attenuation of coda waves in western anatolia abstract by analyzing the decay of coda wave amplitude we have determined coda q qc in western anatolia turkey using the single isotropic scattering model we analyzed 116 earthquakes which registered at the gebze station by using five narrow frequency bands centered at 1 5 3 6 8 and 10 hz coda q values were obtained using different lapse times between 30 and 190 s in steps of 10 s coda qc for western anatolia depends on frequency and lapse time for a lapse time of 30 s the frequency dependence of qc is q c 50 7 1 01 and for a lapse time of 190 s it is q c 183 2 0 76 in this region the exponential value of the qc frequency dependence is practically constant between 0 7 and 1 0 the obtained coda qc values were compared with those estimated in other regions the coda qc values for lapse times between 60 and 100 s for western anatolia and southern spain are practically the same indicating similar coda wave attenuation patterns in both regions of the mediterranean basin

a ground motion predictive model for iran and turkey for horizontal pga pgv and 5 damped response spectrum investigation of possible regional effects we present a ground motion prediction equation gmpe for turkey and iran to investigate the possible regional effects on ground motion amplitudes in shallow active crustal earthquakes the proposed gmpe is developed from a subset of the recently compiled strong motion database of the earthquake model of the middle east region project see data and resources 1 a total of 670 turkish and 528 iranian accelerograms with depths down to 35 km are used to estimate peak ground acceleration peak ground velocity and 5 damped elastic pseudospectral acceleration ordinates of 0 01 s t 4 s the moment magnitude range of the model is 4 m w 8 and the maximum joyner boore distance is r jb 200 km the functional form considers three major fault mechanisms strike slip normal and reverse the nonlinear soil behavior is a function of v s 30 average shear wave velocity in the upper 30 m of soil profile our observations from empirical and estimated ground motion trends advocate regional differences in the territories covered by iran and turkey that originate from the differences in q factors kappa and near surface velocity profiles these factors eventually affect the magnitude and distance dependent scaling of spectral amplitudes in iran and turkey in essence the ground motion amplitudes of these two neighboring countries would draw patterns different than the ground motion estimates of gmpes developed from the strong motion databases of shallow active crustal earthquakes from multiple countries online material matlab code and regression coefficients for computing the response spectrum and distance scaling 1 sec 7

δ13c evidence that high primary productivity delayed recovery from end permian mass extinction euxinia was widespread during and after the end permian mass extinction and is commonly cited as an explanation for delayed biotic recovery during early triassic time this anoxic sulfidic episode has been ascribed to both low and high productivity states in the marine water column leaving the causes of euxinia and the mechanisms underlying delayed recovery poorly understood here we use isotopic analysis to examine the changing chemical structure of the water column through the recovery interval and thereby better constrain paleoproductivity the 13c of limestones from 5 stratigraphic sections in south china displays a negative gradient of approximately 4 from shallow to deep water facies within the lower triassic this intense gradient declines within spathian and lowermost middle triassic strata coincident with accelerated biotic recovery and carbon cycle stabilization model simulations show that high nutrient levels and a vigorous biological pump are required to sustain such a large gradient in 13c indicating that early triassic ocean anoxia and delayed recovery of benthic animal ecosystems resulted from too much productivity rather than too little

the complete synthesis of seismic crustal phases at regional distances using a new method to evaluate green s functions for elastic layered media we compute complete synthetic seismograms at regional distances for an earthquake in the earth crust we choose as source parameters the ones inferred for an earthquake in central france and compare the computed seismograms to the ones recorded at several short period stations of the french seismic network the major features of the records including complexity and duration are well reproduced by the synthetics lg waves which are the prominant phase are shown to be guided waves made up of sh and sv waves incident on the moho at angles of incidence more grazing than the critical angle and multiply reflected within the crust the length of the computed lg wave coda extends between group velocities of 3 5 and 2 8 km s and is in good agreement with the data

s wave attenuation in the sea of marmara turkey abstract this paper presents the estimates of frequency dependent attenuation of s waves for five different regions of the crust in the sea of marmara the estimation method for the s wave attenuation is based on the rate of decay of the s wave to coda wave amplitude ratio with distance qs 1 the epicentral distances of the selected earthquakes are between 15 and 70 km and the duration magnitudes are between 2 4 and 3 9 the quality factors qs are calculated at frequencies 1 5 3 6 and 12 hz and a lapse time 50 s the frequency dependency of average qs values calculated at these frequencies for five regions is 40 5f1 03 0 06 the estimated qs values for five regions ranging from 13 1f1 22 0 05 to 94 3f0 83 0 04 indicate the regional differences in the rheology and tectonic activity of the crust

