tomographic determination of velocity and depth in laterally varying media estimation of reflector depth and seismic velocity from seismic reflection data can be formulated as a general inverse problem the method used to solve this problem is similar to tomographic techniques in medical diagnosis and we refer to it as seismic reflection tomography seismic tomography is formulated as an iterative gauss newton algorithm that produces a velocity depth model which minimizes the difference between traveltimes generated by tracing rays through the model and traveltimes measured from the data the input to the process consists of traveltimes measured from selected events on unstacked seismic data and a first guess velocity depth model usually this first guess model has velocities which are laterally constant and is usually based on nearby well information and or an analysis of the stacked section the final model generated by the tomographic method yields traveltimes from ray tracing which differ from the measured values in recorded data by approximately 5 ms root mean square the i

leachate analyses of volcanic ashes from stromboli volcano a proxy for the volcanic gas plume composition 1 many volcanoes show a change in chemical composition of the gas phase prior to periods of eruptive activity fine grained tephra erupted from active vents and transported through volcanic plumes can adsorb and therefore rapidly scavenge volatile elements such as sulfur halogens and metal species in the form of soluble salts adhering to ash surfaces analysis of such water soluble surface materials is a suitable supplement for remote monitoring of volcanic gases at inaccessible volcanoes in this work ash samples of the 2004 to 2009 eruptive activity of stromboli volcano were sampled leached and analyzed for major and trace elements data analysis and interpretation was focused on determining the relationship between chemical composition of water soluble components adhering to volcanic ash and the volcano s activity state first results show significant temporal variations in ash leachate compositions reflecting changes in the eruptive style of the volcano in particular we reveal that ash leachates s f and mg na ratios showed marked increases prior to a large scale explosion on 15 march 2007

inversion of reflection seismograms by differential semblance analysis algorithm structure and synthetic examples1 seismograms predicted from acoustic or elastic earth models depend very non linearly on the long wavelength components of velocity this sensitive dependence demands the use of special variational principles in waveform based inversion algorithms the differential semblance variational principle is well suited to velocity inversion by gradient methods since its objective function is smooth and convex over a large range of velocity models an extension of the adjoint state technique yields an accurate estimate of the differential semblance gradient non linear conjugate gradient iteration is quite successful in locating the global differential semblance minimum which is near the ordinary least squares global minimum when coherent data noise is small several examples based on the 2d primaries only acoustic model illustrate features of the method and its performance

atmospheric chemistry of a 33 34 hour old volcanic cloud from hekla volcano iceland insights from direct sampling and the application of chemical box modeling 1 on 28 february 2000 a volcanic cloud from hekla volcano iceland was serendipitously sampled by a dc 8 research aircraft during the sage iii ozone loss and validation experiment solve i it was encountered at night at 10 4 km above sea level in the lower stratosphere and 33 34 hours after emission the cloud is readily identified by abundant so2 1 ppmv hcl 70 ppbv hf 60 ppbv and particles which may have included fine silicate ash we compare observed and modeled cloud compositions to understand its chemical evolution abundances of sulfur and halogen species indicate some oxidation of sulfur gases but limited scavenging and removal of halides chemical modeling suggests that cloud concentrations of water vapor and nitric acid promoted polar stratospheric cloud psc formation at 201 203 k yielding ice nitric acid trihydrate nat sulfuric acid tetrahydrate sat and liquid ternary solution h2so4 h2o hno3 sts particles we show that these volcanically induced pscs especially the ice and nat particles activated volcanogenic halogens in the cloud producing 2 ppbv clox this would have destroyed ozone during an earlier period of daylight consistent with the very low levels of ozone observed this combination of volcanogenic pscs and chlorine destroyed ozone at much faster rates than other pscs that arctic winter elevated levels of hno3 and noy in the cloud can be explained by atmospheric nitrogen fixation in the eruption column due to high temperatures and or volcanic lightning however observed elevated levels of hox remain unexplained given that the cloud was sampled at night

