analyzing earthquake clustering features by using stochastic reconstruction 1 on the basis of the epidemic type aftershock sequence etas model and the thinning procedure this paper gives the method about how to classify the earthquakes in a given catalogue into different clusters stochastically the key points of this method are the probabilities of one event being triggered by another previous event and being a background event making use of these probabilities we can reconstruct the functions associated with the characteristics of earthquake clusters to test a number of important hypotheses about the earthquake clustering phenomena we applied this reconstruction method to the shallow seismic data in japan and also to a simulated catalogue the results show the following assertions 1 the functions for each component in the formulation of the space time etas model are good enough as a first order approximation for describing earthquake clusters 2 a background event triggers less offspring in expectation than a triggered event of the same magnitude 3 the magnitude distribution of the triggered event depends on the magnitude of its direct ancestor 4 the diffusion of the aftershock sequence is mainly caused by cascades of individual triggering processes while no evidence shows that each individual triggering process is diffusive and 5 the scale of the triggering region is still an exponential law as formulated in the model but not the same one for the expected number of offspring

mercury emissions and stable isotopic compositions at vulcano island italy abstract sampling and analyses methods for determining the stable isotopic compositions of hg in an active volcanic system were tested and optimized at the volcanic complex of vulcano aeolian islands italy condensed gaseous fumarole hg fum t plume gaseous elemental hg g 0 and plume particulate hg p ii were obtained at fumaroles f0 f5 f11 and fa the average total hg emissions based on hgt so2 in condensed fumarolic gases and plumes range from 2 5 to 10 1 kg y 1 in agreement with published values ferrara r mazzolai b lanzillotta e nucaro e pirrone n 2000 volcanoes as emission sources of atmospheric mercury in the mediterranean basin sci total environ 259 1 3 115 121 aiuppa a bagnato e witt m l i mather t a parello f pyle d m martin r s 2007 real time simultaneous detection of volcanic hg and so2 at la fossa crater vulcano aeolian islands sicily geophys res lett 34 l21307 plume hg p ii increases with distance from the fumarole vent at the expense of hg g 0 and indicates significant in plume oxidation and condensation of fumarole hg fum t relative to the nist srm 3133 hg standard the stable isotopic compositions of hg are 202hg fum t 0 74 0 18 2sd n 4 for condensed gaseous fumarole hg fum t 202hg g 0 1 74 0 36 2sd n 1 for plume gaseous elemental hg g 0 at the f0 fumarole and 202hg p ii 0 11 0 18 2sd n 4 for plume particulate hg p ii the enrichment of hg p ii in the heavy isotopes and hg g 0 in the light isotopes relative to the total condensed fumarolic hg fum t gas complements the speciation data and demonstrates a gas particle fractionation occurring after the gas expulsion in ambient t atmosphere a first order rayleigh equilibrium condensation isotope fractionation model yields a fractionation factor cond gas of 1 00135 0 00058

nontrivial decay of aftershock density with distance in southern california the decay of the aftershock density with distance plays an important role in the discussion of the dominant underlying cause of earthquake triggering here we provide evidence that its form is more complicated than typically assumed and that in particular a transition in the power law decay occurs at length scales comparable to the thickness of the crust this is supported by an analysis of a very recent high resolution catalog for southern california sc and surrogate catalogs generated by the epidemic type aftershock sequence etas model which take into account inhomogeneous background activity short term aftershock incompleteness anisotropic triggering and variations in the observational magnitude threshold our findings indicate specifically that the asymptotic decay in the aftershock density with distance is characterized by an exponent larger than 2 which is much bigger than the observed exponent of approximately 1 35 observed for shorter distances ranging from the main shock rupture length up to a length scale comparable to the thickness of the crust this has also important consequences for time dependent seismic hazard assessment based on the etas model

first simultaneous mercury and major volatiles characterization of atmospheric hydrothermal emissions at the pisciarelli s fumarolic system campi flegrei italy abstract hydrothermal systems with active surface expressions are important natural source of atmospheric mercury here we report on the first simultaneous assessment of gaseous elemental mercury gem and major volatiles h2s and co2 fluxes from the fumarolic system of pisciarelli currently the most active at the campi flegrei caldera cfc naples italy this was achieved via a gps synchronized lumex and multigas survey which extends similar investigations reported elsewhere gem concentrations measured in the fumarolic emissions were consistently above background air level close to the degassing area mean 8 3 ng m 3 on average and ranged up to 12 000 ng m 3 our data evidenced pulsed sequences of gem increases in the fumarole plume closely matched by temporally consistent increases in co2 and h2s r2 0 9 supporting the idea that major volatiles such as co2 acts as potential carrier in transporting gem within the magmatic hydrothermal systems the slope of the best fit calculated for the dispersion of our data provides a gem co2 molar ratio of 1 1 10 8 and a gem h2s of 5 10 6 respectively these ratios are comparable to those reported for both low 100 c and high t 250 c fumaroles from non explosive volcanic hydrothermal degassing systems elsewhere we adopted an ad hoc method that combines video footages and gas measurements to obtain high precision concentration maps of gas emissions used to estimate the total atmospheric gem co2 and h2s flux of about 0 0113 225059 and 511 t y 1 respectively the human health risk assessment related to the gem emissions at pisciarelli confirms that except for the degassing fumarolic area all the main sites affected by the plume dispersion always remain well below the safe threshold recommended by the health authorities

