inference of postseismic deformation mechanisms of the 1923 kanto earthquake 1 coseismic slip associated with the m7 9 1923 kanto earthquake is fairly well understood involving slip of up to 8 m along the philippine sea honshu interplate boundary under sagami bay and its onland extension postseismic deformation after the 1923 earthquake however is relatively poorly understood we revisit the available deformation data in order to constrain possible mechanisms of postseismic deformation and to examine the consequences for associated stress changes in the surrounding crust data from two leveling lines and one tide gage station over the first 7 8 years postseismic period are of much greater amplitude than the corresponding expected interseismic deformation during the same period making these data suitable for isolating the signal from postseismic deformation we consider both viscoelastic models of asthenosphere relaxation and afterslip models a distributed coseismic slip model presented by pollitz et al 2005 combined with prescribed parameters of a viscoelastic earth model yields predicted postseismic deformation that agrees with observed deformation on mainland honshu from tokyo to the izu peninsula elsewhere southern miura peninsula boso peninsula the considered viscoelastic models fail to predict observed deformation and a model of 1 m shallow afterslip in the offshore region south of the boso peninsula with equivalent moment magnitude mw 7 0 adequately accounts for the observed deformation using the distributed coseismic slip model layered viscoelastic structure and a model of interseismic strain accumulation we evaluate the post 1923 stress evolution including both the coseismic and accumulated postseismic stress changes and those stresses contributed by interseismic loading we find that if account is made for the varying tectonic regime in the region the occurrence of both immediate first month post 1923 crustal aftershocks as well as recent regional crustal seismicity is consistent with the predicted stress pattern this suggests that the influence of the 1923 earthquake on regional seismicity is fairly predictable and has persisted for at least seven decades following the earthquake

geologic structure and neotectonics of the north african continental margin south of sicily abstract marine geological and geophysical data together with drilling information indicate that the north african passive continental margin has been subjected to extension and wrenching after it collided with the northern part of sicily the area of the tripolitania basin jarrafa trough melita and medina bank and the ragusa malta plateau has formed part of a sinking passive margin since the dispersal of gondwanaland at about 180 my ago as observed from geohistory diagrams a record of rifting in a nw se direction accompanied by dextral shear along the southern troughs is observed in seismic reflection data the rifting started during the neocomian and lasted until the eocene when activity became minor a pre middle miocene period of northward subduction of oceanic crust is inferred from the geology in ne sicily uplift of the northern part of the african margin after collision in the middle miocene is seen in wells in southern sicily after the messinian a rift and dextral shear zone established itself across the african margin from the strait of sicily to the medina ridge in the lonian basin the zone is marked by up to 1 7 km deep grabens narrow active wrench faulted channels volcanic fissures and local uplifted keilhorsts such as malta this zone which varies in width from 100 to 35 km forms the southern boundary of a microplate which includes sicily we speculate that the present motion of this microplate is partly due to the eastward movement of the calabrian arc with the sicilian block over the last remaining oceanic lithosphere in the eastern mediterranean

simulation of long period ground motion near a large earthquake we estimated the possible range of long period ground motion for sites located on a soft sedimentary basin in the immediate vicinity of a large earthquake since many large cities in the world e g los angeles san francisco and tokyo where many large structures have been recently constructed are located in this type of environment a better understanding of long period ground motion is becoming increasingly important our objective is to estimate the possible range of long period ground motion rather than ground motion for a specific fault model we computed ground motion time series and pseudo velocity response spectra pvs for more than 5 000 models for the 1923 kanto japan earthquake m w 7 9 using 180 slip distributions eight rupture geometry and rupture velocities ranging from 1 5 to 3 0 km sec two seismograms recorded in tokyo during the 1923 kanto earthquake are used for comparison the response spectra computed using seismologically reasonable sets of source parameters for the 1923 kanto earthquake vary by more than an order of magnitude at periods of 10 to 13 sec they range from 25 to 170 cm sec in tokyo for some combinations of model parameters the response spectra exhibit peaks in the range of 10 to 13 sec many of the computed response spectra have peaks at periods longer than 10 sec which is considerably longer than the dominant period 6 to 8 sec estimated from studies of small earthquakes and microtremor measurements thus the dominant period of the subsurface structure determined locally may not be representative of the dominant period of ground motion from a nearby large earthquake which is controlled by rupture directivity and source depth we performed a similar simulation for a hypothetical m w 7 5 earthquake located beneath the los angeles basin for a site just above the center of the fault the ground motion spectral amplitude at a period of 10 sec can vary from 50 to 350 cm sec this range though very large is what is expected for a seismologically plausible range of source parameters

3 d simulations of surface wave propagation in the kanto sedimentary basin japan part 2 application of the surface wave bem abstract the 3 d surface wave boundary element method is applied to the same set of strong motion records as those of part 1 kato et al 1993 namely the long period strong motion with periods around 8 sec recorded at the jma japan meteorological agency stations in yokohama and tokyo during the 1980 izu hanto toho oki earthquake this method simulates exact love and rayleigh waves in a laterally heterogeneous medium including 3 d basin structures the needed computer memory and cpu time are made manageable by assuming the inside and outside of the basin to consist of horizontal flat layers in addition vertical interfaces are assumed between the basin and the outside bedrock for simplicity in this study after checking the range of validity of the flat layer approximation for the kanto sedimentary basin the generation and propagation of surface waves in the basin are numerically investigated in particular our investigation places special emphasis on the cause of the observed long duration which could not be explained in part 1 using the surface wave gaussian beam method when the bedrock outside the western margin of the kanto basin is incorporated into the model the observed long duration at the tokyo station is successfully reproduced this can be explained by the strong surface waves generated by the surface wave to surface wave conversion at the margin and appearing in tokyo after the direct surface waves from the epicenter this result agrees with kinoshita et al 1992 who studied records from an array of seismographs in tokyo moreover when a sedimentary basin of sagami bay is included as was done in part 1 the simulations are greatly improved particularly at the yokohama station which corresponds to the node in the radiation pattern of the source this is due to the fact that the radiation pattern is strongly affected by the near source heterogeneity of the sagami basin all these results together with direct comparisons to 2 d modelings clearly show the strong 3 d effects of the basin structures on the generation and propagation of surface waves for this earthquake

