separation of coseismic and postseismic gravity changes for the 2004 sumatra andaman earthquake from 4 6 yr of grace observations and modelling of the coseismic change by normal modes summation eodspatiale grgs for comparison the release 04 solutions of the center for space research csr are also inves tigated after a spectral windowing or a gaussian spatial smoothing results are shown both in terms of geoid height changes and gravity variations coseismic and postseismic gravitational changes estimated from the different gravity solutions are globally similar although their spa tial extent and amplitude depend on the type of filter used in the processing of grace fields the highest signal to noise ratio is found with the grgs solutions the postseismic signature has a spectral content closer to the grace bandwidth than the coseismic signature and is therefore better detected by grace the coseismic signature consists mainly of a strong gravity decrease east of the sunda trench in the andaman sea a gravity increase is also detected at a smaller scale west of the trench the model for the coseismic gravity changes agrees well with the coseismic signature estimated from grace regarding the overall shape and orientation location with respect to the trench and order of magnitude coseismic gravity changes are followed by a postseismic relaxation that are well fitted by an increasing expo nential function with a mean relaxation time of 0 7 yr the total postseismic gravity change consists of a large scale positive anomaly centred above the trench and extending over 15 of latitude along the subduction after 26 months the coseismic gravity decrease has been partly compensated by the postseismic relaxation but a negative anomaly still remains south of phuket a dominant gravity increase extends over 15 of latitude west of the trench being maximal south of the epicentre area by investigating analyses of two global hydrology models and one ocean general circulation model we show that our grace estimates of the coseismic and postseismic gravitational changes are almost not biased by interannual variations originat ing from continental hydrology and ocean circulation in the subduction area and in the central part of the andaman sea while they are biased by several gal in the malay peninsula

sea cliffs their processes profiles and classification general concavity or convexity of sea cliff profiles is controlled by relative rates of erosion by marine and subaerial processes as well as by positions of more resistant strata in the cliffs profiles supplemented by on site examination can establish the activity and dominance of erosional processes and indicate changes in regimen a sharp angle at the sea cliff base generally indicates active marine erosion whereas a smooth curve at the base means that subaerial erosion may dominate talus shows absence of marine erosion studies of profiles can be useful for estimating stability for residences railroads and highways at the top face and base of sea cliffs generally increased erosion and retreat of sea cliffs are in prospect because of projected regionally wetter and stormier climate rising sea level and increased human activities

investigation on afterslip and steady state and transient rheology based on postseismic deformation and geoid change caused by the sumatra 2004 earthquake the commonly used rheological model for the earth s mantle when considering geological time scales mantle convection is the viscoelastic maxwell model which assumes a steady state creep process however application of this model to phenomena on shorter time scales such as postglacial rebound or postseismic relaxation leads to difficulties in finding a consistent interpretation of obtained viscosities using standard maxwell viscosity of 1e19 pa s to analyze postseismic near field gps time series from the 2004 sumatra andaman earthquake requires large time dependent afterslip with a relaxation time of about 1 year we show that using linear biviscous burgers rheology for the asthenosphere together with a refined coseismic slip model we can drastically reduce the amount of apparent afterslip comparison of predicted geoid change to observations by the grace satellite mission shows that a univiscous maxwell model with afterslip is not compatible with observations since even large afterslip has a more localized effect than transient relaxation due to the main earthquake which in turn is in agreement with observations thus a combination of ground and space based geodetic observations is very useful in differentiating between rheological models an additional independent discrimination between afterslip and biviscous relaxation could be obtained by installing ocean bottom pressure gauges close to the trench

post processing removal of correlated errors in grace data 1 gravity fields produced by the gravity recovery and climate experiment grace satellite mission require smoothing to reduce the effects of errors present in short wavelength components as the smoothing radius decreases these errors manifest themselves in maps of surface mass variability as long linear features generally oriented north to south i e stripes the presence of stripes implies correlations in the gravity field coefficients here we examine the spectral signature of these correlated errors and present a method to remove them finally we apply the filter to a model of surface mass variability to show that the filter has relatively little degradation of the underlying geophysical signals we seek to recover

gravity changes due to the sumatra andaman and nias earthquakes as detected by the grace satellites a reexamination summary in this paper we study the geoid changes caused by the sumatra andaman earthquake 2004 december 26 and the nias earthquake 2005 march 28 using data from the gravity recovery and climate experiment grace satellites new is that we explore the possibility to separate the effects of the sumatra andaman and nias earthquakes based on correlation analysis we investigate the separability of the sumatra andaman and nias signals and the feasibility of separating the non seismic linear trend from the time dependent post seismic relaxation effect as input data we use 76 months of global geopotential coefficients from the gfz release 4 rl04 of grace data to suppress unphysical artefacts in grace data striping the grace coefficients are smoothed with an anisotropic decorrelation filter model parameters are estimated through a bayesian approach we compare our results with geophysical models of both earthquakes calculated based on the viscoelastic gravitational dislocation theory the slip models used are inverted from gps measurements our findings indicate that the inversion of grace data for the sumatra andaman effect will contain significant signal from the nias earthquake and will benefit from removing the modelled nias effect from the data comparing grace measurements to geophysical models reveals significant differences we suggest how the gps calibrated models may be improved to better fit the grace data in the first months after the earthquake we also find evidence for a fast process in the andaman sea possibly due to aseismic slip similar phenomena were observed in previous studies

assessing landslide potential using gis soil wetness modeling and topographic attributes payette river idaho this study utilizes gis modeling to determine if the location of 559 landslides in the 875 km2 catchment of the middle fork of the payette river idaho can be predicted based on topographic attributes and a wetness index generated by the dynwet model slope and elevation were significantly related to landslide occurrence at this landscape scale aspect was also retained as a variable for further analysis because despite a non significant chi square relation to landslide occurrence graphical analysis suggested a relation between aspect and mass wasting chi square analysis indicated that plan and profile curvature flow path length upslope contributing area and the dynwet based moisture index were not significantly related to landsliding a bayesian probability model based on combinations of elevation slope aspect and wetness indicates that elevation exhibits the closest relation to landsliding followed by slope but that neither aspect nor wetness index values help in prediction the bayesian probability model using elevation and slope generates a map of relative landslide risk that can be used to direct activities away from mass wasting prone areas the association between elevation and landslides is perplexing but is perhaps due to the location of logging road at specific elevations roads could not be included in the input data for analysis because they have not been adequately mapped the lack of explanation provided by the dynwet wetness index was also surprising and may be due to the 30 m digital elevation model dem and the soils data having resolutions too coarse to adequately portray local variations key to mass wasting we believe the inadequacy of data to drive the models is typical of the majority of catchment scale setting for now the ability of researchers to effectively model landscape scale landsliding is more limited by the type resolution and quality of available data than by the quality of the landslide models

