on mobilization of lead and arsenic in groundwater in response to co2 leakage from deep geological storage if carbon dioxide stored in deep saline aquifers were to leak into an overlying aquifer containing potable groundwater the intruding co sub 2 would change the geochemical conditions and cause secondary effects mainly induced by changes in ph in particular hazardous trace elements such as lead and arsenic which are present in the aquifer host rock could be mobilized in an effort to evaluate the potential risks to potable water quality reactive transport simulations were conducted to evaluate to what extent and mechanisms through which lead and arsenic might be mobilized by intrusion of co sub 2 an earlier geochemical evaluation of more than 38 000 groundwater quality analyses from aquifers throughout the united states and an associated literature review provided the basis for setting up a reactive transport model and examining its sensitivity to model variation the evaluation included identification of potential mineral hosts containing hazardous trace elements characterization of the modal bulk mineralogy for an arenaceous aquifer and augmentation of the required thermodynamic data the reactive transport simulations suggest that co sub 2 ingress into a shallow aquifer can mobilize significant lead and arsenic contaminating the groundwater near the location of intrusion and further downstream although substantial increases in aqueous concentrations aremore predicted compared to the background values the maximum permitted concentration for arsenic in drinking water was exceeded in only a few cases whereas that for lead was never exceeded less

geochemical and mineralogical impacts of h2so4 on clays between ph 5 0 and 3 0 natural and constructed clay liners are routinely used to contain waste and wastewater the impact of acidic solutions on the geochemistry and mineralogy of clays has been widely investigated in relation to acid mine drainage systems at ph 1 0 the impact of h2so4 leachate characterized by ph 1 0 and potentially negative ph values on the geochemistry and mineralogy of clays is however not clear thus laboratory batch experiments were conducted on three natural clay samples with different mass ratios of smectite illite and kaolinite to investigate the impact of h2so4 on the geochemistry and mineralogy of aluminosilicates from ph 5 0 to 3 0 batch testing was conducted at seven ph treatments 5 0 3 0 1 0 0 0 1 0 2 0 and 3 0 using standardized h2so4 solutions for four exposure periods 14 90 180 and 365 d aqueous geochemical and xrd analyses showed increased dissolution of aluminosilicates with decreasing ph and increasing exposure period that smectite was more susceptible to dissolution than illite and kaolinite precipitation of an amorphous silica phase occurred at ph 0 0 and anhydrite precipitated in ca rich clays at ph 1 0 in addition global dissolution rates were calculated for the clays and showed good agreement to literature smectite illite and kaolinite dissolution rates which suggests global dissolution rates for complex clays could be determined from monomineralic studies a stepwise conceptual model of the impact of h2so4 on aluminosilicate geochemistry and mineralogy between ph 5 0 and 3 0 is proposed

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

the impact of co2 on shallow groundwater chemistry observations at a natural analog site and implications for carbon sequestration in a natural analog study of risks associated with carbon sequestration impacts of co2 on shallow groundwater quality have been measured in a sandstone aquifer in new mexico usa despite relatively high levels of dissolved co2 originating from depth and producing geysering at one well ph depression and consequent trace element mobility are relatively minor effects due to the buffering capacity of the aquifer however local contamination due to influx of brackish waters in a subset of wells is significant geochemical modeling of major ion concentrations suggests that high alkalinity and carbonate mineral dissolution buffers ph changes due to co2 influx analysis of trends in dissolved trace elements chloride and co2 reveal no evidence of in situ trace element mobilization there is clear evidence however that as u and pb are locally co transported into the aquifer with co2 rich brackish water this study illustrates the role that local geochemical conditions will play in determining the effectiveness of monitoring strategies for co2 leakage for example if buffering is significant ph monitoring may not effectively detect co2 leakage this study also highlights potential complications that co2 carrier fluids such as brackish waters pose in monitoring impacts of geologic sequestration

slip history and dynamic implications of the 1999 chi chi taiwan earthquake we investigate the rupture process of the 1999 chi chi taiwan earthquake using extensive near source observations including three component velocity waveforms at 36 strong motion stations and 119 gps measurements a three plane fault geometry derived from our previous inversion using only static data ji et al 2001 is applied the slip amplitude rake angle rupture initiation time and risetime function are inverted simultaneously with a recently developed finite fault inverse method that combines a wavelet transform approach with a simulated annealing algorithm ji et al 2002b the inversion results are validated by the forward prediction of an independent data set the teleseismic p and sh ground velocities with notable agreement the results show that the total seismic moment release of this earthquake is 2 7 10 20 n m and that most of the slip occurred in a triangular shaped asperity involving two fault segments which is consistent with our previous static inversion the rupture front propagates with an average rupture velocity of 2 0 km s 1 and the average slip duration risetime is 7 2 s several interesting observations related to the temporal evolution of the chi chi earthquake are also investigated including 1 the strong effect of the sinuous fault plane of the chelungpu fault on spatial and temporal variations in slip history 2 the intersection of fault 1 and fault 2 not being a strong impediment to the rupture propagation and 3 the observation that the peak slip velocity near the surface is in general higher than on the deeper portion of the fault plane as predicted by dynamic modeling

rapid determination of global moment tensor solutions in an effort to improve data services the national earthquake information center has begun a program in cooperation with the incorporated research institutions for seismology data management center iris dmc to produce rapid estimates of the seismic moment tensor for most earthquakes with a body wave magnitude of 5 8 or greater although this program is still undergoing testing and fine tuning an estimate of the moment tensor can usually be produced within 20 minutes of the arrival of the broadband p waveform data from the iris dmc although the speed with which this data can be obtained varies in many cases a solution can be obtained within two hours of the earthquake these solutions do not vary significantly from the final solutions determined using the entire network because of the manner in which the data and the synthetic seismograms are aligned the method is insensitive to the effects of timing errors epicentral mislocation and lateral heterogeneity in earth structure this procedure was implemented in may 1993 the results from that month are presented here

