volcano monitoring by microgravity and energy budget analysis microgravity monitoring of active volcanoes can provide evidence of sub surface mass and or density changes that precede eruptions if in addition precursory increases in thermal emissions are observed an integrated mechanistic model for volcanic activity may be developed with the potential for forecasting eruptions crater lake volcanoes provide an interesting target for such studies since thermal output can be monitored simply through lake water calotimetry here we summarize 10 years of gravity and thermal data from poas volcano costa rica mass energy balance calculations demonstrate that in the steady state the large thermal inertia of the crater lake acts as a buffer to short term changes in the energy input from the cooling magma feeder pipe since february 1986 it is postulated that there has been gradual emplacement of a shallow magma intrusion associated with vesiculation and gas loss to the surface this follows from unambiguous gravity increases constrained by elevation control that are coincident in time with a period of long term increased energy input to the crater lake progressive reduction of the lake volume by evaporation seepage culminated in an april 1989 ash eruption providing a good documented record of combined gravity and thermodynamic precursors to volcanic activity

hydrothermal element fluxes from copahue argentina a beehive volcano in turmoil copahue volcano erupted altered rock debris siliceous dust pyroclastic sulfur and rare juvenile fragments between 1992 and 1995 and magmatic eruptions occurred in july october 2000 prior to 2000 the copahue crater lake acid hot springs and rivers carried acid brines with compositions that reflected close to congruent rock dissolution the ratio between rock forming elements and chloride in the central zone of the volcano hydrothermal system has diminished over the past few years reflecting increased water rock ratios as a result of progressive rock dissolution magmatic activity in 2000 provided fresh rocks for the acid fluids resulting in higher ratios between rock forming elements and chloride in the fluids and enhanced mg fluxes the higher mg fluxes started several weeks prior to the eruption model data on the crater lake and river element flux determinations indicate that copahue volcano was hollowed out at a rate of about 20 000 25 000 m 3 yr but that void space was filled with about equal amounts of silica and liquid elemental sulfur the extensive rock dissolution has weakened the internal volcanic structure making flank collapse a volcanic hazard at copahue

detecting seasonal variations in seismic velocities within los angeles basin from correlations of ambient seismic noise summary we analyse 3 yr of continuous seismic records from broad band stations of the caltech regional seismic network ci in vicinity of the los angeles basin using correlations of ambient seismic noise relative velocity variations in the order of 0 1 per cent can be measured between all interstation pairs it is the first time that such an extensive study between 861 interstation pairs over such a large area has been carried out we perform these measurements using the stretching technique assuming that one of the two waveforms is merely a stretched version of the other obviously this assumption is always violated and the two waveforms are generally decorrelated due to temporal changes in the earth crust due to different sources or simply because the cross correlations are not fully converged we investigate the stability of these measurements by repeating each measurement over various time windows of equal length on average between all interstation pairs in the los angeles basin a seasonal signal in the relative velocity variation is observed with peaks and troughs during winter and summer time respectively generally the observed signal decreases with increasing interstation distance and relative traveltime perturbations can only be measured up to an interstation distance of 60 km furthermore the traveltime perturbations do not depend on azimuth of station pairs suggesting that they are not related to seasonal variations of the noise sources performing a simple regionalization by laterally averaging measurements over a subset of stations we found the sedimentary basin showing the most consistent signal and conclude that the observed seasonality might be induced either by changes in the ground water aquifer or thermo elastic strain variations that persist down to a depth of 15 22 km

4d in the deepwater gulf of mexico hoover madison and marshall fields the use of time lapse or 4d seismic technology is well established in the north sea and west africa where the application of 4d for reservoir production monitoring and surveillance has resulted in documented gains in recovery efficiency increased reserves and more efficient field operations however for several reasons including challenging acquisition conditions 4d technology has not been widely applied in the deepwater gulf of mexico in late 2005 and early 2006 exxonmobil acquired a deepwater gulf of mexico 4d survey covering the hoover madison and marshall fields in the alaminos canyon east breaks area for simplicity we will refer to this as the hoover survey

temporal evolution of a hydrothermal system in kusatsu shirane volcano japan inferred from the complex frequencies of long period events 1 we present a detailed description of temporal variations in the complex frequencies of long period lp events observed at kusatsu shirane volcano using the sompi method we analyze 35 lp events that occurred during the period from august 1992 through january 1993 the observed temporal variations in the complex frequencies can be divided into three periods during the first period the dominant frequency rapidly decreases from 5 to 1 hz and q of the dominant spectral peak remains roughly constant with an average value near 100 during the second period the dominant frequency gradually increases up to 3 hz and q gradually decreases from 160 to 30 during the third period the dominant frequency increases more rapidly from 3 to 5 hz and q shows an abrupt increase at the beginning of this period and then remains roughly constant with an average value near 100 such temporal variations can be consistently explained by the dynamic response of a hydrothermal crack to a magmatic heat pulse during the first period crack growth occurs in response to the overall pressure increase in the hydrothermal system caused by the heat pulse once crack formation is complete heat gradually changes the fluid in the crack from a wet misty gas to a dry gas during the second period as heating of the hydrothermal system gradually subsides the overall pressure in this system starts to decrease causing the collapse of the crack during the third period

monitoring of phreatic eruptions using interferometry on retrieved cross correlation function from ambient seismic noise results from mt ruapehu new zealand abstract since the last major eruption in 1995 96 mt ruapehu has erupted twice on 4 october 2006 and on 25 september 2007 these events occurred without any clear precursors and were mostly phreatic explosions the technique of interferometry on retrieved cross correlation function from ambient seismic noise irccasn is used to monitor subtle temporal changes of mt ruapehu s elastic properties the computation of cross correlation functions of seismic noise recorded at several stations around the volcano allowed us to observe variations during the 2006 eruption period the comparison between a reference cross correlation function and a current cross correlation function allows us to infer relative seismic velocity variations a 0 8 decrease of relative seismic velocity in the edifice starting two days before the 2006 eruption was observed this drop is due to a reversible and ephemeral effect which can be attributed to a pressurization of a magma pocket beneath the east flank of ruapehu due to new magma entering a small reservoir this pressure increase produced an inflation of the east flank of ruapehu and opened fractures in this area leading to a localised drop of seismic velocity we conducted the same analysis for the 2007 eruption but no significant seismic velocity variation was observed this difference is possibly due to the varying time scales of pressurization for the two events and also the irccasn time resolution an analysis of the seismicity before these two eruptions allows us to propose a conceptual model which explains the velocity drop for the 2006 eruption and the lack of velocity variations for the 2007 eruption since there was no surface deformation recorded by the geonet gps network we modelled the maximum radius and pressure change for a simple mogi point source at 5 km depth that produced no deformation we inferred the maximum fresh magma volume of 0 0017 km 3 entering the reservoir as a detectability threshold for gps ground deformation measurements

dynamics of piton de la fournaise volcano observed by passive image interferometry with multiple references abstract activity of piton de la fournaise pdf volcano in la reunion island modifies the seismic velocities within the edifice using the 2010 and 2011 data from a network of 21 seismic stations in the vicinity of pdf changes of seismic velocities are investigated using passive image interferometry i e interferometry of seismic noise correlations as noise correlations change significantly over time in response to volcanic activity a method is presented that allows us to measure continuous long term velocity changes with high and constant accuracy by using multiple periods as reference a long term velocity increase is found that averages about 0 25 per year this trend is superimposed by short term changes that exhibit a clear connection with summit seismo tectonic earthquakes indicating the effect of volcanic activity characteristic signatures of velocity changes are identified for post eruptive periods of deflation that show an increase of velocity associated with subsidence observed by gps periods of pre eruptive inflation are characterized by decreasing velocity seismic crises can be associated with either increasing or decreasing velocity depending on whether the magma movement leads to deflation due to an eruption emptying the shallow plumbing system or to inflation caused by a non eruptive intrusion with a simple assumption about the spatial sensitivity of the measurements both processes are found to have the strongest effect in the central summit area of the volcano which also shows the strongest surface displacements during the time investigated here we do not observe a dependence of the velocity change on the location of the erupting fissures instead the distribution of changes for the three inflation periods and the two eruptions are similar indicating that the velocity changes observed here reflect the dynamics of a shallow magma reservoir rather than the effect of the eruption at the surface

monitoring velocity variations in the crust using earthquake doublets an application to the calaveras fault california we present a technique that greatly improves the precision in measuring temporal variations of crustal velocities using an earthquake doublet or pair of microearthquakes that have nearly identical waveforms and the same hypocenter and magnitude but occur on different dates we compute differences in arrival times between seismograms recorded at the same station in the freqency domain by cross correlation of short windows of signal a moving window analysis of the entire seismograms including the coda gives t the difference in arrival times versus running time along the seismogram the time resolution of the method is an order of magnitude better than the digitization interval the t technique is illustrated with a pair of microearthquakes m 1 7 and 2 0 that occurred before and after the coyote lake california earthquake m 5 9 of august 6 1979 and on the same segment of the calaveras fault that ruptured during the earthquake the coda wave arrivals for some stations are progressively delayed for the second earthquake in the doublet so that its seismogram appears as a stretched version of the earlier event we interpret this systematic variation in t along the coda as a change in the average s velocity in the upper crust in the time interval between the two doublets s wave velocities appear to have decreased by 0 2 in an oblong region 5 10 km in radius at the south end of the aftershock zone