origin of the fumarolic fluids of vulcano island italy and implications for volcanic surveillance variations in d and 18o values with h2o contents and outlet temperatures indicate that the fumaroles of la fossa crater have discharged mixtures of magmatic water and marine hydrothermal water since 1979 the contribution of meteoric water was low in the period 1979 1982 and very low afterwards the 18o values of the marine hydrothermal component of 5 to 7 2 are due to isotopic exchange with the 18o rich silicates of the rocks under high temperature and low permeability conditions the 18o value of the magmatic end member is generally 3 5 to 4 3 although values as high as 5 5 to 6 5 were reached in the summer of 1988 when magma degassing appears to have extended into the core of the magma body the d values of the end member were close to 20 typical of andesitic waters both the isotopic values and chemical data strongly support a dry model consisting of a central magmatic gas column and a surrounding hydrothermal envelope in which marine hydrothermal brines move along limited fracture zones to undergo total evaporation on approaching the conduits of magmatic fluids the vents at the eastern and western boundaries of the fumarolic field are fed by fluids whose pressure is governed by the coexistence of vapor liquid and halite giving rise to a high risk of phreato magmatic explosions should magma penetrate into these wet environments most la fossa eruptions were triggered by an initial hydrothermal blast and continued with a series of phreatomagmatic explosions the fluids discharged by the forgia vecchia fumaroles are mixed with meteoric water which is largely evaporated although subordinate loss of condensed steam may be responsible for scrubbing most of the acidic gas species the temperatures and pressures and the risk of a sudden pressure increase are low a boiling hydrothermal aquifer at 230 c is present underneath the baia di levante beach this area has a minor risk of hydrothermal explosions

seismicity rate immediately before and after main shock rupture from high frequency waveforms in japan 1 we analyze seismicity rate immediately before and after 82 main shocks with the magnitudes ranging from 3 to 5 using waveforms recorded by the hi net borehole array in japan by scrutinizing high frequency signals we detect 5 times as many aftershocks in the first 200 s as in the japan meteorological agency catalogue after correcting for the changing completeness level immediately after the main shock the aftershock rate shows a crossover from a slower decay with an omori s law exponent p 0 58 0 08 between 20 and 900 s after the main shock to a faster decay with p 0 92 0 04 after 900 s the foreshock seismicity rate follows an inverse omori s law with p 0 73 0 08 from several tens of days up to several hundred seconds before the main shock the seismicity rate in the 200 s immediately before the main shock appears steady with p 0 35 0 50 these observations can be explained by the epidemic type aftershock sequence etas model and the rate and state model for a heterogeneous stress field on the main shock rupture plane alternatively nonseismic stress changes near the source region such as episodic aseismic slip or pore fluid pressure fluctuations may be invoked to explain the observation of small p values immediately before and after the main shock

identification and spatiotemporal organization of aftershocks 1 we propose a fast method able to discriminate between poissonian independent earthquakes and aftershocks the method is based on the evaluation of the variability coefficient defined as the ratio between the standard deviation and the average value of the interoccurrence time between two successive earthquakes we apply this technique to the california and a properly constructed synthetic catalogue in order to estimate the level of background seismicity and identify seismic sequences we then investigate the spatiotemporal organization of aftershocks focusing on the distributions of interevent times and interevent distances between two successive events we find evidence for the existence of a characteristic spatial length scale related to the size of the aftershock zone whereas no typical timescale is detected

the chemical and isotopic composition of fumarolic gases and spring discharges from galeras volcano colombia abstract galeras fumarole discharges have been collected since its reactivation in 1988 through december 1995 the gases are dominated by h2o co2 s as so2 and h2s and hcl the relative proportions of these gases classify them as magmatic thermodynamic equilibrium temperatures of the gases range from 260 to 600 c the relative abundance of inert gases n2 ar and he can be used as tracers to identify the source of the fumarole discharges at galeras the majority of the samples have a composition characteristic of gases originating from arc related magmas with relatively high n2 contents and minor he and ar during 1993 the year of frequent eruptions the gas composition changed to basaltic or mantle derived gases with significantly higher he contents this is interpreted to be the result of injection of volatiles from a basaltic magma body at depth prior to and during the increased eruptive activity of 1993 the 13c values for co2 in fumarole discharges are typical of andesitic volcanoes and may indicate addition of morb derived co2 the 15n values for n2 may indicate significant contribution of n2 from marine sediments and only minor contribution of morb derived n2 the d and 18o values of the discharging steam lie on a mixing trend between the isotopic composition of arc related magmatic water and18o shifted meteoric water the most magmatic discharges have d values of 30 to 35 while the most meteoric discharges have values of 70 to 75 similar to galeras thermal spring waters galeras thermal water discharges consist of acid sulfate and bicarbonate waters s cl ratios in the acid sulfate waters are similar to fumarole ratios suggesting direct absorption of magmatic gases into shallow ground waters this is supported by the essentially meteoric d and 18o values of the discharges and by elevated3he 4he ratios of thermal spring waters the absorption of acid s and cl rich gases yield acid waters which are capable of dissolving rocks the thermal waters however are far from equilibrium with galeras lavas and pyroclastic rocks providing evidence of the immaturity of the galeras hydrothermal system the so4 and cl content as well as the o and h isotopic composition of galeras thermal springs vary with the activity of the volcano the 7 year sampling program at galeras revealed intriguing results concerning the activity of galeras its magmatic hydrothermal system and the origin of the volatiles despite decreasing outlet temperatures since 1992 deep temperatures remain high implying continued unrest in the galeras magmatic system

