undrained shear strength of a glacial clay overconsolidated by desiccation block samples of a boston blue clay crust were used in a detailed study of the relationship between undrained shear strength and consolidation pressure in the compression and extension shear modes the glacial silty clay sample that was mainly composed of quartz feldspar illite and chlorite has developed an overconsolidation ratio near to 3 0 by desiccation the in situ coefficient of earth pressure at rest was near to 0 9 as compared to k0p 0 56 of the normally consolidated young clay in the compression range beyond the preconsolidation pressure in the compression range for each consolidation shear mode undrained shear strength to vertical consolidation pressure ratio as well as shearing induced pore water pressure to vertical consolidation pressure ratio friction angle mobilized at yield and the coefficient of earth pressure at rest were constant and independent of consolidation pressure the mobilized undrained shear strength of the normally consolidated young clay obtained by consolidating s

an experimental study of soil memory and preconsolidation adjacent to an active tectonic structure the meers fault oklahoma usa abstract special consolidation tests were run on undisturbed samples to study the ability of quaternary soils adjacent to the meers fault in southwestern oklahoma to record and remember the maximum effective preconsolidation stresses they experienced during the faulting process the results show that the soils record 60 of the applied total stresses as preconsolidation stresses in 2 s of loading time indicating that these stresses could have been recorded during an earthquake faulting event to record all of the applied total stresses as preconsolidation stresses 100 recording or memory the loading needs to last at least 4 5 min

mapping ground subsidence induced by aquifer overexploitation using advanced differential sar interferometry vega media of the segura river se spain case study differential sar interferometry dinsar is a remote sensing technique with the well proven ability to monitor ground deformations in this work we have applied an advanced dinsar technique the coherent pixels technique cpt to study subsidence phenomena due to the excessive pumping of groundwater in the vega media of the segura river se spain from 1993 to the present the settlement map retrieved with dinsar shows settlement of up to 8 cm at some points of the study area and has been compared with other data provided by ground instruments to analyse the relationship with ground deformation a correlation has been observed between these measurements and the observations from on site testing of piezometric groundwater fluctuations and borehole extensometric settlement however the distribution of damaged buildings well points and basements does not show a clear relationship with measured subsidence values because the occurrence of damage also depends on the structural state of the buildings and the characteristics of their foundations in addition the distribution of pumping wells is not indicative of the distribution of the volume of water withdrawal which is the real conditioning factor of piezometric level changes it can be concluded that the results obtained provide very useful spatial and temporal data about this phenomenon in an urban area at a low cost the data can be used for forecasting purposes and helps to define zones with future ground settlement problems if the same conditions are repeated this technique has also allowed the monitoring of ground subsidence in the vega media of segura river for a period 1993 1995 where no instrument information was available

on the evaluation of undrained shear strength and preconsolidation pressure from common field tests in clay the undrained shear strength is a key parameter in the estimation of the stability of natural slopes and man made constructions in soft clay it is therefore important to develop relevant methods to evaluate the operative strength results from an investigation regarding the effect of excavations at slope crests to increase the stability of clay slopes are presented this study has provided an opportunity to study the effect of overconsolidation on the evaluated parameters from common in situ tests in homogeneous and truly overconsolidated clays certain inconsistencies in the commonly used methods of interpretation of field vane tests cone penetration tests and dilatometer tests are highlighted and modified interpretation methods taking the effects of overconsolidation into account are proposed key words clay overconsolidation undrained shear strength cone penetration test field vane test dilatometer test

india eurasia collision chronology has implications for crustal shortening and driving mechanism of plates the motion of the indian plate is determined in an absolute frame of reference and compared with the position of the southern margin of eurasia deduced from palaeomagnetic data in tibet the 2 600 900 km of continental crust shortening observed is shown to have occurred in three different episodes subduction of continental crust intracontinental thrusting and internal deformation and lateral extrusion the detailed chronology of the collision and plate reorganizations in the indian and pacific oceans supports the hypothesis that slab pull is a dominant driving mechanism of plate tectonics

