active faults in the zagros and central iran abstract active tectonic movements in the northwestern zagros include right lateral slip at the rate of about 10 mm a along the main recent fault which inherits the position of the main thrust now inactive and active thrusting and accompanying folding distributed between several zones southwest of the main recent fault in the southeastern zagros the fars province there are several right lateral faults that extend n s obliquely to the overall trend of the zagros fault and fold belt these may be either branches of the main recent fault or faults accommodating relative broadening of the outer zagros in its southeastern segment the main thrust in the southeastern zagros also remains inactive the ipak north tehran and mosha fault zones and several minor structures in the eastern alborz form the e w trending active fault system with combined reverse and left lateral slip on the ipak and mosha zones lateral movements with the late quaternary mean rate exceeding 1 mm a dominate over vertical fault movements together with right lateral faults stretching northeast of zagros the faults of the alborz may accommodate east directed motion of the iranian microplate

seismicity at warna reservoir near koyna through 1995 the koyna dam site in western india has been seismically active since its impounding in 1962 the seismicity peaked in 1967 when an earthquake of magnitude 6 3 claimed 200 human lives and caused some damage to the dam itself subsequently bursts of seismicity with m 5 earthquakes have occurred during 1973 1980 and 1993 to 1995 the epicenters during the latest burst are concentrated around the newly impounded warna reservoir 25 km south of koyna several shocks of smaller magnitude have occurred in this area since 1967 under the influence of the koyna shivajisagar reservoir but the impoundment of the warna reservoir to over 60 m has led to the enhanced seismic activity in the region the space time pattern of epicenters located for the period 28 august 1993 to 31 december 1995 clearly delineates two parallel trends in the nne ssw direction the correlation between seismic activity and water levels in both the reservoirs suggests that the present activity was influenced more by the warna than the koyna reservoir the discriminatory characteristics of reservoir induced seismicity based on b value foreshock aftershock pattern and decay rate of aftershocks continue to be valid

late pleistocene holocene right slip rate and paleoseismology of the nayband fault western margin of the lut block iran the 290 km long nayband strike slip fault bounds the western margin of the lut block and cuts across a region thought to have been quiescent during the last few millennia cl 36 cosmic ray exposure cre and optically stimulated luminescence osl dating of cumulative geomorphic offsets are used to derive the long term slip rate the measured offsets at two sites along the fault range between 9 1 m and 195 15 m with ages from 6 8 0 6 ka to 100 ka yielding minimum and maximum bounds of late pleistocene and holocene slip rates of 1 08 and 2 45 mm yr 1 respectively this moderate slip rate of 1 8 0 7 mm yr 1 averaged over several earthquake cycles is compared to the paleoseismic record retrieved from the first trench excavated across the fault combining the paleoseismic evidence with 18 osl ages obtained from this trench site demonstrates the occurrence of at least four large m 7 earthquakes during the last 17 4 1 3 ka and of two older wearthquakes one before 23 ka and another before 70 5 ka the exposed sediment succession also indicates a significant gap at the end of mis 2 and the beginning of mis 1 the age of the most recent regional incision is accurately bracketed between 6 1 ka and 7 4 ka sediments from the last 7 ka contain evidence of the three younger earthquakes interestingly the penultimate and antepenultimate events occurred between 6 5 0 4 ka and 6 7 0 4 ka within a time interval lasting at most 1 ka whereas the most recent earthquake occurred within the last millennium such an irregular earthquake occurrence suggests the seismic behavior of the nayband fault is not strictly time dependent but possibly related to clustering from this and taking into account the occurrence of the most recent earthquake within the last 800 years the imminence of an earthquake along the nayband fault cannot be discarded although the most recent surface rupturing event seems to have occurred after ad 1200 this event went unnoticed in the historical records this provides a marked illustration of the incompleteness of the historical seismic catalogs in central iran challenging any assessment of regional seismic hazard without appropriate geologic and geochronological information large and infrequent earthquakes are characteristic of the seismic behavior of the slow slipping strike slip faults slicing central and eastern iran also the slip rates summed across central and eastern iran from the iran plateau up to the afghan lowlands appear in agreement with the most recent gps data

inception of activity and slip rate on the main recent fault of zagros mountains iran abstract we used geological geomorphological markers pull apart basins and drainage patterns to explore totally a new more accurate strike slip offset on the main recent fault mrf of the zagros mountains in sw iran the mrf has a nw se strike that is among the most important structural features within the arabian iranian continental collision zone inception of the mrf has been suggested to be related to the slab break off underneath the zagros during the last 10 5 ma we conclude that the maximum total right lateral offset on the mrf is about 16 km leading to a slip rate of about 1 6 3 2 mm y 1 these figures for the fault inception time and slip rate are consistent according to geodetic estimates and three dimensional mechanical modeling

offset rivers drainage spacing and the record of strike slip faulting the kuh banan fault iran abstract this study concerns the ways in which rivers can record part but not necessarily all of strike slip fault offset the focus is the active right lateral kuh banan fault in eastern iran within the arabia eurasia collision plate convergence has caused thrust and strike slip faulting across sw asia the active slip rate of the kuh banan fault is 1 2 mm yr total displacement is 5 7 km as determined from offset geological markers and the length of a pull apart basin a component of thrusting has generated 1 km of relief which preserves the offset of rivers displaced laterally by the strike slip motion ridge half widths w and river outlet spacings along the fault s are related by the drainage spacing parameter r where r w s published data for older larger mountain ranges have extremely characteristic drainage spacing r 2 1 drainage spacing along the kuh banan fault has a mean value of 1 8 and is much more variable r 1 1 3 1 due to local structural complexities which have influenced river courses most river offsets along the kuh banan fault are small

seismicity faulting and structure of the koyna warna seismic region western india from local earthquake tomography and hypocenter locations although seismicity near koyna reservoir india has persisted for 50 years and includes the largest induced earthquake m 6 3 reported worldwide the seismotectonic framework of the area is not well understood we recorded 1800 earthquakes from 6 january 2010 to 28 may 2010 and located a subset of 343 of the highest quality earthquakes using the tomodd code of zhang and thurber 2003 to better understand the framework we also inverted first arrivals for 3 d vp vs and vp vs and poisson s ratio tomography models of the upper 12 km of the crust epicenters for the recorded earthquakes are located south of the koyna river including a high density cluster that coincides with a shallow depth 1 5 km zone of relatively high vp and low vs also high vp vs and poisson s ratios near warna reservoir this anomalous zone which extends near vertically to at least 8 km depth and laterally northward at least 15 km is likely a water saturated zone of faults under high pore pressures because many of the earthquakes occur on the periphery of the fault zone rather than near its center the observed seismicity velocity correlations are consistent with the concept that many of the earthquakes nucleate in fractures adjacent to the main fault zone due to high pore pressure we interpret our velocity images as showing a series of northwest trending faults locally near the central part of warna reservoir and a major northward trending fault zone north of warna reservoir

block kinematics of the pacific north america plate boundary in the southwestern united states from inversion of gps seismological and geologic data 1 the active deformation of the southwestern united states 30 41 n is represented by a finite number of rotating elastic plastic spherical caps gps derived horizontal velocities geologic fault slip rates transform fault azimuths and earthquake derived fault slip vector azimuths are inverted for block angular velocities creep on block bounding faults permanent strain rates within the blocks and the rotations of 11 published gps velocity fields into to a common north american reference frame gps velocities are considered to be a combination of rigid block rotations recoverable elastic strain rates resulting from friction on block bounding faults and nonrecoverable strain rates resulting from slip on faults within the blocks the resulting pacific north america angular velocity is similar to some published estimates and satisfies transform azimuths and one spreading rate in the gulf of california earthquake slip vectors in the gulf of california and alaska and gps velocities along coastal california and within the pacific basin published fault slip rates are satisfied except in the southern mojave desert where the motion of the mohave block relative to north america is faster than can be explained by mapped faults the largest blocks the sierra nevada great valley and the eastern basin and range show permanent strain rates after removing elastic strain of only a few nanostrain per year demonstrating approximately rigid behavior observed horizontal strain rates correlate strongly with predicted strain rates from known faults suggesting that the short term strains evident in gps velocities are largely elastic in only about 20 of the region is distributed deformation needed to match the data indicating that a plate tectonic style description of the deformation of the western united states is plausible most blocks rotate about vertical axes at approximately the same rate as the pacific relative to north america suggesting that locally spin rates are communicated from block to block arguing against both floating block and ball bearing mechanisms of block rotation the similarities of the blocks spin rates to that of the pacific suggests that the pacific strongly influences their motions through edge tractions however it is shown that the blocks cannot rotate about the pacific north america pole without spinning counter to the sense of pacific north america shear unlike some other broad plate boundaries in the western united states vertical axis rotations take up very little of the slip rate budget across the region

active deformation within the zagros mountains deduced from gps measurements we present and interpret the results of global positioning system gps measurements at 35 stations in and beside the zagros mountain belt sw iran for three campaigns ending march 1998 december 1999 and june 2001 preliminary motion estimates show clearly the change in character along the strike of the belt stations to the se move at 13 22 3 mm a 1 towards n 7 5 e with respect to eurasia most of the shortening indicated by the gps velocities seems to occur in the se zagros along two major seismic zones and along the zagros front to the nw stations move oblique to the trend of the belt towards n 12 8 w at 14 19 3 mm a 1 most of the shortening in the nw zagros seems to occur along the mountain front fault with its major earthquakes as well as along the zagros front the change in direction and magnitude of the velocity vectors across the north south trending kazerun and karebas faults involves extension of up to 4 mm a 1 along the strike of the zagros belt

