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

monitoring volcanic activity using correlation patterns between infrasound and ground motion 1 this paper presents a simple method to distinguish infrasonic signals from wind noise using a cross correlation function of signals from a microphone and a collocated seismometer the method makes use of a particular feature of the cross correlation function of vertical ground motion generated by infrasound and the infrasound itself contribution of wind noise to the correlation function is effectively suppressed by separating the microphone and the seismometer by several meters because the correlation length of wind noise is much shorter than wavelengths of infrasound the method is applied to data from two recent eruptions of asama and shinmoe dake volcanoes japan and demonstrates that the method effectively detects not only the main eruptions but also minor activity generating weak infrasound hardly visible in the wave traces in addition the correlation function gives more information about volcanic activity than infrasound alone because it reflects both features of incident infrasonic and seismic waves therefore a graphical presentation of temporal variation in the cross correlation function enables one to see qualitative changes of eruptive activity at a glance this method is particularly useful when available sensors are limited and will extend the utility of a single microphone and seismometer in monitoring volcanic activity

long period events and tremor at popocatepetl volcano 1994 2000 and their broadband characteristics following an initial phreatic eruption on 21 december 1994 activity at popocatepetl has been dominated by fumarolic emissions interspersed with more energetic emissions of ashes and gases a phase of repetitive dome building and dome destroying episodes began in march 1996 and is still ongoing at present we describe the long period lp seismicity accompanying eruptive activity at popocatepetl from december 1994 through may 2000 using data from a three component broadband seismometer located 5 km from the summit crater the broadband records display a variety of signals with periods ranging in the band 0 04 90 s long period events and tremor with typical dominant periods in the range 0 3 2 0 s are the most characteristic signals observed at popocatepetl these signals appear to reflect volumetric sources driven by pressure fluctuations associated with the unsteady transport of gases beneath the crater very long period vlp signals are also observed in association with lp events and tremor the vlp signals which accompany lp events display ricker like wavelets with periods near 36 s whereas vlp signals associated with tremor waveforms typically show sustained oscillations at periods ranging up to 90 s the spectra and particle motion patterns remain similar from event to event for the majority of lp and tremor signals analyzed during the time span of this study suggesting a repeated non destructive activation of a common source hypocenters determined by phase pick analyses of selected lp events recorded by the seven station permanent popocatepetl short period network suggest that the majority of these events are confined to a source region in the top 1 5 km below the crater floor the repetitive occurrences of vlp signals with closely matched waveform characteristics are consistent with a non destructive reactivation of at least two sources one source appears to coincide with the main source region of lp seismicity whereas the second is a deeper source whose activity appears to be intimately linked with episodes of monochromatic tremor

source mechanism of vulcanian degassing at popocatepetl volcano mexico determined from waveform inversions of very long period signals 1 the source mechanism of very long period vlp signals accompanying volcanic degassing bursts at popocatepetl is analyzed in the 15 70 s band by minimizing the residual error between data and synthetics calculated for a point source embedded in a homogeneous medium the waveforms of two eruptions 23 april and 23 may 2000 representative of mild vulcanian activity are well reproduced by our inversion which takes into account volcano topography the source centroid is positioned 1500 m below the western perimeter of the summit crater and the modeled source is composed of a shallow dipping crack sill with easterly dip of 10 intersecting a steeply dipping crack northeast striking dike dipping 83 northwest whose surface extension bisects the vent both cracks undergo a similar sequence of inflation deflation and reinflation reflecting a cycle of pressurization depressurization and repressurization within a time interval of 3 5 min the largest moment release occurs in the sill showing a maximum volume change of 500 1000 m3 pressure drop of 3 5 mpa and amplitude of recovered pressure equal to 1 2 times the amplitude of the pressure drop in contrast the maximum volume change in the dike is less 200 300 m3 with a corresponding pressure drop of 1 2 mpa and pressure recovery equal to the pressure drop accompanying these volumetric sources are single force components with magnitudes of 108 n consistent with melt advection in response to pressure transients the source time histories of the volumetric components of the source indicate that significant mass movement starts within the sill and triggers a mass movement response in the dike within a few seconds such source behavior is consistent with the opening of a pathway for escape of pent up gases from slow pressurization of the sill driven by magma crystallization the opening of this pathway and associated rapid evacuation of volcanic gases induces the pressure drop pressure recovery in the magma filling the sill is driven by diffusion of gases from the resulting supersaturated melt into bubbles assuming a penny shaped crack at ambient pressure of 40 mpa the observed pressure and volume variations can be modeled with the following attributes crack radius 100 m crack aperture 5 m bubble number density 1010 1012 m 3 initial bubble radius 10 6 m final bubble radius 10 5 m and net decrease of gas concentration in the melt 0 01 wt

