earthquake locations and three dimensional fault zone structure along the creeping section of the san andreas fault near parkfield ca preparing for safod 1 arrival time data from 453 local earthquakes and 6 explosions at parkfield ca are inverted for earthquake locations and three dimensional vp and vp vs structure the structure is dominated by the velocity contrast across the saf with the southwest side about 20 25 faster consistent with previous studies nearly all the earthquakes occur almost directly beneath the fault trace we find high vp vs anomalies that correlate with low resistivity features in a magnetotelluric model that are interpreted to represent fluids we locate a magnitude 2 earthquake that is a potential target event for the final stage of safod drilling yielding a depth of 3 1 km below surface and an epicenter 100 m southwest of the fault trace nonlinear analyses indicate 95 confidence relative and absolute uncertainties on the order of 500 700 m vertically and 200 300 m horizontally for this target earthquake

development and refinement of proxy climate indicators from peats peat especially from acidic mires bogs is a natural archive of past environmental change reconstructions of past climate from bogs commenced in the 19th century through examination of visible peat stratigraphy and later formed the basis for a postglacial climatic scheme widely used in northwest europe nevertheless misconceptions as to how bogs grow led to a 50 year lacuna in peat climate study before the concept of cyclic regeneration in bogs was refuted in recent decades research using proxy climate indicators from bogs has burgeoned a range of proxies for past hydrological change has been developed as well as use of pollen bog oaks and pines and other data to reconstruct past temperatures most of this proxy climate research has been carried out in northern europe but peat based research in parts of asia and north america has increased particularly during the last decade while research has also been conducted in australia new zealand and south america this paper reviews developments in proxy climate reconstructions from peatlands chronicles use of a range of palaeo proxies such as visible peat stratigraphy plant macrofossils peat humification testate amoebae and non pollen palynomorphs and explains the use of wiggle match radiocarbon dating and relationship to climate shifts it details other techniques being used increasingly such as biomarkers stable isotopes inorganic geochemistry and estimation of dust flux and points to new proxies under development although explicit protocols have been developed recently for research on ombrotrophic mires it must be recognised that not all proxies and techniques have universal applicability owing to differences in species assemblages mire formation topographic controls and geochemical characteristics

compilation of non annually resolved holocene proxy climate records stacked holocene peatland palaeo water table reconstructions from northern britain abstract the number and range of holocene palaeoclimate reconstructions from various regions of the world have increased dramatically over the last decade the data density for many regions and proxies now offers the potential of robust regional scale reconstructions that avoid the problems of records from individual sites and improve communication between palaeoclimate subdisciplines and climate modellers however there are problems with chronological uncertainties and quantification of proxies which make compilation of multiple records difficult here we explore a stacking and tuning approach to the derivation of regional records from peatland climate proxies to test its applicability to non annually resolved terrestrial records twelve individual records from northern britain based on water table reconstructions from testate amoebae analysis were divided into four regions records were detrended normalised and compared within regions to identify clear correlative events the original chronologies of the records were tuned using both these events and independent age markers the stacked record for northern britain indicates pronounced changes to wet conditions at 3600 2760 and 1600 cal yr bp with more minor changes at 3060 2050 1260 860 550 and 260 cal yr bp the main wet phases are highly correlated with mid european lake highstands wider north atlantic climate change inferred from ocean and ice core records and solar variability tuning and stacking of non annual terrestrial palaeoclimate records is a new approach to the compilation and reconciliation of individual records within coherent climatic regions and provides a tool for upscaling of palaeoclimate records for climate model data comparisons

detailed imaging of the fault planes of the 2004 niigata chuetsu central japan earthquake sequence by double difference tomography abstract imaging of the hypocentral faults of the niigata chuetsu earthquake sequence was performed by double difference tomography using data obtained by a temporary aftershock observation network densely deployed in the hypocentral region two parallel unfavorly oriented fault planes steeply inclined to the wnw are revealed that of the main shock and that of the largest aftershock as well as a zone of velocity change between the high velocity footwall and the low velocity hanging wall for both p and s waves this suggests that the main shock and the largest aftershock are caused by the reactivation of normal faults in the miocene under the current compressional stress regime parts of the fault planes are also found to be located within the low velocity zone this low velocity zone continues to the lower crust which is imaged by an inversion from the regional data and would correspond with highly fractured zone around the fault plane with high fluid pressure which reactivated the unfavorly oriented fault and triggered the present earthquake large coseismic slip area appears to extend to the northeastern portion with relatively high velocity this suggests that the asperity large coseismic slip area of the main shock possibly correspond with a higher velocity region along the fault plane

