horizontal to vertical spectral ratio and geological conditions the case of garner valley downhole array in southern california the aim of the present article is to further check the use of the hori zontal to vertical h v spectral ratio which has been recently suggested as an indi cator of site effects the data set consists of 1 t0 three component high sensitivity accelerograms recorded at five different depths by the garner valley downhole array gvda in southern california with peak ground accelerations 0 0002 g ag 0 04 g magnitudes 3 0 ml 4 6 and hypocentral distances 16 km r 107 km first the stability of the h v spectral ratio is investigated by computing the mean for the whole data set in different depths the h v spectral ratio on the surface is compared with the surface to depth standard spectral ratio with theoretical s wave transfer functions derived from the vertical geotechnical profile as well as with the h v spectral ratio of synthetic accelerograms generated by the discrete wavenumber method both theoretical and experimental data show a good stability of the h v spectral ratio shape which is in good agreement with the local geological structure and is insensitive to the source location and mechanism however the absolute level of the h v spectral ratio depends on the wave field and is different from the surface to depth spectral ratio consequently the h v spectral ratio tech nique provides only partially the information that can be obtained from a downhole array but surface to depth ratios may also be misleading because they combine effects at surface and at depth

effects of regolith megaregolith insulation on the cooling histories of differentiated asteroids the cooling histories and in particular the core cooling rates of differentiated asteroids are calculated employing a variety of thermal conductivity structures in order to simulate the potential insulating effects of regolith and megaregolith brecciated impact rubble layers the regolith is assumed to have thermal conductivity 0 005 the unbrecciated mantle conductivity and its thickness in our most typical model is assumed to be 0 003 the parent body radius the megaregolith if present is assumed to have thermal conductivity 0 1 that of unbrecciated mantle we find that a combination of relatively thick megaregolith and regolith can potentially reduce the core cooling rate by more than a factor of 10 below the rate predicted by models with conventional thermal conductivity structure for any given measured cooling rate the radius implied for the parent asteroid can potentially be reduced by a factor of 5 from the radius predicted by models with conventional thermal conductivity structure realistically the regolith and megaregolith thicknesses required to engender these extreme effects were probably seldom generated except perhaps within the largest asteroids where even if generated they would quickly be reduced by compaction and sintering nonetheless our results for models with plausible regolith and megaregolith thicknesses indicate that most of the iron meteorites and the pallasites probably formed in relatively small r less than 50 km parent bodies we have parameterized our results so that effects of intermediate configurations can readily be calculated the parameterization also facilitates evaluation of additional variables e g the initial temperature the concentrations of long lived radioactive heat sources etc albeit these variables are far less crucial than the thermal conductivity structure our results indicate that the insulation of even a thin regolith causes metallalographic cooling rates to be relatively uniform and practically independent of depth within a given asteroid stochastic differences in cratering regolith production histories may have engendered radically different cooling rates from asteroids of similar radius or similar cooling rates from asteroids of different radius

a comparison and test of various site response estimation techniques including three that are not reference site dependent abstract we compare various site response estimation techniques using after shock data of the 1989 loma prieta earthquake collected in oakland california because of recent interest in comparing results from weak and strong motion to infer any nonlinearity and between direct s and coda waves we pay particular attention to the uncertainties first sediment to bedrock spectral ratio estimates between pairs of sites are compared with those obtained from various generalized inversion approaches where the source and site effects of multiply recorded events are solved for simultaneously we find that the site amplification factors are very similar among these approaches but that the uncertainties can be significantly different depending on how the data are weighted we also examine and test three site response estimation techniques that do not rely on a reference site to estimate source and path effects the first involves a parameterized source and path effects inversion even when the bedrock data are excluded from consideration this approach is found to reveal the frequency dependence of site response at each of the sediment sites the second technique involves taking horizontal to vertical component spectral ratios receiver function type estimates of shear wave aftershock data these are also found to reveal the frequency dependence of site response at the sediment sites and the results for the bedrock site are relatively flat and near unity the third estimate is formed by taking horizontal to vertical component ratios of ambient seismic noise and these are shown to reveal the fundamental resonant frequency of the sediment sites unfortunately discrepancies exist among all of the site response estimates and with one dimensional predictions with respect to a frequency independent scaling factor nevertheless the highly frequency dependent character of site response is well constrained and the fact that non reference site dependent methods are capable of revealing this is promising for site specific hazard assessments in regions that lack adequate reference sites

s wave velocity structure and site effect parameters derived from microtremor arrays in the western plain of taiwan abstract in this study microtremor array measurements were conducted at 45 sites in the western plain of taiwan the arrays were approximately 30 m or 60 m in radius depending on the site the maximum likelihood frequency wavenumber method was adopted to obtain the phase velocities of rayleigh waves and then a genetic algorithm technique based on an inversion scheme of the fundamental mode of the rayleigh waves dispersion curves was applied to calculate a preliminary s wave velocity vs profile at each site because a layer of thick sediment covers the bedrock in the western plain of taiwan microtremor arrays in this size range cannot estimate the structure of the entire sediment therefore this study implemented further inversion of the horizontal to vertical spectral ratios of the microtremors to estimate the deeper structures up to the bedrock of vs greater than 1000 m s previously logged velocity profiles for different depths at or near our study sites were collected and compared with the vs profiles derived from our microtremor array measurements the results were found to be highly comparable therefore we could delineate the depth distributions for the layer depths for vs 600 m s and 1000 m s in this region the depth for vs 600 m s is approximately 50 m in the piedmont area and approximately 300 m at the coastline moreover the depths for vs 1000 m s increase from 200 m in the piedmont area to approximately 1000 m at the coastline the depths for vs 1 0 km s z1 0 which is an important parameter that accounts for the basin effect in recent ground motion prediction equations are consequently available at the study sites the distribution of z1 0 as a function of vs30 indicates higher similarity to that in japan than in the san francisco bay area

trampling experiments at cova gran de santa linya pre pyrenees spain their relevance for archaeological fabrics of the upper middle paleolithic assemblages the study of fabrics that is the analysis of the orientation and slope of archaeological and sedimentary materials associated with the middle palaeolithic upper palaeolithic mp up transition at cova gran shows substantial differences archaeological assemblages are characterised by greater isotropy in the fabrics than the sedimentary levels within which they are located indicating that these differences may be generated by anthropic processes one of the anthropogenic processes associated with horizontal and vertical displacement of archaeological artefacts is trampling and circulation caused by later occupations in order to evaluate the effect of movement on materials we undertook experiments simulating geological and archaeological conditions at cova gran the results show that human trampling does not cause major isotropy in fabrics but arranges archaeological assemblages towards planar or linear materials according to surface geometry we were not able to replicate the fabric pattern of materials from the archaeological levels of cova gran suggesting that they must be associated with the activities of human occupation at each level