on regional s the character of regional s wave trains is quite complex and consists of two major elements sn waves which principally travel in the upper mantle and lg waves guided in the earth s crust the effect of lateral heterogeneity is to modify the signals for these phases compared with the predictions for horizontally stratified models however complete synthetic seismogram calculations for simple stratified crustal models for a suite of distances out to 950 km including both sn and lg provide a range of insights into the nature of the s wave train in particular late picks of sn arrivals are likely to arise because the actual s onset has been missed in the p coda and a higher amplitude surface multiple phase with an extra crustal delay has been picked instead such a effect was first recognized by lapwood 1955 in a study of the iss readings for a sequence of japanese events recorded at regional distances but has usually not been taken into consideration in studies using regional networks lateral heterogeneity along the propagation path has the effect of inducing interconversion between sn and lg energy and thus alters the character of the s wave train the lower attenuation for s in the uppermost mantle compared with the crust frequently leaves sn as the most prominent phase at ranges greater than 1000 km long range propagation of high frequency lg requires a relatively undisturbed crust

s wave attenuation in the crust in northern greece abstract the attenuation of shear waves in the crust is estimated for frequencies between 1 5 and 12 0 hz by applying a single station method based on the rate of decay of the s wave to coda wave amplitude ratio with distance the data used come from local earthquakes that occurred in the thessaloniki area northern greece during the period 1983 through 1989 and were recorded by the telemetered network of the geophysical laboratory of the university of thessaloniki the q s values obtained are 115 244 477 and 755 for 1 5 3 0 6 0 and 12 0 hz respectively these values are very close to the coda q values estimated for the same area using the s to s single scattering model for lapse times between 30 and 100 sec but they are higher than the coda q values for lapse times between 10 and 30 sec the estimated q s is found to be strongly frequency dependent proportional to f 0 91 which is very close to the frequency dependence of the coda q

crustal attenuation characteristics in northwestern turkey in the range from 1 to 10 hz we have analyzed the aftershocks m l 4 5 following the 1999 izmit earthquake m w 7 4 to infer the frequency dependent attenuation characteristics of both p and s waves in the frequency range from 1 to 10 hz and in the distance range from 10 to 140 km a linear predictive model is assumed to describe the spectral amplitudes in terms of attenuation and source contributions the results show that both p and s waves undergo a strong attenuation along ray paths shorter than 40 km while the secondary arrivals significantly contribute to the spectral amplitudes over the distance range from 40 to 60 km as also confirmed by the computation of synthetic seismograms for longer ray paths the decrease in attenuation suggests an increase in the propagation efficiency with depth finally the spectral attenuation curves are flattened or sloped upward at low frequencies in the range from 100 to 140 km due to the contemporary arrivals of direct waves and postcritical reflections from the moho in terms of geometrical spreading and anelastic attenuation the attenuation in the range from 10 to 40 km is well described by a spreading coefficient n 1 for both p and s waves and the quality factors can be approximated by qs f 17 f 0 80 for 1 f 10 hz and qp f 56 f 0 25 for 2 5 f 10 hz for ray paths in the range from 60 to 80 km the attenuation weakens but the interaction between seismic waves and propagation medium is more complex the multilapse time window analysis mltwa is applied to quantify the amount of scattering loss and intrinsic absorption for s waves the seismic albedo b decreases from 0 5 at 1 hz to 0 3 at 10 hz while the total quality factor qt increases from about 56 to 408 the multiple lapse time window analysis mltwa results provide only an average estimate of the attenuation properties in the range from 10 to 80 km in fact by neglecting the variation of attenuation with depth the mltwa results underestimate attenuation for distances less than 40 km and do not capture the significant features caused by the integrated energy of the secondary arrivals observed in the range from 40 to 60 km

