relationship between dike and volcanic conduit distribution in a highly eroded monogenetic volcanic field san rafael utah usa we mapped 63 conduits 2000 dike segments and 12 sills in the san rafael subvolcanic field utah united states where this pliocene magmatic system is eroded to a depth of 0 8 km and is exceptionally well exposed although the number of mapped conduits dikes and sills might represent minimums depending on the level of erosion and exposure mapped dikes are more numerous around the areally extensive sills and interact with sills and conduits in complex ways we analyze conduit distribution using kernel density methods and compare results with dike and sill distribution we find that the distribution of conduits matches the major features of dike distribution including development of clusters and distribution of outliers these statistical models are then applied to the distributions of volcanoes in several recently active volcanic fields where intrusion distributions must be inferred from very sparse data and compared with san rafael conduit distribution this comparison supports the use of statistical models in probabilistic hazard assessment for distributed volcanism specifically renewed dike intrusion and potential eruptions in active basaltic systems can be assessed probabilistically from the distribution of older volcanoes in distributed volcanic systems

concrete dams as seismic imaging sources 1 we obtained noise correlation functions ncf in northern montana from broadband data that include p and s wave first arrivals and short period surface waves for frequencies extending to nearly 15 hz at offsets of 5 17 km using ambient resonant vibrations of a concrete gravity arch dam as seismic source a seismograph operated close to the dam acted as a virtual source with a compact autocorrelation function making it feasible to use short duration cross correlation time windows to obtain a larger number of ncf stacks with impulsive high frequency body wave first arrivals from recording durations of a single day to several weeks

earthquakes faulting and stress in the los angeles basin since 1920 fourteen moderate sized m l 4 9 6 4 earthquakes have been reported in the los angeles basin these events are associated with both mappable surficial faults and concealed faults beneath the basin sediments to determine the style of faulting and state of stress in the basin single event focal mechanisms for 244 earthquakes of m 2 5 that have occurred during 1977 1989 have been calculated fifty nine percent of the events are strike slip and are mostly located near two of the major northwest striking right lateral strike slip faults in the basin the newport inglewood fault and the palos verdes fault the 1988 pasadena and the 1988 upland earthquakes showed left lateral strike slip on northeast striking faults numerous small earthquakes in the eastern part of the basin show left lateral strike slip faulting and form a northeast trend near yorba linda thirty two percent of the events have reverse mechanisms and are distributed along two broad zones the first the elysian park fold and thrust belt coincides with anticlines along the eastern and northern flank of the los angeles basin extending into santa monica bay the second the torrance wilmington fold and thrust belt coincides with anticlines mapped on the southwest flank of the basin and extends from offshore newport beach to the northwest into santa monica bay oblique faulting that could be inferred by the merging of strike slip and compressional tectonics does not occur in the basin instead the coexistence of zones of thrusting and large strike slip faults in the basin suggests that the thrust and strike slip movements are mostly decoupled a few normal faulting mechanisms appear to be related to faulting orthogonal to the axes of plunging anticlines the trend of the maximum horizontal stress varies from n1 w to n31 e across the basin and consistently forms high angles with the fold axes the stress field that exists along the flanks of the basin has a vertical minimum stress axis this stress field and ongoing folding and thrusting suggest that tectonic deformation is concentrated along the flanks of the deep central basin today the deformation of the basin consists of uplift and crustal thickening and lateral block movement to accommodate the north south compression across the basin

numerical modelling of the hydro mechanical behaviour of fractured rock masses abstract results are presented from an investigation into the hydro mechanical response of a rock mass to changes in effective stress associated with fluid extraction numerical models of regularly and randomly fractured reservoirs have been created using udec the distinct element code relationships between permeability and stress state have been established in regions immediately adjacent to simulated wellbores and more generally throughout the fractured reservoirs the effects of in situ stress state hydraulic boundary conditions and scale have been investigated the results demonstrate that numerical modelling combined with analytical solutions can be employed to investigate coupled flow deformation analysis realistically for simple geological situations the relationships presented here relating fracture pemeability to stress field changes will be helpful in understanding the behaviour of naturally fractured reservoirs during pressure depletion

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

effect of vibrating buildings on free field motion and on adjacent structures the bonefro italy case history abstract during the 2002 molise sequence a shock was recorded in a building that suffered heavy damage mucciarelli et al 2004 the availability of this data along with other similar data led to the organization of an international workshop for structural engineers aimed at the reproduction of the staged evolution of damage observed a goretti and m mucciarelli unpublished manuscript 2007 the aim of this present work is to model the damaged building the adjacent less damaged building and a large section of the subsoil the model should provide some insight into two possible phenomena 1 the soil structure interaction ssi that is the modification of the free field seismic response induced by the presence of the buildings located on soft soil and 2 the possible interaction between the two buildings the study was performed using the 2d chebyshev spectral element method spem for a 2d section the model with topography includes the bedrock limestone with the overlaying clay layer circa 30 m the building is modeled by an equivalent shear wave velocity which is calculated from its identified mechanical properties first the model s ability to reproduce the motions recorded inside and outside the building was verified then one or both of the buildings were removed to study their effect the influence of the presence of buildings on the free field motion is about 40 on spectral values and it is felt up to a distance of about 250 m from the buildings the results also suggest the presence of resonance between buildings

