holocene fault scarps near tacoma washington usa airborne laser mapping confirms that holocene active faults traverse the puget sound metropolitan area northwestern continental united states the mapping which detects forest floor relief of as little as 15 cm reveals scarps along geophysical lineaments that separate areas of holocene uplift and subsidence along one such line of scarps we found that a fault warped the ground surface between a d 770 and 1160 this reverse fault which projects through tacoma washington bounds the southern and western sides of the seattle uplift the northern flank of the seattle uplift is bounded by a reverse fault beneath seattle that broke in a d 900 930 observations of tectonic scarps along the tacoma fault demonstrate that active faulting with associated surface rupture and ground motions pose a significant hazard in the puget sound region

incomplete separability of antarctic plate rotation from glacial isostatic adjustment deformation within geodetic observations geodetic measurements of antarctic solid earth deformation include signals from plate rotation and glacial isostatic adjustment gia through simulation we investigate the degree to which these signals are separable within horizontal gps site velocities that commonly define plate rotation estimates and that promise new constraints on models of gia using a suite of gia model predictions that incorporate both 1 d and 3 d earth rheologies we show that given the present location of gps sites within east antarctica unmodelled or mismodelled gia signal within gps velocities produces biased estimates of plate rotation when biased plate rotation is removed from the gps velocities errors as large as 0 8 mm yr 1 are introduced a value commonly larger than the predicted gia signal magnitude in the absence of reliable forward models of plate rotation or gia then antarctic geodetic velocities cannot totally and unambiguously constrain either process especially gia

itrf2008 plate motion model 1 the itrf2008 velocity field is demonstrated to be of higher quality and more precise than past itrf solutions we estimated an absolute tectonic plate motion model made up of 14 major plates using velocities of 206 sites of high geodetic quality far from plate boundaries deformation zones and glacial isostatic adjustment gia regions derived from and consistent with itrf2008 the precision of the estimated model is evaluated to be at the level of 0 3 mm a wrms no gia corrections were applied to site velocities prior to estimating plate rotation poles as our selected sites are outside the fennoscandia regions where the gia models we tested are performing reasonably well and far from gia areas where the models would degrade the fit antarctica and north america our selected velocity field has small origin rate bias components following the three axis x y z respectively 0 41 0 54 0 22 0 64 and 0 41 0 60 95 per cent confidence limits comparing our model to nnr nuvel 1a and the newly available nnr morvel56 we found better agreement with nnr morvel56 than with nnr nuvel 1a for all plates except for australia where we observe an average residual rotation rate of 4 mm a using our selection of sites we found large global x rotation rates between the two models 0 016 ma and between our model and nnr morvel56 of 0 023 ma equivalent to 2 5 mm a at the earth surface

relationship between deep diagenetic quartz cementation and sedimentary facies in a late ordovician glacial environment sbaa basin algeria abstract production of hydrocarbons from sandstone reservoirs is complicated by their diagenetic history although many aspects of sandstone diagenesis are well studied the character and processes of glacial associated diagenesis remain unknown to address this problem the origin conditions and timing of quartz cementation in glacial ordovician sandstones of the sbaa basin algeria were constrained on the basis of fluid inclusion microthermometry electron microprobe data and quantification by image analysis combined with optical and cathodoluminescence microscopic studies samples of the cambro ordovician formations in the sbaa basin were investigated from four wells at burial depths between 2 0 and 2 5 km and at ambient temperatures between 110 and 130 c quartz cements range in abundance from 1 to 27 of bulk rock volume in all wells three separate phases of quartz cementation are readily distinguished by cathodoluminescence microscopy the main silica sources are interpreted to be dissolution of feldspar grains intergranular quartz dissolution stylolitization and illitization of smectite fluid inclusion data depths indicate that quartz overgrowths precipitated between 100 to 160 c this range of temperature corresponds to the visean namurian burial phase according to the basin thermal history image analysis demonstrates intergranular quartz dissolution also called pressure dissolution in the presence of thin illite coatings around detrital quartz grains these clay coatings were mechanically emplaced below the ordovician ice sheet by pressurized meltwater circulation and subsequent fluid expulsion within sandy subglacial soft bedrock that was initially porous and permeable therefore the subglacial bedrock lithology directly influenced quartz diagenesis because an increase in the content of clay matrix or the presence of an argillaceous layer can block the circulation of fluids flowing below the ice sheet which prevents the formation of clay coatings quartz cements in this environment are favored in less compacted areas without clay coatings and with high porosity the results of this study clearly illustrate the relationships among sedimentary facies ice dynamics and diagenetic architecture of the formation these types of processes may control the porosity permeability distribution in other glacial sandstone successions through quartz cementation and chemical compaction

rise of the ellsworth mountains and parts of the east antarctic coast observed with gps 1 using gps observations from 1996 to 2011 we constrain postglacial rebound in antarctica sites in the ellsworth mountains west antarctica are rising at 5 4 mm yr 95 confidence limits as in the postglacial rebound model of peltier but 10 mm yr slower than in the model of ivins and james therefore significant ice loss from the ellsworth mountains ended by 4 ka and current ice loss there is less than inferred from grace gravity observations in studies assuming the model of ivins and james three sites along the coast of east antarctica are rising at 3 to 4 2 mm yr in viscous response to holocene unloading of ice along the queen maud land coast and elsewhere kerguelen island and seven sites along the coast of east antarctic are part of a rigid antarctica plate o higgins northern antarctic peninsula is moving southeast at 2 3 0 6 mm yr relative to the antarctic plate

testing the inference of creep on the northern rodgers creek fault california using ascending and descending persistent scatterer insar data author s jin l funning gj abstract 2017 american geophysical union all rights reserved we revisit the question of whether the rodgers creek fault in northern california is creeping a question with implications for seismic hazard using imagery acquired by envisat between 2003 and 2010 we process two persistent scatterer interferometric synthetic aperture radar insar data sets one from an ascending track and the other from a descending track covering the northernmost segment of the rodgers creek fault between the cities of santa rosa and healdsburg the two different viewing geometries provided by the two different tracks allow us to distinguish vertical velocities which may reflect nontectonic deformation processes from fault parallel velocities which can be used to identify creep by measuring offsets in insar line of sight velocity from 12 fault perpendicular profiles through both data sets we identify seven locations where we have a high degree of confidence that creep is occurring estimated creep rate is more than two standard deviations above zero the preferred creep rates at these locations are in the range 1 9 6 7 mm yr consistent within uncertainty with alignment array measurements creep is probable p 0 70 at another three locations defining a creeping zone 20 km long in total extending northwest from santa rosa we also estimate the map patterns of fault parallel and vertical velocities in the region covered by both data sets these suggest that the rodgers creek fault immediately southeast of santa rosa remains locked

combined effects of tectonics and glacial isostatic adjustment on intraplate deformation in central and northern europe applications to geodetic baseline analyses 6 1 we use a suite of spherical thin sheet finite element model calculations to investigate 7 the pattern of horizontal tectonic deformation within europe the calculations incorporate 8 the effects of africa eurasia convergence atlantic ridge push forces and changes 9 in the lithospheric strength of the east european and mediterranean subdomains these 10 predictions are compared to the deformation computed for the same region using a 11 spherically symmetric self gravitating viscoelastic earth model of glacial isostatic 12 adjustment the radial viscosity profile and ice history input into the gia model are taken 13 from a model that best fits three dimensional crustal velocities estimated from the 14 bifrost fennoscandian gps network the comparison of the tectonic and gia signals 15 includes predictions of both crustal velocity maps and baseline length changes associated 16 with sites within the permanent itrf2000 and bifrost gps networks our baseline 17 analysis includes reference sites in northern and central europe that are representative of 18 sites at the center edge and periphery of the gia induced deformation baseline length 19 change predictions associated with all three reference sites are significantly impacted 20 by both tectonic and gia effects albeit with distinct geometric sensitivities in this regard 21 several of our tectonic models yield baseline rates from vaas onsala and potsdam to sites 22 below 55 n which are consistent with observed trends we find that a best fit to the 23 itrf2000 data set is obtained by simultaneously considering the effects of gia plus 24 tectonics where the latter is modeled with a relatively weak mediterranean subdomain in 25 this case the tectonic model contributes to the observed shortening between onsala 26 potsdam and sites to the south without corrupting the extension observed for baselines 27 extending from these reference sites and sites to the north this extension is well reconciled 28 by the gia process alone index terms 1208 geodesy and gravity crustal movements 29 intraplate 8110 3210 mathematical geophysics modeling 8110 tectonophysics continental tectonics 30 general 0905 9335 information related to geographic region europe keywords tectonics gia 31 intraplate deformation

interseismic ground deformation and fault slip rates in the greater san francisco bay area from two decades of space geodetic data author s xu w wu s materna k nadeau r floyd m funning g chaussard e johnson cw murray jr ding x burgmann r abstract 2018 american geophysical union all rights reserved the detailed spatial variations of strain accumulation and creep on major faults in the northern san francisco bay area north bay which are important for seismic potential and evaluation of natural hazards remain poorly understood here we combine interferometric synthetic aperture radar data from the ers 1 2 and envisat satellites between 1992 and 2010 with continuous and campaign gps data to obtain a high spatial and temporal coverage of ground deformation of the north bay the sar data from both ascending and descending orbits are combined to separate horizontal and vertical components of the deformation we jointly invert the horizontal component of the mean velocities derived from these data to infer the deep strike slip rates on major locked faults we use the estimated deep rates to simulate the long wavelength deformation due to interseismic elastic strain accumulation along these locked faults after removing the long wavelength signal from the insar horizontal mean velocity field we estimate fault parallel surface creep rates of up to 2 mm year along the central section of the rodgers creek fault and surface creep rates ranging between 2 and 4 mm year along the concord fault no surface creep is geodetically resolved along the west napa and green valley fault zones we identified characteristically repeating earthquakes on the rodgers creek fault the west napa fault the green valley fault and the concord fault nontectonic deformation in the geysers geothermal field and in late cenozoic basins rohnert park and sonoma basins are also observed likely due to hydrological and sediment compaction processes respectively

petroleum generation and charge history of the northern dongying depression bohai bay basin china insight from integrated fluid inclusion analysis and basin modelling abstract the petroleum generation and charge history of the northern dongying depression bohai bay basin was investigated using an integrated fluid inclusion analysis workflow and geohistory modelling one and two dimensional basin modelling was performed to unravel the oil generation history of the eocene shahejie formation es3 and es4 source rocks based on the reconstruction of the burial thermal and maturity history calibration of the model with thermal maturity and borehole temperature data using a rift basin heat flow model indicates that the upper interval of the es4 source rocks began to generate oil at around 35 ma reached a maturity level of 0 7 ro at 31 30 ma and a peak hydrocarbon generation at 24 23 ma the lower interval of the es3 source rocks began to generate oil at around 33 32 ma and reached a maturity of 0 7 ro at about 27 26 ma oil generation from the lower es3 and upper es4 source rocks occurred in three phases with the first phase from approximately 30 20 ma the second phase from approximately 20 5 ma and the third phase from 5 ma to the present day the first and third phases were the two predominant phases of intense oil generation samples from the es3 and es4 reservoir intervals in 12 wells at depth intervals between 2677 7 m and 4323 0 m were investigated using an integrated fluid inclusion workflow including petrography fluorescence spectroscopy and microthermometry to determine the petroleum charge history in the northern dongying depression abundant oil inclusions with a range of fluorescence colours from near yellow to near blue were observed and were interpreted to represent two episodes of hydrocarbon charge based on the fluid inclusion petrography fluorescence spectroscopy and microthermometry data two episodes of oil charge were determined at 24 20 ma and 4 3 ma respectively with the second episode being the predominant period for the oil accumulation in the northern dongying depression the oil charge occurred during or immediately after the modelled intense oil generation and coincided with a regional uplift and a rapid subsidence suggesting that the hydrocarbon migration from the already overpressured source rocks may have been triggered by the regional uplift and rapid subsidence the expelled oil was then charged to the already established traps in the northern dongying depression the proximal locations of the reservoirs to the generative kitchens and the short oil migration distance facilitate the intimate relationship between oil generation migration and accumulation

