surface wave tomography of the western united states from ambient seismic noise rayleigh and love wave phase velocity maps summary we present the results of rayleigh wave and love wave phase velocity tomography in the western united states using ambient seismic noise observed at over 250 broad band stations from the earthscope usarray transportable array and regional networks all available threecomponent time series for the 12 month span between 2005 november 1 and 2006 october 31 have been cross correlated to yield estimated empirical rayleigh and love wave green s functions the love wave signals were observed with higher average signal to noise ratio snr than rayleigh wave signals and hence cannot be fully explained by the scattering of rayleigh waves phase velocity dispersion curves for both rayleigh and love waves between 5 and 40 speriod were measured for each interstation path by applying frequency time analysis the average uncertainty and systematic bias of the measurements are estimated using a method based on analysing thousands of nearly linearly aligned station triplets we find that empirical green s functions can be estimated accurately from the negative time derivative of the symmetric component ambient noise cross correlation without explicit knowledge of the source distribution the average traveltime uncertainty is less than 1 s at periods shorter than 24 s we present rayleigh and love wave phase speed maps at periods of 8 12 16 and 20 s the maps show clear correlations with major geological structures and qualitative agreement with previous results based on rayleigh wave group speeds

strain partitioning and progressive deformation history in a transpressive belt northern appalachians abstract syntectonic fibres within rocks of the gaspetrough a mid paleozoic slate belt within part of the acadian orogen of the canadian appalachians record the complex structural evolution of a transpressive belt the fibres occur around pyrite framboids and can be divided into five segments which record four distinct structural stages all four structural stages are related to a single progressive deformation since fibre segments can be traced continuously from the first segments to the last fibre growth patterns within the gaspetrough clearly indicate that folding occurred during coaxial deformation during the first three structural stages these structural stages are 1 layer parallel shortening 2 combined flattening and rigid body rotation and 3 cleavage development strain associated with vertical extension during these three stages accounts for approximately 50 shortening within the slate belt during the last structural stage deformation resulting from regional simple shear continued to affect the entire slate belt as local flattening within cleavage planes produced horizontal extension and brought about further tightening of folds strain recorded by the horizontal fibre increments produced during simple shear accounts for 25 shortening in this part of the appalachians oblique convergence during the acadian orogeny was partitioned in time between strike slip and reverse faulting convergence was accommodated by folding flattening and reverse faulting during the first part of the deformation and later on by flattening and dextral transcurrent faulting

laterally constrained inversion of ground roll from seismic reflection records seismic reflection data contain surface waves that can be processed and interpreted to supply shear wave velocity models along seismic reflection lines the coverage of seismic reflection data allows the use of automated multifold processing to extract high quality dispersion curves and experimental uncertainties in a moving spatial window the dispersion curves are then inverted using a deterministic laterally constrained inversion to obtain a pseudo 2d model of the shear wave velocity a monte carlo global search inversion algorithm optimizes the parameterization when the strategy is used with synthetic and field data consistent final models with smooth lateral variations are successfully retrieved this method constitutes an improvement over the individual inversion of single dispersion curves

love waves from local traffic noise interferometry surface wave interferometry on local scale usually aims at recovering rayleigh waves this is because of the predominant use of vertical component geophones in exploration seismology and the fact that rayleigh waves occur for any given subsurface structure on the other hand love waves are present only in layered media and require horizontal component geophones for their observation as they depend on shear wave velocity structure and density only the analysis of love waves provides a potentially powerful supplement to rayleigh wave inversion perhaps surprisingly recent studies show that low frequency love waves 0 05 0 1 hz excited by the interaction of ocean waves with the ocean floor the earth s microseism can be recovered by interferometry and that their s n is high compared to rayleigh waves lin et al 2008 on a regional scale jay et al 2012 analyzed the ambient noise field in a volcanic region and found that love waves with frequencies of about 0 3 hz are observed more clearly than c

1 5d inversion of lateral variation of scholte wave dispersion reliable models of in situ shear wave velocities of shallow water marine sediments are important for geotechnical applications lithological sediment characterization and seismic exploration studies we infer the 2d shear wave velocity structure of shallow water marine sediments from the lateral variation of scholte wave dispersion scholte waves are recorded in a common receiver gather generated by an air gun towed behind a ship away from a single stationary ocean bottom seismometer an offset window moves along the common receiver gather to pick up a local wavefield a slant stack produces a slowness frequency spectrum of the local wavefield which contains all modes excited by the air gun amplitude maxima dispersion curves in the local spectrum are picked and inverted for the shear wave velocity depth profile located at the center of the window as the window continuously moves along the common receiver gather a 2d shear wave velocity section is generated in a synthetic example the smooth lateral variation of surficial shear wave velocity is well reconstructed the method is applied to two orthogonal common receiver gathers acquired in the baltic sea northern germany the inverted 2d models show a strong vertical gradient of shear wave velocity at the sea floor along one profile significant lateral variation near the sea floor is observed

