new evidence of a herd of titanosauriform sauropods from the lower berriasian of the iberian range spain abstract a study of the undescribed part of the las cerradicas tracksite in galve teruel spain has revealed 6 trackways made by small sauropods showing gregarious behaviour parallel trackways las cerradicas is located towards the top of the villar del arzobispo formation early berriasian the wide gauge condition the manus pes distance the kidney shaped morphology of the manus and the subtriangular morphology of the pes with a big digit i that swells medially and a narrow heel oriented posterolaterally suggest that the sauropods in question are more similar to sauropodichnus giganteus than to any other sauropod ichnotaxa some of the features point to the titanosauriforms as the best candidates to be the trackmakers recent work in bone histology the differences with respect to other iberian tracksites of similar age and the differences with respect to other sauropod herds of the track record do not allow us to establish whether the sauropods were juvenile or dwarfs the sauropod skeletal record and other large sauropod footprints in the villar del arzobispo formation could tip the scales in favour of the first hypothesis

internal structure of the san jacinto fault zone in the trifurcation area southeast of anza california from data of dense seismic arrays we image the internal structure of the san jacinto fault zone sjfz in the trifurcation area southeast of anza california with seismic records from dense linear and rectangular arrays the examined data include recordings from more than 20 000 local earthquakes and nine teleseismic events automatic detection algorithms and visual inspection are used to identify p and s body waves along with p and s types fault zone trapped waves fztw the location at depth of the main branch of the sjfz the clark fault is identified from systematic waveform changes across lines of sensors within the dense rectangular array delay times of p arrivals from teleseismic and local events indicate damage asymmetry across the fault with higher damage to the ne producing a local reversal of the velocity contrast in the shallow crust with respect to the large scale structure a portion of the damage zone between the main fault and a second mapped surface trace to the ne generates p and s types fztw inversions of high quality s type fztw indicate that the most likely parameters of the trapping structure are width of 70 m s wave velocity reduction of 60 per cent q value of 60 and depth of 2 km the local reversal of the shallow velocity contrast across the fault with respect to large scale structure is consistent with preferred propagation of earthquake ruptures in the area to the nw

a comparison of spectral parameter kappa from small and moderate earthquakes using southern california anza seismic network data kappa is a one parameter estimator of the spectral amplitude decay with frequency of a seismogram low values 5 ms indicate limited attenuation of high frequency energy whereas higher values 40 ms indicate high frequency energy has been removed kappa is often assumed to be a site term and used in seismic designs we address two key questions about kappa 1 how to identify source path and site contributions to kappa and 2 can kappa estimates from smaller earthquakes and more readily accessible weak motion recordings be reasonably extrapolated to esti mate kappa of larger earthquakes the use of small earthquakes ml 3 5 earthquakes inside the network we find kappa from small earthquakes predicts the relative values of kappa for larger earthquakes e g measurements at stations pfo and knw are small compared with those at stations tro and snd for the snd and tro data however kappa values from small earth quakes overpredict those from moderate and large earthquakes site effects are the most important contributor to kappa estimates but the scatter within kappa measure ments at a given station is likely caused by a significant contribution from near the source perhaps related to near source scattering because of this source side varia bility care is recommended in using individual small events as green s functions to study source time effects of moderate and large events

an iberian stegosaurs paradise the villar del arzobispo formation tithonian berriasian in teruel spain since 2002 a number of sites containing stegosaurian remains bones and tracks have been discovered in the villar del arzobispo formation tithonian berriasian in the province of teruel spain mostly in the areas of el castellar and riodeva the material from the latter consists of the postcranial remains of the axial pelvic and appendicular skeleton of several different sized specimens related to the genus dacentrurus the footprints made by a stegosaurian at el castellar site reflect a new type of medium gauge trackway deltapodus ibericus isp nov the presence of these tracks near abundant bones related to dacentrurus highlights this geological formation as a window through which to examine the systematics behaviour and palaeoecology of these thyreophoran dinosaurs since these fossil bones were discovered next to those of other sauropods and ornithopods turiasaurus and ornithopoda indet where there has been virtually no transport of the remains and since stegosaurian tracks have been found in ichnoassociations with the same groups they may have coexisted in the wetlands of restricted tidal environments during the tithonian berriasian the presence of common or at least phylogenetically closely related taxa and ichnotaxa in western europe north america and africa indicates that sea level fall episodes may have occurred during which the fauna of each area may have reached the emerged regions of the others during the late jurassic

frequency dependent seismic attenuation in the eastern united states as observed from the 2011 central virginia earthquake and aftershock sequence abstract ground shaking due to earthquakes in the eastern united states eus is felt at significantly greater distances than in the western united states wus and for some earthquakes it has been shown to display a strong preferential direction shaking intensity variation can be due to propagation path effects source directivity and or site amplification in this paper we use s and lg waves recorded from the 2011 central virginia earthquake and aftershock sequence in the central virginia seismic zone to quantify attenuation as frequency dependent q f in support of observations based on shaking intensity we observe high q values in the eus relative to previous studies in the wus with especially efficient propagation along the structural trend of the appalachian mountains our analysis of q f quantifies the path effects of the northeast trending felt distribution previously inferred from the u s geological survey usgs did you feel it data historic intensity data and the asymmetrical distribution of rockfalls and landslides

