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

ice nucleation and overseeding of ice in volcanic clouds 1 water is the dominant component of volcanic gas emissions and water phase transformations including the formation of ice can be significant in the dynamics of volcanic clouds the effectiveness of volcanic ash particles as ice forming nuclei in is poorly understood and the sparse data that exist for volcanic ash in have been interpreted in the context of meteorological rather than volcanic clouds in this study single particle freezing experiments were carried out to investigate the effect of ash particle composition and surface area on water drop freezing temperature measured freezing temperatures show only weak correlations with ash in composition and surface area our measurements together with a review of previous volcanic ash in measurements suggest that fine ash particles equivalent diameters between approximately 1 and 1000 m from the majority of volcanoes will exhibit an onset of freezing between 250 260 k in the context of explosive eruptions where super micron particles are plentiful this result implies that volcanic clouds are in rich relative to meteorological clouds which typically are in limited and therefore should exhibit distinct microphysics we can expect that such overseeded volcanic clouds will exhibit enhanced ice crystal concentrations and smaller average ice crystal size relative to dynamically similar meteorological clouds and that glaciation will tend to occur over a relatively narrow altitude range

detection of plumes at redoubt and etna volcanoes using the gps snr method abstract detection and characterization of volcanic eruptions is important both for public health and aircraft safety a variety of ground sensors are used to monitor volcanic eruptions data from these ground sensors are subsequently incorporated into models that predict the movement of ash here a method to detect volcanic plumes using gps signals is described rather than carrier phase data used by geodesists the method takes advantage of attenuations in signal to noise ratio snr data two datasets are evaluated the 2009 redoubt volcano eruptions and the 2013 2015 eruptions at mt etna snr based eruption durations are compared with previously published seismic infrasonic and radar studies at redoubt volcano snr based plume detections from mt etna are compared with l band radar and tremor observations to place these snr observations from redoubt and etna in context a model of the propagation of gps signals through both water water vapor and tephra is developed neither water nor fine ash particles will produce the observed attenuation of gps signals while scattering caused by particles 1 cm in diameter potentially could

accuracy of the lightning mapping array 1 the location accuracy of the new mexico tech lightning mapping array lma has been investigated experimentally using sounding balloon measurements airplane tracks and observations of distant storms we have also developed simple geometric models for estimating the location uncertainty of sources both over and outside the network the model results are found to be a good estimator of the observed errors and also agree with covariance estimates of the location uncertainties obtained from the least squares solution technique sources over the network are located with an uncertainty of 6 12 m rms in the horizontal and 20 30 m rms in the vertical this corresponds well with the uncertainties of the arrival time measurements determined from the distribution of chi square values to be 40 50 ns rms outside the network the location uncertainties increase with distance the geometric model shows that the range and altitude errors increase as the range squared r2 while the azimuthal error increases linearly with r for the 13 station 70 km diameter network deployed during steps the range and height errors of distant sources were comparable to each other while the azimuthal errors were much smaller the difference in the range and azimuth errors causes distant storms to be elongated radially in plan views of the observations the overall results are shown to agree well with hyperbolic formulations of time of arrival measurements e g proctor 1971 two appendices describe 1 the basic operation of the lma and the detailed manner in which its measurements are processed and 2 the effect of systematic errors on lightning observations the latter provides an alternative explanation for the systematic height errors found by boccippio et al 2001 in distant storm data from the lightning detection and ranging system at kennedy space center

investigation of magnetic surveying data of buried grave jars in harmanoren necropolis turkey using linear transformations and analytic signal abstract harmanoren necropolis is the third biggest excavated necropolis in southwest anatolia dating back to 2500 b c the individual burials are composed of ceramic jars the dead bodies were placed in the fetal position in buried grave jars which were elongated eastwards buried burnt ceramics can be located by their own magnetic field directions thus magnetic surveying was used in the harmanoren necropolis in three different areas to locate buried grave jars ahead of archaeological excavation magnetic anomalies present some results but to identify these as buried grave jars advanced spectral methods were applied to the magnetic anomalies polarity orientations of magnetic anomalies are different from a north south direction due to remnant magnetization reduction to the pole transformation could not entirely remove disoriented polarities arising from the effect of remnant magnetization analytic signal transformation minimizes the disorientation caused by the effect of remanence magnetic susceptibility measurements of samples from the excavated jars indicate that the observed magnetic anomalies could be caused by them a good correlation was observed between the processed magnetic anomalies and excavation results

