earthquake ground motion estimation using strong motion records a review of equations for the estimation of peak ground acceleration and response spectral ordinates abstract engineering seismology is the link between earth sciences and engineering the main input of engineering seismology in engineering design are loading conditions which must satisfy certain conditions regarding their level and frequency of occurrence during the lifetime of a structure one method for estimating these loading conditions is through equations based on strong ground motion recorded during previous earthquakes these equations have a handful of independent parameters such as magnitude and source to site distance and a dependent parameter such as peak ground acceleration pga or spectral acceleration and the coefficients in the equation are usually found by regression analysis this review examines such equations in terms of data selection accelerogram processing techniques of the strong motion records used to construct the equations the characterisation of earthquake source travel path and local site used and regression techniques employed to find the final equations it is found that little agreement has been reached in the past 30 years of ground motion estimation relation studies workers have chosen their techniques based on the available data which varies greatly with geographical region also it is noted that there is a need to include more independent parameters into ground motion estimation equations if the large uncertainties associated with such equations are to be significantly reduced the data required to do this is unfortunately scarce

a ground motion predictive model for iran and turkey for horizontal pga pgv and 5 damped response spectrum investigation of possible regional effects we present a ground motion prediction equation gmpe for turkey and iran to investigate the possible regional effects on ground motion amplitudes in shallow active crustal earthquakes the proposed gmpe is developed from a subset of the recently compiled strong motion database of the earthquake model of the middle east region project see data and resources 1 a total of 670 turkish and 528 iranian accelerograms with depths down to 35 km are used to estimate peak ground acceleration peak ground velocity and 5 damped elastic pseudospectral acceleration ordinates of 0 01 s t 4 s the moment magnitude range of the model is 4 m w 8 and the maximum joyner boore distance is r jb 200 km the functional form considers three major fault mechanisms strike slip normal and reverse the nonlinear soil behavior is a function of v s 30 average shear wave velocity in the upper 30 m of soil profile our observations from empirical and estimated ground motion trends advocate regional differences in the territories covered by iran and turkey that originate from the differences in q factors kappa and near surface velocity profiles these factors eventually affect the magnitude and distance dependent scaling of spectral amplitudes in iran and turkey in essence the ground motion amplitudes of these two neighboring countries would draw patterns different than the ground motion estimates of gmpes developed from the strong motion databases of shallow active crustal earthquakes from multiple countries online material matlab code and regression coefficients for computing the response spectrum and distance scaling 1 sec 7

some key features of the strong motion data from the m 6 0 parkfield california earthquake of 28 september 2004 the 2004 parkfield california earthquake was recorded by an extensive set of strong motion instruments well positioned to record details of the motion in the near fault region where there has previously been very little recorded data the strong motion measurements obtained are highly varied with significant variations occurring over only a few kilometers the peak accelerations in the near fault region range from 0 13 g to over 1 8 g one of the highest acceleration recorded to date exceeding the capacity of the recording instrument the largest accelerations occurred near the northwest end of the inferred rupture zone these motions are consistent with directivity for a fault rupturing from the hypocenter near gold hill toward the northwest however accelerations up to 0 8 g were also observed in the opposite direction at the south end of the cholame valley near highway 41 consistent with bilateral rupture with rupture southeast of the hypocenter several stations near and over the rupturing fault recorded relatively weak motions consistent with seemingly paradoxical observations of low shaking damage near strike slip faults this event had more ground motion observations within 10 km of the fault than many other earthquakes combined at moderate distances peak horizontal ground acceleration pga values dropped off more rapidly with distance than standard relationships at close in distance the wide variation of pga suggests a distance dependent sigma may be important to consider the near fault ground motion variation is greater than that assumed in shakemap interpolations based on the existing set of observed data higher density of stations near faults may be the only means in the near future to reduce uncertainty in the interpolations outside of the near fault zone the variance is closer to that assumed this set of data provides the first case where near fault radiation has been observed at an adequate number of stations around the fault to allow detailed study of the fault normal and fault parallel motion and the near field s wave radiation the fault normal motions are significant but they are not large at the central part of the fault away from the ends the fault normal and fault parallel motions drop off quite rapidly with distance from the fault analysis of directivity indicates increased values of peak velocity in the rupture direction no such dependence is observed in the peak acceleration except for stations close to the strike of the fault near and beyond the ends of the faulting

new zircon shock phenomena and their use for dating and reconstruction of large impact structures revealed by electron nanobeam ebsd cl eds and isotopic u pb and u th he analysis of the vredefort domethis article is one of a series of papers published in this special issue on the theme of geochronology in honour of tom krogh integrated electron nanobeam ebsd cl eds and isotopic measurements u pb u th he of zircon from the collar and centre of the 80 km wide central uplift of the 2020 3 ma vredefort impact structure reveal new shock features in a microstructural progression related to impact basin formation and degree of u pb age resetting 1 planar fractures in 1k0 and 1k2 orientation during initial shock wave compression 2 curviplanar fractures in 1k1 orientation now annealed which host glassy inclusions of partial melt of the host rock 3 microtwin lamellae in an orientation of 65 about 110 attributed to shock wave rarefaction 4 nucleation of impact age crystallites possibly on microtwins during post shock heating by impact melt and 5 crystal plastic deformation linked to crater modification of the core of the central uplift planar fracturing and microtwinning 20 gpa in cold shock zircon in granitoid at a radial distance of 25 km failed to reset zircon age single grain id tims data

an optimized scheme of lettered marine isotope substages for the last 1 0 million years and the climatostratigraphic nature of isotope stages and substages a complete and optimized scheme of lettered marine isotope substages spanning the last 1 0 million years is proposed lettered substages for marine isotope stage mis 5 were explicitly defined by shackleton 1969 but analogous substages before or after mis 5 have not been coherently defined short term discrete events in the isotopic record were defined in the 1980s and given decimal style numbers rather than letters but unlike substages they were neither intended nor suited to identify contiguous intervals of time substages for time outside mis 5 have been lettered or in some cases numbered piecemeal and with conflicting designations we therefore propose a system of lettered substages that is complete without missing substages and optimized to match previous published usage to the maximum extent possible our goal is to provide order and unity to a taxonomy and nomenclature that has developed ad hoc and somewhat chaotically over the decades our system is defined relative to the lr04 stack of marine benthic oxygen isotope records and thus it is grounded in a continuous record responsive largely to changes in ice volume that are inherently global this system is intended specifically for marine oxygen isotope stages but it has relevance also for oxygen isotope stages recognized in time series of non marine oxygen isotope data and more generally for climatic stages which are recognized in time series of non isotopic as well as isotopic data the terms stage and substage in this context are best considered to represent climatostratigraphic units and thus climatic stages and climatic substages because they are recognized from geochemical and sedimentary responses to climate change that may not have been synchronous at global scale