enhanced ground motions due to large amplitude critical moho reflections sms in the sea of marmara turkey 1 aftershocks of the 17 august 1999 mw 7 4 kocaeli earthquake were used to investigate the large amplitude sms arrivals in the sea of marmara we produced the event record sections from the transverse components of s and sms arrivals at a distance of 10 to 200 km for the data recorded towards the east and west in the sea of marmara for the data recorded towards the west we observed that the amplitude of sms phases enhances the ground motion by a factor of 2 to 3 the dipping moho and or anisotropy in the upper mantle or deep convex structure or deep lens are possible sources for the large amplitude sms phases since the study area has a potential of creating damaging earthquakes in the future the effect of large amplitude sms phases on the ground motion should be considered in the studies of the seismic hazard of the region

estimates of q in central asia as a function of frequency and depth using the coda of locally recorded earthquakes digital recordings of microearthquake codas from shallow and intermediate depth earthquakes in the hindu kush region of afghanistan were used to determine the attenuation factors of the s wave coda qc and primary s waves q an anomalously rapid decay of the coda shortly after the s wave arrival observed also in a study of coda in central asia by rautian and khalturin 1978 seems to be due primarily to depth dependent variations in qc in particular we deduce the average qc in the crust and uppermost mantle 100 km depth is approximately four times lower than the deeper mantle 400 km depth over a wide frequency range 0 4 to 24 hz further while qc generally increases with frequency at any depth the degree of frequency dependence of qc depends on depth except at the highest frequency studied here 48 hz the magnitude of qc at a particular frequency increases with depth while its frequency dependence decreases for similar depths determinations of q and qc agree suggesting a common wave composition and attenuation mechanism for s waves and codas comparison of these determinations of qc in afghanistan with those in other parts of the world shows that the degree of frequency dependence of qc correlates with the expected regional heterogeneity such a correlation supports the prejudice that qc is primarily influenced by scattering and suggests that tectonic processes such as folding and faulting are instrumental in creating scattering environments

regional wave propagation in turkey and surrounding regions this paper was published by the american geophysical union agu copyright 2000 agu see also http www agu org journals gl gl0003 1999gl008375 pdf 1999gl008375 pdf http atlas geo cornell edu turkey publications gok et al 2000 htm

s wave attenuation in the marmara region northwestern turkey the frequency dependent attenuation of shear waves in the crust is estimated by using two different methods based on the rate of time decay of coda wave amplitude qc 1 and the rate of decay of the s wave to coda wave amplitude ratio with distance qs 1 the epicentral distances of selected earthquakes range between 20 and 110 km and magnitudes are around 3 the quality factors qc are calculated at frequencies of 1 5 3 6 12 and 24 hz and lapse times of 40 50 60 and 70 s estimated qc values show a dependence on frequency and lapse time we observed the similarity in the frequency dependency of qc 41 1 07 f1 08 0 03 and qs 50 1 7 f1 09 0 05 for a lapse time of 50 s indicating that the attenuation mechanism for coda waves is similar to that of the direct s waves

ground motion scaling in the marmara region turkey summary predictive relationships for the ground motion in the marmara region northwestern turkey are parametrized after regressing three component waveforms from regional earthquakes in the frequency range 0 4 15 0 hz and in the distance range 10 200 km the data set consists of 2400 three component recordings from 462 earthquakes recorded at 53 stations moment magnitudes m w range between 2 5 and 7 2 the largest event for which we have waveforms available m w 7 2 occurred in duzce on 1999 november 12 the aftershocks of that earthquake together with the aftershocks of the 1999 august 17 izmit event m w 7 4 are included in the dataset regressions are performed independently on fourier velocity spectra and on peak ground velocities for a large number of sampling frequencies a simple model is used to relate the logarithm of the measured ground motion to excitation site and propagation terms results obtained for peak velocities are used to define a piecewise continuous geometrical spreading function g r a frequency dependent q f and a distance dependent duration function the latter is used through random vibration theory rvt in order to predict time domain characteristics i e peak values of the ground motion the complete model obtained for the peak ground motion was used to match the results of the regressions on the fourier amplitudes fourier velocity spectra for the combined horizontal motion are best fit by a hinged quadrilinear geometrical spreading function for observations in the 10 200 km hypocentral distance ranges as a function of frequency f 100 f 1 0 hz r 1 0 for r 30 km r 0 6 for 30 100 km the frequency dependent crustal shearwave quality factor q f coefficient q f 180 f 0 45 the t 5 75 per cent duration window provides good agreement between observed and predicted peak values by modelling the behaviour of the small earthquakes at high frequency we also quantified a regional parameter 0 055 s spectral models with one single corner frequency brune and with two corner frequencies atkinson and silva fit the observed high frequency excitation levels equally well whereas the model by atkinson and silva fits the low frequency observations slightly better than brune s rvt is used to predict the absolute levels of ground shaking following boore s implementation of the stochastic ground motion model boore s smsim codes our regional empirical predictive relationships are compared to the ones adopted in several regions of the world from california to western united states

