ground motion relations for eastern north america predictive relations are developed for ground motions from eastern north american earthquakes of 4 0 m 7 25 at distances of 10 r 500 km the predicted parameters are response spectra at frequencies of 0 5 to 20 hz and peak ground acceleration and velocity the predictions are derived from an empirically based stochastic ground motion model the relations differ from previous work in the improved empirical definition of input parameters and em pirical validation of results the relations are in demonstrable agreement with ground motions from earthquakes of m 4 to 5 there are insufficient data to adequately judge the relations at larger magnitudes although they are consistent with data from the saguenay m 5 8 and nahanni m 6 8 earthquakes the underlying model parameters are constrained by empirical data for events as large as m 6 8

the 2013 russian fireball largest ever detected by ctbto infrasound sensors 1 on 15 february 2013 a large earth impacting fireball disintegrated over the ural mountains this extraordinary event is together with the 1908 tunguska fireball among the most energetic events ever instrumentally recorded it generated infrasound returns after circling the globe at distances up to 85 000 km and was detected at 20 infrasonic stations of the global international monitoring system ims for the first time since the establishment of the ims infrasound network multiple arrivals involving waves that traveled twice round the globe have been clearly identified a preliminary estimate of the explosive energy using empirical period yield scaling relations gives a value of 460 kt of tnt equivalent in the context of the future verification of the comprehensive nuclear test ban treaty this event provides a prominent milestone for studying in detail infrasound propagation around the globe for almost 3 days as well as for calibrating the performance of the ims network

characterizing swells in the southern pacific from seismic and infrasonic noise analyses a temporary network of 10 broad band seismic stations has been installed in french polynesia for the polynesian lithosphere and upper mantle experiment plume all the seismic stations were installed either on volcanic islands or on atolls of the various archipelagos of french polynesia in a manner which complements the geographic coverage provided by the regional permanent stations the primary aim of plume is to image the upper mantle structures related to plate motion and hotspot activity however because of its proximity to all sites the ocean is responsible for a high level of noise in the seismic data and we show that these data can also be used to analyse ocean wave activity the power spectral density psd analyses of the seismic data recorded in french polynesia show clear peaks in the 0 05 0 10 hz band periods between 10 and 20 s which corresponds to swell frequencies clear peaks in this frequency band are also observed in infrasonic data recorded on tahiti ground motion analysis shows that the swell related seismic noise srsn is linearly polarized in the horizontal plane and its amplitude decreases rapidly with the distance from the shore the microseismic and the infrasonic noise amplitudes show very similar variations from station to station and both are strongly correlated with the swell amplitudes predicted by the national oceanic and atmospheric administration noaa wind forced wavewatch models the swell direction can be estimated from srsn polarization analysis but this has to be done with care since for some cases the ground motions are strongly controlled by the islands anisometric shapes and by swell refraction processes we find cases however such as tahiti or roughly circular tuamotu atolls where the azimuth of the swell is in good agreement with the seismic estimates we therefore demonstrate that the srsn and the infrasonic signal observed in french polynesia can be used in such cases as a proxy for swell amplitude and azimuth from the continuous analysis of the data recorded in 2003 at the permanent seismic station pptl in tahiti transfer functions have been obtained this could provide a way to quantify the swell activity during the last two decades and therefore assist in the investigation of climate changes

the moravka meteorite fall 2 interpretation of infrasonic and seismic data the sound production from the mora vka fireball has been examined in detail making use of infrasound and seismic data a detailed analysis of the production and propagation of sonic waves during the atmospheric entry of the mora vka meteoroid demonstrates that the acoustic energy was produced both by the hypersonic flight of the meteoroid producing a cylindrical blast wave and by individual fragmentation events of the meteoroid which acted as small explosions producing quasi spherical shock waves the deviation of the ray normals for the fragmentation events was found to be as much as 30 beyond that expected from a purely cylindrical line source blast the main fragmentation of the bolide was confined to heights above 30 km with a possible maximum in acoustic energy production near 38 km seismic stations recorded both the direct arrival of the airwaves the strongest signal as well as air coupled p waves and rayleigh waves earlier signals in addition deep underground stations detected the seismic signature of the fireball the seismic data alone permit reconstruction of the fireball trajectory to a precision on the order of a few degrees the velocity of the meteoroid is much less well determined by these seismic data the more distant infrasonic station detected 3 distinct signals from the fireball identified as a thermospheric return a stratospheric return and an unusual mode propagating through the stratosphere horizontally and then leaking to the receiver

