soil co2 degassing along tectonic structures of mount etna sicily the pernicana fault abstract carbon dioxide emissions from the soil have been investigated along lines of equally spaced sampling points perpendicular to the pernicana fault on mt etna anomalous values of soil co2 have been found not only along the fault plane but also along directions parallel to it both to the n and to the s of the main fault the acquired data seem to reveal a shallow step like geometry of the pernicana fault system with parallel faults being generally not deeper than the interface between etna s volcanic cover and its sedimentary basement a few hundred meters the distribution of the anomalous co2 emissions has also revealed that the pernicana fault continues at least as far as the ionian sea in an area where only sedimentary rocks crop out this finding would suggest that the main structure is deeper than the base of the volcanic cover thus cutting at least the uppermost portion of etna s sedimentary basement isotopic analyses of c carried out in samples from locations of high co2 seem to indicate that the emitted co2 is a mixture of an organic shallow component and a minor deeper magmatic one both chemical and isotopic data on soil gases emitted in the easternmost part of the studied area distinguished another tectonic structure which seems to be much deeper than the pernicana fault and is roughly directed nne ssw this direction being coincident with an important structural trend of eastern sicily

la fossa caldera breaching and submarine erosion vulcano island italy abstract la fossa caldera lfc on vulcano island in the aeolian archipelago italy is a multi collapse caldera whose north eastern part lies underwater through the integration of marine geophysical surveys and sampling carried out in the last decade its submarine extension and offshore areas have been reconstructed in unprecedented detail strong erosive processes breached the submarine portion of lfc and gradually dismantled the caldera rims and infill leading to the emplacement of a wide volcaniclastic fan from the base of lfc down to over 1000 m the bathy morphologic setting seismoacoustic facies and analyses of sediment samples from the fan together with volumetric considerations suggest that this feature is the pathway deposit of submarine unconfined gravity flows and turbidity currents deriving from the gradual dismantling of lfc submarine erosive processes are still active and the progressive erosion of the northern caldera sector threatens the stability of the active la fossa cone and the nearby coastal settlements

unusual lapilli tuff ejecta erupted at stromboli during the 15 march 2007 explosion shed light on the nature and thermal state of rocks forming the crater system of the volcano abstract textural and mineralogical study of high temperature angular blocks erupted during the stromboli explosion of 15 march 2007 was used to make inferences on the nature and thermal state of rocks forming the subsurface of the volcano summit crater terrace the studied ejecta consist of lapilli tuff that formed as a result of the transformation and high temperature induration sintering of the basaltic scoriae lapilli and ash originally accumulated as loose tephra during the current activity of the volcano the main processes leading to the tephra transformation were investigated through microstructural observations mineral and glass analyses sem eds and emp analyses investigations revealed that subsolidus reactions and partial melting of the tephra occurred at temperatures higher than 600 c and under variable fo 2 conditions from qfm to hm buffering curves in some blocks evidence of high t reheating and partial melting at the expense of secondary hydrothermal minerals was also observed in order to track the subsolidus reheating history of the basaltic pyroclasts a detailed study of the pseudomorphic phases and reactions after olivine driven by iron oxidation under high t conditions was performed the observed mineralogical transformation suggests that the lapilli tuff material originating from the burial of tephra routinely accumulated by persistent strombolian explosions within the crater terrace were in some cases altered by the circulation of acidic fluids and were in any case reheated due to isotherm rise forced by high heat flux and gas streaming delivered by the underlying magma system it is worth noting that the ejection of these unusual volcanic lithotypes was possible because a few days before the 15 march 2007 event the craters were clogged with lapilli tuff material that slid into the crater bottom between 7 and 9 march findings of this study suggest that the scattered permanently active vents and shallow conduits of stromboli are surrounded sideways and underneath the crater terrace by a fairly large volume of high temperature rocks with variable degree of compaction sintering up to partially melted such a spectrum of rock types is in good agreement with the conceptual model of prominent thermal zoning all around sideway and upwards the active magmatic system we speculate that continuous migration upwards of isotherms led to transformation and partial melting of the normal strombolian tephra

new evidence for the form and extent of the pernicana fault system mt etna from structural and soil gas surveying a multidisciplinary study based on structural and soil gas surveys was carried out in order to investigate the relationship between soil co2 degassing and the tectonic setting of the lower northeastern flank of mt etna volcano the results show that anomalous soil co2 emissions occur mainly along faults trending wnw ese and also where these faults intersect the other main fault set trending ne sw that displaces the study area in particular anomalies in co2 degassing were revealed both along the pernicana fault and along another fault fiumefreddo fault which may represent the prolongation of the former towards the ionian sea coast in the areas where these structures show evident surface faulting they are all characterised by left lateral displacements and aseismic creep behaviour furthermore the geochemical survey revealed that these faults join in an area devoid of geological evidence of surface faulting and continue underneath an apparently unfaulted alluvial cover near the coastline in the light of these findings we suggest that the pernicana and fiumefreddo faults are discrete segments of a near continuous left lateral shear zone affecting the whole north eastern flank of mt etna as far as the ionian coast

effect of the volcanic front migration on helium nitrogen argon and carbon geochemistry of hydrothermal magmatic fluids from hokkaido volcanoes japan abstract active volcanoes from hokkaido are distributed along the sw ne trending volcanic front where the subducting pacific plate changes direction from n s to wsw ese one exception is the tokachi volcano which is located approximately 50 km to the north west of the current volcanic front the tokachi oki slab cracking zone represents the transitional zone between the honshu and kurile trenches this change is responsible for the rapid lateral variation of the subduction angle and slab shape we investigate the consequence of this change on the chemical and isotopic compositions from hydrothermal magmatic fluids and mineral separates collected from three volcanoes of hokkaido northern japan namely tarumae tokachi and meakan our data show that these volcanoes have a distinct range of he n and c isotopic compositions meakan fumaroles have a 3he 4he ratio that ranges from 4 46ra to 6 88ra 15n from 2 2 to 3 5 and 13c co2 from 8 47 to 9 81 consistent with subducted sediment contribution tarumae fumaroles have a particularly low 3he 4he ratio 3 08ra in comparison with their hot springs up to 5 24ra and are associated with high co2 3he ratios 2 2 5 3 1011 hydrothermal crustal interactions from the dome or from a deeper hydrothermal system are the main mechanisms that control the 3he 4he and co2 3he ratios in tarumae fumaroles the 15n and 13c co2 values for tarumae volcano range from 0 6 to 3 1 and from 6 34 to 6 43 respectively tokachi fumaroles are characterized by high 3he 4he up to 7 38ra low 15n 2 4 0 1 and low 13c co2 up to 5 32 consistent with mantle contribution and minor subducted sediment contribution the limestone sediment mantle ratio shows a decreasing contribution from subducted sediments starting from tokachi 1 9 to meakan 3 4 and finally tarumae 5 3 this change of isotopic compositions from the sw ne of hokkaido is the result of the tokachi oki slab cracking zone slab dehydration under tokachi occurs at a deeper level 150 200 km than in other hokkaido volcanoes 100 km which produces the migration of the volcanic front therefore we argue that the isotopic signature of tokachi is the result of i a lower sediment contribution from the slab ii a deeper dehydration of the slab and iii a lower degree of partial melting

