biomarkers in lake van sediments reveal dry conditions in eastern anatolia during 110 000 10 000 years b p lipid biomarkers were analyzed in lake van sediments covering the last 600 ka with a focus on the period between 110 and 10 ka when a broad maximum in pore water salinity as a relict from the past suggests dry conditions the occurrence and distribution of biomarkers indicative for terrestrial plants long chain n alkane c29 haptophyte algae methyl alkenones c37 and halophilic archaea archaeol all point toward a dry climate in lake van region during this time interval the hydrogen isotopic composition of c29 n alkanes dc29 and c37 alkenones dc37 is enriched between mis 4 and mis 2 which is interpreted as a decrease in the regional ratio of precipitation to evaporation similarly the low abundance of the acyclic glycerol dialkyl glycerol tetraether gdgt 0 relative to archaeol quantified by the archaeol and caldarchaeol ecometric ace is assumed to reflect the presence of halophilic euryarchaeota adapted to high salinity water the climate around lake van appears in phase with the yammouneh basin 800 km southwest and lake urmia 250 km southeast of lake van over the last two glacial periods the results highlight the potential of combining ace dc29 and dc37 for reconstructing salinity changes and regional precipitation to evaporation ratio from lake sediments

slip distribution of the february 27 2010 mw 8 8 maule earthquake central chile from static and high rate gps insar and broadband teleseismic data 1 the shallow depth underthrust earthquake of february 27 2010 mw 8 8 ruptured the subduction plate interface in central chile between 34 s and 38 s we retrieve the spatial and temporal distribution of slip during this mega earthquake through a joint inversion of teleseismic records insar and high rate gps hrgps data additionally our model is shown to agree with broadband surface waves rupture initiated at about 32 km depth and propagated bilaterally resulting in two main slip zones located ssw and nne of the hypocenter nucleation did not take place within or at the edge of one of these main asperities but in between during the first 30s slip propagated predominantly southwards later on the rupture evolved more slowly and more symmetrically eventually the northern asperity became predominant with maximum slip reaching about 20 m most of the seismic moment was released within 110s a relatively short time explained by the bilateral propagation the overall average rupture velocity is 2 6 km s but propagation occurred initially faster towards the south 3 2 km s large slip did not reach the trench a result consistent with the moderate size of the tsunami down dip rupture stopped at about 50 km depth in agreement with the lower limit of the locked zone inferred by ruegg et al 2009 from pre seismic gps data

surface wave tomography from microseisms in southern california received 5 april 2005 revised 23 may 2005 accepted 9 june 2005 published 26 july 2005 1 since it has already been demonstrated that point topoint seismic propagation green functions can be extracted from seismic noise it should be possible to image earth structure using the ambient noise field seismic noise data from 148 broadband seismic stations in southern california were used to extract the surface wave arrival times between all station pairs in the network the seismic data were then used in a simple but densely sampled tomographic procedure to estimate the surface wave velocity structure within the frequency range of 0 1 0 2 hz for a region in southern california the result compares favorably with previous estimates obtained using more conventional and elaborate inversion procedures this demonstrates that coherent noise field between station pairs can be used for seismic imaging purposes citation sabra k g p gerstoft p roux w a kuperman and m c fehler 2005 surface wave tomography from microseisms in southern california geophys res lett 32 l14311 doi 10 1029 2005gl023155

detection classification and location of seismovolcanic signals with multi component seismic data example from the piton de la fournaise volcano la reunion france we apply three different methods based on the analysis of the multi component seismic data to detect seismovolcanic tremors and other seismovolcanic signals to propose an approach to classify them and to locate their sources we use continuous seismograms recorded during one year by 21 stations at the piton de la fournaise volcano la r eunion france the first method allows to detect seismovolcanic signals based on stability in time of the inter components cross correlations function two other methods based on the simultaneous analysis of the whole network can be used to detect seismovolcanic signals and to locate their sources in the first network based method the seismic wave field is analyzed by calculating the width of the network covariance matrix eigenvalue distribution the second network based method consists in performing the 3d back projection of the inter stations cross correlations in order to calculate the network response function simultaneous analysis of the parameters measured by the three different methodscan be used to classify different types of seismovolcanic tremors our results demonstrate that all three methods efficiently detect seismovolcanic tremors accompanying the 2010 eruptions and the preceding pre eruptive seismic swarms furthermore methods 2 and 3 based on simultaneous analysis of the whole network detect a large number of volcanic earthquakes our location results show that each seismovolcanic tremor is located in a distinct region of the volcano close to the eruptive site at a shallow depth and the pre ceding seismic crisis is located deeper at about the sea level under the summit crater

