suitability of open ocean instrumentation for use in near field tsunami early warning along seismically active subduction zones over the past decade the number of open ocean gauges capable of parsing information about a passing tsunami has steadily increased particularly through national cable networks and international buoyed efforts such as the deep ocean assessment and reporting of tsunami dart this information is analyzed to disseminate tsunami warnings to affected regions however most current warnings that incorporate tsunami are directed at mid and far field localities in this study we analyze the region surrounding four seismically active subduction zones cascadia japan chile and java for their potential to facilitate local tsunami early warning using such systems we assess which locations currently have instrumentation in the right locations for direct tsunami observations with enough time to provide useful warning to the nearest affected coastline and which are poorly suited for such systems our primary findings are that while some regions are ill suited for this type of early warning such as the coastlines of chile other localities like java indonesia could incorporate direct tsunami observations into their hazard forecasts with enough lead time to be effective for coastal community emergency response we take into account the effect of tsunami propagation with regard to shallow bathymetry on the fore arc as well as the effect of earthquake source placement while it is impossible to account for every type of off shore tsunamigenic event in these locales this study aims to characterize a typical large tsunamigenic event occurring in the shallow part of the megathrust as a guide in what is feasible with early tsunami warning

reinterpretation of late quaternary sediment chronology of lake biwa japan from correlation with marine glacial interglacial cycles a review of published stratigraphic records of pollen sediment grain size diatoms and organic matter composition from lake biwa japan identifies four pre holocene episodes of milder climate increased surface runoff and enhanced aquatic productivity indicating intervals of warmer and wetter conditions which are interpreted as being interglacial correlation of these episodes to times of marine interglacial periods revises the age scale of the lake biwa sediment sequence which has been based on fission track dating the revised chronostratigraphic scale proposes an age of ca 430 000 yr b p for the base of the 250 m thick t bed instead of the former age of ca 700 000 yr b p

late pleistocene and holocene paleoenvironments of the north pacific coast abstract unlike the north atlantic the north pacific ocean probably remained free of sea ice during the last glacial maximum lgm 22 000 to 17 000 bp following a eustatic low in sea level of ca 120 m at 19 000 bp a marine transgression had flooded the bering and chukchi shelves by 10 000 bp post glacial sea level history varied widely in other parts of the north pacific coastline according to the magnitude and timing of local tectonism and glacio isostatic rebound glaciers covered much of the continental shelf between the alaska peninsula and british columbia during the lgm maximum glacier extent during the lgm was out of phase between southern alaska and southern british columbia with northern glaciers reaching their outer limits earlier between 23 000 and 16 000 bp compared to 15 000 14 000 bp in the south glacier retreat was also time transgressive with glaciers retreating from the continental shelf of southern alaska before 16 000 bp but not until 14 000 13 000 bp in southwestern british columbia major climatic transitions occurred in the north pacific at 24 000 22 000 15 000 13 000 and 11 000 9000 bp rapid climate changes occurred within these intervals including a possible younger dryas episode an interval of climate warmer and drier than today occurred in the early holocene cooler and wetter conditions accompanied widespread neoglaciation beginning in some mountain ranges as early as the middle holocene but reaching full development after 3000 bp

stress changes and aftershock distribution of the 1994 and 2006 java subduction zone earthquake sequences 1 the mw 7 8 1994 and the mw 7 7 2006 interplate thrust mechanism earthquakes that occurred in the java subduction zone produced dominantly normal faulting aftershocks unusual for large megathrust main shocks various models proposed for these earthquake sequences invoke main shock rupture on an isolated portion of a decoupled plate boundary fault with updip and outer rise extension leading to the normal faulting other models suggest that these aftershocks occurred in a zone of the subduction zone where usually earthquakes cannot propagate or initiate leading to the occurrence of normal faulting aftershocks in the outer rise overriding and subducting plates here we examine a simpler possibility one in which coulomb stress changes cfs imparted by slip during the two large subduction events led to normal faulting events on favorably oriented planes within the slab and near trench region of the subduction zone we compute stress changes resulting from both events and subsequent large aftershocks using both uniform and variable slip models for main shock slip resolved onto both aftershock nodal planes we find that there is not a clear pattern of aftershock occurrence in areas of stress increase due to main shock slip this implies that these aftershocks are not simply triggered by the static stress changes from the main shock and additional complexity should be considered to explain these unusual earthquake sequences

late quaternary vegetation and climate of southern tierra del fuego vegetation and climate over approximately the past 13 000 yr are reconstructed from fossil pollen in a 9 4 m mire section at caleta robalo on beagle channel isla navarino 54 56 s 67 38 w southern tierra del fuego fifty surface samples reflecting modern pollen dispersal serve to interpret the record chronologically controlled by nine radiocarbon dates fossil pollen assemblages are empetrum gramineae gunnera tubuliflorae zone 3b 13 000 11 850 yr b p gramineae empetrum assorted minor taxa zone 3a 11 850 10 000 yr b p nothofagus gramineae tubuliflorae polypodiaceae zone 2 10 000 5000 yr b p nothofagus empetrum zone 1b 5000 3000 yr b p and empetrum nothofagus zone 1a 3000 0 yr b p assemblages show tundra under a cold dry climate zone 3 followed by open woodland zone 2 as conditions became warmer and less dry and later with greater humidity and lower temperatures by closed forest and the spread of mires zone 1 comparisons drawn with records from antarctica new zealand tasmania and the subantarctic islands demonstrate broadly uniform conditions in the circumpolar southern hemisphere the influences of continental and maritime antarctic air masses were apparently considerable in tierra del fuego during cold late glacial time whereas holocene climate was largely regulated by interplay between maritime polar and maritime tropical air

effects of the heterogeneous subducting plate on seismicity constraints from b values in the andaman sumatra java subduction zone abstract the andaman sumatra java subduction zone is characterized by significant spatial variations in subducting plate age subduction velocity and slab bending with i the uplifting controlled by the ninety east ridge in the north ii trench eroding affected by the roo rise in the south and iii the highly deformed warton basin in front of the trench cut through by a series of strike slip faults the entire subducting plate exhibits strong spatial heterogeneity in this paper we investigated the effect of the heterogeneous subducting plate on seismicity based on the comparison between the spatial variations in the b value of the gutenberg richer law and in the tectonic features of the subducting oceanic plate we used the international seismological centre ehb bulletin isc ehb from 1970 to 2013 to conduct a detailed study of b value spatial variations in the andaman sumatra java subduction zone via the inter comparison of tectonic factors we found that the subduction zone was tectonically segmented there are good positive correlations between b value and subducting plate age in two tectonic domains after removing the influence of local tectonic irregularities which implies that the subducting plate density generally controls the stress and coupling between the plates the subduction of local tectonic irregularities such as the fracture zones and seamounts has significantly affected seismicity which prevents the occurrence of large earthquakes and causes the b value to rise in addition the anomalous tectonic environments such as the spreading center and the thrust fault zones could also impact spatial variations of the b value therefore seismicity in subduction zones is a result of the combined impacts of complex tectonic features understanding and clarifying the mechanisms of these tectonic features in relation to b values can help us to better assess seismic risk in subduction zones

subduction of seamounts at the java trench a view with long range sidescan sonar abstract we describe here a 1300 km by 45 km gloria long range sidescan sonar swath along the eastern java trench the swath images the trench axis a narrow strip of oceanic crust to the south and the toe of the accretionary wedge to the north between 108 and 120 e sonar images of the ocean crust show a pattern of normal faults typical of the outer wall of trenches these result from tension related to the bending of the oceanic lithosphere into the subduction zone a number of sub circular seamounts are also seen some of which are currently being subducted isolated ponds of flat lying sediments occur in the trench axis although along much of its length the trench is devoid of such sediment accumulations on the inner trench wall the accretionary wedge is recognised by its distinctive grainy texture with the grain aligned sub parallel to the deformation front where subducting seamounts are colliding with the wedge large crescentic areas of very high backscattering correlate with re entrants in the deformation front and large indentations in the wedge the high backscattering within these collision scars is interpreted to arise from outcropping strata and talus covered slopes resulting from erosion of an inner trench wall shortened and oversteepened by collision with a seamount all of the sediment ponds in the trench axis occur in close association with collision scars strongly suggesting localised erosion of the accretionary wedge in the scar areas however the volume of the indentations appears to be an order of magnitude greater than the volume of eroded sediments deposited in the trench indicating that erosion cannot be the primary mechanism by which indentations are created most of the missing material must be displaced landward by thrusting and folding ahead of the seamount our observations at the java trench are broadly comparable with those made at the japan trench by french and japanese workers however some differences in the detail of the collision process are evident in particular oversteepening and erosion occur from the earliest stage of collision at the java trench while uplift and understeepening initially dominate at the japan trench differences in the effects of subducting seamounts in the two areas are attributed to contrasts between the relatively unlithified strata of the java trench inner wall and the more lithified strata of the non accreting japan trench inner wall

triassic latemar cycle tops subaerial exposure of platform carbonates under tropical arid climate the triassic latemar platform in the dolomites italy is the site of several ongoing controversies perhaps the most interesting debate focuses on apparent cyclic deposition within the latemar platform whose nature and duration are still open to debate further disagreement concerns the lack of meteoric diagenesis related isotope shifts at cycle tops that bear circumstantial petrographic evidence for subaerial emergence here an evaluation of the nature of latemar cycle tops is presented combining evidence from previous work and new field petrographic and geochemical data cycle tops are ranked according to increasing exposure duration and spatial extent type i surfaces lacking unequivocal evidence of prolonged supratidal conditions type ii dolomite caps formed in warm evaporitic intertidal lagoonal waters followed by exposure of perhaps intermediate duration type iii clastic rich red calcareous horizons with some showing platform wide extent representing prolonged supratidal conditions and type iv discontinuities in tepee belts genetically related to type ii and iii surfaces but likely representing shorter lived exposure stages petrographic and geochemical criteria indicate that most diagenesis occurred in the shallow marine and burial domain whilst an extensive meteoric overprint of cycle tops is lacking this is underlined by the scarcity of meteoric diagenetic fabrics such as gravitational cements that where present are here interpreted as marine vadose in origin the scarcity of carbon and oxygen isotope signatures commonly assigned to subaerial exposure stages is best explained in the context of mid triassic climate the low latitude tropical but arid setting of the latemar situated in the western extension of the tethys ocean its isolation from nearby continental areas and overall short term emergence episodes are in agreement with a limited degree of meteoric alteration of most cycle tops high amounts of aeolian clastic material beneath some cycle tops along with high fe and mn elemental abundances argue for intermittent subaerial conditions this study proposes an enhancement of the classical allan and matthews 1982 isotope model for subaerial exposure under strongly arid climates as the subaerial exposure nature of latemar cycle tops and therefore eustasy as the cause for cyclicity have been previously challenged due to the lack of meteoric induced isotopic signatures the outcome of this study is of significance for the ongoing latemar stratigraphic controversy

widespread submarine tephras around japan petrographic and chemical properties abstract in deep sea sediments around the japanese islands tephra layers are frequently recognized and some tephras can be identified by petrographic and chemical features and correlated to source volcanoes of both japan and korea most tephras distributed over more than several hundred kilometers from the source volcanoes were presumably carried away by the dominant westerly wind six characteristic marker tephras in deep sea sediments can be identified and correlated according to their distribution and grain size petrography and chemistry they play an important role in compiling the late quaternary chronology of the deep sea sediments distributed around the japanese islands petrographic and geochemical studies reveal that the refractive index of volcanic glass shards in tephras is controlled by the amount of total transition metal oxides rather than the amount of sio 2 we propose a new equation relating refractive index to glass shard chemistry