array analysis of the ground velocities and accelerations from the 1971 san fernando california earthquake profiles of ground velocity and acceleration displayed as a function of epicentral distance are analyzed for recordings of the 1971 san fernando earthquake three long profiles 50 km and three short profiles 2 km are studied although there is considerable variation in waveforms and peak amplitudes observed along the long profiles there are also many examples of coherent phases seen on adjacent stations there are striking differences in the amplitudes and durations of ground velocity observed at stations located on hard rock sites as opposed to stations located within the large sedimentary basins of the los angeles area furthermore the san fernando basin which is adjacent to the source area seems to respond quite differently from the los angeles basin which is about 30 km from the earthquake source area ground acceleration profiles however show that there is no corresponding change in the duration or amplitude of high frequency shaking with site characteristics we infer that the excitation of surface waves within sedimentary basins is the reason that large peak velocities and displacements are observed for soft sites the ground velocity waveforms are nearly identical along the three short profiles which are all located within the los angeles basin greater variation of waveforms and amplitudes are seen for ground acceleration along these short profiles although strong phase coherence is still observed

seismic precursors to space shuttle shock fronts seismic precursors to space shuttle re entry shock fronts are detected at txar in southwest texas when the ground track of the orbiter vehicle passes within 150 200 km of the observatory these precursors have been termed shuttle quakes because their seismograms superficially mimic the seismograms of small earthquakes from shallow sources analysis of the shuttle quake seismograms however reveals one important difference unlike ordinary earthquakes the propagation azimuths and horizontal phase velocities of the individual phases of the shuttle quakes are functionally related from a theoretical model developed to account for the origin of these precursors it is found that the seismic phases of shuttle quakes are bow waves a bow wave originates at the advancing tip of the shock front trace i e intersection of the re entry shock front with the surface of the earth when the ground speed of the orbiter vehicle exceeds the horizontal phase velocity of a particular seismic phase bow waves are shown to differ in two important respects from the ordinary seismic phases they vanish ahead of the advancing tip of the shock front trace and their propagation azimuths and horizontal phase velocities are functionally related the ground speed of the orbiter vehicle exceeds the horizontal phase velocities of crustal seismic phase over much of the re entry flight profile as a result p s and r g bow waves will be seen as precursors to the re entry shock front at stations located within a few hundred km of its ground track

paleomagnetic constraints on eruption patterns at the pacaya composite volcano guatemala pacaya volcano is an active composite volcano located in the volcanic highlands of guatemala about 40 km south of guatemala city volcanism at pacaya alternates between strombolian and vulcanian and during the past five years there has been a marked increase in the violence of eruptions the volcano is composed principally of basalt flows interbedded with thin scoria fall units several pyroclastic surge beds and at least one welded tuff between 400 and 2000 years bp the w sw sector of the volcano collapsed producing a horseshoeshaped amphitheater 0 65 km3 and providing a window into the cone s infrastructure lava flows and tephra exposed in the amphitheater are more then 200 m thick and when combined with flows erupted recently represent between 30 and 40 of the cone s history pacaya is ideally suited for a paleomagnetic study into the timing and duration of eruption episodes at a large composite volcano we drilled 27 paleomagnetic sites 25 aa flows 1 dike and 1 welded tuff from four lava flow sequences with between 4 and 14 sites per sequence the four sequences represent initial through historic activity at pacaya we resolved what appear to be 22 time independent paleomagnetic sites by averaging together directions from successive sites where the sitemean directions were indistinguishable at the 95 level of confidence however mean sequence directions of individual lava flow sequences yielded unusually high fisher precision parameters k 44 224 and small circles of 63 confidence a63 1 6 6 1 suggesting as few as three or four time independent sites were collected this indicates that activity as pacaya is strongly episodic and that episodes are characterized by voluminous outpouring of lavas modelling the data using holocene psv rates confirms this and shows that differences in within sequence directions 6 11 5 are consistent with emplacement of lava flow sequences in less than 100 years to as many as 300 years relatively larger differences in directions 18 23 between subjacent lava flow sequences indicates that repose is at least 300 500 years and could be even longer

characterization of non elastic ground behavior of a large underground power house cavern by back analysis abstract this paper presents results of a characterization procedure based on back analysis of a nonlinear deformation behavior of a discontinuous rock mass during excavation of a large underground power house cavern the objective is to introduce the concept of isolating effects of nonlinear joint deformation to be back analyzed from measured displacements and to demonstrate the effectiveness of this method for identifying strain distribution and deformational mechanism within a jointed rock mass

