coulomb stress changes following the 2012 mw 7 8 haida gwaii canada earthquake implications for seismic hazard this article examines spatial changes to the local stress field resulting from the 28 october 2012 m w 7 8 haida gwaii earthquake off the west coast of moresby island british columbia this event occurred on a northeast dipping potentially blind thrust fault rather than on the subvertical queen charlotte fault qcf that represents the pacific north american plate boundary this was the largest earthquake along the canadian portion of this plate boundary since the 1949 m s 8 1 queen charlotte earthquake the u s geological survey coulomb software is used to quantitatively estimate the effect of the mainshock on the background stress field the known aftershock nodal planes and the nearby qcf we use two different mainshock finite fault models both of which are seismologically derived by lay et al 2013 and hayes 2013 separately and subsequently adapted by k wang to account for the motion detected at four nearby global positioning system stations see nykolaishen et al 2015 for more information we also use the best located set of aftershocks with information provided by a temporary array of ocean bottom seismometers results indicate an apparent clustering of aftershocks slightly seaward of the main thrust which is consistent with the modeled zone of promoted normal failure likely related to extension in the footwall using existing models we found a high number of aftershocks to be consistent with triggering by the mainshock suggesting that static stress is a dominant control in the months following a large earthquake in this area further we find loading greater than the triggering threshold on the qcf in an area interpreted as a seismic gap this work improves understanding of the evolving seismic hazard along the queen charlotte margin and tests the usefulness of coulomb modeling in this complex tectonic environment online material figures of focal mechanisms and maximum coulomb stress change and table of aftershock moment tensor parameters

geologic investigations of a slip gap in the surficial ruptures of the 1992 landers earthquake southern california a 3 km long gap in the dextral surficial rupture of the 1992 mw 7 3 landers earthquake occurs at the north end of a major fault stepover between the johnson valley and homestead valley faults this gap is situated along a segment of the landers rupture that has been modeled geophysically as having a deficit in average slip at depth to better evaluate the nature of the slip gap we document in detail the character and distribution of surficial rupture within it along the gap is a northwest trending thrust fault rupture with an average of less than 1 rn of northeast directed reverse slip and nearly no oblique right slip we interpret this rupture to be limited to the shallow crust of the northern end of the stepover and to have been the secondary result of dextral shear rather than a mechanism of rigid block slip transfer from the landers kickapoo fault a zone of en echelon extensional ruptures also occurs along the slip gap which we interpret as the secondary result of diffuse dextral shear that accommodated less than 0 5 rn of west northwest extension these secondary ruptures represent a discontinuity in the surficial dextral rupture of the landers earthquake which we propose resulted from the lack of a mature fault connection between the johnson valley and homestead valley faults the rupture pattern of the slip gap implies a significant deficit in net surficial slip which compares favorably with some geophysical models aspects of this rupture pattern also suggest a temporal sequence of rupture that compares favorably with geophysical interpretations of the dynamic rupture propagation

recent sediment accumulation and origin of shelf mud deposits in the yellow and east china seas abstract modern last 100 yr accumulation rates of shelf mud deposits in the yellow and east china seas were investigated using the distribution of excess 210pb 210pbex in sediment core samples compilation and merger of new and previously published data helped clarify sediment accumulation in these seas the estimated accumulation rates together with data of suspended sediment concentrations provided findings on the sediment budget origin and transport pathway of the mud deposits the overall accumulation distribution in the yellow and east china sea shelf revealed a general cross shelf decreasing trend along the sediment dispersal system away from the rivers except for the south sea ssm and southeastern yellow sea seysm mud patches found along the korean coast notably 210pbex activity profiles within the ssm and the seysm yielded a relatively high accumulation rate of 2 5 mm yr implying a sedimentation rate of 4 15 107 tons per year in this coastal zone such an annual accumulation rate is about one order of magnitude greater than the total sediment discharge 6 20 106 tons yr from korean rivers suggesting an additional offshore source the distribution pattern of the well defined suspended plume clearly showed the possible transport and exchange of fine grained sediments between the ecs shelf and the coastal area of korea especially during winter such a high accumulation in korean coastal areas is attributable to the sediments supplied from the mud deposit of the ecs i e swcim with origins in chinese rivers therefore the korean coastal area may be an important sink for some of chinese river sediments being transported from the south by the yellow sea warm current

sediment distribution circulation and provenance in a macrotidal bay garolim bay korea abstract a study of the sedimentary regime in garolim bay has been carried out in connection with a feasibility study for tidal power development at the mouth of the bay sand is shown to be circulating round a central bank between an ebb and a flood channel in the middle bay clay and heavy mineral distributions indicate a zone where finer sediments derived from offshore mix with those originating from the local streams quantities of land derived sediments are presumed to be deposited near the shores during the rainy summer season and these are redistributed during the windy winter season but the concentrations of suspended sediment are generally low the influx of sediment appears to largely balance the increase in sea level siltation over the general area may not be seriously increased after construction of a barrage but local siltation and scour near the barrage could be serious problems

variability and forcing of the east australian current 1 the spatial and temporal variability of the east australian current eac is investigated using 6 years 1993 1998 of surface geostrophic stream function from an optimal interpolation of altimeter sea surface heights and velocities derived from tracking thermal features in satellite imagery variability appears as a series of cyclones and anticyclones propagating southwestward and westward with periods between 90 and 180 days the behavior of the variability changes over the 6 years energy in the mesoscale frequencies moves slowly south and diminishes with more westward propagation in the region where the current separates from the coast we find no evidence for a consistent forcing of the eac by mesoscale signals propagating westward from the south pacific basin we suggest that the observations are consistent with variability originating between 32 s and 35 s through intrinsic instabilities of the current

stratigraphy of late quaternary deposits using high resolution seismic profile in the southeastern yellow sea abstract high resolution chirp and sparker system seismic profiles were analyzed to investigate the sequence stratigraphy of late quaternary deposits in the southeastern yellow sea approximately 1560 line km data of chirp and sparker profiles were acquired together with 11 piston cores two previous long drill cores ysdp 102 and 103 were used for comparison with seismic data high resolution seismic profiles image the holocene mud deposits and the complex sedimentary structure in this area sequence analysis of high resolution seismic profiles reveals that the shelf deposits form a succession of high frequency five order sequences consisting of one depositional sequence developed during the late quaternary the depositional sequence includes five sedimentary units each with different seismic facies and geometry 1 incised channel fill and lowstand deltaic wedge unit sy1 2 sand ridges unit sy2 3 estuarine deltaic mud unit sy3 4 redeposited mud unit sy4 and 5 recent distal mud unit sy5 based on the interpretation of high resolution seismic records and correlation with the ysdp 102 103 long cores and piston cores late quaternary deposits in the southeastern yellow sea consists of a set of the lowstand unit sy1 early transgressive unit sy2 middle transgressive unit sy3 late transgressive unit sy4 and highstand systems tract unit sy5 formed since the last glacial period the rather unusual stratigraphic architecture including three systems tracts is largely controlled by the postglacial sea level changes and regionally circulation pattern associated with sediment erosion and redeposition the results of this study present firstly clear seismic evidence that the southeastern yellow sea mud belt seysm can be divided into three stratigraphic units units sy3 sy4 and sy5 bounded by distinct bounding surfaces

contribution of radar interferometry to a two step inversion of the kinematic process of the 1992 landers earthquake we study the rupture process of the 1992 landers earthquake to limit the trade off between slip amplitude and rupture time that affects solutions using only seismological data we adopt a two step approach we first constrain the slip distribution and its uncertainty by independent geodetic data to recover in the second step the temporal details of the rupture propagation the first step consists of an inversion of interferometric data and global positioning system measurements both independently and together to constrain slip distribution on a three segment fault model along both strike and dip direction we use a genetic algorithm to test the uniqueness of the solution and a least squares formulation to find the model which best fits the data we conclude from the results of these geodetic inversions that interferometric data are rich enough to access the slip distribution in the case of the landers earthquake since the surface deformations are more sensitive to shallow slip in our configuration the slip amplitude is better resolved near the surface than at depth the resulting slip distribution is in agreement with geological observations at the surface and confirms the heterogeneous nature of the landers earthquake most of the slip occurs at shallow depths on the homestead valley fault second segment with a maximum value of around 7 m another high slip zone is observed on the johnson valley fault first segment at 8 km depth in the second step we invert strong motion data with the a priori final slip amplitude and its uncertainty deduced from geodetic data to constrain the time history of the rupture process this second step emphasizes a strong variation of the temporal development of the earthquake fast rupture front velocities appear within high slip zones and the rupture slows when it encounters a resistance along the fault on average the rupture front propagates with velocities close to the s wave velocity and terminates about 20 s after initiation the large variations in both slip amplitude and rupture velocity suggest that the rupture process is better described by successively breaking asperities than by a pulse propagating with constant velocity