ubiquitous brecciation after metamorphism in equilibrated ordinary chondrites our petrographic study of 42 h and l chondrites of types 4 6 revealed 8 that contain rare chondrules or clasts with olivines and pyroxenes having aberrant fe fe mg ratios for example a chondrule in slovak h5 contains olivine with fa 17 22 elsewhere olivine contains fa 17 18 although these chondrites are not obviously brecciated their ingredients could not have experienced the same degree of metamorphism these rocks must be fragmental breccias that were lithified after peak metamorphism regolith breccias and postmetamorphic fragmental breccias both polymict and monomict may constitute a majority of ordinary chondrites comparison of chondritic and achondritic breccias indicates that chondritic fragmental breccias are often very difficult to recognize because they resemble the fine grained mixtures of chondrules and mineral and chondrule fragments from which they formed in addition the chemical and textural uniformity throughout most of the ordinary chondrite bodies ensures that mixtures of materials from different regions are well disguised contrary to the authors claim the van schmus wood classification of ordinary chondrites does not identify rocks with similar thermal histories the petrologic type of a chondrite is only a measure of the average degree of metamorphism experienced by its ingredients thus attempts to correlate physical properties with petrologic types must fail unless breccia and shock properties are considered the extent of brecciation in ordinary chondrites and most achondrites indicates that meter sized unbrecciated rocks must be rare on the surfaces of their parent bodies

development of low background vacuum extraction and graphitization systems for 14c dating of old 40 60 ka samples abstract at the university of arizona s desert laboratory we recently constructed new low background vacuum extraction and graphitization systems that are dedicated to preparing old 40 60 ka samples for 14 c dating these systems are designed to minimize the amount of contaminant carbon specifically atmospheric carbon that is introduced to a sample during laboratory processing excluding contaminants is particularly important for 14 c dating of old samples because the impact of contamination increases with sample age in this study we processed 20 pretreated and 4 untreated aliquots of ceylon graphite a naturally occurring geological graphite to determine the total procedural background level and hence the practical limit of our systems samples were heated under vacuum at 240 c for 1 h to drive off water vapor and other atmospheric gases and then combusted in ultra high purity uhp o 2 at 500 and 850 c to monitor the removal of contaminants and to ensure complete combustion after so x no x and halide species were removed sample co 2 was converted to graphite via catalytic reduction of co fe and zn powders used in the graphitization process were oxidized scrubbed and reduced with uhp o 2 he and h 2 respectively to remove sorbed atmospheric c species graphite targets were stored in uhp ar until measurement by accelerator mass spectrometry ams to avoid potential interaction with atmospheric gases based on the ams results the background level of our system is characterized by a nonlinear inverse relationship with sample mass adjusted r 2 0 75 n 24 for a 1 mg graphite target the total procedural blank including chemical pretreatment combustion cleanup graphitization storage and ams measurement is 0 05 0 01 pmc 2 equivalent to a 14 c age of 61 1 1 8 ka this should not be taken as the upper limit of our system however because if the 14 c activity of a sample is statistically indistinguishable from the appropriate mass dependent blank value at the 95 confidence level 2 then its age is considered to be infinite thus for a 1 mg target the practical limit of our system is actually 55 ka for a 0 5 mg target the practical limit is 50 ka although our extraction system can accommodate inorganic samples e g calcite aragonite the above limits are only applicable to geological graphite charcoal and organic samples that are processed via combustion future work will be directed toward determining the appropriate background levels for inorganic materials

pre screening techniques for identification of samples suitable for radiocarbon dating of poorly preserved bones under certain environmental conditions post depositional diagenetic loss of bone collagen can severely reduce the number of bones from a particular archaeological site that are suitable for stable isotopic analysis or radiocarbon dating this study examined nearly 300 bones from 12 archaeological sites across southern england known to yield poor or variable preservation to try to identify one or more pre screening technique s that would indicate suitable collagen preservation for radiocarbon dating the most reliable method was shown to be the percent nitrogen n of whole bone powder which has an 84 chance of successfully predicting whether or not a bone will yield sufficient i e 1 weight collagen for dating

a mosaic of change the middle upper paleolithic transition as viewed from new mexico and iberia abstract from the cultural archeological perspective there is growing evidence that there was not only considerable variability but also significant change within the block of time that prehistorians call the middle paleolithic mp this was not a period of stasis and thus the actors homo sapiens neanderthalensis in europe were quite capable of adapting to new environmental circumstances in sensu lato likewise the so called upper paleolithic up was a cultural monolith neither in time nor in space in particular humans had to react in significant ways to the environmental crisis of the last glacial maximum that began some 20 14 c kyr after the transition to modernity adaptation is a continuously ongoing process sometimes slow but at other times fast the complementary opposition that has been set up by archeologists between the mp and the up obscures the considerable amount of variation and change that existed both before and after the mythic date of 40 14 c kyr this paper reviews and compares relevant aspects of the records from europe and africa and then focuses on the iberian peninsula to highlight the arbitrary nature of our concept of an mp up transition changes took many forms not all of them novel or abrupt with many examples of up type precursor behaviors and products in the mp many clear cases of continuity across the transition and abundant evidence that the entire phenomenon was a cultural and biological mosaic rather than starkly black and white replacement of one adaptive system by another the iberian evidence is a microcosm of the complexity of the situation which cannot be glossed over for the sake of mere simplification or to continue to prop up 19th century culture historical notions and analytical units

vs30 estimates using constrained h v measurements abstract most seismic codes adopt the average shear wave velocity as a key parameter in the first 30 m of subsoil v s 30 estimates of v s 30 are therefore required for both large and small scale seismic microzonation we propose a technique to measure the v s 30 based on the horizontal to vertical spectral ratio h v of microtremor recorded at a single station the h v is fitted with a synthetic curve using the independently known thickness of a superficial layer of the subsoil as a constraint the proposed procedure consists of three steps 1 identify the depth of a shallow stratigraphic horizon from independent geotechnical data 2 identify its corresponding h v marker and 3 use it as a constraint to fit the experimental h v curve with the theoretical one the synthetic h v curve is calculated by assuming a stratified one dimensional 1d soil model and a tremor wave field from distant random sources that are composed of rayleigh and love waves this technique has been validated on different geological settings following a triple check procedure 1 the theoretical rayleigh wave phase velocity dispersion curves calculated for the model derived from the h v fit were compared to the experimental curves measured with the 2d extended spatial autocorrelation esac method and the 1d refraction microtremor remi array surveys 2 the v s profiles and 3 the v s 30 estimates obtained by the proposed technique were compared to those obtained by using the latter array techniques finally the inferred stratigraphy was compared to the geological model the proposed technique is not meant to provide accurate v s profiles but has the potential to provide v s 30 estimates that are coherent with those measured through esac and remi and to satisfy law requirements furthermore the h v is found to be capable in detecting deviations from 1d subsoil geometry over the length of a few meters the correctness of which was confirmed by direct drilling