observations and interpretations at vredefort sudbury and chicxulub towards an empirical model of terrestrial impact basin formation the structural topographic and other characteristics of the vredefort sudbury and chicxulub impact structures are described assuming that the structures originally had the same morphology the observations interpretations for each structure are compared and extended to the other structures this does not result in any major inconsistencies but requires that the observations be scaled spatially in the case of vredefort and sudbury this is accomplished by scaling the outer limit of particular shock metamorphic features in the case of chicxulub scaling requires a reasoned assumption as to the formation mechanism of an interior peak ring the observations interpretations are then used to construct an integrated empirical kinematic model for a terrestrial peak ring basin the major attributes of the model include a set of outward directed thrusts in the parautochthonous rocks of the outermost environs of the crater floor some of which are pre existing structures that have been reactivated during transient cavity formation inward directed motions along the same outermost structures and along a set of structures at intermediate radial distances during transient cavity collapse structural uplift in the center followed by a final set of radially outward directed thrusts at the outer edges of the structural uplift during uplift collapse the rock displacements on the intermediate inward and innermost outward sets of structures are consistent with the assumption that a peak ring will result from the convergence of the collapse of the transient cavity rim area and the collapse of the structural uplift

revision of the early middle pleistocene calcareous nannofossil biochronology 1 75 0 85 ma the extant nannofossil biostratigraphic and biochronologic framework for the early middle pleistocene time interval has been tested through the micropaleontological analysis of globally distributed high quality low to mid latitude deep sea successions the quantitative temporal distribution patterns of relative abundances of selected taxa were reconstructed in critical intervals and the following biohorizons were defined first occurrence of medium sized gephyrocapsa spp last occurrence of calcidiscus macintyrei first occurrence of large gephyrocapsa spp last occurrence of large gephyrocapsa spp first occurrence of reticulofenestra asanoi re entrance of medium sized gephyrocapsa spp and last occurrence of reticulofenestra asanoi the detailed patterns of abundance change at these biohorizons were used to generate a detailed biostratigraphy and the biostratigraphic data were transformed into a precise biochronology by means of correlation to isotope stratigraphies and astronomical timescales the degree of isochrony or diachrony of the biohorizons was evaluated biohorizons and are isochronous occurring close to marine isotope stages mis 55 and mis 22 respectively and and are slightly diachronous on the order of 30 40 kyr whereas biohorizons and are confirmed as diachronous on the order of 100 80 and 60 kyr respectively some of the events are clearly controlled by environmental conditions e g the last occurrence of r asanoi related to significant environmental changes associated with the first large amplitude glaciation of the late quaternary mis 22

the response of deep water benthic foraminiferal assemblages to changes in paleoproductivity during the pleistocene last 769 2 kyr western south atlantic ocean abstract benthic foraminiferal assemblages and 18 o records in a core from santos basin western south atlantic 2220 m water depth were analyzed to investigate productivity changes during the pleistocene the sediment core recorded the last 770 kyr including marine isotope stages mis 19 to 1 the four dominant benthic foraminiferal assemblages were identified using q mode varimax factor analysis and are represented by globocassidulina crassa bolivina spp epistominella exigua and alabaminella weddellensis from 769 2 kyr mis 19 to 300 kyr mis 8 the highest values of factor 2 bolivina spp assemblage indicate increased influx of organic matter to the seafloor and a slight decrease in the oxygen concentration at the sediment water interface this condition began to change in the stage 8 288 9 kyr to 268 3 kyr and it is characterized by high values of factor 1 when the g crassa assemblage became dominant indicating an increase in oxygen concentrations and a decrease in the influx of organic matter seasonally pulsed organic matter resulting in a distinct phytodetritus layer accumulated mostly during the glacial mis 14 10 8 6 and 5 2 5 1 and in the interglacial stage 11 and the end of 9 as indicated by factor 3 e exigua assemblage and factor 4 a weddellensis assemblage the highest peak of the a weddellensis assemblage during mis 11 401 4 kyr coincides with the mid brunhes event the highest benthic foraminiferal accumulation rates occurred during mostly glacial stages indicating delivery of more organic matter to the seafloor the changes in benthic foraminifera assemblages in the glacial stages during the pleistocene indicate changes in primary productivity in surface waters increasing the amount of organic matter delivered to the seafloor amplified the benthic foraminiferal response

a pressure temperature phase diagram for zircon at extreme conditions abstract hypervelocity impact processes are uniquely capable of generating shock metamorphism which causes mineralogical transformations and deformation that register pressure p and temperature t conditions far beyond even the most extreme conditions created by terrestrial tectonics the mineral zircon zrsio4 responds to shock deformation in various ways including crystal plasticity twinning polymorphism e g transformation to the isochemical mineral reidite formation of granular texture and dissociation to zro2 sio2 which provide robust thermobarometers that record different extreme conditions the importance of understanding these material processes is two fold first these processes can mobilize and redistribute trace elements and thus be accompanied by variable degrees of resetting of the u pb system which is significant for the use of zircon as a geochronometer second some features described herein form exclusively during shock events and are diagnostic criteria that can be used to confirm the hypervelocity origin of suspected impact structures we present new p t diagrams showing the phase relations of zrsio4 polymorphs and associated dissociation products under extreme conditions using available empirical and theoretical constraints we present case studies to illustrate zircon microstructures formed in extreme environments and present electron backscatter diffraction data for grains from three impact structures mistastin lake of canada ries of germany and acraman of australia that preserve different minerals and microstructures associated with different shock conditions for each locality we demonstrate how systematic crystallographic orientation relationships within and between minerals can be used in conjunction with the new phase diagrams to constrain the p t history we outline a conceptual framework for a zircon based approach to extreme thermobarometry that incorporates both direct observation of high p and high t phases as well as inferences for the former existence of phases from orientation relationships in recrystallised products a concept we refer to here as phase heritage this new approach can be used to unravel the pressure temperature history of zircon bearing samples that have experienced extreme conditions such as rocks that originated in the earth s mantle and those shocked during impact events on earth and other planetary bodies

decline of giant impacts on mars by 4 48 billion years ago and an early opportunity for habitability the timing of the wane in heavy meteorite bombardment of the inner planets is debated its timing determines the onset of crustal conditions consistently below the thermal and shock pressure limits for microbiota survival and so bounds the occurrence of conditions that allow planets to be habitable here we determine this timing for mars by examining the metamorphic histories of the oldest known martian minerals 4 476 4 429 gyr old zircon and baddeleyite grains in meteorites derived from the southern highlands we use electron microscopy and atom probe tomography to show that none of these grains were exposed to the life limiting shock pressure of 78 gpa 97 of the grains exhibit weak to no shock metamorphic features and no thermal overprints from shock induced melting by contrast about 80 of the studied grains from bombarded crust on earth and the moon show such features the giant impact proposed to have created mars hemispheric dichotomy must therefore have taken place more than 4 48 gyr ago with no later cataclysmic bombardments considering thermal habitability models we conclude that portions of mars crust reached habitable pressures and temperatures by 4 2 gyr ago the onset of the martian wet period about 0 5 gyr earlier than the earliest known record of life on earth early abiogenesis by 4 2 gyr ago is now tenable for both planets the oldest known minerals from mars have no strong shock features indicating early cessation of giant impacts there according to microanalysis of zircon and baddeleyite grains in meteorites

