early mis 3 occupation of mochena borago rockshelter southwest ethiopian highlands implications for late pleistocene archaeology paleoenvironments and modern human dispersals abstract between 70 and 50 ka bp anatomically modern humans dispersed across and out of africa to eventually populate all inhabitable continents knowledge of paleoenvironments and human behavioral patterns in africa prior to and during these dispersals is crucial for understanding how and why hunter gatherers were able to adapt rapidly to the new environments they encountered however few well dated sites from this time period are known from the horn of africa one of the purported staging areas for population movements into southern arabia and asia excavations at mochena borago rockshelter situated on the western slopes of a dormant volcano where the sw ethiopian highlands meet the ethiopian rift have yielded the first securely dated archaeological sequence for later periods of the dispersal three major lithostratigraphic groups incorporating occupational episodes have yielded charcoal radiocarbon ages 53 38 ka calbp deeper deposits have been tested but remain undated archaeological assemblages consist mainly of obsidian flaked stone artifacts manufactured from small minimally prepared single to multi platform flake cores radially prepared cores are rare and blade cores are absent small unifacial to bifacial points from non radial cores dominate the earliest shaped tool assemblages and backed pieces first appear by 45 ka calbp by 43 ka calbp scrapers and backed pieces are predominant rather than points however there is little evidence for technological change other than the appearance of bipolar technology mochena borago s archaeological sequence thus cannot be neatly classified as middle stone age later stone age or transitional and calls into question some of the principles by which archaeologists have attempted to classify african toolmaking traditions

climate volcanism feedback and the toba eruption of 74 000 years ago abstract a general feedback between volcanism and climate at times of transition in the quaternary climate record is suggested exemplified by events accompanying the toba eruption 74 000 yr ago the largest known late quaternary explosive volcanic eruption the toba paroxysm occurred during the 18o stage 5a 4 transition a period of rapid ice growth and falling global sea level which may have been a factor in creating stresses that triggered the volcanic event toba is estimated to have produced between 1015 and 1016 g of fine ash and sulfur gases lofted in co ignimbrite ash clouds to heights of at least 32 5 km which may have led to dense stratospheric dust and sulfuric acid aerosol clouds these conditions could have created a brief dramatic cooling or volcanic winter followed by estimated annual northern hemisphere surface temperature decreases of 3 to 5 c caused by the longer lived aerosols summer temperature decreases of 10 c at high northern latitudes adjacent to regions already covered by snow and ice might have increased snow cover and sea ice extent accelerating the global cooling already in progress evidence for such climate volcanic feedback following milankovitch periodicities is found at several climatic transitions

the site response of two rock and soil station pairs to strong and weak ground motion abstract the site response to strong and weak ground motion depends largely on the subsurface conditions at the soil site for the two rock soil station pairs studied the first station pair consists of a soft soil site treasure island and a sandstone and shale site yerba buena island these stations recorded strong ground shaking from the loma prieta mainshock and weak ground motion from four aftershocks the range of peak ground acceleration is from approximately 0 00006 to 0 07 g at the rock site compared to the rock site the strong ground motion at the soft soil site is amplified by a factor of about 3 over a frequency range from 0 5 to 2 0 hz the amplification is much higher for weak motion and suggests a dependence on signal amplitude for example near 1 hz the site response shows an increasing amplification as magnitude and the peak velocity at the rock site decreases for events of local magnitude 7 0 4 3 4 1 3 5 and 3 3 the maximum soil site amplifications are 4 12 17 19 and 25 respectively a second station pair consisting of a stiff soil site gilroy 2 and a sandstone site gilroy 1 was also studied with contrasting results these two stations recorded strong ground shaking from the 1979 coyote lake 1984 morgan hill and 1989 loma prieta mainshocks weak ground motion was recorded at these stations after the loma prieta mainshock the range of peak ground acceleration is from 0 006 to 0 43 g at the rock site unlike the results for the soft soil study above the estimated stiff soil site responses are not significantly different for strong and weak motion from 0 5 to 2 0 hz near 0 7 hz the stiff soil site responses range from 2 5 to 4 5 for strong ground shaking from three mainshocks and from 1 5 to 4 0 for weak ground shaking from thirteen aftershocks

a single southern exit of modern humans from africa before or after toba abstract during the late pleistocene anatomically modern humans amh dispersed out of africa they first spread north with game across the sahara to the levant during the eemian interglacial c 125 ka and there is some recent evidence they may also have spread via arabia to the far east at the same time however they failed to continue to europe then occupied by neanderthals the sahara and arabia then reverted to aridity and amh vanished from the fossil record after 92 ka being later replaced in the levant again by neanderthals there is recent fragmentary evidence amh may also have spread via arabia to the far east but the archaeological record fades similarly long before the toba eruption there is no evidence of surviving non african dna lineages dating from anywhere near the eemian to contradict this narrative genetic evidence indicates that amh successfully left africa much later as a single group by the southern route to india since all non african uniparental lineages date to this later exit this appears to have been the only ultimately successful amh exit amh reached the isolated sahul continent at least by 48 ka and possibly by 60 50 ka amh only finally arrived in europe from south asia before 46 ka probably linked to climatic amelioration during mis 3 dating the definitive exit without adequate fossil evidence relies on disputed genetic dates with wide confidence intervals at the top end independent genetic dates combined with ash associated data from malaysia and from india argue for a pre toba exit although the consensus view is still largely post toba recent correction for non linearity due to purifying selection and recalibration of the mtdna clock has improved confidence in genetic dating but reduced the age of the main exit lineage l3 which effectively embodies its maximum estimate to just below that of toba 71 6 ka although relevant 95 confidence intervals ci 57 1 86 6 ka still include the toba event this weakening of the genetic argument puts more pressure on the archaeological evidence associated with toba ash and the need for diagnostic well dated fossil data between 90 70 ka

geostatistical estimation of the transmissivity in a highly fractured metamorphic and crystalline aquifer man danane region western ivory coast abstract this work is aimed at estimating the transmissivity of highly fractured hard rock aquifers using a geostatistical approach the studied aquifer is formed by the crystalline and metamorphic rocks of the western ivory coast west africa in the man danane area the study area covers 7290 km 2 90 km 81 km the fracturing network is dense and well connected without a marked fracture direction a data base comprising 118 transmissivity t values and 154 specific capacity q s values was compiled a significant empirical relationship between t and q s was found which enabled the transmissivity data to be supplemented the variographic analysis of the two variables showed that the variograms of t and q s which are lognormal variables are much more structured than those of log t and log q s which are normal variables this result is contrary to what was previously published and raises the question whether normality is necessary in geostatistical analysis several input and geostatistical estimations of the transmissivity were tested using the cross validation procedure measured transmissivity data supplemented transmissivity data kriging cokriging the cross validation results showed that the best estimation is provided using the kriging procedure the transmissivity field represented by the whole data sample measured estimated using specific capacity and the structural model evaluated solely on the measured transmissivity the geostatistical approach provided in fine a reliable estimation of the transmissivity of the man danane aquifer which will be used as an input in forthcoming modelling

three dimensional simulations of ground motions in the san bernardino valley california for hypothetical earthquakes on the san andreas fault three dimensional finite difference simulations of elastic waves in the san bernardino valley were performed for two hypothetical earthquakes on the san andreas fault a point source with moment magnitude m5 and an extended rupture with m6 5 a method is presented for incorporating a source with arbitrary focal mechanism in the grid synthetics from the 3 d simulations are compared with those derived from 2 d vertical cross section and 1 d flat layered models the synthetic seismograms from the 3 d and 2 d simulations exhibit large surface waves produced by conversion of incident s waves at the edge of the basin seismograms from the flat layered model do not contain these converted surface waves and underestimate the duration of shaking the seismograms from the 3 d simulations have larger amplitude coda than do the seismograms from the 2 d case because of the presence of off azimuth surface wave arrivals in the 3 d simulations that are not included in the 2 d simulations snapshots of the wavefield of the 3 d simulation show that these off azimuth arrivals represent surface waves reflected from the edges of the basin the anelastic attenuation of the sediments is a key parameter controlling the overall duration of motion some of the coda energy at rock sites near the basin edges represents leakage of surface wave energy out of the basin for the m6 5 earthquake simulation the largest ground velocities occur where surface waves reflected from the edge of the basin interfere constructively with the trapped waves that follow the direct s wave maps of maximum ground velocity are produced for two directions of rupture propagation the largest velocities occur in localized portions of the basin the location of the largest velocities changes with the rupture propagation direction contours of maximum shaking are also dependent on asperity positions and radiation pattern

frequency dependent site amplification factors using the s wave coda for the island of hawaii abstract the coda method has been utilized to determine the seismic response at various sites on the island of hawaii using data from the hawaiian volcano observatory hvo seismic network site amplification factors are calculated using spectral ratios of s wave coda amplitude measured for many events and lapse times between 33 and 59 sec for frequencies between 1 5 and 15 0 hz we find that these site amplification factors vary by factors of as much as 12 for a given frequency due to differences in absorption and or impedance properties beneath the site similar to results from japan central california and long valley the coda site amplification factors showed strong correlation with station residuals for magnitude determined by johnson unpublished results for the hvo network between 1 5 and 6 0 hz johnson unpublished results made an independent determination of event magnitudes and station site corrections by measuring averaged windowed amplitudes of the s wave and its coda using a method previously tested with data from the southern california seismic network johnson 1979 station calibrations were simultaneously determined and included the effects of instrument gain and site effect after correcting johnson9s unpublished results results for the instrument gain provided by hvo we obtain correlations similar to the previous works with the best correlation appearing at 3 0 hz despite the complex subsurface structures on the island of hawaii the frequency dependence of our coda site amplification factors displays a remarkable regional trend in some cases plausible causes related to the underlying geologic structures can explain the similar frequency dependence in other cases the similarity cannot be explained or may be coincidental similar frequency dependences among stations accompanied by a large variability in the absolute level of the site effect may be due to inaccurate instrument calibrations

interpreting geoproxies of late quaternary climate change in african drylands implications for understanding environmental change and early human behaviour abstract climate and environmental change in the late quaternary are widely regarded as key drivers of early human development and dispersal in africa robust records of change are required to assess the nature of potential impacts today s late quaternary palaeoenvironmental palaeoclimate reconstructions from the interior southern african basin kalahari are more spatially detailed have a stronger chronometric underpinning and span a longer time range than those of 10 20 years ago but are no less controversial reconstructions for the last 150 ka are usually interpreted in terms of changes in hydrological balance from conditions more humid or more arid than today and expressed in climatological terms as the changing latitudinal interplay between monsoon easterlies and tropical and mid latitude westerlies with more data than ever before why then is the record not yet delivering a more coherent picture of regional climate change this paper deliberately addresses current challenges and controversies including issues often ignored or neglected with the view that it is essential to do so if more robust interpretations of the past are to be generated in the future sources of palaeo data from the interior are predominantly geoproxies reconstructions not based on highly resolved organic or isotope records but on interpretation of spatially extensive geomorphological proxies of past environments despite being increasingly datable using osl their inclusion in syntheses has proved complex not least when interpretations appear to conflict with records from other sources consequently they are sometimes removed from regional syntheses of climate change these omissions are often replaced by spatially exaggerated interpretations of higher quality local records allowing more spatially coherent timeslice interpretations to be presented yet this is counter intuitive to the spatial complexity of conditions present in the palaeoenvironmental proxies or in climatic and environmental systems today in addition the quest to link regional records to master records from ice and ocean cores can force interpretation within a temporal scale that may be inappropriate for their analysis underplaying the reality of complexity within the environmental system there are not necessarily good or bad records of terrestrial palaeoenvironments in interior southern africa rather there are records that contain different suites of information about past land surface hydrological and climate conditions preserved at temporal scales which can sometimes be incomparable consideration of these factors may resolve apparent conflicts between datasets resulting in a better understanding of past environmental dynamics and revealing the nature of environmental variability which may be a key facet to which human development has responded

