seismic tomography a window into deep earth abstract the goal of this paper is to provide an overview of the current state of the art in seismic tomography and trace its origins from pioneering work in the early 1970s to its present status as the pre eminent tool for imaging the earth s interior at a variety of scales due to length limitations we cannot hope to cover every aspect of this diverse topic or include mathematical derivations of the underlying principles rather we will provide a largely descriptive coverage of the methodology that is targeted at readers not intimately familiar with the topic the relative merits of local versus global parameterization ray tracing versus wavefront tracking backprojection versus gradient based inversion and synthetic testing versus model covariance are explored a variety of key application areas are also discussed including body wave traveltime tomography surface wave tomography attenuation tomography and ambient noise tomography established and emerging trends many of which are driven by the ongoing rapid increases in available computing power will also be examined including finite frequency tomography full waveform tomography and joint tomography using multiple datasets several practical applications of seismic tomography including body wave traveltime attenuation and surface waveform are presented in order to reinforce prior discussion of theory

structure of the california coast ranges and san andreas fault at safod from seismic waveform inversion and reflection imaging 1 a seismic reflection and refraction survey across the san andreas fault saf near parkfield provides a detailed characterization of crustal structure across the location of the san andreas fault observatory at depth safod steep dip prestack migration and frequency domain acoustic waveform tomography were applied to obtain highly resolved images of the upper 5 km of the crust for 15 km on either side of the saf the resulting velocity model constrains the top of the salinian granite with great detail steep dip reflection seismic images show several strong amplitude vertical reflectors in the uppermost crust near safod that define an 2 km wide zone comprising the main saf and two or more local faults another prominent subvertical reflector at 2 4 km depth 9 km to the northeast of the saf marks the boundary between the franciscan terrane and the great valley sequence a deep seismic section of low resolution shows several reflectors in the salinian crust west of the saf two horizontal reflectors around 10 km depth correlate with strains of seismicity observed along strike of the saf they represent midcrustal shear zones partially decoupling the ductile lower crust from the brittle upper crust the deepest reflections from 25 km depth are interpreted as crust mantle boundary

dextral shear along the eastern margin of the colorado plateau a kinematic link between laramide contraction and rio grande rifting ca 75 13 ma abstract kinematic data associated with both laramide age and style and rio grande rift related structures show that the latest cretaceous to neogene interaction between the colorado plateau and the north american craton was dominantly coupled with a component of dextral shear consistent with earlier studies minor fault data in this study yielded results of varied kinematics inverted to a common northeast oriented hemisphere the mean trend of kinematic shortening associated with laramide age structures is documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6

finite difference calculation of traveltimes in three dimensions the traveltimes of first arriving seismic rays through most velocity structures can be computed rapidly on a three dimensional numerical grid by finite difference extrapolation head waves are properly treated and shadow zones are filled by the appropriate diffractions differences of less than 0 11 percent are found between the results of this technique and ray tracing for a complex but smooth model this scheme has proven useful for earthquake location and shows promise as an inexpensive well behaved substitute for ray tracing in forward modeling and kirchhoff inversion applications

inversion of seismic refraction and wide angle reflection traveltimes for three dimensional layered crustal structure summary we present a method for the determination of crustal structure by simultaneous inversion of seismic refraction and wide angle reflection traveltimes for 3 d interface geometry and layer velocity crustal structure is represented by layers in which velocity varies linearly with depth separated by smooth interfaces with a cubic b spline parametrization lateral variations in structure are therefore represented by variations in interface depth only the model parametrization we have chosen means that ray paths consist of piecewise circular arc segments for which analytic expressions of trajectory and traveltime are calculated the two point problem of finding the first arrival ray path and traveltime of a specified phase between a given source and receiver is solved using a shooting technique a subspace inversion method is used to solve the inverse problem which is formulated as a non linear optimization problem in which we seek to minimize an objective function that consists of a data residual term and a regularization term before performing the inversion each data pick must be assigned as a refraction or reflection from a particular layer or interface since our method represents structure in terms of interfaces fewer parameters would generally be used in a reconstruction compared to an equivalent 3 d variable velocity inversion the method is well suited to wide angle surveys that consist of many sources and relatively few receivers or vice versa such as marine shot lines used in conjunction with land based receivers data coverage in this kind of survey is often sparse and especially if near offset ray paths are unavailable highly variable a 3 d synthetic test with an array consisting of eight sources lying within a three sided square of 79 receivers is described the test model consists of a three interface structure that includes a layer pinch out and the synthetic data set comprises 987 refraction and 930 reflection travel times contaminated with 75 ms of data noise six iterations of an 18 d subspace method demonstrate that the method can produce an accurate reconstruction that satisfies the data from a 1 d starting model we also find that estimates of a posteriori model covariance and resolution obtained from linear theory are useful in analysing solution reliability despite the non linear nature of the problem application of the method to data collected as part of the 1995 tasgo project in tasmania shows that the method can satisfy 1345 refraction and reflection traveltime picks with a geologically reasonable and robust 254 parameter three interface model the inversion results indicate that the moho beneath nw tasmania varies in depth from 27 km near the coast to 37 km near central tasmania with the major increase in depth occurring across the arthur lineament

applying waveform inversion to wide angle seismic surveys abstract multi scale frequency domain acoustic waveform inversion was applied to refraction and wide angle reflection seismic surveys of the upper crust across the plate bounding san andreas fault california and the chesapeake bay impact structure virginia this paper presents and compares the data the preconditioning and different inversion strategies the inversions start at 3 hz and they are stopped at 15 hz due to increasing non linear artifacts the resulting waveform models show a significant improvement in resolution compared to the traveltime starting models but they do not achieve the resolution demonstrated in synthetic studies possible reasons for this limitation are discussed especially the possibility of insufficient bandwidth and the effect of normalizing amplitudes the comparison of results from normalized amplitude and true amplitude waveform inversions indicates that amplitudes do not strongly constrain the velocity structure phase coherency weights are presented that mitigate the impact of noise maps of phase misfits provide a quantitative overview of the data residuals and some insight into the spatial distribution of errors they are helpful for monitoring the progress of the inversion and for determining if and when it must be stopped