source rupture process of the tecoman colima mexico earthquake of 22 january 2003 determined by joint inversion of teleseismic body wave and near source data the spatial and temporal slip distribution of the tecoman colima mexico earthquake is estimated from near source strong motion and teleseismic body wave data to perform a stable inversion we applied smoothing constraints and determined their optimal relative weights on the observed data using an optimized akaike s bayesian information criterion abic the source parameters are as follows strike dip slip 300 20 93 seismic moment m 2 3 1020 n m source duration 30 sec along strike distance 35 km along dip distance 70 km we found that the rupture process can be divided into three stages the rupture nucleated near the hypocenter stage i then it broke the first asperity centering about 15 km southwest from the epicenter stage ii and the rupture propagated to the northeast and the second asperity was broken stage iii we also estimated the shear stress change due to the rupture process of the mainshock on and around the major fault zone it appears that one cluster of aftershocks for the first 5 days which took place in and adjacent to the zones of stress increased due to the fault rupture during the mainshock but overall correlation between the aftershock location and the stress pattern is not clear manuscript received 14 may 2003

crustal deformation in taiwan results from finite source inversions of six mw 5 8 chi chi aftershocks 1 we inverted strong motion data for the finite source parameters of six large aftershocks of the 1999 chi chi taiwan earthquake to investigate seismogenic structure in taiwan for each event we derived a preferred model by testing different focal mechanisms hypocenters rupture velocities and dislocation risetimes as well as different combinations of stations in more than 1000 inversions we documented how the fits between the waveforms and the corresponding synthetics deteriorated as the hypocenter and focal mechanism deviate from those of the preferred model if the deviation in focal mechanisms and hypocenters is less than 20 and 5 km respectively we generally recovered 80 of the preferred model s synthetic waveform fit unlike the dislocation risetime the rupture velocity used in the inversion had a strong influence on the waveform fits in this study we also used the slip models to study fault geometry two of the aftershocks ruptured on the southern extension of the main shock slip area one strike slip aftershock nucleated within the basement but ruptured mainly within the overlying sedimentary strata suggesting that seismogenic deformation in the basement can influence shallow structures p axes of the derived models have azimuths consistent with current plate motion finally gps displacement derived from the six slip models can explain 80 of the postseismic deformation observed in the aftershock regions indicating that studies of postseismic deformation must take into account the cumulative effects of large shallow aftershocks

seismic remote sensing for the earthquake source process and near source strong shaking a case study of the october 16 1999 hector mine earthquake a new methodology to automatically determine the earthquake source process and near source strong ground motions using regional and local distance data was used to study the october 16 1999 hector mine earthquake mw7 1 broadband displacement data were inverted for the seismic moment tensor and to resolve the fault plane ambiguity independent of aftershock location and surface faulting information the identified nnw striking fault plane was used to invert for the distribution of fault slip over a planar surface the slip model was used to predict near fault peak ground velocity which was found to agree well with the trinet shakemap and also with near fault observations that were not available at the time of the initial analysis our method if automated is capable of providing near source strong ground motion information within 30 minutes of the earthquake origin time even in cases where there are few near fault recording instruments

a very broad band inversion method for the recovery of earthquake source parameters abstract waveform studies of the earthquake source have traditionally been performed in narrow bands of the seismic spectrum waveform matching of p and sh waves emphasizes frequencies near and above the corner frequency normal mode and surface wave analyses on the other hand are performed on data which contain information only below the corner frequency a new method is presented which formally includes the result of a long period centroid moment tensor analysis in an inversion of broad band body wave phases a parametrized source model is used which allows for the recovery of a detailed source time function as well as the direction and magnitude of rupture propagation the technical details and the performance of the method are demonstrated in an analysis of the october 28 1983 borah peak idaho earthquake in particular it is shown how the combination of the long period and broad band data sets in the inversion improves the resolution of both the focal mechanism and the scalar moment the very broad band method is applied in an analysis of the september 19 1985 michoacan m w 8 0 earthquake two concentrations of moment release are identified in the source time function separated by 25 30 s in time the spatial distribution of moment is well explained both by a model of unilateral rupture towards the east with a propagation velocity of 2 4 km s 1 and by two point sources separated by 95 km it is shown that the p wave data are largely insensitive to the scalar moment and that source time functions obtained without consideration of the total moment release exaggerate the heterogeneity of slip on the fault plane source time functions which do contain the total moment show that a large fraction of the moment was released smoothly over the whole duration 80 s of the event the results suggest that the fault plane was characterized by two regions of high stress drop but that a large portion of slip occurred on surrounding weak portions of the plane

moment tensor inversion with single component historical seismograms the 1909 benavente portugal and lambesc france earthquakes summary moment tensor inversion of early xx century mechanical seismograph recordings offers the opportunity to estimate source parameters for a number of important earthquakes this knowledge is crucial for understanding regional tectonics and estimating seismic hazard but processing of the historical seismograms is often difficult especially the rotation of horizontal seismograms into radial p sv and transverse sh components tends to fail for example if one polarity is wrong if the alignment of the seismograms is not correct or if one component is lost to avoid these kind of problems we use a moment tensor inversion scheme that processes the original single component horizontal traces without rotation and rotates the theoretical green s functions instead we show how this approach simplifies the analysis and allows a better use of available data we present moment tensor solutions for two destructive earthquakes in southwestern europe in 1909 the april 23 earthquake near benavente in the lower tagus valley portugal had a moment magnitude mw 6 0 and an estimated centroid depth of 10 km our preferred moment tensor solution indicates reverse faulting nodal planes have strike dip rake of n51 e 52 83 and n242 e 38 99 we propose a blind thrust beneath the tagus valley sediment basin as the responsible fault the june 11 earthquake near lambesc provence france was found to be slightly smaller mw 5 5 and related to oblique reverse faulting at 4 km depth nodal planes of the preferred solution have strike dip rake of n80 e 53 53 and n311 e 50 128 subparallel to the trevaresse fold