survey and explorations of caves in southeastern ethiopia middle stone age and later stone age archaeology and holocene rock art abstract the horn of africa provides the setting for the evolution of early modern humans and their dispersal out of africa as well as for the entry many thousands of years later of pastoralists who brought near eastern and later south asian livestock into africa however significant gaps remain in our understanding of the late upper pleistocene archaeological record of the horn of africa mainly due to the paucity of well stratified sites from the period the discovery in southeastern ethiopia of a number of caves with rich upper pleistocene and holocene archaeological deposits many of which also had rock art depicting domestic animals offers an unprecedented opportunity for exploring the later prehistory of the region in 2007 2008 our survey documented twenty one cave sites and shelters with evidence of cultural deposits including middle stone age msa and later stone age lsa stone artifacts faunal remains and rock art active and fossil speleothems important for paleoclimatic reconstructions and chronology were found from two other caves in eastern and western harerghe test excavations were conducted at three sites with abundant archaeological material documented from stratified deposits at two of these sites gilbo tate and goda buticha the latter is a subject of another paper in this volume rock art was recorded at eighteen sites three of which in western harerghe had not previously been documented at many of the sites much of the art is faded and in a vulnerable state and continued efforts to document and conserve this art are urgently needed

local and regional scale impacts of the 74 ka toba supervolcanic eruption on hominin populations and habitats in india abstract the toba supervolcanic eruption of 74 000 years ago is argued to have devastated homo sapiens populations causing a human population bottleneck through a combination of rapid global climatic deterioration and ecological disruption following the widespread ash fall this dramatic eruption the largest in at least the last 2 million years is hypothesized to have shaped the genetic structure and diversity of human populations today past assessments of toba s human impacts however have been predominantly theoretical using archaeological and geological evidence from sites in india this study addresses toba s local scale impacts on hominin technology behavior demography and habitats in two valleys in india the jurreru and middle son valleys using paleoclimatological and volcanological data regional scale impacts throughout india are inferred a refugia hypothesis is presented that argues for variation in the scale of toba s impact throughout india driven by regional differences in monsoonal dynamics geography and topography areas of north west india the indo gangetic plain and parts of the deccan to the east of the western ghats are argued to have been the most affected whereas areas of southern and eastern india may have preserved the largest refugia for hominin populations

grain size distribution analysis of sediments containing younger toba tephra from ghoghara middle son valley india abstract the toba super eruption in northern sumatra 74 ka was the largest eruption of the quaternary period terrestrial deposits of distal toba tephra have been found across the indian subcontinent although few localities have been adequately described with respect to stratigraphy and sedimentary history this study provides the first detailed description of the ghoghara 1a ash section middle son valley india the sediment analyses provide insights into the depositional processes in the valley before and after the initial period of ash deposition grain size distribution analysis of sediments from ghoghara 1a indicates that 4 5 cm of primary air fall ash was laid down at the time of the toba super eruption this study has implications concerning previous isotopic studies in the middle son valley concluding that reconstructions demonstrative of dramatic ecological changes are questionable

barriers and bridges early human dispersals in equatorial se asia past environments of equatorial se asia must have played a critical role in determining the timing and trajectory of early human dispersal into and through the region however very few reliable terrestrial records are available with which to contextualize human dispersal events this circumstance coupled with a sparse archaeological record and the likelihood that much of the archaeological record is now submerged means we have an incomplete understanding of the role that geography climate and environment played in shaping human pre history in this region from a review of the literature we conclude that there must have been a substantial environmental barrier resulting in a genetic separation between east and west sundaland that persisted even though a terrestrial connection was present for most of the pleistocene this barrier is likely to be a north south corridor of open non forest vegetation and its existence may have encouraged the rapid dispersal of early humans through the interior of sundaland and on to sahul we conclude that more reliable terrestrial palaeoenvironmental records are required to better understand the links between past environments and dispersal events we highlight avenues of particular research value such as focusing on eastern sumatra western southern borneo and the islands in the java sea where the purported savanna corridor most probably existed and including edaphic factors in palaeovegetation modelling

topographical and geological amplifications determined from strong motion and aftershock records of the 3 march 1985 chile earthquake site response experiments were performed 5 months after the ms 7 8 central chile earthquake of 3 march 1985 to identify amplification due to topography and geology topographical amplification at canal beagle a subdivision of vina del mar was hypothesized immediately after the main event when extensive damage was observed on the ridges of canal beagle using frequency dependent spectral ratios of aftershock data obtained from a temporarily established dense array it is shown that there is substantial amplification of motions at the ridges of canal beagle the data set constitutes the first such set depicting topographical amplification at a heavily populated region and correlates well with the damage distribution observed during the main event dense arrays established in vina del mar also yielded extensive data which are quantified to show that in the range of frequencies of engineering interest there was substantial amplification at different sites of different geological formations to substantiate this spectral ratios developed from the strong motion records of the main event are used to show the extensive degree of amplification at an alluvial site as compared to a rock site similarly spectral ratios developed from aftershocks recorded at comparable stations qualitatively confirm that the frequency ranges for which the amplification of motions occur are quite similar to those from strong motion records in case of weak motions the denser arrays established temporarily as described herein can be used to identify the frequency ranges for which amplification occurs to quantify the degree of frequency dependent amplification and used in microzonation of closely spaced localities

site amplification from s wave coda in the long valley caldera region california following the work of phillips 1985 we have computed site amplification factors for coda waves at many sites in the long valley region in the eastern sierra nevada we computed ratios of coda amplitudes measured at 15 stations in and around long valley caldera relative to a granitic site mmpm for six frequency bands centered at 1 5 3 0 6 0 9 0 12 0 and 15 0 hz all station sites located within the caldera experienced large ground motion amplification at 1 5 and 3 0 hz ranging between five and 17 times that of the reference site however at higher frequencies these same sites exhibited significantly less amplification than the reference granite site this is attributed to the competing effects of an impedance contrast between the basement rock and caldera fill and very high absorption in the caldera fill at high frequencies station mmlm located on top of a volcanic plug displayed the largest amplitudes of all the sites studied for frequencies between 9 0 and 15 0 hz a dike structure attached to the plug couples the basement rock to the surface at high frequencies the resulting large amplitudes at mmlm are not due to amplification resulting from a strong impedance contrast rather the absorption under this site is very low perhaps lower than at the reference site mmpm outside the caldera another hard rock site located at devil s postpile mdpm generally behaved like the reference site for all frequencies the lowest amplifications observed came from a site outside the caldera mdcm located on thin pyroclastic ash deposits overlying granitic basement this can be attributed to a dominance of absorption over the amplification caused by lower impedance of this layer variations among sites on similar surface geology may be due to small local variations in impedance and absorption under and adjacent to the site the range in the spectral decay parameter between caldera and rock sites are comparable to results of anderson and hough 1984 for sites on alluvium and rock in the san fernando region these surprisingly different amplifications support the need for additional site specific studies amplifications determined in this study for the frequency range 1 5 and 3 0 hz correlate remarkably well with eaton s 1990 residuals for duration magnitude fmag and amplitude magnitude xmag for the usgs northern california seismic array further supporting the use of coda waves in determining site specific amplification

observation of local site effects at a downhole and surface station in the marina district of san francisco abstract the marina district of san francisco california with its artificial fill and a thick section of sand and clay covering a northwest trending valley in the bedrock suffered extensive damage during the 18 october 1989 loma prieta earthquake following the earthquake the usgs drilled a hole at winfield scott school at beach and divisadero streets the borehole intersects bedrock surface at a 79 5 m depth two three component seismometers one in bedrock at a 88 m depth and one located at the surface have been installed at the site each seismometer consists of one vertical and two orthogonally oriented horizontal geophones having a natural period of 0 5 sec between august 1990 and january 1991 more than 50 earthquakes have been recorded digitally eight among these ranging in magnitude between 2 8 and 3 6 and originating on the calaveras franklin greenville and hayward faults and on faults parallel and close to the san andreas fault generated seismograms with high signal to noise ratio horizontal ground motion amplification expressed as spectral ratio between ground motions at the surface and those in the bedrock has been calculated for motions in two orthogonal directions along divisadero and beach street each ground motion spectrum has been calculated using an entire seismogram consisting of body waves surface waves multiply reflected and scattered coda waves and a short section 2 sec of pre event ambient noise before calculating spectral ratio each spectrum has been smoothed using a truncated gaussian window 0 61 hz wide except for the lowest frequency spectral ratio peak at 1 hz frequency of other peaks depends on earthquake location amplitude of spectral ratio peaks also show variation depending on ground motion direction and earthquake location for example amplitude of the 1 hz spectral ratio peak varies from 7 2 to 12 7 the surface downhole spectral ratio therefore provides only partial information on how ground motions are amplified by sediment deposits if we choose to use this ratio for earthquake engineering applications the ratios from the eight earthquakes give an indication of the variation in spectral ratio to be expected from earthquakes with similar magnitudes and epicentral distances on various bay area faults also noteworthy are the observations that the two horizontal component seismograms recorded by each seismometer have similar coda amplitude and duration regardless of earthquake location and that particle motion polarization becomes complex shortly after the p wave and s wave onset the complex particle motion polarization indicates that wave fields in the bedrock and at the surface are three dimensional the bedrock topography underlying the site has been delineated previously to be three dimensional from drill hole information we suggest from these observations that three dimensional effects need to be considered when modeling site amplification in the marina district finally the eight earthquakes are divided into two groups comprising those whose epicenters are located east of san francisco bay and those whose epicenters are located south of san francisco bay within each group spectral ratio peaks from different earthquakes line up with each other thus showing consistency in spectral ratio peaks as a function of earthquake location

a natural seismic isolating system the buried mangrove effects the belleplaine test site located in the island of guadeloupe french lesser antilles includes a three accelerometer vertical array designed for liquefac tion studies the seismic response of the soil column at the test site is computed using three methods the spectral ratio method using the vertical array data a numerical method using the geotechnical properties of the soil column and an operative fre quency domain decomposition fdd modal analysis method the belleplaine test site is characterized by a mangrove layer overlaid by a stiff sandy deposit this con figuration is widely found at the border coast of the caribbean region which is exposed to high seismic hazard we show that the buried mangrove layer plays the role of an isolation system equivalent to those usually employed in earthquake engineering aimed at reducing the seismic shear forces by reducing the internal stress within the structure in our case the flexibility of the mangrove layer reduces the distortion and the stress in the sandy upper layer and consequently reduces the potential of liquefaction of the site

toba ash on the indian subcontinent and its implications for correlation of late pleistocene alluvium the toba ash occurs extensively in the indian subcontinent and marks a ca 74 000 yr old event in the bay of bengal and indian ocean it is about 10 cm thick whereas in several alluvial basins it is usually 1 3 m thick the latter occurs in a partly reworked state but as nearly chemically pure first cycle sediments the ash has a broad northwesterly dispersal pattern samples of ash from the indian subcontinent compare closely with the youngest 74 000 yr b p toba tuff and the deep sea toba ash in bulk chemical composition ree signature and bubble wall shard morphology however a more proximally located and thicker 2 5 m ash bed from the alluvial basins in the gneissic area and close to east coast has a lower magnitude negative eu anomaly possibly because of minor contamination by feldspathic silt quaternary sediments in the central narmada and middle son basins contain rich late and middle pleistocene mammalian and cultural records based on the presence of the ash layer marker and stratigraphic relations late pleistocene sediments within the subcontinent can be correlated with those from central india and the deep sea

