extracting time domain green s function estimates from ambient seismic noise 1 it has been demonstrated experimentally and theoretically that an estimate of the green s function between two seismic stations can be obtained from the time derivative of the long time average cross correlation of ambient noise between these two stations this tdgf estimate from just the noise field includes all tensor components of the green s function and these green s function estimates can be used to infer earth structure we have computed cross correlations using 1 to 30 continuous days of ambient noise recorded by over 150 broadband seismic stations located in southern california the data processing yielded thousands of cross correlation pairs for receiver separations from 4 500 km which clearly exhibit coherent broadband propagating dispersive wavetrains across frequency band 0 1 2 hz

tropical sea surface temperature reconstruction for the early paleogene using mg ca ratios of planktonic foraminifera 1 to understand the climate dynamics of hypothesized past greenhouse intervals it is essential to constrain tropical sea surface temperatures sst yet existing proxy records give conflicting results here we present the first mg ca based study of pre quaternary sst and investigate early paleogene late paleocene through late middle eocene 58 6 39 8 ma tropical temperatures using planktonic foraminifera belonging to the genus morozovella from ocean drilling program site 865 on allison guyot western central equatorial pacific ocean calcification temperatures similar to or warmer than modern tropical sst are calculated using a range of assumptions regarding diagenesis temperature calibration and seawater mg ca long term warming is observed into the early eocene 54 8 49 0 ma with peak sst between 51 and 48 ma and rapid cooling of 4 c beginning at 48 ma these findings are inconsistent with the 18o based sst previously estimated for this site

surface wave tomography of the western united states from ambient seismic noise rayleigh and love wave phase velocity maps summary we present the results of rayleigh wave and love wave phase velocity tomography in the western united states using ambient seismic noise observed at over 250 broad band stations from the earthscope usarray transportable array and regional networks all available threecomponent time series for the 12 month span between 2005 november 1 and 2006 october 31 have been cross correlated to yield estimated empirical rayleigh and love wave green s functions the love wave signals were observed with higher average signal to noise ratio snr than rayleigh wave signals and hence cannot be fully explained by the scattering of rayleigh waves phase velocity dispersion curves for both rayleigh and love waves between 5 and 40 speriod were measured for each interstation path by applying frequency time analysis the average uncertainty and systematic bias of the measurements are estimated using a method based on analysing thousands of nearly linearly aligned station triplets we find that empirical green s functions can be estimated accurately from the negative time derivative of the symmetric component ambient noise cross correlation without explicit knowledge of the source distribution the average traveltime uncertainty is less than 1 s at periods shorter than 24 s we present rayleigh and love wave phase speed maps at periods of 8 12 16 and 20 s the maps show clear correlations with major geological structures and qualitative agreement with previous results based on rayleigh wave group speeds

barremian danian chemostratigraphic sequences of the cauvery basin india implications on scales of stratigraphic correlation abstract chemostratigraphic concepts postulate that distinct chemozones could be recognized from rock records to help correlate geographically separated strata many studies have upheld this view but were limited to classic boundaries such as cenomanian turonian or cretaceous tertiary only a few elements and isotopic compositions were made use in such studies an attempt to recognize chemozones of barremian danian strata of the cauvery basin south india through whole rock chemistry had revealed many complex signals and depositional events as expressed by bulk geochemical profiles the signals indicate major shift in sedimentation pattern from dynamic depocenter to stable depositional conditions during santonian varying sensitivities of different elements towards prevalent depositional conditions are also inferred trends of geochemical composition indicated domination of single depositional control all through the depositional history basinal configuration that limited terrestrial sediment source and episodic influx of detrital materials presence of distinct change in whole rock geochemistry across geochronological and lithostratigraphic boundaries is deciphered through a statistical tool anova these results demonstrate that visual delineation of chemozones in a long ranging rock record would be tenuous and has to be exercised with caution

abyssal circulation and benthic foraminiferal changes near the paleocene eocene boundary a major change in cenozoic deep sea benthic foraminifera occurred in the atlantic indian and pacific oceans near the paleocene eocene boundary benthic foraminiferal abundance changes began at about 61 5 ma at pacific deep sea drilling project dsdp site 577 a major extinction event followed at 58 57 ma between zones p6a and p6b and a series of first appearances continued until circa 55 5 ma zone p6c these faunal changes occurred during a 6 c warming of pacific bottom water and may indicate that the primary cause was changing temperature other potential causes of the faunal turnover include global changes in surface ocean productivity and changing bottom water source regions comparison of benthic and planktonic 13c records requires no change in the ratio of oceanic phosphorous to carbon during the late paleocene to early eocene which weakens the case for but does not disprove a change in surface ocean productivity at this time interbasinal comparisons of benthic foraminiferal 13c records document that water with high 13c values filled the cape basin during the late paleocene and possibly the early eocene circa 61 57 ma but apparently did not extend into the western basins of the atlantic this pattern suggests a supply of antarctic source water for the cape basin and possible tectonic isolation of the western atlantic basins during at least part of the late paleocene carbon isotope comparisons show that bottom water supply to the cape basin was reduced in the early eocene eolian grain size data suggest that a decrease in zonal wind intensity occurred at the end of the paleocene these late paleocene climatic changes bottom water warming and decreased wind intensity correspond with evidence for an important global tectonic reorganization and extensive subaerial volcanism which may have contributed to climatic warming through increased supply of co2

ground motion prediction of realistic earthquake sources using the ambient seismic field 1 predicting accurate ground motion is critical for earthquake hazard analysis particularly in situations where sedimentary basins trap and amplify seismic waves we exploit the information carried by the ambient seismic field to extract surface wave green s functions between seismic stations and to predict long period ground motion from earthquakes to do so we modify the surface impulse response to correct for the source depth and for the double couple focal mechanism these corrections are derived under the assumption that material properties in the immediate vicinity of the source depend only on depth using this local 1 d assumption we solve the surface wave eigenproblem and compute the fundamental mode displacement eigenfunctions to express the surface wave excitation at the source we validate this technique which we call the virtual earthquake approach by comparing computed seismograms with earthquake waveforms from four moderate earthquakes that occur near broadband stations in southern california the depth and mechanism corrections show clear improvements of the predicted ground motion relative to the surface impulse response

strong shaking in los angeles expected from southern san andreas earthquake 1 the southernmost san andreas fault has a high probability of rupturing in a large greater than magnitude 7 5 earthquake sometime during the next few decades new simulations show that the chain of sedimentary basins between san bernardino and downtown los angeles form an effective waveguide that channels love waves along the southern edge of the san bernardino and san gabriel mountains earthquake scenarios with northward rupture in which the guided wave is efficiently excited produce unusually high long period ground motions over much of the greater los angeles region including intense localized amplitude modulations arising from variations in waveguide cross section

basin scale green s functions from the ambient seismic field recorded by meso net stations seismic waves propagating through the earth can be significantly affected by velocity structures such as sedimentary basins we investigate the propagation characteristics of seismic waves across the kanto basin japan using green s functions extracted from the ambient seismic field we use two stations situated on the eastern and southern edges of the basin as virtual sources and approximately 420 stations which are mainly a part of the metropolitan seismic observation network meso net as receivers using seismometers aligned along two straight lines with the virtual sources we find that several types of waves can be recovered each with different sensitivities to the layers that compose the basin we also show that after amplitude calibration the extracted green s functions can accurately simulate the seismic waves of two moderate mw 4 5 shallow earthquakes that occurred close to the virtual sources furthermore we find that the distribution of the 5 damped pseudovelocity response at a period of 6 s computed from the records of each event and the green s function waveforms have similar amplification patterns this study supports the fact that dense networks recording continuously the ambient seismic field in metropolitan areas can be used to accurately assess seismic hazard at high spatial resolution

bulk calcite size fraction distribution and sr ca composition for deep sea sediments at selected age horizons abstract strontium calcium sr ca ratios in bulk and foraminiferal calcite have been used to constrain the history of sr ca in the oceans and to evaluate calcite diagenetic alteration however bulk sr ca records also may be influenced by differences in sr uptake and or in the diagenetic susceptibility of different calcium carbonate sedimentary components we present data on the sediment size fraction and calcium carbonate distribution in bulk samples sr ca in a range of sedimentary size components and sr ca in bulk sediments ocean drilling program samples from sites on ontong java plateau and ceara rise in the western equatorial pacific and atlantic respectively and from sites in the eastern equatorial pacific were selected to represent progressive stages in the diagenetic pathway from the sea floor through a range of burial depths equivalent to sediment ages of 5 6 9 4 and 37 1 ma samples were subdivided by size to produce a unique data set of size specific sr ca ratios fine fraction