three dimensional finite difference simulations of long period strong motions in the tokyo metropolitan area during the 1990 odawara earthquake mj 5 1 and the great 1923 kanto earthquake ms 8 2 in japan utilizing a crustal velocity model that includes the complexity of the irregular subsurface structure of the kanto basin we have performed three dimensional 3d finite difference fd simulations of near source long period strong ground motions in the tokyo metropolitan area for the 1990 odawara mj 5 1 and the 1923 kanto ms 8 2 earthquakes constraints on the development of the 3d velocity model come from available geological and geophysical data as well as our previous 1d waveform modeling results sato et al 1998a the simulation of the moderate sized odawara earthquake demonstrates that the 3d velocity model works quite well at reproducing the recorded long period t 3 33 sec strong motions including basin generated surface waves for a number of sites located throughout the kanto basin region using this validated 3d model along with the variable slip rupture model of wald and somerville 1995 we then simulate the long period t 4 sec ground motions in this region for the 1923 kanto earthquake the simulation results for the 1923 event show that the largest ground motions occur east of the epicenter along the central and southern part of the boso peninsula these large motions arise from strong rupture directivity effects and are comprised of relatively simple source controlled pulses with a dominant period of about 10 sec north of the epicentral region in the tokyo area 3d basin generated phases are quite significant and these phases produce large amplitude late arriving pulses in the ground motions at station hongo hng which is the only site having digitized and restored near fault strong motion records for this event our 3d simulations compare quite well with the ground motions of the restored imamura seismogram for the restored ewing record our 3d simulations reproduce the phase and amplitude of the initial pulses of motion however the dominant period of the large amplitude later phases is noticeably shorter in the simulations about 5 to 6 sec than in the observation 13 sec these results suggest that the restored imamura seismogram may be a better representation of the gross features of the actual motion than the restored ewing seismogram although the first clipped and restored part of the imamura seismogram may still underestimate the strength of the actual motion

modified frequency wavenumber algorithm for regional seismograms using filon s quadrature modelling of lg waves in eastern north america summary the main focus of this study is to develop an efficient frequency wavenumber code to synthesize high frequency say 10 hz regional seismograms up to a distance of more than 1000 km in a medium consisting of a large number of crustal layers and investigate effects of regional waveguides on lg waves in this newly developed code the frequency wavenumber response is evaluated by using the filon s quadrature at high frequency and the polynomial approximation of bessei s functions implementing trapezoidal integration at low frequency this has reduced the computation time by several folds compared to the time needed for the trapezoidal integration using this algorithm both broad band seismograms at harvard and short period ectn eastern canadian telemetered network seismograms from 1988 november 25 saguenay earthquake were successfully modelled a moment magnitude of 5 9 was used initially an average waveguide was calibrated to successfully excite the regional pnl and snl waves at hrv its near surface structure constrained by matching the recorded frequency content the crust mantle transition zone was constrained by modelling the strength of the broad band snl waves consisting of sn ssmsnsmssms and ssmssms phases relative to the initial pnl waves the model was modified to consist of thin layers with an alternating high and low velocity distribution to match the high frequency ectn lg waves observed from 300 to 600 km away in addition the effect of a near surface irregular receiver structure on the duration of lg waves was also investigated by convolving its response with the regional lg seismograms initial study suggests this method as viable for modelling the entire lg waves including the coda numerical studies suggest that the shapes and peak amplitudes on lg seismograms depend more strongly on the source depth anelasticity and crustal waveguide than do the pnl seismograms

three dimensional topography of the sediment basement interface in the tokyo metropolitan area central japan abstract an extensive seismic refraction experiment was conducted in the tokyo metropolitan area central japan to reveal the three dimensional basin structure in this area sixty three explosions were fired over 14 years and more than 2000 travel times were picked for several phases for our inversion the basement is divided into two homogeneous regions where the sediment is assumed to be of uniform velocity the interface separating the sediment and basement is then parameterized by bi cubic b splines and a smoothness constraint is imposed to avoid oscillatory artifacts in the solution the relative weight of the constraint to data residuals is determined by minimizing akaike9s bayesian information criterion about 1500 travel times of refracted p waves are inverted tomographically and the interface shape determined agrees well with the results of other geophysical surveys such as borehole measurements and gravimetric observations the basement velocities in the northern and southern regions are 5 7 and 5 4 km sec respectively previous two dimensional analyses suggested there is a 4 5 km sec layer in the uppermost part of the southern basement but we ignore it for simplicity so that estimated depths are likely underestimated by 1 2 km in the southern region nevertheless this study provides the first detailed image of the basin structure in the area which will help strong motion and earthquake hazard studies as additional constraints

recent volume loss of british columbian glaciers canada 1 we use the shuttle radar topography mission srtm data and digital terrain models from aerial photography to quantify the change of glacier volume in british columbia bc canada for the period 1985 1999 we note substantial elevation bias in the srtm elevations typically on the order of 12 m km 1 the bias corrected thinning rate is 0 78 0 19 m a 1 which yields an annual volume loss of 22 48 5 53 km 3a 1 this rate of glacier volume loss is 65 of the estimate uncorrected for elevation bias 34 7 km 3a 1 and cautions against the use of uncorrected srtm data for glacier change studies glacier recession in bc could account for ca 0 67 0 12 mm of sea level rise over the period 1985 1999 0 05 0 009 mm yr 1 or about 8 3 of the contribution from mountain glaciers and ice caps the recent rate of glacier loss in the coast mountains 17 0 km 3a 1 is approximately double that observed for the previous two decades

