region specific key seismic parameters for earthquakes in northern iran strong motion accelerograms recorded within northern iran are used to examine the propagation characteristics of shear wave including geometric spreading behavior q value j 0 and horizontal to vertical h v ratio these region specific key seismic parameters are estimated from 259 three component records of 22 earth quakes with magnitude ranging from m 4 9 to m 7 4 in northern iran the geometric spreading follows a trilinear behavior with a strong postcritical reflection from the moho the first and second hinges of the trilinear behavior are at 75 and 150 km respectively the associated q value based on the vertical component is q 87 f 1 46 j0 value for vertical and horizontal components are 0 03 and 0 05 respec tively because of lack of station specific site information the h v ratio is considered to be a rough estimation of generic site amplification the obtained region specific parameters are used to estimate the average stress drop based on three stochastic modeling approaches stochastic point source modeling suggests a brune stress drop of 125 bars whereas stochastic finite fault modeling based on static and dynamic corner frequency approaches suggests a stress drop of 68 bars

attenuation of high frequency seismic waves in eastern iran we investigated the frequency dependent attenuation of the crust in eastern iran by analysis data from 132 local earthquakes having focal depths in the range of 5 25 km we estimated the quality factor of coda waves q c and body waves q p and q s in the frequency band of 1 5 24 hz by applying the single backscattering theory of s coda envelopes and the extended coda normalization method respectively considering records from recent earthquakes rigan m w 6 5 2010 12 20 goharan m w 6 2 2013 5 11 and sirch m w 5 5 2013 1 21 the estimated values of q c q p and q s vary from 151 49 63 6 and 93 14 at 1 5 hz to 1 994 124 945 84 and 1 520 123 at 24 hz respectively the average frequency dependent relationships q q o f n estimated for the region are q c 108 10 f 0 96 0 01 q p 50 5 f 1 01 0 04 and q s 75 6 f 1 03 0 06 these results evidenced a frequency dependence of the quality factors q c q p and q s as commonly observed in tectonically active zones characterized by a high degree of heterogeneity and the low value of q indicated an attenuative crust beneath the entire region

the detection of low magnitude seismic events using array based waveform correlation summary it has long been accepted that occurrences of a known signal are most effectively detected by cross correlating the incoming data stream with a waveform template such matched signal detectors have received very little attention in the field of detection seismology because there are relatively few instances in which the form of an anticipated seismic signal is known a priori repeating events in highly confined geographical regions have been observed to produce very similar waveforms and good signals from events at a given site can be exploited to detect subsequent co located events at lower magnitudes than would be possible using traditional power detectors even greater improvement in signal detectability can be achieved using seismic arrays running correlation coefficients from single sensors can be stacked over an array or network to result in a network correlation coefficient displaying a significant array gain if two events are co located the time separating the corresponding patterns in the wave train as indicated by the cross correlation function is identical for all seismic stations and this property means that the correlation coefficient traces are coherent even when the waveforms are not we illustrate the power of array based waveform correlation using the 1997 august 16 kara sea event the weak event that occurred 4 hr after the main event was barely detected using an sta lta detector on the spits array but is readily detected by signal matching on a single channel the main event was also recorded by the far more distant norsar array but no conventional detection can be made for the second event a clear detection is however made when the correlation coefficient traces are beamformed over all sensors of the array we estimate the reduction in detection threshold of a test signal on a regional seismic array using waveform correlation by scaling down a master signal and immersing it into seismic noise we show that for this case waveform correlation using a single channel detects signals of approximately 0 7 orders of magnitude lower than is possible using an sta lta detector on the array beam waveform matching on the full array provides an additional improvement of approximately 0 4 magnitude units we describe a case study in which small seismic events at the barentsburg coal mine on spitsbergen were detected using the signals from a major rockburst as master waveforms many spurious triggers occurred in this study whereby short sections of signal exhibited coincidental similarity with unrelated incoming wave fronts we demonstrate how such false alarms can almost always be identified and screened out automatically by performing frequency wavenumber analysis upon the set of individual correlation coefficient traces

