estimating locations and magnitudes of earthquakes in southern california from modified mercalli intensities modified mercalli intensity mmi assignments instrumental moment magnitudes m and epicenter locations of thirteen 5 6 m 7 1 training set events in southern california were used to obtain the attenuation relation mmi 1 64 1 41 m 0 00526 h 2 63 log h where h is the hypocentral distance in kilometers and m is moment magnitude intensity magnitudes m i and locations for five 5 9 m 7 3 independent test events were consistent with the instrumental source parameters fourteen historical earthquakes between 1890 and 1927 were then analyzed of particular interest are the m i 7 2 9 february 1890 and m i 6 6 28 may 1892 earthquakes which were previously assumed to have occurred near the southern san jacinto fault a more likely location is in the eastern california shear zone ecsz these events and the 1992 m 7 3 landers and 1999 m 7 1 hector mine events suggest that the ecsz has been seismically active since at least the end of the nineteenth century the earthquake catalog completeness level in the ecsz is m 6 5 at least until the early twentieth century online material figures and table of empirical mmi site corrections

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

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

analysis of the 4 february 1976 chino valley arizona earthquake abstract this m b 4 9 earthquake was located about 20 km north of prescott in the transition zone between the basin and range and colorado plateau provinces several lines of approach were used to determine the focal mechanism p wave first motions surface wave amplitude and phase spectra and synthetic seismograms the preferred focal mechanism displays northwest trending nodal planes with predominantly normal movement the inferred fault plane strikes 120 dips 40 sw with a slip of 100 and a depth of 10 to 15 km the seismic moment is 1 0 10 23 dyne cm the azimuth of least horizontal stress is inferred to be 37 lithostatic stress generated by variations in elevation and density between the crusts of the southern basin and range and colorado plateau may contribute to the inferred stress orientations uplift and resultant extension in this zone of thin lithosphere and relatively high heat flow may also be important microearthquake studies in the chino valley during the summers of 1978 and 1979 indicate a microseismicity rate of 0 3 events per day this is an order of magnitude less than that observed in the intermountain seismic belt

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

intensity attenuation model evaluation for bangladesh with respect to the surrounding potential seismotectonic regimes an effort has been made through this study to evaluate the existing intensity attenuation model ipe for the potential seismotectonic regimes in and around bangladesh to reach the goal the seismicity of the concerned tectonic regimes has been analyzed apart from evaluating the appropriate intensity model this research has also assessed the predictive performance of epicentral intensity estimation different magnitude types have been made uniform by converting into moment magnitude and subsequently into the modified mercalli intensity scale mmi the epicentral intensity conversion following li in chinese earthquakes seismological press beijing 1980 fits best for the study area among the utilized four predictive equations the epicentral intensity conversion from the moment magnitude shows that small to moderate earthquakes get significantly overestimated suitable attenuation models have been applied to the different tectonic regimes based on the criteria of using the ipes among all the utilized ipes the relation of bakun et al bull seismol soc am 93 190 202 2003 exhibits the highest standard deviation 1 61 in attenuation with distance although the szeliga et al s bull seismol soc am 100 2 570 584 2010 attenuation relation has a standard deviation of 1 22 the intensity decay is little even for the greater distance 800 900 km up to mw 7 0 the ipe of bindi et al geophys j int 187 1 327 337 2011 shows realistic attenuation scenario with 1 3 however at lower magnitude range mw 7 0 the intensity starts to decay sharply still the ipe of bindi et al 2011 is more realistic in comparison of the shakemaps of the past and in terms of convincible intensity decay with greater distance 500 900 km however the intensity close to the epicenter gets very high mmi xi or larger value for the major events mw 8 5 although the ipe of chandler and lam j asian earth sci 20 7 775 790 2002 has distance constraints its performance is acceptable considering the attenuation scenario with distance along with the lowest standard deviation 0 92 considering the seismic events from the only strike slip churachandpur mao fault of the study area bakun and wentworth bull seismol soc am 87 6 1502 1521 1997 relation has been applied to determine the attenuation pattern

data driven seismic hazard models prepared for a seismic risk assessment in the dead sea region abstract we derive a probabilistic seismic hazard model for the dead sea region to allow for seismic risk estimation which will be part of a subsequent study this hazard model relies as much as possible on data driven approaches utilizing a seismic catalog compiled for the region by integrating data from different sources we derive seismicity models using two different smoothing approaches and estimate a hypocentral depth distribution from historical observations we do not include paleoseismological evidence apart from the observed seismicity because ground motion records are sparse in the region we formulate the model in the european macroseismic intensity scale from 1998 however the collected macroseismic intensity data are still too few to derive a local intensity prediction equation ipe thus we choose among existing equations derived for different regions and combine them in a logic tree here motivated by scherbaum et al 2010 we propose a two step approach to select the ipes for the logic tree first we cluster a set of 10 candidate ipes to identify groups of models that can be considered similar with respect to the distribution of the predicted values for a selection of the explanatory variables i e magnitude and distance using a k mean approach steinhaus 1956 then we apply different ranking techniques scherbaum et al 2009 kale and akkar 2013 to identify within each cluster the most suitable model to be included in the logic tree the resulting hazard models are consistent with existing probabilistic seismic hazard models for the region we estimate a moderate to high hazard of intensity grade vii viii with 10 probability of exceedance within 50 years in close vicinity to the dead sea transform fault the dominant seismogenic structure in this region

surface slip during large owens valley earthquakes data sets and expanded results contributing to this study are available in the supporting information the earthscope southern and eastern california lidar project available online at http opentopo sdsc edu involved data acquisition and processing for the plate boundary observatory pbo by ncalm http www ncalm org unavco operates the pbo for earthscope http www earthscope org supported by the national science foundation ear 0350028 and ear 0732947 funding for this study was provided by the southern california earthquake center scec project 12140 the geological society of america graduate student research fund the community foundation of san bernardino county and the western washington university geology department we thank g seitz m price and k morgan for assistance in the field and s bacon j arrowsmith r weldon k scharer j unruh c madden madugo and d haddad for helpful discussions constructive reviews by d schwartz r briggs e schermer d clark and one anonymous reviewer substantially improved the paper we also thank the staff at the uc white mountain research center for facilitating this work any use of trade firm or product names is for descriptive purposes only and does not imply endorsement by the u s government

a proposal for a standard procedure of modeling 3 d velocity structures and its application to the tokyo metropolitan area japan abstract most metropolitan areas are located over large scale sedimentary basins since the sediments filling basins amplify ground motions and their velocity structures complicate the propagation of seismic waves it is important for the prediction of strong ground motion and seismic hazard to determine the three dimensional 3 d velocity structures of these urban basins this importance motivated various organizations to carry out extensive geophysical experiments and geological investigations and velocity structure models are being constructed all over japan however a study of a single dataset cannot completely define a 3 d velocity structure so that we propose a standard procedure for modeling the 3 d velocity structure of an urban basin in japan by simultaneously and sequentially using various kinds of datasets such as those from refraction reflection experiments gravity surveys surface geology borehole logging microtremor surveys and earthquake records we then apply the procedure to the tokyo metropolitan area tma over the kanto basin with an area of about 17 000 km2 and the maximum thickness of about 4 km as one of the steps in the procedure a joint inversion of refraction and gravity data has been formulated to determine the 3 d topography of interfaces of the sedimentary layers as well and lateral distribution of the basement slowness we validate the constructed velocity structure model by comparison of observed and synthetic waveforms since this modeling is carried out mainly for strong ground motion prediction the proposed procedure including the joint inversion and validation with ground motion simulations works well for tma and the applicability of the standard procedure has been confirmed for regions with substantial data of experiments and earthquake records in japan

