geology and tectonics of the betic zone se spain abstract the southern margin of the iberian continent comprises a complex geological history which can be traced back into the proterozoic when a gneissic basement was formed a cover of nevado filabride rocks was deposited onto this proterozoic basement during the palaeozoic the permian intrusion of the bedar granite suggests that the palaeozoic sedimentary rocks now exposed in the betic cordilleras have been affected by the hercynian orogeny similar to that of palaeozoic rocks in the adjoining ossa morena zone the hercynian basement was probably covered by alpujarride carbonates in the mesozoic when rifting opened tethys and intruded 140 ma old basic dyke swarms the palaeozoic basement of the betic cordilleras comprises a suture of late cretaceous subduction 80 85 ma b p this can be inferred from hp lt metamorphic facies obducted in coeval thrust slices of nevado filabride rocks the nevado filabride nappes include mesozoic carbonates transformed into marbles macael the suture was probably annnealed after the closure of tethys the mesozoic boundary between africa and europe and the rifting in tethys ceased during the palaeogene when the atlas mountains were formed 36 ma b p subsequently relative movements between africa and europe in the neogene were accommodated by strike slip faults these define the iberian microplate moving eastward by atlantic spreading and possibly subducting under italy neogene deformation of iberia is most intensive in southeastern spain due to emplacement of a mantle diapir under the alboran area this occurred early in the neogene aquitanian and caused nappe spreading involving alpujarride and malaguide rocks the subsequent neogene history has now been studied in great detail and is reviewed here it involves clear examples of calc alkaline volcanism most probably not related to subduction seismic motion along strike slip faults within the iberian microplate and syntectonic deposition in intermontane neogene basins

variations of hydraulic properties of granular sandstones during water inrush effect of small particle migration the evaluation of the hydraulic properties evolution of granular sandstones in relation with groundwater inrush within faults is an important issue for mining engineering applications this paper presents the results of an experimental investigation of small particle migration from granular sandstone samples under different original porosities particle size compositions and water flow pressures a new rock testing system has been setup to carry out the tests based on the results it is observed that the overall permeability evolution during the tests can be divided into four different phases including i re arrangement of large rock fragments ii water inrush with substantial particle migration iii continued moderate particles seepage and iv steady state water flow the crushing of edges and corners of large rock fragments and the evolution of the fracture network has mainly been observed in the first two phases of the tests the results indicate that the migration of small particles has an essential effect on permeability and porosity increase during water inrush through fractured sandstone the samples with higher original porosity higher percentage of fine particles in their formation and under higher water flow pressures achieve higher permeability and porosity values when the test is complete furthermore using the measured data the performances of a number of empirical models for permeability evolution in fractured porous media have been studied the prediction results indicate that not all of the fractures in a sample domain contribute in small particle migration there are parts of the fracture network that are not effective in particle flow a sample with less original porosity more fine particles and under lower water pressure shows less ineffective fractures therefore using the concept of the effective porosity fracture is sufficient enough for the flow calculation

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

fracture roughness and gouge distribution of a granite shear band 1 localization of deformation during fracture mechanical tests leads to the development of shear bands we performed triaxial tests using sidobre granite at four different confining pressures from 20 to 80 mpa we compared two sets of tests one set was stopped immediately after the formation of the shear band a second one included additional shear deformation from the analysis of thin sections of these laboratory samples we characterize the typical microstructures in the shear band mode i and ii cracks riedel cracks cataclastic flow statistical properties of rupture surface roughness and gouge grain size reveals scaling invariance using a mechanical profiler the fracture roughness is measured along parallel profiles and shown to be correctly described over up to 3 orders of magnitude by self affine geometry with a roughness exponent close to 0 80 this property is very similar to tensile crack even if local processes are different the influence of the slip is observed fracture surfaces are rougher along the slip direction 0 74 than perpendicular to it 0 80 the confining pressure is shown to have a weak effect on the fracture roughness it smoothes the surface slight increase of the roughness exponent gouge particles extracted from the shear band present a power law distribution with an exponent ranging from 1 44 to 1 91 this exponent appears to increase with the shearing displacement and the confining pressure when a significant shear of the band is combined with a high confining pressure i e impeded dilation of the band the hallmark of fragmentation is observed for the particle distribution and related to a smoothing of the band boundary

ultrasonic velocity and anisotropy of hydrocarbon source rocks an experimental study of the physical properties of black kerogen rich shales also including maturation analysis scanning electron microscope sem observations and physical modeling revealed fairly peculiar petrophysical parameters specifically these rocks have very low porosity and density but most importantly both p and s ultrasonic velocities normal to bedding are extremely low whereas they are much higher parallel to bedding giving rise to a strong anisotropy even at high confining pressures we found that these parameters primarily reflect kerogen content microstructure and maturation level of these rocks we found also that microcracks inferred from ultrasonic velocity measurements occur only in mature shales these microcracks are parallel to the bedding plane and further enhance strong intrinsic anisotropy notably at low effective pressure our results show that on a small scale kerogen rich shales are transversely isotropic rocks and can be effectively modeled using the thin laye

numerical evaluation of land subsidence induced by groundwater pumping in shanghai to predict the future behavior of land subsidence in shanghai due to pumping of groundwater a numerical model is established in the proposed model groundwater flow in three dimensional conditions and soil deformation in one dimen sional conditions are calculated the model takes into account the multi aquifer aquitard hydrogeological condition of the soft deposit of shanghai the variation of the coefficient of compressibility and coefficient of hydraulic conductivity of the soils with the consolidation process are simulated relationships among land subsidence groundwater withdrawal volume and groundwater level are analyzed comparison between the measured value and calculated value shows that the model simulates the measured value fairly well the future of land subsidence behavior due to groundwater withdrawal is predicted and discussed via consideration of the variation of the following parameters in the future 30 years net withdrawn volume of groundwater pumping layer and pumping region resume un modele numerique est propose afin de predire le comportement futur d un affaissement de sol cause par le pompage de l eau souterraine a shanghai dans le modele propose l ecoulement de l eau souterraine en trois dimensions et la deformation du sol en une dimension sont calcules le modele considere la condition hydrogeologique multi aquifere aquitard du depot mou de shanghai les variations du coefficient de compressibilite et du coefficient de conductivite hy draulique des sols lors du processus de consolidation sont simulees les relations entre l affaissement du sol le volume de retrait de l eau souterraine et le niveau phreatique sont analysees des comparaisons entre les valeurs mesurees et calculees montrent que le modele peut simuler les valeurs mesurees relativement bien le comportement futur du sol en affaissement cause par le retrait de l eau souterraine est predit et discute en considerant les variations pour les prochains 30 ans pour les parametres suivants le volume net d eau souterraine retire la couche de pompage et la region de pompage mots cles pompage de l eau souterraine affaissement du sol ecoulement de l eau souterraine en trois dimensions consoli dation en une dimension prediction traduit par la redaction

shear fracture pattern and microstructural evolution in transpressional fault zones from field and laboratory studies abstract zones of transpressional shear deformation accommodate strike slip and oblique slip displacements field work in a transpressive shear zone and transpressional analogue clay box modelling show that a p oriented foliation and associated p shears are preferentially developed over the more common r 1 riedel shears the carboneras fault system cfs in se spain is a left lateral transpressional shear zone with an internal geometry characterized by first order y oriented faults and widespread p oriented second order faults the mesoscopic to microscopic gouge fabric reflects the regional architecture of the shear zone being dominated by a pervasive poriented foliation and discrete y and p shears friction experiments carried out to investigate the textural evolution of gouge fabrics showed four textural stages of fabric development from foliation formation to extreme shear localization resulting in cross gouge failure transpression clay box models favoured the formation of secondary p oriented shear fractures and p oriented shear lenses further deformation caused differential shear lens rotation and shear lens orientations closer to the mean displacement direction our field studies and laboratory analogue experiments indicate that shear zones dominated by p shears are diagnostic of a transpressional deformation regime

field experiments and numerical simulations of confined aquifer response to multi cycle recharge recovery process through a well summary shanghai is one of the cities suffering from land subsidence in china land subsidence has caused serious financial losses thus artificial recharge measures have been adopted to compensate the drawdown in shallow confined aquifers and thereby control land subsidence in this study a multi cycle recharge recovery field experiment was performed to investigate the response of a shallow confined aquifer to artificial recharge through a well in the experiment a series of recharge recovery cycles with different recharge volumes and durations with and without artificial pressure were performed the water levels monitored in the recharge and observation wells indicated the response of the aquifer to the multi cycle recharge recovery process meanwhile a finite difference method fdm numerical model was established and its parameters were obtained via a reversed numerical analysis on the experimental data the responses of the shallow confined aquifer to the multi cycle recharge recovery process were simulated in detail using the model the calculation results showed that the water level dropped significantly when the recharge ended moreover the efficiency of a multi cycle recharge was found to be higher than that of a concentrated one under the same recharge volume and time the relationship between recharge frequency and efficiency expressed as h 0 29498 f 0 40163 and r 2 0 97264 respectively was obtained through the fdm numerical simulation in the recharge intervals the optimal recharge efficiency was achieved when the water level rose to 40 of the peak