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

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

seismic investigation of the 26 march 2010 sinking of the south korean naval vessel cheonanham a south korean naval vessel sank on 26 march 2010 a seismic event with magnitude ml of 1 5 was observed at the time of vessel sinking seismic waveforms were collected from three local stations the event origin time is refined based on the p and s arrival times at the stations the calculated event location and time are close to the reported vessel sinking location and time suggesting that the observed seismic event is associated with the vessel sinking the amplitudes of s waves are comparable to those of p waves seismic waves coupled from acoustic waves are observed providing additional constraints of epicentral distance and source type the coupled acoustic waves have a dominant frequency of 32 hz the acoustic waves and high p s amplitude ratios suggest an underwater explosion the body wave magnitude based on pn is determined to be 1 46 which is consistent with the reported ml p energy is dominant at around 8 5 hz with multiple frequencies of 17 7 and 34 6 hz the primary frequency suggests the water column thickness in the source region to be 44 m which agrees with the reported value

palaeomagnetic results from the indian heaven volcanic field south central washington summary palaeomagnetic data have been obtained from plio pleistocene rocks of the indian heaven volcanic field ihvf located in the high cascade province in southern washington alternating field demagnetization yielded well defined directions from 56 individual lava flows sites from 23 volcanic units all units sampled were normally magnetized suggesting that volcanic activity within the indian heaven region occurred primarily during the last 0 73 myr and not over the last 3 75 myr as suggested by k ar ages combining palaeomagnetically similar site mean directions from lava flows from the same volcanic unit resulted in n 35 the mean direction calculated from this data set is i 65 2 and d 0 2 095 3 3 k 56 4 while the palaeomagnetic pole calculated using virtual geomagnetic pole vgp data is located at 87 7 n 231 4 e or95 4 7 k 27 2 this pole is not significantly different from the pole determined from all data n 56 or the rotational axis and is slightly near sided with respect to the mean sampling site longitude the between site angular dispersion of the vgps about the mean for n 35 and n 56 although low is not statistically different at the 95 confidence level from the expected value predicted by model f of mcfadden mcelhinny 1984 our data together with other recent data from the western united states do not confirm the presence of a persistent standing non dipole field component in this region during the plio pleistocene as suggested by brown mertzman 1979 additionally these data suggest that vgp angular dispersion associated with the geomagnetic field has been decreasing over the last 5 myr

new back analysis method of slope stability by using field measurements abstract the authors have proposed the idea that landslide movement is caused by both the reduction of shear rigidity at sliding surface and the body force of the sliding block based on this idea the authors have developed a new back analysis method to represent slope movement with without external force this method is applicable to not only natural landslide but also landslide caused by tunnel excavation or cut slope in this method sliding surface has been assumed to be anisotoropic continuous material which has the smallest shear rigidity parallel to the boundary of slide surface the mechanical constants on the sliding surface can be calculated from fitting between the measured and calculated displacement this method can be easily applicable to practical engineering

a practical procedure for the back analysis of slope failures in closely jointed rock masses abstract where closely jointed rock masses are encountered in slopes failure can occur both through the rock mass as a result of combination of macro and micro jointing and through the rock substance determination of the strength of this category of rock mass is extraordinarily difficult since the size of representative specimens is too large for laboratory testing this difficulty can be overcome by using a non linear rock mass failure criterion or by back analysis of such slopes to estimate the rock mass strength in this paper a practical procedure and a computer program are presented for the back determination of shear strength parameters mobilized in slopes cut in closely jointed rock masses which obey a non linear failure criterion rather than a linear one the procedure shows that the constants to derive normal stress dependent shear strength parameters of the failed rock masses can be determined by utilizing a main cross section and without a pre determined value of rock mass rating rmr trials are made for different rmr m and rmr s values corresponding to various possible combinations of the constant m and s which are used in the hoek brown failure criterion satisfying the limit equilibrium condition it is also noted that the procedure provides a quick check for the rock mass rating obtained from the site investigations the method is used in conjunction with the bishop s method of analysis based on circular slip surfaces the procedure outlined in this paper has also been satisfactorily applied to documented slope failure case histories in three open pit mines in turkey

seismic excitation by the space shuttle columbia seismic stations in southern california recorded the atmospheric shock waves generated by the space shuttle columbia on its return to the edwards air force base on 13 august 1989 fig 1 in addition to the shock wave the broad band iris terrascope station at pasadena recorded a distinct pulse with a period of 2 3 seconds which arrived 12 5 seconds before the shock wave fig 2 this pulse was also recorded at the university of southern california near downtown los angeles where it arrived 3 seconds after the shock wave the origin of this pulse could not be readily identified we show here that it was a seismic p wave excited by the motion of high rise buildings in downtown los angeles which were hit by the shock wave the proximity of the natural period of the high rise buildings to that of the los angeles basin enabled efficient energy transfer from shock wave to seismic wave

