elastic wave velocity structure of the crust and upper mantle beneath the north china basin travel time residuals from locally and teleseismically recorded earthquakes are used to determine the three dimensional elastic wave velocity structure beneath the central north china basin and surrounding mountains we calculated p wave and s wave travel time residuals for 200 aftershocks of the 1976 tangshan earthquake and p wave travel time residuals for 194 teleseisms recorded by the beijing network between 1976 and 1983 we performed iterative one and three dimensional block inversions for crust and uppermost mantle structure based solely on the aftershock travel time residuals we also performed iterative three dimensional block inversions for crust and upper mantle structure based solely on the teleseismic travel time residuals and based on the combined aftershock and teleseismic travel time residuals we determined that the average thickness of the crust beneath the north china basin and surrounding mountains is about 35 km beneath the onshore portion of the north china basin however the crust is closer to 32 or 33 km thick the velocity structure of the upper 20 km or so of the crust is well correlated with the surface geology and parallels the short wavelength a few tens of kilometers features of the surface topography rocks with low seismic velocities lie in or beneath the basin rocks with high seismic velocities lie in or beneath the mountains the uppermost mantle and possibly even the lower crust appears to be a zone of transition in velocity structure between that of the upper crust and the mantle the trends of relative highs and lows in the velocity structure of the mantle are nearly opposite that of the crust the mantle material underlying most of the north china basin has higher than average seismic velocities while the material beneath the western mountains has lower than average velocities the velocity structure of the mantle parallels the long wavelength tens to hundreds of kilometers features evident in the gravity and topography of north china the high velocity mantle material presently beneath the basin probably represents mantle processes not directly related to the formation of the north china basin we infer that the transition zone between the short wavelength and long wavelength velocity features represents a zone of decoupling between the lithosphere and asthenosphere specifically the lithosphere beneath the north china block is moving eastward with respect to the asthenosphere

three dimensional p and s velocity structure in the coalinga region california the coalinga earthquake sequence of 1983 provided a unique opportunity to perform a three dimensional velocity and hypocenter inversion in an area of complex three dimensional structure dominated by folding and blind thrusts additionally since other varied geological and geophysical studies have been completed in this area the three dimensional inversion solution could be compared to other interpretations inversion of 7696 p and 1511 s first arrivals from earthquakes and 696 p first arrivals from refraction shots produced a three dimensional velocity model with grid spacing of 1 2 km in the hypocentral area the overall shape and location of velocity features correspond well to the mapped surface geology the three dimensional inversion yields details of folds where the resolution is good and the general shape where resolution is lower the amounts of structural relief inferred for the local folds are similar to values inferred from geologic data the three dimensional velocity solution has several distinctive features there is a linear high velocity body 6 1 6 5 km s about 25 km long from 6 to 8 km depth that may represent a fragment of coast range ophiolite a shallow low velocity zone lvz which extends for 20 km along the fold axis at about 6 km depth and correlates with lvzs observed in both the refraction and the reflection data may indicate high pore pressure caused by lateral compressive strain deeper lvzs occur within inferred franciscan material and are characterized by horizontal or southwest dipping zones of varied thickness 4 8 km wide and 5 10 km long these lvzs may represent multiple thrust faults their locations and geometry are consistent with thrust faults inferred with seismic reflection data the three dimensional velocity solution compares well to prior two dimensional seismic reflection and refraction models and observed gravity the shape of the inferred sedimentary section agrees well with the reflections from the cenozoic strata compared to the refraction model the three dimensional solution has similar velocities and similar locations of velocity features but is more detailed in the hypocentral zone where it uses more data the gravity computed from the three dimensional velocities is similar to the observed gravity in both shape and amplitude both a simple one dimensional initial model and a complex initial model derived from the refraction interpretation were tried a simple starting model gave the best results the s velocity solution has different resolution than the p velocity solution because it uses a different set of stations and it has lower resolution because it uses fewer arrival times while the general patterns of velocity variation are similar for both vp and vs the vs solution tends to have more smearing of velocity features and can have somewhat different locations of velocity features

estimation of fracture height using microseismicity associated with hydraulic fracturing the ratio of horizontal to vertical h v particle velocity in background microseismic radiation associated with hydraulic fracturing is substantially higher in the dilatant low velocity fractured zone than it is outside this provides a useful diagnostic for determining the height of the fractured zone numerical synthesis of guided wave phenomena within the low velocity fractured zone accounts for much of the observed behavior but measured h v patterns are not totally consistent with either pure tensile or pure shear sources a composite model containing both tensile compressional sources and asperity shear failures appears to satisfy the main observations better than either source type does alone this composite is consistent with current models of earthquake aftershock sequences which also have different mechanisms at the edges and in the interior of a fracture zone tensile and shear respectively the h v phenomenon is consistent with a predominance of energy with shear wave polarization traveli

using automated high precision repicking to improve delineation of microseismic structures at the soultz geothermal reservoir an automatic adaptive correlation based algorithm for adjusting phase picks in large digital seismic data sets provides significant improvement in resolution of microseismic structures using only a small fraction of the time and manpower which would be required to re analyze waveforms manually or semi automatically we apply this technique to induced seismicity at the soultz sous forets geothermal site france the method is first applied to a small previously manually repicked subset of the catalogue so that we may compare our results to those obtained from painstaking visual cross correlation based techniques relative centroid adjusted hypocenters show a decrease in median mislocation from 31 to 7 m for preliminary and automatically adjusted picks respectively compared to the manual results narrow intersecting joint features not observed in the preliminary hypocenter cloud but revealed through manual repicking are also recovered using the automatic method we then address a larger catalogue of 7000 microearthquakes after relocating the events using automatic repicks the percentage of events clustering within 5 m of their nearest neighbor increases form 5 to 26 of the catalogue hypocenter relocations delineate narrow linear features previously obscured within the seismic cloud interpreted as faults or fractures which may correspond to fluid propagation paths or to changes in stress as a result of elevated pore pressures rms travel time residuals for the larger data set are reduced by only 0 2 however phase pick biases in the preliminary catalogue have influenced both the velocity model and station correction calculations which will affect location residuals these pick biases are apparent on the adjusted stacked waveforms and correcting them will be important prior to future velocity model refinements

spatial variation of biologically available strontium isotopes 87sr 86sr in an archipelagic setting a case study from the caribbean this paper presents the results of strontium sr isotope analysis of modern and archaeological animal remains and modern plant samples from the caribbean region the goal is to assess if patterns of human mobility can be determined from the archaeological record in an archipelagic setting the range of variability and spatial distribution of biologically available strontium isotope signatures is reported and data evaluated to determine if sufficient heterogeneity exists to permit the identification of mobility despite the presence of potentially large contributions of marine strontium in island and coastal ecosystems the is landscape is divided into several sub regions based on the age and lithology of underlying geology and the variability of

effects of diagenesis on strontium carbon nitrogen and oxygen concentration and isotopic composition of bone abstract paleodietary analysis based on variations in the trace element and stable isotopic composition of inorganic and organic phases in fossil bone depends on the assumption that measured values reflect in vivo values to test for postmortem alteration we measured 87 sr 86 sr 13 c 12 c 18 o 16 o and 15 n 14 n ratios and sr concentrations in modern and prehistoric 610 to 5470 yr old bones of animals with marine or terrestrial diets from greenland bones from modern terrestrial feeders have substantially lower sr concentrations and more radiogenic 87 sr 86 sr ratios than those from modern marine feeders this contrast was not preserved in the prehistoric samples which showed almost complete overlap for both sr concentration and isotopic composition in bones from the two types of animals leaching experiments x ray diffraction analysis and infrared spectroscopy indicate that alteration of the sr concentration and isotopic composition in prehistoric bone probably results from nearly complete exchange with groundwater oxygen isotope ratios in fossil apatite carbonate also failed to preserve the original discrimination between modern terrestrial and marine feeders the c isotope ratio of apatite carbonate did not discriminate between animals with marine or terrestrial diets in the modern samples even so the ranges of apatite 13 c values in prehistoric bone are more scattered than in modern samples for both groups suggesting alteration had occurred 13 c and 15 n values of collagen in modern bone are distinctly different for the two feeding types and this distinction is preserved in most of the prehistoric samples our results suggest that postmortem alteration of dietary tracers in the inorganic phases of bone may be a problem at all archaeological sites and must be evaluated in each case while collagen analyzed in this study was resistant to alteration evaluation of the possibility of diagenetic alteration of its isotopic composition in bones from other contexts is also warranted

