fluorine surface speciation in south andean volcanic ashes abstract fresh volcanic ash samples collected during the eruptions of the hudson 1991 chaiten 2008 puyehue 2011 calbuco 2015 and copahue 2016 volcanoes were analyzed in order to identify the fluorine f bearing phases xps and hr tem was used to determine the solid speciation of f in order to decrease the surface differential charging of samples xps data have been collected using an electron flood gun during spectral acquisition ash leaching at different ph conditions was also performed with the aim of understanding the factors that control the fluoride release to aqueous reservoirs the results indicates that in the studied patagonian ashes f is concentrated onto the ash surface likely in the form of f na and f ca salts but also within the glass lattice forming f si and f al bonds although the main f source in the studied volcanic ashes is the aluminosilicate glass this phase is stable at the neutral ph that dominates the aqueous reservoirs thus the contribution to the pool of dissolved fluoride is minor higher contributions are associated with soluble fluoride salts in addition the presence of coatings of f ca compounds inhibits the release of fluoride within the volcanic glass lattice at least during the initial stages of the ash water interaction

sedimentological maps of the typical loessic units in north pampa argentina abstract application of grain size data allowed the construction of maps of two typical loessic formations of north pampa a sand sea covering the central argentine plain and a peripheral loess belt to the northeast compose the pampean aeolian system a region of 20 000 km 2 in the loess belt santa fe and cordoba provinces was studied thick loess outcrops are located in this region the tezanos pinto loess upper pleistocene lower holocene in age and the san guillermo fm late holocene in age are analysed in this article the silt content has been taken as the main parameter for mapping in general the pattern of the isoplethic curves is similar in both maps these maps show that the silt content in both loessic units progressively increases from ssw to nne in the loess belt the silt content increases from 55 to 60 in the ssw at the transition belt to the sand sea up to 75 80 in the nne along a distance of 120 200 km other sedimentological data of the outcropping loess paleosols sequences are presented as complementary information

first order seismic microzonation of haldia bengal basin india using a gis platform the seismic microzonation of the bengal basin haldia region india is carried out using the analytical hierarchy process ahp on the geographic information system gis three themes are used for the seismic microzonation namely peak ground acceleration pga predominant frequency and elevation map an analysis of the maximum magnitude mmax and the b value is carried out after preparing the earthquake catalogue from various sources on the basis of the tectonic set up and seismicity of the region five seismic zones are delineated which can be a threat to haldia they are broadly classified as zone 1 arakan yoma zone ayz zone 2 himalayan zone hz zone 3 shillong plateau zone spz zone 4 bay of bengal zone bbz and zone 5 shield zone sz the mmax for zones 1 2 3 4 and 5 are 8 30 0 51 9 09 0 58 9 20 0 51 6 62 0 43 and 6 61 0 43 respectively the pga value is computed for haldia following the attenuation relationship taking the mmax of each source zone the expected pga at haldia varies from 0 09 0 19 g the predominant frequency of haldia is also calculated using the h v ratio with a frequency ranging from 0 1 3 0 hz the elevation map of haldia is also generated using the shuttle radar topography mission strm data a first order seismic microzonation map of haldia is prepared in which four zones of hazard have been broadly classified for haldia as very high seismic hazard zone high seismic hazard zone moderate seismic hazard zone and less seismic hazard zone the very high seismic hazard zone is observed along the southern part of haldia where there are major industrial and port facilities the pga for the four hazard zones are 0 09 0 13 g for low hazard zone 0 13 0 15 g for moderate hazard zone 0 15 0 16 g for high hazard zone and 0 16 0 19 g for very high hazard zone

seismic ground motion in napoli for the 1980 irpinia earthquake the seismic ground motion in the urban area of napoli has been computed for the 1980 earthquake m s 6 9 with a hybrid technique based on the mode summation and the finite difference methods the detailed geological setting of each quarter has been reconstructed from several stratigraphies and six geological zones have been recognized shear wave velocity profiles have been assigned based on hole tests and inversion of rayleigh group velocities artificially generated

some mass balance and geological constraints on migration mechanisms oil and gas are not at rest in the sedimentary mantle of the earth they are not in equilibrium whether they are finely dispersed in a potential source rock or whether they are concentrated in a trap in a reservoir rock a wide variety of possible escape mechanisms exists these include diffusion continuous single phase flow solution of oil in gas or gas in oil and solution in water derived from compaction clay diagenesis or meteoric sources the problem is to quantify the possible mechanisms and to rank their relative importance under a given set of physical chemical and geologic conditions the quantitative importance of the various proposed mechanisms can vary by orders of magnitude depending on the physical chemical and geologic conditions during the past decade oil to source correlations have become reliable and the timing of peak generation and concomitant migration has been sufficiently quantified to allow the geologist geochemist to make estimates of when and how much petroleum moved from one location to another combined with a knowledge of the physical chemical and geologic conditions at the time of migration such quantitative descriptions of subsurface petroleum transfer permit an empirical test of the applicability of the various proposed migration mechanisms the application of this technique to selected areas suggests that most of the major commercial oil accumulations of the world left their source rock in a continuous oil phase when bitumen concentrations in the rock are too low for continuous phase flo to exist other migration mechanisms which always are operative will increase in both absolute and relative intensity solution of oil in gas may become significant in thick tertiary delta systems and meteoric water may be a surprising asset in some very specific geologic settings however it is unlikely that solution of oil in water derived from compaction or from dehydration of clay has much to do with the origin of many of the major oil accumulations of the world