summit outgassing as indicated by radon mercury and ph mapping kilauea volcano hawaii abstract surface geochemical mapping of rn hg and ph on the summit of kilauea volcano hawaii has shown some of the characteristics of outgassing rn concentrations measured in shallow ground gas are highest 10 to 155 units i e up to 0 016 nci l222rn over deep structures associated with the summit caldera low 1 to 5 units over the upper rift zones which are underlain by shallow intrusions and low to negative 1 to 3 units over most of the volcanically inactive peripheral areas high rn concentrations were measured over peripheral well developed structures such as the kaoiki and koae fault systems 45 and 12 units respectively the pattern of rn values broadly suggests the existence of a summit wide convection system interrupted locally by specific permeable structures the low ph 3 5 to 5 6 of soils over the caldera is suggested to be largely due to the sulfurous component of the ground gas the low concentrations of hg 5 to 80 ppb in these soils are postulated as being partly a function of subsurface complexing of hg with the abundant sulfur the shallow intrusions below the upper rift zones appear to have outgassed much of their sulfur content so soils in these areas are only slightly acid 5 6 to 6 2 allowing the accumulation of hg to concentrations of several thousands of ppb these conditions change during extrusive and intrusive events with the increases in shallow subsurface temperatures and volatiles in ground gas producing an increase in rn concentration and a decrease in soil hg due to volatilization after such events rn concentration decreases and soil hg increases significantly

statistical features of foreshocks in instrumental and etas catalogs we study the spatial distribution of earthquakes in temporal intervals before and after the occurrence of large shocks mainshocks in the magnitude range m in 2 5 for four different regional catalogs we find that the spatial organization of pre shock seismicity depends on the mainshock magnitude and is independent of the lower magnitude threshold these properties are found to be a stable feature of regional catalogs and cannot be reproduced by epidemic type aftershock sequence models our findings suggest that the area fractured during the mainshock is encoded in the foreshock spatial organization and therefore enhance the prognostic value of foreshocks

the earthquake magnitude is influenced by previous seismicity 1 seismic occurrence is characterized by clustering in space time and magnitude correlations between magnitudes of subsequent events have been recently attributed to catalog incompleteness here we investigate the effect of catalog completeness on the amplitude of magnitude correlations the analysis of two california regions with different levels of catalog accuracy and different lower magnitude thresholds indicate that the amplitude of correlations does not depend on catalog incompleteness conversely correlations are controlled by the probability that two events belong to the same mainshock aftershock sequence numerical simulations of the etas model where magnitude correlations are absent by construction provide a counter test supporting our conclusions

noble gas isotopes in hydrothermal volcanic fluids of la soufriere volcano guadeloupe lesser antilles arc article the ascending magmatic component in la soufriere volcano guadeloupe lesser antilles was investigated by measuring noble gas concentrations and isotopic ratios in thermal springs and fumaroles a clear magmat ic helium signal 4 he 3 he 89 000 r ra 8 equivalent to the morb value is recorded in most fluids 3 he fluxes in both fumarole and springs have been estimated and related to 3 he content in the magma chamber in order to explain the 3 he flux measured at the surface we conclude that the magma chamber must be reg ularly fed by fresh magma batches using our new results and data from literature we propose that the his torical activity of la soufriere volcano can be explained by both abnormal energy inputs from new batches of magma in the chamber and cycles of clogging opening of the hydrothermal system we propose a new sce nario for the origin of the 1976 1977 crisis whereby a fresh batch of magma could have been emplaced prior to 1968 possibly between 1959 and 1962 in the magma chamber the resulting heat flux is not stored in the different aquifers but preferentially evacuated through fractures reactivated or created during the 1956 phre atic eruption only when the self sealing of the hydrothermal system is sufficiently developed can pressure and temperature within the aquifers rapidly increase to trigger a crisis

real time simultaneous detection of volcanic hg and so2 at la fossa crater vulcano aeolian islands sicily 1 measuring hg so2 ratios in volcanic emissions is essential for better apportioning the volcanic contribution to the global hg atmospheric cycle here we report the first real time simultaneous measurement of hg and so2 in a volcanic plume based on lumex and multigas techniques respectively we demonstrate that the use of these novel techniques allows the measurements of hg so2 ratios with a far better time resolution than possible with more conventional methods the hg so2 ratio in the plume of f0 fumarole on la fossa crater vulcano island spanned an order of magnitude over a 30 minute monitoring period but was on average in qualitative agreement with the hg so2 ratio directly measured in the fumarole mean plume and fumarole ratios being 1 09 10 6 and 2 9 10 6 respectively the factor 2 difference between plume and fumarole compositions provides evidence for fast hg chemical processing the plume