the assessment of ree patterns and 143nd 144nd ratios in fish remains abstract the ree content and isotopic composition of sr and nd have been determined in fish teeth ranging in age from the trias to the present and from various localities mostly around the atlantic these measurements have been carried out on selachian and teleost remains from the same locality in togo and show no appreciable difference which suggests with the help of a mass balance calculation of the ce anomaly that diagenetic effects are not responsible for the ree enrichment of biogenic phosphates one group of fossil teeth has about 3 times the ree abundances of shale and a shale normalized pattern with a minimum at sm it is thought to reflect deposition in the open sea environment a second group has ree concentration about 10 times higher than the first group with either a regular light ree enrichment or more frequently a maximum in the middle ree both being probably indicative of deposition in estuarine or near shore conditions the shape of the ree spectra and the size of the ce anomaly can be used semi quantitatively to determine the depth of deposition the results presented here on late cretaceous eocene fish teeth samples from morocco reflect an increasing influx of deep waters with a lowla yb ratio and strong negative ce anomaly which agrees well with the evolution of sediment chemistry and microfauna associations in contrast nd is typical of the water mass in which the fish debris decayed examples of nearly isolated basins identified with nd isotopes include the south atlantic prior to the lutetian nd 13 5 the miocene persian gulf nd 3 1 and bolivia during the late cretaceous nd 12 8 togo and guinea bissau results suggest that in the south atlantic the meridional oceanic circulation had not started before 45 ma ago combination of ree and nd data suggests that the assignment of jurassic cretaceous samples measured so far to open sea water masses is still ambiguous

seismic attenuation in northeastern sonora mexico we studied the attenuation of local and regional earthquake body waves recorded by the seismic network of northeastern sonora mexico red sismica del noreste de sonora resnes the source station paths of the selected data set cover the epicentral region of the may 1887 m w 7 5 sonora earthquake we used the best located earthquakes recorded by resnes between 2003 and 2004 to analyze the spectral amplitude decay of body waves with hypocentral distance the database consists of 44 earthquakes with magnitudes between 1 8 and 3 2 and hypocentral distances between 25 and 150 km we calculated fourier spectral amplitudes from more than 400 records and defined attenuation functions with a nonparametric model by inverting the observed spectral amplitudes at 23 individual frequencies between 0 4 and 63 1 hz we determined regional attenuation curves based on events located more than 100 km northwest of the center of the network and local curves based on earthquakes located near the fault zone that ruptured in the 1887 earthquake the obtained attenuation curves indicate that the spectral amplitudes decay faster in the area of the 1887 rupture than in the surrounding region to analyze the possible sources of attenuation we parameterized the attenuation functions considering three terms one that accounts for geometrical spreading another one for anelastic attenuation and a third for near surface attenuation we found the s wave quality factor q to be similar in both the general region and near the 1887 rupture however in the region of the 1887 rupture the near surface attenuation exceeds the regional average finally in the region of the 1887 rupture the nonparametric attenuation functions and the estimates of q indicate that at between 0 6 and 63 1 hz p waves attenuate more than s waves q p 20 8 f 1 1 whereas q s 83 8 f 0 9

seismic activity of the san francisco bay region moment magnitude m with objective confidence level uncertainties are estimated for felt san francisco bay region earthquakes using bakun and went worth s 1997 analysis strategy for seismic intensity observations the frequency magnitude distribution is well described for m 5 5 events since 1850 by a gutenberg richter relation with a b value of 0 90 the seismic moment rate m yr since 1836 is 2 68 1018 n m yr 95 confidence range 1 29 1018 n m yr to 4 07 1018 n m yr the seismic moment rate since 1850 is nearly the same m yr in the 56 years before 1906 is about 10 times that in the 70 years after 1906 in contrast m yr since 1977 is about equal that in the 56 years before 1906 80 1 14 of the plate motion moment accumulation rate is available for release in earthquakes the historical m yr and the portion of the plate motion moment accumulation rate available for release in earthquakes are used in a seismic cycle model to estimate the rate of seismic activity in the twenty first century high and low rates of future seismic activity are both permissible given the range of possible seismic cycle recurrence times t and the uncertainties in the historical m and in the percentage of plate motion available for release in earthquakes if the historical seismic moment rate is not greater than the estimated 2 68 1018 n m yr and the percentage of the plate motion moment accumulation available for release in earthquakes is not less than the estimated 80 then for all t the rate of seismic moment release from now until the next 1906 sized shock will be comparable to the rate from 1836 to 1905 when m 6 1 2 shocks occurred every 15 to 20 years

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

diet preferences and climate inferred from oxygen and carbon isotopes of tooth enamel of tarbosaurus bataar nemegt formation upper cretaceous mongolia abstract stable isotopes of oxygen and carbon of tooth enamel are increasingly being used as tracers to study palaeoecology and the diet preferences of fossil vertebrates we serially sampled tooth enamel carbonate along the growth axes of five early maastrichtian carnivorous dinosaur teeth tarbosaurus bataar tyrannosaurid from the nemegt formation mongolia in order to identify seasonal climatic variations and determine the diet of this apex predator additional bulk samples of dentine bone and surrounding sediment were analyzed in order to exclude diagenetic obfuscation of the isotopic record enamel samples of potential prey species for dietary studies were also analyzed in the case of the largest specimens the sampled teeth usually recorded annual cycles ranging between two thirds and a full year fluctuations in 18o values in tyrannosaurid teeth suggest seasonality high annual temperatures with distinct precipitation humidity maxima during summer months with mean annual temperatures mat ten degrees higher than those of present day mongolia the seasonal pattern of 18o shows similarities to that of the modern day shijiazhuang global network of isotopes in precipitation station northern china and suggests that the nemegt biota flourished when exposed to a cool temperate monsoon influenced climate herbivore and carnivore carbon isotopes 13c values from tooth enamel imply the presence of a woodland ecosystem dominated by coniferous trees such as araucariaceae and are consistent with the hypothesis that large sauropods and hadrosaurids were the preferred prey of tarbosaurus mean annual precipitation map based on the relationship between modern day c3 gymnosperms and local average map is estimated at 775 835 mm yr these results show that large theropod teeth can serve as valuable archives for palaeoenvironmental studies

