lapse time dependence of coda q anisotropic multiple scattering models and application to the pyrenees abstract the coda quality factor of short period s waves q c excited by local earthquakes in the pyrenees has been measured as a function of the length of the coda window l w for different choices of the onset time of the coda t w in the 2 16 hz frequency band we observe a transient regime characterized by an increase of q c with l w followed by a stabilization around a plateau the value of which depends on the central frequency of the signal using monte carlo simulations of wave transport in a variety of random media 1200 models we demonstrate that the lapse time dependence of q c in the pyrenees may be modeled by multiple anisotropic scattering of seismic waves without invoking any depth dependence of the attenuation properties in the crust in our model anisotropic scattering is quantified by the ratio between the transport mean free path and the mean path l l at 6 hz the data require an anisotropy factor l l 5 a transport mean free path l 400 km and an intrinsic quality factor q i 800 from the frequency dependent plateau of q c at large lapse time we infer an intrinsic quality factor of the form q i 400 f 0 4 in the pyrenees we also show how the rapid increase of the lapse time dependence of q c with frequency may be exploited to put constraints on the power spectrum of heterogeneities in the crust

measurements of intrinsic and scattering seismic attenuation in the crust intrinsic and scattering attenuation parameters qi and qs have been measured in three different tectonic areas for local and shallow earthquakes located close to the receiver the approach developed by wennerberg 1993 which takes into account the numerical correction of the coda q parameter for the multiple scattering formulation of zeng was used to infer from the estimates of coda q and direct s wave q the intrinsic qi and scattering qs q values results for 1 to 12 hz range show that qi is comparable to qs for the etna volcano and for the campi flegrei area while qi for the tectonically active area of granada is lower than qs coda q is close to intrinsic q suggesting that at least in the crust coda q is a good estimate of the intrinsic q volcanic areas show a reasonable higher degree of heterogeneity if compared with the nonvolcanic area of granada

the statistical nature of the upper continental crystalline crust derived from in situ seismic measurements summary in situ measurements in the main borehole of the german continental deep drilling project ktb point to the statistical nature of the continental crystalline crust between 286 and 6000 m depth p wave s wave and density logs display deviations from gaussian distribution functions that may be partly due to the approximately bimodal nature of the lithology because the crust consists mainly of metabasites and paragneisses the autocovariance functions and power spectra of the logs indicate that the velocity and density perturbations have a complex statistical nature but the autocovariance functions can be approximated by a superposition of two exponential functions with correlation lengths of 1 m and 20 m the associated relative standard deviations for each exponential function are about 3 per cent of the mean for the sonic logs and nearly 6 per cent of the mean for the density a vertical seismic profile measured between 3000 and 6000 m depth shows small traveltime fluctuations which can be explained by a generalization of a recently published scattering theory for transverse wavefield fluctuations to include the case of longitudinal fluctuations the theory is valid for harmonic scalar plane wave propagation in random media with isotropic statistics and scattering mainly in the forward direction one important theoretical result is that although longitudinal and transverse autocovariance functions of amplitudes and phases differ the expectations of their respective autovariances are the same the observed traveltime fluctuations agree with theoretical predictions based on normally distributed velocity perturbations that are described by the average of the autocovariance functions of the two p wave logs measured from 286 to 3000 m and between 3000 and 6000 m depth owing to the lack of traveltime information that can be averaged and because the traveltime fluctuations predicted by the theory do not differ sufficiently for 2 d and 3 d random perturbations no statement can be made on how anisotropic the observed random velocity perturbations are the observed heterogeneities are however consistent with the fact that reflection seismic profiles reveal a nearly transparent upper crystalline crust