3 d simulations of surface wave propagation in the kanto sedimentary basin japan part 1 application of the surface wave gaussian beam method abstract the goal of this study is to simulate the displacement waveforms of 8 sec period love waves observed at tokyo and yokohama stations in the kanto sedimentary basin during the izu hanto toho oki earthquake of 29 june 1980 m 0 7 10 25 dyne cm the surface wave gaussian beam method is applied for this purpose on the basis of the 3 d seismic velocity and density structure of the kanto basin and assuming that the earth medium is laterally homogeneous outside the kanto basin waveforms of love waves are synthesized the synthesized seismograms underestimate the observed peak amplitudes at yokohama station this is primarily because the station is located in the direction of the nodal plane of the love wave radiation as indicated by yamanaka et al 1992 a quaternary basin exists in the sagami bay between the source location and the kanto basin we include the sagami basin in our model by the approximation of a circular low velocity region excellent agreement between observed and synthesized waveforms was achieved not only for amplitude but also for phase for the early parts of the wave trains at both stations we conclude that the low velocity quaternary basin in the sagami bay acts like a lens to focus surface wave energy resulting in high amplitudes the later arriving waves in particular the long duration observed at tokyo station however cannot be adequately explained by this method one possible reason for the failure of simulating the later phases is that this method disregards the secondary love waves converted from s waves and or surface waves at a laterally discontinuous boundary although the surface wave gaussian beam method cannot adequately predict the duration of observed seismograms it provides us with a satisfactory prediction of amplitudes and phases for early arrivals in laterally slowly varying media at drastically lower computation costs and less memory requirements than does other methods

streamflow changes in alaska between the cool phase 1947 1976 and the warm phase 1977 2006 of the pacific decadal oscillation the influence of glaciers 1 streamflow data from 35 stations in and near alaska were analyzed for changes between the cool phase 1947 1976 and the warm phase 1977 2006 of the pacific decadal oscillation winter spring and summer flow changes and maximum annual flow changes were different for glaciated basins more than 10 glacier covered area than for nonglaciated basins showing the influence of glaciers on historical streamflow changes mean february flows for example increased for the median of available stations by 45 for glaciated basins and by 17 for nonglaciated ones

glacier change in western north america influences on hydrology geomorphic hazards and water quality the glaciers of western canada and the conterminous united states have dominantly retreated since the end of the little ice age lia in the nineteenth century although average rates of retreat varied from strong in the first half of the twentieth century with glaciers stabilizing or even advancing until 1980 and then resuming consistent recession this retreat has been accompanied by statistically detectable declines in late summer streamflow from glacier fed catchments over much of the study area although there is some geographical variation over recent decades glaciers in northwest bc and southwest yukon have lost mass dominantly by thinning with relatively low rates of terminal retreat and glacier fed streams in that region have experienced increasing flows in many valleys glacier retreat has produced geomorphic hazards including outburst floods from moraine dammed lakes mass failures from oversteepened valley walls and debris flows generated on moraines in addition to these hydrologic and geomorphic changes evidence is presented that glacier retreat will result in higher stream temperatures possibly transient increases in suspended sediment fluxes and concentrations and changes in water chemistry with climate projected to continue warming over the twenty first century current trends in hydrology geomorphology and water quality should continue with a range of implications for water resources availability and management and hydroecology particularly for cool and cold water species such as salmonids copyright 2008 john wiley sons ltd

landsat based inventory of glaciers in western canada 1985 2005 abstract we report on a glacier inventory for the canadian cordillera south of 60 n across the two western provinces of british columbia and alberta containing 30 000 km2 of glacierized terrain our semi automated method extracted glacier extents from landsat thematic mapper tm scenes for 2005 and 2000 using a band ratio tm3 tm5 we compared these extents with glacier cover for the mid 1980s from high altitude aerial photography for british columbia and from landsat tm imagery for alberta a 25 m digital elevation model dem helped to identify debris covered ice and to split the glaciers into their respective drainage basins the estimated mapping errors are 3 4 and arise primarily from seasonal snow cover glaciers in british columbia and alberta respectively lost 10 8 3 8 and 25 4 4 1 of their area over the period 1985 2005 the region wide annual shrinkage rate of 0 55 a 1 is comparable to rates reported for other mountain ranges in the late twentieth century least glacierized mountain ranges with smaller glaciers lost the largest fraction of ice cover the highest relative ice loss in british columbia 24 0 4 6 occurred in the northern interior ranges while glaciers in the northern coast mountains declined least 7 7 3 4

coseismic slip distribution of the 1923 kanto earthquake japan 1 the slip distribution associated with the 1923 m 7 9 kanto japan earthquake is reexamined in light of new data and modeling we utilize a combination of first order triangulation second order triangulation and leveling data in order to constrain the coseismic deformation the second order triangulation data which have not been utilized in previous studies of 1923 coseismic deformation are associated with only slightly smaller errors than the first order triangulation data and expand the available triangulation data set by about a factor of 10 interpretation of these data in terms of uniform slip models in a companion study by nyst et al shows that a model involving uniform coseismic slip on two distinct rupture planes explains the data very well and matches or exceeds the fit obtained by previous studies even one which involved distributed slip using the geometry of the nyst et al two plane slip model we perform inversions of the same geodetic data set for distributed slip our preferred model of distributed slip on the philippine sea plate interface has a moment magnitude of 7 86 we find slip maxima of 8 9 m beneath odawara and 7 8 m beneath the miura peninsula with a roughly 2 1 ratio of strike slip to dip slip motion in agreement with a previous study however the miura slip maximum is imaged as a more broadly extended feature in our study with the high slip region continuing from the miura peninsula to the southern boso peninsula region the second order triangulation data provide good evidence for 3 m right lateral strike slip on a 35 km long splay structure occupying the volume between the upper surface of the descending philippine sea plate and the southern boso peninsula

