combining local and remote infrasound recordings from the 2009 redoubt volcano eruption abstract the explosive phase of the 2009 redoubt volcano eruption produced predominantly short duration high amplitude infrasound signals recorded up to 4500 km away all 19 numbered explosive events were recorded at a local microphone dfr 12 km as well as at an infrasound array in fairbanks alaska i53us 547 km most with high signal to noise ratios the local microphone provides an estimate of the source parameters and comparison between the two datasets allows the unique opportunity to evaluate acoustic source term estimation at a remote array high waveform similarity between dfr and i53us occurs during much of the explosive phase due to strong stratospheric ducting permitting accurate source constraints inferred from i53us data cross correlation analysis after applying a hilbert transform to the i53us data shows how the acoustic energy has passed through a single caustic as predicted by ray theory similar to previous studies significant low frequency infrasound from redoubt recorded at i53us is coincident with high altitude ash emissions the largest events also produced considerable energy at greater than 50 s periods likely related to the initial oscillations of the volcanic plume or jet many of the explosive events have emergent onsets somewhat unusual for explosive short duration eruptions comparison of the satellite derived so2 emissions with the relative amount of acoustic energy at i53us shows a very high statistically significant correlation this study reiterates the utility of using remote infrasound arrays for detection of hazardous emissions and characterization of large volcanic eruptions and demonstrates how under typical meteorological conditions remote infrasound arrays can provide an accurate representation of the acoustic source

eruption chronologies plume heights and eruption styles at tungurahua volcano integrating remote sensing techniques and infrasound article i nfo satellite remote sensing allows volcanic ash plumes to be detected and tracked and routinely aids in hazard mitigation especially to the aviation community although satellite imagery provides valuable information about volcanic plume processes i e plume heights plume composition and plume transport it has its limitations in addition to the observational gaps produced by meteorological clouds as well as temporal and spatial resolution restrictions large volcanic clouds often obscure the vent during an eruption therefore some key information about eruption dynamics and processes are impossible to obtain from satellite images in this paper we investigate four eruptions at tungurahua volcano ecuador during the 2006 2008 time period we integrate satellite derived eruption chronologies plume heights and plume aspect ratios with infrasound data primarily acoustic power and hand held thermal imagery when available integrating these datasets allows us to identify accurate eruption onsets durations and cessations as well as define different types of eruption styles ranging from plinian to weak vulcanian transitions between the different eruption styles were also documented results show that there is a positive correlation between plume height and acoustic power we conclude that combining the two datasets allows better constraints on eruption processes and source parameters using these methods in real time monitoring will allow more accurate eruption monitoring and ash hazard mitigation

new insights into the 1999 eruption of shishaldin volcano alaska based on acoustic data data collected by a pressure sensor provide new insights into the 1999 eruption of shishaldin volcano unimak island alaska on 19 april 1999 after 3 months of unrest and an extended period of low level strombolian activity shishaldin experienced a subplinian eruption ash plume to 16 km followed by several episodes of strong strombolian explosions acoustic data from the pressure sensor allow us to investigate the details of an eruption which was instrumentally well recorded but with few visual observations in the 12 h prior to the subplinian phase the pressure sensor detected a series of small repeated pulses with a constant spectral peak at 2 3 hz the amplitude and occurrence rate of the pulses both grew such that the signal became a nearly continuous hum just before the subplinian eruption this humming signal may represent gas release from rising magma the main subplinian phase was heralded by 1 the abrupt end of the humming signal 2 several pulses of low frequency sound interpreted as ash bursts and 3 a dramatic increase in seismic tremor amplitude the change in acoustic signature at this time allows us to precisely time the start of the subplinian eruption previously approximated as the time of strongest tremor increase the 50 min subplinian phase actually contained several bursts of signal each of which may represent a discrete volume of magma passing through the system following the subplinian event the pressure sensor recorded four discrete episodes of strombolian gas explosions on 19 20 april and another on 22 23 april four of the five episodes were accompanied by strong seismic tremor the fifth has not been previously recog nized and was not associated with anomalous tremor amplitudes in time series these events are similar to explosions recorded at other volcanoes but in general they are much larger with maximum amplitudes of 65 pa at 6 5 km from the vent and they have low 0 7 1 5 hz peak frequencies these large explosions occurred at rates of 3 20 per minute for 1 5 h in each episode the explosions were accompanied by a small 5 km above sea level ash plume and only minor amounts of ejecta were produced thus the explosion activity was domi nated by gas release