evolution of the turfan basin chinese central asia the turfan basin extends approximately 550 km east west by 100 km north south within northwest china and is located between branches of the intracontinental tien shan orogenic belt at present it is an intermontane foreland basin loaded by southward transported thrust sheets at its northern margin this deformation is a long distance manifestation of the india asia collision but the orientation and location of cenozoic structures is strongly influenced by the pre cenozoic history of the region the exposed basement marginal to the turfan basin consists of volcanics granitoids volcaniclastics and deepwater sedimentary rocks associated with the north tien shan island arc and subduction accretion complexes north of the north tien shan fault this arc had accreted to the central tien shan by late carboniferous to early permian times the north tien shan fault represents a major boundary between paleozoic arcs and accretionary complexes to the north and proterozoic basement of the central tien shan and tarim block to the south postcollisional thrusting appears to have provided a tectonic load for lower permian subsidence and sedimentation early postcollisional strata are turbidites but there was a shoaling of facies until the deposition of permo triassic conglomerates no marine sediments have been deposited in the region since the paleozoic at least two mesozoic episodes of compressional deformation are recorded at the northern margin of the basin which was an intermontane foreland basin during this era lower jurassic fluvial and lacustrine clastic rocks lie above a regional unconformity an oligocene unconformity marks the onset of coarse clastic sedimentation in the cenozoic and probably indicates the start of major compressional deformation related to the india asia collision sedimentation rates have increased through the cenozoic the neotectonics of the turfan basin are dominated by a southward directed thrust system emergent within the basin at the fire mountains range southward directed thrusting appears to have been a feature of mesozoic age tectonics and possibly the late paleozoic tectonics of the basin the most important neotectonic structures in the turfan basin follow older structural trends

the deep structure of the iranian plateau high resolution structures of the lithosphere asthenosphere system beneath a seismic profile in iran are obtained by the simultaneous inversion of data from receiver functions and fundamental mode rayleigh wave group velocity and validated by modeling bouguer gravity anomaly data the seismic data are gathered over a profile extending across zagros sanandaj sirjan zone ssz urumieh dokhtar magmatic arc udma central iran alborz binalud mountain ranges and kopeh dagh mountain ranges the results confirm the presence of crustal roots at the north and south of iranian plateau where it meets the arabian plate and eurasia the high velocity lithosphere of the arabian plate gently plunges nne ward beneath central iran supporting the subduction of the continental lithosphere responsible for the seismicity of the area the crust and lithosphere are thinner beneath central iran where two low velocity structures are very likely related to magma sources of the udma and in east of iran around lut block where the volcanism shows calcalkaline subduction related geochemistry the crustal lithospheric root to the north of the iranian plateau may represent the relict of a previous cimmeric subduction zone therefore the iranian lithosphere asthenosphere system could be the result of the coalescence of two separate subduction zones

seismic structure of iran from surface and body wave data summary an investigation of the lithospheric structure of the iranian plateau has been undertaken in order to find complementary information bearing on the tectonic evolution of the plateau the phase velocity dispersion of the fundamental mode rayleigh waves between the wwssn stations shiraz tabriz and mashad and between the sites of the iranian long period array and maio sro have been obtained from well dispersed wavetrains generated by eight great circle earthquakes the aftershocks of the destructive tabas earthquake in central iran which were accurately located by a field survey recorded clear p and s phases at maio providing supplementary travel time information for the interpretation of the phase velocity data the uppermost mantle p wave velocities beneath iran obtained in a previous study asudeh were also used in the analysis an alpine type crust was found for the iranian plateau while uppermost mantle velocities ranging from low velocity mantle in eastern iran to a high velocity shield like structure in the west of the country