how burial diagenesis of chalk sediments controls sonic velocity and porosity based on p wave velocity and density data a new elastic model for chalk sediments is established the model allows the construction of a series of isoframe if curves each representing a constant part of the mineral phase contributing to the solid frame the if curves can be related to the progress of burial diagenesis of chalk which is revised as follows newly deposited carbonate ooze and mixed sediments range in porosity from 60 to 80 depending on the prevalence of hollow microfossils despite the high porosity these sediments are not in suspension as reflected in ifs of 0 1 or higher upon burial the sediments lose porosity by mechanical compaction and concurrently the calcite particles recrystallize into progressively more equant shapes high compaction rates may keep the particles in relative motion whereas low compaction rates allow the formation of contact cement whereby if increases and chalk forms rock mechanical tests show that when compaction requires more than in situ stress porosity reduction is arrested during subsequent burial crystals and pores grow in size as a consequence of the continuing recrystallization the lack of porosity loss during this process testifies to the absence of chemical compaction by calcite calcite pressure dissolution as well as to the porosity preserving effect of contact cementation at sufficient burial stress the presence of stylolites indicates that pressure dissolution takes place between calcite and silicates and depending on pore water chemistry and temperature pore filling cementation may occur over a relatively short depth interval limestone and mixed sedimentary rock form and porosity may be reduced to less than 20 isoframe increases to more than 0 6 in hydrocarbon reservoirs in north sea chalk relatively high porosity and high ifs are found the reason may be that recrystallization and porosity preserving contact cementation progress whereas pore filling cementation is small probably because pressure dissolution along stylolites is arrested pressure dissolution may be arrested for two reasons 1 the introduction of hydrocarbons causes a fall in effective burial stress and 2 adsorption of polar hydrocarbons on the silicates may shield calcite from the silicates

possible evidence for a large decrease in seawater strontium calcium ratios and strontium concentrations during the cenozoic article i nfo few constraints exist on the major element chemistry of ancient oceans turritellid marine snails precipitate aragonitic shells and are abundant in the cenozoic fossil record and therefore may be ideal for reconstructing past seawater chemistry here we report strontium to calcium sr ca ratios of modern and early cenozoic turritellid shells that still retain an aragonitic mineralogy by applying partition coefficients determined from modern specimens to data for paleocene and eocene shells we calculate paleo seawater sr ca values the high sr ca values recorded in fossil shells may imply that seawater sr ca ratios varied from at least 9 5 15 2 mmol mol much higher than modern average seawater values 8 6 mmol mol high paleo seawater sr ca ratios may indicate that substantial changes in the biogeochemical cycling of sr have occurred over the past 37 million years a decrease in seawater strontium concentrations could have arisen from an increase in the proportion of weathered radiogenic silicate rocks relative to carbonates reducing the riverine flux of strontium to the oceans or changes in the exposure and erosion of aragonitic carbonates on tropical shelves due to variations in sea level

the influence of magnitude range on empirical ground motion prediction a key issue in the assessment of seismic hazard in regions of low to moderate seismicity is the extent to which accelerograms obtained from small magnitude earthquakes can be used as the basis for predicting ground motions due to the larger magnitude events considered in seismic hazard analysis in essence the question is whether empirical ground motion prediction equations can be applied outside their strict range of applicability as defined by the magnitude and distance ranges covered by the datasets from which they are derived this question is explored by deriving new spectral prediction equations using an extended strong motion da taset from europe and the middle east covering the magnitude range mw 3 0 7 6 and comparing the predictions with previous equations derived using data from only mw 5 0 and above events the comparisons show that despite their complex func tional form including quadratic magnitude dependence and magnitude dependent attenuation the equations derived from larger magnitude events should not be extra polated to predict ground motions from earthquakes of small magnitude moreover the results suggest not only that ground motion prediction equations cannot be used outside the ranges of their underlying datasets but also that their applicability at the limits of these ranges may be questionable although only tested for smaller magni tudes the results could be interpreted to suggest that predictive equations also cannot be reliably extrapolated to higher magnitudes than those represented in the dataset from which they are derived a finding that has important implications for seismic hazard analysis the conclusion of the study is that empirical derivation of ground motion pre diction equations should be based on datasets extending at least one unit below the lower limit of magnitude considered in seismic hazard calculations the inclusion of small magnitude recordings results in a significant increase in the aleatory varia bility of the equations although it is yet to be established whether this is due to greater uncertainty in the associated metadata or whether ground motion variability is gen uinely dependent on earthquake magnitude

development of long period ground motions from the nankai trough japan earthquakes observations and computer simulation of the 1944 tonankai mw 8 1 and the 2004 se off kii peninsula mw 7 4 earthquakes strong ground motions recorded in central tokyo during the 1944 tonankai mw8 1 earthquake occurring in the nankai trough demonstrate significant developments of very large 10 cm and prolonged 10 min shaking of long period t 10 12 s ground motions in the basin of tokyo located over 400 km from the epicenter in order to understand the process by which such long period ground motions developed in central tokyo and to mitigate possible future disasters arising from large earthquakes in the nankai trough we analyzed waveform data from a dense nation wide strong motion network k net and kik net deployed across japan for the recent se off kii peninsula mw 7 4 earthquake of 5 september 2004 that occurred in the nankai trough the observational data and a corresponding computer simulation for the earthquake clearly demonstrate that such long period ground motion is primarily developed as the wave propagating along the nankai trough due to the amplification and directional guidance of long period surface waves within a thick sedimentary layer overlaid upon the shallowly descending philippine sea plate below the japanese island then the significant resonance of the seismic waves within the thick cover of sedimentary rocks of the kanto basin developed large and prolonged long period motions in the center of tokyo the simulation results and observed seismograms are in good agreement in terms of the main features of the long period ground motions accordingly we consider that the simulation model is capable of predicting the long period ground motions that are expected to occur during future nankai trough m 8 earthquakes

s wave velocity images of the dead sea basin provided by ambient seismic noise abstract based on passive seismic interferometry applied to ambient seismic noise recordings between station pairs belonging to a small scale array we have obtained shear wave velocity images of the uppermost materials that make up the dead sea basin we extracted empirical green s functions from cross correlations of long term recordings of continuous data and measured inter station rayleigh wave group velocities from the daily correlation functions for positive and negative correlation time lags in the 0 1 0 5 hz bandwidth a tomographic inversion of the travel times estimated for each frequency is performed allowing the laterally varying 3 d surface wave velocity structure below the array to be retrieved subsequently the velocity frequency curves are inverted to obtain s wave velocity images of the study area as horizontal depth sections and longitude and latitude depth sections the results which are consistent with other previous ones provide clear images of the local seismic velocity structure of the basin low shear velocities are dominant at shallow depths above 3 5 km but even so a spit of land with a depth that does not exceed 4 km is identified as a salt diapir separating the low velocities associated with sedimentary infill on both sides of the lisan peninsula the lack of low speeds at the sampling depth of 11 5 km implies that there are no sediments and therefore that the basement is near 10 11 km depth but gradually decreasing from south to north the results also highlight the bowl shaped basin with poorly consolidated sedimentary materials accumulated in the central part of the basin the structure of the western margin of the basin evidences a certain asymmetry both whether it is compared to the eastern margin and it is observed in north south direction infill materials down to 8 km depth are observed in the hollow of the basin unlike what happens in the north and south where they are spread beyond the western dead sea shore