five decades of triggered earthquakes in koyna warna region western india a review abstract we review reservoir triggered seismicity rts in the koyna warna region of india since the impoundment of the koyna reservoir in 1962 until the year 2015 we include seismicity that occurred farther south in response to the impoundment of warna reservoir in 1993 about 35 km to the south of koyna reservoir the on going earthquake activity for more than five decades in a small seismic volume of about 30 20 10 km3 has characterized the koyna warna region as globally unique and significant to date 22 earthquakes of m 5 about 200 earthquakes of m 4 and several thousand smaller earthquakes have been recorded by a dense network of stations in the region various seismological geophysical and hydrological studies have been carried out to understand the phenomenon of triggered seismicity including source mechanism fault geometry crustal structure earthquake processes causal relationship with reservoir water level changes and anomalous water level fluctuations in cased bore wells the present review takes stock of all such studies undertaken so far to summarise the understanding on various geo scientific issues and milestone achievements with regard to mechanism of triggered seismicity and source processes fault plane solutions commensurate with geometry of faulting source parameters seismogenic depth crustal structure and the role of reservoir water level two stage increase in seismic energy release coinciding with peaks of annual filling and draining cycle of reservoir with one month delay vis a vis spurt of moderate earthquakes m 5 due to i rapid rise in reservoir level 12 m week ii reservoir water level exceeding the previous maxima and iii duration for which high reservoir level is retained are characteristic features numerical models simulating diffusion of pore fluid pressure fronts during the filling stage of reservoir suggest stress perturbations of the order of 0 75 2 25 bar at hypocentral depth triggering earthquakes on critically stressed pre existing faults in the year 2005 a 13 station digital seismometers network became functional that characterized the distribution of epicentres in the area with increased accuracy and suggested four major seismic zones with well defined clusters scientific drilling carried out recently provide several new information regarding the subsurface geology and structure in the koyna region such as i thickness of deccan traps 933 in the koyna area and 1185 m in the warna area ii presence of granite gneiss basement directly underlying the deccan traps iii absence of infratrappean sediments and iv temperature not exceeding 150 c at hypocentral depth it is planned to establish a deep borehole observatory close to the seismic source zone for direct measurements of physical and mechanical properties of rocks pore fluid pressure hydrology thermal condition and other parameters of an intra plate active fault zone in the near field of earthquakes before during and after their occurrence results from such experiment and long term in situ monitoring of critical parameters would enhance our understanding on the mechanism of triggered earthquakes and the role of reservoir water level fluctuations

analysis of coseismic water level changes in the wells in the koyna warna region western india abstract we test the hypothesis that coseismic water level changes in wells are proportional to coseismic volumetric strain by analyzing available data from the koyna warna region of western india a total of 18 cases of water level changes have been reported at ten wells corresponding to six earthquakes of m 4 3 that occurred in the region from 1997 to 2005 out of these clear unambiguous steplike coseismic water level changes have been observed in ten cases at five confined wells we used basic poroelastic theory to simulate volumetric strain and corresponding water level changes and find that all cases show consistency in sign between reported coseismic water level changes and simulated volumetric strain all confined wells with high strain sensitivity that are located near earthquake epicenters show good agreement in magnitude between simulated and reported volumetric strain thereby supporting this hypothesis

new tectonic configuration in ne iran active strike slip faulting between the kopeh dagh and binalud mountains in this paper a combined approach of geomorphic analyses detailed geological mapping on spot 5 satellite images and field surveys complemented by radiometric dating ar 40 ar 39 allows proposing a new and consistent tectonic configuration for the northeastern arabia eurasia collision zone it favors a simple strike slip faulting mechanism in ne iran accommodating the northward motion of central iran with respect to eurasia between the binalud and kopeh dagh mountains our results demonstrate that similar to 2 mm a similar to 25 of this northward motion has been transferred from the binalud to the kopeh dagh through the meshkan transfer zone since similar to 5 ma the modern state of stress deduced from fault kinematics analyses shows n30 degrees e trending maximum stress axis and confirms a dominant strike slip faulting mechanism combining our geological data with other available data we conclude that kinematics of deformation can be appropriately described by rigid block faulting in ne iran instead the continuous deformation as it has been thought during the last 3 decades

shells a thin shell program for modeling neotectonics of regional or global lithosphere with faults the thin plate method of modeling neotectonics uses isostasy and vertical integration of lithospheric strength to reduce three dimensional problems to two dimensions we introduce new thin shell continuum elements and fault elements which satisfy the completeness and compatibility requirements and permit extension of these methods to the lithospheres of spherical planets even a coarse grid of these elements with elastic rheology can reproduce low order toroidal free oscillations in the program shells a realistic frictional dislocation creep rheology is handled by iteration this method converges to solutions which can be numerically tested to confirm that they satisfy both local equilibrium and the balance of torques on whole plates because this code can incorporate both natural plate shapes with internal faults and realistic rheologies it yields models that are readily tested by their predictions of geodetic velocities stresses and fault slip rates

high precision earthquake locations in koyna warna seismic zone reveal depth variation in brittle ductile transition zone 1 the koyna warna region located in the southwestern part of deccan volcanic province is known for sustained seismicity during the last four decades catalog p and s phase data of local earthquakes recorded by the koyna warna digital network were used to relocate 609 earthquakes using double difference algorithm the relocated seismicity patterns delineate the presence of three fault segments and variation in the brittle ductile transition depths amongst the individual faults as the earthquake foci in the north are limited up to 11 km depth whilst in the south they are confined up to 6 8 km the focal mechanism solutions also indicate distinct styles of faulting amongst the three inferred fault segments the variation in brittle ductile transition zone is probably controlled due to the geometry of the fault system and the effective stress

palaeoseismicity and pottery investigating earthquake and archaeological chronologies on the hajiarab alluvial fan iran for millennia humans have lived in locations that are highly vulnerable to large earthquakes often out of strategic or cultural necessity and or the proximity of these locations to resources necessary for survival despite the often catastrophic effects when large earthquakes occur recent history reveals that human nature is to rebuild rather than relocate implying that seismic activity is not a sufficient deterrent of population growth in tectonically vulnerable areas in order to investigate whether this was the case for ancient civilisations and thus perhaps a fundamental tenet of human behaviour a palaeo earthquake history was developed for the active cheskin and ipak faults in northwestern iran and compared with the well resolved archaeological history of the nearby sagzabad cluster settlements of zagheh 7170 6300 bp ghabristan 6215 4950 bp and sagzabad 4050 2350 bp combining new geologic geomorphic and chronologic datasets revealed the presence of a fault propagated anticline formed by large mw 6 5 7 0 earthquakes on a blind thrust fault that projects to seismogenic depth directly beneath the sagzabad cluster settlement sites large earthquakes with a return period of 90 probability under most faulting scenarios that the energy release from these earthquakes would have been of sufficient magnitude to generate peak horizontal acceleration pha values at the sagzabad cluster in excess of likely threshold values for complete settlement destruction poisson modelling assuming a time displacement repeating model for earthquake recurrence indicates a 66 42 probability of one two earthquakes that would generate pha 0 25 g occurring during occupation of zagheh a 79 55 probability for ghabristan and an 88 65 probability for sagzabad despite the near certainty that the residents of these holocene settlements experienced large destructive earthquakes the near continuous history of occupation at this area suggests that early humans were not apt to relocate in response to earthquake activity environmental e g alluviation stream channel avulsion climate change cultural and or political factors may have been more important drivers of settlement shifts and abandonment at the sagzabad cluster of iran

cenozoic evolution of neotethys and implications for the causes of plate motions africa north america eurasia plate circuit rotations combined with red sea rotations and new estimates of crustal shortening in iran define the cenozoic history of the neotethyan ocean between arabia and eurasia the new constraints indicate that arabia eurasia convergence has been fairly constant at 2 to 3 cm yr since 56 ma with slowing of africa eurasia motion to 1 cm yr near 25 ma coeval with the opening of the red sea ocean closure occurred no later than 10 ma and could have occurred prior to this time only if a large amount of continental lithosphere was subducted suggesting that slowing of africa significantly predated the arabia eurasia collision these kinematics imply that africa s disconnection with the negative buoyancy of the downgoing slab of lithosphere beneath southern eurasia slowed its motion the slow steady rate of northward subduction since 56 ma contrasts with strongly variable rates of magma production in the urumieh dokhtar arc implying magma production rate in continental arcs is not linked to subduction rate