application of wave theoretical seismoacoustic models to the interpretation of explosion and eruption tremor signals radiated by pavlof volcano alaska tremor and explosion signals recorded on september 29 during the fall 1996 pavlof eruption are interpreted using video images field observations and seismic data waveform analysis of tremor and explosions provided estimates of the melt s volcano acoustic parameters and the magma conduit dimensions initial mass fractions of 0 25 water and 0 025 carbon dioxide in the melt can explain the resonance characteristics of the tremor and explosion pulses inferred from seismic data the magma conduit is modeled as a three section rectangular crack we infer that the tremor radiating region consists of the lowermost two sections both with cross sectional areas of 10 m2 the deeper section is 43 m long with magma sound speed of 230 m s density of 2600 kg m3 and viscosity of 1 0 106 pa s the section above it defined by the water nucleation depth is 64 m long with magma sound speed of 91 m s density of 2000 kg m3 and viscosity of 1 4 l06 pa s an average magma flow velocity of 1 2 m s with superposed random oscillations acts as the tremor source explosions are postulated to occur in the uppermost part of the magma conduit after water comes out of solution the explosion source region consists of a 15 m long section with cross sectional area of 20 m2 sound speed of 51 m s density of 1000 kg m3 and viscosity of 1 5 103 pa s a burst pressure of 220 mpa at 14 m depth would generate an acoustic pulse whose amplitude and character match the observed signal waveform analysis of the explosion pulses shows that the explosive event may be preceded by a long period fluid transient which may trigger the metastable magma gas mixture the modeling procedure illustrates the synergy of fluid dynamic seismic and acoustic models and data with geological and visual observations

what is shale to a petrophysicist what is a shale in a recent presentation to the geophysical society of houston rune holt attempted to answer the question by listing three attributes of a shale 1 clay minerals should constitute the load bearing framework 2 shales have nanometer pore sizes and nanodarcy permeability 3 surface area is large and water is adsorbed on surfaces or bound inside clay platelets this is a good definition of shales but perhaps a typical geophysicist may not know how to apply it in practice with typical data sets in particular a geophysicist often has no core data and is limited to well logs this article describes how petrophysicists traditionally distinguish sands from shales using typical well logs in clastic sections only lean shales with minimal organic content are considered here

very long period signals associated with vulcanian explosions at popocatepetl volcano mexico very long period vlp seismic signals associated with large summit eruptions of popocatepetl volcano in the last four years are investigated using data from a broadband seismometer 0 04 120 s deployed on the north flank of the volcano at a radial distance of 5 km from the active crater the vlp signals associated with individual eruptions share similar waveforms discrete vlp signals accompanying long period lp events also share similar signatures and have dominant periods that are nearly identical to those observed in the vlp waveforms of explosions the vlp particle motions for eruption onsets consistently point to a source located a few km beneath the crater the vlp ground displacement response to each explosion is marked by a compression followed by a dilatation and terminating with another compression suggesting a sequence of pressurization depressurization repressurization of the conduit the repetitive nature of the waveforms points to a non destructive source process which has remained active in the magmatic system of popocatepetl at least since april 1997

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

atmospheric expansion wave simulations of popocatepetl explosions 1 we present a compressible gasdynamic numerical model that utilizes a three dimensional adaptive grid to provide high spatial resolution of an expanding compression wave we apply this model to recent explosions of popocatepetl volcano in mexico by incorporating both high resolution topography for a lower boundary and atmospheric stratification based upon climatological thermodynamic soundings explosions are simulated by the instantaneous release of an overpressure in a prescribed volume over the volcano s crater the results show a compression wave that propagates as a supersonic shock close to the explosion transforming into a sonic compression wave at larger distances we validate the model predictions by comparing them to pressure time series measured by a microbarograph located 11 km away from the crater with the model validation we estimate the equivalent initial internal energy of the explosions to range from 2 1013 j to 1 1 1015 j