extension along the australian pacific transpressional transform plate boundary near macquarie island the australian pacific transform plate boundary fault zone along the macquarie and mcdougall segments of the macquarie ridge complex mrc south of new zealand is characterized by dominantly normal faults and pull apart basins in apparent conflict with the regional transpressional tectonic setting we propose that present day curvature of the transform is inherited from a preexisting divergent plate boundary and that the overall extensional kinematics shown by faults along the main plate boundary trace and exposed on macquarie island result from local stresses related to right lateral right stepping en echelon plate boundary faults and not to the current transpressional setting transpression along the australian pacific transform plate boundary has resulted in uplift along the 1500 km long macquarie ridge complex macquarie island the only subaerial exposure of the complex sits atop a 5 km high 50 km wide submarine ridge of oceanic crust and lies 4 5 km east of the major active plate boundary fault zone thus macquarie island and the surrounding seafloor provide a unique opportunity to study an active oceanic transform fault using complementary marine geophysical and land based geological data mapping of recent faults affecting the topography of macquarie island shows that the island is extensively cut by high angle normal faults forming pull apart basins furthermore evidence for reverse motion is rare using marine geophysical data including swath bathymetry reflectivity and seismic reflection data collected along the australian pacific plate boundary north and south of the island we have defined a 5 15 km wide plate boundary zone a series of right stepping en echelon faults within this zone lies along the main plate boundary trace at the right stepping fault terminations elongate depressions 10 km wide and 1 2 km deep parallel the plate boundary which we interpret as extensional relay zones or pull apart basins we propose that transpression is partitioned into en echelon strike slip faults at the plate boundary and a convergent component that flexes the crust causing the anomalous bathymetric ridge and trough morphology of the mcdougall and macquarie segments of the mrc

the peak frequency of direct waves for microseismic events abstractdirect seismic waves p or s waves are used to locate and further characterize microseismic events the resolution of information obtained from direct waves depends on the peak frequencies of the waveforms the peak frequency results from combination of the source propagation and the receiver effects for frequencies below the corner frequency propagation effects control the peak frequency in observed seismograms of microseismic events the frequency dependence of direct body waves can be modeled by attenuation specifically the global attenuation factor this model is consistent with observed data along surface profiles explaining the difference between the peak frequencies of p and s waves in addition the model is consistent with the peak frequencies observed on downhole monitoring arrays this can be used to invert effective attenuation providing additional unique measurement from microseismic events the corner frequency can be estimated from the average stress drop and analytical sour

landslides associated with spheroidally weathered mantle of granite porphyry induced by 2011 typhoon talas in the kii peninsula japan abstract typhoon talas brought heavy rain to the kii peninsula japan during 2 5 september 2011 causing hundreds of debris avalanches and debris flows in the southeastern part of the peninsula we undertook field investigations to understand the geological and geomorphological context of the landslides and found that the most important geological factor is spheroidal weathering of granite porphyry this granite porphyry is deeply weathered with corestones in higher elevations and forms low relief surfaces of which marginal areas were the major sources of debris avalanches corestones that failed were embedded in grus in situ or on nearby slopes of mudstone in which the granite porphyry intruded the corestones are made by spheroidal weathering from well developed columnar joints and sheeting joints sheeting joints in the source granite porphyry acted as sliding surfaces both before and during the occurrence of the 2011 debris avalanches

environmental assessment of the arsenic rich rodalquilar gold copper lead zinc mining district se spain data from soils and vegetation the rodalquilar mineral deposits se spain were formed in miocene time in relation to caldera volcanic episodes and dome emplacement phenomena two types of ore deposits are recognized 1 the el cinto epithermal au as high sulphidation vein and breccia type and 2 peripheral low sulphidation epithermal pb zn cu au veins the first metallurgical plants for gold extraction were set up in the 1920s and used amalgamation cyanide leaching began in the 1930s and the operations lasted until the mid 1960s the latter left a huge pile of 900 000 1 250 000 m3 of abandoned as rich tailings adjacent to the town of rodalquilar a frustrated initiative to reactivate the el cinto mines took place in the late 1980s and left a heap leaching pile of 120 000 m3 adverse mineralogical and structural conditions favoured metal and metalloid dispersion from the ore bodies into soils and sediments whereas mining and metallurgical operations considerably aggravated contamination we present geochemical data for soils tailings and wild plant species compared to world and local baselines both the tailings and soils of rodalquilar are highly enriched in as mean concentrations of 950 and 180 g g 1 respectively regarding plants only the concentrations of as bi and sb in asparagus horridus launaea arborescens salsola genistoides and stipa tenacissima are above the local baselines bioaccumulation factors in these species are generally lower in the tailings which may be related to an exclusion strategy for metal tolerance the statistical analysis of geochemical data from soils and plants allows recognition of two well differentiated clusters of elements as bi sb se sn te and cd cu hg pb zn which ultimately reflect the strong chemical influence of both el cinto and peripheral deposits mineral assemblages

use of s wave attenuation from perforation shots to map the growth of the stimulated reservoir volume in the marcellus gas shale abstract water filled fractures stimulated by hydraulic fracturing will severely attenuate s waves by comparing the p and s wave amplitudes generated from perforation shots in the marcellus gas shale one can infer the existence and constrain the location of stimulated hydraulic fractures the waveforms of the perforation shots in unstimulated gas shale are first analyzed to define the prestimulation radiation pattern then the change of perforation shot s wave waveform is examined for information about the development of hydraulic fractures s wave attenuation validates the existence of offstage hydraulic fractures and the invasion of treatment fluid from another neighbor stage this method might have potential use in designing an active seismic survey to more effectively monitor hydraulic fracture stimulation beyond the current microseismic mapping techniques

a structural model for the seismicity of the arudy 1980 epicentral area western pyrenees france summary the western pyrenees presents a diffuse and moderate m 5 7 instrumental seismicity it nevertheless historically suffered from strong earthquakes i ix msk the seismic sources of these events are not yet clearly identified we focus on the arudy 1980 epicentral area m 5 1 and propose here the reactivation of early cretaceous normal faults of the iberian margin as a potential source the late cretaceous inversion of this basin first in a left lateral strike slip mode and then in a more frontal convergence resulted in a pop up geometry this flower structure attests of the presence of a deep crustal discontinuity the present day geodynamic arrangement suggests that this accident is reactivated in a right lateral mode this reactivation leads to a strain partitioning between the deep discontinuity that accommodates the lateral component of the motion and shallow thrusts rooted on this discontinuity these thrusts accommodate the shortening component of the strain the distribution of the instrumental seismicity fits well the structural model of the arudy basin whatever the compressive regional context the structural behaviour of the system explains too the extensive stress tensor determined for the arudy crisis if we interpret it in terms of strain ellipsoid indeed numerical modelling has shown that this concomitant activity of strike slip and thrust faulting results in an extensive component that can rise 50 per cent of the finite strain we identify too a 25 30 km long potential seismic source for the arudy area the size of the structure and its potential reactivation in a strike slip mode suggest that a maximum earthquake magnitude of 6 5 could be expected the extrapolation of this model at the scale of the western pyrenees allows to propose other potential sources for major regional historical earthquakes

analogue modelling of inclined brittle ductile transpression testing analytical models through natural shear zones external betics abstract the combination of analytical and analogue models gives new opportunities to better understand the kinematic parameters controlling the evolution of transpression zones in this work we carried out a set of analogue models using the kinematic parameters of transpressional deformation obtained by applying a general triclinic transpression analytical model to a tabular shaped shear zone in the external betic chain torcal de antequera massif according to the results of the analytical model we used two oblique convergence angles to reproduce the main structural and kinematic features of structural domains observed within the torcal de antequera massif 15 for the outer domains and 30 for the inner domain two parallel inclined backstops one fixed and the other mobile reproduce the geometry of the shear zone walls of the natural case additionally we applied digital particle image velocimetry piv method to calculate the velocity field of the incremental deformation our results suggest that the spatial distribution of the main structures observed in the torcal de antequera massif reflects different modes of strain partitioning and strain localization between two domain types which are related to the variation in the oblique convergence angle and the presence of steep planar velocity and rheological discontinuities the shear zone walls in the natural case in the 15 model strain partitioning is simple and strain localization is high a single narrow shear zone is developed close and parallel to the fixed backstop bounded by strike slip faults and internally deformed by r and p shears in the 30 model strain partitioning is strong generating regularly spaced oblique to the backstops thrusts and strike slip faults at final stages of the 30 experiment deformation affects the entire model box our results show that the application of analytical modelling to natural transpressive zones related to upper crustal deformation facilitates to constrain the geometrical parameters of analogue models

spatiotemporal changes of seismic attenuation caused by injected co2 at the frio ii pilot site dayton tx usa a continuous active source seismic monitoring cassm dataset was collected with crosswell geometry during co2 injection at the frio ii brine pilot near liberty tx previous studies have shown that spatio temporal changes in the p wave first arrival time reveal the movement of the injected co2 plume in the storage zone to further constrain the co2 saturation particularly at higher saturation levels we investigate spatial temporal changes in the seismic attenuation of the first arrivals the attenuation changes over the injection period are estimated by the amount of the centroid frequency shift computed by local time frequency analysis we observe that 1 at receivers above the injection zone seismic attenuation does not change in a physical trend 2 at receivers in the injection zone attenuation sharply increases following injection and peaks at specific points varying with distributed receivers which is consistent with observations from time delays of first arrivals then 3 attenuation decreases over the injection time the attenuation change exhibits a bell shaped pattern during co2 injection under frio ii field reservoir conditions white s patchy saturation model can quantitatively explain both the p wave velocity and attenuation response observed we have combined the velocity and attenuation change data in a cross plot format that is useful for model data comparison and determining patch size our analysis suggests that spatial temporal attenuation change is not only an indicator of the movement and saturation of co2 plumes even at large saturations but also can quantitatively constrain co2 plume saturation when used jointly with seismic velocity

timing and kinematics of deformation in the malaguide complex internal zone of the betic cordillera southeast spain the betic cordillera of southern spain forms the westernmost of the mediterranean alpine orogenic belts and is divided traditionally into internal and external zones in the external zone fold and thrust belt unmetamorphosed cover rocks of the iberian margin were deformed from the early miocene onward in contrast internal zone rocks are dominantly metamorphic and are generally assumed to have been deformed and metamorphosed in an alpine event resulting from late cretaceous palaeogene convergence between africa and europe in the sierra espuna at the northern edge of the internal zone in the eastern betics the uniquely preserved permo triassic to miocene stratigraphy of the unmetamorphosed malaguide complex offers a rare opportunity to date the internal zone deformation kinematic data thrust geometries and structural facing of folds suggest that the imbricate thrust stack of malaguide rocks formed as a result of nnw directed motion within present geographical coordinates a fossilized front to this thrust stack preserved beneath a thick sequence of oligocene conglomerates indicates that the timing of the thrust deformation is late eocene in age deformation propagated into the foreland basin in the late oligocene with renewed thrusting subsequently the whole stack has been folded into a n nw vergent regional recumbent fold the espuna fold during the early miocene

