a joint monte carlo analysis of seafloor compliance rayleigh wave dispersion and receiver functions at ocean bottom seismic stations offshore new zealand teleseismic body wave imaging techniques such as receiver function analysis can be notoriously difficult to employ on ocean bottom seismic data due largely to multiple reverberations within the water and low velocity sediments in lieu of suppressing this coherently scattered noise in ocean bottom receiver functions these site effects can be modeled in conjunction with shear velocity information from seafloor compliance and surface wave dispersion measurements to discern crustal structure a novel technique to estimate 1 d crustal shear velocity profiles from these data using monte carlo sampling is presented here we find that seafloor compliance inversions and p s conversions observed in the receiver functions provide complimentary constraints on sediment velocity and thickness incoherent noise in receiver functions from the moana ocean bottom seismic experiment limit the accuracy of the practical analysis at crustal scales but synthetic recovery tests and comparison with independent unconstrained nonlinear optimization results affirm the utility of this technique in principle

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

detailed crustal thickness variations beneath the illinois basin area implications for crustal evolution of the midcontinent we present high resolution imaging results of crustal and upper mantle velocity discontinuities across the illinois basin area using both common conversion point stacking and plane wave migration methods applied to p wave receiver functions from the earthscope oiink ozark illinois indiana and kentucky experiment the images reveal unusually thick crust up to 62 km throughout the central and southeastern illinois basin area a significant moho gradient underlies the nw trending ste genevieve fault zone which delineates the boundary between the illinois basin and ozark dome relatively thinner crust 45 km underlies most of the precambrian highlands surrounding the illinois basin and beneath the rift related structures of the reelfoot rift and the rough creek graben we consider four hypotheses to explain the presence of thick crust under the central and southeastern illinois basin crustal thickening may have been produced 1 prior to its accretion to north america around 1 55 ga and is an inherited characteristic of this crustal province 2 by underthrusting or shortening during proterozoic convergent margin tectonics around 1 55 1 35 ga 3 by late precambrian magmatic underplating at the base of older crust associated with the creation of the eastern granite rhyolite province around 1 3 ga and 4 through crustal relamination during an episode of proterozoic flat slab subduction beneath the illinois basin possibly associated with the grenville orogeny

imaging crustal discontinuities and the downgoing slab beneath western crete the migration of teleseismic receiver functions yields high resolution images of the crustal structure of western crete data were collected during two field campaigns in 1996 and 1997 by networks of six and 47 short period three component seismic stations respectively a total of 1288 seismograms from 97 teleseismic events were restituted to true ground displacement within a period range from 0 5 to 7 s the application of a noise adaptive deconvolution filter and a new polarization analysis technique helped to overcome problems with local coda and noise conditions the computation and migration of receiver functions results in images of local crustal structures with unprecedented spatial resolution for this region the crust under crete consists of a continental top layer of 15 20 km thickness above a 20 30 km thick subducted fossil accretionary wedge with a characteristic en echelon fault sequence the downgoing oceanic moho lies at a depth of 40 60 km and shows a topography or undulation with an amplitude of several kilometres as a consequence of slab depth and distribution of local seismicity the mediterranean ridge is interpreted as the recent accretionary wedge

site amplification scattering and intrinsic attenuation in the mississippi embayment from coda waves we estimate site amplification intrinsic q q i and scattering q q s values from three component coda of broadband data recorded by cooperative new madrid sesimic network stations for center frequencies 0 2 0 5 1 0 2 0 and 5 0 hz near 0 5 and 1 0 hz site amplification factors for the transverse component recorded by stations in the mississippi embayment are between 1 7 and 18 compared with stations outside the embayment the amplification factor becomes smaller at frequencies lower than 0 5 hz and higher at those greater than 1 0 hz the radial component shows a similar amplification however the vertical component shows relatively less amplification q i and q s are estimated from coda using an energy flux model for two time windows after the direct s wave and at 0 5 and 1 0 hz center frequencies the two time windows include coda up to and after twice the s wave travel time at each station coda parameters change with the time window and are attributed to a mixture of incoherent coda with coherent s wave reverberations directly after the s wave q i and q s inferred from stations outside of the embayment have higher values than those from stations within the embayment a plane wave model qualitatively explains the lack of coda amplification at high frequencies compared with a low frequency without recourse to anelastic attenuation arguments however the plane wave model cannot explain the very large observed coda amplifications at 1 and 0 5 hz seen in the data suggesting that other wave scattering effects must be occurring in the embayment velocity structure this is consistent with the relatively low q s values inferred from the energy flux model for stations within the embayment in addition to coda amplification we performed a synoptic noise study that revealed that pre event ambient background noise behaves in a similar manner to the coda for stations within and outside of the embayment the presence of large lateral velocity heterogeneities in the embayment may cause q s values to be low there

post critical sspmp and its applications to virtual deep seismic sounding vdss 1 sensitivity to lithospheric 1 d and 2 d structure virtual deep seismic sounding vdss has recently emerged as a novel method to image the moho and potentially other lithospheric boundaries the behaviour of sspmp the post critical reflection phase at the moho that is utilized in vdss is rich with complexities not yet widely considered here motivated by observations from the ordos plateau in north china we use synthetic seismograms computed with a broad range of 1 d models to evaluate how different parts of the lithosphere along the ray path of sspmp affect its phase amplitude and arrival time our findings include 1 when the crust mantle boundary is a sharp discontinuity the sspmp phase shift relative to the direct s wave is controlled by lower crustal v p upper mantle v p and ray parameter this property indicates the possibility of using sspmp to constrain v p in the lower crust and uppermost mantle 2 when the crust mantle boundary is a velocity gradient zone sspmp arrival times vary as different functions of ray parameter from cases with a sharp crust mantle boundary because different rays turn at different depths this feature allows measurement of the vertical velocity gradient in the crust mantle transition zone with sspmp 3 when the virtual source location of s to p conversion at the free surface is in a sedimentary basin sspmp amplitude can be significantly reduced due to low s to p reflected energy at the virtual source this may cause the absence of sspmp despite appropriate source receiver geometry in addition to 1 d models we further conduct 2 d waveform modelling and find that the sspmp arrival time relative to direct s is not only controlled by crustal thickness at the reflection point but also by lateral variation of v s beneath the virtual source and receiver therefore in areas with significant lateral heterogeneity in the lithosphere the accuracy of crustal thickness measurements from sspmp arrival times depends on our knowledge of the variability of lithospheric structure across a broad region

the vertical component p wave receiver function the vertical component p wave receiver function is an important source of data in studies of the crust mantle transfer function for determining earth structure under isolated receivers or under receiver arrays this waveform illuminates a missing aspect of the wave propagation in receiver function studies that employ only the horizontal components of motion and yields complementary constraints on near receiver heterogeneity and p wave propagation the vertical component p wave receiver function is formed using an array estimate for the effective teleseismic source function that is then deconvolved from all the vertical and horizontal components of ground motion at each station in the array one dimensional three dimensional and stochastic wave propagation models are used to test the robustness of the technique breakdown of single station receiver function deconvolution occurs because of high levels of noncorrelated noise between the ground motion components receiver functions for stations of the southern california terrascope array are investigated using the array technique vertical receiver functions for stations in the los angeles basin and long valley caldera show high amplitude secondary arrivals that cannot be explained by simple 1d structures but probably reflect wave propagation in 3d basin structures three component receiver functions from the station at mammoth lakes california show pathological behavior where the horizontal components of ground motion exceed the amplitude of the vertical components suggesting extreme topographic and 3d velocity heterogeneity use of all three components of the receiver function in modern passive array experiments is encouraged to reduce the problems of nonuniqueness in determining earth models

