temporal magnetotellurics reveals mechanics of the 2012 mount tongariro nz eruption monitoring dynamics of volcanic eruptions with geophysics is challenging in august and november 2012 two small eruptions from mount tongariro provided a unique opportunity to image subsurface changes caused by the eruptions a detailed magnetotelluric survey of the tongariro volcanic complex completed prior to the eruption 2008 2010 provides the pre eruption structure of the magmatic system a subset of the initial measurement locations was reoccupied in june 2013 significant changes were observed in phase tensor data at sites close to the eruptive centre although subsurface electrical resistivity changed geometry of the pre eruptive reservoir did not these subsurface resistivity variations are interpreted as being predominantly caused by interaction of partial melt and the overlying brine layer causing volume reduction of the brine layer through phreatic eruption the ability to detect significant changes associated with the magma reservoir suggests that magnetotellurics can be a valuable volcano monitoring tool

the 25 september 2007 eruption of mount ruapehu new zealand directed ballistics surtseyan jets and ice slurry lahars abstract at 20 26 nzdt on 25 september 2007 a moderate gas driven eruption beneath the summit crater lake of mt ruapehu new zealand generated a directed ballistic fallout apron and surtseyan jet that impacted an area of c 2 5 km2 to the north of the vent two climbers were caught in the blast at a hut 600 m from the vent primary ice slurry lahars were generated in two catchments draining the summit region including a flow that entered a commercial ski field the ejecta consists of blocks of andesitic lava and scoria erupted during previous volcanic episodes a variety of mineral cemented lake floor sediments vent fill debris and rare glassy material interpreted to be derived from a fresh batch of magma a minority of clasts contain formerly molten elemental sulphur indicating that vent temperatures at the base of the lake were in excess of 119 c the ballistic deposit is confined to a c 40 wide swath directed northwards that extends up to 2 km from the inferred vent location beneath crater lake the strong directionality of the jetted deposits and ballistic free shadow zones sheltered by intervening topography all point to a relatively low angle directed blast previous similar eruptions at ruapehu also show preferred deposit orientations that are here correlated with an inclined and off centre vent beneath crater lake the 25 september 2007 eruption appears to have resulted from failure of a relatively shallow hydrothermal seal composed of elemental sulphur and other mineral precipitates developed in the vent breccia which breached following overpressurization by a pulse of magmatic gases released from deeper in the conduit this event highlights the potential hazard from relatively minor gas driven eruptions at ruapehu that can occur with little or no warning improved understanding of the eruption mechanism for this style of eruption will inform future risk assessments for ruapehu and other similar volcanoes worldwide

the influence of fluid type on elastic wave velocity and attenuation in volcanic rocks abstract volcano seismic signatures are the convolution of source and path effects the source signature provides important information about the dynamic rock deformation and fluid resonance processes within the volcano but path effects are the result of the volcanic plumbing the edifice physical conditions and the complex geological structure complicating the inversion of seismic data further is the influence of fluid properties here we use ultrasonic experiments to understand the effect of variable fluid viscosity and bulk modulus on p wave attenuation and velocity for volcanic rocks from white island volcano whakaari new zealand our experimental conditions for high porosity ash tuff and low porosity lava resemble shallow and deep volcano facies respectively p wave velocity vp and quality factor qp increase with the viscosity and bulk modulus of the saturating fluid and decrease with porosity and fracture volume tuffs are highly sensitive to saturating fluid with variations in vp of up to 67 and qp of 383 vp and qp in fractured lavas are slightly less sensitive to fluids 24 and 296 respectively but vp can be used to identify lithology for these tuff vs lavas comparison of the experimental data with rock physics models suggests that squirt flow is the dominant attenuation mechanism for viscosities greater than that of water while scattering losses may be important in gas saturated rocks our results have significant implications for the interpretation of seismic tomography studies and for volcano hazard monitoring based on the characteristics of detected seismicity

changes in attenuation related to eruptions of mt ruapehu volcano new zealand abstract temporal variations of seismic attenuation have been observed at different volcanoes around the world and are often claimed to correlate with volcanic activity seismic attenuation and its variation in time at mt ruapehu volcano new zealand was measured for the period october 1990 to may 2005 using local earthquakes originating from a nearby cluster of earthquakes called the waiouru swarm as recorded on 5 permanent seismometer stations cross correlation of p and s waves reveals a similarity of events from this ongoing seismic source which suggests that alterations due to source and path effects are minimized therefore the swarm is suitable for the study of temporal changes in seismic attenuation the attenuation q c 1 of coda waves following the direct p and s waves are calculated for five frequency bands centred at 1 5 3 0 6 0 9 0 and 12 0 hz using the single scattering model a best fit equation of q c q 0 f with q 0 54 7 and 1 02 0 06 shows an overall high frequency dependence of coda attenuation which is characteristic for tectonically active regions small fluctuations of q c 1 are observed at all stations over the entire time period and do not act as an apparent indicator of volcanic activity relative changes in integrated direct wave attenuation t along the whole path are obtained using a spectral ratio method in which spectra of individual 1 second p wave windows are compared to a reference spectrum during the time of volcanic activity the following changes were significant at the 95 confidence level in the low frequency band 1 5 6 hz a high attenuation anomaly with an abrupt increase of t by 0 23 s was detected in waveforms that have travelled through the volcano and a shift from negative to positive t by 0 25 s was observed at a station next to the volcano we suggest that these observations are related to variations detected in seismic anisotropy studies which propose a model of a change in stress caused by pressurisation of magma dykes under the volcano