morpho structural setting of stromboli volcano revealed by high resolution bathymetry and backscatter data of its submarine portions the first high resolution bathymetric and backscatter maps of offshore stromboli island are presented together with an interpretation of its volcanic structural and sedimentary features the volcanic edifice is characterized by a sub conical shape with a quasi bilateral symmetry with respect to a ne sw axis the dimensions of the strombolicchio volcanic centre to the ne of stromboli have been restored by redrawing its morphology before wave action that eroded it in late quaternary time on the ne submarine flank of strombolicchio a n64 e structural trend controls the shape of strombolicchio canyon on the southern side of stromboli the submarine flank has a radial structural trend possibly reflecting a volcanic stress regime landslide scars at various scales are ubiquitous on the submarine slopes of stromboli repeated large scale lateral collapses have affected both the northwestern and southeastern unbuttressed flanks of the volcano producing large debris avalanche deposits

importance of structural history in the summit area of stromboli during the 2002 2003 eruptive crisis inferred from temperature soil co2 self potential and electrical resistivity tomography the 2002 2003 eruptive crisis of stromboli volcano in the aeolian islands raised the question of how to assess the stability of the flanks of this volcanic edifice during such a crisis to provide a response to this question we analyzed a detailed fluid flow mapping plus the reiteration of a profile located in the vicinity of the active vents using the self potential method temperature data soil gas co2 measurements and electric resistivity tomography coupling the interpretation of these methods that are sensitive to the flow of gas and water in the ground indicates the position of areas of mechanical weakness in addition they can be used to monitor the change in the discharge of fluids associated with these features before and during the 2002 2003 eruptive crisis our results emphasize the importance of old structural boundaries such as the large fossa crater in the development of the new set of fractures observed during the 2002 2003 eruptive crisis between october 2002 and january 2003 the use of co2 soil gas technique evidenced an increase in the discharge of co2 outside the large fossa crater boundaries along the failure boundary of the southern sciara del fuoco area self potential and temperature measurements made before the 2002 2003 eruptive crisis reveal significant changes along the main structural boundaries of the fossa area the development of these anomalies is interpreted as an increase of the permeability of the structure from may 2000 to may 2002 between january 2003 and march 2003 the reiteration of self potential temperature and co2 measurements shows an increase of fluid discharge along weakness planes located inside the large fossa crater boundary they evidence no change outside this structural boundary the importance of the large fossa crater boundary in controlling the deformation and fluid flow from january to march 2003 has been attested by the development of the fractures inside the large fossa crater boundary and also with a network of electrooptical distance measurement stations located inside and outside this ancient crater this multidisciplinary approach to fluid flow assessment before and during an eruptive crisis is complementary to geodetic measurements of the deformation of the edifice it demonstrates for the first time the powerful potential of combining electrical resistivity tomography self potential temperature and soil co2 measurements in assessing the position of the planes of mechanical weakness in a volcanic edifice

self potential global tomography including topographic effects this paper is an extension of a previous study in which the principles of self potential ground surface tomography were outlined the new arguments which are here set forth are the proper accounting for the topographic effects and a robust approach to global 3d tomography the 2d case is initially considered in order to facilitate a full understanding of the new method in order to gauge the topographic distortions the concepts of slope effect and surface regularization are introduced as suitable means to compute point by point correction factors of the measured self potential data prior to the recognition of the tomographic images of the primary and induced electric sources underground the tomographic approach is then developed by introducing again the concepts of the scanning function and of the charge occurrence probability function which were amply dealt with in the previous paper the new approach to 3d global tomography means here the composition of charge occurrence probability functions related to any two orthogonal surface components of the natural electric field in order to account fully for the total surface component of the self potential field and hence to elicit the greatest amount of information two field examples are presented to show the full effectiveness of the proposed method they refer respectively to a near surface investigation for archaeological purposes and to a very deep investigation in an active volcanic area

the summit hydrothermal system of stromboli new insights from self potential temperature co2 and fumarolic fluid measurements with structural and monitoring implications accurate and precisely located self potential sp temperature t and co2 measurements were carried out in the summit area of stromboli along 72 straight profiles sp data were acquired every metre and t data every 2 5 m co2 concentrations were acquired with the same density as t but only along seven profiles the high density of data and the diversity of the measured parameters allows us to study structures and phenomena at a scale rarely investigated the shallow summit hydrothermal activity pizzo fossa area is indicated by large positive sp t and co2 anomalies these anomalies are focused on crater faults suggesting that the fracture zones are more permeable than surrounding rocks at stromboli the analysis of the distribution of these linear anomalies coupled with the examination of the geologic photographic and topographic data has led us to propose a new structural interpretation of the summit of stromboli this newly defined structural framework comprises 1 a large pizzo circular crater about 350 m in diameter 2 a complex of two concealed craters nested within the pizzo crater the large and the small fossa craters thought to have formed during the eruption of the pizzo pyroclastites unit the small fossa crater is filled with highly impermeable material that totally impedes the upward flow of hydrothermal fluids and 3 the present complex of active craters on the floor of the fossa short wavelength sp lows are organized in drainage like networks diverging from the main thermal anomalies and converging toward the topographic low in the fossa area inside the small fossa crater they are interpreted as the subsurface downhill flow of water condensed above the thermal anomalies we suspect that water accumulates below the small fossa crater as a perched water body representing a high threat of strong phreatic and phreatomagmatic paroxysms t and co2 anomalies are highly correlated the two types of anomalies have very similar shapes but the sensitivity of co2 measurements seems higher for lowest hydrothermal flux above t anomalies a pronounced high frequency sp signal is observed isotopic analyses of the fluids show similar compositions between the gases rising through the faults of the pizzo and large fossa craters this suggests a common origin for gases emerging along different structural paths within the summit of stromboli a site was found along the large fossa crater fault where high gas flux and low air contamination made gas monitoring possible near the active vents using the alkaline bottle sampling technique

fluid circulation at stromboli volcano aeolian islands italy from self potential and co2 surveys this work addresses the study of fluid circulation of the stromboli island using a dense coverage of self potential sp and soil co2 data a marked difference exists between the northern flank and the other flanks of the island the northern flank exhibits 1 a typical negative sp altitude gradient not observed on the other flanks and 2 higher levels of co2 the general sp pattern suggests that the northern flank is composed of porous layers through which vadose water flows down to a basal water table in contrast to the other flanks where impermeable layers impede the vertical flow of vadose water in the sciara del fuoco and rina grande le schicciole landslide complexes breccias of shallow gliding planes may constitute such impermeable layers whereas elsewhere poorly permeable fine grained pyroclastites or altered lava flows may be present this general model of the flanks also explains the main co2 patterns concentration of co2 at the surface is high on the porous north flank and lower on the other flanks where impermeable layers can block the upward co2 flux the active upper part of the island is underlain by a well defined hydrothermal system bounded by short wavelength negative sp anomalies and high peaks of co2 these boundaries coincide with faults limiting ancient collapses of calderas craters and flank landslides the hydrothermal system is not homogeneous but composed of three main subsystems and of a fourth minor one and is not centered on the active craters the latter are located near its border this divergence between the location of the active craters and the extent of the hydrothermal system suggests that the internal heat sources may not be limited to sources below the active craters if the heat source strictly corresponds to intrusions at depth around the active conduits the geometry of the hydrothermal subsystems must be strongly controlled by heterogeneities within the edifice such as craters caldera walls or gliding planes of flank collapse as suggested by the correspondence between sp co2 anomalies and structural limits the inner zone of the hydrothermal subsystems is characterized by positive sp anomalies indicating upward movements of fluids and by very low values of co2 emanation this pattern suggests that the hydrothermal zone becomes self sealed at depth thus creating a barrier to the co2 flux in this hypothesis the observed hydrothermal system is a shallow one and it involves mostly convection of infiltrated meteoric water above the sealed zone finally on the base of co2 degassing measurements we present evidence for the presence of two regional faults oriented n41 and n64 and decoupled from the volcanic structures