quantifying early aftershock activity of the 2004 mid niigata prefecture earthquake mw6 6 1 we analyze the early aftershock activity of the 2004 mid niigata earthquake using both earthquake catalog data and continuous waveform recordings the frequency magnitude distribution analysis of the japan meteorological agency jma catalog shows that the magnitude of completeness of the aftershocks changes from values around 5 0 immediately after the main shock to about 1 8 12 hours later such a large incompleteness of early events can bias significantly the estimation of aftershock rates to better determine the temporal pattern of aftershocks in the first minutes after the niigata earthquake we analyze the continuous seismograms recorded at six high sensitivity seismograph network hi net stations located close to the aftershock distribution clear aftershocks can be seen from about 35 s after the main shock we estimate that the events we picked on the waveforms recorded at two seismic stations ngoh and ynth situated on opposite sides of the aftershock distribution are complete above a threshold magnitude of 3 4 the c value determined by taking these events into account is about 0 003 days 4 3 min statistical tests demonstrate that a small but nonzero c value is a reliable result we also analyze the decay with time of the moment release rates of the aftershocks in the jma catalog since these rates should be much less influenced by the missing small events the moment rates follow a power law time dependence from few minutes to months after the main shock we finally show that the rate and state dependent friction law or stress corrosion could explain well our findings

applying a three dimensional velocity model waveform cross correlation and cluster analysis to locate southern california seismicity from 1981 to 2005 we compute high precision earthquake locations using southern california pick and waveform data from 1981 to 2005 our latest results are significantly improved compared to our previous catalog by the following 1 we locate events with respect to a new crustal p and s velocity model using three dimensional ray tracing 2 we examine six more years of waveform data and compute cross correlation results for many more pairs than our last analysis and 3 we compute locations within similar event clusters using a new method that applies a robust fitting method to obtain the best locations satisfying all the differential time constraints from the waveform cross correlation these results build on the relocated catalogs of hauksson and shearer 2005 and shearer et al 2005 and provide additional insight regarding the fine scale fault structure in southern california and the relationship between the san andreas fault saf and nearby seismicity in particular we present results for two regions in which the seismicity near the southern saf seems to align on dipping faults

earthquake hazard after a mainshock in california after a strong earthquake the possibility of the occurrence of either significant aftershocks or an even stronger mainshock is a continuing hazard that threatens the resumption of critical services and reoccupation of essential but partially damaged structures a stochastic parametric model allows determination of probabilities for aftershocks and larger mainshocks during intervals following the mainshock the probabilities depend strongly on the model parameters which are estimated with bayesian statistics from both the ongoing aftershock sequence and from a suite of historic california aftershock sequences probabilities for damaging aftershocks and greater mainshocks are typically well constrained after the first day of the sequence with accuracy increasing with time

triggering cascades and statistical properties of aftershocks 1 applying a simple general procedure for identifying aftershocks we investigate their statistical properties for a high resolution earthquake catalog covering southern california we compare our results with those obtained by using other methods in order to show which features truly characterize aftershock sequences and which depend on the definition of aftershocks features robust across methods include the p value in the omori utsu law for large main shocks bath s law and the productivity law with an exponent smaller than the b value in the gutenberg richter law the identification of a typical aftershock distance with the rupture length is a feature we confirm as well as a power law decay in the spatial distribution of aftershocks with an exponent less than 2 other results we obtain but not common to all other works including marsan and lengline 2008 hainzl and marsan 2008 and zhuang et al 2008 are a p values that do not increase with the main shock magnitude b the duration of bare aftershock sequences that scales with the main shock magnitude c an additional power law in the temporal variation at intermediate times in the rate of aftershocks for main shocks of small and intermediate magnitude and d a b value for the gutenberg richter law of background events that is sensibly larger than that of aftershocks tests on synthetic catalogs generated by the epidemic type aftershock sequence model corroborate the validity of our approach

fumarole compositions and mercury emissions from the tatun volcanic field taiwan results from multi component gas analyser portable mercury spectrometer and direct sampling techniques gas emissions from tatun volcanic group northern taiwan were studied for the first time using a multi component gas analyser system multi gas in combination with giggenbach flask methods at fumaroles and mud pools at da you keng dyk and geng tze ping gzp co 2 s molar ratios observed at dyk ranged from 3 17 similar ratios were observed using a multi gas sensor box of 8 16 so 2 at gzp was low higher concentrations were observed at dyk where so 2 h 2 s ratios were close to 1 for both methods a lower co 2 h 2 s ratio was measured via giggenbach flask sampling 7 2 than was found in the plume using the gas sensor at gzp 9 2 this may reflect rapid oxidation of h 2 s as it mixes with background air gaseous elemental mercury gem levels were observed in the fumarole gases using a portable mercury spectrometer these are the first such measurements of mercury at tatun mean gem concentrations in the fumarole plumes were 20 ng m 3 with much higher concentrations observed close to the ground mean gem 130 and 290 ng m 3 at dyk and gzp respectively the gem in the fumarole plume was elevated above concentrations in industrial urban air in northern taiwan and the increase in gem observed when the instrument was lowered suggests high levels of mercury are present in the surrounding ground surface the gem co 2 10 8 and gem s 10 6 ratios observed in the fumarole gases were comparable to those observed at other low temperature fumaroles combining the hg co 2 ratio with a previous co 2 flux value for the area the annual gem flux from the tatun field is estimated as 5 50 kg year 2008 elsevier b v all rights reserved