separation of depth dependent intrinsic and scattering seismic attenuation in the northeastern sector of the italian peninsula summary we investigated the intrinsic dissipation and scattering properties of the lithosphere under the friuli region northeastern italy using two hypotheses i a uniform earth model and ii two reasonable non uniform layered crustal models for case i we measured the coda q and used the multiple lapse time window analysis mltwa technique to obtain separate estimates of intrinsic absorption and scattering attenuation results for the uniform earth model show that the lithosphere in northeastern italy is characterized by a low scattering attenuation small scattering q inverse q 1 and by a relatively high intrinsic attenuation high intrinsic q inverse q 1 a comparison between the investigated region and other areas around the world shows that both q 1 and q 1 for the friuli region are among the lowest values ever measured with the exception of the southern apennines which has the lowest measured q 1 for case ii numerical simulation of the energy envelopes was performed using two layered earth models where the values of the intrinsic and scattering attenuation coefficients are both within reasonable ranges when compared with the geological information the theoretical envelopes calculated for the homogeneous model give a good fit to the synthetic envelopes calculated for the layered models the best fit is obtained for scattering attenuation coefficients of the uniform model always greater than those of the layered model the main result is consequently that scattering q 1 obtained using the mltwa under the assumption of a uniform medium is overestimated on average by a factor 2 finally coda q 1 appears to be closer to the total q 1 than to the intrinsic q 1 a spredicted

fluid induced seismicity guided by a continental fault injection experiment of 2004 2005 at the german deep drilling site ktb 1 recent hydraulic experiments at the ktb site have shown that seismicity induced by long term fluid injection directly into a continental crustal fault remains guided by this fault the seismicity is triggered by pressure perturbations as low as 0 01 1 bars at the hypocenters a combination of sequential one year fluid extraction 2002 2003 and one year fluid injection 2004 2005 experiments has shown that only positive pore pressure perturbation i e injections was able to induce the seismicity moreover the onset of seismicity roughly coincides with the time of compensation of the extracted fluid volume by the following injection this confirms that the pressure diffusion is a dominant mechanism of seismicity triggering by fluid injections the probed fault shows a significant anisotropy and non linearity of its hydraulic behaviour its hydraulic diffusivity is up to one order of magnitude larger than that of surrounding rocks

rock mass characterization using intrinsic and scattering attenuation estimates at frequencies from 400 to 1600 hz intrinsic and scattering s wave quality factors q were estimated using the multiple lapse time window analysis mltwa for microseismic events m 1 with source sensor distance of 45 to 120 m associated with an excavation at 630 m depth in strathcona mine sudbury canada additional information on the rock mass was provided by underground structural mapping data intrinsic q values at 800 hz were on the order of 140 similar to quality factor values obtained in previous studies using spectral decay and coda q methods 120 to 170 the scattering quality factor at this frequency was about 520 an observed frequency dependence of the scattering attenuation suggested that a decrease in the density of scatterers with scale lengths on the order of 2 m exists at the site characteristic fracture scale lengths were considered to range from 4 to 6 m as identified in the mapping data these observations were supported by the increase in scattering found for seismic waves with frequencies less than 1000 hz by assuming that the identified scatters are characteristic faults these scatterers can then be considered to increase nonsimilar behavior in source scaling overall our results suggest that mltwa provides a practical method for remotely characterizing the quality of a rock mass when visual observations are not attainable

seismic attenuation in a nonvolcanic swarm region beneath wakayama southwest japan 1 seismic attenuation in the wakayama swarm area of southwest japan is estimated by optimally fitting the theoretical s coda model to an average s coda envelope in the frequency range of 1 48 hz the average s coda envelope is confirmed to have a common decay curve independent of the source station distance intrinsic attenuation is found to peak at around 4 hz suggesting thermal diffusion in grain size or crack length domains with dimensions of the order of 0 7 1 mm which is reasonable for crustal rock scattering attenuation is well approximated by the relation 0 054f 1 in this frequency range with an inferred peak at 0 5 hz suggesting that the statistical model is characterized by an exponential autocorrelation function with a correlation length of about 1 km and a fractional velocity fluctuation of 21 scattering is the dominant cause of attenuation at frequencies below 2 hz while intrinsic attenuation becomes predominant above 4 hz although values of coda attenuation qc 1 generally lie between the total and intrinsic attenuation the differences between these three values becomes very small above 4 hz indicating that the coda attenuation measurements provide a reasonably good estimate of the total attenuation the total attenuation was found to coincide well with the total apparent attenuation estimated by a linear inversion using direct s waves from swarm earthquakes confirming the validity of the present results