solubility profiles of synthetic apatites and of modern and fossil bones abstract strontium has been shown to vary within trophic levels in natural foodwebs so that previous criteria used to identify biogenic strontium in fossils namely consistent differences between herbivores and carnivores may be inappropriate in this article two alternative approaches are explored these include first experimental studies of the behaviour of synthetic apatites in the solubility profile system and second solubility profile studies of fossils from the pleistocene site of swartkrans the synthetic apatite studies show that simple mixtures of apatites dissolve discretely in the system study of swartkrans specimens reveals that while diagenetic sr is clearly present some recoverable sr varies in a manner similar to that seen in modern african foodwebs and is therefore unlikely to be of diagenetic origin

spatial variation of strontium isotopes 87sr 86sr in the maya region a tool for tracking ancient human migration strontium isotope ratios 87sr 86sr in human bones and teeth have become a useful tool to study migration and sedentism of individuals from archaeological contexts here we analyzed 87sr 86sr of water bedrock soils and plants across a broad geographic region to test the potential of this method in the ancient maya area our aims were two fold first to test if the sources of dietary strontium i e plants and water in humans reflect the 87sr 86sr ratio of exposed bedrock and second to determine whether the ranges of 87sr 86sr values were sufficiently distinct among the principal maya geocultural areas to infer past migration we identified five distinct subregions on the basis of geologic maps and evaluated the variability of 87sr 86sr values values given as mean 87sr 86sr 2 standard deviations number of samples 1 northern lowlands 0 70888 0 00066 n 16 2 southern lowlands 0 70770 0 00052 n 86 3 volcanic highlands and pacific coast 0 70415 0 00023 n 34 4 metamorphic province 0 70743 0 00572 n 50 and 5 the maya mountains of belize 0 71327 0 00167 n 3 although the sample size is small and overlap exists in 87sr 86sr values among some subregions most areas can be readily distinguished from one another on the basis of strontium isotopes these subregional 87sr 86sr differences provide archaeologists with a powerful tool to recognize geographic outliers in ancient maya burials and thereby test hypotheses concerning the origin of specific individuals inferred population migration patterns and the possibility of outside cultural influences in the maya region

natural levee evolution in the rhine meuse delta the netherlands during the first millennium ce this paper presents reconstructions on natural levee development in the rhine meuse delta the netherlands during the first millennium ce covering the full delta plain it is the first study that performs this on a delta scale which allows seeing the delta wide trends on levee forming controls and their feedbacks we mapped the levee morphology and elevation by combining lidar imagery lithological borehole data soil mapping radiocarbon dates archaeological data and gis reconstruction techniques from the detailed levee reconstructions we quantified natural levee dimensions and evaluated the temporal changes therein the dimensions and the changes therein were then linked to external forcings increasing suspended sediment load variable flooding intensity and to natural preconditions e g delta plain width flood basin configuration we show that natural preconditions are an important control on levee shape this is demonstrated for the upper delta where the relatively narrow delta plain combined with strong compartmentation i e the occurrence of many alluvial ridges and enclosed flood basins caused the flood levels to be amplified allowing the natural levees to grow relatively high compartmentation also seems to have stimulated trapping of coarse grained overbank sediments explaining the clear downstream trend in levee width this effect was probably further aided by the clearance of the riparian forests mainly in the upstream and central delta which caused the coarser fraction of the suspended load to be further dispersed into the flood basin leading to wider levees in the first millennium ce several new river courses formed that avoided the areas of natural levee relief of abandoned alluvial ridges on these fossil alluvial ridges the topographical expression gradually reduced because of widespread flood basin trapping of overbank sediment which led to topographic levelling the natural levees that formed during this period along the new courses appear to be relatively high compared to precursor generations in the upper and central delta this is most likely related to the increased suspended sediment supply and intense flooding regime during their formation the hypotheses generated with this new delta wide overview help to better understand the controls in the development of levees which are important elements in river landscapes and in fluvial sedimentary records 2017 elsevier b v

isotope domain mapping of 87sr 86sr biosphere variation on the isle of skye scotland abstract the potential of 87 sr 86 sr isotope composition for tracking and determining the origin of material whether it is humans animals water or wine can be fully realized only if high quality reference datasets are available against which to compare the unknowns this is currently not the case despite the rapid increase in 87 sr 86 sr based provenance studies of biosphere materials there are no well documented maps available most researchers resort to generating reference maps from a variety of geological datasets plus the analysis of sparse environmental9 samples a major reason for this lack of reference material is the investment needed to undertake systematic sampling and analysis over large areas a further problem is associated with the choice of proxy material as organisms differ in their habitat and exploitation of resources in this paper various approaches to isotope biosphere sampling are considered some of the problems are assessed the precision required for the study of human populations is discussed and a first attempt is made to condense all of the available information into an isotope package9 map the work is based on a study undertaken on the isle of skye in the inner hebrides and reduces the complexity of geological and isotope data into five main 87 sr 86 sr packages package 1 northern area 0 705 0 7092 package 2 ne coast 0 7082 0 7102 package 3 granitic rocks 0 716 0 720 package 4 metamorphic rocks 0 7092 0 7188 package 5 seawater 0 7092 0 005 2 the approach of trying to constrain the isotope composition of certain areas and or lithologies offers the possibility of extrapolating to other similar areas without having to sample at the original density

interpretation of microseismicity resulting from gel and water fracturing of tight gas reservoirs we provide a comparative analysis of the spatio temporal dynamics of hydraulic fracturing induced microseismicity resulting from gel and water treatments we show that the growth of a hydraulic fracture and its corresponding microseismic event cloud can be described by a model which combines geometry and diffusion controlled processes it allows estimation of important parameters of fracture and reservoir from microseismic data and contributes to a better understanding of related physical processes we further develop an approach based on this model and apply it to data from hydraulic fracturing experiments in the cotton valley tight gas reservoir the treatments were performed with different parameters such as the type of treatment fluid the injection flow rate the total volume of fluid and of proppant in case of a gel based fracturing the spatio temporal evolution of induced microseismicity shows signatures of fracture volume growth fracturing fluid loss as well as diffusion of the injection pressure in contrast in a water based fracturing the volume creation growth and the diffusion controlled growth are not clearly separated from each other in the space time diagram of the induced event cloud still using the approach presented here the interpretation of induced seismicity for the gel and the water treatments resulted in similar estimates of geometrical characteristics of the fractures and hydraulic properties of the reservoir the observed difference in the permeability of the particular hydraulic fractures is probably caused by the different volume of pumped proppant

