spatial and temporal variation of coda wave attenuation in the faryab region southeast of the sanandaj sirjan zone using aftershocks of the tiab earthquake of 28 february 2006 coda quality factor q c estimates for the faryb region in the southeast zagros have been obtained by using aftershock data of the tiab earthquake of 28 february 2006 recorded within an epicentral distance of 100 km more than 394 earthquakes were recorded by a local temporary network consisting of 9 short period stations installed for one month after 28 february 2006 q c was estimated using the single backscattering model in frequency bands of 0 5 24 hz in this research the spatial and temporal variation of q c in the sanandaj sirjan zone is studied to explore the lateral variation q c is calculated for nine stations and in different parts of the covered area the lowest values are derived in kali station in the southern part and the higher value in baga station in the northern part but generally there is an absence of significant lateral variation in coda q c in the faryab region to investigate the attenuation variation with depth q c value was calculated for eight lapse times the average frequency relation for this region is q c 28 1 1 f 1 14 0 01 at 5 s lapse time window length and q c 105 1 3 f 0 98 0 047 at 30 s lapse time window length q c increases with depth however the rate of increase of q c is not uniform with depth in the study area beneath the faryab region the rate of increase of q c is greater at depths less than 49 km compared to larger depths indicating a low attenuation structure at less than 49 km depth which is the moho depth in this region

tomographic upper mantle velocity structure beneath the iranian plateau the iranian plateau is one of the most structurally complex and tectonically inhomogeneous regions in the world in this study we analyze pn arrival times from regional seismicity in order to resolve lateral velocity variations within the uppermost mantle under the iranian plateau more than 48 000 pn first arrival times selected from the ehb catalog were used with epicentral distances of 200 to 1600 km we used regularized isotropic and anisotropic damped least squares inversion to image lateral velocity variations in the upper mantle our velocity model with high lateral resolution shows positive anomalies in the zagros mountain belt with a distinct transition approximately along the main zagros thrust to the lower mantle velocity zone of central iran anomalously low velocities are observed predominantly beneath nw iran and eastern turkey suggesting a zone of relatively weak mantle low velocity region under the damavand volcano reveals the hot upper mantle beneath the central alborz mountains

lapse time dependence of coda q in the source region of the 1999 chamoli earthquake abstract in the present study the attenuation of seismic wave energy in and around the source area of the chamoli earthquake of 29 march 1999 is estimated using aftershock data most of the analyzed events are from the vicinity of the main central thrust mct which is a well defined tectonic discontinuity in the himalayas the method of a single backscattering model is employed to calculate frequency dependent values of coda q q c a total of 30 aftershock events are used for q c estimation at central frequencies 1 5 3 6 9 12 18 and 24 hz through five lapse time windows from 10 to 50 sec starting at double the travel time of the s wave the observed q c is strongly dependent on frequency which indicates that the region is seismically and tectonically active with high heterogeneities the variation of q c has also been estimated at different lapse times to observe its effect with depth the variation of q c with frequency and lapse time shows that the lithosphere becomes more homogeneous with depth q c values for higher frequencies increase very fast with depth within about the top 63 km of the lithosphere and then become more or less constant beyond this depth this indicates that turbidity at higher frequency decays very fast with depth and the mantle may be transparent to high frequency waves the variation of q c at 1 5 hz with lapse time matches quite well with those predicted by gusev 1995 however the frequency parameter n in the relation q c q 0 f n where q 0 q c at 1 hz does not follow the expected pattern given in his model this could be due to faster depth decay of turbidity as mentioned previously

the attenuation mechanism of s waves in the source zone of the 1999 chamoli earthquake a partial support has been given by italy ingv dpc istituto nazionale di geofisica e vulcanologia and dipartimento di protezione civile projects unrest and speed and by italy s ministry of education prin project seismic hazard in central apennines ur del pezzo

