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

detecting tectonic tremor through frequency scanning at a single station application to the cascadia margin abstract the discovery of episodic tremor and slip ets spurred increased instrumentation and investigation of the cascadia margin which is now typified by the seismic phenomena we utilize established detection and location techniques already present in the region to guide the development of a new single station detection method while detailed network wide investigations have led to exciting discoveries on the source location and migration patterns of tectonic tremor single station detection has the ability to expand our search for tremor to more subduction zones and tectonic settings where instrumentation is not widely available our frequency scanning technique bandpass filters seismic data into three categories 2 5 hz 10 15 hz and 0 02 0 1 hz where we expect prominent signals produced by tectonic tremor local earthquakes and surface waves respectively we combine amplitudes in each category into a ratio to determine tremor detection for a given hour results from our technique are evaluated in two ways 1 combined in a network setting to compare with prominent location and detection methods and 2 assessed at an individual station and compared with other techniques that are capable of single station tremor detection network wide processing over a two year time period in both northern and southern cascadia reveals common identification of larger ets episodes when comparing our technique to both envelope waveform and combined single station detection methods we find slight variations in the total duration of tremor and the onset timing between the different techniques which may be due to the varying stations included in each technique frequency scanning identifies more inter ets episodes than envelope waveform and single station methods particularly in the more sparsely instrumented region of southern oregon our method also reduces erroneous signals more commonly found in other single station methods discerned through comparison of nearby seismograms and spectrograms results at individual stations from northern and southern cascadia are consistent with network setting tremor identifications and have capabilities of detecting tremor up to 50 km away quantification of tremor hours from the frequency scan technique for a range of different episodes demonstrates a linear relationship of geodetic moment release to seismic tremor duration similar to previous results from manual and automated techniques aguiar et al 2009 the greater sensitivity of frequency scanning to inter ets tremor episodes provides a means to estimate aseismic moment release by using the duration of smaller tremor episodes as a proxy for slow slip that is not currently resolvable on gps the computational ease and autonomous nature of a single station technique presents the ability to better characterize long term tremor behavior and search for tremor in new locations

source constraints of tungurahua volcano explosion events the most recent eruptive cycle of tungurahua volcano began in may 2004 and reached its highest level of activity in july 2004 this activity cycle is the last one of a series of four cycles that followed the reawakening and major eruption of tungurahua in 1999 between june 30 and august 12 2004 three temporary seismic and infrasonic stations were installed on the flanks of the volcano and recorded over 2 000 degassing events the events are classified by waveform character and include explosion events the vast majority spanning three orders of pressure amplitudes at 3 5 km from the vent 0 1 180 pa jetting events and sequences of repetitive infrasonic pulses called chugging events travel time analysis of seismic first arrivals and infrasonic waves indicates that explosions start with a seismic event at a shallow depth 200 m followed 1 s later by an out flux of gas ash and solid material through the vent cluster analysis of infrasonic signals from explosion events was used to isolate four groups of similar waveforms without apparent correlation to event size location or time the clustering is thus associated with source mechanism and probably spatial distribution explosion clusters do not exhibit temporal dependence

infrasonic tremor in the diffraction zone 1 volcanic tremor signals recorded by an infrasound array 12 5 km from the active vent of k lauea volcano show clear diurnal amplitude variations and originate from a well defined direction pointing to the active pu u crater complex spectral amplitudes between 0 02 0 3 hz a proxy for wind speed increase when the wind speeds increase during the daytime spectral amplitudes between 0 5 3 hz where infrasonic tremor is concentrated increase when the wind speeds decrease at night power spectrum analysis shows that when ambient noise levels drop infrasonic tremor amplitudes rise array processing confirms this relationship and reveals tremor detections and amplitudes decrease during the day these changes in infrasonic tremor spectral amplitude and coherence are most likely due to diurnal variations in atmospheric boundary layers affecting infrasonic propagation within the diffraction zone recognition of these regional atmospheric patterns is necessary to permit robust infrasonic remote sensing of volcanic processes

propagation of acoustic waves in a viscoelastic two phase system influence of gas bubble concentration abstract volcanic explosions generate pressure perturbations in the atmosphere and a seismic wavefield in the ground the source is therefore well coupled with the atmosphere and the ground the acoustic and elastic wavefields reflect dynamical processes at the source and the viscoelastic properties of the magma gas medium at low pressure 70 strongly affect the propagation properties of the acoustic wavefield we found that the amplitude of the infrasonic wavefield in the atmosphere typically recorded in case of strombolian explosions 2 105 pa can be explained by a deep 50 m source embedded in the magma conduit only if a very large unrealistic pressure drop 1013 pa is assumed the strong damping linked to the poor elastic properties of the shallow magma gas mixture prevents the efficient propagation of the acoustic waves in the magma gas mixture and resonance of body waves cannot occur infrasonic waves can be transmitted from the magma to the atmosphere only when the source is very shallow

evaluation of infrasound signals from the shuttle atlantis using a large seismic network inclement weather in florida forced the space shuttle atlantis to land at edwards air force base in southern california on june 22 2007 passing near three infrasound stations and several hundred seismic stations in northern mexico southern california and nevada the high signal to noise ratio broad receiver coverage and atlantis positional information allow for the testing of infrasound propagation modeling capabilities through the atmosphere to regional distances shadow zones and arrival times are predicted by tracing rays that are launched at right angles to the conical shock front surrounding the shuttle through a standard climatological model as well as a global ground to space model the predictions and observations compare favorably over much of the study area for both atmospheric specifications to the east of the shuttle trajectory there were no detections beyond the primary acoustic carpet infrasound energy was detected hundreds of kilometers to the west and northwest nw of the shuttle trajectory consistent with the predictions of ducting due to the westward summer time stratospheric jet both atmospheric models predict alternating regions of high and low ensonifications to the nw however infrasound energy was detected tens of kilometers beyond the predicted zones of ensonification possibly due to uncertainties in stratospheric wind speeds

