effects of prestress state and rupture velocity on dynamic fault branching 1 we consider a mode ii rupture which propagates along a planar main fault and encounters an intersection with a branching fault using an elastodynamic boundary integral equation formulation allowing the failure path to be dynamically self chosen we study the following questions does the rupture initiate along the branch does it continue is the extensional or compressional side most favored for branching does rupture continue on the main fault too failure is described by a slip weakening law for which the strength at any amount of slip is proportional to normal stress our results show that dynamic stresses around the rupture tip which increase with rupture velocity at locations off the main fault plane relative to those on it could initiate rupture on a branching fault as suggested by prior work whether branched rupture can be continued to a larger scale depends on principal stress directions in the prestress state and on rupture velocity the most favored side for branching rupture switches from the extensional to the compressional side as we consider progressively shallower angles of the direction of maximum compressive prestress with the main fault simultaneous rupturing on both faults can be activated when the branching angle is wide but is usually difficult for a narrow branching angle due to strong stress interactions between faults however it can be also be activated by enhanced dynamic stressing when the rupture velocity is very near the rayleigh velocity natural examples seem consistent with the simulations that we present

role of orbital forcing in east asian monsoon climates during the last 350 kyr evidence from terrestrial and marine climate proxies from core rc14 99 proxy records of northeast asian precipitation marine pollen and northwest pacific sea surface temperatures marine fauna contain concentrations of variance frequency peaks coincident with those of orbital variations eccentricity obliquity and precession time series of these monitors of various components of the east asian monsoon system are coherent with changing solar insolation and climate boundary conditions ice volume snow cover albedo at 41 and 23 kyr frequencies winter sea surface temperature wsst maxima are in phase with global ice volume minima at all three milankovitch frequencies 100 41 and 23 kyr periods wsst maxima are also linearly related to summer insolation at 30 n lagging radiation maxima by 55 3 5 kyr across the precessional frequency band 23 kyr period our east asian monsoon rainfall indicator cryptomeria reaches highest values immediately following summer insolation maxima during periods of low ice volume interglacials across the eccentricity frequency band 100 kyr period cryptomeria maxima are in phase with ice volume minima at the higher frequency of orbital precession monsoon rainfall lags both summer radiation maxima 125 8 kyr and ice volume minima 60 3 8 kyr whereas much of the variation in northwest pacific wsst can be attributed to summer radiation forcing and changes in global climate mechanisms driving east asian monsoon precipitation are more complex involving other possibly internal factors

the frictional behavior of lizardite and antigorite serpentinites experiments constitutive models and implications for natural faults laboratory studies of the frictional behavior of rocks can provide important information about the strength and sliding stability of natural faults we have conducted friction experiments on antigorite and lizardite serpentinites rocks common to both continental and oceanic crustal faults we conducted both velocity step tests and timed hold tests on bare surfaces and gouge layers of serpentinite at room temperature we find that the coefficient of friction of lizardite serpentinite is quite low 0 15 0 35 and could explain the apparent low stresses observed on crustal transform faults while that of antigorite serpentinite is comparable to other crustal rocks 0 50 0 85 the frictional behavior of both types of serpentinite is well described by a two mechanism model combining state variable dominated behavior at high slip velocities and flow dominated behavior at low velocities the two mechanism model is supported by data from velocity step tests and timed hold tests the low velocity behavior of serpentinite is strongly rate strengthening and should result in stable fault creep on natural faults containing either antigorite or lizardite serpentinite

a high resolution radiolarian derived paleotemperature record for the late pleistocene holocene in the norwegian sea polycystine radiolarians are used to reconstruct summer sea surface temperatures sssts for the late pleistocene holocene 600 13 400 14c years bp in the norwegian sea at 13 200 14c years bp the ssst wasclose to the average holocene ssst 12 c it then gradually dropped to 7 1 c in the younger dryas nearthe younger dryas holocene transition 10 000 14c years bp the ssst increased 5 c in about 530 years four abrupt cooling events with temperature drops of up to 2 1 c are recognized during the holocene at 9340 7100 8200 calendar years event 6400 and 1650 14 c years bp radiolarian sssts and the isotopic signalfrom the gisp2 ice core are strongly coupled stressing the importance of the norwegian sea as a mediator ofheat precipitation exchange between the north atlantic the atmosphere and the greenland ice sheet radiolarian and diatom derived sssts display similarities with the former not showing the recently reportedholocene cooling trend

the 2002 denali fault earthquake alaska a large magnitude slip partitioned event the mw moment magnitude 7 9 denali fault earthquake on 3 november 2002 was associated with 340 kilometers of surface rupture and was the largest strike slip earthquake in north america in almost 150 years it illuminates earthquake mechanics and hazards of large strike slip faults it began with thrusting on the previously unrecognized susitna glacier fault continued with right slip on the denali fault then took a right step and continued with right slip on the totschunda fault there is good correlation between geologically observed and geophysically inferred moment release the earthquake produced unusually strong distal effects in the rupture propagation direction including triggered seismicity

vertical distribution of radiolaria in the eastern equatorial atlantic analysis of a multiple series of closely spaced plankton tows radiolaria from the upper 101 and 202 m of eastern equatorial atlantic waters were collected with multiple opening closing nets in combination with an environmental sensing system mocness the abundance and vertical distribution of 40 polycystine and phaeodarian species were measured and compared with physical and chemical water properties measured at the tow sites highest concentrations of radiolaria radiolaria unit volume of water filtered in the upper 100 m occur at depths encompassing thechlorophyll a maximum and thermocline abundance peaks of many of the spumellarian taxa are recorded in samples taken from nets towed at depths at or directly above thechlorophyll a maximum zone six of the nine colonial radiolarians identified are present in highest concentrations in surface waters 0 25 m where the highest levels of dissolved oxygen were recorded most of the nassellarian and phaeodarian taxa counted in these samples reach maximum abundances at depths well below thechlorophyll a maximum the relationships between radiolaria distribution and physical and or chemical properties measured at the two tow sites are statistically significant

cycladophora davisiana abundances as a paleoceanographic and stratigraphic tool in high latitude siliciceous sediments abstract like the oxygen isotope curve the relative abundance curve for cycladophora davisiana hereafter c curve exhibits synchronous fluctuations between high latitude regions it was also thought that high abundances of c davisiana indicated glacial periods although numerous short c curves have been calibrated to oxygen isotope curves spanning the last 100 kyr only two longer c curves have been associated with oxygen isotopes spanning the last 0 425 myr in the southern ocean and 1 1 myr in the sea of okhotsk this lack of well established long c curve calibrations to the oxygen isotope curve decreases the reliability of the c curve for periods beyond 100 ka furthermore recent work indicates that high abundances of c davisiana do not necessary indicate glacial conditions this study sought to establish a long c davisiana curve by directly calibrating the c curve to oxygen isotope records measured from benthic foraminifera in the north pacific over the last 740 kyr to discuss the paleoceanographic significance of the c curve and to check the suitability of the c curve as a stratigraphic tool samples were obtained from core c9001c which was recovered at a water depth of 1180 m east of the shimokita peninsula in the tohoku region of japan the core contained a continuous stratigraphic succession down to marine isotope stage 18 740 ka abundance peaks exceeding 5 of the total radiolarian fauna were defined as davisiana event dae and a total of 20 daes were observed over the last 740 kyr the daes were generally near interglacial glacial period boundary whereas peaks in the radiolarian total abundance reflecting warm surface radiolarian productivity occur mainly within the interglacial intervals the daes appear to reflect hydrological and productivity events in the intermediate water masses of the studied site during climatic transition we correlated the occurrence of 20 daes in shimokita area with c curve davisiana events identified in previous studies the c curve fluctuations appear to be generally synchronized in the north pacific sea of okhotsk and southern ocean supporting the interpretation that daes are intermediate water changes possibly caused by ice cover fluctuations in high latitude regions on the background of the glacial interglacial cycling

on the nature of an unusual wave train observed in the northern tien shan region we describe an unusual wave group that propagates in the northern tien shan region along the border between mountain ranges and the chu and ili depressions to the north this wave group which we call s l stands out against the short period coda on the recordings of local earthquakes and quarry explosions at distances up to 100 km the time t m needed for the s l group to reach maximum amplitude varies between 98 and 131 sec and at the same time the t m value does not depend on epicentral distance at distances up to 30 km the s l group has a very narrow spectrum t 1 5 1 8 sec but when the epicentral distance increases the predominant period also increases up to approximately 2 3 sec at 100 km characteristics of the wave group are significantly different for the zaili fault zone than for the regions to the west of 76 e and to the east of 79 e in the zaili fault region the s l group is characterized by great variability of velocity amplitude and polarization parameters even for nearby paths the s l group maintains an amplitude within 0 7 of its maximum for 4 36 sec depending on the path the polarization of the s l group is in the vertical plane in the zaili fault zone region and in the horizontal plane in other regions particle motion is elliptical or almost circular we suggest that the s l group consists of shear waves propagating in a subvertical wave guide and reflected from a thin upper mantle layer

why the 2002 denali fault rupture propagated onto the totschunda fault implications for fault branching and seismic hazards 1 the propagation of the rupture of the mw7 9 denali fault earthquake from the central denali fault onto the totschunda fault has provided a basis for dynamic models of fault branching in which the angle of the regional or local prestress relative to the orientation of the main fault and branch plays a principal role in determining which fault branch is taken geoearthscope lidar and paleoseismic data allow us to map the structure of the denali totschunda fault intersection and evaluate controls of fault branching from a geological perspective lidar data reveal the denali totschunda fault intersection is structurally simple with the two faults directly connected at the branch point 227 2 km east of the 2002 epicenter the 2002 rupture diverges southeast to become the totschunda fault we use paleoseismic data to propose that differences in the accumulated strain on each fault segment which express differences in the elapsed time since the most recent event was one important control of the branching direction we suggest that data on event history slip rate paleo offsets fault geometry and structure and connectivity especially on high slip rate short recurrence interval faults can be used to assess the likelihood of branching and its direction analysis of the denali totschunda fault intersection has implications for evaluating the potential for a rupture to propagate across other types of fault intersections and for characterizing sources of future large earthquakes

