observing earthquakes triggered in the near field by dynamic deformations we examine the hypothesis that dynamic deformations associated with seismic waves trigger earthquakes in many tectonic environments our analysis focuses on seismicity at close range within the aftershock zone complementing published studies of long range triggering our results suggest that dynamic triggering is not confined to remote distances or to geothermal and volcanic regions long unilaterally propagating ruptures may focus radiated dynamic deformations in the propagation direction therefore we expect seismicity triggered dynamically by a directive rupture to occur asymmetrically with a majority of triggered earthquakes in the direction of rupture propagation bilaterally propagating ruptures also may be directive and we propose simple criteria for assessing their directivity we compare the inferred rupture direction and observed seismicity rate change following 15 earthquakes m 5 7 to m 8 1 that occurred in california and idaho in the united states the gulf of aqaba syria guatemala china new guinea turkey japan mexico and antarctica nine of these mainshocks had clearly directive unilateral ruptures of these nine seven apparently induced an asymmetric increase in seismicity rate that correlates with the rupture direction the two exceptions include an earthquake preceded by a comparable magnitude event on a conjugate fault and another for which data limitations prohibited conclusive results similar but weaker correlations were found for the bilaterally rupturing earthquakes we studied although the static stress change also may trigger seismicity it and the seismicity it triggers are expected to be similarly asymmetric only if the final slip is skewed toward the rupture terminus for several of the directive earthquakes we suggest that the seismicity rate change correlates better with the dynamic stress field than the static stress change manuscript received 1 march 2002

relocation and assessment of seismicity in the iran region summary more than 2000 instrumentally recorded earthquakes occurring in the iran region during the period 1918 2004 have been relocated and reassessed with special attention to focal depth using an advanced technique for 1 d earthquake location a careful review of starting depths association of teleseismic depth phases and the effects of reading errors on these phases are made and when necessary waveforms have been examined to better constrain ehb focal depths uncertainties in ehb epicentres are on the order of 10 15 km in the iran region owing to the earth s lateral heterogeneity and uneven station distribution uncertainties of reviewed ehb focal depth estimates are on the order of 10 km as compared to about 4 km for long period p and sh body waveform inversions nevertheless these ehb depth estimates are sufficiently accurate to resolve robust differences in focal depth distribution throughout the iran region and within their errors show patterns that are in agreement with the smaller number of earthquakes whose depths have been confirmed by body wave modelling or local seismic networks the importance of this result is that future earthquakes with apparently anomalous depths can easily be identified and checked if necessary most earthquakes in the iranian continental lithosphere occur in the upper crust with the crustal shortening produced by continental collision accommodated entirely by thickening and distributed deformation in the zagros mountains nearly all earthquakes are confined to the upper crust depths 20 km and there is no evidence for a seismically active subducted slab dipping ne beneath central iran by contrast in southeastern iran where the arabian seafloor is being subducted beneath the makran coast low level earthquake activity occurs in the upper crust as well as to depths of at least 150 km within a northward dipping subducting slab near the oman line a region transitional between the zagros and the makran seismicity extends to depths of up to 30 45 km in the crust consistent with low angle thrusting of arabian basement beneath central iran in north central iran along the alborz mountain belt seismic activity occurs primarily in the upper crust but with some infrequent events in the lower crust particularly in the western part of the belt the talesh where the south caspian basin underthrusts nw iran earthquakes that occur in a band across the central caspian following the apscheron balkhan sill between azerbaijan and turkmenistan have depths in the range 30 100 km deepening northwards these are thought to be connected with either incipient or remnant northeast subduction of the south caspian basin basement beneath the east west trending apscheron balkhan sill curiously in this region of genuine mantle seismicity there is no evidence for earthquakes shallower than 30 km

a methodology for the study of the relation between coastal cliff erosion and the mechanical strength of soils and rock masses abstract a methodology is proposed to make approximate estimates of the destructive force of waves at the bottoms of cliffs where no accurate bathymetric data are available by means of correlation between the erosion rate of rocky coasts and the mechanical strength of soils and rock masses the correlation used makes it possible to obtain a linear semi logarithmic expression between the long term average erosion rate from an engineering standpoint of coasts consisting of different lithologies wave energy and the uniaxial compressive strength of soils and rock masses forming the cliffs the uniaxial compressive strength of soils consisting of landslide debris was measured using a pocket penetrometer and the rock mass index rmi method was used for rock masses these methods were chosen after critical analysis of the methodologies currently available the proposed approach was tested in the cilento area of southern italy and in particular along a 6 km stretch of coast typified by rock masses and landslide debris that are particularly susceptible to erosion this coastline is exposed to south westerly waves which in deep water reach significant heights between 1 and 3 m and significant wave periods between 4 and 7 s estimates of the coastal erosion rates were made by studying the variations especially in restricted headland areas occurring over two time spans 30 and 45 years respectively by comparing topographic maps and aerial photographs taken at different times these comparisons give approximate indications of retreats of 15 m over the time span of 30 years average erosion rate of 0 5 m year 1 and of 35 m over the time span of 45 years average erosion rate of ca 0 8 m year 1 these data do have a local significance but clearly show how quick these processes sometimes are lastly the study of a notch incised by wave action on a concrete sea wall built to protect a terrace made it possible to quantify the impact of erosion on concrete it was possible to obtain rmi values through field observations furthermore it was possible to obtain the constants of the hoek and brown failure criterion using rmi on the basis of rmi values the rock masses studied were defined as moderately strong to strong and according to the hoek and brown criterion as poor to fair a semilogarithmic linear relation was found between the strength of landslide debris rock masses and concrete as well as their respective long term erosion consequently a rough estimate of the destructive force of waves ca 24 mpa was calculated this value is given by the product of the mean value of their hydraulic pressure for a non dimensional constant which in turn takes into account the sandy pebbly beach sediment at the foot of the cliffs that acts as an abrasive on the rock mass

central zagros fold thrust belt iran new insights from seismic data field observation and sandbox modeling 1 we present five generalized cross sections across the central zagros fold and thrust belt iran these sections show that the fold geometry varies significantly both horizontally and vertically the style is closely related to the changes in the mechanical behavior of the lithostratigraphic horizons and in particular to the presence of intermediate decollements within the sedimentary pile restoration of the sections shows amounts of shortening of the same order from one section to the other however it appears to be unequally distributed suggesting variations in basal decollement shear strength analogue modeling has been performed to systematically investigate the effect of an intermediate decollement level at different depths on the style of folding the models demonstrate that the position of intermediate decollements is an important factor controlling both structural style and fold wavelength models with shallow intermediate decollement show regularly and widely spaced anticlines in these models the fold wavelength depends directly on the thickness of the dominant competent layer and short wavelength superficial structures mask broad anticlines at depth models with deep intermediate decollement are characterized by the rapid propagation of deformation with small rate of shortening along this decollement influencing localization of forthcoming anticlines in the upper levels such propagation favors the development of duplexes and multiwavelength folds on this basis fold kinematics in central zagros is discussed using the variation of structural style along different folds as an indicator of the sequence of deformation detachment folding is the main folding style at least for the initial stages of deformation and thrust faults developed only at later stages some of these faults branched on decollement levels express the progression of folding whereas others are linked to late basement faults cutting through early structures in general the decollement levels are activated sequentially from deeper horizons to shallower ones however in one case gachsaran decollement a shallow decollement is activated during the early stages of folding and then abandoned during the subsequent evolution

southern california coastal response to the 2015 2016 el nino author s young adam p flick reinhard e gallien timu w giddings sarah n guza r t harvey m lenain luc ludka b c melville w kendall o reilly w c