new empirical relationship between resonance frequency and thickness of sediment using ambient noise measurements and joint fit inversion of the rayleigh wave dispersion curve for kangra valley nw himalaya india

assessment of potential seismic hazard and site effect in antakya hatay province se turkey antakya city is at risk because of strong earthquakes occurring in the area and different soil conditions that can produce variation of the ground motion amplification microzonation of cities provides a basis for site specific hazard analysis in urban settlements in particular seismic microzonation can be provided by means of detailed seismic assessment of the area including earthquake recordings and geological studies in this paper we propose a preliminary microzonation map for the city of antakya based on the variation of the dominant periods and shear velocities of the sediments covering the area the periods are retrieved from microtremor measurements conducted at 69 sites using the horizontal to vertical spectral ratio technique the results of microtremor analysis were compared with data obtained from refraction microtremor remi measurements at four profiles crossing the studied area according to the classification of dominant periods antakya city can be divided into five zones probably prone to different levels of seismic hazard the shorter natural periods are in inner antakya and both the sides of asi river i e northern and southern parts the eastern and western parts of antakya have maximum dominant periods the vs30 values were calculated by using the remi method along the profiles antakya city has vs30 values in the range of category c of the national earthquake hazard reduction programme site classification

fission track studies of xenolithic chondrites implications regarding brecciation and metamorphism abstract we have studied fission tracks in phosphates from one gas poor chondrite and three gas rich chondrites to determine their thermal history and brecciation time scales more than 70 percent of the tracks in whitlockites in these meteorites are due to the decay of extinct pu244 whitlockites separated from bhola a gas poor chondrite have pu u 2 6 5 2 and a model fission track age of 4 0 gyr for a pu u 4 55gyr 0 045 brecciation of the bhola meteorite must have occurred at 4 3 gyr to account for the metal data scott and rajan 1981 a minimum cooling rate of 0 9 0 2 0 3 k myr in the temperature interval 800 to 300 k obtained from the track data is a factor of seven higher than the metallographic cooling rate 0 1 k myr for the gas rich chondrites the pu u in whitlockites are weston 32 148 fayetteville 21 227 and st mesmin 26 137 whitlockites from all these meteorites give model fission track ages of 4 4 gyr assuming a pu u 4 55 gyr 0 045 the final brecciation event definitely did not reset the track clock in phosphates of st mesmin our data suggest that it is also true for weston and fayetteville we conclude that our observed fission track ages date the end of metamorphic cooling in the meteorite parent bodies and support the planetesimal model for the formation of xenolithic chondrites

the behavior of actinides phosphorus and rare earth elements during chondrite metamorphism new data on the u pu and p distributions in less metamorphosed h chondrites type 3 5 coupled with literature results permit a provisional picture to be assembled of the chemistry of these elements and for the rare earth elements in ordinary chondrites and the changes brought about by chondritic metamorphism preferential associations of phosphates with metals and or sulndes in all chondrites strongly indicate an initially siderophile or conceivably chalcophile character for p in ordinary chondrite precursor materials with phosphate subsequently formed by oxidation this oxidation occurred prior to or during chondritic metal silicate fractionation uranium is initially concentrated in chondrule glass at 100 ppb levels with phosphates primarily merrillite in h 3 chondrites being essentially u free 20 ppb as chondrule glass devitrified during metamorphism u migrated into phosphates reaching 50 ppb in nadiabondi h 5 merrillite and 200 300 ppb in merrillite from equilibrated chondrites but froze out before total concentration in phosphates occurred relative 244 pu fission track densities in the outer 5 m of olivine and pyroxene grains in contact with merrillite and with chondrule mesostasis in bremervorde h 3 give pu mesostasis pu merrillite 0 01 implying total concentration of pu in phosphates similarly no detectable pu 0 1 ppb was found in chondrule mesostasis in tieschitz and sharps whereas direct measurements of tracks in phosphates in h 3 chondrites are consistent with high 10 ppb pu concentrations thus a strong pu p correlation is indicated for ordinary chondrites there is variable pu u fractionation in all chondritic phosphates reaching an extreme degree in the unequilibrated chondrites therefore the pu u ratio in phosphates appears relatively useless for relative meteorite chronology literature data indicate that the ree are located in chondrules in unequilibrated chondrites most likely in glass thus there may also be strong pu nd fractionation within these meteorites like u the ree migrate into phosphates during metamorphism but unlike u appear to be quantitatively concentrated in phosphates in equilibrated chondrites thus relative ages based on pu nd may be possible for equilibrated chondrites but the same chronological conclusions are probably obtainable from pu concentrations in phosphates i e on the pu p ratio however pu p chronology is possible only for ordinary chondrites so there appears to be no universal reference element to cancel the effects of pu chemical fractionation in all meteorites available data are consistent with but certainly do not prove that variations in pu p represent age differences but if these age differences do not exist then it is conceivable that the solar system 244 pu 238 u ratio important for cosmochronology is still lower than the presently accepted value of 0 007

site characterization through combined analysis of seismic and electrical resistivity data at a site of dhanbad jharkhand india we present the seismic site characterization study using joint modelling of horizontal to vertical spectral ratio hvsr and rayleigh wave phase velocity dispersion curves obtained from multi channel simulation with one receiver msor in a part of dhanbad jharkhand india the joint analysis of these two different but complementary datasets puts stronger constraints on the model parameter search space than one dataset and may help us in finding more unique shear wave velocity model the microtremor data from 12 observation points were utilized to iteratively search 1d shear wave velocity profiles in a predefined model search space these 1d shear wave velocity models were interpolated to generate a 2d shear wave velocity profile of the site using the cubic spline method our results show that the high peak amplitude value of hvsr is associated with low peak period values of hvsr at a distance of 60 m from the southern end of the profile which may indicate the presence of the basin edge effect we identified four layers based on significant changes in the shear wave velocities to a depth of 60 m the major impedance contrasts are located at average depths of 13 m 40 m and 55 m respectively these layers from the surface may indicate the presence of soil highly weathered rock mass moderately weathered rock and bedrock respectively the depth of engineering solid bedrock vs 600 m s is found at the depth of 55 m in the south which gradually decreases to a depth of 40 m in the northern end of the profile the shear wave velocity vs 30 for this area varies between 293 and 357 m s which can be classified as d type site for validation and comparison of our results the electrical resistivity tomography ert data were also recorded along the same traverse using wenner and schlumberger configurations our results show a significant amount of correlation between the 2d shear wave velocity and resistivity profiles obtained from joint analysis of tremor and ert data