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

global seismic event detection using a matched filter on long period seismograms an image derived by stacking long period seismograms is used as an empirical matched filter to detect and locate earthquakes records from 564 events mb 6 recorded at very long periods t 60 s by the 15 to 20 stations of the international deployment of accelerometers ida network are stacked using a method that emphasizes the surface wave arrivals the first 3 hours of this time versus range image are used to construct a matched filter for continuous application to the ida data the output of this filter contains spatial and temporal peaks that define the location and origin time of probable seismic events implementation of this technique to 11 years of ida data from 1981 to 1991 identifies 4061 events these include 65 of cataloged events of mb 5 5 earthquakes which appear anomalously strong relative to their surface wave magnitudes are mainly located on oceanic transform faults and probably represent unusually slow ruptures the method successfully detects two eruptions of the el chichon volcano in southern mexico from the anomalous low frequency energy radiated during the eruptions in addition 32 earthquakes are detected which are not in the standard global catalogs these events appear to be about ms 5 and are mainly located in the southern oceans where there are gaps in the coverage of the high frequency networks although these earthquakes are probably slow since they occur mostly on oceanic transform faults they are not silent as they also can be observed in higher frequency data

source location of the 19 february 2008 oregon bolide using seismic networks and infrasound arrays 1 on 19 february 2008 a bolide traveled across the sky along a southern trajectory ending in a terminal burst above oregon the event was well recorded by the usarray other seismic networks four infrasound arrays and several video cameras we compare the results of locating the burst using these different sensor networks specifically we reverse time migrate acoustic to seismic coupled signals recorded by the usarray out to 800 km range to image the source in 2 d space and time we also apply a grid search over source altitude and time minimizing the misfit between observed and predicted arrival times using 3 d ray tracing with a high resolution atmospheric velocity model our seismic and video results suggest a point source rather than a line source associated with a hypersonic trajectory we compare the seismic source locations to those obtained by using different combinations of observed infrasound array signal back azimuths and arrival times we find that all locations are consistent however the seismic location is more accurate than the infrasound locations due to the larger number of seismic sensors a more favorable seismic source receiver geometry and shorter ranges to the seismometers for the infrasound array locations correcting for the wind improved the accuracy but implementing arrival times while increasing the precision reduced the accuracy presumably due to limitations of the source location method and or atmospheric velocity model we show that despite known complexities associated with acoustic to seismic coupling aboveground infrasound sources can be located with dense seismic networks with remarkably high accuracy and precision

basaltic thermals and subplinian plumes constraints from acoustic measurements at shishaldin volcano alaska the 1999 basaltic eruption of shishaldin vol cano alaska usa included both strombolian and sub plinian activity as well as a pre subplinian phase inter preted as the local coalescence within a long foam in the conduit although few visual observations were made of the eruption a great deal of information regarding gas ve locity gas flux at the vent and plume height may be inferred by using acoustic recordings of the eruption by relating acoustic power to gas velocity a time series of gas velocity is calculated for the subplinian and pre subplinian phases these time series show trends in gas velocity that are inter preted as plumes or for those signals lasting only a short time thermals the subplinian phase is shown to be com posed of a thermal followed by five plumes with a total expelled gas volume of 1 5 10 7 m 3 the initiation of the subplinian activity is probably related to the arrival of a large overpressurised bubble close to the top of the magma column a gradual increase in low frequency 0 01 0 5 hz signal prior to this trigger bubble may be due to the rise of the bubble in the conduit this delay corresponds to a reservoir located at 3 9 km below the surface in good agreement with studies on other volcanoes the presence of two thermal phases is also identified in the middle of the pre subplinian phase with a total gas release of 4 3 10 6 m 3 and 3 6 10 6 m 3 gas veloc ity at the vent is found to be 82 m s 1 and 90 m s 1 for the subplinian plumes and the pre subplinian thermals respectively the agreement is very good between estimates of the gas flux from modelling the plume height and those obtained from acoustic measurements leading to a new method by which eruption physical parameters may be quantified fur thermore direct measurements of gas velocity can be used for better estimates of the so2 flux released during the eruption

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

a study of infrasonic anisotropy and multipathing in the atmosphere using seismic networks we discuss the use of reverse time migration rtm with dense seismic networks for the detection and location of sources of atmospheric infrasound seismometers measure the response of the earth s

location and mechanism of very long period tremor during the 2008 eruption of okmok volcano from interstation arrival times 1 we describe continuous very long period vlp tremor that occurred during the 2008 eruption of okmok volcano alaska due to its low frequency content in band from the 0 2 0 4 hz the wave field of the vlp tremor is relatively free of path effects from continuous recordings of the vlp tremor on 2 three component broadband and 3 single component short period instruments we devise a method to locate the epicenter of the tremor based on interstation arrival times computed with cross correlation we find the epicenter since the vertical and radial components of the vlp tremor wave field are dominated by rayleigh waves and the time shifts are related to lateral propagation over the 4 h period studied this procedure yields a location nnw of cone d close to the new cone built over the course of the eruption similar analysis using the transverse horizontal components from the 2 three component broadband instruments yields strong constraints on the source mechanism of the vlp tremor we observe an anomalous interstation arrival time due to the existence of a nodal plane in the love wave radiation pattern the orientation of a compensated linear vector dipole clvd source estimated from the transverse components closely aligns with the regional maximum horizontal stress direction the depth of the clvd source is constrained by matching the vertical components to the rayleigh wave radiation pattern at all five stations we find the vlp tremor source depth to be 2 km bsl positioned between the magma chamber at okmok 3 km bsl and the surface