radiolarian faunal provinces in surface sediments of the greenland iceland and norwegian gin seas the overall abundance and species composition of the polycystine and phaeodarian radiolaria have been determined in 63 surface sediment samples from the gin seas these results are compared to chemical and physical properties of the overlying water masses there are three abundance maxima in the distribution of radiolarian skeletal debris preserved in these surface sediments centered on the iceland plateau southern norwegian basin and northern norwegian basin the most commonly encountered species were a spumellarida actinomma boreale a leptoderma larcospira minor and phorticium clevei b nassellarida amphimelissa setosa artobotrys boreale lithomelissa setosa lithocampe platycephala pseudodictyophimus gracilipes cycladophora davisiana a ndlithomitra lineata based on factor analysis of the core top assemblages the radiolarian species were grouped into three associations factor 1 a polar and arctic water association dominated by amphimelissa setosa varimax factor score 5 269 high factor component values are found in the iceland plateau area and in a wedge just north of the iceland faeroe ridge factor 2 an atlantic water association dominated by pseudodictyophimus gracilipes 3 247 lithomelissa setosa 2 731 and actinomma boreale 1 851 high factor component values are found in the eastern part of the norwegian sea particularly in the area under the influence of the norwegian current and factor 3 an atlantic and arctic water mixed association dominated by lithocampe platycephala 3 251 lithomelissa setosa 2 176 actinomma leptoderma 1 994 and artobotrys boreale 1 504 high factor component values are found immediately to the east of the iceland plateau in correspondence to the deepest part of the norwegian basin the correlation coefficients obtained between seasonal sea surface temperature and factors 1 r 2 d 0 835 a nd 2 r 2 d 0 891 show a good fit whilst for factor 3 there was a less marked r 2 d 0 497 but still significant at the 5 confidence level correlation for fifth degree polynomial regression functions the factors correlated better with the summer than the winter sea surface temperatures however at 20 50 100 and 200 m depth the correlation became increasingly better particularly so for the winter situation the highest species richness for polycystine radiolarians 28 species was found in the warm atlantic domain the lowest 24 species was found in the colder arctic and polar domains whilst an area approximating the position of the arctic front had between 24 and 28 species 1998 elsevier science b v all rights reserved

variations of east asian summer monsoon since the last deglaciation based on mg ca and oxygen isotope of planktic foraminifera in the northern east china sea 1 variations in mg ca based sea surface temperature and oxygen isotope ratio 18o of the surface water in the northern east china sea ecs were reconstructed with high resolution during the last 18 kyr using planktic foraminifera millennial scale variations between warmer more saline surface water and cooler less saline surface water were recognized during the early deglacial period and the holocene suggesting changes in the mixing ratio between the kuroshio water and the changjiang diluted water stronger east asian summer monsoon easm precipitation events in south china are identified at 10 5 8 8 7 0 5 3 4 7 2 9 1 7 and 0 5 ka based on sea surface salinity sss records of the northern ecs weaker easm precipitation events are also detected at 9 3 8 3 7 3 6 0 3 3 2 3 0 7 and 0 4 ka during the holocene these events agree with the maxima in 18o records of stalagmites from various parts of the changjiang yangtze river drainage this agreement supports that our sss record properly captures the millennial scale dry less easm precipitation events over the drainage basin of the changjiang river during the holocene these dry events are also in good agreement with north atlantic ice rafted events suggesting a teleconnection between north atlantic climate and the easm during the holocene

radiolarian flux at an images site at the western margin of the subarctic pacific and its seasonal relationship to the oyashio cold and tsugaru warm currents seasonal changes of radiolarian flux in the far western area of the western subarctic gyre in the pacific ocean were examined based on samples from a sediment trap experiment deployed at a site off the northern honshu island of japan from june 2002 to may 2003 warm and neritic water species associated with the tsugaru warm current tgc originating from the japan sea were dominant while the cold water species associated with the oyashio cold current were relatively few in spite of the location of the site in the subarctic province r mode cluster analysis was used to divide species specific flux patterns into 5 groups of fauna associated with 1 the tgc forerunner in june 2002 2 the tgc main flow from september to november 2002 3 the neritic water in december 2002 4 the oyashio cold current in may 2003 and 5 surface productivity in the spring of 2002 2003 together with the tgc in summer 2002

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

shortening within underplated oceanic crust beneath the central california margin structures within a tectonically underplated layer of early miocene age oceanic crust indicate that the lower crust of offshore central california has been deformed under compression prior to the inception of the san andreas transform system along the continental margin shortening in the lower crust is inferred from the geometry of two structures the santa lucia monocline and the santa maria antiform delineated by an integrated interpretation of multichannel and wide angle seismic reflection data in conjunction with regional gravity data and teleseismic receiver functions the 700 km of multichannel seismic data and 300 km of wide angle seismic data from the 1986 pacific gas and electric edge seismic experiment form the primary data base used to establish the northwesterly trend and extent of the monocline and the wnw trend of the antiform in cross sectional view the santa lucia monocline is a 30 kink in the oceanic crust while the santa maria antiform is characterized by local thickening of the oceanic crust these structures are probably the result of convergence between the monterey and arguello microplates that took place as subduction along the margin waned the multichannel seismic reflection data image two miocene age shelf basins the santa lucia and offshore santa maria basins that formed within a transtensional stress regime the offshore santa maria basin directly overlies the santa maria antiform suggesting that either the upper and lower crustal stress regimes were completely decoupled in miocene time or that the two features formed in different places differential slip between the upper crust and lower crust may have been accommodated along a detachment zone located above oceanic crust convergence within the oceanic crust and apparent differential motion between upper and lower crust are indicative of the processes that can affect the transition from subduction to an oceanic continental transform zone

automatic reconstruction of fault networks from seismicity catalogs three dimensional optimal anisotropic dynamic clustering 1 we propose a new pattern recognition method that is able to reconstruct the three dimensional structure of the active part of a fault network using the spatial location of earthquakes the method is a generalization of the so called dynamic clustering or k means method that partitions a set of data points into clusters using a global minimization criterion of the variance of the hypocenters locations about their center of mass the new method improves on the original k means method by taking into account the full spatial covariance tensor of each cluster in order to partition the data set into fault like anisotropic clusters given a catalog of seismic events the output is the optimal set of plane segments that fits the spatial structure of the data each plane segment is fully characterized by its location size and orientation the main tunable parameter is the accuracy of the earthquake locations which fixes the resolution i e the residual variance of the fit the resolution determines the number of fault segments needed to describe the earthquake catalog the better the resolution the finer the structure of the reconstructed fault segments the algorithm successfully reconstructs the fault segments of synthetic earthquake catalogs applied to the real catalog constituted of a subset of the aftershock sequence of the 28 june 1992 landers earthquake in southern california the reconstructed plane segments fully agree with faults already known on geological maps or with blind faults that appear quite obvious in longer term catalogs future improvements of the method are discussed as well as its potential use in the multiscale study of the inner structure of fault zones

new northwest pacific radiolarian data as a tool to estimate past sea surface and intermediate water temperatures a new radiolarian data set for transfer function estimates of past sea surface temperature sst and intermediate water temperature was developed in this study for the northwestern pacific ocean covering a region from 1 to 50 n and 120 to 167 e we analyzed 87 sediments surface samples selected 30 species and or species group found in shallow water for estimating past summer sst and 17 species and or species group found in the intermediate water for estimating past intermediate water temperature since the intermediate water temperature changes greatly between 200 and 500 m our estimates provide values at 500 m because temperatures are relatively stable between 500 and 1000 m in this context we estimated past summer sst and intermediate water at 500 m temperature within an error margin of 0 9 and 1 2 c respectively a test of the accuracy of our transfer functions conducted on core samples provided by iodp expedition 346 site u1429 in the northern east china sea showed that the reconstructed summer ssts fluctuated between 17 2 and 26 5 c in selected late pleistocene sequences these temperatures corresponded to modern winter and summer sst respectively which highlights the ability of our new database to accurately reconstruct summer sst the reconstructed intermediate water temperature fluctuates between 3 and 8 c which corresponds to the observed temperature range at depths of 500 m at high and midlatitudes respectively

liquefaction at oceano california during the 2003 san simeon earthquake the 2003 m 6 5 san simeon california earthquake caused liquefaction induced lateral spreading at oceano at an unexpectedly large distance from the seismogenic rupture we conclude that the liquefaction was caused by ground motion that was enhanced by both rupture directivity in the mainshock and local site amplification by unconsolidated fine grained deposits liquefaction occurred in sandy artificial fill and undisturbed eolian sand and fluvial deposits the largest and most damaging lateral spread was caused by liquefaction of artificial fill the head of this lateral spread coincided with the boundary between the artificial fill and undisturbed eolian sand deposits values of the liquefaction potential index in general were greater than 5 at liquefaction sites the threshold value that has been proposed for liquefaction hazard mapping although the mainshock ground motion at oceano was not recorded peak ground acceleration was estimated to range from 0 25 and 0 28 g on the basis of the liquefaction potential index and aftershock recordings the estimates fall within the range of peak ground acceleration values associated with the modified mercalli intensity vii reported at the u s geological survey usgs did you feel it web site

variability of the path of the kuroshio ocean current over the past 25 000 years the kuroshio current is the strong northwestern component of the subtropical north pacific ocean gyre and advects a large amount of heat from the tropics to northern mid latitudes the kuroshio has bimodal stationary flow patterns with small and large meander paths east of central japan1 2 which switch on annual and decadal timescales3 4 these switches seem to be caused by changes in current velocity and volume transport of the north equatorial current that are associated with variations in the trade wind intensity in the eastern equatorial north pacific ocean5 6 here we present alkenone derived sea surface temperature records at multicentennial resolution from sediment cores from the nishishichitou ridge off central japan these 25 000 year records show that the kuroshio path has also fluctuated on millennial timescales this variability resembles that of the subtropical high pressure of the north pacific reconstructed from terrestrial pollen distributions water levels in north american lakes and marine micropalaeontological records7 together these data indicate that climate variability off central japan over the past 25 000 years may be part of a circum pacific phenomenon reflecting the rate of subtropical surface circulation in the north pacific ocean

