passive seismic imaging in the presence of white noise sources passive seismic imaging is based on the relation between the reflection and the transmission responses of the subsurface let one have the transmission responses measured at surface points a and b of a 3d inhomogeneous medium in the presence of white noise sources in the subsurface when these transmission responses are cross correlated one obtains the reflection response of the same medium as if measured at point a in the presence of an impulsive source at point b the quality of the simulated reflection response strongly depends on the whiteness and the distribution of the noise sources reflectors present below the sources cause the appearance of some ghost events random distribution of the noise sources will however weaken these ghost events

esr dating of fault movement using various defect centres in quartz the case in the western south fossa magna japan the dates of movements of the itoigawa shizuoka tectonic line i s t l and minobu fault in the western south fossa magna have been obtained by esr dating measurements were made on various lattice defects of the ohc ge al and e centres in quartz grains of fault clay and quartz veins intruded at the time of movement all the dates obtained from these centres in quartz grains from two localities of the i s t l and iwo localities of the minobu fault fall in the range of 0 30 0 55 ma this suggests that all the centres were annihilated completely and that the obtained age can be admitted as the actual data of the latest fault movement meanwhile esr dates of quartz vein and fault clay in other localities locations 3 6 7 are divided into 0 30 0 55 ma and 1 5 2 0 ma which suggest incomplete resetting the dates of 0 30 0 55 and 1 5 2 0 ma might correspond to the clino unconformities observed in plio pleistocene sequence of this region

transmission to reflection transformation of teleseismic wavefields 1 in this paper we review the transformation of p and sv transmission green s functions into the corresponding reflection quantities for one dimensional elastic media at precritical slownesses to obtain estimates of the transmission green s functions from observed data we apply a recently developed approach that exploits the minimum phase nature of the direct waves and employs autospectra and cross spectra of raw component seismograms representing multiple sources recorded at a single station to accomplish transformation to reflection green s functions we outline a practical recipe that involves amplitude balancing energy normalization cross correlation and removal of free surface effects we assess its performance through application to both synthetic seismograms and data from station hyderabad in all cases we are able to identify the first order scattering contributions from the continental moho the transmission to reflection transformation has potential applications for imaging hitherto elusive shallow mantle discontinuities since interfering forward and back scattering contributions are effectively separated by component in the resulting reflection green s functions

interferometric daylight seismic imaging summary claerbout s daylight imaging concept is generalized to a theory of interferometric seismic imaging ii interferometric seismic imaging is defined to be any algorithm that inverts correlated seismic data for the reflectivity or source distribution as examples we show that ii can image reflectivity distributions by migrating ghost reflections in passive seismic data and generalizes the receiver function imaging method used by seismologists interferometric seismic imaging can also migrate free surface multiples in common depth point cdp data and image source distributions from passive seismic data both synthetic and field data examples are used to illustrate the different possibilities of ii the key advantage of ii is that it can image source locations or reflectivity distributions from passive seismic data where the source position or wavelet is unknown in some cases it can mitigate defocusing errors as a result of statics or an incorrect migration velocity the main drawback with ii is that severe migration artefacts can be created by partial focusing of virtual multiples

high resolution probing of inner core structure with seismic interferometry 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 pkikp 2 and pkiikp 2 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

receiver pair seismic interferometry applied to body wave usarray data with seismic interferometry reflections can be retrieved between stations positioned on the earth s surface in the classical form the reflections are retrieved by a crosscorrelation of observations and an integration over subsurface sources for a specific data set however the actual source distribution might not be sufficient to approximate the source integral yet there might be a dense distribution of receivers allowing an integration over the receiver domain we rewrite the source integral to an integration over receiver pairs and call it receiver pair seismic interferometry rpsi with this formulation reflections can be retrieved even in the limiting case of only a single source we illustrate the new relation both with synthetic data and data from the usarray which is a large grid of stations covering the usa the field observations are from an earthquake in mexico we show that rpsi can be applied both for a line and grid of receivers when using isolated phases recorded over a line of stations inline with the earthquake reflections are retrieved from the core mantle boundary which reflections can be ascribed to specific virtual source and receiver locations within the usarray when using full responses as input to rpsi the retrieved phases are an average over multiple virtual sources and receivers location is then only possible when the integrand is spatially windowed or when a clear leading term is identified when using a grid of receivers the location of the source does not need to be known but spatially averaged instead of localized responses are obtained also when isolated arrivals are used as input to rpsi