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

overview chronology and impacts of the 2016 2017 eruption of bogoslof volcano alaska the 2016 2017 eruption of bogoslof volcano a back arc shallow submarine volcano in alaska s aleutian arc began in december 2016 and included 70 explosive events and at least two episodes of subaerial dome building because the volcano had no local monitoring stations during the eruption a combination of distant seismic stations regional infrasound sensors lightning detection a variety of satellite data and observer reports and a field visit in 2018 were used to recreate the events that occurred during the nine month eruption following precursory seismicity that started in september 2016 the eruption began in december 2016 with a series of explosive events that persisted through mid march 2017 after a 6 week hiatus activity resumed on may 17 and lasted through the end of august 2017 and consisted of additional explosions and two short lived subaerial lava domes that formed in june and august for most of the eruption bogoslof s vent was submerged in shallow seawater though during several of the longer events a subaerial edifice grew and the vent migrated above sea level resulting in more ash rich volcanic clouds eruptive products geophysical signals and eruptive style are all broadly consistent with vulcanian activity where slow magma ascent led to repetitive dome or plug formation overpressurization in the upper conduit and sudden release during short lived explosions infiltration of seawater may have prohibited large domes from forming especially in the first half of the eruption when explosions were closely spaced in time the largest four explosions in the sequence occurred after inter event times of 10 days or more three events produced ashfall on nearby communities and mariners east and south of bogoslof and the eruption resulted in dozens of flight cancelations and flight diversions around the volcano and its ash clouds

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

magnetic mapping ground penetrating radar surveys and magnetic susceptibility measurements for the study of the archaeological site of serra di vaglio southern italy in this work we present the results of a multidisciplinary study for characterising the archaeological site of serra di vaglio basilicata region southern italy the site includes an ancient native settlement arisen between the 8th and the 3rd century bc the investigation has been performed by means of the integrated use of three different high resolution and no invasive geophysical techniques magnetic mapping ground penetrating radar profiling gpr and magnetic susceptibility measurements the integrated approach allows us to detect buried archaeological structures in particular our results helped to define spatial pattern of the buried remains to define the geometry of the anthropogenic settlements and to obtain detailed information about the composition and the manufacturing processes of different building materials the archaeological excavations carried out in one of the investigated sites confirm the usefulness and the reliability of the integrated employment of different geophysical techniques for the archaeological study of ancient buried structures

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

inferring compressible fluid dynamics from vent discharges during volcanic eruptions observations at numerous volcanoes reveal that eruptions are often accompanied by continual radio frequency crf emissions the source of this radiation however has remained elusive until now through experiments and the analysis of field data we show that crf originates from proximal discharges driven by the compressible fluid dynamics associated with individual volcanic explosions blasts produce flows that expand supersonically generating regions of weakened dielectric strength in close proximity to the vent as erupted materialcharged through fragmentation friction or other electrification processtransits through such a region pyroclasts remove charge from their surfaces in the form of small interparticle spark discharges or corona discharge discharge is maintained as long as overpressured conditions at the vent remain beyond describing the mechanism underlying crf we demonstrate that the magnitude of the overpressure at the vent as well as the structure of the supersonic jet can be inferred in real time by detecting and locating crf sources

