geochemistry of sulphate bearing water of akra kaur dam gwadar balochistan pakistan and its assessment for drinking and irrigation purposes this paper is an attempt to study the geochemistry of akra kaur dam akd water north of gwadar city southern balochistan representative water samples were collected from akd reservoir to assess the suitability of water for drinking and agriculture purposes the major ionic composition is suggestive for freshwater the average ionic composition demonstrate so4 ca na cl hco3 mg k the plots on piper diagram reflected ca mg so4 type of water facies high ca so4 and ca mg ratios revealed that the water has influence of gypsum dissolution the negative ratio of chloro alkaline indices indicated reverse exchange between ca and mg in water occurred with na and k in rocks the ph electrical conductivity total dissolved salts ca mg na k hco3 cl and so4 concentrations in the dam water were below the permissible limit however na and so4 were above the desirable limit set by the world health organization important parameters such as residue sodium carbonate sodium percent sodium adsorption ratio permeability index magnesium content and kelley s ratio were calculated to evaluate the suitability of water for irrigation purpose the result were compared with standard permissible limits and found satisfactory the health and agriculture hazards of sulphate bearing water were also discussed

origin of groundwater salinity and hydrogeochemical processes in the confined quaternary aquifer of the pearl river delta china summary the pearl river delta prd located in the coastal area of south china contains a large confined quaternary aquifer this aquifer has been identified to have high concentrations of total dissolved solids ranging from 1 g l in the inland area to 26 8 g l near the southeast shoreline this work aims to investigate the origin of groundwater salinity and the major hydrogeochemical processes controlling the groundwater evolution in the confined basal aquifer of the prd a total of 40 boreholes were drilled in the prd during 2007 2009 and groundwater samples were collected for major ion ca 2 mg 2 na k nh 4 cl so 2 4 and hco 3 and isotope d 18 o d 2 h 3 h d 13 c and 14 c analyses these analyses demonstrate that groundwater in the confined basal aquifer is recharged by local rainwater and seawater and seawater is the major salinity source for groundwater the contribution of seawater varies from less than 1 in the inland areas to 74 near the shoreline so 2 4 reduction and methanogenesis occur in this reducing confined aquifer the results of ion exchange show that mg 2 exchanges mainly with the nh 4 ion which is derived from the mineralization of sedimentary organic matter ion exchange between na

towards a better understanding of the influence of basement heterogeneities and lithospheric coupling on foreland deformation a structural and paleomagnetic study of laramide deformation in the southern bighorn arch wyoming integrated structural anisotropy of magnetic susceptibility ams and paleomagnetic analyses of sedimentary cover rocks along variably oriented major faults and en echelon fold systems in the southern bighorn arch wyoming were undertaken to test kinematic and mechanical models of laramide thick skin deformation the laramide foreland is characterized by an anastomosing network of basement cored arches and associated cover folds that trend overall nw se but in detail are curved range from n s to e w trending and form both right and left stepping en echelon systems development of variably trending laramide arches has been variously attributed to temporal changes in stress directions wrench faulting and localization of deformation related to basement heterogeneities during regional sw ne shortening within the southern bighorn arch widespread but limited layer parallel shortening lps was accommodated mostly by minor faults with conjugate wedge and strike slip geometries early in the deformation history lps directions vary from perpendicular to acute with local fold structural trends consistent with a single shortening episode although internal strain is limited weak ams lineations defined by kinked and rotated phyllosilicates are widely developed and consistently perpendicular to lps directions structurally restored paleomagnetic declinations record only limited non systematic vertical axis rotations indicating that wrenching was not an important component of the deformation field during development of the southern bighorn arch and that curvature of the arch was a primary feature palinspastically restored lps directions are on average wsw ene but display local deflections related to heterogeneities of underlying basement blocks and proximity to major faults some of which were localized along precambrian shear zones and igneous dikes crustal shortening patterns across the laramide foreland are interpreted to reflect deformation partitioning in response to a single far field shortening direction partly related to flat slab subduction along with effects of pre existing basement weaknesses and strain softening during progressive faulting

the 2002 denali fault earthquake alaska a large magnitude slip partitioned event the mw moment magnitude 7 9 denali fault earthquake on 3 november 2002 was associated with 340 kilometers of surface rupture and was the largest strike slip earthquake in north america in almost 150 years it illuminates earthquake mechanics and hazards of large strike slip faults it began with thrusting on the previously unrecognized susitna glacier fault continued with right slip on the denali fault then took a right step and continued with right slip on the totschunda fault there is good correlation between geologically observed and geophysically inferred moment release the earthquake produced unusually strong distal effects in the rupture propagation direction including triggered seismicity

paleo depth of fossil faults estimated from paleostress state applications from the alps and the apennines italy abstract estimating the paleo depth of a fossil fault usually requires the application of complex and highly specialized techniques we propose a new method that is based mainly on field data and simplifies the process calculation of the reduced stress tensor with four variables through inversion of fault slip data calculation of the complete stress tensor i e the two remaining unknowns using the friction and the rupture laws estimation of the paleo depth the friction law is defined by the lower boundary of the cloud of points in the mohr space represented by inherited faults this operation fixes the abscissa origin of the mohr diagram to calculate the rupture law we estimate both intact rock and outcrop quality parameters and need pairs of conjugate faults their dihedral angle fixes a point on the mohr circle where the rupture law has to be tangent thus defining the scale of the axes and the values of the principal stresses to define the paleo depth we estimate the average density of overlying rocks and the hydraulic conditions i e the pore pressure testing of this workflow in three well constrained geological case studies proved its promising reliability showing a good agreement with independent stratigraphic and structural evidence

strike slip earthquakes in the oceanic lithosphere observations of exceptionally high apparent stress summary the radiated energies e s and seismic moments m0 for 942 globally distributed earthquakes that occurred between 1987 to 1998 are examined to find the earthquakes with the highest apparent stresses a e s m0 where is the modulus of rigidity the globally averaged a for shallow earthquakes in all tectonic environments and seismic regions is 0 3 mpa however the subset of 49 earthquakes with the highest apparent stresses a greater than about 5 0 mpa is dominated almost exclusively by strike slip earthquakes that occur in oceanic environments these earthquakes are all located in the depth range 7 29 km in the upper mantle of the young oceanic lithosphere many of these events occur near plate boundary triple junctions where there appear to be high rates of intraplate deformation indeed the small rapidly deforming gorda plate accounts for 10 of the 49 high a events the depth distribution of a which shows peak values somewhat greater than 25 mpa in the depth range 20 25 km suggests that upper bounds on this parameter are a result of the strength of the oceanic lithosphere a recently proposed envelope for apparent stress derived by taking 6 per cent of the strength inferred from laboratory experiments for young less than 30 ma deforming oceanic lithosphere agrees well with the upper bound envelope of apparent stresses over the depth range 5 30 km the corresponding depth dependent shear strength for young oceanic lithosphere attains a peak value of about 575 mpa at a depth of 21 km and then diminishes rapidly as the depth increases in addition to their high apparent stresses which suggest that the strength of the young oceanic lithosphere is highest in the depth range 10 30 km our set of high a earthquakes show other features that constrain the nature of the forces that cause interplate motion first our set of events is divided roughly equally between intraplate and transform faulting with similar depth distributions of a for the two types secondly many of the intraplate events have focal mechanisms with the t axes that are normal to the nearest ridge crest or subduction zone and p axes that are normal to the proximate transform fault these observations suggest that forces associated with the reorganization of plate boundaries play an important role in causing high a earthquakes inside oceanic plates extant transform boundaries may be misaligned with current plate motion to accommodate current plate motion the pre existing plate boundaries would have to be subjected to large horizontal transform push forces a notable example of this is the triple junction near which the second large aftershock of the 1992 april cape mendocino california sequence occurred alternatively subduction zone resistance may be enhanced by the collision of a buoyant lithosphere a process that also markedly increases the horizontal stress a notable example of this is the aleutian trench near which large events occurred in the gulf of alaska in late 1987 and the 1998 march balleny sea m 8 2 earthquake within the antarctic plate

