continuing inflation at three sisters volcanic center central oregon cascade range usa from gps leveling and insar observations uplift of a broad area centered 6 km west of the summit of south sister volcano started in september 1997 onset estimated from model discussed in this paper and was continuing when surveyed in august 2006 surface displacements were measured whenever possible since august 1992 with satellite radar interferometry insar annually since august 2001 with gps and leveling surveys and with continuous gps since may 2001 the average maximum displacement rate from insar decreased from 3 5 cm yr during 1998 2001 to 1 4 cm yr during 2004 2006 the other datasets show a similar pattern i e surface uplift and extension rates decreased over time but deformation continued through august 2006 our best fit model to the deformation data is a vertical prolate spheroidal point pressure source located 4 9 5 4 km below the surface the source inflation rate decreased exponentially during 2001 2006 with a 1 e decay time of 5 3 1 1 years the net increase in source volume from september 1997 to august 2006 was 36 5 41 9 x 106 m3 a swarm of 300 small mmax 1 9 earthquakes occurred beneath the deforming area in march 2004 no other unusual seismicity has been noted similar deformation episodes in the past probably would have gone unnoticed if as we suspect most are small intrusions that do not culminate in eruptions

macaronichnus and contourite depositional settings bottom currents and nutrients as coupling factors abstract the trace fossil macaronichnus segregatis degiberti 7 15 mm in diameter is recorded for the first time in deep marine contourites which were deposited in a late miocene outer shelf to upper slope of the rifian corridor morocco macaronichnus is typical of shallow marine mainly foreshore environments it is produced by deposit feeding opheliid polychaetes in high to intermediate latitudes this record supports the significance of bottom current processes on environmental conditions as a major limiting factor affecting the macrobenthic trace maker community mediterranean overflow water during the late miocene enabled a high nutrient supply to the seafloor favouring colonization by macaronichnus producers thus m s degiberti should be used as an indicator for nutrient availability instead of mainly a palaeodepth indicator this finding provides significant information for oceanographic and environmental reconstructions related to contouritic processes as well as to contourite characterization

dyfamed benthos a long time series benthic survey at 2347 m depth in the northwestern mediterranean general introduction in 1990 a benthic component to the dyfamed dynamics of fluxes in the mediterranean program the dyfamed benthos survey was established to investigate the possible coupling of benthic to pelagic processes at a permanent station in 2700 m water depth 52 km off nice france surface sediment was first sampled at different periods of the year to assess the importance of the biological compartment particularly metazoan meiofauna and its relation to seasonally varying particulate matter input to the sea floor estimated by measuring surface sediment particle size and porosity as well as chloroplastic pigments organic carbon nitrogen and calcium carbonate contents beginning in 1993 surface sediment was sampled at an average interval of 1 4 months for over five consecutive years using multicorers biogeochemical techniques such as deployments of a free vehicle benthic respirometer and a nearbottom sediment trap along with analyses of sediment vertical profiles for dissolved oxygen nutrients and dissolved metals in the porewater were developed in conjunction with more extensive biological analyses to characterize the recycling of organic matter and ultimately increase our understanding of the oceanic carbon cycle this article provides the scientific background and motivation for the development of the on going dyfamed benthos survey the general characteristics of the benthic site as well as a detailed description of the sampling design applied from late 1990 2000 r 2002 elsevier science ltd all rights reserved

near real time radar interferometry of the mw 7 1 hector mine earthquake the hector mine earthquake mw 7 1 16 oc tober 1999 ruptured 45 km of previously mapped and un mapped faults in the mojave desert the ers 2 satellite imagedthemojavedeserton15septemberandagain on20 october just 4 days after the earthquake using a newly developed ground station we acquired both passes and were able to form an interferogram within 20 hours of the second overflight estimates of slip along the main rupture are 1 2 meters greater than slip derived from geological mapping the gradient of the interferometric phase reveals an inter esting pattern of triggered slip on adjacent faults as well as a 30 mm deep sink hole along interstate 40

the 1999 mw 7 1 hector mine california earthquake sequence complex conjugate strike slip faulting the 1999 m w 7 1 hector mine mainshock showed right lateral strike slip faulting with an initial strike of n6 w and vertical dip the mainshock was preceded within 20 hours by 18 recorded foreshocks of 1 5 m 3 8 within a few kilometers distance of the mainshock hypocenter the aftershocks delineate how the hector mine earthquake ruptured with strike n6 w to the south for a distance of 15 km and possibly to the north for a distance of several kilometers the two largest aftershocks of m 5 9 and m 5 7 occurred near the north and south ends of the first mainshock rupture segment the second segment of rupture starting 15 km to the south away from the mainshock hypocenter delineated by strike slip and thrust faulting aftershocks extends 10 km farther away with a strike of s140 e along the bullion fault the aftershocks also outline an unusual third rupture segment extending from about 5 km south of the hypocenter with a strike of n30 w to n35 w for a distance of 20 km approximately 10 to 25 km farther to the north and west of the mainshock epicenter several clusters form a complex aftershock distribution three dimensional vp and vp vs models of the region exhibit only small regional changes as is typical for the mojave region nonetheless the mainshock rupture started within a region of rapidly varying vp and at least three regions of low vp vs are imaged within the aftershock zone the rate of decay for the hector mine earthquake sequence has been slightly above the mean for both p values and b values in southern california the focal mechanisms of the aftershocks and the state of stress are consistent with strike slip faulting including a component of normal faulting most prominent to the north the orientation of the regional maximum horizontal stress the variation in orientation of the mainshock fault segments by 30 and scattered distribution of aftershocks suggest that the mainshock and aftershock deformation field exhibit volumetric shear deformation accommodated by complex conjugate sets of strike slip faults

ichnofacies distribution in the eocene early miocene petra tou romiou outcrop cyprus sea level dynamics and palaeoenvironmental implications in a contourite environment ichnological analysis of the carbonate contourite drift at the petra tou romiou outcrop southern cyprus reveals a relationship between sea level dynamics shoreline position sedimentation rate flow hydrodynamics and trace fossil assemblages the base of the outcrop is composed of chalky deposits showing the zoophycos ichnofacies attributes the transition to the first contouritic interval beds is marked by the gradual disappearance of zoophycos and dominance of horizontal traces this change is caused by a gradual sea level fall determining an increase in proximity and energy conditions in the environment that favoured the development of distal cruziana ichnofacies upper contouritic interval beds contain abundant burrow systems with vertical components increased ichnodiversity particularly among vertical morphologies coincides with the appearance of teichichnus gyrolithes and rare ophiomorpha revealing a transition to the proximal cruziana ichnofacies related with the maintenance of the previous trend toward more proximal and higher energy settings the differentiated ichnofacies in the petra tou roumiou carbonate drifts are controlled by complex interactions between variable environmental factors with sea level dynamics playing a major role

decorrelation in interferometric radar echoes a radar interferometric technique for topographic mapping of surfaces implemented utilizing a single synthetic aperture radar sar system in a nearly repeating orbit is discussed the authors characterize the various sources contributing to the echo correlation statistics and isolate the term which most closely describes surficial change they then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time it is found that there is decorrelation increasing with time but that digital terrain model generation remains feasible the authors present such a map of a forested area in oregon which also includes some nearly unvegetated lava flows such a technique could provide a global digital terrain map

