anomalous infrasound generated by the alaskan earthquake of 28 march 1964 in this paper we present and analyze data recorded at three microphone arrays boulder colorado boston massachusetts and washington dc associated with the alaskan earthquake of 03 h 36 min 13 s ut 28 march 1964 61 05n 147 50w we show that the recordings from all three stations contain not only the epicentral and locally generated air waves reported by other authors but also contain evidence of atmospheric radiation apparently generated from seismic surface waves along the rocky mountains the latter became decoupled from the surface wave and traveled at about 314 m s through the air to the arrays

the vertical propagation of disturbances triggered by seismic waves of the 11 march 2011 m9 0 tohoku earthquake over taiwan in this paper concurrent colocated measurements of seismometers infrasonic systems magnetometers hf cw high frequency continuous wave doppler sounding systems and gps receivers are employed to detect disturbances triggered by seismic waves of the 11 march 2011 m9 0 tohoku earthquake no time delay between colocated infrasonic i e super long acoustic waves and seismic waves indicates that the triggered acoustic and or gravity waves in the atmosphere or seismo traveling atmospheric disturbances stads near the earth s surface can be immediately activated by vertical ground motions the circle method is used to find the origin and compute the observed horizontal traveling speed of the triggered infrasonic waves the speed of about 3 3 km s computed from the arrival time versus the epicentral distance suggests that the infrasonic waves i e stads are mainly induced by the rayleigh waves the agreements in the travel time at various heights between the observation and theoretical calculation suggest that the stads triggered by the vertical motion of ground surface caused by the tohoku earthquake traveled vertically from the ground to the ionosphere with speed of the sound in the atmosphere over taiwan

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

atmospheric torques during the winter of 1989 impact of enso and nao positive phases the axial component of atmospheric angular momentum aam reached a decadal minimum during the winter of 1989 when the cool la nina phase of the enso cycle and the positive phases of the north atlantic oscillation nao and the related arctic oscillation ao were active here we examine the global atmospheric dynamics associated with this event from the torque point of view it will be shown how mountain torques on north america south america and europe related to these oscillations led to the aam minimum partly compensated by a positive enso related mountain torque over asia the friction torque had more nearly equal positive and negative anomalies associated with enso and nao forcing respectively and made a smaller offsetting contribution to the global aam anomaly during this episode

ground coupled air waves and diffracted infrasound from the arequipa earthquake of june 23 2001 1 on june 23 2001 a strong earthquake measuring mw 8 4 occurred along the coast of south central peru coherent infrasonic waves were detected over a period of one hour by the is08 infrasound station in bolivia analysis of the ground coupled air waves shows that the rupture propagated from the northwestern to the southeastern part of the fault with a rupture velocity of 3 3 km s the azimuth variation of the infrasonic waves is attributed to a distribution of secondary sources along the highest mountain ranges which excite infrasonic waves that are diffracted to the ground the predominant source of infrasound is likely distributed along the andean cordillera using the azimuth and arrival time determination the horizontal scale size of the distant source regions of infrasonic waves is reconstructed over distances greater than 400 km

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

regional monitoring of infrasound events using multiple arrays application to utah and washington state summary in this paper we present an integrated set of algorithms for the automatic detection association and location of low frequency acoustic events using regional networks of infrasound arrays here low frequency acoustic events are characterized by transient signals which may arise from a range of natural and anthropogenic sources examples of which include but are not limited to earthquakes volcanic eruptions explosions rockets and bolides first we outline a new technique for detecting infrasound signals that works successfully in the presence of correlated noise we use an f statistic sequentially adapted to ambient noise conditions in order to obtain detections at a given statistical significance while accounting for real background noise at each array individual arrivals are then grouped together based on measured delay times and backazimuths each signal is identified as either a first or later arrival first arrivals at spatially separated arrays are then associated using a grid search method to form events preliminary event locations are calculated from the geographic means and spreads of grid nodes associated with each event we apply the technique to regional infrasound networks in utah and washington state in utah over a period of approximately 1 month we obtain a total of 276 events recorded at three arrays in a geographic region of 6 4 for four groundtruth explosions in utah the automatic algorithm detects associates and locates the events within an average offset of 5 4 km to the actual explosion locations in washington state the algorithm locates numerous events that are associated with a large coalmine in centralia washington an example mining explosion from centralia is located within 8 2 km of the mine the methodology and results presented here provide an initial framework for assessing the capability of infrasound networks for regional infrasound monitoring in particular by quantifying detection thresholds and localization errors

