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

3d multi source model of elastic volcanic ground deformation abstract developments in interferometric synthetic aperture radar insar and gnss global navigation satellite system during the past decades have promoted significant advances in geosciences providing high resolution ground deformation data with dense spatio temporal coverage this large dataset can be exploited to produce accurate assessments of the primary processes occurring in geologically active areas we present a new original methodology to carry out a multi source inversion of ground deformation data to better understand the subsurface causative processes a nonlinear approach permits the determination of location size and three dimensional configuration without any a priori assumption as to the number nature or shape of the potential sources the proposed method identifies a combination of pressure bodies and different types of dislocation sources dip slip strike slip and tensile that represent magmatic sources and other processes such as earthquakes landslides or groundwater induced subsidence through the aggregation of elemental cells this approach has the following features 1 simultaneous inversion of the deformation components and or line of sight los data 2 simultaneous determination of diverse structures such as pressure bodies or dislocation sources representing local and regional effects 3 a fully 3d context and 4 no initial hypothesis about the number geometry or types of the causative sources is necessary this methodology is applied to mt etna southern italy we analyze the ground deformation field derived from a large insar dataset acquired during the january 2009 june 2013 time period the application of the inversion approach models several interesting buried structures as well as processes related to the volcano magmatic plumbing system local subsidence within the valle del bove and seaward motion of eastern flank of the volcano

results for aseismic creep on the hayward fault using polarization persistent scatterer insar abstract we present new results for shallow aseismic creep on the hayward fault in california using a new dinsar technique this method not only provides for the first time the ability to map the displacement field on both sides of the fault it does so over a much shorter time period than earlier results the results provide a good match in the near field to both the regional continuous gps velocities and data from an alinement network that measures long term creep along the fault the average slip rate for the northern segment of the hayward fault is 4 4 mm yr between 2008 and 2011 slightly less than that estimated for longer time periods suggesting that the slip rate may not be constant if the slip rate along the fault is variable on the decadal or longer scale current estimates of its earthquake potential and the associated hazard associated with the slip rate deficit may need to be revised from previous estimates we demonstrate the potential impact of this method to better define the spatial and temporal complexity of aseismic slip and estimate the accumulated elastic strain along one of the most significant sources of seismic hazard in the san francisco bay area

long term monitoring of creep rate along the hayward fault and evidence for a lasting creep response to 1989 loma prieta earthquake we present results from over 30 yr of precise surveys of creep along the hayward fault along most of the fault spatial variability in long term creep rates is well determined by these data and can help constrain 3d models of the depth of the creeping zone however creep at the south end of the fault stopped completely for more than 6 years after the m7 1989 loma prieta earthquake lpeq perhaps delayed by stress drop imposed by this event with a decade of detailed data before lpeq and a decade after it we report that creep response to that event does indeed indicate the expected deficit in creep

distribution of aseismic slip rate on the hayward fault inferred from seismic and geodetic data 1 we solve for the slip rate distribution on the hayward fault by performing a least squares inversion of geodetic and seismic data sets our analysis focuses on the northern 60 km of the fault interferometric synthetic aperture radar insar data from 13 independent ers interferograms are stacked to obtain range change rates from 1992 to 2000 horizontal surface displacement rates at 141 bench marks are measured using gps from 1994 to 2003 surface creep observations and estimates of deep slip rates determined from characteristic repeating earthquake sequences are also incorporated in the inversion the fault is discretized into 283 triangular dislocation elements that approximate the nonplanar attributes of the fault surface south of the city of hayward a steeply east dipping fault geometry accommodates the divergence of the surface trace and the microseismicity at depth the inferred slip rate distribution is consistent with a fault that creeps aseismically at a rate of 5 mm yr to a depth of 4 6 km the interferometric synthetic aperture radar insar data require an aseismic slip rate that approaches the geologic slip rate on the northernmost fault segment beneath point pinole although the insar data might be complicated by a small dip slip component at this location a low slip rate patch of 1 mm yr is inferred beneath san leandro consistent with the source location of the 1868 earthquake we calculate that the entire fault is accumulating a slip rate deficit equivalent to a mw 6 77 0 05 per century however this estimate of potential coseismic moment represents an upper bound because we do not know how much of the accumulated strain will be released through aseismic processes such as afterslip