induced microearthquake patterns and oil producing fracture systems in the austin chalk abstract microearthquakes collected during hydraulic stimulation allowed us to study fracture zones in austin chalk oil reservoirs at two sites in the giddings field texas we deployed three component downhole geophone tools in production wells at depths of 2100 m and greater one near cook s point and two on the matcek lease near caldwell at cook s point we collected 482 microseismic events during a 4000 m 3 25 000 bbl hydraulic stimulation in an offset well we collected 770 events during a similar operation on the matcek lease many seismograms contained reflected phases that constrained location depths to the production zone at the base of the austin chalk by restricting all microearthquake locations to production depths we located 20 of the cook s point events and over 60 of the matcek events at both sites we observed only the fracture wing closest to the observation stations locations formed elongated patterns extending up to 1 km from the stimulation well and trending n60 e parallel to the known regional fracture trend the cook s point seismic zone measured over 100 m in width while long stretches of the matcek seismic zone narrowed to 30 m or less we believe that the width of the seismic zone reflected the density of conductive fractures and thus the volume of the reservoir accessed by the stimulation indeed production rates in the first year following stimulation were much higher at cook s point where we observed the wider of the two seismic zones

upstream and downstream controls of recent avulsions on the taquari megafan pantanal south western brazil avulsion the natural relocation of a river is a key process in the evolution of subaerial fans river floodplains and deltas the causes of avulsion are poorly understood which is partly due to the scarcity of field studies of present avulsions at present two avulsions are occurring on the middle and lower taquari megafan pantanal basin south western brazil here we present an analysis of the causes of these avulsions based on field and remote sensing data and show that avulsions on megafans can be controlled by both upstream and downstream processes the middle fan avulsion started in 1997 1998 is a result of upstream control overbank aggradation was caused by the variable input of sandy sediment into the system which caused channel belt superelevation and also created an easily erodible subsurface favouring bank retreat crevassing and scour of deep floodplain channels the sandy subsurface in this area is inferred to have been a major factor in the causation of this avulsion under conditions of little gradient advantage the lower fan avulsion started c 1990 results from interplay of upstream and downstream controls the latter being related to the local base level the paraguay river floodplain at the toe of the fan channel and overbank aggradation on the lower fan was influenced by fan sub lobe progradation and channel backfilling fan sub lobe progradation caused a significant gradient advantage of the avulsion channel over the parent channel avulsions are commonly supposed to be preferentially triggered by high magnitude floods when there is considerable channel belt superelevation however both avulsions studied by us were triggered by small to average floods with modest channel belt superelevation we conclude that flood magnitude and channel belt superelevation have been overrated as causes of avulsion and demonstrate additional causes that influence the growth of crevasses into avulsions

strontium isotope investigation of ungulate movement patterns on the pleistocene paleo agulhas plain of the greater cape floristic region south africa abstract middle stone age sites located within the greater cape floristic region on the south african southern coast have material culture with early evidence for key modern human behaviors such as projectile weaponry large animal hunting and symbolic behavior in order to interpret how and why these changes evolved it is necessary to understand their ecological context as it has direct relevance to foraging behavior during periods of lowered sea level a largely flat and vast expanse of land existed south of the modern coastline but it is now submerged by higher sea levels this exposed area the paleo agulhas plain likely created an ecological context unlike anything in the region today as evidenced by fossil assemblages dominated by migratory ungulates one hypothesis is that the paleo agulhas plain supported a migration ecosystem of large grazers driven by summer rainfall producing palatable forage during summer in the east and winter rainfall producing palatable forage during winter in the west alternatively ungulates may have been moving from the coastal plain in the south to the interior north of the cape fold mountains as observed for elephants in historic times in this study we assess ungulate movement patterns with inter and intra tooth enamel samples for strontium isotopes in fossil fauna from pinnacle point sites pp13b and pp30 to accomplish our goals we created a bioavailable 87sr 86sr isoscape for the region by collecting plants at 171 sampling sites and developing a geospatial model the strontium isotope results indicate that ungulates spent most of their time on the paleo agulhas plain and avoided dissected plain foothill and mountain habitats located more than about 15 km north of the modern coastline the results clearly exclude a north south coastal interior movement or migration pattern and cannot falsify the east west movements hypothesized in the south coast migration ecosystem hypothesis

improved relative locations of clustered earthquakes using constrained multiple event location a new method for improving relative locations of clustered earthquakes is presented and applied to a suite of microearthquakes induced by hydraulic fracturing the method is based on the assumption that clustering of earthquake hypocenters is obscured by the uncorrelated scatter of individual hypocenters the method is implemented as an additional constraint in a joint hypocenter determination jhd scheme the method shifts event hypocenters toward the center of mass of the events within some volume surrounding the event location if the rms misfit between predicted and measured arrival times does not increase significantly the method uses the same basic assumption of jones and stewart 1997 which is that there is greater clustering in actual earthquake locations than there is in locations determined using conventional techniques our method differs in that it is implemented as part of the jhd process so it operates on raw travel time data rather than on derived hypocenters the method produces hypocenters from a demonstration field dataset that are similar to those obtained by phillips et al 1997 from time consuming precise manual repicking of relative arrival times of events the clustering constraint can easily be incorporated as an additional constraint in earthquake location velocity tomography codes and may lead to improved velocity structure determination and earthquake location pattern identification and interpretation

human caused avulsion in the rhine meuse delta before historic embankment the netherlands although the shifting of deltaic river branches avulsion is a natural process that has become increasingly influenced by humans the impact of early human activities as a driver of avulsion success has remained poorly explored this study demonstrates how two important avulsions in the downstream part of the rhine meuse delta the netherlands were stimulated by human activities in the first millennium ce before historic embankment constrained the river courses peatland reclamation induced land subsidence in the lower delta this effect together with a human induced increase in suspended fluvial sediments and tidal backwater effects allowed for a gradual ingression of tidal creek channels and progradation of fluvial crevasse channels into human occupied and drained peatlands where they eventually connected we reconstructed the initial situation and identified the feedback loops among overbank sedimentation tidal incursion and land drainage subsidence that led to avulsion success the processes and feedbacks resulting from human activities are generic and hence relevant to many other deltas today where humaninduced subsidence results in tidal ingression potentially connecting to rivers and causing unexpected avulsions 2018 geological society of america

high resolution stratigraphy with strontium isotopes the isotopic ratio of strontium 87 to strontium 86 shows no detectable variation in present day ocean water but changes slowly over millions of years the strontium contained in carbonate shells of marine organisms records the ratio of strontium 87 to strontium 86 of the oceans at the time that the shells form sedimentary rocks composed of accumulated fossil carbonate shells can be dated and correlated with the use of high precision measurements of the ratio of strontium 87 to strontium 86 with a resolution that is similar to that of other techniques used in age correlation this method may prove valuable for many geological paleontological paleooceanographic and geochemical problems

middle holocene avulsion belt deposits in the central rhine meuse delta the netherlands abstract the schoonrewoerd fluvial system in the central rhine meuse delta was active as a rhine distributary between 3900 and 3800 14c years bp based on planform patterns cross sectional facies architecture reconstructed paleodischarge and its short period of activity the schoonrewoerd fluvial system is interpreted to represent a failed avulsion the schoonrewoerd system consists of a complex of ribbon channel sand bodies encased in a lens of clayey deposits and it can be traced for more than 35 km in a downstream direction prominent features of the system are longitudinal facies architecture change with channel sand body width thickness ratio decreasing downstream from 40 to 5 and high lateral facies variability multiple anastomosing sand bodies occur in its upper and middle reaches paleodischarge reconstruction indicates that the schoonrewoerd system was only a minor distributary within the rhine meuse deltaic system specific stream power in the lower reach is estimated to have been low 0 5 to 1 8 w m2 the short period of activity of the schoonrewoerd system suggests that very high floodplain sedimentation rates were associated with the avulsion process with the formation of meters thick fine grained sedimentary successions in 100 years the facies architecture of the short lived schoonrewoerd system is interpreted to reflect the first stages of avulsion broadly analogous to the modern saskatchewan river avulsion in canada smith et al 1989 sedimentology v 36 p 1 23 having escaped from later erosion by a more mature channel belt many other systems often partly eroded with similar facies architecture exist in the west central rhine meuse delta suggesting that avulsion belt deposits are a major component of the holocene delta deposits the facies architecture model of the schoonrewoerd avulsion belt deposits presented in this paper may provide clues for the interpretation of fine grained sedimentary successions in ancient fluviodeltaic deposits