shear wave velocity tomography of the lithosphere asthenosphere system beneath the iranian plateau we conducted a tomographic inversion of rayleigh wave dispersion to obtain 2d phase and group velocity tomographic images in the 10 100 s period range and shear wave velocity structures for the iranian plateau for this purpose the fun damental mode of rayleigh waves recorded along 1586 paths by 29 broadband sta tions was identified by applying the frequency time analysis ftan to each epicenter station path which simultaneously satisfies the two station method condi tions the fundamental modes identified by ftan have been used to determine the path average interstation phase and group velocities at selected periods with this pro cedure 243 group and phase velocity dispersion curves were processed to obtain to mographic maps by applying the yanovskaya ditmar formulation for periods in the 10 100 s range averaged dispersion curves of phase and group velocities which represent six rather homogeneous regions are computed finally we used a fully non linear inversion procedure to derive tomographic images of the elastic structure of the lithosphere and asthenosphere of the six main structural and seismotectonic features of the iranian plateau the dense path coverage in the iranian plateau permits us to pro duce images that have substantially higher lateral resolution compared to images cur rently available from global and regional group velocity studies tomographic maps at high frequencies are well correlated with the upper crust structure especially with sediment layers thickness estimated shear wave velocity structures are well corre lated with the shield like lithosphere structure in zagros a low velocity zone lvz is not detected in alborz or the south caspian basin which can imply thrusting of the oceanic crust of the southern caspian sea under the alborz to the south lvzs are derived for the region east of iran central iran and kopeh dagh

spatial variations of seismic attenuation in the north west of iranian plateau from analysis of coda waves abstract in this study spatial variation of coda wave attenuation in the north western nw iranian plateau is explored using local earthquakes single backscattering method is used to map the spatial variations of coda q qc using 14 969 earthquakes which are recorded digitally by sixteen permanent stations observed spatial attenuation maps are well correlated with geological setting of study area north west of iranian plateau is dominated with high attenuation which is well correlated with quaternary deposits as well as the sahnad sabalan volcanic zone and tabriz fault these observation is in accordance with numerous 2d velocity tomograms which have shown very low velocity in the nw iran the region characterized by volcanic structures exhibits mainly higher seismic attenuation than the surrounding regions whereas paleo tethys basin in the eastern part of covered area are categorized by smaller attenuation than the other zone our observation shows good correlation with reported lower crustal low velocity region beneath the sahand and sabalan volcanos the sahand and sabalan volcanoes are very large structures and they dominate the pliocene quaternary magmatic landscape of nw iran in addition our observation has clearly shown existence of a probable fault zone trending in ne sw direction between tabriz city and urmia lake which is consistent with the trend of meizoseismal zone of the deh khareqan modern azarshahr earthquake m 6 8 in 1641

archaeological site formation in rain forests insights from the ituri rock shelters congo abstract this contribution complements the existing literature on rock shelter geoarchaeology and site formation processes by presenting data from 10 granite rock shelters in a tropical rain forest environment geological taphonomic pedological and archaeological data are used to assess the geomorphological evolution of rock shelters in the ituri rain forest northeast democratic republic of congo mechanisms of sediment production and deposition soil formation and related site formation processes were investigated the implications for the preservation of archaeological materials and stratigraphic resolution are discussed rock shelters in the tropical environment of the congo basin are formed by mechanical and chemical denudation of large granite boulders the current geomorphological cycle of rock shelter formation and collapse dates to the late pleistocene and may have been accelerated by anthropogenic forces the sedimentary record includes in situ breakdown products from the rock shelter walls while off site sources are represented by a minor influx of colluvium soil forming forces have acted on these matrices humans introduced charcoal phytoliths endocarps shell animal and human bone as well as inorganic materials such as stone ceramics and metal lags of archaeological materials are common under driplines where fine sediments have been washed away and include artefacts of different ages there is no evidence of extensive bioturbation but limited disturbance by roots burrowing animals and termites has been documented although there is some horizontal and vertical movement of prehistoric artefacts the post depositional translocation of materials is not significant we conclude that the stratigraphic integrity of these granite rock shelter sites with multiple archaeological horizons and the potential for the long term preservation of organic materials in a tropical environment are better than previously thought