contextual technological and chronometric data from cova gran their contribution to discussion of the middle to upper paleolithic transition in northeastern iberia abstract the middle to upper palaeolithic transition in western europe is a central topic in current paleoanthropological research recently neanderthal survival during mis 3 and the emergence of anatomically modern humans have been the focus of much discussion in iberia here we analyse the stratigraphic and contextual resolution of the s1b 497d archaeological levels from cova gran in which a techno typological discontinuity has been identified affecting raw material knapping systems blanks and retouched tools attributes such as radial reduction systems to obtain flakes for subsequent preferential modification into notches and denticulates place level s1b within the mousterian tradition however in 497d attributed to the early upper palaeolithic laminar production intermingles the extraction of blades bladelets and flakes blades were transformed into burins end scrapers and retouched blades and bladelets into microlithic tools such as backed points and backed bladelets these artefacts are associated with a significant assemblage of notches denticulates and scrapers on flakes radiometric data places the end of the mousterian tradition ca 42 ka cal bp and the appearance of the early upper palaeolithic ca 39 38 ka cal bp the geographic and temporal ascription of levels s1b and 497d stimulate discussion on neanderthal survival at the end of mis 3 in northeastern iberia likewise the 497d lithic assemblage is compared to other techno complexes assigned to this chronological range the chatelperronian tradition assigned to neanderthals and protoaurignacian linked to the appearance of anatomically modern humans the archaeological resolution and techno typological discontinuity documented in cova gran are useful points of reference in analysis of the middle to upper palaeolithic transition in northeastern iberia and have implications affecting the characterization of this process across western europe

reclassification and thermal history of trenzano chondrite we present a new single crystal x ray diffraction xrd study performed on a suite of six orthopyroxene grains from the low shocked h6 trenzano meteorite the quenched intracrystalline fe 2 mg ordering state in orthopyroxene preserves the memory of the cooling rate near closure temperature tc thus yielding useful constraints on the last thermal event undergone by the host rock the orthopyroxene tc of 522 13 c calculated using a new calibration equation obtained by stimpfl 2005b is higher than in previously published h chondrite data the orthopyroxene cooling rate at this tc is about 100 c kyr this fast rate is inconsistent with the much slower cooling rate expected for h6 in the onion shell structural and thermal model of chondrite parent bodies a petrographic study carried out at the same time indicated that the trenzano meteorite is an h5 chondrite and not an h6 chondrite as it is officially classified furthermore the two pyroxene equilibrium temperature of trenzano 824 24 c calculated with quilf95 is similar to the two pyroxene temperature of 750 840 c obtained for the carcote h5 chondrite kleinschrot and okrusch 1999

a time lapse study using self potential and electrical resistivity tomography methods for mapping of old mine working across railway tracks in a part of raniganj coalfield india the first coal mining in india was started in the seventeenth century with an unplanned way in raniganj coalfield the coal capital of india the coalfield was possessed by several small private companies which were nationalized in 1973 a part plan of chanch victoria area victoria west colliery bccl raniganj coalfield india indicates an underground coal mine gallery goaf in the begunia coal seam that connects to a light casting factory it was established as barakar iron works in the year 1881 by the government at that time it is understood that the approaching gallery was used for coal supply to the light casting factory by the mining of begunia coal seam mostly these are uncharted and very poorly documented with scarce mine plans so the present study attempts to explore the location depth extension and condition of the old working gallery through time lapse monitoring using a combined study comprising of self potential sp and electrical resistivity tomography ert techniques four sp profiles data along a line and thirteen ert profiles data in four different lines were collected across the expected site with different station electrode spacing covering different profile length in four seasons viz summer may 2016 monsoon august 2016 post monsoon october 2016 and summer april 2017 sp data were analysed using simulated annealing sa optimization technique for the evaluation of model parameters the ert data were acquired using wenner dipole dipole and schlumberger arrays and inversion of the combined data set was performed using the 2 5d zzresinv inversion software prominent negative sp signature with equivalent low resistivity anomaly have been delineated that possibly indicate the presence of the old mine working mine gallery however the overall results of time lapse study inferred that the ground is stable all results are corroborated with available lithology and field photographs

terrasses de la riera dels canyars gava barcelona the landscape of heinrich stadial 4 north of the ebro frontier and implications for modern human dispersal into iberia abstract terrasses de la riera dels canyars is an upper pleistocene fluvial deposit containing the remains of large mammals principally accumulated in the framework of hyena denning in the area as well as a few artifacts radiocarbon dated to 39 6 ka cal bp the time of heinrich stadial hs 4 this site enables us to reconstruct the environmental conditions then prevalent in the ne of the iberian peninsula the concentration in a single locus of finds generated by different agents relates to a flash flood event the rapidity of which combined with the absence of archaeological ecological or paleontological incongruities in the composition of the assemblage warrants an assumption of broad contemporaneity for its contents the ecofactual evidence fauna pollen charcoal phytoliths indicates a steppe dominated environment for the coastal areas between the pyrenees and the ebro delta the dominant elements are cold and dry adapted species but a mediterranean component is present implying a less rigorous climate than farther north in europe the artifacts are clearly upper paleolithic and assignment to the modern human associated aurignacian technocomplex is supported by the radiocarbon dates and the typology of a bilaterally retouched blade this evidence is consistent with the notion that anatomical modernity spread across europe over open landscape niches available pollen data from deep sea cores indicate that during some of the interstadials of marine isotope stage mis 3 a significant vegetation gradient existed at 40 n broadly coincident with the ebro frontier temperate and warm temperate trees expanded significantly to the south while steppe tundra landscapes remained dominant to the north a contrast best seen during greenland interstadial gi 8 such an environmental boundary must have implied a durable barrier to diffusion and migration during interstadials under the cold and arid conditions of hs4 the site of canyars shows that the eurasian steppe tundra extended as far south as the llobregat delta however the environmental reconstructions available for the lower ebro valley and adjacent mountains of the iberian range farther south suggest that they formed at this time a belt of semi desert or steppe desert landscapes thus maintaining the boundary effect despite the climatic reversal the persistence of such a boundary through hs4 and the interstadials that bracket it must have played a role in the delayed arrival of the aurignacian and modern humans to southern and western iberia which continued to be settled by middle paleolithic neanderthals well beyond 40 ka cal bp

