a study on wind driven circulation in the subarctic north pacific using topex poseidon altimeter data time dependent wind driven circulation in the subarctic region in the north pacific is investigated by using topex poseidon t p altimeter data and european centre for medium range weather forecasts ecmwf wind data for about 2 years the first empirical orthogonal function eof of the sea level anomaly sla without the variation related to the steric height change sla represents a basin sized oscillation which is associated with the spin up and spin down of the subarctic gyre moreover the time series of the first eof corresponds to the oyashio current variation measured by the moored current meter at about 1250 m depth the first and third eofs of the wind stress curl fields represent basin sized south north oscillations being associated with changes in intensity and the latitudinal position of the aleutian low time series of both the dominant eofs of the sla and the wind stress curl anomaly are correlated well which suggests that dominant variation of the sla is mainly controlled by the wind stress curl fields represented by the first and third eofs the time series of the first eof of the sla is in agreement with that of sverdrup transport estimated by the wind stress curl near 40 n with a correlation of 0 70 both standard deviations of the t p sla derived transports in the interior and the western boundary regions are consistent with that of the sverdrup transport in the same order of magnitude these results suggest that sea surface height variation in the subarctic north pacific is approximately explained by the time dependent wind driven circulation

impact of eastern arctic shelf waters on the nansen basin intermediate layers the eurasian shelves supply water to the nansen basin intermediate layers in two ways as buoyancy driven plumes of dense winter water and as permanent inflow of the barents sea branch of atlantic water while the plumes are local and seasonal phenomena the barents sea flow is part of the large scale circulation both interact with atlantic water which enters the arctic ocean through fram strait and moves as a subsurface boundary current eastward along the continental slope during the polarstern cruise ark ix 4 in summer 1993 the fram strait branch was observed as a narrow core within tens of kilometers of the barents sea shelf edge here several patches of cold low salinity water spread across the slope down to about 500 m depth their origin is assumed to be the northern barents sea they mix with the warm saline fram strait branch water fsbw so that the core properties of the latter become modified downstream in the eastern nansen basin the fram strait branch is displaced toward the inner basin by inflow of the barents sea branch of atlantic water bsbw this inflow appears as a broad 200 km wedge extending from 200 to 1300 m depth bsbw is colder and less saline than water of the fram strait branch and it is less dense and less stratified than the ambient water both branches appear to undergo vigorous mixing while spreading eastward so that any eastward continuation of the boundary flow transports about 50 bsbw and 50 fsbw above 600 m and about 80 bsbw and 20 fsbw below that level toward the canadian basin according to available observations the barents and kara seas are the only source areas for shelf waters ventilating the nansen basin below the halocline and these waters constitute a freshwater input rather than a salt input winter shelf water from the laptev sea cannot contribute to layers deeper than the upper halocline

a barotropic inverse tidal model for the arctic ocean 1 we describe high resolution 5 km grid linear dynamics and inverse models of arctic ocean barotropic tides obtained with the osu tidal inversion software otis package the 8 constituent dynamics based model uses the latest ibcao bathymetry and open boundary forcing from the recent tpxo 6 2 global barotropic tidal solution this model performs significantly better than the present benchmark arctic tidal model 14 km grid by z kowalik and a proshutinsky as judged by comparisons with 300 coastal tide gauges the greatest improvements are found in the canadian arctic archipelago nares strait and the baffin bay and labrador sea and can be explained by the higher resolution of the new model in these topographically complex regions the new arctic inverse model assimilates coastal and benthic tide gauges and topex poseidon and ers altimetry for further improvements of the 4 dominant constituents m2 s2 k1 and o1

factors controlling regional spatial distribution of 53 elements in coastal sea sediments in northern japan comparison of geochemical data derived from stream and marine sediments abstract in all 53 elements were analyzed in 1406 coastal sea sediment samples collected from an area off hokkaido and the tohoku region of japan during a nationwide marine geochemical mapping project the spatial distribution patterns of the elemental concentrations in coastal seas along with the existing geochemical maps in terrestrial areas were used to define natural geochemical background variation and mass transport processes the terrestrial area is covered by mafic volcanic rocks and accretionary complexes associated with ophiolite which has small amounts of felsic volcanic rocks and granite the spatial distribution patterns of elements enriched in mafic lithologies such as fe total fe 2 o 3 and sc in marine environments are influenced by adjoining terrestrial materials the spatial distribution patterns of cr and ni concentrations which are highly abundant in ultramafic rocks on land are used to evaluate the mass transport from land to the sea and the dispersive processes caused by oceanic currents the scale of mass transport by oceanic currents occurs up to a distance of 100 200 km from the coast along the coastal areas the regional differences of elements rich in felsic lithologies such as k k 2 o nb and la in marine sediments are determined mainly by the relative proportion of minerals and lithic fragments enriching felsic materials to those associated with mafic materials the spatial distribution of elemental concentration is not always continuous between the land areas and coastal sea areas that difference is interpreted as resulting from 1 transportation of marine sediments by oceanic currents and storm waves 2 contribution of volcanic materials such as tephra 3 occurrence of shell fragments and foraminifera tests and 4 distribution of relict sediments of the last glacial age and early transgression age contamination with cu zn cd as mo sn sb hg pb and bi was not observed in marine environments because the study area has little anthropogenic activity terrestrial materials are the dominant source for these metals the mo cd sn sb hg pb and bi are abundant in silty and clayey sediments locally because of early diagenetic processes authigenic precipitation and organic substances associated with these elements the spatial distribution of as concentration shows exceptions it is concentrated in some coarse and fine sands on the shelf the enrichment is explained by adsorption of as sourced from a coal field to fe hydroxide

flow of winter transformed pacific water into the western arctic abstract the dynamics of the flow of dense water through barrow canyon is investigated using data from a hydrographic survey in summer 2002 the focus is on the winter transformed bering water the highest volumetric mode of winter water in the chukchi sea which drains northward through the canyon in spring and summer the transport of this water mass during the time of the survey was 0 2 0 3 sv as the layer flowed from the head of the canyon to the mouth it sank decelerated and stretched strong cyclonic relative vorticity was generated on the seaward side of the jet which compensated for the stretching this adjustment was incomplete however in that it did not extend across the entire current possibly because of internal mixing due to shear instabilities the resulting vorticity structure of the flow at the canyon mouth was conducive for baroclinic instability and eddy formation multiple eddies of winter transformed bering water were observed along the chukchi beaufort shelfbreak those to the west of barrow canyon were in the process of being spawned by the eastward flowing shelfbreak current emanating from herald canyon while the single eddy observed to the east originated from the barrow canyon outflow it is argued that such an eddy formation is a major source of the ubiquitous cold core anti cyclones observed historically throughout the canada basin implications for the ventilation of the upper halocline of the western arctic are discussed