ground motion prediction equations in the san jacinto fault zone significant effects of rupture directivity and fault zone amplification we present a new set of ground motion prediction equations gmpes for horizontal peak ground acceleration peak ground velocity and 5 damped pseudo spectral acceleration psa developed for the san jacinto fault zone sjfz area besides using these equations to quantify seismic shaking in the area the results allow us to examine the physics and local properties controlling the observed ground motions the analyzed dataset includes 30 000 observations from 800 events spanning a magnitude range of 1 5 m 6 0 and recorded by up to 140 stations at epicentral distances ranging from essentially zero to 150 km the local gmpe is developed for the sjfz by applying classical regression techniques with predictive variables that include first distance and magnitude and then site characteristics rupture directivity and fault zone amplification the significance of these effects is determined by measuring the uncertainty reduction of the gmpe due to each factor the results show that in contrast to many regional studies traditional site characteristic has a relatively minor effect on peak amplitudes in our study area however rupture directivity is a significant factor controlling the amplitudes of ground motion even for small events the dense seismic network and newly developed directivity tool enable us to extract efficiently directivity effects with statistical significance using the ground motion dataset during the regression analysis process the obtained rupture directivities are consistent with the main focal mechanism orientations and surface trace orientations known from other studies and predictions for bimaterial ruptures in the trifurcation area of the sjfz fault zone amplification is a second important factor showing strong impact on the peak ground motion values with increasing role for the lower frequency range 10 hz examined in the 5 damped psa values we also observe signatures of large amplitude variances which indicate additional source related control on the distribution of amplitudes besides rupture directivity for aftershocks close in time and location to the m l 5 1 earthquake of march 2013 using the full set of records we present the most complete set of gmpes for the sjfz area including a higher amplitude prediction for regions in the direction of rupture

the late mis 5 mediterranean tephra markers a reappraisal from peninsular italy terrestrial records abstract we present new tephrostratigraphic records from the late mis 5 ca 110 80 ka terrestrial sediments from southern and central italy on the one hand the central italy record consists of an outcropping lacustrine sequence from the sulmona intermountain basin that contains four trachytic phonolitic tephra layers pop3 pop2a pop2b pop1 all of which show a k alkaline affinity that is typical for the roman co magmatic province the pop3 and pop1 layers were dated by 40 ar 39 ar method at 106 2 1 3 ka 2 and 92 4 4 6 ka 2 respectively the sequence in southern italy on the other hand is represented by post tyrrhenian coastal deposits of the cilento area campania which contain two trachytic layers cil2 cil1 that show the same k alkaline affinity based on their chemical compositions and radiometric ages pop3 and pop1 are firmly correlated with the marine tephra layers x 5 105 2 ka and c 22 ca 90 ka which in turn match tephras tm 25 and tm 23 11 respectively in the lacustrine sequence of lago grande di monticchio southern italy of note the pop1 layer also matches the adriatic sea tephra prad 2517 that was previously correlated with the older x 5 layer the tephra couplet pop2a and pop2b ca 103 and 103 5 ka extrapolated ages are compatible with the tm 24b and tm 24 3 tephras in monticchio which match both the stratigraphic positions and the chemical compositions in the cilento area as well as the already described x 6 layer ca 108 ka cil2 we recognise a new stratigraphic superimposed layer cil1 that matches the pop3 tm 25 c 27 x 5 mediterranean marker s in summary the data presented here provide new chemical and 40 ar 39 ar chronological constraints towards a robust late mis 5 tephrostratigraphy of the central mediterranean although at the same time they also reveal how the tephrostratigraphy itself might be flawed when dealing with tephra markers that are not adequately constrained and characterised

stress drop estimates of potentially induced earthquakes in the guy greenbrier sequence we calculate corner frequencies and stress drops for 25 potentially induced earthquakes mw 2 17 2 57 in the guy greenbrier sequence in the central arkansas we use the spectral ratio method employing highly similar earthquakes as empirical green s functions egfs we show that multiple egfs give consistent corner frequency estimates for the same earthquake and find a range of stress drops of 1 02 mpa to 42 50 mpa with a median of 10 57 mpa by using the brune spectral model and the source parameters given by sato and hirasawa 1973 we also analyze stress drop dependence on the assumed spectral models and source parameters and use a bootstrapping analysis to calculate the uncertainty in corner frequency and stress drop estimates the boatwright spectral model leads to lower stress drop estimates than the brune spectral model due to the limited bandwidth and fixed fall off rates we find that the uncertainty in the stress drop of each earthquake is generally much smaller than the range of stress drop estimates the value and range of these stress drops of the potentially induced earthquakes are similar to tectonic earthquakes in california reported by other spectral ratio studies our results highlight the value of spectral ratio analyses of earthquakes in the central united states

high precision 40ar 39ar age for the jehol biota abstract abundant fossils of the terrestrial jehol biota including plants insects dinosaurs birds mammals and freshwater invertebrates were discovered from the yixian formation and the overlying jiufotang formation in inner mongolia hebei province and liaoning province northeastern china because of the exceptional preservation of fossils the jehol biota is one of the most important mesozoic lagerstatten and is referred to as a mesozoic pompeii the jehol biota has provided a rare opportunity to address questions about the origin of birds the evolution of feathers and flight the early diversification of angiosperms and the timing of placental mammal radiation six tuff samples and two basalt samples collected from the tuchengzi the yixian and the jiufotang formations near the classic outcrops in western liaoning ne china yielded high precision 40 ar 39 ar ages we obtain an age of 129 7 0 5 ma for a basaltic lava from the bottom of the yixian formation and an age of 122 1 0 3 ma for a tuff from the lowermost part of the overlying jiufotang formation our age results provide an age calibration of the whole yixian formation and show that the whole formation was deposited entirely within early cretaceous time over an interval of 7 ma

micromorphological evidence of paleoenvironmental changes in northern cilento south italy during the late quaternary abstract three representative soil profiles developed during the late quaternary in northern cilento south italy were studied by optical microscopy and sem eds observation of thin sections to examine soil features as evidence for past climatic fluctuations two of the profiles are polygenetic and the third monogenetic all these have a clear interglacial imprint whereas the polygenetic profiles also contain other features which can be related to periglacial conditions during the stadial glacial periods although in midlatitude coastal areas all the paleosols show a strong marine influence during development which probably resulted from windblown processes or submergence during past interglacial phases

