widespread fault creep in the northern san francisco bay area revealed by multistation cluster detection of repeating earthquakes we search for repeating earthquakes res in the northern san francisco bay area in 1984 2016 by comparing over 670 000 waveforms from 75 000 events we identify candidate clusters of events whos

new global marine gravity model from cryosat 2 and jason 1 reveals buried tectonic structure gravity models are powerful tools for mapping tectonic structures especially in the deep ocean basins where the topography remains unmapped by ships or is buried by thick sediment we combined new radar altimeter measurements from satellites cryosat 2 and jason 1 with existing data to construct a global marine gravity model that is two times more accurate than previous models we found an extinct spreading ridge in the gulf of mexico a major propagating rift in the south atlantic ocean abyssal hill fabric on slow spreading ridges and thousands of previously uncharted seamounts these discoveries allow us to understand regional tectonic processes and highlight the importance of satellite derived gravity models as one of the primary tools for the investigation of remote ocean basins

plate boundary observatory and related networks gps data analysis methods and geodetic products the geodesy advancing geosciences and earthscope gage facility global positioning system gps data analysis centers produce position times series velocities and other parameters for approximately two thousand continuously operating gps receivers spanning a quadrant of earth s surface encompassing the high arctic north america and caribbean the purpose of this review is to document the methodology for generating station positions and their evolution over time and to describe the requisite tradeoffs involved with combination of results gage gps analysis involves formal merging within a kalman filter of two independent loosely constrained solutions one is based on precise point positioning produced with the gps inferred positioning system orbit analysis simulation gipsy oasis software at central washington university cwu and the other is a network solution based on phase and range double differencing produced with the gps at mit gamit software at new mexico institute of mining and technology nmt the primary products generated are the position time series that show motions relative to a north america reference frame and secular motions of the stations represented in the velocity field the position time series themselves contain a multitude of signals in addition to the secular motions co seismic and post seismic signals seasonal signals from hydrology and transient events some understood and other not yet fully explained are all evident in the time series and ready for further analysis and interpretation we explore the impact of analysis assumptions on the reference frame realization and on the final solutions and we compare within the gage solutions and with others

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

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

near real time double difference event location using long term seismic archives with application to northern california we present a real time procedure that uses cross correlation and double difference methods to rapidly relocate new seismic events with high precision relative to past events with accurately known locations waveforms of new events are auto matically cross correlated with those archived for nearby past events to measure accu rate differential phase arrival times these data together with delay times computed from arrival time picks are subsequently inverted for the vector connecting the new event to its neighboring events using the double difference algorithm the new seis mic monitoring technique is applied to earthquakes recorded in northern california using near real time data feeds from the northern california seismic network ncsn and the northern california earthquake data center and a locally stored copy of the ncsn seismic archive new events are automatically relocated in near real time tens of seconds relative to a high resolution double difference earthquake catalog for northern california back testing using past events across northern california indi cates that the real time solutions are on average within 0 08 km laterally and 0 24 km vertically of the double difference catalog locations we show that the precision with which new events are located using this technique will improve with time helped by the continued increase in density of recorded earthquakes and growth of the digital seismic archives real time double difference location allows for monitoring spatio temporal changes in seismogenic properties of active faults with unprecedented res olution and therefore has considerable social and economic impact in the immediate evaluation and mitigation of seismic hazards

spatial variations in fault friction related to lithology from rupture and afterslip of the 2014 south napa california earthquake following earthquakes faults are often observed to continue slipping aseismically it has been proposed that this afterslip occurs on parts of the fault with rate strengthening friction that are stressed by the main shock but our understanding has been limited by a lack of immediate high resolution observations here we show that the behavior of afterslip following the 2014 south napa earthquake in california varied over distances of only a few kilometers this variability cannot be explained by coseismic stress changes alone we present daily positions from continuous and survey gps sites that we remeasured within 12 h of the main shock and surface displacements from the new sentinel 1 radar mission this unique geodetic data set constrains the distribution and evolution of coseismic and postseismic fault slip with exceptional resolution in space and time we suggest that the observed heterogeneity in behavior is caused by lithological controls on the frictional properties of the fault plane

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

continuous exhumation of mantle derived rocks at the southwest indian ridge for 11 million years the global mid ocean ridge system where tectonic plates diverge is traditionally thought of as the largest single volcanic feature on the earth yet wide expanses of smooth sea floor in the easternmost part of the southwest indian ridge in the indian ocean lacks the hummocky morphology that is typical for submarine volcanism at other slow spreading ridges the sea floor can extend by faulting the existing lithosphere along only one side of the ridge axis however the smooth sea floor in the easternmost southwest indian ridge also lacks the corrugated texture created by such faulting instead the sea floor is smooth on both sides of the ridge axis and is thought to be composed of altered mantle derived rocks here we use side scan sonar to image the sea floor and dredge samples to analyse the composition of two sections of the southwest indian ridge between 62 050 e and 64 400 e where the sea floor formed over the past 11 million years we show that the smooth floor is almost entirely composed of seawater altered mantle derived rocks that were brought to the surface by large detachment faults on both sides of the ridge axis faulting accommodates almost 100 of plate divergence and the detachment faults have repeatedly flipped polarity we suggest that this tectonic process could also explain the exhumation of mantle derived rocks at the magma poor margins of rifted continents

the structure of oceanic core complexes controlled by the depth distribution of magma emplacement extension at mid ocean ridges can be accommodated by detachment faults forming oceanic core complexes that develop under low rates of magma intrusion modelling reveals that oceanic core complexes can also form under high rates of magma intrusion if the magma is injected into the lower ductile layer of the crust