a repeating secondary source of infrasound from the wells nevada earthquake sequence 1 the wells nevada earthquake of february 21 2008 generated a complex seismo acoustic wavefield epicentral infrasound was recorded at 5 seismo acoustic arrays in nevada utah and wyoming in addition to epicentral infrasound the earthquake triggered a secondary source of infrasound at the bgu array in utah which was also triggered by subsequent aftershocks by applying simple constraints on the propagation of seismic and infrasound waves we show that the secondary source is an isolated peak floating island that appears to efficiently generate infrasound through the interaction with seismic surface waves this hypothesized source location is broadly consistent with crosswind directions extracted from the ground to space g2s atmospheric model for the appropriate time and source receiver locations although modeling the propagation of infrasound predicts this source location to be within the so called zone of silence in contrast to epicentral infrasound secondary infrasound associated with the wells nevada earthquake sequence appears to be local to each array i e not observed at multiple arrays secondary infrasonic arrivals observed at bgu are much higher in amplitude than epicentral arrivals highlighting the importance of being able to clearly identify and separate epicentral and secondary arrivals for infrasonic event discrimination

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

interannual atmospheric torque and el nino southern oscillation where is the polar motion signal 1 in this paper we investigate the atmospheric excitation of polar motion pm associated with the el nino southern oscillation enso phenomenon enso effects on length of day due to changes in the axial component of atmospheric angular momentum aam have long been recognized but identification of pm excitation with enso induced equatorial aam anomalies has proved more elusive here we use an appropriately modified form of the inverted barometer ib assumption to study enso related atmospheric torques arising from pressure loading on the earth s ellipsoidal bulge and mountains and from frictional wind stress over the earth s land and ocean covered surface the resulting dissipation torques which accommodate adjustment of the oceanic mass distribution to time variable atmospheric loading are found to be small the ellipsoidal torques have the largest amplitude reflecting the order of magnitude discrepancy between the height departures of the earth s bulge 20 km and its surface orography 2 km because of relatively uniform pressure covariances with the southern oscillation index over the continents for the largely land based x component and the uniform ib response for the largely ocean based y component however the enso related pm excitation arising from the ellipsoidal torques is reduced to an amplitude comparable with the sum of regional mountain torques from the individual continents the largest of these are generated over asia and antarctica arising from efficient coupling of enso related surface pressure anomalies with large scale orographic features the geometrical mitigation of the ellipsoidal torques classically expected to dominate equatorial aam forcing accounts for the lack of a detectable atmosphere driven polar motion response to enso

hydrological and oceanic effects on polar motion from grace and models 1 terrestrial water storage tws and ocean bottom pressure obp are major contributors to the observed polar motion excitations second only to atmospheric mass movement however quantitative assessment of the hydrological and oceanic effects on polar motion remains unclear because of the lack of global observations in this paper hydrological and oceanic mass excitations to polar motion are investigated using monthly tws and obp derived from the gravity recovery and climate experiment grace for january 2003 until december 2008 the results from this analysis are compared with hydrological model excitations from the european center for medium range weather forecasts ecmwf and oceanic model excitations obtained from the jet propulsion laboratory jpl using estimating the circulation and climate of the ocean ecco results show that the grace derived obp and tws better explain the geodetic residual polar motion excitations for the px component at the annual period while the grace obp and ecmwf hydrological angular momentum agree better with the geodetic residuals for the annual py excitation grace ocean and hydrology excitations better explain the geodetic residuals for the semiannual py excitation however the jpl ecco and ecmwf models better explain the intraseasonal geodetic residual of polar motion excitation in the px and py components the grace data demonstrate much higher intraseasonal variability than either the models or the geodetic observations