mountain front development by folding and crustal thickening in the internal zone of the betic cordillera alboran sea boundary the boundary between the alboran sea and betic cordillera is a good example of a fold related mountain front in the internal zone of an alpine mountain range since the late miocene nnw sse convergence between the eurasian and african plates has produced shortening and related orthogonal extension to improve the characterisation of the geometry of the deep structure in the region and to establish the recent tectonic evolution of the mountain front well logs and newly acquired geophysical data multichannel reflection seismic and gravimetric surveys have been interpreted and integrated with available surface data the most marked tectonic structure corresponds to large antiforms and synforms of ene wsw trend which are related to mountain ranges and basins respectively the fold belt continues toward the northern continental shelf of the alboran sea the fold vergence is generally northwards and its amplitude decreases progressively towards sse until disappearring in a sharp boundary where the reflectors are undeformed the deep geometry suggests that fold growth started during upper tortonian times and continued its activity up to pliocene or even quaternary times the nnw sse compression produces crustal thickening and a regional and progressive southwards emersion the location of main present day deformation fronts in the internal zones contrasts with classical models where the deformation progresses towards the frontal part of external zones of cordilleras in addition this fold related deformation mountain front has features different from fault related fronts as it does not show a sharp boundary and folds that determine rectilinear mountain boundaries decrease progressively in amplitude or in wavelength up to undeformed areas

a preliminary seismic study of taal volcano luzon island philippines abstract the very active taal volcano lies in the southern part of luzon island only 60 km from manila the capital of the philippines in march 2008 we deployed a temporary seismic network around taal that consisted of 8 three component short period seismometers this network recorded during the period from march to november 2008 about 1050 local events in the early data processing stages unexpected linear drifting of clock time was clearly identified for a number of stations the drifting rates of each problematic station were determined and the errors were corrected before further processing initial location of each event was derived by manually picked p s phases arrival times using hypo71 and a general velocity model based on ak135 since the velocity structure beneath taal is essentially unknown we used travel times of 338 well located events in order to derive a minimum 1d velocity model using velest the resulting locations show that most events occurred at the shallow depth beneath the taal volcano and two major earthquake groups were noticed with one lying underneath the western shore of taal lake and the other one spread around the eastern flank of the taal volcano since there is no reported volcano activities during the operation period of our seismic array we are still not confident to interpret these findings in terms of other natures of volcano at the current stage however our work represents an important pioneer step towards other more advanced seismic studies in taal volcano

thermal monitoring of hydrothermal activity by permanent infrared automatic stations results obtained at solfatara di pozzuoli campi flegrei italy 1 a permanent automatic infrared ir station was installed at solfatara crater the most active zone of campi flegrei caldera after a positive in situ calibration of the ir camera we analyze 2175 thermal ir images of the same scene from 2004 to 2007 the scene includes a portion of the steam heated hot soils of solfatara the experiment was initiated to detect and quantify temperature changes of the shallow thermal structure of a quiescent volcano such as solfatara over long periods ambient temperature is the main parameter affecting ir temperatures while air humidity and rain control image quality a geometric correction of the images was necessary to remove the effects of slow movement of the camera after a suitable correction the images give a reliable and detailed picture of the temperature changes over the period october 2004 to january 2007 which suggests that origin of the changes were linked to anthropogenic activity vegetation growth and the increase of the flux of hydrothermal fluids in the area of the hottest fumaroles two positive temperature anomalies were registered after the occurrence of two seismic swarms which affected the hydrothermal system of solfatara in october 2005 and october 2006 it is worth noting that these signs were detected in a system characterized by a low level of activity with respect to systems affected by real volcanic crisis where more spectacular results will be expected results of the experiment show that this kind of monitoring system can be a suitable tool for volcanic surveillance

spatio temporal changes in seismic velocity associated with the 2000 activity of miyakejima volcano as inferred from cross correlation analyses of ambient noise abstract miyakejima volcano japan showed strong and interesting volcanic activities in 2000 with the occurrence of dike intrusions caldera formation and a large amount of gas emission to understand temporal changes of the volcanic structure associated with this activity we apply ambient noise correlation analyses to the seismic records of five seismic stations at miyakejima volcano from july 1999 to december 2002 we calculate cross correlation functions ccfs for eight available station pairs at frequency bands of 0 4 0 8 hz and 0 8 1 6 hz and retrieve the rayleigh waves propagating with a group velocity of about 1 0 km s comparing ccfs obtained for each day with the reference ccfs that are calculated from a few months of data we estimate seismic velocity changes before and after the 2000 activity results at the two frequency bands show seismic velocity increase and decrease shallow structure at the volcanic edifice on the flanks experienced a seismic velocity increase up to 3 3 on the other hand the regions located close to the collapsed caldera show a seismic velocity decrease down to 2 3 to understand the mechanisms that may introduce these seismic velocity increase and decrease we examine several possible mechanisms of the velocity changes stress changes due to volcanic pressure sources and caldera formation and topographic changes by using the deflation sources previously determined from gps data we calculate the stresses at depths of 0 km and 1 km at the volcano the results suggest that the seismic velocity increases observed at seismic paths on the volcanic flank are explained by the compression caused by the deflation sources associated with magma activity in 2000 stress sensitivities of the seismic velocity changes are estimated to be 1 5 10 2 to 2 2 10 2 mpa 1 and 4 6 10 3 to 2 4 10 2 mpa 1 at frequency bands of 0 4 0 8 hz and 0 8 1 6 hz respectively which are in the range of the previously reported results our three dimensional numerical calculations on seismic wave propagation show that the seismic velocity decreases observed at seismic paths crossing the collapsed caldera can be explained by topographic changes introduced by a caldera we further suggest that the seismic velocity decreases detected around the regions close to the caldera may originate from the dilated regions cause by formation of the caldera

rocks under strain strain induced time lapse time shifts are observed for depleting reservoirs pressure depletion as a result of oil and gas production creates changes in the stress and strain fields of the rock material both inside and outside the reservoir seismic waves propagating through these rocks have different traveltimes before and after depletion because the layer thicknesses change and the seismic velocity is altered by the changes in the stress and strain fields the cumulative change in two way traveltimes with depth is referred to as time lapse time shift

real time monitoring of relative velocity changes using ambient seismic noise at the piton de la fournaise volcano la reunion from january 2006 to june 2007 we present the results of a real time method based on coda wave interferometry from seismic noise cross correlation functions for relative seismic velocity variations monitoring on a volcanic edifice the ambient seismic noise at the piton de la fournaise volcano on la reunion island is analyzed from january 2006 to june 2007 during this period five eruptions occurred showing a great diversity in eruption duration intensity and eruptive fissure location two different methods are used to compute the velocity variations in order to compare their stability in quasi real time routine we compare the obtained velocity variations with the surface deformation observed by gps and extensometers networks this allows us to identify and quantify three major processes at the origin of seismic wave velocity variations in the edifice firstly the observed pre eruptive summit inflation is accompanied by a decrease in seismic velocity secondly the edifice deflation following the opening of an eruptive fissure is characterized by an increase of the velocity finally the summit caldera collapse generates a strong velocity drop coda wave interferometry from seismic noise cross correlation functions in quasi real time may allow us to forecast eruption and constrain the processes taking place in the volcanic plumbing system

kawah ijen volcanic activity a review kawah ijen is a composite volcano located at the easternmost part of java island in indonesia and hosts the largest natural acidic lake in the world we have gathered all available historical reports on kawah ijen s activity since 1770 with the purpose of reviewing the temporal evolution of its activity most of these observations and studies have been conducted from a geochemical perspective and in punctuated scientific campaigns starting in 1991 the seismic activity and a set of volcanic lake parameters began to be weekly available we present a database of those measurements that combined with historical reports allow us to review each eruption unrest that occurred during the last two centuries as of 2010 the volcanic activity is monitored by a new multi disciplinary network including digital seismic stations and lake level and temperature measurements this detailed monitoring provides an opportunity for better classifying seismic events and forecasting volcanic unrest at kawah ijen but only with the understanding of the characteristics of this volcanic system gained from the historical review presented here

degassing and hydrothermal activity at mt spurr alaska during the summer of 2004 inferred from the complex frequencies of long period events 1 results of analyses of unusual long period earthquakes recorded between july and september 2004 at mt spurr alaska are presented the waveforms of these events are characterized by quasi sinusoidal signatures of long duration up to 40 sec with slowly decaying amplitudes bandwidths of 0 5 4 0 hz are typical amplitude spectra are marked by strong and sharp peaks reflecting the quasi monochromatic nature of the signal the temporal variations of the complex frequencies are investigated by use of the sompi method the dominant mode is resolved and its q factor estimated for each available event dominant frequencies are found in the band 0 8 2 2 hz with q varying between 25 and 100 the variations of the complex frequencies show an overall decline with time the dynamic response of a shallow fracture filled with bubbly water to the flux of hot gases from depth is proposed as a possible mechanism for the generation of the observed waveforms

earthquake volcano interaction imaged by coda wave interferometry 1 large earthquakes are often assumed to influence the eruptive activity of volcanoes a major challenge to better understand the causal relationship between these phenomena is to detect and image in detail all induced changes including subtle non eruptive responses we show that coda wave interferometry can be used to image such earthquake induced responses as recorded at yasur volcano vanuatu following a magnitude 7 3 earthquake which occurred 80 km from its summit we use repeating long period events to show that the earthquake caused a sudden seismic velocity drop followed by a slow partial recovery process the spatial distribution of the response amplitude indicates an effect centered on the volcano our result demonstrates that even if no major change in eruptive activity is observed volcanoes will be affected by the propagation of large amplitude seismic waves through their structure suggesting that earthquake volcano interaction is likely a more common phenomenon than previously believed