numerical simulation and prediction of regional land subsidence caused by groundwater exploitation in the southwest plain of tehran iran abstract this study characterizes land subsidence in southwest plain of tehran using numerical modeling and predicts the trend through 2018 excessive groundwater withdrawal has caused severe land subsidence in tehran in the past 28 years 1984 2012 groundwater level has decreased 11 65 m the multi layered aquifer system in the southwestern plain of tehran contains three aquifers and three aquitard units the present model was developed simulation using pmwin modflow for windows first groundwater level and land subsidence were simulated for the end of 2004 the model was calibrated using hydraulic head measurements and insar data the simulation results were in fairly good agreement with the measurement results the calibrated and evaluated model was then used to assess the future evolution of land subsidence and for prediction of subsidence through the end of 2018 numerical results show that assuming a constant rate of pumping in the future land subsidence in the southwestern plain of tehran will reach 33 cm by 2018 the study confirmed that land subsidence caused by groundwater pumping is a serious threat to southwest tehran

desiccation of late quaternary inner shelf sediments microfabric observations abstract palaeo desiccated crusts often form at the top of pre holocene shelf sediments during low sea level stands resulting in significant changes in the mechanical properties to assist in understanding these changes and the implications for quaternary geology the microfabric of sediment samples from the inner shelf off hong kong has been studied using scanning electron microscope techniques incorporating the latest methods of quantitative image analysis these studies have been supported by petrographic observations and chemical analyses of the pore fluids holocene marine sediments usually have a honeycomb fabric while pre holocene marine sediments are more compact in regions of high clay content the palaeo desiccated crust often possesses large planar voids filled with coarse silt sized particles this desiccated crust often contains relics of root traces filled with pyrite showing varying degrees of oxidation the release of amorphous iron acts as a cementation agent and binds large silt small sand grains giving a more compact fabric than that in neighbouring regions cementation in the pre holocene marine deposits creates strengthened open fabric arrangements which may initially withstand moderate loads further evidence of desiccation comes from the presence of halite crystals in the pore fluid which has salt concentrations below that of normal sea water

peculiarities of surface wave propagation across central eurasia abstract the recent installation of six broadband digital iris ida seismic stations in the ussr has provided new opportunities for studying surface wave propagation across eurasia group velocities of fundamental rayleigh and love modes between epicenters and these stations were determined for 35 events that occurred since april 1989 to the middle of july 1990 near eurasia differential phase velocities were found for the same arrivals along paths between several pairs of stations group and phase velocities were obtained in the period range from 15 to 300 sec frequency time polarization analysis was used for studying polarization properties of surface waves in some cases significant anomalies in the particle motion for periods up to 100 sec were observed they are attributed to surface wave refraction and scattering due to lateral inhomogeneities at the boundaries and inside the eurasia continent

crustal mass budget and recycling during the india asia collision abstract the long lasting collision between india and asia has resulted in crustal and lithospheric deformation of both continents providing unequalled opportunities to evaluate their long term mechanisms of deformation we have quantified a crustal mass budget for the collision by comparing the present day and initial crustal volumes of the indian and asian continents involved in the collision initial crustal thickness was estimated from the non deformed parts of the continents whereas their initial extent was mapped from their contours at the onset of collision using seismic tomography we quantify the portion of the initial crustal thickness of both continents stored within the currently thickened crust or redistributed due to extrusion for the indian continent this portion amounts to about 19 km far lower than the mean observed present day crustal thickness of the indian craton of about 38 km we conclude that between 40 and 50 of indian crust has been recycled into the mantle by continental subduction corresponding to a decoupling level at about 15 19 km depth for the asian continent the estimated crustal thickness stored during collision is about 33 km close to the initial asian crustal thickness we estimate that only 3 of the asian crust was recycled into the mantle this corresponds to one episode of continental subduction occurring most probably soon after the initiation of collision along the bangong suture we identify the related slab using seismic tomography the strong contrast between india and asia implies an age dependent capacity of the continental crust to be recycled into the mantle this result has to be taken into account for further analysis of global crustal recycling during earth s history

lithospheric structure of the south central united states recent seismic data in the ouachita mountains area and the gulf of mexico make it possible to construct a lithospheric scale cross section transect from the midcontinent region to the gulf the authors constructed a transect in the form of a gravity model but it incorporates all available seismic drill hole and geologic data as constraints the thrust sheets of the ouachita orogenic belt appear as a thin veneer covering the southern part of the arkoma basin and the preserved paleozoic continental margin mesozoic rifting is evident in three areas 1 southern arkansas and northern louisiana where extension was minor 2 the vicinity of the texas louisiana coastline where modification of the lithosphere and subsidence were considerable and 3 the deep gulf of mexico where rifting was successful a significant variation in the average density of the mantle which could delineate the north american craton as a lithospheric feature was detected near the paleozoic continental margin