using hilbert huang transform hht to extract infrasound generated by the 2013 lushan earthquake in china we applied the hilbert huang transform hht method to extract the infrasound generated by the 2013 lushan earthquake and its following aftershocks in china from a nearly continuous infrasound recode made 130 km from the earthquake epicenter an improved sta lta algorithm was adopted for detecting the ambient infrasonic events from the data record a powerful processing technique for non stationary signal the hht was applied to extract the significant intrinsic mode functions imfs of the infrasonic signal associated with the earthquakes the features of the extracted imfs such as the dominant frequency the maximum amplitude and the spectral entropy were investigated using hilbert spectral analysis regression analysis between the maximum amplitude in the infrasound spectra and the magnitudes of the earthquakes was carried out to verify the source of the infrasound events detected the results demonstrated that the hht method could successfully identify the infrasound related to the earthquakes

calibration of acoustic gauge in the field using seismic lg phase and coupled high frequency local infrasound abstract local microphone field calibration can be performed using seismic signals recorded by a well calibrated seismometer when the 29 may 2004 regional earthquake m w 5 1 occurred off the coast of korea the pn pg and lg seismic phases produced high frequency 1 4 hz local infrasound signals at the chulwon seismo acoustic array chnar an array deployed in the republic of korea instrument corrected waveforms of seismic signals are compared to those of local infrasound signals using time varying coherence estimates to identify the time window and bandwidth for the calibration process based on this assessment the first 6 4 sec of the lg phase and the coupled infrasound signals from 1 to 4 hz are used envelope functions for the instrument corrected lg phase and local infrasound signal are calculated and integrated in the time domain the transfer function from ground velocity to atmospheric pressure perturbation is estimated in the time domain using the ratio of the integrated envelope functions the observed transfer functions estimated in this way are compared to the theoretical transfer function based on a model relating ground velocity to pressure perturbation which is dependent on the density of air and speed of sound at the surface a maximum difference of 4 db is apparent between observed transfer functions and theory for highly correlated seismic and coupled infrasound signals 0 8 six factors are considered as contributors to these differences including the porous hose array attached to each acoustic sensor for noise reduction variations in the density of air or speed of sound local perturbations in air pressure differences in ground velocity at each sensor and differences in acoustic instrument sensitivity variations of the acoustic gauge s sensitivities at chnar are identified using a laboratory calibration procedure and documented as the major contributor to the difference between observed and theoretical transfer function at chnar

dynamics of the bingham canyon rock avalanches utah usa resolved from topographic seismic and infrasound data the 2013 bingham canyon mine rock avalanches represent one of the largest cumulative landslide events in recorded u s history and provide a unique opportunity to test remote analysis techniques for landslide characterization here we combine aerial photogrammetry surveying topographic reconstruction numerical runout modeling and analysis of broadband seismic and infrasound data to extract salient details of the dynamics and evolution of the multi phase landslide event our results reveal a cumulative intact rock source volume of 52 mm3 which mobilized in two main rock avalanche phases separated by 1 5 h we estimate the first rock avalanche had 1 5 2 times greater volume than the second each failure initiated by sliding along a gently dipping 21 highly persistent basal fault before transitioning to a rock avalanche and spilling into the inner pit the trajectory and duration of the two rock avalanches were reconstructed using runout modeling and independent force history inversion of intermediate period 10 50 s seismic data intermediate and shorter period 1 50 s seismic data were sensitive to intervals of mass redirection and constrained finer details of the individual slide dynamics back projecting short period 0 2 1 s seismic energy we located the two rock avalanches within 2 and 4 km of the mine further analysis of infrasound and seismic data revealed that the cumulative event included an additional 11 smaller landslides volumes 104 105 m3 and that a trailing signal following the second rock avalanche may result from an air coupled rayleigh wave our results demonstrate new and refined techniques for detailed remote characterization of the dynamics and evolution of large landslides

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

seismo ionospheric observations modeling and backprojection of the 2016 kaikōura earthquake we processed global navigation satellite system gnss time series data to extract total electron content tec perturbations of the ionosphere caused by the kaik ura earthquake we used ray based modeling to infer which part of the earth s surface coupled significant energy from the solid earth into the atmosphere we compared modeled tec data with the observed time series data and determined that significant coupling occurred north northeast of the initial slip this work corroborates existing analysis made with geodetic and interferometric synthetic aperture radar insar data the tec data suggested that the initial rupture coupled some energy into the atmosphere but later surface displacements 60 s after the initiation caused more significant ionospheric perturbations using an array of gnss stations we were able to track the moveout of the acoustic wave through the ionosphere we used a method commonly used in seismological studies called backprojection to estimate the location of the source of the tec perturbation on earth s surface this is the first time that this method has been applied to tec data and the results are promising the backprojection results are slightly shifted in space from the known area of maximum uplift and we attribute this small discrepancy to the fact that we did not account for horizontal winds in the atmosphere nor the 3d heterogeneity of the real atmosphere in the travel time modeling

