application of stochastic simulation to co2 flux from soil mapping and quantification of gas release 1 conditional sequential gaussian simulations sgs have been applied for the first time to the study of soil diffuse degassing from different volcanic and nonvolcanic systems the application regards five data sets of soil co2 fluxes measured with the accumulation chamber methodology at the volcanic areas of solfatara of pozzuoli italy vesuvio cone italy nisyros greece and horseshoe lake california and at the nonvolcanic degassing area of poggio dell olivo italy the sgs algorithm was used to generate 100 realizations of co2 flux for each area probabilistic summaries of these simulations together with the information given by probability plots were used 1 to draw maps of the probability that co2 fluxes exceed thresholds specific for a background flux i e to define the probable extension of the degassing structures 2 to calculate the total co2 output and 3 to quantify the uncertainty of the estimation the results show that the sgs is a suitable tool to model soil diffuse degassing producing realistic images of the distribution of the co2 fluxes that honor the histogram and variogram of the original data moreover the relation between the sample design and the uncertainty of estimation was investigated leading to an empirical relation between uncertainty and the sampling density that can be useful for the planning of future co2 flux surveys

effects of prestress state and rupture velocity on dynamic fault branching 1 we consider a mode ii rupture which propagates along a planar main fault and encounters an intersection with a branching fault using an elastodynamic boundary integral equation formulation allowing the failure path to be dynamically self chosen we study the following questions does the rupture initiate along the branch does it continue is the extensional or compressional side most favored for branching does rupture continue on the main fault too failure is described by a slip weakening law for which the strength at any amount of slip is proportional to normal stress our results show that dynamic stresses around the rupture tip which increase with rupture velocity at locations off the main fault plane relative to those on it could initiate rupture on a branching fault as suggested by prior work whether branched rupture can be continued to a larger scale depends on principal stress directions in the prestress state and on rupture velocity the most favored side for branching rupture switches from the extensional to the compressional side as we consider progressively shallower angles of the direction of maximum compressive prestress with the main fault simultaneous rupturing on both faults can be activated when the branching angle is wide but is usually difficult for a narrow branching angle due to strong stress interactions between faults however it can be also be activated by enhanced dynamic stressing when the rupture velocity is very near the rayleigh velocity natural examples seem consistent with the simulations that we present

co2 degassing along the san andreas fault parkfield california the fluxes concentrations and carbon isotopic compositions of soil co2 were measured along the parkfield segment of the san andreas fault saf single or double peak co2 flux anomalies 18 g m 2 d 1 were observed along 12 of 16 fault crossing transects at five sites flux anomalies did not coincide with concentration anomalies flux anomalies paralleled the fault trace suggesting zones of high diffusivity permeability one flux anomaly may have been accentuated by a 0 3 mm creep event however values of 13c 23 7 to 21 6 and 14c 110 5 to 111 9 pmc for soil gas co2 are characteristic of co2 of biogenic origin the co2 flux anomalies are therefore consistent with fault related biogenic gas flow and do not yield evidence for degassing of deeply derived co2

a three dimensional numerical model of the waiotapu waikite and reporoa geothermal areas new zealand abstract a large scale three dimensional numerical model of the waiotapu waikite and reporoa geothermal fields new zealand is presented the model covers an area of 450 km 2 and extends to a depth of about 3 6 km it is based on geological geophysical and geochemical data and related interpretations available in the literature the model has been calibrated by varying its permeability structure and the fluid and heat input at its base so that the temperature distribution in the model associated with the convective and advective fluid flow matches the natural state conditions in the three fields good agreement has been obtained between model results and measured downhole temperature data as well as reproducing the location and magnitude of the surface heat discharge for each field in the best fit model 665 kg s of deep thermal fluid is transferred to the surface and to concealed shallow aquifers the subsurface extent of the geothermal reservoirs can be assessed from model blocks at temperatures greater than 220 c the waiotapu reservoir covers about 30 km 2 at a depth of 1 km below sea level whereas the hot zone in the reporoa caldera associated with the reporoa reservoir extends over about 13 km 2 a separate deep thermal upflow is required in the model in order to get a satisfactory match to temperatures in the reporoa field the modelling study shows that the waikite field is an outflow from the waiotapu field and the high temperature region beneath the waikite field only appears at shallow depths 500 mrl and above the model therefore well defines the waiotapu reporoa geothermal system which hosts the three geothermal fields at waiotapu waikite and reporoa