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

the 1989 1990 eruptions of redoubt volcano an introduction abstract redoubt volcano located on the west side of cook inlet in south central alaska erupted explosively on over 20 separate occasions between december 14 1989 and april 21 1990 fourteen lava domes were emplaced in the summit area thirteen of which were subsequently destroyed the eruption caused economic losses estimated at over 160 000 000 making this the second most costly eruption in u s history this economic impact provided the impetus for a integrated comprehensive account of an erupting volcano using both modern and classical research and modern techniques which in turn led to advances in eruption monitoring and interpretation research on such topics as dome formation and collapse and the resulting pyroclastic flows elutriated ash lightning tephra and flooding was blended with the rapid communication of associated hazards to a large user group the seismology successes in predicting and monitoring eruption dynamics were due in part to 1 the recognition of long period seismic events as indicators of the readiness of the volcano to erupt and 2 to the development of new tools that allowed the seismicity to be assessed instantaneously integrated studies of the petrology of erupted products and volatile content over time gave clues as to the progress of the eruption towards completion

using lightning observations as a volcanic eruption monitoring tool lightning commonly occurs in the eruption columns produced by explosive volcanic eruptions there are several different kinds of lightning detection instruments that could be employed to help monitor volcanoes each with their own advantages and disadvantages very low frequency vlf instruments have the ability to detect lightning at long ranges but tend to have low sensitivity due to network geometry and typically can provide only the time and 2 d location of a cloud to ground return stroke or similar high amplitude pulse produced by an intracloud discharge low frequency lf and medium frequency mf instruments typically have more sensitivity than a vlf network but can only be used for detection on a regional scale very high frequency vhf lightning mapping instruments also provide only regional coverage but detect all lightning within their range during the 2009 eruption of redoubt volcano alaska usa each of these types of instruments detected lightning from redoubt s ash plume the vhf system consistently detected lightning before the other two during each distinct explosive event and also detected more lightning than the others by one or two orders of magnitude lightning observations could be used to confirm and in some cases detect explosive volcanic activity the rapid response provided by lightning monitoring is a valuable tool for fast identification of potentially hazardous ash clouds

multiparametric study of the february april 2013 paroxysmal phase of mt etna new south east crater european fp7 med suv mediterranean supersite volcanoes grant number 308665 european research council european fp7 fp 2007 2013 erc grant number 279802 sigma sistema integrato di sensori in ambiente cloud per la gestione multirischio avanzata

observations of volcanic tremor at mount st helens volcano digital recordings of ground motion during tremor episodes accompanying eruptions at mount st helens volcano in the state of washington on august 7 and october 16 18 1980 are studied the spectra of the vertical component waveforms contain at least two dominant peaks at 1 0 and 1 3 hz for all events recorded during both eruptions that were studied spectra of horizontal ground motion show peaks at 0 9 and 1 1 hz the relative amplitude of the two peaks changes between tremor episodes and during single tremor episodes and shows no consistent relation to amplitude of ground motion spectra of long period earthquakes are very similar to those of tremor events suggesting that tremor is composed of many long period earthquakes that occur over a period of time the unique waveform of tremor events observed at mount st helens must be due to a source effect since the relative amplitude of the two dominant peaks changes during tremor episodes the path effect on tremor waveforms is small since there are no peaks in the spectra of waveforms recorded during tectonic earthquakes occurring in the vicinity of mount st helens the consistency of the location of the spectral peaks for the wide range of tremor amplitudes means that there must be a physical length at the source that is constant independent of the amplitude of motion at the source variations in amplitude of motion generated during tremor events must be due to variations in the force driving the tremor amplitudes of ground motion varies between 0 11 and 4 7 m seismic moment rates during the two eruptions are calculated using the model of aki et al 1977 and found to vary between 6 1018 and 1 1020 dynes cm s 1 which are larger than values found by aki et al 1977 who studied amplitudes of shallow tremor events recorded during the october 1963 eruption of kilauea volcano in hawaii study of tremor amplitudes recorded at corvallis oregon leads to the conclusion that tremor accompanying the cataclysmic may 18 1980 eruption was at least one order of magnitude larger in amplitude than tremor during august and october