the stress shadow problem in physics based aftershock forecasting does incorporation of secondary stress changes help main shocks are calculated to cast stress shadows across broad areas where aftershocks occur thus a key problem with stress based operational forecasts is that they can badly underestimate aftershock occurrence in the shadows we examine the performance of two physics based earthquake forecast models coulomb rate state crs based on coulomb stress changes and a rate and state friction law for their predictive power on the 1989 mw 6 9 loma prieta aftershock sequence the crs 1 model considers the stress perturbations associated with the main shock rupture only whereas crs 2 uses an updated stress field with stresses imparted by m 3 5 aftershocks including secondary triggering effects slightly improves predictability but physics based models still underestimate aftershock rates in locations of initial negative stress changes furthermore crs 2 does not explain aftershock occurrence where secondary stress changes enhance the initial stress shadow predicting earthquake occurrence in calculated stress shadow zones remains a challenge for stress based forecasts and additional triggering mechanisms must be invoked

on the east australian current variability encroachment and upwelling 1 observations from an intensive oceanographic field program which took place in 1998 1999 about the separation point of the east australian current eac show significant spatial and temporal variability of the eac upstream of the separation point southward flowing currents are strong with subinertial velocities of up to 130 cm s 1 in the near surface waters whereas downstream currents are highly variable in both strength 1 70 cm s 1 and direction upwelling is observed to occur through both wind driven and current driven processes with wind effects playing a lesser role by contrast the encroachment of the eac upon the coast has a profound effect on the coastal waters accelerating the southward alongshore currents and decreasing the temperature in the bottom boundary layer bbl by up to 5 degreesc as the axis of the jet moves onshore negative vorticity increases in association with an increase in nonlinear acceleration during this time bottom friction is increased the burger number is reduced and the bbl shut down time lengthens the observed upwelling is attributed to enhanced onshore ekman pumping through the bbl resulting from increased bottom stress as the southerly flow accelerates when the eac encroaches across the continental shelf

crustal structure and seismicity distribution adjacent to the pacific and north america plate boundary in southern california new three dimensional 3 d v p and v p v s models are determined for southern california using p and s p travel times from local earthquakes and controlled sources these models confirm existing tectonic interpretations and provide new insights into the configuration of geological structures at the pacific north america plate boundary the models extend from the u s mexico border in the south to the southernmost coast ranges and sierra nevada in the north and have a 15 km horizontal grid spacing and an average vertical grid spacing of 4 km down to 22 km depth the heterogeneity of the crustal structure as imaged by v p and v p v s models is larger within the pacific plate than the north american plate similarly the relocated seismicity deepens and shows more complex 3 d distribution in areas of the pacific plate exhibiting compressional tectonics the models reflect mapped changes in the lithology across major geological terranes such as the mojave desert the peninsular ranges and the transverse ranges the interface between the shallow mono of the continental borderland and the deep moho of onshore california forms a broad zone to the north beneath the western transverse ranges ventura basin and the los angeles basin and a narrow zone to the south along the peninsular ranges the near surface increase in velocity from the surface to up to 8 km depth is rapid and has a logarithmic shape for stable blocks and mountain ranges but is slow with a linear shape for sedimentary basins at midcrustal depths a rapid increase in v p is imaged beneath the sediments of the large sedimentary basins while beneath the adjacent mountain ranges the increase is small or absent

a northern boundary current along australia s southern shelves the flinders current 1 south of australia the monthly mean wind stress curl is positive during both summer and winter and leads to ekman pumping and downwelling throughout the region sverdrup dynamics indicates that this downwelling should lead to a northward transport of around 5 10 sv 1 sv 10 m3 s 1 classical arguments for western boundary currents are adapted to show that this transport should be deflected into an upwelling favorable boundary current that flows from east to west along australia s southern shelves the flinders current support for this proposition is obtained from results of the ocean circulation and climate advanced modelling project occam sverdrup transports and limited observations for the region in addition the occam results show that the northward transport leads to upwelling at depths below 400 m and that the flinders current 1 intensifies from victoria to western australia transport 8 sv with speeds up to 15 cm s 1 2 can extend from the surface to depths of 800 m and 3 is found during both summer and winter during winter the winds are downwelling favorable and lead to a coastal current that flows from west to east and opposes the flinders current further support for the origin and nature of the flinders current is obtained from simple numerical experiments made using a rectangular domain and idealized representations of the summer and winter wind stress

spatial aftershock distribution effect of normal stress we study the spatial clustering of shallow aftershock hypocenters with respect to focal mechanisms of mainshocks we use the harvard centroid moment tensor cmt global catalog the preliminary determination of epicenters pde earthquake list the california institute of technology u s geological survey catalog of earthquakes in southern california and a catalog of focal mechanisms for all earthquakes since 1850 in southern california with magnitude larger than 6 we need to account for possible systematic bias in hypocenter distribution due to the geometry of seismogenic zones especially that of subduction zones we also select only strike slip earthquakes from the catalogs to investigate aftershock clustering in circumstances more favorable for direct observation we compare the spatial distribution of hypocenters before each strong earthquake with the distribution during the first 250 days after the earthquake and for the time interval extending beyond 250 days if the friction coefficient in the coulomb criterion is positive one expects that after a strong earthquake aftershocks and other earthquakes would concentrate in the direction of the p axis dilatational quadrant rather than in the direction of the t axis compression quadrant such correlations have been pointed out previously for selected earthquakes sequences but is such correlation a general feature of earthquake occurrence we study spatial earthquake distributions before and after each event for several choices of focal sphere partition cutoff magnitude focal mechanisms of large events time periods distance from a mainshock etc although some earthquake distributions agree with a nonzero friction coefficient others produce the opposite pattern suggesting that the concentration of events along the p and t axes is due to random effects this result implies that the friction coefficient in the coulomb law is close to zero

a review on the provenance discrimination of sediments in the yellow sea the yellow sea has been extensively studied for the understanding of dispersal patterns and limits of sediments from neighboring countries including china and korea although sedimentological mineralogical and geochemical approaches have been tried to solve the problems especially including the identification of sediment sources in and around the yellow sea the published results are not enough for understanding them suggestions on sediment origins budgets sediment accumulation rates mineralogical and geochemical compositions are not coincident to each other and sometimes even controversial for example conflicts on the distribution patterns of smectite and calcium carbonate the provenance of the southeastern yellow sea mud and sedimentation rates in there the ratios of v al and mn al in korea and china river sediments the origin of ba and pb in sandy sediments of the northeastern yellow sea and so on various geochemical indicators from the literature for the provenance discrimination in the yellow sea are reviewed here in depth and corresponding discussions are described separately research topics for the future study also are suggested for the proper access to the understanding of the origin and dispersal patterns of the yellow sea sediments especially focusing on the geochemical approaches d 2003 elsevier science b v all rights reserved

changes in static stress on southern california faults after the 1992 landers earthquake the magnitude 7 5 landers earthquake of 28 june 1992 was the largest earthquake to strike california in 40 years the slip that occurs in such an earthquake would be expected to induce large changes in the static stress on neighbouring faults these changes in stress should in turn affect the likelihood of future earthquakes stress changes that load faults towards failure have been cited as the cause of small1 5 moderate6 and large7 earthquakes conversely those that relax neighbouring faults have been related to a decrease in seismicity5 here we use an elastic half space model8 to estimate the stress changes produced by the landers earthquake on selected southern california faults including the san andreas we find that the estimated stress changes are consistent with the triggering of four out of the five aftershocks with magnitude greater than 4 5 and that the largest changes 1 10 bar occurring on part of the san bernardino segment of the san andreas fault may have decreased the time to the next magnitude 8 earthquake by about 14 years