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

abyssal hills influence of topography on benthic foraminiferal assemblages abyssal plains often thought of as vast flat areas encompass a variety of terrains including abyssal hills features that constitute the single largest landscape type on earth the potential influence on deep sea benthic faunas of mesoscale habitat complexity arising from the presence of abyssal hills is still poorly understood to address this issue we focus on benthic foraminifera testate protists in the 150 m fraction of megacorer samples 0 1 cm layer collected at five different sites in the area of the porcupine abyssal plain sustained observatory ne atlantic 4850 m water depth three sites are located on the tops of small abyssal hills 200 500 m elevation and two on the adjacent abyssal plain we examined benthic foraminiferal assemblage characteristics standing stock diversity composition in relation to seafloor topography hills vs plain density and rarefied diversity were not significantly different between the hills and the plain nevertheless hills do support a higher species density i e species per unit area a distinct fauna and act to increase the regional species pool topographically enhanced bottom water flows that influence food availability and sediment type are suggested as the most likely mechanisms responsible for these differences our findings highlight the potential importance of mesoscale heterogeneity introduced by relatively modest topography in regulating abyssal foraminiferal diversity given the predominance of abyssal hill terrain in the global ocean we suggest the need to include faunal data from abyssal hills in assessments of abyssal ecology

coseismic displacements from the hector mine california earthquake results from survey mode global positioning system measurements we describe the collection and processing of global positioning system gps data from 77 locations around the hector mine earthquake which we use to estimate coseismic displacements related to this shock the existence of pre event gps data some collected to monitor postseismic displacements from the 1992 landers earthquake and some to establish survey control in the meizoseismal area provided a relatively dense coverage close to the rupture zone the data available were collected mostly within the 2 years prior to the 1999 earthquake we reobserved many points within a few days after the shock and all within 6 months after we include corrections for interseismic motion to provide the best value possible for coseismic motion caused by this earthquake the displacements in general display the pattern expected for a strike slip fault though a few show significant vertical motion the maximum horizontal displacement observed was 2 m one station between fault ruptures showed little horizontal motion but significant uplift

seismic remote sensing for the earthquake source process and near source strong shaking a case study of the october 16 1999 hector mine earthquake a new methodology to automatically determine the earthquake source process and near source strong ground motions using regional and local distance data was used to study the october 16 1999 hector mine earthquake mw7 1 broadband displacement data were inverted for the seismic moment tensor and to resolve the fault plane ambiguity independent of aftershock location and surface faulting information the identified nnw striking fault plane was used to invert for the distribution of fault slip over a planar surface the slip model was used to predict near fault peak ground velocity which was found to agree well with the trinet shakemap and also with near fault observations that were not available at the time of the initial analysis our method if automated is capable of providing near source strong ground motion information within 30 minutes of the earthquake origin time even in cases where there are few near fault recording instruments

a deep sea benthic community exposed to strong near bottom currents on the scotian rise western atlantic abstract this paper gives an overview of the structure of a benthic community at 4626 m depth on the nova scotian continental rise here abundances of polychaetes bivalves isopods and tanaids are conspicuously high compared to those reported from comparable depths bacterial numbers and atp concentrations are also high we suspect that these anomalous abundances result from enhanced food availability caused by the strong near bottom currents that flow through the area the polychaete and bivalve faunas have few adults and high species dominance suggesting that currents create large scale sediment transporting disturbances the composition of the crustacean fauna supports this inference in that it is dominated by forms that can enter the seabed and thereby escape adverse conditions on the sediment surface

biofilms microbial mats and microbe particle interactions electron microscope observations from diatomaceous sediments sediments and diatoms from the mudflats of the bay of bourgneuf in western france were examined in an electron microscope study of biofilms and microbial mats the sediments were kept in an aquarium for study and a diatom culture was made of the benthic diatoms the sediment biofilm was composed of exopolymeric substances eps incorporated clay particles and rarely bacteria this film coated all particles at the sediment water interface its surface morphology reflected its composition and internal structure thin films were smooth whilst a lumpy structure or incorporated fibrils produced either a mammillated or ropy surface and clays in the structure gave rise to a flaky morphology at shallow depths in the sediment column 0 5 cm the biofilm was already degraded the biofilm coating degraded diatom frustules in the benthic diatom culture consisted of eps and bacteria and presented a ragged appearance microbial mats occurred on the surface of the fresh littoral sediments as well as those in the aquarium and on the wall of the aquarium the mat on the surface of the aquarium sediments had an open structure with webs of fibrils and bacteria in the pore space it formed in a relatively quiet environment pore space was more limited in the mat from the surface of the fresh littoral sediments in which direct contact between biofilm coated particles was common in the exposed environment of the aquarium wall there was a thick resistant coating of eps in addition to binding particles together the presence of mats and biofilms in sediments affects sediment physical properties such as porosity and permeability the flux of dissolved substances in pore waters and the dissolution of particles and can therefore influence early diagenesis mats and biofilms seem to be more readily preserved in the geological record than the micro organisms such as bacteria which produce them their identification in the sedimentary record would greatly aid interpretation of sediment genesis and evaluation of the microbial role in sediment formation

sedimentation under deep sea storms fast currents high concentrations of suspended sediment and grooved mud beds are associated with erosion in frequent abyssal storms where a fast deep mean flow is augmented or reversed by intense intermittent currents this occurs about 5 km below the gulf stream or its rings the waning phase of a storm results in development of bedforms and rapid deposition of a mud blanket several other regions of the world ocean display evidence of abyssal storm activity

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

the mechanism of partial rupture of a locked megathrust the role of fault morphology assessment of seismic hazard relies on estimates of how large an area of a tectonic fault could potentially rupture in a single earthquake vital information for these forecasts includes which areas of a fault are locked and how the fault is segmented much research has focused on exploring downdip limits to fault rupture from chemical and thermal boundaries and along strike barriers from subducted structural features yet we regularly see only partial rupture of fully locked fault patches that could have ruptured as a whole in a larger earthquake here we draw insight into this conundrum from the 25 april 2015 m w 7 8 gorkha nepal earthquake we invert geodetic data with a structural model of the main himalayan thrust in the region of kathmandu nepal showing that this event was generated by rupture of a decollement bounded on all sides by more steeply dipping ramps the morphological bounds explain why the event ruptured only a small piece of a large fully locked seismic gap we then use dynamic earthquake cycle modeling on the same fault geometry to reveal that such events are predicted by the physics depending on the earthquake history and the details of rupture dynamics however great earthquakes that rupture the entire seismogenic zone are also possible these insights from nepal should be applicable to understanding bounds on earthquake size on megathrusts worldwide

effects of biological activity on the entrainment of marine sediments nowell a r m jumars p a and eckman j e 1981 effects of biological activity on the entrainment of marine sediments mar geol 42 133 153 the effects of animal tracks and fecal pellet production on the critical entrainment velocity of marine sediments were examined experimentally laboratory measurements in a free surface seawater flume were made using three sediment sizes effects of three species of polychaetes and two species of bivalves were tested boundary shear velocity was calculated from the mean velocity profile in the logarithmic region of the boundary layer measurements were made with a hot film anemometer tracking doubled the boundary roughness and decreased the critical entrainment velocity by 20 ambient or free sediments were more easily entrained than fecal mounds which were restrained from movement by mucous adhesion between the fecal coils isolated pellets such as those egested by amphicteis scaphobranchiata transported readily as bedload over a cohesive sediment surface