fluvial deposits as an archive of early human activity progress during the 20 years of the fluvial archives group fluvial sedimentary archives are important repositories for lower and middle palaeolithic artefacts throughout the old world especially in europe where the beginning of their study coincided with the realisation that early humans were of great antiquity now that many river terrace sequences can be reliably dated and correlated with the globally valid marine isotope record potentially useful patterns can be recognized in the distribution of the find spots of the artefacts that constitute the large collections that were assembled during the years of manual gravel extraction this paper reviews the advances during the past two decades in knowledge of hominin occupation based on artefact occurrences in fluvial contexts in europe asia and africa as such it is an update of a comparable review in 2007 at the end of igcp project no 449 which had instigated the compilation of fluvial records from around the world during 2000 2004 under the auspices of the fluvial archives group an overarching finding is the confirmation of the well established view that in europe there is a demarcation between handaxe making in the west and flake core industries in the east although on a wider scale that pattern is undermined by the increased numbers of lower palaeolithic bifaces now recognized in east asia it is also apparent that although it seems to have appeared at different places and at different times in the later lower palaeolithic the arrival of levallois technology as a global phenomenon was similarly timed across the area occupied by middle pleistocene hominins at around 0 3 ma

two dimensional model for site effect studies of microtremors in the san fernando valley a new model is developed for the resonant response of ground motion in enclosed sedimentary basins in their study of deeply embanked sediment filled valleys bard and bouchon 1980 a b 1985 show that reflections and refractions at the valley s edges generate important conversion of incident sv waves to horizontally propagating p waves which establish lateral resonance patterns our model is related to these results through the use of two approximations reflecting edges and horizontal p waves this model allows us to calculate lateral resonances in a given sedimentary basin for any shape of its borders we apply this model to the actual shape of san fernando valley and account for the large differential amplifications reported by kagami et al 1986 in their two dimensional study of microtremors in this basin we obtain a map of amplifications in the surface of the san fernando valley that shows a remarkable coincidence with the microtremor experimental data

the seismic coda site effects and scattering in alluvial basins studied using aftershocks of the 1986 north palm springs california earthquake as source arrays abstract we use single station recordings of widely distributed earthquake sources to identify heterogeneities in the earth9s crust that scatter energy into the early part of the observed s wave codas we assume that ray theory accurately describes the propagation of body waves from the earthquake sources to the scatterers but we assume no propagation mechanism between the scatterers and the seismic station a grid of hypothetical scatterers is assumed to cover the earth9s surface and the strength of each scatterer is determined by an iterative inversion method our data are recordings of aftershocks of the 1986 north palm springs earthquake recorded at a seismic station in the coachella valley smp and at a station in the morongo valley smc the technique is applied separately to each horizontal component of motion at each station we identify a particular spot at the northwest edge of the quaternary alluvium in the coachella valley that scatters waves into the s coda observed at smp 8 km distant in the valley the geologic structure that causes the strong scattering seems to be the basin edge structure rather than the mountainous terrain 3 km farther west the early coda at smc is dominated by scattering within a few kilometers of smc either in the basin itself or in the morongo valley fault zone this study shows that laterally propagating waves are sometimes observable in the early coda casting doubt on the use of 1 d techniques for estimating site responses the northwest edge of the coachella valley seems to be an especially strong scatterer of incident waves if other basins have similar loci of strong scattering perhaps these places can be identified using microearthquake seismograms and used to predict strong ground motions in the basins

seismic activity offshore martinique and dominica islands central lesser antilles subduction zone from temporary onshore and offshore seismic networks this work focuses on the analysis of a unique set of seismological data recorded by two temporary networks of seismometers deployed onshore and offshore in the central lesser antilles island arc from martinique to guadeloupe islands during the whole recording period extending from january to the end of august 2007 more than 1300 local seismic events were detected in this area a subset of 769 earthquakes was located precisely by using hypoellipse we also computed focal mechanisms using p wave polarities of the best azimuthally constrained earthquakes we detected earthquakes beneath the caribbean forearc and in the atlantic oceanic plate as well at depth seismicity delineates the wadati benioff zone down to 170 km depth the main seismic activity is concentrated in the lower crust and in the mantle wedge close to the island arc beneath an inner forearc domain in comparison to an outer forearc domain where little seismicity is observed we propose that the difference of the seismicity beneath the inner and the outer forearc is related to a difference of crustal structure between the inner forearc interpreted as a dense thick and rigid crustal block and the lighter and more flexible outer forearc seismicity is enhanced beneath the inner forearc because it likely increases the vertical stress applied to the subducting plate

the 74 ka toba super eruption and southern indian hominins archaeology lithic technology and environments at jwalapuram locality 3 hominins living in southern india 74 000 years ago faced a deteriorating environment as the global climate moved from interglacial into full glacial conditions at the same time south asian populations witnessed the widespread deposition of tephra from the sumatran toba super eruption the largest explosive volcanic event of the past two million years here we report new data on the lithic technology and environmental context for a southern indian site with hominin occupation in association with toba tephra deposits jwalapuram locality 3 in the jurreru valley sedimentological and isotopic studies demonstrate that a cooling trend was in effect in this part of southern india prior to the eruption and that thick deposits of ash in the jurreru valley supported grassland communities before more wooded conditions were re established detailed technological analyses of an expanded lithic sample from locality 3 suggest cultural continuity after the eruptive event and comparisons with lithic core technologies elsewhere indicate that homo sapiens cannot be ruled out as the creator of these middle palaeolithic assemblages

simultaneous study of the source path and site effects on strong ground motion during the 1989 loma prieta earthquake a preliminary result on pervasive nonlinear site effects we considered the effects of source propagation path and local site conditions on strong ground motion from the loma prieta earthquake in the following steps first the local site effect was removed from the strong motion records applying the weak motion amplification factors estimated from nearby stations of usgs regional network using the coda method then we confirmed the approximate validity of the 1 r law of geometrical spreading factor for the crustal model applicable to the region and we determined the attenuation parameter q f and source spectrum s f empirically from the site effect corrected spectral amplitude both q f and s f are consistent with the results obtained earlier for major california earthquakes we then synthesized the time history of ground acceleration by applying the stochastic simulation technique the agreement between the observed and predicted records was good for duration and spectral content we found however a strong systematic discrepancy with regard to peak acceleration namely for distances less than 50 km the predicted peak acceleration consistently overestimated the observed for sediment sites and underestimated it for the franciscan formation sites since the above systematic discrepancy applies to all the available stations within about 50 km from the hypocenter it is unlikely that the effect is due to the radiation pattern near source structure or topography it appears that the strong difference in the amplification factor between the franciscan and the sediment sites observed for weak motion disappears at acceleration levels higher than about 0 1 to 0 3 g if this is due to the nonlinear response of the sediment sites it is in the range expected from geotechnical engineering studies

stratigraphic placement and age of modern humans from kibish ethiopia in 1967 the kibish formation in southern ethiopia yielded hominid cranial remains identified as early anatomically modern humans assigned to homo sapiens however the provenance and age of the fossils have been much debated here we confirm that the omo i and omo ii hominid fossils are from similar stratigraphic levels in member i of the kibish formation despite the view that omo i is more modern in appearance than omo ii 40ar 39ar ages on feldspar crystals from pumice clasts within a tuff in member i below the hominid levels place an older limit of 198 14 kyr weighted mean age 196 2 kyr on the hominids a younger age limit of 104 7 kyr is provided by feldspars from pumice clasts in a member iii tuff geological evidence indicates rapid deposition of each member of the kibish formation isotopic ages on the kibish formation correspond to ages of mediterranean sapropels which reflect increased flow of the nile river and necessarily increased flow of the omo river thus the 40ar 39ar age measurements together with the sapropel correlations indicate that the hominid fossils have an age close to the older limit our preferred estimate of the age of the kibish hominids is 195 5 kyr making them the earliest well dated anatomically modern humans yet described

all toba tephra occurrences across peninsular india belong to the 75 000 yr b p eruption abstract a controversy currently exists regarding the number of toba eruptive events represented in the tephra occurrences across peninsular india some claim the presence of a single bed the 75 000 yr old toba tephra others argue that dating and archaeological evidence suggest the presence of earlier toba tephra resolution of this issue was sought through detailed geochemical analyses of a comprehensive suite of samples allowing comparison of the indian samples to those from the toba caldera in northern sumatra malaysia and importantly the sedimentary core at odp site 758 in the indian ocean a core that contains several of the earlier toba tephra beds in addition two samples of toba tephra from western india were dated by the fission track method the results unequivocally demonstrate that all the presently known toba tephra occurrences in peninsular india belong to the 75 000 yr b p toba eruption hence this tephra bed can be used as an effective tool in the correlation and dating of late quaternary sedimentary sequences across india and it can no longer be used in support of a middle pleistocene age for associated acheulian artifacts

the toba volcanic super eruption environmental change and hominin occupation history in india over the last 140 000 years a prolonged interdisciplinary fieldwork program was initiated in india to investigate the impact of the toba super eruption on terrestrial ecosystems and hominins fieldwork was centered on the jurreru river valley and the middle son river valley in southern and northern india archaeological sites span from 140 000 years ago through to the holocene providing a long term view about hominin occupation history primary air fall deposits of the young toba tuff ytt were identified and changes in terrestrial environments prior to and after the super eruption are indicated prior to the toba eruption drying of local ecological settings was underway the emplacement of ash on landscapes and its subsequent erosion had local ecological and hydrological effects although drier conditions are indicated after the deposition of the ash deposits a mosaic of environments was present in india indicating that animals and hominins could have survived the volcanic event evidence indicates that middle paleolithic industries in stratified contexts are present in india prior to and after the toba super eruption middle paleolithic hominins appear to have survived the negative effects of the volcanic eruption and climatic fluctuations in the late pleistocene middle paleolithic industries produced from ca 77e38 000 years ago in india were probably manufactured by homo sapiens

microseismicity and stresses in the lesser antilles dipping seismic zone abstract microearthquake data from a telemetered array have been used to study the central antilles arc system the zone lying between lat 14 17 n and long 59 5 62 w has been investigated during the period 1979 1980 no shock with a magnitude larger than 4 5 was recorded results are well correlated with previous conclusions derived from teleseismic records the dip of the subducting plate is 60 everywhere in this area no composite focal mechanism can be produced for the region north of dominique for the southern region composite focal mechanisms reveal two zones for depths between 45 and 80 km the stress field seems mainly related to the interplate action beneath 80 km the slab dominantly neither in compression nor in tension earthquakes are more likely related to local stress fields a double layered structure has not been found in the earthquake distribution in the subducted plate nor in the stress field deduced from focal mechanisms