reflection of scandinavian ice sheet fluctuations in norwegian sea sediments during the past 150 000 years the record of glacier fluctuations in western scandinavia as reconstructed from continental data has been correlated with records of ice rafted detritus ird from well dated sediment cores from the norwegian sea covering the past 150 000 yr b p the input of ird into the ocean is used as a proxy for ice sheet advances onto the shelf and thus for the calibration of a glaciation curve the marine results generally support land based reconstructions of glacier fluctuations and improve the time control on glacial advances the saalian ice sheet decayed very rapidly approximately 125 000 yr b p in the early weichselian a minor but significant ird maximum indicates the presence of icebergs in isotope substage 5b especially between 95 000 and 83 000 yr b p reduced amounts of calcareous nannofossils indicate that surface waters were influenced by meltwater discharges during isotope substages 5d and 5b an extensive build up of inland ice began again during isotope stage 4 but maximum glaciation was reached only in early stage 3 58 000 53 000 yr b p marine sediments have minimum carbonate content indicating strong dilution by lithogenic ice rafted material generally the ird accumulation rate was considerably higher in stages 4 2 than in stage 5 a marked peak in ird accumulation rates from 47 000 to 43 000 yr b p correlates well with a second middle weichselian ice sheet advance dated by the laschamp olby paleomagnetic event minimum ice extent during the alesund interstade 38 500 32 500 yr b p and several glacial oscillations during the late weichselian are also seen in the ird record of several late weichselian glacial oscillations on the shelf at least four correspond to the north atlantic heinrich events ice sheet behavior was either coupled or linked by external forcing during these events whereas internal ice sheet mechanisms may account for the noncoherent fluctuations

spatial coherence of the seismic wavefield continuously recorded by the usarray we use a method based on the array covariance matrix eigenvalues to study the level of spatial coherence and of isotropy of the seismic wavefield continuously recorded during 2010 by the usarray first we observe that the raw data is often dominated by local sources to remove their influence we apply spectral and temporal normalizations to the input signals we notice that this widely used pre processing in ambient noise seismology does not fully homogenize the seismic wavefield and that some strongly coherent arrivals persist among these persistent signals generated by teleseismic sources we detect 1 seismic waves emitted by strong earthquakes 2 a nearly continuous quasi monochromatic signal at 26 seconds period and 3 multi day coherent wave trends in the spectral band of oceanic microseisms 0 07 0 2 hz for the latter beamforming analysis shows that while most of the signals are composed of surface waves some are dominated by body waves likely generated in the deep ocean

pre processing ambient noise cross correlations with equalizing the covariance matrix eigenspectrum passive imaging techniques from ambient seismic noise requires a nearly isotropic distribution of the noise sources in order to ensure reliable traveltime measurements between seismic stations however real ambient seismic noise often partially fulfils this condition it is generated in preferential areas in deep ocean or near continental shores and some highly coherent pulse like signals may be present in the data such as those generated by earthquakes several pre processing techniques have been developed in order to attenuate the directional and deterministic behaviour of this real ambient noise most of them are applied to individual seismograms before cross correlation computation the most widely used techniques are the spectral whitening and temporal smoothing of the individual seismic traces we here propose an additional pre processing to be used together with the classical ones which is based on the spatial analysis of the seismic wavefield we compute the cross spectra between all available stations pairs in spectral domain leading to the data covariance matrix we apply a one bit normalization to the covariance matrix eigenspectrum before extracting the cross correlations in the time domain the efficiency of the method is shown with several numerical tests we apply the method to the data collected by the usarray when the m8 8 maule earthquake occurred on 2010 february 27 the method shows a clear improvement compared with the classical equalization to attenuate the highly energetic and coherent waves incoming from the earthquake and allows to perform reliable traveltime measurement even in the presence of the earthquake

