glaciotectonically induced water throughflow structures in a late pleistocene drumlin kanrawer county galway western ireland abstract during drumlinisation brecciated bedrock was sheared over the proximal end of a late pleistocene drumlin at kanrawer western ireland high effective water pressures generated by shearing at the ice substrate interface during this event created a marked proximal to distal hydrostatic gradient affecting about 60 of the diamict which forms most of the drumlin sediment pile this resulted in large scale sediment reorganisation by darcian through flow and closed conduit flow of expelled pore waters and subglacial meltwater proximally this is reflected in the development of integrated honeycomb gravel structures formed by glaciotectonic shunting and tortuous throughflow in the diamicts distally the honeycomb structures give way to dish and pillar structures which are connected to gravelly and laminated sandy channel fill facies which cut obliquely across the long axis of the drumlin this facies transition reflects throughflow of pore water rising through the sediment pile and expelled along nye type channels excavated on the distal drumlin surface these proximal to distal sediment transformations suggest that current theoretical models of drumlin formation do not adequately represent the continuum of subglacial processes which accompany drumlinisation

experiment on fluidization in unbounded domains one dimensional fluidization in a bounded domain is a well understood phenomenon however in unbounded domains the formation of an interface between the fluidized and unfluidized regions is a complicated phenomenon that is poorly understood at present this experimental study advances the fundamental understanding of two dimensional fluidization and provides a data base for future numerical modeling the study was performed in a 365 7cm 121 9cm 30 4cm 12ft 4ft 1ft tank filled with sand overlying a small source pipe the back panel contains 143 pressure taps used to determine the hydraulic head distribution for the bed depths tested the lines of constant hydraulic head are horizontal in the fluidized region and curve downward in the unfluidized region the one dimensional theoretical superficial velocity needed to initiate fluidization provides a reasonable approximation of the two dimensional incipient fluidization conditions the average sand concentration in the fluidized region decreases with incr

sand boils induced by the 1993 mississippi river flood could they one day be misinterpreted as earthquake induced liquefaction in areas that are seismically active but lacking clear surficial faulting many paleoearthquake studies depend on the interpretation of ancient liquefaction features sand blows as indicators of prehistoric seismicity sand blows however can be mimicked by nonseismic sand boils formed by water seeping beneath levees during floods we examined sand boils induced by the mississippi river flood of 1993 in order to compare their characteristics with sand blows of the new madrid earthquakes of 1811 1812 we found a number of criteria that allow a distinction between the two types of deposits 1 earthquake induced liquefaction deposits are broadly distributed about an epicentral area whereas flood induced sand boils are limited to a narrow band along a river s levee 2 the conduits of most earthquake induced sand blows are planar dikes whereas the conduits of flood induced sand boils are most commonly tubular 3 depression of the preearthquake ground surface is usual for sand blows not for sand boils 4 flood induced sand boils tend to be better sorted and much finer than sand blow deposits 5 source beds for earthquake induced deposits occur at a wide range of depths whereas the source bed for sand boils is always near surface 6 materials removed from the walls surrounding the vent of a sand blow are seen inside sand blows but are rarely seen inside sand boils in general flood induced sand boils examined are interpreted to represent a less energetic genesis than earthquake induced liquefaction

boiling sand springs dismal river nebraska agents for formation of vertical cylindrical structures and geomorphic change boiling motion not temperature sand springs fed by ground water moving upward along distinct conduits occur along the dismal river in the nebraska sand hills the cylindrical conduits are developed in alluvium and are as large as 10 m in diameter and 44 m deep sides of the spring conduits are firm boiling sand is overlain in several places by a clear layer of water in the spring time varying wave patterns and boils can be observed along the interface between these layers sediment within the conduits is generally well sorted although some debris is present because of their large size firm sides and persistence in time the conduits have the potential for preservation as vertical cylindrical structures comparable to those reported in sedimentary rocks of several ages the discovery of preserved structures is evidence of paleo ground water discharge and therefore the structures are a useful mapping tool for determining position in landscape evolution

the puglia uplift se italy an anomaly in the foreland of the apenninic subduction due to buckling of a thick continental lithosphere the apenninic foreland shows two distinct structural signatures comparing the central adriatic sea and the puglia region during the pliocene pleistocene the central adriatic underwent high subsidence rates due to the eastward rollback of the hinge of the west dipping apenninic subduction the puglia region and the bradanic foredeep are located southward along strike in the same foreland but in contrast with the central adriatic after pliocene early pleistocene subsidence they underwent uplift since the middle pleistocene the geometry and the kinematics of the frontal accretionary wedge and related foreland changed from that moment on between the two areas at the front of the central northern apennines off scraping and subsidence continued whereas the foredeep and foreland of the southern apennines were buckled those differences are interpreted as being due to the larger subduction hinge rollback rate since middle pleistocene of the central adriatic lithosphere 70 km thick with respect to the thicker puglia 110 km the different thicknesses of the continental crust and lithosphere were inherited from the mesozoic rifting that disrupted the adriatic plate the different thicknesses appear to have controlled the variable degree of flexure of the lithosphere and its asthenospheric penetration rate the tremiti e w alignment is the right lateral lithospheric transfer zone of those different tectonic regimes the consequent different dip of the subduction in the two sections steeper west of puglia could also explain the lower elevation of the southern apennines compared to their central northern sector