evaluation of the blocking effect of retaining walls on groundwater seepage in aquifers with different insertion depths abstract in the design of a deep retaining wall it is necessary to consider the blocking effect on groundwater seepage of retaining walls in aquifers in this study both laboratory tests and numerical simulation with finite element method fem were adopted to investigate the blocking effect on groundwater seepage under different insertion depths of retaining wall in aquifer laboratory tests were conducted to analyze this blocking effect in an unconfined aquifer the test results indicate that the effective insertion depth ratio j of a retaining wall in shanghai aquifer sand is about 70 a three dimensional numerical model 3d fem was conducted to analyze the laboratory test results the fem results show that fem is a reliable method to analyze the blocking effect on groundwater seepage in an aquifer based on the same aforementioned procedure a 3d fem model is established to investigate the blocking effect in the confined aquifer in shanghai deposit both laboratory test and fem results show that drawdown of groundwater level decreases with an increase of the insertion depth ratio j of retaining structures in an aquifer the optimal value of j approximately 70 is achieved for retaining wall based on the synthetic results from laboratory test fem analysis and the equation of pujades et al for either unconfined aquifers or confined aquifers of shanghai

deformation mechanisms in granitic rocks at shallow crustal levels abstract microstructural observations of naturally faulted granitic gneisses show that feldspar grains are weaker than quartz grains at temperatures below 325 c and at depths of less than 8 10 km feldspar grains sustained most of the deformation by grain scale faulting slip along cleavage controlled fractures and cataclasis fracture of feldspar grains within fault zones promoted their alteration to kaolinite quartz grains also deformed by fracturing and often healed to form quartz porphyroclasts and mosaics in a comminuted matrix of feldspar and kaolinite syntectonic alteration of the feldspar grains may have weakened the fault zones over time and resulted in foliated textures within the fault zones this study of naturally deformed rocks confirms published experimental results on the behavior of granitic rocks at low temperatures and pressures and taken together these data show that the theology of the upper 10 km of the crust is greatly influenced by cataclastic processes in feldspar

sliding behavior and deformation textures of heated illite gouge abstract the run products of a series of triaxial friction experiments on an illite rich gouge have been examined petrographically to study the relationship between textural development and sliding mode the samples show a complete range of textures from ones in which the entire gouge layer is deformed to ones in which the deformation is concentrated along narrow subsidiary shears and the rest of the gouge layer is massive the samples with a pervasively developed deformation fabric slide stably whereas the samples containing shear bands show stick slip motion if the intersection angles between boundary parallel and cross cutting riedel shears are also relatively high these textural differences suggest that localization of shear combined with higher angle riedel shears are somehow involved in stick slip motion the orientation of riedel type shears in natural fault zones may also have potential as a paleoseismological tool

estimation of effective anisotropy simultaneously with locations of microseismic events passive seismic tomography in which the event locations and the velocity model are inferred simultaneously is seldom used to process microseismic surveys acquired in the oil and gas industry we discuss advantages of applying tomographic ideas to typical microseismic data recorded in a single nearly vertical well to monitor hydraulic stimulation of a shale gas reservoir microseismic events are conventionally located in the energy industry applications using a velocity model derived from sonic logs and perforation shots instead of fixing the model as is normally done we alter it while locating the events this added flexibility not only makes it possible to accurately predict traveltimes of the recorded p and s waves but also provides a convincing evidence for anisotropy of the examined shale formation while we find that velocity heterogeneity does not need to be introduced to explain the data acquired at each stage of hydraulic fracturing the obtained models are suggestive of possible time laps

a methodology for unstructured damped stress inversion of microseismic focal mechanisms application to the vaca muerta formation argentina current methodologies for stress inversion from microseismic focal mechanisms require the assignment of events to a regular grid and then solving for the stress state at each grid node this approach can lead to irregularities in the solution because some nodes may contain few or even no events to address this issue we modified the algorithm to solve for stresses on an irregular unstructured grid we first use the k means algorithm to split the data into suitably sized groups the centroids of these groups are then considered as the nodes of an unstructured grid and we simultaneously solve for the stress state in each group using damped inversion to account for the irregularity of the unstructured grid we use the reciprocal square distance between nodes as weights as opposed to the existing method in which a weight of unity is assigned between adjacent nodes on a regular grid focal planes are selected from the auxiliary plane using the fault instability criterion the method is first applied to synthetic data sets in which we simulate and subsequently invert for the stress field around a mode i fracture at depth in a strike slip and in a normal faulting stress regime results indicate a stress orientation error of 10 and a stress ratio error between 1 and 10 we then consider focal mechanism data from an unconventional shale play in the vaca muerta formation in argentina and our results suggest the presence of a preexisting strike slip faulting stress regime we also find that the unambiguous focal plane picks suggest that the apparent dip slip focal mechanisms are indeed dip slip movement along subvertical natural fractures which correlate well with image log data we suggest that these dip slip events are caused by stress changes induced by the opening of the hydraulic fractures

water saturation effects on elastic wave attenuation in porous rocks with aligned fractures summary elastic wave attenuation anisotropy in porous rocks with aligned fractures is of interest to seismic remote sensing of the earth s structure and to hydrocarbon reservoir characterization in particular we investigated the effect of partial water saturation on attenuation in fractured rocks in the laboratory by conducting ultrasonic pulse echo measurements on synthetic silicacemented sandstones with aligned penny shaped voids fracture density of 0 0298 0 0077 chosen to simulate the effect of natural fractures in the earth according to theoretical models our results show for the first time contrasting variations in the attenuation q 1 o fp and s

neogene extensional collapse in the western mediterranean betic rif alpine orogenic belt implications for the genesis of the gilbraltar arc and magmatic activity the betic rif orogenic belt crops out in the western mediterranean and constitutes the westernmost part of the alpine edifice the building up of this belt by compressional nappe tectonics occured during a series of alpine deformational episodes subsequent neogene extension resulted from the collapse of the previous compressional edifice through major extensional detachment systems this episode was accompanied by cafe alkaline to shoshonitic and lamproitic volcanism tectonic denudation of metamorphic core complexes and emplacement of peridotite bodies as a final consequence of the evolution of detachment systems furthermore we relate the generation of the gibraltar arc and the opening of the alboran sea to this major extensional event finally two main stages of tectonic denudation of these detachment systems are defined 1 nevado filabride stage with ex humation of metamorphic core complexes and 2 ronda beni boussera stage with a more advanced degree of denudation leading to the exhumation of upper mantle peridotites which may be tentatively termed mantle core complexes

countermeasures of water and mud inrush disaster in completely weathered granite tunnels a case study this paper presents a case study of the countermeasures of water and mud inrush disasters in the junchang tunnel in guangxi china this tunnel was constructed in a weathered granite formation and four serious water and mud inrush disasters occurred during construction the geological and hydrological conditions are first reviewed to understand their effects on the water and mud inrush disasters four potential causes of the serious water and mud inrush disasters in the junchang tunnel were proposed including the poor stability of the completely weathered granite the high groundwater level and large groundwater flow rate insufficient pre reinforcement of the surrounding rock and the disturbances caused by tunnel construction water sealing and ground reinforcement measures were suggested before excavation to improve the stability of the surrounding rock and plug the water outflow channels and full face curtain grouting was considered as the first choice furthermore several improvements including the combined utilization of various grouting materials supplementary grouting with steel pipes in collapsed boreholes and dynamically optimized grouting methods were implemented to solve the serious water inflow and collapse problems experienced during the drilling and grouting work a detailed curtain grouting scheme was proposed and applied in practice a comprehensive evaluation based on inspection borehole investigations and p q t analysis indicated that the curtain grouting method yielded satisfactory performance in water sealing and ground reinforcement in addition the groundwater level and settlement data collected in the field validated the effectiveness of the proposed countermeasures

wavefield characterization of perforation shot signals in a shale gas reservoir abstract signals of perforation or string shots which are usually used for calibrating velocity models and estimating the orientation of 3 component down hole receivers during microseismic monitoring are occasionally hard to identify due to poor signal to noise ratios snr or confusion with the events induced during fracturing in adjacent wells a significant feature for distinguishing perforation signals from hydraulic fracturing events is the tube wave which is generated in the treatment well and received in the monitoring well we analyze seismic wavefields from perforations during a hydraulic fracturing operation on a pad well a group of horizontal wells with the wellheads at a same small surface area in a shale gas reservoir to understand the wave propagation phenomena including attenuation and the identification of tube waves guided wave in borehole and their conversions since they are dominated by high frequencies and lack energy at low frequencies the p and s wave arrivals of perforation shots decrease much more rapidly with propagation distance than that of induced events we identify six modes within the wavefields of the perforation or string shots recorded in a nearby well that are related to the tube waves the six modes include p s waves converted from tube waves in the shot treatment well at plugs or the well bottom an up going tube wave in the monitoring well generated by the tube wave in the nearby treatment well a down going tube wave from the treatment wellhead and the multiple a scatting body wave activated by tube waves in the treatment well these wave modes all originate from the waves radiated at the perforation point in the treatment well as tube waves and are then radiated into the formation and received by geophones in the nearby borehole as p s or tube waves if energy from the perforation shot is strong enough the tube wave will turn back from the surface and be reflected at the well bottom or plugs which would excite the further waves based on the features of the wavefield we identify the perforation events and facilitate better use of calibration from the perforation seismic recording for microseismic data processing we also evaluate attenuation of the signals with propagation distance and propose a procedure for developing a plan for monitoring of perforation and string shot signals

