aftershocks of the 2010 mw 7 2 el mayor cucapah earthquake reveal complex faulting in the yuha desert california 1 we detect and precisely locate over 9500 aftershocks that occurred in the yuha desert region during a 2 month period following the 4 april 2010 mw 7 2 el mayor cucapah emc earthquake events are relocated using a series of absolute and relative relocation procedures that include hypoinverse velest and hypodd location errors are reduced to 40 m horizontally and 120 m vertically aftershock locations reveal a complex pattern of faulting with en echelon fault segments trending toward the northwest approximately parallel to the north american pacific plate boundary and en echelon conjugate features trending to the northeast the relocated seismicity is highly correlated with published surface mapping of faults that experienced triggered surface slip in response to the emc main shock aftershocks occurred between 2 km and 11 km depths consistent with previous studies of seismogenic thickness in the region three dimensional analysis reveals individual and intersecting fault planes that are limited in their along strike length these fault planes remain distinct structures at depth indicative of conjugate faulting and do not appear to coalesce onto a throughgoing fault segment we observe a complex spatiotemporal migration of aftershocks with seismicity that jumps between individual fault segments that are active for only a few days to weeks aftershock rates are roughly consistent with the expected earthquake production rates of dieterich 1994 the conjugate pattern of faulting and nonuniform aftershock migration patterns suggest that strain in the yuha desert is being accommodated in a complex manner

shallow fault zone dilatancy recovery after the 2003 bam earthquake in iran earthquakes radiate from slip on discrete faults but also commonly involve distributed deformation within a broader fault zone especially near the surface variations in rock strain during an earthquake are caused by heterogeneity in the elastic stress before the earthquake by variable material properties and geometry of the fault zones and by dynamic processes during the rupture stress changes due to the earthquake slip both dynamic and static have long been thought to cause dilatancy in the fault zone that recovers after the earthquake decreases in the velocity of seismic waves passing through the fault zone due to coseismic dilatancy have been observed followed by postseismic seismic velocity increases during healing dilatancy and its recovery have not previously been observed geodetically here we use interferometric analysis of synthetic aperture radar images to measure postseismic surface deformation after the 2003 bam iran earthquake and show reversal of coseismic dilatancy in the shallow fault zone that causes subsidence of the surface this compaction of the fault zone is directly above the patch of greatest coseismic slip at depth the dilatancy and compaction probably reflects distributed shear and damage to the material during the earthquake that heals afterwards coseismic and postseismic deformation spread through a fault zone volume may resolve the paradox of shallow slip deficits for some strike slip fault ruptures

searching for hidden earthquakes in southern california earthquakes follow a well known power law size relation with smaller events occurring much more often than larger events earthquake catalogs are thus dominated by small earthquakes yet still missing a much larger number of even smaller events caused by signal fidelity issues to overcome these limitations we applied a template matching detection technique to the entire waveform archive of the regional seismic network in southern california this effort resulted in a catalog with 1 81 million earthquakes a factor of 10 increase which provides important new insights into the geometry of fault zones at depth foreshock behavior and nucleation processes and earthquake triggering mechanisms the extraordinary detail resolved in this type of catalog will facilitate a new generation of analyses of earthquakes and faults

el mayor cucapah mw 7 2 earthquake early near field postseismic deformation from insar and gps observations el mayor cucapah earthquake occurred on 4 april 2010 in northeastern baja california just south of the u s mexico border the earthquake ruptured several previously mapped faults as well as some unidentified ones including the pescadores borrego paso inferior and paso superior faults in the sierra cucapah and the indiviso fault in the mexicali valley and colorado river delta we conducted several global positioning system gps campaign surveys of preexisting and newly established benchmarks within 30 km of the earthquake rupture most of the benchmarks were occupied within days after the earthquake allowing us to capture the very early postseismic transient motions the gps data show postseismic displacements in the same direction as the coseismic displacements time series indicate a gradual decay in postseismic velocities with characteristic time scales of 66 9 days and 20 3 days assuming exponential and logarithmic decay respectively we also analyzed interferometric synthetic aperture radar insar data from the envisat and alos satellites the main deformation features seen in the line of sight displacement maps indicate subsidence concentrated in the southern and northern parts of the main rupture in particular at the indiviso fault at the laguna salada basin and at the paso superior fault we show that the near field gps and insar observations over a time period of 5 months after the earthquake can be explained by a combination of afterslip fault zone contraction and a possible minor contribution of poroelastic rebound far field data require an additional mechanism most likely viscoelastic relaxation in the ductile substrate