a 40ar 39ar study of oceanic and continental deformation processes during an oblique collision taconian orogeny in the quebec reentrant of the canadian appalachians received 7 december 2006 revised 9 january 2008 accepted 10 march 2008 published 1 july 2008 1 two phases of penetrative deformation are documented in the taconian hinterland of the appalachian orogen in the gaspepeninsula d1 is associated with the obduction of the mont albert ophiolite onto the paleozoic laurentian margin whereas d2 corresponds to later transport of allochthons across the margin in the metamorphic sole s1 is a se dipping mylonitic fabric with a downdip lineation in underlying metabasalts d1 is characterized by nw overturned and recumbent folds and a subhorizontal s1 schistosity with an ene trending orogen parallel lineation d2 is characterized by a s2 steeply dipping penetrative axial planar crenulation cleavage and ne trending f2 folds the intraoceanic thrusting of ophiolite is dated at 465 ma early d1 whereas emplacement of ophiolite andsubsequentdeformationofthemarginwasrecorded by isotopic signatures between 459 and 456 ma late d1 d2 is dated at 448 ma throughout the hinterland taconian transpressive deformation is related to an oblique collision within the quebec reentrant of the canadian appalachians during the ordovician citation malo m g ruffet a pincivy and a tremblay 2008 a 40 ar 39 ar study of oceanic and continental deformation processes during an oblique collision taconian orogeny in the quebec reentrant of the canadian appalachians tectonics 27 tc4001 doi 10 1029 2006tc002094

crustal structure beneath hudson bay from ambient noise tomography implications for basin formation summary the hudson bay basin is the least studied of four major phanerozoic intracratonic basins in north america and the mechanism by which it formed remains ambiguous we investigate the crustal structure of hudson bay based on ambient noise tomography using 21 months of continuous recordings from 37 broad band seismograph stations that encircle the bay green s functions that emerge from the cross correlation of these ambient noise recordings are dominated by fundamental mode rayleigh waves in the microseismic period band 5 20 s these signals are most prominently expressed in certain preferred azimuths indicative of stationary coastal source regions in southern alaska and labrador seasonal variations are subtle but consistent with more energetic noise sources during winter months when wave heights in the pacific and north atlantic are larger than in the summer noise emanating from hudson bay does not appear to contribute significantly to the cross correlograms group velocity dispersion curves are obtained by time frequency analysis of cross correlation functions we test and implement a signal to noise ratio snr selection method for producing one sided cross correlograms which yields better defined dispersion ridges than the standard two sided averaging approach tomographic maps and cross sections obtained in the 5 40 s period range reveal significantly lower crustal velocities beneath hudson bay than in the bounding archean superior craton the lowest mid crustal velocities correspond to a previously determined region of maximum lithospheric stretching near the centre of the basin pseudosections extracted from the tomographic inversions along profiles across hudson bay provide the first compelling direct evidence for crustal thinning beneath the basin our results are consistent with a recent estimate of 3 km of crustal thinning but not consistent with a proposed model for basin subsidence triggered by eclogitization of a remnant crustal root

paleogeography and tectono sedimentary history at the margin of laurentia during silurian to earliest devonian time the gaspe belt quebec the silurian lower devonian sequence of the gaspe belt at the laurentia margin south of the quebec reentrant and st lawrence promontory was deposited during the period between the two main orogenies that created the northern appalachians the late ordovician taconian and the middle devonian acadian orogenies although this sequence is traditionally considered to have been deposited during a period of quiescence between both orogenies significant tectonic activity attributed to the salinic disturbance began during late llandoverian telychian time and persisted until the acadian orogeny this tectonic activity has profoundly influenced the composition and distribution of the silurian earliest devonian sedimentary facies the shelf and shelf edge history at the laurentia margin along the quebec reentrant st lawrence promontory is summarized according to four broad phases phase 1 is a llandoverian wenlockian regressive phase r1 related to post taconian successor basin filling that culminated with extensive carbonate platform development phase 2 is a late wenlockian ludlovian transgressive phase t1 phase 3 corresponds to a later ludlovian pridolian second regressive phase r2 phases 2 and 3 were accompanied by extensional tectonics that produced shelf faulting and block tilting on top of which block reefs and reef complexes settled and built a reef tract all the way along the gaspe temiscouata shelf phase 4 is an early devonian phase of accelerated subsidence transgression t2 affecting the northwestern part of the segment quebec reentrant area while the southeastern part st lawrence promontory area was already uplifted due to the ongoing collision between laurentia and the western margin of gondwana related terranes to the south composition and distribution of sedimentary facies were controlled by the interaction of tectonics sediment influx and sea level fluctuations construction of a post taconian pre acadian palinspastic map to plot facies has proven to be basic to obtaining a realistic picture of the paleogeography of the shelf and shelf edge of the gaspe temiscouata segment at the margin of the laurentia craton during the silurian earliest devonian time interval