late cenozoic transpression in southwestern mongolia and the gobi altai tien shan connection the gobi altai region of southwestern mongolia is a natural laboratory for studying processes of active transpressional intracontinental mountain building at different stages of development the region is structurally dominated by several major e w left lateral strike slip fault systems the north gobi altai fault system is a seismically active right stepping left lateral strike slip fault system that can be traced along the surface for over 350 km the eastern two thirds of the fault system ruptured during a major earthquake m 8 3 in 1957 whereas degraded fault scarps cutting alluvial deposits along the western third of the system indicate that this segment did not rupture during the 1957 event but has been active during the quaternary the highest mountains in the gobi altai are restraining bend uplifts along the length of the fault system detailed transects across two of the restraining bends indicate that they have asymmetric flower structure cross sectional geometries with thrust faults rooting into oblique slip and strike slip master faults continued ne directed convergence across the fault system coupled with left lateral strike slip displacements will lead to growth and coalescence of the restraining bends into a continuous sublinear range possibly obscuring the original strike slip fault system this may be a common mountain building process the largely unknown gobi tien shan fault system is a major left lateral strike slip fault system 1200 km long that links the southern ranges of the gobi altai with the barkol tagh and bogda shan of the easternmost tien shan in china active scarps cutting alluvial deposits are visible on satellite imagery along much of its central section indicating quaternary activity the total displacement is unknown but small parallel splays have apparent offsets of 20 km suggesting that the main fault zone has experienced significantly more displacement field investigations conducted at two locations in southwestern mongolia indicate that late cenozoic transpressional uplift is still active along the fault system the spatial relationship between topography and active faults in the barkol tagh and bogda shan strongly suggests that these ranges are large coalescing restraining bends that have accommodated the fault s left lateral motion by thrusting oblique slip displacement and uplift thus from a mongolian perspective the easternmost tien shan formed where it is because it lies at the western termination zone of the gobi tien shan fault system the gobi tien shan fault system is one of the longest fault systems in central asia and together with the north gobi altai and other smaller subparallel fault systems is accommodating the eastward translation of south mongolia relative to the hangay dome and siberia these displacements are interpreted to be due to eastward viscous flow of uppermost mantle material in the topographically low e w trending corridor between the northern edge of the tibetan plateau and the hangay dome presumably in response to the indo eurasian collision 2500 km to the south

experimental modelling of orogenic wedges a review abstract experimental modelling applied to the study of orogenic wedge dynamics has been a subject of fruitful research for more than 30 years although the technique dates back as far as the early xix th century on one hand several first order parameters controlling the structural evolution of mountain belts have been intensively investigated using the classic tectonic sandbox models the main parameters are the properties of the basal decollement the deforming material the backstop and fluxes kinematics and surface processes on the other hand the morphological evolution of a mountain relief subjected to changing tectonic or climatic forcing has been addressed using another kind of approach called geomorphic models nowadays the literature is extremely rich particularly for the sandbox technique so that it becomes difficult to have an exhaustive view of the effects of the above parameters on mountain evolution in this article we propose a detailed review of the main results obtained using both tectonic and geomorphic approaches our goal is to provide an almost complete state of the art in the experimental study of relief dynamics to guide present and future researchers in their understanding of mountain belt evolution

orogenesis at the southern tip of the americas the structural evolution of the cordillera darwin metamorphic complex southernmost chile abstract new detailed lithologic and structural data are presented from three separately mapped areas along the southern boundary of the cordillera darwin metamorphic complex of southernmost chile cordillera darwin is a unique uplift because it exposes the highest grade rocks in the andes south of peru and averages 1 km higher in elevation than adjacent areas the structural data indicate that cordillera darwin experienced mid late cretaceous trans pressional deformation with a partitioned strike slip component localized along the beagle channel that forms the southern boundary to the range foliation lineation and fold axis trends indicate ne sw directed contraction and nw se strike slip shearing present directions during progressive d1 d2 andean deformation d2 deformation is marked by outcrop to 10 km scale south southwest vergent folds late cretaceous tertiary brittle ductile and brittle left lateral strike slip faults and shear zones crosscut all d1 d2 structures although limited structural evidence for extensional tectonics was documented in this study apparent normal offsets across both arms of the beagle channel and previously documented field evidence for extension from other areas in cordillera darwin suggest that transtensional displacements also may have occurred in southern cordillera darwin during the late cretaceous early tertiary cordillera darwin s position within the evolving patagonian orocline adjacent to an evolving mesozoic cenozoic left lateral transform boundary between the south american and antarctic plates and later the south american and scotia plates necessitates consideration of the possible effects of regional counterclockwise rotation on development of structures regional counterclockwise rotation of cordillera darwin may have controlled the temporal and spatial transition of deformational regimes within cordillera darwin exhumation of the metamorphic core of cordillera darwin during the late cretaceous early tertiary is interpreted to have been due to rapid uplift and normal rates of erosion rapid uplift may have been due to migration of contraction to northern cordillera darwin and crustal relaxation in southern cordillera darwin as contractional structures rotated into parallelism with 1 and either ceased to be active or were reactivated as strike slip or oblique slip faults rapid isostatic rebound of cordillera darwin may have also been a response to aborted continental subduction of southern cordillera darwin and detachment of a subducted mafic root during mid cretaceous closure of the rocas verdes marginal basin

joint inversion for effective anisotropic velocity model and event locations using s wave splitting measurements from downhole microseismic data abstractan accurate velocity model is essential in microseismic imaging layered sediments and subvertical cracks from tectonic stress and hydraulic fracturing make velocity models more complicated than isotropy or simple anisotropy such as vertical transverse isotropy downhole microseismic acquisition usually cannot achieve sufficient ray coverage that is required to develop a low symmetry anisotropic model from traveltimes alone to solve this problem we have developed a new type of data s wave splitting parameters the delay time of the slow s wave and fast s wave polarization direction to determine anisotropic models a genetic algorithm inversion is adopted to solve for the locations of events and the stiffness tensor of an anisotropic medium simultaneously we applied this method to synthetic waveforms from numerical modeling and successfully recovered the input event locations and the velocity model the effectiveness of this method is further demonstrated by using real microseismic data acqu

reconciliation of crosshole seismic velocities with well information in a layered sedimentary environment in sedimentary environments horizontal fine layering can cause significant complications when analyzing and comparing seismic data with different frequencies and propagation directions at the whitchester test site three boreholes penetrate upper carboniferous cyclical sediments involving interbedded carbonates sandstones and mudstones with seismic velocities ranging from less than 3 0 km s in the mudstones to over 4 5 km s in the carbonates initial crosshole results from two boreholes approximately 200 m deep and 75 m apart showed a poor correlation with the borehole logs recorded in a third intermediate borehole furthermore the tomographic images were inconsistent with the expected geology the objective of this paper is to reconcile the crosshole seismic data with the borehole log information the borehole information must be upscaled to match the resolution of the crosshole experiment however upscaling techniques based on backus averaging lead to the prediction of significant anisotropy of the order of 20 in places with a vertical symmetry axis this anisotropy is a result of a combination of fine layering and the intrinsic mineral anisotropy measured on the core samples although it is the layer induced anisotropy that dominates at the crosshole frequencies of 400 hz this prediction was tested by including anisotropy parameters into the analysis of the crosshole data using anisotropic velocity tomography in the central part of the final anisotropic velocity tomograms where the ray coverage is adequate these crosshole results are consistent with the anisotropy predictions once the anisotropy was properly accounted for the tomographic images are consistent with the layered nature of the geology at the site and they show the location and throw of a known fault in the section we conclude that at this site and at crosshole frequencies seismic layer induced anisotropy plays a significant role and must be accounted for when processing and interpreting crosshole seismic data

morphology and topology of dolostone lithons in the regional carboneras fault zone southern spain abstract dolostones in a neogene strike slip fault zone are described two main types of structural features are recognised i background deformation in the form of a network of bedding perpendicular and hybrid conjugate fractures barren fractures and bedding parallel stylolites ii fault related features include breccias and cataclasites orthorhombic rock lithons are generated from the intersection of fracture sets with bedding and or joints lithon size and morphology change across the dolostone fault block gradually producing a tetragonal or isometric shape the lithons are 1 2 cm in dimension only 20 outside this range and have an average cross sectional aspect ratio of 1 6 irrespective of size or structural position topology is analysed using nodes and branches ranging from isolated i node and i i branch to connected y and x nodes and i c to c c branches respectively the quantitative description of the geometrical and topological analysis of the dolostone lithons suggest that they become more connected and interact within the dolostone fault blocks assessing the change in topology and lithons connectivity have important implications for subsurface reservoirs and aquifers hosted in dolostone fault zones

crustal scale en echelon p shear tensional bridges a possible solution to the batholithic room problem the apparent paradox of voluminous granitoid emplacement in an overall compressional magmatic are has been somewhat alleviated by the idea of pluton emplacement in tension cracks and dilational jogs within arc parallel strike slip fault systems as an alternative hypothesis we propose that an en echelon p shear array provides a continuous batholith scale zone of dilation along the trend of active magmatism and that it is favored by transpressional tectonics in the sierra nevada california the late cretaceous granitoids of the cathedral range intrusive epoch are consistent with emplacement into bridges between p shears because 1 they are elongated oblique to the magmatic trend consistent with p shear orientation within a dextral system 2 they were all emplaced within 5 10 m y along a 300 km trend resulting in a displacement rate of 1 cm yr across the arc and 3 syn to late magmatic dextral shear zones bound and crosscut the plutons as in a p shear tensional bridge

barrier effect of underground structures on aquifers abstract impervious structures below the water table modify the natural groundwater flow in aquifers they act as barriers causing heads to rise upgradient and to fall downgradient we define the barrier effect as the increase in head loss across the barrier with respect to the natural conditions prior to construction we distinguish between regional the minimum head loss observed at long distances and local the maximum head loss observed close to the structure barrier effects we use numerical and analytical methods to derive semi empirical equations to quantify the two barrier effects for semi permeable partially penetrating or fully penetrating but finite in length and barriers with a by pass in confined aquifers the resulting equations depend on the barrier geometry and on the natural head gradient in the aquifer and they are easy to apply we test their validity at two construction sites obtaining excellent agreement between the computed and observed barrier effects

