the present day stress field of australia abstract the unusual present day crustal stress pattern of the australian continent has been the subject of scientific debate for over 25 years the orientation of maximum horizontal present day stress s hmax in continental australia is unlike all other major tectonic plates in that the stress pattern shows regional variability and it is not oriented sub parallel to the direction of absolute plate motion previous studies on the stress pattern of australia revealed that the complex stress pattern of the continent is controlled at a first order by the superposition of plate tectonic forces exerted at the plate boundaries however prior analysis of the contemporary australian crustal stress pattern have been unable to model or explain the stress pattern observed in most of eastern australia and has not extensively addressed the numerous smaller scale variations in stress orientation the recent development of unconventional reservoirs in australia has resulted in a greatly increased amount of new data for stress analysis in previously unstudied or poorly constrained areas in eastern australia in addition stress analysis in conventional hydrocarbon mineral and geothermal exploration in all other parts of the continent provides the opportunity to review and update the australian stress map asm this study presents the new release of the asm with a total of 2150 stress data records in australia increased from 594 data records in 2003 the 2016 asm contains 1359 data records determined from the interpretation of drilling related stress indicators 650 from earthquake focal mechanism solutions 139 from shallow engineering measurements and two from geological indicators the results reveal four distinct regional trends for the s hmax orientation in australia including a nne ssw s hmax trend in northern and northwestern australia which rotates to a prevailing e w orientation in most western and south australia the orientation of s hmax in eastern australia is primarily ene wsw and swings to nw se in southeastern australia a comparison between the new asm database and neotectonic features further confirms the role of contemporary stress in recent deformation of the australian crust the 2016 asm reveals significant discrepancies between newly observed s hmax orientations and predictions by published geomechanical numerical models for the australian continent forces generated at the boundary of indo australian plate remain the major control on the regional crustal stress pattern in continental australia however the increased data density particularly in eastern australia reveals numerous local perturbations of the stress field that were not previously clearly captured hence the key findings of the new release are that local intra plate stress sources are more significant than previously recognized particularly in eastern australian basins and cause substantial local scale rotations of the present day crustal stress pattern that have not been factored into existing australian stress models

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

present day strain accumulation and slip rates associated with southern san andreas and eastern california shear zone faults 1 we present the first results from a dense network of 36 campaign and 46 continuous gps stations located in the eastern transverse ranges province etr a transition zone between the southernmost san andreas fault ssaf and eastern california shear zone ecsz we analyzed the campaign data together with available data from continuous gps stations for the period 1994 2009 we used the gps velocity estimates to constrain elastic block models to investigate fault loading rates representing four hypotheses characterized by different fault block geometries fault block scenarios include blocks bounded by the east striking left lateral pinto mountain blue cut and chiriaco faults of the etr blocks bounded by a right lateral north northwest striking structure the landers mojave earthquake line that cuts obliquely across the etr and mapped mojave desert faults and combinations of these end member hypotheses each model implies significantly different active fault geometries block rotation rates and slip rates for etr and ecsz structures all models suggest that ssaf slip rate varies appreciably along strike generally consistent with rates derived from tectonic geomorphology and paleoseismology with a maximum of 23 mm yr right lateral along the southernmost coachella valley strand decreasing systematically to 10 mm yr right lateral through the san gorgonio pass region slip rate estimates for the san jacinto fault are 12 mm yr for all models tested all four models fit the data equally well in a statistical sense qualitative comparison among models and consideration of geologic slip rates and other independent data reveals strengths and weaknesses of each model

potential for larger earthquakes in the east san francisco bay area due to the direct connection between the hayward and calaveras faults the hayward and calaveras faults two strike slip faults of the san andreas system located in the east san francisco bay area are commonly considered independent structures for seismic hazard assessment we use interferometric synthetic aperture radar to show that surface creep on the hayward fault continues 15 km farther south than previously known revealing new potential for rupture and damage south of fremont the extended trace of the hayward fault also illuminated by shallow repeating micro earthquakes documents a surface connection with the calaveras fault at depths greater than 3 5 km repeating micro earthquakes located 10 km north of the surface connection highlight the 3 d wedge geometry of the junction our new model of the hayward and calaveras faults argues that they should be treated as a single system with potential for earthquake ruptures generating events with magnitudes greater than 7 posing a higher seismic hazard to the east san francisco bay area than previously considered

interseismic strain accumulation and the earthquake potential on the southern san andreas fault system the southern section of the san andreas fault is the only part of the fault that hasn t ruptured in historic times for this reason it is believed to pose the largest seismic risk in california although whether tectonic stress is actually accumulating there is a topic of heated debate using data from radar interferometry satellites yuri fialko has produced a detailed map of surface deformation in the area that shows that elastic stress is accumulating at a fairly high rate during the past 300 years a displacement of 6 to 9 metres has built up this suggests that the southern san andreas fault is nearing the end of the interseismic phase of the earthquake cycle and that increased seismic activity of some kind can be expected the san andreas fault in california is a mature continental transform fault that accommodates a significant fraction of motion between the north american and pacific plates the two most recent great earthquakes on this fault ruptured its northern and central sections in 1906 and 1857 respectively the southern section of the fault however has not produced a great earthquake in historic times for at least 250 years assuming the average slip rate of a few centimetres per year typical of the rest of the san andreas fault the minimum amount of slip deficit accrued on the southern section is of the order of 7 10 metres comparable to the maximum co seismic offset ever documented on the fault1 2 here i present high resolution measurements of interseismic deformation across the southern san andreas fault system using a well populated catalogue of space borne synthetic aperture radar data the data reveal a nearly equal partitioning of deformation between the southern san andreas and san jacinto faults with a pronounced asymmetry in strain accumulation with respect to the geologically mapped fault traces the observed strain rates confirm that the southern section of the san andreas fault may be approaching the end of the interseismic phase of the earthquake cycle

joint correction of ionosphere noise and orbital error in l band sar interferometry of interseismic deformation in southern california the accuracy of l band synthetic aperture radar sar differential interferometry insar on crustal deformation studies is largely compromised by ionosphere path delays on the radar signals the ionosphere effects cause severe ionospheric distortion such as azimuth streaking and long wavelength phase distortion similar to orbital ramp error effective detection and correction of ionospheric phase distortion from l band insar images are necessary to measure and accurately interpret surface displacement in this paper we investigate the performance improvement of l band insar interseismic deformation measurements in southern california through the joint correction of both ionosphere noise and orbital error our results show that this method can effectively remove orbit and ionosphere phase distortions in comparison with in situ gps measurements the achieved insar measurement accuracy is improved from 30 mm to 10 mm by the proposed joint correction method we show that after the joint correction the remaining atmosphere noise can be further mitigated through stacking leading to an rms error of 4 7 mm year in resultant line of sight velocity as compared with 11 3 mm year before the correction our results demonstrate that the proposed joint correction technique provides a promising way to jointly correct orbital and ionospheric artifacts in l band insar studies of crustal deformation