en echelon and orthogonal fault ruptures of the 11 april 2012 great intraplate earthquakes the magnitude 8 7 earthquake that occurred off the coast of the sumatra subduction zone on 11 april 2012 is shown to have had an extraordinarily complex four fault rupture these great ruptures represent large lithospheric deformation that may eventually lead to a localized boundary between the indian and australian plates on 11 april 2012 two of the largest strike slip earthquakes ever recorded at magnitudes of 8 7 and 8 2 occurred in the northeastern indian ocean a few hundred kilometres off the coast of sumatra three groups now report the analysis of seismic data from the days and months before and after these events as well as the events themselves matthias delescluse and co authors show that these earthquakes are part of the ongoing boost of intraplate deformation between india and australia that followed the aceh 2004 and nias 2005 megathrust earthquakes they conclude that the australian plate driven by slab pull forces at the sunda trench is gradually detaching from the indian plate han yue and colleagues show that the 11 april event involved a complex four fault rupture lasting several minutes followed two hours later by a magnitude 8 2 aftershock these great ruptures on a lattice of strike slip faults that extends through the crust and into the upper mantle represent large lithospheric deformation that may eventually create a localized boundary between the indian and australian plates fred pollitz and colleagues show that in the six days following 11 april the global rate of remote earthquakes with magnitudes greater than 5 5 increased nearly fivefold and events up to magnitude 7 seem to have been triggered the unprecedented delayed triggering power of this earthquake may arise from its strike slip source geometry or because it struck at a time of an unusually low global earthquake rate and increased the number of nucleation sites that were very close to failure the indo australian plate is undergoing distributed internal deformation caused by the lateral transition along its northern boundary from an environment of continental collision to an island arc subduction zone1 2 on 11 april 2012 one of the largest strike slip earthquakes ever recorded seismic moment magnitude mw 8 7 occurred about 100 200 kilometres southwest of the sumatra subduction zone occurrence of great intraplate strike slip faulting located seaward of a subduction zone is unusual it results from northwest southeast compression within the plate caused by the india eurasia continental collision to the northwest together with northeast southwest extension associated with slab pull stresses as the plate underthrusts sumatra to the northeast here we use seismic wave analyses to reveal that the 11 april 2012 event had an extraordinarily complex four fault rupture lasting about 160 seconds and was followed approximately two hours later by a great mw 8 2 aftershock the mainshock rupture initially expanded bilaterally with large slip 20 30 metres on a right lateral strike slip fault trending west northwest to east southeast wnw ese and then bilateral rupture was triggered on an orthogonal left lateral strike slip fault trending north northeast to south southwest nne ssw that crosses the first fault this was followed by westward rupture on a second wnw ese strike slip fault offset about 150 kilometres towards the southwest from the first fault finally rupture was triggered on another en echelon wnw ese fault about 330 kilometres west of the epicentre crossing the ninetyeast ridge the great aftershock with an epicentre located 185 kilometres to the ssw of the mainshock epicentre ruptured bilaterally on a nne ssw fault the complex faulting limits our resolution of the slip distribution these great ruptures on a lattice of strike slip faults that extend through the crust and a further 30 40 kilometres into the upper mantle represent large lithospheric deformation that may eventually lead to a localized boundary between the indian and australian plates

stress and strain patterns kinematics and deformation mechanisms in a basement cored anticline sheep mountain anticline wyoming 1 in order to characterize and compare the stress strain record prior to during and just after folding at the macroscopic and the microscopic scales and to provide insights into stress levels sustained by folded rocks we investigate the relationship between the stress strain distribution in folded strata derived from fractures striated microfaults and calcite twins and the development of the laramide basement cored sheep mountain anticline wyoming tectonic data were mainly collected in lower carboniferous to permian carbonates and sandstones in both rock matrix and veins calcite twins recorded three different tectonic stages the first stage is a pre laramide sevier layer parallel shortening lps parallel to fold axis the second one is a laramide lps perpendicular to the fold axis and the third stage corresponds to laramide late fold tightening with compression also perpendicular to the fold axis stress and strain orientations and regimes at the microscale agree with the polyphase stress evolution revealed by populations of fractures and striated microfaults testifying for the homogeneity of stress record at different scales through time calcite twin analysis additionally reveals significant variations of differential stress magnitudes between fold limbs our results especially point to an increase of differential stress magnitudes related to laramide lps from the backlimb to the forelimb of the fold possibly in relation with motion of an underlying basement thrust fault that likely induced stress concentrations at its upper tip this result is confirmed by a simple numerical model beyond regional implications this study highlights the potential of calcite twin analyses to yield a representative quantitative picture of stress and strain patterns related to folding

deformation mechanisms and flow regimes in limestones from the helvetic zone of the swiss alps abstract this paper is based on a combined field transmission electron tem and transmission optical tom microscope study of limestones from the helvetic zone swiss alps and discusses the deformation mechanisms and flow regimes that governed the deformation of these rocks during pre metamorphic regional ductile deformations the limestones deformed by power law dislocation creep with differential stresses probably not exceeding 1 kbar dynamic recrystallization with grain boundary sliding and grain boundary migration allowed the grains to be less elliptical than the strain ellipse a characteristic of the structure is the existence of dislocation free subgrains in the footwall of and approaching the lochseiten calc mylonite along the glarus overthrust grain boundary sliding becomes more important shift to diffusional creep or superplastic flow during a syn and post metamorphic deformation dynamic recovery seems to have become less competitive no dislocation free sub grains and along thrust faults twinning indicates a shift to higher differential stresses at the close of the deformation it was not possible to separate these deformation phases on the basis of the dislocation debris sub grain sizes as observed in tem and tom were identical in limestones that underwent cataclastic deformation the rocks seem to have started breaking up along the grain boundaries the new grain fragments are very small 0 1 0 3 m and are heavily twinned in tem the old large grains show very long straight glide dislocations cleavage and when shattered ring patterns in diffraction

how fast is rupture during an earthquake new insights from the 1999 turkey earthquakes we report that during the two devastating 1999 earthquakes in turkey rupture propagated over a large part of the nearly 200km long fault zone at supershear speed approaching 5km s we present observations and modeling which confirm the original inference of supershear rupture during the izmit earthquake and we show that supershear rupture also occurred during the duzce earthquake we show that the rupture velocity measured about 2 times the shear wave velocity is the value predicted by theoretical studies in fracture dynamics we look for clues to explain these observations

from spatial variation of fracture patterns to fold kinematics a geomechanical approach 1 a vertical compression parallel joint set apparently formed at sheep mountain anticline sma during the early laramide orogeny prior to significant folding field data indicate that these joints occur in fewer locations in the forelimb than in the hinge and backlimb using three dimensional elastic dislocation models we show that early slip along an underlying thrust fault can locally perturb the surrounding stress field inhibiting joint formation above the fault thus we are able to constrain the forelimb kinematics finding that the forelimb was originally located in the hangingwall above the thrust fault furthermore the mode of folding at sma is constrained the anticline developed with a fixed hinge and rotating limbs while the underlying basement rocks deformed internally

from orientation to magnitudes in paleostress determinations using fault slip data abstract determinations of reduced stress tensors using fault slip data yield the orientation of principal stress axes and the ratio of the differences between principal stress magnitudes the use of rupture and friction laws allows determination of the two remaining unknowns that is the reconstruction of the complete stress tensor taking into account the depth of overburden brings an additional constraint the method is applied and discussed in the case of the hoover dam site western u s a where large data sets and rock mechanics information are available differences between intact sample and rock mass properties account for apparent disagreements between paleostress levels determined in similar tectonic environments pore pressure plays an important role where information about pore pressure is absent zero and hydrostatic pore pressure cases should be considered as limits

fingerprinting stress stylolite and calcite twinning paleopiezometry revealing the complexity of progressive stress patterns during folding the case of the monte nero anticline in the apennines italy in this study we show for the first time how quantitative stress estimates can be derived by combining calcite twinning and stylolite roughness stress fingerprinting techniques in a fold and thrust belt first we present a new method that gives access to stress inversion using tectonic stylolites without access to the stylolite surface and compare results with calcite twin inversion second we use our new approach to present a high resolution deformation and stress history that affected meso cenozoic limestone strata in the monte nero anticline during its late miocene pliocene growth in the umbria marche arcuate ridge northern apennines italy in this area an extensive stylolite joint vein network developed during layer parallel shortening lps as well as during and after folding stress fingerprinting illustrates how stress in the sedimentary strata did build up prior to folding during lps the stress regime oscillated between strike slip and compressional during lps before ultimately becoming strike slip again during late stage fold tightening our case study shows that high resolution stress fingerprinting is possible and that this novel method can be used to unravel temporal relationships that relate to local variations of regional orogenic stresses beyond regional implications this study validates our approach as a new powerful toolbox to high resolution stress fingerprinting in basins and orogens combining joint and vein analysis with sedimentary and tectonic stylolite and calcite twin inversion techniques