extensional fault control on the sedimentation patterns in a continental rift basin el castellar formation galve sub basin spain in the galve sub basin the sedimentary record of the upper hauterivian lower barremian el castellar formation is divided into two stages by a marlstone interval with gypsum stage 1 shows a great variety of subenvironments and facies alluvial palustrine and lacustrine whereas in stage 2 an extensive shallow carbonate lake developed sedimentation was controlled by a system of south dipping ene wsw listric normal faults laterally bounded by nnw sse steeper transfer faults faults controlled sedimentation from a basin scale basin margins and main characteristics and evolution of sediments to a regional and a local scale thickness and facies distribution of the synrift series as well as the location and evolution of lakes and minor alluvial fans the changes between stages 1 and 2 are related to the passing from an independent movement of faults to the movement of all the extensional faults as a whole at a sole detachment level the interval with gypsum was caused by underground water flow changes associated with the interrelation and connection of the faults in the transition period these changes have been correlated with the transition from the rift initial stage to the rift climax stage which took place in the hauterivian barremian transition

on corner frequencies attenuation and low frequency earthquakes we have recently suggested that the nearly constant duration of low frequency earthquakes lfes and equivalently the band limitation of tectonic tremor manifests a moment duration scaling that is fundamentally different from regular earthquakes and is most easily explained as rupture on asperities of roughly constant dimension in that work we employed qualitative arguments against potential bias by attenuation here we examine the role of attenuation more quantitatively through an analysis that avoids specification of particular source e g brune models and relies on the particle velocity spectral maximum as the definition of apparent corner frequency the analysis leads to the formal definition of a saturation frequency as the limiting value of apparent corner frequency as the true corner frequency tends infinity the saturation frequency a formal equivalent to fmax can be used to set bounds on path averaged quality factor q we apply these relations to deep crustal and intraslab earthquakes beneath vancouver island to estimate bulk crustal attenuation parameters that are subsequently used to correct apparent corner frequency measurements of lfes reported in our earlier work the attenuation bias due to bulk crustal structure is shown to be small with negligible effect on the principal conclusions of that study however a review of laboratory and seismic refraction measurements of attenuation in oceanic basalts and evidence for high p to s lfe corner frequency ratios raises the possibility that strong highly localized near source attenuation accompanying high pore fluid pressures could cause the bandlimited nature of lfes through the depletion of high frequencies

focal spot imaging based on zero lag cross correlation amplitude fields application to dense array data at the san jacinto fault zone we image the subsurface below a dense seismic array straddling the clark branch of the san jacinto fault zone in southern california the analysis is based on focal spots of surface waves associated with the zero lag amplitudes of noise cross correlations computed between all stations of the dense array local medium properties are inferred from the spatially variable focal spot size and shape based on the first zero crossing of amplitude versus distance distributions the method provides simultaneous estimates of wave speed apparent attenuation and anisotropy without solving a tomographic inverse problem the obtained images of the frequency dependent seismic velocity distributions are consistent with independent estimates from a far field rayleigh wave tomography we observe an anticorrelation between our apparent attenuation coefficient and seismic velocity and a fault parallel alignment of fast propagation directions with greater structural complexity to the southwest of the fault the results imply a complex fault zone structure including a waveguide to the northeast of the fault that is continuous across the observed depth range and a low velocity structure to the southwest associated with a shallow sedimentary basin

rapid environmental changes in southern europe during the last glacial period oxygen isotope records from greenland ice cores1 2 indicate numerous rapid climate fluctuations during the last glacial period north atlantic marine sediment cores show comparable variability in sea surface temperature and the deposition of ice rafted debris3 4 5 in contrast very few continental records of this time period provide the temporal resolution and environmental sensitivity necessary to reveal the extent and effects of these environmental fluctuations on the continents here we present high resolution geochemical physical and pollen data from lake sediments in italy and from a mediterranean sediment core linked by a common tephrochronology our lacustrine sequence extends to the past 102 000 years many of its features correlate well with the greenland ice core records demonstrating that the closely coupled ocean atmosphere system of the northern hemisphere during the last glacial4 extended its influence at least as far as the central mediterranean region numerous vegetation changes were rapid frequently occurring in less than 200 years showing that the terrestrial biosphere participated fully in last glacial climate variability earlier than 65 000 years ago our record shows more climate fluctuations than are apparent in the greenland ice cores together the multi proxy data from the continental and marine records reveal differences in the seasonal character of climate during successive interstadials and provide a step towards determining the underlying mechanisms of the centennial millennial scale variability

transgressive regressive cycles and jurassic palaeogeography of northeast iberia abstract a correlation and sequence stratigraphy study of jurassic successions has been carried out in the main sedimentary basins of northeast iberia i e asturias basque cantabrian and iberian basins based on the identification of transgressive regressive cycles the development and palaeogeographic evolution of the epicontinental carbonate platforms of northeast iberia were largely controlled by major tectonic activity at three main intervals at the beginning of the jurassic in the lower middle jurassic transition and during the uppermost jurassic respectively during early jurassic times northeast iberia was the site of a single and large carbonate ramp opened to the north this carbonate ramp suffered a progressive drowning evolving from an inner to hemipelagic ramp systems with the local development of suboxic environments in the deepest areas located to the north during the middle jurassic different open carbonate platforms were formed including the development of swells in intermediate areas during the upper jurassic the outer ramp areas were progressively moving to the east iberian basin and the ammonite faunas showing a markedly tethyan affinity thereafter three first order t r cycles bounded by major discontinuities associated with significant time gaps are identified they extend respectively from the latest rhaetian to the early aalenian from the middle aalenian to the early oxfordian and from the early oxfordian to the late berriasian major transgressive peaks occurred at the middle toarcian bifrons zone at the late bajocian upper niortense and garantiana zones and at the mid kimmeridgian divisum zone each of the first order cycles includes four second order t r cycles cycles 1 1 1 4 are identified in the northern basins cycles 2 1 2 4 display some differences in age of transgressive peaks from one basin to another cycles 3 1 3 4 are mainly identified in the iberian basin the correlation with other separated boreal and thethysian basins demonstrates that the number and age of t r cycles varies from one basin to another and are mainly controlled by the local or regional tectonic development the transgressive peaks may reflect episodes of eustatic rise during the jurassic however their different age from one basin to another is explained by different subsidence evolution