origin of the pulse like signature of shallow long period volcano seismicity short duration pulse like long period lp events are a characteristic type of seismicity accompanying eruptive activity at mount etna in italy in 2004 and 2008 and at turrialba volcano in costa rica and ubinas volcano in peru in 2009 we use the discrete wave number method to compute the free surface response in the near field of a rectangular tensile crack embedded in a homogeneous elastic half space and to gain insights into the origin of the lp pulses two source models are considered including 1 a vertical fluid driven crack and 2 a unilateral tensile rupture growing at a fixed sub rayleigh velocity with constant opening on a vertical crack we apply cross correlation to the synthetics and data to demonstrate that a fluid driven crack provides a natural explanation for these data with realistic source sizes and fluid properties our modeling points to shallow sources 1 km while a slow rupture failure provides another potential model for these events the synthetics and resulting fits to the data are not optimal in this model compared to a fluid driven source we infer that pulse like lp signatures are parts of the continuum of responses produced by shallow fluid driven sources in volcanoes

a preliminary study of coda q in california and nevada the decay rate of local earthquake coda is characteristic of the area in which the epicenter and stations are located aki 1969 aki and chouet 1975 rautian and khalturin 1978 tsujiura 1978 aki 1980 interpreted the coda decay rate in terms of the attenuation property of s waves in the lithosphere under the area the q of s waves inferred from coda waves is called coda q recently several papers reported temporal changes in coda q prior to the occurrence of large earthquakes they are 1 the tangshan earthquake m 7 8 of 1976 and the haicheng earthquake m 7 4 of 1975 jin and aki 1986 2 three earthquakes m 8 in the kuril kamchatka region gusev and lemzikov 1985 3 the kalapana hawaii earthquake m 7 2 of 1975 wilson et al 1983 and 4 the eastern yamanashi japan earthquake m 6 0 of 8 august 1983 sato 1986 in all these cases the coda q was reported to be anomalously low before the occurrence of the earthquake however in a detailed study by chouet 1979 a strong fluctuation of coda q with time was observed in bear valley california which was not followed by a significant earthquake a recent coda q study in the adak seismic zone by scherbaum and kisslinger 1985 also did not find significant coda q changes that could be related to a mb 5 8 earthquake which occurred in the area of investigation in order to evaluate the feasibility of using coda q for earthquake prediction research in california and nevada we began a systematic study of coda q using digital waveform data from the regional microearthquake networks operated by the u s geological survey and the university of nevada

long period seismicity in the shallow volcanic edifice formed from slow rupture earthquakes volcanic eruptions are often preceded by long period seismic events that were thought to be generated by the resonance of cracks filled with magmatic fluid analysis and modelling of long period seismicity at volcanoes in italy costa rica and peru shows that it could instead be caused by slow rupture along faults in the upper volcanic edifice