deepwater formation in the north pacific during the last glacial termination between approximately 17 500 and 15 000 years ago the atlantic meridional overturning circulation weakened substantially in response to meltwater discharges from disintegrating northern hemispheric glacial ice sheets the global effects of this reorganization of poleward heat flow in the north atlantic extended to antarctica and the north pacific here we present evidence from north pacific paleo surface proxy data a compilation of marine radiocarbon age ventilation records and global climate model simulations to suggest that during the early stages of the last glacial termination deep water extending to a depth of approximately 2500 to 3000 meters was formed in the north pacific a switch of deepwater formation between the north atlantic and the north pacific played a key role in regulating poleward oceanic heat transport during the last glacial termination

stress induced seismic azimuthal anisotropy sand shale content and depth trends offshore north west australia abstractseismic azimuthal anisotropy is apparent when p wave velocities vary with source receiver azimuth and downward propagating s waves split into two quasi s waves polarized in orthogonal directions not accounting for these effects can degrade seismic image quality and result in erroneous amplitude analysis and geologic interpretations there are currently no physical models available to describe how azimuthal anisotropy induced by differential horizontal stress varies with sand shale lithology and depth we develop a model that does so in unconsolidated sand shale sequences offshore north west australia our method naturally introduces two new concepts critical anisotropy and anisotropic depth limit critical anisotropy is the maximum amount of azimuthal anisotropy expected to be observed at the shallowest sediment burial depth where the confining pressure and sediment compaction are minimal the anisotropic depth limit is the maximum depth where the stress induced azimuthal anisotropy is ex

monsoon forcing hydrodynamics of the kuroshio current and tectonic effects on sedimentary carbon and sulfur cycling in the okinawa trough since 90 ka 1 monsoon forcing and hydrodynamic effects controlled carbon and sulfur biogeochemistry over the last 90 ka in a 43 m core from the okinawa trough ot total organic carbon toc contents co vary with summer insolation at 30 n suggesting monsoon forcing of primary productivity and organic carbon burial before the last glacial maximum lgm total sulfur ts contents varied concomitantly with toc however sea level rise and intensified kuroshio inflow during the holocene enhanced deepwater ventilation which resulted in ts depleted sediments with low degree of pyritization dop by contrast dop values were high during the previous highstand at 80 ka bp when sea level was similar to that in the holocene as well as during the lgm when deepwater circulation was relatively weak a topographic barrier is proposed to have sufficiently blocked the kuroshio current out of the ot during the previous sea level highstand which weakened deepwater ventilation and led to reducing diagenetic conditions tectonic rifting in the southern ot at 60 30 ka bp enabled the major change in hydrodynamics and sediment biogeochemistry

intermediate water ventilation change in the subarctic northwest pacific during the last deglaciation 1 the laminated sediments suggest significant depletion in dissolved oxygen of intermediate water in the north pacific during the last deglaciation however the cause of depleted oxygen during deglaciation is still a matter of debate here we present foraminiferal mg ca based intermediate and surface temperatures and 18o of seawater 18ow a proxy of salinity in the oyashio region in order to investigate intermediate water circulation through the last deglaciation results indicate that the intermediate water temperature and 18ow increased in association with ventilation age at the bolling allerod period suggesting that the poor ventilation at that time the surface record shows that the decrease of salinity preceded the slowdown of intermediate ventilation the coupled variation of intermediate and surface water suggests that the supply of cold fresh intermediate water diminished because of poor ventilation at the high latitude due to surface freshening

dynamic 3d simulations of earthquakes on en echelon faults one of the mysteries of earthquake mechanics is why earthquakes stop this process determines the difference between small and devastating ruptures one possibility is that fault geometry controls earthquake size we test this hypothesis using a numerical algorithm that simulates spontaneous rupture propagation in a three dimensional medium and apply our knowledge to two california fault zones we find that the size difference between the 1934 and 1966 parkfield california earthquakes may be the product of a stepover at the southern end of the 1934 earthquake and show how the 1992 landers california earthquake followed physically reasonable expectations when it jumped across en echelon faults to become a large event if there are no linking structures such as transfer faults then strike slip earthquakes are unlikely to propagate through stepover s 5 km wide

double difference tomography the method and its application to the hayward fault california we have developed a double difference dd seismic tomography method that makes use of both absolute and relative arrival times by reducing systematic errors using the more accurate relative arrival times the method produces an improved velocity model simultaneously it yields event locations of a quality equivalent to those of the dd location method while avoiding simplifying assumptions of that method we test this method on a synthetic dataset and find that it produces a more accurate velocity model and event locations than standard tomography we also test this method on a hayward fault california earthquake dataset spanning 1984 1998 the earthquakes relocated by this method collapse to a thin line along the fault trace consistent with previous results the dd velocity model has sharper velocity contrasts near the source region than the standard tomography model

early to middle pleistocene paleoceanographic history of southern japan based on radiolarian data from iodp exp 314 315 sites c0001 and c0002 abstract during the mid pleistocene transition mpt spanning from 0 8 to 1 2 ma the prevailing 41 kyr glacial cycles were replaced by longer cycles with a period of ca 100 kyr this event was also accompanied by important climate changes such as the expansion of the northern hemisphere ice sheet the impact of the mpt on the kuroshio current off southern japan remains unknown however in the absence of a long core covering the period of the mpt in this area preservation of calcareous microfossils is poor but polycystine radiolarians are abundant and well preserved therefore they are an excellent alternative proxy for reconstructing past climate change indeed because numerous studies have examined the geographic distribution of modern radiolarian species the relationships between several radiolarian assemblage groups e g equatorial to sub arctic assemblage groups and climatic conditions are well understood we examined the impact of the mpt on the kuroshio current off the kii peninsula southern japan by investigating radiolarian assemblages in deep sea cores collected during integrated ocean drilling program expedition 314 315 we studied the radiolarian assemblages in 293 samples from cores obtained at site c0001 holes e and f and site c0002 hole d the age models for these cores which are based on biostratigraphy and chemostratigraphy showed that sediments from the period between marine isotope stage mis 15 and mis 8 which includes the mid brunhes event are missing from these cores however continuous data are available between mis 63 1 82 ma and mis 15 0 5 ma therefore using the ecological properties of 11 key radiolarian species we reconstructed regional paleoceanographic changes between 1 82 and 0 5 ma radiolarian fauna revealed that the relative abundance of kuroshio and the central pacific water taxa e g didymocyrtis tetrathalamus and the polysolenia spinosa lappacea group respectively increased drastically during the mpt possibly indicating a northward shift of the kuroshio at that time the relative abundance of rhizosphaera mediana an oyashio kuroshio mixed water species also increased during this interval thus a southward shift of the oyashio current may have occurred synchronously with a northward shift of the kuroshio during the mpt

abrupt ventilation changes in the japan sea over the last 30 ky evidence from deep dwelling radiolarians abstract the japan sea has its own deep circulation system with its deeper parts occupied by cold and highly oxygenated water formed by winter convection in its northwestern reaches we elucidate the modern depth distribution of radiolarian species and their relation to water masses from the study of plankton tows and surface sediments cycladophora davisiana occurs in a depth interval between 1000 m and 2000 m deep layer of jspw japan sea proper water and actinomma boreale leptoderma group in depths below 2000 m bottom layer of jspw the study of seven sediment cores located in water depths ranging from 807 to 3613 m show that the radiolarian assemblages have varied since 30 cal ka bp indicating changes in water ventilation strength in this marginal sea during the interval from 30 to 17 cal ka bp ventilation was restricted to an intermediate layer beneath the low salinity surface water while the deeper zone was filled with static anoxic water deep ventilation began abruptly at 14 cal ka bp cold and oxygen rich water began to sink into the bottom layer as a result of cold oceanic inflow from the northwestern pacific through the tsugaru strait in the north deep convection activity increased from 13 to 12 cal ka bp which coincides with the younger dryas like cooling event and then stopped at 12 11 5 cal ka bp bottom water ventilation during the holocene has been dependent on high salinity inflow through the tsushima strait in the south and winter cooling in the northwestern part of the japan sea deep water was being actively formed in the early holocene in contrast to the static bottom water this bottom water formation has resulted in relatively constant water composition since 9 cal ka bp with the overall increase in high salinity oceanic water inflow although the latter decreased transiently from 7 to 5 cal ka bp in concert with climatic warming

stability of the kuroshio path with respect to glacial sea level lowering 1 we investigate the changes of the kuroshio current in the east china sea during the last glacial maximum based on numerical experiments using an ocean model and geochemical analyses of marine sediments our numerical experimental results indicate that there was little effect of sea level change on the path of the kuroshio during the glacial period geochemical proxy records of marine sediment cores recovered from inside and outside the okinawa trough ot show no significant difference in glacial sea surface temperature and planktonic foraminiferal 18o between the ot and the ryukyu forearc this indicates that the glacial sea surface temperature and salinity were almost the same inside and outside the ot hence during the glacial period kuroshio water most likely intruded into the ot and flowed along the shelf break until it drained out through the tokara strait

controls on sediment distribution in the coastal zone of the central california transform continental margin usa abstract we use 10 000 km of high resolution seismic reflection data together with multibeam bathymetry to document complex and highly variable post last glacial maximum lgm sediment distribution and thickness in the coastal zone 10 m isobath to 5 6 km offshore along a 800 km section of central california s transform continental margin sediment thickness ranges from 0 seafloor bedrock to 64 m with a mean of 8 7 m we delineate 25 coastal zone sediment domains and group them based on common geomorphology and sediment occurrence thickest sediment occurs in mountain front and large river domains which comprise 14 5 and 7 9 of the coastal zone and contain 30 1 and 18 2 of coastal zone sediment respectively in contrast small river domains and sediment poor shelf domains comprise 50 7 and 15 7 of the coastal zone and contain 18 4 and 12 7 of its sediment the distribution and thickness of post lgm sediment in the coastal zone is controlled by a combination of tectonics sediment supply and eustasy sediment is derived from a tectonically controlled coastal landscape of rapidly uplifting mountain fronts more slowly uplifting marine terraces and fault bounded headlands and alluvial estuarine troughs sediment supply is maximized along steep landslide prone mountain fronts and at the mouths of large watersheds and minimized along lower relief terraced coastal landscape drained by smaller rivers and creeks in the offshore coastal zone tectonics generates local uplifts and basins and influences shelf width and gradient as well as the locations of some shelf incised submarine canyons sea level rise raises base level drowns estuaries creates accommodation space on the shelf amount based on gradient and isolates the heads of many submarine canyons at or near the shelfbreak comparison of shelf sediment volumes with estimates of unaltered watershed sediment supply reveals that a relatively small proportion of post lgm sediment supply is preserved on the shelf offshore of some of the largest rivers sediments deposited in shoreline and shelf environments have limited preservation potential and the most complete long term geologic record of the post lgm transgression and highstand is likely represented in slope and submarine fan deposits