chronology of late pleistocene pampa loess from the cordoba area in argentina in argentina loess palaeosol sequences were studied from the two sections at monte ralo and corralito located near to the city of cordoba in the east of the pampean ranges infrared optically stimulated luminescence irsl and thermoluminescence tl dating techniques were applied to set up a more reliable chronological framework for the upper pleistocene loess record irsl ages increase with depth and are stratigraphically consistent the oldest loess exposed correlates at least to the penultimate glaciation the luminescence dating study gives evidence for humid climate conditions with soil formation during the last interglacial period and the middle pleniglacial correlating to marine isotope stage mis 5 and 3 respectively three extended periods of soil formation are recorded in the loess palaeosol sequences at the corralito section these buried soils most likely correlate with the last interglacial and early last glacial period during the middle pleniglacial two palaeosols are intercalated in the loess successions in the cordoba area the periods of increased loess accumulation and deposition of loessic sediments correlate with more arid and glacial periods during the early pleniglacial the middle pleniglacial and the late glacial copyright 2009 john wiley sons ltd

seismic characterization of neapolitan soils detailed shear wave velocity profiles versus depth have been obtained in typical lithostratigraphies of napoli ftan and hedgehog methods have been applied to rayleigh surface waves recorded in refraction seismic surveys the comparison with literature measurements shows good agreement with nearby down and cross hole tests

modeling of ground motion at napoli for the 1688 scenario earthquake the sannio seismogenic area turns out to be responsible for the highest peak ground accelerations pga and seismic response spectra srs at napoli the 1688 earthquake is considered representative of the area and realistic synthetic seismograms have been computed for this scenario earthquake at the historical center and the eastern sector of napoli the use of a hybrid technique based on mode summation and finite difference methods is fully justified by the available detailed knowledge about the geological and geophysical properties of the neapolitan subsoil this modeling makes it possible to recognize that amplifications of 2 for pga and 3 for srs are to be expected because of the pyroclastic soil cover based on the information contained in the available catalogs different magnitudes have been considered taking into account the correlation valid for the italian territory between synthetic pga and observed intensities it turns out that the most probable magnitude m of the 1688 earthquake is 6 7 while m 7 3 should be assigned to a conservative scenario earthquake comparison of the computed response spectra for the 1688 scenario earthquake with the italian seismic building code shows that the code is adequate with respect to the expected effects at the historical center of napoli but that it underestimates the possible ground motion at the eastern sector in particular at the newly developed area built after the 1980 earthquake

an integrated approach to earthquake induced landslide hazard zoning based on probabilistic seismic scenario for phlegrean islands ischia procida and vivara italy abstract in this study we present an integrated approach to assess earthquake induced landslide hazard at the source area of the slope instability process the method has been applied to the case study of ischia procida and vivara islands that represent an integral part of the campi flegrei a densely populated active volcanic area located at the nw margin of the naples bay italy the proposed method follows a stepwise procedure including 1 probabilistic seismic hazard analysis psha 2 assessment of site and topographic effects 3 input of the psha outputs into a classic sliding rigid block analysis for slope instability newmark s approach 4 construction of landslide frequency magnitude curves for the estimate of the slope failure probability as a function of defined newmark s threshold values under different probabilistic seismic scenarios 5 construction of earthquake induced landslide hazard maps at the source area based on the integration of the probabilistic approach and the geological morphological and geotechnical database available for the study area the probabilistic seismic hazard analysis psha is aimed at the definition of the seismic input with different annual exceedance frequency psha results expressed in terms of peak ground acceleration pga at the bedrock are calculated for 14 return periods t ranging from 10 to 2000 yr pga values have been corrected for the site effect associated with geological and morphologic conditions for each selected return period secondly the corrected pga values have been used as an input for the classic sliding rigid block newmark s approach implemented in a geographic information system gis to assess the relative potential for slope failure landslide susceptibility both in static factor of safety fs and dynamic critical acceleration ac conditions the combination of t dependent site corrected pga with the critical acceleration allowed for the calculation of the expected newmark s displacements dn under different probability of exceeding or return periods probabilistic seismic scenarios as a further step in order to estimate the earthquake induced landslide hazard we defined three dn threshold values that have considered capable to trigger shallow seismic induced landslides in the regional context and mapped the sectors with dn values exceeding such thresholds on this basis we constructed frequency magnitude curves to estimate the probability of slope failures at the source areas as a function of dn by correlating the annual probability of landslide occurrence with the number of terrain cells associated with dn values greater than the selected threshold finally based on the estimated annual landslide frequency of the seismic triggering event for each terrain cell we implemented a 1 5000 scale map of earthquake induced landslide hazard for ischia procida and vivara islands the map reports the zoning and ranking of study area into sub zones on a pixel basis according to the degree of the potential hazard from landslides derived by the frequency of the triggering event

a detailed study of the site effects in the volcanic area of campi flegrei using empirical approaches summary campi flegrei is a highly populated active caldera in the south of italy several hundred thousand people live within this area which is characterized by seismicity and ground deformation episodes known as bradyseism for this reason this area falls into a high risk category and thus the italian civil defence requires a detailed site effect estimation to determine the local amplification of the seismic waves for a high number of sites we have analysed the seismic recordings of three seismic networks that have been deployed in the campi flegrei area over different time periods the first network was deployed during the bradyseismic crisis of 1982 1984 we selected 22 of the highest magnitude earthquakes that were recorded during this crisis an additional 22 seismic events were selected from those recorded by the mobile seismic network that has been in operation in the campi flegrei area since 2006 the third data set comprises noise recorded by 34 seismic stations that were deployed during the active serapis experiment in 2001 september the generalized inversion technique and the h v spectral ratio method were applied to the s waves and coda waves of the earthquakes recorded by the first two seismic networks to determine the site transfer functions of the recording stations the seismic noise recorded by the third network was analysed using the nakamura s technique the results show that the high topographical and geological heterogeneity of the sites located inside the caldera has an important influence on the seismic wave amplification consequently the site transfer functions can be different even at sites close to each other the transfer functions of the sites located outside the caldera are much more regular apparently due to the more regular topography and geology