soft sediment deformation in upper proterozoic torridonian sandstones applecross formation at torridon northwest scotland abstract the applecross formation upper proterozoic torridon group northwest scotland was deposited as planar laminated and cross bedded coarse sands in braided streams soft sediment deformation is described from a 97 m thick study section most of which comprises contorted stratification the main structures are cusps and complex recumbent folded cross bedding formed by water escape during fluidization four assemblages of structures are recognized deformation as isolated structures in an otherwise undeformed unit may have been triggered by fluid turbulence discrete and chaotic units record widespread liquefaction and fluidization respectively of the most recently deposited sediment deformation may have been triggered by upwelling groundwater multilayer complexes formed when water escape from a buried layer generated fluidization in the overlying sediment this may have been triggered by seismically induced liquefaction some parts of the succession were disturbed on separate occasions by different processes sediment laden currents are unlikely to have been a major trigger for deformation it is concluded that specific soft sediment deformation structures result from the combination of driving forces deformation mechanism and initial geometry assemblages of structures relate to the timing of deformation and are of more value in identifying the trigger for deformation

cross well seismic tomographic delineation of mineralization in a hard rock environment seismic first arrival times from a cross well experiment are inverted by an iteratively reweighted least squares method for the velocity distribution between boreholes the inversion is carried out in a multiresolution manner in which long wavelength features are reconstructed first and short wavelength features are gradually introduced into the solution model as such the inverse problem is overdetermined at the beginning and becomes mixed determined as the constraint on the solution is relaxed the reconstruction procedure is independent of the initial model and very robust an accurate and efficient first break traveltime calculation scheme is employed to eliminate the possibility of phase mismatches which can arise with traditional ray shooting or bending methods shot static delays are included with the model parameters as unknowns and are recovered simultaneously with the velocity distribution

experimental studies of the fluidization of layered sediments and the formation of fluid escape structures experiments demonstrate that fluid escape structures can be produced as a result of unstable fluidization behaviour where a lower base layer of granular material is inhibited from fluidizing by the presence of an overlying non fluidizing top layer before the base layer can fluidize the weight of the overlying material must be balanced and this is accomplished by base layer material pressing against the bottom surface of the confining top layer forming a static layer this static layer allows the top layer to lift away from the base layer which is then free to fluidize a water filled crack forms below the static layer and as this grows instability causes the static layer and top layer to bend and conical voids to form below the antiformal sections rupture occurs at the apex of the water void allowing the underlying water and fluidizing material to burst out through the top layer the fluidized base layer material then flows through the rupture until all of this material except that in the static layer is deposited above the previously overlying layer and a stable fluidization system results the top layer material is bent upwards around the rupture and the resulting pillar type escape structure is preserved if flow then ceases the vigour of the burst out is greatest when the base layer material has a grain size 15 of the top layer material if the base layer grain size is less than 8 of the top layer then base layer material will pass through the top layer pore spaces without forming an escape structure if cohesive material is present escape structures form when a layer of fine grained cohesive material overlies a layer of cohesionless material at low flow rates small pipes with scattered angular bends pierce the top layer and base layer material passes through them the base layer material is ejected on to the top layer and builds up around the mouth of each pipe to form constructional structures sand volcanoes this is in contrast to the cohesionless experiments where the weight of material being deposited on the top layer caused an ejecta filled depression to form around the rupture if flow then ceases both the pipes and the sand volcanoes are preserved at high flow rates where the base layer fluidizes the top cohesive layer becomes fragmented small fragments circulate within the fluidizing base layer and are preserved as floating clasts large fragments sink to the bottom of the fluidizing base layer erosion of the bottom surface of these larger fragments causes this surface to become convex downward the experimentally derived structures are similar to pillar type structures observed in the field and the processes described can be used to investigate the development of these structures fluidization experiments also demonstrate the genesis of dish structures and the cohesive behaviour can be applied to the deformation of these structures after initial formation

crosshole seismic tomography many tomographic interpretations of crosshole seismic traveltimes have approximated the raypaths with straight lines connecting the source and receiver this approximation is valid where the velocity does not vary greatly but in many regions of interest velocity variations of 10 20 percent or more are observed causing significant ray curvature other work has taken this nonlinear effect into account but there do not appear to be many cases of demonstrated success in its application to the crosshole seismic problem we present here an iterative inversion scheme based on two dimensional ray tracing and its successful application to field data the interpretation method iteratively ray traces and then updates the velocity model within each iteration the differences between the data and the current model traveltimes obtained by ray tracing are related to the unknown velocity perturbations through a system of linear equations a damped least squares method solves for the velocity perturbations which updat