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

infrasound radiated by the gerdec and chelopechene explosions propagation along unexpected paths summary infrasound propagation paths through the atmosphere are controlled by the temporally and spatially varying sound speed and wind speed amplitudes because of the complexity of atmospheric acoustic propagation it is often difficult to reconcile observed infrasonic arrivals with the sound speed profiles predicted by meteorological specifications this paper provides analyses of unexpected arrivals recorded in europe and north africa from two series of accidental munitions dump explosions recorded at ranges greater than 1000 km two explosions at gerdec albania on 2008 march 15 and four explosions at chelopechene bulgaria on 2008 july 3 the recorded signal characteristics include multiple pulsed arrivals celerities between 0 24 and 0 34 km s 1 and some signal frequency content above 1 hz often such characteristics are associated with waves that have propagated within a ground to stratosphere waveguide although the observed celerities extend both above and below the conventional range for stratospheric arrivals however state of the art meteorological specifications indicate that either weak or no ground to stratosphere waveguides are present along the source to receiver paths by incorporating realistic gravity wave induced horizontal velocity fluctuations into time domain parabolic equation models the pulsed nature of the signals is simulated and arrival times are predicted to within 30 s of the observed values 1 per cent of the source to receiver transit time modelling amplitudes is highly dependent upon estimates of the unknown acoustic source strength or equivalent chemical explosive yield current empirical explosive yield relationships derived from infrasonic amplitude measurements from point source chemical explosions suggest that the equivalent chemical yield of the largest gerdec explosion was of the order of 1 kt and the largest chelopechene explosion was of the order of 100 t when incorporating these assumed yields the parabolic equation simulations predict peak signal amplitudes to within an order of magnitude of the observed values as gravity wave velocity perturbations can significantly influence both infrasonic arrival times and signal amplitudes they need to be accounted for in source location and yield estimation routines both of which are important for explosion monitoring especially in the context of the comprehensive nuclear test ban treaty

seismo acoustic evidence for an avalanche driven phreatic eruption through a beheaded hydrothermal system an example from the 2012 tongariro eruption abstract the 6 august 2012 te maari eruption comprises a complex eruption sequence including multiple eruption pulses a debris avalanche that propagated 2 km from the vent and the formation of a 500 m long arcuate chasm located 300 m from the main eruption vent the eruption included 6 distinct impulses that were coherent across a local infrasound network marking the eruption onset at 11 52 18 all times utc an eruption energy release of 3 1012 j was calculated using a body wave equation for radiated seismic energy a similar calculation based on the infrasound record shows that 90 of the acoustic energy was released from three impulses at onset times 11 52 20 20 of total eruption energy 11 52 27 50 and 11 52 31 20 these energy impulses may coincide with eyewitness accounts describing an initial eastward directed blast followed by a westward directed blast and a final vertical blast pre eruption seismic activity includes numerous small unlocatable micro earthquakes that began at 11 46 50 two larger high frequency earthquakes were recorded at 11 49 06 and 11 49 21 followed directly by a third earthquake at 11 50 17 the first event was located within the scarp based on an arrival time location from good first p arrival times and probably represents the onset of the debris avalanche the third event was a tornillo characterised by a 0 8 hz single frequency resonance and has a resonator attenuation factor of q 40 consistent with a bubbly fluid filled resonator this contrasts with a similar tornillo event occurring 2 5 weeks earlier having q 250 1000 consistent with a dusty gas charged resonator we surmise from pre eruption seismicity and the observed attenuation change that the debris avalanche resulted from the influx of fluids into the hydrothermal system causing destabilisation and failure the beheaded hydrothermal system may have then caused depressurisation frothing of the remaining gas charged system leading to the onset of explosive activity

a high frequency magnitude scale a high frequency magnitude scale m is proposed m 2 log a h f 3 where ahf is the high frequency level of the fourier amplitude spectrum of acceleration in cm sec average or random horizontal component at a hypocentral or closest fault distance of 10 km m can be determined from either instrumental data or the felt area of an earthquake the definition of m has been arranged such that m m moment magnitude for events of average stress drop in both eastern north america ena and california m provides a measure of the stress drop if m is also known the observed relationship between m and m indicates that the average stress drop is about 150 bars for ena earthquakes and about 70 bars for california earthquakes the variability of stress drop is much larger in ena than in california the chief justification for the m scale is its utility in the interpretation of the large preinstrumental earthquakes that are so important to seismic hazard estimation in eastern north america for such events m can be determined more reliably than can m or mn nuttli magnitude and forms a much better basis for estimating high frequency ground motions when used as a pair m and m provide a good index of ground motion over the entire engineering frequency band if both of these magnitudes can be defined for an earthquake then a ground motion model such as the stochastic model can be used to obtain reliable estimates of response spectra and peak ground motions

