afterslip evolution on the crustal ramp of the main himalayan thrust fault following the 2015 mw 7 8 gorkha nepal earthquake abstract current afterslip models of the mw 7 8 gorkha earthquake contradict with the depth ranges of relocated aftershock distribution and inter seismic locked creeping transition zone we use both gps and interferometric synthetic aperture radar insar data to image the afterslip evolution in the first 189 post seismic days i e from 25 april to 1 november 2015 in the study region 51 gps stations are divided into three categories based on their observation time 1 25 stations with both pre and post seismic observations 2 16 stations with only post seismic observations and 3 10 stations with only pre seismic observations the secular tectonic motion and seasonal variations are corrected carefully and directly using the fitted functions from the pre seismic position time series during the inversions we adopt the widely accepted flat ramp flat geometrical model of the main frontal thrust fault mft main himalayan thrust fault mht the preferred weight ratios between gps and insar observations are elaborately determined through comprehensive analysis of model resolution and fitting residuals in contrast to previous afterslip models our preferred afterslip distributes on the crustal ramp of the mht from depths of 11 to 29 km which is verified by further inversions using only gps data and checkerboard resolution tests the seismic moment released by the afterslip in the first six months is 3 42 1019 n m only approximately 4 of the mainshock moment the rupture gap between the mainshock and the 12 may aftershock is filled up with post seismic aseismic slip

persistent scatterer interferometric synthetic aperture radar for crustal deformation analysis with application to volcan alcedo galapagos 1 while conventional interferometric synthetic aperture radar insar is a very effective technique for measuring crustal deformation almost any interferogram includes large areas where the signals decorrelate and no measurement is possible persistent scatterer ps insar overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms existing ps methods have been very successful in analysis of urban areas where stable angular structures produce efficient reflectors that dominate background scattering however man made structures are absent from most of the earth s surface furthermore existing methods identify ps pixels based on the similarity of their phase history to an assumed model for how deformation varies with time whereas characterizing the temporal pattern of deformation is commonly one of the aims of any deformation study we describe here a method for ps analysis stamps that uses spatial correlation of interferogram phase to find pixels with low phase variance in all terrains with or without buildings prior knowledge of temporal variations in the deformation rate is not required for their identification we apply stamps to volcan alcedo where conventional insar fails because of dense vegetation on the upper volcano flanks that causes most pixels to decorrelate with time we detect two sources of deformation the first we model as a contracting pipe like body which we interpret to be a crystallizing magma chamber the second is downward and lateral motion on the inner slopes of the caldera which we interpret as landsliding

ambient noise tomography of the pyrenees and the surrounding regions inversion for a 3 d vs model in the presence of a very heterogeneous crust we thank all participants in the fieldwork and the municipalities and landlords that hosted a pyrope temporary station we also acknowledge sismob the french seismic mobile pool a com ponent of the resif research facility for providing us with the seismological instrumentation for the temporary deployments we used data from the fr and rd resif g geoscope and ca institut cartogr afic i geol ogic de catalunya permanent net works resif http portal resif fr is a national research infras tructure recognized as such by the french ministry of higher education and research resif is managed by the resif con sortium composed of 18 research institutions and universities in france resif additionally supported by a public grant overseen by the french national research agency anr as part of the investissements d avenir program reference anr 11 eqpx 0040 andthefrenchministryofecology sustainabledevelopment and energy the pyrope experiment was supported by the french research agency anr blanc program project pyrope anr 09 blan 0229 this is a contribution of the team consolider ingenio 2010 topo iberia csd2006 00041 c

petroleum geology of the puguang sour gas field in the sichuan basin sw china abstract the puguang sour gas field in northeastern sichuan basin is the largest gas discovery in the paleozoic marine strata in china with at least 9 trillion cubic feet tcf of proven gas reserves it is one of the many anticlinal structures formed during the indo sinian orogeny with gas being trapped in a composite structure lithology pool the presence of the upper permian coal measures lower silurian and lower cambrian marine shales provided excellent hydrocarbon source rocks the lower triassic and upper permian oolitic dolomites serve as high quality reservoir rocks with 10 25 porosity and 1 1000 md permeability largely due to diagenetically produced secondary porosity the lower and middle triassic evaporate beds have acted as the direct top seal for the large lower triassic upper permian gas accumulation the thick upper triassic and jurassic mudstone beds regionally cap the underlying marine carbonate strata the deep seated basement faults acted as vertical hydrocarbon migration conduits during faulting and became effective flow barriers when the faulting ceased the deep burial of a paleo oil accumulation in reservoirs rich in sulfate resulted in extensive thermochemical sulfate reduction tsr this together with the new gas injection and structural reconfiguration transformed a paleo oil pool to a large sour gas pool

sichuan basin and beyond eastward foreland growth of the tibetan plateau from an integration of late cretaceous cenozoic fission track and u th he ages of the eastern tibetan plateau qinling and daba shan combining 121 new fission track and u th he ages with published thermochronologic data we investigate the late cretaceous cenozoic exhumation cooling history of the eastern tibetan plateau qinling daba shan and sichuan basin of east central china the qinling orogen shows terminal southwestward foreland growth in the northern daba shan thrust belt at 100 90 ma and in the southern daba shan fold belt at 85 70 ma the eastern margin of tibet plateau experienced major exhumation phases at 70 40 ma exhumation rate 0 05 0 08 mm yr 25 15 ma 1 mm yr in the pengguan massif 0 2 mm yr in the imbricated western sichuan basin and since 11 10 ma along the longmen shan 0 80 mm yr and the interior of the eastern tibet plateau dadu river gorge min shan 0 50 mm yr the sichuan basin records two basin wide denudation phases likely a result of the reorganization of the upper yangtze river drainage system the first phase commenced at 45 ma and probably ended before the miocene 1 km of rocks were eroded from the central and eastern sichuan basin the second phase commenced at 12 ma and denudated the central sichuan basin longmen shan and southern daba shan more than 2 km of rocks were eroded after the lower yangtze river had cut through the three gorges and captured the sichuan basin drainage in contrast to the east qinling which was weakly effected by late cenozoic exhumation the west qinling and daba shan have experienced rapid exhumation cooling since 15 13 ma a result of growth of the tibetan plateau beyond the sichuan basin

an investigation of seismicity induced by hydraulic fracturing in the sichuan basin of china based on data from a temporary seismic networkan investigation of seismicity induced by hydraulic fracturing in the sichuan basin

the evolution and environmental significance of glaciochemistry during the ablation period in the north of tibetan plateau china in order to explore the glaciochemistry of shiyi glacier in the central qilian mountains a total of 142 samples have been collected for fresh snow surface snow snowpit and meltwater from july 2012 to november 2013 the results indicated cations dominated the glaciochemistry especially the high ca2 concentration relatively high cl and na concentrations were mainly contributed by desert dust aerosols and the atmospheric aerosols from warm water bodies such as the black caspian and aral seas the analysis also confirmed the chemical ions in fresh snow are mainly contributed by atmospheric wet deposition surface snow is mainly influenced by dry deposition and snowpits are influenced by both atmospheric deposition and leaching process while meltwater is influenced by water rock interactions the profile of ionic concentration in the snowpit became more smoothed during ablation period owing to the influence of leaching the elution sequence of the snowpit in the shiyi glacier was so42 k ca2 mg2 na cl no3 the chemical concentrations for meltwater are mainly influenced by water dilution and soil thawing the ions in snow in the central qilian mountains showed relatively lower concentrations than in the western qilian mountains tianshan mountains and altai mountains it was closer to balance than in glaciers in the central tibetan plateau but was higher than in the southern tibetan plateau different ionic sources and dissolution process had caused the differences of chemical composition for fresh snow surface snow snowpit and meltwater and these chemical compositions reflected the atmospheric background values in the northern tibetan plateau c 2014 elsevier ltd and inqua all rights reserved

topography of the variscan orogen in europe failed not collapsed the variscan orogenic collage consists of three subduction collision systems rheno hercynian saxo thuringian and massif central moldanubian devonian to early carboniferous marine strata are widespread not only in the individual foreland fold and thrust belts but also in post tectonic basins within these foreland belts and on the cadomian crust of peri gondwanan microcontinental fragments which represent the upper plates of the subduction collision zones these marine basins preclude high elevations in the respective areas and also in their neighbourhood widespread late carboniferous intra montane basins with their coal bearing sequences are likewise incompatible with high and dry plateaus while narrow belts with high elevations remain possible along active margins within the orogen comparison of the variscides with the himalaya tibetan plateau is unfounded plausible reasons for the scarcity of high variscan relief include subduction of oceanic and even continental crust subduction erosion orogen parallel extension and most important lithospheric thinning accompanied by high heat flow and magmatism in many areas timing and areal array of magmatism and ht metamorphism are not compatible with a model of tectonic thickening and subsequent gravitational collapse it is suggested instead that lithospheric thinning and heating are due to mantle activities caused by the tethys rift the lower and middle crust were thermally softened and rendered unfit for stacking and isostatic uplift in terms of topography the variscides represent a failed orogen the ht regime also explains the abundance of granitoids and ht lp metamorphic rocks typical of the variscides melting in the ht regime extracted mafic components from variscan and cadomian crust as well as from cadomian metasomatized lithospheric mantle thus mimicking subduction related magmatism the onset of the ht regime at c 340 ma may also have triggered the final ascent of hp uhp felsic metamorphic rocks

variations in melt layer frequency in the gisp2 ice core implications for holocene summer temperatures in central greenland the rare melt features in the gisp2 central greenland deep ice core have decreased in frequency over the most recent 7000 years calibration of this change in melt frequency against modern spatial variation of melt frequency and temperature in central greenland and against modern temporal variability of temperatures in central greenland indicates that mean mid summer temperatures have cooled over the most recent 7000 years probably by slightly more than l c if variability of summer temperatures has not changed comparison to grip isotopic records from central greenland and to the melt record from the agassiz ice cap arctic canada suggests some seasonal and regional coherence for this cooling signal as well as for a cold event about 8000 8500 bp

