centerless circular array method inferring phase velocities of rayleigh waves in broad wavelength ranges using microtremor records 1 the centerless circular array cca method proposed by ourselves in an earlier work is an algorithm of microtremor exploration which can be used to estimate phase velocities of rayleigh waves by analyzing vertical component records of microtremors that are obtained with an array of three or five seismic sensors placed around a circumference we have confirmed through field tests the applicability of our cca method to arrays on the order of several to several hundred meters in radii and have revealed its remarkably high performance in long wavelength ranges the upper resolution limit extending as far as several 10 times the array radius we have also invented a mathematical model that enables to evaluate signal to noise ratios in a given microtremor field scrutiny of field data has borne out our hypothesis that noise is the principal factor that biases the analysis results of the cca method in long wavelength ranges and that its longest resolvable wavelength is determined by the signal to noise ratio combined use of the cca method and our new method of signal to noise ratio analysis provides a powerful methodological tool that allows one to extract maximal information from microtremor records obtained with a simple seismic array

joint analysis of rayleigh wave dispersion and hvsr of lunar seismic data from the apollo 14 and 16 sites abstract active and passive seismic data from the apollo 14 and 16 missions are analyzed with the aim of determining robust shear wave velocity v s profiles of the uppermost lunar strata while data from the active seismic experiment ase allow the study of rayleigh wave dispersion by means of multiple filter analysis mfa data acquired by the passive seismic experiment pse are used to determine the horizontal to vertical spectral ratio hvsr these two datasets are jointly analyzed according to state of the art procedures in order to overcome the intrinsic limitations of both methodologies when considered independently and with the aim of determining a solution i e the vertical v s profile not affected by non uniqueness of the solution and not based on any a priori assumption obtained results appear in general agreement with the early p wave refraction analyses a sharp contact between a very soft regolith and a stiffer overlain layer is apparent and indicate very low shear wave velocities and very high q values low dissipation also confirmed by a number of seismological studies on moonquakes and meteoroid impacts

tsunami run up associated with co seismic thrust slip produced by the 2011 mw 9 0 off pacific coast of tohoku earthquake japan abstract the 2011 m w 9 0 off pacific coast of tohoku japan earthquake generated a violent tsunami and unexpected high tsunami wave that caused great substantial damage and 18 940 fatalities along the east northeast coast of honshu island of japan analyses of high resolution remote sensing imagery data acquired before and after the earthquake combined with the results of field investigations reveal that i run up height of the tsunami i e the inland limit of tsunami was spatially variable ranging from w 9 0 earthquake and showed a gradual decrease away from this region combined with the ground motion direction revealed by gps and seismic data the distribution of run up height is consistent with that of ground displacement calculated from gps observations and that of co seismic thrusting slip on the source fault plane along the plate boundary calculated from the seismic inversion the results of numerical simulation of tsunami propagation show that i the distributions of tsunami height along the northeast honshu coastline are constrained mainly by thrusting slip on the source fault plane and ii the height of tsunami wave in special areas was strongly affected by the sawtooth geometry of the coastline

data resolution matrix and model resolution matrix for rayleigh wave inversion using a damped least squares method inversion of multimode surface wave data is of increasing interest in the near surface geophysics community for a given near surface geophysical problem it is essential to understand how well the data calculated according to a layered earth model might match the observed data a data resolution matrix is a function of the data kernel determined by a geophysical model and a priori information applied to the problem not the data a data resolution matrix of high frequency 2 hz rayleigh wave phase velocities therefore offers a quantitative tool for designing field surveys and predicting the match between calculated and observed data we employed a data resolution matrix to select data that would be well predicted and we find that there are advantages of incorporating higher modes in inversion the resulting discussion using the data resolution matrix provides insight into the process of inverting rayleigh wave phase velocities with higher mode data to estimate s wave velocity structure discussion also suggested that each near surface geophysical target can only be resolved using rayleigh wave phase velocities within specific frequency ranges and higher mode data are normally more accurately predicted than fundamental mode data because of restrictions on the data kernel for the inversion system we used synthetic and real world examples to demonstrate that selected data with the data resolution matrix can provide better inversion results and to explain with the data resolution matrix why incorporating higher mode data in inversion can provide better results we also calculated model resolution matrices in these examples to show the potential of increasing model resolution with selected surface wave data