gps derived strain rate field within the boundary zones of the eurasian african and arabian plates we use the gps velocity field 1988 1998 for eastern mediterranean and asia minor to determine the crustal deformation strain rate field in an area bounded by 35 n and 43 n and 20 e and 48 e we calculate the normal and shear strain rate components associated with the major faults and compare these qualitatively with seismological data uncertainties in the calculation of the strain rates reach 50 nstrain yr 1 in sparsely observed parts of anatolia whereas we estimate errors 20 nstrain yr 1 in the aegean and marmara regions the largest compressional strain rate components in the eastern part of the study area occur along the greater caucasus mountain front reaching 70 nstrain yr 1 1 nstrain yr 1 0 0317 10 15 s 1 the north anatolian fault zone is the clearest feature in the shear strain rate field it is expressed as a pronounced dextral strike slip fault zone reaching rates of up to 170 nstrain yr 1 this holds true also for the izmit area where the august 17 1999 earthquake occurred central anatolia is almost strain free whereas extension prevails in western anatolia the principal axes of extension vary around the n s direction with strain rates of up to 85 nstrain yr 1 these extensional areas coincide with graben features and normal faulting earthquakes the central and southwestern aegean sea is strain free with values far below 40 nstrain yr 1 the seismic cluster around the dodekanissa islands southeastern aegean sea coincides with nw se oriented extension attaining strain rates of up to 90 nstrain yr 1 this area of extension also exhibits recent active volcanism the entire hellenic arc shows compressional strain rates perpendicular to the arc the pliny strabo troughs along the eastern segment of the arc show left lateral shear strain rates reaching 80 nstrain yr 1 significant extension is found in central greece with a nne ssw oriented maximum of 120 nstrain yr 1 centered around the gulf of corinthos the kephalonia fault zone in nw greece is a distinct dextral fault zone separating apulia from the rapidly moving aegean microplate right lateral shear strain rates reach 150 nstrain yr 1

strong ground motion during the largest aftershock mw 5 8 of the 1999 izmit earthquake turkey abstract we present a preliminary study of strong ground motion during the largest aftershock mw 5 8 of the 1999 izmit earthquake mw 7 4 turkey at 11 55 on 13 september 1999 the peak ground acceleration observed near the epicentre of this aftershock was in agreement with that predicted by standard empirical prediction equations its spectral source parameters of the largest aftershock are also typical for a mw 5 8 earthquake at greater epicentral distances there is an order of magnitude in scatter in peak ground acceleration values for this aftershock which is attributed to site effects the presence of thick layers of low velocity sediments caused significant amplification of s waves in the avcilar district of istanbul at frequencies of 1 hz explaining the observed concentration of damage there as a result of the izmit mainshock

lapse time dependence of coda wave attenuation in central west turkey abstract the attenuation of coda waves has been inferred for central west turkey which is characterized by a very complex tectonic evolution the selected dataset is composed of 440 waveforms from 228 local earthquakes with a magnitude range of 2 9 4 9 the coda quality factor q c was estimated for five central frequencies f c 1 5 3 5 7 10 hz and eight lapse times t l ranging from 25 to 60 s based on the assumption of single isotropic scattering model estimated q c values were strongly dependent on frequency and lapse time the frequency dependence of q c values for each lapse time was inferred from q c f q 0 f n relationships q 0 values change between 32 7 and 82 1 while n values changes between 0 91 and 0 79 for the lapse times of 25 and 60 s respectively the obtained low q 0 values show that the central west turkey region is characterized by a high seismic attenuation in general the whole region was divided into four subregions to examine spatial differences of attenuation characteristics obtained 1 q 0 and n values versus the lapse time for each subregion implies the tectonic complexity of the region lapse time dependencies of attenuation and n values were also examined for subdatasets from two different ranges of event depth h h 10 km and distance r r 40 km high attenuation and its high frequency dependence for long distances manifest the elevation of isotherms and increasing heterogeneity with depth this could be associated with the extensional intra continental plate setting forming regional tectonics in the back arc area

attenuative dispersion of p waves and crustal q in turkey and germany we have measured group delays of the spectral components of high frequency p waves along two portions of the north anatolian fault zone nafz in turkey and in a region of southern germany assuming that the observed dispersion is associated with attenuation in the crust and that it can be described by a continuous relaxation model we obtained q and the high frequency relaxation times for those waves for each of the three regions individual p wave q values exhibit large scatter but mean values in the nafz increase from about 25 to 60 over the distance range 5 90 km mean q values are somewhat higher in the eastern portion of the nafz than in the western portion for measurements made at distances between 10 and 30 km p wave q values in germany range between about 50 and 300 over the hypocentral distance range 20 130 km in that region we separated the effects of q for basement rock 2 10 km depth from that of the overlying sediment 0 2 km depth using a least squares method q varies between 100 and 500 in the upper 8 10 km of basement with mean values for most of the distance range being about 250 q in the overlying sediments ranges between 6 and 10 because of large scatter in the q determinations we investigated possible effects that variations of the source time function of the earthquakes and truncation of the waveform may have on q determinations all of our studies indicate that measurement errors are relatively large and suggest that useful application of the method requires many observations and that the method will be most useful in regions where the number of oscillations following the initial p pulse is minimized even though there is large scatter in our q determinations the mean values that we obtained in turkey are consistent with those found in earlier studies our conclusions that q is significantly higher in the basement rock of germany than in the basement rock of turkey and that q is lower in western turkey than in eastern turkey are also consistent with results of q studies using lg coda