can hydraulic fracture induced microearthquakes show where the fluid went abstract mapping microearthquakes induced by hydraulic fracturing can delineate fracture systems produced by the stimulation and can provide spatial resolution as fine as 10 to 20 m microseismicity provides the only detailed 3 d data about the fracture system away from boreholes yet since the microseismicity results from slip on joints or fractures it may not provide a reliable view of the conductive fractures or joints a more direct approach to identifying fluid pathways is needed the presence of fluids within the rock reduces the seismic wave velocities particularly for shear waves and can provide a direct seismic indication of major fluid paths although seismic tomographic techniques can determine the velocity structure of rock masses only relatively coarse spatial resolution of perhaps 100 200 m has been achieved because of the limited number of observation sites this resolution is not adequate for modeling fracture systems finer spatial resolution may be achieved by imaging of seismic scatterers using their signatures in the waveforms of the microearthquakes this approach exploits secondary arrivals contained within the seismic coda of the microearthquakes these secondary arrivals are presumed to arise because of scattering of seismic waves by some of the major individual fluid paths within the fracture system imaging of the strong scattering features may allow identification of the major fluid paths

a method to allow temporal variation of velocity in travel time tomography using microearthquakes induced during hydraulic fracturing abstract hydraulic injections produce fluid filled fractures that reduce the seismic velocity of the rock compared to intact rock the travel times of microearthquakes induced by the injections may be used to discern changes in the rock velocities as well as locating the microearthquakes determining the volumes of rock where the velocities have changed provides indirect evidence for the location of the injected fluid and the character of the changes produced in the fractured rock available data are generally insufficient to resolve both the spatial and temporal changes within the rock to extract information about temporal changes and to obtain an improved image of the velocity structure we chose a parameterization scheme in which the velocities of each block are allowed to change from the background velocity only after a threshold number of microearthquakes have occurred in the block regularizing by constraining the velocity of all the altered blocks to be similar helps stabilize the inversion the regularization can be relaxed somewhat to allow the velocity of an altered block to be different from other altered blocks if the travel time data are compelling the parameterization scheme is justified since observations show that the volume of the seismically stimulated rock increases linearly with the volume of the injected fluid we applied the method to data collected in a region of precambrian crystalline rock that was injected with 21 600 m 3 of water we use travel times from a total of 3886 microearthquakes that were induced by the injection the mean rms travel time residual decreases about 7 the velocity structure contains a low velocity zone located near the injection region other distinct low velocity zones are identified the pattern of microearthquake locations found using our method appears to contain more structure than the pattern found in locations determined using a homogeneous velocity structure two clear low velocity regions found near the point where water was injected into the rock are separated by a region whose velocity did not change the region of unaltered velocity had a large number of microearthquakes

p wave attenuation anisotropy in fractured media a seismic physical modelling study we used a laboratory scale model to study the effects aligned fractures might have on seismic wave propagation at a larger scale in real earth imaging our main objective was to investigate the effect of aligned fractures on seismic p wave amplitude through the estimation of the induced attenuation the physical model was constructed from a mixture of epoxy resin and silicon rubber with inclusions designed to simulate two sets of inclined fractures at an angle of 29 2 with each other two dimensional reflection data were acquired using the pulse and transmission method in three principal directions relative to the fracture strike azimuth with the model submerged in a water tank we used the quality versus offset qvo method an extension of the classical spectral ratio method for determining attenuation to estimate the induced attenuation inverse of the seismic quality factor from the common mid point cmp pre processed gathers the results of our analysis show that the induced p wave attenuation is anisotropic with elliptical cos2 variations with respect to the survey azimuth angle the minor axis of the q ellipse corresponds to the fracture normal in this direction i e across the material grain the attenuation is a maximum the major axis corresponds to the fracture strike direction parallel to the material grain where minimum attenuation occurs these attenuation results show consistency with the azimuthal anisotropy observed in the stacking velocities in the fractured layer and are all consistent with the physical model and thus provide a physical basis for using attenuation anisotropy to derive fracture properties from seismic data

a new soil mechanics approach to quantify and predict land subsidence by peat compression land subsidence threatens many coastal areas quantifying current and predicting future subsidence are essential to sustain the viability of these areas with respect to rising sea levels despite its scale and severity methods to quantify subsidence are scarce in peat rich subsidence hot spots subsidence is often caused by peat compression we introduce the standard cone penetration test cpt as a technique to quantify subsidence due to compression of peat in a test in the holland coastal plain the netherlands we found a strong relationship between thickness reduction of peat and cone resistance due to an increase in peat stiffness after compression we use these results to quantify subsidence of peat in subsiding areas of sacramento san joaquin delta and kalimantan and found values corresponding with previously made observations these results open the door for cpt as a new method to document past and predict future subsidence due to peat compression over large areas 2016 american geophysical union all rights reserved

trace element and isotopic aspects of predator prey relationships in terrestrial foodwebs abstract strontium calcium ratio sr ca and stable carbon isotope ratio 13c 12c analyses of bone and enamel apatites may be used for reconstructing predator prey relationships in vertebrate fossil assemblages the approach is based on the rationale that 13c 12c in predator apatite closely resemble those of their prey while sr ca is predictably reduced in specific predator prey pairs as an example we compare the relationship of the extant leopard panthera pardus and its preferred prey in modern foodwebs with the relationship of fossil leopards from the member 1 fossil faunal assemblage at swartkrans cave and their likely prey the results suggest that swartkrans member i leopards depended heavily on papio baboons with some lesser contribution from hyrax procavia sp the approach has considerable potential for elucidating the preferred prey of extinct predators such as sabertooth cats

detailed joint structure in a geothermal reservoir from studies of induced microearthquake clusters microearthquake clusters form distinct planar patterns within five study regions of a geothermal reservoir undergoing hydraulic fracturing at fenton hill new mexico the patterns define individual slipping joint surfaces of dimension 40 120 m containing 80 150 events each sharp straight edges truncate the clusters we interpret these as marking intersections with aseismic joints each edge orientation is consistent with an intersection between the active joint and a plane oriented parallel to one of the other clusters we identify therefore it appears that cluster shapes constrain the geometry of seismic and aseismic joints both could be important components of the fluid flow network the distribution of inferred slip plane orientations is consistent with but fails to provide sufficient constraint to differentiate conclusively between two very different stress field estimates one measured using pressurization and wellbore breakouts the other using focal mechanisms of the largest microearthquakes an impermeable joint model requiring pore pressure in excess of the normal stress on a joint before slip can occur was inconsistent with many of the inferred slip plane orientations the high quality locations were possible because events from the same cluster generated nearly similar waveforms permitting the precise determination of relative arrival times standard deviations of arrival time residuals fall between 0 1 and 1 1 ms for these clusters major axes and aspect ratios of the 90 confidence ellipsoids range from 6 to 28 m and 1 5 to 8 respectively small events dominate the seismic energy release and thoroughly populate the identified active joints allowing the hypocenters to reflect details of the joint structure to further investigate the reservoir structure we applied a source array slant stack technique to waveforms from the well located clusters yielding directions that scattered energy left each cluster by studying paths of scattered waves we expected to pinpoint impedance contrasts that might have indicated concentrations of fluid filled joints however results show that scattered energy in the s wave coda left the source region in the same direction as the direct s wave direct waves may have excited borehole tube waves that became trapped in the vicinity of the geophone tool overwhelming any energy scattered from the reservoir