adjoint tomography of the southern california crust using an inversion strategy based on adjoint methods we developed a three dimensional seismological model of the southern california crust the resulting model involved 16 tomographic iterations which required 6800 wavefield simulations and a total of 0 8 million central processing unit hours the new crustal model reveals strong heterogeneity including local changes of 30 with respect to the initial three dimensional model provided by the southern california earthquake center the model illuminates shallow features such as sedimentary basins and compositional contrasts across faults it also reveals crustal features at depth that aid in the tectonic reconstruction of southern california such as subduction captured oceanic crustal fragments the new model enables more realistic and accurate assessments of seismic hazard

accounting for uncertain fault geometry in earthquake source inversions i theory and simplified application the ill posed nature of earthquake source estimation derives from several factors including the quality and quantity of available observations and the fidelity of our forward theory observational errors are usually accounted for in the inversion process epistemic errors which stem from our simplified description of the forward problem are rarely dealt with despite their potential to bias the estimate of a source model in this study we explore the impact of uncertainties related to the choice of a fault geometry in source inversion problems the geometry of a fault structure is generally reduced to a set of parameters such as position strike and dip for one or a few planar fault segments while some of these parameters can be solved for more often they are fixed to an uncertain value we propose a practical framework to address this limitation by following a previously implemented method exploring the impact of uncertainties on the elastic properties of our models we develop a sensitivity analysis to small perturbations of fault dip and position the uncertainties of our fixed fault geometry are included in the inverse problem under the formulation of the misfit covariance matrix that combines both prediction and observation uncertainties we validate this approach with the simplified case of a fault that extends infinitely along strike using both bayesian and optimization formulations of a static slip inversion if epistemic errors are ignored predictions are overconfident in the data and slip parameters are not reliably estimated in contrast inclusion of uncertainties in fault geometry allows us to infer a robust posterior slip model epistemic uncertainties can be many orders of magnitude larger than observational errors for great earthquakes mw 8 not accounting for uncertainties in fault geometry may partly explain observed shallow slip deficits for continental earthquakes similarly ignoring the impact of epistemic errors can also bias estimates of near surface slip and predictions of tsunamis induced by megathrust earthquakes

measuring ground displacements from sar amplitude images application to the landers earthquake ers sar amplitude images are utilized to map ground displacements from a sub pixel correlation method it yields a ground two dimensional displacement field with independent measurements about every 128m in azimuth and 250m in range the accuracy depends on the characteristics of the images for the landers test case the 1 uncertainty is 0 8m in range and 0 4m in azimuth we show that this measurement provides a map of major surface fault ruptures accurate to better than 1km and information on coseismic deformation comparable to the 92 gps measurements available although less accurate this technique is more robust than sar interferometry and provides complementary information since interferograms are only sensitive to the displacement in range

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

fault geometry inversion and slip distribution of the 2010 mw 7 2 el mayor cucapah earthquake from geodetic data author s huang mh fielding ej dickinson h sun j gonzalez ortega ja freed am burgmann r abstract 2016 american geophysical union all rights reserved the 4 april 2010 mw 7 2 el mayor cucapah emc earthquake in baja california and sonora mexico had primarily right lateral strike slip motion and a minor normal slip component the surface rupture extended about 120 km in a nw se direction west of the cerro prieto fault here we use geodetic measurements including near to far field gps interferometric synthetic aperture radar insar and subpixel offset measurements of radar and optical images to characterize the fault slip during the emc event we use dislocation inversion methods and determine an optimal nine segment fault geometry as well as a subfault slip distribution from the geodetic measurements with systematic perturbation of the fault dip angles randomly removing one geodetic data constraint or different data combinations we are able to explore the robustness of the inferred slip distribution along fault strike and depth the model fitting residuals imply contributions of early postseismic deformation to the insar measurements as well as lateral heterogeneity in the crustal elastic structure between the peninsular ranges and the salton trough we also find that with incorporation of near field geodetic data and finer fault patch size the shallow slip deficit is reduced in the emc event by reductions in the level of smoothing these results show that the outcomes of coseismic inversions can vary greatly depending on model parameterization and methodology