seismic attenuation beneath northeastern japan constraints on mantle dynamics and arc magmatism we apply a three step approach to estimate three dimensional 3 d p wave attenuation qp 1 structure beneath northeastern japan first corner frequencies of earthquakes are determined using the spectral ratio method for s coda waves then whole path attenuation terms t and site amplification factors are simultaneously estimated by a joint inversion the set of t is finally inverted for 3 d attenuation structure the results show that the mantle wedge has low attenuation in the fore arc and high attenuation in the back arc a depth profile of qp 1 in the back arc mantle is explained by attenuation expected for a two dimensional 2 d thermal model with qp qs 2 and grain sizes of 1 and 3 cm however an inclined high attenuation zone observed in the back arc mantle wedge which is interpreted as an upwelling flow shows higher attenuation than that calculated from the 2 d thermal model the higher seismic attenuation is probably caused by the concentration of partial melt in the upwelling flow a combined interpretation of seismic attenuation and velocity structures further suggests that the degree of partial melt in the upwelling flow varies along the arc and that volcanoes are clustered transverse to the arc below which the upwelling flow contains a higher degree of melt these observations indicate that magmatism is controlled by a mantle wedge process that depends strongly on spatial variations in the degree of partial melt in the upwelling flow our results further imply the breakdown of hydrous minerals in a hydrous layer above the pacific plate at a depth of 120 km

pn tomographic velocity and anisotropy beneath the iran region we present tomographic velocity and anisotropy models of the uppermost mantle beneath the iran region a total of 74 375 pn phase readings from 86 stations of the iranian network and 133 stations of the international seismological centre are used in the investigation the study uses the pn travel time tomography method proposed by hearn 1996 the tomography results show some interesting anomalies the average pn velocity under the iran region is approximately 8 0 km s and the maximum velocity perturbations are approximately 3 4 high pn velocities under the zagros mountains and the caspian sea may be due to the presence of oceanic crust lithosphere material low pn velocities were found under the alborz and caucasus regions and may be due to higher temperatures or partial melting resulting from volcanoes and mid cenozoic volcanic plutonic rocks in these regions the inversion velocities support the idea that the subduction of the arabian plate into the mantle beneath the iranian plateau may have resulted in the upwelling of hot material the well resolved pn anisotropy model is jointly obtained with a velocity model for the areas with good ray path coverage in the plate collision regions zagros and alborz the fast pn anisotropy direction is oriented parallel to the collision arc and to large reverse faults due to pure shear deformation from cross fault compression and along fault extension under the caucasus regions the pn anisotropy results indicate that the preferred alignment of olivine crystals is parallel to the plate movement direction however the surface fault strike is at an angle of nearly 45 with the crustal movement direction and anisotropy these differing deformations suggest potential decoupling between the crust and upper mantle the possible decoupling and differing deformation between the crust and upper mantle are easily enhanced under high temperatures due to volcanoes and supported by low velocities beneath the caucasus we validate the existence of pn anisotropy under these regions by azimuthal averaging of the apparent pn velocity

calibration of an ml scale in the alborz region northern iran we have calculated empirical attenuation curves for the local magnitude scale ml in the alborz region of northern iran the maximum trace amplitudes de rived from synthetic wood anderson seismograms of 1290 records of 59 events in the distance range of 8 5 550 km recorded by the short period iranian seismic telemetry network istn were inverted for the attenuation curve magnitudes and station cor rections the earthquakes ranged from ml3 25 to 5 65 and were recorded at 26 sta tions in the region we used both nonparametric and parametric least squares methods for inversion the resulting parametric equation is loga0 1 1725logr 0 0021r 0 4450 the two methods yielded very similar results and are very close to richter s original attenuation curve for southern california the station corrections vary between 0 42 and 0 47 suggesting that local site effects may have a strong influence on the amplitudes

tomographic pn velocity and anisotropy structure beneath the anatolian plateau eastern turkey and the surrounding regions an edited version of this paper was published by the american geophysical union agu copyright 2003 agu see also http www agu org pubs crossref 2003 2003gl017391 shtml http atlas geo cornell edu turkey publications al lazki et al 2003 htm