3d simultaneous seismic refraction and reflection tomography of wide angle data from the central chilean margin we present an application of three dimensional 3d simultaneous seismic refraction and reflection tomography for velocity and interface structure the inversion technique and method for developing the starting model are specifically designed for relatively sparse wide angle data acquired across strongly varying structure the data were recorded in a region of seamount subduction on the chilean margin and consist of seven receivers and ten intersecting airgun profiles over a 90 90 km area providing constraint to 25 km depth the tomographic method and the final model are assessed through a comparison with the large scale geologic features of the margin and a resolution test the 3d model shows the valparaiso forearc basin the accretionary wedge the subducting plate and possibly a subducted seamount our results show the potential of relatively sparse 3d wide angle data

morphological analysis of the drainage system in the eastern alps abstract we study the morphology of the major rivers draining the eastern alps to test whether the active tectonics of this part of the orogen is reflected in the shape of channel profiles of the river network in our approach we compare channel profiles measured from digital elevation models with numerically modelled channel profiles using a stream power approach it is shown that regions of high stream power coincide largely with regions of highest topography and largest uplift rates while the forelands and the pannonian basin are characterised by a significantly lower stream power from stream power modelling we conclude that there is young uplift at the very east of the eastern alps in the bohemian massif and in the pohorje range the impact of the pleistocene glaciations is explored by comparing properties of rivers that drain in proximal and distal positions relative to the ice sheet during the last glacial maximum our analysis shows that most knick points wind gaps and other non equilibrium features of catchments covered by ice during the last glaciations salzach enns can be correlated with glacial processes in contrast the ice free catchments of the mur and drava are characterized by channels in morphological equilibrium at the first approximation and are showing only weak evidence of the strong tectonic activity within these catchments finally the channel profiles of the adige and the divide between the upper rhine and danube catchments differ significantly from the other catchments we relate this to the fact that the adige and the rhine respond to different base levels from the remainder of the eastern alps the adige may preserve a record from the messininan base level change and the rhine is subject to the base level lowering in the rhine graben

implications of jurassic cretaceous and proterozoic piercing lines for laramide oblique slip faulting in new mexico and rotation of the colorado plateau discussion and reply discussion cather 1999 1 provided a useful compilation of stratigraphic data relevant to tests of models for possible dextral offset along the east side of the colorado plateau during the laramide orogeny his paper allowed the reader to judge whether this independent data set is consistent with

adaptive traveltime tomography of densely sampled seismic data we present a new 2 d traveltime tomography method for the inversion of densely sampled seismic streamer data this method was especially designed for the efficient inversion of long offset multichannel data a layer interface model is used to fit ray traced traveltime data to observed seismic data the solution of the forward problem is based on initial value ray tracing in a triangulated grid with a linear interpolation of the squared slowness we implement an adaptive model parametrization based on ray density which allows for smaller velocity cells with subsequent iteration steps we solve the inverse problem using an iterative linearized joint inversion of reflection and refraction data for interface and velocity structures adaptive smoothing regularization is implemented in the form of a priori model covariances as the cell sizes decrease with increasing iteration numbers the model covariance ranges are reduced allowing for more detail to emerge in the model we demonstrate the algorithm s ability to invert successfully a realistic crustal velocity structure in a synthetic model several adaptive and non adaptive model parametrizations are tested the joint interface and velocity inversion of real long offset reflection and refraction traveltime data is presented as a second example we demonstrate that our results are in good agreement with independently derived velocity models

effects of surface scattering in full waveform inversion in full waveform inversion of seismic body waves often the free surface is ignored on grounds of computational efficiency asyntheticstudywasperformedtoinvestigatetheeffectsofthissimplification intermsofsizeandfrequency the testmodelanddataconformtoareallong offsetsurveyofthe upper crust across the san andreas fault random fractal variations are superimposed on a background model with strong lateral and vertical velocity variations ranging from 1200to6800m s syntheticdatawerecomputedandinverted forthismodelanddifferenttopographies afullyviscoelastic time domain code was used to synthesize the seismograms and a viscoacoustic frequency domain code was utilized to invert them the inversion was focused on early arrivals which are dominated by p waves but also contain strong p rayleigh wave conversions from the near field of the receiver resulting waveform models show artifacts and a loss of resolution from neglecting the free surface in the inversion but the inversions are stable and they still improve the resolution of kinematic models the extent of deterioration dependsmoreonthesubsurfacethanonthesurfacestructure inversion results were improved at no additional expense by introducing a weak contrast along a staircase function above shotsandreceivers

quantitative imaging of the permo mesozoic complex and its basement by frequency domain waveform tomography of wide aperture seismic data from the polish basin in this study we present the workflow and results of 2d frequency domain waveform tomography applied to the global offset seismic data acquired in central poland along a 50 km long profile during the grundy 2003 experiment the waveform tomography method allows full exploitation of the wide aperture content of these data and produces in a semi automatic way both the detailed p wave velocity model and the structural image i e perturbations in respect to the starting model thirteen frequencies ranging from 4 to 16 hz were inverted sequentially gradually introducing higher wavenumbers and more details into the velocity models although the data were characterised by relatively large shot spacings 1 5 km we obtained clear images both of the mesozoic and permian sedimentary cover velocity patterns indicated facies changes within the jurassic and zechstein strata a high velocity layer ca 5500 m s was found near the base of triassic scythian which made the imaging of a deeper layer difficult nevertheless we were able to delineate the base of the permian i e base of the rotliegend which was not possible to derive from conventional common depth point processing as well as some deeper events attributed to the carboniferous the sub permian events formed a syn form which favoured our previous interpretation of a depression filled with upper carboniferous molasse the validity of the waveform tomography derived model was confirmed by well log data forward ray tracing modelling and synthetic seismograms calculations provided another justification for the key structures present in the waveform tomography model

the 1942 southwest indian ocean ridge earthquake largest ever recorded on an oceanic transform the 1942 southwest indian ocean earthquake is the largest ever recorded on an oceanic transform its mechanism has essentially the expected pure strike slip geometry using long period surface wave techniques the seismic moment is found to be 1 3 1028 dyn cm directivity suggests southwestward rupture propagation over approximately 130 km this shock is then much smaller than previously reported on the basis of its high unified richter magnitude m 8 3 it does not show the slow energy release occasionally found in large transform fault events scaling laws and thermal modeling suggest that seismic slip extended at least to the 600 c isotherm