attenuation of coda waves in the aswan reservoir area egypt abstract coda attenuation characteristics of aswan reservoir area of egypt were analyzed using data recorded by a local earthquake network operated around the reservoir 330 waveforms obtained from 28 earthquakes recorded by a network of 13 stations were used for this analysis magnitude of these earthquakes varied between 1 4 and 2 5 the maximum epicentral distance and depth of focus of these earthquakes were 45 km and 16 km respectively single back scattering method was used for estimation of coda q qc the q0 values qc at 1 hz vary between 54 and 100 and frequency dependence parameter n values vary between 1 and 1 2 for lapse time varying between 15 s and 60 s it is observed that coda q qc and related parameters are similar at similar lapse times to those observed for those for koyna india where reservoir induced seismicity is also observed for both regions these parameters are also similar to those observed for tectonically active regions of the world although aswan is located in a moderately active region and koyna is located in a tectonically stable region however qc does not increase uniformly with increasing lapse time as is observed for several parts of the world converting lapse time to depth distance it is observed that qc becomes lower or remains almost constant at around 70 to 90 km and 120 km depth distance this indicates presence of more attenuative material at those depth levels or distances compared to their immediate surroundings it is proposed that this variation indicates presence of fluid filled fractures and or partial melts at some depths distance from the area of study the qc values are higher than those obtained for the gulf of suez and al dabbab region of egypt at distances greater than 300 km from the study area by other workers the turbidity decreases with depth in the study area

late cenozoic deformation in the south caspian region effects of a rigid basement block within a collision zone abstract active deformation in the south caspian region demonstrates the enormous variation in kinematics and structural style generated where a rigid basement block lies within a collision zone rigid basement to the south caspian basin moves with a westward component relative both to stable eurasia and iran and is beginning to subduct at its northern and western margins this motion is oblique to the approximately north south arabia eurasia convergence and causes oblique shortening to the south and northeast of the south caspian basin thrusting in the alborz and kopet dagh is accompanied by range parallel strike slip faults which are respectively left and right lateral there are also arcuate fold and thrust belts in the region for two principal reasons firstly weaker regions deform and wrap around the rigid block this occurs at the curved transition zone between the alborz and talysh ranges where thrust traces are concave towards the foreland secondly a curved fold and thrust belt can link a deformation zone created by movement of the basement block to one created by the regional convergence west to east thrusts in the eastern talysh represent underthrusting of the south caspian basement but pass via an arcuate fan of fold trains into ssw directed thrusts in the eastern greater caucasus which accommodates part of the arabia eurasia convergence each part of the south caspian region contains one or more detachment levels which vary dependent on the pre pliocene geology buckle folds in the south caspian basin are detached from older rocks on thick mid tertiary mudrocks whereas thrust sheets in the eastern greater caucasus detach on mesozoic horizons in the future the south caspian basement may be largely eliminated by subduction leading to a situation similar to archaean greenstone belts of interthrust mafic and sedimentary slices surrounded by the roots of mountain ranges constructed from continental crust

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

pn tomographic imaging of mantle lid velocity and anisotropy at the junction of the arabian eurasian and african plates an edited version of this paper was published by blackwell publishing in geophysical journal international copyright 2004 blackwell publishing see also http www blackwell synergy com doi abs 10 1111 j 1365 246x 2004 02355 x http atlas geo cornell edu middleeastnorthafrica publications al lazki2004 htm

attenuation of short period seismic waves at etna as compared to other volcanic areas codaq for etna volcano is frequency dependent and theq frequency pattern and the numerical values ranging from about 100 at 1 hz to about 300 at 18 hz are similar to the values obtained for other volcanoes campi flegrei aeolian islands and hawaii moreover the frequency pattern and the numerical values of coda quality factor for most of the seismically active zones of italy are very different from those of the volcanic zones