the measurement of velocity dispersion and frequency dependent intrinsic attenuation in sedimentary rocks a series of experiments to determine the elastic properties of a sequence of saturated sedimentary rocks over as wide a frequency range as possible was carried out at the imperial college borehole test site these experiments fall into four categories vertical seismic profiles vsps within the frequency range 30 280 hz crosshole surveys 0 2 2 3 khz sonic logging 8 24 khz and laboratory measurements 300 900 khz the intrinsic attenuation and velocity of compressional and shear waves were measured whenever possible velocity dispersion is observed for both compressional and shear waves the intrinsic attenuation of compressional waves is frequency dependent with a peak in the attenuation in the sonic frequency band the data were modeled assuming the attenuation is caused by local fluid flow in pores of small aspect ratio the modeling indicates that the intrinsic attenuation may be dominated by cracks with aspect ratios of around 10 super 3 to 10 super 4

morphological changes beach inundation and overwash caused by an extreme storm on a low lying embayed beach bounded by a dune system nw mediterranean abstract the geomorphological evolution of a low lying micro tidal sandy beach in the western mediterranean pals beach was characterized using airborne light detection and ranging lidar data data were collected in prior to and six months after the impact of an extreme storm with a return period of approx 50 years with the aim of characterizing the beach s response to the storm the use of repeated high resolution topographic data to quantify beach geomorphic changes has allowed assessment of the accuracy of different proxies for estimating beach volume changes results revealed that changes in the shoreline position cannot accurately reproduce beach volume changes on low lying beaches where overwash processes are significant observations also suggested that volume estimations from beach profiles do not accurately represent subaerial volume changes at large profile distances on beaches with significant alongshore geomorphological variability accordingly the segmentation of the beach into regularly spaced bins is proposed to assess alongshore variations in the beach volume with the accuracy of the topographic data the morphological evolution of pals beach during the study period showed a net shoreline retreat 4 m and a significant sediment gain on the subaerial beach 7 5 m 3 m the net gain of sediment is mostly due to the impact of the extreme storm driving significant overwash processes that transport sediment landwards increasing volume on the backshore and dunes the increase of volume on the foreshore and the presence of cuspate morphologies along the shoreline also evidence post storm beach recovery observed morphological changes exhibit a high variability along the beach related to variations in beach morphology changes in the morphology and migration of megacusps result in a high variability in the shoreline position and foreshore volume changes on the other hand larger morphological changes on the backshore and larger inundation distances occur when the beach and the dunes are lower favouring the dominance of overwash the observed storm induced morphological changes differ from predicted beach storm impacts because of spatial and temporal variations in the beach morphology suggesting that detailed morphological parameters and indicators used for predicting beach vulnerability to storms should be regularly updated in order to represent the pre storm beach conditions finally observed morphological changes in pals bay evidenced a different behaviour between natural and urban areas with better post storm beach recovery on natural areas where the beach is not artificially narrowed

high biolability of ancient permafrost carbon upon thaw ongoing climate warming in the arctic will thaw permafrost and remobilize substantial terrestrial organic carbon oc pools around a quarter of northern permafrost oc resides in siberian yedoma deposits the oldest form of permafrost carbon however our understanding of the degradation and fate of this ancient oc in coastal and fluvial environments still remains rudimentary here we show that ancient dissolved oc doc 21 000 14 cyears the oldest doc ever reported is mobilized in stream waters draining yedoma outcrops furthermore this doc is highly biolabile 34 0 8 was lost during a 14 day incubation under dark oxygenated conditions at ambient river temperatures mixtures of yedoma stream doc with mainstem river and ocean waters mimicking in situ mixing processes also showed high doc losses 14 days 17 0 8 to 33 1 0 this suggests that this exceptionally old doc is among the most biolabile doc in any previously reported contemporary river or stream in the arctic

