 4s), allowing the localization of the source that generated these secondary waves. This analysis shows that the mainshock is probably a mix of at least two events, the second being 20-30 km further northwest along the fault.

Bounds on quantum collapse models from matter-wave interferometry: calculational details

NASA Astrophysics Data System (ADS)

Toroš, Marko; Bassi, Angelo

2018-03-01

We present a simple derivation of the interference pattern in matter-wave interferometry predicted by a class of quantum master equations. We apply the obtained formulae to the following collapse models: the Ghirardi-Rimini-Weber (GRW) model, the continuous spontaneous localization (CSL) model together with its dissipative (dCSL) and non-Markovian generalizations (cCSL), the quantum mechanics with universal position localization (QMUPL), and the Diósi-Penrose (DP) model. We discuss the separability of the dynamics of the collapse models along the three spatial directions, the validity of the paraxial approximation, and the amplification mechanism. We obtain analytical expressions both in the far field and near field limits. These results agree with those already derived in the Wigner function formalism. We compare the theoretical predictions with the experimental data from two recent matter-wave experiments: the 2012 far-field experiment of Juffmann T et al (2012 Nat. Nanotechnol. 7 297-300) and the 2013 Kapitza-Dirac-Talbot-Lau (KDTL) near-field experiment of Eibenberger et al (2013 Phys. Chem. Chem. Phys. 15 14696-700). We show the region of the parameter space for each collapse model that is excluded by these experiments. We show that matter-wave experiments provide model-insensitive bounds that are valid for a wide family of dissipative and non-Markovian generalizations.

Twenty-Four-Month-Olds' Perception of Word-Medial Onsets and Codas

ERIC Educational Resources Information Center

Wang, Yuanyuan; Seidl, Amanda

2016-01-01

Recent work has shown that children have detailed phonological representations of consonants at both word-initial and word-final edges. Nonetheless, it remains unclear whether onsets and codas are equally represented by young learners since word edges are isomorphic with syllable edges in this work. The current study sought to explore toddler's…

Regionalization and dependence of coda Q on frequency and lapse time in the seismically active Peloritani region (northeastern Sicily, Italy)

NASA Astrophysics Data System (ADS)

Giampiccolo, Elisabetta; Tuvè, Tiziana

2018-05-01

The Peloritani region is one of the most seismically active regions in Italy and, consequently, the quantification of attenuation of the medium plays an important role for seismic risk evaluation. Moreover, it is necessary for the prediction of earth ground motion and future seismic source studies. An in depth analysis has been made here to understand the frequency and lapse time dependence of attenuation characteristics of the region by using the coda of local earthquakes. A regionalization is likewise performed in order to investigate the spatial variation of coda Q across the whole region. Finally, our results are jointly interpreted with those obtained from recently published 3D velocity tomographies for further insights.

Real-time monitoring of the solution concentration variation during the crystallization process of protein-lysozyme by using digital holographic interferometry.

PubMed

Zhang, Yanyan; Zhao, Jianlin; Di, Jianglei; Jiang, Hongzhen; Wang, Qian; Wang, Jun; Guo, Yunzhu; Yin, Dachuan

2012-07-30

We report a real-time measurement method of the solution concentration variation during the growth of protein-lysozyme crystals based on digital holographic interferometry. A series of holograms containing the information of the solution concentration variation in the whole crystallization process is recorded by CCD. Based on the principle of double-exposure holographic interferometry and the relationship between the phase difference of the reconstructed object wave and the solution concentration, the solution concentration variation with time for arbitrary point in the solution can be obtained, and then the two-dimensional concentration distribution of the solution during crystallization process can also be figured out under the precondition which the refractive index is constant through the light propagation direction. The experimental results turns out that it is feasible to in situ, full-field and real-time monitor the crystal growth process by using this method.

Holodiagram: elliptic visualizing interferometry, relativity, and light-in-flight.

PubMed

Abramson, Nils H

2014-04-10

In holographic interferometry, there is usually a static distance separating the point of illumination and the point of observation. In Special Relativity, this separation is dynamic and is caused by the velocity of the observer. The corrections needed to compensate for these separations are similar in the two fields. We use the ellipsoids of the holodiagram for measurement and in a graphic way to explain and evaluate optical resolution, gated viewing, radar, holography, three-dimensional interferometry, Special Relativity, and light-in-flight recordings. Lorentz contraction together with time dilation is explained as the result of the eccentricity of the measuring ellipsoid, caused by its velocity. The extremely thin ellipsoid of the very first light appears as a beam aimed directly at the observer, which might explain the wave or ray duality of light and entanglement. Finally, we introduce the concept of ellipsoids of observation.

Digital Beamforming Interferometry

NASA Technical Reports Server (NTRS)

Rincon, Rafael F. (Inventor)

2016-01-01

Airborne or spaceborne Syntheic Aperture Radar (SAR) can be used in a variety of ways, and is often used to generate two dimensional images of a surface. SAR involves the use of radio waves to determine presence, properties, and features of extended areas. Specifically, radio waves are 10 transmitted in the presence of a ground surface. A portion of the radio wave's energy is reflected back to the radar system, which allows the radar system to detect and image the surface. Such radar systems may be used in science applications, military contexts, and other commercial applications.

Surface-wave potential for triggering tectonic (nonvolcanic) tremor

USGS Publications Warehouse

Hill, D.P.

2010-01-01

Source processes commonly posed to explain instances of remote dynamic triggering of tectonic (nonvolcanic) tremor by surface waves include frictional failure and various modes of fluid activation. The relative potential for Love- and Rayleigh-wave dynamic stresses to trigger tectonic tremor through failure on critically stressed thrust and vertical strike-slip faults under the Coulomb-Griffith failure criteria as a function of incidence angle is anticorrelated over the 15- to 30-km-depth range that hosts tectonic tremor. Love-wave potential is high for strike-parallel incidence on low-angle reverse faults and null for strike-normal incidence; the opposite holds for Rayleigh waves. Love-wave potential is high for both strike-parallel and strike-normal incidence on vertical, strike-slip faults and minimal for ~45?? incidence angles. The opposite holds for Rayleigh waves. This pattern is consistent with documented instances of tremor triggered by Love waves incident on the Cascadia mega-thrust and the San Andreas fault (SAF) in central California resulting from shear failure on weak faults (apparent friction, ????? 0.2). However, documented instances of tremor triggered by surface waves with strike-parallel incidence along the Nankai megathrust beneath Shikoku, Japan, is associated primarily with Rayleigh waves. This is consistent with the tremor bursts resulting from mixed-mode failure (crack opening and shear failure) facilitated by near-lithostatic ambient pore pressure, low differential stress, with a moderate friction coefficient (?? ~ 0.6) on the Nankai subduction interface. Rayleigh-wave dilatational stress is relatively weak at tectonic tremor source depths and seems unlikely to contribute significantly to the triggering process, except perhaps for an indirect role on the SAF in sustaining tremor into the Rayleigh-wave coda that was initially triggered by Love waves.

Surface-wave potential for triggering tectonic (nonvolcanic) tremor-corrected

USGS Publications Warehouse

Hill, David P.

2012-01-01

Source processes commonly posed to explain instances of remote dynamic triggering of tectonic (nonvolcanic) tremor by surface waves include frictional failure and various modes of fluid activation. The relative potential for Love- and Rayleigh-wave dynamic stresses to trigger tectonic tremor through failure on critically stressed thrust and vertical strike-slip faults under the Coulomb-Griffith failure criteria as a function of incidence angle are anticorrelated over the 15- to 30-km-depth range that hosts tectonic tremor. Love-wave potential is high for strike-parallel incidence on low-angle reverse faults and null for strike-normal incidence; the opposite holds for Rayleigh waves. Love-wave potential is high for both strike-parallel and strike-normal incidence on vertical, strike-slip faults and minimal for ~45° incidence angles. The opposite holds for Rayleigh waves. This pattern is consistent with documented instances of tremor triggered by Love waves incident on the Cascadia megathrust and the San Andreas fault (SAF) in central California resulting from shear failure on weak faults (apparent friction is μ* ≤ 0:2). Documented instances of tremor triggered by surface waves with strike-parallel incidence along the Nankai megathrust beneath Shikoku, Japan, however, are associated primarily with Rayleigh waves. This is consistent with the tremor bursts resulting from mixed-mode failure (crack opening and shear failure) facilitated by near-lithostatic ambient pore pressure, low differential stress, with a moderate friction coefficient (μ ~ 0:6) on the Nankai subduction interface. Rayleigh-wave dilatational stress is relatively weak at tectonic tremor source depths and seems unlikely to contribute significantly to the triggering process, except perhaps for an indirect role on the SAF in sustaining tremor into the Rayleigh-wave coda that was initially triggered by Love waves.

The Prosodic Licensing of Coda Consonants in Early Speech: Interactions with Vowel Length

ERIC Educational Resources Information Center

Miles, Kelly; Yuen, Ivan; Cox, Felicity; Demuth, Katherine

2016-01-01

English has a word-minimality requirement that all open-class lexical items must contain at least two moras of structure, forming a bimoraic foot (Hayes, 1995).Thus, a word with either a long vowel, or a short vowel and a coda consonant, satisfies this requirement. This raises the question of when and how young children might learn this…

Bimodal Bilingual Language Development of Hearing Children of Deaf Parents

ERIC Educational Resources Information Center

Hofmann, Kristin; Chilla, Solveig

2015-01-01

Adopting a bimodal bilingual language acquisition model, this qualitative case study is the first in Germany to investigate the spoken and sign language development of hearing children of deaf adults (codas). The spoken language competence of six codas within the age range of 3;10 to 6;4 is assessed by a series of standardised tests (SETK 3-5,…

Reconstruction of a Three-Dimensional Transonic Rotor Flow Field from Holographical Interferogram Data.

DTIC Science & Technology

1985-03-01

interferometry and computer- R - spanwise coordinate, ft assisted tomography ( CAT ) are used to determine the transonic velocity field of a model rotor...and extracting fringe-order functions, the c data are transferred to a CAT code.- The CAT code Ui transmitted wave complex amplitude then calculates...the perturbation velocity in sev- eral planes above the blade surface. The values Ur reference wave complex amplitude from the holography- CAT method

Holographic evaluation of fatigue cracks by a compressive stress (HYSTERESIS) technique

NASA Technical Reports Server (NTRS)

Freska, S. A.; Rummel, W. D.

1974-01-01

Holographic interferometry compares unknown field of optical waves with known one. Differences are displayed as interference bands or fringes. Technique was evaluated on fatigue-cracked 2219-T87 aluminum-alloy panels. Small cracks were detected when specimen was incrementally unloaded.

Residual Microstrain in Root Dentin after Canal Instrumentation Measured with Digital Moiré Interferometry.

PubMed

Lim, Helena; Li, Fang-Chi; Friedman, Shimon; Kishen, Anil

2016-09-01

Residual microstrain influences the resistance to crack propagation in a biomaterial. This study evaluated the residual microstrain and microdefects formed in dentin after canal instrumentation in teeth maintained in hydrated and nonhydrated environments. Canals of 18 extracted human premolars with single-root canals were instrumented in accordance with 3 groups: the ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland) group: ProTaper Universal (S1, S2, F1, and F2) used in rotation, the WaveOne Primary (Dentsply Maillefer) group: the WaveOne (Primary) used in reciprocal motion, and the control group: hand files. Half the specimens (3/group) were maintained in deionized water (hydrated) and half in ambient relative humidity conditions (22°C, 55% RH) for 72 hours (nonhydrated). Customized high-sensitivity digital moiré interferometry was used to qualitatively evaluate pre- and postinstrumentation dentinal microstrain. Subsequently, specimens were examined for dentinal microdefects with micro-computed tomographic imaging and polarized light microscopy. Digital moiré interferometry showed only minor changes in postinstrumentation microstrain in hydrated dentin in all groups, suggestive of a stress relaxation behavior. Nonhydrated dentin in all groups showed localized concentration of postinstrumentation microstrain, which appeared higher in the WaveOne group than in the other groups. No dentinal microdefects were detected by micro-computed tomographic imaging and polarized light microscopy in hydrated and nonhydrated specimens in all groups. This study suggested that the biomechanical response of root dentin to instrumentation was influenced by hydration. Reciprocating, rotary, and hand instrumentation of well-hydrated roots did not cause an increase in residual microstrain or the formation of microdefects in root dentin. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

CMP reflection imaging via interferometry of distributed subsurface sources

NASA Astrophysics Data System (ADS)

Kim, D.; Brown, L. D.; Quiros, D. A.

2015-12-01

The theoretical foundations of recovering body wave energy via seismic interferometry are well established. However in practice, such recovery remains problematic. Here, synthetic seismograms computed for subsurface sources are used to evaluate the geometrical combinations of realistic ambient source and receiver distributions that result in useful recovery of virtual body waves. This study illustrates how surface receiver arrays that span a limited distribution suite of sources, can be processed to reproduce virtual shot gathers that result in CMP gathers which can be effectively stacked with traditional normal moveout corrections. To verify the feasibility of the approach in practice, seismic recordings of 50 aftershocks following the magnitude of 5.8 Virginia earthquake occurred in August, 2011 have been processed using seismic interferometry to produce seismic reflection images of the crustal structure above and beneath the aftershock cluster. Although monotonic noise proved to be problematic by significantly reducing the number of usable recordings, the edited dataset resulted in stacked seismic sections characterized by coherent reflections that resemble those seen on a nearby conventional reflection survey. In particular, "virtual" reflections at travel times of 3 to 4 seconds suggest reflector sat approximately 7 to 12 km depth that would seem to correspond to imbricate thrust structures formed during the Appalachian orogeny. The approach described here represents a promising new means of body wave imaging of 3D structure that can be applied to a wide array of geologic and energy problems. Unlike other imaging techniques using natural sources, this technique does not require precise source locations or times. It can thus exploit aftershocks too small for conventional analyses. This method can be applied to any type of microseismic cloud, whether tectonic, volcanic or man-made.

Seismic interferometry by crosscorrelation and by multidimensional deconvolution: a systematic comparison

NASA Astrophysics Data System (ADS)

Wapenaar, Kees; van der Neut, Joost; Ruigrok, Elmer; Draganov, Deyan; Hunziker, Jürg; Slob, Evert; Thorbecke, Jan; Snieder, Roel

2011-06-01

Seismic interferometry, also known as Green's function retrieval by crosscorrelation, has a wide range of applications, ranging from surface-wave tomography using ambient noise, to creating virtual sources for improved reflection seismology. Despite its successful applications, the crosscorrelation approach also has its limitations. The main underlying assumptions are that the medium is lossless and that the wavefield is equipartitioned. These assumptions are in practice often violated: the medium of interest is often illuminated from one side only, the sources may be irregularly distributed, and losses may be significant. These limitations may partly be overcome by reformulating seismic interferometry as a multidimensional deconvolution (MDD) process. We present a systematic analysis of seismic interferometry by crosscorrelation and by MDD. We show that for the non-ideal situations mentioned above, the correlation function is proportional to a Green's function with a blurred source. The source blurring is quantified by a so-called interferometric point-spread function which, like the correlation function, can be derived from the observed data (i.e. without the need to know the sources and the medium). The source of the Green's function obtained by the correlation method can be deblurred by deconvolving the correlation function for the point-spread function. This is the essence of seismic interferometry by MDD. We illustrate the crosscorrelation and MDD methods for controlled-source and passive-data applications with numerical examples and discuss the advantages and limitations of both methods.

Measurement of Poisson's ratio of nonmetallic materials by laser holographic interferometry

NASA Astrophysics Data System (ADS)

Zhu, Jian T.

1991-12-01

By means of the off-axis collimated plane wave coherent light arrangement and a loading device by pure bending, Poisson's ratio values of CFRP (carbon fiber-reinforced plactics plates, lay-up 0 degree(s), 90 degree(s)), GFRP (glass fiber-reinforced plactics plates, radial direction) and PMMA (polymethyl methacrylate, x, y direction) have been measured. In virtue of this study, the ministry standard for the Ministry of Aeronautical Industry (Testing method for the measurement of Poisson's ratio of non-metallic by laser holographic interferometry) has been published. The measurement process is fast and simple. The measuring results are reliable and accurate.

Twisting Neutron Waves

NASA Astrophysics Data System (ADS)

Pushin, Dmitry

Most waves encountered in nature can be given a ``twist'', so that their phase winds around an axis parallel to the direction of wave propagation. Such waves are said to possess orbital angular momentum (OAM). For quantum particles such as photons, atoms, and electrons, this corresponds to the particle wavefunction having angular momentum of Lℏ along its propagation axis. Controlled generation and detection of OAM states of photons began in the 1990s, sparking considerable interest in applications of OAM in light and matter waves. OAM states of photons have found diverse applications such as broadband data multiplexing, massive quantum entanglement, optical trapping, microscopy, quantum state determination and teleportation, and interferometry. OAM states of electron beams have been used to rotate nanoparticles, determine the chirality of crystals and for magnetic microscopy. Here I discuss the first demonstration of OAM control of neutrons. Using neutron interferometry with a spatially incoherent input beam, we show the addition and conservation of quantum angular momenta, entanglement between quantum path and OAM degrees of freedom. Neutron-based quantum information science heretofore limited to spin, path, and energy degrees of freedom, now has access to another quantized variable, and OAM modalities of light, x-ray, and electron beams are extended to a massive, penetrating neutral particle. The methods of neutron phase imprinting demonstrated here expand the toolbox available for development of phase-sensitive techniques of neutron imaging. Financial support provided by the NSERC Create and Discovery programs, CERC and the NIST Quantum Information Program is acknowledged.

Producing data-based sensitivity kernels from convolution and correlation in exploration geophysics.

NASA Astrophysics Data System (ADS)

Chmiel, M. J.; Roux, P.; Herrmann, P.; Rondeleux, B.

2016-12-01

Many studies have shown that seismic interferometry can be used to estimate surface wave arrivals by correlation of seismic signals recorded at a pair of locations. In the case of ambient noise sources, the convergence towards the surface wave Green's functions is obtained with the criterion of equipartitioned energy. However, seismic acquisition with active, controlled sources gives more possibilities when it comes to interferometry. The use of controlled sources makes it possible to recover the surface wave Green's function between two points using either correlation or convolution. We investigate the convolutional and correlational approaches using land active-seismic data from exploration geophysics. The data were recorded on 10,710 vertical receivers using 51,808 sources (seismic vibrator trucks). The sources spacing is the same in both X and Y directions (30 m) which is known as a "carpet shooting". The receivers are placed in parallel lines with a spacing 150 m in the X direction and 30 m in the Y direction. Invoking spatial reciprocity between sources and receivers, correlation and convolution functions can thus be constructed between either pairs of receivers or pairs of sources. Benefiting from the dense acquisition, we extract sensitivity kernels from correlation and convolution measurements of the seismic data. These sensitivity kernels are subsequently used to produce phase-velocity dispersion curves between two points and to separate the higher mode from the fundamental mode for surface waves. Potential application to surface wave cancellation is also envisaged.

Lapse time and frequency-dependent coda wave attenuation for Delhi and its surrounding regions

NASA Astrophysics Data System (ADS)

Das, Rabin; Mukhopadhyay, Sagarika; Singh, Ravi Kant; Baidya, Pushap R.

2018-07-01

Attenuation of seismic wave energy of Delhi and its surrounding regions has been estimated using coda of local earthquakes. Estimated quality factor (Qc) values are strongly dependent on frequency and lapse time. Frequency dependence of Qc has been estimated from the relationship Qc(f) = Q0fn for different lapse time window lengths. Q0 and n values vary from 73 to 453 and 0.97 to 0.63 for lapse time window lengths of 15 s to 90 s respectively. Average estimated frequency dependent relation is, Qc(f) = 135 ± 8f0.96±0.02 for the entire region for a window length of 30 s, where the average Qc value varies from 200 at 1.5 Hz to 1962 at 16 Hz. These values show that the region is seismically active and highly heterogeneous. The entire study region is divided into two sub-regions according to the geology of the area to investigate if there is a spatial variation in attenuation characteristics in this region. It is observed that at smaller lapse time both regions have similar Qc values. However, at larger lapse times the rate of increase of Qc with frequency is larger for Region 2 compared to Region 1. This is understandable, as it is closer to the tectonically more active Himalayan ranges and seismically more active compared to Region 1. The difference in variation of Qc with frequencies for the two regions is such that at larger lapse time and higher frequencies Region 2 shows higher Qc compared to Region 1. For lower frequencies the opposite situation is true. This indicates that there is a systematic variation in attenuation characteristics from the south (Region 1) to the north (Region 2) in the deeper part of the study area. This variation can be explained in terms of an increase in heat flow and a decrease in the age of the rocks from south to north.

Trade-off of Elastic Structure and Q in Interpretations of Seismic Attenuation

NASA Astrophysics Data System (ADS)

Deng, Wubing; Morozov, Igor B.

2017-10-01

The quality factor Q is an important phenomenological parameter measured from seismic or laboratory seismic data and representing wave-energy dissipation rate. However, depending on the types of measurements and models or assumptions about the elastic structure, several types of Qs exist, such as intrinsic and scattering Qs, coda Q, and apparent Qs observed from wavefield fluctuations. We consider three general types of elastic structures that are commonly encountered in seismology: (1) shapes and dimensions of rock specimens in laboratory studies, (2) geometric spreading or scattering in body-, surface- and coda-wave studies, and (3) reflectivity on fine layering in reflection seismic studies. For each of these types, the measured Q strongly trades off with the (inherently limited) knowledge about the respective elastic structure. For the third of the above types, the trade-off is examined quantitatively in this paper. For a layered sequence of reflectors (e.g., an oil or gas reservoir or a hydrothermal zone), reflection amplitudes and phases vary with frequency, which is analogous to a reflection from a contrast in attenuation. We demonstrate a quantitative equivalence between phase-shifted reflections from anelastic zones and reflections from elastic layering. Reflections from the top of an elastic layer followed by weaker reflections from its bottom can appear as resulting from a low Q within or above this layer. This apparent Q can be frequency-independent or -dependent, according to the pattern of thin layering. Due to the layering, the interpreted Q can be positive or negative, and it can depend on source-receiver offsets. Therefore, estimating Q values from frequency-dependent or phase-shifted reflection amplitudes always requires additional geologic or rock-physics constraints, such as sparseness and/or randomness of reflectors, the absence of attenuation in certain layers, or specific physical mechanisms of attenuation. Similar conclusions about the necessity of extremely detailed models of the elastic structure apply to other types of Q measurements.

Seismic Activity at tres Virgenes Volcanic and Geothermal Field

NASA Astrophysics Data System (ADS)

Antayhua, Y. T.; Lermo, J.; Quintanar, L.; Campos-Enriquez, J. O.

2013-05-01

The volcanic and geothermal field Tres Virgenes is in the NE portion of Baja California Sur State, Mexico, between -112°20'and -112°40' longitudes, and 27°25' to 27°36' latitudes. Since 2003 Power Federal Commission and the Engineering Institute of the National Autonomous University of Mexico (UNAM) initiated a seismic monitoring program. The seismograph network installed inside and around the geothermal field consisted, at the beginning, of Kinemetrics K2 accelerometers; since 2009 the network is composed by Guralp CMG-6TD broadband seismometers. The seismic data used in this study covered the period from September 2003 - November 2011. We relocated 118 earthquakes with epicenter in the zone of study recorded in most of the seismic stations. The events analysed have shallow depths (≤10 km), coda Magnitude Mc≤2.4, with epicentral and hypocentral location errors <2 km. These events concentrated mainly below Tres Virgenes volcanoes, and the geothermal explotation zone where there is a system NW-SE, N-S and W-E of extensional faults. Also we obtained focal mechanisms for 38 events using the Focmec, Hash, and FPFIT methods. The results show normal mechanisms which correlate with La Virgen, El Azufre, El Cimarron and Bonfil fault systems, whereas inverse and strike-slip solutions correlate with Las Viboras fault. Additionally, the Qc value was obtained for 118 events. This value was calculated using the Single Back Scattering model, taking the coda-waves train with window lengths of 5 sec. Seismograms were filtered at 4 frequency bands centered at 2, 4, 8 and 16 Hz respectively. The estimates of Qc vary from 62 at 2 Hz, up to 220 at 16 Hz. The frequency-Qc relationship obtained is Qc=40±2f(0.62±0.02), representing the average attenuation characteristics of seismic waves at Tres Virgenes volcanic and geothermal field. This value correlated with those observed at other geothermal and volcanic fields.

Syllabic Strategy as Opposed to Coda Optimization in the Segmentation of Spanish Letter-Strings Using Word Spotting

ERIC Educational Resources Information Center

Álvarez, Carlos J.; Taft, Marcus; Hernández-Cabrera, Juan A.

2017-01-01

A word-spotting task is used in Spanish to test the way in which polysyllabic letter-strings are parsed in this language. Monosyllabic words (e.g., "bar") embedded at the beginning of a pseudoword were immediately followed by either a coda-forming consonant (e.g., "barto") or a vowel (e.g., "baros"). In the former…

Nonlinear and linear site response and basin effects in Seattle for the M 6.8 Nisqually, Washington, earthquake

USGS Publications Warehouse

Frankel, A.D.; Carver, D.L.; Williams, R.A.

2002-01-01

We used recordings of the M 6.8 Nisqually earthquake and its ML 3.4 aftershock to study site response and basin effects for 35 locations in Seattle, Washington. We determined site amplification from Fourier spectral ratios of the recorded horizontal ground motions, referenced to a soft-rock site. Soft-soil sites (generally National Earthquake Hazard Reduction Program [NEHRP] class E) on artificial fill and young alluvium have the largest 1-Hz amplifications (factors of 3-7) for both the mainshock and aftershock. These amplifications are correlated with areas of higher damage from the mainshock to major buildings and liquefaction. There are several indications of nonlinear response at the soft-soil sites for the mainshock ground motions, despite relatively modest peak accelerations in the S waves of 15%-22%g. First, the mainshock spectral ratios do not show amplification at 2-8 Hz as do the aftershock spectral ratios. Spectral peaks at frequencies below 2 Hz generally occur at lower frequencies for the mainshock spectral ratios than for the aftershock ratios. At one soft-soil site, there is a clear shift of the resonant frequency to a lower frequency for the mainshock compared with the aftershock. The frequency of this resonance increases in the coda of the mainshock record, indicating that the site response during the weaker motions of the coda is more linear than that of the initial S wave. Three of the soft-soil sites display cusped, one-sided mainshock accelerograms after the S wave. These soft-soil sites also show amplification at 10-20 Hz in the S wave, relative to the rock site, that is not observed for the aftershock. The cusped waveforms and 10-20-Hz amplification are symptomatic of nonlinear response at the soft-soil sites. These sites had nearby liquefaction. The largest amplifications for 0.5 Hz occur at soft-soil sites on the southern portion of the Seattle Basin. Stiff-soil sites (NEHRP classes D and C) on Pleistocene-age glacial deposits display similar spectral amplification for the mainshock and aftershock, indicating approximately linear response. The stiff-soil sites generally have moderate amplification (factors of 1.1-2.4) at 0.5 and 1 Hz. Amplifications at 1 and 5 Hz for all sites generally increase with decreasing shear-wave velocity measured in the top 30 m (Vs 30). However, larger amplifications at 0.5 and 1 Hz for sites with similar Vs 30 values are observed for sites in the Seattle Basin, illustrating the amplification from the deeper (>30 m) sediments and the contribution from basin surface waves. Record sections for the mainshock and aftershock show that basin surface waves produce the peak velocities for many of the sites in the Seattle Basin and often dominate the amplitude at 1 Hz and lower frequencies.

Proposal for quantum many-body simulation and torsional matter-wave interferometry with a levitated nanodiamond

NASA Astrophysics Data System (ADS)

Ma, Yue; Hoang, Thai M.; Gong, Ming; Li, Tongcang; Yin, Zhang-qi

2017-08-01

Hybrid spin-mechanical systems have great potential in sensing, macroscopic quantum mechanics, and quantum information science. In order to induce strong coupling between an electron spin and the center-of-mass motion of a mechanical oscillator, a large magnetic gradient usually is required, which is difficult to achieve. Here we show that strong coupling between the electron spin of a nitrogen-vacancy (NV) center and the torsional vibration of an optically levitated nanodiamond can be achieved in a uniform magnetic field. Thanks to the uniform magnetic field, multiple spins can strongly couple to the torsional vibration at the same time. We propose utilizing this coupling mechanism to realize the Lipkin-Meshkov-Glick (LMG) model by an ensemble of NV centers in a levitated nanodiamond. The quantum phase transition in the LMG model and finite number effects can be observed with this system. We also propose generating torsional superposition states and realizing torsional matter-wave interferometry with spin-torsional coupling.

Fine-scale structure of the mid-mantle characterised by global stacks of PP precursors

NASA Astrophysics Data System (ADS)

Bentham, H. L. M.; Rost, S.; Thorne, M. S.

2017-08-01

Subduction zones are likely a major source of compositional heterogeneities in the mantle, which may preserve a record of the subduction history and mantle convection processes. The fine-scale structure associated with mantle heterogeneities can be studied using the scattered seismic wavefield that arrives as coda to or as energy preceding many body wave arrivals. In this study we analyse precursors to PP by creating stacks recorded at globally distributed stations. We create stacks aligned on the PP arrival in 5° distance bins (with range 70-120°) from 600 earthquakes recorded at 193 stations stacking a total of 7320 seismic records. As the energy trailing the direct P arrival, the P coda, interferes with the PP precursors, we suppress the P coda by subtracting a best fitting exponential curve to this energy. The resultant stacks show that PP precursors related to scattering from heterogeneities in the mantle are present for all distances. Lateral variations are explored by producing two regional stacks across the Atlantic and Pacific hemispheres, but we find only negligible differences in the precursory signature between these two regions. The similarity of these two regions suggests that well mixed subducted material can survive at upper and mid-mantle depth. To describe the scattered wavefield in the mantle, we compare the global stacks to synthetic seismograms generated using a Monte Carlo phonon scattering technique. We propose a best-fitting layered heterogeneity model, BRT2017, characterised by a three layer mantle with a background heterogeneity strength (ɛ = 0.8%) and a depth-interval of increased heterogeneity strength (ɛ = 1%) between 1000 km and 1800 km. The scalelength of heterogeneity is found to be 8 km throughout the mantle. Since mantle heterogeneity of 8 km scale may be linked to subducted oceanic crust, the detection of increased heterogeneity at mid-mantle depths could be associated with stalled slabs due to increases in viscosity, supporting recent observations of mantle viscosity increases due to the iron spin transition at depths of ∼1000 km.

The Crsut Structure of Northwest Mexico Through Multipath Surface Waves Analysis

NASA Astrophysics Data System (ADS)

Hincapie, J.; Doser, D. I.; Ortega, R.

2005-12-01

The location of the crystalline basement and other crustal features in Northwestern Mexico (Sonora, and Chihuahua) is not well defined. This information is required to better understand its tectonic setting. Several researchers have carried out preliminary studies with results that show a great uncertainty about the velocity structure of the region as well. The only conclusion those studies agree upon is that the region has remarkable similarities with the southwestern U.S. Our study uses information from earthquakes originating in the Gulf of California, and recorded at broadband stations in the U.S. (Arizona, New Mexico, Texas) to determine the velocity structure of the region. Because earthquake sources occur along a 1200km long zone within the gulf, we are able to sample a variety of travel paths within Northwest Mexico. We will analyze Pnl waveforms, coda dacay, and surface waves to build a regional velocity attenuation model. The results are compared to regional gravity and magnetic maps.

Reliability and validity of CODA motion analysis system for measuring cervical range of motion in patients with cervical spondylosis and anterior cervical fusion.

PubMed

Gao, Zhongyang; Song, Hui; Ren, Fenggang; Li, Yuhuan; Wang, Dong; He, Xijing

2017-12-01

The aim of the present study was to evaluate the reliability of the Cartesian Optoelectronic Dynamic Anthropometer (CODA) motion system in measuring the cervical range of motion (ROM) and verify the construct validity of the CODA motion system. A total of 26 patients with cervical spondylosis and 22 patients with anterior cervical fusion were enrolled and the CODA motion analysis system was used to measure the three-dimensional cervical ROM. Intra- and inter-rater reliability was assessed by interclass correlation coefficients (ICCs), standard error of measurement (SEm), Limits of Agreements (LOA) and minimal detectable change (MDC). Independent samples t-tests were performed to examine the differences of cervical ROM between cervical spondylosis and anterior cervical fusion patients. The results revealed that in the cervical spondylosis group, the reliability was almost perfect (intra-rater reliability: ICC, 0.87-0.95; LOA, -12.86-13.70; SEm, 2.97-4.58; inter-rater reliability: ICC, 0.84-0.95; LOA, -13.09-13.48; SEm, 3.13-4.32). In the anterior cervical fusion group, the reliability was high (intra-rater reliability: ICC, 0.88-0.97; LOA, -10.65-11.08; SEm, 2.10-3.77; inter-rater reliability: ICC, 0.86-0.96; LOA, -10.91-13.66; SEm, 2.20-4.45). The cervical ROM in the cervical spondylosis group was significantly higher than that in the anterior cervical fusion group in all directions except for left rotation. In conclusion, the CODA motion analysis system is highly reliable in measuring cervical ROM and the construct validity was verified, as the system was sufficiently sensitive to distinguish between the cervical spondylosis and anterior cervical fusion groups based on their ROM.