marine incursions of the past 1500 years and evidence of tsunamis at suijin numa a coastal lake facing the japan trench sandy deposits of marine origin underlie the floor of suijin numa a coastal lake midway along the subduction zone marked by the japan trench the deposits form three units that are interbedded with lacustrine peat and mud above a foundation of marine probably littoral sand unlike the lacustrine deposits all three sandy units contain marine and brackish diatoms the middle unit b contains in addition graded beds sug gestive of multiple waves of long wavelength and period the uppermost unit c probably dates to a time in the area s written history when the lake was separated from the sea by a beach ridge plain at least 0 5 km wide and several metres high units a and b postdate ad 540 870 and unit c postdates ad 1030 1640 as judged from radiocarbon dating of leaves and seeds unit b pre dates ad 915 and unit c postdates that year as judged from a tephra within the peat that separates units b and c the age constraints permit correlation of unit b with a tsunami in ad 869 that reportedly devastated at least 100 km of coast approximately centred on sendai unit c may represent a later catastrophic tsunami in 1611 or perhaps a storm surge that inundated much of sendai the lake lacks obvious signs of tsunamis from the region s largest twentieth century earthquakes which were centred to the north in 1933 m 8 1 and directly offshore in 1936 m 7 5 and 1978 mw 7 6

a new gps acoustic method for measuring ocean floor crustal deformation application to the nankai trough 1 we developed a new geodetic method of monitoring crustal deformation on the ocean floor the measurements were conducted at two sites beneath the pacific ocean near the nankai trough where the philippine sea plate subducts into the pacific plate the first site was at a depth of 700 m in suruga bay and the second one was at a depth of 2000 m in the kumano basin at each survey site three seafloor transponders whose positions were repetitively measured were deployed to define a benchmark unit an ultrasonic signal was generated from a surface vessel drifting over the benchmark unit that was transmitting and receiving the signal and the replies from the transponders both sound speed structure and the benchmark unit positions were determined simultaneously using a tomographic technique we repeatedly carried out measurements over the two sites for the kumano basin we made six measurements from july 2004 to august 2005 the benchmark unit location s horizontal precision was 5 cm and its vertical precision was 10 cm for suruga bay we made five measurements and the positions were less accurate with horizontal variation of 7 cm and vertical variation of 16 cm we investigated the reason for the decreased precision in suruga bay with a numerical experiment and the results revealed that the geometry of the measurement that is the vessel s path is one of the most important variables in our method at the kumano basin a 21 5 cm southward displacement of the benchmark unit was detected just below the site before and after a large earthquake mw 7 5 our observation system therefore proved itself capable of detecting seafloor crustal deformation associated with crustal activities in offshore areas

lower tertiary sand development in viking graben north sea a regional study of lower tertiary sands in the viking graben northern north sea involving heavy mineral analysis geophysical log interpretation and palynologic dating has led to the successful differentiation of sand bodies with two distinct source areas being recognized these both lie on the orkney shetland platform one being the metamorphic basement in the north the other the preexisting sediments to the south probably of late jurassic age correlation of sand bodies by these means has led to a more complete breakdown of the depositional history of the area four phases of basinal subsidence and source area uplift have been recognized in this way and these are correlated with similar events in the central north sea the changes in subsidence pattern and source area uplift are related to events in the north atlantic prior to crustal separation between greenland and rockall although provenance is the fundamental control on heavy mineral distribution intrastratal solution also plays a major role solution is largely a function of burial depth and it is estimated that up to 50 of the assemblage may have been lost by this process over a large part of the area

structural analysis of coseismic normal fault zones of the 2011 mw 6 6 fukushima earthquake northeast japan the 2011 m w 6 6 fukushima earthquake occurred in iwaki city 250 km southwest of the epicenter of the 2011 m w 9 0 tohoku japan earthquake and produced two subparallel 15 23 km long surface rupture zones with distinct displacements along two pre existing normal faults the shionohira and yunodake faults which strike north northwest south southeast and northwest southeast both dipping southwest respectively field investigations and structural analysis of the coseismic shear zones developed within the shionohira and yunodake fault zones reveal that 1 the coseismic shear zones consist of a fault core that includes a narrow fault gouge zone of 10 cm in width generally 1 5 cm a fault breccia zone of 50 cm in width and a damage zone of 5 50 m in width that is composed of cataclastic rocks fractures and subsidiary faults 2 the foliations characterized by s c fabrics developed in the shear zones indicate a dominantly normal fault slip sense consistent with that observed along the coseismic surface ruptures and 3 veinlet cataclastic rocks composed of unconsolidated fault gouges and fine grained materials occur as simple discrete veinlets and multiple cross cutting interconnected networks of veinlets these newly documented structural characteristics for two coseismic fault shear zones and associated cataclastic rocks indicate that the locations of coseismic slip zones associated with the 2011 fukushima earthquake were controlled by pre existing fault shear zones central to the shionohira and yunodake faults which have repeatedly moved as seismogenic normal faults since the timing of formation of associated cataclastic rocks our results demonstrate that the structural analyses of coseismic shear fault zones provide a powerful tool to study the nature and active faulting history of seismological faults