analysis of a crater forming meteorite impact in peru 1 the fireball producing a crater forming meteorite fall near carancas peru on 15 september 2007 has been analyzed using eyewitness seismic and infrasound records the meteorite impact which produced a crater of 13 5 m diameter is found to have released of order 1010 j of energy equivalent to 2 3 tons of tnt high explosives based on infrasonic measurements our best fit trajectory solution places the fireball radiant at an azimuth of 82 relative to the crater with an entry angle from the horizontal of 63 from entry modeling and infrasonic energetics constraints we find an initial energy for the fireball to be in the 0 06 0 32 kton tnt equivalent the initial velocity for the meteoroid is restricted to be below 17 km s from orbit considerations alone while modeling suggests an even lower best fit velocity close to 12 km s the initial mass of the meteoroid is in the range of 3 9 tons at impact modeling suggests a final end mass of order a few metric tons and impact velocity in the 1 5 4 km s range we suggest that the formation of such a substantial crater from a chondritic mass was the result of the unusually high strength and corresponding low degree of fragmentation in the atmosphere of the meteoritic body additionally the high altitude of the impact site 3800 m a s l resulted in an almost one order of magnitude higher impact speed than would have been the case for the same body impacting close to sea level

calibration of time history simulation methods abstract ground motion time histories for use in engineering analyses of structures in eastern north america are often simulated from seismological models owing to the paucity of real recordings in the magnitude and distance ranges of interest two simulation methods have been widely used in recent years the stochastic method and the ray theory method in the stochastic method as im plemented in this study ground motion is treated as filtered gaussian noise whose underlying spectrum is determined from an empirical region specific seismological model of the source and propagation processes in the ray theory method as implemented in this study the ground motions are simulated by convolving an empirical source function with theoretical green s functions for a specified crustal structure model this article compares results of the two simulation methods for four well recorded calibration events and assesses the applicability of the methods the assessment is based on comparisons of ground motion parameters from the simulated data with those of the actual recordings ground motion parameters in the frequency range from 1 to 10 hz are sat isfactorily predicted by both methods averaged over the four events studied the stochastic method underpredicts 1 hz response spectra by 20 to 40 but accurately predicts response spectra for frequencies of greater than 2 hz it also accurately predicts peak ground acceleration and velocity the wave propaga tion method underpredicts 1 hz response spectra by 10 to 40 but accurately predicts response spectra for higher frequencies it overpredicts peak ground acceleration and velocity by 10 to 40 both methods are imprecise the stan dard error of an estimate is a factor of about 2 2 the bias and standard error of an estimate for the wave propagation method are generally slightly lower than for the stochastic method if the focal depth of the event can be specified i e as for a past earthquake if the focal depth of the event is not known i e as for a future earthquake then the accuracy and precision of thetwo methods are about the same the chief advantage of the wave propagation method is its predictive power since its attenuation func tion is derived from the focal depth and crustal structure it does not require knowledge of the empirical attenuation function the chief advantage of the stochastic model is its economy and simplicity introduction seismic hazard studies are often used to identify design earthquakes in terms of magnitude and dis tance from a site of interest ground motion time his tories for the desired magnitude s and distance s are then sought to be used as input for engineering analyses of a proposed structure for regions such as california where strong ground motion records are relatively abun dant a suite of recordings from past earthquakes is usu ally available in eastern north america by contrast relevant records for the desired magnitudes and distances are seldom available it is therefore necessary to simu late the required records based on seismological models of earthquake ground motion generation processes two simulation methods have been widely used in recent years the stochastic method and the ray theory method in the stochastic method ground motion is treated as bandlimited finite duration gaussian noise whose underlying spectrum is determined from a seismological model of source and propagation processes in the ray theory method the ground motions are simulated by convolving an empirical source function usually derived from a past event with theoretical green s functions for 400