real time seismic amplitude measurement rsam a volcano monitoring and prediction tool seismicity is one of the most commonly monitored phenomena used to determine the state of a volcano and for the prediction of volcanic eruptions although several real time earthquake detection and data acquisition systems exist few continuously measure seismic amplitude in circumstances where individual events are difficult to recognize or where volcanic tremor is prevalent analog seismic records provide a quick visual overview of activity however continuous rapid quantitative analysis to define the intensity of seismic activity for the purpose of predicing volcanic eruptions is not always possible because of clipping that results from the limited dynamic range of analog recorders at the cascades volcano observatory an inexpensive 8 bit analog to digital system controlled by a laptop computer is used to provide 1 min average amplitude information from eight telemetered seismic stations the absolute voltage level for each station is digitized averaged and appended in near real time to a data file on a multiuser computer system raw realtime seismic amplitude measurement rsam data or transformed rsam data are then plotted on a common time base with other available volcano monitoring information such as tilt changes in earthquake activity associated with dome building episodes weather and instrumental difficulties are recognized as distinct patterns in the rsam data set rsam data for domebuilding episodes gradually develop into exponential increases that terminate just before the time of magma extrusion mount st helens crater earthquakes show up as isolated spikes on amplitude plots for crater seismic stations but seldom for more distant stations weather related noise shows up as low level long term disturbances on all seismic stations regardless of distance from the volcano implemented in mid 1985 the rsam system has proved valuable in providing up to date information on seismic activity for three mount st helens eruptive episodes from 1985 to 1986 may 1985 may 1986 and october 1986 tiltmeter data the only other telemetered geophysical information that was available for the three dome building episodes is compared to rsam data to show that the increase in rsam data was related to the transport of magma to the surface thus if tiltmeter data is not available rsam data can be used to predict future magmatic eruptions at mount st helens we also recognize the limitations of rsam data two examples of rsam data associated with phreatic or shallow phreatomagmatic explosions were not preceded by the same increases in rsam data or changes in tilt associated with the three dome building eruptions

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

geochemical and diatom evidence of transition from freshwater to marine environments in the aira caldera and kagoshima bay japan during post glacial sea level rise abstract the aira caldera in kyushu southwest japan is a huge quaternary caldera that formed as a result of an eruption ca 25 ka most of the caldera is now submerged under the innermost part of kagoshima bay which is part of a large graben the caldera was initially a freshwater lake but eventually became a marine environment previous studies demonstrated that the center part of the bay was occupied by fresh water during sea level lowstand around 18 ka and was invaded by marine water at ca 13 ka during rapid post glacial sea level rise geochemical and fossil diatom assemblages however strongly suggest that seawater was present in the caldera lake during the 18 13 ka interval sediment from this time contains both elevated sedimentary sulfide content and marine diatom species this evidence implies that water in the center part of kagoshima bay was not entirely fresh for the last 18 000 yrs and that the aira caldera changed abruptly from a freshwater lake to a marine environment at 13 ka this abrupt change may have resulted from collapse of part of the caldera wall during eruption of sakurajima volcano

seismo acoustic evidence for an avalanche driven phreatic eruption through a beheaded hydrothermal system an example from the 2012 tongariro eruption abstract the 6 august 2012 te maari eruption comprises a complex eruption sequence including multiple eruption pulses a debris avalanche that propagated 2 km from the vent and the formation of a 500 m long arcuate chasm located 300 m from the main eruption vent the eruption included 6 distinct impulses that were coherent across a local infrasound network marking the eruption onset at 11 52 18 all times utc an eruption energy release of 3 1012 j was calculated using a body wave equation for radiated seismic energy a similar calculation based on the infrasound record shows that 90 of the acoustic energy was released from three impulses at onset times 11 52 20 20 of total eruption energy 11 52 27 50 and 11 52 31 20 these energy impulses may coincide with eyewitness accounts describing an initial eastward directed blast followed by a westward directed blast and a final vertical blast pre eruption seismic activity includes numerous small unlocatable micro earthquakes that began at 11 46 50 two larger high frequency earthquakes were recorded at 11 49 06 and 11 49 21 followed directly by a third earthquake at 11 50 17 the first event was located within the scarp based on an arrival time location from good first p arrival times and probably represents the onset of the debris avalanche the third event was a tornillo characterised by a 0 8 hz single frequency resonance and has a resonator attenuation factor of q 40 consistent with a bubbly fluid filled resonator this contrasts with a similar tornillo event occurring 2 5 weeks earlier having q 250 1000 consistent with a dusty gas charged resonator we surmise from pre eruption seismicity and the observed attenuation change that the debris avalanche resulted from the influx of fluids into the hydrothermal system causing destabilisation and failure the beheaded hydrothermal system may have then caused depressurisation frothing of the remaining gas charged system leading to the onset of explosive activity