seismic wave propagation in shallow layers at the gonaf tuzla site istanbul turkey using the first dataset available from the downhole geophysical observatory of the north anatolian fault we investigated near surface seismic wave propagation on the tuzla peninsula istanbul turkey we selected a dataset of 26 seismograms recorded at tuzla at sensor depths of 0 71 144 215 and 288 m to determine near surface velocities and attenuation structures the waveforms from all sensors were pairwise deconvolved and stacked this produced low noise empirical green s functions for each borehole depth interval from the green s functions we identified reflections from the free surface and a low velocity layer between 90 and 140 m depth the presence of a low velocity zone was also confirmed by a sonic log run in the borehole this structure plus high near surface p and s wave velocities of 3600 4100 and 1800 m s lead to complex interference effects between upgoing and downgoing waves as a result the determination of quality factors q with standard spectral ratio techniques was not possible instead we forward modeled the green s functions in the time domain to determine effective q values and to refine our velocity estimates the effective q p values for the depth intervals of 0 71 0 144 0 215 and 0 288 m were found to be 19 35 39 and 42 respectively for the s waves we obtained an effective q s of 20 in the depth interval of 0 288 m considering the assumptions made in our modeling approach it is evident that these effective quality factors are biased by impedance contrasts between our observation points our results show that even after correcting for a free surface factor of 2 the motion at the surface was found to be 1 7 times greater than that at 71 m depth our efforts also illustrate some of the difficulties of dealing with site effects in a strongly heterogeneous subsurface online material plots of resistivity and caliper logs and the spectra of all 26 events

strong ground motion estimation in the sea of marmara region turkey based on a scenario earthquake we perform a broadband frequency bedrock strong ground motion simulation in the marmara sea region turkey based on several fault rupture scenarios and a source asperity model the technique combines a deterministic simulation of seismic wave propagation at low frequencies with a semi stochastic procedure for the high frequencies to model the high frequencies we applied a frequency dependent radiation pattern model which efficiently removes the effective dependence of the pattern coefficient on the azimuth and take off angle as the frequency increases the earthquake scenarios considered consist of the rupture of the closest segments of the north anatolian fault system to the city of istanbul our scenario earthquakes involve the rupture of the entire north anatolian fault beneath the sea of marmara namely the combined rupture of the central marmara fault and north boundary fault segments we defined three fault rupture scenarios based on the location of the hypocenter selecting a preferred hypocentral location near a fault bend for each case we analysed the effect of location of the asperity within the central marmara fault on the subsequent ground motion as well as the influence of anelasticity on the highfrequency attenuation characteristics the fault and asperity parameters for each scenario were determined from empirical scalings and from results of kinematic and dynamic models of fault rupture we calculated the resulting time series and spectra for ground motion at istanbul and evaluated the sensitivity of the predictions to choice of model parameters the location of the hypocenter is thus shown to be a critical parameter for determining the worst scenario earthquake at istanbul we also found that anelasticity has a significant effect on the regional attenuation of peak ground accelerations our simulated ground motions result in large values of acceleration response spectra at long periods which could be critical for building damage at istanbul during an actual earthquake d 2004 elsevier b v all rights reserved

source process of long period seismic events at taal volcano philippines vapor transportation and condensation in a shallow hydrothermal fissure 1 we analyzed observations of a swarm of more than 40 000 long period lp seismic events at taal volcano philippines in 2010 2011 the event waveforms are strongly correlated to each other consistent with a fixed source location and begin with a dilatational first motion they have a peak frequency around 0 8 hz and a quality factor q of 6 waveform inversion of the events pointed to a tensile crack source dipping 30 60 at a shallow 100 200 m depth a simulation using a fluid filled crack model indicated that the complex frequencies of the waveforms are explained by the fundamental longitudinal mode resonance of a vapor filled crack 188 m long a satellite thermal infrared image acquired during the swarm period suggests that the lp events were not accompanied by surface gas releases we considered a vapor transportation model in which vapor exsolved from magma and rose in a fissure extending to the lp source this model yielded estimates that 105 107 m3 of magma was involved in the lp swarm and that the temperature of vapor in the lp source crack was around 600 k we modeled a triggering mechanism of the crack resonance based on sudden condensation of vapor at the crack tip in a cold aquifer this model explained observed characteristics of the events including the dilatational first motion the total volumetric change and the fixed source location