a method for including path effects in ground motion prediction equations an example using the mw 9 0 tohoku earthquake aftershocks past studies in tectonic regions dominated by subduction zones that result in the creation of volcanic belts such as new zealand and japan have pointed to higher attenuation rates across the volcanic regions this study uses the downhole motions recorded at kik net stations from 117 aftershocks that hit japan after the great m w 9 0 tohoku earthquake to quantify region dependent strong motion attenuation rates to this end an approach to include path effects in the development of ground motion prediction equations gmpes is presented in this approach regional path terms are constrained using the strong motion data the constraint on path terms also makes this methodology suitable for the development of gmpes that permit the removal of the ergodic assumption on path the analysis results indicate the viability of the proposed methodology for constraining regional path terms and provide an estimate of single station single path standard deviations in addition results confirm that the attenuation rate in volcanic regions is significantly higher than in nonvolcanic regions finally a moderate correlation coefficient was found between the attenuation rate for weak and strong ground motions

a seismoacoustic analysis of the gas pipeline explosion near ghislenghien in belgium a high pressure gas pipeline exploded near ghislenghien in belgium on 30 july 2004 seismic energy of this event was recorded at three nearby seismometers the origin time of the explosion was determined by analyzing the rayleigh waves and found to be 06h55m27 2sec coordinated universal time utc ground truth of the explosion was invoked to assess the accuracy of the location derived from infrasound data recorded over western europe different infrasonic phases were identified by using array processing techniques and raytracing through atmospheric models the analysis showed that the derived location was situated 13 km from the true location the total area of the uncertainty ellipse or area to be searched if the source was of unknown origin was 690 km 2 after the origin time and location the yield was calculated by comparing infrasonic stratospheric amplitudes with those from a high explosives dataset and was estimated at 40 9 tons high explosives equivalent in summary this study illustrates the capability of seismic and infrasound data in forensic investigations furthermore the potential of infrasound as a monitoring or verification technique is addressed

passive probing of the sound fixing and ranging channel with hydro acoustic observations from ridge earthquakes the international monitoring system includes a hydro acoustic part to verify the comprehensive nuclear test ban treaty besides explosive signals monitoring stations also detect acoustic waves from earthquakes that travel through the sound fixing and ranging sofar channel the travel times of such detections are listed in the reviewed event bulletin which is statistically evaluated for the stations located in the pacific indian and atlantic oceans the celerities of ridge earthquakes are calculated to build up a homogeneous data set based on similar source mechanisms the celerity is defined as the epicentral distance divided by the travel time the global characteristics of these celerities can be well understood in terms of temperature variations in the sofar channel a detailed velocity profile has been retrieved for the atlantic ocean where large differences 14 m s are found between the southern and northern parts of the basin propagation modeling with normal modes supports these findings which shows that the celerity gives an estimate of the sound speed in the sofar channel these results compare remarkably well with those from active experiments showing the ability of passively probing the sofar channel with hydro acoustic waves from earthquake sources

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

evidence for a meteoritic origin of the september 15 2007 carancas crater on september 15th 2007 around 11 45 local time in peru near the bolivian border the atmospheric entry of a meteoroid produced bright lights in the sky and intense detonations soon after a crater was discovered south of lake titicaca these events have been detected by the bolivian seismic network and two infrasound arrays operating for the comprehensive nuclear test ban treaty organization situated at about 80 and 1620 km from the crater the localization and origin time computed with the seismic records are consistent with the reported impact the entry elevation and azimuthal angles of the trajectory are estimated from the observed signal time sequences and backazimuths from the crater diameter and the airwave amplitudes the kinetic energy mass and explosive energy are calculated using the estimated velocity of the meteoroid and similarity criteria between orbital elements an association with possible parent asteroids is attempted the favorable setting of this event provides a unique opportunity to evaluate physical and kinematic parameters of the object that generated the first actual terrestrial meteorite impact seismically recorded