earthquake source parameters and fault kinematics in the eastern california shear zone based on waveform data from a profile of aftershocks following the north south trace of the 28 june 1992 landers rupture across the mojave desert we construct a new velocity model for the mojave region that features a thin slow crust using this model we obtain source parameters including depth and duration for each of the aftershocks in the profile and in addition any significant m 3 7 joshua tree landers aftershock between april 1992 and october 1994 for which coherent terrascope data were available in all we determine source parameters and stress drops for 45 significant m w 4 earthquakes associated with the joshua tree and landers sequences using a waveform grid search algorithm stress drops for these earthquakes appear to vary systematically with location with respect to previous seismic activity proximity to previous rupture i e with respect to the landers rupture and with tectonic province in general for areas north of the pinto mountain fault stress drops of aftershocks located off the faults involved with the landers rupture are higher than those located on the fault with the exception of aftershocks on the newly recognized kickapoo landers fault stress drops are moderate south of the pinto mountain fault where there is a history of seismic swarms but no single throughgoing fault in contrast to aftershocks in the eastern transverse ranges and related to the 1992 big bear california sequence landers events show no clear relationship between stress drop and depth instead higher stress drop aftershocks appear to correlate with activity on nascent faults or those that experienced relatively small slip during mainshock rupture

mantle flow beneath a continental strike slip fault postseismic deformation after the 1999 hector mine earthquake two recent large earthquakes in the mojave desert california the magnitude 7 3 1992 landers and magnitude 7 1 1999 hector mine earthquakes have each been followed by elevated crustal strain rates over periods of months and years geodetic data collected after the hector mine earthquake exhibit a temporally decaying horizontal velocity field and a quadrant uplift pattern opposite to that expected for localized shear beneath the earthquake rupture we interpret the origin of this accelerated crustal deformation to be vigorous flow in the upper mantle in response to the stress changes generated by the earthquake our results suggest that transient flow in the upper mantle is a fundamental component of the earthquake cycle and that the lower crust is a coherent stress guide coupling the upper crust with the upper mantle

horizontal and vertical distribution of meiofauna in the venezuela basin abstract benthic samples collected in three sedimentary regions of the venezuela basin indicated differences in abundance and distribution of meiofauna among sediments abundance mean 1 s e was greatest in hemipelagic sediments 131 9 14 3 individuals 10 cm 2 less in pelagic 81 2 9 5 and least in turbidite 49 4 8 5 sediments significant differences in abundance between hemipelagic and turbidite sediments were related to percent organic carbon and silt clay significantly more organisms occurred in the upper than lower layer of sediments at all stations with greatest differences occurring between the 0 2 and 2 4 cm layers on a horizontal scale no heterogeneity in meiofauna dispersion at centimeter or kilometer distances was detected for the turbidite and pelagic sediments homogeneity of dispersion was attributed to sediment homogeneity at the turbidite station and small sample size at the pelagic station heterogeneity in meiofauna dispersion at the centimeter scale in hemipelagic sediments was attributed to sediment heterogeneity and high organic input derived from surface production

coseismic deformation of the 2001 mw 7 8 kokoxili earthquake in tibet measured by synthetic aperture radar interferometry the 14 november 2001 m w 7 8 kokoxili earthquake ruptured more than 400 km of the westernmost stretch of the left lateral kunlun fault in northern tibet interferometric synthetic aperture radar data from descending orbits along four adjacent tracks covering almost the entire rupture and 1 m pixel ikonos satellite images are used to map the rupture geometry and the surface displacements produced by the event interferograms are then inverted to solve for coseismic slip on the fault at depth the radar data show that the rupture connected the heituo fault where the earthquake initiated to the main kunlun fault cutting across a pull apart trough in between the two strike slip faults the fault model includes two vertical sections extending to a depth of 20 km and discretized into 5 km 5 km patches using a nonnegative least squares method that includes an appropriate degree of smoothing we solve for the left lateral slip on each fault patch our solution shows that the largest slip occurred at depths between 0 and 5 km reaching 8 m in two areas 200 and 250 km east of the earthquake epicenter significant slip took place below 10 km at both ends of the rupture slip appears to have been highly variable along the fault defining six sections of major moment release these sections correspond to six subsegments of the kunlun fault system defined from the surface morphology of the fault this suggests that fault geometry exerted a predominant influence on controlling the rupture propagation

delayed triggering of the 1999 hector mine earthquake by viscoelastic stress transfer stress changes in the crust due to an earthquake can hasten the failure of neighbouring faults and induce earthquake sequences in some cases1 2 3 4 5 the 1999 hector mine earthquake in southern california magnitude 7 1 occurred only 20 km from and 7 years after the 1992 landers earthquake magnitude 7 3 this suggests that the hector mine earthquake was triggered in some fashion by the earlier event but uncertainties in the slip distribution and rock friction properties associated with the landers earthquake have led to widely varying estimates of both the magnitude and sign of the resulting stress change that would be induced at the location of the hector mine hypocentre with estimates varying from 1 4 bar ref 6 to 0 5 bar ref 7 more importantly coseismic stress changes alone cannot satisfactorily explain the delay of 7 years between the two events here we present the results of a three dimensional viscoelastic model that simulates stress transfer from the ductile lower crust and upper mantle to the brittle upper crust in the 7 years following the landers earthquake using viscoelastic parameters that can reproduce the observed horizontal surface deformation following the landers earthquake our calculations suggest that lower crustal or upper mantle flow can lead to postseismic stress increases of up to 1 2 bar at the location of the hector mine hypocentre during this time period contributing to the eventual occurrence of the 1999 hector mine earthquake these results attest to the importance of considering viscoelastic processes in the assessment of seismic hazard8 9 10 11

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

primary surface rupture associated with the mw 7 1 16 october 1999 hector mine earthquake san bernardino county california the m w 7 1 hector mine earthquake occurred within the mojave desert portion of the eastern california shear zone and was accompanied by 48 km of dextral surface rupture complex northward rupture began on two branches of the lavic lake fault in the northern bullion mountains and also propagated southward onto the bullion fault lesser amounts of rupture occurred across two right steps to the south surface rupture was mapped using postearthquake 1 10 000 scale aerial photography field mapping provided additional detail and more than 400 fault rupture observations of these approximately 300 measurements were used to characterize the slip distribution en echelon surface rupture predominated in areas of thick alluvium whereas in the bedrock areas rupture was more continuous and focused within a narrower zone measured dextral offsets were relatively symmetrical about the epicentral region with a maximum displacement of 5 25 0 85 m 1 vertical slip was a secondary component and was variable with minor west side down displacements predominating in the bullion mountains field and aerial photographic evidence indicates that most of the faults that ruptured in 1999 had had prior late quaternary displacement although only limited sections of the rupture show evidence for prior holocene displacement 1 fn 1

