oblique convergence and deformation along the kuril and japan trenches the hypothesis that present day deformation within the southern kuril forearc is driven by oblique subduction of the pacific plate is tested using 397 horizontal slip directions derived from shallow thrust earthquakes from the kuril and japan trenches for the period 1963 1991 a simple two plate model fits the 397 slip vectors significantly worse than a model that permits strike slip motion of the southern kuril forearc relative to the overlying plate weighted mean slip directions along the southern kuril trench are systematically rotated toward the direction orthogonal to the trench which implies that the net convergence is partitioned into less oblique subduction and trench parallel displacement of the southern kuril forearc the angular discrepancy between the observed slip direction and the direction predicted by the nuvel 1 pacific north america euler vector implies that the southern kuril forearc translates 6 11 mm yr 1 to the southwest relative to the overlying north american plate these results are consistent with geologically geodetically and seismologically observed convergence at the leading edge of the forearc sliver in southern hokkaido and with previously inferred extension at the trailing edge of the sliver which is located at the bussol strait at 46 n the percentage of the oblique component of the rigid plate convergence vector that is transferred into forearc strike slip motion is only 30 which may be evidence that the hokkaido honshu bend in the trench hinders southwest forearc motion or that the greater strength of oceanic forearcs impedes motion along forearc strike slip faults

a 780 year annually resolved record of indian ocean monsoon precipitation from a speleothem from south oman 1 meteorological records of monsoon rainfall in the indian ocean are generally less than 100 years long the relative brevity of these records makes it difficult to investigate monsoon variation on decadal and centennial timescales to determine what factors influence the intensity of rainfall on these timescales or to place possible changes in the twentieth century into a broader historical context development of a geologic proxy for rainfall that records annual variation in the monsoon over much longer time periods than are covered by instrumental records would be a significant step forward we have developed an annually resolved record of monsoon rainfall variation for the past 780 years based on annual layer thickness and stable isotope analyses of a laminated stalagmite from southern arabia our results show that monsoon variation over the past century is not outside of the range of the past 800 years decreasing monsoon rainfall over the past century is related to increasing sea surface temperature in the indian ocean spectral analyses of the record are dominated by cycles that are similar to those observed in records of solar activity on centurial timescales decadal to interannual cycles in the record appear to originate in the tropical pacific ocean index terms 3344 meteorology and atmospheric dynamics paleoclimatology 3354 meteorology and atmospheric dynamics precipitation 1854 1620 global change climate dynamics 3309 1699 global change general or miscellaneous keywords monsoon paleoclimate rainfall indian ocean speleothem oxygen isotopes

tropical sea surface temperatures for the past four centuries reconstructed from coral archives most annually resolved climate reconstructions of the common era are based on terrestrial data making it a challenge to independently assess how recent climate changes have affected the oceans here as part of the past global changes ocean2k project we present four regionally calibrated and validated reconstructions of sea surface temperatures in the tropics based on 57 published and publicly archived marine paleoclimate data sets derived exclusively from tropical coral archives validation exercises suggest that our reconstructions are interpretable for much of the past 400 years depending on the availability of paleoclimate data within and the reconstruction validation statistics for each target region analysis of the trends in the data suggests that the indian western pacific and western atlantic ocean regions were cooling until modern warming began around the 1830s the early 1800s were an exceptionally cool period in the indo pacific region likely due to multiple large tropical volcanic eruptions occurring in the early nineteenth century decadal scale variability is a quasi persistent feature of all basins twentieth century warming associated with greenhouse gas emissions is apparent in the indian west pacific and western atlantic oceans but we find no evidence that either natural or anthropogenic forcings have altered el nino southern oscillation related variance in tropical sea surface temperatures our marine based regional paleoclimate reconstructions serve as benchmarks against which terrestrial reconstructions as well as climate model simulations can be compared and as a basis for studying the processes by which the tropical oceans mediate climate variability and change

interplate quasi static slip off sanriku ne japan estimated from repeating earthquakes 1 space time distribution of quasi static slip on the plate boundary off sanriku northeastern ne japan was estimated by using small repeating earthquakes we found 2509 repeating earthquakes occurring on the plate boundary for the last 17 years based on the interpretation that these events are caused by repeating slips of small asperities surrounded by stable sliding area we regarded these repeating events as creepmeters embedded on the plate boundary the results show that deeper portions of the plate boundary are sliding almost stably and earthquakes with magnitudes more than 6 are accompanied by quasi static slips in the surrounding areas

seasonal and centennial cycles of carbonate mineralisation during the past 2500 years from varved sediment in lake shira south siberia shira lake is a good representative object for detail weather climate modeling due to its local hydroclimatic information and annually laminated bottom sediments carbonate biochemical mineralization in shira lake shows not only seasonal but also centennial pulses over each 450 500 years an age depth model has been built by layer counting combined with 137cs and 14c isotopic dates thermodynamic estimation of the rock water multisystem in conformity with local conditions and source matter provides grounds for interpretation of measured geochemical parameters in sediments including environmental indicators such as temperature salinity and ph scanning x ray fluorescence for sub millimeter microstratigraphic study of varves connects geochemical oscillations of microelement content rb ti ca sr br xrd with seasonality as well as revealing centennial pulses of environmental change quantitative environmental reconstruction using multiple regression for precipitation calibrated by hydrometeorological time series year by year was carried out for the lake over the last 2500 years

evidence for decreasing south asian summer monsoon in the past 160 years from varved sediment in lake xinluhai tibetan plateau 1 we report glacial varves in the sediment of lake xinluhai tibetan plateau independent data of 137cs and 210pb indicate that these are annually deposited varves varves appear as rhythmic units of light colored silt layer capped by a dark clay layer under microscope varve thickness in lake xinluhai is sensitive to precipitation because sediment accumulation is strongly affected by monsoon rainfall in the area a general decreasing trend can be observed in the varve thickness over the past 160 years spectral analyses of the varve record are dominated by cycles which are similar to enso periodicities it implies that the decreasing trend of the south asia monsoon may be linking with enso spatially the decreasing trend can be observed across different proxy records in the south of the tibetan plateau although arguments still remain for the dynamic mechanisms and spatial rainfall difference the south asian summer monsoon could be weakened due to rising temperatures

propagation of slow slip leading up to the 2011 mw 9 0 tohoku oki earthquake many large earthquakes are preceded by one or more foreshocks but it is unclear how these foreshocks relate to the nucleation process of the mainshock on the basis of an earthquake catalog created using a waveform correlation technique we identified two distinct sequences of foreshocks migrating at rates of 2 to 10 kilometers per day along the trench axis toward the epicenter of the 2011 moment magnitude mw 9 0 tohoku oki earthquake in japan the time history of quasi static slip along the plate interface based on small repeating earthquakes that were part of the migrating seismicity suggests that two sequences involved slow slip transients propagating toward the initial rupture point the second sequence which involved large slip rates may have caused substantial stress loading prompting the unstable dynamic rupture of the mainshock