linear iterative refinement method for the rapid simulation of borehole nuclear measurements part 2 high angle and horizontal wells based on previous research we developed and successfully tested a new linear iterative refinement method to rapidly simulate borehole nuclear measurements acquired in vertical wells the approximation considers 2d spatial properties of monte carlo derived flux sensitivity functions fsfs to simulate neutron and density measurements based on new research we implemented the linear iterative refinement method with explicit 3d spatial properties of fsfs to approximate nuclear borehole measurements acquired in high angle and horizontal ha hz wells we used generic neutron and density tools that are close to commercial tool designs to construct 3d fsfs in the proximity of a bed boundary between layers of contrasting petrophysical properties likewise to benchmark the approximation we consider adjacent layers of 5 and 30 porosity water saturated sandstone for the case of neutron measurements variations of azimuthal geometric factors are as large as 20 and 57 for the near and far detectors respecti

vegetation and environmental changes during the last interglacial in eastern anatolia turkey a new high resolution pollen record from lake van a high resolution multi proxy record from lake van eastern anatolia derived from a lacustrine sequence cored at the 357 m deep ahlat ridge ar allows a comprehensive view of paleoclimate and environmental history in the continental near east during the last interglacial li we combined paleovegetation pollen stable oxygen isotope delta o 18 bulk and xrf data from the same sedimentary sequence showing distinct variations during the period from 135 to 110 ka ago leading into and out of full interglacial conditions the last interglacial plateau as defined by the presence of thermophilous steppe forest communities lasted ca 13 5 ka from similar to 129 1 115 6 ka bp the detailed palynological sequence at lake van documents a vegetation succession with several climatic phases i the pistacia zone ca 131 2 129 1 ka bp indicates summer dryness and mild winter conditions during the initial warming ii the quercus ulmus zone ca 129 1 1272 ka bp occurred during warm and humid climate conditions with enhanced evaporation iii the carpinus zone ca 1272 124 1 ka bp suggest increasingly cooler and wetter conditions and iv the expansion of pinus at similar to 124 1 ka bp marks the onset of a colder drier environment that extended into the interval of global ice growth pollen data suggest migration of thermophilous trees from refugial areas at the beginning of the last interglacial analogous to the current interglacial the migration documents a time lag between the onset of climatic amelioration and the establishment of an oak steppe forest spanning 2 1 ka hence the major difference between the last interglacial compared to the current interglacial holocene is the abundance of pinus as well as the decrease of deciduous broad leaved trees indicating higher continentality during the last interglacial finally our results demonstrate intra interglacial variability in the low mid latitudes and suggest a close connection with the high frequency climate variability recorded in greenland ice cores c 2015 elsevier b v all rights reserved

abrupt temperature changes in the western mediterranean over the past 250 000 years a continuous high resolution western mediterranean sea surface temperature sst alkenone record spanning the past 250 000 years shows that abrupt changes were more common at warming than at cooling during marine isotope stage mis 6 sst oscillated following a stadial interstadial pattern but at lower intensities and rates of change than in the dansgaard oeschger events of mis 3 some of the most prominent events occurred over miss 5 and 7 after prolonged warm periods of high stability climate during the whole period was predominantly maintained in interglacial interstadial conditions whereas the duration of stadials was much shorter

coseismic slip distribution of the february 27 2010 mw 8 8 maule chile earthquake 1 static offsets produced by the february 27 2010 mw 8 8 maule chile earthquake as measured by gps and insar constrain coseismic slip along a section of the andean megathrust of dimensions 650 km in length 180 km in width gps data have been collected from both campaign and continuous sites sampling both the near field and far field alos palsar data from several ascending and descending tracks constrain the near field crustal deformation inversions of the geodetic data for distributed slip on the megathrust reveal a pronounced slip maximum of order 15 m at 15 25 km depth on the megathrust offshore lloca indicating that seismic slip was greatest north of the epicenter of the bilaterally propagating rupture a secondary slip maximum appears at depth 25 km on the megathrust just west of concepcion coseismic slip is negligible below 35 km depth estimates of the seismic moment based on different datasets and modeling approaches vary from 1 8 to 2 6 1022 n m our study is the first to model the static displacement field using a layered spherical earth model allowing us to incorporate both near field and far field static displacements in a consistent manner the obtained seismic moment of 1 97 1022 n m corresponding to a moment magnitude of 8 8 is similar to that obtained by previous seismic and geodetic inversions