the 1995 kobe earthquake seismic image of the source zone and its implications for the rupture nucleation in order to understand what may have triggered the 1995 kobe japan earthquake and how the rupture proceeded after initiation we determined high resolution three dimensional 3 d p and s wave velocity and poisson s ratio structures in the kobe epicentral area and relocated the aftershocks with the obtained 3 d velocity model we used 64 337 p and 49 200 s wave high quality arrival times from 3634 kobe aftershocks and local microearthquakes recorded by both permanent seismic networks and portable stations that were set up following the kobe mainshock significant velocity variations of up to 6 are revealed in the aftershock area we found that areas with high aftershock activity are generally associated with low poisson s ratio which may be the strong and competent parts of the fault zone and were apt to generate aftershocks the kobe mainshock hypocenter is located in a distinctive zone characterized by low p and s wave velocities and a high poisson s ratio this anomaly exists in the depth range of 16 to 21 km and extends 15 to 20 km laterally this anomaly may be due to a fluid filled fractured rock matrix that contributed to the initiation of the kobe earthquake our interpretation has been supported by many pieces of evidence from hydrological geochemical seismological and geophysical investigations conducted at the kobe earthquake region

enso s impact on the gap wind regions of the eastern tropical pacific ocean abstractthe recently released ncep climate forecast system reanalysis cfsr is used to examine the response to enso in the northeast tropical pacific ocean netp during 1979 2009 the normally cool pacific sea surface temperatures ssts associated with wind jets through the gaps in the central american mountains at tehuantepec papagayo and panama are substantially warmer colder than the surrounding ocean during el nino la nina events ocean dynamics generate the enso related sst anomalies in the gap wind regions as the surface fluxes damp the ssts anomalies while the ekman heat transport is generally in quadrature with the anomalies the enso driven warming is associated with large scale deepening of the thermocline with the cold thermocline water at greater depths during el nino in the netp it is less likely to be vertically mixed to the surface particularly in the gap wind regions where the thermocline is normally very close to the surface the thermocline deepening is enhanced to the south

altimeter derived surface circulation in the large scale ne pacific gyres part 1 seasonal variability abstract the seasonal variability of sea surface height ssh and currents are defined by analysis of altimeter data in the ne pacific ocean over the region from central america to the alaska gyre the results help to clarify questions about the timing of seasonal maxima in the boundary currents as explained below the long term temporal mean of the ssh values must be removed at each spatial point to remove the temporally invariant and large signal caused by the marine geoid we refer to the resulting ssh values which contain all of the temporal variations as the residual ssh our main findings are 1 the maximum surface velocities around the boundaries of the cyclonic alaska gyre the alaska current and the alaska stream occur in winter at the same time that the equatorward california current is weakest or reversed forming the poleward davidson current the maximum surface velocities in the california current occur in summer these seasonal maxima are coincident with the large scale atmospheric wind forcing over each region 2 most of the seasonal variability occurs as strong residuals in alongshore surface currents around the boundaries of the ne pacific basin directly connecting the boundaries of the subpolar gyre the subtropical gyre and the equatorial current system 3 seasonal variability in the surface velocities of the eastward north pacific current west wind drift is weak in comparison to seasonal changes in the surface currents along the boundaries 4 there is an initial appearance next to the coast and offshore migration of seasonal highs and lows in ssh alongshore velocity and eddy kinetic energy eke in the alaska gyre similar to the previously described seasonal offshore migration in the california current 5 the seasonal development of high ssh and poleward current residuals next to the coast appear first off central america and mainland mexico in may june prior to their appearance in the southern part of the california current in july august and their eventual spread around the entire basin in november december similarly low ssh and equatorward transport residuals appear first off central america and mexico in january february before spreading farther north in spring and summer 6 the maximum values of eke occur when each of the boundary currents are maximum