creep on the rodgers creek fault northern san francisco bay area from a 10 year ps insar dataset 1 deformation in the northern san francisco bay area is dominated by a series of sub parallel strike slip faults existing gps observations provide some constraint on the slip rates of these faults however these have only limited resolution for resolving shallow fault behavior such as brittle creep we use a 30 image permanent scatterer insar ps insar dataset spanning the time interval 1992 2001 to dramatically increase the density of surface deformation observations we find a discontinuity in observed surface velocities across the rodgers creek fault around santa rosa and further north consistent with shallow creep at rates of up to 6 mm yr the creeping segments are located in areas of local transtension suggesting that lowered normal stresses may play a role in the distribution of creep the existence of creep could significantly reduce expected moment release in future earthquakes on the rodgers creek fault and thus has implications for seismic hazard assessment

influence of lithospheric thickness variations on 3 d crustal velocities due to glacial isostatic adjustment 1 predictions of 3 d crustal velocities driven by glacial isostatic adjustment gia have generally been based on spherically symmetric earth models we adopt a finite volume formulation to explore the impact of lateral variations in elastic plate strength including lithospheric thickness changes across the continent ocean interface and plate boundary weak zones on these predictions weak zones introduce horizontal rate perturbations with a plate scale coherency and amplitudes reaching 1 2 mm yr radial velocity perturbations can be as large but are geographically isolated to the weak zones specifically the north atlantic ridge a discontinuity in ocean continent lithospheric thickness significantly impacts rates along continental margins order 1 mm yr for radial rates and generally about half this for tangential rates we conclude that lateral variations in lithospheric strength should be included in future gia analyzes of space geodetic survey results and in assessing the impact of gia on the stability of geodetic reference frames

observation of glacial isostatic adjustment in stable north america with gps 1 motions of three hundred and sixty global positioning system gps sites in canada and the united states yield a detailed image of the vertical and horizontal velocity fields within the nominally stable interior of the north american plate by far the strongest signal is the effect of glacial isostatic adjustment gia due to ice mass unloading during deglaciation vertical velocities show present day uplift 10 mm yr near hudson bay the site of thickest ice at the last glacial maximum the uplift rates generally decrease with distance from hudson bay and change to subsidence 1 2 mm yr south of the great lakes the hinge line separating uplift from subsidence is consistent with data from water level gauges along the great lakes showing uplift along the northern shores and subsidence along the southern ones horizontal motions show outward motion from hudson bay with complex local variations especially in the far field although the vertical motions are generally consistent with the predictions of gia models the horizontal data illustrate the need and opportunity to improve the models via more accurate descriptions of the ice load and laterally variable mantle viscosity

postorogenic origin of the stratiform cu mineralization at lufukwe lufilian foreland democratic republic of congo the central african copperbelt which stretches across the border between zambia and the democratic republic of congo is one of the largest sediment hosted stratiform cu co provinces in the world the triangular shaped lufilian foreland is located to the northeast of the copperbelt recently sediment hosted stratiform copper occurrences have been explored in the foreland including the kinkumbi prospect in the lufukwe anticline although the stratiform copper mineralization in the copperbelt is mainly concentrated in the roan group sedimentary rocks where it is commonly associated with cobalt the lufilian foreland copper mineralization occurs in sedimentary rock units of the nguba and kundelungu groups where it is mainly associated with silver this paper examines the metallogenesis of the stratiform copper mineralization at lufukwe the lufukwe anticline is situated in the eastern part of the lufilian foreland and is composed of neoproterozoic sedimentary rocks belonging to the katanga supergroup the kinkumbi prospect a sediment hosted stratiform copper silver occurrence is located in the northern part of the western flank of the anticline this part of the anticline is characterized by disseminated copper silver mineralization hosted in the lower 10 to 15 m of the monwezi sandstone nguba group a comparison between the location of high copper grades in surface samples and boreholes and the location of structural lineaments visible on aster images indicates that the mineralization is spatially related to northeast southwest to east northeast west southwest strike slip faults these faults are nearly perpendicular to the strike of the host rock and postdate both the lufilian folding and deposition of the entire katanga supergroup the monwezi sandstone was subjected to strong compaction and silica cementation authigenic quartz overgrowths followed by intense feldspar dissolution which resulted in a well developed secondary porosity represented by dissolution cavities copper sulfides are mainly concentrated in these cavities and partially replace the detrital grains the copper mineralization is both hypogene chalcopyrite bornite and chalcocite and supergene digenite covellite and minor native copper with malachite and chrysocolla as the main oxidation products point counting and grain size measurements demonstrate that the sandstone horizons with high copper content 1 25 cu are those with a detrital grain size larger than 175 m more than 35 percent altered feldspars and little or no fine grained matrix microthermometry of fluid inclusions indicates that the authigenic quartz overgrowths precipitated from a moderate temperature 80 130 c high salinity 18 8 23 4 wt cacl2 equiv h2o nacl cacl2 fluid the hypogene copper silver mineralization was deposited from a hot 120 180 c and low to moderate salinity 1 9 7 7 wt nacl equiv h2o nacl fluid with a general trend of increasing homogenization temperatures with increasing salinities the interpretation of the available structural stratigraphic petrographic and fluid inclusion microthermometric data constrain the timing of the mineralization to a time after the lufilian folding and deposition of the entire katanga supergroup the data presented support a postorogenic fluid mixing model in which the mineralization is related to the mixing of a copper rich mineralizing fluid with a temperature 180 c and salinity 7 7 wt percent nacl equiv likely migrating upward along northeast southwest to east northeast west southwest oriented strike slip faults with a colder low salinity reducing fluid in the monwezi sandstone the location and distance between the northeast southwest to east northeast west southwest faults strongly influenced the spatial distribution of the copper mineralization in the anticline and the variability in grain size and composition of the monwezi sandstone caused the preferential lateral migration of the mineralizing fluid through the lower 10 to 15 m copper precipitation was possibly induced by reduction by preexisting noncopper sulfides pyrite and arsenopyrite and hydrocarbons and by the drop in fluid temperature and salinity based on this research the areas with dominant northeast southwest to east northeast west southwest structural lineaments are considered favorable sites for further copper exploration in the lufilian foreland especially where these lineaments cut previously deformed katanga sediments coarse grained sandstones with no fine matrix that underwent intense feldspar dissolution are the most promising host rocks for the late disseminated stratiform copper mineralization in the lufilian foreland airborne gamma ray spectrometric surveys could be used as a powerful exploration tool for targeting ore related k depleted zones in these sandstones

the effects of double fault bends on rupture propagation a geometrical parameter study we use the 2d finite element method to determine how geometrical parameters determine whether rupture will propagate across a linked stepover in a strike slip fault the end segments of the fault system are aligned in the direction of maximum shear and the length and angle of the linking segment are allowed to vary we observe that ruptures propagate through extensional stepovers with steeper angles and longer linking segments than otherwise equivalent compressional step overs these different rupture behaviors form distinct regions in angle stepover length parameter space the boundary between these regions takes the shape of an asymptotic curve in both the extensional and compressional cases models in which the size of the entire fault system was made larger or smaller revealed that the location of the bound aries between regions of different rupture behavior do not scale linearly with the system size it was easier to rupture steeper and relatively longer stepovers in fault systems that were larger overall a separate set of models in which the stress field is rotated so that the parallel end segments were optimally aligned for rupture significantly altered the rupture behavior curves in this stress field it was easier to rupture compressional stepovers with steeper angles and longer linking segments than it was to rupture equivalent extensional stepovers in both the case in which the end segments are aligned with the direction of maximum shear and the case in which the end segments are optimally oriented for rupture the angles at which rupture could no longer propagate through the entire fault corresponded with peaks in the fault s s value

seismic reflection and geomorphic characterization of the onshore palos verdes fault zone los angeles california abstract two high resolution 25 to 110 hz bandwidth seismic reflection profiles acquired along roads crossing the palos verdes fault zone los angeles basin california strongly suggest that some geomorphic lineaments seen on aerial photographs coincide with steeply dipping faults at roughly the midpoint of the palos verdes peninsula the palos verdes fault zone consists of at least three major strands one of the northern strands which has the most apparent vertical displacement is interpreted to dip 55 sw down to 200 m steepening at greater depth other strands appear to dip from 50 to 90 just 3 km to the southeast however the fault zone is composed of at least five strands and is roughly 1 5 km wide apparently younger strands are located northeast of older less active strands across the fault zone recent right lateral offset on the northeastern fault strands is inferred from a deflection of an ancestral los angeles river channel approximately 1 8 km west of the los angeles harbor the channel incises deposits dated to be as young as 120 to 80 ka and is deflected approximately 300 m this deflection if attributed solely to slip on the palos verdes fault zone suggests an average horizontal slip rate between 2 5 and 3 8 mm yr because very little vertical displacement is detectable in the seismic data acquired near the channel offset that also shows little vertical displacement we infer that recent onshore movement in the palos verdes fault zone on the eastern palos verdes peninsula has been predominantly strike slip

influence of multistage oil emplacement on carbonate cementation in the eocene shahejie formation dongying sag bohai bay basin china abstract the influence of multi stage oil emplacement on carbonate cementation was investigated on the basis of determining the sequence of oil emplacement and carbonate cementation in the clastic reservoirs of the upper part of the fourth member of the eocene shahejie formation es4s in the yanxie 229 area dongying sag the sequence of multistage oil emplacement and carbonate cementation was determined by projecting the homogenization temperatures ths of two phase aqueous inclusions on a burial and thermal history plot the ratio of the number of quartz grains with yellow fluorescent oil inclusions therein to the total number of quartz grains ygoi and the ratio of the number of quartz grains with blue fluorescent oil inclusions therein to the total number of quartz grains bgoi were calculated to analyze the paleo oil saturation of each stage of oil emplacement the ygoi and bgoi values reflect the relative level of the paleo oil saturation of the first stage yellow fluorescent fsyf oil and the second stage blue fluorescent ssbf oil respectively a large number of primary pores were preserved in the oil layers whereas only a small number of dissolution pores and micropores were developed in the oil bearing water layers and dry layers calcite dolomite ferrocalcite and ankerite cementation and two stage oil emplacement occurred in the es4s reservoirs the fsyf oil emplacement occurred earlier than the ankerite cementation and ferrocalcite cementation but later than the calcite cementation and dolomite cementation the ssbf oil emplacement occurred later than all phases of carbonate cementation the dolomite cementation was not influenced by the fsyf oil emplacement because it occurred earlier than the fsyf oil emplacement the ankerite cementation was dominantly inhibited by the fsyf oil emplacement in the oil layers and the degree of inhibition increased with the increase in paleo oil saturation of the fsyf oil the ssbf oil emplacement further increased the paleo oil saturation in the oil layers which enhanced the inhibition of the ankerite cementation and even stopped it the ankerite cementation in the dry layers and oil bearing water layers was slowed down or stopped due to the lack of pores and the low transportation rate of external material which was caused by the intense ankerite cementation prior to the ssbf oil emplacement