mississippi delta subsidence primarily caused by compaction of holocene strata coastal subsidence causes sea level rise shoreline erosion and wetland loss which poses a threat to coastal populations this is especially evident in the mississippi delta in the southern united states which was devastated by hurricane katrina in 2005 the loss of protective wetlands is considered a critical factor in the extensive flood damage the causes of subsidence in coastal louisiana attributed to factors as diverse as shallow compaction and deep crustal processes remain controversial current estimates of subsidence rates vary by several orders of magnitude here we use a series of radiocarbon dated sediment cores from the mississippi delta to analyse late holocene deposits and assess compaction rates we find that millennial scale compaction rates primarily associated with peat can reach 5mm per year values that exceed recent model predictions locally and on timescales of decades to centuries rates are likely to be 10 mm or more per year we conclude that compaction of holocene strata contributes significantly to the exceptionally high rates of relative sea level rise and coastal wetland loss in the mississippi delta and is likely to cause subsidence in other organic rich and often densely populated coastal plains

roman and early medieval habitation patterns in a delta landscape the link between settlement elevation and landscape dynamics settlement locations in delta landscapes change through time because of cultural and natural dynamics we assessed the impact of natural landscape dynamics on settlement location shifts for the rhine meuse delta in the netherlands during the roman and early medieval periods 12 bce 450 ce and 450 1050 ce respectively during this time interval major landscape and cultural changes occurred in this area with river avulsions and changes in flooding frequency coinciding with changing settlement patterns in the delta plain the relatively high and dry alluvial ridges of abandoned or active rivers were most favourable for habitation settlement location and elevation patterns were reconstructed in these landscape units using a high resolution elevation map of the alluvial ridges by integrating high resolution palaeo environmental and archaeological datasets for this period we were able to spatially analyse the trends and to assess the effect of environmental changes on habitation results show that settlements progressively shifted towards higher areas between 250 and 750 ce on average by 20 cm over this period deltawide which was coeval with an increased frequency of severe rhine floods the observed spatial differences demonstrate that this trend is most notable in the least elevated segments of the study area in areas where new large river branches developed settlements show a strong shift towards higher elevated parts of the landscape or even became completely abandoned the river probably caused floods to be more frequent and more severe in these areas despite the clear link between changing settlement positions and floods during the studied time interval floods do not seem to have caused long term abandonment of major parts of the study area

seismic monitoring of the growth of a hydraulic fracture zone at fenton hill new mexico the hydraulic fracturing technique is an important method for enhancing hydrocarbon recovery geothermal energy extraction and solid waste disposal determination of the geometry and growth process of a hydraulic fracture zone is important for monitoring and assessing subsurface fractures a relative source location approach based on a waveform correlation and a grid search method has been developed to estimate relative hypocenter locations for a cluster of 157 microearthquakes induced by hydraulic fracturing at the los alamos hot dry rock hdr geothermal site among the 157 events 147 microearthquakes occurred in a tight cluster with a dimension of 40 m roughly defining a vertical hydraulic fracture zone with an orientation of n40 w the length height and width of the hydraulic fracture zone are estimated to be 40 35 and 5 m respectively analysis of the spatial temporal pattern of the induced microearthquakes reveals that the fracture zone grew significantly averaging 0 2 m minute in a two h

high resolution microseismic imaging abstract we examine the feasibility of high resolution microseismic imaging of unconventional reservoirs given frequencies in typical downhole microseismic data that are almost an order of magnitude higher than in seismic reflection data a comparable increase in image resolution might be expected bringing potential resolution of downhole microseismic images to a few meters we demonstrate that such a resolution is indeed achievable and present two case studies illustrating the reservoir features that can be imaged our first example constructed with p waves recorded in the woodford field reveals internal fabric of the woodford reservoir and formations surrounding it allowing us to discriminate the stimulated and unstimulated zones of the lower woodford shale encouraged by those results in our second example this time from the bakken field we use the slow shear waves which are more sensitive to fluids than p waves to find out whether hydraulic fractures themselves could be imaged our seismic v

three dimensional p and s wave velocity structures beneath taiwan deep structure beneath an arc continent collision the island of taiwan is a byproduct of one of the few active collisions between a continent represented by the eurasian continental shelf and an island arc represented by the northern extension of the luzon arc on the philippine sea plate to understand better the evolution and current tectonics of this collision we selected 1260 well recorded earthquakes from an initial set of 50 000 located by the taiwan telemetered seismograph network for the determination of one and three dimensional p and s wave velocity structures beneath the island the results for both structures and earthquake relocations reveal that the island is divided tectonically into three distinct zones in the east the philippine oceanic plate is underthrusting the eurasian plate east of a north south boundary that is well defined by both seismic activity and a region of high velocity in the south the eurasian continental plate is underthrusting the philippine sea plate south of an east west boundary at about 23 n that is sharply defined by both subcrustal seismicity and a zone of relatively low velocities the dip of the subducted continent is shallow until it reaches the luzon island arc 50 km east of the main island structure under the main part of the island north of 230n reveals a shallow dipping zone of low velocities in the west above 25 km depth that narrows and steepens below that depth to at least 50 km beneath the central range the dip of this low velocity region is outlined by a narrow zone of seismicity that extends to depths of 100 km this seismic zone lies in a velocity saddle and marks an apparent offset in the central low velocity region at 24 n evidence for the subduction of the eurasian continent beneath taiwan therefore exists everywhere beneath the island and the low velocity regions in the mantle support but do not require the subduction of some 6 16 km of lower continental crust to depths of at least 50 km the distinct change in both the velocity structure and the seismic activity at 23 n and the offset of the low velocity regions at 24 n argue for abrupt changes in the nature of subduction across these latitudes these changes may be caused by an interaction of the luzon island arc with the subducted continental shelf that mimics a similar interaction evident at the surface finally the velocity structure of the subducting philippine sea plate suggests that the earthquakes beneath 70 km depth are not occurring within the highest velocity regions of the plate but are probably located near the upper edge of the plate there is also evidence from earthquake locations and velocity structure that suggests that the subducting plate is segmented and that subduction is presently occurring as far south as 22 n

seismological studies of a fluid injection in sedimentary rocks east texas induced microseismicity data from a large volume fluid injection into sedimentary rock was analyzed to study the fracture system fluid pathways and state of stress in the lower frio formation in east texas seismicity data are from two arrays of 25 3 component geophone packages sited in two monitoring boreholes from a total of 2 894 event triggers a subset of 54 microearthquakes was chosen for their high quality seismograms and clear p and s arrivals arrival times were picked with a precision of 0 5 to 1 0 ms and microearthquakes were located with hypocentral uncertainties estimated as less than 10 20 m hypocenters farthest from the injection well define a nearly horizontal tube of seismicity approximately aligned in the direction of the injection well a simultaneous inversion of arrival times for transverse isotropic velocity structure and hypocenters yielded p wave anisotropy of 14 and s wave anisotropy of 2 thus velocities along vertical ray paths are higher than those along horizontal paths probably because of lithologic differences single event focal mechanisms were determined for 47 events and many of them are normal fault type the minimum principal stress derived from the focal mechanisms is nearly horizontal and trends approximately north south consistent with the regional stress state an imaging analysis of the seismograms shows the presence of strong seismic scatterers at positions that correlate with boundaries seen in the hypocenters both features probably result from a similar set of heterogeneities this study demonstrates the abundance of information that can be extracted from induced seismicity data and underscores the value of induced seismicity monitoring for studying the fluid and fracture systems created by fluid injections