the subsidence history of the northern hyblean plateau margin southeastern sicily abstract the southeastern corner of sicily is dominated by the hyblean plateau which is composed of carbonate rocks of triassic to miocene age the plateau forms part of the african foreland which collided during tertiary times with the calabrian arc giving rise to the maghrebian thrust belt the present study attempts to reconstruct the subsidence history of the northern hyblean plateau during the neogene climax of the plate collision this area has been a centre for widespread basaltic volcanic activity 8 1 ma and uplift at the close of the collisional events pliocene early pleistocene the area under consideration has been affected by subsidence and the progressive consumption of the northern margin of the hyblean plateau led to the development of the modern foredeep a quantitative analysis was done by one dimensional airy backstripping of seven deep wells located on this crucial part of the hyblean plateau the results of the analysis show that the subsidence history of the northern hyblean plateau area is characterized by four main phases similar to other domains in the central and eastern mediterranean basins these phases are a neotethyan rifting during late triassic early jurassic time b a slow thermal subsidence from early jurassic until late cretaceous time leading to the formation of a widespread mesozoic carbonate platform c compressional phase during late cretaceous palaeogene time which resulted in the formation of fold systems and d uplift and subsidence events during the middle tertiary which are probably the result of the continued collision of the european african plates after the early pleistocene unlike other terranes within the mediterranean an uplift occurred in the northern hyblean plateau following the upper miocene lower pleistocene massive volcanic activity this uplift is probably associated with the latest stages of thrusting along the frontal part of the maghrebian thrust belt

a new 1649 1884 catalog of destructive earthquakes near tokyo and implications for the long term seismic process 1 in order to assess the long term character of seismicity near tokyo we construct an intensity based catalog of damaging earthquakes that struck the greater tokyo area between 1649 and 1884 models for 15 historical earthquakes are developed using calibrated intensity attenuation relations that quantitatively convey uncertainties in event location and magnitude as well as their covariance the historical catalog is most likely complete for earthquakes m 6 7 the largest earthquake in the catalog is the 1703 m 8 2 genroku event seismicity rates from 80 years of instrumental records which include the 1923 m 7 9 kanto shock as well as interevent times estimated from the past 7000 years of paleoseismic data are combined with the historical catalog to define a frequency magnitude distribution for 4 5 m 8 2 which is well described by a truncated gutenberg richter relation with a b value of 0 96 and a maximum magnitude of 8 4 large uncertainties associated with the intensity based catalog are propagated by a monte carlo simulation to estimations of the scalar moment rate the resulting best estimate of moment rate during 1649 2003 is 1 35 1026 dyn cm yr 1 with considerable uncertainty at the 1 level 0 11 0 20 1026 dyn cm yr 1 comparison with geodetic models of the interseismic deformation indicates that the geodetic moment accumulation and likely moment release rate are roughly balanced over the catalog period this balance suggests that the extended catalog is representative of long term seismic processes near tokyo and so can be used to assess earthquake probabilities the resulting poisson or time averaged 30 year probability for m 7 9 earthquakes is 7 11

inversion analysis of site responses in the kanto basin using data from a dense strong motion seismograph array abstract we applied nonlinear inversion analysis to estimate site response in the kanto area using data from 19 moderate sized earthquakes observed at the 843 stations constituting strong motion accelerograph networks of the seismic kanto strong motion network sk net k net and kik net we determined the source parameters seismic moment m 0 corner frequency f c for each event and the quality factor q f for the propagation path based on borehole records we also determined the frequency independent and reference independent site responses the resulting seismic moments are in good agreement with those determined by the national research institute for earth science and disaster prevention nied and are proportional to we found a frequency dependent quality factor for the propagation path q f 107 f 0 52 the site responses averaged over 0 5 1 0 hz correlate well with shear wave velocities for the upper 30 m avs30 correlation coefficient of 0 63 and with depth to the seismic basement the shear wave velocity of which is around 3 0 km sec large site responses are found in areas of unconsolidated sediments such as swampy land the predominant frequencies of our site responses roughly agree with those of the horizontal to vertical h v spectral ratio this indicates that the h v ratio is valid for estimating predominant frequencies of s wave amplification

response of high rise and base isolated buildings to a hypothetical mw 7 0 blind thrust earthquake high rise flexible frame buildings are commonly considered to be resistant to shaking from the largest earthquakes in addition base isolation has become increasingly popular for critical buildings that should still function after an earthquake how will these two types of buildings perform if a large earthquake occurs beneath a metropolitan area to answer this question we simulated the near source ground motions of a m w 7 0 thrust earthquake and then mathematically modeled the response of a 20 story steel frame building and a 3 story base isolated building the synthesized ground motions were characterized by large displacement pulses up to 2 meters and large ground velocities these ground motions caused large deformation and possible collapse of the frame building and they required exceptional measures in the design of the base isolated building if it was to remain functional

a geological and paleomagnetic study of the hyblean volcanic rocks sicily abstract the geological and paleomagnetic study of the hyblean volcanic rocks in southeastern sicily permits the following conclusions 1 1 the upper cretaceous volcanics are considerably more extensive than earlier studies indicated they stretch from north of augusta to the vicinity of siracusa their magnetization is identical to that of the better known outcrops around capo passero of the two new age dates reported here one is younger than any so far reported 2 2 the upper tortonian flows are normally magnetized suggesting a correlation of the carlentini formation with magnetic interval 7 the flows at the top of the tellaro formation are also normally magnetized and are tentatively correlated with the carlentini formation flows shorter reversed intervals within interval 7 may be represented by two less well dated flows 3 3 the lowest pliocene flows have an adequate stratigraphie control and their magnetization is consistent with the extrusion of the pillow lavas during the mammoth event the militello flow sequence together with the francofonte flows appear by indirect argument to lie within the oldest reversed interval i e pre kaena of the matuyama epoch the individual flows in which both normal and reversed directions have been found cannot be assigned positions in magneto stratigraphie scale 4 4 the geomagnetic pole positions are consistent with that of the african plate during the cretaceous and a european plate location during both pliocene and miocene time the pole positions are upper cretaceous 212 3 e 69 3 n upper miocene 200 9 e 82 1 n pliocene 339 3 e 85 9 n