interplate coupling beneath ne japan inferred from three dimensional displacement field 1 the northeastern japan arc is located in a typical subduction zone and is a seismically active region where large interplate earthquakes have occurred repeatedly the nationwide gps network has made it possible to investigate the crustal deformation in unprecedented detail however vertical displacements are less accurate than the horizontal ones and have not been used to constrain interplate coupling models in this study gps carrier phase data are analyzed in order to estimate three components of site displacements the result indicates uplift along the japan sea coast and subsidence along the pacific ocean coast using the vertical site velocities together with the horizontal ones as the data for a geodetic inversion method a new model of interplate coupling is constructed to explain both the horizontal and vertical velocities for the interseismic period from 1997 to 2001 the model demonstrates strong coupling in the area off miyagi and in the area off aomori through the area off tokachi including the areas of asperities the downdip limit of the locked fault zone on the plate boundary has been estimated seismologically to be at a depth of 50 60 km in northeastern japan and the distribution of slip deficits derived in this study indicates that the transition zone extends down to a depth of about 100 km

newly imaged shape of the deep seismic zone within the subducting pacific plate beneath the hokkaido corner japan kurile arc arc junction 1 the geometry of the deep seismic zone associated with the subducting pacific plate beneath the north american plate in the hokkaido corner japan kurile arc arc junction has been investigated based on the hypocenters accurately relocated by a dense local seismographic network with three dimensional p and s wave velocity structures the model suggests that the lateral changes in the dip of the subduction zone are more rapid than previously believed we found that the deep seismic zone in the pacific plate dips at 20 to 30 on the side of the japan arc the dip angle increased in a narrow region around 143 144 e by 10 to 20 and the dip was 40 to 50 on the side of the kurile arc in the transitional zone around 143 144 e an unusual distribution of microearthquakes has been discovered within the pacific plate which was located on a near vertical plane with an area of 50 100 km2 with strike that was perpendicular to the kurile trench axis this feature was named the tokachi oki slab cracking zone we suggest that this is a slab cracking zone torn by the extensional stress due to the rapid lateral changes in the dip of the subduction zone the slab cracking zone may possibly grow into the large disruption or tear of the slab in the future

a possible model for large preseismic slip on a deeper extension of a seismic rupture plane abstract i develop a numerical model for preseismic slip and episodic aseismic slip events slow earthquakes on a deeper extension of a seismogenic plate interface using a rate and state dependent friction law the deep preseismic slip and episodic slow slip were indicated by models based on geodetic observations though they cannot be explained by common rate and state dependent laws i investigate whether this incongruity can be removed by including use of additional known constraints on the frictional property the steady state friction on a model fault is taken to be velocity weakening at low velocities and velocity strengthening at high velocities the transition velocity from velocity weakening friction to velocity strengthening is assumed to be the seismic slip velocity at shallow seismic depths and decreases with depth at deeper parts simulation results for a 2d model of interplate earthquakes at a subduction zone are as follows 1 during an interseismic period between successive large earthquakes at shallow seismogenic depths some episodic aseismic slip events with durations of a few years occur on the plate interface just below the seismogenic depths 2 preseismic slip occurs at nearly the same location where the episodic aseismic slip events occur these may explain some characteristics of observed preseismic slip of the 1944 tonankai earthquake m 7 9 along the nankai trough central japan and episodic aseismic slip events in the same area

pre and post seismic slow slip on the plate boundary off sanriku ne japan associated with three interplate earthquakes as estimated from small repeating earthquake data abstract the spatio temporal variation of quasi static slow slip on the plate boundary before and after three major earthquakes mj 7 1 in 1989 mj 6 9 in 1992 and mj 7 6 in 1994 off sanriku northeastern japan is estimated using small repeating earthquake data the small repeating earthquake sequence employed is considered to correspond to repeated rupture of a small isolated asperity surrounded by a quasi static slipping area and the activity of the source reflects the quasi static slip rate small repeating earthquakes accompanying moderate sized events appear to have been activated prior to the major events under investigation with activity starting 6 days 2 days and 8 months before the occurrence of the 1989 1992 and 1994 events these results indicate that the quasi static slip near the hypocenters of these major earthquakes was accelerated prior to the main shocks causing stress concentration at the asperities responsible for the main shocks this idea is supported by the fact that both the epicenters locations of initial breaks and areas where quasi static slip was accelerated were located on the same side of the main shock asperities migration of quasi static slip acceleration in the off sanriku region was also identified apparent in the aftershock activity of the 1994 event and the earthquake swarms including the 1989 mj 7 1 and 1992 mj 6 9 events the present results reveal that quasi static slip may have played a crucial role in the occurrence of these large earthquakes as well as contributing to aftershock and swarm activity on the plate boundary

water transportation from the subducting slab into the mantle transition zone using a recently developed petrogenetic grid for morb h2o we propose a new model for the transportation of water from the subducting slab into the mantle transition zone depending on the geothermal gradient two contrasting water transportation mechanisms operate at depth in a subduction zone if the geothermal gradient is low lawsonite carries h2o into mantle depths of 300 km with further subduction down to the mantle transition depth approximately 400 km lawsonite is no longer stable and thereafter h2o is once migrated upward to the mantle wedge then again carried down to the transition zone due to the induced convection at this depth hydrous phase olivine is stable and plays a role as a huge water reservoir in contrast if the geothermal gradient is high the subducted slab may melt at 700 900 c at depths shallower than 80 km to form felsic melt into which water is dissolved in this case h2o cannot be transported into the mantle below 80 km between these two endmember mechanisms two intermediate types are present in the high pressure intermediate type the hydrous phase a plays an important role to carry water into the mantle transition zone water liberated by the lawsonite consuming continuous reaction moves upward to form hydrous phase a in the hanging wall which transports water into deeper mantle this is due to a unique character of the reaction because phase a can become stable through the hydration reaction of olivine in the case of low pressure intermediate type the presence of a dry mantle wedge below 100 km acts as a barrier to prevent h2o from entering into deeper mantle 2006 published by elsevier b v on behalf of international association for gondwana research

partitioning between seismogenic and aseismic slip as highlighted from slow slip events in hyuga nada japan 1 we present a numerical method to analyze the gps data and examine slow fault slips in hyuga nada a region in western japan where the philippine sea plate subducts under the eurasian plate and earthquakes of magnitude 7 class are frequent we found that after two large earthquakes in 1996 a slow fault slip expanded from the source area to the north and then triggered another slow event with a characteristic source duration of about one year the aseismic slip has increasingly highlighted a particular site where little slow fault slip takes place but where the subducting plate drags the overriding plate it is noteworthy that the highlighted area is just the site of a past large earthquake we propose that this area is a possible site for a future large earthquake

