hypocentre determination offshore of eastern taiwan using the maximum intersection method summary the maximum intersection maxi method which derives from the master station method msm determines within a 3 d velocity model the absolute hypocentral location based on observed arrival times first the spatial node that better satisfies the arrival time differences computed at all station pairs plus or minus an error tolerance value in seconds is defined as the preliminary hypocentral solution pred second because pred depends neither on the estimate of origin time nor on the residual root mean square rms residual outliers are objectively detected and cleaned out from the original data set without any iterative process or weighting third a statistical minimization residual rms is conducted in a small domain around the pred node which results in a unique final solution the maxi method is applied to the determination of earthquake hypocentres with the proper station correction terms in the southernmost extremity of the ryukyu subduction zone where several dense seismic clusters occur near the seismogenic plate interface the location of earthquakes recorded at both the taiwanese and japanese networks is obtained for about a thousand events between 1992 and 1997 the process uses a detailed 3 d velocity model based on multiple geophysical data sources obtained in the junction area between subduction and collision east of taiwan the earthquake clustering and the significant drop in residual statistics 1 20 0 80 and 0 35 s for taiwanese catalogue msm and maxim solutions respectively indicate the accuracy of the method which can be used to routinely determine absolute hypocentre location based on observed arrival times

boundary layer and cloud structure controls on tropical low cloud cover using a train satellite data and ecmwf analyses abstract the cloud aerosol lidar and infrared pathfinder satellite observations calipso cloudsat radar and the moderate resolution imaging spectroradiometer modis cloud data on the a train constellation complemented with the european centre for medium range forecasts ecmwf analyses are used to investigate the cloud and boundary layer structure across a 10 wide cross section starting at 5 s near the international date line and extending to 35 n near the california coast from march 2008 to february 2009 the mean large scale inversion height and low level cloud tops which correspond very closely to each other are very shallow 500 m over cold ssts and high static stability near california and deepen southwestward to a maximum of 1 5 2 0 km along the cross section as ssts rise deep convection near the itcz occurs at a surface temperature close to 298 k while the boundary layer relative humidity rh is nearly constant where a boundary layer is well defined it drops sharply near cloud top i

geographic variability in the export of moist static energy and vertical motion profiles in the tropical pacific 1 column integrated moist static energy mse budgets were calculated using daily data from three reanalyses 1998 2001 and isccp radiative cooling the mse export by the circulation was separated into vertical and horizontal mse advection components in order to examine how observationally derived vertical motion profiles affect gross moist stability calculations in a 2000 km wide region in the central eastern pacific itcz vertical motions import mse implying a negative gross moist stability horizontal mse advection is negative and of similar magnitude to vertical mse advection in rainy regions geographic differences in export of mse by the vertical circulation are primarily due to differences in the shape of the vertical motion profile in the west pacific warm pool rainy regions mean horizontal convergence extends up to 300 mb while in parts of the pacific itcz where meridional sst gradients are strong the vertical motion profile is bottom heavy with convergence below 800 mb and divergence above on daily timescales the mode of vertical motion variability has little dependence on precipitation rate and is consistent with observed regional differences in the vertical structure of trmm pr reflectivities

the 1999 mw 7 1 hector mine california earthquake sequence complex conjugate strike slip faulting the 1999 m w 7 1 hector mine mainshock showed right lateral strike slip faulting with an initial strike of n6 w and vertical dip the mainshock was preceded within 20 hours by 18 recorded foreshocks of 1 5 m 3 8 within a few kilometers distance of the mainshock hypocenter the aftershocks delineate how the hector mine earthquake ruptured with strike n6 w to the south for a distance of 15 km and possibly to the north for a distance of several kilometers the two largest aftershocks of m 5 9 and m 5 7 occurred near the north and south ends of the first mainshock rupture segment the second segment of rupture starting 15 km to the south away from the mainshock hypocenter delineated by strike slip and thrust faulting aftershocks extends 10 km farther away with a strike of s140 e along the bullion fault the aftershocks also outline an unusual third rupture segment extending from about 5 km south of the hypocenter with a strike of n30 w to n35 w for a distance of 20 km approximately 10 to 25 km farther to the north and west of the mainshock epicenter several clusters form a complex aftershock distribution three dimensional vp and vp vs models of the region exhibit only small regional changes as is typical for the mojave region nonetheless the mainshock rupture started within a region of rapidly varying vp and at least three regions of low vp vs are imaged within the aftershock zone the rate of decay for the hector mine earthquake sequence has been slightly above the mean for both p values and b values in southern california the focal mechanisms of the aftershocks and the state of stress are consistent with strike slip faulting including a component of normal faulting most prominent to the north the orientation of the regional maximum horizontal stress the variation in orientation of the mainshock fault segments by 30 and scattered distribution of aftershocks suggest that the mainshock and aftershock deformation field exhibit volumetric shear deformation accommodated by complex conjugate sets of strike slip faults

the detection of low magnitude seismic events using array based waveform correlation summary it has long been accepted that occurrences of a known signal are most effectively detected by cross correlating the incoming data stream with a waveform template such matched signal detectors have received very little attention in the field of detection seismology because there are relatively few instances in which the form of an anticipated seismic signal is known a priori repeating events in highly confined geographical regions have been observed to produce very similar waveforms and good signals from events at a given site can be exploited to detect subsequent co located events at lower magnitudes than would be possible using traditional power detectors even greater improvement in signal detectability can be achieved using seismic arrays running correlation coefficients from single sensors can be stacked over an array or network to result in a network correlation coefficient displaying a significant array gain if two events are co located the time separating the corresponding patterns in the wave train as indicated by the cross correlation function is identical for all seismic stations and this property means that the correlation coefficient traces are coherent even when the waveforms are not we illustrate the power of array based waveform correlation using the 1997 august 16 kara sea event the weak event that occurred 4 hr after the main event was barely detected using an sta lta detector on the spits array but is readily detected by signal matching on a single channel the main event was also recorded by the far more distant norsar array but no conventional detection can be made for the second event a clear detection is however made when the correlation coefficient traces are beamformed over all sensors of the array we estimate the reduction in detection threshold of a test signal on a regional seismic array using waveform correlation by scaling down a master signal and immersing it into seismic noise we show that for this case waveform correlation using a single channel detects signals of approximately 0 7 orders of magnitude lower than is possible using an sta lta detector on the array beam waveform matching on the full array provides an additional improvement of approximately 0 4 magnitude units we describe a case study in which small seismic events at the barentsburg coal mine on spitsbergen were detected using the signals from a major rockburst as master waveforms many spurious triggers occurred in this study whereby short sections of signal exhibited coincidental similarity with unrelated incoming wave fronts we demonstrate how such false alarms can almost always be identified and screened out automatically by performing frequency wavenumber analysis upon the set of individual correlation coefficient traces

two case histories demonstrating the effect of past earthquakes on liquefaction resistance of silty sand abstractthe paper compares two liquefaction case histories in california 1 the response of the wildlife site in the imperial valley to the 2010 el mayor cucapah earthquake mw 7 2 amax 0 15 g

continuous kurtosis based migration for seismic event detection and location with application to piton de la fournaise volcano la reunion abstract we present an automatic earthquake detection and location technique based on migration of continuous waveform data data are preprocessed using a kurtosis estimator in order to enhance the first arrival information then migrated onto a predefined search grid using precalculated p wave travel times and finally stacked local maxima in the resulting 4d space time grid indicate the locations and origin times of seismic events we applied our technique to earthquake swarms occurring on piton de la fournaise volcano la reunion france we located 5000 events from 12 different swarms that occurred between 2009 and 2011 our automated locations are consistent with those performed using manual picks and indicate that the seismicity concentrates around sea level multiplet analysis of the detected events and subsequent double difference relocation produce sharper images of the earthquake swarms our code waveloc is released in open source online material figures of seismicity distributions from waveloc synthetic test and stack amplitude values versus magnitudes

earthquake monitoring in southern california for seventy seven years 1932 2008 the southern california seismic network scsn has produced the scsn earthquake catalog from 1932 to the present a period of more than 77 yrs this catalog consists of phase picks hypocenters and magnitudes we present the history of the scsn and the evolution of the catalog to facilitate user understanding of its limitations and strengths hypocenters and magnitudes have improved in quality with time as the number of stations has increased gradually from 7 to 400 and the data acquisition and measuring procedures have become more sophisticated the magnitude of completeness m c of the network has improved from m c 3 25 in the early years to m c 1 8 at present or better in the most densely instrumented areas mainshock aftershock and swarm sequences and scattered individual background earthquakes characterize the seismicity of more than 470 000 events the earthquake frequency size distribution has an average b value of 1 0 with m 6 0 events occurring approximately every 3 yrs the three largest earthquakes recorded were 1952 m w 7 5 kern county 1992 m w 7 3 landers and 1999 m w 7 1 hector mine sequences and the three most damaging earthquakes were the 1933 m w 6 4 long beach 1971 m w 6 7 san fernando and 1994 m w 6 7 northridge earthquakes all of these events ruptured slow slipping faults located away from the main plate boundary fault the san andreas fault their aftershock sequences constitute about a third of the events in the catalog the fast slipping southern san andreas fault is relatively quiet at the microseismic level and has not had an m 6 earthquake since 1932 in contrast the slower san jacinto fault has the highest level of seismicity including several m 6 events thus the spatial and temporal seismicity patterns exhibit a complex relationship with the plate tectonic crustal deformation