radiocarbon analysis of the early archaeological site of nauwalabila i arnhem land australia implications for sample suitability and stratigraphic integrity abstract this study presents the results of an extensive radiocarbon dating program at the nauwalabila i site in northern australia the results show that the radiocarbon chronology at nauwalabila is reliable to 130 cm depth but below this depth coarse charcoal has been variably altered during a period in the early holocene when an ephemeral groundwater table reached close to the ground surface of the time below 150 cm none of the radiocarbon ages can be considered to indicate reliably the age of deposition of the sediments luminescence dates near the surface and at 110 cm are concordant with the radiocarbon chronology in the upper part of the sequence and hence the aberrant radiocarbon results below 150 cm do not constitute a reason to doubt the accuracy of the luminescence chronology deeper in the stratigraphy a conservative estimate of the age of the sequence based on extrapolation of results from that portion of the sequence where the radiocarbon chronology is considered to be reliable is consistent with the chronology proposed previously from luminescence dating both chronologies therefore suggest occupation of the site before 50 000 years based on sediment characteristics and the distribution of quartz chert quartzite and quartz crystal artefacts there is no evidence that there has been significant vertical displacement of artefacts relative to the surrounding sand matrix both chemical alteration and physical translocation of charcoal contributed to the aberrant ages at depth in the deposit the results point to the need for careful assessment of the suitability of charcoal for radiocarbon dating prior to analysis and to the dangers of relying on a small number of radiocarbon dates in the development robust site chronologies strategies for screening samples for suitability include i microscopic examination ii not analysing samples unless they survive the full abox pretreatment iii not analysing samples unless the material is significantly larger than the sediment matrix iv using chn analysis on both untreated and pretreated material to check for organic contamination and v using stepped combustion to check for concordancy in the ages of carbon released at successively higher temperatures

volcanic winter and accelerated glaciation following the toba super eruption the eruption of toba in sumatra 73 500 years ago was the largest known explosive volcanic event in the late quaternary1 it could have lofted about 1015 g each of fine ash and sulphur gases to heights of 27 37 km creating dense stratospheric dust and aerosol clouds here we present model calculations that investigate the possible climatic effects of the volcanic cloud the increase in atmospheric opacity might have produced a volcanic winter 2 a brief pronounced regional and perhaps hemispheric cooling caused by the volcanic dust followed by a few years with maximum estimated annual hemispheric surface temperature decreases of 3 5 c the eruption occurred during the stage 5a 4 transition of the oxygen isotope record a time of rapid ice growth and falling sea level3 we suggest that the toba eruption may have greatly accelerated the shift to glacial conditions that was already underway by inducing perennial snow cover and increased sea ice extent at sensitive northern latitudes as the onset of climate change may have helped to trigger the eruption itself4 we propose that the toba event may exemplify a more general climate volcano feedback mechanism

a new synthesis of evidence for the upper pleistocene occupation of 16r dune and its southern asian context the site of 16r dune located at the eastern edge of the thar desert provides a key benchmark for palaeolithic studies in southern asia application of chronometric dating of the excavated sequence at 16r in the 1980 s has permitted significant insights into the timing and nature of cultural evolution in the indian subcontinent recent studies of the 16r dune sedimentary section have presented a revised chronology for the cultural horizons although the impact of this upon the timing of occupation of the site and technological development in the region has not been discussed critically the largest artefact assemblage from the site originally dated by traditional radiocarbon dating to 26 ka and labelled upper palaeolithic is bracketed by recent luminescence dates of 40 80 ka and can better be described as middle palaeolithic the sedimentary and chronological context for the cultural assemblages at 16r dune is reviewed and the resulting synthesis is discussed within its regional context and with respect to contemporary debates regarding the dispersal of modern humans

site amplification and attenuation of strong ground motion abstract at the mcgee creek california site three component strong motion accelerometers are located at depths of 166 m 35 m and 0 m the surface material is glacial moraine to a depth of 30 5 m overlying hornfels accelerations were recorded from two california earthquakes round valley m l 5 8 23 november 1984 18 08 utc and chalfant valley m l 6 4 21 july 1986 14 42 utc anti plane shear strains for the round valley and chalfant valley events are less than 1 8 10 5 and 1 2 10 5 respectively by separating out the sh components of acceleration we were able to determine the orientations of the downhole instruments peak sh accelerations at the surface were 5 7 times greater than those at 166 m in both earthquakes a constant phase velocity haskell thomson model was applied to generate synthetic sh seismograms at the surface using the accelerations recorded at 166 m in the frequency band 0 10 to 10 0 hz we compared the filtered synthetic records to the filtered surface data the onset of the sh pulse and the reflections from the interface at 30 5 m are clearly seen in both the synthetics and the recorded data the synthetic records closely match the data in both amplitude and phase the fit between the synthetic accelerograms and the data indicates that the seismic amplification at the surface is a result of the resonance of the surface layers and the contrast of the impedances shear stiffness of the near surface materials the impedance contrast of the materials does not account for all of the amplification of the peak accelerations at the surface the resonances of the layer system below 10 hz contribute the most to this amplification we find that a linear model predicts the soil response for frequencies up to 10 hz material damping is added to the soil layers of the model in the form of a quality factor q the damping moderates the strong resonance effects by allowing energy to radiate into the half space the quality factor q 10 is constant in this frequency range but does not accurately model the attenuation at frequencies above 10 hz

seismicity and seismic gap in the lesser antilles arc and earthquake hazard in guadeloupe summary a seismic study of the lesser antilles arc has been carried out first for the period 1950 1978 for which we can use local seismic networks to draw maps of instrumental seismicity then for the period 1530 1950 for which we have catalogues of felt earthquakes the striking feature of the spatial distribution of foci is the cluster of epicentres in the northern half of the arc all large earthquakes m 7 5 are located north of 14 latitude seismicity cross sections through the arc show a variable dipping subduction zone along the arc the deep seismic zone is steeper in the centre of the arc than on the extremity the time space diagram for historical seismicity and the evidence of a seismic gap at the east of guadeloupe lead us to consider the northern half arc as a likely site for a large earthquake in the near future the seismic slip rate calculated from all major earthquakes since 1530 is of much greater value than that obtained from recent plate tectonic models suggesting that the recurrence rate of earthquakes is more than many hundreds of years with a possible aseismic creep

experimental study of site effects in the fort de france area martinique island abstract we used weak motion recordings of regional events to quantify the site effects in the fort de france martinique area in the frequency band 1 to 25 hz the studied area extends over three distinct geological units the morne pitault volcanic massif 15 to 11 m a the carbet volcanic massif 4 to 2 m a and the lamentin alluvial plain quaternary age the topography being complex 31 sites were selected in order to get a representative sampling of the various topographical and geological configurations the large number of studied sites also allowed us to define a reference site whose selection was not obvious large broadband amplifications are observed in the lamentin plain instead of the expected peak resonances more surprising such resonance is observed around 2 to 3 hz on several sites of the volcanic vauclain pitault chain though no sedimentary layer is present on the other hand in the inner fort de france where significant effects were expected because of the very complex topography no large amplication is observed except for at one site clear three dimensional 3d effects are also observed at some stations though not very well documented the low frequency behavior deduced from teleseismic observations seems rather different illustrating the difficulty in finding a convenient reference site in such a volcanic area

early human occupation at devil s lair southwestern australia 50 000 years ago abstract new dating confirms that people occupied the australian continent before the earliest time inferred from conventional radiocarbon analysis many of the new ages were obtained by accelerator mass spectrometry 14c dating after an acid base acid pretreatment with bulk combustion aba bc or after a newly developed acid base wet oxidation pretreatment with stepped combustion abox sc the samples charcoal came from the earliest occupation levels of the devil s lair site in southwestern western australia initial occupation of this site was previously dated 35 000 14c yr b p whereas the aba bc ages are indistinguishable from background beyond 42 000 14c yr b p the abox sc ages are in stratigraphic order to 55 000 14c yr b p the abox sc chronology suggests that people were in the area by 48 000 cal yr b p optically stimulated luminescence osl electron spin resonance esr ages u series dating of flowstones and 14c dating of emu eggshell carbonate are in agreement with the abox sc 14c chronology these results based on four independent techniques reinforce arguments for early colonization of the australian continent

risk and reward explosive eruptions and obsidian lithic resource at nabro volcano eritrea abstract despite abundant pleistocene calderas in the east african rift and afar and the significance of regional tephra horizons for archaeological and paleoenvironmental dating the entanglements of volcanoes and their eruptions with human behaviour and paleoecology have received little attention here we focus on the intertwined human and eruptive history at nabro a caldera topped volcanic massif close to the red sea littoral of eritrea nabro exemplifies the antagonism of opportunities and threats posed by a large silicic volcano active at least since the middle pleistocene and as recently as 2011 using argon isotopic measurements we establish the first chronology of key eruptive stages of nabro and neighbouring mallahle revealing a history of explosive and effusive volcanism in the middle and late pleistocene past eruptions were an important source of obsidian that was exchanged over long distances across land and sea during the neolithic we infer that the availability of high quality obsidian combined with nabro s favourable microclimate and proximity to the red sea coast likely attracted humans to this volcanic landmark since the later middle pleistocene drawing on observations of the immediate consequences of the 2011 eruption on landscape and local pastoralist communities we consider also the impacts of past volcanic cataclysms on human populations in addition to the threat to life explosive eruptions of nabro circa 130 ka and 62 ka ago would have abruptly curtailed procurement of its obsidian resource our findings suggest further attention be paid to evaluating the significance of east african volcanic landscapes eruptions and resources for understanding human behaviour in deep antiquity

hydrogeological and hydrochemical characterization of the voltaian basin the afram plains area ghana in the afram plains area groundwater is the main source of water supply for most uses the area is underlain by aquifers of the southern voltaian sedimentary basin which are predominantly sandstones mudstones conglomerates and shale ordinary least squares regression analysis using 41 well test data from aquifers in the afram plains portion of the voltaian system reveals that transmissivity t exists in a non linear relationship with specific capacity sc the analysis reveals that t 0 769sc1 075 with r 2 0 83 for aquifers in the area the mudstone conglomerate aquifer in the area appears to be the most variable in terms of both specific capacity and transmissivity with transmissivity ranging from 0 18 to 197 7 m2 day and 0 5 and 148 5 m3 day m respectively horizontal fractures and joints resulting from secondary fracturing appear to be the main determinants of both transmissivity and specific capacity in the area phreeqc modeling and mineral stability diagrams indicate that groundwater quality in the afram plains area is controlled by the incongruent weathering of silicate minerals in the aquifers these processes concentrate calcium sodium magnesium potassium bicarbonate ion and quartz leading to calcite dolomite and aragonite supersaturation at most locations hierarchical cluster analysis performed on the raw chemical data reveals two main water types or facies the calcium sodium chloride bicarbonate facies and the magnesium potassium sulfate nitrate facies for the southern and northern sections of the afram plains area respectively

palaeohydrological corridors for hominin dispersals in the middle east 250 70 000 years ago abstract the timing and extent of palaeoenvironmental connections between northeast africa the levant and the arabian peninsula during the middle and late pleistocene are critical to debates surrounding dispersals of hominins including movements of homo sapiens out of africa although there is evidence that synchronous episodes of climatic amelioration during the late middle and late pleistocene may have allowed connections to form between northern africa and western asia a number of palaeoclimate models indicate the continued existence of an arid barrier between northern arabia and the levant here we evaluate the palaeoenvironmental setting for hominin dispersals between and within northeast africa and southwest asia during marine isotope stages mis 7 5 using reconstructions of surface freshwater availability as an environmental proxy we use remotely sensed data to map palaeohydrological features lakes wetlands and rivers across the presently hyper arid areas of northern arabia and surrounding regions integrating these results with palaeoclimate models palaeoenvironmental proxy data and absolute dating to determine when these features were active our analyses suggest limited potential for dispersals during mis 7 and 6 but indicate the formation of a palaeohydrological corridor the tabuk corridor between the levant and the arabian interior during the mis 6 5e glacial interglacial transition and during mis 5e a recurrence of this corridor following a slightly different route also occurred during mis 5a these palaeohydrological and terrestrial data can be used to establish when proposed routes for hominin dispersals became viable furthermore the distribution of arabian archaeological sites with affinities to levantine assemblages some of which are associated with homo sapiens fossils and the relative density of middle palaeolithic assemblages within the tabuk corridor are consistent with it being utilised for dispersals at various times