origin of quartz cement in the tirrawarra sandstone southern cooper basin south australia abstract quartz cement is the most abundant authigenic mineral in the fluvio deltaic tirrawarra sandstone and plays an important role in controlling reservoir quality quartz cement ranges from 0 to 19 and is controlled by the original sandstone composition petrographic fluid inclusion electron microprobe and cathodoluminescence cl data from the quartz cement indicate multiple stages of cementation at different temperatures and suggest more than one silica source cl observations indicate up to six stages of quartz cement in some samples the stages of quartz cement can be classified into three zones an innermost zone of brown luminescing cement z1 a middle zone of bright blue luminescing cement z2 and an outer zone of brown luminescing cement z3 dead oil or bitumen is trapped b tween z2 and z3 indicating that z3 formed after oil migration commenced measurements of homogenization temperatures from fluid inclusions in quartz overgrowths indicate that quartz cement precipitated over a temperature range of 65 to 130 c z1 quartz cement formed between 65 and 80 c and z2 cement was precipitated between 80 c and 100 c z3 quartz cement formed later at temperatures around 130 c microprobe analysis shows a consistent variation in aluminum between each quartz cement zone the average aluminum content for z1 z2 and z3 is respectively 237 538 and 58 ppm fluid inclusion precipitation temperatures and aluminum content have been used to help identify the silica sources for different zones of cement a likely source of silica for z1 quartz cement is early alteration of feldspar grains the bright blue cl color in the z2 quartz cement is related to its high aluminum content the source of silica for this cement is likely to have been late dissolution of feldspar grains by acidic fluids generated during kerogen maturation late quartz cement z3 has the lowest aluminum content which is similar to that of detrital quartz grains in the tirrawarra sandstone consi ering the temperature of precipitation very low aluminum content and the presence of z3 cement in facies prone to stylolitization the silica source for the cement is likely to have been pressure solution of detrital quartz at stylolites and grain contacts

anisotropic shear wave velocity structure of the earth s mantle a global model 1 we combine a new large data set of surface wave phase anomalies long period waveforms and body wave travel times to construct a three dimensional model of the anisotropic shear wave velocity in the earth s mantle our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model simultaneous inversion for velocity and anisotropy as well as discontinuity topographies and implementation of nonlinear crustal corrections for waveforms a comparison of our new three dimensional model s362ani with two other models derived from comparable data sets but using different techniques reveals persistent features 1 strong 200 km thick high velocity anomalies beneath cratons likely representing the continental lithosphere underlain by weaker fast anomalies extending below 250 km which may represent continental roots 2 weak velocity heterogeneity between 250 and 400 km depths 3 fast anomalies extending horizontally up to 2000 3000 km in the mantle transition zone beneath subduction zones 4 lack of strong long wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle lower mantle boundary and 5 slow velocity superplumes beneath the pacific and africa the shear wave radial anisotropy is strongest at 120 km depth in particular beneath the central pacific lateral anisotropic variations appreciably improve the fit to data that are predominantly sensitive to the uppermost and lowermost mantle but not to the waveforms that control the transition zone and midmantle depths tradeoffs between lateral variations in velocity and anisotropy are negligible in the uppermost mantle but noticeable at the bottom of the mantle

a new look back at the 1969 santa rosa california earthquakes on 1 october 1969 two damaging earthquakes of richter magnitude ml 5 6 and 5 7 occurred near the city of santa rosa followed by at least 200 aftershocks these are the two largest events to occur in the northern san francisco bay area since the great 1906 san francisco earthquake and its aftershocks the epicentral area coincides with a 1 km right step over from the northwest striking rodgers creek fault to the healdsburg fault zone and a 6 km right step over to the maacama fault the 1969 sequence and its relationship to the healdsburg and rodgers creek faults has taken on greater significance because of the potential for a moment magnitude mw 7 earthquake occurring on the latter possibly in the next several decades we have relocated the five largest events in the 1969 sequence using the largest aftershock recorded by a temporary network operated by the u s geological survey usgs as the master event the locations and focal mechanisms of the principal events in addition to many of the aftershocks are consistent with right lateral strike slip faulting on the northwest striking healdsburg fault an interesting feature of the aftershocks is that they exhibit a cruciform pattern suggesting possible activity on a northeast striking cross fault located within the step over the significance of such a cross structure is that it may act as a barrier to northward rupture from a large earthquake on the rodgers creek fault seismicity since 1969 continues to image an active southern healdsburg fault surrounding a quiescent rupture zone of the 1969 earthquakes and the possible cross fault the rodgers creek fault is generally aseismic during this period

the most recent large earthquake on the rodgers creek fault san francisco bay area the rodgers creek fault rcf is a principal component of the san andreas fault system north of san francisco no evidence appears in the historical record of a large earthquake on the rcf implying that the most recent earthquake mre occurred before 1824 when a franciscan mission was built near the fault at sonoma and probably before 1776 when a mission and presidio were built in san francisco the first appearance of nonnative pollen in the stratigraphic record at the triangle g ranch study site on the south central reach of the rcf confirms that the mre occurred before local settlement and the beginning of livestock grazing chronological modeling of earthquake age using radiocarbon dated charcoal from near the top of a faulted alluvial sequence at the site indicates that the mre occurred no earlier than a d 1690 and most likely occurred after a d 1715 with these age constraints we know that the elapsed time since the mre on the rcf is more than 181 years and less than 315 years and is probably between 229 and 290 years this elapsed time is similar to published recurrence interval estimates of 131 to 370 years preferred value of 230 years and 136 to 345 years mean of 205 years calculated from geologic data and a regional earthquake model respectively importantly then the elapsed time may have reached or exceeded the average recurrence time for the fault the age of the mre on the rcf is similar to the age of prehistoric surface rupture on the northern and southern sections of the hayward fault to the south this suggests possible rupture scenarios that involve simultaneous rupture of the rodgers creek and hayward faults a buried channel is offset 2 2 1 2 0 8 m along one side of a pressure ridge at the triangle g ranch site this provides a minimum estimate of right lateral slip during the mre at this location total slip at the site may be similar to but is probably greater than the 2 0 3 0 2 m measured previously at the nearby beebe ranch site

detailed mapping and rupture implications of the 1 km releasing bend in the rodgers creek fault at santa rosa northern california airborne light detection and ranging lidar topography reveals for the first time the trace of the rodgers creek fault rcf through the center of santa rosa the largest city in the northern san francisco bay area vertical deformation of the santa rosa creek floodplain expresses a composite pull apart basin beneath the urban cover that is part of a broader 1 km wide right releasing bend in the fault high resolution geophysical data illuminate subsurface conditions that may be responsible for the complex pattern of surface faulting as well as for the distribution of seismicity and possibly for creep behavior we identify a dense magnetic basement body bounded by the rcf beneath santa rosa that we interpret as a strong asperity likely part of a larger locked patch of the fault to the south a local increase in frictional resistance associated with the basement body appears to explain 1 distributed fault normal extension above where the rcf intersects the body 2 earthquake activity around the northern end of the body notably the 1969 m l 5 6 and 5 7 events and aftershocks and 3 creep rates on the rcf that are higher to the north of santa rosa than to the south there is a significant probability of a major earthquake on the rcf in the coming decades and earthquakes associated with the proposed asperity have the potential to release seismic energy into the cotati basin beneath santa rosa already known from damaging historical earthquakes to produce amplified ground shaking

reversal of the direction of horizontal velocities induced by gia as a function of mantle viscosity in regions undergoing glacial isostatic adjustment present day horizontal surface motion is observed to point mostly but not always away from the former ice load to interpret these observations we investigate the direction of horizontal velocities using glacial isostatic adjustment models the direction is controlled by the opposing actions of inward mantle flow and outward lithosphere motion in contrast with the prevailing idea that glacial isostatic adjustment induced horizontal velocities point outward we show that velocities can be either outward or inward immediately after deglaciation velocities point inward but change direction to outward after a time that is controlled by mantle viscosity present day horizontal velocities point outward for a uniform mantle viscosity below 1020 pa s and inward for above 1022 pa s with a combination of outward and inward in between our results help to interpret gps observed horizontal velocities in areas with varying mantle viscosity

uniform california earthquake rupture forecast version 2 ucerf 2 the 2007 working group on california earthquake probabilities wgcep 2007 presents the uniform california earthquake rupture forecast version 2 ucerf 2 this model comprises a time independent poisson process earthquake rate model developed jointly with the national seismic hazard mapping program and a time dependent earthquake probability model based on recent earthquake rates and stress renewal statistics conditioned on the date of last event the models were developed from updated statewide earthquake catalogs and fault deformation databases using a uniform methodology across all regions and implemented in the modular extensible open seismic hazard analysis framework the rate model satisfies integrating measures of deformation across the plate boundary zone and is consistent with historical seismicity data an overprediction of earthquake rates found at intermediate magnitudes 6 5 m 7 0 in previous models has been reduced to within the 95 confidence bounds of the historical earthquake catalog a logic tree with 480 branches represents the epistemic uncertainties of the full time dependent model the mean ucerf 2 time dependent probability of one or more m 6 7 earthquakes in the california region during the next 30 yr is 99 7 this probability decreases to 46 for m 7 5 and to 4 5 for m 8 0 these probabilities do not include the cascadia subduction zone largely north of california for which the estimated 30 yr m 8 0 time dependent probability is 10 the m 6 7 probabilities on major strike slip faults are consistent with the wgcep 2003 study in the san francisco bay area and the wgcep 1995 study in southern california except for significantly lower estimates along the san jacinto and elsinore faults owing to provisions for larger multisegment ruptures important model limitations are discussed

a gps velocity field for fennoscandia and a consistent comparison to glacial isostatic adjustment models in fennoscandia the process of glacial isostatic adjustment gia drives ongoing crustal deformation crustal velocities from gps observations have proved to be a useful tool in constraining gia models however reference frame uncertainties plate tectonics intraplate deformations as well as other geophysical processes contaminate the results former studies have shown that different international terrestrial reference frames have large discrepancies especially in the vertical component which hamper geophysical interpretation we present new velocity estimates for the fennoscandian and north european gps network our gps velocity field is directly realized in a gia reference frame using this method named the gia frame approach we are able to constrain gia models with minimal influence of errors in the reference frame or biasing signals from plate tectonics the drawbacks are more degrees of freedom that might mask real but unmodeled signals monte carlo tests suggest that our approach is robust at the 97 level in terms of correctly separating different models of ice history but depending on deformation patterns the identified earth model may be slightly biased in up to 39 of cases we compare our results to different one and three dimensional gia models employing different global ice load histories the gia models generally provide good fit to the data but there are still significant discrepancies in some areas we suggest that these differences are mainly related to inaccuracies in the ice models and or lateral inhomogeneities in the earth structure under fennoscandia thus gia models still need to be improved but the gia frame approach provides a base for further improvements