reflected seismic waves and their effect on strong shaking during the 1989 loma prieta california earthquake our data indicate that critical and postcritical reflections from crustal layers and the moho produced increased shaking at discrete distances along the san francisco peninsula during the 1989 loma prieta earthquake these reflections may have produced an increase in amplitude that is as much as 10 times greater than that of the direct arrival peak amplitude distance patterns measured from explosive sources synthetic seismograms aftershocks and the mainshock of the 1989 loma prieta earthquake indicate that 1 point sources such as explosions produce similar peak amplitude distance relations as distributed double couple sources when the crustal structure is approximately a poisson solid 2 peak amplitudes from smaller point sources explosions may be scaled to those of larger sources earthquakes and 3 reflections caused a pattern of high amplitudes at specific distances along the san francisco peninsula that geographically correlates with areas of reported damage following from the loma prieta mainshock our study indicates that critical and postcritical reflections were stronger influences on the locations of strong shaking than local geology because a number of sites around the san francisco bay that are underlain by unconsolidated sediments experienced much less shaking than sites that were underlain by hard rock furthermore some severely shaken hard rock sites were farther from the epicenter than many of the less severely shaken soft sediment sites models of the regional crustal structure and seismic wave propagation paths may be useful in identifying sites around the san francisco bay region that are at risk due to reflected seismic energy and this type of analysis may be useful in other seismically active regions

long period surface waves of four western united states earthquakes recorded by the pasadena strainmeter long period surface waves recorded on the north south pasadena strainmeter are used to determine the seismic moments and fault parameters of the 19 may 1940 imperial valley california the 16 december 1954 dixie valley and fairview peak nevada and the 18 august 1959 hebgen lake montana earthquakes synthetic strain seismograms are matched with the observed strainmeter seismograms source parameters from the strainmeter modeling are more consistent with source parameters estimated from geodetic and geologic information than parameters estimated from short period 15 sec body wave data long period surface wave moment estimates agree well with geodetic estimates of moment but are 1 5 to 5 times greater than moments obtained from modeling of teleseismic body waves or geologic information the imperial valley earthquake is best modeled as consisting of 5 point sources along a fault 87 5 km in length with a strike rake and dip of 326 180 and 90 the moment for the earthquake was 4 8 10 19 n m the synthetic seismogram that best models the fairview peak and dixie valley earthquakes assumes that the fairview peak earthquake was twice the size of the dixie valley event moments of 5 9 to 13 10 19 and 3 to 6 5 10 19 n m are obtained for these events a moment of 1 5 10 20 n m is obtained for the hebgen lake earthquake love waves of this earthquake are best modeled by a fault striking 102 although surface faulting produced during the earthquake strikes 130

three dimensional finite difference simulations of long period strong motions in the tokyo metropolitan area during the 1990 odawara earthquake mj 5 1 and the great 1923 kanto earthquake ms 8 2 in japan utilizing a crustal velocity model that includes the complexity of the irregular subsurface structure of the kanto basin we have performed three dimensional 3d finite difference fd simulations of near source long period strong ground motions in the tokyo metropolitan area for the 1990 odawara mj 5 1 and the 1923 kanto ms 8 2 earthquakes constraints on the development of the 3d velocity model come from available geological and geophysical data as well as our previous 1d waveform modeling results sato et al 1998a the simulation of the moderate sized odawara earthquake demonstrates that the 3d velocity model works quite well at reproducing the recorded long period t 3 33 sec strong motions including basin generated surface waves for a number of sites located throughout the kanto basin region using this validated 3d model along with the variable slip rupture model of wald and somerville 1995 we then simulate the long period t 4 sec ground motions in this region for the 1923 kanto earthquake the simulation results for the 1923 event show that the largest ground motions occur east of the epicenter along the central and southern part of the boso peninsula these large motions arise from strong rupture directivity effects and are comprised of relatively simple source controlled pulses with a dominant period of about 10 sec north of the epicentral region in the tokyo area 3d basin generated phases are quite significant and these phases produce large amplitude late arriving pulses in the ground motions at station hongo hng which is the only site having digitized and restored near fault strong motion records for this event our 3d simulations compare quite well with the ground motions of the restored imamura seismogram for the restored ewing record our 3d simulations reproduce the phase and amplitude of the initial pulses of motion however the dominant period of the large amplitude later phases is noticeably shorter in the simulations about 5 to 6 sec than in the observation 13 sec these results suggest that the restored imamura seismogram may be a better representation of the gross features of the actual motion than the restored ewing seismogram although the first clipped and restored part of the imamura seismogram may still underestimate the strength of the actual motion

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

palaeoenvironments of the late triassic rhaetian sea implications from oxygen and strontium isotopes of hybodont shark teeth the oxygen and strontium isotopic composition of 125 teeth of the hybodont sharks lissodus and hybodus from various late triassic rhaetian bone bed localities in the central european basin are used as environmental and ecological tracers for the shallow epicontinental rhaetian sea the preservation of tooth enameloid was ascertained by cathodoluminescence microscopy mean 18op values differ regionally across the rhaetian sea with values of 18 6 0 6 near the western gate 16 1 0 8 in the east 15 4 0 6 in the southeast and 17 7 0 9 in the south the 18op values in the eastern rhaetian sea are 4 5 lower relative to tethyan seawater while teeth from the southern and western parts close to the marine gates are less fractionated the strontium isotopic composition of teeth from most localities is more radiogenic in comparison to late triassic seawater the observed spatial 18op trend in the rhaetian sea indicates a shift from marine to brackish conditions in the south and west towards extensively brackish conditions with salinities of less than 16 in the east thus confirming the existence of two marine gates brackish conditions persisted throughout early rhaetian times and were maintained by increased fluvial discharge from the vindelician bohemian and fennoscandian highs as a result of enhanced atmospheric moisture availability in the course of the rhaetian transgression the 18op values of lissodus and hybodus indicate euryhaline behaviour of rhaetian hybodonts by exceeding modern shark intraspecific variability the lack of accordance in 18op values between different isotopically conspicuous localities in the rhaetian sea contradicts a basin wide migration pattern differences between co site taxa might indicate some degree of niche partitioning

the incorporation of uranium into diagenetic phosphorite abstract the behavior of u during the diagenetic formation of marine phosphorite has been modelled the model examines a dissolution reprecipitation replacement of skeletal hydroxyapatite calcium carbonate and earlier generated francolite by francolite the amount of organic matter consumed relative to the mass of francolite formed the replacement reaction progress and the concentration of u in the replaced phases are the important parameters which dictate the concentration of u in the phosphate rock a partition coefficient between apatite and interstitial solution was calculated and is u f 0 57 natural phosphorites have been examined and are discussed in the light of the proposed model the u mass balance in a recent phosphorite is in good accord with theoretical predictions differences in u concentrations between sea floor phosphorites are explained either by the original variation in the organic matter distribution in the corresponding sediments and or by mineralogical differences caco3 vs hydroxyapatite therein senonian phosphate rocks which were formed via the francolite francolite transformation demonstrate that during that process the organic matter content in the sediment was approximately 50 the model supports the idea that phosphorite rock formation is a multistage process

attenuation of intensity for the 1887 northern sonora mexico earthquake abstract contouring the intensity data for the northern sonora earthquake of 1887 yields an area of perceptibility defined by the mm iii isoseismal that is greatly elongated to the southeast of the epicenter along the sierra madre occidental north of the epicenter the isoseismals are compressed due to the change in crustal structure between the colorado plateau and the southern basin and range province the higher intensity isoseismals are more symmetric although local structure strongly influences individual intensity values to evaluate the attenuation of intensity with distance three regression curves are calculated as below all data i 12 0 3 2 0 0015 r 1 5 in r 25 500 km i 12 0 0 69 0 0069 r 0 82 in r isoseismal i 12 0 8 1 0 0031 r 2 3 in r where r is the epicentral distance in kilometers the all data curve is derived from a regression computed using all 171 intensity values the 25 500 km curve eliminates the near and far points and the isoseismal curve is a regression on the average radii of the area enclosed by each isoseismal contour the latter two curves are similar to curves for the western united states as a whole anderson 1978 or the cordilleran curve of howell and schultz 1975 for intensities less than or equal to mm x the curve for all data indicates less attenuation at lower isoseismals than the other two 1887 regressions and falls between the cordilleran and eastern united states models of howell and schultz