physical size of tsunamigenic earthquakes of the northwestern pacific abstract the new scale m t of tsunami magnitude is a reliable measure of the seismic moment of a tsunamigenic earthquake as well as the overall strength of a tsunami source this m t scale was originally defined by abe 1979 in terms of maximum tsunami amplitudes at large distances from the source a method is developed whereby it is possible to determine m t at small distances on the basis of the regional tsunami data obtained at 30 tide stations in japan the relation between log h maximum amplitude m and log a distance of not less than 100 km away from the source km is found to be linear with a slope close to 1 0 using three tsunamigenic earthquakes with known moment magnitudes m w for calibration the relation m t log h log d is obtained where d is 5 80 for single amplitude crest or trough data and 5 55 for double amplitude crest to trough data using a number of tsunami amplitude data m t is assigned to 80 tsunamigenic earthquakes that occurred in the northwestern pacific mostly in japan during the period from 1894 to 1981 the m t values are found to be essentially equivalent to m w for 25 events with known m w the 1952 kamchatka earthquake has the largest m t 9 0 of all the 80 events listed at least seven unusual earthquakes which generated disproportionately large tsunamis for their surface wave magnitude m s are identified from the relation from the viewpoint of tsunami hazard reduction the present results provide a quantitative basis for predicting maximum tsunami amplitudes at a particular site

shallow dynamic overshoot and energetic deep rupture in the 2011 mw 9 0 tohoku oki earthquake strong spatial variation of rupture characteristics in the moment magnitude mw 9 0 tohoku oki megathrust earthquake controlled both the strength of shaking and the size of the tsunami that followed finite source imaging reveals that the rupture consisted of a small initial phase deep rupture for up to 40 seconds extensive shallow rupture at 60 to 70 seconds and continuing deep rupture lasting more than 100 seconds a combination of a shallow dipping fault and a compliant hanging wall may have enabled large shallow slip near the trench normal faulting aftershocks in the area of high slip suggest dynamic overshoot on the fault despite prodigious total slip shallower parts of the rupture weakly radiated at high frequencies whereas deeper parts of the rupture radiated strongly at high frequencies

a two radius circular array method inferring phase velocities of love waves using microtremor records 1 we present a new method to estimate phase velocities of love waves from horizontal motion seismograms of microtremors obtained with seismic sensors placed around two circumferences of different radii under the assumption that the fundamental mode dominates we applied our new method to field data acquired at a test site where the shallow underground seismic velocity profile is known and have confirmed that the phase velocities of the fundamental mode love waves could be inferred with sufficient precision within certain wavelength ranges outside the wavelength ranges suitable for analysis the spectral ratio an intermediary quantity calculated from measurement records prior to phase velocity evaluation deviated from theoretical expectations the pattern of deviations could satisfactorily be accounted for by considering three factors theoretically the presence of higher mode surface waves directional aliasing related to the finite number of sensors and the presence of incoherent noise

the tsunami phenomenon abstract with human activity increasingly concentrating on coasts tsunamis from japanese tsu harbour nami wave are a major natural hazard to today s society stimulated by disastrous tsunami impacts in recent years for instance in south east asia 2004 or in japan 2011 tsunami science has significantly flourished which has brought great advances in hazard assessment and mitigation plans based on tsunami research of the last decades this paper provides a thorough treatise on the tsunami phenomenon from a geoscientific point of view starting with the wave features tsunamis are introduced as long shallow water waves or wave trains crossing entire oceans without major energy loss at the coast tsunamis typically show wave shoaling funnelling and resonance effects as well as a significant run up and backflow tsunami waves are caused by a sudden displacement of the water column due to a number of various trigger mechanisms such are earthquakes as the main trigger submarine and subaerial mass wastings volcanic activity atmospheric disturbances meteotsunamis and cosmic impacts as is demonstrated by giving corresponding examples from the past tsunamis are known to have a significant sedimentary and geomorphological off and onshore response so called tsunamites form allochthonous high energy deposits that are left at the coast during tsunami landfall tsunami deposits show typical sedimentary features as basal erosional unconformities fining upward and landward a high content of marine fossils rip up clasts from underlying units and mud caps all reflecting the hydrodynamic processes during inundation the on and offshore behaviour of tsunamis and related sedimentary processes can be simulated using hydro and morphodynamic numerical models the paper provides an overview of the basic tsunami modelling techniques including discretisation guidelines for appropriate temporal and spatial resolution as well as the nesting method furthermore the boussinesq approximation a simplification of the three dimensional navier stokes equations is presented as a basic theory behind numerical tsunami models which adequately reflects the non linear dispersive wave behaviour of tsunamis the fully non linear boussinesq equations allow the simulation of tsunamis e g in the form of n waves based on the various subtopics presented recommendations for future multidisciplinary tsunami research are made it is especially discussed how the combination of sedimentary and geomorphological tsunami field traces and numerical modelling techniques can contribute to derive locally relevant tsunami sources and to improve the assessment of tsunami hazards considering the individual pre history and physiogeographical setting of a specific region