multi scale aquifer characterization and groundwater flow model parameterization using direct push technologies direct push dp technologies are typically used for cost effective geotechnical characterization of unconsolidated soils and sediments in more recent developments dp technologies have been used for efficient hydraulic conductivity k characterization along vertical profiles with sampling resolutions of up to a few centimetres until date however only a limited number of studies document high resolution in situ dp data for three dimensional conceptual hydrogeological model development and groundwater flow model parameterization this study demonstrates how dp technologies improve building of a conceptual hydrogeological model we further evaluate the degree to which the dp derived hydrogeological parameter k measured across different spatial scales improves performance of a regional groundwater flow model the study area covers an area of 60 km2 with two overlying mainly unconsolidated sand aquifers separated by a 5 7 m thick highly heterogeneous clay layer in north eastern belgium the hydrostratigraphy was obtained from an analysis of cored boreholes and about 265 cone penetration tests cpts the hydrogeological parameter k was derived from a combined analysis of core and cpt data and also from hydraulic direct push tests a total of 50 three dimensional realizations of k were generated using a non stationary multivariate geostatistical approach to preserve the measured k values in the stochastic realizations the groundwater model k realizations were conditioned on the borehole and direct push data optimization was performed to select the best performing model parameterization out of the 50 realizations this model outperformed a previously developed reference model with homogeneous k fields for all hydrogeological layers comparison of particle tracking simulations based either on the optimal heterogeneous or reference homogeneous groundwater model flow fields demonstrate the impact dp derived subsurface heterogeneity in k can have on groundwater flow and solute transport we demonstrated that dp technologies especially when calibrated with site specific data provide high resolution 3d subsurface data for building more reliable conceptual models and increasing groundwater flow model performance

determining crustal structure beneath seismic stations overlying a low velocity sedimentary layer using receiver functions the receiver function rf technique has been widely applied to investigate crustal and mantle layered structures using p to s converted ps phases from velocity discontinuities however the presence of low velocity relative to that of the bedrock sediments can give rise to strong reverberations in the resulting rfs frequently masking the ps phases from crustal and mantle boundaries such reverberations are caused by p to s conversions and their multiples associated with the strong impedance contrast across the bottom of the low velocity sedimentary layer here we propose and test an approach to effectively remove the near surface reverberations and decipher the ps phases associated with the moho discontinuity autocorrelation is first applied on the observed rfs to determine the strength and two way traveltime of the reverberations which are then used to construct a resonance removal filter in the frequency domain to remove or significantly reduce the reverberations the filtered rfs are time corrected to eliminate the delay effects of the sedimentary layer and applied to estimate the subsediment crustal thickness and vp vsusing a h k stacking procedure the resulting subsediment crustal parameters thickness and vp vs are subsequently used to determine the thickness and vp vs of the sedimentary layer using a revised version of the h k stacking procedure testing using both synthetic and real data suggests that this computationally inexpensive technique is efficient in resolving subsediment crustal properties beneath stations sitting on a low velocity sedimentary layer and can also satisfactorily determine the thickness and vp vs of the sedimentary layer

shallow sedimentary structure of the brahmaputra valley constraint from receiver functions analysis in this study receiver functions from ten broadband seismograph stations on cenozoic sediment formations of brahmaputra valley and its neighboring region in northeastern part of india are determined receiver function traces from this region show delay in peak by 1 2 5 s and associated minor peaks with the direct p phase peak based on such observation we try to image sedimentary structure of the brahmaputra valley plain adjacent shillong plateau and himalayan foredeep region an adapted hybrid global waveform inversion technique has been applied to extract sedimentary basin structure beneath each site the sedimentary cover of the basin is about 0 5 6 5 km thick across the valley 0 5 1 0 km on shillong plateau and 2 0 5 0 km in nearby foredeep region we have found that sedimentary thickness increases from sw to ne along the brahmaputra valley and towards the eastern himalayan syntaxes the estimated sediment thickness and s wave velocity structure agree well with the results of previous active source gravity and deep borehole studies carried out in this region the thick crustal low velocity sediment cover in brahmaputra valley is expected to amplify ground motions during earthquakes and therefore important for seismic hazard assessment of the region

determination of compressional wave and shear wave speed profiles in sea ice by crosshole tomography theory and experiment sea ice is a heterogeneous material whose acoustic properties are functions of time and space results of a crosshole tomography experiment conducted in multi year ice with the objective of determining the spatial structure of the compressional and shear wave speeds from travel time measurements made with high frequency pulses are presented here the results of the experiment indicate that the wave speeds can be determined from such a crosshole experiment with good resolution the compressional and shear wave speed contour maps indicate that the spatial variations of the wave speeds are complex with regions of low speed low speed regions observed are likely caused by high brine volume content resolution and variance studies performed on the estimates are also presented material properties such as poisson s ratio salinity and elastic and shear moduli of sea ice are obtained from the estimates of compressional and shear wave speeds by measuring the amplitude of the transmitted and received signals along specific paths estimates of the attenuation coefficients at different depth intervals are obtained spatial variability observed in the estimates is believed to be due to scattering by inhomogeneities in the material

modeling the effect of san andreas fault structure on receiver functions using elastic 3d finite difference abstract teleseismic p wave data collected at the san andreas observatory sao seismic station show strong frequency dependent nonrectilinear particle motions consisting of off azimuth horizontal displacements that are sometimes larger than the vertical displacements the azimuthal dependence of the horizontal components amplitude is directly related to the symmetry of the fault zone a 3d finite difference program frankel and vidale 1992 is used to examine the response of the san andreas fault zone velocity structure to incident teleseismic p waves synthetic seismograms are formed using a 3d representation of an assumed 2d fault zone structure the fault zone velocity model produces large amplitude phases that contain combinations of refracted and internally reflected p to s converted phases diffractions and possible p to rayleigh converted phases the largest amplitude phases observed in the data are nondispersive and have complicated particle motions confined to the vertical plane perpendicular to the fault zone the data are fit best by synthetic receiver functions for field points similar to the location of sao relative to the san andreas fault zone since the velocity model used in the computations is nonunique sensitivity studies were performed by modifying the structure synthetics match the timing and nature of the observed phases at sao showing that assumption of plane layered structure is invalid in the area of this station

determining moho depth beneath sedimentary basins using regional pn multiples the study of the moho beneath thick sedimentary basins involving natural earthquakes is challenging as low velocity materials often cause strong reverberations that mask moho signals here we develop a method to determine the depth of the moho by taking advantage of the presence of the sediments the method utilizes the first pn crustal multiple from regional earthquakes pnpn and its differential travel time with respect to pn pnpn is usually weak in amplitude thus it is difficult to identify in regions without a sedimentary cover however pnpn is significantly amplified in the presence of low velocity sediments because of an increase in the near surface p to p reflection coefficient the arrival time amplitude and wave shape of pnpn if normalized by the reference pn are insensitive to earthquake source parameters such as focal mechanism and focal depth we demonstrate the potential of this method using both 1d and 2d waveform simulations synthetic waveforms suggest that pmppn and pnpmp one pn leg merges to pmp near the source or the receiver largely contribute to the pnpn amplitudes which depend on the near surface structure at their free surface p to p reflection points we further validate the method with two field examples in the imperial valley one is near the united states mexico border and the other is in oklahoma in the central united states both examples suggest that the method can be used to study the moho either near the source or the receiver

an assessment of crustal and upper mantle velocity structure by removing the effect of an ice layer on the p wave response an application to antarctic seismic studies standard p wave receiver function analyses in polar environments can be difficult because reverberations in thick ice coverage often mask important p to s conversions from deeper subsurface structure and increase ambient noise levels thereby significantly decreasing the signal to noise ratio of the data in this study we present an alternative approach to image the subsurface structure beneath ice sheets we utilize downward continuation and wavefield decomposition of the p wave response to obtain the up and downgoing p and s wavefield potentials which removes the effects of the ice sheet the upgoing p wavefield computed from decomposition of the waveform at a reference depth is capable of indicating ice layer thickness this simple step removes the necessity of modeling ice layer effects during iterative inversions and hastens the overall velocity analysis needed for downward continuation the upgoing s wave is employed and modeled using standard inversion techniques as is done with receiver functions at the free surface using a least squares approximation to illustrate our proof of concept data from several antarctic networks are examined and our results are compared with those from previous investigations using p and s wave receiver functions as well as body and surface wave tomographic analyses we demonstrate how our approach satisfactorily removes the ice layer thus creating a dataset that can be modeled for crustal and upper mantle structure solution models indicate crustal thicknesses as well as average crustal and upper mantle shear wave velocities electronic supplement 1 figure of measured data the vertical component stack used in deconvolution and the resultant vertical radial and tangential transfer functions 1 http www bssaonline org lookup suppl doi 10 1785 0120160262 dc1