fracture mapping in the soultz sous forets geothermal field using microearthquake locations 1 in 2003 a massive hydraulic fracturing experiment was carried out at the european geothermal hot dry rock site at soultz sous forets france the 2 week injection of water generated a high level of microseismic activity triggering about 90 000 microearthquakes during and after the fluid injection of these 21 000 events detected at all stations were located individually with a grid search algorithm to characterize the extent of the seismic zones and ultimately of the fracture network the accuracy of these initial locations was around 70 m not sufficient to map detailed fracture patterns a precise relocation effort was undertaken to reduce the location uncertainties using three different techniques joint hypocenter determination jhd collapsing and multiplet analysis the collapsing method was added to the jhd results to further consolidate the hypocenters on the other hand a multiplet analysis was performed on the initial data set for identifying microearthquakes with similar waveforms and hence relocating relatively the correlated events the delays in traveltime were computed by wavelet analysis and the events were relocated using a grid search algorithm we found 7463 events whose seismograms correlated with a correlation coefficient of 0 8 or higher most of which were doublets multiplets are horizontal tube like structures with lengths from a hundred to several hundred meters striking along the direction of the maximum compressive horizontal stress we interpret these structures as the preferential paths where fluid flow is largely confined this hypothesis is reinforced by the good correlation in depth between the events and the fluid outflows observed in the well therefore we believe that these relocated events highlight the zones where the permeability of the reservoir is increased

as a dietary indicator in modern and archaeological bone strontium isotope ratios 87sr86sr in human and animal bone are inherited via foodstuffs from rocks in the areas in which an individual lived if such an area includes more than one rock type with differing 87sr86sr or is coastal region with terrestrial 87sr86sr different from that of the sea then bone strontium isotope ratio measurements provide a measure of the relative importance of foods from each isotopic zone in the southwestern cape of south africa marine and coastal terrestrial areas covered by marine sands should yield foods with 87sr86sr close to the marine average while the cambrian and pre cambrian shales and sandstones of the hinterland ought to be enriched in 87sr from radioactive decay of 87rb during the considerable time elapsed since they were laid down analyses of modern animal bones show that these patterns do prevail furnishing us with a new means of reconstructing prehistoric diets preliminary measurements on archaeological human material recovered from coastal shell midden sites apparently reflect heavy reliance on coastal foods however these bones have been shown to be contaminated with diagenetic marine strontium from the shells in the middens experiments on faunal specimens show that diagenetic strontium can be removed by repeated washing in acetic acid sodium acetate buffer mineral with 87sr86sr similar to the burial environment dissolves first while subsequent washes remove strontium with different 87sr86sr for two coastal human skeletons however the marine coastal terrestrial nature of the isotopic signature remains further experimental work is required in order to establish the limits of the technique however a combination of the solubility profile method and strontium isotope analysis promises to provide a powerful tool for reconstructing palaeodiets

sr isotopic composition of hydroxyapatite from recent and fossil salmon the record of lifetime migration and diagenesis by comparing the sr isotopic composition of migratory fossil salmon which lived in the ocean but died in continental regions to the well established marine sr isotopic record the age of the continental deposit could be determined with high accuracy this approach to marine continental correlation and dating requires 1 that marine resident salmon bear a marine s7sr 86sr value in their bones or teeth and 2 that the original s7sr 86sr value of fossils is not overprinted by diagenesis the vertebrae of modern hatchery reared salmon exhibit sr isotopic variations indicative of freshwater to marine migration during bone growth modern marine s7sr s6sr values were preserved in growth layers formed later in life marine phase growth layers in the bones and teeth of the late miocene migratory salmon oncorhynchus rastrosus were subjected to stepwise selective leaching to separate biogenic hydroxyapatite from diagenetic calcium carbonate and recrystallized hydroxyapatite although the procedure yielded leachates with sr ca and ca p values characteristic of apatite the leachates had 87sr s6sr values consistently less radiogenic than values for late miocene seawater 0 7087 the fossils were substantially contaminated by sr from the hosting clastic sediments specimens in continental deposits differed in 87sr 86sr value from host sediments by 0 0002 to 0 0200 supporting the conclusion that these salmon were migrants from marine waters however because the original sr isotopic composition of fossil bones and teeth cannot be determined with confidence archaeological paleobiological and stratigraphic applications of this technique may be limited

simultaneous inversion for q and source parameters of microearthquakes accompanying hydraulic fracturing in granitic rock an inversion that fits spectra of earthquake waveforms and gives robust estimates of corner frequency and low frequency spectral amplitude has been used to determine source parameters of 223 microearthquakes induced by hydraulic fracturing in granodiorite assuming a 2 source model the inversion fits the p wave spectra of microearthquake waveforms to determine individual values of corner frequency and low frequency spectral amplitude for each event and one average frequency independent q for all source receiver paths we also implemented a constraint that stress drops of all microearthquakes be similar but not equal and found that this constraint did not significantly degrade the quality of the fits to the spectra the waveforms analyzed were recorded by a borehole seismometer the p wave q was found to be 1070 for q values as low as 600 and as high as 3000 the misfit between model and spectra increased by less than 5 per cent and the average corner frequency changed by less than 15 per cent from those obtained with a q of 1070 average stress drop was 3 7 bars seismic moments obtained from spectra ranged from 1013 to 1018 dyne cm the low stress drops are interpreted to result from underestimation of the actual stress drops because of a nonuniform distribution of stress drop and slip along the fault planes spatially varying stress drops and slips result from the strong rock heterogeneity due to the injection of fluid into the rock stress drops were found to be larger near the edges of the seismic zone in regions that had not been seismically active during previous injections the seismic moments determined from spectra were used to obtain a coda length to moment relation then moments were estimated for 1149 events from measurements of coda lengths from events whose moments could not be measured from spectra because of saturation or a low signal to noise ratio the constant of proportionality between cumulative number of events and seismic moment is higher than that found for tectonic regions the slope is so high that the seismic energy release is dominated by the large number of small events in the absence of information about the number of events smaller than we studied we cannot estimate the total seismic energy released by the hydraulic injection

strontium isotopes in biogenic phosphates from a neogene marine formation implications for palaeoseawater studies abstract neogene marine deposits of nw france faluns are rich in a variable array of well preserved phosphatic vertebrate fragments many of these are of the same age as the host sediments and consist of the remains of fish mammals and reptiles whilst others are clearly mesozoic turonian in age we have determined the sr isotopic composition of 24 phosphatic samples in order to study the efficacy of using the method to date the neogene materials and to investigate the effects of diagenesis and seawater alteration on the terrestrial material the sr isotope results obtained on the ichthyoliths and the other neogene marine vertebrates suggest an age of 11 ma for the base of the host sediments tortonian which corresponds precisely with the palaeontological data in contrast the initial isotopic composition of the contemporaneous terrestrial mammals and reptiles which should record higher continental sr ratios are close to the value of their marine counterparts the same trend is observed for a sample of shark s tooth of mesozoic age where the sr isotopic composition approaches a neogene value the results demonstrate that alteration by seawater or interstitial waters is able to introduce significant quantities of sr into the phosphate leaching experiments carried out on the materials does not remove this secondary strontium and we were unable to establish the original values of the terrestrial material our conclusion is that the use of sr isotopes to characterise phosphatic materials must be viewed with caution particularly if the materials are reworked