linear and nonlinear computations of the 1992 nicaragua earthquake tsunami numerical computations of tsunamis are made for the 1992 nicaragua earthquake using different governing equations bottom frictional values and bathymetry data the results are compared with each other as well as with the observations both tide gauge records and runup heights comparison of the observed and computed tsunami waveforms indicates that the use of detailed bathymetry data with a small grid size is more effective than to include nonlinear terms in tsunami computation linear computation overestimates the amplitude for the later phase than the first arrival particularly when the amplitude becomes large the computed amplitudes along the coast from nonlinear computation are much smaller than the observed tsunami runup heights the average ratio or the amplification factor is estimated to be 3 in the present case when the grid size of 1 minute is used the factor however may depend on the grid size for the computation

tsunami simulation by tuned seismic source inversion for the great 2011 tohoku earthquake seismic and tsunami waves were the most destructive phenomena during the 2011 tohoku earthquake here we ask whether the same source model can be used to obtain equally good simulations of the observed strong ground motions and the tsunami waves if so we could use the same source modeling technique for predictions of both tsunami waves and strong ground motions long period 20 200 s strong ground motion data were inverted to determine the rupture process of the 2011 tohoku earthquake the inverted slip distribution shows that large slip area was extended around 150 km to north and 120 km to south from hypocenter and stretched between hypocenter and the trench we estimated two slip models without and with additional constraints the first relatively rough slip model reproduced short period tsunami wave 4 5 min due to better constraint by data of other kind and being relatively smooth the second model reproduces long period tsunami wave 15 25 min as well as keeps good fit of the short period tsunami although short period tsunami becomes underestimated we used a fully nonlinear boussinesq water wave model to model tsunami propagation and used the results to tune the slip model finally we developed a tuned slip model that combines the features of both the first and the second slip models and reproduced both the short and long period tsunami waves while maintaining good fit of the seismic waveforms

3 d modelling of plate interfaces and numerical simulation of long term crustal deformation in and around japan we developed a 3 d simulation model for long term crustal deformation due to steady plate subduction in and around japan by incorporating viscoelastic slip response functions into a realistic 3 d plate interface model constructed on the basis of the topography of ocean floors and hypocenter distributions of earthquakes the lithosphere asthenosphere system is modelled by an elastic surface layer overlying a maxwellian viscoelastic half space kinematic interaction at plate interfaces is rationally represented by the increase of tangential displacement discontinuity fault slip across the interfaces with this model giving the steady slip rates at plate interfaces calculated from nuvel 1a we simulated long term crustal deformation due to steady plate subduction in and around japan the simulated crustal deformation pattern is characterized by steep uplift at island arcs sharp subsidence at ocean trenches and gentle uplift at outer rises the numerical results show the strong dependence of the deformation pattern on the 3 d geometry of plate interfaces

active thrusting of the longquan fault in the central sichuan basin china and the seismotectonic behavior in the longmen shan fold and thrust belt present day convergence within the longmen shan fold and thrust belt lsftb was released by the 2008 mw 7 9 wenchuan earthquake which ruptured multiple thrust ramps beneath the range front structures however it is still unclear whether fault slip propagated eastward into the foreland closer to densely populated areas around chengdu in this study we provide constraints on the 3 d subsurface structure fault activity and seismic hazards of the longquan fault located in the central sichuan basin 100 km east of the range front structures of the lsftb we develop a seismotectonic model and assess the activity of the longquan fault by a combination of methods including interpretation of seismic reflection profiles analysis of satellite images field mapping trench logging and radiocarbon dating our survey reveals that at least two surface rupturing events occurred on the longquan fault in the holocene our 3 d structural model and evidence for late holocene faulting events on the longquan fault reveals that upper crustal shortening in the sichuan basin is accommodated by a frontal thrust system that is linked to the recently active range front blind structures by a shallow detachment we suggest that dynamic weakening following fault activity at the longmen shan range front might unlock the up dip portion of this shallow detachment sending slip eastward into the foreland and to the surface along the longquan thrust ramps our results have important implications for seismic hazards assessment of active frontal thrusts linked by upper crustal detachments in active fold and thrust belts around the world