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

extrusion tectonics and subduction in the eastern south caspian region since 10 ma comment hollingsworth et al 2008 1 proposed a new kinematic model for the complicated tectonic pattern in the eastern south caspian sea region our comment is focused on the ashkhabad fault and the kopeh dagh mountains examining the data and hypothesis used by the authors to support their model

on the consistency of earthquake moment rates geological fault data and space geodetic strain the united states new and dense space geodetic data can now map strain rates over continental wide areas with a useful degree of precision stable strain indicators open the door for space geodesy to join with geology and seismology in formulating improved estimates of global earthquake recurrence in this paper 174 gps vlbi velocities map united states strain rates of 30 0 10 8 yr 1 with regional uncertainties of 5 to 50 per cent kostrov s formula translates these strain values into regional geodetic moment rates two other moment rates m seismic and m geologic extracted from historical earthquake and geological fault catalogues contrast the geodetic rate because m geologic m seismic and m geodetic derive from different views of the earthquake engine each illuminates different features in california the ratio of m geodetic to m geologic is 1 20 the near unit ratio points to the completeness of the region s geological fault data and to the reliability of geodetic measurements there in the basin and range northwest and central united states both m geodetic and m seismic greatly exceed m geologic of possible causes high incidences of understated and unrecognized faults probably drive the inconsistency the ratio of m seismic to m geodetic is everywhere less than one the ratio runs systematically from 70 80 per cent in the fastest straining regions to 2 per cent in the slowest although aseismic deformation may contribute to this shortfall i argue that the existing seismic catalogues fail to reflect the long term situation impelled by the systematic variation of seismic to geodetic moment rates and by the uniform strain drop observed in all earthquakes regardless of magnitude i propose that the completeness of any seismic catalogue hinges on the product of observation duration and regional strain rate slowly straining regions require a proportionally longer period of observation characterized by this product gamma distributions model statistical properties of catalogue completeness as proxied by the ratio of observed seismic moment to geodetic moment i find that adequate levels of completeness should exist in median catalogues of 200 to 300 year duration in regions straining 10 7 yr 1 comparable to southern california similar levels of completeness will take more than 20 000 years of earthquake data in regions straining 10 9 yr 1 comparable to the southeastern united states predictions from this completeness statistic closely mimic the observed m seismic to m godetic ratios and allow quantitative responses to previously unanswerable questions such as what is the likelihood that the seismic moment extracted from an earthquake catalogue of x years falls within y per cent of the true long term rate the combination of historical seismicity fault geology and space geodesy offers a powerful tripartite attack on earthquake hazard few obstacles block similar analyses in any region of the world

slip rate of the kazerun fault and main recent fault zagros iran from 3d mechanical modeling abstract the aim of this work is using gps velocities and 3d mechanical modeling including preexisting faults with frictional properties that obey coulomb failure process to explore the long term slip rates of the mrf fault and kazerun faults in the zagros mountain of iran a model was constructed using spatially varying crustal thickness geothermal gradient and two major faults structural boundaries are derived from the several deep seismic soundings carried out in the area far field gps velocities and late quaternary fault slip rates are used to compare the model results rheological tests show that effective fault friction lower than 0 05 leads to high slip rates that fit with geologically and geodetically determined slip rates of mrf and kazerun fault these results suggest that mrf and kazerun fault are weak faults like san andreas and north anatolian fault

periodic variation of stress field in the koyna warna reservoir triggered seismic zone inferred from focal mechanism studies abstract the koyna warna region in western india is globally recognized as the premier site of reservoir triggered seismicity rts associated with the koyna and warna reservoirs the region is characterized by continuous seismic activity observed since several decades including the world s largest triggered earthquake of m6 3 which occurred in koyna in 1967 while the role of reservoirs in triggering earthquakes has been widely discussed the actual tectonic mechanism controlling earthquake genesis in this region is hardly understood the koyna warna region is exclusively governed by earthquakes of strike slip and normal fault mechanism distinct from the thrust faulting seen in other active zones in the indian region in the present study a comprehensive catalog of 50 focal mechanism solutions of earthquakes that occurred during the last 45 years in the koyna warna region is developed both from previous literature and from moment tensor inversion studies by the authors using broadband data from a local seismic network operating since 2005 the seismicity and fault plane data have enabled precise delineation of trends of the major causative faults which are further accentuated using the double difference technique stress inversion of the focal mechanism data has provided the best fitting principal compressive and tensile stress field of the region which in conjunction with the deciphered fault zones provides a feasible model of seismogenesis in this region based on the observed temporal variation of faulting mechanism a model of alternating cycles of predominantly strike slip and normal faulting is proposed which is attributed to a periodic peaking and relaxation respectively of the horizontal compressive stress field in this region due to the indian plate collision with eurasia

fault interaction and earthquake triggering in the koyna warna region india 1 earthquakes in the koyna warna region of peninsular india are considered to be reservoir triggered however analyses of the available earthquake data indicate that the sustained high seismicity in this region may be influenced also by the geometry of the fault zones and their interactions through stress transfer these distinct fault zones inferred from the earthquake distribution and their focal mechanisms are favourably oriented to each other in such a way that earthquake occurrences in one of the fault zones increase static stress on the other facilitating frequent and continuing occurrence of earthquakes in the region here we show that though the effect of reservoir operations do promote slip on these faults stress triggering appears to be an important cause for continuing high seismicity as it brings some of the stabilized faults closer to failure in the manner consistent with the inferred sense of motion

rupture parameters of the 1999 chamoli earthquake in garhwal himalaya constraints from aftershocks and change in failure stress abstract a positive correlation between areas of increased coulomb stress changes induced by an earthquake and the spatial distribution in the occurrence of aftershocks have been reported in recent years we consider such a correlation between the aftershocks of march 29 1999 chamoli earthquake ms 6 6 that occurred in the garhwal himalaya india and the mainshock induced coulomb stresses to constrain some of the rupture parameters of the mainshock most of the aftershocks occurred above and near the updip edge of the rupture implying reactivation of pre existing thrust fault of the himalayan wedge the 15 12 km2 rupture appears to be lying above the detachment the plate boundary fault between the underthrusting indian shield rocks and the himalayan wedge rocks in the basement thrust front btf zone

active faulting and natural hazards in armenia eastern turkey and northwestern iran active fault zones of armenia se turkey and nw iran present a diverse set of interrelated natural hazards three regional case studies in this cross border zone are examined to show how earthquakes interact with other hazards to increase the risk of natural disaster in northern armenia a combination of several natural and man made phenomena earthquakes landslides and unstable dams with toxic wastes along the pambak sevan sunik fault pssf zone lowers from 0 4 to 0 2 0 3g the maximum permissible level mpl of seismic hazard that may induce disastrous destruction and loss of life in the adjacent vanadzor depression in the ararat depression a large active fault bounded pull apart basin at the junction of borders of armenia turkey iran and azerbaijan an earthquake in 1840 was accompanied by an eruption of ararat volcano lahars landslides floods soil subsidence and liquefaction the case study demonstrates that natural hazards that are secondary with respect to earthquakes may considerably increase the damage and the casualties and increase the risk associated with the seismic impact the north tabriz gailatu fault system poses a high seismic hazard to the border areas of nw iran eastern turkey nakhichevan azerbaijan and southern armenia right lateral strike slip motions along the north tabriz fault have given rise to strong earthquakes which threaten the city of tabriz with its population of 1 2 million the examples illustrate how the concentration of natural hazards in active fault zones increases the risk associated with strong earthquakes in armenia eastern turkey and nw iran this generally occurs across the junctions of international borders hence the transboundary character of active faults requires transboundary cooperation in the study and mitigation of the natural risk

global positioning system measurements of deformations associated with the 1987 superstition hills earthquake evidence for conjugate faulting large station displacements observed from imperial valley global positioning system gps campaigns are attributed to the november 24 1987 superstition hills earthquake sequence thirty sites from a 42 station gps network established in 1986 have been reoccupied during 1988 and or 1990 displacements at three sites within 3 km of the surface rupture approach 0 5 m eight additional stations within 20 km of the seismic zone are displaced at least 10 cm this is the first occurrence of a large earthquake ms 6 6 within a preexisting gps network best fitting uniform slip models of rectangular dislocations in an elastic half space indicate 130 8 cm right lateral displacement along the northwest trending superstition hills fault and 30 10 cm left lateral displacement along the conjugate northeast trending elmore ranch fault the geodetic moments are 9 4 1025 dyn cm and 2 3 1025 dyn cm for the superstition hills and elmore ranch faults respectively consistent with teleseismic source parameters the data also suggest that postseismic slip along the superstition hills fault is concentrated at shallow depths distributed slip solutions using singular value decomposition indicate near uniform displacement along the elmore ranch fault and concentrated slip to the northwest and southeast along the superstition hills fault a significant component of nonseismic secular displacement is observed across the imperial valley which is attributed to interseismic plate boundary deformation

gps measurements of deformation caused by seasonal filling and emptying cycles of four hydroelectric reservoirs in indiagps measurements of deformation caused by seasonal filling and emptying cycles

deciphering oblique shortening of central alborz in iran using geodetic data the alborz is a narrow 100 km and elevated 3000 m mountain belt which accommodates the differential motion between the sanandaj sirjan zone in central iran and the south caspian basin gps measurements of 12 geodetic sites in central alborz between 2000 and 2002 allow to constrain the motion of the belt with respect to western eurasia one site velocity on the caspian shoreline suggests that the south caspian basin moves northwest at a rate of 6 2 mm year with respect to western eurasia north south shortening across the alborz occurs at 5 2 mm year to the south deformation seems to extend beyond the piedmont area probably due to active thrusting on the pishva fault we also observe a left lateral shear of the overall belt at a rate of 4 2 mm year consistent with the geological motion observed along e w active strike slip faults inside the belt e g the mosha fault