empirical attenuation of ground motion spectral amplitudes in southeastern canada and the northeastern united states a database of 1700 digital seismograms from 186 earthquakes of mag nitude mn 2 5 5 6 that occurred in southeastern canada and the northeastern united states from 1990 to 2003 was compiled maximum likelihood regression analysis of the database was performed to determine a model for the attenuation of fourier spectral amplitudes for the shear window for the vertical and horizontal component of motion for frequencies from 0 2 to 20 hz fourier amplitudes follow a hinged trilinear attenuation model fourier spectral amplitudes decay as r 1 3 where r is hypocentral distance within 70 km of the source there is a transition zone from 70 to 140 km as the direct waves are joined by strong postcritical reflections where the attenuation is described as r 0 2 spectral amplitudes actually increase with distance in this range for low frequencies beyond 140 km the attenuation is well described by r 0 5 corresponding to geometric spreading in two dimensions the associated model for the regional quality factor for frequencies greater than 1 hz can be ex pressed as q 893f 032 q can be better modeled over a wider frequency range 0 2 20 hz by a polynomial expression log q 3 052 0 393 log f 0 945 log f 2 0 327 log f 3 the polynomial expression accommodates the observation that q values are at a minimum about 1000 near 1 hz and rise at both lower and higher frequencies correction factors for the spectral amplitude model that describe the effects of focal depth on the amplitudes and their attenuation are developed using the subset of events with known focal depth the attenuation model is similar to that determined from an earlier study with more limited data atkinson and mereu 1992 but the enlarged database indicates more rapid near source amplitude decay and higher q the attenuation model is used to play back attenuation effects to determine the apparent source spectrum for each earthquake in the database and hence determine moment magnitude m and brune stress drop the events have moment magnitude in the range from 2 5 to 5 stress drop increases with moment magnitude for events of m 4 3 then appears to attain a relatively constant level in the range from 100 to 200 bars for the larger events as previously noted in atkinson 1993b the results of this study provide a useful framework for improving regional ground motion relations in eastern north america they further our understanding of attenuation in the region through analysis of an enlarged ground motion database in particular the inclusion of the three component broadband data gathered over the last decade allows extension of attenuation models to both horizontal and vertical components over a broad frequency range 0 2 20 hz

behavior of the cotectic curve en ol in the system leucite olivine quartz under dry conditions to 2 0 gpa 1 the system leucite olivine fo90 quartz has been experimentally studied from 0 5 to 2 0 gpa under dry conditions and the position of the invariant point involving olivine enstatite k rich phase leucite or sanidine and liquid has been determined we find that at 0 5 gpa the olivine ol liquid liq1 enstatite en leucite lc liquid liq2 peritectic occurs at 1205 c and lc31 7qz66 5ol1 8 while at 1 0 gpa at 1265 c it has moved to lc38qz58ol4 as the leucite field contracts a second peritectic reaction lc liq3 sa en liq4 occurs at 1 0 gpa and 1260 c lc37qz60ol3 with increasing pressure from 1 0 gpa the stability field of sanidine increases such that at 1 5 gpa the subsolidus reaction en lc ol san intersects the solidus defining an invariant point at 1290 c lc46qz47 5ol6 5 at 2 0 gpa the leucite field contracts farther toward the leucite corner and the peritectic reaction en liq6 ol sa liq7 takes place at 1350 c lc50qz43ol7 the ol en liq boundary moves from the silica oversaturated field at 0 5 and 1 0 gpa into the silica saturated field at 1 5 gpa and to the silica undersaturated field at 2 0 gpa our new data together with earlier studies of anhydrous and hydrous lc ol qz systems for 2 8 gpa suggest that highly potassic i e with very low na2o contents silica oversaturated magmas with minor contents of water could be direct partial melts of a potassic harzburgite or phlogopite bearing lherzolite mantle at pressures of nearly 1 5 gpa and temperatures of about 1200 1300 c generation of strongly undersaturated k rich magmas requires higher pressures 2 0 gpa and is favored by the presence of dissolved carbon as co3 and or fluorine