a unified source model for the 2011 tohoku earthquake abstract the devastating 2011 tohoku earthquake was observed by dense networks of geophysical instruments a unified source model was constructed through joint inversion of teleseismic strong motion and geodetic datasets the result indicates that the earthquake consists of three main ruptures after small rupture in the initial 50 s the first rupture expanded at a slow speed of 1 8 km s to the northeast and east the second rupture began 20 s later at the slowest speed of 1 5 km s and became dominant with the largest slip of 36 m the third rupture then played the leading role propagating southward at a speed of 2 5 km s only the tsunami inversion requires an extension of the source fault to a shallow part between the first rupture area and the japan trench recovering tsunamigenic slips larger than 40 m the slow rupture speed and tsunamigenic slips can explain the features of the disaster by the earthquake

bayesian inversion of microtremor array dispersion data in southwestern british columbia summary this paper applies bayesian inversion with evaluation of data errors and model parametrization to produce the most probable shear wave velocity profile together with quantitative uncertainty estimates from microtremor array dispersion data generally the most important property for characterizing earthquake site response is the shear wave velocity vs profile the microtremor array method determines phase velocity dispersion of rayleigh surface waves from multi instrument recordings of urban noise inversion of dispersion curves for vs structure is a non unique and non linear problem such that meaningful evaluation of confidence intervals is required quantitative uncertainty estimation requires not only a non linear inversion approach that samples models proportional to their probability but also rigorous estimation of the data error statistics and an appropriate model parametrization this paper applies a bayesian formulation that represents the solution of the inverse problem in terms of the posterior probability density ppd of the geophysical model parameters markov chain monte carlo methods are used with an efficient implementation of metropolis hastings sampling to provide an unbiased sample from the ppd to compute parameter uncertainties and inter relationships nonparametric estimation of a data error covariance matrix from residual analysis is applied with rigorous a posteriori statistical tests to validate the covariance estimate and the assumption of a gaussian error distribution the most appropriate model parametrization is determined using the bayesian information criterion which provides the simplest model consistent with the resolving power of the data parametrizations considered vary in the number of layers and include layers with uniform linear and power law gradients parameter uncertainties are found to be underestimated when data error correlations are neglected and when compressional wave velocity and or density nuisance parameters are fixed in the inversion bayesian inversion of microtremor array data is applied at two sites in british columbia the area of highest seismic risk in canada to study the ability to recover an accurate vs profile in relatively deep and shallow geological settings on the fraser river delta in greater vancouver and in victoria respectively a well resolved vs profile to at least 110 m depth is determined at the fraser river delta site for a power law gradient parametrization at the victoria site a layer with low vs and a weak linear gradient is indicated to 15 18 m depth above much higher velocity material invasive vs measurements from seismic cone penetration testing and or surface to downhole methods are used to assess the reliability of the bayesian microtremor inversion results with excellent agreement obtained at both sites

the coseismic slip distribution of a shallow subduction fault constrained by prior information the example of 2011 tohoku mw 9 0 megathrust earthquake

propagation and amplification of tsunamis at coastal boundaries when tsunamis hit a coastal area they often cause substantial damage and loss of life at locations otherwise well protected from normal even severe wind generated waves an example of such a catastrophe took place on 12 december 1992 when an earthquake of magnitude ms 7 5 occurred in the eastern region of flores island indonesia1 2 one of the areas hardest hit by the resulting tsunamis was babi a small coastal island two villages on the island were completely destroyed even though both were located in sheltered areas where wave conditions are normally calm here we describe the results of numerical and laboratory experiments that show how unlike wind generated waves tsunamis are capable of penetrating into sheltered coastal areas without significantly losing their energy for the case of babi island the original tsunami wave was split into two with one wave propagating around each side of the island the two waves met in the sheltered region and the subsequent amplification of wave amplitude resulted in the destructive flow onto the beach

what is a mega tsunami abstract no unambiguous and widely accepted definition currently exists for the term mega tsunami this is in spite of the rapidly growing popularity of the expression in the scientific literature especially in recent years following the devastation wrought by the 2004 indian ocean and 2011 tohoku oki tsunamis a comprehensive literature search is revealing we find that although there have been several previous attempts at a definition the term mega tsunami has generally been applied in a rather arbitrary fashion to a number of tsunami characteristics such as wave height or amplitude at both source and distant locations run up height geographical extent and impact this haphazard situation is undesirable in response we propose a stricter definition for mega tsunami that is based solely on initial wave height amplitude at source exceeding 100 m 50 m respectively a source related definition conveniently avoids any difficulties associated with the potential influence of coastal physical attributes e g configuration bathymetry geomorphology on tsunami parameters at affected locations using this definition it becomes apparent that mega tsunamis can only include those rare events on geological timescales generated by large bolide impacts violent volcanic activity or oceanic island flank collapse and possibly extreme tsunamigenic submarine earthquakes most seismically triggered events instead fall into the group of souteigai tsunamis i e unexpected tsunamis which are considered exceptional according to historical experience and local perspectives