tectonic triggering of slump sheets in the upper cretaceous carbonate succession of the porto selvaggio area salento peninsula southern italy synsedimentary tectonics in the apulian carbonate platform abstract soft sediment deformation structures crop out in the upper cretaceous carbonate succession in porto selvaggio cove in the western salento peninsula apulian foreland southern italy the deformed interval is about 13 m thick and occurs between shallow water limestones and dolostones formed in peritidal and shallow subtidal environments it comprises well bedded grey mudstones interlayered with dark grey laminated microbioclastic wackestones characterized by couplets of closely spaced dark and bright laminae marked by the parallel orientation of calcareous microbioclasts and thin shelled bivalves the low biological diversity scarcity of burrowing biota and presence of a well preserved fish fauna provide evidence of anoxic conditions occurring in morphological depressions within the platform and a stagnant stratified water body affected by weak bottom currents indicating the sudden development of a localised and short lived intraplatform basin two soft sediment deformation horizons slump sheets separated by undeformed limestones with similar facies occur in this part of the succession the lower thicker slump sheet 1 0 1 3 m thick contains asymmetric and box folds well developed decollement surfaces locally containing thick brecciated zones cut the folds forming small scale thrust sheets and indicating mixed plastic to brittle behaviour the upper thinner slump sheet 0 25 0 35 m thick contains only asymmetric folds indicating plastic behaviour only the differences in deformation style are attributed to differences in facies measurements of fold axis orientations in the slump sheets show that they moved in similar directions recording the development of a local gently dipping palaeoslope autogenic internal trigger mechanisms are ruled out by a detailed consideration of facies the slump sheets were triggered by allogenic tectonic effects either the weakening of sediment by seismic activity or the tectonically induced steepening of slopes or a combination of both tectonically induced steepening is consistent with localised and sudden vertical facies changes related to the creation of an intraplatform basin the occurrence of slump sheets in carbonate platform successions is unusual since carbonate platforms are normally associated with shelves or low angle ramps

traveltime tomography of crosshole ground penetrating radar based on an arctangent functional with compactness constraints abstractregularization has been an effective technique to provide unique and stable solutions for crosshole ground penetrating radar gpr traveltime tomography the traditional form of this method in which a low order differential operator was used commonly yields a smooth solution that may not be appropriate when anomalies occur in block patterns such as voids or irregular objects the minimum support ms functional can be used to improve the resolution of blocky structures however in crosshole gpr traveltime tomography the ms functional is unable to resolve residual artifacts whose departure from an a priori model are smaller than the focusing parameter selected from a trade off curve in addition it would result in severe instability and yield a trade off curve with poorly defined corners when the focusing parameter nears the precision of the apparatus we have developed a new stabilizing functional based on the arctangent at function that effectively removes the artificially small values i

determining the origin of soft sediment deformation structures a case study from upper carboniferous delta deposits in south west wales uk determining the cause of sediment mobilization is a major problem possible triggers include earthquakes sediment loading and wave action a detailed sedimentological and palaeoenvironmental analysis of soft sediment deformation in upper carboniferous deltaic deposits in sw wales uk shows that two styles of deformation occur type a syndepositional convolute stratification affects most sandstone beds and was generated by rapid sedimentation type b localized sandin sand pseudonodules incorporates beds that already contained type a deformation and developed when the substrate was liquefied by disturbance due to movement on a nearsurface gravity slide neither type of deformation was triggered by seismic events

liquefaction fluidization and erosional structures associated with bituminous sands of the bracklesham formation middle eocene of dorset england at hengistbury head dorset the boscombe sands middle eocene bracklesham formation are of estuarine channel facies a mud filled channel is exposed the banks and eastern flank of which have a black carbonaceous stain the degraded remains of a bitumen at the time of deposition the bitumen rendered the sediment firm and it was extensively burrowed by a thalassinoides forming organism crustacean the bituminous sand on the eastern channel bank suffered brecciation and dilation as a result of liquefaction and flowage of the underlying sediments this is thought to have been due to rapid expulsion of pore water possibly as a result of seismic shock the layers of bituminous sand below the surface were ruptured during water escape resulting in localized zones of rapid flow causing fluidization and the development of dewatering pipes up to 1 2 m long the estuarine sediments were subsequently transgressed during which the bituminous sand was exposed on the seafloor when it was eroded into a hummocky topography and heavily burrowed blocks of bituminous sand were reworked into the marine basal conglomerate composed mainly of flints demonstrating the remarkable strength of the bituminous cement

