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

a new model for the emplacement of columbia river basalts as large inflated pahoehoe lava flow fields extensive flows of the columbia river basalt crb group in washington oregon and idaho are dominantly inflated compound pahoehoe sheet lavas early studies recognized that crb lavas are compound pahoehoe flows with textures suggesting low flow velocities but it was thought that the great thickness and extent of the major flows required very rapid emplacement as turbulent floods of lava over a period of days or weeks however small volume 1 km compound pahoehoe flows on kilauea hawai i demonstrate that such flows can thicken by at least an order of magnitude through gradual inflation and the same mechanism has been proposed for larger 10 20 km3 pahoehoe flows in iceland the vertical distribution of vesicles and other morphologic features within crb lava flows indicate that they grew similarly by inflation small pahoehoe lobes at the base and top of many crb pahoehoe lava flows indicate emplacement in a gradual piecemeal manner rather than as a single flood we propose that each thick crb sheet flow was active for months to years and that each group of flows produced by a single eruption a flow field was emplaced slowly over many years

estimates of plume height from infrasound for regional volcano monitoring abstract present efforts in volcano monitoring particularly in southeast asia rely on the combination of local data generally gathered at less than 100 km from the volcano and satellite remote sensing while this combination has its strengths there are still weaknesses that the use of ground based remote sensing data such as distant infrasound measurements could help alleviate infrasound offers tools for detecting and characterizing volcanic plumes independent of cloud cover and time of day larger volcanic eruptions generate infrasound that is related to the plume and offers a unique view into eruption dynamics within the context of monitoring past research has demonstrated that infrasound can be used to estimate source parameters such as the rate at which material is ejected from volcanic vents during eruptions these are key input parameters into empirical and numerical models to estimate the height of volcanic plumes atmospheric ash transport and dispersion here we demonstrate the use of remote infrasound in estimating the height of volcanic plumes including a case study on the may 30 2014 plume from the volcano sangeang api in indonesia we were able to determine the plume height using infrasound gathered from 2000 to over 5000 km distance from the volcano during the january 2020 eruption of taal volcano in the philippines this method was applied to remote infrasound recorded 1650 km to the east we show that our workflow can be implemented in near real time offering an effective tool for rapid plume height measurement including associated uncertainties when volcanic clouds are not visible from the ground or space

observations of surf infrasound in hawai i 1 comparison of ocean buoy measurements with infrasonic array data collected during the epic winter of 2002 2003 shows a clear relationship between breaking ocean wave height and infrasonic signal levels in addition infrasonic arrays allow the identification of distinct breaking zones along the shoreline our observations suggest that infrasonic measurements can be used in conjunction with buoys to estimate wave heights identify regions of high wave action and validate surface wave propagation models

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

thermal erosion by laminar lava flows thermal erosion by hot lavas during their laminar flow over cold ground is investigated both theoretically and experimentally an analysis of the steady forced convective heat transfer by a laminar channel flow at large peclet numbers is presented which is used to determine the final steady state erosion velocity as well as the thicknesses and timescales of the associated thermal boundary layers in both the lava and ground the initial transient period involving the growth and remelting of a basal chill layer is also quantified laboratory experiments are described in which hot molten wax flowed over and thermally eroded an underlying bed of solidified wax the experimental observations of chill formation and thermal erosion are found to be in excellent agreement with the theoretical predictions the theory is applied to predict rates of thermal erosion consistent with those observed in recent flows of basaltic lava in hawaii and of carbonatite lava in tanzania