predicted behavior of a subway station in weathered rock abstract sao paulo subway s fourth line will have part of it s underground excavation placed in a weathered gneiss rock mass fractured highly altered and with vertical ubiquitous joints closely spaced pinheiros underground station will be excavated in unfavourable geotechnical conditions behavior of this excavation was predicted using numerical modelling with distinct elements to analyse rock mass response to excavation the designer evaluated several options of support excavation optimizing it in terms of cost and effectiveness an uncoupled numerical analysis was also made to evaluate water inflow into the excavation rock mass discontinuities present three dominant families one vertical one sub vertical and one sub horizontal besides vertically oriented closely spaced ubiquitous joints several options of support systems were analysed the one with fully grouted rockbolts and shotcrete linings was selected as the most apropriate based on this analysis water inflow inside the excavation was estimated leading to a fully lined station in order to reduce inflow to a minimum

seismic analysis of the 7 january 1998 chemical plant explosion at kean canyon nevada abstract an accident at the sierra chemical company kean canyon plant 16 km east of reno nevada resulted in two explosions 3 52 sec apart that devastated the facility an investigation into a possible cause for the accident required the determination of the chronological order of the explosions we resolved the high precision relative locations and chronology of the explosions using a cross correlation method applied to both seismic and air waves the difference in relative arrival times of air waves between the explosions indicated that the first explosion occurred at the northern site we then determined two station centroid separations between explosions which average about 73 m with uncertainties ranging from 17 to 41 m depending on the alignment of station pairs we estimated a centroid separation of 80 m using p waves with a larger uncertainty of 340 m we performed a grid search for an optimal separation and the azimuth by combining air wave arrivals from three station pairs the best solution for the relative location of the second explosion is 73 2 m s35 e from the first explosion this estimate is well within the uncertainties of the survey by the u s chemical safety and hazard investigation board csb the csb reported a separation of approximately 76 2 m s33 e the spectral amplitudes of p waves are 3 to 4 times higher for the second explosion relative to the first explosion but the air waves have similar spectral amplitudes we suggest that this difference is due to the partitioning of energy between the ground and air caused by downward directivity at the southern explosion and upward directivity at the northern explosion this is consistent with the absence of a crater for the first explosion and a 1 8 m deep crater for the second explosion

numerical investigation of rock heterogeneity effect on rock dynamic strength and failure process using cohesive fracture model abstract in this study a cohesive fracture model cfm which assumes rock material as assemblage of deformable grains joining together at their cohesive boundaries is developed to simulate rock fracture and failure behavior in terms of mineral and cement properties to better represent the structural bonds between the particles and the heterogeneity of rock material a user defined material model umat for the cohesive element with stochastic strengths is incorporated into the developed cfm the capability of the developed model for rock fracture problems under both static and dynamic loads is first explored based on the developed model the heterogeneity effect of rock on its dynamic failure process and dynamic strength is then studied the results demonstrate that the developed cfm can be used to investigate the rock fracture problems under both static and dynamic loads the heterogeneity of rock material not only affects the rock dynamic failure process but also leads to an increase of rock dynamic strength

a magnetostratigraphic and secular variation study of level mountain northern british columbia summary palaeomagnetic results are reported from 50 flows erupted by level mountain which is a composite volcano in northern british columbia fourteen magnetic polarity zones are represented and these allow a magneto stratigraphy to be established which indicates that eruptive activity began about 6 5 myr ago and continued up to very recent times with several hiatuses of up to 1 myr or more most of the flows yield acceptable normal or reversed palaeopoles but two of them record the gauss matuyama polarity transition and a further four yield a tight group of divergent directions which are here interpreted as a geomagnetic excursion near the base of the gauss epoch this observation lends support to an earlier suggestion bingham stone that the geomagnetic field was abnormally disturbed about 3 5 myr ago at least locally in north western north america the overall average palaeopole obtained after filtering out flows with high internal variance and those yielding divergent virtual geomagnetic poles vgps lies at 256 e 85 n n 38 a 7 2 a more representative palaeopole is obtained by combining the results with those of souther symons from mount edziza a closely related contemporaneous volcano some 100 km away this pole lies at 292 e 87 n n 92 ag5 4 1 and again includes the geographic pole within its 95 per cent confidence limits how ever the mean itself is not far sided as wilson s model predicts neither is it left handed as the analysis by merrill mcelhinny predicts the slight near sidedness observed agrees with the global compilation of wilson mcelhinny who show that the north western region of north america is the only area out of 15 regions worldwide to yield a near sided pole the dispersion of the vgps angular standard deviation 22 is a little higher than would be expected from global summaries and secular variation models this was also found to be the case in data from alaska doell cox the angular dispersion the occurrence of geomagnetic excursions and the

