metasomatic replacement in the skaergaard intrusion east greenland preliminary observations abstract several unusual types of replacement structures in the layered series and marginal border series of the skaergaard intrusion indicate that metasomatic changes have altered the modal proportions and in places the mineral composition of the gabbro the geometrical forms and compositional patterns of these features indicate that they result from reactive fluids moving through the rocks at high temperatures shortly after the magma had reached an advanced stage of crystallization the principal effect of metasomatism has been to produce strongly contrasting mafic and felsic rocks

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

the skaergaard layered series part ii magmatic flow and dynamic layering re examination of textural and structural features of the skaergaard intrusion has clarified the process responsible for various forms of layering two general types are distinguished one produced by magmatic flow and another by non dynamic processes such as compaction and varied nucleation and growth of crystals our concern here is mainly with layering of the first type magmatic flow results in contrasting layers and strong foliation accompanied by a linear orientation of elongated minerals it is associated with slumping and cross bedding in a zone near the margins of the intrusion rocks in the interior of the layered series are foliated and commonly layered but have little or no lineation their layering cannot be due solely to deposition from currents the principal structural elements produced by dynamic processes in the magmatic state foliation lineation shear zones folds and current structures define parallel belts mainly around the western and northern margins their distribution suggests that the strongest component of flow was for the western side and that its strength decreased toward the east shear flow trajectories deduced from lineations and kinematic indicators confirm this asymmetry and point to mass movement toward the southeastern part of the floor

pacific north american teleconnection controls on precipitation isotope ratios across the contiguous united states large scale climate teleconnections such as the pacific north american pna pattern strongly influence atmospheric processes and continental climate here we show that precipitation 18o values in the contiguous united states are correlated with an index of the pna pattern the 18o pna relationship varies across the study region and exhibits two prominent modes with positive correlation in the western usa and negative correlation in the east this spatial pattern appears not to reflect variation in local climate variables but rather primarily reflects differences in atmospheric circulation and moisture sources associated with pna our results suggest that strong antiphase variation in paired paleo water 18o proxy records from regions characterized by the two modes of 18o pna correlation especially in the midwest and southwestern usa may provide a robust basis for reconstruction of past variation in the pna pattern

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

oxygen and hydrogen isotopes in the hydrologic cycle changes of the isotopic composition of water within the water cycle provide a recognizable signature relating such water to the different phases of the cycle the isotope fractionations that accompany the evaporation from the ocean and other surface waters and the reverse process of rain formation account for the most notable changes as a result meteoric waters are depleted in the heavy isotopic species of h and o relative to ocean waters whereas waters in evaporative systems such as lakes plants and soilwaters are relatively enriched during the passage through the aquifers the isotope composition of water is essentially a conservative property at ambient temperatures but at elevated temperatures interaction with the rock matrix may perturb the isotope composition these changes of the isotope composition in atmospheric waters surface water soil and groundwaters as well as in the biosphere are applied in the characterization of hydrological system as well as indicators of paleo climatological conditions in proxy materials in climatic archives such as ice lake sediments or organic materials

spatial and temporal variation in precipitation isotopes in the sydney basin australia summary the 2h and 18o composition of 816 precipitation samples collected between february 2005 and october 2009 from four sites across the sydney basin australia were analysed representing the first published precipitation isotope dataset for the region monthly values weighted averages and local meteoric water lines are presented for use in hydrological applications the 4 year precipitation weighted average values ranged from 2h 20 16 18o 4 50 and d 15 88 for lucas heights in the coastal region to 2h 29 48 18o 5 97 and d 18 33 for mt werong in the highlands west of sydney for the sydney basin as a whole we recommend an overall local meteoric water line of 2h 8 01 0 05 18o 16 8 0 3 precipitation in the sydney basin is isotopically different from the nearest gnip sites with a significantly higher d excess high d excess values may be the result of low humidity at the sea surface during evaporation at mid latitude sources however recycling of moisture either locally or along a moisture transport trajectory may also be an important factor a clear coastal effect was observed but generally temperature and amount effects were found to be weak