finite source modeling of the 1999 taiwan chi chi earthquake derived from a dense strong motion network the 1999 chi chi earthquake m w 7 6 20 september 1999 17 47 15 9 utc located at 23 853 n 120 816 e and depth of 7 5 km inicted severe re gional scale damage to taiwan the strong motion waveeld was captured by a dense network of stations with average station spacing of 5 km which represents the most complete strong motion dataset to date to use to study the kinematic source process of an earthquake we inverted velocity waveforms recorded by 21 stations for the spatial variation in slip on a planar fault model composed of 416 subfaults each with a dimension of 3 5 km by 3 5 km the planar model has a strike of n5 e and a dip of 30 e and the inversion solves for the direction and magnitude of the slip to account for possible temporal source complexity we allowed each subfault to slip within 10 overlapping time windows each with a duration of 3 sec the results show that the source is composed primarily of three major asperities the rst of which is mainly dip slip extending from the hypocenter to the northern end of the surface rupture in this asperity slip occurred in two pulses separated in time by 5 sec the dislocation rise time for each pulse is short 3n4 sec yielding an approximate av erage slip velocity of 80 cm sec the second asperity is located at shallow depth near the northern end of the rupture where very large ground velocities were observed this asperity is on average oblique and shows a temporal rake rotation from pure dip slip to strike slip the rotating rake suggests a low initial shear stress on the northern end of the fault slip in this asperity is dominated by a large pulse with a dislocation rise time of 8 sec a station near the northern end of the surface rupture recorded a peak velocity of 390 cm sec which we nd to be due to the constructive interference of energy radiated from the rst two asperities the third asperity is located south of the epicenter the total moment from the three asperities is 4 1 10 27 dyne cm which was released over a period of 30n35 sec within an area of 900 km 2 synthetics calculated from the three asperity model explain 85 of the data and represent 98 of the total variance reduction our results indicate that slip is conned to the shallow region of the fault deep slip patches are less constrained and that the slip distribution may be representative of fault segmentation along the chelungpu fault system

modified frequency wavenumber algorithm for regional seismograms using filon s quadrature modelling of lg waves in eastern north america summary the main focus of this study is to develop an efficient frequency wavenumber code to synthesize high frequency say 10 hz regional seismograms up to a distance of more than 1000 km in a medium consisting of a large number of crustal layers and investigate effects of regional waveguides on lg waves in this newly developed code the frequency wavenumber response is evaluated by using the filon s quadrature at high frequency and the polynomial approximation of bessei s functions implementing trapezoidal integration at low frequency this has reduced the computation time by several folds compared to the time needed for the trapezoidal integration using this algorithm both broad band seismograms at harvard and short period ectn eastern canadian telemetered network seismograms from 1988 november 25 saguenay earthquake were successfully modelled a moment magnitude of 5 9 was used initially an average waveguide was calibrated to successfully excite the regional pnl and snl waves at hrv its near surface structure constrained by matching the recorded frequency content the crust mantle transition zone was constrained by modelling the strength of the broad band snl waves consisting of sn ssmsnsmssms and ssmssms phases relative to the initial pnl waves the model was modified to consist of thin layers with an alternating high and low velocity distribution to match the high frequency ectn lg waves observed from 300 to 600 km away in addition the effect of a near surface irregular receiver structure on the duration of lg waves was also investigated by convolving its response with the regional lg seismograms initial study suggests this method as viable for modelling the entire lg waves including the coda numerical studies suggest that the shapes and peak amplitudes on lg seismograms depend more strongly on the source depth anelasticity and crustal waveguide than do the pnl seismograms

broadband modeling of local earthquakes three component broadband waveforms of two small earthquakes near upland california recorded on the pasadena broadband high dynamic range instrument were modeled to obtain useful green s functions for this path and to examine the sensitivity of the synthetic seismograms to perturbations of the crustal model we assumed that the source of each event was both simple and known as determined from the caltech usgs array first motions a trapezoidal time function was chosen to fit the width of the direct s wave generalized rays reflectivity and finite difference techniques were used to compute the synthetic seismograms we found that a simple layer over a half space model is an adequate approximation of the upper crust along this profile in particular the waveforms are controlled by a relatively slow 4 km thick surficial layer 4 5km s 1 2 6 km s 1 over a faster layer 5 9 km s 1 3 5 km s 1 the relative amplitudes of direct and multiple s indicate that the main shock occurred at a depth of 6 km while the aftershock occurred at a depth of 8 to 9 km sensitivity analyses indicate that for distances less than 50 km and for periods longer than 1 sec the synthetic seismograms are not very sensitive to perturbations of the deep crustal structure analysis of upper crustal model perturbations revealed that the surficial layer is between 3 to 5 km thick in addition the contact between this layer and the underlying material can be smoothed with a 2 km wide velocity gradient without adversely affecting the fit to the data two dimensional finite difference calculations show that a ridge structure beneath the recorder acts as a lowpass filter the lower frequency phases are largely unaffected other two dimensional models with ridges between the source and receiver clearly did not fit the data synthetic seismograms computed for the best fitting model were used to estimate a long period moment of 6 2 1022 dyne cm ml 4 6 and 1 1022 dyne cm ml 3 7 with identical triangular source time durations of 0 3 sec assuming the same fault dimension of 0 4 km from standard scaling laws stress drop estimates of 410 and 70 bars are obtained for the two events respectively generally we found that it is possible to reproduce local waveforms at frequencies up to 1 hz without a complete knowledge of fine structural detail resulting green s functions can be useful in studying historic events and in simulations of large events from a given source region