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

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

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

detecting hidden volcanic explosions from mt cleveland volcano alaska with infrasound and ground coupled airwaves 1 in alaska where many active volcanoes exist without ground based instrumentation the use of techniques suitable for distant monitoring is pivotal in this study we report regional scale seismic and infrasound observations of volcanic activity at mt cleveland between december 2011 and august 2012 during this period twenty explosions were detected by infrasound sensors as far away as 1827 km from the active vent and ground coupled acoustic waves were recorded at seismic stations across the aleutian arc several events resulting from the explosive disruption of small lava domes within the summit crater were confirmed by analysis of satellite remote sensing data however many explosions eluded initial automated analyses of satellite data due to poor weather conditions infrasound and seismic monitoring provided effective means for detecting these hidden events we present results from the implementation of automatic infrasound and seismo acoustic eruption detection algorithms and review the challenges of real time volcano monitoring operations in remote regions we also model acoustic propagation in the northern pacific showing how tropospheric ducting effects allow infrasound to travel long distances across the aleutian arc the successful results of our investigation provide motivation for expanded efforts in infrasound monitoring across the aleutians and contributes to our knowledge of the number and style of vulcanian eruptions at mt cleveland

infrasonic propagation from the 2010 eyjafjallajokull eruption investigating the influence of stratospheric solar tides 1 the stratospheric infrasound duct formed between earth s surface and altitudes of 50 km is sensitive to spatiotemporal variations in stratospheric wind speed and temperature infrasound recorded at long range from the 2010 summit eruption of eyjafjallajokull volcano iceland exhibits temporal variability correlated with diurnal stratospheric solar tidal wind speed variations between 18 and 28 april 2010 signal observations at stations bkni u k range 1745 km and is18 greenland range 2285 km exhibit prominent diurnal variations in infrasonic amplitude bandwidth back azimuth and apparent speed which we identify using the clean spectral analysis algorithm for unevenly sampled time series results of 3 d acoustic ray tracing through operational atmospheric specifications indicate that tidal wind speed variations with amplitudes of 20 m s can generate diurnal variations in the proportion of the acoustic wavefield propagating within the stratospheric acoustic duct range dependent meteorology is required propagation modeling using averaged meteorological profiles fails to predict the leakage of acoustic energy out of the stratospheric acoustic duct at times of low observed signal amplitudes ray tracing correctly predicts the phase of the observed signal amplitude and apparent speed variations diurnal variability in ducting combined with diurnal variations in ambient noise at the sensors can explain the observed signal bandwidth variations back azimuth variations observed only along the eyjafjallajokull to bkni path are not predicted by 3 d ray tracing tidal variations have implications for models of infrasound array network detection capability and for studies that utilize amplitude and bandwidth measurements to make inferences about the acoustic source

infrasonic tremor wavefield of the pu u ō ō crater complex and lava tube system hawaii in april 2007 1 long lived effusive volcanism at the pu u crater complex kilauea volcano hawaii produces persistent infrasonic tremor that has been recorded almost continuously for months to years previous studies showed that this infrasonic tremor wavefield can be recorded at a range of 10 km however the low signal power of this tremor relative to ambient noise levels results in significant propagation effects on signal detectability at this range in april 2007 we supplemented a broadband infrasound array at 12 5 km from pu u mene with a similar array at 2 4 km from the source kipu the additional closer range data enable further evaluation of tropospheric propagation effects and provide higher signal to noise ratios for studying volcanic source processes the infrasonic tremor source appears to consist of at least two separate physical processes we suggest that bubble cloud oscillation in a roiling magma conduit beneath the crater complex may produce a broadband component of the tremor low frequency sound sourced in a shallow magma conduit may radiate infrasound efficiently into the atmosphere due to the anomalous transparency of the magma air interface we further propose that more sharply peaked tones with complex temporal evolution may result from oscillatory interactions of a low velocity gas jet with solid vent boundaries in a process analogous to the hole tone or whistler nozzle the infrasonic tremor arrives with a median azimuth of 67 at kipu additional infrasonic signals and audible sounds originating from the extended lava tube system to the south of the crater complex median azimuth 77 coincided with turbulent degassing activity at a new lava tube skylight our observations indicate that acoustic studies may aid in understanding persistent continuous degassing and unsteady flow dynamics at kilauea volcano

infrasound observations of the 2008 explosive eruptions of okmok and kasatochi volcanoes alaska 1 the recent explosive eruptions of okmok and kasatochi volcanoes provide an opportunity to use seismic local infrasound distant infrasound array and remote sensing data in concert to better monitor volcanoes in the aleutian arc and to better understand the source processes the eruption of okmok volcano began on 12 july 2008 and included a seismically active phase that lasted continuously for about 10 h in contrast the eruption of kasatochi which began on 7 august 2008 consisted of five explosive events that lasted from 26 to 68 min each and had a cumulative duration of 3 4 h given the event times by local seismic stations the corresponding infrasound signals were found in the data recorded by local infrasound sensors and by distant infrasound arrays signals from the okmok eruption were detected by three international monitoring system ims arrays as far away as 4400 km signals from the kasatochi eruption were detected at greater distances up to 5200 km away by seven infrasound arrays including the ones that detected the event at okmok volcano back azimuth propagation and a simple acoustic wave propagation model in unison with known event times were used to confirm that the planar acoustic signals recorded at the arrays had originated from the eruptions the infrasound array data reflected the differences in eruption styles between okmok and kasatochi as the signals from kasatochi were of shorter duration of greater amplitude and detected over greater distances the infrasound array data were also able to distinguish between two types of tremor episodes that occurred at kasatochi volcano based on atmospheric disturbance