high resolution aquifer characterization using seismic cross hole tomography an evaluation experiment in a gravel delta we performed field experiments at a well studied aquifer test site to evaluate the geophysical method of seismic cross hole tomography for high resolution aquifer characterization we address the challenge of finding meaningful relationships between seismic velocity and hydraulic conductivity at the field scale for hydraulic conductivity estimation the resolution of seismic cross hole data is limited by inversion ambiguities and diffraction effects which are not accounted for using conventional ray based inversion algorithms for velocity reconstruction we investigate the impact of diffraction effects on seismic velocity inversion and implications for hydraulic modelling our ray based seismic tomograms correlate well with sedimentary cores and hydraulic conductivity logs allowing us to interpret a zone model with distinct geophysical hydraulic zones we use this zone model to constrain seismic inversions using two approaches for forward modelling ray tracing infinite frequency approximation and wavefield modelling at a realistic frequency which accounts for diffraction we show that using the common ray tracing approach seismic velocities in low velocity zones may be significantly overestimated based on the available data we observe a negative linear relationship between logarithmic hydraulic conductivity and seismic velocity this relationship is used to parameterize hydraulic models based on seismic velocity models computer simulations of advective contaminant transport demonstrate that their results are extremely sensitive to an accurate determination of seismic low velocity zones we conclude that seismic tomography is indeed very useful for high resolution aquifer characterization however an inversion approach that accounts for diffraction effects a priori knowledge of the subsurface structure and additional well data should be applied for quantitative interpretations

finite difference calculation of travel times the travel times of the first arriving seismic waves through any velocity structure can be rapidly computed on a two or three dimensional numerical grid by finite difference extrapolation from point to point wavefronts rather than the traditional rays are tracked head waves are properly treated and shadow zones are filled by the appropriate diffractions differences of less than 0 03 per cent are found between the results of this technique and raytracing for a complex two dimensional model this scheme is useful for the windowing of finite difference calculations to increase computing speed and promises to aid in earthquake location tomographic inversion and kirchhoff migration in structures that have strong lateral velocity gradients

crosshole seismic tomography with cross firing geometry abstractwe have developed a case study of crosshole seismic tomography with a cross firing geometry in which seismic sources were placed in two vertical boreholes alternatingly and receiver arrays were placed in another vertical borehole there are two crosshole seismic data sets in a conventional sense these two data sets are used jointly in seismic tomography because the local sediment is dominated by periodic flat thin layers there is seismic anisotropy with different velocities in the vertical and horizontal directions the vertical transverse isotropy anisotropic effect is taken into account in inversion processing which consists of three stages in sequence first isotropic traveltime tomography is used for estimating the maximum horizontal velocity then anisotropic traveltime tomography is used to invert for the anisotropic parameter which is the normalized difference between the maximum horizontal velocity and the maximum vertical velocity finally anisotropic waveform tomography is impl

anisotropic crosshole vsp traveltime tomography through triangular cell model with a normalized jacobian matrix and multistage inversion strategy to overcome the difficulty in forward and inversion problem in complex geological model including undulated topography and irregular subsurface interface we in this paper realize a multistage triangular shortest path method for multi phase seismic ray tracing and combine a nonlinear inversion solver damped minimum norm and constrained least squares problem solved by a conjugated gradient method to simultaneously invert four elastic parameters or four thomsen parameters in anisotropic media using combined direct and reflected arrival times for trading off between different parameter updating we normalize the sensitivity functions traveltimes derivatives with respect to different elastic or thomsen parameter changes to balance four updated elastic or thomsen parameters in simultaneous inversion process due to the magnitude and pattern of partial derivatives more sensitive to different phase slowness angles in addition in order to solve the multi solution problems of qsv wave inversion a strategy of multistage inversion is proposed for testing the efficiency and correctness of proposed inversion method we use the picked traveltimes in synthetic seismograms as the observed traveltimes in the inversion the results show that both inverted images by taking the picked traveltimes in synthetic seismograms as the observed data and by taking predicted traveltimes using ray tracing method as observed data have a similar imaging pictures which verify the efficiency and correctness of the proposed inversion method furthermore the inverted results by normalized kernel functions are better than that of inversion without applying the normalized kernel functions for both qp and qsv data and the results of the multistage inversion are better than that of the simultaneous inversion without multistage inversion applied in qsv wave inversion in addition both elastic and thomsen parameter inversions for the same anisotropic model indicate that there are no big differences between the two inverted results even though the sensitivity kernels related to the thomsen parameters have relatively large values

3 d imaging using higher order fast marching traveltimes recently fast marching methods fmm beyond first order have been developed for producing rapid solutions to the eikonal equation in this paper we present imaging results for 3 d prestack kirchhoff migration using traveltimes computed using the first order and second order fmm on several 3 d prestack synthetic and real data sets the second order traveltimes produce a much better image of the structure moreover insufficiently sampled first order traveltimes can introduce consistent errors in the common reflection point gathers that affect velocity analysis first order traveltimes tend to be smaller than analytic traveltimes which in turn affects the migration velocity analysis falsely indicating that the interval velocity was too low