tracing the differences between vulcanian and strombolian explosions using infrasonic and thermal radiation energy abstract eruptive plume dynamics is a direct expression of explosive style where duration and altitude of eruptive clouds and dispersion of erupted products is proportional to the degree of fragmentation we present an analysis of infrasonic and thermal records for explosions at villarrica chile stromboli italy santiaguito and fuego guatemala volcanoes across these four systems magma composition spans from basaltic to dacitic and explosive activity is typically described as ranging from strombolian to vulcanian we use this analysis to provide a quantitative geophysically based description of and discrimination between the different explosive styles that characterize the four volcanoes while infrasound is directly related to the emission of over pressurized gas and thus solely reflects the plume emission both plume emission and ascent are detected thermally thus the two data sets together provide a complete description of the plume dynamics in particular while infrasound solely reflects the gas thrust phase driving plume emission thermal radiation energy is also affected by buoyancy during plume ascent thermal radiation energy estimated for explosions at stromboli and villarrica 10 4 10 7 j is lower than that for events at santiaguito and fuego 10 8 10 9 j but infrasonic energies overlap this suggests a greater contribution of buoyancy for eruptive clouds at santiaguito and fuego when compared with stromboli and villarrica we further investigated the plume dynamics by comparing infrasonic energy which reflects gas thrust e gt with the difference between thermal radiation and infrasonic energies which mostly reflects buoyancy e b our data distribution reveals two separate clusters explosions at stromboli and villarrica share low values of buoyancy pointing to a gas thrust dominated emission efficient coupling of the infrasonic source to the atmosphere and a strombolian type source process to generate a plume rich in coarse fragments in contrast explosions at santiaguito and fuego share large buoyancy e b and are consistent with vulcanian type events in which a large part of infrasonic energy is spent in magma fragmentation leading to ascent of buoyant ash rich plumes we demonstrate that the comparison between thermal radiation and infrasonic energies of explosions allows a quantitative discrimination between and characterization of strombolian and vulcanian type explosions which leads us to suggest that such an approach may be used as an index to further and quantitatively discriminate between eruptive styles

relative partitioning of acoustic and seismic energy during strombolian eruptions the relative elastic energy partitioning during strombolian eruptions can be estimated from acoustic pressure and seismic velocity records we outline methods for determining acoustic and seismic energies for sensors deployed within several kilometers of erupting vents we use these energies to introduce the concept of the volcano acoustic seismic ratio g or vasr which is the ratio of elastic energy propagated through the atmosphere and into the earth eruption vasr is a physical diagnostic of explosive degassing that is appropriate for comparing eruption mechanisms at individual and between various volcanoes here we assess acoustic and seismic energies and corresponding vasr for discrete strombolian explosive events at karymsky and erebus volcanoes we attribute the relatively high and stable vasr at erebus g 8 standard deviation 41 to repeatable source conditions occurring at the surface of a persistent lava lake with accompanying strong coupling to the atmosphere lower and more variable vasr at karymsky g 0 18 in 1998 to g 1 51 in 1991 with standard deviations of 93 and 313 respectively is attributed to changing conditions within a narrow partially choked conduit variable seismoacoustic energy partitioning for karymsky as manifested by the large vasr standard deviation suggests that conduit conditions affecting vasr which include magma properties conduit obstruction or fragmentation depths can evolve both during the course of an explosion and between successive events d 2005 elsevier b v all rights reserved

anatomy of a lava dome collapse the 20 march 2000 event at soufriere hills volcano montserrat abstract a second extrusive phase of the currently ongoing 1995 2003 eruption of soufriere hills volcano shv montserrat commenced in mid november 1999 following 19 months during which no fresh lava had reached the surface by mid march 2000 a new andesite lava dome constructed within a collapse scar girdled by remnants of the 1995 1998 dome complex had attained an estimated volume of 29 3 million m3 mm3 on 20 march 2000 during a period of heavy rainfall on the island a significant collapse event ensued that removed 95 of the new lava dome 28 3 mm3 during 5 hours of activity that generated 40 pyroclastic flows and at least one magmatic explosion the associated ash cloud reached an altitude of 9 km and deposited ash on the island of guadeloupe to the southeast and a number of lahars and debris flows occurred in valleys on the flanks of shv a large quantity of observational data including contemporaneous field observations and continuous data from the broadband seismic network on montserrat allow a detailed reconstruction of this dome collapse event in contrast to most of the large dome collapses at shv the 20 march 2000 event is distinguished by a lack of short term precursory elevated seismicity at shallow depths beneath the lava dome broadband seismic amplitude data recorded during the event are used to infer the cumulative volume of collapsed dome as the collapse progressed these data indicate that the high velocity pyroclastic flows observed at the climax of the event removed by far the largest portion 68 of the lava dome at peak discharge rates estimated from the seismic record of 2 104 m3 s 1 following the 20 march 2000 collapse lava dome growth recommenced immediately and continued without significant interruption until another larger dome collapse occurred on 29 july 2001 the 29 july 2001 event also coincided with heavy rainfall on montserrat matthews et al 2002 geophys res lett 29 doi 10 1029 2002gl014863 and lacked precursory elevated seismic activity we attribute the initiation of the 20 march 2000 collapse to a prolonged spell of heavy rainfall on the lava dome prior to and during the event the precise causal mechanism remains controversial though some combination of mechanical erosion and or destabilization of a critically poised face of the lava dome the action of pressurized steam or water on potential failure surfaces within the dome rapid cooling of hot lava and small phreatic explosions seems likely anecdotal evidence exists for other rainfall induced activity on montserrat and the triggering of explosive or pyroclastic flow activity by rainfall has been noted at dome forming volcanoes elsewhere including merapi indonesia voight et al 2000 j volcanol geotherm res 100 69 138 unzen japan yamasato et al 1997 papers meteorol geophys 48 santiaguito guatemala smithsonian institution global volcanism network bull 15 1990 and mount st helens usa mastin 1994 geol soc am bull 106 175 185 hazard mitigation plans at dome forming volcanoes would therefore benefit from the inclusion of meteorological forecasting and rain monitoring equipment particularly in the tropics