methods for inferring regional surface mass anomalies from gravity recovery and climate experiment grace measurements of time variable gravity 1 the gravity recovery and climate experiment grace will deliver monthly averages of the spherical harmonic coefficients describing the earth s gravity field from which we expect to infer time variable changes in mass averaged over arbitrary regions having length scales of a few hundred kilometers and larger to accuracies of better than 1 cm of equivalent water thickness these data will be useful for examining changes in the distribution of water in the ocean in snow and ice on polar ice sheets and in continental water and snow storage we describe methods of extracting regional mass anomalies from grace gravity coefficients spatial averaging kernels were created to isolate the gravity signal of individual regions while simultaneously minimizing the effects of grace observational errors and contamination from surrounding glacial hydrological and oceanic gravity signals we then estimated the probable accuracy of averaging kernels for regions of arbitrary shape and size

coseismic gravity changes of the 2010 earthquake in central chile from satellite gravimetry 1 the first map of coseismic changes in gravity and geoid height has been drawn using the data from the gravity recovery and climate experiment grace satellites for the 2004 sumatra andaman earthquake here we present the second case of coseismic gravity change observation by satellite gravimetry i e the change caused by an interplate thrust earthquake that occurred on 27 february 2010 in central chile mw 8 8 gravity showed a negative jump with the largest drop of 5 gal on the back arc side the observed changes agree with those calculated assuming the realistic earth and fault parameters inferred from coseismic displacements of global positioning system gps stations gravity in this area shows large seasonal and inter annual variability and postseismic gravity changes could be isolated only by carefully removing hydrological signals

ocean contribution to co seismic crustal deformation and geoid anomalies application to the 2004 december 26 sumatra andaman earthquake large earthquakes do not only heavily deform the crust in the vicinity of the fault they also change the gravity field of the area affected by the earthquake due to mass redistribution in the upper layers of the earth besides that for sub oceanic earthquakes deformation of the ocean floor causes relative sea level changes and mass redistribution of water that have again a significant effect on the gravity field to model these deformations sea level changes and gravity field perturbations self consistently we use an adapted version of the sea level equation sle that has been used for glacial isostatic adjustment studies the sea level equation next to our normal mode model for seismic solid earth modeling allows us to compute a gravitationally self consistent solution for the co seismic relative sea level surface deformation and geoid height changes we apply our geographically detailed models to the case of the 2004 december 26 sumatra andaman earthquake recent studies that have modeled the ocean mass effect on co seismic gravity change for this specific earthquake show model results that indicate a broad negative change in geoid height around the fault due to ocean water redistribution de linage et al 2009 melini et al 2010 our model results for the ocean contribution to geoid height differ from these studies in the sense that we find a pattern similar to the elongated dipole pattern of the solid earth model outputs for gravity and vertical deformation together with a relatively small broad negative geoid height change we explain the relation between outcomes for geoid height relative sea level and vertical deformation of the ocean floor and we confront our model results with a least squares estimation of the co seismic discontinuity in grace derived gravity field time series we show that taking into account the contribution of ocean water redistribution to the co seismic geoid height change next to a compressible solid earth model is essential to explain the predominant negative co seismic geoid anomalies from the grace gravity field solutions besides we introduce a detailed approach to modeling an earthquake in a normal mode model that better approximates realistic continuous slip on the fault plane than models that do not distribute slip with depth to demonstrate the importance of the slip distribution we show the differences in outcomes for modeled geoid height and vertical deformation

spatiospectral localization of global geopotential fields from the gravity recovery and climate experiment grace reveals the coseismic gravity change owing to the 2004 sumatra andaman earthquake 1 regional mass fluxes owing to transport and adjustment within the earth system that are implicitly contained in the monthly gravity recovery and climate experiment grace global geopotential coefficients are revealed by localizing global spectra using spatiospectrally concentrated window functions we have analyzed 45 monthly global grace harmonic coefficient series in order to find the coseismic signature associated with the 2004 great sumatra andaman earthquake a significant gravity change after the earthquake is found in the time series of the grace coefficients after localization with a single band limited window centered near the north of the island of sumatra this change is undetectable from the original global coefficients or from coefficients localized elsewhere on the globe a step function with its discontinuity at 26 december 2004 usefully models the coseismic gravity change the localized grace coefficients contain the jumps associated with the earthquake up to degree and order 55 although not all of them within this band produce changes that are statistically significant the gravity change calculated from the localized grace coefficients displays 30 gal peak to peak variations that are very well correlated with an independently derived seismic model based on elastic dislocation theory

viscoelastic gravitational deformation by a rectangular thrust fault in a layered earth previous papers in this series have been concerned with developing the numerical techniques required for the evaluation of vertical displacements which are the result of thrust faulting in a layered elastic gravitational earth model this paper extends these methods to the calculation of fully time dependent vertical surface deformation from a rectangular dipping thrust fault in an elastic gravitational layer over a viscoelastic gravitational half space the elastic gravitational solutions are used together with the correspondence principle of linear viscoelasticity to give the solution in the laplace transform domain the technique used here to invert the displacements into the time domain is the prony series technique wherein the transformed solution is fit to the transformed representation of a truncated series of decaying exponentials purely viscoelastic results obtained are checked against results found previously using a different inverse transform method and agreement is excellent the major advantage in using the prony series technique is that deformations can be computed for arbitrary time intervals a series of results are obtained for a rectangular 30 dipping thrust fault in an elastic gravitational layer over viscoelastic gravitational half space time dependent displacements are calculated out to 50 half space relaxation times a or 100 maxwell times 2 m a significant effects due to gravity are shown to exist in the solutions as early as several a the difference between the purely viscoelastic solution and the viscoelastic gravitational solutions grows as time progresses typically the solutions with gravity reach an equilibrium value after 10 20 relaxation times when the purely viscoelastic solutions are still changing significantly additionally the length scaling which was apparent in the purely viscoelastic problem breaks down in the viscoelastic gravitational problem two independent length scales one of which changes with time are now seen to characterize the problem