a temporal change in coda wave attenuation observed during an eruption of mount st helens during the past few years there have been numerous reports of changes in coda wave attenuation occurring before major earthquakes these observations are important because they may provide insight into stress related structural changes taking place in the focal region prior to the occurrence of large earthquakes the results of these studies led us to suspect that temporal changes in coda wave attenuation might also accompany volcanic eruptions by measuring power decay envelopes for earthquakes at mount st helens recorded before during and after an eruption that took place during september 3 6 1981 we found that coda q sup 1 for frequencies between 6 and 30 hz was 20 30 higher before the eruption than after the change is attributed to an increase in the density of open microcracks in the rock associated with inflation of the volcano prior to the eruption q sup 1 was found to be only weakly dependent on frequency and displayed a slight peak near 10 hz the weak frequency dependence is attributed to the dominance of intrinsic attenuation over scattering attenuation since it is generally accepted that intrinsic attenuation is constant with frequency whereas scattering attenuation decreases strongly at higher frequencies the weak frequency dependence of q sup 1 more at mount st helens contrasts with results reported for studies in nonvolcanic regions the peak in q sup 1 near 10 hz at mount st helens is attributed to the scale length of heterogeneity responsible for generating backscattered waves results for nonvolcanic regions have shown this peak to occur near 0 5 hz thus a smaller scale length of heterogeneity is required to explain the 10 hz peak at mount st helens copyright american geophysical union 1988 less

mg rich clay mineral formation associated with marine shallow water hydrothermal activity in an arc volcanic caldera setting abstract shallow water hydrothermal activity represented by venting of hydrothermal fluid around 200 c occurs in the wakamiko submarine crater at 200 m water depth in kagoshima bay southwest japan the crater is the center of large eruptions that formed a volcanic caldera which is semi submerged at present the crater is covered with thick volcanic sediments of felsic composition we studied the distribution and chemical composition of hydrothermal clay minerals that are abundant in the sediment collected by piston coring we also conducted chemical analysis of pore fluids squeezed from the sediment to understand hydrothermal interactions that resulted in formation of these clay minerals the pc 2 core 340 cm in length collected in the vicinity of a high temperature fluid venting site was characterized by abundant mg saponite that is limited to a layer between 270 and 300 centimeters below the seafloor cmbsf and montmorillonite throughout the core below 55 cmbsf vertical profiles of pore fluid chemistry suggest that saponite formation is related to the interface between the seawater and the hydrothermal component in the sediment layer formation temperatures of the montmorillonite were estimated to be 118 163 c based on oxygen isotope thermometry formation of the montmorillonite is attributed to hydrothermal interaction between seawater dominant pore fluid and volcanic glass the formation temperature of the saponite was estimated to be 164 c based on oxygen isotope thermometry formation of the saponite is attributed to hydrothermal interaction between seawater dominant pore fluid and the montmorillonite which had been formed at a prior stage the pc 1 core 240 cm in length collected from a relatively low temperature fluid shimmering site was characterized by the occurrence of kerolite in the lower section 210 240 cmbsf vertical profiles of pore fluid chemistry suggest that the kerolite formation occurred at the interface between seawater and the hydrothermal component of the sediment layer formation temperature of the kerolite was estimated to be about 211 c based on oxygen isotope thermometry formation of the kerolite is attributed to precipitation from a fluid that was a mixture of a hydrothermal component and seawater this study revealed the occurrence of mg rich clay minerals saponite and kerolite beneath a submarine hydrothermal field that developed within sediment of felsic composition during hydrothermal interactions that formed these clay minerals seawater penetrated into the sediment and was an important mg source formation of mg rich clay minerals saponite and kerolite are controlled by pore fluid chemistry which varies from a seawater dominant to hydrothermal dominant component exclusive formation of mg rich clay minerals at different sites could be explained by different water rock ratios of the hydrothermal interaction saponite formation at low water rock ratio and kerolite precipitation at high water rock ratio occurrence of mg rich clay minerals provides clues to the hydrological structure in sediment covered hydrothermal systems in an arc volcanic caldera setting

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

intrinsic and scattering attenuation images of usu volcano japan we present intrinsic and scattering q attenuation images for usu volcano japan by analyzing over 1800 vertical seismograms by fitting the observed envelopes to the diffusion model we obtained intrinsic and scattering attenuation values at three different frequency bands using a back projection method and assuming a gaussian type weighting function we obtained the 2d images of intrinsic and scattering attenuation resolution tests confirm the robustness and reliability of the obtained images we found that scattering attenuation is the dominant process of energy loss in the frequency range analyzed which suggests strong spatial heterogeneity the resultant scattering attenuation images show an increase of attenuation toward the southwest from toya caldera which may correspond to deepening of the basement we also identify an area of low intrinsic and scattering attenuation at the summit of usu volcano which could be associated with old magma intrusions our results demonstrate a strong spatial relation between structural heterogeneities and attenuation processes in volcanic areas and confirm the efficiency of the method which can be used together with conventional imaging techniques

volcanic tremor and plume height hysteresis from pavlof volcano alaska the march 2016 eruption of pavlof volcano alaska produced an ash plume that caused the cancellation of more than 100 flights in north america the eruption generated strong tremor that was recorded by seismic and remote low frequency acoustic infrasound stations including the earthscope transportable array the relationship between the tremor amplitudes and plume height changes considerably between the waxing and waning portions of the eruption similar hysteresis has been observed between seismic river noise and discharge during storms suggesting that flow and erosional processes in both rivers and volcanoes can produce irreversible structural changes that are detectable in geophysical data we propose that the time varying relationship at pavlof arose from changes in the tremor source related to volcanic vent erosion this relationship may improve estimates of volcanic emissions and characterization of eruption size and intensity