crater lake temperature changes of the 2005 eruption of santa ana volcano el salvador central america a sudden eruption at santa ana occurred on 1 october 2005 producing an ash and gas plume to a height in excess of 10 km above the volcano several days before thermal infrared images of the crater provided precursory signals of the eruption a significant increase in the extent and intensity of the fumarolic field inside the crater rim and of the surface temperature of the crater s lake was observed changes in energy input was also estimated to explain the increase in lake temperature based on energy mass balance calculations

analogue modeling of instabilities in crater lake hydrothermal systems 1 we carried out analogue experiments on two phase boiling systems using a porous vertical cylinder saturated with water the base of the cylinder was heated and the top was cooled as in a natural hydrothermal system previous work had shown that once the two phase zone reached a certain level thermal instabilities would develop we made measurements of the acoustic energy related to boiling and we found that high levels of acoustic noise were associated with the part of the cycle in which there was upward water movement we repeated our experiments with a cooling water tank at the top of the system representing a crater lake this showed that periodic thermal instabilities still developed in this situation we then compared our analogue measurements to two natural systems known to exhibit periodic behavior there is good agreement between the thermal and acoustic cycling seen in our model and the observations made at inferno crater lake in the waimangu geothermal area new zealand whose level cycles by nearly 10 m with a typical period of 38 days particularly notable is how in both systems high levels of acoustic noise are associated with rising water level the much larger ruapehu crater lake also in new zealand cycled with a period of several months to a year for over a decade prior to the 1995 eruption strong acoustic and seismic energy usually occurred just before the lake temperature started to rise this suggests a slightly different model in which the increasing two phase flow zone triggers more general convection once it reaches the base of the lake

long term dynamics of piton de la fournaise volcano from 13 years of seismic velocity change measurements and gps observations we study the piton de la fournaise pdf volcano dynamics through the observation of continuous seismic velocity changes from 2000 to 2013 we compute the cross correlations of ambient seismic noise recorded at more than 30 short period and broadband stations of the undervolc temporary seismic experiment and of the pdf volcano observatory network the velocity changes are estimated from the travel time delay measured on the cross correlations computed between pairs of stations we average the relative velocity changes for all pairs of stations and obtain a time series of the velocity change of piton de la fournaise volcano over 13 years from the period 0 5 to 4 s the depth sensitivity of the velocity change is ranging from approximately 100 m to 2500 m a slow decrease of velocity is measured from 2000 and ends with a major eruption that occurred in april 2007 this eruptive episode is followed by an increase of the velocity these long term changes are compared to the deformation of the piton de la fournaise edifice estimated from geodetic measurements an analysis of baseline change between gps stations indicates an inflation of the volcanic edifice prior to april 2007 followed by a deflation since then this deflation predominantly affects the terminal cone seismic velocity changes and deformation have similar long term trends with velocity decrease observed during inflation and velocity increase during deflation however the velocity change magnitude is about 2 orders of magnitude greater than the deformation this suggests nonlinear relation between velocity changes and deformation

using the composition of fluid seepage from the magmatic hydrothermal system of kawah ijen volcano indonesia as a monitoring tool abstract the lake waters of kawah ijen volcano are concentrated hyperacidic brines that obtain their composition from volcanic gases and water rock interaction lake water and hydrothermal fluids seep through the western flank of the volcano where they precipitate gypsum and form the hyperacid banyu pahit river in this contribution we present compositional data from bi weekly samples taken from the banyu pahit between 2015 and 2018 to evaluate whether these fluids can be used to monitor the hydrothermal system and compare the fluids to the record of variability documented by the precipitated gypsum understanding the causal links between variability of the banyu pahit and the magmatic hydrothermal processes operating in the kawah ijen system and establishing a baseline for quiescence are pre requisites to using the river for monitoring fluid samples were analysed at the ijen observatory for so4 cl ratio using baso4 turbidity and agcl gravimetry and subsequently sent for icp ms and icp oes analyses the data shows a first order seasonal variation that can be explained by variable input of neutral groundwater but is underlain by more subtle trends temporally there is a shift in the system from 2015 to 2016 to 2017 when the fluid contains a higher proportion of elements derived from rock alteration the shift occurs at the peak of the rainy season and coincides with a substantial rainfall increase in 2017 compared to 2015 2016 at the start of 2018 there is a marked increase in cu coinciding with a gas burst in march 2018 we suggest that an increased meteoric water input led to an increase in water rock interaction and dissolution of a cu sulphide phase in the hydrothermal system the variability of the fluids over the 3 year sampling period does not exceed that of the longer record preserved by the gypsum precipitates indicating that it is typical for the current style of activity

geochemistry of the magmatic hydrothermal system of kawah ijen volcano east java indonesia samples from kawah ijen crater lake spring and fumarole discharges were collected between 1990 and 1996 for chemical and isotopic analysis an extremely low ph 0 3 lake contains so 4 cl waters produced during absorption of magmatic volatiles into shallow ground water the acidic waters dissolve the rock isochemically to produce immature solutions the strong d and 18 o enrichment of the lake is mainly due to enhanced evaporation at elevated temperature but involvement of a magmatic component with heavy isotopic ratios also modifies the lake d and 18 o content the large so4 s d 23 8 26 4 measured in the lake suggest that dissolved so 4 forms during disproportionation of magmatic so 2 in the hydrothermal conduit at temperatures of 250 280 c the lake 18 o so4 and 18 o h2o values may reflect equilibration during subsurface circulation of the water at temperatures near 150 c significant variations in the lake s bulk composition from 1990 to 1996 were not detected however we interpret a change in the distribution and concentration of polythionate species in 1996 as a result of increased so 2 rich gas input to the lake system thermal springs at kawah ijen consist of acidic so 4 cl waters on the lakeshore and neutral ph hco 3 so 4 cl na waters in blawan village 17 km from the crater the cation contents of these discharges are diluted compared to the crater lake but still do not represent equilibrium with the rock the so 4 cl ratios and water and sulfur isotopic compositions support the idea that these springs are mixtures of summit acidic so 4 cl water and ground water the lakeshore fumarole discharges t 170 245 c have both a magmatic and a hydrothermal component and are supersaturated with respect to elemental sulfur the apparent equilibrium temperature of the gas is 260 c the proportions of the oxidized so 2 dominated magmatic vapor anti of the reduced h 2 s dominated hydrothermal vapor in the fumaroles varied between 1979 and 1996 this may be the result of interaction of so 2 bearing magmatic vapors with the summit acidic hydrothermal reservoir this idea is supported by the lower h 2 s so 2 ratio deduced for the gas producing the so 4 cl reservoir feeding the lake compared with that observed in the subaerial gas discharges the condensing gas may have equilibrated in a liquid vapor zone at about 350 c elemental sulfur occurs in the crater lake environment as banded sediments exposed on the lakeshore and as a subaqueous molten body on the crater floor the sediments were precipitated in the past during inorganic oxidation of h 2 s in the lake water this process was not continuous but was interrupted by periods of massive silica poorly crystallized precipitation similar to the present day lake conditions we suggest that the factor controlling the type of deposition is related to whether h 2 s or silica rich volcanic discharges enter the lake this could depend on the efficiency with which the lake water circulates in the hydrothermal cell beneath the crater quenched liquid sulfur products show 34 s values similar to those found in the banded deposits suggesting that the subaqueous molten body simply consists of melted sediments previously accumulated at the lake bottom

integrated thermal infrared imaging and structure from motion photogrammetry to map apparent temperature and radiant hydrothermal heat flux at mammoth mountain ca usa abstract this work presents a method to create high resolution cm scale orthorectified and georeferenced maps of apparent surface temperature and radiant hydrothermal heat flux and estimate the radiant hydrothermal heat emission rate from a study area a ground based thermal infrared tir camera was used to collect 1 a set of overlapping and offset visible imagery around the study area during the daytime and 2 time series of co located visible and tir imagery at one or more sites within the study area from pre dawn to daytime daytime visible imagery was processed using the structure from motion photogrammetric method to create a digital elevation model onto which pre dawn tir imagery was orthorectified and georeferenced three dimensional maps of apparent surface temperature and radiant hydrothermal heat flux were then visualized and analyzed from various computer platforms e g google earth arcgis we demonstrate this method at the mammoth mountain fumarole area on mammoth mountain ca time averaged apparent surface temperatures and radiant hydrothermal heat fluxes were observed up to 73 7 c and 450 w m 2 respectively while the estimated radiant hydrothermal heat emission rate from the area was 1 54 kw results should provide a basis for monitoring potential volcanic unrest and mitigating hydrothermal heat related hazards on the volcano

time lapse seismic reservoir monitoring time lapse seismic reservoir monitoring has advanced rapidly over the past decade there are currently about 75 active projects worldwide and more than 100 cumulative projects in the past decade or so the present total annual expenditures on 4 d seismic projects are on the order of 50 100 million us this currently represents a much smaller market than 3 d seismic but the use of 4 d seismic has grown exponentially over the past decade and is expected to continue to do so