correlated increase in co2 fumarolic content and diffuse emission from la fossa crater vulcano italy evidence of volcanic unrest or increasing gas release from a stationary deep magma body 1 the peculiarity of the quiescent la fossa volcano is the occurrence of crises characterized by strong increases of fumarole t and output and by chemical changes indicative of an increasing input of magmatic fluids several surveys carried out during a new crisis began in november 2004 indicate that the total diffuse co2 emission for the crater area increases by one order of magnitude during crises up to 1600 ton d 1 in december 2005 concern exists on the possibility that these crises be related to an unrest process leading to eruption the repetition along decades of the same gas compositional variations during crises their temporal coincidence with increases of the local shallow seismicity and the lack of any significant ground motion rather suggest that they correspond to moments of increasing volatile release from a stationary magma system

comparative soil co2 flux measurements and geostatistical estimation methods on masaya volcano nicaragua we present a comparative study of soil co2 flux f rm co 2 measured by five groups groups 1 5 at the iavcei ccvg eighth workshop on volcanic gases on masaya volcano nicaragua groups 1 5 measured f rm co 2 using the accumulation chamber method at 5 m spacing within a 900 m2 grid during a morning am period these measurements were repeated by groups 1 3 during an afternoon pm period measured f rm co 2 ranged from 218 to 14 719 g m 2 day 1 the variability of the five measurements made at each grid point ranged from 5 to 167 however the arithmetic means of fluxes measured over the entire grid and associated total co2 emission rate estimates varied between groups by only 22 all three groups that made pm measurements reported an 8 19 increase in total emissions over the am results based on a comparison of measurements made during am and pm times we argue that this change is due in large part to natural temporal variability of gas flow rather than to measurement error in order to estimate the mean and associated co2 emission rate of one data set and to map the spatial f rm co 2 distribution we compared six geostatistical methods arithmetic and minimum variance unbiased estimator means of uninterpolated data and arithmetic means of data interpolated by the multiquadric radial basis function ordinary kriging multi gaussian kriging and sequential gaussian simulation methods while the total co2 emission rates estimated using the different techniques only varied by 4 4 the f rm co 2 maps showed important differences we suggest that the sequential gaussian simulation method yields the most realistic representation of the spatial distribution of f rm co 2 but a variety of geostatistical methods are appropriate to estimate the total co2 emission rate from a study area which is a primary goal in volcano monitoring research

improved predictions of saturated and unsaturated zone drawdowns in a heterogeneous unconfined aquifer via transient hydraulic tomography laboratory sandbox experiments summary interpretation of pumping tests in unconfined aquifers has largely been based on analytical solutions that disregard aquifer heterogeneity in this study we investigate whether the prediction of drawdown responses in a heterogeneous unconfined aquifer and the unsaturated zone above it with a variably saturated groundwater flow model can be improved by including information on hydraulic conductivity k and specific storage s s from transient hydraulic tomography tht we also investigate whether these predictions are affected by the use of unsaturated flow parameters estimated through laboratory hanging column experiments or calibration of in situ drainage curves to investigate these issues we designed and conducted laboratory sandbox experiments to characterize the saturated and unsaturated properties of a heterogeneous unconfined aquifer specifically we conducted pumping tests under fully saturated conditions and interpreted the drawdown responses by treating the medium to be either homogeneous or heterogeneous we then conducted another pumping test and allowed the water table to drop similar to a pumping test in an unconfined aquifer simulations conducted using a variably saturated flow model revealed 1 homogeneous parameters in the saturated and unsaturated zones have a difficult time predicting the responses of the heterogeneous unconfined aquifer 2 heterogeneous saturated hydraulic parameter distributions obtained via tht yielded significantly improved drawdown predictions in the saturated zone of the unconfined aquifer and 3 considering heterogeneity of unsaturated zone parameters produced a minor improvement in predictions in the unsaturated zone but not the saturated zone these results seem to support the finding by mao et al 2011 that spatial variability in the unsaturated zone plays a minor role in the formation of the s shape drawdown time curve observed during pumping in an unconfined aquifer