seasonal variation of upwelling in the alaskan beaufort sea impact of sea ice cover 1 data from a mooring array deployed from august 2002 to september 2004 are used to characterize differences in upwelling near the shelf break in the alaskan beaufort sea due to varying sea ice conditions the record is divided into three ice seasons open water partial ice and full ice the basic response is the same in each of the seasons roughly 8 h after the onset of easterly winds the shelf break jet reverses followed approximately 10 h later by upwelling of saltier water which is cold near the shelf break pacific winter water and warm at depth atlantic water the secondary circulation at the outer shelf is to first order consistent with a two dimensional ekman balance of offshore flow in the upper layer and onshore flow at depth there are however important seasonal differences in the upwelling overall the response is strongest in the partial ice season and weakest in the full ice season it is believed that these differences are dictated by the degree to which wind stress is transmitted through the pack ice as the strength of the wind forcing was comparable over the three seasons an eof based upwelling index is constructed using information about the primary flow secondary flow and hydrography the ability to predict upwelling using the wind record alone is explored which demonstrates that 90 of easterly wind events exceeding 9 5 m s 1 drive significant upwelling during certain periods the ice cover on the shelf became landfast which altered the upwelling and circulation patterns near the shelf break

potential transport pathways of terrigenous material in the gulf of papua t this work discusses potential transport pathways of plume water may infrequently enter the torres straits terrigenous material in the gulf of papua gop new because of sub tidal water elevation differences between guinea using lagrangian tracers as proxies for clay the gop and the arafura sea modeling studies have been minerals and finer particles the tracers are transported by used in conjunction with measurement programs to elucicurrents from the east asia seas implementation of the date dispersal mechanisms for noncohesive sediments in the navy coastal ocean model the results suggest that clay gop wolanski el al 1984 1995 hemer et al 2004 minerals input from rivers along the northwest coast of the 4 this study complements earlier work by examining gop accumulate on the inner shelf with high concentrations the dispersal of dissolved and fine grained suspended ternear the mouth of the fly and purari rivers finer particles rigenous material within the gop for a year long interval which are also representative of dissolved metals are using a combination of hydrodynamic and lagrangian transported eastward along the gop coast into the solomon tracer modeling furthermore because of the large model sea as well as into the torres strait to the west the results domain used in this study we are able to study the impact of also suggest that some finer particles are entrained by eddies large scale flows on transport patterns without imposing within the northern coral sea these results are in artificial boundary conditions the use of tracers to examine qualitative agreement with observations from the region complex multidisciplinary problems in oceanography has citation keen t r d s ko r l slingerland s riedlinger led to understanding the behavior of both suspended and and p flynn 2006 potential transport pathways of terrigenous dissolved constituents in a range of ocean environments material in the gulf of papua geophys res lett 33 l04608 nakano and povinec 2003 mcmanus and prandle 1997

crustal tilting derived from holocene sea level observations along the east coast of hokkaido in japan and upper mantle rheology late holocene sea level observations at sites along the east coast of hokkaido in japan indicate a gradual decrease of the altitude of relative sea level eastward toward the tip of nemuro peninsula these observations in seismically active areas can be explained by glaciohydroisostatic adjustment due to the last deglaciation for an earth model with a thin lithosphere of 30 40 km thickness and with no low viscosity layer or with a 25 km lithosphere overlying a low viscosity layer less than 50 km although more data as a function of time are needed to distinguish these models thus the vertical crustal displacement associated with the subduction of the pacific plate seems to has not been cumulated on a time scale of 103 104 years

characteristics of sediments and their dispersal systems along the shelf and slope of an active forearc margin eastern hokkaido northern japan abstract this study revealed sediment distributions and their dispersal systems in a shelf slope setting along an active forearc margin off eastern hokkaido northern japan where the pacific plate is being subducted beneath the okhotsk north american plate at the 7 km deep kuril trench the findings were based on analyses of the textures and structures of surface sediments components of the sampled sand fractions high resolution acoustic reflection records and sediment budgets the studied margin has a 20 30 km wide shelf and steep 5 10 slope marked by faults and folds associated with transpressional tectonics the shelf sediments are classified into gravelly coarse to fine sand from the shelf edge to the uppermost slope 110 1000 m water depth gravel and coarse sand on the shelf off hanasaki fine sand on the middle outer shelf off kiritappu and very fine sand on the shelf off akkeshi the coarse sediments on the eastern shelf off hanasaki and the shelf margin are interpreted to represent lag deposits from coastal erosion associated with a post glacial transgression across topographic highs the two depocenters of shelf sediments subsequent to the last glacial maximum are situated in the middle outer shelf off kiritappu and in the inner middle shelf off akkeshi these are interpreted as transgressive highstand sequences whose locations were controlled by ridges on the shelf margin and topographic highs on the shelf the shelf sediment thickness reaches 20 m and the total volume is estimated at ca 6 km3 the slope sediments are grouped into medium fine sand on the uppermost and upper slopes 150 2000 m water depth and mud dominated sediments on the upper to middle slope 1000 3000 m water depth the sandy sediments on the slope at water depths greater than 1000 m are regarded as being derived from the shelf break by gravitational redistribution the occurrence of diamictite like sediments around gullies that incise into the slope indicates that mass movement and sediment gravity flows play an important role in the redistribution of sediments upon the slope on the upper middle slope hemipelagic fallout and advection of turbid water from the shelf edge provide a supply of suspended material the main contributor of sediment supply to the area is coastal erosion 1 81 mt y 1 along with a lesser contribution from fluvial input 0 10 mt y 1 during the latest quaternary the rates of sediment accumulation upon the shelf are estimated to have been 0 47 mt y 1 the remainder of the material transported into the sea is probably redistributed to deeper parts of the slope via gravitational sediment flows or transported outside of the study area by alongshore and tidal currents the studied shelf that kept less than a quarter of the mass from land is comparable with other active margin shelves of new zealand and california although they are fed by high sediment laden rivers