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

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

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

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

the 2013 seismic swarm in chihuahua mexico evidence of active extensional deformation in the southern basin and range abstract an earthquake swarm took place from 27 august 2013 to december 2013 in the southern basin and range province of chihuahua mexico during this period the seismological service of mexico located approximately 60 earthquakes in the region the largest earthquake took place on 21 september 2013 m w 5 3 a temporary seismic network was installed in the area for a period of two weeks the hypocenters were relocated using the double difference algorithm the results show a cluster of seismicity along the vallecillo fault where most of the seismicity took place and on the penasco fault these two faults lie within the foothills of the sierras of the same name that bound the el caballo desert basin the seismicity suggests that both faults bounding the el caballo basin slipped during the swarm the main event of 27 august 2013 apparently took place on the vallecillo fault a third cluster of seismicity was located on sierra la mezcalera about 20 km to the south of the vallecillo fault at the western end of the la boquilla dam focal mechanisms of the larger events indicate right lateral slip with extensional deformation on the vallecillo fault with t axes oriented in a northeast southwest direction these source mechanisms reflect a regime of extensional tectonics in the southern basin and range province the vallecillo and penasco fault system is exposed for approximately 12 km along strike scaling relations suggest that earthquakes as large as m w 6 4 may take place on them this magnitude is similar to that of the 1928 parral earthquake that occurred about 125 km to the south of the swarm however segmented faults may rupture sequentially and generate a larger earthquake than the one predicted on the basis of the length of individual mapped faults

structural configuration of the otates fault southern basin and range province and its rupture in the 3 may 1887 mw 7 5 sonora mexico earthquake abstract during the great 3 may 1887 sonoran earthquake surface rupture end to end length 101 8 km m w 7 5 0 3 an array of three north south striking basin and range province faults from north to south pitaycachi teras and otates slipped along the western margin of the sierra madre occidental plateau of northern mexico this detailed field survey of the previously undocumented 1887 earthquake rupture zone along the otates fault includes mapping the rupture scarp and measurements of surface deformation at 25 sites the surface rupture coincides with the mapped trace of the otates fault dips 68 w and has an end point to end point length of 18 2 km the lateral rupture terminations are controlled by cross faults striation measurements and the style of rupture indicate extensional dip slip without significant lateral displacement the average shortening p and extension t kinematic axes inferred from the striations are similar to published composite focal mechanisms of the microseismicity recorded in the epicentral region of the 1887 earthquake based on surface deformation maximum slip along the otates fault in the 1887 earthquake was 270 cm and the average slip was 189 cm a quadratic best fit to the along rupture surface offsets indicates an asymmetric distribution with the maximum offset near the northern end of the rupture segment which can be explained by the mechanical interaction of the teras and otates surface rupture segments through their stress fields the average recurrence interval of 1887 sized earthquakes on the otates fault is 30 42 kyr based on the long term geologic dip slip rate of the fault 0 06 mm yr and its amount of slip in the 1887 earthquake

fast characterization of sources of recent italian earthquakes from macroseismic intensities abstract we analysed the intensity data collected immediately after three strong earthquakes mw 6 that occurred in italy in the last decade to infer location orientation and size of the relevant seismogenic faults using the boxer method we show that starting from a few hours after the earthquake such macroseismic method could have provided a characterization of the seismogenic source comparable to instrumental methods some of which would have required much more time to provide stable results particularly for the 6 april 2009 earthquake the analysis of macroseismic survey data could have been able to accurately constrain starting already from the early afternoon of the day of the main shock location orientation and size of the area of maximum coseismic displacement related to the activation of the paganica s demetrio fault system for the 20 may 2012 emilia and the 24 august 2016 amatrice earthquakes preliminary macroseismic surveys were carried out within a few days from the main shocks but their data were made available publicly a month later for the 20 may 2012 emilia earthquake the orientation of the fault could have been correctly determined even if the size would have been underestimated for the 24 august 2016 amatrice earthquake both the orientation and the size could have been correctly assessed we also compared such macroseismic determinations with those obtained for some historical earthquakes in the same areas the analysis of the cumulate intensities observed after the shocks of 24 august 26 and 30 october 2016 indicates an overall mw 6 8 comparable to that mw 6 9 of the largest earthquake occurred in the same section of the apennines 14 january 1703 even if the inferred orientations of the 2016 and 1703 boxes are very similar the epicentres differ of about 20 km indicating a probable distinct fault system for the two earthquakes

mmi attenuation and historical earthquakes in the basin and range province of western north america earthquakes in central nevada 1932 1959 were used to develop a modified mercalli intensity mmi attenuation model for estimating moment mag nitude m for earthquakes in the basin and range province of interior western north america m is 7 4 7 5 for the 26 march 1872 owens valley california earthquake in agreement with beanland and clark s 1994 m 7 6 that was estimated from geologic field observations m is 7 5 for the 3 may 1887 sonora mexico earthquake in agreement with natali and sbar s 1982 m 7 4 and suter s 2006 m 7 5 both estimated from geologic field observations mmi at sites in california for earthquakes in the nevada basin and range appar ently are not much affected by the sierra nevada except at sites near the sierra nevada where mmi is reduced this reduction in mmi is consistent with a shadow zone produced by the root of the sierra nevada in contrast mmi assignments for earthquakes located in the eastern sierra nevada near the west margin of the basin and range are greater than predicted at sites in california these higher mmi values may result from critical reflections due to layering near the base of the sierra nevada

long period seismic amplification in the kanto basin from the ambient seismic field tokyo like many seismically threatened cities is situated atop a sedimentary basin that has the potential to trap and amplify seismic waves from earthquakes we study amplification in the kanto basin by exploiting the information carried by the ambient seismic field we use 375 seismic stations from the high sensitivity seismograph network across central honshu as virtual sources and 296 seismic stations of the metropolitan seismic observation network shallow borehole seismometers within the basin as receivers to map the basin response we find a linear relationship between ground motion and basin depth at periods of 2 10 s that could be used to represent 3 d basin effects in ground motion prediction equations we also find that the strength of basin seismic amplification depends strongly on the direction of illumination by seismic waves