evaluation of six nehrp b c crustal amplification models proposed for use in western north america we evaluate six crustal amplification models based on national earthquake hazards reduction program nehrp b c crustal profiles proposed for use in western north america wna and often used in other active crustal regions where crustal properties are unknown one of the models is based on an interpolation of generic rock velocity profiles previously proposed for wna and central and eastern north america cena in conjunction with material densities based on an updated velocity density relationship a second model is based on the velocity profile used to develop amplification factors for the next generation attenuation nga west2 project a third model is based on a near surface velocity profile developed from the nga west2 site database a fourth model is based on velocity and density profiles originally proposed for use in cena but recently used to represent crustal properties in california we propose two alternatives to this latter model that more closely represent wna crustal properties we adopt a value of site attenuation for each model that is either recommended by the author of the model or proposed by us stochastic simulation is used to evaluate the fourier amplification factors and their impact on response spectra associated with each model based on this evaluation we conclude that among the available models evaluated in this study the nehrp b c amplification model of boore 2016 best represents median crustal amplification in wna although the amplification models based on the crustal profiles of kamai et al 2013 2016 unpublished manuscript see data and resources 1 and yenier and atkinson 2015 the latter adjusted to wna crustal properties can be used to represent epistemic uncertainty 1 sec 9

applicability of the site fundamental frequency as a vs30 proxy for central and eastern north america we introduce a new proxy measure for v s 30 time averaged shear wave velocity in the upper 30 m for central and eastern north america cena the new proxy is the site fundamental frequency f peak measured from the horizontal to vertical h v spectral ratios of recorded ground motion or ambient noise in this study h v spectral ratios are obtained from 5 damped pseudospectral acceleration psa from seismograph stations in cena using the next generation attenuation east nga east database we correlate the measured v s 30 values at recording stations with the corresponding f peak values to obtain a predictive relationship for v s 30 the uncertainty of the v s 30 estimate using the f peak based model is small 0 14log10 units in comparison to that for the proxy based methods e g topographic slope and surface geology proxies used in the nga east database 0 25log10 units however values of f peak can be obtained for only about 23 of the nga east recording stations due to data and site type limitations reducing the error in v s 30 estimates can potentially reduce the variability of ground motion prediction equations gmpes to test this hypothesis we use the f peak based v s 30 estimates and select one of the proponent nga east gmpe models for a selected database we are able to reduce the gmpe variability by 3 on average for psa at 1 10 hz just using the f peak based proxy to estimate v s 30 greater variability reductions could be achieved by replacing v s 30 with improved site characterization parameters including f peak in the gmpes

estimates of shear wave q and κ0 for unconsolidated and semiconsolidated sediments in eastern north america measured and calculated values of the effective quality factor qef and the site attenuation parameter 0 for unconsolidated and semiconsolidated sediments in eastern north america ena indicate that the latter is strongly dependent on sediment thickness estimates of 0 for national earthquake hazard reduction program nehrp bc site profiles sediment plus hard rock in the mississippi embayment and the atlantic coastal plain were found to increase from about 9 to 31 msec for sedi ment thicknesses ranging from 116 to 600 m stochastic simulations using the 175 m thick hypothetical nehrp bc site profile used to estimate ena ground motions in the nationalseismichazardmapsbytheu s geologicalsurvey usgs indicatethat 0 20 msec provides a smaller estimate of amplification that agrees more closely with the low strain short period site coefficients in the nehrp recommended provisions for seismic regulations for new buildings and other structures nehrpprovisions than the10msecvalueusedbytheusgs alinearregressionofthe 0 estimatescompiledin this study indicates that 0 20 msec corresponds to a relatively thick bc sediment thickness of 460 116 m these same stochastic simulations indicate that the rela tivelyshallowusgssiteprofileprovidesestimatesofamplificationthataresmallerthan thelow strainlong periodsitecoefficientsinthenehrpprovisions thedependenceof bothsiteattenuationandsiteamplificationonsedimentthicknesssuggeststhattheuseof a single reference site condition for hazard mapping might not be appropriate instead theseresultsimplythateitheraregionalsetofreferencesiteprofilesshouldbedeveloped or that a more uniform site condition such as hard rock should be used to define a more stable reference site condition in ena

earthquake ground motion prediction using the ambient seismic field 1 the waves generated by faulting represent the primary threat posed by most large earthquakes the effect of complex geological structures such as sedimentary basins on earthquake ground motion is a source of particular concern we show that it is possible to extract reliable phase and amplitude response that includes the effects of complex structure for the elastodynamic green s function from the ambient seismic field using deconvolution we demonstrate the accuracy of the approach by predicting complex ground motion for a moderate mw 4 6 earthquake in southern california as recorded in the los angeles basin this suggests a novel approach to seismic hazard analysis in which ground motion from hypothetical future earthquakes is simulated directly without the need for modeling the detailed heterogeneity of the earth s crust as an intermediate step

tertiary oxygen isotope synthesis sea level history and continental margin erosion tertiary benthic and planktonic foraminiferal oxygen isotope records are correlated to a standard geomagnetic polarity time scale making use of improved chronostratigraphic control and additional oligocene isotope data synchronous changes in both benthic and planktonic 18o values which occurred in the oligocene to miocene 36 5 2 ma are interpreted in part to represent ice growth and decay the inferred ice growth events correlate with erosion on passive continental margins as interpreted from seismic and chronostratigraphic records this association is consistent with a link between oligocene to miocene erosional events and rapid 15 m m y glacioeustatic lowerings of about 50 m high benthic foraminiferal 18o values suggest the presence of continental ice sheets during much of the oligocene to recent 36 0 ma substantially ice free conditions probably existed throughout the paleocene and eocene 66 36 ma the mechanisms and rates of sea level change apparently were different between the early and late tertiary with glacioeustatic changes restricted to the past 36 m y pre oligocene erosion on passive continental margins was caused by eustatic lowerings resulting from global spreading rate changes we apply a model which suggests that large areas of the continental shelves were subaerially exposed during such tectonoeustatic lowstands stimulating slope failure and submarine erosion the different mechanisms and rates of eustatic change may have caused contrasting erosional patterns between the early and late tertiary on passive continental margins this speculation needs to be confirmed by examination of data from several passive margins

rock and stiff soil site amplification dependency on vs30 and kappa κ0 abstract a ground motion prediction equation gmpe specific to rock and stiff soil sites is derived using seismic motion recorded on high v s 30 sites in japan this gmpe applies to events with 4 5 m w 6 9 and v s 30 ranging from 500 to 1500 m s stiff soil to rock sites the empirical site coefficients obtained and the comparison with the simulated site functions show that seismic motion on rock and stiff soil sites does not depend only on v s 30 but also on the high frequency attenuation site properties 0 the effects of the site specific 0 on site amplification are analyzed using stochastic simulations with the need to take into account both of these parameters for rock site adjustments adding the site specific 0 into the gmpes thus appears to be essential in future work the rock site stochastic ground motion simulations show that the site specific 0 controls the frequency corresponding to the maximum response spectral acceleration f amp 1 this observation is used to link the peak of the response spectral shape to 0 in this specific japanese dataset and then to add the effects of high frequency attenuation into the previous gmpe from the peak ground acceleration and up to periods of 0 2 s the inclusion of 0 allows the observed bias to be corrected for the intraevent residuals and thus reduces sigma however this 0 determination is limited to a minimum number of rock site records with m w 4 5 and to distances of less than 50 km

cenozoic pelagic sr ca records exploring a link to paleoproductivity 1 recent studies have revealed that sr ca ratios of coccolithophores may be affected by productivity here we compile published sr ca data from bulk carbonate fine fraction sediment and planktonic foraminiferal sr ca records that span the past 60 myr and attempt to place these records into a paleoceanographic framework we account for changes in seawater sr ca ratios using the curve of lear et al 2003 and discuss our observations with respect to changes in the partitioning coefficient of sr through time we discuss limitations associated with postburial processes temporal changes in the coccolith planktonic foraminiferal rain ratio and the coccolith species composition of the sediment despite these caveats we are able to show that in the bulk and fine fraction carbonate records there are two broad periods of enhanced partitioning of sr relative to today the oligocene and the middle to late miocene early pliocene because these are two intervals for which we can cite evidence for a relatively productive ocean on the regional or global scale we believe that the sr ca ratios of bulk carbonate can be explained at least in part by the effects of oceanic nutrient levels on sr uptake during calcification of coccoliths which make up the vast majority of these sediments within the limits of the inferred seawater sr ca record the results of this study contribute a geologic perspective to recent laboratory and field studies that have raised the possibility that sr incorporation into biogenic calcite is controlled by biogeochemical processes