the roza member columbia river basalt group a gigantic pahoehoe lava flow field formed by endogenous processes we present studies on the physical volcanology of the 15 ma roza member of the wanapum formation in the columbia river basalt group the roza member represents a compound pahoehoe flood basalt lava flow field with an area of 40 300 km 2 and a volume of 1300 km 3 it consists of 4 major lava flows each composed of numerous decimeter to kilometer long pahoehoe lobes roza lavas feature a wide range of pahoehoe surface structures such as lava rise plateaus tumuli and surface breakouts and we illustrate that the lava morphology is inconsistent with previous proposals of rapid emplacement for these lavas an integral component of the roza flow field is the sheet lobe with internal structures identical to those of inflated pahoehoe sheet lobes from hawaii and iceland both at the same scale and at much larger scales we identify a three part division of the sheet lobes into basal crust lava core and lava crust which are interpreted as the equivalent to the bottom crust the liquid lava core and the surface crust of an active inflating pahoehoe lobe the upper lava crust grows continuously during lava emplacement and its growth rate can be approximated by conductive cooling this relationship is used to calculate the emplacement time for individual roza sheet lobes and to derive a first order estimate on the duration of the roza eruption the results indicate that the emplacement of individual roza lobes lasted for months to years and that the lava flow field was constructed over a period of at least 14 years we propose that the roza flows achieved great areal dimensions and thicknesses by inflation and endogenous growth as the lava flowed from vent to flow front it traveled under an insulating crust which maintained cooling rates of 0 1 c km and allowed for efficient transport of lava over distances up to 300 km

finite difference synthesis of infrasound propagation through a windy viscous atmosphere application to a bolide explosion detected by seismic networks summary a finite difference time domain fdtd algorithm has been developed to model linear infrasound propagation through a windy viscous medium the algorithm has been used to model signals from a large bolide that burst above a dense seismic network in the us pacific northwest on 2008 february 19 we compare synthetics that have been computed using a g2s ecmwf atmospheric model to signals recorded at the seismic networks located along an azimuth of 210 from the source the results show that the timing and the range extent of the direct stratospherically ducted and thermospherically ducted acoustic branches are accurately predicted however estimates of absorption obtained from standard attenuation models sutherland bass predict much greater attenuation for thermospheric returns at frequencies greaterthan0 1hzthanisobserved weconcludethateitherthestandardabsorptionmodelfor the thermospheric is incorrect or that thermospheric returns undergo non linear propagation at very high altitude in the former case a better understanding of atmospheric absorption at high altitudes is required in the latter a fully non linear numerical method is needed to test our hypothesis that higher frequency arrivals from the thermosphere result from non linear propagation at thermospheric altitudes

utilizing the solution of sound diffraction by a thin screen to evaluate infrasound waves attenuated around volcano topography abstract the observation of infrasound signals in the vicinity of volcanoes is a powerful tool to understand the source of explosive volcanic activity although the propagation of infrasound signals is affected by the local topography such effects are often ignored in the analysis leading to potential misinterpretation of the source parameters in this study we propose a simple low cost method of evaluating the attenuation of infrasound signals by topographical barriers in this method the first step approximates the elevation profile between the source and station into one thin screen like barrier then a mathematically exact solution of a sound diffraction problem is adopted to evaluate the attenuation of the infrasound amplitudes to assess the validity of this method the obtained estimates are compared with actual infrasound data observed at sakurajima volcano japan the results show that the estimates of relative amplitude to a reference station are more accurate than those considering only geometrical spreading suggesting that the proposed method provides a useful first order investigation of the attenuation of infrasound signals the spatial distribution of the attenuation in the entire area of the volcano was also estimated revealing a significant contrast between the eastern and western sides of the study area variations in signal attenuation also depend on the radial distance from the crater and were mainly attributed to variations of the relative screen height to the incident wavelength

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

100 years of earthquakes in the pamir region as recorded in juniper wood a case study of tajikistan abstract active tectonics reflect high seismicity rates in the pamir and surrounding areas long lived trees growing in the western pamir alay mountains are affected by ground accelerations and seismic induced geomorphic processes at a high mountain site in the pamir alay 45 juniper trees were sampled in order to analyze the potential role of these trees in the reconstruction of disturbance events although the trees have a maximum age c 500 years only the period of the last 100 years was analyzed aiming for the dendrochronological identification of earthquake events known by historic documents and measurements analysis mainly showed non climatic growth suppression and releases these signals were identified as the results of tectonic disturbances tree ring data recorded many earthquakes from which the most distinct were 1907 1923 1943 1955 1982 and 1998 the 1907 and 1923 large earthquakes took place after the vegetation period therefore growth reduction appeared in the following year the 1943 1955 1982 and 1998 events occurred just before or during the vegetation period and therefore induced the immediate reduction of tree rings in the earthquake year the identification of the characteristic growth ring patterns which are a response to large earthquakes will enable the reconstruction of these events in the past on the basis of centuries long dendrochronological records