a predictive model for wave induced cliff erosion with application to pacific coasts of japan a model for predicting the rate of short term bluff recession originally derived from wave tank experiments is tested under field conditions the fundamental equation is dx dt k c ln gh sc where dx dt is the recession rate h is the wave height at the cliff base sc is the compressive strength of the cliff forming material is the density of water g is the acceleration due to gravity c is a nondimensional constant and k is a constant with units of lt 1 the critical wave height to initiate erosion hcrit is given by hcrit sce c g this model is applied to two eroding tertiary cliffs in japan both facing the pacific ocean results show that 1 the larger but rarer waves only cause cliff erosion compared with the smaller but more common waves and 2 the erosion rate at each site is greatly affected by the occurrence frequency of waves higher than hcrit

stochastic simulation of episodic soft coastal cliff recession probabilistic methods provide a means of demonstrating the potential variability in predictions of coastal cliff recession they form the basis for risk based land use planning cliff management and engineering decision making a range of probabilistic methods for predicting soft coastal cliff recession has now been developed including statistical techniques process based simulation and structured use of expert judgement a new episodic stochastic simulation model is introduced which models the duration between cliff falls as a gamma process and fall size as a log normal distribution the method is applied to cliff recession data from a coastal site in the uk using maximum likelihood and bayesian parameter estimation techniques the bayesian parameter estimation method enables expert geomorphological assessment of the local landslide characteristics and measurements of individual cliff falls to be combined with sparse historic records of cliff recession an episodic simulation model is often preferable to conventional regression models which are based on assumptions that are seldom consistent with the physical process of cliff recession

bayesian probabilities of earthquake occurrences in greece and surrounding areas the bayesian extreme value distribution of earthquake occurrences has been adopted to estimate the seismic hazard in some seismogenic zones in greece and surrounding regions seismic moment slip rate earthquake recurrence rate and magnitude were considered as basic parameters for computing the prior estimates of the seismicity these estimates are then updated in terms of bayes theorem and historical estimates of seismicity associated with each zone high probabilities for earthquakes withm 6 0 have been obtained for the northwestern part of greece as well as for the southwestern part of the hellenic arc

coseismic and post seismic signatures of the sumatra 2004 december and 2005 march earthquakes in grace satellite gravity s u m m a r y the grace satellite mission has been measuring the earth s gravity field and its temporal variations since 2002 april although these variations are mainly due to mass transfer within the geofluid envelops they also result from mass displacements associated with phenomena including glacial isostatic adjustment and earthquakes however these last contributions are difficult to isolate because of the presence of noise and of geofluid signals and because of grace s coarse spatial resolution 400 km half wavelength in this paper we show that a wavelet analysis on the sphere helps to retrieve earthquake signatures from grace geoid products using a wavelet analysis of grace geoids products we show that the geoid variations caused by the 2004 december m w 9 2 and 2005 march m w 8 7 sumatra earthquakes can be detected at grace resolution the 2004 december earthquake produced a strong coseismic decrease of the gravity field in the andaman sea followed by relaxation in the area affected by both the andaman 2004 and the nias 2005 earthquakes we find two characteristic timescales for the relaxation with a fast variation occurring in the vicinity of the central andaman ridge we discuss our coseismic observations in terms of density changes of crustal and upper mantle rocks and of the vertical displacements in the andaman sea we interpret the post seismic signal in terms of the viscoelastic response of the earth s mantle the transient component of the relaxation may indicate the presence of hot viscous material beneath the active central andaman basin

reconceptualising the role of organisms in the erosion of rock coasts a new model attempts to understand the morphodynamics of rock coasts focus on the nature and rate of erosion and how this influences the evolution of coastal profiles over century to millennial timescales biological contributions to this process are often ignored or treated in a rather simplistic way as merely producing microscale decreases in rock strength using a combination of field observations and literature review we address two key issues hampering a more rounded assessment of biological impacts erosion of coastal rocks firstly we reconceptualise the biological contributions to erosion of rock coasts into direct and facilitative types and secondly we discuss the need for more appropriate reporting of rates of bioerosion for direct bioerosion this means clearly documenting the percentage of platform surfaces affected by bioerosive agents and quantifying the volume of material eroded and the amount of fine sediment produced for facilitative bioerosion we must quantify the roles of biota in changing the material properties of rocks creating or altering surface morphologies and or weakening joint boundaries in this way facilitative bioerosion is one of several processes mediating geomorphic alteration of rock surfaces contributing to the production of landforms and or reducing the resisting force of rock subsequently we build on these ideas to produce a new conceptual model which more accurately portrays the multiple and cross scalar ways that biological processes notably bioerosion influence the resistance of coastal rocks to erosive forces such a model provides a stronger basis for numerical modelling and understanding the morphodynamics of rock coasts in the future and allows a quantitative assessment of the role of biota

gravitational gradient changes following the 2004 december 26 sumatra andaman earthquake inferred from grace summary it has been demonstrated that the gravity recovery and climate experiment grace spaceborne gravimetry data are capable of observing coseismic gravity changes resulting from great earthquakes such as the 2004 december 26 sumatra andaman event mw 9 1 9 3 here we show for the first time that refined deformation signals from the 2004 december 26 sumatra andaman earthquake mw 9 1 9 3 together with the 2005 march 28 nias earthquake mw 8 6 can be revealed by deriving the full gravitational gradient tensor from grace monthly gravitational field the grace inferred coseismic gravitational gradient changes agree well with coseismic slip model predictions since the high frequency contents in gravitational field variation can be amplified by deriving the gravitational gradients the grace derived coseismic gravitational gradient changes clearly delineate the fault lines locate significant slips and better define the extent of the coseismic deformation

estimation of regional material yield from coastal landslides based on historical digital terrain modelling high resolution historical 1942 and recent 1994 digital terrain models were derived from aerial photographs along the big sur coastline in central california to measure the long term volume of material that enters the nearshore environment during the 52 year measurement time period an average of 21 000 3100 m3 km 1 a 1 of material was eroded from nine study sections distributed along the coast with a low yield of 1000 240 m3 km 1 a 1 and a high of 46 700 7300 m3 km 1 a 1 the results compare well with known volumes from several deep seated landslides in the area and suggest that the processes by which material is delivered to the coast are episodic in nature in addition a number of parameters are investigated to determine what influences the substantial variation in yield along the coast it is found that the magnitude of regional coastal landslide sediment yield is primarily related to the physical strength of the slope forming material coastal highway 1 runs along the lower portion of the slope along this stretch of coastline and winter storms frequently damage the highway the california department of transportation is responsible for maintaining this scenic highway while minimizing the impacts to the coastal ecosystems that are part of the monterey bay national marine sanctuary this study provides environmental managers with critical background data on the volumes of material that historically enter the nearshore from landslides as well as demonstrating the application of deriving historical digital terrain data to model landscape evolution published in 2005 by john wiley sons ltd

