inversion of seismic surface wave data to resolve complex profiles for a complex layered site development of a shear wave velocity profile from inversion of seismic surface wave data can yield nonunique results one class of solutions provides depth averaged profiles that are useful but do not detail the local velocity anomalies simulated annealing inversion can be used to establish whether nonuniqueness is a concern for a particular case and if so focus results to allow a solution that is expected based on independent knowledge of site conditions a two step process is recommended whereby the model parameters are first optimized using simulated annealing and then fine tuned by unconstrained linearized inversion the process also yields useful confidence measures one example of a complex layered site where the proposed procedure is helpful is a desert profile with high velocity cemented layers interspersed among uncemented sediments

new relationships between vs thickness of sediments and resonance frequency calculated by the h v ratio of seismic noise for the cologne area germany noise measurements were carried out in the cologne area germany and the resonance frequency of each site was estimated from the main peak in the spectral ratio between the horizontal and vertical component for 32 of these sites the thickness of the sedimentary cover was known from boreholes and a clear correlation between resonance frequency and sediment thickness was observed a formula that correlates cover thickness with frequency of the main peak in the horizontal to vertical spectral ratio was derived in addition a best fitting shear wave velocity distribution with depth vs z as well as a relationship between average shear wave velocity vs and thickness of the sedimentary cover was calculated by using all of the noise measurements and applying the derived relationships we obtained a subsoil classification for the cologne area

thermal history of type 3 chondrites from the antarctic meteorite collection determined by raman spectroscopy of their polyaromatic carbonaceous matter abstract this paper is focused on the characterization of the thermal history of 151 cv co and unequilibrated ordinary chondrites uocs from the nasa antarctic meteorite collection using an approach based on the structure of the included polyaromatic carbonaceous matter determined by raman spectroscopy 114 out of these 151 chondrites provided raman spectra of carbonaceous matter and allowing to assign a petrologic type which mostly reflects the peak temperature experienced by the rock on the parent body a thorough review of literature shows however that it is not possible to deduce a peak temperature because accurate calibration is not available twenty three new weakly metamorphosed chondrites have been identified mil 07671 cv3 1 dom 08006 co3 0 dom 03238 mil 05024 mil 05104 mil 07193 co3 1 til 82408 lar 06279 ll3 05 3 1 eet 90628 l3 0 gro 06054 que 97008 l3 05 alha 77176 eet 90066 lar 04380 met 96515 mil 05050 l3 1 alha 78133 eet 87735 eet 90909 lew 87208 pre 95401 l3 05 3 1 mcy 05218 h3 05 3 1 and met 00506 h3 1 this study confirms that the width of the d band fwhmd and the ratio of the peak intensity of the d and g bands id ig are the most adapted tracers of the extent of thermal metamorphism in type 3 chondrites it also unambiguously shows thanks to the large number of samples that the width of the g band fwhmg does not correlate with the maturity of polyaromatic carbonaceous matter this parameter is nevertheless very valuable because it shows that raman spectra of cv chondrites preserve memory of either the metamorphic conditions possibly oxidation controlled by aqueous alteration or the nature of the organic precursor oxidation memory is our preferred interpretation however an extensive petrologic characterization of this cv series is required to get firm conclusions pre graphitic carbonaceous matter is reported in seven chondrites and is even the only carbonaceous material detected in the chondrites alha 78119 and dav 92302 this pre graphitic carbonaceous matter cannot be formed through radiogenic thermal metamorphism without metal catalysis shock metamorphism is another possible process for accounting its formation but it appears less plausible

inverse modelling of elastic thickness by convolution method the eastern alps as a case example an unconventional scheme is used to estimate the flexural rigidity or equivalently the elastic thickness of the lithosphere given the topography and gravity data the flexural rigidity is the parameter that governs the flexural response of the lithosphere in the frame of the thin plate flexure model the scheme is an alternative to the widely used calculation of admittance of topography sea floor or continental topography and gravity bearing some advantages which are explained in the paper the scheme involves the inversion of the gravity data in order to formulate a model of the crust mantle interface cmi undulations in a second step the flexure parameter is then evaluated from the relation between topography and cmi variations instead of calculating the admittance function using a spectral analysis a set of point load response functions are used in order to retrieve the optimal flexure parameter this has two main advantages instabilities of the numerical admittance evaluation at wavenumbers with low spectral energy in the topography are overcome and the analysis can be made over an area which is not necessarily rectangular as required for the spectral analysis the proposed method allows a higher space resolution of elastic thickness than any spectral method for validation the numerical strategy is applied to the situation of a realistic synthetic model where all inputs and outputs are known a priori finally the spatial variations of the elastic thickness are studied in an area across the eastern alps 4 2002 elsevier science b v all rights reserved

a reappraisal of the metamorphic history of eh3 and el3 enstatite chondrites abstract the thermal history of a series of eh3 and el3 chondrites has been investigated by studying the degree of structural order of the organic matter om located and characterized in matrix areas by raman micro spectroscopy by comparison with unequilibrated ordinary chondrites uocs and co and cv carbonaceous chondrites the following petrologic types have been assigned to various e chondrites sahara 97096 and allan hills 84206 3 1 3 4 allan hills 85170 and parsa 3 5 allan hills 85119 3 7 qingzhen macalpine hills 88136 and macalpine hills 88184 3 6 3 7 the petrologic type of qingzhen is consistent with the abundance of the p3 noble gas component a sensitive tracer of the grade of thermal metamorphism the petrologic types are qualitatively consistent with the abundance of fine grained matrix for the whole series no significant effects of shock processes on the structure of om were observed however such processes certainly compete with thermal metamorphism and the possibility of an effect cannot be fully discarded in particular in the less metamorphosed objects the om precursors accreted by the eh3 and el3 parent bodies appear to be fairly similar to those of uocs and co and cv carbonaceous chondrites raman data however show some slight structural differences that could be partly accounted for by shock processes the metamorphic history of eh3 and el3 chondrites has often been described as complex in particular regarding the combined action of shock and thermal metamorphism because om maturity is mostly controlled by the temperature of peak metamorphism it is possible to distinguish between the contributions of long duration thermal processes and that of shock processes comparison of the petrologic types with the closure temperatures previously derived from opaque mineral assemblages has revealed that the thermal history of eh3 and el3 chondrites is consistent with a simple asteroidal onion shell model thermal metamorphism in enstatite chondrites appears to be fairly similar to that which takes place in other chondrite classes the complex features recorded by mineralogy and petrology and widely reported in the literature appear to be mostly controlled by shock processes

microtremors as a geophysical exploration tool applications and limitations the usefulness of microtremors as a geophysical exploration tool has been analyzed this application is possible due to the relationship between the main resonance frequency of a given soil obtained from the h v spectral ratios of microtremors its thickness and average shear velocity we first measured the ambient noise at 33 sites and determined their main resonance frequency detailed geotechnical information was available for 23 of the sites thereby allowing us to establish a quantitative relationship between the resonance frequency and the thickness of the soil and indirectly between either of them and the shear velocity of the soil the practical application of this relationship has revealed its usefulness in determining the surface structure of a valley with excellent accuracy with an error of only 15 in the depths calculated these errors are due to the simplification of the problem that this method implies it requires that the shear velocity vary constantly with depth throughout the study region which is evidently not always so and that the input data themselves intrinsically have a certain degree of uncertainty this method is therefore not valid when there is no mechanical contrast between the study soil and the underlying layer or when the shear velocity varies irregularly with depth in the study area

evolution of the raman spectrum of carbonaceous material in low grade metasediments of the glarus alps switzerland terra nova 22 354 360 2010 abstract the raman spectrum of carbonaceous material cm from advanced diagenesis 200 c to low grade metamorphism 320 c is documented in the helvetic flysch of the glarus alps switzerland the spectrum is complex with several defect bands at 1200 d4 1350 d1 1500 d3 and 1620 d2 cm 1 we document the evolution of these bands relative to the graphite g band with increasing metamorphic grade and we show that this qualitative evolution may be used as a proxy for temperature in the glarus alps we develop a robust peak fitting method and propose quantitative parameters that may be used as proxies for thermal metamorphism in this region further work in other geological contexts is needed to assess whether the spectral evolution observed in the glarus alps may be generalized and to critically assess the potential for calibrating a general empirical and quantitative thermometer based on the raman spectrum of cm in low grade rocks

the classification and complex thermal history of the enstatite chondrites we have carried out instrumental neutron activation analyses of 11 enstatite chondrites and electron microprobe analyses of 17 enstatite chondrites most of which were previously little described we report here the third known eh5 chondrite lew 88180 and an unusual el6 chondrite lew 87119 new data on four el3 chondrites alh 85119 eet 90299 pca 91020 and mac 88136 which is paired with mac 88180 and mac 88184 the second el5 chondrite til 91714 and an unusual metal rich and sulfide poor el3 chondrite lew 87223 the often discussed differences in mineral composition displayed by the eh and el chondrites are not as marked after the inclusion of the new samples in the database and the two classes apparently experienced a similar range of equilibration temperatures however texturally the el chondrites appear to have experienced much higher levels of metamorphic alteration than eh chondrites of similar equilibration temperatures most of the petrologic type criteria are not applicable to enstatite chondrites and unlike the ordinary chondrites texture and mineralogy reflect different aspects of the meteorite history we therefore propose that the existing petrologic type scheme not be used for enstatite chondrites we suggest that while textural type reflects peak metamorphic temperatures the mineralogical type reflects equilibration during postmetamorphic probably regolith processes unlike the ordinary chondrites and eh chondrites el chondrites experienced an extensive low temperature metamorphic episode there are now a large number of enstatite meteorite breccias and impact melts and apparently surface processes were important in determining the present nature of the enstatite chondrites