Visco-elastic controlled-source full waveform inversion without surface waves

NASA Astrophysics Data System (ADS)

Paschke, Marco; Krause, Martin; Bleibinhaus, Florian

2016-04-01

We developed a frequency-domain visco-elastic full waveform inversion for onshore seismic experiments with topography. The forward modeling is based on a finite-difference time-domain algorithm by Robertsson that uses the image-method to ensure a stress-free condition at the surface. The time-domain data is Fourier-transformed at every point in the model space during the forward modeling for a given set of frequencies. The motivation for this approach is the reduced amount of memory when computing kernels, and the straightforward implementation of the multiscale approach. For the inversion, we calculate the Frechet derivative matrix explicitly, and we implement a Levenberg-Marquardt scheme that allows for computing the resolution matrix. To reduce the size of the Frechet derivative matrix, and to stabilize the inversion, an adapted inverse mesh is used. The node spacing is controlled by the velocity distribution and the chosen frequencies. To focus the inversion on body waves (P, P-coda, and S) we mute the surface waves from the data. Consistent spatiotemporal weighting factors are applied to the wavefields during the Fourier transform to obtain the corresponding kernels. We test our code with a synthetic study using the Marmousi model with arbitrary topography. This study also demonstrates the importance of topography and muting surface waves in controlled-source full waveform inversion.

Explosively Driven Shock Induced Damage in OFHC Copper

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

Koller, D. D.; Hixson, R. S.; Gray, G. T. III

OFHC Cu samples were subjected to shock loading using plane wave HE lenses to produce a uniaxial Taylor wave profile (shock followed by immediate release). Upon arrival of the shock wave at the free surface of the sample, the wave is reflected and propagates back into the sample as a release wave. It is the interaction of initial and reflected release waves that place the material in a localized state of tension which can ultimately result in damage and possibly complete failure of the material. The peak tensile stress and its location in the material are determined by the wavemore » shape. Damage evolution processes and localized behavior are discussed based on results from time-resolved free surface velocity (VISAR) interferometry and post shock metallurgical analysis of the soft recovered samples.« less

Ultrasonic monitoring of spontaneous imbibition experiments: Precursory moisture diffusion effects ahead of water front

NASA Astrophysics Data System (ADS)

David, Christian; Sarout, Joël.; Dautriat, Jérémie; Pimienta, Lucas; Michée, Marie; Desrues, Mathilde; Barnes, Christophe

2017-07-01

Fluid substitution processes have been investigated in the laboratory on 14 carbonate and siliciclastic reservoir rock analogues through spontaneous imbibition experiments on vertical cylindrical specimens with simultaneous ultrasonic monitoring and imaging. The motivation of our study was to identify the seismic attributes of fluid substitution in reservoir rocks and to link them to physical processes. It is shown that (i) the P wave velocity either decreases or increases when the capillary front reaches the Fresnel clearance zone, (ii) the P wave amplitude is systematically impacted earlier than the velocity is, (iii) this precursory amplitude decrease occurs when the imbibition front is located outside of the Fresnel zone, and (iv) the relative variation of the P wave amplitude is always much larger than that of the P wave velocity. These results suggest that moisture diffuses into the pore space ahead of the water front. This postulate is further supported by a quantitative analysis of the time evolution of the observed P wave amplitudes. In a sense, P wave amplitude acts as a precursor of the arrival of the capillary front. This phenomenon is used to estimate the effective diffusivity of moisture in the tested rocks. The effective moisture diffusivity estimated from the ultrasonic data is strongly correlated with permeability: a power law with exponent 0.96 predicts permeability from ultrasonic monitoring within a factor 3 without noticeable bias. When the effective diffusivity is high, moisture diffusion affects ultrasonic P wave attributes even before the imbibition starts and impacts the P wave reflectivity as evidenced by the variations recorded in the waveform coda.

The Impact of Sonority on Onset-Rime and Peak-Coda Lexical Decision and Naming of Lexical Items by Children with Different Spelling Ability

ERIC Educational Resources Information Center

Leong, Che Kan

2008-01-01

The present study used the lexical decision (making YES/NO decision) and the vocalization (naming) paradigms in two reaction time experiments to examine the cohesiveness of onset-rime and peak-coda in the syllable structure of English lexical items. The aim was to study the effect of sonority hierarchy of liquids, nasals and obstruents on the…

Detonation charge size versus coda magnitude relations in California and Nevada

USGS Publications Warehouse

Brocher, T.M.

2003-01-01

Magnitude-charge size relations have important uses in forensic seismology and are used in Comprehensive Nuclear-Test-Ban Treaty monitoring. I derive empirical magnitude versus detonation-charge-size relationships for 322 detonations located by permanent seismic networks in California and Nevada. These detonations, used in 41 different seismic refraction or network calibration experiments, ranged in yield (charge size) between 25 and 106 kg; coda magnitudes reported for them ranged from 0.5 to 3.9. Almost all represent simultaneous (single-fired) detonations of one or more boreholes. Repeated detonations at the same shotpoint suggest that the reported coda magnitudes are repeatable, on average, to within 0.1 magnitude unit. An empirical linear regression for these 322 detonations yields M = 0.31 + 0.50 log10(weight [kg]). The detonations compiled here demonstrate that the Khalturin et al. (1998) relationship, developed mainly for data from large chemical explosions but which fits data from nuclear blasts, can be used to estimate the minimum charge size for coda magnitudes between 0.5 and 3.9. Drilling, loading, and shooting logs indicate that the explosive specification, loading method, and effectiveness of tamp are the primary factors determining the efficiency of a detonation. These records indicate that locating a detonation within the water table is neither a necessary nor sufficient condition for an efficient shot.

Frequency dependent Qα and Qβ in the Umbria-Marche (Italy) region using a quadratic approximation of the coda-normalization method

NASA Astrophysics Data System (ADS)

de Lorenzo, Salvatore; Bianco, Francesca; Del Pezzo, Edoardo

2013-06-01

The coda normalization method is one of the most used methods in the inference of attenuation parameters Qα and Qβ. Since, in this method, the geometrical spreading exponent γ is an unknown model parameter, the most part of studies assumes a fixed γ, generally equal to 1. However γ and Q could be also jointly inferred from the non-linear inversion of coda-normalized logarithms of amplitudes, but the trade-off between γ and Q could give rise to unreasonable values of these parameters. To minimize the trade-off between γ and Q, an inversion method based on a parabolic expression of the coda-normalization equation has been developed. The method has been applied to the waveforms recorded during the 1997 Umbria-Marche seismic crisis. The Akaike criterion has been used to compare results of the parabolic model with those of the linear model, corresponding to γ = 1. A small deviation from the spherical geometrical spreading has been inferred, but this is accompanied by a significant variation of Qα and Qβ values. For almost all the considered stations, Qα smaller than Qβ has been inferred, confirming that seismic attenuation, in the Umbria-Marche region, is controlled by crustal pore fluids.

High lateral resolution exploration using surface waves from noise records

NASA Astrophysics Data System (ADS)

Chávez-García, Francisco José Yokoi, Toshiaki

2016-04-01

Determination of the shear-wave velocity structure at shallow depths is a constant necessity in engineering or environmental projects. Given the sensitivity of Rayleigh waves to shear-wave velocity, subsoil structure exploration using surface waves is frequently used. Methods such as the spectral analysis of surface waves (SASW) or multi-channel analysis of surface waves (MASW) determine phase velocity dispersion from surface waves generated by an active source recorded on a line of geophones. Using MASW, it is important that the receiver array be as long as possible to increase the precision at low frequencies. However, this implies that possible lateral variations are discarded. Hayashi and Suzuki (2004) proposed a different way of stacking shot gathers to increase lateral resolution. They combined strategies used in MASW with the common mid-point (CMP) summation currently used in reflection seismology. In their common mid-point with cross-correlation method (CMPCC), they cross-correlate traces sharing CMP locations before determining phase velocity dispersion. Another recent approach to subsoil structure exploration is based on seismic interferometry. It has been shown that cross-correlation of a diffuse field, such as seismic noise, allows the estimation of the Green's Function between two receivers. Thus, a virtual-source seismic section may be constructed from the cross-correlation of seismic noise records obtained in a line of receivers. In this paper, we use the seismic interferometry method to process seismic noise records obtained in seismic refraction lines of 24 geophones, and analyse the results using CMPCC to increase the lateral resolution of the results. Cross-correlation of the noise records allows reconstructing seismic sections with virtual sources at each receiver location. The Rayleigh wave component of the Green's Functions is obtained with a high signal-to-noise ratio. Using CMPCC analysis of the virtual-source seismic lines, we are able to identify lateral variations of phase velocity inside the seismic line, and increase the lateral resolution compared with results of conventional analysis.

Making waves.

NASA Astrophysics Data System (ADS)

Townes, C. H.

The author takes the reader on a behind-the-scenes tour of his way of working. Along the way, one learns about how the author came upon his surprising findings and how he managed to avoid obstacles in his path. He introduces the reader to the wonders of the universe, from the submicroscopic, most minute - the workings of atoms and the even smaller particles that make them up - to the vast outer reaches of space. His tour takes one along paths Townes pioneered: quantum electronics, microwave spectroscopy and the frontiers of our galaxy where he explored the dark, rarefied clouds of gas and dust where new stars form. The book concludes with a uniquely personal coda in which Townes suggests that science and religion occupy the same terrain.

Path-Specific Effects on Shear Motion Generation Using LargeN Array Waveform Data at the Source Physics Experiment (SPE) Site

NASA Astrophysics Data System (ADS)

Pitarka, A.; Mellors, R. J.; Walter, W. R.

2016-12-01

Depending on emplacement conditions and underground structure, and contrary to what is theoretically predicted for isotropic sources, recorded local, regional, and teleseismic waveforms from chemical explosions often contain shear waves with substantial energy. Consequently, the transportability of empirical techniques for yield estimation and source discrimination to regions with complex underground structure becomes problematic. Understanding the mechanisms of generation and conversion of shear waves caused by wave path effects during explosions can help improve techniques used in nuclear explosion monitoring. We used seismic data from LargeN, a dense array of three and one component geophones, to analyze far-field waveforms from the underground chemical explosion recorded during shot 5 of the Source Physics Experiment (SPE-5) at the Nevada National Security Site. Combined 3D elastic wave propagation modeling and frequency-wavenumber beam-forming on small arrays containing selected stations were used to detect and identify several wave phases, including primary and secondary S waves, and Rgwaves, and determine their direction of propagation. We were able to attribute key features of the waveforms, and wave phases to either source processes or propagation path effects, such as focusing and wave conversions. We also found that coda waves were more likely generated by path effects outside the source region, rather than by interaction of source generated waves with the emplacement structure. Waveform correlation and statistical analysis were performed to estimate average correlation length of small-scale heterogeneity in the upper sedimentary layers of the Yucca Flat basin in the area covered by the array. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS- 699180

Modeling Events in the Lower Imperial Valley Basin

NASA Astrophysics Data System (ADS)

Tian, X.; Wei, S.; Zhan, Z.; Fielding, E. J.; Helmberger, D. V.

2010-12-01

The Imperial Valley below the US-Mexican border has few seismic stations but many significant earthquakes. Many of these events, such as the recent El Mayor-Cucapah event, have complex mechanisms involving a mixture of strike-slip and normal slip patterns with now over 30 aftershocks with magnitude over 4.5. Unfortunately, many earthquake records from the Southern Imperial Valley display a great deal of complexity, ie., strong Rayleigh wave multipathing and extended codas. In short, regional recordings in the US are too complex to easily separate source properties from complex propagation. Fortunately, the Dec 30 foreshock (Mw=5.9) has excellent recordings teleseismically and regionally, and moreover is observed with InSAR. We use this simple strike-slip event to calibrate paths. In particular, we are finding record segments involving Pnl (including depth phases) and some surface waves (mostly Love waves) that appear well behaved, ie., can be approximated by synthetics from 1D local models and events modeled with the Cut-and-Paste (CAP) routine. Simple events can then be identified along with path calibration. Modeling the more complicated paths can be started with known mechanisms. We will report on both the aftershocks and historic events.

Reflection imaging of the Moon's interior using deep-moonquake seismic interferometry

NASA Astrophysics Data System (ADS)

Nishitsuji, Yohei; Rowe, C. A.; Wapenaar, Kees; Draganov, Deyan

2016-04-01

The internal structure of the Moon has been investigated over many years using a variety of seismic methods, such as travel time analysis, receiver functions, and tomography. Here we propose to apply body-wave seismic interferometry to deep moonquakes in order to retrieve zero-offset reflection responses (and thus images) beneath the Apollo stations on the nearside of the Moon from virtual sources colocated with the stations. This method is called deep-moonquake seismic interferometry (DMSI). Our results show a laterally coherent acoustic boundary around 50 km depth beneath all four Apollo stations. We interpret this boundary as the lunar seismic Moho. This depth agrees with Japan Aerospace Exploration Agency's (JAXA) SELenological and Engineering Explorer (SELENE) result and previous travel time analysis at the Apollo 12/14 sites. The deeper part of the image we obtain from DMSI shows laterally incoherent structures. Such lateral inhomogeneity we interpret as representing a zone characterized by strong scattering and constant apparent seismic velocity at our resolution scale (0.2-2.0 Hz).

Hydrogen Lines in Mira Stars Through Interferometry and Polarimetry

NASA Astrophysics Data System (ADS)

Fabas, N.; Chiavassa, A.; Millour, F.; Wittkowski, M.

2015-12-01

Balmer lines in emission are the most prominent features in Mira stars spectra and have a strong potential as a proxy to study the lower atmosphere's dynamics. In Fabas et al. ([1]), we accumulated spectropolarimetric observations of Balmer lines in emission. As the shock is propagating outwards, linear polarization rate increases and the angle of this polarization evolves. Assuming that linear polarization arises from anisotropic scattering, it has the potential of telling us about the geometric structure of the shock as it propagates and the study of such atmospheric structures can typically be performed with interferometry. In 2012, AMBER data on the Mira star omicron Ceti were collected in which the Brackett γ line is studied. The data show signatures in the interferometric observables around this line. Olivier Chesneau was in the jury evaluating the PhD thesis of N. Fabas and he was seduced by the idea to study these shock waves with interferometry and use polarimetry as a complementary study.

Experimental comparison of autodyne and heterodyne laser interferometry using an Nd:YVO₄ microchip laser.

PubMed

Jacquin, Olivier; Lacot, Eric; Glastre, Wilfried; Hugon, Olivier; Guillet de Chatellus, Hugues

2011-08-01

Using an Nd:YVO₄ microchip laser with a relaxation frequency in the megahertz range, we have experimentally compared a heterodyne interferometer based on a Michelson configuration with an autodyne interferometer based on the laser optical feedback imaging (LOFI) method regarding their signal-to-noise ratios. In the heterodyne configuration, the beating between the reference beam and the signal beam is realized outside the laser cavity, while in the autodyne configuration, the wave beating takes place inside the laser cavity, and the relaxation oscillations of the laser intensity then play an important part. For a given laser output power, object under investigation, and detection noise level, we have determined the amplification gain of the LOFI interferometer compared to the heterodyne interferometer. LOFI interferometry is demonstrated to show higher performance than heterodyne interferometry for a wide range of laser powers and detection levels of noise. The experimental results are in good agreement with the theoretical predictions.

Experimental determination of third-order elastic constants of diamond.

PubMed

Lang, J M; Gupta, Y M

2011-03-25

To determine the nonlinear elastic response of diamond, single crystals were shock compressed along the [100], [110], and [111] orientations to 120 GPa peak elastic stresses. Particle velocity histories and elastic wave velocities were measured by using laser interferometry. The measured elastic wave profiles were used, in combination with published acoustic measurements, to determine the complete set of third-order elastic constants. These constants represent the first experimental determination, and several differ significantly from those calculated by using theoretical models.

Summary of NASA Advanced Telescope and Observatory Capability Roadmap

NASA Technical Reports Server (NTRS)

Stahl, H. Phil; Feinberg, Lee

2006-01-01

The NASA Advanced Telescope and Observatory (ATO) Capability Roadmap addresses technologies necessary for NASA to enable future space telescopes and observatories operating in all electromagnetic bands, from x-rays to millimeter waves, and including gravity-waves. It lists capability priorities derived from current and developing Space Missions Directorate (SMD) strategic roadmaps. Technology topics include optics; wavefront sensing and control and interferometry; distributed and advanced spacecraft systems; cryogenic and thermal control systems; large precision structure for observatories; and the infrastructure essential to future space telescopes and observatories.

Summary of NASA Advanced Telescope and Observatory Capability Roadmap

NASA Technical Reports Server (NTRS)

Stahl, H. Philip; Feinberg, Lee

2007-01-01

The NASA Advanced Telescope and Observatory (ATO) Capability Roadmap addresses technologies necessary for NASA to enable future space telescopes and observatories operating in all electromagnetic bands, from x-rays to millimeter waves, and including gravity-waves. It lists capability priorities derived from current and developing Space Missions Directorate (SMD) strategic roadmaps. Technology topics include optics; wavefront sensing and control and interferometry; distributed and advanced spacecraft systems; cryogenic and thermal control systems; large precision structure for observatories; and the infrastructure essential to future space telescopes and observatories.

Multi-Axis Heterodyne Interferometry (MAHI)

NASA Astrophysics Data System (ADS)

Thorpe, James

The detection and measurement of gravitational waves represents humanity’s next, and final, opportunity to open an entirely new spectrum with which to view the universe. The first steps of this process will likely take place later this decade when the second-generation ground-based instruments such as Advanced LIGO approach design sensitivity. While these events will be historic, it will take a space-based detector to access the milliHertz gravitational wave frequency band, a band that is rich in both number and variety of sources. The Laser Interferometer Space Antenna (LISA) concept has been developed over the past two decades in the US and Europe to provide access to this band. The European Space Agency recently selected The Gravitational Universe as the science theme for the 3rd Large-class mission in the Cosmic Visions Programme, with the assumption that a LISA-like instrument would be implemented for launch in 2034. NASA has expressed interest in partnering on this effort and the US community has made its own judgment on the scientific potential of a space-based gravitational wave observatory through the selection of LISA as the 3rd flagship mission in the 2010 Decadal Survey. Much of the effort has been in retiring risk for the unique technologies that comprise a gravitational wave detector. A prime focus of this effort is LISA Pathfinder (LPF), a dedicated technology demonstrator mission led by ESA with contributions from NASA and several member states. LPF’s primary objective is to validate drag-free flight as an approach to realizing an inertial reference mass. Along the way, several important technologies will be demonstrated, including picometer-level heterodyne interferometry. However, there are several important differences between the interferometry design for LISA and that for LPF. These mostly result from the fact that LISA interferometry involves multiple lasers on separate spacecraft whereas LPF can use a single laser on a single spacecraft. We propose to develop a laboratory prototype of a LISA-like interferometric metrology system capable of simultaneously making picometer-level position and nanoradian-level attitude measurements of a free-flying target. In the LISA application, this prototype would represent the short-arm interferometer, measuring the displacement and relative attitude between the gravitational test mass and the spacecraft. This measurement is used both to drive the drag-free attitude and control system as well as to extract the gravitational wave science signal. In addition to the LISA application, such a system would have broader applications in future geodesy and formation-flying missions. The prototype free-flying metrology system will consist of the following subcomponents: an optical bench providing stable pathlengths, an optical target mounted on a precision actuator, a low-noise quadrant photoreceiver for generating differential wavefront signals, and a phase measurement system to measure the individual heterodyne signals and convert them into quantities such as position and angle. In addition to the moving target, the optical bench will include a pair of fixed targets to be used as references. Comparing the two reference interferometers will provide an estimate of the noise performance of the measurement system, while comparing a reference interferometer with the free-flying target will allow us to demonstrate measurement over a large dynamic range. In addition to making performance measurements, we will use this prototype system to explore a number of system-level issues related to free-flying interferometry including initial acquisition, beam-walk effects, and jitter couplings.

Holographic Interferometry of Oil Films and Droplets in Water with a Single-Beam Mirror-Type Scheme

DTIC Science & Technology

2011-03-01

A simple scheme of holographic interferometry is shown in Fig. 1. A beam from an He-Ne laser (wave- length 0.632/ym), expanded by a lens (F-5cm...1 March 2011 r\\i rii cos 9 - ra2cos9f fii cos 9 + n2cos9, 2nj cos 9 t\\2 = 1 + r\\2 nx cos 9 + n2cos9, (3) Here 9r is the transmission angle ...which is related to the incidence angle by cos 9, — .11 - I tii sin9\\2 n% It follows from Eq. (3) that, for n2 > «i (as in our case of the air

Deep frequency modulation interferometry.

PubMed

Gerberding, Oliver

2015-06-01

Laser interferometry with pm/Hz precision and multi-fringe dynamic range at low frequencies is a core technology to measure the motion of various objects (test masses) in space and ground based experiments for gravitational wave detection and geodesy. Even though available interferometer schemes are well understood, their construction remains complex, often involving, for example, the need to build quasi-monolithic optical benches with dozens of components. In recent years techniques have been investigated that aim to reduce this complexity by combining phase modulation techniques with sophisticated digital readout algorithms. This article presents a new scheme that uses strong laser frequency modulations in combination with the deep phase modulation readout algorithm to construct simpler and easily scalable interferometers.

Imaging issues for interferometry with CGH null correctors

NASA Astrophysics Data System (ADS)

Burge, James H.; Zhao, Chunyu; Zhou, Ping

2010-07-01

Aspheric surfaces, such as telescope mirrors, are commonly measured using interferometry with computer generated hologram (CGH) null correctors. The interferometers can be made with high precision and low noise, and CGHs can control wavefront errors to accuracy approaching 1 nm for difficult aspheric surfaces. However, such optical systems are typically poorly suited for high performance imaging. The aspheric surface must be viewed through a CGH that was intentionally designed to introduce many hundreds of waves of aberration. The imaging aberrations create difficulties for the measurements by coupling both geometric and diffraction effects into the measurement. These issues are explored here, and we show how the use of larger holograms can mitigate these effects.

New Experimental Setup for High-Pressure High-Temperature Gigahertz Ultrasonic Interferometry

NASA Astrophysics Data System (ADS)

Kantor, A. P.; Kantor, I. Y.; Dubrovinsky, L. S.; Jacobsen, S. D.

2005-12-01

The only direct information about Earth's interior comes from seismological observations of sound wave velocities. In order to create compositional and mineralogical model from seismological data knowledge of the elastic properties and crystal chemistry of minerals is necessary. Gigahertz ultrasonic interferometry (GUI) is a relatively new tool used to measure single-crystal compressional and shear-wave travel times, which are converted to sound velocities and elastic moduli for direct application to problems in geophysics. Although possibility of simultaneous high-pressure and high-temperature GUI measurements in diamond anvil cell was demonstrated before up to temperature of 250°C, in situ pressure measurements were not possible. We developed new experimental setup for simultaneous GUI and pressure determination using a ruby fluorescence gouge. A diamond anvil cell is equipped with a miniature internal resistive heater with thermocouple fixed at a very small distance from the sample chamber. DAC is mounted at the rotating stage with 5 degrees of freedom (XYZ and two tilting degrees), that can be fixed in three different positions: on top of a P-buffer rod for compressional wave velocities measurement, on top of S-buffer rod for shear wave velocities measurement and under the microscope, equipped with laser and portable high-resolution spectrometer for ruby fluorescence measurement. DAC under high temperature could be moved between these three positions, and independent pressure, temperature, S and P wave velocities measurements could be done simultaneously at each data point. In addition to single-crystal elasticity measurements, ability of GUI for elasticity measurements of liquids was demonstrated. Compressional wave velocities in liquid argon were measured at high pressures and temperatures, showing the ability of GUI for studies equation of state of a liquid.

Multilevel animal societies can emerge from cultural transmission

PubMed Central

Cantor, Maurício; Shoemaker, Lauren G.; Cabral, Reniel B.; Flores, César O.; Varga, Melinda; Whitehead, Hal

2015-01-01

Multilevel societies, containing hierarchically nested social levels, are remarkable social structures whose origins are unclear. The social relationships of sperm whales are organized in a multilevel society with an upper level composed of clans of individuals communicating using similar patterns of clicks (codas). Using agent-based models informed by an 18-year empirical study, we show that clans are unlikely products of stochastic processes (genetic or cultural drift) but likely originate from cultural transmission via biased social learning of codas. Distinct clusters of individuals with similar acoustic repertoires, mirroring the empirical clans, emerge when whales learn preferentially the most common codas (conformism) from behaviourally similar individuals (homophily). Cultural transmission seems key in the partitioning of sperm whales into sympatric clans. These findings suggest that processes similar to those that generate complex human cultures could not only be at play in non-human societies but also create multilevel social structures in the wild. PMID:26348688

Diffuse Waves and Energy Densities Near Boundaries

NASA Astrophysics Data System (ADS)

Sanchez-Sesma, F. J.; Rodriguez-Castellanos, A.; Campillo, M.; Perton, M.; Luzon, F.; Perez-Ruiz, J. A.

2007-12-01

Green function can be retrieved from averaging cross correlations of motions within a diffuse field. In fact, it has been shown that for an elastic inhomogeneous, anisotropic medium under equipartitioned, isotropic illumination, the average cross correlations are proportional to the imaginary part of Green function. For instance coda waves are due to multiple scattering and their intensities follow diffusive regimes. Coda waves and the noise sample the medium and effectively carry information along their paths. In this work we explore the consequences of assuming both source and receiver at the same point. From the observable side, the autocorrelation is proportional to the energy density at a given point. On the other hand, the imaginary part of the Green function at the source itself is finite because the singularity of Green function is restricted to the real part. The energy density at a point is proportional with the trace of the imaginary part of Green function tensor at the source itself. The Green function availability may allow establishing the theoretical energy density of a seismic diffuse field generated by a background equipartitioned excitation. We study an elastic layer with free surface and overlaying a half space and compute the imaginary part of the Green function for various depths. We show that the resulting spectrum is indeed closely related to the layer dynamic response and the corresponding resonant frequencies are revealed. One implication of present findings lies in the fact that spatial variations may be useful in detecting the presence of a target by its signature in the distribution of diffuse energy. These results may be useful in assessing the seismic response of a given site if strong ground motions are scarce. It suffices having a reasonable illumination from micro earthquakes and noise. We consider that the imaginary part of Green function at the source is a spectral signature of the site. The relative importance of the peaks of this energy spectrum, ruling out non linear effects, may influence the seismic response for future earthquakes. Partial supports from DGAPA-UNAM, Project IN114706, Mexico; from Proyect MCyT CGL2005-05500-C02/BTE, Spain; from project DyETI of INSU-CNRS, France, and from the Instituto Mexicano del Petróleo are greatly appreciated.

Interpreting Continental Break-Up From Surface Observations: Analysis of 1D Partial Melting Using Synthetic Waveform Propagation

NASA Astrophysics Data System (ADS)

Franken, T.; Armitage, J. J.; Fuji, N.; Fournier, A.

2017-12-01

Low shear-wave velocity zones underneath margins of continental break-up are believed to be related to the presence of melt. Many models attempt to model the process of melt production and transportation during mantle upwelling, yet there is a disconnect between geodynamic models, seismic observations, and petrological studies of melt flow velocities. Geodynamic models that emulate melt retention of 2 %, suggested by shear-wave velocity anomalies (Forsyth & MELT Seismic Team, 1998), fail to adequately reproduce the seismic signal as seen in receiver functions (Rychert, 2012; Armitage et al., 2015). Furthermore, numerical models of melt migration conclude mean melt flow velocities up to 1,3 m yr-1(Weatherley & Katz, 2015), whereas Uranium isotope migration rates advocate velocities up to two orders of magnitude higher. This study aims to reconcile the diverting assertions on the partial melting process by analysing the effect of melt presence on the coda of the seismic signal. A 1D forward model has been created to emulate melt production and transportation in an upwelling mantle environment. Scenarios have been modelled for variable upwelling velocities v (1 - 100 mm yr-1), initial temperatures T0 (1200 - 1800 °C) and permeabilities k0 (10-9 - 10-5 m2). The 1D model parameters are converted to anharmonic seismic parameters using look-up tables from phase diagrams (Goes et al., 2012) to generate synthetic seismograms with the Direct Solution Method. The maximum frequency content of the synthetics is 1,25 Hz, sampled at 20 Hz with a low-pass filter of 0,1 Hz. A comparison between the synthetics and seismic observations of the La Reunion mantle plume from the RER Geoscope receiver is performed using a Monte-Carlo approach. The synthetic seismograms show highest sensitivity to the presence of melt in S-waves within epicentral distances of 0-20 degrees. In the 0-10 degree range only a time-shift is observed proportional to the melt fraction at the onset of melting. Within the 10-20 degree range the presence of melt causes an additional change in the coda of the signal compared to a no-melt model. By analysing these altered synthetic waveforms we search for a seismic signature corresponding to melt presence to form a benchmark for the comparison between the Monte-Carlo results and the seismic observations.

Inferences on the Physical Nature of Earth's Inner Core Boundary Region from Observations of Antipodal PKIKP and PKIIKP Waves

NASA Astrophysics Data System (ADS)

Cormier, V. F.; Attanayake, J.; Thomas, C.; Koper, K. D.; Miller, M. S.

2017-12-01

The Earth's Inner Core Boundary (ICB) is considered a uniform and sharp liquid-to-solid transition in standard Earth models such as PREM and AK135-F. By analysing seismic wave reflections emanating from the ICB, this hypothesis of a simple ICB can be tested. Observed absolute and relative amplitudes and coda of the PKiKP phase that is reflected on the topside of the ICB suggest that the ICB is neither uniform nor has a simple structure. Similarly, waves that are reflected from the underside of the ICB - PKIIKP phase - can be used to determine the physical nature of the region immediately below the ICB. Using high-frequency synthetic waveform experiments, we confirm that antipodal PKIIKP amplitudes can discriminate the state of the uppermost 10 km of the inner core: A standard liquid-to-solid ICB (high shear velocity/shear modulus discontinuity) produces a maximum PKIIKP amplitude equal to only a factor of 0.14 of the PKIKP amplitude, whereas a non-standard liquid-to-near liquid ICB (low shear velocity/shear modulus discontinuity) can produce PKIIKP amplitudes comparable to PKIKP. We searched for PKIIKP in individual and stacked array waveforms in the 170° - 180° distance range for the 2000 to 2016 time period globally to compare with our synthetic results. We attribute a lack of PKIIKP detection in the stacked array recordings due to (1) ranges closer to 170° and not 180°, where the PKIIKP signal-to-noise ratio is very poor; (2) scattered coda following PKIKP masking the PKIIKP phase; and (3) large azimuthal variations of array recordings closer to 180° preventing the formation of an accurate beam. Envelopes of individual recordings in the 178° - 180° distance range, however, clearly show energy peaks correlating with the travel time of PKIIKP phase. Our global set of PKIIKP/PKIKP energy ratio measurements vary between 0.1 and 1.1, indicating significant structural complexity immediately below the ICB. While a complex inner core anisotropy structure and ICB topography could influence these energy ratios, we favor a hypothesis of a thin transition layer of thickness < 10 km below the ICB having a laterally varying shear modulus (or shear velocity) to explain observed rapid lateral variations of PKIIKP/PKIKP energy ratios.

P-wave attenuation in the Pacific slab beneath northeastern Japan revealed by the spectral ratio of intraslab earthquakes

NASA Astrophysics Data System (ADS)

Shiina, Takahiro; Nakajima, Junichi; Matsuzawa, Toru

2018-05-01

We investigate P-wave attenuation, Qp-1, in the Pacific slab beneath northeastern (NE) Japan, adopting for the first time the spectral ratio technique for intraslab earthquakes. When seismograms of two earthquakes are recorded at a station and their ray paths to the station are largely overlapped, station-dependent amplification and structural effects on the overlapped rays can be canceled out from the ratio of the spectral amplitudes of the seismograms. Therefore, adopting the spectral ratio technique for intraslab earthquakes has a great advantage for the precise evaluation of Qp-1 in the slab because the structural effects above the slab, including the high-attenuation mantle wedge, are removed. For estimating the intraslab Qp-1, we determined corner frequency of the intraslab earthquakes using the S-coda wave spectral ratio as the first step. Then, we evaluated the inter-event path attenuation, Δt*, from the ratio of the spectral amplitudes of P waves. The obtained result shows that P-wave attenuation in the Pacific slab marks Qp-1 of 0.0015 (Qp of ∼670) at depths of 50-250 km. This indicates that the P-wave attenuation in the Pacific slab is weaker than that in the mantle wedge. The relatively high-Qp-1 is correlated with the distributions of intraslab earthquakes, suggesting that the P-wave amplitude is more attenuated around active seismicity zones in the slab. Therefore, our observations likely indicate the presence of fractures, hydrous minerals, and dehydrated fluid around seismogenic zones in the slab at intermediate depths.