hydrological and oceanic excitations to polar motion andlength of day variation summary water mass redistributions in the global hydrosphere including continental water storage change and non steric sea level change introduce variations in the hydrological angular momentum ham and the oceanic angular momentum oam under the conservation of angular momentum ham and oam variations are signi cant excitation sources of the earth rotational variations at a wide range of timescales in this paper we estimate ham and oam variations and their excitations to polar motion and length of day variation using soil moisture and snow estimates and non steric sea level change determined by topex poseidon satellite radar altimeter observations and a simpli ed steric sea level change model the results are compared with the variations of polar motion and lod that are not accounted for by the atmosphere this study indicates that seasonal continental water storage change provides signi cant contributions to both polar motion and lod variation especially to polar motion x and the non steric sea level change is responsible for a major part of the remaining excitations at both seasonal scale and high frequencies particularly in polar motion y and lod the good correlation between oam contributions and the remaining excitations shows that large scale non tidal mass variation exists in the oceans and can be detected by topex poseidon altimeter observations

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

aerial seismology using balloon based barometers seismology on venus has long eluded planetary scientists due to extreme temperature and pressure conditions on its surface which most electronics cannot withstand for mission durations required for ground based seismic studies we show that infrasonic low frequency pressure fluctuations generated as a result of ground motion produced by an artificial seismic source known as a seismic hammer and recorded using sensitive microbarometers deployed on a tethered balloon are able to replicate the frequency content of ground motion we also show that weak artificial seismic activity thus produced may be geolocated by using multiple airborne barometers the success of this technique paves the way for balloon based aero seismology leading to a potentially revolutionary method to perform seismic studies from a remote airborne station on the earth and solar system objects with substantial atmospheres such as venus and titan

infrasound associated with the 2002 denali fault earthquake alaska 1 infrasonic waves associated with the november 3 2002 magnitude 7 9 earthquake in alaska were detected by the microphone array i53us in fairbanks alaska the epicenter of the earthquake lay some 150 km south of the fairbanks array both seismic and acoustic signals were recorded successively by the microphone array the fault rupture of the earthquake moved east southeast along the denali totschunda system fault for approximately 294 km the northern side of the fault moved to the east and vertically upward relative to the southern side displacements up to 8 8 meters were measured at various points along the fault eberhart phillps et al 2003 the seismic p wave signal arrived at the array approximately 27 seconds after initiation of the rupture with a trace velocity of 5 km sec this was followed some 12 minutes later by an infrasonic wavetrain that had an average trace velocity of 0 34 km sec and lasted about ten minutes the azimuth of arrival of the infrasonic waves steadily moved eastward throughout the wave train apparently following the rupture s leading edge along the fault the largest infrasonic signals reaching over 12 pa came from the azimuth of the regions of largest ground motion along the fault the source of the infrasound is taken to be the sudden local motion of the mountains in the alaska range along the denali fault as they responded to the eastward propagating fault rupture

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

infrasonic imaging of the kunlun mountains for the great 2001 china earthquake 1 on november 14 2001 a strong earthquake occurred on the high plateau of western china at a distance of 1800 km from the epicenter coherent infrasonic waves were detected for more than one hour using both an inverse location procedure and a complete simulation of the radiated pressure field distant source regions are accurately located the seismo acoustic coupling along a mountain belt is clearly demonstrated such an event offers an opportunity to validate velocity models in the atmosphere as well as to improve the understanding of the amplification of ground displacement caused by the topography