mechanical models of fracture reactivation and slip on bedding surfaces during folding of the asymmetric anticline at sheep mountain wyoming abstract we use finite element methods to investigate the reactivation of fractures opening and shearing and the development of bedding surface slip during the deformation of the asymmetric anticline at sheep mountain wyoming a series of numerical simulations were run to show the effect of mechanical stratigraphy layer thickness slip on bedding surfaces and tectonic shortening of the fold on the response of a representative three layer ductile brittle ductile two dimensional system the model uses large deformation frictional contact mechanics to capture the response of existing fractures and slip along bedding surfaces and considers both elastic and elastoplastic layer properties the computational results demonstrate the relationships among overall configuration of the multilayer slip on bedding surfaces and the sequence and mode of deformation opening versus shearing of bed perpendicular fractures we show that fractures located in the hinge are mainly reactivated as joints and that those in the forelimb are predominantly reactivated as thrust faults a flexural slip mechanism develops during folding when the layers bounded by frictional bedding surfaces have similar stiffnesses in contrast when the difference in the layer stiffnesses is significant softer outer layers the deformation is accommodated within the softer units without exceeding the frictional strength of the bedding surfaces a reduction of the middle layer thickness from 100 m to 10 m has a minor quantitative effect on the slip along the bedding surfaces we compare the numerical results with fracture data collected at sheep mountain anticline and discuss the similarities and differences between the field observations and the model results

relative timing of calcite twinning strain and fold thrust belt development hudson valley fold thrust belt new york u s a coarse grained limestone samples were collected across the hudson valley fold thrust belt with the aim of determining the temporal and spatial relationship between calcite twinning strain and fold thrust belt development the majority of the samples have well defined oblate strain ellipsoids with the maximum shortening axes e3 perpendicular to bedding strike and e3 magnitudes that range from 1 5 to 6 5 whereas twinning magnitude does not vary systematically through the fold thrust belt twinning fabrics fall into two populations based on the presence of outcrop scale deformational features calcite twinning strain preserved in samples from limestone layers absent of any small scale penetrative deformation such as cleavage and or microfaults are defined as component a strains component a strains generally have maximum shortening axes e3 inclined consistently less than but in the same e w direction as bedding dip the second population of calcite twinning strain population b occurs in limestones pervasively cut by cleavage and or microfaults component b strains has maximum shortening axes e3 that are horizontal irrespective of bedding dip strain population a initiated as a pre folding layer parallel shortening strain that was subsequently modified to its present orientation by active grain scale rotation during flexural folding strain population b reflects post folding superimposed homogeneous strain and is restricted to limestone samples with relatively high clay content 0 1998 elsevier science ltd

determination of the tectonic evolution from fractures faults and calcite twins on the southwestern margin of the indochina block in polyphase tectonic zones integrating a study of fault and fracture with calcite twin analysis can determine the evolving paleostress magnitudes and principle stress directions that affected the area this paper presents the results of the analyses of fractures striated faults and calcite twins collected within the khao khwang fold thrust belt in central thailand se asia here we attempt to reconstruct the orientation of the principal stresses that developed during the tectonic evolution of this highly deformed polyphase orogen tectonic data were collected in the permian carbonates of the khao khad formation of the saraburi group and five successive tectonic stages are determined that are interpreted to have developed before during and after the triassic indosinian orogeny the first three stages predate the main deformation event the first stage is interpreted as a pre indosinian n s extensional stage the second stage described a n s strike slip and compressional regime largely perpendicular to the fold axes of the main structures while the third stage is associated with an e w compressional strike slip phase a further two stages took place after or during the main folding event and correspond to n s compression and to an e w composite strike slip contractional stage the latter which is interpreted to represent cenozoic deformation related to the india asia collision

paleostress magnitudes in folded sedimentary rocks using sheep mountain anticline wyoming usa as a case study we propose a new approach to quantify effective paleo principal stress magnitudes in the uppermost crust the proposed mechanical scenario relies on a well documented kinematic and chronological sequence of development of faults fractures and microstructures in the folded strata paleostress orientations and regimes as well as differential stress magnitudes based on calcite twinning paleopiezometry are combined with rock mechanics data in a mohr construction to derive principal stress magnitudes related to the successive steps of layer parallel shortening and to late stage fold tightening such quantification also provides original insights into the evolution of the fluid over pressure and amount of syn folding erosion

supershear rupture on multiple faults for the mw 8 6 off northern sumatra indonesia earthquake of april 11 2012 1 we perform a back projection method to image the rupture propagation and short period energy release of the 2012 off northern sumatra earthquake mw8 6 using hi net data recorded in japan the results show a complex pattern of four conjugate faults over about 180 sec there is a striking correspondence between the lengths and orientations of our rupture pattern with the distribution of aftershocks each of the first three stages of the rupture corresponds to a clear lineation in the aftershocks with lengths of 200 to 400 km rupture speeds for several of the fault segments were very high about 5 km s and exceed the local s wave velocity this is the first example of an oceanic earthquake with supershear rupture speed

fracture porosity creation and persistence in a basement involved laramide fold upper cretaceous frontier formation green river basin usa fracture hosted porosity and quartz distribution along with crack seal texture and fluid inclusion assemblage sequences in isolated bridging quartz deposits show that open fractures can persist through protracted burial and uplift in foreland basins fractures oriented at a high angle to current maximum compressive stress remain open and were weak mechanical discontinuities for millions of years even at great depth upper cretaceous frontier formation sandstones in the basement involved laramide table rock anticline eastern greater green river basin wyoming sampled by two horizontal wells cut parallel or nearly parallel to bedding and at a high angle to steeply dipping fractures have 41 5 m of rock in four cores at depths of 4538 4547 m cores intersect older e striking set 1 fractures are abutted by or locally cross cut by n striking set 2 fractures both sets contain quartz and porosity sequenced using quartz crack seal cement texture maps set 1 fluid inclusion assemblage fia trapping temperatures increase progressively from 140 to 165 c then decrease to c 150 c compatible with fracture opening over c 15 ma during rapid burial followed by uplift in eocene oligocene time set 2 opened at c 160 c probably near maximum burial after a period of quiescence set 2 reopened at c 5 ma at c 140 c on a cooling trajectory intermittent set 2 movement could reflect local basement involved fault movement followed after a pause by further set 2 reactivation in the modern stress field during uplift interpretations are sensitive to available burial thermal histories which have considerable uncertainty

fe and mn levels regulated by agricultural activities in alluvial groundwaters underneath a flooded paddy field abstract iron and mn concentrations in fresh groundwaters of alluvial aquifers are generally high in reducing conditions reflecting low so4 concentrations the mass balance and isotopic approaches of this study demonstrate that reduction of so4 supplied from agricultural activities such as fertilization and irrigation is important in lowering fe and mn levels in alluvial groundwaters underneath a paddy field this study was performed to investigate the processes regulating fe and mn levels in groundwaters of a point bar area which has been intensively used for flood cultivation four multilevel groundwater samplers were installed to examine the relationship between geology and the vertical changes in water chemistry the results show that fe and mn levels are regulated by the presence of no3 at shallow depths and by so4 reduction at the greater depths isotopic and mass balance analyses revealed that no3 and so4 in groundwater are mostly supplied from the paddy field suggesting that the fe and mn rich zone of the study area is confined by the agricultural activities for this reason the geologic conditions controlling the infiltration of agrochemicals are also important for the occurrence of fe mn rich groundwaters in the paddy field area

determination of deviatoric stress tensors based on inversion of calcite twin data from experimentally deformed monophase samples preliminary results abstract following previous successful paleo stress determinations from numerically generated aggregates and naturally deformed samples preliminary results about stress reconstructions based on inversion of calcite twin data from experimentally deformed monophase samples are reported this new study carried out on samples of carrara marble and crinoidic limestone from eastern france provides a test of the validity of stress reconstructions using inverse methods which had not been properly calibrated before the percentages of correlated twins are discussed for each stress tesnor and the range of uncertainties on the determination of stress orientations and differential stress magnitudes is evaluated

the origin of high sulfate concentrations in a coastal plain aquifer long island new york ion exchange batch experiments were run on cretaceous magothy aquifer clay cores from a nearshore borehole and an inland borehole on long island ny to determine the origin of high so4 concentrations in ground water desorption batch tests indicate that the amounts of so4 released from the core samples are much greater 980 4700 mg g of sediment than the concentrations in ground water samples the locally high so4 concentrations in pore water extracted from cores are consistent with the overall increase in so4 concentrations in ground water along magothy flow paths results of the sorption batch tests indicate that so4 sorption onto clay is small but significant 40 120 mg g of sediment in the low ph 5 pore water of clays and a significant part of the so4 in magothy pore water may result from the oxidation of fes2 by dissolved fe iii the acidic conditions that result from fes2 oxidation in acidic pore water should result in greater sorption of so4 and other anions onto protonated surfaces than in neu