seismo acoustic signals associated with degassing explosions recorded at shishaldin volcano alaska 2003 2004 in summer 2003 a chaparral model 2 microphone was deployed at shishaldin volcano aleutian islands alaska the pressure sensor was co located with a short period seismometer on the volcano s north flank at a distance of 6 62 km from the active summit vent the seismo acoustic data exhibit a correlation between impulsive acoustic signals 1 2 pa and long period lp 1 2 hz earthquakes since it last erupted in 1999 shishaldin has been characterized by sustained seismicity consisting of many hundreds to two thousand lp events per day the activity is accompanied by up to 200 m high discrete gas puffs exiting the small summit vent but no significant eruptive activity has been confirmed the acoustic waveforms possess similarity throughout the data set july 2003 november 2004 indicating a repetitive source mechanism the simplicity of the acoustic waveforms the impulsive onsets with relatively short 10 20 s gradually decaying codas and the waveform similarities suggest that the acoustic pulses are generated at the fluid air interface within an open vent system so2 measurements have revealed a low so2 flux suggesting a hydrothermal system with magmatic gases leaking through this hypothesis is supported by the steady state nature of shishaldin s volcanic system since 1999 time delays between the seismic lp and infrasound onsets were acquired from a representative day of seismo acoustic data a simple model was used to estimate source depths the short seismo acoustic delay times have revealed that the seismic and acoustic sources are co located at a depth of 240 200 m below the crater rim this shallow depth is confirmed by resonance of the upper portion of the open conduit which produces standing waves with f 0 3 hz in the acoustic waveform codas the infrasound data has allowed us to relate shishaldin s lp earthquakes to degassing explosions created by gas volume ruptures from a fluid air interface

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

improved prediction and tracking of volcanic ash clouds abstract during the past 30 years more than 100 airplanes have inadvertently flown through clouds of volcanic ash from erupting volcanoes such encounters have caused millions of dollars in damage to the aircraft and have endangered the lives of tens of thousands of passengers in a few severe cases total engine failure resulted when ash was ingested into turbines and coating turbine blades these incidents have prompted the establishment of cooperative efforts by the international civil aviation organization and the volcanological community to provide rapid notification of eruptive activity and to monitor and forecast the trajectories of ash clouds so that they can be avoided by air traffic ash cloud properties such as plume height ash concentration and three dimensional ash distribution have been monitored through non conventional remote sensing techniques that are under active development forecasting the trajectories of ash clouds has required the development of volcanic ash transport and dispersion models that can calculate the path of an ash cloud over the scale of a continent or a hemisphere volcanological inputs to these models such as plume height mass eruption rate eruption duration ash distribution with altitude and grain size distribution must be assigned in real time during an event often with limited observations databases and protocols are currently being developed that allow for rapid assignment of such source parameters in this paper we summarize how an interdisciplinary working group on eruption source parameters has been instigating research to improve upon the current understanding of volcanic ash cloud characterization and predictions improved predictions of ash cloud movement and air fall will aid in making better hazard assessments for aviation and for public health and air quality

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

detection of gravity waves across the usarray a case study abstract barometers deployed as part of the usarray transportable array ta recorded large 300 pa peak to peak gravity waves or gust fronts that originated near a severe tornadic storm system in the southern united states on april 27 2011 we present a new method in which the ta is divided into a large number of elemental sub arrays each 3 element sub array triad is sufficiently closely spaced so that the long period gravity wave signal is coherent but large enough to provide a robust estimate of the signal s direction and speed the results from each triad are combined to follow the progress of gravity waves as they propagate across the ta over 2 days in late april 2011 we observe a large high amplitude gravity wave spanning a region over 200 000 km2 progressing to the nnw away from the tornadic storm region we also observe gravity waves with lower amplitudes and smaller spatial extent along the gulf coast propagating southward away from the storm region this study demonstrates the functionality of the usarray pressure sensors for analyzing gravity wave dynamics over periods greater than 40 min and across a wide region in principle the method could be applied to study other long period wave phenomena recorded by any dense large scale network and is not limited to gravity waves

volcanic lightning and plume behavior reveal evolving hazards during the april 2015 eruption of calbuco volcano chile soon after the onset of an eruption model forecasts of ash dispersal are used to mitigate the hazards to aircraft infrastructure and communities downwind however it is a significant challenge to constrain the model inputs during an evolving eruption here we demonstrate that volcanic lightning may be used in tandem with satellite detection to recognize and quantify changes in eruption style and intensity using the eruption of calbuco volcano in southern chile on 22 and 23 april 2015 we investigate rates of umbrella cloud expansion from satellite observations occurrence of lightning and mapped characteristics of the fall deposits our remote sensing analysis gives a total erupted volume that is within uncertainty of the mapped volume 0 56 0 28 km3 bulk observations and volcanic plume modeling further suggest that electrical activity was enhanced both by ice formation in the ash clouds 10 km above sea level and development of a low level charge layer from ground hugging currents