characterizing surface geology liquefaction potential and maximum intensity in the kachchh seismic zone western india through microtremor analysis abstract this study presents results of microtremor analysis carried out over diverse geological formations and liquefaction sites in the kachchh seismic zone of western india which is host to the deadliest intraplate earthquake m w 7 7 microtremors were recorded at 36 sites with single stations and 7 sites with an array the microtremor array measurements were made using triangular arrays with sensors kept at 30 90 m radii the rayleigh wave velocities are estimated from the array data using high resolution frequency wavenumber f k analysis and the 1d shear wave velocity structure is determined by inversion we found a good correlation between surface geology resonant frequency and amplitude of the horizontal to vertical spectral ratio hvsr curve and shear wave velocity the ground vulnerability index k g values in the liquefied areas are found to be higher than those in the adjacent areas devoid of liquefaction broad or multiple peaks in the hvsr curves and large variations in the shear velocity models could be attributable to the structural and tectonic complexity in the maximum intensity area further our results show that the average fundamental frequencies are around 0 32 hz for the quaternary 0 80 hz for tertiary 1 8 hz for cretaceous 1 8 hz for jurassic and 2 3 hz for the deccan trap formations the inverted s wave velocity varies from 190 to 1350 m s down to a depth of 200 m for the quaternary 220 to 680 m s down to 100 m for tertiary 236 to 1160 m s for cretaceous 670 to 1780 m s for jurassic and 260 to 2440 m s for the deccan trap sites the results of microtremor analysis corroborate the observations from the available geophysical geological and borehole data

the influence of the ne winter monsoon on productivity changes in the gulf of aden nw arabian sea during the last 530ka as recorded by foraminifera abstract benthic and selected planktic foraminifera and stable isotope records were determined in a piston core from the gulf of aden nw arabian sea that spans the last 530 ka the benthic foraminifera were grouped into four principal assemblages using q mode principal component analyses comparison of each of these assemblages with the fauna of the nearby regions enabled us to identify their specific environmental requirements as a function of variability in food supply and strength of the oxygen minimum zone and by that to use them as indicators of surface water productivity the benthic foraminiferal productivity indicators coupled with the record of globigerina bulloides a planktic foraminifer known to be sensitive to productivity changes in the region all indicate higher productivity during glacial intervals and productivity similar to present or even reduced during interglacial stages this trend is opposite to the productivity pattern related to the sw summer monsoon of the arabian sea and indicates the role of the ne winter monsoon on the productivity of the gulf of aden a period of exceptionally enhanced productivity is recognized in the gulf of aden region between 60 and 13 kyr indicating the intensification of the ne winter monsoon to its maximal activity contemporaneous indication of increased productivity in other parts of the arabian sea unexplained so far by the sw summer monsoon variability might be related to the intensification of the ne winter monsoon another prominent event of high productivity second in its extent to the last glacial productivity event is recognized between 430 and 460 kyr these two events seem to correspond to periods of similar orbital positioning of rather low precession and eccentricity amplitude for a relatively long period glacial boundary conditions seem to control to a large extent the ne winter monsoon variability as also indicated by the dominance of the 100 ka cycle in the investigated time series secondary in their importance are the 23 and 41 ka cycles which seem also to contribute to the ne monsoonal variability following the identification of productivity events related to the ne winter monsoon in the gulf of aden it is possible now to extend this observation to other parts of the arabian sea and consider the contribution of this monsoonal system to the productivity fluctuations preserved in the sedimentary records

new geochemical evidence for the youngest toba tuff in india abstract new geochemical data on tephra samples from a layer present at several archeological sites in india support correlation of this layer to the youngest toba tuff erupted from northern sumatra about 74 000 yr ago the data show that the indian tephra layer is not a correlative of older tephra erupted from toba as has been suggested on the basis of artifact assemblages previously published geochemical data on the indian tephra beds was based on bulk ash samples containing mineral and clay contaminants and the resulting variability in analyses did not allow identification or discrimination of individual eruptive events our new data were collected on individual glass shards and small purified glass separates which have greater resolving power in fingerprinting acheulian and paleolithic artifacts found at some of the indian tephra sites do not reflect the antiquity of the tephra bed as they occur in fluvial sediments and may be reworked

middle paleolithic occupation on a marine isotope stage 5 lakeshore in the nefud desert saudi arabia major hydrological variations associated with glacial and interglacial climates in north africa and the levant have been related to middle paleolithic occupations and dispersals but suitable archaeological sites to explore such relationships are rare on the arabian peninsula here we report the discovery of middle paleolithic assemblages in the nefud desert of northern arabia associated with stratified deposits dated to 75 000 years ago the site is located in close proximity to a substantial relict lake and indicates that middle paleolithic hominins penetrated deeply into the arabian peninsula to inhabit landscapes vegetated by grasses and some trees our discovery supports the hypothesis of range expansion by middle paleolithic populations into arabia during the final humid phase of marine isotope stage 5 when environmental conditions were still favorable

directional site resonances and the influence of near surface geology on ground motion the authors examine the horizontal motions at close stations from earthquakes in the loma prieta and whittier narrows sequences to study the shear wave polarizations they use a dense six station array recording 10 aftershocks for the former and use two events and 11 stations across the los angeles area for the latter they compute the average azimuth of strongest shaking in the shear wave as a function of frequency from 1 to 18 hz for each record of each earthquake the direction of shaking at a given frequency often correlates much better with an empirical site resonance direction than with the direction of shaking expected from the focal mechanism of the earthquake the effect tends to be greatest at the frequencies that are the most amplified this phenomenon can complicate determination of the earthquake source at frequencies higher than 1 hz further since sites only 25 meters apart show different preferred directions very near surface geology is probably responsible estimation of directional site resonances may prove useful for seismic design

subduction seismicity and tectonics in the lesser antilles arc we have studied the mechanisms of 17 earthquakes along the lesser antilles subduction zone to examine a site where very old lithosphere subducts at a slow convergence rate no large thrust earthquakes occurred during the 1950 1978 study period the three large magnitude seven events are all normal faults one is a normal faulting event seaward of the trench its aftershock sequence includes strike slip events on differently oriented faults probably due to lateral block motion in response to the main shock a second indicates extension within the slab at depth these observations suggest that subduction in this region is primarily decoupled and aseismic unless the time interval studied is unrepresentative the third normal fault earthquake occurred within the upper plate with fault planes perpendicular to the arc and trench this unusual geometry may represent a flexural response to the subduction of the barracuda ridge a major bathymetric high with uncompensated excess mass at depth which seems analogous to flanking ridges found along some mid atlantic ridge fracture zones thus the barracuda ridge is not buoyant and does not affect benioff zone dip strike slip faulting occurs at depth in the subduction zone along a concentration normal to the arc and maymore indicate a fossil fracture zone there is no direct evidence in the shallow seismicity for the hypothetical north america south america caribbean triple junction through some of the oceanic intraplate seismicity is consistent with such a boundary less

late middle palaeolithic surface sites occurring on dated sediment formations in the thar desert abstract the dominance of erosional sedimentary processes in desert regions results in palaeolithic records rich in surface scatters engaging with this abundant archaeological resource including incorporating them within absolute chronologies or schemes of environmental variability is critical to understanding hominin habitation in arid landscapes extensive archaeological surveys in the thar desert of india and pakistan over the past 60 years have identified a large number of palaeolithic surface sites in a diverse range of geographic contexts in the past twenty years a rich upper pleistocene palaeoenvironmental record has been developed within the region due to the application of chronometric dating techniques however as yet there have been few attempts by archaeologists to survey previously dated sediment formations in the thar desert and capitalise upon the potential to attribute preliminary terminus post quem dates to surface sites surface survey has been undertaken targeting sediment deposits that may preserve evidence for hominin behaviour between marine isotope stage 5 and 3 a period in which technological and demographic overhauls in hominin populations appear to occur in south asia following brief review of the palaeolithic archaeology and palaeoenvironmental history of the thar desert the results of recent archaeological survey of dated sediments at chamu karna and shergarh tri junction are presented the results offer tentative evidence for the presence of late middle palaeolithic populations in the region which are evaluated and discussed within the context of contemporary occupations across southern asia

palaeoenvironmental dynamics and palaeolithic occupation at katoati thar desert india late pleistocene palaeoenvironments in the thar desert india located at the eastern extent of the saharo arabian desert belt have fluctuated considerably as a result of the varying range and intensity of the indian summer monsoon phases of widespread pleistocene aridity are well documented in the thar desert but research focusing on humid proxies is critical to examine how the region may have facilitated population expansions across southern asia at katoati located on the northeast margin of the thar desert the combination of field recording of sediment sections with detailed analyses micromorphology stable isotope loss on ignition magnetic susceptibility and x ray fluorescence from an archaeological site identify a series of hominin occupations during phases of enhanced humidity between 96 and 60 ka a gradient of humidity on the eastern margin of the thar desert during the late pleistocene is identified with the periodic humidity evident at katoati occurring more frequently and with longer duration towards the southern margin this uneven distribution of humidity in the thar desert is likely to have strongly influenced when and where hominin populations could expand into and across the region

a new late pleistocene fauna from arid coastal india implications for inundated coastal refugia and human dispersals abstract a diverse late pleistocene fossil assemblage was recovered from a sea cliff locality near gopnath in gujarat northwestern india these remains are the first large sample of pleistocene faunal materials from arid northwestern india several taxa known primarily from coarse alluvial deposits of central india are documented for the first time from an undisturbed open air site adjoining the great indian desert the sample includes a new species of antelope from a lineage considered extinct outside of africa since the early pleistocene the paleoenvironmental context faunal composition and type of fossil preservation reported here is unique the gopnath fauna accumulated in a pond within a carbonate dune field that formed part of a larger coastal oasis ecosystem this paleoscape occupied the cambay gulf during hyper arid glacial low stands the gopnath fossils are correlated to late acheulean lithics from a coastal cliff locality

applicability of method to estimate transmissivity based on yield drawdown analysis in mountainous fractured rock aquifers a case study in taiwan abstract the observation of yield drawdown response in the course of pumping test as well as its derived application for aquifer characterization is an essential practice in a geotechnical investigation on the basis of that for providing a reasonable estimate of aquifer transmissivity on site a number of empirical models have therefore been proposed yet the majority of previous studies are conducted based on investigations at homogeneous alluvial plain very few particularly in the case of taiwan are carried out focusing on mountainous fractured rock aquifers aiming to address this problem the observation data of 53 pumping tests obtained from a multi years in situ geological investigation program are analyzed and the applicability of empirical log log linear relationship between t and q s is examined our analysis reveals that the yield drawdown responses derived from different geologic formations are quantitatively distinct and those empirical rules derived from the alluvial landform should be used with care when applying in mountainous fractured rock aquifers based on the analysis of statistical results in our study with a systematic investigation and clarification of the q s relationship in advance a satisfactory and cost effective solution is obtained