character mass distribution and origin of tephra fall deposits from the 2009 eruption of redoubt volcano alaska highlighting the significance of particle aggregation abstract the 2009 eruption of redoubt volcano included 20 tephra producing explosions between march 15 2009 and april 4 2009 utc next generation radar nexrad data show that plumes reached heights between 4 6 km and 19 km asl and were distributed downwind along nearly all azimuths of the volcano explosions lasted between 0 8 mm thick including communities along the kenai peninsula 80 100 km and the city of anchorage 170 km trace ash on march 15 a small 4 6 km asl phreatic explosion containing minor non juvenile ash erupted through the summit ice cap the first five magmatic explosions events 1 5 occurred within a 6 hour period on march 23 plumes rose to heights between 5 5 km and 14 9 km asl during 2 to 20 minute duration explosions and were dispersed mainly along a nne trajectory trace ash fall was reported as far as fairbanks owing to a shift in wind direction and heavy snowfall during these events field discrimination among many of these layers was possible all deposits comprise a volumetrically significant amount of particle aggregates yet only event 5 deposits contain coarse clasts including glacier ice the most voluminous tephra fall was deposited on march 24 event 6 from a 15 minute explosion that sent a plume to 18 3 km asl and dispersed tephra to the wnw within 10 km of the vent this deposit contains 1 11 cm pumice clasts in a matrix of 1 2 mm aggregate lapilli a small dome was presumably emplaced between march 23 and march 26 and was subsequently destroyed during 1 14 minute magmatic explosions of events 7 8 march 26 that sent plumes between 8 2 km and 19 km asl ash fell along a broad swath to the ese covering communities along the kenai peninsula with up to 1 mm of ash proximal deposits are largely composed of aggregate lapilli of 1 2 mm with very little coarse juvenile material events 9 18 march 27 sent plumes between 5 2 km and 15 5 km asl during particle size data showing a preponderance of fine ash even in the most proximal locations along with the abundance of aggregate lapilli documented in most samples confirms that particle aggregation played a significant role in the 2009 eruption and induced premature fallout of fine ash

observations of volcanic lightning during the 2009 eruption of redoubt volcano abstract observations of volcanic lightning during the eruption of redoubt volcano in march and april 2009 were made with the lightning mapping array during the eruption twenty three distinct episodes of volcanic lightning were observed electrical activity occurred as either a volcanic lightning storm with up to thousands of lightning discharges or as a weak electrical event with only a handful of lightning discharges during the volcanic lightning storms we observed two phases of electrical activity the explosive phase and the plume phase the explosive phase consisted of very small discharges on the order of 10 100 m occurring directly above the vent while an explosive eruption was ongoing whereas the plume phase was comprised of discharges occurring throughout the plume subsequent to the explosive eruption the area of discharges during the explosive phase ranged from less than 1 km2 to 50 km2 or more the electrical activity at the beginning of the plume phase was dominated by small discharges over time the horizontal extent of the flashes increased with the largest flashes occurring at the end of the plume phase the distribution of the horizontal size of the discharges over the lifetime of the storm indicate that the charge structure of the plume evolved from a complex and clumpy structure to a more simple horizontally stratified structure plume height was shown to be a key factor in the quantity of lightning in a storm the volcanic lightning storms occurred in plumes with column heights greater than 10 km the tall plumes may contribute to the efficiency of charge generation through ice collisions by providing strong updrafts from the large thermal energy input from the eruption