sedimentology and stratigraphy of box cores from the hebble site on the nova scotian continental rise abstract fifty box cores were obtained from the 2 4 km site of the high energy benthic boundary layer experiment hebble on the lower nova scotian continental rise at 4820 m the oldest unit occurring in two gravity cores is a pre holocene dark grey gravelly mud probably of debris flow origin above this is a soft grey mud overlain by brown sandy mud whose sand is largely foraminiferal with some terrigenous material from interbedded turbidites in some places this unit has a stiff brown gravelly mud at its base which is always overlain by sandy mud containing dispersed gravel it is suggested that the dispersed gravel originated from the underlying gravelly mud and has been dispersed upwards by the action of burrowing organisms foraminifera indicate a holocene age down to about 65 cm and thus a net accumulation rate of about 6 cm ka 1 the surface unit of brown mud named the hebble mud is spatially variable in both thickness and sand content which average about 4 cm and 6 respectively sand percentage is not related to silt size or percentage but varies inversely with deposition rate and thickness suggesting a relation to local winnowing the size and peak height of the main silt mode 10 17 m are closely correlated and the peak height is inversely related to the percentage of clay this is attributed to fractionation during deposition of the mud wherein fine silt and clay deposition is suppressed at flow speeds from 10 to 18 cm s 1 leaving coarser silt there is more clay on the upstream and downstream sides of a low spur suggesting spatial variation of shear stress that may be due to a standing internal wave added to the mean flow silt mode size is variable downcore although clay percentages are similar to those at the surface the overall silt size is probably controlled by turbidite input thus silt size is likely to be an unreliable indicator of current speeds down core though peak height of the silt mode may be satisfactory

megafaunal variation in the abyssal landscape of the clarion clipperton zone abstract the potential for imminent polymetallic nodule mining in the clarion clipperton fracture zone ccz has attracted considerable scientific and public attention this concern stems from both the extremely large seafloor areas that may be impacted by mining and the very limited knowledge of the fauna and ecology of this region the environmental factors regulating seafloor ecology are still very poorly understood in this study we focus on megafaunal ecology in the proposed conservation zone area of particular environmental interest 6 study area centred 17 16 n 122 55 w we employ bathymetric data to objectively define three landscape types in the area a level bottom flat an elevated ridge a depressed trough water depth 3950 4250 m that are characteristic of the wider ccz we use direct seabed sampling to characterise the sedimentary environment in each landscape detecting no statistically significant differences in particle size distributions or organic matter content additional seafloor characteristics and data on both the metazoan and xenophyophore components of the megafauna were derived by extensive photographic survey from an autonomous underwater vehicle image data revealed that there were statistically significant differences in seafloor cover by nodules and in the occurrence of other hard substrata habitat between landscapes statistically significant differences in megafauna standing stock functional structuring diversity and faunal composition were detected between landscapes the flat and ridge areas exhibited a significantly higher standing stock and a distinct assemblage composition compared to the trough geomorphological variations presumably regulating local bottom water flows and the occurrence of nodule and xenophyophore test substrata between study areas may be the mechanism driving these assemblage differences we also used these data to assess the influence of sampling unit size on the estimation of ecological parameters we discuss these results in the contexts of regional benthic ecology and the appropriate management of potential mining activities in the ccz and elsewhere in the deep ocean

analysis of a longitudinal ripple from the nova scotian continental rise abstract a longitudinal ripple was obtained in a box core taken from the nova scotian continental rise in july 1982 soft brown mud comprising 1 5 10 sand 60 silt and 35 of m clay forms the 5 cm high and 40 cm wide ripple a maximum thickness of 8 cm of this mud under the crest thinning to 2 cm on the ripple s flank overlies stiff muddy foram ooze the vane shear strength of the brown mud is 0 4 kpa whereas that of the ooze is 4 kpa x radiographs show the mud to contain many fine burrows and a few larger ones as well as winnowed horizons rich in foraminifera of both benthonic and planktonic origin gentle wet sieving of the sand fraction on board ship showed the sand fraction to contain very few faecal pellets thus it appears unlikely that bedload movement played a large part in formation of the ripple rapid initial deposition from a concentrated suspension is suggested to have formed the structure but this was followed by periods of erosion to yield winnowed horizons and further rebuilding with material deposited from suspension radiochemical data 234 th and 210 pb and x radiographs suggest intense particle mixing d b 90 cm 2 yr 1 and rapid sediment deposition 1 5 cm month 1 thus it is possible that the bedform and associated structures are destroyed and recreated on a time scale of a few months

transient stress coupling between the 1992 landers and 1999 hector mine california earthquakes a three dimensional finite element model fem of the mojave block region in southern california is constructed to investigate transient stress coupling between the 1992 landers and 1999 hector mine earthquakes the fem simulates a poroelastic upper crust layer coupled to a viscoelastic lower crust layer which is decoupled from the upper mantle fem predictions of the transient mechanical be havior of the crust are constrained by global positioning system gps data inter ferometric synthetic aperture radar insar images fluid pressure data from water wells and the dislocation source of the 1999 hector mine earthquake two time dependent parameters hydraulic diffusivity of the upper crust and viscosity of the lower crust are calibrated to 10 2 m 2 sec 1 and 5 10 18 pasec respectively the hydraulic diffusivity is relatively insensitive to heterogeneous fault zone permeabil ity specifications and fluid flow boundary conditions along the elastic free surface at the top of the problem domain the calibrated fem is used to predict the evolution of coulomb stress during the interval separating the 1992 landers and 1999 hector mine earthquakes the predicted change in coulomb stress near the hypocenter of the hector mine earthquake increases from 0 02 to 0 05 mpa during the 7 yr interval separating the two events this increase is primarily attributed to the recovery of decreased excess fluid pressure from the 1992 landers coseismic undrained strain field coulomb stress predictions are insensitive to small variations of fault plane dip and hypocentral depth estimations of the hector mine rupture

biological activity and associated sedimentary structures in hebble area deposits western north atlantic abstract biological and sedimentologic samples along with x radiographs of sediment slabs were taken from box cores in the hebble area 4700 m on the lower continental rise of nova scotia these data suggest that this bottom region is influenced by periods of strong near bottom currents which erode and physically transport sediments these high periods alternate with periods of weaker flow biogenic reworking of sediments by an active benthic infauna dominates particle transport during low flow conditions

spatial and temporal variability of meiobenthic density in the blanes submarine canyon nw mediterranean abstract meiofaunal density distribution was studied from 400 m to 1500 m depth inside blanes submarine canyon nw mediterranean and on the eastern open slope in autumn 2003 and spring 2004 our multidisciplinary approach allowed to study the hydrodynamics and sedimentary processes in the blanes canyon that characterize it as highly heterogeneous environment inside the canyon area particle fluxes were higher than on the slope area increased from autumn to spring and mostly consisted of lithogenic material moreover the canyon s locations experienced more intense bottoms currents and sediment disturbance being reflected in a greater variability of meiobenthic densities both between stations and sampling times than on the open slope no clear trends e g declining densities associated with increasing depths were observed contrary in the open slope current velocities were relatively lower compared with the canyon area and showed lower temporal variability at the same time the nutritional quality of the particle fluxes at deeper grounds were higher probably allowing the meiofaunal densities not to change over time in conclusion the meiobenthos in our system apparently showed a higher temporal variability inside the canyon area strongly affected by particle fluxes or erosive and sediment mixing processes linked to current modifications induced by the canyon topography