quantitative imaging of complex structures from dense wide aperture seismic data by multiscale traveltime and waveform inversions a case study an integrated multiscale seismic imaging flow is applied to dense onshore wideaperture seismic data recorded in a complex geological setting thrust belt an initial p wave velocity macromodel is first developed by first arrival traveltime tomography this model is used as an initial guess for subsequent full waveform tomography which leads to greatly improved spatial resolution of the p wave velocity model however the application of full waveform tomography to the high frequency part of the source bandwidth is difficult due to the non linearity of this kind of method moreover it is computationally expensive at high frequencies since a finitedifference method is used to model the wave propagation hence full waveform tomography was complemented by asymptotic prestack depth migration to process the full source bandwidth and develop a sharp image of the short wavelengths the final traveltime tomography model and two smoothed versions of the final full waveform tomography model were used as a macromodel for the prestack depth migration in this study wide aperture multifold seismic data are used after specific preprocessing of the data 16 frequency components ranging from 5 4 hz to 20 hz were inverted in cascade by the full waveform tomography algorithm the full waveform tomography successfully imaged sw dipping structures previously identified as highresistivity bodies the relevance of the full waveform tomography models is demonstrated locally by comparison with a coincident vertical seismic profiling vsp log available on the profile the prestack depth migrated images inferred from the traveltime and the smoothed full waveform tomography macromodels are shown to be on the whole consistent with the final full waveform tomography model a more detailed analysis based on common image gather computations and local comparison with the vsp log revealed that the most accurate migrated sections are those obtained from the full waveform tomography macromodels a resolution analysis suggests that the asymptotic prestack depth migration successfully migrated the wideaperture components of the data allowing medium wavelengths in addition to the short wavelengths of the structure to be imaged

the buried shape of an alpine valley from gravity surveys seismic and ambient noise analysis summary it has long been observed that damage due to earthquakes depends greatly on local geological conditions alpine valleys represent a typical populated environment where large amplifications can take place owing to the presence of surface soils with poor mechanical properties combined to complex topography of the rock basin in the framework of the eu interreg iiib sismovalp project seismic hazard and alpine valley response analysis a stretch of the tagliamento river valley trv located in the north western part of the friuli region italy and close to the epicentre of the 1976 mw 6 4 earthquake has been investigated with the aim to define the buried shape of the valley itself two non invasive low cost independent geophysical methods were used i detailed gravity survey and ii h v spectral ratio hvsr of microtremors because of structural geological complexity and active tectonics of the friuli region an irregular valley shape was expected in this area the independent analysis performed by gravity and passive noise and complemented with refraction seismic velocity profiles confirms this hypothesis and leads to two models that were consistent but for some small scale details the maximum depth estimated is about 400 450 m in the southern part of the valley while a mean value of 150 180 m is estimated in the northern part the sediment thickness obtained for this stretch of the trv is quite large if compared to eastern alps plio quaternary rates therefore the valley shape imaged by this study better corresponds to the top of carbonate rocks finally on the basis of the obtained morphology and some direct measurements we conclude that the trv features an overall 1 d seismic response i e the resonance is related only to the sediment thickness rather than to the cross section shape but in its deepest part some limited 2 d effects could take place

multiscale seismic imaging of the eastern nankai trough by full waveform inversion 1 classical active seismic methods fail to sharply image the earth s deep crust we present the first crustal scale application of 2 d full waveform inversion based on dense ocean bottom seismic data to investigate the eastern nankai subduction system japan this approach allows to quantify seismic velocities up to an unprecedented degree of resolution results reveal compressive tectonic features within both the subducting oceanic crust and the backstop at depth velocity anomalies along major faults and structural discontinuities bring evidence for the presence of fluids and weakened material and also for a possible coseismic slip partitioning structure index terms 0902 exploration geophysics computational methods seismic 3025 marine geology and geophysics marine seismics 0935 8010 structural geology fractures and faults 8105 tectonophysics continental margins and sedimentary basins 1212 citation dessa j x s operto s kodaira a nakanishi g pascal j virieux and y kaneda 2004 multiscale seismic imaging of the eastern nankai trough by full waveform inversion geophys res lett 31 l18606 doi 10 1029 2004gl020453

high resolution seismic attenuation imaging from wide aperture onshore data by visco acoustic frequency domain full waveform inversion summary here we assess the potential of the visco acoustic frequency domain full waveform inversion fwi to reconstruct p wave velocity vp and p wave attenuation factor q from surface onshore seismic data first we perform a sensitivity analysis of the fwi based upon a grid search analysis of the misfit function and several synthetic fwi examples using velocity and q models of increasing complexity subsequently we applied both the acoustic and viscoacousticfwitorealsurfacewide apertureonshoreseismicdatafromthepolishbasin wherea strongattenuationoftheseismicdataisobserved thesensitivityanalysisofthevisco acoustic fwi suggests that the fwi can jointly reconstruct the velocity and the attenuation factor if the signatureoftheattenuationissufficientlystronginthedata asyntheticexamplecorresponding to a homogeneous background model with an inclusion shows a reliable reconstruction of vp and q in the inclusion when q is as small as 90 and 50 in the background model and in the inclusion respectively a first application of acoustic fwi to real data shows that a heuristic normalization of the data with offset allows us to compensate for the effect of the attenuation in the data and reconstruct a reliable velocity model alternatively we show that visco acoustic fwi allows us to reconstruct jointly both a reliable velocity model and a q model from the true amplitude data we propose a pragmatical approach based upon seismic modelling and source wavelet estimation to infer the best starting homogeneous q model for visco acoustic fwi we find the source wavelet estimation quite sensitive to the quality of the velocity and attenuation models used for the estimation for example source to source wavelets are significantly more consistent when computed in the final fwi model than in the initial one a good kinematic and amplitude match between the early arriving phases of the real and time domain synthetic seismograms computed in the final fwi model provides an additional evidence of the reliability of the final fwi model we find the recovered velocity and attenuation models consistent with the expected lithology and stratigraphy in the study area we link high attenuation zones with the increased clay content and the presence of the mineralized fluids