crustal structure and seismicity distribution adjacent to the pacific and north america plate boundary in southern california new three dimensional 3 d v p and v p v s models are determined for southern california using p and s p travel times from local earthquakes and controlled sources these models confirm existing tectonic interpretations and provide new insights into the configuration of geological structures at the pacific north america plate boundary the models extend from the u s mexico border in the south to the southernmost coast ranges and sierra nevada in the north and have a 15 km horizontal grid spacing and an average vertical grid spacing of 4 km down to 22 km depth the heterogeneity of the crustal structure as imaged by v p and v p v s models is larger within the pacific plate than the north american plate similarly the relocated seismicity deepens and shows more complex 3 d distribution in areas of the pacific plate exhibiting compressional tectonics the models reflect mapped changes in the lithology across major geological terranes such as the mojave desert the peninsular ranges and the transverse ranges the interface between the shallow mono of the continental borderland and the deep moho of onshore california forms a broad zone to the north beneath the western transverse ranges ventura basin and the los angeles basin and a narrow zone to the south along the peninsular ranges the near surface increase in velocity from the surface to up to 8 km depth is rapid and has a logarithmic shape for stable blocks and mountain ranges but is slow with a linear shape for sedimentary basins at midcrustal depths a rapid increase in v p is imaged beneath the sediments of the large sedimentary basins while beneath the adjacent mountain ranges the increase is small or absent

high resolution mapping of two large scale transpressional fault zones in the california continental borderland santa cruz catalina ridge and ferrelo faults new mapping of two active transpressional fault zones in the california continental borderland the santa cruz catalina ridge fault and the ferrelo fault was carried out to characterize their geometries using over 4500 line km of new multibeam bathymetry data collected in 2010 combined with existing data faults identified from seafloor morphology were verified in the subsurface using existing seismic reflection data including single channel and multichannel seismic profiles compiled over the past three decades the two fault systems are parallel and are capable of large lateral offsets and reverse slip during earthquakes the geometry of the fault systems shows evidence of multiple segments that could experience throughgoing rupture over distances exceeding 100 km published earthquake hypocenters from regional seismicity studies further define the lateral and depth extent of the historic fault ruptures historical and recent focal mechanisms obtained from first motion and moment tensor studies confirm regional strain partitioning dominated by right slip on major throughgoing faults with reverse oblique mechanisms on adjacent structures transpression on west and northwest trending structures persists as far as 270 km south of the transverse ranges extension persists in the southern borderland a logjam model describes the tectonic evolution of crustal blocks bounded by strike slip and reverse faults which are restrained from northwest displacement by the transverse ranges and the southern san andreas fault big bend because of their potential for dip slip rupture the faults may also be capable of generating local tsunamis that would impact southern california coastlines including populated regions in the channel islands

fundamental questions of earthquake statistics source behavior and the estimation of earthquake probabilities from possible foreshocks abstract estimates of the probability that an m l 4 8 earthquake which occurred near the southern end of the san andreas fault on 24 march 2009 would be followed by an m 7 mainshock over the following three days vary from 0 0009 using a gutenberg richter model of aftershock statistics reasenberg and jones 1989 to 0 04 using a statistical model of foreshock behavior and long term estimates of large earthquake probabilities including characteristic earthquakes agnew and jones 1991 i demonstrate that the disparity between the existing approaches depends on whether or not they conform to gutenberg richter behavior while gutenberg richter behavior is well established over large regions it could be violated on individual faults if they have characteristic earthquakes or over small areas if the spatial distribution of large event nucleations is disproportional to the rate of smaller events i develop a new form of the aftershock model that includes characteristic behavior and combines the features of both models this new model and the older foreshock model yield the same results when given the same inputs but the new model has the advantage of producing probabilities for events of all magnitudes rather than just for events larger than the initial one compared with the aftershock model the new model has the advantage of taking into account long term earthquake probability models using consistent parameters the probability of an m 7 mainshock on the southernmost san andreas fault is 0 0001 for three days from long term models and the clustering probabilities following the m l 4 8 event are 0 00035 for a gutenberg richter distribution and 0 013 for a characteristic earthquake magnitude frequency distribution our decisions about the existence of characteristic earthquakes and how large earthquakes nucleate have a first order effect on the probabilities obtained from short term clustering models for these large events

the ml scale in southern california measurements 9 941 of peak amplitudes on wood anderson instruments or simulated wood anderson instruments in the southern california seismographic network for 972 earthquakes primarily located in southern california were studied with the aim of determining a new distance correction curve for use in determining the local magnitude m l events in the mammoth lakes area were found to give an unusual attenuation pattern and were excluded from the analysis as were readings from any one earthquake at distances beyond the first occurrence of amplitudes less than 0 3 mm the remaining 7 355 amplitudes from 814 earthquakes yielded the following equation for m l distance correction log a 0 log a 0 1 110log r 100 0 00189 r 100 3 0 where r is hypocentral distance in kilometers a new set of station corrections was also determined from the analysis the standard deviation of the m l residuals obtained by using this curve and the station corrections was 0 21 the data used to derive the equation came from earthquakes with hypocentral distances ranging from about 10 to 700 km and focal depths down to 20 km with most depths less than 10 km the log a 0 values from this equation are similar to the standard values listed in richter 1958 for 50 200 km the effect at close distances is consistent with that found in several other studies and is simply due to a difference in the observed 1 r geometrical spreading for body waves and the 1 r 2 spreading assumed by gutenberg and richter in the construction of the log a 0 table m l s computed from our curve and those reported in the caltech catalog show a systematic dependence on magnitude small earthquakes have larger magnitudes than in the catalog and large earthquakes have smaller magnitudes by as much as 0 6 units to a large extent these systematic differences are due to the nonuniform distribution of data in magnitude distance space small earthquakes are preferentially recorded at close distances relative to large earthquakes for large earthquakes however the difference in the two magnitudes is not solely due to the new correction for attenuation magnitudes computed using richter s log a 0 curve are also low relative to the catalog values the differences in that case may be due to subjective judgment on the part of those determining the catalog magnitudes the use of data other than the caltech wood anderson seismographs the use of different station corrections or the use of teleseismic magnitude determinations whatever their cause the departures at large magnitude may explain a 1 0 0 7 proportionality found by luco 1982 between m l s determined from real wood anderson records and those from records synthesized from strong motion instruments if it were not for the biases in reported magnitudes luco s finding would imply a magnitude dependent shape in the attenuation curves we studied residuals in three magnitude classes 2 0 m l 3 5 3 5 m l 5 5 and 5 5 m l 7 0 and found no support for such a magnitude dependence based on our results we propose that local magnitude scales be defined such that m l 3 correspond to 10 mm of motion on a wood anderson instrument at 17 km hypocentral distance rather than 1 mm of motion at 100 km this is consistent with the original definition of magnitude in southern california and will allow more meaningful comparison of earthquakes in regions having very different attenuation of waves within the first 100 km

aftershock detection thresholds as a function of time results from the anza seismic network following the 31 october 2001 ml 5 1 anza california earthquake we examine aftershock detectability thresholds for events in the initial part of the 31 october 2001 m l 5 1 sequence in southern california this sequence occurred directly below the broadband anza seismic network which recorded continuous waveform data at 13 azimuthally well distributed stations within the study region seven had epicentral distances 20 km of the 608 aftershocks 0 m l 2 8 in the initial 2 hr of this sequence the first five aftershocks recorded were only identifiable at stations within 30 km after applying a high pass filter using a cluster radius 1 1 km of 200 representative aftershocks we track the maximum seismogram amplitude versus earthquake magnitude this relationship helps us quantify the visibility of aftershocks within the mainshock coda and assess our detection capabilities we estimate that detectable aftershocks within the mainshock coda include 1 those over magnitude 3 that are within 15 km of the network centroid that occur 12 sec or more into the sequence and 2 those over magnitude 2 that are within 30 km of the centroid of the network that occur 60 sec or more into the sequence we find a lack of large aftershocks in this sequence the largest aftershock m l 2 8 is substantially smaller than the mainshock m l 5 1 we suggest this relatively large magnitude differential is dictated by a combination of factors that includes complexity of the san jacinto fault system and the lack of large earthquakes in the region in the past 20 years online material quicktime movies juxtaposing a 3 2 aftershock in the coda of a 5 1 mainshock

mineralogy of primary carbonate bearing hypabyssal kimberlite lac de gras slave province northwest territories canada abstract a suite of fresh late cretaceous to eocene hypabyssal kimberlites from the lac de gras field were studied in order to understand better carbonate silicate and oxide paragenesis the samples have excellent preservation of textures and primary mineralogy and are archetypal or group 1 kimberlite five kimberlite localities are identified as calcite bearing based on the presence of high sr ba calcite as phenocrysts microphenocrysts and in segregations three kimberlite localities are identified as dolomite bearing based on the presence of mixed calcite dolomite segregations containing oscillatory and banded textures of calcite dolomite solid solution and dolomite magnesite sr ba calcite are characterized by high xca 0 95 and are enriched in sr 4900 11 100 ppm and ba 3200 14 200 ppm the calcite dolomite and dolomite magnesite solid solution compositions span the xca range from 0 42 to 0 95 and typically have sr and ba contents in the range of 1000 4000 ppm the carbonate silicate and oxide mineral compositions suggest that the origin of the calcite bearing versus dolomite bearing kimberlites studied is related to subtle differences in parent magma composition in particular the co2 h2o ratio formation of the carbonates reflects the latter part of a protracted magmatic crystallization sequence in which sr ba calcite precipitates from an evolved kimberlite melt subsequently calcite dolomite solid solution and dolomite is precipitated from localized mg rich carbonate fluids at relatively high temperatures higher than serpentine stability