interaction between the enso and the asian monsoon in a coral record of tropical climate the oxygen isotopic composition of a banded coral from the western equatorial indian ocean provides a 150 year long history of the relation between the el nino southern oscillation enso phenomenon and the asian monsoon interannual cycles in the coral time series were found to correlate with pacific coral and instrumental climate records suggesting a consistent linkage across ocean basins despite the changing frequency and amplitude of the enso however decadal variability that is characteristic of the monsoon system also dominates the coral record which implies important interactions between tropical and midlatitude climate variability one prominent manifestation of this interaction is the strong amplitude modulation of the quasi biennial cycle

application of palynological data to the chronology of the palaeogene lava fields of the british province implications for magmatic stratigraphy new high precision ages determined from palynomorph assemblages within intercalated sedimentary deposits are presented for the palaeogene lava fields skye mull and antrim of the british province these data reveal very rapid averaged eruption rates 1 m 200 years and the non synchronous formation of the lava fields eruption of the volumetrically dominant transitional to mildly alkaline lavas of the skye 58 25 58 0 ma and mull post 55 ma lava fields the skye main lava series and the plateau group of mull respectively is separated by the eruption of the morb like preshal more flows of olivine tholeiite found at the top of the preserved sequence on skye and at the base of the mull lava field the lower formation of the antrim lava field correlates with the skye lava field and the upper formation correlates with the preshal more flows the new ages indicate that the eruption of the preshal more flows was synchronous with the main ocean floor spreading event which occurred 500 km to the nw at c 55 ma during chron 24r a combined thinspot and channelized plume model may best explain the temporal and spatial distributions of the lava fields and associated subvolcanic complexes of the british province

influence of static stress changes on earthquake locations in southern california earthquakes induce changes in static stress on neighbouring faults that may delay hasten or even trigger subsequent earthquakes1 10 the length of time over which such effects persist has a bearing on the potential contribution of stress analyses to earthquake hazard assessment but is presently unknown here we use an elastic half space model11 to estimate the static stress changes generated by damaging magnitude m 5 earthquakes in southern california over the past 26 years and to investigate the influence of these changes on subsequent earthquake activity we find that in the 1 5 year period following a m 5 earthquake any subsequent nearby m 5 earthquake almost always ruptures a fault that is loaded towards failure by the first earthquake after this period damaging earthquakes are equally likely to rupture loaded and relaxed faults our results suggest that there is a short period of time following a damaging earthquake in southern california in which simple coulomb failure stress models could be used to identify regions of increased seismic hazard

space time model for repeating earthquakes and analysis of recurrence intervals on the san andreas fault near parkfield california we propose a stochastic model for characteristically repeating earthquake sequences to estimate the spatiotemporal change in static stress loading rate these earthquakes recur by a cyclic mechanism where stress at a hypocenter is accumulated by tectonic forces until an earthquake occurs that releases the accumulated stress to a basal level renewal processes are frequently used to describe this repeating earthquake mechanism variations in the rate of tectonic loading due to large earthquakes and aseismic slip transients however introduce nonstationary effects into the repeating mechanism that result in nonstationary trends in interevent times particularly for smaller magnitude repeating events which have shorter interevent times these trends are also similar among repeating earthquake sites having similar hypocenters therefore we incorporate space time structure represented by cubic b spline functions into the renewal model and estimate their coefficient parameters by maximizing the integrated likelihood in a bayesian framework we apply our model to 31 repeating earthquake sequences including 824 events on the parkfield segment of the san andreas fault and estimate the spatiotemporal transition of the loading rate on this segment the result gives us details of the change in tectonic loading caused by an aseismic slip transient in 1993 the 2004 parkfield m6 earthquake and other nearby or remote seismic activities the degree of periodicity of repeating event recurrence intervals also shows spatial trends that are preserved in time even after the 2004 parkfield earthquake when time scales are normalized with respect to the estimated loading rate

offshore geodetic data conducive to the estimation of the afterslip distribution following the 2003 tokachi oki earthquake a cable based seafloor observatory located offshore of hokkaido japan provides the world s first direct observation of offshore post seismic displacement after removing thermal noise this data is used to constrain the distribution of offshore afterslip from a great interplate earthquake mw 8 0 that occurred during 2003 along the southern kuril trench a checkerboard resolution test showed a great contribution of the offshore data to improving the spatial resolution on the plate interface slip near the trench the 1 yr afterslip is distributed in a u shaped pattern encircling its co seismic slip area this result indicates that the stick slip frictional properties of the plate interface are distributed in a patch like pattern as opposed to a banding pattern as previously assumed in young subduction zones

the 2003 m8 0 tokachi oki earthquake how much has the great event paid back slip debts 1 a great earthquake with m8 0 the 2003 tokachi oki earthquake occurred on september 26 2003 on the plate boundary south of hokkaido at about the same epicenter as that of the 1952 m8 2 tokachi oki earthquake we estimated the coseismic slip distribution using gps data to obtain consistent results with that inferred from waveform inversions a maximum slip larger than 5m exists around 30km nne from the epicenter though the slip deficit estimated there 80 mm yr by our recent study is based on a rather short period of observation 5 years to discuss the whole seismic cycle the maximum coseismic slip roughly accounts for the slip deficit accumulated in the past 51 years assuming that the back slip rate has been nearly constant since 1952 besides the area of the largest slip however an accumulated slip deficit still remains and should be released by seismic or aseismic slip which is now actually observed in part as postseismic slip

space time heterogeneity in aftershock activity summary for a number of aftershock sequences in and around japan we examine detrended space time coordinates after fitting the omori utsu occurrence rate to each aftershock sequence the case studies in conjunction with the fault locations and orientations of the main shocks and focal large aftershocks indicate that the region of deficit and surplus in the aftershock activity well corresponds to the decreased and increased region of coulomb failure stress respectively caused by various aseismic slips we illustrate the relation between the transient stress changes and the anomalous aftershock activity in a local subregion by six scenarios derived from the rate and state dependent friction law of dietrich