advancement in source estimation techniques using broadband regional seismograms one important constraint on source retrieval from regional seismograms comes from the amplitude difference between various phases such as pnl surface wave sv sh because the misfit errors used in some waveform inversions are normalized by the data and synthetics the amplitude information in the data has not been fully utilized in this article we modify the cut and paste source estimation technique zhao and helmberger 1994 by removing this type of normalization it is shown that the modified method increases the stability and resolution of inversion when multiple stations at different distance ranges are used a distance scaling factor is introduced to compensate for the amplitude decay with distance by applying the technique to the terrascope data we have determined source mechanisms and depths of 335 southern californian events with m l 3 5 the amplitude decays with distance are r 1 13 for pnl r 0 55 for love waves and r 0 74 for rayleigh waves in contrast to generally shallow source depths reported by the southern california short period network the depth distribution from waveform inversion shows a strong peak around 12 km with few earthquakes occurring above 5 km and below 20 km

redox driven dissolution of clay minerals by uranium under high pressure co2 conditions article i nfo geologic sequestration of supercritical co2 is one technology proposed to mitigate global warming increased acidity of brine due to co2 injection could lead to mineral dissolution of cap rock and well seals and mobilization of contaminants e g u pb as in this study we examined the dissolution of nontronite nau 2 an fe iii rich clay mineral and partially reduced nontronite r nau 2 in a synthetic brine 0 33 m na2so4 under high pres sure co2 conditions pt 9 66 bar pco2 8 66 bar co2 t 2 0 c and in 1 40 m h3po4 0 50 m h2so4 uranyl vi or biogenic uraninite iv was added as a redox active contaminant and reaction kinetics were measured over a 15 d period unaltered nontronite 3 4 fe ii dissolved very little under high pressure co2 conditions however chemically reduced nontronite 48 fe ii dissolved more rapidly half life of 78 4 d under high pressure co2 conditions 17 8 h in h3po4 h2so4 structural fe ii in reduced nontronite r nau 2 fe ii was preferentially dissolved compared to structural fe iii in unaltered nontronite nau 2 fe iii no redox reactions were observed between r nau 2 fe ii and u vi in contrast uraninite was oxidized by nau 2 fe iii faster and to a greater extent under high pressure co2 conditions as compared to ambient pressure conditions pt 1 0 bar 95 5 n2 h2 redox reactions between uraninite and nau 2 fe iii enhanced the dissolution of both clay and u indicative of potential risks associated with geologic carbon sequestration 2014 elsevier b v all rights reserved

evaluation of the impact of co2 co contaminant gas aqueous fluid and reservoir rock interactions on the geologic sequestration of co2 lowering the costs of front end processes e g separation in the geologic sequestration of co2 can dramatically lower the overall costs one possible approach is to sequester less pure co2 waste streams that are less expensive or require less energy to separate from flue gas or a coal gasification process etc the objective of this research is to evaluate the impacts of co2 itself as well as an impure co2 waste stream on geologic sequestration using reaction progress models reactive transport simulators and analogous reactive transport experiments run in a plug flow reactor specifically we are investigating the potential for co injecting the sox nox and h2s present in coal fired waste streams along with the co2 we present here the results of reactive transport simulations made to investigate the long term impact of dissolved co2 h2s and so2 on carbon sequestration in the frio fm tx the results suggest that addition of relatively large amounts of h2s to a co2 injection should not adversely impact injectivity or sequestration compared to the injection of co2 alone the co injection of so2 however could produce significantly different results if conditions are such that so2 can oxidize to sulfate in the long term the simulations suggest that carbonate mineral formation can sequester a significant fraction of the injected carbon through the formation of calcite magnesite and dawsonite

the chi chi earthquake sequence active out of sequence thrust faulting in taiwan we combined precise focal depths and fault plane solutions of more than 40 events from the 20 september 1999 chi chi earthquake sequence with a synthesis of subsurface geology to show that the dominant structure for generating earthquakes in central taiwan is a moderately dipping 20 to 30 thrust fault away from the deformation front a second subparallel seismic zone lies about 15 kilometers below the main thrust these seismic zones differ from previous models indicating that both the basal decollement and relic normal faults are aseismic

automated near realtime cmt inversion the earthquake research institute eri of the university of tokyo has completely automated the process of determining source mechanisms of earthquakes using waveform data the solutions are automatically distributed using the internet without being checked the process is initiated by receipt of e mail giving the origin time and location of an earthquake to determine the source mechanism we apply the harvard centroid moment tensor cmt inversion method to long period body wave data the portion of the seismogram from the first arrival to the initial surface wave the method has been successfully applied since october 1993 to all of the major earthquakes in the world for which we received event e mail 108 of the 242 cmt solutions in 1994 were determined within 6 hours of the event with an average delay of 3 8 hours for local events e g events around japan it is also possible to determine cmt solutions within 30 minutes from the occurrence of the earthquakes using an efficient dialup data retrieval system operated by eri

rupture process of the 2004 sumatra andaman earthquake the 26 december 2004 sumatra andaman earthquake initiated slowly with small slip and a slow rupture speed for the first 40 to 60 seconds then the rupture expanded at a speed of about 2 5 kilometers per second toward the north northwest extending 1200 to 1300 kilometers along the andaman trough peak displacements reached 15 meters along a 600 kilometer segment of the plate boundary offshore of northwestern sumatra and the southern nicobar islands slip was less in the northern 400 to 500 kilometers of the aftershock zone and at least some slip in that region may have occurred on a time scale beyond the seismic band