rainwater and ash leachate analysis as proxies for plume chemistry at soufriere hills volcano montserrat chloride and sulphate concentrations in rainwater and water soluble leachates from volcanic ash samples track the compositions of gas emissions at the soufriere hills volcano montserrat from 1996 to 2001 there are both systematic spatial and temporal variations in the chloride sulphate ratio expressed as the equivalent hcl so2 mass ratio in rainwater and ash leachates temporal variations reflect changes in eruption rate and eruptive style mass ratios of hcl so2 in ash leachates correspond closely with those obtained by open path fourier transform infrared op ftir spectroscopy and reflect changes in volatile emissions throughout the eruption both leachate and op ftir spectroscopic analyses show mass ratios of hcl so2 1 during dome growth and hcl so2 1 during non eruptive periods the hcl so2 mass ratios in rainwater samples from 1996 and 1997 show temporal variations that correlate with changes in extrusion rate the hcl so2 ratios in plume affected rainwater and ash leachates from june and july 2001 correlate positively with increasing rockfall energy and with increasing eruption rate prior to a dome collapse event the hcl so2 mass ratios in water soluble ash leachates and rainwater samples collected at the same time and from the same sites are linearly correlated with rainwater hcl so2 ratios systematically two to three times higher than ash leachate ratios spatial patterns of rainwater ph and hcl so2 in rainwater and ash leachates are principally influenced by the proximity of the sampling sites to the active dome and to the typical pattern of dispersion of the plume by tropospheric winds these results demonstrate that rainwater chemistry and ash leachate analysis provides a useful indicator of volcanic activity and represents a valuable supplement to volcano surveillance efforts

major ion bulk deposition around an active volcano mt etna italy bulk atmospheric deposition of major cations na k ca mg and anions cl f so4 were measured at 15 sites around an active volcano mount etna from 2001 to 2003 their composition indicates several natural sources among which deposition of plume derived volcanogenic gas compounds is prevalent for f cl and s plume derived acidic compounds are also responsible for the prevailing acidic composition of the samples collected on the summit of the volcano ph in the 2 45 5 57 range cation species have complex origin including deposition of plume volcanogenic ash and aerosols and soil dust wind re suspension of either volcanic or carbonate sedimentary rocks

oxygen and sulfur isotopic composition of volcanic sulfate aerosol at the point of emission volcanic sulfate aerosol is emitted from the vents of many active volcanoes but its origin has not yet been explained we report the first measurements of the isotopic compositions of near vent volcanic aerosol sulfate and use the combined sulfur and oxygen isotope systematics of the aerosol and magma at masaya volcano nicaragua to draw preliminary conclusions about the production mechanism of near source volcanic sulfate the sulfate aerosol does not display a significant mass independent oxygen or sulfur isotopic signature which suggests that primary volcanic aerosol does not contribute to the larger mass independent anomalies found in some ambient atmospheric aerosols and as preserved in ice cores the oxygen isotope composition of the sulfate appeared to become heavier on the particle filters with increasing amount of sample collected and suggests that the 18o value of the sulfate aerosol is 8 the sulfur isotopic composition of the sulfate did not vary with sample loading on the filters and had a mean 34s value of 7 7 0 8 similar to that of the magma 6 6 0 2 the low 17o value the 18o value of the magma 6 6 0 3 and the high 18o value of atmospheric oxygen 23 5 suggest that known atmospheric oxidation pathways at ambient temperatures are not the major routes of production for this sulfate instead the isotopic systematics of aerosol and magma are consistent with sulfate production either by high temperature equilibration of the magmatic gas mixture with small amounts of atmospheric oxygen or by direct emission of so4 2 from the magma

seismic wave equation demigration migration reverse time migration is a well known method based on a single scattering approximation it is designed to obtain seismic images in the case of a complex subsurface it can however be a very time consuming task because the number of computations is directly proportional to the number of processed sources in the context of velocity model building iterative approaches require that one derives a series of migrated sections for different velocity models we propose to replace the summation over sources by a summation over depth offsets or time delays defined in the subsurface for that we have developed a new relationship between two migrated sections obtained for two different velocity models starting from one of the two images we obtain a second section correctly and efficiently for each time delay we compute a generalized source term by extending the concept of exploding reflector to nonzero offset we obtain the final migrated section by solving the same wave equation in the perturbed model with the modified source term our work included testing the methodology on 2d synthetic data sets particularly when the initial and perturbed velocity models differ greatly