shakeout d ground motion estimates using an ensemble of large earthquakes on the southern san andreas fault with spontaneous rupture propagation 1 we simulate ground motion in southern california from an ensemble of 7 spontaneous rupture models of large mw7 8 northwest propagating earthquakes on the southern san andreas fault shakeout d compared to long period spectral accelerations from the next generation attenuation nga empirical relations shakeout d predicts similar average rock site values i e within roughly their epistemic uncertainty but significantly larger values in los angeles and ventura basins due to wave guide focusing effects the shakeout d ground motion predictions differ from those of a kinematically parameterized geometrically similar scenario rupture 1 the kinematic rock site predictions depart significantly from the common distance attenuation trend of the nga and shakeout d results and 2 shakeout d predictions of long period spectral acceleration within the basins of the greater los angeles area are lower by factors of 2 3 than the corresponding kinematic predictions we attribute these differences to a less coherent wavefield excited by the complex rupture paths of the shakeout d sources

making the most of available site information for empirical ground motion prediction this article proposes a new framework for the inclusion of site effects in empirical ground motion prediction equations gmpes by characterizing stations through their one quarter wavelength velocities and assessed confidence limits the approach is demonstrated for 14 stations of the french accelerometric network reseau accelerometrique permanent this method can make use of all the available information about a given site for example the surface geology the soil profile standard penetration test measurements near surface velocity estimated from the topographic slope depth to bedrock and crustal structure these data help to constrain the velocity profile down to a few kilometers based on a statistical study of 858 real profiles from three different regions japan western north america and france physically realistic profiles are generated that comply with the information available for each site in order to evaluate the confidence limits for the shear wave velocity profiles and derived site amplifications for each station a stochastic method is adopted several thousand profiles are randomly generated based on parameters derived in the statistical study and the constraints available for each station then the one quarter wavelength assumption is used to estimate the amplification for each station it is found that a good knowledge of near surface attenuation i e or q is mandatory for obtaining precise amplification estimates at high frequencies nevertheless the proposed scheme highlights the important differences in the uncertainties of the site amplifications depending on the information available for a given station we suggest that these results could therefore be used when developing gmpes by weighting records from each station depending on the variability in the computed one quarter wavelength velocities this approach relies on the assumption that local site effects are only one dimensional which is far from true especially in sedimentary basins however most gmpes only model one dimensional site effects so this is not an issue specific to this study finally a way to improve this technique is to use earthquakes or noise recorded at the stations to further constrain the shear wave velocity profiles and to consequently derive more accurate one quarter wavelength velocities

delayed holocene reappearance of g menardii the planktonic foraminifera globorotalia menardii absent in the atlantic ocean during the last glacial period reappeared during the holocene as it was present in the indian ocean during glacial time its reappearance might be thought to have been connected to rejuvenation of conveyor circulation but as first shown by glenn jones and confirmed here it was a significant contributor to the atlantic s foraminifer population only after 7000 years ago

broadband simulations for mw 7 8 southern san andreas earthquakes ground motion sensitivity to rupture speed using the high performance computing resources of the southern california earthquake center we simulate broadband 0 10 hz ground motions for three m w 7 8 rupture scenarios of the southern san andreas fault the scenarios incorporate a kinematic rupture description with the average rupture speed along the large slip portions of the fault set at 0 96 0 89 and 0 84 times the local shear wave velocity consistent with previous simulations a southern hypocenter efficiently channels energy into the los angeles region along the string of basins south of the san gabriel mountains however we find the basin ground motion levels are quite sensitive to the prescribed rupture speed with peak ground velocities at some sites varying by over a factor of two for variations in average rupture speed of about 15 these results have important implications for estimating seismic hazards in southern california and emphasize the need for improved understanding of earthquake rupture processes

shock metamorphism of planetary silicate rocks and sediments proposal for an updated classification system we reevaluate the systematics and geologic setting of terrestrial lunar martian and asteroidal impactites resulting from single or multiple impacts for impactites derived from silicate rocks and sediments we propose a unified and updated system of progressive shock metamorphism shock metamorphosed rocks occur as lithic clasts or melt particles in proximal impactites at impact craters and rarely in distal impactites they represent a wide range of metamorphism typically ranging from unshocked to shock melted as the degree of shock metamorphism at a given shock pressure depends primarily on the mineralogical composition and the porosity of a rock or sediment sample different shock classification systems are required for different types of planetary rocks and sediments we define shock classification systems for eight rock and sediment classes which are assigned to three major groups of rocks and sediments 1 crystalline rocks with classes f m a and u 2 chondritic rocks class c and 3 sedimentary rocks and sediments with classes sr se and re the abbreviations stand for felsic f mafic m anorthositic a ultramafic u sedimentary rocks sr unconsolidated sediments se and regoliths re in each class the progressive stages of shock metamorphism are denominated s1 to sx these progressive shock stages are introduced as s1 s7 for f s1 s7 for m s1 s6 for a s1 s7 for u s1 s7 for c s1 s7 for sr s1 s5 for se and s1 s6 for re s1 stands for unshocked and sx variable between s5 and s7 stands for whole rock melting we propose a sequence of symbols characterizing the degree of shock metamorphism of a sample i e f s1 to f s7 with the option to add the tabulated pressure ranges in gpa in parentheses

terashake2 spontaneous rupture simulations of mw 7 7 earthquakes on the southern san andreas fault abstract previous numerical simulations terashake1 of large m w 7 7 southern san andreas fault earthquakes predicted localized areas of strong amplification in the los angeles area associated with directivity and wave guide effects from northwestward propagating rupture scenarios the terashake1 source was derived from inversions of the 2002 m w 7 9 denali alaska earthquake that source was relatively smooth in its slip distribution and rupture characteristics owing both to resolution limits of the inversions and simplifications imposed by the kinematic parameterization new simulations terashake2 with a more complex source derived from spontaneous rupture modeling with small scale stress drop heterogeneity predict a similar spatial pattern of peak ground velocity pgv but with the pgv extremes decreased by factors of 2 3 relative to terashake1 the terashake2 source excites a less coherent wave field with reduced along strike directivity accompanied by streaks of elevated ground motion extending away from the fault trace the source complexity entails abrupt changes in the direction and speed of rupture correlated to changes in slip velocity amplitude and waveform features that might prove challenging to capture in a purely kinematic parameterization despite the reduced pgv extremes northwest rupturing terashake2 simulations still predict entrainment by basin structure of a strong directivity pulse with pgvs in los angeles and san gabriel basins that are much higher than predicted by empirical methods significant areas of those basins have predicted pgv above the 2 probability of exceedance poe level relative to current attenuation relationships even when the latter includes a site term to account for local sediment depth and wave guide focusing produces localized areas with pgv at roughly 0 1 0 2 poe about a factor of 4 5 above the median in contrast at rock sites in the 0 100 km distance range the median terashake2 pgvs are in very close agreement with the median empirical prediction and extremes nowhere reach the 2 poe level the rock site agreement lends credibility to some of our source modeling assumptions including overall stress drop level and the manner in which we assigned dynamic parameters to represent the mechanical weakness of near surface material future efforts should focus on validating and refining these findings assessing their probabilities of occurrence relative to alternative rupture scenarios for the southern san andreas fault and incorporating them into seismic hazard estimation for southern california