postseismic deformation of the andaman islands following the 26 december 2004 great sumatra andaman earthquake 1 two years after the great sumatra andaman earthquake the 3 1 m wsw coseismic displacement at port blair andaman islands had increased by 32 cm postseismic uplift initially exceeded 1 cm per week and decreased to 1 mm week by 2007 points near port blair had risen more than 20 cm a 24 reversal of coseismic subsidence uplift at eight gps sites suggests a gradual eastward shift of the coseismic neutral axis separating subsidence from uplift simulations of the gps postseismic displacements as viscoelastic relaxation of coseismic stress change and as slip on the plate interface indicate that slip down dip of the seismic rupture dominates near field deformation during the first two years postseismic slip beneath the andaman islands released moment equivalent to a magnitude mw 7 5 earthquake and the distribution suggests deep slip in the stable frictional regime accelerated to catch up to the coseismic rupture

landslide susceptibility analysis and verification using the bayesian probability model the bayesian probability model using the weight of evidence method was applied to the task of evaluating landslide susceptibility using gis data the location chosen for the study was the janghung area in korea which suffered substantial landslide damage following heavy rain in 1998 using the location of the landslides as well as topographic factors such as soil forest and land use the weight of evidence method was used to calculate each factor s rating tests of conditional independence were performed for the selection of the factors allowing the large number of combinations of factors to be analyzed for each factor rating the contrast values w and w were overlaid for landslide susceptibility mapping the results of the analysis were verified using the observed landslide locations and among the combinations the slope aspect curvature soil material and wood types show the best results

the impact of climatic and seismic events on the short term evolution of seacliffs based on 3 d mapping northern monterey bay california abstract coastal cliff retreat along the central california coast is episodic occurring in response to single large storms or seismic events traditional approaches to the study of long term seacliff retreat utilize historical aerial photography and maps to delineate the landward migration of the top edge of the cliff over periods of tens of years to a century while these methods yield cumulative retreat amounts they provide little or no information on the character of the individual retreat events nor the physical processes of retreat this study addresses the processes of episodic and short term coastal cliff retreat through the analysis of seacliff failure styles and retreat magnitudes the study areas are three 1 km long sections of cliffed coast in northern monterey bay the earliest data set is vertical aerial photography from october 18 1989 taken the day following the magnitude 7 1 loma prieta earthquake more recent photography collected in late january early february and early march of 1998 captured seacliff failure in response to the severe storms associated with the 1997 1998 el nino for each data set high resolution digital photogrammetric techniques are used to identify the top edge of the cliff at each cliff failure location its position failure length and character are documented results suggest that on a regional scale the seacliffs respond to seismic and climatic forcing differently we have found variation in the magnitude of cliff response along the three sections of coast in the study area large scale climatic events such as the 1997 1998 el nino have a greater impact on both the linear extent of seacliff failure and the amount of cliff retreat

rain waves and short term evolution of composite seacliffs in southern california abstract a four year time series of nine airborne lidar surveys were used to assess the roles of wave attack and rainfall on the erosion of 42 km of southern california seacliffs nine continuous seacliff sections separated by coastal lagoon mouths all show maximum seacliff erosion in the rainiest time period when wave energy was not particularly elevated and in most sections the squared correlations between rainfall and erosion time series exceeded 0 8 although rain and associated subaerial mechanisms such as groundwater seepage triggered most of the observed seacliff failures wave attack accelerated seacliff erosion with erosion rates of cliffs exposed to wave attack five times higher than at adjacent cliffs not exposed to waves the results demonstrate the importance of both waves and rain in the erosion of southern california seacliffs and suggest that the combined influences of marine and subaerial processes accelerate the erosion rate through positive feedbacks

correcting grace gravity fields for ocean tide effects 1 the grace mission will be launch in early 2002 and will map the earth s gravity fields and its variations with unprecedented accuracy during its 5 year lifetime unless ocean tide signals and their load upon the solid earth are removed from the grace data their long period aliases obscure more subtle climate signals which grace aims at the difference between two existing ocean tide models can be used as an estimate of current tidal model error for the m2 s2 k1 and o1 constituents when compared with the expected accuracy of the grace system both expressed as spherical harmonic degree variances we find that the current ocean tide models are not accurate enough to correct grace data at harmonic degrees lower that 35 the accumulated tidal errors may affect the grace data up to harmonic degree 56 furthermore the atmospheric radiation tides may cause significant errors in the ocean tide model if altimetry corrected for inverted barometer effects was used in its derivation to study the temporal characteristics of the ocean tidal constituents when sampled by grace approximate alias frequencies were derived assuming a sampling of half a sidereal day those results show that the ocean tide errors will not cancel in the grace monthly averaged temporal gravity fields the s2 and the k2 terms have alias frequencies much longer than 30 days so they remain almost unreduced in the monthly averages

enhanced gps inversion technique applied to the 2004 sumatra earthquake and tsunami 1 since the devastating earthquake and tsunami in 2004 offshore sumatra many source models have been put forward recent studies clearly show that modern gps processing could achieve high resolving power for slip in near real time which is crucial for determining tsunami initial conditions provided accurate gps processing and inversion here we propose an inversion technique with improved representation of the subduction zone geometry and physically justified boundary conditions we show that the discrepancy between the inversion of near and far field gps data for the 2004 event which is often explained by postseismic slip can be eliminated by using our inversion method and iasp91 earth model inverted source models including versions with splay faulting are shown to be consistent with satellite altimetry data of offshore tsunami wave height suggesting that displacement at the splay fault might have been present but was likely a second order process