esr studies for absolute dating of fault movements the principle of absolute dating of fault movements is based on the initialization or resetting of some clock system by faulting in the case of esr dating heating is more effective in resetting esr signals than fracturing according to a computer simulation of resetting by shear heating during faulting the esr signals can never be completely reset at depths of less than 100 200 m below the surface of the earth therefore esr samples must be collected from depth by coring or tunnelling or from outcrop with consideration of the rate of exhumation of the fault outcrop in general unpaired electrons trapped at lattice defects in crystals can diffuse much more easily than atoms hence samples for other dating methods which are based on the diffusion of atoms should be collected at even greater depth on the other hand if no esr signal is observed from unfractured quartz in the wall rocks one may directly determine the age of the fault movement using esr signals in the fractured quartz whose precursors were formed by faulting the age obtained t should then satisfy the following relationship t b t t e where t b and t e are the ages of the beginning and end of the fault movements and it may show the time of a fault movement

interferometric seismic imaging of crustal structure using scattered teleseismic waves 1 the deployment of a dense seismic array of portable broadband stations has presented a number of imaging opportunities using scattered teleseismic waves interferometric seismic imaging isi of surface related multiple reflections extracted from cross correlations of teleseismic waves among pairs of receiver stations was investigated for possible applications and compared to receiver function rf method synthetic seismograms simulated by the elastic pseudospectral method for a simple 2 d crustal model demonstrate the potential imaging capabilities of isi for the moho structure with high spatial resolution isi has also been applied to teleseismic data from dense array experiments conducted at the northern fossa magna basin in central japan the results indicate that the moho phase with positive polarity at a depth of 38 40 km in the isi profile is consistent with the lower crustal structure estimated by rf imaging

removing free surface multiples from teleseismic transmission and constructed reflection responses using reciprocity and the inverse scattering series we develop a new way to remove free surface multiples from teleseismic p transmission and constructed reflection responses we consider two types of teleseismic waves with the presence of the free surface one is the recorded waves under the real transmission geometry the other is the constructed waves under a virtual reflection geometry the theory presented is limited to 1d plane wave acoustic media but this approximation is reasonable for the teleseismic p wave problem resulting from the steep emergence angle of the wavefield using one way wavefield reciprocity we show howtheteleseismicreflectionresponsescanbereconstructed from the teleseismic transmission responses we use the inverse scattering series to remove free surface multiples from the original transmission data and from the reconstructed reflection response we derive an alternative algorithm for reconstructing the reflection response from the transmission data that is obtained by taking the difference between the teleseismic transmission waves before and after free surface multiple removal numerical tests with 1d acoustic layered earthmodelsdemonstratethevalidityofthetheorywedevelop noisetestshowsthatthealgorithmcanworkwiths nratioaslowas5comparedtoactualdatawiths nratiofrom30 to 50 testing with elastic synthetic data indicates that the acousticalgorithmisstilleffectiveforsmallincidenceangles oftypicalteleseismicwavefields