fracture controlled paleohydrogeology in a basement cored fault related fold sheep mountain anticline wyoming united states new geochemical and microstructural data constrain the origins and pathways of paleofluids during the growth of sheep mountain anticline wyoming united states oxygen carbon and strontium isotope studies were performed on prefolding and fold related calcite veins and their sedimentary host rocks and combined to fluid inclusion microthermometry results we show that most of the cements precipitated from paleogene meteoric fluid stable isotopes and fluid inclusion homogenization temperatures further indicate that most veins were mineralized from upward moving fluids after these fluids were heated at depth t 110 c this implies that fluids migrated along the basement thrust underlying the fold and or at the base of the cover above the fault tip the fluids circulated rapidly in the diffuse synfolding and early folding fracture network the zone of preferential migration of the warm fluids is currently located in the backlimb of the fold which supports some of the previously published structural interpretation of the subsurface this study also highlights the potential of combined fracture analysis and geochemical analyses of paleofluid flows in fractures to constrain both the deformation history and the fluid flow during basement involved shortening in laramide style forelands

slow earthquakes along oceanic fracture zones evidence for asthenospheric flow away from hotspots abstract the regime of strain release along transform faults of the mid oceanic ridge system is studied it is shown that earthquakes along certain fracture zones exhibit systematic discrepancies between values of their magnitudes measured at short and long periods implying a regime of slower strain release also observed in a pattern of complex body waveshapes these slow fracture zones do not correlate with simple geographic or kinematic properties but usually occur in the neighborhood of hotspot volcanism frequently also characterized by gravity and bathymetry anomalies we propose that regimes of slow strain release may be due to a partial lubrication of the fault along these fracture zones which may itself be due to asthenospheric flow from the nearby hotspots along the pattern of pipelines described by vogt and johnson and by morgan

palaeostress estimation using calcite twinning experimental calibration and application to nature abstract by means of high temperature deformation experiments on calcite rocks of different grain sizes we have established the relationships between differential stress and twinning incidence twin density and volume fraction and the way that these relationships depend on grain size both twinning incidence and volume fraction increase with grain size at a constant level of differential stress log twin density is proportional to stress but is independent of grain size at a given grain size volume fraction of twinning increases non linearly with differential stress twinning activity measured by twinning incidence increases linearly with stress the behaviour of each of these parameters is independent of temperature strain and strain rate these relationships can be used as a basis for the estimation of palaeostress values in naturally deformed calcite rocks this is illustrated by a study of twinning activity in limestones close to thrust faults in the cantabrian zone of the variscan orogenic belt in northwestern spain high peak differential stresses were measured ranging from 150 to 250 mpa using the turner dynamic analysis technique however it is clear that shear stresses resolved parallel to the fault planes were very low the attainment of high stress differences when the resistance to faulting was low is attributed either to bending forces induced during the motion of the non planar surfaces relative to each other or to the stress peak being attained prior to the localization of deformation onto the fault surfaces

mapping permeable subsurface fracture networks a case study on the cooper basin australia abstract the spatial distribution of permeable fracture networks is constrained in the subsurface cooper basin australia through the integration of most positive curvature k analysis of five three dimensional 3d seismic surveys wellbore fracture data and geomechanical modelling the k provides the likely distribution of subsurface extensional fractures based on the stress redistribution along the outer arc of an anticline these results are reprocessed into the semblance similarity attribute to improve the signal noise ratio prior to being extracted along the gas rich and low permeability patchawarra formation the subsurface fracture distribution maps show the geometry and density of extensional fractures that have been shown to facilitate fluid migration in this province particularly those striking se nw and e w as these are properly oriented to undergo tensile reactivation the density of these permeable se nw and e w striking fracture sets is predicted to significantly increase along e w elongate anticlines and may contribute to improved hydrocarbon recovery in this low permeability stratigraphic interval we show that wellbore fracture data n 917 in the patchawarra formation presents a close relationship to k results and can be used to generate high density structural data in this basin with the methodology applicable to other subsurface and offshore provinces

the role of fractures in the structural interpretation of sheep mountain anticline wyoming the development of fractures in the sedimentary layers of sheep mountain anticline a laramide asymmetric fault cored fold of the bighorn basin is documented and interpreted to constrain the kinematic evolution of the fold the fracture pattern is interpreted to identify five main fracture sets a fracture set striking 110 set i oblique to the future fold trend is interpreted as a regional fracture set that predates laramide compression a joint set set ii striking 045 and present in the hinge and backlimb is related to the ne oriented laramide compression just prior to and during initial anticline growth joints striking 135 set iii parallel to the fold trend are found within the hinge and are interpreted to have developed in response to the bending of layers the two youngest fracture sets are attributed to a late stage of fold growth a joint set set iv in the backlimb striking parallel to the set i fractures but vertical and a fracture set in the forelimb consisting of set i fractures reactivated as reverse faults the relative chronology mode of formation opening vs shearing and structural locations of these fractures suggest the following kinematics of folding at sheep mountain anticline little or no lateral fold propagation no hinge migration and limb rotation with only minor limb flexure and stretching

3d seismic analysis investigating the relationship between stratigraphic architecture and structural activity in the intra cratonic cooper and eromanga basins australia abstract this research uses four three dimensional 3d seismic surveys located in australia s largest onshore hydrocarbon province the intra cratonic cooper and eromanga basins to present an approach that extracts important structural and stratigraphic information from geophysical data that can then be used to define the tectonostratigraphic evolution of subsurface provinces the methodology consists of 1 analysing isopach maps 2 cross section interpretation of stratigraphic features erosional surfaces and faults and 3 constraining the evolution of fault activity most faults within this province are basement involved with high dip angles the primary fault set is ne sw striking with secondary sets striking n s e w and nw se these high angle faults most likely developed as normal faults before being reactivated by five of the six major tectonic events field scale nw se strike slip faults are prolific and can often be overlooked due to the low seismic resolution a close relationship between on lapping features and present day structural highs was found during each of the major structural events particularly within hydrocarbon rich permian stratigraphy inferring that present day structures were present throughout basin development and intermittently reactivated significant stratal package thinning and a high presence of on lapping features were associated with regional basement involved faults particularly along the gidgealpa merrimelia innamincka and murteree nappacoongee ridges initial structural trap development occurred during the early permian but was most significant during the late triassic hydrocarbon accumulations were unaffected by structural growth after the critical moment in the petroleum system 90 ma as the final period of fault activity was during the late cretaceous this research constrains the tectonostratigraphic evolution of the intra cratonic cooper and eromanga basins while detailing an approach that extracts and analyses important structural and stratigraphic information from geophysical data where outcrop is not accessible

geomechanical modeling of stress and strain evolution during contractional fault related folding abstract understanding stress states and rock mass deformation deep underground is critical to a range of endeavors including oil and gas exploration and production geothermal reservoir characterization and management and subsurface disposal of co 2 geomechanical modeling can predict the onset of failure and the type and abundance of deformation features along with the orientations and magnitudes of stresses this approach enables development of forward models that incorporate realistic mechanical stratigraphy e g including competence contrasts bed thicknesses and bedding planes include faults and bedding slip surfaces as frictional sliding interfaces reproduce the overall geometry of the fold structures of interest and allow tracking of stress and strain through the deformation history use of inelastic constitutive relationships e g elastic plastic behavior allows permanent strains to develop in response to the applied loads this ability to capture permanent deformation is superior to linear elastic models which are often used for numerical convenience but are incapable of modeling permanent deformation or predicting permanent deformation processes such as faulting fracturing and pore collapse finite element modeling results compared with field examples of a natural contractional fault related fold show that well designed geomechanical modeling can match overall fold geometries and be applied to stress fracture and subseismic fault prediction in geologic structures geomechanical modeling of this type allows stress and strain histories to be obtained throughout the model domain

new approach for the quantification of paleostress magnitudes application to the soultz vein system rhine graben france abstract quartz veins often appear in pre existing cracks and are the witnesses of paleofluid flows a new method of paleostress magnitude quantification is proposed in this paper based on the knowledge of i the geometrical distribution of vein poles ii empirical considerations of rupture criteria and iii the fluid pressure stress axis orientations deduced from the geometrical distribution of the vein poles define angular relations allowing the reduced stress tensor and the ratio characterization p f values quantified with fluid inclusion studies and intrinsic curves drawn with empirical relations depending on the rheologic properties of the pre fractured rock are combined to graphically fit the final mohr circle the resulting absolute stress magnitudes take into account the fluid pressure influence application of this method on the quartz vein system of soultz sous forets rhine graben france gives realistic magnitudes of the oligocene extension and are similar to those found in previous study with other methods