test of goodness of the nga ground motion equations to predict the strong motions of the 2012 ahar varzaghan dual earthquakes in northwestern iran in the first part of this study a set of 87 ground motion records with closest distance to the rupture plane r rup less than 200 km and averaged shear wave velocity over the top 30 m of the subsurface v s 30 between 175 and 1400 m s recorded during the 2012 ahar varzaghan dual earthquakes m w1 6 4 m w2 6 3 were taken into account to examine the predictive capabilities of the next generation attenuation nga ground motion prediction equations gmpes via a set of comparative analyses and tests the first applied method to assess the performance of the nga gmpes is based on the intraevent residual analysis the primary database i e 87 records was also used to develop an event specific gmpe in the case of the ahar varzaghan dual earthquakes by means of regression analyses the derived event specific gmpe has been compared with the nga gmpes for two different site conditions that is v s 30 375 m s rock site and v s 30 375 m s soil site the residual analysis results indicate that the nga gmpes perform better in predicting data recorded at rock sites compared to soil sites for soil sites and at large periods t 2 0 s the observed spectral accelerations are overpredicted by the nga gmpes furthermore as the second part of this study to select the most adequate gmpes 14 strong motion records from the 1997 ardebil earthquake m w 6 1 were added to the primary database the implementation of the likelihood lh and log likelihood methods as modern lh based ranking assessment techniques as well as the nash sutcliffe index reveal that the nga gmpes show good compatibility at short medium periods t 1 0 s on the basis of the data recorded during the 2012 ahar varzaghan dual and 1997 ardebil earthquakes i e 101 records however in the long period range the dispersion in the data does not allow the authors to draw a comprehensible conclusion

simulations of ground motion in the los angeles basin based upon the spectral element method we use the spectral element method to simulate ground motion generated by two recent and well recorded small earthquakes in the los angeles basin simulations are performed using a new sedimentary basin model that is constrained by hundreds of petroleum industry well logs and more than 20 000 km of seismic reflection profiles the numerical simulations account for 3d variations of seismic wave speeds and density topography and bathymetry and attenuation simulations for the 9 september 2001 m w 4 2 hollywood earthquake and the 3 september 2002 m w 4 2 yorba linda earthquake demonstrate that the combination of a detailed sedimentary basin model and an accurate numerical technique facilitates the simulation of ground motion at periods of 2 sec and longer inside the basin model and 6 sec and longer in the regional model peak ground displacement velocity and acceleration maps illustrate that significant amplification occurs in the basin

strong ground motion from the michoacan mexico earthquake the network of strong motion accelerographs in mexico includes instruments that were installed under an international cooperative research program in sites selected for the high potenial of a large earthquake the 19 september 1985 earthquake magnitude 8 1 occurred in a seismic gap where an earthquake was expected as a result there is an excellent descripton of the ground motions that caused the disaster

long period ground motion simulation of a subduction earthquake using the offshore onshore ambient seismic field large earthquakes that occur in subduction zones are likely to generate long period ground motions that can cause severe damage even at great distances from the epicenter we extracted surface to surface impulse response functions from the ambient seismic field recorded by offshore ocean bottom seismometers located atop the nankai subduction zone and onshore stations we showed that these offshore onshore impulse response functions can be used to accurately simulate the long period ground motions generated by an offshore moderate subduction earthquake moreover we also found that the distributions of the earthquake and impulse response function pseudovelocity response spectra have similar maximum amplifications in the same area close to the earthquake epicenter this suggests that the ambient seismic field recorded by the increasing number of ocean bottom seismometers around the world can be used to assess seismic hazard related to offshore subduction earthquakes without prior knowledge of the velocity structure

a comparison of nga ground motion prediction equations to italian data abstract ground motion prediction equations gmpes have recently been developed in the next generation attenuation nga project for application to shallow crustal earthquakes in tectonically active regions we investigate the compatibility of those models with respect to magnitude scaling distance scaling and site scaling implied by italian strong motion data this is of interest because 1 the italian data are principally from earthquakes in extensional regions that are poorly represented in the nga dataset and 2 past practice in italy has been to use local gmpes based on limited datasets that cannot resolve many significant source path and site effects we find that the magnitude scaling implied by the italian data is compatible with four nga relations however the italian data attenuate faster than implied by the four ngagmpes at short periods the differences are statistically significant comparison with the fifth one was not possible because it was developed for rock conditions only three regression coefficients are reevaluated for the four ngagmpes to reflect the faster attenuation a constant term a term controlling the slope of distance attenuation and a source fictitious depth term the scaling of ground motion with respect to site shear wave velocity is consistent between the nga models and italian data moreover the data are found to contain a nonlinear site effect that is generally compatible with nga site terms the intraevent scatter of italian data is higher than in the nga models although interevent scatter is comparable to nga recommendations when the faster distance attenuation is considered on the basis of these findings we recommend using the nga relations with the aforementioned minor modifications to evaluate ground motions for seismic hazard analysis in italy

seismic wavefield imaging of long period ground motion in the tokyo metropolitan area japan long period ground motions due to large earthquakes can cause devastating disasters especially in urbanized areas located on sedimentary basins to assess and mitigate such damage it is essential to rapidly evaluate seismic hazards for infrastructures which can be simulated by seismic response analyses that use waveforms at the base of each infrastructure as an input ground motion the present study reconstructs the seismic wavefield in the tokyo metropolitan area located on the kanto sedimentary basin japan from seismograms of the metropolitan seismic observation network meso net the obtained wavefield fully explains the observed waveforms in the frequency band of 0 10 0 20 hz this is attributed to the seismic wavefield imaging technique proposed by kano et al 2017 which implements the replica exchange monte carlo method to simultaneously estimate model parameters related to the subsurface structure and source information further investigation shows that the reconstructed seismic wavefield lower than 0 30 hz is of high quality in terms of variance reduction which quantifies a misfit in waveforms but that the variance reduction rapidly worsens in higher frequencies meanwhile the velocity response spectra show good agreement with observations up to 0 90 hz in terms of the combined goodness of fit which is a measure of misfit in the velocity response spectra inputting the reconstructed wavefield into seismic response analyses we can rapidly assess the overall damage to infrastructures immediately after a large earthquake

depth variations of azimuthal anisotropy beneath the tian shan mt range nw china from ambient noise tomography abstract seismic anisotropy beneath the tian shan mt range has been well studied with shear wave splitting the origin of asthenospheric anisotropy is mainly attributed to the north south shortening however the crustal anisotropy and its depth variation are poorly constrained in this study we focus on inversion of rayleigh wave phase velocity azimuthal anisotropy in the 5 35 s period bands beneath the tian shan mt range through analysis of continuous seismic ambient noise we use approximately 7 months of available continuous seismic data recorded by 31 broadband seismic stations deployed in the tian shan mt range the tomographic results reveal substantial variations in the azimuthal anisotropy with an increase in the depth in the upper crustal depths the orogen parallel or orogen subparallel azimuthal anisotropy observed in the tian shan mt range likely originates from the lattice preferred orientation of crustal minerals in response to compression whereas the orogen perpendicular or orogen sub perpendicular azimuthal anisotropy in the southern and northern piedmont of the tian shan mt range is related to the stress alignment of cracks fractures due to ongoing north south shortening the pattern of azimuthal anisotropy in the middle to lower crustal and upper most mantle is different from that at the upper crustal depths an orogen perpendicular or orogen sub perpendicular fast direction associated with prominent lower velocities has been observed north and south of lake issyk kul the spatial correlation between the azimuthal anisotropy and the lower velocity anomalies at the middle to lower crustal and upper most mantle depths may suggest a warm melt rich upper mantle below the tian shan mt range which could be attributed to the upwelling asthenospheric mantle flow in that region