plankton biochronology for the last 772 000 years from the western south atlantic ocean abstract calcareous microfossils have potential in the biostratigraphy of pleistocene sediments and a clear relationship with paleoceanographic studies conversely there are few quantitative biostratigraphic studies of chronologically tuned events or sections in the western south atlantic in order to improve the stratigraphical framework for south atlantic paleoceanographic studies the present work attempts to review the last 772 000 years by carrying out a quantitative analysis of the calcareous nannofossil and planktonic foraminiferal assemblages by comparing them with a high resolution marine isotopic record 18 o this work is based on the analysis of two piston cores obtained from the continental slope of the santos basin in the santos drift southeastern brazilian continental margin twelve pleistocene calcareous nannofossil events and twenty planktonic foraminifera events calibrated with oxygen isotopes and correlated with literature stratigraphies are discussed this is the first calcareous plankton biochronology study for the last 772 kyr in the western south atlantic ocean more studies in this region will help to establish a more precise biochronology for these calcareous microfossils this study also presents six new biostratigraphic events of isotopically caibrated planktonic foraminifera which can be used as markers in the western south atlantic

seasonal variability of the south equatorial current bifurcation in the atlantic ocean a numerical study abstract in this study a reduced gravity primitive equation ogcm is used to investigate the seasonal variability of the bifurcation of the south equatorial current sec into the brazil current bc to the south and the north brazil undercurrent current nbuc nbc system to the north annual mean meridional velocity averaged within a 2 longitude band off the south american coast shows that the sec bifurcation occurs at about 10 14 s near the surface shifting poleward with increasing depth reaching 27 s at 1000 m in both observations and model the bifurcation latitude reaches its southernmost position in july 17 s in the top 200 m and its northernmost position in november 13 s in the top 200 m the model results show that most of the seasonal variability of the bifurcation latitude in the upper thermocline is associated with changes in the local wind stress curl due to the annual north south excursion of the marine itcz complex as the sec bifurcation latitude moves south north the nbuc tra

anatomy of a suspended seafloor in the dense brine waters of the deep hypersaline urania basin abstract when micron sized particles are suspended into the dense brine waters of a deep hypersaline basin in the absence of biological packaging their settling velocities should be greatly attenuated we observed this phenomenon in the anoxic brine water of the urania basin in the eastern mediterranean we found that the deepest part of this basin is filled with a high density about 110 m thick homogenous fluid mud layer mainly containing microfossils of coccoliths and nannoplankton of pleistocene and pliocene age that float in a hot methane laden brine overlaid by a clear brine the top of the fluid mud forms a secondary suspended seafloor that has been stable for at least the last two decades since the discovery of the basin the geochemical characteristics of the fluid mud e g lower salinity than the clear brine methane rich point to a deep source for the fluids while the age of the microfossils suggests that the floating biogenic particles came from shallower post messinian pelagic deposits such as those exposed along the walls and the rim of the urania basin we hypothesize that catastrophic gravity failures and mass mobilization of the post messinian sedimentary layers triggered by earthquake activity are one of the main sources of the sediment in the fluid mud because of both the dense brine fluids the continuous mixing by thermal convection and the very fine grained nature of the particles the re mobilized sediments have never settled and stay suspended as if they were frozen in time the prolonged residence time of the supersaturated fluids and the associated microbial activity have also fostered the precipitation of the authigenic gypsum crystals and micron sized authigenic carbonates that occur mixed with the fluid mud sediments

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

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

a review of calcareous nannofossil astrobiochronology encompassing the past 25 million years this paper presents a review of astrobiochronological calibration of recent to late oligocene calcareous nannofossil datum events biohorizons included in the paper are those of the widely used standard nannofossil zonations of martini e 1971 standard tertiary and quaternary calcareous nannoplankton zonation in farinacci a ed proceedings of the second international conference on planktonic microfossils roma rome ed tecnosci vol 2 pp 739 785 and okada h and bukry d 1980 supplementary modification and introduction of code numbers to the low latitude coccolith biostratigraphy zonation bukry 1973 1975 marine micropaleontology 51 321 325 as well as supplementary biohorizons proposed in the literature the biohorizons have been selected on the basis of the unambiguous taxonomy of the index taxa and their biostratigraphic usefulness we emphasise the application of rigorous methodology in nannofossil studies which permits an evaluation of biohorizons in terms of reliability and calibrates their potential correlatability astrochronological age estimates rely on the geologic timescale developed by the ics in 2004 with some new calibrations included we provide an overview of the relative position of biohorizons versus the astronomically calibrated ages of magnetic reversals and reference isotope stratigraphies surprisingly there are still few high resolution quantitative biostratigraphic studies of astrochronologically tuned sections in spite of the central role of such studies in addressing fundamental problems such as the tempo and mode of plankton evolution

partially nonergodic empirical ground motion models for predicting horizontal and vertical pgv pga and 5 damped linear acceleration response spectra using data from the iranian plateau we present new ground motion prediction equations gmpes to estimate horizontal and vertical strong ground motion intensity measures gmims generated by shallow active crustal earthquakes occurring within the iranian plateau to this end a dataset containing 688 records from 152 earthquakes with moment magnitudes ranging from 4 7 to 7 4 and joyner boore distances up to 250 km has been used the effects of the local site condition are taken into account using the time averaged shear wave velocities in the upper 30 m v s 30 we decided not to include the style of faulting term in the final functional form because the total standard deviation is reduced 10 by removing this term from the functional form we used a nonlinear mixed effects regression to determine the coefficients of the functional form and to separate out the between event and between station standard deviations from the total standard deviation significant standard deviation of site to site variability demonstrates that the ergodic assumption is not able to account for the spatial variability of ground motions we introduced random effects coefficients to capture regional variations between different tectonic regions of the iranian plateau such as alborz and zagros in the regression analysis to investigate the effects of regionalization on gmpes the results showed that although the effects of regional variations for considered regions are negligible at close distances they are significant at longer distances the complexity and performance of the final functional form is justified by comparing akaike and bayesian information criteria values over many trial functional forms moreover the distribution of between event site to site and event station corrected residuals demonstrates that no trends are evident implying satisfactory performance of the proposed gmpes therefore the derived gmpes can be employed to predict gmims and to do seismic hazard assessments within the iranian plateau electronic supplement 1 lists of the events and stations considered in the final dataset and derived coefficients of the functional form 1 http www bssaonline org lookup suppl doi 10 1785 0120160205 dc1