structural architecture of oceanic plateau subduction offshore eastern java and the potential implications for geohazards the region offshore eastern java represents one of the few places where the early stage of oceanic plateau subduction is occurring we study the little investigated roo rise oceanic plateau on the indian plate subducting beneath eurasia the presence of the abnormal bathymetric features entering the trench has a strong effect on the evolution of the subduction system and causes additional challenges on the assessment of geohazard risks we present integrated results of a refraction wide angle reflection tomography gravity modelling and multichannel reflection seismic imaging using data acquired in 2006 south of java near 113 e the composite structural model reveals the previously unresolved deep geometry of the oceanic plateau and the subduction zone the oceanic plateau crust is on average 15 km thick and covers an area of about 100 000 km2 within our profile the roo rise crustal thickness ranges between 18 and 12 km the upper oceanic crust shows high degree of fracturing suggesting heavy faulting the forearc crust has an average thickness of 14 km with a sharp increase to 33 km towards java as revealed by gravity modelling the complex geometry of the backstop suggests two possible models for the structural formation within this segment of the margin either accumulation of the roo rise crustal fragments above the backstop or alternatively uplift of the backstop caused by basal accumulation of crustal fragments the subducting plateau is affecting the stress field within the accretionary complex and the backstop edge which favours the initiation of large potentially tsunamogenic earthquakes such as the 1994 mw 7 8 tsunamogenic event

new statistical grain size method for evaluating the hydraulic conductivity of sandy aquifers abstract a new statistical grain size method of evaluating the hydraulic conductivity and transmissivity of sandy aquifers is presented the new equation is of the form k cd 2 10 and is similar to the existing equations but in this case the coefficient c which is normally taken as a constant is actually shown to be a variable that depends on the nature of the geologic environment source rock transportation deposition and post deposition history etc it is established that c for unconsolidated and poorly cemented sandy materials is 6 0 for moderately consolidated cemented rocks c 3 8 while for fairly well compacted and cemented rocks its value is about 2 0 with these coefficients the new statistical grain size method gives k and t values that compare favourably with those determined from pumping test methods

a methodology for near field tsunami inundation forecasting application to the 2011 tohoku tsunami existing tsunami early warning systems in the world can give either one or a combination of estimated tsunami arrival times heights or qualitative tsunami forecasts before the tsunami hits near field coastlines a future tsunami early warning system should be able to provide a reliable near field tsunami inundation forecast on high resolution topography within a short time period here we describe a new methodology for near field tsunami inundation forecasting in this method a precomputed tsunami inundation and precomputed tsunami waveform database is required after information about a tsunami source is estimated tsunami waveforms at nearshore points can be simulated in real time a scenario that gives the most similar tsunami waveforms is selected as the site specific best scenario and the tsunami inundation from that scenario is selected as the tsunami inundation forecast to test the algorithm tsunami inundation along the sanriku coast is forecasted by using source models for the 2011 tohoku earthquake estimated from gps w phase or offshore tsunami waveform data the forecasting algorithm is capable of providing a tsunami inundation forecast that is similar to that obtained by numerical forward modeling but with remarkably smaller cpu time the time required to forecast tsunami inundation in coastal sites from the sendai plain to miyako city is approximately 3 min after information about the tsunami source is obtained we found that the tsunami inundation forecasts from the 5 min gps 5 min w phase 10 min w phase fault models and 35 min tsunami source model are all reliable for tsunami early warning purposes and quantitatively match the observations well although the latter model gives tsunami forecasts with highest overall accuracy the required times to obtain tsunami forecast from the above four models are 8 min 9 min 14 min and 39 min after the earthquake respectively or in other words 3 min after receiving the source model this method can be useful in developing future tsunami forecasting systems with a capability of providing tsunami inundation forecasts for locations near the tsunami source area

investigation of the best coseismic fault model of the 2006 java tsunami earthquake based on mechanisms of postseismic deformation abstract we investigate three available coseismic fault models of the 2006 m7 8 java tsunami earthquake as reported by fujii and satake 2006 bilek and engdahl 2007 and yagi and fukahata 2011 in order to find the best coseismic model based on mechanisms of postseismic deformation associated with viscoelastic relaxation and afterslip we construct a preliminary rheological model using vertical data obtaining a final rheological model after we include horizontal and vertical components of afterslip in the further process our analysis indicates that the coseismic fault model of fujii and satake 2006 provides a better and more realistic result for a rheological model than the others the best fit rheological model calculated using the coseismic fault model of fujii and satake 2006 comprises a 60 5 km elastic layer thickness with a viscosity of 2 0 1 0 10 17 pa s in the asthenosphere also we find that afterslip is dominant over the horizontal displacements while viscoelastic relaxation is dominant over the vertical displacement additionally in comparison to the coseismic displacement found through gps data taken at bako station our calculation indicates that fujii and satake 2006 modeled coseismic displacements with less gps data misfit than the other examined models finally we emphasize that our methodology for evaluating the best coseismic fault model can satisfactorily explain the postseismic deformation of the 2006 java tsunami earthquake

aragonite to calcite transformation during fresh water diagenesis of carbonates insights from pore water chemistry dissolved strontium and calcium concentrations in fresh water lenses fwl and associated mixing zones mz on two small holocene ooid sand islands in the schooner cays bahamas were monitored during a 1 yr period to quantitatively analyze the transformation of aragonite to calcite the observed characteristics of this mass transfer are functions of climate and hydrology aragonite to calcite transformation in all hydrologic zones is primarily associated with meteoric recharge the transformation occurs throughout the fwl and in the mz to relative salinities of 19 and 36 sea water on the two islands rates of transformation are rapid in all zones and are greatest in the fwl a limestone composed of 100 calcite should form from an aragonite precursor within 4 700 to 15 600 yr in the fwl and within 8 700 to 60 000 yr in the upper mz efficiencies of transformation can vary between hydrologic zones due to pco2 effects yet the efficiency of the entire system fwl mz is high 87 this indicates that most caco3 derived from aragonite dissolution is reprecipitated as calcite somewhere in the fresh water system or upper mixing zone co2 effects fresh water sea water mixing and the differing solubilities between aragonite and calcite all drive the mass transfer the latter is the most significant accounting for up to nine times more mass transfer than co2 effects and at least ten times more mass transfer than fresh water sea water mixing differing solubilities should also cause mass transfer to occur throughout the hydrologic cycle but it apparently becomes ineffective after the rainy season possibly due to the inhibition of calcite precipitation

sources of tsunami and tsunamigenic earthquakes in subduction zones we classified tsunamigenic earthquakes in subduction zones into three types earth quakes at the plate interface typical interplate events earthquakes at the outer rise within the subducting slab or overlying crust intraplate events and tsunami earthquakes that generate considerably larger tsunamis than expected from seismic waves the depth range of a typical interplate earthquake source is 10 40km controlled by temperature and other geological parameters the slip distribution varies both with depth and along strike recent examples show very different temporal change of slip distribution in the aleutians and the japan trench the tsunamigenic coseismic slip of the 1957 aleutian earthquake was concentrated on an asperity located in the western half of an aftershock zone 1200km long this asperity ruptured again in the 1986 andreanof islands and 1996 delarof islands earthquakes by contrast the source of the 1994 sanriku oki earthquake corresponds to the low slip region of the previous interplate event the 1968 tokachi oki earthquake tsunamis from intraplate earthquakes within the subducting slab can be at least as large as those from interplate earthquakes tsunami hazard assessments must include such events similarity in macroseismic data from two southern kuril earthquakes illustrates difficulty in distinguishing interplate and slab events on the basis of historical data such as felt reports and tsunami heights most moment release of tsunami earthquakes occurs in a narrow region near the trench and the concentrated slip is responsible for the large tsunami numerical modeling of the 1996 peru earthquake confirms this model which has been proposed for other tsunami earthquakes including 1896 sanriku 1946 aleutian and 1992 nicaragua

climate and environmental changes for the past 44 ka clarified by pollen and algae composition in the ulleung basin east sea japan sea abstract the pollen and algae records derived from core kces 1 in the east sea japan sea reveal vegetation and climate changes during the past 44 ka from 44 to 36 cal ka bp forest vegetation in the coastal regions of ulleung basin was composed predominantly of subalpine conifer forest open grassland covered the exposed continental shelves indicating a cool and dry climate during the period of 36 28 3 cal ka bp a warmer and wetter climate caused the contraction of subalpine conifer forest in the coastal regions of ulleung basin and the expansion of marsh in the exposed continental shelves from 28 3 to 17 6 cal ka bp the sea level decline restricted the herbs pollen originates in the exposed shelf of east china sea and yellow sea inflow into the east sea japan sea and caused the reduction of herbs pollen in the site location during the time interval of 17 6 15 1 cal ka bp a great expansion of subalpine conifer forest can be regarded as the consequence of enhanced east asian winter monsoon eawm the obvious increase in temperate deciduous broadleaved trees spores and algae can be attributable to the rising of sea level and the warming of climate from 15 1 to 12 1 cal ka bp during the period of 12 1 to 5 3 cal ka bp broadleaved taxa increased especially during the time period of 9 5 5 3 cal ka bp evergreen broadleaved trees pollen reach the highest values throughout the core as a result of the holocene climate optimum condition vegetation changes controlled by humid impacts occurred at the late holocene as indicated by an increase in pinus pollen

postglacial environmental change of the pacific ocean off the coasts of central japan abstract downcore changes in microfossil assemblages and oxygen isotope ratios in three piston cores recovered from the northwestern pacific off central japan show that the subtropical kuroshio front was located to the south of c 4 core site lat 33 n during the last glacial the front then advanced northward passing over the c 4 site and the c 6 site 34 6 n at about 13 ka and 10 ka respectively and reached the c 1 core site 36 n at about 7 ka after 5 5 ka it retreated to the area between the c 1 and c 6 sites a brief but significant cold event the readvance of the cold oyashio current is recognized between 11 and 10 ka in the two northern cores but the current did not reach the southern c 4 site a contemporaneous cold event is known in the north atlantic and the cooling was probably a global phenomenon likely to be associated with lowering of sea level contamination of isotopically light water is apparent between 14 and 11 ka in the marked change in isotopic composition of benthic foraminifers oxygen isotope ratios of planktonic foraminifers show that prior to the advance of the kuroshio front the surface water at these core sites was isotopically lighter than the kuroshio water at that time

the rupture extent of low frequency earthquakes near parkfield ca the low frequency earthquakes lfes that constitute tectonic tremor are often inferred to be slow to have durations of 0 2 to 0 5 s a factor of 10 to 100 longer than those of typical m w 1 2 earthquakes here we examine lfes near parkfield ca in order to assess several proposed explanations for lfes long durations we determine lfe rupture areas and location distributions using a new approach similar to directivity analysis where we examine how signals coming from various locations within lfes finite rupture extents create differences in the apparent source time functions recorded at various stations we use synthetic ruptures to determine how much the lfe signals recorded at each station would be modified by spatial variations of the source station travel time within the rupture area given various possible rupture diameters and then compare those synthetics with the data our synthetics show that the methodology can identify inter station variations created by heterogeneous slip distributions or complex rupture edges and thus lets us estimate lfe rupture extents for unilateral or bilateral ruptures to obtain robust estimates of the sources similarity across stations we stack signals from thousands of lfes using an empirical green s function approach to isolate the lfes apparent source time functions from the path effects our analysis of lfes in parkfield implies that lfes apparent source time functions are similar across stations at frequencies up to 8 to 16 hz depending on the family the inter station coherence observed at these relatively high frequencies or short wave lengths down to 0 2 to 0 5 km suggest that lfes in each of the 7 families examined occur on asperities they are clustered in patches with sub 1 km diameters the individual lfes rupture diameters are estimated to be smaller than 1 1 km for all families and smaller than 0 5 km and 1 km for the two shallowest families which were previously found to have 0 2 s durations coupling the diameters with the durations suggests that it is possible to model these m w 1 2 lfes with earthquake like rupture speeds around 70 of the shear wave speed however that rupture speed matches the data only at the edge of our uncertainty estimates for the family with highest coherence the data for that family are better matched if lfes have rupture velocities smaller than 40 of the shear wave speed or if lfes have different rupture dynamics they could have long rise times contain composite sub ruptures or have slip distributions that persist from event to event