new constraints on upper mantle s velocity structure and crustal thickness of the iranian plateau using partitioned waveform inversion summary the continental collision between the african and eurasian plates resulted in a tectonically young and complex deformation in the iranian plateau the present day iranian plateau is characterized by diverse tectonic domains including the continental collisions e g zagros and alborz and the oceanic plate subduction e g makran partitioned waveform inversion method is used here to image the s velocity structure of the upper mantle and moho depth variations in the iranian plateau of nearly 3000 waveforms originally selected for the analysis we have fitted 974 waveforms from 101 events and 39 stations which result in 11 688 linear constraints on the upper mantle s velocity structure and moho depth for the region our new seismic images show seismically faster upper mantle beneath the zagros and the arabian plate compared to the central iran and alborz this high velocity anomaly has descended beneath the central iran along the main zagros thrust across the zagros collision zone the tomographic images show a slab stagnation in the transition zone at about 410 km depth in the form of a horizontal high velocity zone which does not penetrate the deeper parts of the mantle the lowest s velocities are concentrated beneath the central iran and alborz according to our velocity models a strong high velocity anomaly is resolved beneath the trapped south caspian basin with clear indication of westward underthrusting beneath the talesh and western alborz in makran southeast iran there is a clear evidence of subduction of oceanic crust of the arabian plate beneath the makran belt which is correlated with seismicity pattern across the makran zone also the inverted moho map using a priori information of crustal thickness constraints shows the large crustal thickness beneath the zagros suture zone in some places to a maximum depth of 65 km which indicates the influence of crustal thickening and shortening beneath arabian eurasian plate boundary a significantly crustal thinning is observable across the south caspian basin compared to its margins

the attenuation mechanism of seismic waves in northwestern himalayas summary we analysed local earthquake waveforms recorded on a broad band seismic network in northwestern himalayas to compute the intrinsic and scattered attenuation parameters from coda waves similar to other tectonically active and heterogeneous regions attenuation frequency relation for western himalaya is q 1 113 7 f 1 01 0 05 where qc is the coda q parameter intrinsic q 1 and scattering q 1 attenuations was separated using qc and direct s wave q data qd it is observed that estimated q 1 is close to q 1 and both of them are much larger than q 1 suggesting that coda decay is predominantly caused by intrinsic attenuation at higher frequencies both the attenuation parameters qc and qd are similar indicating that coda is predominantly composed of back scattered s waves at these frequencies

hydrothermal alteration of plagioclase and growth of secondary feldspar in the hengill volcanic centre sw iceland dissolution of igneous feldspar and the formation and occurrence of secondary feldspar in tholeiitic basalts from the hengill volcanic centre in sw iceland was studied by microprobe analysis of cuttings from two ca 2000 m deep geothermal wells well ng 7 in nesjavellir represents a geothermal system in a rift zone where the intensity of young insignificantly altered intrusions increases with depth well khg 1 in kolvioarholl represents the margin of a rift zone where the intensity of intrusives is lower and the intensity of alteration higher this marginal well represents altered basaltic crust in an early retrograde state the secondary plagioclase in both wells is mainly oligoclase occurring in association with k feldspar and chlorite actinolite the texture of this assemblage depends on the lithology and intensity of alteration in nesjavellir ng 7 the composition of secondary albite oligoclase is correlated with the host rock composition this connection is not apparent in more intensely altered samples from kolvioarholl khg 1 the influence of temperature on composition of secondary na feldspar is unclear in both wells although ca is expected to increase with temperature any temperature dependence may be suppressed by the influence of rock composition in nesjavellir and by retrograde conditions at kolvioarhall the absence of clear compositional gradients between igneous plagioclase and secondary feldspar and between na feldspar and k feldspar suggests that secondary feldspars formed by dissolution precipitation reactions c 2002 elsevier science b v all rights reserved less