seismic interferometry reconstructing the earth s reflection response in1968 jonclaerboutshowedthatthereflectionresponseofa 1dacousticmediumcanbereconstructedbyautocorrelatingthe transmission response since then several authors have derived relationships for reconstructing green s functions at the surface using crosscorrelations of noise recordings that were taken at thesurfaceandthatderivedfromsubsurfacesources foracousticmedia wereviewrelationsbetweenthereflection response and the transmission response in 3d inhomogeneous lossless media these relations are derived from a one way wavefield reciprocity theorem we use modeling results to show howtoreconstructthereflectionresponseinthepresenceoftransientsubsurfacesourceswithdistinctexcitationtimes aswellas inthepresenceofsimultaneouslyactingnoisesourcesinthesubsurface weshowthatthequalityofreconstructedreflectionsdepends on the distribution of the subsurface sources for a situation with enough subsurface sources that is for a distribution that illuminates the subsurface area of interest from nearly all directions the reconstructed reflection responses and the migrated depth image exhibit all the reflection events and the subsurface structures of interest respectively with only a few subsurface sources that is with insufficient illumination the reconstructed reflection responses are noisy and can even become kinematically incorrect at the same time however the depth image which was obtained from their migration still shows clearly all the illuminated subsurface structures at their correct positions for the elastic case we review a relationship between the reflection green s functions and the transmission green s functionsderivedfromatwo waywavefieldreciprocitytheorem usingmodelingexamples weshowhowtoreconstructthedifferent components of the particle velocity observed at the surface and resulting from a surface traction source this reconstruciton is achievedusingcrosscorrelationsofparticlevelocitycomponents measured at the surface and resulting from separate p and s wavesourcesinthesubsurface

tectonic history of granitic bodies in the south fossa magna region central japan new evidence from fission track analysis of zircon abstract a fission track ft analysis of zircons has been performed to clarify tectonic history of the tertiary granitic bodies in the northern part of the izu bonin arc and the south fossa magna region of central japan a total of 30 ft ages was obtained from the kaikoma tsuburai ashigawa tokuwa and tanzawa granitic bodies confined ft lengths were also measured on 11 zircon samples from the granitic rocks to obtain more information on the thermal history of the region the ft ages and confined ft length data from the kaikoma indicate that this granitic body cooled below the isotherm of zircon 240 c at 9 4 0 4 ma 2 the tsuburai ashigawa tokuwa and tanzawa granitic bodies which have a similar lithology and tectonic setting lie from northwest to southeast respectively the ft ages for these bodies are 15 0 0 6ma for the tsuburai 11 9 0 4 ma for the ashigawa 12 5 1 4 ma for the tokuwa which is comparable with the ft age of the ashigawa 7 1 2 0 ma for the tanzawa which is the youngest the data indicate a differential uplift of the granitic bodies in the south fossa magna region in general the ft ages become younger as one proceeds southeastwards approaching the izu bonin arc the ft age data provide constraints on the tectonic effects of the collision of the izu bonin arc with the central honshu of the japan arc

teleseismic shot profile migration the shot profile migration approach of wave equation migration generates subsurface images using the interferometric principle of crosscorrelating two passive wavefields these wavefields are typically a source wavefield containing energy from an excited source and a receiver wavefield comprised of scattered source wavefield energy by the discontinuous earth structure shot profile migration can be recast as a novel way of imaging the earth s lithosphere using teleseismic wavefield data where the source wavefield is the directly arriving wavefront and the receiver wavefield is the following wavefield coda we demonstrate that the shot profile technique can be tailored to suit teleseismic acquisition geometry and wavefields assuming an acoustic framework and 2 5d experimental geometry we develop procedures that enable kinematic and structural imaging migration using both transmission and free surface reflected passive wavefields experiments with synthetic data demonstrate the method s applicability a

shallow structure of deception island antarctica from correlations of ambient seismic noise on a set of dense seismic arrays summary we investigated the shallow velocity structure of deception island volcano antarctica using correlations of ambient seismic noise we selected long records of noise obtained by eight seismic arrays deployed along the inner coast of deception during the period 2003 2005 using these data we calculated average dispersion curves and estimated local 1 d velocity models for the array sites the combination of these profiles allowed us to obtain a comprehensive model of the shallow velocity structure of the island the volcano is composed of relatively soft layers of pyroclastic deposits and sediments extending to a depth of about 400 m with different degrees of compaction two layers with thicknesses of about 100 and 300 m and s wave velocities of around 0 2 0 8 and 0 7 1 1 km s 1 respectively can be differentiated the deeper structure is highly variable in terms of wave velocities and layer depths although the resolving capabilities are reduced for these layers the larger s wave velocities in the range 1 3 2 8 km s 1 indicate that they can be associated with pre caldera structures and products there are substantial differences between the different models which can be spatially related to heterogeneities in the volcano structure the lowest s wave velocities may be related to the alterations produced by hydrothermal activity near the surface on the contrary the largest velocities occur near the caldera border revealing the presence of compact materials at shallow depths sharp lateral variations can also be observed in the northwest of the bay which points to the presence of nw se faults and or strong velocity gradients