groundwater arsenic in the chaco pampean plain argentina case study from robles county santiago del estero province in large parts of rural argentina people depend on groundwater whose as content exceeds the argentine drinking water standards 0 05 mg l 1 the most affected areas are located in the chaco pamp

measurement and modelling of diffusion porosity and other pore level characteristics of sandstones abstract the diffusion coefficients of methane iso butane and n butane through dry and water saturated sandstones and their dependence on relative molar mass are discussed the diffusion of iso butane is anomalously fast in dry sandstones and that of methane is anomalously low in water saturated sandstones a three dimensional computer model of the pores and throats in the sandstone has been developed simulations have been made of the sandstone s porosity surface area pore and throat size distribution tortuosity mercury porosimetry primary drainage curve average pore connectivity and diffusion coefficient for mixed gaseous alkanes

irpinia italy 1980 earthquake waveform modelling of strong motion data summary several strong motion records of the irpinia southern italy 1980 earthquake have been modelled for a total time duration of about 180 s with the use of the rnultimode summation of waves of p sv and sh type if waveform modelling is applied to unfiltered accelerations the best that can be done at present is amplitude envelope matching in time and frequency domain the early phase of the studied event can be synthesized by 12 main episodes of different sizes modelling the rupturing process the space time distribution of such episodes suggests that the rupturing process did propagate in a bilateral fashion this model of the seismic source gives rise to synthetic velocity records which match quite well the experimental ones to avoid the problems connected with the large instability of displacements obtained from direct numerical integration of observed accelerograms the synthetic signals can be first used to perform acceleration or velocity fitting of experimental data an estimate of the ground displacement above 1 hz can then be obtained by analytical integration of the synthetic velocities

the quantification of diffusive hydrocarbon losses through cap rocks of natural gas reservoirs a reevaluation discussion 1 a calculation scheme is presented to estimate the quantities of diffusive gas loss through the water saturated cap rock of natural gas reservoirs over geologic time reexamination of earlier calculations in a 1982 paper by leythaeuser et al revealed that the estimate of the rate of diffusive hydrocarbon losses through the cap rock of the harlingen netherlands natural gas reservoir was based on oversimplified assumptions concerning the boundary conditions at the reservoir cap rock interface according to this recalculation the time required to reduce the present day methane content of the harlingen gas field by one half is approximately 70 m y not the previously published value of 4 5 m y consequently diffusion losses through the cap rock appear to affect the long erm stability of natural gas reservoirs to a lesser extent than suggested by the earlier results

a proposed new type of arsenian pyrite composition nanostructure and geological significance this report describes a new form of arsenian pyrite called as3 pyrite in which as substitutes for fe fe as s2 in contrast to the more common form of arsenian pyrite as1 pyrite in which as1 substitutes for s fe as s 2 as3 pyrite has been observed as colloformic overgrowths on as free pyrite in a hydrothermal gold deposit at yanacocha peru xps analyses of the as3 pyrite confirm that as is present largely as as3 empa analyses show that as3 pyrite incorporates up to 3 05 at of as and 0 53 at 0 1 at 0 27 at 0 22 at 0 08 at and 0 04 at of pb au cu zn ni and co respectively incorporation of as3 in the pyrite could be written like as3 y au 1 y 2 fe2 where au and vacancy help to maintain the excess charge hrtem observations reveal a sharp boundary between as free pyrite and the first overgrowth of as3 pyrite 20 40 nm thick and co linear lattice fringes indicating epitaxial growth of as3 pyrite on as free pyrite overgrowths of as3 pyrite onto as free pyrite can be divided into three groups on the basis of crystal size 8 20 nm 100 300 nm and 400 900 nm and the smaller the crystal size the higher the concentration of toxic arsenic and trace metals the yanacocha deposit in which as3 pyrite was found formed under relatively oxidizing conditions in which the dominant form of dissolved as in the stability field of pyrite is as3 in contrast reducing conditions are typical of most environments that host as1 pyrite as3 pyrite will likely be found in other oxidizing hydrothermal and diagenetic environments including high sulfidation epithermal deposits and shallow groundwater systems where probably kinetically controlled formation of nanoscale crystals such as observed here would be a major control on incorporation and release of as3 and toxic heavy metals in oxidizing natural systems

comments on calculation of diffusion coefficients from hydrocarbon concentration profiles in rocks geologic note diffusion of hydrocarbons is an important transport process in the geologic environment it has applications in the primary migration of hydrocarbons and in the sealing properties of shales previous work in the literature reports effective diffusivities calculated from hydrocarbon concentration profiles in rocks those effective diffusivities may be applied to transport within rocks similar to the sampled rocks but the effective diffusivities comprise several factors that must be considered when one applied them to different rocks for example with increasing carbon number the reported effective diffusivities show a large decrease that results not from a trend in the intrinsic diffusivity but from a trend in the organic carbon water partitioning of the hydrocarbons as such the effective diffusivities do not apply to rocks with little or no organic carbon this note presents a model whereby the previously published effective diffusion coefficients are interpreted with respect to diffusion within the water saturated pore space and partitioning between the aqueous and organic carbon phases of the rock this model allows a more accurate extrapolation of diffusion measurements to new systems however the model does not conflict with the previous qualitative conclusion that aqueous diffusion is an important transport mechanism for light hydrocarbons only