modeling the rupture process of the 2003 september 25 tokachi oki hokkaido earthquake using 1 hz gps data received 10 september 2004 accepted 3 october 2004 published 3 november 2004 1 high rategpshasthepotentialtorecoverbothdynamic and static displacements accurately we analyze 1 hz gps data recorded during the 2003 tokachi oki earthquake the 1 hz gps displacement waveforms show good agreement with integrated accelerometer records except for low frequency noise that are inherently present in integrated seismic records the gps waveforms were inverted to model the spatio temporal evolution of the fault slip during the rupture the slip is found to propagate downdip in the subduction zone with largest moment release 50 km northwest of the hypocenter the region of largest slip agrees in general with traditional seismic studies indicating that 1 hz gps can be used for finite fault studies the 1 hz gps slip model shows clearer contrast with afterslip distributions than those inferred from strong motion data possibly because 1 hz gps is more sensitive to cumulative slip distribution index terms 1294 geodesy and gravity instruments and techniques 7209 seismology earthquake dynamics and mechanics 7212 seismology earthquake ground motions and engineering citation miyazaki s k m larson k choi k hikima k koketsu p bodin j haase g emore and a yamagiwa 2004 modeling the rupture process of the 2003 september 25 tokachi oki hokkaido earthquake using 1 hz gps data geophys res lett 31 l21603 doi 10 1029 2004gl021457

quasi static slip on the plate boundary associated with the 2003 m8 0 tokachi oki and 2004 m7 1 off kushiro earthquakes japan abstract we analyzed small repeating earthquakes recorded over a 13 year period and gps data recorded over an 8 month period to estimate interplate quasi static slip associated with the 2003 tokachi oki earthquake m8 0 and the 2004 off kushiro earthquake m7 1 the repeating earthquake analysis revealed that the slip rate near the source region of the tokachi oki earthquake was relatively low

may september precipitation in the bhutan himalaya since 1743 as reconstructed from tree ring cellulose δ18o 1 we developed a 50 year tree ring 18o chronology for each of three tree species juniperus indica larix griffithii and picea spinulosa using a total of 12 trees four trees per species from the bhutan himalaya despite originating from different species sampled at two different altitudes the 18o chronologies are highly correlated with one another r 0 76 0 89 response analyses reveal that tree ring 18o values are controlled mainly by summer precipitation irrespective of species based on these results a robust 269 year 18o chronology was established to reconstruct the amount of may september precipitation based on data from four larch trees our tree ring 18o data show significant correlations with those from other regions of the himalaya and the tibetan plateau indicating that common signals related to monsoon activity are recorded in the data however at centennial timescales our data from bhutan show normal conditions during the 20th century whereas records from sites in western nepal and the southern eastern tibetan plateau show weakening trends in monsoon intensity during the last 100 200 years the weakening trends may be the result of a reduction in the meridional sea surface temperature gradient in the indian ocean during this time at continental scales the tree ring records show that areas more from ocean basins are particularly sensitive to reduced monsoon circulation correlation analyses suggest that the el nino southern oscillation enso plays an important role in modulating summer precipitation however the teleconnected relationship disappears during the period 1951 1970 coinciding with a negative phase of the pacific decadal oscillation pdo implying interdecadal modulation of the pdo on the influence of the enso on precipitation in bhutan

existence of interplane earthquakes and neutral stress boundary between the upper and lower planes of the double seismic zone beneath tohoku and hokkaido northeastern japan abstract using data from the recently constructed nationwide dense seismic network we determined the hypocenters and focal mechanisms of many intermediate depth intraslab earthquakes within the pacific slab beneath northeastern japan the results show that in addition to the upper and lower planes of the double seismic zone a considerable number of intraslab earthquakes also occur between the two planes this interplane earthquake activity is not homogeneously distributed in space being high beneath eastern hokkaido and the fore arc regions of southeast and central tohoku the focal mechanisms of the interplane earthquakes tend to be of the down dip compressional type dc in tohoku and the hokkaido corner but down dip tensional type de in eastern hokkaido upper plane earthquakes are characterized by dc type stress while lower plane earthquakes are de type in both tohoku and eastern hokkaido the existence of interplane earthquakes enables estimation of the position of the neutral plane between the upper plane dc stress and the lower plane de stress we did so by applying stress tensor inversions to focal mechanism data obtained in the present study and japan meteorological agency jma data the results show that the neutral plane is located about 22 km beneath the upper plate interface beneath tohoku but only about 10 km beneath the upper surface beneath eastern hokkaido this difference in the location of the neutral plane may be due to the difference in buoyancy force exerted by the less dense metastable olivine wedge that is a result of the oblique plate subduction beneath hokkaido comparison of large intraslab earthquakes beneath the two regions shows that their aftershock areas are limited by the neutral plane suggesting that large earthquake ruptures are confined to either the dc or de stress field and do not go beyond the neutral plane

seismic velocity discontinuities in the crust and uppermost mantle beneath the kanto district central japan identified from receiver function imaging and repeating earthquake activity abstract we constructed vertical cross sections of depth converted receiver function images to estimate the seismic velocity structure of the crust and uppermost mantle beneath the kanto district central japan repeating earthquake data for the plate boundary were also used to estimate geometries of the subducting philippine sea plate and the subducting pacific plate as a result we present images of some major seismic discontinuities the upper boundary of the pacific plate dips to the northwest in northern kanto and to the west southwest in southern kanto with some undulations on the other hand the upper boundary of the philippine sea plate as a whole dips to the northwest however it is concave to the northeast in the southern boso peninsula we suggest that the low velocity mantle wedge may be indicated on the top of both subducting plates plate thickness gradually decreases to the northeast the northeastern end of the philippine sea plate is interpreted to be at depths of 45 90 km the moho discontinuity in the overriding plate is deeper than 25 km in the northern kanto it contacts the subducting philippine sea plate in the southwestern part near 35 8 n

space time distribution of afterslip following the 2003 tokachi oki earthquake implications for variations in fault zone frictional properties 1 gps time series following the september 25 2003 ut tokachi oki earthquake m w 8 0 reveal significant deformation we use the network inversion filter to invert for the spatial and temporal evolution of afterslip in the 30 days following the earthquake afterslip is concentrated adjacent to the coseismic rupture zone between the 2003 rupture and the inferred source regions of the 1968 tokachi oki and the 1973 nemuro oki earthquakes the inversion shows a rapid decay of slip rate in the 2003 rupture zone with slower deceleration in the surrounding regions the stress velocity paths for the afterslip regions approximately follow d d in v 0 6 mpa suggestive of steady state velocity strengthening friction the complementary spatial pattern of coseismic rupture and afterslip may indicate along strike spatial variations of frictional properties although other interpretations can not be ruled out