late cretaceous paleocene formation of the proto zagros foreland basin lurestan province sw iran late cretaceous emplacement of ophiolitic radiolaritic thrust sheets over the arabian passive margin was the first manifestation of the protracted closure of the neotethys ocean which ended with the continental collision between arabia and central iran and the formation of the present zagros fold belt this tectonic stacking produced a flexural basin the amiran basin 400 200 km in size in the northwest zagros that was filled with a 1225 m thick shallowing upward detrital succession made up of the amiran taleh zang and kashkan formations this succession sits unconformably above the late cretaceous gurpi formation and is overlain by the oligocene miocene shahbazan asmari carbonate succession dating of the amiran kashkan succession is based on detailed biostratigraphy using large foraminifera and calcareous nannoplankton the cretaceous tertiary k t boundary is located within the uppermost 25 45 m of the gurpi formation the overlying amiran and taleh zang formations have been dated as paleocene in age however the base of the paleocene within the gurpi formation lacks np1 and np2 zones implying a hiatus of 2 m y at ca 65 5 ma which is inferred to correspond to an early folding phase near the cretaceous paleocene boundary the upper part of the kashkan formation is dated to the earliest eocene by palynostratigraphy a large hiatus or very slow deposition lasting about 15 m y occurs between the kashkan and shahbazan formations in the studied region the base of the prograding shahbazan platform deposits is dated by 87sr 86sr stratigraphy at ca 33 9 ma the upper part of the asmari formation is dated as early middle miocene using foraminifera associations reconstruction of the amiran taleh zang kashkan succession of the amiran basin indicates a thickening of the basin fill from the southern pinch out along the se flank of the kabir kuh anticline to sw of the khorramabad anticline where the flexure is at least 900 m in contrast the ne part of the basin underwent coeval contraction and uplift of 1300 m superimposed smaller undulations onto the large scale flexure are interpreted as late cretaceous paleocene folds regional comparisons se zagros oman and turkey indicate that late cretaceous early tertiary deformation affected the entire ne margin of arabia but that compression was not synchronous being younger in lurestan than in the nw persian gulf where inversion tectonics occurred from turonian to mid campanian times the long sedimentary hiatus spanning most of the middle and late eocene must have been related to deep lithospheric processes linked to the initial events of the protracted closure of the neotethys ocean between arabia and central iran the tectono sedimentary history recorded in the zagros basin may help to understand early foreland basin growth in other orogens in which subsequent continental collision has obliterated these early events

fold patterns and multilayer rheology of the lurestan province zagros simply folded belt iran abstract anticlines of the lurestan province in the zagros fold thrust belt have been studied by integrating field based analysis with the use of high resolution satellite images and data available from the literature the distribution of folds in the southeastern lurestan province expressed in terms of axial length and wavelength distribution shows a direct link with the characteristics of the sedimentary multilayer in which the folds developed within the carbonate deposits of the late cretaceous bangestan group the transition from pelagic to neritic facies determines a threefold increase in anticline spacing and promotes the development of thrust structures in the forelimb of anticlines the oligocene miocene shahbazan asmari unit folds harmonically with the bangestan group except in the areas where the palaeogene deposits interposed between the two units exceed 1300 m of thickness in these areas the shahbazan asmari carbonates display short wavelength folds indicating a complete decoupling from the underlying folds of the bangestan group it is suggested that this decoupling occurs because the summed thickness of the incompetent units separating the two carbonate units exceeds the extension of the zone of effective contact strain of the bangestan group folds

identifying the behavioural characteristics of clay cliffs using intensive monitoring and geotechnical numerical modelling abstract coastal monitoring is routinely undertaken to provide an archival record of cliff line movement that can be used in the development and validation of predictive coast retreat and evolution models however coastal monitoring is often purely quantitative in nature and financial necessity requires deployment over extensive coastal sections as a result for local site conditions in particular only limited geomorphological data are available or included during the development of such predictive models this has resulted in many current models incorporating a simplistic or generalised representation of cliff behaviour an approach that progressively loses local credibility when deployed over extensive heterogeneous coastlines this study addresses this situation at a site of extreme coastline retreat holderness uk through the application of intensive monitoring of six representative cliff sections nested within a general geomorphological appraisal of the wider coastline as a whole the data from these surveys have been used to validate a finite difference based geotechnical modelling assessment of clay cliff stability once validated the geotechnical model was used to simulate a range of scenarios that were sufficient to represent the range of topographic hydrogeological geological and littoral conditions exhibited throughout the region our assessment identified that the cliff retreat occurs through the combined influence of direct marine erosion of the cliff with shallow structurally controlled failures or substantial mass failures critically the predisposition to any one of these failure mechanisms arises principally as a result of initial cliff height the results of the numerical modelling have been combined into an empirical slope model that derives the rate of landslide induced retreat that would arise from mass failures under various future scenarios results of this study can be used in the selection and development of retreat models at coastlines of similar physiographic setting to that found at holderness the results represent a key step in linking material deformation properties to the processes of cliff change and the subsequent range of landforms found on clay cliffs as such the results could also be used more generally to illustrate the likely cliff behaviour of other soft rock coastlines

the impact of cover rock rheology on the style of folding in the zagros fold thrust belt abstract the present day morphology of the zagros fold thrust belt is dominated by magnificent exposures of nw se trending folds these folds differ in their size and geometry and these differences are related mainly to the rheological profile of the cover rock the cover rock succession of the zagros consists of a sequence of competent and incompetent units which vary both along and across the belt field based study combined with the use of satellite images reveals that the thickness and facies distribution of the cover rock succession has a significant impact on the style of deformation during the shortening linked to the current convergence of the arabian and iranian plates the incompetent units act as detachment horizons which localise thrusting and which act as decollement above which detachment folds form in addition where these incompetent units are thick e g 1 km they allow the deformation above and below them to become completely decoupled enabling disharmonic folding to occur as a result the folds above and below the incompetent units in the central part of the zagros folded belt have significantly different geometries and wavelengths as the zagros folds host the majority of the hydrocarbon reserves in iran and iraq an understanding of the processes that influence their geometry and spatial organization at different levels in the cover rock is crucial for the future exploration in the region

epicenter distribution and magnitude of earthquakes in fold thrust belts insights from sandbox models scaled analogue models are used to illustratethe eect of basal friction and erosion on fault activity andhence on epicentre distribution and magnitude of earth quakes in the sedimentary cover of active fold thrust belts model results suggest that in fold thrust belts shortenedabove low friction ductile decollements rock salt or over pressured mudstone low to moderate magnitude earth quakes mw 5 3 5 6 distributed over a wide area occuralong several long lived thrust faults conversely in areasshortened above high friction decollements large magnitudeearthquakes mw 6 6 6 8 distributed over a narrowzone are likely to occur along few short lived thrust ramps calculated magnitude of earthquakes from models and theirdistribution are in agreement with recorded earthquake pat tern from the zagros mountain belt which is partially short ened above a ductile decollement of hormuz salt formation model results also showed that erosion reactivates older in active thrusts and promotes formation of out of sequencethrusts

structure of the mountain front flexure along the anaran anticline in the pusht e kuh arc nw zagros iran insights from sand box models this is a contribution of the group of dynamics of the lithosphere gdl financed by a collaborative project between the institute of earth sciences jaume almera csic of barcelona spain and statoilhydro tehran and statoilhydro research centre with the partial support of project team consolider ingenio 2010 no csd 2006 00041

automated fault model discretization for inversions for coseismic slip distributions 1 geoscientists increasingly rely on coseismic slip distributions inferred from geodetic observations to drive sophisticated models of the seismic cycle to date little work has been done on optimizing the parameterization of these fault models so that they reflect the resolving power of observed surface displacements the locations of noisy surface displacement observations are often widely scattered far from features we wish to analyze in the subsurface and result in highly variable model resolution with depth the few attempts to produce variably discretized fault planes are arduously constructed by hand and may not correctly reflect the ability of the data to resolve slip features motivated by the increasing size of geodetic data pools and the need for distributed slip models that accurately represent features the data can resolve we present a fully automated algorithm that iteratively adjusts the sizes of dislocations in a fault model we use the concept of smoothing scales derived from the model resolution matrix to resize dislocations so that each dislocation is sized appropriately given the area over which slip in that region of the fault would be smoothed we present a series of synthetic tests that utilize both sparse and dense data sets and we compare our variably discretized inversions to traditional regularly discretized inversions we also use our approach to invert for slip from geodetic observations of the 2004 mw 6 0 parkfield california earthquake and the 1995 mw 8 1 antofagasta chile earthquake

decadal scale coastal cliff retreat in southern and central california abstract airborne lidar data collected in 1998 and 2009 2010 were used to measure coastal cliff erosion and retreat between the mexico california border and bodega head california cliff erosion was detected along 44 of the 595 km of shoreline evaluated while the remaining cliffs were relatively stable the mean cliff top retreat rate was 0 12 m yr while mean retreat averaged over the entire cliff face was 0 04 m yr the maximum cliff top and face retreat rates were 4 2 and 3 8 m yr respectively historical 1930s to 1998 and recent retreat rates were significantly inversely correlated for areas with large historical or recent cliff retreat such that locations with elevated historical retreat had low levels of recent retreat and locations with elevated recent retreat were preceded by low rates of historical retreat the strength of this inverse correlation increased with cliff change magnitudes up to r2 of 0 91 for cliff top retreat rates 2 9 m yr mean recent retreat rates were 52 83 lower than mean historical retreat rates although beaches can protect cliffs against wave driven erosion cliffs fronted by beaches retreated 49 more than cliffs without beaches on average unarmored cliff faces retreated 0 05 m yr between 1998 and 2009 2010 about three times faster than artificially armored cliffs alongshore metrics of wave cliff impact precipitation and cliff hardness were generally not well correlated with recent cliff changes a cliff hazard metric is used to detect cliff steepening and areas prone to future cliff top failures