v s of the uppermost crust structure of the campi flegrei caldera southern italy from ambient noise rayleigh wave analysis abstract shear wave velocities v s are defined in the uppermost 1 2 km of the campi flegrei caldera through the non linear inversion of the group velocity dispersion curves of fundamental mode rayleigh waves extracted from ambient noise cross correlations between two receivers noise recordings three months long at 12 seismic stations are cross correlated between all couples of stations the experiment provided successful results along 54 paths inter stations distance of which 27 sampled a depth 1 km v s contour lines are drawn from 0 06 km b s l to 1 km depth b s l and show difference between the offshore gulf of pozzuoli and coastline and the onshore areas at 0 06 km b s l the gulf of pozzuoli and the coastline are characterized by v s of 0 3 0 5 km s and of 0 5 0 7 km s respectively such velocities are typical of neapolitan pyroclastic soils and fractured or altered tuffs the inland shows v s in the range 0 7 0 9 km s typical of neapolitan compact tuffs velocities increase with depth and at 1 km depth b s l velocities lower than 1 5 km s are still present in the gulf and along the coastline while velocities higher than 1 9 km s characterize the eastern sector grossly coincident with the neapolitan yellow tuff caldera rim the s vito plain and the area between solfatara and sw of astroni such features are much more evident along two cross sections drawn in the offshore and onshore sectors by integrating our v s models with literature data our models join previous noise cross correlation studies at greater scale at depths of 0 7 0 8 km hence the picture of the campi flegrei caldera is shown up to a depth of 15 km v s of about 1 7 km s corresponding to compression velocities v p of about 3 km s computed by using the v p v s ratio resulted in the inversion are found at depths of 1 1 km in the centre of the gulf of pozzuoli and at a depth of about 0 7 km b s l onshore an increment of v s velocity 1 9 2 0 km s is locally observed onshore which might be attributed to a layer of tuffs and tuffites interbedded with thin lava beds according to the correlation of v s with stratigraphies in the deep drillings of s vito

vs models in the historical centre of naples southern italy from noise cross correlation abstract ambient noise measurements have been performed in the historical centre of naples southern italy along 40 paths inter receiver distances with a length ranging from 300 m to 1550 m for recording time variable from few hours to several months synchronous noise recordings at two receivers 1 bit normalized have been cross correlated in order to estimate the empirical green s function surface wave train of the medium between them the fundamental mode raleigh waves have been extracted at periods ranging from 0 15 s to 1 s by using the frequency time analysis technique average group velocity dispersion curves with error bar have been evaluated along 28 paths and inverted with a non linear approach to get v s profiles extending to depths of 50 300 m comparison of v s with some deep drillings and two down hole measurements lets to argue important findings first of all there is a good agreement with shallow about 35 m point down hole measurements the historical centre of naples results to be characterized by a cover of man made ground and pyroclastics of recent activity with thickness of 15 30 m and v s lower than 400 m s the products of the neapolitan yellow tuff eruption have a thickness of about 80 m and are characterized by v s of 500 700 m s in the shallower altered and fractured part and of 700 900 m s in the deeper compact part below them separated by a thin layer of the campanian ignimbrite that cannot be resolved by the data ancient tuffs or marine sands are present which are locally responsible of velocity decrease v s of 1100 1300 m s ascribable to intercalations of volcanic and sedimentary marls conglomerates and marly sands rocks are detected at 200 m depth in the ancient part of the historical centre rising to 100 m depth in the north east of it this study also gives an important contribution to microzoning studies the top of the lithoid neapolitan yellow tuff cannot be considered as the top of the seismic bedrock being characterized by 500 m s s s 800 m s is deeper sometimes at depths 100 m

diffusion of methane and ethane through the reservoir cap rock implications for the timing and duration of catagenesis to maintain natural gas reserves for even short periods of geologic time there must be an influx of gas to the reservoir to balance any loss because molecular diffusion through the reservoir cap rock is generally regarded as the slowest loss mechanism the minimum influx rate necessary to maintain the reserves is the same as the diffusive loss rate fick s first law of diffusion modified with the stokes einstein relation and the archie equation provides a conservative estimate for the rate of diffusion through a porous medium such as the reservoir cap rock as an example the diffusive flux of methane and ethane through the cap rock of the mcclave field in southeastern colorado was calculated assuming a shale cap rock porosity of only 5 the entire volume of methane would have to be replaced in less than 2 3 m y and 5 3 m y for ethane to maintain the reserves using 10 porosity the replacement time falls to less than 500 000 yr for methane and 1 2 m y for ethane unless natural gas fields are short lived ephemeral phenomena there must be ongoing generation and migration of gas to the reservoir to at least balance the diffusional loss this balance requires that catagenesis be an ongoing and recent phenomenon

a review of the source behaviour and distribution of arsenic in natural waters the range of as concentrations found in natural waters is large ranging from less than 0 5 g l 1 to more than 5000 g l 1 typical concentrations in freshwater are less than 10 g l 1 and frequently less than 1 g l 1 rarely much higher concentrations are found particularly in groundwater in such areas more than 10 of wells may be affected defined as those exceeding 50 g l 1 and in the worst cases this figure may exceed 90 well known high as groundwater areas have been found in argentina chile mexico china and hungary and more recently in west bengal india bangladesh and vietnam the scale of the problem in terms of population exposed to high as concentrations is greatest in the bengal basin with more than 40 million people drinking water containing excessive as these large scale natural as groundwater problem areas tend to be found in two types of environment firstly inland or closed basins in arid or semi arid areas and secondly strongly reducing aquifers often derived from alluvium both environments tend to contain geologically young sediments and to be in flat low lying areas where groundwater flow is sluggish historically these are poorly flushed aquifers and any as released from the sediments following burial has been able to accumulate in the groundwater arsenic rich groundwaters are also found in geothermal areas and on a more localised scale in areas of mining activity and where oxidation of sulphide minerals has occurred the as content of the aquifer materials in major problem aquifers does not appear to be exceptionally high being normally in the range 1 20 mg kg 1 there appear to be two distinct triggers that can lead to the release of as on a large scale the first is the development of high ph 8 5 conditions in semi arid or arid environments usually as a result of the combined effects of mineral weathering and high evaporation rates this ph change leads either to the desorption of adsorbed as especially as v species and a range of other anion forming elements v b f mo se and u from mineral oxides especially fe oxides or it prevents them from being adsorbed the second trigger is the development of strongly reducing conditions at near neutral ph values leading to the desorption of as from mineral oxides and to the reductive dissolution of fe and mn oxides also leading to as release iron ii and as iii are relatively abundant in these groundwaters and so4 concentrations are small typically 1 mg l 1 or less large concentrations of phosphate bicarbonate silicate and possibly organic matter can enhance the desorption of as because of competition for adsorption sites a characteristic feature of high groundwater as areas is the large degree of spatial variability in as concentrations in the groundwaters this means that it may be difficult or impossible to predict reliably the likely concentration of as in a particular well from the results of neighbouring wells and means that there is little alternative but to analyse each well arsenic affected aquifers are restricted to certain environments and appear to be the exception rather than the rule in most aquifers the majority of wells are likely to be unaffected even when for example they contain high concentrations of dissolved fe