seismic exploration scale velocities and structure from ambient seismic noise 1 hz the successful surface waves retrieval in solid earth seismology using long time correlations and subsequent tomographic images of the crust have sparked interest in extraction of subsurface information from noise in the exploration seismology subsurface information in exploration seismology is usually derived from body wave reflections 1 hz which is challenging for utilization of ambient noise we use 11 h of noise recorded in the sirte basin libya first we study the characteristics of the noise we show that the bulk of the noise is composed of surface waves at frequencies below 6 hz some noise panels contain nearly vertically traveling events we further characterize these events using a beamforming algorithm from the beamforming we conclude that these events represent body wave arrivals with a fairly rich azimuthal distribution having body wave arrivals in the noise is a prerequisite for body wave reflections retrieval we crosscorrelate and sum the recorded ambient noise panels to retrieve common source gathers following two approaches using all the noise and using only noise panels containing body wave arrivals likely to contribute to the reflections retrieval comparing the retrieved gathers with active seismic data we show that the two way traveltimes at short offsets of several retrieved events coincide with those of reflections in the active data and thus correspond to apexes of reflections we then compare retrieved stacked sections of the subsurface from both approaches with the active data stacked section and show that the reflectors are consistent along a line the results from the second approach exhibit the reflectors better

evaluation of hydrocarbon potential of the paleozoic cambrian devonian source rocks of the gaspe peninsula quebec canada geochemical characterization expulsion efficiency and erosion scenario several petroleum source rocks and reservoirs are recognized in the gaspe peninsula quebec canada and numerous geochemical data were published on source rocks for wells drilled in both the cambrian ordovician and silurian devonian series the aim of this work is to evaluate their respective contribution of oil and gas prospects and to prepare geochemical input data for a further basin modeling study rocks samples were collected from both series 46 from the cambrian ordovician formations and 275 from the silurian devonian formations they were collected mainly from well cuttings and a few of them come from outcrops most of the silurian devonian rocks are lean rocks with organic carbon content corg lower than 0 5 they exhibit systematic abnormal s1 free hydrocarbons and s2 potential hydrocarbons peaks from rock eval 6 profiles with compounds detected before and after the s2 peak however typical s2 peak profiles were obtained in isolated kerogens after solvent extraction kerogens were sorted with increasing depth between 1200 and 2600 m 3937 8530 ft the observed hydrogen index hi value decrease is correlated with an h c ratio decrease and a vitrinite reflectance ro increase the amount of extract is about 200 mg g c whatever the burial depth these results suggest that silurian devonian rocks underwent thermal maturation between 0 8 and 1 4 ro their capacity to expel oil seems to be very limited however they have potential as gas shale finally a minimum regional erosion thickness about 4300 m 14 108 ft was derived by comparing the computed hi evolution with the observed trend for a geothermal gradient at 23c km for the cambrian ordovician rocks corg values are richer in both immature and mature samples the s1 and s2 peaks from rock eval 6 profiles are standard with hi values more than 300 to 400 mg g c the ro being more than 1 6 these source rocks are more oil than gas prone

retrieving 2d structures from surface wave data by means of space varying spatial windowing abstractsurface wave techniques are mainly used to retrieve 1d subsurface models however in 2d environments the 1d approach usually neglects the presence of lateral variations and because the surface wave path crosses different materials the resulting model is a simplified or misleading description of the site we tested a processing technique to retrieve 2d structures from surface wave data acquired with a limited number of receivers our technique was based on a two step process first we extracted several local dispersion curves along the survey line using a spatial windowing based on a set of gaussian windows with different shapes the window maxima span the survey line so that we were able to extract a dispersion curve from the seismic record for every window this provided a set of local dispersion curves each of them referring to a different subsurface portion this space varying spatial windowing provided a good compromise between wavenumber resolution and the lateral resolution of the obtain

shear wave imaging from traffic noise using seismic interferometry by cross coherence we apply the cross coherence method to the seismic interferometry of traffic noise which originates from roads and railways to retrieve both body waves and surface waves our preferred algorithm in the presence of highly variable and strong additive random noise uses cross coherence which uses normalization by the spectral amplitude of each of the traces rather than crosscorrelation or deconvolution this normalization suppresses the influence ofadditive noise and overcomes problems resulting from amplitudevariations among input traces by using only the phase information and ignoring amplitude information the method effectively removes the source signature from the extracted response and yields a stable structural reconstruction even in the presence of strong noise this algorithm is particularly effective where the relative amplitude among the original traces is highly variable from trace to trace we use the extracted reflected shear waves from the traffic noise data to construct a stackedandmigratedimage andweusetheextractedsurfacewaves love waves to estimate the shear velocity as a function of depth this profile agrees well with the interval velocity obtained from the normal moveout of the reflected shear waves constructed by seismic interferometry these results are useful in a wide range of situations applicable to both geophysics and civil engineering

characterization of shallow geology by high frequency seismic noise tomography summary to study the applicability of the passive seismic interferometry technique to near surface geological studies seismic noise recordings from a small scale 2 d array of seismic stations were performed in the test site of nauen germany rayleigh wave green s functions were estimated for different frequencies a tomographic inversion of the traveltimes estimated for each frequency from the green s functions is then performed allowing the laterally varying 3 d surface wave velocity structure below the array to be retrieved at engineering geotechnical scales furthermore a 2 d s wave velocity cross section is obtained by combining 1 d velocity structures derived from the inversion of the dispersion curves extracted at several points along a profile where other geophysical analyses were performed it is shown that the cross section from passive seismic interferometry provides a clear image of the local structural heterogeneities that are in excellent agreement with georadar and geoelectrical results such findings indicate that the interferometry analysis of seismic noise is potentially of great interest for deriving the shallow 3 d velocity structure in urban areas