radiolarian based transfer function for the estimation of sea surface temperatures in the southern ocean atlantic sector a new radiolarian based transfer function for sea surface temperature sst estimations has been developed from 23 taxa and taxa groups in 53 surface sediment samples recovered between 35 and 72 s in the atlantic sector of the southern ocean for the selection of taxa and taxa groups ecological information from water column studies was considered the transfer function allows the estimation of austral summer sst december march ranging between 1 and 18 c with a standard error of estimate of 1 2 c sst estimates from selected late pleistocene squences were sucessfully compared with independent paleotemperature estimates derived from a diatom transfer function this shows that radiolarians provide an excellent tool for paleotemperature reconstructions in pleistocene sediments of the southern ocean

source and site characteristics of earthquakes that have caused exceptional ground accelerations and velocities abstract this study investigates the characteristics of the free field strong motion records that have yielded the 100 largest peak accelerations and the 100 largest peak velocities in a relatively complete database of accelerograms recorded through the summer of 2007 the peak is defined as the maximum zero to peak amplitude of the acceleration or velocity vector during the strong shaking this compilation includes 35 records with peak acceleration greater than 1 g 980 cm sec 2 and 40 records with peak velocities greater than 100 cm sec the results sample an estimated 150 000 instrument years of strong motion recordings the geometric mean of the two horizontal components of acceleration or velocity as used in many ground motion prediction equations is typically 0 76 times the magnitude of this vector peak accelerations in the top 100 come from earthquakes as small as magnitude 4 8 while velocities in the top 100 all come from earthquakes with magnitude 5 7 or larger these records are dominated by crustal earthquakes with thrust oblique thrust or strike slip mechanisms normal faulting mechanisms in crustal earthquakes constitute under 5 of the records in the databases searched and an even smaller percentage of the 100 largest acceleration or velocity records all national earthquake hazard reduction program site categories have contributed exceptional records in proportions similar to the extent that they are represented in larger databases

spatial distribution pattern of living polycystine radiolarian taxa baseline study for paleoenvironmental reconstructions in the southern ocean atlantic sector the horizontal and vertical distribution of living polycystine radiolarian taxa was investigated at seven locations on a n s transect between the antarctic zone 54 s in the southern ocean and the subtropical zone 30 s in the southeastern south atlantic during austral autumn four to five depth intervals from 0 to 1000 m depth were sampled with 55 m mesh opening closing nets in combination with a hydrographic ctd survey a factor analysis for the delineation of specific assemblages and the relation between different taxa and taxa groups resulted in eight factors of which five represent surface and subsurface factors and three deep water factors the spatial distribution pattern of the factors shows that distinct radiolarian assemblages are closely related to water depth distribution of water masses hydrographic boundaries such as frontal systems and nutrients this documents that the distribution of individual radiolarian assemblages is controlled by specific hydrographic conditions and water depth and allows the definition and consolidation of the autecological demands these data are crucial for the paleoenvironmental interpretation of fossil polycystine radiolarian assemblages the comparison of living polycystine radiolarian taxa with those preserved in surface sediments shows general similarities this study includes the first documentation on the distribution of living cycladophora davisiana in circumpolar deep water and supports previous studies stating that c davisiana also lives in deep water masses

dynamics of fault interaction parallel strike slip faults we use a two dimensional finite difference computer program to study the effect of fault steps on dynamic ruptures our results indicate that a strike slip earthquake is unlikely to jump a fault step wider than 5 km in correlation with field observations of moderate to great sized earthquakes we also find that dynamically propagating ruptures can jump both compressional and dilational fault steps although wider dilational fault steps can be jumped dilational steps tend to delay the rupture for a longer time than compressional steps do this delay leads to a slower apparent rupture velocity in the vicinity of dilational steps these dry cases assumed hydrostatic or greater pore pressures but did not include the effects of changing pore pressures in an additional study we simulated the dynamic effects of a fault rupture on undrained pore fluids to test sibson s 1985 1986 suggestion that wet dilational steps are a barrier to rupture propagation our numerical results validate sibson s hypothesis by demonstrating that the effect of the rupture on the undrained pore fluids is to inhibit the rupture from jumping dilational stepovers the basis of our result differs from sibson s hypothesis in that our model is purely elastic and does not necessitate the opening of extension fractures between the fault segments

surface water evolution of the eastern east china sea during the last 36 000 years abstract planktic foraminifera have been studied in two high resolution cores raised from the continental slope of the eastern east china sea ecs to reconstruct the surface water history ams 14c dating on fifteen horizons revealed that the two cores kh82 4 14 and rn80 pc3 contain continuous records of the last 36 and 17 thousand cal years respectively thirty one planktic foraminiferal species which are commonly found in the present western north pacific and the ecs are recognized in down core samples three faunal phases iii ii and i distinguished by characteristic planktic foraminiferal assemblages suggest three major paleoenvironmental stages of the surface water of the eastern ecs since 36 000 yr b p 1 a stage influenced by coastal water from 36 000 to 19 500 yr b p 2 a stage also influenced by coastal water and extremely low salinity from 19 500 to 10 500 yr b p and 3 a stage controlled by the modern open sea water related to the kuroshio with both higher temperature and higher salinity since 10 5 8 5 thousand years b p oxygen isotope records of the planktic foraminiferal species g bulloides show that the three planktic foraminiferal faunal phases correspond to the last glacial deglacial and postglacial stages respectively the planktic foraminiferal assemblage during the deglacial stage which is represented by high percentages of g quinqueloba is quite different from those during the glacial and postglacial stages linked to a large amount of river discharge from the chinese continent a negative oxygen isotope excursion in g bulloides during the same period is highly correlated to the g quinqueloba anomaly also indicating a decrease in surface water salinity furthermore the sedimentation rate of core kh82 4 14 during 19 15 thousand years b p is much higher than the rates during the glacial and postglacial stages suggesting a great increase in the supply of terrigenous material related to an increased river and sediment discharge during the early deglaciation the coastal water influenced stage of the eastern ecs terminated gradually at 10 5 8 5 thousand years b p since the warm kuroshio current and its branches flowed in the eastern ecs as today the formation of the postglacial surface water circulation pattern in the eastern ecs was closely related to the flow patterns of the kuroshio current

the vertical distribution of radiolaria in the waters surrounding japan abstract geographic and vertical distribution patterns of living radiolaria are closely related to the characters of the water column we studied living radiolaria in samples collected at closely spaced depth intervals in the waters surrounding japan in order to understand their vertical distribution and its controlling factors such information is needed to reconstruct past vertical water mass structure the japanese islands are surrounded by the marginal japan sea and the north pacific ocean and from approximately 46 n to 26 n they thus extend across a large latitudinal range and are exposed to a similarly wide range of environmental conditions inducing the warm kuroshio tsushima and tsugaru currents and the cold oyashio current we performed plankton tows mesh size 63 mm from late may to early june 2002 at eight sites sampling the upper 200 m of the water column at seven depth intervals we recognized five radiolarian assemblages the upper surface assemblage 0 40 m the lower surface assemblage 40 80 m the surface assemblage 0 80 m the subsurface assemblage 80 200 m and the lower surface subsurface assemblage 40 200 m groups pseudodictyophimus gracilipes and tetrapyle octacantha juvenile show tropical submergence i e they live at the surface in high latitudes and at greater depth in low latitudes four taxa live at specific temperature and salinity acrosphaera spinosa larcopyle butschlii challengeron diodon and stichocorys seriata four taxa are associated with characteristic temperatures neosemantis distephanus arachnocorys umbellifura antarctissa sp 1 and saccospyris conithorax

paleoceanographic history of the northwest pacific ocean over the past 740kyr discerned from radiolarian fauna abstract the northwest pacific ocean is characterized by a strong mixing of water masses due to the interplay of three distinct currents i e the kuroshio the tsugaru and the oyashio the c9001c drill core site located east of the shimokita peninsula and directly influenced by the tsugaru warm current and the oyashio subarctic current was used here to reconstruct the paleoceanographical history of this region especially focusing on the mid brunhes event mbe and its consequences this core provides a continuous record from marine isotope stage mis 18 740 ka to the present polycystine radiolarian assemblages were analyzed to highlight paleoceanographic and sea surface temperature changes at this site based on the radiolarian fauna seven time periods are defined which coincide with changes in the dynamics of the tsugaru and oyashio currents respectively the oldest time interval covered by our analysis i e vii 740 621 ka was marked by generally sluggish ocean circulation the tsugaru current influence increased during the following interval vi 621 478 ka which encompasses interglacials mis 15 and 13 while the oyashio current strengthened during the interval v 478 337 i e from glacials mis 12 to 10 these latter intervals vi to v constitute a long climatic transitional period where tsugaru current and oyashio current influences are strengthened in the time period from interval iv to interval i 0 337 ka the warming intensity of interglacials mis 9 mis 5 appears to be close to the modern one however several unusually warm glacials associated with a relatively strong tsugaru current flow were identified during this interval e g mis 8 and mis 6 radiolarian productivity data suggest that during intervals vii to v deep water masses are rich in nutrient content however a high vertical mixing event is recorded after interval iv when high nutrient concentrations appear to shift to the surface layer

geometry and late pleistocene displacement of the shoreline and oceano fault zones san luis obispo bay californiageometry and late pleistocene displacement of the shoreline and oceano fault zones

