geochemical cycling of redox sensitive metals in sediments from lake malawi a diagnostic paleotracer for episodic changes in mixing depth changes in heat balance wind stress and lake level can affect the efficiency of mixing and depth of oxygen penetration in deep tropical lakes this study examines how transient changes in these parameters as reflected by the redox state of bottom waters are recorded in the sedimentary record of lake malawi we measured concentration profiles of redox sensitive metals across a layer of oxidized sediment deposited within a sequence composed of reduced sediments in a core taken at 298 m water depth 100 m below the present day chemocline by examining a range of metals that exhibit different geochemical behaviors mobilization under reducing fe mn versus oxidizing u conditions formation of insoluble sulfides cd mo pb zn susceptibility to scavenging onto fe or mn oxyhydroxide precipitates co mo pb v zn we are able to outline a sequence of events consistent with the formation of this feature 1 at some time before 11 ky bp there was an episode of penetration of oxygenated waters to depths close to or greater than that of this core i e substantially deeper in the lake basin than at present at this time diagenetically remobilized fe and mn were oxidized and precipitated in a near surface sediment horizon 2 fe and mn oxyhydroxides that precipitated from the water column as metal rich anoxic waters were mixed upward into oxygenated waters were deposited in an immediately overlying layer of the sediment such material continued to accumulate in surface sediments for a few hundred years until oxic conditions no longer prevailed in overlying waters 3 as the depth of the chemocline rose relative to the present day lake surface this authigenic material was in turn overlain by reducing sediments 4 subsequent diagenetic remobilization at the top and bottom of this redox sandwich resulted in formation of horizons enriched in u mo and sulfide forming metals notably cd along the redox gradients both above and to a lesser extent below the layer of oxidized sediment these enrichments immobilized under reducing conditions will remain as permanent markers of the episode of deepening of the chemocline even after reduction and remobilization of the oxidized fe and mn solids in addition such markers may be useful in determining whether observed episodic interruptions in deposition of varved sediments in the deep anoxic basins of lake malawi are due to bioturbation brought on by episodes of deeper oxygen penetration in the water column

space geodetic tools provide early warnings for earthquakes and volcanic eruptions development of space geodetic techniques such as global navigation satellite system and synthetic aperture radar in last few decades allows us to monitor deformation of earth s surface in unprecedented spatial and temporal resolution these observations combined with fast data transmission and quick data processing enable us to quickly detect and locate earthquakes and volcanic eruptions and assess potential hazards such as strong earthquake shaking tsunamis and volcanic eruptions these techniques thus are key parts of early warning systems help identify some hazards before a cataclysmic event and improve the response to the consequent damage

tsunami simulation method assimilating ocean bottom pressure data near a tsunami source region a new method was developed to reproduce the tsunami height distribution in and around the source area at a certain time from a large number of ocean bottom pressure sensors without information on an earthquake source a dense cabled observation network called s net which consists of 150 ocean bottom pressure sensors was installed recently along a wide portion of the seafloor off kanto tohoku and hokkaido in japan however in the source area the ocean bottom pressure sensors cannot observe directly an initial ocean surface displacement therefore we developed the new method the method was tested and functioned well for a synthetic tsunami from a simple rectangular fault with an ocean bottom pressure sensor network using 10 arc min or 20 km intervals for a test case that is more realistic ocean bottom pressure sensors with 15 arc min intervals along the north south direction and sensors with 30 arc min intervals along the east west direction were used in the test case the method also functioned well enough to reproduce the tsunami height field in general these results indicated that the method could be used for tsunami early warning by estimating the tsunami height field just after a great earthquake without the need for earthquake source information

quasi real time fault model estimation for near field tsunami forecasting based on rtk gps analysis application to the 2011 tohoku oki earthquake mw 9 0 1 real time crustal deformation monitoring is extremely important for achieving rapid understanding of actual earthquake scales because the measured permanent displacement directly gives the true earthquake size seismic moment mw information which in turn provides tsunami forecasting we have developed an algorithm to detect estimate static ground displacements due to earthquake faulting from real time kinematic gps rtk gps time series the new algorithm identifies permanent displacements by monitoring the difference of a short term average sta to a long term average lta of the gps time series we assessed the noise property and precision of the rtk gps time series with various baseline length conditions and orbits and discerned that the real time ephemerides based on the international gnss service igs are sufficient for crustal deformation monitoring with long baselines up to 1 000 km we applied the algorithm to data obtained in the 2011 off the pacific coast of tohoku earthquake mw 9 0 to test the possibility of coseismic displacement detections and further we inverted the obtained displacement fields for a fault model the inversion estimated a fault model with mw 8 7 which is close to the actual mw of 9 0 within five minutes from the origin time once the fault model is estimated tsunami waveforms can be immediately synthesized using pre computed tsunami green s functions the calculated waveforms showed good agreement with the actual tsunami observations both in arrival times and wave heights suggesting that the rtk gps data by our algorithm can provide reliable rapid tsunami forecasting that can complement existing tsunami forecasting systems based on seismic observations

distribution of stable isotopes in surface snow along the route of the 1990 international trans antarctica expedition this paper presents the distri bution of average od and 6180 values for the top i m of surface snow for a large area of antarctica the samples were collected on the 1990 internatio nal trans antarctica expedition which crossed the continent from the northern tip of the antarctic penins ula to mirny station the empirical rel ationships between the isotopes temperature and elevation are computed the slopes of od with respect to the surface temperature for the segments west patriot hills v ostok and east ofvostok komso molskaya mirny are not signifi cantly different to that obse rved between dumont d urville and dome c lorius and merlivat 1977 which are often used to inte rpret deep ice core isotopic profiles there is however a noti ceable shift between the two regression lines