shot and angle domain wave equation traveltime inversion of reflection data synthetic and field data examples abstractfull waveform inversion requires the accurate simulation of the dynamics and kinematics of wave propagation this is difficult in practice because the amplitudes cannot be precisely reproduced for seismic waves in the earth wave equation reflection traveltime tomography wt is proposed to avoid this problem by directly inverting the reflection traveltime residuals without the use of the high frequency approximation we inverted synthetic traces and recorded seismic data for the velocity model by wt our results demonstrated that the wave equation solution overcame the high frequency approximation of ray based tomography was largely insensitive to the accurate modeling of amplitudes and mitigated problems with ambiguous event identification the synthetic examples illustrated the effectiveness of the wt method in providing a highly resolved estimate of the velocity model a real data example from the gulf of mexico demonstrated these benefits of wt but also found the limitations in traveltime

atmospheric dispersion environmental effects and potential health hazard associated with the low altitude gas plume of masaya volcano nicaragua masaya volcano 560 m a s l nicaragua re sumed its degassing activity in mid 1993 with the con tinuous emission of so 2 at rates increasing from 600 metric tons t day 1 7 0 kg s 1 in 1995 to 1800 t day 1 21 0 kg s 1 in 1999 the low altitude gas plume is typically blown westward by the prevailing wind across the masaya caldera and las sierras high lands which are at a higher elevation than the gas vent in this study the areal distribution of atmospheric so 2 concentrations was monitored within 44 km of the vent with a network of passive samplers measured so 2 air concentrations ranged from 2 to 90 ppbv in 1998 and from 2 to 230 ppbv in 1999 the data suggest that the volcanic emissions influenced air quality across a 1 250 km2 area downwind local topography exerts a strong control on plume dispersal and hilltops are particularly prone to fumigation and thus to high ambient so 2 lev els in a zone 22 km2 in size located within 15 km of the source the response of vegetation to sustained exposure to high atmospheric dose of volcanic so 2 and hf result ed in a strong reduction in the number of plant communi ties a transition zone of somewhat indefinite boundary surrounds the devastated zones and exhibits vegetation damage in the form of leaf injury in addition to the envi ronmental impacts of the volcanic emissions both short and long term public health hazards may exist in areas most exposed to the plume the harmful effects of the volcanic emissions on cultivated vegetation could be di minished by using windbreaks made of gas tolerant trees and shrubs such as eugenia jambos brosimum utile and clusia rosea the current gas crisis at masaya volcano provides an unique opportunity for investigating the at mospheric environmental and medical impacts of volca nic gases and aerosols

depletion rates of sulfur dioxide in tropospheric volcanic plumes the tropospheric sulfur cycle has been closely studied from the standpoint of anthropogenic emissions but less so with respect to volcanic sources we document here evidence for wide variation in lifetimes of volcanic so2 in the troposphere at one extreme our observations of the plume associated with the lavadome eruption of soufriere hills volcano montserrat suggest loss of gaseous so2 at rates exceeding 10 3 s 1 while this efficent so2 depletion reflects unusual environmental factors published measurements for mount etna s plume approach these rapid rates in such cases source strengths of so2 must significantly exceed apparent fluxes measured several kilometres downwind this implies that meteorological and geographic factors as well as volcanic degassing rates should be considered in the interpretation of fluxes of so2 measured beyond source vents with ramifications for volcano monitoring and eruption prediction furthermore since most calculations of global volcanic fluxes of sulfur and other species to the troposphere are based on extrapolation of so2 flux data they may underestimate true source strengths finally we consider that fast sulfur chemistry may also prevail in convecting eruption columns resulting in partial tropospheric scrubbing of sulfur from stratosphere bound plumes