local seismic and infrasound observations of the 2009 explosive eruptions of redoubt volcano alaska article i nfo local seismic and infrasound data are used to characterize the march april 2009 eruptions of redoubt volca no alaska data are from a network of ten seismic stations ranging from 2 6 to 21 km from the vent and a single infrasound sensor 12 2 km from the vent measurements were made for more than 30 explosive erup tions including the 19 numbered events that were identified during the eruption response more than 30 smaller explosions were also identified measured parameters include onset time duration reduced dis placement dr pressure seismic energy and acoustic energy results were compared with complementary gas and lightning data based on ratios of pressure to dr and acoustic to seismic energy we find that the initial group of explosive eruptions on 23 24 march was relatively stronger seismically and included the four highest dr values we infer that these represent vent enlargement or stronger coupling between the magma and wall rocks one event at 12 31 ut on 23 march had an extremely high pressure of 250 pa for the initial pulse and was likely weakly seismically coupled a second group of explosive eruptions on 27 29 march was relatively stronger acoustically deposits were finer grained and of different lithology with less scoria and more dense clasts these two groups may represent different modes of gas release cumulative acoustic energy as a function of time correlates well with comparable lightning and so2 data suggesting that all three provide insight regarding different factors of gas release for the eruption as a whole the number of events identified depends on criteria measured and depends on the goals of the investigations overall the eruptions were substantially stronger than recent eruptions in alaska with some durations exceeding 1 h and pressures an order of magnitude higher

an overview of the 2009 eruption of redoubt volcano alaska abstract in march 2009 redoubt volcano alaska erupted for the first time since 1990 explosions ejected plumes that disrupted international and domestic airspace sent lahars more than 35 km down the drift river to the coast and resulted in tephra fall on communities over 100 km away geodetic data suggest that magma began to ascend slowly from deep in the crust and reached mid to shallow crustal levels as early as may 2008 heat flux at the volcano during the precursory phase melted 4 of the drift glacier atop redoubt s summit petrologic data indicate the deeply sourced magma low silica andesite temporarily arrested at 9 11 km and or at 4 6 km depth where it encountered and mixed with segregated stored high silica andesite bodies the two magma compositions mixed to form intermediate silica andesite and all three magma types erupted during the earliest 2009 events only intermediate and high silica andesites were produced throughout the explosive and effusive phases of the eruption the explosive phase began with a phreatic explosion followed by a seismic swarm which signaled the start of lava effusion on march 22 shortly prior to the first magmatic explosion early on march 23 2009 utc more than 19 explosions or events were produced over 13 days from a single vent immediately south of the 1989 90 lava domes during that period multiple small pyroclastic density currents flowed primarily to the north and into glacial ravines three major lahars flooded the drift river terminal over 35 km down river on the coast tephra fall deposited on all aspects of the edifice and on several communities north and east of the volcano and at least two and possibly three lava domes were emplaced lightning accompanied almost all the explosions a shift in the eruptive character took place following event 9 on march 27 in terms of infrasound signal onsets the character of repeating earthquakes and the nature of tephra ejecta more than nine additional explosions occurred in the next two days followed by a hiatus in explosive activity between march 29 and april 4 during this hiatus effusion of a lava dome occurred whose growth slowed on or around april 2 the final explosion pulverized the very poorly vesicular dome on april 4 and was immediately followed by the extrusion of the final dome that ceased growing by july 1 2009 and reached 72 m m 3 in bulk volume the dome remains as of this writing effusion of the final dome in the first month produced blocky intermediate to high silica andesite lava which then expanded by means of lava injection beneath a fracturing and annealing cooling surface crust in the first week of may a seismic swarm accompanied extrusion of an intermediate to high silica andesite from the apex of the dome that was highly vesicular and characterized by lower p 2 o 5 content the dome remained stable throughout its growth period likely due to combined factors that include an emptied conduit system steady degassing through coalesced vesicles in the effusing lava and a large crater pit created by the previous explosions we estimate the total volume of erupted material from the 2009 eruption to be between 80 m and 120 m m 3 dense rock equivalent dre the aim of this report is to synthesize the results from various datasets gathered both during the eruption and retrospectively and which are represented by the papers in this publication we therefore provide an overall view of the 2009 eruption and an introduction to this special issue publication

an empirical model of the earth s horizontal wind fields hwm07 1 the new horizontal wind model hwm07 provides a statistical representation of the horizontal wind fields of the earth s atmosphere from the ground to the exosphere 0 500 km it represents over 50 years of satellite rocket and ground based wind measurements via a compact fortran 90 subroutine the computer model is a function of geographic location altitude day of the year solar local time and geomagnetic activity it includes representations of the zonal mean circulation stationary planetary waves migrating tides and the seasonal modulation thereof hwm07 is composed of two components a quiet time component for the background state described in this paper and a geomagnetic storm time component dwm07 described in a companion paper