slip distribution of the 1952 tokachi oki earthquake m 8 1 along the kuril trench deduced from tsunami waveform inversion 1 we inverted 13 tsunami waveforms recorded in japan to estimate the slip distribution of the 1952 tokachi oki earthquake m 8 1 which occurred southeast off hokkaido along the southern kuril subduction zone the previously estimated source area determined from tsunami travel times hatori 1973 did not coincide with the observed aftershock distribution our results show that a large amount of slip occurred in the aftershock area east of hatori s tsunami source area suggesting that a portion of the interplate thrust near the trench was ruptured by the main shock we also found more than 5 m of slip along the deeper part of the seismogenic interface just below the central part of hatori s tsunami source area this region which also has the largest stress drop during the main shock had few aftershocks large tsunami heights on the eastern hokkaido coast are better explained by the heterogeneous slip model than previous uniform slip fault models the total seismic moment is estimated to be 1 87 1021 n m giving a moment magnitude of mw 8 1 the revised tsunami source area is estimated to be 25 2 103 km2 3 times larger than the previous tsunami source area out of four large earthquakes with m 7 that subsequently occurred in and around the rupture area of the 1952 event three were at the edges of regions with relatively small amount of slip we also found that a subducted seamount near the edge of the rupture area possibly impeded slip along the plate interface

shelf sequence and characteristic bounding surfaces in a wave dominated setting latest pleistocene holocene examples from northeast japan abstract this paper presents modern models for coastal to shelf sequences in a microtidal and wave dominated setting based on detailed analyses of latest pleistocene holocene sequences on the pacific side of northeast japan the latest pleistocene holocene sequences on the pacific side of northeast japan created in response to sea level changes for the last 30 kyr can be assigned to lowstand transgressive and highstand systems tracts related to sea level changes and show characteristic bounding surfaces and depositional systems these basically support the sequence architecture model of vail however transgression and regression occurred almost simultaneously with rise and fall of sea level in the study areas and so inflection points of sea level curves where the absolute slope or the rate of change is greatest are less significant for these high frequency sequences the characteristic bounding surfaces are a sequence boundary a transgressive surface which is the boundary between the lowstand and the transgressive systems tracts a ravinement surface which is found mainly in deposits of the transgressive systems tract and a maximum flooding surface which is the boundary between the transgressive and the highstand systems tracts the sequence boundary was created in response to falling sea level fluvial entrenchment shifted seaward with falling sea level therefore the boundary is a time transgressive unconformity and is not an isochronous boundary the transgressive surface is a nearby isochronous boundary that occurred when the shoreline had started to move landward from its maximum seaward excursion the ravinement surface is a diachronous surface created by shoreface erosion during transgression the shoreface erosion shifted landward with rising sea level and so the erosion surface created is time transgressive this surface is the most distinct bounding surface in the shelf sequence these characteristics of the bounding surfaces support and clarify the model of thorne and swift 1991 the transgressive systems tract on the shelf can be divided into two backstepping wedges separated by the ravinement surface the lower wedge consists of coastal plain and fluvial systems and the upper wedge is composed of transgressive sand and or sand ridges both the wedges show a backstepping depositional pattern which can be recognized in seismic records and cores these wedges correspond to the backstep backbarrier wedge and backstep shelf wedge of thorne and swift 1991 respectively

provenance of sand on the poverty bay shelf the link between source and sink sectors of the waipaoa river sedimentary system abstract the poverty shelf north island new zealand is a segment of the waipaoa sedimentary system wss a margins source to sink focus site our petrographic analysis of sand from shelf core samples indicates that the sand fraction is mainly derived from intra and potentially extrabasinal sources but surprisingly the major fluvial system that drains into poverty bay the waipaoa river mean qfl xqyfzl is not the dominant source only one vibracore at the mouth of poverty bay contained sand qfl xqyfzl potentially derived from the waipaoa river the shelf sand mean qfl xqyfzl more strongly resembles beach sand mean qfl xqyfzl collected along the coast which is likely sourced from pervasive local cliff erosion of miocene pliocene sedimentary units that exhibit similar sandstone detrital modes mean qfl xqyfzl texturally coarser more poorly sorted and more angular sand is located along the outer shelf while finer well sorted sand characterizes the mid shelf these findings suggest a shorter transport history for the material near the outer shelf bathymetric high areas and this observation along with the composition data suggests that they were sourced by erosion of locally exposed miocene pliocene units a potential extrabasinal source of shelf sediment is indicated by anomalous prolate and equant shaped greywacke torlesse and minor red chert pebbles collected in two outer shelf box cores on the lachlan anticline these are not lithologies found within the terrestrial segment of the wss or strata comprising the outer shelf highs the clast shapes are also distinctly different from the oblate shaped pebble sized greywacke gravel clasts on beaches in hawke bay rather these sediments are more similar to torlesse stream gravel seismic and multibeam data support the possibility that during the most recent sea level lowstand the hawke bay fluvial system flowed into poverty canyon bringing these unique gravels onto what is now the poverty outer shelf the presence of the torlesse gravel is significant in that it highlights how the wss was not a closed sedimentary system in the past just as recent sedimentary research has shown in the case today

modern accumulation rates and a sediment budget for the eel shelf a flood dominated depositional environment the northern california continental margin is periodically impacted by geologically significant storms which have a marked influence on terrigenous sediment supply flood deposition and long term accumulation of fine grained sediment on the eel shelf accumulation of eel river muds on the adjacent shelf was investigated using 210pb and 137cs geochronologies in order to understand the fate of sediment discharged by the eel river and to relate patterns of net sediment accumulation 100 yr time scale to sediment dynamics 210pb data demonstrate that modern accumulation of river mud occurs from the 50 m isobath seaward across shelf accumulation rates decrease from maximum mid shelf values of 0 6 1 7 g cm 2 yr 1 to values of 0 2 0 4 g cm 2 yr 1 at the shelf break with a spatially weighted mean of 0 5 g cm 2 yr 1 0 4 cm yr for the entire shelf 210pbxs sediment depth profiles from the region of highest accumulation rate are characterized by subsurface intervals of low and uniform activity which are produced by flood deposition in some cores particular 210pbxs activity intervals may be associated with major eel river floods of 1955 1964 and 1974 it is postulated that because of the coincidence of high river flow events and southerly winds during cyclonic winter storms net northward transport allows for preferential deposition of fine grained sediment north of the river mouth over the past 100 years fluvial sediment input combined with marine dispersal processes have produced a mid shelf depocenter evident by both the spatial distribution of 210pb accumulation rates and by clay rich flood layers partially preserved in shelf deposits a fine grained sediment budget for the dispersal system based on hydrological data and 210pb geochronologies demonstrates that a maximum of 20 3 109 kg yr of the mean annual supply of fluvial mud 14 109 kg yr is trapped on the shelf the results of this study demonstrate that 1 short term sedimentation processes associated with floods can influence sediment accumulation on longer time scales and 2 a major fraction of fine grained sediment supplied to tectonically active margins by flood prone mountainous rivers bypasses narrow continental shelves