characteristics of groundwater seepage with cut off wall in gravel aquifer i field observations1 this paper presents a case history of the leakage behavior during dewatering tests in the gravel strata of an excavation pit of a metro station in hangzhou china the groundwater system at the tes

interpretation of increased deformation rate in aquifer iv due to groundwater pumping in shanghai shanghai is a typical example of a region in china suffering from severe land subsidence previous investigations have shown that land subsidence is strongly related to groundwater pumping in both the temporal and spatial domains a series of field investigations shows that the deformation rate of aquifer iv aqiv has increased contributing significantly to the total subsidence in shanghai to predict the deformation behavior of aqiv in shanghai due to groundwater pumping four different models have been applied in this study i a model based on groundwater flow theory ii an elastic model based on cauchy mechanics iii a creep model incorporated into cauchy mechanics and iv a recently proposed land subsidence model by budhu based on cosserat mechanics based on a number of assumptions budhu s concept was extended to consider the time dependent behavior of groundwater potential in aquifers and the consolidation behavior of overburdened aquitards the calculated results of aqiv s deformation we

structural geology and kinematic history of rocks formed along low angle normal faults death valley california several late cenozoic low angle normal or detachment faults on the western flank of the black mountains are each characterized by the following in descending structural order 1 a hanging wall of upper tertiary to quaternary sedimentary and volcanic strata that displays little evidence for fault related damage other than widely spaced planar or listric normal faults 2 a sharp planar and locally striated principal slip plane forming the lower boundary of the hanging wall 3 an upper zone zone i of very fine grained fault generated rocks composed dominantly of gouge 4 a lower zone zone ii of coarser grained fault rocks consisting chiefly of foliated breccia and 5 a variably damaged footwall consisting of partly mylonitic precambrian units or tertiary plutonic rocks that has been exhumed from depths of 10 12 km since late miocene time the fault rocks which were mostly derived from the footwalls preserve evidence for cataclastic and particulate flow fault rocks contain authigenic minerals but lack the cyclically deformed mineral filled syntectonic veins that are abundant in some other late cenozoic high angle and strike slip faults meso and microscale fabrics in zones i and ii indicate that finite shear strains increase progressively upward toward the principal slip plane in a conceptual kinematic model of a shear box displacements of the hanging wall produced a shearing flow in the fault rocks below some of the slip on the principal slip plane was also partitioned into localized slip on discrete sliding surfaces in zones i and ii since 770 ka during the latest stages of incremental deformation in the brittle shear zones distributed flow in the fault rocks alternated with slip that was chiefly localized on the principal slip planes in this respect the detachment faults differ from inactive segments of the san andreas system along which displacements were progressively and irreversibly localized onto a single principal slip surface the strain gradients and corresponding changes in grain size in the shear zones resemble those in mylonitic shear zones except in their symmetry strain gradients in the black mountains are notably asymmetric they are present only below the principal slip planes not above

environmental protection using dewatering technology in a deep confined aquifer beneath a shallow aquifer abstract this paper presents an innovative technology referred to as dual function well dfw which has been developed in order to reduce the construction costs of dewatering when excavation is conducted in an aquitard over a confined aquifer dfw technology is a method to lower both shallow groundwater and deep groundwater either separately or simultaneously using one well the dfw includes two or more independent screens corresponding to each aquifer and a valve is located between the screens inside a steel pipe when the valve is closed groundwater is pumped from the upper screen in the shallow aquifer when the valve is open groundwater is pumped from the screens in both the shallow and deep aquifers dfw technology is used to replace the traditional method involving two sets of wells in which the first set of wells pumps groundwater from the shallow aquifer and a second set pumps groundwater from the deep aquifer to investigate the effectiveness of dfw field pumping tests using a dfw were conducted and both groundwater head and settlement were monitored numerical simulation was adopted to simulate the results of the pumping tests comparison between the results from the dfw and from an ordinary mixing well indicates that the use of a dfw with the valve closed can reduce the pumping time from a deep aquifer and can reduce the ground settlement caused by dewatering the results indicate the dfw technology is feasible and effective

comparative geometry of the san andreas fault california and laboratory fault zones textural examination of fault gouge deformed in triaxial friction experiments has revealed differences in the orientations of secondary shear sets between the stably sliding and stick slip samples in order to determine whether such differences can be identified in natural faults maps of recently active breaks along the san andreas fault from point arena to cajon pass california were examined to compare the types and orientations of secondary structures mapped in the creeping and locked sections the fault zone was divided into 52 geometrically defined segments of uniform strike which were then grouped into 7 sections 4 straight and 2 curved sections and cholame valley one of the straight sections is the creeping section between san juan bautista and cholame in central california the rest of the sections are locked many of the gross geometric characteristics of the individual segments such as length width and stepover size reflect their position in either a straight or a curved section in contrast with respect to the orientations of the recent breaks within the segments the single creeping section differs from all of the locked sections both straight and curved as follows 1 the traces of recent breaks with a more west ward orientation than the local strike of the fault zone p traces dominate over those with a more northward orientation r traces in the creeping section whereas the opposite relationship holds in the locked sections and 2 the more northward oriented r traces make larger angles to the local strike of the fault zone in the locked sections than in the creeping section the latter result is consistent with the orientations of r shears in our various laboratory samples the former result was unexpected because of the predominance of r shears in most laboratory samples but a small number of samples are analogous to the creeping section in terms of their p shear abundances r shear orientations and sliding behavior the causes of these distinguishing characteristics are not yet understood

q model building using one way wave equation migration q analysis part 2 3d field data test in part one of this paper we presented an inversion based method wave equation migration q analysis to estimate the quality factor q model for seismic attenuation to demonstrate the feasibility of this method we applied this method to a 3d seismic dataset acquired in the north sea attenuation problems caused by a shallow gas and a shallow channel are observed in this field this study aims at characterizing these attenuation anomalies these attenuation anomalies are correlated with low interval velocities the provided velocity model does not accurately reflect the low velocity anomalies therefore we first applied wave equation migration velocity analysis to update the provided velocity model the updated velocity shows low velocity regions around the gas and channel features the subsurface angle gathers migrated using the updated velocity model are flatter and the events in the migrated images after velocity updating are more coherent then we applied wave equation migration q analysis to inv

experimental fracture strain and subsidence patterns over en echelon strike slip faults implications for the structural evolution of pull apart basins abstract claybox experiments show that with progressive left lateral displacement on basal left stepping en echelon strike slip faults an extremely complicated zone of evolving fracture strain and subsidence patterns develops in the overlying clay the fracture pattern is more complex than predicted by theoretical models and consists of a progressively widening array of riedel shears conjugate riedel shears and tension gashes above basal master faults conjugate riedel shears rotate anticlockwise and lengthen forming s shaped fractures riedel shears rotate both anticlockwise and clockwise those that rotate anticlockwise eventually open as tension gashes other tension gashes open where the ends of riedel and conjugate riedel shears link strain contours in the deformed clay show an asymmetrical z shaped pattern over the stepover area between basal en echelon faults in the early stages of displacement strain is distributed penetratively over a progressively broadening zone in later stages of displacement strain is partitioned into a narrow middle zone maximum strain is sustained always in the middle of the sheared zone and increases exponentially with progressive displacement subsidence is accommodated in the stepover area by oblique slip on many riedel and conjugate riedel shears distributed throughout the stepover area subsidence y exhibits a linear relationship with master fault displacement x described by y 0 36 x 1 4 the experimental fracture strain and subsidence patterns in clay over en echelon faults can be used as interpretive and predictive tools with which to constrain interpretations of static field examples especially in pull apart basins on the crustal scale where many similarities with the models exist

analog models of restraining stepovers in strike slip fault systems scaled sandbox models have successfully simulated the geometries and progressive evolution of antiformal pop up structures developed in a weak sedimentary cover above restraining stepovers in offset sinistral strike slip fault systems in rigid basement models were run both with and without synkinematic sedimentation which was added incrementally to cover the growing antiformal structures vertical and horizontal sections of the completed models permit the full three dimensional 3 d structure of the pop ups to be analyzed in detail three representative end member experiments are described 30 underlapping restraining stepovers 90 neutral restraining stepovers and 150 overlapping restraining stepovers the experimental pop ups are typically sigmoidal to lozenge shaped antiformal structures having geometries that are dependent on both the stepover angle and stepover width in the underlying basement faults underlapping restraining stepovers typically form elongate lozenge shaped pop ups 90 neutral restraining stepovers produce shorter squat rhomboidal pop ups and overlapping restraining stepovers produce sigmoidal antiformal pop ups trans pop up cross fault systems are characteristic at large displacements on the basement fault system above the offset principal displacement zones the pop ups are commonly small narrow positive flower structures whereas in the stepover region they widen out and become markedly asymmetric this pop up asymmetry switches across the center of the stepover where the pop ups are largely symmetical maximum rotations measured within the central highly uplifted region of the pop ups increase from 7 counterclockwise for the underlapping 30 stepovers to 14 counterclockwise for the neutral 90 stepovers to 16 counterclockwise for the overlapping 150 stepovers in models where no synkinematic sediments were added during deformation the pop up structures are bound by convex flattening upward oblique slip reverse fault systems that link downward to the offsets in the basement fault system in contrast in the begin page 234 experiments where synkinematic sediments were added incrementally during deformation the pop ups are formed by oblique slip reverse faults that steepen upward into the synkinematic strata with the formation of fault propagation growth folds the analog models are compared with natural examples of pop up structures and show strong similarities in structural geometries and stratal architectures these models may provide structural templates for seismic interpretation of complex contractional structures in offset strike slip fault systems