source parameters of earthquakes in the nevada seismic zone 1915 1943 the nevada seismic zone has historically been one of the most active seismic regions of the intermountain west although all large m 7 0 earthquakes located within this zone occurred prior to the establishment of a worldwide seismograph network most have been well recorded instrumentally this study uses available instrumental data to determine the source parameters for some of the earliest earthquakes occurring within the region namely the 1915 m 7 6 pleasant valley and 1932 m 7 2 cedar mountain earthquakes and several smaller events of 5 5 m 6 5 occurring within the cedar mountain region between 1934 and 1943 results of body waveform inversions suggest that the pleasant valley earthquake at the northern end of the nevada seismic zone is a complex event best fit by a multiple source time function waveform and first motion information for the cedar mountain earthquake located within the walker lane suggest the earthquake was composed of two events each having significant components of right lateral strike slip motion rakes of 176 to 179 waveforms of the m 6 5 excelsior mountain earthquake located only 40 km southwest of cedar mountain suggest the earthquake was a simple rupture along a normal fault rake of 90 20 although surface faulting indicates that the event had a component of left lateral strike slip motion

centroid moment tensor solutions for 35 earthquakes in western north america 1977 1983 abstract seismic records from the gdsn sro asro dwwssn rstn and ida networks were used to obtain long period t 45 sec focal mechanisms for 35 earthquakes in western north america longitude 140 to 110 latitude 30 to 60 employing the centroid moment tensor method of dziewonski et al 1981 and dziewonski and woodhouse 1983 the same algorithm was applied to all events the smallest m 0 6 4 10 23 dyne cm being an aftershock to the 1979 imperial valley california earthquake and the largest m 0 8 5 10 26 dyne cm the 1980 eureka california earthquake all events were analyzed with and without the constraint m r m r 0 on the moment tensor an ad hoc criterion on the relative variance reduction was employed to determine a favored solution our solutions show general agreement with other published results as well as with tectonic structures agreement with results obtained using the abundant local and regional data confirms the adequacy of the method in determining long period source parameters and verifies its applicability in regions where local and regional data are scarce or nonexistent in some cases disagreement between our solution and results from first motion studies appears to be related to source complexities our moment tensor represents the total stress release of the composite event a consistent westward movement of the centroid locations reflects lateral heterogeneities in the crust and mantle

cathodoluminescence tools provide clues to depositional history in miocene and pliocene mammalian teeth abstract this paper presents the results of a study which used cathodoluminescence cl observations optical images and sem spectra as a tool for assessing diagenetic processes during fossilisation of continental mammalian teeth the study was performed on fossil teeth of large mammals gomphotheriidae rhinocerotidae and hippopotamidae from namibia and from kenya with ages from the lower and middle miocene to pliocene the fossil sites are distinguished by their environmental conditions they include floodplain deposits fluvial deposits of the proto orange river and aeolianite deposits in namibia and fluvio lacustrine deposits of different ages in kenya optical cl provides information about the sites environments and diagenetic processes related to those environments a blue intrinsic luminescence for the aeolianite deposits and purple to yellowish for floodplain or fluvial deposits the cl spectra of these samples show sharp emission bands which are classically related to late recent incorporation of rare earth elements ree substituting in the ca 2 sites high resolution mapping of the distribution of these ree shows a gradient from the enamel interior low concentrations to the outer enamel margin high concentrations

reinterpretation by ray tracing of a transverse refraction seismic profile through the california sierra nevada part i abstract this study reanalyzes a refraction seismic profile from nts nevada to san francisco transverse to the high sierra nevada three models of the earth9s crust with an asymmetrical mountain root constructed by different authors are tested by the use of ray tracing model cqm carer et al 1970 with a maximum crustal thickness of 35 km centered about 50 km west of the crest of the sierra models a and b pakiser and brune 1980 with a mountain root extending to a depth of 55 km below the sierra in the latter guided and diffracted waves are used to explain seismic p n energy in the shadow zone of the root the preferred model a has a high velocity layer dipping from west to east in the upper crust while model b does not the present study demonstrates how fallacies in interpretation of complicated structures can occur if all ray types are not quantitatively traced the influence of the p wave gradient in the upper mantle on the length of the shadow zone is shown to be important and it is demonstrated that a modified cqm model explains the observed travel times when diffracted waves are included cqm does not however explain why the p n travel times on a separate refraction profile along the sierra nevada from a truckee earthquake are so great model b interprets the p n signals at 200 km as diffracted waves but the computed travel times do not fit the observations the dipping wave guide in model a does not work as expected and perhaps should be ruled out

determining location and magnitude of historical pre 1963 events in the rio grande rift region using intensity information abstract we used intensity information from five calibration earthquakes to estimate an intensity attenuation model for the rio grande rift region encompassing west texas new mexico and southern colorado the attenuation model lies between similar models developed for the basin and range province and central and eastern north america analysis of two test earthquakes occurring in 1931 and 2014 validated that the intensity attenuation relation adequately predicted the events magnitudes and epicenters we then analyzed intensity information for nine historical 1906 1960 earthquakes to determine their magnitudes and epicenters our results indicate that the largest earthquakes of the 1906 socorro new mexico sequence had intensity magnitudes m i 5 7 5 9 and may represent north to south migration of seismicity associated with the socorro magma body moderate earthquakes in 1935 and 1960 also are associated with the magma body the 1938 arizona new mexico border earthquake sequence occurred about 50 km northeast of the ongoing 2014 arizona new mexico border sequence the 17 september earthquake of the 1938 sequence had an m i 4 1 that was about 1 0 units less than that of the 29 june 2014 arizona new mexico event m i 4 9

geometry of the 1954 fairview peak dixie valley earthquake sequence from a joint inversion of leveling and triangulation data in 1954 four earthquakes greater than ms 6 0 occurred within a 30 km radius and in a period of 6 months elevation and angle changes calculated from repeated leveling and triangulation surveys which span the coseismic period provide constraints on the fault geometries and coseismic slip of the faults which were activated the quality of the coseismic geodetic data is assessed corrections are applied to the leveling data for subsidence due to groundwater withdrawal in the fallon area and a rod miscalibration error of 150 30 ppm is isolated in leveling surveys made in 1967 the leveling and triangulation observations are then simultaneously inverted using the single value decomposition svd inversion method to determine fault geometries and coseismic slip using svd it is possible to determine on which faults slip is resolvable given the data distribution the faults are found to dip between 50 and 80 and extend to depths of 5 to 14 km the geodetically derived slip values are generally equal to or greater than the maximum observed displacement along the surface scarps where slip is resolvable the geodetic data indicates the 1954 sequence contained a significant component of right lateral slip this is consistent with the n15 w trending shear zone which geodetic surveys have detected in western nevada