estimates of regional and local strong motions during the great 1923 kanto japan earthquake ms 8 2 part 2 forward simulation of seismograms using variable slip rupture models and estimation of near fault long period ground motions abstract this article addresses the forward simulation of regional and local strong motions from the 1923 kanto japan earthquake ms 8 2 using two variable slip rupture models the wald and somerville 1995 slip model ws slip model derived from geodetic and teleseismic data and a resampled version of the takeo and kanamori 1992 slip model tk slip model that was obtained from the forward simulation of the ewing seismoscope record at hongo hng epicentral distance r 60 km green9s functions are calculated using flat layered velocity models for specific source receiver paths which were developed in our first article sato et al 1998 for regional stations sendai r 350 km and gifu r 220 km the ws slip model provides a much better match to the waveform data than the tk slip model for local station hng the first 40 sec of the n77 e imamura seismogram is successfully reproduced by both of the slip models although the arrivals are delayed in the tk slip model the large amplitude long duration long period 13 sec later phases in the southwest component ewing seismogram are not reproduced by either of the slip models our results suggest that the ws slip model gives a better representation of the overall rupture process of the 1923 event than the tk slip model does near fault long period ground motions calculated at several stations using the ws slip model suggest that the motions at hng were not the largest in the tokyo metropolitan area during the 1923 event in addition we estimate that the ground motions near the southern margin of the fault plane were significantly larger than the recorded near fault motions of recent magnitude 7 earthquakes such as northridge and kobe for periods longer than several seconds this suggests that design codes based on the experience of these recent events may not adequately describe the long period response expected during a magnitude 8 earthquake

modeling three dimensional site response effects in the marina district basin san francisco california abstract loma prieta aftershock data recorded in the marina district of san francisco clearly show a large amplification in ground motion and a much longer duration of shaking relative to the response recorded at nearby rock sites for frequencies between 1 and 10 hz some of the amplification can be explained by the difference in impedance between the marina sites and the rock sites however 1d models underpredict the amplification in the range 1 to 3 hz and cannot account for the increased durations the available geologic information within the marina district indicates lateral variations in sediment thickness and composition our previous experience with modeling wave propagation in these types of basin environments has shown that these structures can greatly amplify and prolong the duration of the signals observed at sites within the basin in this study the seismic response of the marina basin is modeled with a 3d finite difference wave field simulation technique results from the numerical simulations at the basin sites indicate that the large amplitude arrivals following the direct s wave are surface waves traveling at relatively slow apparent velocities in general the surface waves contain the strongest recorded motions and produce the long duration of shaking observed at these sites in addition spectral ground motions from the 3d basin models do fairly well in reproducing the observed spectral amplification near 1 hz that is characteristic of the basin sites the simulation results suggest that focusing effects due to the geometry of the basin structure itself have a significant impact in determining the resonant periods at these basin sites

three dimensional simulation of earthquakes on the los angeles fault system we have used a 3d finite difference method to simulate ground motion from elastodynamic propagating ruptures with constant slip on faults in the metropolitan area of los angeles california simulations are carried out for hypothetical m 6 75 earthquakes on the palos verdes and elysian park faults and for comparison an approximation to the 17 january 1994 m 6 7 northridge earthquake the dominant subsurface features of this area are the deep sedimentary los angeles basin and the smaller and shallower san fernando basin simulated ground motions are restricted to the frequency range 0 0 to 0 4 hz ground motion time histories show that in general sites associated with the largest particle velocities and cumulative kinetic energies are located 1 in the epicentral area 2 above the deepest parts of the basins and 3 near the steepest edges of the los angeles basin we find maximum particle velocities for the palos verdes elysian park and northridge simulations of 0 44 0 67 and 0 58 m sec respectively in each case both the directivity of the rupture and the lower impedance of the basins significantly amplify the ground motion although the gross radiation pattern from these ruptures is observable the 3d basin structure distorts the wave field and becomes a source for edge generated waves signal durations at some basin sites last beyond 90 sec due to love waves and refracted s waves that propagate into the sediments from the basin edges compared with the palos verdes event the durations are generally smaller for the elysian park earthquake due to a smaller amount of love waves generated at the basin edges a simple approximation to the northridge earthquake reproduces the overall spatial pattern of the long period particle velocities successfully predicts the timing of late arriving waves and matches the peak velocities with discrepancies generally less than a factor of 2 however for localized areas immediately north and south of the santa monica mountains the computed ground motion underpredicts the observed horizontal peak velocities but matches the vertical ones the pattern of simulated total cumulative kinetic energies is similar to that for the damage intensities observed near the epicenter of the northridge event while the northridge earthquake caused damage in the los angeles area the 3d simulations show that earthquakes with the same magnitude on the palos verdes or elysian park faults produce more severe ground shaking in the los angeles basin

love wave propagation in a three dimensional sedimentary basin abstract a simplified three dimensional finite element method has been developed for simulation of love wave propagation in three dimensional sedimentary basins the eigenfunctions for the fundamental mode surface waves are employed as interpolation functions in the finite element scheme by reducing the number of degrees of freedom the method enables us to analyze wave propagation in an area of 2000 km 2 as large as the southern part of the kanto plain japan time histories of the near izu ohshima earthquake of 1990 are calculated and compared with observation calculated displacement snapshots show the effect of three dimensional topography on direction of love wave propagation the three dimensional simulation is also compared with a two dimensional one demonstrating amplitude increase and extended duration time histories and their spectra from the three dimensional model show better agreement with the observations than those from the two dimensional model