toward mapping surface deformation in three dimensions using insar 1 one of the limitations of deformation measurements made with interferometric synthetic aperture radar insar is that an interferogram only measures one component of the surface deformation in the satellite s line of sight we investigate strategies for mapping surface deformation in three dimensions by using multiple interferograms with different imaging geometries geometries for both current and future missions are evaluated and their abilities to resolve the displacement vector are compared the north component is always the most difficult to determine using data from near polar orbiting satellites however a satellite with an inclination of about 60 120 would enable all three components to be well resolved we attempt to resolve the 3d displacements for the 23 october 2002 nenana mountain alaska earthquake the north component s error is much larger than the signal but proxies for eastward and vertical motion can be determined if the north component is assumed negligible inversions of hypothetical coseismic interferograms demonstrate that earthquake model parameters can be well recovered from two interferograms acquired on ascending and descending tracks

slip rates and spatially variable creep on faults of the northern san andreas system inferred through bayesian inversion of global positioning system data fault creep depending on its rate and spatial extent is thought to reduce earthquake hazard by releasing tectonic strain aseismically we use bayesian inversion and a newly expanded gps data set to infer the deep slip rates below assigned locking depths on the san andreas maacama and bartlett springs faults of northern california and for the latter two the spatially variable interseismic creep rate above the locking depth we estimate deep slip rates of 21 5 0 5 13 1 0 8 and 7 5 0 7 mm yr below 16 km 9 km and 13 km on the san andreas maacama and bartlett springs faults respectively we infer that on average the bartlett springs fault creeps from the earth s surface to 13 km depth and below 5 km the creep rate approaches the deep slip rate this implies that microseismicity may extend below the locking depth however we cannot rule out the presence of locked patches in the seismogenic zone that could generate moderate earthquakes our estimated maacama creep rate while comparable to the inferred deep slip rate at the earth s surface decreases with depth implying a slip deficit exists the maacama deep slip rate estimate 13 1 mm yr exceeds long term geologic slip rate estimates perhaps due to distributed off fault strain or the presence of multiple active fault strands while our creep rate estimates are relatively insensitive to choice of model locking depth insufficient independent information regarding locking depths is a source of epistemic uncertainty that impacts deep slip rate estimates

surface deformation and coherence measurements of kilauea volcano hawaii from sir c radar interferometry the shuttle imaging radar c x synthetic aperture radar sir c x sar radar on board the space shuttle endeavor imaged kilauea volcano hawaii in april and october 1994 for the purpose of measuring active surface deformation by the methods of repeat pass differential radar interferometry observations at 24 cm l band and 5 6 cm c band wavelengths were reduced to interferograms showing apparent surface deformation over the 6 month interval and over a succession of 1 day intervals in october a statistically significant local phase signature in the 6 month interferogram is coincident with the pu u o o lava vent interpreted as deformation the signal implies centimeter scale deflation in an area several kilometers wide surrounding the vent peak deflation is roughly 14 cm if the deformation is purely vertical centered southward of the pu u o o caldera delays in the radar signal phase induced by atmospheric refractivity anomalies introduce spurious apparent deformation signatures at the level of 12 cm peak to peak in the radar line of sight direction though the phase observations are suggestive of the wide area deformation measured by global positioning system gps methods the atmospheric effects are large enough to limit the interpretation of the result it is difficult to characterize centimeter scale deformations spatially distributed over tens of kilometers using differential interferometry without supporting simultaneous spatially distributed measurements of refractivity along the radar line of sight studies of the interferometric correlation of images acquired at different times show that l band is far superior to c band in the vegetated areas even when the observations are separated by only 1 day these results imply longer wavelength instruments are more appropriate for studying surfaces by repeat pass observations

the seismicity of the adelaide geosyncline south australia a network of seismograph stations has been operational in south australia since 1963 a magnitude 2 event is locatable practically anywhere in the state presently about 250 earthquakes yr are being located the greatest concentration of earthquakes occurs in the flinders ranges of the adelaide geosyncline the other major zones are eyre peninsula and the southeast corner of the state in the last 100 yr south australia has experienced 10 earthquakes of magnitude larger than 5 the most recent being in 1986 the largest earthquake to have occurred in the state s history was the beachport kingston earthquake of 1897 ml 6 1 2 the focal depths for most south australian earthquakes are quite shallow being confined to the upper crust focal mechanisms have been obtained for six earthquakes occuring in the central flinders ranges the predominant principal stress is northeast southwest compression this is consistent with surface uplift of the ranges causing crustal thickening the population center of adelaide has the highest earthquake risk of any capital city in australia the 1954 ml 5 adelaide earthquake involved 30 000 insurance claims totalling 11 million u s currency epicenters for microearthquakes in the adelaide region show a correlation with known faults seismicity here appears to be associated with normal block faulting of the st vincent gulf graben structure

potential and limits of insar to characterize interseismic deformation independently of gps data application to the southern san andreas fault system the evaluation of long wavelength deformation associated with interseismic strain accumulation traditionally relies on spatially sparse gps measurements or on high spatial resolution insar velocity fields aligned to a gps based model in this approach the insar contributes only short wavelength deformation and the two data sets are dependent thereby challenging the evaluation of the insar uncertainties and the justification of atmospheric corrections here we present an analysis using 7 years of envisat insar data to characterize interseismic deformation along the southern san andreas fault saf and the san jacinto fault sjf in southern california where the saf bifurcates onto the mission creek mcf and the banning bf fault strands we outline the processing steps for using insar alone to characterize both the short and long wavelength deformation and evaluate the velocity field uncertainties with independent continuous gps data insar line of sight los and continuous gps velocities agree within 1 2 mm yr in the study area suggesting that multiyear insar time series can be used to characterize interseismic deformation with a higher spatial resolution than gps we investigate with dislocation models the ability of this mean los velocity field to constrain fault slip rates and show that a single viewing geometry can help distinguish between different slip rate scenarios on the saf and sjf 35 km apart but multiple viewing geometries are needed to differentiate slip on the mcf and bf 12 km apart our results demonstrate that interseismic models of strain accumulation used for seismic hazards assessment would benefit from the consideration of insar mean velocity maps

uncertainties in slip rate estimates for the mission creek strand of the southern san andreas fault at biskra palms oasis southern california this study focuses on uncertainties in estimates of the geologic slip rate along the mission creek strand of the southern san andreas fault where it offsets an alluvial fan t2 at biskra palms oasis in southern california we provide new estimates of the amount of fault offset of the t2 fan based on trench excavations and new cosmogenic 10be age determinations from the tops of 12 boulders on the fan surface we present three alternative fan offset models a minimum a maximum and a preferred offset of 660 m 980 m and 770 m respectively we assign an age of between 45 and 54 ka to the t2 fan from the 10be data which is significantly older than previously reported but is consistent with both the degree of soil development associated with this surface and with ages from u series geochronology on pedogenic carbonate from t2 described in a companion paper by fletcher et al this volume these new constraints suggest a range of slip rates between 12 and 22 mm yr with a preferred estimate of 14 17 mm yr for the mission creek strand of the southern san andreas fault previous studies suggested that the geologic and geodetic slip rate estimates at biskra palms differed we find however that considerable uncertainty affects both the geologic and geodetic slip rate estimates such that if a real discrepancy between these rates exists for the southern san andreas fault at biskra palms it cannot be demonstrated with available data