observations and modeling of long period ground motion amplification across northeast china basin resonances can significantly amplify and prolong ground shaking and accurate site amplification estimates are crucial for mitigating potential seismic hazards within metropolitan basins in this work we estimate the site amplification of long period 2 10 s ground motions across northeast china for both surface waves and vertically incident shear waves the spatial distribution of relatively large site amplifications correlates strongly with known sedimentary basins for both wave types however the site response of surface waves is typically twice as high as that of shear waves at most basin sites we further show that these site amplification features can be well explained by predictions based on the local one dimensional structure at each site our results highlight the importance of accounting for surface wave contributions and demonstrate the usefulness of semi analytical theory for surface wave amplification which may be broadly applicable in future seismic hazard analysis

ecological and physiological variability of sr ca and ba ca in mammals of west european mid wurmian food webs the middle to upper paleolithic transition in western europe is characterized from an ecological point of view by large ungulate communities adapted to cold climatic conditions the aim of this study is to reconstruct the trophic relationships prevailing in these paleoecosystems which have no equivalent in the modern world bone and dentine remains representing five mammalian assemblages dated around 35 ka bp one of which included a neandertal specimen are investigated for sr ca and ba ca of bioapatites examination of the n content and u ree luminescence of bulk material ca p ratios and mn and ca contents of purified samples demonstrates that the sr ca and the ba ca ratios of bone and dentine samples are not significantly altered by diagenesis as a consequence of the biological discrimination of sr and ba in relation to ca sr ca and ba ca values are impoverished with increasing trophic position and are strongly correlated within a trophic web the slopes of the linear regressions between sr ca and ba ca are consistent with modern variability furthermore a statistical difference was found between ba ca of foregut and hindgut herbivores when coexisting collagen is preserved the sr ba ca and 15n are strongly correlated the distribution of values suggests that the 15n range is mainly controlled by the variability of soil conditions whereas the 13c range may be related to resource availability

three dimensional seismic model of the sierra nevada arc california and its implications for crustal and upper mantle composition a three dimensional p wave velocity model of south central california from the coast ranges to the sierra nevada shows that the crust under most of the southern sierra nevada batholith has seismic velocities 5 9 6 3 km s below the continental average the crust is not much thicker on average about 35 km than in the adjacent great valley and basin and range province apart from a small northward thickening crustal root under the western sierra nevada that reaches a depth of 42 km crustal velocities above the continental average are observed beneath much of the great valley due to a high velocity body underlying the sedimentary basin and the foothills metamorphic belt 6 4 7 0 km s upper mantle velocities are generally low 7 8 km s but span a wide range 7 4 8 2 km s we display the velocity model in several cross sections and maps of moho depth and average crustal velocity the measured velocities in the upper and mid crust of the sierra nevada batholith are in good agreement with laboratory measurements on sierra nevada tonalites after corrections for density and temperature peridotite xenoliths from the eastern sierra nevada suggest strong upper mantle anisotropy which could explain some of the velocity heterogeneity in the sierra nevada mantle by the time cretaceous subduction related magmatism ceased the sierra nevada arc must have had a thick mafic lower crust yet a principal result of our work is that today the batholith has a crust of mainly felsic composition throughout a subcrustal layer with velocities below normal pn velocities 7 6 km s may indicate the presence of lower crustal material in eclogite facies

diffusion of rare earth elements in fish teeth from deep sea sediments the distribution of rare earth elements rees in biogenic phosphate phases in sediments such as the remains of fish teeth has been proposed as an indicator of the depositional environment in the water column recording for example palaeo redox conditions1 and isotope geochemical2 5 and hydrothermal6 7 processes enrichment of these phases in rees takes place only during early diagenesis8 9 for which reason the ree signal has often been assumed to represent the unfractionated record of ree distribution in the water column overlying the sediment surface1 4 5 10 here we report on studies of ree zoning in fish teeth from pacific sediments from which we extract a ree diffusion coefficient of 70 mm2 myr 1 this value suggests that diffusion of rees from sea water into the fish teeth before burial is too slow to produce the enrichments observed instead the ree distributions must derive from the surrounding sediment pore fluids the use of these distributions as palaeoceanographic indicators is therefore called into question

the ree and end of 40 70 ma old fish debris from the west african platform ree concentrations and nd isotopic compositions have been determined in late cretaceous early cenozoic fish debris from west african and israeli platform sediments and show a strong regional control independent of time except for those from the northern morocco it is suggested that although diagenetic fluids do not contribute ree s directly to the phosphatic debris they may significantly change the ce anomaly and the end t value of the epicontinental seas which in turn control the ree in marine phosphates it is shown that over the investigated period the north moroccan shelf seawater was progressively flushed by deep north atlantic water

luminescence of uranium bearing opals origin and use as a ph record abstract fluorescence of minerals has been long used for u exploration it is proposed here that opal fluorescence can be used as a probe of the ph of the formation solution bringing constraints for modeling u speciation and sequestration at the earth s surface we present a study of fluorescence spectroscopy of u in opals resulting from low temperature 29 c alteration of mineralized rhyolitic lavas nopal i u deposit sierra pena blanca mexico these opals show green fluorescence with a concentric distribution at microscopic scale which is unambiguously assigned to uranyl groups oxidized form of u spectra appear typical of uranyl in opal as reported in literature for other localities according to peak positions when considering also the lifetime of fluorescence spectra with time resolved laser fluorescence spectroscopy fingerprinting indicates that uranyl occurs either as phosphate or hydroxo polynuclear complexes trapped onto the opal internal surface data are indicative of a ph of opal formation around 8 as derived from both conditions of laboratory experiments and reference to calculated diagrams of speciation this ph value is consistent with the nopal geological formations that were potentially in contact with the aquifer involved in the hydrothermal process in addition the microscopic zoning of u suggests that the speciation has been stable since opal formation more than 50 ka ago which allows the record of ph that prevailed at that time

regional intensity attenuation models for france and the estimation of magnitude and location of historical earthquakes summary intensity assignments for 33 calibration earthquakes were used to develop intensity attenuation models for the alps armorican provence pyrenees and rhine regions of france intensity decreases withmost rapidly in the french alps provence and pyrenees regions and least rapidly in the armorican and rhine regions the comparable armorican and rhine region attenuation models are aggregated into a french stable continental region model and the com parable provence and pyrenees region models are aggregated into a southern france model we analyse msk intensity assignments using the technique of bakun wentworth which provides an objective method for estimating epicentral location and intensity magnitude m i m i for the 1356 october 18 earthquake in the french stable continental region is 6 6 for a location near basle switzerland and moment magnitude m is 5 9 7 2 at the 95 per cent 2 confidence level m i for the 1909 june 11 trevaresse lambesc earthquake near marseilles in the southern france region is 5 5 and m is 4 9 6 0 at the 95 per cent confidence level bootstrap resampling techniques are used to calculate objective reproducible 67 per cent and 95 per cent confidence regions for the locations of historical earthquakes these confidence re gions for location provide an attractive alternative to the macroseismic epicentre and qualitative location uncertainties used heretofore