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

geochemical evidence of the renewal of volcanic activity inferred from co2 soil and so2 plume fluxes the 2007 stromboli eruption italy on 27 february 2007 a new eruption occurred on stromboli which lasted until 2 april it was characterized by effusive activity on the sciara del fuoco and by a paroxysmal event 15 march this crisis represented an opportunity for us to refine the model that had been developed previously 2002 2003 eruption and to improve our understanding of the relationship between the magmatic dynamics of the volcano and the geochemical variations in the fluids in particular the evaluation of the dynamic equilibrium between the volatiles co2 and so2 released from the magma and the corresponding fluids discharged from the summit area allowed us to evaluate the level of criticality of the volcanic activity one of the major accomplishments of this study is a 4 year database of summit soil co2 flux on the basis of which we define the thresholds low medium high for this parameter that are empirically based on the natural volcanological evolution of stromboli the so2 fluxes of the degassing plume and the co2 fluxes emitted from the soil at pizzo sopra la fossa are also presented it is noteworthy that geochemical signals of volcanic unrest have been clearly identified before during and after the effusive activity these signals were found almost simultaneously in the degassing plume so2 flux and in soil degassing co2 flux at the summit although the two degassing processes are shown to be clearly different the interpretation of the results will be useful for future volcanic surveillance at stromboli

radon surveys and real time monitoring at stromboli volcano influence of soil temperature atmospheric pressure and tidal forces on 222rn degassing abstract we used a network of stations to perform systematic radon surveys at stromboli volcano the time series of periodic measurements show that monthly average 222rn emissions reflect changes in volcanic activity and exhibit increasing trends prior and during the last major eruptive cycles maps of radon emissions indicate that diffuse degassing is operative at stromboli volcano concentrated degassing essentially occurs in the summit area and within a sector proximal to the two major ne trending faults these sites were chosen for deploying the two real time stations that are currently operating at stromboli in these devices the 222rn electronic dosimeters are connected to a radiomodem for wireless data transfer to a receiving station at the volcano observatory radon activity soil temperature and atmospheric pressure data are sampled and instantaneously transferred via web so that they can be checked remotely collected time series reveal an overall inverse correlation between radon emissions and seasonal temperature variations radon emissions in sectors of diffuse degassing are modulated by tidal forces as well radon activities recorded at the summit station located along the fracture zone where the gas flux is concentrated are positively correlated with changes in atmospheric pressure and confirm the occurrence of the atmospheric stack effect we finally emphasize that real time radon monitoring is an innovative technique that may be systematically applied in volcano surveillance

self potential signals generated by the corrosion of buried metallic objects with application to contaminant plumes abstractlarge amplitude 100 mv negative electric self potential anomalies are often observed in the vicinity of buried metallic objects and ore bodies or over groundwater plumes associated with organic contaminants to explain the physical and chemical mechanisms that generate such electrical signals a controlled laboratory experiment was carried out involving two metallic cylinders buried with vertical and horizontal orientations and centered through and in the capillary fringe within a sandbox the 2d and 3d self potential sp data were collected at several time steps along with collocated ph and redox potential measurements large dipolar sp and redox potential anomalies developed in association with the progressive corrosion of the vertical pipe although no anomalies were observed in the vicinity of the horizontal pipe this discrepancy was due to the orientation of the pipes with the vertical pipe subjected to a significantly larger eh gradient accounting for the electrical conductivity dis

morphotectonic control on drainage network evolution in the perachora peninsula greece abstract in tectonically active areas drainage systems are often influenced by the type geometry and recent activity of regional and local faults in the perachora peninsula eastern gulf of corinth greece most drainage networks are influenced by neotectonic processes and eustasy two major east west trending fluvial systems perachora and pissia in the southwestern part of the peninsula are affected by faults of similar orientation detailed geomorphological mapping was performed focusing on knickpoints gorges planation and depositional surfaces alluvial fans and talus cones longitudinal river profiles and hypsometric curves of their basins were constructed utilizing gis technology the two drainage systems exhibit opposite network asymmetries the pissia network is well developed south of the main channel while the perachora extends to the north the analysis of the longitudinal profiles of the main stream channels denotes that they exhibit different evolutionary trends the pissia stream has a transverse drainage crossing the active loutraki fault while the perachora stream has a parallel evolution as it has the same orientation as the loutraki fault the drainage system of pissia is much older than the perachora as a large part of the latter was underwater in late pleistocene times the combination of eustacy and vertical tectonic movements has led to the development of four marine terraces corresponding to previous high sea level stands during oxygen isotope stages ois 5e 7e 9c and 11c following the analysis of the longitudinal profiles and the hypsometric curves two depositional surfaces were verified at perachora village the first surface at 280 360 m and the second one between 120 and 160 m are probably related to marine terraces 11c and 7e respectively the development of the present drainage systems of perachora and pissia in the late quaternary depends mostly on the fault tectonism of the two main offshore fault systems of xylokastro and loutraki resulting in the uplift of marine terraces to heights of more than 300 m but also due to the inland faults pissia and alepochori which created depositional surfaces and knickpoints sea level changes have played a secondary role in the development of the drainage systems

3 d density structure and geological evolution of stromboli volcano aeolian islands italy inferred from land based and sea surface gravity data we present the first density model of stromboli volcano aeolian islands italy obtained by simultaneously inverting land based 543 and sea surface 327 relative gravity data modern positioning technology a 1 1 m digital elevation model and a 15 15 m bathymetric model made it possible to obtain a detailed 3 d density model through an iteratively reweighted smoothness constrained least squares inversion that explained the land based gravity data to 0 09 mgal and the sea surface data to 5 mgal our inverse formulation avoids introducing any assumptions about density magnitudes at 125 m depth from the land surface the inferred mean density of the island is 2380 kg m 3 with corresponding 2 5 and 97 5 percentiles of 2200 and 2530 kg m 3 this density range covers the rock densities of new and previously published samples of paleostromboli i vancori neostromboli and san bartolo lava flows high density anomalies in the central and southern part of the island can be related to two main degassing faults crossing the island n41 and n64 that are interpreted as preferential regions of dyke intrusions in addition two low density anomalies are found in the northeastern part and in the summit area of the island these anomalies seem to be geographically related with past paroxysmal explosive phreato magmatic events that have played important roles in the evolution of stromboli island by forming the scari caldera and the neostromboli crater respectively