crustal structure beneath the dabie orogenic belt from ambient noise tomography abstract the qinling dabie sulu orogenic belt in east central china is the largest high and ultrahigh pressure hp and uhp metamorphic zone in the world the dabie mountains are the central segment of this orogenic belt between the north china and yangtze cratons this work studies the nature of the crustal structure beneath the dabie orogenic belt to better understand the orogeny to do that we apply ambient noise tomography to the dabie orogenic belt using ambient noise data from 40 stations of the china national seismic network cnsn between january 2008 and december 2009 we retrieve high signal noise ratio snr rayleigh waves by cross correlating ambient noise data between most of the station pairs and then extract phase velocity dispersion measurements from those cross correlations using a spectral method taking those dispersion measurements we obtain high resolution phase velocity maps at 8 35 second periods by inverting rayleigh wave phase velocity maps we construct a high resolution 3d shear velocity model of the crust in the dabie orogenic belt the resulting 3d model reveals interesting crustal features related to the orogeny high shear wave velocities are imaged beneath the hp uhp metaphoric zones at depths shallower than 9 km suggesting that hp uhp metaphoric rocks are primarily concentrated in the upper crust underlying the high velocity hp uhp metamorphic zones low shear velocities are observed in the middle crust probably representing ductile shear zones and or brittle fracture zones developed during the exhumation of the hp uhp metamorphic rocks strong high velocities are present beneath the northern dabie complex unit in the middle crust possibly related to cooling and crystallization of intrusive igneous rocks in the middle crust resulting from the post collisional lithosphere delamination and subsequent magmatism a north dipping moho is revealed in the eastern dabie with the deepest moho appearing beneath the northern dabie complex unit consistent with the model of triassic northward subduction of the yangtze craton beneath the north china craton

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

petroleum generation and migration in the cambro ordovician laurentian margin succession of nw scotland fluid inclusion and organic biomarker data show that there was formerly a hydrocarbon system in the cambro ordovician laurentian margin rocks of nw scotland oil fluid inclusions occur in stylolitized eriboll formation sandstone in k feldspar cements with an 40 ar 39 ar age of 415 5 5 5 8 ma 2 analytical precision full external precision organic extracts from durness group black limestones yield biomarker ratios characteristic of high thermal maturity organic maturation to yield oil probably occurred during orogenic deformation along the moine thrust zone the recognition of a hydrocarbon system in scotland adds to a huge hydrocarbon province in laurentian rocks including north america and greenland supplementary material technical data for ar ar dating are available at https doi org 10 6084 m9 figshare c 3879616

high resolution 3d shallow crustal structure in long beach california application of ambient noise tomography on a dense seismic array ambient noise tomography has proven to be effective in resolving shallow earth structure we applied ambient noise tomography on a dense seismic array in long beach california the array was composed of more than 5200 stations with an average spacing close to 100 m three weeks of passive ambient noise were crosscorrelated between each station pair which resulted in more than 13 5 million crosscorrelations within the area clear fundamental mode rayleigh waves were observed between 0 5 and 4 hz which were most sensitive to structure above 1 km depth for each station pair we applied frequency time analysis to determine the phase traveltime dispersion and for each frequency we applied eikonal tomography to determine the rayleigh wave phase velocity map the eikonal tomography accounted for ray bending by tracking the wavefront and allowed uncertainties to be estimated through statistical analysis the compilation of phase velocity maps was then used to invert for 3d shear velocity structure the inverted model showed clear correlation with the known geologic features such as the shallow south north velocity dichotomy and a deeper fast anomaly associated with the newport inglewood fault zone our results can potentially be used to complement traditional active source studies

time lapse monitoring of internal erosion in earthen dams and levees using ambient seismic noise earthen dams and levees are prone to progressive failure through internal erosion of their structure internal erosion is often invisible to current methods of inspection until it manifests itself

a comprehensive comparison between the refraction microtremor and seismic interferometry methods for phase velocity estimation abstractpassive source seismic noise based surface wave methods are now routinely used to investigate the near surface geology in urban environments these methods estimate the s wave velocity of the near surface and two methods that use linear recording arrays are seismic interferometry si and refraction microtremor remi these two methods process noise data differently and thus can yield different estimates of the surface wave dispersion the data used to estimate the s wave velocity we have systematically compared these two methods using synthetic data with different noise source distributions we arrange sensors in a linear survey grid which is conveniently used in urban investigations e g along roads we find that both methods fail to correctly determine the low frequency dispersion characteristics when outline noise sources become stronger than inline noise sources we also identify an artifact in the remi method and theoretically explain the origin of this artifact we determine that si