a three dimensional simulation of seismic waves in the santa clara valley california from a loma prieta aftershock abstract the finite difference method is used to propagate elastic waves through a 3 d model of the santa clara valley an alluvium filled basin that underlies the city of san jose california the model was based on depth to bedrock information from water wells in the area the simulation corresponded to a region 30 east west by 22 north south by 6 depth km and contained about 4 million grid points synthetic seismograms from the simulation are accurate at frequencies up to 1 hz motions from a magnitude 4 4 aftershock of the loma prieta earthquake were modeled snapshots of ground motion and synthetic seismograms from the simulation are presented the simulation illustrates s to surface wave conversion at the edges of the basin and the large amplitude and long duration of ground motion in the basin compared to the surrounding rock love waves produced at the edge of the basin are the largest arrivals in the transverse synthetics because of the slow group velocity of the love waves sites near the center of the basin have longer durations of significant motions than basin sites near the valley edges sites near the center of the basin also show larger peak amplitudes on the transverse component array analysis of the synthetic seismograms indicates that love waves tend to propagate parallel to the eastern and western edges of the valley rayleigh waves are produced along the southern margin of the basin from incident s waves large radial motions occur where a rayleigh wave impinges on the northeast margin of the valley some rayleigh waves travel westward across the basin after being scattered from the eastern edge of the valley synthetic seismograms from the simulation have similar peak amplitudes as seismograms recorded by the sunnyvale dense array for this aftershock although the duration of the tranverse component is not matched by the synthetic seismogram using this basin model the simulation indicates that the love waves observed on the actual seismograms were produced by conversion of incident s waves at the southern margin of the santa clara valley 2 d simulations show how the s to love wave conversion is affected by the angle of incidence of the s wave and the sharpness of the velocity transition between the alluvium and bedrock as more accurate basin models are developed 3 d simulations should become valuable for predicting ground motions in sedimentary basins for future large earthquakes

pantelleria rift crustal extension in a convergent intraplate setting the pantelleria rift system is a wide zone of post miocene northwest trending grabens and horsts beneath the sicily strait the central grabens host volcanics of predominantly alkalic composition which are exposed on the islands of pantelleria and linosa on the maltese islands along the northeastern shoulder of the rift an oligocene miocene carbonate succession exposed above sea level allows structural analysis and determination of shallow crustal stresses within the otherwise largely submarine rift system an older northeast trending set of normal faults is probably the expression of an oligocene miocene crustal extension event which produced continental rifts in western europe and led to passive margin formation in the western mediterranean younger northwest trending grabens of the pantelleria rift system cut the older faults almost at right angles and define a zone of lithospheric stretching between tunisia and sicily the northwest trending grabens which subsided dramatically since the beginning of pliocene time appear to be connected by east trending dextral and more rarely north trending sinistral transforms displacement along the transforms is probably in the order of a few kilometres in situ stress measurements carried out on the maltese islands show maximum horizontal compression sh parallel to the rift this suggests that in general 1 vertical and 2 horizontal and parallel to the rift are of about the same magnitude both exceed 3 sh which trends northeasterly slight intraplate convergence in a nw se direction seems to be more than balanced by extension in a ne sw direction neotectonics of the region possibly reflects an asthenospheric flow pattern which became established during the messinian salinity crisis the mechanism of recent intraplate deformation of the pelagian shelf has relevance for the understanding of more anciently subsided platforms of the apulian plate

source study of the 1906 san francisco earthquake all quality teleseismic recordings of the great 1906 san francisco earthquake archived in the 1908 carnegie report by the state earthquake investigation commission were scanned and digitized first order results were obtained by comparing complexity and amplitudes of teleseismic waveforms from the 1906 earthquake with well calibrated similarly located more recent earthquakes 1979 coyote lake 1984 morgan hill and 1989 loma prieta earthquakes at nearly co located modern stations peak amplitude ratios for calibration events indicated that a localized moment release of about 1 to 1 5 10 27 dyne cm was responsible for producing the peak the teleseismic body wave arrivals at longer periods 50 to 80 sec we found spectral amplitude ratios of the surface waves require a total moment release between 4 and 6 10 27 dyne cm for the 1906 earthquake comparable to previous geodetic and surface wave estimates thatcher 1975 we then made a more detailed source analysis using morgan hill s body waves as empirical green s functions in a finite fault subevent summation the morgan hill earthquake was deemed most appropriate for this purpose as its mechanism is that of the 1906 earthquake in the central portion of the rupture from forward and inverse empirical summations of morgan hill green s functions we obtained a good fit to the best quality teleseismic waveforms with a relatively simple source model having two regions of localized strong radiation separated spatially by about 110 km assuming the 1906 epicenter determined by bolt 1968 this corresponds with a large asperity on the order of the loma prieta earthquake in the golden gate san francisco region and one about three times larger located northwest along strike between point reyes and fort ross this model implies that much of the 1906 rupture zone may have occurred with relatively little 10 to 20 sec radiation consideration of the amplitude and frequency content of the 1906 teleseismic data allowed us to estimate the scale length of the largest asperity to be less than about 40 km with rough constraints on the largest asperity size and magnitude we produced a suite of estimated synthetic ground velocities assuming a slip distribution similar to that of the loma prieta earthquake but with three times as much slip for purposes of comparison with the recent abundant loma prieta strong motion data set we moved the largest 1906 asperity into loma prieta region peak ground velocity amplitudes are substantially greater than those recorded during the loma prieta earthquake and are comparable to those predicted by the attenuation relationship of joyner and boore 1988 for a magnitude m w 7 7 earthquake

variability and trends in runoff in the rivers of british columbia s coast and insular mountains this study examines the 1914 2015 runoff trends and variability for 136 rivers draining british columbia s bc s coast and insular mountains rivers are partitioned into eastward and westward flowing rivers based on flow direction from the coast mountains thus eastward and westward runoff trends and influence of topography on runoff are explored our findings indicate that rivers flowing eastward to the nechako and chilcotin plateaus contribute the lowest annual runoff compared to westward rivers where runoff is high low interannual runoff variability is evident in westward rivers and their alpine watersheds whereas eastward rivers exhibit high interannual runoff variability on vancouver island some of the rivers with the highest annual runoff exhibit high interannual variability a significant p 1 trends in annual and seasonal runoff from the middle to the late period across the study domain most positive detectable seasonal runoff trends in the middle period occur in spring in glacierized westward rivers located 1200 m whereas in the late period they all occur in fall and are regionally coherent around vancouver island and south coastal bc rivers draining eastward exhibit more positive trends over 1986 2015 compared to westward rivers this study provides crucial information on the hydrology of mountain watersheds across bc s coast in response to pacific decadal oscillation phase changes the elevational amplification of regional climate change and their influences on precipitation and glacier retreat