seismically induced slumps in lower maastrichtian peritidal carbonates of the apulian platform southern italy abstract in the southeastern murge apulian foreland southern italy a lower maastrichtian carbonate section showing soft sediment deformation structures is composed of peritidal lithofacies associations developed in a wide low energy inner platform system shear induced soft sediment deformation structures correspond to multilayer deformed horizons 1 5 to 2 m in thickness sandwiched between undeformed layers overturned and recumbent folds lying on decollement surfaces and asymmetrical fault inception folds allow us to interpret the observed deformed horizons as slump sheets the detailed description of the main morphological features of the deformed beds and the recognition of unconformable surfaces and undeformed beds between slumped beds allow us to distinguish three different events of deformation preferential orientation of slump folds has been measured and every slumped bed shows a different direction of shortening randomly oriented direction of shortening suggests that each deformation event was driven by the presence of local very gentle gradients developed in peritidal settings by excluding other potential trigger mechanisms of deformation the observed slumps are interpreted as seismically induced slides even if no data about the distance of the seismic source may be obtained near field earthquake tectonics affected the apulian platform during late cretaceous times

microseismic joint location and anisotropic velocity inversion for hydraulic fracturing in a tight bakken reservoir abstractto improve the accuracy of microseismic event locations we developed a new inversion method with double difference constraints for determining the hypocenters and the anisotropic velocity model for unconventional reservoirs we applied this method to a microseismic data set monitoring a middle bakken completion in the beaver lodge area of north dakota geophone arrays in four observation wells improved the ray coverage for the velocity inversion using an accurate anisotropic velocity model is important to correctly assess the height growth of the hydraulically induced fractures in the middle bakken our results showed that 1 moderate to strong anisotropy exists in all studied sedimentary layers especially in the upper and lower bakken shale formations where the thomsen parameters and can be greater than 0 4 2 all the events selected for high signal to noise ratio and used for the joint velocity inversion are located in the bakken and overlying lodgepole formations i e no events a

tertiary geodynamic evolution of the southern adria microplate the southern adria microplate is the common foreland for the hellenide and southern apennine thrust belts the apulian platform dominates the microplate outcrop well and seismic data allow us to trace the carbonate platform edge whilst structural analysis geophysical and palaeomagnetic data provide important clues to the geodynamic evolution of the region the present structural fabric of apulia is dominated by several e w lineaments that divide the region into different blocks rospo plateau gargano promontory murge ridge salento peninsula apulian plateau one such lineament the pescara dubrovnik line a prominent feature traversing the adriatic sea between central italy and southern croatia has been active since the early mesozoic when it acted as a major transform fault controlling sedimentation along the northern margin of southern adria during the cenozoic the pescara dubrovnik underwent predominantly vertical and oblique movement due to a differential flexural response of the platform and the adjacent pelagic sequences to the thrust belt loading in tertiary time the southern adria microplate was partly involved in heilenide collision the apulian platform can be considered as an area of thicker crust more resistant to underthrusting than the surrounding basins during the orogenic events it acted as a passive rigid indentor causing local distortion of the most external hellenide structures the dextral transpressive activity recorded along the south east margin of this indentor kephallinia line can be interpreted as the result of the oblique collision between the margin of the thick apulian platform in this zone nne ssw striking and the nw se striking hellenic thrust belt horizontal stress generated during the collision was partly transmitted to the rigid foreland re activating palaeo e w faults within the south adria microplate in a dextral strike slip sense the clockwise rotation recorded in the salento peninsula can be explained by the rotation of several nw se striking faulted blocks the rotation was accompanied by the opening of small transtensional basins between blocks this block rotation was caused by the dextral shear that is expressed along the north and the south salento fault zones

experimental soft sediment deformation structures formed by the liquefaction of unconsolidated sands and some ancient examples the effects of liquefaction in saturated sand bodies under a variety of driving forces are described from shaking table experiments and structures from the geological record are presented which are analogous to the experimental structures the collapse of sloping heaps of cross bedded sand under a gravitational body force generates low angle essentially uncontorted stratification a basal zone of shearing may be present with steepened and folded foresets stretching of foresets may be accommodated on normal faults and bottomsets may be contorted into inclined folds in natural systems the substrate may also liquefy causing deformation driven by an unevenly distributed confining load stratification in the surface bedform is flattened and stratification in the substratum contorted experiments failed to produce relative displacement at the interface between stacked sand bodies liquefaction of gravitationally unstable systems in sands generates load structures comparable to those from sand mud systems recumbent folded deformed cross bedding is formed by current shear over a liquefied bed as has been inferred from field and theoretical analyses shear of nonliquefied sand forms angular folds other deformation mechanisms such as fluidization or seepage may generate structures similar to all of these local water escape structures driven by fluidization occur in the upper parts of some liquefied sand bodies they include cusps sand volcanoes and clastic dykes transient cavities formed in some experiments and seemed to be preserved as breached cusps although the experiments tried to isolate individual driving forces driving forces may operate together and there may be a continuum between deformation driven by water escape and deformation driven by loading different structures from those described here may form where liquefaction develops in a buried layer as opposed to at the sediment surface