reservoir characterization using oil production induced microseismicity clinton county kentucky abstract microseismic monitoring tests were conducted from 1993 to 1995 in the seventy six oil field clinton county kentucky oil is produced from low porosity fractured carbonate rocks at 3 no injection operations were conducted gross changes in production rate correlate with event rate event rate lags changes in production rate by 2 to 3 weeks hypocenters and first motion data have revealed previously undetected low angle thrust faults above and below the currently drained depth intervals production history well logs and drill tests indicate that the seismically active faults or fractures are previously drained intervals that have subsequently recovered to hydrostatic pressure via brine invasion storage capacity computed for one of these drained fractures implies that total oil production represents about 20 of total pore volume correlation of older production intervals and well log porosity anomalies with the seismically active faults indicate that the oil reservoir in the study area is primarily a set of compartmentalized low angle thrust faults although low angle fracture sets have not previously been considered in the exploration and development of the area the mapped thrust faults are consistent with other investigators interpretations of oil associated with secondary fracture sets occurring along deeper seated wrench fault structures stress determined from composite focal mechanisms indicates a near surface

seismic imaging using microearthquakes induced by hydraulic fracturing abstractseismic imaging using microearthquakes induced by hydraulic fracturing produces a three dimensional 3 d s wave velocity model of the fractured zone improves the calculated locations of the microearthquakes and may lead to better estimates of fractureplane orientations fracture density and water flow paths such information is important for predicting the amount of heat energy that may be extracted from geothermal reservoir a fractured zone was created at the los alamos hot dry rock reservoir in north central new mexico within otherwise impermeable basement rock by injecting 21000 m3 of water into a borehole under high pressure at a depth of 3 5 km induced microearthquakes were observed using four borehole seismometers the p wave and s wave arrival times have been inverted to find the 3 d velocity structures and the microearthquake locations and origin times the inversion was implemented using the separation of parameters technique and constraints were incorporated to require smooth vel

spatial orientation and distribution of reservoir fractures from scattered seismic energy wepresentthedetailsofanewmethodfordeterminingthereflection and scattering characteristics of seismic energy from subsurface fractured formations the method is based upon observations we have made from 3d finite difference modeling of the reflected and scattered seismic energy over discrete systems of vertical fractures regularly spaced discrete vertical fracture corridors impart a coda signature which is a ringing tail of scatteredenergy toanyseismicwaveswhicharetransmittedthrough or reflected off of them this signature varies in amplitude and coherence as a function of several parameters including 1 the difference in angle between the orientation of the fractures and the acquisition direction 2 the fracture spacing 3 the wavelength of the illuminating seismic energy and 4 the compliance or stiffness of the fractures this coda energy is most coherent when the acquisition direction is parallel to the strike of thefractures ithasthelargestamplitudewhentheseismicwavelengths are tuned to the fracture spacing and when the fractures have low stiffness our method uses surface seismic reflection tracestoderiveatransferfunctionthatquantifiesthechangeinan apparent source wavelet before and after propagating through a fracturedinterval thetransferfunctionforanintervalwithnoor low amounts of scattering will be more spikelike and temporally compact the transfer function for an interval with high scattering will ring and be less temporally compact when a 3d survey is acquired with a full range of azimuths the variation in the derived transfer functions allows us to identify subsurface areas with high fracturing and to determine the strike of those fractures wecalibratedthemethodwithmodeldataandthenapplied ittotheemiliofieldwithafracturedreservoir themethodyielded results which agree with known field measurements and previously published fracture orientations derived from ps anisotropy

the role of long term human impact on avulsion and fan development this study aims to understand mainly qualitatively the long term role of human impact on avulsion processes and the development of fluvial mega fans in semi arid environments in this paper we refer to human impact as the direct influences of actions on the river s hydraulics i e flow regulation flow diversion and channel engineering in five case studies drawn from the khuzestan plains in southwest iran we have analysed the setup and triggering conditions of specific avulsions that occurred in the past timescale of millennia and identified the role of human interference in their causation our analysis is based on the integration of historical archaeological geomorphological and geological data through this study we demonstrate that avulsions in the khuzestan plains are the result of long term and complex interplay between multiple human induced and natural causes in similar ways human induced actions may play important roles during different phases of avulsion development the success of an avulsion in the post triggering phase may be defined by human induced setup causes as well as morphodynamic processes we suggest that present day flood events may be partly inherited from long term human alterations of the natural processes these finding could have implications for any fluvial system e g distributive fluvial systems deltas where avulsion plays a major role in their development and research tends to emphasize on natural mechanisms copyright 2016 john wiley sons ltd

mobility of bell beaker people revealed by strontium isotope ratios of tooth and bone a study of southern bavarian skeletal remains in order to contribute to the continuing discussion of the mobility of the late neolithic bell beaker people 69 skeletons from southern bavaria were analyzed for the 87sr 86sr isotope ratios in tooth enamel and compact bone whereas sr isotope ratios in the enamel of the first permanent molar match the sr isotopic composition at the place of early childhood the respective value in the adult femoral bone matches the sr isotope ratio characteristic of the place of residence over the last few years prior to death significant differences between 87sr 86sr in these tissues indicate that 17 5 25 of these individuals changed residence during their lifetime the overall direction of the migration according to archaeological finds from the area was toward the southwest a relative surplus of migrating females and two cases of evidence for migration in children argue for the movement of small groups exogamy might explain the higher numbers of immigrating females with regard to current information on migration rates in prehistory the southern bavarian bell beaker people were indeed highly mobile especially since the archaeometric method used in this study is likely to underestimate movement

petroleum reservoir characterization using downhole microseismic monitoring imaging of microseismic data is the process by which we use information about the source locations timing and mechanisms of the induced seismic events to make inferences about the structure of a petroleum reservoir or the changes that accompany injections into or production from the reservoir a few key projects were instrumental in the development of downhole microseismic imaging most recent microseismic projects involve imaging hydraulic fracture stimulations which has grown into a widespread fracture diagnostic technology this growth in the application of the technology is attributed to the success of imaging the fracture complexity of the barnett shale in the fort worth basin texas and the commercial value of the information obtained to improvecompletions and ultimately production in the field the use of commercial imaging in the barnett is traced back to earlier investigations to prove the technology with the cotton valley imaging project and earlier experiments at the m site in the piceance

quantitative analysis of land transformation in a holocene delta an example from the tama river lowland central japan abstract human activities such as the expansion of agricultural and urban land use on subaerial deltas and landfilling of subaqueous deltas have large impacts on holocene deltas here we quantified the volume of the holocene deltaic deposits in the tama river lowland located in the tokyo metropolitan area by analyzing 3872 existing borehole sections using gis and evaluated artificial land transformation the total volume of deltaic deposits accumulated during the past 9000 years was estimated to be 3925 106 m3 of which artificially deformed near surface material ad 676 106 m3 occupies approximately 17 this ratio is much larger than that in the nobi plain 4 6 in the nagoya metropolitan area suggesting that the impact of anthropogenic disturbance on the delta has been greater in tokyo than in the nagoya metropolitan area approximately 71 of ad is distributed in the seaward area where landfills were created mainly after the taisho period 1912 1926 the source of the ad is considered to be dredged soil construction waste soil and mountain sand the remaining 29 of ad occurred in the landward area floodplain and delta plain and likely originates from the in situ disturbed sediments of the delta plain and floodplain in addition to earth fill the seaward ad deposits including redeposition by dredging within the delta accumulated at a rate of 4 79 106 m3 year which is much higher than that of the accumulation of natural deltaic deposits during the holocene 0 36 106 m3 year this clearly shows that anthropogenic forcing has become a strong influence on geomorphological and sedimentological processes within the delta