detection of a locked zone at depth on the parkfield california segment of the san andreas fault the parkfield california segment of the san andreas fault is transitional in character between the creeping segment of the fault to the northwest and the locked carrizo plain segment to the southeast the rate of shallow fault slip decreases from 25 30 mm yr northwest of the epicenter of the 1966 parkfield earthquake to zero at the southeastern end of the 1966 rupture zone data from a network of trilateration lines spanning the san andreas fault near parkfield and extending to the pacific coast near san luis obispo shed light on the rate of fault slip at depth since the 1966 earthquake in this study average rates of line length change and shallow fault slip were inverted to determine the slip rate at depth on the parkfield fault segment the fault is taken to be a vertical surface with unknown distribution of strike slip displacement in an elastic half space a striking result of the inversions is that all solutions providing acceptable fits to the data exhibit a locked zone essentially coincident with the rupture surface of the 1966 parkfield earthquake the data require that the locked zone extend nearly as far north as the 1966 epicenter however the vertical extent of the locked zone is not well resolved over much of the parkfield segment the fault is slipping faster at the earth s surface than it is at seismogenic depths in order to fit the trilateration measurements it is necessary to include a component of contraction normal to the trend of the san andreas the inversion results suggest a spatially uniform normal strain of 0 06 strain yr the orientation of the contraction is compatible with geologic and seismic evidence of active folding and reverse faulting in the region the magnitude of the contraction is consistent with convergence rates inferred from global plate motion models

the nature of the crust under cayman trough from gravity abstract considerable crustal thickness variations are inferred along cayman trough a slow spreading ocean basin in the caribbean sea from modeling of the gravity field the crust to a distance of 50 km from the spreading center is only 2 3 km thick in agreement with dredge and dive results crustal thickness increases to 5 5 km at distances between 100 and 430 km west of the spreading center and to 3 5 6 km at distances between 60 and 370 km east of the spreading center the increase in thickness is interpreted to represent serpentinization of the uppermost mantle lithosphere rather than a true increase in the volume of accreted ocean crust serpentinized peridotite rocks have indeed been dredged from the base of escarpments of oceanic crust rocks in cayman trough laboratory measured density and p wave speed of peridotite with 40 50 serpentine are similar to the observed speed in published refraction results and to the inferred density from the model crustal thickness gradually increases to 7 8 km at the far ends of the trough partially in areas where sea floor magnetic anomalies were identified basement depth becomes gradually shallower starting 250 km west of the rise and 340 km east of the rise in contrast to the predicted trend of increasing depth to basement from cooling models of the oceanic lithosphere the gradual increase in apparent crustal thickness and the shallowing trend of basement depth are interpreted to indicate that the deep distal parts of cayman trough are underlain by highly attenuated crust not by a continuously accreted oceanic crust

drilling constraints on lithospheric accretion and evolution at atlantis massif mid atlantic ridge 30 n expeditions 304 and 305 of the integrated ocean drilling program cored and logged a 1 4 km section of the domal core of atlantis massif postdrilling research results summarized here constrain the structure and lithology of the central dome of this oceanic core complex the dominantly gabbroic sequence recovered contrasts with predrilling predictions application of the ground truth in subsequent geophysical processing has produced self consistent models for the central dome the presence of many thin interfingered petrologic units indicates that the intrusions forming the domal core were emplaced over a minimum of 100 220 kyr and not as a single magma pulse isotopic and mineralogical alteration is intense in the upper 100 m but decreases in intensity with depth below 800 m alteration is restricted to narrow zones surrounding faults veins igneous contacts and to an interval of locally intense serpentinization in olivine rich troctolite hydration of the lithosphere occurred over the complete range of temperature conditions from granulite to zeolite facies but was predominantly in the amphibolite and greenschist range deformation of the sequence was remarkably localized despite paleomagnetic indications that the dome has undergone at least 45 degrees rotation presumably during unroofing via detachment faulting both the deformation pattern and the lithology contrast with what is known from seafloor studies on the adjacent southern ridge of the massif there the detachment capping the domal core deformed a 100 m thick zone and serpentinized peridotite comprises similar to 70 of recovered samples we develop a working model of the evolution of atlantis massif over the past 2 myr outlining several stages that could explain the observed similarities and differences between the central dome and the southern ridge

spreading rate dependence of melt extraction at mid ocean ridges from mantle seismic refraction data a variety of observations indicate that mid ocean ridges produce less crust at spreading rates below 20 mm yr 1 refs 1 3 reflecting changes in fundamental ridge processes with decreasing spreading rate the nature of these changes however remains uncertain with end member explanations being decreasing shallow melting or incomplete melt extraction each due to the influence of a thicker thermal lid here we present results of a seismic refraction experiment designed to study mid ocean ridge processes by imaging residual mantle structure our results reveal an abrupt lateral change in bulk mantle seismic properties associated with a change from slow to ultraslow palaeo spreading rate changes in mantle velocity gradient basement topography and crustal thickness all correlate with this spreading rate change these observations can be explained by variations in melt extraction at the ridge with a gabbroic phase preferentially retained in the mantle at slower spreading rates the estimated volume of retained melt balances the approximately 1 5 km difference in crustal thickness suggesting that changes in spreading rate affect melt extraction processes rather than total melting

surface displacements and source parameters of the 2003 bam iran earthquake from envisat advanced synthetic aperture radar imagery 1 the mw 6 6 26 december 2003 bam iran earthquake was one of the first earthquakes for which envisat advanced synthetic aperture radar asar data were available using interferograms and azimuth offsets from ascending and descending tracks we construct a three dimensional displacement field of the deformation due to the earthquake elastic dislocation modeling shows that the observed deformation pattern cannot be explained by slip on a single planar fault which significantly underestimates eastward and upward motions se of bam we find that the deformation pattern observed can be best explained by slip on two subparallel faults eighty five percent of moment release occurred on a previously unknown strike slip fault running into the center of bam with peak slip of over 2 m occurring at a depth of 5 km the remainder occurred as a combination of strike slip and thrusting motion on a southward extension of the previously mapped bam fault 5 km to the east