heat flow heat production and lithospheric thermal regime in the iberian peninsula abstract the first heat flow and heat production maps of the iberian peninsula and its margins using previously acquired data are presented the surface heat flow map includes 553 determinations carried out on water and mining exploration wells oil exploration wells and on the seafloor the surface heat flow varies noticeably from the iberian mainland 65 10 mw m 2 to the atlantic and the mediterranean margins where the heat flow reaches values of about 40 50 mw m 2 and 80 100 mw m 2 respectively the heat production map consists of 664 determinations carried out on rock samples from the variscan iberian massif and the betics the higher values are obtained for granitic rocks 2 5 3 5 w m 3 whereas metasediments and basic rocks reach values of 1 2 5 w m 3 and nearly zero respectively the lithospheric structure deduced for the iberian peninsula by combining heat flow heat production and elevation data indicates that most of the iberian mainland is characterized by a lithospheric thickness of 110 5 km this value is maintained across the west atlantic margin whereas towards the mediterranean margin the lithospheric thickness decreases down to 60 40 km this study also suggests that the heat production in the southern variscan iberian massif must be noticeably higher 3 7 0 5 w m 3 than in the rest of the areas in order to fit the measured heat flow crustal thickness and elevation data

the 2019 m w 5 7 changning earthquake sichuan basin china a shallow doublet with different faulting styles the increased seismic activity of the last 10 years in changning county of sichuan province comprised just small mostly ml 5 0 injection induced earthquakes the mw 5 7 earthquake of june 17 2019 is the largest event ever reported there moment tensor of the mainshock was remarkably dominated by a compensated linear vector dipole we resolve its fine structure showing it was a doublet allowing approximation by a thrust and strike slip subevent the mainshock nucleated as thrust faulting which together with the largest aftershocks can be linked with previously known reverse faults favorably oriented to regional stress field contrarily the strike slip segment of the mainshock less favorably oriented was probably facilitated by elevated pore pressure due to previous injections shallow active strike slip faulting not yet mapped in the region is a new feature important for future hazard assessment

a wide angle seismic reconnaissance survey of the crust and upper mantle in the celtiberian chain of eastern spain abstract data from seismic refraction profiles to investigate the crust and upper mantle in the celtiberian chain are presented and discussed a rather heterogeneous deep crustal structure with lateral variations can be inferred from the available data in the central part of the chain crustal depths of about 32 km are coincident with those in the iberian meseta whereas close to the mediterranean shore the moho is located at about 20 km depth the varying thickness of the crust can be interpreted in terms of different tectonic regimes the shallowing towards the mediterranean is associated with the neogene rifting process which has its main expression in the gulf of valencia but whose effects seem to reach well towards the interior of iberia the upper mantle has a structure typical for the hercynian domain in europe a seismic phase reflected from about 80 km is the most important feature this may be interpreted as a mantle discontinuity with a positive velocity jump or alternatively as an indication for the bottom of the lithosphere

three dimensional gravity and magnetic modeling of crustal indentation and wedging in the western pyrenees cantabrian mountains 1 the complex crustal structure of the boundary zone between the iberian and european plates from the western pyrenees to the cantabrian mountains is probed by three dimensional 3 d gravity and magnetic modeling constrained by deep seismic profiles the 3 d modeling results support the presence of a continuous iberian crustal root and suggest that the geometry of the orogenic belt that formed in latest cretaceous tertiary times along the northern margin of iberia was conditioned by oblique structures separating areas characterized by different tectonic styles in the western pyrenees and the basque cantabrian basin a thick mesozoic basin presently incorporated to the pyrenean cantabrian belt the relatively narrow thinning of the crust inherited from the mesozoic rifting stage conditioned a structural style in which portions of the southward indenting european lower crust are interpreted to be back thrusted toward the north and uplifted to shallow depths promoting the appearance of significant potential field anomalies in the basque cantabrian basin the strongest aeromagnetic anomaly of the whole iberian mainland is superimposed on the eastern part of a well defined positive gravity anomaly similar in amplitude and wavelength to those located along the north pyrenean zone these observations suggest that the eastern part of the dense lower crustal causative body is strongly magnetized and may correspond to a gabbroic cumulate originated in the axis of the ancient mesozoic rift to the west tertiary compression affected the north iberian cantabrian passive continental margin whose geometry and inherited structures conditioned the formation of a double crustal delamination and the uplift of the cantabrian mountains

tectonosedimentary evolution related to extreme crustal thinning ahead of a propagating ocean example of the western pyrenees 1 in this paper we describe the tectonosedimentary evolution and its subsequent inversion of a basin that underwent extreme crustal thinning in a transtensional setting ahead of a propagating ocean in the western pyrenees the labourd mauleon area situated in the western pyrenees at the termination of the v shaped bay of biscay is an ideal natural laboratory to study how such complex basins evolve in time and space because of a mild inversion of the basin during pyrenean compression the rift structures and their relations to basement rocks and sediments are exposed and can be directly studied in the field the basin shows a complex polyphase evolution that starts with left lateral dominated transtension in latest jurassic early aptian time this event is overprinted by a late aptian early albian extension that is related to the counterclockwise rotation of iberia away from europe leading to the opening of the bay of biscay during this stage the late triassic to jurassic carbonate platform was stretched salt migrated and detachment faults exhumed upper and lower crustal and mantle rocks to the seafloor the final structure of the basin resembles a sag basin floored by exhumed rocks overlain by extensional allochthons and compartmentalized by n40 to n60 transfer faults the sedimentary architecture is characterized by late aptian synrift sediments e g urgonian limestones that were deposited in fault bounded basins and are overlain by thick latest aptian to albo cenomanian sediments e g flysch noir that define a sag sequence the complex tectonosedimentary evolution of the basin is associated with salt tectonics and overprinted by a major magmatic thermal event that postdates mantle exhumation

crustal thinning in the southwestern iberia margin the mode of crustal thinning in the southwestern margin of the iberian peninsula is investigated along a transect that extends from onshore iberia to the eastern end of the horseshoe abyssal plain on onshore areas the crustal structure has been deduced using wide angle seismic reflection data whereas offshore we have used coincident steep and wide angle reflection data along a ne sw oriented seismic profile that extends from cape san vicente to the horseshoe abyssal plain in addition 2d gravity modelling has been performed to validate the crustal structure deduced from seismic data our model results reveal that the crust undergoes a strong but continuous thinning from 31 km onshore iberia to less than 15 km in the horseshoe abyssal plain and that thinning occurs over horizontal distances of about 120 km

high rate injection is associated with the increase in u s mid continent seismicity an unprecedented increase in earthquakes in the u s mid continent began in 2009 many of these earthquakes have been documented as induced by wastewater injection we examine the relationship between wastewater injection and u s mid continent seismicity using a newly assembled injection well database for the central and eastern united states we find that the entire increase in earthquake rate is associated with fluid injection wells high rate injection wells 300 000 barrels per month are much more likely to be associated with earthquakes than lower rate wells at the scale of our study a well s cumulative injected volume monthly wellhead pressure depth and proximity to crystalline basement do not strongly correlate with earthquake association managing injection rates may be a useful tool to minimize the likelihood of induced earthquakes

melt features in ice cores from site j southern greenland some implications for summer climate since ad 1550 horizontal and vertical distributions of melt features ice layers were examined using two ice cores 206 6 and 101 5 m deep 1 m apart from site j 66 51 9 n 46 15 9 w 2030 m a s l the temperature at 10 m was 16 3 c we observed 2804 melt features with a total thickness of 30 32 m in the 206 6 m core corresponding to 16 4 by volume of the ice equivalent core length horizontal distribution of melt features was examined by correlating melt feature thicknesses in the two cores the correlation coefficient was 0 71 n 514 for each melt feature in the two cores it was maximum for data passed through 5 and 40 year low pass filters a significant relationship p 0 005 n 36 was obtained for the vertical distribution of melt features and the june temperature on the west coast of greenland jakobshavn using this june temperatures at jakobshavn since 1550 were estimated there are three periods 1685 1705 1835 70 and 1933 45 during which mean june temperatures clearly decreased when they were estimated to he 0 1 0 4 and 0 2 c lower than the average for the whole period 1550 1989 the first two cold periods have been identified in melt features of the dye 3 and devon island ice cores and in a tree ring profile from yukon territory canada melt feature percentages in the site j ice core have increased since about 1945 probably reflecting summer temperature warming on the ice sheet

on the tectonic origin of iberian topography the present day topography of the iberian peninsula can be considered as the result of the mesozoiccenozo ic tectonic evolution of the iberian plate including rifting and basin formation during the mesozoic and compression and mountain building processes at the borders and inner part of the plate during the tertiary followed by neogene rifting on the mediterranean side and surface processes acting during the quaternary the northern central part of iberia corresponding to the geological units of the duero basin the iberian chain and the central system shows a mean elevation close to one thousand meters above sea level in average some hundreds of meters higher than the southern half of the iberian plate this elevated area corresponds to i the top of sedimentation in tertiary terrestrial endorheic sedimentary basins paleogene and neogene and ii planation surfaces developed on paleozoic and mesozoic rocks of the mountain chains surrounding the tertiary sedimentary basins both types of surfaces can be found in continuity along the margins of some of the tertiary basins the bouguer anomaly map of the iberian peninsula indicates negative anomalies related to thickening of the continental crust correlations of elevation to crustal thickness and elevation to bouguer anomalies indicate that the dierent landscape units within the iberian plate can be ascribed to dierent patterns 1 the negative bouguer anomaly in the iberian plate shows a rough correlation with elevation the most important gravity anomalies being linked to the iberian chain 2 most part of the so called iberian meseta is linked to intermediate elevation areas with crustal thickening this pattern can be applied to the two main intraplate mountain chains iberian chain and central system 3 the main mountain chains pyrenees and betics show a direct correlation between crustal thickness and elevation with higher elevation crustal thickness ratio for the central systemvs the betics and the pyrenees other features of the iberian topography namely the longitudinal pro le of the main rivers in the iberian peninsula and the distribution of present day endorheic areas are consistent with the tertiary tectonic evolution and the change from an endorheic to an exorheic regime during the late neogene and the quaternary some of the problems involving the timing and development of the iberian meseta can be analysed considering the youngest reference level constituted by the shallow marine upper cretaceous limestones that indicates strong dierences induced by i the overall tertiary and recent compression in the iberian plate responsible for dierences in elevation of the reference level of more than 6 km between the mountain chains and the endorheic basins and ii the eect of neogene extension in the mediterranean margin responsible for lowering several thousands of meters toward the east and uplift of rift shoulders a part of the recent uplift within the iberian plate can be attributed o sostatic uplift in zones of crustal thickening