Analysis and suppression of passive noise in surface microseismic data

NASA Astrophysics Data System (ADS)

Forghani-Arani, Farnoush

Surface microseismic surveys are gaining popularity in monitoring the hydraulic fracturing process. The effectiveness of these surveys, however, is strongly dependent on the signal-to-noise ratio of the acquired data. Cultural and industrial noise generated during hydraulic fracturing operations usually dominate the data, thereby decreasing the effectiveness of using these data in identifying and locating microseismic events. Hence, noise suppression is a critical step in surface microseismic monitoring. In this thesis, I focus on two important aspects in using surface-recorded microseismic seismic data: first, I take advantage of the unwanted surface noise to understand the characteristics of these noise and extract information about the propagation medium from the noise; second, I propose effective techniques to suppress the surface noise while preserving the waveforms that contain information about the source of microseisms. Automated event identification on passive seismic data using only a few receivers is challenging especially when the record lengths span over long durations of time. I introduce an automatic event identification algorithm that is designed specifically for detecting events in passive data acquired with a small number of receivers. I demonstrate that the conventional STA/LTA (Short-term Average/Long-term Average) algorithm is not sufficiently effective in event detection in the common case of low signal-to-noise ratio. With a cross-correlation based method as an extension of the STA/LTA algorithm, even low signal-to-noise events (that were not detectable with conventional STA/LTA) were revealed. Surface microseismic data contains surface-waves (generated primarily from hydraulic fracturing activities) and body-waves in the form of microseismic events. It is challenging to analyze the surface-waves on the recorded data directly because of the randomness of their source and their unknown source signatures. I use seismic interferometry to extract the surface-wave arrivals. Interferometry is a powerful tool to extract waves (including body-wave and surface-waves) that propagate from any receiver in the array (called a pseudo source) to the other receivers across the array. Since most of the noise sources in surface microseismic data lie on the surface, seismic interferometry yields pseudo source gathers dominated by surface-wave energy. The dispersive characteristics of these surface-waves are important properties that can be used to extract information necessary for suppressing these waves. I demonstrate the application of interferometry to surface passive data recorded during the hydraulic fracturing operation of a tight gas reservoir and extract the dispersion properties of surface-waves corresponding to a pseudo-shot gather. Comparison of the dispersion characteristics of the surface waves from the pseudo-shot gather with that of an active shot-gather shows interesting similarities and differences. The dispersion character (e.g. velocity change with frequency) of the fundamental mode was observed to have the same behavior for both the active and passive data. However, for the higher mode surface-waves, the dispersion properties are extracted at different frequency ranges. Conventional noise suppression techniques in passive data are mostly stacking-based that rely on enforcing the amplitude of the signal by stacking the waveforms at the receivers and are unable to preserve the waveforms at the individual receivers necessary for estimating the microseismic source location and source mechanism. Here, I introduce a technique based on the tau - p transform, that effectively identifies and separates microseismic events from surface-wave noise in the tau -p domain. This technique is superior to conventional stacking-based noise suppression techniques, because it preserves the waveforms at individual receivers. Application of this methodology to microseismic events with isotropic and double-couple source mechanism, show substantial improvement in the signal-to-noise ratio. Imaging of the processed field data also show improved imaging of the hypocenter location of the microseismic source. In the case of double-couple source mechanism, I suggest two approaches for unifying the polarities at the receivers, a cross-correlation approach and a semblance-based prediction approach. The semblance-based approach is more effective at unifying the polarities, especially for low signal-to-noise ratio data.

Velocity variations associated with the large 2010 eruption of Merapi volcano, Java, retrieved from seismic multiplets and ambient noise cross-correlation

NASA Astrophysics Data System (ADS)

Budi-Santoso, Agus; Lesage, Philippe

2016-07-01

We present a study of the seismic velocity variations that occurred in the structure before the large 2010 eruption of Merapi volcano. For the first time to our knowledge, the technique of coda wave interferometry is applied to both families of similar events (multiplets) and to correlation functions of seismic noise. About half of the seismic events recorded at the summit stations belong to one of the ten multiplets identified, including 120 similar events that occurred in the last 20 hr preceding the eruption onset. Daily noise cross-correlation functions (NCF) were calculated for the six pairs of short-period stations available. Using the stretching method, we estimate time-series of apparent velocity variation (AVV) for each multiplet and each pair of stations. No significant velocity change is detected until September 2010. From 10 October to the beginning of the eruption on 26 October, a complex pattern of AVV is observed with amplitude of up to ±1.5 per cent. Velocity decrease is first observed from families of deep events and then from shallow earthquakes. In the same period, AVV with different signs and chronologies are estimated from NCF calculated for various station pairs. The location in the horizontal plane of the velocity perturbations related with the AVV obtained from NCF is estimated by using an approach based on the radiative transfer approximation. Although their spatial resolution is limited, the resulting maps display velocity decrease in the upper part of the edifice in the period 12-25 October. After the eruption onset, the pattern of velocity perturbations is significantly modified with respect to the previous one. We interpret these velocity variations in the framework of a scenario of magmatic intrusion that integrates most observations. The perturbation of the stress field associated with the magma migration can induce both decrease and increase of the seismic velocity of rocks. Thus the detected AVVs can be considered as precursors of volcanic eruptions in andesitic volcanoes, without taking their sign into account.

The MOON micro-seismic noise : first estimates from meteorites flux simulations

NASA Astrophysics Data System (ADS)

Lognonne, P.; Lefeuvre, M.; Johnson, C.; Weber, R.

2008-12-01

The Moon is considered to be a seismically quiet planet and most of the time, the Apollo seismograms were flat when not quakes was occuring. We show in this paper that this might not be the case if more sensitive data are recorded by future instruments and that a permanent micro-seismic noise is existing due to the continuous impacts of meteorites. We perform a modeling of this noise by using, as calibrated seismic data, those generated by the impacts of the Apollo S4B or LEM, by taking care on the scaling law, necessary to express the seismic force with respect to the mass and velocity of the impactors. We also parametrize the dependence of the amplitude of the seismic coda, associated to the maximum amplitude of the seismograms, with respect to the epicentral distance and to the source geometry. This enabling us to use the seismic data of the S4B impacts as empirical waveforms for the modeling of the natural impacts. The frequency/size law of meteoroids impacting the Moon and the associated probability of NEO impacts are however not known precisely. Uncertainties as large as a factor of 3-5 remain, especially for the moderate-sized impacts which are not observed on the Earth, due to the shielding by the atmosphere. We therefore use several meteoroid mass/frequency laws from the literature to generate, with a random simulator, a history of impacts on the Moon during a given period. The seismic signals generated by succession of seismic sources and estimate the frequency/amplitude relationship of such seismic signals. Our results finally provide an estimate for the meteoritic seismic background on the Moon. This background noise was not recorded by the Apollo seismic experiment due insufficient resolution. Such an estimate can be used in designing a new generation of lunar seismometers, for estimating the probability of detecting proposed impacts due to nuggets of strange quark matter , and to inform future lunar based experiments, which require very stable ground, such as optical interferometry moon-based telescopes or gravity waves detectors.

LISA: Astrophysics Out to z Approximately 10 with Low-Frequency Gravitational Waves

NASA Technical Reports Server (NTRS)

Stebbins, Robin T.

2008-01-01

This viewgraph presentation reviews the Laser Interferometer Space Antenna (LISA). LISA os a joint ESA-NASA project to design, build and operate a space-based gravitational wave detector. The 5 million Kilometer long detector will consist of three spacecraft orbiting the Sun in a triangular formation. Space-Time strains induced by gravitational waves are detected by measuring changes in the separation of fiducial masses with laser interferometry. LISA is expected to detect signals from merging massive black holes, compact stellar objects spiraling into super massive black holes in galactic nuclei, thousands of close binaries of compact objects in the Milky way and possible backgrounds of cosmological origin.

Algorithms to eliminate the influence of non-uniform intensity distributions on wavefront reconstruction by quadri-wave lateral shearing interferometers

NASA Astrophysics Data System (ADS)

Chen, Xiao-jun; Dong, Li-zhi; Wang, Shuai; Yang, Ping; Xu, Bing

2017-11-01

In quadri-wave lateral shearing interferometry (QWLSI), when the intensity distribution of the incident light wave is non-uniform, part of the information of the intensity distribution will couple with the wavefront derivatives to cause wavefront reconstruction errors. In this paper, we propose two algorithms to reduce the influence of a non-uniform intensity distribution on wavefront reconstruction. Our simulation results demonstrate that the reconstructed amplitude distribution (RAD) algorithm can effectively reduce the influence of the intensity distribution on the wavefront reconstruction and that the collected amplitude distribution (CAD) algorithm can almost eliminate it.

Time-lapse changes in velocity and anisotropy in Japan's near surface after the 2011 Tohoku earthquake

NASA Astrophysics Data System (ADS)

Snieder, R.; Nakata, N.

2012-12-01

A strong-motion recording network, KiK-net, helps us to monitor temporal changes in the near surface in Japan. Each KiK-net station has two seismometers at the free surface and in a borehole a few hundred meters deep, and we can retrieve a traveling wave from the borehole receiver to the surface receiver by applying deconvolution based seismic interferometry. KiK-net recorded the 2011 Tohoku earthquake, which is one of the largest earthquakes in recent history, and seismicity around the time of the main shock. Using records of these seismicity and computing mean values of near-surface shear-wave velocities in the periods of January 1--March 10 and March 12--May 26 in 2011, we detect about a 5% reduction in the velocity after the Tohoku earthquake. The area of the velocity reduction is about 1,200 km wide, which is much wider than earlier studies reporting velocity reductions after larger earthquakes. The reduction partly recovers with time. We can also estimate the azimuthal anisotropy by detecting shear-wave splitting after applying seismic interferometry. Estimating mean values over the same periods as the velocity, we find the strength of anisotropy increased in most parts of northeastern Japan, but fast shear-wave polarization directions in the near surface did not significantly change. The changes in anisotropy and velocity are generally correlated, especially in the northeastern Honshu (the main island in Japan).

Laser Interferometry for Gravitational Wave Observation: LISA and LISA Pathfinder

NASA Technical Reports Server (NTRS)

Guzman, Felipe

2010-01-01

The Laser Interferometer Space Antenna (LISA) is a planned NASA-ESA gravitational wave observatory in the frequency range of 0.1mHz-100mHz. This observation band is inaccessible to ground-based detectors due to the large ground motions of the Earth. Gravitational wave sources for LISA include galactic binaries, mergers of supermasive black-hole binaries, extreme-mass-ratio inspirals, and possibly from as yet unimagined sources. LISA is a constellation of three spacecraft separated by 5 million km in an equilateral triangle, whose center follows the Earth in a heliocentric orbit with an orbital phase offset oF 20 degrees. Challenging technology is required to ensure pure geodetic trajectories of the six onboard test masses, whose distance fluctuations will be measured by interspacecraft laser interferometers with picometer accuracy. LISA Pathfinder is an ESA-launched technology demonstration mission of key LISA subsystems such us spacecraft control with micro-newton thrusters, test mass drag-free control, and precision laser interferometry between free-flying test masses. Ground testing of flight hardware of the Gravitational Reference Sensor and Optical Metrology subsystems of LISA Pathfinder is currently ongoing. An introduction to laser interferometric gravitational wave detection, ground-based observatories, and a detailed description of the two missions together with an overview of current investigations conducted by the community will bc discussed. The current status in development and implementation of LISA Pathfinder pre-flight systems and latest results of the ongoing ground testing efforts will also be presented

Dispersion analysis of passive surface-wave noise generated during hydraulic-fracturing operations

USGS Publications Warehouse

Forghani-Arani, Farnoush; Willis, Mark; Snieder, Roel; Haines, Seth S.; Behura, Jyoti; Batzle, Mike; Davidson, Michael

2014-01-01

Surface-wave dispersion analysis is useful for estimating near-surface shear-wave velocity models, designing receiver arrays, and suppressing surface waves. Here, we analyze whether passive seismic noise generated during hydraulic-fracturing operations can be used to extract surface-wave dispersion characteristics. Applying seismic interferometry to noise measurements, we extract surface waves by cross-correlating several minutes of passive records; this approach is distinct from previous studies that used hours or days of passive records for cross-correlation. For comparison, we also perform dispersion analysis for an active-source array that has some receivers in common with the passive array. The active and passive data show good agreement in the dispersive character of the fundamental-mode surface-waves. For the higher mode surface waves, however, active and passive data resolve the dispersive properties at different frequency ranges. To demonstrate an application of dispersion analysis, we invert the observed surface-wave dispersion characteristics to determine the near-surface, one-dimensional shear-wave velocity.

Direct-to-digital holography reduction of reference hologram noise and fourier space smearing

DOEpatents

Voelkl, Edgar

2006-06-27

Systems and methods are described for reduction of reference hologram noise and reduction of Fourier space smearing, especially in the context of direct-to-digital holography (off-axis interferometry). A method of reducing reference hologram noise includes: recording a plurality of reference holograms; processing the plurality of reference holograms into a corresponding plurality of reference image waves; and transforming the corresponding plurality of reference image waves into a reduced noise reference image wave. A method of reducing smearing in Fourier space includes: recording a plurality of reference holograms; processing the plurality of reference holograms into a corresponding plurality of reference complex image waves; transforming the corresponding plurality of reference image waves into a reduced noise reference complex image wave; recording a hologram of an object; processing the hologram of the object into an object complex image wave; and dividing the complex image wave of the object by the reduced noise reference complex image wave to obtain a reduced smearing object complex image wave.

Matter-wave coherence limit owing to cosmic gravitational wave background

NASA Astrophysics Data System (ADS)

Steane, Andrew M.

2017-12-01

We study matter-wave interferometry in the presence of a stochastic background of gravitational waves. It is shown that if the background has a scale-invariant spectrum over a wide bandwidth (which is expected in a class of inflationary models of Big Bang cosmology), then separated-path interference cannot be observed for a lump of matter of size above a limit which is very insensitive to the strength and bandwidth of the fluctuations, unless the interferometer is servo-controlled or otherwise protected. For ordinary solid matter this limit is of order 1-10 mm. A servo-controlled or cross-correlated device would also exhibit limits to the observation of macroscopic interference, which we estimate for ordinary matter moving at speeds small compared to c.

Poisson's spot and Gouy phase

NASA Astrophysics Data System (ADS)

da Paz, I. G.; Soldati, Rodolfo; Cabral, L. A.; de Oliveira, J. G. G.; Sampaio, Marcos

2016-12-01

Recently there have been experimental results on Poisson spot matter-wave interferometry followed by theoretical models describing the relative importance of the wave and particle behaviors for the phenomenon. We propose an analytical theoretical model for Poisson's spot with matter waves based on the Babinet principle, in which we use the results for free propagation and single-slit diffraction. We take into account effects of loss of coherence and finite detection area using the propagator for a quantum particle interacting with an environment. We observe that the matter-wave Gouy phase plays a role in the existence of the central peak and thus corroborates the predominantly wavelike character of the Poisson's spot. Our model shows remarkable agreement with the experimental data for deuterium (D2) molecules.

Phonetic Encoding of Coda Voicing Contrast under Different Focus Conditions in L1 vs. L2 English.

PubMed

Choi, Jiyoun; Kim, Sahayng; Cho, Taehong

2016-01-01

This study investigated how coda voicing contrast in English would be phonetically encoded in the temporal vs. spectral dimension of the preceding vowel (in vowel duration vs. F1/F2) by Korean L2 speakers of English, and how their L2 phonetic encoding pattern would be compared to that of native English speakers. Crucially, these questions were explored by taking into account the phonetics-prosody interface, testing effects of prominence by comparing target segments in three focus conditions (phonological focus, lexical focus, and no focus). Results showed that Korean speakers utilized the temporal dimension (vowel duration) to encode coda voicing contrast, but failed to use the spectral dimension (F1/F2), reflecting their native language experience-i.e., with a more sparsely populated vowel space in Korean, they are less sensitive to small changes in the spectral dimension, and hence fine-grained spectral cues in English are not readily accessible. Results also showed that along the temporal dimension, both the L1 and L2 speakers hyperarticulated coda voicing contrast under prominence (when phonologically or lexically focused), but hypoarticulated it in the non-prominent condition. This indicates that low-level phonetic realization and high-order information structure interact in a communicatively efficient way, regardless of the speakers' native language background. The Korean speakers, however, used the temporal phonetic space differently from the way the native speakers did, especially showing less reduction in the no focus condition. This was also attributable to their native language experience-i.e., the Korean speakers' use of temporal dimension is constrained in a way that is not detrimental to the preservation of coda voicing contrast, given that they failed to add additional cues along the spectral dimension. The results imply that the L2 phonetic system can be more fully illuminated through an investigation of the phonetics-prosody interface in connection with the L2 speakers' native language experience.

Phonetic Encoding of Coda Voicing Contrast under Different Focus Conditions in L1 vs. L2 English

PubMed Central

Choi, Jiyoun; Kim, Sahayng; Cho, Taehong

2016-01-01

This study investigated how coda voicing contrast in English would be phonetically encoded in the temporal vs. spectral dimension of the preceding vowel (in vowel duration vs. F1/F2) by Korean L2 speakers of English, and how their L2 phonetic encoding pattern would be compared to that of native English speakers. Crucially, these questions were explored by taking into account the phonetics-prosody interface, testing effects of prominence by comparing target segments in three focus conditions (phonological focus, lexical focus, and no focus). Results showed that Korean speakers utilized the temporal dimension (vowel duration) to encode coda voicing contrast, but failed to use the spectral dimension (F1/F2), reflecting their native language experience—i.e., with a more sparsely populated vowel space in Korean, they are less sensitive to small changes in the spectral dimension, and hence fine-grained spectral cues in English are not readily accessible. Results also showed that along the temporal dimension, both the L1 and L2 speakers hyperarticulated coda voicing contrast under prominence (when phonologically or lexically focused), but hypoarticulated it in the non-prominent condition. This indicates that low-level phonetic realization and high-order information structure interact in a communicatively efficient way, regardless of the speakers’ native language background. The Korean speakers, however, used the temporal phonetic space differently from the way the native speakers did, especially showing less reduction in the no focus condition. This was also attributable to their native language experience—i.e., the Korean speakers’ use of temporal dimension is constrained in a way that is not detrimental to the preservation of coda voicing contrast, given that they failed to add additional cues along the spectral dimension. The results imply that the L2 phonetic system can be more fully illuminated through an investigation of the phonetics-prosody interface in connection with the L2 speakers’ native language experience. PMID:27242571

Pinpointing the North Korea Nuclear tests with body waves scattered by surface topography

NASA Astrophysics Data System (ADS)

Wang, N.; Shen, Y.; Bao, X.; Flinders, A. F.

2017-12-01

On September 3, 2017, North Korea conducted its sixth and by far the largest nuclear test at the Punggye-ri test site. In this work, we apply a novel full-wave location method that combines a non-linear grid-search algorithm with the 3D strain Green's tensor database to locate this event. We use the first arrivals (Pn waves) and their immediate codas, which are likely dominated by waves scattered by the surface topography near the source, to pinpoint the source location. We assess the solution in the search volume using a least-squares misfit between the observed and synthetic waveforms, which are obtained using the collocated-grid finite difference method on curvilinear grids. We calculate the one standard deviation level of the 'best' solution as a posterior error estimation. Our results show that the waveform based location method allows us to obtain accurate solutions with a small number of stations. The solutions are absolute locations as opposed to relative locations based on relative travel times, because topography-scattered waves depend on the geometric relations between the source and the unique topography near the source. Moreover, we use both differential waveforms and traveltimes to locate pairs of the North Korea tests in years 2016 and 2017 to further reduce the effects of inaccuracies in the reference velocity model (CRUST 1.0). Finally, we compare our solutions with those of other studies based on satellite images and relative traveltimes.

Optical frequency-domain chromatic dispersion measurement method for higher-order modes in an optical fiber.

PubMed

Ahn, Tae-Jung; Jung, Yongmin; Oh, Kyunghwan; Kim, Dug Young

2005-12-12

We propose a new chromatic dispersion measurement method for the higher-order modes of an optical fiber using optical frequency modulated continuous-wave (FMCW) interferometry. An optical fiber which supports few excited modes was prepared for our experiments. Three different guiding modes of the fiber were identified by using far-field spatial beam profile measurements and confirmed with numerical mode analysis. By using the principle of a conventional FMWC interferometry with a tunable external cavity laser, we have demonstrated that the chromatic dispersion of a few-mode optical fiber can be obtained directly and quantitatively as well as qualitatively. We have also compared our measurement results with those of conventional modulation phase-shift method.

Site response variation due to the existence of near-field cracks based on strong motion records in the Shi-Wen river valley, southern Taiwan

NASA Astrophysics Data System (ADS)

Wu, Chi-Shin; Yu, Teng-To; Peng, Wen-Fei; Yeh, Yeoin-Tein; Lin, Sih-Siao

2014-10-01

Site effect analysis has been applied to investigate soil classification, alluvium depth, and fracture detection, although the majority of previous studies have typically focused only on the response of large-scale single structures. In contrast, we investigated the site effect for small-scale cracks using a case study in southern Taiwan to provide a means of monitoring slope stability or foundation integrity in situ using only an accelerometer. We adopted both the reference site and horizontal-to-vertical spectral ratio methods. We obtained seismographs associated with the typhoon-related development of a crack set (52 m long, 5 m deep) in a steep slope and compared the resonance frequency between two conditions (with and without cracks). Moreover, we divided the seismic waves into P, S, and coda waves and examined the seismic source effect. Our results demonstrate that frequencies of 14.5-17.5 Hz are most sensitive to these cracks, particularly for the E-W component of the P-waves, which coincides with the crack’s strike. Peak ground acceleration, which is controlled by seismic moment and attenuated distance, is another important factor determining the resonance results. Our results demonstrate that the ratio of temporal seismic waves can be used to detect the existence of nearby subsurface cracks.

Ambient Noise Interferometry and Surface Wave Array Tomography: Promises and Problems

NASA Astrophysics Data System (ADS)

van der Hilst, R. D.; Yao, H.; de Hoop, M. V.; Campman, X.; Solna, K.

2008-12-01

In the late 1990ies most seismologists would have frowned at the possibility of doing high-resolution surface wave tomography with noise instead of with signal associated with ballistic source-receiver propagation. Some may still do, but surface wave tomography with Green's functions estimated through ambient noise interferometry ('sourceless tomography') has transformed from a curiosity into one of the (almost) standard tools for analysis of data from dense seismograph arrays. Indeed, spectacular applications of ambient noise surface wave tomography have recently been published. For example, application to data from arrays in SE Tibet revealed structures in the crust beneath the Tibetan plateau that could not be resolved by traditional tomography (Yao et al., GJI, 2006, 2008). While the approach is conceptually simple, in application the proverbial devil is in the detail. Full reconstruction of the Green's function requires that the wavefields used are diffusive and that ambient noise energy is evenly distributed in the spatial dimensions of interest. In the field, these conditions are not usually met, and (frequency dependent) non-uniformity of the noise sources may lead to incomplete reconstruction of the Green's function. Furthermore, ambient noise distributions can be time-dependent, and seasonal variations have been documented. Naive use of empirical Green's functions may produce (unknown) bias in the tomographic models. The degrading effect on EGFs of the directionality of noise distribution forms particular challenges for applications beyond isotropic surface wave inversions, such as inversions for (azimuthal) anisotropy and attempts to use higher modes (or body waves). Incomplete Green's function reconstruction can (probably) not be prevented, but it may be possible to reduce the problem and - at least - understand the degree of incomplete reconstruction and prevent it from degrading the tomographic model. We will present examples of Rayleigh wave inversions and discuss strategies to mitigate effects of incomplete Green's function reconstruction on tomographic images.

Infrasonic interferometry applied to synthetic and measured data

NASA Astrophysics Data System (ADS)

Fricke, Julius T.; Evers, Läslo G.; Ruigrok, Elmer; Wapenaar, Kees; Simons, Dick G.

2013-04-01

The estimation of the traveltime of infrasound through the atmosphere is interesting for several applications. For example, it could be used to determine temperature and wind of the atmosphere, since the traveltime depends on these atmospheric conditions (Haney, 2009). In this work the traveltime is estimated with infrasonic interferometry. In other words, we calculate the crosscorrelations of data of spatially distributed receivers. With this method the traveltime between two receivers is determined without the need for ground truth events. In a first step, we crosscorrelate synthetic data, which are generated by a raytracing model. This model takes into account the traveltime along the rays, the attenuation of the different atmospheric layers, the spreading of the rays and the influence of caustics. In these numerical experiments we show that it is possible to determine the traveltime through infrasonic interferometry. We present the results of infrasonic interferometry applied to measured data. Microbaroms are used in the crosscorrelation approach. Microbaroms are caused by ocean waves and are measured by the 'Large Aperture Infrasound Array' (LAIA). LAIA is being installed by the Royal Netherlands Meteorological Institute (KNMI) in the framework of the radio-astronomical 'Low Frequency Array' (LOFAR) initiative. LAIA consists currently of around twenty receivers (microbarometers) with an aperture of around 100 km, allowing for several inter-station distances. Here, we show the results of crosscorrelations as a function of receivers distance, to assess the signal coherency. This research is made possible by the support of the 'Netherlands Organization for Scientific Research' (NWO). Haney, M., 2009. Infrasonic ambient noise interferometry from correlations of microbaroms, Geophysical Research Letters, 36, L19808

Microwave interferometry technique for obtaining gas interface velocity measurements in an expansion tube facility

NASA Technical Reports Server (NTRS)

Laney, C. C., Jr.

1974-01-01

A microwave interferometer technique to determine the front interface velocity of a high enthalpy gas flow, is described. The system is designed to excite a standing wave in an expansion tube, and to measure the shift in this standing wave as it is moved by the test gas front. Data, in the form of a varying sinusoidal signal, is recorded on a high-speed drum camera-oscilloscope combination. Measurements of average and incremental velocities in excess of 6,000 meters per second were made.

Skin friction measurements by laser interferometry in swept shock wave/turbulent boundary-layer interactions

NASA Technical Reports Server (NTRS)

Kim, Kwang-Soo; Settles, Gary S.

1988-01-01

The laser interferometric skin friction meter was used to measure wall shear stress distributions in two interactions of fin-generated swept shock waves with turbulent boundary layers. The basic research configuration was an unswept sharp-leading-edge fin of variable angle mounted on a flatplate. The results indicate that such measurements are practical in high-speed interacting flows, and that a repeatability of + or - 6 percent or better is possible. Marked increases in wall shear were observed in both swept interactions tested.

Dual-wavelength phase-shifting digital holography selectively extracting wavelength information from wavelength-multiplexed holograms.

PubMed

Tahara, Tatsuki; Mori, Ryota; Kikunaga, Shuhei; Arai, Yasuhiko; Takaki, Yasuhiro

2015-06-15

Dual-wavelength phase-shifting digital holography that selectively extracts wavelength information from five wavelength-multiplexed holograms is presented. Specific phase shifts for respective wavelengths are introduced to remove the crosstalk components and extract only the object wave at the desired wavelength from the holograms. Object waves in multiple wavelengths are selectively extracted by utilizing 2π ambiguity and the subtraction procedures based on phase-shifting interferometry. Numerical results show the validity of the proposed technique. The proposed technique is also experimentally demonstrated.

Non-linear resonant coupling of tsunami edge waves using stochastic earthquake source models

USGS Publications Warehouse

Geist, Eric L.

2016-01-01

Non-linear resonant coupling of edge waves can occur with tsunamis generated by large-magnitude subduction zone earthquakes. Earthquake rupture zones that straddle beneath the coastline of continental margins are particularly efficient at generating tsunami edge waves. Using a stochastic model for earthquake slip, it is shown that a wide range of edge-wave modes and wavenumbers can be excited, depending on the variability of slip. If two modes are present that satisfy resonance conditions, then a third mode can gradually increase in amplitude over time, even if the earthquake did not originally excite that edge-wave mode. These three edge waves form a resonant triad that can cause unexpected variations in tsunami amplitude long after the first arrival. An M ∼ 9, 1100 km-long continental subduction zone earthquake is considered as a test case. For the least-variable slip examined involving a Gaussian random variable, the dominant resonant triad includes a high-amplitude fundamental mode wave with wavenumber associated with the along-strike dimension of rupture. The two other waves that make up this triad include subharmonic waves, one of fundamental mode and the other of mode 2 or 3. For the most variable slip examined involving a Cauchy-distributed random variable, the dominant triads involve higher wavenumbers and modes because subevents, rather than the overall rupture dimension, control the excitation of edge waves. Calculation of the resonant period for energy transfer determines which cases resonant coupling may be instrumentally observed. For low-mode triads, the maximum transfer of energy occurs approximately 20–30 wave periods after the first arrival and thus may be observed prior to the tsunami coda being completely attenuated. Therefore, under certain circumstances the necessary ingredients for resonant coupling of tsunami edge waves exist, indicating that resonant triads may be observable and implicated in late, large-amplitude tsunami arrivals.