iron in ice cores from law dome a record of atmospheric iron deposition for maritime east antarctica during the holocene and last glacial maximum total dissolvable iron tdfe was measured in sections of ice cores recovered from law dome on the coast of wilkes land east antarctica these samples include ice dating from the last glacial maximum lgm the last deglaciation and the early and mid holocene as well as samples from the anthropocene that have been dated with seasonal to annual resolution combining our tdfe concentration data with estimates of the ice accumulation rate we estimate the atmospheric iron deposition for law dome and the adjacent southern ocean during these periods our results indicate that the atmospheric iron deposition flux to this region during the lgm 8 mol fe m 2 yr 1 was an order of magnitude higher than the average holocene deposition flux 0 8 mol fe m 2 yr 1 this holocene flux estimate is significantly higher than recent estimates of atmospheric iron deposition based on the analysis of iron in samples of the dome c epica ice core implying that there are significant meridional gradients in eolian iron flux to the antarctic region our data also suggest that there have been significant variations in atmospheric iron deposition to law dome and adjacent ocean waters over seasonal to decadal timescales during the past century analysis of ice samples dating from calendar years 1927 to 1928 indicates an anomalously high flux of tdfe to the law dome region amounting to around half the maximum lgm flux possibly as a result of severe drought conditions on the australian continent given that chronic iron deficiency is thought to limit phytoplankton production in much of the ocean around antarctica such large secular variations in atmospheric iron supply are likely to have had profound impacts on year to year primary production and ecosystem structure in antarctic waters

coda wave interferometry for estimating nonlinear behavior in seismic velocity in coda wave interferometry one records multiply scattered waves at a limited number of receivers to infer changes in the medium over time with this technique we have determined the nonlinear dependence of the seismic velocity in granite on temperature and the associated acoustic emissions this technique can be used in warning mode to detect the presence of temporal changes in the medium or in diagnostic mode where the temporal change in the medium is quantified

investigating crater lake warming using aster thermal imagery case studies at ruapehu poas kawah ijen and copahue volcanoes abstract a two channel or split window algorithm designed to correct for atmospheric conditions was applied to thermal images taken by the advanced spaceborne thermal emission and reflection radiometer aster of lake yugama on kusatsu shirane volcano in japan in order to measure the temperature of its crater lake these temperature calculations were validated using lake water temperatures that were collected on the ground overall the agreement between the temperatures calculated using the split window method and ground truth is quite good typically 1 5 c for cloud free images data from fieldwork undertaken in the summer of 2004 at kusatsu shirane allow a comparison of ground truth data with the radiant temperatures measured using aster imagery further images were analyzed of ruapehu poas kawah ijen and copahue volcanoes to acquire time series of lake temperatures a total of 64 images of these 4 volcanoes covering a wide range of geographical locations and climates were analyzed results of the split window algorithm applied to aster images are reliable for monitoring thermal changes in active volcanic lakes these temperature data when considered in conjunction with traditional volcano monitoring techniques lead to a better understanding of whether and how thermal changes in crater lakes aid in eruption forecasting

subevents of long period seismicity implications for hydrothermal dynamics during the 2004 2008 eruption of mount st helens 1 one of the most striking aspects of seismicity during the 2004 2008 eruption of mount st helens msh was the precise regularity in occurrence of repetitive long period lp or drumbeat events over sustained time periods however this precise regularity was not always observed and at times the temporal occurrence of lp events became more random in addition accompanying the dominant lp class of events during the 2004 2008 msh eruption there was a near continuous randomly occurring series of smaller seismic events these subevents are not always simply small amplitude versions of the dominant lp class of events but appear instead to result from a separate random process only loosely coupled to the main lp source mechanism we present an analysis of the interevent time and amplitude distributions of the subevents using waveform cross correlation to separate lp events from the subevents we also discuss seismic tremor that accompanied the 8 march 2005 phreatic explosion event at msh this tremor consists of a rapid succession of lps and subevents triggered during the explosion in addition to broadband noise from the sustained degassing immediately afterward seismicity returned to the pre explosion occurrence pattern this triggering in relation to the rapid ejection of steam from the system and subsequent return to pre explosion seismicity suggests that both seismic event types originated in a region of the subsurface hydrothermal system that was 1 in contact with the reservoir feeding the 8 march 2005 phreatic explosion but 2 not destroyed or drained by the explosion event finally we discuss possible thermodynamic conditions in a pressurized hydrothermal crack that could give rise to seismicity pressure drop estimates for typical lp events are not generally large enough to perturb pure water in a shallow hydrothermal crack into an unstable state however dissolved volatiles such as co2 may lead to a more unstable system increasing the seismogenic potential of a hydrothermal crack subject to rapid heat flux the interaction of hydrothermal and magmatic systems beneath msh in 2004 2008 thus appears able to explain a wide range of observed phenomena including subevents lp events larger md 2 events and phreatic explosions

stratification at the earth s largest hyperacidic lake and its consequences volcanic lakes provide windows into the interior of volcanoes as they integrate the heat flux discharged by a magma body and condense volcanic gases volcanic lake temperatures and geochemical compositions therefore typically serve as warnings for resumed unrest or prior to eruptions if acidic and hot these lakes are usually considered to be too convective to allow any stratification within their waters kawah ijen volcano featuring the largest hyperacidic lake on earth volume of 27 million m3 is less homogeneous than previously thought hourly temperature measurements reveal the development of a stagnant layer of cold waters 30 c overlying warmer and denser water generally above 30 c and density 1 083 kg m3 examination of 20 yrs of historical records and temporary measurements show a systematic thermal stratification during rainy seasons the yearly rupture of stratification at the end of the rainy season causes a sudden release of dissolved gases below the cold water layer which appears to generate a lake overturn i e limnic eruption and a resonance of the lake i e a seiche highlighting a new hazard for these extreme reservoirs a minor non volcanic event such as a heavy rainfall or an earthquake may act as a trigger the density driven overturn requires specific salinity temperature conditions for the colder and less saline top water layer to sink into the hot saline water spectacular degassing occurs when the dissolved gases progressively stored during the rainy season due to a weakened diffusion of carbon dioxide in the top layer are suddenly released these findings challenge the homogenization assumption at acidic lakes and stress the need to develop appropriate monitoring setups

imaging preeruptive and coeruptive structural and mechanical changes of a volcano with ambient seismic noise 1 forecasting the location of an eruption is of primary importance for risk management in volcanic regions locating the underground structural changes associated with a potential eruption is also a key issue to better understand the dynamics at work in a volcano using recent results in wave physics we develop an imaging procedure that is based on the sensitivity of multiply scattered waves to weak changes in heterogeneous media this procedure allows to locate changes in both mechanical and scattering properties of the studied medium we study ambient seismic noise from 19 broadband stations at the active volcano piton de la fournaise on reunion island recorded from june to december 2010 during this period two volcanic eruptions occurred at two different locations we calculate the noise cross correlations and study two types of changes in the coda apparent velocity variations related to changes in the elastic properties of the medium and waveform decoherence associated with variations in the scattering and thus the geological structures we observe that the temporal variations of both of these parameters provide potential precursors of volcanic eruptions at piton de la fournaise the locations determined from the preeruptive and coeruptive changes in both parameters are in good agreement with the actual eruptive activities these data demonstrate that the coda of ambient noise correlations contains deterministic information on the locations of the eruptive processes in an active volcano our analysis offers an original and significant constraint for the localization of forthcoming volcanic eruptions

emissivity of terrestrial materials in the 3 5 μm atmospheric window remotely sensed infrared radiance emitted by a surface is a function both of its kinetic temperature and its spectral emissivity consequently assumptions are usually made about the emissivity of earth surface materials to allow their temperatures to be determined or vice versa to increase the accuracy of these assumptions the directional hemispherical spectral reflectance of a wide range of natural earth surface materials has been measured and is summarized here these include igneous metamorphic and sedimentary rocks desert varnish soils vegetation water and ice kirchhoff s law can be used to predict directional spectral emissivity from these data

source mechanism of long period events at kusatsu shirane volcano japan inferred from waveform inversion of the effective excitation functions abstract we investigate the source mechanism of long period lp events observed at kusatsu shirane volcano japan based on waveform inversions of their effective excitation functions the effective excitation function which represents the apparent excitation observed at individual receivers is estimated by applying an autoregressive filter to the lp waveform assuming a point source we apply this method to seven lp events the waveforms of which are characterized by simple decaying and nearly monochromatic oscillations with frequency in the range 1 3 hz the results of the waveform inversions show dominant volumetric change components accompanied by single force components common to all the events analyzed and suggesting a repeated activation of a sub horizontal crack located 300 m beneath the summit crater lakes based on these results we propose a model of the source process of lp seismicity in which a gradual buildup of steam pressure in a hydrothermal crack in response to magmatic heat causes repeated discharges of steam from the crack the rapid discharge of fluid causes the collapse of the fluid filled crack and excites acoustic oscillations of the crack which produce the characteristic waveforms observed in the lp events the presence of a single force synchronous with the collapse of the crack is interpreted as the release of gravitational energy that occurs as the slug of steam ejected from the crack ascends toward the surface and is replaced by cooler water flowing downward in a fluid filled conduit linking the crack and the base of the crater lake