soil co2 emissions as a proxy for heat and mass flow assessment taupō volcanic zone new zealand the quantification of heat and mass flow between deep reservoirs and the surface is important for understanding magmatic and hydrothermal systems here we use high resolution measurement of carbon dioxide flux co2 and heat flow at the surface to characterize the mass co2 and steam and heat released to the atmosphere from two magma hydrothermal systems our soil gas and heat flow surveys at rotokawa and white island in the taup volcanic zone new zealand include over 3000 direct measurements of co2 and soil temperature and 60 carbon isotopic values on soil gases carbon dioxide flux was separated into background and magmatic hydrothermal populations based on the measured values and isotopic characterization total co2 emission rates co2 of 441 84 t d 1 and 124 18 t d 1 were calculated for rotokawa 2 9 km2 and for the crater floor at white island 0 3 km2 respectively the total co2 emissions differ from previously published values by 386 t d 1 at rotokawa and 25 t d 1 at white island demonstrating that earlier research underestimated emissions by 700 rotokawa and 25 white island these differences suggest that soil co2 emissions facilitate more robust estimates of the thermal energy and mass flux in geothermal systems than traditional approaches combining the magmatic hydrothermal sourced co2 emission constrained using stable isotopes with reservoir h2o co2 mass ratios and the enthalpy of evaporation the surface expression of thermal energy release for the rotokawa hydrothermal system 226 mwt is 10 times greater than the white island crater floor 22 5 mwt

identifying blind geothermal systems with soil co2 surveys abstract diffuse soil co2 flux surveys are a widely applied approach for delineating zones of elevated heat and mass transfer in areas with geothermal surface features including hot springs mud pools and geysers however many geothermal systems are capped by relatively impermeable layers that diminish the surface expression of potential resources present at depth here we report diffuse soil co2 flux survey results with complementary 13co2 values and shallow soil temperatures for the ngatamariki geothermal system taupo volcanic zone new zealand a largely surface blind system in an effort to explore the utility of such data as indicators of magmatic carbon emission in geothermal systems with low co2 flux our results include that 1 the majority 54 of the soil co2 flux measurements are below background levels 15 gco2 m 2 day 1 2 only 5 6 of the shallow 10 cm soil temperatures exceed 30 c and 3 no correlation is present between soil temperature and co2 flux at ngatamariki these results belie the fact that a recently developed geothermal resource is present beneath ngatamariki yet 13co2 values when interpreted in the context of soil gas co2 concentrations demonstrate that the magmatic hydrothermal system beneath ngatamariki can be distinguished from soil zone carbon sources using diffuse soil gas geochemical tracers modeling the ngatamariki co2 system as a simple mixture of geothermal biogenic and atmospheric end members allows for the apportionment of co2 flux at different locations across the field based on these findings we suggest that delineating potential geothermal sites and assessing the relative contributions of mixed fluid end members is possible even with low diffuse co2 flux and limited surface expression of geothermal systems at depth

plume chemistry provides insights into mechanisms of sulfur and halogen degassing in basaltic volcanoes abstract this paper deals with sulfur chlorine and fluorine abundances in the eruptive volcanic plume of the huge october 2002 january 2003 eruption of mount etna aiming at relating the relevant compositional variations observed throughout with changes in eruption dynamics and degassing mechanisms the recurrent sampling of plume acidic volatiles by filter pack methodology revealed that during the study period s cl and cl f ratios ranged from 0 1 6 8 and 0 9 5 6 respectively plume s cl ratios increased by a factor of 10 as volcanic activity drifted from paroxysmal lava fountaining mid and late november to passive degassing and minor effusion early january and then decreased to the low values s cl 0 1 typical of the final stages of the eruption parallel variations in chlorine to fluorine ratios were also observed a theoretical model is proposed for quantitative interpretation of these changes in plume composition the model calculates the composition of a volatile phase exsolving from an ascending etna magma based on knowledge of solubilities and abundances in the undegassed melt of sulfur and halogens t m gerlach eos 72 1991 249 254 255 according to this model degassing of etnean basaltic melt at high pressures and depths 100 mpa 3 km is likely to release a co2 h2o rich vapor phase with s cl molar ratios 1 extensive sulfur and chlorine degassing from the melt would take place at shallower depth p

soil degassing at the los humeros geothermal field mexico abstract the los humeros geothermal field is the third most important producer of geothermal electricity 70 mw in mexico geothermal fluids are hosted in fractured andesitic lavas and mostly consist of high enthalpy steam with limited water content vapor fraction 0 9 despite the high reservoir temperature 300 400 c thermal manifestations at the surface are scarce and locally appear as steaming grounds weak steam vents and advanced argillic alteration geothermal fluid upflow from the reservoir towards the surface is limited by welded ignimbrite deposits that act as a low permeability barrier in this study we present the first measurements of co2 ch4 and h2s degassing rates from the soil performed at los humeros flux measurements were complemented with 13c composition of degassing co2 and soil temperatures to discuss gas origin and thermal anomalies we measured high soil degassing rates up to 7530 g m 2 d 1 co2 33 g m 2 d 1 ch4 and 22 g m 2 d 1 h2s in three localized areas humeros north hn humeros south hs and xalapazco xa as well as high soil temperatures reaching the boiling temperature at the local altitude 90 6 c the particular location of these three areas suggests that the steam dominated reservoir degases to the surface through permeable faults crossing the ignimbritic deposits the remaining surveyed areas are characterized by weak co2 fluxes 44 g m 2 d 1 non detectable ch4 and h2s fluxes and lower soil temperatures 5 21 c the compositions in 13cco2 from hn hs xa areas 13cco2 7 94 to 2 73 reflect a magmatic source with some possible contribution from the sedimentary basement as well as fractionation induced by boiling and co2 dissolution in shallow water bodies we also discuss the processes causing the spread in co2 ch4 flux ratios finally we estimate the heat output from the three high degassing areas to a value of 16 4 mwt