organic matter and metamorphic history of co chondrites abstract the metamorphic grades of a series of eight co3 chondrites alha77307 colony kainsaz felix lance ornans warrenton and isna have been quantified the method used was based on the structural grade of the organic matter trapped in the matrix which is irreversibly transformed by thermal metamorphism the maturation of the organic matter is independent with respect to the mineralogical context and aqueous alteration this metamorphic tracer is thus valid whatever the chemical class of chondrites moreover it is sensitive to the peak metamorphic temperature the structural grade of the organic matter was used along with other metamorphic tracers such as petrography of opaque minerals fa and fs silicate composition in type i chondrules presolar grains and noble gas p3 component abundance the deduced metamorphic hierarchy and the attributed petrographic types are the following alha77307 3 03 for most metamorphosed objects the peak metamorphic temperature can be estimated using a geothermometer calibrated with terrestrial metasediments beyssac o goffe b chopin c and rouzaud j n 2002 raman spectrum of carbonaceous material in metasediments a new geothermometer j metamorph geol 20 859 871 a value of 330 c was obtained for allende cv chondrite warrenton and isna consistent with temperatures estimated from fe diffusion weinbruch s armstrong j and palme h 1994 constraints on the thermal history of the allende parent body as derive from olivine spinel thermometry and fe mg interdiffusion in olivine geochim cosmochim acta 58 2 1019 1030 from the ni content in sulfide metal assemblages zanda b bourot denise m and hewins r 1995 condensate sulfide and its metamorphic transformations in primitive chondrites meteorit planet sci 30 a605 and from the d002 interlayer spacing in poorly graphitized carbon rietmeijer f and mackinnon i 1985 poorly graphitized carbon as a new cosmothermometer for primitive extraterrestrial materials nature 315 733 736 the trapped noble gas and c content appear to be sensitive but not precise metamorphic tracers indicating that the ornans paradox does not exist major problems with the current petrologic types derived from induced thermoluminescence are pointed out

raman spectra of carbonaceous material in metasediments a new geothermometer metasedimentary rocks generally contain carbonaceous material cm deriving from the evolution of organic matter originally present in the host sedimentary rock during metamorphic processes this organic matter is progressively transformed into graphite s s and the degree of organisation of cm is known as a reliable indicator of metamorphic grade in this study the degree of organisation of cm was systematically characterised by raman microspectroscopy across several mesozoic and cenozoic reference metamorphic belts this degree of organisation including within sample heterogeneity was quantified by the relative area of the defect band r2 ratio the results from the schistes lustres western alps and sanbagawa japan cross sections show that 1 even through simple visual inspection changes in the cm raman spectrum appear sensitive to variations of metamorphic grade 2 there is an excellent agreement between the r2 values calculated for the two sections when considering samples with an equivalent metamorphic grade and 3 the evolution of the r2 ratio with metamorphic grade is controlled by temperature t along the tinos cross section greece which is characterised by a strong gradient of greenschist facies overprint on eclogite facies rocks the r2 ratio is nearly constant consequently the degree of organisation of cm is not affected by the retrogression and records peak metamorphic conditions more generally analysis of 54 samples representative of high temperature low pressure to high pressure low temperature metamorphic gradients shows that there is a linear correlation between the r2 ratio and the peak temperature t c 445 r2 641 whatever the metamorphic gradient and probably the organic precursor the raman spectrum of cm can therefore be used as a geothermometer of the maximum temperature conditions reached during regional metamorphism temperature can be estimated to 50 c in the range 330 650 c a few technical indications are given for optimal application

an exact solution for the gravity curvature bullard b correction the complete bouguer reduction includes in addition to the simple bouguer slab correction bullard a both curvature bullard b and terrain bullard c corrections a new closed form formula for the curvature correction is derived for which the calculated values differ from those published by swick by more than 0 5 mgal for high elevations these corrections reduce those of an infinite slab bullard a to that of a spherical cap having a surface radius of 166 7 km the spherical cap produces a lesser effect than the infinite slab because of the truncation of that part of the slab above the earth and extending to infinity but it produces a greater effect than the slab because of subslab earth resulting from curvature the physical significance of the correction lies in the combination of these two differences which are each a function of elevation the bullard b surface radius 166 7 km outer radius of the hayford bowie system is reaffirmed by the exact formula to be appropriate for exploration su

reproduction of microseism h v spectral features using a three dimensional complex topographical model of the sediment bedrock interface in the osaka sedimentary basin summary estimating the velocity structure of microseisms based on the horizontal to vertical spectral ratio hvsr is an extremely practical means of modelling the subsurface structure necessary for strong ground motion predictions thus beyond the traditional framework of the 1 d velocity structure the hvsr derived from observation records of microseisms microtremors with a frequency of about 1 hz or lower originating from ocean waves in areas where the sediment bedrock interface has irregular topographies was reproduced by finite differential method fdm based simulation this study was conducted for the osaka sedimentary basin the sediment bedrock interface of which is three dimensionally complicated and contains grabens steps and ramps because high precision models for this basin have been constructed based on a wide range of existing exploration information the hvsrs of two components the east west direction and the north south direction to the vertical direction derived from the fdm simulations were both well reproduced in terms of not only the peak frequency hvfp but also the spectral curves for a number of observation sites above the sediment bedrock interface with complex geological features these results suggest that with a sufficient number of observation sites for microtremors and highly accurate a priori information on geophysical constants in the sedimentary layer that spatially serves as the reference the irregular shaped sediment bedrock interface may be estimated based on how well the hvsr curves and the hvfp agree between the observations and simulations furthermore the fdm simulations confirmed observed phenomena such as the polarization of the amplitude of horizontal motions and broad or plateau like hvsr peaks of microseisms in grabens and step structures it was determined that the hvfps in areas with these strong irregularities are higher than the peak frequency of rayleigh wave ellipticity for the fundamental mode rhvfp based on the 1 d velocity structure in addition there was a difference of about 20 per cent at most between the hvfp derived from fdm simulations and the rhvfp in areas where the depth of the sediment bedrock interface varies only slightly

local site effects on weak and strong ground motion abstract this is a review of the current state of the art in characterizing effects of local geology on ground motion a new horizon is clear in this aspect of strong motion studies non linear amplification at sediment sites appears to be more pervasive than seismologists used to think several recent observations about the weak motion and the strong motion suggest that the non linear amplification at sediment sites may be very common first on average the amplification is always greater at the younger sediment sites for all frequencies up to 12 hz in the case of weak motion while the relation is reversed for frequencies higher than 5 hz in the case of strong motion secondly the application of the amplification factor determined from weak motion overestimates significantly the strong motion at sediment sites observed during the loma prieta earthquake within the epicentral distance of about 50 km thirdly the variance of peak ground acceleration around the mean curve decreases with the increasing earthquake magnitude finally the above non linear effects are expected from geotechnical studies both in the magnitude of departure from the linear prediction and in the threshold acceleration level beyond which the non linearity begins

the lithospheric density structure of the eastern alps the three dimensional 3d lithospheric density structure of the eastern alps was investigated by integrating results from reflection seismics receiver function analyses and tomography the modelling was carried out with respect to the bouguer gravity and the geoid undulations and emphasis were laid on the investigations of the importance of deep lithospheric features although the influence of inhomogeneities at the lithosphere asthenosphere boundary on the potential field is not neglectable they are overprinted by the response of the density contrast at the crust mantle boundary and intra crustal density anomalies the uncertainties in the interpretations are in the same order of magnitude as the gravity field generated by the deep lithosphere after including the deep lithospheric geometry from the tomographic model it is shown that full isostatic equilibrium is not achieved below the eastern alps however calculation of the isostatic lithospheric thickness shows two areas of lithospheric thickening along the central axis of the eastern alps with a transition zone below the area of the transalp profile this is in agreement with the tomographic model which features a change in lithospheric subduction direction c 2005 elsevier b v all rights reserved