changes in the as solid speciation during weathering of volcanic ashes a xas study on patagonian ashes and chacopampean loess abstract x ray absorption spectroscopy xas was used to determine the oxidation state of as local chemical coordination and the relative proportion of different as species in recent and ancient andean volcanic ashes as well as in chaco pampean loess as k edge xanes analysis indicates that in loess sediments the dominant species is as v i e 91 conversely as iii is dominant in all ash samples in the puyehue sample only as iii species were determined while in both the chaiten and the ancient tephra samples as iii species accounts for 66 of the total as the remaining 34 corresponds to as 1 in the chaiten sample and to as v in the weathered tephra the proposed exafs models fit well with the experimental data suggesting that in ancient and recent volcanic ashes as iii is likely related to as atoms present as impurities within the glass structure forming hydroxide species bound to the al si network in addition the identified as 1 species is related to arsenian pyrite while in the ancient volcanic ash as v was likely a product of incipient weathering in loess sediments the identified as v species represents arsenate ions adsorbed onto fe oxy hydr oxides forming inner sphere surface complexes in a bidentate binuclear configuration

peculiarities of surface wave propagation across central eurasia abstract the recent installation of six broadband digital iris ida seismic stations in the ussr has provided new opportunities for studying surface wave propagation across eurasia group velocities of fundamental rayleigh and love modes between epicenters and these stations were determined for 35 events that occurred since april 1989 to the middle of july 1990 near eurasia differential phase velocities were found for the same arrivals along paths between several pairs of stations group and phase velocities were obtained in the period range from 15 to 300 sec frequency time polarization analysis was used for studying polarization properties of surface waves in some cases significant anomalies in the particle motion for periods up to 100 sec were observed they are attributed to surface wave refraction and scattering due to lateral inhomogeneities at the boundaries and inside the eurasia continent

primary migration by diffusion through kerogen ii hydrocarbon diffusivities in kerogen abstract laboratory experiments were performed to assess diffusion through kerogen as a mechanism of liquid hydrocarbon transport through fine grained rocks such transport can be important in primary migration within source rocks and in leakage through seals previous work with organic coated model cores has shown that hydrocarbon diffusion through organic matter networks can be substantially greater than hydrocarbon diffusion through aqueous pore space in the present work natural kerogen networks were evaluated experiments with five natural source rocks showed that kerogen increased the experimental hydrocarbon flux over the calculated hydrocarbon flux through pore water in only one of these source rocks the richest 2 2 toc carbonate sample effective diffusivities through kerogen were calculated for the two experimental hydrocarbons through this sample the results were extended with the wilke chang correlation to yield diffusivities of several other hydrocarbons through similar source rocks

role of diffusion in primary migration of hydrocarbons the following effective diffusion coefficients d cm2 sec were determined for the diffusion of light hydrocarbons through the water saturated pore space of shales methane 2 12 10 6 ethane 1 11 10 6 propane 5 55 10 7 iso butane 3 75 10 7 n butane 3 01 10 7 n pentane 1 57 10 7 n hexane 8 20 10 8 n heptane 4 31 10 8 and n decane 6 08 10 9 on the basis of these new data a deterministic dynamic model was set up to simulate the diffusive transport of light hydrocarbons c1 to c10 from source rocks for eight documented source rock units representing a wid range of geologic conditions maturities of 0 40 to 1 35 mean vitrinite reflectance oil to gas prone kerogens the cumulative amounts of hydrocarbons escaping with time were calculated thus it was shown that diffusion represents an effective process for primary migration of gas but not for oil the rate of mass transport for gas from source rocks with geologic time can be sufficiently high to account for the origin of commercial size gas fields for example a cumulative amount of 109 kg of methane 1 5 109 std m3 or 5 3 1010 scf has escaped by diffusion in 540 000 years from a certain volume 1 000 km2 by 200 m thick of a high mature gas prone mesozoic source rock in western canada the origin of hydrocarbon accumulations with high gas to oil ratios in low mature sediments in geologically young basins early gases and condensates can be explained by an early phase of primary migration predominantly based on diffusion during the initial stages of the accumulation history of those fields extending up to millions of years under certain conditions the reservoir gas changes with geologic time from a methane rich to a wet gas composition at low maturity levels below about 0 6 rm even oil prone source rocks yield methane rich light hydrocarbon mixtures by migration through diffusion compositional trends among reservoir gases of several multiple pay gas fields in louisiana represent evidence for diffusive transport of hydrocarbons the variation in gas composition between the individual pay zones is controlled by increasing distances of diffusive transport of the hydrocarbons from a uniform source rock at depth to their present accumulation sites in the shallow pay zones compounds of high diffusivity are enriched for example in the sligo gas field of louisiana the methane ethane and the iso butane n butane ratios increase from 10 2 to 36 0 and from 0 86 to 1 13 respectively from the deepest to the shallowest of the five productive reservoir sands which are spread over a a depth interval of 5 500 ft 1 676 m diffusion of light hydrocarbons in the subsurface can also have economically adverse effects for example existing gas accumulations can be destroyed by dissipation the rate of this destruction was calculated for the harlingen gas field holland by diffusive loss through 400 m of shale cap rock the initial amount of methane in place of 1 93 109 std m3 6 8 1010 scf is reduced by one half over a period of 4 5 million years this leads us to propose the concept that large gas accumulations can persist through extended periods of geologic time only as dynamic systems reaching some kind of steady state equilibrium between diffusive loss through the cap rock and continuous replenishment from the source rock