holocene slip rate on the gowk strike slip fault and implications for the distribution of tectonic strain in eastern iran we provide the first quantitative estimate of the holocene slip rate on the gowk strike slip fault in eastern iran the main active strand of the fault cuts lakebed sediments within the south golbaf pull apart basin numerous channels incised into the palaeolake surface are displaced right laterally by 30 5 m at the fault radiocarbon dating of two terrestrial wood fragments constrains the lake desiccation at a maximum of 7 9 0 1 cal ka bp from which we estimate a minimum slip rate for the gowk fault of 3 8 0 7 mm yr22121 this estimate indicates that the gowk fault is one of the most important structures in the accommodation of regional tectonic strain in eastern iran the gowk fault has generated five destructive earthquakes in the past 30 yr at a minimum rate of 3 8 0 7 mm yr22121 the average interval between earthquakes assuming that the fault typically fails in events involving 223c3 m of slip will be 6602013960 yr the southern 223c90 km of the gowk fault the sarvestan segment has no record of historical earthquakes and constitutes a considerable remaining hazard in this region our estimated rate is consistent with geodetic measurements of deformation across the same area and hence suggests that the slip rate on the gowk fault has been constant since at least 223c8 ka ago determining whether or not holocene and late quaternary variations in slip rate occur in general across eastern iran requires similar quantitative studies of fault slip rate across the major faults of eastern iran

strike slip kinematics in central and eastern iran estimating fault slip rates averaged over the holocene 1 according to gps measurements the right lateral shear between central iran and afghan blocks amounts to 16 mm yr a model based on very long term estimates of fault rates suggests the current shear originated about 5 ma ago and has been accommodated by strike slip faulting limited to the western 2 mm yr gowk nayband fault and eastern 14 mm yr sistan system fault edges of the lut block we have used high resolution spot5 pixel size 2 5 m images to measure recent cumulative offsets and estimate slip rates over shorter time periods that average several seismic cycles only recent offsets a few tens of meters have been found along the anar fault inside the central iran plateau and along the sistan faults east of the lut the offset morphologies postdate the last incision of the network and are most probably of holocene age 12 2 ka the corresponding slip rates range between 0 5 0 75 mm yr 1 75 2 5 mm yr 1 5 mm yr 1 2 5 mm yr for the anar east neh west neh and asagie fault respectively these estimates suggest the gps shear rate across the lut may not extrapolate over the holocene they also indicate strike slip faulting is not confined to the lut edges but also occurs in central iran suggesting the ongoing strike slip tectonics might have originated between 8 and 22 ma ago earlier than considered previously and consistent with observations in ne iran

present day kinematics of the eastern california shear zone from a geodetically constrained block model we use global positioning system gps data from 1993 2000 to determine horizontal velocities of 65 stations in eastern california and western nevada between 35 and 37 n we relate the geodetic velocities to fault slip rates using a block model that enforces path integral constraints over geologic and geodetic time scales and that includes the effects of elastic strain accumulation on faults locked to a depth of 15 km the velocity of the sierra nevada block with respect to nevada is 11 1 0 3 mm yr with slip partitioned across the death valley 2 8 0 5 mm yr panamint valley 2 5 0 8 mm yr and airport lake owens valley 5 3 0 7 4 6 0 5 mm yr faults the western mojave block rotates at 2 1 0 8 my clockwise with 3 7 0 7 mm yr of left lateral motion across the western garlock fault we infer 11 2 mm yr of right lateral motion across the mojave region of the eastern california shear zone

source parameters of koyna earthquakes india abstract a seismic zone in southwestern india extending 30 km south from koyna dam has witnessed more than 150 earthquakes of m 4 and 10 of m 5 during the last 34 years during august 1993 to december 1994 a spurt of earthquakes occurred in the vicinity of the newly impounded warna reservoir 25 km south of koyna dam the epicenters are located between the two reservoirs but more near the new reservoir during 1994 digital data acquisition systems were deployed by the national geophysical research institute in the vicinity of the koyna warna reservoirs to help in understanding the physical processes responsible for generating earthquakes in the area source parameters were estimated at three stations using s wave spectrum for 193 selected earthquakes of m 1 5 to 4 7 that were recorded during october 1994 to june 1995 seismic moments of 10 11 to 10 16 n m source radii from 94 to 538 m and stress drops of 0 03 to 19 mpa for earthquakes of magnitude 1 5 to 4 7 were obtained from this analysis it is observed that earthquakes of m 3 are associated with larger stress drops of more than 2 mpa the larger energy release through more numbers of m 3 earthquakes and higher stress drop values are found in 0 to 1 km and 5 to 13 km depth ranges depth range of 1 to 4 km has low seismicity and low stress drop earthquakes higher energy release and stress drops are possibly caused by higher stress concentration and incremental stress on rocks with fluids in subhydrostatic conditions in 0 to 1 km depth range and suprahydrostatic conditions in 5 to 13 km depth range spatially the earthquakes of m 3 and high stress drop are now less near koyna reservoir but frequent near the new reservoir

the present day deformation of the central zagros from gps measurements 1 in 1997 and in 2000 we measured the distances between 14 geodetic benchmarks across the central zagros mountain belt the results show that about 10 mm yr of shortening in the central zagros is distributed across the mountain belt this shortening corresponds to roughly 50 of the total convergence between arabia and eurasia and is consistent in direction the persian gulf does not deform significantly the main zagros reverse fault is not an active kinematic boundary the internal deformation of the folded belt is rather homogeneous at the scale of our survey which does not allow us to detect any individual active blind fault however the strain pattern suggests that n s dextral strike slip faults may accommodate part of the deformation

stress triggering of normal aftershocks due to strike slip earthquakes in compressive regime abstract a few cases of occurrence of normal aftershocks after strike slip earthquakes in compressive regime have been reported in the literature occurrence of such aftershocks is intriguing as they occurred despite the apparent stabilizing influence of compressive plate tectonic stresses on the normal faults to investigate the occurrence processes of such earthquakes we calculate change in static stress on optimally oriented normal and reverse faults in the dilational and compressional step over zones respectively due to slip on a vertical strike slip fault under compressive regime we find that change in static stress is much more pronounced on normal faults as compared to that on reverse faults for all values of fault friction change in static stress on reverse fault is marginally positive only when the fault friction is low whereas for normal faults it is positive for all values of fault friction and is maximum for high fault friction we suggest that strike slip faulting in compressive regime creates a localized tensile environment in the dilational step over zone which causes normal faulting in that region the aftershocks on such normal faults are considered to have occurred as an almost instantaneous response of stress transfer due to strike slip motion

low deformation rate in the koyna warna region a reservoir triggered earthquake site in west central stable india abstract we analyse nine years of gps measurements of crustal deformation from the koyna warna region within the stable india plate the koyna warna region experienced a strong earthquake on 10 december 1967 m 6 3 that is considered to have been induced by the impoundment of the koyna reservoir and the continuing earthquake activity in the region is considered to be associated with the koyna and warna reservoirs the earthquakes occur in a very small region of 30 10 km2 in two well defined seismic zones the nne ssw trending koyna seismic zone and the nnw sse trending warna seismic zone these zones are characterised by predominantly left lateral strike slip motion and normal motion respectively in 2003 we initiated campaign mode gps measurements in the region analysis of the gps data collected over nine years indicate low to moderate deformation rate

present day kinematics and fault slip rates in eastern iran derived from 11 years of gps data we analyze new gps data spanning 11 years at 92 stations in eastern iran we use these data to analyze the present day kinematics and the slip rates on most seismogenic faults in eastern iran the east lut west lut kuhbanan anar dehshir and doruneh faults are confirmed as the major faults and are found to currently slip laterally at 5 6 0 6 4 4 0 4 3 6 1 3 2 0 0 7 1 4 0 9 and 1 3 0 8 mm yr respectively slip is right lateral on the ns striking east lut west lut kuhbanan anar and dehshir faults and left lateral on the ew doruneh fault the ns faults slice the eastern iranian crust into five blocks that are moving northward at 6 13 mm yr with respect to the stable afghan crust at the eastern edge of the collision zone the collective behavior of the ns faults might thus allow the arabian promontory to impinge northward into the eurasian crust the ns faults achieve additional ns shortening by rotating counterclockwise in the horizontal plane at current rates up to 0 8 ma modeling the gps and available geological data with a block rotation model suggests that the rotations have been going on at a similar rate 1 0 4 ma over the last 12 ma we identify large strains at the tips of the rotating east lut west lut and kuhbanan faults which we suspect to be responsible for the important historical and instrumental seismicity in those zones

cumulative right lateral fault slip rate across the zagros makran transfer zone role of the minab zendan fault system in accommodating arabia eurasia convergence in southeast iran the zendan minab zone is the transition zone between the zagros collision to the west and makran subduction to the east it is also linked to the north with the nayband gowk fault system that bounds the lut block to the east the total convergence rate between arabia and eurasia is estimated to range between 23 and 35 mm yr 1 in a nne trending direction the deformation through the minab zendan system is accommodated within two fault systems the western n160 e trending minab zendan fault system and the eastern north south sabzevaran jiroft fault system the study area is characterized by a well defined succession of quaternary deposit levels the age of these deposits was estimated by archaeological data regional palaeoclimate correlations and constrained by additional in situ10be dating in another paper in this study these deposits exhibit offsets both lateral and vertical that are evaluated by satellite image analysis and gps profiles thanks to offsets and ages the strike slip rates associated with the minab zendan and the sabzevaran jiroft fault systems are calculated to be 5 1 1 3 or 6 6 1 5 and 6 2 0 7 mm yr 1 respectively these results allow an evaluation of the velocity vector of the musandam peninsula oman with respect to the lut block of 11 4 2 0 or 12 9 2 2 mm yr 1 in a n10 15 e direction close to the gps estimates this study also constrains the in plane slip rates for each fault previous works indicate that the zagros accommodates only 10 mm yr 1 of shortening while 10 mm yr 1 should be accommodated by the alborz mountains in northern iran this last 10 mm yr 1 may be accommodated through the nayband gowk system and the east iranian ranges implying that the two fault systems constituting the zagros makran transfer zone have different geodynamic roles the western minab zendan fault system links the makran and zagros deforming zones whereas the northwestern jiroft sabzevaran fault system is transmitting the deformation to the nayband gowk system and then to the alborz ranges the presence of another such strike slip zone within the makran seems to indicate that the accommodation zone between the zagros and makran is wide of the order of 400 km we interpret this deformation pattern that accompanies the genesis of the immature transform zone by a flexure of the slab under the zagros makran transfer zone instead of a tear in the slab that may be expected to induce a sharper transition zone