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

holocene stable isotope record of insolation and rapid climate change in a stalagmite from the zagros of iran abstract we explore holocene climatic changes recorded by geochemical proxies in a single well dated stalagmite from the northern zagros mountains of iran a region where stalagmite records have so far only provided short glimpses of holocene climatic changes stalagmite kt 3 from katalekhor cave began growing 9 5 ka under wet early holocene conditions coincident with the timing of sapropel 1 at this time 18o values were at or below 9 0 stalagmite growth diameter was at its maximum 234u 238u0 activity values were low and trace element contents indicate flushing of the epikarst progressive reduction in winter precipitation amount after 7 0 ka is recorded by increasing 18o and 234u 238u0 activity values and reduction in trace element contents and growth diameter until 2 0 ka these trends follow the reduction in summer insolation and agree with model simulated changes in total rainfall and rainwater isotopes sub centennial scale variability is not a feature of the 18o or trace element records this suggests a stable winter recharge regime a feature that might militate against kt 3 18o recording changes in the seasonality of rainfall kt 3 13c compositions are enriched relative to lower altitude stalagmites in the levant implying low soil co2 contribution thin montane soils however a broadly decreasing millennial scale trend in 13c suggests that soil carbon contributions increased with time despite the progressive reduction in winter precipitation amount the 13c changes probably reflect decreasing summer temperatures and less extreme wintertime coldness driven by reducing summer and increasing winter insolation respectively these combined effects decreased effective evaporation and improved soil moisture availability favouring vegetation development during the growth season the 13c values also show 1 5 centennial scale variability with higher 13c values between 9 0 and 8 7 ka 8 3 7 7 ka 6 5 5 5 ka 5 4 4 5 ka and 4 3 2 0 ka three of these correspond with rapid climate change rcc events based on non seasalt potassium k in greenland ice cores higher 13c values indicate poor soil development caused by aridity the centennial scale 13c anomaly 8 3 7 7 ka is in part overprinted by the 160 year long 8 2 ka cold dry event but culmination 7 7 ka corresponds with other records suggesting an intensified siberian high pressure system affecting regional climate the centennial scale 13c anomaly between 4 3 and 2 0 ka overlaps the 2 65 to 2 50 ka assyrian megadrought evident in stalagmite stable isotope records in northern iraq the kt 3 record is key in better understanding holocene climate change in the central zagros region representative of montane fertile crescent environments

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

tectonic affinity of nisutlin and anvil assemblage strata from the teslin tectonic zone northern canadian cordillera constraints from neodymium isotope and geochemical evidence we present geochemical and isotopic data for nisutlin assemblage metasedimentary rocks and anvil assemblage greenstones from the teslin tectonic zone of the northern canadian cordillera this study aims to establish the tectonic setting of formation for the sedimentary and basaltic protoliths of these highly deformed and metamorphosed rocks and thereby place constraints on the origin of these enigmatic rocks for which differing tectonic models have been proposed for the nisutlin assemblage metasedimentary rocks the geochemical and isotopic data show that two widely different source regions contributed detritus to the original sediments one source region was felsic upper crustal material with nd isotopic compositions compatible with ultimate derivation from the north american continent depleted mantle model age tdm 2 5 2 8 ga the second source region is deduced to be chemically primitive crust basaltic andesitic with a short crustal residence history 0 9 ga for the anvil assemblage greenstones immobile trace element abundances are dissimilar to within plate oceanic arc and normal mid ocean ridge basalts and similar to calc alkaline basalts in active continental margin settings we interpret the paleosetting for the nisutlin assemblage to be at the outermost margin of the ancestral north american continent in an area which received detrital input from the distal north american craton in the early paleozoic however this area also received detritus from a chemically and isotopically juvenile magmatic arc source a source type not known from paleozoic metasedimentary rocks from the miogeoclinal sequence on the basis of similar nd isotopic relationships recorded elsewhere in deformed paleozoic rocks of the orogen we infer that these geochemical signals reflect tectonic processes of regional extent the trace element geochemistry of the anvil assemblage greenstones does not support a correclation with known paleozoic greenstones of the slide mountain terrane which some tectonic models have advocated