elastic reverse time migration elastic prestack reverse time finite difference migration of two component seismic surface data requires data extrapolation and application of an imaging condition data extrapolation involves synchronous driving of the vertical component and horizontal component finite difference meshes with the time reverse of the recorded vertical and horizontal traces respectively extrapolation uses the coupled elastic wave equation for variable velocity solved with a second order explicit finite difference scheme the imaging condition at any point in the grid is the one way traveltime from the source to that point elastic migrations of both synthetic test data and real two component common source gathers produce simpler images than acoustic migrations because of the coalescing of double reflections compressional waves and shear waves into single loci

the freshwater budget and under ice spreading of mackenzie river water in the canadian beaufort sea based on salinity and 18o 16o measurements in water and ice observations of salinity and oxygen isotope composition 18o were made for the beaufort shelf mackenzie estuary waters in september 1990 just prior to ice formation and for both the water column and ice in april may 1991 at the end of winter these measurements are used to determine the apportioning of fresh water in the estuary between its two main sources runoff and sea ice melt changes in disposition of water between seasons and amounts frozen into the growing ice sheet are also derived two domains are considered in order to construct a freshwater budget for the mackenzie shelf the nearshore within which landfast ice grows in winter and the outer shelf most of the winter inflow from the mackenzie river appears to remain impounded as liquid under the ice within the landfast zone at the end of winter and about 15 of it is incorporated into the landfast ice oxygen isotopes 18o in ice cores collected from across the shelf record the progress beneath the ice of new mackenzie inflow as it invades the nearshore throughout winter rates of spreading are about 0 2 cm s 1 away from the coast and 1 3 cm s 1 along the coast as this inflow spreads across the shelf it progressively shuts off convection driven by brine production at locations within the landfast ice salinity and 18o in the offshore water column suggest that about 3 m of sea ice was formed in the outer shelf domain since both brine and newly formed sea ice can be advected off the shelf a complete budget for brine or sea ice production cannot be established without first measuring the advection of one of these two components

local earthquake wave propagation through mississippi embayment sediments part ii influence of local site velocity structure on qp qs determinations elastic near surface structure and receiver depth effects are seen to control body wave amplitude spectra in the band from 2 to 50 hz for local earthquake observations in the new madrid seismic zone p and s wave spectral peaks are created by resonance in shallow low velocity zones and spectral nulls are created by interference of direct and free surface reflections due to receiver depth these wave propagation effects dominate sp s spectral ratios and mimic anelastic attenuation effects by making it appear that s waves are deficient in higher frequencies relative to sp waves there is no evidence from sp s spectral ratios that unconsolidated sediments of the mississippi embayment are highly attenuating dominance of p and s wave resonance suggests that the unconsolidated sediments amplify rather than attenuate seismic waves at high frequency this has important implications for estimating hazards from strong ground motions in the area in the absence of any identifiable anelastic attenuation effect in the spectral ratio the only allowable q p q s relationship for embayment sediments is that q s 3 q p based on consideration of wave travel times manuscript received 11 march 2003

sequential h κ stacking to obtain accurate crustal thicknesses beneath sedimentary basins abstract low velocity sedimentary basins introduce error in many standard receiver function rf analysis techniques including common conversion point dueker and sheehan 1997 and crustal thickness v p v s ratio h stacking zhu and kanamori 2000 we describe a simple rf analysis method for obtaining accurate crustal thickness below seismic stations located in sedimentary basins the method extends the methods of zhu and kanamori 2000 it employs an iterative two layer depth v p v s stacking approach that first characterizes sediment properties thickness and v p v s allowing for the accurate interpretation of moho conversions without accounting for sedimentary layers standard rf analysis can mischaracterize crustal thickness based on ps phase delay by 10 km beneath deep basins we test the technique with synthetic seismograms and with data from us array transportable array ta stations from regions with sediment thicknesses that are well determined through other means we find sequential h stacking for sediment properties to be a simple technique that can benefit many rf analysis studies and can play an important role in crustal seismic studies in areas with thick or variable sediments

wave field continuation and decomposition for passive seismic imaging under deep unconsolidated sediments abstract the coastal plains of the central and eastern united states contain deep sections of unconsolidated to poorly consolidated sediments these sediments mask deeper crustal and upper mantle converted phases in teleseismic receiver functions through large amplitude near surface reverberations thick sediments also amplify ambient noise levels to generally reduce data signal to noise ratios removing shallow sediment wave propagation effects is critical for imaging deep lithospheric structures a propagator matrix formalism is used to downward continue the wave field for teleseismic p waves into the midcrust and then to separate the upgoing s wave field from the total teleseismic response of the p wave to expose deep sp conversions this method requires that the earth model from the surface to the reference depth be known teleseismic p wave data for the memphis tennessee station mph are analyzed using a reference station deconvolution technique to produce vertical and radial p wave transfer functions these transfer functions are modeled using a simple model parameterization for sediment structure through grid inversion the inverted earth model is incorporated into the wave field continuation and decomposition technique to estimate the upgoing s wave field at 10 km depth in the crust moho and possible deeper ps conversions are identified with this process

a study of the evolution of the under ice water layer during summer melt phase in an arctic bay an acoustic ice tomography experiment which extended over a 12 month period was conducted in the sabine bay area of the canadian archipelago acoustic transmitter and receiver arrays were deployed in the ice for this experiment the vertical arrays penetrated through the ice and extended into the water column the acoustic data collected from the transmitter receiver pairs in the water column are analyzed to investigate the changes in the sound speed structure of the water column analysis of the acoustic data shows significant changes in the sound speed structure in the upper 2 m of the water column during the summer melt phase we associate these changes in sound speed with the influx of fresh water caused by the melting of ice cover snow and runoff from rivers other features of the acoustic data suggest 1 that the fresh water remained stagnant and the ice growth during the winter months was due to the freezing of the fresh water and 2 that ice formed around the transducers as the fresh water came into contact with it as the study presented in this paper was not one of the goals of the tomography experiment support measurements to validate the conclusions from the acoustic data such as measurement of temperature and salinity in the water column were not made however the analysis presented is a demonstration of the usefulness of this technique to monitor the changes that take place in the region beneath the ice cover

crustal and upper mantle velocity structure in the vicinity of the eastern tennessee seismic zone based upon radial p wave transfer functions teleseismic transfer function analysis is used to investigate crust and upper mantle velocity structure in the vicinity of the active eastern tennessee seismic zone etsz the etsz is associated with the new york alabama ny al magnetic lineament a prominent aeromagnetic anomaly indicative of grenville age basement structure radial component p wave transfer functions for 10 short period stations operated by the center for earthquake research and information are inverted for velocity structure velocity profiles are also determined for three broadband stations by converting the instrument response to that of an s 13 short period seismometer distinct differences in the velocity profiles are found for stations located on either side of the ny al magnetic lineament velocities west of the lineament are lower than velocities to the east of the lineament in the upper 10 km and in the depth range 30 to 50 km a gradational moho boundary is found beneath several stations located in the valley and ridge province a moho boundary is absent at four valley and ridge stations located east of the magnetic lineament and south of 35 5 n