observations of infrasound from surf in southern california 1 we observe 10 000 s of infrasound signals annually in the frequency range from 1 5 hz at the i57us infrasound array in southern california 75 of these signals arrive at i57us at azimuths between 260 and 320 degrees there is a good correlation between the amplitudes of signals from 260 320 and wave height measurements offshore southern california providing firm evidence that the signals from these azimuths are caused by surf action by modeling the propagation of infrasound for specific time periods using 3d ray tracing and up to date atmospheric models we show that amplitudes of signals recorded at i57us are also dependent upon atmospheric winds the modeled rays that return in the stratosphere fit observations more closely than modeled rays that return in the troposphere suggesting the signals are from stratospheric returns our findings are the first observations of surf infrasound at a long range from the source region this suggests that surf signals might serve as a probe of the atmosphere much like microbarom signals are used to probe the atmosphere at greater range

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

the source of infrasound associated with long period events at mount st helens 1 during the early stages of the 2004 2008 mount st helens eruption the source process that produced a sustained sequence of repetitive long period lp seismic events also produced impulsive broadband infrasonic signals in the atmosphere to assess whether the signals could be generated simply by seismic acoustic coupling from the shallow lp events we perform finite difference simulation of the seismo acoustic wavefield using a single numerical scheme for the elastic ground and atmosphere the effects of topography velocity structure wind and source configuration are considered the simulations show that a shallow source buried in a homogeneous elastic solid produces a complex wave train in the atmosphere consisting of p sv and rayleigh wave energy converted locally along the propagation path and acoustic energy originating from the source epicenter although the horizontal acoustic velocity of the latter is consistent with our data the modeled amplitude ratios of pressure to vertical seismic velocity are too low in comparison with observations and the characteristic differences in seismic and acoustic waveforms and spectra cannot be reproduced from a common point source the observations therefore require a more complex source process in which the infrasonic signals are a record of only the broadband pressure excitation mechanism of the seismic lp events the observations and numerical results can be explained by a model involving the repeated rapid pressure loss from a hydrothermal crack by venting into a shallow layer of loosely consolidated highly permeable material heating by magmatic activity causes pressure to rise periodically reaching the pressure threshold for rupture of the valve sealing the crack sudden opening of the valve generates the broadband infrasonic signal and simultaneously triggers the collapse of the crack initiating resonance of the remaining fluid subtle waveform and amplitude variability of the infrasonic signals as recorded at an array 13 4 km to the nw of the volcano are attributed primarily to atmospheric boundary layer propagation effects superimposed upon amplitude changes at the source

a lava flow without a source the cohassett flow and its compositional components sentinel bluffs member columbia river basalt group abstract the eruption of sentinel bluffs member lava flows at approximately 15 5 ma marked the end of grande ronde basalt volcanism the most voluminous period of the columbia river basalt group more than 10 000 km3 of lava erupted from northerly trending feeder dikes in eastern washington and northern oregon and flowed westward down an ancestral paleoslope covering more than 169 700 km2 of the flood basalt province the sentinel bluffs member consists of six phases or types defined by their compositions lava flows having the first compositional type were the most voluminous and reached the pacific ocean the volume of later lava flows having the other compositional types declined with time until the final eruption produced the second largest volume of basalt at the source area compositional variation in sentinel bluffs lava flows is relatively small this homogeneity allows the individual compositional types and thus phases of the eruption to be easily recognized farther west however composition