lower satellite gravimetry estimates of antarctic sea level contribution a new model of glacial isostatic adjustment used in conjunction with grace satellite data suggests that ice loss from antarctica is contributing 0 19 millimetres per year to global mean sea level which is substantially less than previous grace based estimates estimates for recent mass loss from antarctica vary widely making it difficult to calculate any subsequent contributions to sea level rise one prominent approach uses the grace gravity recovery and climate experiment satellites to detect changes in gravity but the final estimates are dependent on the modelled response of the continent to changes in ice loading over time and to changes in lithospheric elastic rebound matt king and colleagues apply a new model of this glacial isostatic adjustment to the grace data and estimate antarctic mass loss between 2002 and 2010 to be about 69 gigatonnes per year much lower than previous estimates and equivalent to an annual sea level rise of about 0 2 millimetres recent estimates of antarctica s present day rate of ice mass contribution to changes in sea level range from 31 gigatonnes a year gt yr 1 ref 1 to 246 gt yr 1 ref 2 a range that cannot be reconciled within formal errors3 time varying rates of mass loss2 4 5 6 contribute to this but substantial technique specific systematic errors also exist3 in particular estimates of secular ice mass change derived from gravity recovery and climate experiment grace satellite data are dominated by significant uncertainty in the accuracy of models of mass change due to glacial isostatic adjustment7 8 gia here we adopt a new model of gia developed from geological constraints which produces gia rates systematically lower than those of previous models and an improved fit to independent uplift data9 after applying the model to 99 months from august 2002 to december 2010 of grace data we estimate a continent wide ice mass change of 69 18 gt yr 1 0 19 0 05 mm yr 1 sea level equivalent this is about a third to a half of the most recently published grace estimates2 5 which cover a similar time period but are based on older gia models plausible gia model uncertainties and errors relating to removing longitudinal grace artefacts destriping confine our estimate to the range 126 gt yr 1 to 29 gt yr 1 0 08 0 35 mm yr 1 sea level equivalent we resolve 26 independent drainage basins and find that antarctic mass loss and its acceleration is concentrated in basins along the amundsen sea coast outside this region we find that west antarctica is nearly in balance and that east antarctica is gaining substantial mass

fluid inclusions record thermal and fluid evolution in reservoir sandstones khatatba formation western desert egypt a case for fluid injection a fluid inclusion and petrographic study focused on quartz overgrowths was performed in reservoir sandstones from the jurassic khatatba formation salam oil field egypt s western desert the combination of detailed fluid inclusion petrography and scanning electron microscope sem cathodoluminescence imaging has allowed us to relate individual fluid inclusion assemblages that is the most finely discriminated groups of petrographically associated fluid inclusions to specific growth zones of authigenic quartz establishing the relative timing of entrapment of the inclusions after entrapment fluid inclusions in authigenic quartz have been preserved without reequilibration as indicated by the narrow ranges of homogenization temperatures 4 5 degreesc in most fluid inclusion assemblages three main growth zones are distinguished under sem cathodoluminescence in the quartz overgrowths and are termed q1 q2 and q3 from the oldest to the youngest zone q1 is further subdivided into three subzones and contains abundant primary aqueous inclusions their homogenization temperatures range from 162 to 130 degreesc with the earliest assemblages having the highest temperatures and with some large temperature fluctuations indicated between successive assemblages most q1 inclusions have salinities in the freshwater to seawater range with a trend toward increasing salinity through time zone q2 contains primary aqueous inclusions with homogenization temperatures overall range 148 125 degreesc also recording large temperature fluctuations and cooling events the q2 fluid inclusions have high salinities 5 20 wt nacl equivalent with salinity increasing through time zone q3 contains both aqueous and oil inclusions of primary origin the q3 aqueous inclusions have homogenization temperatures overall range 134 112 degreesc recording overall cooling and high salinities 21 24 wt nacl equivalent in early q3 subzones oil inclusions appear to be of medium gravity undersaturated with respect to gas in later q3 subzones oil inclusions are of gas saturated lighter oil our results indicate that fluid flow involving drastic changes in temperature and salinity was responsible for the precipitation of some of the quartz cement the earliest quartz q1 precipitated from freshwater and seawater at temperatures significantly higher than those expected from the burial history and thermal maturity of these rocks this quartz is interpreted to have precipitated during cooling of injected fluids that originated as hot connate fluids from deeper parts of the basin the q2 precipitation is interpreted to have resulted from episodes of injection of hot saline brines from below late quartz cement q3 precipitated during oil charge from progressively cooler and more saline brines interpreted to have refluxed from the surface it preserves a record of increasing oil maturity and gas saturation through time

gypsum a joint tomographic model of mantle density and seismic wave speeds 1 gypsum is a 3 d model of mantle shear wave s speeds compressional wave p speeds and density the model is developed through simultaneous inversion of seismic body wave travel times p and s and geodynamic observations while using realistic mineral physics parameters linking wave speeds and density geodynamic observations include the global free air gravity field divergence of the tectonic plates dynamic topography of the free surface and the flow induced excess ellipticity of the core mantle boundary gypsum is built with the philosophy that heterogeneity that most closely resembles thermal variations is the simplest possible solution models of the density field from earth s free oscillations have provided great insight into the density configuration of the mantle but are limited to very long wavelength solutions alternatively scaling higher resolution seismic images to obtain density anomalies generates density fields that do not satisfy geodynamic observations the current study provides a 3 d density model for the mantle that directly satisfies geodynamic and seismic observations through a joint seismic geodynamic inversion process notable density field observations include high density piles at the base of superplume structures supporting the general results of past normal mode studies however we find that these features are more localized and have lower amplitude than past studies would suggest when we consider both fast and slow seismic anomalies in gypsum we find that p and s wave speeds are strongly correlated throughout the mantle however we find a low correlation of fast s wave zones in the deep mantle 1500 km depth with the corresponding p wave anomalies suggesting a systematic divergence from simplified thermal effects in ancient subducted slab anomalies the cratonic lithosphere and d regions are shown to have strong compositional signatures however we argue that temperature variations are the primary cause of p wave speed s wave speed and density anomalies throughout most of the mantle

geothermometry and geobarometry of overpressured lower paleozoic gas shales in the jiaoshiba field central china insight from fluid inclusions in fracture cements the wufeng longmaxi organic rich shales host the largest shale gas fields of china this study examines sealed fractures within core samples of the wufeng longmaxi shales in the jiaoshiba shale gas field in order to understand the development of overpressures in terms of magnitude timing and burial in wufeng longmaxi shales and thus the causes of present day overpressure in these paleozoic shale formations as well as in all gas shales quartz and calcite fracture cements from the wufeng longmaxi shale intervals in four wells at depth intervals between 2253 89 m and 3046 60 m were investigated and the fluid composition temperature and pressure during natural fracture cementation determined using an integrated approach consisting of petrography raman spectroscopy and microthermometry many crystals in fracture cements were found to contain methane inclusions only and aqueous two phase inclusions were consistently observed alongside methane inclusions in all cement samples indicating that fluid inclusions trapped during fracture cementation are saturated with a methane hydrocarbon fluid homogenization temperatures of methane saturated aqueous inclusions provide trends in trapping temperatures that th values concentrate in the range of 198 5 c 229 9 c 196 2 c 221 7 c for quartz and calcite respectively pore fluid pressures of 91 8 139 4 mpa for methane inclusions calculated using the raman shift of c h symmetric stretching v1 band of methane and equations of state for supercritical methane indicate fluid inclusions trapped at near lithostatic pressures high trapping temperature and overpressure conditions in fluid inclusions represent a state of temperature and overpressure of wufeng longmaxi shales at maximum burial and the early stage of the yanshanian uplift which can provide a key evidence for understanding the formation and evolution of overpressure our results demonstrate that the main cause of present day overpressure in shale gas deposits is actually the preservation of moderate high overpressure developed as a result of gas generation at maximum burial depths

the antarctica component of postglacial rebound model ice 6g_c vm5a based on gps positioning exposure age dating of ice thicknesses and relative sea level histories

glacial isostatic adjustment on a rotating earth summary we extend and complete previous work to compute the influence of perturbations to the rotation vector on a suite of observables associated with glacial isostatic adjustment gia we emphasize observables relevant to present and future geodetic missions for example present day 3 d crustal motions relative sea level change and geoid or absolute sea level variations our calculations adopt spherically symmetric self gravitating maxwell viscoelastic earth models while incorporating realistic mass ice plus ocean load and rotation variations the predicted rotation induced signals are dominated by the influence of true polar wander tpw the spatial geometry of the tpw induced relative sea level geoid and radial velocity fields is primarily that of a degree two order one surface spherical harmonic the spatial variation of the horizontal velocity vectors is given by the gradient of this harmonic the peak radial and horizontal velocities are of the order of 0 5 mm yr 1 however we show that this value is sensitive to the adopted profile of mantle viscosity we also demonstrate that an accurate prediction of tpw induced sea level and 3 d crustal deformation rates requires that a realistic number of glacial cycles be incorporated into the ice load history we conclude that geodetic observations of the gia process should be analysed using a gia theory valid for a rotating planet finally we also consider variations in rotation driven by simple present day polar melting scenarios and predict the influence of these variations on a suite of geophysical observables we find that the rotational feedback associated with greenland melting is capable of significantly perturbing both relative and absolute sea level variations

reduced ice mass loss and three dimensional viscoelastic deformation in northern antarctic peninsula inferred from gps we consider the viscoelastic rheology of the solid earth under the antarctic peninsula due to ice mass loss that commenced after the breakup of the larsen b ice shelf we extend the previous analysis of nearby continuous gps time series to include five additional years and the additional consideration of the horizontal components of deformation they show strong uplift from 2002 to 2011 followed by reduced uplift rates to 2018 modelling the gps derived uplift as a viscoelastic response to ongoing regional ice unloading from a new ice model confirms earlier estimates of low upper mantle viscosities of 0 3 3 1018 pa s in this region but allows a wide range of elastic lithosphere thickness the observed and modelled north coordinate component shows little nonlinear variation due to the location of ice mass change to the east of the gps sites however comparison of the observed and modelled east coordinate component constrains the upper mantle viscosity to be less than 9 1018 pa s consistent with the viscosity range suggested by the uplift rates alone and providing important largely independent confirmation of that result our horizontal analysis showed only marginal sensitivity to modelled lithospheric thickness the results for the horizontal components are sensitive to the adopted plate rotation model with the estimate based on itrf2014 suggesting that the sum of residual plate motion and pre 2002 glacial isostatic adjustment is likely less than 0 5 mm yr 1 in the east component

multiscale seismic imaging of active fault zones for hazard assessment a case study of the santa monica fault zone los angeles california high resolution seismic reflection profiles at two different scales were acquired across the transpressional santa monica fault of north los angeles as part of an integrated hazard assessment of the fault the seismic data confirm the location of the fault and related shallow faulting seen in a trench to deeper structures known from regional studies the trench shows a series of near vertical strike slip faults beneath a topographic scarp inferred to be caused by thrusting on the santa monica fault analysis of the disruption of soil horizons in the trench indicates multiple earthquakes have occurred on these strike slip faults within the past 50 000 years with the latest being 1000 to 3000 years ago a 3 8 km long high resolution seismic reflection profile shows reflector truncations that constrain the shallow portion of the santa monica fault upper 300 m to dip northward between 30 and 55 most likely 30 to 35 in contrast to the 60 to 70 dip interpreted for the deeper portion of the fault pr