separation of scattering and intrinsic attenuation at asama volcano japan evidence of high volcanic structural contrasts abstract in this study we show 2d intrinsic and scattering q images of asama volcano obtained by analyzing 2320 waveforms from active data observed energy envelopes were fitted to the diffusion model and separate intrinsic and scattering q images were produced using a back projection method based on a gaussian type weighting function synthetic tests indicate robustness and reliability of the results areas of high scattering attenuation coincide with the volcanic edifice and the summit at which recent eruptions took place the intrinsic dissipation pattern shows a strong contrast between the east and west side of the volcanic structure with the low values observed in the west interpreted as solidified magma bodies our results demonstrate a strong relationship between structural heterogeneities and attenuation processes in volcanic areas and confirm the effectiveness of the present technique which can be used as an imaging tool complementary to conventional techniques

marine shallow water hydrothermal activity and mineralization at the wakamiko crater in kagoshima bay south kyushu japan abstract submarine hydrothermal fluid emanation from a small sediment mound associated with bubbling gas was observed in the wakamiko crater that is located 5 km offshore at 200 m depth in kagoshima bay southern kyushu japan in 2003 and 2005 surface sediments up to 30 cm from inside and outside of the hydrothermal mound were sampled using the submersible rov hyper dolphine jamstec chemistry of pore fluids inside the mound showed a clear difference from those collected from outside the mound which is explained by mixing of the ascending hydrothermal component and seawater estimated chemical composition of the hydrothermal end member suggests that the fluid experienced hydrothermal interaction at a temperature range of about 175 to 200 c this is consistent with the observed mound temperature of 137 c hydrothermal minerals such as barite stibnite and realgar were identified in the mound sediment suggesting their precipitation due to mixing of the ascending hydrothermal fluid with seawater isotopic composition of the hydrothermal endmember can be explained by mixing product of seawater magmatic water and meteoric water the marine shallow water hydrothermal system in the wakamiko crater is considered to be driven by a magmatic heat source beneath the crater which also contributes elements such as arsenic antimony mercury and magmatic water to the hydrothermal fluid

seafloor hydrothermal clay alteration at jade in the back arc okinawa trough mineralogy geochemistry and isotope characteristics seafloor hydrothermal activity at jade has resulted in extensive alteration of the host epiclastic sediments and pumiceous tuffs forming mica kaolins kaolinite and halloysite mg rich chlorite talc montmorillonite and a mixed layer mineral of dioctahedral chlorite and montmorillonite chl mont clay mineral assemblages show a vertical variation which reflects variable amounts of cold seawater incorporated into hot hydrothermal fluids in subsurface sediments and tuff however mixing alone cannot explain the occurrence of abundant kaolin minerals at jade the formation of kaolin minerals requires much more acidic fluid than expected from simple mixing of hydrothermal fluids and cold seawater low ph values are likely attained by oxidation of h2s either dissolved in the hydrothermal fluid or released from the fluid during decompression the fluid reaching the seafloor is discharged into cold seawater which caused precipitation of sulfides close to vents and native sulfur and barite at the margins of the vent areas halloysite barite and anhydrite show sr isotope compositions similar to marine sr indicating the derivation of marine sr directly from seawater or by the dissolution of calcareous nannoplanktons the isotopic compositions of kaolinite 18o 7 4 d 23 chl mont 18o 7 0 d 32 and mica 18o 5 4 to 9 9 d 30 to 26 suggest fluids of a heated seawater origin the o isotopic data yielded formation temperatures of 170 c for kaolinite 61 to 110 c for halloysite and 145 to 238 c for mica barite 34s values 21 0 to 22 5 are very similar to the marine sulfate value confirming that the barite formation took place due to mixing of ba bearing hydrothermal fluids and sulfate rich seawater native sulfur shows a large variation in 34s in one hand specimen probably because of rapid disequilibrium precipitation of s during fluid exhalation on the seafloor sulfur in hydrothermal fluids is usually consumed to form metal sulfides therefore abundant native sulfur at jade suggests high h2s metals ratios of the hydrothermal fluids the alteration assemblages and isotopic data of hydrothermal minerals from jade are very similar to those of kuroko type barite deposits of middle miocene age which formed from fluids of high s metals ratios at less than 200 c at jade there is only one black smoker actively discharging high temperature 320 c fluid but there are many fossil sulfide chimneys and mounds in the area the mineralogy and high au and cu in these precipitates suggest highly metalliferous hydrothermal activity in the past these activities likely resulted in discharge of hydrothermal plumes and fall outs of sulfides and sulfates on the seafloor these fall outs were incorporated in sediments far from the vent areas they are now recorded as high metal contents in sediments with no petrographic and mineralogical evidence of in situ hydrothermal activity some are high as 8 100 ppm for cu 12 500 ppm for zn 1 000 ppm for as 100 ppm for ag and 21 000 ppm for pb detrital grains of montmorillonite in such sediments are coated with fe oxyhydroxides during the suspension in seawater before settling on the seafloor the depths of such metal anomalies in sediments suggest high levels of metalliferous hydrothermal activities from 1 800 to 300 ybp