seismic attenuation tomography using the frequency shift method we present a method for estimating seismic attenuation based on frequency shift data in most natural materials seismic attenuation increases with frequency the high frequency components of the seismic signal are attenuated more rapidly than the low frequency components as waves propagate as a result the centroid of the signal s spectrum experiences a downshift during propagation under the assumption of a frequency independent q model this downshift is proportional to a path integral through the attenuation distribution and can be used as observed data to reconstruct the attenuation distribution tomographically the frequency shift method is applicable in any seismic survey geometry where the signal bandwidth is broad enough and the attenuation is high enough to cause noticeable losses of high frequencies during propagation in comparison to some other methods of estimating attenuation our frequency shift method is relatively insensitive to geometric spreading reflection and transmission effects source and receiver coupling and radiation patterns and instrument responses tests of crosswell attenuation tomography on 1 d and 2 d geological structures are presented

effects of porosity and clay content on wave velocities in sandstones the ultrasonic compressional vp and shear vs velocities and first arrival peak amplitude ap were measured as functions of differential pressure to 50 mpa and to a state of saturation on 75 different sandstone samples with porosities ranging from 2 to 30 percent and volume clay content c ranging from 0 to 50 percent respectively both vp and vs were found to correlate linearly with porosity and clay content in shaly sandstones at confining pressure of 40 mpa and pore pressure of 1 0 mpa the best least squares fits to the velocity data are vp km s 5 59 6 93 2 18c and vs km s 3 52 4 91 1 89c deviations from these equations are less than 3 percent and 5 percent for vp and vs respectively the velocities of clean sandstones are significantly higher than those predicted by the above linear fits about 7 percent for vp and 11 percent for vs which indicates that a very small amount of clay 1 or a few percent of volume fraction significantly reduces the elastic moduli of sandstones for shaly

pseudotachylyte bearing strike slip duplex structures in the fort foster brittle zone s maine abstract detailed 1 60 scale mapping of the fort foster brittle zone in the mylonitic rye formation of southernmost maine has revealed the intricate internal duplex structure of a system of probable paleozoic age dextral strike slip faults that have produced abundant pseudotachylyte and minor breccia the internal configuration of this brittle zone consists of a mosaic of individual pseudotachylyte generation zones as slab duplex structures individual duplex zones are up to 100 m in length and 1 m or less in width and are defined by pairs of layer parallel slip surfaces along which frictional melts were produced these slab duplex structures are interpreted as zones of displacement transfer between long overlapping layer parallel en echelon strike slip fault surfaces contractional duplexes develop layer parallel compressional structures that tend to shorten and thicken the fault bounded slabs by the formation of lateral ramps and conjugate faults kinks and asymmetric folds extensional duplexes develop layer parallel stretching and thinning by the formation of oblique dextral shears high angle conjugate pairs and localized fault breccias the production of pseudotachylyte by friction melting along layer parallel fault surfaces in these exposures is attributed to rapid slip during paleoseismic events the rupture structures developed during these events may be characteristic of fault structure and mechanics at near focal depths in a strike slip seismogenic zone

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

pumping tests in non uniform aquifers the linear strip case abstract many pumping tests are performed in geologic settings that can be conceptualized as a linear infinite strip of one material embedded in a matrix of differing flow properties a semi analytical solution is presented to aid the analysis of drawdown data obtained from pumping tests performed in settings that can be represented by such a conceptual model integral transform techniques are employed to obtain a solution in transform space that can be numerically inverted to real space examination of the numerically transformed solution reveals several interesting features of flow in this configuration if the transmissivity of the strip is much higher than that of the matrix linear and bilinear flow are the primary flow regimes during a pumping test if the contrast between matrix and strip properties is not as extreme then radial flow should be the primary flow mechanism sensitivity analysis is employed to develop insight into the controls on drawdown in this conceptual model and to demonstrate the importance of temporal and spatial placement of observations changes in drawdown are sensitive to the transmissivity of the strip for a limited time duration after that time only the total drawdown remains a function of strip transmissivity in the case of storativity both the total drawdown and changes in drawdown are sensitive to the storativity of the strip for a time of quite limited duration after that time essentially no information can be gained about the storage properties of the strip from drawdown data an example analysis is performed using data previously presented in the literature to demonstrate the viability of the semi analytical solution and to illustrate a general procedure for analysis of drawdown data in complex geologic settings this example reinforces the importance of observation well placement and the time of data collection in constraining parameter correlation a major source of the uncertainty that arises in the parameter estimation procedure

hydraulic fracturing induced strain and microseismic using in situ distributed fiber optic sensing abstract hydraulic fracturing operations in unconventional reservoirs are monitored using distributed fiber optic sensing through which physical effects such as temperature strain and microseismic activity can be measured when combined with treatment curves and other reservoir information these measurements give engineers more data to understand the effectiveness of a treatment program and make future reservoir management decisions distributed fiber optic data are acquired within a borehole that is actively being fractured and is subsequently used as an observation well for treatments of a neighboring well the large aperture and finely sampled data acquisition provides a variety of measurements at different resolution scales as changes are induced in the reservoir distributed acoustic sensing microseismic events are observed with magnitudes above 2 the spatial distribution of events up to 500 m from the observation well allows us to estimate diffusivity and fracturing trends for nearby treatmen

mid crustal detachment in the betic system of southeast spain abstract the tertiary orogenic belts of eastern spain can be interpreted using the principles of thin skinned thrusting with a fundamental detachment at mid crustal level in the eastern betics the compression involves an oblique restacking of a stretched continental margin much of the shortening is transmitted on permian and triassic detachments which emerge as forward and back thrust duplexes an interpretation of the guadarrama range of central spain is presented in which significant shortening is shown on a mid crustal detachment propagating from the southeast it is suggested that this represents the external limit of a compressive system linked to the betics the pyrenees and eastern cantabrians are a separate tertiary compressive system again resulting from restacking of an extensional basin during the collision of iberia and france previous authors have proposed mid crustal detachment in the pyrenees observation of the geological map of the iberian ranges suggests a broadly similar structural origin may apply in which case the iberian ranges may represent the most external zone of a major pyrenean system again linked by a mid crustal detachment thus it is suggested that the whole of eastern spain is made up of two major compressive systems linked at mid crustal level

analogue models of second order faults genetically linked to a circular strike slip system abstract sandbox experiments with sand and sand silicone models were performed above a circular strike slip fault to understand the influence of curvature on the development of second order faults riedel r faults appear already at low displacements in the concave side of the circular plate where they always form more numerous they are followed by r faults in the convex side and eventually by throughgoing d faults that join the r faults and that develop parallel to the underlying circular fault the angle between the riedel faults and the trace of the main circular fault at the surface of the models is c 26 on the concave side and 15 on the convex side we infer a larger obliquity of 1 in the concave side of the circular plate which corresponds to a larger transpressional component than in the convex side of the main wrench fault due to the more confined volume of deforming sand in sand experiments most of the faults root into the underlying strike slip fault in sand silicone experiments instead the faults form close to the displacement discontinuity in case of a high displacement rate only uplifted areas are located all along the main fault in sand experiments in sand silicone experiments they are mostly located in wedges defined by the riedel faults and the main wrench fault and the width of these uplifted areas appear to be related to the length and activity of the riedel faults our results differ significantly from those of experiments with straight strike slip faults where strain and second order faults are symmetrically arranged on both sides of the main fault

dewatering of a deep excavation undertaken in a layered soil in order to carry out deep excavations under the water table in urban environments the safety of the work site and of the adjacent buildings is a major cause for concern one of the most common and effective methods of undertaking these excavations involves combining the cut and cover method with a dewatering system the success of a construction depends on the stability of the excavation bottom the effects produced outside the excavation by dewatering soil movements and or the state of the enclosure defects in the diaphragm walls this study proposes a realistic multidisciplinary procedure to address these issues the work emphasizes the importance of soil characterisation and underlines the need to perform a watertightness assessment test wtat before the excavation stage the procedure was applied to the excavation of a deep shaft of the high speed train hst tunnel in barcelona an earlier geological characterisation at large scale ruled out the use of deep pumping wells however a subsequent hydrogeological characterisation which involved borehole logging grain size analyses natural gamma ray and pumping tests revealed the presence of thin transmissive layers inside the low hydraulic conductivity materials the dewatering system was designed by considering different model scenarios and the safest design was selected for the excavation depths of the enclosure and of the pumping wells differed in accordance with the scenarios the impacts settlements due to pumping and the stability in each scenario were computed the state of the enclosure underwent a wtat before the start of the excavation but after constructing the enclosure to verify its low permeability the test consisted in pumping inside the enclosure and monitoring the groundwater behaviour outside the enclosure numerical interpretation of this test showed a defect in the diaphragm walls below the excavation bottom since this defect was not repaired because of its location below the bottom of the excavation the dewatering system had to be redesigned to ensure safety surface settlements which were also a source of concern were small they were computed using coupled hydro mechanical models

alteration characteristics of granite contact zone and treatment measures for inrush hazards during tunnel construction a case study abstract several large scale mud and water inrush events occurred during excavation of the denghuazhai tunnel at a depth of 175 m in the contact zone between geodic granite and tuff by analyzing the inrush process the characteristics of the inrush hazards such as high pressure abundant water high mud and sand content and strong destructive power were revealed in addition the inrush hazards were intermittent uncertain and sudden an intrusive contact zone between geodic granite and tuff was revealed by regional geological investigation large scale alteration occurred both in geodic granite and tuff near the contact zone petrographic analyses indicated that alteration to albite sericite and kaolinite occurred in geodic granite and alteration to quartz and montmorillonite took place in tuff gradually toward the contact zone furthermore the changes were gradational within and between various alteration grades the closer to the contact zone the higher degree of alteration the less the primary minerals including quartz k feldspar and plagioclase the more the secondary minerals such as sericite and clay minerals tests on porosity saturated water content and uniaxial compressive strength indicated that alteration led to significant deterioration of physical and mechanical properties of rocks except for silicified tuff especially for the zonal clay in the central area of contact zone the physical and mechanical properties were poor and obvious swelling disintegration and argillation were observed tunnel excavation triggered swelling disintegration and argillation of clay leading to several large scale inrush events in terms of treatment of inrush hazards first of all a comprehensive exploration method based on petrographic analyses geophysical detection and borehole drilling was established according to the alteration characteristics so as to identify the scale and composition of the altered zone the principle of consolidation before removal was adopted to deal with the inrush deposits for breach sealing and reinforcement energy release and stress reduction during tunnel construction and regular drainage during operation were achieved by dewatering measures namely drainage supplemented by sealing water drainage and solids remaining reinforcement measures including full face curtain grouting and double layer pipe sheds were adopted to reinforce and seal the highly disturbed rock and soil in advance finally technical measures including bench excavation enhancement of support stiffness and timely installation of secondary support were employed to effectively prevent large deformation in disturbed rock masses with the above measures the left and right tunnels of the denghuozhai tunnel have passed through the altered zone successfully