modelling of the total electronic content and magnetic field anomalies generated by the 2011 tohoku oki tsunami and associated acoustic gravity waves summary in this work numerical simulations of the atmospheric and ionospheric anomalies are performed for the tohoku oki tsunami 2011 march 11 the tsunami atmosphere ionosphere tai coupling mechanism via acoustic gravity waves agws is explored theoretically using the tai coupled model for the modelled tsunami wave as an input the coupled model simulates the wind density and temperature disturbances or anomalies in the atmosphere and electron density magnetic anomalies in the f region of the ionosphere also presented are the gps total electron content tec and ground based magnetometer measurements during the first hour of tsunami and good agreements are found between modelled and observed anomalies at first within 6 min from the tsunami origin the simulated wind anomaly at 250 km altitude and tec anomaly appear as the dipole shaped disturbances around the epicentre then as the concentric circular wave fronts radially moving away from the epicentre with the horizontal velocity 800 m s 1 after 12 min followed by the slow moving horizontal velocity 250 m s 1 wave disturbance after 30 min the detailed vertical horizontal propagation characteristics suggest that the anomalies appear before and after 30 min are associated with the acoustic and gravity waves respectively similar propagation characteristics are found from the gps tec and magnetic measurements presented here and also reported from recent studies the modelled magnetic anomaly in the f region ionosphere is found to have similar temporal variations with respect to the epicentre distance as that of the magnetic anomaly registered from the ground based magnetometers the high frequency component 10 min of the simulated wind tec and magnetic anomalies in the f region develops within 6 7 min after the initiation of the tsunami suggesting the importance of monitoring the high frequency atmospheric ionospheric anomalies for the early warning these anomalies are found to maximize across the epicentre in the direction opposite to the tsunami propagation suggesting that the large atmospheric ionospheric disturbances are excited in the region where tsunami does not travel

infrasound associated with 2004 2005 large sumatra earthquakes and tsunami 1 large earthquakes that occurred in the sumatra region in 2004 and 2005 generated acoustic waves recorded by the diego garcia infrasound array the progressive multi channel correlation pmcc analysis is performed to detect the seismic and infrasound signals associated with these events the study is completed by an inverse location procedure that permitted reconstruction of the source location of the infrasonic waves the results show that ground motion near the epicenter and vibrations of nearby land masses efficiently produced infrasound the analysis also reveals unique evidence of long period pressure waves from the tsunami earthquake m9 0 of december 26 2004

a joint seismic and acoustic study of the washington state bolide observations and modeling 1 on 3 june 2004 a bolide was observed over british columbia washington oregon and idaho in addition to eyewitness accounts the event was recorded on videotape and at 100 seismometers located in washington state and southern british columbia seismic records are consistent with a terminal burst rather than the hypersonic shock of the meteors passage through the atmosphere arrival times from seismic waveform data are used to obtain an accurate source location for this terminal burst the source location can effectively be considered to be ground truth for assessing current atmospheric models and infrasound propagation algorithms we observe clear infrasonic signals associated with the terminal burst of the fireball at infrasound stations i56us and i57us in washington state and california respectively at i56us we observe at least four distinct acoustic arrivals for which we are able to model three using a state of the art atmospheric model the ground to space g2s model and both ray tracing and parabolic equation propagation algorithms to our knowledge this is the first study in which a complex sequence of arrival packets at an individual station has been successfully modeled by range dependent ducting and specular reflection off terrain gradients at i57us a single coherent acoustic signal was observed which we are unable to satisfactorily model this could be due to errors in the specification of the background atmosphere incorrect assumptions and approximations inherent to the acoustic propagation algorithms and the greater range of propagation which amplifies the effect of errors in source location and the atmospheric specifications