the elution of ions through field and laboratory snowpacks it has been recognised for many years that the first fraction of meltwater from a melting snowpack contains a much higher concentration of ions than that of the bulk or average snow of which the pack is comprised foster 1 978 johannessen and henriksen 1978 this process leads to the so called acid flush in the spring and can have severe ecological effects on lakes and streams hagen and langeland 1 973 leivestad and muniz 1 976 national research council of canada 1 981 we have studied elution of ions through a snowpack on folgefonna near bergen norway and in the laboratory in the field we collected meltwater samples at hourly intervals for a period of 4 d at the start of the melt season and analyzed them for ph no so ci na mg2 ca2 and k 2 m cores were also collected at the beginning and end of the experiment in order to study bulk changes in snow composition the meltwaters showed a diurnal cycle with high ionic concentrations around noon with no and so levels rising by factors of up to four and six fold compared to the average concentrations on the first day cllevels peaked much later after the no and so levels had decreased and only reached 2 3 times their lowest concentrations ph values were strongly correlated with no and s02levels suggesting that a significant proportion of these ani ns wer in the form of strong acids the laboratory experiments involved slow melting of snow samples collected in the cairngorm mountains scotland and also showed that no and so and also mg2 and k ions were removed from the snow preferentially whilst na and cltended to remain longer the position of h within the ion elution sequence is unclear due to uncertainties in the absolute determination of ph in the field measurements but the laboratory experiments confirm the differential rates of elution shown in the norwegian snowpack and reaffirms its importance in the acidification of streams during spring

tethys atlantic interaction along the iberia africa plate boundary the betic rif orogenic system abstract initial se dipping slow subduction of the ligurian tethys lithosphere beneath africa from late cretaceous to middle oligocene twisting to a later faster e dipping subduction of the subcrustal lithosphere is proposed as an efficient geodynamic mechanism to structure the arcuate betic rif orogenic system this new subduction related geodynamic scenario is supported by a kinematic model constrained by well dated plate reconstructions tectonic sedimentary and metamorphic data sets the slow initial se dipping subduction of the ligurian tethys realm beneath the malaguide upper plate unit is sufficient to subduct alpujarride and nevado filabride rocks to few tens of kilometers of depth in middle eocene times the shift from se to e dipping subduction during latest oligocene early miocene was possibly caused by both the inherited geometry of the highly segmented ligurian tethys domain and by the fast roll back of the subducted lithospheric slab the early miocene rather synchronous multiple crustal and subcrustal processes comprising the collision along the betic front the exhumation of the hp lt metamorphic complexes the opening of the alboran basin its flooring by hp alpujarride rocks and subsequent ht imprint can be explained by the fast nw and w directed roll back of the ligurian tethys subcrustal lithospheric slab the w retreat of the ligurian tethys lithosphere in middle late miocene times could partly explain the initiation of its lateral tear and consequent subcrustal processes from latest miocene onward the betic rif system evolved under both the northerly push of africa resulting in tightening at crustal and subcrustal levels and by the distinct current dynamics of the steep lithospheric slab the sw directed scape of the rif fold belt is one of the most striking evidences linked to the recent evolution of the squeezed betic rif system between africa and iberia

inversion of surface deformation data for rapid estimates of source parameters and uncertainties a bayesian approach new satellite missions e g the european space agency s sentinel 1 constellation advances in data downlinking and rapid product generation now provide us with the ability to access space geodetic data within hours of their acquisition to truly take advantage of this opportunity we need to be able to interpret geodetic data in a prompt and robust manner here we present a bayesian approach for the inversion of multiple geodetic data sets that allows a rapid characterization of posterior probability density functions pdfs of source model parameters the inversion algorithm efficiently samples posterior pdfs through a markov chain monte carlo method incorporating the metropolis hastings algorithm with automatic step size selection we apply our approach to synthetic geodetic data simulating deformation of magmatic origin and demonstrate its ability to retrieve known source parameters we also apply the inversion algorithm to interferometric synthetic aperture radar data measuring co seismic displacements for a thrust faulting earthquake 2015 mw 6 4 pishan earthquake china and retrieve optimal source parameters and associated uncertainties given its robustness and rapidity in estimating deformation source parameters and uncertainties our bayesian framework is capable of taking advantage of real time geodetic measurements thus our approach can be applied to geodetic data to study magmatic tectonic and other geophysical processes especially in rapid response operational settings e g volcano observatories our algorithm is fully implemented in a matlab based software package geodetic bayesian inversion software that we make freely available to the scientific community

evidence for slab rollback in westernmost mediterranean from improved upper mantle imaging this work is funded by the picasso project nsf grant ear 0808939 the deployment and data processing for spanish stations was funded by consolider ingenio 2010 project topo iberia csd2006 00041 as well as alert es cgl2010 19803 c03 02

geophysical evidence of a mantle derived intrusion in sw iberia 1 deep seismic reflection data acquired as part of the sw iberia europrobe project across the transpressional variscan orogen sample three tectonic terranes the south portuguese zone the ossa morena zone and the central iberian zone the seismic data reveal the existence of a mid crustal reflective body 140 km long and of variable thickness up to 5 km the iberian reflective body the conductivity image provided by coincident mt soundings the amplitude characteristics of the seismics mineralization studies related to magmatic ore deposits and the surface geology suggest that the irb is a mantle derived mafic intrusion the geophysical geological and petrological data suggest that the irb is most probably an early carboniferous approximately at 350 340 ma mantle derived intrusion possibly linked to plume activity that took place in europe in the carboniferous and permian

crustal deformation in the india eurasia collision zone from 25 years of gps measurements the india eurasia collision zone is the largest deforming region on the planet direct measurements of present day deformation from global positioning system gps have the potential to discriminate between competing models of continental tectonics but the increasing spatial resolution and accuracy of observations have only led to increasingly complex realizations of competing models here we present the most complete accurate and up to date velocity field for india eurasia available comprising 2576 velocities measured during 1991 2015 the core of our velocity field is from the crustal movement observation network of china i ii 27 continuous stations observed since 1999 56 campaign stations observed annually during 1998 2007 1000 campaign stations observed in 1999 2001 2004 and 2007 260 continuous stations operating since late 2010 and 2000 campaign stations observed in 2009 2011 2013 and 2015 we process these data and combine the solutions in a consistent reference frame with stations from the global strain rate model compilation then invert for continuous velocity and strain rate fields we update geodetic slip rates for the major faults some vary along strike and find that those along the major tibetan strike slip faults are in good agreement with recent geological estimates the velocity field shows several large undeforming areas strain focused around some major faults areas of diffuse strain and dilation of the high plateau we suggest that a new generation of dynamic models incorporating strength variations and strain weakening mechanisms is required to explain the key observations seismic hazard in much of the region is elevated not just near the major faults

lithospheric structure beneath the alboran basin results from 3d gravity modeling and tectonic relevance a three dimensional gravity modeling combined with integrated heat flow and elevation modeling is conducted to map out the crustal and lithospheric mantle thickness in the alboran basin in the westernmost mediterranean a sediment corrected bouguer anomaly has been derived using a depth to the basement map and densities determined from well logs and seismic data the gravity effect of the base of the lithosphere has been removed from the sediment corrected bouguer anomaly to obtain a crustal bouguer anomaly which has been inverted for crustal thickness the resulting lithospheric structure is further constrained by elevation data under the assumption of local isostasy the low residual elevation anomalies obtained 100 m in average suggest that the area is in local isostasy particularly the medium and long wavelength topography features variations in crustal thickness range from 36 km underneath the betic and rif chains to 12 km beneath the easternmost part of the alboran sea basin in the transition to the south balearic basin in western alboran the moho lies at a rather constant depth of 18 km deepening sharply toward the gibraltar strait down to 30 32 km the base of the lithosphere shallows from 140 km depth in the gibraltar strait to 45 km depth in the easternmost alboran sea lithospheric thinning penetrates to the southeastern side of the iberian margin crosscutting topographic highs of the central and eastern betic chain our results favor mantle delamination produced by detachment and subsequent peeling away of the lithospheric mantle rather than convective removal of the lithospheric mantle either by orogenic collapse or detachment and sinking of a lithospheric slab

ongoing lithospheric removal in the western mediterranean evidence from ps receiver functions and thermobarometry of neogene basalts picasso project the western mediterranean tectonic system consists of the betic mountains in southern spain and the rif mountains in northern morocco curved around the back arc extensional alboran basin multiple tectonic models have been developed to explain the coeval compressional and extensional tectonic processes that have affected the western mediterranean since the oligocene in order to provide constraints on these evolutionary models we use ps teleseismic receiver functions rf thermobarometric analyses of post oligocene basalts and previous teleseismic tomography images to investigate the lithospheric structure of the region ps rfs were calculated using seismic data from 239 broadband seismic stations in southern iberia and northern morocco and thermobarometric analysis was performed on 19 volcanic samples distributed throughout the region the rf images reveal a highly variable moho depth 25 to 55 km as well as a strong positive sub moho horizon between 45 and 80 km depth beneath the central betic and rif mountains which we interpret to be the top of the previously imaged alboran sea slab thermobarometric constraints from magmas in the eastern betics and rif indicate mantle melting depths between 40 and 60 km typical of melting depths beneath mid oceanic ridges where little to no lithosphere exists together the rf and thermobarometric data suggest ongoing and recent slab detachment resulting from delamination of the continental lithosphere

structural assemblage of high pressure mantle and crustal rocks in a subduction channel cabo ortegal nw spain 1 high pressure metamorphic fold nappes and ductile thrusts occur in the cabo ortegal upper allochthons they involve arc root lithospheric mantle peridotites high pressure volcanic arc granulites normal mid oceanic ridge basalt eclogites and shallow crustal volcanosedimentary high pressure gneiss units confluence of units from such disparate tectonic settings occurred at an eo hercynian convergent plate margin their internal deformation juxtaposition and high pressure synmetamorphic reworking resulted from kinematically simple but intense and polyphase ductile deformations fold nappes exhibit a remarkable sheath like form and contain mineral and stretching lineations defined by high pressure mineral assemblages subparallel to fold axes we argue that these structures outline the internal organization of high pressure sheets at deep tectonic realms of an oblique subduction collision orogenic channel

understanding induced seismicity fluid injection induced seismicity has become increasingly widespread in oil and gas producing areas of the united states 1 3 and western canada it has shelved deep geothermal energy projects in switzerland and the united states 4 and its effects are especially acute in oklahoma where seismic hazard is now approaching the tectonic levels of parts of california unclear in the highly charged debate over expansion of shale gas recovery has been the role of hydraulic fracturing fracking in causing increased levels of induced seismicity opponents to shale gas development have vilified fracking as directly responsible for this increase in seismicity however this purported causal link is not substantiated the predominant view is that triggering in the midwestern united states is principally a result of massive reinjection of energy coproduced wastewaters on page 1406 of this issue bao and eaton 5 identify at least one example of seismicity developed from hydraulic fracturing for shale gas in the alberta basin