inversion of three dimensional wide angle seismic data from the southwestern canadian cordillera seismic refraction wide angle reflection data were recorded on a triangular array in southwestern british columbia centered on the boundary between the coast belt to the southwest and the intermontane belt to the northeast the experiment part of the lithoprobe southern cordillera transect enabled determination of the three dimensional 3 d velocity structure of the crust and upper mantle an algorithm for the inversion of wide angle seismic data to determine 3 d velocity structure and depth to reflecting interfaces is developed the algorithm is based on existing procedures for the inversion and forward modeling of first arrival travel times and forward modeling of reflection travel times including 1 forward modeling using a 3 d finite difference algorithm and 2 a simple velocity model parameterization for the inversion which eliminates the need to solve a large system of equations the existing procedure is extended to allow 1 the inversion of reflection times to solve for depth to a reflecting interface and or velocity structure 2 the inversion of first arrival travel times to solve for depth to a refracting interface and 3 layer stripping application of the algorithm to southern cordillera data uses pg to constrain upper crustal velocity structure pmp to constrain lower crustal velocity structure and depth to moho and pn to constrain upper mantle velocities and depth to moho the 3 d velocity model for the southwestern canadian cordillera is characterized by 1 significant lateral velocity variations at all depths that do not in general correlate with surface geological features or gravity data 2 a relatively high velocity middle and lower crust in the southwestern part of the study area which correlates with a strong relative gravity high and outlines the eastern extent of lower wrangellia an accreted terrane forming the insular belt to the west 3 a narrow zone of slower velocity in the lower crust and change in crustal thickness associated with the fraser fault system lending additional support to the view that it is a crustal penetrating fault 4 an average upper mantle velocity of 7 85 km s and 5 a depth to moho of 33 36 km in the intermontane belt and 36 38 km throughout most of the coast belt decreasing in the west to 33 km near the insular coast contact horizontal velocity structure slices and an interpreted cross section based on these and other results show the complexity of crustal structure in the region

application of waveform tomography to marine seismic reflection data from the queen charlotte basin of western canada to obtain a higher resolution quantitative p wave velocity model 2d waveform tomography was applied to seismic reflection data from the queen charlotte sedimentary basin off the west coast of canada the forward modeling and inversion were implemented in the frequency domain using the visco acoustic wave equation field data preconditioning consisted of f k filtering 2d amplitude scaling shot to shot amplitude balancing and time windowing the field data were inverted between 7 and 13 66 hz with attenuation introduced for frequencies 10 5 hz to improve the final velocity model two different approaches to sampling the frequencies were evaluated the limited maximum offset of the marine data 3770 m and the relatively high starting frequency 7 hz were the main challenges encountered during the inversion an inversion strategy that successively recovered shallow to deep structures was designed to mitigate these issues the inclusion of later arrivals in the waveform tomography resulted in a veloci

full waveform tomographic images of the peak ring at the chicxulub impact crater peak rings are a feature of large impact craters on the terrestrial planets and are generally believed to be formed from deeply buried rocks that are uplifted during crater formation the precise lithology and kinematics of peak ring formation however remains unclear previous work has revealed a suite of bright inward dipping reflectors beneath the peak ring at the chicxulub impact crater and that the peak ring was formed from rocks with a relatively low seismic velocity new two dimensional full waveform tomographic velocity images show that the uppermost lithology of the peak ring is formed from a thin 100 200 m thick layer of low velocity 3000 3200 m s rocks this low velocity layer is most likely composed of highly porous allogenic impact breccias our models also show that the change in velocity between lithologies within and outside the peak ring is more abrupt than previously realized and occurs close to the location of the dipping reflectors across the peak ring velocity appears to correlate well with predicted shock pressures from a dynamic model of crater formation where the rocks that form the peak ring originate from an uplifted basement that has been subjected to high shock pressures 10 50 gpa and lie above downthrown sedimentary rocks that have been subjected to shock pressures of 5 gpa these observations suggest that low velocities within the peak ring may be related to shock effects and that the dipping reflectors underneath the peak ring might represent the boundary between highly shocked basement and weakly shocked sediments

seismic imaging of the naga thrust using multiscale waveform inversion this case study images the structural features related to the naga thrust fault northeast india using a combination of multiscale waveform inversion and prestack depth migration psdm the waveform model and the psdm image complement each other the former provides a physical property map p wave velocity model and the latter provides a structural image the velocity model encompassing the starting model for waveform inversion is constructed using joint inversion of first and reflected traveltimes the 4 8 hz data are inverted consecutively in 1 hz bandwidths to yield the final waveform model which in turn is used for psdm the psdm image and the waveform model are consistent with the lithological interpretation of an inline exploratory well when interpreted jointly the psdm image and the waveform model reveal the presence of a conjugate fault system in the naga thrust and fold belt

multiscale imaging of complex structures from multifold wide aperture seismic data by frequency domain full waveform tomography application to a thrust belt summary an application of full waveform tomography to dense onshore wide aperture seismic data recorded in a complex geological setting thrust belt is presented the waveform modelling and tomography are implemented in the frequency domain the modelling part is solved with a finite difference method applied to the visco acoustic wave equation the inversion is based on a local gradient method only the p wave velocity is involved in the inversion the inversion is applied iteratively to discrete frequency components by proceeding from low to high frequencies this defines a multiscale imaging in the sense that high wavenumbers are progressively incorporated in images the linearized waveform tomography requires an accurate starting velocity model that has been developed by first arrival traveltime tomography after specific pre processing of the data 16 frequency components ranging between 5 4 and 20 hz were inverted ten iterations were computed per frequency component leading to 160 tomographic models the waveform tomography has successfully imaged southwest dipping structures previously identified from other geophysical data as being associated with high resistivity bodies the relevance of the tomographic images is locally demonstrated by comparison of a velocity depth function extracted from the waveform tomography models with a coincident vertical seismic profiling vsp log available on the profile moreover comparison between observed and synthetic seismograms computed in the starting traveltime and waveform tomography models demonstrates unambiguously that the waveform tomography successfully predicts for wide angle reflections from southwest dipping geological structures this study demonstrates that the combination of first arrival traveltime and frequency domain full waveform tomographies applied to dense wide aperture seismic data is a promising approach to quantitative imaging of complex geological structures indeed wide aperture acquisition geometries offer the opportunity to develop an accurate background velocity model for the subsequent waveform tomography this is critical because the building of the macromodel remains an open question when only near vertical reflection data are considered

