relationships among seismic velocity metamorphism and seismic and aseismic fault slip in the salton sea geothermal field region the salton sea geothermal field is one of the most geothermally and seismically active areas in california and presents an opportunity to study the effect of high temperature metamorphism on the properties of seismogenic faults the area includes numerous active tectonic faults that have recently been imaged with active source seismic reflection and refraction we utilize the active source surveys along with the abundant microseismicity data from a dense borehole seismic network to image the 3 d variations in seismic velocity in the upper 5 km of the crust there are strong velocity variations up to 30 that correlate spatially with the distribution of shallow heat flow patterns the combination of hydrothermal circulation and high temperature contact metamorphism has significantly altered the shallow sandstone sedimentary layers within the geothermal field to denser more feldspathic rock with higher p wave velocity as is seen in the numerous exploration wells within the field this alteration appears to have a first order effect on the frictional stability of shallow faults in 2005 a large earthquake swarm and deformation event occurred analysis of interferometric synthetic aperture radar data and earthquake relocations indicates that the shallow aseismic fault creep that occurred in 2005 was localized on the kalin fault system that lies just outside the region of high temperature metamorphism in contrast the earthquake swarm which includes all of the m 4 earthquakes to have occurred within the salton sea geothermal field in the last 15 years ruptured the main central fault mcf system that is localized in the heart of the geothermal anomaly the background microseismicity induced by the geothermal operations is also concentrated in the high temperature regions in the vicinity of operational wells however while this microseismicity occurs over a few kilometer scale region much of it is clustered in earthquake swarms that last from hours to a few days and are localized near the mcf system

detecting tides and gravity at europa from multiple close flybys 1 this paper presents the expected accuracy of the tides and gravity of europa that can be measured by tracking a spacecraft during close flybys of europa a reference trajectory was designed for flyby science observations and consists of a total of 36 flybys of europa at 100 km altitude earth based doppler measurements were created during 2 hours of each periapsis passage and were simulated with realistic dynamical and measurement assumptions the result shows that the degree 2 tidal love number k2 can be estimated to k2 0 045 and k2 0 009 1 sigma formal uncertainty assuming x band and ka band tracking capabilities respectively which is sufficient to confirm the existence of a global subsurface ocean

enso simulated by intermediate coupled models and evaluated with observations over 1970 98 part ii role of the off equatorial ocean and meridional winds introducing new parameterizations of subsurface temperature and atmospheric convection in the cane and zebiak model allows the reproducing of oscillations with a period close to 4 yr equatorial wind anomalies that are located close to the date line and realistic amplitudes of sst wind and thermocline anomalies in the equatorial pacific both in warm and cold phases when the weight given to the atmospheric convection term is increased the simulated wind maximum along the equator is displaced farther west and the amplitude and duration of the warm events decrease compared to the simulations with the standard parameterization the enso like oscillations are not lost when the friction is increased with a decay time ranging from 30 to 12 months off equatorial baroclinic ocean and wind anomalies are much less strong but still necessary for the system to oscillate unrealistic easterlies are still present in the eastern pacific replacing the atmospheric model by a statistical relationship between sst and wind stress anomalies allows further reducing of these deficiencies the simulated enso like events are in good agreement with observed oceanic and atmospheric fields in terms of amplitude and spatial patterns within 158 of the equator sensitivity tests to the statistics prescribed in the atmospheric component show that the model simulates warm events with duration and amplitude that increase with the eastern penetration of the westerlies in the central pacific whereas cold events do not last longer and easterlies remain located at the date line whatever their strength after warm events the model simulates a gain of heat content on average in the north and similar features are found in

combination of precise leveling and insar data to constrain source parameters of the mw 6 5 26 december 2003 bam earthquake we used new precise leveling data acquired 40 days after the bam earthquake in combination with radar interferometry observations from both ascending and descending orbits to investigate static deformation associated with the 2003 bam earthquake we invert this geodetic data set to gain insight into the fault geometry and slip distribution of the rupture the best fitting dislocation model is a steeply east dipping right lateral strike slip fault that has a size of 11 by 8 km and strikes n2 w we find that such smooth geometry fits available geodetic data better than previously proposed models for this earthquake our distributed slip model indicates a maximum strike slip of 3 m occurring about 3 to 5 km deep the slip magnitude and depth of faulting taper to the north where the fault approaches the bam city inclusion of crustal layering increases the amount of maximum slip inferred at depth by about 4

ball and socket tectonic rotation during the 2013 mw7 7 balochistan earthquake abstract the september 2013 m w 7 7 balochistan earthquake ruptured a 200 km long segment of the curved hoshab fault in southern pakistan with 10 0 2 m of peak sinistral and 1 7 0 8 m of dip slip this rupture is unusual because the fault dips 60 15 towards the focus of a small circle centered in northwest pakistan and despite a 30 increase in obliquity along strike the ratios of strike and dip slip remain relatively uniform surface displacements and geodetic and teleseismic source inversions quantify a bilateral rupture that propagated rapidly at shallow depths from a transtensional jog near the northern end of the rupture static friction prior to rupture was unusually weak 0 05 and friction may have approached zero during dynamic rupture here we show that the inward dipping hoshab fault defines the northern rim of a structural unit in southeast makran that rotates akin to a 2 d ball and socket joint counter clockwise in response to india s penetration into the eurasian plate this rotation accounts for complexity in the chaman fault system and in principle reduces seismic potential near karachi nonetheless these findings highlight deficiencies in strong ground motion equations and tectonic models that invoke anderson byerlee faulting predictions