magma origin and evolution of white island whakaari volcano bay of plenty new zealand white island is an active composite stratovolcano in the bay of of the north island the pacific plate is being subducted plenty new zealand that comprises many small volume westwards under the australian plate at a rate of 50 mm yr to form the taupo hikurangi arc trench with phenocryst contents of 15 44 minor high mg basaltic system volcanic activity is now concentrated in the andesite explosive eruptions such as those of 1976 1992 may taupo volcanic zone tvz the youngest expression have occurred at intervals throughout the history of white island of 22 ma cenozoic continental margin arc volcanism in but are rarely preserved these alternate with major episodes of the north island of new zealand cole 1990 tvz andesite dacite lava extrusion the high mg magmas form by fig 1 inset is at the southern end of the 2800 km hydrous melting of mantle metasomatized by fluids from the tonga kermadec taupo volcanic arc system and the dehydrating slab at the slab mantle wedge interface that rise lau basin havre trough ngatoro basin back arc basin rapidly to shallow magma chambers 2 7 km where limited system southern havre trough and tvz are offset mixing and contamination occurs before eruption some of this sinistrally by 40 50 km and wright 1992 believes the magma remains in the magma chamber where it interacts with the offset to be accommodated by a series of dextrally oblique crystal mush from which it inherits phenocrysts to form so called and en echelon bookshelf faults the southwestern limit dirty lavas total phenocryst content of these lavas is correspondingly of this fault system is placed 20 km north of white higher as more magma is intruded into the chamber the heat flux island and has nw se orientation fig 1 inset will increase and melt fraction will eventually rise to the surface to tvz extends offshore into the bay of plenty as a form high silica andesite dacite magma clean lavas with fewer graben structure of 45 km width fig 1 bounded by the inherited phenocrysts similar multi magma chamber plumbing tauranga fault zone to the west and the white island systems with complex evolution involving fractionation and confault zone to the east wright 1992 the eastern side tamination probably occur in most andesite dacite arc volcanoes of tvz coincides with the current active volcanic front and a broadly linear alignment of andesitic volcanoes extends from ruapehu in the southwest to whakatane

rates of carbon dioxide plume degassing from mount etna volcano 1 we report here on the real time measurement of co2 and so2 concentrations in the near vent volcanic gas plume of mount etna acquired by the use of a field portable gas analyzer during a series of periodic field surveys on the volcano s summit during the investigated period september 2004 to september 2005 the plume co2 so2 ratio ranged from 1 9 to 10 8 with contrasting composition for northeast and voragine crater plumes scaling the above co2 so2 ratios by uv spectroscopy determined so2 emission rates we estimate co2 emission rates from the volcano in the range 0 9 67 5 kt d 1 average 9 kt d 1 about 2 kt of co2 were emitted daily on average during quiescent passive degassing whereas co2 emission rates from etna s summit were 10 40 times larger during the 2004 2005 effusive event with a cumulative co2 release of 3800 kt during the 6 months of the eruption such a syneruptive increase ascribed to the replenishment of the shallow 6 km volcanic plumbing system by co2 rich 0 25 wt more primitive magmas supports the potential of co2 output rates as key parameters for volcanic hazard assessment

quasi static analysis of strike fault growth in layered media summary we study the effects of structural inhomogeneity on the quasi static growth of strike slip faults a layered medium is considered made up of an upper layer bounded by a free surface and welded to a lower half space with different elastic property mode iii crack is employed as a mathematical model of strike slip fault which is nucleated in the lower half space and then propagates towards the interface we adopt fem newly proposed analysis method for failure to simulate the quasi statistic crack growth governed by the stress distribution in layered media our results show that along planar traces across interfaces a compliant upper layer has significant effects on promoting suppressing crack growth before after its extension into the layer and vice versa for a rigid one this proposes a possibility that surface breaks due to strike slip faulting could be arrested by deposit layers at the topmost part of the earth s crust