seismic observations of meteors coupling theory and observations to date coupling of acoustic waves directly with the earth s surface represents the bulk of the observed meteor related seismic signals while precursory and impact related seismic waves remain an observational rarity with proliferation of infrasound and seismic monitoring systems new opportunities exist to explore the relationship between earth s atmosphere andsurface continued studyofmeteorseismologywillleadto new methods to constrain energies sizes and fluxes for moderately cm to m sized meteoroids on earth and potentially on mars

v s profiles from noise cross correlation at local and small scale ambient noise measurements have been performed at local and small scales in the neapolitan and surrounding areas campania southern italy by employing two broad band kinemetrics q330 stations equipped with episensor es t three component accelerometers in both experiments frequency time analysis ftan method has been performed on the vertical and radial components of noise cross correlations to retrieve the rayleigh wave dispersion green s function at local scale over an interstation distance of about 26 km the group velocity dispersion values have been compared with those obtained from ftan analysis on recordings of two earthquakes with similar path at small scale measurements have been carried out over an interstation distance of about 440 m in the public gardens of scampia the northernmost quarter of naples the rayleigh wave group velocity dispersion data obtained from noise cross correlation have been combined with those from active seismic experiment along the same alignment but shorter 120 m offset the non linear inversion of such a dispersion curve has allowed the definition of v s models to depths of 100 m in agreement with nearby stratigraphy moreover a good agreement has resulted for the resonance frequency among the h v ratio the ellipticity of the fundamental mode computed for the chosen v s model and the average two dimensional 2d spectral amplification computed along a cross section representative of the scampia quarter

the restless resurgent campi flegrei nested caldera italy constraints on its evolution and configuration abstract we have collected new stratigraphic data in the campi flegrei caldera through surface geological mapping and study of cores drilled to various depths we integrate these data with geological geochronological and geophysical constraints available in the literature to reconstruct the volcanic and deformational history of the caldera the caldera is a resurgent nested structure resulting from two main collapses related to the campanian ignimbrite 37 ka and the neapolitan yellow tuff 12 ka eruptions while the structure is affected by a broad subsidence ongoing local resurgence and unrest occur inside the younger nested caldera structure although most of the caldera floor consists of multiple structural blocks due to long term deformations magmas were able to erupt only in one sector of the resurgent part the caldera has shown signs of unrest during the past 25 years with short term deformations that have generated a net uplift of 3 5 m the short term deformations are related to the neapolitan yellow tuff caldera resurgence and interpreted as the net result of brittle and ductile components the long term deformations likely represent the sum of the permanent brittle component of each short term deformational event

s waves profiles from noise cross correlation at small scale abstract cross correlations of ambient seismic noise recordings are studied to infer shear wave velocities vs profiles versus depth experiments are performed over inter station distances ranging from 60 m to about 400 m in the crowded and noisy historical centre of napoli where the conditions for the use of active controlled source seismic spreadings are prohibitive even for just one receiver from the noise cross correlation group velocity dispersion curves are extracted with ftan method and their non linear inversion supplies vs profiles versus depth the information of nearby stratigraphies and the range of vs variability for samples of neapolitan soils and rocks confirms the validity and reliability of the results obtained with our expeditious procedure if successfully tested in other geological settings the proposed approach is a low cost methodology to get reliable vs velocity profiles versus depth

loess of southern south america abstract loess and loessoid loess like reworked loess sediments extend across the chaco pampean plains and the nw mountain environments of argentina and in neighbouring countries paraguay brazil uruguay bolivia loessoid sediments are much more abundant than primary loess the beginning of the loessoid sedimentation cycle was related to a phase of late miocene orogeny in the andes the plio pleistocene record is mostly composed of loessoid sediments modified by pedogenesis which produced welded palaeosols the late pleistocene holocene loess record reveals a heterogeneous composition across the region coarse textures and an andean derived volcanic composition prevail in the southern pampas finer textures and material coming from the andes and the other two sources sierras pampeanas and the parana basin characterize the loess deposits of the northern pampas and the eastern chaco a southern patagonian source is also suggested for the mountain valley loess of tucuman although a western andean provenance has been proposed it is believed that the material in the western chaco was derived from the bolivian andes loess deposition was related to a multistage transport mechanism involving fluvial and aeolian processes inferred westerly and southwesterly wind directions as dominant carriers of the aeolian deposits are in agreement with westerly palaeowind simulations using climate models however the role played by westerly tropospheric winds and northerly winds remains to be established