high resolution imaging of hydrothermal heat flux using optical and thermal structure from motion photogrammetry abstract quantifying hydrothermal heat flux at meter scale resolution over 0 25 km2 is required to bridge in situ heat flux and satellite based measurements we advance a methodology that blends ground based daytime optical and nighttime thermal infrared tir imagery using structure from motion photogrammetry to map radiant hydrothermal heat flux over these scales at sites with low signal to noise ratios that would otherwise be difficult to characterize using for example unmanned aerial systems the improved method uses a computerized telescopic mount to relocate and align daytime optical acquisitions with nighttime tir imagery thereby enabling tir acquisition from multiple camera orientations positioned throughout a study area this facilitates mapping of thermal features at sites of varying size and complexity and helps to ameliorate topographic occlusion effects and geometric distortions that can bias radiant hydrothermal heat flux estimates derived from the resulting orthorectified thermal maps we assessed detection thresholds of this method at three sites across central california which range in size topography and heat flux conditions we found that blending of optical and thermal acquisitions successfully detected anomalous heat flux even in cases where temperatures were only slightly greater than background this approach might be applied to a variety of volcanic and hydrothermal systems to quantify the spatial distribution of heat flux and how this may relate to factors such as the distribution of ground fractures and lava flow rheology

nature of radio echo layering in the antarctic ice sheet detected by a two frequency experiment a two frequency radio echo sounding experiment was carried out at dome fuji the second highest dome in east antarctica and along a 1150 km long traverse line from the dome to the coast the goal was to determine the dominant causes of the radio echo internal reflections and to investigate their possible changes with depth ranges and regions from the two frequency 60 mhz and 179 mhz radio echo responses at various sites we distinguished four zones each of the zones is characterized by a dominant cause of radio echo internal reflection as follows in the pd zone changes in dielectric permittivity are mainly due to density fluctuations in the pcof zone changes in dielectric permittivity are mainly due to changes in crystal orientation fabrics and in the ca zone changes in electrical conductivity are mainly due to changes in acidity induced by past volcanic eruptions in each of these three zones the changes occur commonly along isochrones in addition a basal echo free zone the fourth zone was found to appear always below the pcof zone these four zones and their distribution suggested variations of the physical conditions within the ice sheet

bathymetry heat output and convection in ruapehu crater lake new zealand abstract bathymetric observations of ruapehu crater lake show that it became shallower and its volume decreased by 3 10 6 m 3 between 1965 and 1970 it is likely that this was due to lava moving upwards in the region under the lake from the regular measurements of crater lake temperature outflow and chloride and magnesium ion concentrations the inflows of steam cold water and chloride and magnesium ions were calculated using the 1970 volume only about half the precipitation falling on and around the lake mixes with the lake water since the cold fresh water floats on top of the denser lake water and travels to the outlet without mixing with the main body of water in the lake the chloride content of the input steam appears to vary with time in a similar fashion to that of white island fumaroles temperature and density profiles of the lake in 1965 and 1966 indicated that convection was occurring the temperature profile of the top 175 m of the lake agreed with a model of turbulent convection in small cells giving a temperature gradient at any level in the lake proportional to the heat flux at that level the convection model predicted that the temperature at depth would exceed the local boiling point if the thermal power input reached a value which would sustain a surface temperature approaching 60 c this prediction of instability was not inconsistent with observations convection in the present crater lake probably occurs in the form of thermal plumes from small sources

volcano surveillance using infrared cameras abstract volcanic eruptions are commonly preceded accompanied and followed by variations of a number of detectable geophysical and geochemical manifestations many remote sensing techniques have been applied to tracking anomalies and eruptive precursors and monitoring ongoing volcanic eruptions offering obvious advantages over in situ techniques especially during hazardous activity whilst spaceborne instruments provide a distinct advantage for collecting data remotely in this regard they still cannot match the spatial detail or time resolution achievable using portable imagers on the ground or aircraft hand held infrared camera technology has advanced significantly over the last decade resulting in a proliferation of commercially available instruments such that volcano observatories are increasingly implementing them in monitoring efforts improved thermal surveillance of active volcanoes has not only enhanced hazard assessment but it has contributed substantially to understanding a variety of volcanic processes drawing on over a decade of operational volcano surveillance in italy we provide here a critical review of the application of infrared thermal cameras to volcano monitoring following a summary of key physical principles instrument capabilities and the practicalities and methods of data collection we discuss the types of information that can be retrieved from thermal imagery and what they have contributed to hazard assessment and risk management and to physical volcanology with continued developments in thermal imager technology and lower instrument costs there will be increasing opportunity to gather valuable observations of volcanoes it is thus timely to review the state of the art and we hope thereby to stimulate further research and innovation in this area

stress and mass changes at a wet volcano example during the 2011 2012 volcanic unrest at kawah ijen volcano indonesia since 2010 kawah ijen volcano has been equipped with seismometers and its extremely acid volcanic lake has been monitored using temperature and leveling sensors providing unprecedented time resolution of multiparametric data for an acidic volcanic lake the nature of stress and mass changes of the volcano is studied by combining seismic analyses and volcanic lake measurements that were made during the strongest unrest ever recorded by the seismic network at kawah ijen the distal vt earthquake swarm that occurred in may 2011 was the precursor of volcanic unrest in october 2011 that caused an increase in shallow earthquakes the proximal vt earthquakes opened pathways for fluids to ascend by increasing the permeability of the rock matrix the following months were characterized by two periods of strong heat and mass discharge into the lake and by the initiation of monochromatic tremor mt activity when steam gases interacted with shallow portions of the aquifer significant seismic velocity variations concurrent with water level rises in which water contained a large amount of steam gas were associated with the crises that caused an although the unrest did not affect the shallow hydrothermal system at a large scale whereas shallow vt earthquakes likely reflect a magmatic intrusion mt and relative seismic velocity changes are clearly associated with shallow hydrothermal processes these results will facilitate the forecast of future crises

chemical evolution and volcanic activity of the active crater lake of poas volcano costa rica 1993 1997 abstract concentrations of chloride and sulfate and ph in the hot crater lake laguna caliente at poas volcano and in acid rain varied over the period 1993 1997 these parameters are related to changes in lake volume and temperature and changes in summit seismicity and fumarole activity beneath the active crater during this period lake level increased from near zero to its highest level since 1953 lake temperature declined from a maximum value of 70 c to a minimum value of 25 c and ph of the lake water increased from near zero to 1 8 in may 1993 when the lake was nearly dry chloride and sulfate concentrations in the lake water reached 85 400 and 91 000 mg l 1 respectively minimum concentrations of chloride and sulfate after the lake refilled to its maximum volume were 2630 and 4060 mg l 1 respectively between january 1993 and may 1995 most fumarolic activity was focused through the bottom of the lake after may 1995 fumarolic discharge through the bottom of the lake declined and reappeared outside the lake within the main crater area the appearance of new fumaroles on the composite pyroclastic cone coincided with a dramatic decrease in type b seismicity after january 1996 between may 1995 and december 1997 enhanced periods of type a seismicity and episodes of harmonic tremor were associated with an increase in the number of fumaroles and the intensity of degassing on the composite pyroclastic cone adjacent to the crater lake increases in summit seismic activity type a b and harmonic tremor and in the height of eruption plumes through the lake bottom are associated with a period of enhanced volcanic activity during april september 1994 at this time visual observations and remote fumarole temperature measurements suggest an increase in the flux of heat and gases discharged through the bottom of the crater lake possibly related to renewed magma ascent beneath the active crater a similar period of enhanced seismic activity that occurred between august 1995 and january 1996 apparently caused fracturing of sealed fumarole conduits beneath the composite pyroclastic cone allowing the focus of fumarolic degassing to migrate from beneath the lake back to the 1953 1955 cone changes in the chemistry of summit acid rain are correlated changes in volcanic activity regardless of whether fumaroles are discharging into the lake or are discharging directly into the atmosphere

a new source process for evolving repetitious earthquakes at ngauruhoe volcano new zealand abstract since early 2005 ngauruhoe volcano has produced repeating low frequency earthquakes with evolving waveforms and spectral features which become progressively enriched in higher frequency energy during the period 2005 to 2009 with the trend reversing after that time the earthquakes also show a seasonal cycle since january 2006 with peak numbers of events occurring in the spring and summer period and lower numbers of events at other times we explain these patterns by the excitation of a shallow two phase water gas or water steam cavity having temporal variations in volume fraction of bubbles such variations in two phase systems are known to produce a large range of acoustic velocities 2 300 m s and corresponding changes in impedance contrast we suggest that an increasing bubble volume fraction is caused by progressive heating of melt water in the resonant cavity system which in turn promotes the scattering excitation of higher frequencies explaining both spectral shift and seasonal dependence we have conducted a constrained waveform inversion and grid search for moment position and source geometry for the onset of two example earthquakes occurring 17 and 19 january 2008 a time when events showed a frequency enrichment episode occurring over a period of a few days the inversion and associated error analysis in conjunction with an earthquake phase analysis show that the two earthquakes represent an excitation of a single source position and geometry the observed spectral changes from a stationary earthquake source and geometry suggest that an evolution in both near source resonance and scattering is occurring over periods from days to months