atmospheric propagation heterogeneities revealed by ers 1 interferometry spaceborne synthetic aperture radar sar repeat pass interferometry is a technique based on the exploitation of the interference pattern of two sar images acquired in similar geometric conditions at two different dates this measure contains geometric atmospheric topographic and land deformation information in this paper we focus on the atmospheric information first we show theoretically that an adequate processing is sufficient to remove homogeneous atmospheric effects and that heterogeneities as tropospheric turbulences rain falls and ionospheric phenomena can be detected with sar interferometry then we interpret several observations and we present interferometric images of cumulus and turbulences due to relief sar interferometry could be a new remote sensing tool for the study of tropospheric turbulences at a high horizontal resolution 40 m

late quaternary rate of slip along the san jacinto fault zone near anza southern california the anza section of the san jacinto fault southern california has not experienced a groundbreaking earthquake since at least 1918 and probably since before 1899 leading previous workers to designate this 20 km long fault segment as a seismic gap study of displaced pleistocene and holocene alluvial fan and fluvial deposits across the san jacinto fault near anza california dated using 14c and soil development age control indicates a minimum right lateral slip rate of 9 2 2 mm yr since 9 5 ka and a slip rate of 11 9 5 mm yr since 14 ka 12 9 5 mm yr since 17 ka and 13 10 6 mm yr since 50 ka these estimates agree with a previously determined 700 ka to present minimum slip rate of 10 2 mm yr based on an estimated average slip rate of 12 mm yr from the longer term slip rate estimates about 0 8 m of potential slip has accumulated if the 1918 earthquake broke the anza segment over 1 1 m of potential slip has accumulated if the last earthquake occurred prior to 1899 these data attest to the potential for an earthquake m6 5 for this section of the fault

atmospheric effects in interferometric synthetic aperture radar surface deformation and topographic maps interferogram images derived from repeat pass spaceborne synthetic aperture radar systems exhibit artifacts due to the time and space variations of atmospheric water vapor other tropospheric variations such as pressure and temperature also induce distortions but the effects are smaller in magnitude and more evenly distributed throughout the interferogram than the wet troposphere term spatial and temporal changes of 20 in relative humidity lead to 10 cm errors in deformation products and perhaps 100 m of error in derived topographic maps for those pass pairs with unfavorable baseline geometries in wet regions such as hawaii these are by far the dominant errors in the spaceborne imaging radar c and x band synthetic aperature radar sir c x sar interferometric products the unknown time delay from tropospheric distortion is independent of frequency and thus multiwavelength measurements such as those commonly used to correct radar altimeter and global positioning system gps ionospheric biases cannot be used to rectify the error in the topographic case the errors may be mitigated by choosing interferometric pairs with relatively long baselines as the error amplitude is inversely proportional to the perpendicular component of the interferometer baseline for the sir c x sar hawaii data we found that the best longest baseline pair produced a map supporting 100 m contouring whereas the poorest baseline choice yielded an extremely noisy topographic map even at this coarse contour interval in the case of deformation map errors the result is either independent of baseline parameters or else very nearly so here the only solution is averaging of independent interferograms so in order to create accurate deformation products in wet regions many multiple passes may be required rules for designing optimal data acquisition and processing sequences for interferometric analyses in nondesert parts of the world are 1 to use the longest radar wavelengths possible within ionospheric scintillation and faraday rotation limits 2 for topography maximize interferometer baseline within decorrelation limits and 3 for surface deformation use multiple observations and average the derived products following the above recipe yields accuracies of 10 m for digital elevation models and 1 cm for deformation maps even in very wet regions such as hawaii

geodetic slip rates in the southern san andreas fault system effects of elastic heterogeneity and fault geometry 1 we use high resolution interferometric synthetic aperture radar and gps measurements of crustal motion across the southern san andreas fault system to investigate the effects of elastic heterogeneity and fault geometry on inferred slip rates and locking depths geodetically measured strain rates are asymmetric with respect to the mapped traces of both the southern san andreas and san jacinto faults two possibilities have been proposed to explain this observation large contrasts in crustal rigidity across the faults or an alternate fault geometry such as a dipping san andreas fault or a blind segment of the san jacinto fault we evaluate these possibilities using a two dimensional elastic model accounting for heterogeneous structure computed from the southern california earthquake center crustal velocity model cvm h 6 3 the results demonstrate that moderate variations in elastic properties of the crust do not produce a significant strain rate asymmetry and have only a minor effect on the inferred slip rates however we find that small changes in the location of faults at depth can strongly impact the results our preferred model includes a san andreas fault dipping northeast at 60 and two active branches of the san jacinto fault zone in this case we infer nearly equal slip rates of 18 1 and 19 2mm yr for the san andreas and san jacinto fault zones respectively these values are in good agreement with geologic measurements representing average slip rates over the last 10 10 years implying steady long term motion on these faults

dislocation model for aseismic crustal deformation at hollister california geodetic observations at many active plate margins reveal relatively steady aseismic motion during the time between major earthquakes we model the aseismic motion by the relative motion between several blocks that suffer frictional resistance in the upper crust frictional drag is represented by uniform dislocation on a fault surface we assume that friction occurs only on the upper brittle zone of each block boundary and that frictionless sliding occurs below this zone using a bayesian inversion procedure we invert geodetic data to determine the parameters of the block and dislocation model parameters to be estimated include the two horizontal components of velocity for each block and the dislocation rate dip angle slip angle and width of each rectangular fault patch for hollister we assume five blocks and nine rectangular fault patches rates of length change on 92 lines observed by trilateration make up the data triangulation leveling very long baseline interferometry satellite ranging and global positioning system data can also be easily included in our model our inversion procedure uses prior estimates of all block and fault parameters based on geological and seismological data the block parameters are estimated from geological observations of fault displacement rates while the widths of the fault patches are estimated from earthquake hypocentral depths we choose prior estimates of the dislocation rate to match observed creep rates the estimated block motion is well resolved by the geodetic data and agrees well with the geological estimates this suggests that the block motion is steady on time scales from 10 years to 1 m y the net motion across the san andreas calaveras fault system is 38 3 mm yr oriented s38 e thus some additional displacement possibly offshore is needed to match the rate of 56 mm yr predicted by plate tectonic models the depth of the transition from frictional to free sliding varies considerably from 0 4 km on the southern calaveras to 11 km on the central san andreas fault two segments of the san andreas north of 36 50 and south of 36 40 have the greatest potential for moderate to large earthquakes