infrasound events detected with the southern california seismic network 1 we examine continuous data from the southern california seismic network from 2003 and identify infrasound acoustic waves from 76 previously undetected events using waveform cross correlation of the signal envelope functions we determine their relative arrival times and estimate source locations the waves travel at acoustic speeds of 320 m s and are observed in seismic records up to 450 km from their probable source locations off the west coast of southern california the dominant daylight occurrence of the events points to a man made source related to military activity the events are mostly recorded in the winter and spring when atmospheric conditions trap acoustic energy near the earth s surface and favor propagation to the west these results suggest that data from regional and global seismic networks can supplement observations from infrasound arrays for comprehensive test ban treaty monitoring and geophysical applications such as volcano monitoring bolide detection atmospheric acoustic sources and atmospheric tomography

a global study of volcanic infrasound characteristics and the potential for long range monitoring abstract volcanic infrasound from explosive eruptions is detectable at distances up to 1000 s of km and is often recorded on the international monitoring system ims infrasound network though infrasound produced by individual volcanoes has previously been studied more general relationships between infrasound characteristics and eruption parameters remain unclear therefore using a dataset comprising 110 events at 39 globally distributed volcanoes we assess the ability of the ims to monitor remote volcanoes and investigate whether volcanic infrasound exhibits consistent trends across a range of eruption styles and intensities acoustic pressure amplitude and frequency content of the volcanic infrasound were measured and acoustic energy was also calculated these were compared along with the maximum distance of detection for each event to the maximum plume height reported for the event which was used as a proxy for event intensity of the events investigated 62 were detected by at least one infrasound station the maximum distance at which an event was detected generally increased with the plume height and infrasound produced during the eruption of manam png in january 2005 which produced a plume which rose over 20 km above the summit was detected at a distance of 10 671 km total acoustic energy and acoustic pressure amplitude corrected for geometrical spreading increased with plume height whilst the lowest frequency present in the volcanic infrasound decreased additionally relationships seen between infrasound characteristics and eruption plume height indicate that analyses of this data alone could constrain vital estimates of plume heights for otherwise un observed eruptions taken together these findings indicate that if made available for this purpose in the future the ims infrasound network could complement existing monitoring techniques by detecting and characterising eruptions at remote volcanoes which often have no local monitoring networks

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

airwaves generated by an underwater explosion implications for volcanic infrasound 1 a shallow explosion in a fluid is one of the fundamental processes of airwave generation in volcanic eruptions to better understand the mechanism of the airwave generation underwater explosion experiments were conducted although the underwater explosions have been intensely studied over the last century airwaves have received little attention in this study pressure waves were measured in air and under water and the corresponding motion of the water surface was captured by a high speed video camera airwaves and associated styles of the surface motion show similarities determined by the scaled depth defined as the depth divided by the cubic root of the explosion energy the air waveforms are quite different from the pressure waves measured in the water and cannot be completely explained by linear transmission of pressure waves from water to air the mechanism of airwave generation is a combination of wave transmission and dynamics of the interface boundary the first mechanism directly reflects the explosion source and the same source is also observed as the underwater pressure waves on the other hand the second is not necessarily visible in the underwater pressure waves but will provide information on the mechanical properties and behavior of the material above the explosion source each mechanism is analyzed in the experiments

interpretation and utility of infrasonic records from erupting volcanoes abstract in the most basic seismo acoustic studies at volcanoes infrasound monitoring enables differentiation between sub surface seismicity and the seismicity associated with gas release under optimal conditions complicated degassing signals can be understood relative explosion size can be assessed and variable seismo acoustic energy partitioning can be interpreted the extent to which these points may be investigated depends upon the quality of the infrasonic records a function of background wind noise microphone sensitivity and microphone array geometry and the type of activity generated by the volcano frequency of explosions bandwidth of the signals and coupling efficiency of the explosion to elastic energy to illustrate the features benefits and limitations of infrasonic recordings at volcanoes we showcase acoustic and seismic records from five volcanoes characterized by explosive degassing these five volcanoes erebus in antarctica karymsky in russia and sangay tungurahua and pichincha in ecuador were the focus of seismo acoustic experiments between 1997 and 2000 each case study provides background information about the volcanic activity an overview of visual observations during the period of monitoring and examples of seismo acoustic data we discuss the benefits and utility of the infrasound study at each respective volcano finally we compare the infrasound records and eruptive activity from these volcanoes with other volcanoes that have been the focus of previous seismo acoustic experiments

mapping complex vent eruptive activity at santiaguito guatemala using network infrasound semblance pyroclastic laden explosive eruptions from santiaguito volcano guatemala are vented from the 200 m diameter caliente dome summit and result in a superposition of spatially extensive and temporally sustained tens of seconds to minutes acoustic sources a network of infrasonic microphones distributed on various sides of the volcano record distinct waveforms which are poorly correlated across the network and suggestive of acoustic interference from multiple sources presuming the infrasound wavefield is a linear superposition of spatially and temporally distinct sub events we introduce a semblance mapping technique to recover the time history of the spatially evolving sources during successive time windows coincident high resolution video footage corroborates that both rapid dome uplift and individual explosive pulses are likely sources of high semblance infrasound that are identifiable during short 2 s time windows this study suggests that complex and network variable infrasound waveforms are produced whenever a volcanic vent source dimension is large compared to the wavelength of the sound being produced non compact infrasound radiators are probably commonplace at silicic volcanic systems where venting often occurs across a dome surface