atmospheric and oceanic excitation of the earth s wobbles during 1980 2000 1 because of the action of various geophysical excitation mechanisms the earth does not rotate about its figure axis so it wobbles as it rotates here the effectiveness of atmospheric and oceanic processes in exciting the earth s wobbles during 1980 2000 is evaluated using estimates of atmospheric angular momentum from the national centers for environmental prediction national center for atmospheric research ncep ncar reanalysis project and estimates of oceanic angular momentum from the estimating the circulation and climate of the ocean ecco consortium s simulation of the general circulation of the oceans on intraseasonal timescales atmospheric surface pressure changes are found to be the single most effective process exciting the earth s wobbles explaining about twice as much of the observed variance as do either atmospheric wind or ocean bottom pressure changes and nearly 4 times as much of the observed variance as do oceanic currents however on interannual timescales ocean bottom pressure changes are found to be the single most effective process exciting the earth s wobbles explaining more than 5 times as much of the observed variance as do atmospheric wind and pressure changes combined and more than twice as much of the observed variance as do oceanic currents within the chandler band it is found that during 1980 2000 atmospheric and oceanic processes have enough power to excite the chandler wobble and are significantly coherent with it the single most important mechanism exciting the chandler wobble is found to be ocean bottom pressure variations atmospheric and oceanic processes do not appear to have enough power to excite the earth s wobbles to their observed levels on pentadal and longer timescales although series longer than the 21 yearlong series used here need to be studied in order to obtain greater statistical significance of this result

calibrating infrasonic to seismic coupling using the stardust sample return capsule shockwave implications for seismic observations of meteors 1 shock waves produced by meteoroids are detectable by seismograph networks but a lack of calibration has limited quantitative analysis of signal amplitudes we report colocated seismic and infrasound observations from reentry of nasa s stardust sample return capsule ssrc on 15 january 2006 the velocity of the ssrc initially 12 5 km s was the highest ever for an artificial object lying near the low end of the 11 2 72 km s range typical of meteoroids our infrasonic seismic recordings contain an initial n wave produced by the hypersonic shock front followed 10 s later by an enigmatic series of weak secondary pulses the seismic signals also include an intervening dispersed wave train with the characteristics of an air coupled rayleigh wave we determine an acoustic seismic coupling coefficient of 7 3 0 2 m ms 1 pa this represents an energy admittance of 2 13 0 15 several orders of magnitude larger than previous estimates derived from earthquake or explosive analogs theoretical seismic response was computed using in situ vp and vs measurements together with laboratory density measurements from samples of the clay rich playa treatment of the air ground interface as an idealized air solid contact correctly predicts the initial pulse shape but underestimates its seismic amplitude by a factor of 2 full wave synthetic seismograms simulate the air coupled rayleigh wave and suggest that the secondary arrivals are higher order airy phases part of the infrasound signal appears to arise from coupling of ground motion into the air much like earthquake induced sounds

seismic velocity variations at tcdp are controlled by mjo driven precipitation pattern and high fluid discharge properties using seismic noise based monitoring techniques we find that seismic velocity variations dv v observed with the borehole array of the taiwan chelungpu fault drilling project tcdp are controlled by strong precipitation events associated with the madden julian oscillation mjo a dynamic intraseasonal atmospheric pattern in the tropical atmosphere high frequency noise 1 hz excited by steady anthropogenic activity in the vicinity of the tcdp allows daily resolution of dv v time series relatively large fluid discharge properties control the equilibration of the ground water table and hence seismic velocities on time scales smaller than the average precipitation recurrence interval this leads to the observed synchronous 50 80 day periodicity in dv v and rainfall records in addition to the dominant annual component further evidence for the governing role of hydraulic properties is inferred from the similarity of observed dv v timing amplitude and recovery properties with dv v synthetics generated by a combined model of ground water table changes and diffusive propagation of seismic energy the lapse time dependent increase of dv v amplitudes is controlled by the sensitivity of the diffuse wave field sampled at 1100 m depth to shallower water level fluctuations the significant vertical offset between stations and water level explains the direct dependence which is opposite to the trend previously inferred from measurements at the surface