variable microstructural response of baddeleyite to shock metamorphism in young basaltic shergottite nwa 5298 and improved u pb dating of solar system events abstract the accurate dating of igneous and impact events is vital for the understanding of solar system evolution but has been hampered by limited knowledge of how shock metamorphism affects mineral and whole rock isotopic systems used for geochronology baddeleyite monoclinic zro2 is a refractory mineral chronometer of great potential to date these processes due to its widespread occurrence in achondrites and robust u pb isotopic systematics but there is little understanding of shock effects on this phase here we present new nano structural measurements of baddeleyite grains in a thin section of the highly shocked basaltic shergottite northwest africa nwa 5298 using high resolution electron backscattered diffraction ebsd and scanning transmission electron microscopy stem techniques to investigate shock effects and their linkage with u pb isotopic disturbance that has previously been documented by in situ u pb isotopic analyses the shock altered state of originally igneous baddeleyite grains is highly variable across the thin section and often within single grains analyzed grains range from those that preserve primary magmatic twinning and trace element zonation baddeleyite shock group 1 to quasi amorphous zro2 group 2 and to recrystallized micro granular domains of baddeleyite group 3 these groups correlate closely with measured u pb isotope compositions primary igneous features in group 1 baddeleyites n 5 are retained in high shock impedance grain environments and an average of these grains yields a revised late amazonian magmatic crystallization age of 175 30 ma for this shergottite the youngest u pb dates occur from group 3 recrystallized nano to micro granular baddeleyite grains indicating that it is post shock heating and new mineral growth that drives much of the isotopic disturbance rather than just shock deformation and phase transitions our data demonstrate that a systematic multi stage microstructural evolution in baddeleyite results from a single cycle of shock loading heating and cooling during transit to space and that this leads to variable disturbance of the u pb isotope system furthermore by linking in situ u pb isotopic measurements with detailed micro to nano structural analyses it is possible to resolve the timing of both endogenic crustal processes and impact events in highly shocked planetary materials using baddeleyite this opens up new opportunities to refine the timing of major events across the solar system

review and revision of cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the geomagnetic polarity and astronomical time scale planktonic foraminifera are widely utilized for the biostratigraphy of cretaceous and cenozoic marine sediments and are a fundamental component of cenozoic chronostratigraphy the recent enhancements in deep sea drilling recovery multiple coring and high resolution sampling both offshore and onshore has improved the planktonic foraminiferal calibrations to magnetostratigraphy and or modified species ranges this accumulated new information has allowed many of the planktonic foraminiferal bioevents of the cenozoic to be revised and the planktonic foraminiferal calibrations to be reassessed we incorporate these developments and amendments into the existing biostratigraphic zonal scheme in this paper we present an amended low latitude tropical and subtropical cenozoic planktonic foraminiferal zonation we compile 187 revised calibrations of planktonic foraminiferal bioevents from multiple sources for the cenozoic and have incorporated these recalibrations into a revised cenozoic planktonic foraminiferal biochronology we review and synthesize these calibrations to both the geomagnetic polarity time scale gpts of the cenozoic and astronomical time scale ats of the neogene and late paleogene on the whole these recalibrations are consistent with the previous work however in some cases they have led to major adjustments to the duration of biochrons recalibrations of the early middle eocene first appearance datums of globigerinatheka kugleri hantkenina singanoae guembelitrioides nuttalli and turborotalia frontosa have resulted in large changes in the durations of biochrons e7 e8 and e9 we have introduced upper oligocene zone o7 utilizing the biostratigraphic utility of paragloborotalia pseudokugleri for the neogene period major revisions are applied to the fohsellid lineage of the middle miocene and we have modified the criteria for recognition of zones m7 m8 and m9 with additional adjustments regarding the globigerinatella lineage to zones m2 and m3 the revised and recalibrated datums provide a major advance in biochronologic resolution and a template for future progress of the cenozoic time scale

developing a map of geologically defined site condition categories for california consideration of site conditions is a vital step in analyzing and predicting earthquake ground motion the importance of amplification by soil conditions has long been recognized but though many seismic instrument sites have been characterized by their geologic conditions there has been no consistent simple classification applied to all sites as classification of sites by shear wave velocity has become more common the need to go back and provide a simple uniform classification for all stations has become apparent within the pacific earthquake engineering research center s next generation attenuation equation project developers of attenuation equations recognized the need to consider site conditions and asked that the california geological survey provide site conditions information for all stations that have recorded earthquake ground motion in california to provide these estimates we sorted the available shear wave velocity data by geologic unit generalized the geologic units and prepared a map so that we could use the extent of the map units to transfer the velocity characteristics from the sites where they were measured to sites on the same or similar materials this new map is different from the california geological survey preliminary site conditions map of california in that 19 geologically defined categories are used rather than national earthquake hazards reduction program categories although this map does not yet cover all of california when completed it may provide a basis for more precise consideration of site conditions in ground motion calculations

southern ocean pleistocene calcareous nannofossil events calibration with isotope and geomagnetic stratigraphies abstract several cores recovered from the northern belt of the southern ocean were analysed to study the pleistocene calcareous nannofossil records calcareous nannofossil events previously described in medium and low latitudes were identified and calibrated with the oxygen isotope and geomagnetic time scales although sedimentation rates hiatuses and degree of calcareous nannofossil preservation sometimes prevent the identification and or accurate calibration of some of these events a useful stratigraphic framework was obtained the possibility of using these calibrated events from high to low latitudes facilitates correlations and should facilitate isotope event identification in a region with low temperature where calcareous plankton stratigraphies are in general restricted in general pleistocene southern high latitude calcareous nannofossil events show synchronism with those observed in warm and temperate surficial waters small discrepancies in the assigned ages are sometimes related to low sampling resolution due to low sedimentation rates the first occurrence fo of emiliania huxleyi and the last occurrence lo of pseudoemiliania lacunosa are observed in marine isotope stages mis 8 and 12 respectively a reversal in abundance between gephyrocapsa muellerae and e huxleyi is observed close to the mis 4 5 boundary mis 6 is characterised by an increase in g muellerae and mis 7 features a dramatic decrease in the proportion of gephyrocapsa caribbeanica this latter species began to increase its proportions from the mis 13 14 boundary to mis13 showing diachronism between the different sites the lo of reticulofenestra asanoi is observed at mis 22 confirming this event as a global synchronous reference datum by contrast the fo of r asanoi occurs at mis 35 and is diachronous with the existing data from other oceanic regions a re entry of medium sized gephyrocapsa 3 5 m maximum diameters can be identified in some cores close to mis 25 although the low abundance of this taxon prevents an accurate calibration it may be concluded that this event is diachronous as compared with the existing low latitude data the lo of large morphotypes of gephyrocapsa is well correlated with mis 37 showing synchronism with other oceanic regions whereas the fo of this species is not well calibrated due to the absence of age control points