shallow slip deficit due to large strike slip earthquakes in dynamic rupture simulations with elasto plastic off fault response summary slip inversions of geodetic data from several large magnitude 7 strike slip earthquakes point to coseismic slip deficit at shallow depths 3 4 km that is coseismic slip appears to decrease towards the earth surface while the inferred slip distribution may be consistent with laboratory derived rate and state friction laws suggesting that the uppermost brittle crust may be velocity strengthening there remains a question of how the coseismic slip deficit is accommodated throughout the earthquake cycle the consequence of velocity strengthening fault friction at shallow depths is that the deficit of coseismic slip is relieved by post seismic afterslip and interseismic creep however many seismic events with inferred shallow slip deficit were not associated with either resolvable shallow interseismic creep or robust shallow afterslip hence the origin of shallow slip deficit remains uncertain in this study we investigate whether inelastic failure in the shallow crust due to dynamic earthquake rupture can explain the inferred deficit of shallow slip evidence for such failure is emerging from geologic seismic and geodetic observations we find that the amount of shallow slip deficit is proportional to the amount of inelastic deformation near the earth surface such deformation occurs under a wide range of parameters that characterize rock strength in the upper crust however the largest magnitude of slip deficit in models accounting for off fault yielding is 2 4 times smaller than that inferred from kinematic inversions of geodetic data to explain this discrepancy we further explore to what extent assumptions in the kinematic inversions may bias the inferred slip distributions inelastic deformation in the shallow crust reduces coseismic strain near the fault introducing an additional artificial deficit of up to 10 per cent of the maximum slip in inversions of geodetic data that are based on purely elastic models the largest magnitude of slip deficit in our models combined with the bias in inversions accounts for up to 25 per cent of shallow slip deficit which is comparable but still smaller than 30 60 per cent deficit inferred from kinematic inversions we discuss potential mechanisms that may account for the remaining discrepancy between slip deficit predicted by elasto plastic rupture models and that inferred from inversions of space geodetic data

inelastic surface deformation during the 2013 mw 7 7 balochistan pakistan earthquake comprehensive quantification of the near field deformation associated with an earthquake is difficult due to the inherent complexity of surface ruptures the a d 2013 m w 7 7 balochistan pakistan earthquake dominated by left lateral motion with some reverse component ruptured a 200 km long section of the hoshab fault we characterize the coseismic rupture in detail along its entire length optical and radar satellite images are combined to derive the full three dimensional far field displacement 115 m pixel size and the high resolution 2 5 m pixel horizontal displacement field resulting from the earthquake we show that the vertical deformation is significant in several locations the high resolution near field horizontal displacement 1 km around the rupture reveals inelastic shortening at the fault surface significantly larger than expected from simple elastic modeling a zone of extension in the hanging wall as much as 1 km wide concentrating numerous tensile cracks visible in submeter scale optical images compensates for this excess shortening

surface slip and off fault deformation patterns in the 2013 mw 7 7 balochistan pakistan earthquake implications for controls on the distribution of near surface coseismic slip comparison of 398 fault offsets measured by visual analysis of worldview high resolution satellite imagery with deformation maps produced by cosi corr subpixel image correlation of landsat 8 and spot5 imagery reveals significant complexity and distributed deformation along the 2013 mw 7 7 balochistan pakistan earthquake average slip along the main trace of the fault was 4 2 m with local maximum offsets up to 11 4 m comparison of slip measured from offset geomorphic features which record localized slip along the main strand of the fault to the total displacement across the entire width of the surface deformation zone from cosi corr reveals 45 off fault deformation while previous studies have shown that the structural maturity of the fault exerts a primary control on the total percentage of off fault surface deformation large along strike variations in the percentage of strain localization observed in the 2013 rupture imply the influence of important secondary controls one such possible secondary control is the type of near surface material through which the rupture propagated we therefore compared the percentage off fault deformation to the type of material bedrock old alluvium and young alluvium at the surface and the distance of the fault to the nearest bedrock outcrop a proxy for sediment thickness along this hybrid strike slip reverse slip fault we find significantly more off fault deformation in younger and or thicker sediments accounting for and predicting such off fault deformation patterns has important implications for the interpretation of geologic slip rates especially for their use in probabilistic seismic hazard assessments the behavior of near surface materials during coseismic deformation and the future development of microzonation protocols for the built environment

simulation of the tropical pacific climate with a coupled ocean atmosphere general circulation model part ii interannual variability abstract two multiyear simulations with a coupled ocean atmosphere general circulation model gcm totaling 45 years are used to investigate interannual variability at the equator the model consists of the ucla global atmospheric gcm coupled to the gfdl oceanic gcm dynamically active over the tropical pacific multichannel singular spectrum analysis along the equator identifies enso like quasi biennial qb and quasi quadrennial qq modes both consist of predominantly standing oscillations in sea surface temperature and zonal wind stress that peak in the central or east pacific accompanied by an oscillation in equatorial thermocline depth that is characterized by a phase shift of about 90 across the basin with west leading east simulated interannual variability is weaker than observed in both simulations one of these is dominated by the qb the other by the qq mode although the two differ only in details of the surface layer parameterizations