halogens in volcanic systems the transport degassing and atmospheric release of halogens from active volcanism on earth have been the focus of increasing interest over the last few decades and have recently been the subject of the 1st workshop on halogens in volcanic systems and their environmental impacts that was held in december of 2007 at yosemite lodge in yosemite national park california as an introduction to this chemical geology special issue collecting contributions from many of the participants at the workshop we review here recent advances in this field including experimental and theoretical investigations of halogen behaviour in volcanic and related magmatic systems we discuss previous research on several aspects of halogen geochemistry including halogen abundances in the mantle and magmas on earth the effects of halogens on phase equilibria and melt viscosities their partitioning between melt and fluid phase s upon decompression cooling and crystallisation of magmas in the earth s crust and their final atmospheric release as volcanic gases the role of halogens in the genesis of hydrothermal systems and in the transport of ore forming metals is also reviewed and we discuss our current understanding of atmospheric processing of volcanic halogens in both the troposphere and stratosphere and their consequent impacts in spite of these recent advancements our current understanding of halogen geochemistry at active volcanoes is still far too fragmentary and the key questions that require answers from future research are summarised in our conclusions

plinian airfall deposits of basaltic composition two widespread scoria fall deposits locally known as the fontana lapilli and san judas formation are demonstrated to have issued from masaya caldera complex nicaragua and to be the first documented plinian airfall deposit of basaltic composition data from maps of median grain size average maximum pyroclast diameter and average maximum diameter of lithic fragments provide conclusive evidence of the plinian nature of both deposits the volume within the 1 mm isopach of the fontana lapilli is 12 km3 3 4 km3 dense rock equivalent and within the san judas formation it is 1 2 km3 0 35 km3 dre theoretical eruption parameters calculated for the fontana lapilli and san judas formation respectively include muzzle velocity 170 m s and 150 m s column height 50 km and 18 km volume eruption rate 2 105 m3 s and 1 104 m3 s and duration 2 h and 10 h these are all similar to the calculated parameters for silicic plinian eruptions basaltic magmas are generally considered incapable of erupting in the manner characteristic of plinian eruptions recognition of them argues that factors other than high viscosity may be of fundamental importance

so2 loss rates in the plume emitted by soufriere hills volcano montserrat to improve interpretation of volcanic so2 flux data it is necessary to quantify and understand reactions involving so2 in volcanic plumes so2 is lost in volcanic plumes through a number of mechanisms here we report so2 measurements made with miniature ultraviolet spectrometers at soufriere hills volcano montserrat a low altitude volcano 1000 m above sea level whose plume entrains humid marine air in the planetary boundary layer traverses very near 2 km downwind from soufriere hills volcano significantly underestimate at source so2 emission rates on the order of 70 146 when not accounting for the decay rate similar so2 loss is likely to occur in plumes from other tropical low altitude volcanoes under conditions of high relative humidity 20 of active volcanoes worldwide these results suggest that the global volcanic so2 emission rate may be underestimated as the estimates are based on measurements taken downwind of volcanoes by which time significant loss of so2 may have taken place the loss rates calculated here could be used in conjunction with downwind so2 fluxes to estimate at source so2 emission rates from volcanoes with similar environmental conditions to those at soufriere hills volcano