the ad1315 tarawera and waiotapu eruptions new zealand contemporaneous rhyolite and hydrothermal eruptions driven by an arrested basalt dike system a series of large hydrothermal eruptions occurred across the waiotapu geothermal field at about the same prehistoric time as the ad1315 kaharoa rhyolite magmatic eruptions from tarawera volcano vents 10 20 km distant triggering of the waiotapu hydrothermal eruptions was previously attributed to displacement of the adjacent ngapouri fault the kaharoa rhyolite eruptions are now recognised as primed and triggered by multiple basalt intrusions beneath the tarawera volcano a 1000 t day pulse of co2 gas is recorded by alteration mineralogy and fluid inclusions in drill core samples from waiotapu geothermal wells this co2 pulse is most readily sourced from basalt intruded at depth and although not precisely dated it appears to be associated with the waiotapu hydrothermal eruptions we infer that the hydrothermal eruptions at waiotapu were primed by intrusion of the same arrested basalt dike system that drove the rhyolite eruptions at tarawera this dike system was likely similar at depth to the dike that generated basalt eruptions from a 17 km long fissure that formed across the tarawera region in ad1886 fault ruptures that occurred in the waiotapu area in association with both the ad1886 and ad1315 eruptions are considered to be a result rather than a cause of the dike intrusion processes

atmospheric dispersion of natural carbon dioxide emissions on vulcano island italy la fossa quiescent volcano and its surrounding area on the island of vulcano italy are characterized by intensive persistent degassing through both fumaroles and diffuse soil emissions periodic degassing crises occur with marked increase in temperature and steam and gas output mostly co2 from crater fumaroles and in co2 soil diffuse emission from the crater area as well as from the volcano flanks and base the gas hazard of the most inhabited part of the island vulcano porto was investigated by simulating the co2 dispersion in the atmosphere under different wind conditions the disgas dispersion of gas code an eulerian model based on advection diffusion equations was used together with the mass consistent diagnostic wind model numerical simulations were validated by measurements of air co2 concentration inside the village and along the crater s rim by means of a soil co2 automatic station and a tunable diode laser device the results show that in the village of vulcano porto the co2 air concentration is mostly due to local soil degassing while the contribution from the crater gas emission is negligible at the breathing height for humans and always remains well below the lowest indoor co2 concentration threshold recommended by the health authorities 1000 ppm outdoor excess co2 maxima up to 200 ppm above local background co2 air concentration are estimated in the center of the village and up to 100 ppm in other zones however in some ground excavations or in basements the health code threshold can be exceeded in the crater area because of the combined effect of fumaroles and diffuse soil emissions co2 air concentrations can reach 5000 7000 ppm in low wind conditions and pose a health hazard for visitors

magmatic volatiles to assess permeable volcano tectonic structures in the los humeros geothermal field mexico abstract magmatic volatiles can be considered as the surface fingerprint of active volcanic systems both during periods of quiescent and eruptive volcanic activity the spatial variability of gas emissions at earth s surface is a proxy for structural discontinuities in the subsurface of volcanic systems we conducted extensive and regular spaced soil gas surveys within the los humeros geothermal field to improve the understanding of the structural control on fluid flow surveys at different scales were performed with the aim to i identify areas of increased gas emissions reservoir scale ii their relation to un known volcano tectonic structures fault scale favoring fluid flow and iii determine the origin of gas emissions herein we show results from a co2 efflux scouting survey which was performed across the main geothermal production zone 6 km 4 km together with soil temperature measurements we identified five areas with increased co2 emissions where further sampling was performed with denser sampling grids to understand the fault zone architecture and local variations in gas emissions co2 efflux values range from below detection limit of the device to 1464 g m 2 d 1 with a total output of 87 t d 1 across an area of 13 7 km2 furthermore 13cco2 and 3he 4he analyses complemented the dataset in order to assess the origin of soil gases carbon isotopic data cover a broad spectrum from biogenous to endogenous sources determined 3he 4he ratios indicate a mantle component in the samples of up to 65 being most evident in the northwestern and southwestern part of the study area we show that a systematic sampling approach on reservoir scale is necessary for the identification and assessment of major permeable fault segments the combined processing of co2 efflux and 13cco2 facilitated the detection of permeable structural segments with a connection to the deep high temperature geothermal reservoir also in areas with low to intermediate co2 emissions the results of this study complement existing geophysical datasets and define further promising areas for future exploration activities in the north and southwestern sector of the production field