the slip history of the 1994 northridge california earthquake determined from strong motion teleseismic gps and leveling data we present a rupture model of the northridge earthquake determined from the joint inversion of near source strong ground motion recordings p and sh teleseismic body waves global positioning system gps displacement vectors and permanent uplift measured along leveling lines the fault is defined to strike 122 and dip 40 to the south southwest the average rake vector is determined to be 101 and average slip is 1 3 m the peak slip reaches about 3 m our estimate of the seismic moment is 1 3 0 2 10 26 dyne cm potency of 0 4 km3 the rupture area is small relative to the overall aftershock dimensions and is approximately 15 km along strike nearly 20 km in the dip direction and there is no indication of slip shallower than about 5 to 6 km the up dip strong motion velocity waveforms are dominated by large s wave pulses attributed to source directivity and are comprised of at least 2 to 3 distinct arrivals a few seconds apart stations at southern azimuths indicate two main s wave arrivals separated longer in time about 4 to 5 sec these observations are best modeled with a complex distribution of subevents the initial s wave arrival comes from an asperity that begins at the hypocenter and extends up dip and to the north where a second larger subevent is centered about 12 km away the secondary s arrivals at southern azimuths are best fit with additional energy radiation from another high slip region at a depth of 19 km 8 km west of the hypocenter the resolving power of the individual data sets is examined by predicting the geodetic gps and leveling displacements with the dislocation model determined from the waveform data and vice versa and also by analyzing how well the teleseismic solution predicts the recorded strong motions the general features of the geodetic displacements are not well predicted from the model determined independently from the strong motion data likewise the slip model determined from geodetic data does not adequately reproduce the strong motion characteristics whereas a particularly smooth slip pattern is sufficient to satisfy the geodetic data the strong motion and teleseismic data require a more heterogeneous slip distribution in order to reproduce the velocity amplitudes and frequency content although the teleseismic model can adequately reproduce the overall amplitude and frequency content of the strong motion velocity recordings it does a poor job of predicting the geodetic data consequently a robust representation of the slip history and heterogeneity requires a combined analysis of these data sets

effects of sedimentary layers on surface wave propagation abstract earthquake ground motions in the period range from 3 to 10 sec observed in the kanto plain japan during the western nagano earthquake of 1984 were predominantly trapped within sedimentary layers the dispersion observed in the transverse component on sedimentary rock is similar to the dispersion calculated for the fundamental love wave in a 1 d velocity model derived from the results of the seismic surveys forward modeling with a 2 d finite difference method shows good agreement with observed seismograms when realistic 2 d underground structures derived from seismic surveys are used

geometry and relative motion of the philippine sea plate and pacific plate beneath the kanto tokai district japan the recent acquisition of high density and improved seismic data by the kanto tokai k t observational network of the national research institute of earth science and disaster prevention requires the revision of conventional plate configuration models for the k t district we propose a new interpretation of the configuration and relative motion of the philippine sea phs plate pacific pac plate and eurasian eur plate on the basis of the distribution of hypocenters velocity structure and focal mechanisms in the k t district the new model for the configuration of the phs and pac slabs clearly delineates the phs slab subducting northwestward beneath the k t district from the sagami and suruga troughs and the pac slab subducting westward beneath the phs slab from the japan trench the thickness of the descending phs slab is estimated to be 30 5 km the proposed configuration of the phs slab is significantly different from those obtained by other researchers including our own previous study the new model is fully consistent with global plate motion data the new model leads to an interpretation of the tectonic processes taking place beneath the k t district for the sagami trough wing of the phs slab the northeastern portion of the slab is dipping northwestward in direct contact with the upper surface of the pac slab the southwestern portion carrying the izu peninsula has been bent upward because of its buoyancy producing the observed contorted shape for the suruga trough wing the dip direction of the phs slab gradually changes from northwestward at the eastern portion to northward at the western portion the new model also indicates the presence of offset within the phs slab between the sagami and suruga trough wings this area is characterized by a low level of seismic activity the absence of a high velocity structure and the presence of quaternary volcanoes it seems reasonable to speculate that the distribution of quaternary volcanic edifice construction is controlled by the location of the offset within the phs slab in view of this new model the tectonic processes of large earthquakes which occurred recently in the studied area are also reexamined

the 1923 kanto earthquake reevaluated using a newly augmented geodetic data set 1 this study revisits the mechanism of the 1923 ms 7 9 kanto earthquake in japan we derive a new source model and use it to assess quantitative and qualitative aspects of the accommodation of plate motion in the kanto region we use a new geodetic data set that consists of displacements from leveling and angle changes from triangulation measurements obtained in surveys between 1883 and 1927 two unique aspects of our analysis are the inclusion of a large number of second order triangulation measurements and the application of a correction to remove interseismic deformation the geometry of the fault planes is adopted from a recent seismic reflection study of the kanto region we evaluate the minimum complexity necessary in the model to fit the data optimally our final uniform slip elastic dislocation model consists of two adjacent 20 dipping low angle planes accommodating reverse dextral slip of 6 0 m on the larger eastern plane and 9 5 m on the smaller western plane with azimuths of 163 and 121 respectively the earthquake was located in the sagami trough where the philippine sea plate subducts under honshu compared to the highly oblique angle of plate convergence the coseismic slip on the large fault plane has a more orthogonal orientation to the strike of the plate boundary suggesting that slip partitioning plays a role in accommodation of plate motion what other structure is involved in the partitioning is unclear uplift records of marine coastal terraces in sagami bay document 7500 years of earthquake activity and predict average recurrence intervals of 400 years for events with vertical displacement profiles similar to those of the 1923 earthquake this means that the average slip deficit per recurrence interval is 50 of the relative plate convergence these findings of plate motion partitioning and slip deficit lead us to suggest that instead of a simple recurrence model with characteristic earthquakes additional mechanisms are necessary to describe the accommodation of deformation in the kanto region so far obvious candidates for these alternative mechanisms have not been discovered