east australian current volume transports at 30 s estimates from the world ocean circulation experiment hydrographic sections pr11 p6 and the pcm3 current meter array between september 1991 and march 1994 the oceanic region off the east coast of australia at 30 s was the subject of an intense observational program part of the world ocean circulation experiment the objective was to improve our understanding of the dynamics of the east australian current eac and to measure its volume and energy flux the two main components were the pacific current meter array 3 pcm3 with six moorings spanning a total distance of 120 km and repeat high resolution hydrographic surveys the long term average frompcm3 shows the eac as a narrow swift and highly variable current centered at 40 km from the coast with strong shear in the upper 1000 m and mean southward velocities of 0 6 m s 1 in the core the measurements also revealed a thick countercurrent underneath the poleward flow the mean volume transport for the entire section covered by the array between the coast and 154 4 e was 22 1 4 6 sv toward the south with an rms variability of 30 sv combining the data from the pcm3 array with the hydrographic sections generated nine detailed snapshots of the absolute geostrophic current field the snapshots were used to evaluate the reliability of the pcm3 data for determining volume transports the rms difference between transports derived from direct current observations and from hydrographie data was 3 8 sv indicating that the pcm3 array can be used to describe the current variability despite the sparse spatial distribution of velocity measurements transport variability was dominated by periods between 90 and 140 days which are attributed to eddy shedding in the region occasional intense northward flow events were observed where total transports reached up to 50 sv northward on those occasions the southward boundary current changed from being surface intensified and mainly baroclinic to northward and more barotropic related to the northward migration past the array of the eac coastal separation point

partitioning of transgressive deposits in the southeastern yellow sea a sequence stratigraphic interpretation abstract the last glacio eustatic sea level fluctuation in the southeastern part of the yellow sea formed a number of unconformity bounded sedimentary sequences these sequences comprise 1 regressive to transgressive incision fills unit c 2 transgressive sand ridges and swales unit b and 3 transgressive to highstand muds lower mud unit a2 upper mud unit a1 the sequence boundary between unit c and the lower unit comprises erosional surface which can be traced for the entire study area the even and sharp boundary between the incision fills unit c and the sand ridges unit b represents a transgressive surface of erosion the depositional boundary between the lower mud unit a2 and the upper mud unit a1 suggests a change in oceanographic conditions the boundary is confined landward and correlated offshore with the top of units b and c that is exposed on the seafloor these transgressive deposits show partitioning controlled by currents tides and sediment supply as well as physiography of the seafloor

a numerical modeling study of the east australian current encircling and overwashing a warm core eddy 1 warm core eddies wces often form in the meanders of western boundary currents wbcs wces are frequently overwashed with less dense waters sourced from the wbc we use the regional ocean modelling system to investigate the ocean state during the overwashing of one such wce in october 2008 in the east australian current eac comparisons of model outputs with satellite sea surface temperature and vertical profiles show that the model provides a realistic simulation of the eddy during the period when the eac encircled and then overwashed the eddy during the encircling stage an eddy with closed circulation persisted at depth in the surface eac water entered from the north encircled the eddy and exited to the east the overwashing stage was initiated by the expulsion of cyclonic vorticity for the following 8 days after the expulsion waters from the eac washed over the top of the eddy transferring heat and anticyclonic vorticity radially inward after approximately one rotation period of overwashing the eddy separated the overwashing creates a two layer system that forms a subsurface maximum velocity at the interface of the two layers analysis of water mass properties eulerian tracer dynamics and lagrangian particle tracks show that the original eddy sinks 10 50 m during the overwashing period overwashing has been observed in many wbcs and occurs in most wces in the western tasman sea

earthquakes as beacons of stress change aftershocks occurring on faults in the far field of a large earthquake rupture can generally be accounted for by changes in static stress on these faults caused by the rupture1 2 this implies that faults interact and that the timing of an earthquake can be affected by previous nearby ruptures3 4 5 6 here we explore the potential of small earthquakes to act as beacons for the mechanical state of the crust we investigate the static stress changes resulting from the 1992 landers earthquake in southern california which occurred in an area of high seismic activity stemming from many faults we first gauge the response of the regional seismicity to the landers event with a new technique and then apply the same method to the inverse problem of determining the slip distribution on the main rupture from the seismicity assuming justifiable parameters we derive credible matches to slip profiles obtained directly from the landers mainshock7 8 our results provide a way to monitor mechanical conditions in the upper crust and to investigate processes leading to fault failure

sediment distribution dispersal and budget in the yellow sea abstract information on the surface sediment distribution in the yellow sea is newly compiled based on all available data produced by chinese and korean workers and is used to refine the dispersal patterns and budget of sediments derived from the adjoining landmass the central yellow sea is largely covered with fine grained sediments originating from the huanghe river 2 2 10 8 t yr about 20 of the total discharge thick sediment accumulation exceeding 5 mm yr occurs in the gulf of bohai and around the shandong peninsula about two thirds of the total huanghe river discharge the old huanghe delta suffers from reworking by strong tides and waves and forms a mud patch southwest of cheju island accumulation rate 2 10 7 t yr more than half of the sediments derived from the changjiang river are deposited along the coast of the east china sea the remainder accumulate on the inner shelf off the river mouth in the southeastern yellow sea the keum river dominates sediment discharge forming a holocene mud belt along the southwestern coast of korea accumulation rate 5 10 6 t yr turbid water plumes occur nearshore throughout the year and their suspended sediments are transported along the tip of the peninsula to the western coastal embayments in the south sea the nakdong river discharge of 1 10 7 t yr is responsible for the eastern nearshore mud of the south sea relict sands occur in the northern part of the yellow sea in the northern east china sea and in the korea strait

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size 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

triggering of seismicity at short timescales following californian earthquakes 1 a method for measuring seismicity rate changes caused by the occurrence of major earthquakes in the surrounding crust is proposed it is based on a nonstationary poisson modeling of earthquake activity an estimate of the seismicity rate change and a probability measure of seismicity triggering following a large shock are derived and the removal of the influence of independent aftershock sequences of other nearby previous earthquakes is attempted without using more traditional declustering techniques the seismicity rate change estimator is corrected for its natural bias in favor of positive changes at short timescales that has so far strongly hindered measures of seismicity quiescences three californian earthquakes are examined using this method the 1989 m7 1 loma prieta the 1992 m7 3 landers and the 1994 m6 7 northridge earthquakes positive triggering is very commonly observed as expected but quiescence is however more seldomly obtained for timescales up to 100 days after the main shock this relative absence of quiescence as compared to typical predictions of coulomb modeling for example is also independently observed through direct correlation analyses of californian seismicity the possibility that the stresses caused by the main shock are spatially highly variable may explain these observations

further evidence of fine grained sediment dispersal in the southeastern yellow sea abstract a large portion of the yellow sea is floored by fine grained clastics derived largely from the hwangho and yangtze rivers coarse grained sediments only prevail in the eastern part of the sea derived probably from the short and steep korean rivers near the keum estuary the coarse grained sediments contain substantial amounts of fine fractions detrital clays such as kaolinite and chlorite are abundant in the fine fractions and this trend extends for about 120 km both toward the northwest and the southwest the distributions of some trace elements in the bulk sediments also follow the same trend the close correspondence between mineralogical and geochemical evidence and hydrographic data suggests that the bulk of fine grained sediments in the southeastern yellow sea originates from the keum river and is subsequently transported by prevailing nearshore currents both northwestward during summer and dominantly southwestward in winter illite is dominant in the rest south of 35 n of the sea influenced by the discharge of hwangho river and possibly yangtze river the effect of the kuroshio in transporting illite into the southeastern yellow sea appears to be minimal

subsurface recirculation and larval retention in the lee of a small headland a variation on the upwelling shadow theme 1 the interaction of alongshore coastal currents with large headlands has been shown to increase the retention of planktonic organisms through the formation of headland eddies or upwelling shadows in their lee this study investigates the circulation within bodega bay in the lee of a small headland in an upwelling region and the potential for retention of plankton during the upwelling season of 2004 time series of temperature and velocity were recorded throughout bodega bay conductivity temperature depth ctd surveys were conducted and surface drifters were released during upwelling downwelling and relaxation conditions postlarval settlement was monitored daily over two periods coinciding with ctd surveys under strong upwelling favorable conditions wind driven surface currents were equatorward both offshore and throughout the bay however there was significant current shear along the eastern shore of the bay where cold bottom waters move poleward counter to the direction of the wind driven surface flow during downwelling and relaxation conditions flow was poleward throughout the water column along the eastern shore of the bay postlarvae settled during all wind conditions but greatest settlement was observed at the onset of upwelling favorable conditions while no typical upwelling shadow is evident in the lee of the bodega headland subsurface recirculation driven by the alongshore flow past bodega head may facilitate the retention of plankton in the bay previous studies have generally focused on large headlands however it is likely that other small embayments in the lee of small headlands may also provide retention opportunities for planktonic organisms in upwelling regions