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

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

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

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

evaporation and transport of water isotopologues from greenland lakes the lake size effect abstract isotopic compositions of evaporative flux from a lake are used in many hydrological and paleoclimate studies that help constrain the water budget of a lake and or to infer changes in climate conditions the isotopic fluxes of evaporation from a water surface are typically computed using a zero dimensional 0 d model originally conceptualized by craig and gordon 1965 such models generally have laminar and turbulent layers assume a steady state condition and neglect horizontal variations in particular the effect of advection on isotopic variations is not considered while this classical treatment can be used for some sections of large open surface water bodies such as an ocean or a large lake it may not apply to relatively small water bodies where limited fetch does not allow full equilibration between air from land and the water surface both horizontal and vertical gradients in water vapor concentration and isotopic ratios may develop over a lake these gradients in turn affect the evaporative fluxes of water vapor and its isotopic ratios which is not adequately predicted by a 0 d model we observed for the first time the vertical as well as horizontal components of vapor and isotopic gradients as relatively dry and isotopically depleted air advected over the surfaces of several lakes up to a 5 km fetch under winds of 1 5 m s in kangerlussuaq greenland we modeled the vapor and isotopic distribution in air above the lake using a steady state 2 d model in which vertical diffusive transport balances horizontal advection the model was verified by our observations and then used to calculate evaporative fluxes of vapor and its isotopic ratios in the special case of zero wind speed the model reduces to 1 d results from this 1 d model are compared with those from the 2 d model to assess the discrepancy in isotopic fluxes between advection and no advection conditions since wind advection above a lake alters the concentrations gradients and evaporative fluxes of water isotopes it alters the water balance and isotope ratios of the lake and the relationship between them these effects are greatest for small lakes if wind advection is neglected in the inference of water balance from lake isotopes an error is thus introduced the magnitude of which depends on lake size we refer to this as the lake size effect for lakes less than 500 m in length along the wind direction the average 18o and d of vapor flux are at least 2 lower than the corresponding flux values from the 1 d model the magnitude of the resulting relative error in water balance calculations is much greater if using 18o than d in mass balance calculations the former is about eight times the latter this result argues that water balance calculated with d is less sensitive to the difference in lake size and or its change over time the 1 d model result is also compared with that from a comparable 0 d model since vertical vapor and isotope gradients always exist even under no advection conditions one may not obtain correct flux values if the relative humidity and isotopic ratios in ambient air measured at an arbitrary height are used for the 0 d model calculation typically the standard meteorological measurements at 2 or 10 m would result in an underestimate of the 18o and d values of the vapor flux this work has provided the first quantification on the effect of advection on isotopic fluxes of evaporation the method of mobile vapor analysis combined with 2 d modeling can be applied to other environmental settings in which the size of advection effect on isotopic fluxes depends upon relationships among local meteorological and hydrological variables our results also suggest that incorporating isotopic vapor measurements can help constrain modeled evaporation rates which is worth exploring further in future studies

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

a new precipitation weighted method for determining the meteoric water line for hydrological applications demonstrated using australian and global gnip data summary the relationship between 2h and 18o in precipitation at a site known as the local meteoric water line lmwl is normally defined using an ordinary least squares regression olsr which gives equal weighting to all data points regardless of the precipitation amount they represent however smaller precipitation amounts are more likely to have a lower d excess due to re evaporation of raindrops below the cloud base or biases in the sampling method in this paper we present an equation for a precipitation amount weighted least squares regression pwlsr that will correct these biases for use in groundwater and surface hydrology applications new lmwl equations are presented for australian sites in the global network of isotopes in precipitation gnip where the pwlsr consistently produces a lmwl with a larger gradient than the olsr perth and alice springs exhibit the largest change in slope this is consistent with the higher frequency of small monthly precipitation amounts with low d excess values occurring at these sites in summer for perth and throughout the year for alice springs the pwlsr method was also applied to 288 stations in the gnip data base n 36 and the difference between the slopes of the lmwls a slopepwlsr slopeolsr calculated for these stations the mean change in slope a was 0 12 with 56 of sites showing an increase in slope or positive a value and 44 having a decrease in slope or negative a sites with mediterranean climates showed the greatest increase in slope the magnitude of the change in slope followed some general trends showing a positive correlation with average 2h and 18o composition and rainfall variability and negative correlation with period of record n