constraining models of postglacial rebound using space geodesy a detailed assessment of model ice 5g vm2 and its relatives summary using global positioning system very long baseline interferometry satellite laser ranging and doppler orbitography and radiopositioning integrated by satellite observations including the canadian base network and fennoscandian bifrost array we constrain in models of postglacial rebound the thickness of the ice sheets as a function of position and time and the viscosity of the mantle as a function of depth we test model ice 5g vm2 t90 rot which well fits many hundred holocene relative sea level histories in north america europe and worldwide ice 5g is the deglaciation history having more ice in western canada than ice 4g vm2 is the mantle viscosity profile having a mean upper mantle viscosity of 0 5 1021 pa s and a mean uppermost lower mantle viscosity of 1 6 1021 pa s t90 is an elastic lithosphere thickness of 90 km and rot designates that the model includes rotational feedback earth s response to the wander of the north pole of earth s spin axis towards canada at a speed of 1 myr 1 the vertical observations in north america show that relative to ice 5g the laurentide ice sheet at last glacial maximum lgm at 26 ka was 1 much thinner in southern manitoba 2 thinner near yellowknife northwest territories 3 thicker in eastern and southern quebec and 4 thicker along the northern british columbia alberta border or that ice was unloaded from these areas later thicker or earlier thinner than in ice 5g the data indicate that the western laurentide ice sheet was intermediate in mass between ice 5g and ice 4g the vertical observations and grace gravity data together suggest that the western laurentide ice sheet was nearly as massive as that in ice 5g but distributed more broadly across northwestern canada vm2 poorly fits the horizontal observations in north america predicting places along the margins of the laurentide ice sheet to be moving laterally away from the ice centre at 2 mm yr 1 in ice 4g and 3 mm yr 1 in ice 5g in disagreement with the observation that the interior of the north american plate is deforming more slowly than 1 mm yr 1 substituting vm5a t60 for vm2 t90 that is introducing into the lithosphere at its base a layer with a high viscosity of 10 1021 pa s greatly improves the fit of the horizontal observations in north america ice 4g vm5a t60 rot predicts most of the north american plate to be moving horizontally more slowly than 1 mm yr 1 in agreement with the data ice 5g vm5a t60 rot well fits both the vertical and horizontal observations in europe the space geodetic data cannot distinguish between models with and without rotational feedback in the vertical because the velocity of earth centre is uncertain and in the horizontal because the areas of the plate interiors having geodetic sites is not large enough to detect the small differences in the predictions of rotational feedback going across the plate interiors

a deglacial model for antarctica geological constraints and glaciological modelling as a basis for a new model of antarctic glacial isostatic adjustment abstract we present a new reconstruction of the antarctic ice sheets between 20 ka bp and the present day our reconstruction is derived using a numerical model to generate a physically consistent ice surface across the whole of the continent we define the extent of the ice sheet at five time slices 20 15 10 5 and 0 ka bp assuming an equilibrium state for the 20 ka bp time slice and a transient state for the deglacial time slices the evolution of the ice sheet within the numerical model is driven by variations in temperature accumulation rate and relative sea level in order to reconstruct the concave profile of the ice sheet in marine grounded regions such as the ross and weddell seas we force our model to develop channels of faster flow by defining greater basal sliding along the trajectory of former ice streams we find a strong dependence upon the basal sliding parameters and also the position of the grounding line we use an extensive data base of geological and glaciological data to constrain our ice sheet reconstruction grounding line extent is prescribed from marine geological data and we test ice sheet thickness against onshore geological data at 62 sites of the five time slices considered our 20 ka bp reconstruction is the best constrained by data and has an rms misfit of 147 6 m when compared to observations of ice thickness change between 20 ka bp and the present day across all time slices there are large regions of the ice sheet which are poorly constrained especially after 20 ka bp we estimate the spatial distribution of uncertainty in our ice sheet reconstruction and note that the solutions are least reliable in regions of complex topography we predict that the antarctic ice sheets contributed 9 1 5 m of eustatic sea level to the global ocean between 20 ka bp and the present and our reconstruction with minimum misfit contributes 8 m eustatic sea level during this period these values which we argue are an upper bound are lower than many previous estimates the reconstructed pattern of ice unloading can serve as a new input for glacial isostatic models

the dynamics of strike slip step overs with linking dip slip faults fault step overs with linking dip slip faults are common features on long strike slip fault systems worldwide it has been noted by various researchers that under some circumstances earthquakes can jump across fault step overs to cascade into large events while under other circumstances rupture is arrested at step overs there is also evidence that fault step overs may be preferential locations for earthquake nucleation the present work uses the 3d finite element method to model the dynamics of strike slip fault systems with step overs and linking dip slip faults i find that the presence of a linking normal or thrust fault greatly increases the ability of earthquake rupture to propagate across the step over leading to a larger event additionally dilational step overs with linking normal faults are more prone to through going rupture than compressional step overs with linking thrust faults this difference is due to the sign of the normal stress increment on the dip slip fault caused by slip on the strike slip segments slip on the strike slip segments causes a negative unclamping normal stress increment on the linking normal fault in a dilational step over whereas the opposite effect occurs on the linking thrust fault in a compressional step over even in cases for which both dilational and compressional step overs can experience through going rupture dilational step overs typically experience higher slip particularly on the linking normal fault in the compressional case rupture nucleation on the linking thrust fault may increase the likelihood of through going rupture compared to nucleation on one of the strike slip segments near the intersections between the fault segments the stress interaction between the fault segments also causes a significant rotation of rake away from that which would be inferred from the regional stress field the results help to emphasize the importance of two way interactions between nearby fault segments during the earthquake rupture process the results also may have implications for the probability of large earthquakes along geometrically complex strike slip fault systems and may help explain why step overs sometimes act as barriers and other times as nucleation locations for large earthquakes

origin of quartz cement in the lower ordovician dongjeom formation korea abstract this study deals with the origin of quartz cement developed in deeply buried mature sandstones intercalated in a thick carbonate sequence the dongjeom formation early ordovician korea is composed of three coarsening upward sequences and is divided into two facies according to depositional conditions with respect to changes in relative sea level transgressive facies and regressive facies the transgressive facies are characterized by calcite cemented allochem bearing sandstones whereas the regressive facies is characterized by non calcareous quartzose to arkosic sandstones quartz overgrowths occupy significant amounts of pore space average 16 in the regressive facies sandstones fluid inclusions reveal that quartz overgrowths precipitated between 110 and 165 c petrographical study and homogenization temperatures indicate that quartz overgrowths precipitated mostly during and after chemical compaction during the late diagenetic stage considering the 18 o values of detrital quartz grains and the volumes of quartz overgrowth the 18 o values of quartz overgrowth are estimated to range from 14 4 to 19 0 smow on the basis of mass balance silica for quartz overgrowths was principally derived from chemical compaction pressure solution of detrital quartz quartz overgrowths in the dongjeom sandstones precipitated from formation waters 2 1 to 2 5 smow that evolved from contemporary meteoric waters by diffusion

san andreas fault geometry in the parkfield california region in map view aftershocks of the 2004 parkfield earthquake lie along a line that forms a straighter connection between san andreas fault segments north and south of the parkfield reach than does the mapped trace of the fault itself a straightedge laid on a geologic map of central california reveals a 50 km long asymmetric northeastward warp in the parkfield reach of the fault the warp tapers gradually as it joins the straight creeping segment of the san andreas to the northwest but bends abruptly across cholame valley at its southeast end to join the straight locked segment that last ruptured in 1857 we speculate that the san andreas fault surface near parkfield has been deflected in its upper 6 km by nonelastic behavior of upper crustal rock units these units and the fault surface itself are warped during periods between large 1857 type earthquakes by the presence of the 1857 locked segment to the south which buttresses intermittent coseismic and continuous aseismic slip on the parkfield reach because of nonelastic behavior the warping is not completely undone when an 1857 type event occurs and the upper portion of the three dimensional fault surface is slowly ratcheted into an increasingly prominent bulge ultimately the fault surface probably becomes too deformed for strike slip motion and a new more vertical connection to the earth s surface takes over perhaps along the southwest fracture zone when this happens a wedge of material currently west of the main trace will be stranded on the east side of the new main trace

influence of releasing step overs on surface fault rupture and fault segmentation examples from the 17 august 1999 izmit earthquake on the north anatolian fault turkey the 17 august 1999 izmit earthquake broke four distinct structural segments of the north anatolian fault from east to west the karadere sakarya sapanca and golcuk fault segments these segments are separated from one another and the adjoining yalova and duzce fault segments to the west and east respectively by distinct right releasing step over and or gaps in the fault trace these include from east to west the eften lake step over 2 4 km wide akyazi gap 6 13 km long sapanca step over 1 2 km wide golcuk step over 1 2 km wide and karamursel step over 4 5 km wide the earthquake nucleated within or near the golcuk step over with bilateral rupture propagation to the west and east to the west about 4 5 5 m of surface rupture up to 7 m of subsurface rupture on the golcuk segment was mostly if not entirely arrested by the 4 to 5 km wide karamursel step over to the east about 3 4 m of surface rupture about 4 m of subsurface rupture propagated through the 1 to 2 km wide sapanca step over triggering up to 4 5 5 5 m of surface rupture up to 5 6 m of subsurface rupture on the sakarya segment rupture on the sakarya segment stepped across the akyazi gap triggering 1 1 5 m of rupture on the karadere segment rupture on the karadere segment was arrested by the 2 to 4 km wide eften lake step over modeling of the transient stress field associated with the rupture propagation agrees well with the field observations the modeled fault rupture of 5 m on the golcuk segment appears to decrease the transient stress on the eastern tip of the adjoining yalova segment across the 4 to 5 km wide karamursel step over even if we allow rupture on the golcuk segment to extend along the entire southern margin of the step over our model shows that regardless of the amount of slip in a generic sense it is difficult to increase stress on the tip of an adjoining fault segment across a 5 km wide step over on the other hand fault rupture of 3 m on the western tip of the sapanca fault segment significantly increases the transient stress on the adjoining sakarya segment across the 1 to 2 km wide sapanca step over allowing rupture propagation across the basin an evaluation of 30 historical strike slip earthquakes involving 59 step over basins supports our field observations and stress modeling of the izmit fault rupture historical strike slip events with small to large displacements usually propagate through step overs less than 1 2 km wide with increasing displacement larger and larger step overs can be ruptured through the empirical data generally show a ratio ranging from 2 1 to 1 1 between step over width in kilometers and strike slip displacement in meters for a through going rupture however step overs of 4 to 5 km width appear to always arrest fault rupture regardless of the amount of displacement these results therefore provide important constraints for evaluating the probability of multisegment ruptures on segmented strike slip faults manuscript received 20 august 2000