stacking velocity inversion with borehole constraints for tilted ti media transversely isotropic models with a tilted symmetry axis ttiplayanincreasinglyimportantroleinseismicimaging especially near salt bodies and in active tectonic areas here we present a 2d parameter estimation methodology for tti media based on combining p wave normal moveoutnmo velocities zero offset traveltimes and reflection time slopes with borehole data that include check shot traveltimes as well as the reflector depths and dips for a dipping tti layer withthesymmetryaxisconfinedtothedipplaneofthereflector simultaneous estimation of the symmetry direction velocityvp0 theanisotropyparameters and andthetilt of the symmetry axis proves to be ambiguous despite the borehole constraints if the symmetry axis is orthogonal to the reflector vp0 and can be recovered with high accuracy even when the symmetry axis deviates by 5 from the reflector normal theparameter however cannotbeconstrainedfor dips smaller than 60 without using nonhyperbolic moveout toinvertfortheintervalparametersoflayeredttimedia we apply 2d stacking velocity inversion supplemented with the sameboreholeconstraints thedipplanesinalllayersareassumed to be aligned and the symmetry axis is set orthogonal to the reflector in each layer information about reflector dips can be replaced with near offset walkaway vertical seismic profiling vsp traveltimes tests on noise contaminated data demonstrate that the algorithm produces stable estimatesoftheintervalparametersvp0and iftherangeofdips does not exceed 30 our method can be used to build an accurate initialtti model for post migration reflection tomography and other techniques that employ migration velocity analysis

water upwelling pipes and soft sediment deformation structures in lower pleistocene calcarenites salento southern italy a thin sedimentary blanket consisting mostly of subtidal unconformity bounded calcarenite units was deposited in the small novoli graben apulian foreland southern italy in pliocene2pleistocene time in a limited part of the study area the lower pleistocene calcarenite di gravina forming the thicker part of this blanket is crossed by continuous to discontinuous cylindrical pipes as much as 12 m high most commonly consisting of stacked concaveupward laminae locally grading upward into soft sediment deformation features and large dishes the evidence favors an origin linked to upwelling of overpressured groundwater from a large karstic reservoir hosted in the mesozoic carbonate rocks the reservoir periodically developed a relatively high hydrostatic head due to tertiary to pleistocene cover acting as an aquitard or aquiclude as a result submarine springs were generated the activity of which was primarily controlled by relative sea level fluctuations it is suggested that the pipes were located in those points where the hydrostatic pressure was sufficient to fluidize the overlying sediment and could be released without notably affecting the surrounding sediments some pipes cross calcarenitic infills of karstic sinkholes developed in the underlying units whereas others follow the course of vertical to high angle extensional synsedimentary tectonic fractures generated when the calcarenites were still in an unconsolidated to semiconsolidated state the former relationships suggest that vertical routes of water upwelling during highstand of base level commonly coincided with axes of vadose solution during base level lowstand the latter suggest that opening of fractures enhanced the connection of the deep aquifer with the surface hence intensifying water upwelling we think that fluidization along the fractures was not hindered by the partially coherent state and that pipes with a cylindrical geometry could form in spite of the planarity of the fractures the formation of the pipes and their internal structure of stacked concave upward laminae is thought to be consistent with a process of fluidization due to through flowing waters we believe that essential in this process is the role of upward migrating transient water filled cavities akin to the voidage waves hassett s 1961a 1961b parvoids experimentally reproduced by several authors in liquid fluidized beds and regarded as true instability phenomena of a fluidized suspension occurring above minimum fluidization velocity it is suggested that the process is akin to the production of the dish structure it consists of the filling of transient upward migrating water filled cavities through steady fallout of particles from the cavity roof their redeposition in a more consolidated state and subsidence of the roof due to water seepage upward from the cavity the process was accompanied by segregation of grains according to their size and density as well by elutriation of finest particles and led to a new pattern of sediment texture packing and fabric with respect to the surrounding calcarenites

crosshole seismic imaging for sulfide orebody delineation near sudbury ontario canada crosshole seismic instrumentation based on a piezoelectric source and hydrophone detectors were used to gather seismograms between boreholes at the mcconnell orebody near sudbury ontario high frequency seismograms were recorded across rock sections 50 to 100 m wide containing a continuous zone of massive sulfide ore first arrival traveltimes obtained from a detailed scan were used to create a p wave velocity tomogram that clearly delineated the ore zone refraction ray tracing on a discrete layer model confirmed the main features of the tomogram the survey demonstrated that it is possible to conduct cost effective high resolution crosshole seismic surveys to delineate ore bodies on a scale useful for planning mining operations