on the mechanics of earthquake afterslip we propose a model for earthquake afterslip based on rate and state variable friction laws in the model afterslip is attributed to the interaction of a velocity weakening region at depth within which earthquakes nucleate with an upper region of velocity strengthening frictional behavior the existence of this upper region is supported by independent seismologic observations and the results of laboratory friction experiments in our model afterslip is the result of relaxation of a stress perturbation within the velocity strengthening region which arises when an earthquake propagates into that region from below we derive the stress perturbation and its decay from the friction constitutive law using a simple 1 degree of freedom approximation for the elastic interaction between the fault and its surroundings this approximation is based on thickness averaged displacements and slip velocities within the velocity strengthening region which is assumed to slip as a rigid block coseismic and postseismic slip are coupled through the thickness averaged stiffness k of the velocity strengthening region we assume k to be inversely proportional to the thickness of this region which means that thicker velocity strengthening regions have a greater tendency to arrest coseismic slip we model the afterslip time histories of the 1966 parkfield and 1987 superstition hills earthquakes and relate the model parameters to physical parameters which may govern the rheologic behavior of the faults in accord with field observations our model predicts 1 that afterslip on some faults scales with the thickness of the unconsolidated sedimentary cover and 2 that proportionally more afterslip occurs for earthquakes in which coseismic surface slip is small compared with coseismic slip at depth velocity strengthening frictional behavior is to be expected for faults within poorly consolidated sediments and for those that contain significant gouge zones about 500 m within their shallow regions 3 5 km combining our results with those of recent laboratory friction studies indicates that relatively young faults with little accumulated fault gouge should exhibit little afterslip

depth segmentation of the seismogenic continental crust the 2008 and 2009 qaidam earthquakes 1 the seismic hazard in the immediate vicinity of an earthquake is usually assumed to be reduced after rupture of a continental fault with along strike portions being brought closer to failure and aftershocks being significantly smaller this period of reduced hazard will persist as strain re accumulates over decades or centuries however this is only realised if the entire seismogenic layer ruptured in the event here we use satellite radar measurements to show the ruptures of two mw 6 3 earthquakes occurring in almost the same epicentral location ten months apart in the qaidam region china were nearly coplanar the 2008 earthquake ruptured the lower half of the seismogenic layer the 2009 event the upper half fault segmentation with depth allows a significant seismic hazard to remain even after a moderate and potentially devastating earthquake this depth segmentation possibly exists in the case of the 2003 bam earthquake where satellite radar and aftershock measurements showed that it ruptured only the upper half of the 15 20 km deep seismogenic region jackson et al 2006 and that the lower unruptured part may remain as a continuing seismic hazard

delayed seismicity rate changes controlled by static stress transfer on 15 june 2010 a m w5 7 earthquake occurred near ocotillo california in the yuha desert this event was the largest aftershock of the 4 april 2010 m w7 2 el mayor cucapah emc earthquake in this region the emc mainshock and subsequent ocotillo aftershock provide an opportunity to test the coulomb failure hypothesis cfs we explore the spatiotemporal correlation between seismicity rate changes and regions of positive and negative cfs change imparted by the ocotillo event based on simple cfs calculations we divide the yuha desert into three subregions one triggering zone and two stress shadow zones we find the nominal triggering zone displays immediate triggering one stress shadowed region experiences immediate quiescence and the other nominal stress shadow undergoes an immediate rate increase followed by a delayed shutdown we quantitatively model the spatiotemporal variation of earthquake rates by combining calculations of cfs change with the rate state earthquake rate formulation of dieterich 1994 assuming that each subregion contains a mixture of nucleation sources that experienced a cfs change of differing signs our modeling reproduces the observations including the observed delay in the stress shadow effect in the third region following the ocotillo aftershock the delayed shadow effect occurs because of intrinsic differences in the amplitude of the rate response to positive and negative stress changes and the time constants for return to background rates for the two populations we find that rate state models of time dependent earthquake rates are in good agreement with the observed rates and thus explain the complex spatiotemporal patterns of seismicity

evidence of fault immaturity from shallow slip deficit and lack of postseismic deformation of the 2017 mw 6 5 jiuzhaigou earthquake

seismogeodesy of the 2014 mw6 1 napa earthquake california rapid response and modeling of fast rupture on a dipping strike slip fault real time high rate geodetic data have been shown to be useful for rapid earthquake response systems during medium to large events the 2014 mw6 1 napa california earthquake is important because it provides an opportunity to study an event at the lower threshold of what can be detected with gps we show the results of gps only earthquake source products such as peak ground displacement magnitude scaling centroid moment tensor cmt solution and static slip inversion we also highlight the retrospective real time combination of gps and strong motion data to produce seismogeodetic waveforms that have higher precision and longer period information than gps only or seismic only measurements of ground motion we show their utility for rapid kinematic slip inversion and conclude that it would have been possible with current real time infrastructure to determine the basic features of the earthquake source we supplement the analysis with strong motion data collected close to the source to obtain an improved postevent image of the source process the model reveals unilateral fast propagation of slip to the north of the hypocenter with a delayed onset of shallow slip the source model suggests that the multiple strands of observed surface rupture are controlled by the shallow soft sediments of napa valley and do not necessarily represent the intersection of the main faulting surface and the free surface we conclude that the main dislocation plane is westward dipping and should intersect the surface to the east either where the easternmost strand of surface rupture is observed or at the location where the west napa fault has been mapped in the past