coseismic slip variation assessed from terrestrial lidar scans of the el mayor cucapah surface rupture abstract we analyze high resolution 103 points m2 terrestrial lidar surveys of the 4 april 2010 el mayor cucapah earthquake rupture baja california mexico collected at three sites 12 18 days after the event using point cloud based tools in an immersive visualization environment we quantify coseismic fault slip for hundreds of meters along strike and construct densely constrained along strike slip distributions from measurements of offset landforms uncertainty bounds for each offset determined empirically by repeatedly measuring offsets at each site sequentially illuminate measurement uncertainties that are difficult to quantify in the field these uncertainties are used to define length scales over which variability in slip distributions may be assumed to reflect either recognizable earthquake mechanisms or measurement noise at two sites characterized by 2 3 m of concentrated right oblique slip repeat measurements yield 2 uncertainties of 11 12 each site encompasses 200 m along strike and a smoothed linear slip gradient satisfies all measurement distributions implying along fault strains of 10 3 conversely the common practice of defining the slip curve by the local slip maxima distorts the curve overestimates along fault strain and may overestimate actual fault slip by favoring measurements with large positive uncertainties at a third site characterized by 1 2 5 m of diffuse normal slip repeat measurements of fault throw summed along fault perpendicular profiles yield 2 uncertainties of 17 here a low order polynomial fit through the measurement averages best approximates surface slip however independent measurements of off fault strain accommodated by hanging wall flexure suggest that over the 200 m length of this site a linear interpolation through the average values for the slip maxima at either end of this site most accurately represents subsurface displacement in aggregate these datasets show that given uncertainties of greater than 11 2 slip distributions over shorter scales are likely to be less uneven than those derived from a single set of field or lidar based measurements this suggests that the relatively smooth slip curves we obtain over 102 m distances reflect real physical phenomena whereas short wavelength variability over 100 101 m distances can be attributed to measurement uncertainty

near field deformation from the el mayor cucapah earthquake revealed by differential lidar large moment magnitude m w 7 continental earthquakes often generate complex multifault ruptures linked by enigmatic zones of distributed deformation here we report the collection and results of a high resolution nine returns per square meter airborne light detection and ranging lidar topographic survey of the 2010 m w 7 2 el mayor cucapah earthquake that produced a 120 kilometer long multifault rupture through northernmost baja california mexico this differential lidar survey completely captures an earthquake surface rupture in a sparsely vegetated region with pre earthquake lower resolution 5 meter pixel lidar data the postevent survey reveals numerous surface ruptures including previously undocumented blind faults within thick sediments of the colorado river delta differential elevation changes show distributed kilometer scale bending strains as large as 10 3 microstrains in response to slip along discontinuous faults cutting crystalline bedrock of the sierra cucapah

the 2010 m w 7 2 el mayor cucapah earthquake sequence baja california mexico and southernmost california usa active seismotectonics along the mexican pacific margin the el mayor cucapah earthquake sequence started with a few foreshocks in march 2010 and a second sequence of 15 foreshocks of m 2 up to m4 4 that occurred during the 24 h preceding the mainshock the foreshocks occurred along a north south trend near the mainshock epicenter the mw 7 2 mainshock on april 4 exhibited complex faulting possibly starting with a m6 normal faulting event followed 15 s later by the main event which included simultaneous normal and right lateral strike slip faulting the aftershock zone extends for 120 km from the south end of the elsinore fault zone north of the us mexico border almost to the northern tip of the gulf of california the waveform relocated aftershocks form two abutting clusters each about 50 km long as well as a 10 km north south aftershock zone just north of the epicenter of the mainshock even though the baja california data are included the magnitude of completeness and the hypocentral errors increase gradually with distance south of the international border the spatial distribution of large aftershocks is asymmetric with five m5 aftershocks located to the south of the mainshock and only one m5 7 aftershock but numerous smaller aftershocks to the north further the northwest aftershock cluster exhibits complex faulting on both northwest and northeast planes thus the aftershocks also express a complex pattern of stress release along strike the overall rate of decay of the aftershocks is similar to the rate of decay of a generic california aftershock sequence in addition some triggered seismicity was recorded along the elsinore and san jacinto faults to the north but significant northward migration of aftershocks has not occurred the synthesis of the el mayor cucapah sequence reveals transtensional regional tectonics including the westward growth of the mexicali valley and the transfer of pacific north america plate motion from the gulf of california in the south into the southernmost san andreas fault system to the north we propose that the location of the 2010 el mayor cucapah as well as the 1992 landers and 1999 hector mine earthquakes may have been controlled by the bends in the plate boundary