regional stratigraphy of the zagros fold thrust belt of iran and its proforeland evolution the latest neoproterozoic through phanerozoic stratigraphy of the zagros fold thrust belt of iran has been revised in the light of recent investigations the revised stratigraphy consists of four groups of rocks each composed of a number of unconformity bounded megasequences representing various tectonosedimentary settings in the lowest group ranging in age from latest precambrian to devonian the uppermost neoproterozoic to middle cambrian rocks constitute a megasequence of evaporites siliciclastic deposits and interlayered carbonates which were deposited in pull apart basins that developed by the najd strike slip fault system this megasequence is overlain by a second one middle to late cambrian in age which consists of shallow marine siliciclastic and carbonate rocks representing deposition in an epicontinental platform the overlying shales siltstones and partly volcanogenic sandstones of ordovician silurian and devonian age are local remnants of stratigraphic units that were extensively eroded during development of several major unconformities the second group consists of two megasequences one permian and the other triassic composed of widespread transgressive basal siliciclastic rocks and overlying evaporitic carbonates of an equatorial epi pangean very shallow platformal sea the third group is composed of four megasequences formed of shallow and deep water carbonates with some siliciclastic and evaporite deposits which accumulated on a neo tethyan continental shelf during earliest jurassic through late turonian time the fourth group comprises siliciclastic and carbonate deposits of a largely underfilled nw to se trending forward and backward migrating late cretaceous to recent proforeland basin which has evolved as an integral part of the zagros orogen this last group consists of three megasequences ix x and xi with distinctive lateral and vertical facies variations which reflect specific tectonic events megasequence ix comprises uppermost turonian to middle maastrichtian prograding and retrograding siliciclastic and carbonate deposits whose accumulations reflect emplacement obduction of ophiolite slivers and subsequent collisional events in the zagros orogen megasequence x consists of uppermost maastrichtian to upper eocene siliciclastic and carbonate rocks which deposited first progradationally in front of the zagros orogenic wedge with reduced contractional tectonic activity and then retrogradationally due to intensified thrust stacking in the interior parts of the orogen megasequence xi consists of oligocene and lower miocene carbonate strata deposited retrogradationally shortly after a period of intensified late eocene thrust faulting in the deformational wedge and an overlying succession of upward coarsening northeasterly derived siliciclastic deposits of lower miocene to recent age which are composed of erosional byproducts of the southwest vergent zagros thrust sheets

extended canadian middle atmosphere model zonal mean climatology and physical parameterizations 1 this paper describes the energetics and zonal mean state of the upward extension of the canadian middle atmosphere model which extends from the ground to 210 km the model includes realistic parameterizations of the major physical processes from the ground up to the lower thermosphere and exhibits a broad spectrum of geophysical variability the rationale for the extended model is to examine the nature of the physical and dynamical processes in the mesosphere lower thermosphere mlt region without the artificial effects of an imposed sponge layer which can modify the circulation in an unrealistic manner the zonal mean distributions of temperature and zonal wind are found to be in reasonable agreement with observations in most parts of the model domain below 150 km analysis of the global average energy and momentum budgets reveals a balance between solar extreme ultraviolet heating and molecular diffusion and a thermally direct viscous meridional circulation above 130 km with the viscosity coming from molecular diffusion and ion drag below 70 km radiative equilibrium prevails in the global mean in the mlt region between 70 and 120 km many processes contribute to the global energy budget at solstice there is a thermally indirect meridional circulation driven mainly by parameterized nonorographic gravity wave drag this circulation provides a net global cooling of up to 25 k d 1

insar slip rate determination on the altyn tagh fault northern tibet in the presence of topographically correlated atmospheric delays 1 the interseismic strain across the altyn tagh fault at 85 e has been measured using 59 interferograms from 26 ers 1 2 sar acquisitions on a single track for the period 1993 2000 using an atmospheric delay correction that scales linearly with height we estimate the left lateral strike slip motion to be 11 1 5 mm yr assuming no relative vertical motion and a 15 km fault locking depth this is in agreement with sparse gps measurements the atmospheric delay corrections agree well with coarse contemporaneous modelled weather data reinforcing the importance of correcting for atmospheric delays in insar studies of interseismic strain accumulation particularly in areas of high topographic relief that strongly correlate with the expected tectonic signal we also find that in addition to the tropospheric water vapour wet delay the hydrostatic dry delay makes a significant contribution to the signal

surface displacements and source parameters of the 2003 bam iran earthquake from envisat advanced synthetic aperture radar imagery 1 the mw 6 6 26 december 2003 bam iran earthquake was one of the first earthquakes for which envisat advanced synthetic aperture radar asar data were available using interferograms and azimuth offsets from ascending and descending tracks we construct a three dimensional displacement field of the deformation due to the earthquake elastic dislocation modeling shows that the observed deformation pattern cannot be explained by slip on a single planar fault which significantly underestimates eastward and upward motions se of bam we find that the deformation pattern observed can be best explained by slip on two subparallel faults eighty five percent of moment release occurred on a previously unknown strike slip fault running into the center of bam with peak slip of over 2 m occurring at a depth of 5 km the remainder occurred as a combination of strike slip and thrusting motion on a southward extension of the previously mapped bam fault 5 km to the east

characteristics of sea cliff erosion induced by a strong winter storm in the eastern mediterranean abstract changes in sea cliff morphologies along the 30 km long sharon escarpment segment of israel s weakly cemented mediterranean eolianite cliff line were analyzed to gain quantitative insights into erosion characteristics associated with a high energy winter storm 10 20 year return interval ground based repeat lidar measurements at five sites along the cliff line captured perturbations of cliff stability by basal wave scouring during the storm subsequent post storm gravity driven slope failures in the cliff face above and return of the system to transient stability within several months post storm erosion which amounted to 70 of the total volume of cliff erosion documented resulted in dramatic local effects of up to 8 m of cliff top retreat and yet at the larger scale of the 30 km cliff line examined erosion during the storm and the year that followed affected less than 4 of the cliff length and does not appear to be above the average cliff length annual erosion implied by previously published decadal scale retreat rates along this sea cliff our results do not support a direct association between strong storm events and elevated erosion and retreat at the cliff line scale

retreat rates modalities and agents responsible for erosion along the coastal chalk cliffs of upper normandy the contribution of terrestrial laser scanning in order to follow all the changes affecting the coastal chalk cliff face in upper normandy and improve knowledge about cliff erosion repeated terrestrial laser scanning tls surveys were carried out frequently between 2010 and 2013 every 4 5 months they were conducted at two sites with similar lithostratigraphic characteristics but different exposures to marine actions the former being an abandoned cliff and the latter an active cliff they provide a quantification of the production of debris with centimeter precision from 0 01 to 0 04 m these surveys provided three major outcomes 1 cliff retreat rates were measured at high spatial resolution with retreat values unsurprisingly 3 4 times higher for an active cliff than for an abandoned cliff this result highlights that marine actions should be seen as not only a transport agent but also a particularly effective erosion agent 2 a significant proportion of debris fall production about 25 in the total active cliff retreat was identified and 3 one of the modalities of retreat was visualized as the creation of a basal notch which propagates instability towards the upper part of the cliff face later this instability generates rock falls coming from the whole cliff face

a reappraisal of earthquake focal mechanisms and active shortening in the zagros mountains of iran summary the zagros mountains of sw iran are one of the most seismically active intra continental fold and thrust belts on earth and an important element in the active tectonics of the middle east surface faulting associated with earthquakes is extremely rare and so most information about the active faulting comes from earthquakes we use long period teleseismic p and sh body waves to determine the orientation and depth of faulting in 16 new earthquakes and then evaluate and synthesize all the available teleseismic data on earthquake source parameters in the zagros we use this information to investigate the style and distribution of active faulting in the zagros and how it contributes to the n s shortening of the arabia eurasia collision when the data are ranked in quality and carefully evaluated simple patterns are seen that are not apparent when routine catalogue data are taken at face value an important change in the fault configuration occurs along strike of the belt in the nw overall convergence is oblique to the trend of the belt and the surface anticlines and is achieved by a spatial separation partitioning of the orthogonal strike slip and shortening components on separate parallel fault systems by contrast in the se overall convergence is orthogonal to the regional strike and achieved purely by thrusting in the central zagros between these two structural regimes deformation involves parallel strike slip faults that rotate about vertical axes allowing extension along the strike of the belt the overall configuration is similar to that seen in other curved shortening belts such as the himalaya and the java sumatra trench all the zagros earthquakes we have been able to check have centroids shallower than 20 km and are confined to the upper crust many of the larger earthquakes are likely to occur in the basement beneath the sedimentary cover which is active even beneath areas of known shallow structural decollement such as the dezful embayment the dominant style of shortening is high angle reverse faulting with dips 30 though some lower angle thrusting occurs in places active thrust and reverse faulting is relatively confined to the lower topography on the sw edge of the belt today and only strike slip faulting affects the higher topography profound vertical changes in structural and stratigraphic level indicate that a similar style of deformation was once active across the width of the simple folded belt but has progressively migrated sw over the last 5 ma there is no evidence for a seismically active structural decollement such as a low angle thrust beneath the zagros nor is there any seismic evidence for active subduction either beneath the zagros or beneath central iran instead the arabian margin seems to have shortened by distributed thickening of the basement only in the syntaxis of the oman line at the se end of the zagros is there any evidence for a low angle thrust of regional extent here earthquakes continue 50 km north of the zagros thrust line the geological suture between the arabian margin and central iran reaching depths of 30 km and may represent thrusting of arabian basement beneath central iran to this extent