the emergence of seismic cycles from stress feedback between intra plate faulting and far field tectonic loading abstract using numerical modeling we show the emergence of cyclic slip behavior of faults from stress feedback through an idealized fault its surrounding plates and far field tectonic stress the tectonic stress is exerted on the fault through a force applied along an idealized plate margin acting on the fault resulting from the interactions of viscous embedding and external plates we find that in such coupled system the interaction of plates results into feedback with periodic deformation slip along the fault and episodic plate margin motions the viscosity of the embedding and loading plates primarily control the stress loading time and hence the slip recurrence interval for an earth like range of lithospheric viscosities we derive a power law with negative exponent 0 99 to 0 5 scaling the recurrence period with loading rate providing an explanation for the observables from paleoseismology and geodesy the feedback between single fault and far field stress that arises from interactions of deforming plates provides a context to understand the earthquake cycle within continents while reconciling the short term seismic deformation to the long term plate tectonics frame

hydrogeochemistry of the koyna river basin india hydrogeochemistry of the koyna river basin famous for the koyna earthquake magnitude 7 of 1967 has been studied basalt is the primary aquifer laterites alluvium and talus deposits form aquifers of secondary importance groundwater generally occurs under water table conditions in shallow aquifers deeper aquifers are associated only with basalts one hundred and 87 water samples were collected from various sources such as dugwells borewells springs and surface water including 40 samples for analysis of iron only major constituents were analyzed analyses show that the concentrations of ca2 exceed that of mg2 in almost all water samples the concentrations of na are generally next to ca2 and are always higher than that of k and co32 and so42 are very low and are often negligible groundwater in borewells tapping deeper aquifers has higher mineralization compared to that in dugwells representing shallow aquifers majority of the water samples are dominated by alkaline earths ca2 mg2 and weak acids hco3 co32 groundwater from shallow aquifers is generally calcium bicarbonate type 53 and calcium magnesium bicarbonate type 27 in case of deeper aquifer it is mostly calcium magnesium bicarbonate type 29 sodium bicarbonate type 24 calcium bicarbonate type 19 calcium magnesium sodium bicarbonate type 19 and sodium calcium bicarbonate type 9 groundwater water is generally fit for drinking and irrigation purposes except in the lower reaches of the koyna river basin which is affected by near water logging conditions

crustal stress map of iran insight from seismic and geodetic computations we used the focal mechanisms of crustal earthquakes depth 40 km in the period 1909 2012 and the available gps velocities derived from the data collected between 1999 to 2011 to estimate the magnitude and directions of maximum principal stress and strain rates in iran the pearson product moment correlation was used to find the correlation between the stress field obtained from the focal mechanism stress inversion and that obtained using the seismic and geodetic strain rates our assumption is that stresses in a continuum are produced by tectonic forces and the consequent deformation on the crustal scale therefore the direction of the stress and strain or strain rate are ideally to be the same our results show a strong correlation between the directions of the principal components of stress and strain rate obtained using the different data methods using weighted average analysis we present a new stress map for iran

long term fault slip rates distributed deformation rates and forecast of seismicity in the iranian plateau in this paper the long term crustal flow of the iranian plateau is computed using a kinematic finite element model neokinema software based on the iterated weighted least squares method the models are fitted to the newest data set of iran including updated fault traces geologic fault offset rates geodetic benchmark velocities principal stress directions and velocity boundary conditions we are successful to find the best kinematic model in which geological slip rates geodetic velocities and interpolated stress directions are fitted at levels of 0 35 1 0 and 1 0 datum standard deviation respectively the best fitted model for the first time provides long term fault slip rates velocity and anelastic strain rate field in the iranian plateau from all available kinematic data in order to verify the model the estimates of fault slip rates are compared to slip rates from merely analyzing geodetic benchmark velocities or paleoseismological studies or published geological rates which have not been used in the model our estimated rates are all in the range of geodetic rates and are even more consistent with geological rates than previous gps based estimates using the selected model long term average seismicity maps and long term moment rates are produced on the basis of the shift hypothesis and previous global calibrations our kinematic model also provides a new constraint on ratio of seismic deformation to total deformation for different seismic zones of iran the resulting slip rates and the proposed seismic fraction of deformation provide the necessary input data for future time dependent hazard studies in iran moreover spatial distribution and total number of strong m 6 and major m 7 earthquakes which dominate the seismic hazard are all compatible with the regional seismic catalog

oroclinal bending distributed thrust and strike slip faulting and the accommodation of arabia eurasia convergence in ne iran since the oligocene regional shortening is accommodated across ne iran in response to the collision of arabia with eurasia we examine how n s shortening is achieved on major thrust systems bounding the eastern branch of the alborz east of 57 e sabzevar and kuh e sorkh mountain ranges which lie south of the kopeh dagh mountains in ne iran although these ranges have experienced relatively few large earthquakes over the last 50 yr they have been subject to a number of devastating historical events at neyshabur esfarayen and sabzevar a significant change in the tectonics of the eastern alborz occurs directly south of the central kopeh dagh near 57 e to the east shortening occurs on major thrust faults which bound the southern margin of the range resulting in significant crustal thickening and forming peaks up to 3000 m high active shortening dies out eastward into afghanistan which is thought to belong to stable eurasia the rate of shortening across thrust faults bounding the south side of the eastern alborz north of neyshabur is determined using optically stimulated luminescence dating of displaced river deposits and is likely to be 0 4 1 7 mm yr 1 shortening across the sabzevar range 150 km west of neyshabur has previously been determined at 0 4 0 6 mm yr 1 although reassessment of the rate here suggests it may be as high as 1 mm yr 1 migration of thrust faulting into foreland basins is common across ne iran especially in the esfarayen region near 57 e where the northward deflection of the east alborz range reaches a maximum of 200 20 km from its presumed linear e w strike at the beginning of the oligocene west of 57 e the tectonics of the alborz are affected by the westward motion of the south caspian region which results in the partitioning of shortening onto separate thrust and left lateral strike slip faults north and south of the range at the longitude of 59 e published gps velocities indicate that 50 per cent of the overall shortening across ne iran is accommodated in the kopeh dagh the remaining 50 per cent regional shortening must therefore be accommodated south of the kopeh dagh in the eastern alborz and kuh e sorkh ranges assuming present day rates of slip and the fault kinematics are representative of the late cenozoic deformation in ne iran the total 200 20 km n s shortening across the eastern alborz and kopeh dagh mountains since the beginning of uplift of the kopeh dagh basin would be accommodated in 30 8 ma although this extrapolation may be inappropriate over such a long timescale the age is nevertheless consistent with geological estimates of post early to middle oligocene 30 ma for the onset of kopeh dagh uplift

active tectonics and late cenozoic strain distribution in central and eastern iran 1 right lateral shear between central iran and afghanistan is accommodated on n s right lateral strike slip faults surrounding the aseismic dasht e lut north of 34 n the right lateral shear is accommodated on left lateral faults that rotate clockwise about vertical axes little is known of the late tertiary and younger offsets and slip rates on the active fault systems results that are important for understanding the regional tectonics we use observations from satellite imagery to identify displaced geological and geomorphological markers which we use in conjunction with the overall morphology and orientation of the active fault systems to estimate the total cumulative right lateral shear estimates of cumulative fault movements from offset features and inferred vertical axis rotation of fault bounded blocks suggest that the late cenozoic strain is concentrated toward the eastern margin of iran along the sistan shear zone where bedrock offsets of at least 70 km are observed across the active faults the geomorphology of the deh shir anar and great kavir strike slip faults in central iran suggest that although little shortening is accommodated across this region they might still be active and hence capable of producing earthquakes present day activity on these faults in central iran would not be expected from distributions of instrumental and historical earthquakes although speculative the late tertiary strain distribution described in this paper is consistent with what we know of the present day rates of shear in eastern iran and provides a framework to which later more detailed work can be added

extension in nw iran driven by the motion of the south caspian basin contrasted tectonic styles occur in northern iran west of kopet dagh the south caspian basin is an aseismic and possibly rigid blockinvolved inthecollisionzonebetweeneurasiaandarabia tothenw largescalevelocityfield ofirangivenbyrecentrepeated gps surveys suggests 8 mm yr of right lateral displacement for the wnw ese faults in the tabriz region more surprisingly geodetic motion also suggests a prominent n 30 extension north to the tabriz fault where compression would be expected in order to quantify more precisely the right lateral movement of the tabriz region the extension of nw iran and the motion of the south caspian basin we deployed a dense gps network in nw iran from central iran to the turkish armenian and azerbaijan borders three repeated surveys from 2002 to 2004 assess that the tabriz fault concentrates entirely the 8 mm yr of right lateral movement observed in nw iran this rate is in good agreement with a recurrence interval time of 250 300 yr proposed from historical seismicity studies we found also two zones of extension one just north of the tabriz fault in the south of the talesh plateau and another close from the azerbaijan border north of the talesh plateau we suggest that the existence of a northward subduction of the south caspian basin could explain such an extension in the core of the arabia eurasia collision increasing evidences of quaternary extensional tectonics in the region from armenia to alborz may lead to significantly alter our understanding of the northern iran tectonics and challenge the traditional arabian indenter plate tectonics