arsenic associations in sediments from the loess aquifer of la pampa argentina groundwater from the quaternary loess aquifer of la pampa central argentina has significant problems with high concentrations of as up to 5300 g l 1 as well as other potentially toxic trace elements such as f b mo u se and v total as concentrations in 45 loess samples collected from the aquifer have a range of 3 18 mg kg 1 with a mean of 8 mg kg 1 these values are comparable to world average sediment as concentrations five samples of rhyolitic ash from the area have as concentrations of 7 12 mg kg 1 chemical analysis included loess sediments and extracted porewaters from two specially cored boreholes results reveal a large range of porewater as concentrations being generally higher in the horizons with highest sediment as concentrations the displaced porewaters have as concentrations ranging up to 7500 g l 1 as well as exceptionally high concentrations of some other oxyanion species including v up to 12 mg l 1 the highest concentrations are found in a borehole located in a topographic depression which is a zone of likely groundwater discharge and enhanced residence time comparison of sediment and porewater data does not reveal unequivocally the sources of the as but selective extract data acid ammonium oxalate and hydroxylamine hydrochloride suggest that much of the as and v is associated with fe oxides primary oxides such as magnetite and ilmenite may be partial sources but given the weathered nature of many of the sediments secondary oxide minerals are probably more important extract compositions also suggest that mn oxide may be an as source the groundwaters of the region are oxidising with dissolved o2 no3 and so4 normally present and as v usually the dominant dissolved as species under such conditions the solubility of fe and mn oxides is low and as mobilisation is strongly controlled by sorption desorption reactions desorption may be facilitated by the relatively high ph conditions of the groundwaters in the region 7 0 8 8 and high concentrations of potential competitors e g v p hco3 phreeqc modelling suggests that the presence of v at the concentrations observed in the pampean porewaters can suppress the sorption of as to hydrous fe iii oxide hfo by up to an order of magnitude bicarbonate had a comparatively small competitive effect oxalate extract concentrations have been used to provide an upper estimate of the amount of labile as in the sediments a near linear correlation between oxalate extractable and porewater as in one of the cored boreholes investigated has been used to estimate an approximate kd value for the sediments of 0 94 l kg 1 this low value indicates that the sediments have an unusually low affinity for as

the uppermost crust structure of ischia southern italy from ambient noise rayleigh waves abstract ambient noise measurements were performed at the island of ischia southern italy along alignments of 2 4 7 km by using two three component seismic stations synchronous noise recordings of 2 20 h were cross correlated over 20 30 s windows stacked and iteratively band pass filtered to enhance the dispersive wave trains frequency time analysis was performed on the vertical and radial components of cross correlations and the fundamental mode rayleigh wave group velocity was obtained validation of the dispersion data was possible with those obtained from an earthquake recording along a close path the non linear inversion of average rayleigh wave group velocity dispersion curves along 13 paths receiver inter distances allowed the definition of shear wave velocity models in the uppermost 1 2 km of the crust the correlation of vs profiles vs depth and drilling stratigraphy allowed to attribute vs lower than 1 km s to tuffs and vs of 1 41 km s to very fractured lavas higher vs are found in the central area of the island in correspondence of the resurgent area the top of the trachytic lava basement with vs of 2 2 2 4 km s and density of 2 3 g cm3 is about 0 6 0 7 km deep b s l in the centre of ischia below altered very fractured lava or thermally altered tuff

arsenic and iron speciation in uranium mine tailings using x ray absorption spectroscopy abstract in northern saskatchewan canada high grade u ores and the resulting tailings can contain high levels of as an environmental concern in the u mining industry is the long term stability of as within tailings management facilities tmfs and its potential transfer to the surrounding groundwater to mitigate this problem u mill effluents are neutralized with lime to reduce the aqueous concentration of as this results in the formation of predominantly fe 3 as 5 secondary mineral phases which act as solubility controls on the as in the tailings discharged to the tmf because the speciation of as in natural systems is critical for determining its long term environmental fate characterization of as bearing mineral phases and complexes within the deposited tailings is required to evaluate its potential transformation solubility and long term stability within the tailings mass in this study synchrotron based bulk x ray absorption spectroscopy xas was used to study the speciation of as and fe in mine tailings samples obtained from the deilmann tmf at key lake saskatchewan comparisons of k edge x ray absorption spectra of tailings samples and reference compounds indicate the dominant oxidation states of as and fe in the mine tailings samples are 5 and 3 respectively largely reflecting their generation in a highly oxic mill process deposition in an oxidized environment and complexation within stable oxic phases linear combination fit analyses of the k edges for the fe x ray absorption near edge spectra xanes to reference compounds suggest fe is predominantly present as ferrihydrite with some amount of the primary minerals pyrite 8 15 in some samples and chalcopyrite 5 15 in some samples extended x ray absorption fine structure exafs analysis of as k edge spectra indicates that as 5 arsenate present in tailings samples is adsorbed to the ferrihydrite though an inner sphere bidentate linkage

geochemistry of a late quaternary loess paleosol sequence in central argentina implications for weathering sedimentary recycling and provenance abstract a loess paleosol sequence in the pampean plain central argentina was analyzed geochemically in order to evaluate the weathering signature and sedimentary recycling as well as to analyze the origin of these loessic sediments corralito i sequence is composed of three paleosols and a buried soil separated by loess layers the loess paleosol sequence shows a similar geochemical composition throughout suggesting that pedogenesis has not been intense enough to mask the chemical signature of the parent material weathering indices cia ciw pia and lwi elemental ratios rb sr cao tio2 and na2o tio2 and the a cn k ternary diagram indicate incipient chemical alteration for this sequence compatible with a weathering limited regime as expected paleosols cias 60 exhibit a slightly higher chemical alteration than loess layers cias 58 mass balance calculations reveal the losses of some major oxides i e cao na2o and sr in the buried soil and paleosols compared to its loess mantles reflecting the weathering of plagioclase besides the losses of k2o and ba in the buried soil and paleosols i and ii when compared to its loess layers suggest the chemical alteration of k feldspar the chemical alteration of volcanic glass is evidenced by the relative losses of as in almost all levels conversely the relative gains of fe2o3 and mgo reveal that pyroxenes and amphiboles or fe oxy hydroxides are concentrated in paleosols and the buried soil compared to its loess mantles the geochemical approach used to constrain the origin of these pampean plain loessic sediments indicates they derive mainly from the andean region conversely the pampean ranges the parana river basin and uruguayan precambrian outcrops which were pointed out as minor local sources do not contribute significantly to the loess deposits this work also shows that corralito i loess paleosol sequence and other loess samples from argentina do not evidence sedimentary recycling suggesting that these pampean plain loess deposits are mainly composed by young materials derived from undifferentiated volcanic rocks