stratigraphy of the intra crater volcaniclastic deposits of the victor northwest kimberlite northern ontario canada abstract the victor northwest vnw kimberlite is one of several steep sided pipes in the victor kimberlite complex in this paper detailed logging of 4 2 km of drill core and petrographic studies of hundreds of samples and thin sections are used to reconstruct the intra crater stratigraphy of the vnw kimberlite and to constrain the emplacement history of the pipe the results show that the vnw pipe comprises numerous contrasting small volume volcanic facies including dark and competent kimberlite sedimentary country rock breccias pyroclastic kimberlite and resedimented volcaniclastic kimberlite we interpret that the vnw pipe was formed by two separate eruption cycles during the first eruption cycle the main vnw crater is excavated and partly filled the second eruption cycle excavates a smaller nested crater within the existing lithified pipe fill both eruption cycles can be subdivided into three comparable stages the first stage in both cycles comprises a highly explosive eruption involving crater excavation and deposition of pyroclastic kimberlite the eruption products contain abundant broken olivines small angular country rock fragments and kimberlite ash all these features indicate high degrees of fragmentation resulting from high eruption intensities the high proportion of country rock fragments in these deposits suggests continuous pipe wall erosion the second stage in both cycles is represented by dark and competent deposits which have low country rock fragment abundances and mostly intact olivines based on contact relationships and textures within these units it is suggested that these rock types are formed by lower energy eruptions during which no major pipe wall erosion took place the eruption came to an end during the third and last stage in both cycles the uppermost deposits record resedimentation of kimberlite by water major pipe wall collapse results in the formation of voluminous sedimentary country rock breccia deposits that cap all previous deposits

effect of mine dewatering on the peatlands of the james bay lowland the role of marine sediments on mitigating peatland drainage the wetlands of the james bay lowland comprise one of largest wetland complexes in the world in part due to the properties thickness and hydraulic conductivity of the marine sediment ms that underlay them dewatering of an open pit diamond mine is depressurizing the surrounding silurian bedrock below the ms prior to mining it was assumed that these ms would largely isolate the overlying peatlands from the depressurized regional bedrock aquifer to assess this isolation we instrumented a 1 5 km long transect of wells and piezometers located within the zone of the mine s influence that crossed a sequence of bogs fens and bedrock outcrops bioherms results were differentiated between those areas with no ms near bioherms and those underlain by ms non bioherm along the transect between 2007 and 2010 at near bioherm and non bioherm locations average peat water tables declined 71 and 31 cm and hydraulic head declined 66 and 32 cm in bioherm and non bioherm locations respectively gradients varied from near zero 0 001 at the start of dewatering to 0 03 after 5 years in non bioherm areas and from 0 20 to 0 45 in near bioherm areas these gradients corresponded to fluxes groundwater recharge of approximately 0 26 mm day and 2 1 mm day in non and near bioherm areas respectively specific discharge recharge determined using the known mine dewatering rate and drawdown cone heads and areas corresponded well with measured recharge determined in the non bioherm transect locations a simple rearrangement of darcy s law used to calculate the specific discharge highlighted how the ratio of hydraulic conductivity to the thickness of the ms can be used to assess vulnerable areas therefore given the increasing development in ontario s far north considerable attention must be given to both the thickness and hydraulic conductivity of ms copyright 2013 john wiley sons ltd

the source scanning algorithm mapping the distribution of seismic sources in time and space summary we introduce a new method which we call the source scanning algorithm ssa for imaging the distribution of seismic sources in both time and space using trial locations and origin times the method calculates the brightness function by summing the absolute amplitudes observed at all stations at their respective predicted arrival times the spatial and temporal distribution of sources is then identified by a systematic search throughout the model space and time for the maximum brightness the greatest advantages of this method are that 1 it exploits waveform information both arrival times and relative amplitudes without the need to calculate highfrequency synthetic seismograms and 2 it requires neither pre assembled phase picking data nor any a priori assumptions about the source geometry a series of tests using synthetic data have shown that this method is robust and can faithfully recover the input source configuration to within 1 grid interval finally we demonstrate the value of the algorithm by locating a typical tremor event with emergent waveforms that occurred during the recent episodic tremor and slip ets sequence in the northern cascadia subduction zone

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

metal binding to dissolved organic matter and adsorption to ferrihydrite in shallow peat groundwaters application to diamond exploration in the james bay lowlands canada the speciation and solubility of kimberlite pathfinder metals ni nd ba and k in shallow peat groundwaters is investigated over the yankee zulu and golf kimberlites in the attawapiskat region james bay lowlands canada the purpose of this study is to examine the relationship between dissolved organic matter dom complexation with kimberlite pathfinder metals and determine the spatial distribution of those metals in shallow peat groundwaters along sampling transects over subcropping kimberlites nickel nd ba and k complexation with dom and the adsorption of these metals onto ferrihydrite were calculated using visual minteq 3 0 and the nica donnan database calculations predict almost 100 of soluble nd ni and ba form complexes with dom at sampling sites with little to no contribution from upwelling groundwater i e dissolved organic c doc concentrations 40 132 mg l ph 3 9 5 5 and log ionic strength 6 3 in only the most ombrotrophic peat groundwater conditions does a majority fraction of k bind to dom by contrast under conditions with large contributions from upwelling groundwaters i e doc concentrations 640 mg l ph 5 5 6 5 and log ionic strength 3t o 2 as little as 10 of nd and ni and 0 k and ba are predicted to complex with dom the modeling calculations suggest the dominant control on metal dom complexation particularly with respect to ni and nd is competitive effects for dom binding sites due to elevated ionic strength where there is evidence of strong groundwater upwelling visual minteq modeling of metal adsorption on ferrihydrite surfaces predicts that under strong upwelling conditions ni and nd are scavenged from solution due to increased ferrihydrite precipitation and decreased fractions of metals complexed with dom analytical geochemical data are consistent with model predictions of metal adsorption on ferrihydrite total dissolved ni and nd concentrations at sites of strong upwelling are up to five times lower than waters with little to no upwelling and log ferrihydrite saturation indices logsi ferr indicate precipitation values up to 5 at sites of strong groundwater upwelling where the majority of ni and nd complex with dom and ferrihydrite is highly under saturated logsiferr 18 to 5 the concentrations of total ni and nd are elevated compared to other sites along sampling transects metal complexation with dom effectively inhibits metal scavenging from solution via adsorption and or from forming secondary mineral precipitates also because alkaline earth metals do not compete strongly with ni and nd for adsorption sites on ferrihydrite surfaces but do compete strongly for insoluble organic sites ni and nd are more likely to adsorb onto ferrihydrite

complex rupture of an immature fault zone a simultaneous kinematic model of the 2019 ridgecrest ca earthquakes the july 4 2019 mw6 4 and subsequent july 6 2019 mw7 1 ridgecrest sequence earthquakes ruptured orthogonal fault planes in the little lake fault zone a low slip rate 1 mm yr dextral fault zone in the area linking the eastern california shear zone and walker lane this region accommodates nearly one fourth of plate boundary motion and has been proposed to be an incipient transform fault system that could eventually become the main tectonic boundary replacing the san andreas we investigate the rupture process of these events using a novel simultaneous kinematic slip method with joint inversion of high rate gnss strong motion gnss static offset and insar data we model the coulomb stress change to evaluate how the first mainshock may have affected the second our findings suggest complex interactions between several fault structures including dynamic and static triggering and provide important context for regional seismic source characterization and hazard models

rare earth element concentrations and speciation in organic rich blackwaters of the great dismal swamp virginia usa concentrations of rare earth elements ree major inorganic solutes and dissolved organic carbon doc were measured in waters from the great dismal swamp in southeastern virginia including lake drummond ph 4 3 and its principal surface inflows and outflow concentrations of ree are high in the lake average nd 8 nmol kg and the acidic doc rich inflow and out flow waters i e nd 12 5 nmol kg in jericho washington ditch and 8 nmol kg in feeder ditch respectively the slightly acidic ph 6 6 4 inflow waters from west of the suffolk scarp that comprise the chief source of surface water flow into lake drummond exhibit lower ree concentrations nd 3 4 7 nmol kg great dismal swamp waters are all enriched in the middle rees compared to the light and heavy rees lree and hree when normalized to upper continental crustal ucc values rare earths are positively correlated to doc concentrations in great dismal swamp waters and inversely correlated with ph speciation calculations using a modified version of the well established humic ion binding model v predict that organic matter complexes are the predominant form of dissolved rees in great dismal swamp waters despite significant competition from aqueous fe and al for organic matter binding sites adsorptive cathodic stripping voltammetry acsv was employed using a previously developed competitive ligand equilibration approach that involved adding the o cresolphthalexon ocp ligand to directly investigate ree complexation with natural organic ligands in great dismal swamp waters although preliminary the results of the acs voltammetric titrations are consistent with dominance of organic matter complexes of rees in great dismal swamp waters the results of the speciation modeling and the voltammetric titrations all point towards control of dissolved rees in great dismal swamp waters by complexation of these heavy metals with natural organic matter

analysis of temporal and spatial heterogeneity of magnitude frequency distribution inferred from earthquake catalogues summary statistical models are introduced for the simultaneous estimation of the changes of the b value and detection rate of earthquakes in a catalogue which develops in time or varies in space the three characteristic parameters including b for the magnitude frequency distribution of detected earthquakes are represented by respective three b spline functions of time or location in a space an objective bayesian method is adopted for the optimal estimate of such functions with many unknown coefficients the present procedure is applied to earthquake catalogues for japanese seismic activity

california integrated seismic network cisn local magnitude determination in california and vicinity determining local magnitude m l in a manner that is uniform and internally consistent for earthquakes throughout california and the vicinity is an important component of the california integrated seismic network cisn we present a new local magnitude attenuation function and corresponding station adjustments that are valid throughout california the new attenuation function is an analytic function of the radial hypocentral distance between 1 and 500 km associated station adjustments are also available for 1185 horizontal seismometer and accelerometer channels from five seismic networks operating in california the new attenuation function and adjustments provide several advantages to cisn they allow a more robust m l computation the m ls are more consistent between northern and southern california than they have been in the past and because adjustments are now available for more station network channel location codes sncls m ls can be computed for small earthquakes in more locations than was previously possible in addition to describing our method for calibrating the new cisn m l we also present a tool for adding adjustments for new or upgraded stations