triggering of earthquake aftershocks by dynamic stresses it is thought that small static stress changes due to permanent fault displacement can alter the likelihood of or trigger earthquakes on nearby faults many studies of triggering in the near field particularly of aftershocks rely on these static changes as the triggering agent and consider them only in terms of equivalent changes in the applied load on the fault here we report a comparison of the aftershock pattern of the moment magnitude mw 7 3 landers earthquake not only with static stress changes but also with transient oscillatory stress changes transmitted as seismic waves that is dynamic stresses dynamic stresses do not permanently change the applied load and thus can trigger earthquakes only by altering the mechanical state or properties of the fault zone these dynamically weakened faults may fail after the seismic waves have passed by and might even cause earthquakes that would not otherwise have occurred we find similar asymmetries in the aftershock and dynamic stress patterns the latter being due to rupture propagation whereas the static stress changes lack this asymmetry previous studies have shown that dynamic stresses can promote failure at remote distances but here we show that they can also do so nearby

earthquake source scaling relationships from 1 to 5 ml using seismograms recorded at 2 5 km depth the scaling relationships of earthquake sources less than about magnitude 3 have been the subject of considerable controversy over the last two decades studies of such events have shown a tendency for the constant stress drop self similarity of larger earthquakes to breakdown at small magnitudes and an apparent minimum source dimension of about 100 m has been observed other studies showed that this apparent breakdown in scaling could be an artifact of severe near surface attenuation limiting the spatial resolution of surface data in this study source parameters are determined for over 100 nearby tectonic earthquakes from recordings at a depth of 2 5 km in granite in the cajon pass scientific drill hole southern california comparison of the seismograms recorded at this depth with those at the wellhead clearly demonstrates the effect of the severe attenuation in the upper kilometers of the earth s crust source parameters are calculated by spectral modeling of three component p and s waves assuming four source models based on the brune 2 n 2 model in model l n 2 is fixed and q of p and s waves is determined to be 912 581 1433 and 1078 879 1323 respectively the numbers in parentheses are 1 standard deviation in model 2 qp qs 1000 is assumed and n is allowed to vary the 2 model is a good average for the data set but there is some real scatter supported by the data in model 3 qp qs 1000 is also assumed and 2 is constrained and in model 4 attenuation is ignored and n is allowed to vary source dimensions of less than 10m are observed for all four models 10 times smaller than the proposed minimum no breakdown in constant stress drop scaling is seen in the downhole data approximately ml 1 to 5 5 m0 109 1016 nm the ratio between radiated seismic energy estimated by integrating the velocity squared spectra with adequate signal bandwidth and seismic moment appears to decrease gradually with decreasing moment in the magnitude range 1 to 7 this is not incompatible with a constant stress drop but could result from errors in calculating energy the ratio of the s wave energy to that radiated by the p waves is about 14 after correction for attenuation this low value is consistent with the corner frequency shift of about 1 3 this corner frequency shift is observed for all four source models and therefore is interpreted as being source controlled

azimuthal dependence of the ground motion variability from scenario modeling of the 2014 mw6 0 south napa california earthquake using an advanced kinematic source model strong ground motion simulations require physically plausible earthquake source model here i present the application of such a kinematic model introduced originally by ruiz et al geophys j int 186 226 244 2011 the model is constructed to inherently provide synthetics with the desired omega squared spectral decay in the full frequency range the source is composed of randomly distributed overlapping subsources with fractal number size distribution the position of the subsources can be constrained by prior knowledge of major asperities stemming e g from slip inversions or can be completely random from earthquake physics point of view the model includes positive correlation between slip and rise time as found in dynamic source simulations rupture velocity and rise time follows local s wave velocity profile so that the rupture slows down and rise times increase close to the surface avoiding unrealistically strong ground motions rupture velocity can also have random variations which result in irregular rupture front while satisfying the causality principle this advanced kinematic broadband source model is freely available and can be easily incorporated into any numerical wave propagation code as the source is described by spatially distributed slip rate functions not requiring any stochastic green s functions the source model has been previously validated against the observed data due to the very shallow unilateral 2014 mw6 south napa california earthquake the model reproduces well the observed data including the near fault directivity seism res lett 87 2 14 2016 the performance of the source model is shown here on the scenario simulations for the same event in particular synthetics are compared with existing ground motion prediction equations gmpes emphasizing the azimuthal dependence of the between event ground motion variability i propose a simple model reproducing the azimuthal variations of the between event ground motion variability providing an insight into possible refinement of gmpes functional forms

a vs30 map for california with geologic and topographic constraints abstract for many earthquake engineering applications site response is estimated through empirical correlations with the time averaged shear wave velocity to 30 m depth v s 30 these applications therefore depend on the availability of either site specific v s 30 measurements or v s 30 maps at local regional and global scales because v s 30 measurements are sparse a proxy frequently is needed to estimate v s 30 at unsampled locations we present a new v s 30 map for california which accounts for observational constraints from multiple sources and spatial scales such as geology topography and site specific v s 30 measurements we apply the geostatistical approach of regression kriging rk to combine these constraints for predicting v s 30 for the v s 30 trend we start with geology based v s 30 values and identify two distinct trends between topographic gradient and the residuals from the geology v s 30 model one trend applies to deep and fine quaternary alluvium whereas the second trend is slightly stronger and applies to pleistocene sedimentary units the rk framework ensures that the resulting map of california is locally refined to reflect the rapidly expanding database of v s 30 measurements throughout california we compare the accuracy of the new mapping method to a previously developed map of v s 30 for california we also illustrate the sensitivity of ground motions to the new v s 30 map by comparing real and scenario shakemaps with v s 30 values from our new map to those for existing v s 30 maps online material california statewide v s 30 and shakemaps for loma prieta