comprehensive comparison among the campbell bozorgnia nga west2 gmpe and three gmpes from europe and the middle east campbell and bozorgnia 2006 compared their newly developed next generation attenuation west1 project nga west1 ground motion prediction equation gmpe with a contemporary gmpe developed for the active crustal region of europe and the middle east based on that comparison they proposed that their gmpe could be used to estimate ground motions in these regions later studies by a number of investigators confirmed this proposal for several of the nga gmpes using available pan european gmpes and european strong motion data in this study i performed a detailed comparison of the nga west2 gmpe of campbell and bozorgnia 2014 with three newly developed gmpes for the pan european region the comparisons were performed in terms of median predictions standard deviations and residual analyses with respect to the nga west2 database used to develop the nga west2 gmpe these comparisons indicate that the scaling characteristics of all four gmpes are generally comparable in terms of attenuation and linear site response but differ in terms of scaling with magnitude source depth style of faulting and nonlinear site effects these differences are not scientifically significant and are not found to be statistically significant for the pan european events of similar magnitude in the nga west2 database as a result i propose that the gmpe of campbell and bozorgnia 2014 can be used to estimate ground motions from moderate to large magnitude earthquakes in pan europe as a means of more reliably extending these estimates to large magnitudes and short distances of greater engineering interest and to include ground motion scaling features that are not currently included in pan european gmpes

a new geomagnetic polarity time scale for the late cretaceous and cenozoic we have constructed a magnetic polarity time scale for the late cretaceous and cenozoic based on an analysis of marine magnetic profiles from the world s ocean basins this is the first time since heirtzler et al 1968 published their time scale that the relative widths of the magnetic polarity intervals for the entire late cretaceous and cenozoic have been systematically determined from magnetic profiles a composite geomagnetic polarity sequence was derived based primarily on data from the south atlantic anomaly spacings in the south atlantic were constrained by a combination of finite rotation poles and averages of stacked profiles fine scale information was derived from magnetic profiles on faster spreading ridges in the pacific and indian oceans and inserted into the south ariantic sequence based on the assumption that spreading rates in the south atlantic were smoothly varying but not necessarily constant a time scale was generated by using a spline function to fit a set of nine age calibration points

interference of long period seismic wavefield observed by the dense hi net array in japan 1 in order to recover small signals of long period ground motions recorded by a short period seismometer we designed a time domain recursive filter that simulates seismic waves recorded with broadband seismometers we applied the time domain filter to seismograms recorded by the dense hi net array which consists of 800 stations at intervals of approximately 20 km the effectiveness of the time domain filter is demonstrated through the comparison of broadband waveforms obtained by the filter and sts 2 true broadband seismograms from the f net at the same site good agreement is observed between filtered and true broadband waveforms with high correlation coefficients for periods of up to 100 s for waveforms from the 2007 sumatra earthquake m7 9 which occurred approximately 5000 5800 km away from japan the applicability of the time domain filter to the recovery of long period signals from the record of a short period seismometer depends on the signal to noise ratio as a result a limited bandwidth of broadband signal is recovered for smaller earthquake from the spatiotemporal variation of the long period t 20 100 s wavefield obtained by the time domain filter we newly found an anomalous phase pattern of splitting of polarity along the wavefront particularly for the relatively short period band of from 20 50 s array analysis of the dense broadband waveforms revealed multipathing of the rayleigh waves which propagated toward central japan from two directions with slightly different slowness vectors the interference of two rayleigh waves caused such splitting of wavefield

lithologic controls on calcite recrystallization in cenozoic deep sea sediments abstract interpretations of calcite strontium calcium records in terms of ocean history and calcite diagenesis require distinguishing the effects on deep sea calcite sediments of changes in ocean chemistry of different mixes of calcite depositing organisms as sediment contributors through time and space and of the loss of sr during diagenetic calcite recrystallization in this paper sr ca and 18 o values of bulk calcium carbonate sediments are used to estimate the relative extent of calcite recrystallization in samples from four time points core tops 5 6 9 4 and 37 1 ma at eight ocean drilling program sites in the equatorial atlantic ceara rise and equatorial pacific ontong java plateau and two eastern equatorial pacific sites the possibility that site to site differences in calcite sr ca at a given time point originated from temporal variations in ocean chemistry was eliminated by careful age control of samples for each time point with sample ages differing by less than the oceanic residence times of sr and ca the sr ca and 18 o values of 5 6 and 9 4 ma samples from the less carbonate rich eastern equatorial pacific sites and ceara rise site 929 appear to be less diagenetically altered than the sr ca and 18 o values of contemporaneous samples from the more carbonate rich sites it is evident from these data that both sr ca and 18 o in bulk calcite have been diagenetically altered in some samples 5 6 ma and older these data indicate that noncarbonate sedimentary components like clay and biogenic silica have partially suppressed recrystallization at the lower carbonate sites sr ca data from the less altered carbonate poor sites indicate higher oceanic sr ca relative to today at 5 6 and 9 4 ma

source location of the 26 sec microseism from cross correlations of ambient seismic noise 1 very strong narrow band rayleigh wave arrivals peaking near 26 sec are observed in cross correlations of long time sequences of ambient noise records on us european and african stations with apparent arrival times that are typically smaller than expected for propagation along the great circle linking the stations use of these apparent travel times to locate the source of narrow band arrivals shows that the waves originate off the west african coast in the gulf of guinea and propagate with an average speed of about 3 5 km s i e close to the expected group speed of rayleigh waves at this period using data from different months demonstrate that the source location is temporally stable with amplitudes that maximize during the southern hemisphere winter a microseism with similar features but with a slightly broader spectral peak is observed at stations in east asia and in the western pacific and apparently originates in the north fiji basin the nearly antipodal location of the two source regions leads to the hypothesis that the 26 sec signals are excited by a single source located in the gulf of guinea the pacific inter station cross correlations may be for major arc propagation

mantle heterogeneities and the scec reference three dimensional seismic velocity model version 3 we determine upper mantle seismic velocity heterogeneities below southern california from the inversion of teleseismic travel time residuals teleseismic p wave arrival times are obtained from three temporary passive experiments and southern california seismic network scsn stations producing good raypath coverage the inversion is performed using a damped least squares conjugate gradient method lsqr the inversion model element spacing is 20 km before the inversion the effects of crustal velocity heterogeneities represented by the southern california earthquake center scec seismic velocity model version 2 are removed from the teleseismic travel times the p wave inversion produces a variance reduction of 43 s wave velocities are determined from laboratory vp vs ratios the most prominent features imaged in the results are high p wave velocities 3 in the uppermost mantle beneath the northern los angeles basin and the previously reported tabular high velocity anomaly 3 to depths of 200 km beneath the transverse ranges crosscutting the san andreas fault we incorporate the upper mantle seismic velocity heterogeneities into the scec southern california reference seismic velocity model the prior accounting for the crustal velocity heterogeneity demonstrates the utility of the top down method of the scec seismic velocity model development

phyllosilicates and zeolite assemblages in the carbonate periplatform of the great bahama bank origin and relation to diagenetic processes odp leg 166 sites 1006 and 1007 abstract the western flank of the great bahama bank drilled during odp leg 166 at seven sites represents a prograding carbonate sequence from late oligocene to holocene eberli et al proc odp init reports 166 1997 the signatures of the detrital input and of diagenetic alteration are evident in clay enriched intervals from the most distal sites 1006 and 1007 in the straits of florida mineralogical and chemical investigations xrd tem sem icp ms run on bulk rocks and on the clay fractions enable the origin and evolution of silicate parageneses to be characterized plio pleistocene silt and clay interbeds contain detrital clay assemblages comprising chlorite illite interstratified illite smectite smectite kaolinite and palygorskite the greater smectite input within late pliocene units than in pleistocene oozes may relate either varying source areas or change in paleoclimatic conditions and weathering intensity the clay intervals from miocene upper oligocene wackestone sections are fairly different with prevalent smectite in the fine fraction whose high crystallinity and mg contents that point towards an authigenic origin the lower miocene section below 1104 mbsf at depths where compaction features are well developed is particularly characterized by abundant authigenic na k clinoptilolite filling foraminifer tests the authigenic smectite and clinoptilolite paragenesis is recorded by the chemical trends both of the sediment and the interstitial fluid this diagenetic evolution implies si and mg rich fluids circulating in deeper and older sequences for lack of any local volcaniclastic input the genesis of zeolite and the terms of water rock interaction are discussed the location of the diagenetic front correlates with that of the seismic sequence boundary p2 dated as 23 2 ma this correspondence may allow the chronostratigraphic significance of some specific seismic reflections to be reassessed