sensitivity of northern hemisphere air temperatures and snow expansion to north pacific sea surface temperatures in the goddard institute for space studies general circulation model circum pacific marine and terrestrial records indicate a series of temperature inferred oscillations during the late glacial while many previous studies have probed the role of the north atlantic in these oscillations we test the sensitivity of the northern hemisphere air temperatures to north pacific sea surface temperature sst oscillation in the goddard institute for space studies general circulation model the effect of a colder north pacific is to cool air temperatures over north america as well as parts of europe and asia the colder ssts result in a large hemispheric response due to the loss of water vapor as a greenhouse gas the large sensitivity of the northern hemisphere to a north pacific sst change has implications for the ice age climate as well as the late glacial interval the results of this experiment provide a rapid mechanism for widespread cooling which has not been previously addressed

geochemistry of meteoric diagenesis in carbonate islands of the northern bahamas 2 geochemical modelling and budgeting of diagenesis geochemical characterization and numerical modelling of surface water and ground water combined with hydrological observations provide quantitative estimates of meteoric diagenesis in pleistocene carbonates of the northern bahamas meteoric waters equilibrate with aragonite but water rather than mineral controlled reactions dominate dissolutional lowering of the undifferentiated bedrock surface is an order of magnitude slower than that within soil filled topographic hollows generating small scale relief at a rate of 65 140 mm ka 1 and a distinctive pocketed topography oxidation of organic matter within the subsoil and vadose zones generates an average pco2 of 4 0 10 3 atm which drives dissolution during vadose percolation and or at the water table however these dissolution processes together account for 60 of the average rock derived calcium in groundwaters pumped from the freshwater lens the additional calcium may derive from oxidation of organic carbon within the lens accounting for the high pco2 of the lens waters mixing between meteoric waters of differing chemistry is diagenetically insignificant but evapotranspiration from the shallow water table is an important drive for subsurface cementation porosity generation in the shallow vadose zone averages 1 6 3 2 ka 1 phreatic meteoric diagenesis is focused near the water table where dissolution generates porosity at 1 4 2 8 ka 1 maximum dissolution rates however are similar to those of evaporation driven precipitation which occludes porosity of 4 0 s 0 6 ka 1 this drives porosity inversion from primary interparticle to secondary mouldic vug and channel porosity in the deeper freshwater lens oxidation of residual organic carbon and reoxidation of reduced sulphur species from deeper anaerobic oxidation of organic carbon may generate porosity up to 0 06 ka 1 meteoric diagenesis relies critically on hydrological routing and vadose thickness controlled by sea level as well as the geochemical processes active a thin vadose zone permits direct evaporation from the water table and drives precipitation of meteoric phreatic cements even where mineral stabilization is complete copyright 2007 john wiley sons ltd

heterogeneous distributions of co 2 may be more important for dissolution and karstification in coastal eogenetic limestone than mixing dissolution mixing dissolution a process whereby mixtures of two waters with different chemical compositions drive undersaturation with respect to carbonate minerals is commonly considered to form cavernous macroporosity e g flank margin caves and banana holes in eogenetic karst aquifers on small islands macroporosity commonly originates when focused dissolution forms globular chambers lacking entrances to the surface suggesting that dissolution processes are decoupled from surface hydrology mixing dissolution has been thought to be the primary dissolution process because meteoric water would equilibrate rapidly with calcium carbonate as it infiltrates through matrix porosity and because pco2 was assumed to be homogeneously distributed within the phreatic zone here we report data from two abandoned well fields in an eogenetic karst aquifer on san salvador island bahamas that demonstrate pco2 in the phreatic zone is distributed heterogeneously the pco2 varied from less than log 2 0 to more than log 1 0 atm over distances of less than 30 m generating dissolution in the subsurface where water flows from regions of low to high pco2 and cementation where water flows from regions of high to low pco2 using simple geochemical models we show dissolution caused by heterogeneously distributed pco2 can dissolve 2 5 to 10 times more calcite than the maximum amount possible by mixing of freshwater and seawater dissolution resulting from spatial variability in pco2 forms isolated globular chambers lacking initial entrances to the surface a morphology that is characteristic of flank margin caves and banana holes both of which have entrances that form by erosion or collapse after cave formation our results indicate that heterogeneous pco2 rather than mixing dissolution may be the dominant mechanism for observed spatial distribution of dissolution cementation and macroporosity generation in eogenetic karst aquifers and for landscape development in these settings copyright 2015 john wiley sons ltd

interplate coupling model off the southwestern coast of java indonesia based on continuous gps data in 2008 2010 abstract we present an interplate coupling model of the australia java plate interface off the southwestern coast of java indonesia based on data from the indonesian permanent gps station network from 2008 to 2010 the majority of vertical data indicate uplift while the baseline change rate indicates coastal contraction in the middle of the network and coastal extension in the eastern part of the network using the rate of baseline length changes and the absolute rate of vertical displacements we apply a geodetic inversion method by yabuki and matsu ura 1992 from the inversion result we interpret the main source of the observed velocity in west java as resulting from contributions of 1 interplate coupling off ujung kulon pelabuhan ratu at 20 to 40 km depth with a slip rate range from 48 to 56 mm yr 2 interplate coupling off pangandaran at 37 to 45 km depth with a slip rate of 48 to 55 mm yr 3 afterslip off pangandaran within the rupture area of the 2006 m7 8 java earthquake in the depth range of 15 20 km with a slip excess rate of 57 61 mm yr the absence of a megathrust earthquake for at least 300 years in this region implies seismic moment accumulation during this time period of 1 6 10 21 nm mw 8 7 off ujung kulon pelabuhan ratu and 3 9 10 21 nm mw 8 3 off pangandaran unless episodic slow slips release tectonic stress

multi proxy records of holocene hydroclimatic and environmental changes on the southern coast of south korea abstract a well dated sediment core from the goheung area of the southern coast of the korean peninsula was used to reconstruct the history of environmental and vegetation changes in response to variability in the east asian summer monsoon easm and the sea level change during the holocene a multi proxy analysis palynomorphs mean grain size toc ts c n ratio and 13ctoc data indicated that the study area underwent a change in environment from a fluvio coastal a fluvial to intertidal zone to a subtidal zone due to a sea level rise at ca 7500 cal yr bp since ca 6000 cal yr bp it has gradually returned to a brackish dominant environment intertidal zone due to coastal regression with a decrease in relative sea level palynological data show that the climate of the southern coast of the korean peninsula underwent a gradual cooling trend after ca 5900 cal yr bp due to weakening easm intensity in response to decreasing insolation in the northern hemisphere therefore the long term vegetation dynamics in this study area were controlled primarily by solar insolation driven temperature changes during the holocene they were also associated with sea surface temperature sst changes in the western tropical pacific wtp the vegetation dynamics sharp reduction of broad leaved trees and freshwater discharge indicators in our study area indicate cold and dry climatic conditions since ca 4500 cal bp which may have been caused by the decreasing sst in the wtp in addition the strong link between the holocene vegetation dynamics in the east asian coastal area especially quercus lepidobalanus and pinus diploxylon and sst variation in the wtp may suggest that the centennial timescale recurring variations in easm activity have been controlled by low latitude ocean forcing induced by el nino southern oscillation activity

climatic change at the end of the last glaciation in japan inferred from pollen in three cores from the northwest pacific ocean abstract late glacial pollen time series from high sedimentation rate marine cores kh79 3 c6 ch84 04 and ch84 14 show the rise of successional vegetation typified by betula during the replacement of boreal forest types picea and pinus by thermophilous quercus forests variations in these three marine pollen records replicate the trends and timing of pollen records from japan and the structure and timing of vegetation and climatic changes on the pacific coast of japan since the last glacial maximum in marine cores kh79 3 c6 ch84 04 and ch84 14 oxygen isotope and or marine faunal data have been interpreted as evidence of a cooling event in the northwest pacific ocean which is coeval with the younger dryas chronozone pollen records from these northwest pacific cores like those from japan do not exhibit a regionally replicated statistically robust pollen assemblage which can be unambiguously interpreted as evidence of a late glacial climatic reversal between ca 11 000 and 10 000 yr b p the apparent disparity between the terrestrial pollen and marine evidence for a climatic oscillation during the younger dryas chron in northeast asia further complicates the variable record of this brief late glacial event

comparison of marine and terrestrial holocene climatic reconstructions from northeastern north america quantitative climate reconstructions based on marine dinocysts and terrestrial pollen sequences are consistent through the holocene in northeastern north america principal components analysis pca indicates a large scale climate signal in the dinocysts and pollen the combined and separate analyses of marine and nearby terrestrial pollen sequences from hudson bay labrador and the st lawrence estuary differentiate tun dra boreal forest and deciduous forest assemblages in time and space these analyses indicate that the marine pollen record reflects vegetation changes of the regional terrestrial environment and allows direct correlations between the marine and terrestrial stratigraphies sea surface temperatures estimated from dinocysts and terres trial air temperatures from pollen using the method of modern analogs show that the three regions had differing climate histories associated with their location with respect to deglaciation and air mass boundaries high frequency climatic changes reconstructed

late quaternary environmental changes on pacific islands controversy certainty and conjecture the late quaternary history of the pacific islands is poorly known most details about pleistocene history come from studies of ocean floor sediments although a few insular pollen records extend back into the last glacial stage there is limited evidence for last glacial maximum lgm aridity and a rise in lgm early holocene precipitation associated with strengthening of the southern oscillation the middle holocene warming is best represented by sea level records which from all parts of the pacific now show a contemporary maximum ca 5000 3000 yr bp late holocene cooling and precipitation increase were probably more widespread than available data suggest the advent of humans into pacific island environments mostly during the late holocene is critically reviewed vegetation change may have at least in part been the result of climate change many pacific island grasslands may be climatogenic rather than anthropogenic fires may have occurred naturally long before people arrived on pacific islands ideas about early human impacts on pacific island enviroments need to be critically reviewed 1997 john wiley sons ltd

seismology breaking the slab two chains of seamounts on the pacific plate subduct beneath central japan in the process a fragment of the pacific slab has become wedged in the subduction zone and may be the source of recurring deep thrust earthquakes beneath tokyo