using microtremors to assess potential earthquake site response a case study in flushing meadows new york city abstract we have used portable 5 sec period seismometers to record ambient noise across a glacially cut valley filled with unconsolidated holocene sediments the valley located in flushing meadows new york city is surrounded by a densely populated urban environment microtremors were recorded at several sites on and adjacent to the valley while some raw spectra of valley site microtremors exhibit no predominant peaks spectral ratios taken with respect to recordings made at a reference station outside the valley show a sharp peak near 0 8 hz a secondary peak near 2 4 hz is also visible in some of the spectral ratios the frequency of the predominant peak remains constant across the valley width while the relative amplitude decreases systematically from a maximum at the valley center to background levels near the valley edge resonant frequencies predicted by one dimensional modeling of the valley center site response show excellent agreement with observations the 0 8 hz spectral ratio peak is interpreted as the fundamental resonance mode and the 2 4 hz peak is interpreted as the first harmonic of the region above the base of an organic clay layer observed in borehole data the amplification factors implied by the observed spectral ratios are unrealistically high up to 100 which can be attributed to the close proximity of microtremor sources an experiment involving the use of a pile driver source located outside the valley was also performed signals obtained at valley sites during times when the pile driver was in operation show a two fold increase in the amplitude of a spectral peak when compared to signals obtained when the pile driver was turned off this observation gives additional evidence that observed spectral peaks represent soil layer resonances in the valley based on the results of this and other previous studies we conclude that easily obtained microtremor measurements can contribute valuable microzonation and site response information to a study of regional earthquake hazard

mineralogy and petrology of amoeboid olivine inclusions in co3 chondrites relationship to parent body aqueous alteration petrographic and mineralogic studies of amoeboid olivine inclusions aois in co3 carbonaceous chondrites reveal that they are sensitive indicators of parent body aqueous and thermal alteration as the petrologic subtype increases from 3 0 to 3 8 forsteritic olivine fa0 1 is systematically converted into ferroan olivine fa60 75 we infer that the fe si and o entered the assemblage along grain boundaries forming ferroan olivine that filled fractures and voids as temperatures increased fe 2 from the new olivine exchanged with mg 2 from the original aoi to form diffusive haloes around low feo cores cations of mn 2 ca 2 and cr 3 were also mobilized the systematic changes in aoi textures and olivine compositional distributions can be used to refine the classification of co3 chondrites into subtypes in subtype 3 0 olivine occurs as small forsterite grains fa0 1 free of ferroan olivine in petrologic subtype 3 2 narrow veins of feo rich olivine have formed at forsterite grain boundaries with increasing alteration these veins thicken to form zones of ferroan olivine at the outside aoi margin and within the aoi interior by subtype 3 7 there is a fairly broad olivine compositional distribution in the range fa63 70 and by subtype 3 8 no forsterite remains and the high fa peak has narrowed fa64 67 even at this stage there is incomplete equilibration in the chondrite as a whole e g data for coarse olivine grains in isna co3 8 chondrules and lithic clasts show a peak at fa39 we infer that the mineral changes in aoi identified in the low petrologic types required aqueous or hydrothermal fluids whereas those in subtypes 3 3 largely reflect diffusive exchange within and between mineral grains without the aid of fluids

the buried shape of an alpine valley from gravity surveys seismic and ambient noise analysis summary it has long been observed that damage due to earthquakes depends greatly on local geological conditions alpine valleys represent a typical populated environment where large amplifications can take place owing to the presence of surface soils with poor mechanical properties combined to complex topography of the rock basin in the framework of the eu interreg iiib sismovalp project seismic hazard and alpine valley response analysis a stretch of the tagliamento river valley trv located in the north western part of the friuli region italy and close to the epicentre of the 1976 mw 6 4 earthquake has been investigated with the aim to define the buried shape of the valley itself two non invasive low cost independent geophysical methods were used i detailed gravity survey and ii h v spectral ratio hvsr of microtremors because of structural geological complexity and active tectonics of the friuli region an irregular valley shape was expected in this area the independent analysis performed by gravity and passive noise and complemented with refraction seismic velocity profiles confirms this hypothesis and leads to two models that were consistent but for some small scale details the maximum depth estimated is about 400 450 m in the southern part of the valley while a mean value of 150 180 m is estimated in the northern part the sediment thickness obtained for this stretch of the trv is quite large if compared to eastern alps plio quaternary rates therefore the valley shape imaged by this study better corresponds to the top of carbonate rocks finally on the basis of the obtained morphology and some direct measurements we conclude that the trv features an overall 1 d seismic response i e the resonance is related only to the sediment thickness rather than to the cross section shape but in its deepest part some limited 2 d effects could take place

observation of 1 to 5 second microtremors and their application to earthquake engineering part iii a two dimensional study of site effects in the san fernando valley abstract a two dimensional study of the influence of deep sediment on seismic ground motions was conducted by recording and analyzing long period microtremors in the san fernando valley california the recordings were made at 50 regularly distributed sites in the valley three reference sites were employed at the baserock outcrop around the valley so as to observe the time dependent characteristics of the microtremors 1 amplitudes in a period range of several seconds correlate with the thicknesses of the sedimentary layers 2 a site amplification effect which was evaluated in terms of sediment to rock spectral ratios is qualitatively consistent with available geological and strong motion data 3 the practical field observation procedure designed for this study the two dimensional approach can be easily used in other surveys for estimating the spatial characteristics of earthquake ground motions in the period range of several seconds

assessment of the stability of h v spectral ratios from ambient noise and comparison with earthquake data in the cologne area germany abstract situated in an active tectonic region the highly industrialised cologne area germany suffers from moderate sized earthquakes our contribution to the mitigation of earthquake risk includes a microzonation study using ambient seismic noise and earthquake recordings from two field campaigns an analysis of these data using the horizontal to vertical h v as well as the classical spectral ratio csr technique led to the following observations and conclusions 1 the spatial variation in the thickness of the sedimentary cover is reliably retrieved using the fundamental resonance frequency estimated from the peak in the h v ratio of ambient noise 2 this fundamental resonance frequency is stable in time but the amplitude of the peak the amplification factor is not 3 the relative amplification variation of the h v ratio in the area should therefore be checked systematically with repeated measurements before drawing conclusions about its significance 4 the analysis of the h v ratio of ambient noise provides the lower frequency bound above which amplification may occur 5 the shapes of the spectral ratios obtained by the different methods are generally in good agreement however the analysis of earthquake data shows that significant amplification of ground motion may also occur at frequencies higher than the fundamental one even when thick sediments are present

shock metamorphism of ordinary chondrites a revised petrographic classification of progressive stages of shock metamorphism of ordinary chondrites is proposed six stages of shock s1 to s6 are defined based on shock effects in olivine and plagioclase as recognized by thin section microscopy the characteristic shock effects of each shock stage are s1 unshocked sharp optical extinction of olivine s2 very weakly shocked undulatory extinction of olivine s3 weakly shocked planar fractures in olivine s4 moderately shocked mosaicism in olivine s5 strongly shocked isotropization of plagioclase maskelynite and planar deformation features in olivine and s6 very strongly shocked recrystallization of olivine sometimes combined with phase transformations ringwoodite and or phases produced by dissociation reactions s6 effects are always restricted to regions adjacent to melted portions of a sample which is otherwise only strongly shocked in stages s3 to s6 localized melting results from stress and temperature peaks which locally deviate from the equilibration shock pressure due to differences in shock impedance these melting effects are a opaque melt veins shock veins b melt pockets with interconnecting melt veins c melt dikes and d troilite metal deposits in fractures based on a critical evaluation of data from shock recovery experiments a shock pressure calibration for the six shock stages is proposed which defines the s1 s2 s2 s3 s3 s4 s4 s5 and s5 s6 transitions at 5 5 10 15 20 30 35 and 45 55 gpa respectively whole rock melting and formation of impact melt rocks or melt breccias occurs at about 75 90 gpa the symbol for the shock stage may be used in combination with the symbol for the petrologic type to abbreviate the complete classification of a chondrite e g h5 s3 we propose this new shock classification and pressure calibration system to replace previous systems which are out of date with respect to the pressure calibration nominally restricted to l chondrites and based on incomplete and in part illdefined sets of shock effects we have classified seventy six ordinary chondrites using the new classification system and conclude the following 1 1 shock effects and the sequence of progressively increasing degrees of shock metamorphism are very similar in h l and ll groups differences in the frequency distribution of shock stages are relatively minor e g l chondrites appear to have the largest fraction with stages s5 and s6 this suggests that the collisional histories of the h l and ll parent bodies were similar 2 2 petrologic type 3 chondrites are deficient in stages s4 to s6 and with increasing petrologic type the frequency of stages s4 to s6 increases we suggest that the more porous and volatile rich type 3 chondrites are subject to melting at a lower shock pressure than the nonporous chondrites of higher petrologic type volatiles trapped in pores cause shock induced dispersal of the shocked and melted material into small particles which are not expected to survive as meteorites 3 3 stage s3 is the most abundant in nearly all petrologic types 4 4 at shock pressures in excess of about 35 gpa s5 and s6 4he and 40ar are almost completely lost pressures below 10 gpa s1 and s2 do not cause noble gas losses

extrapolation of irregular subsurface structures using the horizontal to vertical spectral ratio of long period microtremors one of the key problems in modeling the 3d subsurface structure of sedimentary basins is extrapolation and or interpolation from 2d models constructed from reflection and refraction surveys the use of microtremor horizontal to vertical h v spectral ratios allowing simple and quick microtremor measurements may be suitable for this purpose the validity and usefulness of long period microtremor h v spectral ratios are investigated as a possible tool for extrapolation in 3d basin structure modeling three component microtremor observations were conducted at 51 stations in the northern section of the osaka basin which encompasses the most complex geological structures in the basin the microtremor h v spectral ratios were measured in the range 1 to 5 sec to reproduce these observations three 2d finite element models have been developed that account for the irregular shape of subsurface structures deduced from seismic reflection studies microtremor array studies and deep drilling data the 3d model obtained by combining the 2d models is consistent with geological information for the area such as surface geology and the location of active faults furthermore compared with the basement structure derived from the gravity prospecting this 3d model is more detailed and offers higher resolution than the gravitational method therefore the microtremor h v spectral ratio represents a useful technique of extrapolation and interpolation for modeling 3d basin structures