an automated method for producing synoptic regional maps of river gradient variation procedure accuracy tests and comparison with other knickpoint mapping methods abstract the study of abrupt changes in longitudinal river profiles or knickpoints is currently approached through an empirical power law the slope area relationship results based on digital elevation model dem analyses and stream extractions are generally intended to determine crustal uplift rates and identify transient landscape conditions in this article we present an alternative geomorphometric method for locating knickpoints and knickzones based on local slope gradient and curvature attributes intended as a rapid regional scale automated knickpoint detection technique the accuracy of this slope curvature method is tested on two digital elevation grids nasa s srtm ground resolution of 90 m resampled here to 75 m and the aster dem 15 m in the sierra nacimiento new mexico usa a basement cored mountain range recently exhumed by waves of headward drainage integration in response to remote tectonic deformation in the adjacent rio grande rift out of every 10 gradient anomalies detected by the srtm derived numeric routine up to 8 are certifiable knickpoints recognized among a population of georeferenced occurrences surveyed in the field an independent comparison with the slope area method provided a further accuracy test which was particularly useful at sites that could not be validated in the field for practical reasons given the low tectonic activity of the study area the majority of knickpoints was also found to coincide with lithologic boundaries making it difficult without further geomorphological data to single out dynamic knickpoints directly caused by the upstream propagation of channel instabilities relating to base level change

shape and structure of the salzach valley austria from seismic traveltime tomography and full waveform inversion summary a 3 km long wide angle seismic survey across the salzach valley in the eastern alps austria provides a detailed characterization of its structure reflection and refraction traveltime tomography with adaptive gridding was applied to obtain a minimum structure model more detailed images of the valley fill were derived by acoustic full waveform inversion a multiscale frequency domain method was applied to data in the 4 26 hz range to improve the resolution from several hundred metres to less than fifty metres the starting frequency is unusually low for the size of the survey and it provides additional control of the long wavelengths of the background model which mitigates the non linearities of the inversion the final image is controlled by independent constraints from resistivity data and shallow wells it shows a confined upper aquifer that overlies a 150 m thick unsaturated zone no strong evidence was found for consolidated sediments at the bottom of the basin this and the large maximum depth to bedrock of 480 m suggests that the valley fill was repeatedly removed during strong glacial periods exposing the bedrock to deep erosion

implications of jurassic cretaceous and proterozoic piercing lines for laramide oblique slip faulting in new mexico and rotation of the colorado plateau discussion and reply discussion cather 1999 1 reevaluated piercing lines created by depositional pinch outs and truncations of jurassic cretaceous strata across the rio grande rift to conclude that a minimal dextral offset of 85 km of these rocks postdates their deposition his graphical depiction of the data and analysis of

simultaneous inversion of reflection and refraction seismic data and application to field data from the northern rio grande rift summary an inversion scheme that determines a velocity model simultaneously from normalincidence reflection and refraction wide angle reflection seismic data has been developed tested and applied to real seismic data simultaneous inversion minimizes the non uniqueness of inversion results a common midpoint cmp stacked reflection section provides a detailed image of the structural configuration in time refraction or wide angle reflection data can be used to derive a velocity model if both refraction data and normal incidence reflection data are available along coincident profiles simultaneous inversion of the data sets can produce an improved model with the extra control of the interface depth provided by reflection data it is also possible to avoid ambiguity of phase identification the commonly used damped least squares dls inversion method often results in significant inversion artefacts we provide effective methods for reducing inversion artefacts using both damping and smoothing from tests using synthetic data we conclude that the simultaneous inversion scheme can improve resolution and can be applied to velocity models with a reasonably complex structure the simultaneous inversion scheme has been successfully applied to coincident seismic reflection and refraction data recorded by the sage program in 1990 1991 in the western boundary area of the rio grande rift near abiquiu new mexico in this example the simultaneous inversion derived a velocity model in which stratigraphic units and extensional fault blocks can be resolved

inverse theory applied to multi source cross hole tomography part 1 acoustic wave equation method1 frequency domain methods are well suited to the imaging of wide aperture cross hole data however although the combination of the frequency domain with the wavenumber domain has facilitated the development of rapid algorithms such as diffraction tomography this has also required linearization with respect to homogeneous reference media this restriction and association restrictions on source receiver geometries are overcome by applying inverse techniques that operate in the frequency space domain in order to incorporate the rigorous modelling technique of finite differences into the inverse procedure a nonlinear approach is used to reduce computational costs the method of finite differences is applied directly to the frequency domain wave equation the use of high speed high capacity vector computers allow the resultant finite difference equations to be factored in place in this way wavefields can be computed for additional source positions at minimal extra cost allowing inversions to be generated using data from a very large number of source positions synthetic studies show that where weak scatter approximations are valid diffraction tomography performs slightly better than a single iteration of non linear inversion however if the background velocities increase systematically with depth diffraction tomography is ineffective whereas non linear inversion yields useful images from one frequency component of the data after a single iteration further synthetic studies indicate the efficacy of the method in the time lapse monitoring of injection fluids in tertiary hydrocarbon recovery projects

paleomagnetic and structural evidence for oblique slip in a fault related fold grayback monocline colorado significant fold axis parallel slip is accommodated in the folded strata of the grayback monocline northeastern front range colorado without visible large strike slip displacement on the fold surface in many cases oblique slip deformation is partitioned fold axis normal slip is accommodated within folds and fold axis parallel slip is resolved onto adjacent strike slip faults unlike partitioning strike parallel slip onto adjacent strike slip faults fold axis parallel slip has deformed the forelimb of the grayback monocline mean compressive paleostress orientations in the forelimb are deflected 15 37 clockwise from the regional paleostress orientation of the northeastern front range paleomagnetic directions from the permian ingleside formation in the forelimb are rotated 16 42 clockwise about a bedding normal axis relative to the north american permian reference direction the paleostress and paleomagnetic rotations increase with the bedding dip angle and decrease along strike toward the fold tip these measurements allow for 50 120 m of fold axis parallel slip within the forelimb depending on the kinematics of strike slip shear this resolved horizontal slip is nearly equal in magnitude to the 180 m vertical throw across the fold for 200 m of oblique slip displacement 120 m of strike slip and 180 m of reverse slip the true shortening direction across the fold is n90 e indistinguishable from the regionally inferred direction of n90 e and quite different from the s53 e fold normal direction recognition of this deformational style means that significant amounts of strike slip can be accommodated within folds without axis parallel surficial faulting