paleostress magnitudes associated with development of mountain belts insights from tectonic analyses of calcite twins in the taiwan foothills determinations of stress magnitudes based on inversion of calcite twin data from fault related folds in the taiwan foothills show a decrease of differential stresses during synfolding erosion and exhumation suggesting that paleodepth of burial largely controlled the levels of differential stresses sustained by rocks regional frictional conditions linked to shallow and or deep decollement tectonics probably also influenced stress magnitudes combination of the twin inversion technique with fracture analysis and rock mechanics data provides first order estimates of principal stress values related to the major pleistocene shortening event in taiwan these stress estimates are compared to previous stress estimates in fold thrust belts and to available data on differential stress magnitudes in foreland and hinterland domains of orogens at the scale of an entire orogenic system the most striking point is a decrease of differential stresses from the hinterland toward the foreland this decrease not only reflects tectonic stress attenuation away from the plate boundary but also suggests a major control by the depth of deformation differential stresses estimated from natural deformation consequently provide an independent support to the depth dependent strength and the frictional behavior of the upper continental crust deduced from laboratory experiments and stress measurements in deep boreholes

evolution of coastal sandy aquifer system in kalpitiya peninsula sri lanka sedimentological and geochemical approach the study on the evolution of groundwater sources has arisen because of growing concern about deterioration of groundwater resources due to overexploitation the chemical nature of a coastal aquifer depends on the initial composition of aquifer media internal geochemical processes and external chemical inputs therefore geochemical characteristics of an aquifer can be used as indicative components on elaborating the origin of aquifer media and its evolutionary processes this study was aimed at understanding the evolution of quaternary coastal aquifers of the kalpitya area sri lanka by studying groundwater quality and aquifer media the textural mineralogical and chemical characteristics of aquifer media and chemical nature of groundwater of the area imply that the aquifer media may not have been derived from marine processes and paleo coastal formations of the western coast but are indicative of a fluvial origin due to past strong fluvial processes fluviatile sand depositions had taken place initially and with the gradual sea level rise deposits were transported sorted and then re deposited to form barrier islands parallel to the coast these have evolved to the present state during the quaternary period intermittent climatic changes caused several changes in the depositional pattern of the aquifer material and the chemical nature of the aquifer present day groundwater geochemistry indicates an evolution of a fresh water aquifer with relics of ionic constituents showing paleo geochemical processes that were active during the evolution in addition anthropogenic activities have also significantly altered the geochemical nature of groundwater in the present aquifer system

emergent marine record and paleoclimate of the last interglaciation along the northwest alaskan coast the last interglacial high sea level stand the pelukian transgression of isotope substage 5e is recorded along the western and northern coasts of alaska by discontinuous but clearly traceable marine terraces and coastal landforms up to about 10 m altitude the stratigraphy indicates that sea level reached this altitude only once during the last interglacial cycle from the type area at nome to st lawrence island in the bering sea to the eastern limit of the beaufort sea pelukian deposits contain extralimital faunas indicating that coastal waters were warmer than present amino acid ratios in molluscs from these deposits decrease to the north toward barrow consistent with the modern regional temperature gradient fossil assemblages at nome and st lawrence island suggest that the winter sea ice limit was north of bering strait at least 800 km north of its present position and the bering sea was perennially ice free microfauna in pelukian sediments recovered from boreholes indicate that atlantic water may have been present on the shallow beaufort shelf suggesting that the arctic ocean was not stratified and the arctic sea ice cover was not perennial for some period in coastal regions of western alaska spruce woodlands extended westward beyond their modern range and in northern alaska on the arctic coastal plain spruce groves may have entered the upper colville river basin the flaxman member of the gubik formation on the alaskan arctic coastal plain was deposited during marine isotope substage 5a and records the breakup of an intra stage 5 ice sheet over northwestern keewatin

a review of deformation pattern templates in foreland basin systems and fold and thrust belts implications for the state of stress in the frontal regions of thrust wedges aesthetically appealing thrust systems and related large scale anticlines in both active and fossil foreland fold and thrust belts and the economic potential associated with the m have captured the interest of structural geologists for many decades as a consequence a large amount of data on sub seismic deformation patterns from thrust related an ticlines is available in the literature we provide a review of deformation pattern templates from fi eld data in foreland fold and thrust belts and show that the most frequent tre nds of sub seismic syn orogenic deformation structures hosted in km scale thrust related folds frequently and pa radoxically indicate a syn th rusting strike slip stress fi eld con fi guration with a near vertical 2 and a sub horizontal 3 rather than a contractional one where the latter is expected to be the vertical principal axis of the stress ellipsoid this a pparent inconsistency between sub seismic syn orogenic deformation structures and stress fi eld orientation is here named the 2 paradox field data support a possible expla nation of the paradox provided by the major role played by i nherited early orogenic extensional deformation struc tures on thrust fault nucleation nucleation of major thru sts and their propagation is facilitated and driven by the positive inversion and linkage of the early orogenic sub s eismic extensional inheritance developed in the foreland basin this process eventually leads to the development of l argereversefaultzonesandcanoccurbothincontractional and strike slip stress fi eld con fi gurations

global patterns of radiated seismic energy and apparent stress radiated energies from shallow earthquakes with magnitudes 5 8 that occurred between 1986 and 1991 are used to examine global patterns of energy release and apparent stress in contrast to traditional methods which have relied upon empirical formulas these energies are computed through direct spectral analysis of broadband seismic waveforms velocity squared spectra of body waves are integrated after they have been corrected for effects arising from depth phases frequency dependent attenuation and focal mechanism the least squares regression fit of energy es to surface wave magnitude ms for a global set of 397 earthquakes yields log es 4 4 1 5ms which implies that the gutenberg richter relationship overestimates the energies of earthquakes the least squares fit between es and seismic moment m0 is given by the relationship es 1 6 10 5 m0 which yields 0 47 mpa as the average global value of apparent stress however the regression lines of both es ms and es m0 yield poor empirical predictors for the actual energy radiated by any given earthquake the scatter of data is more than an order of magnitude about each of the regression lines on the other hand global variations between es and mo while large are not random when subsets of es m0 are plotted as a function of seismic region and faulting type the scatter in data is substantially reduced the es m0 fits for many seismic regions and tectonic environments are very distinctive and a characteristic apparent stress c can be derived the lowest apparent stresses 3 0 mpa are associated with strike slip earthquakes that occur at oceanic ridge ridge transforms and in intraplate environments seaward of island arcs intermediate values of apparent stress 1 5 a 3 0 mpa are associated with strike slip earthquakes at incipient or transitional plate boundaries in general the dominant mode of failure for a tectonic environment is associated with the faulting type that has the lowest apparent stress an energy magnitude me can complement moment magnitude mw in describing the size of an earthquake me being derived from velocity power spectra is a measure of seismic potential for damage mw being derived from the low frequency asymptote of displacement spectra is more physically related to the final static displacement of an earthquake when earthquake size is ranked by moment a list of the largest events is dominated by earthquakes with thrust mechanisms when earthquake size is ranked by energy the list of the largest events is dominated by strike slip earthquakes

depth dependency of stress ratios during the sedimentation of nw gyeongsang basin cretaceous southeast korea estimate of stress parameters and timing of tectonic episodes abstract the natural stress state in the lithosphere consists of the vertical load and poisson ratio and then additional horizontal compression and extension denoted by h and t respectively are assumed to be superimposed upon this gravitational stress field the resulting stress state is composed of the maximum medium and minimum stresses denoted by 1 2 and 3 respectively the stress ratio is given as 2 3 1 3 a linear relation is found between or 1 and the vertical load in wrench faulting and extensional stress regimes respectively the slope and intercept of the linear relation result in the additional horizontal stresses and level of average paleo surface respectively stress ratio is also determinable by the stress tensor inversion of fault slip data the earliest tectonic event t 1 event in the cretaceous gyeongsang basin consists of coexisting e w compression and n s extensional faulting episodes plots of or 1 against the burial depth or vertical load display several linear trends two clusters in extensional episodes and two or three clusters in wrench faulting episodes because h is assumed to be null or negligible in the extensional regime t is determinable from the slopes of two linear clusters as being 2 5 to 4 0 mpa in wrench faulting episodes the values of h are given to be 61 6 101 4 mpa by applying determined additional horizontal extensions determined levels of average paleo surfaces and those of syndepostional structures illustrate that more than five wrench faulting or extensional episodes have occurred during the t 1 event whose active age consequently ranges from the barremian to the coniacian this supports that the coexisting coaxial faulting episodes with the same extension may correspond to the alternation of wrench faulting and extensional episodes

a reassessment of the rupture characteristics of oceanic transform earthquakes 1 we investigate the long period source spectra of oceanic transform earthquakes and find that previously proposed slow rupture components can be explained as artifacts generated by the modeling procedure we use low frequency 20 mhz rayleigh and love waves to calculate the amplitude spectra of five earthquakes on the romanche and chain transform faults in the equatorial mid atlantic ocean we find that errors and approximations in the centroid depth focal mechanism and earth structure at the source have significant effects on the shape of the source spectra if global catalog values and an average crustal model are assumed the spectra exhibit apparent anomalous energy at long periods which has previously been interpreted as a result of slow rupture we recalculate the source spectra using precise independently determined depths and moment tensors and a more realistic oceanic crustal structure in the source region the resulting source spectra are flat at long periods with no indication of anomalous long period energy our results imply that oceanic transform earthquakes do not commonly have detectable slow rupture components