gps observed horizontal ground extension at the hutubi china underground gas storage facility and its application to geomechanical modeling for induced seismicity abstract induced earthquakes and ground displacements were seldom reported in relation to gas injection or extraction the hutubi underground gas storage hugs facility is the largest one in china and is also a unique case with both earthquakes and ground displacements detected during multiple cycles of injection and extraction since 9 june 2013 unlike previous studies with a primarily seismological focus here we conducted quantitative analysis on the geomechanics of seismicity induced by the hugs through developing a hydrogeologic framework which systematically integrated geodetic geophysical and geological data first we measured horizontal ground extension and shortening on the order of cm in response to gas injection and extraction of the hugs at depth using a local gps network which was not reported in other regions with induced seismicity second we synthesized a variety of data including seismic reflection profiles a newly acquired local velocity model rock physics measurements well drilling and logging data to build up a 2d geomechanical model for the hugs third based on fully coupled poroelasticity we proposed two methods to optimize the permeability of the upper aquifers as well as the reservoir porosity and permeability with constraints from well level gps and well pressure data numerical simulations using the calibrated 2d model revealed that the horizontal extension due to the reservoir dilation is larger than ground uplift the observed seismicity on faults without hydraulic connections to the gas repository was probably induced by the poroelastic effect of reservoir dilation our study provided a prototype scheme for detecting and characterizing the geomechanical behavior of cyclic fluid injection and extraction in a deep reservoir which would be applicable to other ugs facilities

crust and mantle lithospheric structure of the iberian peninsula deduced from potential field modeling and thermal analysis abstract we investigate the lithospheric structure of the iberian peninsula and lateral crustal density variations using a three step approach first the crustal and mantle lithosphere thicknesses are calculated from joint geoid and elevation modeling combined with thermal analysis further constrained by seismic data we then compute the 3d gravity effect of the resulting lithospheric structure to separate the measured bouguer anomaly into its regional and local components finally we invert the residual gravity anomalies to highlight lateral average crustal density variations and discuss them in terms of crustal structures our results show that for the majority of the study area the crustal thickness does correlate with the regional topography pattern the highest topography above 1500 m shows thicknesses above 44 km with local values up to 48 km crustal thicknesses in the range of 36 40 km are obtained in the uplifted alpine areas while a thinner crust is observed in sedimentary basins and in the iberian massif 30 to 35 km with the exception of sw iberia region where the crust thins from 30 to 28 km thick lithosphere above 140 km is found along the pyrenees the cantabrian mountains the iberian chain and in the betics while the thinnest lithosphere is found in sw iberia 90 km 3d inversion of residual anomalies show that for the majority of the area the average density of the crust is in the range of 2810 10 kg m 3 the denser crust is found in the nw and sw regions of the iberian massif 30 kg m 3 on average and locally in the pyrenees above 70 kg m 3 nw of the iberian chain 15 kg m 3 on average and in the southern internal betics 70 kg m 3 the least dense crust is found in the central and western betic chain 30 kg m 3 on average and in sedimentary basin depocenters

the november 2017 mw 5 5 pohang earthquake a possible case of induced seismicity in south korea the moment magnitude mw 5 5 earthquake that struck south korea in november 2017 was one of the largest and most damaging events in that country over the past century its proximity to an enhanced geothermal system site where high pressure hydraulic injection had been performed during the previous 2 years raises the possibility that this earthquake was anthropogenic we have combined seismological and geodetic analyses to characterize the mainshock and its largest aftershocks constrain the geometry of this seismic sequence and shed light on its causal factors according to our analysis it seems plausible that the occurrence of this earthquake was influenced by the aforementioned industrial activities finally we found that the earthquake transferred static stress to larger nearby faults potentially increasing the seismic hazard in the area

seasonal variability of ionic concentrations in surface snow and elution processes in snow firn packs at the pgpi site on urumqi glacier no 1 eastern tien shan china to investigate the effects of both non meltwater and meltwater related post depositional processes on chemical species within the snow firn pack a research program the program for glacier processes investigation was initiated in july 2002 by the tien shan glaciological station chinese academy of sciences the seasonal variability of the ionic concentrations in surface snow samples and ion elution behavior in the snow firn pack were assessed from surface samples collected year round and 1011 samples collected from a snow pit at weekly intervals from september 2003 through september 2004 the results indicate that elevated ionic concentrations in spring and summer result from asian dust storm derived aerosol input and other aerosols entrained in precipitation potential sources of these chemical species are explored using correlation and factor analyses the elution sequence through the snow firn pack was determined to be so4 2 c a 2 n a n o3 c l k m g 2 n h4 the elution of ions at the sampling site was found to be driven primarily by air temperature and became evident when a diurnal mean temperature of 3 68c was attained at 0 38c all of the year round new ionic input was leached from the snow

a detailed view of the injection induced seismicity in a natural gas reservoir in zigong southwestern sichuan basin china 1 seismicity at a gas reservoir located in the relatively stable sichuan basin china mirrors the injection pressure of unwanted water suggesting that the seismicity is injection induced injection under high pressure on a routine basis began on 9 january 2009 and continued to july 2011 during the injection period over 120 000 m3 of water was pumped under a wellhead pressure of up to 6 2 mpa into the limestone formation of permian 2 45 to 2 55 km beneath the surface the injection induced more than 7000 surface recorded earthquakes including 2 m4 the largest one was ml4 4 20 m3 and more than 100 m2 events data observed by a nearby local seismic network and five temporal stations provide a detailed view of the spatiotemporal distribution of the induced earthquakes most events were limited to depths ranging from 2 5 to 4 km which is consistent with the limestone formation of permian in a map view hypocenters are concentrated in a nnw extended ellipsoidal zone approximately 6 km long and approximately 2 km wide centered approximately at the injection well multisources of evidence such as the shear mechanism pattern of hypocenter distribution and small elevated pore pressure as compared with the least principal stress in the region show that the induced earthquakes occurred as a result of lowering of the effective normal stress on known or unknown preexisting blind faults which are critically loaded under the regional stress field epidemic type aftershock sequence modeling results indicate that injection inducing and earthquake triggering are both important during earlier periods of injection while later periods are dominated by forced injection induced seismicity

some comments on climatic reconstructions from ice cores drilled in areas of high melt poor consideration has been given in many arctic circum polar ice core studies to the effect of summer snow melt on chemistry stable isotope concentrations and time scales many of these corps are drilled close to the firn line where melt is intense some come from below the firn line where accumulation is solely in the form of super imposed ice in all cases seasonal signals are reduced or removed and in some time gaps develop during periods of excessive melting which situate the drill site in the ablation zone consequently cross correlations of assumed synchronous events among the cores are invalid so that time scales along the same cores differ between authors by factors of over 2 many so called climatic signals are imaginary rather than real by reference to published analyses of cores from the superimposed ice zone on devon ice cap koerner 1970 and meighen ice cap koerner and paterson 1974 it is shown how melt affects all the normally well established ice core proxies and leads to their misinterpretation despite these limitations the cores can give valuable low resolution records for all or part of the holocene they show that the thermal maximum in the circum polar arctic occurred in the early holocene this maximum effected negative balances on all the ice caps and removed the smaller ones cooler conditions in the second half of the holocene have caused the regrowth of these same ice caps

coseismic slip distribution of the 2008 mw 7 9 wenchuan earthquake from joint inversion of gps and insar data on 12 may 2008 the m w 7 9 wenchuan earthquake occurred at the eastern margin of the tibetan plateau along the longmen shan fault based on previous geological and geophysical studies and offset maps from advanced land observing satellite phased array type l band synthetic aperture radar alos palsar data a layered crustal structure and a five segment rupture model are established to study the coseismic deformation of this event using the constrained least squares method a preferred coseismic slip model is derived from global positioning system gps and interferometric synthetic aperture radar insar data in particular the helmert variance component estimation hvce method is used to determine the relative weight ratio between the gps and insar data in contrast to the initial weight ratio 0 752 0 246 0 002 among three type observations gps horizontal gps vertical and insar los displacement the final optimal weight ratio is found to be 0 473 0 279 0 248 and the overall root mean square rms misfit for all three datasets decreases from 9 15 cm without hvce to 5 46 cm with hvce as revealed by the preferred slip the slip changes obviously along the strike direction from southwest to northeast and exhibits four asperities close to hongkou town yuejiashan town beichuan county and nanba town respectively two major asperities are located on the hongkou and beichuan segments with the maximum slip close to 10 m the slips of hongkou yuejiashan and beichuan segments are dominated by the thrust movement with a significant right lateral strike slip component the qingchuan segment experiences a dominant right lateral strike slip with an average magnitude of 1 2 m most of the slip asperities are shallower than 10 km depth except for the southwest part near the hypocenter where the slip may exceed 20 km the seismic moment of the wenchuan earthquake is 8 19 1020 n m m w 7 91 based on the layered crust model which is slightly larger than that using a corresponding homogeneous crust model m w 7 87

anthropogenic sulfate and asian dust signals in snow from tien shan northwest china snow samples were collected from a 0 5 m snowpack at glacier no i and near bogda feng eastern tien shan northwest china samples that were melted in the field were analyzed for chloride nitrate sulfate sodium potassium magnesium calcium and microparticles eight samples were returned frozen and were analyzed for the above ions plus ammonium acetate formate methylsulfonate and hydrogen peroxide there was no significant difference in measured major ion concentrations between the melted and frozen samples measured cations in both sets of samples were two to three times greater than measured anions calcium and sodium are the dominant cations while sulfate is the dominant measured anion high ion burdens are associated with dusty layers in the snowpack indicating that dust from the vast arid regions of central asia is the dominant source for major ions in tien shan snow the significant increase in sulfate and decrease in the cation anion ratio in bogda eng snow relative to glacier no i snow suggest that anthropogenic emissions from urtimqi are an important source of sulfate to precipitation downwind from the city

superimposed folding and oblique structures in the palaeomargin derived units of the central betics sw spain the subbetic units consist of a deformed wedge of sedimentary rocks deriving from the south iberian palaeomargin in the westernmost segment of the alpine mediterranean orogenic belt in the central betics shortening produced folding thrusting and nappe stacking the structural trend is ne sw to ene wsw and the internal structure of the thrust sheets which shows no preferred vergence is strongly controlled by the rheology of the decollement level a viscous layer of triassic evaporites and of the overlying carbonate rock sequence the relationships of piggyback basin miocene sediments with the main structures show that the latter developed during the aquitanian burdigalian transition superimposed folding is described for the first time in the study area the origin of the interference cannot be determined at present but may be related to initially oblique structures refolded during progressive deformation a revision of previously published palaeomagnetic data in the light of the data presented in this paper in conjunction with a model of the structural evolution of the subbetic units of the western betics permits us to establish milestones of the tectonic evolution of the external zones in the northern branch of the gibraltar arc