distribution of suspended sediment in the korea strait and southeastern yellow sea onset of winter monsoons abstract high energy conditions in the yellow sea begin each year with the onset of monsoon winds in late october these transitional season surges of cold air initiate sediment resuspension vertical mixing of suspended sediments and a wind driven coastal current that flows to the south during the summer to winter transition suspended sediment concentrations in the southeastern yellow sea range from 5 100 mg l 1 at the surface and 5 500 mg l 1 at the bottom the highest concentrations occur off the southwest tip of the korean peninsula and the lowest occur in the central part of the korea strait the rate of transitional season destratification may depend on the timing and intensity of monsoonal surges whereas a late onset of monsoon winds allows waters to remain longer in their moderately stratified summer condition an early onset of monsoon winds tends to destratify the water column by mid november resulting in a nearly uniform high concentration of suspended sediments from surface to bottom the band of more turbid coastal water ends abruptly 25 50 km offshore as a turbidity front in waters 20 80 m deep a wind driven residual flow to the south appears to transport large volumes of this turbid water into the korea strait and perhaps as far as the sea of japan

is chemical index of alteration cia a reliable proxy for chemical weathering in global drainage basins the chemical weathering of silicate rocks in continents as an important sink of atmospheric co2 is of great significance for global environmental change rivers play a key role in earth surface processes and are regarded as the most important carrier of terrigenous materials into the sea the chemical index of alteration cia has been widely used as a proxy for chemical weathering in sediment source area in this paper the cia values of suspended particulate matters from 44 rivers worldwide are recalculated the cia values vary significantly with the highest average value occurring in african rivers and the lowest in north american rivers the correlation analyses suggest that on a global scale the cia is sensitive to land surface temperature latitude at river mouth and soil depth in the drainage basins but poorly correlated with drainage area precipitation average elevation and runoff however the cia of the rivers draining east china are closely related to temperature precipita tion latitude and runoff primarily reflecting the dominant control of monsoon climate on chemical weathering in the catchments it is therefore unrealistic to find a simple law of regulating chemical weathering in continents the cia actually reflects the integrated weathering history in the drainage basins and therefore caution should be taken while using it as a direct and quantitative proxy for evaluating the intensity of instantaneous chemical weathering in continents

seismic hazard in the marmara sea region following the 17 august 1999 izmit earthquake on 17 august 1999 a destructive magnitude 7 4 earthquake occurred 100 km east of istanbul near the city of izmit on the north anatolian fault this 1 600 km long plate boundary 1 2 slips at an average rate of 2 3 cm yr 1 refs 3 5 and historically has been the site of many devastating earthquakes 6 7 this century alone it has ruptured over 900 km of its length 6 models of earthquake induced stress change 8 combined with active fault maps 9 had been used to forecast that the epicentral area of the 1999 izmit event was indeed a likely location for the occurrence of a large earthquake 9 10 here we show that the 1999 event itself significantly modifies the stress distribution resulting from previous fault interactions 9 10 our new stress models take into account all events in the region with magnitudes greater than 6 having occurred since 1700 ref 7 as well as secular interseismic stress change constrained by gps data 11 these models provide a consistent picture of the long term spatio temporal behaviour of the north anatolian fault and indicate that two events of magnitude equal to or greater than the izmit earthquake are likely to occur within the next decades beneath the marmara sea south of istanbul

the 5500 km long boundary flow off western and southern australia 1 the path of the shelf edge flow off southwestern australia is documented using results from satellite altimetry and sea surface temperature sst and a climatogical in situ analysis during austral winter a continuous current is shown to extend from its origin at north west cape to the southern tip of tasmania a distance of 5500 km satellite sst observations and surface buoy tracks confirm the location and continuity of the current trajectory while the leeuwin current is forced by the strong alongshore pressure gradient associated with the meridional portion of the western australian coastal boundary our results suggest that the essentially zonal shelf edge flow along the southern australian coast arises from the setup of coastal sea level by onshore ekman flow driven by the winter westerly wind and possibly a further alongshore pressure gradient the timing of these two different forcing mechanisms means that the west coast pressure gradient delivers the leeuwin current to the south coast just as the winds reverse and are thus able to maintain the eastward passage of the current the shelf edge flow consists of two main water masses a low salinity warm water type of tropical origin associated with the leeuwin current and a high salinity warm water inflow formed on the western end of the great australian bight continental shelf a naming convention is proposed the leeuwin current representing flow from north west cape to the great australian bight gab the south australian current between the eastern gab and western bass strait and the zeehan current off western tasmania

an investigation of the accuracy of coulomb stress changes inferred from geodetic observations following subduction zone earthquakes earthquake clustering along plate boundaries suggests that earthquakes may interact and static coulomb stress change csc is commonly invoked as one possible mechanism for stress transfer between earthquakes and nearby faults previous work has addressed the precision of csc predictions that are influenced by observational noise inversion regularization and simplified modeling assumptions here we address the accuracy of csc predictions informed by geodetic observations in subduction zones where inversion model resolution is poor we conduct synthetic tests to quantify the degree to which the sign and magnitude of csc can be reliably inferred from slip distributions inverted from various geodetic observations insar gps seafloor observations we find that in an idealized subduction zone csc can only be confidently inferred for receiver faults far 10s of km from the earthquake source though this distance shortens with the addition of synthetic seafloor observations we apply this methodology to the 2010 mw8 8 maule earthquake and identify 13 aftershocks from a population of 475 documented events for which we can confidently resolve co seismic stress changes these results demonstrate that the low model resolution of fault slip inversions in subduction zones limits our ability to address fundamental questions about earthquake sources and stress interactions nonetheless our results highlight that stress change predictions are considerably more accurate after the introduction of seafloor geodetic observations additionally we show that insar observations are not required to substantially improve stress change approximations in regions where gps may be the only viable observation such as in island arcs settings

analysis of broadband records from the 28 june 1992 big bear earthquake evidence of a multiple event source the 28 june 1992 big bear earthquake occurred at 15 05 21 gmt and is considered to be an aftershock of the earlier m w 7 3 landers earthquake from overall aftershock locations and long period focal studies rupture is generally assumed to have propagated northeast no surface rupture was found however and the mainshock locations determined from both strong motion and terrascope data are mutually consistent and do not lie on the assumed fault plane further directivity analysis of records from the terrascope array suggests significant short and long period energy propagating northwest along the presumed antithetic fault plane this observation is supported by significant early aftershocks distributed along both the presumed rupture plane and the antithetic plane to the northwest an empirical green s function egf approach using both the m w 5 2 28 june 1992 14 43 gmt foreshock and the m w 5 0 17 august 1992 aftershock produces consistent results and suggests that the big bear event comprised at least two substantial subevents from the egf results we infer that the second and possibly a third subevent occurred on the presumed northeast striking mainshock rupture surface but that significant moment release occurred on the antithetic northwest striking surface we present results from line source fault modeling of broadband displacement recordings of the big bear mainshock which indicate that a two fault event is necessary to produce the observed waveforms the limitations imposed by the mainshock location and directivity analysis require that the initial rupture be towards the northwest striking 320 this was followed approximately 4 sec later by bilateral rupture along a northeast southwest fault that strikes 50 east of north

eddy shedding and energy conversions in the east australian current 1 mesoscale variability and eddy shedding in the tasman sea particularly of the east australian current eac is studied through the analysis of remotely sensed observations and outputs from a global ocean model previous observations of the western boundary current separation from the coast showed strong variability at periods ranging between 90 and 140 days we show from satellite altimetric observations that rapid northward migration of the separation point of the eac follows the formation of large eddies at periods of 100 days after an eddy separation event the normally southward flowing current swiftly assumes a more zonal configuration near the separation latitude with a cyclonic circulation developing inshore the formation of large separation eddies is preceded by the southward propagation of sea level anomalies along the east australian continental slope from 25 s sea level anomalies grow as they travel south eventually being pinched off in the form of large anticyclones at 32 s in the current retroflection area energy conversion terms in a global ocean model and in altimetric data suggest both barotropic and baroclinic instability may account for the growth of these anomalies as they propagate south east of the main eac jet there is evidence that eddies may be feeding potential energy back to the mean flow