postearthquake relaxation evidence for laterally variable viscoelastic structure and water content in the southern california mantle i reexamine the lower crust and mantle relaxation following two large events in the mojave desert the 1992 m7 3 landers and 1999 m7 1 hector mine california earthquakes time series from continuous gps sites out to 300 km from the ruptures are used to constrain models of postseismic relaxation crustal motions in the mojave desert region are elevated above background for several years following each event to account for broadscale relaxation of the lower crust and mantle the burgers body model is employed involving transient and steady state viscosities joint afterslip postseismic relaxation modeling of the gps time series up to one decade following the hector mine earthquake reveals a significant rheological contrast between a northwest trending southwest domain that envelopes the san andreas fault system and western mojave desert and an adjacent northeast domain that envelopes the landers and hector mine rupture areas in the central mojave desert the steady state viscosity of the northeast domain mantle asthenosphere is inferred to be 4 times greater than that of the southwest domain this pattern is counter to that expected for regional heat flow which is higher in the northeast domain but it is explicable by means of a nonlinear rheology that includes dependence on both strain rate and water concentration i infer that the southwest domain mantle has a relatively low steady state viscosity because of its high strain rate and water content the relatively low mantle water content of the northeast domain is interpreted to result from the continual extraction of water through igneous and volcanic activity over the past 20 myr

measurement of interseismic strain across the haiyuan fault gansu china by insar the haiyuan fault is part of a major left lateral fault system at the northeastern edge of the tibet qinghai plateau two m8 earthquakes 1920 and 1927 occurred along the fault bracketing an unbroken section of the fault identified as the tianzhu seismic gap we use interferometric synthetic aperture radar data from descending orbits of the ers satellites acquired between 1993 and 1998 along two adjacent tracks covering the gap to measure the current surface movements and better understand the present day mechanical behavior of this fault section the analysis of the radar data involves first the combined correction of orbital errors and errors associated with the phase delay through the troposphere a subset of the data is then selected based on the analysis of the residual noise spectra for each pair of data the selected interferograms are stacked and the average phase change rate is converted in fault parallel velocity assuming that the ground movement is horizontal and parallel to the fault velocity maps from both tracks show a zone of high velocity gradient across the fault a few kilometers wide consistent with left lateral slip on the haiyuan fault the average velocity field from the two tracks in their overlapping area is well fit with a single screw dislocation model in an elastic half space the derived fault slip rate at depth 4 2 8 mm yr is consistent with recent gps results the corresponding shallow apparent locking depth 0 4 2 km can be explained by a current low stress accumulation on the fault due to creep almost on the entire fault plane however unless it is transient this creep would be paradoxical with the occurrence of past large earthquakes along this fault section as revealed by paleoseismology an alternative model implying both shallow creep in the brittle upper crust and deep aseismic slip beneath the seismogenic layer separated by a locked section would be consistent with insar observations and with the potential for large earthquakes on the fault as well a two dislocation model with slip at 5 mm yr beneath 15 km and a transient creep rate of 11 mm yr between 2 and 7 km fits the insar data however the width and creep rate of the shallow creeping zone and their possible along strike variations are still poorly resolved with the present data set

topography correlated atmospheric delay correction in radar interferometry using wavelet transforms 1 atmospheric delay is one of the major sources of error in repeat pass interferometry we propose a new approach for correcting the topography correlated components of this artifact to this aim we use multiresolution wavelet analysis to identify the components of the unwrapped interferogram that correlate with topography by using a forward wavelet transform we break down the digital elevation model and the unwrapped interferogram into their building blocks based on their frequency properties we apply a cross correlation analysis to identify correlated coefficients that represent the effect of the atmospheric delay thus the correction to the unwrapped interferogram is obtained by down weighting the correlated coefficients during inverse wavelet transform we test this approach on real and synthetic data sets that are generated over the san francisco bay area we find that even in the presence of tectonic signals this method is able to reduce the correlated component of the atmospheric delay by up to 75 and improves the signal in areas of high relief the remaining part is most likely due to 3d heterogeneities of the atmosphere and can be reduced by integrating temporal information or using complementary observations or models of atmospheric delay

holocene geologic slip rate for the banning strand of the southern san andreas fault southern california northwest directed slip from the southern san andreas fault is transferred to the mission creek banning and garnet hill fault strands in the northwestern coachella valley how slip is partitioned between these three faults is critical to southern california seismic hazard estimates but is poorly understood in this paper we report the first slip rate measured for the banning fault strand we constrain the depositional age of an alluvial fan offset 25 5 m from its source by the banning strand to between 5 1 0 4 ka 95 confidence interval ci and 6 4 3 7 2 1 ka 95 ci using u series dating of pedogenic carbonate clast coatings and 10be cosmogenic nuclide exposure dating of surface clasts we calculate a holocene geologic slip rate for the banning strand of 3 9 2 3 1 6 mm yr median 95 ci to 4 9 1 0 0 9 mm yr median 95 ci this rate represents only 25 35 of the total slip accommodated by this section of the southern san andreas fault suggesting a model in which slip is less concentrated on the banning strand than previously thought in rejecting the possibility that the banning strand is the dominant structure our results highlight an even greater need for slip rate and paleoseismic measurements along faults in the northwestern coachella valley in order to test the validity of current earthquake hazard models in addition our comparison of ages measured with u series and 10be exposure dating demonstrates the importance of using multiple geochronometers when estimating the depositional age of alluvial landforms

integrated satellite interferometry tropospheric noise gps estimates and implications for interferometric synthetic aperture radar products interferometric synthetic aperture radar insar like other astronomic and space geodetic techniques is limited by the spatially and temporally variable delay of electromagnetic waves propagating through the neutral atmosphere statistical analysis of these variations from a wide variety of instruments reveals a power law dependence on frequency that is characteristic of elementary kolmogorov turbulence a statistical model for a major component of the delay fluctuations the wet component has previously been developed by treuhaft and lanyi 1987 for very long baseline interferometry a continuous global positioning system gps network is now in place in southern california that allows estimation of along with geodetic parameters the total delay due to the atmosphere above each site on a subhourly basis these measurements are shown to conform to the treuhaft and lanyi tl statistical model both temporally and spatially the tl statistical model is applied to the problem of insar and used to produce the covariance between two points separated in time and or space the error due to the atmospheric variations for sar products such as topography and surface deformation is calculated via propagation of errors there are two methods commonly cited to reduce the effect of atmospheric distortion in products from sar interferometry stacking and calibration stacking involves averaging independent interferograms to reduce the noise calibration involves removing part or all of the delay using data from an independent source such as total zenith delay estimates from continuous gps networks despite the relatively poor spatial density of surface measurements calibration can be used to reduce noise if the measurements are sufficiently accurate reduction in tropospheric noise increases with increasing number of measurement points and increasing accuracy up to a maximum of n where n is the number of points stacking and calibration are shown to be complementary and can be used simultaneously to reduce the noise to below that achievable by either method alone