structural and microstructural evolution of the rattlesnake mountain anticline wyoming usa new insights into the sevier and laramide orogenic stress build up in the bighorn basin the rocky mountains in western us provide among the best examples of thick skinned tectonics following a period of thin skinned tectonics related to the sevier orogeny the compressional reactivation of basement faults gave birth to the so called laramide uplifts arches the bighorn basin located in wyoming is therefore a key place to study the transition from thin to thick skinned tectonics in orogenic forelands especially in terms of microstructural and stress strain evolution our study focuses on a classic laramide structure the rattlesnake mountain anticline rma wyoming usa a basement cored anticline located in the western part of the bighorn basin stress and strain evolution analysis in folded sedimentary layers and underlying faulted basement rocks were performed on the basis of combined analyses of fractures fault slip data and calcite twinning paleopiezometry most of the fractures are related to three main tectonic events the sevier thin skinned contraction the laramide thick skinned contraction and the basin and range extension serial balanced cross sections of rma and displacement profiles suggest that all thrust faults were coeval evidencing strain distribution in the basement during faulting the comparison of rma with another structure located in the eastern edge of the bighorn basin i e the sheep mountain anticline sma allows to propose a conceptual model for the geometric and kinematic evolution of laramide related basement cored anticlines finally the stress evolution is reconstructed at both the fold scale and the basin scale we show that the evolution of stress trends and magnitudes was quite similar in both structures rma and sma during laramide times thick skinned tectonics in spite of different stress regimes during sevier thin skinned tectonics and post laramide times stress trends and fracture patterns were different in these two structures these results suggest that the distance to the orogenic front influenced the fracture patterns but not the foreland stress magnitudes which were likely controlled by the structural style

the influence of a finite glaciation phase on predictions of post glacial isostatic adjustment we predict relative sea level rsl variations present day three dimensional 3d crustal deformation rates and baseline velocities and a set of anomalies in the gravitational field of the planet using a suite of models for the space time geometry of the pleistocene ice sheets these models are distinguished on the basis of the details of the glaciation phase and they include the cases of an infinite glaciation phase i e an assumption of isostatic equilibrium at the time of the last glacial maximum lgm a steady uniform glaciation and a glaciation in which the bulk of the accumulation is limited to the final stages of the growth phase comparison of the observational records of postglacial rsl change with predictions based on the assumption of isostatic equilibrium at lgm have commonly been used to infer both the space time geometry of the final deglaciation event and the mantle viscosity we conclude that both these applications may be influenced significantly by the incorporation of a finite glacial cycle as an example rsl predictions which assume isostatic equilibrium at lgm and those which incorporate a relatively rapid glaciation phase can differ by a factor of 2 or more at some sites within previously glaciated regions when an earth model characterized by a lower mantle viscosity of 1022 pa s is adopted we have also found that differences in the adopted model for the glaciation event are capable of explaining entirely the discrepancies 0 2 mm yr between previously published predictions of present day tangential velocities in north america these discrepancies are characterized by a dominant long wavelength signal and hence they do not necessarily influence strongly predictions of baseline velocities variations in the glaciation model can also have an important effect on predictions of peak gravity anomalies over previously glaciated regions and secular variations in the zonal harmonics of the earth s geoid in both cases the effect may be sufficient to alter significantly the signal from other geophysical processes which may need to be invoked to reconcile the observational constraints

sedimentary and diagenetic controls on the multiscale fracturing pattern of a carbonate reservoir the madison formation sheep mountain wyoming usa a multidisciplinary approach has been applied to characterize the madison formation in the sheep mountain anticline at different scales in order to illustrate the relationship between sedimentology diagenesis and fracturing pattern sedimentary facies are organized into three types of elementary facies sequences showing different vertical evolutions of their petrophysical properties this is controlled by the double influence of the initial sedimentary facies and the diagenetic evolution three main sets of fractures related to the sevier and laramide compressive phases and to the folding of sheep mountain have been described at three orders of scale at small scale the sevier related set i and folding related set iii are the most abundant set ii dated from the early stage of the laramide compression exhibits the highest fracture intensity there is also a clear faciologic control on the fracture intensity small scale mechanical units correspond to entire facies sequences when no or little petrophysical property contrasts between beds are observed conversely small scale mechanical units correspond to each bed of a facies sequence in the case of high contrasts of petrophysical properties between beds at intermediate scale set ii is not present and sets i and iii show the highest fracture intensities the latter are partly controlled by the mechanical unit thickness intermediate and large scale mechanical unit distribution is mainly controlled by the overall faciologic vertical stacking pattern and by the position across the sheep mountain anticline forelimb or backlimb sheep mountain outcrops provide a good spatial representation of the carbonate reservoir heterogeneities from the micro to the field scale illustrating the complexity of fractured carbonate reservoirs

on moment length scaling of large strike slip earthquakes and the strength of faults 1 several large strike slip earthquakes have occurred in various tectonic settings in the past 5 years adding well documented data to the global collection of moment and length estimates for such earthquakes based on this augmented dataset we reexamine the controversial issue of scaling of seismic moment with length of rupture we find that the global dataset of large strike slip earthquakes follows a bi modal distribution most oceanic and or intraplate strike slip earthquakes have stress drops that are 5 times larger than interplate continental ones when distinguishing these two classes the scaling is compatible with that predicted by simple dislocation theory

the 2012 mw 8 6 sumatra earthquake evidence of westward sequential seismic ruptures associated to the reactivation of a n s ocean fabric 1 the 11 april 2012 mw 8 6 earthquake offshore sumatra is the largest of the rare great intraplate earthquakes of the instrumental era this major strike slip event occurred in the diffuse zone of deformation that accommodates differential rotation between indian and australian plates we perform a back projection analysis calibrated with well located aftershocks of short period teleseismic p waves recorded by the european array to image the rupture process during the mainshock in complement a love wave analysis is conducted for tracking azimuthal change in the apparent global source duration due to the source spatio temporal extent the combined analysis reveals a complex rupture pattern characterized by three main episodes of energy release the latest being located 370 km west of the epicenter on the ninety east ridge with a delay of 120 s we interpret the 11 april 2012 mw 8 6 offshore sumatra earthquake as a complex westward propagating sequence of dynamically triggered strike slip fault ruptures associated to the reactivation of the inherited nne striking sea floor fabric the dynamic triggering mechanism could result from the interaction between transient surface wave stress perturbations and fluids

the 2010 qinghai china earthquake a moderate earthquake with supershear rupture abstract from analyses using near field and teleseismic data we estimate the rupture speed of the 2010 qinghai china earthquake m w 6 9 comparisons of model calculations of the initiations to the observed near field seismogram at station yus indicate a fast supershear rupture propagation of about 5 0 km s from the teleseismic analyses using an envelope deconvolution method with an empirical green s function event two high frequency pulses are identified at 6 5 km and 41 8 km southeast of the epicenter indicating two subevents the location and timing of the high frequency events also show a supershear rupture velocity of 4 7 to 5 8 km s the supershear speed of the rupture likely contributed to the severe damage caused in the forward direction of the rupture toward the town of yushu

uplift induced residual strain release and late thrusting extension in the anaran mountain front anticline zagros iran abstract in this work we present and discuss the pattern of extensional faults of the anaran anticline lurestan province of the zagros iran one of the most aesthetically appealing mountain front anticlines of the zaros this 100 km long structure is affected by extensional faults occurring in different along strike sectors of the anticline running parallel and oblique to the local trend of the fold hinge line and having displacements of hundreds of metres relationships between fold growth and extensional deformation are investigated by quantitatively analysing the attributes i e curvature elevation and throw across faults of a 3d surface representing the top of the ilam formation results indicate that the main stage of extensional deformation occurred during folding in particular we deduce that extensional faulting was associated with the erosional uplift of the crestal sector of the anticline where exhumation of previously shortened strata implied release of residual compressive strain with consequent annihilation of the horizontal stress component paralleling the tectonic transport direction this determined the onset of a large scale extensional regime at the shallower structural levels of the growing anticline