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

mesozoic extensional tectonics stratigraphy and crustal evolution during the alpine cycle of the eastern iberian basin abstract sequence stratigraphy subsidence analysis and the integration of the basin fill data allow to the identification of four successive evolutionary stages in the basins of the eastern iberian margin during mesozoic extension 1 triassic rift late permian hettangian 2 early and middle jurassic postrift sinemurian oxfordian 3 late jurassic and early cretaceous rift kimmeridgian middle albian and 4 late cretaceous postrift late albian maastrichtian the present day crustal structure of the eastern iberian range and evidence of its evolution are deduced from the analysis of a new gravity map and other geophysical data a regional gravity low along the iberian range is interpreted in terms of crustal thickening beneath the orogen as a result of the collision between the ebro block and the iberian plate during the paleogene the boundary between these blocks coincides with a magnetic lineament that is interpreted as an inherited signature of the thinning that occurred during mesozoic extension a geodynamic scenario for the crustal evolution of the eastern part of the iberian peninsula based on the evaluation of mesozoic extensional tectonics and an analysis of the available geophysical data includes three main successive evolutionary stages 1 1 mesozoic crustal thinning 2 2 paleogene crustal thickening 3 3 neogene crustal thinning based on new geological and geophysical arguments this study offers an alternative and a more complete geodynamic history of the eastern iberian basins related to the evolution of the iberian plate and the central north atlantic

variability in earthquake stress drop and apparent stress 1 we apply empirical green s function coda based analysis to four earthquake sequences in japan that span a magnitude range of 1 8 to 6 9 to measure radiated energy corner frequency and stress drop we find no systematic dependence of apparent stress or stress drop on seismic moment for these sequences and find they both are log normally distributed however we identify several anomalous events both energetic and enervated that show sharply different spectral signatures from the rest of the population these events indicate that much of the variation in apparent stress and stress drop is statistically significant which may have important implications for seismic hazard analysis

regional correlations of vs30 and velocities averaged over depths less than and greater than 30 meters using velocity profiles from sites in japan california turkey and europe we find that the time averaged shear wave velocity to 30 m vs30 used as a proxy for site amplification in recent ground motion prediction equations gmpes and building codes is strongly correlated with average velocities to depths less than 30 m vsz with z being the averaging depth the correlations for sites in japan corresponding to the kik net network show that vs30 is systematically larger for ag ivenvsz than for profiles from the other regions the difference largely results from the placement of the kik net station locations on rock and rocklike sites whereas stations in the other regions are generally placed in urban areas underlain by sediments using the kik net velocity profiles we provide equations relating vs30 to vsz for z ranging from 5 to 29 m in 1 m increments these equations and those for california velocity profiles given in boore 2004b can be used to estimate vs30 from vsz for sites in which velocity profiles do not extend to 30 m the scatter of the residuals decreases with depth but even for an averaging depth of 5 m a variation in logvs30 of 1 standard deviation maps into less than a 20 uncertainty in ground motions given by recent gmpes at short periods the sensitivity of the ground motions to vs30 uncertainty is considerably larger at long periods but is less than a factor of 1 2 for averaging depths greater than about 20 m we also find that vs30 is correlated with vsz for z as great as 400 m for sites of the kik net network providing some justification for using vs30 as a site response variable for predicting ground motions at periods for which the wavelengths far exceed 30 m online material estimates of vs30 at k net stations

tracing volcanic events in the ngrip ice core and synchronising north atlantic marine records during the last glacial period five basaltic tephra horizons have been identified in the ngrip ice core during the last glacial period geochemical analyses indicate that these tephras are of icelandic origin with one horizon identified as the faroe marine ash zone iii fmaz iii an important marker horizon in several marine records within the faroe islands margin the fmaz iii is a few millimetres thick and is constrained to 38 122 723 yr b2k before year ad 2000 according to the greenland ice core chronology gicc05 this event falls directly at the thermal peak of greenland interstadial 8 gi 8 and a marine ice correlation based on the position of this tephra suggests a close coupling of the marine and atmospheric systems at this time the remaining tephras originate from the eastern volcanic zone with the katla volcanic system pinpointed as the dominant source these are thought to represent previously unknown volcanic events which add considerably to our knowledge of icelandic volcanism during this period independent ages are assigned to these events and together with major element characterisation form the backbone of the tephrochronology framework presented here despite the identification of these tephras this study also demonstrates that the sulphate record may not always act as a suitable proxy for the identification of tephra horizons in ice core records

the campanian ignimbrite and codola tephra layers two temporal stratigraphic markers for the early upper palaeolithic in southern italy and eastern europe tephra layers from archaeological sites in southern italy and eastern europe stratigraphically associated with cultural levels containing early upper palaeolithic industry were analysed the results confirm the occurrence of the campanian ignimbrite tephra ci ca 40 cal ka bp at castelcivita cave southern italy temnata cave bulgaria and in the kostenki borshchevo area of the russian plain this tephra originated from the largest eruption of the phlegrean field caldera represents the widest volcanic deposit and one of the most important temporal stratigraphic markers of western eurasia at paglicci cave and lesser sites in the apulia region we recognise a chemically and texturally different tephra which lithologically chronologically and chemically matches the physical and chemical characteristics of the plinian eruption of codola a poorly known late pleistocene explosive event from the neapolitan volcanoes likely somma vesuvius for this latter we propose a preliminary age estimate of ca 33 cal ka bp and a correlation to the widespread c 10 marine tephra of the central mediterranean the stratigraphic position of both ci and codola tephra layers at castelcivita and paglicci help date the first and the last documented appearance of early upper palaeolithic industries of southern italy to ca 41 40 and 33 cal ka bp respectively or between two interstadial oscillations of the monticchio pollen record to which the ci and codola tephras are physically correlated corresponding to the greenland interstadials 10 9 and 5 in eastern europe the stratigraphic and chronometric data seem to indicate an earlier appearance of the early upper palaeolithic industries which would predate of two millennia at least the overlying ci tephra the tephrostratigraphic correlation indicates that in both regions the innovations connected with the so called early upper palaeolithic encompassing subsistence strategy and stone tool technology appeared and evolved during one of the most unstable climatic phases of the last glacial period on this basis the marked environmental unpredictability characterising this time span is seen as a potential ecological factor involved in the cultural changes observed

