statistical analyses and characteristics of volcanic tremor on stromboli volcano italy a study of volcanic tremor on stromboli is carried out on the basis of data recorded daily between 1993 and 1995 by a permanent seismic station str located 1 8 km away from the active craters we also consider the signal of a second station tf1 which operated for a shorter time span changes in the spectral tremor characteristics can be related to modifications in volcanic activity particularly to lava effusions and explosive sequences statistical analyses were carried out on a set of spectra calculated daily from seismic signals where explosion quakes were present or excluded principal component analysis and cluster analysis were applied to identify different classes of spectra three clusters of spectra are associated with two different states of volcanic activity one cluster corresponds to a state of low to moderate activity whereas the two other clusters are present during phases with a high magma column as inferred from the occurrence of lava fountains or effusions we therefore conclude that variations in volcanic activity at stromboli are usually linked to changes in the spectral characteristics of volcanic tremor site effects are evident when comparing the spectra calculated from signals synchronously recorded at str and tf1 however some major spectral peaks at both stations may reflect source properties statistical considerations and polarization analysis are in favor of a prevailing presence of p waves in the tremor signal along with a position of the source northwest of the craters and at shallow depth

ground deformation and seismicity related to the propagation and drainage of the dyke feeding system during the 2007 effusive eruption at stromboli volcano italy abstract the 2007 effusive eruption of stromboli volcano produced a ground deformation detected by two high resolution borehole tiltmeters installed at an elevation 500 masl and at a distance of

source mechanisms of explosions at stromboli volcano italy determined from moment tensor inversions of very long period data 1 seismic data recorded in the 2 30 s band at stromboli volcano italy are analyzed to quantify the source mechanisms of strombolian explosions during september 1997 to determine the source centroid location and source mechanism we minimize the residual error between data and synthetics calculated by the finite difference method for a point source embedded in a homogeneous elastic medium that takes topography into account two source centroids are identified each representative of the distinct event types associated with explosive eruptions from two different vents the observed waveforms are well reproduced by our inversion and the two source centroids that best fit the data are offset 220 and 260 m beneath and 160 m northwest of the active vents the source mechanisms include both moment tensor and single force components the principal axes of the moment tensor have amplitude ratios 1 1 2 which can be interpreted as representative of a crack if one assumes the rock matrix at the source to have a poisson ratio n 1 3 a value appropriate for hot rock both imaged cracks dip 60 to the northwest and strike northeast southwest along a direction parallel to the elongation of the volcanic edifice and a prominent zone of structural weakness as expressed by lineaments dikes and brittle structures for our data set the volume changes estimated from the moments are 200 m 3 for the largest explosion from each vent together with the volumetric source is a dominantly vertical force with a magnitude of 10 8 n consistent with the inferred movement of the magma column perched above the source centroid in response to the piston like rise of a slug of gas in the conduit index terms 7215 seismology earthquake parameters 7280 seismology volcano seismology 8419 8414 volcanology eruption mechanisms keywords very long period seismicity moment tensor inversions eruption mehanics

the onset of the 2007 stromboli effusive eruption recorded by an integrated geophysical network abstract the stromboli volcano erupted on february 27 2007 after an intense strombolian activity lasted about 2 months the eruption was characterized by a series of rapidly evolving phenomena like the propagation of an effusive fracture along the crater rim the opening of lateral effusive vents an unusually large effusive flux 10 m 3 s the collapse of the crater system and a major strombolian explosion this eruption was monitored by an integrated network of multiparameter instruments broad band seismometers infrasonic array thermal cameras and bore hole tiltmeters all the information collected and processed in real time allowed to draw a clear picture of the eruption dynamics thermal imagery documented in real time how the effusive fracture propagated at 12 24 gmt of february 27 along the northern rim of the ne crater towards the ne direction the infrasonic array showed that explosive and degassing activity ceased at 10 32 gmt a couple of hours before the opening of the effusive fractures the end of the explosive activity coincided with an intense phase of high frequency 4 22 hz tremor which showed two episodes of harmonic spectrum gliding from 4 7 hz to 22 hz the end of this phase was characterized at 18 26 gmt by a strong infrasonic signal located by the array in the sciara del fuoco and associated with the landslide induced by the opening of a lateral effusive vent at 400 m of elevation this eruption provided a clear example on how the strategy of integrating in near real time geophysical information can pinpoint the transition from explosive to effusive activity of the shallow volcanic system at stromboli

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

infrasonic harmonic tremor and degassing bursts from halema uma u crater kilauea volcano hawaii 1 the formation evolution collapse and subsequent resurrection of a vent within halema uma u crater kilauea volcano produced energetic and varied degassing signals recorded by a nearby infrasound array between 2008 and early 2009 after 25 years of quiescence a vent clearing explosive burst on 19 march 2008 produced a clear complex acoustic signal near continuous harmonic infrasonic tremor followed this burst until 4 december 2008 when a period of decreased degassing occurred the tremor spectra suggest volume oscillation and reverberation of a shallow gas filled cavity beneath the vent the dominant tremor peak can be sustained through helmholtz oscillations of the cavity while the secondary tremor peak and overtones are interpreted assuming acoustic resonance the dominant tremor frequency matches the oscillation frequency of the gas emanating from the vent observed by video tremor spectra and power are also correlated with cavity geometry and dynamics with the cavity depth estimated at 219 m and volume 3 106 m3 in november 2008 over 21 varied degassing bursts were observed with extended burst durations and frequency content consistent with a transient release of gas exciting the cavity into resonance correlation of infrasound with seismicity suggests an open system connecting the atmosphere to the seismic excitation process at depth numerous degassing bursts produced very long period 0 03 0 1 hz infrasound the first recorded at kilauea indicative of long duration atmospheric accelerations kilauea infrasound appears controlled by the exsolution of gas from the magma and the interaction of this gas with the conduits and cavities confining it