interdecadal change of the structure of the enso mode and its impact on the enso frequency in the late 1970s the enso cycle exhibited frequency change the oscillation period increased from 2 4 yr high frequency during 1962 75 to 4 6 yr low frequency during 1980 93 observations suggest that this frequency change was accompanied by a significant change in the structure of the coupled enso mode in comparison with the high frequency regime the structure of the coupled mode in the low frequency regime shows three distinctive features during the warm phase of enso the eastward shift of the westerly anomalies the meridional expansion of the westerly anomalies and the weaker intensity of the easterly anomalies in the eastern pacific to test the robustness of the relationship between the oscillation period and the structure of the coupled mode the authors designed empirical atmospheric models based on observations and coupled them with the ocean model of zebiak and cane numerical experiments demonstrate that the enso period is sensitive to changes in the wind anomaly pattern in a way much like the observed enso frequency structure relation the increase of the enso period after 1980 is mainly due to the eastward shift of the zonal wind stress with respect to the sst anomalies physical explanations of the dependence of enso frequency on the structure of the coupled mode are provided by diagnosing the relative contributions of the thermocline feedback and zonal advection feedback on enso evolution

automated fault model discretization for inversions for coseismic slip distributions 1 geoscientists increasingly rely on coseismic slip distributions inferred from geodetic observations to drive sophisticated models of the seismic cycle to date little work has been done on optimizing the parameterization of these fault models so that they reflect the resolving power of observed surface displacements the locations of noisy surface displacement observations are often widely scattered far from features we wish to analyze in the subsurface and result in highly variable model resolution with depth the few attempts to produce variably discretized fault planes are arduously constructed by hand and may not correctly reflect the ability of the data to resolve slip features motivated by the increasing size of geodetic data pools and the need for distributed slip models that accurately represent features the data can resolve we present a fully automated algorithm that iteratively adjusts the sizes of dislocations in a fault model we use the concept of smoothing scales derived from the model resolution matrix to resize dislocations so that each dislocation is sized appropriately given the area over which slip in that region of the fault would be smoothed we present a series of synthetic tests that utilize both sparse and dense data sets and we compare our variably discretized inversions to traditional regularly discretized inversions we also use our approach to invert for slip from geodetic observations of the 2004 mw 6 0 parkfield california earthquake and the 1995 mw 8 1 antofagasta chile earthquake

a spontaneously generated tropical atmospheric general circulation abstract a series of idealized atmospheric general circulation model agcm experiments are presented these experiments examine whether and how atmospheric deep moist convection in the absence of meridional gradients in external forcing interacts with the large scale flow becoming spatially organized and yielding a coherent general circulation in a control simulation where the sst and the incident solar flux are prescribed to be independent of latitude longitude and time a well defined intertropical convergence zone itcz forms this result suggests that the interaction between convection and the rotation of the earth causes convection and a corresponding general circulation to organize the actual latitude that the itcz forms at however may be parameterization dependent in this control simulation the sst is not interactive and cannot respond to the spatial variations of the heat flux into the ocean that result from the organization of the circulation in order to examine the circulation tha

magnetic remote sensing of europa s ocean tides abstract recent analyses of galileo magnetometer and gravity data justifies approximations that allow estimates of the magnetic fields generated by europa s ocean tides to be made even though some of the ocean parameters that would generally be required are unavailable we show solutions for the magnetic fields generated by published estimates of ocean tides on europa and provide simple scaling formulas that can be used to estimate the magnetic field amplitudes for other choices for the ocean tidal state because of the distinguished spatial temporal form of these fields it is expected that europa s ocean tides can be inferred from remote magnetic sensing by an orbiter of sufficient duration

slip history of the 2016 mw 7 0 kumamoto earthquake intraplate rupture in complex tectonic environment rupture history of the 2016 mw 7 0 kumamoto earthquake is constrained by using the waveforms of strong motion observations teleseismic broadband body waves and long period surface waves its fault geometry is modeled with hinagu orienting 205 and dipping 73 and futagawa orienting 235 and dipping 60 two segments the result reconciles the difference between moment tensor solutions and the surface fault trace it reveals a complex rupture process that initiated on the hinagu segment in dextral motion propagated northeastward unilaterally and after 15 s ceased near aso volcano with normal fault motion the average slip rise time and slip rate are 1 8 m 2 0 s and 1 2 m s respectively the rupture broke through an 30 fault intersection without notable delay which can be a result of dynamic unclamping the northeast boundary of the largest asperity might mark the bottom of the seismogenic zone which becomes shallower gradually near aso volcano

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

a network inversion filter combining gnss and insar for tectonic slip modeling studies of the earthquake cycle benefit from long term time dependent slip modeling as it can be a powerful means to improve our understanding on the interaction of earthquake cycle processes such as interseismic coseismic postseismic and aseismic slip observations from interferometric synthetic aperture radar insar allow us to model slip at depth with a higher spatial resolution than when using gnss alone while the temporal resolution of insar has typically been limited the recent fleet of sar satellites including sentinel 1 cosmo skymed and radarsat 2 permits the use of insar for time dependent slip modeling at intervals of a few days when combined with the vast amount of sar data available simultaneous data inversion of all epochs becomes challenging here we expanded the original network inversion filter to include insar observations of surface displacements in addition to gnss in the nif framework geodetic observations are limited to those of a given epoch with a stochastic model describing slip evolution over time the combination of the kalman forward filtering and backward smoothing allows all geodetic observations to constrain the complete observation period combining gnss and insar allows modeling of time dependent slip at unprecedented spatial resolution we validate the approach with a simulation of the 2006 guerrero slow slip event we highlight the importance of including insar covariance information and demonstrate that insar provides an additional constraint on the spatial extent of the slow slip