local infrasound observations of large ash explosions at augustine volcano alaska during january 11 28 2006 1 we present and interpret acoustic waveforms associated with a sequence of large explosion events that occurred during the initial stages of the 2006 eruption of augustine volcano alaska during january 11 28 2006 13 large explosion events created ash rich plumes that reached up to 14 km a s l and generated atmospheric pressure waves that were recorded on scale by a microphone located at a distance of 3 2 km from the active vent the variety of recorded waveforms included sharp n shaped waves with durations of a few seconds impulsive signals followed by complex codas and extended signals with emergent character and durations up to minutes peak amplitudes varied between 14 and 105 pa inferred acoustic energies ranged between 2 108 and 4 109 j a simple n shaped short duration signal recorded on january 11 2006 was associated with the vent opening blast that marked the beginning of the explosive eruption sequence during the following days waveforms with impulsive onsets and extended codas accompanied the eruptive activity which was characterized by explosion events that generated large ash clouds and pyroclastic flows along the flanks of the volcano continuous acoustic waveforms that lacked a clear onset were more common during this period on january 28 2006 the occurrence of four large explosion events marked the end of this explosive eruption phase at augustine volcano after a transitional period of about two days characterized by many small discrete bursts the eruption changed into a stage of more sustained and less explosive activity accompanied by the renewed growth of a summit lava dome

infrasonic observations of the june 2009 sarychev peak eruption kuril islands implications for infrasonic monitoring of remote explosive volcanism abstract sarychev peak sp located on ostrov matua kurils erupted explosively during 11 16 june 2009 whereas remote seismic stations did not record the eruption we report atmospheric infrasound acoustic wave 0 01 20 hz observations of the eruption at seven infrasound arrays located at ranges of 640 6400 km from sp the infrasound arrays consist of stations of the international monitoring system global infrasound network and additional stations operated by the korea institute of geoscience and mineral resources signals at the three closest recording stations is44 643 km petropavlovsk kamchatskiy kamchatka krai russia is45 1690 km ussuriysk russia and is30 1774 km isumi japan represent a detailed record of the explosion chronology that correlates well with an eruption chronology based on satellite data terra noaa mtsat the eruption chronology inferred from infrasound data has a higher temporal resolution than that obtained with satellite data atmosphere corrected infrasonic source locations determined from backazimuth cross bearings of first arrivals have a mean centroid 15 km from the true location of sp scatter in source locations of up to 100 km result from currently unresolved details of atmospheric propagation and source complexity we observe systematic time variations in trace velocity backazimuth deviation and signal frequency content at is44 preliminary investigation of atmospheric propagation from sp to is44 indicates that these variations can be attributed to solar tide variability in the thermosphere it is well known that additional information about active volcanic processes can be learned by deploying infrasonic sensors with seismometers at erupting volcanoes this study further highlights the significant potential of infrasound arrays for monitoring volcanic regions such as the kurils that have only sparse seismic network coverage

global morphology of infrasound propagation i atmospheric sound waves in the 0 02 10 hz region also known as infrasound exhibit long range global propagation characteristics measurable infrasound is produced around the globe on a daily basis by a variety of natural and man made sources as a result of weak classical attenuation 0 01 db km 1 at 0 1 hz these acoustic signals can propagate thousands of kilometers in tropospheric stratospheric and lower thermospheric ducts to model this propagation accurately detailed knowledge of the background atmospheric state variables the global winds and temperature fields from the ground to 170 km is required for infrasound propagation calculations we have developed a unique atmospheric specification system g2s that is capable of providing this information using acoustic ray tracing methods and detailed g2s atmospheric specifications we investigate the major aspects of the spatiotemporal variability of infrasound propagation characteristics

observation of infrasonic and gravity waves at soufriere hills volcano montserrat 1 the sudden ejection of material during an explosive eruption generates a broad spectrum of pressure oscillations from infrasonic to gravity waves an infrasonic array installed at 3 5 km from the soufriere hills volcano has successfully detected and located in real time the infrasound generated by several pyroclastic flows pf estimating mean flow speeds of 30 75 m s on july 29 and december 3 2008 two differential pressure transducers co located with the array recorded ultra long period ulp oscillations at frequencies of 0 97 and 3 5 mhz typical of atmospheric gravity waves associated with explosive eruptions the observation of gravity waves in the near field 6 km at frequencies as low as about 1 mhz is unprecedented during volcanic eruptions