earthquakes induced by water injection at 3 km depth within the rongchang gas field chongqing china 1 unwanted water amounting more than 1 million m 3 has been injected intermittently at a pumping pressure of 2 1 2 9 mpa over hydrostatic at 2 6 2 9 km depth within the rongchang gas field western chongqing china since july 1988 the injections have induced more than 32 000 surface recorded earthquakes including 2 of m l 5 14 of m l 4 and more than 100 of m l 3 up until the end of 2006 we examined the epidemic type aftershock sequence etas model and the temporal evolution of several statistics of the earthquake sequence the random component in the etas model can be considered as an indicator of fluid driven activity while the rate of omori law type aftershocks indicates stress triggering of the preceding earthquakes we observed three distinct seismic activity phases that were coincident with different injection periods phase i corresponds to initial injections with low injection rate long time interval and shows a vast majority of omori type events and only 8 externally forced activity phase ii corresponds to a period of high injection rates and shows intense earthquake activity characterized by a high percentage 45 of fluid driven earthquakes phase iii demonstrates decreasing seismicity as a result of a lowering in the injection rate more than 70 of earthquakes occurred randomly over time indicating the dominance of external triggering the physical mechanism that induced the rongchang earthquake sequence was a change in coulomb s failure stress caused by pore pressure diffusion and transformed from seismic slip of preceding earthquakes a pressure increase of 2 1 2 9 mpa at the injection well is more than sufficient to induce failure within the local formations

gravity constraints on the deep structure of the pyrenean belt along the ecors profile abstract in order to furnish further constraints to modelling the ecors pyrenees deep seismic profile gravity data were collected along a stripe 20 km wide and 220 km long containing the seismic line a total of 4020 stations have been used to derive a bouguer anomaly map of the area a large and roughly symmetrical negative anomaly 100 mgal is centered on the axial zone a local positive anomaly over the north pyrenean zone disturbs the negative regional trend somewhat detailed densities were assigned to the sedimentary cover on the basis of borehole samples refraction data and a velocity density relationship were used to constrain the densities adopted for the deeper layers the results of the two dimensional gravity modelling confirm the asymmetrical shape of the crust mantle boundary beneath the pyrenean belt the downward deflection of the iberian moho from the ebro basin leads to a maximum depth of 65 km under the paleozoic axial zone whereas a depth of 35 km is found for the european moho under the north pyrenean zone two extreme models are proposed for the northern limit of the iberian crust a vertical contact in the downward continuity of the north pyrenean fault or a 70 northward sloping interface the positive anomalies beneath the north pyrenean zone may be explained by dense intracrustal mantle slices or lower crustal sheets the outcrop of granulitic basic gneiss within the labourd massif suggests that the anomaly results from lower crustal sheets

main results of the ecors pyrenees profile abstract the 250 km long deep seismic reflection survey across the pyrenees from one foreland ebro basin to the other aquitaine basin was designed to study the structure of the deformed mesozoic boundary between the iberian and european plates the results are 1 1 the entire crust shows well defined reflectors with a general fan shape geometry 2 2 a deep layered domain is evident above the moho discontinuity 3 3 near the surface in the external domains reflectors accurately define the geometry of major thrusts and structures affecting the mesozoic and cenozoic cover of the pyrenees 4 4 the middle crust shows two major sets of seismic events interpreted as hercynian structures using these results a balanced structural section of the pyrenean belt is proposed the mode of thickening of the crust during the alpine orogeny is briefly discussed only the iberian crust was significantly thickened by a southward stacking of slabs

trace element and physical response to melt percolation in summit greenland snow surface melt on a glacier can perturb the glaciochemical record beyond the natural variability while the centre of the greenland ice sheet is usually devoid of surface melt many higharctic and alpine ice cores document frequent summertime melt events current hypotheses interpreting melt affected ice core chemistry rely on preferential elution of certain major ions however the precise nature of chemistry alteration is unknown because it is difficult to distinguish natural variability from melt effects in a perennially melt affected site we use eight trace element snow chemistry records recovered from summit greenland to study spatial variability and melt effects on insoluble trace chemistry and physical stratigraphy due to artificially introduced meltwater differences between non melt and melt affected chemistry were significantly greater than the spatial variability in chemistry represented by nearest neighbour pairs melt perturbed trace elements particularly rare earth elements retained their seasonal stratigraphies suggesting that trace elements may serve as robust chemical indicators for annual layers even in melt affected study areas results suggest trace element transport via meltwater percolation will deposit eluted material down pit in refrozen areas below the nearest surface chemistry peak in our experiments snow chemistry analyses are more sensitive to melt perturbations than density changes or unprocessed near infrared digital imagery

hydraulic properties of injection formations constrained by surface deformation author s shirzaei m manga m zhai g abstract 2019 the author s wastewater injection over the past decade has increased seismicity in the central usa in some cases accompanied by detectable surface uplift here we use this uplift to constrain subsurface properties and pore pressure evolution we apply an advanced multitemporal interferometric algorithm to 35 synthetic aperture radar images acquired by alos satellite over four years before the 2012 earthquake sequence in east texas where large volumes of wastewater are disposed at depths of 800 m and 1800 m to solve for the hydraulic diffusivity of the injection layers we jointly inverted the injected volume and uplift data considering a poroelastic layered half space we find diffusivity values of 0 3 0 1 m 2 s and 0 7 0 15 m 2 s for shallow and deep injection layers respectively which combined with seismically derived bulk moduli yields permeability values of 5 5 2 6 10 14 m 2 and 1 9 0 25 10 13 m 2 for these layers consistent with permeability range reported for rodessa formation and well test values hydraulic conductivity determines the evolution of pore pressure and thus the origin and location of induced seismicity this study highlights the value of geodetic observations to constrain key hydrogeological properties of injection layers and to monitor the evolution of the subsurface pressure change

cenozoic vertical motions of the catalan coastal ranges ne spain the role of tectonics isostasy and surface transport 1 we analyze the cenozoic topographic evolution of the catalan coastal ranges ne spain and the role of fault activity erosion sedimentation and isostasy in controlling uplift and subsidence a forward numerical model constrained by an extensive geological and geophysical data set is used to examine the temporal and spatial record of cenozoic vertical motions we show that the effect of isostasy erosion and sedimentation is as important as the contribution of fault deformation to the topography of the catalan coastal ranges the model predicts that paleogene topography generation by thrusting was compensated by erosion up to 1 3 km and isostatic subsidence up to 1 2 km resulting in a 1 2 1 9 km high mountain range by the end of compression 29 ma during the neogene strong tectonic subsidence related to normal faulting and the consequent flexural uplift of 0 7 1 2 km surface erosion as much as 1 6 2 3 km and sedimentation up to 4 5 km led to the present landscape configuration extension rates along the barcelona fault controlled flexural uplift and in combination with erosion and sedimentation processes led to the migration of the topographic maximum of the prelitoral range toward the easternmost ebro basin

a deep seismic crustal transect from the ne iberian peninsula to the western mediterranean the crustal structure of the transition from the ne iberian peninsula to the western mediterranean is characterized by large scale variations related to its successive compressional and extensional cenozoic tectonics the spanish esci spanish acronym for seismic studies of the iberian crust program recorded 450 km of deep vertical reflection profiles on land and at sea to complete a first crustal transect from the pyrenees to the south balearic basin highly energetic north dipping reflections imaged by combining the etude continentale et oceanique par reflexion et refraction sismique ecors and esci land profiles mark a crustal thickening toward the pyrenees the reflective band becomes horizontal beneath the catalan coastal ranges and the moho is found at 11s no evidence of crustal thinning affecting the iberian mainland is observed the transition to the mediterranean basin is constrained by complementary onshore offshore recordings forward modeling combined with multichannel processing of the wide angle data set shows that a strong thinning of the continental crust by a factor of 2 over a distance of 50 km affects both the catalan and balearic flanks of the valencia trough this thinning affects mainly the deep crust characterized by low velocities of 6 4 6 5 km s suggesting a removal of part of the lower crust during the rifting processes velocities of 7 8 7 9 km s are interpreted in the uppermost mantle with no evidence of underplating the moho appears as a marked discontinuity throughout the transect the nw part of the balearic promontory is characterized by a thick and reflective crust from 12 to 30 km depth an intensely fracturated evaporitic sequence is seen for 100 km along the south balearic basin the seismic images of the continent ocean transition are disturbed by these prominent sediments however the deep reflectivity suggests a crustal thinning moho at 6 7 s to be related to the middle miocene present extensional tectonics

are the oroclines of the variscan belt related to late variscan strike slip tectonics terra nova 23 241 247 2011 abstract early variscan structures and magnetic anomalies delineate four oroclines along the variscan belt the arcs bend the lithostratigraphic zones of the autochthon and the allochthonous terranes which include ophiolites of the rheic suture and units of gondwanan derivation subducted on both sides of the rheic ocean a transcurrent model dominated by right lateral motion explains the genesis and evolution of the oroclines and a simple plate tectonics scenario links late variscan dextral strike slip movements in the variscides to a broad intracontinental shear zone kinematically equivalent to a transform fault terra nova 00 1 7 2011

uppermost mantle seismic velocity and anisotropy in the euro mediterranean region from pn and sn tomography summary in the last 10 15years the number of high quality seismic stations monitoring the euromediterranean region has increased significantly allowing a corresponding improvement in structural constraints we present here new images of the seismic velocity and anisotropy variations in the uppermost mantle beneath this complex area compiled from inversion of pn and sn phases sampling the whole region the method of hearn has been applied to the traveltime arrivals of the international seismological center catalogue for the time period 1990 2010 a total of 579 753 pn arrivals coming from 12 377 events recorded at 1 408 stations with epicentral distances between 220km and 1400km have been retained after applyingstandardqualitycriteria maximumdepth minimumnumberofrecordings maximum residual values our results show significant features well correlated with surface geology and evidence the heterogeneous character of the euro mediterranean lithosphere the station terms reflect the existence of marked variations in crustal thickness consistent with available moho depths inferred from active seismic experiments the highestpnvelocities are observed along a continuous band from the po basin to the northern ionian sea other high velocity zones include the ligurian basin the valencia trough the southern alboran sea and central part of the algerian margin most significant low velocity values are associated to orogenic belts betics pyrenees alps apennines and calabrian arc dinarides hellenides and lowvelocityzonesarealsoidentifiedbeneathsardiniaandthebalearicislands theintroductionof an anisotropic term enhances significantly the lateral continuity of the anomalies in particular in the most active tectonic areas pn anisotropy shows consistent orientations subparallel to major orogenic structures such as betics apennines calabrian arc and alps the sn tomographic image has lower resolution but confirms independently most of the features evidenced in the pn tomography