simulated recovery of europa s global shape and tidal love numbers from altimetry and radio tracking during a dedicated flyby tour the fundamental scientific objectives for future spacecraft exploration of jupiter s moon europa include confirmation of the existence of subsurface ocean beneath the surface ice shell and constraints on the physical properties of the ocean here we conduct a comprehensive simulation of a multiple flyby mission we demonstrate that radio tracking data can provide an estimate of the gravitational tidal love number k2 with sufficient precision to confirm the presence of a liquid layer we further show that a capable long range laser altimeter can improve determination of the spacecraft position improve the k2 determination 1 error and enable the estimation of the planetary shape and love number h2 3 4 error which is directly related to the amplitude of the surface tidal deformation these measurements in addition to the global shape accurately constrained by the long altimetric profiles can yield further constraints on the interior structure of europa

the retrospective prediction of el nino southern oscillation from 1881 to 2000 by a hybrid coupled model i sea surface temperature assimilation with ensemble kalman filter in this study we assimilated sea surface temperature sst data of the past 120 years into an oceanic general circulation model ogcm for el nino southern oscillation enso retrospective predictions using ensemble kalman filter enkf it was found that the ensemble covariance matrix in enkf can act as a time variant transfer operator to project the sst corrections onto the subsurface temperatures effectively when initial perturbations of ensemble were constructed using vertically coherent random fields as such the increments of subsurface temperatures can be obtained via the transfer operator during assimilation cycles the results show that the sst assimilation improves the model simulation skills significantly not only for the sst anomalies over the whole assimilated domain but also for the subsurface temperature anomalies of the upper 100 m over the tropical pacific off the equator along the equator the improvement of the assimilation is confined within the mixing layer because strong upwelling motions there prevent the downward transfer of sst information the retrospective prediction skills of enso over the past 120 years from 1881 to 2000 were significantly improved by the sst assimilation at all leads of 1 12 months especially for the 3 6 months leads compared with those initialized by the control run without assimilation the skilful predictions by the assimilation allow us to further study enso predictability using this coupled model

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

enso simulation and prediction with a hybrid coupled model a hybrid coupled model hcm consisting of a tropical pacific ocean and global atmosphere is presented the ocean component is a linear reduced gravity model of the upper ocean in the tropical pacific the atmospheric component is a triangular 30 horizontal resolution global spectral general circulation model with 18 unevenly spaced levels in the vertical in coupling these component models an anomaly coupling strategy is employed a 40 yr simulation was made with hcm and the variability in the tropical pacific was compared to the observed variability the hcm produces irregular enso events with a broad spectrum of periods between 12 and 48 months on longer timescales approximately 48 months the simulated variability was weaker than the observed and on shorter timescales approximately 24 months the simulated variability was too strong the simulated variability is asymmetric in the sense that the amplitude of the warm events is realistic but there are no significant cold events an ensemble of 60 hindcast predictions was made with the hcm and the skill was compared to other prediction systems in forecasting sea surface temperature anomalies in the eastern pacific the hcm is comparable to the other prediction systems for lead times up to 10 months the anomaly correlation coefficient for the eastern pacific ssta remains above 0 6 for lead times of up to 11 months consistent with the 40 yr simulation hindcasts of cold events have little skill particularly when compared to hindcasts of warm events specific hindcasts also demonstrate that the hcm also has difficulty predicting the transition from warm conditions to normal or cold conditions

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

on and off fault deformation associated with the september 2013 mw 7 7 balochistan earthquake implications for geologic slip rate measurements abstract the 24 september 2013 mw7 7 balochistan pakistan earthquake ruptured a 200 km long stretch of the hoshab fault in southern pakistan and produced the second largest lateral surface displacement observed for a continental strike slip earthquake we remotely measured surface deformation associated with this event using high resolution 0 5 m pre and post event satellite optical imagery we document left lateral near field on fault offsets 10 m from fault using 309 laterally offset piercing points such as streams terrace risers and roads peak near field displacement is 13 6 2 5 3 4 m we characterize off fault deformation by measuring medium 350 m from fault displacement using manual 259 measurements and automated image cross correlation methods respectively off fault peak lateral displacement values are 15 m and exceed on fault displacement magnitudes for 85 of the rupture length our observations suggest that for this rupture coseismic surface displacement typically increases with distance away from the surface trace of the fault however nearly 100 of total surface displacement occurs within a few hundred meters of the primary fault trace furthermore off fault displacement accounts for on average 28 of the total displacement but exhibits a highly heterogeneous along strike pattern the best agreement between near field and far field displacements generally corresponds to the narrowest fault zone widths our analysis demonstrates significant and heterogeneous mismatches between on and off fault coseismic deformation and we conclude that this phenomenon should be considered in hazard models based on geologically determined on fault slip rates

volume strain within the geysers geothermal field during the 1970s and 1980s the geysers geothermal region was rapidly developed as a site of geothermal power production the likelihood that this could cause significant strain within the reservoir with corresponding surface displacements led to a series of deformation monitoring surveys in 1973 1975 1977 and 1980 the geysers region was surveyed using first order class i spirit leveling in 1994 1995 and 1996 many of the leveling control monuments were resurveyed using high precision global positioning system receivers the two survey methods are reconciled using the geoid96 geoid model the displacements are inverted to determine volume strain within the reservoir for the period 1980 1994 peak volume strains in excess of 5x10 sup 4 are imaged there is an excellent correlation between the observed changes in reservoir steam pressures and the imaged volume strain if reservoir pressure changes are inducing volume strain then the reservoir quasi static bulk modulus k must be 4 6x10 sup 9 pa however seismic velocities indicate a much stiffer reservoir with k 3 4x10 sup 10 pa this apparent discrepancy is shown to be consistent with predicted frequency dependence in k for fractured and water saturated rock inversion of surface deformation data therefore appears to be a powerful method for imaging pressure change withinmore the body of the reservoir correlation between induced seismicity at the geysers and volume strain is observed however earthquake distribution does not appear to have a simple relationship with volume strain rate c 1999 american geophysical union less