subduction of aseismic ridges beneath the caribbean plate implications for the tectonics and seismic potential of the northeastern caribbean normal seafloor entering the puerto rico and northern lesser antillean trenches in the northeastern caribbean is interrupted by a series of aseismic ridges on the north and south american plates these topographic features lie close to the expected trend of fracture zones created about 80 110 m y ago when this seafloor was formed at the mid atlantic ridge the northernmost of the ridges that interact with the lesser antillean subduction zone the barracuda ridge intersects the arc in a region of high seismic activity some of this seismicity including a large shock in 1974 occurs within the overthrust plate and may be related to the deformation of the caribbean plate as it overrides the ridge a large bathymetric high the main ridge is oriented obliquely to the puerto rico trench and intersects the subduction zone north of the virgin islands in another cluster of seismic activity along the inner wall of the trench data from a seismic network in the northeastern caribbean indicate that this intersection is also characterized by both interpolate and intraplate seismic activity magnetic anomalies bathymetric trends and the pattern of deformed sediments on the inner wall of the trench strongly suggest that the main and barracuda ridges are parts of a formerly continuous aseismic ridge a segment of which has recently been overridden by the caribbean plate reconstruction of mid miocene to recent plate motions also suggest that at least two aseismic ridges and possibly fragments of the bahama platform have interacted with the subduction zone in the northeastern caribbean the introduction of these narrow segments of anomalous seafloor into the subduction zone has segmented the arc into elements about 200 km long these ridges may act as tectonic barriers or asperities during the rupture processes involved in large earthquakes they also leave a geologic imprint on segments of the arc with which they have interacted a 50 km landward jump of the locus of island arc volcanism occurred in late miocene time along the northern half of the lesser antilles we postulate that the subduction of a segment of seafloor of anomolously thick crust being more buoyant than adjacent seafloor resulted in a marked shoaling in the dip of the descending slab and therefore a shift of the locus of volcanism in the region near western puerto rico and eastern hispanolia plio pleistocene interaction with a similar feature in this case a part of the bahama platform about 3 4 m y ago led to a jump in the locus of subduction as evidenced by a gap in the downgoing seismic zone that segment of the bahama platform interferred with the subduction process and was subsequently sutured onto the caribbean plate when the boundary jumped about 60 km to the northeast the maximum size of historic shallow earthquakes along the lesser antillean arc varies from about 7 0 7 5 in the center of the arc where the dip of the shallow part of the plate boundary is steep to 8 0 8 5 along the northern part of the arc where the dip is shallow the interaction of anomalous seafloor as along the northern lesser antilles can lead to the development of a wider than normal zone of interplate contact and hence to earthquakes that are larger than those associated with more typical seafloor entering subduction zones major seismic gaps and regions of high seismic potential currently exist along the northern lesser antilles and to the north of puerto rico both gaps are bounded by anomalous features on the downgoing plate the intersection of these features with the plate boundary created large asperities that may be good places to search for precursors to future large earthquakes a great shock in 1787 may have ruptured an existing seismic gap north of puerto rico between 65 and 67 w thus that gap can be expected to eventually rupture again in a great shock and not to accommodate plate motion by totally aseismic processes

a three dimensional simulation of seismic waves in the santa clara valley california from a loma prieta aftershock abstract the finite difference method is used to propagate elastic waves through a 3 d model of the santa clara valley an alluvium filled basin that underlies the city of san jose california the model was based on depth to bedrock information from water wells in the area the simulation corresponded to a region 30 east west by 22 north south by 6 depth km and contained about 4 million grid points synthetic seismograms from the simulation are accurate at frequencies up to 1 hz motions from a magnitude 4 4 aftershock of the loma prieta earthquake were modeled snapshots of ground motion and synthetic seismograms from the simulation are presented the simulation illustrates s to surface wave conversion at the edges of the basin and the large amplitude and long duration of ground motion in the basin compared to the surrounding rock love waves produced at the edge of the basin are the largest arrivals in the transverse synthetics because of the slow group velocity of the love waves sites near the center of the basin have longer durations of significant motions than basin sites near the valley edges sites near the center of the basin also show larger peak amplitudes on the transverse component array analysis of the synthetic seismograms indicates that love waves tend to propagate parallel to the eastern and western edges of the valley rayleigh waves are produced along the southern margin of the basin from incident s waves large radial motions occur where a rayleigh wave impinges on the northeast margin of the valley some rayleigh waves travel westward across the basin after being scattered from the eastern edge of the valley synthetic seismograms from the simulation have similar peak amplitudes as seismograms recorded by the sunnyvale dense array for this aftershock although the duration of the tranverse component is not matched by the synthetic seismogram using this basin model the simulation indicates that the love waves observed on the actual seismograms were produced by conversion of incident s waves at the southern margin of the santa clara valley 2 d simulations show how the s to love wave conversion is affected by the angle of incidence of the s wave and the sharpness of the velocity transition between the alluvium and bedrock as more accurate basin models are developed 3 d simulations should become valuable for predicting ground motions in sedimentary basins for future large earthquakes

middle stone age reduction strategies at the desert s edge a multi site comparison across the gebel akhdar of northeast libya abstract haua fteah cave situated between the mediterranean coast and the gebel akhdar of northeast libya preserves rich middle stone age msa and late stone age lsa cultural horizons excavated in the 1950s and more recently the richness and time depth of the cave s archaeological record are unsurpassed by any other site in northern cyrenaica as a result the haua fteah sequence has long been used to represent the culture history of the region as a whole recent geoarchaeological surveys of the gebel akhdar as well as pre desert and desert biomes further to the south have resulted in the discovery of numerous msa and lsa sites the vast majority of these sites consist of surface lithics that cannot be dated currently in contrast parts of the haua fteah sequence have been dated using various chronometric methods using data collected through lithic attribute analysis coupled with various statistical approaches including discriminant function analysis or dfa this paper explores variation in core reduction strategies within haua fteah from the early msa to early lsa collections of cores from various sites located throughout the landscape are contrasted against those from haua fteah by comparing undated cores from the landscape with those from different occupation phases at haua fteah dfa classification is tested as a method for imparting an approximate chronology to the former the results indicate notable variation in reduction strategies within the msa at haua fteah and notable similarities between early msa pre aurignacian and early lsa early dabban core morphologies and technologies because of the latter in particular together with several other factors that may be underpinning spatio temporal variability in core reduction strategies caution is recommended in loosely assigning approximate chronologies to surface lithic sites

man and megafauna in tasmania closing the gap abstract recent discussion on the late pleistocene extinction of the australian megafauna has revolved around interpretation of several key fossil sites in tasmania it has been suggested that humans did not arrive in tasmania until after the megafauna became extinct or did not hunt now extinct megafauna and therefore that humans cannot be implicated in the extinctions radiocarbon results from these sites indicate that the youngest extinct megafauna are close to charcoal ages from the oldest archaeological deposits although difficulties have arisen in establishing chronologies because most relevant sites have ages near the limit for radiocarbon analysis we report a series of new radiocarbon ages 13 c 15 n and c n ratios on collagen and dentine fractions from skeletal remains in the mount cripps karst area and the mowbray swamp both in northwestern tasmania and discuss the reliability of ages from these and other sites we also report the discovery of an articulated simosthenurus occidentalis skeleton at mt cripps that represents only the second directly dated extinct megafaunal taxon with a reliable age our results suggest that c n ratios measured on collagen or dentine are not an infallible guide to radiocarbon age reliability we confirm previous reports of a temporal overlap between the megafaunal and archaeological records in tasmania but the presence of archaeological evidence and megafauna with the same age at the same site has not yet been demonstrated at least two megafaunal taxa the now extinct protemnodon anak and a giant pleistocene form of the extant macropus giganteus were still present in tasmania after 43 ka when human crossing of the bassian landbridge from mainland australia first became sustainable

late acheulean hominins at the marine isotope stage 6 5e transition in north central india single grain optically stimulated luminescence dating was applied to late quaternary sediments at two sites in the middle son valley madhya pradesh india designated bamburi 1 and patpara these sites contain late acheulean stone tool assemblages which we associate with non modern hominins age determinations of 140 120 ka place the formation of these sites at around the marine oxygen isotope stage 6 5 transition placing them among the youngest acheulean sites in the world we present here the geochronology and sedimentological setting of these sites and consider potential implications of late pleistocene archaic habitation in north central india for the initial dispersal of modern humans across south asia

desert speleothems reveal climatic window for african exodus of early modern humans one of the fi rst movements of early modern humans out of africa occurred 130 100 thousand years ago ka when they migrated northward to the levant region the climatic conditions that accompanied this migration are still under debate using high precision multicollector inductively coupled plasma mass spectrometry mc icp ms u th methods we dated carbonate cave deposits speleothems from the central and southern negev desert of israel located at the northeastern margin of the saharan arabian desert speleothems grow only when rainwater enters the unsaturated zone and this study reveals that a major cluster of wet episodes the last recorded in the area occurred between 140 and 110 ka this episodic wet period coincided with increased monsoonal precipitation in the southern parts of the saharanarabian desert the disappearance at this time of the desert barrier between central africa and the levant and particularly in the sinai negev land bridge between africa and asia would have created a climatic window for early modern human dispersion to the levant

middle to late pleistocene human habitation in the western nefud desert saudi arabia abstract the nefud desert is crucial for resolving debates concerning hominin demography and behaviour in the saharo arabian belt situated at the interface between the mediterranean westerlies and african monsoonal climate systems the nefud lies at the centre of the arid zone crossed by homo sapiens dispersing into eurasia and the edges of the southernmost known extent of the neanderthal range in 2013 the palaeodeserts project conducted an intensive survey of the western nefud to 1 evaluate pleistocene population dynamics in this important region of the saharo arabian belt and 2 contribute towards understanding early modern human range expansions and interactions between different hominin species thirteen lower and middle palaeolithic sites were discovered in association with palaeolake basins one of the sites t is al ghadah may feature the earliest middle palaeolithic assemblage of arabia preliminary analyses show that the lower and middle palaeolithic sites discovered display diverse technological characteristics indicating that the nefud was important for population turnovers and exchanges throughout the pleistocene periodic environmental amelioration appears to have attracted hominin incursions into the region and subsequent ephemeral occupations structured around lakes and to a lesser extent raw material sources however differences between the lower and middle palaeolithic sites are indicative of greater mobility during the later pleistocene a rarity of formal tools but strong similarities in lithic production techniques are also suggestive of demographic affinities across the nefud during the pleistocene and perhaps beyond these preliminary results support the view that the arabian peninsula was a critically important region of southwest asia during the late pleistocene in which demographic responses to climatic amelioration may have structured connectivity across the saharo arabian belt the levant and as far as india

moment tensor solutions along the central lesser antilles using regional broadband stations abstract using waveform data gathered from the seismological networks of the lesser antilles we calculate 38 moment tensors for earthquakes with m 3 from 2013 to middle of 2015 by full waveform inversion nine of these moment tensor solutions are in good agreement with those previously reported by other institutions it provides some guarantee for 29 new moment tensors for the central region of the lesser antilles for earthquakes within the upper caribbean lithosphere our results evidence that extensional and strike slip focal mechanisms are predominant resulting from the intra plate deformation produced by the subduction of the north america and south american plates under the caribbean plate whereas very few thrust events are observed for deeper earthquakes 90 km our results compare well with older focal mechanisms from previous studies showing normal oblique or strike slip faulting within the subducted slab however the inversion for most of the deeper events is less reliable as documented for example by their larger condition numbers we use the newly obtained moment magnitudes to estimate the scaling relationship with the local magnitude mlv computed by the regional seismic network the two magnitudes are consistent for earthquakes with magnitudes m 4 with a slope close to unity further work is needed to precise the scaling relation for m