repeating aftershocks of the great 2004 sumatra and 2005 nias earthquakes abstract we investigate repeating aftershocks associated with the great 2004 sumatra andaman mw 9 2 and 2005 nias simeulue mw 8 6 earthquakes by cross correlating waveforms recorded by the regional seismographic station psi and teleseismic stations we identify 10 and 18 correlated aftershock sequences associated with the great 2004 sumatra and 2005 nias earthquakes respectively the majority of the correlated aftershock sequences are located near the down dip end of a large afterslip patch we determine the precise relative locations of event pairs among these sequences and estimate the source rupture areas the correlated event pairs identified are appropriately referred to as repeating aftershocks in that the source rupture areas are comparable and significantly overlap within a sequence we use the repeating aftershocks to estimate afterslip based on the slip seismic moment scaling relationship and to infer the temporal decay rate of the recurrence interval the estimated afterslip resembles that measured from the near field geodetic data to the first order the decay rate of repeating aftershocks as a function of lapse time t follows a power law decay 1 t p with the exponent p in the range 0 8 1 1 both types of observations indicate that repeating aftershocks are governed by post seismic afterslip

recurrence intervals of characteristic m4 8 0 1 earthquakes off kamaishi ne japan comparison with creep rate estimated from small repeating earthquake data abstract we examined the cause of the fluctuation in recurrence intervals of an m4 8 0 1 characteristic earthquake sequence off kamaishi ne japan by comparing the recurrence intervals with creep quasi static slip rates around the asperity estimated from small repeating earthquake data the eight recurrence intervals 5 52 yrs on average of the sequence are almost constant but have small fluctuations standard deviation of 0 68 yrs characterized by a longer recurrence interval following a shorter one from the analysis of small repeating earthquakes from 1990 to 2003 we found a significant acceleration of creep on the plate boundary during and after an earthquake swarm in 1992 to the east of the m4 8 0 1 event the acceleration seems to have migrated from east shallower part of the plate boundary to west deeper part over about 80 km in 2 yrs to reach the asperity of the m4 8 0 1 events the 1995 event that occurred with the shortest recurrence interval was probably advanced by this acceleration of creep in around 1994 we also found similar earthquake swarms prior to the 1962 and 1973 characteristic events that occurred after the second and third shortest recurrence intervals respectively therefore it is possible that the 1962 and 1973 events were also advanced by creep accelerations the three pairs of longer and shorter recurrence intervals we observed suggest the existence of creep deceleration following the acceleration we conclude that the recurrence interval fluctuations of the m4 8 0 1 events are mainly controlled by temporal changes of creep around its asperity

possible mechanism of precursory seismic quiescence regional stress relaxation due to preseismic sliding we propose a new model to physically explain the seismic quiescence precursory to a large interplate earthquake a numerical simulation is performed to quantitatively examine possible stress changes prior to a great interplate earthquake in a subduction zone in the present study the frictional force following a laboratory derived friction law in which the friction coefficient is dependent on slip rate and slip history is assumed to act on a dip slip fault plane of infinite width in a uniform elastic half space the values of friction parameters are determined so that the result of numerical simulation may explain some properties of great interplate earthquakes in subduction zones such as the recurrence interval and the seismic coupling coefficient the result of simulation reveals that significant quasi stable sliding occurs prior to a great earthquake and accordingly stresses are changed on and around the plate boundary in a relatively wide area of the overriding continental plate the compres sional horizontal stress perpendicular to the trench axis is decreased for a few years before the occurrence of a great earthquake this decrease in regional compressional stress may account for the appearance of seismic quiescence prior to a great interplate earthquake

influence of interaction between small asperities on various types of slow earthquakes in a 3 d simulation for a subduction plate boundary recently the occurrence of slow earthquakes such as low frequency earthquakes and very low frequency earthquakes have been recognized at depths of about 30 km in southwest japan and cascadia these slow earthquakes occur sometimes in isolation and sometimes break into chain reaction producing tremor that migrates at a speed of about 5 15 km day and suggesting a strong interaction among nearby small asperities in this study we formulate a 3 d subduction plate boundary model with two types of small asperities chained along the trench at the depth of 30 km our simulation succeeds in representing various types of slow earthquakes including low frequency earthquakes and rapid slip velocity in the same asperity and indicates that interaction between asperities may cause the very low frequency earthquakes our simulation also shows chain reaction along trench with propagation speed that can be made consistent with observations by adjusting model parameters which suggests that the interactions also explain the observed migration of slow earthquakes

seismic velocity reductions caused by the 2003 tokachi oki earthquake 1 we use four repeating earthquake sequences located near hokkaido to identify velocity changes caused by the mw 8 0 2003 tokachi oki earthquake using a moving window cross correlation technique we identify delays in the arrival time of seismic waves that accumulate linearly with time into the seismogram this behavior is indicative of multiple scattering within a medium where the seismic velocity has been reduced for all of our earthquake receiver geometries we find evidence of significant velocity reductions close to the receiver the correlation of the size of the velocity reductions with both strong shaking and site characteristics suggests that these velocity reductions are caused by damage to near surface materials created by nonlinear strong ground motion for earthquake receiver geometries where the seismic waves cross the tokachi oki rupture zone we identify particularly large reductions in velocity as a result of the earthquake for these geometries we believe that the rupture zone of the tokachi oki earthquake or the shallow crust above it represents a second region where seismic velocities are reduced as a result of the main shock

a 2 300 year long annually resolved record of the south american summer monsoon from the peruvian andes decadal and centennial mean state changes in south american summer monsoon sasm precipitation during the last 2 300 years are detailed using an annually resolved authigenic calcite record of precipitation 18o from a varved lake in the central peruvian andes this unique sediment record shows that 18o peaked during the medieval climate anomaly mca from a d 900 to 1100 providing evidence that the sasm weakened considerably during this period minimum 18o values occurred during the little ice age lia between a d 1400 and 1820 reflecting a prolonged intensification of the sasm that was regionally synchronous after the lia 18o increased rapidly particularly during the current warm period cwp a d 1900 to present indicating a return to reduced sasm precipitation that was more abrupt and sustained than the onset of the mca diminished sasm precipitation during the mca and cwp tracks reconstructed northern hemisphere and north atlantic warming and a northward displacement of the intertropical convergence zone itcz over the atlantic and likely the pacific intensified sasm precipitation during the lia follows reconstructed northern hemisphere and north atlantic cooling el nino like warming in the pacific and a southward displacement of the itcz over both oceans these results suggest that sasm mean state changes are sensitive to itcz variability as mediated by western hemisphere tropical sea surface temperatures particularly in the atlantic continued northern hemisphere and north atlantic warming may therefore help perpetuate the recent reductions in sasm precipitation that characterize the last 100 years which would negatively impact andean water resources