h2s fluxes from mt etna stromboli and vulcano italy and implications for the sulfur budget at volcanoes abstract we present here new measurements of sulfur dioxide and hydrogen sulfide emissions from vulcano etna and stromboli italy made by direct sampling at vents and by filter pack and ultraviolet spectroscopy in downwind plumes measurements at the f0 and fa fumaroles on vulcano yielded so 2 h 2 s molar ratios of 0 38 and 1 4 respectively from which we estimate an h 2 s flux of 6 to 9 t d 1 for the summit crater for mt etna and stromboli we found so 2 h 2 s molar ratios of 20 and 15 respectively which combined with so 2 flux measurements suggest h 2 s emission rates of 50 to 113 t d 1 and 4 to 8 t d 1 respectively we observe that source and plume so 2 h 2 s ratios at vulcano are similar suggesting that hydrogen sulfide is essentially inert on timescales of seconds to minutes this finding has important implications for estimates of volcanic total sulfur budget at volcanoes since most existing measurements do not account for h 2 s emission

estimations of mercury fluxes emitted by mount etna volcano a sampling and measuring device which enables the assessment of atmospheric particulate and gaseous mercury concentrations has been tested on mount etna volcano particulate matter is collected on a whatman gf c of 1 0 m pore size gaseous mercury species on a au column the analysis is carried out in two steps 1 the mercury species collected on the filter or the au column are transferred to a fixed analytical au column 2 mercury liberated from this column during the second step is detected with a mercury vapour monitor average concentrations of gaseous and particulate mercury in ambient sampling sites on mount etna are 3 8 ng m 3 and 0 49 ng m 3 respectively average concentrations of gaseous and particulate mercury in the plume of bocca nuova on mount etna are 15 ng m 3 and 24 ng m 3 respectively an estimation of the total mercury discharge from mount etna amounts to 2 5 10 2 tons day 1

accurate measurement of volcanic so2 flux determination of plume transport speed and integrated so2 concentration with a single device 1 ground based measurements of volcanic sulfur dioxide fluxes are important indicators of volcanic activity with application in hazard assessment and understanding the impacts of volcanic emissions upon the environment and climate these data are obtained by making traverses underneath the volcanic plume a few kilometers from source with an ultraviolet spectrometer measuring integrated so2 concentrations across the plume s cross section and multiplying by the plume s transport speed however plume velocities are usually derived from ground based anemometers located many kilometers from the traverse route and hundreds of meters below plume altitude complicating the experimental design and introducing large flux can be 100 errors here we present the first report of a single instrument capable of accurate volcanic so2 flux measurements this device records integrated so2 concentrations and plume heights during traverses between traverses two in plume so2 time series are measured from underneath the plume with the instrument corresponding to zenith and inclined user specified angle from vertical in the direction of the volcano fields of view respectively the distance between the points of intersection of the two views with the plume is found on the basis of the determined plume height and the two signals are cross correlated to determine the lag between them enabling accurate derivation of the wind speed we present flux data with errors 12 obtained in this way at mt etna during july 2004

collateral variations between the concentrations of mercury and other water soluble ions in volcanic ash samples and volcanic activity during the 2014 2016 eruptive episodes at aso volcano japan abstract during 2014 2016 the aso volcano located in the center of the kyushu islands japan erupted and emitted large amounts of volcanic gases and ash two episodes of the eruption were observed firstly strombolian magmatic eruptive episodes from 25 november 2014 to the middle of may 2015 and secondly phreatomagmatic and phreatic eruptive episodes from september 2015 to february 2016 bulk chemical analyses on total mercury hg and major ions in water soluble fraction in volcanic ash fall samples were conducted during the strombolian magmatic eruptive episodes total hg concentrations averaged 1 69 0 87 ng g 1 n 33 with a range from 0 47 to 3 8 ng g 1 in addition the temporal variation of total hg concentrations in volcanic ash varied with the amplitude change of seismic signals in the aso volcano the volcanic tremors are always observed during eruptive stages and quiet interludes and the amplitudes of tremors increase at eruptive stages so the temporal variation of total hg concentrations could provide an indication of the level of volcanic activity during the phreatomagmatic and phreatic eruptive episodes on the other hand total hg concentrations in the volcanic ash fall samples averaged 220 88 ng g 1 n 5 corresponding to 100 times higher than those during the strombolian eruptive episode therefore it is possible that total hg concentrations in volcanic ash samples are largely varied depending on the eruptive type in addition the ash fall amounts were also largely different among the two eruptive episodes this can be also one of the factors controlling hg concentrations in volcanic ash