quasi static dislocations in three dimensional inhomogeneous media we present an approximate perturbation method for computing surface displacement fields due to quasi static dislocations in inhomogeneous elastic half spaces extending the work of du et al 1994 to three dimensions three dimensional methods are required to model geodetic observations the perturbation method allows one to include more realistic earth structure in the analysis of surface deformation measurements and is computationally efficient enough to be used in inversions for source properties as an example we investigate the effect of material inhomogeneity on the location of the fault plane for the 1989 kalapana hawaii earthquake inversion of coseismic elevation changes assuming a homogeneous half space yielded a finite source depth markedly shallower than the mainshock and principal aftershocks arnadottir et al 1991 incorporation of lateral and vertical variations in shear modulus consistent with velocity and density data yields a source depth more consistent with the seismic results failure to account for variations in elastic properties can bias estimates of source depth and moment

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

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

some thoughts on measuring earthquake deformation using optical imagery optical imagery has been proven to be an effective tool for measuring earthquake deformation in continental regions since its first application in the 1999 izmit earthquake in this article we compile and analyze all the earthquakes that have been investigated with optical image matching by 2019 based on which we comment on various issues regarding measuring earthquake deformation with optical imagery new generations of very high resolution vhr data are effective for earthquake studies but orthorectification of the vhr images is the major source of error which is often ignored we found that the displacements derived from the worldview images strongly correlate with the errors in the shuttle radar topography mission srtm digital elevation model dem that was used in orthorectification based on the observed correlation between displacements and topography we propose a new dem based method using the advanced land observing satellite alos world 3 d dem to reduce the orthorectification errors combining the published optical data of earthquake deformation we re analyze the coseismic slip distribution and shallow slip deficit ssd the ssd model states that the coseismic slip in many strike slip earthquakes decreases in magnitude toward the surface but this model remains arguable because the interferometric synthetic aperture radar insar derived slip is usually not well constrained at shallow depths due to decorrelation because optical matching directly measures the surface slip we re examine the slip distribution of 11 strike slip earthquakes and find that the ssd model may primarily be artifacts in the insar measurements it is therefore of great importance to include the optical data in earthquake studies to constrain coseismic slip inversions

assessing long term postseismic deformation following the m7 2 4 april 2010 el mayor cucapah earthquake with implications for lithospheric rheology in the salton trough the 4 april 2010 mw 7 2 el mayor cucapah emc earthquake provides the best opportunity to date to study the lithospheric response to a large m6 magnitude earthquake in the salton trough region through analysis of global positioning system gps data in conjunction with the earthscope plate boundary observatory pbo we installed six new continuous gps stations in the months following the emc earthquake to increase station coverage in the epicentral region of northern baja california mexico we modeled the pre emc deformation field using available campaign and continuous gps data for southern california and northern baja california and inferred a pre emc secular rate at each new station location through direct comparison of the pre and post emc secular rates we calculate long term changes associated with viscoelastic relaxation in the salton trough region we fit these velocity changes using numerical models employing an elastic upper crustal layer underlain by a viscoelastic lower crustal layer and a mantle half space forward models that produce the smallest weighted sum of squared residuals have an upper mantle viscosity in the range 4 6 1018 pa s and a less well resolved lower crustal viscosity in the range 2 1019 to 1 1022 pa s a high viscosity lower crust despite high heat flow in the salton trough region is inconsistent with felsic composition and might suggest accretion of mafic lower crust associated with crustal spreading obscured by thick sedimentary cover

superficial simplicity of the 2010 el mayor cucapah earthquake of baja california in mexico the geometry of faults is usually thought to be more complicated at the surface than at depth and to control the initiation propagation and arrest of seismic ruptures the fault system that runs from southern california into mexico is a simple strike slip boundary the west side of california and mexico moves northwards with respect to the east however the m w 7 2 2010 el mayor cucapah earthquake on this fault system produced a pattern of seismic waves that indicates a far more complex source than slip on a planar strike slip fault here we use geodetic remote sensing and seismological data to reconstruct the fault geometry and history of slip during this earthquake we find that the earthquake produced a straight 120 km long fault trace that cut through the cucapah mountain range and across the colorado river delta however at depth the fault is made up of two different segments connected by a small extensional fault both segments strike n130 e but dip in opposite directions the earthquake was initiated on the connecting extensional fault and 15 s later ruptured the two main segments with dominantly strike slip motion we show that complexities in the fault geometry at depth explain well the complex pattern of radiated seismic waves we conclude that the location and detailed characteristics of the earthquake could not have been anticipated on the basis of observations of surface geology alone