comparison of source areas of m4 8 0 1 repeating earthquakes off kamaishi ne japan are asperities persistent features abstract m4 8 0 1 earthquakes have occurred regularly since 1957 with a recurrence interval of 5 52 0 68 yr at the same location of the plate boundary off kamaishi iwate prefecture the last event m4 7 occurred on 11 13 2001 16 44 jst and the previous one m4 8 on 3 11 1995 10 30 jst waveforms of these events are similar to each other to examine the hypothesis that this characteristic earthquake sequence is caused by repeating ruptures of an asperity frictionally locked patch surrounded by creeping areas we compared the rupture area of the 2001 event with that of the 1995 event by a waveform inversion method estimated spatial extents of the rupture areas of the 2001 and 1995 events are almost the same and are estimated to be about 1 5 1 5 km 2 the rupture area of the 2001 event is almost completely overlapped with that of the 1995 event although the ruptures of the two events were initiated from different points the present observations clearly show that the 1995 and 2001 events are caused by the repeating ruptures of the same asperity patch and support the hypothesis of persistent asperities

summer thermal structure and anticyclonic circulation of lake erie 1 in most thermally stratified lakes the summer thermocline has the shape of a dome with a shallower depth offshore than nearshore this configuration is accompanied by a lake wide cyclonic circulation lake wide observations of subsurface temperature in central lake erie revealed an atypical depressed or bowl shaped thermocline in late summer with a deeper thermocline in the middle of the lake and a shallower thermocline nearshore currents measured in the central basin when the bowl shaped thermocline was observed were anticyclonic forming a single basin wide gyre it is suggested that the unusual bowl shaped thermocline is the result of ekman pumping driven by anticyclonic vorticity in surface winds the bowl shaped thermocline can lead to greater hypoxia in bottom waters and negative effects on biota by reducing the hypolimnetic volume

new pliocene pleistocene 40ar 39ar ages fill in temporal gaps in the nicaraguan volcanic record abstract the volcanic record of western nicaragua documents a significant lull in volcanic activity that has persisted from the late miocene 7 ma to the formation of the modern volcanic front around 350 ka this study fills this gap for the first time with samples collected in northwest nicaragua between cosiguina and san cristobal volcanoes and with samples collected from the nicaraguan depression we found two previously unknown volcanic units ranging from 3 6 to 1 3 ma and the improved volcanic record allows us to reconstruct the geochemical evolution of the nicaraguan arc u th values increased by nearly threefold since the miocene following the carbonate crash at 10 ma when dominantly carbonate sediment deposition shifted toward hemipelagic sediment deposition this transition was thought to be abrupt however our new data show that it took place gradually over the last 7 ma northwest nicaragua is a particularly interesting case study because it contains middle miocene volcanism on either side of the nicaraguan depression the coyol formation 25 7 ma to the east and the tamarindo formation 14 7 11 7 ma to the west the presence of mid miocene volcanism on either side of the nicaraguan depression has led to the hypothesis that the two coeval units currently separated by 100 km were once connected and have since been separated by extension here we present data suggesting that the tamarindo and coyol are geochemically distinct and therefore cannot be considered part of the same unit