shelf slope sedimentation during the late quaternary on the southwestern kuril forearc margin northern japan abstract we studied an active forearc margin off eastern hokkaido northern japan to identify the main influences on stratigraphic development from the last glacial to the present highstand this paper presents new data on the environment texture and sedimentation rates of forearc shelf slope sediments based on more than 300 samples of seafloor sediments and densely gridded sub bottom profiling records lowstand sedimentary wedges developed upon the shelf margins in areas with a large sediment supply and without incising canyons the transgressive and highstand deposits formed on the shelf in extensive low gradient and topographically low areas the narrow shelf is covered by sandy sediments where winnowed fines are likely to have escaped to the slope via gravity driven across shelf transport or ocean current induced along shelf transport the slope has a mid slope mud belt at water depths of 700 1600 m the sedimentation rates on the slope subsequent to 15 ka the late transgressive to highstand stage were just 10 70 of the rates prior to this period these changes in sedimentation rates are ascribed to spatially variable topography high sedimentation rates were maintained at topographically low and gently sloping areas even during highstand periods due to concentrations of nepheloid layers or deposition via sediment gravity flows on the other hand low sedimentation rates were recognized on topographic highs of interfluves on the upper slope or on axes of anticlines where main flows or overspills of turbidity currents decreased as sealevel rose these results suggest that sedimentologic and stratigraphic variations are tied to variations in the physical configuration of the shelf slope system being influenced by the local topography in addition to the climatic and oceanographic processes

inversion of long period p waves from great earthquakes along subduction zones abstract long period p waves from subduction zone earthquakes in the moment range from 7 1027to 8 1029dyn cm are analyzed using an iterative deconvolution method in addition to discrete subevents which effectively contribute to the observed seismograms the long period component of the moment rate function is derived with the constraint that the total seismic moment is equal to the moment determined from long period surface waves it is shown that great earthquakes can be described by several subevents with a duration of about 10 s which changes little from earthquake to earthquake in the above moment range the long period component of the moment rate function becomes larger for a greater earthquake the greatest earthquakes of mw 9 additionally involve subevents with another duration scale much longer than 10 s it is also shown that the local stress drop is 1 order of magnitude larger than the stress drop averaged over the entire fault plane the constancy of the local stress drop as well as the average stress drop holds among various magnitudes of earthquakes these observations suggest an essential similarity in the mode of dislocation distribution

japan s sediment flux to the pacific ocean revisited abstract quantifying volumes and rates of delivery of terrestrial sediment from island arcs to subduction zones is indispensable for refining estimates of the thickness of trench fills that may eventually control the location and timing of submarine landslides and tsunami generating mega earthquakes despite these motivating insights knowledge about the rates of erosion and sediment export from the japanese islands to their pacific subduction zones remains patchy regardless of the increasing availability of highly resolved data on surface deformation climate geology and topography traditionally natural erosion rates across the island arc have been estimated from regression of topographic catchment metrics and reservoir sedimentation rates that were recorded over several years to decades we review current research in this context correct for a systematic bias in one of the most widely used predictions and present new estimates of decadal to millennial scale erosion rates of japan s terrestrial inner forearc we draw on several independent and unprecedented inventories of mass wasting reservoir sedimentation and concentrations of cosmogenic 10be in river sands we find that natural 10be derived denudation rates of several mm yr 1 in the japanese alps have been sustained over several centuries to millennia and are within error roughly consistent with sediment yields inferred from artificial reservoir sedimentation local exceptions may likely result from release of sediment storage or regional landsliding episodes that trigger transient sediment pulses our synopsis further reveals that catchments draining japan s eastern seaboard differ distinctly in their tectonic lithological topographic and climatic characteristics between the tohoku japanese alps and nankai inner forearc segments which is underscored by a marked asymmetric pattern of erosion rates along the island arc erosion rates are highest up to at least 3 mm yr 1 in the japanese alps that mark the collision of two subduction zones where high topographic relief hillslope and bedrock channel steepness foster rapid denudation by mass wasting comparable if slightly lower erosion rates characterise the nankai inner forearc in southwest japan most likely due to higher typhoon driven rainfall totals and variability rather than its high topographic relief in contrast our estimated erosion and flux rates are lowest in the tohoku inner forearc catchments that feed sediment into the japan trench we conclude that collisional mountain building of the japanese alps drives some of the highest erosion rates in the island arc despite similar uplift and precipitation controls in southwest japan we infer that prior to extensive river damming reservoir construction and coastal works the gross of japan s total sediment export to the pacific ocean entered the accretionary margin of the nankai trough as opposed to the comparatively sediment starved japan trench compared to documented contemporary rates of sediment flux from mountainous catchments elsewhere in the pacific the rivers draining japan s inner forearc take an intermediate position despite high relief steep slopes very high seismicity and frequent rainstorms however the average rates of millennial scale denudation in the japanese alps particularly are amongst the highest reported worldwide local mismatches between these late holocene and modern rates emphasise the anthropogenic fingerprint on sediment retention that may have significantly reduced the island arc s mass flux to its subduction zones as is the case elsewhere in east and southeast asia

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

surface cyclones in the era 40 dataset 1958 2001 part i novel identification method and global climatology abstract a novel method is introduced to generate climatological frequency distributions of meteorological features from gridded datasets the method is used here to derive a climatology of extratropical cyclones from sea level pressure slp fields a simple and classical conception of cyclones is adopted where a cyclone is identified as the finite area that surrounds a local slp minimum and is enclosed by the outermost closed slp contour this cyclone identification procedure can be applied to individual time instants and climatologies of cyclone frequency fc are obtained by simple time averaging therefore unlike most other climatologies the method is not based on the application of a tracking algorithm and considers the size of cyclones in combination with a conventional cyclone center tracking algorithm that allows the determination of cyclone life times and the location of cyclogenesis and cyclolysis additional frequency fields can be obtained for special categories of cyclones that are gener

quaternary siliciclastic sequence stratigraphy of western mediterranean passive and tectonically active margins the role of global versus local controlling factors