the 2007 stromboli eruption event chronology and effusion rates using thermal infrared data accepted for publication in journal of geophysical research copyright 2009 american geophysical union further reproduction or electronic distribution is not permitted

long range acoustic observations of the eyjafjallajokull eruption iceland april may 2010 1 the april may 2010 summit eruption of eyjafjallajokull iceland was recorded by 14 atmospheric infrasound sensor arrays at ranges between 1 700 and 3 700 km indicating that infrasound from modest size eruptions can propagate for thousands of kilometers in atmospheric waveguides although variations in both atmospheric propagation conditions and background noise levels at the sensors generate fluctuations in signal to noise ratios and signal detectability array processing techniques successfully discriminate between volcanic infrasound and ambient coherent and incoherent noise the current global infrasound network is significantly more dense and sensitive than any previously operated network and signals from large volcanic explosions are routinely recorded because volcanic infrasound is generated during the explosive release of fluid into the atmosphere it is a strong indicator that an eruption has occurred therefore long range infrasonic monitoring may aid volcanic explosion detection by complementing other monitoring technologies especially in remote regions with sparse ground based instrument networks

onset of the persistent activity at stromboli volcano italy stromboli known worldwide as the lighthouse of the mediterranean is commonly believed to have been in a state of persistent activity for the past 2000 2500 years however historical sources older than 1000 a d are not accurate enough to assess if the activity of the volcano was exactly the same as we see at present in order to attempt to identify the onset of the present eruptive regime and assess if it has been maintained with the same characteristics through time stratigraphic and radiometric studies of the recent tephra deposits were undertaken up to 4 m deep stratigraphic trenches dug at a height of approximately 500 m on the ne flank of the volcano exposed a conformable tephra pile containing charcoal fragments one of the most interesting finds was the discovery of a 7 cm thick weathered bed rich in organic matter thin palaeosol approximately 3 m below the surface the sequence underneath the palaeosol consists of decimetre thick lapilli fallout beds alternating with ash deposits bearing small charcoals with calibrated ages of between the fourth century b c and the first century a d the sequence above the palaeosol is charcoal free and consists of coarse ash deposits with discrete centimetre thick lapilli fallout beds composed of crystal poor golden pumice and subordinate crystal rich black scoriae similar to scoria pumice pairs emitted during the more energetic explosions of the present day activity the data collected indicate that between the third and seventh centuries a d after a period of quiescence the activity resumed with an eruptive style identical to the present one we conclude that the lighthouse of the mediterranean actually began its activity in a period much later than previously thought

ground penetrating radar study of north padre island implications for barrier island internal architecture model for growth of progradational microtidal barrier islands and gulf of mexico sea level cyclicity abstract padre island is the widest and longest barrier island in the world it is 200 km long up to 3 km wide and 10 15 m thick this 2 000 year old barrier island was formed predominantly from northward longshore drifted sediments from the rio grande river delta a 3 km long shore normal 50 mhz ground penetrating radar gpr profile was collected across padre island from the gulf of mexico to laguna madre at the northern end of the padre island national seashore a 1 km long shore parallel gpr profile was also collected and intersects the shore parallel profile approximately 1 km landward of the gulf of mexico vibracores taken along the shore normal profile at the beach foreshore in the center of the island at the lagoon margin and at a recent washover fan were used in conjunction with the description of a deep rotary core taken through the northern part of the island to constrain the gpr interpretations in the shore normal profile gpr reflectors indicate both seaward and landward dipping clinoforms as well as concave upward scour and fill features seaward dipping reflectors indicate approximately 2 km of progradation of the barrier island suggesting an average progradation rate of 1 m year landward dipping reflectors in the landward 1 km of the gpr profile indicate approximately 1 km of landward growth suggesting an average landward growth rate of 0 5 m year nested concave upward scour and fill features in the central part of the island are interpreted as tidal and washover channels 3 8 m deep in strike cross section these scours are channel form in outline and contain nearly horizontal to slightly inclined radar reflectors the presence of channel form scours supports the interpretation that landward growth was dominantly due to deposition by short lived tidal deltas and storm washovers even though there was periodic landward island growth north padre island has been progradational throughout its history due to a high sediment supply the understanding of the architecture and growth history of padre island provides much needed information about the internal geometry and the evolution of modern barrier island systems in addition systematic variations in scour depths across the island suggest that storm frequency and intensity varied during the island s history and provides a proxy for estimating sea level fluctuations