precursory swarms of long period events at redoubt volcano 1989 1990 alaska their origin and use as a forecasting tool abstract during the eruption of redoubt volcano from december 1989 through april 1990 the alaska volcano observatory issued advance warnings of several tephra eruptions based on changes in seismic activity related to the occurrence of precursory swarms of long period lp seismic events dominant period of about 0 5 s the initial eruption on december 14 occurred after 23 years of quiescence and was heralded by a 23 hour swarm of lp events that ended abruptly with the eruption after a series of vent clearing explosions over the next few days dome growth began on december 21 another swarm with lp events similar to those of the first began on the 26th and ended in a major tephra eruption on january 2 eruptions continued over the next two weeks and then ceased until february 15 when a large eruption initiated a long phase of repetitive dome building and dome destroying episodes that continued into april warnings were issued before the major events on december 14 and january 2 but as the eruptive sequence continued after january 2 the energy of the swarms decreased and forecasting became more difficult a significant but less intense swarm preceded the february 15 eruption which was not forecast this eruption destroyed the only seismograph on the volcanic edifice and stymied forecasting until march 4 when the first of three new stations was installed within 3 km of the active vent from march 4 to the end of the sequence on april 21 there were eight eruptions six of which were preceded by detectable swarms of lp events although weak these swarms provided the basis for warnings issued before the eruptions on march 23 and april 6 the initial swarm on december 13 had the following features 1 short duration 23 hours 2 a rapidly accelerating rate of seismic energy release over the first 18 hours of the swarm followed by a decline of activity during the 5 hours preceding the eruption 3 a magnitude range from 0 4 to 1 6 4 nearly identical lp signatures with a dominant period near 0 5 s 5 dilatational first motions everywhere and 6 a stationary source location at a depth of 1 4 km beneath the crater this occurrence of long period events suggests a model involving the interaction of magma with groundwater in which magmatic gases steam and water drive a fixed conduit at a stationary point throughout the swarm the initiation of that sequence of events is analogous to the failure of a pressure relief valve connecting a lower supercharged magma dominated reservoir to a shallow hydrothermal system a three dimensional model of a vibrating fluid filled crack recently developed by chouet is found to be compatible with the seismic data and yields the following parameters for the lp source crack length 280 380 m crack width 140 190 m crack thickness 0 05 0 20 m crack stiffness 100 200 sound speed of fluid 0 8 1 3 km s compressional wave speed of rock 5 1 km s density ratio of fluid to rock 0 4 and ratio of bulk modulus of fluid to rigidity of rock 0 03 0 07 the fluid filled crack is excited intermittently by an impulsive pressure drop that varies in magnitude within the range of 0 4 to 40 bar such disturbance appears to be consistent with a triggering mechanism associated with choked flow conditions in the crack

mapping pressurized volcanic fluids from induced crustal seismic velocity drops volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth here we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations we used records of seismic noise from the japanese hi net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude m w 9 0 tohoku oki earthquake we interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves we suggest therefore that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems

use of a weather buoy to derive improved heat and mass balance parameters for ruapehu crater lake abstract heat and mass balance calculations are important for monitoring volcanoes with heated crater lakes but for these lakes the critical process of evaporation can be substantially affected by the lake s influence on the air mass above it measurements in 2010 using a weather station on a buoy floating in ruapehu crater lake enabled us to derive a relation between wind velocity above the lake and that measured at nearby weather stations as well as providing direct evidence of the effect of the warm lake on the air above it this supported the use of evaporation equations that allowed for the changing air conditions as incoming air became warmer and wetter from interaction with the lake so decreasing the overall evaporation rate heat and mass balance calculations using these parameters and equations during the period 2003 to early 2007 as crater lake filled before it overflowed confirm the previously observed high ratio of total heat flow to steam volume

assessment of resolution and accuracy of the moving window cross spectral technique for monitoring crustal temporal variations using ambient seismic noise summary temporal variations in the elastic behaviour of the earth s crust can be monitored through the analysis of the earth s seismic response and its evolution with time this kind of analysis is particularly interesting when combined with the reconstruction of seismic green s functions from the cross correlation of ambient seismic noise which circumvents the limitations imposed by a dependence on the occurrence of seismic events in fact because seismic noise is recorded continuously and does not depend on earthquake sources these cross correlation functions can be considered analogously to records from continuously repeating doublet sources placed at each station and can be used to extract observations of variations in seismic velocities these variations however are typically very small of the order of 0 1 per cent such accuracy can be only achieved through the analysis of the full reconstructed waveforms including later scattered arrivals we focus on the method known as moving window cross spectral analysis that has the advantage of operating in the frequency domain where the bandwidth of coherent signal in the correlation function can be clearly defined we investigate the sensitivity of this method by applying it to microseismic noise cross correlations which have been perturbed by small synthetic velocity variations and which have been randomly contaminated we propose threshold signal to noise ratios above which these perturbations can be reliably observed such values are a proxy for cross correlation convergence and so can be used as a guideline when determining the length of microseismic noise records that are required before they can be used for monitoring with the moving window cross spectral technique

fluid volcano interaction in an active stratovolcano the crater lake system of poas volcano costa rica rowe g l jr brantley s l fernandez m fernandez j f borgia a and barquero j 1992 fluid volcano interaction in an active stratovolcano the crater lake system of po is volcano costa rica j volcanol geotherm res 49 2351 seismic and geochemical data collected at po is volcano costa rica since 1978 suggest that temperature and chemical variations recorded in subaerial fumaroles and the crater lake are related to episodic release of heat and volatiles associated with hydrofracturing of the upper margin of the shallow magma body power outputs associated with these events approach 600 mw and are superimposed on a baseline energy flux of approximately 200 mw the baseline heat flux suggests a magma solidification rate of 0 012 km3 yr and background volatile release rates of 1000 t d h20 66 t d s 13 t d ci and 0 5 t d f these fluxes are comparable to fluxes of f c1 and s exiting the magmatic hydrothermal system through acidic flank springs and are about a factor of five less than estimated volatile fluxes through summit fumaroles during the high temperature event of 1981 1983 mass balance considerations suggest that heat released at the lake surface is primarily supplied by the ascent of heated brines supplemented by condensation of fumarolic steam calculated average seepage rates out of the lake 450 kg s indicate rapid convection of acidic lake brine through underlying lake sediments and pyroclastic deposits circulation of the extremely corrosive lake brine through the volcanoclastic material beneath the lake may enhance subsurface permeabilities fluxes of rock forming elements observed in the rio agrio basin on the northwest flank of po is suggest that dissolution and removal of volcano elastic material occurs at a rate of approximately 1650 m3 yr however estimated sulfur fluxes from the cooling magma body suggest that porosity created by this dissolution could quickly be filled by the deposition of native sulfur finally analysis of heat and water budgets for the crater lake over the period 1978 1989 indicates that the recent decline and disappearance of the lake was caused by variations in summit rainfall combined with an increase in subsurface heat flow to the lake in 1987 1988 the increase in heat flow is related to continued degassing of high temperature volatiles following a hydrofracturing magma ascent episode that occurred in 1986

investigating the source characteristics of long period lp seismic events recorded on piton de la fournaise volcano la reunion abstract magmatic and hydrothermal processes play a significant role in generating seismicity at active volcanoes these signals can be recorded at the surface and can be used to obtain an insight into the volcano s internal dynamics long period lp events are of particular interest as they often accompany or precede volcanic eruptions but they are still not well understood piton de la fournaise volcano la reunion island is one of the most active volcanoes in the world however lp events are rarely recorded there a seismic network of 20 broadband seismometers has been operational on piton de la fournaise volcano since november 2009 between november 2009 and january 2011 the volcano erupted five times but only 15 lp events were recorded three of these eruptions were preceded by lp events and several lp events were recorded during an intrusive phase a family of three repeating lp events exists within the dataset in order to characterize these events we locate and perform moment tensor inversion on the lp family the lp events are located within the summit crater at shallow depths

a model for seasonal changes in gps positions and seismic wave speeds due to thermoelastic and hydrologic variations it is known that gps time series contain a seasonal variation that is not due to tectonic motions and it has recently been shown that crustal seismic velocities may also vary seasonally in order to explain these changes a number of hypotheses have been given among which thermoelastic and hydrology induced stresses and strains are leading candidates unfortunately though since a general framework does not exist for understanding such seasonal variations it is currently not possible to quickly evaluate the plausibility of these hypotheses to fill this gap in the literature i generalize a two dimensional thermoelastic strain model to provide an analytic solution for the displacements and wave speed changes due to either thermoelastic stresses or hydrologic loading which consists of poroelastic stresses and purely elastic stresses the thermoelastic model assumes a periodic surface temperature and the hydrologic models similarly assume a periodic near surface water load since all three models are two dimensional and periodic they are expected to only approximate any realistic scenario but the models nonetheless provide a quantitative framework for estimating the effects of thermoelastic and hydrologic variations quantitative comparison between the models and observations is further complicated by the large uncertainty in some of the relevant parameters despite this uncertainty though i find that maximum realistic thermoelastic effects are unlikely to explain a large fraction of the observed annual variation in a typical gps displacement time series or of the observed annual variations in seismic wave speeds in southern california hydrologic loading on the other hand may be able to explain a larger fraction of both the annual variations in displacements and seismic wave speeds neither model is likely to explain all of the seismic wave speed variations inferred from observations however more definitive conclusions cannot be made until the model parameters are better constrained

hydroacoustic noise precursors of the 1990 eruption of kelut volcano indonesia abstract the results of a hydroacoustic monitoring experiment in the kelut crater lake indonesia prior to its 1990 eruption are presented with the benefit of hindsight indeed the underwater noise levels in three widely separated frequency bands together with the lake water temperature was radio transmitted and almost continuously recorded from a period of quiescence of the volcano till the onset of its 10 february 1990 eruption which destroyed the monitoring buoy the comparative analysis of the noise variations in the three bands together with seismic and temperature data have shed light on the mechanisms underlying the pre eruptive activity the three acoustic levels had shown conspicuous yet distinctive changes prior to the eruption acoustic level in the low frequency 1 50 hz band which increased one year before the resumption of seismic activity and the lake warming up is interpreted as the result of boiling at depth the source of high acoustic level in the audiometric 500 5000 hz range is clearly the bubbling of volcanic gases occurring as a strong convective column in the middle of the lake from the variations of this audiometric level we have estimated that the degassing rate in the lake increased by a hundred fold during the pre eruptive period variations of ultrasonic 20 100 khz frequency acoustic level seem to be related with pressure and thermal changes within the hydrothermal system and its rock matrix beneath the lake in conclusion this experiment demonstrates the potential of hydroacoustic monitoring as an early warning system at crater lake volcanoes