geochemical characterization of quaternary tephras from the campanian province italy the campanian province has a rich history of human interaction with volcanic eruptions in a region currently inhabited by 3 million people it is crucial to have precise and accurate geochemical characterization of volcanic units within the region so as to identify the spatial distribution of past events furthermore tephrochronology is becoming an important tool in the region for correlating past environmental records unfortunately many of the key units have been geochemically analysed using relatively imprecise methods making correlation problematic although robust correlations have been established in the campanian province using a range of methods including stratigraphy and geochronology more distal correlation requires precise geochemical characterisation of individual glass shards here we report major oxide data geochemically characterising 17 key tephra units within the campanian province using wavelength dispersive spectrometry wds the new data confirm the trachytic nature of most of the eruptions to effect more precise correlations between units especially in distal locations proximal units must be individually analysed for major oxides using wds on the vitreous phase and statistically analysed for robust correlations in cases where similar geochemistry exists analysis of trace and rare earth elements may be necessary

selecting empirical green s functions in regions of fault complexity a study of data from the san jacinto fault zone southern california abstract to constrain an earthquake s source properties the path and site effect contributions to the seismic waveform can be approximated using another earthquake as an empirical green s function egf an ideal egf earthquake is smaller in magnitude than the mainshock and shares a similar focal mechanism and hypocenter here we quantify how to optimally select egf events using data from the spatially complex san jacinto fault zone sjfz in southern california the sjfz s high seismicity rate allows us to test the egf method for 51 target 3 m w 200 for each mainshock we purposefully select a large population of inappropriate egfs in order to identify thresholds and restrictions that optimize egf selection criteria for each mainshock egf pair we compute the spectral ratio fit the mainshock corner frequency and measure the variability of these corner frequencies across the network we assume a suitable egf event will produce similar corner frequency estimates at every station we discover that limiting hypocentral separation distances between mainshock and egf events to online material map of earthquake locations within our study region color coded to indicate the mapped spatial differential between the original catalog location in the anza catalog and the location in the lin et al 2007 relocated catalog

source parameters of the 23 april 1992 m 6 1 joshua tree california earthquake and its aftershocks empirical green s function analysis of geos and terrascope data source parameters of the m 6 1 23 april 1992 joshua tree mainshock and 86 m 1 8 to 4 9 aftershocks are determined using an empirical green s function methodology for the aftershocks deconvolved p and s wave spectra are calculated for 126 pairs of closely spaced events recorded on portable geos stations s wave spectra from the two horizontal components are averaged the deconvolved spectra are fit by a ratio of omega square source models yielding an optimal least squares corner frequency for both the large and the small event in each pair we find no resolved difference between the inferred p and s wave corner frequencies using the standard brune model for stress drop we also find no resolved nonconstant scaling of stress drop with moment although we also conclude that detailed scaling systematics would be difficult to resolve in particular a weak increase of stress drop with moment over a limited moment magnitude cannot be ruled out for magnitudes smaller than m 3 to 3 5 the inferred stress drop values will be limited by the maximum observable corner frequency value of 60 hz for the mainshock source time functions are obtained from mainshock recordings at three terrascope stations pfo pas and gsc using an m 4 3 foreshock as an empirical green s function the results indicate a fairly simple single pulse source time function with clear south to north directivity and an inferred rupture radius of 5 to 6 km the deconvolved source time functions are inverted to obtain a finite rupture model that gives a robust estimate of rupture dimension early aftershocks are found to lie along the perimeters of regions with high mainshock slip the inferred mainshock stress drop value 56 bars is within the range determined for the aftershocks our derived mainshock source spectra do not show resolvable deviation from the omega square model

tephrostratigraphy study for the last 18 000 14 c years in a deep sea sediment sequence for the south adriatic abstract a detailed tephrostratigraphy supported by accelerator mass spectrometry ams 14c dating and isotopic and geochemical analyses has been carried out for a deep sea core collected from the southern adriatic sea which spans the last 18 14c kyr fourteen ash layers have been recognized in the marine core and the origin was determined by comparing their age and geochemistry with tephra detected in terrestrial deposits the geochemical signatures of marine ash layers indicate a prevailing campanian and subordinate etnean and eolian provenances collectively they are attributed to sources in the phlegraean fields lam lagno amendolare ln1 ln2 gm1 c 2 nyt neapolitan yellow tuff c 1 agnano pomici principali ams pf agnano monte spina ast astroni somma vesuvius l9 pomici di base l8 greenish mount etna et1 y1 biancavilla ignimbrite lipari e 1 gabellotto fiumebianco and palinuro seamount pal 1 some of these eruptions have been detected for the first time in marine cores astroni lam l9 l8 and three were detected and dated by marine tephra ln1 ln2 and pal 1 providing new more precise stratigraphic markers for the last 18 kyr in the south adriatic marine record

lacustrine system evolution during early rifting el castellar formation galve sub basin central iberian chain abstract a detailed sedimentological study of the first synrift deposits recorded in the galve sub basin of ne spain during the early cretaceous aided in the reconstruction of climatic and tectonic influences the el castellar formation is composed of siliciclastics and carbonates unit 1 claystones gypsum and carbonates unit 2 and marls and limestones unit 3 unit 1 facies formed in alluvial and palustrine plains a local alluvial fan and low energy shallow lake subenvironments low energy lacustrine facies characterised unit 2 in contrast palustrine low and high energy lake facies were identified for unit 3 the spatial and temporal distribution of lithofacies representing the several environments were used to propose a general lacustrine system evolution from isolated ponds and marshes to low energy shallow lakes and finally to an extensive high energy lake lake evolution is related to changes in the subsidence pattern from local to basin scale subsidence which was ultimately related to the transition from the initial rift to rift climax stage shallowing upwards lacustrine successions have been interpreted as climatically forced and linked to sediment and water supply both tectonics and climate determined the change from an overfilled to a balanced fill lake basin through time