paleomagnetism of miocene volcanics on sao tome paleosecular variation at the equator and a comparison to its latitudinal dependence over the last 5 myr a collection was made in january 2009 of 10 oriented samples from each of 54 sites in lavas on sao tome island nominal location 0 3o n 6 5o e some sites were affected by lightning leaving a total of 42 sites for analysis of paleosecular variation overall magnetic properties were excellent highly stable magnetizations carried by pseudo single domain magnetite after principal component analysis of progressive alternating field demagnetization data for the samples twenty two sites had normal polarity magnetizations d 0 6o i 8 3o 95 4 3o 53 1 and 20 had reverse magnetizations d 176 0o i 4 2o 95 7 3o 20 8 the directions are within 5 of antiparallel yielding a positive reversal test the combined data set of 42 site mean virtual geomagnetic poles converted to common normal polarity yields a pole position at 86 0 n 211 5oe a95 3 1o ar ar and k ar dating reveals that these rocks are miocene in age 5 11 ma old enough to allow northerly plate motion to help explain the slightly far sided pole position the between site dispersion in virtual geomagnetic poles was estimated as the angular standard deviation sb and equaled 11 4 with 95 confidence interval between 9 9 and 13 4 this article is protected by copyright all rights reserved

experimental and numerical evidence of the clustering effect of structures on their response during an earthquake a case study of three identical towers in the city of grenoble france in this article interpretation of an equivalent to a macroseismic intensity survey performed in three identical stand alone buildings located in grenoble france after an m l 4 1 earthquake reveals a clustering effect resulting in different levels of perception of seismic loading by inhabitants the clustering effect is confirmed using numerical simulation the variation of the seismic response of the building in the middle of the cluster depends on the azimuth of the seismic source relative to the building cluster the major effect is the splitting of its resonance frequency accompanied by a decrease in vibration amplitude we conclude that clustering has an impact on urban effects calling into question the validity of seismic design which considers buildings in urban areas as stand alone constructions and the interpretation of macroseismic intensity surveys conducted in dense urban areas

interpretation by numerical modelling of changes of fracture system hydraulic conductivity induced by fluid injection distinct element modelling of naturally fractured reservoirs is used to investigate changes of hydraulic conductivity induced by fluid injection general conclusions are drawn relating to the effects of uniform changes of pore pressure on conductivity anisotropy in connected joint systems the influence of cross cutting discontinuous joints on the conductivity of the joints against which they terminate is emphasized results from a two dimensional model are related to the observed performance of a granitic geothermal reservoir on emploie le modele a elements distincts des reservoirs fractures de facon naturelle pour etudier les changements dans la conductivite induits par l injection de fluide des conclusions generales sont tirees concernant les effets de changements uniformes de pression interstitielle dans des systemes de joints relies sur l anisotropie de conductivite on accentue l influence exercee sur la conductivite des joints par des joints discontinus transversaux des resultats obtenus a parti

site city seismic interaction in mexico city like environments an analytical study recent destructive earthquakes have confirmed the importance of hazard and vulnerability studies to predict and prevent the impact of large seisms most seismic risk analysis considers the buildings as a passive constituent integrated into the vulnerability analysis this approach neglects the possible contribution of the building vibration to the free field this article describes an analysis of site city effects that is the seismic interaction of the city with soft soil layers an analytic method derived from soil structure interaction studies is described and applied to the roma norte zone of mexico city the building parameters are derived from detailed studies of the ja and pc buildings the soil city system is subjected to the mexican m w 7 3 14 september 1995 earthquake the simulated ground surface motions which incorporate the wave field radiated from the buildings of roma norte district are compared to seismic records from this zone analytical procedures reproduce the long time duration and beating of the observed ground motion in mexico city parametric analysis are also performed to identify the predominant factors e g urbanization density soil to city stiffness ratio that favor the site city interaction effects a simple relation is proposed to estimate the expected efficiency of the site city interaction effects for any city

a meteorite crater on earth formed on september 15 2007 the carancas hypervelocity impact on september 15 2007 a bright fireball was observed and a big explosion was heard by many inhabitants near the southern shore of lake titicaca in the community of carancas peru a 13 5 m crater and several fragments of a stony meteorite were found close to the site of the impact the carancas event is the first impact crater whose formation was directly observed by several witnesses as well as the first unambiguous seismic recording of a crater forming meteorite impact on earth we present several lines of evidence that suggest that the carancas crater was a hypervelocity impact an event like this should have not occurred according to the accepted picture of stony meteoroids ablating in the earths atmosphere therefore it challenges our present models of entry dynamics we discuss alternatives to explain this particular event this emphasizes the weakness in the pervasive use of average parameters such as tensile strength fragmentation behavior and ablation behavior in current modeling efforts this underscores the need to examine a full range of possible values for these parameters when drawing general conclusions from models about impact processes

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

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

numerical methods in rock mechanics the purpose of this civilzone review paper is to present the techniques advances problems and likely future development directions in numerical modelling for rock mechanics and rock engineering

seismic observations of meteors coupling theory and observations to date coupling of acoustic waves directly with the earth s surface represents the bulk of the observed meteor related seismic signals while precursory and impact related seismic waves remain an observational rarity with proliferation of infrasound and seismic monitoring systems new opportunities exist to explore the relationship between earth s atmosphere andsurface continued studyofmeteorseismologywillleadto new methods to constrain energies sizes and fluxes for moderately cm to m sized meteoroids on earth and potentially on mars