strontium and its isotopic composition in interstitial waters of marine carbonate sediments abstract the concentrations and isotopic compositions of strontium in interstitial waters from several dsdp sites where sediments consist chiefly of carbonate oozes and chalks are used as indicators of carbonate diagenesis by reference to a recently produced curve showing detailed variations in the87sr 86sr ratio of seawater with time carbonate sediments of the walvis ridge show increases in interstitial sr2 concentrations in the upper carbonate ooze sections with the highest concentrations near the ooze chalk boundary where maximum rates of carbonate recrystallization occur below this in situ production of sr2 diminishes and there is a diffusive flux of sr to an underlying sink presumably volcanogenic sediments or basalts leading to sr isotopic disequilibrium between carbonates and interstitial waters in some other sites however there is no apparent sr sink at depth and isotopic equilibrium is retained overall diffusive smoothing of profiles exerts an important control on the87sr 86sr ratios although lower ratios than contemporaneous seawater values in the carbonate oozes often correlate with zones of mg2 loss and reflect a combination of a flux of sr2 from the zone of maximum recrystallization rates together with a contribution from the in situ alteration of volcanic matter

carbonate dissolution and abyssal hydrography in the atlantic ocean abstract surface sediment samples from two regions in the eastern atlantic angola basin and cape verde basin and two regions in the western atlantic brazil basin and vema channel were examined to evaluate the relationship among carbonate dissolution abyssal hydrography and carbonate chemistry of the water column at each of these locations the position of the lysocline was determined carbonate saturation 1 was calculated and major deep water mass boundaries were identified as previously observed the correlation among these variables is strikingly different between the eastern and western atlantic in the vema channel and the brazil basin there is a first order correlation among the position of the lysocline the benthic thermocline aabw nadw boundary and the transition from saturation to undersaturation with respect to carbonate this relationship breaks down in the eastern atlantic where there is no noticeable benthic thermocline and the lysocline occurs significantly deeper than the saturation undersaturation transition

extracting coherent wave fronts from acoustic ambient noise in the ocean a method to obtain coherent acoustic wave fronts by measuring the space time correlation function of ocean noise between two hydrophones is experimentally demonstrated though the sources of ocean noise are uncorrelated the time averaged noise correlation function exhibits deterministic waveguide arrival structure embedded in the time domain green s function a theoretical approach is derived for both volume and surface noise sources shipping noise is also investigated and simulated results are presented in deep or shallow water configurations the data of opportunity used to demonstrate the extraction of wave fronts from ocean noise were taken from the synchronized vertical receive arrays used in the frame of the north pacific laboratory npal during time intervals when no source was transmitting

investigating the capability to extract impulse response functions from ambient seismic noise using a mine collapse event using recordings of a mine collapse event mw 4 2 in south korea in january 2015 we demonstrated that the phase and amplitude information of impulse response functions irfs can be effectively retrieved using seismic interferometry this event is equivalent to a single downward force at shallow depth using quantitative metrics we compared three different seismic interferometry techniques deconvolution coherency and cross correlation to extract the irfs between two distant stations with ambient seismic noise data the azimuthal dependency of the source distribution of the ambient noise was also evaluated we found that deconvolution is the best method for extracting irfs from ambient seismic noise within the period band of 2 10 s the coherency method is also effective if appropriate spectral normalization or whitening schemes are applied during the data processing

reconstructing past sea surface temperatures correcting for diagenesis of bulk marine carbonate abstract a numerical model which describes oxygen isotope exchange during burial and recrystallization of deep sea carbonate is used to obtain information on how sea surface temperatures have varied in the past by correcting measured 18o values of bulk carbonate for diagenetic overprinting comparison of bulk carbonate and planktonic foraminiferal 18o records from odp site 677a indicates that the oxygen isotopic composition of bulk carbonate does reflect changes in sea surface temperature and 18o at odp site 690 we calculate that diagenetic effects are small and that both bulk carbonate and planktonic foraminiferal 18o records accurately reflect paleogene warming of high latitude surface oceans biased from diagenesis by no more than 1 c the same is likely to be true for other high latitude sites where sedimentation rates are low at dsdp sites 516 and 525 the effects of diagenesis are more significant measured 18o values of eocene bulk carbonates are more than 2 lower at deeply buried site 516 than at site 525 consistent with the model prediction that the effects of diagenesis should be proportional to sedimentation rate model corrections reconcile the differences in the data between the two sites the resulting paleotemperature reconstruction indicates a 4 c cooling of mid latitude surface oceans since the eocene at low latitudes the contrast in temperature between the ocean surface and bottom makes the carbonate 180 values particularly sensitive to diagenetic effects most of the observed variations in measured 18o values are accounted for by diagenetic effects rather than by sea surface temperature variations we show that the data are consistent with constant equatorial sea surface temperatures through most of the cenozoic with the possible exception of the early eocene when slightly higher temperatures are indicated we suggest that the lower equatorial sea surface temperatures for the eocene and oligocene reported in other oxygen isotope studies are artifacts of diagenetic recrystallization and that it is impossible to reconstruct accurately equatorial sea surface temperatures without explicitly accounting for diagenetic overprinting

near field observations of an offshore mw 6 0 earthquake from an integrated seafloor and subseafloor monitoring network at the nankai trough southwest japan an mw 6 0 earthquake struck 50 km offshore the kii peninsula of southwest honshu japan on 1 april 2016 this earthquake occurred directly beneath a cabled offshore monitoring network at the nankai trough subduction zone and within 25 35 km of two borehole observatories installed as part of the international ocean discovery program s nantroseize project the earthquake s location close to the seafloor and subseafloor network offers a unique opportunity to evaluate dense seafloor geodetic and seismological data in the near field of a moderate sized offshore earthquake we use the offshore seismic network to locate the main shock and aftershocks seafloor pressure sensors and borehole observatory data to determine the detailed distribution of seafloor and subseafloor deformation and seafloor pressure observations to model the resulting tsunami contractional strain estimated from formation pore pressure records in the borehole observatories equivalent to 0 37 to 0 15 strain provides a key to narrowing the possible range of fault plane solutions together these data show that the rupture occurred on a landward dipping thrust fault at 9 10 km below the seafloor most likely on the plate interface pore pressure changes recorded in one of the observatories also provide evidence for significant afterslip for at least a few days following the main shock the earthquake and its aftershocks are located within the coseismic slip region of the 1944 tonankai earthquake mw 8 0 and immediately downdip of swarms of very low frequency earthquakes in this region illustrating the complex distribution of megathrust slip behavior at a dominantly locked seismogenic zone

pressure solution and hydrothermal recrystallization of carbonate sediments an experimental study reply abstract the extent of calcite recrystallization was determined in pressure solution and hydrothermal experiments which were conducted on deep sea carbonates of low mg calcite iceland spar and reagent grade calcite powder in the pressure solution experiments wet sediments were subjected to confining pressures of 500 1500 bars and pore pressures of 150 500 bars at temperatures between 22 and 180 c for 21 240 h the hydrothermal experiments were performed in sealed teflon coated bombs at 200 c zero effective stress in sulfate free sea water for two weeks the hydrothermal system was solution dominated the extent of calcite recrystallization was determined by measuring the oxygen isotopic compositions of the pore fluids and solids before and after each experiment scanning electron microscope observations porosity and specific surface area measurements were performed in fine grained carbonate samples subjected to high effective stresses the mechanism for recrystallization apparently involves both relief of strain energy at grain to grain contacts and decrease in surface free energy by decreasing the surface area while in coarse grained carbonates relief of strain energy appears to be the most important control of recrystallization in the hydrothermal experiments however decrease in surface free energy is the only driving force for recrystallization effective stress increased the rate of calcite recrystallization in both pressure solution and hydrothermal experiments clay minerals retarded the reaction the effects of diatomite and basaltic glass on the extent of calcite recrystallization was investigated only in the hydrothermal experiments both admixed non carbonate materials retarded the reaction diatomite being the most effective inhibitor surface chemical reactions seem to be responsible for the observed inhibitions of calcite recrystallization increases in the extent of calcite recrystallization with increasing ionic strength were observed in hydrothermal experiments in nacl solutions of five different ionic strengths