can the okhotsk plate be discriminated from the north american plate the plate geometry in northeast asia has been a long standing question with a major issue being whether the sea of okhotsk and northern japanese islands are better regarded as part of the north american plate or as a separate okhotsk plate this question has been difficult to resolve because earthquake slip vectors along the kuril and japan trenches are consistent with either pacific north america or pacific okhotsk plate motion to circumvent this difficulty we also use slip vectors of earthquakes along sakhalin island and the eastern margin of the japan sea and compare them to the predicted eurasia okhotsk and eurasia north america motions for a model with a separate okhotsk plate we invert 10 eurasia okhotsk and 255 pacific okhotsk slip vectors with pacific north america and eurasia north america nuvel 1 data alternatively for a model without an okhotsk plate those eurasia okhotsk and pacific okhotsk data are regarded as eurasia north america and pacific north america data respectively the model with an okhotsk plate fits the data better than one in which this region is treated as part of the north american plate because the improved fit exceeds that expected purely from the additional plate the data indicate that the okhotsk plate can be resolved from the north american plate the motions on the okhotsk plate s boundaries predicted by the best fitting euler vectors are generally consistent with the recent tectonics the eurasia okhotsk pole is located at northernmost sakhalin island and predicts right lateral strike slip motion on the nne striking fault plane of the may 27 1995 neftegorsk earthquake consistent with the centroid moment tensor focal mechanism and the surface faulting along the northern boundary of the okhotsk plate the north america okhotsk euler vector predicts left lateral strike slip consistent with the observed focal mechanisms on the nw boundary of the okhotsk plate the eurasia okhotsk euler vector predicts e w extension discordant with the limited focal mechanisms and geological data this misfit may imply that another plate is necessary west of the magadan region in southeast siberia but this possibility is hard to confirm without further data such as might be obtained from space based geodesy

biogenic opal indicating less productive northwestern north pacific during the glacial ages 1 biogenic opal and ice rafted detritus ird data from sediments in the okhotsk sea and the neighboring north pacific revealed the remarkable reduction in opal production and southward advancement of sea ice covered area during the last glacial maximum resulting also southward shift of high biological productive area in the northwestern north pacific it implies that the substantial reduction in outflux of co2 to the atmosphere in northwestern north pacific and the pronounced increase in co2 sequestering in temperate north pacific this could be an additional co2 reduction mechanism of atmospheric co2 in the last glacial period

distribution and modification of north pacific intermediate water in the kuroshio oyashio interfrontal zone abstract a multiship ctd survey was conducted in the kuroshio oyash interfrontal zone in the area of 30 41 n 140 e 180 from may to june 1992 to examine the distribution modification process and formation site of north pacific intermediate water npiw low salinity oyashio water and high salinity kuroshio water merge along the kuroshio extension just off the east coast of japan and together flow eastward eastward geostrophic transport and salinity across the kuroshio strong current indicate that the mixture of the kuroshio and oyashia waters along the kuroshio extension can produce new npiw transport estimate suggests that the new npiw bifurcates into the interfrontal zone and into the recirculation of the subtropical gyre a salinity minimum structure can he also created due to the isopycnal mixing along the kuroshio extension between the oyashio and kuroshio waters which have different salinity and vertical velocity structures the low salinity oyashio water seen along the oyashio branches and t

on the circulation of atlantic water in the arctic ocean an idealized eddy resolving numerical model and an analytic three layer model are used to develop ideas aboutwhatcontrolsthecirculationofatlanticwaterinthearctic ocean thenumericalmodelisforcedwith a surface heat flux uniform winds and a source of low salinity water near the surface around the perimeter of an arctic basin despite this idealized configuration the model is able to reproduce many general aspects of the arctic ocean circulation and hydrography including exchange through fram strait circulation of atlantic water a halocline ice cover and transport surface heat flux and a beaufort gyre the analytic model depends on a nondimensional number and provides theoretical estimates of the halocline depth stratification freshwater content and baroclinic shear in the boundary current an empirical relationship between freshwater content and sea surface height allows for a prediction of the transport of atlantic water in the cyclonic boundary current parameters typical of the arctic ocean produce a cyclonic boundary current of atlantic water of o 1 2 2sv where 1sv 10 6 m 3 s 21 and a halocline depth of o 200m in reasonable agreement with observations the theory compares well with a series of numerical model calculations in which mixing and environmental parameters are varied thus lending credibility to the dynamics of the analytic model in these models lateral eddy fluxes from the boundary and vertical diffusion in the interior are important drivers of the halocline and the circulation of atlantic water in the arctic ocean

role of oblique convergence in the active deformation of the himalayas and southern tibet plateau noting similarities with subduction along curved oceanic trenches and using a simple block model we show that radial vergence evident in earthquake slip vectors along the himalayan deformation front east west extension on north trending normal faults in the himalayas and southern tibet and right lateral strike slip on the karakorum jiali fault zone can all result from basal shear caused by the indian plate sliding obliquely beneath tibet along a gently dipping arcuate plate boundary within the framework of this mechanism the normal faults in the himalayas and southern tibet are not proxies for the uplift history of tibet the distribution and style of the faults in the himalayas and southern tibet suggest that the basal drag from the underthrusting indian lithosphere extends northward beneath most of southern tibet

erosion thresholds and suspended sediment yields waipaoa river basin new zealand characteristics of the suspended sediment load in the waipaoa river new zealand and in two of its tributaries mangatu and te arai rivers are examined for evidence of different dominant erosion processes in the basins upstream different shapes of the suspended sediment concentration water discharge relations lead to differences in long term average yield event yield magnitude frequency relations and relative importance of large flows and rare events in the mangatu river frequent runoff events 2 1 are relatively more important to the long term yield 11 540 t km yr half of the long term average load is transported by events with return periods less than 1 year and there is little evidence of an erosion threshold limitation on sediment supply this is consistent with the predominance in the mangatu basin of hillslope erosion processes that involve scour by surface and channelized runoff particularly gully erosion this contrasts with the te arai river where sediment concentration tends to be much lower at low and moderate flows frequent runoff events transport less of the long term yield 4600 t km 2 yr than do rarer large magnitude flood events event sediment yields are an order of magnitude lower during events with subannual return periods and half of the long term average load is transported during events with a return period of 2 years some of these characteristics appear to result in part from two populations of runoff events in the te arai basin nonetheless they are consistent with field evidence that most of the sediment supplied to the te arai stream network is generated by shallow landslides which are activated once a rainfall threshold is exceeded