the 2011 mw 7 1 van eastern turkey earthquake 1 we use interferometric synthetic aperture radar insar body wave seismology satellite imagery and field observations to constrain the fault parameters of the mw 7 1 2011 van eastern turkey reverse slip earthquake in the turkish iranian plateau distributed slip models from elastic dislocation modeling of the insar surface displacements from envisat and cosmo skymed interferograms indicate up to 9 m of reverse and oblique slip on a pair of en echelon nw 40 54 dipping fault planes which have surface extensions projecting to just 10 km north of the city of van the slip remained buried and is relatively deep with a centroid depth of 14 km and the rupture reaching only within 8 9 km of the surface consistent with the lack of significant ground rupture the up dip extension of this modeled wsw striking fault plane coincides with field observations of weak ground deformation seen on the western of the two fault segments and has a dip consistent with that seen at the surface in fault gouge exposed in quaternary sediments no significant coseismic slip is found in the upper 8 km of the crust above the main slip patches except for a small region on the eastern segment potentially resulting from the mw 5 9 aftershock on the same day we perform extensive resolution tests on the data to confirm the robustness of the observed slip deficit in the shallow crust we resolve a steep gradient in displacement at the point where the planes of the two fault segments ends are inferred to abut at depth possibly exerting some structural control on rupture extent

new perspectives on geological strain rates calculated from both naturally deformed and actively deforming rocks abstract a value of 10 14 s 1 is commonly cited as an average geological strain rate this value was first suggested for finite strain across an orogen but based on more limited information than the combined geophysical geological and experimental data now available on active and ancient rock deformation thus it is timely to review the data constraining strain rates in the continents and to consider the quantifiable range of crustal strain rates here where resolution allows both spatial and temporal strain rate variations are explored this review supports that a strain rate of 10 14 1 s 1 arises from geological estimates of bulk finite strains microstructural arguments combining laboratory derived piezometers and viscous flow laws however imply local rates that are orders of magnitude faster geodetic rates in contrast are typically 10 15 s 1 in actively deforming areas about an order of magnitude slower than the bulk rates estimated from geological observations this difference in estimated strain rates may arise from either low spatial resolution or the fact that surface velocity fields can not capture strain localisation in the mid to lower crust integration of geological and geodetic rates also shows that strain rates can vary in both space and time over both single and multiple earthquake cycles overall time averaged geological strain rates are likely slower than the strain rates in faults and shear zones that traverse the crust or lithosphere

seismic properties of layer 2 basalts summary in this paper the physical properties of oceanic layer 2 basalts are examined with the emphasis on micro crack porosity and alteration related changes in physical properties over 160 core samples from some of the more significant deep sea drilling project ocean drilling program holes including 417d 418a 504b and 801c are included in the present investigation overall physical property relationships are discussed in the first half of this study at 200 mpa confining pressure compressionaland shear wave velocities of the sample suite have modal values of 6 1 kms 1 and 3 5 kms 1 respectively a poisson s ratio of 0 28 characterizes the majority of the basalts samples that have experienced extensive low temperature alteration identified through elevated kzo and decreased cao and mgo contents exhibit low velocities and densities and high poisson s ratios the microcrack porosity in the basalt suite is examined using velocity pressure data a pore aspect ratio inversion scheme and scanning electron microscope sem imaging microcracks sealed by alteration minerals such as smectite and calcite or healed by late crystallization are common throughout the sample set rocks from the transition zone and sheeted dyke section of hole 504b are marked by numerous smectite and chlorite filled cracks more significantly the data indicate an increase of low aspectratio open microcracks with increasing depth in samples from several dsdp holes particularly hole 504b these microcracks also observed using the sem are attributed to stress relief as the original drill cores were removed from in situ pressure conditions stress relief micro cracking is apparently more severe in the holocrystalline coarsergrained samples from massive flows than in the phyric basalts with fine grained groundmasses characteristic of pillow units this difference in micro cracking is explained through basic fracture theory

interseismic and postseismic shallow creep of the north qaidam thrust faults detected with a multitemporal insar analysis understanding the mechanisms by which earthquake cycles produce folding and accommodate shortening is essential to quantify the seismic potential of active faults and integrate aseismic slip within our understanding of the physical mechanisms of the long term deformation however measuring such small deformation signals in mountainous areas is challenging with current space geodesy techniques due to the low rates of motion relative to the amplitude of the noise here we successfully carry out a multitemporal interferometric synthetic aperture radar analysis over the north qaidam fold thrust system in ne tibet where eight mw 5 2 earthquakes occurred between 2003 and 2009 we report various cases of aseismic slip uplifting the thickened crust at short wavelengths we provide a rare example of a steep shallow 13 km long and 6 km wide afterslip signal that coincides spatially with an anticline and that continues into 2011 in response to a mw 6 3 event in 2003 we suggest that a buried seismic slip during the 2003 earthquake has triggered both plastic an elastic folding and aseismic slip on the shallow thrusts we produce a first order two dimensional model of the postseismic surface displacements due to the 2003 earthquake and highlight a segmented slip on three fault patches that steepen approaching the surface this study emphasizes the fundamental role of shallow aseismic slip in the long term and permanent deformation of thrusts and folds and the potential of interferometric synthetic aperture radar for detecting and characterizing the spatiotemporal behavior of aseismic slip over large mountainous regions