derivation of a heterogeneous lithic fragment in the bovedy l group chondrite from impact melted porphyritic chondrules the bovedy l group chondrite contains a light colored poikilitic lithic fragment with olivine low ca pyroxene and kamacite compositions characteristic of porphyritic chondrules from unequilibrated ordinary chondrites its texture compositional similarities to porphyritic chondrules and low na2o k2o and p2o5 content indicate that the fragment represents a solidified slightly fractionated impact melt formed from a source that was rich in porphyritic chondrules the fragment is heterogeneous with a progressive increase in the bulk mgofeo ratio and in mgo content of olivines and low ca pyroxenes across its length 39ar40ar analyses of the fragment and host indicate that the meteorite experienced extensive degassing due to reheating the approximate age of 0 5 0 94 byr dates the reheating event and not the formation of the lithic fragment or the bovedy breccia this reheating event renders the fragment s and host s metallographic cooling rate of 5 c myr through 500 c imprecise however the absence of martensite and the presence of kamacite zoned taenite and tetrataenite in the fragment and host are consistent with such slow cooling through 500 c this cooling rate must have resulted from burial of the fragment host assemblage beneath insulating material on the bovedy parent body if the thermal diffusivity of this overburden was approximately comparable to that of the lunar regolith 10 4cm2 sec then the fragment was buried at a depth 6 5 km if k 10 2 cm2 sec similar to chondritic material then the fragment was buried at a depth 65 km

synchronization of the ngrip grip and gisp2 ice cores across mis 2 and palaeoclimatic implications abstract we here present a synchronization of the ngrip grip and gisp2 ice cores based mainly on volcanic events over the period 14 9 32 45 ka b2k before ad 2000 corresponding to marine isotope stage 2 mis 2 and the end of mis 3 the matching provides a basis for applying the recent ngrip based greenland ice core chronology 2005 gicc05 time scale to the grip and gisp2 ice cores thereby making it possible to compare the synchronized palaeoclimate profiles of the cores in detail and to identify relative accumulation differences between the cores based on the matching a period of anomalous high accumulation rates in the gisp2 ice core is detected within the period 16 5 18 3 ka b2k the 18 o and ca 2 profiles of the three cores are presented on the common gicc05 time scale and generally show excellent agreement across the stadial interstadial transitions and across the two characteristic dust events in greenland stadial 3 however large differences between the 18 o and ca 2 profiles of the three cores are seen in the same period as the 7 9 increase in the gisp2 accumulation rate we conclude that changes of the atmospheric circulation are likely to have occurred in this period altering the spatial gradients in greenland and resulting in larger variations between the records

revisiting 26al 26mg systematics of plagioclase in h4 chondrites zinner and gopel 1992 2002 found clear evidence for the former presence of 26al in the h4 chondrites ste marguerite and forest vale they assumed that the 26al 26mg systematics of these chondrites date metamorphic cooling of the h4 parent body plagioclase in these chondrites can have very high al mg ratios and low mg concentrations making these ion probe analyses susceptible to ratio bias which is inversely proportional to the number of counts of the denominator isotope ogliore et al 2011 zinner and gopel 2002 used the mean of the ratios to calculate the isotope ratios which exacerbates this problem we analyzed the al mg ratios and mg isotopic compositions of plagioclase grains in thin sections of ste marguerite forest vale beaver creek and sena to evaluate the possible influence of ratio bias on the published initial 26al 27al ratios for these meteorites we calculated the isotope ratios using total counts a less biased method of calculating isotope ratios the results from our analyses are consistent with those from zinner and gopel 2002 indicating that ratio bias does not significantly affect 26al 26mg results for plagioclase in these chondrites ste marguerite has a clear isochron with an initial 26al 27al ratio indicating that it cooled to below 450 c 5 2 0 2 myr after cais the isochrons for forest vale and beaver creek also show clear evidence that 26al was alive when they cooled but the initial 26al 27al ratios are not well constrained sena does not show evidence that 26al was alive when it cooled to below the al mg closure temperature given that metallographic cooling rates for ste marguerite forest vale and beaver creek are atypical 5000 c myr at 500 c compared with most h4s including sena which have cooling rates of 10 50 c myr at 500 c scott et al 2014 we conclude that the al mg systematics for ste marguerite forest vale and beaver creek are the result of impact excavation of these chondrites and cooling at the surface of the parent body instead of undisturbed cooling at depth in the h chondrite parent body like many have assumed

thermal history of mesosiderites quantitative constraints from compositional zoning and fe mg ordering in orthopyroxenes abstract we have derived mathematical relations to calculate cooling rates from the extent of compositional zoning developed during cooling across the interface of a natural diffusion couple these relations were used to calculate the high temperature cooling rates of the mesosiderites lowicz and clover springs from the available data on compositional zoning across core overgrowth interface of orthopyroxene grains we have also determined the cation ordering in four selected orthopyroxene crystals from bondoc and estherville mesosiderites with very high precision and used these data to calculate their low temperature cooling rates the compositional zoning of orthopyroxene crystals reflects extremely rapid cooling rates at least 1 c 100 years in the temperature range 850 1150 c however simultaneous consideration of both metallographic and cation ordering data for estherville within the framework of either an asymptotic or an exponential cooling model requires a cooling rate of l c ma near 250 c the cation ordering data for bondoc for which no metallographic data are yet available are suggestive of even slower cooling rate which implies excavation from a somewhat greater depth in the parent body however within the limits of their uncertainties the measured site occupancies of the orthopyroxene crystals from bondoc can be reconciled with a cooling rate similar to that of estherville the calculated cooling rates at both high and low temperatures have been used to develop a thermal evolution model of mesosiderites the suggested model is not incompatible with an asteroidal parent body for these meteorites further it is shown that the closure temperature of ar ar age must be tied to the slow cooling rate below 500 c

shear wave velocity as an indicator for rheological changes in clay materials lessons from laboratory experiments 1 clay rich geological formations are responsible for many landslides the dynamics of which are still poorly understood and intensely debated analysis of landslide motion shows that slow clayey slope movements can suddenly accelerate and fluidize as a result of sudden loading or heavy rainfall this solid fluid transition which involves disorganization of the particle network is accompanied by a loss in rigidity that could potentially be monitored by s wave velocity vs variations to investigate this hypothesis two types of laboratory experiments were performed on clay samples originating from an area affected by numerous landslides trieves french alps first creep and oscillatory rheometric tests revealed the thixotropic behavior of the clay with a highly pronounced viscosity bifurcation at a critical stress c in relation with this reduction in apparent viscosity a significant drop in vs is also observed over c second at zero stress acoustic surface wave propagation experiments showed a rapid linear vs decrease with the gravimetric water content w in the plastic domain and a much lower decay in the liquid domain the geotechnically defined liquid limit then appears as a break in thevs wcurve for water contents in the liquid domain in particular both experiments gave consistent results these laboratory results demonstrate that rheological changes in clay can be revealed through vs variations offering the possibility of monitoring solid to fluid transitions in the field