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

coupled htm modelling of cold water injection in fractured hydrocarbon reservoirs abstract this paper presents a numerical modelling approach for analyzing the coupled hydro thermo mechanical htm behaviour of fractured hydrocarbon reservoirs the coupled htm approach is applied to generic models of five spot reservoirs with different fracture patterns the presence of fractures was shown to have important effects on cold water injectivity and sweep efficiency due to high fluid velocities along fractures local areas particularly close to fracture intersections cannot be saturated with cold water the volume of oil by passed by the displacing water was found to be strongly dependent on fracture geometry and was generally larger if the fracture conductivity enhancement due to fracture deformation is taken into consideration the thermo poro elastic stress changes due to cold water injection were found to induce significant normal and shear displacements and conductivity changes along the fractures another important result of the numerical modelling is the possibility of creating secondary tensile fracturing close to existing fractures the secondary fractures are generally oriented perpendicular to the natural fractures and are expected to help in draining the oil from the rock matrix towards the fractures

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

thermohydromechanics of partially saturated geological media governing equations and formulation of four finite element models this paper presents the general governing equations for coupled thermohydromechanical thm processes in saturated and unsaturated geologic formations and reviews four finite element codes for modeling of such system three of the codes are developed for the special purpose of analyzing coupled thm processes in unsaturated porous and fractured geological media and the fourth is a commercial code that has been used in its standard version with a few adaptations for this specialized problem the basic assumptions and fundamental equations for coupled thm processes in unsaturated porous fractured rock are presented and formulations of the four finite element models are compared

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

evaluation of soil building resonance effect in the urban area of the city of matera italy abstract this study discusses the effect of buildings vibrations in the urban field in the context of local seismic response studies in order to evaluate the possible occurrence of double resonance effects during strong motions the aim is to recognise the interaction effect between near surface geology and all overlying buildings in the urban area of the city of matera southern italy single station seismic ambient noise measurements 230 were performed on the main lythologies 134 and on the principal building typologies 96 soil and building measurements allowed estimating the main frequencies and relative amplitudes of the soil fundamental peaks as well as the first vibrational frequency of buildings the period height linear relationship derived by experimental results made it possible estimating the fundamental frequency for all the matera s buildings having also estimated the frequencies at each point of the urban soil it was thus possible to obtain a soil building resonance map in the linear elastic domain matera represents an important case study because the first vibration frequency for most of the buildings is quite close to those of the foundation soils about 21 of buildings show high probability of occurrence of soil building resonance effect about 63 of the buildings are characterised by a medium resonance level while about 16 are at zero or very low level the proposed approach makes it also possible to identify the areas of the city characterised by these different probabilities of resonance levels

a hybrid discrete continuum approach to model hydro mechanical behaviour of jointed rocks a hybrid discrete continuum approach has been presented in this paper to simulate water flow in the near and far fields of deformable fractured rocks in the near field the discrete model is used while in the far field the equivalent continuum model is employed the discrete element method with the static relaxation algorithm is used in the near field and the boundary integral equation method in the far field along the interface of these two domains both mechanical and hydraulic compatibility conditions are satisfied fully coupled hydro mechanical analysis can be conducted in the combined near and far fields application to a dam foundation problem has demonstrated the capability of the developed approach

construction of geostatistical aquifer models integrating dynamic flow and tracer data using inverse technique natural aquifers are heterogeneous and geostatistical methods are widely used to simulate the heterogeneity of aquifer properties due to limited available data it is essential to integrate as much information as possible to reduce the uncertainty in aquifer models and flow predictions traditional geostatistical techniques efficiently consider static hard and soft information such as core data and seismic data however dynamic flow and transport data such as flow rates pressure and tracer breakthrough are important information that are not easily considered with the traditional techniques integrating such dynamic data into a model requires the solution of a difficult inverse problem since dynamic data and aquifer properties are related to each other through the non linear flow and transport equations a recently developed geostatistically based inverse technique the sequential self calibration ssc method is introduced to integrate those dynamic data the ssc method is an iterative inverse technique that is coupled with an optimization procedure it provides for fast generation of multiple realizations of aquifer property models that jointly match pressure and tracer breakthrough data yet display the same geostatistical characteristics this method is flexible computationally efficient and robust the main features of ssc include 1 a master point concept that reduces the number of parameters 2 a perturbation mechanism based on kriging that accounts for the spatial correlation of the aquifer properties 3 a fast streamline based tracer flow simulator for integration of tracer data and 4 a new semi analytical streamline based method for computing sensitivity coefficients of tracer breakthrough applications of the ssc method are demonstrated with a synthetic data set results show that tracer breakthrough data carry important information on the spatial variation of aquifer permeability in the inter well areas as a contrast pressure data provide information at near well bore areas only integrating pressure and breakthrough data jointly leads to significant improvement in the aquifer heterogeneity representation and a reduction in the uncertainty of aquifer model the accuracy of flow and transport predictions can be dramatically improved by integrating dynamic data