faster better shear wave velocity to 100 meters depth from refraction microtremor arrays current techniques of estimating shallow shear velocities for assessment of earthquake site response are too costly for use at most construction sites they require large sources to be effective in noisy urban settings or specialized independent recorders laid out in an extensive array this work shows that microtremor noise recordings made on 200 m long lines of seismic refraction equipment can estimate shear velocity with 20 accuracy often to 100 m depths the combination of commonly available equipment simple recording with no source a wavefield transformation data processing technique and an interactive rayleigh wave dispersion modeling tool exploits the most effective aspects of the microtremor spectral analysis of surface wave sasw and multichannel analysis of surface wave masw techniques the slowness frequency wavefield transformation is particularly effective in allowing accurate picking of rayleigh wave phase velocity dispersion curves despite the presence of waves propagating across the linear array at high apparent velocities higher mode rayleigh waves body waves air waves and incoherent noise two locations illustrate the application of this technique in detail coincident with a large accelerometer microtremor array in reno nevada and atop a borehole logged for shear velocity in newhall california refraction equipment could duplicate microtremor results above 3 hz but could not estimate velocities deeper than 100 m refraction microtremor cannot duplicate the detail in the velocity profile yielded by a suspension logger but can match the average velocity of 10 to 20 m depth intervals and suggest structure below the 100 m logged depth of the hole eight additional examples from southern california and new zealand demonstrate that the refraction microtremor technique quickly produces good results from a wide range of hard and soft sites

seismic surface waves in a suburban environment active and passive interferometric methods seismic interferometry refers to a new range of methods where inter receiver wavefields those that would have been recorded if one of each pair of receivers had been a source can be estimated by cross correlation of wavefields recorded at each of the receivers these methods have found many applications in different fields of seismology including creating virtual sources in wells under complex overburdens computational full wavefield modelling and passive construction of surface wave waveforms from background noise in the earth curtis et al 2006 provide an overview of various applications of seismic interferometry referred to herein and more in depth works can be found in the special supplement on seismic interferometry in the july august issue of geophysics

v s profiles from noise cross correlation at local and small scale ambient noise measurements have been performed at local and small scales in the neapolitan and surrounding areas campania southern italy by employing two broad band kinemetrics q330 stations equipped with episensor es t three component accelerometers in both experiments frequency time analysis ftan method has been performed on the vertical and radial components of noise cross correlations to retrieve the rayleigh wave dispersion green s function at local scale over an interstation distance of about 26 km the group velocity dispersion values have been compared with those obtained from ftan analysis on recordings of two earthquakes with similar path at small scale measurements have been carried out over an interstation distance of about 440 m in the public gardens of scampia the northernmost quarter of naples the rayleigh wave group velocity dispersion data obtained from noise cross correlation have been combined with those from active seismic experiment along the same alignment but shorter 120 m offset the non linear inversion of such a dispersion curve has allowed the definition of v s models to depths of 100 m in agreement with nearby stratigraphy moreover a good agreement has resulted for the resonance frequency among the h v ratio the ellipticity of the fundamental mode computed for the chosen v s model and the average two dimensional 2d spectral amplification computed along a cross section representative of the scampia quarter

interferometric multichannel analysis of surface waves imasw abstract refraction microtremor remi and multichannel analysis of surface waves masw are effective approaches to estimate shallow shear wave velocity v s structure often needed to estimate ground motions using recent ground motion prediction relations interferometric masw imasw uses slowness frequency slant stack analyses combined with interferometric time domain dispersion analyses to improve resolution of lower frequency rayleigh wave dispersion to better constrain v s cross correlation interferometry is used to obtain deterministic correlation green s function cgf imasw seismograms from ambient noise and or active source wave fields contained in remi and or masw data the cgfs are processed using the multiple filter technique to estimate phase and group dispersion in the imasw approach active seismic sources ensure that the stationary phase contributions to cross correlations dominate cgf responses in a single imasw profile each geophone represents a virtual source and the imasw approach stacks cgf common offset data from all virtual sources to obtain a single averaged forward and reverse record section cgf time domain and slowness frequency phase slowness estimates are combined with cgf time domain group slowness estimates for a consistency check on dispersion picks a multistate monte carlo approach is used to estimate mean slowness depth and slowness uncertainties imasw is evaluated with passive remi data from two sites and active source imasw at six sites with independent downhole velocity depth logs comparison of six p s suspension log imasw profile pairs across the van norman complex in northern san fernando valley shows that on average 30 m depth shear wave velocity estimates between the two methods differed by p s suspension log measurements of v s were made at the imasw profile midpoint the imasw v s depth inversions resolve 3 m thickness v s variations accurately to the bottom of one borehole at 40 m depth and to 100 m depth at a 200 m deep borehole site

a workshop examination of shallow seismic reflection surveying in september 1996 the office of basic energy sciences of the u s department of energy doe sponsored a research workshop in berkeley california where approximately 20 participants analyzed the potential and limitations of near surface seismic reflection methods