the evolution of the waiotapu geothermal system new zealand based on the chemical and isotopic composition of its fluids minerals and rocks abstract the waiotapu geothermal system is hosted by silicic rocks of the taupo volcanic zone new zealand exploration drilling in the late 1950s down to 1100 m provided physical information on the system measured temperatures show a boiling profile to 295 c with shallow inversions particularly in the north total discharge fluid samples were collected the geothermometry and measured temperatures show that fluids derive mainly from a shallow 400 m deep reservoir at about 225 c petrologic study of drillcore samples recovered from seven wells reveals an alteration assemblage of quartz and albite adularia with a variable distribution of chlorite pyrite calcite zeolites epidote pyrrhotite sphene leucoxene apatite and minor base metal sulfides white mica is a late overprint particularly well developed at shallow depths surficial alteration of kaolin cristobalite alunite and smectite clays reflect alteration by acid sulfate steam heated waters the activities of components in minerals determined from microprobe analyses and composition activity relations and fluids speciated to reservoir conditions indicate equilibrium now exists between the fluids and white mica the na k ratio of the fluid is being controlled by dissolution of albite and adularia while its h 2 h 2 s ratio is buffered by pyrite replacing pyrrhotite the fluids are now slightly undersaturated with respect to calcite the present deep fluids boil adiabatically from at least 300 c to 230 c at depths of 500 m this ascending chloride fluid is variably diluted by a steam heated water of zero chloride that lies over and occurs on the margin of the system like a discontinuous umbrella the steam heated water is relatively co2 rich 0 1 m the cooling at shallow levels by this mixing has shifted the alteration from albite adularia stability to white mica stability this shift is enhanced by the co2 rich nature of the diluent dilution of ascending chloride fluids by shallow waters is also supported by the oxygen and hydrogen isotopic composition of the mixture with the deep fluid being enriched in 18o and d from local meteoric by 7 and 10 respectively the patterns in whole rock 18o indicate that they were largely shifted in isotopic composition prior to incursion of steam heated waters possibly induced by a series of hydrothermal eruptions 900 years ago in contrast the 18o composition of late vug calcite indicates its formation is related to the initial incursion of steam heated groundwater and subsequent cooling this is supported by fluid inclusion evidence the d shift from local groundwater composition and the 13c composition of co2 determined from calcite 4 to 6 may be evidence for a magmatic input to the meteoric convection cell the shallow portion of the waiotapu geothermal system has recently evolved both chemically and physically by incursion of fluids from a steam heated carapace continued refluxing of these relatively cool hybrid fluids progressively deeper with their recycled co2 content will hasten hydrolytic leaching in contrast to a single pass of adiabatically cooling deep fluids this action accompanied by argillic alteration may eventually seal the deeper portions of the system hastening its demise there is evidence for similar events occurring in the fossil environment at epithermal depths

volcanic co2 flux measurement at campi flegrei by tunable diode laser absorption spectroscopy near infrared room temperature tunable diode lasers tdl have recently found increased usage in atmospheric chemistry and air monitoring research but applications in volcanology are still limited to a few examples here we explored the potential of a commercial infrared laser unit gasfinder 2 0 from boreal laser ltd for measurement of volcanic co2 mixing ratios and ultimately for estimating the volcanic co2 flux our field tests were conducted at campi flegrei near pozzuoli southern italy where the gasfinder was used during three campaigns in october 2012 january 2013 and may 2013 to repeatedly measure the path integrated mixing ratios of co2 along cross sections of the atmospheric plumes of two major fumarolic fields solfatara and pisciarelli by using a tomographic post processing routine we resolved for each of the two fields the contour maps of co2 mixing ratios in the atmosphere from the integration of which and after multiplication by the plumes transport speeds the co2 fluxes were finally obtained we evaluate a total co2 output from the campi flegrei fumaroles of 490 mg day in line with independent estimates based on in situ multi gas observations we conclude that tdl technique may enable co2 flux quantification at other volcanoes worldwide

carbon dioxide dynamics in kelud volcanic lake 1 in november 2007 the extrusion of a new lava dome evaporated kelud volcanic lake in java indonesia four months before a detailed echo sounding survey of the volcanic lake coupled to floating accumulation chamber measurements detected abnormally high carbon dioxide emissions it constituted the earliest sign of the volcanic unrest well before any other monitored parameter co2 flux is quantified using an empirical equation based on the volume of bubbles backscattered in the water column its comparison with the fluxes retrieved from the floating chamber method better constrain carbon dioxide dynamics in the volcanic lake it reveals that 70 of the carbon dioxide enters the lake in a dissolved form while the remaining 30 is supplied to the lake on a gaseous state almost three quarter of the ascending bubbles dissolve in the water column leaving the majority of the 330 tons day 1 of carbon dioxide diffusing at the air water interface