wedge geometry frictional properties and interseismic coupling of the java megathrust abstract the mechanical interaction between rocks at fault zones is a key element for understanding how earthquakes nucleate and propagate therefore estimating frictional properties along fault planes allows us to infer the degree of elastic strain accumulation throughout the seismic cycle the java subduction zone is an active plate boundary where high seismic activity has long been documented however very little is known about the seismogenic processes of the megathrust especially its shallowest portion where onshore geodetic networks are insensitive to recover the pattern of elastic strain here we use the geometry of the offshore accretionary prism to infer frictional properties along the java subduction zone using coulomb critical taper theory we show that large portions of the inner wedge in the eastern part of the java subduction megathrust are in a critical state where the wedge is on the verge of failure everywhere we identify four clusters with an internal coefficient of friction int of 0 8 and hydrostatic pore pressure within the wedge the average effective coefficient of friction ranges between 0 3 and 0 4 reflecting a strong decollement our results also show that the aftershock sequence of the 1994 mw 7 9 earthquake halted adjacent to a critical segment of the wedge suggesting that critical taper wedge areas in the eastern java subduction interface may behave as a permanent barrier to large earthquake rupture in contrast in western java topographic slope and slab dip profiles suggest that the wedge is mechanically stable i e deformation is restricted to sliding along the decollement and likely to coincide with a seismogenic portion of the megathrust we discuss the seismic hazard implications and highlight the importance of considering the segmentation of the java subduction zone when assessing the seismic hazard of this region

quaternary forest and climate history of hokkaido japan from marine sediments abstract pollen data from quaternary marine sediments deposited in central hokkaido northern japan provide insight into northeast asian vegetation and climatic changes over the last few million years during the early pleistocene coniferous forest dominated by picea and cryptomeria japonica and taiga composed of larix and picea developed under cool wet and cold dry climates respectively strong climatic contrasts are inferred from late pleistocene interglacial and glacial pollen assemblages which precede the last glacial cycle in the former cool temperate broad leaf forest mainly composed of fagus reflects a warmer and wetter climate than now in the latter taiga similar to that now found in northern sakhalin apparently flourished in hokkaido the composition of pollen assemblages correlated with oxygen isotope stage 5 changed from cool temperate forest of quercus ulmus and juglans substage 5e to picea larix taiga substage 5d cool temperate forest of quercus and ulmus substage 5c and picea abies forest substage 5b compared with present conditions climate during stage 5 in northern japan apparently fluctuated from warmer wetter to colder drier taiga composed of picea pinus and larix indicating colder dry conditions during stage 4 was replaced by picea abies forest and picea larix taiga in stage 3 suggesting relatively cool and cold dry environments taiga and mixed forest with taiga and cool temperate components characterize stage 2 holocene forests with juglans betula and quercus juglans were succeeded by picea and abies during the early holocene warm interval 7000 bp subsequently quercus ulmus and abies alnus assemblages reflect climatic deterioration pan mixed forest has been developed in hokkaido since 2000 bp

cold climatic episode of younger dryas age in tierra del fuego pronounced climatic change during the last glacial maximum is recognized as global in extent and has been attributed to orbital forcing1 not readily explained in a global context because of the equivocal nature of the evidence are the late glacial climatic events of short 100 1 000 yr duration the cold climate of the younger dryas chron 11 000 10 000 yr bp for example is known to have been particularly pronounced over the north atlantic and parts of europe and north america2 3 whereas in the southern hemisphere cold conditions for that time are not well established here we present evidence for late glacial climatic cooling in southernmost south america from studies of radiocarbon dated glacial and pollen stratigraphy at sites along the beagle channel in tierra del fuego where a forest tundra tension zone in the region is especially sensitive to shifting climate we conclude that the cold episode corresponds with the time of the younger dryas in europe when a drop in temperature ascribed most recently to colder sea surface temperatures and production rate of deep water in the north atlantic4 5 apparently occurred worldwide

tomographic evidence for a subducted seamount beneath the gulf of nicoya costa rica the cause of the 1990 mw 7 0 gulf of nicoya earthquake 1 tomographic images constrain the existence of a subducted seamount beneath the gulf of nicoya costa rica the subducted seamount is found at a depth of 30 km within the rupture area of the march 25 1990 mw 7 0 gulf of nicoya earthquake the gulf of nicoya earthquake was a typical thrust type subduction earthquake and occurred on a shallow dipping thrust fault parallel or along the boundary between the subducting cocos plate and the overriding plate precise relocation of the mainshock and its aftershocks in a 3 d p wave velocity model shows that the area of the mainshock rupture is coincident with the imaged subducted seamount most of the aftershocks are relocated within or close to the inferred subducted seamount above the subducting oceanic plate we interpret the subducted seamount as an asperity whose rupture caused the 1990 gulf of nicoya earthquake

tsunami earthquakes possibly widespread manifestations of frictional conditional stability 1 tsunami earthquakes shallow events that produce larger tsunamis than expected given their surface wave magnitudes ms typically have long durations and a source spectrum depleted in short period energy seven cases of underthrusting tsunami earthquakes provide information on the rupture processes but little constraint on geographic distribution or frequency we compare their rupture characteristics with smaller magnitude earthquakes on circum pacific interplate thrust faults comparable moment release time histories are found for large tsunami earthquakes and for many smaller shallow subduction zone earthquakes with significantly longer durations and additional source complexity than for events deeper than 15 km thus very shallow interplate earthquake ruptures are scale invariant with variable frictional properties on the plate interface controlling the depth dependent rupture process widespread occurrence of small shallow interplate earthquakes with long durations suggests that many subduction faults have frictional properties that may enable large tsunami generating earthquakes to occur fortunately large shallow ruptures are infrequent

early holocene climatic instability in japan organic geochemical evidence in sediment cores from lake biwa lake kizaki and the japan sea abstract sediment cores from lake biwa shiga prefecture and lake kizaki nagano prefecture provide evidence of variations in the climate of japan subsequent to the end of the last glacial period concentrations of organic carbon increase in sediments deposited after the pleistocene holocene boundary as wetter climates washed in more soil nutrients and aquatic productivity increased organic matter c n ratios simultaneously decrease indicating smaller proportions of land derived plant matter lake biwa c n ratios and organic carbon isotope ratios fluctuate markedly between 10 and 4 kya suggesting that both delivery of land derived organic matter and production of lake derived organic matter were variable during this period of time similar variability in biotic paleoceanographic indicators has been reported in sediments from the oki ridge in the japan sea and has been interpreted to record early holocene fluctuations in the intensity of the tsushima current such fluctuations in this warm water current are likely to have caused concordant fluctuations in climate on honshu a relationship that explains the variability in rainfall evident in the organic matter of the lake sediments

tsunamigenic structures in a creeping section of the alaska subduction zone segments of subduction zones that are capable of generating tsunamigenic earthquakes appear to have characteristic structural configurations these structures include heterogeneous plate interfaces a small wedge of deformed sediment at the toe of the overriding plate the frontal prism and splay faults in the crust of the overriding plate that root within the plate boundary megathrust here we use seismic reflection imaging to show that these features also exist within a creeping segment of the alaska subduction zone the shumagin gap we identify an active crustal scale normal fault system that dips landward and resembles that involved in the 2011 tohoku oki earthquake in japan we also find that the shumagin gap has a small frontal prism a deep water splay fault and that the plate interface here is rough and thinly sedimented we propose that lateral propagation of rupture from a neighbouring segment into the shumagin gap may explain a tsunamigenic earthquake that occurred there in 1788 and that tsunamigenic potential should be considered in hazard assessments for the region our results demonstrate that structural configurations similar to those in tohoku may exist in other subduction zones including within creeping segments or segments with no record of historical megathrust earthquakes but are under recognized identifying similar configurations globally may improve our ability to anticipate regions capable of generating large tsunamis creeping subduction zones are unlikely to generate tsunamigenic earthquakes analysis of a creeping part of the alaskan subduction zone reveals fault structures similar to those in tohoku suggesting it may host large earthquakes and tsunamis

extreme runup from the 17 july 2006 java tsunami 1 the 17 july 2006 magnitude mw 7 8 earthquake off the south coast of western java indonesia generated a tsunami that effected over 300 km of coastline and killed more than 600 people with locally focused runup heights exceeding 20 m this slow earthquake was hardly felt on java and wind waves breaking masked any preceding withdrawal of the water from the shoreline making this tsunami difficult to detect before impact an international tsunami survey team was deployed within one week and the investigation covered more than 600 km of coastline measured tsunami heights and run up distributions were uniform at 5 to 7 m along 200 km of coast however there was a pronounced peak on the south coast of nusa kambangan where the tsunami impact carved a sharp trimline in a forest at elevations up to 21 m and 1 km inland local flow depth exceeded 8 m along the elevated coastal plain between the beach and the hill slope we infer that the focused tsunami and runup heights on the island suggest a possible local submarine slump or mass movement

sea surface temperature of the western equatorial pacific ocean during the younger dryas high resolution 200 yr sample spacing records of sea surface temperature for the past 15 000 yr have been inferred from planktonic foraminiferal assemblages in a sediment core from the south china sea although the assemblages imply a large glacial to interglacial temperature change 7 c for winter temperatures they give no indication of a cooling during younger dryas time this suggests that the younger dryas increase in 18o observed in cores from the western equatorial pacific is not due to a climatic cooling but rather to a change in the isotopic composition of the oceans

teleseismic estimates of radiated seismic energy the e m 0 discriminant for tsunami earthquakes we adapt the formalism of boatwright and choy for the computation of radiated seismic energy from broadband records at teleseismic distances to the real time situation when neither the depth nor the focal geometry of the source is known accurately the analysis of a large data set of more than 500 records from 52 large recent earthquakes shows that this procedure yields values of the estimated energy ee in good agreement with values computed from available source parameters for example as published by the national earthquake information center neic the average logarithmic residual being only 0 26 units we analyze the energy to moment ratio by defining log10 ee m0 for regular earthquakes this parameter agrees well with values expected from theoretical models and from the worldwide neic catalogue there is a one to one correspondence between values of that are deficient by one full unit or more and the so called tsunami earthquakes previously identified in the literature as having exceedingly slow sources and believed due to the presence of sedimentary structures in the fault zone our formalism can be applied to single station measurements and its coupling to automated real time measurements of the seismic moment using the mantle magnitude mm should significantly improve real time tsunami warning

deposition pattern and sources of palynomorphs on the continental margin off hokkaido island northwest pacific abstract hokkaido island in northern japan is located in a cool temperate to boreal climate zone influenced by summer monsoons and typhoons during summer autumn while its eastern area is influenced by the subarctic oyashio current palynomorph pollen and spores distribution was investigated in surface sediments from the shelf and slope 40 2300 m water depth in the offshore area of tokachi plain central eastern hokkaido island the objective of this study was to examine the source transportation and deposition of palynomorphs in marine environments the majority of palynomorphs were transported from the tokachi coastal plain by both strong local winds from the mountain areas during the spring summer and the floods caused by heavy monsoon and typhoon rainfall approximately 10 of all palynomorphs were transported from both southwest and west areas by the wind palynomorph transportation by the oyashio current could not be discriminated because the same vegetation is present in hokkaido and the islands in upper streams of the oyashio current the total grain abundance was dependent on water depth high concentrations were observed at depths of 700 1500 m which is a region associated with high levels of fine silt and clay suggesting that the transportation and deposition of palynomorphs are controlled by their grain sizes this study supported a strong correlation between the distribution of sediments and the concentration of palynomorphs