attenuation of high frequency shear waves in the crust measurements from new york state south africa and southern california we compare the attenuation of high frequency 3 30 hz shear waves for crustal paths in new york state south africa and southern california over source receiver distances of about 10 400 km the data consist of digital recordings of s waves 5 100 km and lg waves 100 400 km produced by earthquakes we use a coda normalization method to remove the effects of site amplification and source excitation from the amplitudes of the s and lg waves over the entire distance range studied 10 400 km the amplitude decay of 3 hz shear wave energy is considerably less for the tectonicaily stable areas of new york and south africa than for the tectonicaily active region of southern california high frequency 30 hz s wave attenuation is significantly less for new york and south africa than for southern california for distances between 15 and 90 km we parameterize the decay with distance r of coda normalized shear wave amplitudes with a frequency independent q and geometrical spreading exponent where geometrical spreading is proportional to r for new york state the s wave amplitude decay 3 30 hz is well described by a frequency independent q of 2100 330 490 and of 1 3 0 1 the decay of lg wave amplitudes from 3 to 15 hz in the new york state region is fit with a frequency independent q of 1600 280 330 of 0 70 0 2 the s wave amplitudes 3 30hz in south africa yield a q of 1500 190 380 and of 1 3 0 1 fixing the geometrical spreading at r 0 5 produces an lg wave q estimate at 3 hz in south africa of 360 50 80 this lg wave q is low considering that south africa is a cratonic tectonicaily stable area the s wave amplitudes from southern california are described with a frequency independent q of 800 150 240 and a large geometrical spreading exponent of of 1 9 0 2 we find an lg wave q at 3 hz of 260 30 for southern california after constraining the geometrical spreading at r 0 5

long period seismic source characterization at popocatepetl volcano mexico 1 the seismicity of popocatepetl is dominated by long period and very long period signals associated with hydrothermal processes and magmatic degassing we model the source mechanism of repetitive long period signals in the 0 4 2 s band from a 15 station broadband network by stacking long period events with similar waveforms to improve the signal to noise ratio the data are well fitted by a point source located within the summit crater 250 m below the crater floor and 200 m from the inferred magma conduit the inferred source includes a volumetric component that can be modeled as resonance of a horizontal steam filled crack and a vertical single force component the long period events are thought to be related to the interaction between the magmatic system and a perched hydrothermal system repetitive injection of fluid into the horizontal fracture and subsequent sudden discharge when a critical pressure threshold is met provides a non destructive source process

shallow magma pathway geometry at mt etna volcano 1 a fundamental goal of volcano seismology is to understand the dynamics of active magmatic systems in order to assess eruptive behavior and the associated hazard imaging of magma conduits quantification of magma transport and investigation of long period seismic sources together with their temporal variations are crucial for the comprehension of eruption triggering mechanisms at mt etna volcano several intense episodes of tremor activity were recorded during 2007 in association with strombolian activity and or intense fire fountaining episodes occurring from the south east crater sec the locations of the tremor sources and of the long period seismic events are used here to constrain both the area and the depth range of magma degassing highlighting the geometry of the shallow conduits feeding sec the imaged conduits consist of two connected resonating dike like bodies nnw sse and nw se oriented extending from sea level to the surface in addition we show how tremor long period lp and very long period vlp event locations and signatures reflect pressure fluctuations in the plumbing system associated with the ascent discharge of gas rich magma linked to the lava fountains the evidence here reported also corroborated by ground deformation variations can help develop a better prediction and early warning system for those eruptions effusive or explosive that apparently manifest no clear precursors