biological and physical signatures in the tropical and subtropical atlantic the variability of sea surface chlorophyll concentration in the tropical and subtropical atlantic during the first year of sea viewing wide field of view sensor seawifs imagery is examined an ocean general circulation model ogcm is used along with topex poseidon dynamic height observations and global gridded wind stress data sets to explain the physical forcing of surface ocean color signals regions of high surface chlorophyll are strongly correlated with mesoscale and large scale physical processes such as the strong upwelling off the west coast of africa the relatively high oceanic production within the guinea dome region and the generation and propagation of large anticyclonic eddies along the coast of south america north of the equator the major river outflows amazon orinoco and congo have strong signatures with plumes of apparently high chl a in excess of 10 mg m 3 near their deltas the fall bloom in the eastern tropical atlantic observed by the coastal zone color scanner czcs was absent in 1997 whereas a bloom was observed in this region in july september 1995 which was not observed by the czcs we attribute these apparent anomalies to the projection of the 1997 1998 el nino event into the tropical atlantic basin these signals are correlated with sea surface temperature anomalies known to be associated with enso the seawifs images show that there are seasonal blooms within the hydrographic provinces of the guinea and angola domes these hydrographic provinces are characterized by the dynamic uplift of the thermocline at the north equatorial current southern boundary guinea dome and the benguela current eastern boundary angola dome within these domes the ekman pumping and transport are significant due to the strong trade winds at the surface the ekman drift plays a major role in the spreading of surface blooms the spreading of the oceanic bloom at 12 n 30 w the congo river plume and the areal extent of the upwelling blooms off the coast of africa parallels the strength and extent of the ekman surface drift upwelling when broadly defined to include large scale vertical excursions of the thermocline explains virtually all of the surface chlorophyll observations in excess of 0 5 mg m 3 except in the river plumes i

modeling summer circulation and thermal structure of lake erie athree dimensionalprimitiveequationnumericalmodelwasappliedtolakeerieona2kmgridtostudyitssummercirculation andthermalstructure modelresultswerecomparedtolong termobservationsofcurrentsandtemperaturemadein2005at severallocations mostlyinitscentralbasin intheshallowandmostlyunstrati edwesternbasincirculationisdrivenbydetroitriverin ow modi edtosomeextentbywind andisfromwesttoeast inthecentralbasin which isofintermediate depthandhasarelatively atbottom themodeledcirculationisanticyclonic clockwise drivenbyanticyclonicvorticityinthesurfacewind andthethermocline isbowl shaped inlinewithobservations inthedeeppartoftheeastern basin the thermoclineisdome shapedandcirculationiscyclonic counter clockwise duetodensitygradients acon gurationtypicalforotherlargedeeplakes whileshallower areasareoccupiedbyanticyclonic circulationdrivenbyanticyclonic windvorticity inthe centralbasin modeledtemperatureandcirculationpatternsare quitesensitivetothespeci cationofthe wind eld anticyclonicwindvorticityleadstothinningofthehypolimnion inthecentralbasinandearlierdestrati cationinthefall

mean three dimensional circulation in the northeast tropical pacific abstract historical xbt data are used to construct a mean climatology of the three dimensional geostrophic circulation in the northeast tropical pacific southwest of mexico and central america and are diagnosed based on linear dynamics forced with satellite scatterometer winds unlike the familiar central tropical pacific where the zonal scales are very large and the wind forcing nearly a function of latitude alone the north pacific east of about 120 w is strongly influenced by wind jets blowing through gaps in the central american cordillera the curl imposed by these wind jets imprints on the ocean producing a distinctive pattern of thermocline topography and geostrophic currents that are consistent with the sverdrup balance notably the weakening of the north equatorial countercurrent near 110 w is due to the wind forcing given the observed stratification and wind stress curl planetary vorticity conservation also determines the distribution of vertical velocity in the region with about 3 5 sv

the obduction of equatorial 13 c water in the pacific identified by a simulated passive tracer the obduction of equatorial 13 degrees c water in the pacific is investigated using a simulated passive tracer of the consortium for estimating the circulation and climate of the ocean ecco the result shows that the 13 degrees c water initialized in the region 8 degrees n 8 degrees s 130 degrees 90 degrees w enters the surface mixed layer in the eastern tropical pacific mainly through upwelling near the equator in the costa rica dome and along the coast of peru approximately two thirds of this obduction occurs within 10 years after the 13 degrees c water being initialized with the upper portion of the water mass reaching the surface mixed layer in only about a month the obduction of the 13 degrees c water helps to maintain a cool sea surface temperature year round equivalent to a surface heat flux of about 6 0 w m 2 averaged over the eastern tropical pacific 15 degrees s 15 degrees n 130 degrees w eastern boundary for the period of integration 1993 2006 during el nino years when the thermocline deepens as a consequence of the easterly wind weakening the obduction of the 13 degrees c water is suppressed and the reduced vertical entrainment generates a warming anomaly of up to 10 w m 2 in the eastern tropical pacific and in particular along the coast of peru providing explanations for the warming of sea surface temperature that cannot be accounted for by local winds alone the situation is reversed during la nina years