tectonic stress field in the indian subcontinent a map of maximum horizontal compressive stress orientation in the indian subcontinent has been prepared using orientations derived from three different stress indicators borehole elongation breakouts in situ hydraulic fracturing measurements and earthquake focal mechanisms most part of the subcontinent appears to be characterized by a compressional stress regime thrust and strikeslip faulting imposed by plate boundary forces although shmax orientations do not in general show clear correlation with the direction of motion of the indian plate four provinces are recognized on the basis of regionally consistent orientations these are the midcontinent stress province the southern shield the bengal basin and the assam wedge their boundaries have been determined taking into consideration regional tectonics and seismicity central and northern india including the shillong plateau stretching up to the great himalaya pakistan and nepal are included in a broad midcontinent stress province characterized by nne ene oriented shmax the mean orientation of shmax in this province is n23 e subparallel to the direction of compression expected to arise from the net resistive forces at the himalayan collision zone suggesting that it is largely determined by the tectonic collision processes much of southern india mysore plateau and the high grade metamorphic terrain south of the plateau appears to be part of a second stress province characterized by nw oriented shmax these appear close to those of the intraplate stress field prevailing in the central indian ocean a third stress province was recognized in the bengal basin including parts of west bengal tripura manipur and mizoram in northeastern india and most of bangladesh this province extends eastward from the marginal fault in the western margin of the bengal basin to the indo burma subduction zone and is bounded on the north by the e w striking dauki fault shmax within the sedimentary pile of the bengal basin is oriented in e w direction while p axes of earthquakes within the basement and the crust beneath the basin and within the subducted slab of the indian plate beneath the indo burman ranges generally trend north n30 e shmax orientations within the sedimentary pile of the basin are parallel to the local approximately e w direction of the convergence of indian and burmese plates suggesting a casual relation to the resistive forces at the subduction zone in the indo burma region interestingly the stress field in the basement and the crust beneath the bengal basin and in the subducted slab is similar to the one prevailing in the midcontinent stress province assam wedge stress region occupies the northeastern corner of the indian plate including upper assam arunachal pradesh and much of nagaland this region subducts beneath a sharply bent continental collision boundary consisting of the northeastern limb of the himalayan and northern limb of the indo burman fold belts as a result the stress field in this province is depth differentiated and most likely responsible for the absence of consistent shmax directions

location of the pilot borehole for investigations of reservoir triggered seismicity at koyna india abstract artificial water reservoir triggered earthquakes are now known to have occurred at over 120 sites globally the part played by the reservoirs in triggering is not exactly known due to lack of near field observations of triggered earthquakes koyna located near the west coast of india where triggered earthquakes have been occurring since 1962 provides an excellent site for near field observations of the target m 2 earthquakes a 6 borehole seismic network has been deployed recently in the koyna region at depths of 981 1522 m to improve the hypocenter locations during may december 2015 a total of 1039 earthquakes of m l 0 5 were located using the borehole seismic network the region is also monitored through a dense network of 23 surface broad band stations our analysis indicates a significant improvement in the estimation of absolute locations of earthquakes with errors of the order of 300 m combining both the networks based on seismicity and logistics a block of 2 2 km 2 area has been chosen for drilling the first pilot borehole of 3 km depth where m 2 earthquakes have been occurring frequently since 2005

tectonic and non tectonic crustal deformation in kumaun garhwal himalaya abstract a detailed characterization of the crustal deformation in the himalaya is important to understand the tectonic and non tectonic deformation processes responsible for the strain build up and transients in deformation in the present work we have characterised the present day tectonic and non tectonic deformations in the kumaun garhwal himalaya estimated from the continuous gps measurements we observed strong seasonal variations in the horizontal and vertical displacement components i e north east and vertical the transient surface deformation estimated from global hydrological models is found to explain 40 60 of the observed seasonal variations at sites plate convergence rate and variation of slip deficit on the main himalayan thrust mht are calculated using site velocity estimated after removal of seasonal variations from the gps time series we report an excessive compression with an average principal shortening rate of 0 09 strain yr in the north northeast direction the derived plate convergence rate is 18 1 mm yr and the width of locked frontal part of mht is 100 15 km the quiescence of major to great earthquakes in the region since at least past 200 years and high rate of strain build up make this region vulnerable for a potentially devastating earthquake of mw 8 in near future

devonian orogen parallel opposed extension in the central norwegian caledonides comment and reply braathen et al 2000 1 described early to middle devonian extensional faults around the central norway basement window one of many tectonic windows exposing basement in the scandinavian caledonides here these basement rocks are called tectonic window basement extension was orogen parallel

holocene historical volcanism and active faults as natural risk factors for armenia and adjacent countries abstract examples of holocene historical volcanism in the territory of armenia and adjacent areas of eastern anatolia and western iran are discussed holocene historical activity is proved for the volcanoes of tskhouk karckar porak vaiyots sar smbatassar and ararat based on the analysis of remote sensing data field work and historical and archeological information it is demonstrated that there was a considerable number of cases of volcanic activity in armenia and adjacent regions of turkey syria and iran during the historical period the holocene volcanic centers are situated within pull apart basin structures and controlled by active faults situated in an area prone to many types of natural hazards armenia and adjacent countries face high natural risk the evidence presented shows that volcanic hazard also contributes to the natural risk for these countries

waveform inversion of broad band data of local earthquakes in the koyna warna region western india summary the koyna warna region in western india is the best example of reservoir triggered seismicity the world s largest triggered earthquake of magnitude 6 3 occurred in koyna in 1967 followed by several moderate to small earthquakes ever since a digital seismograph network deployed for seismic monitoring during 2005 august to 2008 december has indicated a shift in concentration of seismicity towards south in the warna region including a new zone of seismic activity to the southwest during the observation period 13 earthquakes of magnitude 4 and greater have occurred of which 11 occurred near the warna region while only two occurred in koyna in this study we modelled broad band waveform data of six of these earthquakes near warna using waveform inversion approach initially a new velocity model was determined using a joint hypocentral determination approach that simultaneously solves for the velocity structure as well as the hypocentral parameters a trap thickness of 1 2km with a p wave velocity of 4 40kms 1 and an upper crustal layer down to 10km with a velocity of 5 96kms 1 are obtained the new model not only provides the minimum residual error for the traveltimes but consistently provides the least mismatch error in the waveform inversion of all the events performing better than any of the previously determined velocity models in general focal mechanisms of normal type with ns to nnw sse oriented fault planes are obtained for all these events that are correlated with probable faults inferred from satellite images and aeromagnetic anomalies focal depths in the range of 5 6km are obtained for earthquakes in the warna region based on the sensitivity of whole waveform inversion at local distances it is felt that joint inversion of waveform data of several earthquakes with a wider spatial distribution along with the velocity structure would help in precisely characterizing the faulting mechanism and seismogenic depth range for the koyna warna region in future

contribution of archaeological data to studies of earthquake history in the iranian plateau we use archaeological evidence to identify ancient earthquakes in the vicinity of large 20th century events in the iranian plateau two large earthquakes on the zagros main recent fault were preceded by historical earthquakes in ad 1008 and ad 1107 and by earthquakes in the intervals ad 224 459 and 1650 1600 bc giving return times of 1800 2100 500 800 and 850 950 years the ad 1962 ms 7 2 bo in zahra earthquake on the ipak fault in north central iran was preceded by an earthquake in 2000 1500 bc recorded at the sagzabad mound a return time of 3500 4000 years if there are no missing events the ad 1990 ms 7 3 rudbar tarom earthquake in the western alborz mountains was preceded by an earthquake in 1000 800 bc recorded at the marlik mound a return time of 2800 3000 years the ad 1948 ms 7 2 kopeh dagh earthquake that destroyed ashkabad capital of turkmenistan was preceded by an earthquake in 10 bc ad 10 recorded at mithradatkert nesa mound and by an earthquake in 2000 bc recorded at ak tapeh mound assuming no missing earthquakes this region has an earthquake return time of about 2000 years in khorasan province which was struck by a sequence of large earthquakes from ad 1936 to 1997 a mosque at qa en was destroyed in the mid 11th century ad probably the historical earthquake of ad1066 in the absence of palaeoseismic investigations archaeology offers the promise of recording earthquakes through more than one seismic cycle in different regions of iran q 2001 elsevier science ltd all rights reserved

constraints on arabian plate motion and extensional history of the red sea analysis of the geologic and geophysical data from the western and northern margin of the arabian plate combined with data from the red sea gulf of aden leads to an interpretation of arabian plate motion that supports an episodic extensional history in the red sea and gulf of aden phase 1 extension began in medial to late eocene and was caused by the nw propagation of the reoriented central indian ridge spreading center it stretched and thinned continental crust along numerous wrench and normal faults that reactivated preexisting structures first phase extension stopped when the arabian plate terminally sutured to eurasia in the medial miocene and halted northward movement of arabia relative to africa the combined african arabian plates moved north more slowly constricting and thickening continental crust in the bitlis zagros sutures while the red sea remained technically quiescent and accumulated salt by the early pliocene continued northward movement was accommodated by lateral extrusion of large continental wedges north of the bitlis zagros sutures this allowed arabia to move northward faster than africa and reopen the red sea where phase 2 extension was expressed by seafloor spreading extension within the red sea gulf of aden rift system has been controlled by the interactions and effects of two factors 1 convergent processes between the north margin of the arabian plate and the eurasian plate to the north and 2 northwest propagation of extension associated with the medial eocene reorganization of the central indian spreading center