unstable forearc stress in the eastern nankai subduction zone for the last 2 million years abstract transpressional tectonics characterizes the sw japan arc however we will show in this article that offshore seismic profiles and onshore mesoscale faults indicate that the eastern part of the forearc was subject to transtensional tectonics since ca 2 0 ma offshore normal faults imaged on the profiles run parallel to the nankai trough and started activity at 1 0 ma but transtensional tectonics commenced the onshore area earlier in order to understand the stress history in the forearc region we collected fault slip data from onshore mesoscale faults in plio pleistocene sedimentary rocks in the kakegawa area at the northeastern extension of the offshore normal faults most of the mesoscale faults are oblique normal indicating that the area was subject to transtensional tectonics the faults suggest that the compressional tectonic regime was followed by the transtensional one at 2 0 ma in agreement with regional tectonostratigraphic data which indicate that folding ceased at that time present compressional stress followed the transtensional tectonic regime sometime in the late pleistocene transtensional or extensional tectonic zone shifted from the kakegawa area to the offshore region these observations indicate that the state of stress just behind the accretionary prism of the eastern nankai subduction zone has been unstable in the last 2 million years suggesting that the forearc wedge has been at critical state in that gravitational force and basal shear traction on the wedge have been balanced but the forearc tectonics has been susceptible to small perturbations possible factors compatible with the observed stress history include the change of subduction direction of the plate at 1 0 ma and the rapid uplift of central japan thereafter

paleoseismicity along the southern kuril trench deduced from submarine fan turbidites abstract large m 8 damaging interplate earthquakes occur frequently in the eastern hokkaido region northern japan where the pacific plate is subducting rapidly beneath the okhotsk north american plate at approximately 8 cm yr 1 with the aim of estimating the long term recurrence intervals of earthquakes in this region seven sediment cores were obtained from a submarine fan located on the forearc slope along the southern kuril trench japan the cores contain a number of turbidites some of which can be correlated among the cores on the basis of the analysis of lithology chronology and the composition of sand grains foraminiferal assemblages and the composition of sand grains indicate that the upper middle slope 1000 m water depth is the source of the turbidites the deep sea origin of the turbidites is consistent with the hypothesis that they were derived from slope failures initiated by strong shaking associated with earthquake events the recurrence intervals of turbidite deposition are 113 439 yr for events that occurred over the past 7 kyr the short intervals are recorded in the cores obtained from levees on the middle fan although many large earthquakes 150 cm s 2 of peak ground acceleration at the inferred slump sources occurred during the 19th and 20th centuries the pilot core from the upper fan contains only three turbidites located stratigraphically above layers of 17th century volcanic ash the results of 210pbex and 137cs dating combined with simulations of the ground accelerations of historical earthquakes enable correlation of the three turbidites with known historical earthquakes the 1952 tokachi oki and the 1961 and 1973 nemuro oki earthquakes the turbidites within the sampled cores potentially record about half of the large earthquakes known to have occurred over the interval covered by the cores the fact that any single core records only a portion of the known seismic events suggests that the recurrence interval of earthquakes in this region is less than 113 yr during holocene

wintertime warming of an arctic shelf in response to large scale atmospheric circulation 1 observations on the west spitsbergen shelf have shown that the dynamic response of the shelf to wind forcing has a profound effect on the heat content of the water hydrographic and atmospheric data have been analysed with respect to the relative importance of surface heat fluxes and advective processes on ocean temperature during the arctic winter of 2005 06 periods of sustained along shelf winds generated upwelling and cross shelf exchange causing extensive flooding of the coastal waters with warm atlantic water from the west spitsbergen current the winter temperature of the west spitsbergen shelf reverted to that typical of fall interrupting the normal cycle of sea ice formation in the region

holocene sediment deposition on the poverty slope margin by the muddy waipaoa river east coast new zealand the margin off the raukumara peninsula east coast north island of new zealand is characterised by high terrigenous sediment flux the dramatic effects of historic land use change the rapid uplift of mesozoic and soft tertiary sediments and by complex sediment tectonic interactions on a steep and unstable continental slope the poverty bay shelf and slope indentation are adjacent to the waipaoa river which delivers 15 mt year 1 of mud this study presents new data from the poverty slope the seaward extension of the waipaoa dispersal system a 3 km3 lobe of postglacial sediment emerges from the poverty gap and feathers down onto the upper slope downslope the poverty indentation has received a significant holocene flux of terrigenous sediment accumulating in two mid slope basins the paritu trough and a smaller lower slope basin below the south paritu ridge hemipelagic sediment has accumulated on the mid slope at around 0 05 g cm 2 year 1 0 06 cm year 1 since the mid late holocene seismic reflection echo type and backscatter imagery indicate mud deposits on the mid slope debris at the base of regularly spaced upper slope gullies and a large avalanche deposit in the upper paritu trough the consistency of the tephrostratigraphy indicates that despite slope instability hemipelagic sedimentation is the dominant background process operating at millennial time scales at least since the mid holocene the poverty slope should be included in any budget calculation of post colonisation increased sediment yield for the margin the poverty canyon has probably been largely inactive during the holocene highstand

episodic emergence in the past 3000 years at the akkeshi estuary hokkaido northern japan at the akkeshi estuary rapid emergence interrupted holocene submergence at least four times in the past 3000 years each emergence event produced an upward change from estuarine mud to freshwater peat while the estuarine mud abounds in brackish and marine diatoms freshwater taxa dominate the peat emergence events occurred from 1700 to 2300 1000 to 1300 and 500 to 700 cal yr b p an additional emergence event predated by several decades a volcanic ash that erupted in a d 1694 at least three of the events produced contacts abrupt enough to represent uplift during earthquakes such uplift may reconcile seemingly conflicting records of vertical crustal movement in eastern hokkaido this tectonically active area which is being subducted by the pacific plate at 8 cm yr contains marine terraces that imply 0 1 0 5 mm yr of net uplift in the late quaternary however these terraces adjoin tide gages that recorded 8 9 mm yr of steady submergence in the 20th century the terrace uplift need not conflict with the gaged submergence if the region is subject to occasional coseismic uplift as during the emergence events implied by holocene geology near akkeshi