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

infrasonic tremor observed at kīlauea volcano hawai i 1 infrasonic array data collected at k lauea volcano hawai i during november 12 21 2002 indicate that the active vents and lava tube system near the pu u vent complex emit almost continuous infrasound in the 0 3 10 hz frequency band the spectral content of these infrasonic signals matches well that of synchronous seismic tremor in sites protected from wind noise significant signal to noise ratios were recorded as far as 13 km from the crater of pu u the infrasonic recordings suggest that one or more tremor sources may be close to the surface in addition these results demonstrate that adequate site and instrument selections for infrasonic arrays are essential in order to obtain consistent and reliable infrasonic detections

high broadband seismoacoustic signature of vulcanian explosions at popocatepetl volcano mexico author s matoza robin samuel arciniega ceballos a sanderson r w mendo perez g rosado fuentes a chouet b a

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

long period seismic source characterization at popocatepetl volcano mexico 1 the seismicity of popocatepetl is dominated by long period and very long period signals associated with hydrothermal processes and magmatic degassing we model the source mechanism of repetitive long period signals in the 0 4 2 s band from a 15 station broadband network by stacking long period events with similar waveforms to improve the signal to noise ratio the data are well fitted by a point source located within the summit crater 250 m below the crater floor and 200 m from the inferred magma conduit the inferred source includes a volumetric component that can be modeled as resonance of a horizontal steam filled crack and a vertical single force component the long period events are thought to be related to the interaction between the magmatic system and a perched hydrothermal system repetitive injection of fluid into the horizontal fracture and subsequent sudden discharge when a critical pressure threshold is met provides a non destructive source process

the giant popocatepetl stirs in about 800 ad the mexican volcano popocatepetl exploded sending up several cubic kilometres of ash and pumice and burying the surrounding area since then it has been relatively quiet but every few decades it threatens to explode again which could this time be catastrophic as the area is now one of the most densely populated in mexico seismic activity and eruptions are now increasing with ash falls even 70 km away in mexico city

planktogenic eustatic control on cratonic oceanic carbonate accumulation data on mass age distributions and latitudinal limits of mesozoic cenozoic shelf carbonate on cenozoic deepening of the ccd in all major ocean basins and on the abundance of pelagic chalk in epicontinental carbonate sequences indicate that the primary locus of global limestone deposition has gradually shifted from shallow cratonic to deep oceanic settings since jurassic time this change is generally coincident with progressive emergence of continents during global regression as well as with taxonomic diversification of calcareous plankton and implicates one or both processes as the primary control on carbonate sediment partitioning between shallow and deep marine reservoirs widespread pelagic carbonate does not occur with phanerozoic ophiolite sequences until the late mesozoic and generally corresponds to origins of planktonic foraminifera and diversification of coccolithophorids similarly cratonic chalk is largely re stricted to cretaceous sections correlation of mesozoic cenozoic positions of t

dissection of a composite volcanic earthquake at santiaguito guatemala 1 volcano earthquake sources associated with eruptions at santiaguito volcano in guatemala are complex rock fracture fluid flow and gas expansion occur at variable time scales and induce superposed ground motions including both static and dynamic deformation and atmospheric pressure disturbances dissection of this composite event is facilitated through extra seismic observations such as infrasound geodetic and visual monitoring multi parametric investigation of an eruptive event on jan 4th 2009 reveals increased degassing apparent as both geodetic tilt and harmonic seismo infrasonic tremor preceding an explosive event the explosive event itself entails surface dome uplift multiple eruptive pulses and subsequent re equilibration of the volcanic edifice manifested in derived tilt we report here on an integrated approach to discerning the physical processes at the actively effusing and exploding santiaguito volcano and describe the composite earthquake that occurs here

acoustically induced seismic waves when an airborne acoustic wave is incident at the ground surface energy is coupled into the ground as seismic motion in a previous publication sabatier et al j acoust soc am 78 1345 1352 1986 the ground surface was modeled as an air filled poroelastic layer overlying a semi infinite nonporous elastic substrate in this work the model is extended to include calculations of the normal seismic transfer function ratio of the normal soil particle velocity at a depth d to the acoustic pressure at the surface measurements of the seismic transfer function for three sites are considered and compared to the predicted values generally good agreement between theory and experiment is achieved by best fits assuming the soil or seismic attenuation this is accomplished by specifying the ratio of the imaginary to real part of the measured seismic p and s wave speeds the seismic transfer functions quite typically exhibit minima and maxima which are associated with the seismic layering of the ground su

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