sulfur and halogen gases at masaya caldera complex nicaragua total flux and variations with time santiago crater of masaya caldera complex near managua nicaragua entered a phase of intense magmatic degassing in late 1979 the flux of so2 increased rapidly from a previous average of 380 t d 1 to approximately 1200 t d 1 in february 1980 we report on results of a study of the gas flux and geochemistry conducted as part of a broader interdisciplinary study of the volcano and its impact on the adjacent environment masaya is an unusual volcano because of its low shield like form consistent tholeiitic basaltic composition frequent activity and especially because of the approximately 25 year cycle of major non eruptive degassing crises we have used a combination of techniques involving remote sensing using a correlation spectrometer cospec of the flux of so2 and direct filter sampling of the ratios of the sulfur and halogen gases and aerosols to quantify the flux of all of these species the three stage filters successively trap aerosols halogen acid gases and sulfur dioxide and are analyzed by ion chromatography we have used the ratios of various species with the cospec measurements of the flux of so2 to calculate that the average flux of so2 is 1275 t d 1 hcl is 830 t d 1 hf is about 16 t d 1 and hbr is at most 1 t d 1 h2s and so4 are only minor sulfur species the flux of so2 and hcl represents the largest reported noneruptive sustained volcanic release of these species in the world masaya contributed 7 of the total so2 estimated to have been released by volcanoes worldwide in 1981 the flux of so2 has declined by about 9 each year since 1979 and can be modeled as a first order kinetic rate law with a decay constant of approximately 0 04 yr 1 approximately 2 2 106 tons of so2 has been released between september 1979 and september 1985 the ratio s cl has declined more rapidly than the flux of so2 reflecting the greater solubility of hcl than so2 in the magma the so2 flux at santiago varies more widely within a single day than observed at other degassing volcanoes and may be controlled at least in part by effects of the solid earth tide an area larger than 500 km2 has been severely impacted downwind of the volcano downwind ground level concentrations of so2 of 0 25 ppm are frequently encountered acid rain unusually chloride rich has a ph as low as 2 63 s cl ratios in the gas plume increase downwind probably as a result of the high solubility and dry deposition velocity of hcl preliminary analyses of primary concentrations of sulfur and chlorine in the magma of the present lava lake are used to calculate that at least 1 2 km3 has been completely degassed with respect to sulfur to provide the observed flux this implies that 10 km3 have been degassed by previous crises in the past century and further suggests a magma supply rate of approximately 0 1 km3 yr comparable with kilauea or etna volcanoes during historic time only two lava flows have been extruded implying an unusually low ratio of extrusion intrusion of only 0 0007

trace elements in the particulate phase of the plume of masaya volcano nicaragua masaya volcano nicaragua has been passively degassing since 1993 this gas crisis provides a unique opportunity for investigating the degassing of magmatic volatiles here we studied the chemical composition of the volcanic particulate phase collected directly from the plume the objective was to gain new insights into the volatilities and emission rates of trace elements the results indicate enrichments in the aerosol phase of all analyzed trace elements including not only those known to be volatile such as cu and te but also elements considered as refractory such as rare earth elements rees and th rees were fractionated with a significant enrichment of light rare earth elements lrees over heavy rare earth elements hrees this pattern suggests degassing of lrees as chlorides in general the emission of most trace elements in volcanic plumes is governed by the primary degassing of chloride compounds however sem eds data and chemical analysis of aerosol filters allow us to state that trace elements can also be released as sulphate and chloro sulphate compounds the trace element emission rates at masaya are significant and place this volcano as a major gas emitter however for some elements like cu masaya s contribution to the global volcanic flux seems disproportionate probably pointing to the poor dataset available for other degassing volcanoes

traveltime information based wave equation inversion we propose a new wave equation inversion method that mainly depends on the traveltime information of the recorded seismic data unlike the conventional method we first apply a p transform to the seismic data to form the delayed shot seismic record back propagate the transformed data and then invert the velocity model by maximizing the wavefield energy around the shooting time at the source locations data fitting is not enforced during the inversion so the optimized velocity model is obtained by best focusing the source energy after a back propagation therefore inversion accuracy depends only on the traveltime information embedded in the seismic data this method may overcome some practical issues of waveform inversion in particular it relaxes the dependency of the seismic data amplitudes and the source wavelet

a differential semblance criterion for inversion of multioffset seismic reflection data mean square error leading to least squares inversion of multioffset reflection seismograms is insensitive to velocity trend information except in the immediate vicinity of a kinematically correct model in contrast differential semblance retains sensitivity to velocity trend changes over a wide range of models the differential semblance criterion combines mean square error with the mean square differences of inverted models from data sets at neighboring shot positions or offsets or slownesses differential semblance compares model estimates at nearby acquisition parameters which are similar even when the model velocity trends are incorrect because the method inverts the data so that the estimated model amplitudes are meaningful simple differences between the unstacked model estimates give a reliable measure of velocity error a mathematical investigation indicates that the differential semblance criterion is smooth and convex over a large range of velocity models numerical simulation using synthetic data sets verifies this contention