grain size and depositional environment as predictors of permeability in coastal marine sands more than half of the surface sediments covering the continental shelves are sandy which may permit substantial sub seafloor pore water advection knowledge of sediment permeability is required for quantifying advection and associated solute transport but studies of marine sediments typically report grain size analyses rather than permeability here data from 23 studies were examined to determine the range in permeabilities reported for sublittoral marine sands and to assess the utility of permeability grain size relationships in this setting in the resulting database the permeability of small w30 cm undisturbed cores collected from the sea floor all fell between 2 10 12 and 4 10 10 m 2 a range where advective transport induced by wave and current action should be pervasive the range in grain size was very similar for near shore 10 m water depth but the permeability of the continental shelf samples was consistently lower for the same median grain size empirical permeability grain size relationships generated a poor fit r 2 0 35 for the aggregate data but separate relationships for near shore and continental shelf samples were significantly better r 2 0 66 and 0 77 respectively permeability grain size relationships thus may be useful for sublittoral sands but a larger database needs to be accumulated before reliable fit parameters and variability can be predicted thus it is recommended that permeability be routinely determined when characterizing sedimentological properties of marine sand deposits concurrent determinations of sediment bulk density and porosity may further improve estimates of permeability 2008 published by elsevier ltd

characteristics of groundwater seepage with cut off wall in gravel aquifer ii numerical analysis this paper presents a numerical investigation into the leakage behavior of cut off walls in gravel strata due to dewatering in a deep excavation pit the calculated values of the groundwater head and surface settlement using a model agree well with the measured values values of the hydraulic conductivity k and storage coefficient ss of each soil layer are obtained from the test results when the cut off wall is 43 m deep the leakage through the cut off wall in gravel is analyzed by considering a variation in hydraulic conductivity in different sections of the cut off wall the simulated results show that a significant leakage occurred in the 54 m deep cut off wall although leakage did occur in the full cut off wall in the confined aquifer the full cut off wall is still more efficient in preventing groundwater seepage than the partial cut off wall the relative depths of the cut off wall and of the wells have a significant effect on ground surface settlement during the withdrawal of groundwater the

improved compound support system for coal mine tunnels in densely faulted zones a case study of china s huainan coal field abstract when tunnelling in densely faulted zones of coal mines serious deformation often occurs due to adverse geological conditions such as extremely broken and weak rock mass high tectonic stress fissure water to investigate a more efficient support strategy for tunnels passing through densely faulted zones a tunnel in china s huainan mining area is taken as an experimental site to study an improved support method some key factors associated with the stability of tunnels in the densely faulted zone are analysed based on the analysis of failure characteristics of a previously excavated tunnel a detailed procedure for the improved support method is proposed in which a long pipe pre grouting method together with a new kind of grouting cable are applied finally the improved support strategy is implemented in the experimental tunnel the monitoring results suggest that serious deformation is avoided and the improved compound support method is feasible for tunnels in densely faulted zones

simultaneous inversion of multiple microseismic data for event locations and velocity model with bayesian inference abstractwe have applied bayesian inference for simultaneous inversion of multiple microseismic data to obtain event locations along with the subsurface velocity model the traditional method of using a predetermined velocity model for event location may be subject to large uncertainties particularly if the prior velocity model is poor our study indicated that microseismic data can help to construct the velocity model which is usually a major source of uncertainty in microseismic event locations the simultaneous inversion eliminates the requirement for an accurate predetermined velocity model in microseismic event location estimation we estimate the posterior probability density of the velocity model and microseismic event locations with the maximum a posteriori estimation and the posterior covariance approximation under the gaussian assumption this provides an efficient and effective way to quantify the uncertainty of the microseismic location estimation and capture the correlation between the velo

grouting for water and mud inrush control in weathered granite tunnel a case study abstract this paper presents a case study of curtain grouting to prevent water and mud inrush disasters for a weathered granite tunnel in guangxi china first the basic information of the junchang tunnel is given including ground conditions water and mud inrush disasters and the subsequent prevention countermeasures then we present the original grouting design and procedure and the field operation of 25 grouting cycles and excavations for the evaluation of the grouting effect and suggestion for future grouting work based on the field investigation the values of the major grouting parameters are suggested including grouting thickness of 5 8 m grouting length of 15 18 m 3 3 6 times of thickness and per meter grouting volume of 34 2 m3 furthermore the guidelines for composite materials selection are proposed for the various flowing water environments moreover the space positions and water quality of the inspection boreholes and the original water richness of the ground should be taken into consideration in the grouting evaluation criteria the optimized grouting parameters materials selection and evaluation criteria provide important references for disasters prevention in similar projects

the geodynamic evolution of the internal zone of the betic cordilleras south east spain a model based on structural analysis and geothermobarometry the internal zone of the betic cordilleras consists of several superimposed major thrust sheets with different p t t evolutions on the basis of an integrated field microscopic and laboratory study the tectono metamorphic history of the mulhacen complex and almanzora unit has been reconstructed in detail the mulhacen complex has been af ected by at least five phases of penetrative deformation which have been labelled dx d dx d and dx d and d are related to continent continent collision which is indicated by high pressure low temperature wilt and subsequent intermediate pit metamorphic conditions d is related to crustal thinning and heterogeneous extension during this event the almanzora unit was juxtaposed against the mulhacen complex this phase was succeeded by the establishment of low pressure high temperature lpiht conditions and at least two phases of folding and overthrusting the almanzora unit shows a comparable tectono metamorphic evolution pt d however the pit conditions prior to d indicate a higher crustal position with respect to the mulhacen complex during the collisional event key w alpine orogeny betic cordilleras spain continent continent collision crustal thickening crustal thinning deformation structures geothermobarometry p t t path

attenuation of p and s waves as a method of distinguishing gas and condensate from oil and water compressional and shear wave attenuation data were calculated from sonic waveforms in three wells the results show that at similar porosities and at in situ conditions gas and condensate sandstone reservoirs exhibit higher p wave attenuation lower p wave quality factor q p than either fully water or partially oil water saturated sandstones however s wave attenuation and quality factor q s do not show such a strong dependence on pore fluids furthermore q p q s 1 indicates presence of gas or condensate while q p q s i indicates full water or oil water saturation these field data are consistent with laboratory data and theoretical predictions by various researchers the crossovers of p swave attenuation and q p q s quality factors proved useful for distinguishing gas and condensate from oil and water reservoirs they may be used in conjunction with vp vs and other logs as an aid in formation evaluation for the detection of gas condensate and oil several case studies in the literature report high p wave energy absorption at seismic frequencies below gas and condensate pools this suggests that it is not unreasonable to assume that this method could also be used in seismic exploration as an aid for distinguishing gas and condensate from oil and water formations

geologic evolution of the betic cordilleras in the western mediterranean miocene to the present abstract the betic cordilleras were formed during the eo meso and neo alpine evolution of the western mediterranean area during the neo alpine stage the northward subduction of the african plate took place and the algerian provencal basin opened with the creation of oceanic floor associated space problems produced the expulsion and extensive stretching of the internal zones to the west which in turn disrupted and deformed the external zones of the betic and rif cordilleras these occurrences essentially took place in the burdigalian and continued with diminished intensity into the middle miocene following the suturing of the transcurrent contact between the internal and external zones important n60 90 e and nw se faults occurred the betic cordilleras are characterized as having been deformed by regional horizontal shortening compression oriented wnw ese or nw se which gradually rotated to the nnw sse in the late miocene when its most important intramontane neogene basins were formed the alboran basin with a thinned continental crust was formed as a western prolongation of the opening of the algerian provencal basin with its basic features already apparent in the burdigalian the volcanism present in the southeast of the betic cordilleras and in northeast morocco crossing the alboran basin is mainly late miocene in age it is linked to fracturing and exhibits chemistry related to the different thickness of the crust

characteristics of dewatering induced drawdown curve under blocking effect of retaining wall in aquifer summary for deep excavation pits that require the pumping of confined groundwater a combination of a retaining wall and dewatering with large diameter wells is usually adopted during excavation to improve safety since a retaining wall has a much lower hydraulic conductivity than the surrounding material in the aquifer blocking of seepage to prolong the seepage path of the groundwater outside of the pit is effective the retaining walls used during excavation dewatering cause hydraulic head drawdown inside the pit much faster than outside the pit thus difference in hydraulic head between inside and outside of the pit increases to investigate the mechanism of the blocking effect numerical simulation using the finite difference method fdm was conducted to analyze the effects of pumping in the pit the fdm results show that drawdown varies along the depth of the confined aquifer the influence factors of drawdown inside and outside the pit include insertion depth of retaining walls anisotropy of a confined aquifer and screen length of pumping wells in addition fdm results also show that the drawdown time curve can be divided into four stages in stage i drawdown inside the pit is very small and outside the pit it is almost zero in stage ii drawdown increases quickly with time in stage iii the drawdown curve is parallel to the cooper jacob curve on semi log axes and in stage iv the drawdown becomes constant these characteristics of the drawdown curve under the blocking effect of a retaining wall in an aquifer provide a way of estimating hydrogeological parameters according to pumping test results