identifying 2d resonance in microtremor wave fields to predict local site effects during earthquakes we must know the geometrical and mechanical properties of local sedimentary structures and their resonance behavior we present a concept to identify resonance modes for 2d structures this is done for synthetic as well as measured microtremor wave fields the microtremor data were investigated by using the reference station and horizontal to vertical h v methods analyzing the synthetic microtremor data in profiles across 2d structures the reference station method rsm turned out to be much more suitable for the detection of 2d resonances than the h v method we therefore focused on rsm when analyzing the measurement data from two test sites in switzerland the st jakob tullingen trough near basel in the north and a site in the rhone valley near the village vetroz in the south the results of these two test sites led to different conclusions whereas the spectral peaks in data of the st jakob tullingen trough were not well developed and could only tentatively be interpreted those from the rhone valley clearly exhibited 2d resonance effects the sh 00 and the sv fundamental mode could be successfully identified at 0 32 0 03 and 0 35 0 03 hz respectively

combining hvsr microtremor observations with the spac method for site resonance study of the tamar valley in launceston tasmania australia summary the presence of the deep and narrow tamar valley in the city of launceston tasmania australia in filled with soft sediments above hard dolerite bedrock induces a complex pattern of resonance across the city horizontal to vertical spectrum ratio hvsr microtremor observations are combined with 1 d shear wave velocity swv profiles evaluated from spatially averaged coherency spectra spac observations of the vertical component of the microtremor wavefield to complete a site resonance study in a valley environment such as the tamar valley using the methodology developed in a previous paper 1 d swv profiles are interpreted from observed coherency spectra axial coh above the deepest point of the tamar valley using pairs of sensors spatially separated parallel to the valley axis the 1 d swv profiles interpreted at five sites suggest the depth to bedrock interface varies from approximately z 25 m north of the city to z 250 m above the deepest point of the valley numerical simulations of the propagation of surface waves in a 2 d model representation of the tamar valley compare well with hvsr observations recorded on two profiles transverse to the valley axis hvsr observations can identify the in plane shear sv frequency of resonance above the deepest part of the valley on two separate profiles transverse to the valley axis by computing the ellipticity curves from the preferred swv profiles interpreted by the spac method the antiplane shear sh modes of resonance expected to develop in the tamar valley are identified modes which hvsr observations alone fail to locate with precision hvsr observations suggest a complex mix of 1 d and 2 d patterns of resonance develops across the valley the results from this paper suggest that hvsr microtremor observations can be combined with spac microtremor method to characterize the geology and the pattern of resonance in a 2 d narrow structure such as the tamar valley

seismic soil effect in an embanked deep alpine valley a numerical investigation of two dimensional resonance this paper presents a 2d numerical study of the seismic response of a deep embanked sediment filled valley rhone valley switzerland to incident sh and sv waves the 2d modeling is performed with a program developed by pedersen et al 1995 based on the ibem technique this valley exhibits variation in subsurface geometry therefore three representative cross sections are considered in order to investigate the influence of symmetric and asymmetric morphology on the seismic response comparison between 1d and 2d modeling shows that both resonant frequencies and amplification values differ to a large extent looking in the central part of the valley the 2d predicted amplification value is about twice higher than in the 1d case whereas the fundamental resonant frequency value is higher by a factor of 1 7 moreover 2d modeling results show that this valley presents a twodimensional resonance due to its shape ratio and shear wave velocity contrast the main characteristic is the unchanged position of the fundamental resonance frequency regardless of the surface site along the cross section under consideration and the incidence angle however the asymmetric cross section induces a specific spectral amplification pattern at the surface site and along the cross section which is also a function of the direction of incidence of the seismic wave such results show the importance of considering the morphology of a deep and narrow valley when investigating the local seismic response

first measurement of ice bedrock interface of alpine glaciers by cosmic muon radiography the shape of the bedrock underneath alpine glaciers bears vital information on the erosional mechanism related to the flow of ice so far several geophysical exploration methods have been proposed to map the bedrock topography though with limited accuracy here we illustrate the first results from a technology called cosmic ray muon radiography newly applied in glacial geology to investigate the bedrock geometry beneath the aletsch glacier situated in the central swiss alps for this purpose we installed new cosmic muon detectors made of emulsion films at three sites along the jungfrau railway tunnel and measured the shape of the bedrock under the uppermost part of aletsch glacier jungfraufirn our results constrain the continuation of the bedrock ice interface up to a depth of 50 m below the surface where the bedrock underneath the glacier strikes ne sw and dips at 45 5 this documents the first successful application of this technology to a glaciated environment

landform characterization using geophysics recent advances applications and emerging tools abstract this paper presents an overview of the strengths and limitations of existing and emerging geophysical tools for landform studies the objectives are to discuss recent technical developments and to provide a review of relevant recent literature with a focus on propagating field methods with terrestrial applications for various methods in this category including ground penetrating radar gpr electrical resistivity er seismics and electromagnetic em induction the technical backgrounds are introduced followed by section on novel developments relevant to landform characterization for several decades gpr has been popular for characterization of the shallow subsurface and in particular sedimentary systems novel developments in gpr include the use of multi offset systems to improve signal to noise ratios and data collection efficiency amongst others and the increased use of 3d data multi electrode er systems have become popular in recent years as they allow for relatively fast and detailed mapping novel developments include time lapse monitoring of dynamic processes as well as the use of capacitively coupled systems for fast non invasive surveys em induction methods are especially popular for fast mapping of spatial variation but can also be used to obtain information on the vertical variation in subsurface electrical conductivity in recent years several examples of the use of plane wave em for characterization of landforms have been published seismic methods for landform characterization include seismic reflection and refraction techniques and the use of surface waves a recent development is the use of passive sensing approaches the use of multiple geophysical methods which can benefit from the sensitivity to different subsurface parameters is becoming more common strategies for coupled and joint inversion of complementary datasets will once more widely available benefit the geophysical study of landforms three cases studies are presented on the use of electrical and gpr methods for characterization of landforms in the range of meters to 100 s of meters in dimension in a study of polygonal patterned ground in the saginaw lowlands michigan usa electrical resistivity tomography was used to characterize differences in subsurface texture and water content associated with polygon swale topography also a sand filled thermokarst feature was identified using electrical resistivity data the second example is on the use of constant spread traversing cst for characterization of large scale glaciotectonic deformation in the ludington ridge michigan multiple cst surveys parallel to an 60 m high cliff where broad 100 m synclines and narrow clay rich anticlines are visible illustrated that at least one of the narrow structures extended inland a third case study discusses internal structures of an eolian dune on a coastal spit in new zealand both 35 and 200 mhz gpr data which clearly identified a paleosol and internal sedimentary structures of the dune were used to improve understanding of the development of the dune which may shed light on paleo wind directions

disentangling nebular and asteroidal features of co3 carbonaceous chondrite meteorites abstract analyses of olivines and low ca pyroxenes in a suite of porphyritic chondrules of types ia and ii in each of ten co3 chondrites and comparisons with similar chondrules in ll chondrites suggest that the co3 chondrites may be divided into a metamorphic sequence of subtypes 3 0 to 3 7 chondrules in allan hills a77307 and colony which we classify as type 3 0 show only igneous zoning whereas in the other more metamorphosed type 3 1 3 7 co chondrites chondrule silicates are enriched in feo most markedly in olivine crystals near the rims of type ia chondrules and along cracks the feo enrichments in metamorphosed chondrules result largely from equilibration by solid state diffusion between chondrules and feo rich matrices type 3 1 3 7 co chondrites were formed from chondrites like colony and alh a77307 in heated asteroids or planetesimals we find no evidence for nebular condensation of fayalite rims around these chondrules as reported for cv3 chondrites or nebular modification of chondrule silicates as favored by some workers metallic fe ni in alh a77307 contains up to 0 1 1 wt cr si and p as in the least metamorphosed ordinary chondrites and cm2 chondrites and grains of cohenite fe3c and haxonite fe23c6 these carbides which are the first reported in carbonaceous chondrites are associated with pentlandite and magnetite as in certain ll3 chondrites we assign the following petrologic subtypes to other co chondrites kainsaz 3 1 felix 3 2 alh 82101 and ornans 3 3 lance and alh a77029 3 4 alh a77003 3 5 warrenton 3 6 and isna 3 7