influence of lithosphere viscosity structure on estimates of fault slip rate in the mojave region of the san andreas fault system 1 it is well known that slip rate estimates from geodetic data are nonunique because they depend on model assumptions and parameters that are often not known a priori estimates of fault slip rate on the mojave segment of the san andreas fault system derived from elastic block models and gps data are significantly lower than estimates from geologic data to determine the extent to which the slip rate discrepancy might be due to the oversimplified models of the rheology of the lithosphere we develop a two dimensional linear maxwell viscoelastic earthquake cycle model and simultaneously estimate fault slip rates and lithosphere viscosity structure in the mojave region the model consists of episodic earthquakes in an elastic crust overlying layers with different viscosities that represent the lower crust uppermost mantle and upper mantle we use gps measurements of postseismic relaxation following the 1992 landers earthquake triangulation measurements spanning 1932 1977 gps measurements of the contemporary velocity field and paleoseismic data along the san andreas fault we infer lower crustal 15 30 km depth viscosity of 1019 10 20 pa s uppermost mantle 30 60 km viscosity of 10 20 22 pa s and underlying upper mantle viscosity of 10 18 10 19 pa s consistent with inferences from laboratory experiments of relatively high viscosity lithospheric mantle and lower viscosity lower crust and underlying asthenospheric mantle we infer a 20 30 mm yr slip rate on the san andreas fault in agreement with the lower end of geologic estimates inversions of geodetic data with models that do not incorporate layered viscosity structure may significantly misestimate slip rates

interferometric synthetic aperture radar atmospheric correction gps topography dependent turbulence model 1 over the last two decades repeat pass interferometric synthetic aperture radar insar has been widely used as a geodetic technique for measuring the earth s surface including topography and deformation like other astronomical and space geodetic techniques repeat pass insar is limited by the variable spatial and temporal distribution of atmospheric water vapor in this paper a topography dependent turbulence model gttm for short has been developed using gps data only to produce zenith path delay difference maps for insar atmospheric correction application of the gttm model to ers tandem data over the los angeles southern california integrated gps network area has shown that use of the gttm can reduce water vapor effects on interferograms from 10 mm down to 5 mm which is of great interest to a wide community of geophysicists the principal finding of this paper is that interpolation methods should be applied to zenith total delay ztd differences from different times instead of ztd values themselves for the purpose of insar atmospheric correction this is crucial to reduce if not completely remove topographic effects on ztd values

southern san andreas san jacinto fault system slip rates estimated from earthquake cycle models constrained by gps and interferometric synthetic aperture radar observations we use ground geodetic and interferometric synthetic aperture radar satellite observations across the southern san andreas saf san jacinto sjf fault systems to constrain their slip rates and the viscosity structure of the lower crust and upper mantle on the basis of periodic earthquake cycle maxwell viscoelastic finite element models key questions for this system are the saf and sjf slip rates the slip partitioning between the two main branches of the sjf and the dip of the saf the best fitting models generally have a high viscosity lower crust 10 21 pa s overlying a lower viscosity upper mantle 10 19 pa s we find considerable trade offs between the relative time into the current earthquake cycle of the san jacinto fault and the upper mantle viscosity with reasonable assumptions for the relative time in the earthquake cycle the partition of slip is fairly robust at around 24 26 mm a for the san jacinto fault system and 16 18 mm a for the san andreas fault models for two subprofiles across the saf sjf systems suggest that slip may transfer from the western coyote creek branch to the eastern clark superstition hills branch of the sjf from nw to se across the entire system our best fitting model gives slip rates of 2 3 12 9 12 9 and 17 3 mm a for the elsinore coyote creek clark and san andreas faults respectively where the large uncertainties in the slip rates for the sjf branches reflect the large uncertainty in the slip rate partitioning within the sjf system

dem error correction in insar time series we present a mathematical formulation for the phase due to the errors in digital elevation models dems in synthetic aperture radar sar interferometry insar time series obtained by the small baseline sb or the small baseline subset method we show that the effect of the dem error in the estimated displacement is proportional to the perpendicular baseline history of the set of sar acquisitions this effect at a given epoch is proportional to the perpendicular baseline between the sar acquisition at that epoch and the reference acquisition therefore the dem error can significantly affect the time series results even if sb interferograms are used we propose a new method for dem error correction of insar time series which operates in the time domain after inversion of the network of interferograms for the displacement time series this is in contrast to the method of berardino 2002 in which the dem error is estimated in the interferogram domain we show the effectiveness of this method using simulated insar data we apply the new method to fernandina volcano in the galapagos islands and show that the proposed dem error correction improves the estimated displacement significantly

statistical estimation of the seismicity level change around hokkaido northern japan the temporal seismicity change in two seismically active zones around hokkaido northern japan was investigated using the statistical estimate of the seismicity level sesl 09 procedure hypocenter data provided by the japan meteorological agency from 1960 to 2013 were analyzed the seismicity of two geographically different zones formed by pacific plate subduction and amurian plate convergence showed different statistical characteristics low cross correlation values between the two zones also suggest independent seismic processes for each area however an anomalously high cross correlation period was identified from 1996 to 2000 with a time lag of 8 weeks a 6 month seismic quiescence period before the strongest hokkaido toho oki earthquake 4 october 1994 mj 8 2 was observed on the pacific side

a unified analysis of crustal motion in southern california 1970 2004 the scec crustal motion map 1 to determine crustal motions in and around southern california we have processed and combined trilateration data collected from 1970 to 1992 vlbi data from 1979 to 1992 and gps data from 1986 to 2004 a long temporal coverage required in part by the occurrence of several large earthquakes in this region from a series of solutions for station positions we have estimated interseismic velocities coseismic displacements and postseismic motions within the region from 31 n to 38 n and east to 114 w the final product includes estimated horizontal velocities for 1009 gps 190 trilateration and 16 vlbi points with ties between some of these used to stabilize the solution all motions are relative to the stable north american reference frame snarf as realized through the velocities of 20 gps stations this provides a relatively dense set of horizontal velocity estimates with well tested errors for the past quarter century over the plate boundary from 31 n to 36 5 n these velocities agree well with those from the plate boundary observatory which apply to a later time period we also estimated vertical velocities 533 of which have errors below 2 mm yr most of these velocities are less than 1 mm yr but they show 2 4 mm yr subsidence in the ventura and los angeles basins and in the salton trough our analysis also included estimates of coseismic and postseismic motions related to the 1992 landers 1994 northridge 1999 hector mine and 2003 san simeon earthquakes postseismic motions increase logarithmically over time with a time constant of about 10 days and generally mimic the direction and relative amplitude of the coseismic offsets

where is the real transform boundary in california 1 the zone of highest geodetically defined strain rate in california does not everywhere coincide with the surface trace of the san andreas fault saf to determine whether this reflects the pattern of long term permanent deformation we analyzed the velocity field on swaths across the transform located so as to avoid intersections among the major fault strands slip rates and flexural parameters for each fault were determined by finding the best fit to the velocity profile using a simple arctan model representing the interseismic strain accumulation our slip rates compare well with current geologic estimates which suggests that the present day velocity field is representative of long term motions we find that the transform is a zone of high strain rate up to 80 km wide that is straighter than the saf and has an overall trend closer to the relative plate motion vector than the saf most sections of the saf take up less than half of the total slip rate and slip is transferred from one part of the system to another in a way that suggests that the saf should not be considered as a unique locator of the plate boundary up to half of the total displacement takes place on faults outside the high strain rate zone distributed over several hundred kilometers on either side our findings substantiate previous suggestions that the transform has the characteristics of a macroscopic ductile shear zone cutting the continental lithosphere around which stress and strain rate decrease on a length scale controlled by the length of the transform