seasonal and spatial variations of 17oexcess and dexcess in antarctic precipitation insights from an intermediate complexity isotope model an intermediate complexity isotope model icm is used to investigate the sensitivity of water isotope ratios in precipitation including 17oexcess to climate variations in the southern hemisphere the icm is forced with boundary conditions from seasonal ncep doe ii reanalysis data perturbations to the surface temperature and humidity fields are used to investigate the isotopic sensitivity the response of 17oexcess to a uniform temperature change is insignificant over the ocean while there is a large magnitude response over the ice sheet particularly in east antarctica a decrease of ocean surface relative humidity produces increased 17oexcess and dexcess with a coherent response over both the ocean and antarctica for interior east antarctica the model simulates a seasonal cycle in 17oexcess that is positively correlated with 18o and of large magnitude 50 per meg consistent with the observations from vostok the seasonal cycle in 17oexcess for interior west antarctica is predicted to be considerably smaller in magnitude 12 per meg and is negatively correlated with 18o consistent with new data from a firn core near the west antarctic ice sheet divide site over the ocean the icm predicts much smaller seasonal cycles in 17oexcess oceanic source changes i e humidity are insufficient to explain the amplitude of the simulated seasonal cycle over the antarctic continent spatial differences in the seasonal response of 17oexcess to local temperature reflect the balance of equilibrium and kinetic fractionation during snow formation

common millennial scale variability of antarctic and southern ocean temperatures during the past 5000 years reconstructed from the epica dome c ice core measurements of the two water stable isotopes dd and d18o along epica european project for ice coring in antarctica dome c ice core are combined with simple isotopic modelling distillation models to reconstruct the variability of both the site temperature east antarctica and the moisture source temperature nowadays probably the subantarctic indian ocean we discuss the difference between the reconstructed site and source temperature pro les with respect to the initial isotopic data we show that i the early holocene optimum appears rst in antarctica and 800 years later in the southern ocean and ii during the last 5000 years the site and source temperatures co vary at the centennial timescale an 833 year periodicity is observed only on deuterium and site temperature and therefore probably of local origin

oxygen isotope and total beta radioactivity measurements on 10 m ice cores from the antarctic peninsula as part of the glaciology of the antarctic peninsula gap programme the snow cover at 25 stations was sampled to 10 m depth for oxygen isotope and total radioactivity analysis the mean annual oxygen isotope ratio correlates satisfactorily with 10 m temperature despite the complex topography of the area and suggests on average that climatic trends in the region are fairly systematic the relationship with temperature is similar to that derived from a simple model in which an air mass initially of maritime subtropical characteristics is progressively cooled as it moves towards the region the detailed isotope profiles show that for future deep drilling the most easily interpretable climatic information will be found in the more continental areas on the cast coast and on the plateau in the south of the region the degree of continentality of particular sites is reflected in the amplitude of the annual wave in the upper portion of the isotope ratio profile as well as in the accumulation rate

a new greenland deep ice core the polar ice sheets are rich sources of information on past atmospheric conditions including paleoclimates a new deep ice core has been drilled in south greenland comparison of the oxygen isotopic profile with that from camp century and with a deep sea foraminifera record indicates that the new core reaches back to about 90 000 years before present in a continuous sequence the details in the wisconsin part of the ice core records seem to be climatically significant and the general trends reveal all of the relevant emiliani stages recorded in deep sea cores the redated camp century record suggests a dramatic termination of the eem sangamon interglacial

early diagenesis of trace metals cd cu co ni u mo and v in the freshwater reaches of a macrotidal estuary vertical profiles from the water column including the maximum turbidity zone mtz to the consolidated sediment were sampled in september 2000 in the freshwater reaches of the gironde estuary during a complete neap tide spring tide cycle the vertical distributions of dissolved major redox parameters and metals mn fe cd cu v co ni mo and u were determined reactive particulate metal fractions were also determined from selective leaching the studied system is characterized by density layers functioning at different time scales consisting of two mobile layers i e the liquid lm and the soft mud sm overlying consolidated sediments cs this results in a three zone diagenetic regime where 1 o2 dynamics are fast enough to show depletion in the rapidly mixed lm sequence tidal time scale 2 denitrification occurs on the weekly time scale mixing sm sequence and 3 the mn fe and sulfate cycling occurs in the cs layer annual time scale the studied trace metals show differential behavior during early diagenesis 1 cd cu and v are released into pore water preferentially from organic matter in the sm 2 co ni and u are released in the cs from mn and fe oxides during reductive dissolution and 3 mo from both processes transient conditions i e oscillations of redox fronts and reoxidation processes due to the dynamics of the mobile layers strongly influence the trace metal distributions as inducing resolubilization cd cu and mo in the cs authigenic metal phases accumulate either by direct precipitation with sulfides cu cd or co precipitation with fe sulfides mo microbially mediated reduction of fe oxides is proposed to control u removal from pore water by reduction of u vi to u iv at depth however a significant fraction of the trace metals is trapped in the sediment in exchangeable forms and therefore is susceptible to be mobilized due to resuspension of estuarine sediment during strong river flood periods and or dredging activities

stable isotope air temperature relationships in ice cores from dolleman island and the palmer land plateau antarctic peninsula whilst stable isotope analysis of ice cores yields the best quantitative evidence for past climate there remains considerable uncertainty about the detailed relationship between the isotopic composition and air temperature analysis of two ice cores from the antarctic peninsula a 47 2 m core from the palmer land plateau 74 oi s 70 38 w and a 32 m core from dolleman island 70035 2 s 60055 5 w has shown that an oxygen isotope temperature relationship exists at a resolution of inter annual variations during the period 1938 86 all the major regional temperature anomalies known from climatic records at several stations are visible in the isotope profiles including the overall temperature increase between 1960 and 1980 an isotope temperature gradient of 0 5 o 6 c is indicated for the climatic interpretation of isotopic fluctu

near field tsunami models with rapid earthquake source inversions from land and ocean based observations the potential for forecast and warning computation of tsunami models in the region adjacent to large earthquakes immediately after rupture initiation remains a challenging problem limitations of traditional seismological instrumentation in the near field and concern by tsunami modelers regarding the nonuniqueness of source inversions and the use of indirect observations have in the past been hurdles for such efforts employing near field data from the mw 9 0 2011 tohoku oki data we test source models obtained from newly developed algorithms and multisensor data we demonstrate the ability of such source models determined from land based coseismic data from the combination of gps and strong motion sensors to forecast near source tsunamis we also demonstrate that rapid ingestion of offshore shallow water 100 1000 m wave gauge data substantially improves the earthquake source and tsunami forecast to assess the success of such tsunami models we rely on detailed comparisons to 2000 tsunami survey measurements collected after the event we argue that deployments of shallow water wave gauges coupled with land based geophysical sensors can in the future provide enough information to issue timely and accurate forecasts of tsunami intensity immediately or shortly after rupture initiation of large earthquakes