constraints on deformation mechanisms during folding provided by rock physical properties a case study at sheep mountain anticline wyoming usa summary the sheep mountain anticline wyoming usa is a well exposed asymmetric basementcored anticline that formed during the laramide orogeny in the early tertiary in order to unravel the history of strain during folding we carried out combined anisotropy of magnetic susceptibility ams anisotropy of p wave velocity apwv and fry strain analyses the results are compared to previously published stress strain data from calcite twins at the microscopic scale and from fracture sets at the mesoscopic scale and are used to discuss the kinematics and mechanics of forced folding the results obtained in sandstone and carbonate lithologies demonstrate a good agreement between 1 the principal axes of the ams and apwv tensors 2 stress strain tensors derived from calcite twins 3 fry strain axes and mesoscopic fracture sets furthermore these tensors are coaxial with the main structural trends of the anticline the differences between ams and apwv fabrics on one hand and the differential stress values of the forelimb and the backlimb on the other hand emphasize how the macroscopic asymmetry of sheep mountain anticline affects the strain pattern at the microscopic scale the data set presented in this paper offers a consistent mechanical scenario for the development of sheep mountain anticline

rupture imaging of the mw 7 9 12 may 2008 wenchuan earthquake from back projection of teleseismic p waves 1 the mw 7 9 wenchuan earthquake of 12 may 2008 was the most destructive chinese earthquake since the 1976 tangshan event tens of thousands of people were killed hundreds of thousands were injured and millions were left homeless here we infer the detailed rupture process of the wenchuan earthquake by back projecting teleseismic p energy from several arrays of seismometers this technique has only recently become feasible and is potentially faster than traditional finite fault inversion of teleseismic body waves therefore it may reduce the notification time to emergency response agencies using the iris dmc we collected 255 vertical component broadband p waves at 30 95 from the epicenter we found that at periods of 5 s and greater nearly all of these p waves were coherent enough to be used in a global array we applied a simple down sampling heuristic to define a global subarray of 70 stations that reduced the asymmetry and sidelobes of the array response function arf we also considered three regional subarrays of seismometers in alaska australia and europe that had apertures less than 30 and p waves that were coherent to periods as short as 1 s individual arfs for these subarrays were skewed toward the subarrays however the linear sum of the regional subarray beams at 1 s produced a symmetric arf similar to that of the groomed global subarray at 5 s for both configurations we obtained the same rupture direction rupture length and rupture time we found that the wenchuan earthquake had three distinct pulses of high beam power at 0 23 and 57 s after the origin time with the pulse at 23 s being highest and that it ruptured unilaterally to the northeast for about 300 km and 110 s with an average speed of 2 8 km s it is possible that similar results can be determined for future large dip slip earthquakes within 20 30 min of the origin time using relatively sparse global networks of seismometers such as those the usgs uses to locate earthquakes in near real time

earthquake in a maze compressional rupture branching during the 2012 mw 8 6 sumatra earthquake seismological observations of the 2012 moment magnitude 8 6 sumatra earthquake reveal unprecedented complexity of dynamic rupture the surprisingly large magnitude results from the combination of deep extent high stress drop and rupture of multiple faults back projection source imaging indicates that the rupture occurred on distinct planes in an orthogonal conjugate fault system with relatively slow rupture speed the east southeast west northwest ruptures add a new dimension to the seismotectonics of the wharton basin which was previously thought to be controlled by north south strike slip faulting the rupture turned twice into the compressive quadrant against the preferred branching direction predicted by dynamic coulomb stress calculations orthogonal faulting and compressional branching indicate that rupture was controlled by a pressure insensitive strength of the deep oceanic lithosphere

aquifer geochemistry at potential aquifer storage and recovery sites in coastal plain aquifers in the new york city area usa abstract the effects of injecting oxic water from the new york city nyc drinking water supply and distribution system into a nearby anoxic coastal plain aquifer for later recovery during periods of water shortage aquifer storage and recovery or asr were simulated by a 3 dimensional reactive solute transport model the cretaceous aquifer system in the nyc area of new york and new jersey usa contains pyrite goethite locally occurring siderite lignite and locally varying amounts of dissolved fe and salinity sediment from cores drilled on staten island and western long island had high extractable concentrations of fe mn and acid volatile sulfides avs plus chromium reducible sulfides crs and low concentrations of as pb cd cr cu and u similarly water samples from the lloyd aquifer cretaceous in western long island generally contained high concentrations of fe and mn and low concentrations of other trace elements such as as pb cd cr cu and u all of which were below us environmental protection agency usepa and ny maximum contaminant levels mcls in such aquifer settings asr operations can be complicated by the oxidative dissolution of pyrite low ph and high concentrations of dissolved fe in extracted water the simulated injection of buffered oxic city water into a hypothetical asr well increased the hydraulic head at the well displaced the ambient groundwater and formed a spheroid of injected water with lower concentrations of fe mn and major ions in water surrounding the asr well than in ambient water both the dissolved o 2 concentrations and the ph of water near the well generally increased in magnitude during the simulated 5 a injection phase the resultant oxidation of fe 2 and attendant precipitation of goethite during injection provided a substrate for sorption of dissolved fe during the 8 a extraction phase the baseline scenario with a low 0 001 m concentration of pyrite in aquifer sediments indicated that nearly 190 more water with acceptably low concentrations of dissolved fe could be extracted than was injected scenarios with larger amounts of pyrite in aquifer sediments generally resulted in less goethite precipitation increased acidity and increased concentrations of dissolved fe in extracted water in these pyritic scenarios the lower amounts of goethite precipitated and the lower ph during the extraction phase resulted in decreased sorption of fe 2 and a decreased amount of extractable water with acceptably low concentrations of dissolved fe 5 4 10 6 m a linear decrease in recovery efficiency with respect to dissolved fe concentrations is caused by pyrite dissolution and the associated depletion of dissolved o 2 do and increase in acidity simulations with more than 0 0037 m of pyrite which is the maximum amount dissolved in the baseline scenario had just over a 50 recovery efficiency the precipitation of ferric hydroxide minerals goethite at the well screen and a possible associated decrease in specific capacity of the asr well was not apparent during the extraction phase of asr simulations but the model does not incorporate the microbial effects and biofouling associated with ferric hydroxide precipitation the host groundwater chemistry in calcite poor cretaceous aquifers of the nyc area consists of low alkalinity and moderate to low ph the dissolution of goethite in scenarios with unbuffered injectate indicates that corrosion of the well could occur if the injectate is not buffered simulations with buffered injectate resulted in greater precipitation of goethite and lower concentrations of dissolved fe in the extracted water dissolved fe concentrations in extracted water were highest in simulations of aquifers 1 in which pyrite and siderite in the aquifer were in equilibrium and 2 in coastal areas affected by saltwater intrusion where high dissolved cation concentrations provide a greater exchange of fe 2 fex 2 results indicate that asr in pyrite bearing cretaceous aquifers of the nyc area can be a cost effective way to both store drinking water supplies and significantly reduce ambient concentrations of dissolved fe

imaging short period seismic radiation from the 27 february 2010 chile mw 8 8 earthquake by back projection of p pp and pkikp waves 1 teleseismic short period 0 5 5 s p waves from the 27 february 2010 chile earthquake mw 8 8 are back projected to the source region to image locations of coherent short period seismic wave radiation several receiver array configurations are analyzed using different p wave arrivals including networks of stations in north america p japan pkikp and europe pp as well as a global configuration of stations with a broad azimuthal distribution and longer period p waves 5 20 s coherent bursts of short period radiation from the source are concentrated below the chilean coastline along the downdip portion of the megathrust the short period source region expands bilaterally with significant irregularity in the radiation comparison with finite fault slip models inverted from longer period seismic waves indicates that the regions of large slip on the megathrust are located updip of the regions of short period radiation a manifestation of frequency dependent seismic radiation similar to observations for the great 2011 tohoku earthquake mw 9 0 back projection of synthetic p waves generated from the finite fault models demonstrates that if the short period energy had radiated with the same space time distribution as the long period energy back projection analysis would image it in the correct location updip we conclude that back projection imaging of short period signals provides a distinct view of the seismic source that is missed by studies based only on long period seismic waves geodetic data and or tsunami observations

palaeostress magnitudes in the khao khwang fold thrust belt new insights into the tectonic evolution of the indosinian orogeny in central thailand using the khao khwang fold thrust belt in central thailand as case study we handled data from calcite twinning analysis in order to propose the quantification of the effective principal palaeostresses magnitudes since the onset of the early stages of the indosinian orogeny we also combined the differential stress estimates from mechanically induced calcite twins with geochronological data in order to constrain the timing of the palaeoburial depth and subsequent uplift by folding within the khao khwang fold thrust belt the proposed mechanical scenario is based on the time constrained kinematic sequence of fracturing faulting and folding in the strata of the carbonate formations of the saraburi group cross checking the data on the palaeostress orientations regimes and differential stress magnitudes with rock mechanics analysis we provided data on the principal stress magnitudes for each tectonic stage that developed during the indosinian orogeny further 40ar 39ar and u pb geochronological data allowed to place reliable constraints on the amount and rate of vertical uplift of the carbonate formations of the saraburi group