features of glacial valley profiles simply explained 1 glacial occupation of alpine valleys results in a distinct signature in the long valley profile including steepening of the profile in the headwaters flattening at lower elevations and a step in the profile at the convergence of headwater tributaries we present analytic results for glacial erosion patterns by making the following assumptions 1 the initial profile is linear 2 the width of the valley is uniform 3 the annual mass balance varies linearly with elevation 4 the glacier at any time is quasi steady 5 the erosion rate is proportional to ice discharge per unit valley width and 6 glacial erosion rates far exceed fluvial erosion rates a steady glacier under these conditions would erode a parabolic divot in the longitudinal valley profile with its maximum depth coinciding with the down valley position of the equilibrium line altitude ela the calculated flattening of the valley floor down valley of the ela and the steepening of it up valley captures the essence of the glacial signature when a reasonable probability distribution of elas is allowed the predicted erosion peaks at 30 40 of the down valley distance to the glacial limit and the pattern merges smoothly with the steeper fluvial profile downstream of the glacial limit profiles of mass balance that are capped at a maximum value produce shorter glaciers and a slight asymmetry in the expected erosion pattern only when we mimic the tributaries of glacial headwaters by specifying a valley width distribution do we obtain the upper step observed in many valley profiles

detecting near surface objects with seismic waveform tomography three shallow high velocity rubble filled targets are imaged using waveform tomography in an engineering scale clay embankment at seven sisters falls manitoba canada to locate targets buried at approximately 7 m as a blind test of geophysical imaging methods previous studies use near offset reflection methods to image the targets however this test uses waveform tomography of the long offset refracted arrivals to image p velocity and seismic attenuation the targets are invisible to standard traveltime tomography using weight drop data with frequencies of 20 150 hz the subwavelength targets are resolved in the velocity images and complementary images of seismic q are produced the interpreted target locations are consistent with limited survey information from the embankment construction multiple quality control efforts paired with a very good fit between model and observed data indicate the reliability of the results

implications of jurassic cretaceous and proterozoic piercing lines for laramide oblique slip faulting in new mexico and rotation of the colorado plateau discussion and reply discussion cather s 1999 1 paper concerning the amount of laramide right slip along northerly trending faults on the east side of the colorado plateau in northern new mexico contains two major flaws and several minor ones that cause his estimate of a minimum of 85 km of right slip to be highly

implications of jurassic cretaceous and proterozoic piercing lines for laramide oblique slip faulting in new mexico and rotation of the colorado plateau regional isopach patterns and pinch out data for nine stratigraphic units of jurassic and cretaceous age are either permissive or supportive of significant dextral slip of laramide age along the eastern colorado plateau boundary in new mexico the best constrained dextral offset estimates are for the sand hill nacimiento fault system 20 33 km and the previously published 13 km estimate for the defiance monocline which together yield a cumulative offset of 33 46 km mesozoic stratigraphic constraints for other laramide fault systems are less precise and typically provide only maximum limits for possible dextral offsets because of widely spaced control points and broad areas of tertiary erosion these less precise constraints allow as much as 40 60 km of laramide dextral slip along what is now the rio grande rift and as much as 110 km across the entire breadth of the laramide deformed zone in central and northern new mexico well documented dextral offsets of proterozoic lithologies and structures across the tusas picuris fault system 15 km and picuris pecos fault 37 km probably represent minimum laramide displacements because of the need to account for sinistral components related to other deformations these displacements when combined with dextral offsets along sand hill nacimiento and defiance structures yield a minimum dextral offset of 85 km for laramide structures in northern new mexico this minimum dextral offset is approximately equivalent to the amount of laramide crustal shortening on and northward of the colorado plateau a result that argues against nearby euler pole locations for laramide rotation of the colorado plateau relative to cratonic north america geological constraints allow 0 to 3 of laramide clockwise rotation of the colorado plateau additional clockwise plateau rotation during late cenozoic development of the rio grande rift was 1 to 1 5 geological constraints thus indicate that clockwise rotation of the colorado plateau from combined laramide and rio grande rift deformations was between about 1 and 4 5

two dimensional velocity models from wide angle seismic data by wavefield inversion summary modern wide angle surveys are often multi fold and multi channel with densely sampled source and receiver spacings such closely spaced data are potentially amenable to multi channel techniques involving wavefield propagation methods such as those commonly used in reflection data processing however the wide angle configuration requires techniques capable of handling very general wave types including those not commonly used in reflection seismology this is a situation analogous to that faced in cross borehole seismics where similar wave types are also recorded in a real cross borehole example we compare pre stack migration traveltime tomography and wavefield inversion we find that wavefield inversion produces images that are quantitative in velocity as are the tomograms but are of significantly higher resolution the wavefield inversion results have a resolution comparable to that of the qualitative pre stack migration images we seek to extend this novel development to the larger scale problem of crustal imaging an essential element of the approach we adopt is its formulation entirely within the temporal frequency domain this has three principal advantages 1 we can choose to decimate the data by selecting only a limited number of frequency components to invert thus making inversion of data from large numbers of source positions feasible 2 we can mitigate the notorious non linearity of the seismic inverse problem by progressing from low frequency components in the data to high frequency components and 3 we can include in the model any arbitrary frequency dependence of inelastic attenuation factors q and indeed solve for the spatial distribution of q an initial synthetic test with an anomaly located within the middle crust yields a velocity image with the correct structural features of the anomaly and the correct magnitude of velocity anomaly this is related to the fact that the reconstruction is obtained from forward scattered waves under these conditions the method thus behaves much like tomography a second test with a deeper more extensive anomaly yields an image with the correct velocity polarity and the correct location but with a deficiency in low and high wavenumbers in this case this is because the reconstruction is obtained from backscattered waves under these conditions the method behaves not like tomography but like migration a more extensive test based on a large wide angle survey in south eastern california and western arizona demonstrates a real potential for high resolution imaging of crustal structures although our results are limited by the acoustic approximation and by the relatively low frequencies that we can model today the images are sufficiently encouraging to warrant future research the problem of local minima in the objective function is the most significant practical problem with our method but we propose that appropriate layer stripping methods can handle this problem