numerical simulation of the atmospheric signature of artificial and natural seismic events the mechanical coupling between solid planets and their atmospheres enables seismically induced acoustic waves to propagate in the atmosphere we numerically simulate this coupled system for two application cases active seismic experiments ases and passive seismic experiments a recent ase krishnamoorthy et al 2018 https doi org 10 1002 2018gl077481 observed the infrasonic signals produced by a seismic hammer to measure the sensitivity of observations to seismic parameters we attempt to reproduce the results from this experiment at short range by considering a realistic unconsolidated subsurface and an idealized rock solid subsurface at long range we investigate the influence of the source by using two focal mechanisms we found surface waves generate an infrasonic plane head wave in the ase case of the rock solid material for the passive seismic experiments the amplitude of atmospheric infrasound generated by seismic surface waves is investigated in detail despite some limitations the simulations suggest that balloon measurement of seismically induced infrasound might help to constrain ground properties

effects of confinement on short period surface waves observations from a new dataset the source phenomenology experiment spe was conducted during the summer of 2003 in arizona single fired chemical shots were detonated and recorded at two locations including a coal mine in the black mesa district of northern arizona this article reports on research into the effects of confinement on the generation of short period fundamental mode rayleigh waves rg using a subset of the spe data results show important differences between the rg amplitudes of confined and unconfined explosions which must be understood to develop discriminants for mining explosions which are an important aspect of nuclear test monitoring rg energy and frequency content depend on explosive weight and confinement and unconfined explosions generate up to eight times less energy than equivalent confined explosions for this reason unconfined mining explosions cannot be simulated using a mueller and murphy 1971 source without including an empirical chemical decoupling factor rg chemical decoupling factors for unconfined shots vary from 0 5 to 8 2 at frequencies between 0 5 and 11 hz the effects of the bench free face are evident in radiation patterns explosions on the topographic bench show increased spectral energies for rg by a factor of 1 5 at azimuths behind the bench this suggests that a discriminant basedmore on the relative azimuthal spectral energies of rg may be a possibility less

infrasound radiated during the montana earthquake of 1959 august 18 summary seismic waves caused by earthquakes radiate infrasound into the atmosphere as they proceed over the earth s surface several instances of such sound waves radiated locally by seismic waves passing through the washington d c area have been observed at the infrasonic station there a notable instance was the great montana earthquake of 1959 august 18 measurements of the radiated infrasound gave data on the seismic waves including their travel times local speeds directions of travel amplitudes and waveforms

length of day variations caused by el nino southern oscillation and quasi biennial oscillation two prominent interannual atmospheric fluctuations the el nino southern oscillation in the troposphere ocean system and the quasi biennial oscillation in the equatorial stratosphere account for most of the observed interannual length of day lod variation from 1964 through 1987 with a relative contribution of about 2 to 1 thus the atmosphere lod connection extends from seasonal and shorter periods to interannual periods up to about 10 years

detection of artificially generated seismic signals using balloon borne infrasound sensors abstract we conducted an experiment in pahrump nevada in june 2017 where artificial seismic signals were created using a seismic hammer and the possibility of detecting them from their acoustic signature was examined in this work we analyze the pressure signals recorded by highly sensitive barometers deployed on the ground and on tethers suspended from balloons our signal processing results show that wind noise experienced by a barometer on a free flying balloon is lower compared to one on a moored balloon this has never been experimentally demonstrated in the lower troposphere while seismoacoustic signals were not recorded on the hot air balloon platform owing to operational challenges we demonstrate the detection of seismoacoustic signals on our moored balloon platform our results have important implications for performing seismology in harsh surface environments such as venus through atmospheric remote sensing

yield and emplacement depth effects on acoustic signals from buried explosions in hard rockyield and emplacement depth effects on acoustic signals from buried explosions in hard rock

seismoacoustic recordings of small earthquakes in the pyrenees experimental results an experiment was conducted in the lesponne valley central french pyrenees to record the sounds that frequently accompany earthquakes in this region seismic and acoustic signals of a short period seismometer and a condenser microphone were continuously monitored for ten months during this period four small m l p transmission but also sv to p conversion into the atmosphere are identified thus confirming former hypotheses formulated by hill et al 1976 unambiguous quantitative constraints on the seismic to acoustic conversion are provided by the computation of transmission coefficients the dominant audio frequencies are recorded in the 5 to 60 hz band that is at the boundary between sounds and infrasounds and at the lower bound of human audibility high frequency infrasounds about 8 hz are interpreted as the transmission to the atmosphere of rayleigh waves induced locally by a thin soil layer