a new statistical test for static stress triggering application to the 1987 superstition hills earthquake sequence over the past several years many investigators have argued that static stress changes caused by large earthquakes influence the spatial and temporal distributions of subsequent regional seismicity with earthquakes occurring preferentially in areas of stress increase and reduced seismicity where stress decreases some workers have developed quantitative methods to test for the existence of such static stress triggering but no firm consensus has yet been reached as to the significance of these effects we have developed a new test for static stress triggering in which we compute the change in coulomb stress on the focal mechanism nodal planes of a set of events spanning the occurrence of a large earthquake we compare the statistical distributions of these stress changes for events before and after the mainshock to decide if we can reject the hypothesis that these distributions are the same such rejection would be evidence for stress triggering we have applied this test to the november 24 1987 elmore ranch superstition hills earthquake sequence and find that those post mainshock events that experienced stress increases of at least 0 01 0 03 mpa 0 1 0 3 bar or that occurred from 1 4 to 2 8 years after the mainshocks are consistent with having been triggered by mainshock generated static stress changes

dispersal of fine grained sediments in the southeastern yellow sea a steady state model a large portion of the yellow sea is floored by fine grained clastics derived largely from the hwangho and yangtze rivers in the southeastern yellow sea however coarse grained sediments prevail derived probably from the short and steep korean rivers farther east the coarse grained sediments contain substantial amounts of fine fractions near the keum estuary detrital clays such as kaolinite and chlorite are abundant in the free fractions and this trend extends for about 120 km both toward the northwest and the southwest illite appears to be dominant in the rest of the yellow sea the data suggest that the bulk of fine grained sediments in the southeastern yellow sea originates from the keum river the sediments are subsequently transported by prevailing nearshore currents both northwestward during summer and southwestward in winter the tidal currents may also play a role the close correspondance between the oceanographic data and the mineralogic evidence suggests that the dispersal of fine grained sediments in the southeastern yellow sea occurs largely under the steady state conditions

shallow seismic stratigraphy and distribution pattern of late quaternary sediments in a macrotidal bay gunhung bay west coast of korea abstract the shallow seismic stratigraphy of late quaternary sediments in gunhung bay a macrotidal coastal embayment of western korea was investigated by means of analyzing high resolution seismic profiles and sediment samples late quaternary sediments up to 20 m thick overlie the irregular surface of the acoustic basement the sediments consist mainly of sands muddy sands and sandy muds and show a zonal facies distribution the distribution pattern appears to be largely controlled by the tidal currents in the bay the sedimentary column above the acoustic basement can be divided into two sequences by a relatively strong mid reflector which is interpreted as the erosional pre holocene surface formed during low sea level many v shaped erosional patterns in this reflector indicate the existence of old tidal channels the sediments underlying the mid reflector are interpreted to be semi consolidated pre holocene tidal deposits presumably deposited during the last interglacial period while the sediments overlying this reflector represent the late holocene tidal desposits deposition of the late holocene sediments began probably at about 5000 yrs b p when sea level approached its present level

high resolution acoustic characteristics of epicontinental sea deposits central eastern yellow sea abstract large amounts 45390 line km of closely spaced 2 2 4 4 km high resolution subbottom profiles chirp 2 7 khz made it possible to identify detailed echo types and their distribution in an epicontinental shelf environment on the basis of seafloor morphology surface bedforms and subbottom acoustic characters 10 echo types were identified in the uppermost sedimentary sequence of the central eastern yellow sea flat seafloor with sharp bottom echoes echo types 1 1 1 2 and 1 3a transgressive sediment sheets or relict sands is widespread in the offshore area and underlain to the west by an acoustically transparent wedge echo type 1 3b highstand muds mounded seafloor with either smooth surface or superposed bedforms echo types 2 1 2 2 and 2 3 tidal ridges and flat seafloor with regularly spaced wavy bedforms echo type 1 4 large scale dunes are dominant in the eastern nearshore area large scale mounds with continuous inclined internal reflectors echo type 2 4 giant mud bank occur in the southeastern nearshore area various scale eroded seafloor echo types 3 1 and 3 2 channels and flat seafloor with regularly spaced wavy bedforms echo type 1 4 large scale dunes are present in the northern part of the sea the distribution pattern of echo types in the central eastern yellow sea reflects depositional processes and sediment dispersal systems during the holocene transgression and highstand period 1 development of tidal ridges and large scale dunes in response to strong tidal currents and waves in the eastern nearshore area 2 construction of transgressive to highstand mud bank huksan mud belt by deposition of muds derived from the keum river in the southeastern nearshore area 3 active erosion due to intensified currents in the northern part and 4 highstand mud deposition derived from the huanghe river on the transgressive sediment sheets in the offshore area

stress coupling between earthquakes in northwest turkey and the north aegean sea we have investigated the coulomb stress interactions of 29 earthquakes m s greater than or equal to 6 0 that have occurred in the region of northwest turkey and north aegean sea since 1912 of these events 23 may be related to earlier events and 16 are clearly related to earlier events all events after 1967 are related to previous events events in the early part of our time interval that show no correlation could be related to historical events as yet unidentified in some cases faults that have received a stress reduction from earlier events are prepared for an event by an earthquake occurring a few years before that creates a local coulomb stress rise thus regions of coulomb stress shadow can become regions where a damaging earthquake may occur the relation between smaller events and the coulomb stress distribution is less clear but may be related to poor data quality and practical limitations of our modeling technique nonetheless there are 4 times as many events per unit area in regions of enhanced stress than where stress is reduced we discuss the contemporary distribution of coulomb stress and argue that it is possible to identify the likely locations of future damaging earthquakes including identifying the most likely candidate faults

sensitivity of static stress calculations to the earthquake slip distribution 1 the apparent strong correlation between coulomb stress changes and the spatial distribution of aftershocks suggests the possibility of making near real time estimations of areas at risk of experiencing off fault aftershocks in order to do this in practice a number of issues must first be addressed including the extent to which the main shock slip must be known in detail before a meaningful stress map can be constructed here we investigate this issue by constructing a time ordered sequence of slip solutions for the landers earthquake computing coulomb stress changes for each solution and quantitatively comparing the stress field with the observed aftershocks by 1 resolving the coulomb stress change onto the aftershock nodal planes and calculating the percentage of events consistent with triggering and 2 constructing a two dimensional map of coulomb stress and computing the correlation coefficient between the positive and negative areas and the locations of the aftershocks we find that slip solutions based on empirical relations and either focal mechanism or moment tensor data produce stress fields inconsistent with the observed spatial distribution of aftershocks whereas slip solutions incorporating the correct rupture geometry but greatly simplified slip produce stress fields consistent with the aftershock distribution when very near fault events are excluded we further find that resolving stress perturbations onto earthquake nodal planes and computing the percentage of events experiencing positive coulomb stress provides a poor measure of success because of the limited range of structures on which events occur and the compatibility of the main shock stress field with these structures our results support the hypothesis that coulomb stress changes affect the spatial distribution of aftershocks and suggest that meaningful calculations of coulomb stress can be made as soon as an earthquake s rupture geometry is well constrained

observations on shelf and subtidal channel flow implications of sediment dispersal seaward of the keum river estuary korea although much of the fine grained sediment in the south eastern yellow sea is attributed to discharge from the keum river dispersal of these sediments by tide or wind has never been determined by direct current measurements in this paper we provide in situ observations of currents in two dispersal systems immediately seaward of the keum river entrance one of these is a subtidal channel system that defines flow from the shallow subtidal region seaward to the shelf and the other is the inner shelf mudstream where mixing is maintained primarily by tides subtidal channels have moderate current speeds but low suspended sediment concentrations instantaneous current speeds during spring tide were of the order 100 cm s 1 and suspended sediment concentrations were typically less than 10 mg l 1 at the surface and 40 mg l 1 at the bottom under fair weather conditions subtidal channels play a negligible role in offshore sediment dispersal since sediment concentrations during flood appear to equal or exceed those during ebb instantaneous currents at two stations on the shelf were of the same order as those in subtidal channels but displayed net flow to the south at speeds of 7 8 and 3 8 cm s 1 we speculate that subtidal channels provide the conduits for transporting sediments directly offshore during winter monsoons on an annual time scale one model for sedimentation would be low sediment influx from rivers but high influx from tidal flats to the coast during winter when north winds generate large waves in the yellow sea and the reverse in summer when winds from the south produce little wave activity coastal muds would thus be eroded in winter and replenished by high river discharge in summer further it is reasonable to assume that residual flow to the south would strengthen in winter as the monsoon season progressed thus the introduction of resuspended tidal flat sediments would coincide with the best developed dispersal system