quantifying volcanic ash dispersal and impact of the campanian ignimbrite super eruption 1 we apply a novel computational approach to assess for the first time volcanic ash dispersal during the campanian ignimbrite italy super eruption providing insights into eruption dynamics and the impact of this gigantic event the method uses a 3d time dependent computational ash dispersion model a set of wind fields and more than 100 thickness measurements of the ci tephra deposit results reveal that the ci eruption dispersed 250 300 km 3 of ash over 3 7 million km 2 the injection of such a large quantity of ash and volatiles into the atmosphere would have caused a volcanic winter during the heinrich event 4 the coldest and driest climatic episode of the last glacial period fluorine bearing leachate from the volcanic ash and acid rain would have further affected food sources and severely impacted late middle early upper paleolithic groups in southern and eastern europe citation costa a a folch g macedonio b giaccio r isaia and v c smith 2012 quantifying volcanic ash dispersal and impact of the campanian ignimbrite super eruption geophys res lett 39 l10310 doi 10 1029 2012gl051605

investigating uncertainties in empirical green s function analysis of earthquake source parameters i use a well recorded earthquake sequence to investigate the uncertainties of earthquake stress drops calculated using an empirical green s function egf approach the earthquakes in the largest m 2 1 repeating sequence targeted by the san andreas observatory at depth safod parkfield california are recorded by multiple borehole stations and have simple sources well constrained stress drops and abundant smaller earthquakes to use as egfs i perform three tests to estimate quantitatively the likely uncertainties to arise in less optimal settings i use egf earthquakes with a range of cross correlation values and separation distances from the main earthquakes the stress drop measurements decrease by a factor of 3 as the quality of the egf assumption decreases a good egf must be located within approximately one source dimension of the large earthquake with high cross correlation i subsample the large number of measurements for the main earthquakes to investigate the expected stress drop uncertainties in studies where fewer stations or egfs are available if only one measurement is available the uncertainties are likely to be at least 50 the uncertainties decrease to 20 with five or more measurements using multiple egfs is a good alternative to multiple stations to investigate the effects of limited frequency bandwidth i recalculate the corner frequencies after progressively decimating the sample rate decreasing the high frequency limit of the bandwidth decreases the estimate of the corner frequency and stress drop the corner frequency may be underestimated if it is within a factor of 3 of the maximum frequency of the signal

characteristics and sources of tephra layers in the epica dome c ice record east antarctica implications for past atmospheric circulation and ice core stratigraphic correlations thirteen discrete air fall tephra layers were identified in the last 200 000 yr section of the epica dome c ice record drilled in the east antarctic plateau 75 06 s 123 21 e quantitative grain size glass particle morphology and the grain discrete major element composition of the glass fraction of these layers were investigated through comparison with literature data on the rock composition of quaternary volcanic centres located within and around antarctica five tephra layers were attributed to south sandwich volcanoes in the south atlantic ocean two to south shetland volcanoes northern antarctic peninsula two to andean volcanoes and four to antarctic marie byrd land and melbourne provinces the abundance of layers originating in the southern part of the atlantic confirms that westerly atmospheric circulation spiralling towards east antarctica prevailed over the last 200 ka moreover the record of events from antarctic centres suggests that atmospheric trajectories from west to east antarctica can also be significant a few ash layers are geochemically distinct and appear equivalent to levels from vostok and dome fuji deep ice records located ca 600 km and ca 2000 km respectively from dome c on the antarctic plateau these layers provide unambiguous markers for future correlation with other antarctic ice cores and circumpolar marine climatic records they also provide reliable constraints to get a common timescale by glaciological modelling and represent a first step towards absolute ice core dating

comprehensive analysis of earthquake source spectra in southern california we compute and analyze p wave spectra from earthquakes in southern california between 1989 and 2001 using a method that isolates source receiver and path dependent terms we correct observed source spectra for attenuation using both fixed and spatially varying empirical green s function methods estimated brune type stress drops for over 60 000 m l 1 5 to 3 1 earthquakes range from 0 2 to 20 mpa with no dependence on moment or local b value median computed stress drop increases with depth in the upper crust from about 0 6 mpa at the surface to about 2 2 mpa at 8 km where it levels off and remains nearly constant in the midcrust down to about 20 km however the results at shallow depths could also be explained as reduced rupture velocities near the surface rather than a change in stress drop spatially coherent variations in median stress drop are observed with generally low values for the imperial valley and northridge aftershocks and higher values for the eastern transverse ranges and the north end of the san jacinto fault we find no correlation between observed stress drop and distance from the san andreas and other major faults significant along strike variations in stress drop exist for aftershocks of the 1992 landers earthquake which may correlate with differences in main shock slip

characterizing the uppermost 100 m structure of the san jacinto fault zone southeast of anza california through joint analysis of geological topographic seismic and resistivity data

what we can and cannot learn about earthquake sources from the spectra of seismic waves earthquake sources are commonly viewed as shear dislocations this imposes distinct limitations on what source parameters can be realistically determined from radiated shear wave spectra first the slip velocity on the fault is the real parameter that controls the strength of the high frequency radiation it can be directly determined from acceleration spectra by fitting their high frequency level second the relationship between corner frequency of the spectrum and the radius of the source is fundamentally unclear as a result the source dimensions cannot be accurately determined from the spectra such an estimate would be as accurate as any other informed guess third the stress drop only serves as a proxy for the source radius in the relationship between the radius and the corner frequency it thus cannot be reliably determined from the spectra the quantity usually obtained from the spectra and referred to as the stress drop is a poorly defined parameter that may bear little relevance to the actual stresses acting on faults this parameter has little meaning unless converted to the maximum slip velocity which is the only quantity that can be accurately determined from the spectra the typical value of stress drop of 100 bars established from the spectra of california events may imply that the typical slip velocities have been on the order of 0 5 m sec although it is more accurate to determine slip velocities directly from the spectra