tree ring cellulose δ18o of fokienia hodginsii in northern laos a promising proxy to reconstruct enso 1 a tree ring cellulose 18o chronology of fokienia hodginsii from 1951 to 2002 is established by four cores from four different trees to explore its potential for reconstructing climatic variations in northern laos this chronology is the first tree ring 18o chronology from laos as well as the first for this species we compare variations of tree ring cellulose 18o and ring width between cores the results suggest that the 18o time series are more strongly correlated between different trees than ring width time series are in addition correlation analysis shows a significantly negative correlation between tree ring cellulose 18o and the may october palmer drought severity index pdsi while the tree ring width indices have a poor correlation with pdsi the spatial correlation analysis between tree ring cellulose 18o and global sea surface temperature and the time series correlation analysis between tree ring cellulose 18o and the multivariate el nino southern oscillation enso index mei during the investigated period 1951 2002 reveal that enso has an important effect on tree ring cellulose 18o in laos our results indicate that the tree ring cellulose 18o of fokienia hodginsii is a promising proxy to reconstruct pdsi in southeast asian countries such as laos and to discuss their teleconnections with global atmospheric circulations such as enso

a 400 year record of hydroclimate variability and local enso history in northern southeast asia inferred from tree ring δ18o abstract we present here a chronology of tree ring cellulose 18 o for the period 1588 2002 based on individual measurements of seven fokienia hodginsii trees growing in northern laos response function analysis of meteorological data revealed that this oxygen isotope chronology has a significant negative correlation with monsoon season precipitation the water level of the mekong river and the palmer drought severity index pdsi our reconstructed monsoon season pdsi which accounts for 41 5 of pdsi variance showed that wetter phases occurred during the periods ad 1660 1695 and ad 1705 1790 that the main drier periods were ad 1630 1660 ad 1900 1940 and ad 1954 2002 and that there has been a trend of decreasing moisture during the monsoon season over the last 200 years a reduction in monsoon activity can also be seen in various tree ring oxygen isotope records from the himalaya tibet plateau and southeast asia rising sea surface temperatures over the tropical pacific and indian ocean could be responsible for this reduction in the asian summer monsoon by combining proxies sensitive to the el nino southern oscillation enso in northern laos and vietnam we were able to reconstruct the annual multivariate enso index mei and local enso event history and so improve our understanding of long term variations in enso and its influences on southeast asia

precursory seismic quiescence before the mw 8 3 tokachi oki japan earthquake on 26 september 2003 revealed by a re examined earthquake catalog 1 the 2003 tokachi oki earthquake mw 8 3 occurred on 26 september 2003 off the pacific coast of hokkaido japan in the present study an earthquake catalog is used that lists 2 000 earthquakes with m 3 3 all of the earthquake waveforms were recorded by the institute of seismology and volcanology hokkaido university in the present study these waveforms are manually re examined and hypocenters and magnitudes are re calculated a detailed analysis of the re determined earthquake catalog between 1994 and 2003 using a gridding technique zmap shows that the 2003 tokachi oki earthquake is preceded by two neighboring seismic quiescence anomalies that start around the beginning of 1999 and last about 5 years until the main shock occurs these quiescence anomalies are located around the asperity ruptured by the main shock and the z values are 3 9 and 4 0 for a time window of tw 4 years using a sample size of n 100 earthquakes the detected seismic quiescences can be interpreted as being caused by a decrease of 50 in the stressing rate based on dieterich s theory it is proposed that a quasi static pre slip occurs at the northeastern edge of the asperity ruptured by the main shock and lasts for five years until the main shock occurs by calculating the change in the coulomb failure stress cfs it is found that negative cfs areas are consistent with the two quiescence anomalies and a positive cfs area corresponds to the hypocenter of the main shock indicating that the quasi static pre slip model is a plausible one

tomographic imaging of hydrated crust and mantle in the subducting pacific slab beneath hokkaido japan evidence for dehydration embrittlement as a cause of intraslab earthquakes abstract we estimate detailed three dimensional seismic velocity structures in the subducting pacific slab beneath hokkaido japan using a large number of arrival time data from 6902 local earthquakes a remarkable low velocity layer with a thickness of 10 km is imaged at the uppermost part of the slab and is interpreted as hydrated oceanic crust the layer gradually disappears at depths of 70 80 km suggesting the breakdown of hydrous minerals there we find prominent low velocity anomalies along the lower plane of the double seismic zone and above the aftershock area of the 1993 kushiro oki earthquake m7 8 since seismic velocities of unmetamorphosed peridotite are much higher than the observations hydrous minerals are expected to exist in the lower plane as well as the hypocentral area of the 1993 earthquake on the other hand regions between the upper and lower planes where seismic activity is not so high compared to the both planes show relatively high velocities comparable to those of unmetamorphosed peridotite our observations suggest that intermediate depth earthquakes occur mainly in regions with hydrous minerals which support dehydration embrittlement hypothesis as a cause of earthquake in the subducting slab

seismological studies at parkfield vi moment release rates and estimates of source parameters for small repeating earthquakes abstract waveform data from a borehole network of broadband seismographic stations have been used to study microearthquakes along the parkfield segment of the san andreas fault saf analysis of almost 10 years of such data demonstrates that much of the seismicity in this region consists of repeating sequences quasiperiodic sequences of earthquakes that are essentially identical in terms of waveform size and location scalar seismic moments have been estimated for 53 of these repeating sequences and combined with equivalent estimates from 8 similar but larger event sequences from the stone canyon section of the fault and the main parkfield sequence these estimates show that seismic moment is being released as a function of time in a very regular manner measurements of the moment release rate combined with an assumed tectonic loading rate lead to estimates of the seismic parameters source area slip and recurrence interval such parameters exhibit a systematic dependence upon source size over a range of 10 10 in seismic moment that can be described by three simple scaling relationships several implications of these scaling relationships are explored including the repeat time of earthquakes average stress drop strength of the fault and heat generated by earthquakes what emerges from this analysis of moment release rates is a quantitative description of an earthquake process that is controlled by small strong asperities that occupy less than 1 of the fault area this means that the fault is highly heterogeneous with respect to stress strength and heat generation such heterogeneity helps to explain many of the apparent contradictions that are encountered in the study of earthquakes such as why faults appear weak why significant heat flow is not observed how significant high frequencies can be generated by large earthquakes and how various geologic features such as pseudotachylytes might form

characteristics of sedimentary varve chronologies a review abstract we constructed a varve data base vdb to study the worldwide distribution of varved sediment records and the fidelity of their varve chronologies clusters of lakes with varved sediments exist in central north america in the canadian arctic and in northern and central europe among the 108 sites included in the vdb varved records are typically 200 500 cm long and cover a period of 1000 2000 years their varve chronologies are often based on counting of annual layers from fresh sediment surfaces and photographs or from epoxy embedded sediment blocks and thin sections the vdb indicates that chronological errors associated with counting sedimentary varves fall generally between 1 and 3 but only 57 of published records are providing quantitative error estimations for their chronologies with a careful documentation of varves and by applying radiometric dating methods to surface sediments as well as using historical events as time markers there is the potential of having centennial long varved records with a very precise age depth control however it is unrealistic to expect errors significantly below 1 from several millennia long sections we found no indication that varve chronologies would have been substantially more accurate and precise in some parts of the world than in others or statistically dependent on varve thickness or temporal extension of a varved sequence according to the vdb close to 90 of the published varve chronologies have been cross checked with some independent dating methods