the huntzinger flow evidence of surface mixing of the columbia river basalt and its petrogenetic implications variation in chemical composition within flows of the columbia river basalt group crbg is typically small but one flow the huntzinger flow exhibits a large intraflow compositional range the composition varies both vertically and laterally but mass balance calculations for both major minor oxides and trace elements show that the variation can be explained by simple binary mixing between two end members these end member compositions are identical to two saddle mountains basalt flows the basalt of lapwai wilbur creek member and the asotin member primary intraflow features of the huntzinger flow are highly variable which is atypical for most crbg flows in addition to common features such as a scoriaceous flow top an entablature and a colonnade the flow exhibits evidence of invasion into sediments pillow hyaloclastic zones ophimottling and veins ophimottling and veins can be directly related to compositional variations veins occur in zones of mixing between the two end members and ophimottling is confined to zones dominated by the asotin composition the huntzinger flow is dominated by clinopyroxene and plagioclase with lesser amounts of olivine and variable amounts of glass the mineralogies of the two end member compositions are similar to those of the asotin and lapwai flows from the clear water embayment the intermediate compositions of the huntzinger flow contain characteristics of both flows suggesting mixing of the two the compositional variation indicates that mixing increases from the eastern part of the pasco basin where the asotin composition occurs in the center of the flow and is surrounded by lapwai to the western side where there is almost complete mixing of the lapwai and asotin this pattern is analogous to that produced when two flows mix by free turbulent flow from a free jet based upon this analogy a flow emplacement model is proposed in which the basalt of lapwai is initially emplaced in the pasco basin and prior to solidification is invaded by and mixed with the asotin lava this model places several petrogenetic constraints on this interval of the saddle mountains basalt the close spatial and temporal association of the asotin member and basalt of lapwai with yet a third flow the wahluke flow wilbur creek member allows the rate of eruption to be estimated and constrains the rate of magma recharge to a storage chamber the role of crustal contamination can also be evaluated from this model the conditions required for surface mixing suggest that this may not have been a unique occurrence and that other crbg flows may be composite flows resulting from mixing

infrasound from earthquakes 1 infrasonic signals have been observed from 31 earthquakes by arrays of microphones operated by the los alamos national laboratory between 1983 and 2003 the properties of the signals are presented signal amplitudes corrected for propagation and distance show a relation with seismic magnitude the variance in the relation is understood primarily in terms of the uncertainties or errors in the ground motion deduced from an independent data set and the stratospheric winds which strongly influence signal propagation signal durations can extend over many minutes a relation is found between signal duration and magnitude to understand this we propose a model in which regions distant from the epicenter are excited by seismic surface waves the surface motion of these regions in turn produces signals which precede or follow the signals from the epicenter analysis failed to detect signals from 56 earthquakes during the observation period predicted signal to noise ratios for these earthquakes indicated that the signals would have been too weak for detection

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

a study of acoustic propagation from a large bolide in the atmosphere with a dense seismic network 1 a large meteor entered the atmosphere above northeastern oregon on 19 february 2008 at 530 pst several hundreds of broadband seismic stations in the u s pacific northwest recorded acoustic to seismic coupled signals from this event the travel times of the first arriving energy are consistent with a terminal explosion source model suggesting that the large size of the explosion masked any signals associated with a continuous line source along its supersonic trajectory several infrasound arrays in north america also recorded this event both the seismic and infrasound data have been used to locate the explosion in 3 d space and time climatological atmospheric velocity models predict that infrasound signals from sources that occur at mid northern latitudes in winter are usually ducted to the east due to eastward zonal winds in this paper we analyze travel time picks and use 3 d ray tracing to generate synthetic travel times based on various atmospheric models to show that the seismic network data instead reveal a predominant westward propagation direction a sudden stratospheric warming event that reversed the zonal wind flow explains this westward propagation the seismic data illuminate in unprecedented spatial detail the range and azimuthal definition of shadow zones out to a range of 500 km suggesting that dense seismic networks can be used to study infrasound propagation at spatial resolutions that exceed that which can be done with only a handful of globally distributed infrasound arrays