dynamics of the indian monsoon and enso relationships in the sintex global coupled model this paper uses recent gridded climatological data and a coupled general circulation model gcm simulation in order to assess the relationships between the interannual variability of the indian summer monsoon ism and the el nino southern oscillation enso the focus is on the dynamics of the ism enso relationships and the ability of the state of the art coupled gcm to reproduce the complex lead lag relationships between the ism and the enso the coupled gcm is successful in reproducing the ism circulation and rainfall climatology in the indian areas even though the entire ism circulation is weaker relative to that observed in both observations and in the simulation the ism rainfall anomalies are significantly associated with fluctuations of the hadley circulation and the 200 hpa zonal wind anomalies over the indian ocean a quasi biennial time scale is found to structure the ism dynamical and rainfall indices in both cases moreover ism indices have a similar interannual variability in the simulation and observations the coupled model is less successful in simulating the annual cycle in the tropical pacific a major model bias is the eastward displacement of the western north pacific inter tropical convergence zone itcz near the dateline during northern summer this introduces a strong semiannual component in pacific walker circulation indices and central equatorial pacific sea surface temperatures another weakness of the coupled model is a less than adequate simulation of the southern oscillation due to an erroneous eastward extension of the southern pacific convergence zone spcz year round despite these problems the coupled model captures some aspects of the interannual variability in the tropical pacific enso events are phase locked with the annual cycle as observed but are of reduced amplitude relative to the observations wavelet analysis of the model nino34 time series shows enhanced power in the 2 4 year band as compared to the 2 8 year range for observations during the 1950 2000 period the ism circulation is weakened during enso years in both the simulation and the observations however the model fails to reproduce the lead lag relationship between the ism and nino34 sea surface temperatures ssts furthermore lag correlations show that the delayed response of the wind stress over the central pacific to ism variability is insignificant in the simulation these features are mainly due to the unrealistic interannual variability simulated by the model in the western north pacific the amplitude and even the sign of the simulated surface and upper level wind anomalies in these areas are not consistent with observed patterns during weak strong ism years the ism and western north pacific itcz fluctuate independently in the observations while they are negatively and significantly correlated in the simulation this isolates the pacific walker circulation from the ism forcing these systematic errors may also contribute to the reduced amplitude of enso variability in the coupled simulation most of the unrealistic features in simulating the indo pacific interannual variability may be traced back to systematic errors in the base state of the coupled model

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

probing europa s hidden ocean from tidal effects on orbital dynamics recent observations of europa suggest that the jovian satellite may have a liquid ocean underneath its icy surface geophysical models indicate that the tidal love number k2 has a strong dependence on the presence or absence of an ocean the k2 dependence on the ice shell thickness is also significant measurements of the static and tidal gravity fields through their dynamic effects on the trajectory of a low europan orbiter can be essential in the detection of an ocean and inference of other internal structures covariance analyses have been carried out to assess accuracies using simulated doppler tracking data with 15 days of tracking from 2 earth stations the uncertainties for k2 mantle libration amplitude and the epoch radial position of the spacecraft are expected to be 0 0004 2 8 arcsec and 5 7 m respectively these tight constraints will strongly contribute to ocean detection and ice thickness determination when combined with altimeter measurements

surface temperature patterns associated with the southern oscillation abstract the typical global and large scale regional temperature patterns associated with the low warm and high cold phases of the southern oscillation so are investigated a total of 12 separate regions were found to have consistent temperature patterns associated with low phase of the so while 11 areas were found to have temperature patterns associated with the high phase of these areas 9 have expected temperature patterns during both phases of the so in the tropics temperature anomalies are of the same sign as the so related sea surface temperature sst anomaly in all land regions except for one area in the west pacific three extratropical responses to the low phase of the so are found over north america and one is found in japan high so temperature patterns were found in the extratropies for japan western europe and northwestern north america the identified temperature responses are more consistent in tropical regions than in the extratropies the so can influence the estimation of

three dimensional surface displacements and rotations from differencing pre and post earthquake lidar point clouds 1 the recent explosion in sub meter resolution airborne lidar data raises the possibility of mapping detailed changes to earth s topography we present a new method that determines three dimensional 3 d coseismic surface displacements and rotations from differencing pre and post earthquake airborne lidar point clouds using the iterative closest point icp algorithm tested on simulated earthquake displacements added to real lidar data along the san andreas fault the method reproduces the input deformation for a grid size of 50 m with horizontal and vertical accuracies of 20 cm and 4 cm values that mimic errors in the original spot height measurements the technique also measures rotations directly resolving the detailed kinematics of distributed zones of faulting where block rotations are common by capturing near fault deformation in 3 d the method offers new constraints on shallow fault slip and rupture zone deformation in turn aiding research into fault zone rheology and long term earthquake repeatability

symmetric and antisymmetric mass exchanges between the equatorial and off equatorial pacific associated with enso 1 mass exchanges in the upper ocean between the equatorial and off equatorial pacific ocean associated with the el nino southern oscillation enso are investigated using the national centers for environmental prediction ncep ocean assimilation data the data show that enso related meridional mass transport in the northern hemisphere nh is larger than that in the southern hemisphere sh we found that the antisymmetric characteristics are mainly due to a southward shift of themaximum zonal wind stress anomaly during the enso mature phase the ekman and geostrophic transports associated with enso are separated into symmetric and antisymmetric components for the symmetric part the mass divergence over the equatorial pacific by the geostrophic transport is generally larger than the convergence by the ekman transport during the el nino mature phase therefore mass is transported from the equator to off the equator at this time as for the antisymmetric part the ekman transport due to antisymmetric wind stress dominates the geostrophic transport so that the mass is transported from the sh to the nh during the el nino mature phase the net mass transport in the nh is larger than that in the sh a theoretical interpretation and intermediate model experiments support these arguments index terms 4522 oceanography physical el nino 4572 oceanography physical upper ocean processes 4512 oceanography physical currents 4504 oceanography physical air sea interactions 0312 4215 oceanography general climate and interannual variability 3309 keywords enso mass exchange wind stress antisymmetry