complex multifault rupture during the 2016 mw 7 8 kaikōura earthquake new zealand the 2016 moment magnitude m w 7 8 kaik ura earthquake was one of the largest ever to hit new zealand hamling et al show with a new slip model that it was an incredibly complex event unlike most earthquakes multiple faults ruptured to generate the ground shaking a remarkable 12 faults ruptured overall with the rupture jumping between faults located up to 15 km away from each other the earthquake should motivate rethinking of certain seismic hazard models which do not presently allow for this unusual complex rupture pattern science this issue p eaam7194 1 1 lookup doi 10 1126 science aam7194

post large earthquake seismic activities mediated by aseismic deformation processes abstract two aseismic deformation processes are commonly invoked to explain the transient geodetic surface displacements that follow a major earthquake afterslip and viscoelastic relaxation both induce time dependent stress variations in the crust potentially affecting aftershock occurrence however the two mechanisms relative impacts on crustal deformation and seismicity remain unclear we find for the case of the 2010 mw 7 2 el mayor cucapah emc earthquake not only that afterslip likely drove clustered seismicity after the earthquake but also that long range earthquake interactions were likely modulated by viscoelastic relaxation at large scales in space 5 times the fault rupture length and time 7 yr this has important implications for the study of the seismic cycle and for seismic hazard estimation since post seismic deformation related to a single mw 7 2 earthquake affects interseismic velocities and regional seismicity rates for more than a decade

dynamic rupture modeling of the m7 2 2010 el mayor cucapah earthquake comparison with a geodetic model author s kyriakopoulos c oglesby dd funning gj ryan kj abstract 2017 american geophysical union all rights reserved the 2010 mw 7 2 el mayor cucapah earthquake is the largest event recorded in the broader southern california baja california region in the last 18nyears here we try to analyze primary features of this type of event by using dynamic rupture simulations based on a multifault interface and later compare our results with space geodetic models our results show that starting from homogeneous prestress conditions slip heterogeneity can be achieved as a result of variable dip angle along strike and the modulation imposed by step over segments we also considered effects from a topographic free surface and find that although this does not produce significant first order effects for this earthquake even a low topographic dome such as the cucapah range can affect the rupture front pattern and fault slip rate finally we inverted available interferometric synthetic aperture radar data using the same geometry as the dynamic rupture model and retrieved the space geodetic slip distribution that serves to constrain the dynamic rupture models the one to one comparison of the final fault slip pattern generated with dynamic rupture models and the space geodetic inversion show good agreement our results lead us to the following conclusion in a possible multifault rupture scenario and if we have first order geometry constraints dynamic rupture models can be very efficient in predicting large scale slip heterogeneities that are important for the correct assessment of seismic hazard and the magnitude of future events our work contributes to understanding the complex nature of multifault systems

synthetic aperture radar interferometry to measure earth s surface topography and its deformation synthetic aperture radar interferometry insar from earth orbiting spacecraft provides a new tool to map global topography and deformation of the earth s surface radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter scale accuracy these data sets aid in the analysis and interpretation of tectonic and volcanic landscapes if the earth s surface deformed between two radar image acquisitions a map of the surface dis placement with tens of meters resolution and subcentimeter accuracy can be con structed this review gives a basic overview of insar for earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of insar for mapping the topography and deformation of the earth

the 2016 m7 kumamoto japan earthquake slip field derived from a joint inversion of differential lidar topography optical correlation and insar surface displacements

real time centroid moment tensor determination for large earthquakes from local and regional displacement records summary we present an algorithm to rapidly determine the moment tensor and centroid location for large earthquakes employing local and regional real time high rate displacement records from gps the algorithm extracts the coseismic offset from the displacement waveforms and uses the information to invert for the moment tensor the green s functions for a layered earth are obtained numerically from open source code edgrn to determine the centroid multiple inversions are simultaneously performed within a grid of inversion nodes and the node with the smallest misfit is then assigned the centroid location we show results for two large earthquakes replayed in simulated real time mode using recorded 1 hz gps displacements the 2003 mw 8 3 tokachi oki and the 2010 mw 7 2 el mayor cucapah earthquakes we demonstrate that it is feasible to obtain accurate cmt solutions within the first 2 3 min after rupture initiation without any prior assumptions on fault characteristics demonstrating an order of magnitude improvement in latency compared to existing seismic methods for the two earthquakes studied this methodology is useful for rapid earthquake response tsunami prediction and as a starting point for rapid finite fault modelling