Enhanced sensitivity of the LIGO gravitational wave detector by using squeezed states of light

NASA Astrophysics Data System (ADS)

Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Affeldt, C.; Aguiar, O. D.; Ajith, P.; Allen, B.; Amador Ceron, E.; Amariutei, D.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Ast, S.; Aston, S. M.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Austin, L.; Aylott, B. E.; Babak, S.; Baker, P. T.; Ballmer, S.; Bao, Y.; Barayoga, J. C.; Barker, D.; Barr, B.; Barsotti, L.; Barton, M. A.; Bartos, I.; Bassiri, R.; Batch, J.; Bauchrowitz, J.; Behnke, B.; Bell, A. S.; Bell, C.; Bergmann, G.; Berliner, J. M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bhadbhade, T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biscans, S.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Bock, O.; Bodiya, T. P.; Bogan, C.; Bond, C.; Bork, R.; Born, M.; Bose, S.; Bowers, J.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Breyer, J.; Bridges, D. O.; Brinkmann, M.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Buckland, K.; Brückner, F.; Buchler, B. C.; Buonanno, A.; Burguet-Castell, J.; Byer, R. L.; Cadonati, L.; Camp, J. B.; Campsie, P.; Cannon, K.; Cao, J.; Capano, C. D.; Carbone, L.; Caride, S.; Castiglia, A. D.; Caudill, S.; Cavaglià, M.; Cepeda, C.; Chalermsongsak, T.; Chao, S.; Charlton, P.; Chen, X.; Chen, Y.; Cho, H.-S.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S. S. Y.; Chung, C. T. Y.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J. A.; Constancio Junior, M.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Cumming, A.; Cunningham, L.; Dahl, K.; Damjanic, M.; Danilishin, S. L.; Danzmann, K.; Daudert, B.; Daveloza, H.; Davies, G. S.; Daw, E. J.; Dayanga, T.; Deleeuw, E.; Denker, T.; Dent, T.; Dergachev, V.; Derosa, R.; Desalvo, R.; Dhurandhar, S.; di Palma, I.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doravari, S.; Drasco, S.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edwards, M.; Effler, A.; Ehrens, P.; Eikenberry, S. S.; Engel, R.; Essick, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fairhurst, S.; Fang, Q.; Farr, B. F.; Farr, W.; Favata, M.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Finn, L. S.; Fisher, R. P.; Foley, S.; Forsi, E.; Fotopoulos, N.; Frede, M.; Frei, M. A.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fujimoto, M.-K.; Fulda, P. J.; Fyffe, M.; Gair, J.; Garcia, J.; Gehrels, N.; Gelencser, G.; Gergely, L. Á.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Gil-Casanova, S.; Gill, C.; Gleason, J.; Goetz, E.; González, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Goßler, S.; Graef, C.; Graff, P. B.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Griffo, C.; Grote, H.; Grover, K.; Grunewald, S.; Guido, C.; Gustafson, E. K.; Gustafson, R.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Haris, K.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Heefner, J.; Heintze, M. C.; Hendry, M. A.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Holtrop, M.; Hong, T.; Hooper, S.; Hough, J.; Howell, E. J.; Huang, V.; Huerta, E. A.; Hughey, B.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Iyer, B. R.; Izumi, K.; Jacobson, M.; James, E.; Jang, H.; Jang, Y. J.; Jesse, E.; Johnson, W. W.; Jones, D.; Jones, D. I.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kasturi, R.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Keitel, D.; Kelley, D. B.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, B. K.; Kim, C.; Kim, K.; Kim, N.; Kim, Y.-M.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kline, J.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Korth, W. Z.; Kozak, D.; Kozameh, C.; Kremin, A.; Kringel, V.; Krishnan, B.; Kucharczyk, C.; Kuehn, G.; Kumar, P.; Kumar, R.; Kuper, B. J.; Kurdyumov, R.; Kwee, P.; Lam, P. K.; Landry, M.; Lantz, B.; Lasky, P. D.; Lawrie, C.; Lazzarini, A.; Le Roux, A.; Leaci, P.; Lee, C.-H.; Lee, H. K.; Lee, H. M.; Lee, J.; Leong, J. R.; Levine, B.; Lhuillier, V.; Lin, A. C.; Litvine, V.; Liu, Y.; Liu, Z.; Lockerbie, N. A.; Lodhia, D.; Loew, K.; Logue, J.; Lombardi, A. L.; Lormand, M.; Lough, J.; Lubinski, M.; Lück, H.; Lundgren, A. P.; MacArthur, J.; MacDonald, E.; Machenschalk, B.; Macinnis, M.; MacLeod, D. M.; Magaña-Sandoval, F.; Mageswaran, M.; Mailand, K.; Manca, G.; Mandel, I.; Mandic, V.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martin, I. W.; Martin, R. M.; Martinov, D.; Marx, J. N.; Mason, K.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; May, G.; Mazzolo, G.; McAuley, K.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; Meadors, G. D.; Mehmet, M.; Meier, T.; Melatos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Miller, J.; Mingarelli, C. M. F.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mokler, F.; Mohapatra, S. R. P.; Moraru, D.; Moreno, G.; Mori, T.; Morriss, S. R.; Mossavi, K.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nanda Kumar, D.; Nash, T.; Nayak, R.; Necula, V.; Newton, G.; Nguyen, T.; Nishida, E.; Nishizawa, A.; Nitz, A.; Nolting, D.; Normandin, M. E.; Nuttall, L. K.; O'Dell, J.; O'Reilly, B.; O'Shaughnessy, R.; Ochsner, E.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oppermann, P.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Ou, J.; Overmier, H.; Owen, B. J.; Padilla, C.; Pai, A.; Pan, Y.; Pankow, C.; Papa, M. A.; Paris, H.; Parkinson, W.; Pedraza, M.; Penn, S.; Peralta, C.; Perreca, A.; Phelps, M.; Pickenpack, M.; Pierro, V.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Pöld, J.; Postiglione, F.; Poux, C.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Privitera, S.; Prokhorov, L. G.; Puncken, O.; Quetschke, V.; Quintero, E.; Quitzow-James, R.; Raab, F. J.; Radkins, H.; Raffai, P.; Raja, S.; Rakhmanov, M.; Ramet, C.; Raymond, V.; Reed, C. M.; Reed, T.; Reid, S.; Reitze, D. H.; Riesen, R.; Riles, K.; Roberts, M.; Robertson, N. A.; Robinson, E. L.; Roddy, S.; Rodriguez, C.; Rodriguez, L.; Rodruck, M.; Rollins, J. G.; Romie, J. H.; Röver, C.; Rowan, S.; Rüdiger, A.; Ryan, K.; Salemi, F.; Sammut, L.; Sandberg, V.; Sanders, J.; Sankar, S.; Sannibale, V.; Santamaría, L.; Santiago-Prieto, I.; Santostasi, G.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R. L.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schuette, D.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sergeev, A.; Shaddock, D. A.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siemens, X.; Sigg, D.; Simakov, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G. R.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, R. J. E.; Smith-Lefebvre, N. D.; Son, E. J.; Sorazu, B.; Souradeep, T.; Stefszky, M.; Steinert, E.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stevens, D.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S. E.; Stroeer, A. S.; Stuver, A. L.; Summerscales, T. Z.; Susmithan, S.; Sutton, P. J.; Szeifert, G.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, R.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Torres, C. V.; Torrie, C. I.; Traylor, G.; Tse, M.; Ugolini, D.; Unnikrishnan, C. S.; Vahlbruch, H.; Vallisneri, M.; van der Sluys, M. V.; van Veggel, A. A.; Vass, S.; Vaulin, R.; Vecchio, A.; Veitch, P. J.; Veitch, J.; Venkateswara, K.; Verma, S.; Vincent-Finley, R.; Vitale, S.; Vo, T.; Vorvick, C.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A.; Wade, L.; Wade, M.; Waldman, S. J.; Wallace, L.; Wan, Y.; Wang, M.; Wang, J.; Wang, X.; Wanner, A.; Ward, R. L.; Was, M.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; Wiseman, A. G.; White, D. J.; Whiting, B. F.; Wiesner, K.; Wilkinson, C.; Willems, P. A.; Williams, L.; Williams, R.; Williams, T.; Willis, J. L.; Willke, B.; Wimmer, M.; Winkelmann, L.; Winkler, W.; Wipf, C.; Wittel, H.; Woan, G.; Wooley, R.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yancey, C. C.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yum, H.; Zanolin, M.; Zhang, F.; Zhang, L.; Zhao, C.; Zhu, H.; Zhu, X. J.; Zotov, N.; Zucker, M. E.; Zweizig, J.

2013-08-01

Nearly a century after Einstein first predicted the existence of gravitational waves, a global network of Earth-based gravitational wave observatories is seeking to directly detect this faint radiation using precision laser interferometry. Photon shot noise, due to the quantum nature of light, imposes a fundamental limit on the attometre-level sensitivity of the kilometre-scale Michelson interferometers deployed for this task. Here, we inject squeezed states to improve the performance of one of the detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) beyond the quantum noise limit, most notably in the frequency region down to 150 Hz, critically important for several astrophysical sources, with no deterioration of performance observed at any frequency. With the injection of squeezed states, this LIGO detector demonstrated the best broadband sensitivity to gravitational waves ever achieved, with important implications for observing the gravitational-wave Universe with unprecedented sensitivity.

Three-Dimensional Passive-Source Reverse-Time Migration of Converted Waves: The Method

NASA Astrophysics Data System (ADS)

Li, Jiahang; Shen, Yang; Zhang, Wei

2018-02-01

At seismic discontinuities in the crust and mantle, part of the compressional wave energy converts to shear wave, and vice versa. These converted waves have been widely used in receiver function (RF) studies to image discontinuity structures in the Earth. While generally successful, the conventional RF method has its limitations and is suited mostly to flat or gently dipping structures. Among the efforts to overcome the limitations of the conventional RF method is the development of the wave-theory-based, passive-source reverse-time migration (PS-RTM) for imaging complex seismic discontinuities and scatters. To date, PS-RTM has been implemented only in 2D in the Cartesian coordinate for local problems and thus has limited applicability. In this paper, we introduce a 3D PS-RTM approach in the spherical coordinate, which is better suited for regional and global problems. New computational procedures are developed to reduce artifacts and enhance migrated images, including back-propagating the main arrival and the coda containing the converted waves separately, using a modified Helmholtz decomposition operator to separate the P and S modes in the back-propagated wavefields, and applying an imaging condition that maintains a consistent polarity for a given velocity contrast. Our new approach allows us to use migration velocity models with realistic velocity discontinuities, improving accuracy of the migrated images. We present several synthetic experiments to demonstrate the method, using regional and teleseismic sources. The results show that both regional and teleseismic sources can illuminate complex structures and this method is well suited for imaging dipping interfaces and sharp lateral changes in discontinuity structures.

Sounds of earthquakes in West Bohemia: analysis of sonic and infrasonic records

NASA Astrophysics Data System (ADS)

Fischer, Tomáš; Vilhelm, Jan; Kuna, Václav; Chum, Jaroslav; Horálek, Josef

2013-04-01

Earthquake sounds are usually observed during the occurrence of small earthquakes. The observations of audible manifestations of earthquakes date back to the ancient age and have been recently analyzed in more detail based both on macroseismic observations and audio recordings. In most cases the earthquake sounds resemble low-frequency underground thundering that is generated by seismic-acoustic conversion of P and SV waves at the earth surface. This is also supported by the fact that earthquake sounds usually precede shaking caused by S-waves. The less frequent are explosion-type sounds whose origin remains unclear. We analyze the observations of sounds associating the occurrence of earthquake swarms in the area of West Bohemia/Vogtland, Central Europe. Macroseismic data include 250 reports of sounds with 90% thundering and 10% of explosions. Additional data consist of sonic and infrasonic records acquired by microphones and microbarographs at seismic stations in the area. All the sonic and infrasonic records correspond to sounds of the thunder type; no explosions were recorded. Comparison of these records enabled to determine the seismic wave - air pressure transfer function. The measurements using a 3D microphone array confirm that in the epicentral area the sonic wave is propagating subvertically. We also compared the coda of seismograms and sonic records. It turned out that additional to seismo-acoustic coupling, a later acoustic wave of thunder type arrives at the observation site whose arrival time corresponds to sonic propagation from the epicenter. We analyse the possible generation mechanisms of this type of sonic wave.

Seismic anisotropy in the vicinity of the Alpine fault, New Zealand, estimated by seismic interferometry

NASA Astrophysics Data System (ADS)

Takagi, R.; Okada, T.; Yoshida, K.; Townend, J.; Boese, C. M.; Baratin, L. M.; Chamberlain, C. J.; Savage, M. K.

2016-12-01

We estimate shear wave velocity anisotropy in shallow crust near the Alpine fault using seismic interferometry of borehole vertical arrays. We utilized four borehole observations: two sensors are deployed in two boreholes of the Deep Fault Drilling Project in the hanging wall side, and the other two sites are located in the footwall side. Surface sensors deployed just above each borehole are used to make vertical arrays. Crosscorrelating rotated horizontal seismograms observed by the borehole and surface sensors, we extracted polarized shear waves propagating from the bottom to the surface of each borehole. The extracted shear waves show polarization angle dependence of travel time, indicating shear wave anisotropy between the two sensors. In the hanging wall side, the estimated fast shear wave directions are parallel to the Alpine fault. Strong anisotropy of 20% is observed at the site within 100 m from the Alpine fault. The hanging wall consists of mylonite and schist characterized by fault parallel foliation. In addition, an acoustic borehole imaging reveals fractures parallel to the Alpine fault. The fault parallel anisotropy suggest structural anisotropy is predominant in the hanging wall, demonstrating consistency of geological and seismological observations. In the footwall side, on the other hand, the angle between the fast direction and the strike of the Alpine fault is 33-40 degrees. Since the footwall is composed of granitoid that may not have planar structure, stress induced anisotropy is possibly predominant. The direction of maximum horizontal stress (SHmax) estimated by focal mechanisms of regional earthquakes is 55 degrees of the Alpine fault. Possible interpretation of the difference between the fast direction and SHmax direction is depth rotation of stress field near the Alpine fault. Similar depth rotation of stress field is also observed in the SAFOD borehole at the San Andreas fault.

Constraints on small-scale heterogeneity in the lowermost mantle from observations of near podal PcP precursors

NASA Astrophysics Data System (ADS)

Zhang, Baolong; Ni, Sidao; Sun, Daoyuan; Shen, Zhichao; Jackson, Jennifer M.; Wu, Wenbo

2018-05-01

Volumetric heterogeneities on large (∼>1000 km) and intermediate scales (∼>100 km) in the lowermost mantle have been established with seismological approaches. However, there are controversies regarding the level of heterogeneity in the lowermost mantle at small scales (a few kilometers to tens of kilometers), with lower bound estimates ranging from 0.1% to a few percent. We take advantage of the small amplitude PcP waves at near podal distances (0-12°) to constrain the level of small-scale heterogeneity within 250 km above the CMB. First, we compute short period synthetic seismograms with a finite difference code for a series of volumetric heterogeneity models in the lowermost mantle, and find that PcP is not identifiable if the small-scale heterogeneity in the lowermost mantle is above 2.5%. We then use a functional form appropriate for coda decay to suppress P coda contamination. By comparing the corrected envelope of PcP and its precursors with synthetic seismograms, we find that perturbations of small-scale (∼8 km) heterogeneity in the lowermost mantle is ∼0.2-0.5% beneath regions of the China-Myanmar border area, Okhotsk Sea and South America. Whereas strong perturbations (∼1.0%) are found beneath Central America. In the regions studied, we find that this particular type of small-scale heterogeneity in the lowermost mantle is weak, yet there are some regions requiring heterogeneity up to 1.0%. Where scattering is stronger, such as under Central America, more chemically complex mineral assemblages may be present at the core-mantle boundary.

Broadband Evaluation of DPRK Explosions, Collapse Event, and Induced Aftershocks

NASA Astrophysics Data System (ADS)

Mayeda, K.; Roman-Nieves, J. I.; Wagner, G.; Jeon, Y. S.

2017-12-01

We report on the past 6 declared DPRK nuclear explosions, a collapse event, and recent associated induced shear dislocation sources using long-period waveform modeling, direct regional phases, and stable P-coda and S-coda spectral ratios. We find that the recent September 3rd, 2017 explosion is well modeled with an MM71 explosion source model at normal scale depth, but the previous 5 smaller yield explosions exhibit much larger relative high frequency radiation, strongly suggesting they are all over buried by varying amounts. The collapse event that occurred 8 minutes following the September 3rd DPRK explosion shares significant similarities with a number of NTS collapse events for explosions of comparable yield, both in absolute amplitude and spectral fall-off. A large number of smaller sources have been observed, which from stable coda spectral analysis and waveform modeling, are consistent with shallow shear dislocations likely caused by stress redistribution following the past nuclear explosions. We conclude with testing of a new discriminant that is specific to this region.

Seismic interferometry by multidimensional deconvolution as a means to compensate for anisotropic illumination

NASA Astrophysics Data System (ADS)

Wapenaar, K.; van der Neut, J.; Ruigrok, E.; Draganov, D.; Hunziker, J.; Slob, E.; Thorbecke, J.; Snieder, R.

2008-12-01

It is well-known that under specific conditions the crosscorrelation of wavefields observed at two receivers yields the impulse response between these receivers. This principle is known as 'Green's function retrieval' or 'seismic interferometry'. Recently it has been recognized that in many situations it can be advantageous to replace the correlation process by deconvolution. One of the advantages is that deconvolution compensates for the waveform emitted by the source; another advantage is that it is not necessary to assume that the medium is lossless. The approaches that have been developed to date employ a 1D deconvolution process. We propose a method for seismic interferometry by multidimensional deconvolution and show that under specific circumstances the method compensates for irregularities in the source distribution. This is an important difference with crosscorrelation methods, which rely on the condition that waves are equipartitioned. This condition is for example fulfilled when the sources are regularly distributed along a closed surface and the power spectra of the sources are identical. The proposed multidimensional deconvolution method compensates for anisotropic illumination, without requiring knowledge about the positions and the spectra of the sources.

The generation of higher-order Laguerre-Gauss optical beams for high-precision interferometry.

PubMed

Carbone, Ludovico; Fulda, Paul; Bond, Charlotte; Brueckner, Frank; Brown, Daniel; Wang, Mengyao; Lodhia, Deepali; Palmer, Rebecca; Freise, Andreas

2013-08-12

Thermal noise in high-reflectivity mirrors is a major impediment for several types of high-precision interferometric experiments that aim to reach the standard quantum limit or to cool mechanical systems to their quantum ground state. This is for example the case of future gravitational wave observatories, whose sensitivity to gravitational wave signals is expected to be limited in the most sensitive frequency band, by atomic vibration of their mirror masses. One promising approach being pursued to overcome this limitation is to employ higher-order Laguerre-Gauss (LG) optical beams in place of the conventionally used fundamental mode. Owing to their more homogeneous light intensity distribution these beams average more effectively over the thermally driven fluctuations of the mirror surface, which in turn reduces the uncertainty in the mirror position sensed by the laser light. We demonstrate a promising method to generate higher-order LG beams by shaping a fundamental Gaussian beam with the help of diffractive optical elements. We show that with conventional sensing and control techniques that are known for stabilizing fundamental laser beams, higher-order LG modes can be purified and stabilized just as well at a comparably high level. A set of diagnostic tools allows us to control and tailor the properties of generated LG beams. This enabled us to produce an LG beam with the highest purity reported to date. The demonstrated compatibility of higher-order LG modes with standard interferometry techniques and with the use of standard spherical optics makes them an ideal candidate for application in a future generation of high-precision interferometry.

Prevalence of phonological disorders and phonological processes in typical and atypical phonological development.

PubMed

Ceron, Marizete Ilha; Gubiani, Marileda Barichello; Oliveira, Camila Rosa de; Gubiani, Marieli Barichello; Keske-Soares, Márcia

2017-05-08

To determine the occurrence of phonological disorders by age, gender and school type, and analyze the phonological processes observed in typical and atypical phonological development across different age groups. The sample consisted of 866 children aged between 3:0 and 8:11 years, recruited from public and private schools in the city of Santa Maria/RS. A phonological evaluation was performed to analyze the operative phonological processes. 15.26% (n = 132) of the sample presented atypical phonological acquisition (phonological disorders). Phonological impairments were more frequent in public school students across all age groups. Phonological alterations were most frequent between ages 4 -to 6, and more prevalent in males than females in all but the youngest age group. The most common phonological processes in typical phonological acquisition were: cluster reduction; nonlateral liquid deletion in coda; nonlateral liquid substitution in onset; semivocalization of lateral liquids in coda; and unstressed syllable deletion. In children with phonological disorders, the most common phonological processes were: lateral and nonlateral liquid substitution in onset position; nonlateral liquid deletion; fronting of fricatives in onset position; unstressed syllable deletion; semivocalization of nonlateral liquid in coda; and nonlateral liquid deletion in coda position. Phonological processes were highly prevalent in the present sample, and occurred more often in boys than in girls. Information regarding the type and frequency of phonological processes in both typical phonological acquisition and phonological disorders may contribute to early diagnosis and increase the efficiency of treatment planning.

Polarimetric Interferometry

DTIC Science & Technology

2007-02-01

frequency radio wave propagation through the ionosphere , where the earths magnetic field lines break this reciprocity symmetry and as a result the cross...polarisation terms are no longer equal. This observation can be used to calibrate the effects of Faraday rotation due to trans- ionospheric ...currently under investigation is polarimetric SAR tomography , which is the extension of conventional two-dimensional SAR imaging principle to three

ESA Atmospheric Toolbox

NASA Astrophysics Data System (ADS)

Niemeijer, Sander

2017-04-01

The ESA Atmospheric Toolbox (BEAT) is one of the ESA Sentinel Toolboxes. It consists of a set of software components to read, analyze, and visualize a wide range of atmospheric data products. In addition to the upcoming Sentinel-5P mission it supports a wide range of other atmospheric data products, including those of previous ESA missions, ESA Third Party missions, Copernicus Atmosphere Monitoring Service (CAMS), ground based data, etc. The toolbox consists of three main components that are called CODA, HARP and VISAN. CODA provides interfaces for direct reading of data from earth observation data files. These interfaces consist of command line applications, libraries, direct interfaces to scientific applications (IDL and MATLAB), and direct interfaces to programming languages (C, Fortran, Python, and Java). CODA provides a single interface to access data in a wide variety of data formats, including ASCII, binary, XML, netCDF, HDF4, HDF5, CDF, GRIB, RINEX, and SP3. HARP is a toolkit for reading, processing and inter-comparing satellite remote sensing data, model data, in-situ data, and ground based remote sensing data. The main goal of HARP is to assist in the inter-comparison of datasets. By appropriately chaining calls to HARP command line tools one can pre-process datasets such that two datasets that need to be compared end up having the same temporal/spatial grid, same data format/structure, and same physical unit. The toolkit comes with its own data format conventions, the HARP format, which is based on netcdf/HDF. Ingestion routines (based on CODA) allow conversion from a wide variety of atmospheric data products to this common format. In addition, the toolbox provides a wide range of operations to perform conversions on the data such as unit conversions, quantity conversions (e.g. number density to volume mixing ratios), regridding, vertical smoothing using averaging kernels, collocation of two datasets, etc. VISAN is a cross-platform visualization and analysis application for atmospheric data and can be used to visualize and analyze the data that you retrieve using the CODA and HARP interfaces. The application uses the Python language as the means through which you provide commands to the application. The Python interfaces for CODA and HARP are included so you can directly ingest product data from within VISAN. Powerful visualization functionality for 2D plots and geographical plots in VISAN will allow you to directly visualize the ingested data. All components from the ESA Atmospheric Toolbox are Open Source and freely available. Software packages can be downloaded from the BEAT website: http://stcorp.nl/beat/

Holographic nondestructive tests performed on composite samples of ceramic-epoxy-fiberglass sandwich structure

NASA Technical Reports Server (NTRS)

Kurtz, R. L.; Liu, H. K.

1974-01-01

When a hologram storing more than one wave is illuminated with coherent light, the reconstructed wave fronts interfere with each other or with any other phase-related wave front derived from the illuminating source. This multiple wave front comparison is called holographic interferometry, and its application is called holographic nondestructive testing (HNDT). The theoretical aspects of HNDT techniques and the sensitivity of the holographic system to the geometrical placement of the optical components are briefly discussed. A unique HNDT system which is mobile and possesses variable sensitivity to stress amplitude is discribed, the experimental evidence of the application of this system to the testing of the hidden debonds in a ceramic-epoxy-fiberglass structure used for sample testing of the radome of the Pershing missile system is presented.

Bose-Einstein condensation in microgravity.

PubMed

van Zoest, T; Gaaloul, N; Singh, Y; Ahlers, H; Herr, W; Seidel, S T; Ertmer, W; Rasel, E; Eckart, M; Kajari, E; Arnold, S; Nandi, G; Schleich, W P; Walser, R; Vogel, A; Sengstock, K; Bongs, K; Lewoczko-Adamczyk, W; Schiemangk, M; Schuldt, T; Peters, A; Könemann, T; Müntinga, H; Lämmerzahl, C; Dittus, H; Steinmetz, T; Hänsch, T W; Reichel, J

2010-06-18

Albert Einstein's insight that it is impossible to distinguish a local experiment in a "freely falling elevator" from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter.

Preparing for InSight - using the continuous seismic data flow to investigate the deep interior of Mars

NASA Astrophysics Data System (ADS)

Hempel, S.; Garcia, R.; Weber, R. C.; Schmerr, N. C.; Panning, M. P.; Lognonne, P. H.; Banerdt, W. B.

2016-12-01

Complementary to investigating ray theoretically predictable parameters to explore the deep interior of Mars (see AGU contribution by R. Weber et al.), this paper presents the waveform approach to illuminate the lowermost mantle and core-mantle boundary of Mars. In preparation to the NASA discovery mission InSight, scheduled for launch in May, 2018, we produce synthetic waveforms considering realistic combinations of sources and a single receiver, as well as noise models. Due to a lack of constraints on the scattering properties of the Martian crust and mantle, we assume Earth-like scattering as a minimum and Moon-like scattering as a maximum possibility. Various seismic attenuation models are also investigated. InSight is set up to deliver event data as well as a continuous data flow. Where ray theoretical approaches will investigate the event data, the continuous data flow may contain signals reflected multiple times off the same reflector, e.g. the underside of the lithosphere, or the core-mantle boundary. It may also contain signals of individual events not detected or interfering wavefields radiated off multiple undetected events creating 'seismic noise'. We will use AxiSEM to simulate a continuous data flow for these cases for various 1D and 2D Mars models, and explore the possibilities of seismic interferometry to use seismic information hidden in the coda to investigate the deep interior of Mars.

Information Content in Radio Waves: Student Investigations in Radio Science

NASA Astrophysics Data System (ADS)

Jacobs, K.; Scaduto, T.

2013-12-01

We describe an inquiry-based instructional unit on information content in radio waves, created in the summer of 2013 as part of a MIT Haystack Observatory (Westford, MA) NSF Research Experiences for Teachers (RET) program. This topic is current and highly relevant, addressing science and technical aspects from radio astronomy, geodesy, and atmospheric research areas as well as Next Generation Science Standards (NGSS). Projects and activities range from simple classroom demonstrations and group investigations, to long term research projects incorporating data acquisition from both student-built instrumentation as well as online databases. Each of the core lessons is applied to one of the primary research centers at Haystack through an inquiry project that builds on previously developed units through the MIT Haystack RET program. In radio astronomy, students investigate the application of a simple and inexpensive software defined radio chip (RTL-SDR) for use in systems implementing a small and very small radio telescope (SRT and VSRT). Both of these systems allow students to explore fundamental principles of radio waves and interferometry as applied to radio astronomy. In ionospheric research, students track solar storms from the initial coronal mass ejection (using Solar Dynamics Observatory images) to the resulting variability in total electron density concentrations using data from the community standard Madrigal distributed database system maintained by MIT Haystack. Finally, students get to explore very long-baseline interferometry as it is used in geodetic studies by measuring crustal plate displacements over time. Alignment to NextGen standards is provided for each lesson and activity with emphasis on HS-PS4 'Waves and Their Applications in Technologies for Information Transfer'.

Imaging acoustic vibrations in an ear model using spectrally encoded interferometry

NASA Astrophysics Data System (ADS)

Grechin, Sveta; Yelin, Dvir

2018-01-01

Imaging vibrational patterns of the tympanic membrane would allow an accurate measurement of its mechanical properties and provide early diagnosis of various hearing disorders. Various optical technologies have been suggested to address this challenge and demonstrated in vitro using point scanning and full-field interferometry. Spectrally encoded imaging has been previously demonstrated capable of imaging tissue acoustic vibrations with high spatial resolution, including two-dimensional phase and amplitude mapping. In this work, we demonstrate a compact optical apparatus for imaging acoustic vibrations that could be incorporated into a commercially available digital otoscope. By transmitting harmonic sound waves through the otoscope insufflation port and analyzing the spectral interferograms using custom-built software, we demonstrate high-resolution vibration imaging of a circular rubber membrane within an ear model.

Surface based detection schemes for molecular interferometry experiments - implications and possible applications

NASA Astrophysics Data System (ADS)

Juffmann, Thomas; Milic, Adriana; Muellneritsch, Michael; Arndt, Markus

2011-03-01

Surface based detection schemes for molecular interferometry experiments might be crucial in the search for the quantum properties of larger and larger objects since they provide single particle sensitivity. Here we report on molecular interferograms of different biomolecules imaged using fluorescence microscopy. Being able to watch the build-up of an interferogram live and in situ reveals the matter-wave behavior of these complex molecules in an unprecedented way. We examine several problems encountered due to van-der-Waals forces between the molecules and the diffraction grating and discuss possible ways to circumvent these. Especially the advent of ultra-thin (1-100 atomic layers) diffraction masks might path the way towards molecular holography. We also discuss other possible applications such as coherent molecular microscopy.

Earthquake Source Parameters Inferred from T-Wave Observations

NASA Astrophysics Data System (ADS)

Perrot, J.; Dziak, R.; Lau, T. A.; Matsumoto, H.; Goslin, J.

2004-12-01

The seismicity of the North Atlantic Ocean has been recorded by two networks of autonomous hydrophones moored within the SOFAR channel on the flanks of the Mid-Atlantic Ridge (MAR). In February 1999, a consortium of U.S. investigators (NSF and NOAA) deployed a 6-element hydrophone array for long-term monitoring of MAR seismicity between 15o-35oN south of the Azores. In May 2002, an international collaboration of French, Portuguese, and U.S. researchers deployed a 6-element hydrophone array north of the Azores Plateau from 40o-50oN. The northern network (referred to as SIRENA) was recovered in September 2003. The low attenuation properties of the SOFAR channel for earthquake T-wave propagation results in a detection threshold reduction from a magnitude completeness level (Mc) of ˜ 4.7 for MAR events recorded by the land-based seismic networks to Mc=3.0 using hydrophone arrays. Detailed focal depth and mechanism information, however, remain elusive due to the complexities of seismo-acoustic propagation paths. Nonetheless, recent analyses (Dziak, 2001; Park and Odom, 2001) indicate fault parameter information is contained within the T-wave signal packet. We investigate this relationship further by comparing an earthquake's T-wave duration and acoustic energy to seismic magnitude (NEIC) and radiation pattern (for events M>5) from the Harvard moment-tensor catalog. First results show earthquake energy is well represented by the acoustic energy of the T-waves, however T-wave codas are significantly influenced by acoustic propagation effects and do not allow a direct determination of the seismic magnitude of the earthquakes. Second, there appears to be a correlation between T-wave acoustic energy, azimuth from earthquake source to the hydrophone, and the radiation pattern of the earthquake's SH waves. These preliminary results indicate there is a relationship between the T-wave observations and earthquake source parameters, allowing for additional insights into T-wave propagation.

Accurate source location from waves scattered by surface topography: Applications to the Nevada and North Korean test sites

NASA Astrophysics Data System (ADS)

Shen, Y.; Wang, N.; Bao, X.; Flinders, A. F.

2016-12-01

Scattered waves generated near the source contains energy converted from the near-field waves to the far-field propagating waves, which can be used to achieve location accuracy beyond the diffraction limit. In this work, we apply a novel full-wave location method that combines a grid-search algorithm with the 3D Green's tensor database to locate the Non-Proliferation Experiment (NPE) at the Nevada test site and the North Korean nuclear tests. We use the first arrivals (Pn/Pg) and their immediate codas, which are likely dominated by waves scattered at the surface topography near the source, to determine the source location. We investigate seismograms in the frequency of [1.0 2.0] Hz to reduce noises in the data and highlight topography scattered waves. High resolution topographic models constructed from 10 and 90 m grids are used for Nevada and North Korea, respectively. The reference velocity model is based on CRUST 1.0. We use the collocated-grid finite difference method on curvilinear grids to calculate the strain Green's tensor and obtain synthetic waveforms using source-receiver reciprocity. The `best' solution is found based on the least-square misfit between the observed and synthetic waveforms. To suppress random noises, an optimal weighting method for three-component seismograms is applied in misfit calculation. Our results show that the scattered waves are crucial in improving resolution and allow us to obtain accurate solutions with a small number of stations. Since the scattered waves depends on topography, which is known at the wavelengths of regional seismic waves, our approach yields absolute, instead of relative, source locations. We compare our solutions with those of USGS and other studies. Moreover, we use differential waveforms to locate pairs of the North Korea tests from years 2006, 2009, 2013 and 2016 to further reduce the effects of unmodeled heterogeneities and errors in the reference velocity model.

Seismic Interferometry of Cultural Noise: Body Waves Extracted from Auto and Train Traffic

NASA Astrophysics Data System (ADS)

Quiros, D. A.; Brown, L. D.; Kim, D.

2014-12-01

Here we report results of two experiments designed to evaluate the utility of anthropogenic noise as a source for generating body waves via interferometry. In particular we address the suggestion that traffic noise might prove effective at producing P and S waves at frequencies and amplitudes appropriate for crustal scale refraction and reflection imaging. The first experiment recorded routine traffic for about 10 days along a straight stretch of a rural highway between the towns of Elmira and Ithaca in upstate New York. The array was deployed along the highway using two different spacings: an inner segment with Δx ~ 25 m, bracketed between flanking segments with Δx ~ 100 m. In addition to strong surface waves, direct and reflected P waves were clearly apparent on most of the virtual shot gathers. These P-waves match the velocities of P-waves recorded from a conventional, small scale refraction survey carried out at the same site with a shotgun source and an engineering seismograph. The second experiment was located in the Rio Grande rift near Belen New Mexico, where relatively isolated train traffic was recorded for about 6 days parallel to a busy section of the BNRF railway that bisects New Mexico. Interferometric processing of the data produced virtual shot gathers with strong surface waves, as expected, but also linear arrivals that exhibit apparent velocities similar to those reported for the shallow Tertiary-Quaternary alluvium based on the original COCORP vibroseis surveys nearby. However the virtual shot gathers derived from the train sources are more complex that those obtained from the auto noise, which we suspect is due to the extended length of the train source relative to the spread length. Both experiments confirm that cultural noise can be used for subsurface imaging, though the cost effectiveness of this approach depends, among other factors, upon the total length of recording time needed to probe to depths of interest. They are both sources that clearly lend themselves to exploitation by the new generation of large N array technologies.

Hybrid shearing and phase-shifting point diffraction interferometer

DOEpatents

Goldberg, Kenneth Alan; Naulleau, Patrick P.