bayesian analysis of extreme earthquake occurrences part i probabilistic hazard model bayesian probability theory in conjunction with the model of extremes is used to develop a bayesian distribution of extreme earthquake occurrences by assuming that earthquakes represent a poisson process with exponential distribution of magnitudes the bayesian distribution represents the probability that m max the largest earthquake expected to occur within a period of t years will exceed some specified magnitude m and may be computed from the relationship p m max m t 1 t t t 1 f m n where n and t represent updated posterior bayesian estimates of the number of earthquakes and the time period of observation respectively and f m is the bayesian distribution of magnitudes each updated from prior estimates of seismicity using historical observations of earthquake occurrences through the application of bayesian probability theory the above distribution contains two features that make it more powerful and reliable than the conventional extreme value distribution first it incorporates statistical uncertainty in the estimation of seismicity in addition to the inherent uncertainty associated with the random nature of earthquake occurrences second it provides a rigorous means of combining prior information on seismicity such as geologica data with available historical observations of earthquake occurrences the last feature represents a major step toward the ability of earthquake engineers to systematically use information from geologists and seismologists regarding the seismic potential of faults and small regions in the probabilistic assessment of seismic hazards and provides a means of periodically updating estimates of earthquake occurrence probabilities as new seismicity data become available

retrieving earthquake signature in grace gravity solutions summary the grace satellites have been orbiting the earth since 2002 monitoring the time variable gravity field some of the observed fluctuations are due to geodynamic causes but they are often hidden in the complex signal composed of hydrology ocean atmosphere and geodynamics the signal of geodynamic origin being usually the smallest in addition dealiasing residuals and noise make the separation of the signal from the different causes more difficult we proposed a method based on the empirical orthogonal function decomposition to extract the signal of physical origin under the hypothesis that the physical signal is spatially more consistent than the noise and aliasing incomplete correction we used synthetic geoid variations associated with earthquakes located at nearly 2000 positions at the earth surface based on several examples of large actual subduction events we show that with the present day accuracy we can retrieve the geoid variations associated with more than 98 per cent of the earthquakes of magnitude 9 or above around 60 per cent for magnitude 8 8 40 per cent for magnitude 8 6 and 33 per cent for magnitude 8 3 some events with the right properties and location can be detected with magnitude as low as 8 we then applied the method to the grace solutions and retrieved the hokkaido event 2003 and the sumatra event 2004 which is in agreement with the retrieval rates mentioned here above

the problem of heat flow density determination from inaccurate data abstract we present an inverse method for processing rough data from oil wells in order to evaluate the heat flow density assuming that the evaluations of temperatures and thermal resistivities present gaussian uncertainties we give formulas for computing the optimal value of the heat flow density and its standard deviation a synthetic example using likely assumptions on various uncertainties leads to the prediction that a standard deviation of about 10 mw m 2 could apply to heat flow estimates from oil well data for typical situations

a unified gps based earthquake catalog for the sumatran plate boundary between 2002 and 2013 we have compiled the first self consistent gps based earthquake catalog for the sumatran plate boundary using continuous daily position time series from the sumatran gps array sugar we document 30 earthquakes which occurred within or outside the sugar network from august 2002 through the end of 2013 and we provide estimates of both vertical and horizontal coseismic offsets associated with 1 m9 2 3 m8 6 m7 19 m6 and 1 m5 9 earthquakes as well as postseismic decay amplitudes and times associated with 9 m 7 earthquakes and 1 m6 7 earthquake for most of the previously studied earthquakes our geodetic catalog provides more complete coseismic displacements than those published showing consistent patterns of motion across a large range of distances for many of the moderate to large earthquakes we publish their coseismic displacements for the first time providing new constraints on their locations and slip distributions for the postseismic time series we have tackled the challenge of separating the signals for individual events from the overlapping effects of many other earthquakes as a result we have obtained either new or much longer time series than previously published based on our long time series we find logarithmic decay times ranging from several days to more than 20 years and sometimes a second decay time is needed suggesting that when studying large to great sumatran earthquakes we need to consider multiple postseismic mechanisms our geodetic catalog provides rich spatial and temporal sumatran earthquake cycle information for future studies of the physics and dynamics of the sumatran plate boundary

processes of coastal bluff erosion in weakly lithified sands pacifica california usa abstract coastal bluff erosion and landsliding are currently the major geomorphic processes sculpting much of the marine terrace dominated coastline of northern california in this study we identify the spatial and temporal processes responsible for erosion and landsliding in an area of weakly lithified sand coastal bluffs located south of san francisco california using the results of a five year observational study consisting of site visits terrestrial lidar scanning and development of empirical failure indices we identify the lithologic and process controls that determine the failure mechanism and mode for coastal bluff retreat in this region and present concise descriptions of each process bluffs composed of weakly cemented sands unconfined compressive strength ucs between 5 and 30 kpa fail principally due to oversteepening by wave action with maximum slope inclinations on the order of 65 at incipient failure periods of significant wave action were identified on the basis of an empirical wave run up equation predicting failure when wave run up exceeds the seasonal average value and the bluff toe elevation the empirical relationship was verified through recorded observations of failures bluffs composed of moderately cemented sands ucs up to 400 kpa fail due to precipitation induced groundwater seepage which leads to tensile strength reduction and fracture an empirical rainfall threshold was also developed to predict failure on the basis of a 48 hour cumulative precipitation index but was found to be dependent on a time delay in groundwater seepage in some cases

coseismic slip distributions of the 26 december 2004 sumatra andaman and 28 march 2005 nias earthquakes from gps static offsets static offsets produced by the 26 december 2004 m 9 sumatra andaman earthquake as measured by global positioning system gps reveal a large amount of slip along the entire 1300 km long rupture most seismic slip inversions place little slip on the andaman segment whereas both near field and far field gps offsets demand large slip on the andaman segment we compile available datasets of the static offset to render a more detailed picture of the static slip distribution we construct geodetic offsets such that postearthquake positions of continuous gps sites are reckoned to a time 1 day after the earthquake and campaign gps sites are similarly corrected for postseismic motions the newly revised slip distribution m w 9 22 reveals substantial segmentation of slip along the andaman islands with the southern quarter slipping 15 m in unison with the adjacent nicobar and northern sumatran segments of length 700 km we infer a small excess of geodetic moment relative to the seismic moment a similar compilation of gps offsets from the 28 march 2005 nias earthquake is well explained with dip slip averaging several meters mw 8 66 distributed primarily at depths greater than 20 km online material offset estimation procedure comparison of results to other stud ies and simpler solutions and tables of coseismic offsets