the betic segment of the lithospheric trans alboran shear zone during the late miocene abstract the betic sinistral transcurrent shear zone betic cordilleras crosses the southeastern part of spain the study of the geodynamics of this area is approached from tectonic sedimentary magmatic and geophysical data large strike slip movements tectono sedimentary processes and magmatic events are seen at the boundary between two different lithospheric slabs they are located in a thinned compartment with a high geothermal gradient the large scale movements vertical and horizontal and the intensity of magmatic activity are the expression of the mechanical behaviour of this hot and thin crust all the geological events from the late miocene to recent are integrated in a crustal scale cross section which shows that the betic sinistral transcurrent shear zone widely affects the lithosphere it appears that subduction zones are not the only geodynamic context in which calc alkaline magmatism occurs

the determination of the seismic quality factor q from vsp data a comparison of different computational methods1 ten methods for the computation of attenuation have been investigated namely amplitude decay analytical signal wavelet modelling phase modelling frequency modelling rise time pulse amplitude matching technique spectral modelling and spectral ratio in particular we have studied the reliability of each of these methods in estimating correct values of q using three synthetic vsp seismograms for plane p waves with different noise contents the investigations proved that no single method is generally superior rather some methods are more suitable than others in specific situations depending on recording noise or geology the analytical signal method has been demonstrated to be superior if true amplitude recordings are available otherwise spectral modelling or in the noise free case the spectral ratio method is optimal finally two field vsps in sediments are investigated only in the case of the highest quality vsp can significant information be deduced from the computed attenuation

landslide susceptibility mapping by correlation between topography and geological structure the janghung area korea the purpose of this study is to develop and apply the technique for landslide susceptibility analysis using geological structure in a geographic information system gis in the study area the janghung area of korea landslide locations were detected from indian remote sensing irs satellite images by change detection where the geological structure of foliation was surveyed and analysed the landslide occurrence factors location of landslide geological structure and topography were constructed into a spatial database then strike and dip of the foliation and the aspect and slope of the topography were compared and the results which were verified using landslide location data show that foliation of gneiss has a geometrical relation to the joint or fault that leads to a landslide using the geometrical relations the landslide susceptibility was assessed and verified the verification results showed satisfactory agreement between the susceptibility map and the landslide location data

investigation of field installation effects of horizontal twin jet grouting in shanghai soft soil deposits this paper presents a case study of an investigation into the responses of the surrounding ground to the horizontal twin jet grouting method htjgm in soft soil deposits of shanghai during the fi

groundwater control around a large basement melbourne s crown casino was constructed on a site bordering the yarra river and underlain by problem soils of the coode island silt formation the development needed to provide two levels of basement car park over the entire site an innovative approach to groundwater control around the excavation was required to avoid depressurisation of adjoining soils leading to settlements analysis showed a conventional bentonite cut off wall would still allow depressurisation by lateral flow through the coode island silt during the construction period the high cost and construction difficulty of a very low permeability wall mitigated against it an hydraulic wall was proposed in conjunction with a conventional cut off wall this comprised a curtain of wick drains surrounding the cut off wall and charged with water control of seepage through an underlying aquifer by a cut off wall was considered but a more cost effective method using recharge by wells was adopted when shown necessary monitoring of groundwater p

spatial and temporal variation of seismic attenuation during hydraulic fracturing of a sandstone block subjected to triaxial stress q factors estimated with spectral ratios describe the attenuation experienced by seismic arrivals in their travel from the source s to the receiver s when q is not the same along the travel path of each arrival the formulation must incorporate two q factors making the problem indeterminate here we show that by assuming that q is a random variable the parameters of its probability distribution can be recovered through a mapping workflow using the spectral ratios an advantage of such a workflow is that uncertainties in source location and velocity model can also be incorporated by representing these elements as random variables we apply such a methodology to an acoustic emission ae dataset from a laboratory experiment of hydraulic fracturing in a colton sandstone block we assume that the probability distribution of q is normal anisotropic mean q values correlate with the triaxial stress conditions imposed at the boundaries of the block with higher stress corresponding with less attenuation the q values estimated within time intervals in the direction perpendicular to the hydraulic fracture plane correlate with stress build up at the borehole during fracture propagation and borehole pressure relaxation or drop during fracture closure the standard deviations q reflect the attenuation heterogeneity within the sampled regions an increase in heterogeneity is correlated with pressure build up at the borehole which we interpret to reflect a dynamic stress gradient formed from the hydraulic fracture towards the surroundings

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

tan lu fault system and its significance in oil accumulation in the central liaodong bay subbasin bohai bay basin china the tan lu fault system in the central liaodong bay subbasin bohai bay basin has complex structural characteristics and its tectonism during the cenozoic is an important factor in oil accumulation three dimensional seismic data were used to document the structural features and evolution of the system variations in source rock occurrence oil catchment area and faulting intensity were comprehensively evaluated to discuss the heterogeneity of oil occurrence along the system detailed analysis of the seismic data indicates a right lateral slip for the tan lu fault system transpression and transtension occur on two branches of the tan lu fault with different orientations indicating a likely slip azimuth that is between the two orientations i e 30 35 the strike slip began at the middle stage of deposition of the shahejie formation and reached its climax during deposition of the first and second members of the dongying formation to date the slip is still continuing in the transpressional system the lower strata on opposite sides of the strike slip fault were shortened and folded whereby the upper strata were stretched and normal faulted as a result a negative flower structure developed immediately above a positive flower structure strain distribution in this system is similar to that in a classic fold moderate tectonic deformation could enlarge the oil catchment area benefiting oil accumulation weak or intense deformation is unfavorable for commercial oil accumulation because of a small oil catchment area and poor oil preservation respectively

simultaneous inversion for microseismic event location and velocity model in vaca muerta formation velocity models play a key role in locating microseismic events however it is usually challenging to construct them reliably traditional model building strategies depend on availability of well logs or perforation shots we simultaneously invert for microseismic event locations and a velocity model under the bayesian inference framework and apply it in a field dataset acquired in the vaca muerta formation at neuquen argentina this methodology enables uncertainty and posterior covariance analysis by matching the moveouts of the p and s wave arrival times we were able to estimate a 1d velocity model to achieve improved event locations various analyses indicate the superiority of this model over a model built with the traditional strategy with this algorithm we can perform microseismic monitoring to fracturing treatments where no perforation data is available in addition we can also apply it for long term passive seismicity reservoir monitoring where changes of reservoir properties are expected

the geometry and evolution of a transpressional strike slip system the carboneras fault se spain the carboneras fault system is a 40 km long 1 km wide neogene ne sw trending left lateral transpressional strike slip fault system which is part of the trans alboran shear zone in se spain the carboneras fault system is an anastomosing array of sub vertical individual fault planes or fault zones which surround pods or lenses of less intensely strained rocks displacements along the individual fault planes exhibit reverse components of slips and form positive flower structures faults have either sharp boundaries or wider bands of gouge typically a few metres thick and are hundreds of metres in length second order fault splays are well developed and usually exhibit p shear rather than riedel shear orientations these are interpreted to be related to the transpressional displacement and may also characterize other oblique convergent zones elsewhere the second order faults are interpreted to have formed as shear strain increased along the first order fault and was transferred laterally to branch segments this process produced pods or shear lenses bounded by the fault segments the length to width aspect ratios of the shear lenses were found to be scale independent across five orders of magnitude with the most common values between 3 l and 6 l a model is proposed for the development of the fault zone by incremental finite displacements along the segmented fault surfaces this model is based on field evidence that displacement switched with time from one fault strand to another

workability compressibility and hydraulic conductivity of zeolite amended clayey soil calcium bentonite backfills for slurry trench cutoff walls soil bentonite slurry trench cutoff walls using backfill consisting of on site sandy soil and na bentonite are extensively used as engineering barriers for the purpose of achieving relatively low hydraulic conductivity the amendments such as zeolite to backfill are considered to improve the contaminant sorptive capacity at some sites local clayey soil ca bentonite and natural zeolite may be available for an alternate backfill however studies on the workability in terms of slump compressibility and hydraulic conductivity of such zeolite amended clayey soil ca bentonite backfills for the cutoff walls are very limited this paper presents a comprehensive laboratory investigation on the workability compressibility and hydraulic conductivity of fine grained zeolite amended clayey soil ca bentonite backfills using several series of slump and oedometer tests kaolin is used as the model clayey soil and it is amended with various amounts of ca bentonite 7 8 8 4 and zeolite 10 40 to prepare zeolite amended kaolin bentonite backfills the test results are compared with previous studies on zeolite amended sandy soil na bentonite backfills as well as compacted zeolite bentonite liners to assess the effects of zeolite content and zeolite grain size on the compressibility and hydraulic conductivity the results indicate that the water content required to achieve a target slump 100 150 mm for the backfills increases with increasing zeolite content liquid limit can be a useful index for a preliminary estimation of the water content required to achieve the target slump for the backfills presented in this study and zeolite amended sandy soil na bentonite backfills reported in previous studies the results reveal that the hydraulic conductivity of the zeolite amended clayey soil ca bentonite backfills with void ratio ranging from 0 54 to 1 45 is generally lower than the typical regulatory limit 10 9 m s the addition of fine grained zeolite has insignificant influence on the compressibility and hydraulic conductivity of both clayey soil ca bentonite and sandy soil na bentonite backfills a proposed empirical method based on the framework of kozeny carman equation can predict the hydraulic conductivity of zeolite amended clayey soil ca bentonite backfills values within the range of 1 3 to 3 times those calculated from the oedometer tests the proposed method is also shown to estimate the hydraulic conductivity of the compacted zeolite bentonite liners from previous studies with reasonable accuracy additional research is recommended to evaluate the proposed zeolite amended backfill using tap water and also by direct measurement of hydraulic conductivity using falling head or constant head testing method