doppler weather radar observations of the 2009 eruption of redoubt volcano alaska abstract the u s geological survey usgs deployed a transportable doppler c band radar during the precursory stage of the 2009 eruption of redoubt volcano alaska that provided valuable information during subsequent explosive events we describe the capabilities of this new monitoring tool and present data captured during the redoubt eruption the minimax 250 c mm 250c radar detected seventeen of the nineteen largest explosive events between march 23 and april 4 2009 sixteen of these events reached the stratosphere above 10 km within 2 5 min of explosion onset high column and proximal cloud reflectivity values 50 to 60 dbz were observed from many of these events and were likely due to the formation of mm sized accretionary tephra ice pellets reflectivity data suggest that these pellets formed within the first few minutes of explosion onset rapid sedimentation of the mm sized pellets was observed as a decrease in maximum detection cloud height the volcanic cloud from the april 4 explosive event showed lower reflectivity values due to finer particle sizes related to dome collapse and related pyroclastic flows and lack of significant pellet formation eruption durations determined by the radar were within a factor of two compared to seismic and pressure sensor derived estimates and were not well correlated ash dispersion observed by the radar was primarily in the upper troposphere below 10 km but satellite observations indicate the presence of volcanogenic clouds in the stratosphere this study suggests that radar is a valuable complement to traditional seismic and satellite monitoring of explosive eruptions

evidence of atmospheric gravity waves during the 2008 eruption of okmok volcano from seismic and remote sensing observations 1 okmok volcano erupted on july 12 2008 following an 11 year hiatus detailed inspection of the syn eruptive seismograms revealed the presence of an ultra long period mode at a frequency of 1 7 mhz which is not a characteristic of the background seismic noise at okmok data collected by the national oceanic and atmospheric administration geostationary operational environmental satellite goes and national aeronautical and space administration moderate resolution imaging spectroradiometer modis sensors displayed the propagation of a vigorous ash and steam plume up to about 17 km above sea level we suggest that the observed ultra long period signals represent the response of the seismometer to changes in gravity associated with buoyancy oscillations set off in the lower atmosphere above okmok by the emplacement of the eruption column calculations based on simple modeling of these effects allowed estimation of peak atmospheric pressure perturbations associated with the eruption of less than 1 mbar

evaluation of redoubt volcano s sulfur dioxide emissions by the ozone monitoring instrument abstract the 2009 eruption of redoubt volcano alaska provided a rare opportunity to compare satellite measurements of sulfur dioxide so2 by the ozone monitoring instrument omi with airborne so2 measurements by the alaska volcano observatory avo herein we 1 compare omi and airborne so2 column density values for redoubt s tropospheric plume 2 calculate daily so2 masses from mount redoubt for the first three months of the eruption 3 develop simple methods to convert daily measured so2 masses into emission rates to allow satellite data to be directly integrated with the airborne so2 emissions dataset 4 calculate cumulative so2 emissions from the eruption and 5 evaluate omi as a monitoring tool for high latitude degassing volcanoes a linear correlation r2 0 75 is observed between omi and airborne so2 column densities omi daily so2 masses for the sample period ranged from 60 1 kt on 24 march to below detection limit with an average daily so2 mass of 6 7 kt the highest so2 emissions were observed during the initial part of the explosive phase and the emissions exhibited an overall decreasing trend with time omi so2 emission rates were derived using three methods and compared to airborne measurements this comparison yields a linear correlation r2 0 82 with omi derived emission rates consistently lower than airborne measurements the comparison results suggest that omi s detection limit for high latitude springtime conditions varies from 2000 to 4000 t d cumulative so2 masses calculated from daily omi data for the sample period are estimated to range from 542 to 615 kt with approximately half of this so2 produced during the explosive phase of the eruption these cumulative masses are similar in magnitude to those estimated for the 1989 90 redoubt eruption strong correlations between daily omi so2 mass and both tephra mass and acoustic energy during the explosive phase of the eruption suggest that omi data may be used to infer relative eruption size and explosivity further when used in conjunction with complementary datasets omi daily so2 masses may be used to help distinguish explosive from effusive activity and identify changes in lava extrusion rates the results of this study suggest that omi is a useful volcano monitoring tool to complement airborne measurements capture explosive so2 emissions and provide high temporal resolution so2 emissions data that can be used with interdisciplinary datasets to illuminate volcanic processes