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

an entry model for the tagish lake fireball using seismic satellite and infrasound records we present instrumental observations of the tagish lake fireball and interpret the observed characteristics in the context of two different models of ablation from these models we estimate the pre atmospheric mass of the tagish lake meteoroid to be 56 tonnes and its porosity to be between 37 and 58 with the lowest part of this range most probable these models further suggest that some 1300 kg of gram sized or larger tagish lake material survived ablation to reach the earth s surface representing an ablation loss of 97 for the fireball satellite recordings of the tagish lake fireball indicate that 1 1 1012 j of optical energy were emitted by the fireball during the last 4 s of its flight the fraction of the total kinetic energy converted to light in the satellite pass band is found to be 16 infrasonic observations of the airwave associated with the fireball establish a total energy for the event of 1 66 0 70 kt tnt equivalent energy the fraction of this total energy converted to acoustic signal energy is found to be between 0 10 and 0 23 examination of the seismic recordings of the airwave from tagish lake have established that the acoustic energy near the sub terminal point is converted to seismic body waves in the upper most portion of the earth s crust the acoustic energy to seismic energy coupling efficiency is found to be near 10 6 for the tagish lake fireball the resulting energy estimate is near 1 7 kt corresponding to a meteoroid 4 m in diameter the seismic record indicates extensive nearly continuous fragmentation of the body over the height intervals from 50 to 32 km seismic and infrasound energy estimates are in close agreement with the pre atmospheric mass of 56 tonnes established from the modeling the observed flight characteristics of the tagish lake fireball indicate that the bulk compressive strength of the pre atmospheric tagish lake meteoroid was near 0 25 mpa while the material compressive strength most appropriate to the recovered meteorites was closer to 0 7 mpa these are much lower than values found for fireballs of ordinary chondritic composition the behavior of the tagish lake fireball suggests that it represents the lowest end of the strength spectrum of carbonaceous chondrites or the high end of cometary meteoroids the bulk density and porosity results for the tagish lake meteoroid suggest that the low bulk densities measured for some small primitive bodies in the solar system may reflect physical structure dominated by microporosity rather than macroporosity and rubble pile assemblages

tracing a meteoric trajectory with infrasound 1 a bright bolide appeared over the netherlands on the evening of 2003 february 19 infrasound generated by this bolide was detected at two nearby infrasound arrays as two distinct events the origins of the infrasonic signals were located in the stratosphere at heights of 30 and 57 km the results were obtained independently of visual observations of the bolide but confirm the reported time of occurrence the ability to distinguish between a moving and static source is crucial for the application of infrasound as a monitoring technique this study also illustrates the dependence of the infrasound technique on signal coherency inter array distance and atmospheric knowledge

fall recovery and characterization of the novato l6 chondrite breccia the novato l6 chondrite fragmental breccia fell in california on 17 october 2012 and was recovered after the cameras for allsky meteor surveillance cams project determined the meteor s trajectory between 95 and 46 km altitude the final fragmentation from 42 to 22 km altitude was exceptionally well documented by digital photographs the first sample was recovered before rain hit the area first results from a consortium study of the meteorite s characterization cosmogenic and radiogenic nuclides origin and conditions of the fall are presented some meteorites did not retain fusion crust and show evidence of spallation before entry the meteoroid was 35 5 cm in diameter mass 80 35 kg with a cosmic ray exposure age of 9 1 ma if it had a one stage exposure history a two stage exposure history is more likely with lower shielding in the last few ma thermoluminescence data suggest a collision event within the last similar to 0 1 ma novato probably belonged to the class of shocked l chondrites that have a common shock age of 470 ma based on the u th he age of 420 220 ma the measured orbits of novato jesenice and innisfree are consistent with a proposed origin of these shocked l chondrites in the gefion asteroid family perhaps directly via the 5 2 mean motion resonance with jupiter novato experienced a stronger compaction than did other l6 chondrites of shock stage s4 despite this a freshly broken surface shows a wide range of organic compounds less

luminescence chronology of aeolianites from the section at givat olga coastal plain of israel abstract the eastern mediterranean coastal plain of israel is composed mainly of loam sand and gravel of pleistocene to holocene age indicating an alternation of marine coastal and continental environments owing to the complexity of the numerous exposures of aeolianites kurkar and soils hamra in the elongated ridges along the coastal plain it is difficult to set up a reliable stratigraphy a systematic luminescence dating study was carried out on loose sand kurkar and hamra deposits in the coastal plain between netanya and haifa sixteen samples were taken and investigated from the section at givat olga the chronological results show excellent agreement between the infrared optically stimulated luminescence irsl and thermoluminescence tl techniques indicating that the former sand dunes were well bleached prior to deposition the irsl and tl age estimates range from about 75 3 ka for the aeolianites indicating that this kurkar ridge formed during an older period of the last glaciation likely before 50 ka