the effect of lateral heterogeneity on horizontal to vertical spectral ratio of microtremors inferred from observation and synthetics abstract horizontal to vertical h v spectral ratios of microtremors hvrm have been traditionally interpreted as representing either the s wave amplification directly or the rayleigh wave ellipticity for a horizontally layered structure however based on the diffuse field theory we have derived an alternative theoretical basis that hvrm corresponds to the square root of the ratio between the imaginary part of the horizontal green s function and that of the vertical one under that condition the 1d horizontal layering assumption is not needed to interpret hvrm as observational evidence of such non 1d hvrm we discovered significant directional dependency at a site on the uji campus kyoto university japan the observed microtremor north south vertical spectral ratios are quite stable and have only one peak around 0 5 hz on the other hand the east west vertical spectral ratios are smaller in amplitude and have higher peak frequencies and sometimes two separated peaks the directional dependency of observed hvrm is aligned to the axis of the 2d basin structure we performed numerical analyses by spectral element method using a unit load on the surface to examine the effect of the 2d basin structure on the imaginary parts of the green s functions we found that the 2d basin structure clearly changes the characteristics of the h v spectral ratios in both perpendicular and parallel directions relative to the basin axis thus we succeeded in theoretically simulating the qualitative difference between the h v spectral ratios for two orthogonal horizontal components of the hvrm observed on the uji campus online material snapshots and animations of wave propagation

joint inversion of surface wave velocity and gravity observations and its application to central asian basins shear velocity structure 1 we implement and apply a method to the jointly inverted of surface wave group velocities and gravity anomalies observations surface wave dispersion measurements are sensitive to seismic shear wave velocities and the gravity measurements supply constraints on rock density variations our goal is to obtain a self consistent three dimensional shear velocity density model with increased resolution of shallow geologic structures we apply the method to investigate the structure of the crust and upper mantle beneath two large central asian sedimentary basins the tarim and junggar the basins have thick sediment sections that produce substantial regional gravity variations up to several hundred milligals we used gravity observations extracted from the global gravity model derived from the gravity recovery and climate experiment grace satellite mission we combine the gravity anomalies with high resolution surface wave slowness tomographic maps that provide group velocity dispersion values in the period range between 8 and 100 s for a grid of locations across central asia to integrate these data we use a relationship between seismic velocity and density constructed through the combination of two empirical relations one determined by nafe and drake most appropriate for sedimentary rocks and a linear birch s law more applicable to denser rocks the basement an iterative damped least squares inversion including smoothing is used to jointly model both data sets using shear velocity variations as the primary model parameters results show high upper mantle shear velocities beneath the tarim basin and suggest differences in lower crust and upper mantle shear velocities between the eastern and western tarim

analysis and modeling of hvsr in the presence of a velocity inversion the case of venosa italy the aim of this work is to check the stability of the horizontal to vertical spectral ratios hvsrs calculated at the venosa station site italy this site lies over a layer of anthropogenic fill 4 m thick a rigid layer of conglomerates 15 m thick and a thick layer of clays about 300 m thick above the seismic bedrock the velocity inversion which takes place at the conglomerates clays interface is of main importance for the amplification behavior of this site we have analyzed nearly 2 years of data composed of 244 triggered noise records and 44 earthquakes the results obtained by the two data sets show different site response characteristics in particular the earthquake hvsr is not deamplified in the frequency range 1 8 hz like the triggered noise hvsr to find out the origin of this difference we modeled both the triggered noise and the earthquakes taking advantage of an improved ver sion of the thompson haskell propagation matrix method the differences between triggered noise and earthquake amplification functions might be explained by the difference in composition and propagation of the seismic wave fields moreover we show that the nonlinear behavior of the anthropogenic fill might explain the presence of the misfit of the resonance frequency attributed to this layer between triggered noise and earthquakes

characteristics of long period microtremors and their applicability in exploration of deep sedimentary layers abstract applicability of long period microtremors in inferring subsurface structure is examined using measurements of microtremors in the northwestern part of the kanto plain in japan short term continuous measurements of long period microtremors at both sediment and basement sites were taken a spectral peak at a period of 4 to 5 sec is stable with time while peaks at periods less than 2 sec are time variant suggesting a variation of microtremor sources however it was found that the spectral ratio between vertical and horizontal microtremors ellipticity at each site is stable with time good agreement was found between ellipticities of microtremors at the sediment site and those computed for rayleigh waves in which the structure of the sediments beneath the site was taken into account we also found that the ellipticities of rayleigh waves in earthquake ground motions were consistent with those of the microtremors these comparisons provide strong evidence that long period microtremors in the area studied consist mainly of rayleigh waves the ellipticity of microtremors was investigated by observing microtremors at temporary observation sites in the kanto plain where the sediment thickness varied from 0 to 1 km the subsurface structures were deduced by trial and error fitting of observed ellipticities with theoretical ellipticities that were calculated assuming rayleigh waves these results show that ellipticity of long period microtremors is effective for deducing structure from microtremor data at a single site

s wave velocity measurements applied to the seismic microzonation of basel upper rhine graben summary an extensive s wave velocity survey had been carried out in the frame of a recent seismic microzonation study of basel and the border areas between switzerland france and germany the aim was to better constrain the seismic amplification potential of the surface layers the survey included single station h v spectral ratios and ambient vibration array measurements carried out by the swiss team as well as active s wave velocity measurements performed by the german and french partners this paper is focused on the application of the array technique which consists in recording ambient vibrations with a number of seismological stations several practical aspects related to the field measurements are outlined the signal processing aims to determine the dispersion curves of surface waves contained in the ambient vibrations the inversion of the dispersion curve provides a 1 d s wave velocity model for the investigated site down to a depth related to the size of the array since the size of arrays is theoretically not limited arrays are known to be well adapted for investigations in deep sediment basins such as the upper rhine graben including the area of the city of basel in this region 27 array measurements with varying station configurations have been carried out to determine the s wave velocity properties of the geological layers down to a depth of 100 250 m for eight sites the outputs of the array measurements have been compared with the results of the other investigations using active sources the spectral analysis of surface waves sasw and s wave reflection seismics borehole information available for a few sites could be used to calibrate the geophysical measurements by this comparison the advantages and disadvantages of the array method and the other techniques are outlined with regard to the effectiveness of the methods and the required investigation depth the dispersion curves measured with the arrays and the sasw technique were also combined and inverted simultaneously to use the advantages of both methods finally the paper outlines and discusses the contribution of the s wave velocity survey to the new seismic microzonation of the basel region in this regard one major outcome of the survey is the quantification of vertical and lateral changes of the s wave velocity due to changing lithology or changing compaction and degree of weathering of the layers

shape and structure of the salzach valley austria from seismic traveltime tomography and full waveform inversion summary a 3 km long wide angle seismic survey across the salzach valley in the eastern alps austria provides a detailed characterization of its structure reflection and refraction traveltime tomography with adaptive gridding was applied to obtain a minimum structure model more detailed images of the valley fill were derived by acoustic full waveform inversion a multiscale frequency domain method was applied to data in the 4 26 hz range to improve the resolution from several hundred metres to less than fifty metres the starting frequency is unusually low for the size of the survey and it provides additional control of the long wavelengths of the background model which mitigates the non linearities of the inversion the final image is controlled by independent constraints from resistivity data and shallow wells it shows a confined upper aquifer that overlies a 150 m thick unsaturated zone no strong evidence was found for consolidated sediments at the bottom of the basin this and the large maximum depth to bedrock of 480 m suggests that the valley fill was repeatedly removed during strong glacial periods exposing the bedrock to deep erosion

the origin and evolution of chondrites recorded in the elemental and isotopic compositions of their macromolecular organic matter extraterrestrial organic matter in meteorites potentially retains a unique record of synthesis and chemical thermal modification by parent body nebular and even presolar processes in a survey of the elemental and isotopic compositions of insoluble organic matter iom from 75 carbonaceous ordinary and enstatite chondrites we find dramatic variations within and between chondrite classes there is no evidence that these variations correlate with the time and or location of chondrite formation or with any primary petrologic or bulk compositional features that are associated with nebular processes e g chondrule and volatile trace element abundances nor is there evidence for the formation of the iom by fischer tropsch type synthesis in the nebula or in the parent bodies the elemental variations are consistent with thermal maturation and or oxidation of a common precursor for reasons that are unclear there are large variations in isotopic composition within and between chondrite classes that do not correlate in a simple way with elemental composition or petrologic type nevertheless because of the pattern of elemental variations with petrologic type and the lack of any correlation with the primary features of the chondrite classes at present the most likely explanation is that all iom compositional variations are the result of parent body processing of a common precursor if correct the range of isotopic compositions within and between chondrite classes implies that the iom is composed of several isotopically distinct components whose relative stability varied with parent body conditions the most primitive iom is found in the cr chondrites and bells cm2 isotopically the iom from these meteorites resembles the iom in interplanetary dust particles chemically their iom resembles the chon particles of comet halley despite the large isotopic anomalies in the iom from these meteorites it is uncertain whether the iom formed in the interstellar medium or the outer solar system although the former is preferred here