virtual shear source makes shear waves with air guns we demonstrate a novel application of the virtual source method to create shear wave sources at the location of buried geophones these virtual downhole sources excite shear waves with a different radiation pattern than known sources they can be useful in various shear wave applications here we focus on the virtual shear check shot to generate accurate shear velocity profiles in offshore environments using typical acquisition for marine walkaway vertical seismic profiling vsp the virtual source method is applied to walkaway vsp data to obtain new traces resembling seismograms acquired with downhole seismic sources at geophone locations thus bypassing any overburden complexity the virtual sources can be synthesized to radiate predominantly shear waves by collecting converted wave energy scattered throughout the overburden we illustrate the concept in a synthetic layered model and demonstrate the method by estimating accurate p and s wave velocity profiles below salt using a walkaway vsp from the deepwater gulf of mexico

postglacial rebound in a non newtonian spherical earth using finite elements we study the postglacial rebound in an axisymmetric earth with a non newtonian rheology our approach allows for the first time a self consistent study of the effect of a power law creep on the long wavelength deformations which cannot be performed using flat models we show that for a non newtonian upper mantle the time variations of the low degree stokes coefficients become largely insensitive to the viscosity of the lower mantle this is in contrast with previous evidence based on newtonian models which emphasized the importance of the low degree signatures for constraining the lower mantle viscosity

surface wave array tomography in se tibet from ambient seismic noise and two station analysis i phase velocity maps summary empirical green s functions egfs between pairs of seismographs can be estimated from the time derivative of the long time cross correlation of ambient seismic noise these egfs reveal velocity dispersion at relatively short periods which can be used to resolve structures in the crust and uppermost mantle better than with traditional surface wave tomography we combine rayleigh wave dispersion estimates from egfs and from traditional two station ts analysis into a new approach to surface wave array tomography with data from dense receiver arrays we illustrate the methodology with continuous broad band recordings from a temporary seismographic network on the southeastern part of the tibetan plateau in sichuan and yunnan provinces sw china the egfs are robust under temporal changes in regional seismicity and the use of either ambient noise approximated by records without signal from events with magnitude mb 5 or 4 or surface wave coda produces similar results the egfs do not strongly depend on the presence of large earthquakes but they are not reciprocal for stations aligned in the n s direction this directionality reflects the paucity of seismicity to the north of the array using a far field representation of the surface wave green s function and an image transformation technique we infer from the egfs the rayleigh wave phase velocity dispersion in the period band from 10 30 s a classical ts approach is used to determine rayleigh wave phase velocity dispersion between 20 120 s together they constrain phase velocity variations for t 10 120 s which can be used to study the structure from the crust to the upper mantle beneath se tibet short and intermediate period 10 80 s phase velocities are prominently low suggesting that the crust and upper mantle beneath se tibet is characterized by slow shear wave propagation

remarks on esr dating of fault movements laboratory experiments and detailed investigations of natural fault gouge indicate that it is in principle possible to date the last movement of a fault by esr this paper gives a brief introduction to esr dating and outlines the specific problems that have to be addressed before esr can be established as a reliable technique for the dating of fault movements

analysis of intermediate period correlations of coda from deep earthquakes abstract 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