stalagmite evidence for the precise timing of north atlantic cold events during the early last glacial evidence of millennial scale cold events following the last interglacial are well preserved in north atlantic marine cores greenland ice and pollen records from europe however their timing was previously undetermined by radiometric dating we report the first precise radiometric ages for two such events c23 105 1 0 9 ka to 102 6 0 8 ka and c24 112 0 0 8 ka and 108 8 1 0 ka based on stable carbon and oxygen isotope measurements on a stalagmite from italy cc28 in addition to providing new information on the duration of these events in southern europe the age data provide invaluable tuning points for the melisey i c24 and montaigu c23 pollen zones identified in western europe the former event is of particular significance because it represents the end of the eemian interglacial forest phase in western europe the new age data will also allow fine tuning of the timing and duration of greenland stadial 24 equivalent to c23 in the north greenland ice core project ice core and via a common gasage chronology tuning of the vostok and epica european project for ice coring in antarctica ice cores

late quaternary climatic changes in northern cilento southern italy an integrated geomorphological and paleopedological study abstract this paper reports a contribution to the knowledge of the local morphodynamic and pedogenetic response to late quaternary climatic changes in northern cilento southern italy three representative geomorphological units and associated paleosols have been characterised in detail by field work chemical and mineralogical analyses and micromorphological observations of thin sections the data confirm an intense degree of weathering and a complex history of soil formation often representing different environments in contrast with the present pedoclimatic regime two of the three profiles reveal a polygenetic character recording typical interglacial conditions characterised by high temperatures and humidity with important soil development followed by the occurrence of periglacial conditions possibly occurring during cold glacial stages namely the last glacial at mid latitude coastal regions of southern italy the third paleosol appears essentially monogenetic and developed under interglacial like conditions

scaling law between corner frequency and seismic moment of microearthquakes is the breakdown of the cube law a nature of earthquakes 1 the corner frequency fc and the seismic moment m0 of microearthquakes local magnitude from 1 3 to 1 3 are estimated from the records of sensors located at an 1800 m deep borehole at the nojima fault central japan the digital waveforms of each event are recorded with two different sampling rates 10 khz and 100 hz the source parameters estimated from high sampling data satisfy a relationship of m0 fc 3 corresponding to a constant stress drop law while those calculated from low sampling data follow a relationship of m0 fc 4 a lack of high frequency components in the 100 hz sampling data seem to be obvious indicating that the value of fc and m0 are incorrectly estimated and the relationship of m0 fc 4 is an artifact caused by the limited frequency band of these data the scaling relationship of m0 fc 3 is thus also valid for microearthquakes and the breakdown of the constant stress drop law reported in the literature is not well founded

an inter laboratory comparison of the electron probe microanalysis of glass geochemistry abstract tephrochronology commonly relies upon grain discrete analysis of glass shards to reveal the subtle geochemical differences between tephras from past explosive volcanic eruptions the use of electron probe microanalysis for this purpose is widely accepted by tephrochronologists it is widely recognised that both precision and accuracy must be maximised and that rigorous standardisation procedures must be followed in this paper the performances of seven northern european electron microprobe centres are compared using a geochemically homogeneous obsidian secondary standard the results reveal that a number of tephra oriented probe centres could benefit from exercises similar to the programme outlined within in particular it is evident that a number of these centres undertaking tephrochronological investigations have generated geochemical data that may be inadequate in terms of distinguishing between tephras inaccuracy in the determination of sodium is seen to be the main difficulty in recent years the application of distal tephrochronology to stratigraphical problems in the northern european quaternary record has become increasingly common geochemical standardisation is essential at an early stage in the development of a regional tephrochronological framework and we hope exercises such as presented here will encourage the production of reliable tephra geochemical data

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

three orders of regional sea level changes control facies and stacking patterns of shallow platform carbonates in the maestrat basin tithonian berriasian ne spain middle tithonian berriasian shallow platform carbonates of the maestrat basin salzedella and montanejos sections ne spain are stacked in sequence stratigraphic units of different orders higher order sequences parasequences and subunits have a shallowing or deepening shallowing evolution they have been related to the short term eccentricity and precession cycles major facies changes and stacking pattern of parasequences reveal the presence of two 2nd order sequences the lower sequence is middle tithonian mid early berriasian in age the upper sequence extends up to the mid late berriasian it is suggested that local subsidence changes along with regional sea level changes controlled the long term evolution of accommodation in the maestrat basin facies evolution stacking pattern and sharp lithological changes have allowed the definition of five 3rd order sequences in the lower sequence in montanejos the transgressive deposits are characterised by the progressive absence of the restricted lagoon facies and the presence of deepening upward intervals in the parasequences the highstand deposits display an increase in siliciclastics and a progressive predominance of restricted lagoon facies some of the 3rd order sequence boundaries match the sequence boundaries identified in other european basins and may be related to sea level falls induced by the long term eccentricity cycle enhanced during periods of long term loss of accommodation

new information about the stratigraphic position and age of the sauropod aragosaurus ischiaticus from the early cretaceous of the iberian peninsula the sauropod aragosaurus ischiaticus sanz buscalioni casanovas santafe 1987 was the first dinosaur to be described in spain the holotype was recovered from the site of las zabacheras galve teruel province this site has traditionally been situated in the el castellar formation in the lower part of the wealden facies recently it has been proposed that the remains of aragosaurus stem from the villar del arzobispo formation late tithonian upper part of the early berriasian which would mean that the sauropod was almost 15 million years older than previously thought detailed field work has been carried out making it possible to pinpoint the position of the low angle unconformity between the villar del arzobispo formation and the el castellar formation this unconformity originated as a result of block tilting that occurred during the early stages of the early cretaceous rifting episode the upper levels of the jurassic sequence i e the villar del arzobispo formation were exposed to erosion and karstification leading to the formation of a discontinuous conglomeratic level this level has been locally preserved at the bottom of the wealden syn rift sequence i e the el castellar formation the results of our detailed mapping demonstrate that the aragosaurus holotype was found in the lower part of the el castellar formation moreover our revision of the existing datings suggests that the el castellar formation as a whole is valanginian early barremian in age given that aragosaurus was located in its lower part it is probably valanginian hauterivian in age