dynamic response characteristics and deformation evolution of loess slopes under seismic loads abstract the loess plateau is one of the most seismically and geologically active regions in china the related catastrophic earthquakes and geological disasters have caused more than 1 4 million deaths in the plateau in this study the slopes on the edge of the loess tableland in pingliang city gansu province the core area of the loess plateau are investigated based on large scale shaking table model tests and discrete element numerical simulation particle flow code pfc 2d the dynamic response characteristics and deformation evolution process of fissured and non fissured loess slopes under different seismic loads are studied the test results show that with increasing seismic load input the peak ground displacement pgd of the loess slopes increases gradually with increasing slope height for the two types of slopes the acceleration amplification effects in the slope with horizontal direction load are larger than those of the vertical direction load the amplification factor of the peak ground acceleration pga at the shoulder of the fissured slope is significantly larger than that of the non fissured slope according to the numerical simulation results of the fissured slope when the seismic load is small the bond failures are distributed densely in the initial fissured structural plane and at the model bottom regarding the non fissured slope the bond failures in the slope are mainly distributed at the bottom of the model with increasing acceleration amplitude the number of bond failures in the slopes increases rapidly when the input load increases to 0 40 g two potential slip surfaces occur in the shallow surface of the fissured slope and a potential slip surface appears at the back edge of the non fissured slope

airborne i doas measurements at mt etna bro and oclo evolution in the plume abstract spatial distributions of bromine monoxide bro chlorine dioxide oclo and sulfur dioxide so 2 were determined in the volcanic emissions of mt etna on 8th and 9th of july 2011 by airborne imaging differential optical absorption spectroscopy ai doas slant column densities scds in units of molec cm 2 of up to 4 2 10 14 for bro 1 5 10 14 for oclo and 4 6 10 18 for so 2 were detected assuming so 2 to be a stable tracer to overcome dilution effects measurements of bro so 2 and oclo so 2 ratios from distances of 1 19 km to the summit crater region were used to investigate the evolution of bro and oclo within corresponding plume ages of 2 34 min along the centerline of the plume relatively constant bro so 2 ratios of 1 4 10 4 and 2 0 10 4 were detected on 8th and 9th of july 2011 respectively furthermore the bro so 2 ratio was investigated along several cross sections of the volcanic plume on both days significant increases by a factor of 2 3 in the bro so 2 ratio from the center to the edge of the plume were seen from simultaneous measurements of bro and oclo the mixing ratios of clo could be inferred to range from about 80 to 300 ppt in addition decreases in the bro so 2 ratio with time could be observed by measurements three to four hours before the culmination of a paroxysm at mt etna on 9th july 2011

degassing of halogens from basaltic volcanism insights from volcanic gas observations abstract the currently available data set of s cl f abundances in volcanic gas plumes and high temperature fumarolic gas samples from basaltic volcanism is reviewed here in the attempt to derive constraints on the modes of halogen degassing from mafic silicate melts apart from large volcano to volcano variations reflecting remarkable differences in volatile abundances in the source magmas each of the explored volcanoes displays large changes of so2 hcl and so2 hf ratios with the style of volcanic activity with hcl hf staying fairly constant halogen abundances are low and so2 hcl and so2 hf are high when fresh volatile rich magmas sustain degassing as during explosive eruptions at the onset of eruptive cycles or shortly before paroxysmal events low so2 hcl and so2 hf ratios are instead characteristic of late stages of volcanic degassing typically being observed in the concluding stages of basaltic eruptions or during periods of reduced magma supply at persistently degassing volcanoes these observations are taken as evidence of halogens being less keen to enter the gas phase relative to s during degassing of basaltic magmas and quantitatively interpreted in light of a rayleigh type open system degassing model the model though simple quantitatively reproduces the range of volcanic gas compositions observed at basaltic volcanoes worldwide and allows prediction of vapour melt partitioning contrasts of factors 9 and 36 for the volatile couples s cl and s f respectively these predictions require validation from appropriately designed experiments of halogen partitioning between magmatic vapours and silicate melts over a range of p t x conditions

velocity inversion by differential semblance optimization differential semblance optimization dso is an approach to inversion of reflection seismograms which avoids the severe convergence difficulties associated with nonlinear least squares inversion the method exploits both moveout and amplitude characteristics of reflections we have implemented a version appropriate to plane wave p tau seismograms and layered constant density acoustic earth models theoretical and numerical analyses of this version of dso indicate that stable and reasonably accurate estimates of both velocity trend and reflectivity can be derived to test dso further we applied it to a marine data set from the gulf of mexico where the method produced results which compare favorably to well log information the method can be extended to incorporate laterally heterogeneous velocity models