resetting experiment of e centres by natural faulting the case of the nojima earthquake fault in japan abstract the resetting state of e centres in quartz in fault clay gouge has been examined using the nojima earthquake fault that moved during the southern hyogo prefecture earthquake in 1995 as a result the e centres have never been reset by this faulting event furthermore there is no regular tendency among the d e values obtained from the grain samples and the plateau region of the esr ages does not exist in the case of the nojima fault therefore it is not possible to judge the complete resetting of esr signals by natural faulting on the other hand the increase of radiation sensitivity of the e centres may be ascribed to the formation of the precursors by rays emitted from the radioactive elements adhered around the grain samples since the adherence of the radioactive elements may begin with fracturing the quartz grains by faulting the esr ages obtained from the unsaturated e centres with high radiation sensitivity may give the age of beginning of the fault movements the esr ages obtained from these unsaturated e centres of the nojima fault 0 88 0 3 ma 1 51 0 51 ma or 1 07 0 36 ma 1 75 0 59 ma are consistent with the geological age estimate of the beginning of the fault movements

increase of radiation sensitivity of esr centres by faulting and criteria of fault dates abstract the esr spectra and ages of the fractured rocks along the itoigawa shizuoka tectonic line a major fault in japan were measured the esr signal intensities tend to become larger with decreasing distance from the fault boundary because the radiation sensitivities of the esr centres have increased by faulting according to fracturing and heating experiments when the radiation sensitivities of esr centres have visibly increased the signals may have been almost completely reset by faulting as a result of the increase of radiation sensitivity the error range of the td values for incompletely reset esr signals is comparatively large whereas it is smaller in the case of completely reset signals therefore by assessing the error range of td values we can determine whether esr signals were completely reset at the time of faulting

global phase seismic interferometry unveils p wave reflectivity below the himalayas and tibet a number of seismic methods exist to image the lithosphere below a collection of receivers using distant earthquakes in the current practice especially mode conversions in teleseismic phases are utilized we present a new method that takes advantage of the availability of global phases this method is called global phase seismic interferometry glopsi with glopsi zero offset reflections are extracted from reverberations near the array caused by global seismicity we exemplify glopsi with data from the hi climb experiment 2002 2005 and migrate the obtained reflection responses this results in a 800 km long reflectivity profile through the himalayas and a large part of the tibetan plateau

applicability of esr dating using multiple centres to fault movement the case of the itoigawa shizuoka tectonic line a major fault in japan abstract no direct method for dating the fault movement has been hitherto established except esr dating whose applicability is disputed however the most serious question in esr dating is whether accumulated esr signals are completely reset at the time of fault movement when the defect centres are partially preserved at the time of previous faulting the date obtained is uncertain we have shown fukuchi et al 1985 1986 however that we can judge correctly whether esr signals were completely reset or not when the esr signal counting is done for multiple esr centres of different stabilities for resetting from the data for completely reset centres actual date of fault movement can be calculated this multiple centre method was tested with samples whose esr signal intensities are judged to be about zero at the time of fault movement the result which confirms the applicability for the fault movement dated back to 100 ka bp is presented in this paper

green s functions extraction and surface wave tomography from microseisms in southern california we use crosscorrelations of seismic noise data from 151 stations in southern california to extract the group velocities of surface waves between the station pairs for the purpose of determining the surface wave velocity structure we developed an automated procedure for estimating the green s functions and subsequent tomographic inversion from the 11 325 station pairs based on the characteristics of the noise field we eliminate specific events by a procedure that does not introduce any spurious spectral distortion in the band of interest 0 05 0 2 hz further we only used the emerging arrival structure above a threshold signal to noise ratio the result is that mostly station pairs with their axes oriented toward the sea are used consistent with the noise having a microseism origin finally it is the time derivative of the correlation function that is actually related to the green s function the emergence of the time domain green s function is proportional to the square root of the recording time and inversely proportional to the square root of the distance between stations the tomographic inversion yields a surface wave velocity map that compares favorably with more conventional and elaborate experimental procedures