crustal and velocity structure of the valencia trough western mediterranean part i a combined refraction wide angle reflection and near vertical reflection study abstract in november 1988 a 2 ship seismic survey was carried out in the valencia trough western mediterranean to collect normal incidence seismic reflection profile data and six expanding spread profiles along the continental shelf and trough velocity depth solutions derived from the analysis of the esp show a pattern that corresponds with that of continental type crust except in the northeastern part of the basin where oceanic type crust is present along the iberian margin and centre of the trough the seismic data show a well developed neogene and quaternary sequence with velocities ranging from 1 6 to 4 8 km s 1 whereas along the mallorca margin these deposits are absent at the base of the neogene there is a tertiary unconformity which marks the top of the pre rift mesozoic carbonate platform the carbonates which have velocities from 5 4 to 5 9 km s 1 thin towards the axis of the trough along both margins the upper and middle crust is characterised by an almost transparent layer of variable thickness 6 9 km with velocities ranging from 6 1 to 6 4 km s 1 dipping reflections are observed however in the southern part of the trough these reflections are the result of a locally thick mesozoic sequence a 6 km thick highly reflective lower crust with velocities from 6 4 to 7 0 km s 1 is seen beneath the iberian margin along the mallorca margin the lower crust is variably reflective with a velocity of about 6 6 km s 1 in the centre of the trough the total crustal thickness is less than 14 km which thickens asymmetrically towards the flanks reaching values of 20 21 km off shore the iberian peninsula and 23 km in the mallorca margin the seismic moho increases in depth from 13 to 16 km in a ne sw direction relatively low upper mantle velocities from 7 6 to 8 0 km s 1 have been found throughout the basin indicating a slightly anomalous uppermost mantle or a crust mantle transitional layer in the northeast the velocities for the sediments are similar to those described above however the crustal velocity solution can be characterised by three velocity gradient layers ranging from 4 8 6 1 6 1 6 7 to 6 7 7 2 km s 1

high resolution moho topography map beneath iberia and northern morocco from receiver function analysis abstract crustal thickness maps at regional scales are typically compiled using estimations inferred from different geophysical datasets providing a variable coverage of the investigated area consequently spurious effects related to changes in data resolution or artifacts in grid interpolation may affect significant zones of those maps the topoiberia iberarray broad band seismic network covering the iberian peninsula and northern morocco with stations distributed on a regular 60 60 km grid provides a unique opportunity to avoid such technical problems and to obtain a crustal thickness map derived from a same method sampling evenly all the region data from more than 340 stations has been gathered and analyzed using the p to s conversion phases at the moho discontinuity receiver functions the crustal thickness has been inferred applying the classical h stacking technique though in regions of complex crustal structure we have preferred to estimate the thickness directly from the arrival time of the converted phase at some sites the topography of the moho discontinuity is strongly correlated with tectonic processes the investigated area extending from the sahara platform to the bay of biscay has a great geodynamic diversity including north to south crustal imbrication in the pyrenean and cantabrian range a large and relatively undisturbed variscan massif in the center of iberia and areas of complex and still not completely understood geodynamics in the alboran crust domain and the atlas range the crustal thickness map reflects this diversity showing variations reaching 30 km between the thickest and thinnest zones of continental crust the final map has an overall similarity with previous estimations of the crustal thickness using independent data as those coming from more sparse deep seismic sounding profiles but provides further constraints at regional scale

global review of human induced earthquakes the human induced earthquake database hiquake is a comprehensive record of earthquake sequences postulated to be induced by anthropogenic activity it contains over 700 cases spanning the period 1868 2016 activities that have been proposed to induce earthquakes include the impoundment of water reservoirs erecting tall buildings coastal engineering quarrying extraction of groundwater coal minerals gas oil and geothermal fluids excavation of tunnels and adding material to the subsurface by allowing abandoned mines to flood and injecting fluid for waste disposal enhanced oil recovery hydrofracturing gas storage and carbon sequestration nuclear explosions induce earthquakes but evidence for chemical explosions doing so is weak because it is currently impossible to determine with 100 certainty which earthquakes are induced and which not hiquake includes all earthquake sequences proposed on scientific grounds to have been human induced regardless of credibility challenges to constructing hiquake include under reporting which is 30 of m 4 events 60 of m 3 events and 90 of m 2 events the amount of stress released in an induced earthquake is not necessarily the same as the anthropogenic stress added because pre existing tectonic stress may also be released thus earthquakes disproportionately large compared with the associated industrial activity may be induced knowledge of the magnitude of the largest earthquake that might be induced by a project mmax is important for hazard reduction observed mmax correlates positively with the scale of associated industrial projects fluid injection pressure and rate and the yield of nuclear devices it correlates negatively with calculated inducing stress change likely because the latter correlates inversely with project scale the largest earthquake reported to date to be induced by fluid injection is the 2016 m 5 8 pawnee oklahoma earthquake by water reservoir impoundment the 2008 m 8 wenchuan people s republic of china earthquake and by mass removal the 1976 m 7 3 gazli uzbekistan earthquake the minimum amount of anthropogenic stress needed to induce an earthquake is an unsound concept since earthquakes occur in the absence of industrial activity the minimum amount of stress observed to modulate earthquake activity is a few hundredths of a megapascal and possibly as little as a few thousandths equivalent to a few tens of centimeters of water table depth faults near to failure are pervasive in the continental crust and induced earthquakes may thus occur essentially anywhere in intraplate regions neither infrastructure nor populations may be prepared for earthquakes human induced earthquakes that cause nuisance are rare but in some cases may be a significant problem e g in the hydrocarbon producing areas of oklahoma usa as the size of projects and density of populations increase the potential nuisance of induced earthquakes is also increasing and effective management strategies are needed

modeling the evolution of the guadalquivir foreland basin southern spain 1 previous quantitative studies dealing with the origin of foreland basins have focused primarily either on the rheological basis of the lithosphere mechanical response or on the relationship between orogenic loading and sediment geometry to link the evolution of the guadalquivir foreland basin south iberia with the thermomechanical stratification of the iberian lithosphere we combine quantitative approaches to deep and shallow processes thrust loading lithospheric flexure thickness changes of the crust and the lithospheric mantle and surface mass transport a planform flexural analysis of the present day load distribution shows that basement subsidence is related not only to upper crustal thrusting but also to a deep seated additional load on the basis of the observed gravity and geoid fields we propose this additional load to be related to a lithospheric mantle thickening larger than the coeval crustal thickening further modeling of the evolution of a basin cross section reveals that the architecture of the sedimentary basin is additionally related to the lithosphere rheological response the quantitative study of the evolution of basement faulting and the forebulge uplift of sierra morena leads us to conclude that viscous stress relaxation and or plastic yielding within the lithosphere are key processes to explain the flexural evolution of the basin

fault slip distribution of the 1999 mw 7 1 hector mine california earthquake estimated from satellite radar and gps measurements we use a combination of satellite radar and gps data to estimate the slip distribution of the 1999 m w 7 1 hector mine earthquake a right lateral strikeslip earthquake that occurred on a northwest southeast striking fault in the southern california mojave desert the data include synthetic aperture radar interferograms insar from both ascending and descending orbits radar amplitude image offset fields sario for both ascending and descending azimuth directions and campaign gps observations from 55 stations provided by agnew et al 2002 we model the fault with nine segments derived from the field mapped fault rupture the sario data and aftershock locations we first estimate the dip of each fault segment as well as a single constant strike slip component across each segment resulting in an average dip of 83 to the northeast and slip of up to 5 6 m then we fix the optimal fault segment dip discretize the fault segments into 1 5 km 1 5 km patches and solve for the variable slip distribution using a nonnegative least squares method that includes an appropriate degree of smoothing our preferred solution has both right lateral strike slip and reverse faulting the estimated geodetic moment is 5 93 10 19 n m m w 7 1 similar to seismological estimates indicating that there are insignificant interseismic and postseismic deformation signals in the data we find strike slip displacements of up to 6 0 m and reverse faulting of up to 1 6 m with the maximum slip located just northwest of the epicenter most of the slip is concentrated northwest and south of the epicenter little slip is found on the northeastern branch of the fault the sario data and our modeling indicate that the amount and extent of surface fault rupture were underestimated in the field

a new method for measuring deformation on volcanoes and other natural terrains using insar persistent scatterers 1 we present here a new insar persistent scatterer ps method for analyzing episodic crustal deformation in non urban environments with application to volcanic settings our method for identifying ps pixels in a series of interferograms is based primarily on phase characteristics and finds low amplitude pixels with phase stability that are not identified by the existing amplitude based algorithm our method also uses the spatial correlation of the phases rather than a well defined phase history so that we can observe temporally variable processes e g volcanic deformation the algorithm involves removing the residual topographic component of flattened interferogram phase for each ps then unwrapping the ps phases both spatially and temporally our method finds scatterers with stable phase characteristics independent of amplitudes associated with man made objects and is applicable to areas where conventional insar fails due to complete decorrelation of the majority of scatterers yet a few stable scatterers are present

mantle lithosphere bodies in the alboran crustal domain ronda peridotites betic rif orogenic belt abstract geological and geophysical data are used to demonstrate the existence of intracrustal high density high p wave velocity bodies in the western betics these bodies appear to correspond to buried peridotites similar to those that outcrop in the ronda area a gravity study shows how the gravity field is mainly the result of a combined effect of crustal thinning and the presence of ultramafic bodies the size of the buried high density body as interpreted from gravity and seismic results shows maximum dimensions of about 40 km in length nnw sse about 8 km in thickness and a lateral extension ene wsw of about 70 km the thinning of the crust from 32 35 km to 20 22 km takes place in a narrow area less than 35 km wide our results are compatible with an interpretation in terms of an unrooted peridotite slab dismembering of an initial slab of ultramafic rocks is a possible consequence of the extensional regime that originated the alboran basin