depressurization of a hydrothermal system following the august and november 2012 te maari eruptions of tongariro new zealand in 2012 two phreatic eruptions occurred at new zealand s tongariro volcano for the first time in over a century interferometric synthetic aperture radar data collected by the italian space agency s cosmo skymed satellite constellation indicates up to 20 mm yr of post eruptive subsidence focused across a 4 km2 region in the vicinity of the eruption site modeling of the deformation data indicates a shallow source at 500 m depth 1100 m asl consistent with the depth of the hydrothermal system we estimate an annual volume loss of 35 000 m3 leading to a pressure loss of 0 09 mpa yr we suggest that fracturing associated with the eruptions has enabled the continued depressurization of the shallow hydrothermal system and that subsidence will continue until the fractures become resealed

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

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

migration of seismic activity associated with phreatic eruption at merapi volcano indonesia abstract phreatic activity of merapi started after nearly 2 years of quiescence following the october november 2010 eruption which was the largest in more than 100 years a dozen eruptions identified by visual and or seismic observations took place between august 2012 and april 2014 we present in this work the results of a detailed analysis of the april 20 2014 phreatic eruption we attempted to reconstruct the eruptive process which lasted for over 30 min to this end we determined the wavefield composition by polarization analysis located high frequency earthquakes occurring in the initial part of the eruption process and then determined the seismic source migration of low frequency part of the tremor like signal 0 3 3 hz over time source depth of low frequency signal was obtained by comparing the slowness vector calculated using 3 stations of the seismic antenna with a slowness vector model obtained by ray tracing in the structure taking into account the topography and a 1d velocity model obtained by spatial auto correlation analysis the results allow to distinguish 3 different phases 1 high frequency transients interpreted as the result of a sudden decompression caused by the transition of the volcanic fluid to a gaseous phase that occurred approximately 1 5 km deep this decompression process in the hydrothermal system generated a migration of the low frequency seismic source from 900 m to 1800 m above sea level 2 a second decompression process revealed by high frequency micro seismicity and associated to the migration of the low frequency tremor source which is marked first by a descent phase followed by a sharp ascent until reaching the surface the evolution of the back azimuth during the migration process indicates a slight inclination of the conduit presumably in the orientation of the dome fracture in the nw se direction this direction is consistent with the alignment of regional tectonic structures and with the directivity of eruption deposits 3 the seismic source then remains positioned at the altitude of the dome for over 10 min this phase probably corresponds to the ash emission process the average migration speed of the low frequency seismic source from the starting eruptive process to ash emission is about 5 m s

mechanisms of mg phyllosilicate formation in a hydrothermal system at a sedimented ridge middle valley juan de fuca we present results of a detailed mineralogical and geochemical study of the progressive hydrothermal alteration of clastic sediments recovered at odp site 858 in an area of active hydrothermal venting at the sedimented axial rift valley of middle valley northern juan de fuca ridge these results allow a characterization of newly formed phyllosilicates and provide constraints on the mechanisms of clay formation and controls of mineral reactions on the chemical and isotopic composition of hydrothermal fluids hydrothermal alteration at site 858 is characterized by a progressive change in phyllosilicate assemblages with depth in the immediate vent area at hole 858b detrital layers are intercalated with pure hydrothermal precipitates at the top of the section with a predominance of hydrothermal phases at depth sequentially downhole in hole 858b the clay fraction of the pure hydrothermal layers changes from smectite to corrensite to swelling chlorite and finally to chlorite in three pure hydrothermal layers in the deepest part of hole 858b the clay minerals coexist with neoformed quartz neoformed and detrital components are clearly distinguished on the basis of morphology as seen by sem and tem and by their chemical and stable isotope compositions corrensite is characterized by a 24 a stacking sequence and high si and mg contents with fe fe mg ratio of 0 08 we propose that corrensite is a unique possibly metastable mineralogical phase and was precipitated directly from seawater dominated hydrothermal fluids hydrothermal chlorite in hole 858b has a stacking sequence of 14 a with fe fe mg ratios of 0 35 the chemistry and structure of swelling chlorite suggest that it is a corrensite chlorite mixed layer phase the mineralogical zonation in hole 858b is accompanied by a systematic decrease in 18o reflecting both the high thermal gradients that prevail at site 858 and extensive sediment fluid interaction precipitation of the mg phyllosilicates in the vent region directly controls the chemical and isotopic compositions of the pore fluids this is particularly evident by decreases in mg and enrichments in deuterium and salinity in the pore fluids at depths at which corrensite and chlorite are formed structural formulae calculated from tem edx analyses were used to construct clay h2o oxygen isotope fractionation curves based on oxygen bond models our results suggest isotopic disequilibrium conditions for corrensite quartz and swelling chlorite quartz precipitation but yield an equilibrium temperature of 300 c 30 for chlorite quartz at 32 m below the surface this estimate is consistent with independent estimates and indicates steep thermal gradients of 10 11 m in the vent region