seismic evidence for large scale compositional heterogeneity of oceanic core complexes long lived detachment faults at mid ocean ridges exhume deep seated rocks to form oceanic core complexes occs using large offset 6 km multichannel seismic data we have derived two dimensional seismic tomography models for three of the best developed occs on the mid atlantic ridge our results show that large lateral variations in p wave velocity occur within the upper 0 5 1 7 km of the lithosphere we observe good correlations between velocity structure and lithology as documented by in situ geological samples and seafloor morphology and we use these correlations to show that gabbros are heterogeneously distributed as large tens to 100 km2 bodies within serpentinized peridotites neither the gabbros nor the serpentinites show any systematic distribution with respect to along isochron position within the enclosing spreading segment indicating that melt extraction from the mantle is not necessarily focused at segment centers as has been commonly inferred in the spreading direction gabbros are consistently present toward the terminations of the detachment faults this suggests enhanced magmatism during the late stage of occ formation due either to natural variability in the magmatic cycle or to decompression melting during footwall exhumation heat introduced into the rift valley by flow and crystallization of this melt could weaken the axial lithosphere and result in formation of new faults and it therefore may explain eventual abandonment of detachments that form occs detailed seismic studies of the kind described here when constrained by seafloor morphology and geological samples can distinguish between major lithological units such as volcanics gabbros and serpentinized peridotites at lateral scales of a few kilometers thus such studies have tremendous potential to elucidate the internal structure of the shallow lithosphere and to help us understand the tectonic and magmatic processes by which they were emplaced

age and spreading history of the cayman trough as determined from depth heat flow and magnetic anomalies the opening of the cayman trough records aspects of relative motion between the north american and caribbean plates essential to accurate reconstruction of caribbean evolution assessment of opening rates based upon basement subsidence analysis as well as magnetic anomaly interpretation shows that the trough may have opened at one third to one half previously proposed rates depths to basement show that the crust has subsided away from the present axis in two stages a younger stage characterized by substantial and asymmetric greater to the east subsidence preceded by an older stage of slight increases of depth with distance depth to age relations calculated from subsidence curves which accommodate lateral as well as vertical cooling of the accreting slab indicate that the trough has opened at an overall rate of less than 15 mm yr since 25 30 ma and at 20 30 mm yr prior to 30 ma marine magnetic anomalies show lineations perpendicular to the trough including a distinct central anomaly but the pattern is neither well defined nor symmetrical about the present axis however partial anomaly sequences can be identified on both sides of the axis and the distribution of these sequences indicates that spreading may have involved frequent short ridge jumps mostly eastward the overall rate of opening as indicated by this interpretation of the magnetics is about 15 and 30 mm yr since and prior to 26 ma both subsidence and magnetics indicate that the trough opened by at least 45 50 ma

quantitative relationship between aseismic slip propagation speed and frictional properties recent observations show evidence of propagation of postseismic slip which may contain information about the mechanical properties of faults here we develop a new analytical relationship between the propagation speed of aseismic slip transients and fault frictional properties modeled by a rate and state dependent friction law the relationship explains the propagation speed of afterslip in 3 d numerical simulations to first order based on this relationship we identify systematic dependencies of afterslip propagation speed on effective normal stress and frictional properties the coefficients a and a b which quantify the instantaneous and the steady state velocity dependence of friction respectively and the characteristic slip distance l of fault state evolution lower values of the parameter a a cause faster propagation in areas where the passage of the postseismic slip front induces large shear stress changes compared to a which are typically located near the mainshock rupture in areas where a is small typically more distant from the mainshock afterslip propagation speed is more sensitive to a b the propagation speed is proportional to initial slip velocity and under the condition that loading span is significantly shorter than the passage of postseismic slip inversely proportional to l the relationship developed here should be useful to constrain the frictional properties of faults based on observed propagation speeds independently of rock laboratory experiments which can then be used in predictive numerical simulations of aseismic slip phenomena

independent component analysis and parametric approach for source separation in insar time series at regional scale application to the 2017 2018 slow slip event in guerrero mexico

episodic magmatism and serpentinized mantle exhumation at an ultraslow spreading centre mid ocean ridges spreading at ultraslow rates of less than 20 mm yr 1 can exhume serpentinized mantle to the seafloor or they can produce magmatic crust however seismic imaging of ultraslow spreading centres has not been able to resolve the abundance of serpentinized mantle exhumation and instead supports 2 to 5 km of crust most seismic crustal thickness estimates reflect the depth at which the 7 1 km s 1 p wave velocity is exceeded yet the true nature of the oceanic lithosphere is more reliably deduced using the p to s wave velocity vp vs ratio here we report on seismic data acquired along off axis profiles of older oceanic lithosphere at the ultraslow spreading mid cayman spreading centre we suggest that high vp vs ratios greater than 1 9 and continuously increasing p wave velocity changing from 4 km s 1 at the seafloor to greater than 7 4 km s 1 at 2 to 4 km depth indicate highly serpentinized peridotite exhumed to the seafloor elsewhere either magmatic crust or serpentinized mantle deformed and uplifted at oceanic core complexes underlies areas of high bathymetry the cayman trough therefore provides a window into mid ocean ridge dynamics that switch between magma rich and magma poor oceanic crustal accretion including exhumation of serpentinized mantle covering about 25 of the seafloor in this region

contrasts in compliant fault zone properties inferred from geodetic measurements in the san francisco bay area author s materna k burgmann r abstract 2016 american geophysical union all rights reserved in crustal fault zones regions of damaged rock characterized by reduced elastic shear modulus can influence patterns of near field interseismic deformation in order to study these compliant fault zones cfzs and how they might develop over the lifetimes of faults we compare two fault segments with contrasting fault age and lithology along the san andreas fault in the san francisco bay area new geodetic measurements of the interseismic velocity fields at each location are used to constrain fault zone parameters through a markov chain monte carlo method at black mountain in the santa cruz mountains of the san francisco peninsula we do not find evidence for a compliant fault zone instead we find that the geodetic data are more consistent with a model of a single fault in a homogeneous elastic half space at lake san andreas a younger fault segment 35nkm farther north we find evidence for a compliant fault zone about 3 4 1 1 1 4nkm wide containing a shear modulus of about 40 of the shear modulus of the surrounding rock we also find that the best fitting cfz model at this location unlike the best fitting homogeneous half space model has a locking depth that agrees well with the observed depth of microseismicity based on differences in fault age cumulative displacement and lithology between black mountain and lake san andreas we infer that lithology plays an important and in this case perhaps a dominant role in the accumulation of fault zone damage structures and the development of cfzs over the lifetime of a fault