role of pressure solution in the formation of bedding parallel calcite veins in an immature shale cretaceous southern uk bedding parallel fibrous calcite veins in black shales cretaceous southern uk were investigated using a combined field stable isotopic geochemistry petrographic and crystallographic method to examine their formation mechanism calcite veins occur in all shale beds and are most abundant in the bituminous shales of the chief beef beds the calcite fibres in these veins exhibit either an antitaxial fibre growth with curvy stylolites as the median zone or a predominantly syntaxial upwards growth the calcite veins range from 0 49 to 1 78 of 13c values and 6 53 to 0 03 of 18o values which are both similar to those of their host shales our petrographic observations demonstrate that subhorizontal and interconnecting microstylolite networks commonly occur within the calcite veins equant calcite grains in the median zones exhibit indenting truncating and also interpenetrating grain contacts it is interpreted that the fibrous calcite veins were sourced by neomorphic calcite from their host shales with evidence from the 13c signatures pressure solution features stylolites microstylolites and grain contact styles and embedded fossil ghosts within the veins the diagenetic fluids from which calcite was precipitated were a mixing of the original seawaters and 18o depleted meteoric waters development of bedding parallel calcite veins is considered to have been enhanced by pressure solution as a positive feedback mechanism which was facilitated by the overburden pressure as the maximum principal stress calcite fibres with a predominant subvertical c axis orientation exhibit a displacive growth in porous shales and a replacive growth at vein limestone contacts this study highlights the critical role of pressure solution in the formation of bedding parallel calcite veins during burial and diagenesis of immature black shales

displacement and geometrical characteristics of earthquake surface ruptures issues and implications for seismic hazard analysis and the process of earthquake rupture there now exist about three dozen historical earthquakes for which in vestigators have constructed maps of earthquake rupture traces accompanied by de scriptions of the coseismic slip observed along the fault strike the maps and slip distributions are compiled here to place observational bounds on aspects of seismic hazard analysis and fault mechanics analysis leads to an initial statistical basis to predict the end points of rupture and the amount of surface slip expected at sites along the strike during earthquakes on mapped faults the observations also give support to the ideas that there exists a process zone or volume of about 3 4 km in dimension at the fronts of large laterally propagating earthquake ruptures within which stress changes may be sufficient to trigger slip on adjacent faults and that the ultimate length of earthquake ruptures is controlled primarily by the geometrical complexity of fault traces and variations in accumulated stress levels along faults that arise due to the location of past earthquakes to this may be added the observation that the form of earthquake surface slip distributions is better described by asymmetric rather than symmetric curve forms and that earthquake epicenters do not appear to correlate in any systematic manner to regions of maximum surface slip observed along strike online material maps of surface ruptures digitized values and curve fits to surface slip distributions and notes and references for tables 1 and 2

antarctic contribution to sea level rise observed by grace with improved gia correction antarctic volume changes during the past 21 thousand years are smaller than previously thought and here we construct an ice sheet history that drives a forward model prediction of the glacial isostatic adjustment gia gravity signal the new model in turn should give predictions that are constrained with recent uplift data the impact of the gia signal on a gravity recovery and climate experiment grace antarctic mass balance estimate depends on the specific grace analysis method used for the method described in this paper the gia contribution to the apparent surface mass change is re evaluated to be 55 13 gt yr by considering a revised ice history model and a parameter search for vertical motion predictions that best fit the gps observations at 18 high quality stations although the gia model spans a range of possible earth rheological structure values the data are not yet sufficient for solving for a preferred value of upper and lower mantle viscosity nor for a preferred lithospheric thickness grace monthly solutions from the center for space research release 04 csr rl04 release time series from january 2003 to the beginning of january 2012 uncorrected for gia yield an ice mass rate of 2 9 29 gt yr the new gia correction increases the solved for ice mass imbalance of antarctica to 57 34 gt yr the revised gia correction is smaller than past grace estimates by about 50 to 90 gt yr the new upper bound to the sea level rise from the antarctic ice sheet averaged over the time span 2003 0 2012 0 is about 0 16 0 09 mm yr

contemporary seismicity active faulting and seismic hazards of the coast ranges between san francisco bay and healdsburg california contemporary seismicity in the northern california coast ranges from san francisco bay to the town of healdsburg and east of the seismically quiescent north coast segment of the san andreas fault is generally confined to the intensely deformed santa rosa block relative to the adjacent sebastopol block much of this activity is concentrated along the rodgers creek healdsburg bennett valley and maacama faults a prominent gap in microseismicity exists along much of the 43 km long rodgers creek fault although paleoseismological evidence suggests that the fault has generated at least three paleoearthquakes of moment magnitude mw 7 or greater during the late holocene budding et al 1991 earthquakes in the region are generally confined to upper crustal depths of less than 10 12 km right lateral strike slip faulting on both northwest and north striking faults is currently the primary mode of regional crustal deformation based on observed focal mechanisms although both reverse faulting especially in the vicinity of the major quaternary faults and normal faulting occur within the region the tectonic stress field in the region is dominated by north northeast to northeast directed compressive stresses although the rodgers creek fault may pose the highest known level of seismic hazard in the region in the next few decades abundant geological evidence and the contemporary seismicity suggest that faults such as the healdsburg bennett valley and maacama faults also pose significant hazards because of their potential to generate mw 6 7 earthquakes

ongoing deformation of antarctica following recent great earthquakes antarctica s secular motion is thought to be almost everywhere governed by horizontal rigid plate rotation plus three dimensional deformations due to past and present changes in ice ocean loading known as glacial isostatic adjustment gia we use geodetic data to investigate deformation following the 1998 m 8 2 antarctic intraplate earthquake and show sustained three dimensional deformation along east antarctica s coastline 600 km from the rupture location using a model of viscoelastic deformation we are able to match observed northward velocity changes and either east or height but not all three directions simultaneously apparently partly due to lateral variations in mantle rheology our modeling predicts that much of antarctica may still be deforming with further deformation possible from the 2004 m 8 macquarie ridge earthquake this previously unconsidered mode of antarctic deformation affects geodetic estimates of plate motion and gia its viscous nature raises the prospect of further present day deformation due to earlier great earthquakes

a fault scarp in an urban area identified by lidar survey a case study on the itoigawa shizuoka tectonic line central japan abstract a light detection and ranging lidar survey was conducted in a densely built up area to generate a high resolution digital elevation model dem to look for active faults the urban district of matsumoto city in central japan is located in a 3 km 2 basin along the itoigawa shizuoka tectonic line active fault system one of japanese onshore fault systems with the highest earthquake probability a high resolution dem at a 0 5 m grid interval was obtained after removing the effects of laser returns from buildings clouds and vegetation it revealed a continuous scarp up to 2 m in height borehole data and archaeological studies indicate the scarp was formed during the most recent faulting event associated with historical earthquakes in addition the fault scarp strongly supports that the urban district is in a pull apart basin related to a fault step over between two left lateral strike slip faults consequently accurate interpretation of fault geometry is crucial to provide estimates of future surface deformation and to allow modeling of basin structure and strong ground motion thus the lidar mapping survey in urban districts is effective for detailed active fault mapping in order to constrain basin structure and to forecast the exact location of surface rupturing associated with large earthquakes

approximating edges of source bodies from magnetic or gravity anomalies cordell and grauch 1982 1985 discussed a technique to estimate the location of abrupt lateral changes in magnetization or mass density of upper crustal rocks the final step of their procedure is to identify maxima on a contoured map of horizontal gradient magnitudes we attempt to automate their final step our method begins with gridded magnetic or gravity anomaly data and produces a plan view of inferred boundaries of magnetic or gravity sources the method applies to both local surveys and to continent wide compilations of magnetic and gravity data e g zietz 1982 simpson et al 1983a kane et al 1982

seismic velocity structure and seismotectonics of the eastern san francisco bay region california the hayward fault system is considered the most likely fault system in the san francisco bay area california to produce a major earthquake in the next 30 years to better understand this fault system we use microseismicity to study its structure and kinematics we present a new 3d seismic velocity model for the eastern san francisco bay region using microseismicity and controlled sources which reveals a 10 velocity contrast across the hayward fault in the upper 10 km with higher velocity in the franciscan complex to the west relative to the great valley sequence to the east this contrast is imaged more sharply in our localized model than in previous regional scale models thick cenozoic sedimentary basins such as the livermore basin which may experience particularly strong shaking during an earthquake are imaged in the model the accurate earthquake locations and focal mechanisms obtained by using the 3d model allow us to study fault complexity and its implications for seismic hazard the relocated hypocenters along the hayward fault in general are consistent with a near vertical or steeply east dipping fault zone the southern hayward fault merges smoothly with the calaveras fault at depth suggesting that large earthquakes may rupture across both faults the use of the 3d velocity model reveals that most earthquakes along the hayward fault have near vertical strike slip focal mechanisms consistent with the large scale orientation and sense of slip of the fault with no evidence for zones of complex fracturing acting as barriers to earthquake rupture online material velocity model validation experiments and additional seismicity plots

slip rate earthquake recurrence and seismogenic potential of the rodgers creek fault zone northern california initial results instrumental seismicity defines a seismic gap along the rodgers creek fault zone rcfz between santa rose and san pablo bay results of a paleoseismicity study within the gap using offset channels in late holocene alluvial deposits as piercing points indicate a minimum slip rate of 2 1 to 5 8 mm yr for the past 1 300 years a preferred range for the maximum recurrence interval of 248 to 679 years and a surface offset of 2 0 3 minus 0 2 m during the most recent event the rcfz has produced past m7 earthquakes and historical seismicity data indicate a minimum elapsed time of 182 years since the most recent earthquake of this size

application of airborne lidar to mapping seismogenic faults in forested mountainous terrain southeastern alps slovenia results are presented of the first airborne lidar survey ever flown in europe for the purpose of mapping the surface expression of earthquake prone faults detailed topographic images derived from lidar data of the idrija and ravne strike slip faults in nw slovenia reveal geomorphological and structural features that shed light on the overall architecture and kinematic history of both fault systems the 1998 mw 5 6 and 2004 mw 5 2 ravne fault earthquakes and the historically devastating 1511 m 6 8 idrija earthquake indicate that both systems pose a serious seismic hazard in the region because both fault systems occur within forested terrain a tree removal algorithm was applied to the data the resulting images reveal surface scarps and tectonic landforms in unprecedented detail importantly two sites were discovered to be potentially suitable for fault trenching and palaeo seismological analysis this study highlights the potential contribution of lidar surveying in both low relief valley terrain and high relief mountainous terrain to a regional seismic hazard assessment programme geoscientists working in other tectonically active regions of the world where earthquake prone faults are obscured by forest cover would also benefit from lidar maps that have been processed to remove the canopy return and reveal the forest floor topography

on postglacial sea level summary an exact method is presented for calculating the changes in sea level that occur when ice and water masses are rearranged on the surface of elastic and viscoelastic non rotating earth models the method is used to calculate the instantaneous elastic and delayed vi scoelastic sea level changes following the partial melting of late quaternary ice sheets we find that there can be large errors in the usual assumption that changes in sea level are uniform over the ocean basins if a quantity of ice equivalent to a uniform 100 m rise in sea level melts from the laurentide and fennoscandian ice sheets then in the south pacific the instantaneous rise in sea level can be as large as 120m in the north atlantic the instantaneous rise is always less than 100 m there is a zone in the north atlantic with almost no sea level change and near greenland and norway the sea level falls rather than rises by over 100 m one thousand years after the melting a forebulge migrating towards the ice loads causes water to flow from the south pacific into the north pacific suggesting that raised beaches should occur in the south pacific the gravitational attraction of an ice mass upon a nearby ocean tends to hold sea level high in the vicinity of the ice this extra load near the ice may have a significant influence on postglacial isostatic adjustment