seismoacoustic coupling induced by the breakup of the 15 february 2013 chelyabinsk meteor on 15 february 2013 around 03 20 00 utc the largest meteor reported since the 1908 tunguska event was observed as a fireball traveling through the earth s atmosphere exploding in an air burst near the city of chelyabinsk russia the rarity of such an event provides a unique window on the physics of meteoroid collision we report the fine seismic detection of rayleigh waves produced by the coupling of ground motion with the incident shock wave at distances up to 4000 km from the event combining information from seismic beam forming analysis recon structed trajectory from casual video records and remote sensing we identify the rayleigh waves as being initiated by the shock wave produced by the main blast that occasioned damages and injuries in chelyabinsk from the rayleigh wave observations we report a magnitude ms 3 7 seismic source

displacement back analysis for a steep slope at the three gorges project site abstract this paper contributes to two aspects of displacement back analysis of rock slopes first a novel method for displacement back analysis is presented based on error back propagation neural network and genetic algorithm ga the bp network replaces the time consuming finite element method thus enhancing the efficiency of the analysis the ga is used as an optimization method whose global search strategy can effectively improve the reliability of the analysis thereby making the back analyzed results independent of the initial values application of this methodology is illustrated with a numerical example secondly the deformation mechanism of rock mass is duly taken into account in the displacement back analysis of profile 17 17 of the permanent shiplock slope at the three gorges project site by treating the disturbed zones as weakened media yielding reasonable results

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

earthquake sound perception 1 sound is an effect produced by almost all earthquakes using a web based questionnaire on earthquake effects that included questions relating to seismic sound we collected 77 000 responses for recent shallow italian earthquakes an analysis of audibility attenuation indicated that the decrease of the percentage of respondents hearing the sound was proportional to the logarithm of the epicentral distance and linearly dependent on earthquake magnitude in accordance with the behavior of ground displacement even if this result was based on italian data qualitative agreement with the results of theoretical displacement and of a similar study based on french seismicity suggests wider validity we also found that given earthquake magnitude audibility increased together with the observed macroseismic intensity leading to the possibility of accounting for sound audibility in intensity assessment magnitude influenced this behavior making small events easier to recognize as suggested by their frequency content

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

paleomagnetic results from the snake river plain contribution to the time averaged field global database 1 this study presents paleomagnetic results from the snake river plain srp in southern idaho as a contribution to the time averaged field global database paleomagnetic samples were measured from 26 sites 23 of which 13 normal 10 reverse yielded site mean directions meeting our criteria for acceptable paleomagnetic data flow ages on 21 sites range from 5 ka to 5 6 ma on the basis of 40ar 39ar dating methods the age and polarity for the 21 dated sites are consistent with the geomagnetic reversal time scale except for a single reversely magnetized site dated at 0 39 ma this is apparently the first documented excursion associated with a period of low paleointensity detected in both sedimentary and igneous records combining the new data from the srp with data published from the northwest united states between the latitudes of 40 and 50 n there are 183 sites in all that meet minimum acceptability criteria for legacy and new data the overall mean direction of 173 normally magnetized sites has a declination of 2 3 inclination of 61 4 a fisher concentration parameter of 58 and a radius of 95 confidence 95 of 1 4 reverse sites have a mean direction of 182 4 declination 58 6 inclination of 50 and 95 of 6 9 normal and reversed mean directions are antipodal and indistinguishable from a geocentric axial dipole field at the 95 confidence level virtual geomagnetic pole dispersion was found to be circularly symmetric while the directional data were elongate north south an updated and corrected database for the northwestern u s region has been contributed to the magnetics information consortium magic database at http earthref org

coupled thermo hydro mechanical analysis of a heater test in fractured rock and bentonite at kamaishi mine comparison of field results to predictions of four finite element codes four computer codes were applied for a prediction of coupled thermo hydro mechanical responses during an in situ heater experiment which simulates a nuclear waste deposition hole with a waste over

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

the stability of a laminated voussoir beam back analysis of a historic roof collapse using dda abstract the stability of a horizontally bedded and vertically jointed roof referred to here as a laminated voussoir beam is studied using careful documentation of a historic roof collapse which occurred in an ancient underground water storage reservoir dated back to ca 1000 b c the roof of the opening failed immediately after the excavation leaving a dome shaped loosened zone with a span of 7 m and height of 2 5 m consisting of horizontal beds and vertical joints with mean spacing of 50 and 25 cm respectively the ancient engineers erected a massive pillar at the center of the dome in order to passively support the failed roof and the opening remained in service for several hundred years following the failure analysis of the roof using iterative voussoir beam procedure beer g and meek j l design curves for roofs and hanging walls in bedded rock based on voussoir beam and plate solutions trans inst min metall 1982 91 a18 22 shows that the roof was more sensitive to failure by shear along the abutments rather than by crushing at hinge zones and that the required friction angle req for stability would have been 36 the available friction angle is estimated between 38 6 and 46 4 and therefore the result of the iterative solution is considered unconservatively wrong results of dda shi g h and goodman r e two dimensional discontinuous deformation analysis int j numer anal methods geomech 1989 13 359 380 shi g h block system modeling by discontinuous deformation analysis computational mechanics publications southampton 1993 pp 209 however indicate that req must have been greater than 60 a shear strength which was not available at the time of construction thus the immediate failure using dda we further demonstrate that req is related to joint spacing or block length in a parabolic function with increasing joint spacing req decreases to a minimum value and than increases with further increase in joint spacing this result is attributed to the interaction of two competing forces one is the stabilizing axial thrust which increases with increasing moment arm in individual blocks a function of joint spacing or block length the other is the destabilizing vertical load which increases with increasing weight of overlying blocks