refining the shallow slip deficit geodetic slip inversions for three major m w 7 strike slip earthquakes 1992 landers 1999 hector mine and 2010 el mayor cucapah show a 15 60 per cent reduction in slip near the surface depth 2 km relative to the slip at deeper depths 4 6 km this significant difference between surface coseismic slip and slip at depth has been termed the shallow slip deficit ssd the large magnitude of this deficit has been an enigma since it cannot be explained by shallow creep during the interseismic period or by triggered slip from nearby earthquakes one potential explanation for the ssd is that the previous geodetic inversions lack data coverage close to surface rupture such that the shallow portions of the slip models are poorly resolved and generally underestimated in this study we improve the static coseismic slip inversion for these three earthquakes especially at shallow depths by 1 including data capturing the near fault deformation from optical imagery and sar azimuth offsets 2 refining the interferometric synthetic aperture radar processing with non boxcar phase filtering model dependent range corrections more complete phase unwrapping by snaphu statistical non linear approach for phase unwrapping assuming a maximum discontinuity and an on fault correlation mask 3 using more detailed geologically constrained fault geometries and 4 incorporating additional campaign global positioning system gps data the refined slip models result in much smaller ssds of 3 19 per cent we suspect that the remaining minor ssd for these earthquakes likely reflects a combination of our elastic model s inability to fully account for near surface deformation which will render our estimates of shallow slip minima and potentially small amounts of interseismic fault creep or triggered slip which could make up a small percentages of the coseismic ssd during the interseismic period our results indicate that it is imperative that slip inversions include accurate measurements of near fault surface deformation to reliably constrain spatial patterns of slip during major strike slip earthquakes

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

the combined inversion of seismic and geodetic data for the source process of the 16 october 1999 mw 7 1 hector mine california earthquake we investigate the source process of the m w 7 1 hector mine earthquake by inverting broadband regional and local seismic displacement waveforms com bined with global positioning system gps and synthetic aperture radar interfer ometry insar geodetic measurements we find that the three data sets individually produce remarkably similar slip distributions over a multisegment fault a simulta neous inversion of the three data sets is presented and the sensitivity of the combined inversion to the weighting of the three independent data sets is examined the results indicate that the overall length of the fault that slipped is 42 km with a peak slip of 5 50 m and total scalar seismic moment of 6 8 10 19 n m the majority of slip is located on the western branch of the lavic lake fault to the northwest of the hypo center although the overall rupture is bilateral with appreciable slip on the bullion fault to the southeast some slip is located on an eastern branch of the lavic lake fault an apparent bifurcation which is also evident from aftershock locations the average slip and stress drops are 2 70 1 62 1 60 m and 78 36 and 55 bars for the western lavic lake the eastern lavic lake and bullion faults respectively the results also indicate that the overall rupture process is relatively slow which is char acterized by a several second delay before the onset of significant slip a 1 8 km sec rupture velocity of the primary asperity and long spatially variable dislocation rise times

seismicity of the hengill area sw iceland details revealed by catalog relocation and collapsing seismicity of the hengill area sw iceland details revealed by catalog relocation and collapsing

the 2020 mw 6 8 elazig turkey earthquake reveals rupture behavior of the east anatolian fault the 2020 mw 6 8 elazig earthquake was the largest along the eastern anatolian fault eaf in over a century and so provides valuable insights into its rupture behavior because the eaf is of low to

the effect of elastic layering on inversions of gps data for coseismic slip and resulting stress changes strike slip earthquakes we investigate the effect of depth dependent elasticity on slip inversions and coseismic stress change estimates for large strike slip earthquakes using a series of hypothetical models and the 1999 izmit turkey earthquake as examples slip inversions are performed using both semianalytical and finite element solutions for surface displacements due to a shear dislocation in layered and uniform elastic earth models we find that incorporating realistic increases to shear modulus with depth in our inversions increases recovered centroid depth and seismic potency relative to uniform elastic half space models recovered seismic moment is up to 40 greater for models incorporating depth dependent than it is for uniform elastic half space models incorporating depth dependent also increases our estimate of the maximum slip depth for the izmit turkey earthquake to at least 20 km our estimates of coseismic stress change in the upper crust do not change significantly when we incorporate depth dependent elasticity in our inversions as long as slip at depth is tuned increased to match surface displacements coseismic differential stresses in the lower crust increase by up to a factor of 3 in the near field but further from the fault stresses from layered and uniform elastic models are approximately equal with increasing depth in the mantle the ratio of modeled differential stresses for the layered and uniform elastic models approaches the ratio of mantle values for these two models we conclude that models of postseismic viscoelastic relaxation following large strike slip earthquakes should incorporate depth dependent elasticity but that uniform elastic half space models are adequate to calculate coseismic coulomb stresses in the upper crust for most triggering studies