the influence of a mature cyclonic eddy on particle export in the lee of hawaii abstract mesoscale eddies may enhance primary production pp in the open ocean by bringing nutrient rich deep waters into the euphotic zone potentially leading to increased transport of particles to depth this hypothesis remains controversial however due to a paucity of direct particle export measurements in this study we investigated particle dynamics using 234 th 238 u disequilibria within a mesoscale cold core eddy cyclone opal which formed in the lee of the hawaiian islands 234 th samples were collected along two transects across cyclone opal as well as during a time series within the eddy core during a decaying diatom bloom particulate carbon pc particulate nitrogen pn and biogenic silica bsio 2 fluxes at 150 m varied spatially and temporally within the eddy and strongly depended on the 234 th model formulation used e g steady state versus non steady state inclusion of upwelling etc particle fluxes estimated from a steady state model assuming an upwelling rate of 2 m day 1 yielded the best fit to sediment trap data these 234 th derived particle fluxes ranged from 332 14 to 1719 53 mol c m 2 day 1 27 3 to 114 12 mol n m 2 day 1 and 33 20 to 309 73 mol si m 2 day 1 although pp rates within cyclone opal were elevated by a factor of 2 3 pc and pn fluxes were the same within error inside and outside of cyclone opal the ratio of pc export to pp remained surprisingly low at 2 fluxes within the eddy core were three times higher detailed analyses of 234 th depth profiles consistently showed excess 234 th at 100 175 m associated with the remineralization and possible accumulation of suspended and dissolved organic matter from the surface we suggest that strong microzooplankton grazing facilitated particulate organic matter recycling and resulted in the export of empty diatom frustules thus while eddies may increase pp they do not necessarily increase pc and pn export to deep waters this may be a general characteristic of wind driven cyclonic eddies of the north pacific subtropical gyre and suggests that eddies may preferentially act as a silica pump thereby playing an important role in promoting silicic acid limitation in the region

ocean and atmosphere teleconnections modulate east tropical pacific productivity at late to middle pleistocene terminations the modern eastern equatorial pacific eep is a key oceanographic region for regulating the earth s climate system accounting for between 5 10 of global marine production whilst also representing a major source of carbon dioxide efflux to the atmosphere changes in ocean dynamics linked to the nutrient supply from the southern ocean have been suggested to have played a dominant role in regulating eep productivity over glacial interglacial timescales of the past 500 ka yet the full extent of the climate and oceanic teleconnections and the mechanisms promoting the observed increase of productivity occurring at glacial terminations remain poorly understood here we present multi proxy micropaleontological geochemical and sedimentological records from the easternmost eep to infer changes in atmospheric patterns and oceanic processes potentially influencing regional primary productivity over glacial interglacial cycles of the mid late pleistocene 0 650 ka these proxy data support a leading role for the north south migration of the intertropical convergence zone itcz in shaping past productivity variability in the eep productivity increases during glacial periods and notably peaks at major and extra glacial terminations those occurring 1 2 precession cycles after some major terminations coincident with the inferred southernmost position of the itcz the comparison of our reconstructions with proxy records of climate variability suggests the intensification of related extratropical atmospheric and oceanic teleconnections during deglaciation events these processes may have re activated the supply of southern sourced nutrients to the eep potentially contributing to enhanced productivity in the eep and thus counterbalancing the oceanic carbon dioxide outgassing at glacial terminations