a new way to detect volcanic plumes 1 detection of volcanic plumes especially ash laden ones is important both for public health and aircraft safety a variety of geophysical tools and satellite data are used to monitor volcanic eruptions and to predict the movement of ash however satellite based methods are restricted by time of day and weather while radars are often unavailable because of cost portability here a method is proposed to detect volcanic plumes using gps signal strength data the strengths and limitations of the method are assessed using gps data collected during the 2008 and 2009 eruptions of the okmok and mt redoubt volcanoes plume detections using this gps technique are consistent with independently collected seismic and radar data

infrasonic component of volcano seismic eruption tremor air ground and ground air elastic wave coupling are key processes in the rapidly developing field of seismoacoustics and are particularly relevant for volcanoes during a sustained explosive volcanic eruption it is typical to record a sustained broadband signal on seismometers termed eruption tremor eruption tremor is usually attributed to a subsurface seismic source process such as the upward migration of magma and gases through the shallow conduit and vent however it is now known that sustained explosive volcanic eruptions also generate powerful tremor signals in the atmosphere termed infrasonic tremor we investigate infrasonic tremor coupling down into the ground and its contribution to the observed seismic tremor our methodology builds on that proposed by ichihara et al 2012 and involves cross correlation coherence and cross phase spectra between waveforms from nearly collocated seismic and infrasonic sensors we apply it to datasets from mount st helens tungurahua and redoubt volcanoes

an overview of volcano infrasound from hawaiian to plinian local to global abstract volcano infrasound is an increasingly useful technique for detecting locating characterizing and quantifying eruptive activity and can be used to constrain eruption source parameters in recent years studies of infrasound data from active volcanoes have shown clear progress towards mitigating volcanic hazards and understanding volcanic source processes volcano acoustic sources are shallow or aerial thus volcano infrasound data provide valuable information on eruption dynamics and are readily combined with direct and remote observations of gas ash and other eruptive phenomena the infrasound signals produced by volcanoes are indicative of the eruption style and dynamics here we review the diversity of infrasound signals generated by a wide variety of volcanic eruptions from hawaiian to plinian and the physical processes inferred to produce them we place particular emphasis on regional 15 250 km distance and global 250 km distance volcano infrasound studies as recent work in this area has made significant advances in monitoring and characterizing remote and difficult to monitor eruptions long range infrasonic detection of explosive volcanic eruptions is possible due to the energetic source mechanisms involved minor atmospheric attenuation at low frequencies and the existence of waveguides in the atmosphere however accurate characterization of the atmosphere and its spatiotemporal variability is required for reliable long range sound propagation modeling and correct interpretation of global infrasound recordings conversely because volcanic explosions are energetic and sometimes repetitive infrasound sources they can be used to validate atmospheric and acoustic propagation models

a multi sensor plume height analysis of the 2009 redoubt eruption abstract during an explosive volcanic eruption accurately determining the height of a volcanic plume or cloud is essential to accurately forecast its motion because volcanic ash transport and dispersion models require the initial plume height as an input parameter the direct use of satellite infrared temperatures for height determination one of the most commonly employed methods at the alaska volcano observatory often does not yield unique solutions for height this result is documented here for the 2009 eruption of redoubt volcano satellite temperature heights consistently underestimated the height of ash plumes in comparison to other methods such as ground based radar and multi angle imaging spectroradiometer misr stereo heights for ash plumes below the tropopause increasing transparency of a plume begins to affect the accuracy of simple temperature height retrievals soon after eruption with decreasing opacity plume temperature heights become increasingly inaccurate comparison with dispersion models and aircraft gas flight data confirms that radar and misr stereo heights are more accurate than basic satellite temperature heights even in the cases in which satellite temperature results appeared to be relatively accurate e g for plumes below the tropopause a mixed signal of plume and ground radiation still presented an issue for almost every event studied this was true regardless of the fact that a band differencing method was used to remove presumably translucent pixels the data presented here make a strong case for the use of data fusion in volcano monitoring as there is a need to confirm satellite temperature heights with other height data if only basic satellite temperature heights are available for a given eruption then these heights must be considered with a significant margin of error