degassing water around air bubbles entrapped in the vadose zone as a mechanism of carbonate precipitation a hypothesis abstract irreversible water degassing connected with periodic entrapment of pore air and formation of bubbles after the wetting of unsaturated sediments followed by the subsequent release of air from the bubbles after the sediments dry is proposed as a possible mechanism for the precipitation of calcium carbonate in the vadose zone the process involves an initial stage during rainy periods when pore air may be entrapped due to preferential water flow in large pores equilibration of the water air system causes pressure in the entrapped air bubbles to decrease to a value close to the sum of atmospheric and capillary pressure 40 95 of atmospheric pressure this pressure decrease leads to degassing of pore water adjacent to the bubbles bubble expansion and a shift in the equilibrium of all aqueous reactions involving dissolved gases in particular the degassing must accelerate carbonate precipitation a second stage develops when entrapped air is released during lowering of the groundwater table and or drying of sediment release of entrapped air that has been subjected to a pressure lower than atmospheric should draw in a portion of free pore air towards the water air interface that free pore air has a lower gas concentration compared to that in the released air which causes fast mixing between the two in addition transfer of a portion of the degassed water towards the groundwater occurs in combination these processes cause the degassing and corresponding geochemical processes in the zone of air entrapment and release to be irreversible the proposed degassing mechanism of carbonate precipitation may take place in the wetting front zone that passes through unsaturated sediments from the land surface downwards after rainy periods this mechanism may also occur at the upper boundary of the fluctuating capillary fringe of phreatic aquifers including perched groundwater periodically formed within unsaturated sediments that lie upon more clayey less permeable layers for a sandy capillary fringe the minimum rate of carbonate precipitation by this mechanism is estimated in a wide range of 120 to 175 200 mg m 2 yr 1 at these rates within a 1 m zone of capillary fringe fluctuations sand might become cemented until pourability is lost for from 800 to 1 170 000 years

rupture evolution of the 2006 java tsunami earthquake and the possible role of splay faults abstract the 2006 mw 7 8 java earthquake was a tsunami earthquake exhibiting frequency dependent seismic radiation along strike high frequency global back projection results suggest two distinct rupture stages the first stage lasted 65 s with a rupture speed of 1 2 km s while the second stage lasted from 65 to 150 s with a rupture speed of 2 7 km s high frequency radiators resolved with back projection during the second stage spatially correlate with splay fault traces mapped from residual free air gravity anomalies these splay faults also colocate with a major tsunami source associated with the earthquake inferred from tsunami first crest back propagation simulation these correlations suggest that the splay faults may have been reactivated during the java earthquake as has been proposed for other tsunamigenic earthquakes such as the 1944 mw 8 1 tonankai earthquake in the nankai trough

radiated seismic energy and earthquake source duration variations from teleseismic source time functions for shallow subduction zone thrust earthquakes 1 earthquake source time functions deconvolved from teleseismic broadband p wave recordings are used to examine rupture variations for 417 underthrusting earthquakes located on the interplate interface in circum pacific subduction zones moment scaled duration of significant moment release varies with depth with longer duration events occurring in the shallowest 20 km of the megathrusts the source time functions are also used to estimate radiated seismic energy two estimates are obtained a simple scaled triangle substitution for the moment release history provides a minimum estimate while integration of the time function shape provides an estimate limited only by the bandwidth of the teleseismic deconvolutions while these energy calculations underestimate total energy they enable systematic comparisons of rupture process within and between subduction zones we do not find significant depth dependence for radiated energy overall but some regions do show mild trends of increasing energy seismic moment ratios e mo with increasing source depth that correspond to rupture duration variations in those regions the observations of longer rupture duration at shallow depth with moderate e mo may be due to heterogeneous friction and structural features on the shallow plate interface index terms 7215 seismology earthquake parameters 7230 seismology seismicity and seismotectonics 8164 tectonophysics stresses crust and lithosphere keywords radiated energy shallow subduction source parameters

pre computed tsunami inundation database and forecast simulation in pelabuhan ratu indonesia we built a pre computed tsunami inundation database in pelabuhan ratu one of tsunami prone areas on the southern coast of java indonesia which can be employed for a rapid estimation of tsunami inundation during an event the pre computed tsunami waveforms and inundations are from a total of 340 scenarios ranging from 7 5 to 9 2 in moment magnitude scale mw including simple fault models of 208 thrust faults and 44 tsunami earthquakes on the plate interface as well as 44 normal faults and 44 reverse faults in the outer rise region using our tsunami inundation forecasting algorithm neartif we could rapidly estimate the tsunami inundation in pelabuhan ratu for three different hypothetical earthquakes the first hypothetical earthquake is a megathrust earthquake type mw 9 0 offshore sumatra which is about 600 km from pelabuhan ratu to represent a worst case event in the far field the second hypothetical earthquake mw 8 5 is based on a slip deficit rate estimation from geodetic measurements and represents a most likely large event the third hypothetical earthquake is a tsunami earthquake type mw 8 1 which often occurs south of java we compared the tsunami inundation maps produced by the neartif algorithm with results of direct forward inundation modeling for the hypothetical earthquakes the tsunami inundation maps produced from both methods are similar for the three cases however the tsunami inundation map from the inundation database can be obtained in much shorter time 1 min than the one from a forward inundation modeling 40 min these indicate that the neartif algorithm based on pre computed inundation database is reliable and useful for tsunami warning purposes this study also demonstrates that the neartif algorithm can work well though the earthquake source is located outside the area of fault model database because it uses a time shifting procedure for the best fit scenario searching

meteoric versus burial control on porosity evolution of the smackover formation whole rock 13c 18o and sr compositions of the uppermost ooid grainstones of the smackover formation at black creek field in mississippi reveal characteristics of a meteoric system in this area the trend in 13c signatures indicates that meteoric water acquired its low carbon values at a soil zone and was buffered completely with the host rock before entering the meteoric lens identical 18o data suggest that allochems stabilized at the same temperatures in waters of similar 18o compositions during early meteoric diagenesis that is calcitization continued to completion before the onset of burial sr concentrations reveal differential transformation mechanisms low sr values in the phreatic zones are attributed to slow stabilization by exchange with the bulk solution high sr compositions in the vadose zone resulted from rapid incremental transformation meteoric cementation was sparse therefore grainstones entered the burial realm with all of their porosity intact modification of porosity was a burial process and was directly related to the intensity of chemical compaction which itself was controlled by three factors 1 the degree of early cementation 2 grain type and 3 grain size early cemented intervals experienced low to moderate compaction regardless of grain size or grain type in the absence of early cementation grain type and grain size were the dominant factors of porosity control coarse grained intervals that were composed of micritic grains experienced less compaction than fine grained oolitic intervals average volumetric percentages of cements as determined by point counting of 63 samples are as follows 1 marine and meteoric cements 1 5 2 prebitumen calcite 6 5 3 saddle dolomite 1 4 postbitumen calcite 4 3 5 pyrobitumen 1 total cement sum of 1 5 total burial cement sum of 2 5 and total burial carbonate cement volumes sum of 2 4 average 14 13 and 12 respectively out of an original porosity of 40 13 porosity units were lost by cementation and 27 porosity units were reduced by compaction mechanical and chemical present day intergranular porosity of these grainstones is zero whether they belonged to the vadose zone or the phreatic interval burial cementation and compaction destroyed all intergranular porosity regardless of early diagenetic overprint or textural variables the reservoir became compartmentalized during burial some intervals were active producers of calcium carbonate others were passive recipients

application of an improved algorithm to high precision relocation of isc test events abstract new location features for possible implementation by the international seismological centre in its standard location procedures are tested using a set of 156 well located and geographically well distributed earthquakes and explosions the tests are performed using the engdahl et al engdahl e r van der hilst r d buland r p 1998 global teleseismic earthquake relocation with improved travel times and procedures for depth determination bull seism soc am 88 3295 3314 ehb location algorithm with the 1 d reference earth model ak135 kennett b l n engdahl e r buland r 1995 constraints on seismic velocities in the earth from travel times geophys j int 122 108 124 weighting by phase variance as a function of distance improves location accuracy by 7 use of later phase arrival times does not result in a significant improvement in location or depth for events with observing stations well distributed in azimuth however with application of an improved phase identification technique depth phases provide significantly better estimates of focal depth

the mode and mechanism of the last deglaciation oceanic evidence changes in ocean temperature carbonate productivity and ice rafted detritus in the north atlantic suggest that half of the northern hemisphere ice volume at the last glacial maximum had disappeared by 13 000 yr b p despite the still extensive limits of the ice sheets this early thinning of the ice sheets occurred during a time when summer insolation values were slowly rising but when pollen evidence south of the ice margins indicates cold dry air masses we infer that this rapid early ice disintegration 16 000 13 000 yr b p was caused by oceanic mechanisms 1 rising sea level causing increased calving along ice margins 2 the chilling of the sea surface by icebergs and meltwater reducing moisture extraction by the atmosphere and transport to the ice sheets and 3 winter freezing of the low salinity meltwater layer suppressing local moisture extraction and the regional influx of moisture bearing storms from lower latitudes in winter and hence starving the ice sheets these oceanic feedback mechanisms were strongest from 16 000 to 13 000 yr b p and weaker but still active from that date until the end of deglaciation at 6000 yr b p

geochemistry of meteoric diagenesis in carbonate islands of the northern bahamas 1 evidence from field studies processes driving carbonate diagenesis in islands of the northern bahamas are investigated using major ion dissolved oxygen and dissolved organic carbon analyses of water samples from surface and ground waters and measurements of soil gas pco2 meteoric waters equilibrate with aragonite but reactions are water controlled rather than mineral controlled and drive dissolution rather than concurrent precipitation of calcite surface runoff waters equilibrate with atmospheric pco2 and rapidly recharge the vadose zone limiting subaerial bedrock dissolution to only 6 6 15 mg l 1 ca pco2 of soil gas measured in the summer wet season 7 4 s 3 7 10 3 atm is elevated compared with that of the atmosphere despite the thin skeletal organic nature of the soil and the discontinuous soil cover soil waters retained in surface pockets are equilibrated with respect to aragonite and have dissolved 51 s 19 mg l 1 ca this is substantially less than the 93 s 18 mg l 1 ca in samples from pumping boreholes that sample meteoric waters from the freshwater lens the high pco2 of the freshwater lens 16 s 8 3 10 3 atm for pumping boreholes suggests that significant additional co2 may be derived by oxidation of soil and surface derived organic carbon within the lens the suboxic nature of the majority of the freshwater lens and the observed depletion in sulphate support this suggestion and indicate that both aerobic and anaerobic oxidation may take place shallow lens samples from observation boreholes are calcite supersaturated and have a lower pco2 than deeper lens waters indicating that co2 degasses from the water table driving precipitation of calcite cements we suggest that the geochemical evolution of waters in the vadose zone and upper part of the freshwater lens may be determined by the presence of a body of ground air with pco2 controlled by production in the freshwater lens and soil and by degassing to the atmosphere copyright 2007 john wiley sons ltd

environmental change in the yangtze river delta since 12 000 years b p abstract a 52 m core from qidong at the tip of the yangtze river chang jiang delta provides a history of sea level change deltaic development and vegetational and climatic changes during the last 12 000 yr about 12 000 yr ago when sea level was about 60 m below the present level the coring site was situated in the innermost part of the exposed continental shelf the late pleistocene vegetation on the uplands of the lower yangtze river valley was a mixed forest of deciduous and broadleaved evergreen trees in which betula ulmus tsuga and cupressaceae were slightly more abundant than at present abies and picea were probably present as relict populations on mountains bordering the region rapidly rising sea level converted the qidong area to a coastal or estuarine environment between 11 000 and 10 800 yr b p leading to widespread development of wetlands dominated by gramineae and cyperaceae during the next 2500 yr coastal erosion due to marine transgression obliterated the sedimentary record deltaic sedimentation predominated from 8300 to 3800 yr b p as the yangtze river delta prograded by successively building a series of estuarine sand bars during the mid holocene the climate was slightly warmer and more humid than at present allowing the subtropical broadleaved evergreen trees to increase their populations pinus and quercus became more abundant after 3800 yr b p in response to climatic cooling the present deltaic plain in qidong formed less than 200 yr ago