lithospheric transition from the variscan iberian massif to the jurassic oceanic crust of the central atlantic abstract a 1000 km long lithospheric transect running from the variscan iberian massif vim to the oceanic domain of the northwest african margin is investigated the main goal of the study is to image the lateral changes in crustal and lithospheric structure from a complete section of an old and stable orogenic belt the variscan iberian massif to the adjacent jurassic passive margin of sw iberia and across the transpressive and seismically active africa eurasia plate boundary the modelling approach incorporates available seismic data and integrates elevation gravity geoid and heat flow data under the assumptions of thermal steady state and local isostasy the results show that the variscan iberian crust has a roughly constant thickness of 30 km in opposition to previous works that propose a prominent thickening beneath the south portuguese zone spz the three layers forming the variscan crust show noticeable thickness variations along the profile the upper crust thins from central iberia about 20 km thick to the ossa morena zone omz and the ne region of the south portuguese zone where locally the thickness of the upper crust is

the 800 year long ion record from the lomonosovfonna svalbard ice core we present a high resolution record of water soluble ion chemistry from a 121 m ice core spanning about 800 years the core is well dated to 2 3 depth using cycle counting and reference horizons and a simple but close fitting model for the lower 1 3 of the core this core suffers from modest seasonal melt and so we present concentration data in decadal running means to minimize percolation effects sea salt ions na cl mg2 and k account for more than 70 of all ions in general sea salt ion concentrations are rather variable and have no clear association with climatic variations sulfate with 74 being from non sea salt sources has higher concentrations than seen on vestfonna ice cap but lower than in ny alesund aerosols suggesting central spitsbergen receives more marine westerly air masses than ny alesund but more sulfate enriched easterly air masses than nordaustlandet clear anthropogenic impacts are found for sulfate nitrate and ammonium and probably excess chloride after the mid twentieth century with sulfate showing a significant rise by the end of the nineteenth century sulfate and methanesulfonate concentrations correlate well during the twentieth century and it is clear that most of the preindustrial sulfate is of biogenic origin terrestrial component ca2 has the highest concentrations in the coldest part of the little ice age suggesting more windy conditions transporting local terrestrial dust to the ice cap all ion concentrations decrease at the end of the twentieth century which reflects loss of ions by runoff with non sea salt magnesium being particularly sensitive to melting

high resolution imaging of the pyrenees and massif central from the data of the pyrope and iberarray portable array deployments the lithospheric structures beneath the pyrenees which holds the key to settle long standing controversies regarding the opening of the bay of biscay and the formation of the pyrenees are still poorly known the temporary pyrope and iberarray experiments have recently filled a strong deficit of seismological stations in this part of western europe offering a new and unique opportunity to image crustal and mantle structures with unprecedented resolution here we report the results of the first tomographic study of the pyrenees relying on this rich data set the important aspects of our tomographic study are the precision of both absolute and relative traveltime measurements obtained by a nonlinear simulated annealing waveform fit and the detailed crustal model that has been constructed to compute accurate crustal corrections beneath the massif central the most prominent feature is a widespread slow anomaly that reflects a strong thermal anomaly resulting from the thinning of the lithosphere and upwelling of the asthenosphere our tomographic images clearly exclude scenarios involving subduction of oceanic lithosphere beneath the pyrenees in contrast they reveal the segmentation of lithospheric structures mainly by two major lithospheric faults the toulouse fault in the central pyrenees and the pamplona fault in the western pyrenees these inherited hercynian faults were reactivated during the cretaceous rifting of the aquitaine and iberian margins and during the cenozoic alpine convergence therefore the pyrenees can be seen as resulting from the tectonic inversion of a segmented continental rift that was buried by subduction beneath the european plate

three dimensional flexural modelling of the ebro basin ne iberia summary the ebro basin the southern foreland basin of the pyrenees has undergone a complex evolution in which apart from the pyrenees the iberian range and the catalan coastal ranges have played an important role both as sediment sources and as basin confining structures the deflected basement underlying the ebro basin dips north suggesting a lithospheric scale control on the structure of this basin this is compatible with the results of subsidence analyses which show that the study area is not in a local mode of isostatic compensation in order better to understand the mechanisms that led to the present configuration of the ebro basin and particularly the relevance of the various kinds of un loading e g surrounding fold and thrust belts basin topography subsurface loads we carried out a 3 d kinematic modelling study that accounts for the flexural state of the lithosphere subjected to various loads applied at its lateral boundaries and the sedimentary fill of the basin we also included the effect of neogene extensional tectonics along the eastern basin margin which is related to the opening of the valencia trough we show the suitability of the 3 d lithospheric scale flexural modelling approach to the study of ne iberia modelling results point to a relatively strong lithosphere in this area with values of effective elastic thickness ranging from 10 to 35 km in the ebro basin increasing towards the pyrenees we also find that the topographic tectonic load itself is insufficient to explain the observed basement deflection thus an extra subsurface load beneath the pyrenees corresponding to the underthrusted iberian lithosphere is required the effect of lithospheric stretching in the valencia trough on the ebro basin is appreciable only in its eastern part where the lithosphere was uplifted this had considerable repercussions on the sedimentary and erosional regime of the ebro basin we have analysed the link between the stretching related tectonically uplifted areas and the erosional patterns observed onshore northeast iberia

seismotectonics of the 2013 lushan mw 6 7 earthquake inversion tectonics in the eastern margin of the tibetan plateau on 20 april 2013 an unexpected mw 6 7 earthquake occurred in lushan county at the southern longmen shan the eastern margin of the tibetan plateau a high resolution seismic reflection profile was combined with near surface geological data earthquake relocation and geodetic measurements and a recent deep artificial seismic reflection profile to identify the active fault and seismotectonics of this earthquake three dimensional imaging of the aftershocks was used to identify two planar faults that together form a y shape f1 and f2 seismic interpretations suggest that fault f1 did not break through the overlying mesozoic and cenozoic rocks and is a typical blind fault geodetic measurements suggest that the coseismic deformation is consistent with the geometry and kinematics of shear fault bend folding deep seismic data indicate the syndepositional nature of fault f1 a preexisting normal fault older than the triassic which underwent positive inversion tectonics during the late cenozoic a thrust fault f3 converges with f1 at a depth of approximately 12 km with an accumulated slip 3 6 km this 2013 lushan earthquake triggered by blind faults is a hidden earthquake blind and reactivated faults increase the potential risk and uncertainty related to earthquakes in the eastern margin of the tibetan plateau

lithospheric folding in iberia integration of stress indicator data gravity data crustal kinematics data and analysis of topography and recent vertical motions demonstrates the occurrence of consistently oriented spatial patterns of large scale alpine to recent intraplate deformation in iberia the inferred upper crustal and lithospheric deformation patterns and the timing of the associated expressions at or near the surface support the existence of a close coupling with plate boundary processes operating at the margins of iberia patterns of lithosphere and upper crustal folds are oriented perpendicular to the main axis of present day intraplate compression in iberia inferred from structural analysis of stress indicator data and focal mechanism solutions these findings suggest the presence of lithospheric folds with wavelengths compatible with theoretical predictions of folding wavelengths of variscan lithosphere stress induced intraplate deformation set up by plate interactions is compatible with indications for the absence of present day deep mantle lithosphere interactions inferred from seismic tomography

paleomagnetic structural and stratigraphic constraints on transverse fault kinematics during basin inversion the pamplona fault pyrenees north spain 1 the pamplona fault in the pyrenees is a major transverse structure that has been classically interpreted as a strike slip fault however lack of consensus concerning the sense of movement casts doubt on its actual kinematics and as a consequence its role in the cenozoic evolution of the pyrenees remains controversial in order to assess its kinematics we have conducted a paleomagnetic structural and stratigraphic study focused on the mesozoic and tertiary sedimentary rocks that outcrop around the southern segment of the fault restoration of balanced cross sections allows us to examine the present day spatial relationship of the sedimentary sequences on both sides of the fault and to reconstruct the geometry of the extensional basins formed during mesozoic rifting episodes in the bay of biscay and pyrenean domains paleomagnetic results indicate that no significant tectonic rotations occurred around the fault during tertiary inversion of the pyrenees the lack of tectonic rotations and revaluation of previous hypotheses argues against a strike slip movement of the fault we propose a new model in which the pamplona fault is treated as a large scale hanging wall drop fault whose kinematics was determined by variations in the geometry and thickness of mesozoic sequences on both sides of the fault these variations influenced the geometry of the thrust sheet developed during tertiary compression we are unaware of any other transverse fault that has been interpreted in this fashion thus the pamplona fault serves as a case study for the evolution of transverse faults involved in basin inversion processes

crustal structure beneath the iberian peninsula and surrounding waters a new compilation of deep seismic sounding results abstract we present here an updated compilation of crustal parameters beneath the iberian peninsula and surrounding waters inferred from extensive deep seismic exploration performed in the last three decades firstly the more relevant experiments developed in both terrestrial and marine domains are revisited together with the corresponding seismic velocity depth models published that reveal the characteristics of the different tectonic domains sampled including oceanic zones continental margins orogenic and rift belts the results are summarized in three crustal transects sketched along representative directions secondly we compiled the moho depths along all the available seismic profiles to produce a geo referred database this database has then been interpolated using kriging algorithms to obtain a continuous moho depth model in the form of a regular grid file this integrative moho map for a key area in the western mediterranean documenting the interaction between european and african plates can contribute to constrain further regional studies either at crustal lithospheric or mantle scales

glacial isostatic adjustment in the static gravity field of fennoscandia in the central part of fennoscandia the crust is currently rising because of the delayed response of the viscous mantle to melting of the late pleistocene ice sheet this process called glacial isostatic adjustment gia causes a negative anomaly in the present day static gravity field as isostatic equilibrium has not been reached yet several studies have tried to use this anomaly as a constraint on models of gia but the uncertainty in crustal and upper mantle structures has not been fully taken into account therefore our aim is to revisit this using improved crustal models and compensation techniques we find that in contrast with other studies the effect of crustal anomalies on the gravity field cannot be effectively removed because of uncertainties in the crustal and upper mantle density models our second aim is to estimate the effects on geophysical models which assume isostatic equilibrium after correcting the observed gravity field with numerical models for gia we show that correcting for gia in geophysical modelling can give changes of several kilometer in the thickness of structural layers of modeled lithosphere which is a small but significant correction correcting the gravity field for gia prior to assuming isostatic equilibrium and inferring density anomalies might be relevant in other areas with ongoing postglacial rebound such as north america and the polar regions