short term surface deformation on the northern hayward fault ca and nearby landslides using polarimetric sar interferometry polinsar in this study we analyze 25 radarsat 2 images from ascending and descending geometries to study the creep rate on the hayward fault and landslide motions near berkeley ca we applied a coherence optimization technique from polarimetric synthetic aperture radar interferometry polinsar to increase the accuracy of the measurements we resolve 3 5 mm year of motion along the hayward fault in agreement with earlier creep estimates we identify a potential motion on secondary fault northeast and parallel to the hayward fault which is creeping at a lower rate of 1 5 mm year in addition we identify a number of landslides along the hills east of the fault that agree with earlier results from advanced interferometric synthetic aperture radar sar analysis and field investigations we investigate four particular slope instabilities one of which was marked as moderately active and three as highly active by earlier field investigations the resolved along hill slope displacement is estimated at 23 mm year our results demonstrate that polinsar is an effective method to increase the interferometric coherence and provide improved resolution of deformation features associated with natural hazards

seismic activity of the san francisco bay region moment magnitude m with objective confidence level uncertainties are estimated for felt san francisco bay region earthquakes using bakun and went worth s 1997 analysis strategy for seismic intensity observations the frequency magnitude distribution is well described for m 5 5 events since 1850 by a gutenberg richter relation with a b value of 0 90 the seismic moment rate m yr since 1836 is 2 68 1018 n m yr 95 confidence range 1 29 1018 n m yr to 4 07 1018 n m yr the seismic moment rate since 1850 is nearly the same m yr in the 56 years before 1906 is about 10 times that in the 70 years after 1906 in contrast m yr since 1977 is about equal that in the 56 years before 1906 80 1 14 of the plate motion moment accumulation rate is available for release in earthquakes the historical m yr and the portion of the plate motion moment accumulation rate available for release in earthquakes are used in a seismic cycle model to estimate the rate of seismic activity in the twenty first century high and low rates of future seismic activity are both permissible given the range of possible seismic cycle recurrence times t and the uncertainties in the historical m and in the percentage of plate motion available for release in earthquakes if the historical seismic moment rate is not greater than the estimated 2 68 1018 n m yr and the percentage of the plate motion moment accumulation available for release in earthquakes is not less than the estimated 80 then for all t the rate of seismic moment release from now until the next 1906 sized shock will be comparable to the rate from 1836 to 1905 when m 6 1 2 shocks occurred every 15 to 20 years

radar polarimetry analysis tools and applications the authors have developed several techniques to analyze polarimetric radar data from the nasa jpl airborne sar for earth science applications the techniques determine the heterogeneity of scatterers with subregions optimize the return power from these areas and identify probable scattering mechanisms for each pixel in a radar image these techniques are applied to the discrimination and characterization of geologic surfaces and vegetation cover and it is found that their utility varies depending on the terrain type it is concluded that there are several classes of problems amenable to single frequency polarimetric data analysis including characterization of surface roughness and vegetation structure and estimation of vegetation density polarimetric radar remote sensing can thus be a useful tool for monitoring a set of earth science parameters

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

time dependent land uplift and subsidence in the santa clara valley california from a large interferometric synthetic aperture radar data set 1 we invert 115 differential interferograms derived from 47 synthetic aperture radar sar scenes for a time dependent deformation signal in the santa clara valley california the time dependent deformation is calculated by performing a linear inversion that solves for the incremental range change between sar scene acquisitions a nonlinear range change signal is extracted from the ers insar data without imposing a model of the expected deformation in the santa clara valley cumulative land uplift is observed during the period from 1992 to 2000 with a maximum uplift of 41 18 mm centered north of sunnyvale uplift is also observed east of san jose seasonal uplift and subsidence dominate west of the silver creek fault near san jose with a maximum peak to trough amplitude of 35 mm the pattern of seasonal versus long term uplift provides constraints on the spatial and temporal characteristics of water bearing units within the aquifer the silver creek fault partitions the uplift behavior of the basin suggesting that it acts as a hydrologic barrier to groundwater flow while no tectonic creep is observed along the fault the development of a low permeability barrier that bisects the alluvium suggests that the fault has been active since the deposition of quaternary units

earthquake potential along the northern hayward fault california the hayward fault slips in large earthquakes and by aseismic creep observed along its surface trace dislocation models of the surface deformation adjacent to the hayward fault measured with the global positioning system and interferometric synthetic aperture radar favor creep at 7 millimeters per year to the bottom of the seismogenic zone along a 20 kilometer long northern fault segment microearthquakes with the same waveform repeatedly occur at 4 to 10 kilometer depths and indicate deep creep at 5 to 7 millimeters per year the difference between current creep rates and the long term slip rate of 10 millimeters per year can be reconciled in a mechanical model of a freely slipping northern hayward fault adjacent to the locked 1868 earthquake rupture which broke the southern 40 to 50 kilometers of the fault the potential for a major independent earthquake of the northern hayward fault might be less than previously thought