nonlinear traveltime inversion scheme for crosshole seismic tomography in tilted transversely isotropic media crosshole seismic tomography often is applied to image the velocity structure of an interwell medium if the rocks are anisotropic the tomographic technique must be adapted to the complex situation otherwise it leads to a false interpretation we propose a nonlinear kinematic inversion method for crosshole seismic tomography in composite transversely isotropic media with known dipping symmetry axes this method is based on a new version of the first order traveltime perturbation equation it directly uses the derivative of the phase velocity rather than the eigenvectors of the body wave modes to overcome the singularity problem for application to the two quasi shear waves we applied an iterative nonlinear solver incorporating our kinematic ray tracing scheme and directly compute the jacobian matrix in an arbitrary reference medium this reconstructs the five elastic moduli or thomsen parameters from the first arrival traveltimes of the three seismic body waves qp qsv qsh in strongly and weakly anisotropic media we conducted three synthetic experiments that involve determining anisotropic parameters for a homogeneous rock reconstructing a fault embedded in a strongly anisotropic background and imaging a complicated four layer model containing a small channel and a buried dipping interface we compared results of our nonlinear inversion method with isotropic tomography and the traditional linear anisotropic inversion scheme which showed the capability and superiority of the new scheme for crosshole tomographic imaging

inference of multi gaussian relative permittivity fields by probabilistic inversion of crosshole ground penetrating radar data abstractin contrast to deterministic inversion probabilistic bayesian inversion provides an ensemble of solutions that can be used to quantify model uncertainty we have developed a probabilistic inversion approach that uses crosshole first arrival traveltimes to estimate an underlying geostatistical model the subsurface structure and the standard deviation of the data error simultaneously the subsurface is assumed to be represented by a multi gaussian field which allows us to reduce the dimensionality of the problem significantly compared with previous applications in hydrogeology novelties of this study include an improvement of the dimensionality reduction algorithm to avoid streaking artifacts it is the first application to geophysics and the first application to field data the results of a synthetic example show that the model domain enclosed by one borehole pair is generally too small to provide reliable estimates of geostatistical variables a real data example based on two borehole pairs

use of liquefaction induced features for paleoseismic analysis an overview of how seismic liquefaction features can be distinguished from other features and how their regional distribution and properties of source sediment can be used to infer the location and strength of holocene paleo earthquakes abstract liquefaction features can be used in many field settings to estimate the recurrence interval and magnitude of strong earthquakes through much of the holocene these features include dikes craters vented sand sills and laterally spreading landslides the relatively high seismic shaking level required for their formation makes them particularly valuable as records of strong paleo earthquakes this state of the art summary for using liquefaction induced features for paleoseismic interpretation and analysis takes into account both geological and geotechnical engineering perspectives the driving mechanism for formation of the features is primarily the increased pore water pressure associated with liquefaction of sand rich sediment the role of this mechanism is often supplemented greatly by the direct action of seismic shaking at the ground surface which strains and breaks the clay rich cap that lies immediately above the sediment that liquefied discussed in the text are the processes involved in formation of the features as well as their morphology and characteristics in field settings whether liquefaction occurs is controlled mainly by sediment grain size sediment packing depth to the water table and strength and duration of seismic shaking formation of recognizable features in the field generally requires a low permeability cap above the sediment that liquefied field manifestations are controlled largely by the severity of liquefaction and the thickness and properties of the low permeability cap criteria are presented for determining whether observed sediment deformation in the field originated by seismically induced liquefaction these criteria have been developed mainly by observing historic effects of liquefaction in varied field settings the most important criterion is that a seismic liquefaction origin requires widespread regional development of features around a core area where the effects are most severe in addition the features must have a morphology that is consistent with a very sudden application of a large hydraulic force this article discusses case studies in widely separated and different geological settings coastal south carolina the new madrid seismic zone the wabash valley seismic zone and coastal washington state these studies encompass most of the range of settings and the types of liquefaction induced features likely to be encountered anywhere the case studies describe the observed features and the logic for assigning a seismic liquefaction origin to them also discussed are some types of sediment deformations that can be misinterpreted as having a seismic origin two independent methods for estimating prehistoric magnitude are discussed briefly one method is based on determination of the maximum distance from the epicenter over which liquefaction induced effects have formed the other method is based on use of geotechnical engineering techniques at sites of marginal liquefaction in order to bracket the peak accelerations as a function of epicentral distance these accelerations can then be compared with predictions from seismological models

geochronology and geochemistry of high pressure granulites of the arthur river complex fiordland new zealand cretaceous magmatism and metamorphism on the palaeo pacific margin the arthur river complex is a suite of gabbroic to dioritic orthogneisses in northern fiordland new zealand the arthur river complex separates rocks of the median tectonic zone a mesozoic island arc complex from palaeozoic rocks of the palaeo pacific gondwana margin and is itself intruded by the western fiordland orthogneiss new shrimp u pb single zircon data are presented for magmatic metamorphic and deformation events in the arthur river complex and adjacent rocks from northern fiordland the arthur river complex orthogneisses and dykes are dominated by magmatic zircon dated at 136 129 ma a dioritic orthogneiss that occurs along the eastern margin of the complex is dated at 154 4 3 6 ma and predates adjacent plutons of the median tectonic zone rims on zircon cores from this sample record a thermal event at c 120 ma attributed to the emplacement of the western fiordland orthogneiss migmatitic palaeozoic orthogneiss from the arthur river complex 346 6 ma is interpreted as deformed wall rock very fine rims 5 20 lm also indicate a metamorphic age of c 120 110 ma a post tectonic pegmatite 81 8 1 8 ma may be related to phases of crustal extension associated with the opening of the tasman sea the arthur river complex is interpreted as a batholith emplaced at mid crustal levels and then buried to deep crustal levels due to convergence of the median tectonic zone arc and the continental margin