the 2003 kanto large bolide s trajectory determined from shockwaves recorded by a seismic network and images taken by a video camera 1 anomalous loud sounds like booms were heard in a wide area in the kanto region japan on june 16 2003 since the sky was thickly clouded the source of the sounds which was supposed to be a meteoroid penetrating the atmosphere was hardly witnessed and photographed it was recorded by only one video camera we searched the shockwaves from the meteoroid recorded by a dense seismographic network shockwave signals were identified at 40 stations of the network deployed in the region we report here the trajectory of the meteoroid determined by an analysis of seismic data combining the trajectory with the video camera data we determined the precise velocity of the bolide in the atmosphere

paleosecular variation of brunhes age lava flows from british columbia canada 1 brunhes age lava flows have been sampled for paleosecular variation studies from several volcanic fields of southern british columbia silverthrone garibaldi lake mt meager clearwater wells gray park and kelowna area a total of 52 lava flows were sampled and 7 to 10 samples were drilled at each site previous radiometric studies indicate that the ages of these lava flows range from 2 3 to 760 ka stepwise thermal demagnetization 14 to 21 steps was carried out for all the samples in each site and af demagnetization was performed on one sample per site forty five sites were selected based on rigorous criteria 95 5 to calculate a mean direction d 356 9 i 70 2 95 2 8 that is statistically indistinguishable from the direction of the dipole field at the area i 68 3 virtual geomagnetic poles vgps do not show the far sided effect and the angular standard deviation is 17 5 a value in agreement with the paleomagnetic field dispersion for that latitude these high quality results are expected to improve the time averaged field taf and secular variation models

real time infrasonic monitoring of the eruption at a remote island volcano using seismoacoustic cross correlation s u m m a r y on 2013 november 20 a submarine eruption started close to nishinoshima island which lies 1000 km south of tokyo real time monitoring of the eruption is crucial for understanding the formation processes of the new volcano island and related disaster prevention in situ monitoring however is difficult in practice because the closest inhabited island chichijima is 130 km away from nishinoshima this study presents an infrasonic monitoring method that uses cross correlating records at a pair of online stations on chichijima one is the horizontal ground velocity recorded at a permanent seismic station operated by the japan meteorological agency jma the seismic records were corrected for atmospheric pressure using an empirical ground response to infrasound the other is the air pressure recorded at the jma meteorological observatory for each station we divided the whole records into 3600 s segments to suppress outliers each segment was normalized by the envelope function we then calculated cross correlation functions between the pair of stations using the fast fourier transform they present clear successive arrivals of infrasound coming from nishinoshima we also conducted an offline tripartite array observation using three low frequency microphones with a station spacing of 50 m installed in 2013 may the array analysis supports the results obtained from the online stations the typical root mean squared amplitude is on the order of 0 01 pa and the typical duration is several days the amplitudes were primarily controlled by the effective sound velocity structure from nishinoshima to chichijima the infrasonic observations together with the meteorological observation at chichijima suggest that infrasonic activity was not present in the first two weeks in 2015 january with the help of a more quantitative estimation of the meteorological effect we could infer eruptive activity in real time now many online seismic stations are available worldwide this study shows that installation of another infrasonic sensor close to the existing seismic station 1 km is useful for monitoring a remote island volcano in real time

response of fractured rock subject to fluid injection part iii practical application abstract the results of the distinct element modelling are used to interpret field observations of injection pressures two additional examples of the qualitative use of the model are presented the sensitivity of reservoirs to even brief periods of high rate injection and the value of using dynamic coupled models to interpret field performance are emphasised

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

a holocene paleosecular variation record from 14c dated volcanic rocks in western north america 1 a paleosecular variation psv curve for western north america is presented on the basis of 94 virtual geomagnetic poles vgps from dated volcanic rocks sampled at 446 sites approximately 60 of the paleomagnetic database has been previously published a curve defined by spherical smoothed splines is fitted to the vgps ranked by the quality of the age determinations where the data density is highest between 3690 and 30 years before present b p a d 1950 between 7800 and 7050 years b p and between 14 060 and 12 700 years b p the younger segments of the curve derived from volcanic rocks are similar but less complex than other high resolution psv curves derived from lacustrine sediments particularly the record at fish lake oregon the psv record from lava flows psvl however is perhaps more reliable in its general shape and chronology because of the higher fidelity of volcanic rocks as magnetic field recorders and because of the greater density of 14c dates the new psvl record provides a partial holocene master curve for western north america and will be of particular value in dating geological and archeological materials using paleomagnetic directions