the kinematics of crustal deformation in java from gps observations implications for fault slip partitioning abstract our understanding of seismic risk in java has been focused primarily on the subduction zone where the seismic records during the last century have shown the occurrence of a number of tsunami earthquakes however the potential of the existence of active crustal structures within the island of java itself is less well known historical archives show the occurrence of several devastating earthquake ruptures north of the volcanic arc in west java during the 18th and the 19th centuries suggesting the existence of active faults that need to be identified in order to guide seismic hazard assessment here we use geodetic constraints from the global positioning system gps to quantify the present day crustal deformation in java the gps velocities reveal a homogeneous counterclockwise rotation of the java block independent of sunda block consistent with a ne sw convergence between the australian plate and southeast asia continuous gps observations show a time dependent change in the linear rate of surface motion in west java which we interpret as an ongoing long term post seismic deformation following the 2006 m w 7 7 java earthquake we use an elastic block model in combination with a viscoelastic model to correct for this post seismic transient and derive the long term inter seismic velocity which we interpret as a combination of tectonic block motions and crustal faults strain related deformation there is a north south gradient in the resulting velocity field with a decrease in the magnitude towards the north across the kendeng thrust in the east and the baribis thrust in the west we suggest that the baribis thrust is active and accommodating a slow relative motion between java and the sunda block at about 5 0 2 mm yr we propose a kinematic model of convergence of the australian plate and the sunda block involving a slip partitioning between the java trench and a left lateral structure extending e w along java with most of the convergence being accommodated by the java megathrust and a much smaller parallel motion accommodated along the baribis 5 0 2 mm yr and kendeng 2 3 0 7 mm yr thrusts our study highlights a correlation between the geodetically inferred active faults and historical seismic catalogs emphasizing the importance of considering crustal fault activity within java in future seismic assessments

do subducting seamounts generate or stop large earthquakes seamount subduction is a common process in subduction zone tectonics contradicting a widely held expectation that subducting seamounts generate large earthquakes seamounts subduct largely aseismically producing numerous small earthquakes on rare occasions when they do produce relatively large events the ruptures tend to be complex suggesting multiple rupture patches or faults we explain that the seismogenic behavior of these seamounts is controlled by the development and evolution of an adjacent fracture network during subduction and cannot be described using the frictional behavior of a single fault the complex structure and heterogeneous stresses of this network provide a favorable condition for aseismic creep and small earthquakes but an unfavorable condition for the generation and propagation of large ruptures

coda wave seismic structure beneath the indian ocean region and its implications to seismotectonics and structural heterogeneity abstract the indian ocean region is one of the challenging areas for seismological research because of its complex seismotectonic settings and intricate structural heterogeneity prevails beneath the indian ocean region in order to address the problem we attempted to determine the attenuation structure for the indian ocean region using coda wave generation by single backscattering model in this study the central frequency of interest has been considered between 1 5 and 12 0 hz with lapse time window ltw of 20 30 40 50 and 60 s measured from the origin time of the earthquake we obtained the attenuation relation for different seismotectonic zones associated with varying estimate of attenuation parameters spreading zone qc spz 171f1 10 subduction zone qc sz 220f0 961 triple point junction qc tpj 156f1 15 prominent faults of indian ocean region qc pfioz 197f0 99 and volcanic and hotspot qc vz hs 209f0 97 we estimated average frequency dependent attenuation parameters of q0 that varies as 156 32 q0 220 33 with corresponding variability in frequency parameter as 0 96 0 05 1 15 0 09 at 40 s ltw for the entire indian ocean region suggesting that the entire indian ocean is seismo tectonically highly active and is attributed to the nature and extent of attenuation due to varying amount of structural heterogeneity in different tectonic zones characterized by the occurrence of earthquakes of varying strengths in the seismically active tectonic zones of the region we found that the triple junction rtj is associated with low qc and high attenuation because of deposition of a variety of sediments at the rtj which is in unison to the geological mapping of the region we observed that our estimated attenuation model is comparable that of the aleutian islands the adak seismic zone at low frequency 5 hz and to the philippine sea subduction zone petukhin at higher frequency range 5 hz which is very much correlative to seismo tectonic settings we infer that our assimilated attenuation model has potential to provide information on intricate seismotectonics and seismogenesis for computing earthquake source parameters and earthquake hazards that may be useful for assimilating detailed seismic velocity structure beneath the indian ocean region

sea level surface salinity of the japan sea and the younger dryas event in the northwestern pacific ocean abstract the japan sea was profoundly different during glacial times than today available 18 o evidence indicates that sea surface salinity was lower by several per mil this probably increased the stability of the water column and caused anoxic sedimentary conditions in the deep sea as shown by the absence of benthic microfossils and the presence of laminated sediment these changes are likely related to the effects of late quaternary sea level change on the shallow sills ca 130 m across which the japan sea exchanges with the open ocean the hwang he yellow river has previously been implicated as the source of fresh water to the japan sea during glaciation but the possible roles of the amur river and excess precipitation over evaporation must also be considered ambiguous radiocarbon chronologies for the latest quaternary of japan sea cores do not adequately constrain the timing of salinity lowering previous studies have suggested that lowest sea surface salinity was achieved 27 000 to 20 000 14 c yr b p however if global sea level fall restricted exchange with the open ocean circulation then lowest salinity in the japan sea may have occurred as recently as 15 000 to 20 000 yr ago when sea level was lowest if this alternative is correct then as sea level abruptly rose about 12 000 yr ago relatively fresh water must have been discharged to the open pacific this might have affected the dynamics of outflow local faunal and floral expression of the polar front and stable isotope ratios in foraminifera these environmental changes could be misinterpreted as evidence for the cooling of younger dryas age which has not been identified in nearby terrestrial records

the impact of cold north atlantic sea surface temperatures on climate implications for the younger dryas cooling 11 10 k the sensitivity of global climate to colder north atlantic sea surface temperatures is in vestigated with the use of the giss general circulation model north atlantic ocean temperatures 18 000 b p resembling those prevalent during the younger dryas were incorporated into the model of the present climate and also into an experiment using orbital parameters and land ice characteristic of 11 000 b p the results show that with both 11 000 b p and present conditions the colder ocean temperatures produce cooling over western and central europe in good agreement with younger dryas paleoclimatic evidence cooling also occurs over extreme eastern north america although the precise magnitude and location depends upon the specification of ocean temperature change in the western atlantic despite the presence of increased land ice and colder ocean temperatures the younger dryas summer air temperatures at northern hemisphere midlatitudes in the model are warmer than those of today due to changes in the orbital parameters chiefly precession and atmospheric subsidence at the perimeter of the ice sheets

the java convergent margin structure seismogenesis and subduction processes the java margin is characterized by a distinct variation in lower to upper plate material transfer and recurring catastrophic tsunamogenic earthquakes both processes are closely linked to the subduction of oceanic basement relief resulting in varying degrees of fore arc deformation tomographic models of refraction seismic profiles and reflection seismic lines in combination with high resolution multibeam bathymetric data reveal the variability in the deep structure and deformation of the java fore arc shallow subduction processes are governed by the sediment supply in the trench as well as by the nature and fabric of the oceanic lithosphere the deep structure of the fore arc reveals a shallow upper plate crust mantle transition present along the entire java margin section the serpentinized fore arc mantle wedge governs the depth extent of the seismogenic zone here which is narrower compared to its sumatran analogue in addition offshore central java high relief oceanic basement features potentially act as asperities as well as barriers to seismic rupture limiting the possible magnitude of subduction thrust earthquakes however the potential for geohazards in particular tsunamis is high along the entire margin this results from tsunamogenic earthquakes ubiquitous splay faults and potentially tsunamogenic landslides which further increase the risk of future tsunamis

the 1994 java tsunami earthquake slip over a subducting seamount on june 2 1994 a large subduction thrust earthquake ms 7 2 produced a devastating tsunami on the island of java this earthquake had a number of unusual characteristics it was the first recorded large thrust earthquake on the java subduction zone all of the aftershock mechanisms exhibit normal faulting no mechanisms are similar to the main shock also the large tsunami and the relatively low energy radiated by the main shock have led to suggestions that this earthquake might have involved slow shallow rupture near the trench similar to the 1992 nicaragua earthquake we first relocate the main shock and the aftershocks we then invert long period surface waves and broadband body waves to determine the depth and spatial distribution of the main shock slip a dip of 12 hypocenter depth of 16 km and moment of 3 5 l020 n m mw 7 6 give the best fit to the combined seismic data and are consistent with the plate interface geometry the source spectrum obtained from both body and surface waves has a single corner frequency between 10 and 20 mhz implying a stress drop of 0 3 mpa the main energy release was preceded by a small subevent lasting 12 s the main slip occurred at 20 km depth downdip and to the nw of the hypocenter this area of slip is collocated with a prominent high in the bathymetry that has been identified as a subducting seamount we interpret the java earthquake as slip over this subducting seamount which is a locked patch in an otherwise decoupled subduction zone we find no evidence for slow shallow rupture no thrust aftershocks are expected if the entire locked zone slipped during the main shock but extension of the subducting plate behind the seamount would promote normal faulting as observed it seems probable that such a source model could also explain the size and timing of the observed tsunami

along strike variability of rupture duration in subduction zone earthquakes 1 subduction zone earthquakes exhibit a wide spectrum of rupture times that reflect conditions on the megathrust fault tsunami earthquakes are examples of slower than expected ruptures that produce anomalously large tsunamis relative to the surface wave magnitude one model explaining tsunami earthquakes suggests slip within patches of low rigidity material at shallow depths heterogeneous fault conditions such as having patches of low rigidity material surrounded by higher strength material should produce heterogeneous earthquake rupture parameters here we investigate along strike variation in rupture duration for 427 shallow thrust earthquakes mw 5 0 7 0 in the peru chile alaska tonga kuril izu and java sumatra subduction zones to explore how heterogeneous seismic and tectonic characteristics such as differences in sediment type thickness and roughness of subducting bathymetry affect earthquake properties earthquake source parameters including rupture durations are estimated using multi station deconvolution of teleseismic p and sh waves to solve for earthquake source time functions and all events are relocated using additional depth phase information we classify events into shallow 26 km and deep 26 km and 61 km groups based on the overall mean depth and focus on the longest duration events with moment normalized rupture durations of 1 standard deviation above the mean duration for each group we find long duration events at all depths within the study regions except peru and chile we find no correlation with incoming sediment thickness or type and limited spatial correlation with regions of past tsunami earthquakes regions of observed afterslip and subducting bathymetric features

earthquake rupture stalled by a subducting fracture zone we showed that the rupture produced by the great peru earthquake moment magnitude 8 4 on 23 june 2001 propagated for 70 kilometers before encountering a 6000 square kilometer area of fault that acted as a barrier the rupture continued around this barrier which remained unbroken for 30 seconds and then began to break when the main rupture front was 200 kilometers from the epicenter the barrier had relatively low rupture speed slip and aftershock density as compared to its surroundings and the time of the main energy release in the earthquake coincided with the barrier s rupture we associate this barrier with a fracture zone feature on the subducting oceanic plate