metallic minerals thermal histories and parent bodies of some xenolithic ordinary chondrite meteorites we have studied metal grains in the hosts and lithic fragments of widely differing petrologic types in four xenolithic chondrftes using reflected light microscopy and electron probe analysis in weston and fayetteville which both contain solar flare tracks and solar wind gases kamacite taenite and tetrataenite ordered feni and troilite show a variety of textures on a wood plot of central ni content vs dimension taenite analyses scatter as if metal grains cooled at rates of 10 1000 and 1 100 k myr respectively through 700 k although metal in an h6 clast in fayetteville plots coherently with a cooling rate of 50 k myr we propose that metal grains cooled at these rates in chondritic clasts at different locations before host and clasts were compacted and were not subsequently heated above 650 k we predict a similar history for all gas rich ordinary chondrites by contrast metallic minerals throughout bhola and mezo madaras show more uniform textures and plot coherently giving cooling rates in the range 750 to 600 k of 0 1 and 1 k myr respectively we conclude that host and xenoliths in both chondrites were slowly cooled after compaction thus clasts in these chondrites experienced peak metamorphic temperatures and slow cooling through 700 k in different environments according to the conventional onion shell model for h l or ll chondrite parent bodies material of petrologic types 3 5 was arranged in successive shells around a type 6 core prior to catastrophic collisions which mixed all types intimately but if peak metamorphic temperatures were reached during not after accretion as seems plausible maximum metamorphism may have occurred in planetesimals 10 km in radius cooling through 700 k may then have occurred in larger bodies that accreted from these planetesimals iron meteorites mesosiderites and some achondrites may also have experienced melting in planetesimals and slow cooling in larger bodies

the greenland ice core chronology 2005 15 42 ka part 2 comparison to other records a new greenland ice core chronology gicc05 based on multi parameter counting of annual layers has been obtained for the last 42 ka here we compare the glacial part of the new time scale which is based entirely on records from the northgrip ice core to existing time scales and reference horizons covering the same period these include the grip and northgrip modelled time scales the meese sowers gisp2 counted time scale the shackleton fairbanks grip time scale sfcp04 based on 14c calibration of a marine core the hulu cave record three volcanic reference horizons and the laschamp geomagnetic excursion event occurring around greenland interstadial 10 gicc05 is generally in good long term agreement with the existing greenland ice core chronologies and with the hulu cave record but on shorter time scales there are significant discrepancies around the last glacial maximum there is a more than 1 ka age difference between gicc05 and sfcp04 and a more than 0 5 ka discrepancy in the same direction between gicc05 and the age of a recently identified tephra layer in the northgrip ice core both sfcp04 and the tephra age are based on 14c dated marine cores and fixed marine reservoir ages for the laschamp event gicc05 agrees with a recent independent dating within the uncertainties

chrono stratigraphy of the upper pleistocene and holocene archaeological sequence in cova gran south eastern pre pyrenees iberian peninsula the cova gran de santa linya lleida spain is a recently discovered site with a broad chrono cultural sequence that contains archaeological levels dating to the middle palaeolithic early upper palaeolithic late upper palaeolithic neolithic and early bronze age we present the chronometric and stratigraphic context of these occupations which were dated using 14c accelerator mass spectrometry and thermoluminescence the sequence provides important indicators that aid in the reconstruction of the history of human occupation on the southern slopes of the spanish pyrenees over the past 50 000 years copyright 2011 john wiley sons ltd

the magdalenian in catalonia northeast iberia the magdalenian is the first upper palaeolithic period to show a widespread human occupation throughout the northeastern territories of iberia several sites have been located in both the plains and mountains extending from the pyrenean valleys of the segre river to the mouth of the ebro river the oldest dates in the xixth millennium cal bp were obtained at the open air site of montlleo in the pyrenean valley of cerdanya most of the magdalenian sites have yielded information about short or seasonal occupations related with the exploitation of natural resources parco cave preserves a good stratigraphic sequence ranging from middle to upper and late upper magdalenian from xviith to xivth millennium cal bp in this site various human activities were organized around a significant number of hearths they were related with animal and mineral processing the data obtained at parco and montlleo sites have enabled the reconstruction of the late upper pleistocene palaeoenvironment for the southeastern pyrenees area however other sites from the southern part of the country are also providing very interesting information about climate as well as faunal and floral elements with more recent radiocarbon dates xvth to xivth millennium cal bp some malacological remains found in montlleo come from the mediterranean coast but others come from the cantabrian area thus indicating a route of connection between the two seas during the magdalenian there is also limited artistic evidence in taverna cave moli del salt l hort de la boquera sant gregori and parellada iv sites one of the most significant findings of the research is the archaeological confirmation of the existence of human movements across the pyrenees during the magdalenian some raw materials found in montlleo are of french origin others come from the southern slopes of the pyrenees and still others could come from either side the site is near the westernmost route opened during the last glaciation for crossing the pyrenees thus people and materials may well have circulated across the pyrenees through this corridor

site effect evaluation using spectral ratios with only one station the spectral ratio technique is a common useful way to estimate empirical transfer function to evaluate site effects in regions of moderate to high seismicity the purpose of this paper is to show that it is possible to estimate empirical transfer function using spectral ratios between horizontal and vertical components of motion without a reference station the technique originally proposed by nakamura to analyze rayleigh waves in the microtremor records is presented briefly and it is discussed why it may be applicable to study the intense s wave part in earthquake records results are presented for three different cities in mexico oaxaca oax acapulco gro and mexico city these cities are very different by their geological and tectonic contexts and also by the very different epicentral distances to the main seismogenic zones affecting each city each time we compare the results of nakamura s technique with standard spectral ratios in all three cases the results are very encouraging we conclude that if site effects are caused by simple geology a first estimate of dominant period and local amplification level can be obtained using records of only one station

minor and trace element concentrations in adjacent kamacite and taenite in the krymka chondrite we report in situ nanosims siderophile minor and trace element abundances in individual fe ni metal grains in the unequilibrated chondrite krymka ll3 2 associated kamacite and taenite of 10 metal grains in four chondrules and one matrix metal were analyzed for elemental concentrations of fe ni co cu rh ir and pt the results show large elemental variations among the metal grains however complementary and correlative variations exist between adjacent kamacite taenite this is consistent with the unequilibrated character of the chondrite and corroborates an attainment of chemical equilibrium between the metal phases the calculated equilibrium temperature is 446 9 c this is concordant with the range given by kimura et al 2008 for the krymka post accretion thermal metamorphism based on ni diffusivity in taenite a slow cooling rate is estimated of the krymka parent body that does not exceed 1k myr which is consistent with cooling rates inferred by other workers for unequilibrated ordinary chondrites elemental ionic radii might have played a role in controlling elemental partitioning between kamacite and taenite the bulk compositions of the krymka metal grains have non solar mostly subsolar element ni ratios suggesting the fe ni grains could have formed from distinct precursors of non solar compositions or had their compositions modified subsequent to chondrule formation events