numerical experiments on interactions between wave motion and variable density coastal aquifers a comprehensive two dimensional cross shore process based numerical model of nearshore hydrodynamics based on the navier stokes equations k e turbulence closure and the volume of fluid method beach morphology and variable density groundwater flow seawat 2000 was developed this model which was applied at the field scale relaxes simplifications in existing models that do not include such detailed mechanistic descriptions numerical experiments were conducted to investigate the effects of varying aquifer beach and wave characteristics e g inland groundwater head sand grain size different wave heights and periods on the coupled system spilling and plunging breakers on dissipative and intermediate beaches were simulated for a given set of boundary conditions the model was run for 1 y without the hydrodynamic sub model to achieve a realistic salt freshwater interface then the hydrodynamic component was run for 15 min and the model results analyzed the main features considered were groundwater circulation saltwater wedge position in exfiltration across the beach face and beach morphology the predictions of the numerical model agree well with existing understanding and experimental measurements for an inland watertable that is lower than the still water level swl such that the groundwater flow is mainly landward on both coarse and fine sand beaches the addition of wave motion moves the saltwater wedge further landward for an inland watertable that is higher than the swl the opposite behavior occurred the numerical experiments showed that more sediment transport takes place on intermediate beaches than on dissipative beaches in addition beach profile variations are greater under plunging breakers while coarse sand beaches are steeper than fine sand beaches for the same wave conditions there is a strong correlation between in exfiltration and beach face deposition erosion for the coarse beaches while in exfiltration has a slight effect on sediment transport for fine beaches the model is capable of simulating the short term evolution of foreshore profile changes and beach watertable and saltwater wedge movement due to interactions between wave motion and coastal groundwater

complex faulting deduced from broadband modeling of the 28 february 1990 upland earthquake ml 5 2 the 1990 upland earthquake was one of the first sizable local events to be recorded broadband at pasadena where the green s functions appropriate for the path are known from a previous study the synthetics developed in modeling the 1988 upland sequence were available for use in rapid assessment of the activity first motion studies from the caltech usgs array data gave two solutions for the 1990 main shock based on the choice of regional velocity models although these focal mechanisms differ by less than 5 in strike and 20 rake it proved possible to further constrain the solution using these derived green s functions and a three component waveform inversion scheme we obtain from long period waves a fault plane solution of 216 77 5 0 m 0 2 5 10 24 dyne cm depth 6 km and a source duration of 1 2 sec for which the orientation and source depth are in good agreement with the first motion results of hauksson and jones 1991 comparisons of the broadband displacement records with the high pass wood anderson simulations suggests the 1990 earthquake was a complicated event with a strong asperity at depth double point source models indicate that about 30 per cent of the moment was released from a 9 km deep asperity following the initial source by 0 0 to 0 5 sec our best fitting distributed fault model indicates that the timing of our point source results is feasible assuming a reasonable rupture velocity the rupture initiated at a depth of about 6 km and propagated downward on a 3 5 by 3 5 km length by width fault both the inversion of long period waves and the distributed fault modeling indicate that the main shock did not rupture the entire depth extent of the fault defined by the aftershock zone a relatively small asperity about 1 0 km 2 with a greater than 1 kbar stress drop controls the short period wood anderson waveforms this asperity appears to be located in a region where seismicity shows a bend in the fault plane

determination of the fault plane using a single near field seismic station with a finite dimension source model summary we explore the possibility of determining the actual fault plane of an earthquake from the inversion of near source displacement seismograms of one station when a finitedimension source is used instead of a point source model and when the complete displacement is taken into account including near field waves tests on synthetic seismograms and real data recorded at local distances show that this is possible even with a single three component station a single accelerogram available for the erzincan turkey 1992 march 13 m s 6 8 earthquake is inverted and the solution found is compatible with other seismological studies and with the mechanism expected for the north anatolian fault

moment tensor inversions using strong motion waveforms of taiwan tsmip data 1993 2009 abstract earthquake source parameters are important for earthquake studies and seismic hazard assessment moment tensors are among the most important earthquake source parameters and are now routinely derived using modern broadband seismic networks around the world similar waveform inversion techniques can also apply to other available data including strong motion seismograms strong motion waveforms are also broadband and recorded in many regions since the 1980s thus strong motion data can be used to augment moment tensor catalogs with a much larger dataset than that available from the high gain broadband seismic networks however a systematic comparison between the moment tensors derived from strong motion waveforms and high gain broadband waveforms has not been available in this study we inverted the source mechanisms of taiwan earthquakes between 1993 and 2009 by using the regional moment tensor inversion method using digital data from several hundred stations in the taiwan strong motion instrumentation program tsmip by testing different velocity models and filter passbands we were able to successfully derive moment tensor solutions for 107 earthquakes of m w 4 8 the solutions for large events agree well with other available moment tensor catalogs derived from local and global broadband networks however for m w 5 0 or smaller events we consistently over estimated the moment magnitudes by 0 5 to 1 0 we have tested accelerograms and velocity waveforms integrated from accelerograms for the inversions and found the results are similar in addition we used part of the catalogs to study important seismogenic structures in the area near meishan taiwan which was the site of a very damaging earthquake a century ago and found that the structures were dominated by events with complex right lateral strike slip faulting during the recent decade the procedures developed from this study may be applied to other strong motion datasets to compliment or fill gaps in catalogs from regional broadband networks and teleseismic networks

moment tensor inversion for offshore earthquakes east of taiwan and their implications to regional collision reliable determination of source parameters for offshore earthquakes east of taiwan with mb 5 5 was a difficult task because of the poor azimuthal coverage by local network and the lack of signals at teleseismic distances we take advantage of the recently established broadband array in taiwan for seismology bats to invert seismic moment tensors for 7 such events occurred in 1996 to cope with different patterns of background noise and unknown structural details we utilize variable frequency bands in the inversion and adapt a two step procedure to select best velocity models for individual epicenter station paths our results are consistent with the overall patterns of regional collision and indicate that the resulting compressive stress has caused significant intraplate deformation within the philippine sea plate simulation of the region s geological evolution and orogenic processes should take this factor into account and allow the philippine sea plate to deform internally