the 15 march 2007 explosive crisis at stromboli volcano italy assessing physical parameters through a multidisciplinary approach basaltic volcanoes are dominated by lava emission and mild explosive activity nevertheless many basaltic systems exhibit from time to time poorly documented and little understood violent explosions a short lived multiblast explosive crisis paroxysmal explosion occurred on 15 march 2007 during an effusive eruptive crisis at stromboli italy the explosive crisis which started at 20 38 14 ut had a total duration of 5 min the combined use of multiparametric data collected by the permanent instrumental networks seismic acoustic and thermal records and a field survey carried out immediately after the event enabled us to constrain the eruptive dynamics and quantify physical parameters the eruption consisted of three major pulses in the first lithic blocks and ash were ejected at speeds of 100 155 m s and 130 210 m s respectively the high solid load of the eruptive jet resulted in the partial collapse of the column with the formation of a small volume pyroclastic density current the second 12 s long pulse emitted 2 2 2 7 107 kg of tephra mass discharge rate 1 9 2 3 106 kg s forming a 3 km high convective plume dispersing tephra up to the west coast and a dilute density current with limited dispersal downslope of the craters a final 30 s long phase formed a scoria flow with a volume of 1 5 1 7 104 m3 mass discharge rate 5 9 6 7 105 kg s a total runout of 200 m and a velocity of 45 m s the total gas volume involved in the explosion was 1 3 1 9 104 m3 with an initial overpressure of 7 9 0 4 mpa we compared the 15 march 2007 event with historical paroxysms in particular with that of 5 april 2003 which was remarkably similar

conditions of magma storage degassing and ascent at stromboli new insights into the volcano plumbing system with inferences on the eruptive dynamics stromboli is known for its persistent degassing and rhythmic strombolian activity occasionally punctuated by paroxysmal eruptions the basaltic pumice and scoria emitted during paroxysms and strombolian activity respectively differ in their textures crystal contents and glass matrix compositions which testify to distinct conditions of crystallization degassing and magma ascent we present here an extensive dataset on major elements and volatiles co2 h2o s and cl in olivine hosted melt inclusions and embayments from pyroclasts emplaced during explosive eruptions of variable magnitude magma saturation pressures were assessed from the dissolved amounts of h2 oa nd co2 taking into account the melt composition evolution both pressures and melt inclusion compositions indicate that 1 ca basaltic melts entrapped in high mg olivines fo89 90 generate stromboli basalts through crystal fractionation and 2 the stromboli plumbing system can be imaged as a succession of magma ponding zones connected by dikes the 7 10 km interval where magmas are stored and differentiate is periodically recharged by new magma batches possibly ranging from ca basalts to basalts with a co2 rich gas phase these deep recharges promote the formation of bubbly basalt blobs which are able to intrude the shallow plumbing system 2 4 km where co2 gas fluxing enhances h2o loss crystallization and generation of crystal rich dense degassed magma chlorine partitioning into the h2o co2 bearing gas phase accounts for its efficient degassing 69 under the open system conditions of strombolian activity paroxysms however are generated through predominantly closed system ascent of basaltic magma batches from the deep storage zone in this situation crystallization is negligible and sulfur exsolution starts at 170 mpa chlorine remains dissolved in the melt until lower pressures only 16 being lost upon eruption finally we propose a continuum in explosive eruption energy from strombolian activity to large paroxysmal events ultimately controlled by variable pressurization of the deep feeding system associated with magma and gas recharges

the vei 7 millennium eruption changbaishan tianchi volcano china dprk new field petrological and chemical constraints on stratigraphy volcanology and magma dynamics abstract field relations petrography bulk and micro scale chemistry reveal that the most recent history of hazardous changbaishan tianchi volcano should be revised with important implications for volcanic hazard in ne asia currently the two most recent large eruptions are identified separately as a vei 5 trachytic baguamiao eruption bgm and the much heralded vei 7 late 946 ce common era millennium eruption me of comendite however we find that the former is part of the latter based on the following evidence 1 trachytic fallout of the bgm lies directly on the comendite tephra of the me without any indication of depositional hiatus 2 abundant mingled trachyte comendite pumice in the tephra deposits 3 similar chemistry of mingled pumice and its components to those in the bgm and me products 4 correlation of bimodal glass shard compositions in the distal b tm ash from the japan sea with comendite and trachyte glass from the bgm and me products based on the above evidence we suggest that the great millennium eruption of 946 ce should be revised finally to include the bgm trachyte as its final stage furthermore deposits attributed to two other trachytic eruptions in 1668 and or 1702 ce also called baguamiao by some authors and 1903 ce referred to in historic accounts were also examined our field observations petrography bulk and micro scale chemistry combined with previously published ra th ages indicate that all these trachytes are either primary deposits of the me or its reworked deposits thus our findings do not support two separate post me eruptions and require that volcanic hazard assessment at changbaishan volcano include this new interpretation recently published geochronological data integrated with our new petrochemical and volcanological framework informs the magma dynamics leading to the me the me comendite derived from a parental trachyte similar to the bgm started accumulating at shallow levels around 12 ka to 8 ka around 4 to 1 6 ka the bgm trachyte sensu strictu separated from its basaltic parent and started accumulating and crystallizing separately from the me comendite just prior to the me eruption mingling of trace amounts of a third more mafic hybrid is implicated by the composition of mafic glass selvedges the strong evidence for mixing of all these endmembers in the eruption products suggests that recharge mixing and overturn of this predominantly comendite trachyte system occurred during the 1 ka me the common occurrence of comendite and trachyte in the last 100 ka also maybe 1 ma at changbaishan tianchi suggests that conditions for trachyte comendite magma interactions are prevalent in the magma system of changbaishan and maybe crucial in catastrophic eruptions there