high resolution records of late holocene climate change and carbon accumulation in two north west european ombrotrophic peat bogs the peat stratigraphy plant macrofossils colorimetric humification pollen non pollen microfossils carbon nitrogen ratios of three replicate cores from a raised peat bog in the uk walton moss and a single core from a raised peat bog in denmark lille vildmose were examined in an attempt to investigate the relation between long term climate change and changes in species composition of the peat forming vegetation nine wet shifts identified in the monoliths from walton moss and lille vildmose mainly occurred during periods of increasing atmospheric c 14 content because fluctuations in holocene atmospheric radiocarbon concentrations have been shown to be due to variations in solar activity the little ice age lia climatic deteriorations registered in both peat bogs were probably driven by changes in solar activity climatic deteriorations in the three replicate cores from walton moss are not all consistently registered and may reflect the internal variability in the extent of hollow lawn hummock microforms within raised peat bog ecosystems the lowest carbon accumulation values for the walton moss monoliths between ca cal ad 1300 and 1800 and between ca cal ad 1490 and 1580 for lille vildmose occurred during the course of lia climatic deteriorations peat bog primary productivity may have been reduced during the lia owing to lower spring summer temperatures and shorter growing seasons for the peat forming plants species specific higher decomposition rates may have also caused the lower carbon accumulation rates in the peat bogs during the lia c 2002 elsevier science b v all rights reserved

imaging the source area of the 1995 southern hyogo kobe earthquake m7 3 using double difference tomography abstract to understand the generation process of inland earthquake we determined the seismic velocity structure in and around the source area of the 1995 southern hyogo kobe earthquake m7 3 in sw japan we adopted the double difference dd tomography method zhang h and c thurber double difference tomography the method and its application to the hayward fault california bull seism soc am 93 2003 1875 1889 we inverted arrival times recorded by a dense temporary seismic network for aftershocks and seismic networks routinely operated by japanese universities obtained results are summarized as follows 1 low velocity zones of a few kilometers width are distributed along the fault or along the aftershock alignment suggesting that the fault of the 1995 earthquake is located primarily in a low velocity zone 2 amount of velocity decrease within this low velocity zone varies along the strike of the fault most of large slip areas asperities seem to correspond to higher velocity areas relative to the surroundings on the fault rather than to lower velocity areas

characteristics of wind generated rings in the eastern tropical pacific ocean eddies are generated in the eastern tropical pacific 3 s 23 n 75 105 w by winds blowing through central american mountain passes from the atlantic we used coastal zone color scanner czcs and advanced very high resolution radiometer avhrr satellite imagery complemented with monthly in situ sea surface temperature and wind series from the comprehensive ocean atmosphere data set coads to study these eddies and their effect on pigment concentrations in the region pigment values in the gulf of tehuantepec generally reach higher values in november march before those in the gulf of papagayo the eddies generated in the gulf of tehuantepec are associated with passages of cold fronts across the gulf of mexico from the north while the eddies off papagayo and panama are associated with increases in trade wind intensity czcs images showed larger numbers of eddies per season than have been previously reported on the basis of in situ and avhrr observations or numerical simulations we counted 13 eddies in 1979 1980 8 in 1984 1985 and 6 in 1985 1986 the eddies transfer both energy and biological constituents from the continental margin to the offshore tropical pacific the eddies frequently moved distances in excess of 1500 km from their point of origin both anticyclonic and cyclonic eddies are generated but in general there are more anticyclones anticyclonic eddies generally moved to the southwest some cyclonic eddies moved to the south and southeast along the central american coast and appeared to be trapped by the cyclonic costa rica thermal dome eddies traveled at speeds varying between 9 and 21 cm s 1 and had diameters of 100 500 km phytoplankton concentrations associated with the eddies varied from 2 to 10 mg m 3 within 70 km of the coast to 1 mg m 3 up to 600 km of the coast between late april and october fewer eddies were observed and phytoplankton concentrations were lower 0 25 mg m 3 and more uniform over the region