systematic insar tropospheric phase delay corrections from global meteorological reanalysis data 1 despite remarkable successes achieved by differential insar estimations of low tectonic strain rates remain challenging in areas where deformation and topography are correlated mainly because of the topography related atmospheric phase screen aps in areas of high relief empirical removal of the stratified component of the aps may lead to biased estimations of tectonic deformation rates here we describe a method to correct interferograms from the effects of the spatial and temporal variations in tropospheric stratification by computing tropospheric delay maps coincident with sar acquisitions using the era interim global meteorological model the modeled phase delay is integrated along vertical profiles at the era i grid nodes and interpolated at the spatial sampling of the interferograms above the elevation of each image pixel this approach is validated on unwrapped interferograms we show that the removal of the atmospheric signal before phase unwrapping reduces the risk of unwrapping errors in areas of rough topography

some thoughts on the use of insar data to constrain models of surface deformation noise structure and data downsampling repeat pass interferometric synthetic aperture radar insar provides spatially dense maps of surface deformation with potentially tens of millions of data points here we estimate the actual covariance structure of noise in insar data we compare the results for several independent interferograms with a large ensemble of gps observations of tropospheric delay and discuss how the common approaches used during processing of insar data affects the inferred covariance structure motivated by computational concerns associated with numerical modeling of deformation sources we then combine the data covariance information with the inherent resolution of an assumed source model to develop an efficient algorithm for spatially variable data resampling or averaging we illustrate these technical developments with two earthquake scenarios at different ends of the earthquake magnitude spectrum for the larger events our goal is to invert for the coseismic fault slip distribution for smaller events we infer the hypocenter location and moment we compare the results of inversions using several different resampling algorithms and we assess the importance of using the full noise covariance matrix

a multiscale approach to estimating topographically correlated propagation delays in radar interferograms when targeting small amplitude surface deformation using repeat orbit interferometric synthetic aperture radar insar observations can be plagued by propagation delays some of which correlate with topographic variations these topographically correlated delays result from temporal variations in vertical stratification of the troposphere an approximate model assuming a linear relationship between topography and interferometric phase has been used to correct observations with success in a few studies here we present a robust approach to estimating the transfer function k between topography and phase that is relatively insensitive to confounding processes earthquake deformation phase ramps from orbital errors tidal loading etc our approach takes advantage of a multiscale perspective by using a band pass decomposition of both topography and observed phase this decomposition into several spatial scales allows us to determine the bands wherein correlation between topography and phase is significant and stable when possible our approach also takes advantage of any inherent redundancy provided by multiple interferograms constructed with common scenes we define a unique set of component time intervals for a given suite of interferometric pairs we estimate an internally consistent transfer function for each component time interval which can then be recombined to correct any arbitrary interferometric pair we demonstrate our approach on a synthetic example and on data from two locations long valley caldera california which experienced prolonged periods of surface deformation from pressurization of a deep magma chamber and one coseismic interferogram from the 2007 mw 7 8 tocapilla earthquake in northern chile in both examples the corrected interferograms show improvements in regions of high relief independent of whether or not we pre correct the data for a source model we believe that most of the remaining signals are predominately due to heterogeneous water vapor distribution that requires more sophisticated correction methods than those described here

structure and origin of the fleurieu and nackara arcs in the adelaide fold thrust belt south australia salient and recess development in the delamerian orogen abstract the regional map pattern of structural trends in the early paleozoic adelaide fold thrust belt of south australia resembles an upright letter s in general structures in the fold thrust belt verge toward the gawler craton to the west so the northern curve nackara arc of the s is a salient whereas the southern curve fleurieu arc is a recess the map view axial trace of the nackara arc coincides with the thickest portion of the adelaidean late proterozoic basin and the map view axial trace of the fleurieu arc coincides with the intersection between the adelaidean and kanmantoo cambrian basins our structural analysis of the adelaide fold thrust belt demonstrates that the cross sectional structural geometry of the nackara arc contrasts markedly with that of the fleurieu arc in the nackara arc the belt consists of open detachment folds that probably formed above an evaporite hosted decollement whereas in the fleurieu arc the belt consists of an imbricate fan of basement involved thrusts further the foreland edge of the nackara arc coincides with a blind ramp whose strike parallels fold axes of the arc whereas the foreland edge of the fleurieu arc coincides with emergent thrusts that cut obliquely across earlier formed folds of the arc in the transition region between the two arcs the fold thrust belt consists of an intensely sheared basal duplex overlain by open folds structural contrasts between the nackara and fleurieu arcs indicate that the two curves did not form in the same way we present a model for development of these curves based on a comparison of their structural features to those of curves in other fold thrust belts and based on previous studies of curve formation using sandbox analogs we suggest that curvature of the nackara arc reflects the control of basin stratigraphy on the width of a fold thrust belt while curvature of the fleurieu arc reflects oroclinal bending of the fold thrust belt when it impinged on the southeastern corner of the gawler craton our model explains the structural contrast between the two arcs and illustrates correlations between fold thrust belt curve formation and pre deformational basin geometry

correction for interferometric synthetic aperture radar atmospheric phase artifacts using time series of zenith wet delay observations from a gps network 1 radar interferograms provide precise millimeter level measurements of crustal deformation at fine resolution over wide areas the dominant error source in many interferograms results from spatial heterogeneity of the wet component of atmospheric refractivity resulting in excess path length of the radar signal propagating through the neutral atmosphere in this report we introduce a method to compensate for atmospheric phase artifacts in a radar interferogram using spatially interpolated zenith wet delay zwd data obtained from a network of global positioning system gps receivers in the region imaged by the radar our method based on taylor s frozen flow hypothesis uses gps data recorded prior to and after the individual radar acquisition times to infer denser spatial networks of control points for interpolation than is suggested by the sparse and irregular spatial distribution of gps receivers we test this approach by correcting phase fluctuations observed in a radar interferogram over an area covered by the southern california integrated gps network stations using maps of atmospheric delay interpolated from the denser network of gps zwd measurements generated by our method we find that the largest improvement results from removing an altitude dependent model derived from the gps data the uncorrected interferogram in our example has an rms fluctuation of 16 1 mm which falls to 8 6 mm after the altitude correction a map derived from zwd measurements recorded only at the instances of radar acquisition reduced overall fluctuations in the data from 8 6 to 8 1 mm rms while using the inferred denser network reduces the error further to 7 5 mm rms most of this residual variation is due to decorrelation of the signal and does not result from atmospheric propagation however after smoothing to remove decorrelation noise the residual drops from 4 7 to 3 9 mm gps stations only and then to 2 7 mm rms when the denser network algorithm is used