physical and chemical characteristics of potential seal strata in regions considered for demonstrating geological saline co2 sequestration capture and geological sequestration of co2 from energy production is proposed to help mitigate climate change caused by anthropogenic emissions of co2 and other greenhouse gases performance goals set by the us department of energy for co2 storage permanence include retention of at least 99 of injected co2 which requires detailed assessments of each potential storage site s geologic system including reservoir s and seal s the objective of this study was to review relevant basin wide physical and chemical characteristics of geological seals considered for saline reservoir co2 sequestration in the united states results showed that the seal strata can exhibit substantial heterogeneity in the composition structural and fluid transport characteristics on a basin scale analysis of available field and wellbore core data reveal several common inter basin features of the seals including the occurrence of quartz dolomite illite calcite and glauconite minerals along with structural features containing fractures faults and salt structures in certain localities within the examined basins some seal strata also serve as source rock for oil and gas production and can be subject to salt intrusions the regional features identified in this study can help guide modeling laboratory and field studies needed to assess local seal performances within the examined basins

joint inversion of insar gps teleseismic and strong motion data for the spatial and temporal distribution of earthquake slip application to the 1999 izmit mainshock the space time distribution of slip of the 17 august 1999 izmit earthquake is investigated by inverting synthetic aperture radar sar interferometry and global positioning system gps data together with teleseismic broadband and near field strong motion records surface offsets are used as an added constraint special emphasis is given to analysis of the resolution of the different data sets we use a four segment finite fault model and a nonlinear inversion scheme allowing slip to vary in amplitude direction and duration as well as variable rupture velocity from the inversion of synthetic data we find that the best spatial resolution can be expected in the upper half of the fault model above 12 km where coverage of the interferometric sar data is good western half of the rupture and near the gps and strong motion stations teleseismic data are found to have a lower resolution that is more evenly distributed over the fault model the joint inversion of all the data sets has an increased resolving power compared with the separate inversions and gives a more robust description of the space and time distribution of slip our study shows the importance of resolution tests in evaluating the reliability of earthquake kinematic models and it confirms that an excellent fit of a single kind of data does not necessarily imply a good retrieval of the kinematic properties of an earthquake the izmit rupture which is almost pure right lateral strike slip faulting is dominated by the bilateral breaking of a central asperity located between 29 7 e about 10 km west of the city of golcuk and 30 4 e eastern margin of sapanka lake with slip reaching 6 8 m in the depth range 6 12 km the western termination of the rupture is found near the city of yalova but large slip ends around 29 7 e about 10 km east of hersek delta a second area of large slip is required by all the data sets further east toward the city of duzce between 30 7 e and 31 1 e karadere and duzce faults this eastern slip zone which is separated from the main central asperity by an area of greatly reduced slip is less well constrained by the data however a strong motion station near the city of duzce helps to locate a high slip patch near 31 1 e in the depth range 6 12 km the total seismic moment resulting from the joint inversion is 2 4 1027 dyne cm most of the energy release occurred in a short time less than 15 sec corresponding to the bilateral breaking of the central asperity rupture propagation is relatively uniform and fast toward the west with a rupture velocity close to 3 5 km sec propagation of large slip toward the east is initially slower but it accelerates during a short time interval about 10 sec after rupture nucleation eastward progression then slows down to less than 2 km sec after 15 sec and rupture almost vanishes in amplitude ca 20 sec after initiation rupture propagation then proceeds on the easternmost karadere and duzce fault segments east of 30 7 e from 22 to ca 50 sec supershear rupture propagation is not required for modeling the waveforms considered in this study the hypocenter of the duzce earthquake which occurred 3 months later 12 november 1999 m w 7 2 is located in the immediate vicinity of the easternmost slip patch of the izmit earthquake manuscript received 28 july 2000

moment tensor solutions for three 1982 arkansas swarm earthquakes by waveform modeling moment tensor solutions of three earthquakes recorded in the 1982 arkansas swarm area haar et al 1984 are obtained since a correct model is essential in such analysis the earthquake of 29 june 1982 07h 00m 27 94s was used as the calibration event for the final structural model an essential component of the analysis consisted of low pass filtering of both observed and predicted seismograms to minimize the effect of different p and s wave pulse shapes due to source dynamics the choice of a 15 hz corner frequency was governed by corner frequency estimates of 10 to 13 hz for these events haar et al 1984 the focal mechanisms of these events are determined to be predominantly strike slip with east to northeast trending pressure axes compatible with single event focal mechanisms for other earthquakes in the swarm area johnston and metzger 1982 chiu et al 1984 haar et al 1984 the major difference is in the estimates of seismic moments two to ten times smaller than those determined using frequency domain techniques haar et al 1984 the value of this detailed analysis lies in its ability to calibrate local structure which will hopefully permit deconvolution of the propagation effects to characterize the source properties

spatial and temporal distribution of slip for the 1992 landers california earthquake we have determined a source rupture model for the 1992 landers earthquake m w 7 2 compatible with multiple data sets spanning a frequency range from zero to 0 5 hz geodetic survey displacements near field and regional strong motions broadband teleseismic waveforms and surface offset measurements have been used explicitly to constrain both the spatial and temporal slip variations along the model fault surface our fault parameterization involves a variable slip multiple segment finite fault model which treats the diverse data sets in a self consistent manner allowing them to be inverted both independently and in unison the high quality data available for the landers earthquake provide an unprecedented opportunity for direct comparison of rupture models determined from independent data sets that sample both a wide frequency range and a diverse spatial station orientation with respect to the earthquake slip and radiation pattern in all models consistent features include the following 1 similar overall dislocation patterns and amplitudes with seismic moments of 7 to 8 10 26 dyne cm seismic potency of 2 3 to 2 7 km 3 2 very heterogeneous unilateral strike slip distributed over a fault length of 65 km and over a width of at least 15 km though slip is limited to shallower regions in some areas 3 a total rupture duration of 24 sec and an average rupture velocity of 2 7 km sec and 4 substantial variations of slip with depth relative to measured surface offsets the extended rupture length and duration of the landers earthquake also allowed imaging of the propagating rupture front with better resolution than for those of prior shorter duration strike slip events our imaging allows visualization of the rupture evolution including local differences in slip durations and variations in rupture velocity rupture velocity decreases markedly at shallow depths as well as near regions of slip transfer from one fault segment to the next as rupture propagates northwestward along the multiply segmented fault length the rupture front slows as it reaches the northern limit of the johnson valley landers faults where slip is transferred to the southern homestead valley fault an abrupt acceleration is apparent following the transfer this process is repeated and is more pronounced as slip is again passed from the northern homestead valley fault to the emerson fault although the largest surface offsets were observed at the northern end of the rupture our modeling indicates that substantial rupture was also relatively shallow less than 10 km in this region