influence of pressure and mineralogy on seismic velocities in oceanic gabbros implications for the composition and state of the lower oceanic crust 1 we have analyzed the relationship between p wave velocities measured at pressures of 40 100 and 200 mpa and modal mineralogy in oceanic gabbro samples from ocean drilling program holes 735b 894g and 923a at all pressures increasing velocities correspond to increasing pyroxene contents and decreasing alteration phyllosilicate and amphibole content but indicate little or no variation of olivine content in part because the olivine compositions are in the range fo65 to fo73 a voigt reuss hill inverse model reveals that the effective bulk density and elastic moduli of olivine in the gabbros are low even relative to fo73 possibly because the olivine grains contain ubiquitous networks of cracks even if the cracks are not present in situ on average gabbros with velocities typical of seismic layer 3 6 7 7 0 km s 1 contain 5 15 alteration products including 5 15 amphibole and 0 5 phyllosilicates these results suggest that the lower crust is on average slightly to moderately altered

widespread active detachment faulting and core complex formation near 13 n on the mid atlantic ridge oceanic core complexes are massifs in which lower crustal and upper mantle rocks are exposed at the sea floor1 2 3 they form at mid ocean ridges through slip on detachment faults rooted below the spreading axis2 3 4 5 6 to date most studies of core complexes have been based on isolated inactive massifs that have spread away from ridge axes here we present a survey of the mid atlantic ridge near 13 n containing a segment in which a number of linked detachment faults extend for 75 km along one flank of the spreading axis the detachment faults are apparently all currently active and at various stages of development a field of extinct core complexes extends away from the axis for at least 100 km our observations reveal the topographic characteristics of actively forming core complexes and their evolution from initiation within the axial valley floor to maturity and eventual inactivity within the surrounding region there is a strong correlation between detachment fault morphology at the ridge axis and high rates of hydroacoustically recorded earthquake seismicity preliminary examination of seismicity and seafloor morphology farther north along the mid atlantic ridge suggests that active detachment faulting is occurring in many segments and that detachment faulting is more important in the generation of ocean crust at this slow spreading ridge than previously suspected

deep structure of the ocean continent transition in the southern iberia abyssal plain from seismic refraction profiles the iam 9 transect at 40 20 n we present a crust and mantle velocity structure for the west iberia passive continental margin derived from a 320 km long wide angle seismic profile acquired in the southern iberia abyssal plain we observe a 170 km wide ocean continent transition zone which includes a pair of overlapping peridotite ridges and is bounded by oceanic crust and landward by fault bounded blocks of continental crust the profile lies 40 km south of the transect sampled by ocean drilling program odp legs 149 and 173 the transition zone structure can be divided into an upper layer 2 4 km thick with velocities of between 4 5 and 7 0 km s 1 and generally a high velocity gradient 1 s 1 and a lower layer up to 4 km thick with a velocity of 7 6 km s 1 and a low velocity gradient a weak moho reflection in this zone was seen only on wide angle profiles at an offset of 30 km the upper layer has a distinctly lower velocity than thinned continental crust adjacent to the continental slope conversely the lower layer has too high a velocity to be magmatically intruded or underplated lower continental crust on the coincident seismic reflection profile fault bounded crustal blocks identified in unequivocal extended continental crust are not observed in the transition zone the upper layer has velocity bounds and gradient similar to oceanic layer 2 observed west of the peridotite ridges but no oceanic layer 3 velocity structure is present while magnetic anomalies have been identified within the transition zone they have not been modeled successfully as seafloor spreading magnetic anomalies nor do they generally form long linear margin parallel features finally odp boreholes 40 km north of our profile and within the interpreted transition zone have recovered up to 140 m thick sections of serpentinite and serpentinized peridotites with little evidence of mafic igneous material we conclude that the transition zone cannot be dominantly composed of either extended continental crust or oceanic crust although current melting models predict a considerably thicker crust of decompression melt products we interpret this region as exposed upper mantle peridotite with little or no synrift extrusive material and limited amounts of synrift material intruded within the serpentinized peridotite

long term afterslip of the 2004 m 6 0 parkfield california earthquake implications for forecasting amount and duration of afterslip on other major creeping faults abstract we present the longest record of surface afterslip on a continental strike slip fault for the 2004 m 6 0 parkfield california earthquake from which we can derive critical information about the duration and predictability of afterslip relevant to urban displacement hazard applications surface slip associated with this event occurred entirely postseismically along the interseismically creeping 0 6 1 5 cm yr main trace of the san andreas fault using the first year of afterslip data the program after correctly predicted the cumulative surface afterslip maximum 35 cm eventually attained by 1 yr postearthquake observed afterslip had accumulated to only 74 of its modeled final value u f in units of length the 6 yr data suggested final slip would be reached everywhere by 6 12 yrs parkfield s afterslip lasted much longer 6 12 yrs than afterslip following a 2014 m 6 0 event in napa california where no interseismic creep was known and its afterslip neared completion 97 of u f by 1 yr the uncertainty in u f for the napa event fell to 2 cm in only three months versus in 2 yrs for the parkfield event mostly because duration of the power law stage of afterslip at parkfield is much longer 1000 493 1666 days versus 100 35 421 days for napa because the urban hayward fault near san francisco california like the parkfield section exhibits interseismic creep in a similar geological regime significant afterslip might last for up to a decade following an anticipated m 6 7 earthquake potentially delaying postearthquake recovery electronic supplement tables of afterslip observations and coefficients for computing afterslip