multiple sector collapses at stromboli volcano italy how they work this paper demonstrates that four large sector collapses have affected the nw flank of the stromboli volcano in the past 13 ka alternating with growth phases in order to contribute to the evaluation of the critical conditions which trigger lateral collapses a reconstruction of the geometry of each collapse of the volcano edifice in the four stages that preceded the relative collapse events is also presented and a computation of the landslide volume this reconstruction is based on new field data plotted in three dimensions prior to the initial 13 ka collapse the volcano was 1125 100 m high above sea level the collapse had a volume of 2 23 0 87 km3 whereas the pre collapse volcano volume was 218 8 7 7 km3 the next edifice that failed was 900 70 m high a s l the collapse volume was 1 0 54 km3 with a precollapse volcano volume of 201 4 5 4 km3 the edifice then grew to 1000 60 m a s l the third collapse had a volume of 1 08 0 39 km3 and occurred within a volcano with a volume of 209 1 4 6 km3 this was followed by a new growth phase followed by the last collapse with a volume of 0 73 0 22 km3 the volcano volume was about the same as the present one the present active crater zone is at 780 m a s l in the first three collapses sliding surfaces cut the main magma conduit in the last collapse the upper scarp coincided with the conduit location dyking along a main ne trending weakness zone across the volcano summit exerted a lateral force for collapse inception the decrease of the landslide volumes with the age and the concentric scarps of the four collapses suggest that the younger sliding planes tended to become more superficial and to decrease the areal extent this is interpreted as due to a successively weaker eruptive products from dominantly lavas to dominantly pyroclastics and b the feedback effects between collapses and dykes that injected along the lateral segments of the first collapse slide plane

interaction of seismic and air waves recorded at stromboli volcano explosion quake seismograms recorded at stromboli show that seismic phases with a high amplitude and high frequency content propagate with a velocity of approximately 330 m s the sound speed the analysis of seismograms recorded at a distance of 500 m from one of the three active vents shows for the first onset a low frequency and particle motion characteristic of a p wave which loses its longitudinal polarization with the onset of the air wave recording the explosion quakes simultaneously with a microphone we could ascertain that the high frequency onset coincided with the air wave s in order to better understand the seismic wavefield generated by the atmospheric pressure we performed a controlled source experiment at stromboli using a seismic gun seismograms with the same two phases and particle motions comparable with the volcano seismic data were obtained a second experiment demonstrated that the air wave propagates at least in the uppermost 1 m of the ground we suggest that the seismic source of the corresponding seismograms is an explosion at the top of the magma column and conclude that the p and air waves are both generated in the same point and at the same time

dike propagation driven by volcano collapse a general model tested at stromboli italy 1 analogue experiments investigate how flank collapse affects dike propagation within volcanoes water magma analogue is injected within a gelatin cone volcano analogue with a lateral collapse the injections form dikes that away from the collapse become radial the dikes propagating nearby the collapse focus towards the collapse sides becoming subparallel to them because of the stress reorientation due to the unbuttressing only dikes formed along the collapse axis passing through the mean points of the collapse map view propagate radially within the collapse this general model is applied at stromboli the stromboli dikes cluster along and parallel to the collapse sides similar to the experiments nevertheless the current location of the conduit along the collapse axis leads to dike propagation within the collapse infill rather than at its sides this may have occurred during the 2002 03 eruption when diking in the collapse triggered a landslide and tsunami within the collapse

characteristics of puffing activity revealed by ground based thermal infrared imaging the example of stromboli volcano italy puffing i e the frequent 1 s ca release of small 0 1 10 m3 over pressurized pockets of magmatic gases is a typical feature of open conduit basaltic volcanoes worldwide despite its non trivial contribution to the degassing budget of these volcanoes and its recognized role in volcano monitoring detection and metering tools for puffing are still limited taking advantage of the recent developments in high speed thermal infrared imaging we developed a specific processing algorithm to detect the emission of individual puffs and measure their duration size volume and apparent temperature at the vent as a test case we applied our method at stromboli volcano italy studying snapshots of 1 min collected in the years 2012 2013 and 2014 at several vents in all 3 years puffing occurred simultaneously at three or more vents with variable features at the scale of the single vent a direct relationship links puff temperature and radius suggesting that the apparent temperature is mostly a function of puff thickness while the real gas temperature is constant for all puffs once released in the atmosphere puffs dissipate in less than 20 m on a broader scale puffing activity is highly variable from vent to vent and year to year with a link between average frequency temperature and volume from 136 puffs per minute 600 k above ambient temperature 0 1 m3 and the occasional ejection of pyroclasts to 20 puffs per minute 3 k above ambient 20 m3 and no pyroclasts frequent small hot puffs occur at random intervals while as the frequency decreases and size increases an increasingly longer minimum interval between puffs up to 0 5 s appears these less frequent and smaller puffs also display a positive correlation between puff volume and the delay from the previous puff our results suggest an important role of shallow bubble coalescence in controlling puffing activity the smaller and more frequent puffing at hotter vents is in agreement with the rapid rise of small gas pockets with only limited coalescence while slower rise allowing more time for coalescence leads to larger but less frequent puffing at colder vents this link between puffing style and vent thermal state points to a feedback between gas flux and magma temperature and viscosity where higher gas flux stirs and heats the magma which by getting less viscous becomes a preferential way for bubble rise such a link has implications for the monitoring of the state of the shallow conduit at open vent volcanoes as well as for determination of their total gas budget relevant for hazard forecast and environmental studies