lagrangian transport pathways in the northeast atlantic and their environmental impact this study focused on mapping the general transport pathways of the northeast atlantic ocean by using the regional oceanic modeling system to calculate ocean current velocity components u v w and ariane an off line fortran code dedicated to the computation of three dimensional streamlines from velocity fields to calculate the transport of particles around the numerical model domain the study was undertaken using a 10 year climatic simulation statistical comparisons with satellite and in situ data showed that the ocean circulation model captured known regional oceanographic features four depth ranges showed different lagrangian transport pathways 0 10 m 20 200 m 300 500 m and 600 2000 m confirming that these routes are consistent with the known ocean circulation patterns our results were supported by multiple sources i connectivity between the african coast and the canary islands for sardine sardina pilchardus anchovy engraulis encrasicolus ii panmixia of lobsters scyllarides latus and palinurus elephas and european conger eel conger conger iii connectivity between azores and canary archipelagos for sponge phorbas fictitius and iv observed drifting of crude oil from the prestige oil tanker spill these results should help guide future observational campaigns as well as the interpretation of open ocean transport patterns and the distribution of marine organisms and chemical tracers in the northeast atlantic region

evolution of late quaternary mud deposits and recent sediment budget in the southeastern yellow sea abstract analysis of high resolution seismic reflection profiles and sediment samples has revealed the evolution and sediment budget of the southeastern yellow sea mud belt seysm along the southwestern korean peninsula the seysm up to 50 m thick over 250 km long and 20 55 km wide can be divided into three stratigraphic units a1 a2 and b from oldest to youngest unit a1 overlying the acoustic basement comprises the northern part of the seysm unit a2 comprises the southern part of the seysm much of unit a2 is exposed at the seafloor unit b completely covers unit a1 and pinches out southward 14c data suggest that evolution of each unit is closely related to the postglacial sea level changes unit a1 consists of estuarine deltaic or shallow water muds deposited during the early to middle stage of postglacial sea level rise ca 14 000 7000 yr b p unit a2 corresponds to relict muds deposited during the last deceleration stage of sea level rise ca 7000 3 500 yr b p unit b consists of shelf muds deposited during the recent sea level highstand ca very low background activities of 210pb of the surface sediment of unit a2 suggest that the present day sediment accumulation is negligible in the southern seysm on the other hand 210pb excess activity profiles in unit b yield an average sediment accumulation rate of 3 9 mm yr indicating active sediment accumulation in the northern seysm the annual sink 3 0 10 7 tons yr of fine grained sediment in unit b is about an order of magnitude greater than can be explained by the sediment input from the korean rivers alone we propose that reworking of unit a2 has provided large volumes of muds to unit b resulting in excessive sediment accumulation in the northern seysm much of unit a2 in turn is likely to have originated from erosion of unit a1 in the north this rather unique erosional depositional regime of the seysm is probably owing to the tidal and regional currents characteristic in the southeastern yellow sea

sediment accumulation in a modern epicontinental shelf setting the yellow sea sediment accumulation in the yellow sea epicontinental shelf environment is investigated on 100 yr and 1000 yr time scales using 210pb and 14c geochronologies the distribution of modern 210pb accumulation rates in the yellow sea reveals that the loci of modern huanghe sediment accumulation are the topset 1 2 mm yr foreset 4 9 mm yr and proximal bottomset deposits 2 4 mm yr of the shandong subaqueous delta which extends south from the shandong peninsula 210pb rates in the distal bottomset deposits of the subaqueous delta in the central and southern yellow sea are generally low 0 3 0 9 mm yr a sediment budget demonstrates that between 9 15 of the annual huanghe discharge is accumulating in the yellow sea about two thirds of this sediment is accumulating in the topset foreset and proximal bottomset deposits of the shandong subaqueous delta with the remaining third accumulating as widespread distal bottomset deposits 14c age dates of subaqueous delta sediments indicate that the thick 40m clinoform structure formed predominantly between 6200 and 4060 yrs b p at rates approaching 20 mm yr observations in the yellow sea as well as on the amazon and ganges brahmaputra shelves demonstrate that subaqueous deltaic stratigraphy is the general rule where major rivers enter energetic shelves whether epicontinental or pericontinental the development of extensive bottomset deposits may be restricted to epicontinental shelf environments and may be diagnostic of sedimentation in this type of setting

depositional patterns of sand ridges in tide dominated shallow water environments yellow sea coast and south sea of korea abstract the continental shelf of the yellow sea and the korean south sea is a tide dominated shelf a number of sand ridges occur in this area which form bathymetric highs surveyed were one large sand ridge jangan satoe along the western yellow sea coast and a group of mid shelf sand ridges in the south sea to delineate their depositional pattern and probable origin in tide dominated shallow water environments analyses of sediment samples side scan sonographs and seismic profiles reveal that these ridges show regionally different characteristics in morphology bedforms and sediment the sand ridge in the yellow sea shows a composite form of various bedforms including sand waves and megaripples this ridge is interpreted to be in an accretional active stage maintained by strong tidal currents in contrast the sand ridges on the mid shelf of the south sea show rounded single forms without bedforms on them they are interpreted to represent moribund type sand ridges in the shelf environment which were formed near the shoreline during the holocene sea level transgression these ridges developed off the paleo seomjin river during a period of a stillstand or slow sea level rise approximately between 10 000 and 7000 yrs b p

spatial and temporal distribution of slip for the 1992 landers california earthquake we have determined a source rupture model for the 1992 landers earthquake m w 7 2 compatible with multiple data sets spanning a frequency range from zero to 0 5 hz geodetic survey displacements near field and regional strong motions broadband teleseismic waveforms and surface offset measurements have been used explicitly to constrain both the spatial and temporal slip variations along the model fault surface our fault parameterization involves a variable slip multiple segment finite fault model which treats the diverse data sets in a self consistent manner allowing them to be inverted both independently and in unison the high quality data available for the landers earthquake provide an unprecedented opportunity for direct comparison of rupture models determined from independent data sets that sample both a wide frequency range and a diverse spatial station orientation with respect to the earthquake slip and radiation pattern in all models consistent features include the following 1 similar overall dislocation patterns and amplitudes with seismic moments of 7 to 8 10 26 dyne cm seismic potency of 2 3 to 2 7 km 3 2 very heterogeneous unilateral strike slip distributed over a fault length of 65 km and over a width of at least 15 km though slip is limited to shallower regions in some areas 3 a total rupture duration of 24 sec and an average rupture velocity of 2 7 km sec and 4 substantial variations of slip with depth relative to measured surface offsets the extended rupture length and duration of the landers earthquake also allowed imaging of the propagating rupture front with better resolution than for those of prior shorter duration strike slip events our imaging allows visualization of the rupture evolution including local differences in slip durations and variations in rupture velocity rupture velocity decreases markedly at shallow depths as well as near regions of slip transfer from one fault segment to the next as rupture propagates northwestward along the multiply segmented fault length the rupture front slows as it reaches the northern limit of the johnson valley landers faults where slip is transferred to the southern homestead valley fault an abrupt acceleration is apparent following the transfer this process is repeated and is more pronounced as slip is again passed from the northern homestead valley fault to the emerson fault although the largest surface offsets were observed at the northern end of the rupture our modeling indicates that substantial rupture was also relatively shallow less than 10 km in this region

temperate shelf water dispersal by australian boundary currents implications for population connectivity boundary currents have been recognized as potential drivers of spatial heterogeneity in the ocean because of their role in physical transport and influence on large scale coastal processes in this study we used particle tracking methods in a data assimilating eddy resolving ocean circulation model to determine the effect of multiple boundary currents on connectivity around temperate australia during the austral winter results demonstrated that oceanographic connectivity was asymmetric around australia having greater eastward trajectories due to more favorable ocean boundary currents during this season we validated connectivity patterns with genetic data from an ecologically important species the kelp ecklonia radiata which has greater genetic similarity between the west and south coasts of australia compared with the east coast likely due to predominantly eastward propagule dispersal boundary current circulation was a coarse predictor of kelp genetic connectivity on multigeneration time scales and the nature of these relationships varied among the three boundary current systems according to mean current strength

structural constraints on the spatial distribution of aftershocks 1 calculations of static stress changes due to large earthquakes have shown that the spatial distribution of aftershocks is predictable to first order with aftershocks primarily occurring in areas experiencing positive stress changes delineation of these areas relies on resolving the stress perturbation onto planes with known orientations common practice is to use poorly constrained regional stress information to compute optimally oriented failure planes assuming that they exist everywhere here we show that this assumption is not supported by observation but rather that aftershock failure planes are controlled by geological structure we argue that useful aftershock hazard estimates are better made by replacing information on regional stress with statistical measures of structural orientations