waveform tomography at a groundwater contamination site surface reflection data wehaveappliedacoustic waveformtomographyto452d seismic profiles to image the 3d geometry of a buried paleochannel at a groundwater contamination site at hill air force base in utah the paleochannel which is incised into an alluvium covered clay aquitard acts as a trap for dense nonaqueous phase liquids dnapls that contaminate the shallowest groundwater system in the study area the 2d profiles were extracted from a 3d surface reflection data set first arrival traveltime tomography provided initial velocity models for the waveform tomography we inverted for six frequency components in the band 30 90 hz of the direct and refracted waves to produce 45 2d velocity models the flanks and bottom of a channel with a maximum depth of about 15 m were well modeled in most of the 45 parallel 2d slices whichallowedustoconstructa3dimageofthechannel by combining and interpolating between the 45 image slices the 3d model of the channel will be useful for siting extraction wells within the site remediation program the alluvium that fills the channel showed marked vertical and lateral velocity heterogeneity traveltime tomography and waveform tomography can be complementary approaches used together they can provide high resolution images of complicatedshallowstructures

three dimensional velocity structure in northern california coast ranges from inversion of local earthquake arrival times abstract the three dimensional p wave velocity structure in the upper crust in the northern california coast ranges from santa rosa to ukiah is obtained by simultaneous inversion of local earthquake and refraction travel time data for velocity and hypocentral parameters in this region where there are lateral heterogeneities the three dimensional inversion provides important results not found in two dimensional refraction studies the medium is parameterized with velocities at the intersections gridpoints of a nonuniform three dimensional grid travel times are calculated with approximate ray tracing along arcuate paths which are reasonable for lateral distances less than 45 km inversions with 5 to 10 and 2 to 3 km gridspacing achieved 80 per cent decreases in data variance the inversion with 2 to 3 km gridspacing reduced the rms residual level to approximately the level of timing error anomalously low velocities to at least 6 km depth are found along the maacama and healdsburg rodgers creek hrc fault zones the low velocity region is widest at the en echelon junction of the maacama and hrc fault zones low velocities are associated with the clear lake basin where there is a thick sequence of volcanics interbedded with sedimentary deposits there is a high velocity body located southeast of the geysers between the maacama and collayomi fault zones which may be associated with igneous intrusives or high grade metamorphism related to an underlying inferred partial melt body modeled in previous teleseismic travel time studies there is some indication in the vapor dominated geothermal reservoir of lower velocities relative to surrounding water saturated rock as has been shown in some laboratory experiments hypocenter locations obtained in the inversion show little variation from hypocenters obtained through inversion for one dimensional velocity model and station corrections for the inversion with 2 to 3 km gridspacing however some groups of events become more tightly clustered

balancing lateral orogenic float of the eastern alps abstract oligocene to miocene post collisional shortening between the adriatic and european plates was compensated by frontal thrusting onto the molasse foreland basin and by contemporaneous lateral wedging of the austroalpine upper plate balancing of the upper plate shortening by horizontal retrodeformation of lateral escaping and extruding wedges of the austroalpine lid enables an evaluation of the total post collisional deformation of the hangingwall plate quantification of the north south shortening and east west extension of the upper plate is derived from displacement data of major faults that dissect the austroalpine wedges indentation of the south alpine unit corresponds to 64 km north south shortening and a minimum of 120 km of east west extension lateral wedging affected the eastern alps east of the giudicarie fault west of the giudicarie fault north south shortening was compensated by 50 to 80 km of backthrusting in the lombardian thrust system of the southern alps the main structures that bound the escaping wedges to the north are the inntal fault system ca 50 km sinistral offset the konigsee lammertal traunsee klt fault 10 km and the salzach ennstal mariazell puchberg semp fault system 60 km these faults as well as a number of minor faults with displacements less than 10 km root in the basal detachment of the alps the thin skinned nature of lateral escape related structures north of the semp line is documented by industry reflection seismic lines crossing the northern calcareous alps nca and the frontal thrust of the eastern alps complex triangle zones with passive roof backthrusts of middle miocene molasse sediments formed in front of the laterally escaping wedges of the northern eastern alps the aim of this paper is a semiquantitative reconstruction of the upper plate of the eastern alps most of the data is published elsewhere

fracture network of the ferron sandstone member of the mancos shale east central utah usa abstract the fracture network at the outcrop of the ferron sandstone member of the mancos shale was studied to gain an understanding of the tectonic history of the region and to contribute data to studies of gas and water transmissivity related to the occurrence and production of coal bed methane about 1900 fracture readings were made at 40 coal outcrops and 62 sandstone outcrops in the area from willow springs wash in the south to farnham dome in the north of the study area in east central utah two sets of regional vertical to nearly vertical systematic face cleats were identified in ferron coals a northwest striking set trends at a mean azimuth of 321 and a northeast striking set has a mean azimuth of 55 cleats were observed in all coal outcrops examined and are closely spaced and commonly coated with thin films of iron oxide two sets of regional systematic joint sets in sandstone were also identified and have mean azimuths of 321 and 34 the joints of each set are planar long and extend vertically to nearly vertically through multiple beds the northeast striking set is more prevalent than the northwest striking set in some places joints of the northeast striking set occur in closely spaced clusters or joint zones flanked by unjointed rock both sets are mineralized with iron oxide and calcite and the northwest striking set is commonly tightly cemented which allowed the northeast striking set to propagate across it all cleats and joints of these sets are interpreted as opening mode mode i fractures abutting relations indicate that the northwest striking cleats and joints formed first and were later overprinted by the northeast striking cleats and joints burial curves constructed for the ferron indicate rapid initial burial after deposition the ferron reached a depth of 3000 ft 1000 m within 5 2 million years m y and this is considered a minimum depth and time for development of cleats and joints the sevier orogeny produced southeast directed compressional stress at this time and is thought to be the likely mechanism for the northwest striking systematic cleats and joints the onset of the laramide orogeny occurred at about 75 ma within 13 7 m y of burial and is thought to be the probable mechanism for development of the northeast striking systematic cleats and joints uplift of the ferron in the late tertiary contributed to development of butt cleats and secondary cross joints and probably enhanced previously formed fracture sets using a study of the younger blackhawk formation as an analogy the fracture pattern of the ferron in the subsurface is probably similar to that at the surface at least as far west as the paradise fault and joe s valley graben farther to the west on the wasatch plateau the orientations of ferron fractures may diverge from those measured at the outcrop