infrasound monitoring of volcanoes to probe high altitude winds 1 active volcanoes in the vanuatu archipelago permanently generate infrasonic waves their monitoring over 1 year exhibits clear seasonal trends in the direction of arrival of the detected signals from summer to winter the azimuth variation reaches 15 this deviation is essentially due to the reversibility of the zonal stratospheric wind with season which strongly affects the deflection of the ray direction a three dimensional 3 d ray tracing modeling roughly explains the observed seasonal trend in the azimuth variation but underestimates its amplitude the discrepancy between the measurements and the results of simulation is explained by undervalued wind speeds in the upper atmosphere infrasonic observations are used as input of an inversion scheme for adjusting the vertical structure of the wind in the upper stratosphere and mesosphere it is shown that the mesospheric zonal winds are underestimated by at least 20 m s throughout the year with differences reaching 50 m s

western u s infrasonic catalog illuminating infrasonic hot spots with the usarray 1 in this study reverse time migration is applied to signals recorded by the 2007 08 usarray presumably due to acoustic to seismic coupling to detect and locate in two dimensional space and time 901 sources of atmospheric infrasound defining the western united states infrasonic catalog wusic the detections are visually inspected and ranked uncertainties are estimated using a bootstrap technique the method correctly locates most rocket motor detonations in utah and a bolide explosion in oregon with an average spatial accuracy of 50 km and 25 km respectively the origin time statistics for 2007 and 2008 events are nearly identical and suggest a predominant human origin the event locations illuminate repeating sources of infrasound or infrasonic hot spots in nevada utah and idaho that are spatially associated with active military areas the infrasonic arrivals comprise several branches that are observed to a range between 200 and 1500 km to the east and west of the epicenter in the winter and summer respectively the optimum group velocities are gaussian distributed and centered at 295 m s a seasonal variation in optimum group velocities exhibits good correlation with atmospheric temperature the results show that relatively dense seismic networks fill in the gaps between sparsely located infrasound arrays and provide valuable information for regional infrasonic source location and propagation studies specifically the catalogs presented here can be used to statistically validate and improve propagation models especially above the middle stratosphere where winds are not directly measured by ground based weather stations or meteorological satellites

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

volcanic lightning global observations and constraints on source mechanisms lightning and electrification at volcanoes are important because they represent a hazard in their own right they are a component of the global electrical circuit and because they contribute to ash particle aggregation and modification within ash plumes the role of water substance water in all forms in particular has not been well studied here data are presented from a comprehensive global database of volcanic lightning lightning has been documented at 80 volcanoes in association with 212 eruptions the volcanic explosivity index vei could be determined for 177 eruptions eight percent of vei 3 5 eruptions have reported lightning and 10 of vei 6 but less than 2 of those with vei 1 2 these findings suggest consistent reporting for larger eruptions but either less lightning or possible under reporting for small eruptions ash plume heights 142 observations show a bimodal distribution with main peaks at 7 12 km and 1 4 km the former are similar to heights of typical thunderstorms and suggest involvement of water substance whereas the latter suggest other factors contributing to electrical behavior closer to the vent reporting of lightning is more common at night 56 and less common in daylight 44 reporting also varied substantially from year to year suggesting that a more systematic observational strategy is needed several weak trends in lightning occurrence based on magma composition were found the bimodal ash plume heights are obvious only for andesite to dacite basalt and basaltic andesite evenly span the range of heights and rhyolites are poorly represented the distributions of the latitudes of volcanoes with lightning and eruptions with lightning roughly mimic the distribution of all volcanoes which is generally flat with latitude meteorological lightning on the other hand is common in the tropics and decreases markedly with increasing latitude as the ability of the atmosphere to hold water decreases poleward this finding supports the idea that if lightning in large deep eruptions depends on water substance then the origin of the water is primarily magma and not entrainment from the surrounding atmosphere seasonal effects show that more eruptions with lightning were reported in winter bounded by the respective autumnal and vernal equinoxes than in summer this result also runs counter to the expectations based on entrainment of local water vapor

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

remote sensing of volcanoes and volcanic processes integrating observation and modelling introduction volcanoes are often remote and have footprints that may extend across many hundreds or thousands of square kilometres they are generally inaccessible during eruption and may continue to be inaccessible for extended periods of time after eruption while their products can be scattered or dispersed over regional or global scales consequently since direct measurement can only provide us with part of the picture of many volcanic processes remote sensing is now playing an increasingly important role in advancing understanding of the science underlying volcanic behaviour on this planet and beyond e g mouginis mark et al 2000 sparks et al 2012 satellite airborne and ground based remote sensing are increasingly vital tools for monitoring active or potentially active volcanoes and assessing their likely real time or time averaged impact fig 1 at the same time the synoptic scale surveys that are often well suited to remote sensing techniques allow us to address questions about the fundamental processes that control volcano behaviour in a way that is not necessarily possible from individual case studies new research is often driven by technological advancements in the development of novel sensors or launching of new platforms meaning that the space agencies are increasingly involved in identifying scientific questions and priorities e g ferruci et al 2012 multiple and complementary data streams are increasingly being used both to monitor active volcanoes and advance volcanological science the key geophysical parameters that comprise monitoring data streams typically include the categories of i seismicity ii surface deformation iii thermal measurements and iv gas flux and composition data as major components while measurements of seismicity remain the domain of ground based seismometers remote sensing techniques have made major contributions in each of the others this special publication volume is concerned with the use of remote sensing at volcanoes it is split into three parts roughly arranged from the subsurface to the surface and then further afield as volcanic products are injected and dispersed into the atmosphere the papers span a range of applications of remote sensing techniques to monitor and understand a surface deformation b surface thermal anomalies and c gas fluxes as well as tracking ash and gas plumes from eruptions to gain insights into the extent of a volcano s impacts volcanology is driven in part by the operational concerns surrounding volcano monitoring and hazard and crisis management but the goal of volcanological science is at its heart to understand the processes that underlie volcanic activity this special publication is also concerned with how we go from observations to this deeper understanding including the progress that can be made by integrating observations and modelling while this volume focuses mainly on satellite based remote sensing integrating datasets from different platforms is also of vital importance and so papers on airborne remote sensing and measurement from both manned and unmanned aircraft are also included