coastal cliff recession the use of probabilistic prediction methods a range of probabilistic methods is introduced for predicting coastal cliff recession which provide a means of demonstrating the potential variability in such predictions they form the basis for risk based land use planning cliff management and engineering decision making examples of probabilistic models are presented for a number of different cliff settings the simulation of recession on eroding cliffs the use of historical records and statistical experiments to model the behaviour of cliffs affected by rare episodic landslide events the adaptation of an event tree approach to assess the probability of failure of protected cliffs taking into account the residual life of the existing defences and the evaluation of the probability of landslide reactivation in areas of pre existing landslide systems these methods are based on a geomorphological assessment of the episodic nature of the recession process together with historical records

andaman postseismic deformation observations still slipping after all these years more than six years after the great m w 9 2 sumatra andaman earthquake postevent processes responsible for relaxation of the coseismic stress change remain controversial modeling of andaman islands global positioning system gps displacements indicated early near field motions were dominated by slip down dip of the rupture but various researchers ascribe elements of relaxation to dominantly poroelastic dominantly viscoelastic and dominantly fault slip processes depending primarily on their measurement sampling and modeling tools used after subtracting a pre 2004 interseismic velocity significant transient motion during the 2008 5 2010 5 epoch confirms that postseismic relaxation processes continue in andaman modeling three component velocities as viscoelastic flow yields a weighted root mean square wrms misfit that always exceeds the wrms of the measured signal 26 3 mm yr the best fitting models are those that yield negligible deformation indicating the model parameters have no real physical meaning gps velocities are well fit wrms 4 0 mm yr by combining a viscoelastic flow model that best fits the horizontal velocities with 50 cm yr thrust slip down dip of the coseismic rupture both deep slip and flow respond to stress changes and each can significantly change stress in the realm of the other it therefore is reasonable to expect that both transient deep slip and viscoelastic flow will influence surface deformation long after a great earthquake

slow postseismic recovery of geoid depression formed by the 2004 sumatra andaman earthquake by mantle water diffusion 1 earthquakes are accompanied with mass redistributions and cause changes in gravity field and shape of geoid an equipotential surface coincident with the mean sea surface such coseismic changes were detected by satellite gravimetry after the 2004 sumatra andaman earthquake but little has been known on what happens on geoid after the earthquake here we report slow postseismic recovery of coseismic geoid depression from satellite measurements this cannot be explained with simple afterslip or viscous relaxation of maxwellian upper mantle it suggests the relaxation of coseismic dilatation and compression by the diffusion of supercritical h2o abundant in the upper mantle such a self healing system of coseismic geoid undulations a brand new role of water in mantle would significantly reduce the amount of permanent shifts of the earth s rotation axis by earthquakes

coseismic gravity changes of the 2011 tohoku oki earthquake from satellite gravimetry 1 the massive tohoku oki earthquake of a moment magnitude mw of 9 0 occurred on 11 march 2011 off the pacific coast of the northeastern japan the mass redistribution in and around the focal region associated with this earthquake was studied using the gravity changes detected by gravity recovery and climate experiment grace satellite after the 2004 sumatra andaman and the 2010 central chile maule earthquakes the present study presents the third case of clear detection of coseismic gravity changes by grace the observed gravity changes were dominated by decrease over the back arc region of 7 gal or less this reflects to a large extent coseismic crustal dilatation of the landward plate they agree well with the changes calculated with the green s function for the realistic earth using fault parameters inferred from coseismic crustal movements the spatial patterns of the gravity changes of these earthquakes are very similar because they are all shallow angle reverse faulting at convergent plate boundaries we found linear relationship between gravity decreases and seismic moments

predictive modelling of rainfall induced landslide hazard in the lesser himalaya of nepal based on weights of evidence abstract landslide hazard mapping is a fundamental tool for disaster management activities in mountainous terrains the main purpose of this study is to evaluate the predictive power of weights of evidence modelling in landslide hazard assessment in the lesser himalaya of nepal the modelling was performed within a geographical information system gis to derive a landslide hazard map of the south western marginal hills of the kathmandu valley thematic maps representing various factors e g slope aspect relief flow accumulation distance to drainage soil depth engineering soil type landuse geology distance to road and extreme one day rainfall that are related to landslide activity were generated using field data and gis techniques at a scale of 1 10 000 landslide events of the 1970s 1980s and 1990s were used to assess the bayesian probability of landslides in each cell unit with respect to the causative factors to assess the accuracy of the resulting landslide hazard map it was correlated with a map of landslides triggered by the 2002 extreme rainfall events the accuracy of the map was evaluated by various techniques including the area under the curve success rate and prediction rate the resulting landslide hazard value calculated from the old landslide data showed a prediction accuracy of 80 the analysis suggests that geomorphological and human related factors play significant roles in determining the probability value while geological factors play only minor roles finally after the rectification of the landslide hazard values of the new landslides using those of the old landslides a landslide hazard map with 88 prediction accuracy was prepared the methodology appears to have extensive applicability to the lesser himalaya of nepal with the limitation that the model s performance is contingent on the availability of data from past landslides

insight into the 2004 sumatra andaman earthquake from gps measurements in southeast asia data collected at 60 global positioning system gps sites in southeast asia show the crustal deformation caused by the 26 december 2004 sumatra andaman earthquake at an unprecedented large scale small but significant co seismic jumps are clearly detected more than 3 000 km from the earthquake epicentre the nearest sites still more than 400 km away show displacements of 10 cm or more here we show that the rupture plane for this earthquake must have been at least 1 000 km long and that non homogeneous slip is required to fit the large displacement gradients revealed by the gps measurements our kinematic analysis of the gps recordings indicates that the centroid of released deformation is located at least 200 km north of the seismological epicentre it also provides evidence that the rupture propagated northward sufficiently fast for stations in northern thailand to have reached their final positions less than 10 min after the earthquake hence ruling out the hypothesis of a silent slow aseismic rupture data culled from gps stations in indonesia malaysia singapore thailand india and china have answered more questions relating to the 26 december sumatra andaman megathrust earthquake permanent displacements were seen 3 000 km away final displacements occurred within 10 minutes of the earthquake ruling out slow aseismic slip on the fault