acoustical characterization of sediments by parasound and 3 5 khz systems related sedimentary processes on the southeastern weddell sea continental slope antarctica subbottom profiling was performed during four polarstern expeditions to the southeastern weddell sea continental slope northwest of lyddan ice rise antarctica analogue records from high resolution seismic reflection systems 3 5 khz and parasound were used to classify sediment echo types a comparison between the two systems shows the advantage of the parasound system the smaller beam angle produces a higher spatial resolution which reduces the diffraction hyperbolae considerably the higher vertical resolution and deeper penetration provide more detailed information concerning seismic stratification using four basic echo categories p prolonged l layered d diffraction hyperbolae w wedging subbottoms ten discrete sediment echo patterns were distinguished their regional distribution and the depth of acoustic signal penetration into the sediment were mapped sw ne trending sediment ridges with channels running parallel on the southeastern side of the ridges were traced in the eastern part of the study area the prolonged and highly reflective echo types of the channel bottoms indicate deposition of predominantly coarse grained sediments affected by erosional processes these channels are interpreted as drainage systems for bottom water currents derived from the shelf and steep upper slope the flow direction is towards the northeast counter to the weddell gyre in contrast the sediment ridges show up to 80 m subbottom penetration and an echo type of distinct multi layered reflectors running parallel to subparallel with the surface reflector the sediments of the ridges are interpreted to be levee sediments overspilled from the channels and preferentially deposited on the northwestern flank due to the coriolis force sedimentary units separated by wedge shaped reflectors are widespread on the gently inclined terrace in the middle part of the continental slope these sediments are presumed to be produced by syn sedimentary slumping and proximal debris flows having a northeastern direction of movement

waters of the makarov and canada basins abstract hydrographic measurements from the 1994 arctic ocean section show how the makarov and canada basins of the arctic ocean are related and demonstrate their oceanographic connections to the eurasian basin the inflow into the makarov basin consists largely of well ventilated water within a broad band of densities from a boundary flow over the siberian end of the lomonosov ridge the boundary flow contains a significant component of dense shelf water likely originating in the barents kara and laptev seas earlier ice camp data show that the canada basin is relatively more isolated from this ventilation source in the canada basin shelf sources influenced by bering sea water appear to add cold waters with high silicate concentrations to the halocline and deeper in 1994 the halocline silicate maximum over the central makarov basin was absent evidence of the recent displacement of the upper s 33 1 halocline water from the chukchi east siberian sea region by water from the eurasian basin much of the makarov basin water in and below the halocline is in fact from the eurasian basin with admixture of waters from the canada basin suggested by their higher silicate concentrations mid depth eddies may transport anomalous properties into the central arctic and create property gradients or fronts in mid depth and deep waters the complex topography of the mendeleyev ridge chukchi plateau region also may assist spreading of water from the boundary into the interior atlantic layer characteristics in 1994 differed from previous general depictions in particular the core temperatures at the chukchi mendeleyev boundary were at least 0 2 c warmer on average than indicated in earlier work the recent warming at intermediate depth has resulted from inflow of atlantic waters that have been cooled relatively little during their transit of the norwegian sea

variations in sediment texture on the northern monterey bay national marine sanctuary continental shelf abstract the storm protected continental shelf of monterey bay part of the monterey bay national marine sanctuary north central california is subject to abundant episodic sediment input from fluvial sources north of monterey bay conditions of reduced sediment supply combined with the exposed nature of the shelf provide an effective laboratory for studying the contrasting effects of storm versus fluvial dominated conditions on modern sedimentation textural analyses performed on surface sediment samples collected from more than 380 box cores and multicores document the existence of a clearly defined mud belt occupying the mid shelf throughout the region inshore sands combined with these mid shelf muds represent deposits from modern sedimentation processes in monterey bay where episodic fluvial input from winter storms dominates sedimentation the mid shelf mud belt extends across the shelf to the shelf break north of monterey bay where sediment loads are reduced and both oceanographic and storm processes dominate the mid shelf mud belt is bordered by relict sediments occupying the outer shelf in the study area mass accumulation rates established by radiochemical studies support the contention that storm induced along shelf processes result in northward transport of sediment within the mud belt the continuity of transport however is interrupted by topographic highs which are barriers or inhibitors to sediment transport created by wrench style tectonics associated with the san andreas fault system

significant role of the north icelandic jet in the formation of denmark strait overflow water the largest dense water plume feeding the lower limb of the atlantic meridional overturning circulation from the nordic seas comes from denmark strait overflow water measurements of hydrography and water velocity north of iceland and ocean model simulations indicate that a significant part of this water is supplied by the north icelandic jet

across shelf sediment transport since the last glacial maximum southern california margin correlation of continental shelf slope stratigraphy in santa monica bay southern california with ocean drilling program records for nearby slope basin sites has illuminated the timing and scale of terrigenous sediment dispersal on margin since the last glacial maximum lgm marine flooding surfaces preserved in a transgressive sequence on the santa monica shelf provide a key link between base level elevation and sediment transport across shelf sediment accumulation rates at slope basin sites were maximal ca 15 10 ka well after the lgm decreased during the 12 9 ka transition from fluvial estuarine to fully marine conditions on the shelf and decelerated throughout the holocene to 30 75 of their values at the lgm the deceleration is interpreted to manifest a landward shift in the margin depocenter with the onset of transgressive sedimentation beginning when sea level surmounted the shelf edge ca 13 ka as predicted by sequence stratigraphic models however the records make clear that factors other than base level modulated slope basin accumulation rates during the deglaciation

collision rotation and back arc spreading in the region of the okhotsk and japan seas the india eurasia collision caused extensive deformation in the eurasia continent since late eocene time we propose that back arc spreading in the okhotsk and japan seas was related to the movement of microplates relevant to the india eurasia collision the kuril basin of the okhotsk sea and the basins of the japan sea were formed as back arc basins simultaneously their late oligocene to middle miocene age is constrained by sediment stratigraphy basement depth and heat flow data the movements of two microplates the okhotsk and amuria plates are significant for the tectonics of the okhotsk and japan seas simultaneous retreat of both microplates from trench hinge lines caused back arc spreading in the kuril basin and the japan sea the amuria plate moved north northeastward due to the india eurasia collision this caused pull apart opening of the baikal rift along a transform boundary between the siberia and amuria plates and a collision along the stanovoy range at its northern margin this movement triggered a clockwise rotation of the okhotsk plate with a component of dextral collision between the okhotsk and amuria plates which is well observed along the central zone of the sakhalin hokkaido islands between the two back arc plates the clockwise rotation of the okhotsk plate is suggested by the southwestward fan shaped opening of the kuril basin the kuril basin narrows to the northeast and terminates south of the kamchatka peninsula where a relative rotation pole between the okhotsk and kuril forearc plates is located the kamchatka peninsula was a zone of collision on the other side of the clockwise rotating okhotsk plate during the opening of the kuril basin the sredinny range in the kamchatka peninsula is one of the results of the collision between the okhotsk plate and the forearc plate of the kuril arc the bending of the japanese islands occurred in association with the back arc spreading of the yamato basin of the japan sea