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

the mercury gravity field orientation love number and ephemeris from the messenger radiometric tracking data abstract the mercury gravity field spin pole axis rotation period love number and ephemeris have been determined using the complete four years of messenger tracking data from march 2011 to april 2015 the pole location and obliquity 1 99 0 12 arcmin is consistent with previous determinations since messenger was in a highly elliptical orbit with periapsis in the far northern hemisphere the gravity resolution over the surface of mercury varies greatly from harmonic degree n 12 at the south pole to n 154 in a small region near the north pole which was covered with exceptionally low periapsis data near the end of mission the gravity field mess160a is determined to n 160 and shows notable improvement in the correlation with topography three different constraint methods are used to generate the gravity field the nominal method is a kaula power law of 5 10 5 n2 to constraint the coefficients one alternate constraint uses surface acceleration measurements which only constrains the unobserved portion of the gravity field the other constraint method sets the gravity uncertainties using the harmonic spectrum of the gravity derived from topography the mercury tidal love number solution k2 0 53 0 03 is larger than previous results but within suggested error bounds in addition the technique for estimating the mercury ephemeris is discussed

oceanic rossby wave dynamics and the enso period in a coupled model abstract tropical ocean wave dynamics associated with the el nino southern oscillation cycle in a coupled model are examined the ocean atmosphere model consists of statistical atmosphere coupled to a simple reduced gravity model of the tropical pacific ocean the statistical atmosphere is simple enough to allow for the structure and position of the wind stress anomalies to be externally specified in a control simulation where the structure of the wind stress anomaly is determined from observations the model produces a regular 5 yr oscillation this simulation is consistent with the so called delayed oscillator theory in that subsurface wave dynamics determine the slow timescale of the oscillation and surface layer processes are found to be of secondary importance kelvin and rossby wave propagation is detected along the equator with periods considerably shorter than the simulated oscillation period the way in which these relatively fast waves are related to the simulated 5 yr oscillation is discusse

imaging the distribution of transient viscosity after the 2016 mw 7 1 kumamoto earthquake the deformation of mantle and crustal rocks in response to stress plays a crucial role in the distribution of seismic and volcanic hazards controlling tectonic processes ranging from continental drift to earthquake triggering however the spatial variation of these dynamic properties is poorly understood as they are difficult to measure we exploited the large stress perturbation incurred by the 2016 earthquake sequence in kumamoto japan to directly image localized and distributed deformation the earthquakes illuminated distinct regions of low effective viscosity in the lower crust notably beneath the mount aso and mount kuju volcanoes surrounded by larger scale variations of viscosity across the back arc this study demonstrates a new potential for geodesy to directly probe rock rheology in situ across many spatial and temporal scales

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

sensitivity of an intermediate ocean atmosphere coupled model of the tropical pacific to its oceanic vertical structure an intermediate ocean atmosphere coupled model icm of the tropical pacific is used to investigate the sensitivity of the coupled system to the oceanic vertical structure the model consists of a three baroclinicmode tropical pacific ocean and a gill tropical atmosphere the mixed layer is similar to the zebiak and cane zc coupled atmosphere ocean model but uses a different parameterization for subsurface temperature derived from xbt data a 100 yr simulation is made and the long term variability of the icm is briefly discussed and compared with the the observations and the zc model the icm reproduces regular enso events with a spectrum peak centered at the period 3 5 yr the presence of higher order vertical modes in the oceanic component of the model allows for reduced off equatorial variability of zonal current and thermocline anomalies and for finer meridional scale for sst anomaly variability in comparison with a simulation with one baroclinic mode only the nature of the processes sustaining the oscillations in the icm is then investigated based on the coupled instabilities and delayed oscillator theories it

toward full exploitation of coherent and incoherent information in sentinel 1 tops data for retrieving surface displacement application to the 2016 kumamoto japan earthquake sentinel 1 s continuous observation program over all major plate boundary regions makes it well suited for earthquake studies however decorrelation due to large displacement gradients and limited azimuth resolution of the terrain observation by progressive scan tops data challenge acquiring measurements in the near field of many earthquake ruptures and prevent measurements of displacements in the along track direction here we propose to fully exploit the coherent and incoherent information of tops data by using standard interferometric synthetic aperture radar insar split bandwidth interferometry in range and azimuth swath burst overlap interferometry and amplitude cross correlation to map displacements in both the line of sight and the along track directions application to the 2016 kumamoto earthquake sequence reveals the coseismic displacements from the far field to the near field by adding near field constraints the derived slip model reveals more shallow slip than obtained when only using far field data from insar highlighting the importance of exploiting all coherent and incoherent information in tops data