forecasting the evolution of seismicity in southern california animations built on earthquake stress transfer 1 we develop a forecast model to reproduce the distribution of main shocks aftershocks and surrounding seismicity observed during 1986 2003 in a 300 310 km area centered on the 1992 m 7 3 landers earthquake to parse the catalog into frames with equal numbers of aftershocks we animate seismicity in log time increments that lengthen after each main shock this reveals aftershock zone migration expansion and densification we implement a rate state algorithm that incorporates the static stress transferred by each m 6 shock and then evolves coulomb stress changes amplify the background seismicity so small stress changes produce large changes in seismicity rate in areas of high background seismicity similarly seismicity rate declines in the stress shadows are evident only in areas with previously high seismicity rates thus a key constituent of the model is the background seismicity rate which we smooth from 1981 to 1986 seismicity the mean correlation coefficient between observed and predicted m 1 4 shocks the minimum magnitude of completeness is 0 52 for 1986 2003 and 0 63 for 1992 2003 a control standard aftershock model yields 0 54 and 0 52 for the same periods four m 6 0 shocks struck during the test period three are located at sites where the expected seismicity rate falls above the 92 percentile and one is located above the 75 percentile the model thus reproduces much but certainly not all of the observed spatial and temporal seismicity from which we infer that the decaying effect of stress transferred by successive main shocks influences seismicity for decades finally we offer a m 5 earthquake forecast for 2005 2015 assigning probabilities to 324 10 10 km cells

extended cooling and viscous flow of large hot rhyolite lavas implications of numerical modeling results abstract a common misconception about rhyolite lava flows is that they cannot advance far from their vents and are constrained to be small due to their high viscosities although a high viscosity lava will indeed flow quite slowly it may advance a great distance if the lava efficiently retains heat and thus mobility and if the available magma supply is large to evaluate this possibility a finite difference numerical model was used to determine the rate of heat loss from units interpreted to be large rhyolite lavas cooling of such 100 300 m thick units is very slow and is further retarded by a vesicular carapace and by evolution of latent heat thermal history alone suggests that large thick lava flows could remain active for several decades to constrain the duration of flow advance of these units their inferred apparent viscosities are compared with those of active lava flows mean flow velocity of some large rhyolites in southwestern idaho usa was estimated based on the observation that the units must still have been advancing by viscous flow at the start of spherulite crystallization indicating perhaps a 10 to 18 year flow duration based on studies of obsidian dome california mean flow velocities would have been roughly 0 59 to 2 5 km yr and calculated average apparent viscosities of the flows ranged from 1 8 to 3 6 orders of magnitude greater than the viscosity of the lava itself this relationship also holds for active andesite and basaltic andesite block lava flows which have apparent viscosities 2 7 to 4 orders of magnitude greater than lava viscosities this implies that large rhyolites may indeed have been emplaced in the same manner as less silicic block lavas and that long distance viscous flow is not unrealistic for rhyolite lavas a good example of a large volume lava is the 15 km 3 rhyolite of the badlands sw idaho where vent relations show that lava effused from a fissure and advanced up to 9 km more extensive rhyolites could also be emplaced solely by effusion extended flow of these lavas may lead to the remelting and removal of basal crumble breccias and to the formation of welded shard textures in their margins both processes tending to obscure the lava flow origin of the units the great dimensions of lava like rhyolitic units with volumes of 10 to at least 200 km 3 are not a sufficient reason to assume they erupted as ignimbrites

variable fault tip propagation rates affected by near surface lithology and implications for fault displacement hazard assessment abstract the fabric of reverse fault zones close to the surface is usually partitioned in between a narrow discrete rupture zone and a more distributed one where folding is predominant this makes quite challenging the adoption of proper setbacks in surface rupture hazard studies for critical facilities or microzoning some of the parameters controlling fault zone fabric are related to mechanics of near surface geology lithology overburden thickness cohesion and water content whose interaction is complex and only partially understood nevertheless these can be seldom measured or derived kinematic models conversely express such an interaction of complex variables as simple synthetic parameters such as the amount of upward propagation of the fault tip for unit of slip usually referred to as the p s ratio propagation on slip here we discuss results on the trishear kinematic inverse modeling of a contractional fault propagation fold at monte netto hill capriano del colle n italy observing a two stage fault and fold growth evolution marked by a significant shift in the p s parameter at this site exceptional sequence of exposures due to ca 10 years of quarry excavations allowed to obtain a series of cross sections across the fault zone we use this detailed high resolution example as a natural analogue for more general large scale surface ruptures involving a thick alluvial cover a very common setting for the siting of critical facilities during the early stage of displacement the fault cut through clast supported fluvial gravels with a high propagation rate p s 7 and a discrete rupture width then during the latest movements of the thrust fault tip propagation slowed down to p s 2 9 as the fault started cutting through several stacked bodies of clays and silty clays pedogenized aeolian silts and overbank deposits causing a pronounced folding of the layers over a wider deformation zone these results strongly suggest that lithological changes in the underlying shallow stratigraphy common in an alluvial plain depositional setting would significantly affect the potential for surface faulting across the same tectonic structure with relevant implications in the fault displacement hazard assessment

omori like decay of postseismic velocities following continental earthquakes various mechanisms have been proposed to explain the transient enhanced surface deformation rates following earthquakes unfortunately these different mechanisms can produce very similar surface deformation patterns leading to difficulty in distinguishing between them here we return to the observations themselves and compile near field postseismic velocity measurements following moderate to large continental earthquakes we find that these velocities have a remarkably consistent pattern with velocity inversely proportional to time since the earthquake this suggests that postseismic velocities show an omori like decay and that postseismic displacements increase logarithmically over time these observations are inconsistent with simple linear maxwell or burgers body viscoelastic relaxation mechanisms but are consistent with rate and state frictional afterslip models and power law shear zone models the results imply that near field postseismic surface deformation measurements are primarily the result of fault zone processes and therefore that the inference of lower crustal viscosities from near field postseismic deformation requires care