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

unified structural representation of the southern california crust and upper mantle we present a new 3d description of crust and upper mantle velocity structure in southern california implemented as a unified structural representation usr the usr is comprised of detailed basin velocity descriptions that are based on tens of thousands of direct velocity vp vs measurements and incorporates the locations and displacement of major fault zones that influence basin structure these basin descriptions were used to developed tomographic models of crust and upper mantle velocity and density structure which were subsequently iterated and improved using 3d waveform adjoint tomography a geotechnical layer gtl based on vs30 measurements and consistent with the underlying velocity descriptions was also developed as an optional model component the resulting model provides a detailed description of the structure of the southern california crust and upper mantle that reflects the complex tectonic history of the region the crust thickens eastward as moho depth varies from 10 to 40 km reflecting the transition from oceanic to continental crust deep sedimentary basins and underlying areas of thin crust reflect neogene extensional tectonics overprinted by transpressional deformation and rapid sediment deposition since the late pliocene to illustrate the impact of this complex structure on strong ground motion forecasting we simulate rupture of a proposed m 7 9 earthquake source in the western transverse ranges the results show distinct basin amplification and focusing of energy that reflects crustal structure described by the usr that is not captured by simpler velocity descriptions we anticipate that the usr will be useful for a broad range of simulation and modeling efforts including strong ground motion forecasting dynamic rupture simulations and fault system modeling the usr is available through the southern california earthquake center scec website http www scec org

hierarchical interlocked orthogonal faulting in the 2019 ridgecrest earthquake sequence a nearly 20 year hiatus in major seismic activity in southern california ended on 4 july 2019 with a sequence of intersecting earthquakes near the city of ridgecrest california this sequence included a foreshock with a moment magnitude mw of 6 4 followed by a mw 7 1 mainshock nearly 34 hours later geodetic seismic and seismicity data provided an integrative view of this sequence which ruptured an unmapped multiscale network of interlaced orthogonal faults this complex fault geometry persists over the entire seismogenic depth range the rupture of the mainshock terminated only a few kilometers from the major regional garlock fault triggering shallow creep and a substantial earthquake swarm the repeated occurrence of multifault ruptures as revealed by modern instrumentation and analysis techniques poses a formidable challenge in quantifying regional seismic hazards

groundwater flow patterns in a large peatland abstract groundwater flow patterns and geochemistry were studied in the mer bleue bog near ottawa ontario canada groundwater flow patterns alternated between recharge i e head gradients producing flow from the surface of the peatland to the deeper peat and discharge i e head gradients indicating flow from the deeper peat towards the surface of the peatland during the summer of 1998 the patterns were controlled by changes in precipitation evapotranspiration and the differential head response of catotelm peat lower layer to changes in water table elevation above average rainfall in the spring created recharge patterns of groundwater flow in the peatland evapotranspiration exceeded precipitation for a three week period in mid summer decreasing head at the water table and reversing flow from recharge to discharge a sustained moisture deficit maintained a flow reversal for 32 days until a 46 mm rainfall raised the water table reversing the vertical hydraulic gradients and restoring recharge flow the mixing of meteoric water and deeper groundwater controls geochemical profiles diffusion modeling shows that the peatland is a long term recharge system however electrical conductivity and cation concentrations in peat pore waters increase up to 60 during a flow reversal and then decrease when recharge conditions are re established the redistribution of substrates from reversed flow is likely important to peatland biogeochemical function

effect of mine dewatering on peatlands of the james bay lowland the role of bioherms the james bay lowland host one of the largest wetland complexes in the world in part due to the low permeability of marine sediments that suppress groundwater seepage losses dewatering of an open pit diamond mine in the area has depressurized the regional bedrock aquifer bioherms fractured limestone outcroppings formed from ancient coral reefs that protrude to the peatland surface lack this mantle of low permeability sediments and provide a direct connection between the peatland surficial and the regional bedrock aquifers well transects and piezometer nests were installed around seven bioherms in the depressurized zone and one in a non affected zone control to monitor the water table drawdown and change in hydraulic gradients around the bioherms water tables in the affected bioherms decreased between 2 and 4 m in the first 4 years of dewatering the drawdown in the bioherms caused a localized water table drawdown in the peat surrounding the bioherms that extended to approximately 30 m from the edge of the bioherm during a dry period under wet conditions drawdown was similar to that at the control site hydraulic gradients in the peat which typically are very small increased over the field seasons and in a few locations exceeded 1 these gradients represented significant losses to the local near bioherm system as at many of the locations surrounding the bioherms vertical seepage losses ranged between 1 and 4 mm day which are similar to the seasonal average evaporative water loss of 3 mm day the bioherms are acting as efficient drainage nodes however their influence is localized to the peat immediately 30 m surrounding them copyright 2012 john wiley sons ltd

applying a three dimensional velocity model waveform cross correlation and cluster analysis to locate southern california seismicity from 1981 to 2005 we compute high precision earthquake locations using southern california pick and waveform data from 1981 to 2005 our latest results are significantly improved compared to our previous catalog by the following 1 we locate events with respect to a new crustal p and s velocity model using three dimensional ray tracing 2 we examine six more years of waveform data and compute cross correlation results for many more pairs than our last analysis and 3 we compute locations within similar event clusters using a new method that applies a robust fitting method to obtain the best locations satisfying all the differential time constraints from the waveform cross correlation these results build on the relocated catalogs of hauksson and shearer 2005 and shearer et al 2005 and provide additional insight regarding the fine scale fault structure in southern california and the relationship between the san andreas fault saf and nearby seismicity in particular we present results for two regions in which the seismicity near the southern saf seems to align on dipping faults

earthquake hazard after a mainshock in california after a strong earthquake the possibility of the occurrence of either significant aftershocks or an even stronger mainshock is a continuing hazard that threatens the resumption of critical services and reoccupation of essential but partially damaged structures a stochastic parametric model allows determination of probabilities for aftershocks and larger mainshocks during intervals following the mainshock the probabilities depend strongly on the model parameters which are estimated with bayesian statistics from both the ongoing aftershock sequence and from a suite of historic california aftershock sequences probabilities for damaging aftershocks and greater mainshocks are typically well constrained after the first day of the sequence with accuracy increasing with time

geology of the victor kimberlite attawapiskat northern ontario canada cross cutting and nested craters abstract the pipe shapes infill and emplacement processes of the attawapiskat kimberlites including victor contrast with most of the southern african kimberlite pipes the attawapiskat kimberlite pipes are formed by an overall two stage process of 1 pipe excavation without the development of a diatreme sensu stricto and 2 subsequent pipe infilling the victor kimberlite comprises two adjacent but separate pipes victor south and victor north the pipes are infilled with two contrasting textural types of kimberlite pyroclastic and hypabyssal like kimberlite victor south and much of victor north are composed of pyroclastic spinel carbonate kimberlites the main features of which are similar clast supported discrete macrocrystal and phenocrystal olivine grains pyroclastic juvenile lapilli mantle derived xenocrysts and minor country rock xenoliths are set in serpentine and carbonate matrices these partly bedded juvenile lapilli bearing olivine tuffs appear to have been formed by subaerial fire fountaining airfall processes the victor south pipe has a simple bowl like shape that flares from just below the basal sandstone of the sediments that overlie the basement the sandstone is a known aquifer suggesting that the crater excavation process was possibly phreatomagmatic in contrast the pipe shape and internal geology of victor north are more complex the northwestern part of the pipe is dominated by dark competent rocks which resemble fresh hypabyssal kimberlite but have unusual textures and are closely associated with pyroclastic juvenile lapilli tuffs and country rock breccias volcaniclastic kimberlite current evidence suggests that the hypabyssal like kimberlite is in fact not intrusive and that the northwestern part of victor north represents an early formed crater infilled with contrasting extrusive kimberlites and associated breccias the remaining main part of victor north consists of two macroscopically similar but petrographically distinct pyroclastic kimberlites that have contrasting macrodiamond sample grades the juvenile lapilli of each pyroclastic kimberlite can be distinguished only microscopically the nature and relative modal proportion of primary olivine phenocrysts in the juvenile lapilli are different indicating that they derive from different magma pulses or phases of kimberlite and thus represent separate eruptions the initial excavation of a crater cross cutting the earlier northwestern crater was followed by emplacement of phase i a low grade olivine phenocryst rich pyroclastic kimberlite and the subsequent eruption of phase ii a high grade olivine phenocryst poor pyroclastic kimberlite as two separate vents nested within the original phase i crater the second eruption was accompanied by the formation of an intermediate mixed zone with moderate grade thus the final pyroclastic pipe infill of the main part of the victor north pipe appears to consist of at least three geological macrodiamond grade zones in conclusion the victor kimberlite was formed by several eruptive events resulting in adjacent and cross cutting craters that were infilled with either pyroclastic kimberlite or hypabyssal like kimberlite which is now interpreted to be of probable extrusive origin within the pyroclastic kimberlites of victor north there are two nested vents a feature seldom documented in kimberlites elsewhere this study highlights the meaningful role of kimberlite petrography in the evaluation of diamond deposits and provides further insight into kimberlite emplacement and volcanism