predicting coastal cliff erosion using a bayesian probabilistic model abstract regional coastal cliff retreat is difficult to model due to the episodic nature of failures and the along shore variability of retreat events there is a growing demand however for predictive models that can be used to forecast areas vulnerable to coastal erosion hazards increasingly probabilistic models are being employed that require data sets of high temporal density to define the joint probability density function that relates forcing variables e g wave conditions and initial conditions e g cliff geometry to erosion events in this study we use a multi parameter bayesian network to investigate correlations between key variables that control and influence variations in cliff retreat processes the network uses bayesian statistical methods to estimate event probabilities using existing observations within this framework we forecast the spatial distribution of cliff retreat along two stretches of cliffed coast in southern california the input parameters are the height and slope of the cliff a descriptor of material strength based on the dominant cliff forming lithology and the long term cliff erosion rate that represents prior behavior the model is forced using predicted wave impact hours results demonstrate that the bayesian approach is well suited to the forward modeling of coastal cliff retreat with the correct outcomes forecast in 70 90 of the modeled transects the model also performs well in identifying specific locations of high cliff erosion thus providing a foundation for hazard mapping this approach can be employed to predict cliff erosion at time scales ranging from storm events to the impacts of sea level rise at the century scale

non isotropic filtering of grace temporal gravity for geophysical signal enhancement summary monthly mass variations within the earth system produce temporal gravity changes which are observable by the nasa gfz gravity recovery and climate experiment grace twin satellite system mass load changes with spatial scales larger than 1000 km have been observed using conventional filters based on a gaussian smoother which applies a weight to grace spherical harmonic sh coefficients depending only on sh degree this practice is consistent with a degree dependent error model for grace monthly geopotential solutions the gaussian filters effectively dampen all power of ill determined higher degree components in the estimates however the spatial sampling provided by grace yields errors that vary with both sh degree and order the consequence is that maps of spatial loads shall not be smoothed with an isotropic degree only filter but shall be constructed using anisotropic smoothing thus also yielding better spatial resolution in latitude we have developed a non isotropic filter to optimize the smoothing of grace temporal gravity observations by considering the degree and order dependent quality of grace estimates the latter analysed from the correlation with the predicted signals of hydrologic and ocean models in order to retain grace coefficients in the filtering process that show reasonable correlation with the geophysical hydrology and ocean models we applied gaussian type smoothing but with averaging radius depending on the order of the geopotential coefficient estimates applied to 2 yr of grace data we showed that the resulting non isotropic filter yields enhanced grace signals with significantly higher resolution in latitude and the same resolution in longitude without reducing the accuracy as compared to the conventional gaussian smoother

equilibrium responses of cliffed coasts to changes in the rate of sea level rise abstract basic formulae have long been used to predict the effects of sea level rise on coastal recession for instance the geometric bruun rule and its modifications has often been applied to sandy coasts both low lying and steep however the behavior of rocky coasts whether strongly or poorly lithified should be significantly different than that of sandy coasts given that rocky coast evolution depends upon the irreversible breakdown of rock whereas sandy and depositional systems are controlled by the transport and related transport gradients of mobile sediment here we investigate the basis of a modeled relationship which suggests with a number of caveats that the equilibrium soft rock cliff recession rate can be estimated by the square root of the relative change in sea level rise rate although this relationship was derived using the numerical model scape soft cliff and platform erosion which simulates a broad soft rock cliffed coastal system driven by stochastic environmental forces here we show that a simplified modeling approach also reproduces the relationship we then extend this approach to develop a general theoretical framework within which it is possible to consider the potential responses of the different types of cliffed coasts to changes in the rate of sea level rise although a wide variety of processes affect different coastal settings this framework demonstrates how the strength and the nature of feedbacks within cliffed system control their response to sea level rise this suggests that cliffed environments controlled by different processes can still respond in similar ways to changes in the rate of sea level rise most rocky coasts would be expected to respond as a damped or negative feedback system between the extremes of a no feedback system that is unresponsive to sea level rise rate and an instant response system characterized by a linear response similar to the bruun rule this framework suggests that a potential inverse feedback case could also exist in which increased rates of sea level rise reduce the rate of coastal recession in almost all cases it is apparent that cliffed coast response to sea level rise depends not only upon the total elevation change of sea level but on the rate of the sea level rise these theoretical investigations and the classifications presented provide a framework to understand the behavior of systems affected by a wide array of processes and provide expectations that can be tested using more complex models of cliffed coast evolution in a variety of environments whether sandy or rocky hard or soft

plate wide deformation before the sumatra andaman earthquake rock is weak to shear stress and the energy released by the 26th december 2004 m 9 2 sumatra andaman earthquake the largest earthquake for four decades must have accumulated over enormous volumes of crust and mantle certainly plate wide possibly world wide here we report evidence for plate wide stress accumulation changes in seismic shear wave splitting monitor stress induced changes in the geometry of the microcrack distributions in almost all rocks in the earth s crust such changes observed in iceland show stress accumulation beginning at least four years before the sumatra andaman earthquake these changes were recognised as monitoring stress accumulation before an impending large earthquake and 10 stress forecasts were emailed to iceland meteorological office for some 29 months forecasting an impending large earthquake the remarkable sensitivity of critical systems of microcrack geometry to miniscule changes of stress had not been recognised at that time and the stress accumulation was expected to lead to a m 7 earthquake somewhere in iceland only now is it recognised that the changes in shear wave splitting were monitoring stress accumulation which would eventually lead to the sumatra andaman earthquake at a distance of some 10 500 km on the opposite side of the eurasian plate this extreme sensitivity confirms the critical nature of fluid saturated stress aligned microcracks in the earth s crust

implications of postseismic gravity change following the great 2004 sumatra andaman earthquake from the regional harmonic analysis of grace intersatellite tracking data 1 we report gravity recovery and climate experiment grace satellite observations of coseismic displacements and postseismic transients from the great sumatra andaman islands thrust event mw 9 2 earthquake in december 2004 instead of using global spherical harmonic solutions of monthly gravity fields we estimated the gravity changes directly using intersatellite range rate data with regionally concentrated spherical slepian basis functions every 15 day interval we found significant step like coseismic and exponential like postseismic behavior in the time series of estimated coefficients from may 2003 to april 2007 for the spherical slepian functions after deriving coseismic slip estimates from seismic and geodetic data that spanned different time intervals we estimated and evaluated postseismic relaxation mechanisms with alternate asthenosphere viscosity models the large spatial coverage and uniform accuracy of our grace solution enabled us to clearly delineate a postseismic transient signal in the first 2 years of postearthquake grace data our preferred interpretation of the long wavelength components of the postseismic gravity change is biviscous viscoelastic flow we estimated a transient viscosity of 5 1017 pa s and a steady state viscosity of 5 1018 1019 pa s additional years of the grace observations should provide improved steady state viscosity estimates in contrast to our interpretation of coseismic gravity change the prominent postearthquake positive gravity change around the nicobar islands is accounted for by seafloor uplift with less postseismic perturbation in intrinsic density in the region surrounding the earthquake