varves in lake sediments a review abstract downcore counting of laminations in varved sediments offers a direct and incremental dating technique for high resolution climatic and environmental archives with at least annual and sometimes even seasonal resolution the pioneering definition of varves by de geer 1912 had been restricted to rhythmically deposited proglacial clays one century later the meaning of varve has been expanded to include all annually deposited laminae in terrestrial and marine settings under favourable basin configurations and environmental conditions limnic varves are formed due to seasonality of depositional processes from the lake s water column and or transport from the catchment area subsequent to deposition of topmost laminae the physical preservation of the accumulating varved sequence requires the sustained absence of sediment mixing for example via wave action or macrobenthic bioturbation individual sub laminae in varved lake sediments typically express contrasting colours always differ in terms of their organic chemical and or mineralogical compositions and often also differ with regard to grain size various predominating climatic and depositional conditions may result in clastic biogenic or endogenic incl evaporitic varved sediments and their mixtures to reliably establish a varve chronology the annual character of laminations needs to be determined and verified in a multidisciplinary fashion sources and influences of possible errors in varve chronologies are best determined and constrained by repeated varve counts and by including radioisotopes and correlation with historically documented events a well established varve chronology greatly enhances the scientific value of laminated limnic archives by securely anchoring the wealth of multi proxy palaeoenvironmental information in the form of time series for multidisciplinary investigations applications of varved records are discussed with special reference to advances since the 1980s these span fields like calibrating radiometric dating methods reconstructing past changes of the earth s magnetic field or detecting fluctuations in solar forcing once a varve chronology is established it can be applied to precisely date events like volcanic ash layers earthquakes or human impact as well as short and long term climate temperature precipitation wind hydroclimatic conditions or flooding and environmental changes eutrophication pollution due to their exceptional high temporal resolution and in combination with their robust and accurate internal time scale in calendar years annually laminated sediments can be regarded as one of the most precious environmental archives on the continents these records are necessary to extend temporally limited instrumental records back in time as such they have societal relevance with regard to risk assessments related to natural hazards arising from e g flooding or volcanic eruptions

episodic aseismic slip in a two degree of freedom block spring model 1 we consider a two degree of freedom block spring model in which two blocks block 1 and block 2 are connected by a spring and driven by a slowly moving driver assuming a rate and state dependent friction law we set the friction parameters such that dynamic instability occurs at block 1 episodic aseismic slip occurs at block 2 when its frictional parameters are near the stability transition when the stress has accumulated to approximately a steady state level during an interseismic period block 2 starts a slow slip quasi static oscillation in the stress and slip velocity occurs with decaying fluctuation amplitudes leading to the steady state values the decaying oscillation could be a plausible generation mechanism of the episodic aseismic slip observed in the tokai district japan since 2001 we also consider various slip modes on a plate boundary based on this two block model associated with the interaction between different frictional properties

subducting plate boundary beneath the northeastern japan arc estimated from sp converted waves abstract in the tohoku district the northeastern part of honshu japan a conspicuous phase is frequently observed between p and s phases in seismograms for events in the lower seismic plane of the double planed deep seismic zone this phase is dominant in the vertical component and has an apparent velocity almost equal to or slightly smaller than the p phase we have never found this phase in seismograms for events in the upper seismic plane from these characteristics the phase is interpreted as sp converted from s to p at the upper boundary of the descending oceanic plate ubp using the travel times of the sp waves we estimated the location of the ubp beneath the tohoku district to be just above the upper seismic plane of the double planed deep seismic zone this position is consistent with those determined from the analyses of the travel times of the scsp and ps waves which are respectively the seismic wave converted from scs to p and that from p to s at the ubp

earthquake triggering by migrating slow slip initiated by m8 earthquake along kuril trench japan 1 evidence of a slow slip temporally ahead of the m7 earthquake doublet that occurred in november december 2004 offshore of eastern hokkaido japan was registered in continuous gps measurements the gps data suggest that a slow slip around a forthcoming rupture zone on the plate boundary triggered these earthquakes this slow slip episode was itself triggered by the m8 tokachi earthquake of september 2003 this is a demonstration of the geodetic visualization of the mechanism of a triggering of a subsequent earthquake caused by a preceding large earthquake the geodetic data will improve the reliability of the warning of an occurrence of a subsequent earthquake after a large one that is currently dependent on only co seismic static stress increase

plate boundary slip associated with the 2003 off tokachi earthquake based on small repeating earthquake data 1 plate boundary slip associated with the 2003 off tokachi earthquake northern japan is determined by analysis of repeating earthquakes in the source region a total of 251 repeating earthquake groups consisting of 666 events are identified in and around the aftershock region from october 1 2000 to may 31 2004 although a number of the repeating earthquakes in this region occurred before the main shock there are many events that occurred after the main event the repeating earthquakes are located in the major afterslip region and distributed to the southeast based on this analysis it is estimated that the areas to the east and southeast of the coseismic area undergone approximately 50 cm of slip over three months following the earthquake and less than 5 cm over the three years prior to the earthquake repeating earthquakes can provide afterslip data in offshore areas where resolution from land based gps is poor

recurring slow slip events and earthquake nucleation in the source region of the m 7 ibaraki oki earthquakes revealed by earthquake swarm and foreshock activity

temporal variation of intermediate depth earthquakes around the time of the m9 0 tohoku oki earthquake author s delbridge bg kita s uchida n johnson cw matsuzawa t burgmann r abstract 2017 american geophysical union all rights reserved the temporal evolution of intermediate depth seismicity before and after the 2011 m9 0 tohoku oki earthquake reveals interactions between plate interface slip and deformation in the subducting slab we investigate seismicity rate changes in the upper and lower planes of the double seismic zone beneath northeast japan using both a statistic approach and a temporal epidemic type aftershock sequence model we do not observe an anomalous precursory increase in intermediate depth earthquake activity preceding the mainshock however following the mainshock we observe a rate increase for the intermediate depth earthquakes in the upper plane the average ratio of upper plane to lower plane activity and the mean deep aseismic slip rate both increased by factor of 2 an increase of downdip compression in the slab resulting from coseismic and postseismic deformation enhanced seismicity in the upper plane which is dominated by events accommodating downdip shortening from plate unbending