faulting in vertically inhomogeneous media and its geophysical implications faulting of strike slip type in vertically inhomogeneous media is analyzed using the classical fracture theory the analysis makes it possible to get a better insight into various aspects of faulting and earthquakes in real media the major conclusions are that both low rigidity media and those with regions in which a rapid transition from high to low pore pressure occurs may form barriers for a propagating rupture the permanent deficit of the driving stress small or negative stress drop in sediments that represent the most distinguished class of such media may be one of the main reasons of the generally observed lack of seismicity and rupture suppression there

joint inversion of fault zone head waves and direct p arrivals for crustal structure near major faults a newly recognized class of seismic phases namely fault zone head waves arising from refraction at a transfault velocity contrast provides additional constraints to direct p waves in inversions of near fault arrival time data for earthquake location and velocity structure incorporation of fault zone head waves in the inversion process increases the available data and broadens the spatial coverage of ray paths between sources and receivers equally important the explicit recognition of fault zone head waves eliminates a source of error resulting from misidentifying head wave first arrivals as direct p waves a simple algorithm for the joint inversion of fault zone head waves and direct p phases is illustrated with observed and synthetic data application to a small data set recorded by the borehole seismic network at parkfield california provides separate seismic velocity depth profiles for the crustal blocks on the two sides of the san andreas fault for depths less than 3 km the obtained velocity contrast is 10 20 for greater depths it decreases to 3 7 numerical tests with synthetic data show that for sources with known locations and for well located local earthquakes randomized mislocation errors of up to 600 m proper use of fault zone head waves can significantly improve the accuracy of the fitted velocity structure the results of this work motivate the inclusion of fault zone head waves in state of the art joint structure hypocenter inversions using high quality near fault data

testing the tunable diode laser system in extreme environments measuring high and low co2 concentrations in both active volcanic and geothermal settings abstract measuring co2 emissions in geothermal and volcanic areas is sometimes difficult because of large areas to cover and sites often inaccessible measuring high levels of co2 concentration can provide information on hidden structure in geothermal areas and recording changes in co2 concentration on volcanic areas can help monitor the level of volcanic activity the purpose of this study was to use the tunable laser diode tdl absorption spectroscopy method to test levels of co2 concentrations at two extreme environments white island volcano the most active volcano of new zealand with large and concentrated gas fluxes and ngapouri geothermal area a small geothermal area in the taupo volcanic zone new zealand with relatively low and diffuse gas emissions in 2017 for the first time using tdl at white island co2 concentration measurements performed across the active fumarole fields had the highest co2 concentrations of 657 ppm tdl survey measurements were also conducted across fault strands near the ngapouri geothermal area and the results complemented co2 flux results obtained with the accumulation chamber method higher co2 concentrations were measured close to the mapped ngapouri splays with a maximum of 484 ppm the maximum co2 flux measured in the same area was 100 g m 2 day 1 however the highest co2 fluxes measured along the transects and by the mapped faults were less clear but the co2 concentrations increased closer to the fault splays advantages and disadvantages of using a tdl system have been described and compared to the accumulation chamber method the results from the tdl system demonstrated that co2 concentrations can be used as a tool with other geophysical tools for both detecting and highlighting geological structures where no obvious thermal activity is present and for monitoring purposes on active volcanoes

diffuse co2 soil degassing and co2 and h2s concentrations in air and related hazards at vulcano island aeolian arc italy ingv dpc programme project v5 diffuse degassing in italy airplane firb project of the italian ministry of the university and research

variations in co2 emissions at a mud volcano at the southern base of mt etna are they due to volcanic activity interference or a geyser like mechanism mud volcanoes are often associated with large areas of co2 and ch4 emission that are potentially dangerous due to sudden paroxysmal gas and mud eruptions despite the interest in understanding such natural environments they have not yet been thoroughly investigated and a single interpretative framework remains to be elaborated this lack of knowledge may be due to the difficulty in measuring in plume co2 as there is very little contrast with atmospheric co2 coupled with the complex organizational strategies required for long term monitoring this work features three different methods that were used to evaluate the co2 flux at the salinelle mud volcano in the foothills of mt etna italy carried out periodically from december 2013 to april 2018 we computed in plume co2 flux indirectly using a tunable laser and a portable multigas and directly measuring the gas volumetric flux from bubbling pools the morphological variations of the mud field were recorded using unmanned aerial vehicle uav imagery which provided information on the migration of vents in relation to the observed variations in measured gas output our analysis shows that the three methods gave comparable values indicating the feasibility of this approach our findings suggest a pseudo cyclical pattern in the bulk co2 emitted at salinelle introducing a new interpretation of the processes involved in mud volcano dynamics we theorize that the periodic variation of the gas emitted at the salinelle may be attributed to a geyser like mechanism that may be subject to interruption or changes in magnitude by volcanic or seismic events