empirical distance attenuation and the local magnitude scale for northwest iran abstract we have derived an empirical attenuation curve for a local magnitude scale in northwest iran using a large data set of local earthquakes that occurred from 1996 to 2009 investigation shows that using one half the peak to peak value tends to underestimate the magnitude of an event by as much as 0 07 magnitude units in comparison with using the zero to peak value additionally using a vector sum of horizontal measurements overestimates the m l values by 0 16 magnitude units in comparison with magnitude values that are determined using arithmetic means of horizontal measurements we simulated the corresponding wood anderson seismograms for over 133 000 available waveforms after preliminary analysis the data set was subdivided in order to derive a local magnitude scale for northwestern iran the distance attenuation curve station correction terms and the magnitude of events were simultaneously estimated using parametric and nonparametric approaches in both approaches estimations and separate attenuation curves were determined by using vertical and horizontal measurements these two approaches yielded very similar results the distance attenuation curves that resulted in a nonparametric approach are given by log a 0 0 9252log 0 0030 0 8496 and log a 0 0 9993log 0 0029 0 7114 for the vertical and horizontal components respectively where is the epicentral distance in kilometers the distances considered ranged from 1 to 500 km applying these distance correction terms to the data set show that there are no obvious trends in magnitude residual with distance also using the station corrections reduces the magnitude residuals by as much as 0 07 magnitude units

pn attenuation for a spherically symmetric earth model this paper presents the results of a theoretical study of the sensitivity of pn attenuation to the elastic and anelastic structure of the uppermost mantle for frequencies between 1 and 15 hz and distances between 200 and 1000 km synthetic seismograms are computed using wavenumber integration for an elastic model consisting of a crastal layer over an upper mantle with a slight linear velocity gradient approximately equal to the earth flattening transformation of a spherically symmetric homogeneous upper mantle these are compared to synthetic seismograms for a crustal layer over a mantle halfspace pure elastic head wave we find that earth sphericity alone causes a significant departure in pn attenuation from that of a canonical head wave almost two orders of magnitude at 1000 km and 15 hz and that high frequencies attenuate less rapidly than low frequencies if the spherical earth velocity gradient is greater than or equal to zero this implies that methods that assume frequency independent pn geometric spreading will produce biased estimates of the anelasticity of the upper mantle this is demonstrated using synthetic seismograms computed for an anelastic spherical earth model these results show that the velocity structure must be carefully considered when relating observed pn spectral amplitudes to the anelastic structure of the upper mantle

ground motion attenuation and source spectral shape for earthquakes in eastern iran abstract we study source path and site effects for eastern iran earthquake based on regression analysis of 243 three component fourier acceleration spectra from 32 eastern iran earthquakes with moment magnitude m 4 4 7 4 recorded at hypocentral distances from 5 to 250 km the geometric spreading follows a trilinear behavior the first and second hinges of the trilinear behavior are at 87 and 119 km respectively the associated quality factor q based on the horizontal components is q f 166 f 1 13 the site dependent parameters 0 for vertical and horizontal components are 0 035 and 0 048 respectively because of lack of station specific site information the horizontal to vertical ratio is considered to be a rough estimation of generic site amplification the mean value of brune stress drops estimated for the events is 81 bars to construct an empirical model for source spectra horizontal component of the shear wave spectrum for m 4 4 7 4 we tested several functional forms including those suggested for california and eastern north america to search for the best combination of the coefficients that minimizes the average residual errors the model we attained is a function of two multiplicative corner frequencies of f a and f b and a parameter in which log f a 2 69 0 56 m log f b 3 40 0 53 m and