spatial and frequency dependent properties of site amplification factors in japan derived by the coda normalization method we have estimated broadband f 0 5 8 hz site amplification factors at 1800 sites in japan based on the coda normalization method using 4001 seismograms obtained from 48 events the results show that in the low frequency band f 0 5 1 hz the site amplification factor varies over a wide range from 4 to 24 db with larger site amplification factors 8 db in such major basins as kushiro rumoi sapporo aomori sendai niigata tokyo toyama nagoya osaka oita and kagoshima on the other hand the site amplification factor in the high frequency band f 4 8 hz varies over a relatively narrow range from 0 to 18 db at each station and has no clear correlation with the surface geology of each station we then examined the contribution of the site amplification at each station to the anomalous distribution of the intensity pattern during large earthquakes by correcting the observed ground accelerations at each k net and kik net station with their corresponding estimated site amplification factors the corrected pattern of intensity shows simple concentric isoseismal intensity contours around the hypocenter indicating the applicability of our estimates to strong motion predictions we confirmed that our estimates are superior to those derived from geology such as those based on the regression of the averaged s wave velocity from the surface to a depth of 30 m graphic 1 with a smaller standard deviation of intensity variations based on a standard decay function of intensity versus hypocentral distance 1 embed inline graphic 1 gif

interpretation of seismic data from hydraulic fracturing experiments at the fenton hill new mexico hot dry rock geothermal site an attempt was made to synthesize the results of active seismic experiments carried out by the los alamos national laboratory s hot dry rock project staff for determining the geometrical and physical properties of the fracture system produced by hydraulic fracturing in a hot low permeability rock interpretation of data from several reflection transmission and attenuation experiments using seismic probes in the frequency range from a few hundred to more than 10 sup 4 hz led us to postulate the existence of a highly complex fracture system consisting of major discrete vertical cracks intersected by several inclined joints which are surrounded by a large volume of rock containing small scale cracks we found an interesting coincidence between the mean square fluctuation of p arrival time and q sup 1 of coda waves both are increased by nearly the same amount 35approx 40 when fluid pressure in the reservoir is increased another coincidence is the scale length of the inhomogeneity of roughly 3 m obtained from the frequency dependence of attenuation and also from the spatial variation of p arrival time these results suggest that the seismic attenuation in the fractured region is caused primarily by scattering

spatial distribution of scattering loss and intrinsic absorption of short period s waves in the lithosphere of japan on the basis of the multiple lapse time window analysis of hi net data summary propagation of short period s waves through the crust is strongly controlled by scattering loss and intrinsic absorption scattering loss controls the shape of the seismic envelope and the spatial distribution of the energy while intrinsic absorption produces an exponential decay as a function of time which is independent of the coordinates since both parameters have a different effect it is possible to compute them by means of the multiple lapse time window analysis mltwa in this paper high resolution maps of japan for both seismic s wave attenuation parameters are obtained by using the mltwa with data provided by the hi net seismic network the maps show strong regional variation of the parameters the variations depend mainly on the tectonic setting of each region and volcanism mechanisms in the scattering loss maps in the 1 2 hz map there is a very different behaviour between the northeast stronger scattering loss and the southwest much weaker scattering loss in the northeast of japan areas with strong scattering loss correspond mainly to the location of the volcanic arcs in southwest japan chugoku region and the west side of kii peninsula show strong scattering levels for the 4 8 hz and higher frequency bands in hokkaido strong scattering loss and intrinsic absorption can be observed for the lower frequency bands in the sendai plain we find strong scattering loss for all the frequency bands under all these areas low velocity anomalies have been detected in previous works in tohoku area the east side shows lower intrinsic attenuation than the west side this characteristic seems to extend to the southern part of hokkaido and to central japan in kanto area the values of intrinsic absorption are lower than in the surrounding areas but in the region around the itoigawa shizuoka tectonic line and in its western side strong absorption areas are observed the behaviour of each area for intrinsic absorption is similar to the behaviour observed in the q 1c maps the mltwa is based on the hypothesis of multiple isotropic scattering in a medium with the homogeneous distribution of scattering mean free path and intrinsic absorption although these hypotheses are very simple the results are very informative on the characteristics of each region and show the usefulness of studying the properties of scattered seismic waves in the understanding of the properties of the crust