the 2009 april 6 mw 6 3 l aquila central italy earthquake finite fault effects on intensity data summary we analyse the spatial distribution of the intensity data points surveyed after the mw 6 3 2009 l aquila central italy earthquake with the aim to recognize and quantify finite fault and directivity effects the study is based on the analysis of the residuals evaluated with respect to attenuation with distance models calibrated for l aquila earthquake we apply a non parametric approach considering both the epicentral and the rupture distance which accounts for the finite extension of the source then starting from a simplified kinematic rupture model of the l aquila fault we compute four directivity predictors proposed in literature and assess their correlation with intensity residuals we derive a so called intensity directivity factor by the correlation between theoretical predictors and observed residuals that allows us to identify and quantify the intensity data points affected by forward and backward directivity during l aquila earthquake we find that the effects are more pronounced in the forward directivity direction and increments up to 1 mcs intensity unit are expected moreover the directivity predictor that accounts for radiation pattern poorly correlates with residuals these results show that the spatial distribution of the l aquila macroseismic field is affected by source effects and in particular that directivity induced amplification effects can be recognized we show that the quasi unilateral rupture propagation along the fault can explain the high intensity patterns observed along specific direction at relatively large distance from the instrumental epicentre in accordance with the seismological source models derived from the analysis of instrumental observations

the influence of critical moho reflections on strong ground motions recorded in san francisco and oakland during the 1989 loma prieta earthquake the amplitudes of strong ground motions from the loma prieta earthquake recorded in the san francisco and oakland areas exceeded the levels predicted by standard empirical attenuation relations preliminary analysis of accelerograms having known trigger times strongly suggests that the elevation of ground motion amplitudes in the distance range of approximately 40 to 100 km was due to critical reflections from the base of the crust these reflections which are identified on the basis of their arrival times and phase velocity and by comparison with simulated accelerograms were large and occurred at relatively close range because of the deep focal depth of the earthquake and the strong velocity gradient at the base of the crust these motions were further amplified presumably by impedance contrast effects at soft soil sites in san francisco and oakland the effect of the critical reflections in amplifying peak accelerations of the loma prieta earthquake in the san francisco and oakland regions was as large as the effect of soft soil site conditions focal depth has an important influence on strong motion attenuation at distances beyond about 40 km and empirical attenuation relations derived from shallow crustal earthquakes may underpredict the ground motions of deeper crustal events in this distance range further analyses using an expanded data base that includes recordings of aftershocks are required to rigorously test the proposed explanation of the ground motions recorded in san francisco and oakland and the conclusions drawn from that explanation

seismicity in the epicentral region of the 1887 northeastern sonoran earthquake mexico the 1887 sonoran earthquake in northeastern sonora mexico has an 80 km rupture length with an average 3 m displacement and an assumed 16 km depth of rupture this corresponds to a seismic moment of 1 27 x 1027 dyne cm and an ms of 7 4 seven to ten portable seismographs with an average spacing of 10 km were operated in a 2800 km 2 region surrounding the 1887 fault scarp thirtythree earthquakes were detected during 30 days of usable recording for all events 1 3 m 2 the most accurate locations horizontal error 5 km define a west dipping normal range bounding fault all events occurred within 15 km of the surface the name pitaycachi fault after the most prominent peak of the horst block is proposed for this zone of active faulting seismicity along the zone terminates abruptly 13 km north of the fault scarp and extends to the south for at least 32 km beyond the southern a composite focal mechanism from events at the southern end of the 1887 scarp indicates a normal fault striking n35 e and dipping 72 to the northwest

anomalous propagation of long period ground motions recorded in tokyo during the 23 october 2004 mw 6 6 niigata ken chuetsu japan earthquake unusually large 5 cm and prolonged shaking associated with long period ground motions at periods of about 7 sec were observed in central tokyo during the mw 6 6 niigata ken chuetsu earthquake of 23 october 2004 the long period ground motions caused significant resonance in high rise buildings of about 70 floors in height thus it is an urgent matter to understand the development and amplification properties of long period ground motions in tokyo associated with large earthquakes in this study we use numerous waveform records from 585 stations in a nationwide accelerometer network k net kik net and 495 intensity meters in the area around tokyo the data reveal that the long period ground motion is characterized in most part by a surface rayleigh wave generated at the northern edge of kanto basin and the surface wave is developed as propagating through a thick cover of sediments 3000 4000 m that overlies rigid bedrock to complement the observational data we conducted a large scale computer simu lation of seismic wave propagation by employing the earth simulator supercomputer with a detailed source slip model and a high resolution 3d sedimentary structural model of central japan the results of the computer simulation demonstrate that the anomalously prolonged ground shaking of the long period signal recorded in the center of tokyo occurred because of the stagnation of seismic energy resulting from the multipathing and focusing of rayleigh waves toward the bottom of the kanto basin from surrounding mountain regions with interaction to the 3d basin structure

geometry and relative motion of the philippine sea plate and pacific plate beneath the kanto tokai district japan the recent acquisition of high density and improved seismic data by the kanto tokai k t observational network of the national research institute of earth science and disaster prevention requires the revision of conventional plate configuration models for the k t district we propose a new interpretation of the configuration and relative motion of the philippine sea phs plate pacific pac plate and eurasian eur plate on the basis of the distribution of hypocenters velocity structure and focal mechanisms in the k t district the new model for the configuration of the phs and pac slabs clearly delineates the phs slab subducting northwestward beneath the k t district from the sagami and suruga troughs and the pac slab subducting westward beneath the phs slab from the japan trench the thickness of the descending phs slab is estimated to be 30 5 km the proposed configuration of the phs slab is significantly different from those obtained by other researchers including our own previous study the new model is fully consistent with global plate motion data the new model leads to an interpretation of the tectonic processes taking place beneath the k t district for the sagami trough wing of the phs slab the northeastern portion of the slab is dipping northwestward in direct contact with the upper surface of the pac slab the southwestern portion carrying the izu peninsula has been bent upward because of its buoyancy producing the observed contorted shape for the suruga trough wing the dip direction of the phs slab gradually changes from northwestward at the eastern portion to northward at the western portion the new model also indicates the presence of offset within the phs slab between the sagami and suruga trough wings this area is characterized by a low level of seismic activity the absence of a high velocity structure and the presence of quaternary volcanoes it seems reasonable to speculate that the distribution of quaternary volcanic edifice construction is controlled by the location of the offset within the phs slab in view of this new model the tectonic processes of large earthquakes which occurred recently in the studied area are also reexamined

regional seismic intensity anomalies in the korean peninsula and its implications for seismic hazard potentials the strength of seismic ground motion is a consequence of seismic source strength and medium response the dependence of seismic amplitudes and seismic intensity on regional geological structures and crustal properties in the stable intraplate region around the korean peninsula is investigated an instrumental seismic intensity scale based on spectral accelerations are proposed after calibrating with the reported macroseismic intensities a representative seismic intensity attenuation curve for the korean peninsula is given by i m text l l h 0 998 pm 0 222 1 72 pm 0 04 m text l 0 322 pm 0 027 text ln l 2 h 2 0 00608 pm 0 00049 sqrt l 2 h 2 where i m text l l h is the seismic intensity at an epicentral distance l in km for an earthquake with local magnitude m text l and focal depth h in km seismic intensities decay slowly with distance in the korean peninsula the observed decay rate for the korean peninsula is comparable with those for other stable intraplate regions while are lower than those for active regions the regional seismic intensity anomalies present a characteristic correlation with geological structures positive seismic intensity anomalies appear in the yeongnam massif okcheon belt and gyeongsang basin while negative seismic intensity anomalies in the gyeonggi massif the regional seismic intensity anomalies display positive correlations with crustal thicknesses crustal amplifications and seismicity density and negative correlations with heat flows positive seismic intensity anomalies are observed in the yeongnam massif and gyeongsang basin suggesting high seismic hazard potentials in the regions the regional crustal properties may provide useful information on potential seismic hazards