deformation partitioning during folding and transposition of quartz layers abstract banded iron formation bif from the quadrilatero ferrifero southeastern brazil shows a compositional layering with alternating iron rich and quartz rich layers this layering was intensively folded and transposed at a centimeter millimeter scale through a component of bedding parallel shear related to flexural slip at middle to high greenschist facies conditions 400 450 c the microstructure and c axis fabrics of normal limbs inverted limb and hinge zones of a selected isoclinal fold were analyzed combining optical and scanning electron microscopy sem and digital image analysis in the normal limbs recrystallized quartz grains show undulose extinction relatively dry grain boundaries c axes at high angle to foliation and a pervasive grain shape fabric gsf indicating operation of crystal plastic processes in the inverted limb quartz grains show more serrated and porous wet grain boundaries the gsf is similar to that of the normal limb but c axes are oriented at 90 to those of the normal limb we interpreted these characteristics as reflecting operation of solution precipitation deformation in inverted limbs as a consequence of grains having been rotated to an orientation that was hard to basal a glide but easy to dissolution precipitation creep this deformation partitioning between crystal plasticity and solution transfer during folding transposition of quartz may explain the common occurrence of layered quartz rocks where individual layers show alternating c axis fabrics with opposite asymmetries but a consistent gsf orientation such characteristics may reflect an earlier event of pervasive folding transposition of a preexisting layering

infrasonic jet noise from volcanic eruptions 1 the lowermost section of a vulcanian or plinian volcanic eruption column may be thought of as a momentum driven turbulent free shear jet flow we propose that large amplitude and long duration infrasonic 20 hz signals recorded at ranges of tens of kilometers during powerful eruptions at mount st helens usa and tungurahua ecuador represent a low frequency form of jet noise a preliminary test of this hypothesis is made by comparing the observed infrasonic spectra to the empirically derived similarity spectra for pure air jets although the spectral shapes are in approximate agreement the observed volcanic signals have additional complexities not present in the pure air laboratory data these features may result from multiphase flow containing solid particles and liquid droplets very high temperatures and perhaps complex crater morphology however the overall similarity between the volcanic signals and jet noise indicates that broadband infrasound measurements at volcanoes may provide a quantitative link to eruption jet dynamics and would aid substantially in the remote assessment of volcanic hazard

characterization of the 2008 kasatochi and okmok eruptions using remote infrasound arrays 1 the 2008 plinian eruptions of kasatochi and okmok volcanoes were recorded by six remote international monitoring system infrasound arrays high amplitude infrasound at these stations combined with remote sensing permits insight into important volcanic source parameters such as origin times durations and source characteristics infrasound from the 7 8 august kasatochi eruption consists of three well defined eruption pulses with the first two steam rich and the last ash rich pulse 2 is the most energetic and impulsive okmok produced over 9 h of continuous infrasound on 12 13 july acoustic propagation modeling for the okmok eruption and first kasatochi pulse predict thermospheric ducting and origin times consistent with seismic and satellite observations however theoretical acoustic origin times of pulses 2 3 are predicted to occur 15 min earlier than the seismic stratospheric ducting for these later pulses provides more consistent origin times although both volcanoes ejected ash into the stratosphere 15 km kasatochi produced higher amplitude infrasound than okmok previous studies have shown sustained infrasound with frequencies 2000 km and does not seem to be appreciably affected by changes in ash content between the eruption pulses

swelling of a lava plug associated with a vulcanian eruption at sakurajima volcano japan as revealed by infrasound record case study of the eruption on january 2 2007 in order to clarify the time relation of the expansion of a gas pocket and failure of its overlying plug of lava during vulcanian eruptions infrasound records and video images of the vulcanian eruption that occurred at sakurajima volcano on january 2 2007 were analyzed with respect to their origin times weak 3 pa and slowly increasing air pressure preceded the impulsive compression phase by 0 25 0 32 s and a longer period rarefaction phase of infrasound waves was recognized at all microphone stations the velocity of the compression phase was assumed to be supersonic ca 400 m s up to 850 m above the crater bottom from other recent explosions on the other hand the propagation velocity of the preceding weak signal was regarded to be similar to the air sound velocity because the lack of impulsiveness is unlikely to be related to the main compression phase therefore the estimated origin time of the main compression phase was delayed by 0 5 0 7 s from the preceding phase the origin time of the preceding phase coincided with the onset of the isotropic expansion process of the pressurized gas pocket which was obtained by the waveform inversion of the explosion earthquake in contrast the origin time of the main impulsive phase coincided with the time when the expansion rate reached its peak this observation suggests that the volumetric increase of the gas pocket caused swelling of the surface of the crater bottom and its subsequent failure when the expansion velocity exceeded a threshold level the main impulsive compression phase radiated with a high velocity by the sudden releases of the pressurized gases the volumetric change at the source was estimated to be 280 560 m3 from the preceding phase of the infrasound this volume change indicates that the vertical displacement of the swelling ground was on the order of 1 0 m assuming the radius of the lava plug was ca 10 m