comparative study of geophysical and soil gas investigations at the hartousov czech republic natural co2 degassing site our study at this natural analog site contributes to the evaluation of methods within a hierarchical monitoring concept suited for the control of co2 degassing it supports the development of an effective monitoring concept for geological co2 storage sites carbon capture and storage as one of the pillars of the european climate change efforts this study presents results of comprehensive investigations along a 500 m long profile within the hartousov czech republic natural co2 degassing site and gives structural information about the subsurface and interaction processes in relation to parameters measured measurements of co2 concentrations and investigation of the subsurface using electrical resistivity tomography and self potential methods provide information about subsurface properties for their successful application it is necessary to take seasonal variations e g soil moisture temperature meteorological conditions into consideration due to their influence on these parameters locations of high co2 concentration in shallow depths are related to positive self potential anomalies low soil moistures and high resistivity distributions as well as high 13c values and increased radon concentrations co2 ascends from deep geological sources via preferential pathways and accumulates in coarser sediments repetition of measurements which includes the effects of seasonal variations revealed similar trends and allows us to identify a clear prominent zone of anomalous values coarser unconsolidated sedimentary layers are beneficial for the accumulation of co2 gas the distribution of such shallow geological structures needs to be considered as a significant environmental risk potential whenever sudden degassing of large gas volumes occurs

self potential survey near the craters of stromboli volcano italy inference for internal structure and eruption mechanism the presence of self potentials on the upper part of stromboli volcano is associated with the existence of convection cells of gases and condensed liquids whose rising parts are situated above the hot zones a model of a convection cell fed by a hot fluids through its lower middle part was calculated and applied to the various structures of the upper part of the volcano this model which takes account of a process which is probably fairly common in volcanic system gives a clear explanation of the various potential zones

radar doppler velocimetry of volcanic eruptions theoretical considerations and quantitative documentation of changes in eruptive behaviour at stromboli volcano italy summary the use of radar doppler velocimetry for the observation of volcanic activity is new we used this method to continuously observe the activity of one vent of stromboli volcano italy from the end of 2000 april until early may during this period we recorded 702 eruptions 132 of which occurred before a strong rain storm passed over the island on april 29 in order to interpret the recorded doppler data we developed a program that simulates different strombolian eruption scenarios for which we then calculate the theoretical doppler spectra comparing our theoretical data with the observed data we are able to show that most of the eruptions are nearly vertical although we did observe only one component of the eruption vector with our doppler radar one of the most interesting features of the data set is a significant change in eruptive behaviour that correlates with the occurrence of the rain storm we find that on average the eruption duration increased by a factor of 2 eruptive velocities were much higher and indirect evidence indicates that the average particle diameter of the erupted material decreased this change may have several causes but the coincidence with the rain storm may be evidence of magma water interaction and feedback on the volcanic activity if the fluid source rain changing the eruptive style is at the surface and in near surface layers then the main control on final eruption dynamics at stromboli volcano must also be in rather shallow regions

identification of a hidden thermal fissure in a volcanic terrain using a combination of hydrothermal convection indicators and soil atmosphere analysis abstract mapping and characterizing fracturing in a volcanic terrain is facilitated by the analysis of physical and chemical properties of soils the parameters analyzed include the temperature at shallow depth the spontaneous potential sp and the 4 he 44 co 2 and 222 rn contents of soil gases as measured in situ by mass spectrometry and counter this analysis allowed a distinction of deep fissures not accompanied by thermal loss characterized by a negative sp anomaly and high he levels and of a hidden fissure with thermal loss characterized by a positive sp anomaly and high he rn and co 2 levels this fissure has no visible surface manifestations this method of analysing the convective thermal transfer is useful when analysing fracturing in volcanic structures to estimate their eruptive potential

a model of diffuse degassing at three subduction related volcanoes and 13c in soil gas were measured at three active subduction related stratovolcanoes arenal and poas costa rica galeras colombia in general rn co2 and 13c values are higher on the lower flanks of the volcanoes except near fumaroles in the active craters the upper flanks of these volcanoes have low rn concentrations and light 13c values these observations suggest that diffuse degassing of magmatic gas on the upper flanks of these volcanoes is negligible and that more magmatic degassing occurs on the lower flanks where major faults and greater fracturing in the older lavas can channel magmatic gases to the surface these results are in contrast to findings for mount etna where a broad halo of magmatic co2 has been postulated to exist over much of the edifice differences in radon levels among the three volcanoes studied here may result from differences in age the degree of fracturing and faulting regional structures or the level of hydrothermal activity volcanoes such as those studied here act as plugs in the continental crust focusing magmatic degassing towards crater fumaroles faults and the fractured lower flanks

caldera rim collapse a hidden volcanic hazard following the emblematic flank collapse of mount st helens in 1981 numerous models of flank sliding have been proposed these models have allowed to largely improve the understanding of mechanisms involved in such landslides which represent a tremendous risk for populations living around volcanoes in this article a new mode of landslide formation related to buried calderas is described the model emphasizes the paramount importance of the hidden ring fault that even when the caldera is buried still remains a plane of weakness in the core of the edifice under certain conditions this plane of weakness becomes activated as the upper part of a pre existing critical slip surface and is used in the emplacement of huge landslides which travel downslope at a very high velocity a natural example is taken from piton de la fournaise volcano la reunion island indian ocean it reveals that the primary cause triggering caldera rim collapse is partial unbuttressing of the flank of the volcano in the natural example this occurs through regressive erosion that excavates deep canyon in the direction of the buried caldera but other mechanisms may exist on account of the large volumes of material involved in caldera rim collapse as well as their long runout distances such a volcanic hazard should be taken into account on every volcano where buried calderas are suspected

zeta potential estimation of volcanic rocks on 11 island arc type volcanoes in japan implication for the generation of local self potential anomalies 1 from streaming potential measurements we deduced the zeta potential of 73 volcanic rock samples collected in 11 volcanoes where self potential sp surveys had also been conducted experiments with crushed rock samples and 0 001 mol l nacl solution showed a large variation in streaming potential coefficient which ranged from 2860 to 2280 mv mpa deduced zeta potential ranged from 45 1 to 37 2 mv among the 73 samples 9 samples showed positive values and 11 samples showed small absolute values less than 10 mv even in a volcano the zeta potential values of rocks were sometimes highly variable to investigate the reason for the variation in zeta potential we performed x ray fluorescence xrf measurements on the rock samples however no significant correlations between zeta potential or isoelectric point and weight percentage of major elements were found implying that the zeta potential of the volcanic rocks is not controlled by chemical composition but by mineralogical composition or crystalline structure in volcanic areas rocks with positive or small absolute values of zeta potential which are considered to be unusual frequently exist in areas along with local positive sp anomalies although positive sp anomalies are usually interpreted as an indication of hydrothermal upflow this correlation suggests that in addition to the groundwater flow pattern the polarity of zeta potential should also be considered for interpretation of sp data therefore in cases where detailed zeta potential measurements have not been conducted local positive sp anomalies should be interpreted with caution