evolution of geochemical variations along the central american volcanic front 1 new geochemical analyses of volcanic rocks in el salvador add to existing data from nicaragua and costa rica to create a comprehensive set of geochemical data for central american volcanics these data coupled with previously published 40ar 39ar ages covering the past 30 ma show that costa rica and nicaragua had similar u th and ba la values until 10 ma when the region developed the distinctive along arc variations that made this margin famous u th values increased in nicaragua since the miocene while remaining unchanged along the rest of the volcanic front this coincides temporally with the carbonate crash which caused a transition in cocos plate sediments from low u carbonates to high u organic rich hemipelagic muds increases in uranium are not observed in costa rica because its lower slab dip produces a more diffuse zone of partial melting and because of the contribution from galapagos derived tracks dilutes this signal ba la has been used as a geochemical proxy for contributions from the subducting slab however our analyses indicate that the ba concentrations do not vary significantly along strike either in the subducting sediment or the volcanic front along arc variation is controlled by changes in la an indicator of the degree of partial melting or source enrichment trace element models of five segments of the volcanic front suggest that a subducting sediment component is more important to magmas produced in el salvador and nicaragua than in costa rica where the geochemistry is controlled by recent 10 ma recycling of galapagos tracks

relations among fault behavior subsurface geology and three dimensional velocity models the development of three dimensional p wave velocity models for the regions surrounding five large earthquakes in california has lead to the recognition of relations among fault behavior and the material properties of the rocks that contact the fault at seismogenic depths regions of high moment release appear to correlate with high seismic velocities whereas rupture initiation or termination may be associated with lower seismic velocities these relations point toward a physical understanding of why faults are divided into segments that can fail independently an understanding that could improve our ability to predict earthquakes and strong ground motion

tomography of the source area of the 1995 kobe earthquake evidence for fluids at the hypocenter seismic tomography revealed a low seismic velocity 5 and high poisson s ratio 6 anomaly covering about 300 square kilometers at the hypocenter of the 17 january 1995 magnitude 7 2 kobe earthquake in japan this anomaly may be due to an overpressurized fluid filled fractured rock matrix that contributed to the initiation of the kobe earthquake

three dimensional velocity structure seismicity and fault structure in the parkfield region central california this study examines the three dimensional velocity structure in a 60 by 80 km region containing the parkfield segment of the san andreas fault we use local earthquake and shot p arrival times in an iterative simultaneous inversion for velocity and hypocentral parameters using the three dimensional model we relocated 5251 events that occurred from 1969 to 1991 as well as the 1966 aftershocks and computed 664 fault plane solutions the san andreas fault saf characterized by a sharp across fault velocity gradient is the primary feature in the velocity solution there is a 5 20 lateral change in velocity over a 4 km width the contrast being sharper where there is better resolution the model also shows significant variations in the velocity and in the complexity of the velocity patterns along the saf the largest across fault velocity difference is below middle mountain where a large volume of low velocity material impinges on the saf from the northeast this material is inferred to be overpressured and may be key to understanding the unusual behavior in the parkfield preparation zone a 20 km long high velocity slice is imaged northeast of the saf near gold hill its along fault length corresponds to the length of the maximum slip in 1966 the relocated seismicity shows that the san andreas fault is a planar vertical fault zone at seismogenic depths ninety percent of the fault plane solutions that are on or near the saf were right lateral strike slip on subvertical fault planes that parallel the saf thus the surface fault complexities do not appear to extend to depth and therefore do not explain the rupture character at parkfield at parkfield variations in material properties play a key role in fault segmentation and deformation style our observations suggest that there may be a general relation between increasing velocity and increasing ability of the rocks to store strain energy and release it as brittle failure