productivity of the glacial ocean discussion of the iron hypothesis an increase in the productivity of the glacial age southern ocean has been postulated to explain the decrease in pc0 of the atmosphere observed in ice cores a plausible mechanism has been proposed elsewhere that productivity is limited by the availability of fe in this region and that the greater supply of eolian dust during glacial time removed this limit recently published evidence from cores from the southern ocean suggests that in fact there was no change in productivity in the assumed manner glacial age productivity was indeed greatly increased in the equatorial pacific and in the eastern boundary upwelling systems the cause presumably was the mechanical action of glacial age winds rather than a greater supply of fe however a role of increased supply of micronutrients from the continents in the increase of equatorial productivity during glacial time cannot be excluded such enhancement from increased supply of dust would have the interesting corollary of more efficient export transfer to depth possibly contributing to nutrient depletion in glacial age deep intermediate waters there is some indication as well of a general decrease in nutrient content in the tropical thermocline in the western pacific during the last several million years a depletion that may have been fostered by increasing supply of dust from emerging asian highlands alternative explanations are available the case for fe as a major modifier of productivity and biogenic sedimentation on geological time scales cannot be made in the absence of criteria diagnostic for fe supply as opposed to stirring and upwelling

the rate and consequences of sr diagenesis in deep sea carbonates we have used a diffusion advection reaction model for sr exchange during deep sea carbonate diagenesis to determine the rate and consequences of sr exchange between porewaters and bulk carbonate at six dsdp sites 590b 575 593 516 305 and 289 where the required sr concentration and isotopic composition data for the interstitial waters are available from the literature the model can reproduce both the sr2 and 87sr 86sr profiles in the porewaters at each of the sites by adjusting the rate of sr exchange due to solution reprecipitation as a function of sediment age we find that the rate of solution reprecipitation at all of the sites is highest for the youngest sediment 1 10 m y and decreases by about an order of magnitude over the first 10 m y of sediment age the effect of this exchange on the properties of the bulk carbonate is to reduce the sr content by 5 25 depending primarily on the sedimentation rate and shift the 87sr 86sr by as much as 0 00004 from the value the sediment had when first deposited isotopic shifts of this magnitude are large compared to present analytical uncertainties and therefore should be corrected for when using bulk carbonate 87sr 86sr for stratigraphic correlation the average sr loss in the carbonate sections studied is about 15 from which we conclude that the sr flux from carbonate sediments to the overlying ocean is of the order of 15 of the riverine sr flux we also show that the isotopic composition of the diagenetic sr flux is at all times quite close to the contemporaneous seawater value and therefore this flux plays a very minor role in the overall sr budget that determines the sr isotopic composition of seawater the range of sr losses from bulk carbonate due to diagenesis that we calculate is too small to account for the typical decrease in sr content seen in pelagic carbonates as a function of age about 70 over the first 100 m y we conclude that this decrease is not the result of diagenesis and must involve some changing property of the ocean itself

tertiary paleoceanic chemical variability unintended consequences of simple geochemical models five lines of concrete quantitative evidence about oceanic chemical composition during the past 65 m y can provide insights into the controlling processes and their temporal variations but the system constraints are not yet fully understood the calcium carbonate compensation depth mean carbon isotopic ratio and strontium isotopic ratio have all changed significantly during this time while changes in lithium to calcium and strontium to calcium ratios have been much smaller when these tracers are considered separately simple scenarios of changes in geochemical and geological factors can be used to explain the historical records these factors include 1 increases in continental chemical weathering rates and net continental fluxes to the oceans 2 changes in the isotopic composition of material weathered from continents to the oceans 3 decreases in the proportion of calcium carbonate deposited on continental shelves 4 changes in the deposition or weathering rates of certain types of sediments and 5 changes in hydrothermal circulation because these geochemical cycles are linked to each other and to others such as nutrients and global atmospheric carbon dioxide an explanation invoked for one tracer must satisfy the direction magnitude and timing of the patterns for all the tracers several simple scenarios for geochemical variations have been evaluated for their consequences both intended and unintended and compared to the historical records despite the attractiveness and possible justifications of some simple hypotheses for example decreases in organic carbon burial rates increases in carbonate weathering rates on the continents or increases in all continental weathering rates no one simple scenario appears to be consistent with both the timing and magnitude of the changes observed during the past 65 m y for all tracers considered the contradictions uncovered can be useful in defining what knowledge is crucial to further understanding of oceanic chemical history better knowledge is needed of absolute deep ocean sediment accumulation rates and their temporal variability of the extent and time scale of variability in the net carbon isotope input to the ocean from continental weathering of steady state fluxes for oceanic mass balances and the extent to which these mass balances approach steady state behavior and of the links and interactions between the geochemical cycles of various elements

foraminiferal mg ca increase in the caribbean during the pliocene western atlantic warm pool formation salinity influence or diagenetic overprint we constructed a high resolution mg ca record on the planktonic foraminifer globigerinoides sacculifer in order to explore the change in sea surface temperature sst due to the shoaling of the isthmus of panama as well as the impact of secondary factors like diagenesis and large salinity fluctuations the study covers the latest miocene and the early pliocene 5 6 3 9 ma and was combined with 18o to isolate changes in sea surface salinity sss before 4 5 ma sstmg ca and sss show moderate fluctuations indicating a free exchange of surface ocean water masses between the pacific and the atlantic the increase in 18o after 4 5 ma represents increasing salinities in the caribbean due to the progressive closure of the panamanian gateway the increase in mg ca toward values of maximum 7 mmol mol suggests that secondary influences have played a significant role evidence of crystalline overgrowths on the foraminiferal tests in correlation with aragonite sr ca and productivity cyclicities indicates a diagenetic overprint on the foraminiferal tests laser ablation inductively coupled plasma mass spectrometry analyses however do not show significantly increased mg ca ratios in the crystalline overgrowths and neither do calculations based on pore water data conclusively result in significantly elevated mg ca ratios in the crystalline overgrowths alternatively the elevated mg ca ratios might have been caused by salinity as the 18o record of site 1000 has been interpreted to represent large fluctuations in sss and cultivating experiments have shown an increase in mg ca with increasing salinity we conclude that the mg ca record 4 5 ma can only reliably be considered for paleoceanographical purposes when the minimum values not showing any evidence of secondary influences are used resulting in a warming of central caribbean surface water masses after 4 5 ma of 2 c

a study of celestine equilibrium in marine sediments using the entire odp iodp porewater data base abstract the stability of celestine srso 4 in marine sediments has been investigated through the calculation of its saturation index at the in situ temperature and pressure using the entire odp iodp porewater composition data base 14 416 samples recovered from sediments collected during 95 odp and iodp legs that has been thoroughly corrected for missing data and inconsistencies the porewater in situ pressure has been obtained from depth data and the in situ sample temperature has been calculated from the bottom seawater temperature and from the measured thermal gradient when the latter is unavailable a default value of 35 c km or an assumed gradient similar to that of a site located close to the study area has been used molarities have been converted to molalities through the calculation of the porewater densities which have represented by an empirical function of the total dissolved solids load up to 150 g l ocean bottom waters are largely undersaturated with respect to celestine yet sediment porewater saturation is not uncommon it is reached in 83 boreholes i e about 10 of all boreholes drilled during 22 odp iodp legs celestine equilibrium can be reached through two different non exclusive causes a strontium increase in porewater linked to the dissolution of sr rich aragonite or biogenic calcite and precipitation of sr poor calcite carbonate recrystallization or an increase in the strontium and sulfate porewater concentrations linked to a salinity increase due to the presence of brines sediments at most of the sites exhibiting celestine equilibrium share common characteristics such as a carbonate rich lithology typically higher than 80 wt and a low organic carbon content generally below 1 wt these results indicate that modification of porewaters during burial diagenesis can easily lead to celestine saturation especially in carbonate rich sediments we then briefly discuss former interpretations of the presence of celestine in ancient and recent marine sediments as well as the consequences of the incorporation of celestine formation in diagenetic models using the porewater sr content and sr isotopic composition