a record of late quaternary vegetation from davis lake southern puget lowland washington abstract pollen and macrofossil analyses of a core spanning 26 000 yr from davis lake reveal late pleistocene and holocene vegetational patterns in the puget lowland the core ranges lithologically from a basal inorganic clay to a detritus gyttja to an upper fibrous peat and includes eight tephra units the late pleistocene pollen sequence records two intervals of tundra parkland vegetation the earlier of these has high percentages of picea gramineae and artemisia pollen and represents the vegetation during the evans creek stade fraser glaciation ca 25 000 17 000 yr b p the later parkland interval is dominated by picea tsuga mertensiana and gramineae it corresponds to the maximum ice advance in the puget lowland during the vashon stade fraser glaciation ca 14 000 yr b p an increase in pinus ontorta pollen between the two tundra parkland intervals suggests a temporary rise in treeline during an unnamed interstade after 13 500 yr b p a mixed woodland of subalpine and lowland conifers grew at davis lake during a period of rapid climatic amelioration in the early holocene the prolonged expansion of pseudotsuga and alnus woodland suggests dry temperate conditions similar to those of present rainshadow sites in the puget lowland more mesic forests of tsuga eterophylla thuja plicata and pseudotsuga similar to present lowland vegetation appeared in the late holocene ca 5500 yr b p

stable isotope and lithologic evidence of late glacial and holocene oceanography of the northwestern pacific and its marginal seas abstract stable isotopes geochemical lithological and micropaleontological results from cores from the far northwest fnw pacific and the okhotsk and bering seas are used to reconstruct the regional environment for the last glaciation the deglacial transition and the holocene 18 o records of planktonic foraminifera of the region show two light shifts during deglacial time provoked by the freshening of the surface water and climate warming these north pacific terminal events t1anp and t1bnp with ages of 12 500 and 9300 yr b p respectively occur almost simultaneously with two episodes of accelerated glacier melting around the north atlantic along with the isotopic shifts the caco 3 content in regional sediments increased abruptly 1a and 1b carbonate peaks probably due to changes of productivity and pore water chemistry of surface sediments organic matter and opal concentration increased during the transition between t1anp and t1bnp events in the sediments of the fnw pacific and the southern part of the bering sea and opal content increased in the holocene in the bering and okhotsk seas 13 c records of cores from the okhotsk and bering seas and the fnw pacific do not contradict the hypothesis of increased intermediate water formation in the region during glaciation during deglaciation accumulation of the coarse terrigenous component decreased in sediments of the bering sea and the fnw pacific before the t1anp event probably as a result of rising sea level and opening of the bering strait

shallow subduction zone earthquakes and their tsunamigenic potential summary we have examined the source spectra of all shallow subduction zone earthquakes from 1992 to 1996 with moment magnitude 7 0 or greater as well as some other interesting events in the period range 1 20 s by computing moment rate functions of teleseismic p waves after comparing the source spectral characteristics of tsunami earthquakes earthquakes that are followed by tsunamis greater than would be expected from their moment magnitude with regular events we identified a subclass of this group slow tsunami earthquakes this subclass consists of the 1992 nicaragua the 1994 java and the february 1996 peru earthquakes we found that these events have an anomalously low energy release in the 1 20 s frequency band with respect to their moment magnitude although their spectral drop ov is comparable to those of the other earthquakes from an investigation of the centroid and body wave locations it appears that most earthquakes in this study conformed to a simple model in which the earthquake nucleates in a zone of compacted and dehydrated sediments and ruptures up dip until the stable sliding friction regime of unconsolidated sediments stops the propagation sedimentstarved trenches e g near jalisco can produce very shallow slip because the fault material supports unstable sliding the slow tsunami earthquakes also ruptured up dip however their centroid is located unusually close to the trench axis the subduction zones in which these events occurred all have a small accretionary prism and a thin layer of subducting sediment ocean surveys show that in these regions the ocean floor close to the trench is highly faulted we suggest that the horst and graben structure of a rough subducting oceanic plate will cause contact zones with the overriding plate making shallow earthquake nucleation and up dip propagation to the ocean floor possible the rupture partly propagates in sediments making the earthquake source process slow two factors have to be considered in the high tsunami generating potential of these events first the slip propagates to shallow depths in low rigidity material causing great deformation and displacement of a large volume of water second the measured seismic moment may not represent the true earthquake displacement because the elastic constants of the source region are not taken into account in the standard cmt determination

the 17 july 2006 java tsunami earthquake the 17 july 2006 java earthquake involved thrust faulting in the java trench and excited a deadly tsunami 5 8 m that inundated the southern coast of java the earthquake s size estimates vary significantly with seismic wave period very long period signals 300 500 s indicate a seismic moment of 6 7 10 20 nm m w 7 8 m s 20 s 7 2 m b 1 s 6 2 while shaking intensities 3 10 hz were mmiv the large tsunami relative to ms characterizes this event as a tsunami earthquake like previous tsunami earthquakes the java event had an unusually low rupture speed of 1 0 1 5 km s and occurred near the up dip edge of the subduction zone thrust fault most large aftershocks involved normal faulting the rupture propagated 200 km along the trench with several pulses of shorter period seismic radiation superimposed on a smooth background rupture with an overall duration of 185 s

geochemical and physical controls on vadose zone hydrology of holocene carbonate sands grand bahama island this paper explores the relationship between vadose zone hydrology and geochemical changes in mixed mineralogy carbonate sands from a bahamian coastal dune of holocene age cores were taken from two sites at site a a shallow humic entisol is developed beneath open scrub vegetation while at site b a deeper more organic rich inceptisol has formed beneath a mature hardwood coppice x ray diffraction analysis reveals significant contrasts in mineralogy both within and between the two sites with partial stabilization of high mg calcite and aragonite to low mg calcite stabilization is greater at site b and is accompanied by a significant increase in total porosity diagenetic changes in pore size distribution have implications for residence times of percolating water as determined using measurements of moisture retention characteristics using pressure plate apparatus and hydrological models of unsaturated zone moisture flux the diagenetically more mature sands from site b have a 50 100 per cent higher moisture retention although unsaturated hydraulic conductivity is also higher particularly at greater suctions the increase in water retention is likely to enhance further rates of mineral controlled reactions while development of an organic rich soil also enhances the geochemical drive for dissolution carbonate diagenesis thus appears to be strongly linked to vadose zone hydrology and the interactions identified here have important consequences for the nature and long term rates of mineral stabilization

anatomy of the western java plate interface from depth migrated seismic images newly pre stack depth migrated seismic images resolve the structural details of the western java forearc and plate interface the structural segmentation of the forearc into discrete mechanical domains correlates with distinct deformation styles approximately 2 3 of the trench sediment fill is detached and incorporated into frontal prism imbricates while the floor sequence is underthrust beneath the decollement western java however differs markedly from margins such as nankai or barbados where a uniform continuous decollement reflector has been imaged in our study area the plate interface reveals a spatially irregular nonlinear pattern characterized by the morphological relief of subducted seamounts and thicker than average patches of underthrust sediment the underthrust sediment is associated with a low velocity zone as determined from wide angle data active underplating is not resolved but likely contributes to the uplift of the large bivergent wedge that constitutes the forearc high our profile is located 100 km west of the 2006 java tsunami earthquake the heterogeneous decollement zone regulates the friction behavior of the shallow subduction environment where the earthquake occurred the alternating pattern of enhanced frictional contact zones associated with oceanic basement relief and weak material patches of underthrust sediment influences seismic coupling and possibly contributed to the heterogeneous slip distribution our seismic images resolve a steeply dipping splay fault which originates at the decollement and terminates at the sea floor and which potentially contributes to tsunami generation during co seismic activity

teleseismic relocation and assessment of seismicity 1918 2005 in the region of the 2004 mw 9 0 sumatra andaman and 2005 mw 8 6 nias island great earthquakes the m w 9 0 2004 sumatra andaman islands and m w 8 6 nias island great earthquake sequences have generated over 5000 catalog reported earthquakes along 1700 km of the sumatra andaman and western sunda regions studies of prior regional seismicity have been limited to global catalog locations that often have poorly constrained epicenters and depths approximately 3650 teleseismically well recorded earthquakes occurring in this region during the period 1918 2005 are relocated with special attention to focal depth reduced uncertainties of epicenters and depths in the region on the order of 15 and 10 km respectively foster interpretation of focal mechanism data and provide additional details about the subducting indian and australian plates the revised earthquake dataset reveals a sharp delineation between aftershocks of the 2004 and 2005 earthquakes near simeulue island and a steepening in slab dip from south to north the downdip width of the aftershock zone of the 2004 m w 9 0 earthquake varies from 200 km at its northern end to 275 km at its southern end and events located between 35 and 70 km focal depth occur more frequently in the southernmost section of this aftershock zone outer rise and near trench normal and strike slip faulting earthquakes also increase in frequency following the 2004 and 2005 earthquakes earthquake swarms triggered along the andaman backarc spreading center both north of sumatra and near siberut island 100 km south of the nias island aftershock sequence illustrate the complex and variable nature of seismicity following these great earthquakes

three dimensional crustal architecture beneath the sikkim himalaya and its relationship to active deformation we study the 3 d variation of the crustal structure of the sikkim himalaya using broadband seismological data acquired from a focused network of seven stations spanning the lesser higher and tethyan himalaya common conversion point stacking of receiver functions recorded along an across strike profile of the himalaya reveals first order northward dip on the main himalayan thrust mht a midcrustal discontinuity and the moho along with higher order lateral variations three dimensional images generated from joint inversion of receiver functions and surface wave dispersions show that the mht has a ramp flat ramp geometry the ramps are located beneath the lesser himalaya and the tethyan himalaya with dips of 7 and 15 respectively connected by flat segments the ramp beneath the lesser himalaya forms a dome structure upwarping the thrust sheets associated with the peling and main central thrust the erosional surface of this dome forms the arcuate geometry of thrusts observed in the lesser himalaya the thickness of the underthrust indian crust is 35 42 km and has an average vs of 3 63 km s similar to that of the indian shield crust the moho also has dome like structures separated by elongated deeper sections trending nw se these are intersected by steeply dipping transverse low velocity zones oblique to the strike of the himalaya we conjecture that these low velocity zones are the dextral strike slip faults known to be active beneath the sikkim himalaya the observed alternate shallow and deep segments of the moho must be a consequence of several cycles of strike slip displacement on these transverse faults

paleoceanographic implications of a 90 000 year long diatom record in piston core kh94 3 lm 8 off ne japan abstract q mode principal component analysis pca of a fossil diatom assemblage reveals the late quaternary paleoceanography of the nw pacific margin based on submarine core kh94 3 lm 8 recovered off the sanriku coast of ne japan 38 53 46 n 143 22 19 e overall diatoms were abundant during interglacials but low in abundance and poor in preservation during the last glacial with each oxygen isotope stage having its own characteristic assemblage the results of pca are principal component 1 pc1 is composed mainly of thalassionema nitzschioides which predominated during the coldest oxygen isotopic stages 4 75 58 ka and 2 25 11 ka and by allochthonous taxa the diatom tests are poorly preserved and the diatom mass accumulation rate dmar is the lowest in these stages pc2 is characterized by ice related diatoms that predominate in stage 3 the interstadial whereas pc3 which is characterized by neodenticula seminae and odontella aurita shows high values in stage 1 diatom assemblages exhibit drastic changes between oxygen isotopic stages 3 and 1 11 0 ka distinct increases of dmar occurred during both periods we infer an intensified advection of sea ice from the sea of okhotsk toward the area off sanriku during stage 3 this interpretation explains the high dmar in stage 3 owing to high productivity at the sea ice edge our study can contribute to marine environmental reconstruction since the last glaciation because fewer micropaleontological data exist in the nw pacific margin for these time intervals compared with other oceans