rupture imaging of the mw 7 9 12 may 2008 wenchuan earthquake from back projection of teleseismic p waves 1 the mw 7 9 wenchuan earthquake of 12 may 2008 was the most destructive chinese earthquake since the 1976 tangshan event tens of thousands of people were killed hundreds of thousands were injured and millions were left homeless here we infer the detailed rupture process of the wenchuan earthquake by back projecting teleseismic p energy from several arrays of seismometers this technique has only recently become feasible and is potentially faster than traditional finite fault inversion of teleseismic body waves therefore it may reduce the notification time to emergency response agencies using the iris dmc we collected 255 vertical component broadband p waves at 30 95 from the epicenter we found that at periods of 5 s and greater nearly all of these p waves were coherent enough to be used in a global array we applied a simple down sampling heuristic to define a global subarray of 70 stations that reduced the asymmetry and sidelobes of the array response function arf we also considered three regional subarrays of seismometers in alaska australia and europe that had apertures less than 30 and p waves that were coherent to periods as short as 1 s individual arfs for these subarrays were skewed toward the subarrays however the linear sum of the regional subarray beams at 1 s produced a symmetric arf similar to that of the groomed global subarray at 5 s for both configurations we obtained the same rupture direction rupture length and rupture time we found that the wenchuan earthquake had three distinct pulses of high beam power at 0 23 and 57 s after the origin time with the pulse at 23 s being highest and that it ruptured unilaterally to the northeast for about 300 km and 110 s with an average speed of 2 8 km s it is possible that similar results can be determined for future large dip slip earthquakes within 20 30 min of the origin time using relatively sparse global networks of seismometers such as those the usgs uses to locate earthquakes in near real time

the 7 8 august 2008 eruption of kasatochi volcano central aleutian islands alaska 1 kasatochi volcano in the central aleutian islands erupted unexpectedly on 7 8 august 2008 kasatochi has received little study by volcanologists and has had no confirmed historical eruptions the island is an important nesting area for seabirds and a long term biological study site of the u s fish and wildlife service after a notably energetic preeruptive earthquake swarm the volcano erupted violently in a series of explosive events beginning in the early afternoon of 7 august each event produced ash gas plumes that reached 14 18 km above sea level the volcanic plume contained large amounts of so2 and was tracked around the globe by satellite observations the cumulative volcanic cloud interfered with air travel across the north pacific causing many flight cancelations that affected thousands of travelers visits to the volcano in 2008 2009 indicated that the eruption generated pyroclastic flows and surges that swept all flanks of the island accumulated several tens of meters of pyroclastic debris and increased the diameter of the island by about 800 m pyroclastic flow deposits contain abundant accidental lithic debris derived from the inner walls of the kasatochi crater juvenile material is crystal rich silicic andesite that ranges from slightly pumiceous to frothy pumice fine grained pyroclastic surge and fall deposits with accretionary lapilli cover the lithic rich pyroclastic flow deposits and mark a change in eruptive style from episodic explosive activity to more continuous ash emission with smaller intermittent explosions pyroclastic deposits completely cover the island but wave erosion and gully development on the flanks have begun to modify the surface mantle of volcanic deposits

explosions and periodic tremor at karymsky volcano kamchatka russia summary the explosions of karymsky volcano often produce signals containing a sequence of repeating pulses recorded on acoustic and seismic sensors known as chugging the amplitudes of these pulses correlate with the time interval between pulses for a given measured acoustic pressure seismic amplitudes take on arbitrary values up to a specific empirically determined threshold conversely events with a small seismic amplitude yielded acoustic waves with large variations and large amplitude seismic events corresponded to large acoustic waves these observations are not consistent with a source modelled by a resonating conduit rather a model consisting of a sequence of discrete pulses explains the data and provides a framework for understanding the dynamics of degassing at the vent the physical model for chugging involves a time varying narrowing vent where gasses are released in a series of oscillations which appear to be harmonic but instead are modelled as short term transients or discrete pulses suggestive of choked flow

blast waves from violent explosive activity at yasur volcano vanuatu 1 infrasonic and seismic waveforms were collected during violent strombolian activity at yasur volcano vanuatu averaging 3000 seismic events showed stable waveforms evidencing a low frequency 0 1 0 3 hz signal preceding 5 6 s the explosion infrasonic waveforms were mostly asymmetric with a sharp compressive 5 106 pa onset followed by a small long lasting rarefaction phase regardless of the pressure amplitude the ratio between the positive and negative phases was constant these waveform characteristics closely resembled blast waves infrared imagery showed an apparent cold spherical front 20 m thick which moved between 342 and 405 m s before the explosive hot gas fragments cloud we interpret this cold front as that produced by the vapor condensation induced by the passage of the shock front we suggest that violent strombolian activity at yasur was driven by supersonic dynamics with gas expanding at 1 1 mach number inside the conduit