a total volatile inventory for masaya volcano nicaragua nerc project magma dynamics at persistently degassing basaltic volcanoes a novel approach to linking volcanic gases and magmatic volatiles within a physical model ne f004222 1 and ne f005342 1

avo sensitive semblance analysis for wide azimuth data conventional semblance based moveout analysis models prestack reflection data with events that have hyperbolic move out and no amplitude variation with offset avo substantial amplitude variation and even phase change with offset do not significantly compromise the semblance operator however polarity reversal associated with a change in the sign of the reflection coefficient may cause conventional semblance to fail an existing modification of the semblance operator that takes amplitude variations into account so called ak semblance is limited to narrow azimuth data and cannot handle nonhyperbolic moveout at large offsets we employ a 3d nonhyperbolic moveout inversion algorithm to extend the ak semblance method to wide azimuth data recorded on long spreads to preserve velocity resolu tion the ratio k of the avo gradient and intercept is kept constant within each semblance window in the presence of azimuthal anisotropy however the parameter k has to be azimuthally dependent synthetic tests con

sweet chestnut castanea sativa leaves as a bio indicator of volcanic gas aerosol and ash deposition onto the flanks of mt etna in 2005 2007 sweet chestnut leaves castanea sativa collected from the flanks of mt etna volcano in 2005 2007 were analysed by inductively coupled plasma mass spectrometry to investigate the spatial and temporal variability of element concentrations the aim of this work was to determine whether these leaves are a bio indicator for volcanic gas aerosol and ash deposition and to gain new insights into the environmental effects of quiescent and eruptive volcanic plumes results show a positive correlation between sample variability in the concentration of elements in castanea sativa and enrichment factors of elements in the plume the spatial and temporal variability of chalcophilic elements as cd cu mo tl zn is consistent with prevailing winds transporting eruptive plumes to the south east of the summit resulting in enhanced plume deposition onto the flanks of the volcano similar spatial and temporal variability was found for the halide forming elements cs k rb and intermediate elements al co mn the spatial variability of chalcophilic intermediate and halide forming elements during quiescent periods was diminished relative to eruptive periods and could not be explained by plume deposition in contrast the concentrations of lithophilic elements ba ca mg sr did not show any clear spatial variability even during eruptive periods comparisons between enrichment factors for elements in castanea sativa and literature values for enrichment factors of the volcanic plume groundwater and lichen were made whilst castanea sativa offers insights into the spatial and temporal variability of deposition the species may not be a bio indicator for plume composition due to biological fractionation

volcanic plume monitoring at mount etna by diffusive passive sampling 1 this paper reports the use of diffusive tubes in determining hf hcl and so2 in the volcanic plume of mount etna in an attempt to highlight the potential of this method in studying volcanoes in a first application a network of 18 diffusive tubes was installed on etna s flanks aimed at evaluating the atmospheric dispersion of the volcanic plume on a local scale results showed a monotonic decrease in volatile air concentrations with distance from the craters hf from 0 15 to 0 003 mol m 3 hcl from 2 to 0 01 mol m 3 and so2 from 11 to 0 04 mol m 3 revealing the prevalently volcanic contribution matching of so2 hcl and hcl hf volatile ratios with contemporaneous measurements at the summit craters validated the use of diffusive tubes in tracing the chemical features of a volcanic plume from remote locations a first tentative assessment of dry deposition rates of volcanogenic acidic gases was also made yielding 2 5 74 t d 1 so2 0 6 17 t d 1 hcl and 0 02 0 6 t d 1 hf and revealing the potential environmental impact of gas emissions in a second experiment carried out during the recent october 2002 to february 2003 eruption of etna diffusive tubes provided a continuous record of the chemical composition of the eruptive plume from a safe distance of 1 km from the vents thus considerably decreasing the risks involved in sampling this highlighted a clear time decrease in so2 concentrations and so2 hcl ratios which was interpreted as due to progressive exhaustion of volatile degassing and eruption energy