a 420 000 year deuterium excess record from east antarctica information on past changes in the origin of precipitation at vostok here we present and analyze the complete vostok ice cores deuterium excess record which spans the last four climatic cycles back to 420 000 years b p to extract paleoclimate information from this record we use isotopic modeling showing that changes in deuterium excess d d 8 18o of vostok precipitation reflect changes in the average temperature of oceanic moisture sources over the last 250 000 years the deuterium excess is strongly anticorrelated with changes in earth s obliquity this reflects changes in the relative contribution of low and high latitudes to the vostok precipitation resulting from changes in the latitudinal annual mean insolation gradient governed by the obliquity however this modulation by obliquity is not observed prior to 250 000 years b p we attribute this difference to the ice flow the deeper ice under vostok station having accumulated in a location upstream vostok receiving precipitation from different oceanic origins despite this difference between the earlier and the later portions of the record the deuterium excess changes during all the glacial inceptions are similar in amplitude and timing relative to the deuterium decrease the glacial inceptions are characterized by high deuterium excess indicating the significant role of the tropics in supplying moisture to the already cold poles

parameterization of the annual surface temperature and mass balance of antarctica this study entails the parameterization by means of a linear multiple regression analysis of the annual surface temperature and mass balance of antarctica the analysis was performed for the entire ice cap as well as for three separate regions ice shelves elevation less than 200 m the interior elevation above 1500 m and the escarpment region in between it was found that temperature can be parameterized very well in terms of elevation and latitude the latitudinal gradient on the ice shelves can be explained by the super adiabatic lapse rate along the surface and latitudinal temperature gradient in the interior assuming adiabatic descent of air in the inversion layer from the interior region towards the coast and an axisymmetric spreading over the ice shelves the surface mass balance can be parameterized reliably only in the interior where it has a strong positive correlation with the saturation vapour pressure of the free atmosphere and a significant correlation with the shape of the dome the convex shape of the dome contributes to the mass balance by inducing subsidence of the relatively moist air of the free atmosphere into the inversion layer this results in precipitation as radiative cooling in the inversion exceeds adiabatic warming an estimate is made of the annual horizontal and vertical advective velocities in the free atmosphere above the interior based on regression results and a physical analysis of the precipitation processes in this region a temperature sensitivity analysis was performed for the current mass balance distribution for a 1 k rise in surface temperature the regression estimate of the increase in accumulation on the grounded ice sheet is equivalent to a rate of sea level lowering of 0 2 mm a 1 this is about 30 less than estimates based on the current mass balance perturbated by the increase in saturation vapour pressure of the free atmosphere

the trace metal content of recent organic carbon rich sediments implications for cretaceous black shale formation organic carbon rich sediments are enriched in several redox sensitive and stable sulfide forming trace metals tm and form an important sink in global tm cycles in today s ocean such sediments are deposited in coastal upwelling areas like those in the gulf of california off peru or off the namibian coast and euxinic basins like the black sea in an attempt to distinguish both environments by their specific tm patterns some important conclusions may be drawn 1 the tm enrichment seen in both environments broadly is rather similar 2 upwelling sediments are often enriched in cd and p and depleted in co and mn 3 sapropels have a tendency towards higher enrichments in ba and mo s re as cu ni sb and fe reflecting the strong sulfidation in an anoxic water column 4 upwelling systems cover a broad range of environmental settings where the steepness of the slope the proximity of h2s to the sediment seawater interface and the intensity of bio accumulation and regeneration play an important role for tm accumulation 5 the tm content of anoxic basins is mainly controlled by tm availability in the water column and sedimentation rate 6 enhanced bio productivity is the main switch turning an oxygenated into an anoxic environment cretaceous black shales oae 2 exhibit tm signatures of both coastal upwelling areas and sapropels the strong enrichments in cd mo tl v cu ni bi and sb demonstrate that bio accumulation and presence of h2s in the water column and associated sulfidation processes persisted during this time interval in large parts of the proto atlantic the usefulness of ba as a paleoproductivity proxy is obscured by diagenesis the extreme accumulation in ag and zn requires either an additional tm source for instance hydrothermal input or a different tm seawater composition during the cretaceous the geochemical data suggest that the major driving force for the widespread occurrence of c t black shales seems to be the increase in volcanic activity and associated co2 input throughout the cretaceous the ocean atmosphere system operated in a mode different from today during this time interval after conversion of the nutrient co2 into organic matter the system switched back into the normal operational mode

linear and nonlinear computations of the 1992 nicaragua earthquake tsunami numerical computations of tsunamis are made for the 1992 nicaragua earthquake using different governing equations bottom frictional values and bathymetry data the results are compared with each other as well as with the observations both tide gauge records and runup heights comparison of the observed and computed tsunami waveforms indicates that the use of detailed bathymetry data with a small grid size is more effective than to include nonlinear terms in tsunami computation linear computation overestimates the amplitude for the later phase than the first arrival particularly when the amplitude becomes large the computed amplitudes along the coast from nonlinear computation are much smaller than the observed tsunami runup heights the average ratio or the amplification factor is estimated to be 3 in the present case when the grid size of 1 minute is used the factor however may depend on the grid size for the computation

enrichment of trace metals in surface sediments from the northern part of point calimere se coast of india this study deals with the geochemical nature of distribution enrichment of total trace metals fe mn cr cu ni co pb zn cd in bulk sediments and its association with sediment texture carbonates and organic carbon sixty surface sediment samples were collected during two different seasons in 2002 and 2003 along the coastal regions in three transects from nagapattinam town north of point calimere in southeast coast of india the sediments are mostly sandy silt and are dominated by the carbonate content organic carbon distribution indicates that they are brought in by the minor river input enrichment of trace metals is clearly identified by the domination of pb zn cd with high values than the average crustal values and comparison of trace metals from other coastal regions in the southeast coast of india statistical analysis clearly indicates that fe and mn control the distribution of trace metals and are concentrated in the finer particles and organic carbon fraction the increase in concentration signifies the need for regular monitoring of the offshore coastal region in southeast coast of india which was recently destroyed by the 2004 december tsunami event and which is also located near the sethu samuthram ship canal project