air sea interaction over the eastern pacific warm pool gap winds thermocline dome and atmospheric convection high resolution satellite observations are used to investigate air sea interaction over the eastern pacific warm pool in winter strong wind jets develop over the gulfs of tehuantepec papagayo and panama accelerated by the pressure gradients between the atlantic and pacific across narrow passes of central american cordillera patches of cold sea surface temperatures ssts and high chlorophyll develop under these wind jets as a result of increased turbulent heat flux from the ocean and enhanced mixing across the base of the ocean mixed layer despite a large decrease in sst exceeding 38c in seasonal means the cold patches associated with the tehuantepec and papagayo jets do not have an obvious effect on local atmospheric convection in winter since the intertropical convergence zone itcz is located farther south the cold patch of the panama jet to the south on the other hand cuts through the winter itcz and breaks it into two parts a pronounced thermocline dome develops west of the gulf of papagayo with the 208c isotherm only 30 m deep throughout the year in summer when the panama jet disappears and the other two wind jets weaken sst is 0 58c lower over this costa rica dome than the background this cold spot reduces local precipitation by half punching a hole of 500 km in diameter in the summer itcz the dome underlies a patch of open ocean high chlorophyll this thermocline dome is an ocean dynamic response to the positive wind curls south of the papagayo jet which is optimally oriented to excite ocean rossby waves that remotely affect the ocean to the west the meridionally oriented tehuantepec and panama jets by contrast only influence the local thermocline depth with few remote effects on sst and the atmosphere the orographical triggered air sea interaction described here is a good benchmark for testing high resolution climate models now under development

wind generation of the costa rica dome upwelling in the costa rica dome is seasonal and the result of the localized cyclonic wind stress curl fluctuations in the wind stress curl in the fall release the upwelled region as a rossby wave similar low latitude domes are hypothesized to be ubiquitous to those oceans where a localized cyclonic wind stress curl is associated with an intertropical convergence zone

deciphering latitudinal shifts in coccolith accumulation in the eastern tropical pacific ocean through the pleistocene abstract middle and late pleistocene coccolithophore assemblages from ocean drilling program odp sites 1241 and 1242 in the northeastern tropical pacific north etp were analyzed to reconstruct coccolithophore productivity and surface water conditions over the last 925 kyr stratigraphic control was provided by 18o data and geomagnetic time scales and the identification of synchronous calcareous nannofossil events formerly described in mid and low latitudes changes in sea surface coccolithophore productivity were inferred by estimates of the so called n ratio an independent proxy on conversion to accumulation rates and the total coccolith derived carbonate accumulation rate car car variations follow those of the n ratio but show larger amplitude changes fluctuations in the n ratio and total car values imply coccolithophore productivity maxima during glacial times most likely as a result of a shallower nutri thermocline defined as the boundary beneath the sea surface at which nutrient rich cool and nutrient poor warm waters are separated low interglacial values of the n ratio and car suggest lower coccolithophore productivity and a deeper nutri thermocline deep stratification of the mixed layer this result implies that coccolithophore productivity controlled cars and dissolution were driven by the ratio between caco3 production and organic matter oxidation and that effects of dissolution were enhanced when coccolith production fell the data suggest high coccolithophore productivity and a shallow nutri thermocline during mis 22 through mis 6 likely due to the reinforcement of northeastern wind driven advection of nutrient rich waters which is compatible with a la nina like state the dominance of gephyrocapsa caribbeanica during the mid brunhes event mbe is consistent with this eutrophic environment conversely data from mis 5 suggests a weakening of trade winds in the etp which would have reduced the normal upwelling of cool water and warmed sst and which is compatible with the oligotrophic setting of an el nino like state during mis 4 through mis 1 coccolithophore productivity was not significantly different from mis 5 and therefore not indicative of a prominent la nina like state as previously reported for the equatorial cold tongue ect comparison with coccolithophore data from site 1240 supports a reduction of coccolithophore productivity and nutri thermocline deepening from the ect to the costa rica margin and suggests that nutrient availability was the primary control on the distribution of the whole assemblage during the past 925 kyr

a meta database of peatland palaeoecology in great britain we present and appraise a large compilation of peatland palaeoecological research in great britain and discuss the value of these data for secondary analysis we identify 475 radiocarbon dated palaeoecological records from british peatlands published since 1970 peatland palaeoecological research has been widespread but with some clear spatial biases reflecting factors such as accessibility and the location and interests of active researchers we show that basic details such as stratigraphic descriptions site coordinates and full details of radiocarbon dates are omitted from publications with surprising frequency and note the large quantity of data that only ever appears in phd theses to allow papers to remain concise while presenting essential background information we propose a system of standardised meta data in online supplementary material the extensive body of palaeoecological data for british peatlands has been relatively unexploited the compilation we present will be a valuable aid in making better use of this data resource