the response of the ubaye valley france for incident sh and sv waves comparison between measurements and modeling l this paper presents a detailed study of the response of an alluvial valley in the alps france the structure ubaye valley was chosen 1 for its moderate dimensions 500 m wide and 65 m thick which allow an accu rate determina tion of the deposit characteristics and 2 for the relatively high seismicity of the region the study included the deployment of five temporary seismological stations a seismic survey of the valley for determining the dynamic proper1ies and the geometry of the soft deposits and 1 d and 2d numerical modeling for incident sh and sv waves comparisons between observed and computed amplifications show a good agreement for frequencies lower than 10hz and the particular direction of arrivai of the input motions corresponding to the 2d case when the ear1h quake sources are not located in the continuation of the line of seismometers the spectral ratios exhibit a great variability between different groups of similar events these observations indicate the azimuthal dependence of the site response and the need for 3d modeling

estimation of transmissivity from specific capacity data in fractured carbonate rock aquifer central jordan transmissivity of an aquifer is determined from pumping test analysis but due to the difficulty of performing such tests as well as the relatively high cost of these test it is often estimated from specific capacity data in this study an empirical relation is derived using 237 pairs of transmissivity and specific capacity values that are obtained from groundwater wells penetrating a fractured and karstified carbonate aquifer linear and logarithmic regression functions have been performed and it is found that the logarithmic relationship predicting transmissivity from specific capacity data has a better correlation r 0 95 than linear one r 0 84 this is logically true because both transmissivity and specific capacity are lognormally distributed the spatial distribution of transmissivity is also affected by the presence of fracturing and karstification phenomena within the aquifer matrix

the greening of arabia multiple opportunities for human occupation of the arabian peninsula during the late pleistocene inferred from an ensemble of climate model simulations climate models are potentially useful tools for addressing human dispersals and demographic change the arabian peninsula is becoming increasingly significant in the story of human dispersals out of africa during the late pleistocene although characterised largely by arid environments today emerging climate records indicate that the peninsula was wetter many times in the past suggesting that the region may have been inhabited considerably more than hitherto thought explaining the origins and spatial distribution of increased rainfall is challenging because palaeoenvironmental research in the region is in an early developmental stage we address environmental oscillations by assembling and analysing an ensemble of five global climate models ccsm3 cosmos hadcm3 kcm and noresm we focus on precipitation as the variable is key for the development of lakes rivers and savannas the climate models generated here were compared with published palaeoenvironmental data such as palaeolakes speleothems and alluvial fan records as a means of validation all five models showed to varying degrees that the arabia peninsula was significantly wetter than today during the last interglacial 130 ka and 126 125 ka timeslices and that the main source of increased rainfall was from the north african summer monsoon rather than the indian ocean monsoon or from mediterranean climate patterns where available 104 ka mis 5c 56 ka early mis 3 and 21 ka lgm timeslices showed rainfall was present but not as extensive as during the last interglacial the results favour the hypothesis that humans potentially moved out of africa and into arabia on multiple occasions during pluvial phases of the late pleistocene

continuity and change in the lithic industries of the jurreru valley india before and after the toba eruption lithic assemblage variability is synthesized and discussed for seven open sites and one rockshelter from the jurreru valley in the kurnool district of southern india the sites span the last c 77 000 years and provide an invaluable record of cultural change spanning the toba super eruption 74 thousand years ago ka as well as the transition to the microlithic lithic evidence documents long term continuities before and after the eruption that indicates the toba eruption had a minimal impact on the underlying system of flake production in the valley the analysis also indicates that many cores from above and below the toba ash are technologically extremely similar to those from early modern human sites in sub saharan africa southeast asia and australia suggesting modern humans may have entered india before the toba eruption as part of an early eastward dispersal from africa

a southern indian middle palaeolithic occupation surface sealed by the 74 ka toba eruption further evidence from jwalapuram locality 22 this paper reports further evidence from an archaeological occupation surface in southern india that was buried by tephra from the toba volcanic super eruption ca 74 000 years ago the open air site designated jwalapuram locality 22 and located in the kurnool district of andhra pradesh preserves more than 1600 stone artefacts assigned to the indian middle palaeolithic sedimentological isotopic and lithic data along with optically stimulated luminescence ages confirm the site as occupied closely prior to the eruption the hominin taxon responsible for creating the site is not known but the stone tool evidence is most consistent with contemporaneous homo sapiens technologies in africa and to the east of south asia the findings have relevance for understanding indian middle palaeolithic technology and for identifying the behavioural and environmental adaptations of the hominin group s that occupied india when toba erupted

aplanktonic zones in the red sea abstract we use micropalaeontological and stable isotope results for a series of cores from north to south through the red sea to assess temporal and spatial patterns of change in planktonic foraminiferal faunas leading up to the remarkable full glacial red sea aplanktonic zones aplanktonic zones reflect salinities in the red sea in excess of the lethal 49 p s u limit caused by reduced exchange transport through the strait of bab el mandab due to glacial sea level lowering concerning the last glacial cycle aplanktonic conditions began at 39 ka bp in the north where salinities eventually reached 55 57 p s u paradoxically planktonic faunas are reported to have survived the last glacial maximum in the northern gulf of aqaba suggesting a poorly understood freshwater dilution at that time aplanktonic conditions s 49 p s u reached the south central red sea by 22 ka bp while planktonic foraminiferal faunas continued albeit in very low abundances and limited diversity s 45 p s u in the southernmost red sea during marine isotope stage mis 6 the 49 p s u isohaline appears to have resided in the central red sea between cores kl11 and md921017 we observe a systematic sequence of species disappearances before all glacial maxima of the last 500 kyr absence of a logical relationship with sea levels suggests that the disappearance sequences are not related to a general salinity increase instead we argue that the sequences were driven by complex reorganisations in hydrography stratification productivity food availability and subsurface oxygenation reproduction habitats the onset is marked by dramatic basin wide expansion of conditions that today are restricted to only the southern red sea suggesting an expansion of the dominance of ne monsoonal circulation over the entire red sea this expansion occurred 15 or more kyr before the aplanktonic zones of mis 12 6 and 2 and also before mis 10 and 8 which never reach the aplanktonic stage regarding the last glacial cycle this event occurred as early as 75 ka bp mis 4 5 boundary after this major climatic reorganisation we reconstruct progressive intensification of the new conditions especially marked by northward expansion and intensification of the subsurface oxygen minimum zone omz during the last glacial cycle a shallow and very distinct omz affected the central red sea as early as 68 ka bp and the north as late as 55 ka bp the omz expansion intensification appears to have been interrupted by episodes of increased ventilation

earthquake site response estimation a weak motion case study using weak motion recordings of aftershocks of the 1989 loma prieta earthquake recorded in oakland california near the failed nimitz freeway two methods have been applied to estimate the site response of an alluvium site and three mud over alluvium sites the first estimate is the traditional spectral ratio and the second utilizes the cross spectrum recordings obtained at a nearby bedrock site are used as estimates of the sediment site input motions while the two site response estimates produce similar peaks and troughs there is an approximate factor of 2 difference in amplitudes this discrepancy is evidence that there is a much greater level of noise than would be expected from the pre event ambient noise we interpret this as signal generated noise produced by scattering from heterogeneities which causes the true sediment site input to differ significantly from the bedrock site recording given this level of noise the cross spectrum estimate suffers a severe downward bias by a factor of 2 in this study and should probably not be used when the input motion is estimated from a bedrock site recording the spectral ratio estimates are relatively unbiased but the level of noise introduces a large degree of uncertainty therefore inferences about site response from individual spectral ratios should probably be avoided on the other hand ensemble averages of the estimates significantly reduce the scatter to reveal resonances that agree quite well in frequency and overall shape with those of one dimensional models whose parameters were determined independently a discrepancy of higher observed amplitudes than predicted by theory remains unexplained but most likely results from the effects of boundary layer topography which are not accounted for by the simple one dimensional models

the great arc of dispersal of modern humans africa to australia abstract during the late pleistocene anatomically modern humans amh dispersed out of africa across the continents their routes obeyed the limitations placed on any large terrestrial mammal dependent on daily drinking water following certain climate permissive corridors amh first spread north with game across the sahara to the levant during the eemian interglacial c 125 ka but failed to continue to europe then occupied by neanderthals the savannah ecosystem in north africa and the middle east then dried up and amh vanished from the levantine fossil record being replaced there by neanderthals later amh successfully left africa as a single group by the southern route to india the added ability to make short but deliberate open water crossings allowed them first to cross the mouth of the red sea from eritrea and subsequently wallace s line to reach the isolated sahul continent at least by 48 000 years ago and possibly by 60 50 000 years ago they only finally arrived in europe from south asia around 45 50 000 years ago probably linked to climatic amelioration during ois 3

environmental impact of the 73 ka toba super eruption in south asia abstract the cooling effects of historic volcanic eruptions on world climate are well known but the impacts of even bigger prehistoric eruptions are still shrouded in mystery the eruption of toba volcano in northern sumatra some 73 000 years ago was the largest explosive eruption of the past two million years with a volcanic explosivity index of magnitude 8 but its impact on climate has been controversial in order to resolve this issue we have analysed pollen from a marine core in the bay of bengal with stratified toba ash and the carbon isotopic composition of soil carbonates directly above and below the ash in three sites on a 400 km transect across central india pollen evidence shows that the eruption was followed by initial cooling and prolonged desiccation reflected in a decline in tree cover in india and the adjacent region carbon isotopes show that c 3 forest was replaced by wooded to open c 4 grassland in central india our results demonstrate that the toba eruption caused climatic cooling and prolonged deforestation in south asia and challenge claims of minimal impact on tropical ecosystems and human populations

3 d wave propagation in the los angeles basin for the whittier narrows earthquake abstract elastic wave propagation within and around the los angeles basin during the whittier narrows earthquake in 1988 is simulated with a 3 d finite difference method the model consists mainly of a sedimentary layer over the basement but lateral variations inside the sedimentary basin is also included to approximate observed variations in surface shear velocity the minimum shear velocity is 1 km sec on the surface and fairly reliable results are obtained up to 0 75 hz the total simulation lasts 26 sec our simulation can reproduce the general amplification pattern small east of the epicenter and large in the l a basin and the san fernando valley due to thick sediments of low velocity in these areas surface waves are generated by the primary s wave and trapped inside the basins in the southern part of the l a basin a distinct later phase delayed by 5 to 6 sec relative to the primary s wave is produced in our simulation which matches some strong motion records

the effect of topography on earthquake ground motion a review and new results a brief review of experimental and theoretical results about the effect of topography on seismic motion shows that they are consistent only on a qualitative basis amplification at mountain tops for wavelengths comparable with mountain widths is predicted and observed but the numerical simulations often underestimate the actual observed effects we propose that this disagreement is because current models are not complex enough we therefore computed the response to incident sh waves of a set of different complex configurations that include two dimensional surface topography with or without periodic ridges and subsurface layering the results show that 1 the topographic effect in itself is difficult to isolate from other effects like surface layering and therefore the amplification on top of geomorphologically complex sites cannot be predicted by a priori estimations based solely on topography and 2 the high crest base amplification ratio observed in the field cannot usually be matched even with complex two dimensional structures with incident plane sh waves which suggests that more complex models are needed to incorporate more complex wave fields e g sv surface and three dimensional geologic configurations