comparison of radiolarian vertical distributions in the okhotsk sea near the kuril islands and in the northwestern north pacific off hokkaido island abstract the vertical distribution of radiolarians was investigated by using a closing type net with 63 m mesh in the okhotsk sea station nu 2 near bussol strait down to 1000 m depth and in the northwestern north pacific oyashio region station x down to 500 m depth both stations were sampled in september 1995 radiolarian standing stocks were high between 50 and 200 m at both stations and generally decreased with depth the depth integrated living total radiolarian standing stock from 0 to 500 m at station nu 2 was more than three times higher than that at station x the maximum standing stocks of polycystine radiolarians occurred in the 50 100 m depth interval but there were also significant abundance peaks of phaeodarian radiolarians in the 100 200 m interval at both stations the radiolarian production is likely to be associated with not only phytoplankton production in upper waters but also with microbial production in intermediate waters a total of 79 taxa were encountered 25 spumellaria 41 nassellaria and 13 phaeodaria five radiolarian groups were obtained based on r mode cluster analysis group a lower intermediate water dwellers 300 1000 m group b taxa with different distributions in the okhotsk sea 300 1000 m and in the oyashio region 0 100 m group c upper intermediate water dwellers 200 500 m group d surface subsurface water dwellers 0 200 m and group e taxa with pronounced 200 m

radiolarians in the sea of okhotsk and their ecological implication for paleoenvironmental reconstructions to assess the relationship of radiolarian production species distribution in water and surface sediment to water mass characteristics biological productivity and export regimes in the sea of okhotsk sok we accomplished a quantitative analysis of radiolarian assemblages obtained from 35 surface sediment samples and 115 plankton samples recording the radiolarian depth distribution in the upper 1000 m of the water column at 23 locations this study augments the knowledge on the autecological demands of radiolarians dwelling in a specific hydrographic and biological environment and extracts new information on the significance of radiolarians for the assessment of past oceanographic and climatic development in high latitudes highest radiolarian accumulation rates and seasonal radiolarian standing stocks are encountered in the western part of the sok close to sakhalin marking the environmental conditions in this area as most favorable for radiolarian production maximum standing stocks occur during summer indicating that the radiolarian signal preserved in the sediment record is mainly produced during this season when the mesopelagic biomass is at highest activity we identified seven radiolarian species and groups related to specific water mass characteristics depth habitats and productivity regimes of those dictyophimus hirundo and cycladophora davisiana are most prominent in the sea of okhotsk intermediate water 200 1000 m the latter representing an indicator of the occurrence of cold and well ventilated intermediate deep water and enhanced export of organic matter from a highly productive ocean surface while antarctissa sp 1 is typically related to the cold water sea of okhotsk dicothermal layer sodl ranging between 50 and 150 m water depth the surface waters above the sodl affected by strong seasonal variability are inhabited predominantly by taxa belonging to the spongodiscidae having a broad environmental tolerance taxa only found in the sediment record show that the plankton study did not cover all assemblages occurring in the modern sok this accounts for an assemblage restricted to the western kurile basin and apparently related to environmental conditions influenced by north pacific and japan sea waters other important taxa include species of the plagoniidae group representing the most prominent contributors to the sok plankton and surface sediments these radiolarians show a more opportunistic occurrence and are indicative of high nutrient supply in a hydrographic environment characterized by pronounced stratification enhancing heterotrophic activity and phytodetritus export r 2005 elsevier ltd all rights reserved

ventilation of the glacial deep pacific ocean measurements of the age difference between coexisting benthic and planktic foraminifera from western equatorial pacific deep sea cores suggest that during peak glacial time the radiocarbon age of water at 2 kilometers depth was no greater than that of today these results make unlikely suggestions that a slowdown in deep ocean ventilation was responsible for a sizable fraction of the increase of the ratio of carbon 14 14c to carbon in the atmosphere and surface ocean during glacial time comparison of 14c ages for coexisting wood and planktic foraminifera from the same site suggests that the atmosphere to surface ocean 14c to c ratio difference was not substantially different from today s

subsurface geometry of the san andreas calaveras fault junction influence of serpentinite and the coast range ophiolite while an enormous amount of research has been focused on trying to understand the geologic history and neotectonics of the san andreas calaveras fault saf cf junction fundamental questions concerning fault geometry and mechanisms for slip transfer through the junction remain we use potential field geologic geodetic and seismicity data to investigate the 3 d geologic framework of the saf cf junction and identify potential slip transferring structures within the junction geophysical evidence suggests that the san andreas and calaveras fault zones dip away from each other within the northern portion of the junction bounding a triangular shaped wedge of crust in cross section this wedge changes shape to the south as fault geometries change and fault activity shifts between fault strands particularly along the calaveras fault zone cfz potential field modeling and relocated seismicity suggest that the paicines and san benito strands of the cfz dip 65 to 70 ne and form the southwest boundary of a folded 1 to 3 km thick tabular body of coast range ophiolite cro within the vallecitos syncline we identify and characterize two steeply dipping seismically active cross structures within the junction that are associated with serpentinite in the subsurface the architecture of the saf cf junction presented in this study may help explain fault normal motions currently observed in geodetic data and help constrain the seismic hazard the abundance of serpentinite and related cro in the subsurface is a significant discovery that not only helps constrain the geometry of structures but may also help explain fault behavior and the tectonic evolution of the saf cf junction

a radiolarian based palaeoclimate history of core y9 northeast of campbell plateau new zealand for the last 160 kyr abstract sea surface temperatures ssts based on radiolarian assemblage changes are estimated for the last 160 kyr from a sediment core y9 recovered from pukaki saddle northeast of campbell plateau site y9 lies beneath subantarctic surface water saw immediately to the north of the subantarctic front saf which in this region is bathymetrically constrained by the edges of campbell plateau and defines the northern boundary of the antarctic circumpolar current acc radiolarian assemblages are characterised by an exceptionally high abundance of the antarctic to subantarctic species antarctissa spp up to 68 especially during glacial intervals sst estimates are derived using factor analysis and the modern analog technique both methods capture the glacial interglacial g i pattern the sst reconstructions show the changing relative influence of distinct water masses during the past g i cycle with major temperature variations of the order of 7 9 c at glacial terminations glacials marine isotope stages mis 6 and 2 are associated with particularly cool ssts that are indicative of a more vigorous saf acc and an enhancement of the inflow through pukaki saddle and or frequent development of cold core eddies at the saf by contrast the influence of warmer waters and relaxation of the acc during interglacials can be inferred from temperatures slightly warmer e g mid holocene and or comparable to present day e g mis 5e during these intervals relatively warmer temperatures most likely indicate a higher warm core eddy activity due to a strengthened subtropical front and or a weakened inflow of cool water through pukaki saddle and or an increased stratification in the campbell plateau region furthermore the sst record is characterised by an abrupt warming at ca 10 kyr i e termination i the occurrence of a reversal at termination i and a warming event at the end of mis 4 coinciding with the a4 event in the byrd ice core these characteristics together with the pronounced g i cycle shown by the sst estimates suggest that site y9 is influenced by major oceanographic changes in the sw pacific and responds to thermal changes at high southern latitudes

the origin of the north pacific intermediate water possible source regions of the north pacific intermediate water npiw were investigated with synoptic conductivity temperature depth surveys in the okhotsk sea kuril basin a pycnostad referred to as the okhotsk sea mode water osmw was found in the density range of 26 6 27 the pycnostad is not seen in the western subarctic gyre wsag thus it is an indicative water peculiar to the okhotsk sea the maximum thickness is at 26 7 26 9 centered at 26 8 which coincides with the npiw density range in the north pacific subtropical gyre in the oyashio area east of the southern kuril islands and hokkaido waters that have intermediate temperature salinity and potential vorticity between the osmw and the wsag water were distributed suggesting a following transport route of the npiw source water the thick thus low q q is potential vorticity and low salinity water mass outflowing from the okhotsk sea mixes with the relatively warm saline and high q wsag water to form the oyashio water a coastal part of the oyashio water flows southwestward along the east coast of the southern kuril islands and hokkaido retaining the pycnostad q minimum a large part of the low q oyashio water flows further southward and merges with the kuroshio extension and then flows eastward forming new npiw in this process a salinity minimum develops and the q minimum disappears because of the mixing with a saline kuroshio water old npiw without a pycnostad in the npiw density range these results suggest that the origin of npiw is the water mass in the okhotsk sea osmw and the density of the water mass primarily determines the npiw density centered at around 26 8

powerful low frequency vibrators for active seismology in the past two decades active seismology studies in russia have made use of powerful 40 and 100 ton low frequency vibrators these sources create a force amplitude of up to 100 tons and function in the 1 5 3 3 6 and 5 10 hz frequency bands the mobile versions of the vibrator have a force amplitude of 40 tons and a 6 12 hz frequency band recording distances for the 100 ton vibrator are as large as 350 km enabling the refracted waves to penetrate down to 50 km depths vibrator operation sessions are highly repeatable having distinct summer or winter spectral patterns a long profile of seismic records allows estimation of fault zone depths using changes in recorded spectra other applications include deep seismic profiling seismic hazard mapping structural testing stress induced anisotropy studies seismic station calibration and large structure integrity testing the theoretical description of the low frequency vibrator is given in the appendices which contain numerical examples

temporal and spatial flux changes of radiolarians in the northwestern pacific ocean during 1997 2000 abstract in order to examine the radiolarian fluxes and evaluate their relationship to the physical and biological environments time series sediment traps were deployed at three stations stations 50n knot and 40n in the northwestern north pacific from 1997 to 2000 station 50n 50 n 165 e 3260 m is located in the center of western subarctic gyre wsag station knot 44 n 155 e 2957 m is located toward the margin of wsag and station 40n 40 n 165 e 2986 m is located in the subarctic boundary total radiolaria fluxes at station 40n showed higher values than those at the other two stations and were mainly attributed to the influence of relatively high temperature and high salinity subtropical gyre waters correlation coefficients between total mass fluxes mainly composed of diatoms and radiolarian fluxes at three stations were relatively low this is primarily because of the wide vertical distribution of radiolarians and various trophic patterns corresponding to their niche radiolarian species were classified according to their geographic water mass and vertical distributions based on previous studies using sediment samples as a result seasonal changes of radiolarian fluxes in each water mass showed patterns corresponding to particular controlling factors such as physical hydrography and food conditions among these patterns temporal changes in radiolarian taxonomic composition in the upper layer 0 100 m seemed to reflect well the sea surface temperature anomaly ssta changes affected by el nino and la nina events at station 40n therefore radiolarian assemblages can be used to reconstruct past ssta changes and to understand the past el nino and la nina teleconnection in the kuroshio oyashio extension region