seismotectonics of the zagros continental collision zone and a comparison with the himalayas accurate focal depths of 16 medium to large zagros earthquakes were determined from identification of surface reflected phases by comparing observed long period p waves with synthetic seismograms all events are shallow 6 12 km and show no tendency to deepen toward the main zagros thrust geological and geophysical evidence suggests that most of these earthquakes probably occurred within the uppermost precambrian basement because the focal mechanisms of these events indicate high angle reverse faulting the events do not occur on a single detachment surface but rather reflect horizontal shortening of the basement on numerous short segmented 8 probably occurred along this detachment a comparative study of the zagros with the himalayas suggests that the active tectonics of the zagros continental collision zone and the iranian blocks arc similar to those of the himalayas and the tibetan terranes in oligocene time

structural framework of the zagros fold thrust belt iran abstract data gleaned from the literature on the zagros have been compiled and used in conjunction with new interpretations to provide a better picture of the structures sedimentation history and deformation of this hydrocarbon rich mountain belt the belt parallel mountain front the n s trending kazerun izeh and e w trending bala rud fault zones are defined as the master structural elements of the belt these fault zones divide the zagros basin into zones with different stratigraphic successions and different rheological profiles this resulted in different structural styles developing along the belt during the subsequent collision the kazerun and izeh fault zones acted as the depositional system transition zone between the lurestan and fars regions in jurassic cretaceous time and partly controlled the distribution of the kazhdumi formation one of the major source rocks by the end of the cretaceous the nw se trending mountain front fault divided the present folded belt of the zagros into a major foreland basin to the southwest and a piggyback basin to the northeast activity along other major transfer fault zones including the izeh kazerun and bala rud fault zones occurred at this time and controlled the sedimentation and subsidence of the dezful embayment the main target region for hydrocarbon exploration these fault zones controlled the thickness of the asmari formation one of the main reservoirs and also the considerable thickness and facies changes of the gachsaran formation the major seal to the asmari formation the present morphology of the mountain belt is interpreted as being mainly related to the pinning of the mountain front fault to the northwest of the dezful embayment and to the north of the strait of hormuz

tracking the rupture of the 2008 wenchuan earthquake by using the relative back projection method on 12 may 2008 the m w 7 9 wenchuan earthquake occurred along the longmen shan fault in the northwestern sichuan province of china resulting in huge damage as well as loss of human lives rapid estimation of the rupture process is essential for emergency response in this paper the relative back projection method based on nonplane wave array technology was applied to reconstruct the rupture process of this earthquake first the principle of the relative back projection method was briefly introduced then the method was used to obtain the rupture process using the broadband data of 16 stations from the australian national seismic network from the incorporated research institutions for seismology iris data management center the results showed that this earthquake ruptured mostly unilaterally along the longmen shan fault its rupture time was about 98 s rupture length was about 290 km and mean rupture velocity was about 3 0 km s starting from the initial rupture point epicenter 31 00 n 103 32 e the great earthquake ruptured northeastward along the longmen shan fault with two major energy releasing peaks one was located about 50 km northeast of the epicenter at about 20 s after the earthquake began and the other about 140 km northeast at about 50 s which coincided with macrodamage at those two places

source model for the mw 6 7 23 october 2002 nenana mountain earthquake alaska from insar 1 the 23 october 2002 nenana mountain earthquake mw 6 7 occurred on the denali fault alaska to the west of the mw 7 9 denali earthquake that ruptured the same fault 11 days later we used 6 interferograms constructed using radar images from the canadian radarsat 1 and european ers 2 satellites to determine the coseismic surface deformation and a source model data were acquired on ascending and descending satellite passes with incidence angles between 23 and 45 degrees and time intervals of 72 days or less modeling the event as dislocations in an elastic half space suggests that there was nearly 0 9 m of right lateral strike slip motion at depth on a near vertical fault and that the maximum slip in the top 4 km of crust was less than 0 2 m the nenana mountain earthquake increased the coulomb stress at the future hypocenter of the 3 november 2002 denali earthquake by 30 60 kpa

zagros phantom earthquakes reassessed the interplay of seismicity and deep salt flow in the simply folded belt unraveling the contributions of main shock slip aftershocks aseismic afterslip and postseismic relaxation to the deformation observed in earthquake sequences heightens our understanding of crustal rheology triggering phenomena and seismic hazard here we revisit two recent earthquakes in the zagros mountains iran which exhibited unusual and contentious aftereffects the mw 6 earthquakes at qeshm 2005 and fin 2006 are both associated with large interferometric synthetic aperture radar insar signals consistent with slip on steep reverse faults in carbonate rocks of the middle sedimentary cover but small aftershocks detected with local seismic networks were concentrated at significantly greater depths this discrepancy can be interpreted in one of two ways either 1 there is a genuine vertical separation between main shock and aftershocks reflecting a complex stress state near the basement cover interface or 2 the aftershocks delimit the main shock slip and the insar signals were caused by shallow updip afterslip phantom earthquakes with very similar magnitudes mechanisms and geographical positions as the original earthquakes here we show that main shock centroid depths obtained from body waveform modeling which in this instance is the only method that can reveal for certain the depth at which seismic slip was centered strongly support the first interpretation at qeshm microseismic aftershock depths are centered at the level of the hormuz formation an infracambrian sequence of intercalated evaporitic and nonevaporitic sediments these aftershocks may reflect the breaking up of harder hormuz sediments and adjacent strata as the salt flows in response to main shock strain at the base of the cover this work bolsters recent suggestions that most large earthquakes in the zagros are contained within carbonate rocks in the midlower sedimentary cover and that the crystalline basement shortens mostly aseismically

variation of structural style and basin evolution in the central zagros izeh zone and dezful embayment iran abstract structural style and its relationship to sedimentary facies and the evolution of sedimentary depocenters since late cretaceous times have been studied on the basis of one regional balanced transect and several updated isopach maps in the izeh zone and the dezful embayment central zagros this study relies on fieldwork data existing geological maps seismic data and well information a new structural classification for part of the zagros sedimentary cover is presented to highlight the different mechanical behavior of the formations in the stratigraphic column it shows the existence of several local decollement levels activated during folding these decollement levels separate lithotectonic units which accommodate shortening in different ways the lower paleozoic is the basal decollement level throughout the studied area triassic evaporites albian shales eocene marls and miocene evaporites can act as intermediate decollement levels and present variable facies in the central zagros lateral facies and thickness variations the sedimentary overburden and the close relationship with inherited fault patterns influenced the wavelength amplitude and style of folding in the study area furthermore surface structures do not necessarily coincide with deeper objectives where these disharmonic levels are involved in folding the evolution of sedimentary depocenters from the late cretaceous obduction episode until early miocene collision is described based on updated isopach maps and tectonic subsidence curves this analysis shows continuous compression and movements along n s and nw se trending faults in the zagros basement which predate the neogene zagros folding and influence sedimentation history it also indicates a southwestward migration of the depocenters through time in addition to the basement involvement below some folds during the zagros orogeny