quantifying near field and off fault deformation patterns of the 1992 mw 7 3 landers earthquake coseismic surface deformation in large earthquakes is typically measured using field mapping and with a range of geodetic methods e g insar lidar differencing and gps current methods however either fail to capture patterns of near field coseismic surface deformation or lack preevent data consequently the characteristics of off fault deformation and the parameters that control it remain poorly understood we develop a standardized method to fully measure the surface near field coseismic deformation patterns at high resolution using the cosi corr program by correlating pairs of aerial photographs taken before and after the 1992 m w 7 3 landers earthquake cosi corr offers the advantage of measuring displacement across the entire zone of surface deformation and over a wider aperture than that available to field geologists for the landers earthquake our measured displacements are systematically larger than the field measurements indicating the presence of off fault deformation we show that 46 of the total surface displacement occurred as off fault deformation over a mean deformation width of 154 m the magnitude and width of off fault deformation along the rupture is primarily controlled by the macroscopic structural complexity of the fault system with a weak correlation with the type of near surface materials through which the rupture propagated both the magnitude and width of distributed deformation are largest in stepovers bends and at the southern termination of the surface rupture we find that slip along the surface rupture exhibits a consistent degree of variability at all observable length scales and that the slip distribution is self affine fractal with dimension of 1 56

inferred rheological structure and mantle conditions from postseismic deformation following the 2010 mw 7 2 el mayor cucapah earthquake author s dickinson lovell h huang mh freed am fielding e burgmann r andronicos c abstract the author s 2017 the 2010mw7 2elmayor cucapah earthquake provides a unique target of postseismic study as deformation extends across several distinct geological provinces including the coldmesozoic arc crust of the peninsular ranges and newly formed hot extending lithosphere within the salton trough we use five years of global positioning system measurements to invert for afterslip and constrain a 3 d finite element model that simulates viscoelastic relaxation we find that afterslip cannot readily explain far field displacements more than 50 km from the epicentre these displacements are best explained by viscoelastic relaxation of a horizontally and vertically heterogeneous lower crust and upper mantle lower viscosities beneath the salton trough compared to the peninsular ranges and other surrounding regions are consistent with inferred differences in the respective geotherms our inferred viscosity structure suggests that the depth of the lithosphere asthenosphere boundary lab is 65 km below the peninsular ranges and 32 km beneath the salton trough these depths are shallower than the corresponding seismic lab this suggests that the onset of partial melting in peridotite may control the depth to the base of the mechanical lithosphere in contrast the seismic lab may correspond to an increase in the partial melt percentage associated with the change from a conductive to an adiabatic geotherm

joint inversion of seismic and geodetic data for the source of the 2010 march 4 mw 6 3 jia shian sw taiwan earthquake

effects of superficial layers on coseismic displacements for a dip slip fault and geophysical implications summary we study the effect of a superficial layer overlying a half space on the surface displacements created by a dip slip dislocation on a planar rectangular fault using a 2 d finite element model the effect of the density and poisson s ratio is negligible on the other hand the contrast in young s modulus between the top layer and the half space below significantly affects the modelled coseismic displacements the horizontal displacements are more sensitive than the vertical displacements to the existence of the top layer near the fault a low rigidity layer with a young s modulus of 10 gpa can increase the horizontal displacements by up to 40 per cent an analytical 3 d half space model is used to interpret this effect in terms of an equivalent homogeneous model the presence of a top layer can be partly simulated in a homogeneous half space by perturbing the depth and the slip on the fault from their real values to equivalent values for a given displacement field observed at the surface the perturbations in fault depth and slip can reach 1 km and 25 per cent respectively the fault dip angle is not model dependent we conclude that for the accurate estimation of fault depth and slip from coseismic geodetic data rigidity contrasts existing within the upper crust must be taken into account not taking into account the effect of an existing low rigidity layer also leads to an underestimation of seismic moment release this may in part be the cause of apparent discrepancies between seismic and geodetic moment releases in particular areas such as the gulf of corinth greece