field observations on the initial lava flow and the fracture system developed during the early days of the stromboli 2007 eruption abstract the february april 2007 stromboli eruption was followed by numerous scientists and well documented from an integrated geophysical analysis by contrast direct visual observations on the summit craters and bastimento area were difficult during the first three days of the eruption because of bad weather conditions in this paper we report field observations on the fracture system after the crisis of february 27th and before the summit explosion on march 15th the observations were focused on the early lava flow emplacement and deformation at elevations between 400 and 700 m a s l i e between the summit crater area and the lateral fissure eruption along the sciara del fuoco sdf

spectroscopic capture of 1 hz volcanic so2 fluxes and integration with volcano geophysical data 1 here we present a novel spectroscopic approach to capturing with unprecedented time resolution and accuracy volcanic so2 fluxes this is based on two usb2000 spectrometers coupled to cylindrical lens telescopes each collecting light which has transited horizontal sections of the rising plume we report on field data from stromboli volcano in which the entire emission rate from the volcano was measured as well as flux signatures associated with individual crater explosions the latter were integrated with seismic and thermal data demonstrating correlations in both cases and representing the first such geophysical geochemical data corroboration on this timescale such a holistic empirical capability could significantly expedite our understanding of explosive volcanic processes

integrating puffing and explosions in a general scheme for strombolian style activity strombolian eruptions are among the most common subaerial styles of explosive volcanism worldwide distinctive features of each volcano lead to a correspondingly wide range of variations of magnitude and erupted products but most papers focus on a single type of event at a single volcano here in order to emphasize the common features underlying this diversity of styles we scrutinize a database from 35 different erupting vents including 21 thermal infrared videos from stromboli italy etna italy yasur vanuatu and batu tara indonesia from puffing through rapid explosions to normal explosions with variable ejection parameters and relative abundance of gas ash and bombs using field observations and high speed thermal infrared videos processed by a new algorithm we identify the distinguishing characteristics of each type of activity and how they may relate and interact in particular we record that ash poor normal explosions may be preceded and followed by the onset or the increase of the puffing activity while ash rich explosions are emergent i e with inflation of the free surface followed directly by emission of increasingly large gas pockets overall we see that all strombolian activities form a continuum arising from a common mechanism and are modulated by the combination of two well established controls 1 the length of the bursting gas pocket with respect to the vent diameter and 2 the presence and thickness of a high viscosity layer in the uppermost part of the volcanic conduit

magnetic features of the magmatic intrusion that occurred in the 2007 eruption at stromboli island italy significant changes in the local magnetic field marked the resumption of eruptive activity at stromboli volcano on february 27 2007 after differential magnetic fields were obtained by filtering out external noise using adaptive filters and seasonal thermal noise using temperature data we identified step like changes of 1 4 nt coincident with the opening of eruptive fissures in the upper part of the sciara del fuoco the magnetic variations detected at two stations are closely related to the propagation of a shallow ne sw magmatic intrusion extending beyond the summit craters area these observations are consistent with those calculated using piezomagnetic models in which stress induced changes in rock magnetization are produced by the magmatic intrusion no significant magnetic changes were observed when the first fractures opened along the ne crater rim indeed the stress induced magnetization caused by this magmatic activity is expected to be too low because of the structural weakness and or thermal state of the summit area the continuous long term decay characterizing the post eruptive magnetic pattern can be related to a time dependent relaxation process a maxwell rheology was assumed and the temporal evolution of the piezomagnetic field was evaluated this allowed us to estimate the rheological properties of the medium in particular an average viscosity ranging between 1016 and 1017 pa s was a relaxation time of about 38 days

radiative heat power at stromboli volcano during 2000 2011 twelve years of modis observations abstract twelve years of night time modis moderate resolution imaging spectroradiometer observations has been analysed to detect and quantify the radiative heat power emitted by stromboli volcano from march 2000 to september 2011 using an accurate background subtraction of the modis signal at 4 m we were able to discriminate two main regimes of thermal radiation related to different levels of volcanic activity effusive eruptions occurred on december 28 2002 and february 27 2007 radiated at an average of 186 mw with a frequency of alert detection of 50 95 conversely during the typical strombolian activity an average of 9 mw is radiated with a frequency of alert detection of 0 45 although during the effusive eruptions the radiative power is basically controlled by the lava discharge rate our results suggest that during non effusive periods strombolian regime both the intensity and the frequency of modis alerts are controlled by the height of the magmatic column feeding the activity at the surface in particular we found that a radiative power of 50 mw corresponds to a high magma column which is exposed in the vent area at the same rate in which the deeper gas rich magma is typically supplied within the feeding system of stromboli 0 3 m3 s 1 in this condition the magmatic system approaches steady state regimes above this threshold a transition from strombolian to effusive regimes may occur as shown by the detection of 50 mw 8 10 days before the onset of both the last two major flank eruptions these values were reached after 1 2 months of gradual increase of the radiative power which was likely associated the rising of the magma column within the shallowest portion of the conduit in addition our data suggest that over the years 2000 2011 several cycles of rise and fall of the magma column have occurred which however did not culminate into an effusive eruption but only into recurrent episodes of sustained spattering or fountaining and summit overflows these fluctuations has substantially increased in frequency and intensity after the 2007 eruption thus suggesting that this event has perturbed in some way the shallow plumbing system of stromboli we stress that the detection of a radiative power higher than 50 mw is a clear evidence of a very high magma column which may prelude the onset of an effusive eruption and or periods of sustained vent activity in conclusion we suggest that systematic analysis of modis data can be used to detect variations in the intensity of strombolian activity and may considerably improve volcano surveillance at stromboli as well as at other open system volcanoes