modeling of the 2011 japan tsunami lessons for near field forecast during the devastating 11 march 2011 japanese tsunami data from two tsunami detectors were used to determine the tsunami source within 1 5 h of earthquake origin time for the first time multiple near field tsunami measurements of the 2011 japanese tsunami were used to demonstrate the accuracy of the national oceanic and atmospheric administration noaa real time flooding forecast system in the far field to test the accuracy of the same forecast system in the near field a total of 11 numerical models with grids telescoped to 2 arcsec 60 m were developed to hindcast the propagation and coastal inundation of the 2011 japanese tsunami along the entire east coastline of japan using the noaa tsunami source computed in near real time the model results of tsunami propagation are validated with tsunami time series measured at different water depths offshore and near shore along japan s coastline the computed tsunami runup height and spatial distribution are highly consistent with post tsunami survey data collected along the japanese coastline the computed inundation penetration also agrees well with survey data giving a modeling accuracy of 85 5 for the inundation areas along 800 km of coastline between ibaraki prefecture north of kashima and aomori prefecture south of rokkasho the inundation model results highlighted the variability of tsunami impact in response to different offshore bathymetry and flooded terrain comparison of tsunami sources inferred from different indirect methods shows the crucial importance of deep ocean tsunami measurements for real time tsunami forecasts the agreement between model results and observations along japan s coastline demonstrate the ability and potential of noaa s methodology for real time near field tsunami flooding forecasts an accurate tsunami flooding forecast within 30 min may now be possible using the noaa forecast methodology with carefully placed tsunameters and large scale high resolution inundation models with powerful computing capabilities

tsunami magnitudes determined from ocean bottom pressure gauge data around japan 1 we develop a method to calculate tsunami magnitude from ocean bottom pressure gauge data around japan direct application of abe s equations to ocean bottom pressure gauge data underestimates tsunami magnitudes by about an order of magnitude this is because abe s equations were derived only from tsunami amplitudes measured at coastal tide gauges where tsunamis are amplified by the shoaling of waves and reflection at the coastline for offshore bottom pressure records we introduce correction factors to abe s original equations to account for tsunami amplitudes measured in open oceans the modified equations produce pressure gauge determined tsunami magnitudes close to those determined using coastal tide gauges

tsunami early warning using gps shield arrays 1 the 2004 catastrophic indian ocean tsunami has strongly emphasized the need for reliable tsunami early warning systems another giant tsunamigenic earthquake may occur west of sumatra close to the large city of padang we demonstrate that the presence of islands between the trench and the sumatran coast makes earthquake induced tsunamis especially sensitive to slip distribution on the rupture plane as wave heights at padang may differ by more than a factor of 5 for earthquakes having the same seismic moment magnitude and rupture zone geometry but different slip distribution hence reliable prediction of tsunami wave heights for padang cannot be provided using traditional earthquake magnitude based methods we show however that such a prediction can be issued within 10 minutes of an earthquake by incorporating special types of near field gps arrays gps shield these arrays measure both vertical and horizontal displacements and can resolve higher order features of the slip distribution on the fault than the seismic moment if placed above the rupture zone or are less than 100 km away of the rupture zone stations in the arrays are located as close as possible to the trench and are aligned perpendicular to the trench i e parallel to the expected gradient of surface coseismic displacement in the case of sumatra and java the gps shield arrays should be placed at mentawai islands located between the trench and sumatra and directly at the sumatra and java western coasts we demonstrate that the gps shield can also be applied to northern chile where giant earthquakes may also occur in the near future moreover this concept may be applied globally to many other tsunamigenic active margins where the land is located above or close to seismogenic zones

local tsunami warnings perspectives from recent large events we demonstrate a flexible strategy for local tsunami warning that relies on regional geodetic and seismic stations through retrospective analysis of four recent tsunamigenic events in japan and chile we show that rapid earthquake source information provided by methodologies developed for earthquake early warning can be used to generate timely estimates of maximum expected tsunami amplitude with enough accuracy for tsunami warning we validate the technique by comparing to detailed models of earthquake source and tsunami propagation as well as field surveys of tsunami inundation our approach does not require deployment of new geodetic and seismic instrumentation in many subduction zones and could be implemented rapidly by national monitoring and warning agencies we illustrate the potential impact of our method with a detailed comparison to the actual timeline of events during the recent 2015 mw8 3 illapel chile earthquake and tsunami that prompted the evacuation of 1 million people

cool tropical temperatures shift the global δ18o t relationship an explanation for the ice core δ18o borehole thermometry conflict the discrepancy between central greenland borehole temperatures and the isotopic composition of last glacial maximum ice can be explained by a shift in the 5180 t relationship for the hydrological cycle linked to cooler tropical temperatures this concept is illustrated using a simple rayleigh distillation model an estimate for o a 5180 at lgm holocene of 0 37 o oc is determined with a simple graphical technique

kinematic earthquake source inversion and tsunami runup prediction with regional geophysical data rapid near source earthquake source modeling relying only on strong motion data is limited by instrumental offsets and magnitude saturation adversely affecting subsequent tsunami prediction seismogeodetic displacement and velocity waveforms estimated from an optimal combination of high rate gps and strong motion data overcome these limitations supplementing land based data with offshore wave measurements by seafloor pressure sensors and gps equipped buoys can further improve the image of the earthquake source and prediction of tsunami extent inundation and runup we present a kinematic source model obtained from a retrospective real time analysis of a heterogeneous data set for the 2011 mw9 0 tohoku oki japan earthquake our model is consistent with conceptual models of subduction zones exhibiting depth dependent behavior that is quantified through frequency domain analysis of slip rate functions the stress drop distribution is found to be significantly more correlated with aftershock locations and mechanism types when off shore data are included the kinematic model parameters are then used as initial conditions in a fully nonlinear tsunami propagation analysis notably we include the horizontal advection of steeply sloping bathymetric features comparison with post event on land survey measurements demonstrates that the tsunami s inundation and runup are predicted with considerable accuracy only limited in scale by the resolution of available topography and bathymetry we conclude that it is possible to produce credible and rapid kinematic source models and tsunami predictions within minutes of earthquake onset time for near source coastal regions most susceptible to loss of life and damage to critical infrastructure regardless of earthquake magnitude