spectral analysis of k net and kik net data in japan part ii on attenuation characteristics source spectra and site response of borehole and surface stations abstract in this study we apply a nonparametric spectral inversion scheme to a data set of accelerograms recorded by the k net and kik net networks in japan in order to derive attenuation characteristics source spectra and site response for this purpose we use a total of more than 67 000 s wave records from 2178 earthquakes m jma 2 7 8 obtained at 1555 stations at the earth s surface and more than 29 000 records from 1826 events recorded at 637 borehole stations at depths of 100 to 3000 m attenuation characteristics are investigated in five separate regions showing that crustal q depicts lower values in central compared to southern japan and a significant frequency dependence is observed in every region the source spectra follow the 2 model with higher stress drops for subcrustal earthquakes as compared with crustal ones while strong amplification effects dominate the site contributions for the surface sensors those for the borehole sensors are characterized by smaller variability nevertheless consistent with observations from deconvolution of borehole surface recording pairs downgoing wave effects are visible in the site contributions for many borehole stations finally the site amplification functions obtained at the surface are compared with surface to borehole s b and horizontal to vertical h v spectral ratios showing that the s b ratios generally provide better estimates of the horizontal amplification than the h v ratios due to amplification of the vertical component of ground motion

repeatable site and path effects on the ground motion sigma based on empirical data from southern california and simulated waveforms from the cybershake platform in this study we use two sets of residuals of the response spectral values to identify the repeatable effects due to specific ray paths and sites that are generally included in the standard deviation of the ground motion prediction equations gmpes one empirical set of residuals from the abrahamson et al 2014 gmpe and one set derived from simulated waveforms of the cybershake platform comparisons of the residuals at an oscillator period of 3 s lower usable limit of the 3d cybershake simulations show similarities between the site effects estimated from the two datasets with a correlation coefficient of 0 63 but the path effects are not similar correlation coefficient 0 for more than half of the sites evaluated comparing the cybershake path effects for moderate m w 6 5 and large m w 8 earthquakes showed that in most cases path effects from large magnitude earthquakes can be approximated using path effects from smaller earthquakes that have the same closest point to a site attention should be used when very large magnitude m w 8 events are involved and the fault crosses the sites finally the method for performing a fully nonergodic site specific probabilistic seismic hazard analysis including source path and site terms is outlined

site response attenuation and source spectra of s waves along the guerrero mexico subduction zone acceleration spectra from nine earthquakes and up to 11 stations per earthquake are inverted to find the source spectra the site response and the quality factor q of s waves this method is applied to moderate earthquakes 4 0 0 8 hz does not follow a simple linear relation as observed in previous studies of attenuation in other regions when the source spectra are interpreted in terms of brune s model the stress drops obtained are less than 20 bars for the four larger events analyzed the site functions obtained indicate that although all the stations used are on rock the effect of the near surface geology caused important amplifications at some stations

listening to sounds from an exploding meteor and oceanic waves low frequency sound infrasound measurements have been selected within the comprehensive nuclear test ban treaty ctbt as a technique to detect and identify possible nuclear explosions the seismology division of the royal netherlands meteorological institute knmi operates since 1999 an experimental infrasound array of 16 micro barometers here we show the rare detection and identification of an exploding meteor above northern germany on november 8th 1999 with data from the deelen infrasound array dia at the same time sound was radiated from the atlantic ocean south of iceland due to the atmospheric coupling of standing ocean waves called microbaroms occurring with only 0 04 hz difference in dominant frequency dia proved to be able to discriminate between the physically different sources of infrasound through its unique lay out and instruments the explosive power of the meteor being 1 5 kt tnt is in the range of nuclear explosions and therefore relevant to the ctbt

trail in the atmosphere of the 29 december 2000 meteor as recorded in tahiti characteristics and trajectory reconstitution 1 on 29 december 2000 a meteor entry in the atmosphere produced several bright lights in the sky of tahiti and intense sonic booms around midnight local time this event was detected by the laboratoire de detection et de geophysique french polynesian seismic network and by the is24 infrasound station in tahiti operating for the comprehensive test ban treaty organization ctbto both seismic and infrasonic signals indicated that the altitude of the meteor s last explosion was 45 km from the wave azimuth and incidence angle determined through infrasonic data processing the meteor trajectory has been backtracked over 55 km determination of the azimuth and incidence angle of the infrasonic arrivals permitted the determination of a 55 km segment of the meteor trajectory the velocity of the meteor decreased from 17 to 15 km s in 4 s while its altitude changed from 55 to 45 km the diameter and the kinetic energy of the bolide are evaluated using the infrasonic measurements and numerical simulations