remote and in situ plume measurements of acid gas release from la soufriere volcano guadeloupe this paper presents the first remote measurements of la soufriere gas emissions since the fumarolic and seismic reactivation in 1992 the chemical composition of the plumes has been measured from may 2003 to september 2004 using an open path fourier transform infrared op ftir spectrometer up to 15 m downwind the south crater hcl is clearly detected concentration between 2 4 and 12 ppmv whereas so2 and h2s generally remain below the detection limit of the op ftir direct measurements of so2 and h2s near the south crater with a lancom iii analyzer show a fast decrease of their concentrations with the distance calculated cl s mass ratios are high from 9 4 1 7 at 15 m from the vent to 2 8 0 6 at 140 m the enrichment in hcl of the gas emitted at la soufriere observed since 1998 corresponds to the degassing of a magma enriched in cl and depleted in s this result agrees with isotopic measurements which suggest a magmatic origin of the gases readjustments inside the volcanic system may have taken place during the seismic activity beginning in 1992 and enhance the transfer of magmatic gases to the summit

the volcanic activity of la soufriere of guadeloupe lesser antilles structural and tectonic implications abstract among observations made on la soufriere volcano guadeloupe to monitor its its activity are temperature measurements temperature of fumaroles hot springs ground surface and water inside two boreholes 80 and 90 m deep those measurements proved to be of prime importance in understanding mechanisms working in the volcano and governing its activity they lead with other observations such as self potential measurements and geochemical analysis of fumaroles and hot springs to a possible interpretation of phreatic activity rather different from the one retained earlier which was essentially based on seismic data in this model the magma reservoir is only in a stable state and in particular supplies heat at a constant rate to the overlying geological structures the cycle of volcanic activity and period of quiescence is interpreted as due to a cycle of clogging and reopening of the system of fractures transferring heat from a lower aquifer to an upper one and eventually to the atmosphere the model is discussed in regard of other geophysical observations in particular seismicity some inferences are made concerning a new phase of activity and suitable observations to predicit it

mercury gas emissions from la soufriere volcano guadeloupe island lesser antilles abstract quantifying mercury hg emissions from active volcanoes is of particular interest for better constraining the global cycle and environmental impact of this highly toxic element here we report on the abundance of total gaseous tgm hg 0 g hg ii g and particulate hg p mercury in the summit gas emissions of la soufriere andesitic volcano guadeloupe island lesser antilles where enhanced degassing of mixed hydrothermal magmatic volatiles has been occurring since 1992 from the southern summit crater we demonstrate that hg in volcanic plume occurs predominantly as gaseous mercury with a mean tgm hg p mass ratio of 63 combining the mean tgm h 2 s mass ratio of the volcanic plume 3 2 10 6 measured close to the source vent with the h 2 s plume flux 0 7 t d 1 determined simultaneously allows us to estimate a gaseous mercury emission rate of 0 8 kg yr 1 from la soufriere summit dome somewhat lower tgm s tot mass ratio in fumarolic gases from the source vent 4 4 10 7 suggests that plume chemical composition is not well represented by the emission source fumaroles due to chemical processes prior to or upon discharge current mercury emission from la soufriere volcano represents a very small contribution to the estimated global volcanic budget for this element

rapid oxidation of mercury hg at volcanic vents insights from high temperature thermodynamic models of mt etna s emissions a major uncertainty regarding the environmental impacts of volcanic hg is the extent to which hg is deposited locally or transported globally an important control on dispersion and deposition is the oxidation state of hg compounds hg 0 is an inert insoluble gas while hg ii occurs as reactive gases or in particles which deposit rapidly and proximally near the volcanic vent using a new high temperature thermodynamic model we show that although hg in etna s magmatic gases is almost entirely hg 0 i e gaseous elemental mercury significant quantities of hg ii are likely formed at etna s vents as gaseous hgcl2 when magmatic gases are cooled and oxidised by atmospheric gases these results contrast with an earlier model study and allow us to explain recent measurements of hg speciation at the crater rim of etna without invoking rapid 1 min low temperature oxidation processes we further model hg speciation for a series of additional magmatic gas compositions compared to etna hg ii production i e hg ii hgtot is enhanced in more hcl rich magmatic gases but is independent of the hg hbr and hi content of the magmatic gases hg ii production is not strongly influenced by the initial oxidation state of magmatic gases above nno although production is hindered in more reduced magmatic gases the model and results are widely applicable to other open vent volcanoes and may be used to improve the accuracy of chemical kinetic models for low temperature hg speciation in volcanic plumes

mercury content and speciation in the phlegrean fields volcanic complex evidence from hydrothermal system and fumaroles abstract mercury is outstanding among the global environmental pollutants of continuing concern although degassing of active volcanic areas represents an important natural source of mercury into the atmosphere still little is known about the amount and behaviour of hg in volcanic aquifers especially regarding its chemical speciation in order to assess the importance of mercury emissions from active volcanoes thermal waters were sampled in the area surrounding la solfatara pozzuoli bay this is the most active zone of the phlegrean fields complex coastal area north west of naples with intense hydrothermal activity at present day studied groundwaters show total hg thg concentrations range from 56 to 171 ng l and are lower than the 1000 ng l threshold value for human health protection fixed by the world health organization who 1993 we also carefully discriminated the different aqueous species of hg in the collected water samples besides original data on hg determination in gaseous manifestations at la solfatara crater are also reported we measured volcanogenic mercury concentration and hg s tot ratio both in the volcanic plume and in fumarolic condensates in order to better constrain hg reactivity once emitted into the atmosphere data on hg s tot reveal that there is no significant difference between hg volcanic composition at the venting source fumaroles and in near vent diluted volcanic plumes 1 6 10 5 and 1 9 10 5 respectively suggesting that there is limited hg chemical processing in volcanic fumarole plumes at least on the timescales of a few seconds investigated here combining the mean fumaroles hg co 2 mass ratio of about 1 3 10 8 molar ratio 2 1 10 9 with the hydrothermal soil diffuse co 2 degassing of the area the annual hg flux from la solfatara is estimated as 7 kg y 1 0 007 t y 1 current mercury emission from la solfatara volcano represents a very small contribution to the estimated global volcanic budget for this element and the estimated hg flux is considerably lower than that estimated from open conduit active basaltic volcanoes