infrasound from tungurahua volcano 2006 2008 strombolian to plinian eruptive activity abstract strombolian to plinian activity from tungurahua volcano ecuador has been recorded by the autonomous infrasound arrays of the acoustic surveillance for hazardous eruptions ashe project since early 2006 our studies suggest that acoustic energy release during large eruptions does appear to broadly scale with eruption intensity this manuscript provides a detailed chronology and characterization of tungurahua s eruptive activity between 2006 and 2008 and demonstrates the ability to constrain source parameters of significant eruptions such as onset duration and escalation at regional distances by combining infrasound and remote sensing techniques the ashe system in ecuador automatically detected over 20 000 volcanic explosions at an array 37 km from tungurahua and was successful at notifying the onset escalation and cessation of a hazardous february 2008 eruption with a latency of 5 min elevated infrasonic energy from sustained and intense tungurahua eruptions correlates well with ash column heights and their lateral extent during the study period the spectra of these sustained explosive eruptions appear to be recurrent readily recognizable and indicative of volcanic jetting and significant atmospheric ash injection the paroxysmal plinian phase of the august 2006 eruption produced an ash cloud that extended well into the stratosphere 24 km coinciding with a shift of the dominant jetting frequency from 0 25 hz to below 0 1 hz and radiation of over 5 107 w of acoustic power transient explosions were often marked by minor or no ash release and are presumed to be more gas rich a change in the acoustic spectrum of volcanic jetting was also detected in the transition from a sustained to collapsed eruption column at the end of the july 14 2006 eruption the jetting spectrum at tungurahua during a period of sustained pyroclastic density current production changes from a typical double peaked to a single peaked spectrum suggesting remote acoustic monitoring can help ascertain the stability and dynamics of an eruptive column

emplacement of the final lava dome of the 2009 eruption of redoubt volcano alaska abstract after more than 8 months of precursory activity and over 20 explosions in 12 days redoubt volcano alaska began to extrude the fourth and final lava dome of the 2009 eruption on april 4 by july 1 the dome had filled the pre 2009 summit crater and ceased to grow by means of analysis and annotations of time lapse webcam imagery oblique image photogrammetry techniques and capture and analysis of forward looking infrared flir images we tracked the volume textural effusive style and temperature changes in near real time over the entire growth period of the dome the first month of growth april 4 may 4 produced blocky intermediate to high silica andesite lava 59 62 3 wt sio 2 that initially formed a round dome expanding by endogenous growth breaking the surface crust in radial fractures and annealing them with warmer fresh lava on or around may 1 more finely fragmented and scoriaceous andesite lava 59 8 62 2 wt sio 2 began to appear at the top of the dome coincident with increased seismicity and gas emissions the more scoriaceous lava spread radially over the dome surface while the dome continued to expand from endogenous growth and blocky lava was exposed on the margins and south side of the dome by mid june the upper scoriaceous lava had covered 36 of the dome surface area vesicularity of the upper scoriaceous lava range from 55 to 66 some of the highest vesicularity measurements recorded from a lava dome we suggest that the stability of the final lava dome primarily resulted from sufficient fracturing and clearing of the conduit by preceding explosions that allowed efficient degassing of the magma during effusion the dome was thus able to grow until it was large enough to exceed the magmastatic pressure in the chamber effectively shutting off the eruption

the seismicity of the 2009 redoubt eruption article redoubt volcano erupted in march 2009 following 6 months of precursory seismic activity the 4 5 month long eruptive sequence was accompanied by phreatic and magmatic explosions periods of steady dome growth lahars seismic swarms extended episodes of volcanic tremor and changes in the background seismicity rate this study presents a seismic chronology of the eruption and places it in context with the variety of other geological and geophysical data that were recorded during the eruptive period we highlight 6 notable seismic swarms 3 of which preceded large explosions the swarms varied from an hour to several days in duration and contained tens to over 7000 earthquakes many of the swarms were dominated by low frequency type earthquakes that contained families of repeating events seismic tremor varied considerably in frequency amplitude and duration during the eruption with distinct characteristics accompanying different types of volcanic activity the explosion signals during march 23 24 were the most energetic and the explosions on march 26 29 contained proportionally more low frequency energy 0 033 0 3 hz two seismic stations were particularly well suited to recording lahars that flowed down the drift river valley data from these stations showed that lahars were generated by the majority of the explosion events as well as during the continuous eruptive activity on march 29 when no large explosions occurred we also examine the seismicity which occurred outside of the explosion and swarm episodes and find several families of repeating vt earthquakes which begin shortly before the april 4 explosion and that continue

the wake of a legendary earthquake although quiet this century the cascadia subduction zone has produced big earthquakes in the past but how big an ingenious study involving documents written 300 years ago suggests that they can be giants