global review of human induced earthquakes the human induced earthquake database hiquake is a comprehensive record of earthquake sequences postulated to be induced by anthropogenic activity it contains over 700 cases spanning the period 1868 2016 activities that have been proposed to induce earthquakes include the impoundment of water reservoirs erecting tall buildings coastal engineering quarrying extraction of groundwater coal minerals gas oil and geothermal fluids excavation of tunnels and adding material to the subsurface by allowing abandoned mines to flood and injecting fluid for waste disposal enhanced oil recovery hydrofracturing gas storage and carbon sequestration nuclear explosions induce earthquakes but evidence for chemical explosions doing so is weak because it is currently impossible to determine with 100 certainty which earthquakes are induced and which not hiquake includes all earthquake sequences proposed on scientific grounds to have been human induced regardless of credibility challenges to constructing hiquake include under reporting which is 30 of m 4 events 60 of m 3 events and 90 of m 2 events the amount of stress released in an induced earthquake is not necessarily the same as the anthropogenic stress added because pre existing tectonic stress may also be released thus earthquakes disproportionately large compared with the associated industrial activity may be induced knowledge of the magnitude of the largest earthquake that might be induced by a project mmax is important for hazard reduction observed mmax correlates positively with the scale of associated industrial projects fluid injection pressure and rate and the yield of nuclear devices it correlates negatively with calculated inducing stress change likely because the latter correlates inversely with project scale the largest earthquake reported to date to be induced by fluid injection is the 2016 m 5 8 pawnee oklahoma earthquake by water reservoir impoundment the 2008 m 8 wenchuan people s republic of china earthquake and by mass removal the 1976 m 7 3 gazli uzbekistan earthquake the minimum amount of anthropogenic stress needed to induce an earthquake is an unsound concept since earthquakes occur in the absence of industrial activity the minimum amount of stress observed to modulate earthquake activity is a few hundredths of a megapascal and possibly as little as a few thousandths equivalent to a few tens of centimeters of water table depth faults near to failure are pervasive in the continental crust and induced earthquakes may thus occur essentially anywhere in intraplate regions neither infrastructure nor populations may be prepared for earthquakes human induced earthquakes that cause nuisance are rare but in some cases may be a significant problem e g in the hydrocarbon producing areas of oklahoma usa as the size of projects and density of populations increase the potential nuisance of induced earthquakes is also increasing and effective management strategies are needed

site amplification from coda waves validation and application to s wave site response abstract the subject of this article is to see if the response to s waves at a specific site can be determined from coda waves we used aftershock records of the 1992 landers and big bear earthquakes observed at four terrascope stations pas pfo svd and gsc in southern california the wide dynamic range of the terrascope instrument provided a broadband seismogram for s waves and at the same time coda waves over a long lapse time window we analyzed a total of 708 three component waveforms from 65 events whose magnitudes ranged from 3 3 to 5 4 the station svd is located on quaternary alluvium and the remaining stations are on rocks of cretaceous age we first evaluated the coda site amplification factor using a spectral ratio method may eda et al 1991 koyanagi et al 1992 for frequency bands centered at 0 75 1 0 1 5 2 0 3 0 4 0 and 6 0 hz for lapse time windows after 70 sec from the origin time we found that the site amplification factor for the radial component is similar to that for the transverse component this similarity was expected because codas consist of backscattered waves coming from all directions into the station resulting in a directionally averaged site response we then evaluated the s wave site amplification factor using an inversion method andrews 1986 on the direct s wave portion of the same data set we found that the coda site response agrees with the s wave site response within a factor of about 1 5 supporting the earlier findings by tsujiura 1978 and justifying the use of coda waves in determining site specific amplification for s waves this agreement between s wave site response and coda site response is understandable if we assume that coda waves are dominated by s waves as theoretically predicted by aki 1992 and zeng 1993