velocity calibration for microseismic monitoring a very fast simulated annealing vfsa approach for joint objective optimization to accurately locate microearthquakes that are genetically related to hydraulic fracture stimulation a thorough knowledge of the velocity structure between monitoring and fracturing treatment wells is essential very fast simulated annealing vfsa is implemented to invert for a flat layered velocity model between wells using perforation or string shot data a two point ray tracing method is used to find the ray parameter p for a ray traveling from a source to a receiver the original traveltime calculation formula is modified to account for the borehole source receiver geometry vfsa is used as a tool to optimize p and s wave velocities simultaneously unlike previous applications of vfsa two improvements result from a new study 1 both p and s wave arrival time misfits are considered in a joint objective function and 2 p and s wave velocities are perturbed simultaneously during annealing the inverted velocities follow the true values closely with a very small root mean square error indicating the inverted model is close to the global minimum solution whose rms error should be zero for synthetic examples data noise contaminates inverted models but not substantially in synthetic test results a comparison of models inverted using vfsa and occam s inversion technique indicates that inverted models using vfsa are superior to those using occam s method in terms of velocity accuracy

sr and sr ca in marine and terrestrial foodwebs in the southwestern cape south africa abstract strontium and calcium have been measured in a range of plants and animals both marine and terrestrial from the southwestern cape of south africa as part of an investigation of modern and prehistoric foodwebs in the region first the meat of marine molluscs and crustaceans are shown to have sr and sr ca values comparable to those of terrestrial plants thus the consumption of these marine foods in this region cannot produce the markedly elevated sr levels seen in archaeological human skeletons from coastal sites such levels are shown to be a diagenetic phenomenon second reduction in sr ca in higher trophic levels is seen only when predators are compared with their prey however individual herbivore or carnivore species cannot be taken to represent other animals in their respective trophic level these data imply that sr ca is inappropriate for determining meat intake in complex prehistoric human diets in this region the technique may be more useful in examining specific prey predator relationships including those in the early hominid fossil record

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

velocity structure of the pamir hindu kush region possible evidence of subducted crust the arrival times of compressional p and shear s waves from approximately 580 microearthquakes recorded by a temporary array in the pamir hindu kush region in central asia are used to deduce one and three dimensional velocity structures of this region the results for one dimensional structures imply that the moho is at 70 5 depth also there is a velocity reversal near 160 km depth which is inferred to be the beginning of the low velocity zone this reversal continues to depths of approximately 230 km below 230 km velocities are somewhat higher than those of normal mantle at similar depths 9 3 km s versus 8 4 km s for p waves the outstanding feature of the results for three dimensional velocity structures is a broad 40 km centrally located region with 8 to 10 lower velocities than those in the surrounding regions this low velocity region envelopes the seismic zone at depths between 70 and 150 km the region may actually extend beyond these depths but the results for shallower and deeper structure lack sufficient resolution to decide several tests using both hypothetical and real data were performed to estimate the reliability of the three dimensional solutions the results of these tests suggest that the inferred velocities are reasonably accurate representations of the average velocities in the blocks although one must be cautious of the effects of averaging in interpreting the solution the low velocity region is inferred to be a manifestation of substantial quantities of subducted continental crust therefore while subduction has occurred in the pamir hindu kush the results of the three dimensional inversions suggest that continental rather than only oceanic lithosphere has been subducted to depths of at least 150 km appendices are available with the entire article on microfiche order from american geophysical union 2000 florida avenue n w washington d c 20009 document j81 013 1 00 payment must accompany order

strontium increases and crystallinity changes in taphonomic and archaeological bone bone strontium levels and hydroxyapatite crystal sizes increased with time in two exposed wildebeest skeletons the strontium increases could not be removed by sequential washing according to the method of sillen a 1986 biogenic and diagenetic srca in plio pleistocene fossils of the omo shungura formation paleobiology12 311 323 human subfossil bone recovered archaeologically also showed evidence of extensive diagenetic reworking that resulted in crystal growth and elevated strontium levels the increase in bone strontium content was independent of nonapatitic contaminating crystal phases

locating microearthquakes induced by hydraulic fracturing in crystalline rock microearthquakes induced by hydraulic fracturing in crystalline rock at a depth of 3 5 km were located with a precision of better than 30 m to obtain information about the geometry and dimensions of the fracture system produced the induced microseismicity was monitored by a network of five vorehole seismic stations a total of about 800 induced events were reliably located from arrival times event locations show a tabular distribution that strikes 350 sup 0 and dips 65 sup 0 east subparallel to the injection well the injection was intended to produce a fracture system that would hydraulically connect two subparallel wells a lack of fluid communication between them is consistent with a lack of induced microearthquakes near the target wellbore the 150 m thickness of the zone of seismicity far exceeds the relative locational uncertainties the injected fluid appears to have stimulated a zone of rock rather than simply a single fracture the distribution of microseismic events presumably envelopes the zone of fluid paths created by the fracture experiment

evaluating the impact of acetic acid chemical pre treatment on old and cremated bone with the perio spot technique and perios endos profiles abstract the impacts of diagenesis on archaeological and palaeontological bone complicate investigations of in vivo chemical and isotopic characteristics such bone is often pre treated in an attempt to remove diagenetic alteration prior to trace element or isotopic analyses although very few standardized approaches exist for evaluating pre treatment effectiveness in this pilot study we characterize the diagenetic alteration and assess the impact of acetic acid chemical pre treatment on the trace element and structural characteristics of four bones from belgium including an early medieval cremated bone from broechem and three representative old bones of different ages ca 40 130 ka from the late pleistocene sedimentary sequence of scladina cave each bone was analyzed before and after acetic acid pre treatment using the perio spot technique and perios endos profiles we measured trace element concentrations with laser ablation inductively coupled plasma mass spectrometry la icp ms and micro x ray fluorescence spectroscopy xrf structural characteristics were investigated with raman spectroscopy and fourier transform infrared spectroscopy ftir our results indicate that chemical pre treatment had little to no significant impact on the trace element content of the early medieval cremated bone had the most impact on the youngest bone from scladina cave and had less impact on the trace element content of two older bones from scladina cave this suggests that the effectiveness of acetic acid chemical pre treatment is greater for bones undergoing early diagenetic processes has minimal impact on highly crystalline cremated bone and may preferentially leach in vivo signatures from bones undergoing later diagenesis the weights of leachates removed from each bone also correspond well with their hypothetical diagenetic states indicating that researchers could potentially assess the diagenetic state of bones by weighing the leachates produced during acetic acid pre treatment therefore our new approach may provide a valuable step toward effectively and consistently differentiating among in and ex vivo trace element signatures and by proxy those of their isotopes in archaeological and palaeontological bone

seismological studies at parkfield i simultaneous inversion for velocity structure and hypocenters using cubic b splines parameterization a model for the 3d p and s wave velocity structure at parkfield has been developed by the systematic inversion of arrival times for microearthquakes and surface vibroseis sources recorded by nearby calnet stations and by the local borehole installed 10 station high resolution seismic network there a modification of the linear b splines model parameterization method of thurber 1983 to a cubic b splines formulation through tests inverting synthetic data sets for the parkfield configuration is found to produce smooth velocity distributions that still retain some small scale features application of the method to 953 p wave and 288 s wave arrivals from 111 microearthquakes and 8 vibroseis locations throughout the study area yields a velocity structure having variable resolution a low velocity zone appears to coincide with the creeping segment of the san andreas fault zone northwest of the 1966 parkfield earthquake epicenter an increase of about 15 per cent in seismic velocities is seen from the northeast to southwest across this segment of the fault zone the higher velocities to the southwest apparently correspond to the granitic basement the contrast across the fault is subdued to the southeast along the 1966 rupture zone a high vp vs ratio of 1 9 is seen in a 2 km wide volume near the location of the 1966 main shock hypocenter presumably the nucleation zone for the expected m 6 parkfield earthquake