streaming electrical potential anomaly along faults in geothermal areas electrical potential anomalies are often measured associated with geothermal areas and volcanoes in these systems fluid flow is usually mostly restricted to faults and fracture networks an equation describing electrical potential anomalies of electrokinetic nature associated with fluid upflow induced by a thermal source along faults is derived the electrical potential anomaly is related to the depth of the thermal reservoir the temperature difference between the surface and the reservoir of the geothermal area the thermal expansion of water and the streaming electrical potential coupling coefficient in the fault zone a quantitative calculation of the electrokinetic anomaly is provided by comparing this model to a self potential survey of the cerro prieto geothermal field fitterman and corwin 1982 the predictions of the model agree well with the field measurements

evidence for a twelfth large earthquake on the southern hayward fault in the past 1900 years we present age and stratigraphic evidence for an additional paleoearth quake at the tyson lagoon site the acquisition of 19 additional radiocarbon dates and the inclusion of this additional event has resolved a large age discrepancy in our earlier earthquake chronology the age of event e10 was previously poorly con strained thus increasing the uncertainty in the mean recurrence interval ri a critical factor in seismic hazard evaluation reinspection of many trench logs revealed sub stantial evidence suggesting that an additional earthquake occurred between e10 and e9 within unit u45 strata in older u45 are faulted in the main fault zone and overlain by scarp colluviums in two locations we conclude that an additional surface rupturing event e9 5 occurred between e9 and e10 since 91 a d 40 yr 1 11 paleoearthquakes preceded the m 6 8 earthquake in 1868 yielding a mean ri of 161 65 yr 1 standard deviation of recurrence intervals however the standard error of the mean sem is well determined at 10 yr since 1300 a d the mean rate has increased slightly but is indistinguishable from the overall rate within the uncertainties recurrence for the 12 event sequence seems fairly regular the coeffi cient of variation is 0 40 and it yields a 30 yr earthquake probability of 29 the apparent regularity in timing implied by this earthquake chronology lends support for the use of time dependent renewal models rather than assuming a random process to forecast earthquakes at least for the southern hayward fault online material twelve event oxcal model for paleoearthquakes of the hayward fault

numerical modeling of strike slip creeping faults and implications for the hayward fault california abstract the seismic potential of creeping faults such as the hayward fault san francisco bay area ca depends on the rate at which moment slip deficit accumulates on the fault plane thus it is important to evaluate how the creep rate observed at the surface is related to the slip on the fault plane the surface creep rate scr depends on the geometry of locked and free portions of the fault and on the interaction between the fault zone and the surrounding lithosphere using a viscoelastic finite element model we investigate how fault zone geometries and physical characteristics such as frictionless or locked patches affect the observed surface creep when the system is driven by far field plate motions these results have been applied to creep observations of the hayward fault this analysis differs from most previous fault creeping models in that the fault in our model is loaded by a distributed viscous flow induced by far field velocity boundary conditions instead of imposed slip beneath the major faults of the region the far field velocity boundary conditions simulate the relative motion of the stable pacific plate respect to the rigid sierra nevada block leaving the rheology fault geometry and mechanics locked or free to creep patches to determinate the patterns of fault creep our model results show that the fault geometry e g length and depth of creeping and the local rheology influence the surface creep rate scr and the slip on the fault plane in particular we show that the viscoelastic layer beneath the elastic seismogenic zone plays a fundamental role in loading the fault additionally the coupling with the surrounding lithosphere results in a smooth transition from regions free to creep to locked patches

mineralogy and sedimentology of the miocene gocenoluk borate deposit kirka district western anatolia turkey the miocene boratiferous district of kirka in western anatolia turkey is the most important na borate borax resource in the world two separate deposits in the kirka district are located near the villages of sarikaya and gocenoluk eskisehir province borax is intensively exploited in open pit mines in the sarikaya deposit while only small quarries of colemanite are known in the gocenoluk deposit recent exploratory drilling in the gocenoluk area intersected a thick succession of dolostones tuffs and three borate bearing units lower intermediate and upper borate units in them the most abundant borate mineral is ulexite ca na borate passing at depth to probertite borax na borate is only present in the intermediate borate unit minor amounts of colemanite ca borate and hydroboracite ca mg borate occur at the base and or top of each mineralized unit pyroclastic layers within the borate units show intense alteration by alkaline boron bearing waters and formation of diagenetic clay minerals smectites zeolites analcime and borosilicates searlesite the gocenoluk succession is interpreted as a shallow ephemeral alkaline lake deposit in which carbonates formed as stromatolites and travertines borate precipitation in the gocenoluk area took place interstitially within muddy and carbonate sediments in a lateral progression from marginal ca borates towards na ca borates and rarely to na borates in the center of the lake authigenic silicate mineral distribution shows parallel changes toward the center of the lake that reflect increasing ph gradient