southern california hypocenter relocation with waveform cross correlation part 1 results using the double difference method we present the results of relocating 327 000 southern california earthquakes that occurred between 1984 and 2002 we apply time domain waveform cross correlation for p and s waves between each event and 100 neighboring events identified from the catalog based on a 3d velocity model to simplify the computation we first divide southern california into five polygons such that there are 100 000 events or less in each region the polygon boundaries are chosen to lie in regions of sparse seismicity we calculate and save differential times from the peaks in the cross correlation functions and use a spline interpolation method to achieve a nominal timing precision of 0 001 sec these differential times together with existing p and s phase picks are input to the double difference program of waldhauser and ellsworth 2000 2002 to calculate refined hypocenters we divide the southern california region into grid cells and successively relocate hypocenters within each grid cell the overall resulting pattern of seismicity is more focused than the previously determined pattern from 1d or 3d models the new improved locations are more clustered in many cases by a factor of two or three and often show clear linear alignments in particular the depth distribution is improved and less affected by layer boundaries in velocity models or other similar artifacts

structure of peat soils and implications for water storage flow and solute transport a review update for geochemists abstract global peatlands are a valuable but vulnerable resource they represent a significant carbon and energy reservoir and play major roles in water and biogeochemical cycles peat soils are highly complex porous media with distinct characteristic physical and hydraulic properties pore sizes in undecomposed peat can exceed 5 mm but significant shrinkage occurs during dewatering compression and decomposition reducing pore sizes the structure of peat soil consists of pores that are open and connected dead ended or isolated the resulting dual porosity nature of peat soils affects water flow and solute migration which influence reactive transport processes and biogeochemical functions advective movement of aqueous and colloidal species is restricted to the hydrologically active or mobile fraction of the total porosity i e the open and connected pores peat may attenuate solute migration through molecular diffusion into the closed and dead end pores and for reactive species also through sorption and degradation reactions slow diffusion limited solute exchanges between the mobile and immobile regions may give rise to pore scale chemical gradients and heterogeneous distributions of microbial habitats and activity in peat soils while new information on the diversity and functionalities of peat microbial communities is rapidly accumulating the significance of the geochemical and geomicrobial study on peat stands to benefit from a basic understanding of the physical structure of peat soils in this paper we review the current knowledge of key physical and hydraulic properties related to the structure of globally available peat soils and briefly discuss their implications for water storage flow and the migration of solutes this paper is intended to narrow the gap between the ecohydrological and biogeochemical research communities working on peat soils

minimum magnitude of completeness in earthquake catalogs examples from alaska the western united states and japan we mapped the minimum magnitude of complete reporting m c for alaska the western united states and for the junec earthquake catalog of japan mc was estimated based on its departure from the linear frequency magnitude relation of the 250 closest earthquakes to grid nodes spaced 10 km apart in all catalogs studied mc was strongly heterogeneous in offshore areas the mc was typically one unit of magnitude higher than onshore on land also mc can vary by one order of magnitude over distance less than 50 km we recommend that seismicity studies that depend on complete sets of small earthquakes should be limited to areas with similar mc or the minimum magnitude for the analysis has to be raised to the highest com mon value of mc we believe that the data quality as reflected by the mc level should be used to define the spatial extent of seismicity studies where mc plays a role the method we use calculates the goodness of fit between a power law fit to the data and the observed frequency magnitude distribution as a function of a lower cutoff of the magnitude data mc is defined as the magnitude at which 90 of the data can be modeled by a power law fit mc in the 1990s is approximately 1 2 0 4 in most parts of california 1 8 0 4 in most of alaska aleutians and panhandle excluded and at a higher level in the junec catalog for japan various sources such as ex plosions and earthquake families beneath volcanoes can lead to distributions that cannot be fit well by power laws for the hokkaido region we demonstrate how neglecting the spatial variability of m c can lead to erroneous assumptions about deviations from self similarity of earthquake scaling

determination of earthquake energy release and ml using terrascope we estimated the energy radiated by earthquakes in southern california using on scale very broadband recordings from terrascope the method we used involves time integration of the squared ground motion velocity and empirical determination of the distance attenuation function and the station corrections the time integral is typically taken over a duration of 2 min after the p wave arrival the attenuation curve for the energy integral we obtained is given by q r cr n exp kr r 2 2 h ref 2 with c 0 49710 n 1 0322 k 0 0035 km 1 and h ref 8 km where is the epicentral distance a similar method was used to determine m l using terrascope data the station corrections for m l are determined such that the m l values determined from terrascope agree with those from the traditional optical wood anderson seismographs for 1 5 6 5 m l saturates the ratio e s m 0 m 0 seismic moment a measure of the average stress drop for six earthquakes the 1989 montebello earthquake m l 4 6 the 1989 pasadena earthquake m l 4 9 the 1990 upland earthquake m l 5 2 the 1991 sierra madre earthquake m l 5 8 the 1992 joshua tree earthquake m l 6 1 and the 1992 landers earthquake m w 7 3 are about 10 times larger than those of the others that include the aftershocks of the 1987 whittier narrows earthquake the sierra madre earthquake the joshua tree earthquake and the two earthquakes on the san jacinto fault the difference in the stress drop between the mainshock and their large aftershocks may be similar to that between earthquakes on a fault with long and short repeat times the aftershocks which occurred on the fault plane where the mainshock slippage occurred had a very short time to heal hence a low stress drop the repeat time of the major earthquakes on the frontal fault systems in the transverse ranges in southern california is believed to be very long a few thousand years hence the events in the transverse ranges may have higher stress drops than those of the events occurring on faults with shorter repeat times such as the san andreas fault and the san jacinto fault the observation that very high stress drop events occur in the transverse ranges and the los angeles basin has important implications for the regional seismic potential the occurrence of these high stress drop events near the bottom of the seismogenic zone strongly suggests that these fault systems are capable of supporting high stress that will eventually be released in major seismic events characterization of earthquakes in terms of the e s m 0 ratio using broadband data will help delineate the spatial distribution of seismogenic stresses in the los angeles basin and the transverse ranges

source parameters of the 1933 long beach earthquake regional seismographic network and teleseismic data for the 1933 m l 6 3 long beach earthquake sequence have been analyzed both the teleseismic focal mechanism of the main shock and the distribution of the aftershocks are consistent with the event having occurred on the newport inglewood fault the focal mechanism had a strike of 315 dip of 80 to the northeast and rake of 170 relocation of the foreshock main shock aftershock sequence using modern events as fixed reference events shows that the rupture initiated near the huntington beach newport beach city boundary and extended unilaterally to the northwest to a distance of 13 to 16 km the centroidal depth was 10 2 km the total source duration was 5 sec and the seismic moment was 5 10 25 dyne cm which corresponds to an energy magnitude of m w 6 4 the source radius is estimated to have been 6 6 to 7 9 km which corresponds to a brune stress drop of 44 to 76 bars both the spatial distribution of aftershocks and inversion for the source time function suggest that the earthquake may have consisted of at least two subevents when the slip estimate from the seismic moment of 85 to 120 cm is compared with the long term geological slip rate of 0 1 to 1 0 mm yr along the newport inglewood fault the 1933 earthquake has a repeat time on the order of a few thousand years

evidence for widespread anoxia in the proglacial zone of an arctic glacier the major ion so42 hco3 no3 and stable isotope composition 18o h2o 18o so42 34s so42 and dic 13c of ground and surface water samples collected from the proglacial zone of a retreating high arctic glacier finsterwalderbreen svalbard indicate the widespread occurrence of microbially mediated processes under anoxic conditions the 18o so42 of active layer groundwaters lake and stream waters is strongly depleted in 18o compared to the 18o h2o and stable isotope mass balance arguments indicate that 75 95 of so42 in these waters is produced by the oxidation of sulphide minerals using fe iii and no3 under anoxic conditions consistent with this is the frequent loss or depletion of no3 from ground and surface waters so42 concentrations and 18o so42 and 18o h2o data suggest that much of the so42 is generated anoxically early in the melt season in 18o depleted snowmelt and is immobilized as sulphate salts in near surface moraine due to evaporative concentration these salts are remobilized later in the season by rainfall and glacial flood events and cause the 18o so42 of proglacial meltwaters to be 18o h2o the latter become isotopically heavy through the melt season due to evaporation the lack of any relationship between 34s so42 and 18o so42 and relatively heavy dic 13c values in proglacial waters suggests that sulphate reduction is not a significant process acidity produced during anoxic oxidation of sulphides appears to drive chemical weathering in the proglacial zone enabling high chemical weathering rates to be maintained despite the absence of dissolved oxygen similar findings have been reported from subglacial environments where anoxic sulphide oxidation is widely observed the absence of evidence for sulphate reduction in the proglacial groundwaters however suggests that the degree of anoxia in deglaciated settings may not be widespread as in subglacial environments where significant sulphate reduction has been observed