hotspot origin of the mississippi embayment and its possible impact on contemporary seismicity abstract previous authors have related the late cretaceous early tertiary subsidence of the mississippi embayment to the opening of the gulf of mexico but the gulf opened earlier in triassic jurassic time we offer an alternative hypothesis that development of the embayment was coeval with the passage of the mississippi valley graben system over the bermuda hotspot about 90 ma several lines of evidence of significant uplift of the embayment axis accompanying mid cretaceous magmatism and prior to late cretaceous subsidence support this proposal first reactivation of the pascola arch in the northern embayment is recorded by flanking deposits of basal upper cretaceous gravel second beneath a regional mid cretaceous unconformity subcrops of jurassic and early cretaceous strata define a pronounced southwest plunging arch in the southern embayment this arch is collinear with an arch revealed in paleozoic rocks after restoration to mid cretaceous structural geometries third a deep weathering profile on mid cretaceous alkalic plutons along the western embayment margin is nonconformably overlain by paleocene sediments and rapid mid cretaceous cooling of these intrusions has been interpreted from apatite fission tracks moreover exploratory holes along the embayment axis encountered similar weathered alkalic intrusions nonconformably overlain by basal upper cretaceous strata fourth there was an anomalous influx of clastic sediment into the northern gulf of mexico during mid cretaceous time and subsequent clastic facies patterns suggest the mississippi river drainage began to enter the gulf in the late cretaceous passage of the mississippi valley graben over the bermuda hotspot during elevated hotspot activity of cretaceous time may have significantly weakened the previously rifted lithosphere rifted continental margin at charleston south carolina also passed over this hotspot in latest cretaceous time similarly the st lawrence rift system passed over the great meteor hotspot during the cretaceous it is important to note that these rift systems are the principal loci of strong seismicity in eastern north america and thus weakening by increased cretaceous hotspot activity may be an important common factor for these seismic rift zones

post critical sspmp and its applications to virtual deep seismic sounding vdss 3 back projection imaging of the crust mantle boundary in a heterogeneous lithosphere theory and application

local earthquake wave propagation through mississippi embayment sediments part i body wave phases and local site responses p and s body waves from microearthquakes in the new madrid seismic zone nmsz are investigated at selected sites in an effort to understand wave propagation from future large earthquakes earthquake body waveforms display distinctive features that constrain the nature of p and s wave local site responses and wave propagation within the unconsolidated mississippi embayment sediments modeling of the waveforms demonstrates that a near surface low velocity zone is characteristic of structure within the upper 60 m of the sedimentary column and produces large p and s wave resonance effects that can be used to infer near site conditions site resonance effects change because of velocity heterogeneity between individual receivers but imply that embayment sediments will substantially amplify ground motions at high frequencies site resonance affects p and s wave amplitude spectra and can bias estimates of source and anelastic attenuation parameters travel times of observed body wave phases such as p ppphp the first p wave reverberation within the entire sedimentary column ps sp s and ssphp can be used to estimate the average wave slownesses and poisson s ratio within the embayment sediments an average poisson s ratio of 0 44 is obtained for the central nmsz under station pebm detailed s wave velocities are derived for a nafe drake sediment model using acoustic well logs and the travel time constraints of observed seismic phases v p v s ratios vary from 5 5 near the surface to approximately 2 4 at the base of the sediments use of the well log data in wave calculations also explains much of the nature of p and s wave coda within the waveforms and shows that 1d heterogeneity is a first order influence on seismic wave propagation within the mississippi embayment manuscript received 11 march 2003

cocorp and the continental crust this is a speculative paper on the continental crust a major frontier of modern earth science seismic reflection profiling data from the cocorp project coupled with other kinds of geophysical and geological observations suggest some fresh perspectives on the crust for example there is evidence for great differences within the basement at a single site and from one cocorp site to another a simple layered model is surely not an adequate representation of the crust in most areas there is however the puzzling and rather common occurrence of limited zones of parallel though not always flat layered features at various depths in certain parts of the crust are the corresponding rocks metasedimentary or igneous or both there are transparent zones from which little or no coherent reflected seismic energy is detected are the corresponding rocks intrusions or highly deformed metasediments can degree of deformation suggest whether rocks were deformed in the hanging wall or footwall of a thrust there is evidence for large scale thrusting and related features that emphasizes the great importance of the wilson cycle to continental tectonics and that raises the possibility that water and rocks of sedimentary origin are trapped deep in the crust by the thrusting process and remain there for long periods with a variety of possible rheological and petrological consequences in some places the modern moho and adjacent rocks may correspond to parts of former oceanic or continental margin sections that have been emplaced at depth as a result of thrusting the widely held concept of the moho as a consistent boundary that is everywhere similar and that always separates the same kinds of rocks may be a major barrier to further progress in understanding the continental crust

a procedure for modelling shallow dislocation sources summary expressions for displacements on the surface of a layered half space due to an arbitrary oriented shear dislocation are given in terms of generalized ray expansions useful approximations of these expressions for shallow events as recorded at teleseismic distances for realistic earth models are presented the results of this procedure are used to generate synthetic p sv and sh waveforms for various assumptions of stress drop

crustal structure at a young continental rift a receiver function study from the tanganyika rift the southern tanganyika rift within the western rift africa has earthquakes to depths of 37 km yet few constraints exist on crustal thickness or of early stage rifting processes in apparently amagmatic rift sectors the aim of the tanga14 experiment was to constrain bulk crustal properties to test whether magmatic processes modify the lithosphere in areas of deep seismicity and the degree of lithospheric thinning we use eleven broadband seismometers to implement receiver function analysis using h stacking a method sensitive to crustal thickness and vp vs ratio to determine bulk crustal properties analyses include extensive error analysis through bootstrap variance and phase weighted stacking results show the archean tanzanian craton and bangweulu block are characterized by vp vs ratios of 1 75 1 77 implying a felsic bulk composition crust beneath the fault bounded basins has high vp vs 1 9 anorthosite bodies and surface sediments within the region may contribute to localized high vp vs however elevated vp vs values within fault bounded extensional basins where elevated heat flow hydrothermal vent sites and deep earthquakes are observed suggest that magma may be intruding the lower crust beneath the southern tanganyika rift crustal thicknesses on near the relatively un extended tanzanian craton and bangweulu block are 41 6 42 0 km this contrasts with the tanganyika rift where crustal thicknesses are 31 6 km to 39 km from north to south our results provide evidence for 20 crustal thinning localized to fault bounded basins taken together they suggest a previously unrecognized role of magma intrusion in early stage continental rifting in the western rift africa

monotonic and dilatory pore pressure decay during piezocone tests in clay during a pause in cone penetration in fine grained soils pore water pressure dissipation tests are performed to evaluate the coefficient of consolidation for standard piezocones with shoulder fil

tomography of southern california via bayesian joint inversion of rayleigh wave ellipticity and phase velocity from ambient noise cross correlations the data used in this work are archived and distributed by the southern california earthquake data center scedc http scedc caltech edu research tools waveform html and the iris earthquake data center https ds iris edu ds nodes dmc both the scec community velocity models used in this work cvms 4 26 and cvmh 15 1 0 are available from the southern california earthquake center https github com sceccode ucvmc this study was supported by the southern california earthquake center award 17195 the national science foundation grants cybersees 1442665 and ear 162061 and the king abdullah university of science and technology award ocrf 2014 crg3 2300 we also thank the reviewers of this paper an anonymous individual and jan dettmer for their valuable insight and constructive reviews of the manuscript the 3 d shear wave velocity model will be available from iris data services products earth model collaboration https ds iris edu ds products emc

the seismic reflection character of the continental mohorovicic discontinuity the continental mohorovicic discontinuity is most often interpreted as a step function velocity boundary however on deep crustal seismic reflection profiles reflections at depths where refraction data places the moho have laminated character and are laterally discontinuous these observations on continental reflection data point to a model of the moho that has thin layered rather than block structure previous workers who have synthetically generated seismic responses from various crust mantle boundary models have shown that thin layered models of alternating high and low velocity generate responses that best emulate observed moho arrivals geologic interpretations of the thin layering include relatively undeformed metasediments cumulate layering tectonic banding and lenses of partial melt to obtain more direct geologic evidence a synthetic seismogram is generated from geologic cross sections of the ivrea verbano zone an exposed section through the lower crust and upper mantle the synthetic shows laminations similar to those observed on reflection data without more direct evidence no single geologic interpretation of the moho is reasonable indeed the moho may be a laterally variable boundary its composition and structure dependent upon the geologic history of the overlying crust