the 2006 march 25 fin earthquakes iran insights into the vertical extents of faulting in the zagros simply folded belt summary we investigate the depth of faulting and its connection with surface folding in the zagros simply folded belt of iran our focus is a sequence of earthquakes mw 5 7 5 5 5 2 5 0 4 9 that struck the fin region in the south eastern simply folded belt on 2006 march 25 modelling ground displacements measured with radar interferometry we find that either n or s dipping model reverse faults can reproduce the observed fringe patterns despite the uncertainty in fault orientation we can constrain the vertical extents of rupture to between a top depth of 5 6 km and a bottom depth of 9 10 km consistent with the 8 km centroid depth of the largest earthquake we suggest that the faulting ruptured the thick competent group of paleozoic and mesozoic conglomerates and platform carbonates which makes up the lower part of the sedimentary cover the rupture probably terminated within the precambrian hormuz salt at its base and the cretaceous gurpi marls at its top these mechanically weak layers act as barriers to rupture separating faulting within the competent group from deformation in the layers above and below the pattern of coseismic surface uplift is centred on the common limb of the fin syncline and guniz anticline but is oblique by 20 to the trend of these open symmetric whaleback folds and also overlaps a section of the fin syncline axis these observations suggest that locally surface folding is decoupled from the underlying reverse faulting although the fin syncline and guniz anticline are symmetric structures some other nearby folds show a strong asymmetry with steep or overturned southern limbs consistent with growth above n dipping reverse faults this suggests that the simply folded belt contains a combination of forced folds and detachment folds we also investigate the distribution of locally recorded aftershocks in the weeks following the main earthquakes most of these occurred at depths of 10 30 km with a particularly high concentration of events at 20 25 km these aftershocks therefore lie within the crystalline basement rather than the sedimentary cover and are vertically separated from the main rupture this study confirms earlier suggestions that earthquakes of mw 5 6 are capable of being generated within the thick competent group of paleozoic and mesozoic sediments as well as in the basement below the hormuz salt formation

the 12 november 2017 mw 7 3 ezgeleh sarpolzahab iran earthquake and active tectonics of the lurestan arc

structural variation along the zagros and the nature of the dezful embayment structure varies along strike in the zagros fold and thrust belt of iran which is a principal element in the arabia eurasia continental collision pre collision late cretaceous ophiolite nappes kermanshah neyriz and related nappes of deep marine sediments radiolarite series were emplaced next to two regions pusht e kuh arc fars which later developed a consistent structural style across the range from the high zagros fault to the foreland limit of deformation the intervening area has a zone of highly imbricated arabian plate strata the bakhtyari culmination thrust southwest towards and over a low relief low elevation region the dezful embayment there are no ophiolite nappes northeast of the bakhtyari culmination isopachs reflect these different structural patterns from late cretaceous time but not earlier in late cretaceous time the dezful embayment recorded less deposition than adjacent areas to the northwest and southeast in the palaeogene there was little net difference between the dezful embayment and its margins the dezful embayment has been a depocentre since roughly 35 ma which is the likely time of initial collision between arabia and eurasia we propose that the syn collision structure and stratigraphy of the zagros is therefore strongly influenced by the variation in late cretaceous ophiolite emplacement but the original cause of this variation is not clear

geodetic investigation of the 13 may 1995 kozani grevena greece earthquake the ms 6 6 13 may 1995 kozani grevena earthquake struck a region of low historical seismic activity which includes a 10 year old triangulation network in northern greece after the earthquake monuments from this network were occupied with gps to measure co seismic displacements inversion of the co seismic displacement field to yield a source mechanism is achieved by use of a hybrid simplex monte carlo method which requires no a priori constraints the model focal mechanism agrees well with the global cmt solution and locally observed aftershocks but implies a significantly higher scalar moment than do seismological or sar interferometry studies and has a longer fault length than the model based on sar interferometry

seismic versus aseismic deformation in iran inferred from earthquakes and geodetic data summary a combined analysis of the geodetic strain rate field and the strain rate field deduced from the seismicity allows us to define the style of deformation and to distinguish seismic from aseismic deformation we perform this analysis in iran where the present day tectonics results from the north south convergence between the plates of arabia to the south and eurasia to the north the data consist of velocities measured with a gps network of 28 benchmarks and of instrumental and historical earthquake catalogues the axes of the seismic strain rate tensor have similar orientations to those deduced from the gps velocity field this indicates that the seismicity can be used to improve gps information on the style and the orientation of the deformation comparison of seismic and geodetic strain rates indicates that highly strained zones experience mainly aseismic deformation in southern iran and seismic deformation in northern iran a large contrast is observed between the zagros less than 5 per cent seismic deformation and the alborz kopet dag regions more than 30 100 per cent seismic deformation the distribution of the seismic geodetic ratio correlates with the distribution of large earthquakes intensive low magnitude seismicity is observed in the zagros whereas the largest earthquakes occur in northern iran the contrast of seismic deformation between the zagros and peri caspian mountains is confirmed considering 300 or 1000 yr of seismicity rather than 100 or 200 yr

the impact of climatic and seismic events on the short term evolution of seacliffs based on 3 d mapping northern monterey bay california abstract coastal cliff retreat along the central california coast is episodic occurring in response to single large storms or seismic events traditional approaches to the study of long term seacliff retreat utilize historical aerial photography and maps to delineate the landward migration of the top edge of the cliff over periods of tens of years to a century while these methods yield cumulative retreat amounts they provide little or no information on the character of the individual retreat events nor the physical processes of retreat this study addresses the processes of episodic and short term coastal cliff retreat through the analysis of seacliff failure styles and retreat magnitudes the study areas are three 1 km long sections of cliffed coast in northern monterey bay the earliest data set is vertical aerial photography from october 18 1989 taken the day following the magnitude 7 1 loma prieta earthquake more recent photography collected in late january early february and early march of 1998 captured seacliff failure in response to the severe storms associated with the 1997 1998 el nino for each data set high resolution digital photogrammetric techniques are used to identify the top edge of the cliff at each cliff failure location its position failure length and character are documented results suggest that on a regional scale the seacliffs respond to seismic and climatic forcing differently we have found variation in the magnitude of cliff response along the three sections of coast in the study area large scale climatic events such as the 1997 1998 el nino have a greater impact on both the linear extent of seacliff failure and the amount of cliff retreat

locations of selected small earthquakes in the zagros mountains the zagros mountains of southern iran are marked by a zone of high seismicity and accommodate a significant portion of the convergence between arabia and eurasia due to the lack of dense local seismic or geodetic networks the inferred kinematics of the collision in iran is mainly based on catalogs of teleseismically determined earthquake locations we surveyed all mw 4 5 earthquakes in the harvard centroid moment tensor hcmt and international seismological centre isc catalogs that occurred in the zagros mountains during the period 1992 2002 and that were spanned by interferometric synthetic aperture radar insar images from the ers 1 and 2 satellites we invert the observed deformation for the best fitting point source single fault plane and distributed fault slip for four earthquakes and one unexplained deformation event we find that we can precisely locate earthquakes that are too small to be well located by either the hcmt or isc catalogs allowing us to tie specific earthquakes to active geologic structures

coastal cliff monitoring and analysis of mass wasting processes with the application of terrestrial laser scanning a case study of rugen germany abstract an active landslide affecting a composite sea cliff section of the island of rugen germany was investigated and monitored using terrestrial laser scanning biannual surveys were performed from 2006 to 2011 high resolution scans were used to delineate landslide extensions monitor the spatial and temporal changes and evaluate the processes of mass wasting along the cliff section between may 2006 and may 2011 the multi temporal analysis documents a strong landward progression of the landslide that resulted in an increase in the planimetric area by 32 in the same period 9365 m 3 of soil volume has been removed primarily due to rainfall triggered surface runoff erosion and the resulting slumping this volume loss correlates with the preferential erosion of weak and unconsolidated sediments building up the major part of the cliff face this produced a maximum cliff top retreat of 17 32 m with an average retreat rate of 3 46 m yr 1 the quantification of the mass wasting processes and cliff top retreat demonstrates the substantial effect of local cliff lithology on slope stability and supports a prognosis of the near future development of the landslide furthermore the absence of local wave attack indicators or human activity highlights the major role of subaerial processes in the erosion of the sea cliff these results can be transferred to cliff locations in the urbanised cliff top area nearby that currently suffer similar cliff erosion processes and episodic events of large cliff top retreats the study therefore provides reliable data for the local authorities in charge of hazard assessment and planning and implementation of adaptive countermeasures

seismotectonics of the bitlis zagros fold and thrust belt in northern iraq and surrounding regions from moment tensor analysis northern iraq represents part of the convergent plate boundary between the arabian and eurasian plates the collision zone between these two plates is manifested by the bitlis zagros fold and thrust belt this belt is one of the most seismically active regions among the present active belts this study intends to improve our knowledge on the seismotectonic activities in northern iraq and the surrounding areas to reach this goal we used the waveform moment tensor inversion method to determine the focal depths moment magnitudes fault plane solutions and directions of the principal stress axes of 25 events with magnitudes 3 5 the seismic data of these events were collected from 54 broadband stations which belong to the kandilli observatory and earthquake research institute the incorporated research institutions for seismology the observatories and research facilities for european seismology and the iraqi seismological network computer programs in seismology version 3 30 herrmann and ammon2004 was used for analysis the results show that the focal depth of these events ranged from 15 to 25 km in general the fault plane solutions show that the strike slip mechanism is the most dominant mechanism in the study area usually with a reverse component the stress regime shows three major directions north south northeast southwest and east west these directions are comparable with the tectonic regime in the region