earthquake source spectra in eastern north america source spectra for earthquakes of 3 m 7 in eastern north america ena are determined from regional seismograph recordings strong motion records teleseismic data and modified mercalli intensity data the inclusion of mmi data is made possible by the finding that the felt area of an earthquake is an accurate measure of its high frequency spectral level at the source current ground motion relations for ena are based on a brune source model with a stress parameter of 100 bars this model is a poor fit to ena source spectra for events of m 4 at high frequencies 5 to 10 hz observed spectral amplitudes are more nearly matched by a brune stress parameter of 200 bars intermediate frequency amplitudes near 1 hz are matched by a stress parameter of approximately 50 bars an empirical two corner source model is proposed to describe ena source spectra for events of 4 m 7

earthquake ground motion prediction equations for eastern north america new earthquake ground motion relations for hard rock and soil sites in eastern north america ena including estimates of their aleatory uncertainty vari ability have been developed based on a stochastic finite fault model the model incorporates new information obtained from ena seismographic data gathered over the past 10 years including three component broadband data that provide new in formation on ena source and path effects our new prediction equations are similar to the previous ground motion prediction equations of atkinson and boore 1995 which were based on a stochastic point source model the main difference is that high frequency amplitudes f 5 hz are less than previously predicted by about a factor of 1 6 within 100 km because of a slightly lower average stress parameter 140 bars versus 180 bars and a steeper near source attenuation at frequencies less than 5 hz the predicted ground motions from the new equations are generally within 25 of those predicted by atkinson and boore 1995 the prediction equations agree well with available ena ground motion data as evidenced by near zero average residuals within a factor of 1 2 for all frequencies and the lack of any significant residual trends with distance however there is a tendency to positive residuals for moderate events at high frequencies in the distance range from 30 to 100 km by as much as a factor of 2 this indicates epistemic uncertainty in the prediction model the positive residuals for moderate events at 100 km could be eliminated by an increased stress parameter at the cost of producing negative residuals in other magnitude distance ranges adjustment factors to the equations are provided that may be used to model this effect

model validations and comparisons of the next generation attenuation of ground motions nga west project abstract the earthquake ground motion prediction equations developed for the next generation attenuation of ground motions nga west project in 2008 have established a new baseline for the estimation of ground motion parameters such as peak ground acceleration peak ground velocity and spectral acceleration for shallow crustal earthquakes in active tectonic regions we perform statistical goodness of fit analyses to quantitatively compare the predictive capabilities of the nga models and their predecessors using several testing subsets of the master database used in model development in addition we perform a blind comparison test using 1060 ground motion records from seven recent earthquakes recorded in california the 2003 m 6 5 san simeon event 2004 m 6 0 parkfield event 2005 m 5 2 anza event 2007 m 5 4 alum rock event 2008 m 5 4 chino hills event 2010 m 7 2 baja event and 2010 m 5 7 ocotillo event we assess how modeling decisions regarding the regression dataset functional forms input parameters and model complexity influence the models predictive capabilities by comparing the performance of each model we discuss various ground motion modeling strategies and offer recommendations for model development we find that increased model complexity does not necessarily lead to increased prediction accuracy that the inclusion of aftershocks in regression datasets may result in decreased predictive capabilities for mainshocks and that the use of measured site characteristics leads to greatly improved ground motion predictions a model validation framework is introduced to assess the prediction accuracy of ground motion prediction equations and to aid in their future development

observations on regional variability in ground motion amplitudes for small to moderate earthquakes in north america abstract the regional variability in earthquake ground motion amplitudes for a given magnitude and distance in western north american environments was examined using shakemap data from small to moderate events the abundance of data for small to moderate events in california allows average ground motion levels as a function of magnitude and distance to be resolved with a high level of confidence ground motion amplitudes in northern california are lower on average than those for southern california for events of the same magnitude at distances in the range from 120 to 250 km over all frequencies the observed regional variations could be indicative of regional differences in attenuation effects or site effects an unexpected result of the study is the finding that ground motions for events of m m m m

region specific spatial cross correlation model for stochastic simulation of regionalized ground motion time histories stochastic simulation of spatially distributed ground motion time histor ies is important for performance based earthquake design of geographically distrib uted systems in this study we develop a novel technique to stochastically simulate regionalized ground motion time histories by taking account of the influence of regional site conditions for this purpose a transient acceleration time history is char acterized by wavelet packet parameters proposed by yamamoto and baker 2013 the wavelet packet parameters can fully characterize ground motion time histories in terms of energy content time frequency domain characteristics and time frequency nonstationarity this study further investigates the spatial cross correlations of wavelet packet parameters based on geostatistical analysis of 1500 regionalized ground motion data from eight well recorded earthquakes in california mexico japan and taiwan the linear model of coregionalization lmc is used to develop a permissible spatial cross correlation model for each parameter group the geostatistical analysis of ground motion data from different regions reveals significant dependence of the lmc structure on regional site conditions which can be characterized by the correlation range of vs30 in each region in general the spatial correlation and cross correlation of wavelet packet parameters are stronger if the site condition is more homogeneous the pro posed region specific correlation model improves stochastic simulation of spatially correlated ground motions as is demonstrated in illustrative examples in this article the developed method has great potential to be used in computationally based seismic analysis and loss estimation in a regional scale

late quaternary central mediterranean biochronology jorissen f j asioli a borsetti a m capotondi l de visser j p hilgen f j rohling e j van der borg k vergnaud grazzini c and zachariasse w j 1993 late quaternary central mediterranean biochronology mar micropaleontol 21 169 189 a high resolution biochronology is presented for the late quaternary of the central mediterranean in the late pleistocene holocene successions three assemblage zones are distinguished on the basis of frequency patterns of planktic foraminifera the age of these zones is determined by accelerator mass spectrometry ams t4c dating the zonal boundaries are dated at 12 700 yr b p the end of termination la and 9600 yr b p the start of termination ib respectively the ams dates show that major changes in the planktic and benthic realms occurred synchronously over wide areas although records of individual species may show important regional differences in the studied areas resedimentation processes revealed by anomalous successions of 14c dates play a far more important role than indicated by the sedimentological and micropaleontological data possibly these processes contribute to the very high accumulation rates in the glacial zone ill although the ams technique has increased the accuracy of lac measurements of older carbonate may still lead to substantial age differences between areas with different sedimentary regimes

testing the depths to 1 0 and 2 5 km s velocity isosurfaces in a velocity model for japan and implications for ground motion modeling

radiocarbon simulations for the glacial ocean the effects of wind stress southern ocean sea ice and heinrich events simulations of oceanic radiocarbon for the last glacial maximum are presented using a three dimensional global ocean circulation model forced with glacial background states according to various reconstructions we investigate the influence of sea surface temperatures sea ice margins wind stress and antarctic sea ice formation on the glacial tracer distribution and meridional overturning circulation the aim of these sensitivity studies is to reconcile available radiocarbon data from marine sediments with reconstructed sea surface temperatures and estimated sea ice production rates model runs with a modified freshwater balance in the southern ocean mimicking increased brine release due to enhanced divergence of antarctic sea ice arrive at radiocarbon values close to observations these experiments also yield abyssal temperatures and salinities which are consistent with recent inferences in the simulation with the best agreement with radiocarbon observations north atlantic deep water export is reduced by 40 compared to present day while antarctic bottom water flow is intensified to similar strength in the south atlantic transient simulations show that glacial freshwater discharge into the north atlantic can cause abrupt increases of atmospheric radiocarbon as observed during heinrich event 1 however the effect is only significant in scenarios with a massive short time discharge at the beginning which is followed by low level freshwater input for the rest of the event or if it is assumed that the meridional overturning circulation was already in a modern operational mode