origin of hydrogen and carbon dioxide in fault gases and its relation to fault activity gases occluded in fracture zones of active faults are characterized by a high concentration of h 2 and or co 2 a predominant gas species h 2 or co 2 is related to the lithofacies which the fault cuts carbon dioxide concentration in sediments fluctuates with temperature this evidence and sigma 13 c of co 2 about 20 suggests that co 2 originates from organic materials carbon dioxide with sigma 13 c of 5 to 17 in brecciated gneiss containing marble may have been produced by interaction between organically derived co 2 and the marble or alternatively may have been magmatically derived hydrogen usually occurs in sheared silicate rocks and its concentration fluctuates a great deal the concentration of h 2 from active faults associated with historical earthquakes usually amounts to as high as several percent in maximum whereas the concentration of h 2 from quaternary faults not associated with historical earthquakes is at most 1

structural pattern and co2 ch4 degassing of ustica island southern tyrrhenian basin brittle tectonics and ground degassing including fracture field soil gas and exhalation flux analyses of co2 and ch4 were studied at ustica island a pleistocene volcanic complex in the southern tyrrhenian sea the mesoscopic fracture pattern perfectly fits an e w trending left lateral strike slip master fault in agreement with the main morpho structural submarine alignment including ustica island and anchise seamount along the sw ne high angle normal arso fault geological evidence of reactivation with different kinematics left to right lateral displacements was recognised major co2 and ch4 degassing with fluxes up to 93 750 and 20 t km 2 a 1 respectively and soil gas concentrations of 11 3 and 5 7 ppm occur over the arso fault although this fault is mapped just in the sw sector of the island soil gas co2 anomalies point out its clear continuation up to the ne margin of the island these data together with those of previous geophysical and geochemical results from off shore ustica suggest that the arso fault is the local evidence of a more important active gas bearing structure this tectonic feature is interpreted as a reactivation of a preexistent sw ne trend inherited as a second order structure of the e w deep shear zone the reactivation is related to the interplay among different structures of the southern tyrrhenian basin

source location variability and volcanic vent mapping with a small aperture infrasound array at stromboli volcano italy stromboli volcano in italy is a persistently active complex volcanic system in may 2002 activity was confined to 3 major summit craters within which several active vents hosted multiple explosions each hour during a 5 day field campaign an array of 3 low frequency microphones was installed to investigate the coherent infrasound produced by degassing from these vents consistent phase lags across the 3 stations indicate distinct sources that are subsequently investigated to determine the associated vent location apparent depth and origin time the cross correlation routine allows for variations in comparison window length waveform filtering bandwidth and correlation and consistency thresholds allowing for improved detection of certain types of degassing sources identification of activity at the various vents could be subsequently corroborated with 3 channels of synchronously acquired thermal data and video during the may 2002 experiment persistent energetic infrasound was observed from a passive degassing source within the central crater cc and transient infrasound produced by discrete strombolian explosions was identified at 4 additional vents the continuous infrasound produced by the cc exhibits variable frequency dependent correlation lag times that are interpreted as a diffraction effect due to the acoustic radiator s recessed location within a steep walled crater such dispersion has important implications for accurate eruption source modeling because it indicates that infrasonic waveforms may be significantly filtered during propagation transient explosion signals from the northeast crater nec and southwest crater swc vents also exhibit dynamic correlation lag times but this scatter may be more reasonably attributed to variable epicentral locations explosions from the nec west vent for instance appear to emanate from a diffuse zone with a lateral extent in excess of 10 m

geochemical monitoring of the 2002 2003 eruption at stromboli volcano italy precursory changes in the carbon and helium isotopic composition of fumarole gases and thermal waters significant changes in the helium and carbon isotopic composition of shallow thermal waters vs gas and a crater fumarolic gas have been recorded at stromboli prior and during the 2002 2003 eruption the3he 4he ratios corrected for air contamination rc ra and 13c of fumarolic gases gradually increased from may to november 2002 before the eruption onset these variations imply early degassing of a gas rich magma at depth that likely fed both the intense strombolian activity and small lava overflows recorded during that period the lava effusion of late december 2002 was shortly preceded by a marked rc ra decrease both in water and fumarolic gases comparison of he co2 and ch4 co2 ratios in dissolved gas and with rm delta 13 rm c rm co 2 values rules out the rc ra decrease due to an increasing input of radiogenic4he the rc ra decrease is attributed to the he isotope fractionation during rapid magma ascent and degassing a new uprising of 3he rich magma probably occurred in january to february 2003 when rc ra ratios displayed the highest values in dissolved gases ever measured before 4 56 rc ra the increase in he co2 and ch4 co2 ratios and decrease in 13c of dissolved co2 was recorded after the 5 april 2003 explosive paroxysm likely caused by enhanced gas water interaction inducing co2 dissolution no anomalous rc ra values were recorded in the same period when usual strombolian activity gradually resumed

the structure of a hydrothermal system from an integrated geochemical geophysical and geological approach the ischia island case study the complexity of volcano hosted hydrothermal systems is such that thorough characterization requires extensive and interdisciplinary work we use here an integrated multidisciplinary approach combining geological investigations with hydrogeochemical and soil degassing prospecting and resistivity surveys to provide a comprehensive characterization of the shallow structure of the southwestern ischia s hydrothermal system we show that the investigated area is characterized by a structural setting that although very complex can be schematized in three sectors namely the extra caldera sector ecs caldera floor sector cfs and resurgent caldera sector rcs this contrasted structural setting governs fluid circulation geochemical prospecting shows in fact that the caldera floor sector a structural and topographic low is the area where co2 rich 40 cm3 l hydrothermally mature log mg na ratios 150 g m 2 d 1 is clearly captured by electrical resistivity tomography ert and transient electromagnetic tem surveys as a highly conductive resistivity 10 000 mg l and poorly conductive meteoric derived tds 4 000 mg l waters are observed respectively we finally integrate our observations to build a general model for fluid circulation in the shallowest 0 5 km part of ischia s hydrothermal system

self potential signals associated with preferential groundwater flow pathways in sinkholes 1 two self potential sp surveys have been conducted at a test site located in normandy in the northwest of france in a chalk karst in spring and summer 2005 the spring survey showed circular negative sp signals associated with the position of sinkholes and crypto sinkholes while the survey conducted during the summer showed fewer anomalies with lesser magnitudes the negative sp anomalies observed in the spring survey were several tens of millivolts less than a reference located outside the ridge along which the sinkholes are located in addition to the sp surveys we also performed a dc electrical resistivity survey the electrical resistivity tomogram shows the position of the interfaces between the chalk and the overlying clay with flint and loess covers and the position of the sinkholes a linear relationship is observed between the sp signals and the thickness of the loess layer in addition large negative sp anomalies are associated with the sinkholes themselves these sp signals are explained by solving the boundary value problem for the coupled hydroelectric problem we fixed the boundary condition at the ground surface in terms of hydraulic flux associated with the infiltration of the meteoric water and a no flow condition on the vertical boundaries a finite element numerical simulation of this coupling is performed and a fairly good agreement is obtained between the simulation and the observed sp signals we show for the first time how the sp signals reflect mainly the topography of the clay with flint loess interface and help to identify the location of sinkholes three dimensional tomography algorithms are proposed to locate the source of these self potential signals in the ground