volcano infrasound a review abstract exploding volcanoes which produce intense infrasound are reminiscent of the veritable explosion of volcano infrasound papers published during the last decade volcano infrasound is effective for tracking and quantifying eruptive phenomena because it corresponds to activity occurring near and around the volcanic vent as opposed to seismic signals which are generated by both surface and internal volcanic processes as with seismology infrasound can be recorded remotely during inclement weather or in the dark to provide a continuous record of a volcano s unrest moreover it can also be exploited at regional or global distances where seismic monitoring has limited efficacy this paper provides a literature overview of the current state of the field and summarizes applications of infrasound as a tool for better understanding volcanic activity many infrasound studies have focused on integration with other geophysical data including seismic thermal electromagnetic radiation and gas spectroscopy and they have generally improved our understanding of eruption dynamics other work has incorporated infrasound into volcano surveillance to enhance capabilities for monitoring hazardous volcanoes and reducing risk this paper aims to provide an overview of volcano airwave studies from analog microbarometer to modern pressure transducer and summarizes how infrasound is currently used to infer eruption dynamics it also outlines the relative merits of local and regional infrasound surveillance highlights differences between array and network sensor topologies and concludes with mention of sensor technologies appropriate for volcano infrasound study

array tracking of infrasonic sources at stromboli volcano 1 infrasonic arrays are a powerful tool for volcanic monitoring and hazard assessment explosions were recorded at stromboli using a small aperture array of 4 infrasonic stations allowing precise vent location the acoustic signals were delayed and summed revealing the existence of two main groups of infrasonic waves the ne crater produces short 3 s high amplitude 20 80 pa pressure waves while the sw crater produces small acoustic pressure 10 30 pa with long 5 15 s coda the two groups reflect different in explosive styles and similar spectral content centered on 5 6 hz when stacked together acoustic waveforms for each crater reveal the same pressure pulse which indicates a common source process we infer that the acoustic onset at both craters is generated by the burst of a large gas bubble while the acoustic coda is controlled by a sustained pressure release

three dimensional volcano acoustic source localization at karymsky volcano kamchatka russia abstract we test two methods of 3 d acoustic source localization on volcanic explosions and small scale jetting events at karymsky volcano kamchatka russia recent infrasound studies have provided evidence that volcanic jets produce low frequency aerodynamic sound jet noise similar to that from man made jet engines for man made jet noise noise sources localize along the turbulent jet flow downstream of the nozzle discrimination of jet noise sources along the axis of a volcanic jet requires high resolution in the vertical dimension which is very difficult to achieve with typical volcano acoustic network geometries at karymsky volcano an eroded edifice dvor caldera adjacent to the active cone provided a platform for the deployment of five infrasound sensors in july 2012 with intra network relief of 600 m the network was designed to target large scale jetting but unfortunately only small scale jetting and explosions were recorded during the 12 day experiment a novel 3 d inverse localization method srcloc is tested and compared against a more common grid search semblance technique simulations using synthetic signals show that srcloc is capable of determining vertical solutions to within 150 m or better for signal to noise ratios 1 for this network configuration however srcloc locations for explosions and small scale jetting at karymsky volcano show a persistent overestimation of source elevation and underestimation of sound speed the semblance method provides more realistic source locations likely because it uses a fixed realistic sound speed of 340 m s explosion waveforms exhibit amplitude relationships and waveform distortion strikingly similar to those theorized by modeling studies of wave diffraction around the crater rim we suggest that the delay of acoustic signals and apparent elevated source locations are due to raypaths altered by topography and or crater diffraction effects implying that topography in the vent region must be accounted for when attempting 3 d volcano acoustic source localization though the data presented here are insufficient to resolve small scale jet noise sources similar techniques may be successfully applied to large volcanic jets in the future

seismoacoustic investigations of paroxysmal activity at mt etna volcano new insights into the 16 november 2006 eruption 1 on 16 november 2006 a 1 day long paroxysmal eruption occurred at the summit craters of mt etna volcano a multiparametric approach consisting of analyzing infrasonic seismic and video camera recordings was carried out to follow its evolution volcanological and geophysical observations identified three eruptive phases in the first phase infrasonic and seismic characteristics reflected the highly explosive nature of the activity waveform characterization of infrasound events confirmed the activity of the several explosive vents at the summit of southeast crater sec during the second phase results highlighted the decoupling between seismic and infrasonic sources which was due to the decrease in explosive activity and the reactivation of effusive vents located south of bocca nuova and on the saddle between bocca nuova and sec the third phase was the most intense and was characterized by various volcanic phenomena pyroclastic flows jets of dark ash and white steam the very high radiated infrasonic energy together with infrasound event features led us to infer a gas enrichment of the shallow magma column preceding by a few minutes and likely related to the pyroclastic flows in the sec area after the eruption at sec variations in infrasound events related to the activity of northeast crater nec were found the observed spectral changes and the source mechanism modeling of the nec infrasound events suggest the existence of a link in the plumbing system feeding the two craters