the abrupt termination of the younger dryas climate event previous studies on two deep greenland ice cores have shown that a long series of climate oscillations characterized the late weichselian glaciation in the north atlantic region1 and that the last glacial cold period the younger dryas ended abruptly 10 700 years ago2 here we further focus on this epoch defining event and present detailed heavy isotope and dust concentration profiles which suggest that in less than 20 years the climate in the north atlantic region turned into a milder and less stormy regime as a consequence of a rapid retreat of the sea ice cover a warming of 7 c in south greenland was completed in about 50 years

quantification of source uncertainties in seismic probabilistic tsunami hazard analysis sptha this article has been accepted for publication in geophysical journal internationa 2016 published by oxford university press on behalf of the royal astronomical society all rights reserved

real time centroid moment tensor determination for large earthquakes from local and regional displacement records summary we present an algorithm to rapidly determine the moment tensor and centroid location for large earthquakes employing local and regional real time high rate displacement records from gps the algorithm extracts the coseismic offset from the displacement waveforms and uses the information to invert for the moment tensor the green s functions for a layered earth are obtained numerically from open source code edgrn to determine the centroid multiple inversions are simultaneously performed within a grid of inversion nodes and the node with the smallest misfit is then assigned the centroid location we show results for two large earthquakes replayed in simulated real time mode using recorded 1 hz gps displacements the 2003 mw 8 3 tokachi oki and the 2010 mw 7 2 el mayor cucapah earthquakes we demonstrate that it is feasible to obtain accurate cmt solutions within the first 2 3 min after rupture initiation without any prior assumptions on fault characteristics demonstrating an order of magnitude improvement in latency compared to existing seismic methods for the two earthquakes studied this methodology is useful for rapid earthquake response tsunami prediction and as a starting point for rapid finite fault modelling

near field tsunami forecasting from cabled ocean bottom pressure data 1 we propose a method for near field tsunami forecasting from data acquired by cabled offshore ocean bottom tsunami meters obtms in real time we first invert tsunami waveforms recorded at obtms to estimate the spatial distribution of initial sea surface displacements in the tsunami source region without making any assumptions about fault geometry and earthquake magnitude then we synthesize the coastal tsunami waveforms from the estimated sea surface displacement distribution to improve the reliability of the tsunami forecasting we use updated obtm data to repeat the forecast calculation at 1 min intervals we tested our method by simulating the 1896 sanriku tsunami earthquake which caused a devastating tsunami with maximum runup height of 38 m along the pacific coast of northeastern japan instead of real obtm records proxies were used the simulation demonstrated that our method provided accurate estimations of coastal arrival times and amplitudes of the first peak of the tsunami more than 20 min before the maximum amplitude wave reached the coastal site nearest to the source we also applied the method to real data of a small tsunami that was caused by a local earthquake and successfully forecasted the tsunami at coastal tide stations we found that accuracy of our estimated coastal tsunami amplitudes can be affected by the spatial relationship between the tsunami source and the offshore observation stations our numerical simulation showed that even more accurate tsunami amplitude forecasts would be achieved by deployment of additional offshore stations separated by a distance comparable to the trench parallel length of the tsunami source

new insights into southern hemisphere temperature changes from vostok ice cores using deuterium excess correction abstract the combination of both vostok ice core deuterium and deuterium excess histories over the last four climate cycles back to 420 ka bp offers a unique opportunity for reconstructions of vapor source region and local temperature variations tsource and tsite respectively relative to their modern values our study is based on an inversion of ice isotopic composition using a rayleigh based isotopic model which estimates the dependence of vostok precipitation isotopic composition on different climate controls moisture source temperature local deposition temperature and ocean isotopic composition both reconstructed local and source temperatures show no substantial effects from this correction in the sense that none of the rapid or large variations in raw deuterium and deuterium excess profiles can be entirely attributed to a second order climate control our discussion is focused on moisture source temperature and meridional temperature gradient history tsource tsite first using sea surface temperature time series we confirm that moisture source temperature signal recorded in vostok deuterium excess over the last 150 ka fully reflects the obliquity time varying relative contribution of low and high ocean latitudes to vostok precipitation second comparisons of source to site meridional temperature gradient with the vostok sodium record over 420 ka suggest that moisture transport and sea salt transport to the ice sheet are controlled by processes in different latitudes the sea salt being more of a high latitude signal

space and time variation of δ18o and δd in antarctic precipitation revisited 1 to better understand the variations over time of precipitation water isotopes measured in polar ice cores we have developed an intermediate complexity model icm of atmospheric water vapor transport and associated isotopic distillation the model builds directly from earlier work by d fisher and m hendricks and is calibrated against the measured modern spatial distribution of d and deuterium excess d model improvements include a correction to the equation governing advective transport which solves a major puzzle arising from the earlier work the new model shows isotopic data to be consistent with dominance of eddy diffusive transport at high latitudes model experiments are used to show that a wide variety of climate changes in subtropical source regions can affect antarctic d and that such d changes are consistently anticorrelated with changes of d magnitudes of d d are 1 to 5 and are much higher at the ice sheet margin than in the interior of the continent changes in the relative dominance of diffusive and advective transport are also shown to cause anticorrelated changes of similar magnitude isotopic sensitivities to temperature change d t are shown to also vary spatially with low values in marginal zones and higher values inland effects of ocean surface relative humidity on antarctic d are shown to be nearly uniform across the continent in contrast to earlier results given by petit et al 1991 but quantitatively small the method used by vimeux et al 2001 for folding humidity effects into source temperature effects is supported we draw attention to a pervasive misapplication of marine composition corrections to antarctic d records arguments are made in support of simple interpretations of calibrated ice core isotopic time series in terms of temperature changes despite the potential complexities in the system