seismic and acoustic detection of a bolide airburst in the gulf of naples southern italy 1 on 10 september 2005 at 1711 lt 1511 ut a loud boom was heard on the ischia island a clear seismic signal was also recorded by the seismic monitoring network of the neapolitan volcanic areas ischia campi flegrei and mount vesuvius and on a regional station mount massico on the basis of the seismic recordings and on acoustic phenomena reports we relate this event to the atmospheric explosion airburst of a bolide about 15 km sw of ischia at an elevation of about 11 5 km the location has been obtained through nonlinear traveltime inversion in a realistic atmospheric model including wind effects we show using statistical estimators how the traveltime pattern is due to both atmospheric winds and the bolide trajectory using the same reasoning we discard a human origin supersonic jet or sea air missile in addition we also propose a new algorithm for fast acoustic traveltime computation for a supersonic moving source

the villalbeto de la pena meteorite fall i fireball energy meteorite recovery strewn field and petrography an impressive daylight fireball was observed from spain portugal and the south of france at 16h46m45s utc on january 4 2004 the meteoroid penetrated into the atmosphere generating shock waves that reached the ground and produced audible booms the associated airwave was recorded at a seismic station located 90 km north of the fireball trajectory in spain and at an infrasound station in france located 750 km north east of the fireball the absolute magnitude of the bolide has been determined to be 18 1 from a casual video record the energy released in the atmosphere determined from photometric seismic and infrasound data was about 0 02 kilotons kt a massive fragmentation occurred at a height of 28 0 2 km resulting in a meteorite strewn field of 20 6 km the first meteorite specimen was found on january 11 2004 near the village of villalbeto de la pena in northern palencia spain to date about 4 6 kg of meteorite mass have been recovered during several recovery campaigns the meteorite is a moderately shocked s4 l6 ordinary chondrite with a cosmic ray exposure age of 48 5 ma radioisotope analysis shows that the original body had a mass of 760 150 kg which is in agreement with the estimated mass obtained from photometric and seismic measurements

evanescent wave coupling in a geophysical system airborne acoustic signals from the mw 8 1 macquarie ridge earthquake atmospheric low frequency sound i e infrasound from underwater events has not been considered thus far due to the high impedance contrast of the water air interface making it almost fully reflective here we report for the first time on atmospheric infrasound from a large underwater earthquake mw 8 1 near the macquarie ridge which was recorded at 1325 km from the epicenter seismic waves coupled to hydroacoustic waves at the ocean floor after which the energy entered the sound fixing and ranging channel and was detected on a hydrophone array the energy was diffracted by a seamount and an oceanic ridge which acted as a secondary source into the water column followed by coupling into the atmosphere the latter results from evanescent wave coupling and the attendant anomalous transparency of the sea surface for very low frequency acoustic waves

seismic ground motions from a bolide shock wave 1 an intensely brilliant bolide accompanied by an audible sonic boom occurred on the night of 3 november 2003 2150 lt or 4 november 2003 0350 ut in northeastern arkansas the sonic boom was well recorded by 22 three component stations of the center for earthquake research and information cooperative seismic network arrival times and wave polarizations were used to reconstruct the acoustic wave front propagating across the network and to estimate trajectory parameters of the bolide a grid search location technique constrains the trajectory and gives a reference height of 50 100 km above the southern edge of the network an azimuth of propagation of 270 290 toward the northwest and a plunge of 38 48 downward the trajectory and date of the bolide event are consistent with a taurid shower meteor transient ground motions from the sonic boom were studied using plane wave cagniard dehoop and propagator matrix theory for an incident pressure pulse impinging on a layered elastic earth model general characteristics of the vertical and radial polarization and wave frequency content require acoustic coupling within a thin 10 m near surface layer with low p wave 0 25 km s and s wave 0 125 km s velocities ground motions are generally confined to this near surface layer are not sensitive to deeper earth structure within the mississippi embayment unconsolidated sediments and display both leaky mode pl a type of dispersed p type seismic wave and locked mode rayleigh wave propagation acoustic wave ground motion coupling studies may be a useful way to analyze near surface site responses to determine velocity structure in earthquake shaking hazard studies