a trial estimation of frictional properties focusing on aperiodicity off kamaishi just after the 2011 tohoku earthquake motivated by the fact that temporal earthquake aperiodicity was observed off kamaishi just after the 2011 tohoku earthquake we performed numerical simulations of chain reactions due to the postseismic slip of large earthquakes by applying rate and state dependent friction laws if the repeater is composed of single asperity our results show that i a mixture of partial and whole rupturing of a single asperity can explain some of the observed variability in timing and size of the repeating earthquakes off kamaishi ii the partial rupturing can be reproduced with moderate frictional instability with the aging law and not the slip or nagata laws iii the perturbation of the activated earthquake hypocenters observed mostly in the ese wnw direction may reflect the fact that the large postseismic slip of the 2011 tohoku earthquake propagated from ese to wnw off kamaishi iv the observed region of repeating earthquake quiescence may reflect the strong plate coupling of megathrust earthquakes

fault slip rates at depth from recurrence intervals of repeating microearthquakes unique attributes in sequences of recurring similar microearthquakes at parkfield california provide a means for inferring slip rate at depth throughout the active fault surface from the time intervals between sequence events application of the method using an 11 year microseismicity record revealed systematic spatial and temporal changes in the slip rate that were synchronous with earthquake activity and other independent measures of fault zone slip if this phenomenon is found to be generally common behavior in active faults it forms the basis for a method to monitor the changing strain field throughout a seismogenic fault zone

co seismic slip post seismic slip and largest aftershock associated with the 1994 sanriku haruka oki japan earthquake 1 we analyzed continuous gps data to investigate the spatio temporal distribution of co seismic slip post seismic slip and largest aftershock associated with the 1994 sanriku haruka oki japan earthquake mw 7 7 to get better resolution for co seismic and post seismic slip distribution we imposed a weak constraint as a priori information of the co seismic slip determined by seismic wave analyses we found that the post seismic slip during 100 days following the main shock amount to as much moment release as the main shock and that the sites of co seismic slip and post seismic slip are partitioning on a plate boundary region in complimentary fashion the major post seismic slip was triggered by the mainshock in western side of the co seismic slip and the extent of the post seismic slip is almost unchanged with time it rapidly developed a shear stress concentration ahead of the slip area and triggered the largest aftershock

quaternary rupture behavior of the karakoram fault and its relation to the dynamics of the continental lithosphere nw himalaya western tibet abstract the karakoram fault is a major strike slip system that partitions strain between the compressional regime of the nw himalaya and the translational and extensional fault systems of western tibet although seismic and geodetic observations suggest that the fault is currently locked a high millennial slip rate infers a dominant role in the deformation of western tibet we examine all quaternary data available for the karakoram fault and attempt to explain the temporal and spatial variability of fault slip rate we show that the karakoram fault stress level could be modulated by coulomb stress changes associated with varying seismicities on the subducting indian plate beneath western tibet our model has implications for the understanding of stress transfer between large fault systems and their interaction with lithosphere deformation we suggest that while the long term deformation of tibet may be modeled as a partially viscous medium the slip rates of major faults may vary by one order of magnitude during the quaternary our analysis may resolve the frequently observed discrepancy between millennial and decadal records of fault slip rates

stress transferred by the 1995 mw 6 9 kobe japan shock effect on aftershocks and future earthquake probabilities the kobe earthquake struck at the edge of the densely populated osaka kyoto corridor in southwest japan we investigate how the earthquake transferred stress to nearby faults altering their proximity to failure and thus changing earthquake probabilities we find that relative to the pre kobe seismicity kobe aftershocks were concentrated in regions of calculated coulomb stress increase and less common in regions of stress decrease we quantify this relationship by forming the spatial correlation between the seismicity rate change and the coulomb stress change the correlation is significant for stress changes greater than 0 2 1 0 bars 0 02 0 1 mpa and the nonlinear dependence of seismicity rate change on stress change is compatible with a state and rate dependent formulation for earthquake occurrence we extend this analysis to future mainshocks by resolving the stress changes on major faults within 100 km of kobe and calculating the change in probability caused by these stress changes transient effects of the stress changes are incorporated by the state dependent constitutive relation which amplifies the permanent stress changes during the aftershock period earthquake probability framed in this manner is highly time dependent much more so than is assumed in current practice because the probabilities depend on several poorly known parameters of the major faults we estimate uncertainties of the probabilities by monte carlo simulation this enables us to include uncertainties on the elapsed time since the last earthquake the repeat time and its variability and the period of aftershock decay we estimate that a calculated 3 bar 0 3 mpa stress increase on the eastern section of the arima takatsuki tectonic line attl near kyoto causes fivefold increase in the 30 year probability of a subsequent large earthquake near kyoto a 2 bar 0 2 mpa stress decrease on the western section of the attl results in a reduction in probability by a factor of 140 to 2000 the probability of a mw 6 9 earthquake within 50 km of osaka during 1997 2007 is estimated to have risen from 5 6 before the kobe earthquake to 7 11 afterward during 1997 2027 it is estimated to have risen from 14 16 before kobe to 16 22

real data assimilation for optimization of frictional parameters and prediction of afterslip in the 2003 tokachi oki earthquake inferred from slip velocity by an adjoint method

deep slab subduction and dehydration and their geodynamic consequences evidence from seismology and mineral physics abstract we present new pieces of evidence from seismology and mineral physics for the existence of low velocity zones in the deep part of the upper mantle wedge and the mantle transition zone that are caused by fluids from the deep subduction and deep dehydration of the pacific and philippine sea slabs under western pacific and east asia the pacific slab is subducting beneath the japan islands and japan sea with intermediate depth and deep earthquakes down to 600 km depth under the east asia margin and the slab becomes stagnant in the mantle transition zone under east china the western edge of the stagnant pacific slab is roughly coincident with the ne sw daxing anling taihangshan gravity lineament located west of beijing approximately 2000 km away from the japan trench the upper mantle above the stagnant slab under east asia forms a big mantle wedge bmw corner flow in the bmw and deep slab dehydration may have caused asthenospheric upwelling lithospheric thinning continental rift systems and intraplate volcanism in northeast asia the philippine sea slab has subducted down to the mantle transition zone depth under western japan and ryukyu back arc though the seismicity within the slab occurs only down to 200 300 km depths combining with the corner flow in the mantle wedge deep dehydration of the subducting pacific slab has affected the morphology of the subducting philippine sea slab and its seismicity under southwest japan slow anomalies are also found in the mantle under the subducting pacific slab which may represent small mantle plumes or hot upwelling associated with the deep slab subduction slab dehydration may also take place after a continental plate subducts into the mantle

stress release process along an intraplate fault analogous to the plate boundary a case study of the 2017 m5 2 akita daisen earthquake ne japan stress accumulation and release in the crust remains poorly understood compared to that at the plate boundaries spatiotemporal variations in foreshock and aftershock activities can provide key con