local and regional p wave spectral attenuation model for iran a robust frequency dependent local and regional p wave attenuation model is estimated for continental paths in the iranian plateau in order to calculate the average attenuation parameters 46 337 vertical component waveforms related to 9267 earthquakes which are recorded at the iranian seismological center irsc stations have been selected in the distance range 10 1000 km the majority of the event s magnitudes are less than 4 5 this collection of records provides high spatial ray path coverage results indicate that the shape of attenuation p wave curve versus distance is not uniform and has three distinct sections with hinges at 90 and 175 km a trilinear model for attenuation of p wave amplitude in the frequency range 1 10 hz is proposed in this study fourier spectral amplitudes are found to decay as r 1 2 where r is hypocentral distance corresponding to geometric spreading within 90 km from the source there is a section from 90 to 175 km where the attenuation is described as r 0 8 and the attenuation is described well beyond 175 km by r 1 3 moreover the average quality factor for pg and pn waves qpg and qpn related to anelastic attenuation is obtained as qpg 54 2 2 6 f 1 0096 0 07 and qpn 306 8 7 4 f 0 51 0 05 there is a good agreement between the results of the model and observations also the attenuation model shows compatibility with the recent regional studies from the results it turns out that the amplitude of p waves attenuates more rapidly in comparison with the global models in local distances

attenuation of ground motion spectral amplitudes and its variations across the central alborz mountains we selected 136 earthquakes recorded at stations of the institute of geo physics of the university of tehran igut during 1996 2007 in order to estimate the average attenuation parameters and variations of station corrections across the central alborz mountains the northern extension of the alpine himalayan orogeny in wes tern asia the selected events provide 1260 high signal to noise ratio snr records with relatively good spatial coverage we graphically find the distances at which the nature of geometrical spreading attenuation r b changes significantly using a locally weighted scatterplot smoothing lowess local regression smoothing method called robust lowess a trilinear function with hinges at distances of about 80 and 160 km describes the geometric spreading attenuation with distance by regressing to the hinged trilinear function we found that b1 1 15 0 21 b2 0 09 0 31 and a fixed b3 0 5 minimize the average absolute value of the fourier spectrum amplitude residuals using an anelastic attenuation coefficient at different frequencies the direct quality factor q in the central alborz region is obtained as q 109 2f 0 64 0 04 the geographical distribution of station corrections at 1 hz can be clearly separated along a dividing line connecting the north tehran mosha and attari faults into two regions the northern low attenuating and the southern high attenuating regions the stations with strong positive station corrections clearly align along the dividing line this suggests the existence of a higher attenuation zone south of the dividing line the presence of thick tertiary quaternary sedimentary rocks with thick layers of salt in the southern region may explain the observed greater attenuation of seismic waves

a new attenuation relation for peak horizontal acceleration of strong earthquake ground motion in japan abstract a new attenuation relation for peak horizontal acceleration applicable to the near source region in japan is developed the data base consists of 1372 horizontal components of peak ground acceleration from 28 earthquakes in japan and 15 earthquakes in the united states and other countries coefficients describing the decrease in acceleration with increasing distance found by most previous studies of japanese data are significantly smaller than those found by analyzing individual earthquakes this phenomenon is examined and found to result from use of general nonstratified multiple regression analyses the present analysis uses a two step stratified regression procedure and an attenuation model that accounts for geometrical spreading and anelastic attenuation but has magnitude independent shape at very short distances the resulting relation in japan is log 10 a 0 41 m log 10 r 0 032 10 0 41 m 0 0034 r 1 30 where a is the mean of the peak acceleration from two horizontal components at each site cm sec 2 r the shortest distance between site and fault rupture km and m the surface wave magnitude the median estimate of peak horizontal acceleration at the source region is 620 cm sec 2 independent of earthquake magnitude effects of four different ground condition rock hard medium and soft soils on the attenuation relation are also examined average peak horizontal accelerations for the rock and the soft soil sites are 60 and 140 per cent respectively of the value predicted from the equation