a three step maximum a posteriori probability method for insar data inversion of coseismic rupture with application to the 14 april 2010 mw 6 9 yushu china earthquake 1 we develop a three step maximum a posteriori probability method for coseismic rupture inversion which aims at maximizing the a posterior probability density function pdf of elastic deformation solutions of earthquake rupture the method originates from the fully bayesian inversion and mixed linear nonlinear bayesian inversion methods and shares the same posterior pdf with them while overcoming difficulties with convergence when large numbers of low quality data are used and greatly improving the convergence rate using optimization procedures a highly efficient global optimization algorithm adaptive simulated annealing is used to search for the maximum of a posterior pdf mode in statistics in the first step the second step inversion approaches the true solution further using the monte carlo inversion technique with positivity constraints with all parameters obtained from the first step as the initial solution then slip artifacts are eliminated from slip models in the third step using the same procedure of the second step with fixed fault geometry parameters we first design a fault model with 45 dip angle and oblique slip and produce corresponding synthetic interferometric synthetic aperture radar insar data sets to validate the reliability and efficiency of the new method we then apply this method to insar data inversion for the coseismic slip distribution of the 14 april 2010 mw 6 9 yushu china earthquake our preferred slip model is composed of three segments with most of the slip occurring within 15 km depth and the maximum slip reaches 1 38 m at the surface the seismic moment released is estimated to be 2 32e 19 nm consistent with the seismic estimate of 2 50e 19 nm

space based mapping of glacier changes using aster and gis tools we describe an investigation that combines space based observations of glacier parameters with historical glaciological data derived by traditional means to predict changes in ice extent and volume for the ak shirak range in the interior tien shan of central asia a variety of geographic information systems and photogrammetric tools are used to extract glacier outlines derive of a digital elevation model and compute area versus elevation distribution functions from data acquired by the advanced spaceborne thermal emission and reflection radiometer these products are then used in a glaciological methodology that can predict the response of glacier systems to changes in local climate

surface ruptures and building damage of the 2003 bam iran earthquake mapped by satellite synthetic aperture radar interferometric correlation 1 we use the interferometric correlation from envisat synthetic aperture radar sar images to map the details of the surface ruptures related to the 26 december 2003 earthquake that devastated bam iran the main strike slip fault rupture south of the city of bam has a series of four segments with left steps shown by a narrow line of low correlation in the coseismic interferogram this also has a clear expression in the field because of the net extension across the fault just south of the city limits the surface strain becomes distributed over a width of about 500 m probably because of a thicker layer of soft sedimentary material another fault north of bam shows offset and low correlation over a wider zone in the interferograms but it has no discrete surface rupture possibly because of a net shortening across this fault taking the difference between the interferometric correlation for an interval including the earthquake and an interval before the earthquake separates the changes due to the earthquake from other effects in the partially vegetated city of bam we map the damage to buildings by measuring the change from high correlation to low correlation where buildings were destroyed by the earthquake

coseismic deformation from the 1999 mw 7 1 hector mine california earthquake as inferred from insar and gps observations we use interferometric synthetic aperture radar insar and global positioning system gps observations to investigate static deformation due to the 1999 m w 7 1 hector mine earthquake that occurred in the eastern california shear zone interferometric decorrelation phase and azimuth offset measurements indicate regions of surface and near surface slip which we use to constrain the geometry of surface rupture the inferred geometry is spatially complex with multiple strands the southern third of the rupture zone consists of three subparallel segments extending about 20 km in length in a n45 w direction the central segment is the simplest with a single strand crossing the bullion mountains and a strike of n10 w the northern third of the rupture zone is characterized by multiple splays with directions subparallel to strikes in the southern and central the average strike for the entire rupture is about n30 w the interferograms indicate significant along strike variations in strain which are consistent with variations in the ground based slip measurements using a variable resolution data sampling routine to reduce the computational burden we invert the insar and gps data for the fault geometry and distribution of slip we compare results from assuming an elastic half space and a layered elastic space results from these two elastic models are similar although the layered space model predicts more slip at depth than does the half space model the layered model predicts a maximum coseismic slip of more than 5 m at a depth of 3 to 6 km contrary to preliminary reports the northern part of the hector mine rupture accommodates the maximum slip our model predictions for the surface fault offset and total seismic moment agree with both field mapping results and recent seismic models the inferred shallow slip deficit is enigmatic and may suggest that distributed inelastic yielding occurred in the uppermost few kilometers of the crust during or soon after the earthquake