a geochemical and geophysical investigation of the hydrothermal complex of masaya volcano nicaragua abstract masaya volcano nicaragua is a persistently active volcano characterized by continuous passive degassing for more than 150 years through the open vent of santiago crater this study applies self potential soil co 2 and ground temperature measurements to highlight the existence of uprising fluids associated to diffuse degassing structures throughout the volcano the diffuse degassing areas are organized in a semi circular pattern and coincide with several visible and inferred surface volcanic structures cones fissure vents and likely consist of a network of buried faults and dykes that respectively channel uprising flow and act as barrier to gravitational groundwater flow water depths have been estimated by multi scale wavelet tomography of the self potential data using wavelets from the poisson kernel family compared to previous water flow models our water depth estimates are shallower and mimic the topography typically less than 150 m below the surface between 2006 and 2010 the depths of rising fluids along the survey profiles remained stable suggesting that hydrothermal activity is in a steady state this stable activity correlates well with the consistency of the volcanic activity expressed at the surface by the continuously passive degassing when compared to previous structural models of the caldera floor it appears that the diffuse degassing structures have an important effect on the path that shallow groundwater follows to reach the laguna de masaya in the eastern part of the caldera the hydrogeological system is therefore more complex than previously published models and our new structural model implies that the flow of shallow groundwater must bypass the intrusions to reach the laguna de masaya furthermore these diffuse degassing structures show clear evidence of activity and must be connected to a shallow magmatic or hydrothermal reservoir beneath the caldera as such the heat budget for masaya must be significantly larger than previously estimated

structural controls on fluid circulation at the caviahue copahue volcanic complex ccvc geothermal area chile argentina revealed by soil co 2 and temperature self potential and helium isotopes abstract natural geothermal systems are limited areas characterized by anomalously high heat flow caused by recent tectonic or magmatic activity the heat source at depth is the result of the emplacement of magma bodies controlled by the regional volcano tectonic setting in contrast at a local scale a well developed fault fracture network favors the development of hydrothermal cells and promotes the vertical advection of fluids and heat the southern volcanic zone svz straddling chile and argentina has an important yet unexplored and undeveloped geothermal potential studies on the lithological and tectonic controls of the hydrothermal circulation are therefore important for a correct assessment of the geothermal potential of the region here new and dense self potential sp soil co 2 and temperature t measurements and helium isotope data measured in fumaroles and thermal springs from the geothermal area located in the north eastern flank of the copahue volcanic edifice within the caviahue caldera the caviahue copahue volcanic complex ccvc are presented our results allowed to the constraint of the structural origin of the active thermal areas and the understanding of the evolution of the geothermal system ne striking faults in the area characterized by a combination of sp co 2 and t maxima and high 3 he 4 he ratios up to 8 16 0 21ra whereas atmospheric ra is 1 382 10 6 promote the formation of vertical permeability preferential pathways for fluid circulation wnw striking faults represent low permeability pathways for hydrothermal fluid ascent but promote infiltration of meteoric water at shallow depths which dilute the hydrothermal input the region is scattered with sp co 2 and t minima representing self sealed zones characterized by impermeable altered rocks at depth which create local barriers for fluid ascent the ne striking faults seem to be associated with the upflowing zones of the geothermal system where the boiling process produces a high vapor dominated zone close to the surface whereas the wnw striking faults could act as a boundary of the copahue geothermal area to the south

thermal surveys of the vulcano fossa fumarole field 1994 1999 evidence for fumarole migration and sealing abstract between 1994 and 1999 we carried out five thermal surveys of the vulcano fossa fumarole field each consisted of 485 1213 vent temperature measurements distributed across the field these show that the field has been cooling and expanding where mean and maximum vent temperatures decreased from 216 to180 c and 541 to 428 c respectively between 1994 and 1997 however expansion of the field resulted in increased heat loss from 45 to 67 mw we suggest that cooling and expansion has been caused by increased gas flux and or permeability where increased flow of fluids of magmatic origin during 1996 is implied by chemical and isotopic data capasso g favara r francofonte s inguaggiato s 1999 chemical and isotopic variations in fumarolic discharge and thermal waters at vulcano island aeolian islands italy during 1996 evidence of resumed volcanic activity j volcanol geotherm res 88 1999 167 175 we propose that the size of the conduit has increased causing the fumarole field to expand and vent temperatures to generally decline as gas and heat losses become distributed over a wider area the increase in exhaling area has outweighed the modulating effect of cooling on total heat losses so that heat loss has increased due to an increased input from the magmatic source and or an increase in system permeability within these field wide trends the rim and then the middle zones have been cooling conversely the lower zone showed evidence of warming during 1994 98 before cooling in 1999 throughout the measurement period a se s thermal migration has been apparent and a new hot zone has developed on the field s southern edge we suggest that sealing of fumaroles by complete boiling of marine fluids on the northern edge of the system and higher permeability on the southern edge may have influenced this expansion direction if vent temperatures drop below 100 c then shallow sulfur sealing will quickly diminish fumarole life expectancy and contribute to the abandonment of vents in cooling zones in our model increased gas flux and or permeability e g due to increased magmatic degassing and or fracturing is the primary mechanism driving observed changes in the field temperature size and location deep and shallow conduit sealing are secondary mechanisms influencing the location of new zones once increased gas and heat fluxes have been triggered

evidence of a dyke sheet intrusion at stromboli volcano inferred through continuous tilt a tiltmeter installed in the northern sector of the island of stromboli aeolian archipelago tyrrhenian sea recorded a co seismic offset at the time of the main shock ml 3 7 of the 7 november 1994 swarm located 5 km north of the island during the three months following this event a transient tilt anomaly which was interpreted as due to a lateral intrusion and modelled through a dyke sheet dislocation was recorded the tilt data were used in an analytical inversion based on a propagating tensile source with length and width increasing in time the final result is consistent with the tectonic and structural framework of the volcano area

review of ten years of volcano deformations recorded by the ground based insar monitoring system at stromboli volcano a tool to mitigate volcano flank dynamics and intense volcanic activity abstract stromboli volcano southern italy is one of the most monitored volcano in the world with a surveillance network that includes a permanently sited ground based sar interferometer gbinsar this work is the review of the gbinsar data gained from the last decade of monitoring activity the analysis of the entire dataset of gbinsar measurements allowed the assessment of the deformation field of the northern part of the summit crater area and the sciara del fuoco depression in detail the main displacements recognized can be related to different factors 1 the inflation deflation respectively immediately before and after each new effusive event 2 the bulging of localized sectors of the volcano involved in the vent opening 3 the gravitational sliding of the sciara del fuoco infill 4 the movement of lava flows accelerations in this sector are related to sheet intrusions while the possibility of vent opening associated with small sliding or catastrophic flank failure are related to highly overpressurized sheets able to produce high displacement rate in the sciara del fuoco in the summit crater area the increases in the displacement rate are related to the pressurization of the shallow conduit system as the consequence of the variation in the magma level magmastatic pressure or to the lateral magma migration lateral conduit expansion or dike intrusion in response to the increase of the overpressure component fluctuations in the displacement rate in the summit crater area can be related to the magma overturning within the conduit with the increases in displacement rate during the upwelling of less dense magma while displacement rate decreases as the degassed magma column is pushed out from the conduit lava flows or overflows instead the decrease in the displacement rate without coeval lava outpouring could be related to the sink of the degassed magma due to density contrast between the gas poor and the gas charged magmas using the displacement rate in the summit crater area as a proxy for the variation in the pressure condition in conduit both magmastatic and overpressure components thresholds for the crises characterized by the occurrence of overflows eventually associated with major explosions and flank effusions eventually associated with paroxysmal explosions are identified small conduit overpressure will produce overflows sometimes associated with crater rim collapses while large magma overpressure will laterally expand the conduit forming ne sw striking sheets feeding eruptive vents at the base of the summit crater area and within the sciara del fuoco generating conditions of instability that can evolve into catastrophic collapse of the instable flank