structural styles in the zagros simple folded zone iran arabia eurasia convergence is achieved in the nw zagros by a combination of shortening on nw se trending folds and thrusts mainly in the simple folded zone and by right lateral strike slip on the nw se trending main recent fault a balanced and restored cross section across this part of the range indicates c 49 km of shortening this probably occurred since c 5 ma providing an estimate of the long term shortening rate across the simple folded zone of c 10 mm a 1 the geometries of exposed structures suggest both basement thrusts and thin skinned decollement levels with major folds possibly nucleated above basement faults fold geometries indicate several decollement horizons shale units are candidates as well as evaporites in the neogene mesozoic lower palaeozoic and upper proterozoic successions the se part of the simple folded zone deforms by north south shortening on broadly east west trending folds and thrusts the link between these regions occurs via a set of fault blocks c 400 km wide in total each bounded by north south right lateral faults incremental changes in the strike of some of the folds occur across these right lateral faults with more east west orientations to the east

statistical analysis of factors influencing cliff erosion along a section of the west wales coast u k cliff erosion along a section of the west wales coastline is described rockfalls mudslides and retreating fencelines are evidence of current activity measurements over a two year period 1983 85 gave mean annual recession figures of up to 0 25 m yr 1 for glacial embayments wave refraction modelling and longshore beach surveys confirmed the existence of high and low beaches factors influencing variation in recession rates were identified and measured regression analysis suggested that the volume of beach face material was the dominant explanatory variable in short term cliff erosion

phantom earthquakes and triggered aseismic creep vertical partitioning of strain during earthquake sequences in iran 1 we present evidence for significant aseismic fault slip at shallow depth above a pair of mainshock aftershock sequences in the zagros mountains of iran the two mw 5 9 earthquakes are each spanned by high quality geodetic imagery and have well recorded sequences of aftershocks that occurred beneath a salt decollement earlier studies of the geodetic data inferred that the mainshocks were located above the decollement requiring a 10 km spatial separation between aftershock cluster and earthquake centroid we find that the geodetic data simultaneously allow two slip sources of similar magnitude one within the basement collocated with aftershocks and one shallow source also equivalent to mw 6 responsible for the primary signal apparent in the geodetic imagery should this phenomenon be widespread in the zagros it would partially explain a previously noted discrepancy between observed seismic moment release in the zagros and current convergence rates between the arabian and eurasian plates

slip in the 2010 2011 canterbury earthquakes new zealand the 3rd september 2010 mw 7 1 darfield and 21st february 2011 mw 6 3 christchurch new zealand earthquakes occurred on previously unknown faults we use insar ground displacements sar amplitude offsets field mapping aerial photographs satellite optical imagery a lidar dem and teleseismic body wave modeling to constrain the pattern of faulting in these earthquakes the insar measurements reveal slip on multiple strike slip segments and secondary reverse faults associated with the darfield main shock fault orientations are consistent with those expected from the gps derived strain field the insar line of sight displacement field indicates the main fault rupture is about 45 km long and is confined largely to the upper 10 km of the crust slip on the individual fault segments of up to 8 m at 4 km depth indicate stress drops of 6 10 mpa in each event rupture initiated on a reverse fault segment before continuing onto a strike slip segment the non double couple seismological moment tensors for each event are matched well by the sum of double couple equivalent moment tensors for fault slip determined by insar the slip distributions derived from insar observations of both the darfield and christchurch events show a 15 km long gap in fault slip south west of christchurch which may present a continuing seismic hazard if a further unknown fault structure of significant size should exist there

the 2005 qeshm island earthquake iran a link between buried reverse faulting and surface folding in the zagros simply folded belt summary the 2005 november 27 qeshm island earthquake m w 6 0 provides an excellent opportunity to study coseismic deformation in the zagros simply folded belt with synthetic aperture radar interferometry insar typical of reverse faulting in the zagros slip in the qeshm island earthquake did not rupture the surface however ascending and descending track interferograms spanning the earthquake both show an elliptical pattern of surface deformation in the central part of the island we invert the interferometric data to attain a set of source parameters these show 1 m slip on a steep 50 north dipping reverse fault extending from a maximum depth of 8u p to 4 km below the surface limited aeromagnetic data suggests the fault ruptured the sedimentary cover whether its deepest parts also affected the crystalline basement is not clear source parameters from seismic body wave modelling agree with those from the interferometric modelling using the insar derived model we produce a map of coseismic vertical displacements with which we compare the surface structure of the island coseismic uplift is centred on the eastern end of a major anticline which trends e w parallel with the fault the long term growth of this fold may be controlled primarily by repeated earthquakes on this fault however the uplifted region extends to parts of other nearby folds whose long term growth must have other controls moreover a region of coseismic subsidence lies very close to a part of the qeshm island coastline that displays raised beaches evidence of quaternary uplift therefore the link between reverse faulting and surface folding is not wholly evident from this earthquake alone the local structure is complicated by orthogonal fold axes it may take a large earthquake in a simpler structural setting within the zagros to establish convincingly whether a one to one correlation between faulting and folding exists

temporal patterns and processes of retreat of drumlin coastal cliffs strangford lough northern ireland abstract monthly measurements of erosion pins at sixteen sites around the very low energy marine environment of strangford lough northern ireland were used to investigate temporal patterns and processes of retreat of low cliffs of glacial material erosion rates were extremely varied the mean was 76 49 03 mm a 1 erosion is strongly seasonal with 86 6 of the total erosion occurring during winter september to march periods this seasonal pattern was most exaggerated in some of the more rapidly eroding sites on the exposed eastern side of the lough preparatory processes heavy rainfall desiccation and frost action reduce the compressive strength of the cliff materials and act as important forcing of the erodibility of the cliffs direct wave attack on cliffs around the lough takes place when threshold conditions of wind speed and tidal heights are met tidal levels 1 50 m above o d with wind speed of 15 4 m s 1 30 knots maintaining for more than 4 h during the study period eighteen events exceeding the above criteria were identified extremely low atmospheric pressure has also been identified as important in raising water levels slumps falls topples and slides were the forms of cliff failure observed

comparison of short term seacliff retreat measurement methods in del mar california article i nfo seacliff retreat has been variously characterized as the recession rate of the cliff top of the cliff base and as the bulk recession rate based on volumetric changes of the entire cliff face here these measures of retreat are compared using nine semi annual airborne lidar light detection and ranging surveys of southern california seacliffs changes in the cliff base location where the steeply sloping cliff face intersects the beach include cliff retreat owing to basal erosion but also reflect changes in beach sand level and basal talus deposits averaged over the 2 5 km alongshore study span the cliff base actually prograded seaward about 12 cm during the 4 year study cliff top change was dominated by few relatively large several meters localized retreats cliff face changes that include failures and deposits anywhere on the cliff profile had a relatively small mean magnitude compared to cliff top changes and were more widely distributed alongshore however the similar alongshore averaged cumulative cliff top and net bulk cliff face end point retreat 14 and 19 cm respectively suggest that mean cumulative cliff top retreat can potentially be a viable surrogate for mean net cumulative cliff wide erosion and vice versa over relatively short time periods cliff face erosion occurred repeatedly at some locations confirming the presence of seacliff erosion hot spots during the study period