a sediment nutrient oxygen feedback responsible for productivity variations in late miocene sapropel sequences of the western mediterranean abstract cyclic sediments observed throughout the mediterranean during the late miocene have been related to precessional forcing of ocean stratification individual couplets typically 2 m thick sequences of sapropels and diatom rich marls can be reliably traced from western spain to crete and were formed in restricted marginal basins micropaleontological evidence indicates paradoxically that the organic carbon rich sapropels were formed under low productivity conditions marked by surface water stratification and deep anoxia whereas the diatom rich marls were formed under high productivity conditions marked by upwelling here we present geochemical evidence mainly from detailed phosphorus determinations and paleo redox proxies indicating that a sediment nutrient oxygen feedback herein dubbed the sno effect is in part responsible for driving the observed productivity variations during stratification anoxic conditions in these basins cause the release of the limiting nutrient phosphorus from reducible oxide phases in the sediments basin stagnation causes the buildup of phosphorus below the photic zone subsequent overturn driven by precessionally driven winds injects phosphorus rich bottom waters into the photic zone the biotic response to this overturn is high productivity in marls directly overlying the sapropels culminating in diatom mat formation exhaustion of the stored excess phosphorus results in lower productivity marls which grade back into sapropels due to lower wind stresses and the return of stagnant basin conditions these findings indicate that the sno effect may in part be responsible for precessional scale productivity variations observed in parts of the mediterranean and perhaps present in other restricted ocean basins like the miocene monterey formation and the modern santa barbara basin

s waves profiles from noise cross correlation at small scale abstract cross correlations of ambient seismic noise recordings are studied to infer shear wave velocities vs profiles versus depth experiments are performed over inter station distances ranging from 60 m to about 400 m in the crowded and noisy historical centre of napoli where the conditions for the use of active controlled source seismic spreadings are prohibitive even for just one receiver from the noise cross correlation group velocity dispersion curves are extracted with ftan method and their non linear inversion supplies vs profiles versus depth the information of nearby stratigraphies and the range of vs variability for samples of neapolitan soils and rocks confirms the validity and reliability of the results obtained with our expeditious procedure if successfully tested in other geological settings the proposed approach is a low cost methodology to get reliable vs velocity profiles versus depth

application of a complete workflow for 2d elastic full waveform inversion to recorded shallow seismic rayleigh waves abstractthe s wave velocity of the shallow subsurface can be inferred from shallow seismic rayleigh waves traditionally the dispersion curves of the rayleigh waves are inverted to obtain the local s wave velocity as a function of depth two dimensional elastic full waveform inversion fwi has the potential to also infer lateral variations we have developed a novel workflow for the application of 2d elastic fwi to recorded surface waves during the preprocessing we apply a line source simulation spreading correction and perform an a priori estimation of the attenuation of waves the iterative multiscale 2d elastic fwi workflow consists of the preconditioning of the gradients in the vicinity of the sources and a source wavelet correction the misfit is defined by the least squares norm of normalized wavefields we apply our workflow to a field data set that has been acquired on a predominantly depth dependent velocity structure and we compare the reconstructed s wave velocity model with the result

multichannel analysis of passive surface waves based on crosscorrelations abstractpassive seismic methods in highly populated urban areas have gained much attention from geophysics and civil engineering communities because traditional seismic surveys especially in complex urbanized environments might be improperly applied in passive seismic methods directional noise sources will inevitably bring azimuthal effects and spatial aliasing to dispersion measurements due to the fact that true randomness of ambient noise cannot be achieved in reality to solve these problems multichannel analysis of passive surface maps waves based on long noise sequence crosscorrelations is proposed we have introduced a hybrid method of seismic interferometry and the roadside passive multichannel analysis of surface waves masw using crosscorrelation to produce common virtual source gathers from 1 h multichannel noise records common virtual source gathers are then used to do dispersion analysis with an active scheme based on phase shift measurement synthetic tests demonstrated the advantage

palinspastic restoration of a post taconian successor basin deformed within a transpressive regime northern appalachians restoration of transpressional orogens requires a three dimensional analysis of the strain state in order to take into account both the pure shear and simple shear components of the deformation and assess their relative contribution throughout the deformation history restoration of the post taconian successor basin the gaspe belt located within the external part of the acadian orogen in the canadian appalachians was performed by using a step by step method based on the successive removal of strain increments the pure shear component contributed 70 of the total strain during the first stages of the deformation whereas the simple shear component contributed 30 of the total strain during the last stages three retrodeformation steps are defined starting with restoration of the last deformation stage and working back to the first deformation stage the first step is to restore slip along acadian strike slip faults the second step is to restore shortening related to the horizontal extension during the acadian regional simple shear event finally the third step is to restore vertical extension related to the pure shear event by removing slip along the reverse faults unfolding and removing internal strain associated with cleavage development retrodeformation of the simple shear component of the transpressive deformation during the first two steps is performed on a horizontal view of the gaspe belt basin which contains the horizontal extension direction and which is perpendicular to the acadian nw se directed compression likewise restoration of the pure shear component is performed in vertical sections which contain the vertical extension and which are perpendicular to the acadian nw se directed compression the palinspastic map presented here is a much more appropriate base map for the basin and allows for a more realistic paleogeographic interpretation of the gaspe belt