the skaergaard layered series part vii sr and nd isotopes the initial isotopic ratios of strontium and neodymium in the skaergaard layered series vary both vertically and laterally on every scale from the intrusion as a whole down to coexisting minerals in a single rock the magma that filled the skaergaard chamber was contaminated to various degrees with the metamorphic rocks through which it rose and was never completely homogenized after being intruded the contamination was most pronounced in contact zones and aureoles around rare xenoliths the greater concentrations of lithophile trace elements in the upper border series was previously attributed to assimilation of buoyant fragments of gneiss that collected under the roof but most of the rocks of the upper border series are isotopically indistinguishablefromthoseofthelayeredseries itisdoubtful therefore that this part of the intrusion assimilated much more of the metamorphic basement than did the rest of the magma similarly the marked increase in the concentrations of excluded elements in the upper part of the layered series is not matched by a change in the isotopic character of the rocks and cannot be attributed to a later influx of new magma analyses of minerals separated from rocks with exceptionally mafic or felsic modal compositions revealed marked inhomogeneities in the isotopic compositions of their constituent minerals for example coexisting plagioclase and pyroxene from closely associated anorthosites and pyroxenites have very different initial isotopic ratios of both strontium and neodymium the same is true of mafic and felsic layers in modally graded gabbros these differences are unrelated to the low temperature alteration shown by oxygenisotopes they must have been introduced when the original gabbro was largely crystallized and underwent local metasomatic replacement by nearly mono mineralic mafic and felsic assemblages

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

stable isotopic characteristic of taiwan s precipitation a case study of western pacific monsoon region abstract the stable oxygen and hydrogen isotopic features of precipitation in taiwan an island located at the western pacific monsoon area are presented from nearly 3 500 samples collected during the past decade for 20 stations results demonstrate that moisture sources from diverse air masses with different isotopic signals are the main parameter in controlling the precipitation s isotope characteristics the air mass from polar continental pc region contributes the precipitation with high deuterium excess values up to 23 and relatively enriched isotope compositions e g 3 2 for 18o during the winter with prevailing northeasterly monsoon by contrast air masses from equatorial maritime em and tropical maritime tm supply the precipitation with low deuterium excess values as low as about 7 and more depleted isotope values e g 8 9 and 6 0 for 18o of tm and em respectively during the summer with prevailing southwesterly monsoon thus seasonal differences in terms of 18o d and deuterium excess values are primarily influenced by the interactions among various precipitation sources while these various air masses travel through taiwan secondary evaporation effects further modify the isotope characteristics of the inland precipitation such as raindrop evaporation reduces the deuterium excess of winter precipitation and moisture recycling increases the deuterium excess of summer precipitation the semi quantitative estimations in terms of evaluation for changes in the deuterium excess suggest that the raindrop evaporation fractions for winter precipitation range 7 to 15 and the proportions of recycling moisture in summer precipitation are less than 5 additionally the isotopic altitude gradient in terms of 18o for summer precipitation is 0 22 100 m greater than 0 17 100 m of winter precipitation the greater isotopic gradient in summer can be attributed to a higher temperature vs altitude gradient relative to winter the observed spatial and seasonal stable isotopic characteristics in taiwan s precipitation not only contribute valuable information for regional monsoon research crossing the continent ocean interface of east asia but also can serve as very useful database for local water resources management