biological pumping upwards of the coarse fraction of deep sea sediments abstract in a restricted part of an area intensively sampled by box coring approximately 50 samples from a 2 4 km rectangle a stiff muddy glacial gravel till is encountered at a depth of 30 40 cm x radiographs of the upper 15 to 20 cm of the cores reveal gravel in overlying foraminiferal mud only from the area where there is the deeper till layer the localization strongly suggests that the material in the top of the cores has its source in the deeper layer i postulate that burrowing organisms move gravel upward by pushing aside the particles that are too large to be eaten because the strength of the enclosing mud decreases upwards the gravel particles move preferentially upward the upward decrease in shear strength of he sediment is rapid at an interface occurring 4 cm below the surface on average thus hydrostatic pressures of 20 to 200 g cm2 exerted by vermiform burrowing animals act within an environment of asymmetrical sediment property permitting an asymmetrical response to the uniformly directed body pressure this asymmetrical response a pumping mechanism affecting material that does not pass through the gut is contrasted with the mixing of finer sediments that are eaten and excreted documented by many other workers dimensional arguments suggest the flux of material is related to the ratio of biological mixing rate to sedimentation rate the mechanism is also applicable to maintenance of mn nodules and their nuclei at the surface if macrofossils have behaved like gravel some s ell beds may have been generated and some stratigraphic anomalies caused by this means

temporal variability in living deep sea benthic foraminifera a review the deep ocean environment is disturbed by various processes many of which involve episodic inputs of organic matter some inputs e g phytodetritus at mid high latitudes in the north atlantic and northeast pacific are seasonally pulsed others e g falls of whale carcasses are irregular and unpredictable but together they evoke a variety of responses from the benthic biota in the case of deep sea foraminifera only those responses arising from seasonal food pulses have been fairly well documented the population dynamics of deep sea benthic foraminifera total live populations and individual species appear to be controlled largely by two inversely related parameters the flux of organic matter to the seafloor and concentrations of oxygen in the sediment porewater organic matter food inputs are most intense along bathyal continental margins and their oxidation often leads to the depletion of oxygen in surface sediments under these conditions foraminiferal faunas are dominated by low oxygen tolerant infaunal species the abundance of which fluctuate in response to seasonally varying amounts of food and oxygen at some sites e g sagami bay off japan species migrate up and down in the sediments tracking critical oxygen concentrations where oxygen concentrations are consistently low less than about 0 5 ml l 1 as in parts of the california borderland foraminifera may undergo population increases solely in response to food pulses in the abyssal north atlantic and in some continental margin areas of this ocean organic matter inputs are weaker and do not lead to oxygen depletion within surface sediments these systems are food limited and seasonal population fluctuations reflect the availability of food phytodetritus rather than oxygen here the species which respond to phytodetritus are mainly epifaunal or shallow infaunal opportunists which represent a small proportion of highly diverse communities 2 or 3 out of 120 species per core of 25 5 cm2 surface area seasonal phytodetrital pulses to the deep seafloor and hence foraminiferal population dynamics are not entirely predictable being dependent on climatic and upper ocean processes they vary in intensity from year to year and occasionally e g at the porcupine abyssal plain pap in 1997 fail to materialise foraminiferal responses to irregular non seasonal organic matter inputs are poorly known however there is some evidence that whale falls turbidite deposits hydrothermal vents and seeps are exploited by species typical of organically enriched low oxygen environments rather than by a specialised fauna fossil foraminiferal assemblages from bathyal and abyssal environments may provide evidence for an increase or decrease in the seasonality of surface production as well as for longer term changes in palaeoproductivity however the accurate interpretation of this record depends on filling the many gaps which remain in our understanding of relations between benthic foraminiferal ecology and seasonal phenomena in the deep ocean

early postseismic deformation from the 16 october 1999 mw 7 1 hector mine california earthquake as measured by survey mode gps the 16 october 1999 m w 7 1 hector mine earthquake was the largest earthquake in california since the 1992 m w 7 3 landers event the hector mine earthquake occurred in the eastern mojave desert where the density of permanent global positioning system gps stations is relatively low since the earthquake groups from the united states geological survey university of southern california university of california los angeles university of california san diego and massachusetts institute of technology have made postseismic survey mode observations to increase the spatial coverage of deformation measurements a total of 55 sites were surveyed with markers from a few meters to 100 km from the surface rupture we present velocity estimates for the 32 sites that had enough repeated observations between 17 october 1999 and 26 march 2000 to provide reliable results these survey mode data complement the temporal and spatial coverage provided by newly installed southern california integrated geodetic network permanent gps stations and future interferometric synthetic aperture radar postseismic results we then use the postseismic velocity estimates to compute a simple afterslip model results of inversions show that the observed velocities are consistent with deep afterslip occuring underneath the coseismic rupture area

the fauna of the hebble site patterns in standing stock and sediment dynamic effects abstract at the high energy benthic boundary layer experiment hebble site at 4820 m depth on the nova scotia rise 40 27 n 62 20 w abundances of polychaetes bivalves tanaids and isopods were conspicuously greater than expected for the depth whereas those of nematodes and harpacticoids the two dominant meiofaunal taxa were not further the abundances of polychaetes bivalves tanaids and nematodes were consistent over time and appeared to be unaffected by the periods of strong near bottom flow that characterized the site in contrast isopods and harpacticoid copepods were less abundant in samples taken as a storm abated apparently because they were eroded during benthic storms we explore implications of the difference between macrofaunal and meiofaunal abundance for community structure in addition because a goal of the hebble project was the parameterization of sediment transport in the deep sea we summarize ways that the biota affects sediment transport at this high energy site

the coseismic geodetic signature of the 1999 hector mine earthquake the m 7 1 hector mine earthquake ruptured the lavic lake fault near twentynine palms ca at 09 46 utc october 16 1999 because it occurred near the eastern edge of the southern california integrated gps network scign a network of permanent continuously recording gps receivers for measuring the crustal deformation field around los angeles ca it was possible to determine the deformation associated with the earthquake with unprecedented speed and reliability thirty four stations recorded displacements over the 3 sigma level the displacements measured with gps can be modeled by a fault 46 2 2 6 km long 8 2 1 0 km wide striking 330 dipping 84 east with 301 36 cm right lateral strike slip and 145 36 cm of east up dip slip yielding a potency of 1 3 km and geodetic moment of 3 8 1026 dyne cm the trace and dip of the model fault is consistent with the observed ground rupture and seismic focal mechanisms

coseismic surface deformation from air photos the kickapoo step over in the 1992 landers rupture coseismic deformation of the ground can be measured from aerial views taken before and after an earthquake we chose the area of the kickapoo landers step over along the 1992 landers earthquake zone using air photos scale 1 40 000 scanned at 0 4 m resolution two photos acquired after the earthquake are used to assess the accuracy and to evaluate various sources of noise optical distortions film deformation scanning errors or errors in viewing parameters can yield metric bias at wavelength larger than 1 km offset field at shorter wavelength is more reliable and mainly affected by temporal decorrelation of the images induced by changes in radiometry with time temporal decorrelation and resulting uncertainty on offsets are estimated locally from the correlation degree between the images relative surface displacements are measured independently every about 15 m and with uncertainty typically below 10 cm rms the offset field reveals most of the surface ruptures mapped in the field the fault slip is accurate to about 7 cm rms and measured independently every 200 m from stacked profiles slip distribution compares well with field measurements at the kilometric scale but reveals local discrepancies suggesting that deformation is generally although not systematically localized on the major fault zone located in the field this type of data can provide useful insight into the fault zone s mechanical properties our measurements indicate that elastic coseismic strain near the fault zone can be as large as 0 5 10 3 while anelastic yielding was attained for strain in excess of about 1 2 10 3