separation of tectonic and local components of horizontal gps station velocities a case study for glacial isostatic adjustment in east antarctica accurate measurement of the local component of geodetic motion at gps stations presents a challenge due to the need to separate this signal from the tectonic plate rotation a pressing example is the observation of glacial isostatic adjustment gia which constrains the earth s response to ice unloading and hence contributions of ice covered regions such as antarctica to global sea level rise following ice mass loss while both vertical and horizontal motions are of interest in general we focus on horizontal gps velocities which typically contain a large component of plate rotation and a smaller local component primarily relating to gia incomplete separation of these components introduces significant bias into estimates of gia motion vectors we present the results of a series of tests based on the motions of gps stations from east antarctica 1 signal separation for sets of synthetic data that replicate the geometric character of non separable and separable gia like horizontal velocities and 2 signal separation for real gps station data with an appraisal of uncertainties for both synthetic and real motions we compare results where the stations are unweighted and where each station is areal weighted using a metric representing the inverse of the spatial density of neighbouring stations from the synthetic tests we show that a gia like signal is recoverable from the plate rotation signal providing it has geometric variability across east antarctica we also show that areal weighting has a very significant effect on the ability to recover a gia like signal with geometric variability and hence on separating the plate rotation and local components for the real data assuming a rigid antarctic plate fitted plate rotation parameters compare well with other studies in the literature we find that 25 out of 36 gps stations examined in east antarctica have non zero local horizontal velocities at the 2 level after signal separation we make the code for weighted signal separation available to assist in the consistent appraisal of separated signals and the comparison of likely uncertainty bounds for future studies

using surface creep rate to infer fraction locked for sections of the san andreas fault system in northern california from alignment array and gps data surface creep rate observed along five branches of the dextral san andreas fault system in northern california varies considerably from one section to the next indicating that so too may the depth at which the faults are locked we model locking on 29 fault sections using each section s mean long term creep rate and the consensus values of fault width and geologic slip rate surface creep rate observations from 111 short range alignment and trilateration arrays and 48 near fault global positioning system station pairs are used to estimate depth of creep assuming an elastic half space model and adjusting depth of creep iteratively by trial and error to match the creep observations along fault sections fault sections are delineated either by geometric discontinuities between them or by distinctly different creeping behaviors we remove transient rate changes associated with five large m 5 5 regional earthquakes estimates of fraction locked the ratio of moment accumulation rate to loading rate on each section of the fault system provide a uniform means to inform source parameters relevant to seismic hazard assessment from its mean creep rates we infer the main branch the san andreas fault ranges from only 20 10 locked on its central creeping section to 99 100 on the north coast from mean accumulation rates we infer that four urban faults appear to have accumulated enough seismic moment to produce major earthquakes the northern calaveras m 6 8 hayward m 6 8 rodgers creek m 7 1 and green valley m 7 1 the latter three faults are nearing or past their mean recurrence interval online material high resolution fault system map and tables of creep observations and geographic coordinates of fault model

long term creep rates on the hayward fault evidence for controls on the size and frequency of large earthquakes the hayward fault hf in california exhibits large m w 6 5 7 1 earthquakes with short recurrence times 161 65 yr probably kept short by a 26 78 aseismic release rate including postseismic its interseismic release rate varies locally over time as we infer from many decades of surface creep data earliest estimates of creep rate primarily from infrequent surveys of offset cultural features revealed distinct spatial variation in rates along the fault but no detectable temporal variation since the 1989 m w 6 9 loma prieta earthquake lpe monitoring on 32 alinement arrays and 5 creepmeters has greatly improved the spatial and temporal resolution of creep rate we now identify significant temporal variations mostly associated with local and regional earthquakes the largest rate change was a 6 yr cessation of creep along a 5 km length near the south end of the hf attributed to a regional stress drop from the lpe ending in 1996 with a 2 cm creep event north of there near union city starting in 1991 rates apparently increased by 25 above pre lpe levels on a 16 km long reach of the fault near oakland in 2007 an m w 4 2 earthquake initiated a 1 2 cm creep event extending 10 15 km along the fault using new better constrained long term creep rates we updated earlier estimates of depth to locking along the hf the locking depths outline a single 50 km long locked or retarded patch with the potential for an m w 6 8 event equaling the 1868 hf earthquake we propose that this inferred patch regulates the size and frequency of large earthquakes on hf online material 2007 event creep models plots of creepmeter data maps and cross sections of relocated microearthquakes and active fault traces and iterative solutions for depth of creep

depositional and compositional controls on sandstone diagenesis the tetori group middle jurassic early cretaceous central japan abstract the tetori group is a representative middle jurassic to lower cretaceous deposit in the northern central part of honshu japan the tetori group is divided into the kuzuryu itoshiro and akaiwa subgroups with decreasing age it consists mainly of a marine sequence in the lower part kuzuryu subgroup and non marine sequence in the upper part akaiwa subgroup with transitional sequence in the middle part itoshiro subgroup diagenesis of tetori group sandstones comprises compaction cementation and replacement early diagenetic events include mechanical compaction and pore filling cementation of calcite siderite dolomite and formation of kaolinite late diagenesis includes formation of quartz cement and albitization of feldspar and formation of illite chlorite calcite ankerite and pyrite among the diagenetic minerals carbonate forms the major cement in tetori group sandstones calcite of each subgroup is subdivided into two or three types based on cathodoluminescence tetori group sandstones of marine fresh water and mixed depositional environments are characterized by distinct chemical compositions of early diagenetic calcites late diagenesis seems to have been mainly influenced by detrital compositions of the sequence burial temperatures and partially hydrothermal processes especially late diagenetic carbonate and authigenic clay minerals seem to have formed mainly from ions released from clay mineral transformations in the adjacent shales based on the illite crystallinity ic the kuzuryu subgroup exhibits higher diagenetic grades than the overlying itoshiro and akaiwa subgroups indicating that the diagenesis of the tetori group was mainly affected by depth of burial

large scale relocation of two decades of northern california seismicity using cross correlation and double difference methods 1 we simultaneously reanalyzed two decades 1984 2003 of the digital seismic archive of northern california using waveform cross correlation cc and double difference dd methods to improve the resolution in hypocenter locations in the existing earthquake catalog generated at the northern california seismic network ncsn by up to three orders of magnitude we used a combination of 3 billion cc differential times measured from all correlated pairs of events that are separated by less than 5 km and 7 million p wave arrival time picks listed in the ncsn bulletin data were inverted for precise relative locations of 311 273 events using the dd method the relocated catalog is able to image the fine scale structure of seismicity associated with active faults and revealed characteristic spatiotemporal structures such as streaks and repeating earthquakes we found that 90 of the earthquakes have correlated p wave and s wave trains at common stations and that 12 are colocated repeating events an analysis of the repeating events indicates that uncertainties at the 95 confidence level in the existing network locations are on average 0 7 km laterally and 2 km vertically correlation characteristics and relative location improvement are remarkably similar across most of northern california implying the general applicability of these techniques to image high resolution seismicity caused by a variety of plate tectonic and anthropogenic processes we show that consistent long term seismic monitoring and data archiving practices are key to increase resolution in existing hypocenter catalogs and to estimate the precise location of future events on a routine basis

rapid ice unloading in the fleming glacier region southern antarctic peninsula and its effect on bedrock uplift rates rapid regional warming in the antarctic peninsula has led to the significant retreat and eventual collapse of several major ice shelves since the 1970s triggering the subsequent acceleration and thinning of their feeding glaciers the wordie ice shelf lying off the west coast of the antarctic peninsula has undergone long term disintegration since the 1960s with a substantial calving event occurring around 1989 followed by continuous steady retreat and its almost complete disappearance the dynamic response of the upstream glaciers to the ice shelf collapse and the response of the solid earth to the associated mass loss are not fully understood to quantify the mass loss from the system we generated a digital elevation model dem using airborne vertical and oblique imagery from 1966 and compared it to a dem derived from 2008 spot data this analysis reveals lowering over that time of approximately 60 m at the front of fleming glacier using icebridge and icesat 2 glas data spanning 2002 2014 we show an increased rate of mean ice surface lowering with rates post 2008 more than twice those of 2002 2008 we use these load change data as a basis for the simulation of viscoelastic solid earth deformation we subtract modeled elastic deformation rates and a suite of modeled viscous rates from gps derived three dimensional bedrock velocities at sites to the south of fleming glacier to infer properties of earth rheology assuming the pre breakup bedrock uplift was positive due to post last glacial maximum lgm ice retreat our viscoelastic corrected gps uplift rates suggest upper mantle viscosities are 2 1019pas and likely 1 1020pas in this region 1 2 orders of magnitude greater than previously found for the northern antarctic peninsula horizontal velocities at the gps site nearest the fleming glacier after the application of elastic and plate tectonic corrections point away from marguerite bay rather than the present glacier front this suggests that horizontal motion in the region reflects the earlier retreat of the glacier system following the lgm compatible with a relatively strong mantle in this region these findings highlight the need for improved understanding of ice load changes in this region through the late holocene in order to accurately model glacial isostatic adjustment

gravity and magnetic expression of the san leandro gabbro with implications for the geometry and evolution of the hayward fault zone northern california the hayward fault one of the most hazardous faults in northern california trends north northwest and extends for about 90 km along the eastern san francisco bay region at numerous locations along its length distinct and elongate gravity and magnetic anomalies correlate with mapped mafic and ultramafic rocks the most prominent of these anomalies reflects the 16 km long san leandro gabbroic block inversion of magnetic and gravity data constrained with physical property measurements is used to define the subsurface extent of the san leandro gabbro body and to speculate on its origin and relationship to the hayward fault zone modeling indicates that the san leandro gabbro body is about 3 km wide dips about 75 80 northeast and extends to a depth of at least 6 km one of the most striking results of the modeling which was performed independently of seismicity data is that accurately relocated seismicity is concentrated along the western edge or stratigraphically lower bounding surface of the san leandro gabbro the western boundary of the san leandro gabbro block is the base of an incomplete ophiolite sequence and represented at one time a low angle roof thrust related to the tectonic wedging of the franciscan complex after repeated episodes of extension and attenuation the roof thrust of this tectonic wedge was rotated to near vertical and in places the strike slip hayward fault probably reactivated or preferentially followed this preexisting feature because earthquakes concentrate near the edge of the san leandro gabbro but tend to avoid its interior we qualitatively explore mechanical models to explain how this massive igneous block may influence the distribution of stress the microseismicity cluster along the western flank of the san leandro gabbro leads us to suggest that this stressed volume may be the site of future moderate to large earthquakes improved understanding of the three dimensional geometry and physical properties along the hayward fault will provide additional constraints on seismic hazard probability earthquake modeling and fault interactions that are applicable to other major strike slip faults around the world manuscript received 11 january 2002

basin structure beneath the santa rosa plain northern california implications for damage caused by the 1969 santa rosa and 1906 san francisco earthquakes regional gravity data in the northern san francisco bay region reflect a complex basin configuration beneath the santa rosa plain that likely contributed to the significant damage to the city of santa rosa caused by the 1969 m 5 6 5 7 santa rosa earthquakes and the 1906 m 7 9 san francisco earthquake inversion of these data indicates that the santa rosa plain is underlain by two sedimentary basins about 2 km deep separated by the trenton ridge a shallow west northwest striking bedrock ridge west of santa rosa the city of santa rosa is situated above the 2 km wide protruding northeast corner of the southern basin where damage from both the 1969 and 1906 earthquakes was concentrated ground motion simulations of the 1969 and 1906 earthquakes two events with opposing azimuths using the gravity defined basin surface show enhanced ground motions along the northeastern edge of this corner suggesting that basin edge effects contributed to the concentration of shaking damage in this area in the past and may also contribute to strong shaking during future earthquakes