tomographic inversion of local earthquake data from the hengill grensdalur central volcano complex iceland parameters is generally low however a quantitative analysis of resolution provides an unambiguous assessment of well resolved volumes within the better resolved regions of the model the averaging volumes are 1 2 km and 2 4 km in vertical and horizontal extent respectively results of tomographic inversion image three distinct bodies of anomalously high velocity two of these extend from near the surface to a depth of about 3 km these high velocity volumes are located directly beneath the surface expressions of the extinct grensdalur volcano and the extinct husmuli basalt shield the third high velocity structure occurs in the depth range of 3 4 km but does not extend to the surface these three high velocity bodies are interpreted to be solidified magmatic intrusions relatively low velocities underlay limited portions of the trace of the present accretionary axis and a low velocity body is imaged in the roots of the active hengill volcano the volume of lower velocities located beneath the surface expression of the hengill volcano is interpreted to be a region of partial melt

joint inversion of coseismic and early postseismic slip to optimize the information content in geodetic data application to the 2009 m w 6 3 l aquila earthquake central italy when analyzing the rupture of a large earthquake geodetic data are often critical these data are generally characterized by either a good temporal or a good spatial resolution but rarely both as a consequence many studies analyze the coseismic rupture with data that also include one or more days of early postseismic deformation here we invert simultaneously for the coseismic and postseismic slip with the condition that the sum of the two models remains compatible with data covering the two slip episodes we validate the benefits of this approach with a toy model and an application to the 2009 m w 6 3 l aquila earthquake using a bayesian approach and accounting for epistemic uncertainties for the l aquila earthquake we find that if early postseismic deformation is not an explicitly acknowledged coseismic signal coseismic slip models may overestimate the peak amplitude while long term postseismic models may largely underestimate the total postseismic slip amplitude this example illustrates how the proposed approach could improve our comprehension of the seismic cycle fault frictional properties and the spatial and temporal relationship between seismic rupture afterslip and aftershocks

oceanic core complex development at the ultraslow spreading mid cayman spreading center roughly a third of the global mid ocean ridge system spreads at 6 km spreading centers and thought to accrete some of the thinnest 3 km crust the mcsc generates end member mid ocean ridge basalt compositions and hosts recently discovered hydrothermal vents multibeam bathymetric data reveal that axial depth varies along the mcsc with intraridge rift walls defined by kilometer scale escarpments and massifs dredging and near bottom work has imaged and sampled predominantly basaltic lavas from the greatest axial depths and 15 peridotite surrounded by gabbroic rocks from the prominent massifs the gabbroic rocks exhibit wide compositional variation troctolites to ferrogabbros and in many places contain high temperature amphibolite to granulite facies shear zones gabbroic compositions primarily reflect the accumulation of near liquidus phases that crystallized from a range of basaltic melts as well as from interactions with interstitial melts in a subaxial mush zone magnetization variations inverted from aeromagnetic data are consistent with a discontinuous distribution of basaltic lavas and structurally asymmetric spreading these observations support an oceanic core complex model for mcsc seafloor spreading potentially making it a type example of ultraslow seafloor spreading through mush zone and detachment fault crustal processes

slow and fast ruptures on a laboratory fault controlled by loading characteristics recent geodetic observations indicate that a single fault may slip slowly and silently or fast and seismically in different circumstances we report laboratory experiments that demonstrate how the mode of faulting can alternate between fast stick slip events 70 to 500 mm s sliding rates and slow silent events 0 001 to 30 mm s as a result of loading conditions rather than friction properties or stiffness of the loading machine the 760 mm long granite sample is close to the critical nucleation length scale for unstable slip so small variations in nucleation properties result in measurable differences in slip events slow events occur when instability cannot fully nucleate before reaching the sample ends dynamic events occur after long healing times or abrupt increases in loading rate which suggests that these factors shrink the spatial and temporal extents of the nucleation zone arrays of slip strain and ground motion sensors installed on the sample allow us to quantify seismic coupling and study details of premonitory slip and afterslip we find that seismic coupling decreases when slip rates fall below about 70 mm s the slow slip events we observe are primarily aseismic less than 1 of the seismic coupling of faster events and produce swarms of very small m 6 to m 8 events these mechanical and seismic interactions suggest that faults with transitional behavior where creep small earthquakes and tremor are often observed could become seismically coupled if loaded rapidly either by a slow slip front or dynamic rupture of an earthquake that nucleated elsewhere

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

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

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

a bayesian method for incorporating self similarity into earthquake slip inversions distributions of coseismic slip help illuminate many properties of earthquakes including fault geometry stress changes frictional properties and potential future hazard slip inversions take observations and calculate slip at depth but there are a number of commonly adopted assumptions such as minimizing the second spatial derivative of slip the laplacian that have little physical basis and potentially bias the result in light of growing evidence that fault slip shows fractal properties we suggest that this information should be incorporated into slip inversions as a form of regularization instead of laplacian smoothing we have developed a bayesian approach to efficiently solve for slip incorporating von karman regularization in synthetic tests our approach retrieves fractal slip better than laplacian regularization as expected but even performs comparably or better when the input slip is not fractal we apply this to the 2014 mw 6 0 napa valley earthquake on a two segment fault using interferometric synthetic aperture radar insar and global positioning system gps data we find the von karman and laplacian inversions give similar slip magnitude but in different locations and the von karman solution has much tighter confidence bounds on slip than the laplacian solution differences in earthquake slip due to the regularization technique could have important implications for the interpretation and modeling of stress changes on the causative and neighboring faults we therefore recommend that choice of regularization method should be routinely made explicit and justified and that von karman regularization is a better default than laplacian