testing the global applicability of ground motion prediction equations for active shallow crustal regions abstract large research initiatives such as the global earthquake model gem or the seismic hazard harmonization in europe share projects concentrate a great collaborative effort on defining a global standard for seismic hazard estimations in this context there is an increasing need for identifying ground motion prediction equations gmpes that can be applied at both global and regional scale with increasing amounts of strong motion records that are now available worldwide observational data can provide a valuable resource to tackle this question using the global dataset of allen and wald 2009 we evaluate the ability of 11 gmpes to predict ground motion in different active shallow crustal regions worldwide adopting the approach of scherbaum et al 2009 we rank these gmpes according to their likelihood of having generated the data in particular we estimate how strongly data support or reject the models with respect to the state of noninformativeness defined by a uniform weighting such rankings derived from this particular global dataset enable us to explore the potential of gmpes to predict ground motions in their host region and also in other regions depending on the magnitude and distance considered in the ranking process we particularly focus on the influence of the distribution of the testing dataset compared with the gmpe s native dataset one of the results of this study is that some nonindigenous models present a high degree of consistency with the data from a target region two models in particular demonstrated a strong power of geographically wide applicability in different geographic regions with respect to the testing dataset the models of akkar and bommer 2010 and chiou et al 2010

shock experiments on pre heated α and β quartz ii x ray and tem investigations quartz single crystals pre heated to different temperatures 20 275 540 and 630 c were experimentally shocked to pressures ranging from 20 to 40 gpa with the shock front propagating parallel to 1010 or 0001 shocked quartz pre heated to 630 c is nearly x ray amorphous at 26 gpa while quartz shocked at room temperature still displays several x ray diffraction lines up to 30 gpa all samples that were still crystalline when shocked above 25 gpa exhibit lattice expansion internal strain and reduced crystallite sizes lattice expansion was up to 1 for the constants a o and co and up to 3 for the cell volume v o quartz shocked parallel to 1010 always shows larger lattice constants and is more strained than quartz shocked parallel to 0001 indicating that shock effects are controlled by the structural anisotropy internal strain is anisotropic with minimum strain in the planes belonging to 1012 the dominant shock defect revealed by tem are sets of parallel lamellae consisting of pure sio 2 glass so called planar deformation features pdfs below 25 gpa pdfs are extremely rare and thin 30 nm at pressures above 25 gpa however pdfs occur frequently and are about ten times thicker this qualitative observation of increasing pdf frequency and thickness with increasing pressure is quantified by calculations of the amount of glass using x ray and density data the results of this study substantiate the crucial role of pdfs for the lattice expansion of quartz and the formation of diaplectic glass and lechatelierite lattice expansion is ascribed to the enormous expansion of pdfs during decompression leading to elastic stretching in adjacent crystalline areas the observation that pdfs occur predominantly parallel to 1012 where minimum strain is present supports this hypothesis the increasing amount of pdfs above 25 gpa is interpreted as the cause for the formation of diaplectic glass shock temperature calculations support the assumption that these pdfs consist under compression of superheated melt the heat is possibly sufficient to melt crystalline areas adjacent to the superheated pdfs at enhanced pressures such molten bands coalesce to a total melt which is quenched upon decompression thus diaplectic glass represents a quenched high pressure melt while lechatelierite sio 2 glass with a fluidal texture is interpreted as quenched low pressure melt

an evaluation of the applicability of nga west2 ground motion models for japan and new zealandan evaluation of the applicability of nga west2 gmms for japan and new zealand

u pb isotopic dating of titanite microstructures potential implications for the chronology and identification of large impact structures identifying and dating large impact structures is challenging as many of the traditional shock indicator phases can be modified by post impact processes refractory accessory phases such as zircon while faithful recorders of shock wave passage commonly respond with partial u pb age resetting during impact events titanite is an accessory phase with lower pb closure temperature than many other robust chronometers but its potential as indicator and chronometer of impact related processes remains poorly constrained in this study we examined titanite grains from the sudbury ontario canada and vredefort south africa impact structures combining quantitative microstructural and u pb dating techniques titanite grains from both craters host planar microstructures and microtwins that show a common twin host disorientation relationship of 74 about in the vredefort impact structure the microtwins deformed internally and developed high and low angle grain boundaries that resulted in the growth of neoblastic crystallites u pb isotopic dating of magmatic titanite grains with deformation microtwins from the sudbury impact structure yielded a 207pb 206pb age of 1851 12 ma that records either the shock heating or the crater modification stage of the impact event the titanite grains from the vredefort impact structure yielded primarily pre impact ages recording the cooling of the ultra high temperature ventersdorp event but domains with microtwins or planar microstructures show evidence of u pb isotopic disturbance despite that the identified microtwins are not diagnostic of shock metamorphic processes our contribution demonstrates that titanite has great potential to inform studies of the terrestrial impact crater record

pleistocene calcareous nannofossil stratigraphy for odp leg 177 atlantic sector of the southern ocean abstract seven ocean drilling program odp sites recovered during odp leg 177 in the atlantic sector of the southern ocean were analyzed to study the pleistocene calcareous nannofossil record calcareous nannofossil events previously described from intermediate and low latitudes were identified and calibrated with available geomagnetic and stable isotope stratigraphic data in general pleistocene southern high latitude calcareous nannofossil events show synchronicity with those observed from warm and temperate latitudes the first occurrence fo of emiliania huxleyi and the last occurrence lo of pseudoemiliania lacunosa are observed in marine isotope stages mis 8 and 12 respectively a reversal in abundance between gephyrocapsa muellerae and e huxleyi is observed at mis 5 mis 6 is characterized by an increase in g muellerae and mis 7 features a dramatic decrease in the proportion of gephyrocapsa caribbeanica this latter species began to increase its proportions from mis 14 to 13 the lo of reticulofenestra asanoi is observed within subchron c1r 1r and the fo of r asanoi occurs at the top of c1r 2r a re entry of medium sized gephyrocapsa can be identified in some cores during subchron c1r 1n the lo of large morphotypes of gephyrocapsa is well correlated through the studied area and occurs during the middle low part of subchron c1r 2r synchronous with other oceanic regions the fo of calcidiscus macintyrei and fo of medium sized gephyrocapsa occur in the studied area close to 1 6 ma