evaluation of deep sediment velocity structure in the new madrid seismic zone detailed knowledge of the physical properties of the sediments filling the mississippi embayment has proven critical to both unravel the tectonic frame work operating in the region and assess the seismic hazards posed by the new madrid seismic zone in this article we show that independent geotechnical estimates for p and s wave velocities are compatible with a sedimentary model of k feldspar clasts embeded in water and we test its validity by modeling receiver functions at a number of broadband stations by constraining the bulk sediment thicknesses beneath each station from independent reflection profiling estimates we have been able to recover the depth to the top of the cretaceous from the receiver function data at individual stations our receiver function modeling thus provides confidence in the velocity and density structures extrapolated from in situ geotechnical measurements in the upper mississippi embayment

constraining sedimentary structure using frequency dependent p wave particle motion a case study of the songliao basin in ne china knowledge on sedimentary structure within a basin is of great importance for exploring petroleum resources and predicting strong ground motions caused by earthquakes although 3 d seismic data acquisition is common nowadays in petroleum industry it is still impossible to conduct dense 3 d seismic surveys at a whole basin scale passive seismic imaging thus can play a significant role in obtaining large scale sedimentary structure of basins with a reasonably good resolution here we present a new method to estimate the sedimentary structure beneath a seismic station using frequency dependent nonlinear particle motion of the teleseismic p wave that is a delay in the p wave arrival time on the horizontal component forward modeling suggests that the delay time and its variations over frequency are caused by interference of the direct p wave with the p to s conversions at the base of the sediments as well as sediment reverberations and hence can be used to constrain the thickness and seismic velocity of the sediments beneath the station we further develop a 2 d grid search technique to estimate the optimum sediment thickness z and surface s wave velocity 0 by minimizing the residuals between the observed and calculated apparent p wave splitting times the grid search yields reasonably robust estimates of z and 0 although it has some trade off between the two parameters in the case of thin and unconsolidated sediments we apply the method to 30 broadband stations inside the songliao basin and the estimated sedimentary structures beneath these stations agree well with previous results

undulating moho beneath a near uniform surface of central tibet abstract we present 805 reliable estimates of crustal thickness in central tibet revealing an undulating moho beneath a near uniform surface of the highest and the largest plateau in the world our results are derived from wide angle reflections of p waves from virtual seismic sources near seismographs virtual deep seismic sounding vdss the virtual sources are produced by large earthquakes well distributed in back azimuth and we also utilize obvious changes of measured arrival times as a function of ray parameter to constrain independently bulk thickness and p wave speed of the crust about 6 3 km s so there is little trade off between the two parameters additionally we consider effects of known heterogeneities in the upper mantle in regions surrounding the hi climb linear array there is an eastward trend in addition to the previously proposed northward trend of crustal thinning respectively these trends are approximately parallel and normal to the indian mantle front imf or the northern leading edge of underthrust lithospheric mantle of india deduced from a collection of additional geophysical evidence the moho near the imf also shows large 3 d variations in depths prompting us to propose that the leading edge of intact indian lower crust or the indian crustal front icf that accompanied the underthrusting indian lithospheric mantle beneath tibet lies along the zone of disturbed moho based on results from about a dozen permanent broadband seismographs of the china national seismic network more or less flat lying and thus presumably stable cratonic indian moho south of the icf apparently extends eastward for another 500 km to about 93 e

contour mapping of relic structures in the precambrian basement of the reelfoot rift north american midcontinent a new contour map of the basement of the reelfoot rift constructed from drill hole and seismic reflection data shows the general surface configuration as well as several major and minor structural features the major features are two asymmetric intrarift basins bounded by three structural highs and the rift margins the basins are oriented normal to the northeast trend of the rift two of the highs appear to be ridges of undetermined width that extend across the rift the third high is an isolated dome or platform located between the basins the minor features are three linear structures of low relief oriented subparallel to the trend of the rift two of these located within the rift basins may divide the rift basins into paired subbasins these mapped features may be the remnants of initial extensional rifting half graben faulting and basement subsidence the rift basins are interpreted as having formed as opposing half graben and the structural highs are interpreted as having formed as associated accommodation zones some of these features appear to be reactivated seismogenic structures within the modern midcontinent compressional stress regime a detailed knowledge of the geometries of the reelfoot rift s basement features therefore is essential when evaluating their seismic risk potential

limits in determining permeability from on the fly ucpt sounding limits are defined for the transition from partially drained to undrained penetration during ucpt testing these limits prescribe the range of cone metrics for which coefficient of permeability mag

influence of non low plastic fines on cone penetration and liquefaction resistance abstract uncertainties prevail at the current liquefaction screening method based on the cone penetration test cpt as to whether the existence of fines increases liquefaction resistance or decrease cone penetration resistance in this study field based data are used to evaluate the effects of non low plastic fines on liquefaction resistance at the current cpt based liquefaction assessment method the first part of this paper examines the effects of the coefficient of consolidation or drainage characteristics of soils containing fines on cone penetration resistance the coefficient of consolidation is influenced by the fines content and the relative density of the soil the second part of this paper investigates the contribution of fines content less than 30 by weight on the liquefaction resistance of soils at different relative densities fines content over 30 by weight and or high plasticity of fines can cause additional complications therefore it needs different valuation methods which is beyond the scope of this paper the liquefaction resistance of sands and silty sands is reinterpreted from the current cpt based liquefaction assessment method the trend which presents the change of liquefaction resistance with fines content at the same relative density is compared with the available laboratory based data in the literature the results show that the interpreted trend is not consistent with the laboratory based correlations obtained by several previous researchers therefore there will be probably some inaccuracies in estimation of liquefaction potential of silty sand using the current cpt based liquefaction assessment method

an integrated study of crustal structure and regional wave propagation for southeastern missouri teleseismic receiver function analysis and published refraction studies are used to infer the existence of first order discontinuities within the crust and mantle of the ozark uplift at the incorporated research institutions in seismology iris station cathedral cave missouri ccm this information is then used to study the nature of regional wave propagation from the new madrid seismic zone to ccm across the ozark dome to interpret broadband seismograms written by small events receiver function inversion indicates a crust 40 km thick characterized by smooth velocity gradients down to the moho secondary ps conversions late in the receiver functions show the existence of a high velocity mantle layer 10 to 15 km thick at approximately 60 km depth with p wave velocity of about 8 5 km sec the data resolve both the top and bottom of the layer such high velocities suggest rocks with eclogite or dunite compositions regional data from the 26 september 1990 cape girardeau earthquake m 1 4 7 are used to model average crustal velocities and the nature of the velocity gradient near the moho through inversion of relative arrival times of observed phases regional p and s waveforms are exceptionally simple at ranges of 180 km showing the mantle head waves pn and sn with a triplicated pg and sg arriving within a few seconds respectively sp is quite prominent and is an accurate indicator of source depth for the cape girardeau event which occurred between 14 and 16 km depth there is no evidence for other major phases except rg after the sg arrival confirming the observation that the crust is dominated by smooth velocity gradients a grid search technique is used to model relative phase amplitudes to obtain the focal mechanism for the cape girardeau event allowable focal mechanisms are dominated by thrust faults striking ns or ne sw the inferred earth structure is used to model the 4 may 1991 risco event m 1 4 6 but observed differences in relative arrival times between p s and rayleigh phases suggest that crustal velocities are slightly lower within the mississippi embayment and that the uppermost mantle has a higher positive gradient than further northwest nevertheless sp constrains the source depth between 7 and 9 km and p sv and sh wave amplitudes yield mechanisms consistent with that obtained by the portable array for numerical data acquisition panda deployment waveforms from two small events with poor signal to noise ratios are compared with waveforms of the larger events to infer source depths modeling broadband waveforms from small local and regional events shows great promise in determining source parameters and inferring details of crustal and upper mantle structure however lateral heterogeneity in velocity structure will remain one of the principal obstacles to overcome