on the limitation of the h v spectral ratio using seismic noise as an exploration tool application to the grenoble valley france a small apex ratio basin the h v spectral ratio method based on seismic noise hvsrn was used in the grenoble basin france an alpine valley characterized by a small apex ratio the resonance frequencies obtained in the experiments were compared to the thickness of the sediments deduced from a microgravimetric survey and to the 1 d theoretical assessment of site responses given the abundance of data on the sediments and depth of the basin the values of the theoretical resonance frequency fo can be determined quite accurately however it has been observed that the effects of basin geometry can disturb fo measurements using the hvsr method in particular for a case like the grenoble basin which has a small apex ratio w h and strong suspected 2 d and or 3 d effects interpretation of fo values in terms of bedrock depth gives rise to estimation errors of about 10 in certain cases with the most significant errors 50 occurring on the edges of the basin where subsurface layers are characterised by larger heterogeneities and where the basin topography is accentuated this study suggests that great care must be taken when using the hvsrn method as an exploration tool at least in valleys with a small apex ratio

chemical and physical studies of type 3 chondrites iv annealing studies of a type 3 4 ordinary chondrite and the metamorphic history of meteorites abstract samples of a type 3 4 chondrite have been annealed at 400 1000 c for 1 200 hours their thermoluminescence properties determined and analyzed for k na mn sc and ca by instrumental neutron activation analysis after annealing at 900 c the samples showed a 50 decrease in tl sensitivity while after annealing at 1000 c it fell to 0 1 0 01 times its unannealed value and loss of na and k occurred the tl and compositional changes resemble those observed for the equilibrated kernouve chondrite after similar annealing treatments except that the sharp tl decrease and element loss occurred at 1100 c this difference is presumably due to petrographic differences in the feldspar of the two meteorites the temperature and the width of the tl peak showed a discontinuous increase after annealing at 800 c peak temperature jumped from 130 to 200 c and peak width increased from 90 to 150 c the activation energies for these tl changes are 7 10 kcal mole similar increases in the tl peak temperature have been reported in tl studies of amelia va albite where they were associated with the low to high temperature transformation however the activation energy for the transformation is 80 kcal mole these changes in tl emission characteristics resemble trends observed in type 3 ordinary chondrites and it is suggested that type 3 3 3 5 chondrites have a low feldspar as tl phosphor and 3 5 have high feldspar as the phosphor thermoluminescence therefore provides a means of palaeothermometry for type 3 ordinary chondrites

petrography stable isotope compositions microraman spectroscopy and presolar components of roberts massif 04133 a reduced cv3 carbonaceous chondrite here we report the mineralogy petrography c n o stable isotope compositions degree of disorder of organic matter and abundances of presolar components of the chondrite roberts massif rbt 04133 using a coordinated multitechnique approach the results of this study are inconsistent with its initial classification as a renazzo like carbonaceous chondrite and strongly support rbt 04133 being a brecciated reduced petrologic type 3 3 vigarano like carbonaceous cv chondrite rbt 04133 shows no evidence for aqueous alteration however it is mildly thermally altered up to approximately 440 c which is apparent in its whole rock c and n isotopic compositions the degree of disorder of c in insoluble organic matter low presolar grain abundances minor element compositions of fe ni metal chromite compositions and morphologies and the presence of unequilibrated silicates sulfides within type i chondrules from rbt 04133 appear to be pre accretionary i e did not form via aqueous alteration providing further evidence that some sulfide minerals formed prior to accretion of the cv chondrite parent body the thin section studied contains two reduced cv3 lithologies one of which appears to be more thermally metamorphosed indicating that rbt 04133 like several other cv chondrites is a breccia and thus experienced impact processing linear foliation of chondrules was not observed implying that rbt 04133 did not experience high velocity impacts that could lead to extensive thermal metamorphism presolar silicates are still present in rbt 04133 although presolar sic grain abundances are very low indicating that the progressive destruction or modification of presolar sic grains begins before presolar silicate grains are completely unidentifiable

southern ocean sea ice control of the glacial north atlantic thermohaline circulation 1 a coupled model simulates a shallower and weaker north atlantic deep water circulation at the last glacial maximum compared to the modern with an enhanced intrusion of antarctic bottom water into the north atlantic these circulation changes are caused by the enhanced antarctic bottom water formation which is triggered by the enhanced equatorward sea ice transport ultimately by increased westerlies in the southern ocean at the last glacial maximum

combining borehole log stratigraphies and ambient vibration data to build a 3d model of the lower var valley nice france abstract in seismic hazard studies site effects assessment is based on an accurate knowledge of mechanical properties and geometry of superficial geological formations the lower var valley nice southeastern france is a 2 km wide fluvial sedimentary basin where site effects have been observed on earthquake recordings in addition this area is a significant economically developing zone including the second largest airport of france therefore it is highly important to define a 3d sub surface model of the basin to understand the ground motion amplifications based on the compilation of several years of geotechnical and geophysical studies the quaternary alluvial deposits of the lower var valley were investigated using 331 borehole log stratigraphies and 439 ambient vibration measurements these data were combined in a commercial software that models and allows to visualize geoscientific data and geological models in 3d the borehole log stratigraphies helped to define a representative lithostratigraphic soil profile and the geometry of the different sedimentary layers only few boreholes are reaching the engineering bedrock pliocene conglomerates characterized by a s wave velocity larger than 800 m s 1 from the ambient vibration data the fundamental resonance frequency identified from h v curves indicates the bedrock depth using the well known f0 vs 4h relationship these h v curves were interpreted using geological knowledge of the studied zone our results show that the bedrock depth varies in the center of the valley between 50 m in the northern part of the studied zone and more than 100 m on the river estuary first the average s wave velocity in the alluvial deposits is estimated according to combined analysis of the borehole log stratigraphies and h v calculations on ambient vibration measurements the spatial variability of this velocity has been translated into a velocity zonation of the valley second this zonation allows us to extrapolate the quaternary pliocene limit in the whole valley the 3d model of the lower var valley will be useful in future numerical simulations of seismic ground motions in order to evaluate and mitigate seismic risk in the area

post messinian drainage changes triggered by tectonic and climatic events eastern southern alps italy abstract the messinian quaternary history of tectonic and climatic control on sedimentation in the eastern southern alps northern italy was reconstructed using an integrated petrographic and sedimentological analysis of five sedimentary successions these units mainly consist of fluvial conglomerates of the tagliamento sequence deposited within the eastern southern alps since the upper miocene messinian salinity crisis at that time the closure of marine gateways between the atlantic ocean and the mediterranean sea caused a drop in sea level causing exchanged fluvial erosion and widening of the alpine catchments sediment composition in the upper miocene to lower pliocene units shows an abrupt change in the source areas from sediments characterized by carbonate rock fragments to detritus rich in low grade metamorphic grains in spite of tectonic activity within the eastern southern alps no major modifications in sediment supply took place during the pliocene early pleistocene time span in the middle pleistocene the first major expansion of the alpine glaciers triggered a change in drainage patterns and a marked increase in erosion rates predominantly climatic control on sedimentation in the tagliamento basin and the erosion of the carnic alps produced sediments rich in quartz siltstone and metamorphic rock fragments deposited in the upper pleistocene unit and in modern river sediments

petrographic chemical and spectroscopic evidence for thermal metamorphism in carbonaceous chondrites i ci and cm chondrites abstract we present a comprehensive description of petrologic chemical and spectroscopic features of thermally metamorphosed ci like and cm and cm like chondrites only two such ci chondrites have so far been discovered i e y 86029 and y 82162 thermal metamorphism in these chondrites is apparent in their low contents of h2o c and the most thermally labile trace elements partial dehydration of matrix phyllosilicates and abundance of thermally decomposed ca mg fe mn carbonates which apparently resulted from heating of mg fe carbonate precursors the cm chondrites exhibit a wide range of aqueous and thermal alteration characteristics this alteration was almost complete in y 86720 and y 86789 which also escaped alternating episodes of oxidation and sulfidization experienced by the others thermal metamorphism in the cm chondrites is apparent in loss of thermally labile trace elements and also in partial to almost complete dehydration of matrix phyllosilicates heating was less uniform in them than in ci chondrites this dehydration is also evident in strength and shapes of integrated intensities of the 3 m bands except in pca 91008 which experienced extensive terrestrial weathering tochilinite is absent in all but y 793321 probably due to heating textural evidence for thermal metamorphism is conspicuous in blurring or integration fusion of chondrules with matrix in the more extensively heated 600 c cm chondrites like pca 91008 and b 7904 tem and xrd analyses reveal that phyllosilicate transformation to anhydrous phases proceeds via poorly crystalline highly desiccated and disordered intermediate phases in the least and moderately heated 400 600 c carbonaceous chondrites like wis 91600 pca 91008 and y 86029 these findings are significant in that they confirm that these phases occur in meteorites as well as terrestrial samples thermal alteration in these meteorites can be used to identify other carbonaceous chondrites that were thermally metamorphosed in their parent bodies combining rnaa trace element data for experimentally heated murchison cm2 samples with petrographic and spectroscopic data these thermally metamorphosed carbonaceous chondrites can be ordered by severity of open system heating as 400 c y 793321