crustal and upper mantle structure in the amazon region brazil determined with broadband mobile stations 1 three broadband stations operated from march 1997 to september 1998 in the amazon region north of manaus brazil which including the iris station ptga pitinga covered an area of roughly 60 200 km applying the receiver function technique to determine the crustal structure there is evidence for an increase of the moho depth from about 38 km below the amazon basin to approximately 48 km north of the basin in addition we analyzed the polarization of sks waves to determine anisotropy the observed splitting parameters in a majority of the data set can be accounted for by a layer of axial symmetric anisotropy with the fast direction oriented roughly n110e this direction cannot be associated with the present day plate motion of the south american plate however the anisotropy may be related to a lithospheric fabric that was generated during the early tectonic history of the amazonian craton

engineering geological model of the segura river flood plain se spain a case study for engineering planning this article presents a sedimentological and geotechnical study of the surficial sediments in the segura river valley se spain we formulate an engineering geological model consisting of four zones each characterized by its geotechnical properties and by various geotechnical problems namely low bearing capacity significant ground settlement and liquefaction of sandy sediments the model quantifies the geotechnical properties and potential problems in each zone it serves as a useful tool for preliminary geotechnical investigations the model also enables a better design of field surveys as well as optimal selection of geotechnical investigation techniques for future civil engineering works

influence of geology and geological processes on the geotechnical properties of a plastic clay abstract the complex properties of postglacial clay at winnipeg canada have major impact on civil engineering construction in the city problems include house foundation movements low stability of riverbanks poor highway pavement performance difficult excavation and a high incidence of watermain breaks the research in this paper presents an understanding of the geologic factors that cause these problems and how to ameliorate their effects in engineering design the geotechnical properties of the clay were measured from carefully sampled 76 mm diameter triaxial specimens the clay is nonhomogeneous anisotropic active overconsolidated and fissured these properties are related to the depositional and post depositional geology of the area the depositional geology of the extensive lake agassiz clays is straightforward and well known however it does not fully explain the measured geotechnical properties attention is then directed towards post depositional geological processes such as regional groundwater hydrology cementation aging freeze thaw and desiccation consideration of effective stress strengths quasi elastic anisotropy the variation of overconsolidation ratio with depth yielding and porewater pressure generation suggests strongly that the clay is cemented by carbonates and sulphates from upwards movement of salt rich groundwater freeze thaw disturbance causes marked changes in behaviour especially at low stresses

preconsolidation stress of aquifer systems in areas of induced land subsidence aquifer systems in the eloy picacho area arizona the houston galveston area texas and the tulare wasco area and santa clara valley california appear to have been overconsolidated by an amount that ranged approximately from 1 6 to 6 2 bars 16 to 63 m of water before man began to withdraw groundwater from them the relation between land subsidence and water level decline in these areas consists of two linear segments in these areas subsidence per unit water level decline was approximately constant until water levels had declined an amount that ranged from 16 to 63 m when water levels declined past these values subsidence per unit water level decline increased to larger constant values although slow drainage from aquitards may have contributed to this response it is interpreted here to be caused primarily by natural overconsolidation of the compacting part of the aquifer system the water level decline at which the ratio of subsidence to unit water level decline changed indicates approximately the amount by which the preconsolidation stress exceeded the overburden stress on the aquifer system that existed before groundwater withdrawals began

regional tectonic framework structure and evolution of the western marginal basins of india abstract the kutch saurashtra cambay and narmada basins are pericontinental rift basins in the western margin of the indian craton these basins were formed by rifting along precambrian tectonic trends interplay of three major precambrian tectonic trends of western india dharwar nnw sse aravalli delhi ne sw and satpura ene wsw controlled the tectonic style of the basins the geological history of the basins indicates that these basins were formed by sequential reactivation of primordial faults the kutch basin opened up first in the early jurassic rifting was initiated in late triassic along the delhi trend followed by the cambay basin in the early cretaceous along the dharwar trend and the narmada basin in late cretaceous time along the satpura trend the evolution of the basins took place in four stages these stages are synchronous with the important events in the evolution of the indian sub continent its breakup from gondwanaland in the late triassic early jurassic its northward drifting during the jurassic cretaceous and collision with the asian continent in the early tertiary the most important tectonic events occurred in late cretaceous time the present style of the continental margins of india evolved during early tertiary time the saurashtra arch the extension of the aravalli range across the western continental shelf subsided along the eastern margin fault of the cambay basin during the early cretaceous it formed an extensive depositional platform continuous with the kutch shelf for the accumulation of thick deltaic sediments a part of the saurashtra arch was uplifted as a horst during the main tectonic phase in the late cretaceous the present high thermal regime of the cambay bombay high region is suggestive of a renewed rifting phase