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

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

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

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

diurnal to interannual rainfall δ 18 o variations in northern borneo driven by regional hydrology the relationship between climate variability and rainfall oxygen isotopic 18o variability is poorly constrained especially in the tropics where many key paleoclimate records rely on past rainfall isotopes as proxies for hydroclimate here we present a daily resolved 5 yr long timeseries of rainfall 18o from gunung mulu national park located in northern borneo 4 n 114 e in the heart of the west pacific warm pool and compare it to local and regional climatic variables daily rainfall 18o values range from 0 7 to 18 5 and exhibit a weak but significant inverse relationship with daily local precipitation amount r 0 19 p 0 05 consistent with the tropical amount effect day to day 18o variability at mulu is best correlated to regional precipitation amount averaged over the preceding week r 0 64 p 0 01 the inverse relationship between mulu rainfall 18o and local regional precipitation amount increases with increased temporal averaging reaching r 0 56 r 0 72 on monthly timescales large negative multi day rainfall 18o anomalies of up to 16 occur every 30 90 days and are closely associated with wet phases of the intraseasonal madden julian oscillation a weak semi annual seasonal cycle in rainfall 18o of 2 3 bears little resemblance to seasonal precipitation variability pointing to a complex sequence of moisture sources and or trajectories over the course of the year interannual rainfall 18o variations of 6 8 are significantly correlated with indices of the el nino southern oscillation with increased rainfall 18o during relatively dry el nino conditions and vice versa during la nina events we find that mulu rainfall 18o outperforms mulu precipitation amount as a tracer of basin scale climate variability highlighting the time and space integrative nature of rainfall 18o taken together our results suggest that rainfall 18o variability at mulu is significantly influenced by the strength of regional convective activity as such our study provides further empirical support for the interpretation of 18o based paleo reconstructions from northern borneo stalagmites as robust indicators of regional scale hydroclimate variability where higher 18o reflects regional drying

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

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

climate reconstruction using data assimilation of water isotope ratios from ice cores water isotope data from ice cores particularly 18o have long been used in paleoclimatology although 18o has been primarily interpreted as a proxy for local air temperature isotope enabled climate models have established that there are many nonlocal and nontemperature related climatic influences on isotopic signals at coring locations moreover recent observational studies have linked ice core isotopes to nonlocal patterns of climate variability particularly to midlatitude atmospheric circulation patterns and to variations in tropical climate therefore paleoclimate reconstructions may better utilize ice core isotope proxies by combining them with isotope enabled climate models here we employ a data assimilation based technique that fuses isotopic proxy information with the dynamical constraints of climate models through several idealized and real proxy experiments we assess the spatial and temporal extent to which isotope records can reconstruct surface temperature 500 hpa geopotential height and precipitation we find local reconstruction skill to be most robust across the reconstructions particularly for temperature and geopotential height as well as limited nonlocal skill in the tropics these results are in agreement with long held views that isotopes in ice cores have clear value as local climate proxies particularly for temperature and atmospheric circulation these results also show that in principle nonlocal climate information may also be inferred from ice cores however the spatial range of this information is nonuniform and depends on skillful modeling of the proxy data within the reconstruction process

a strontium isotopic study of newberry volcano central oregon structural and thermal implications abstract ratios of 87 sr 86 sr were determined in twenty seven basaltic rocks from newberry these ratios range from 0 70330 to 0 70414 most fall between 0 7035 and 0 7038 covariance of al 2 o 3 feo ratio tio 2 content and th content with 87 sr 86 sr suggests that some isotopic ratios reflect shallow crustal contamination but the data also suggest that two mantle sources a prominent one at 0 7036 and a less prominent one at 0 7033 or less are represented the hypothesis of crustal contamination is supported by variations in 87 sr 86 sr ratios with locations of the vents from which these rocks erupted sr tends to be more radiogenic in rocks from vents either close to a silicic complex such as the caldera of the volcano or the amota butte sugar pine ridge complex or close to axes of the fault zones that underlie the edifice presumably local heating of the upper crust facilitates contamination of basaltic magma rising through it

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

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