2003-06-03

A new interferometry configuration combines the strengths of two existing interferometry methods, improving the quality and extending the dynamic range of both. On the same patterned mask, placed near the image-plane of an optical system under test, patterns for phase-shifting point diffraction interferometry and lateral shearing interferometry coexist. The former giving verifiable high accuracy for the measurement of nearly diffraction-limited optical systems. The latter enabling the measurement of optical systems with more than one wave of aberration in the system wavefront. The interferometry configuration is a hybrid shearing and point diffraction interferometer system for testing an optical element that is positioned along an optical path including: a source of electromagnetic energy in the optical path; a first beam splitter that is secured to a device that includes means for maneuvering the first beam splitter in a first position wherein the first beam splitter is in the optical path dividing light from the source into a reference beam and a test beam and in a second position wherein the first beam splitter is outside the optical path: a hybrid mask which includes a first section that defines a test window and at least one reference pinhole and a second section that defines a second beam splitter wherein the hybrid mask is secured to a device that includes means for maneuvering either the first section or the second section into the optical path positioned in an image plane that is created by the optical element, with the proviso that the first section of the hybrid mask is positioned in the optical path when first beam splitter is positioned in the optical path; and a detector positioned after the hybrid mask along the optical path.

Non-contact fluid characterization in containers using ultrasonic waves

DOEpatents

Sinha, Dipen N [Los Alamos, NM

2012-05-15

Apparatus and method for non-contact (stand-off) ultrasonic determination of certain characteristics of fluids in containers or pipes are described. A combination of swept frequency acoustic interferometry (SFAI), wide-bandwidth, air-coupled acoustic transducers, narrowband frequency data acquisition, and data conversion from the frequency domain to the time domain, if required, permits meaningful information to be extracted from such fluids.

Mesospheric gravity wave momentum flux estimation using hybrid Doppler interferometry

NASA Astrophysics Data System (ADS)

Spargo, Andrew J.; Reid, Iain M.; MacKinnon, Andrew D.; Holdsworth, David A.

2017-06-01

Mesospheric gravity wave (GW) momentum flux estimates using data from multibeam Buckland Park MF radar (34.6° S, 138.5° E) experiments (conducted from July 1997 to June 1998) are presented. On transmission, five Doppler beams were symmetrically steered about the zenith (one zenith beam and four off-zenith beams in the cardinal directions). The received beams were analysed with hybrid Doppler interferometry (HDI) (Holdsworth and Reid, 1998), principally to determine the radial velocities of the effective scattering centres illuminated by the radar. The methodology of Thorsen et al. (1997), later re-introduced by Hocking (2005) and since extensively applied to meteor radar returns, was used to estimate components of Reynolds stress due to propagating GWs and/or turbulence in the radar resolution volume. Physically reasonable momentum flux estimates are derived from the Reynolds stress components, which are also verified using a simple radar model incorporating GW-induced wind perturbations. On the basis of these results, we recommend the intercomparison of momentum flux estimates between co-located meteor radars and vertical-beam interferometric MF radars. It is envisaged that such intercomparisons will assist with the clarification of recent concerns (e.g. Vincent et al., 2010) of the accuracy of the meteor radar technique.

Organ of Corti Micromechanics with Local Electrical Stimulation

NASA Astrophysics Data System (ADS)

Chen, Fangyi; Zheng, Jiefu; Choudhury, Niloy; Jaques, Steve; Nuttall, Alfred L.

2009-02-01

Optical low coherence interferometry is able to both image and measure the vibration of the cellular and non-cellular structures of the organ of Corti in vivo. In this study we applied an electric current to the basal turn from a pair of electrodes, one in scala tympani and the other in scala vestibuli, at the location corresponding to ~17 kHz when interferometry measurements were made. The coherence gate of the interferometer was positioned 1) at the basilar membrane (BM) near the radial location of the outer hair cells (OHCs) (approximately 1/2 the width of the BM) and 2) at the reticular lamina (RL) where the OHCs are located. We confirmed that electrical stimulation with a frequency sweep (12 kHz -25 kHz) caused a mechanical BM displacement with a peak and a traveling wave-like phase delay as we reported previously using laser Doppler velocimetry and reflective beads on the BM. Reflective beads were not used in the current study. The vibration of the RL had little or no phase delay that would characterize a traveling wave. These data suggest a very high compliance system for the electrically activated cellular structure of the organ.

Spectral Interferometry with Electron Microscopes

PubMed Central

Talebi, Nahid

2016-01-01

Interference patterns are not only a defining characteristic of waves, but also have several applications; characterization of coherent processes and holography. Spatial holography with electron waves, has paved the way towards space-resolved characterization of magnetic domains and electrostatic potentials with angstrom spatial resolution. Another impetus in electron microscopy has been introduced by ultrafast electron microscopy which uses pulses of sub-picosecond durations for probing a laser induced excitation of the sample. However, attosecond temporal resolution has not yet been reported, merely due to the statistical distribution of arrival times of electrons at the sample, with respect to the laser time reference. This is however, the very time resolution which will be needed for performing time-frequency analysis. These difficulties are addressed here by proposing a new methodology to improve the synchronization between electron and optical excitations through introducing an efficient electron-driven photon source. We use focused transition radiation of the electron as a pump for the sample. Due to the nature of transition radiation, the process is coherent. This technique allows us to perform spectral interferometry with electron microscopes, with applications in retrieving the phase of electron-induced polarizations and reconstructing dynamics of the induced vector potential. PMID:27649932

Atom Interferometry with the Sr Optical Clock Transition.

PubMed

Hu, Liang; Poli, Nicola; Salvi, Leonardo; Tino, Guglielmo M

2017-12-29

We report on the realization of a matter-wave interferometer based on single-photon interaction on the ultranarrow optical clock transition of strontium atoms. We experimentally demonstrate its operation as a gravimeter and as a gravity gradiometer. No reduction of interferometric contrast was observed for a total interferometer time up to ∼10  ms, limited by geometric constraints of the apparatus. Single-photon interferometers represent a new class of high-precision sensors that could be used for the detection of gravitational waves in so far unexplored frequency ranges and to enlighten the boundary between quantum mechanics and general relativity.

NASA capabilities roadmap: advanced telescopes and observatories

NASA Technical Reports Server (NTRS)

Feinberg, Lee D.

2005-01-01

The NASA Advanced Telescopes and Observatories (ATO) Capability Roadmap addresses technologies necessary for NASA to enable future space telescopes and observatories collecting all electromagnetic bands, ranging from x-rays to millimeter waves, and including gravity-waves. It has derived capability priorities from current and developing Space Missions Directorate (SMD) strategic roadmaps and, where appropriate, has ensured their consistency with other NASA Strategic and Capability Roadmaps. Technology topics include optics; wavefront sensing and control and interferometry; distributed and advanced spacecraft systems; cryogenic and thermal control systems; large precision structure for observatories; and the infrastructure essential to future space telescopes and observatories.

Magnetoacoustic Spectroscopy in Superfluid He3-B

NASA Astrophysics Data System (ADS)

Davis, J. P.; Choi, H.; Pollanen, J.; Halperin, W. P.

2008-01-01

We have used the acoustic Faraday effect in superfluid He3 to perform high resolution spectroscopy of an excited state of the superfluid condensate, called the imaginary squashing mode. With acoustic cavity interferometry we measure the rotation of the plane of polarization of a transverse sound wave propagating in the direction of the magnetic field from which we determine the Zeeman energy of the mode. We interpret the Landé g factor, combined with the zero-field energies of this excited state, using the theory of Sauls and Serene, to calculate the strength of f-wave interactions in He3.

Waveform tomography of crustal structure in the south San Francisco Bay region

USGS Publications Warehouse

Pollitz, F.F.; Fletcher, J.P.

2005-01-01

We utilize a scattering-based seismic tomography technique to constrain crustal tructure around the southern San Francisco Bay region (SFBR). This technique is based on coupled traveling wave scattering theory, which has usually been applied to the interpretation of surface waves in large regional-scale studies. Using fully three-dimensional kernels, this technique is here applied to observed P, S, and surface waves of intermediate period (3-4 s dominant period) observed following eight selected regional events. We use a total of 73 seismograms recorded by a U.S. Geological Survey short-period seismic array in the western Santa Clara Valley, the Berkeley Digital Seismic Network, and the Northern California Seismic Network. Modifications of observed waveforms due to scattering from crustal structure include (positive or negative) amplification, delay, and generation of coda waves. The derived crustal structure explains many of the observed signals which cannot be explained with a simple layered structure. There is sufficient sensitivity to both deep and shallow crustal structure that even with the few sources employed in the present study, we obtain shallow velocity structure which is reasonably consistent with previous P wave tomography results. We find a depth-dependent lateral velocity contrast across the San Andreas fault (SAF), with higher velocities southwest of the SAF in the shallow crust and higher velocities northeast of the SAF in the midcrust. The method does not have the resolution to identify very slow sediment velocities in the upper approximately 3 km since the tomographic models are smooth at a vertical scale of about 5 km. Copyright 2005 by the American Geophysical Union.

Ultrasonic monitoring of spontaneous imbibition experiments: Acoustic signature of fluid migration

NASA Astrophysics Data System (ADS)

David, Christian; Barnes, Christophe; Desrues, Mathilde; Pimienta, Lucas; Sarout, Joël.; Dautriat, Jérémie

2017-07-01

Capillary rise experiments (spontaneous imbibition tests) were conducted in the laboratory with ultrasonic and X-ray monitoring on the Sherwood sandstone and the Majella grainstone. The aim was to provide a direct comparison between the variation in seismic attributes (amplitude, velocity, spectral content, and energy) and the actual fluid distribution in the rock. Two pairs of ultrasonic P wave sensors located at different heights on a cylindrical rock specimen recorded every 5 s the waveforms when capillary forces make water rise up into the rock from the bottom in contact with a water tank. Simultaneously, computerized tomography scan images of a vertical cross section were also recorded. Two important results were found. (i) The amplitude of the first P wave arrival is impacted by the upward moving fluid front before the P wave velocity is, while the fluid front has not yet reached the sensors level. In contrast, the P wave velocity decreases when the fluid front reaches the Fresnel clearance zone. The spectral analysis of the waveforms shows that the peak frequency amplitude is continuously decreasing without noticeable frequency shift. (ii) A methodology based on the calculation of the analytical signal and instantaneous phase was designed to decompose each waveform into discrete wavelets associated with direct or reflected waves. The energy carried by the wavelets is very sensitive to the fluid substitution process: the coda wavelets related to reflections on the bottom end face of the specimen are impacted as soon as imbibition starts and can be used as a precursor for the arriving fluid.

Ambient Seismic Noise Interferometry on the Island of Hawai`i

NASA Astrophysics Data System (ADS)

Ballmer, Silke

Ambient seismic noise interferometry has been successfully applied in a variety of tectonic settings to gain information about the subsurface. As a passive seismic technique, it extracts the coherent part of ambient seismic noise in-between pairs of seismic receivers. Measurements of subtle temporal changes in seismic velocities, and high-resolution tomographic imaging are then possible - two applications of particular interest for volcano monitoring. Promising results from other volcanic settings motivate its application in Hawai'i, with this work being the first to explore its potential. The dataset used for this purpose was recorded by the Hawaiian Volcano Observatory's permanent seismic network on the Island of Hawai'i. It spans 2.5 years from 5/2007 to 12/2009 and covers two distinct sources of volcanic tremor. After applying standard processing for ambient seismic noise interferometry, we find that volcanic tremor strongly affects the extracted noise information not only close to the tremor source, but unexpectedly, throughout the island-wide network. Besides demonstrating how this long-range observability of volcanic tremor can be used to monitor volcanic activity in the absence of a dense seismic array, our results suggest that care must be taken when applying ambient seismic noise interferometry in volcanic settings. In a second step, we thus exclude days that show signs of volcanic tremor, reducing the dataset to three months, and perform ambient seismic noise tomography. The resulting two-dimensional Rayleigh wave group velocity maps for 0.1 - 0.9 Hz compare very well with images from previous travel time tomography, both, for the main volcanic structures at low frequencies as well as for smaller features at mid-to-high frequencies - a remarkable observation for the temporally truncated dataset. These robust results suggest that ambient seismic noise tomography in Hawai'i is suitable 1) to provide a three-dimensional S-wave model for the volcanoes and 2) to be used for repeated time-sensitive tomography, even though volcanic tremor frequently obscures ambient noise analyses. However, the noise characteristics and the wavefield in Hawai'i in general remain to be investigated in more detail in order to measure unbiased temporal velocity changes.

Optical analysis of laser systems using interferometry

NASA Astrophysics Data System (ADS)

Viswanathan, V. K.; Liberman, I.; Lawrence, G.; Seery, B. D.

1980-06-01

It is noted that previous approaches of predicting focal spot parameters involved the digitization of interference patterns of the optical components and propagation of the complex amplitude and phase of the wave front throughout the system. The present paper describes an approach in which the computational procedure is extended to produce computer plots of the final emerging wave front. It is shown that this enables direct comparison with the experimentally produced wave front of the total system and makes possible the optical analysis, design, and possible optimization of laser systems. A description is given of the computational procedure and the Twyman-Green and Smartt IR interferometers constructed to verify this approach. Finally, consideration is given to the implications of the results.

Multiwavelength digital holography with wavelength-multiplexed holograms and arbitrary symmetric phase shifts.

PubMed

Tahara, Tatsuki; Otani, Reo; Omae, Kaito; Gotohda, Takuya; Arai, Yasuhiko; Takaki, Yasuhiro

2017-05-15

We propose multiwavelength in-line digital holography with wavelength-multiplexed phase-shifted holograms and arbitrary symmetric phase shifts. We use phase-shifting interferometry selectively extracting wavelength information to reconstruct multiwavelength object waves separately from wavelength-multiplexed monochromatic images. The proposed technique obtains systems of equations for real and imaginary parts of multiwavelength object waves from the holograms by introducing arbitrary symmetric phase shifts. Then, the technique derives each complex amplitude distribution of each object wave selectively and analytically by solving the two systems of equations. We formulate the algorithm in the case of an arbitrary number of wavelengths and confirm its validity numerically and experimentally in the cases where the number of wavelengths is two and three.

Feet and syllables in elephants and missiles: a reappraisal.

PubMed

Zonneveld, Wim; van der Pas, Brigit; de Bree, Elise

2007-01-01

Using data from a case study presented in Chiat (1989), Marshall and Chiat (2003) compare two different approaches to account for the realization of intervocalic consonants in child phonology: "coda capture theory" and the "foot domain account". They argue in favour of the latter account. In this note, we present a reappraisal of this argument using the same data. We conclude that acceptance of the foot domain account, in the specific way developed by the authors, is unmotivated for both theoretical and empirical reasons. We maintain that syllable-based coda capture is (still) the better approach to account for the relevant facts.

Use of abstracts, orientations, and codas in narration by language-disordered and nondisordered children.

PubMed

Sleight, C C; Prinz, P M

1985-11-01

In this study language-disordered and nondisordered children viewed a nonverbal film, wrote the story, and narrated it to language-disordered and nondisordered peers who were unfamiliar with the film. The narratives were analyzed for the use of abstracts, orientations (background information), and codas. Language-disordered children made fewer references to the orientation clauses of props and activities than nondisordered children. Neither group modified their language in the areas examined to take into account the communicative status of their listeners. Therapeutic implications for the language-disordered children are presented as are suggestions for future research.

Constraints on Small-scale Heterogeneity in the Lowermost Mantle from Observations of Near Podal PcP Precursors

NASA Astrophysics Data System (ADS)

Zhang, B.; Ni, S.; Sun, D.; Shen, Z.; Jackson, J. M.; Wu, W.

2017-12-01

Volumetric heterogeneity on large scales ( >1000 km) and intermediate scales ( >100km) in the lowermost mantle have been established with seismological approaches. However, there are controversies regarding the level of heterogeneity in lowermost mantle at small scales (a few kilometers to tens of kilometers), with lower bound estimates ranging from 0.1% to a few percent. We take advantage of the small amplitude PcP waves at near podal distances (0-12°) to constrain the level of small-scale heterogeneity in the lowermost mantle. First, we compute short period synthetic seismograms with a finite difference code for a series of volumetric heterogeneity models in the lowermost mantle, and find that PcP is not identifiable if the small-scale heterogeneity in the lowermost mantle is above 2.0%. And then we use a functional form appropriate for coda decay to suppress P coda contamination. By comparing the corrected envelope of PcP and its precursors with synthetic seismograms, we find that perturbation of small-scale ( 8 km) heterogeneity in the lowermost mantle is 0.2% beneath regions to the east of China-Myanmar border area, north of Okhotsk Sea and South America. The perturbation is 0.5% beneath south of Okhotsk Sea and west of China-Myanmar border area, whereas strong perturbations ( 1.0%) are found beneath Central America. In the regions studied, we find that this particular type of small scale heterogeneity in lowermost mantle is weak, yet there are some regions requiring heterogeneity up to 1.0%. Where scattering is stronger, such as under Central America, more chemically complex mineral assemblages may be present at the core-mantle boundary.

Attenuation and scattering tomography of the deep plumbing system of Mount St. Helens

USGS Publications Warehouse

De Siena, Luca; Thomas, Christine; Waite, Greg P.; Moran, Seth C.; Klemme, Stefan

2014-01-01

We present a combined 3-D P wave attenuation, 2-D S coda attenuation, and 3-D S coda scattering tomography model of fluid pathways, feeding systems, and sediments below Mount St. Helens (MSH) volcano between depths of 0 and 18 km. High-scattering and high-attenuation shallow anomalies are indicative of magma and fluid-rich zones within and below the volcanic edifice down to 6 km depth, where a high-scattering body outlines the top of deeper aseismic velocity anomalies. Both the volcanic edifice and these structures induce a combination of strong scattering and attenuation on any seismic wavefield, particularly those recorded on the northern and eastern flanks of the volcanic cone. North of the cone between depths of 0 and 10 km, a low-velocity, high-scattering, and high-attenuation north-south trending trough is attributed to thick piles of Tertiary marine sediments within the St. Helens Seismic Zone. A laterally extended 3-D scattering contrast at depths of 10 to 14 km is related to the boundary between upper and lower crust and caused in our interpretation by the large-scale interaction of the Siletz terrane with the Cascade arc crust. This contrast presents a low-scattering, 4–6 km2 “hole” under the northeastern flank of the volcano. We infer that this section represents the main path of magma ascent from depths greater than 6 km at MSH, with a small north-east shift in the lower plumbing system of the volcano. We conclude that combinations of different nonstandard tomographic methods, leading toward full-waveform tomography, represent the future of seismic volcano imaging.

Beam shaping optics to enhance performance of interferometry techniques in grating manufacture

NASA Astrophysics Data System (ADS)

Laskin, Alexander; Laskin, Vadim; Ostrun, Aleksei

2018-02-01

Improving of industrial holographic and interferometry techniques is of great importance in interference lithography, computer-generated holography, holographic data storage, interferometry recording of Bragg gratings as well as gratings of various types in semiconductor industry. Performance of mentioned techniques is essentially enhanced by providing a light beam with flat phase front and flat-top irradiance distribution. Therefore, transformation of Gaussian distribution of a TEM00 laser to flat-top (top hat, uniform) distribution is an important optical task. There are different refractive and diffractive beam shaping approaches used in laser industrial and scientific applications, but only few of them are capable to fulfil the optimum conditions for beam quality demanding holography and interferometry. As a solution it is suggested to apply refractive field mapping beam shaping optics πShaper, which operational principle presumes almost lossless transformation of Gaussian to flat-top beam with flatness of output wavefront, conserving of beam consistency, providing collimated low divergent output beam, high transmittance, extended depth of field, negligible wave aberration, and achromatic design provides capability to work with several lasers with different wavelengths simultaneously. High optical quality of resulting flat-top beam allows applying additional optical components to build various imaging optical systems for variation of beam size and shape to fulfil requirements of a particular application. This paper will describe design basics of refractive beam shapers and optical layouts of their applying in holography and laser interference lithography. Examples of real implementations and experimental results will be presented as well.

Static and dynamic micro deformable mirror characterization by phase-shifting and time-averaged interferometry

NASA Astrophysics Data System (ADS)

Liotard, Arnaud; Zamkotsian, Frédéric

2017-11-01

The micro-opto-electro-mechanical systems (MOEMS), based on mature technologies of micro-electronics, are essential in the design of future astronomical instruments. One of these key-components is the microdeformable mirror for wave-front correction. Very challenging topics like search of exo-planets could greatly benefit from this technology. Design, realization and characterization of micro-Deformable Mirrors are under way at Laboratoire d'Astrophysique de Marseille (LAM) in collaboration with Laboratoire d'Analyse et d'Architecture des Systèmes (LAAS). In order to measure the surface shape and the deformation parameters during operation of these devices, a high-resolution Twyman-Green interferometer has been developed. Measurements have been done on a tiltable micro-mirror (170*100μm2) designed by LAM-LAAS and realized by an American foundry, and also on an OKO deformable mirror (15mm diameter). Static characterization is made by phase shifting interferometry and dynamic measurements have been made by quantitative time-averaged interferometry. The OKO mirror has an actuator stroke of 370+/-10nm for 150V applied and its resonant frequency is 1170+/-50 Hz, and the tiltable mirror has a rotation cut-off frequency of 31+/-3 kHz.

Single spontaneous photon as a coherent beamsplitter for an atomic matter-wave

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

Tomkovič, Jiří; Welte, Joachim; Oberthaler, Markus K.

2014-12-04

In free space the spontaneous emission of a single photon destroys motional coherence. Close to a mirror surface the reflection erases the which-path information and the single emitted photon can be regarded as a coherent beam splitter for an atomic matter-wavewhich can be verified by atom interferometry. Our experiment is a realization of the recoiling slit Gedanken experiment by Einstein.

Laser Development for Interferometry in Space

NASA Technical Reports Server (NTRS)

Numata, Kenji; Camp, Jordan

2012-01-01

We are developing a laser (master oscillator) and optical amplifier for interferometric space missions, including the gravitational-wave missions NGO and OpTIIX experiment on the international space station. Our system is based on optical fiber and semiconductor laser technologies, which have evolved dramatically in the past decade. We will report on the latest status of the development work, including noise measurements and space qualification tests.

Elastic Wave Imaging of in-Situ Bio-Alterations in a Contaminated Aquifer

NASA Astrophysics Data System (ADS)

Jaiswal, P.; Raj, R.; Atekwana, E. A.; Briand, B.; Alam, I.

2014-12-01

We present a pioneering report on the utility of seismic methods in imaging bio-induced elastic property changes within a contaminated aquifer. To understand physical properties of contaminated soil, we acquired 48 meters long multichannel seismic profile over the Norman landfill leachate plume in Norman Oklahoma, USA. We estimated both the P- and S- wave velocities respectively using full-waveform inversion of the transmission and the ground-roll coda. The resulting S-wave model showed distinct velocity anomaly (~10% over background) within the water table fluctuation zone bounded by the historical minimum and maximum groundwater table. In comparison, the P-wave velocity anomaly within the same zone was negligible. The Environmental Scanning Electron Microscope (ESEM) images of samples from a core located along the seismic profile clearly shows presence of biofilms in the water table fluctuation zone and their absence both above and below the fluctuation zone. Elemental chemistry further indicates that the sediment composition throughout the core is fairly constant. We conclude that the velocity anomaly in S-wave is due to biofilms. As a next step, we develop mechanistic modeling to gain insights into the petro-physical behavior of biofilm-bearing sediments. Preliminary results suggest that a plausible model could be biofilms acting as contact cement between sediment grains. The biofilm cement can be placed in two ways - (i) superficial non-contact deposition on sediment grains, and (ii) deposition at grain contacts. Both models explain P- and S- wave velocity structure at reasonable (~5-10%) biofilm saturation and are equivocally supported by the ESEM images. Ongoing attenuation modeling from full-waveform inversion and its mechanistic realization, may be able to further discriminate between the two cement models. Our study strongly suggests that as opposed to the traditional P-wave seismic, S-wave acquisition and imaging can be a more powerful tool for in-situ imaging of biofilm formation in field settings with significant implication for bioremediation and microbial enhanced oil recovery monitoring.

Coherence in the presence of absorption and heating in a molecule interferometer

PubMed Central

Cotter, J. P.; Eibenberger, S.; Mairhofer, L.; Cheng, X.; Asenbaum, P.; Arndt, M.; Walter, K.; Nimmrichter, S.; Hornberger, K.

2015-01-01

Matter-wave interferometry can be used to probe the foundations of physics and to enable precise measurements of particle properties and fundamental constants. It relies on beam splitters that coherently divide the wave function. In atom interferometers, such elements are often realised using lasers by exploiting the dipole interaction or through photon absorption. It is intriguing to extend these ideas to complex molecules where the energy of an absorbed photon can rapidly be redistributed across many internal degrees of freedom. Here, we provide evidence that center-of-mass coherence can be maintained even when the internal energy and entropy of the interfering particle are substantially increased by absorption of photons from a standing light wave. Each photon correlates the molecular center-of-mass wave function with its internal temperature and splits it into a superposition with opposite momenta in addition to the beam-splitting action of the optical dipole potential. PMID:26066053

Dynamic properties of ceramic materials

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

Grady, D.E.

1995-02-01

The present study offers new data and analysis on the transient shock strength and equation-of-state properties of ceramics. Various dynamic data on nine high strength ceramics are provided with wave profile measurements, through velocity interferometry techniques, the principal observable. Compressive failure in the shock wave front, with emphasis on brittle versus ductile mechanisms of deformation, is examined in some detail. Extensive spall strength data are provided and related to the theoretical spall strength, and to energy-based theories of the spall process. Failure waves, as a mechanism of deformation in the transient shock process, are examined. Strength and equation-of-state analysis ofmore » shock data on silicon carbide, boron carbide, tungsten carbide, silicon dioxide and aluminum nitride is presented with particular emphasis on phase transition properties for the latter two. Wave profile measurements on selected ceramics are investigated for evidence of rate sensitive elastic precursor decay in the shock front failure process.« less

Laser Interferometer Measurements of the Viscoelastic Properties of Tectorial Membrane Mutants

NASA Astrophysics Data System (ADS)

Jones, Gareth; Russell, Ian; Lukashkin, Andrei

2011-11-01

The visco-elastic properties of the tectorial membrane (TM) can be determined by measuring the propagation velocity of travelling waves over a range of frequencies. This study presents a new method using laser interferometry and compares the TM's material properties (sheer storage modulus, G' and viscosity, η) at basal and apical locations in wild-type mice and basal locations of three mutant groups (TectaY1870C/+, Tectb-/- and Otoa-/-). The G' and η values calculated for the wild-type mice are similar to estimates derived using other methods whereas the mutant groups all exhibit slower wave propagation velocities and reduced longitudinal coupling.

Laser system development for gravitational-wave interferometry in space

NASA Astrophysics Data System (ADS)

Numata, Kenji; Yu, Anthony W.; Camp, Jordan B.; Krainak, Michael A.

2018-02-01

A highly stable and robust laser system is a key component of the space-based Laser Interferometer Space Antenna (LISA) mission, which is designed to detect gravitational waves from various astronomical sources. The baseline architecture for the LISA laser consists of a low-power, low-noise Nd:YAG non-planar ring oscillator (NPRO) followed by a diode-pumped Yb-fiber amplifier with 2 W output. We are developing such laser system at the NASA Goddard Space Flight Center (GSFC), as well as investigating other laser options. In this paper, we will describe our progress to date and plans to demonstrate a technology readiness level (TRL) 6 LISA laser system.

Constraints on temporal velocity variations associated with an underground gas storage in the Gulf of Valencia using earthquake and seismic ambient noise data

NASA Astrophysics Data System (ADS)

Ugalde, Arantza; Gaite, Beatriz; Villaseñor, Antonio

2016-04-01

During September 2013, the injection of the base gas in a depleted oil reservoir used as an underground natural gas storage (CASTOR) caused a sudden seismic activity increase in the eastern coast of Spain. As a result, a compact cluster of more than 550 earthquakes with magnitudes mbLg > 0.7 were located in the shallow offshore area of the Gulf of Valencia during two months. The strongest event, having a magnitude of Mw=4.2, was followed by two Mw=4.1 events the day after and took place once the gas injection activities had finished. Using the seismic data recorded by permanent stations at more than 25 km from the injection well, we applied coda wave interferometry to monitor changes in seismic velocity structure between similar earthquakes. Then we solved for a continuous function of velocity changes with time by combining observations from all the closely located earthquake sources. The rate of repeating events allowed measurements of relative velocity variations for about 30 days on a daily scale. To extend the analysis in time, we also processed the continuous data using the autocorrelation of band-pass filtered ambient seismic noise. A 10-day average was required to achieve a sufficient signal-to-noise ratio in the 0.2-0.5 Hz and 0.5-1 Hz frequency bands. We quantified the time lags between two traces in the frequency and time domains by means of the Moving Window Cross Spectral Analysis and a Dynamic Time Warping technique, respectively. Injection of fluids in geologic formations causes variations in seismic velocities associated to changes in fluid saturation, increase in pore pressure or opening or enlargement of cracks due to the injection process. Time delays associated with stress changes caused by moderate to large earthquakes have also been established. In this work, we found no velocity changes during the gas injection period nor on the occasion of the Mw 4.2 earthquake. The sensitivity of the method is dependent on the seismic network geometry and the lateral extent of the velocity anomaly. With the given network configuration we conclude that any temporal changes in seismic velocities in the CASTOR gas storage area must be smaller than 0.05%.

Numerous large and long-duration seismic events during the Bárðarbunga volcanic eruption in 2014: What do they tell us about the caldera subsidence?

NASA Astrophysics Data System (ADS)

Hjörleifsdóttir, Vala; Jónsdóttir, Kristín; Hensch, Martin; Guðmundsson, Gunnar; Roberts, Matthew; Ófeigsson, Benedikt; Vogfjörð, Kristín; Magnússon, Eyjólfur; Tumi Gudmundsson, Magnús

2015-04-01

The volcanic unrest in and around the Bárðarbunga volcano was followed by a sequence of large events occurring on the caldera rim. Between Aug 16th and Dec 31st 2014, more than 70 events occurring close to the caldera rim, with Mw >= 5 had been reported by Iceland Meterological Office (IMO). The events are in many aspects unusual: 1) Moment tensors for the events have a large negative vertical CLVD component (see Hensch et al, and Cesca et al., this conference). Similar events, but with a large positive vertical CLVD component, occurred in Bárðarbunga during the 1990s, and were interpreted to result from near simultaneous motion on a significant part of the caldera ringfault, as a piston of material above the magma chamber was rising (Nettles and Ekström 1998, Tcalcic et al 2009). The large negative CLVD component observed in events during this eruption, could then indicate subsidence on the ring fault, consistent with the observed subsidence of the caldera floor. 2) Many of the largest events are accompanied by a sudden subsidence at the center of the caldera (see Roberts et al, this conference). A GPS station was installed in the caldera in early september and has been nearly continuously operating since. The steps are seen to be decreasing with time, even for events of the same magnitude. 3) The events have a very long duration for their size. This is evidenced by a large difference between centroid and hypocentral time and a difference between magnitudes estimated from short period P-waves (NEIC) and those estimated from long-period body- and surface waves over time. This difference seems to be increasing with time. As part of this work, we plan to present independent estimates of the durations of the events, based on P-wave modeling in process. 4) Event hypocenters are very shallow. An accelerometer was installed on the ice cap (possibly the first time in history?) in the 7x11 km wide subglacial caldera next to the cGPS instrument in early November, and shows very small ts-tp times for all caldera events, indicating depths of 3 km or less. 5) Relatively relocated M~2 events (see Vogfjord et al, this conference) show a near vertical southern caldera rim with a fault plane reaching down to several km, although the exact depth extent may be influenced by the velocity model used. The seismicity along the northern caldera rim seems more diffuse and appears to be dipping towards the north, outward from the caldera. 6) We present a preliminary results from a waveform correlation analysis by correlating. waveforms of over 1000 caldera events with each other and group them into families of highly similar events. Looking at the occurrence of these families we find that individual families are usually clustered in time and they represent events of similar magnitudes. Using families including many events we analyse individual events within a family using coda wave interferometry in order to track temporal stress changes in the medium between the source and the receiver. In this presentation we describe the earthquakes and discuss the their connection to the ongoing subsidence.

Vocal clans in sperm whales (Physeter macrocephalus).