analytic expressions for the velocity sensitivity to the elastic moduli for the most general anisotropic media for non linear kinematic inversion of elastic anisotropy parameters and related investigations of the sensitivity of seismic data the derivatives of the wavespeed phase velocity and group velocity with respect to the individual elastic moduli are required this paper presents two analytic methods called the eigenvalue and eigenvector methods to compute the derivatives of the wavespeeds for wave propagation in a general anisotropic medium which may be defined by up to 21 density normalized elastic moduli the first method employs a simple and compact form of the eigenvalue phase velocity and a general form of the group velocity and directly yields general expressions of the derivatives for the three wave modes qp qs 1 qs 2 the second method applies simple eigenvector solutions of the three wave modes and leads to other general forms of the derivatives these analytic formulae show that the derivatives are in general functions of the 21 elastic moduli as well as the wave propagation direction and they reflect the sensitivity of the wavespeeds to the individual elastic moduli meanwhile we give results of numerical investigations with some examples for particular simplified forms of anisotropy they show that the eigenvalue method is suitable for the qp qs 1 and qs 2 wave computations and mitigates the singularity problem for the two quasi shear waves the eigenvector method is preferable to the eigenvalue method for the group velocity and the derivative of the phase velocity because it involves simpler expressions and independent computations but for the derivative of the group velocity the derivative of the eigenvector is required both methods tackle the singularity problem and are applicable to any degree of seismic anisotropy for all three wave modes

inferring earth structure from combined measurements of rotational and translational ground motions we introduce a novel variant of seismic tomography that is based on colocated measurements of rotational and translational ground motions our aim is to assess whether rotations may be incorporated successfully into seismic inverse problems to produce better resolved and more realistic tomographic images our methodology is based on the definition of apparent s wave speed as the ratio of rms velocity and rotation amplitudes the principal advantages of this definition are that 1 no traveltimes measurements are needed and 2 the apparent s wave speed is independent of source magnitude and source timing we derive finite frequency kernels for apparent s wave speed by using a combination of the adjoint method and ray approximation the properties of these kernels as a function of frequency bandwidth can be illustrated along with their usefulness for seismic tomography in multifrequency synthetic inversions we consider local crosshole tomography and regional scale earthquake tomography our results indicate that s wave speed variations can be retrieved accurately from colocated rotation and translation measurements suggesting that our methodology is a promising extension of conventional seismic tomography further apparent s wave speed can be used to increase vertical resolution in teleseismic tomography for local structures

water transfer cylindrical structures in the late proterozoic eolian sandstones in the taoudeni basin west africa abstract vertical cylindrical structures have already been described in literature but none in periglacial eolian dune deposits two types of vertical cylindrical structures have been observed in the late precambrian of western mali type 1 exhibits concentric laminae in subhorizontal transversal section and a cone in cone internal organization in type 2 laminations inherited from the parent sediments are partially preserved the two types are early post depositional cylindrical features both were caused by upward fluid flow responsible for liquefaction fluidization and entire type 1 or partial type 2 remobilization of eolian cross stratification in a proposed hypothetical reconstruction scheme a local overpressure caused by an unknown external impulse creates liquefaction cells which evolve either in an upward explosive way type 2 or in an upward moving liquefaction front type 1

soft sediment deformation induced by sinkhole activity in shallow marine environments a fossil example in the apulian foreland southern italy abstract soft sediment deformation structures are exposed in sea cliffs in the lower part of the calcarenite di gravina formation late pliocene early pleistocene in the cala corvino area n of monopoli adriatic sector of the apulian foreland southern italy deformation affects a thickness of about 5 m involving a lower calcareous terrigenous sand and gravel unit and an upper heavily bioturbated grainstone and packstone unit deformation is absent from the overlying part of the succession large scale soft sediment deformation structures are collapse features comprising irregularly elongated conical zones of sinking in vertical section narrow drop zones occur in the lower sandy gravelly facies and large gentle folds in the upper grainstone packstone beds the degree of deformation decreases upwards small scale soft sediment deformation structures adjacent to the large scale conical collapse structures are narrow vertically elongated load structures about 2 m high and 30 50 cm wide that involve only the basal terrigenous facies the distribution of small and large scale soft sediment deformation structures corresponds closely to zones of fracturing in the underlying cretaceous limestones and the elongation directions of soft sediment deformation structures correspond to the orientation of major fractures in the limestones the soft sediment deformation occurred due to collapse associated with karstic sinkhole formation along fractures in the bedrock geometrical relationships between deformed and undeformed sedimentary units show that deformation occurred in a shallow marine environment the structures at cala corvino provide a rare outcrop scale record of sinkhole induced soft sediment deformation occurring in a shallow marine environment