adsorption of rare earth elements onto carrizo sand experimental investigations and modeling with surface complexation rare earth element ree adsorption onto sand from a well characterized aquifer the carrizo sand aquifer of texas has been investigated in the laboratory using a batch method the aim was to improve our understanding of ree adsorption behavior across the ree series and to develop a surface complexation model for the rees which can be applied to real aquifer groundwater systems our batch experiments show that ree adsorption onto carrizo sand increases with increasing atomic number across the ree series for each ree adsorption increases with increasing ph such that when ph 6 0 98 of each ree is adsorbed onto carrizo sand for all experimental solutions including when actual groundwaters from the carrizo sand aquifer are used in the experiments rare earth element adsorption was not sensitive to ionic strength and total initial ree concentrations in our batch experiments it is possible that the differences in experimental ionic strength conditions i e 0 002 0 01 m nacl chosen were insufficient to affect ree adsorption behavior however cation competition e g ca mg and zn did affect ree adsorption onto carrizo sand especially for light rare earth elements lrees at low ph rare earth element adsorption onto carrizo sand can be successfully modeled using a generalized two layer surface complexation model our model calculations suggest that ree complexation with strong surface sites of carrizo sand exceeds the stability of the aqueous complexes lnoh 2 lnso4 and lnco3 but not that of ln co3 2 or lnpo4 in carrizo groundwaters thus at low ph 7 3 where major inorganic ligands did not effectively compete with surface sites for dissolved rees free metal ion ln 3 adsorption was sufficient to describe ree adsorption behavior however at higher ph 7 3 where solution complexation of the dissolved rees was strong rees were adsorbed not only as free metal ion ln 3 but also as aqueous complexes e g as ln co3 2 in carrizo groundwaters because heavy rare earth elements hrees were preferentially adsorbed onto carrizo sand compared to lrees original hree enriched fractionation patterns in carrizo groundwaters from the recharge area flattened along the groundwater flow path in the carrizo sand aquifer due to adsorption of free and solution complexed rees copyright 2005 elsevier ltd

local magnitudes and apparent variations in seismicity rates in southern california redetermination of local magnitudes for moderate earthquakes recorded by the southern california seismographic network scsn from 1932 to 1990 has shown that the magnitudes have not been consistently determined over that time period the amplitudes of ground velocities recorded on wood anderson instruments were systematically overestimated prior to 1944 compared to present reading procedures leading to a significant overestimation of local magnitudes in addition the change from human to computerized estimation of event magnitude from a suite of amplitudes in 1975 led to slightly lower event magnitudes for the time after 1975 compared to the time before these changes contribute to an apparently higher rate of seismicity in the 1930s and 1940s than later in the catalog which had been interpreted as a decrease in seismicity rate after the 1952 kern county m w 7 5 earthquake wood anderson amplitudes have been reread and consistent magnitudes recalculated using uniform procedures for all earthquakes with a catalog magnitude of 4 5 and greater within the scsn from 1932 to 1943 and those with a catalog magnitude of 4 8 and greater from 1944 to 1990 so as to create a complete list of all earthquakes with a modern local magnitude of 5 0 or greater using these new magnitudes we find that the rate of m l 5 0 and greater earthquakes in southern california over this 59 year period to be poissonian with no changes in rate significant above the 90 level from this rate in any 30 year period the poissonian probability of a m 6 earthquake is 99 7 the probability of an m 7 earthquake is 65 and the probability of an m 8 event is 18

anomalously deep crustal earthquakes in the ventura basin southern california earthquakes at depths of 20 30 km occur beneath the ventura basin in southern california the epicentral distribution of deep seismicity outlines an east trending ellipse which corresponds closely with the mapped santa clara syncline the main structural element of the ventura basin with 15 km thickness of sediments clear pn and pg phases are seen for even the deepest earthquakes which demonstrate that these earthquakes are occurring within the crust travel time curves from shallow and deep earthquakes in the western transverse ranges require that the depth to the moho under the ventura basin must be depressed by 7 10 km relative to the surrounding area indicating crustal thickening of 20 35 other researchers have shown that the ventura basin has the lowest heat flow in western california thus low heat flow exceptionally thick 15 km sediments rapid shortening of the crust the deep earthquakes and a depressed moho all coincide within a small area strongly suggesting a common cause for all five phenomena the confinement of the deep earthquakes and depressed moho to the ventura region suggests that the rapid shortening of the ventura basin is anomalous and not representative of the rate of shortening across all of the western transverse ranges

karst hydrogeology within a subarctic peatland attawapiskat river hudson bay lowland canada abstract the attawapiskat river has cut through 30 m of mid silurian limestone 90 km west of james bay in the hudson bay lowland limestone cliffs of 12 15 m provide local relief along the river but inland the terrain is flat covered by 1 5 m or more of peat the area emerged from the tyrrell sea 4400 yr b p since that time two karst hydrogeological zones have become established these are 1 a vadose fluvio karst zone in the exposed limestone along the river represented by disappearing lakes and streams and 2 an organo karst zone represented by sinkholes on or next to limestone bioherms within the peat mantle they occupy 16 and 13 of the study area respectively

synthesis of wood anderson seismograms from broadband digital records abstract wood anderson torsion seismograms are synthesized by convolution with cosited broadband digital seismograph recordings and compared with the photographically recorded wood anderson seismograms at berkeley and mt hamilton the objective is to use routinely the synthesized seismograms to determine local magnitude comparison of local magnitude values calculated from both synthesized and photographic seismograms shows that the variation in local magnitude between the two types of seismograms is less than the variation among the photographic seismograms consequently broadband digital recordings can provide reliable local magnitude estimates without introducing significant bias it is shown that the static magnification of standard t s 0 8 sec wood anderson torsion seismographs determined from measurement of the free period and tilt sensitivity is 2080 60 and not 2800 as often reported this discrepancy is due to the erroneous assumption that the taught wire suspension in a wood anderson seismograph does not distort significantly thus leading to an incorrect estimate of the radius of gyration and consequently to a theoretical geometrical magnification of 2800

the 1992 landers earthquake sequence seismological observations the m w 6 1 7 3 6 2 1992 landers earthquakes began on april 23 with the m w6 1 1992 joshua tree preshock and form the most substantial earthquake sequence to occur in california in the last 40 years this sequence ruptured almost 100 km of both surficial and concealed faults and caused aftershocks over an area 100 km wide by 180 km long the faulting was predominantly strike slip and three main events in the sequence had unilateral rupture to the north away from the san andreas fault the m w6 1 joshua tree preshock at 33 n58 and 116 w19 on 0451 ut april 23 was preceded by a tightly clustered foreshock sequence m 4 6 beginning 2 hours before the mainshock and followed by a large aftershock sequence with more than 6000 aftershocks the aftershocks extended along a northerly trend from about 10 km north of the san andreas fault northwest of indio to the east striking pinto mountain fault the m w7 3 landers mainshock occurred at 34 n13 and 116 w26 at 1158 ut june 28 1992 and was preceded for 12 hours by 25 small m 3 earthquakes at the mainshock epicenter the distribution of more than 20 000 aftershocks analyzed in this study and short period focal mechanisms illuminate a complex sequence of faulting the aftershocks extend 60 km to the north of the mainshock epicenter along a system of at least five different surficial faults and 40 km to the south crossing the pinto mountain fault through the joshua tree aftershock zone towards the san andreas fault near indio the rupture initiated in the depth range of 3 6 km similar to previous m 5 earthquakes in the region although the maximum depth of aftershocks is about 15 km the mainshock focal mechanism showed right lateral strike slip faulting with a strike of n10 w on an almost vertical fault the rupture formed an arclike zone well defined by both surficial faulting and aftershocks with more westerly faulting to the north this change in strike is accomplished by jumping across dilational jogs connecting surficial faults with strikes rotated progressively to the west a 20 km long linear cluster of aftershocks occurred 10 20 km north of barstow or 30 40 km north of the end of the mainshock rupture the most prominent off fault aftershock cluster occurred 30 km to the west of the landers mainshock the largest aftershock was within this cluster the m w6 2 big bear aftershock occurring at 34 n10 and 116 w49 at 1505 ut june 28 it exhibited left lateral strike slip faulting on a northeast striking and steeply dipping plane the big bear aftershocks form a linear trend extending 20 km to the northeast with a scattered distribution to the north the landers mainshock occurred near the southernmost extent of the eastern california shear zone an 80 km wide more than 400 km long zone of deformation this zone extends into the death valley region and accommodates about 10 to 20 of the plate motion between the pacific and north american plates the joshua tree preshock its aftershocks and landers aftershocks form a previously missing link that connects the eastern california shear zone to the southern san andreas fault