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

cyclic processes and factors leading to phreatic eruption events insights from the 25 september 2007 eruption through ruapehu crater lake new zealand abstract a dangerous block ash eruption occurred without warning from ruapehu crater lake on 25 september 2007 ending a 6 month period of temperature decline in the lake the northerly directed blast sent ballistics of up to 2 m diameter more than 2 km from the source the ejecta comprised a variety of volcano lacustrine lithologies many showing evidence of intense hydrothermal alteration petrographic studies of the ballistics reveal numerous examples of pores vesicles being filled with assemblages of elemental sulphur anhydrite pyrite and natroalunite and many ballistics exuded liquid sulphur from their pores during cooling at atmospheric pressure up to 5 of the ash was comprised of fine grained juvenile glass material confirming the presence of magma in the shallow vent environment a long recognised characteristic of this volcano is the thermal cycling behaviour of the crater lake behaviour which has remained effectively unchanged through two magmatic eruption events in 1945 and in 1995 96 airborne measurements of co2 and so2 flux from the volcano since 2003 show a strong positive correspondence with temperature cycling in the lake pointing to a definitive link between heat and mass discharge through the system low so2 emission rates and c s mole ratios 30 were typical of the period 2003 to early 2007 and appear to reflect vigorous scrubbing of s gases in the hydrothermal system during this time to better understand the chemical and physical processes operating in this very dynamic volcanic hydrothermal system and its propensity to develop potentially dangerous hydrothermal seals we have developed an integrated finite difference tough2 heat mass transport simulation of the hydrothermal environment the model which is constrained by observed heat and mass flux characteristics of the volcano demonstrates the transient nature of the heating cycles on the vent lake system of particular interest is the role of co2 as a relatively inert pressure transmitting medium in the hydrothermal environment seal formation was simulated using the reactive transport code x1t which showed that condensation of magmatic vapour into a highly porous medium of andesitic composition leads to rapid formation of an elemental sulphur anhydrite natroalunite mineral assemblage and a drastic reduction in permeability we suggest that since the 1995 96 vent clearing eruptions a shroud of elemental sulphur and other alteration phases formed along the margins of the 2 phase liquid vapour region enclosing the conduit this effectively seals the upper portion of the vent from the adjacent hydrostatically controlled environment and allows for development of pressurised vapour static gas columns beneath the northern and central vents

temporal variations of repeating low frequency volcanic earthquakes at ngauruhoe volcano new zealand abstract a persistent swarm of micro earthquakes was observed at ngauruhoe volcano new zealand from 2005 to 2010 marking the first unrest episode at the volcano since 1975 detailed waveform and spectral analysis of the continuous seismic record revealed eight earthquake families f1 f8 within a sequence of 8561 low frequency earthquakes an analysis of stacked waveforms of each family allowed the families to be linked systematically into four super families that may indicate four different mechanisms and or source locations or geometries the first super family mostly occurred in 2005 and showed stable waveforms and no significant evolution the second super family was dominant over a two year period starting in mid 2006 and displayed a slow evolution with progressively higher frequency the third super family emerged from early 2008 with intermittent occurrence and high seismicity and progressed to higher peak frequency in 2010 the fourth super family was mainly observed from late 2008 to mid 2009 and had the highest peak frequency in 2009 the observed evolutionary pattern may be driven by a modest multi year input of gas and heat from a deeper relict magmatic zone into the shallow volcano hydrothermal system the interplay of gas from below and seasonal meltwater from above may have modulated the seismic activity and may relate to repeated over pressurization and failure of constricted evolving pathways within a pervasive crack system

antimony quartz and antimony gold quartz veins from northern portugal abstract antimony and pb sb quartz veins from the braganca district portugal are mainly hosted by silurian phyllites antimony au quartz veins from the durico beira region are mainly hosted by a cambrian schist metagraywacke complex as well as ordovician phyllites and quartzites the deposits were mostly exploited in the late 19th century mineralogical characteristics and chemical compositions of individual ore minerals are similar in the two areas first and second generations of arsenopyrite precipitated at 390 and 300 c respectively berthierite and stibnite are the most abundant sb bearing minerals and precipitated between 225 and 128 c native antimony at

deposition of talc kerolite smectite smectite at seafloor hydrothermal vent fields evidence from mineralogical geochemical and oxygen isotope studies abstract talc kerolite smectite smectite chlorite smectite and chlorite samples from sediments chimneys and massive sulfides from six seafloor hydrothermal areas have been analyzed for mineralogy chemistry and oxygen isotopes samples are from both peridotite and basalt hosted hydrothermal systems and basaltic systems include sediment free and sediment covered sites mg phyllosilicates at seafloor hydrothermal sites have previously been described as talc stevensite or saponite in contrast new data show tri octahedral mg phyllosilicates ranging from pure talc and fe rich talc through kerolite rich kerolite smectite to smectite rich kerolite smectite and tri octahedral smectite the most common occurrence is mixed layer kerolite smectite which shows an almost complete interstratification series with 5 to 85 smectitic layers the smectite interstratified with kerolite is mostly tri octahedral the degree of crystal perfection of the clay sequence decreases generally from talc to kerolite smectite with lower crystalline perfection as the proportion of smectite layers in kerolite smectite increases our studies do not support any dependence of the precipitated minerals on the type subtype of hydrothermal system oxygen isotope geothermometry demonstrates that talc and kerolite smectite precipitated in chimneys massive sulfide mounds at the sediment surface and in open cracks in the sediment near seafloor are high temperature 250 c phases that are most probably the result of focused fluid discharge the other end member of this tri octahedral mg phyllosilicate sequence smectite is a moderate temperature 200 250 c phase forming deep within the sediment 0 8 m chlorite and chlorite smectite which constitute the alteration sediment matrix around the hydrothermal mounds are lower temperature 150 200 c phases produced by diffuse fluid discharge through the sediment around the hydrothermal conduits in addition to temperature other two controls on the precipitation of this sequence are the silica activity and mg al ratio i e the degree of mixing of seawater with hydrothermal fluid higher silica activity favors the formation of talc relative to tri octahedral smectite vent structures and sedimentary cover preclude complete mixing of hydrothermal fluid and ambient seawater resulting in lower mg al ratios in the interior parts of the chimneys and deeper in the sediment which leads to the precipitation of phyllosilicates with lower mg contents talc and kerolite smectite have very low trace and rare earth element contents some exhibit a negative or flat eu anomaly which suggests eu depletion in the original hydrothermal fluid such eu depletion could be caused by precipitation of anhydrite or barite sinks for eu2 deeper in the system ree abundances and distribution patterns indicate that chlorite and chlorite smectite are hydrothermal alteration products of the background turbiditic sediment