retrieval of local surface wave velocities from traffic noise an example from the la barge basin wyoming abstract in regions where active source seismic exploration is constrained by limitations of energy penetration and recovery cost and logistical concerns or regulatory restrictions analysis of natural source seismic data may provide an alternative in this study we investigate the feasibility of using locally generated seismic noise in the 2 6 hz band to obtain a subsurface model via interferometric analysis we apply this technique to three component data recorded during the la barge passive seismic experiment a local deployment in south western wyoming that recorded continuous seismic data between november 2008 and june 2009 we find traffic noise from a nearby state road to be the dominant source of surface waves recorded on the array and observe surface wave arrivals associated with this source up to distances of 5 kms the orientation of the road with respect to the deployment ensures a large number of stationary points leading to clear observations on both in line and cross line virtual source receiver pairs this results in a large number of usable interferograms which in turn enables the application of standard active source processing methods like signal processing common offset stacking and traveltime inversion we investigate the dependency of the interferograms on the amount of data on a range of processing parameters and on the choice of the interferometry algorithm the obtained interferograms exhibit a high signal to noise ratio on all three components rotation of the horizontal components to the radial transverse direction facilitates the separation of rayleigh and love waves though the narrow frequency spectrum of the surface waves prevents the inversion for depth dependent shear wave velocities we are able to map the arrival times of the surface waves to laterally varying group and phase velocities for both rayleigh and love waves our results correlate well with the known geological structure we outline a scheme for obtaining localized surface wave velocities from local noise sources and show how the processing of passive data benefits from a combination with well established exploration seismology methods we highlight the differences with interferometry applied to crustal scale data and conclude with recommendations for similar deployments

surface wave tomography from microseisms in southern california received 5 april 2005 revised 23 may 2005 accepted 9 june 2005 published 26 july 2005 1 since it has already been demonstrated that point topoint seismic propagation green functions can be extracted from seismic noise it should be possible to image earth structure using the ambient noise field seismic noise data from 148 broadband seismic stations in southern california were used to extract the surface wave arrival times between all station pairs in the network the seismic data were then used in a simple but densely sampled tomographic procedure to estimate the surface wave velocity structure within the frequency range of 0 1 0 2 hz for a region in southern california the result compares favorably with previous estimates obtained using more conventional and elaborate inversion procedures this demonstrates that coherent noise field between station pairs can be used for seismic imaging purposes citation sabra k g p gerstoft p roux w a kuperman and m c fehler 2005 surface wave tomography from microseisms in southern california geophys res lett 32 l14311 doi 10 1029 2005gl023155

extracting earth s elastic wave response from noise measurements recent research has shown that noise can be turned from a nuisance into a useful seismic source in seismology and other fields in science and engineering the estimation of the system response from noise measurements has proven to be a powerful technique to convey the essence of the method we first treat the simplest case of a homogeneous medium to show how noise measurements can be used to estimate waves that propagate between sensors we provide an overview of physics research dating back more than 100 years showing that random field fluctuations contain information about the system response this principle has found extensive use in surface wave seismology but can also be applied to the estimation of body waves because noise provides continuous illumination of the subsurface the extracted response is ideally suited for time lapse monitoring we present examples of time lapse monitoring as applied to the softening of soil after the 2011 tohoku oki earthquake the detection of a precursor to a landslide and temporal changes in the lunar soil

ambient noise rayleigh wave tomography in western sichuan and eastern tibet abstract we perform rayleigh wave tomography in western sichuan and eastern tibet by applying the ambient noise method to broadband data recorded at 49 stations from the sichuan digital seismic network cross correlations of vertical component ambient noise data are computed in one hour segments and stacked over 7 months from june to december 2007 then rayleigh wave group dispersion curves from 6 to 48 s were measured using the multiple filter analysis method group velocity maps at periods from 8 to 44 s were inverted the resulting group velocity maps generally show good correlations with tectonic features the sichuan basin is clearly resolved with lower group velocities at the short periods 8 to 20 s due to thick sedimentary layers and a prominent low velocity zone exhibits in the middle crust beneath the eastern margin of the tibetan plateau the longmen shan thrust belt marks not only the rapid lateral velocity variation between the topographically high tibetan plateau and low elevation sichuan basin but also the transition from the thick crust beneath the tibetan plateau to the normal continental crust beneath the sichuan basin

precession related sapropelites of the messinian sorbas basin south spain paleoenvironmental significance abstract the sorbas basin southern spain is a narrow and elongated basin located in the betic corridor that formed the northern connection between the atlantic and the paleomediterranean during the late miocene in the centre of the basin about 120 m of well preserved cyclic marine sediments crop out ranging in age from 7 2 to 6 myr these cycles make up the abad member and are an excellent example of precession control over sedimentation in the upper part of the sequence upper abad member the cycles include organic rich laminated brown marls sapropelites alternating with homogeneous marls displaying diatomite layers the om rich laminated marls are the westernmost sapropelites of the mediterranean this paper is a geochemical mineralogical sedimentological and micropaleontological analysis of three cycles with sapropelites the data enable us to distinguish two main climatic scenarios the climate which dominated each of these scenarios regulated the sedimentology and the physico chemistry of the water column resulting in the sapropelite homogeneous marl cyclic alternations the sapropelites developed during a climate characterised by a long period of temperate and humid conditions that occur at times of precession minima these climatic conditions changed progressively to a subarid and drier weather during which homogeneous sediments were deposited the changes between these scenarios were gradual as expected from precession dynamics our data suggest that the change from the subarid to the humid climate transition from homogeneous marls to laminated sapropelites took place at a faster rate or at least was recorded more rapidly by the sediments than the transition from the humid interval to the sub arid period