earthquake locations and three dimensional crustal structure in the coyote lake area central california previous work on the simultaneous inversion method has been improved and extended to incorporate iterative solution for earthquake locations and laterally heterogeneous structure approximate ray tracing and parameter separation are important elements of the improved method application of the method to p wave arrival time data recorded by stations of the u s geological survey central california network yields a three dimensional model for the velocity structure of the upper crust in an area encompassing the rupture zone of the coyote lake earthquake of august 1979 very strong correlations between the velocity model and the geology and gravity and magnetic anomalies are observed improved estimates of the locations of earthquakes in the study area are also determined the relocation of explosions indicates epicentral accuracies of the order of a kilometer or better based on the revised hypocentral locations it is concluded that the san andreas fault is vertical in this area with no actual offset between the epicenters and the fault trace in contrast the calaveras has two or more active fault surfaces one nearly vertical and another dipping 75 to the northeast

multistage multidirectional tertiary shortening and compression in north central new mexico the nature of laramide deformation in the southern rocky mountains remains highly debated advocates of north south strike slip faulting favor transpression and northward displacement of the colorado plateau whereas advocates of east west shortening by thrust faulting contest evidence for large right lateral displacements minor faults n 2552 were measured to determine the laramide to holocene structural evolution of north central new mexico multimodal slickenline and ideal 1 orientations as well as consistent crosscutting relationships indicate multiphase multidirectional faulting the oldest set of thrust and strike slip faults indicates east northeast to east trending shortening and compression the faults cut rocks as young as the upper paleocene lower eocene diamond tail formation strike slip faults from a second phase of northeast to north northeast trending shortening and compression cut the eocene galisteo formation but do not cut the 27 ma galisteo dike elsewhere later north striking strike slip faults cut 24 ma igneous units indicating north northeast to north trending shortening and compression of mid tertiary age subsequent north striking normal faults related to rio grande rifting commonly reactivate the mid tertiary strike slip fault planes these results show the validity of both strike slip and thrust hypotheses in north central new mexico although neither is adequate in exclusion of the other early laramide east west thrusting probably formed the north trending laramide arches of the region later counterclockwise rotation of regional shortening and compression directions may have caused transpression opening some late laramide axial basins and causing limited northward displacement of the colorado plateau subsequent mid tertiary strike slip deformation may be a missing link between paleogene laramide shortening and neogene rio grande rifting

least squares inversion of spatial seismic refraction data a method is demonstrated for recording and inverting in line and broadside seismic refraction and reflection data to obtain three dimensional structure and velocity information this technique of spatial seismic refraction recording produces a superabundance of common ray intersections at the target horizon the full power of the linear least squares inversion method may be used in the overconstrained case a large number of recording instruments are required to perform the experiment efficiently but this has the advantage of reducing the number of sources and difficult source corrections a damped least squares inversion method has been found to give rapid convergence even in the case of complex faulted models using noisy data the spatial seismic refraction recording method has been applied in a suboptimal experiment over the williston basin in southern saskatchewan the crustal structure consists of several normally faulted blocks defined by aeromagnetic anomalies over an area notable for its thick crust local seismicity and a linear conductive anomaly

compressional velocity and porosity in sand clay mixtures laboratory measurements of porosity and compressional velocity were conducted on unconsolidated brine saturated clean ottawa sand pure kaolinite and their mixtures at various confining pressures a peak in p velocity versus clay content in unconsolidated sand clay mixtures at 40 percent clay by weight was found the peak in velocity is 20 30 percent higher than for either pure clay or clean sand a minimum in porosity versus clay content at 20 40 percent clay by weight is also observed such behavior is explained using a micro geometrical model for mixtures of sand and clay in which two classes of sediments are considered 1 sands and shaley sands in which clay is dispersed in the pore space of load bearing sand and thus reduces porosity and increases the elastic moduli of the pore filling material and 2 shales and sandy shales in which sand grains are dispersed in a clay matrix for these sediments the model reproduces the extrema in velocity and porosity and accounts for much of the scatter in

efficient waveform tomography for lithospheric imaging implications for realistic two dimensional acquisition geometries and low frequency data summary we provide a series of numerical experiments designed to test waveform tomography under i a reduction in the number of input data frequency components efficient waveform tomography ii sparse spatial subsampling of the input data and iii an increase in the minimum data frequency used these results extend the waveform tomography results of a companion paper using the same third party 2 d wide angle synthetic viscoelastic seismic data computed in a crustal geology model 250 km long and 40 km deep with heterogeneous p velocity s velocity density and q factor structure accurate velocity models were obtained using efficient waveform tomography and only four carefully selected frequency components of the input data 0 8 1 7 3 6 and 7 0 hz this strategy avoids the spectral redundancy present in full waveform tomography and yields results that are comparable with those in the companion paper for an 88 per cent decrease in total computational cost because we use acoustic waveform tomography the results further justify the use of the acoustic wave equation in calculating p wave velocity models from viscoelastic data the effect of using sparse survey geometries with efficient waveform tomography were investigated for both increased receiver spacing and increased source spacing sampling theory formally requires spatial sampling at maximum interval of one half wavelength 2 5 km at 0 8 hz for data with receivers every 0 9 km conforming to this criterion artefacts in the tomographic images were still minimal when the source spacing was as large as 7 6 km three times the theoretical maximum larger source spacings led to an unacceptable degradation of the results when increasing the starting frequency image quality was progressively degraded acceptable image quality within the central portion of the model was nevertheless achieved using starting frequencies up to 3 0 hz at 3 0 hz the maximum theoretical sample interval is reduced to 0 67 km due to the decreased wavelengths the available sources were spaced every 5 0 km more than seven times the theoretical maximum and receivers were spaced every 0 9 km 1 3 times the theoretical maximum higher starting frequencies than 3 0 hz again led to unacceptable degradation of the results