a physical model for seismic noise generation from sediment transport in rivers measuring sediment flux in rivers remains a significant problem in studies of landscape evolution recent studies suggest that observations of seismic noise near rivers can help provide such measurements but the lack of models linking observed seismic quantities to sediment flux has prevented the method from being used here we develop a forward model to describe the seismic noise induced by the transport of sediment in rivers the model provides an expression for the power spectral density psd of the rayleigh waves generated by impulsive impacts from saltating particles which scales linearly with the number of particles of a given size and the square of the linear momentum after incorporating expressions for the impact velocity and rate of impacts for fluvially transported sediment we observe that the seismic noise psd is strongly dependent on the sediment size such that good constraints on grain size distribution are needed for reliable estimates of sediment flux based on seismic noise observations the model predictions for the psd are consistent with recent measurements and based on these data a first attempt at inverting seismic noise for the sediment flux is provided

two dimensional seismic attenuation images of stromboli island using active data in this work we present intrinsic and scattering seismic attenuation 2 d images of stromboli volcano we used 21 953 waveforms from air gun shots fired by an oceanographic vessel and recorded at 33 inland and 10 ocean bottom seismometer seismic stations coda wave envelopes of the filtered seismic traces were fitted to the energy transport equation in the diffusion approximation obtaining a couple of separate qi and qs in six frequency bands using numerically estimated sensitivity kernels for coda waves separate images of each quality factor were produced results appear stable and robust they show that scattering attenuation prevails over intrinsic attenuation the scattering pattern shows a strong concordance with the tectonic lineaments in the area while an area of high total attenuation coincides with the zone where most of the volcanic activity occurs our results provide evidence that the most important attenuation effects in volcanic areas are associated with the presence of geological heterogeneities

microbial and inorganic control on the composition of clay from volcanic glass alteration experiments biological activity plays a substantial role in the geochemistry of the earth s surface particularly interesting are effects on clay formation because clays are abundant and have high surface to volume ratio resulting in clays making up a large fraction of the overall mineral fluid interface and having an effective control of mineral reactions thus biological control on clay composition would affect element budget globally and the mineralogy of subsequent diagenetic processes biological acceleration of clay production would result in enhanced clay control of mineral reactions and faster organic c sequestration by adsorption on clay minerals with implications for the c and related cycles we investigated the combined effect of microbial activity and water chemistry on the composition of neoformed clay by reacting volcanic glass with natural waters covering a large composition range fresh water from a lake and a spring seawater and hypersaline water the microbes bacteria fungi and algae were totally or partially identified using molecular and microscopy techniques the solid alteration products were analyzed using cryo sem to investigate the mineral microbe interface and tem aem to study the composition of the neoformed clay the solution chemistry was also investigated we found that clay composition was controlled mainly by glass chemistry rather than biological activity through a mechanism of in situ transformation the resulting clay was al rich dioctahedral composition in one case inorganic experiment freshwater lake the specific inorganic conditions of ph and mg and si concentration promoted formation of mg rich trioctahedral clay microbes however did influence clay composition by confining glass grains in biofilms where water chemistry is significantly different from the bulk solution alteration in such conditions generated significant amounts of trioctahedral mg rich clay in the hypersaline water experiment whereas it favored production of dioctahedral al rich clay in the freshwater lake experiment it is thus demonstrated that biofilms can exert an effective control on clay mineralogy

the erua earthquake cluster and seismic anisotropy in the ruapehu region new zealand 1 we use seismicity generated from the erua earthquake cluster a consistently active area of seismicity about 20 km to the west of mount ruapehu over the last 12 years to study seismic anisotropy in the ruapehu region in particular we search for changes associated with two minor phreatic eruptions on the 4th of october 2006 and the 25th of september 2007 the seismicity rate magnitude of completeness focal mechanisms and b value of the cluster are also examined to investigate whether the characteristics of the seismicity changed over the duration of the study the hypocenters were relocated which revealed a westward dip in the shallow seismicity shear wave splitting results revealed a decrease in delay time in the 2006 2007 period and a significant variation in the fast shear wave polarization in the same time period the b value also increased significantly from 1 0 0 2 in 2004 to a peak of 1 8 0 2 in 2007 but no other parameters were found to vary significantly over this time period we attribute these changes to an increase in pore fluid pressure in the erua region due to fluid movement and suggest that this fluid movement may be associated with the eruptions in 2006 and 2007