seismo acoustic analysis of the buncefield oil depot explosion in the uk 2005 december 11 summary a massive vapour cloud explosion occurred at the buncefield fuel depot near hemel hempstead uk in the morning of 2005 december 11 the explosion was the result of an overflow from one of the storage tanks with the release of over 300 tons of petrol and generating a vapour cloud that spread over an area of 80 000 m2 before being ignited considerable damage was caused in the vicinity of the explosion and a total of 43 people were injured the explosion was detected by seismograph stations in the uk and the netherlands and by infrasound arrays in the netherlands we analysed the seismic recordings to determine the origin time of 06 01 31 45 0 5 s utc from p wave arrival times uncertainties in determination of origin time from acoustic arrival times alone were less than 10 s amplitudes of p lg and primary acoustic waves were measured to derive decay relationships as function of distance from the seismic amplitudes we estimated a yield of 2 10 tons equivalent to a buried explosion most seismic stations recorded primary and secondary acoustic waves we used atmospheric ray tracing to identify the various travel paths which depend on temperature and wind speed as function of altitude leading to directional variation refracted waves were observed from the troposphere stratosphere and thermosphere with a good match between observed and calculated traveltimes the various wave types were also identified through array processing which provides backazimuth and slowness of recordings from an infrasound array in the netherlands the amplitude of stratospheric refracted acoustic waves recorded by the array microbarometers was used to estimate a yield of 21 6 5 tons tnt equivalent we have demonstrated through joint seismo acoustic analysis of the explosion that both the seismic velocity model and the atmospheric model are sufficient to explain the observed traveltimes

infrasound detection of the chelyabinsk meteor at the usarray abstract on february 15 2013 a small asteroid entered earth s atmosphere near chelyabinsk russia this extremely rare event was recorded by the 400 station usarray deployed in the continental united states and alaska these stations recorded infrasound signals from the event at distances from 6000 to 10 000 km across a sector spanning 55 that encompassed the north pole this dense extensive network permitted a detailed study of long range infrasound propagation and source characteristics we observe long wavetrains at all stations ranging to over 100 min but clear variations in the character of the wavetrains across the network ray tracing through a spatially and temporally varying atmospheric model indicates the source excited resonance in the thermospheric duct to all stations resonance was also excited in a persistent stratospheric duct between the source and stations in alaska and along the west coast of the united states due to favorable winds at those azimuths leading to higher group velocities and frequency content at these stations than those to the east an attenuation formula derived from parabolic equation simulations is used to estimate infrasound transmission losses at all stations using simplified models of the effective sound speed along each source receiver path observed variations in signal energies from higher than expected at stations in the thermospheric duct in the eastern united states to lower than expected in alaska at azimuths nearly orthogonal to the asteroid s mach cone lead us to conclude that 1 the source was dominantly isotropic and 2 the model overestimates attenuation in the thermospheric duct

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

infrasound connecting the solid earth oceans and atmosphere the recently reinvigorated field of infrasonics is poised to provide insight into atmospheric structure and the physics of large atmospheric phenomena just as seismology has shed considerable light on the workings and structure of earth s solid interior although a natural tool to monitor the atmosphere and shallow earth for nuclear explosions it is becoming increasingly apparent that infrasound also provides another means to monitor a suite of natural hazards the frequent observation of geophysical sources such as the unsteady sea surface volcanoes and earthquakes that radiate energy both up into the atmosphere and down into the liquid or solid earth and transmission of energy across earth s boundaries reminds us that earth is an interconnected system this review details the rich history of the unheard sound in the atmosphere and the role that infrasonics plays in helping us understand the earth system

structures textures and cooling histories of columbia river basalt flows flood basalt flows of the columbia river basalt group commonly exhibit well developed colonnade and entablature structures formed during cooling of individual flows the colonnade refers to the well defined columnar structure of many flows which appears in the lowermost 10 to 30 and in places the uppermost 10 to 20 entablature refers to those parts of a flow that have smaller column diameters and more irregular pattern fractures than those of colonnade entablature commonly occupies the central 60 to 70 of a flow in some cases however the entablature is interrupted by colonnade in such cases the entablature and colonnade may be repeated once or twice within a single flow in other cases flows may lack an entablature entirely petrographic examination reveals a pronounced correlation between structural and textural features thin sections of colonnade basalt have relatively coarse cruciform or octahedral fe ti oxide crystals and 20 glassy mesostasis the central entablature basalt in contrast has much more mesostasis as much as 60 and has textural features such as feathery fe ti oxide crystals indicative of more rapid cooling these features are the reverse of what might be expected for normal conductive cooling because cooling rates at the flow margins should be greater than those in the flow interior we reconciled the observed basalt textures with thermal models by taking into account rainfall and deranged drainage during crystallization of the flow downward migration of water through cracks would cause convective cooling of underlying unsolidified lava this effect and its consequences have been modeled numerically in order to clarify the physical constraints on the mechanism by which the central part of the lava can be quenched we have found that a water infiltration front can explain the presence of a thick quenched flow interior provided that the infiltration front moves downward just behind the lava solidification front despite heavy rainfall on hawaii for example 250 cm yr at kilauea iki exposed prehistoric lava flows on that island exhibit only colonnades we deduce from this that heavy rainfall alone is inadequate to quench flow interiors extensive flooding by deranged drainage or perhaps extremely heavy rainfall 250 cm yr is apparently required to produce entablatures the model also can be used to explain the occurrence of repeated entablature and colonnade by considering the effects of intermittent inundation the imposition of boundary conditions that mimic the removal and reoccurrence of flooding yields cooling histories that are consistent with the development of multiple colonnades and entablatures