isotopic diversity in interplanetary dust particles and preservation of extreme 16o depletion two interplanetary dust particles idps investigated by nanosims reveal diverse oxygen isotope compositions at the micrometre scale the oxygen isotope values recorded at different locations across the single idp fragments cover a wider range than the bulk values available from all idps and bulk meteorites measured to date measurement of h c and n isotopes by nanosims and the use of scanning and transmission electron microscopy sem and tem to determine elemental compositions and textural information allows for a better understanding of the lithologies and organic signatures associated with the oxygen isotope features idp balmoral a 15 m sized fragment with a chondritic porous cp idp like texture contains a region a few micrometres in size characterised by 16o depleted isotope signatures in the range 17o 18o 80 to 200 the remainder of the fragment has a more 16o rich composition 18o 0 20 similar to many other idps and bulk meteorites other than in discrete pre solar grains such extreme 16o depletions have only been observed previously in rare components within the matrix of the acfer 094 meteorite however tem imaging and feo mgo si ion ratios indicate that the 16o depleted regions in balmoral did not form by the same mechanism as that proposed for the 16o depleted phases in acfer 094 as the level of 16o depletion is consistent with that expected from isotope selective self shielding it is likely that the 16o depleted reservoir was located close to that where oxygen self shielding effects were most pronounced i e the outer solar nebula or even interstellar medium individual regions within idp lumley cover a range in 18o from 30 to 19 with the oxygen isotope values broadly co varying with d 13c 15n light element ratios and texture the relationships observed in lumley indicate that the parent body incorporated material at the micrometre scale from discrete diverse isotopic reservoirs some of which are represented by inner solar system material but others which must have formed in the outer solar system the idp fragments support a model whereby primary dust from the early solar nebula initially formed a variety of reservoirs in the outer solar nebula with those at lower au incorporating a higher proportion of inner solar system chondritic dust than those at larger au these reservoirs were subsequently disrupted into micrometre sized clasts that were re incorporated into idp parent bodies presumably at large au these results reveal that any models accounting for mixing processes in the early solar nebula must also account for the presence of an extremely 16o depleted reservoir in the comet forming region

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

determination of the petrologic type of cv3 chondrites by raman spectroscopy of included organic matter abstract this paper reports the first reliable quantitative determination of the thermal metamorphism grade of a series of nine cv3 chondrites allende axtell bali mokoia grosnaja efremovka vigarano leoville and kaba the maturity of the organic matter in matrix determined by raman spectroscopy has been used as a powerful metamorphic tracer independent of the mineralogical context and extent of aqueous alteration this tracer has been used along with other metamorphic tracers such as fe zoning in type i chondrules of olivine phenocrysts presolar grain abundance and noble gas abundance bulk and p3 component the study shows that the petrologic types determined earlier by induced thermoluminescence were underestimated and suggests the following values pt allende axtell 3 6 pt bali mokoia grosnaja 3 6 pt efremovka leoville vigarano 3 1 3 4 pt kaba 3 1 the most commonly studied cv3 allende is also the most metamorphosed bali is a breccia containing clasts of different petrologic types the attribution suggested by this study is that of clasts of the highest petrologic types as pointed out by iom maturity and noble gas bulk abundance cv3 chondrites have complex asteroidal backgrounds with various degrees of aqueous alteration and or thermal metamorphism leading to complex mineralogical and petrologic patterns fe mg chemical zoning in olivine phenocrysts on the borders of type i chondrules of porphyritic olivine and pyroxene rich textural types has been found to correlate with the metamorphism grade this suggests that chemical zoning in some chondrules often interpreted as exchanges between chondrules and nebular gas may well have an asteroidal origin furthermore the compositional range of olivine matrix is controlled both by thermal metamorphism and aqueous alteration this does not support evidence of a nebular origin and does not necessarily mirror the metamorphism grade through fe mg equilibration on the other hand it may provide clues on the degree of aqueous alteration vs thermal metamorphism and on the timing of both processes in particular mokoia experienced significant aqueous alteration after the metamorphism peak whereas grosnaja which has similar metamorphism grade did not

site amplification in the san fernando valley california variability of site effect estimation using the s wave coda and h v methods during the months that followed the 17 january 1994 m 6 7 northridge california earthquake portable digital seismic stations were deployed in the san fernando basin to record aftershock data and estimate site amplification factors this study analyzes data recorded on 31 three component stations from 38 aftershocks ranging from m 3 0 to m 5 1 and depths from 0 2 to 19 km site responses from the 31 stations are estimated from coda waves s waves and ratios of horizontal to vertical h v recordings for the coda and the s waves site response is estimated using both direct spectral ratios and a generalized inversion scheme results from the inversions indicate that the effect of qs can be significant especially at high frequencies site amplifications estimated from the coda of the vertical and horizontal components can be significantly different from each other depending on the choice of the reference site the difference is reduced when an average of six rock sites is used as a reference site in addition when using this multi reference site the coda amplification from rock sites is usually within a factor of 2 of the amplification determined from the direct spectral ratios and the inversion of the s waves however for nonrock sites the coda amplification can be larger by a factor of 2 or more when compared with the amplification estimated from the direct spectral ratios and the inversion of the s waves the h v method for estimating site response is found to extract the same predominant peaks as the direct spectral ratio and the inversion methods the amplifications determined from the hiv method are however different from the amplifications determined from the other methods finally the stations were grouped into classes based on two different classifications general geology and a more detailed classification using a quaternary geology map for the los angeles and san fernando areas average site response estimates using the site characterization based on the detailed geology show better correlation between amplification and surface geology than the general geology classification

local site response in an alpine valley from recorded earthquakes and ambient noise analysis local response is estimated within the sediment fill of the tagliamento river valley thv northeastern italy using about 90 weak to medium local and regional earthquakes ground motion is recorded at six stations deployed in a linear array across the valley site amplification factors are determined using the standard spectral ratio the generalized inversion technique and evaluations of receiver functions results obtained from earthquake data are then compared with ambient noise analysis azimuthal effects in the seismic response are observed locally for waves coming from the east southeast aligned with the longitudinal axis of the valley the seismic responses evaluated at the mid valley and at the valley edge are then convolved with the 1976 m w 6 4 friuli mainshock recorded at accelerometric station tlm1 located close to the array the local response at the valley edge in the town of cavazzo carnico is responsible for an enhancement of the input motion of an average factor of about 4 in the frequency range from 2 to 8 hz the elastic demand from the current national regulation for a 475 year return period and specific for cavazzo carnico is overcome by the 5 damped pseudoacceleration response spectrum estimated at the valley edge the underestimation of the italian code is mostly due to a 2d amplification effect at the valley edge rather than a simple inadequacy of the v s 30 site classification online material figures showing locations of historical earthquakes distribution of fundamental frequency of vibration waveforms of the m d 5 1 kobarid earthquake s wave velocity versus depth and git and rf amplification median values and spectra tables of seismic station locations and soil type and of local and regional earthquakes

spectral amplification in a sediment filled valley exhibiting clear basin edge induced waves various site response estimates are presented for a linear array deployed in the coachella valley california during the 1992 landers big bear aftershock sequence this systematic comparison is unique in that the response of the site is clearly dominated by basin edge induced waves average sediment to bedrock spectral ratios for long s wave windows which include the basin edge induced waves exhibit amplification factors as high as 18 below 7 hz the deep basin structure which gives rise to the obvious multi dimensional effects produces a fundamental resonant peak that shifts between basin sites from 0 23 to 0 48 hz as the depth to bedrock changes above 0 6 hz where the largest amplifications occur the response is remarkably similar between sites and appears to be dominated by a near surface layer that is relatively uniform across the valley the apparent fundamental resonant frequency of this layer is between 0 8 and 1 hz sediment to bedrock spectral ratios computed using shorter windows that exclude the basin edge induced waves imply that the multi dimensional effects are significant only below 4 hz where they increase amplifications by an approximate factor of 2 spectral ratios computed using coda windows taken at twice the s wave travel time exhibit amplifications that are an average factor of 1 7 greater between 1 and 4 hz than those of the s wave estimates this discrepancy does not improve by taking coda windows later at four times the s wave travel time horizontal to vertical component s wave spectral ratios do not agree with the sediment to bedrock ratios however they do exhibit a clear peak at the fundamental resonant frequency of the deep basin structure sediment to bedrock spectral ratios of ambient seismic noise are also inconsistent with the s wave estimates however horizontal to vertical noise ratios exhibit clear peaks near the fundamental resonant frequencies of both the deep basin structure below 0 6 hz and the suspected near surface layer between 0 8 and 1 hz therefore ambient noise data appear to provide valuable constraints on the basin structure ongoing efforts involve multi dimensional modeling of the observed basin edge induced phases and resonant frequencies

observation of 1 to 5 second microtremors and their application to earthquake engineering part ii evaluation of site effect upon seismic wave amplification due to extremely deep soil deposits abstract the usefulness of long period microtremor observation for earthquake engineering problems at extremely deep soil deposit site was examined in this study microtremor observations were made in the niigata plain japan and in los angeles california where depths to the basement rock are several kilometers these two locations were selected because strong motion records obtained during the niigata earthquake of 1964 and the san fernando earthquake of 1971 contain large long period amplitudes understanding why these predominate long period motions were recorded is important for the evaluation of seismic input motions for large scale structures long period microtremor observations were carried out in both areas in order to evaluate the characteristics of deep soil observations were performed simultaneously at a number of stations to distinguish the nature of deep soil deposit the result of fourier analysis showed that amplitude of microtremors in long period range increases systematically from the point of basement rock outcrop to deep deposit site with the increase corresponding to the depth to basement rock this relationship coincides with that observed in the strong motion earthquake records these analyses indicated that simultaneous observation of long period microtremors at a number of stations can provide insight to the characteristic of deep soil amplification and therefore permit estimation of seismic input motions for large scale structures