global scale seismic interferometry theory and numerical examples progress in the imaging of the mantle and core is partially limited by the sparse distribution of natural sources the earthquake hypocenters are mainly along the active lithospheric plate boundaries this problem can be approached with seismic interferometry in recent years there has been considerable progress in the development of seismic interferometric techniques the term seismic interferometry refers to the principle of generating new seismic responses by cross correlating seismic observations at different receiver locations the application of interferometric techniques on a global scale could create sources at locations where no earthquakes occur in this way yet unknown responses would become available for the application of travel time tomography and surface wave dispersion studies the retrieval of a dense enough sampling of source gathers would largely benefit the application of reflection imaging we derive new elastodynamic representation integrals for global scale seismic interferometry the relations are different from other seismic interferometry relations for transient sources in the sense that they are suited for a rotating closed system like the earth we use a correlation of an observed response with a response to which free surface multiple elimination has been applied to account for the closed system despite the fact that the rotation of the earth breaks source receiver reciprocity the seismic interferometry relations are shown to be valid the coriolis force is included without the need to evaluate an extra term we synthesize global scale earthquake responses and use them to illustrate the acoustic versions of the new interferometric relations when the sampling of real source locations is dense enough then both the responses with and without freesurface multiples are retrieved when we do not take into account the responses from the sources in the direct neighborhood of the seismic interferometry constructed source location the response with free surface multiples can still be retrieved even when only responses from sources at a certain range of epicentral distances are available some events in the green s function between two receiver locations can still be retrieved the retrieved responses are not perfect but the artefacts can largely be ascribed to numerical errors the reconstruction of internal events the response as if there was a source and a receiver on major contrasts within the model could possibly be of use for imaging with modelling it is possible to discover in which region of the correlation panel stationary phases occur that contribute to the retrieval of events this knowledge opens up a new way of filtering out undesired events and of discovering whether specific events could be retrieved with a given source receiver configuration

the earth s coda correlation wavefield rise of the new paradigm and recent advances abstract seismology has come a long way in providing insights into earth s internal structure and dynamics among many forward and inverse geophysical techniques developed full waveform modelling seismic tomography and receiver based studies enabled detailed imaging of earth s subsurface the invention of ambient noise tomography within the last two decades revolutionized studies of earth s subsurface based on the cross correlation of the earth s ambient noise that method in particular enabled imaging of earth structure in places where earthquakes or receivers do not exist at the same time progress in imaging the earth s deepest shells has been impeded by the lack of geometric coverage of body waves due to uneven global distribution of seismic sources and receivers and the fact that the ambient noise studies cannot reach deeper than the uppermost earth s shells near its surface in seeking the ways forward global seismologists started experimenting with cross correlating the part of the seismograms recorded many hours after the first arrivals of body waves the so called earthquake coda as in many science disciplines initial work on this topic resulted in controversies but also led to new realisations and discoveries that all contributed to the rise of a new paradigm the earthquake coda correlation wavefield which is the focus of this review paper we do not attempt here to provide a review of ambient noise correlation although we use some familiar concepts to introduce coda correlation our main goal is to review theoretical and observational work to date that resulted in a better understanding of the coda correlation wavefield both as a phenomenon and a powerful method the features in global correlograms exist due to many cross terms of reverberating body waves a principle fundamentally different from the reconstruction of surface waves in the ambient noise correlograms once the coda correlation wavefield is fully understood through theoretical developments the method becomes a powerful way to study earth s deep structure apart from providing a review of the most important results to date we scrutinise the process of making global correlograms and analyse their characteristics while taking into consideration various aspects such as the time after the earthquake the source receiver geometries the level of seismicity and the type of earthquake mechanism furthermore we provide practical examples on how to build correlograms and interpret correlogram features using programming language python our review seeks to promote the topic of coda correlation among already experienced researchers as well as students who embark on this interesting research which may play a central role in global and planetary seismology in the coming decades

measurements of frictional heating in granite a large 150 150 40 cm granite sample sawn diagonally in half to simulate a fault was deformed in a biaxial rock press at normal stress up to 6 41 mpa displacements and local shear stress were monitored along the fault 200 40 cm temperature transients as large as 10 m c were recorded following stick slip events at distances of 0 2 to 1 0 cm from the fault and were related to stress displacement and total work the temperature measurements were used to calculate the heat generated on the fault during slip frictional heating was found to be 94 2 of the total work expended in each event implying a seismic efficiency of 4 8 when water was injected onto the fault both fractional stress drop and static frictional stress increased the efficiency of frictional heating was not lowered by the presence of water heat generated during deformation of a 0 15 cm thick layer of simulated gouge was also measured for sliding rates from 0 09 to 9 1 m s in these gouge experiments temperature rises were less than 0 1 c and were proportional to sliding rate