the heat source of ruapehu crater lake deductions from the energy and mass balances abstract regular observations of temperature outflow rates and water chemistry of crater lake mt ruapehu new zealand have been made for the last 25 years these data have been used to derive a model of the dynamics of the lake and determine the input of energy mass and chloride from the volcano to the crater lake the recent relatively quiescent state of the volcano when virtually no heat has been input to the lake has also enabled an assessment to be made of the surface heat loss characteristics which play an important role in the model of the lake the modelling suggests that since about 1982 the ratio of the volcanic heat to mass added to the base of the lake is about 6 mj kg which is not compatible with heating of the lake by magmatic steam alone thus only about 50 of the heating has been by magmatic steam it is suggested that heat could be transferred from a magmatic source to the region below the lake by a heat pipe mechanism commonly associated with geothermal systems the simultaneous upward movement of vapour phase and downward movement of liquid phase from condensed vapour allows efficient heat transfer without overall mass transfer the permeability necessary to supply the required heat is of the order of 10 darcy and is consistent with a rubble filled vent for at least the last five years there has been a characteristic pattern in the crater lake temperature record with alternate heating and cooling phases the heating phase generally lasts for one or two months while the cooling phase lasts for six months to a year a possible explanation for this cyclic behaviour is the presence of a layer of liquid sulphur under crater lake acting as a partial barrier between the heat pipe and the lake the unusual variations of the viscosity of liquid sulphur with temperature will mean that at temperatures greater than 160 c the layer of sulphur becomes highly viscous and would block any upwards steam flow and hence stop the heat input to crater lake so producing a cooling phase this blockage would last until the heating from below raised the temperature of the sulphur beyond the high viscosity region so gases could again pass through the sulphur

high productivity seabed time lapse seismic data acquisition using simultaneous sources enabled by seismic apparition a synthetic data study seismic apparition is a recent signal processing advance that trades signal interference and aliasing between different spatial and temporal dimensions in particular an important application of seismic apparition is for simultaneous source separation to better exploit the available data space in the frequency wavenumber f k domain with energy from different simultaneous sources the introduction of periodic modulation functions in seismic acquisition produces an effect where parts of the energy of one or more sources are partially shifted to different empty parts within the f k domain this so called apparated energy then can be used to perfectly predict at low frequencies the remaining part of the signal in the regions of the f k domain where the wavefields from the different sources overlap and to deterministically separate the sources at predetermined repeated positions a prerequisite for 4d seismic processing at higher frequencies the apparition separation is dealiased using directional

fluid dynamics inside a wet volcano inferred from the complex frequencies of long period lp events an example from papandayan volcano west java indonesia during the 2011 seismic unrest abstract we present results of our study aimed at understanding the dynamics of fluids inside a wet volcano through the analysis of swarms of long period lp events accompanying the 2011 seismic unrest at papandayan volcano west java indonesia prior to this unrest we measured an extremely high percentage 100 of co2 in the ground at the summit crater however with a very low value of so2 flux 6 tons day increase in volcanic activity was also observed from the records of a tiltmeter a long term inflation was followed by an abrupt deflation that took place concurrently with the swarms of lp events thereafter swarms of local tectonic lt and volcano tectonic vt earthquakes started we focus here on analyzing the lp events in the following manner first we estimate the source location of lp events by applying a 3 d non linear hypocenter localization algorithm which includes topography we then study the waveforms and spectral characteristics of lp events recorded at different stations and investigate whether or not these characteristics are due to source effects subsequently we compute the oscillation frequencies f and the decay characteristics q factor in the complex frequency domain of the coda part of the lp events by using the sompi method which is based on a homogeneous auto regressive ar equation the rectangular fluid filled crack model is used to estimate the physical processes related to the observed temporal variations in the complex frequencies we divide the swarms of lp events into two intervals the first interval occurred between june and july 2011 48 lp events while the second interval extended from september to october 2011 36 lp events the frequencies of lp events observed during these intervals range between 1 1 and 6 2 hz while the q factors are widely scattered between 20 and 400 we estimate the compositions of fluids inside the crack during both intervals as either water foam mixtures of water and h2o gas steam or misty gas mixtures of water droplets and h2o gas steam we finally suggest that if an eruption were to have taken place following the 2011 unrest it would have been in phreatic style rather than magmatic style the results of our study therefore contribute to the effort in the prediction of the behavior of future eruptions and to volcanic hazards assessment and therefore to volcanic risk mitigation

depth sensitivity of seismic coda waves to velocity perturbations in an elastic heterogeneous medium summary numerous monitoring applications make use of seismic coda waves to evaluate velocity changes in the earth this raises the question of the spatial sensitivity of coda wave based measurements here we investigate the depth sensitivity of coda waves to local velocity perturbations using 2 d numerical wavefield simulations we calculate the impulse response at the surface before and after a slight perturbation of the velocity within a thin layer at depth is introduced we perform a parametric analysis of the observed apparent relative velocity changes e obs versus the depth of the thin perturbed layer through the analysis of the decay of e obs we can discriminate two different regimes one for a shallow perturbation and the other for a deep perturbation we interpret the first regime as the footprint of the 1 d depth sensitivity of the fundamental surface wave mode to interpret the second regime we need to model the sensitivity of the multiply scattered body waves in the bulk we show that the depth sensitivity of coda waves can be modelled as a combination of bulk wave sensitivity and surface wave sensitivity the transition between these two regimes is governed by mode conversions due to scattering we indicate the importance of surface waves for the sensitivity of coda waves at shallow depths and at early times in the coda at later times bulk waves clearly dominate the depth sensitivity and offer the possibility of monitoring changes at depths below the sensitivity of the surface waves based on the transition between the two regimes we can discriminate a change that occurs at the surface from a change that occurs at depth this is illustrated for shallow depth perturbations through an example from lunar data

new insights into the kawah ijen hydrothermal system from geophysical data corentin caudron 1 2 3 guillaume mauri 4 glyn williams jones 5 thomas lecocq2 devy kamil syahbana 6 raphael de plaen 7 loic peiffer 8 alain bernard 3 ginette saracco 9 1 earth observatory of singapore nanyang technological university 50 nanyang av block n2 01a 15 singapore 639798 2 royal observatory of belgium seismology section 3 avenue circulaire 1180 uccle belgium 3 department of earth environmental sciences universite libre de bruxelles 50 ave roosevelt 1050 brussels belgium 4 center for hydrogeology and geothermics university of neuchtel neuchtel switzerland 5 department of earth sciences simon fraser university 8888 university drive burnaby british columbia v5a 1s6 canada 6 centre for volcanology and geological hazard mitigation geological agency ministry of energy and mineral resources jalan diponegoro 57 bandung 40122 indonesia 7 university of luxembourg faculte des sciences de la technologie et de la communication 6 rue richard coudenhove kalergi l 1359 luxembourg 8 instituto de energi as renovables universidad nacional auto noma de me xico privadaxochicalco s n centro 62580 temixco morelos mexico 9 cnrs umr7330 centre europeen de recherche et d enseignement en geosciences de l environnement cerege equipe modelisation aix marseille universite amu europole de l arbois bp 80 13545 aix en provence cedex 4 france ginet cerege fr corresponding author e mail corentin caudron gmail com abstract the magmatic hydrothermal system of kawah ijen volcano is one of the most exotic on earth featuring the largest acidic lake on the planet a hyper acidic river and a passively degassing silicic dome while previous studies have mostly described this unique system from a geochemical perspective to date there has been no comprehensive geophysical investigation of the system in our study we surveyed the lake using a thermocouple a thermal camera an echo sounderand co2 sensors furthermore we gained insights into the hydrogeological structures by combining self potential surveys with ground and water temperatures our results show that the hydrothermal system is self sealed within the upper edifice and releases pressurized gas only through the active crater we also show that the extensive hydrological system is formed by not one but three aquifers a south aquifer that seems to be completely isolated a west aquifer that sustains the acidic upper springs and an east aquifer that is the main source of fresh water for the lake in contrast with previous research we emphasize the heterogeneity of the acidic lake illustrated by intense subaqueous degassing these findings provide new insights into this unique hazardous hydrothermal system which may eventually improve the existing monitoring system