dynamic crystallization studies on the grande ronde pillow basalts central washington dynamic crystallization experiments were performed to reproduce textural and mineralogic features of some grande ronde columbia river pillow basalts and thereby estimate cooling rates of the various pillow textural zones the essential petrographic features of these pillows can be experimentally duplicated by melting at the liquidus temperature 1140 c followed by isothermal drop crystallization at 1125 c and then linear cooling to subsolidus temperatures at rates between 2400 c hr to reproduce vitrophyric rims and 10o hr to reproduce the holocrystalline interiors in both cooling experiments and the pillows the al content of pyroxenes and the fe content of plagioclase display a systematic variation with respect to cooling rate or position within the pillow pyroxene grain size data derived from the cooling experiments display a linear relationship with cooling rate but are strongly influenced by the original melting temperature pyroxenes crystallized during experiments originally melted at liq

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

crustal genesis on the oregon plateau the areal and temporal distribution and the chemical and isotopic characteristics of cenozoic volcanic rocks from the oregon plateau reflect the changing tectonic conditions affecting this area over the last 20 m y following subduction zone related calc alkaline volcanism flood basalt eruptions occurred in the time interval 18 14 ma this primarily basaltic volcanism is interpreted to be the result of a major shift in spreading orientation of the juan de fuca ridge that resulted in changes in the geometry of subduction against the pacific northwest the compositions of the mid miocene flood basalts show signs of extensive crystal fractionation in some cases accompanied by crustal contamination roughly 11 m y ago basalt eruptions showed an increasing tendency toward smaller volumes and less evolved compositions this implies that as extension in the oregon plateau proceeded the crust became less of an impediment to the passage of relatively unfractionated mantle melts initial sr nd and pb isotopic compositions of all the basalts show more correlation with the geographic position of eruption than with the composition of the lava primary control over the isotope systematics appears to be due to changes in the age and chemical characteristics of the crust and mantle throughout this area these observations suggest that an area of some 130 000 km2 of crust and basalt depleted subcontinental mantle has been added to northwestern north america over the last 20 m y the intensity of basalt volcanism as manifest in the columbia river group and in the oregon plateau does not appear to reflect the presence of a hot spot beneath the area both the areal and temporal distribution of the lavas and their geochemical characteristics are more easily reconciled with the suggestion that this crustal section grew by back arc spreading in a manner analogous to the formation of the marginal basins of the western pacific this spreading initiated along the western border of the archean wyoming craton with the location of mantle ascent melt production and extraction controlled by the changing geometry of subduction the existence of a zone of lithospheric weakness and the presence of a thick low density subcontinental mantle keel existing beneath the archean craton in this area

chemical discrimination of columbia river basalt flows 1 the homogeneity and distinctive chemical composition of individual columbia river basalt flows are illustrated in a series of chemical plots and the procedure for flow identification is outlined the unique characterization of many individual eruptions permits units to be mapped from feeder dike to flow margins across the columbia plateau for hundreds of kilometers and so provides critical constraints on the physical and chemical evolution of this continental flood basalt province