along strike acadian structural variations in the quebec appalachians consequence of a collision along an irregular margin the quebec appalachians have been shaped by two major orogenies the middle to late ordovician taconian and the middle devonian acadian thrust faults and nappe structures characterized the taconian deformation throughout the quebec appalachians whereas structural styles pertaining to the acadian orogeny differ from southern quebec to the gaspe peninsula structural analysis of late ordovician to middle devonian supracrustal rocks shows two different acadian deformational regimes strike slip tectonics in the gaspe peninsula and thrust or dip slip tectonics in southern quebec in southern quebec acadian regional deformation produced folds which vary from upright to overturned and tight to isoclinal from the nw to the se major faults e g la guadeloupe are northwestward directed thrust faults marked by highly ductile shear zones outlined by mylonite in the gaspe peninsula structural trend is ne and major e w dextral strike slip faults transect this trend folds are open and upright inclined and tighter near the major faults where they have a clockwise rotation like the regional cleavage major faults e g grand pabos follow corridors delimiting high strain zones where the fabrics developed are indicative of a ductilebrittle regime of deformation in the temiscouata region major structural features of both southern quebec and the gaspe peninsula are recognized structures of this region consist of ene trending dextral strike slip faults and high angle wnw verging reverse faults parallel to major nne folds these structures reflect the transition from purely horizontal movement along major strike slip faults of the gaspe peninsula to vertical movement along thrust faults in southern quebec acadian structural variations within the quebec appalachians are interpreted in terms of a continental collision of gondwana along the irregular margin of laurentian and its taconian accreted terranes

review and new aspects concerning the formation of eastern mediterranean sapropels abstract in this paper it is proposed that the formation of eastern mediterranean sapropels occurred in an anti estuarine type of circulation which was to some degree weakened relative to the present in response to reduction of the eastern mediterranean excess of evaporation over freshwater input this reduction of excess evaporation would have been imposed by intensifications of 1 the indian ocean summer sw monsoon influencing the eastern mediterranean via increased nile discharge and 2 the system of mediterranean depressions an element of the westerly atlantic system causing increased precipitation and decreased evaporation both the indian ocean summer monsoon and the westerly atlantic system would be intensified in response to the occurrence of distinct minima in the cycle of precession it is demonstrated that reduced excess evaporation whether or not coinciding with global phases of deglaciation would lead to reduction of surface water salinities in the eastern mediterranean causing isolation of previously formed high salinity cooler deep water thus mixing was severely reduced possibly even restricted to eddy diffusion with only occasional convective events that because of the existing density gradient hardly ever would reach the deepest parts of the basin the consequently diminished oxygen advection down from a few hundred meters in the water column favoured preservation of the sinking organic matter this would however suffice only to enable the formation of sapropels with low organic carbon contents the high organic carbon contents observed in various sapropels are argued to reflect superimposed increases of export production the described scenario accounts for previously reported 1 increases of organic carbon content with increasing depth of deposition within individual sapropels and 2 asymmetrical sequences of sapropel deposition characterized by gradual build up and rather abrupt ending it is furthermore in agreement with 3 isotopic and faunal reconstructions of the history of exchange transports through both the strait of sicily and the strait of gibraltar and 4 faunal and floral reflections of the presence or absence of a distinct deep chlorophyll maximum with its associated increases in export production indicating the presence or absence of a shallow pycnocline within the euphotic layer moreover the described scenario 5 is in no way conflicting with the reports of sapropels in the western mediterranean and 6 seems to be endorsed by occasionally intercalated intervals suggestive of somewhat improved oxygenation amidst anoxic benthic desert levels a situation that has been observed in a few quaternary and pliocene sapropels

sulphidic mediterranean surface waters during pliocene sapropel formation sapropels organic matter rich layers are common in neogene sediments of the eastern mediterranean sea the formation of these layers has been attributed to climate related increases in organic matter production1 2 3 and increased organic matter preservation due to oxygen depletion in more stagnant bottom waters2 3 here we report that eastern mediterranean pliocene sapropels4 contain molecular fossils of a compound isorenieratene known to be synthesized by photosynthetic green sulphur bacteria suggesting that sulphidic euxinic and therefore anoxic conditions prevailed in the photic zone of the water column these sapropels also have a high trace metal content which is probably due to the efficient scavenging of these metals by precipitating sulphides in a euxinic water column the abundance and sulphur isotope composition of pyrite are consistent with iron sulphide formation in the water column we conclude that basin wide water column euxinia occurred over substantial periods during pliocene sapropel formation in the eastern mediterranean sea and that the ultimate degradation of the increased organic matter production was strongly influential in generating and sustaining the euxinic conditions