hydrological evolution and chemical structure of a hyper acidic spring lake system on whakaari white island nz abstract white island has a long and varied history of acid spring discharge and shallow ephemeral lake formation on its main crater floor in the 12 months prior to the onset of the 1976 2000 eruptive episode mass discharge from the spring system increased ca 10 fold pointing to a strong coupling of the hydrothermal environment to the evolving magmatic system between 1976 and 1978 the formation of numerous eruption vents to 200 m depth in the western sub crater abruptly changed the hydraulic gradients in the volcano resulting in the reversal of groundwater flow in the massif towards the newly formed crater s this affected not only the style of volcanic activity leading to phreatic phreatomagmatic magmatic eruption cycles but also led to the demise of the spring system with discharge from the main crater declining by a factor 100 by 1979 eruptive activity ended shortly after a moderate strombolian eruption in mid 2000 after which ephemeral lakes started to form in the eruption crater complex between 2003 and 2015 there were three complete lake filling and evaporative cycles reflecting varying heat flow through the conduit system beneath the lake over these cycles lake water concentrations of cl and so 4 varied between ca 35 150 and 5 45 g l respectively with ph values temporally ranging from 1 5 to 1 springs appeared on the main crater floor in 2004 and their discharges varied with lake level pointing to the lake level being a primary control over the piezometric surface in the crater area springs closest to the crater complex show direct evidence of crater lake water infiltration into the crater floor aquifer whereas distal spring discharges show compositional variations reflecting vertical displacement of the interface between shallow dilute condensate and underlying acidic brine fluids source components for the spring fluids include magmatic vapour dissolved andesitic host rocks seawater and meteoric water lake waters on the other hand consist predominantly of magmatic vapour meteoric water and solutes derived from host andesites and their altered derivatives 2 h and 18 o signatures of the enclosing acid brine fluids indicate they are predominantly seawater which have been affected by both vapour loss but also mixing with arc type vapour an interesting finding of this study is that crater floor deformation correlates directly to both lake level and volatile emissions in an apparent poroelastic response to the establishment of a hydrostatic water column in the eruption crater complex and a net decrease in permeability owing to hydrothermal mineralization in the conduit predominantly elemental sulfur and sulfate minerals the hydrostatic pressurization of the vent environment also leads to increased gas pressures and flows through fumarolic channels and consequent expansion of fumarolic areas on the main crater floor a period of unrest which commenced in august 2012 and lasted until october 2013 included the extrusion of a small dome into the eruption crater complex this activity and related high heat flow led once again to evaporation of the lake and ongoing phreatic eruption activity which has provided interesting insights into the role which elemental sulfur associated hydrothermal alteration minerals and of course water play in regulating pressures in the magmatic hydrothermal environment

soil co2 emissions at furnas volcano sao miguel island azores archipelago volcano monitoring perspectives geomorphologic studies and land use planning application accepted for publication in journal of geophysical research copyright 2010 american geophysical union

a new light on arresting mechanism of dynamic earthquake faulting classic analyses have shown that dynamic growth of a shear crack cannot be arrested in a uniformly stressed elastic medium with homogeneously distributed fracture strengths this leads to a general supposition that earthquake rupture growth is arrested by inhomogeneities in the distributions of strengths or stresses we propose a novel idea for arresting mechanism of dynamic crack growth in the simulation with no constraints on the crack geometry our analysis shows that the arresting occurs spontaneously soon after crack bending even in the homogeneous medium and that inhomogeneities are indispensable not for stopping crack growth but for its promotion

on faulting in inhomogeneous media 1 faulting of strike slip type in a vertically inhomogeneous medium is analyzed using antiplane models it is shown that asperities boundaries where slip exhibits significant change may be associated with regions in which a rapid transition occurs from high to low rigidity and or from high to low pore pressure these boundaries are connected with stress concentrations within the ruptured regions where tectonic stress increases after faulting release of these stresses aftershocks interseismic earthquakes aseismic faulting and tectonic loading makes asperities boundaries a probable initiation site of a major earthquake during the following crustal deformation cycle the present results also show that low rigidity layers should be deprived of driving stress during consecutive earthquake cycles which explains the suppression of major earthquake ruptures and low level of seismicity that is generally observed in sediments