multi interferogram method for measuring interseismic deformation denali fault alaska summary studies of interseismic strain accumulation are crucial to our understanding of continental deformation the earthquake cycle and seismic hazard by mapping small amounts of ground deformation over large spatial areas insar has the potential to produce continental scale maps of strain accumulation on active faults however most insar studies to date have focused on areas where the coherence is relatively good e g california tibet and turkey and most analysis techniques stacking small baseline subset algorithm permanent scatterers etc only include information from pixels which are coherent throughout the time span of the study in some areas such as alaska where the deformation rate is small and coherence very variable it is necessary to include information from pixels which are coherent in some but not all interferograms we use a three stage iterative algorithm based on distributed scatterer interferometry we validate our method using synthetic data created using realistic parameters from a test site on the denali fault alaska and present a preliminary result of 10 5 5 0 mm yr 1 for the slip rate on the denali fault based on a single track of radar data from ers1 2

geodetic exploration of the elastic properties across and within the northern san andreas fault zone abstract relying on densely spaced gps data collected between 1996 and 2007 and on insar data spanning the 1992 2001 time period we explore the effects of lateral rheological heterogeneities across the san andreas fault near point reyes on the interseismic velocity field we evaluate heterogeneous elastic dislocation models including an asymmetric model with contrasting rigidities on either side of the san andreas fault and models with a narrow compliant fault zone that lead to high near fault strain rates we show that we cannot resolve a compliant zone from interseismic surface displacement measurements unless independent constraints on the locking depth exist we infer an 18 1 mm yr 1 slip rate on the san andreas fault with a 10 2 km locking depth and a 40 higher rigidity to the sw of the fault at bodega bay gps and edm data suggest a compliant zone on the saf with a 50 to 60 rigidity decrease but 25 km further south we find no evidence for a weak fault zone this suggests substantial variability in fault zone properties along the san andreas fault

resolving vertical tectonics in the san francisco bay area from permanent scatterer insar and gps analysis using a combination of gps measured horizontal velocities of 200 sites and 115 487 range change rates determined with the permanent scatterer interferometric synthetic aperture radar insar method in the san francisco bay area we resolve vertical motions in the region at sub mm yr precision the highest displacement rates are due to nontectonic processes such as active landslides subsidence and rebound over aquifers and rapid settling of unconsolidated sediments along the bay margins residual displacement rates are determined by removing the contribution of the gps derived horizontal velocity field from the insar range change rates to isolate vertical tectonic rates we use only those insar measurements made on material that was not quaternary substrate which is susceptible to nontectonic and seasonally varying ground motions the insar residuals indicate significant uplift over the southern foothills of the active mount diablo anticlinorium the mission hills stepover region of the hayward and calaveras faults and the central and southern santa cruz mountains located along a restraining bend of the san andreas fault

dynamics of slow moving landslides from permanent scatterer analysis high resolution interferometric synthetic aperture radar insar permanent scatterer data allow us to resolve the rates and variations in the rates of slow moving landslides satellite to ground distances range changes on landslides increase at rates of 5 to 7 millimeters per year indicating average downslope sliding velocities from 27 to 38 millimeters per year time series analysis shows that displacement occurs mainly during the high precipitation season during the 1997 1998 el nino event rates of range change increased to as much as 11 millimeters per year the observed nonlinear relationship of creep and precipitation rates suggests that increased pore fluid pressures within the shallow subsurface may initiate and accelerate these features changes in the slope of a hill resulting from increases in the pore pressure and lithostatic stress gradients may then lead to landslides

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

slip in the 1868 hayward earthquake from the analysis of historical triangulation data despite the importance of the hayward fault for earthquake hazards in the san francisco bay area neither the rupture length nor the average coseismic slip in the most recent major earthquake which occurred in 1868 is well known we estimate slip in the 1868 earthquake by analyzing triangulation data collected between 1853 1860 and 1876 1891 we apply a denuisancing procedure that projects out the dependence of that data on station coordinates allowing their displacements to be estimated directly the best fit to the data is obtained with a 52 km long by 10 km deep rupture that extends from warm springs to near berkeley considerably longer than the 30 km of reported surface breakage the estimated slip for an earthquake of this length is 1 9 0 4 m and the seismic moment is m0 3 0 0 7 1019 n m corresponding to mw 7 0 the data are inconsistent with regionally high strain rate prior to the 1906 earthquake as had been previously suggested the triangulation data record northeastward displacement of station loma prieta presumably as a result of the 1865 earthquake the fault normal displacement is not easily explained by slip on either the san andreas fault or the 1989 loma prieta rupture surface this observation is however consistent with an mw 6 3 4 thrust event northeast of the san andreas fault in the southern santa cruz mountains thrust belt