short term patterns and processes of coastal cliff erosion in santa barbara california abstract sequential terrestrial lidar scans and 3d volumetric change were used to document coastal cliff erosion at several sites along the coast of santa barbara california retreat rates along the base middle and cliff top were calculated for six different scans throughout the el nino of 2015 16 to quantitatively link wave action to cliff base erosion and two seasonal scans were taken during 2017 to investigate patterns in erosion and retreat rates retreat rates along the cliff base middle and top converged over the course of the study period and observations and patterns in erosion help characterize the fundamental mechanisms that govern the retreat of soft shale cliffs the base and middle of the cliff preferentially eroded during high energy swell events and are strongly coupled whereas cliff top erosion is temporally variable and retreat rates increased with higher seasonal rainfall totals we observe that the cliff base experiences erosion from both abrasion and mechanical wave action but the dominant processes is segregated by elevation above the cliff toe abrasion was found to be the dominant processes at elevations up to 0 8 m above the cliff toe whereas block removal from mechanical wave action was dominant at elevations above 0 8 m threshold behavior was observed for cliff base retreat rates and spearman correlation coefficients suggest strong relationships with the sum of the wave energy flux imparted to the cliff base r2 0 84 the sum of the wave energy flux 35 000 w m r2 0 82 and the average total water level above the cliff toe r2 0 85 threshold behavior and maximum retreat rates occurred when average total water levels were 0 8 m above the cliff toe seasonal schmidt hammer measurements suggest that energy thresholds are modulated by weathering rates which remain poorly understood these thresholds when exceeded produced the highest cliff base retreat rates during the study period and reinforce the expectation that coastal cliff retreat rates will increase with rising sea levels

mapping landslide susceptibility from small datasets a case study in the pays de herve e belgium a landslide susceptibility map is proposed for the pays de herve e belgium where large landslides affect cretaceous clay outcrop areas based on a bayesian approach this gis supported probabilistic map identifies the areas most susceptible to deep landslides the database is comprised of the source areas of ten pre existing landslides i e a sample of 154 grid cells and of six environmental data layers namely lithology proximity to active faults slope angle and aspect elevation and distance to the nearest valley floor a 30 m resolution dem from the belgian national geographical institute is used for the analysis owing to the small size of the sample a special cross validation procedure of the susceptibility map is performed which uses in an iterative way each of the landslides to test the predictive power of the map derived from the other landslides four different sets of variables are used to produce four susceptibility maps whose prediction curves are compared while the prediction rates associated with the models not involving the proximity to active fault criterion are comparable to those of the models considering this variable strong weaknesses inherent in the fault data on which the latter rely suggest that the final susceptibility map should be based on a model that excludes any reference to fault this highlights the difference between a triggering factor and determining factors and in the same time broadens the scope of the produced map a single reactivated slide is also used to test the possibility of predicting future reactivation of existing landslides in the area finally the need for geomorphological control over the mathematical treatment is underlined in order to obtain realistic prediction maps 2007 elsevier b v all rights reserved

applicability of parametric beach morphodynamic state classification on embayed beaches abstract use of parametric classification of beach morphodynamic state has been steadily increasing in coastal research despite identification of several shortcomings of their representativeness as elementary beach descriptors in this paper we analyse the parametric classification of beach morphodynamic state in a set of six embayed beaches in southwestern portugal exposed to diverse settings from high energy dissipative to intermediate to low energy intermediate to reflective conditions applicability of parametric approaches considered within the dimensionless space defined by dimensionless fall velocity and rtr relative tidal range according to averaged wave tide and sediment characteristics of beaches was assessed in association with a probabilistic analysis implemented through a bayesian network model that considered the full range of wave tide and sediment conditions at each site both parametric approaches were compared to field based beach state classification implemented using a novel hierarchical framework for beach state analysis the classification obtained within a probabilistic framework provided an innovative approach for analysis of beach state and mobility extending the insights on beach morphodynamic behaviour obtained from averaged environmental parameters reflective to lower intermediate beach conditions showed better agreement with parametric approaches while poor beach state differentiation was achieved for intermediate beach types limitations in the application of beach classification models result from i an inadequacy of existing beach state types in differentiating beaches particularly within the intermediate domain and for geologically controlled embayed beaches and ii shortcomings involved in the parametric approaches the beach state models disregard the major role of geological control in embayed beach morphodynamic behaviour in modulating beach shape and segmentation influencing sediment size and availability causing alongshore variations in the wave field and creating topographically induced nearshore circulations existing beach state models are unable to adequately represent the widely variable conditions observed in embayed beaches

estimating cliff retreat in southern california considering sea level rise using a sand balance approach abstract a sand balance coastal profile model for estimating cliff and shoreline retreats considering sea level rise is discussed the model specifically designed for cliffed coasts fronted by sandy beaches conditionally permits beach and cliff retreat to occur independently and includes subaerial cliff erosion and external beach sand sources the model accommodates complex nearshore and inland topography high volume beaches and variable cliff composition and is suitable where local sand balance is thought to be a primary controller of coastal evolution over decade century time scales designating an upper active beach boundary and beach cliff intersection divides the coastal profile into active beach and cliff sections separated by a back beach buffer the buffer acts as a sand reservoir and delays marine driven cliff erosion resulting in lower estimated cliff retreat compared to previous models neglecting protective beaches the model was applied on 21 km of cliffs in marine corps base camp pendleton california considering sea level rise ranging from 0 5 to 2 m over 100 yrs using 207 profiles sand budget deficits estimated from historical data and sand inputs from terrestrial erosion estimated from a time series of lidar data modeled mean and maximum scenario cliff retreats ranged from 4 87 m and 21 179 m respectively and provide order of magnitude estimates but are reliant on model assumptions and do not include potential coastal changes unrelated to local sand balance the results underscore the influence of protective beaches on cliff retreat