rupture process of the 2011 tohoku oki earthquake and absolute elastic strain release 1 on 11 march 2011 the tohoku oki earthquake in eastern japan and the devastating tsunami that followed it caused severe damage and numerous deaths to clarify the rupture process of the earthquake we inverted teleseismic p wave data applying a novel formulation that takes into account the uncertainty of green s function which has been a major error source in waveform inversion the estimated seismic moment is 5 7 1022 nm mw 9 1 associated with a fault rupture 440 km long and 180 km wide along the plate interface the source process is characterized by asymmetric bilateral rupture propagation but we also found continuous slips up dip from the hypocenter which led to a large maximum slip 50 m long slip duration 90 s and a large stress drop 20 mpa the long slip duration large stress drop extensional normal faulting aftershocks in a previously compressional stress regime and low angle normal slips at approximately the depth of the plate interface suggest that the earthquake released roughly all of the accumulated elastic strain on the plate interface owing to exceptional weakening of the fault the stress accumulated on the plate interface was about 20 mpa near the trench and 0 10 mpa in the down dip source region

local tsunamis and distributed slip at the source variations in the local tsunami wave field are examined in relation to heterogeneous slip distributions that are characteristic of many shallow subduction zone earthquakes assumptions inherent in calculating the coseismic vertical displacement field that defines the initial condition for tsunami propagation are examined by comparing the seafloor displacement from uniform slip to that from an ideal static crack we demonstrate that dip directed slip variations significantly affect the initial cross sectional wave profile because of the hydrodynamic stability of tsunami wave forms these effects directly impact estimates of maximum runup from the local tsunami in most cases an assumption of uniform slip in the dip direction significantly underestimates the maximum amplitude and leading wave steepness of the local tsunami whereas dip directed slip variations affect the initial wave profile strike directed slip variations result in wavefront parallel changes in amplitude that are largely preserved during propagation from the source region toward shore owing to the effects of refraction tests of discretizing slip distributions indicate that small fault surface elements of dimensions similar to the source depth can acceptably approximate the vertical displacement field in comparison to continuous slip distributions crack models for tsunamis generated by shallow subduction zone earthquakes indicate that a rupture intersecting the free surface results in approximately twice the average slip therefore the observation of higher slip associated with tsunami earthquakes relative to typical subduction zone earthquakes of the same magnitude suggests that tsunami earthquakes involve rupture of the seafloor whereas rupture of deeper subduction zone earthquakes may be imbedded and not reach the seafloor

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

effects of longitudinal valley slopes on runup of the 2011 tohoku tsunami on the sanriku coast northeastern japan abstract the 2011 tohoku earthquake and tsunami caused heavy damage in low lying river valleys of the sanriku coast northeastern japan the landward extent of inundation by the tsunami varied considerably among the valleys indicating that tsunami runups were strongly affected by the subaerial fluvial morphology of the valleys we used detailed tsunami inundation maps to investigate tsunami runups along river valleys along the sanriku coast considering both the protected areas landward of coastal seawalls and levees protected zone and areas on the river side of levees channel zone we determined the mean longitudinal slopes of all river valleys and used them in conjunction with published tsunami inundation maps to determine the distances and heights of tsunami runups in 68 valleys along the sanriku coast runup heights tended to be higher and inundation distances longer in the channel zone than in the protected zone comparisons of runups among valleys with different longitudinal valley slopes showed that inundation distance decreased with increasing valley slope and that runup height increased with increasing slope during runup some of the kinetic energy of a tsunami is consumed as frictional work and some is transformed upslope to potential energy the steeper the longitudinal slope the greater the amount of energy transformed and stored as potential energy and consequently the amount of energy consumed by frictional work declines and inundation distance shortens in the protected zone more energy is consumed by frictional work during destruction of artificial structures such as houses and inundation distance is shorter than in the channel zone our analysis of 2011 tsunami data clarified relationship among tsunami runups shoreline tsunami heights geometry of the coastline and longitudinal valley slopes among sanriku ria coast coastline geometry appears to be a secondary influence on the shoreline tsunami height and runup that the shoreline tsunami height was not the dominant influence on tsunami runup emphasizes the importance of subaerial topography on tsunami runup especially in narrow steep valleys which are often of the topography along coasts that face plate margins