thrust type subduction zone earthquakes and seamount asperities a physical model for seismic rupture a thrust type subduction zone earthquake of m sub w 7 6 ruptures an area of approximately 6 000 km sup 2 has a seismic slip of approximately 1 m and is nucleated by the rupture of an asperity approximately 25km across a model for thrust type subduction zone seismicity is proposed in which basaltic seamounts jammed against the base of the overriding plate act as strong asperities that rupture by stick slip faulting a m sub w 7 6 event would correspond to the near basal rupture of a approximately 2 km tall seamount the base of the seamount is surrounded by a low shear strength layer composed of subducting sediment that also deforms between seismic events by distributed strain viscous flow planar faults form in this layer as the seismic rupture propagates out of the seamount at speeds of kilometers per second the faults in the shear zone are disrupted after the event by aseismic slow viscous flow of the subducting sediment layer consequently the extent of fault rupture varies for different earthquakes nucleated at the same seamount asperity because new fault surfaces form in the surrounding subducting sediment layer during each fast seismic rupture

assessment of scardec source parameters of global large mw 7 5 subduction earthquakes rapid and accurate source characterizations of large shallow subduction earthquakes are key for improved tsunami warning efforts we assess the quality of source parameters of large magnitude mw 7 5 shallow subduction earthquakes of the past 20 yr determined using scardec a recent fully automated broad band body wave source inversion technique for the fast estimation of the moment magnitude depth focal mechanism and source time functions of global events we find that scardec source parameters agree well with those reported in the global centroid moment tensor gcmt catalogue with only the fault dip angle showing a tendency for steeper scardec dip values than gcmt we investigate this discrepancy through independent validation tests of the source models by i testing how well they explain data not used in their construction notably low frequency normal mode data and ii assessing the data fit using 3 d forward modelling tools more sophisticated than those used to build the source models specifically we use a spectral element method for a 3 d earth model we find that scardec source parameters explain normal mode data reasonably well compared to gcmt solutions in addition for the 3 d earth model used in our experiments scardec dip angles explain body wave data similarly or slightly better than gcmt moreover scardec dip angles agree well with results from individual earthquake studies in the literature and with geophysical constraints for different subduction zones our results show that scardec is a reliable technique for rapid determinations of source parameters of large mw 7 5 subduction earthquakes since the scardec method provides realistic source time functions allowing the fast identification of long duration tsunami earthquakes it is complementary to existing methods routinely used for earthquake monitoring and suitable for ocean wide tsunami warning purposes

steady state freshwater seawater mixing zone in stratified coastal aquifers summary the mixing zone between freshwater and intruding seawater which controls regional groundwater flow dynamics and reactive transport processes is the most important component in coastal aquifers laboratory experiments and numerical simulations were conducted to investigate the effects of aquifer stratification on the thickness of a steady state freshwater seawater mixing zone a series of experiments were implemented in a laboratory tank packed with three layers of coastal sands and manipulated by two flow cells for maintaining constant head boundary conditions packed aquifers included a homogenous aquifer a high hydraulic conductivity k low k high k stratified aquifer and a low k high k low k stratified aquifer both tank scale and field scale density dependent models were developed to simulate the laboratory experiments and to systematically investigate aquifer stratification effects on the thickness of a steady mixing zone with varying layer configurations results showed that when an aquifer layer with a low k overlies a layer with a relatively high k slanting upward flow of diluted saltwater and re circulated seawater flow are refracted at the interface between the two layers resulting in streamline separation and a broad mixing zone in the low k layer by contrast the mixing zone in a high k layer is slightly narrowed when it overlies a layer with a relatively low k because flow refraction squeezes the streamlines within the mixing zone the mixing zone profile in head controlled systems is a function of k contrast but independent of the magnitude of k our results demonstrated the significant impact of aquifer stratification on controlling groundwater flow and solute transport in coastal subsurface environments and would have significant implications for studying physical chemical and biological processes in coastal subsurface environments as aquifer stratification is naturally prevalent

late quaternary atmospheric and oceanographic variations in the western pacific inferred from pollen and radiolarian analyses abstract pollen and radiolarian analyses of sediment from four piston cores located along a south north transect 28 44 n off the east coast of japan yield detailed records of variations in terrestrial and marine climate of this region for the last 140 ka the last interglacial climate of the southern half of japan was characterized by increased temperature and precipitation at least across central japan compared with today off southern japan surface were cooler during summer than at present off central japan both summer and winter sea surface temperatures were cooler than today early glacial 115 71 ka bp climate across central and southern japan alternated between wet and dry warm temperate with surface waters offshore warmer in summer and winter than during the penultimate interglacial temperatures and precipitation in japan reached low levels early during the full glacial phase and remained relatively low throughout much of the full glacial 71 14 ka bp cold sea surface temperatures at all our sites coincided with these cold conditions on land temperatures across much of japan began to increase steadily during the deglacial with surface waters offshore remaining at or near their glacial lows holocene vegetation patterns which continued to reflect an increase in temperature reached a maximum during early to mid holocene surface waters offshore however remained relatively cool during the early holocene with temperature maxima at most western pacific sites occurring in mid to late holocene we propose specific changes in the seasonal positions of atmospheric pressure cells to explain these climate variations that have occurred across the northeast asian northwest pacific region through the most recent interglacial glacial cycle results of this exercise show that there are no major discrepancies between climate reconstructions for mainland japan inferred from pollen and those for the western pacific derived from radiolarians

sedimentary deposits from the 17 july 2006 western java tsunami indonesia use of grain size analyses to assess tsunami flow depth speed and traction carpet characteristics the 2006 western java tsunami deposited a discontinuous sheet of sand up to 20 cm thick flooded coastal southern java to a depth of at least 8 m and inundated up to 1 km inland in most places the primarily heavy mineral sand sheet is normally graded and in some it contains complex internal stratigraphy structures within the sand sheet probably record the passage of up to two individual waves a point noted in eyewitness accounts we studied the 2006 tsunami deposits in detail along a flow parallel transect about 750 m long 15 km east of cilacap the tsunami deposit first becomes discernable from the underlying sediment 70 m from the shoreline from 75 to 300 m inland the deposit has been laid down in rice paddies and maintains a thickness of 10 20 cm landward of 300 m the deposit thins dramatically reaching 1 mm by 450 m inland from 450 m to the edge of deposition around 700 m inland the deposit remains 1 mm thick deposition generally attended inundation along the transect the tsunami deposited sand to within about 40 m of the inundation limit the thicker part of the deposit contains primarily sand indistinguishable from that found on the beach 3 weeks after the event but after about 450 m and roughly coinciding with the decrease in thickness the tsunami sediment shifts to become more like the underlying paddy soil than the beach sand grain sizes within the deposit tend to fine upward and landward although overall upward fining takes place in two discrete pulses with an initial section of inverse grading followed by a section of normal grading the two inversely graded sections are also density graded with denser grains at the base and less dense grains at the top the two normally graded sections show no trends in density the inversely graded sections show high density sediment to the base and become less dense upward and represents traction carpet flows at the base of the tsunami these are suggestive of high shear rates in the flow because of the grain sorting in the traction carpet the landward fining trends usually seen in tsunami deposits are masked although lateral changes of mean sediment grain size along the transect do show overall landward fining with more variation as the deposit tapers off the deposit is also thicker in the more seaward portions than would be produced by tsunamis lacking traction carpets

the sedimentary record of the post glacial transgression on the gulf of cadiz continental shelf southwest spain abstract four seismic units ta to td have been identified from the analysis and interpretation of high resolution seismic profiles in a sector of the gulf of cadiz shelf they constitute a composite seismic unit attributed to the transgressive systems tract tst of the last depositional sequence the earliest transgressive unit was deposited on the outer shelf and represents the distal facies of a coastal deposit a process of shelf partitioning seems to have occurred during the formation of the three later transgressive parasequences the shelf sector offshore from the guadiana river mouth was a high energy environment dominated by storm events by contrast the shelf sector offshore from the donana national park was a low gradient shelf where large barrier island and lagoon systems were formed the sparse occurrence of marine deposits within the tst is a consequence of the episodic nature of the sea level rise the generation and preservation of these transgressive deposits results from the interaction of the following controlling processes 1 relative sea level rise the formation of coastal transgressive deposits is related to intervals of reduced sea level rise or stillstands within a period of continuous sea level rise those sea level changes were probably driven by short term periods of colder climate during the late pleistocene holocene deglaciation the younger dryas interval is the most widely recognised climatic event of this type but probably other events of similar characteristics had the same effect on the glacio eustatic sea level rise 2 sediment supply changes short lived climatic events probably also involved changes in the sediment supply to the continental shelf due to changes in erosion rates and river regimes of the river basin hinterlands 3 effect of the paleophysiography paleogeography the sedimentary environments differentiation processes are associated to the formation of an exposed coastal promontory offshore from the guadiana river mouth and a semi protected embayment offshore from donana national park this coastal configuration was controlled by previous tectonic evolution and influenced the non uniform landward migration of the coastline

historical tsunamis and present tsunami hazard in eastern indonesia and the southern philippines 1 eastern indonesia and the southern philippines comprise a huge and seismically highly active region that has received less than the deserved attention in tsunami research compared with the surrounding areas exposed to the major subduction zones in an effort to redress the balance the tsunami hazard in this region is studied by establishing a tsunami event database which in combination with seismological and tectonic information from the region has allowed us to define and justify a number of credible worst case tsunami scenarios these scenarios have been used in numerical simulations of tsunami generation and propagation to study maximum water level along potentially affected shorelines the scenarios have in turn been combined to provide regional tsunami hazard maps in many cases the simulations indicate that the maximum water level may exceed 10 m locally and even reach above 20 m in the vicinity of the source which is of the same order as what is forecasted along the sumatra and java trenches for comparable return periods for sections of coastlines close to a source a tsunami may strike only a few minutes after it is generated providing little time for warning moreover several of the affected areas are highly populated and are therefore also high risk areas the combination of high maximum water levels short warning times dense populations and relatively short return periods suggests strongly that the tsunami hazard and risk in these regions are alarmingly high

tsunami earthquakes as transient phenomena 1 recent modeling of tsunami waveforms caused by tsunami earthquakes indicates that fault slip occurred along the subduction boundary close to the trench axis on the other hand it is well known that seismicity is generally very low within ca 50 km from the trench axis and this has been attributed to the stable frictional sliding properties of the subducted unconsolidated sediments this makes tsunamigenic slip near the trench difficult to explain in order to solve this dilemma i propose that transition from stable sliding to nearly zero friction with a velocity weakening property occurs as a result of areal increase of zones of elevated fluid pressure which may make fairly rapid seismic slip possible following the breakage of asperities at normal seismogenic depths this transition can be identified as seismic reflections with negative polarities which may help to rate hazards for a coming large tsunami earthquake

rupture characterization and aftershock relocations for the 1994 and 2006 tsunami earthquakes in the java subduction zone 1 two tsunami earthquakes occurred in the java subduction zone within the last 12 years providing multiple well recorded tsunami events for analysis the june 2 1994 mw 7 8 and july 17 2006 mw 7 7 reverse mechanism earthquakes produced tsunami with locally large 8 m runups were deficient in high frequency energy relative to long period radiation had primarily normal faulting aftershocks and occurred near subducting seamounts previous models of the 1994 event and aftershocks suggested extension in the outer rise due to slip at depth at a subducted seamount here we relocate aftershocks for the 1994 and 2006 events and compare to slip distributions and bathymetry most 1994 aftershocks occurred within the slab updip of the mainshock consistent with the extensional hypothesis but the 2006 aftershocks have a more complex pattern regional subducting features as asperities and barriers may influence both events but in different ways