long term fault slip rates distributed deformation rates and forecast of seismicity in the western united states from joint fitting of community geologic geodetic and stress direction data sets 1 the long term average velocity field of the western united states is computed with a kinematic finite element code community data sets include fault traces geologic offset rates geodetic velocities principal stress directions and euler poles there is an irreducible minimum amount of distributed permanent deformation which accommodates one third of pacific north america relative motion in california much of this may be due to slip on faults not included in the model all data sets are fit at a common rms level of 1 8 datum standard deviations experiments with alternate weights fault sets and euler poles define a suite of acceptable community models in pseudoprospective tests fault offset rates are compared to 126 additional published rates not used in the computation 44 are consistent another 48 have discrepancies under 1 mm a 1 and 8 have larger discrepancies updated models are then computed novel predictions include dextral slip at 2 3 mm a 1 in the brothers fault zone two alternative solutions for the mendocino triple junction slower slip on some trains of the san andreas fault than in recent hazard models and clockwise rotation of some domains in the eastern california shear zone long term seismicity is computed by assigning each fault and finite element the seismicity parameters coupled thickness corner magnitude and spectral slope of the most comparable type of plate boundary this long term seismicity forecast is retrospectively compared to instrumental seismicity the western united states has been 37 below its long term average seismicity during 1977 2008 primarily because of temporary reduced activity in the cascadia subduction zone and san andreas fault system

rapid strain accumulation on the ashkabad fault turkmenistan from atmosphere corrected insar 1 we have measured interseismic deformation across the ashkabad strike slip fault using 13 envisat interferograms covering a total effective timespan of 30 years atmospheric contributions to phase delay are significant and variable due to the close proximity of the caspian sea in order to retrieve the pattern of strain accumulation we show it is necessary to use data from envisat s medium resolution imaging spectrometer meris instrument as well as numerical weather model outputs from the european centre for medium range weather forecasts ecmwf to correct interferograms for differences in water vapor and atmospheric pressure respectively this has enabled us to robustly estimate the slip rate and locking depth for the ashkabad fault using a simple elastic dislocation model our data are consistent with a slip rate of 5 12 mm yr below a locking depth of 5 5 17 km for the ashkabad fault and synthetic tests support the magnitude of the uncertainties on these estimates our estimate of slip rate is 1 25 6 times higher than some previous geodetic estimates with implications for both seismic hazard and regional tectonics in particular supporting fast relative motion between the south caspian block and eurasia this result reinforces the importance of correcting for atmospheric contributions to interferometric phase for small strain measurements we also attempt to validate a recent method for atmospheric correction based on ecmwf era interim model outputs alone and find that this technique does not work satisfactorily for this region when compared to the independent meris estimates

exploratory models of long term crustal flow and resulting seismicity across the alpine aegean orogen 1 long term crustal flow is computed with a kinematic finite element model based on iterated weighted least squares fits to data and prior constraints data include 773 fault traces 106 fault offset rates 510 geodetic velocities 2566 principal stress azimuths and velocity boundary conditions representing the rigid parts of the eurasia africa and anatolia plates model predictions include long term velocities fault slip rates and distributed permanent strain rates between faults one model assumes that geodetic velocities measured adjacent to the aegean trench reflect a temporarily locked subduction zone in this case long term subduction velocity averages 45 mm yr and rapid crustal extension is predicted in the southern aegean sea another model assumes steady creeping subduction in this case subduction velocity averages only 29 mm yr and the eastern aegean seafloor is predicted to be more nearly rigid long term seismicity maps are computed for each model on the basis of the shift hypotheses and previous global calibrations of plate boundary earthquake production retrospective comparisons to seismic catalogs are encouraging map patterns spatial distribution functions and total earthquake counts are all comparable while neither model accurately predicts earthquake rates at all magnitudes the creeping subduction model is more accurate for strong m6 events which dominate the seismic hazard

accommodation of late cenozoic oblique shortening in the alborz range northern iran abstract the alborz range northern iran deforms by strain partitioning of oblique shortening onto range parallel left lateral strike slip and thrust faults deformation is due to the north south arabia eurasia convergence and westward motion of the adjacent south caspian relative to iran roughly north south shortening occurs on thrusts that dip inwards from the range margins precambrian basement is not exposed because of detachment along upper proterozoic evaporites and the thickness of overlying strata 10 km other detachments occur within phanerozoic sediments active left lateral strike slip faults trend ene in the east of the range wnw in the west the eastern mosha fault has a left lateral offset of 30 35 km shortening across the range is 30 km 25 30 at the longitude of tehran this is hard to reconcile with the crustal thickness of 35 km which is similar to adjacent basins percentage shortening across the alborz is similar to the adjacent kopet dagh but because the latter is twice as wide finite shortening is roughly half the difference may be accommodated by subduction of the adjacent south caspian basin northwards under the middle caspian south caspian sediments began folding in the pliocene the present kinematics of the alborz may have begun at this time including a reversal from range parallel right lateral to left lateral strike slip faulting but the regional stratigraphy indicates uplift as early as the mid tertiary

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

morphotectonic and geodetic evidence for a constant slip rate over the last 45 kyr along the tabriz fault iran iran is an active continental domain accommodating the convergence between the arabia and eurasia plates in northwestern iran deformation between the central iranian block and the caucasus domain is mainly accommodated by right lateral strike slip on the tabriz fault cities and villages including the city of tabriz have been destroyed by several strong historical earthquakes m similar to 7 in this study we compare the slip rates estimated from geodetic measurements radar interferometry and ups with those determined by dating a geomorphological offset of an alluvial fan along the tabriz fault the gps measurements along two profiles normal to the tabriz fault suggest a slip rate of 7 3 1 3 mm yr 1 the persistent scatterer radar interferometry analysis of envisat satellite archives from 2003 to 2010 shows a velocity gradient 6 3 mm yr 1 across the tabriz fault in agreement with gps results moreover it reveals that most of the area located south of the tabriz fault is affected by subsidence and that some sections of the fault probably act as barriers to fluid migration which may have an impact on its mechanical behaviour west of tabriz morphotectonic investigations on an alluvial fan surface show a right lateral cumulative offset of 320 40 m luminescence analyses of the coarse matrix alluvial fan deposits provide an age of 46 3 ka this yields a slip rate comprised between 6 5 and 7 3 mm yr 1 along this segment these results suggest that the late quaternary slip rate is in agreement with the present day slip rate estimated by geodetic measurements showing no slip rate changes during the past 45 000 yr short term variations within the 45 000 yr related to temporal earthquake clustering over few seismic cycles cannot be ruled out but if they exist they do not affect the geodetic and the geomorphological estimates this study is in agreement with previous ones suggesting that long term slip rates i e averaged over several tens of seismic cycles are consistent with geodetic estimated slip rates i e extrapolated from few years of interseismic observations and suggests that perturbations of fault slip rates are related to variations over few seismic cycles

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

seismogenesis and earthquake triggering during the van turkey 2011 seismic sequence article i nfo article history a unique and very interesting earthquake of magnitude mw 7 2 occurred in the van region of turkey on october 23 2011 that caused a heavy loss of human lives and properties the earthquake occurred on a blind oblique thrust fault oriented towards the ne sw direction and dipping towards nw as evidenced by focal mechanism solution and aftershock distribution in this study we analyzed the seismogenesis and earthquake triggering during this sequence with the help of estimated seismological parameters b value of frequency magnitude relation p value of aftershocks temporal decay and d value of fractal dimension 2d mapping of b and p values 3d mapping of b value and coseismic coulomb stress modeling the estimat ed seismic b value equal to 0 89 reveals that the mainshock occurred in a highly stressed region and sequence comprised larger magnitude aftershocks due to the presence of large size asperities within the rupture zone the normal estimate of p value 0 98 suggests a tectonic genesis of the aftershocks sequence the estimated d value equal to 1 80 reveals that rupture propagated in a two dimensional plane filled up by fractures the spatial 2d and 3d mapping of seismic b value suggests that the van earthquake originated in a highly hetero geneous fractured rock matrix with fluid intrusions into it at deeper depth beneath the mainshock hypocen ter region the estimated coseismic coulomb stress using the variable slip model for depth range 0 30 km exhibits a butterfly pattern and most of the aftershocks fall 90 in the region of enhanced coulomb stress this suggests that most of the aftershock activities have been triggered by transfer of positive coulomb stress due to coseismic slip of the mainshock the results estimated in the present study have potential useful im