scattering behaviour at merapi volcano java revealed from an active seismic experiment summary the seismic structure of the stratovolcano merapi java indonesia was studied using an active seismic experiment three 3 km long seismic profiles each consisting of up to 30 three component seismometers with an interstation distance of 100 m were built up in an altitude range between 1000 and 2000 m above sea level the detailed study of the seismic properties of the propagation media in active volcanic regions is important to understand the natural seismic signals used for eruption forecasting the seismic experiment at merapi therefore concentrates on the heterogeneous structure within a radius of 5 km from the active dome where the sources of most of the natural volcanic seismic events are located the cone of merapi volcano consists of different materials changing on a small scale due to the layering of eruptive material additionally the topography of the erosion valleys leads to an irregular deposition which cannot be described by a simple 1 d layering these inhomogeneities have a strong influence on seismic signals the direct p and s waves are attenuated quickly and show only small amplitudes on seismograms the energy lost from the direct waves however is not changed into heat but scattered and can be observed as seismic coda following the direct waves the observed seismograms show a spindle like amplitude increase after the direct p phase this shape of the envelope can be explained by the diffusion model according to this model there are so many strong inhomogeneities that the direct wave can be neglected and all energy is concentrated in multiple scattered waves besides the envelope the coherence and polarization properties of the wavefield also indicate strong scattering only the first onset shows coherence over a station spacing of 100 m whereas the late phases carrying the major part of the energy are mainly incoherent the horizontal components of the seismograms have larger amplitudes than the vertical component but within the horizontal plane the polarization is almost arbitrary corresponding to waves arriving from scatterers located arbitrarily in space as a result of the inversion using the diffusion model we obtain values of the s wave scattering attenuation coefficient gs and the s wave intrinsic absorption coefficient gi in the frequency range of 4 20 hz used in this study the scattering attenuation is at least one order of magnitude larger than the intrinsic absorption gs gi the mean free path of s waves is as low as 100 m gs1 100 m the scattering coefficient is independent of frequency gsyf 0 0 whereas the coefficient of intrinsic attenuation increases with increasing frequency giyf 1 6 the natural seismic signals at merapi volcano show similar characteristics to the artificial shots the first onsets have only small amplitudes and the energy maximum arrives delayed compared to the direct waves therefore these signals appear to be strongly affected by multiple scattering also

radiative transfer and diffusion of waves in a layered medium new insight into coda q summary this paper is devoted to the study of the seismic coda in inhomogeneous media exhibiting a discontinuity of physical properties at a given depth we focus on the problem of a layer overlying a half space and analyse the precise effect of a contrast of wave velocities and or scattering strengths between them in order to model s codawave envelopes we solve the radiative transfer equation by the monte carlo method thereby neglecting the polarization i e the acoustic approximation we pay special attention to the transition towards the diffusion regime under the assumption of an almost isotropic intensity field a diffusion equation can be derived from the radiative transfer equation and we accurately determine the boundary conditions associated with our models analytical solutions of the diffusion equation have been obtained and systematically compared to the numerical solutions of the radiative transfer equation we identify the domain of validity of the diffusion approximation which provides a simple analytical form for the decay in the late coda we apply our theoretical investigations to the continental lithosphere if the scattering strengths of the mantle and the crust are assumed to be of the same order a velocity contrast at the moho will according to our theory amplify the coda signal since part of the energy is trapped in the crust an amplification factor is defined and given explicitly as a function of the reflection coefficients and the velocity contrast at the moho the shape of the long time decay is of the algebraic form f 3 2 like that of a uniform half space on the other hand if the scattering strength of the mantle is small with respect to that of the crust the decay in the diffusive regime is predicted to be of the form r i exp 2nft qa where q is a function of the reflection coefficients at the moho the mean free path of waves in the crust and frequencyf the coefficient q quantifies the rate at which the partially trapped energy leaks from the crust into the mantle this formula has the same form as that proposed by aki chouet 1975 to fit coda observations which has since been widely used to deduce the qc parameter with realistic model parameters we find that q roughly equals the parameter qc deduced from observations this shows that the effect of partial trapping of energy in the crust may be significant consequently seismic albedos of the crust may have been underestimated in previous studies in our theory the energy decay of seismic coda waves is determined by the layered structure of the earth that is a highly heterogeneous crust overlying a rather homogeneous mantle such structure is confirmed by geological and geochemical studies