delineating complex spatiotemporal distribution of earthquake aftershocks an improved source scanning algorithm summary conventional earthquake location methods depend critically on the correct identification of seismic phases and their arrival times from seismograms accurate phase picking is particularly difficult for aftershocks that occur closely in time and space mostly because of the ambiguity of correlating the same phase at different stations in this study we introduce an improved source scanning algorithm issa for the purpose of delineating the complex distribution of aftershocks without time consuming and labour intensive phase picking procedures the improvements include the application of a ground motion analyser to separate p and s waves the automatic adjustment of time windows for brightness calculation based on the scanning resolution and a modified brightness function to combine constraints from multiple phases synthetic experiments simulating a challenging scenario are conducted to demonstrate the robustness of the issa the method is applied to a field data set selected from the ocean bottom seismograph records of an offshore aftershock sequence southwest of taiwan although visual inspection of the seismograms is ambiguous our issa analysis clearly delineates two events that can best explain the observed waveform pattern

simulating vertical flow in large peatlands ground water flow simulations are used to evaluate the importance of three parameters on vertical flow in peatlands regional slope permeability of the mineral soil underlying the peat and peatland topography our results indicate that the extent of vertical ground water flow in peatlands is primarily controlled by mineral soil permeability local ground water flow cells that form under small water table mounds at bog domes can drive peat pore water into permeable mineral soil however when peat forms over low permeability mineral soil vertical movement of peat pore water becomes negligible and lateral flow of water in the upper portion of the peat column dominates the peatland hydrology this effect is not due to the low permeability of humified peat layers as is commonly assumed in many peatland studies field data from the hudson bay lowland canada and the glacial lake agassiz peatlands of northern minnesota confirm the validity of these models these results are relevant in settings other than peatlands where relief is low and small topographic mounds exist

anisotropy and depth related heterogeneity of hydraulic conductivity in a bog peat i laboratory measurements anisotropy and heterogeneity of hydraulic conductivity k are suspected of greatly affecting rates and patterns of ground water seepage in peats a new laboratory method termed here the modified cube method was used to measure horizontal and vertical hydraulic conductivity kh and kv of 400 samples of bog peat the new method avoids many of the problems associated with existing field and laboratory methods and is shown to give relatively precise measurements of k in the majority of samples tested kh was much greater than kv indicating that the bog peat was strongly anisotropic log10kh log10kv and log10 kh kv were found to vary significantly with depth although none of the relationships was simple we comment on the scale dependency of our measurements

spatial separation of large earthquakes aftershocks and background seismicity analysis of interseismic and coseismic seismicity patterns in southern california we associate waveform relocated background seismicity and aftershocks with the 3 d shapes of late quaternary fault zones in southern california major earthquakes that can slip more than several meters aftershocks and near fault background seismicity mostly rupture different surfaces within these fault zones major earthquakes rupture along the mapped traces of the late quaternary faults called the principal slip zones pszs aftershocks occur either on or in the immediate vicinity of the pszs typically within zones that are 2 km wide in contrast the near fault background seismicity is mostly accommodated on a secondary heterogeneous network of small slip surfaces and forms spatially decaying distributions extending out to distances of 10 km from the pszs we call the regions where the enhanced rate of background seismicity occurs the seismic damage zones one possible explanation for the presence of the seismic damage zones and associated seismicity is that the damage develops as faults accommodate bends and geometrical irregularities in the pszs the seismic damage zones mature and reach their finite width early in the history of a fault during the first few kilometers of cumulative offset alternatively the similarity in width of seismic damage zones suggests that most fault zones are of almost equal strength although the amount of cumulative offset varies widely it may also depend on the strength of the fault zone the time since the last major earthquake as well as other parameters in addition the seismic productivity appears to be influenced by the crustal structure and heat flow with more extensive fault networks in regions of thin crust and high heat flow

absolute location of 2019 ridgecrest seismicity reveals a shallow mw 7 1 hypocenter migrating and pulsing mw 7 1 foreshocks and duplex mw 6 4 ruptures

a field scale natural gradient solute transport experiment in peat at a newfoundland blanket bog a field scale natural gradient solute transport experiment conducted at a newfoundland blanket bog resulted in an asymmetrical plume owing to solute retardation in the dual porosity matrix an order of magnitude decrease in hydraulic conductivity 10 20 m downslope of the spill caused the transport rate to decrease and lateral dispersion to increase most transport occurred near the watertable and the transport rate increased as the watertable rose hydraulic conductivity between a depth of 0 and 0 2 m was 1 6 10 2 m s 1 whereas at a depth of 0 5 m it was 5 6 orders of magnitude lower owing to greater compaction and humification of the peat with depth at a depth of 0 4 0 45 m diffusion may have become the dominant transport mechanism in spite of the retardation process the solute front s rate of movement was relatively high about 2 3 m day 1 owing to a combination of the high watertable during the study and a relatively steep hydraulic gradient of 0 055 rain caused dilution and mixing of solute near the watertable evaporation did not have an appreciable effect on solute concentration which is attributable to the high transport rate

detailed 3d fault representations for the 2019 ridgecrest california earthquake sequence we present new 3d source fault representations for the 2019 m 6 4 and m 7 1 ridgecrest earthquake sequence these representations are based on relocated hypocenter catalogs expanded by template matching and focal mechanisms for m 4 and larger events following the approach of riesner et al 2017 we generate reproducible 3d fault geometries by integrating hypocenter nodal plane and surface rupture trace constraints we used the southwest northeast striking nodal plane of the 4 july 2019 m 6 4 event to constrain the initial representation of the southern little lake fault sllf both in terms of location and orientation the eastern little lake fault ellf was constrained by the 5 july 2019 m 7 1 hypocenter and nodal planes of m 4 and larger aftershocks aligned with the main trend of the fault the approach follows a defined workflow that assigns weights to a variety of geometric constraints these main constraints have a high weight relative to that of individual hypocenters ensuring that small aftershocks are applied as weaker constraints the resulting fault planes can be considered averages of the hypocentral locations respecting nodal plane orientations for the final representation we added detailed field mapped rupture traces as strong constraints the resulting fault representations are generally smooth but nonplanar and dip steeply the sllf and ellf intersect at nearly right angles and cross on another the ellf representation is truncated at the airport lake fault to the north and the garlock fault to the south consistent with the aftershock pattern the terminations of the sllf representation are controlled by aftershock distribution these new 3d fault representations are available as triangulated surface representations and are being added to a community fault model cfm plesch et al 2007 2019 nicholson et al 2019 for wider use and to derived products such as a cfm trace map and viewer su et al 2019

imaging stress and faulting complexity through earthquake waveform similarity while the rupture processes of nearby earthquakes are often highly similar characterizing the differences can provide insight into the complexity of the stress field and fault network in which the earthquakes occur here we perform a comprehensive analysis of earthquake waveform similarity to characterize rupture processes in the vicinity of ridgecrest california we quantify how similar each earthquake is to neighboring events through cross correlation of full waveforms the july 2019 ridgecrest mainshocks impose a step reduction in earthquake similarity which suggests variability in the residual stress field and activated fault structures on length scales of hundreds of meters or less among these aftershocks we observe coherent spatial variations of earthquake similarity along the mainshock rupture trace and document antisimilar aftershock pairs with waveforms that are nearly identical but with reversed polarity these observations provide new high resolution constraints on stress transfer and faulting complexity throughout the ridgecrest earthquake sequence

stress history controls the spatial pattern of aftershocks case studies from strike slip earthquakes earthquake ruptures perturb stress within the surrounding crustal volume and as it is widely accepted now these stress perturbations strongly correlates with the following seismicity here we have documented five cases of the mainshock aftershock sequences generated by the strike slip faults from different tectonic environments of world in order to demonstrate that the stress changes resulting from large preceding earthquakes decades before effect spatial distribution of the aftershocks of the current mainshocks the studied mainshock aftershock sequences are the 15 october 1979 imperial valley earthquake mw 6 4 in southern california the 27 november 1979 khuli boniabad mw 7 1 the 10 may 1997 qa enat mw 7 2 and the 31 march 2006 silakhor mw 6 1 earthquakes in iran and the 13 march 1992 erzincan earthquake mw 6 7 in turkey in the literature we have been able to find only these mainshocks that are mainly characterized by dense and strong aftershock activities along and beyond the one end of their ruptures while rare aftershock occurrences with relatively lower magnitude reported for the other end of their ruptures it is shown that the stress changes resulted from earlier mainshock s that are close in both time and space might be the reason behind the observed aftershock patterns the largest aftershocks of the mainshocks studied tend to occur inside the stress increased lobes that were also stressed by the background earthquakes and not to occur inside the stress increased lobes that fall into the stress shadow of the background earthquakes we suggest that the stress shadows of the previous mainshocks may persist in the crust for decades to suppress aftershock distribution of the current mainshocks considering active researches about use of the coulomb stress change maps as a practical tool to forecast spatial distribution of the upcoming aftershocks for earthquake risk mitigation purposes in near real time it is further suggested that the background mainshocks along the neighbouring faults should be taken into account in producing the stress change maps for commenting on aftershock occurrences

a kinematic model of southern california we propose a kinematic model for southern california based on late quaternary slip rates and orientations of major faults in the region internally consistent motions are determined assuming that these faults bound rigid blocks relative to north america most of california west of the san andreas fault is moving parallel to the san andreas fault through the transverse ranges and not parallel to the motion of the pacific plate this is accomplished by counterclockwise rotation of california south of the san andreas fault and by the westward movement of central california north of the gar lock fault the velocities of the blocks are calculated along several paths in southern california that begin in the mojave desert and end off the california coast a path that crosses the western transverse ranges accumulates the accepted relative north america pacific plate velocity whereas paths to the north and south result in a significant missing component of motion this implies the existence of a zone of active deformation in southern california that is interpreted to include the western transverse ranges and northwest trending predominately strike slip faults close to the coast both north and south of the transverse ranges strain on this system accounts for about a third of the total north america pacific plate motion