modeling of the koyna india aftershock of 12 december 1967 short period teleseismic and near regional long period waveforms from a large aftershock mb 5 3 origin time 06 18 36 8 utc of the 10 december 1967 koyna main event were modeled to determine source depth and focal mechanism identification of pp and sp on the short period waveforms yielded a well constrained source depth of 3 5 to 4 0 km the focal mechanism was determined using a systematic trial and error grid testing technique in which seven p first motions two sh first motions two teleseismic pp p ratios one teleseismic sp p ratio and one regional sh p ratio were included this heterogeneous but sparse data set yielded a constrained normal fault mechanism at 100 20 strike 40 10 dip and 240 20 rake rupture directivity is inferred from consistently high surface reflection direct wave amplitude ratios a circular fault of 1 km radius with a rupture initiation point at the lower edge and an assumed rupture velocity of 0 9 vs explains the anomalously high amplitude ratios and yields a seismic moment of 3 8 1023 dyne cm the shallow source depth is similar to that found for the main event 4 5 km and the 13 september foreshocks 5 km in previous modeling studies and is consistent with the premise that the koyna earthquakes were triggered by the impoundment of the koyna reservoir however the normal fault mechanism differs substantially from the previous events which were left lateral strike slip faults trending nne the differing aftershock mechanism is probably due to the reactivation of old faults in the koyna area caused by stress readjustment after the koyna main event

late cenozoic reorganization of the arabia eurasia collision and the comparison of short term and long term deformation rates the arabia eurasia collision deforms an area of 3 000 000 km2 of continental crust making it one of the largest regions of convergent deformation on earth there are now estimates for the active slip rates total convergence and timing of collision related deformation of regions from western turkey to eastern iran this paper shows that extrapolating the present day slip rates of many active fault systems for 3 7 million years accounts for their total displacement this result means that the present kinematics of the arabia eurasia collision are unlikely be the same as at its start which was probably in the early miocene 16 23 ma or earlier in some but not all active fault systems short term 10 year and long term 5 million year average deformation rates are consistent there is little active thickening across the turkish iranian plateau and possibly the interior of the greater caucasus these are two areas where present shortening rates would need more than 7 million years to account for the total crustal thickening and where there are structural and or stratigraphic data for pre late miocene deformation we suggest that once thick crust up to 60 km built up in the turkish iranian plateau and the greater caucasus convergence took place more easily by crustal shortening in less elevated regions such as the zagros simple folded zone the south caspian region and foothills of the greater caucasus or in other ways such as westward transport of turkey between the north and east anatolian faults the time and duration of this changeover are not known for certain and are likely be diachronous although deformation started or intensified in many of the currently active fault systems at 5 2 ma

probabilistic seismic hazard estimation for peninsular india peninsular india 10 0 n 28 0 n 68 0 e 90 0 e is one of the oldest and seismically most stable landmasses of the indian plate recent seismic history however shows that more than five damaging earthquakes with magnitudes greater than mw 6 0 have occurred in this region highlighting the importance of seismic hazard assessment for the region this article estimates the probabilistic seismic hazard associated with peninsular india with a zoneless approach incorporating the observed seismic activity and known geological characteristics of the region the seismicity parameters for hazard assessment have been estimated incorporating com pleteness criteria for various spans of the catalog data the spatial and temporal variations of seismic activity have been modeled using different source models seis mic source zones for the region have been defined on the basis of large scale geo logical features which are used for assigning the maximum possible earthquake potential due to the poorly known attenuation characteristics of the study region three appropriate attenuation models have been used for the estimation of ground motion parameters hazard maps for peninsular india have been developed using a convolution scheme based on weighting and incorporating various uncertainties in volved while modeling different parameters the comparison of the probabilistic seismic hazard map developed herein with the hazard map specified in the indian standards shows that the design parameters in the indian standards may significantly underestimate the seismic hazard in some regions of peninsular india

active tectonics of the east alborz mountains ne iran rupture of the left lateral astaneh fault system during the great 856 a d qumis earthquake the 856 a d qumis earthquake m7 9 is the most destructive earthquake to have occurred in iran killing more than 200 000 people and destroying the cities of damghan and the old parthian capital of shahr i qumis hecatompylos this study combines evidence of historical seismicity with observations of the geomorphology and paleoseismology to provide the first detailed description of active faulting in the damghan region of the east alborz mountains iran regional left lateral shear is accommodated on the astaneh damghan and north damghan faults quaternary alluvial fans have been displaced along the astaneh fault with 15 20 m stream offsets recording the cumulative displacement over the last two to five earthquakes a paleoseismology study from a single trench along a 5 10 km segment of the astaneh fault reveals a rupture prior to 1300 a d and significantly later than 600 b c despite the limitations of a single trench in documenting the spatial and temporal evolution of the fault over the late quaternary we are nevertheless able to bracket the last event to a time period consistent with the 856 a d earthquake two older earthquakes were also identified during the holocene occurring between 600 b c and 4600 b c and between 4600 b c and 9600 b c the location of our trench within a bend on the astaneh fault which could act as a barrier to rupture propagation means the three earthquakes recovered from our trench over the holocene may represent a minimum further trenching will reveal how the astaneh fault ruptures over repeated earthquakes and consequently the magnitude and extent of slip during the 856 a d earthquake

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

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

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

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

seismogenic structure in the source zone of the 1918 m7 5 nanao earthquake in the northern south china sea abstract as a typical rifted margin the coastal region of the northern south china sea has experienced many large crustal earthquakes in the past 400 years for example two destructive earthquakes with m7 0 in 1600 and m7 5 in 1918 occurred close to the nanao island however the mechanism of these earthquakes and seismotectonics of the region are still unclear in this work we make the first study of the detailed three dimensional crustal structure in the source zone of the 1918 nanao earthquake m7 5 using newly acquired wide angle seismic reflection data our results show that current seismicity mostly occurred in a midcrustal low velocity zone or its nearby high to low velocity transitional areas we ascertain locations of the ene strike littoral fault zone and the nw strike huanggangshui fault based on the seismic reflection profiles these faults have caused a large scale vertical dislocation of the sedimentary basement the structure of the upper crust is very heterogeneous containing many high or low velocity anomalies however the lower crustal structure is less heterogeneous mainly characterized by low velocity mostly in the northern part of the study area and high velocity mainly in the southern part the crust in the seismicity zone shows strong heterogeneity reflecting highly cracked structural features possibly caused by destructive earthquakes we infer that the midcrustal low velocity zone and the intersection between the littoral fault zone and the huanggangshui fault could reflect weak structures in the crust and form a local stress buildup which strongly affected or controlled the generation of intraplate seismicity the 1918 nanao earthquake very likely occurred within the current seismicity zone with a depth range of 15 25 km estimated from our tomographic images and previous geological and geophysical results

the binalud mountains a key piece for the geodynamic puzzle of ne iran 1 we applied a combined approach of morphotectonic analyzes of spot 5 satellite images and field surveys complemented by in situ produced10be exposure dating to determine the kinematics and rate of active faulting in the binalud mountains bounded by the neyshabur fault system to the southwest and the mashhad fault zone to the northeast three regional episodes of alluvial surface abandonment were dated at 4 8 ka q1 105 ka q3 and 255 ka s3 along the neyshabur fault system cumulative offsets recorded by q3fan surfaces yield slip rates of 2 4 0 5 and 2 8 0 6 mm yr for right lateral and reverse components of active faulting corresponding to an oblique slip rate of 3 6 1 0 mm yr respectively reconstructing the cumulative right lateral offset recorded by s3surfaces a maximum slip rate of 1 3 0 1 mm yr is suggested for the mashhad fault zone these imply an overall rate of 3 7 0 6 mm yr for the range parallel displacement and an uplift rate of 2 8 mm yr due to the range normal shortening 1 6 2 2 mm yr during late quaternary the binalud mountains are deformed as a soft linked restraining relay zone taking up the motion between central iran and eurasia at a rate of 4 0 1 3 mm yr this translates central iran in the n340 e direction our data favor localized faulting instead of distributed deformation at the northeastern boundary of the arabia eurasia collision zone

palaeoseismic evidence for a medieval earthquake and preliminary estimate of late pleistocene slip rate on the firouzkuh strike slip fault in the central alborz region of iran the 55 km long firouzkuh fault is located in the central alborz mountains of iran it is a left lateral fault which dips to the south and possesses a small dip slip component of motion that we interpret to result from extension the ratio of horizontal to vertical displacement across the fault calculated from the cumulative displacement of landscape features is 7 6 we provide constraints on the timing of the last earthquake on the firouzkuh fault from two trenches t1 and t2 across the fault zone excavated in 2004 and located east of firouzkuh city the trenches expose faulted sedimentary deposits two optically stimulated luminescence osl ages from sediments in the lower part of trench t1 date from the late pleistocene 15 9 0 9 ka and 27 1 1 7 ka the younger of the two dated units in t1 is displaced vertically across the fault by 2 2 4 4 m from which we estimate a strike slip displacement of 18 2 33 4 m and hence a average horizontal slip rate of 1 1 2 2 mm yr the sediments exposed in t1 do not yield constraints on the most recent earthquake history in trench t2 however human skeletal remains of a middle aged male which yield a radiocarbon age of 1159 28 bp corresponding to a mean calendar age of 791 ad were found within a faulted alluvial layer at a depth of 60 70 cm from the surface the existence of these medieval human places shows that a surface rupturing earthquake occurred at some time after 1159 28 bp the amount of slip in each earthquake on the firouzkuh fault is difficult to estimate but assuming the entire 55 km fault length ruptures in each event they will have had a maximum magnitude of 7 1 at our estimated late quaternary slip rate of 1 1 2 2 mm yr magnitude 7 1 earthquakes involving 1 2 m average displacement would be expected to occur every 1100 540 years as the last earthquake on the firouzkuh fault may be up to 700 years in age we suggest that the firouzkuh fault is a major hazard for earthquakes in the near future