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

rapid bedrock uplift in the antarctic peninsula explained by viscoelastic response to recent ice unloading abstract since 1995 several ice shelves in the northern antarctic peninsula have collapsed and triggered ice mass unloading invoking a solid earth response that has been recorded at continuous gps cgps stations a previous attempt to model the observation of rapid uplift following the 2002 breakup of larsen b ice shelf was limited by incomplete knowledge of the pattern of ice unloading and possibly the assumption of an elastic only mechanism we make use of a new high resolution dataset of ice elevation change that captures ice mass loss north of 66 s to first show that non linear uplift of the palmer cgps station since 2002 cannot be explained by elastic deformation alone we apply a viscoelastic model with linear maxwell rheology to predict uplift since 1995 and test the fit to the palmer cgps time series finding a well constrained upper mantle viscosity but less sensitivity to lithospheric thickness we further constrain the best fitting earth model by including six cgps stations deployed after 2009 the larissa network with vertical velocities in the range 1 7 to 14 9 mm yr this results in a best fitting earth model with lithospheric thickness of 100 140 km and upper mantle viscosity of 6 10 17 2 10 18 pa s much lower than previously suggested for this region combining the larissa time series with the palmer cgps time series offers a rare opportunity to study the time evolution of the low viscosity solid earth response to a well captured ice unloading event

large earthquakes and creeping faults faults are ubiquitous throughout the earth s crust the majority are silent for decades to centuries until they suddenly rupture and produce earthquakes with a focus on shallow continental active tectonic regions this paper reviews a subset of faults that have a different behavior these unusual faults slowly creep for long periods of time and produce many small earthquakes the presence of fault creep and the related microseismicity helps illuminate faults that might not otherwise be located in fine detail but there is also the question of how creeping faults contribute to seismic hazard it appears that well recorded creeping fault earthquakes of up to magnitude 6 6 that have occurred in shallow continental regions produce similar fault surface rupture areas and similar peak ground shaking as their locked fault counterparts of the same earthquake magnitude the behavior of much larger earthquakes on shallow creeping continental faults is less well known because there is a dearth of comprehensive observations computational simulations provide an opportunity to fill the gaps in our understanding particularly of the dynamic processes that occur during large earthquake rupture and arrest

present tectonic motion across the coast ranges and san andreas fault system in central california geodetic results from very long baseline interferometry vlbi satellite laser ranging slr and the global positioning system gps are used to estimate angular velocities between the sierran microplate pacific plate and north american plate the sierra pacific pole of rotation lies nearer to the san andreas fault than does the pacific north america pole of rotation and leads to different tectonic implications than if the latter is used the angular velocities show that the san andreas fault system and central california coast ranges accommodate motion of 39 2 mm yr mainly by strike slip faulting all confidence limits following signs in this paper are 95 confidence limits fault normal motion is small is mainly convergent at rates up to 3 3 1 0 mm yr and varies along the coast but is divergent at 2 6 1 2 mm yr across san pablo bay and associated topographic lows across which the sierran and central valley watershed drains to the pacific ocean the mountain ranges tend to be larger where the fault normal convergence rates are larger the low convergence rate 0 5 1 8 mm yr normal to the san andreas fault in the carrizo plain differs sharply from that previously inferred 8 2 1 2 mm yr and 4 9 1 6 mm yr by feigl et al 1993 the difference is due to differences between their and our elastic strain accumulation models and between how their and our pacific plate reference frames are defined the ranges in most places require a minimum of 4 2 1 m y of fault normal convergence at the present rate to attain their present cross sectional area if erosion is neglected more if it is not the amount of convergence previously estimated from a balanced cross section across the diablo range in central california requires 10 8 3 m y of convergence at the present rate the former is consistent with widely held views about the onset of the coast range orogeny but the latter is not both are consistent however with the recent plate reconstructions by s cande j stock and colleagues which indicate that pacific plate motion relative to north america changed to a more convergent direction 20 25 clockwise of its prior direction at ca 8 to 6 ma and not at 3 5 ma as had been previously inferred the inferred change in direction of plate motion is large compared with the present angle of convergence across the straight and narrow segment of the san andreas fault of 0 7 4 7 from which we infer that the sierran microplate changed motion relative to north america at the same time ca 8 to 6 ma as did the pacific plate we further infer that the motion accommodated across the great basin must also have changed at the same time we also examine the hypothesis that stable sliding occurs along the san andreas fault and other northwest striking strike slip faults in central california where the fault normal convergence rate is low or negative and that these faults are unstable where the fault normal convergence rate is high such a relationship appears to hold in general but fails in detail in particular there are substantial sections of fault with small inferred rates of fault normal convergence across which the san andreas fault is locked moreover the creeping section of the san andreas fault i e the section between parkfield and the calaveras junction is the locus of greater fault normal convergence 3 2 1 4 mm yr than is the locked part of the fault 0 5 1 8 mm yr south of parkfield thus this hypothesis is at best a partial explanation for the observed distribution of locked and nonlocked sections of the fault

global shear speed structure of the upper mantle and transition zone s u m m a r y the rapid expansion of broad band seismic networks over the last decade has paved the way for a new generation of global tomographic models significantly improved resolution of global upper mantle and crustal structure can now be achieved provided that structural information is extracted effectively from both surface and body waves and that the effects of errors in the data are controlled and minimized here we present a new global vertically polarized shear speed model that yields considerable improvements in resolution compared to previous ones for a variety of features in the upper mantle and crust the model sl2013sv is constrained by an unprecedentedly large set of waveform fits 3 4 of a million broad band seismograms computed in seismogram dependent frequency bands up to a maximum period range of 11 450 s automated multimode inversion of surface and s wave forms was used to extract a set of linear equations with uncorrelated uncertainties from each seismogram the equations described perturbations in elastic structure within approximate sensitivity volumes between sources and receivers going beyond ray theory we calculated the phase of every mode at every frequency and its derivative with respect to sand p velocity perturbations by integration over a sensitivity area in a 3 d reference model the normally small perturbations of the 3 d model required to fit the waveforms were then linearized using these accurate derivatives the equations yielded by the waveform inversion of all the seismograms were simultaneously inverted for a 3 d model of shear and compressional speeds and azimuthal anisotropy within the crust and upper mantle elaborate outlier analysis was used to control the propagation of errors in the data source parameters timing at the stations etc the selection of only the most mutually consistent equations exploited the data redundancy provided by our data set and strongly reduced the effect of the errors increasing the resolution of the imaging our new shear speed model is parametrized on a triangular grid with a 280 km spacing in well sampled continental domains lateral resolution approaches or exceeds that of regionalscale studies the close match of known surface expressions of deep structure with the distribution of anomalies in the model provides a useful benchmark in oceanic regions spreading ridges are very well resolved with narrow anomalies in the shallow mantle closely confined near the ridge axis and those deeper down to 100 120 km showing variability in their width and location with respect to the ridge major subduction zones worldwide are well captured extending from shallow depths down to the transition zone the large size of our waveform fit data set also provides a strong statistical foundation to re examine the validity field of the jwkb approximation and surface wave ray theory our analysis shows that the approximations are likely to be valid within certain time frequency portions of most seismograms with high signal to noise ratios and these portions can be identified using a set of consistent criteria that we apply in the course of waveform fitting

detection of subtle tectonic geomorphic features in densely forested mountains by very high resolution airborne lidar survey abstract despite successes elsewhere in the world 2 m resolution dems from a standard airborne lidar survey failed to detect small tectonic geomorphic features in densely forested high relief mountains of central japan our new 0 5 m dems from an unprecedentedly high resolution lidar survey along the neodani fault now reveal a number of previously unknown fault scarps as well as other hidden geomorphic features the survey achieves a ground return density of 6 2 m 2 out of a total shot density of as much as 12 7 m 2 the main factor to gain sufficient ground returns in unfavorable conditions is a large side lap of 70 between flight swaths which means that any specific area in the target zone is scanned three or more times from different angles evaluation of dems with resolution from 0 25 to 10 m assures that a 0 5m resolution lidar dem is necessary for the detection of subtle tectonic breaks another key factor for complete detection of small tectonic geomorphic features is the application of a recently developed dem visualization red relief image map rrim which allows mapping of all the small features with various sizes orientations and morphology overcoming major drawbacks of classic dem visualizations a very high resolution lidar survey aided with rrim visualization as used in this study provides a more reliable approach for the detailed mapping of slight active fault traces hidden under dense vegetation

effects of early petroleum charge and overpressure on reservoir porosity preservation in the giant kela 2 gas field kuqa depression tarim basin northwest china kela 2 is a giant gas field with a proven reserve of 597 tcf in the kuqa depression northern tarim basin widespread overpressures have been encountered in the eocene and cretaceous sandstone reservoirs of the field with pressure coefficients up to 2 1 from drill stem tests and well log data analysis disequilibrium compaction associated with horizontal tectonic compression may be the dominant overpressure mechanism in the sandstone reservoirs because the overpressured sandstone with a maximum burial depth over 6000 m 19 685 ft displays anomalously high porosity and low density the causes for sandstone reservoirs with anomalously high porosity in the kela 2 gas field were studied based on an integrated investigation of sandstone reservoir characteristics paleo oil water contact petroleum charge history and overpressure evolution collective evidence indicates that early oil charge had retarded the porosity reduction of the reservoir sandstone and resulted in disequilibrium compaction from overburden rocks and overpressure from disequilibrium compaction and horizontal tectonic compression at the beginning of the rapid subsidence and deposition in the kela 2 gas field again contributed to the preservation of the reservoir porosity 1 overpressured mudstones in the kela 2 gas field are characteristic of normal compaction and overpressure was generated by horizontal tectonic compression instead of disequilibrium compaction 2 the reservoir sandstones with high porosity and permeability are associated with high paleo oil saturation as indicated by quantitative grain fluorescence qgf responses and anomalous qgf on extract intensity 3 sandstone units below the paleo oil water contact have very low porosity and permeability and 4 three episodes of oil and one episode of gas charge are identified in the sandstone reservoirs of the kela 2 gas field and the later two episodes of oil charge occurred circa 5 5 4 5 ma which corresponds to the beginning of the rapid tectonic subsidence and deposition in the kuqa depression the initially charged oil in the sandstone reservoirs was subsequently displaced by gas at circa 3 2 ma through fault activation at the edge of the anticline trap the overpressure evolution for the k1bs reservoir sandstone in the kela 2 gas field indicates that the apparent overpressure development in the sandstone reservoir began at 5 ma following the major oil charge and has been maintained to the present overpressure development from 5 ma in the sandstone reservoirs of the kela 2 gas field is believed to be the dominant cause of the porosity preservation