spatial variations of seismic attenuation and heterogeneity in the pyrenees coda q and peak delay time analysis abstract lateral variations of seismic attenuation in the pyrenees are explored from the analysis of local earthquake records scattering loss and intrinsic absorption both control the propagation of short period s waves through the crust the role of intrinsic and scattering attenuation is analyzed in two steps firstly the coda quality factor q c which quantifies the energy decay of coda waves is estimated at large lapse time in five frequency bands and interpreted as intrinsic absorption next we systematically measure the peak delay time defined as the time lag from the direct s wave onset to the maximum amplitude arrival this parameter quantifies the strength of multiple forward scattering due to random inhomogeneities along the seismic ray path comparison of coda q and peak delay time measurements allows a qualitative interpretation of the origin of seismic attenuation scattering absorption in the pyrenean crust at low frequency coda q variations mainly depend on the tectonic units of the pyrenees with stronger absorption in sedimentary basins and smaller absorption in paleozoic basements at high frequency coda q is low at the location of neogene structures in the eastern pyrenees a more enigmatic low q c anomaly is also observed at the location of the maladeta massif in the central pyrenees in all frequency bands peak delay time measurements systematically show stronger scattering in the western pyrenees in the labourd mauleon area absorption and scattering are both important at low frequency the western pyrenees also correspond to a high velocity density anomaly revealed from tomography and gravity data analysis this suggests that the high level of inhomogeneities and absorption may be related to intrusion of mantle and or lower crustal materials in the eastern pyrenees absorption appears dominant over scattering at high frequency we hypothesize that the strong absorption observed in this area may be related to volcanic structures

residence time of diffuse waves in the crust as a physical interpretation of coda q application to seismograms recorded in mexico summary we consider a simple model for elastic wave propagation in the earth s litho sphere consisting of a heterogeneous and scattering crust overlying a homogeneous mantle that is we neglect backscattering from the upper mantle this rough condition is not strictly valid everywhere but this model allows us to investigate the effects of variations of diffracting properties between crust and mantle on the coda decay the free parameters describing the wave propagation are the mean free path of the waves and the intrinsic absorption in the crust in the framework of the radiative transfer theory we treat accurately jumps in s wave speed and the mean free path at the moho without intrinsic absorption this configuration yields a synthetic coda decay 1 texp 2 ft qc a form similar to that proposed by aki chouet 1975 to parametrize the observations the exponential decay in our purely elastic model is due to the partial leakage of diffuse energy into the mantle in order to test the applicability of our model we have determined the coda q parameter qc in the 1 15 hz frequency band from data recorded at four stations in mexico in the low frequency regime around 1 hz we suggest that the energy leakage significantly affects coda q whilst at higher frequencies around 10 hz the anelastic attenuation dominates a weak intrinsic absorption expressed by a frequency independent parameter qi of about 1000 accounts satisfactorily for the observed qc values in the whole frequency range our very simple model has only two free parameters and offers an attractive alternative physical interpretation of coda q in mexico this model is sufficient to interpret the coda observations according to our model in regions where the mean free path is much larger than the crustal thickness weakly heterogeneous crust the leakage effect should be small and the observed qc will mainly be due to the intrinsic absorption on the other hand when the mean free path is of the order of the crustal thickness strongly heterogeneous crust we predict a strong sensitivity of the decay rate of the coda to the crustal thickness this dependence may be important for the interpretation of the regional variations of coda q we propose introducing a new parameter d the residence time of diffuse energy in the crust which is physically more meaningful than a quality factor to quantify the leakage effect

offset on the main recent fault of nw iran and implications for the late cenozoic tectonics of the arabia eurasia collision zone summary we use drainage patterns geological markers and geomorphological features to determine a right lateral offset of 50 km and possibly as much as 70 km on the main recent fault in nw iran this fault trends nw se and forms the ne border of the zagros mountains it accommodates the strike slip component of the n s convergence between arabia and eurasia with the ne sw shortening component being accommodated in the zagros fold belt its 50 km strike slip offset implies a shortening of 50 km in the fold belt and 70 km total n s convergence accommodated in the nw zagros this is a substantial fraction of the 85 140 km overall arabia eurasia convergence expected over the last 3 5 ma if the main recent fault initiated at that time as seems likely from geological arguments it has a horizontal slip rate of at least 10 17 mm yr 1 and should be the source of frequent earthquakes of ms 6 7 as has been seen in the 20th century and the earlier historical record the similarity of the offsets and probable ages of the north anatolian and main recent faults suggests that they have been active as an almost continuous zone of right lateral shear on the north edge of the arabian and anatolian plates since the early pliocene