joint inversion of rayleigh wave phase velocity and ellipticity using usarray constraining velocity and density structure in the upper crust rayleigh wave ellipticity or h v ratio observed on the surface is particularly sensitive to shallow earth structure in this study we jointly invert measurements of rayleigh wave h v ratio and phase velocity between 24 100 and 8 100 sec period respectively for crust and upper mantle structure beneath more than 1000 usarray stations covering the western united states upper crustal structure in particular is better constrained by the joint inversion compared to inversions based on phase velocities alone in addition to imaging vs structure we show that the joint inversion can be used to constrain vp vs and density in the upper crust new images of uppermost crustal structure 3 km depth are in excellent agreement with known surface features with pronounced low vs low density and high vp vs anomalies imaged in the locations of several major sedimentary basins including the williston powder river green river denver and san juan basins these results demonstrate not only the consistency of broadband h v ratios and phase velocity measurements but also that their complementary sensitivities have the potential to resolve density and vp vs variations

bulk sediment qp and qs in the mississippi embayment central united states we have estimated p wave ands wave anelastic attenuation coefficients for the thick unconsolidated sediments of the mississippi embayment central united states using the spectral distance decay of explosion p and rayleigh waves the sediment trapped p wave psed is observed to ranges of 80 km at 10 hz and 1 hz rayleigh waves are observed out to 130 km from a 5000 lb borehole explosion in the northern part of the embayment rayleigh waves of 4 hz are seen to distances of 3 km from a smaller 50 lb explosion analysis of the group velocity and amplitude distance decay of both waves yields an average qs of 100 and qp of 200 for embay ment sediments that are independent of frequency scatter in the q estimates comes from interference of multiple p wave reverberations and rayleigh wave modes the attenuation model is self consistent in that it is the same as obtained by the analysis of synthetic seismograms using the inferred q values inferred qp and qs values are more than three times higher than previous estimates and imply that unconsolidated sediments of the embayment do not significantly attenuate small strain earthquake ground motions these estimates represent a lower bound to q of the sediments since significant scattering is observed in the waveform data that contributes to the distance decay of wave amplitude higher q values also imply that the unconsolidated sedi ments of the embayment will form an efficient wave guide for surface waves radiated from shallow earthquakes or large earthquakes that rupture into the sediments pro ducing high amplitude long duration wave trains that should be considered in earth quake hazard assessments

lithospheric structure of the aegean obtained from p and s receiver functions combined p and s receiver functions from seismograms of teleseismic events recorded at 65 temporary and permanent stations in the aegean region are used to map the geometry of the subducted african and the overriding aegean plates we image the moho of the subducting african plate at depths ranging from 40 km beneath southern crete and the western peloponnesus to 160 km beneath the volcanic arc and 220 km beneath northern greece however the dip of the moho of the subducting african plate is shallower beneath the peloponnesus than beneath crete and rhodes and flattens out beneath the northern aegean observed p to s conversions at stations located in the forearc indicate a reversed velocity contrast at the moho boundary of the aegean plate whereas this boundary is observed as a normal velocity contrast by the s to p conversions our modeling suggests that the presence of a large amount of serpentinite more than 30 in the forearc mantle wedge which generally occurs in the subduction zones may be the reason for the reverse sign of the p to s conversion coefficient moho depths for the aegean plate show that the southern part of the aegean crustal thickness of 20 22 km has been strongly influenced by extension while the northern aegean sea which at present undergoes the highest crustal deformation shows a relatively thicker crust 25 28 km this may imply a recent initiation of the present kinematics in the aegean western greece crustal thickness of 32 40 km is unaffected by the recent extension but underwent crustal thickening during the hellenides mountains building event the depths of the aegean moho beneath the margin of the peloponnesus and crete 25 28 and 25 33 km respectively show that these areas are also likely to be affected by the aegean extension even though the cyclades crustal thickness of 26 30 km were not significantly involved in this episode the aegean lithosphere asthenosphere boundary lab mapped with s receiver functions is about 150 km deep beneath mainland greece whereas the lab of the subducted african plate dips from 100 km beneath crete and the southern aegean sea to about 225 km under the volcanic arc this implies a thickness of 60 65 km for the subducted african lithosphere suggesting that the aegean lithosphere was not significantly affected by the extensional process associated with the exhumation of metamorphic core complexes in the cyclades

testing the limits of virtual deep seismic sounding via new crustal thickness estimates of the australian continent we apply virtual deep seismic sounding vdss to data collected from both permanent and temporary seismic stations in australia with the goal of examining i the resilience of the method to the presence of complex lithospheric structure and ii the effectiveness of different approaches for estimating bulk crustal properties namely thickness and vp data from the permanent wrab in the northern territory station is ideal for benchmarking vdss large number and favourable distribution of recorded earthquakes with the results from several approaches agreeing on a thickness of 40 42 km application of vdss to data from the temporary bilby array a linear distribution of broadband stations that traverses central australia shows that strong moho reflections can be retrieved with as few as two earthquakes even at the transition between crustal blocks of different character and in the presence of thick sedimentary basins crustal thickness varies between 36 54 km and compare well with the reflectivity character of nearby deep seismic reflection lines furthermore we find that off line estimates of crustal thickness calculated by binning the source regions according to back azimuth produce estimates of crustal thickness that are consistent with the regional geology overall we find that vdss is a powerful technique for estimating crustal thickness and velocity due to its insensitivity to complex short wavelength structure and requirement of a small number earthquakes to produce a stable result however not all schemes tested for extracting bulk crustal properties appear to be robust and stringent data quality checking is still required during implementation

evidence for a major late precambrian tectonic event rifting in the eastern midcontinent region united states recently acquired gravity and aeromagnetic data delineate a large linear gravity anomaly which extends through eastern kentucky and tennessee and coincides with a zone of complex high amplitude magnetic anomalies basement lithologies in the area can be interpreted as a bimodal volcanic suite which is locally peralkaline in nature these volcanics appear to be metamorphosed where they lie east of the grenville front suggesting they predate the grenville metamorphic event the available gravity aeromagnetic seismic refraction and petrologic data along with regional correlations suggest that the best tectonic interpretation of these data is that a keweenawan rift zone extended through the area this rift can be roughly outlined by the gravity high which is locally offset suggesting the presence of transform faults the boundaries of this rift have been locally reactivated and in fact a recent earthquake was located along its western boundary in northern kentucky

array analysis of the large aperture array of the 1988 89 passcal basin and range passive source seismic experiment summary the 1988 89 passcal basin and range passive source seismic experiment consisted of two array deployments the large and small aperture arrays the large aperture array consisted of seven stations with three component mid period seismometers and independently triggered prototype passcal data recorders with goes clocks the array spatial distribution and the synchronized data have permitted us to employ simple beamforming operations to improve receiver function estimation from single teleseismic events the beamforming reinforces the coherent teleseismic p wave and the deterministic portions of the p wave coda primarily generated by interactions at major lithospheric interfaces microseismic background noise is incoherent across the array and is attenuated by beamforming beamforming also diminishes those portions of the coda due to scattering by inhomogeneities that appear random on the scale of the array aperture the enhanced signal to noise ratio of the teleseismic recording dramatically improves the single event receiver function deconvolution results

velocity structure of the northern mississippi embayment sediments part ii inversion of teleseismic p wave transfer functions abstract detailed shear and compressional gradient velocity structure for the unconsolidated sediments of the mississippi embayment me have been obtained through simultaneous inversion of radial and vertical teleseismic transfer functions for 60 broadband stations inside the me transfer functions were calculated by deconvolving a vertical array beam from the radial and vertical displacement at each station inside the embayment the vertical array beam was constructed by stacking all the vertical components of motions for stations on the bedrock and outside the embayment to reduce the effect of incoherent scattering improving estimates of the source time function and stabilizing the deconvolution a bounded variable least squares inversion technique was applied to invert for velocity nodes on the top and bottom of the sediment layer p wave velocity changes from 1 0 km s near the surface and increases with depth from 3 5 to 4 km s in deeper parts s wave velocity varies from 0 3 km s and increases to 1 6 km s in deeper sections to the south electronic supplement gradient velocity structure of the northern mississippi embayment sediments for 60 broadband stations