co eruptive tremor from bogoslof volcano seismic wavefield composition at regional distances we analyze seismic tremor recorded during eruptive activity over the course of the 2016 2017 eruption of bogoslof volcano alaska only regional recordings of the tremor wavefield exist for bogoslof making it a challenge to place the recordings in context with other eruptions that are normally captured by local seismic data we apply a technique of time frequency polarization analysis to three component seismic data to reveal the wavefield composition of bogoslof eruption tremor we find that at regional distances the tremor is dominated by p waves in the band from 1 5 to 10 hz using this information along with an enriched bogoslof earthquake catalog we obtain estimates of average reduced displacement dr for eruption tremor during 25 of the 70 bogoslof events dr reaches as high as approximately 40 cm2 for two of the major events similar to other vei 3 eruptions in alaska overall average reduced displacement displays a weak correlation to plume height during the first half of the 9 month long eruption sequence with a few notable exceptions the two events with the highest dr values also generated measurable eruption tremor at very long periods vlp between 0 05 and 0 15 hz

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

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

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

changes to the turbulent kinematics of a volcanic plume inferred from lightning data the 2009 redoubt volcano eruption produced a series of explosive events the largest of which produced episodes of volcanic lightning similar to thunderstorms flash energy spectra were calculated from lightning mapping data collected during the eruption the spectra were compared to the turbulence characteristics expected from each stage of plume development small flash length scales present at early times were associated with the gas thrust and initial convective stages increases in flash length scales and flash energy as the explosive events progressed were associated with an increase in volume of the plume spectra with a large range in flash length scales 0 2 10 km and a spectral peak at small flash length scales 1 km were associated with a superposition of spectra from gas thrust convective and umbrella ash cloud regions an approximate 5 3 power law slope was observed on the order of 10 min after gas thrust forcing had ended and the transition to a drifting ash cloud was underway which may reflect the dissipating state of the drifting ash cloud

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

late quaternary paleoseismic history and surface rupture characteristics of the eastern awatere strike slip fault new zealand the recurrence and magnitude of paleo earthquakes on the eastern section of the dextral strike slip awatere fault 105 km long are determined from stratigraphic evidence in a fault trench and measurement of fault displaced geomorphic features we identify at least six ground rupturing events younger than 8330 8610 yr the youngest being a historically recorded mw 7 5 event in a d 1848 that ruptured the entire eastern section the maximum mean recurrence interval is 1 4 k y although repeat intervals range from 605 235 to 2500 600 yr the smallest fault offsets on the easternmost 27 km of the onshore part of the fault indicate a mean strike slip displacement of 4 9 m during the 1848 event the second smallest offsets are approximately double the smallest displacements suggesting that the last two events were ruptures of comparable dimensions 105 km and magnitude because the awatere fault terminates 20 km northeast of the study area the penultimate rupture probably extended inland perhaps rupturing the entire eastern section further evidence of characteristic earthquake behavior is preserved in the fault trench where a regular event subsidence of 50 cm per event is indicated during the last two events a slip maximum of 7 1 m occurred on a 5 5 km long fault subsection consisting of adjacent restoring and releasing fault bends these bends define a 1 km wide side step in the fault that although of short wavelength apparently strongly influences the amount of coseismic slip and moment release new data on the age of late quaternary alluvial surfaces in the awatere valley when combined with observed horizontal displacements indicate that strike slip has accrued on the awatere fault at a constant rate of 6 mm yr for at least the past 20 k y

volcanic eruptions observed with infrasound 1 infrasonic airwaves produced by active volcanoes provide valuable insight into the eruption dynamics because the infrasonic pressure field may be directly associated with the flux rate of gas released at a volcanic vent infrasound also enhances the efficacy of volcanic hazard monitoring and continuous studies of conduit processes here we present new results from erebus fuego and villarrica volcanoes highlighting uses of infrasound for constraining quantitative eruption parameters such as eruption duration source mechanism and explosive gas flux