second order moment of central california seismicity 1969 1982 the second order moment cross correlation function of earthquakes in the u s geological survey central california catalog between 1969 and 1982 was calculated with respect to a magnitude threshold m 4 0 over interevent distances up to 80 km and interevent times up to 320 days the statistical procedure results in a representation of the spatial temporal structure of the catalog associated with m 4 0 earthquakes and is capable of revealing patterns too weak to be detected in the space time distribution of seismicity for individual earthquake sequences a method is introduced for identifying aftershocks based on a physical two parameter model of the earthquake interaction process the results show that the aftershock process dominates the second order moment and may even obscure the statistical expression of a precursory process a concentration of foreshocks within 15 km and 3 days of m 4 0 main shocks exhibits an apparent migration toward the main shock loci with velocity 2 6 5 3 km d this concentration may be related to an observed tendency for m 4 0 events to cluster auto correlate over this interevent range with the identified aftershocks removed the residual catalog is poissonion in space and time when two m 4 0 earthquakes occur within 80 km and 40 days of each other aftershock productivity appears to be relatively enhanced in the earlier sequence this suggests that aftershock populations are not solely dependent on their main shocks and that unusually productive aftershock sequences may be predictors of future moderate earthquakes

soil water flow dynamics in a managed cutover peat field quebec field and laboratory investigations in this paper concerned with soil water dynamics in a managed cutover peat field the microscale hydrological processes and parameters governing water flow and storage through variably saturated peat are investigated an open water ditch reservoir enhanced wetting of adjacent cutover peat maintaining the water table depth above 43 cm during the summer surface soil moisture above 45 and water tension in the surface layer above 245 mbar desaturation of pores was noted in the 22 and 210 cm depths but at 230 and 250 cm a decrease in moisture content of several percent was associated with compression of the peat as the water table dropped air entry occurred only at pressures below 215 mbar seasonal subsidence resulted in cumulative vertical displacement in excess of 10 cm during the study period typical settlements in the peat ranged between 11 and 23 of the lowering of the water table considerable hysteresis was observed and vertical displacement was 5 times greater in response to water loss compared to rewetting the specific storage s s in the 180 cm thick deposit averaged 9 4 3 10 24 cm 21 during drying periods but averaged only 2 6 3 10 24 cm 21 on rewetting s s was more important than specific yield sy in the overall aquifer storativity transient hydraulic properties resulted from the shifting soil structure the increase in peat bulk density caused by drying increased the water retention capacity and decreased hydraulic conductivity mean saturated hydraulic conductivity was 15 cm d 21 and decreased 2 orders of magnitude as the degree of saturation dropped from 1 to 0 4 the horizontal vertical anisotropy ratio was 4 the changing surface elevation in response to seasonal subsidence had a profound influence on the nature of the storage changes and hydraulic parameters of the peat soil

erratum to rupture process of the 2019 ridgecrest california mw 6 4 foreshock and mw 7 1 earthquake constrained by seismic and geodetic data

geochemistry of peat over kimberlites in the attawapiskat area james bay lowlands northern canada abstract the james bay lowlands which is the se part of the hudson bay lowlands canada and within the paleozoic limestone terrane is covered mostly by peatlands peat samples were examined in the attawapiskat area a region of discontinuous permafrost where more than 19 kimberlite pipes have been found beneath a cover of peat 2 4 m thick and quaternary sediments up to 20 m thick of tyrell sea clay beds and glacial tills pore water at a depth of 40 cm in the peat has a consistently low ph the compositions of peat show spatial variation with the distribution of kimberlites suggesting that they are influenced by the underlying rocks even through there are thick layers of tills and sediments between the bedrocks and peat however elevated concentrations of pathfinder elements of kimberlites in bulk peat samples and aa5 leach are not necessarily directly above kimberlites the diffused metal anomalies around kimberlites are attributed to the dissolution precipitation of secondary phases carbonates and fe o oh in acidic and reduced waters in peat and the movement of waters through peat this pilot study suggests that peat compositions do reflect the underlying bedrock compositions for kimberlite exploration a geochemical survey of peat is useful to discriminate concealed kimberlites from other anomalies defined by geophysical and other techniques however such a geochemical survey is not suitable for delineating the shapes of the concealed kimberlites due to broad dispersed anomalies

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

response of the san jacinto fault zone to static stress changes from the 1992 landers earthquake we perform an analysis of the seismicity response of the san jacinto fault zone to static coulomb stress changes from the 1992 landers earthquake sequence results show that in general stress changes forecast rate changes well we find a significant positive correlation between the change in rate and the magnitude of the coulomb stress change with a correlation coefficient of 0 76 equivalent to 5 6 when compared to a 0 null hypothesis furthermore although the correlations are less clear over negative than positive stress changes there is evidence of some coulomb stress dependent quiescence on stress shadows models that account for heterogeneity in reference seismicity show clear improvements in their predictions of spatial variability of aftershock rates compared to those that assume uniform reference we find also that better performance is obtained 1 using a time dependent coulomb rate state model compared to a time independent exponential model and 2 using structurally constrained rather than optimal target fault orientations these results are an important step in the validation of coulomb stress based methods for quantitative seismicity forecasting we conclude that the correspondence between the predictions of coulomb stress models for aftershock seismicity may be sensitive to strong heterogeneity in aftershock locations and orientations associated with the presence of large scale structure in aftershock study areas in these cases we suggest that where the regional structure is mapped incorporating it explicitly into coulomb stress models may improve the performance of quantitative coulomb stress based forecasts

seismicity and fault kinematics through the eastern transverse ranges california block rotation strike slip faulting and low angle thrusts hypocentral locations and first motion data from the southern california seismic network are used to infer the present pattern of deformation along the southern san andreas fault the study area lies between the san jacinto fault and desert hot springs and includes the san bernardino mountains and san gorgonio pass this region has some of the deepest earthquakes observed anywhere along the entire san andreas system exhibits a complex surface geology characterized by both right and left lateral faults has high topographic relief as a result of recent uplift and is a potential site for the nucleation of a great earthquake although this area is unusually seismogenic little activity can be directly associated with major throughgoing faults seismicity is also generally absent in the upper 5 km the predominant style of faulting above 10 12 km is oblique slip with a large reverse component the spatial distribution of relocated hypocenters and first motion data suggests the presence of a system of left slip faults striking northeast this pattern of faulting in conjunction with an unusual set of normal and reverse focal mechanisms is interpreted as the clockwise rotation of a small set of crustal blocks subject to regional right lateral shear at depths greater than about 10 km seismicity defines a wedge shaped volume undergoing pervasive internal deformation on a combination of strike slip and low angle thrust faults velocity structures determined from earthquake arrival times suggest a low velocity zone at about 10 km below the san bernardino mountains but not below the san jacinto mountains this is nearly the same depth as the transition between the two layers of different kinematic behavior seen south of the mill creek mission creek branch of the san andreas fault and the maximum depth of seismicity seen north of that fault the low velocity zone and the transition between block rotations and the deeper deformation may thus correspond to a detachment under much of this region and would imply that the overthrust san bernardino mountains are allochthonous the present pattern of seismic deformation in shocks of small to moderate size may only characterize the interval between large earthquakes and may change systematically as the region prepares to accommodate large right lateral displacements

comparison of the behaviour of rare earth elements in surface waters overburden groundwaters and bedrock groundwaters in two granitoidic settings eastern sweden this work which was done within the swedish nuclear waste management program was carried out in order to increase the understanding of the mobility and fate of rare earth elements rees in natur

linking major and trace element concentrations in a headwater stream to doc release and hydrologic conditions in a bog and peaty riparian zone abstract in the organic rich environments of peatlands and peaty riparian zones dissolved organic matter dom can act as a carrier for major and trace elements however the mobilization and export patterns of elements from these systems are largely unknown this study elucidates the annual and short term event based dynamics of major and trace element concentrations in a headwater stream draining an ombrotrophic peatland and a peaty riparian zone elements are expected to exhibit specific export patterns depending on their biogeochemical reactivity and source area we hypothesize that most elements are released during organic matter decomposition and are co transported with dom in the bog catchment whereas in the riparian zone other element pools such as shallow groundwater also play a major role most of the variance in the data as revealed by principal component analysis integrated the dom concentration pattern element loadings 0 8 al ca fe mg mn zn li co as sr cd pb and doc ca mg and sr were also found to load on this principal component suggesting that the main control on element mobilization is not dom but rather similar source areas and mobilization processes the dom related export was driven by plant uptake plant decomposition and the bog water level in terms of hydrologic connectivity the differences between the bog and the riparian zone were mainly driven by different hydrologic conditions and additional elemental sources such as mineral weathering the export patterns of rb cs k no3 and so42 were predominantly controlled by the season and plant uptake and they were particularly exported by a surficial fast flow path in addition to other elements ga y and ba were enriched in the upper peat and organic soil layer likely due to anthropogenic pollution the specific export pattern of these latter elements indicates their predominant mobilization by the dissolution of dust particles and their subsequent mobilization by coupling to dom