the contribution of fluid geochemistry to the volcano monitoring of stromboli abstract the persistent open vent mild explosive activity of stromboli volcano is episodically interrupted by more violent and dangerous explosive events major explosions and paroxysms according to the nature of erupted products paroxysms can be related either to the explosion of overpressured gas pockets located in the proximity of the magma column or to the sudden uprise of hot gas rich magma from a deep part of the plumbing system in both cases these more energetic explosive events should be preceded by an escape or a preferential uprise of the highly mobile volatiles which in turn should produce gas leakage anomalies at the surface in sites of high vertical permeability such as deep reaching faults in order to identify such gas leaking sites a systematic co2 soil flux survey has been carried out on the island using an accumulation chamber four hundred sixty one points have been measured with a high density in the summit crater area where high flux values have been found 10 3 10 2 cm s anomalous points are concentrated along the main ne sw axial feeding system of the volcano co2 soil flux decreases from the crater zone to the base of the volcanic cone where however an interesting gas leakage anomaly occurs pizzillo mofette in the pizzillo area thermal water wells also occur whose chemistry indicates an origin by sea water heated by hot gas soil gases have been sampled in the sites with the highest co2 flux in the crater area and at the base of the cone chemical and isotopic analyses indicate the presence of a deep gas component especially in the crater zone samples high co2 appreciable contents of he and h2 3he 4he values up to 3 55 13c of co2 2 the sc5 low flux fumarole on the crater rim has shown during six years a remarkable persistence of temperature 93 95 c with only minor fluctuations of chemistry appearance of anomalous peaks of h2 in correspondence with strombolian explosions was observed during a 2 h 30 min experiment of continuous recording of hydrogen content of the fumarole together with previous data on h2o co2 and he this experiment confirms that strombolian blasts produce rapid fluctuations in the fumarolic gas composition in the light of this study sc5 fumarole and pizzillo mofette look promising sites for the testing of a continuous geochemical monitoring system of stromboli volcano

regional stress field in the area of stromboli italy insights into structural data and crustal tectonic earthquakes abstract crustal tectonic seismicity on stromboli is here discussed along with the regional tectonic and geodynamic context of the aeolian archipelago italy the aim of this paper is to contribute to the reduction of the crucial gap in information concerning the tectonic activity originating at the volcano stromboli in the last decade it is indeed well known that strombolian eruptions related to the persistent state of activity on this volcano allow a fast collection of seismic data which are mainly represented by explosion quakes and tremor however only some sporadic information concerns tectonic earthquakes due to their low occurrence rate a catalog of 150 crustal tectonic earthquakes recorded at stromboli from 1985 to 1996 is presented here the analyses of the seismograms were carried out on the basis of the records of the station str located in the southwestern part of the island the magnitude considered ranged from 1 5 to 3 7 hypocentral location indicates foci at less than 12 km although for the majority of the earthquakes which are not recorded at the seismic stations deployed on the other islands of the aeolian archipelago a shallower within a few kilometers depth can be hypothesized the strain release associated with the 150 tectonic earthquakes of our catalog was also evaluated the low levels of occurrence and seismic energy release reached throughout the ca twelve years analyzed here confirm the minor role played by processes of brittle failure of rocks this aspect of seismic activity is nevertheless important as it can provide a contribution to the knowledge of the dynamics of this volcano the focal mechanisms available integrated with data from the literature show the t axes oriented about ne sw and nw se these findings are consistent with the deformative and tectonic characteristics of this volcanic edifice and of the aeolian archipelago which shows the same two directions of extension this is in agreement with subduction which is very old or which passively evolves towards the final stages and is controlled by the transform activity of the aeolian tindari giardini fault system

characterizing unsaturated flow from packed scoriated lapilli application to strombolian cone hydrodynamic behavior summary over the past 30 years numerous studies have been carried out into groundwater behavior in volcanic areas with particular attention being paid to unsaturated volcanic tuffs the volcanic formations of the chaine des puys massif central france have long been regarded as valuable sources of fresh water and many aquifers associated with volcanic flows have been tapped for domestic water supply or as sources of bottled mineral water it has often been postulated that these volcanic flows are recharged by groundwater from the volcanic cones located upstream although no efforts have been made to validate this theory we tested the physical basis of this hypothesis by characterizing the unsaturated hydrodynamic properties of the packed lapilli and scoria that form the most important constituents of the strombolian cones in this area the model derived from the results of the characterization experiments was compared with data obtained from a field site the unsaturated properties of this site puy de louchadiere strombolian cone are discussed qualitatively and in terms of memory effect further investigations are now needed to determine the exact behavior of the strombolian cone and to produce complete models of the saturated and unsaturated zones of the aquifer system

three dimensional inversion of self potential data used to constrain the pattern of groundwater flow in geothermal fields 1 we propose an algorithm to invert self potential signals measured at the ground surface of the earth to localize hydromechanical disturbances or to the pattern of groundwater flow in geothermal systems the self potential signals result from the divergence of the streaming current density groundwater flow can be either driven by topography of the water table free convection or deformation of the medium the algorithm includes the electrical resistivity distribution of the medium obtained independently by dc resistance tomography or electromagnetic methods or by coding the assumed geology in terms of distribution of the electrical resistivity accounting for the effect of the temperature and salinity distributions and possibly constraints from borehole measurements inversion of the distribution of the source current density from ground surface and borehole self potential measurements is achieved by solving the inverse problem using tikhonov regularization solutions that are compatible with the physics of the primary flow problem by introducing assumptions regarding the smoothness or the compactness of the source and the three dimensional distribution of the electrical resistivity of the system the inverse problem can be solved in obtaining the three dimensional distribution of the current source density in the ground however an annihilator can be added to the inverted source geometry without affecting the measured self potential field annihilators can be obtained from boundary conditions synthetic models and a sandbox experiment are discussed to demonstrate the validity of the algorithm an application is presented to the geothermal field of cerro prieto baja california mexico using literature data inversion of the self potential and resistivity data allows observing a plume of hot groundwater rising to the ground surface in the central part of the investigated area and discharging to the ground surface in the southwest part the temperature anomaly associated with the existence of this plume is independently observed by interpolating borehole temperature measurements we found a good agreement between the distribution of the temperature and the inverted source current density the proposed method appears therefore as a noninvasive method for remote detection and three dimensional mapping of subsurface groundwater flow