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

explosive volcanic activity at mt yasur a characterization of the acoustic events 9 12th july 2011 abstract volcanic processes occur in a wide range of temporal and spatial scales however a key step of magma ascent is recognizable in the dynamics of gas and magma in the shallow plumbing system where volatiles play a fundamental role in controlling the eruptive style with the aim of investigating shallow degassing processes an experimental setup was deployed at mt yasur an active volcano located in tanna island vanuatu arc from 9th to 12th july 2011 the setup comprised high speed and thermal cameras as well as a microphone capable of recording both in the infrasonic and audible range the analysis of acoustic signals validated by observing images from the high speed and thermal cameras has enabled characterizing the explosive activity during the investigated period two types of explosions distinct for spectral features and waveforms were observed i minor events corresponding to small overpressurized bursts occurring almost continuously ii major events characterizing the strombolian activity at mt yasur by investigating variation in the occurrence rate of the minor events we found that on a short timescale the dynamics responsible for the two types of explosions are decoupled these results together with previous literature data bring additional evidence of the existence of distinct sources of degassing finally major events can be distinguished as emergent events i e long lasting signals corresponding to ash rich explosions and impulsive events featuring shorter duration and larger amplitude

seismic observations of redoubt volcano alaska 1989 2010 and a conceptual model of the redoubt magmatic system abstract seismic activity at redoubt volcano alaska has been closely monitored since 1989 by a network of five to ten seismometers within 22 km of the volcano s summit major eruptions occurred in 1989 1990 and 2009 and were characterized by large volcanic explosions episodes of lava dome growth and failure pyroclastic flows and lahars seismic features of the 1989 1990 eruption were 1 weak precursory tremor and a short 23 hour long intense swarm of repetitive shallow long period lp events centered 1 4 km below the crater floor 2 shallow volcano tectonic vt and hybrid earthquakes that separated early episodes of dome growth 3 13 additional swarms of lp events at shallow depths precursory to many of the 25 explosions that occurred over the more than 128 day duration of eruptive activity and 4 a persistent cluster of vt earthquakes at 6 to 9 km depth in contrast the 2009 eruption was preceded by a pronounced increase in deep lp dlp events at lower crustal depths 25 to 38 km that began in mid december 2008 two months of discontinuous shallow volcanic tremor that started on january 23 2009 a strong phreatic explosion on march 15 and a 58 hour long swarm of repetitive shallow lp events the 2009 eruption consisted of at least 23 major explosions between march 23 and april 5 again accompanied by shallow vt earthquakes several episodes of shallow repetitive lp events and dome growth continuing until mid july increased vt earthquakes at 4 to 9 km depth began slowly in early april possibly defining a mid crustal magma source zone magmatic processes associated with the 2009 eruption seismically activated the same portions of the redoubt magmatic system as the 1989 1990 eruption although the time scales and intensity vary considerably among the two eruptions the occurrence of precursory dlp events suggests that the 2009 eruption may have involved the rise of magma from lower crustal depths based on the evolution of seismicity during the 1989 1990 and 2009 eruptions the redoubt magmatic system is envisioned to consist of a shallow system of cracks extending 1 to 2 km below the crater floor a magma storage or source region at roughly 3 to 9 km depth and a diffuse magma source region at 25 to 38 km depth close tracking of seismic activity allowed the alaska volcano observatory to successfully issue warnings prior to many of the hazardous explosive events that occurred in 2009