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

textural and mineralogical changes associated with the incipient hydrothermal alteration of glassy dacite at the submarine pacmanus hydrothermal system eastern manus basin variably altered dacite from the pacmanus vent field in the eastern manus back arc basin papua new guinea was studied to determine the textural and mineralogical characteristics of hydrothermal alteration taking place in the immediate subsurface of this modern seafloor hydrothermal system detailed textural investigations show that fluid flow through the glassy dacite has been strongly controlled by the primary volcanic textures quench fractures and networks of interconnected perlitic cracks linking vesicles provided pathways for hydrothermal fluids flowing up to the seafloor hydrothermal alteration along these pathways resulted in the formation of pseudoclastic textures textural evidence suggests that alteration of the glassy dacite has not been sustained the samples have been affected by incipient hydrothermal alteration that is typically not preserved in ancient volcanic rock hosted massive sulfide deposits interaction of the glassy dacite with hydrothermal fluids primarily resulted in the conversion of volcanic glass to dioctahedral smectite only minor amounts of trioctahedral smectite were formed destruction of the volcanic glass and the formation of smectite caused pronounced changes in the chemistry of the dacite samples in particular a decrease in the sio2 whole rock content and the na2o k2o ratio the two alkali elements behaved differently during hydrothermal alteration due to preferential incorporation of k into the interlayer position of the newly formed dioctahedral smectite smectite formation occurred under rock dominated conditions although the addition of mg was required to form trioctahedral smectite from the silicic volcanic glass primary plagioclase was resistant to hydrothermal alteration highlighting the fact that the destruction of volcanic glass and feldspar are not necessarily contemporaneous in massive sulfide forming hydrothermal systems incipient alteration of the glassy dacite close to the seafloor occurred at temperatures below 150 c in an environment that allowed the development of steep temperature gradients comparison of the new data to the findings of deep drilling during odp leg 193 suggests that the smectite rich alteration in the immediate subsurface of the pacmanus hydrothermal vent field represents the low temperature equivalent of illite and chlorite rich alteration associations forming in the upflow zones of the hydrothermal fluids in the deeper portion of the volcanic sequence

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

eruption source processes derived from seismic and acoustic observations of the 25 september 2007 ruapehu eruption north island new zealand abstract mt ruapehu erupted on 25 september 2007 at 20 26 pm nzdt 8 26 ut generating a steam column to about 15 000 ft 4600 m a directed ballistic and surge deposit of coarse blocks and ash to the north of the crater lake and initiated lahars in the whangaehu catchment and whakapapa ski field the eruption was recorded on three broadband seismometers and two acoustic pressure sensors which indicated broadly coherent waveform characteristics across the network the eruption had a duration of less than 1 min as indicated by strong seismic and acoustic pulses the acoustic wave coincided with observed very long period vlp seismic signal 2 25 s period the acoustic pulse had a positive pressure indicating an explosion and travelled at a velocity of 320 m s the syn eruptive vlp was composed of surface waves having strong radial and transverse components the immediate aftermath of the eruption produced about 4 min of continued high amplitude spasmodic tremor signals that probably resulted from post explosion phase associated vent backfill stabilisation the eruption was preceded by minor volcano tectonic earthquakes and tremor bursts which began 10 min before the main eruption two smaller vlp signals were associated with these tremor pulses at 20 17 and 20 25 these pre eruptive vlp signals had particle motions indicating body and surface waves from a sub surface source region modelling of the vlp sources using a 3d finite difference method shows that that the pre eruption vlp signals are consistent with a volume fluctuation at 3 7 km depth from a radially symmetric source the main eruption vlp was consistent with a south and downward directed single force in response to a northward directed jet and northward directed ballistic deposits

nested strike slip duplexes and other evidence for late cretaceous palaeogene transpressional tectonics before and during india eurasia collision in thailand myanmar and malaysia the late cretaceous palaeogene structural and tectonic events in the northern region of sundaland represent a poorly known but potentially important orogenic development in se asia extensive late cretaceous s type granites extending from malaysia through thailand to myanmar have long been used to infer an episode of crustal thickening an inference supported by the presence of late cretaceous eocene ophiolites in myanmar however structural evidence for a well developed associated fold and thrust belt has been lacking apatite and zircon fission track studies of thailand indicate a broad regional uplift from about 80 ma to 40 ma suggesting an episode of crustal thickening but the uplift amount is modest and not that expected for a major fold and thrust belt left lateral motion on major nw se trending strike slip fault zones mae ping and three pagodas faults in myanmar and thailand has been attributed to himalayan tibetan escape tectonics this paper demonstrates that the fault zones are considerably more complicated than just nw se trends they are a network of branching faults with important north south trends as well as nw se trends they form large scale nested strike slip duplex structures and affect a region over 1000 km long and up to 250 km wide this diffuse branching network of strike slip fault trends may represent a substantial late cretaceous palaeogene transpressional belt himalayan escape tectonics represent later increments of deformation with both oligocene sinistral and late oligocene recent dextral reactivation