geodetic observations of postseismic creep in the decade after the 1999 izmit earthquake turkey implications for a shallow slip deficit the relationship between aseismic slip and tectonic loading is important for understanding both the pattern of strain accumulation along a fault and its ability to generate large earthquakes we investigate the spatial distribution and temporal evolution of aseismic creep on the western north anatolian fault naf using time series analysis of envisat interferometric synthetic aperture radar insar data covering the full extent of the 1999 izmit and duzce earthquake ruptures and spanning 2002 2010 discontinuities in the line of sight velocity across the fault imply that fault creep reaches the earth s surface at an average fault parallel rate of 5 mm yr along an 80 km section of the naf by combining insar and published gps velocities we are able to extract the vertical and east west components of motion and show that the adapazari basin is subsiding at a rate of 6 mm yr vertical motions have biased previous estimates of creep in this region the displacement time series close to the fault is consistent with an afterslip model based on rate and state friction which predicts a rapid deceleration in fault creep rate after the izmit earthquake to a near steady state 5 mm yr after 5 years projecting our model 200 years into the future we find that the cumulative displacement of 1 1 3 m is insufficient to account for the shallow coseismic slip deficit observed in previous studies distributed off fault deformation in the shallow crust or transient episodes of faster slip are likely required to release some of the long term strain during the earthquake cycle

adaptive regularization of earthquake slip distribution inversion abstract regularization is a routine approach used in earthquake slip distribution inversion to avoid numerically abnormal solutions to date most slip inversion studies have imposed uniform regularization on all the fault patches however adaptive regularization where each retrieved parameter is regularized differently has exhibited better performances in other research fields such as image restoration in this paper we implement an investigation into adaptive regularization for earthquake slip distribution inversion it is found that adaptive regularization can achieve a significantly smaller mean square error mse than uniform regularization if it is set properly we propose an adaptive regularization method based on weighted total least squares wtls this approach assumes that errors exist in both the regularization matrix and observation and an iterative algorithm is used to solve the solution a weight coefficient is used to balance the regularization matrix residual and the observation residual an experiment using four slip patterns was carried out to validate the proposed method the results show that the proposed regularization method can derive a smaller mse than uniform regularization and resolution based adaptive regularization and the improvement in mse is more significant for slip patterns with low resolution slip patches in this paper we apply the proposed regularization method to study the slip distribution of the 2011 mw 9 0 tohoku earthquake the retrieved slip distribution is less smooth and more detailed than the one retrieved with the uniform regularization method and is closer to the existing slip model from joint inversion of the geodetic and seismic data

locating distributed faulting contributions from insar imaging to probabilistic fault displacement hazard analysis pfdha abstract prediction of location and amount of slip for distributed faulting associated to strong earthquakes is a recently explored issue with major implications in terms of hazard assessment currently the best practice involves the applications of probabilistic fault displacement hazard analysis pfdha whose results fit sufficiently well real data in the near range of the primary fault but show considerable inaccuracies in the far range we believe that this inaccuracy descends from the biased earthquake databases used for regression analysis whose data relative to old earthquakes were largely collected only by field surveys focused close to the primary fault i e near range remotely sensed data i e interferometric radar imaging insar offer the opportunity to precisely measure the surface deformation induced by strong earthquakes and thus to explore its possible relation with distributed faulting we analyze the l aquila earthquake case study 29th april 2009 mw 6 3 and explore the correlation between location and slip on distributed faulting and insar derived deformation field we find a significant correlation between occurrence of distributed faulting and profile curvature of the dislocation field in spite of the distance from the primary fault moreover distributed faults tend to occur within the area deformed by the earthquake as imaged by insar data and whose extent is directly proportional to the earthquake magnitude mw according to a dataset of 30 recent earthquakes we then propose that these observations have to be incorporated into the present pfdha practice as limit boundaries to possible scenarios of probabilistic analysis and that an integrated use of field based and remotely data collection have to be implemented following strong earthquakes

stress triggering of the 1999 hector mine earthquake by transient deformation following the 1992 landers earthquake the m 7 3 june 28 1992 landers and m 7 1 october 16 1999 hector mine earthquakes california both right lateral strike slip events on nnw trending subvertical faults occurred in close proximity in space and time in a region where recurrence times for surface rupturing earthquakes are thousands of years this sug gests a causal role for the landers earthquake in triggering the hector mine earth quake previous modeling of the static stress change associated with the landers earthquake shows that the area of peak hector mine slip lies where the coulomb failure stress promoting right lateral strike slip failure was high but the nucleation point of the hector mine rupture was neutrally to weakly promoted depending on the assumed coefficient of friction possible explanations that could account for the 7 year delay between the two ruptures include background tectonic stressing dissi pation of fluid pressure gradients rate and state dependent friction effects and post landers viscoelastic relaxation of the lower crust and upper mantle by employing a viscoelastic model calibrated by geodetic data collected during the time period between the landers and hector mine events we calculate that postseismic relaxa tion produced a transient increase in coulomb failure stress of about 0 7 bars on the impending hector mine rupture surface the increase is greatest over the broad surface that includes the 1999 nucleation point and the site of peak slip further north since stress changes of magnitude greater than or equal to 0 1 bar are associated with documented causal fault interactions elsewhere viscoelastic relaxation likely con tributed to the triggering of the hector mine earthquake this interpretation relies on the assumption that the faults occupying the central mojave desert i e both the landers and hector mine rupturing faults were critically stressed just prior to the landers earthquake

the complete 3 d surface displacement field in the epicentral area of the 1999 mw7 1 hector mine earthquake california from space geodetic observations we use interferometric synthetic aperture radar insar data to derive continuous maps for three orthogonal components of the co seismic surface displacement field due to the 1999 m w7 1 hector mine earthquake in southern california vertical and horizontal displacements are both predominantly antisymmetric with respect to the fault plane consistent with predictions of linear elastic models of deformation for a strike slip fault some deviations from symmetry apparent in the surface displacement data may result from complexity in the fault geometry