global mercury flux from volcanic and geothermal sources abstract the global hg flux from natural sources is poorly known we present data on hg levels in volcanic fumaroles that in combination with sulfur analyses and published so 2 flux data lead to new global hg flux estimates the volcanogenic hg flux from passively degassing volcanoes is small 30 mg hg yr the flux from erupting volcanoes is much larger but less well constrained we estimate it at about 800 mg yr these data are interpreted as evidence for early hg degassing from magmas geothermal sources contribute roughly 60 mg yr hg to the atmosphere an estimate based on average hg contents of hot springs and global convective heat transport total natural hg emissions from land amount to 1290 mg yr including a revised soil vapor flux of 400 mg yr estimates of anthropogenic contributions to the atmospheric hg budget vary between 3000 and 11 500 mg yr and are substantial compared to our natural hg flux estimate

waveform relocated earthquake catalog for southern california 1981 to june 2011 we determine a new relocated catalog hys catalog 2011 for southern california from 1981 through june 2011 about 75 3 of the hypocenters are calculated with absolute and differential travel time picks and 24 7 could be relocated only by using absolute travel time picks with 3d or 1d velocity models the total catalog consists of more than 502 000 earthquakes in the region extending from baja california in the south to coalinga and owens valley in the north the catalog consists of three m 7 1 m 7 2 and m 7 3 mainshocks their foreshocks and aftershocks and background seismicity caused by tectonic and other processes in the southern california crust hypocenters in the new relocated catalog exhibit tighter spatial clustering of seismicity than does the routinely generated catalog and the depth distribution is tighter and reflects the thickness of the seismogenic zone more accurately compared to the standard catalog the relocated hypocenters are more easily related to other data sets such as mapped late quaternary faults

short term properties of earthquake catalogs and models of earthquake source i review the short term properties of earthquake catalogs in particular the time and size distributions and the completeness of the early part of aftershock sequences for strong shallow earthquakes i determine the parameters of the omori and gutenberg richter laws for aftershocks close in time to a mainshock aftershock sequences of large earthquakes in southern california 1952 kern county 1992 joshua tree landers big bear sequence 1994 northridge and 1999 hector mine recorded in the caltech catalog are analyzed to demonstrate that at the beginning of these series many small earthquakes are absent from the catalog the number of missing earthquakes increases with the magnitude range of a catalog and for some data sets exceeds the number of aftershocks close to a mainshock listed in a catalog comparing global earthquake catalogs harvard centroid moment tensor and preliminary determination of epicenter with local data sets indicates that the catalogs based on longer period waves miss many early aftershocks even when their magnitudes are well above the stated magnitude threshold such short term incompleteness may introduce significant biases to the statistical analysis of the seismicity pattern in particular for branching models of earthquake occurrence incorporating the omori law for such models the likelihood function strongly depends on close aftershocks i review the techniques to alleviate this problem analyzing the source rupture process of several recent large earthquakes suggests that rupture propagation is highly inhomogeneous in space time and focal mechanism these random variations in the rupture process can be viewed as an extension of the aftershock stochastic generating mechanism toward the origin time of a mainshock i review various models of the earthquake rupture process and suggest that fractal distributions of microevents in time space and focal mechanism constitute the development of an earthquake the final identification of an individual earthquake depends on both objective and subjective factors manuscript received 21 may 2003

carbon and helium isotopes in thermal springs of la soufriere volcano guadeloupe lesser antilles implications for volcanological monitoring abstract la soufriere guadeloupe lesser antilles is one of the most active and dangerous volcanoes of the lesser antilles arc the renewal of the volcanic activity at la soufriere requires replenishment of the volatile poor andesitic stored magma with more primitive volatile rich basaltic magma this event will trigger early release of large quantities of highly volatile species like co 2 and helium in the hydrothermal system to use these precursors first their baseline abundances and their behaviour in the hydrothermal system must be known during the current phase of dormancy in this study we have combined a previous systematic investigation of noble gases with carbon data of hydrothermal fluids flowing out of la soufriere the results for dissolved gases reveal that an intense interaction between rising magmatic volatiles and groundwaters currently takes place at la soufriere we show that the pristine magmatic composition with a 13 c co2 value of 3 19 0 03 a 3 he 4 he ratio of 8 1 0 2 r a and a co 2 3 he ratio of 1 03 0 18 10 10 may vary during the ascent of magmatic fluids due to either fractionation or mixing processes with meteoric water and or an organic component here we provide a baseline for co 2 and helium isotopes at each monitored spring and describe the superficial processes affecting both elemental and isotopic ratios