strengths of serpentinite gouges at elevated temperatures serpentinite has been proposed as a cause of both low strength and aseismic creep of fault zones to test these hypotheses we have measured the strength of chrysotile lizardite and antigorite rich serpentinite gouges under hydrothermal conditions with emphasis on chrysotile which has thus far received little attention at 25 c the coefficient of friction of chrysotile gouge is roughly 0 2 whereas the lizardite and antigorite rich gouges are at least twice as strong the very low room temperature strength of chrysotile is a consequence of its unusually high adsorbed water content when the adsorbed water is removed chrysotile is as strong as pure antigorite gouge at room temperature heating to 200 c causes the frictional strengths of all three gouges to increase limited data suggest that different polytypes of a given serpentine mineral have similar strengths thus deformation induced changes in polytype should not affect fault strength at 25 c the chrysotile gouge has a transition from velocity strengthening at low velocities to velocity weakening at high velocities consistent with previous studies at temperatures up to 200 c however chrysotile strength is essentially independent of velocity at low velocities overall chrysotile has a restricted range of velocity strengthening behavior that migrates to higher velocities with increasing temperature less information on velocity dependence is available for the lizardite and antigorite gouges but their behavior is consistent with that outlined for chrysotile the marked changes in velocity dependence and strength of chrysotile with heating underscore the hazards of using room temperature data to predict fault behavior at depth the velocity behavior at elevated temperatures does not rule out serpentinite as a cause of aseismic slip but in the presence of a hydrostatic fluid pressure gradient all varieties of serpentine are too strong to explain the apparent weakness of faults such as the san andreas

a radiolarian based modern analogue dataset for palaeoenvironmental reconstructions in the southwest pacific abstract radiolarian species relative abundances have been estimated for a suite of 88 surface sediment samples obtained from a broad area of the southwest pacific southern ocean bounded by 10 s to 65 s in latitude and 145 e to 170 w in longitude this allowed the documentation of a long environmental gradient 28 8 to 1 4 c for mean annual sea surface temperature sst and covered the most important surface oceanographic features in the area including the subtropical stf subantarctic saf and antarctic polar apf fronts the most abundant species in the dataset show strong relationships to surface hydrography examples are antarctissa spp 5 abundance isoline is a good indicator for the average position of the saf colonials 5 isoline approximates the average location of the tasman front between new zealand and australia dictyocoryne profunda and tetrapyle octacantha essentially absent in subantarctic antarctic waters and documenting warm water connections to higher latitudes being present in the tasmanian retroflection region and or on the campbell plateau the factor analysis model with a calibration error of 1 3 c was based on 93 taxa of the 243 taxa recognised in this study and 7 factors assemblages which explained 87 4 of the total information contained in the dataset the first five assemblages are readily interpreted in terms of water masses oceanographic fronts and regions subtropical water tasman front factor 1 circumpolar surface water factor 2 equatorial pacific factor 3 subantarctic water campbell plateau factor 4 and as a subfactor for subtropical water factor 5 a canonical correspondence analysis identified sea surface temperature as the main environmental explanatory variable for samples with sst 7 c 28 c due to the elevated nitrate concentrations in high southern latitude surface waters nitrate concentration is the main explanatory variable when all samples are considered in a companion paper this modern analogue dataset has been applied to relative abundance data from sediment core y9 in order to reconstruct the sst changes over the last 160 ka at the easternmost boundary of the campbell plateau east of new zealand

tropical sea surface temperatures and the earth s orbital eccentricity cycles the tropical oceanic warm pools are climatologically important regions because their sea surface temperatures ssts are positively related to atmospheric greenhouse effect and the cumulonimbus cirrus cloud anvil such a warm pool is also present in the central tropical indian ocean paleo ssts estimated by the radiolarian transfer functions for the last 200 1400 kiloyears ka in a deep sea sediment core from this warm pool fluctuated within 2 75 c 26 14 28 89 c around the threshold temperature 27 c for the super greenhouse effect it is possible that this sst variation might have led to the corresponding fluctuation in the greenhouse effect and the cirrus cloud anvil in the geological past these paleo ssts also exhibited cyclicities at 100 and 400 ka corresponding to the earth s orbital eccentricity cycles results therefore imply that the tropical indian ocean warm pool persisted during the quaternary and the paleo ssts fluctuating at the orbital eccentricity frequencies might have modulated the intensity of greenhouse effect

radiolarian based paleotemperatures during the last 160 kyr at odp site 1089 southern ocean atlantic sector two cores site 1089 odp leg 177 and ps2821 1 recovered from the same location 40 56 ps 9 54pe at the subtropical front stf in the atlantic sector of the southern ocean provide a high resolution climatic record with an average temporal resolution of less than 600 yr a multi proxy approach was used to produce an age model for core ps2821 1 and to correlate the two cores both cores document the last climatic cycle from marine isotopic stage 6 mis 6 ca 160 kyr bp ka to present summer sea surface temperatures sssts have been estimated with a standard error of ca 8 1 16 c for the down core record by using q mode factor analysis imbrie and kipp method the paleotemperatures show a 7 c warming at termination ii last interglacial transition from mis 6 to mis 5 this transition from glacial to interglacial paleotemperatures with maximum temperatures ca 3 c warmer than present at the core location occurs earlier than the corresponding shift in n 18 o values for benthic foraminifera from the same core this suggests a lead of southern ocean paleotemperature changes compared to the global ice volume changes as indicated by the benthic isotopic record the climatic evolution of the record continues with a progressive temperature deterioration towards mis 2 high frequency millennial scale climatic instability has been documented for mis 3 and part of mis 4 with sudden temperature variations of almost the same magnitude as those observed at the transitions between glacial and interglacial times these changes occur during the same time interval as the dansgaard oeschger cycles recognized in the n 18 oice record of the grip and gisp ice cores from greenland and seem to be connected to rapid changes in the stf position in relation to the core location sudden cooling episodes younger dryas yd type and antarctic cold reversal acr type of events have been recognized for both termination i acr i and yd i events and ii acr ii and yd ii events and imply that our core is located in an optimal position in order to record events triggered by phenomena occurring in both hemispheres spectral analysis of our ssst record displays strong analogies particularly for high sub orbital frequencies to equivalent records from vostok antarctica and from the subtropical north atlantic ocean this implies that the climatic variability of widely separated areas the antarctic continent the subtropical north atlantic and the subantarctic south atlantic can be strongly coupled and co varying at millennial time scales a few to 10 ka periods and eventually induced by the same triggering mechanisms climatic variability has also been documented for supposedly warm and stable interglacial intervals mis 1 and 5 with several cold events which can be correlated to other southern ocean and north atlantic sediment records d 2002 elsevier science b v all rights reserved

geometry and earthquake potential of the shoreline fault central california abstract the shoreline fault is a vertical strike slip fault running along the coastline near san luis obispo california much is unknown about the shoreline fault including its slip rate and the details of its geometry here i study the geometry of the shoreline fault at seismogenic depth as well as the adjacent section of the offshore hosgri fault using seismicity relocations and earthquake focal mechanisms the optimal anisotropic dynamic clustering oadc algorithm ouillon et al 2008 is used to objectively identify the simplest planar fault geometry that fits all of the earthquakes to within their location uncertainty the oadc results show that the shoreline fault is a single continuous structure that connects to the hosgri fault discontinuities smaller than about 1 km may be undetected but would be too small to be barriers to earthquake rupture the hosgri fault dips steeply to the east while the shoreline fault is essentially vertical so the hosgri fault dips towards and under the shoreline fault as the two faults approach their intersection the focal mechanisms generally agree with pure right lateral strike slip on the oadc planes but suggest a non planar hosgri fault or another structure underlying the northern shoreline fault the shoreline fault most likely transfers strike slip motion between the hosgri fault and other faults of the pacific north america plate boundary system to the east a hypothetical earthquake rupturing the entire known length of the shoreline fault would have a moment magnitude of 6 4 6 8 a hypothetical earthquake rupturing the shoreline fault and the section of the hosgri fault north of the hosgri shoreline junction would have a moment magnitude of 7 2 7 5

radiolarian based transfer functions for estimating mean surface ocean temperatures and seasonal range new radiolarian based transfer functions to estimate sea surface temperature sst and seasonal range are presented the transfer fonctions are based on the approach originated by imbrie and kipp 1971 the transfer functions differ from previous studies in the following three important ways 1 extensions to q mode factor analysis provide an objective method to cull species in the very diverse radiolarian population 2 a log transform of the relative abundance data is used to normalize the species percent data and 3 rather than writing equations for specific seasons which are not independent data sets statistically independent equations are developed to predict mean annual sea surface temperatures as well as seasonal temperature range one hundred and seventy surface sediment samples from the pacific ocean are used to generate the sst and season temperature range transfer functions all samples were counted using a standardized radiolarian taxonomy forty one radiolarian species were used in the final regression equation q mode factor analysis of this data set identified seven assemblages these assemblages the tropical transitional antarctic bering sea western pacific central gyre and eastern boundary current are named for the oceanographic regions where these assemblages are important the seven assemblages are used in a regression analysis to predict sst and seasonal temperature range the standard error of estimates for both mean sst and seasonal temperature range is 1 6 c comparison between radiolarian based ssts and sst estimates from alkenone uk37 in a 20 000 year long record from the northeast pacific shows excellent agreement comparison of mean sst estimates for the last glacial maximum lgm based on radiolarian and foraminifera in 10 eastern equatorial pacific also show excellent concordance these new lgm estimates suggest that the original climate long range investigation mapping and prediction climap reconstruction for this region underestimated surface ocean cooling