recovery of secular deformation field of mojave shear zone in southern california from historical terrestrial and gps measurements the 1992 mw 7 3 landers and 1999 mw 7 1 hector mine earthquakes struck the eastern california shear zone ecsz in the mojave desert southern california coseismic and postseismic deformation from these events affect efforts to use global positioning system gps observations collected since these events to establish a secular surface velocity field especially in the near field of the coseismic ruptures we devise block motion models constrained by both historical pre landers triangulation and trilateration observations and post landers gps measurements to recover the secular deformation field and differentiate the postseismic transients in the mojave region postseismic transients are found to remain in the southern california earthquake center crustal motion map version 4 plate boundary observatory and scripps orbit and permanent array center gps velocity solutions in the form of 2 3 mm yr excess right lateral shear across the landers and hector mine coseismic ruptures the cumulative deformation rate across the mojave ecsz is 13 2 14 4 mm yr at least twice the geologic rate since the late pleistocene 6 2 1 9 mm yr postseismic gps time series based on our secular velocity field reveal enduring late stage transient motions in the near field of the coseismic ruptures that provide new constraints on the rheological structure of the lower crust and upper mantle

rapid strain accumulation on the ashkabad fault turkmenistan from atmosphere corrected insar 1 we have measured interseismic deformation across the ashkabad strike slip fault using 13 envisat interferograms covering a total effective timespan of 30 years atmospheric contributions to phase delay are significant and variable due to the close proximity of the caspian sea in order to retrieve the pattern of strain accumulation we show it is necessary to use data from envisat s medium resolution imaging spectrometer meris instrument as well as numerical weather model outputs from the european centre for medium range weather forecasts ecmwf to correct interferograms for differences in water vapor and atmospheric pressure respectively this has enabled us to robustly estimate the slip rate and locking depth for the ashkabad fault using a simple elastic dislocation model our data are consistent with a slip rate of 5 12 mm yr below a locking depth of 5 5 17 km for the ashkabad fault and synthetic tests support the magnitude of the uncertainties on these estimates our estimate of slip rate is 1 25 6 times higher than some previous geodetic estimates with implications for both seismic hazard and regional tectonics in particular supporting fast relative motion between the south caspian block and eurasia this result reinforces the importance of correcting for atmospheric contributions to interferometric phase for small strain measurements we also attempt to validate a recent method for atmospheric correction based on ecmwf era interim model outputs alone and find that this technique does not work satisfactorily for this region when compared to the independent meris estimates

interferometric synthetic aperture radar gps integration interseismic strain accumulation across the hunter mountain fault in the eastern california shear zone 1 the principal limitations of interferometric synthetic aperture radar insar to measure subtle long wavelength deformation are uncertainties associated with the satellite orbits we propose a method to remove orbital phase errors from the insar data by integrating insar and continuous gps time series we model the along track variation of the baseline errors as second order polynomials and estimate the coefficients using the continuous gps measurements we apply this method to a 600 km long region encompassing the basin and range and the eastern california shear zone comparison of the corrected insar velocities with independent gps data shows that this method removes the long wavelength insar errors the insar data reveal a region of sharp variation in the line of sight velocity across the hunter mountain fault we model the deformation as interseismic elastic strain accumulation across a strike slip fault the modeling suggests a fault slip rate of 4 9 0 8 mm yr and a locking depth of 2 0 4 km the shallow locking depth suggests that the hunter mountain fault is a transfer fault between low angle normal faults in the area

long term slip rate of the southern san andreas fault from 10be 26al surface exposure dating of an offset alluvial fan we determine the long term slip rate of the southern san andreas fault in the southeastern indio hills using 10 be and 26 al isotopes to date an offset alluvial fan surface field mapping complemented with topographic data air photos and satellite images allows precise determination of piercing points across the fault zone that are used to measure an offset of 565 80 m a total of 26 quartz rich cobbles from three different fan surfaces were collected and dated the tight cluster of nuclide concentrations from 19 samples out of 20 from the offset fan surface implies a simple exposure history negligible prior exposure and erosion and yields an age of 35 5 2 5 ka the long term slip rate of the san andreas fault south of biskra palms is thus 15 9 3 4 mm yr this rate is about 10 mm yr slower than geological 0 14 ka and short term geodetic estimates for this part of the san andreas fault implying changes in slip rate or in faulting behavior this result puts new constraints on the slip rate of the san jacinto and on the eastern california shear zone for the last 35 kyr our study shows that more sites along the major faults of southern california need to be targeted to better constrain the slip rates over different timescales

chronology and stratigraphy of late quaternary sediments in the konya basin turkey results from the kopal project abstract the late quaternary environmental history of the konya plain in south central turkey is used to examine sediment facies changes in a shallow non outlet basin which has experienced major climatically driven changes in lake extent two principal types of sedimentary archive are used to reconstruct a palaeoenvironmental record namely alluvial sequences on the carsamba alluvial fan and sediments from residual lakes the latter have been used to investigate broader climatic and vegetational histories via palaeolimnological techniques including pollen diatom and stable isotope analysis these changes are dated here by radiometric techniques including radiocarbon ams and conventional osl and u th chronological agreement is generally good between the different dating techniques although typically there is greatly reduced precision beyond ca 25 ka lake sediment cores investigated have basal ages beyond the range of 14c dating but contain hiatuses as a result of subsequent alternation between phases of lacustrine sedimentation and aeolian deflation in contrast to most deepwater non outlet lake systems the konya basin may have been occupied by a single extensive lake for as little as 10 of late quaternary time mainly around the time of the lgm this lake highstand was followed by an important arid interval in the absence of unbroken chronostratigraphic sequences palaeohydrological investigation of shallow non outlet lakes may require analysis of basin wide changes in sedimentation rather than reliance on single core records stratigraphic continuity in such sedimentary environments cannot be assumed and requires independent chronological control through radiometric dating

high resolution interseismic velocity data along the san andreas fault from gps and insar 1 we compared four interseismic velocity models of the san andreas fault based on gps observations the standard deviations of the predicted secular velocity from the four models are larger north of the san francisco bay area near the creeping segment in central california and along the san jacinto fault and the east california shear zone in southern california a coherence spectrum analysis of the secular velocity fields indicates relatively high correlation among the four models at longer wavelengths 15 40 km with lower correlation at shorter wavelengths to improve the short wavelength accuracy of the interseismic velocity model we integrated interferometric synthetic aperture radar insar observations initially from advanced land observing satellite alos ascending data spanning from the middle of 2006 to the end of 2010 totaling more than 1100 interferograms with gps observations using a sum remove filter restore approach the final insar line of sight data match the point gps observations with a mean absolute deviation of 1 5 mm yr we systematically evaluated the fault creep rates along major faults of the san andreas fault and compared them with creepmeters and alignment array data compiled in uniform california earthquake rupture forecast version 2 ucerf2 moreover this insar line of sight dataset can constrain rapid velocity gradients near the faults which are critical for understanding the along strike variations in stress accumulation rate and associated earthquake hazard