estimation of primaries by sparse inversion from passive seismic data for passive seismic data surface multiples are used to obtain an estimate of the subsurface responses usually by a crosscorrelation process this crosscorrelation process relies on the assumption that the surface has been uniformly illuminated by subsurface sources in terms of incident angles and strengths if this is not the case the crosscorrelation process cannot give a true amplitude estimation of the subsurface response furthermore cross terms in the crosscorrelation result are not related to actual subsurface inhomogeneities we have developed a method that can obtain true amplitude subsurface responses without a uniform surface illumination assumption our methodology goes beyond the crosscorrelation process and estimates primaries only from the surface related multiples in the available signal we use the recently introduced estimation of primaries by sparse inversion epsi methodology in which the primary impulse responses are considered to be the unknowns in a large scale inversion process with some modifications the epsi method can be used for passive seismic data the output of this process is primary impulse responses with point sources and receivers at the surface which can be used directly in traditional imaging schemes the methodology was tested on 2d synthetic data

monitoring changes in velocity and q using non physical arrivals in seismic interferometry application of seismic interferometry to records from receivers at the earth s surface from sources in wells retrieves the reflection response measured at the receivers as if from virtual sources located also at the surface when the wavefields experience intrinsic losses during propagation non physical arrivals ghosts would appear in the retrieved result these ghosts appear due to waves that reflect inside a subsurface layer thus a ghost contains information about the seismic properties of the specific layer we show how such ghosts can be used to monitor layer specific changes in the velocity and intrinsic losses in the subsurface we show how to identify the ghosts using numerical modelling results from a vertical well and how to estimate the layer specific velocity and quality factor changes using numerical modelling results from a horizontal well as well as ultrasonic s wave laboratory data

imaging the d reflector with noise correlations the lowermost mantle of the earth is characterized by seismic structures that range from a few tens to thousands of kilometers at present it is difficult to test hypotheses put forward to explain seismic observations due to poor seismic coverage as particular earthquake station geometries are needed we demonstrate here that seismic noise correlations can be used to robustly image deep mantle reflections with larger stacked amplitudes of reflected waves compared with earthquake data in a comparison between noise and earthquake data we find that the arrival times and the slowness of reflected waves both sampling a region beneath siberia agree with those for a reflector at 2530 km depth and the small amplitude reflections are sufficiently clear in the noise correlations to compare them reliably with synthetic data our data open exciting prospects for illuminating new target zones in the deep mantle to further constrain the dynamics and mineralogy of the deep earth

esr dating of fault gouge the effect of grain size abstract esr signals of quartz grains in fault gouge have been partially or completely reset by movements on the fault which allows the dating of the last fault movement in order to better understand the zeroing process we have studied the variation in esr signal ad and age in various grain sizes since it can be expected that larger grains will be less affected by stress than smaller grains we propose that a plateau of constant lower age for the smallest grains indicates total resetting this is confirmed in gouge from a fault in california only such samples should be used for dating

usarray design implications for wavefield imaging in the lithosphere and upper mantle although seismic tomography is currently the mainstay of global seismic imaging the large scale deployment of portable instruments to be conducted as the usarray component of earthscope over the next decade will allow much higher resolution imaging of the solid earth using migration inversion methods similar to those used in petroleum exploration direct wavefield imaging in solid earth structural seismology has been uncommon in comparison to practices in exploration seismology generally due to the large separation between seismic stations with the development of portable observatory quality broadband 0 01 20 hz seismographs and acquisition of modest numbers of them for the passcal instrument pool over the past decade a number of academic field programs have had receiver spacing dense enough for wavefield back projection and imaging recordings from these experiments have been used in several different imaging schemes all of which are outgrowths of and bear resemblance to either post or prestack d