the removal of free surface interactions from three component seismograms summary the effect of the free surface can be removed from three component seismic recordings to recover the incident upgoing wavefield if the slowness and azimuth of the current wavefront are known as a function of time for a single threecomponent station it is usually possible to estimate an azimuth for an event from the first arriving p waves but slowness estimates are less reliable when more than one wavetype is presented in the seismic wavetrain however the free surface correction operators are generally slowly varying functions of slowness and so some error in slowness can be tolerated effective approximations for the removal of the free surface effects can be made for hard rock sites to cover slowness bands for the main regional phases pn pg sn and lg by applying these operators in turn over group velocity windows appropriate to the particular phases the relative amplitude of the p sv and sh contributions to the wavefield can be estimated because the free surface amplification effects have been removed the amplitudes can be compared directly and provide useful constraints on the radiation characteristics of the source this procedure is therefore helpful for developing discrimination measures for different classes of sources

station site characteristics of wwssn stations in india and southern asia the continental boundary between the eurasian and indian plates is of great geophvsical significance because it is one of the rare instances of presently active continent continent collision the region has been instrumented with a relatively large number of wwssn stations the crustal structure beneath these stations has been studied by examining their crustal transfer characteristics for incident teleseismic p waves at those stations well removed from the collision boundary poo kod ndi shi and msh the crustal structure appears to be relatively flat lying so that long period body waves are regularly polarized for these cases p to s converted phases from the moho have been identified in the records and modeled with synthetic seismograms to measure crustal thickness the depth to the moho beneath these stations falls within the usual continental range but shows no systematic variation between the indian and eurasian plates those stations which lie on or near the collision boundary que kbl and nil show evidence of strongly dipping structure teleseismic p waves recorded there generally contain prominent tangential arrivals the tangential phases are strong for waves approaching from all azimuths indicating that they are due to complex three dimensional structures rather than planar layers with a single direction of dip

constraints on crustal structure and complex moho topography beneath pinon flat california from teleseismic receiver functions abstract we use teleseismic p waves recorded at pinon flat observatory pfo to constrain the three dimensional crustal and upper mantle velocity structure beneath the station by forward modeling radial receiver function waveforms we construct a one dimensional crustal model that includes a significant shear velocity inversion at 9 km in depth arrivals on the tangential components indicate dip of at least the uppermost discontinuity complicated moho topography deepening to the northwest of pfo is suggested by azimuthal dependence of travel times and amplitudes of the receiver functions and travel times of crustal p wave reverberations although fine details cannot be resolved each of those sets of observations plus mislocation vectors provide strong indications of abrupt moho topography possibly including step offsets of several kilometers this is not only consistent with gravity data in implying airy isostasy with compensation at moho depth but extends that model to a much finer length scale than had been resolved

seismic evidence for an ancient rift beneath the cumberland plateau tennessee a detailed analysis of broadband teleseismic p waveforms broadband receiver functions developed from teleseismic p waveforms recorded on the midperiod passband of regional seismic test network station rscp are inverted for vertical velocity structure beneath the cumberland plateau tennessee the detailed broadband receiver functions are obtained by stacking source equalizd horizontal components of teleseismic p waveforms the resulting receiver functions are most sensitive to the shear velocity structure near the station a time domain inversion routine utilizes the radial receiver function to determine this structure assuming a crustal model parameterized by many thin flat lying homogeneous layers lateral changes in structure are identified by examining azimuthal variations in the vertical structure the results reveal significant rapid lateral changes in the midcrustal structure beneath the station that are interpreted in relation to the origin of the east continent gravity high located northeast of rscp the results from events arriving from the northeast show a high velocity midcrustal layer not present in results from the southeast azimuth this velocity structure can be shown to support the idea that this feature is part of a keweenawan rift system another interesting feature of the derived velocity models is the indication that the crust mantle boundary beneath the cumberland plateau is a thick probably laminated transition zonemore between the depths of 40 and 55 km a result consistent with interpretations of early refraction work in the area less

the steeply subducting edge of the cocos ridge evidence from receiver functions beneath the northern talamanca range south central costa rica the deep structure of the south central costa rican subduction zone has not been studied in great detail so far because large parts of the area are virtually inaccessible we present a receiver function study along a transect of broadband seismometers through the northern flank of the cordillera de talamanca south costa rica below moho depths the receiver functions image a dipping positive conversion signal this is interpreted as the subducting cocos plate slab compatible with the conversions in the individual receiver functions in finite difference modeling a dipping signal such as the one imaged can only be reproduced by a steeply 80 dipping structure present at least until a depth of about 70 100 km below this depth the length of the slab cannot be determined because of possible scattering effects the proposed position of the slab agrees with previous results from local seismicity local earthquake tomography and active seismic studies while extending the slab location to greater depths and steeper dip angle along the trench no marked change is observed in the receiver functions suggesting that the steeply dipping slab continues until the northern flank of the cordillera de talamanca in the transition region between the incoming seamount segment and cocos ridge considering the time predicted for the establishment of shallow angle underthrusting after the onset of ridge collision the southern costa rican subduction zone may at present be undergoing a reconfiguration of subduction style where the transition to shallow underthrusting may be underway but still incomplete

array observations of microseismic noise and the nature of h v in the mississippi embayment abstract ambient ground motion data were collected using phased seismic arrays in fall 2002 and spring 2007 within the mississippi embayment and at a single station external to the embayment these data allowed us to determine the wave field composition of ambient noise for understanding wave propagation mechanisms giving rise to spectral peaks using nakamura s h v technique ambient ground motions in the frequency band of 0 1 0 33 hz 10 3 sec period were dominated by spatially localized rayleigh and love wave microseisms generated by high ocean waves along the north american seaboard in the time periods of analysis seismic waves important in forming the h v peak near 4 sec period are composed of relatively high phase velocity rayleigh and love waves that convert to propagating homogeneous shear waves in the thick unconsolidated sediments of the embayment the h v resonant period is controlled by both constructive and destructive interference of these shear waves a simple relationship for the h v peak is given using a propagator matrix formulation that predicts the resonance frequency of a layered medium for surface wave motion at the base of the system the amplitude of the observed h v peak however does not give an accurate estimate of shear wave amplification because it depends on the slowness of the incident wave the inconsistency in estimated average shear wave velocities using the h v method and differential travel times of local earthquake sp phases in the mississippi embayment may be explained by misidentification of sp wave conversion points from deeper interfaces

estimating coefficient of consolidation from piezocone tests data have been reviewed from sites in europe and north and south america as well as published data from south africa the review has concentrated on dissipation data from piezocone tests cptu to

structure of the southern keweenawan rift from cocorp surveys across the midcontinent geophysical anomaly in northeastern kansas this is the published version copyright 1984 american geophysical union all rights reserved

three dimensional seismic velocity model for the unconsolidated mississippi embayment sediments from h v ambient noise measurements abstract the horizontal to vertical h v technique by nakamura 1989 was applied to data from 30 new field stations and 64 other broadband temporary and permanent seismic stations within the mississippi embayment of the central united states to develop a 3d model of unconsolidated sediment shear wave velocity structure using the dart 1992 map of sediment thickness as a basis two self consistent models of average shear wave velocity versus sediment thickness were developed by utilizing the theoretical linear relationship between the frequency of the h v peak and shear wave velocity one model was based on the observation that the h v peak period t p s versus sediment thickness h m was seen to be approximately linear with the relationship t p 0 003266 h 1 084 the second model was developed by considering peak frequency f p versus sediment thickness parameterized to follow ln f p 8 325 10 7 h 2 0 00232 h 0 01796 overall the models show low average shear wave velocity near the edge of the mississippi embayment with velocities increasing with increasing sediment thickness consistent with increased sediment compaction these models will be useful in studies of site resonance and amplification for earthquake shaking hazards and for wave propagation computations for the region