an ml scale in northeastern iran local magnitude scales are derived for northeastern iran khorasan province from waveform data recorded at six stations from 205 local earthquakes ranging in distance from 10 to 600 km by averaging the horizontal components in a single measure we used 1506 zero to peak amplitudes from synthetic wood anderson seismograms to determine in a least squares sense the appropriate loga0 attenuation functions the event local magnitude and the station corrections both a parametric and a nonparametric description of loga0 is considered while performing the inversions in both cases the constraint of 1 mm motion recorded at 100 km for m 3 0 earthquakes was used to evaluate the distance correction curves in determining the local magnitude ml in northeastern iran we applied both linear and trilinear inversions to our datasets the result of the linear inversion for dis tance correction is given by loga0 1 370 0 050logr 100 0 0020 0 0001r 100 3 for trilinear inversion we have applied the monte carlo technique the resulting coefficients evaluated for the area are r1 106 5 km r2 347 49 km n1 1 380 0 045 n2 0 597 0 132 n3 0 415 0 236 k 0 0033 0 0003 where n1 n2 and n3 are the coefficients of geometrical spreading for distances from the source to r1 r1 to r2 and beyond r2 k is the coef ficient of inelastic attenuation the remarkable agreement between the parametric and nonparametric results confirms that both linear and trilinear attenuation functions that we made for deriving the parametric distance correction are equally reasonable more over inversion of bootstrap replications of our dataset furnished stable solutions sta tion magnitude corrections range between 0 17 and 0 27 suggesting a variable and noticeable effect of station site properties on recorded amplitudes

seismic imaging of the lithospheric structure of the zagros mountain belt iran we present a synthesis and a comparison of the results of two temporary passive seismic experiments installed for a few months across central and northern zagros the receiver function analysis of teleseismic earthquake records gives a high resolution image of the moho beneath the seismic transects on both cross sections the crust has an average thickness of 43 2 km beneath the zagros fold and thrust belt and the central domain the crust is thicker beneath the hanging wall of the main zagros reverse fault mzrf with a larger maximum moho depth in central 69 2 km than in northern zagros 56 2 km the thickening affects a narrower region 170 km beneath the sanandaj sirjan zone of central zagros and a wider region 320 km in northern zagros we propose that this thickening is related to overthrusting of the crust of the arabian margin by the crust of central iran along the mzrf considered as a major thrust fault cross cutting the whole crust the fault is imaged as a lowvelocity layer in the receiver function data of the northern zagros profile moreover the crustal scale thrust model reconciles the imaged seismic moho with the bouguer anomaly data measured on the central zagros transect at upper mantle depth p wave tomography confirms the previously observed strong contrast between the faster velocities of the arabian margin and the lower velocities of the iranian micro blocks our higher resolution tomography combined with surface wave analysis locates the suture in the shallow mantle of the sanandaj sirjan zone beneath central zagros the arabian upper mantle has shield like shear wave velocities while the lower velocities of the iranian upper mantle are likely due to higher temperature but these velocities are not low enough and the low velocity layer not thick enough to conclude on a delamination of the lithospheric mantle lid beneath iran the lack of a high velocity anomaly in the mantle beneath central iran suggests that the neotethyan oceanic lithosphere is probably detached from the arabian margin

a crust and upper mantle model of eurasia and north africa for pn travel time calculation abstract we develop a regional seismic travel time rstt model and method for use in routine seismic analysis the model parameterization is a global tessellation of nodes with a velocity profile at each node interpolation of the velocity profiles generates a 3d crust and laterally variable upper mantle velocity the upper mantle velocity profile at each node is represented as a linear velocity gradient which enables travel time computation in approximately 1 millisecond this computational speed allows the model to be used in routine analyses in operational monitoring systems we refine the model using a tomographic formulation that adjusts the average crustal velocity mantle velocity at the moho and the mantle velocity gradient at each node while the rstt model is inherently global our first rstt tomographic effort covers eurasia and north africa where we have compiled a data set of approximately 600 000 pn arrivals ten percent of the data set is randomly selected and set aside for testing purposes travel time residual variance for the validation data is reduced by 32 based on a geographically distributed set of validation events with epicenter accuracy of 5 km or better epicenter error using 16 pn arrivals is reduced by 46 from 17 3 km ak135 model to 9 3 km rstt model after tomography the median uncertainty ellipse area is reduced by 68 from 3070 km 2 ak135 to 994 km 2 rstt and the number of ellipses with area less than 1000 km 2 which is the area allowed for onsite inspection under the comprehensive nuclear test ban treaty is increased from 0 ak135 to 51 rstt