estimating earthquake location and magnitude from seismic intensity data analysis of modified mercalli intensity mmi observations for a training set of 22 california earthquakes suggests a strategy for bounding the epicentral region and moment magnitude m from mmi observations only we define an intensity magnitude m i that is calibrated to be equal in the mean to m m i mean m i where m i mmi i 3 29 0 0206 i 1 68 and i is the epicentral distance km of observation mmi i the epicentral region is bounded by contours of rms m i rms m i m i rms m i m i where rms is the root mean square rms m i m i is the minimum rms over a grid of assumed epicenters and empirical site corrections and a distance weighting function are used empirical contour values for bounding the epicenter location and empirical bounds for m estimated from m i appropriate for different levels of confidence and different quantities of intensity observations are tabulated the epicentral region bounds and m i obtained for an independent test set of western california earthquakes are consistent with the instrumental epicenters and moment magnitudes of these earthquakes the analysis strategy is particularly appropriate for the evaluation of pre 1900 earthquakes for which the only available data are a sparse set of intensity observations

revisiting the 1872 owens valley california earthquake the 26 march 1872 owens valley earthquake is among the largest historical earthquakes in california the felt area and maximum fault displacements have long been regarded as comparable to if not greater than those of the great san andreas fault earthquakes of 1857 and 1906 but mapped surface ruptures of the latter two events were 2 3 times longer than that inferred for the 1872 rupture the preferred magnitude estimate of the owens valley earthquake has thus been 7 4 based largely on the geological evidence reinterpreting macroseismic accounts of the owens valley earthquake we infer generally lower intensity values than those estimated in earlier studies nonetheless as recognized in the early twentieth century the effects of this earthquake were still generally more dramatic at regional distances than the macroseismic effects from the 1906 earthquake with light damage to masonry buildings at nearest fault distances as large as 400 km macroseismic observations thus suggest a magnitude greater than that of the 1906 san francisco earthquake which appears to be at odds with geological observations however while the mapped rupture length of the owens valley earthquake is relatively low the average slip was high the surface rupture was also complex and extended over multiple fault segments it was first mapped in detail over a century after the earthquake occurred and recent evidence suggests it might have been longer than earlier studies indicated our preferred magnitude estimate is mw 7 8 7 9 values that we show are consistent with the geological observations the results of our study suggest that either the owens valley earthquake was larger than the 1906 san francisco earthquake or that by virtue of source properties and or propagation effects it produced systematically higher ground motions at regional distances the latter possibility implies that some large earthquakes in california will generate significantly larger ground motions than san andreas fault events of comparable magnitude

seismic moment rates in the utah region an estimate of the long term seismicity of utah is obtained through the calculation of seismic moment rates from available geologic data on quaternary faulting the recurrence rates calculated from these geologic seismic moment rates agree well with recurrence rates estimated from historical earthquake data a return period of 80 to 190 yr for a magnitude 7 0 to 7 5 earthquake in the utah region is predicted by historical seismic and geologic data the estimation of recurrence rates from geologic data requires the use of a moment versus magnitude relationship for earthquakes characteristic of the utah region spectral studies of 19 utah earthquakes define this relationship in addition moment tensors and other source parameters are estimated for these earthquakes a resultant strain tensor for utah indicates the amount of horizontal east west extensional strain is nearly equal to the amount of vertical compressional strain in the region

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

luminescence of uranium and rare earth elements in apatite of fossil fish teeth abstract time delayed laser induced luminescence of uranium and rare earth elements ree in apatite of fossil fish teeth from the phosphorites of the senonian mishash formation israel were investigated before and after thermal treatment the unheated samples show luminescence of uo 2 2 luminescence of ree 3 sm eu pr is observed only after heating the samples at 1100 k in air the spectral properties indicate that uo 2 2 in the unheated samples is located in two different positions as aqua complexes of uranyl ions and associated with organic matter the ree in the unheated samples are accommodated in non luminescent form after heating the ree 3 sm eu pr are located in the ca 2 ii site presumably due to thermal diffusion

m 6 earthquakes in southern california during the twentieth century no evidence for a seismicity or moment deficit abstract a broadly based report on seismic hazards in southern california wgcep 1995 concluded that the predicted seismicity exceeds that observed since 1850 a subsequent independent analysis argued that infrequent huge m 8 earthquakes are needed to explain the low rate of large earthquakes jackson 1996 frequency magnitude relationships and earthquake reporting suggest that the 1903 to 1997 catalog we present here with a b value of 1 0 and a rate of m 6 shocks of 0 42 to 0 49 yr 1 is nearly complete in contrast the 1850 to 1994 catalog used by wgcep is incomplete before the turn of the century and thus its reported seismicity rate of 0 32 m 6 shocks yr 1 is too low principally because the wgcep 1995 model results in b values of up to 4 0 for regions of lesser and blind faults the rate of m 6 shocks off the san andreas system predicted by the wgcep 1995 model is three times greater than that observed in this century because they obtained b 0 4 for m b 2 2 for m 7 3 on major faults their expected rate of m 7 san andreas shocks is twice as high as observed thus part of the seismicity and moment discrepancy identified by wgcep was caused by use of an incomplete catalog and part was caused by inappropriate b values we obtain a southern california moment release rate of 8 to 12 10 18 n m yr 1 which cannot be distinguished from the moment release estimated by fault slip or the moment accumulation inferred from plate motions or geodetically measured shear strain we thus find no evidence for a moment deficit significant aseismic moment release or for rare m 8 earthquakes off the san andreas fault system finally the number of m 6 earthquakes per decade does not depart significantly from a poisson process during this century and thus we find no evidence that the rate of seismicity is increasing now or at any other time since 1900

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

oxygen and strontium isotopes from fossil shark teeth environmental and ecological implications for late palaeozoic european basins article i nfo fossil shark remains occur in both marine and nonmarine late palaeozoic deposits therefore their palaeo ecology is controversial the oxygen and strontium isotopic composition of biogenic fluorapatite in 179 teeth scales and spines predominantly of hybodontid lissodus and xenacanthiform orthacanthus xenacanthus bohemiacanthus triodus sharks from various late carboniferous moscovian to early permian artinskian basins of europe are used as ecological tracers to decipher diadromous or obligate freshwater lifestyle of the investigated taxa the 18 op values of the different shark teeth range from 11 7 to 20 2 within the different basins with mean values of 16 9 0 5 for the bohemian massif 16 2 0 8 for eastern germany 18 2 1 0 for southwestern germany 18 5 0 7 for southern central spain 17 6 0 4 for