original structures and fragmentation and reassembly histories of asteroids evidence from meteorites abstract if chondritic meteorites were internally heated after accretion had ended then the hottest material would have been buried the deepest and should have cooled the slowest if this is correct there ought to be a correlation between cooling rate and petrographic type a measure of the extent to which chondrites were metamorphosed i e heated published and new cooling rates derived from the compositions of metallic iron nickel grains do not display this correlation implying either that chondrite parent asteroids never had onion shell structures or that bodies with onion shell structures were broken up and reassembled prior to cooling to below 500 c the temperature at which cooling rate information is recorded in metallic iron nickel chondritic regolith breccias formed from materials that resided on the surfaces of their parent asteroids metallic iron nickel grains in h and l chondrite regolith breccias indicate that the breccia constituents cooled at rates ranging from 1 to 1000 k myr based on thermal calculations these cooling rates suggest that the materials spread out on the surfaces of h and l chondrite parent asteroids originated at depths ranging from about one kilometer to several tens of kilometers craters deep enough to excavate tens of kilometers cannot form on typical asteroidal bodies only 100 to 300 km in diameter without disrupting them therefore it appears that at least some asteroids namely the parent bodies of h and l chondrites were disrupted after cooling to below 300 c and then reassembled to create surfaces containing rocks that originated at a wide range of depths these results support theoretical calculations suggesting that many asteroids were broken up and subsequently reassembled into gravitationally bound rubble piles

an estimate of eros s porosity and implications for internal structure abstract earth based spectral measurements and near shoemaker magnetometer x ray and near infrared spectrometer data are all consistent with eros having a bulk composition and mineralogy similar to ordinary chondrite meteorites oc by comparing the bulk density of 433 eros 2 67 0 03 g cm 3 with that of ocs 3 40 g cm 3 we estimate the total porosity of the asteroid to be 21 33 macro or structural porosity best estimated to be 20 is constrained to be between 6 and 33 we conclude that eros is a heavily fractured body but we find no evidence that it was ever catastrophically disrupted and reaccumulated into a rubble pile

site effects in the city of lourdes france from h v measurements implications for seismic risk evaluation abstract the pilgrimage city of lourdes in the french pyrenees has been heavily damaged by earthquakes in the seventeenth and eighteenth centuries assessments of local seismic hazard have been performed through a seismic microzonation of the city a campaign of urban noise recording has been conducted at about 180 points to determine seismic wave amplification by means of spectral ratios of the horizontal to vertical h v components a comparison of this ratio obtained from ambient noise measurements with spectral ratios obtained from earthquake s wave recording h href reveals that the fundamental resonance frequency is well estimated but that the site amplification is generally underestimated resonance frequencies and amplitudes exhibit coherent patterns that relate to the geological structure bedrock sites are generally characterized by flat spectra whatever the geological nature of bedrock unless topography or karst are present along the river in particular at the pilgrimage site thick sediments induce low resonance frequencies with large amplifications along and across valleys north and east of the city h v spectra show systematic variations according to sediment filling properties finally on the hill flanks east of the city h v spectra rather relate to topography an additional issue with h v spectral ratios based on ambient noise is whether this indicator reflects meaningful geological variations this question is tested on sites where the s wave ground velocity structure is known a first test consists of estimating h v spectral ratios by means of simulation of urban noise through the summation of synthetic seismograms with random properties a second test consists of estimating h href spectral ratios by propagating an earthquake record through a 1d soil profile these two modelings successfully predict most of the observed spectrum characteristics in addition they give some information on the nature of the urban noise which may include a significant amount of shear energy

formation processes and stratigraphic integrity of the middle to upper palaeolithic sequence at cova gran de santa linya southeastern prepyrenees of lleida iberian peninsula sediments from cova gran de santa linya southeastern prepyrenees of lleida iberia are investigated by geoarchaeological means micromorphological textural quartz grain morphoscopy and geochemical analyses are coupled with stratigraphic and sedimentary macroscopic data to provide new insights into the formation processes and the integrity of the occupation layers and embedded sterile deposit documented at the middle to upper palaeolithic boundary direct indicators of the anthropogenic and natural dynamics involved in the deposition and alteration of the sediments investigated are provided results reveal the presence of in situ combustion structures as a major sedimentary indicator of human activity and occupation surfaces at the site the overall good preservation of the combustion residues indicates that occupation layers have been preserved in their original context of deposition traits of surface exposure in parallel to progressive lessening of evidence related to human activity at the top of the middle palaeolithic sequence suggest discontinuity in the occupation of the site and a possible abandonment of the rock shelter at the end of this period formation processes of the sterile deposit documented between the mousterian and the early upper palaeolithic levels involved the accumulation of debris from local sediments and soils as well as from the structure of the rock shelter soil forming dynamics related to palaeoenvironmental moisture fluctuations have also been recorded throughout the sequence investigated and indicate periods of surface stability during the formation of the sterile deposit environmental dynamics active during the formation of the sterile partially disturbed the top of the mousterian layer however our data indicate that such dynamics did not substantially affect the overall integrity of the archaeological record our results highlight the crucial contribution of geoarchaeology and microstratigraphy to the characterisation and assessment of the anthropogenic and natural dynamics involved in the accumulation and taphonomy of middle to upper palaeolithic sequences

problems with radiocarbon dating the middle to upper palaeolithic transition in italy abstract radiocarbon dating of material from late pleistocene archaeological sites is challenging small amounts of modern 14c labelled contamination will significantly affect the reliability of dates from the period producing erroneous results recent developments in sample pre treatment chemistry have shown that problems in reliable age determination during this period are surmountable in this paper we provide an example of one such case from the middle to upper palaeolithic transitional site of the grotta di fumane in northern italy we ams dated two fractions of the same charcoal samples derived from a series of superimposed mousterian aurignacian and gravettian levels excavated at the site one fraction was treated using the routine acid base acid aba method the other with the more rigorous acid base oxidation stepped combustion abox sc method the latter method produced consistently older and almost certainly more reliable results the eruption of the known age campanian ignimbrite from the phlegrean fields near present day naples at 39 3 ka yr bp seals ulluzzian and proto aurignacian levels in the south of italy equivalent cultural levels are present at fumane and the results obtained with the abox sc methods are consistent with the ages inferred for sites in the south of italy based on the presence of the campanian ignimbrite new results from a sample found beneath the campanian ignimbrite at the russian site of kostenki obtained using both the aba and abox sc methods are also presented they support the conclusion reached at fumane by demonstrating that in many cases the abox sc treatment effectively removes contamination where the aba treatment does not the results of the work offer a sobering examination of the problems inherent in the current radiocarbon database relating to the period and highlight the dangers of an uncritical use of the corpus of 14c results obtained over the last few decades based on our results we predict that more than 70 of the 53 previously available determinations from fumane are erroneously young a way forward is suggested using these improved chemical preparation methods applying analytical methods to characterise the material dated and testing existing site chronologies to establish which previous determinations are liable to be inaccurate