tfish rapid rapid improvement of near field tsunami forecasting based on offshore tsunami data by incorporating onshore gnss data we have developed a new algorithm that improves near field tsunami forecasting based on offshore tsunami data soon after an earthquake by incorporating real time onshore global navigation satellite system gnss data in our algorithm called tfish rapid tsunami forecasting based on inversion for initial sea surface height real time automatic detection method for permanent displacement the initial sea surface height distribution estimated from rapidly acquired gnss data provides robust finite source size information that is incorporated into an offshore tsunami data inversion for reliable tsunami predictions along the near field coast our algorithm can be applicable to arbitrary types of large tsunamigenic earthquakes when the static displacements are substantial enough to be detected at onshore gnss stations we retrospectively applied our algorithm to the 2011 mw 9 0 tohoku earthquake and demonstrated its ability to provide information about disastrous tsunamis approaching wide areas along the near field coast furthermore arrival times and wave heights of large amplitude short period tsunamis affecting specific near field coasts can be predicted at least 5 min before the actual tsunami arrivals

tsunami source of the 2011 tohoku oki earthquake japan inversion analysis based on dispersive tsunami simulations 1 the large tsunami of the 2011 tohoku oki earthquake was clearly recorded by the ocean bottom pressure and gps wave gauges deployed in and around japan we estimated the initial tsunami water height distribution by inversion analysis of the waveforms based on dispersive tsunami simulations the distribution is characterized by a peak height of 8 m located near the trench and the high water 2m region extending landward with a width of 100 km a series of numerical simulations suggests that a relatively steep peak located near the trench is necessary in order to simultaneously reproduce the dispersive wave at a far field station and the near field waveforms furthermore we estimated the coseismic slip distribution at the plate boundary which indicates that large slip 30 m occurred at a depth of 20 km which corresponds to a large slip deficit area in the interseismic period another slip 25 m occurred at the shallower part 10 km during the rupture

time reversal imaging of the 2015 illapel tsunami source studies of the 2015 illapel earthquake show large variance in the east west location of the principal slip and it is also controversial if there is significant slip near the trench in this study we derive the initial water elevation from tsunami waves based on the time reversal imaging technique this approach does not make assumptions on the fault geometry required by finite fault inversions we adopt 4 out of total 24 stations based on their azimuthal coverage in the time reversal analysis additionally we introduce a correction that scales the wave amplitude at each station by the epicentral distance to account for the 2 d spreading effects the results show a focused region of water elevation with a maximum height of 2 0 m located approximately 30 km from the trench by comparison to the initial deformation predicted by several finite fault models our results indicate minimum slip distribution near the trench

organic matter degradation in sediments of the york river estuary effects of biological vs physical mixing abstract we investigated the influence of biological and physical seabed disturbance on the degradation of bulk organic matter and source specific lipid biomarker compounds by measuring downcore changes in bulk elemental composition bulk stable isotopic 13c and 15n signatures and lipid biomarker compounds in sediment cores collected from two sites in the york river a subestuary of the chesapeake bay usa one site ly is influenced by biological mixing bioturbation restricted to the upper 15 20 cm while the other site pod experiences intense episodic physical mixing events that penetrate 50 100 cm into the sediment we utilized a suite of auxiliary measurements to constrain the sources of organic matter depositional environments and general ages of the cores diagenetic modeling of total organic carbon and total nitrogen in sediments yielded higher apparent rate constants for pod than ly suggesting that the physical mixing regime promotes enhanced degradation of bulk organic matter apparent rate constants for select lipids representing distinct sources of organic matter were also higher at pod than ly for all but the most labile i e diatom derived fatty acids biomarkers differences in stanol stenol ratios also supported enhanced diagenesis of stenols at pod the source specific biomarkers while useful in qualitatively identifying the sources of sedimentary organic matter likely do not represent the full spectrum of its reactivity however based on our results we hypothesize that the intense sediment disturbance at pod promotes degradation of more recalcitrant organic material due to prolonged exposure to oxygen and other electron acceptors e g no3 mn and fe oxides in contrast the degradation of more labile constituents is equally facilitated by biological and physical disturbance

methodology for use of isotopic climate forcings in ice sheet models in ice sheet models an internally consistent calculation of climatic temperature forcing from ice core isotopic records requires that corrections be made for an ice core site s elevation changes such corrections can be important for two reasons first elevation change at an ice divide can be large compared to elevation change at the migrating ice margin resulting in erroneous estimates of marginal melt rate second the of precipitation at an ice divide responds less to regional climatic temperature changes than to local temperature changes of the same magnitude that are caused by elevation changes significant elevation change corrections may also be necessary for inferring the relationships used to calculate climatic temperature from a simple methodology incorporating both of these elevational effects is presented here further i recommend that the to temperature conversion relations used in ice sheet models should derive from independently reconstructed temperature and time series rather than from spatial correlations and justify this recommendation based on current understanding of the atmospheric isotopic distillation system

tsunami waveform inversion incorporating permanent seafloor deformation and its application to tsunami forecasting 1 we propose a method of tsunami waveform inversion to accurately estimate a tsunami source by incorporating the effect of permanent seafloor deformation recorded by ocean bottom pressure gauges obpgs within the source region we developed a general expression of water depth fluctuation recorded at an obpg following seafloor deformation of arbitrary spatiotemporal distribution by assuming that coseismic rupture propagates with infinite velocity the general expression can be reduced to an equation relating observed obpg waveforms to initial sea surface displacement at the source by using a green s function consisting of two terms the green s function used in regular tsunami inversion and a correction term to account for water depth change in response to permanent seafloor deformation by using the two term green s functions the effect of seafloor deformation can be taken into account in tsunami source estimation we applied the revised inversion method to observations of coseismic seafloor deformation and tsunami during the 2003 tokachi oki earthquake mw 8 3 at two obpg stations near the kuril trench the tsunami source model we estimated is consistent with models previously derived using various other geophysical data sets furthermore the coastal tsunami waveforms we modeled match the observed tsunami well forecasts of tsunami arrival times and first peak amplitudes by our method can be obtained 20 min after an earthquake and can be provided to the coastal communities nearest to the source with a lead time of 10 min