preconsolidation stress in the vega baja and media areas of the river segura se spain causes and relationship with piezometric level changes financiado por el ministerio de ciencia y tecnologia y feder proyecto tec 2005 06863 por la generalitat valenciana proyecto gv06 179 y grupos03 085 y por la universidad de alicante proyecto vigrob 157

the 2001 bhuj earthquake tomographic evidence for fluids at the hypocenter and its implications for rupture nucleation 1 the january 26 2001 bhuj earthquake mw 7 6 is one of the most catastrophic indian earthquakes we have investigated the 3 d seismic velocity and poisson s ratio structures of the bhuj source area to understand the probable cause of triggering the earthquake we used 1948 p and 1865 s wave high quality arrival times from 331 aftershocks recorded at a temporary seismic network significant variations up to 5 in velocity and 10 in poisson s ratio are revealed in the aftershock area the mainshock is located in a distinctive zone characterized by high vp low vs and high poisson s ratio in the depth range of 20 to 30 km and extending 15 to 30 km laterally this feature is very similar to that of the 1995 kobe earthquake zhao et al 1996 the anomaly may be due to a fluid filled fractured rock matrix which might have contributed to the initiation of the bhuj earthquake

passive source seismic imaging of the crust and upper mantle beneath the 2001 mw 7 7 bhuj earthquake region gujarat india abstract variations in crustal and lithospheric thicknesses below the kachchh rift kr zone have been investigated employing the joint inversion of p receiver functions rf and rayleigh wave and love wave group velocity dispersion 5 70 s on the broadband waveforms of teleseismic events estimated crustal and lithospheric thicknesses at 15 broadband sites led to the delineation of an updoming of 4 7 km in the moho and 6 12 km in the asthenosphere beneath the central kr relative to the surrounding unrifted regions the moho depths vary from 35 to 42 km and lithospheric thicknesses range from 62 to 78 km the observed marked shear velocity reduction 2 6 at the lithosphere asthenosphere boundary lab over an area of 120 km 80 km suggests the presence of patches of partial melt in the asthenosphere below the kr evidencing the possible presence of imprints of the deccan reunion mantle plume the coincidence of the area of updoming of the moho and asthenosphere and the confined aftershock activity below the central kr implies that these patches could provide a high input of volatile co 2 into the lower crust which might play a key role in generating the continued aftershock activity in the region since the occurrence of the 2001 m w 7 7 bhuj mainshock

geologic and geotechnical effects of an impact caused by an airplane crash abstract a turkish airlines thy boeing 737 400 plane crashed into alluvial soils creating an approximately 13 m deep and 30 m wide crater near the village of adatepe ceyhan in southern turkey effects of the impact on the soils in and around the crater were investigated from both the geological and soil mechanics point of view the results show that the impact caused severe deformations in the soils in and around the crater the soils deformed similar to metamorphic rocks seen at many terrestrial hypervelocity impact craters around the world and became overconsolidated up to a distance of about 10 m from the crater wall as a result of the impact also the crash was recorded as a 2 7 magnitude earthquake by a nearby microtremor seismograph which provided both the location epicenter and time of the crash which was not known immediately after the crash

the deadliest intraplate earthquake the recent earthquake in the bhuj region took a toll of at least 30 000 lives in their perspective gupta et al 1 discuss what may be the cause of the large but infrequent earthquakes in this region which is not near any tectonic plate boundary the earthquake hazard in the region was well recognized before the disaster however and adherence to the building codes for high risk areas may have prevented much human tragedy 1 http www sciencemag org cgi content full 291 5511 2101

study of the land subsidence in orihuela city se spain using psi data distribution evolution and correlation with conditioning and triggering factors this paper presents a study about the subsidence affecting the city of orihuela placed on the western sector of the vega baja of the segura river basin se spain the study is based on deformation data obtained by differential sar interferometry dinsar and more precisely by the coherent pixels technique cpt an algorithm of the persistent scatterers interferometry psi family images acquired between june 1993 and april 2009 by ers and envisat satellite sensors have been processed by the cpt technique in order to retrieve the ground subsidence affecting this area accumulated deformation maps and displacement time series are analyzed moreover these data have been contrasted with subsidence triggering and conditioning factors by means of a geographical information system gis interface the performed analysis shows that there exists a relationship between subsidence and piezometric level evolution in time moreover the correlations among subsidence and location of pumping wells distance to the river geology and soil thickness have been derived from this analysis