sedimentological and archaeological fabrics in palaeolithic levels of the south eastern pyrenees cova gran and roca dels bous sites lleida spain abstract the comparative study of sedimentary fabrics in relation to archaeological fabrics in various levels of the sites of cova gran de santa linya middle and early upper palaeolithic and the roca dels bous middle palaeolithic has made it possible to analyse the formation dynamics of the deposits and determine the extent of disturbance of the archaeological levels by natural processes to achieve this diagrams and two and three dimensional indices were calculated from the azimuth and dip angle of natural clasts and artefacts the results indicate that the sedimentary levels were formed mainly by planar fabric shape gravitational processes low depositional angles which differ notably from the archaeological fabrics they contain characterised by a greater degree of isotropy this difference in the fabrics would reflect human activity and indicates that the archaeological levels both in cova gran and roca dels bous have not been subject to significant natural modifications and are preserved in situ

s wave velocity profiling by joint inversion of microtremor dispersion curve and horizontal to vertical h v spectrum a joint inverse analysis using both microtremor dispersion curve and horizontal to vertical h v spectrum is proposed for estimating the s wave velocity vs profiles of subsurface soils in the inversion both microtremor dispersion and h v data are assumed to be the rayleigh wave dispersion curve and the surface both rayleigh and love wave h v spectrum that have been theoretically derived by taking into account the effects of their fundamental and higher modes the proposed joint inversion as well as the conventional one using dispersion data alone is per formed at four sites where shallow vs profiles down to engineering bedrock are available the vs profiles estimated by the proposed joint inversion are more con sistent with available down hole velocity logs than those by the conventional method in particular the proposed inversion shows significant improvement in estimating bedrock vs structures compared to the conventional inversion sensitivity analyses indicate that the surface wave h v ratio is sensitive to the bedrock vs structure more than the rayleigh wave phase velocity confirming that the proposed joint inversion including h v spectrum is promising

the greenland ice core chronology 2005 15 42 ka part 1 constructing the time scale the greenland ice core chronology 2005 gicc05 is extended back to 42 ka b2k before 2000 ad i e to the end of greenland stadial 11 the chronology is based on independent multi parameter counting of annual layers using comprehensive high resolution measurements available from the north greenland ice core project ngrip these are measurements of visual stratigraphy conductivity of the solid ice electrolytical melt water conductivity and the concentration of na c a 2 s o 4 n o 3 n h 4 a n uncertainty estimate of the time scale is obtained from identification of uncertain annual layers which are counted as 0 570 5 years the sum of the uncertain annual layers the so called maximum counting error of the presented chronology ranges from 4 in the warm interstadial periods to 7 in the cold stadials the annual accumulation rates of the stadials and interstadials are on average one third and half of the present day values respectively and the onset of the greenland interstadials 2 3 and 8 based on 20 year averaged d 18 o

are microtremors useful in site response evaluation we have reviewed the applicability of microtremor measurements to evaluate site response of soft soils to this end we evaluated three different techniques commonly used to estimate site effects from microtremor measurements interpretation of fourier amplitude spectra computation of spectral ratios relative to a firm reference station and finally computation of spectral ratios of horizontal components relative to the vertical component of ground motion nakamura s technique these techniques are applied to microtremor records obtained in three cities in mexico mexico city oaxaca and acapulco these cities differ in their local geological conditions and in their seismotectonic environment in order to evaluate the results obtained from microtremor measurements we compare them with standard spectral ratios of the intense s wave part of weak or strong motion records obtained at the same sites our results showed that microtremor measurements can be used to estimate the dominant period of a site with very acceptable reliability in the range 0 3 to 5 hz the best results were obtained with nakamura s technique which also gives a rough estimate of amplification of seismic waves when the local geology is relatively simple simple numerical simulations indicate that the underlying assumptions of nakamura s technique are consistent with the propagation of rayleigh waves these simple numerical simulations also explain why different researchers have been able to successfully characterize 1d site effects using microtremor records regardless of whether they consider microtremors to consist of surface or body waves our results strongly suggest that the technique by nakamura effectively compensates for source effects in microtremor measurements which eliminates a major limitation to their application in earthquake engineering

metal phases of l chondrites their formation and evolution in the nebula and in the parent body abstract metal phases of six three equilibrated and three unequilibrated l chondrites were studied by inaa sem and mossbauer spectroscopy characteristics retained in the bulk metals of unequilibrated chondrites abundant carbon high contents of cr v mn and low contents of w mo and ga compared to metals of equilibrated chondrites less enrichment of w than mo and fractionation of co from ni demonstrate that chondrite metals are not nebular condensates all those characteristics can be well explained by melting chondrite metals are not melting remnants of previously condensed metals rather they were produced by reduction of ci or cm like material during the melting process the complementarity in composition and the similarity in melting feature suggest that chondritic metals and chondrules are the complementary components of the same melting event distribution of trace siderophile elements between taenite and bulk metal indicates that kamacite and taenite can only be the low temperature diffusion products and must have been developed in the chondrite parent body the difference in the taenite composition between equilibrated and unequilibrated chondrites reveals that the equilibrated chondrites were located near the surface while the unequilibrated chondrites were in the interior if they were derived from the common parent body thus while the exsolution of chondrite metal into kamacite and taenite was due to the internal thermal activity the crystallization of eoc silicates resulted from an external heating the internal metamorphism was mild 400 600 c and long whereas the external heating was intense with a maximum temperature in range of 800 950 c and short tetrataenite is present not only in uocs but also in eocs suggesting that the external heating occurred during the internal metamorphism i e within 100 myr of chondrite formation

quartzite selection in fluvial deposits the n12 level of roca dels bous middle palaeolithic southeastern pyrenees abstract the exploitation of rocks from secondary deposits is attested widely in the european middle palaeolithic however few studies have focused on analysing the implications derived from the management of these deposits the fluvial terraces near the mousterian site of roca dels bous have been sampled to determine their lithological composition and cobble morphology comparison with artefacts recovered from level n12 indicate selection patterns in the fluvial deposits of black quartzite as well as preferential management of blanks with specific morphological and volumetric characteristics this approach reveals behaviours involved in the acquisition transport transformation and discard of stone tools necessary for neanderthal subsistence and indicates interest in the study of secondary deposits and local raw materials in middle palaeolithic contexts