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

effect of confining pressure on the diffusion of hto 36cl and 125i in a layered argillaceous rock opalinus clay diffusion perpendicular to the fabric abstract the through and out diffusion of hto 36cl and 125i in opalinus clay an argillaceous rock from the northern part of switzerland was studied under different confining pressures between 4 and 15 mpa the direction of diffusion and the confining pressure were perpendicular to the bedding confining pressure had only a small effect on diffusion an increase in pressure from 4 to 15 mpa resulted in a decrease of the effective diffusion coefficient of 20 diffusion accessible porosities were not measurably affected the values of the effective diffusion coefficients de ranged between 5 6 0 4 10 12 and 6 7 0 4 10 12 m2 s 1 for hto 7 1 0 5 10 13 and 9 1 0 6 10 13 m2 s 1 for 36cl and 4 5 0 3 10 13 and 6 6 0 4 10 13 m2 s 1 for 125i the rock capacity factors measured were circa 0 14 for hto 0 040 for 36cl and 0 080 for 125i because of anion exclusion effects anions diffuse slower and exhibit smaller diffusion accessible porosities than the uncharged hto unlike 36cl 125i sorbs weakly on opalinus clay resulting in a larger rock capacity factor the sorption coefficient kd for 125i is of the order of 1 2 10 5 m3 kg 1 the effective diffusion coefficient for hto is in good agreement with values measured in other sedimentary rocks and can be related to the porosity using archie s law with exponent m 2 5

storms and flow reversals at the hebble site abstract we examine a 20 month long abyssal current meter record obtained from the hebble site about 40 27 n 62 22 w as expected the westward flowing abyssal western boundary current described by richardson et al 1981 and weatherly and kelley 1982 generally passes over this site we call this current the cold filament current cfc and conclude that it is appreciably stronger than suggested by weatherly and kelley 1984 15 cm s 1 as compared to 10 cm s 1 after comparing the abyssal current record with charts showing the surface location of the gulf stream and rings we conclude that the majority of abyssal storms at the hebble site are due to the presence of the cfc passing by and the absence of a meander or ring overhead the presence of a ring or meander overhead apparently results in the cfc being displaced out of the hebble site as suggested by kelley 1984 at such times the near bottom flow appears to respond to the barotropic component of the overlying ring or meander

the 1999 mw 7 1 hector mine california earthquake near field postseismic deformation from ers interferometry interferometric synthetic aperture radar insar data over the area of the hector mine earthquake mw 7 1 16 october 1999 reveal postseismic defor mation of several centimeters over a spatial scale of 0 5 to 50 km we analyzed seven sar acquisitions to form interferograms over four time periods after the event the main deformations seen in the line of sight los displacement maps are a region of subsidence 60 mm los increase on the northern end of the fault a region of uplift 45 mm los decrease located to the northeast of the primary fault bend and a linear trough running along the main rupture having a depth of up to 15 mm and a width of about 2 km we correlate these features with a double left bending right lateral strike slip fault that exhibits contraction on the restraining side and extension along the releasing side of the fault bends the temporal variations in the near fault postseismic deformation are consistent with a characteristic time scale of 135 42 or 25 days which is similar to the relaxation times following the 1992 landers earthquake high gradients in the los displacements occur on the fault trace con sistent with afterslip on the earthquake rupture we derive an afterslip model by inverting the los data from both the ascending and descending orbits our model indicates that much of the afterslip occurs at depths of less than 3 to 4 km

continuous gps observations of postseismic deformation following the 16 october 1999 hector mine california earthquake mw 7 1 rapid field deployment of a new type of continuously operating global positioning system gps network and data from southern california integrated gps network scign stations that had recently begun operating in the area allow unique observations of the postseismic deformation associated with the 1999 hector mine earthquake innovative solutions in fieldcraft devised for the 11 new gps stations provide high quality observations with 1 year time histories on stable monuments at remote sites we report on our results from processing the postseismic gps data available from these sites as well as 8 other scign stations within 80 km of the event a total of 19 sites from these data we analyze the temporal character and spatial pattern of the postseismic transients data from some sites display statistically significant time variation in their velocities although this is less certain the spatial pattern of change in the postseismic velocity field also appears to have changed the pattern now is similar to the pre landers pre 1992 secular field but laterally shifted and locally at twice the rate we speculate that a 30 km 50 km portion of crust near twentynine palms which was moving at nearly the north american plate rate to within 3 5 mm yr of that rate prior to the 1992 landers sequence now is moving along with the crust to the west of it as though it has been entrained in flow along with the pacific plate as a result of the landers and hector mine earthquake sequence the inboard axis of right lateral shear deformation at lower crustal to upper mantle depth may have jumped 30 km farther into the continental crust at this fault junction that comprises the southern end of the eastern california shear zone

static stress impact of the 1992 landers earthquake sequence on nucleation and slip at the site of the 1999 m 7 1 hector mine earthquake southern california the proximity in time 7 years and space 20 km between the 1992 m 7 3 landers earthquake and the 1999 m 7 1 hector mine event suggests a possible link between the quakes we thus calculated the static stress changes following the 1992 joshua tree landers big bear earthquake sequence on the 1999 m 7 1 hector mine rupture plane in southern california resolving the stress tensor into rake parallel and fault normal components and comparing with changes in the post landers seismicity rate allows us to estimate a coefficient of friction on the hector mine plane seismicity following the 1992 sequence increased at hector mine where the fault was unclamped this increase occurred despite a calculated reduction in right lateral shear stress the dependence of seismicity change primarily on normal stress change implies a high coefficient of static friction 0 8 we calculated the coulomb stress change using 0 8 and found that the hector mine hypocenter was mildly encouraged 0 5 bars by the 1992 earthquake sequence in addition the region of peak slip during the hector mine quake occurred where coulomb stress is calculated to have increased by 0 5 1 5 bars in general slip was more limited where coulomb stress was reduced though there was some slip where the strongest stress decrease was calculated interestingly many smaller earthquakes nucleated at or near the 1999 hector mine hypocenter after 1992 but only in 1999 did an event spread to become a m 7 1 earthquake

a non linear geodetic data inversion using abic for slip distribution on a fault with an unknown dip angle summary we have developed a method of geodetic data inversion for slip distribution on a fault with an unknown dip angle a common strategy for obtaining slip distribution in previous studies is to first determine the fault geometry by minimizing the square misfit under the assumption of a uniform slip on a rectangular fault and then apply the usual linear inversion technique to estimate a slip distribution on the determined fault it is not guaranteed however that the fault determined under the assumption of a uniform slip gives the best fault geometry for a spatially variable slip distribution the inverse problem is non linear for cases with unknown fault geometries but the non linearity of the problems is actually weak when we can assume the fault surface to be a flat plane in particular when a clear trace of coseismic faults is observed on the earth s surface only the dip angle is an unknown parameter to determine the fault geometry then we regarded the dip angle as an hyperparameter that prescribed the structure of parametric models and obtained the best estimate of the dip angle using akaike s bayesian information criterion abic with the best estimate of the dip angle we can obtain the slip distribution on the fault based on the maximum likelihood principle we applied the method to the insar data of the 1995 dinar turkey earthquake and obtained a much lower dip angle than the previous analyses

boundary skin friction and sediment transport about an animal tube mimic a flume study was made of fluid flow boundary skin friction and sediment transport about an animal tube mimic the effect of a tube on momentum transfer depends most strongly on its height a tube increases the net boundary skin friction locally and tends to promote sediment entrainment near its base flow in this region appears to be governed by the same similarity laws that apply to cylinders with much larger body reynolds number particles travelling as suspended load may be deposited immediately downstream of the tube the net sedimentological effect of any tube i e deposition or scour will depend both on its height and on the boundary shear stress imposed by the external flow the near wake region of a tube is dominated by a strong cross stream exchange of momentum wake perturbations decay downstream seemingly in accordance with similarity laws which also govern mounted two dimensional structures