the influences of ecological factors on tiger bush and dotted bush patterns along a gradient from mali to northern burkina faso seven catenas across contracted vegetation patterns including tiger bush and dotted bush were studied in the gourma region in mali and in northern burkina faso mean annual rainfall 200 550 mm the tiger bush encompasses an alternate succession of bands oriented nearly perpendicularly to the wind direction ne sw sandy grassy microdune sloped band of bare crusted ground and woody depressive band a similar succession without wind orientation is found for the dotted bush in this region tiger bush develops under specific conditions 1 same orientation but opposite direction of wind and slope 2 sedimentary and metamorphic rocks sandstone and schist ironcrust 3 shallow 1 m and impervious soils under such circumstances the dynamics of banded patterns result from alternate and successive action of water and wind erosion field evidences showed that vegetation bands migrate upwards with a velocity of 0 2 0 7 m yr 1

imaging short period seismic radiation from the 27 february 2010 chile mw 8 8 earthquake by back projection of p pp and pkikp waves 1 teleseismic short period 0 5 5 s p waves from the 27 february 2010 chile earthquake mw 8 8 are back projected to the source region to image locations of coherent short period seismic wave radiation several receiver array configurations are analyzed using different p wave arrivals including networks of stations in north america p japan pkikp and europe pp as well as a global configuration of stations with a broad azimuthal distribution and longer period p waves 5 20 s coherent bursts of short period radiation from the source are concentrated below the chilean coastline along the downdip portion of the megathrust the short period source region expands bilaterally with significant irregularity in the radiation comparison with finite fault slip models inverted from longer period seismic waves indicates that the regions of large slip on the megathrust are located updip of the regions of short period radiation a manifestation of frequency dependent seismic radiation similar to observations for the great 2011 tohoku earthquake mw 9 0 back projection of synthetic p waves generated from the finite fault models demonstrates that if the short period energy had radiated with the same space time distribution as the long period energy back projection analysis would image it in the correct location updip we conclude that back projection imaging of short period signals provides a distinct view of the seismic source that is missed by studies based only on long period seismic waves geodetic data and or tsunami observations

an infrasound array study of mount st helens the ongoing activity of mount st helens provides an opportunity to study the infrasonic wavefield produced by an active silica rich volcano in late october 2004 as a pilot experiment for the acoustic surveillance for hazardous eruptions ashe project we deployed two infrasound arrays each co located with a broadband seismometer and weather station to continuously record seismo acoustic signals from mount st helens the nearest array coldwater was deployed on the northern flank of the volcano 13 km from the summit the second array sacajawea was deployed 250 km east of the volcano at a distance where stratospherically ducted acoustic waves may be expected during the winter this paper presents an overview of the experimental setup and preliminary results from this unique data set eruptions on january 16th 2005 and march 9th 2005 produced strong infrasonic signals the aseismic january 16th eruption signal lasted 9 4 min beginning at 11 20 44 01 16 05 utc while the march 9th eruption signal lasted 52 8 min beginning at 01 26 17 03 09 05 utc with the main steam and ash venting stage probably lasting 7 2 min the march 9th signal was an order of magnitude larger than the january 16th signal and was clearly recorded 250 km east at the sacajawea array infrasonic expressions of long period lp seismic events drumbeats have also been intermittently observed and are recorded as acoustic waves mimicking the waveform and temporal sequence of their seismic counterparts these acoustic observations provide important constraints for source models of long period events and eruptions

the effects of palygorskite on chemical and physico chemical properties of soils a review abstract very little was known about how palygorskite affects soil properties when it constitutes a significant component of the soil clay fraction this constituted a serious impediment for the proper management of palygorskite containing soils under irrigated agriculture the present review is intended to summarize studies on the effects of palygorskite on chemical and physico chemical properties of soils carried out in recent years and to discuss future research required in this area when palygorskite containing soils are involved in irrigation practices release of mg from palygorskite into the soil solution will occur magnesium as an exchangeable cation in turn is known to decrease aggregate stability and to enhance the dispersivity of the soil clay fractions on the other hand magnesium as a dissolved cation is known to improve phosphorus availability in arid soils knowledge of factors affecting rheological properties of soil clay suspensions is essential for understanding of mechanisms of water and solid particle transfer through the soil profile the rheological behavior of soil clay suspensions is however complex and cannot be predicted from that of suspensions of standard clays although the flocculation value of palygorskite at near neutral ph is significantly lower than that of smectite the presence of palygorskite in the soil clay fraction will not affect the flocculation value of the soil clay since smectite which is always present in the clay fraction of palygorskite containing soils has a dispersive effect on palygorskite palygorskite has the strongest disaggregation potential and the highest ability to migrate in the soil among common phyllosilicates such as smectite and kaolinite palygorskite particles are thus likely to move preferentially over smectite and kaolinite downward in the soil profile and eventually to clog soil pores disaggregation and migration of palygorskite from the surface soil during rainfall and or irrigation may have an effect on the degree of erosion as well palycretes duripans in which the cementing material is dominantly composed of palygorskite can be formed in some landscapes where palycretes occur close to the surface plant growth is severely impeded palycretes also reduce water permeability of the soils creating water logged conditions that necessitate drainage installation although some progress has been made recently in understanding the effects of palygorskite on chemical and physico chemical properties of soils much research remains to be done performing some additional studies on disaggregation potential and migration ability of palygorskite under conditions close to those in the field is strongly desirable scanning electron microscopy observations on possible changes in aggregation of palygorskite in soils following intensive irrigation might be useful studies of the rheological behavior of soil clays with different mineralogical composition and palygorskite containing soil clays in particular are strongly encouraged there is a need as well to study interactions of various contaminants both organic and inorganic with palygorskite containing soil clays