finite fault inversion of the september 25 1999 mw 6 4 taiwan earthquake implications for gps displacements of chi chi taiwan earthquake sequence 1 the september 25 1999 chi chi taiwan aftershock mw 6 4 occurred on a down dip extension of the fault ruptured in the mainshock strong motion data were used to invert for the finite source process and test for the causative fault plane we performed a grid search over a range of focal mechanisms and found a preferred model strike 5 dip 30 slip 100 different from teleseismic studies strike 28 10 dip 27 5 slip 106 9 but similar to the mainshock strike 5 dip 34 slip 65 the aftershock asperity has a dimension of 10 km 10 km with a maximum slip of 1 8 m and a static stress drop of 8 mpa we forward predict the gps displacements and found up to 0 033 m of surface horizontal displacements at some gps sites indicating that studies of post seismic deformation may need to account for the effects of large aftershocks

fault rupture process of the 20 september 1999 chi chi taiwan earthquake we modeled the source rupture process of the 20 september 1999 chi chi taiwan earthquake mw 7 6 using an integrated dataset of near field strong ground motion and global positioning system observations this large inland thrust earthquake produced a surface break more than 80 km long along the chelungpu fault the event triggered over 700 strong motion instruments on the island of tai wan this large ground motion dataset provides the best opportunity to date to un derstand earthquake source processes in a major earthquake first we develop a 3d curved fault model consistent with the surface rupture data and aftershock distribu tion the subsurface fault plane has an average dip of 30 to the east and measures 96 km along strike and 40 km down dip next we applied a genetic algorithm to reconstruct the source rupture process the inversion results indicate a complex slip distribution with a generally broad triangular shaped slip zone that points down dip most of the displacement occurred over a 15 km depth range in the northern segment of the fault with the maximum slip exceeding 20 m the average slip is 3 8 m and the average rupture velocity is 2 6 km sec the mainshock slip distribution clearly complements the aftershock location distribution slip rise times range from 8 to 6 sec over most of the primary slip area and decrease slightly as rupture propagates south to north this relatively long rise time resulted in a low dynamic stress drop and low peak ground accelerations observed at surface stations the rake angle rotates across the rupture plane from predominantly dip slip in the southern segment to mostly left lateral oblique slip in the north we find that geometrical irregularities over the fault plane played an important role in controlling the temporal rupture behavior at fault bends rupture tends to decelerate the rake angle rotates to a near dip slip orientation and the shear stress increases as rupture tries to overcome the bending barriers the total seismic moment from our inversion is 2 9 10 27 dyne cm in good agreement with the harvard and the u s geological survey moment estimation

moment tensor inversions for local earthquakes using surface waves recorded at terrascope we have developed a method to determine moment tensors for local earthquakes using short period 10 to 50 sec surface waves recorded at terrascope stations to correct for the substantial lateral variations in crustal structure we applied phase corrections to the data using a regionalized phase velocity model we have determined moment tensors for over 180 events in the last 3 yr in southern california for magnitudes as small as 3 2 and as large as 6 5 the results are consistent with those obtained from first motion data as well as other waveform inversions when continuous data telemetry from the stations becomes available this method can yield moment tensors for earthquakes in southern california and adjacent regions within minutes after the occurrence of an event our results confirm the relation log m o seismic moment 1 5m l local magnitude obtained by an earlier study

an evaluation of the scsn moment tensor solutions robustness of the mw magnitude scale style of faulting and automation of the method we have generated moment tensor solutions and moment magnitudes m w for 1700 earthquakes of local magnitude m l 3 0 that occurred from september 1999 to november 2005 in southern california the method is running as an automated real time component of the southern california seismic network scsn with solutions available within 12 min of event nucleation for local events the method can reliably obtain good quality solutions for m w with m l 3 5 and for the moment tensor for events with m l 4 0 the method uses the 1d time domain inverse code tdmt invc software package dreger 2003 the green s functions have been predetermined for various velocity profiles in southern california which are used in the inversion of observed three component broadband waveforms 10 100 sec using data from at least four stations moment tensor solutions have an assigned quality factor dependent on the number of stations in the inversion and the goodness of fit between synthetic and observed data if a minimum quality factor is attained the m l or m w is 5 0 or greater and if the event is in the southern california reporting regions the m w will be the official scsn cisn magnitude the m w from the high quality solutions determined from our method generally correlate very well with reviewed m l except in regions at the perimeter of the network the m w reported here indicates the scsn m l systematically underestimates the magnitude in the mexicali region of baja california mono lakes area coso region and the brawley seismic zone and overestimates the magnitude in the coastal ranges comparisons of the moment tensors determined using this model are made with harvard centroid moment tensors generated for larger earthquakes in the california region and recent 3d models for events in the los angeles region with excellent correlation most of the earthquakes with good quality solutions exhibit strike slip faulting in particular along the major late quaternary strike slip faults thrust faulting on east west striking planes is observed along the southern edge of the transverse ranges while northwest striking thrust faulting is observed in the coastal ranges normal faulting is most common in baja california and southern sierra nevada including the western basin and range region poor quality solutions with unreliable m w are caused by excessive background noise in the waveforms small events m l 4 0 can be affected by ambient noise or teleseisms but larger events can also have unreliable solutions if they follow a recent large regional event