on near source earthquake triggering 1 when one earthquake triggers others nearby what connects them two processes are observed static stress change from fault offset and dynamic stress changes from passing seismic waves in the near source region r 50 km for m 5 sources both processes may be operating and since both mechanisms are expected to raise earthquake rates it is difficult to isolate them we thus compare explosions with earthquakes because only earthquakes cause significant static stress changes we find that large explosions at the nevada test site do not trigger earthquakes at rates comparable to similar magnitude earthquakes surface waves are associated with regional and long range dynamic triggering but we note that surface waves with low enough frequency to penetrate to depths where most aftershocks of the 1992 m 5 7 little skull mountain main shock occurred 12 km would not have developed significant amplitude within a 50 km radius we therefore focus on the best candidate phases to cause local dynamic triggering direct waves that pass through observed near source aftershock clusters we examine these phases which arrived at the nearest 200 270 km broadband station before the surface wave train and could thus be isolated for study direct comparison of spectral amplitudes of presurface wave arrivals shows that m 5 explosions and earthquakes deliver the same peak dynamic stresses into the near source crust we conclude that a static stress change model can readily explain observed aftershock patterns whereas it is difficult to attribute near source triggering to a dynamic process because of the dearth of aftershocks near large explosions

comparison of short term and time independent earthquake forecast models for southern california we have initially developed a time independent forecast for southern california by smoothing the locations of magnitude 2 and larger earthquakes we show that using small m 2 earthquakes gives a reasonably good prediction of m 5 earthquakes our forecast outperforms other time independent models kagan and jackson 1994 frankel et al 1997 mostly because it has higher spatial resolution we have then developed a method to estimate daily earthquake probabilities in south ern california by using the epidemic type earthquake sequence model kagan and knopoff 1987 ogata 1988 kagan and jackson 2000 the forecasted seismicity rate is the sum of a constant background seismicity proportional to our time independent model and of the aftershocks of all past earthquakes each earthquake triggers aftershocks with a rate that increases exponentially with its magnitude and decreases with time following omori s law we use an isotropic kernel to model the spatial distribution of aftershocks for small m 5 5 mainshocks for larger events we smooth the density of early aftershocks to model the density of future aftershocks the model also assumes that all earthquake magnitudes follow the gutenberg richter law with a uniform b value we use a maximum likelihood method to estimate the model parameters and test the short term and time independent forecasts a retro spective test using a daily update of the forecasts between 1 january 1985 and 10 march 2004 shows that the short term model increases the average probability of an earthquake occurrence by a factor 11 5 compared with the time independent forecast

small particles in plumes of mount st helens particles in the size range of 0 1 25 micrometers were sampled by aircraft carrying a quartz crystal microcascade in the mount st helens plume on three dates in august and september 1980 two of the sampling dates represented typical emissions of the volcano between plinian eruptions one sampling flight was made 1 4 hours before the small plinian eruption of august 7 1980 when the plume had become discontinuous and visibly darker size distributions were determined and individual particles were studied by using scanning electron microscopy the plume sampled on august 7 before the eruption contained mainly approximately 2 micrometer diameter silicic glass particles fragments of the mount st helens magma the typical plumes sampled on september 22 and august 6 had much smaller concentrations of particles trimodal size distributions with peaks at 10 0 4 and 0 1 micrometers the particles were largely nonsilicate and apparently represented cu zn oxide 10 micrometer peak al sulfate chloride and oxide and sulfuric acid smallest size peak the characterization of small particles in the plume may give information about approaching activity and possibly about changing conditions in the subsurface magma body

migration of early aftershocks following the 2004 parkfield earthquake a significant number of the early aftershocks following large shallow earthquakes are missing in existing earthquake catalogues an analysis of the waveforms of 3 647 relocated earthquakes along the parkfield section of the san andreas fault reveals 11 times more aftershocks within three days of the 2004 parkfield earthquake than listed in a standard catalogue large shallow earthquakes are immediately followed by numerous aftershocks a significant portion of these events is missing in existing earthquake catalogues mainly because seismicity after the mainshock can be masked by overlapping arrivals of waves from the mainshock and aftershocks1 2 3 4 however recovery of the missing early aftershocks is important for understanding the physical mechanisms of earthquake triggering2 3 4 and for tracking postseismic deformation around the rupture zone associated with the mainshock5 6 7 here we use the waveforms of 3 647 relocated earthquakes8 along the parkfield section of the san andreas fault as templates9 10 to detect missing aftershocks within three days of the 2004 magnitude 6 0 parkfield earthquake we identify 11 times more aftershocks than listed in the standard catalogue of the northern california seismic network we find that the newly detected aftershocks migrate in both along strike and down dip directions with logarithmic time since the mainshock consistent with numerical simulations of the expansion of aftershocks caused by propagating afterslip11 12 the cumulative number of early aftershocks increases linearly with postseismic deformation in the first two days supporting the view that aftershocks are driven primarily by afterslip13 14