crustal structure of the gujarat region india new constraints from the analysis of teleseismic receiver functions abstract in this study receiver function analysis is carried out at 32 broadband stations spread all over the gujarat region located in the western part of india to image the sedimentary structure and investigate the crustal composition for the entire region the powerful genetic algorithm technique is applied to the receiver functions to derive s velocity structure beneath each site a detail image in terms of basement depths and moho thickness for the entire gujarat region is obtained for the first time gujarat comprises of three distinct regions kachchh saurashtra and mainland in kachchh region depth of the basement varies from around 1 5 km in the eastern part to 6 km in the western part and around 2 3 km in the northern part to 4 5 km in the southern part in the saurashtra region there is not much variation in the depth of the basement and is between 3 km and 4 km in gujarat mainland part the basement depth is 5 8 km in the cambay basin and western edge of narmada basin in other parts of the mainland it is 3 4 km the depth of moho beneath each site is obtained using stacking algorithm approach the moho is at shallower depth 26 30 km in the western part of kachchh region in the eastern part and epicentral zone of the 2001 bhuj earthquake large variation in the moho depths is noticed 36 46 km in the saurashtra region the crust is more thick in the northern part it varies from 36 38 km in the southern part to 42 44 km in the northern part in the mainland region the crust is more thick 40 44 km in the northern and southern part and is shallow in cambay and narmada basins 32 36 km the large variations of poisson s ratio across gujarat region may be interpreted as heterogeneity in crustal composition high values of 0 30 at many sites in kachchh and few sites in saurashtra and mainland regions may be related to the existence of high velocity lower crust with a mafic ultramafic composition and locally to the presence of partial melt the existing tectono sedimentary models proposed by various researchers were also examined

lithospheric structure of the southern french alps inferred from broadband analysis abstract broadband receiver functions analysis is commonly used to evaluate the fine scale s velocity structure of the lithosphere we analyse teleseismic p waves and their coda from 30 selected teleseismic events recorded at three seismological stations of to the french tgrs network in the alpes maritimes receiver functions are computed in the time domain using an svd matrix inversion method dipping moho and lateral heterogeneities beneath the array are inferred from the amplitude arrival time and polarity of locally generated ps phases we propose that the moho dips 11 towards 25 10 n below station calf in the outer part of the alpine belt at this station we determine a moho depth of about 20 2 km the same depth is suggested below saof station also located in the fold trust belt beneath station stet located in the inner part of the alpine belt the moho depth increases to 30 km and dips towards the n nw moreover 1d modelling of summed receiver function from stet station constrains a crustal structure significantly different from that observed at stations located in the outer part of the alps indeed beneath calf and saof stations we need a 2 km thick shallow low velocity layer to fit best the observed receiver functions whereas this layer seems not to be present beneath stet station because recent p coda studies have shown that near receiver scattering can dominate teleseismic p wave recordings in tectonically complicated areas we account for effect of scattering energy in our records from array measurements as the array aperture is wide relative to the heterogeneity scale length in the area the array analysis produces only smooth imaging of scatterers beneath the stations

seismic ground motions from a bolide shock wave 1 an intensely brilliant bolide accompanied by an audible sonic boom occurred on the night of 3 november 2003 2150 lt or 4 november 2003 0350 ut in northeastern arkansas the sonic boom was well recorded by 22 three component stations of the center for earthquake research and information cooperative seismic network arrival times and wave polarizations were used to reconstruct the acoustic wave front propagating across the network and to estimate trajectory parameters of the bolide a grid search location technique constrains the trajectory and gives a reference height of 50 100 km above the southern edge of the network an azimuth of propagation of 270 290 toward the northwest and a plunge of 38 48 downward the trajectory and date of the bolide event are consistent with a taurid shower meteor transient ground motions from the sonic boom were studied using plane wave cagniard dehoop and propagator matrix theory for an incident pressure pulse impinging on a layered elastic earth model general characteristics of the vertical and radial polarization and wave frequency content require acoustic coupling within a thin 10 m near surface layer with low p wave 0 25 km s and s wave 0 125 km s velocities ground motions are generally confined to this near surface layer are not sensitive to deeper earth structure within the mississippi embayment unconsolidated sediments and display both leaky mode pl a type of dispersed p type seismic wave and locked mode rayleigh wave propagation acoustic wave ground motion coupling studies may be a useful way to analyze near surface site responses to determine velocity structure in earthquake shaking hazard studies

velocity structure of the northern mississippi embayment sediments part i teleseismic p wave spectral ratios analysis abstract the mississippi embayment overlies the new madrid seismic zone in the central united states and consists of a thick succession of unconsolidated sediments that covers the paleozoic basement rock the high velocity contrast at the basement sediment interface and the near vertical ray paths of teleseismic p waves generate very large p to s conversions on the radial component and large p reverberations on the vertical component this characteristic of p wave propagation is used to study p and s wave resonance in the sedimentary layer horizontal to vertical h v and vertical to horizontal v h power spectral ratios are calculated for a time window around the teleseismic p wave arrivals at broadband stations of the usarray transportable array northern embayment lithosphere experiment and the new madrid cooperative seismic network in the embayment using a map of sediment thickness we developed models for average p and s wave velocity versus sediment thickness the resulting shear wave velocity model matches very well with the model obtained from an h v ambient noise study in the region the shear wave velocity model shows low velocity near the edges of the embayment with average velocities increasing with increasing sediment thickness consistent with increased sediment compaction fundamental resonance frequency for s waves ranges from 0 2 to 0 4 hz for the embayment sediments electronic supplement two figures showing the synthetic test results and a table that includes peak resonance frequency and average v p and v s

estimating crustal thickness using sspmp in regions covered by low velocity sediments imaging the moho beneath the southeastern suture of the appalachian margin experiment sesame array se atlantic coastal plain

explosion source strong ground motions in the mississippi embayment two strong motion arrays were deployed for the october 2002 embay ment seismic excitation experiment to study the spatial variation of strong ground motions in the deep unconsolidated sediments of the mississippi embayment because there are no comparable strong motion data from natural earthquakes in the area each linear array consisted of eight three component k2 accelerographs spaced 15 m apart situated 1 2 and 2 5 km from 2268 kg and 1134 kg borehole explosion sources respectively the array data show distinct body wave and surface wave arrivals that propagate within the thick unconsolidated sedimentary column the high velocity basement rocks and small scale structure near the surface time domain coherence of body wave and surface wave arrivals is computed for acceleration velocity and displacement time windows coherence is high for relatively low frequency vertical component rayleigh waves and high frequency p waves propagating across the ar ray prominent high frequency ps conversions seen on radial components a proxy for the direct s wave from earthquake sources lose coherence quickly over the 105 m length of the array transverse component signals are least coherent for any ground motion and appear to be highly scattered horizontal phase velocity is com puted by using the ratio of particle velocity to estimates of the strain based on a plane wave propagation model the resulting time dependent phase velocity map is a useful way to infer the propagation mechanisms of individual seismic phases and time windows of three component waveforms displacement gradient analysis is a complementary technique for processing general spatial array data to obtain hori zontal slowness information

hydraulic conductivity measurement from on the fly ucpt sounding and from viscpt detailed profiles of hydraulic conductivity are recovered from the deployment of direct push permeameters at the geohydrologic experimental and monitoring site kansas measurements with thin tapered tips and with standard cone penetration test ucpt tips show only minor differences suggesting that tip local disturbance effects are small and that routine ucpt measurements are therefore representative of pristine conditions permeameter measurements are correlated against closely deployed ucpt measurements estimates of hydraulic conductivity from ucpt sounding correlations and from grain size correlations derived from both vision cpt viscpt and from cone metrics on the fly evaluations of hydraulic conductivity require that the tip local pressure field is both steady and partially drained continuous penetration is shown to yield pore pressures sufficiently close to steady to enable conductivities to be directly determined cone metrics of cone resistance sleeve friction and pore pressure ratio are shown to be sufficient to discriminate between partially drained and undrained behavior and therefore to define the permissible regime where conductivities may be determined from ucpt sounding data estimates of hydraulic conductivities from ucpt sounding data are shown to correlate with independently measured magnitudes of hydraulic conductivity recovered using the permeameter tests however most of hydraulic conductivities from the permeameter tests 4 5 cm length screen are underpredicted suggesting that storage effects the inability to reach a steady state or the effects of dilation may influence the response profiles of hydraulic conductivities evaluated from the on the fly method also correlate well with the permeameter measurements predictions from soil classification and from viscpt methods are also capable of estimating conductivities with soil classifications giving the closest correlations of these two for this particular suite of data