regard a new gnss based real time finite fault modeling system for geonet the short period seismometer based magnitude saturation problem especially for events with magnitude 8 can be improved by a real time global navigation satellite system gnss positioning technique which has enabled rapid estimation of a finite fault model for a large earthquake without any saturation a new real time fault modeling system based on the gnss earth observation network geonet is developed and is under experimental operation in japan in this paper we present the newly developed system regard the real time geonet analysis system for rapid deformation monitoring which consists of real time gnss positioning automatic detection of coseismic displacement by the event and quasi real time finite fault model inversion routines the performance of the automatic event detection system is tested through experimental real time operation based on geonet data for two months furthermore we also test the reliability of the finite fault model inversion routines using real raw gnss data observed for past large earthquakes the 2003 tokachi oki earthquake moment magnitude mw 8 3 the 2011 tohoku earthquake mw 9 0 and the 2011 off ibaraki earthquake mw 7 7 a simulated 1707 hoei type nankai trough earthquake mw 8 7 is also tested the real time experimental operation shows that real time gnss positioning is precise enough to detect all the tested earthquakes and the inversion results demonstrate that the regard can reliably estimate the earthquake size and its extent within 3 min after the origin time these results suggest that the regard system will complement the seismometer based magnitude determination system

vostok ice core a continuous isotope temperature record over the last climatic cycle 160 000 years a continuous deuterium profile along the 160 000 year vostok ice core antarctica is interpreted in terms of atmospheric temperature changes this climatic record is the awaited terrestrial complement of the deep sea records supporting the existence of a relation between the pleistocene climate and orbital forcing

deuterium excess in an east antarctic ice core suggests higher relative humidity at the oceanic surface during the last glacial maximum a continuous deuterium excess profile d d 8 18o was obtained from the dome c ice core spanning 32 000 yr it exhibits significant variations over this period in particular d was 4 5 lower around 18 000 yr bp than over the past 7 500 yr interpreted as reflecting higher relative humidity estimated 90 over the oceanic areas providing moisture for antarctic precipitation

a 3 d model for the antarctic ice sheet a sensitivity study on the glacial interglacial contrast on the longer climatic time scales changes in the elevation and extent of the antarctic ice sheet have an important role in modulating global atmospheric and oceanographic processes and contribute significantly to world wide sea levels in this paper a 3 d time dependent thermomechanical model for the entire ice sheet is presented that is subsequently used to examine the effects of glacial interglacial shifts in environmental boundary conditions on its geometry the model takes into account a coupled ice shelf grounding line dynamics basal sliding and isostatic bed adjustment and considers the fully coupled velocity and temperature fields ice flow is calculated on a fine mesh 40 km horizontal grid size and 10 layers in the vertical for grounded and floating ice and a stress transition zone in between at the grounding line where all stress components contribute in the effective stress in the flow law there is free interaction between ice sheet and ice shelf so that the entire geometry is internally generated a simulation of the present ice sheet reveals that the model is able to yield realistic results a series of sensitivity experiments are then performed in which lower temperatures reduced accumulation rates and lower global sea level stands are imposed either singly or in combination by comparing results of pairs of experiments the effects of each of these environmental changes can be determined in agreement with glacial geological evidence we found that the most pronounced changes show up in the west antarctic ice sheet configuration they appear to be essentially controlled by variations in eustatic sea level whereas typical glacial interglacial changes in temperature and ice deposition rates tend to balance one another these findings support the hypothesis that the antarctic ice sheet basically follows glacial episodes in the northern hemisphere by means of sea level teleconnections grounding occurs more readily in the weddell sea than in the ross sea and long time scales appear to be involved it may take up to 30 40000 years for these continental shelf areas to become completely grounded after an initial stepwise perturbation in boundary conditions according to these reconstructions a steady state antarctic ice sheet may contribute some 16 m to global sea level lowering at maximum glaciation

rapid modeling of the 2011 mw 9 0 tohoku oki earthquake with seismogeodesy 1 rapid characterization of finite fault geometry and slip for large earthquakes is important for mitigation of seismic and tsunamigenic hazards saturation of near source weak motion and problematic integration of strong motion data into displacements make this difficult in real time combining gps and accelerometer data to estimate seismogeodetic displacement waveforms overcomes these limitations by providing mm level three dimensional accuracy and improved estimation of coseismic deformation compared to gps only methods we leverage collocated gps and accelerometer data from the 2011 mw 9 0 tohoku oki japan earthquake by replaying them in simulated real time mode using a novel approach to account for fault finiteness we generate an accurate centroid moment tensor solution independently of any constraint on the slab geometry followed by a finite fault slip model the replay of gps and seismic data demonstrates that robust models could have been made available within 3 min of earthquake initiation

glacial interglacial changes in ocean surface conditions in the southern hemisphere the stable isotope signatures of oxygen and hydrogen in the water of preserved ice and snow are both widely used to infer local temperatures of past environments a derived quantity based on these two signatures the deuterium excess 1 provides additional palaeoclimatic information2 3 4 as this parameter depends on the meteorological and oceanic characteristics of the water s source regions in particular their temperature2 3 and relative humidity4 published studies mainly focus on records from the past 40 000 years here we present a deuterium excess history obtained from ice cores from vostok east antarctica spanning the full glacial interglacial cycle of the past 150 000 years the deuterium excess record shows a strong anticorrelation with the earth s orbital obliquity 41 000 year periodicity and values are markedly higher during the cold stage 5d following the last interglacial than during the other cold stages we interpret the relationship with obliquity as resulting from changes in the latitudinal insolation gradient affecting ocean surface conditions and thus the delivery of moisture to the polar region we argue that the high 5d values relative to other cold stages are driven by relatively less moisture delivered from high latitudes and more from low latitudes the deuterium excess in antarctic precipitation thus provides long term spatially integrated information on ocean surface conditions and ocean atmosphere circulations in the southern hemisphere

a global oxygen isotope model semi empirical zonally averaged a simple model which is zonally averaged for the transport of atmospheric water vapour is presented which uses as input the zonally averaged evaporation field and the mean meridional travel distance of tropospheric water vapour as functions of latitude the model demonstrates that for polar regions each of the 10 latitude strips poleward of 25 is of equal importance as a moisture source the model is used to predict zonal averages of 6 1s 0 for the present day and 18 ka bp both annual average values and seasonal amplitudes are presented and compared to observations sea ice cover is an important factor in determining both annual averages and seasonal amplitudes today and at 18 ka bp an earlier model jouzel and others 1983 linking 6eso the deuterium excess and sea salt content in an antarctic ice core to the relative humidity of the source region is based on a single source atmospheric water vapour cycle type model and is re ev aluated using the present model