neogene history of the west pacific warm pool kuroshio and leeuwin currents 1 foraminiferal analysis of miocene to recent strata of the northwest shelf of australia is used to chart west pacific warm pool wpwp influence the assemblage is typified by larger foraminifera with ingressions of the indo pacific smaller taxa asterorotalia and pseudorotalia at around 4 ma and from 1 6 to 0 8 ma a review of recent and fossil biogeography of these taxa suggests their stratigraphic distribution can be used to document wpwp evolution from 10 to 4 4 ma a lack of biogeographic connectivity between the pacific and indian ocean suggests indonesian throughflow itf restriction during this period the collision of australia and asia trapped warmer waters in the pacific creating a central wpwp biogeographic province from the equator to 26 n by 3 ma indo pacific species migrated to japan with the initiation of the modern kuroshio current coinciding with the intensification of the north pacific gyre and northern hemisphere ice sheet expansion indo pacific taxa migrated to the northwest australia from 4 4 to 4 ma possibly because of limited itf the absence of indo pacific taxa in northwest australia indicates possible itf restriction from 4 to 1 6 ma full northwest australian biogeographic connectivity with the wpwp from 1 6 to 0 8 ma suggests an unrestricted stronger itf compared to today and the initiation of the modern leeuwin current the extinction of some indo pacific species in northwest australia after 0 8 ma may be related to the effects of large glacial interglacial oscillations and uplift of the indonesian archipelago causing indonesian seaway restriction

seismicity of south central coastal california october 1987 through january 1997 earthquakes recorded along south central coastal california from october 1987 through january 1997 by the pacific gas and electric company9s 20 station central coast seismic network and the u s geological survey9s northern and southern california networks are used to study their relation to previous seismicity mapped quaternary faults and regional tectonic features we developed p and s wave velocity models station corrections and duration magnitude calibrations to process 1184 reliable earthquake locations and 212 well constrained focal mechanisms seismicity generally coincides with mapped quaternary faults and areas of tectonic uplift including the southern offshore santa maria basin and areas to the west and the uplifted blocks within the los osos tectonic domain comparison of our data to previous microearthquake locations 1969 1987 and larger m 5 historical earthquakes shows that these patterns have been persistent seismically quiescent areas have few or no mapped quaternary faults and typically are structural lows the base of the seismogenic zone is about 12 km in depth above the relic oceanic crust microearthquake locations and strike slip focal mechanisms document the strike slip nature of the hosgri fault zone and its step over to the san simeon fault along the western boundary of the los osos domain uplifting blocks within the los osos domain are most seismically active toward their western ends along the hosgri fault zone and they exhibit reverse and oblique faulting consistent with block uplift and interaction with the hosgri fault zone the observed patterns and character of microseismicity and macroseismicity clearly show transpressional deformation associated with the hosgri fault zone overprinted by rotation and westward migration of the western transverse ranges within this tectonic setting clockwise rotation of the western transverse ranges causes internal deformation of the los osos domain and westward migration of the ranges appears to deflect the hosgri fault zone westward and causes east west directed crustal shortening in the southern offshore santa maria basin

depth related radiolarian assemblage in the water column and surface sediments of the japan sea plankton tows and surface sediments from the japan sea a marginal sea of the northwestern pacific were examined to study the depth distribution of modern radiolarians the depth distribution patterns between the living assemblage in the water column and the thanatocoenose in surface sediments are similar to each other indicating that the depth related assemblage in sediments is closely related to the living depths of major species four clear restrictions of many species to discrete depth zones are recognized in the water column from the surface down to 2000 m 1 upper subsurface water species which are abundant from 40 to 120 m larcopyle butschlii juvenile form spirocyrtis subscalaris spongodiscus resurgens and lipmanella virchowii 2 lower subsurface water species which are abundant from 40 to 300 m larcopyle butschlii adult form ceratocyrtis histricosa and spongotrochus glacialis 3 intermediate water species which have population maxima from 160 to 300 m ceratospyris borealis and 4 deep water species which have maxima between 1000 and 2000 m cycladophora davisiana and actinomma boreale only a few specimens of a boreale were found in the water column ranging from 1000 to 2000 m depth although this is a dominant species in surface sediments from depths below 2000 m of which the dominance increases with water depth a boreale may live mainly in the bottom water cycladophora davisiana and a boreale which characterize the japan sea deep assemblage are naturally shallow or intermediate dwellers in other oceans on the other hand the typical deep dwellers e g cornutella profunda cyrtopera languncula and peripyramis circumtexta of other oceans have not been found in the japan sea such a peculiar deep assemblage is a result of the deep circulation system in the japan sea and the shallow depths of the sills around it

oceanographic conditions associated with high abundances of the radiolarian cycladophora davisiana abstract the cosmopolitan radiolarian cycladophora davisiana usually comprises less than 5 of the radiolarian fauna in holocene sediments in recent sediments from the sea of okhotsk however this species frequently represents more than 20 of the radiolarian assemblage at times during the late pleistocene abundances of this species in excess of 40 are recorded in marine sediments from high latitude oceans 40 of both hemispheres the sea of okhotsk apparently represents a modern analogue of climatic and oceanographic conditions that existed throughout large portions of high latitude oceans at times during the late pleistocene the near surface water structure of the sea of okhotsk is characterized by a low salinity surface layer with a strong temperature minimum near its base the low surface salinities are responsible for maintaining near freezing subsurface temperatures as well as establishing relatively stable temperatures and salinities at depths below the temperature minimum this water structure is produced at least in part by intense freezing of sea ice in winter with subsequent summer melting the physical characteristics of the upper water column affect the abundance and activity of shallow dwelling flora and fauna while providing a stable subsurface environment for deeper dwelling fauna

seismotectonics and fault structure of the california central coast abstract i present and interpret new earthquake relocations and focal mechanisms for the california central coast the relocations improve upon catalog locations by using 3d seismic velocity models to account for lateral variations in structure and by using relative arrival times from waveform cross correlation and double difference methods to image seismicity features more sharply focal mechanisms are computed using ray tracing in the 3d velocity models seismicity alignments on the hosgri fault confirm that it is vertical down to at least 12 km depth and the focal mechanisms are consistent with right lateral strike slip motion on a vertical fault a prominent newly observed feature is an 25 km long linear trend of seismicity running just offshore and parallel to the coastline in the region of point buchon informally named the shoreline fault this seismicity trend is accompanied by a linear magnetic anomaly and both the seismicity and the magnetic anomaly end where they obliquely meet the hosgri fault focal mechanisms indicate that the shoreline fault is a vertical strike slip fault several seismicity lineations with vertical strike slip mechanisms are observed in estero bay events greater than about 10 km depth in estero bay however exhibit reverse faulting mechanisms perhaps reflecting slip at the top of the remnant subducted slab strike slip mechanisms are observed offshore along the hosgri san simeon fault system and onshore along the west huasna and rinconada faults while reverse mechanisms are generally confined to the region between these two systems this suggests a model in which the reverse faulting is primarily due to restraining left transfer of right lateral slip

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

biogeography of radiolaria polycystina protista in the world ocean abstract analysis of 307 species of radiolaria polycystina in a worldwide dataset of 4774 plankton sediment trap and surface sediment samples allows recognizing six major biogeographic domains five of them are circumglobal polar north polar south bi subpolar transitional and tropical subtropical and one is restricted to the eastern equatorial pacific each domain is characterized by a particular suite of species all of which however occur widely albeit sparsely in one or more other domains of the eight environmental variables evaluated temperature correlates best with the partitions established species distributions in the water column and in the sediments are generally in agreement but in the sediments cold water forms extend farther towards the equator than do warm water radiolarians towards the poles in the recent sedimentary record of planktonic foraminifera the same phenomenon is magnified by the higher dissolution rates of warm water species as compared with the cold water ones of the three major oceans the pacific was the most speciose but estimates based on data corrected for sample size show much smaller inter oceanic differences with 10 radiolarians probably being absent from either basin the radiolarian biogeographic pattern is generally similar to those based on other planktonic and nektonic open ocean organisms but the degree of uniqueness of the domains as well as the position of the intervening boundaries are variable which reflects methodological differences as well as taxon specific traits partitions of the world ocean defined on the basis of species ranges resemble the major divisions presumably functionally homogeneous units established on the basis of physical traits and chlorophyll fields but secondary divisions nested within the latter are not reflected by any of the biogeographic schemes based on species distribution ranges this conflict raises questions about the importance of several physical mechanisms for structuring pelagic communities and or on the coupling of structure and function in the pelagic realm

relocations of five yingjiang sequences china myanmar border details of seismogenic faults abstract five moderate sized earthquakes struck the yingjiang area china myanmar border where there is a lack of historical earthquakes and provided us an opportunity to study the seismogenic fault we relocate sequences via the hypodd method using the cross correlated arrival times the phase picking errors by the human analysts had only 0 01 s difference before and after 2009 however the p phase picking precision increased from the tenths to the hundredths place after 2009 and the relocation errors of hypodd simultaneously decreased by a factor of 2 the rupture dimensions are about 2 4 km for the five sequences the hypodd relocation errors are only 0 36 or 0 63 km for the two test clusters which are much smaller than the dimensions of the rupture areas the synthetic tests show no location bias from the distribution of the yunnan regional seismic network the relocations identify four linear features with the northwest north northwest or northeast direction for the 21 march 2008 3 september 2008 10 march 2011 and 30 may 2014 sequences orthogonal to the known major fault traces the relocations also suggest that the 10 march 2011 sequence is on a double layered fault dipping roughly 71 to the southwest focal mechanisms reveal a mixture of strike slip normal and reverse faulting