one minute after strong motion map effective epicenter and effective magnitude abstract this article reports the recent progress on real time seismic monitoring in taiwan particularly the real time strong motion monitoring by the taiwan central weather bureau9s telemetered seismic network cwbsn which is presently aiming at rapid reporting immediately after a large earthquake occurrence if rapid reporting can be achieved before the arrival of the strong shaking earthquake early warning will become possible cwbsn has achieved the generation of the intensity map epicenter and magnitude within 1 min of the occurrence of a large earthquake both rapid reporting and early warning are principally applied to large m 5 events the requirement of on scale waveform recording prompted cwbsn in 1995 to integrate strong motion sensors e g force balance accelerometers into its telemetered seismic monitoring system time domain recursive processing is applied to the multi channel incoming seismic signals by a group of networked personal computers to generate the intensity map from the isoseismal contours an effective epicenter is immediately identified that resides in the middle of the largest usually the 100 gal contour curve of the intensity map an effective magnitude is also defined that can be derived immediately from the surface area covered by the largest usually the 100 gal contour curve for a large event with a finite rupture surface the epicenter and magnitude so derived are more adequate estimates of the source location and of the strength of destruction the effective epicenter gives the center of the damage area it stands in contrast with the conventional epicenter location which only gives the initial point of rupture nucleation the effective magnitude reflects more closely the earthquake damage potential instead of the classical magnitude definition that emphasizes the total energy release the cwbsn has achieved in obtaining the above crucial source information well within 1 min this time can further be reduced to better than 30 sec as illustrated by the example in this article showing that earthquake early warning is indeed an achievable goal the rapid reporting and early warning information is electronically transmitted to users to allow rapid response actions with or without further human intervention

evidence for fault lubrication during the 1999 chi chi taiwan earthquake mw7 6 the ground motion data of the 1999 chi chi taiwan earthquake exhibit a striking difference in frequency content between the north and south portions of the rupture zone in the north the ground motion is dominated by large low frequency displacements with relatively small high frequency accelerations the pattern is opposite in the south with smaller displacements and larger accelerations we analyze the fault dynamics in light of a fault lubrication mechanism using near field seismograms and a detailed rupture model the fault zone contains viscous material e g gouge in which pressure increases following the reynolds lubrication equation when the displacement exceeds a threshold lubrication pressure becomes high enough to widen the gap thereby reducing the area of asperity contact with less asperity contact the fault slips more smoothly suppressing high frequency radiation

rupture process of the 1999 kocaeli turkey earthquake estimated from strong motion waveforms the multiple time window linear waveform inversion is applied to study the source process of the 1999 kocaeli turkey earthquake using strong motion data two peculiar observations characterize this event the first one is a conflicting observation of the long surface ruptures and short source duration resulting from the observed strong motion waveforms the second is an anomalously short s p time observed at a station skr considering its hypocentral distance a supershear rupture propagation ellsworth and celebi 1999 and the p wave triggering of an asperity anderson et al 2000 were both proposed to explain the record at skr our waveform inversion study is aimed to examine these possibilities in order to clarify the relation between the spatial distribution of the surface ruptures and coseismic slips we divide the assumed fault plane into three parts and look for the first time window front propagation velocity propagation velocity of triggering front of the first time window at each subfault in each part by performing numerous inversions changing the first time window front propagation velocity separately in each part and selecting the best first time window propagation velocities that give largest variance reduction at the same time appropriate smoothness of spatiotemporal slip distribution is searched for by performing inversions with different strength of smoothing constraints against the observational equations and judging the relative appropriateness of inversion results in terms of the akaike s bayesian information criterion the best source model is characterized by an asperity that is about 35 km east of the epicenter and near a segment boundary at sapanca lake triggered by the first time window front with 5 8 km sec close to p wave velocity the time progression of the rupture suggests a scenario where a p wave arriving from the hypocenter or somewhere around the hypocenter triggered the second largest asperity near the junction of the segments at sapanca lake which is a preferable interpretation the first time window propagation velocities west of the hypocenter and east of skr are expected to be 3 0 km sec manuscript received 20 august 2000

source parameters of the sierra madre earthquake from regional and local body waves we inverted the three component long period data recorded by the terrascope array for the june 28 1991 sierra madre california event to determine the seismic moment and source orientation of the mainshock ml 5 8 remarkably four of the six stations were located 159 2 0 7 km from the epicenter variations in absolute traveltime were smaller than 2 and 3 for pn and sn whereas the surface waves displayed greater variation similarities in the waveforms and the small variance in traveltime suggest that a common green s function can be used to invert the data we used the whole waveforms excluding the fundamental surface waves at the more distant stations to invert for source parameters the results of the inversion indicated that this event was predominately a thrust type earthquake where the strike rake and dip were determined to be 235 74 and 50 respectively the seismic moment was determined to be 2 5 1024 dyne cm the source duration was found to be about 1 0 seconds by direct measurement of the s wave recorded at the pasadena station located 21 km from the epicenter considering circular rupture we obtain a stress drop of 460 bars

tomographic imaging of lithospheric structures under taiwan abstract tomographic images of the crustal and mantle velocity structures under taiwan are obtained by simultaneous inversion of local earthquake p wave arrival times for hypocenters and p wave velocity structures in northern taiwan a high velocity zone coinciding with the wadati benioff zone can readily be identified as the subducted philippine sea plate the imaged zone dips toward the north at an angle of 40 from a depth range of 20 55 to 100 130 km an upper mantle low velocity wedge ranging from 40 to 80 km in depth exists above the subducted slab above this wedge is the ilan plain of northern taiwan which lies at the west end of the okinawa trough a well recognized back arc basin the crustal velocities under the plain are also relatively low the well defined high velocity zone and the low velocity wedge provide some constraints on the thermal structures of the subduction system under northern taiwan in tomographic images across the central section of taiwan thickening of the crust and up arching of the lower crustal materials under the central range are commonly observed the crust under the western foothills region is clearly thinner and the near surface low velocity layers are well developed the structures under the central range show that although the taiwan orogeny is quite young a root deeper in the north and shallowing to the south has formed the results of our tomography show that a significant portion of the lithosphere is involved in the taiwan orogeny