seismogram envelope inversion for the spatial distribution of high frequency energy radiation from the earthquake fault application to the 1994 far east off sanriku earthquake japan incoherency of high frequency seismic waves leads to the idea to analyze seismogram envelopes disregarding phase information for the source study we develop an inversion method for estimating high frequency above 1 hz energy radiation from the earthquake fault and site amplification factors from observed mean square s wave seismogram envelopes the inversion is executed by using the s wave envelope green function from the onset to coda for a point shear dislocation source in a scattering medium which is formulated based on an extended version of the radiative transfer theory the use of the envelope green function enables us to estimate the spatial distribution of high frequency energy radiation on a fault plane this has been difficult by conventional waveform inversion methods the rupture velocity and the duration time of energy radiation on each subfault are also estimated by grid search method we apply this new method to the 1994 far east off sanriku northeastern japan earthquake mw 7 7 which ruptured a 90 km segment of the plate boundary along the japan trench inverting observed seismogram envelopes at 10 strong motion stations in japan it is concluded that above 90 of the high frequency energy was radiated from the western half of the fault with the largest energy radiation near the deep side edge the rupture velocity is estimated to be 2 7 km s the estimated site amplification factors ranging between 0 3 and 15 are consistent with those independently estimated by the coda normalization method

depth dependent intrinsic and scattering seismic attenuation in north central italy summary in this study the attenuation mechanism of seismic wave energy in north central italy is estimated using low magnitude earthquake local data recorded at six stations managed by ingv most of the analysed events are located along the alpine chain in the zone of iseo and garda lakes while a minor part in the po valley the zone investigated is characterized by the occurrence of significantly intense earthquakes magnitude up to 6 6 the most recent occurred in 2004 close to the city of salo on the coast of the garda lake mw 5 0 due to the high population density and presence of industrial activity the investigated area is characterized by a high seismic risk first the ordinary multiple lapse time window analysis mltwa method is applied in the assumption of uniform velocity and scattering and the couple of b0 the seismic albedo and le 1 the extinction length inverse corresponding to the total attenuation coefficient is calculated in the frequency bands of 1 5 3 6 and 12 hz to retrieve more realistic estimates the obtained values of b0 and le 1 are corrected taking into account the effects of a depth dependent earth model consisting of an earth structure characterized by a transparent upper mantle and a heterogeneous crust we find that the corrected intrinsic and scattering attenuation parameters which are proportional to the inverse of the intrinsic scattering quality factors q 1i and q 1s are strongly frequency dependent with a prevalence of scattering attenuation over the intrinsic dissipation the corrected and uncorrected values of total q are in agreement with the total q values obtained with different approaches for the same area

monte carlo simulation of seismogram envelopes in scattering media the analysis of the seismogram coda envelopes of local and regional earthquakes is one of the most effective strategies for investigating the heterogeneous lithospheric structure characterized by the seismic scattering and attenuation in order to synthesize the coda envelope we introduce a numerical scheme called the direct simulation monte carlo method which has been used in the field of the kinetic theory of gases because of the simplicity of the algorithm the method has several advantages over previous methods in terms of the flexibility of the numerical calculation to incorporate various factors required to construct realistic seismogram envelopes on the basis of coda envelope simulations including multiple scattering we show that an increase of seismic velocity with depth severely affects the shape of the coda envelope the effects of ray bending due to the velocity increase at the moho and the reflection at the free surface are clearly found in the synthesized envelope for a shallow earthquake our simulation demonstrates that the amplitude of the envelope is magnified by stagnation of seismic energy at shallow depths due to the positive velocity gradient with depth because of this effect for an a priori assumption of a homogeneous velocity model the measurement of the scattering coefficient by conventional methods may be overestimated