PubMed Central

Rendell, L E; Whitehead, H

2003-01-01

Cultural transmission may be a significant source of variation in the behaviour of whales and dolphins, especially as regards their vocal signals. We studied variation in the vocal output of 'codas' by sperm whale social groups. Codas are patterns of clicks used by female sperm whales in social circumstances. The coda repertoires of all known social units (n = 18, each consisting of about 11 females and immatures with long-term relationships) and 61 out of 64 groups (about two social units moving together for periods of days) that were recorded in the South Pacific and Caribbean between 1985 and 2000 can be reliably allocated into six acoustic 'clans', five in the Pacific and one in the Caribbean. Clans have ranges that span thousands of kilometres, are sympatric, contain many thousands of whales and most probably result from cultural transmission of vocal patterns. Units seem to form groups preferentially with other units of their own clan. We suggest that this is a rare example of sympatric cultural variation on an oceanic scale. Culture may thus be a more important determinant of sperm whale population structure than genes or geography, a finding that has major implications for our understanding of the species' behavioural and population biology. PMID:12614570

White Light Heterodyne Interferometry SNR

DTIC Science & Technology

2015-04-09

interferometers in the visible- and near-IR, where shot - noise -limited detectors are available. In the LWIR, the advantage of a direct detection...wavebands where shot - noise -limited detection is possible with direct detection systems, the relationship changes in the mid-wave infrared (MWIR) and...flux, without either having to split the light N – 1 ways or take the extra shot - noise penalty from Fizeau beam combining light from all apertures

Atom Interferometry on Atom Chips - A Novel Approach Towards Precision Inertial Navigation System - PINS

DTIC Science & Technology

2010-06-01

Demonstration of an area-enclosing guided-atom interferometer for rotation sensing, Phys. Rev. Lett. 99, 173201 (2007). 4. Heralded Single- Magnon Quantum...excitations are quantized spin waves ( magnons ), such that transitions between its energy levels ( magnon number states) correspond to highly directional...polarization storage in the form of a single collective-spin excitation ( magnon ) that is shared between two spatially overlapped atomic ensembles

Background-Free 3D Nanometric Localization and Sub-nm Asymmetry Detection of Single Plasmonic Nanoparticles by Four-Wave Mixing Interferometry with Optical Vortices

NASA Astrophysics Data System (ADS)

Zoriniants, George; Masia, Francesco; Giannakopoulou, Naya; Langbein, Wolfgang; Borri, Paola

2017-10-01

Single nanoparticle tracking using optical microscopy is a powerful technique with many applications in biology, chemistry, and material sciences. Despite significant advances, localizing objects with nanometric position precision in a scattering environment remains challenging. Applied methods to achieve contrast are dominantly fluorescence based, with fundamental limits in the emitted photon fluxes arising from the excited-state lifetime as well as photobleaching. Here, we show a new four-wave-mixing interferometry technique, whereby the position of a single nonfluorescing gold nanoparticle of 25-nm radius is determined with 16 nm precision in plane and 3 nm axially from rapid single-point measurements at 1-ms acquisition time by exploiting optical vortices. The precision in plane is consistent with the photon shot-noise, while axially it is limited by the nano-positioning sample stage, with an estimated photon shot-noise limit of 0.5 nm. The detection is background-free even inside biological cells. The technique is also uniquely sensitive to particle asymmetries of only 0.5% ellipticity, corresponding to a single atomic layer of gold, as well as particle orientation. This method opens new ways of unraveling single-particle trafficking within complex 3D architectures.

Generalized interferometry - I: theory for interstation correlations

NASA Astrophysics Data System (ADS)

Fichtner, Andreas; Stehly, Laurent; Ermert, Laura; Boehm, Christian

2017-02-01

We develop a general theory for interferometry by correlation that (i) properly accounts for heterogeneously distributed sources of continuous or transient nature, (ii) fully incorporates any type of linear and nonlinear processing, such as one-bit normalization, spectral whitening and phase-weighted stacking, (iii) operates for any type of medium, including 3-D elastic, heterogeneous and attenuating media, (iv) enables the exploitation of complete correlation waveforms, including seemingly unphysical arrivals, and (v) unifies the earthquake-based two-station method and ambient noise correlations. Our central theme is not to equate interferometry with Green function retrieval, and to extract information directly from processed interstation correlations, regardless of their relation to the Green function. We demonstrate that processing transforms the actual wavefield sources and actual wave propagation physics into effective sources and effective wave propagation. This transformation is uniquely determined by the processing applied to the observed data, and can be easily computed. The effective forward model, that links effective sources and propagation to synthetic interstation correlations, may not be perfect. A forward modelling error, induced by processing, describes the extent to which processed correlations can actually be interpreted as proper correlations, that is, as resulting from some effective source and some effective wave propagation. The magnitude of the forward modelling error is controlled by the processing scheme and the temporal variability of the sources. Applying adjoint techniques to the effective forward model, we derive finite-frequency Fréchet kernels for the sources of the wavefield and Earth structure, that should be inverted jointly. The structure kernels depend on the sources of the wavefield and the processing scheme applied to the raw data. Therefore, both must be taken into account correctly in order to make accurate inferences on Earth structure. Not making any restrictive assumptions on the nature of the wavefield sources, our theory can be applied to earthquake and ambient noise data, either separately or combined. This allows us (i) to locate earthquakes using interstation correlations and without knowledge of the origin time, (ii) to unify the earthquake-based two-station method and noise correlations without the need to exclude either of the two data types, and (iii) to eliminate the requirement to remove earthquake signals from noise recordings prior to the computation of correlation functions. In addition to the basic theory for acoustic wavefields, we present numerical examples for 2-D media, an extension to the most general viscoelastic case, and a method for the design of optimal processing schemes that eliminate the forward modelling error completely. This work is intended to provide a comprehensive theoretical foundation of full-waveform interferometry by correlation, and to suggest improvements to current passive monitoring methods.

Dynamic speckle interferometry of microscopic processes in solid state and thin biological objects

NASA Astrophysics Data System (ADS)

Vladimirov, A. P.

2015-08-01

Modernized theory of dynamic speckle interferometry is considered. It is shown that the time-average radiation intensity has the parameters characterizing the wave phase changes. It also brings forward an expression for time autocorrelation function of the radiation intensity. It is shown that with the vanishing averaging time value the formulas transform to the prior expressions. The results of experiments with high-cycle material fatigue and cell metabolism analysis conducted using the time-averaging technique are discussed. Good reproducibility of the results is demonstrated. It is specified that the upgraded technique allows analyzing accumulation of fatigue damage, detecting the crack start moment and determining its growth velocity with uninterrupted cyclic load. It is also demonstrated that in the experiments with a cell monolayer the technique allows studying metabolism change both in an individual cell and in a group of cells.

Accuracy concerns in digital speckle photography combined with Fresnel digital holographic interferometry

NASA Astrophysics Data System (ADS)

Zhao, Yuchen; Zemmamouche, Redouane; Vandenrijt, Jean-François; Georges, Marc P.

2018-05-01

A combination of digital holographic interferometry (DHI) and digital speckle photography (DSP) allows in-plane and out-of-plane displacement measurement between two states of an object. The former can be determined by correlating the two speckle patterns whereas the latter is given by the phase difference obtained from DHI. We show that the amplitude of numerically reconstructed object wavefront obtained from Fresnel in-line digital holography (DH), in combination with phase shifting techniques, can be used as speckle patterns in DSP. The accuracy of in-plane measurement is improved after correcting the phase errors induced by reference wave during reconstruction process. Furthermore, unlike conventional imaging system, Fresnel DH offers the possibility to resize the pixel size of speckle patterns situated on the reconstruction plane under the same optical configuration simply by zero-padding the hologram. The flexibility of speckle size adjustment in Fresnel DH ensures the accuracy of estimation result using DSP.

The Abcd Formula of Phase Definition in Optical Interferometry: Combined Effect of Air Dispersion and Broad Passband

NASA Astrophysics Data System (ADS)

Mathar, Richard J.

Long-baseline interferometry detects fringes created by superposition of two beams of light collected by two telescopes pointing into a common direction. The external path difference is commonly compensated by adding a variable optical path length (delay) through air for one beam such that the optical path difference between the beams remains close to zero near the detector. The ABCD formula assigns a (wrapped) phase to the signals A to D of an interference pattern shifted by multiples of 90 degrees in phase. We study the interplay between a broad spectral passband of the optics and the dispersion of the air in the compensating delay, which leads to small deviations between the ABCD phase and the reduced, monochromatic group-delay representation of the wave packets. This adds dispersion to the effects that have been discussed for evacuated interferometers before (Milman 2005).

Input signal shaping based on harmonic frequency response function for suppressing nonlinear optical frequency in frequency-scanning interferometry

NASA Astrophysics Data System (ADS)

Zhu, Yu; Liu, Zhigang; Deng, Wen; Deng, Zhongwen

2018-05-01

Frequency-scanning interferometry (FSI) using an external cavity diode laser (ECDL) is essential for many applications of the absolute distance measurement. However, owing to the hysteresis and creep of the piezoelectric actuator inherent in the ECDL, the optical frequency scanning exhibits a nonlinearity that seriously affects the phase extraction accuracy of the interference signal and results in the reduction of the measurement accuracy. To suppress the optical frequency nonlinearity, a harmonic frequency synthesis method for shaping the desired input signal instead of the original triangular wave is presented. The effectiveness of the presented shaping method is demonstrated through the comparison of the experimental results. Compared with an incremental Renishaw interferometer, the standard deviation of the displacement measurement of the FSI system is less than 2.4 μm when driven by the shaped signal.

Very-long-baseline interferometry techniques applied to problems of geodesy, geophysics, planetary science, astronomy, and general relativity

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

Counselman, C.C. III

1973-09-01

Very-long-baseline interferometry (VLBI) techniques have already been used to determine the vector separations between antennas thousands of kilometers apart to within 2 m and the directions of extragalactic radio sources to 0.1'', and to track an artificial satellite of the earth and the Apollo Lunar Rover on the surface of the Moon. The relative loostions of the Apollo Lunar Surface Experiment Package (ALSEP) transmitters on the lunar surface are being measured within 1 m, and the Moon's libration is being messured to 1'' of selenocentric src. Attempts are under way to measure the solar gravitational deflection of radio waves moremore » accurately than previously possible, by means of VLBI. A wide variety of scientific problems is being attacked by VLBI techniques, which may soon be two orders of magnitude more accurate than at present. (auth)« less

Interaction of an ultrarelativistic electron bunch train with a W-band accelerating structure: High power and high gradient

DOE PAGES

Wang, D.; Antipov, S.; Jing, C.; ...

2016-02-05

Electron beam interaction with high frequency structures (beyond microwave regime) has a great impact on future high energy frontier machines. We report on the generation of multimegawatt pulsed rf power at 91 GHz in a planar metallic accelerating structure driven by an ultrarelativistic electron bunch train. This slow-wave wakefield device can also be used for high gradient acceleration of electrons with a stable rf phase and amplitude which are controlled by manipulation of the bunch train. To achieve precise control of the rf pulse properties, a two-beam wakefield interferometry method was developed in which the rf pulse, due to themore » interference of the wakefields from the two bunches, was measured as a function of bunch separation. As a result, measurements of the energy change of a trailing electron bunch as a function of the bunch separation confirmed the interferometry method.« less

On the Piezoelectric Detection of Guided Ultrasonic Waves

PubMed Central

2017-01-01

In order to quantify the wave motion of guided ultrasonic waves, the characteristics of piezoelectric detectors, or ultrasonic transducers and acoustic emission sensors, have been evaluated systematically. Such guided waves are widely used in structural health monitoring and nondestructive evaluation, but methods of calibrating piezoelectric detectors have been inadequate. This study relied on laser interferometry for the base displacement measurement of bar waves, from which eight different guided wave test set-ups are developed with known wave motion using piezoelectric transmitters. Both plates and bars of 12.7 and 6.4 mm thickness were used as wave propagation media. The upper frequency limit was 2 MHz. Output of guided wave detectors were obtained on the test set-ups and their receiving sensitivities were characterized and averaged. While each sensitivity spectrum was noisy for a detector, the averaged spectrum showed a good convergence to a unique receiving sensitivity. Twelve detectors were evaluated and their sensitivity spectra determined in absolute units. Generally, these showed rapidly dropping sensitivity with increasing frequency due to waveform cancellation on their sensing areas. This effect contributed to vastly different sensitivities to guided wave and to normally incident wave for each one of the 12 detectors tested. Various other effects are discussed and recommendations on methods of implementing the approach developed are provided. PMID:29156579

Spherical grating based x-ray Talbot interferometry.

PubMed

Cong, Wenxiang; Xi, Yan; Wang, Ge

2015-11-01

Grating interferometry is a state-of-the-art x-ray imaging approach, which can acquire information on x-ray attenuation, phase shift, and small-angle scattering simultaneously. Phase-contrast imaging and dark-field imaging are very sensitive to microstructural variation and offers superior contrast resolution for biological soft tissues. However, a common x-ray tube is a point-like source. As a result, the popular planar grating imaging configuration seriously restricts the flux of photons and decreases the visibility of signals, yielding a limited field of view. The purpose of this study is to extend the planar x-ray grating imaging theory and methods to a spherical grating scheme for a wider range of preclinical and clinical applications. A spherical grating matches the wave front of a point x-ray source very well, allowing the perpendicular incidence of x-rays on the grating to achieve a higher visibility over a larger field of view than the planer grating counterpart. A theoretical analysis of the Talbot effect for spherical grating imaging is proposed to establish a basic foundation for x-ray spherical gratings interferometry. An efficient method of spherical grating imaging is also presented to extract attenuation, differential phase, and dark-field images in the x-ray spherical grating interferometer. Talbot self-imaging with spherical gratings is analyzed based on the Rayleigh-Sommerfeld diffraction formula, featuring a periodic angular distribution in a polar coordinate system. The Talbot distance is derived to reveal the Talbot self-imaging pattern. Numerical simulation results show the self-imaging phenomenon of a spherical grating interferometer, which is in agreement with the theoretical prediction. X-ray Talbot interferometry with spherical gratings has a significant practical promise. Relative to planar grating imaging, spherical grating based x-ray Talbot interferometry has a larger field of view and improves both signal visibility and dose utilization for pre-clinical and clinical applications.

Spherical grating based x-ray Talbot interferometry

PubMed Central

Cong, Wenxiang; Xi, Yan; Wang, Ge

2015-01-01

Purpose: Grating interferometry is a state-of-the-art x-ray imaging approach, which can acquire information on x-ray attenuation, phase shift, and small-angle scattering simultaneously. Phase-contrast imaging and dark-field imaging are very sensitive to microstructural variation and offers superior contrast resolution for biological soft tissues. However, a common x-ray tube is a point-like source. As a result, the popular planar grating imaging configuration seriously restricts the flux of photons and decreases the visibility of signals, yielding a limited field of view. The purpose of this study is to extend the planar x-ray grating imaging theory and methods to a spherical grating scheme for a wider range of preclinical and clinical applications. Methods: A spherical grating matches the wave front of a point x-ray source very well, allowing the perpendicular incidence of x-rays on the grating to achieve a higher visibility over a larger field of view than the planer grating counterpart. A theoretical analysis of the Talbot effect for spherical grating imaging is proposed to establish a basic foundation for x-ray spherical gratings interferometry. An efficient method of spherical grating imaging is also presented to extract attenuation, differential phase, and dark-field images in the x-ray spherical grating interferometer. Results: Talbot self-imaging with spherical gratings is analyzed based on the Rayleigh–Sommerfeld diffraction formula, featuring a periodic angular distribution in a polar coordinate system. The Talbot distance is derived to reveal the Talbot self-imaging pattern. Numerical simulation results show the self-imaging phenomenon of a spherical grating interferometer, which is in agreement with the theoretical prediction. Conclusions: X-ray Talbot interferometry with spherical gratings has a significant practical promise. Relative to planar grating imaging, spherical grating based x-ray Talbot interferometry has a larger field of view and improves both signal visibility and dose utilization for pre-clinical and clinical applications. PMID:26520741

Spherical grating based x-ray Talbot interferometry

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

Cong, Wenxiang, E-mail: congw@rpi.edu, E-mail: xiy2@rpi.edu, E-mail: wangg6@rpi.edu; Xi, Yan, E-mail: congw@rpi.edu, E-mail: xiy2@rpi.edu, E-mail: wangg6@rpi.edu; Wang, Ge, E-mail: congw@rpi.edu, E-mail: xiy2@rpi.edu, E-mail: wangg6@rpi.edu

2015-11-15

Purpose: Grating interferometry is a state-of-the-art x-ray imaging approach, which can acquire information on x-ray attenuation, phase shift, and small-angle scattering simultaneously. Phase-contrast imaging and dark-field imaging are very sensitive to microstructural variation and offers superior contrast resolution for biological soft tissues. However, a common x-ray tube is a point-like source. As a result, the popular planar grating imaging configuration seriously restricts the flux of photons and decreases the visibility of signals, yielding a limited field of view. The purpose of this study is to extend the planar x-ray grating imaging theory and methods to a spherical grating scheme formore » a wider range of preclinical and clinical applications. Methods: A spherical grating matches the wave front of a point x-ray source very well, allowing the perpendicular incidence of x-rays on the grating to achieve a higher visibility over a larger field of view than the planer grating counterpart. A theoretical analysis of the Talbot effect for spherical grating imaging is proposed to establish a basic foundation for x-ray spherical gratings interferometry. An efficient method of spherical grating imaging is also presented to extract attenuation, differential phase, and dark-field images in the x-ray spherical grating interferometer. Results: Talbot self-imaging with spherical gratings is analyzed based on the Rayleigh–Sommerfeld diffraction formula, featuring a periodic angular distribution in a polar coordinate system. The Talbot distance is derived to reveal the Talbot self-imaging pattern. Numerical simulation results show the self-imaging phenomenon of a spherical grating interferometer, which is in agreement with the theoretical prediction. Conclusions: X-ray Talbot interferometry with spherical gratings has a significant practical promise. Relative to planar grating imaging, spherical grating based x-ray Talbot interferometry has a larger field of view and improves both signal visibility and dose utilization for pre-clinical and clinical applications.« less

Near-surface versus fault zone damage following the 1999 Chi-Chi earthquake: Observation and simulation of repeating earthquakes

USGS Publications Warehouse

Chen, Kate Huihsuan; Furumura, Takashi; Rubinstein, Justin L.

2015-01-01

We observe crustal damage and its subsequent recovery caused by the 1999 M7.6 Chi-Chi earthquake in central Taiwan. Analysis of repeating earthquakes in Hualien region, ~70 km east of the Chi-Chi earthquake, shows a remarkable change in wave propagation beginning in the year 2000, revealing damage within the fault zone and distributed across the near surface. We use moving window cross correlation to identify a dramatic decrease in the waveform similarity and delays in the S wave coda. The maximum delay is up to 59 ms, corresponding to a 7.6% velocity decrease averaged over the wave propagation path. The waveform changes on either side of the fault are distinct. They occur in different parts of the waveforms, affect different frequencies, and the size of the velocity reductions is different. Using a finite difference method, we simulate the effect of postseismic changes in the wavefield by introducing S wave velocity anomaly in the fault zone and near the surface. The models that best fit the observations point to pervasive damage in the near surface and deep, along-fault damage at the time of the Chi-Chi earthquake. The footwall stations show the combined effect of near-surface and the fault zone damage, where the velocity reduction (2–7%) is twofold to threefold greater than the fault zone damage observed in the hanging wall stations. The physical models obtained here allow us to monitor the temporal evolution and recovering process of the Chi-Chi fault zone damage.

Rg to Lg Scattering Observations and Modeling

NASA Astrophysics Data System (ADS)

Baker, G. E.; Stevens, J. L.; Xu, H.

2005-12-01

Lg is important to explosion yield estimation and earthquake/explosion discrimination, but the source of explosion generated Lg is still an area of active investigation. We investigate the contribution of Rg scattering to Lg. Common spectral nulls in vertical component Rg and Lg have been interpreted as evidence that scattered Rg is the dominant source of Lg in some areas. The nulls are assumed to result from non-spherical components of the explosion source, modeled as a CLVD located above the explosion. We compare Rg with 3-component Sg and Lg spectra in different source areas. Wavenumber synthetics and nonlinear source calculations constrain the predicted source spectra of Rg and directly generated Lg. Modal scattering calculations place bounds on the contribution of Rg to Lg relative to pS, S*, and directly generated S-waves. Rg recorded east and west of the Quartz 3 Deep Seismic Sounding explosion have persistent spectral nulls, but at different frequencies. The azimuthal dependence of the source spectra suggests that it may not be simply related to a CLVD source. The spectral nulls of Sg, Lg, and Lg coda do not correspond to the Rg spectral nulls, so for this overburied source, the spectral observations do not indicate that Rg scattering is a dominant contributor to Lg. Preliminary comparisons of Rg with Lg spectra for events from the Semipalatinsk Test Site yield a similar result. We compare Rg at 20-100 km with Lg at 650 km for Balapan and Degelen explosions with known yield and source depth. The events range from 130 to 50 percent of theoretical containment depth, so relative contributions from a CLVD are expected to vary significantly. For studied previously NTS and Kazakh depth of burial data, the use of 3-components provides further insight into scattering between components. In a complementary analysis, to assess whether S-wave generation is affected by source depth or scaled depth, we have examined regional phase amplitudes of 13 Degelen explosions with known yields and source depths. Initial Pn, the entire P wavetrain, Sn, Lg, and Lg coda have similar log amplitude vs. log yield curves. The slope of those curves varies with frequency, from approximately 0.84 at 0.6 Hz to 0.65 at 6 Hz. We will complement these results with similar observations of Balapan explosion records.

Ultrafast and Doppler-free femtosecondoptical ranging based on dispersivefrequency-modulated interferometry.

PubMed

Xia, Haiyun; Zhang, Chunxi

2010-03-01

An ultrafast and Doppler-free optical ranging system based on dispersive frequency-modulated interferometry is demonstrated. The principle is similar to the conventional frequency-modulated continuous-wave interferometry where the range information is derived from the beat frequency between the object signal and the reference signal. However, a passive and static frequency scanning is performed based on the chromatic dispersion of a transform-limited femtosecond pulse in the time domain. We point out that the unbalanced dispersion introduced in the Mach-Zehnder interferometer can be optimized to eliminate the frequency chirp in the temporal interferograms pertaining to the third order dispersion of the all-fiber system, if the dynamic range being considered is small. Some negative factors, such as the polarization instability of the femtosecond pulse, the power fluctuation of the optical signal and the nonuniform gain spectrum of the erbium-doped fiber amplifier lead to an obvious envelope deformation of the temporal interferograms from the Gaussian shape. Thus a new data processing method is proposed to guarantee the range resolution. In the experiment, the vibration of a speaker is measured. A range resolution of 1.59 microm is achieved with an exposure time of 394 fs at a sampling rate of 48.6 MHz.

Hardware Verification of Laser Noise Cancellation and Gravitational Wave Extraction using Time-Delay Interferometry

NASA Astrophysics Data System (ADS)

Mitryk, Shawn; Mueller, Guido

The Laser Interferometer Space Antenna (LISA) is a space-based modified Michelson interfer-ometer designed to measure gravitational radiation in the frequency range from 30 uHz to 1 Hz. The interferometer measurement system (IMS) utilizes one-way laser phase measurements to cancel the laser phase noise, reconstruct the proof-mass motion, and extract the gravitational wave (GW) induced laser phase modulations in post-processing using a technique called time-delay interferometry (TDI). Unfortunately, there exist few hard-ware verification experiments of the IMS. The University of Florida LISA Interferometry Simulator (UFLIS) is designed to perform hardware-in-the-loop simulations of the LISA interferometry system, modeling the characteris-tics of the LISA mission as accurately as possible. This depends, first, on replicating the laser pre-stabilization by locking the laser phase to an ultra-stable Zerodur cavity length reference using the PDH locking method. Phase measurements of LISA-like photodetector beat-notes are taken using the UF-phasemeter (PM) which can measure the laser BN frequency to within an accuracy of 0.22 uHz. The inter-space craft (SC) laser links including the time-delay due to the 5 Gm light travel time along the LISA arms, the laser Doppler shifts due to differential SC motion, and the GW induced laser phase modulations are simulated electronically using the electronic phase delay (EPD) unit. The EPD unit replicates the laser field propagation between SC by measuring a photodetector beat-note frequency with the UF-phasemeter and storing the information in memory. After the requested delay time, the frequency information is added to a Doppler offset and a GW-like frequency modulation. The signal is then regenerated with the inter-SC laser phase affects applied. Utilizing these components, I will present the first complete TDI simulations performed using the UFLIS. The LISA model is presented along-side the simulation, comparing the generation and measurement of LISA-like signals. Phasemeter measurements are used in post-processing and combined in the linear combinations defined by TDI, thus, canceling the laser phase and phase-lock loop noise to extract the applied GW modulation buried under the noise. Nine order of magnitude common mode laser noise cancellation is achieved at a frequency of 1 mHz and the GW signal is clearly visible after the laser and PLL noise cancellation.

A study of the stress wave factor technique for the characterization of composite materials

NASA Technical Reports Server (NTRS)

Govada, A. K.; Duke, J. C., Jr.; Henneke, E. G., II; Stinchcomb, W. W.

1985-01-01

This study has investigated the potential of the Stress Wave Factor as an NDT technique for thin composite laminates. The conventional SWF and an alternate method for quantifying the SWF were investigated. Agreement between the initial SWF number, ultrasonic C-scan, inplane displacements as obtained by full field moire interferometry, and the failure location have been observed. The SWF number was observed to be the highest when measured along the fiber direction and the lowest when measured across the fibers. The alternate method for quantifying the SWF used square root of the zeroth moment (square root of M sub o) of the frequency spectrum of the received signal as a quantitative parameter. From this study it therefore appears that the stress wave factor has an excellent potential to monitor damage development in thin composite laminates.

Temporal characterization of the wave-breaking flash in a laser plasma accelerator

NASA Astrophysics Data System (ADS)

Miao, Bo; Feder, Linus; Goers, Andrew; Hine, George; Salehi, Fatholah; Wahlstrand, Jared; Woodbury, Daniel; Milchberg, Howard

2017-10-01

Wave-breaking injection of electrons into a relativistic plasma wake generated in near-critical density plasma by sub-terawatt laser pulses generates an intense ( 1 μJ) and ultra-broadband (Δλ 300 nm) radiation flash. In this work we demonstrate the spectral coherence of this radiation and measure its temporal width using single-shot supercontinuum spectral interferometry (SSSI). The measured temporal width is limited by measurement resolution to 50 fs. Spectral coherence is corroborated by PIC simulations which show that the spatial extent of the acceleration trajectory at the trapping region is small compared to the radiation center wavelength. To our knowledge, this is the first temporal and coherence characterization of wave-breaking radiation. This work is supported by the US Department of Energy, the National Science Foundation, and the Air Force Office of Scientific Research.

Stress Drops of Earthquakes on the Subducting Pacific Plate in the South-East off Hokkaido, Japan

NASA Astrophysics Data System (ADS)

Saito, Y.; Yamada, T.

2013-12-01

Large earthquakes have been occurring repeatedly in the South-East of Hokkaido, Japan, where the Pacific Plate subducts beneath the Okhotsk Plate in the north-west direction. For example, the 2003 Tokachi-oki earthquake (Mw8.3 determined by USGS) took place in the region on September 26, 2003. Yamanaka and Kikuchi (2003) analyzed the slip distribution of the earthquake and concluded that the 2003 earthquake had ruptured the deeper half of the fault plane of the 1952 Tokachi-oki earthquake. Miyazaki et al. (2004) reported that a notable afterslip was observed at adjacent areas to the coseismic rupture zone of the 2003 earthquake, which suggests that there would be significant heterogeneities of strength, stress and frictional properties on the surface of the Pacific Plate in the region. In addition, some previous studies suggest that the region with a large slip in large earthquakes permanently have large difference of strength and the dynamic frictional stress level and that it would be able to predict the spatial pattern of slip in the next large earthquake by analyzing the stress drop of small earthquakes (e.g. Allmann and Shearer, 2007 and Yamada et al., 2010). We estimated stress drops of 150 earthquakes (4.2 ≤ M ≤ 5.0), using S-coda waves, or the waveforms from 4.00 to 9.11 seconds after the S wave arrivals, of Hi-net data. The 150 earthquakes were the ones that occurred from June, 2002 to December, 2010 in south-east of Hokkaido, Japan, from 40.5N to 43.5N and from 141.0E to 146.5E. First we selected waveforms of the closest earthquakes with magnitudes between 3.0 and 3.2 to individual 150 earthquakes as empirical Green's functions. We then calculated source spectral ratios of the 150 pairs of interested earthquakes and EGFs by deconvolving the individual S-coda waves. We finally estimated corner frequencies of earthquakes from the spectral ratios by assuming the omega-squared model of Boatwright (1978) and calculated stress drops of the earthquakes by using the model of Madariaga (1976). The estimated values of stress drop range from 1 to 10 MPa with a little number of outliers(Fig.(a)). Fig.(b) shows the spatial distribution of stress drops in south-east off Hokkaido, Japan. We found that earthquakes occurred around 42N 145E had larger stress drops. We are going to analyze smaller earthquakes and investigate the spatial pattern of the stress drop in the future. Fig. (a) Estimated values of stress drop with respect to seismic moments of earthquakes. (b) Spatial distribution of stress drops.

Spectroscopy and nonthermal processes

NASA Technical Reports Server (NTRS)

Querci, Monique

1987-01-01

Stellar spectra are analyzed to determine nonthermal processes for cool stars. A shock wave crossing model is supported by a study of the behavior of absorption and emission spectra. The shock waves are attributed to atmospheric kinetics. Circumstellar spectral lines are studied for information about gaseous circumstellar layers. The description of stellar envelopes is carried on through circumstellar dust. Characteristic properties of polarization in the dust are described in the case of specific stars, emphasizing narrowband observations in Mira, semiregular, and supergiant stars. Finally, the direct approach to measuring the angular diameters of stars and mapping the distribution of circumstellar dust and gas by lunar occultation or interferometry is discussed, using two prototype stars, an M supergiant and a dusty carbon star.

Guest Editorial Precision Surface Metrology

NASA Astrophysics Data System (ADS)

Wyant, James C.

1984-08-01

During the past two decades there have been many changes in precision surface metrology. The introduction of the laser and the large computer during the 1960s and 1970s produced many changes in testing capabilities and requirements. Several commercial interferometers became available in the 1970s, enabling people who were not necessarily experts in interferometry to use interferometers to produce better optics. Since both buyers and sellers could test optics, the quality of the optics manufactured and sold improved greatly. If a person ordered 1/10 wave optics, he would probably get 1/10 wave or better optics; if he got optics of lower quality, he would know it, and he could prove it and return it.

Toward 2D Seismic Wavefield Monitoring: Seismic Gradiometry for Long-Period Seismogram and Short-Period Seismogram Envelope applied to the Hi-net Array

NASA Astrophysics Data System (ADS)

Maeda, T.; Nishida, K.; Takagi, R.; Obara, K.

2015-12-01

The high-sensitive seismograph network Japan (Hi-net) operated by National Research Institute for Earth Science and Disaster Prevention (NIED) has about 800 stations with average separation of 20 km. We can observe long-period seismic wave propagation as a 2D wavefield with station separations shorter than wavelength. In contrast, short-period waves are quite incoherent at stations, however, their envelope shapes resemble at neighbor stations. Therefore, we may be able to extract seismic wave energy propagation by seismogram envelope analysis. We attempted to characterize seismic waveform at long-period and its envelope at short-period as 2D wavefield by applying seismic gradiometry. We applied the seismic gradiometry to a synthetic long-period (20-50s) dataset prepared by numerical simulation in realistic 3D medium at the Hi-net station layout. Wave amplitude and its spatial derivatives are estimated by using data at nearby stations. The slowness vector, the radiation pattern and the geometrical spreading are extracted from estimated velocity, displacement and its spatial derivatives. For short-periods at shorter than 1 s, seismogram envelope shows temporal and spatial broadening through scattering by medium heterogeneity. It is expected that envelope shape may be coherent among nearby stations. Based on this idea, we applied the same method to the time-integration of seismogram envelope to estimate its spatial derivatives. Together with seismogram envelope, we succeeded in estimating the slowness vector from the seismogram envelope as well as long-period waveforms by synthetic test, without using phase information. Our preliminarily results show that the seismic gradiometry suits the Hi-net to extract wave propagation characteristics both at long and short periods. This method is appealing that it can estimate waves at homogeneous grid to monitor seismic wave as a wavefield. It is promising to obtain phase velocity variation from direct waves, and to grasp wave packets originating from scattering from coda, by applying the seismic gradiometry to the Hi-net.

Mass, height of burst, and source–receiver distance constraints on the acoustic coda phase delay method

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

Albert, Sarah; Bowman, Daniel; Rodgers, Arthur

Here, this research uses the acoustic coda phase delay method to estimate relative changes in air temperature between explosions with varying event masses and heights of burst. It also places a bound on source–receiver distance for the method. Previous studies used events with different shapes, height of bursts, and masses and recorded the acoustic codas at source–receiver distances less than 1 km. This research further explores the method using explosions that differ in mass (by up to an order of magnitude) and are placed at varying heights. Source–receiver distances also cover an area out to 7 km. Relative air temperaturemore » change estimates are compared to complementary meteorological observations. Results show that two explosions that differ by an order of magnitude cannot be used with this method because their propagation times in the near field and their fundamental frequencies are different. These differences are expressed as inaccuracies in the relative air temperature change estimates. An order of magnitude difference in mass is also shown to bias estimates higher. Small differences in height of burst do not affect the accuracy of the method. Finally, an upper bound of 1 km on source–receiver distance is provided based on the standard deviation characteristics of the estimates.« less

Mass, height of burst, and source–receiver distance constraints on the acoustic coda phase delay method

DOE PAGES

Albert, Sarah; Bowman, Daniel; Rodgers, Arthur; ...