displacement above the hypocenter of the 2011 tohoku oki earthquake the moment magnitude m w 9 0 2011 tohoku oki mega thrust earthquake occurred off the coast of northeastern japan combining global positioning system gps and acoustic data we detected very large sea floor movements associated with this event directly above the focal region an area with more than 20 meters of horizontal displacement that is four times larger than those detected on land stretches several tens of kilometers long along the trench the largest amount reaches about 24 meters toward east southeast just above the hypocenter furthermore nearly 3 meters of vertical uplift occurred contrary to observed terrestrial subsidence

estimation of tsunami characteristics from deposits inverse modeling using a deep learning neural network tsunami deposits provide information for estimating the magnitude and flow conditions of paleotsunamis and inverse models have potential for reconstructing hydraulic conditions of tsunamis from th

the use of rayleigh wave ellipticity for site specific hazard assessment and microzonation application to the city of lucerne switzerland summary the sediments underlying the city of lucerne switzerland consisting of fluvio lacustrine deposits of quaternary age have the potential to produce strong amplification of the seismic wavefield to obtain a reliable estimation of the deep soil structure we combine different methodologies based on ambient noise recordings such as single station horizontal to vertical ratios and three component array analysis two novel techniques to estimate rayleigh wave ellipticity from ambient noise recordings are tested these are based on a single and a multistation approach respectively the first utilizes the continuous wavelet transform to perform a decomposition of the noise wavefield and to isolate and extract the rayleigh wave contribution the second conversely relies on a high resolution f k method to achieve the same result we compare the results from the two techniques to provide an evaluation of their capabilities and limitations a two step inversion scheme is then presented to improve resolution on the bedrock depth in particular the surface wave dispersion information is initially used to constrain the soft sediment part while the rayleigh wave ellipticity peak is subsequently used for constraining the bedrock depth it is shown that such an approach is beneficial to map the bedrock geometry over dense urban areas the output velocity model is then used to compute the local seismic amplification by means of gridded 1 d approximation

joint inversion of h v ratios and dispersion curves from seismic noise estimating the s wave velocity of bedrock 1 a joint inversion of phase velocity and h v ratio curves both obtained from seismic noise recordings permits the retrieval of the shear wave velocity structure of local sedimentary cover our inversion scheme uses a genetic algorithm and considers the influence of higher modes on the data sets encouraged by the results published previously on joint inversion parolai et al 2005 we went one step further we found using a synthetic data set that the impedance contrast at the sediment bedrock interface has a strong influence on the shape of the h v ratio curve which therefore allows the bedrock s wave velocity to be well constrained in the joint inversion procedure our observations were further confirmed using a real data set

tsunami generation by horizontal displacement of ocean bottom tsunami generation by an earthquake is generally modeled by water surface displacement identical to the vertical deformation of ocean bottom due to faulting the effect of horizontal deformation is usually neglected however when the tsunami source is on a steep slope and the horizontal displacement is large relative to the vertical displacement the effect becomes significant we show this for two recent earthquakes which generated much larger tsunamis than expected from seismic waves in the case of the 1994 june 2 java indonesia earthquake the focal mechanism was a very shallow dipping thrust and the source was near a very steep trench slope in the case of the 1994 nov 14 mindoro philippines earthquake strike slip faulting extended from ocean to land perpendicular to the coast line in both cases we found that the horizontal motion of slope had an important contribution to the tsunami generation

three dimensional crustal s wave velocity structure in japan using microseismic data recorded by hi net tiltmeters 1 we developed a three step method for three dimensional 3 d s wave velocity tomography by fitting synthetic cross spectra to the observed ones of ambient seismic noise we applied this method to the recording of hi net tiltmeters in japan at 679 stations from june 2004 to december 2004 first we calculated normalized cross spectra between radial components and those between transverse components for every pair of stations the first step is local 1 d s wave velocity inversion for each station assuming small lateral heterogeneity under a 100 km circle of a station we measured the dispersion curves of fundamental rayleigh waves fundamental love waves and first overtone of love waves by fitting the synthetic cross spectra to the observed ones between pairs of stations within the circle we inverted the measured dispersion curves for obtaining a 1 d s wave velocity model the second step is the inversion of the observed cross spectra for obtaining path averaged 1 d s wave velocity structure the third step is the inversion of the resultant path averaged structures for obtaining 3 d s wave velocity structure 0 1 0 1 1 km grid from the surface to a depth of 50 km using ray approximation the resultant s wave velocity structures show clear low velocity anomalies along tectonic lines from the surface to a depth of 20 km in particular along the hidaka mountain range we observed s wave perturbation more extreme than 20 they also show low velocity anomalies under volcanoes in kyusyu and tohoku in the southwestern part of shikoku our results show a clear low velocity anomaly corresponding to an accretional belt shimanto belt below 20 km we observe a low velocity anomaly in the center of japan which suggests a thick crust citation nishida k h kawakatsu and k obara 2008 three dimensional crustal s wave velocity structure in japan using microseismic data recorded by hi net tiltmeters j geophys res 113 b10302 doi 10 1029 2007jb005395