nw iran eastern turkey present day kinematics results from the iranian permanent gps network abstract a network of continuous gps stations has been installed in nw iran since 2005 to complement the survey gps network already existing in the region we present the 1999 2009 gps derived velocity field for this region based on the continuous and survey mode observations the results confirm a right lateral slip of 7 1 mm yr for the north tabriz fault in agreement with previous studies this rate is consistent with earthquakes of magnitude 7 7 3 and recurrence times of 250 300 yr the higher spatial coverage of the new network shows that deformation is localized in the vicinity of the chalderan south gailatu siah cheshmeh khoy fault and the north tabriz fault however the eastern end of the north tabriz fault appears to cross mount bozgush rather than following its southern foothills this new velocity field does not indicate the 8 mm yr of nne ssw extension suggested earlier for the region but rather shows lower extension of 1 2 1 mm yr across the eastern segment of the north tabriz fault and the talesh to the west the chalderan and the western north tabriz fault segment act like pure strike slip faults without significant extension or compression the denser network in the rudbar earthquake region ms 7 3 1992 shows no significant motion across the fault suggesting that the recurrence time of earthquakes like the rudbar event must be very long the lack of substantial compressive strain and the sharp azimuth change of the velocity vectors in the transition zone from arabia to lesser caucasus motion imply that processes other than extrusion possibly related to old subduction or delamination contribute to active deformation

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

active tectonics of the turkish iranian plateau 1 this paper examines how active faulting in the turkey iran caucasus region accommodates the arabia eurasia collision and the velocity field observed by gps the overall shortening across the zone is in general spatially separated partitioned into right lateral strike slip in the turkish iranian plateau and thrusting in the greater caucasus a band of counterclockwise rotating nw se right lateral strike slip faults accommodates a nw se gradient in ne directed velocity relative to eurasia between the black and caspian seas a nnw sse band of previously unrecognized oblique normal faults is present on the turkey iran border we estimate the offsets on faults from geomorphological features and show that these offsets can be achieved in 5 2 ma at present rates this implies a reorganization of deformation in the collision zone at that time after the initial collision at 12 ma probably in response to mantle induced dynamic uplift

variation of coda wave attenuation in the alborz region and central iran summary more than 340 earthquakes recorded by the institute of geophysics university of tehran igut short period stations from 1996 to 2004 were analysed to estimate the s coda attenuation in the alborz region the northern part of the alpine himalayan orogen in western asia and in central iran which is the foreland of this orogen the coda quality factor qc was estimated using the single backscattering model in frequency bands of 1 25 hz in this research lateral and depth variation of qc in the alborz region and central iran are studied it is observed that in the alborz region there is absence of significant lateral variation in qc the average frequency relation for this region is qc 79 2f1 07 0 08 two anomalous high attenuation areas in central iran are recognized around the stations las and raz the average frequency relation for central iran excluding the values of these two stations is qc 94 2f0 97 0 12 to investigate the attenuation variation with depth qc value was calculated for 14 lapse times 25 30 35 90s for two data sets having epicentral distance range r 100 km data set 1 and 100 r 200 km data set 2 in each area it is observed that qc increases with depth however the rate of increase of qc with depth is not uniform in our study area beneath central iran the rate of increase of qc is greater at depths less than 100 km compared to that at larger depths indicating the existence of a high attenuation anomalous structure under the lithosphere of central iran in addition below 180 km the qc value does not vary much with depth under both study areas indicating the presence of a transparent mantle under them

seismic coda q and turbidity coefficient at the phlegraean fields volcanic area preliminary results digital recordings of microearthquake codas from shallow seismic events in the phlegraean fields region south central italy were used to calculate the attenuation factor qc