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

a seismic geotraverse across the iberian variscides orogenic shortening collisional magmatism and orocline development 1 a crustal geotraverse through the iberian variscides is presented by integrating the available geological and seismic profiling data different modes of orogenic shortening are identified with varying degrees of coupling between upper and lower crust in northern and southern regions of the geotraverse a decoupling in the middle crust permits the lower crust to subduct underthrust thus compensating for strong upper crustal shortening this behavior does not result in great crustal thickening except in sectors of crustal underthrusting in southern central iberia moderate upper crustal shortening is due to a mechanically strong lower crust impeded to subduct underthrust in this region shortening is partitioned between upper and lower crust deformation being distributed in the upper crust while localized at major fault zones in the lower crust finally the central region of the geotraverse northern central iberia shows a coupled crustal deformation having given way to the largest orogenic thickening in the iberian variscides the thermal maturity of this much thickened crust originated voluminous crustal melting and concomitant normal fault detachments developed while shortening dominated in other regions theoretical models suggest that compressive stresses may prevail in the lower crust beneath the extending upper crust thus explaining the efficient syncollisional exhumation in this part of the orogen a particular feature of the iberian variscan geotraverse is the great importance of out of section mass movements mainly left lateral shear zones concentrated in two suture boundaries which displaced to the nw present coordinates central and northern iberia with respect to southern iberia

a rapid method to map the crustal and lithospheric thickness using elevation geoid anomaly and thermal analysis application to the gibraltar arc system atlas mountains and adjacent zones we present a method based on the combination of elevation and geoid anomaly data together with thermal field to map crustal and lithospheric thickness the main assumptions are local isostasy and a four layered model composed of crust lithospheric mantle sea water and the asthenosphere we consider a linear density gradient for the crust and a temperature dependent density for the lithospheric mantle we perform sensitivity tests to evaluate the effect of the variation of the model parameters and the influence of rms error of elevation and geoid anomaly databases the application of this method to the gibraltar arc system atlas mountains and adjacent zones reveals the presence of a lithospheric thinning zone sw ne oriented this zone affects the high and middle atlas and extends from the canary islands to the eastern alboran basin and is probably linked with a similarly trending zone of thick lithosphere constituting the western betics eastern rif rharb basin and gulf of cadiz a number of different even mutually opposite geodynamic models have been proposed to explain the origin and evolution of the study area our results suggest that a plausible slab retreating model should incorporate tear and asymmetric roll back of the subducting slab to fit the present day observed lithosphere geometry in this context the lithospheric thinning would be caused by lateral asthenospheric flow an alternative mechanism responsible for lithospheric thinning is the presence of a hot magmatic reservoir derived from a deep ancient plume centred in the canary island and extending as far as central europe

deformation and seismicity in the coso geothermal area inyo county california observations and modeling using satellite radar interferometry interferometric synthetic aperture radar insar data collected in the coso geothermal area eastern california during 1993 1999 indicate ground subsidence over a 50 km 2 region that approximately coincides with the production area of the coso geothermal plant the maximum subsidence rate in the peak of the anomaly is 3 5 cm yr 1 and the average volumetric rate of subsidence is of the order of 10 6 m 3 yr 1 the radar interferograms reveal a complex deformation pattern with at least two irregular subsidence peaks in the northern part of the anomaly and a region of relative uplift on the south we invert the insar displacement data for the positions geometry and relative strengths of the deformation sources at depth using a nonlinear least squares minimization algorithm we use elastic solutions for a prolate uniformly pressurized spheroidal cavity in a semi infinite body as basis functions for our inversions source depths inferred from our simulations range from 1 to 3 km which corresponds to the production depths of the coso geothermal plant underpressures in the geothermal reservoir inferred from the inversion are of the order of 0 1 1 mpa except a few abnormally high underpressures that are apparently biased toward the small source dimensions analysis of the insar data covering consecutive time intervals indicates that the depths and or horizontal extent of the deformation sources may increase with time this increase presumably reflects increasing volumes of the subsurface reservoir affected by the geothermal exploitation we show that clusters of microearthquakes associated with the geothermal power operation may result from perturbations in the pore fluid pressure as well as normal and shear stresses caused by the deflation of the geothermal reservoir

preliminary results from measurements of selected trace metals in the snow firn pack on urumqi glacier no 1 eastern tien shan china we present preliminary results on the occurrence of pb cd zn al and fe in dated samples collected from snow firn packs at an altitude of 4130 m on urumqi glacier no 1 eastern tien shan extreme precautions for avoiding contamination were taken throughout the sampling processing transportation and analysis procedures the concentrations of trace metals were determined by a double focusing inductively coupled plasma mass spectrometer in an ultra clean room the average concentrations for these metals in surface snow are in ng g 1 pb 2 4 cd 0 05 zn 10 0 al 100 0 and fe 130 0 these are higher concentrations especially for pb and zn than those in the polar and or low latitude remote areas the data show that the input of trace metals to the snow has a clear seasonal change lower concentrations in surface snow can be found in july through september and higher concentrations from october to march with an exception for january the mean concentrations of the elements in the snow firn pack also indicate seasonal variations and show a marked inverse relationship with temperature possibly a result of meltwater percolation in the snow firn pack

seismic evidence of alpine crustal thickening and wedging from the western pyrenees to the cantabrian mountains north iberia 1 the alpine collision between the iberian and european plates resulted in a complex crustal structure beneath the northern iberian peninsula as revealed from a new set of seismic refraction wide angle reflection profiles the study area is characterized by two major e w ranges the cantabrian mountains and the pyrenees which are relayed to the south by the iberian chain important variations in crustal thickness and velocity distribution are found in a 560 km long e w transect in contrast to the typical 30 to 32 km thick european variscan crust of the western end of the profile a continuous alpine crustal root is evidenced from the cantabrian mountains to the central pyrenees with a moho depth of 46 48 km locally rising to 40 km depth in between beneath the basque cantabrian basin another outstanding feature is the inferred presence of high velocities of 6 40 6 75 km s at midcrustal depths which can be associated with portions of a lower crustal wedge from the northern european domain indenting the southern iberian crust during the alpine stage of compression this indentation produces the delamination of the iberian crust with northward underthrusting of its lower half and the consequent crustal thickening the indenting wedge has a discontinuous presence along the longitudinal section as it was controlled and or affected by n s to ne sw structures further evidence of the northward subduction of the iberian plate is provided by another profile toward the aquitaine basin while a n s profile across the iberian chain reveals an alpine midcrustal thickening beneath this belt with moho depths of 42 km

reservoir evaluation of the lower silurian longmaxi formation shale gas in the southern sichuan basin of china abstract the lower silurian longmaxi formation the palaeozoic is organic rich black shale in the southern sichuan basin the yangtze plate of china this study analyses the lateral extent and thickness burial depth total organic carbon content and thermal maturity of the longmaxi formation black shale as the key features of the shale gas reservoir the thickness of the black shale ranges from 10 to 170 m the thickest reservoir is located in changning naxi yongchuan region the toc of the shale at the bottom of the formation 50 m thickness is above 2 0 the lateral distribution of toc varies with the lateral distribution of thickness with the maximum toc in the gongxian luzhou yongchuan region the burial depth ranges from 2000 to 4500 m the shale is thermally over mature the evaluation of reservoir characteristics indicates that the longmaxi formation has conditions appropriate for shale gas accumulation and thus resource potential in the southern sichuan basin of china the objective of this preliminary evaluation of the reservoir characteristics is to locate potential areas favourable for exploration the most favourable areas are defined here as those where the thickness of black shale is more than 100 m and the burial depth is less than 3000 m these cover approximately 12 600 km 2 the most favourable areas which cover an area of approximately 5100 km 2 are located in the northeast luzhou region

geochemistry of dust aerosol over the eastern pamirs abstract the pamirs are situated in the inner part of the asian continent a region which plays a critical role in asian dust emission and transport this study measured the elemental composition of atmospheric dust aerosol samples collected during the period between july 2004 and april 2006 at mt muztagata eastern pamirs at a high altitude 38 17 n 75 01 e 4430 m the muztagata aerosol samples show ca al 0 7 and fe al 0 7 ratios that are distinguishable from those from other sites the la th ratios averaging 2 30 2 36 and th u ratios averaging 2 75 3 11 indicate typical eolian deposition the dust aerosol samples have very similar rare earth element ree patterns with relative enrichment of light ree a slight depletion of heavy ree and a strongly negative europium anomaly eu values averaging 0 65 the muztagata dust shows homogeneity of composition during the sampling period with minor variations due to seasonal effects and possible different air mass suggesting the possibility of a well mixed atmospheric background dust on a regional scale the zonal westerlies dominate and the longitude circulations are relatively very weak for dust transport dynamics in the pamirs and tien shan regions our results demonstrate a distinct difference in elemental composition between dust over the eastern pamirs and that over inilchek central tien shan indicating that the asian dust emission regions have great variations in their chemical properties and provide a better constraint on the climatic impact of asian dust

on the post 25 ma geodynamic evolution of the western mediterranean during the neogene and quaternary western mediterranean geodynamics were dominated by the eastward migration of the apenninic arc and associated back arc basins the migration was controlled by retreat of the apenninic slab and was associated with boudinage of the lithosphere in the back arc area palaeo reconstruction of the kinematics of the arc suggests about 775 km of migration from the late oligocene to present along a transect from the gulf of lions to calabria a maximum of 135 km of n s converge occurred between africa and europe during the same time span the western mediterranean was thus mainly shaped by the migration of the slab related to west directed subduction it is hypothesized that minor n s convergence deformed the arc but was not the cause of its formation 1998 elsevier science b v all rights reserved

subsidence at the geysers geothermal field n california from a comparison of gps and leveling surveys between 1994 and 1996 three gps surveys were conducted in the geysers region of northern california our aim was to constrain models of the stresses and strains induced by geothermal power production in that region each survey spanned the geysers geothermal field and consisted of typically 40 monuments these monuments had been previously employed in a series of first order leveling surveys during the 1970 s this earlier study had determined that the geysers region was subsiding with a maximum rate of 0 048 0 0055 m yr between 1973 and 1977 in order to be able to directly compare the leveling and gps surveys we transform them to the same reference frame using the geoid 96 geoid model for the period 1977 1996 we determine a maximum susbsidence rate of 0 047 0 002 m yr we then model this subsidence using a series of point sources of contraction and find their optimal configuration by applying the random cost method and the f test the minimum volume strain that we find consistent with this subsidence is approximately 5 10 4 such a strain cannot be explained by a thermoelastic mechanism but does seem to be consistent with poroelastic deformation and a quasi static reservoir bulk modulus k of 3 6 109 pa