geodetic data inversion using a bayesian information criterion for spatial distribution of fault slip summary we developed a new inversion method to reconstruct static images of seismic sources from geodetic data using akaike s bayesian information criterion abic coseismic surface displacements are generally related with a slip distribution on a fault surface by linear integral equations parametric expansion of the fault slip distribution by a finite number of known basis functions yields a set of observation equations expressed in a simple vector form incorporating prior constraints on the smoothness of slip distribution with the observation equations we construct a bayesian model with unknown hyperparameters the optimal values of the hyperparameters which control the structure of the bayesian model are objectively determined from observed data by using abic once the values of hyperparameters are determined we can use the maximum likelihood method to find the optimal distribution of fault slip we examined the validity of this method through a numerical experiment using theoretical data with random noise we analysed geodetic data associated with the 1946 nankaido earthquake ms 8 2 by using this method the result shows that the fault slip distribution of this earthquake has two main peaks of 4 and 6 m located off kii peninsula and muroto promontory these two high slip areas are clearly separated by a low slip zone extending along kii strait such a slip distribution corresponds with the fact that the rupture process of this earthquake in the western part is notably different from that in the eastern part

a method for the joint inversion of geodetic and seismic waveform data using abic application to the 1997 manyi tibet earthquake geodetic imaging data and seismicwaveformdata have complementary strengthswhen considering the modelling of earthquakes the former particularly modern space geodetic techniques such as interferometric synthetic aperture radar insar permit high spatial density of observation and thus fine resolution of the spatial pattern of fault slip the latter provide precise and accurate timing information and thus the ability to resolve how that fault slip varies over time in order to harness these complementary strengths we propose a method through which the two data types can be combined in a joint inverse model for the evolution of slip on a specified fault geometry we present here a derivation of akaike s bayesian information criterion abic for the joint inversion of multiple data sets that explicitly deals with the problem of objectively estimating the relative weighting between data sets as well as the optimal influence of model smoothness constraints in space and time we demonstrate our abic inversion scheme by inverting insar displacements and teleseismic waveform data for the 1997 manyi tibet earthquake we test using a simplified fault geometry three cases insar data inverted alone vertical component teleseismic broad band waveform data inverted alone and a joint inversion of both data sets the insar only model and seismic only model differ significantly in the distribution of slip on the fault plane that they predict the joint inversion model however has not only a similar distribution of slip and fit to the insar data in the insar only model suggesting that those data provide the stronger control on the pattern of slip but is also able to fit the seismic data at a minimal degradation of fit when compared with the seismic only model the rupture history of the preferred joint inversion model indicates bilateral rupture for the first 20 s of the earthquake followed by a further 25 s of westward unilateral rupture afterwards with slip peaking at 7m in the upper 6 km of the fault this joint inversion approach is thus shown to be a viable method for the study of large shallow continental earthquakes and may be of particular benefit in cases where near field seismic observations are not available the authors 2014 published by oxford university press on behalf of the royal astronomical society

restoration of interplate locking after the 2005 off miyagi prefecture earthquake detected by gps acoustic seafloor geodetic observation 1 a 7 2 magnitude earthquake occurred on the plate boundary off miyagi prefecture northeastern japan on 16 august 2005 from seafloor geodetic observations using the gps acoustic combination technique in this area we have detected notable seafloor movements associated with and subsequent to this event the time series of horizontal coordinates obtained at the seafloor reference point mygw located about 10 km east of the epicenter indicates that the strain accumulated for the interseismic period was partly released by the event and a constant strain accumulation restarted after 1 2 years of the post seismic period with an erratic movement the horizontal velocity of mygw after the restart above is estimated to be about 5 7 cm year toward wnw relative to the eurasian plate our result is consistent with those derived from terrestrial gps measurements and implies that the interplate locking was restored in the rupture area of the 2005 event around 2007

runup of tsunami waves in u shaped bays the problem of tsunami wave shoaling and runup in u shaped bays such as fjords and underwater canyons is studied in the framework of 1d shallow water theory with the use of an assumption of the uniform current on the cross section the wave shoaling in bays when the depth varies smoothly along the channel axis is studied with the use of asymptotic approach in this case a weak reflection provides significant shoaling effects the existence of traveling progressive waves propagating in bays when the water depth changes significantly along the channel axis is studied within rigorous solutions of the shallow water theory it is shown that traveling waves do exist for certain bay bathymetry configurations and may propagate over large distances without reflection the tsunami runup in such bays is significantly larger than for a plane beach