infrasonic monitoring at stromboli volcano during the 2003 effusive eruption insights on the explosive and degassing process of an open conduit system 1 stromboli is an open conduit volcano characterized by persistent conduit degassing and explosive dynamics during the 2003 effusive eruption we monitored this activity with a five element array deployed at 450 m from the active craters the array allows us to track in real time changes of explosive activity in terms of source position and excess pressure release infrasonic monitoring located the new active vents in the same preeruptive position revealing that the collapse of the crater terrace has not changed the geometry of the shallow feeding system elevation of the infrasonic source is stable at 750 m above sea level coincident with the elevation of the crater terrace this suggests a shallow position of the magma column or if the source is embedded in the conduit diffraction at the crater rim at the end of the eruption back azimuth analysis indicates that explosive activity was progressively reestablished at all of the craters following a ne toward sw direction along the collapsed trench the array detected significant small amplitude 1 pa infrasonic activity occurring at a rate of approximately one pulse every 2 s and generally located in only one vent at a time this persistent activity is not related to strombolian explosion but we infer it is reflecting the overpressurized degassing of the magma column amplitude distribution of 7 million infrasonic signals shows that this degassing is 1 order of magnitude more energetic than the explosions besides infrasonic amplitude distribution presents a decay with a double slope indicating that explosions and degassing are driven by conduit dynamics acting at two different rates

monitoring crater wall collapse at active volcanoes a study of the 12 january 2013 event at stromboli crater wall collapses are fairly frequent at active volcanoes and they are normally studied through the analysis of their deposits in this paper we present an analysis of the 12 january 2013 crater wall collapse occurring at stromboli volcano investigated by means of a monitoring network comprising visible and infrared webcams and a ground based interferometric synthetic aperture radar the network revealed the triggering mechanisms of the collapse which are comparable to the events that heralded the previous effusive eruptions in 1985 2002 2007 and 2014 the collapse occurred during a period of inflation of the summit cone and was preceded by increasing explosive activity and the enlargement of the crater weakness of the crater wall increasing magmastatic pressure within the upper conduit induced by ascending magma and mechanical erosion caused by vent opening at the base of the crater wall and by lava fingering are considered responsible for triggering the collapse on 12 january 2013 at stromboli we suggest that the combination of these factors might be a general mechanism to generate crater wall collapse at active volcanoes

time variability of low temperature fumaroles at stromboli island italy and its application to volcano monitoring the constant and mild activity of stromboli volcano italy is occasionally interrupted by effusive events and or more energetic explosions referred to as major explosions and paroxysms which are potentially dangerous for the human community although several premonitory signals for effusive phases have been identified precursors of major explosions and paroxysms still remain poorly understood with the aim of contributing to the identification of possible precursors of energetic events this work discusses soil temperature data acquired in low temperature fumaroles at stromboli in the period 2006 2010 data analysis revealed that short term anomalies recorded in the thermal signal are potentially useful in predicting state changes of the volcano in particular sudden changes in fumarole temperatures and their hourly gradients were observed from several days to a few hours prior to fracturing and paroxysmal events heralded by peculiar waveforms of the recorded signals the qualitative interpretation is supported by a quantitative theoretical treatment that uses circuit theory to explain the time dependence of the short period temperature variations showing a good agreement between theoretical and observational data

automatic recognition of landslides based on neural network analysis of seismic signals an application to the monitoring of stromboli volcano southern italy in the last 9 years the amount and the quality of geophysical and volcanological observations of stromboli s activity have undergone a marked increase this new information highlighted that the landslides on the sciara del fuoco flank are tightly linked to the volcanic activity actually at the beginning of the december 28 2002 effusive eruption the seismic monitoring network was less dense than now and therefore it is not known if there was an increase in the landslide rate before the eruption despite this it is known that a big landslide occurred 2 days after the beginning of the eruption which caused a tsunami december 30 2002 more recently the effusive eruption in february 2007 was preceded by an increase in landslides on the sciara del fuoco flank which were recorded by the seismological monitoring system that had been improved after the 2002 2003 crisis these episodes led us to believe that monitoring the sciara del fuoco flank instability is an important topic and that landslides might be significant short term precursors of effusive eruptions at the stromboli volcano to automatically detect landslide signals we have developed a specialized neural algorithm this can distinguish between landslides and the other types of seismic signals usually recorded at the stromboli volcano i e explosion quakes and volcanic tremor the discrimination results show an average performance of 98 67 according to the experience of the crisis of 2007 to identify changes that can be considered as precursors of effusive eruptions we set up an automatic decision making method based on the neural network responses this method can operate on a continuous data stream it calculates a landslide percentage index lpi that depends on the number of records that are classified by the net as landslides over a given time interval we tested the method on february 27 2007 including the beginning of the effusive phase the index showed an increase as early as at 09 00 utc on that day and reached its maximum value 100 at 12 00 about 40 min before the onset of the eruption after the beginning of the effusive phase the index remains high due to the blocks that roll down along the slope from the front of the lava flow on the basis of these tests we propose a decision making method that is able to recognize a trend in the lpi similar to that of 2007 eruption allowing the identification of precursors of effusive phases at the stromboli volcano