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

estimates of regional and local strong motions during the great 1923 kanto japan earthquake ms 8 2 part 1 source estimation of a calibration event and modeling of wave propagation paths this article is the first of a pair of articles that estimate regional and local strong motions from the 1923 kanto japan earthquake this ms 8 2 earthquake caused the most devastating damage in the metropolitan area in tokyo history in this article we first calibrate wave propagation path effects with a moderate sized modern event this event the odawara earthquake of 5 august 1990 m 5 1 is the first earthquake larger than m 5 in the last 60 years near the hypocenter of the 1923 kanto earthquake we estimate the source parameters based on a grid search technique using body waveform data bandpass filtered from 1 to 10 sec at four local stations because accurate source parameters are critical for calibrating the propagation effects we find that the odawara earthquake had a depth of 15 3 km a dip of 35 a rake of 40 a strike of 215 a seismic moment of 3 3 10 23 dyne cm a source duration of 0 65 sec and a stress drop of 170 bars next we investigate the effects of the propagation paths to the local and regional stations where seismograms of the 1923 kanto earthquake were recorded by comparing recorded waveforms with synthetic seismograms built with the calibration event path specific flat layered velocity models are estimated along travel paths from the event to stations hongo epicentral distance r 82 km in tokyo gifu r 213 km and sendai r 374 km using forward modeling in constructing the velocity model for the gifu station we use sts 1 broadband seismograms recorded at the nearby inuyama station consequently at periods greater than 3 sec the velocity models for stations hongo and gifu can successfully reproduce both body waves and direct surface waves and the velocity model for sendai station can explain the predominant direct surface waves in the companion article sato et al 1998 these velocity models are used to examine the adequecy of the variable slip rupture models of the 1923 kanto earthquake wald and somerville 1995 takeo and kanamori 1992 to explain recorded seismograms and also to simulate strong motions from that event

variable slip rupture model of the great 1923 kanto japan earthquake geodetic and body waveform analysis abstract the available geodetic and teleseismic data sets for the 1923 kanto earthquake m s 8 1 have been combined into a joint inversion for both temporal and spatial slip variations we assumed an initial faulting model to be consistent with the geometry determined by kanamori 1971 on the basis of first motion data aftershock area and the amplitude of surface waves at teleseismic distances and also to enclose the slipped area estimated by matsu9ura et al 1980 from the geodetic data employed here we then inverted for a heterogeneous distribution of slip of the fault plane the leveling routes and triangulation stations used consisting of 225 bench marks and 31 triangulation points are from matsu9ura et al 1980 we chose to first determine the overall static slip distribution by inverting the geodetic data alone we then proceeded to gradually increase the importance of the teleseismic data always requiring a good fit to the geodetic leveling and horizontal displacements in this way we could provide a constraint on the overall static slip characteristics from the geodetic data and provide stability for the teleseismic inversion yet determine the degree of slip heterogeneity and time history most suitable for matching the waveform data and for simulating strong ground motions our analysis yields a seismic moment of 7 to 8 10 27 dyne cm m w 7 8 to 7 9 with a maximum slip of approximately 8 m the most concentrated slip is in the shallow central and western portion of the fault the location of the concentrated slip on the fault plane has important consequences for the amplitude duration and frequency content of the resulting ground motions as documented by takeo and kanamori 1993

broadband ground motion reconstruction for the kanto basin during the 1923 kanto earthquake ground motions of the 1923 kanto earthquake inside the kanto basin are numerically simulated in a wide frequency range 0 10 hz based on new knowledge of the earthquake s source processes the sedimentary structure of the basin and techniques for generating broadband source models of great earthquakes the kanto earthquake remains one of the most important exemplars for ground motion prediction in japan due to its size faulting geometry and location beneath the densely populated kanto sedimentary basin we reconstruct a broadband source model of the 1923 kanto earthquake from inversion results by introducing small scale heterogeneities the corresponding ground motions are simulated using a hybrid technique comprising the following four calculations 1 low frequency ground motion of the engineering basement modeled using a finite difference method 2 high frequency ground motion of the engineering basement modeled using a stochastic green s function method 3 total ground motion of the engineering basement i e 1 2 and 4 ground motion at the surface in response to the total basement ground motion we employ a recently developed three dimensional 3d velocity structure model of the kanto basin that incorporates prospecting data microtremor observations and measurements derived from strong ground motion records our calculations reveal peak ground velocities pgv exceeding 50 cm s in the area above the fault plane to the south where the fault plane is shallowest pgv reaches 150 200 cm s at the engineering basement and 200 250 cm s at the surface intensity 7 the maximum value in the japan meteorological agency s intensity scale is calculated to have occurred widely in sagami bay which corresponds well with observed house collapse rates due to the 1923 event the modeling reveals a pronounced forward directivity effect for the area lying above the southern shallow part of the fault plane the high pgv and intensity seen above the southeastern corner of the fault plane and further east are largely due to this effect waveforms above the fault plane contain both short and long period components but the short period components are not observed further afield away from the fault long period waves 2 s dominate the ground motion and in areas where the base of the third layer is relatively deep the predominant period is 5 s levels of long period ground motion in the southern part of the study area around sagami bay and the southern parts of boso peninsula and tokyo bay exceed that recorded at tomakomai during the 2003 tokachi oki earthquake when large oil storage tanks collapsed in response to sloshing generated by strong long period motions