heavy metals in the ganga hooghly river estuary sediment column evaluation of association geochemical cycling and anthropogenic enrichment in this study the distribution of heavy metals co cr cu ni zn and pb in a sediment core from the ganga hooghly river estuary has been investigated the data on concentrations of heavy metals together with the concentrations of al fe mn carbonate organic carbon corg and nitrogen norg have been used to understand 1 the phase association of metals 2 their geochemical cycling in the sediment column and 3 if metals are enriched by anthropogenic contributions the metals show significant positive correlations with fe and mn indicating that fe mn oxyhydroxide phases are the major host of metals in the sediment core this observation together with significant negative correlations of fe mn and the heavy metals with c n org provides the evidence for diagenetic redistribution of metals in the sediment column and their partitioning into the fe mn oxyhydroxides the increasing upward exchangeable mn concentrations and association of metals with fe and or mn in the exchangeable phases provide the supporting evidence for digenetic remobilization of the metals and their cycling with the fe mn oxyhydroxides down core variations of the metal concentrations generally match with that of mn and fe the results of calculations for enrichment factors ef show that ef 1 5 for pb in the sediment core suggestive of non crustal sources the elevated concentrations of pb with ef 1 5 in the sediment samples of the effluent water that drain into the estuary suggest that industries are an important source of pb to the hooghly river estuary sediments the results and observations of this study suggest that an assessment of temporal variation of metal pollution in estuaries will require understanding of phase association and cycling of metals in the sediment column

sea ice control of water isotope transport to antarctica and implications for ice core interpretation 1 sea ice in the southern ocean is important for antarctic climate and hydrology the dependence of water isotope abundance 18o and deuterium excess on the winter sea ice state is examined with the isotopic version of the melbourne university general circulation model reductions in the ice concentration provide warmer temperatures in winter and allow higher precipitation totals further south while the reverse occurs with increased ice extent the model shows clear demarcation between the changes in the isotopic conditions over the sea ice pack where local changes in surface exchange dominate and those of the continent interior which depend on the long ranged transport aloft while less sensitive to the forcing the interior response is influenced by changes in turbulent mixing over the ice pack and modification of the vertical transport associated with diabatic heating the interior deuterium excess response is more strongly affected by sea ice as it captures changes in temperature over the ice rather than just the final vapor mass traditional reconstruction of temperature from a single isotopic nuclide would give erroneous interpretation of change in the global mean temperature unless the sea ice changes in parallel instead the spatial structure of the sea ice response gives some hope for extracting past sea ice conditions from multicore analysis this study begins to explore the role of entropy production during transport such that the isotopic interpretation is more closely tied to the dynamics of the atmosphere than is expressed by idealized parcel analysis

rapid determination of earthquake magnitude using gps for tsunami warning systems 1 the 26 december 2004 sumatra earthquake mw 9 2 9 3 generated the most deadly tsunami in history yet within the first hour the true danger of a major oceanwide tsunami was not indicated by seismic magnitude estimates which were far too low mw 8 0 8 5 this problem relates to the inherent saturation of early seismic wave methods here we show that the earthquake s true size and tsunami potential can be determined using global positioning system gps data up to only 15 min after earthquake initiation by tracking the mean displacement of the earth s surface associated with the arrival of seismic waves within minutes displacements of 10 mm are detectable as far away as india consistent with results using weeks of data after the event these displacements imply mw 9 0 0 1 indicating a high tsunami potential this suggests existing gps infrastructure could be developed into an effective component of tsunami warning systems

near field tsunami inundation forecast using the parallel tunami n2 model application to the 2011 tohoku oki earthquake combined with source inversions to contribute to tsunami early warning systems we investigated the currently achievable speed of tsunami inundation simulations on a parallel computer as well as the benefits of high resolution and faster than real time inundation predictions we found that a 5 m resolution inundation simulation can be 75 times faster than real time requiring only 1 5 min to overview the inundation situation in sendai city for the 2011 tohoku tsunami we developed a novel parallel tsunami model based on the well known tunami n2 model and achieved 9 17 tera floating point operations per second flops on 9469 cpu cores the present model can accurately hindcast the observed inundated regions of the 2011 tohoku tsunami using tsunami source estimations of the tfish and tfish rapid algorithms which can be instantly derived from real time observation data the present high resolution predictions can provide clear images of imminent hazards disasters and can provide guidance for appropriate evacuation actions

preservation of organic matter and alteration of its carbon and nitrogen isotope composition during simulated and in situ early sedimentary diagenesis abstract the carbon and nitrogen isotope composition of organic matter has been widely used to trace biogeochemical processes in marine and lacustrine environments in order to reconstruct past environmental changes from sedimentary organic matter it is crucial to consider potential alteration of the primary isotopic signal by bacterial degradation in the water column and during early diagenesis in the sediments in a series of oxic and anoxic incubation experiments we examined the fate of organic matter and the alteration of its carbon and nitrogen isotopic composition during microbial degradation the decomposition rates determined with a double exponential decay model show that the more reactive fraction of organic matter degrades at similar rates under oxic and anoxic conditions however under oxic conditions the proportion of organic matter resistent to degradation is much lower than under anoxic conditions within three months of incubation the 13c of bulk organic matter decreased by 1 6 with respect to the initial value the depletion can be attributed to the selective preservation of 13c depleted organic compounds during anoxic decay the 15n values continuously decreased to about 3 below the initial value the decrease probably results from bacterial growth adding 15n depleted biomass to the residual material in the oxic experiment 15n values increased by more then 3 before decreasing to a value indistinguishable from the initial isotopic composition the dissimilarity between oxic and anoxic conditions may be attributed to differences in the type timing and degree of microbial activity and preferential degradation in agreement with the anoxic incubation experiments sediments from eutrophic lake lugano are on average depleted in 13c 1 5 and 15n 1 2 with respect to sinking particulate organic matter collected during a long term sediment trap study

a 150 000 year climatic record from antarctic ice during much of the quaternary the earth s climate has undergone drastic changes most notably successive glacial and interglacial episodes the past 150 kyr includes such a climatic cycle the last interglacial the last glacial and the present holocene interglacial a new climatic time series for this period has been obtained using 18 o data from an antarctic ice core