radiolarians under the seasonally sea ice covered conditions in the okhotsk sea flux and their implications for paleoceanography abstract four time series sediment traps at two stations and three piston cores from the okhotsk sea were quantitatively examined for coarse sized radiolarian shells 63 m traps were deployed at 300 m and 1550 m at station m4 53 01 n 145 30 e and at 300 m and 700 m at station m6 49 30 n 146 28 e during august 1998 through may 2000 the chronologies of the piston cores were established applying 18 o and paleomagnetic intensity variations they provide records extending back to marine isotope stage mis 5 51 the modern and past changes in radiolarian assemblages are associated with environmental and productivity changes radiolarian fluxes in the sediment traps exhibited significant summer to autumn flux peaks with suppressed values during the winter when sea ice covered the sea surface at the trap sites total radiolarian accumulation rate rar variations in each core tended to correspond to glacial interglacial cycles and increased during the last deglaciation in particular the temporal rar variation in core xp98 pc1 off kamchatka showed a similar trend with the climatic changes expressed by 18 o values during the glacial interglacial cycles for the last 125 kyr regional differences were also apparent rars showed extremely low values during 12 40 kyr and 63 70 kyr in core xp98 pc2 central okhotsk sea indicating the enhanced sea ice impact the sea ice coverage might have continued for a significant part of the year during the intervals since radiolarians did not appear to increase even during the summer to autumn rar variations in core xp98 pc4 off sakhalin showed higher values than xp98 pc2 during mis 2 and 4 thus in eastern sakhalin around site xp98 pc4 sea ice coverage might have been seasonal but not perennial even during mis 2 and 4 among the radiolarian taxa cycladophora davisiana was the most abundant species at the lower traps and in all cores the fluxes of c davisiana at lower traps showed much higher values than those of upper traps and also showed similar temporal patterns with the fluxes of aluminum and terrigenous materials therefore c davisiana fluxes may be associated with terrigenous organic materials increased nutrient supply from the continental shelves presumably transported by seasonal sea ice and released by sea ice melting might be mainly responsible for the high production of c davisiana in the okhotsk sea especially during the last deglaciation

nonuniform prestress from prior earthquakes and the effect on dynamics of branched fault systems 1 to examine the effects of branched fault geometry on the dynamics of fault systems in the long term we perform multicycle simulations on generic faulting models an explicit finite element algorithm is used to simulate spontaneous dynamic rupture of earthquakes the fault stress during the interseismic period is evaluated by an analytical viscoelastic model we find that the fault prestress field becomes highly nonuniform near the branch point and on the two branch segments over multiple earthquake cycles owing to the branched fault geometry and stress interaction between the two segments the principal prestress on faults rotates over multiple earthquake cycles and departs from the regional stress field significantly near the branch point after a number of earthquake cycles the branched fault systems evolve to a steady state in which several patterns of the fault prestress and earthquake rupture repeat the nonuniform prestress developed from previous earthquakes has large effects on the rupture and slip patterns several different rupture scenarios can occur on a given branched fault system in addition backward branching can occur in the nonuniform prestress field either driven by slip on the stem of the fault system or through a triggering mechanism these modeling results may have important implications for understanding fault branching behavior observed in the 1992 landers the 1999 hector mine and the 2002 denali fault earthquakes and for seismic hazard analysis in the areas where branched fault systems exist

radiolarian assemblages in surface sediments along longitude 175 e in the pacific ocean abstract this study of 24 surface sediment samples along longitude 175 e between latitudes 48 n and 14 s in the western pacific ocean documents the relationship between the modern distribution of radiolarian assemblages and present oceanographic conditions ninety two species were classified into eight clusters by using r mode cluster analysis q mode cluster analysis was used to distinguish five geographical zones which were interpreted to represent the tropical southern subtropical northern subtropical transitional and subarctic climatic zones species richness diversity and equitability are highest in the tropical and transitional zones we attempted to formulate new regression equations considering ecological information on the vertical distribution of radiolarian species transfer functions were derived from regression analysis of radiolarian assemblages to observed sea surface temperature sst values the transfer functions have a standard error of 1 16 c in the estimate of winter sst 0 81 c in that of summer sst

observations of basin ground motions from a dense seismic array in san jose california we installed a dense array of 41 digital seismographs in san jose california to evaluate in detail the effects of a deep sedimentary basin and shallow sedimentary deposits on earthquake ground motions this urban array is located near the eastern edge of the santa clara valley and spans the evergreen sedimentary basin identified by gravity data average station spacing is 1 km with three stations initially spaced 110 m apart despite the high noise urban environment the stations of the array successfully triggered on and recorded small local earthquakes m 2 5 2 8 at 10 25 km distance and larger regional events such as the m 5 0 bolinas earthquake 90 km distance m 4 6 5 6 earthquakes near mammoth lakes 270 km distance m 4 9 5 6 events in western nevada 420 km distance and the m 7 1 hector mine earthquake 590 km distance maps of spectral ratios across the array show that the highest amplitudes in all frequency bands studied 0 125 8 hz are generally observed at stations farther from the eastern edge of the santa clara valley larger spectral amplitudes are often observed above the western edge of the evergreen basin snapshots of the recorded wavefield crossing the array for regional events to the east reveal that large low frequency 0 125 0 5 hz arrivals after the s wave travel from south to north across the array a moving window cross correlation analysis finds that these later arrivals are surface waves traveling from the south the timing and propagation direction of these arrivals indicates that they were likely produced by scattering of incident s waves at the border of the santa clara valley to the south of the array it is remarkable that the largest low frequency phases at many of the valley sites for regional events to the east are basin surface waves coming from a direction about 70 degrees different from that of the epicenters basin surface waves emanating from the eastern edge of the valley are also identified by the cross correlation analysis

subsurface structure and kinematics of the calaveras hayward fault stepover from three dimensional vp and seismicity san francisco bay region california the calaveras and hayward faults are major components of the san andreas fault system in the san francisco bay region dextral slip is presumed to transfer from the calaveras fault to the hayward fault in the mission hills region an area of uplift in the contractional stepover between the two faults here the estimated deep slip rates drop from 15 to 6 mm yr on the calaveras fault and slip begins on the hayward fault at an estimated 9 mm yr a lineament of microseismicity near the mission fault links the seismicity on the calaveras and hayward faults and is presumed to be related directly to this slip transfer however geologic and seismologic evidence suggest that the mission fault may not be the source of the seismicity and that the mission fault is not playing a major role in the slip transfer we perform a joint inversion for hypocenters and the 3d p wave velocity structure of the stepover region using 477 earthquakes we find strong velocity contrasts across the calaveras and hayward faults corroborated by geologic gravity and aeromagnetic data detailed examination of two seismic lineaments in conjunction with the velocity model and independent geologic and geophysical evidence suggests that they represent the southern extension of a northeasterly dipping hayward fault that splays off the calaveras fault directly accounting for the deep slip transfer the mission fault appears to be accommodating deformation within the block between the hayward and calaveras faults thus the calaveras and hayward faults need to be considered as a single system for developing rupture scenarios for seismic hazard assessments online material 3d interactive visualizations of the mission and alum rock hypocenters

vertical distribution of polycystine radiolarians in the northern east china sea abstract the east china sea ecs is a marginal sea influenced by the kuroshio current kc and by freshwater discharged by the changjiang river in this study the vertical distribution of polycystine radiolarians in the northern ecs was investigated we collected plankton tow samples from the water column at five stations in the northern ecs stations 11 and 11 were on the ecs continental shelf and stations 1 8 and 12 were in the northeastern ecs which is influenced by the kc we identified six distinct depth intervals by a q mode cluster analysis at stations 1 8 and 12 radiolarians were abundant and species diversity was high in the surface waters standing stocks of subtropical species such as didymocyrtis tetrathalamus phorticium pylonium pterocanium praetextum spongaster tetras tetras and the tetrapyle octacantha groups were high reflecting the influence of the warm kc in contrast at intermediate water depths standing stocks of subarctic radiolarians such as actinomma leptodermum cycladophora bicronis haliommetta miocenica pseudodyctiophimus gracilipes and lithelius minor were relatively high which may reflect the influence of a subarctic water mass that probably originated in the north pacific at stations 11 and 11 on the shelf the influence of freshwater from the changjiang river is high and radiolarians were absent in the upper 20 m of the water column and scarce at depths of 20 100 m where three species dominated archipera triclavigera pseudocubus obeliscus and cryptogyrus calvatus

high resolution satellite imagery mapping of the surface rupture and slip distribution of the mw 7 8 14 november 2001 kokoxili earthquake kunlun fault northern tibet china the mw 7 8 kokoxili earthquake of 14 november 2001 which ruptured a 450 km long stretch of the sinistral kunlun strike slip fault at the northeastern edge of the tibet plateau china ranks as the largest strike slip event ever recorded instrumentally in asia newly available high resolution satellite hrs images pixel size 1 m acquired in the months following the earthquake proved a powerful tool to complement field investigations and to produce the most accurate map to date of the coseismic displacements along the central kusai hu segment of the rupture the coseismic rupture geometry south and west of buka daban feng near the earthquake epicenter was also investigated in detail along the kusai hu segment slip parti tioning is for the first time observed to occur simultaneously during a single event with two parallel strands 2 km apart localizing almost pure strike slip and normal faulting in all 83 new hrs coseismic offset measurements some of which calibrated by field work show large well constrained variations 100 of the slip function over distances of only25 km tension cracks opening ahead of the shear dislocation and later offset by the upward propagating strike slip rupture were observed dem onstrating that the rupture front propagated faster at depth than near the surface the triple junction between the central kusai hu segment the kunlun pass fault where the rupture ended and the xidatan dongdatan segment which could be the next segment to fail along the main kunlun fault acted as a strong barrier implying that direct triggering of earthquake rupture on the xidatan dongdatan segment by kokoxili type earthquakes may not be the rule

displacement and geometrical characteristics of earthquake surface ruptures issues and implications for seismic hazard analysis and the process of earthquake rupture there now exist about three dozen historical earthquakes for which in vestigators have constructed maps of earthquake rupture traces accompanied by de scriptions of the coseismic slip observed along the fault strike the maps and slip distributions are compiled here to place observational bounds on aspects of seismic hazard analysis and fault mechanics analysis leads to an initial statistical basis to predict the end points of rupture and the amount of surface slip expected at sites along the strike during earthquakes on mapped faults the observations also give support to the ideas that there exists a process zone or volume of about 3 4 km in dimension at the fronts of large laterally propagating earthquake ruptures within which stress changes may be sufficient to trigger slip on adjacent faults and that the ultimate length of earthquake ruptures is controlled primarily by the geometrical complexity of fault traces and variations in accumulated stress levels along faults that arise due to the location of past earthquakes to this may be added the observation that the form of earthquake surface slip distributions is better described by asymmetric rather than symmetric curve forms and that earthquake epicenters do not appear to correlate in any systematic manner to regions of maximum surface slip observed along strike online material maps of surface ruptures digitized values and curve fits to surface slip distributions and notes and references for tables 1 and 2