upper crustal seismic velocity heterogeneity as derived from a variety of p wave sonic logs sonic log measurements provide detailed 1 d information on the distribution of elastic properties within the upper crystalline crust at scales from about one metre to several kilometres 10 p wave sonic logs from six upper crustal drill sites in europe and north america have been analysed for their second order statistics the penetrated lithological sequences comprise archean volcanic sequences proterozoic mafic layered intrusions and precambrian to phanerozoic gneisses and granites despite this variability in geological setting tectonic history and petrological composition there are notable similarities between the various data sets after removing a large scale deterministic component from the observed velocity depth function the residual velocity fluctuations of all data sets can be described by autocovariance functions corresponding to band limited self affine stochastic processes with quasi gaussian probability density functions depending on the maximum spatial wavelength present in the stochastic part of the data the deterministic trend can be approximated either by a low order polynomial best fit or by a moving average of the original sonic log data the choice of the trend has a significant impact on the correlation length and on the standard deviation of the residual stochastic component but does not affect the hurst number for trends defined by low order polynomial best fits correlation lengths were found to range from 60 to 160 m whereas for trends defined by a moving average the correlation lengths are dominated by the upper cut off wavenumber of the corresponding filter regardless of the trend removed the autocovariance functions of all data sets are characterised by low hurst numbers of around 0 1 0 2 or equivalently by power spectra decaying as 1 k a possible explanation of this statistical uniformity is that sonic log fluctuations are more sensitive to the physical state in particular to the distribution of cracks than to the petrological composition of the probed rocks

intrinsic and scattering attenuation of the mt fuji region japan summary mount fuji is the focus of intense study because of its potential hazard signaled by seismic geologic and historical activity based on extensive seismic data recorded in the vicinity of mt fuji coda quality factor q 1c using a single scattering model hypothesis and intrinsic and scattering quality factor q 1i and q 1s using the multiple lapse time window mltw method were measured to focus the study on the magmatic structure below mt fuji the data were separated into two groups a near fuji region of rays traversing an area with radius 5 km around the summit r 20 km this classification shows the largest discrepancy of q 1c at a range of sampling volumes corresponding to overlapped sampling depth of about 80 km further the spatial division shows significant difference of q 1i and q 1s at hypocentral distance of 80 km the large difference of q 1s in bandwidths 2 4 and 4 8 hz indicates lithospheric heterogeneity beneath mt fuji with a characteristic heterogeneity scale length of about 1 km the results have a small error range due to the large data sample showing that all q 1 values in the near fuji area are greater than those of the far fuji area and q 1i for both the near and far fuji areas is higher than q 1s at high frequencies the q 1i and q 1s values for far fuji are in the range of values for typical non volcanic areas the q 1i values of the near fuji area are lower than those of other volcanic areas considered where as values of q 1s are not the low q 1i for the volcanic region of near fuji suggests that the magmatic activity indicated by percent partial melt in the vicinity of mt fuji is not as active as hot spot volcanoes such as kilauea hawaii

it s a matter of size magnitude and moment estimates for microseismic data microseismic mapping is a valuable tool for assessing hydraulic fracture stimulations during a stimulation treatment borehole near surface or surface geophones record passive seismic data the microseismic events are thought to be shear failures that occur around the opening of a tensile hydraulic fracture as it grows over the past several years there has been a large growth in the number of hydraulic fracture monitoring surveys along with the number of vendors who acquire and process microseismic data here we discuss two attributes of microseismic data which are associated with the size of the passive event seismic moment and magnitude