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

global variations of stress drop for moderate to large earthquakes 1 we investigate the global variation of earthquake stress drops using spectra of about 2000 events of mb 5 5 between 1990 and 2007 we use an iterative least squares method to isolate source displacement spectra from travel path and receiver contributions based on a convolutional model the observed p wave source spectra are corrected with a globally averaged empirical correction spectrum and estimates of near source attenuation assuming a brune type source model we estimate corner frequencies and compute stress drops stress drop estimates for individual earthquakes range from about 0 3 to 50 mpa but the median stress drop of about 4 mpa does not vary with moment implying earthquake self similarity over the mw 5 2 to 8 3 range of our data a comparison of our results with previous studies confirms this observation over most of the instrumentally observable magnitude range while the absolute values of our estimated stress drops depend upon the assumed source model we identify relative regional variations of stress drop that are robust with respect to the processing parameters and modeling assumptions which includes an inherent assumption of constant rupture velocity we find a dependence of median stress drop on focal mechanism with a factor of 3 5 times higher stress drops for strike slip earthquakes and also find a factor of 2 times higher stress drops for intraplate earthquakes compared to interplate earthquakes

convergence history across zagros iran constraints from collisional and earlier deformation the zagros orogen provides a unique opportunity within the alpine system to evaluate the interplay between a young tertiary collision and earlier subduction obduction processes within the crush zone and the sanandaj sirjan internal zone separating the zagros fold belt from central iran we document several major tectonic events taking place at the end of the cretaceous of the eocene and from the mio pliocene onwards ca 20 15 ma contrary to recent interpretations our data cross sections and description of the overall deformation style strongly suggest that the main zagros thrust mzt is deeply rooted possibly to moho depths and that the suture zone effectively runs along the mzt field observations show that the final resorption of the oceanic domain took place slightly after 35 ma and that collision must have started before ca 23 25 ma in northern zagros the shortening rate across the crush zone since the mid miocene 20 15 ma is estimated at a minimum 3 4 mm year shear movements in the crush zone during the eocene oligocene period and extensional strike slip movements in the internal zones during the late cretaceous point to an oblique setting early in the convergence history a geotectonic scenario for convergence from the time of obduction to the present is finally proposed

the role of groundwater in cliff instability an example at cape blanc nez pas de calais france cliff retreat in northern boulonnais is described the distribution of the amount of retreat is related to structural and topographic factors both control the runoff infiltration balance and therefore the mechanical behaviour of the rocks which determines the modes of failure the spatial variability of the retreat rate is explained but predicting the temporal variability of the retreat rate which is central to risk management is much more difficult rainfall and piezometric surface data enhanced a piston flow mechanism during november 2000 the result of its occurrence on the stability of the cliff and conditions of its recurrence are examined with a view to better understanding the rate of recession of coastal cliffs and wiser management of risk copyright 2005 john wiley sons ltd

the varzaghan ahar iran earthquake doublet mw 6 4 6 2 implications for the geodynamics of northwest iran on 2012 august 11 a pair of large damaging earthquakes struck the varzaghan ahar region in northwest iran in a region where there was no major mapped fault or any well documented historical seismicity to investigate the active tectonics of the source region we applied a combination of seismological methods local aftershock network calibrated multiple event relocation and focal mechanism studies field observations structural geology and geomorphological and inversions for the regional stress field the epicentral region is north of the north tabriz fault the first main shock is characterized by right lateral strike slip motion on an almost e w fault plane of about 23 km length extending from the surface to a depth of about 14 km the second main shock occurred on an ene striking fault that dips at 60 70a degrees to the nw independent inversions of focal mechanisms and geologically determined fault kinematic data for the active stress state yield a transpressional tectonic regime with sigma 1 oriented n132e for the region northeast of the north tabriz fault the presence of rigid lithosphere of the south caspian basin implies the kinematic adjustment by northward transferring of the contracted masses through both distributed deformation and structural deflections our results suggest that the kinematic adjustment inside a contracting wedge may occur along interacting crosswise or conjugate faults to accommodate low rates of internal deformation at a global scale our results indicate that despite the basic assumption of rigid blocks in geodetic plate modelling internal deformation of block like regions could control the kinematics of deformation and the level of seismic hazard within and around such regions of low deformation rate

statistical and empirical analyses of the triggers of coastal chalk cliff failure the triggering factors of rock falls remain unknown due to a lack of exhaustive regular and accurate surveys based on an inventory of 331 rock falls collected weekly between 2002 and 2009 from veules les roses to le treport upper normandy the relationships between coastal chalk cliff rock falls dates and geomorphological features and external factors commonly agreed as triggering rainfall temperature variations tide and wind are studied the combination of multivariate statistical and empirical analyses indicates that 1 cold and dry weather and high rainfall and high wind are the conditions most likely to trigger rock falls 2 the main triggering factors of rock falls are effective rainfall for rock falls mostly between 200 and 1400 m3 or larger than 10 000 m3 and coming from the whole cliff face freeze thaw cycles especially for rock falls smaller than 200 m3 and coming from the foot and top of the cliff face and marine roughness rock falls mainly smaller than 200 m3 and coming from the cliff foot however the contribution of each factor to triggering is difficult to determine because of combinations of factors 85 of 331 cases relays of processes and hysteresis phenomena in view of these first results it is still presumptuous to predict the location and time of triggering of rock falls however the statistical and naturalistic approaches adopted and the observations made in this study are from an original database and constitute a real starting point for the prediction and prevention of the hazard of coastal chalk cliff rock falls in upper normandy copyright 2015 john wiley sons ltd

mechanical stratigraphy and folding style of the lurestan region in the zagros fold thrust belt iran abstract the structural style of the folds from the central part of the lurestan salient located in the nw portion of the zagros fold thrust belt has been studied by constructing a regional balanced cross section from field data existing geological maps seismic profiles stratigraphic surface sections and well data the regional balanced structural cross section that is constructed from the high zagros fault to the mountain front fault highlights the difference in the folding style across the area the vertical and lateral changes in the style of the folding indicate the influence of mechano stratigraphic contrast between the sedimentary units three main decollement levels the basal lower palaeozoic the intermediate triassic and the upper upper cretaceous lower palaeocene have been interpreted folds developed during the zagros fold thrust belt evolution above and below these decollement horizons are decoupled from each other and are different in both geometry and size similarly thickness and facies changes of some formations across the region cause lateral variation in folding pattern from the north to the south polyharmonic folds exist in the south where the different structural levels are relatively strongly coupled to the north however strongly disharmonic folding occurs where a combination of increased decollement thickness and decreased mechanical competence has led to decoupling at different structural levels this change in folding style has a direct impact on hydrocarbon exploration in the area to reduce structural risk in exploration the incorporation of high resolution deep seismic data with the surface geology is recommended for future hydrocarbon exploration activities within the lurestan region

source parameters of the 1 october 1995 dinar turkey earthquake from sar interferometry and seismic bodywave modelling abstract the 1 october 1995 m s 6 1 dinar earthquake ruptured a 10 km section of the nw se dinar civril fault there are discrepancies between the published source parameters from seismic data with seismic moments in disagreement by over a factor of two we use both sar interferometry and seismic bodywave modelling to determine earthquake source parameters an interferogram generated from ers 1 2 sar imagery spanning the event and separated by 5 months is used to derive source parameters by a downhill simplex inversion with multiple monte carlo restarts we model the displacements in the satellite line of sight initially using uniform slip on a rectangular dislocation in an elastic half space the resultant model fault plane agrees in strike and location with the observed surface break but systematic residuals exist in the line of sight deformation field resulting in a r m s residual of 20 mm in the interferogram the residuals are reduced if the depth distribution of slip is allowed to vary spatially in four segments along a continuous fault plane our best fitting solution with a r m s misfit of 8 mm reveals two distinct areas of slip on the fault plane strike 145 dip 49 rake 270 a main rupture slipping by 1 44 m between depths of 1 and 8 km becoming deeper to the se and matching the observed surface rupture and an along strike continuation to the nw of the same fault plane but between depths of 8 and 13 km and not associated with a surface break the total geodetic moment 4 5 0 1 10 18 nm is more than twice as large as published seismic moments based on the inversion of p waveforms alone but close to the harvard cmt moment 4 7 10 18 nm we use sh waveforms in addition to the p waves used previously to determine an alternative seismic source mechanism sh waves constrain the depth to be shallower than solutions based on p waves alone agreeing with the depths from the interferometric inversion and resulting in a larger moment 3 1 0 4 10 18 nm than the previous bodywave estimates 2 2 1 10 18 nm the cmt moment reduces in magnitude to a similar size 3 3 10 18 nm if the centroid depth and fault dip are constrained to the values determined from bodywave modelling and interferometry thus the geodetic moment is 40 bigger than the moment determined from seismology

orogenic plateau growth expansion of the turkish iranian plateau across the zagros fold and thrust belt 1 this paper shows how the turkish iranian plateau grows laterally by incrementally incorporating adjacent parts of the zagros fold and thrust belt the limit of significant seismogenic thrusting in the zagros mw 5 occurs close to the regional 1250 m elevation contour the seismicity cutoff is not a significant bedrock geology boundary elevations increase northward toward regional plateau elevations of 2 km implying that another process produced the extra elevation between the seismogenic limit of thrusting and the suture this process is a plausibly ductile thickening of the basement suggesting depth dependent strain during compression similar depth dependant crustal strain may explain why the tibetan plateau has regional elevations 1500 m greater than the elevation limit of seismogenic thrusting at its margins we estimate 68 km shortening across the zagros simply folded belt in the fars region and 120 km total shortening of the arabian plate the dezful embayment is a low strain zone in the western zagros deformation is more intense to its northeast in the bakhtyari culmination the orogenic taper across strike topographic gradient across the dezful embayment is 0 0004 and across the bakhtyari culmination 0 022 lateral plateau growth is more pronounced farther east fars where a more uniform structure has a taper of 0 010 up to elevations of 1750 m a 100 km wide region of the zagros further northeast has a taper of 0 002 and is effectively part of the turkish iranian plateau internal drainage enhances plateau development but is not a pre requisite aspects of the seismicity structure and geomorphology of the zagros do not support critical taper models for fold and thrust belts