shear wave velocities and primary influencing factors of campi flegrei neapolitan deposits abstract the campi flegrei caldera italy has been the site of intense seismic activity over the past decades this area is densely populated and includes important towns such as napoli with historical sites and supporting many industries for the proper use and management of the region the evaluation of the dynamic properties of near surface rocks is necessary the volcanological pattern has been reconstructed from the lithostratigraphies of several drillings the most interesting and widespread pyroclastic products are the pozzolana deposit soil and the neapolitan yellow tuff rock both pozzolana and tuff products are covered by recent eluvial and coastal sandy deposits and younger volcanic products

generation accumulation and resource potential of biogenic gas biogenic gas is generated at low temperatures by decomposition of organic matter by anaerobic microorganisms more than 20 of the world s discovered gas reserves are of biogenic origin a higher percentage of gases of predominantly biogenic origin will be discovered in the future biogenic gas is an important target for exploration because it occurs in geologically predictable circumstances and in areally widespread large quantities at shallow depths in rapidly accumulating marine sediments a succession of microbial ecosystems leads to the generation of biogenic gas after oxygen is consumed by aerobic respiration sulfate reduction becomes the dominant form of respiration methane generation and accumulation become dominant only after sulfate in sediment pore water is depleted the most important mechanism of methane generation in marine sediments is the reduction of co2 by hydrogen electrons produced by the anaerobic oxidation of organic matter co2 is the product of either metabolic decarboxylation or chemical decarboxylation at slightly higher temperatures the factors that control the level of methane production after sediment burial are anoxic environment sulfate deficient environment low temperatu e availability of organic matter and sufficient space the timing of these factors is such that most biogenic gas is generated prior to burial depths of 1 000 m in marine sediments most of the biogenic gas formed can be retained in solution in the interstitial pore waters because of higher methane solubility at the higher hydrostatic pressures due to the weight of the overlying water column under certain conditions of high pressures and or low temperatures biogenic methane combines with water to form gas hydrates biogenic gas usually can be distinguished from thermogenic gas by chemical and isotopic analyses the hydrocarbon fraction of biogenic gas consists predominantly of methane the presence of as much as 2 of heavier hydrocarbons can be attributed to admixture of minor thermogenic gas due to low temperature degradation of organic matter the amounts of hydrocarbon components other than methane generally are proportional to temperature age and organic matter content of the sediments biogenic methane is enriched in the light isotope 12c dgr13c1 lighter than 55 ppt owing to kinetic isotope fractionation by methanogens the variations in isotopic composition of biogenic methane are controlled primarily by dgr13c of the original co2 substrate which reflects the net isotopic effect of both addition and removal of co2 the methane isotopic composition also can be affected by mixing of isotopically heavier thermogenic gas the possible complicating factors require that geologic chemical and isotopic evidence be considered in attempts to interpret the origin of gas accumulations accumulations of biogenic gas have been discovered in canada germany italy japan trinidad the united states and ussr in cretaceous and younger rocks at less than 3 350 m of burial and in marine and nonmarine rocks other gas accumulations of biogenic origin have undoubtedly been discovered however data that permit their recognition are not available

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

a physically sound way of using noise measurements in seismic microzonation applied to the urban area of napoli noise measurements have been done in the urban area of napoli italy a densely and crowded populated city of southern italy with historical architectonic heritage often damaged by tectonic earthquakes noise has been recorded by kinemetrics q330 station with a 3 component episensor broadband accelerometer the h v ratio between the mean of the fourier spectra of the horizontal components and the spectrum of the vertical component has been computed for 20 s windows and averaged on about 150 windows of noise data noise has been measured at sites with detailed shear wave velocity profiles obtained from the non linear inversion hedgehog method of the group velocity dispersion curve of rayleigh fundamental mode extracted with ftan method from active seismic surveys ellipticities of all modes rayleigh waves and spectral amplifications both with sophisticated algorithms like mode summation and finite difference techniques and simplified 1 d techniques have been computed it turns out that the fundamental and at times also higher modes rayleigh waves are present at the resonance frequency of the soil cover where the maximum spectral value of noise h v shows resemblance to the main peak of computed spectral amplifications although the match at the resonance frequency realistic computed amplifications must be assumed for seismic microzonation hence a novel use of noise measurements is proposed which consists of a rapid detailed mapping of the computed spectral amplifications and average physical properties starting from the fit of the main peak frequency 2007 elsevier b v all rights reserved

an overview on the seismic zonation and microzonation studies in india abstract the present study presents a review on the progressive development of the seismic zonation map of india both from official agencies and also from independent individual studies the zonation map have been modified and updated regularly with the occurrence of major destructive earthquakes over the years in the indian subcontinent with the addition of new data this study discusses the criteria chosen for the progressive zonation and the major earthquakes that were responsible for retrospection of the earlier published maps the seismic zonation maps of india have also been prepared by various independent workers by adopting different approaches to achieve the purpose of the zonation despite the endeavors from various sources to provide a solution for the problem of earthquake hazards in india there were many limitations on the zonation map as it gives the picture at a regional scale mostly on the bedrock level without addressing the local site conditions but nevertheless the seismic zonation map gives basic guidelines for any region to know the hazard scenario and if any city or urban population is under threat from seismic point of view further site specific seismic microzonation may be carried out in the international scenario the global seismic hazard assessment program gshap in 1999 prepared a hazard map for world in terms of peak ground acceleration pga with a 10 probability of exceedance in 50 years but it turned out to be an underestimation of the hazard parameter when compared with the observed pga to tackle the problem of seismic hazards there was a need to have a detail study on the local site conditions in terms of its geological geophysical and geotechnical properties with the advent of better instrumentation and knowledge on the mechanics of earthquakes it was possible to identify zones of hazards at a local level and this gives rise to the study of seismic microzonation seismic microzonation work has been carried out in india in some of the strategic important mega cities and industrial build up that has the potential of being damaged from future earthquakes as has been shown in the past though the microzonation map is not the final output map as it can still be updated at later stage with more input data it does provide a more realistic picture on the site specific seismic hazard