reference s wave velocity profile and attenuation models for ground motion prediction equations application to japan defining the reference rock or soil condition related to ground motion prediction is an important aspect of seismic hazard analysis in a previous study by the authors a method was proposed to establish a reference rock profile for switzerland through the comparison of empirical amplification functions with shear wave velocity profiles at 27 selected sites of the swiss national seismic network the retrieved velocity profile served as reference for a regional ground motion prediction equation however a lacking piece of information remained the anelastic attenuation for such a reference profile reference attenuation is essential to correctly model and interpret amplification at high frequencies in the present study we extended our approach to simultaneously model both the reference shear wave velocity profile and the corresponding attenuation for japan we compared site specific attenuation measurements with quarter wavelength average velocities at 36 soil and rock sites from the japanese kik net strong motion network the selected sites are characterized by a lack of observed resonance phenomena in order to avoid trade off between amplification and attenuation effects we establish a parametric model through regression analysis the resulting model gives us the possibility to estimate anelastic attenuation of a rock site with a given velocity profile and provides the base for host to target adjustments of real or modeled ground motion

sr ca ratios as indicators of varying modes of pelagic carbonate diagenesis in the ooze chalk and limestone realms abstract there has been an interest in the application of sr ca ratios in pelagic carbonates to reconstruct paleoceanographic conditions such as changes in the oceanic ca and sr budgets or calcareous nannoplankton productivity but the effect of burial diagenesis on primary sr ca records has not been sufficiently understood in order to clearly document sr ca records of pelagic carbonates relative to original paleoceanography or secondary diagenetic processes sr ca analyses were performed on bulk sediments from an 822 5 m thick ooze chalk limestone sequence at the mid pacific mountains deep sea drilling project site 463 the sr ca ratios exponentially decrease from 2 3 to 1 1 mmol mol with increasing burial depth in the ooze chalk interval 0 452 0 m below seafloor mbsf the sr ca ratios further decline to as low as 0 4 mmol mol in the limestone interval 452 0 mbsf with relatively high values of 1 1 mmol mol at carbonate poor lithology around 620 mbsf the stratigraphic sr ca trends appear to be consistent with porosity profile and similar sr ca porosity covariation in association with diagnetic changes in lithologies is also common in ontong java plateau sections by adopting a recent diagenetic model from backscattered electron image analysis of ontong java plateau sections it is postulated for site 463 that exponential sr ca decrease in the ooze chalk interval is due to the release of sr into interstitial water via recrystallization i e purification effect and that further decrease in sr ca ratios in the limestone interval is most likely due to acquisition of sr depleted calcite cement at the chalk limestone transition newly proposed as the dilution effect specifically sr ca ratios of deeply buried pelagic limestones are sensitive to the amount of calcite cement that is acquired in proportion to caco3 content i e carbonate rich lithology facilitates precipitation of secondary calcite at the chalk limestone transition therefore paleoceanographic interpretation by means of sr ca ratios in pelagic carbonates will become valid only when these diagenetic effects are appropriately constrained

sr isotopes in interstitial waters of marine sediments from deep sea drilling project cores sr isotopic compositions of interstitial sea waters have been documented in detail with cores from 37 deep sea drilling project sites the 87sr 86sr ratios are sensitive indicators of diagenetic reactions involving alteration of volcanic matter dispersed in sediments and recrystallization of carbonates effects of basalt alteration reactions except possibly for hydrothermal signals and of alteration of continental debris are minimal carbonate recrystallization has a significant effect on the geochemical mass balance of sr but diffusion of unradiogenic strontium from interstitial waters has only a small effect on the 87sr 86sr ratio of ocean water

broad band acceleration time histories synthesis by coupling low frequency ambient seismic field and high frequency stochastic modelling in this study information carried by the ambient seismic field is exploited to extract impulse response functions between two seismic stations using one as a virtual source interferometry by deconvolution method is used and validated by comparing the extracted ambient noise impulse response waveforms with records of moderate magnitude earthquakes from m w 4 to 5 8 that occurred close to the virtual source station in japan as the information is only available at low frequencies less than 0 25 hz the ambient seismic field approach is coupled to a non stationary stochastic model to simulate time domain accelerograms up to 50 hz this coupling allows the predicted ground motion to have both the deterministic part at low frequencies coming from the source and the crust structure and the high frequency random contribution from the seismic waves scattering the resulting combined accelerograms for an m w 5 8 event show a good agreement with observed ground motions from a real earthquake

factors contributing to the catastrophe in mexico city during the earthquake of september 19 1985 the extensive damage to high rise buildings in mexico city during the september 19 1985 earthquake is primarily due to the intensity of the ground shaking exceeding what was previously considered credible for the city by mexican engineers there were two major factors contributing to the catastrophe resonance in the sediments of an ancient lake that once existed in the valley of mexico and the long duration of shaking compared with other coastal earthquakes in the last 50 years both of these factors would be operative again if the guerrero seismic gap ruptured in a single earthquake

trace metal mg ca and sr ca analyses of single coccoliths by secondary ion mass spectrometry here we present the first multi species comparison of modern and fossil coccolith trace metal data obtained from single liths we present both trace metal analyses sr ca mg and al and distribution maps of individual paleogene fossil coccoliths obtained by secondary ion mass spectrometry sims we use this data to determine the effects of variable coccolith preservation and diagenetic calcite overgrowths on the recorded concentrations of strontium and magnesium in coccolith calcite the analysis of coccoliths from deep ocean sediments spanning the eocene oligocene transition demonstrates that primary coccolith calcite is resistant to the neomorphism that is common in planktonic foraminifera from similar depositional environments instead where present diagenetic calcite forms distinct overgrowths over primary coccolith calcite rather than replacing this calcite diagenetic overgrowths on coccoliths are easily distinguished in sims analyses on the basis of relatively higher mg and lower sr concentrations than co occurring primary coccolith calcite this interpretation is confirmed by the comparable sims analyses of modern cultured coccoliths of coccolithus braarudii further with diagenetic calcite overgrowth being the principle source of bias in coccolith based geochemical records we infer that lithologies with lower carbonate content deposited below the palaeo lysocline are more likely to produce geochemical records dominated by primary coccolith calcite than carbonate rich sediments where overgrowth is ubiquitous the preservation of primary coccolith carbonate in low carbonate lithologies thus provides a reliable geochemical archive where planktonic foraminifera are absent or have undergone neomorphism

simulations of long period ground motions from a large earthquake using finite rupture modeling and the ambient seismic field long period ground motions generated by large earthquakes slowly attenuate with distance and can be significantly amplified by local velocity structures even at large distances we take advantage of the wave propagation information carried by the ambient seismic field to simulate the long period ground motions of the 2008 mw 6 9 iwate miyagi nairiku earthquake which occurred in the tohoku region japan we extract green s functions between pairs of stations by regarding seismometers located in the vicinity of the mainshock fault plane as virtual sources and others as receivers we calibrate the amplitude of the extracted green s functions using records of a mw 5 0 aftershock with a reverse faulting focal mechanism similar to that of the mainshock we use scaling relations between small and large earthquakes to construct several finite fault models that are used together with the extracted green s functions to simulate the ground motions of the mainshock among the different models a uniform finite source model with a rupture velocity of 1 95 km s combined with the green s functions extracted using one virtual source station located at the center of the fault plane yields the best fit between the simulated and observed long period ground motions this study demonstrates the potential of the ambient seismic field combined with finite source modeling to assess the seismic hazard related to long period ground motions that could be generated by forthcoming large earthquakes

a local ground motion predictive model for turkey and its comparison with other regional and global ground motion models we examined the differences between the ground motion estimations of local and global prediction equations and explored some seismological parameters that may explain these differences to achieve this objective we first derived a set of ground motion prediction equations gmpes for estimating peak horizontal accel eration velocity and pseudospectral acceleration using the recently compiled turkish ground motion database the new gmpes are comparable with the recent global gmpes in terms of model sophistication and they are based on a well studied national dataset using global gmpes from the next generation attenuation of ground motions project power et al 2008 and the pan european akkar and bommer 2010 model we observed that the discrepancy between local and global gmpes is more prominent at small magnitudes provided that the gmpes possess similar mag nitude limits our more detailed comparisons with the pan european akkar and bom mer 2010 predictive model as well as with the estimations from a combined italian and turkish accelerometric dataset indicate that depth can be of importance for delineating the differences between local and global gmpes