the cold core eddy and strong upwelling off the coast of new south wales in early 2007 abstract during the austral summer of 2006 07 a series of extreme oceanic events occurred in the tasman sea following a series of strong wind driven upwelling events an intense cold core eddy developed off sydney australia a data assimilating eddy resolving ocean model is used to create a three dimensional time varying reanalysis of these events the reanalysis indicates that the cold anomalies associated with the upwellings were in excess of 5 c near the coast where sea level decreased by as much as 0 2 m the reanalysed three dimensional structure of the cold core eddy shows the eddy leaning to the west north west in towards the continental shelf the diameter of the eddy is about 100 km and the sea level anomaly at the eddy centre peaks at around 1 m with an associated sub surface temperature anomaly in excess of 8 c at 200 m depth corresponding to an upward isotherm excursion of 600 m the circulation around the cyclonic eddy is ageostrophic with upwelling in the southern sector of the eddy where flow is onshore and climbing the continental slope and downwelling in the northern sector where flow is descending off the slope three dimensional trajectories of water parcels around the eddy involve 50 100 m vertical excursions based on the reanalysed circulation and composite satellite images of chlorophyll a we hypothesise that the circulation around the eddy led to significant nutrient enrichment in the euphotic zone around the perimeter of the eddy

seasonal variation of sedimentary processes in a semi enclosed bay hampyong bay korea abstract multi annual sedimentological observations on tidal flat sediments were carried out in hampyong bay southeastern yellow sea to infer the budget of modern muddy sediments in the bay sedimentation rates over a four year period show contrasting types of seasonal sedimentary cycles occurring in the tidal flats within the elongated bay both sides of the bay are largely sheltered from winter waves resulting in surface mud deposition during winter and erosion during summer in contrast tidal flats along the head of the bay are influenced by winter waves resulting in a reversed trend where erosion occurs during winter and deposition during summer tidal flats near the bay mouth however show a sedimentary cycle disrupted by the construction of sea walls undergoing consistent erosion throughout the observational period the shoreline artificially straightened seems to cause tidal currents to bypass the tidal flat and hence to be much stronger these differences in sedimentary cycles suggest the critical importance of the orientation of tidal flats relative to the propagating direction from n nw of the monsoon winter storm waves on the tidal flat sedimentation in the eastern coastal area of the yellow sea the preliminary budget estimation for the tidal flat mud suggests that the tidal flats in hampyong bay are subject to the slight but consistent erosion as a whole

the effect of sediment stratification on tidal dynamics and sediment transport patterns 1 the western tip of southwest korea is characterized by a tidally dominated turbid coastal environment there are well developed tidal flats along the coast and around islands together with offshore sand ridges several tens of kilometers long in the west the effects of bottom boundary layer bbl sediment stratification on sediment transport and tidal dynamics in this environment were examined using a sediment transport model coupled with a three dimensional tidal hydrodynamic model model experiments using two scenarios with and without the effect of sediment induced stratification showed that bbl sediment stratification influenced the spatial distribution and reduced the magnitude of net sedimentation the presence of a sediment stratified bbl also led to a reduction in suspended sediment fluxes and an increase in the vertical gradient of sediment concentrations in the water column these variations occurred because sediment induced bbl stratification leads to not only a reduction in bottom shear stress but also a decrease in buoyancy production ofturbulent kinetic energy and an associated dampening ofturbulence the significant reductions in turbulence and bottom shear stress result in changes to the vertical current structure of the m 2 tide including alteration of the tidal ellipse configuration and an increase in vertical shears of the tidal current amplitude and phase these reductions also lead to a slight increase in tidal amplitudes due to the decreased tidal energy dissipation the model results indicate that feedback between the sediment transport dynamics and hydrodynamics is an important factor in modeling sediment transport dynamics in tidally dominated turbid coastal environments such environments include the west coast of korea and the yellow sea a suitable approach to simulating the effects of this feedback may be the use of a modified bottom drag coefficient as a stability function together with the inclusion of the effect of sediment stratification on the hydrodynamics

geochemistry of surface sediments off the southern and western coasts of korea abstract the continental shelf off the southern and western side of the korean peninsula is part of a modern epicontinental sea and is an effective sediment trap for clastic material derived from china and korea we have analyzed 179 surface sediment samples from this shelf for al fe na k mg ca ti p mn sr ba v cr co ni cu zn organic carbon and calcium carbonate in order to determine the geochemical characteristics of these sediments results showed a wide range of element contents which are mainly related to the textural variability of sediments exceptions to this were found in the contents of ca k sr and ba the ca and sr contents were largely determined by the amounts of carbonate present the k content on the other hand appeared to be influenced by both the contents of illite and feldspar and ba of potassium feldspar for muds i e sediments deposited under present day conditions it is possible to distinguish those in the central yellow sea from those in the keum estuary the former are characterized by high contents of fe na k mg ca and v and the latter by high contents of mn ba and co these differences become more apparent when these elements are normalized relative to al in order to minimize grain size effects the distribution of v al ratios is different from that of other elements the highest v al values occur in muds from the central yellow sea derived from the huanghe the yellow river in china whereas the highest values of mn al are found in the nearshore area adjacent to the korean peninsula based on these results it is suggested that the sources of fine sediments in the yellow and south seas can be distinguished from the geochemical characteristics of the surface sediments in the yellow sea two different sources of fine grained sediments can be seen the huanghe and the keum river the former is characterized by higher v contents and the latter by higher mn contents using the v al ratio as an end member component of the two source materials the dispersal patterns of the fine sediments 6o were also derived

sedimentary processes of fine grained material and the effect of seawall construction in the daeho macrotidal flat nearshore area northern west coast of korea abstract sedimentary processes on the lower tidal flat of the reclaimed seosan bay daeho tidal flat at the west coast of korea have undergone significant changes since 1984 when seawalls over 8 km long were constructed at the bay mouth comparison of pre and post construction tidal flow models indicates that in general tidal currents have increased considerably in front of the daeho tidal flat with tidal flow directions having changed from shore normal to shore parallel the 12 h measurements of currents and suspended sediment concentrations at four anchored hydrographic stations show nearshore suspended sediments drifting southward throughout the year bypassing the daeho tidal flat cyclic seasonal variations occur prominently in the grain texture of the tidal flat sediments and associated sedimentation rates in summer fine grained sediments deposit at a rate of 2 6 mm month particularly in sheltered places during the winter monsoon erosional processes are greatly enhanced by the interplay of tidal currents and waves up to 30 mm month this sedimentary seasonality is reflected in the variations in the concentration of nearshore suspended matter the concentration of suspended matter is much higher in winter 60 80 mg l because of vigorous resuspension activities compared with the summer concentration 10 30 mg l the direct effect of seawall construction coupled with strong natural seasonality can be seen from the continuous monitoring of sedimentation rates on the tidal flat the 2 year 1993 1995 measurements indicate that the entire daeho tidal flat was eroded during that period at the abnormally high average rate of 10 cm year the causal blocking of bayward sediment and water movements by any artificial structure might lead to similar erosional conditions to many other bays facing the yellow sea on the both chinese and korean coastlines subjected to energetic winter wave attack

geochemical compositions and provenance discrimination of the central south yellow sea sediments geochemical compositions and sedimentation rates of surface and core sediments in the central south yellow sea were analyzed for the identification of sediment origins the sediment accumulation rates measured by 210 pb geochronology decrease significantly from the western part to the central area calcium carbonate total organic carbon and most elements are more enriched in the western muddy sediments than in the sandy eastern part overall geochemical compositions of the central south yellow sea sediments vary between those of chinese and korean river sediments supplied into the sea although caco3 content exhibits regional variations in the central south yellow sea the discrimination diagram of sc al vs cr th distinctly suggests that the muddy holocene sediments in the central western part are derived ultimately from chinese rivers especially the huanghe river whereas the eastern sandy sediments primarily came from the korean rivers during the postglacial transgression 2007 elsevier b v all rights reserved

tasman leakage in a fine resolution ocean model tasman leakage the westward flow of thermocline waters south of australia from the pacific to the indian ocean is one of the lesser studied of the inter ocean exchanges here some of the properties of the tasman leakage are inferred from lagrangian particles integrated using the three dimensional velocity fields of the 1 10 degree resolution ofes model the mean tasman leakage in this model is 4 2 sv with a standard deviation of 4 3 sv the heat flux associated with this leakage lies in the range 0 08 0 18 pw there is large variability in the tasman leakage on both sub weekly and inter annual scales but no trend over the 1983 1997 period despite the large weekly variability with peaks of more than 20 sv it appears that less than half of the tasman leakage is carried within eddies