2018-04-23

Here, this research uses the acoustic coda phase delay method to estimate relative changes in air temperature between explosions with varying event masses and heights of burst. It also places a bound on source–receiver distance for the method. Previous studies used events with different shapes, height of bursts, and masses and recorded the acoustic codas at source–receiver distances less than 1 km. This research further explores the method using explosions that differ in mass (by up to an order of magnitude) and are placed at varying heights. Source–receiver distances also cover an area out to 7 km. Relative air temperaturemore » change estimates are compared to complementary meteorological observations. Results show that two explosions that differ by an order of magnitude cannot be used with this method because their propagation times in the near field and their fundamental frequencies are different. These differences are expressed as inaccuracies in the relative air temperature change estimates. An order of magnitude difference in mass is also shown to bias estimates higher. Small differences in height of burst do not affect the accuracy of the method. Finally, an upper bound of 1 km on source–receiver distance is provided based on the standard deviation characteristics of the estimates.« less

Extreme ultraviolet interferometry

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

Goldberg, Kenneth A.

EUV lithography is a promising and viable candidate for circuit fabrication with 0.1-micron critical dimension and smaller. In order to achieve diffraction-limited performance, all-reflective multilayer-coated lithographic imaging systems operating near 13-nm wavelength and 0.1 NA have system wavefront tolerances of 0.27 nm, or 0.02 waves RMS. Owing to the highly-sensitive resonant reflective properties of multilayer mirrors and extraordinarily tight tolerances set forth for their fabrication, EUV optical systems require at-wavelength EUV interferometry for final alignment and qualification. This dissertation discusses the development and successful implementation of high-accuracy EUV interferometric techniques. Proof-of-principle experiments with a prototype EUV point-diffraction interferometer for themore » measurement of Fresnel zoneplate lenses first demonstrated sub-wavelength EUV interferometric capability. These experiments spurred the development of the superior phase-shifting point-diffraction interferometer (PS/PDI), which has been implemented for the testing of an all-reflective lithographic-quality EUV optical system. Both systems rely on pinhole diffraction to produce spherical reference wavefronts in a common-path geometry. Extensive experiments demonstrate EUV wavefront-measuring precision beyond 0.02 waves RMS. EUV imaging experiments provide verification of the high-accuracy of the point-diffraction principle, and demonstrate the utility of the measurements in successfully predicting imaging performance. Complementary to the experimental research, several areas of theoretical investigation related to the novel PS/PDI system are presented. First-principles electromagnetic field simulations of pinhole diffraction are conducted to ascertain the upper limits of measurement accuracy and to guide selection of the pinhole diameter. Investigations of the relative merits of different PS/PDI configurations accompany a general study of the most significant sources of systematic measurement errors. To overcome a variety of experimental difficulties, several new methods in interferogram analysis and phase-retrieval were developed: the Fourier-Transform Method of Phase-Shift Determination, which uses Fourier-domain analysis to improve the accuracy of phase-shifting interferometry; the Fourier-Transform Guided Unwrap Method, which was developed to overcome difficulties associated with a high density of mid-spatial-frequency blemishes and which uses a low-spatial-frequency approximation to the measured wavefront to guide the phase unwrapping in the presence of noise; and, finally, an expedient method of Gram-Schmidt orthogonalization which facilitates polynomial basis transformations in wave-front surface fitting procedures.« less

Numerical simulation of time delay interferometry for a LISA-like mission with the simplification of having only one interferometer

NASA Astrophysics Data System (ADS)

Dhurandhar, S. V.; Ni, W.-T.; Wang, G.

2013-01-01

In order to attain the requisite sensitivity for LISA, laser frequency noise must be suppressed below the secondary noises such as the optical path noise, acceleration noise etc. In a previous paper (Dhurandhar, S.V., Nayak, K.R., Vinet, J.-Y. Time delay interferometry for LISA with one arm dysfunctional. Class. Quantum Grav. 27, 135013, 2010), we have found a large family of second-generation analytic solutions of time delay interferometry with one arm dysfunctional, and we also estimated the laser noise due to residual time-delay semi-analytically from orbit perturbations due to Earth. Since other planets and solar-system bodies also perturb the orbits of LISA spacecraft and affect the time delay interferometry (TDI), we simulate the time delay numerically in this paper for all solutions with the generation number n ⩽ 3. We have worked out a set of 3-year optimized mission orbits of LISA spacecraft starting at January 1, 2021 using the CGC2.7 ephemeris framework. We then use this numerical solution to calculate the residual optical path differences in the second-generation solutions of our previous paper, and compare with the semi-analytic error estimate. The accuracy of this calculation is better than 1 cm (or 30 ps). The maximum path length difference, for all configuration calculated, is below 1 m (3 ns). This is well below the limit under which the laser frequency noise is required to be suppressed. The numerical simulation in this paper can be applied to other space-borne interferometers for gravitational wave detection with the simplification of having only one interferometer.

CURIE: Cubesat Radio Interferometry Experiment

NASA Astrophysics Data System (ADS)

Sundkvist, D. J.; Saint-Hilaire, P.; Bain, H. M.; Bale, S. D.; Bonnell, J. W.; Hurford, G. J.; Maruca, B.; Martinez Oliveros, J. C.; Pulupa, M.

2016-12-01

The CUbesat Radio Interferometry Experiment (CURIE) is a proposed two-element radio interferometer, based on proven and developed digital radio receivers and designed to fit within a Cubesat platform. CURIE will launch as a 6U Cubesat and then separate into two 3U Cubesats once in orbit. CURIE measures radio waves from 0.1-19MHz, which must be measured from space, as those frequencies fall below the cutoff imposed by Earth's ionosphere. The principal science objective for CURIE is to use radio interferometry to study radio burst emissions from solar eruptive events such as flares and coronal mass ejections (CMEs) in the inner heliosphere, providing observations important for our understanding of the heliospheric space weather environment. The influence of space weather can be felt at Earth and other planets, as radiation levels increase and lead to auroral activity and geomagnetic effects. CURIE will be able to determine the location and size of radio burst source regions and then to track their movement outward from the Sun. In addition to the primary objective CURIE will measure the gradients of the local ionospheric density and electron temperature on the spatial scale of a few kilometers, as well as create an improved map of the radio sky at these unexplored frequencies. A space based radio interferometry observatory has long been envisioned, in orbit around the Earth or the Moon, or on the far side of the Moon. Beyond its important science objectives, CURIE will prove that the concept of a dedicated space-based interferometer can be realized by using relatively cheap Cubesats. CURIE will therefore not only provide new important science results but also serve as a pathfinder in the development of new space-based radio observation techniques for helio- and astro-physics.

A novel type of very long baseline astronomical intensity interferometer

NASA Astrophysics Data System (ADS)

Borra, Ermanno F.

2013-12-01

This article presents a novel type of very long baseline astronomical interferometer that uses the fluctuations, as a function of time, of the intensity measured by a quadratic detector, which is a common type of astronomical detector. The theory on which the technique is based is validated by laboratory experiments. Its outstanding principal advantages comes from the fact that the angular structure of an astronomical object is simply determined from the visibility of the minima of the spectrum of the intensity fluctuations measured by the detector, as a function of the frequency of the fluctuations, while keeping the spacing between mirrors constant. This would allow a simple setup capable of high angular resolutions because it could use an extremely large baseline. Another major interest is that it allows for a more efficient use of telescope time because observations at a single baseline are sufficient, while amplitude and intensity interferometers need several observations at different baselines. The fact that one does not have to move the telescopes would also allow detecting faster time variations because having to move the telescopes sets a lower limit to the time variations that can be detected. The technique uses wave interaction effects and thus has some characteristics in common with intensity interferometry. A disadvantage of the technique, like in intensity interferometry, is that it needs strong sources if observing at high frequencies (e.g. the visible). This is a minor disadvantage in the radio region. At high frequencies, this disadvantage is mitigated by the fact that, like in intensity interferometry, the requirements of the optical quality of the mirrors used are far less severe than in amplitude interferometry so that poor quality large reflectors (e.g. Cherenkov telescopes) can be used in the optical region.

Ambient seismic noise interferometry in Hawai'i reveals long-range observability of volcanic tremor

USGS Publications Warehouse

Ballmer, Silke; Wolfe, Cecily; Okubo, Paul G.; Haney, Matt; Thurber, Clifford H.

2013-01-01

The use of seismic noise interferometry to retrieve Green's functions and the analysis of volcanic tremor are both useful in studying volcano dynamics. Whereas seismic noise interferometry allows long-range extraction of interpretable signals from a relatively weak noise wavefield, the characterization of volcanic tremor often requires a dense seismic array close to the source. We here show that standard processing of seismic noise interferometry yields volcanic tremor signals observable over large distances exceeding 50 km. Our study comprises 2.5 yr of data from the U.S. Geological Survey Hawaiian Volcano Observatory short period seismic network. Examining more than 700 station pairs, we find anomalous and temporally coherent signals that obscure the Green's functions. The time windows and frequency bands of these anomalous signals correspond well with the characteristics of previously studied volcanic tremor sources at Pu'u 'Ō'ō and Halema'uma'u craters. We use the derived noise cross-correlation functions to perform a grid-search for source location, confirming that these signals are surface waves originating from the known tremor sources. A grid-search with only distant stations verifies that useful tremor signals can indeed be recovered far from the source. Our results suggest that the specific data processing in seismic noise interferometry—typically used for Green's function retrieval—can aid in the study of both the wavefield and source location of volcanic tremor over large distances. In view of using the derived Green's functions to image heterogeneity and study temporal velocity changes at volcanic regions, however, our results illustrate how care should be taken when contamination by tremor may be present.

Laser-launched flyer plate and confined laser ablation for shock wave loading: validation and applications.

PubMed

Paisley, Dennis L; Luo, Sheng-Nian; Greenfield, Scott R; Koskelo, Aaron C

2008-02-01

We present validation and some applications of two laser-driven shock wave loading techniques: laser-launched flyer plate and confined laser ablation. We characterize the flyer plate during flight and the dynamically loaded target with temporally and spatially resolved diagnostics. With transient imaging displacement interferometry, we demonstrate that the planarity (bow and tilt) of the loading induced by a spatially shaped laser pulse is within 2-7 mrad (with an average of 4+/-1 mrad), similar to that in conventional techniques including gas gun loading. Plasma heating of target is negligible, in particular, when a plasma shield is adopted. For flyer plate loading, supported shock waves can be achieved. Temporal shaping of the drive pulse in confined laser ablation allows for flexible loading, e.g., quasi-isentropic, Taylor-wave, and off-Hugoniot loading. These techniques can be utilized to investigate such dynamic responses of materials as Hugoniot elastic limit, plasticity, spall, shock roughness, equation of state, phase transition, and metallurgical characteristics of shock-recovered samples.

Off-axis digital holographic microscopy with LED illumination based on polarization filtering.

PubMed

Guo, Rongli; Yao, Baoli; Gao, Peng; Min, Junwei; Zhou, Meiling; Han, Jun; Yu, Xun; Yu, Xianghua; Lei, Ming; Yan, Shaohui; Yang, Yanlong; Dan, Dan; Ye, Tong

2013-12-01

A reflection mode digital holographic microscope with light emitting diode (LED) illumination and off-axis interferometry is proposed. The setup is comprised of a Linnik interferometer and a grating-based 4f imaging unit. Both object and reference waves travel coaxially and are split into multiple diffraction orders in the Fourier plane by the grating. The zeroth and first orders are filtered by a polarizing array to select orthogonally polarized object waves and reference waves. Subsequently, the object and reference waves are combined again in the output plane of the 4f system, and then the hologram with uniform contrast over the entire field of view can be acquired with the aid of a polarizer. The one-shot nature in the off-axis configuration enables an interferometric recording time on a millisecond scale. The validity of the proposed setup is illustrated by imaging nanostructured substrates, and the experimental results demonstrate that the phase noise is reduced drastically by an order of 68% when compared to a He-Ne laser-based result.

Shock wave interactions in hypervelocity flow

NASA Astrophysics Data System (ADS)

Sanderson, S. R.; Sturtevant, B.

1994-08-01

The impingement of shock waves on blunt bodies in steady supersonic flow is known to cause extremely high local heat transfer rates and surface pressures. Although these problems have been studied in cold hypersonic flow, the effects of dissociative relaxation processes are unknown. In this paper we report a model aimed at determining the boundaries of the possible interaction regimes for an ideal dissociating gas. Local analysis about shock wave intersection points in the pressure-flow deflection angle plane with continuation of singular solutions is the fundamental tool employed. Further, we discuss an experimental investigation of the nominally two-dimensional mean flow that results from the impingement of an oblique shock wave on the leading edge of a cylinder. The effects of variations in shock impingement geometry were visualized using differential interferometry. Generally, real gas effects are seen to increase the range of shock impingement points for which enhanced heating occurs. They also reduce the type 4 interaction supersonic jet width and influence the type 2-3 transition process.

Nitromethane ignition observed with embedded PDV optical fibers

NASA Astrophysics Data System (ADS)

Mercier, P.; Bénier, J.; Frugier, P. A.; Debruyne, M.; Crouzet, B.

For a long time, the nitromethane (NM) ignition has been observed with different means such as high-speed cameras, VISAR or optical pyrometry diagnostics. By 2000, David Goosmann (LLNL) studied solid high-explosive detonation and shock loaded metal plates by measuring velocity (Fabry-Pérot interferometry) in embedded optical fibers. For six years Photonic Doppler Velocimetry (PDV) has become a major tool to better understand the phenomena occurring in shock physics experiments. In 2006, we began to use in turn this technique and studied shock-to-detonation transition in NM. Different kinds of bare optical fibers were set in the liquid; they provided two types of velocity information; those coming from phenomena located in front of the fibers (interface velocity, shock waves, overdriven detonation wave) and those due to phenomena environing the fibers (shock or detonation waves). We achieved several shots; devices were composed of a high explosive plane wave generator ended by a metal barrier followed by a cylindrical vessel containing NM. We present results.

Applications of optical holography to applied mechanics.

NASA Technical Reports Server (NTRS)

Aprahamian, R.

1972-01-01

This paper provides a brief summary of applications of optical holography and holographic interferometry to applied solid mechanics. Basic equations commonly used in fringe interpretation are described and used to reduce the data contained on holographic interferograms. A comparison of data obtained holographically with analytical prediction is given wherever possible. Applications contained herein include front surface physics, study of bomb breakup, transverse wave propagation, study of mode shapes of panels at elevated temperatures, nondestructive testing, and vibration analysis.

Franson Interference Generated by a Two-Level System

NASA Astrophysics Data System (ADS)

Peiris, M.; Konthasinghe, K.; Muller, A.

2017-01-01

We report a Franson interferometry experiment based on correlated photon pairs generated via frequency-filtered scattered light from a near-resonantly driven two-level semiconductor quantum dot. In contrast to spontaneous parametric down-conversion and four-wave mixing, this approach can produce single pairs of correlated photons. We have measured a Franson visibility as high as 66%, which goes beyond the classical limit of 50% and approaches the limit of violation of Bell's inequalities (70.7%).

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

Blaut, Arkadiusz

We present the results of the estimation of parameters with LISA for nearly monochromatic gravitational waves in the low and high frequency regimes for the time-delay interferometry response. Angular resolution of the detector and the estimation errors of the signal's parameters in the high frequency regimes are calculated as functions of the position in the sky and as functions of the frequency. For the long-wavelength domain we give compact formulas for the estimation errors valid on a wide range of the parameter space.

Interference, focusing and excitation of ultracold atoms

NASA Astrophysics Data System (ADS)

Kandes, M. C.; Fahy, B. M.; Williams, S. R.; Tally, C. H., IV; Bromley, M. W. J.

2011-05-01

One of the pressing technological challenges in atomic physics is to go orders-of-magnitude beyond the limits of photon-based optics by harnessing the wave-nature of dilute clouds of ultracold atoms. We have developed parallelised algorithms to perform numerical calculations of the Gross-Pitaevskii equation in up to three dimensions and with up to three components to simulate Bose-Einstein condensates. A wide-ranging array of the physics associated with atom optics-based systems will be presented including BEC-based Sagnac interferometry in circular waveguides, the focusing of BECs using Laguerre-Gauss beams, and the interactions between BECs and Ince-Gaussian laser beams and their potential applications. One of the pressing technological challenges in atomic physics is to go orders-of-magnitude beyond the limits of photon-based optics by harnessing the wave-nature of dilute clouds of ultracold atoms. We have developed parallelised algorithms to perform numerical calculations of the Gross-Pitaevskii equation in up to three dimensions and with up to three components to simulate Bose-Einstein condensates. A wide-ranging array of the physics associated with atom optics-based systems will be presented including BEC-based Sagnac interferometry in circular waveguides, the focusing of BECs using Laguerre-Gauss beams, and the interactions between BECs and Ince-Gaussian laser beams and their potential applications. Performed on computational resources via NSF grants PHY-0970127, CHE-0947087 and DMS-0923278.

Relative role of intrinsic and scattering attenuation beneath the Andaman Islands, India and tectonic implications

NASA Astrophysics Data System (ADS)

Singh, Chandrani; Biswas, Rahul; Srijayanthi, G.; Ravi Kumar, M.

2017-10-01

The attenuation characteristics of seismic waves traversing the Andaman Nicobar subduction zone (ANSZ) are investigated using high quality data from a network of broadband stations operational since 2009. We initially studied the Coda wave attenuation (Qc-1) under the assumption of a single isotropic scattering model. Subsequently, following the multiple isotropic scattering hypothesis, we isolated the relative contributions of intrinsic (Qi-1) and scattering (Qsc-1) attenuation employing the Multiple Lapse Time Window Analysis (MLTWA) method within a frequency range 1.5-18 Hz. Results reveal a highly attenuative nature of the crust, with the values of Qc being frequency dependent. The intrinsic absorption is mostly found to be predominant compared to scattering attenuation. The dominance of Qi-1 in the crust may be attributed to the presence of fluids associated with the subducted slab. Our results are consistent with the low velocity zone reported for the region. A comparison of our results with those from other regions of the globe shows that the ANSZ falls under the category of high intrinsic attenuation zone. Interestingly, the character of ANSZ is identical to that of eastern Himalaya and southern Tibet, but entirely different from the Garhwal-Kumaun Himalaya and the source zone of Chamoli earthquake, due to the underlying mechanisms causing high attenuation.

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

NASA Astrophysics Data System (ADS)

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

2013-05-01

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

Coherency of seismic noise, Green functions and site effects

NASA Astrophysics Data System (ADS)

Prieto, G. A.; Beroza, G. C.

2007-12-01

The newly rediscovered methodology of cross correlating seismic noise (or seismic coda) to retrieve the Green function takes advantage of the coherency of the signals across a set of stations. Only coherent signals are expected to emerge after stacking over a long enough time. Cross-correlation has a significant disadvantage for this purpose, in that the Green function recovered is convolved with the source-time function of the noise source. For seismic waves, this can mean that the microseism peak dominates the signal. We show how the use of the transfer function between sensors provides a better resolved Green function (after inverse Fourier transform), because the deconvolution process removes the effect of the noise source-time function. In addition, we compute the coherence of the seismic noise as a function of frequency and distance, providing information about the effective frequency band over which Green function retrieval is possible. The coherence may also be used in resolution analysis for time reversal as a constraint on the de-coherence length (the distance between sensors over which the signals become uncorrelated). We use the information from the transfer function and the coherence to examine wave propagation effects (attenuation and site effects) for closely spaced stations compared to a reference station.

Observations of changes in waveform character induced by the 1999 M w7.6 Chi-Chi earthquake

USGS Publications Warehouse

Chen, K.H.; Furumura, T.; Rubinstein, J.; Rau, R.-J.

2011-01-01

We observe changes in the waveforms of repeating earthquakes in eastern Taiwan following the 1999 Mw7.6 Chi-Chi earthquake, while their recurrence intervals appear to be unaffected. There is a clear reduction in waveform similarity and velocity changes indicated by delayed phases at the time of the Chi-Chi event. These changes are limited to stations in and paths that cross the 70 ?? 100 km region surrounding the Chi-Chi source area, the area where seismic intensity and co-seismic surface displacements were largest. This suggests that damage at the near-surface is responsible for the observed waveform changes. Delays are largest in the late S-wave coda, reaching approximately 120 ms. This corresponds to a path averaged S wave velocity reduction of approximately 1%. There is also evidence that damage in the fault-zone caused changes in waveform character at sites in the footwall, where source-receiver paths propagate either along or across the rupture. The reduction in waveform similarity persists through the most recent repeating event in our study (November 15, 2007), indicating that the subsurface damage induced by the Chi-Chi earthquake did not fully heal within the first 8 years following the Chi-Chi earthquake. ?? 2011 by the American Geophysical Union.

Speckle reduction in optical coherence tomography images based on wave atoms

PubMed Central

Du, Yongzhao; Liu, Gangjun; Feng, Guoying; Chen, Zhongping

2014-01-01

Abstract. Optical coherence tomography (OCT) is an emerging noninvasive imaging technique, which is based on low-coherence interferometry. OCT images suffer from speckle noise, which reduces image contrast. A shrinkage filter based on wave atoms transform is proposed for speckle reduction in OCT images. Wave atoms transform is a new multiscale geometric analysis tool that offers sparser expansion and better representation for images containing oscillatory patterns and textures than other traditional transforms, such as wavelet and curvelet transforms. Cycle spinning-based technology is introduced to avoid visual artifacts, such as Gibbs-like phenomenon, and to develop a translation invariant wave atoms denoising scheme. The speckle suppression degree in the denoised images is controlled by an adjustable parameter that determines the threshold in the wave atoms domain. The experimental results show that the proposed method can effectively remove the speckle noise and improve the OCT image quality. The signal-to-noise ratio, contrast-to-noise ratio, average equivalent number of looks, and cross-correlation (XCOR) values are obtained, and the results are also compared with the wavelet and curvelet thresholding techniques. PMID:24825507

Data-based diffraction kernels for surface waves from convolution and correlation processes through active seismic interferometry

NASA Astrophysics Data System (ADS)

Chmiel, Malgorzata; Roux, Philippe; Herrmann, Philippe; Rondeleux, Baptiste; Wathelet, Marc

2018-05-01

We investigated the construction of diffraction kernels for surface waves using two-point convolution and/or correlation from land active seismic data recorded in the context of exploration geophysics. The high density of controlled sources and receivers, combined with the application of the reciprocity principle, allows us to retrieve two-dimensional phase-oscillation diffraction kernels (DKs) of surface waves between any two source or receiver points in the medium at each frequency (up to 15 Hz, at least). These DKs are purely data-based as no model calculations and no synthetic data are needed. They naturally emerge from the interference patterns of the recorded wavefields projected on the dense array of sources and/or receivers. The DKs are used to obtain multi-mode dispersion relations of Rayleigh waves, from which near-surface shear velocity can be extracted. Using convolution versus correlation with a grid of active sources is an important step in understanding the physics of the retrieval of surface wave Green's functions. This provides the foundation for future studies based on noise sources or active sources with a sparse spatial distribution.

Focusing optical waves with a rotationally symmetric sharp-edge aperture

NASA Astrophysics Data System (ADS)

Hu, Yanwen; Fu, Shenhe; Li, Zhen; Yin, Hao; Zhou, Jianying; Chen, Zhenqiang

2018-04-01

While there has been various kinds of patterned structures proposed for wave focusing, these patterned structures usually involve complicated lithographic techniques since the element size of the patterned structures should be precisely controlled in microscale or even nanoscale. Here we propose a new and straightforward method for focusing an optical plane wave in free space with a rotationally symmetric sharp-edge aperture. The focusing phenomenon of wave is realized by superposition of a portion of the higher-order symmetric plane waves generated from the sharp edges of the apertures, in contrast to previously focusing techniques which usually depend on a curved phase. We demonstrate both experimentally and theoretically the focusing effect with a series of apertures having different rotational symmetry, and find that the intensity of the hotspots could be controlled by the symmetric strength of the sharp-edge apertures. The presented results would advance the conventional wisdom that light would diffract in all directions and become expanding when it propagates through an aperture. The proposed method is easy to be processed, and might open potential applications in interferometry, image, and superresolution.

Simulating Responses of Gravitational-Wave Instrumentation

NASA Technical Reports Server (NTRS)

Armstrong, John; Edlund, Jeffrey; Vallisneri. Michele

2006-01-01

Synthetic LISA is a computer program for simulating the responses of the instrumentation of the NASA/ESA Laser Interferometer Space Antenna (LISA) mission, the purpose of which is to detect and study gravitational waves. Synthetic LISA generates synthetic time series of the LISA fundamental noises, as filtered through all the time-delay-interferometry (TDI) observables. (TDI is a method of canceling phase noise in temporally varying unequal-arm interferometers.) Synthetic LISA provides a streamlined module to compute the TDI responses to gravitational waves, according to a full model of TDI (including the motion of the LISA array and the temporal and directional dependence of the arm lengths). Synthetic LISA is written in the C++ programming language as a modular package that accommodates the addition of code for specific gravitational wave sources or for new noise models. In addition, time series for waves and noises can be easily loaded from disk storage or electronic memory. The package includes a Python-language interface for easy, interactive steering and scripting. Through Python, Synthetic LISA can read and write data files in Flexible Image Transport System (FITS), which is a commonly used astronomical data format.

Compression wave studies in Blair dolomite

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

Grady, D.E.; Hollenbach, R.E.; Schuler, K.W.

Dynamic compression wave studies have been conducted on Blair dolomite in the stress range of 0-7.0 GPa. Impact techniques were used to generate stress impulse input functions, and diffuse surface laser interferometry provided the dynamic instrumentation. Experimental particle velocity profiles obtained by this method were coupled with the conservation laws of mass and momentum to determine the stress-strain and stress-modulus constitutive properties of the material. Comparison between dynamic and quasistatic uniaxial stress-strain curves uncovered significant differences. Energy dissipated in a complete load and unload cycle differed by almost an order of magnitude and the longitudinal moduli differed by as muchmore » as a factor of two. Blair dolomite was observed to yield under dynamic loading at 2.5 GPa. Below 2.5 GPa the loading waves had a finite risetime and exhibited steady propagation. A finite linear viscoelastic constitutive model satisfactorily predicted the observed wave propagation. We speculate that dynamic properties of preexisting cracks provides a physical mechanism for both the rate dependent steady wave behavior and the difference between dynamic and quasistatic response.« less

Time-lapse CO2 monitoring using ambient-noise seismic interferometry: a feasibility study from Ketzin, Germany

NASA Astrophysics Data System (ADS)

Boullenger, Boris; Verdel, Arie; Paap, Bob; Thorbecke, Jan; Draganov, Deyan

2015-04-01

Seismic interferometry applied to ambient-noise measurements allows retrieval of the Green's function between two seismic receivers, by cross-correlating their recordings, as if from a source at one of the receivers. We propose to use ambient-noise seismic interferometry (ANSI) to retrieve reflection data. The time-lapse differences between different vintages of the retrieved data may help characterize property changes within a geologic reservoir with varying CO2 saturation. We test the feasibility of this time-lapse passive seismic method with numerical experiments based on the CO2-storage site of Ketzin, Germany. Ambient-noise recordings from Ketzin exhibit significant passive body-wave energy (from natural tremors or induced seismicity in the vicinity of the reservoir), which is advantageous to retrieve reflections with ANSI. The ANSI numerical experiments aim to understand what the requirements are for the recorded body-wave noise to retrieve the time-lapse reflection signal caused by an increase of CO2 saturation in the reservoir. For this purpose, we design two velocity scenarios at Ketzin: a base scenario before the injection of CO2, and a repeat scenario corresponding to a P-wave velocity decline in the reservoir by 20 percent. For both scenarios, we simulate passive seismic experiments of body-wave noise recordings that may take several days or months to record in the field. The passive recordings are obtained by modelling global (direct wave, internal and surface multiples) transmission responses from band-limited subsurface noise sources, randomly triggered in space and time. The time-lapse reflection signal is obtained by taking the differences between the base and the repeat retrieved reflection data (virtual common-shot gathers). We found that the time-lapse signal is still recovered with ANSI even if the base and repeat retrieved reflection data are partially polluted with artifacts. This means that uneven illumination of the array does not necessarily exclude acceptable time-lapse signal retrieval. Furthermore, the clarity of the time-lapse signal at the reservoir level increases with increasing repeatability of the two passive experiments. The increase in repeatability is achieved when the contributing noise sources form denser clusters that share analogous spatial coverage. To support the merits of the numerical experiments, we applied ANSI (by auto-correlation) to three days of Ketzin passive field-data and compare the retrieved responses with the modelling results. The data are recorded at a permanent array of sensors (hydrophones and geophones) installed above the injection site. We used the records from the buried line of the array that consists of sensors lying at 50-meters depth. These records are less contaminated with surface noise and preserve passive body-wave events better than surface-recorded data. The retrieved responses exhibit significant correspondence with the existing active-seismic field data as well as with our modelled ANSI and active responses. Key reflection events seem to be retrieved at the expected arrival times and support the idea that the settings and characteristics of the ambient noise at Ketzin offer good potential for time-lapse ANSI to monitor CO2 sequestration.

Python based integration of GEM detector electronics with JET data acquisition system

NASA Astrophysics Data System (ADS)

Zabołotny, Wojciech M.; Byszuk, Adrian; Chernyshova, Maryna; Cieszewski, Radosław; Czarski, Tomasz; Dalley, Simon; Hogben, Colin; Jakubowska, Katarzyna L.; Kasprowicz, Grzegorz; Poźniak, Krzysztof; Rzadkiewicz, Jacek; Scholz, Marek; Shumack, Amy

2014-11-01

This paper presents the system integrating the dedicated measurement and control electronic systems for Gas Electron Multiplier (GEM) detectors with the Control and Data Acquisition system (CODAS) in the JET facility in Culham, England. The presented system performs the high level procedures necessary to calibrate the GEM detector and to protect it against possible malfunctions or dangerous changes in operating conditions. The system also allows control of the GEM detectors from CODAS, setting of their parameters, checking their state, starting the plasma measurement and to reading the results. The system has been implemented using the Python language, using the advanced libraries for implementation of network communication protocols, for object based hardware management and for data processing.

Atmospheric Phase Delay in Sentinel SAR Interferometry

NASA Astrophysics Data System (ADS)

Krishnakumar, V.; Monserrat, O.; Crosetto, M.; Crippa, B.

2018-04-01

The repeat-pass Synthetic Aperture Radio Detection and Ranging (RADAR) Interferometry (InSAR) has been a widely used geodetic technique for observing the Earth's surface, especially for mapping the Earth's topography and deformations. However, InSAR measurements are prone to atmospheric errors. RADAR waves traverse the Earth's atmosphere twice and experience a delay due to atmospheric refraction. The two major layers of the atmosphere (troposphere and ionosphere) are mainly responsible for this delay in the propagating RADAR wave. Previous studies have shown that water vapour and clouds present in the troposphere and the Total Electron Content (TEC) of the ionosphere are responsible for the additional path delay in the RADAR wave. The tropospheric refractivity is mainly dependent on pressure, temperature and partial pressure of water vapour. The tropospheric refractivity leads to an increase in the observed range. These induced propagation delays affect the quality of phase measurement and introduce errors in the topography and deformation fields. The effect of this delay was studied on a differential interferogram (DInSAR). To calculate the amount of tropospheric delay occurred, the meteorological data collected from the Spanish Agencia Estatal de Meteorología (AEMET) and MODIS were used. The interferograms generated from Sentinel-1 carrying C-band Synthetic Aperture RADAR Single Look Complex (SLC) images acquired on the study area are used. The study area consists of different types of scatterers exhibiting different coherence. The existing Saastamoinen model was used to perform a quantitative evaluation of the phase changes caused by pressure, temperature and humidity of the troposphere during the study. Unless the phase values due to atmospheric disturbances are not corrected, it is difficult to obtain accurate measurements. Thus, the atmospheric error correction is essential for all practical applications of DInSAR to avoid inaccurate height and deformation measurements.

The evaluation of phasemeter prototype performance for the space gravitational waves detection.