how well do surface slip measurements track slip at depth in large strike slip earthquakes the importance of fault structural maturity in controlling on fault slip versus off fault surface deformation abstract comparisons of observed surface displacements with geodetically inferred slip at depth in six large m w 7 1 strike slip earthquakes reveal a correlation between the structural maturity of the fault and the ratio of deep slip to surface slip that occurs on localized zones of surface rupture specifically structurally immature faults 25 km of total displacement manifest only 50 60 of total slip on narrow fault surface traces versus 85 95 for structurally mature faults 85 km total slip the same pattern holds when structurally simple parts of a surface rupture are analyzed separately from parts that exhibit obvious structural complexity e g discontinuous or multiple traces or significant dip slip these results imply that geologic measurements of surface slip along structurally immature faults are likely to significantly underestimate the true slip at depth in large earthquakes this observation has implications for a number of important problems including determination of fault slip rates which are based on surface offsets earthquake probability assessments which are based on geologic fault slip rates comparisons of geologic and geodetic rate data in the search for strain transients the structural evolution of fault zones estimation of paleo earthquake magnitudes based on geomorphic offsets analyses of the relative importance of faulting vs distributed deformation in accommodating relative plate motions in continental crust the design and construction of infrastructure built near active faults and possibly for the prediction of strong ground motions which may at least partially depend on the degree of slip localization to the surface

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

lateral offsets on surveyed cultural features resulting from the 1999 izmit and duzce earthquakes turkey surveys of offset linear cultural features that cross the surface ruptures of the 17 august and 12 november 1999 earthquakes on the north anatolian fault in turkey yield slip values as large as or larger than those recorded by near field measurements in the same areas immediately after the earthquake using long linear alignments of trees fence lines walls and canals we demonstrate as much as a 2 m increase in observed slip over the initial field measurements on an average we observed about 15 of the total lateral slip as off fault deformation with values ranging from 0 to 40 of the total slip part of this lateral deformation is accom modated by bending or drag in a zone as much as 30 m in width although usually the zone varies between 5 and 20 m in width this supports the idea that substantial nonbrittle off fault deformation is associated with ruptures in areas of alluvial fill alternatively there may have been substantial afterslip although none has been recognized on postearthquake repaired structures our observations suggest that post earthquake measurements of fault slip using tape measures on offset geomorphic features may underestimate the actual amount of slip in that event where the non linearity of the offset feature does not allow recognition of the warping surveys of multiple tree lines within groves of poplar trees planted in straight lines across the fault prior to the earthquake show surprisingly large lateral varia tions in one grove slip increases by nearly 1 8 m or 35 of the maximum measured value over a lateral distance of nearly 100 m this and other observations along the 1999 ruptures suggest that the lateral variability of slip observed from displaced geomorphic features in many earthquakes of the past may represent a combination of 1 actual differences in slip at the surface and 2 the difficulty in recognizing distributed nonbrittle deformation

coseismic fault zone deformation revealed with differential lidar examples from japanese mw 7 intraplate earthquakes abstract we use two recent japanese earthquakes to demonstrate the rich potential as well as some of the challenges of differencing repeat airborne light detection and ranging lidar topographic data to measure coseismic fault zone deformation we focus on densely vegetated sections of the 14 june 2008 iwate miyagi m w 6 9 and 11 april 2011 fukushima hamadori m w 7 1 earthquake ruptures each covered by 2 m resolution pre event and 1 m resolution post event bare earth digital terrain models dtms obtained from commercial lidar providers three dimensional displacements and rotations were extracted from these datasets using an adaptation of the iterative closest point icp algorithm these displacements remain coherent close to surface fault breaks as well as within dense forest despite intervals of 2 years iwate miyagi and 4 years fukushima hamadori encompassed by the lidar scenes differential lidar analysis is thus complementary to interferometric synthetic aperture radar insar and sub pixel correlation techniques which often break down under conditions of long time intervals dense vegetation or steep displacement gradients although the icp displacements are much noisier than overlapping insar line of sight displacements they still provide powerful constraints on near surface fault slip in the fukushima hamadori case near fault displacements and rotations are consistent with decreased primary fault slip at very shallow depths of a few tens of meters helping to account for the large along strike heterogeneity in surface offsets observed in the field this displacement field also captures long wavelength deformation resulting from the 11 march 2011 tohoku great earthquake

prediction of nino 3 sea surface temperatures using linear inverse modeling abstract linear inverse modeling is used to predict sea surface temperatures ssts in the nino 3 region predictors in three geographical locations are used the tropical pacific ocean the tropical pacific and indian oceans and the global tropical oceans predictions did not depend crucially on any of these three domains and evidence was found to support the assumption that linear dynamics dominates most of the record the prediction model performs better when sst anomalies are rapidly evolving than during warm events when large anomalies persist the rms prediction error at a lead time of 9 months is about half a degree celsius

simulation of enso with a global atmospheric gcm coupled to a high resolution tropical pacific ocean gcm abstract a global atmospheric general circulation model gcm coupled to an oceanic gcm that is dynamically active only in the tropical pacific simulates variability over a broad spectrum of frequencies even though the forcing the annual mean incoming solar radiation is steady of special interest is the simulation of a realistically irregular southern oscillation between warm el nino and cold la nina states its time scale is on the order of 5 years the spatial structure is strikingly different in the eastern and western halves of the ocean basin sea surface temperature changes have their largest amplitude in the central and eastern tropical pacific but the low frequency zonal wind fluctuations are displaced westward and are large over the western half of the basin these zonal wind anomalies are essentially confined to the band of latitudes 10 to 10 s so that they form a jet and have considerable latitudinal shear during el nino the associated curl contributes to a pair of pronounced minima in th