the effects of environmental parameters on diffuse degassing at stromboli volcano insights from joint monitoring of soil co2 flux and radon activity abstract soil co 2 flux and 222 rn activity measurements may positively contribute to the geochemical monitoring of active volcanoes the influence of several environmental parameters on the gas signals has been substantially demonstrated therefore the implementation of tools capable of removing or minimising the contribution of the atmospheric effects from the acquired time series is a challenge in volcano surveillance here we present 4 years long continuous monitoring from april 2007 to september 2011 of radon activity and soil co 2 flux collected on the ne flank of stromboli volcano both gases record higher emissions during fall winter up to 2700 bq m 3 for radon and 750 g m 2 day 1 for co 2 than during spring summer seasons short time variations on 222 rn activity are modulated by changes in soil humidity rainfall and changes in soil co 2 flux that may be ascribed to variations in wind speed and direction the spectral analyses reveal diurnal and semi diurnal cycles on both gases outlining that atmospheric variations are capable to modify the gas release rate from the soil the long term soil co 2 flux shows a slow decreasing trend not visible in 222 rn activity suggesting a possible difference in the source depth of the of the gases co 2 being deeper and likely related to degassing at depth of the magma batch involved in the february april 2007 effusive eruption to minimise the effect of the environmental parameters on the 222 rn concentrations and soil co 2 fluxes two different statistical treatments were applied the multiple linear regression mlr and the principal component regression pcr these approaches allow to quantify the weight of each environmental factor on the two gas species and show a strong influence of some parameters on the gas transfer processes through soils the residual values of radon and co 2 flux i e the values obtained after correction for the environmental influence were then compared with the eruptive episodes that occurred at stromboli during the analysed time span 2007 2011 but no clear correlations emerge between soil gas release and volcanic activity this is probably due to i the distal location of the monitoring stations with respect to the active craters and to ii the fact that during the investigated period no major eruptive phenomena paroxysmal explosion flank eruption occurred comparison of mlr and pcr methods in time series analysis indicates that mlr can be more easily applied to real time data processing in monitoring of open conduit active volcanoes like stromboli where the transition to an eruptive phase may occur in relatively short times

practical evaluation of steady heat discharge from dormant active volcanoes case study of vulcarolo fissure mount etna italy abstract from a theoretical approach combined with experimental study i propose a method to compute both sensible and latent heat transfer in a thermally active volcanic area this method is applied to a fumarolic thermal fissure located on the south flank on mount etna italy the method involves four steps 1 mapping of self potential sp to quickly identify thermal anomalies 2 mapping of ground temperature t at constant depth in the area defined by sp mapping 3 measurement of vertical t profiles at selected representative stations including the coldest and hottest and 4 direct measurements of vapor flow where the convective heat flux reaches the surface when heat flux values vary in the range 10 300 w m 2 t measurements at a depth equal to about 1 m are sufficient to estimate the absolute flux value to within an absolute error less than 30 and 10 for the relative value ground temperature measurement is an easy and accurate method for estimating heat discharge on a limited surface to define the fissure system monitor time variations of heat flux or to calibrate remote sensing results on the ground

effects of handling storage and chemical treatments on δ13c values of terrestrial fossil organic matter with the need to interpret small isotopic variations 13c analyses of sedimentary organic matter are more and more widespread in the field of paleo climatology recent developments require an evaluation of the reliability and reproducibility of the whole data acquisition chain literature abounds in protocols for sediment pretreatment prior to physical measurements these procedures differ at every step from sampling handling and storage conditions to leaching procedure without cross evaluation in this study we focus on two sediment samples a modern temperate soil and a 70 ka typical loess we review different protocols that characterize each step of the sediment pretreatment handling and storage conditions are tested e g finger skin contact mild to high temperature oven dry and freeze drying likewise different decarbonation protocols are compared wet decarbonation under cold 0 6 n hcl 2 n hcl and boiling 1 n hcl and acid fuming with 36 hcl this study identifies up to 1 5 isotopic shifts linked to experimental bias this large bias might be at the origin of erroneous paleoclimatic interpretation on the basis of these results we propose specific treatments adapted to the sample type

mafic and ultramafic xenoliths in san bartolo lava field new insights on the ascent and storage of stromboli magmas mafic and ultramafic xenoliths are well represented within a large basaltic lava field of stromboli these basalts known as san bartolo lavas show a high k calc alkaline hkca affinity and were erupted 5 ka bp xenoliths consist of olivin gabbro gabbronorite anorthosite dunite wehrlite and clinopyroxenite thermobarometric estimates for the crystallization of gabbroic materials show minima equilibration pressures of 0 17 0 24 gpa at temperatures ranging from 940 to 1 030 c these materials interacted with hydrous ascending hkca basaltic magmas with temperatures of 1 050 1 100 c at pressures of about 0 2 0 4 gpa these pressure regimes are nearly identical to those found for the crystallization of phenocrystic phases within hkca basaltic lavas gabbroic inclusions are regarded as cumulates and represent crystallized portions of earlier hkca strombolian basalts

estimation of the water table throughout a catchment using self potential and piezometric data in a bayesian framework information about spatial variations of the water table that occur throughout catchments is useful to infer large scale flow patterns but conventional mapping using piezometric data is invasive slow and expensive water flow in the subsurface generates an electrical current called the streaming current the resulting self potential sp electrostatic signals can be measured non intrusively quickly and inexpensively at the ground surface we considered two conceptual models to relate sp signals to the water table the infiltration model relates sp signals to the thickness of the vadose zone while the water table model relates sp signals to the distribution of the water table in unconfined aquifers these models are first calibrated against field data before a bayesian method is applied to update a kriged map of the water table obtained from piezometric observations using a kriged sp map the estimated water tables based on the two conceptual models were combined into one final model using concepts from bayesian model averaging the method was applied to a small agricultural catchment not vert similar1 km2 in southern france the posterior water table estimates were improved mainly on the slopes surrounding the basin understanding the variations in the water table on these slopes is important because infiltration in these areas feed the basin with groundwater flow the bayesian framework is useful to avoid overconfident predictions when using sp data in hydrogeological estimation because it provides realistic uncertainty estimates

shallow resistivity structure of asama volcano and its implications for magma ascent process in the 2004 eruption asama volcano is an active volcano with many historical records of vulcanian eruptions its most recent eruptions occurred in 2004 at the summit crater in this paper we argue the resistivity structure shallower than 3 km obtained by a dense magnetotelluric survey the magnetotelluric data were obtained at 74 measurement sites mainly along the four survey lines across the volcano the resistivity profiles obtained by two dimensional inversions are characterized by a resistive surface layer and an underlying conductive layer the dominant feature of the profiles is the existence of resistive bodies at a depth range of a few hundred meters to a few kilometers surrounded by a highly conductive region considering that the location of resistive bodies correspond to the old eruption centers one corresponds to the 24 ka collapse caldera and the other to the 21 ka lava dome the resistive bodies imply zones of old and solidified intrusive magma with low porosity because geothermal activities exist near the resistive bodies the enclosing highly conductive regions are interpreted as a hydrothermal system driven by the heat from the old solidified magma beneath the resistive body under the collapsed caldera intrusion of magma is inferred from the studies of volcano tectonic earthquakes and continuous global positioning system gps observation implying the structural control of magma activity within the volcano in this study we propose that the magma ascent was impeded by the old and solidified remnant magma and partly migrated horizontally to the east and finally ascended to the summit resulting in the 2004 eruptions