aseismic faulting following the 1973 nemuro oki earthquake hokkaido japan a retrospective study tidal records at hanasaki southeastern hokkaido are analysed to clarify the post seismic crustal vertical movement in the 1973 nemuro oki japan earthquake the result shows that the post seismic uplift as speculated bykasahara 1975 terminated in late 1975 and reverted to the previous rate of rapid subsidence of about 1 cm yr ceasing of the post seismic uplift which occurred much earlier than previously speculated could be explained by supplementary mechanisms such as frictional resistance against creeping at the fault surface this unexpected mode of movement however raises a new question about the accumulation of tectonic movements in this district since the subsidence rate extrapolated from geomorphological data for the past several thousand years is almost one order of magnitude lower than the recent rate as mentioned above we have to provide some alternative explanation for the discrepancy between the two rates in other words simple repetition of co post and inter seismic movements in seismic cycles due to plate subduction must be modified in this district several possible modifications to the subduction process are suggested and a brief discussion of vertical movements expected in each case is given

the atlantic water boundary current in the nansen basin transport and mechanisms of lateral exchange data from a shipboard hydrographic survey near 30 e in the nansen basin of the arctic ocean are used to investigate the structure and transport of the atlantic water boundary current two high resolution synoptic crossings of the current indicate that it is roughly 30 km wide and weakly mid depth intensified using a previously determined definition of atlantic water the transport of this water mass is calculated to be 1 6 0 3 sv which is similar to the transport of atlantic water in the inner branch of the west spitsbergen current at the time of the survey a small anti cyclonic eddy of atlantic water was situated just offshore of the boundary current the data suggest that the feature was recently detached from the boundary current and due to compensating effects of temperature and salinity on the thermal wind shear the maximum swirl speed was situated below the hydrographic property core two other similar features were detected within our study domain suggesting that these eddies are common and represent an effective means of fluxing warm and salty water from the boundary current into the interior an atmospheric low pressure system transiting south of our study area resulted in southeasterly winds prior to and during the field measurements a comparison to hydrographic data from the pacific water boundary current in the canada basin under similar atmospheric forcing suggests that upwelling was taking place during the survey this provides a second mechanism related to cross stream exchange of heat and salt in this region of the nansen basin this article is protected by copyright all rights reserved

the origin of summit basins of the aleutian ridge implications for block rotation of an arc massif it is proposed that many summit basins along the aleutian arc form from the clockwise rotation of blocks of the arc massif summit basins are arc parallel grabens or half grabens formed within the arc massif and are commonly located near or along the axis of late cenozoic volcanism geomorphically the aleutian arc appears to consist of contiguous rhombic blocks of varying size tens to hundreds of kilometers in length the boundaries between adjacent blocks are delineated by fault controlled canyons that cut the southern slope of the arc transverse to its regional trend evidence that these blocks have rotated clockwise is provided by the triangular shaped summit basins bordering the blocks to the north oblique physiographic trends offsets in the summit platform and broad deflections in the southern slope of the arc we present a model for block rotation that involves translation of blocks parallel to an arc it is suggested that block rotation which appears to have accelerated in late cenozoic time is linked to 1 a shift in the euler pole for the pacific plate 2 the consequential start up of late cenozoic volcanism 3 improved interplate coupling instigated by sediment flooding of the aleutian trench and 4 westward subduction of northeast striking segments of the inactive kula pacific ridge

controls of tectonics and sediment source locations on along strike variations in transgressive deposits on the northern california margin abstract we identify two surfaces in the shallow subsurface on the eel river margin offshore northern california a lowstand erosion surface likely formed during the last glacial maximum and an overlying surface likely formed during the most recent transgression of the shoreline the lowstand erosion surface which extends from the inner shelf to near the shelfbreak and from the eel river to trinidad head 80 km truncates underlying strata on the shelf above the surface inferred transgressive coastal and estuarine sedimentary units separate it from the transgressive surface on the shelf early in the transgression eel river sediment was likely both transported down the eel canyon and dispersed on the slope allowing transgressive coastal sediment from the smaller mad river to accumulate in a recognizable deposit on the shelf the location of coastal mad river sediment accumulation was controlled by the location of the paleo mad river throughout the remainder of the transgression dispersed sediment from the eel river accumulated an average of 20 m of onlapping shelf deposits the distribution and thickness of these transgressive marine units was strongly modified by northwest southeast trending folds thick sediment packages accumulated over structural lows in the lowstand surface the thinnest sediment accumulations 0 10 m were deposited over structural highs along faults and uplifting anticlines the eel margin an active margin with steep high sediment load streams has developed a thick transgressive systems tract on this margin sediment accumulates as rapidly as the processes of uplift and downwarp locally create and destroy accommodation space sequence stratigraphic models of tectonically active margins should account for variations in accommodation space along margins as well as across them

seventeenth century uplift in eastern hokkaido japan shores of eastern hokkaido rose by perhaps i m a few centuries ago the uplifted area extended at least 50km along the southern kuril trench it included the estuaries akkeshi ko and hichirippu on

interplate coupling in northeast japan deduced from inversion analysis of gps data abstract the spatial distribution of the strength of interplate coupling between the subducting pacific plate and the overlying continental plate in northeast japan was investigated through an inversion analysis of gps data employing akaike s bayesian information criterion the gps data used for the inversion analysis are rates of baseline length changes and vertical displacement rates of crustal movements during the period from april 6 1996 to march 20 1998 which were obtained at 161 continuous gps observation stations operated by the geographical survey institute of japan the result shows the average drag rates of the overriding plate on the model source regions off the tohoku and hokkaido districts are 6 7 cm yr and 6 8 cm yr respectively which are 0 85 and 0 87 as interplate coupling ratio these values are much higher than those in previous studies the average directions of drag rates are oriented n73 w 15 and n78 w 13 on the model source regions off the tohoku and hokkaido districts respectively these directions agree well with the direction of coseismic slip of the foot wall side n75 w of the 1978 miyagiken oki earthquake m 7 4 but differ slightly from the direction estimated from the plate motion model n65 w seno et al j geophys res 101 1996 11305 11315 we also found afterslip of 5 5 cm yr associated with the 1994 sanriku haruka oki earthquake m 7 5 off aomori prefecture interestingly enough large afterslip occurred on the plate boundary even when more than a year had passed after the sanriku haruka oki earthquake the amount of drag rate becomes dramatically small at depths greater than about 50 km on the model source regions indicating weak interplate coupling there