PubMed

Liu, He-Shan; Dong, Yu-Hui; Li, Yu-Qiong; Luo, Zi-Ren; Jin, Gang

2014-02-01

Heterodyne laser interferometry is considered as the most promising readout scheme for future space gravitational wave detection missions, in which the gravitational wave signals disguise as small phase variances within the heterodyne beat note. This makes the phasemeter, which extracts the phase information from the beat note, the key device to this system. In this paper, a prototype of phasemeter based on digital phase-locked loop technology is developed, and the major noise sources which may contribute to the noise spectra density are analyzed in detail. Two experiments are also carried out to evaluate the performance of the phasemeter prototype. The results show that the sensitivity is achieved 2π μrad/√Hz in the frequency range of 0.04 Hz-10 Hz. Due to the effect of thermal drift, the noise obviously increases with the frequencies down to 0.1 mHz.

The evaluation of phasemeter prototype performance for the space gravitational waves detection

NASA Astrophysics Data System (ADS)

Liu, He-Shan; Dong, Yu-Hui; Li, Yu-Qiong; Luo, Zi-Ren; Jin, Gang

2014-02-01

Heterodyne laser interferometry is considered as the most promising readout scheme for future space gravitational wave detection missions, in which the gravitational wave signals disguise as small phase variances within the heterodyne beat note. This makes the phasemeter, which extracts the phase information from the beat note, the key device to this system. In this paper, a prototype of phasemeter based on digital phase-locked loop technology is developed, and the major noise sources which may contribute to the noise spectra density are analyzed in detail. Two experiments are also carried out to evaluate the performance of the phasemeter prototype. The results show that the sensitivity is achieved 2π μrad/√Hz in the frequency range of 0.04 Hz-10 Hz. Due to the effect of thermal drift, the noise obviously increases with the frequencies down to 0.1 mHz.

Droplet characteristic measurement in Fourier interferometry imaging and behavior at the rainbow angle.

PubMed

Briard, Paul; Saengkaew, Sawitree; Wu, Xuecheng; Meunier-Guttin-Cluzel, Siegfried; Chen, Linghong; Cen, Kefa; Gréhan, Gérard

2013-01-01

This paper presents the possibility of measuring the three-dimensional (3D) relative locations and diameters of a set of spherical particles and discusses the behavior of the light recorded around the rainbow angle, an essential step toward refractive index measurements. When a set of particles is illuminated by a pulsed incident wave, the particles act as spherical light wave sources. When the pulse duration is short enough to fix the particle location (typically about 10 ns), interference fringes between these different spherical waves can be recorded. The Fourier transform of the fringes divides the complex fringe systems into a series of spots, with each spot characterizing the interference between a pair of particles. The analyses of these spots (in position and shape) potentially allow the measurement of particle characteristics (3D relative position, particle diameter, and particle refractive index value).

Atomic Interferometric Gravitational-Wave Space Observatory (AIGSO)

NASA Astrophysics Data System (ADS)

Gao, Dong-Feng; Wang, Jin; Zhan, Ming-Sheng

2018-01-01

We propose a space-borne gravitational-wave detection scheme, called atom interferometric gravitational-wave space observatory (AIGSO). It is motivated by the progress in the atomic matter-wave interferometry, which solely utilizes the standing light waves to split, deflect and recombine the atomic beam. Our scheme consists of three drag-free satellites orbiting the Earth. The phase shift of AIGSO is dominated by the Sagnac effect of gravitational-waves, which is proportional to the area enclosed by the atom interferometer, the frequency and amplitude of gravitational-waves. The scheme has a strain sensitivity < {10}-20/\\sqrt{{Hz}} in the 100 mHz-10 Hz frequency range, which fills in the detection gap between space-based and ground-based laser interferometric detectors. Thus, our proposed AIGSO can be a good complementary detection scheme to the space-borne laser interferometric schemes, such as LISA. Considering the current status of relevant technology readiness, we expect our AIGSO to be a promising candidate for the future space-based gravitational-wave detection plan. Supported by the National Key Research Program of China under Grant No. 2016YFA0302002, the National Science Foundation of China under Grant Nos. 11227803 and 91536221, and the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No. XDB21010100

New Astrometric Limits on the Stochastic Gravitational Wave Background

NASA Astrophysics Data System (ADS)

Darling, Jeremiah K.; Truebenbach, Alexandra; Paine, Jennie

2018-06-01

We present new limits on the low frequency (f < 10-8 Hz) stochastic gravitational wave background using correlated extragalactic proper motions. The familiar methods for gravitational wave detection are ground- and space-based laser interferometry, pulsar timing, and polarization of the cosmic microwave background. Astrometry offers an additional path to gravitational wave detection because gravitational waves deflect the light rays of extragalactic objects, creating apparent proper motions in a quadrupolar (and higher order modes) pattern. Astrometry is sensitive to gravitational waves with frequencies between roughly 10-18 Hz and 10-8 Hz (between H0 and 1/3 yr-1), which overlaps and bridges the pulsar timing and CMB polarization regimes. We present the methods and results of two complementary approaches to astrometric gravitational wave detection: (1) a small ~500-object radio interferometric sample with low per-source proper motion uncertainty but large intrinsic proper motions caused by radio jets, and (2) a thousand-fold larger sample with large per-source uncertainties that has small intrinsic proper motions (Gaia active galactic nuclei). Both approaches produce limits on ΩGW, the energy density of gravitational waves as a fraction of the cosmological critical energy density.The authors acknowledge support from the NSF grant AST-1411605 and the NASA grant 14-ATP14-0086.

Rupture Dynamics and Ground Motion from Earthquakes in Heterogeneous Media

NASA Astrophysics Data System (ADS)

Bydlon, S.; Dunham, E. M.; Kozdon, J. E.

2012-12-01

Heterogeneities in the material properties of Earth's crust scatter propagating seismic waves. The effects of scattered waves are reflected in the seismic coda and depend on the relative strength of the heterogeneities, spatial arrangement, and distance from source to receiver. In the vicinity of the fault, scattered waves influence the rupture process by introducing fluctuations in the stresses driving propagating ruptures. Further variability in the rupture process is introduced by naturally occurring geometric complexity of fault surfaces, and the stress changes that accompany slip on rough surfaces. We have begun a modeling effort to better understand the origin of complexity in the earthquake source process, and to quantify the relative importance of source complexity and scattering along the propagation path in causing incoherence of high frequency ground motion. To do this we extended our two-dimensional high order finite difference rupture dynamics code to accommodate material heterogeneities. We generate synthetic heterogeneous media using Von Karman correlation functions and their associated power spectral density functions. We then nucleate ruptures on either flat or rough faults, which obey strongly rate-weakening friction laws. Preliminary results for flat faults with uniform frictional properties and initial stresses indicate that off-fault material heterogeneity alone can lead to a complex rupture process. Our simulations reveal the excitation of high frequency bursts of waves, which radiate energy away from the propagating rupture. The average rupture velocity is thus reduced relative to its value in simulations employing homogeneous material properties. In the coming months, we aim to more fully explore parameter space by varying the correlation length, Hurst exponent, and amplitude of medium heterogeneities, as well as the statistical properties characterizing fault roughness.

Holographic measurement of wave propagation in axi-symmetric shells

NASA Technical Reports Server (NTRS)

Evensen, D. A.; Aprahamian, R.; Jacoby, J. L.

1972-01-01

The report deals with the use of pulsed, double-exposure holographic interferometry to record the propagation of transverse waves in thin-walled axi-symmetric shells. The report is subdivided into sections dealing with: (1) wave propagation in circular cylindrical shells, (2) wave propagation past cut-outs and stiffeners, and (3) wave propagation in conical shells. Several interferograms are presented herein which show the waves reflecting from the shell boundaries, from cut-outs, and from stiffening rings. The initial response of the shell was nearly axi-symmetric in all cases, but nonsymmetric modes soon appeared in the radial response. This result suggests that the axi-symmetric response of the shell may be dynamically unstable, and thus may preferentially excite certain circumferential harmonics through parametric excitation. Attempts were made throughout to correlate the experimental data with analysis. For the most part, good agreement between theory and experiment was obtained. Occasional differences were attributed primarily to simplifying assumptions used in the analysis. From the standpoint of engineering applications, it is clear that pulsed laser holography can be used to obtain quantitative engineering data. Areas of dynamic stress concentration, stress concentration factors, local anomalies, etc., can be readily determined by holography.

The LISA benchtop simulator at the University of Florida

NASA Astrophysics Data System (ADS)

Thorpe, James; Cruz, Rachel; Guntaka, Sridhar; Mueller, Guido

2006-11-01

The Laser Interferometer Space Antenna (LISA) is a joint NASA-ESA mission to detect gravitational radiation in space. The detector is designed to see gravitational waves from various exciting sources in the frequency range of 3x10-5 to 1 Hz. LISA consists of three spacecraft forming a triangle with 5x10^9 m long arms. The spacecraft house proof masses and act to shield the proof masses from external forces so that they act as freely-falling test particles of the gravitational radiation. Laser interferometry is used to monitor the distance between proof masses on different spacecraft and will be designed to see variations on the order of 10 pm. Pre-stabilization, arm-locking, and time delay interferometry (TDI) will be employed to meet this sensitivity. At the University of Florida, we are developing an experimental LISA simulator to test aspects of LISA interferometry. The foundation of the simulator is a pair of cavity-stabilized lasers that provide realistic, LISA-like phase noise for our measurements. The light travel time between spacecraft is recreated in the lab by use of an electronic phase delay technique. Initial tests of the simulator have focused on phasemeter implementation, first-generation TDI, and arm-locking. We will present results from these experiments as well as discuss current and future upgrades in the effort to make the LISA simulator as realistic as possible.

Optical Diagnostic System For Observation Of Laser-Produced Shock Waves

NASA Astrophysics Data System (ADS)

Wilke, Mark D.; Stone, Sidney N.

1980-11-01

Several standard plasma and gas dynamic diagnostic techniques have been integrated into a system for observing the formation and propagation of high-power Nd:glass-laser generated one- and two-dimensional shockwaves in air from 0.1 torr to atmospheric pres-sures. Diagnostics include either single-frame, two-wavelength holographic ruby-laser interferometry or single-frame, single-wavelength interferometry with ten frames of shadow-graphy. Streaks or ten frames of the early luminous shocked region also are taken on all shots, as well as time-resolved luminosity measurements using high-speed biplanar vacuum photodiodes with various wavelength interference filters. Shadowgraphy frames are 200-ns long at 1-μs intervals, while emission frames are variable with a maximum 10-ns exposure and 50-ns interval. Both the streak mode and emission measurements with the vacuum diode allow subnanosecond time resolution. The interferometry provides 20-ns exposures from 500 ns to late times. Methods for reducing and interpreting the data have been, or are currently being, developed. Interactive computer programs for digitizing the fringe patterns provide fringe-shift profiles for Abel inversion. This has provided neutral gas and electron density information in the spherical, one-dimensional cases. Diagrams and photographs of the experiment will be shown as well as examples of the data that have been taken. Methods for data reduction will be outlined and some of the results shown.

High-resolution Imaging of the Philippine Sea Plate subducting beneath Central Japan

NASA Astrophysics Data System (ADS)

Padhy, S.; Furumura, T.

2016-12-01

Thermal models predict that the oceanic crust of the young (<20 Ma) and warmer Philippine-sea plate (PHP) is more prone to melting. Deriving a high-resolution image of the PHP, including slab melting and other features of the subduction zone, is a key to understand the basics of earthquake occurrence and origin of magma in complex subduction zone like central Japan, where both the PHP and Pacific (PAC) Plates subduct. To this purpose, we analyzed high-resolution waveforms of moderate sized (M 4-6), intermediate-to-deep (>150 km) PAC earthquakes occurring in central Japan and conducted numerical simulation to derive a fine-scale PHP model, which is not constrained in earlier studies. Observations show spindle-shaped seismograms with strong converted phases and extended coda with very slow decay from a group of PAC events occurring in northern part of central Japan and recorded by high-sensitivity seismograph network (Hi-net) stations in the region. We investigate the mechanism of propagation of these anomalous waveforms using the finite difference method (FDM) simulation of wave propagation through the subduction zone. We examine the effects on waveform changes of major subduction zone features, such as the melting of oceanic crust in PHP, serpentinized mantle wedge, hydrated layer on the PAC due to slab dehydration, and anomaly in upper mantle between the PAC and PHP. Simulation results show that the waveform anomaly is primarily explained by strong scattering and absorption of high-frequency energy by the low-velocity anomalous mantle structure, with a strong coda excitation yielding spindle-shaped waveforms. The data are secondarily explained by melting of PHP in the basaltic crust. The location of the mantle anomaly is tightly constrained by the observation and evidence of PAC thinning in the region; these localized low-velocity structures aid in ascending the slab-derived fluids around the slab thinning. We expect that the results of this study will enhance our present understanding on the mechanism of intermediate to deep earthquakes in the region.

Deep heterogeneous structure of active faults in the Kinki region, southwest Japan: Inversion analysis of coda envelopes

NASA Astrophysics Data System (ADS)

Nishigami, K.

2006-12-01

It is essential to estimate the deep structure of active faults related to the earthquake rupture process as well as the crustal structure related to the propagation of seismic waves, in order to improve the accuracy of estimating strong ground motion caused by future large inland earthquakes. In the Kinki region, southwest Japan, there are several active fault zones near large cities such as Osaka and Kyoto, and the evaluation of realistic strong ground motion is an important subject. We have been carrying out the Special Project for Earthquake Disaster Mitigation in Urban Areas, in the Kinki region for these purposes. In this presentation we will show the result of estimating the fault structure model of the Biwako-seigan, Hanaore, and Arima- Takatsuki fault zones. We estimated a 3-D distribution of relative scattering coefficients in the Kinki region, also in the vicinity of each active fault zone, by inversion of coda envelopes from local earthquakes. We analyzed 758 seismograms from 52 events which occurred in 2003, recorded at 50 stations of Kyoto Univ., Hi- net, and JMA. The preliminary result shows that active fault zones can be imaged as higher scattering than the surroundings. Based on previous studies of scattering properties in the crust, we consider that the relatively weaker scattering (namely more homogeneous) part on the fault plane may act as an asperity during future large earthquakes, and also that the part with relatively stronger scattering (namely more heterogeneous part) may become an initiation point of rupture. We are also studying the detailed distribution of microearthquakes, b-values, and velocity anomalies along these active fault zones. Combining these results, we will construct a possible fault model for each of the active fault zones. This study is sponsored by the Special Project for Earthquake Disaster Mitigation in Urban Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan.

IRIS DMC products help explore the Tohoku earthquake

NASA Astrophysics Data System (ADS)

Trabant, C.; Hutko, A. R.; Bahavar, M.; Ahern, T. K.; Benson, R. B.; Casey, R.

2011-12-01

Within two hours after the great March 11, 2011 Tohoku earthquake the IRIS DMC started publishing automated data products through its Searchable Product Depository (SPUD), which provides quick viewing of many aspects of the data and preliminary analysis of this great earthquake. These products are part of the DMC's data product development effort intended to serve many purposes: stepping-stones for future research projects, data visualizations, data characterization, research result comparisons as well as outreach material. Our current and soon-to-be-released products that allow users to explore this and other global M>6.0 events include 1) Event Plots, which are a suite of maps, record sections, regional vespagrams and P-coda stacks 2) US Array Ground Motion Visualizations that show the vertical and horizontal global seismic wavefield sweeping across US Array including minor and major arc surface waves and their polarizations 3) back-projection movies that show the time history of short-period energy from the rupture 4) R1 source-time functions that show approximate duration and source directivity and 5) aftershock sequence maps and statistics movies based on NEIC alerts that self-update every hour in the first few days following the mainshock. Higher order information for the Tohoku event that can be inferred based on our products which will be highlighted include a rupture duration of order 150 sec (P-coda stacks, back-projections, R1 STFs) that ruptured approximately 400 km along strike primarily towards the south (back-projections, R1 STFs, aftershock animation) with a very low rupture velocity (back-projections, R1 STFs). All of our event-based products are automated and consistently produced shortly after the event so that they may serve as familiar baselines for the seismology research community. More details on these and other existing products are available at: http://www.iris.edu/dms/products/

Equatorial anisotropy of the Earth's inner-inner core

NASA Astrophysics Data System (ADS)

Song, X.; Wang, T.; Xia, H.

2015-12-01

Anisotropy of Earth's inner core is a key to understand its evolution and the generation of the Earth's magnetic field. All the previous inner core anisotropy models have assumed a cylindrical anisotropy with the symmetry axis parallel (or nearly parallel) to the Earth's spin axis. However, we have recently found that the fast axis in the inner part of the inner core is close to the equator from inner-core waves extracted from earthquake coda. We obtained inner core phases, PKIIKP2 and PKIKP2 (round-trip phases between the station and its antipode that passes straight through the center of the Earth and that is reflected from the inner core boundary, respectively), from stackings of autocorrelations of the coda of large earthquakes (10,000~40,000 s after Mw>=7.0 earthquakes) at seismic station clusters around the world. We observed large variation of up to 10 s along equatorial paths in the differential travel times PKIIKP2 - PKIKP2, which are sensitive to inner-core structure. The observations can be explained by a cylindrical anisotropy in the inner inner core (IIC) (with a radius of slightly less than half the inner core radius) that has a fast axis aligned near the equator and a cylindrical anisotropy in the outer inner core (OIC) that has a fast axis along the north-south direction. We have obtained more observations using the combination of autocorrelations and cross-correlations at low-latitude station arrays. The results further confirm that the IIC has an equatorial anisotropy and a pattern different from the OIC. The equatorial fast axis of the IIC is near the Central America and the Southeast Asia. The drastic change in the fast axis and the form of anisotropy from the IIC to the OIC may suggest a phase change of the iron or a major shift in the crystallization and deformation during the formation and growth of the inner core.

Composite-Light-Pulse Technique for High-Precision Atom Interferometry

NASA Astrophysics Data System (ADS)

Berg, P.; Abend, S.; Tackmann, G.; Schubert, C.; Giese, E.; Schleich, W. P.; Narducci, F. A.; Ertmer, W.; Rasel, E. M.

2015-02-01

We realize beam splitters and mirrors for atom waves by employing a sequence of light pulses rather than individual ones. In this way we can tailor atom interferometers with improved sensitivity and accuracy. We demonstrate our method of composite pulses by creating a symmetric matter-wave interferometer which combines the advantages of conventional Bragg- and Raman-type concepts. This feature leads to an interferometer with a high immunity to technical noise allowing us to devise a large-area Sagnac gyroscope yielding a phase shift of 6.5 rad due to the Earth's rotation. With this device we achieve a rotation rate precision of 120 nrad s-1 Hz-1 /2 and determine the Earth's rotation rate with a relative uncertainty of 1.2%.

Design and construction of prototype radio antenna for shortest radio wavelengths

NASA Technical Reports Server (NTRS)

Leighton, R. B.

1975-01-01

A paraboloid radio antenna of 10.4 meters diameter, 0.41 meter focal length was constructed and its successful completion is described. The surface accuracy of the antenna is at least four times better than any existing antenna in its class size (50 micrometers rms). Antenna design specifications (i.e., for mounting, drive motors, honeycomb structures) are discussed and engineering drawings and photographs of antenna components are shown. The antenna will be used for millimeter-wave interferometry and sub-millimeter wave radiometry over a full frequency range (up to approximately 860 GHz). The antenna will also be moveable (for interferometric use) between reinforced concrete pads by rail. The effects of the weather and gravity on antenna performance are briefly discussed.

Polarization interferometry for real-time spectroscopic plasmonic sensing.

PubMed

Otto, Lauren M; Mohr, Daniel A; Johnson, Timothy W; Oh, Sang-Hyun; Lindquist, Nathan C

2015-03-07

We present quantitative, spectroscopic polarization interferometry phase measurements on plasmonic surfaces for sensing applications. By adding a liquid crystal variable wave plate in our beam path, we are able to measure phase shifts due to small refractive index changes on the sensor surface. By scanning in a quick sequence, our technique is extended to demonstrate real-time measurements. While this optical technique is applicable to different sensor geometries-e.g., nanoparticles, nanogratings, or nanoapertures-the plasmonic sensors we use here consist of an ultrasmooth gold layer with buried linear gratings. Using these devices and our phase measurement technique, we calculate a figure of merit that shows improvement over measuring only surface plasmon resonance shifts from a reflected intensity spectrum. To demonstrate the general-purpose versatility of our phase-resolved measurements, we also show numerical simulations with another common device architecture: periodic plasmonic slits. Since our technique inherently measures both the intensity and phase of the reflected or transmitted light simultaneously, quantitative sensor device characterization is possible.

Phase coherence and Andreev reflection in topological insulator devices

DOE PAGES

Finck, A. D. K.; Kurter, C.; Hor, Y. S.; ...

2014-11-04

Topological insulators (TIs) have attracted immense interest because they host helical surface states. Protected by time-reversal symmetry, they are robust to nonmagnetic disorder. When superconductivity is induced in these helical states, they are predicted to emulate p-wave pairing symmetry, with Majorana states bound to vortices. Majorana bound states possess non-Abelian exchange statistics that can be probed through interferometry. Here, we take a significant step towards Majorana interferometry by observing pronounced Fabry-Pérot oscillations in a TI sandwiched between a superconducting and a normal lead. For energies below the superconducting gap, we observe a doubling in the frequency of the oscillations, arisingmore » from an additional phase from Andreev reflection. When a magnetic field is applied perpendicular to the TI surface, a number of very sharp and gate-tunable conductance peaks appear at or near zero energy, which has consequences for interpreting spectroscopic probes of Majorana fermions. Our results show that TIs are a promising platform for exploring phase-coherent transport in a solid-state system.« less

Experimental demonstration of deep frequency modulation interferometry.

PubMed

Isleif, Katharina-Sophie; Gerberding, Oliver; Schwarze, Thomas S; Mehmet, Moritz; Heinzel, Gerhard; Cervantes, Felipe Guzmán

2016-01-25

Experiments for space and ground-based gravitational wave detectors often require a large dynamic range interferometric position readout of test masses with 1 pm/√Hz precision over long time scales. Heterodyne interferometer schemes that achieve such precisions are available, but they require complex optical set-ups, limiting their scalability for multiple channels. This article presents the first experimental results on deep frequency modulation interferometry, a new technique that combines sinusoidal laser frequency modulation in unequal arm length interferometers with a non-linear fit algorithm. We have tested the technique in a Michelson and a Mach-Zehnder Interferometer topology, respectively, demonstrated continuous phase tracking of a moving mirror and achieved a performance equivalent to a displacement sensitivity of 250 pm/Hz at 1 mHz between the phase measurements of two photodetectors monitoring the same optical signal. By performing time series fitting of the extracted interference signals, we measured that the linearity of the laser frequency modulation is on the order of 2% for the laser source used.

Concepts and technology development towards a platform for macroscopic quantum experiments in space

NASA Astrophysics Data System (ADS)

Kaltenbaek, Rainer

Tremendous progress has been achieved in space technology over the last decade. This technological heritage promises enabling applications of quantum technology in space already now or in the near future. Heritage in laser and optical technologies from LISA Pathfinder comprises core technologies required for quantum optical experiments. Low-noise micro-thruster technology from GAIA allows achieving an impressive quality of microgravity, and passive radiative cooling approaches as in the James Webb Space Telescope may be adapted for achieving cryogenic temperatures. Developments like these have rendered space an increasingly attractive platform for quantum-enhanced sensing and for fundamental tests of physics using quantum technology. In particular, there already have been significant efforts towards ralizing atom interferometry and atomic clocks in space as well as efforts to harness space as an environment for fundamental tests of physics using quantum optomechanics and high-mass matter-wave interferometry. Here, we will present recent efforts in spacecraft design and technology development towards this latter goal in the context of the mission proposal MAQRO.

One-shot phase-shifting phase-grating interferometry with modulation of polarization: case of four interferograms.

PubMed

Rodriguez-Zurita, Gustavo; Meneses-Fabian, Cruz; Toto-Arellano, Noel-Ivan; Vázquez-Castillo, José F; Robledo-Sánchez, Carlos

2008-05-26

An experimental setup for optical phase extraction from 2-D interferograms using a one-shot phase-shifting technique able to achieve four interferograms with 90 degrees phase shifts in between is presented. The system uses a common-path interferometer consisting of two windows in the input plane and a phase grating in Fourier plane as its pupil. Each window has a birefringent wave plate attached in order to achieve nearly circular polarization of opposite rotations one respect to the other after being illuminated with a 45 degrees linear polarized beam. In the output, interference of the fields associated with replicated windows (diffraction orders) is achieved by a proper choice of the windows spacing with respect to the grating period. The phase shifts to achieve four interferograms simultaneously to perform phase-shifting interferometry can be obtained by placing linear polarizers on each diffraction orders before detection at an appropriate angle. Some experimental results are shown.

Wideband acoustic records of explosive volcanic eruptions at Stromboli: New insights on the explosive process and the acoustic source

NASA Astrophysics Data System (ADS)

Goto, A.; Ripepe, M.; Lacanna, G.

2014-06-01

Wideband acoustic waves, both inaudible infrasound (<20 Hz) and audible component (>20 Hz), generated by strombolian eruptions were recorded at 5 kHz and correlated with video images. The high sample rate revealed that in addition to the known initial infrasound, the acoustic signal includes an energetic high-frequency (typically >100 Hz) coda. This audible signal starts before the positive infrasound onset goes negative. We suggest that the infrasonic onset is due to magma doming at the free surface, whereas the immediate high-frequency signal reflects the following explosive discharge flow. During strong gas-rich eruptions, positively skewed shockwave-like components with sharp compression and gradual depression appeared. We suggest that successive bursting of overpressurized small bubbles and the resultant volcanic jets sustain the highly gas-rich explosions and emit the audible sound. When the jet is supersonic, microexplosions of ambient air entrained in the hot jet emit the skewed waveforms.

Sleep underpins the plasticity of language production.

PubMed

Gaskell, M Gareth; Warker, Jill; Lindsay, Shane; Frost, Rebecca; Guest, James; Snowdon, Reza; Stackhouse, Abigail

2014-07-01

The constraints that govern acceptable phoneme combinations in speech perception and production have considerable plasticity. We addressed whether sleep influences the acquisition of new constraints and their integration into the speech-production system. Participants repeated sequences of syllables in which two phonemes were artificially restricted to syllable onset or syllable coda, depending on the vowel in that sequence. After 48 sequences, participants either had a 90-min nap or remained awake. Participants then repeated 96 sequences so implicit constraint learning could be examined, and then were tested for constraint generalization in a forced-choice task. The sleep group, but not the wake group, produced speech errors at test that were consistent with restrictions on the placement of phonemes in training. Furthermore, only the sleep group generalized their learning to new materials. Polysomnography data showed that implicit constraint learning was associated with slow-wave sleep. These results show that sleep facilitates the integration of new linguistic knowledge with existing production constraints. These data have relevance for systems-consolidation models of sleep. © The Author(s) 2014.

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

Biedermann, G. W.; McGuinness, H. J.; Rakholia, A. V.

Here, we demonstrate matter-wave interference in a warm vapor of rubidium atoms. Established approaches to light-pulse atom interferometry rely on laser cooling to concentrate a large ensemble of atoms into a velocity class resonant with the atom optical light pulse. In our experiment, we show that clear interference signals may be obtained without laser cooling. This effect relies on the Doppler selectivity of the atom interferometer resonance. Lastly, this interferometer may be configured to measure accelerations, and we demonstrate that multiple interferometers may be operated simultaneously by addressing multiple velocity classes.

Development of a Thermal Wave Interferometry System for Thin-Film Characterisation

DTIC Science & Technology

2012-10-01

describes a condition where the properties of the interface influence the phase and amplitude of the temperature oscillations at the surface. In the...The measured phase profiles are shown in Figure 13. Overall, the phase variation across the sample is significant, with a strong discontinuity in phase ...d eg ) 91.2 Hz 30 Hz 7 Hz 4 Hz Figure 13: Phase measurements across the coated sample. L1 L2 L3 L4 L5 A more rigorous validation of the

Subduction zone guided waves in Northern Chile

NASA Astrophysics Data System (ADS)

Garth, Thomas; Rietbrock, Andreas

2016-04-01

Guided wave dispersion is observed in subduction zones as high frequency energy is retained and delayed by low velocity structure in the subducting slab, while lower frequency energy is able to travel at the faster velocities associated with the surrounding mantle material. As subduction zone guided waves spend longer interacting with the low velocity structure of the slab than any other seismic phase, they have a unique capability to resolve these low velocity structures. In Northern Chile, guided wave arrivals are clearly observed on two stations in the Chilean fore-arc on permanent stations of the IPOC network. High frequency (> 5 Hz) P-wave arrivals are delayed by approximately 2 seconds compared to the low frequency (< 2 Hz) P-wave arrivals. Full waveform finite difference modelling is used to test the low velocity slab structure that cause this P-wave dispersion. The synthetic waveforms produced by these models are compared to the recorded waveforms. Spectrograms are used to compare the relative arrival times of different frequencies, while the velocity spectra is used to constrain the relative amplitude of the arrivals. Constraining the waveform in these two ways means that the full waveform is also matched, and the low pass filtered observed and synthetic waveforms can be compared. A combined misfit between synthetic and observed waveforms is then calculated following Garth & Rietbrock (2014). Based on this misfit criterion we constrain the velocity model by using a grid search approach. Modelling the guided wave arrivals suggest that the observed dispersion cannot be solely accounted for by a single low velocity layer as suggested by previous guided wave studies. Including dipping low velocity normal fault structures in the synthetic model not only accounts for the observed strong P-wave coda, but also produces a clear first motion dispersion. We therefore propose that the lithospheric mantle of the subducting Nazca plate is highly hydrated at intermediate depths by dipping low velocity normal faults. Additionally, we show that the low velocity oceanic crust persists to depths of up to 200 km, well beyond the depth range where the eclogite transition is expected to have occurred. Our results suggest that young subducting lithosphere also has the potential to carry much larger amounts of water to the mantle than has previously been appreciated.

About three cases of ulceroglandular tularemia, is this the re-emergence of Francisella tularensis in Belgium?

PubMed

Dupont, E; Van Eeckhoudt, S; Thissen, X; Ausselet, N; Fretin, D; Stefanescu, I; Glupczynski, Y; Delaere, B

2015-10-01

Tularemia is a zoonosis caused by Francisella tularensis that can be transmitted by several ways to human being and cause different clinical manifestations. We report three clinical cases of tularemia with ulceroglandular presentation in young males acquired during outdoor activities in Southern Belgium. Confirmation of the diagnosis was established by serology. Only three cases of tularemia have been reported in Belgium between 1950 and 2012 by the National Reference Laboratory CODA-CERVA (Ref Lab CODA-CERVA) but re-emergence of tularemia is established in several European countries and F. tularensis is also well known to be present in animal reservoirs and vectors in Belgium. The diagnosis of tularemia has to be considered in case of suggestive clinical presentation associated with epidemiological risk factors.

Seismic scatterers in the mid-lower mantle beneath Tonga-Fiji

NASA Astrophysics Data System (ADS)

Kaneshima, Satoshi

2018-01-01

We analyze deep and intermediate-depth earthquakes at the Tonga-Fiji region in order to reveal the distribution of scattering objects in the mid-lower mantle. By array processing waveform data recorded at regional seismograph stations in the US, Alaska, and Japan, we investigate S-to-P scattering waves in the P coda, which arise from kilometer-scale chemically distinct objects in the mid-lower mantle beneath Tonga-Fiji. With ten scatterers previously reported by the author included, twenty-three mid-lower mantle scatterers have been detected below 900 km depth, while scatterers deeper than 1900 km have not been identified. Strong mid-lower mantle S-to-P scattering most frequently occurs at the scatterers located within a depth range between 1400 km and 1600 km. The number of scatterers decreases below 1600 km depth, and the deeper objects tend to be weaker. The scatterer distribution may reflect diminishing elastic anomalies of basaltic rocks with depth relative to the surrounding mantle rocks, which mineral physics has predicted to occur. The predominant occurrence of strong S-to-P scattering waves within a narrow depth range may reflect significant reduction of rigidity due to the ferro-elastic transformation of stishovite in basaltic rocks. Very large signals associated with mid-mantle scatterers are observed only for a small portion of the entire earthquake-array pairs. Such infrequent observations of large scattering signals, combined with quite large event-to-event differences in the scattering intensity for each scatterer, suggest both that the strong arrivals approximately represent ray theoretical S-to-P converted waves at objects with a plane geometry. The plane portions of the strong scatterers may often dip steeply, with the size exceeding 100 km. For a few strong scatterers, the range of receivers showing clear scattered waves varies substantially from earthquake-array pair to pair. Some of the scatterers are also observed at different arrays that have significantly different directions of incident waves to the scatterers. Furthermore, weak but coherent P-to-P scattered waves as well as S-to-P waves are observed for a few of the scatterers. These observations indicate that the locally plane scatterers also possess substantial topography.