inversion of calcite twin data for paleostress orientations and magnitudes a new technique tested and calibrated on numerically generated and natural data abstract the inversion of calcite twin data is a powerful tool to reconstruct paleostresses sustained by carbonate rocks during their geological history following etchecopar s 1984 pioneering work this study presents a new technique for the inversion of calcite twin data that reconstructs the 5 parameters of the deviatoric stress tensors from both monophase and polyphase twin datasets the uncertainties in the parameters of the stress tensors reconstructed by this new technique are evaluated on numerically generated datasets the technique not only reliably defines the 5 parameters of the deviatoric stress tensor but also reliably separates very close superimposed stress tensors 30 of difference in maximum principal stress orientation or switch between 3 and 2 axes the technique is further shown to be robust to sampling bias and to slight variability in the critical resolved shear stress due to our still incomplete knowledge of the evolution of the critical resolved shear stress with grain size our results show that it is recommended to analyze twin data subsets of homogeneous grain size to minimize possible errors mainly those concerning differential stress values the methodological uncertainty in principal stress orientations is about 10 it is about 0 1 for the stress ratio for differential stresses the uncertainty is lower than 30 applying the technique to vein samples within mesozoic limestones from the monte nero anticline northern apennines italy demonstrates its ability to reliably detect and separate tectonically significant paleostress orientations and magnitudes from naturally deformed polyphase samples hence to fingerprint the regional paleostresses of interest in tectonic studies

geochemical and microbiological zonation of the middendorf aquifer south carolina we consider the nature and origin of the chemical and microbiological zonation of the cretaceous middendorf aquifer in the coastal plain of south carolina in light of the chemical evolution of groundwater along a flow path there some types of microbial activity most notably aerobic respiration and iron reduction lead to a net generation of acid as co2 but reaction of groundwater with minerals in the aquifer consumes the acid driving up ph and controlling the evolution of the groundwater s major ion chemistry the thermodynamic energy available to the various functional groups of microbes except the autotrophic hydrogen oxidizing methanogens is everywhere along the flow path sufficient to drive microbial growth the concentrations of acetate formate and lactate do not vary systematically from zone to zone along the flow path as might be expected if each zone were dominated by a single functional group of microbes the overall rate of microbial respiration in the aquifer appears to be limited by the rate of the initial fermentation of organic matter we found no compelling evidence indicating that one functional group of microbes excludes others from any of the aquifer s zones sulfate reduction for example may be non existent in the high iron zone associated with iron reduction or may account for up to 90 of the respiration occurring there zonation of the groundwater into high iron and low iron facies may result from a minor change along the aquifer in the balance between the activities of iron and sulfate reducers

layer parallel shortening across the sevier fold thrust belt and laramide foreland of wyoming spatial and temporal evolution of a complex geodynamic system abstract varying patterns of layer parallel shortening lps and vertical axis rotations from the thin skin sevier fold thrust belt to the thick skin laramide foreland of wyoming are quantified from integrated structural anisotropy of magnetic susceptibility ams and paleomagnetic analyses within the sevier belt widespread early lps was accommodated by spaced cleavage fracture sets minor folds and minor faults lps directions are subperpendicular to structural trends of systematically curved thrust sheets of the wyoming salient reflecting a combination of primary dispersion and secondary rotation during thrusting within the laramide foreland limited lps was accommodated mostly by minor faults with conjugate wedge and strike slip geometries lps directions in gentler fold limbs vary from perpendicular to acute with structural trends of variably oriented anastomosing basement cored arches steep forelimbs display more complex relations including younger fault sets that developed during evolving stress states and localized vertical axis rotations although internal strain is limited weak ams lineations defined by kinked and rotated phyllosilicates are widely developed and consistently oriented perpendicular to measured lps directions palinspastically restored lps directions corrected for paleomagnetically determined vertical axis rotations vary on average from w e in the sevier belt to wsw ene in the laramide foreland in detail lps directions display deflections related to primary sedimentary wedge geometry and basement fabrics lps in the sevier belt is interpreted to partly reflect stress transmitted from the hinterland through the growing orogenic wedge and topographic stress along the front of the wedge lps in the laramide foreland is interpreted to partly reflect basal traction during flat slab subduction beneath thick cratonic lithosphere with spatial temporal variations in stress trajectories related to basement heterogeneities and evolving fault systems evidence for significant late n s laramide shortening as proposed by multi stage shortening models is not observed

subevent location and rupture imaging using iterative backprojection for the 2011 tohoku mw 9 0 earthquake summary knowledge of the rupture speed and spatial temporal distribution of energy radiation of earthquakes is important for earthquake physics backprojection of teleseismic waves is commonly used to image the rupture process of large events the conventional backprojection method typically performs temporal and spatial averaging to obtain reliable rupture features we present an iterative backprojection method with subevent signal stripping to determine the distribution of subevents large energy bursts during the earthquake rupture we also relocate the subevents initially determined by iterative backprojection using the traveltime shifts from subevent waveform cross correlation which provides more accurate subevent locations and source times a bootstrap approach is used to assess the reliability of the identified subevents we apply this method to the mw 9 0 tohoku earthquake in japan using array data in the united states we identify 16 reliable subevents in the frequency band 0 2 1 hz which mostly occurred around or west of the hypocentre in the downdip region analysis of tohoku aftershocks shows that depth phases can often produce artefacts in the backprojection image but the position and timing of our main shock subevents are inconsistent with depth phase artefacts our results suggest a complicated rupture with a component of bilateral rupture along strike the dominant energy radiation between 0 2 and 1 hz is confined to a region close to the hypocentre during the first 90 s a number of subevents occurred around the hypocentre in the first 90 s suggesting a low initial rupture speed and repeated rupture or slip near thehypocentre therupturereachedthecoastalregionabout106kmnorthwestofthehypocentreat43sandtheregionabout110kmnorthofthehypocentreat105swithanorthwardrupture speed 2 0 kms 1 at 60 110 s after 110 s a series of subevents occurred about 120 220 km southwest of the hypocentre consistent wit ha3k ms 1 along strike rupture speed the abundant high frequency radiation in the downdip region close to the coast suggests intermittent rupture probably in the brittle ductile transition zone the lack of high frequency radiation in the updip region suggests the rupture near the trench was more continuous probably due to more homogeneous frictional properties of the shallow slab interface the lack of early aftershocks in the updip region indicates that most of the accumulated slip in the updip region during the interseismic period was probably released during the main shock

geochemistry of dissolved inorganic carbon in a coastal plain aquifer 1 sulfate from confining beds as an oxidant in microbial co2 production a primary source of dissolved inorganic carbon dic in the black creek aquifer of south carolina is carbon dioxide produced by microbially mediated oxidation of sedimentary organic matter groundwater chemistry data indicate however that the available mass of inorganic electron acceptors oxygen fe iii and sulfate and observed methane production is inadequate to account for observed co2 production although sulfate concentrations are low approximately 0 05 0 10 mm in aquifer water throughout the flow system sulfate concentrations are greater in confining bed pore water 0 4 20 mm the distribution of culturable sulfate reducing bacteria in these sediments suggests that this concentration gradient is maintained by greater sulfate reducing activity in sands than in clays calculations based on fick s law indicate that possible rates of sulfate diffusion to aquifer sediments are sufficient to explain observed rates of co2 production about 10 5 mmoll 1 year 1 thus eliminating the apparent electron acceptor deficit furthermore concentrations of dissolved hydrogen in aquifer water are in the range characteristic of sulfate reduction 2 6 nm which provides independent evidence that sulfate reduction is the predominant terminal electron accepting process in this system the observed accumulation of pyrite and calcite cemented sandstones at sand clay interfaces is direct physical evidence that these processes have been continuing over the history of these sediments

recent and future trends in paleopiezometry in the diagenetic domain insights into the tectonic paleostress and burial depth history of fold and thrust belts and sedimentary basins paleopiezometry provides an access to the past stress magnitude key to better understand the behaviour of the earth s crust over long period of time this contribution presents a review of some paleopiezometric techniques that can be used in the diagenetic domain in fold and thrust belts and sedimentary basins calcite twinning and stylolite roughness techniques have been selected and are presented through a critical description of their methodologies along with approaches to further reconstruct the complete effective stress tensor major geological lessons learned over the past decades from published studies are summarized and discussed along with a way forward to potential breakthroughs

determination of principal stress magnitudes using calcite twins and rock mechanics data abstract this paper proposes a new method for determining principal stress magnitudes based on the use of the deviatoric stress tensor determined from computer inversion of calcite twin data additional evaluation of the vertical stress weight of overburden or of the mean stress is enough to calculate the complete stress tensor we emphasize that the best reasoning consists of combining calcite twin analysis with rock mechanics data failure friction criteria because the determination of the six parameters of the absolute stress tensor is overconstrained