frequency dependent attenuation of coda waves in the crust in southwest anatolia turkey the attenuation of coda waves in the earth s crust in southwest sw anatolia is estimated by using the coda wave method which is based on the decrease of coda wave amplitude in time and distance a total of 159 earthquakes were recorded between 1997 and 2010 by 11 stations belonging to the koeri array the coda quality factor q c is determined from the properties of scattered coda waves in a heterogeneous medium firstly the quality factor q 0 the value of q c at 1 hz and its frequency dependency are determined from this method depending on the attenuation properties of scattered coda waves for frequencies of 1 5 3 0 6 0 8 0 12 and 20 hz secondly the attenuation coefficients are estimated the shape of the curve is controlled by the scattering and attenuation in the crustal volume sampled by the coda waves the average q c values vary from 110 15 to 1 436 202 for the frequencies above the q 0 and values vary from 63 7 to 95 10 and from 0 87 0 03 to 1 04 0 09 respectively for sw anatolia in this region the average coda q f relation is described by q c 78 9 f 0 98 0 07 and 0 012 km 1 the low q 0 and high are consistent with a region characterized by high tectonic activity the q c values were correlated with the tectonic pattern in sw anatolia

strike slip fault geometry in turkey and its influence on earthquake activity the geometry of turkish strike slip faults has been reviewed and described from this data set it appears that fault geometry the distribution of discontinuities such as bends and stepovers along the main fault trace plays an important role in controlling the location of large earthquake rupture segments along the fault zones large earthquake ruptures generally do not propagate past individual stepovers that are wider than 5 km or bends that have angles greater than about 30 more important than the size of each discontinuity however is the total geometric pattern i e the distribution of adjacent bends and stepovers based not only on distance from one another but also on relative discontinuity size certain geometric patterns restraining single or double bends are particularly common and can be viewed as responsible for strain accumulation along portions of the fault zone fault geometry not only plays a role in the extent of earthquake rupture but also in characteristics of earthquake behavior for example large earthquake epicenters often occur near restraining bends or double bends furthermore aftershocks and swarm activity can often be associated with releasing areas areas along the strike slip fault that are undergoing a relatively large amount of extension

cumulative attenuation along source to receiver paths in northwestern turkey the attenuation of shear waves propagating in the crust of northwestern turkey has been investigated in the frequency range 1 10 hz a standard spectral inversion scheme is applied to a data set of 245 aftershocks m l 4 5 of the 1999 izmit earthquake the obtained attenuation with distance curves have been described in terms of the t cumulative attenuation parameter and its dependence on frequency and distance investigated at 1 hz q 1 evaluated by normalizing t to the travel time is generally larger than 0 025 for source to station distances smaller than 40 km indicating the presence of a highly attenuating upper crust in the area over longer distances q 1 decreases suggesting a decrease in the attenuation with depth by contrast the normalized t computed for earthquakes recorded at stations having almost the same distance from the sources do not show a strong dependence on the backazimuth these results suggest that the decrease of q 1 with depth is more significant than its lateral variations regarding its frequency dependence q 1 almost linearly decreases with frequency finally the near surface attenuation parameter k is evaluated at 12 stations and the results discussed in terms of site event and propagation contributions the event contribution is not negligible and shows a significant positive correlation with magnitude the site term is smaller than 0 020 sec for rock or topographic sites while it assumes values of 0 036 sec and 0 042 sec for two stations installed over thick soft sedimentary layers

attenuation of high frequency p and s waves in garhwal himalaya india abstract tectonics of a region plays important role on the attenuation characteristics of the region attenuation characteristics have been estimated to understand the effect of the heterogeneity of the region in a tectonically active garhwal region of himalaya seismic body wave attenuation characteristics in the region is studied using 234 short period seismic observations from local events the p wave attenuation qp 1 and s wave attenuation qs 1 were estimated by applying the state of the art extended coda normalization method for the frequency range from 1 5 to 24 hz estimates of qp 1 and qs 1 decrease from 15 86 0 90 10 3 and 5 35 0 51 10 3 at 1 5 hz to 0 54 0 11 10 3 and 0 34 0 06 10 3 at 24 hz respectively the values of qp 1 and qs 1 show strong frequency dependence and fit the power law relation qp 1 f 27 43 3 15 10 3f 1 16 0 06 and qs 1 f 8 05 0 74 10 3f 0 93 0 05 respectively obtained results are in the range of those reported for qp 1 and qs 1 of the other seismically active regions the ratio of qp 1 qs 1 is larger than unity in the entire analyzed frequency range and may suggest high degree of heterogeneity in the region