origin and dispersal of recent clay minerals in the yellow sea abstract the clay minerals in the by considering the clay minerals supplied by rivers in china the old and present day huanghe river and korea the keum and yeongsan to the yellow sea continental shelf and the spatial variation in the distribution of clay minerals in the yellow sea this study indicates that the provenance of the cysm may be closely related to the old and present day huanghe river system whereas the clay minerals in the seysm seem to be largely associated with the keum and yeongsan rivers in addition smectite may be suggested as an important clay mineral in differentiating between cysm and seysm and understanding the sources of these two mud categories

origin of inner shelf mud deposit in the southeastern yellow sea huksan mud belt abstract a variety of previous sedimentological results together with newly obtained hydrodynamic data are summarized and reinterpreted with respect to the most likely origin of the huksan mud belt hmb in the southeastern yellow sea the hmb consists of two mud units that have similar grain texture and clay mineralogy but can be differentiated on seismic profiles because the lower unit is generally harder than the watery upper unit the hydrographic measurements together with satellite imagery clearly indicate that the suspended plume covering the hmb originates from the west coast of korea the suspended plume becomes enhanced by winter monsoon winds beginning in late fall most of the studies of clay mineralogy geochemistry and isotherm distribution also suggest that the hmb has been derived from the west coast of korea particularly from the keum river an approximate evaluation of the depositional time for the hmb based on its dimensions and the discharge rate of the keum river suggests a time duration of the order of 14 000 years hydrodynamic measurements across two transects over the northernmost hmb reveal that suspended matter travels southwest toward the main body of the hmb in a well constrained corridor ultimately connected with the keum river time series 12 5 h hydrodynamic measurements at a site over the hmb suggest that the winter season suspended plume carries concentrations of suspended matter one to two orders of magnitude higher than those of the summer silt grains of 5 6 well sorted through numerous resuspension events settle out onto the hmb forming distinctive silt laminae alternating with clay rich laminae

on the origin of diverse aftershock mechanisms following the 1989 loma prieta earthquake summary we test the hypothesis that the origin at the diverse suite of aftershock mechanisms following the 1989 m 7 1 loma prieta california earthquake is related to the post main shock static stress field we use a 3 d boundary element algorithm to calculate static stresses combined with a coulomb failure criterion to calculate conjugate failure planes at aftershock locations the post main shock static stress field is taken as the of a sum of a pre existing stress field and changes in stress due to the heterogeneous slip across the loma prieta rupture plane the background stress field is assumed to be either a simple shear parallel to the regional trend of the san andreas fault or approximately fault normal compression a suite of synthetic aftershock mechanisms from the conjugate failure planes is generated and quantitatively compared allowing for uncertainties in both mechanism parameters and earthquake locations to well constrained mechanisms reported in the us geological survey northern california seismic network catalogue we also compare calculated rakes with those observed by resolving the calculated stress tensor onto observed focal mechanism nodal planes assuming either plane to be a likely rupture plane various permutations of the assumed background stress field fractional coefficients of aftershock fault planer methods of comparisons etc explain between 52 and 92 per cent of the aftershock mechanisms we can explain a similar proportion of mechanisms however by comparing a randomly reordered catalogue with the various suites of synthetic aftershocks the inability to duplicate aftershock mechanisms reliably on a one to one basis is probably a function of the combined uncertainties in models of main shock slip distribution the background stress field and aftershock locations in particular we show theoretically that any specific main shock slip distribution and a reasonable background stress field are able lo generate a highly variable suite of failure planes such that quite different aftershock mechanisms may be expected to occur within a kilometre of less of each other this scale of variability is less than the probable location error of aftershock earthquakes in the loma prieta region we successfully duplicate a measure of the variability in the mechanisms of the entire suite of aftershocks if static stress changes are responsible for the generation of aftershock mechanisms we are able to place quantitative constraints on the level of stress that must have existed in the upper crust prior to the loma prieta rupture this stress level appears to be too low to generate the average dip across the main shock rupture plane possible reasons for this result range from incorrect initial assumptions of homogeneity in the background stress field friction and fault geometry to driving stresses that arise from deeper in the crust or upper mantle alternatively aftershock focal mechanisms may be determined by processes other than or in addition to static stress changes such as pore pressure changes or dynamic stresses

a review of the shelf slope circulation along australia s southern shelves cape leeuwin to portland abstract a review is presented of the ocean circulation along australia s southern shelves and slope uniquely the long zonal shelf is subject to an equatorward sverdrup transport that gives rise to the flinders current a small sister to the world s major western boundary currents the flinders current is strongest near the 600 m isobath where the current speeds can reach 20 cm s and the bottom boundary layer is upwelling favourable it is larger in the west but likely intermittent in both space and time due to possibly opposing winds thermohaline circulation and mesoscale eddies the flinders current may be important to deep upwelling within the ubiquitous canyons of the region during winter the leeuwin current and local winds act to drive eastward currents that average up to 20 30 cm s the currents associated with the intense coastal trapped wave field 6 12 day band are of order 25 30 cm s and can peak at 80 90 cm s wintertime winds and cooling also lead to downwelling to depths of 200 m or more and the formation of dense coastal water within the great australian bight and the south australian sea within the great australian bight the thermohaline circulation associated with this dense water is unknown but may enhance the eastward shelf edge south australian current the dense salty water formed within spencer gulf is known to cascade as a gravity current to depths of 200 m off kangaroo island this dense water outflow and meanders in the shelf circulation also fix the locations of a sequence of quasi permanent mesoscale eddies between the eyre peninsula and portland during summer the average coastal winds reverse and surface heating leads to the formation of warm water in the western great australian bight and the south australian sea no significant exchange of shelf water and gulf water appears to occur due to the presence of a dense nutrient rich sub surface pool that is upwelled off kangaroo island the winds lead to weak average coastal currents increasing evidence suggests that el nino events 4 7 year period can have a major impact on the winter and summer circulation these events propagate from the pacific ocean and around the shelf slope wave guide of west australia and into the great australian bight during winter el nino events the average shelf currents may be largely shut down during summer the thermocline may be raised by up to 150 m the nature and role of tides and surface waves is also discussed along with uncertainties in the general circulation and future research

heightened odds of large earthquakes near istanbul an interaction based probability calculation we calculate the probability of strong shaking in istanbul an urban center of 10 million people from the description of earthquakes on the north anatolian fault system in the marmara sea during the past 500 years and test the resulting catalog against the frequency of damage in istanbul during the preceding millennium departing from current practice we include the time dependent effect of stress transferred by the 1999 moment magnitude m 7 4 izmit earthquake to faults nearer to istanbul we find a 62 15 probability one standard deviation of strong shaking during the next 30 years and 32 12 during the next decade

multielement geochemistry of offshore sediments in the southeastern yellow sea and implications for sediment origin and dispersal abstract in total 116 surface sediments were collected from an offshore area of the southeastern yellow sea including a large mud belt southeastern yellow sea mud seysm and analyzed for grain size and geochemical composition organic carbon and 42 elements principal component analysis revealed that elemental compositions of the offshore sediments were mostly controlled by common aluminosilicate clay minerals and quartz most elements heavy minerals hf zr u th rare earth elements rees biogenic calcium carbonates ca sr feldspar and mica k ba pb and mn oxides mn oxide coatings on sand grains notably total ree concentrations may be associated with heavy minerals possibly zircon and monazite especially in silty grains even though heavy ree hrees concentrations are more strongly controlled by clay minerals in muddy sediments the diagnostic discrimination plots of geochemical compositions e g fe vs al mg vs al light ree vs hree and la lu ucc vs la y ucc suggested that the offshore sediments especially in seysm deposits were composed of a mixture of korean river derived silts and chinese river derived clays this demonstrated that chinese river sediments especially clay particles largely contributed to the formation of the giant mud belt in the korean coastal area furthermore the observed geochemical end members provide new markers of sediment provenance which can be used to track dispersal patterns and sediment limits from chinese and or korean rivers

near field investigations of the landers earthquake sequence april to july 1992 the landers earthquake which had a moment magnitude m w of 7 3 was the largest earthquake to strike the contiguous united states in 40 years this earthquake resulted from the rupture of five major and many minor right lateral faults near the southern end of the eastern california shear zone just north of the san andreas fault its m w 6 1 preshock and m w 6 2 aftershock had their own aftershocks and foreshocks surficial geological observations are consistent with local and far field seismologic observations of the earthquake large surficial offsets as great as 6 meters and a relatively short rupture length 85 kilometers are consistent with seismological calculations of a high stress drop 200 bars which is in turn consistent with an apparently long recurrence interval for these faults