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

radon mapping automatic measurements and extremely high 222rn emissions during the 2002 2007 eruptive scenarios at stromboli volcano abstract we report additional radon data collected at stromboli during 2002 2007 the whole data set of periodic measurements has been systematically analyzed to retrieve the values of background threshold and anomaly for all the stations of the network maps of radon concentrations in space and time correlate with changes in volcanic activity higher radon emissions are essentially concentrated at summit stations and may also affect some stations located onto the summit eastern sector of the cone along the n60 e fracture zone as well as two stations placed at the ne edge of sciara del fuoco most of these stations are well above their threshold values during effusive eruptions namely 2002 2003 and 2007 due to the progressive structural adjustment of the volcano edifice coupled with the opening and resetting of the fracture network a two year long timeseries of automatic 222 rn measurements 2005 2007 was analyzed together with local environmental parameters and selected geophysical data on seismic tremor and infrasonic puffing the data show good correlation between radon and the latter parameters particularly during periods of high strombolian activity march april 2006 and before the onset of the february 27 2007 lava effusion with radon emissions being well above 20 000 bq m 3 extremely high radon emissions up to 1 7 10 6 bq m 3 were recorded along the fractures of the sw crater during the first two months of the 2002 2003 effusive eruption very high radon emissions up to 470 000 bq m 3 for 222 rn and 780 000 bq m 3 for 220 rn respectively were also detected by the automatic measurements at the summit station during june 20 early july 2007 i e just prior to the resuming of the strombolian activity at summit craters these data give us the opportunity to estimate the relative depths of the summit fractures during fracturing being constrained between 200 and 310 m this is in good agreement with the hypocentral depths of the so called hybrid events and the source of the very long period seismic signals vlp localized at a depth of about 500 m a s l below the upper central part of the sciara del fuoco

gas bubble dynamics model for shallow volcanic tremor at stromboli volcanic tremor at stromboli aeolian islands italy is correlated to small infrasonic transients ripepe et al 1996 which repeat almost rhythmically in time in a range between 0 8 and 1 2 s we demonstrate that infrasonic transients are associated to small gas bubble 0 5 m burstings which produces no transients in the seismic signal tremor ground displacement attenuates with the inverse of the distance from the craters indicating that the source is shallow short term energy release shows that infrasonic and seismic signals are linked to the same dynamical process while at the long term scale it is evident that the two signals are controlled by two distinctive mechanisms we suggest that the possible physical model acts in two steps first gas coalescence and then gas bursting in our model the seismic signal is related to the coalescence of a gas bubble from a layer of small bubbles while the infrasonic signal is linked to the bursting of the bubble when it reaches the magma surface gas bubbles could form by free coalescence in magma or could be forced to coalesce by a structural barrier we calculate that forced coalescence induces in magma a pressure change 104 pa 2 orders of magnitude higher than free coalescence and it explains best the tremor ground displacement 10 5 m recorded at stromboli moreover forced coalescence evidences the role of a structural barrier such as a dike in volcanic tremor source dynamics in this gas dynamic process the delay time of 1 2 s between infrasonic pulses could reflect the gas nucleation interval of basaltic magma thomas et al 1993 manga 1996 we propose that the source function for the shallow volcanic tremor at stromboli could be the viscoelastic reaction of the magma to the pressure decrease induced by gas bubble growth rate under constant depressurization the spectrum of our source function is controlled by the time duration of the pressure pulse which represents the viscoelastic relaxation time of the magma and gas bubble growth rate the predicted asymptotic decay of the frequency contents fits the spectral behavior of the volcanic tremor ground displacement recorded at stromboli we show that the same spectral behavior can be found in ground displacement spectra of volcanic tremor recorded on different volcanoes

effusive to explosive transition during the 2003 eruption of stromboli volcano the persistent explosive activity of stromboli volcano italy ceased in december 2002 and correlated with the onset of a seven month long effusive eruption on the volcano flank from new vents that opened just below the summit craters we intensively monitored this effusive event collecting and interpreting in real time an extensive multiparametric geophysical data set the resulting data synergy allowed detailed insights into the conduit dynamics that drove the eruption and the transition back to the typical strombolian activity we present a direct link between gas flux magma volume flux and seismicity supporting a gas driven model whereby the balance between gas flux and gas overpressure determines whether the system will support effusive or explosive activity this insight enabled us to monitor the migration of the magma column up the conduit and to explain the onset of explosive activity

integrated petrochemical and geophysical data reveals thermal distribution of the feeding conduits at stromboli volcano italy 1 samples of scoriae erupted at stromboli volcano during its persistent strombolian activity were collected between 2005 and 2008 chemical and mineralogical compositions were obtained on products erupted from the three main crater sectors sw central and ne small chemical variations indicate a different degree of evolution coupled with small difference of magma temperature 10 c analysis of the acoustic data for the same time period as the scoria sampling indicates that puffing a persistent overpressurized bubble degassing was on average mainly observed at the central craters and at times moved to the ne sector the cross check of the two independent data sets allowed us to assess correlation between composition of products and puffing activity at vents the hotter products are always erupted from the vents where puffing occurs indicating that slightly higher temperature can be the expression of an enhanced two phase bubble flow dynamics