long period seismicity and very long period infrasound driven by shallow magmatic degassing at mount pagan mariana islands long period lp seismicity and very long period infrasound ivlp were recorded during continuous degassing from mount pagan mariana islands in july 2013 to january 2014 the frequency content of the lp and ivlp events and delay times between the two arrivals were remarkably stable and indicate nearly co located sources using phase weighted stacking over similar events to dampen noise we find that the lp source centroid is located 60 m below and 180 m west of the summit vent the moment tensor reveals a volumetric source modeled as resonance of a subhorizontal sill intersecting a dike we model the seismoacoustic wavefields with a coupled earth air 3 d finite difference code the ratios of pressure to velocity measured at the infrasound arrays are an order of magnitude larger than the synthetic ratios so the ivlp is not the result of lp energy transmitting into the atmosphere at its epicenter based on crater shape and dimensions determined by structure from motion we model the ivlp as acoustic resonance of an exponential horn the source of the continuous plume from gas analysis is shallow magmatic degassing which repeatedly pressurized the dike sill portion of the conduit over the 7 months of observation periodic gas release caused the geologically controlled sill to partially collapse and resonate while venting of gas at the surface triggered resonance in the crater lp degassing only accounts for 12 of total degassing indicating that most degassing is relatively aseismic and that multiple active pathways exist beneath the vent

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

the two types of el nino and their impacts on the length of day at the interannual to decadal timescale the changes in the earth rotation rate are linked with the el nin o southern oscillation phenomena through changes in the atmospheric angular momentum as climatic studies demonstrate that there were two types of el nin o events namely eastern pacific ep and central pacific cp events we investigate how each of them affect the atmospheric angular momentum we show in particular that ep events are associated with stronger variations of the atmospheric angular momentum and length of day we explain this difference by the stronger pressure gradient over the major mountain ranges due to a stronger and more efficiently localized pressure dipole over the pacific ocean in the case of ep events

temperature dependent remineralization and carbon cycling in the warm eocene oceans metabolic rates in heterotrophic bacteria are more sensitive to temperature than rates of primary production e g lopez urrutia et al 2006 regaudie de gioux and duarte 2012 consequently faster bacterial respiration rates in a warmer ocean may result in more efficient remineralization of sinking organic matter higher in the water column with implications for carbon and nutrient cycling during warm climate states this is supported by a series of reconstructed 13cdic depth profiles based on well preserved planktonic foraminifera assemblages from tanzania from the warm eocene epoch 55 5 33 7 ma when global surface and deep ocean temperatures exceeded those of the modern day john et al 2013 these results indicate relatively sharp 13cdic gradients in the upper water column which supports the hypothesis that high metabolic rates in warm eocene oceans led to more efficient recycling of organic matter and reduced burial rates of organic carbon olivarez lyle and lyle 2006 shallower remineralization depths would also cause an upward displacement and intensification of the oxygen minimum zone which is consistent with evidence for a pelagic ecosystem that was focused in a narrow depth range near the surface during the warm early and middle eocene here we use the earth system model cgenie that incorporates a new temperature dependence of remineralization rates to illustrate the potential effects of temperature on particulate organic carbon fluxes and hence vertical 13cdic gradients modeled 13cdic vertical profiles off the coast of tanzania for the eocene agree well with the reconstructed 13cdic profiles supporting our interpretations based on temperature dependent remineralization

ionospheric f2 region perturbed by the 25 april 2015 nepal earthquake seismic waves can be detected in the earth s atmosphere and ionosphere however their impacts on ionospheric electron density ne structures near the altitude of peak ne hmf2 have not yet been fully determined due to the lack of sufficient observations sampled in the vertical direction here we apply a ground based global positioning system gps receiving network in asia as well as the space based gps occultation experiment on board the formosat 3 cosmic f3 c satellite to vertically scan the ionospheric ne structures which were perturbed by the magnitude mw7 8 nepal earthquake that occurred on 25 april 2015 the f3 c altitudinal ne profiles show that the nepal earthquake induced air perturbations penetrate into the ionosphere at supersonic speeds of approximately 800 m s and change the ne structure by 10 near hmf2 the vertical scale of the ne perturbation is 150 km while the hmf2 is uplifted by more than 30 km within 1 min those results reveal that the earthquake induced ground displacement should be considered as a significant force that perturbs the vertical ne structure of the ionosphere