seismic properties of the upper crust in the central friuli area northeastern italy based on petrophysical data abstract the compressional and shear wave velocities have been measured at room temperature and pressure up to 450 mpa on 5 sedimentary rock samples representative of the most common lithologies of the upper crust in the central friuli area northeastern italy at 400 mpa confining pressure the triassic dolomitic rock shows the highest velocities vp 7 km s vs 3 6 km s the jurassic and triassic limestones samples intermediate velocities vp 6 3 s vs 3 5 km s and the cenozoic and paleozoic sandstones the lowest velocities vp 6 15 km s vs 3 35 km s the paleozoic sandstone sample is characterized by the strongest anisotropy 10 and significant birefringence 0 2 km s is found only on the cenozoic sandstone sample we elaborated the synthetic profiles of seismic velocities density elastic parameters and reflection coefficient related to 4 one dimensional geological models extended up to 22 km depth the synthetic profiles evidence high rheological contrasts between triassic dolomitic rocks and the soft sandstones and the jurassic limestones the vp profiles obtained from laboratory measurements match very well the in situ vp profile measured by sonic log for the limestones and dolomitic rocks supporting our one dimensional modelling of the calcareous carbonatic stratigraphic series the vp and vs values of the synthetic profiles are compared with the corresponding ones obtained from the 3 d tomographic inversion of local earthquakes the laboratory vp are generally higher than the tomographic ones with major discrepancies for the dolomitic lithology the comparison with the depth location of seismicity reveals that the seismic energy is mainly released in correspondence of high contrast rheological boundaries

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

organic thermometry for chondritic parent bodies abstract a unique spectroscopic feature has been identified in a study of twenty five different samples of meteoritic insoluble organic matter iom spanning multiple chemical classes groups and petrologic types using carbon x ray absorption near edge structure xanes spectroscopy the intensity of this feature a 1s exciton appears to provide a precise measure of parent body metamorphism the intensity of this exciton is also shown to correlate well with a large negative paramagnetic shift observed through solid state 13c nmr experiments reveal that upon heating primitive iom is transformed into material that is indistinguishable from that in thermally processed chondrites including the development of the 1s exciton a thermo kinetic expression is derived from the experimental data that allows the intensity of the 1s exciton to be used to estimated the effective temperature integrated over time a good correlation is observed between the intensity of the 1s exciton and previously published microraman spectral data these data provide a self consistent organic derived temperature scale for the purpose of calibrating raman based thermometric expressions

microtremor measurements used to map thickness of soft sediments the observations about the behavior of microtremor spectra presented here show that noise measurements can be used as a powerful tool to determine the thickness of soft cover layers the most suitable method for this determination is nakamura s technique which is the ratio of the horizontal component noise spectrum and that of the vertical component i i v spectrum the frequency of the main peak in these spectral ratios correlates well with the sediment thickness at the site using an extensive database of microtremor measurements carried out in the western lower rhine embayment germany it was possible to show that this correlation is clearly valid for a wide range of thickness namely from tens of meters to more than 1000 m a simple formula was derived that for the sediments to be found in the area investigated directly calculates the cover thickness from the frequency of the main peak in the h v spectrum a comparison with calculated resonant frequencies sug gests the relation derived from the noise measurements depending on the velocity depth function of the shear wave classical spectral ratios are shown to be strongly influenced by the noise level and are therefore less reliable in determining the res onant frequency of the subsoil the practical relevance of the investigation is illus trated by means of cross sections constructed from results of the microtremor anal yses which provide a convincing image of the surficial structure of the areas investigated

determination of shallow shear wave velocity profiles in the cologne germany area using ambient vibrations summary we have used both single station and array methods to determine shallow shear velocity site profiles in the vicinity of the city of cologne germany from ambient vibration records based on fk analysis we assume that fundamental mode rayleigh waves dominate the analysed wavefield in the frequency range of 0 7 2 2 hz according to this view a close relation exists between h v spectral ratios and the ellipticity of the contributing rayleigh waves the inversion of the shape of h v spectral ratios then provides quantitative information concerning the local shear wave velocity structure however based on tests with synthetic data believed to represent a typical situation in the lower rhine embayment dispersion curves were found to provide stronger constraints on the absolute values of the velocity depth model than the ellipticities the shape of the ellipticities was found to be subject to a strong trade off between the layer thickness and the average layer velocity we have made use of this observation by combining the inversion schemes for dispersion curves and ellipticities such that the velocity depth dependence is essentially constrained by the dispersion curves while the layer thickness is constrained by the ellipticities in order to test this method in practice we have used array recordings of ambient vibrations from three sites where the subsurface geology is fairly well known and geotechnical information is at least partially available in order to keep the parameter space as simple as possible we attempted to fit only a single layer over a half space model however owing to earlier studies from the region we assume a power law depth dependence for sediment velocities for all three sites investigated the inversion resulted in models for which the shear wave velocity within the sediment layer both in absolute value at the surface and in depth dependence are found to be remarkably similar to the results obtained by budny from downhole measurements this is strong support for the interpretation of h v spectral ratios as rayleigh wave ellipticities for all three sites the predicted sh wave site amplification factors at the fundamental frequency are of the order of 5 6 with a slightly smaller value south of cologne

continuous measurements of microtremors on sediments and basement in los angeles california abstract continuous measurement of microtremors at two sites on basement rock and sediments was carried out in los angeles california in order to understand the fundamental characteristics of microtremors a predominant peak with a period of about 6 5 sec was found in the microtremor spectra in both media the spectral amplitude of the peaks varied gradually with time in a similar manner at the two sites their time variant characteristics are in agreement with change in oceanic swell height observed at an oceanic buoy in the southwest of los angeles this suggests that they originate from an oceanic disturbance on the other hand a clear daily variation of spectral amplitudes at a period of 0 3 sec indicates that short period microtremors are caused by cultural noises it was found that the spectral ratio of long period microtremors between the basement and the sediments was repeatable although the spectral amplitudes at the two sites were time variant the spectral ratio of the long period microtremors was similar to that derived from strong motion records this suggests the applicability of spectral ratios of microtremors to assess the effects of deep sediments on long period earthquake ground motion

standardization in gravity reduction gravity reduction standards are needed to improve anomaly quality for interpretation and to facilitate the joining together of different data sets to the extent possible data reduction should be quantitative objective and comprehensive leaving ambiguity only to the interpretation process that involves qualitative subjective and geological decisions the term bouguer anomaly describes a field intended to be free of all nongeologic effects not modified by a partial geologic interpretation measured vertical gradients of gravity demonstrate considerable variation but do not suggest as often reported that the normal free air gradient is in error or needs to be locally adjusted such gradients are strongly influenced by terrain and to a lesser extent by the same geologic sources which produce bouguer anomalies a substantial body of existing literature facilitates the comprehensive treatment of terrain effects which may be rigorously implemented with current computer technology although variations in topographic rock density are a major source of bouguer anomalies a constant density appropriate to the area under investigation is normally adopted as a data reduction standard leaving a treatment of the density variations to the interpretation a field example from british columbia illustrates both the variations in vertical gravity gradients which can be encountered and the conclusion that the classical approach to data reduction is practically always suitable to account for the observed effects standard data reduction procedures do not and should not include reduction to datum the interpreter must be aware however that otherwise smooth regional bouguer anomalies caused by regional sources do contain high frequency components in areas of rugged topography

new gravity maps of the eastern alps and significance for the crustal structures abstract the deep seismic profile t ransalp crosses from north to south germany austria and italy the gravity measurements for each country were made by national agencies with different reference systems and data reduction methods within the frame of the t ransalp project a comprehensive database of the eastern alps was compiled covering an area of 3 5 by 4 in longitude and latitude 275 by 445 km respectively to increase the data coverage in the south alpine area two gravity surveys were carried out resulting in 469 areally distributed new stations of which 215 have been measured with the intent to improve the geoid in the area of the planned brenner basistunnel bbt the resulting gravity database is the best in terms of resolution and data quality presently available for the eastern alps here the free air bouguer and isostatic gravity fields are critically discussed the spatial density of existing gravity stations in the three countries is discussed on the italian side of the alps the spatial density is rather sparse compared to the austrian side the bouguer gravity field varies between 190 10 5 m s2 and 25 10 5 m s2 with the minimum located along the alpine high topographic chain but with a small offset a few tens of km to the greatest topographic elevation showing that the airy type local isostatic equilibrium does not fully apply here the maximum of the bouguer anomaly has an elongated shape of 100 by 50 km located between the towns of verona and vicenza and covers the venetian tertiary volcanic province vtvp a feature not directly related to the plate collision in the eastern alps the gravity high is only partly explainable by high density magmatic rocks and requires also a deeper source like a shallowing of the moho the isostatic residual anomalies airy model are in the range 50 10 5 m s2 with the greatest positive anomaly corresponding to the location of the vtvp indicating here under compensation of masses at last a discussion of a 2d density model based on reflection seismic data and receiver functions is made