seismic network evaluation through simulation an application to the italian national seismic network abstract a properly organized seismic network is a valuable tool for monitoring seismic zones and assessing seismic hazards in this paper we propose a new method seismic network evaluation through simulation snes to evaluate the performance of hypocenter location of a seismic network the snes method gives as a function of magnitude hypocentral depth and confidence level the spatial distribution of the number of active stations in the location procedure and their relative azimuthal gaps along with confidence intervals in hypocentral parameters the application of the snes method also permits evaluation of the magnitude of completeness m c the background noise levels at the stations and assessment of the appropriateness of the velocity model used in location routine italy sits on a tectonically active plate boundary at the convergence of the eurasian and african lithospheric plates and has a high level of seismicity in this paper we apply the snes method to the italian national seismic network rete sismica nazionale centralizzata dell istituto nazionale di geofisica e vulcanologia rsnc ingv which has monitored italian seismicity since the early 1980s following the destructive 1980 irpinia earthquake in recent years the rsnc ingv has grown significantly in fact in february 2010 it received signals from 305 seismic stations 258 with wideband three component sensors we constructed snes maps for magnitudes of 1 5 2 2 5 and 3 fixing the hypocentral depth at 10 km and the confidence level at 95 through the application of the snes method we show that the rsnc ingv provides the best monitoring coverage in the apennine mountains with errors that for m 2 are less than 2 and 4 km for epicenter and hypocentral depth respectively at m 2 5 this seismic network is capable of constraining earthquake hypocenters to depths of about 150 km for most of the italian peninsula this seismic network provides a threshold of completeness down to m 2 for almost the entire italian territory

regionalization of crustal coda q in the continental united states a contour map of crustal q sub 0 values for the entire united states is presented based on a scattering model to explain the coda waves of local and near regional earthquakes these coda q sub 0 values are in good agreement with q of lg waves data are obtained from over 250 local earthquakes with most magnitudes between 3 0 and 5 0 recorded by 25 wwssn and 27 lrsm stations throughout the continental united states these two sets of data provide a range of frequencies from 0 5 to 3 5 hz a frequency dependence of q is observed in the range of frequencies considered a power law dependence of the form q q sub 0 f f sub 0 sup eta is assumed the value of frequency dependence eta is found to be maximum in the tectonically active western united states and least in the stable regions of the central and south central united states the lowest q sub 0 values are obtained in the western united states with values ranging from 140 to 200 in the coastal plains average crustal q sub 0 values for the basin and range province vary from 200 to 300 increasing gradually to 400 in the colorado plateau region q sub 0 valuesmore in the columbia plateau vary from 200 to 400 q sub 0 values increase very rapidly along the central and southern rocky mountains from 400 to 800 east of the rocky mountains q sub 0 values increase gradually in the interior plains to a maximum value of around 1300 in the mississippi embayment region farther east q sub 0 values decrease gradually to an almost constant value of 1000 along the appalachian mountains coastal regions of eastern and northeastern united states have a crustal q sub 0 value between 900 to 700 regions of north central and gulf coastal plains show low q sub 0 values ranging from 600 to 400 and less the source factor b f sub p a measure of the intensity of scattering was obtained for several different regions of the continental united states regions of high q sub 0 values exhibit low intensity of scattering less

attenuation of high frequency p and s waves in the crust of the east central iran summary we simultaneously estimated qp 1 and qs 1 by applying the extended coda normalization method at 39 stations of three local networks in the east central iran we measured frequencydependent attenuation of both p and s waves for the frequency range of 1 5 3 0 6 0 12 and 24 hz we have analysed 266 three component seismograms of 53 local earthquakes having focal depths less than 25 km which occurred from 2003 december 28 to 2005 april 11 by fitting power law frequency dependence to the estimated values over the whole stations we obtained qp 1 25 3 10 3 f 0 99 0 04 and qs 1 19 2 10 3 f 1 02 0 06 in the upper crust of the east central iran where f is frequency in hz our results are in the range of those estimated for qp 1 and qs 1 of the other seismically active regions