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

effects of biological activity by abyssal benthic macroinvertebrates on a sedimentary structure in the venezuela basin abstract macrobenthic standing stock estimates from the venezuela basin were in agreement with those calculated from other ocean basins biomass and density values were significantly higher at a site characterized by hemipelagic sedimentation compared to two sites characterized by carbonate and turbidite sedimentation the higher standing stock is probably related to the higher input of organic matter to that site vertical distribution of fauna suggests that sediment was well mixed to 6 8 cm depth at the carbonate and turbidite sites and to 10 12 cm depth at the hemipelagic site infrequent mixing probably extends to 30 cm at the turbidite site 18 cm at the hemipelagic site and 10 cm at the carbonate site mixing rates were predicted to be the highest at the hemipelagic site where benthic standing stocks were highest these mixing depths and rates were in general agreement with those determined by radiochemical methods and by visual and x ray photographic observations gradients of decreased porosity and increased density were probably the result of biological activity burrowing and tube dwelling as opposed to effects of overburden pressure sediment shear strength was controlled by biological activity coupled with biologically mediated chemical bonding at the redox discontinuity layer destruction of sand sized foraminiferan tests by faunal ingestion of sediments contributes to a reduction in mean grain size at the sediment surface

trophic structure of macrobenthos in the gulf of st lawrence and on the scotian shelf abstract the gulf of st lawrence and scotian shelf provide a diversity of oceanographic conditions in a continental margin setting climate is markedly seasonal and bathymetry and hydrodynamic conditions cover a broad range significantly influencing the patterns of organic matter sedimentation and potentially benthic community dynamics samples for analysis of benthic macrofauna and sediment microorganisms were collected at six stations in the gulf of st lawrence gsl and the scotian shelf during winter and summer cruises as part of the canadian joint global ocean flux study multivariate analyses indicate significant site related trends in trophic guilds benthic assemblages and microbial activity some of which are related to geomorphological characteristics bathymetry topography and substratum macrofaunal trophic guild data show that the stations with relatively deep settling basins cabot strait and emerald basin dominated by surface deposit feeders were distinct from stations with sloping bottoms anticosti gyre and anticosti channel where subsurface deposit feeders dominated or surface and subsurface deposit feeders were equally abundant deposit feeders surface and subsurface trophic groups made up 60 of the benthic communities except at the scotian slope station where they represented 44 of the total benthic abundances based on the data collected in both the water column and the sediment at three deep stations in the gsl we hypothesize that the proportion of surface and subsurface deposit feeders and thus the nature of bioturbation activity is related to the magnitude and pattern of organic matter supply from the euphotic zone

benthic foraminifera living in gulf of mexico bathyal and abyssal sediments community analysis and comparison to metazoan meiofaunal biomass and density abstract benthic foraminiferal biomass density and species composition were determined at 10 sites in the gulf of mexico during june 2001 and 2002 sediment samples were collected with a gomex box corer a 7 5 cm diameter subcore was taken from a box core collected at each site and sliced into 1 cm or 2 cm sections to a depth of 2 or 3 cm the 63 m fraction was examined shipboard for benthic foraminifera individual foraminifers were extracted for adenosine triphosphate atp using a luciferin luciferase assay which indicated the total atp content per specimen that data was converted to organic carbon foraminiferal biomass and density varied substantially 2 53 mg c m 2 3600 44 500 individuals m 2 respectively and inconsistently with water depth although two 1000 m deep sites were geographically separated by only 75 km the foraminiferal biomass at one site was relatively low 9 mg c m 2 while the other site had the highest foraminiferal biomass 53 mg c m 2 although most samples from sigsbee plain 3000 m had low biomass one sigsbee site had 20 mg foraminiferal c m 2 the foraminiferal community from all sites i e bathyal and abyssal locales was dominated by agglutinated rather than calcareous or tectinous species foraminiferal density never exceeded that of metazoan meiofauna at any site foraminiferal biomass however exceeded metazoan meiofaunal biomass at 5 of the 10 sites indicating that foraminifera constitute a major component of the gulf s deep water meiofaunal biomass

short term earthquake prediction by reverse analysis of lithosphere dynamics abstract short term earthquake prediction months in advance is an elusive goal of earth sciences of great importance for fundamental science and for disaster preparedness here we describe a methodology for short term prediction named rtp reverse tracing of precursors using this methodology the san simeon earthquake in central california magnitude 6 5 dec 22 2003 and the tokachi oki earthquake in northern japan magnitude 8 1 sept 25 2003 were predicted 6 and 7 months in advance respectively the physical basis of rtp can be summed up as follows an earthquake is generated by two interacting processes in a fault network an accumulation of energy that the earthquake will release and a rise of instability triggering this release energy is carried by the stress field instability is carried by the difference between the stress and strength fields both processes can be detected and characterized by premonitory patterns of seismicity or other relevant fields here we consider an ensemble of premonitory seismicity patterns rtp methodology is able to reconstruct these patterns by tracing their sequence backwards in time the principles of rtp are not specific to earthquakes and may be applicable to critical transitions in a wide class of hierarchical non linear systems

insight into the 2016 menyuan m w 5 9 earthquake with insar a blind reverse event promoted by historical earthquakes in 2016 the mw 5 9 menyuan earthquake occurred at the western end of the tianzhu seismic gap in the middle segment of the left lateral strike slip haiyuan fault system studying the focal mechanism of the menyuan earthquake and its correlation with historical seismicity is of great significance in understanding the tectonic style of the haiyuan fault system and assessing the tianzhu gap seismic risk using sentinel 1a radar imagery we obtain the coseismic deformation field of the menyuan earthquake in the los direction and invert the deformation field slip distribution model based on the interseismic deformation field reflected by gps data and the relocated results of aftershocks provided by previous studies we then analyze the seismogenic nodal plane of the menyuan earthquake and consider the west dipping model to be the most likely seismogenic solution the west dipping model indicates that the average slip of the menyuan earthquake is 0 41 m and the average rake angle is 68 with a magnitude of mw 5 905 considering the historical strong earthquakes and viscoelastic layered crust the results from coulomb failure stress modeling indicate that the coulomb stress loading caused by the historical strong events promoted the occurrence of the 2016 menyuan earthquake both the low seismicity within the tianzhu gap and the cluster phenomenon of medium earthquakes on the lao hu shan lhs and leng long ling lll faults have strong correlations with the stress change distribution resulting from the historical strong earthquakes a series of medium events occurring on the north side of the lll fault represented by the 2016 menyuan earthquake would raise the seismic risk on the western end of the tianzhu gap

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

near field investigations of the landers earthquake sequence april to july 1992 the landers earthquake which had a moment magnitude m w of 7 3 was the largest earthquake to strike the contiguous united states in 40 years this earthquake resulted from the rupture of five major and many minor right lateral faults near the southern end of the eastern california shear zone just north of the san andreas fault its m w 6 1 preshock and m w 6 2 aftershock had their own aftershocks and foreshocks surficial geological observations are consistent with local and far field seismologic observations of the earthquake large surficial offsets as great as 6 meters and a relatively short rupture length 85 kilometers are consistent with seismological calculations of a high stress drop 200 bars which is in turn consistent with an apparently long recurrence interval for these faults