influence of atmospheric structure and topography on infrasonic wave propagation the effects of topography and atmospheric structures on infrasonic wave propagation from a volcanic source were investigated using observations and numerical modeling this paper presents the first long term observational data set showing spatiotemporal variations in patterns of infrasound propagation at distances of up to 60 km from a persistently active infrasound source sakurajima volcano japan the data show that the amplitudes of infrasonic waves received at distant stations relative to those received at a reference station close to the source can vary up to an order of magnitude over short time intervals and short distances and that they do not follow the theoretical geometric decay expected for homogeneous media moreover waveforms also change significantly in both time and space numerical simulations were performed using a two dimensional finite difference time domain 2 d fdtd method effects of atmospheric structure and topography are included in a vertical section parallel to the wave propagation direction the simulation successfully reproduced the variations of amplitudes and waveforms results are interpreted in terms of wave refraction due to sound and wind speed gradients and wave diffraction at topographic barriers our numerical results indicate that both atmospheric and topographic propagation effects are nonnegligible to evaluate the propagation effects and determine source processes in spatially and temporally varying infrasound data atmospheric data with a time resolution higher than is currently available are required if the data are available the present results suggest that the propagation effects could be evaluated using 2 d fdtd modeling at realistic calculation times

paleomagnetic correlation of columbia river basalt flows using secular variation a statistical method is developed to evaluate stratigraphic correlations that are based on the similarity of paleomagnetic directions it involves comparison of the probabilities that such directions could have arisen by either simultaneous or random samplings of the ancient magnetic field to calculate these probabilities one must estimate the effects of paleomagnetic errors and paleosecular variation respectively the method is tested successfully on sections of 8 10 grande ronde basalt columbia river basalt group flows at sentinel gap and umtanum ridge which are separated by only 25 km and contain two flows thought to be the same on geological grounds more significantly for widely separated sections at sentinel gap and butler canyon the analysis again shows that simultaneous magnetization is a much more likely explanation of the general similarity of paleomagnetic directions than chance agreement of ancient field directions the simplest interpretation of this result is that many of the flows at the two sites are the same implying that series of grande ronde flows extended over distances of several hundred kilometers

multistation infrasonic observations of the chilean earthquake of 2005 june 13 summary on 2005 june 13 a major earthquake m7 8 occurred in the tarapaca region north chile within the region of high mountains at large distances from the epicentre this event produced coherent infrasonic waves detected by three infrasound stations that are part of the international monitoring system the observed azimuth variations and the long signal durations suggest that wide regions in the andes mountains radiated infrasonic waves from these observations the main sources regions are reconstructed such an event recorded by multiple stations offers an unique opportunity to evaluate the relative contributions of the different source mechanisms involved in large earthquakes as well as to improve our understanding of the amplification of ground displacement caused by the topography with a review of infrasound signals from past earthquakes extended empirical scaling relations are derived we show that beyond the seismic magnitude both seismic source and topographic features also play a predominant role in the generation of infrasound

a study of infrasound propagation using dense seismic network recordings of surface explosions abstract we use dense seismic network recordings of accurately located surface explosions in northern utah to shed light on the propagation of infrasound through the stratosphere the data clearly show propagation of infrasound downwind from the source as expected the data also clearly show the penetration of infrasound into geometric shadow zones near the source and the spread of infrasound to a distance of 800 km from the source the spread of infrasound both toward and away from the source is not predicted by applying either ray theory or the full wave finite difference technique to smooth ground to space g2s models the mismatch between synthetics and data suggest a missing component in these models possibly a small scale gravity wave structure comparison of the network recordings of approximately 1500 infrasound signals with travel time predictions based on rays shows no significant average bias in the travel times on average recorded signals arrived 1 s earlier than predictions travel time residuals are normally distributed about the mean with a standard deviation of 15 s the small bias of the travel time predictions indicates that despite the fact that small scale structure is averaged out of commonly used g2s models the large scale structure of the atmosphere is accurately represented the scatter of travel time residuals is suggestive of small scale structure missing from the models that we used to make the predictions but firm conclusions would require a more in depth study

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