subsurface oceans on europa and callisto constraints from galileo magnetometer observations magnetic field perturbations measured during galileo flybys of europa and callisto are consistent with dipole fields induced by the temporal variations of the ambient jovian magnetospheric field these fields are close to those expected for perfectly conducting moons we investigate the implications of these observations for the electrical structure of the moon s interiors using a simple shell model it is found that europa and callisto must possess regions where the conductivity exceeds 0 06 and 0 02 s m at a depth of less than 200 and 300 km below the surface respectively this conductivity is unattainable in ice or silicates unless the ice layer is at least partially molten or very large temperature gradients can be maintained below the ice an ionosphere or a cloud of pick up ions are probably also insufficiently conductive global earth like oceans under the surface of both moons could account for the observations provided they are at least a few kilometers thick c 2000 academic press

on the dependence of hindcast skill on ocean thermodynamics in a coupled ocean atmosphere model abstract three different mechanisms for the generation of enso sst anomalies within a simplified tropical pacific ocean model are examined thermocline depth changes ekman induced upwelling anomalies and zonal advection changes the effect of varying the relative influence of these terms on the realism of tropical pacific coupled models is analyzed the principal tool used to assess such realism is hindcast skill with forced ocean and oscillatory behavior also being examined of the mechanisms considered thermocline perturbations are shown to be crucially important for high coupled model hindcast skill furthermore it is concluded that the realism of the model as measured by hindcast skill deteriorates markedly when the influence on sst of ekman upwelling becomes greater than a small fraction of the thermocline influence this provides strong evidence for the hypothesis that ekman upwelling anomalies which are essentially a local response to wind stress anomalies have only a small influence on th

expected precision of europa clipper gravity measurements abstract the primary gravity science objective of nasa s clipper mission to europa is to confirm the presence or absence of a global subsurface ocean beneath europa s icy crust gravity field measurements obtained with a radio science investigation can reveal much about europa s interior structure here we conduct extensive simulations of the radio science measurements with the anticipated spacecraft trajectory and attitude 17f12v2 and assets on the spacecraft and the ground including antenna orientations and beam patterns transmitter characteristics and receiver noise figures in addition to two way doppler measurements we also include radar altimeter crossover range measurements we concentrate on 2 h intervals centered on the closest approach of each of the 46 flybys our covariance analyses reveal the precision with which the tidal love number k2 second degree gravity coefficients c 20 and c 22 and higher order gravity coefficients can be determined the results depend on the deep space network dsn assets that are deployed to track the spacecraft we find that some dsn allocations are sufficient to conclusively confirm the presence or absence of a global ocean given adequate crossover range performance it is also possible to evaluate whether the ice shell is hydrostatic

galileo magnetometer measurements a stronger case for a subsurface ocean at europa on 3 january 2000 the galileo spacecraft passed close to europa when it was located far south of jupiter s magnetic equator in a region where the radial component of the magnetospheric magnetic field points inward toward jupiter this pass with a previously unexamined orientation of the external forcing field distinguished between an induced and a permanent magnetic dipole moment model of europa s internal field the galileo magnetometer measured changes in the magnetic field predicted if a current carrying outer shell such as a planet scale liquid ocean is present beneath the icy surface the evidence that europa s field varies temporally strengthens the argument that a liquid ocean exists beneath the present day surface

europa s differentiated internal structure inferences from four galileo encounters radio doppler data from four encounters of the galileo spacecraft with the jovian moon europa have been used to refine models of europa s interior europa is most likely differentiated into a metallic core surrounded by a rock mantle and a water ice liquid outer shell but the data cannot eliminate the possibility of a uniform mixture of dense silicate and metal beneath the water ice liquid shell the size of a metallic core is uncertain because of its unknown composition but it could be as large as about 50 percent of europa s radius the thickness of europa s outer shell of water ice liquid must lie in the range of about 80 to 170 kilometers

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

collective role of thermocline and zonal advective feedbacks in the enso mode the vertical advection of anomalous subsurface temperature by the mean upwelling and the zonal advection of mean sea surface temperature sst by anomalous current are known to be essential for the equatorial sst anomaly associated with the el nino southern oscillation enso in the coupled model these two processes are referred to as the thermocline feedback and the zonal advective feedback respectively using a version of a recharge oscillator model for enso obtained from the stripped down approximation of the cane zebiak type model it is demonstrated that these two feedbacks which are linked dynamically through the geostrophic approximation tend constructively to contribute to the growth and phase transition of enso however these two feedbacks control the leading coupled mode in different ways the thermocline feedback leads to a coupled mode through the merging of the damped sst mode and ocean adjustment mode whereas the zonal advective feedback tends to destabilize the gravest ocean basin mode with both of these feedbacks the leading modes of the coupled model still can be traced back to these different origins under moderate changes in the model setup the main consequence of these sensitivities is that the growth rate and frequency of the enso mode may be sensitive to slight changes in basic state parameters which control the strength of these feedbacks

tides on europa and the thickness of europa s icy shell 1 it has been shown previously that measurements of tides on jupiter s moon europa can be used to determine whether there is a liquid ocean beneath this moon s icy outer shell in this paper we examine the further possibility of constraining the thickness of the icy shell in the case where a liquid ocean exists by combining measurements of tidal gravity obtained from tracking an orbiting spacecraft with measurements of vertical tidal surface displacements obtained from a precise onboard altimeter by simulating a 1 month europa mapping mission we demonstrate that this combination of tidal measurements would provide a much better estimate of ice thickness than could be obtained using either tracking or altimeter measurements alone the thickness value inferred from the combined data would also require an estimate of the shear modulus of europa s icy shell this introduces an additional uncertainty in the thickness estimate that is approximately proportional to the uncertainty in the inverse of the shear modulus