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

application of the sbas dinsar technique to fault creep a case study of the hayward fault california we present a quantitative assessment of the capability of the differential sar interferometry dinsar technique referred to as small baseline subset sbas approach to investigate fault creep phenomena in particular we have computed via the sbas dinsar algorithm time series of the surface displacements relevant to the hayward fault zone within the san francisco bay area california from the european space agency s ers 1 2 satellite radar data for the 1992 to 2000 time period starting from the dinsar time series we measured the relative displacements across the fault with no need for any atmospheric filtering step these results have been systematically compared to the measurements available from the alignment arrays that are located along the fault our analysis shows that the standard deviation of the differences between the dinsar and the in situ measurements is on the order of 2 mm moreover the estimated mean deformation rates have an accuracy that is better than 1 mm year

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

spatiotemporal evolution of surface creep in the parkfield region of the san andreas fault 1993 2004 from synthetic aperture radar the parkfield section of the san andreas fault saf is defined as a transitional portion of the fault between slip release behavior types in the creeping section of the saf to the northwest and the apparently locked section to the southeast the parkfield section is characterized by complex frictional fault behavior because it represents a transition zone from aseismic creep to stick slip regime at least six historic earthquakes of mw 6 have occurred in this area in 1881 1901 1922 1934 1966 and 2004 it was observed in the 2004 mw 6 0 parkfield earthquake that 70 of the total coseismic and postseismic moment release occurred aseismically to understand the saf behavior in this area it is of particular interest to measure and analyze not only the spatial evolution of the surface displacement in this area but also its evolution over time using radar data acquired by the european space agency s european remote sensing ers1 2 satellites we constructed descending interferograms and retrieved time series of surface displacements along the central saf for the decade preceding the 2004 parkfield earthquake we focus on characterizing the space and time evolution of surface creep in the parkfield and cholame sections the spatial pattern of the interseismic displacement rate indicates that tectonic strain was not uniformly distributed along the strike of the fault between 1993 and 2004 our data indicate not only a decrease in the creep rate from the parkfield section to south of highway 46 from 1 4 0 3 cm y to 0 6 0 3 cm y but also a small but significant creep rate increase in the cholame section to 0 2 0 1 cm y the evidence for episodic creep in the cholame section of the saf south east of parkfield is in contrast with previously published interpretations of gps and trilateration data the cholame section of the saf merits close monitoring because it was likely the nucleation site of the 1857 fort tejon earthquake and because it has shown recent evidence of deep slow slip as revealed by deep tremors

slicing up the san francisco bay area block kinematics and fault slip rates from gps derived surface velocities received 26 october 2004 revised 11 february 2005 accepted 10 march 2005 published 16 june 2005 i observations of surface deformation allow us to determine the kinematics of faults in the san francisco bay area we present the bay area velocity unification bavu bay view a compilation of over 200 horizontal surface velocities computed from campaign style and continuous global positioning system gps observations from 1993 to 2003 we interpret this interseismic velocity field using a three dimensional block model to determine the relative contributions of block motion elastic strain accumulation and shallow aseismic creep the total relative motion between the pacific plate and the rigid sierra nevada great valley sngv microplate is 37 9 0 6 mm yr 1 directed toward n30 4 w 0 8 at san francisco 2 fault slip rates from our preferred model are typically within the error bounds of geologic estimates but provide a better fit to geodetic data notable right lateral slip rates in mm yr 1 san gregorio fault 2 4 1 0 west napa fault 4 0 3 0 zone of faulting along the eastern margin of the coast range 5 4 1 0 and mount diablo thrust 3 9 1 0 of reverse slip and 4 0 0 2 of right lateral strike slip slip on the northern calaveras is partitioned between both the west napa and concord green valley fault systems the total convergence across the bay area is negligible poles of rotation for bay area blocks progress systematically from the north america pacific to north america sngv poles the resulting present day relative motion cannot explain the strike of most bay area faults but fault strike does loosely correlate with inferred plate motions at the time each fault initiated