the last 140 ka in the afro asian arid semi arid transitional zone abstract during the last ten years a great number of geological or other proxy records provided radiocarbon u th or tl dated information on the past climatic oscillations in the arid semi arid zones extending between the atlantic and the pacific comparisons and a synthetic view of these results can now be attempted for the last 140 ka and compared with global changes as registered in oceanic or ice cores and with palaeomonsson models for this purpose wide spatial and time scales have to be used on the whole arid humid alternations roughly fit global changes cold phases corresponding to an extension of the arid areas to the south warm phases corresponding to the shrinking of the same to the north the last interglacial is associated with an increase of precipitation throughout the area considered isotopic stage 4 brings no evidence whatsoever of humid conditions two wetter episodes are registrated during stage 3 a major rainfall decrease is everywhere associated with the last glacial maximum 21 15 ka in most regions the arid or semi arid zones extending several hundred kilometers southwards relative to the present day pattern the two abrupt deglaciation steps and the younger dryas are recorded in all of the most sensitive regions at the margins of the present day monsoonal range during the holocene the precipitation increases everywhere by 100 400 mn relative to the present day values the optimum being at 8 5 6 5 ka a climatic deterioration follows with an irregular pattern of dry wet episodes according to the different geographic conditions the humid phase terminates at 3 5 3 ka in the whole transitional zone the major southward shift of the monsoonal precipitation range since its optimum some 8000 years ago fits the astronomical neoglacial trend and may possibly be correlated with past stage 5d although its rapidity and spatial importance may just reflect one of the sharp successive cold warm variations registered by grip during the whole stage 5

limited global change due to the largest known quaternary eruption toba 74 kyr bp abstract the 74 kyr bp super eruption of toba volcano in sumatra is the largest known quaternary eruption on the basis of preserved deposits the eruption magnitude has been estimated at 7 10 15 kg 2800 km 3 of dense magma the largest sulphate anomaly in the greenland ice sheet project 2 core has been identified as fallout from toba s stratospheric aerosol veil correlation of the sulphate and oxygen isotope stratigraphy of the ice core suggests that the toba eruption might have played a role in triggering a millennium of cool climate prior to dansgaard oeschger event 19 although a comparable stadial preceded event 20 a possible 6 yr duration volcanic winter immediately following the eruption has also been proposed as the cause of a putative bottleneck in human population supporting in a general way the garden of eden model for the origin of modern humans however along with counter arguments regarding the timing of any demographic crash there remain major gaps in our understanding of the 74 kyr bp toba eruption that hinder attempts to model its global atmospheric and climatic and hence human consequences the tephra record reveals basic aspects of the eruption style but calculations of the duration and hence intensity and plume height of the event are poorly constrained furthermore estimates of the sulphur yield of the erupting magma central to predictions of its atmospheric and climatic impacts vary by two orders of magnitude 3 5 330 10 10 kg previous estimates of globally averaged surface cooling of 3 5 c after the eruption are probably too high a figure closer to 1 c appears more realistic the volcanological uncertainties need to be appreciated before accepting arguments for catastrophic consequences of the toba super eruption

the human colonisation of australia optical dates of 53 000 and 60 000 years bracket human arrival at deaf adder gorge northern territory the date at which people entered australia has important implications for the debate on modern human origins thermoluminescence dates of 50 60 ka reported for initial occupation of the malakunanja ii site in northern australia have been used as a means of calibrating the rate of mitochondrial and nuclear dna evolution in modern humans optical dating of unburnt quartzose sediments from a rock shelter site nauwalabila i lindner site in deaf adder gorge 70 km south of malakunanja ii provides new evidence for the timing of the colonisation of the continent optical dates were determined for several stratigraphic levels within a 3 m deep excavation in which flaked stone artefacts and ground pigments were found in primary depositional setting the lowest human occupation levels are bracketed by dates of 53 4 5 4 ka and 60 3 6 7 ka while the upper levels show good agreement between optical and calibrated 14c age estimates high quality haematite with ground facets and striations is associated directly with the 53 ka level and indicates the use of pigments by these early australians the optical dates independently confirm evidence for the colonisation of northern australia shortly after 60 ka and should be seen in the context of this region as having been a likely entry route for the first human movements into sahul

climatic change recorded in the sediments of the chew bahir basin southern ethiopia during the last 45 000 years abstract east african paleoenvironments are highly variable marked by extreme fluctuations in moisture availability which has far reaching implications for the origin evolution and dispersal of homo sapiens in and beyond the region this paper presents results from a pilot core from the chew bahir basin in southern ethiopia that records the climatic history of the past 45 ka with emphasis on the african humid period ahp 15 5 ka calbp geochemical physical and biological indicators show that chew bahir responded to climatic fluctuations on millennial to centennial timescales and to the precessional cycle since the last glacial maximum potassium content of the sediment appears to be a reliable proxy for aridity showing that chew bahir reacted to the insolation controlled humidity increase of the ahp with a remarkably abrupt onset and a gradual termination framing a sharply defined arid phase 12 8 11 6 ka calbp corresponding to the younger dryas chronozone the chew bahir record correlates well with low and high latitude paleoclimate records demonstrating that the site responded to regional and global climate changes

ground motion amplification in the marina district abstract following the 18 october 1989 loma prieta earthquake triggered seismographs were deployed in and around the marina district to investigate site amplification in the 3 weeks after the mainshock 16 aftershocks were recorded by two or more of these stations two additional stations deployed in march 1990 recorded three earthquakes that occurred in contra costa county by recasting the method of spectral ratios into a generalized inverse problem we combine the shear wave spectra from these 19 aftershocks to estimate the relative site amplification as a function of frequency all five stations located in the marina district are amplified by factors of 6 to 10 at 1 hz and 2 to 4 at 3 hz relative to a station located on franciscan sandstone at fort mason irrespective of whether they are sited on artificial fill or beach sand two stations located on dune sand just outside the marina district are amplified by factors of 2 to 4 for frequencies above 1 hz four stations located on franciscan sandstone in pacific heights nob hill rincon hill and diamond heights show little relative amplification conditional estimates of the mainshock spectra can be determined at stations that only recorded aftershocks if they can be linked to stations that recorded the mainshock these estimates are predicated on the assumption that the ground behaved linearly in the mainshock an assumption that is clearly violated for those sites where there was ground failure using this method of extrapolation for a site in the marina district that showed no evidence of ground failure yields mainshock spectra that are slightly greater than the mainshock spectra from the outer harbor wharf in oakland and near the pacific park plaza in emeryville and that significantly exceed the mainshock spectra from all the free field accelerograms located in san francisco

subduction and seismic hazard in the northern lesser antilles revision of the historical seismicity an important set of french and british archives on the historical seismicity of the northern lesser antilles is analyzed we present the most significant data which help to constrain the 8 february 1843 the 16 may 1851 and the 29 april 1897 earthquakes the 1843 event is the largest reported historical earthquake of the lesser antilles subduction arc and produced intensity ix on a segment about 100 km long between antigua and grande terre guadeloupe which contradicts the 300 km long proposed by other authors who mainly rely on robson s catalog 1964 this suggests a magnitude 7 5 to 8 0 the absence of tsunami and noticeable vertical deformation of the coasts in the source area makes very unlikely a normal fault mechanism but does not rule out the possibility of a subduction event because of the low dip angle of the interplate plane the dominance of moderate instrumental thrust earthquakes in the source area suggests a subduction mechanism for the 1843 event the northern and southern limits of the 1843 source area roughly coincide with the barracuda ridge and the tiburon ridge respectively which may have acted as barriers during the rupture process the northwestern portion of the tiburon ridge is associated with a lack of instrumental seismicity near grande terre which could indicate a possible magnitude 7 5 to 8 0 event in the next future moreover its mechanism could be normal which would provide the additional risk of a damaging tsunami the evaluation of seismic hazard must also take into account possible shallow moderate earthquakes as the 1851 and the 1897 events which produced intensities vii to viii in guadeloupe and may be related to observed major plioquaternary faults in this island

the environmental context of paleolithic settlement at jebel faya emirate sharjah uae abstract key to the understanding of pleistocene human dispersals and settlement dynamics is knowledge about the distribution of human habitats in space and time to add information about the characteristics of inhabited environments along the south arabian dispersal route this paper presents paleo environmental data from deposits excavated at jebel faya fay ne1 in the emirate of sharjah uae the sedimentary sequence at fay ne1 spans a period of about 125 000 years including the last interglacial and the holocene particle size and phytolith content of samples from two sediment columns were analyzed including both archaeology bearing layers and archaeologically sterile layers the results demonstrate that human occupation of the site is related to pluvial periods assemblage c dated to about 127 123 ka was deposited during a wet phase with an environment characterized by an increased proportion of c 3 grasses grassland with sedges but lacking tree cover characterize ecological conditions during the youngest of the paleolithic occupation periods assemblage a dated to about 45 40 ka environmental conditions during periods lacking archaeological remains are characterized by the absence of vegetation cover during phases of desiccation there is no evidence for human presence at the site between 38 and 11 ka

shallow velocity structure and site effects at mt vesuvius italy from hvsr and array measurements of ambient vibrations abstract ambient vibrations were recorded by two dense short period seismic arrays located on mount vesuvius the aim of this study is to derive the surface velocity structure through the application of array techniques and to interpret it in terms of resonance effects mount vesuvius which is located in proximity to the apennines earthquake source zone is one of the most dangerous volcanoes of the world we compared different array techniques to derive the dispersive properties of the surface waves composing the noise wave field the frequency wavenumber f k spectral method applied to the data recorded by array a furnished the rayleigh waves and love waves dispersive functions and proved the time space stationarity of the noise wave field the existence of a stochastic wave field justifies the use of the spatial autocorrelation spac method and the time stationarity autocorrelation tsac method which appear to be most effective at the lowest frequencies the tsac method which time averages is confirmed as the most user friendly because it does not require circular geometries the knowledge of the surface structure is an important goal in site effects studies and is used to determine the frequency response of the near surface geology velocity models have been derived from the dispersion curves using both trial and standard inversion procedure the results are compared with those obtained from array measurements in adjacent areas scarpa et al 2003 revealing similar mechanical properties in the cover deposits and heterogeneities down to 40 m of depth the shear wave velocity profiles derived at the array sites are used to model the 1d transfer functions for vertically incident shear waves the fundamental resonance frequencies agree with the peak frequencies observed in the microtremor horizontal to vertical spectral ratios the frequency band of amplification is also compatible with the results obtained from local earthquakes at sites located at the same elevation on mount vesuvius galluzzo et al 2009

dhaba an initial report on an acheulean middle palaeolithic and microlithic locality in the middle son valley north central india this paper presents the first report on dhaba a newly discovered locality in the middle son valley north central india the locality preserves acheulean middle palaeolithic and microlithic artefacts within a late quaternary stratified alluvial sequence initial information is provided on the sedimentary sequence archaeological survey and excavation topographical mapping and lithic technological analysis of dhaba 1 the largest excavation at the locality the assemblage is situated within the regional geomorphological and hominin occupation sequences noting that while dhaba lies within a kilometre of toba tephra deposits no temporal link between the tephra and the artefact bearing sediments is possible at present dhaba currently provides the only known extensive occurrence of middle palaeolithic artefacts in the middle son valley that lacks handaxes

palaeoenvironmental response to the 74 ka toba ash fall in the jurreru and middle son valleys in southern and north central india distal deposits of rhyolitic volcanic ash from the 74 ka supervolcanic eruption of toba in northern sumatra are preserved in numerous river valleys across peninsular india the toba eruption is hypothesized to have resulted in climate change and the devastation of ecosystems and hominin populations this study reports the results of the analysis of sediments and stratigraphical sequences from sites in the jurreru and middle son valleys in southern and north central india the aim of the study is to determine the extent of palaeoenvironmental change in both valleys as a result of the ash fall inferences based on evidence from the jurreru valley are more detailed where pre and post toba palaeoenvironmental changes are divided into seven phases the results indicate that ash fall deposits in both valleys underwent several phases of reworking that possibly lasted for several years indicating that ash was mobile in the landscape for a considerable period of time prior to burial this could have enhanced and lengthened the detrimental effects of the ash on vegetation and water sources as well as animal and hominin populations