structure from motion photogrammetry a low cost effective tool for geoscience applications abstract high resolution topographic surveying is traditionally associated with high capital and logistical costs so that data acquisition is often passed on to specialist third party organisations the high costs of data collection are for many applications in the earth sciences exacerbated by the remoteness and inaccessibility of many field sites rendering cheaper more portable surveying platforms i e terrestrial laser scanning or gps impractical this paper outlines a revolutionary low cost user friendly photogrammetric technique for obtaining high resolution datasets at a range of scales termed structure from motion sfm traditional softcopy photogrammetric methods require the 3 d location and pose of the camera s or the 3 d location of ground control points to be known to facilitate scene triangulation and reconstruction in contrast the sfm method solves the camera pose and scene geometry simultaneously and automatically using a highly redundant bundle adjustment based on matching features in multiple overlapping offset images a comprehensive introduction to the technique is presented followed by an outline of the methods used to create high resolution digital elevation models dems from extensive photosets obtained using a consumer grade digital camera as an initial appraisal of the technique an sfm derived dem is compared directly with a similar model obtained using terrestrial laser scanning this intercomparison reveals that decimetre scale vertical accuracy can be achieved using sfm even for sites with complex topography and a range of land covers example applications of sfm are presented for three contrasting landforms across a range of scales including an exposed rocky coastal cliff a breached moraine dam complex and a glacially sculpted bedrock ridge the sfm technique represents a major advancement in the field of photogrammetry for geoscience applications our results and experiences indicate sfm is an inexpensive effective and flexible approach to capturing complex topography

earthquake classification location and error analysis in a volcanic environment implications for the magmatic system of the 1989 1990 eruptions at redoubt volcano alaska abstract determination of the precise locations of seismic events associated with the 1989 1990 eruptions of redoubt volcano posed a number of problems including poorly known crustal velocities a sparse station distribution and an abundance of events with emergent phase onsets in addition the high relief of the volcano could not be incorporated into the hypoellipse earthquake location algorithm this algorithm was modified to allow hypocenters to be located above the elevation of the seismic stations the velocity model was calibrated on the basis of a posteruptive seismic survey in which four chemical explosions were recorded by eight stations of the permanent network supplemented with 20 temporary seismographs deployed on and around the volcanic edifice the model consists of a stack of homogeneous horizontal layers setting the top of the model at the summit allows events to be located anywhere within the volcanic edifice detailed analysis of hypocentral errors shows that the long period lp events constituting the vigorous 23 hour swarm that preceded the initial eruption on december 14 could have originated from a point 1 4 km below the crater floor a similar analysis of lp events in the swarm preceding the major eruption on january 2 shows they also could have originated from a point the location of which is shifted 0 8 km northwest and 0 7 km deeper than the source of the initial swarm we suggest this shift in lp activity reflects a northward jump in the pathway for magmatic gases caused by the sealing of the initial pathway by magma extrusion during the last half of december volcano tectonic vt earthquakes did not occur until after the initial 23 hour long swarm they began slowly just below the lp source and their rate of occurrence increased after the eruption of 01 52 ast on december 15 when they shifted to depths of 6 to 10 km after january 2 the vt activity migrated gradually northward this migration suggests northward propagating withdrawal of magma from a plexus of dikes and or sills located in the 6 to 10 km depth range precise relocations of selected events prior to january 2 clearly resolve a narrow steeply dipping pencil shaped concentration of activity in the depth range of 1 7 km which illuminates the conduit along which magma was transported to the surface a third event type named hybrid which blends the characteristics of both vt and lp events originates just below the lp source and may reflect brittle failure along a zone intersecting a fluid filled crack the distribution of hybrid events is elongated 0 2 0 4 km in an east west direction this distribution may offer constraints on the orientation and size of the fluid filled crack inferred to be the source of the lp events

high spatio temporal resolution observations of crater lake temperatures at kawah ijen volcano east java indonesia the crater lake of kawah ijen volcano east java indonesia has displayed large and rapid changes in temperature at point locations during periods of unrest but measurement techniques employed to date have not resolved how the lake s thermal regime has evolved over both space and time we applied a novel approach for mapping and monitoring variations in crater lake apparent surface skin temperatures at high spatial 32 cm and temporal every 2 min resolution at kawah ijen on 18 september 2014 we used a ground based flir t650sc camera with digital and thermal infrared tir sensors from the crater rim to collect 1 a set of visible imagery around the crater during the daytime and 2 a time series of co located visible and tir imagery at one location from pre dawn to daytime we processed daytime visible imagery with the structure from motion photogrammetric method to create a digital elevation model onto which the time series of tir imagery was orthorectified and georeferenced lake apparent skin temperatures typically ranged from 21 to 33 c at two locations apparent skin temperatures were 4 and 7 c less than in situ lake temperature measurements at 1 5 and 5 m depth respectively these differences as well as the large spatio temporal variations observed in skin temperatures were likely largely associated with atmospheric effects such as the evaporative cooling of the lake surface and infrared absorption by water vapor and so2 calculations based on orthorectified tir imagery thus yielded underestimates of volcanic heat fluxes into the lake whereas volcanic heat fluxes estimated based on in situ temperature measurements 68 to 111 mw were likely more representative of kawah ijen in a quiescent state the ground based imaging technique should provide a valuable tool to continuously monitor crater lake temperatures and contribute insight into the spatio temporal evolution of these temperatures associated with volcanic activity

volcanic lake systematics i physical constraints volcanic lakes have a wide range of characteristics and we make an attempt to delineate the limiting physical conditions for several lake classes the ratio between heat input and heat dissipation capacity of a lake constrains the temperature for perfectly mixed steady state volcanic lakes poorly mixed lakes are also conditioned by this ratio but their temperature structure is also strongly influenced by the hydrodynamics resulting from different mechanisms of heat transfer the steady state temperatures of volcanic lakes are largely determined by the magnitude of the volcanic heat influx relative to the surface area of the lake small lakes have only a small capacity for heat dissipation and their temperature rises quickly with only small heat inputs large lakes are buffered against variations in heat input both the heat dissipation and meteoric water input into a lake are functions of lake surface area and therefore each lake water temperature demands a certain precipitation rate for mass conservation independent of lake size the results of energy mass balance modeling shows that under common atmospheric conditions most steady state volcanic lakes are unlikely to maintain a temperature in excess of 45 50 c validation of the volcanic lake model was performed using published data from yugama lake japan and the keli mutu lakes indonesia also the model was applied to 24 natural systems to provide a baseline assessment of energy fluxes under the model assumptions so future work on those systems can identify nuances in individual systems that deviate from the simple model conditions we recommend the model for use in assessing temperature variations and volcanic lake stability in settings with known physical and atmospheric conditions application of the energy mass balance calculations of model lakes provides a genetic classification scheme largely based on physical process parameters

comprehensive observation and modeling of earthquake and temperature related seismic velocity changes in northern chile with passive image interferometry we report on earthquake and temperature related velocity changes in high frequency autocorrelations of ambient noise data from seismic stations of the integrated plate boundary observatory chile project in northern chile daily autocorrelation functions are analyzed over a period of 5 years with passive image interferometry a short term velocity drop recovering after several days to weeks is observed for the mw 7 7 tocopilla earthquake at most stations at the two stations pb05 and patcx we observe a long term velocity decrease recovering over the course of around 2 years while station pb05 is located in the rupture area of the tocopilla earthquake this is not the case for station patcx station patcx is situated in an area influenced by salt sediment in the vicinity of salar grande and presents a superior sensitivity to ground acceleration and periodic surface induced changes due to this high sensitivity we observe a velocity response of several regional earthquakes at patcx and we can show for the first time a linear relationship between the amplitude of velocity drops and peak ground acceleration for data from a single station this relationship does not hold true when comparing different stations due to the different sensitivity of the station environments furthermore we observe periodic annual velocity changes at patcx analyzing data at a temporal resolution below 1 day we are able to identify changes with a period of 24 h too the characteristics of the seismic velocity with annual and daily periods indicate an atmospheric origin of the velocity changes that we confirm with a model based on thermally induced stress this comprehensive model explains the lag time dependence of the temperature related seismic velocity changes involving the distribution of temperature fluctuations the relationship between temperature stress and velocity change plus autocorrelation sensitivity kernels

the hazards of eruptions through lakes and seawater abstract eruptions through crater lakes or shallow seawater referred to here as subaqueous eruptions present hazards from hydromagmatic explosions such as base surges lahars and tsunamis which may not exist at volcanoes on dry land we have systematically compiled information from eruptions through surface water in order to understand the circumstances under which these hazards occur and what disastrous effects they have caused in the past subaqueous eruptions represent only 8 of all recorded eruptions but have produced about 20 of all fatalities associated with volcanic activity in historical time excluding eruptions that have resulted in about a hundred deaths or less lahars have killed people in the largest number of historical subaqueous eruptions 8 followed by pyroclastic flows excluding base surges 5 tsunamis 4 and base surges 2 subaqueous eruptions have produced lahars primarily on high 1000 m steep sided volcanoes containing small

synchronizing seismic networks with ambient noise summary the technique of retrieving green s functions by pairwise correlation of a random wavefield is used to estimate the stability of the timing system of a seismic network the method is demonstrated with data from a network consisting of stations with four independent clocks and gps receivers for a two years period daily measurements of the timing error of each of the four systems are obtained these measurements can be used to correct the timing of the data in periods without gps reception the accuracy of this method can exceed the precision of the internal station clocks already after a single day of uncorrected drift

pressure and porosity influences on vp vs ratio in unconsolidated sands elevated pore pressures commonly encountered in the shallow unconsolidated section of the sedimentary column present a significant hazard during the drilling and completion of offshore wells the porosity of the ocean floor sediments is high and a cover of low permeability clay can prevent the underlying sediments from draining even at very shallow depths below the seafloor as further deposition loads the sediment the entrapped fluids impede normal compaction by becoming pressurized the lowered effective stress that results from the higher pore fluid pressure produces a proportional drop in the strength of non cohesive sediments resulting in very weak shallow sands this weakness can result in washouts or fracturing in the shallow strata potentially leading to the loss of the well and of neighboring wells