late quaternary slip rate gradient defined using high resolution topography and 10be dating of offset landforms on the southern san jacinto fault zone california 1 recent studies suggest the san jacinto fault zone may be the dominant structure accommodating pa na relative plate motion however because the late quaternary slip history of the southern san andreas fault system is insufficiently understood it is difficult to evaluate the partitioning of deformation across the plate boundary and its evolution landforms displaced by the clark fault of the southern san jacinto fault zone were mapped using high resolution airborne laser swath topography and selected offset landforms were dated using cosmogenic 10be beheaded channels at rockhouse canyon displaced by 500 70 m and 220 70 m have been dated to 47 8 ka and 28 9 ka respectively farther south near the southern santa rosa mountains an alluvial deposit displaced by 51 9 m has been dated to 35 7 ka from these sites the slip rate of the clark fault is determined to diminish southward from 8 9 2 0 to 1 5 0 4 mm yr this implies a slip rate decrease along the clark fault from anza southeastward to its surface termination near the salton trough where slip is transferred to the coyote creek fault and additional deformation is compensated by folding and thrusting in the basin these data suggest that since 30 to 50 ka the slip rate along the southern san jacinto fault zone has been lower than or equivalent to the rate along the southernmost san andreas fault accordingly either the slip rate of the san jacinto fault has substantially decreased since fault initiation or fault slip began earlier than previously suggested

fault network modeling of crustal deformation in california constrained using gps and geologic observations abstract we have developed a kinematic fault network model of crustal deformation in an elastic half space surface deformation is calculated using this model assuming each fault segment slipping beneath a locking depth each fault segment connects to its adjacent elements with slip vector continuity imposed at fault nodes or intersections the degree of the constraints determines whether deformation is block like or not we apply this model to invert gps observations for slip rates on major faults in california with geological rate constraints based on the f test result we find that lesser block like models fit the data significantly better than the strictly block like model our final inversion shows a slip rate varying from 20 to 23 mm yr along the northern san andreas from the santa cruz to the north coast segment slip rates vary from 9 to 13 mm yr along the hayward to the maacama fault segment and from 15 to 3 mm yr along the central calaveras to the west napa fault segment for the central california creeping zone the result suggests a depth dependent creep rate with an average of 22 mm yr over the top 5 km and 32 mm yr underneath from the mojave to san bernardino mountain segments we also find a significant decrease in slip rate along the san andreas in comparison with the geologic rates in contrast to a significant increase in slip rate on faults along the eastern california shear zone along the southern san andreas slip rates vary from 21 to 25 mm yr from the coachella valley to imperial valley segments slip rates range from 0 to 3 mm yr across the western transverse ranges faults which is consistent with the regional crustal thickening overall slip rates derived from geodetic observations correlate strongly with the geologic slip rates statistically suggesting high compatibility between geodetic and geologic observations

global positioning system constraints on fault slip rates in southern california and northern baja mexico we use global positioning system gps estimates of horizontal site velocity to constrain slip rates on faults comprising the pacific north america plate boundary in southern california and northern mexico we enlist a simple elastic block model to parameterize the distribution and sum of deformation within and across the plate boundary we estimate a pacific north america relative plate motion rate of 49 3 mm yr one standard deviation consistent with nuvel 1a estimates we are able to resolve robust slip rate estimates for the southernmost san andreas san jacinto and elsinore faults 26 2 9 2 and 6 2 mm yr respectively and for the imperial and cerro prieto faults 35 2 and 42 1 mm yr respectively accounting for about 86 of the total plate motion the remaining 14 appears to be accommodated to the west of these fault systems probably via slip along the san clemente fault and or the san miguel vallecitos rose canyon and newport inglewood fault systems these results are highly consistent with paleoseismic estimates for slip rates implying that off fault strain accumulation within the deforming zone of the plate boundary is largely elastic we estimate that the seismically quiescent southernmost san andreas fault has incurred about 8 2 m of slip deficit over the last few hundred years presumably to be recovered during a future large earthquake

on the temporal variability of the surface gulf stream and near bottom flows long 3 4 years time series of the surface gulf stream position and near bottom flow south of nova scotia support earlier findings of a barotropic semimonthly periodicity in the region a bimodal gulf stream path downstream of the new england seamount chain and a seasonal shift in the gulf stream position new results are 1 a marked reduction of the meridional shifts of the surface gulf stream when it is in its north position mode 2 the semimonthly periodicity seeming to be related at times to the mf tide the most energetic long period tide and 3 an energetic highly coherent but out of phase motion with a near 40 day period in the surface gulf stream position and near bottom flow

fault slip rates effects of elastic heterogeneity on geodetic data and the strength of the lower crust in the salton trough region southern california 1 in southernmost california the salton trough sedimentary basin lies between the subparallel san jacinto and san andreas faults that together with the elsinore fault accommodate 80 of the 50 mm yr of pacific north american relative motion the slip rates on the san andreas and san jacinto faults have been a matter of recent debate and one source of uncertainty has been the influence of crustal strength heterogeneity due to elastically weak basin sediments on geodetic data to evaluate these effects we have modeled regional kinematics with elastic and viscoelastic finite element models that incorporate laterally and vertically varying crustal material properties we find that in general the effects of the sedimentary basin on surface deformation are relatively small and that to explain the geodetic velocity data the slip rate on the san andreas must be higher than that on the san jacinto fault consistent with traditional geologic estimates we also conclude that a relatively strong lower crust of viscosity 5 x 10 19 pa s exists in this region

thirty years of seismic network recording in south australia selected results abstract the year 1993 marks 30 years of seismic network recording of earthquakes in south australia the network currently comprises 17 short period instruments of which six use digital recording and five employ triaxial sensors approximately 350 earthquakes are located within the state each year using a computerised seismic analysis system developed by the phillip institute of technology a duration based magnitude scale equivalent to the richter m l scale has been developed for most stations the pre network historical record of earthquake activity in south australia dates back to 1837 epicentres are available for just 45 earthquakes of these ten are of magnitude five or greater the instrumental data over the last 30 years show a similar trend in epicentral pattern to the historical earthquakes with the major zones being the flinders ranges eyre peninsula and the southeast there have been 40 earthquakes of magnitude four or greater since 1963 the largest earthquake being of magnitude six in the musgrave ranges during 1986 mine and quarry blasts within the state have been useful in calibration of the network both in terms of hypocentral location and amplitude studies the explosions have also furnished valuable information on the crustal velocity distribution epicentral co ordinates of mine blasts are generally good to within 3 5 km the explosions yield richter magnitudes of one charge size 1 or 2 tonnes to 2 5 charge size 50 tonnes the crustal s waves used in earthquake magnitude determinations exhibit an amplitude distance decay coefficient of 1 2 the p wave velocity function of the crust increases non linearly with depth from about 5 0 km s 1 near the surface to 6 4 km s 1 at 20 km depth where the gradient reduces with the velocity reaching a value of about 7 4 km s 1 at a depth of 40 km