a paleoecological and paleobiogeographic evaluation of helicosphaera inversa gartner theodoridis and the diachrony of its first occurrence abstract the distribution pattern of helicosphaera inversa gartner theodoridis is examined from a mid latitude north atlantic core md01 2446 and two mediterranean cores ocean drilling program odp site 975 and core kc01b through marine isotope stage mis 13 to 9 the earliest rare occurrences are observed from the uppermost part of mis 12 while common and continuous abundances characterize mis 11 the paleoenvironmental framework of the study cores suggests that the taxon thrived in warm surface waters correlation with new data from planktonic foraminifera also suggests that h inversa may have only flourished within a limited salinity range comparison with previous findings highlights major diachrony in the fo of the taxon between low and mid latitude records it first occurred at lower latitude in the pacific as early as 0 8 ma while in the mid latitude north atlantic regions it is not recorded before 0 51 ma the distribution of the taxon in the north atlantic ocean also apparently varies in relation with surface water masses and hydrographic fronts the results suggest that the fo of h inversa is ecologically controlled and needs to be used with caution in worldwide stratigraphic correlation nevertheless the distribution of the species within the mediterranean basin can produce an invaluable ecostratigraphical signal

intra event spatial correlations for cumulative absolute velocity arias intensity and spectral accelerations based on regional site conditions abstract spatial correlations of ground motion intensity measures ims are essential for seismic analysis of spatially distributed systems in this paper geostatistical analysis is conducted to calculate the spatial correlations for cumulative absolute velocity cav arias intensity ia and spectral accelerations sa using a total number of more than 1500 earthquake records from nine recent earthquakes occurred in taiwan california and japan the results indicate that the spatial correlations for these ims are closely related to the regional site conditions and they can be predicted based on the spatial correlations of shear wave velocity in the top 30 m v s 30 in general an im recorded from a relatively homogeneous regional site condition tends to have a larger spatial correlation range than that from a heterogeneous site condition due to their intrinsic similarity to represent the integration of acceleration time histories cav and ia have similar spatial correlation coefficients besides the range of spatial correlation of sa generally increases as the spectral period increases simple predictive equations are proposed in this study to quantify the spatial correlations of cav ia and sa based on regional site conditions methods for data correction are also proposed to eliminate artificial correlations due to biased distance scaling and v s 30 estimation in the database finally monte carlo method is used to generate spatially distributed ims the results demonstrate that the annual frequency of exceedance curves for spatially distributed ims differ significantly if different ranges of spatial correlations are used

radiocarbon calibration curve spanning 0 to 50 000 years bp based on paired 230 th 234 u 238 u and 14 c dates on pristine corals abstract radiocarbon dating is the most widely used dating technique in the world recent advances in accelerator mass spectrometry ams and sample preparation techniques have reduced the sample size requirements by a factor of 1000 and decreased the measurement time from weeks to minutes today it is estimated that more than 90 percent of all measurements made on accelerator mass spectrometers are for radiocarbon age dates the production of 14 c in the atmosphere varies through time due to changes in the earth s geomagnetic field intensity and in its concentration which is regulated by the carbon cycle as a result of these two variables a radiocarbon age is not equivalent to a calendar age four decades of joint research by the dendrochronology and radiocarbon communities have produced a radiocarbon calibration data set of remarkable precision and accuracy extending from the present to approximately 12 000 calendar years before present this paper presents high precision paired 230 th 234 u 238 u and 14 c age determinations on pristine coral samples that enable us to extend the radiocarbon calibration curve from 12 000 to 50 000 years before present we developed a statistical model to properly estimate sample age conversion from radiocarbon years to calendar years taking full account of combined errors in input ages and calibration uncertainties our radiocarbon calibration program is publicly accessible at http www radiocarbon ldeo columbia edu along with full documentation of the samples data and our statistical calibration model

spectral scaling of the 1985 to 1988 nahanni northwest territories earthquakes abstract the sequence of earthquakes that began in october 1985 near the nahanni river northwest territories canada provides an exceptional opportunity to study the variation with magnitude of the source spectra from intraplate earthquakes we study the spectral scaling for the seven largest events using p waves recorded at stations of the western canada telemetred network wctn the eastern canada telemetred network ectn and the global digital seismograph network gdsn these earthquakes range in size from m 4 8 to m 6 8 we compare predictions from various source scaling models with observed spectral ratios and source acceleration spectra for the suite of events the spectral ratios show a strong azimuthal dependence which is probably due to differences in the focal mechanisms or rupture characteristics of the events taking the average of the ratios from individual gdsn stations as the best representation of the spectral ratios an squared model with a constant stress parameter or one that increases slightly with moment magnitude gives a simultaneous fit to both the spectral ratios and to the absolute spectra the high frequency spectral levels by themselves imply a somewhat stronger dependence of the stress parameter on moment than found from fitting the overall spectra the stress parameters for the scaling laws are less than 35 bars for earthquakes as large as m 7 recently proposed scaling laws in which the corner frequency is proportional to the inverse quarter root of seismic moment for an squared model are not consistent with the data and neither are cubed models the spectral scaling for the sequence of nahanni earthquakes may not be representative of intraplate magnitude scaling in general since there is some evidence that aftershocks do not exhibit the same scaling as main shocks the high frequency spectral levels of the aftershocks of both the nahanni and the 9 january 1989 miramichi new brunswick earthquakes imply stress parameters that increase with magnitude by contrast the spectral levels for a series of main shocks in eastern north america show less magnitude dependence of the stress and generally higher stress levels when compared to aftershocks of the same magnitude

new shock microstructures in titanite catisio5 from the peak ring of the chicxulub impact structure mexico accessory mineral geochronometers such as apatite baddeleyite monazite xenotime and zircon are increasingly being recognized for their ability to preserve diagnostic microstructural evidence of hypervelocity impact processes to date little is known about the response of titanite to shock metamorphism even though it is a widespread accessory phase and a u pb geochronometer here we report two new mechanical twin modes in titanite within shocked granitoid from the chicxulub impact structure mexico titanite grains in the newly acquired core from the international ocean discovery program hole m0077a preserve multiple sets of polysynthetic twins most commonly with composition planes k1 1 11 and shear direction 1 and less commonly with the mode k1 130 1 in some grains 130 deformation bands have formed concurrently with the deformation twins indicating dislocation slip with burgers vector b can be active during impact metamorphism titanite twins in the modes described here have not been reported from endogenically deformed rocks we therefore propose this newly identified twin form as a result of shock deformation formation conditions of the twins have not been experimentally calibrated and are here empirically constrained by the presence of planar deformation features in quartz 12 5 and 17 5 gpa and the absence of shock twins in zircon 20 gpa while the lower threshold of titanite twin formation remains poorly constrained identification of these twins highlight the utility of titanite as a shock indicator over the pressure range between 12 and 17 gpa given the challenges to find diagnostic indicators of shock metamorphism to identify both ancient and recent impact evidence on earth microstructural analysis of titanite is here demonstrated to provide a new tool for recognizing impact deformation in rocks where other impact evidence may be erased altered or did not manifest due to generally low 20 gpa shock pressure