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

high resolution 3d shallow crustal structure in long beach california application of ambient noise tomography on a dense seismic array ambient noise tomography has proven to be effective in resolving shallow earth structure we applied ambient noise tomography on a dense seismic array in long beach california the array was composed of more than 5200 stations with an average spacing close to 100 m three weeks of passive ambient noise were crosscorrelated between each station pair which resulted in more than 13 5 million crosscorrelations within the area clear fundamental mode rayleigh waves were observed between 0 5 and 4 hz which were most sensitive to structure above 1 km depth for each station pair we applied frequency time analysis to determine the phase traveltime dispersion and for each frequency we applied eikonal tomography to determine the rayleigh wave phase velocity map the eikonal tomography accounted for ray bending by tracking the wavefront and allowed uncertainties to be estimated through statistical analysis the compilation of phase velocity maps was then used to invert for 3d shear velocity structure the inverted model showed clear correlation with the known geologic features such as the shallow south north velocity dichotomy and a deeper fast anomaly associated with the newport inglewood fault zone our results can potentially be used to complement traditional active source studies

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

depth migration of seismovolcanic tremor sources below the klyuchevskoy volcanic group kamchatka determined from a network based analysis we present a method for automatic location of dominant sources of seismovolcanic tremor in 3 d based on the spatial coherence of the continuously recorded wavefield at a seismic network we analyze 4 5 years of records from the seismic network at the klyuchevskoy volcanic group in kamchatka russia when four volcanoes experienced tremor episodes after enhancing the tremor signal with spectral whitening we compute the daily cross correlation functions related to the dominant tremor sources from the first eigenvector of the spectral covariance matrix and infer their daily positions in 3 d we apply our technique to the tremors beneath shiveluch klyuchevskoy tolbachik and kizimen volcanoes and observe the yearlong preeruptive volcanic tremor beneath klyuchevskoy from deep to shallow parts of the plumbing system this observation of deep volcanic tremor sources demonstrates that the cross correlation based method is a very powerful tool for volcano monitoring

spectral structure in the earth s microseismic background between 20 and 40 seconds the long term behavior of a narrow band peak near 26 sec in the microseismic background of the earth has been studied over many years at several sites the amplitude of this peak has been determined to be a function of the earth s weather seasons it is larger during the southern hemisphere winter in addition the microseismic background between 20 and 40 sec has been scanned for peaks in the spectra three more lower level peaks have been identified with the possible presence of more

changing surface water conditions for the last 500 ka in the southeast atlantic implications for variable influences of agulhas leakage and benguela upwelling the southeast atlantic ocean is an important component of global ocean circulation as it includes heat and salt transfer into the atlantic through the agulhas leakage as well as the highly productive benguela upwelling system here we reconstruct sea surface temperatures ssts from ocean drilling program odp site 1087 in the southeast atlantic to investigate surface ocean circulation patterns during the late pleistocene 0 500 ka the uk 37 index and dinoflagellate cyst assemblages are used to reconstruct ssts dalkenone is used to reconstruct changes in sea surface salinity and mass accumulation rates of alkenones and chlorine pigments are quantified to detect changing marine export productivity the greatest amplitude of sst warming precedes decreases in benthic 18o and therefore occurs early in the transition from glacials to interglacials the dalkenone as a salinity indicator increases before ssts suggesting that the pattern of agulhas leakage is more complex than suggested by sst proxies marine isotope stage mis 10 shows an anomalous pattern it is marked by a pronounced increase in chlorine concentration which may be related to enhanced expanded benguela upwelling reaching the core site we find no evidence of an absence of agulhas leakage throughout the record suggesting that there is no agulhas cutoff even during mis 10 finally the odp site 1087 record shows an increasing strength of agulhas leakage towards the present day which may have impacted the intensity of the atlantic meridional overturning circulation as a result the new analyses from odp site 1087 demonstrate a complex interaction between influences of the benguela upwelling and the agulhas leakage through the late pleistocene which are inferred here to reflect changing circulation patterns in the southern ocean and in the atmosphere