quantifying the environmental controls on erosion of a hard rock cliff linking hard rock coastal cliff erosion to environmental drivers is challenging with weak relationships commonly observed in comparisons of marine and subaerial conditions to the timing and character of erosion the aim of this paper is to bring together datasets to explore how best to represent conditions at the coast and to test relationships with erosion which on this coast is primarily achieved via rockfalls on the n yorkshire coast in the uk we compare a continuously monitored microseismic dataset regionally monitored coastal environmental conditions modelled at cliff conditions and periodic high resolution 3d monitoring of changes to the cliff face over a 2 year period cliff top microseismic ground motions are generated by a range of offshore nearshore and at cliff sources we consider such ground motions as proxies for those conditions that promote the occurrence of rockfalls and erosion both these data and modelled at cliff water levels provide improved insight into conditions at and wave energy transfer to the cliff the variability in microseismic modelled and regionally monitored environmental data derives statistically significant relationships with increases in the occurrence of rockfalls the results demonstrate a marine control on the total volume and size characteristics of rockfalls the strongest relationships found are with rockfalls sourced from across the entire cliff rather than just at the toe indicating that the marine influence albeit indirectly extends above and beyond the area inundated these results identify failure mechanisms driving erosion where a range of processes unique to the coast trigger failure but in a manner beyond purely wave action at the cliff toe greater erosion occurs at the cliff toe however comparing water level inundation frequency microseismic energy transfer and erosion we observe that heights up the cliff that correspond with water levels associated with low frequency high energy storms or more frequent inundation do not experience increased erosion our results describe the relationship between inundation duration energy transfer and erosion of hard rock cliffs and illustrate the relative intensity of erosion response to variations in these conditions implicitly our data suggests that in future cliffed rocky coasts may be relatively quick to respond to changes in environmental forcing

recent deep seated coastal landsliding at san onofre state beach california abstract airborne lidar collected during the period 1998 2010 and differential gps surveys conducted over 2008 2013 show recent reactivation and movement of a large deep seated coastal landslide at san onofre state beach san diego county california the overall slide complex extends about 700 m alongshore 150 m inland and an unknown distance offshore differencing digital elevation models and tracking field monuments benchmarks provide time series of quantitative topographic landslide changes and new insight in to the slide motion sequences and mechanics the slide contains several distinct primary and secondary regions moving and deforming at different rates primary slide motion includes slow seaward translational motion rotational slipping and upward offshore movement secondary processes of basal wave erosion and new inland cliffline failures contribute to primary landslide destabilization the landslide exhibits lithologic and structural controls is driven by a combination of marine and subaerial processes influences local beach morphology and deviates from typical southern california coastal cliff processes which mostly involve shallow landslides and topples large scale cross shore slide rotation has recently created new nearshore reefs eroded cliff sediments provide a local beach sand source and probably influence local nearshore ecosystems all known time periods of major historical landslide activity were preceded by elevated seasonal rainfall and analysis suggests elevated rainfall generated primary slide motion as opposed to wave action as of spring 2013 landslide activity has slowed but continued positive feedbacks including toe removal by wave activity suggest that future landsliding will probably threaten coastal infrastructure

numerical analysis of coastal cliff failure along the pembrokeshire coast national park wales uk cliff stability within the pembrokeshire coast national park was evaluated using a numerical model applied at four sites representative of rock mass failure phenomena and major sedimentary geological sequences the sites were mill bay old red sandstone st govan s head carboniferous limestone dinantian druidston millstone grit namurian and lower coal measures westphalian and wiseman s bridge lower coal measures westphalian the study integrated a range of geotechnical parameters measured in the field and laboratory into a model to predict the likely failure mechanisms the model is based on the existence of rock prisms delineated by structural parameters i e joints bedding planes and critical tension fractures behind the cliff face an iterative approach is used to define the dip of the most probable stepped failure surface at the base of any potentially unstable multiblock system and to calculate the sliding and toppling forces for each block in the cliff mass prediction compared favourably with field observations at three of the four selected sites i e druidston st govan s head and wiseman s bridge at druidston sliding is predicted and dominates in the basal blocks whilst toppling is confined to the upper cliff and is dependent on movement of the lower structural units st govan s head is shown to have a low risk of toppling and sliding and this was predicted except where basal undercutting reaches a depth of 1 0 m or lateral forces exceed 100 kn m 2 when failure could occur copyright 1998 john wiley sons ltd

temporal and spatial variations of chalk cliff retreat in east sussex 1873 to 2001 spatial and temporal variations of chalk cliff retreat rates over a 130 yr period are examined for 22 km of the east sussex chalk coastline between brighton and belle toutetout lighthouse england data are derived from maps surveyed between 1873 and 1925 28 and air photographs dating from 1973 and 2001 the long term average cliff retreat rate over the period 1873 to 1973 is 0 36 m y 1 and from 1873 to 2001 is 0 35 m y 1 over the whole 23 km study area rates calculated over shorter time slices indicate a decline in cliff retreat 0 37 m y 1 between 1873 and 1925 28 0 35 m y 1 between 1925 28 and 1973 0 27 m y 1between 1973 and 2001 temporal variations are unlikely to be due to variations in precipitation and frost days though the relationship remains uncertain due to the resolution of available cliff retreat and climatic data changes in wave climate are small and cannot be responsible for the decline in cliff retreat the study suggests that the most important factors causing the measured decline in cliff retreat rates are firstly the loss of cliff toe beaches over time and secondly widening of the rocky shore platforms that front the cliffs some of the spatial variability in retreat rates can be explained by local variations in lithology

new views on earthquake faulting in the zagros fold and thrust belt of iran the zagros fold and thrust belt is amongst the world s most seismically active mountain ranges and is influential in our understanding of continental collisions the presence of hormuz salt at the base of the 10 km thick folded sedimentary cover together with the general absence of coseismic surface rupturing have led to an assumption that earthquakes are concentrated within the basement here we reinterpret the seismicity of the zagros in light of insar studies that show some recent earthquakes ruptured the competent group of mechanically strong strata in the lower sedimentary cover local network data demonstrate that microseismicity occurs within the basement reaching depths of 20 km and in places 30 km centroid depths of larger mw 5 earthquakes are mostly 4 14 km with rare events up to 20 km and 28 km along the oman line within the simply folded belt most of these events are contained within the competent group and are limited to mw 6 5 earthquakes occur earthquakes within the competent group can account for much of the overall shortening at this level but the seismic strain rate in the basement is much lower it is unclear whether the basement deforms by aseismic creep or folding beneath the sfb or by ductile shortening beneath the high zagros or iranian plateau

active accommodation of plate convergence in southern iran earthquake locations triggered aseismic slip and regional strain rates 1 we present a catalog of interferometric synthetic aperture radar insar constraints on deformation that occurred during earthquake sequences in southern iran between 1992 and 2011 and explore the implications on the accommodation of large scale continental convergence between saudi arabia and eurasia within the zagros mountains the zagros mountains a salt laden fold and thrust belt involving 10 km of sedimentary rocks overlying precambrian basement rocks have formed as a result of ongoing continental collision since 10 20 ma that is currently occurring at a rate of 3 cm yr we first demonstrate that there is a biased misfit in earthquake locations in global catalogs that likely results from neglect of 3 d velocity structure previous work involving two m 6 earthquakes with well recorded aftershocks has shown that the deformation observed with insar may represent triggered slip on faults much shallower than the primary earthquake which likely occurred within the basement rocks 10 km depth we explore the hypothesis that most of the deformation observed with insar spanning earthquake sequences is also due to shallow triggered slip above a deeper earthquake effectively doubling the moment release for each event we quantify the effects that this extra moment release would have on the discrepancy between seismically and geodetically constrained moment rates in the region finding that even with the extra triggered fault slip significant aseismic deformation during the interseismic period is necessary to fully explain the convergence between eurasia and saudi arabia

himalayan seismic hazard the devastating earthquake in bhuj on 26 january 2001 highlighted the high earthquake risk in the indian region of gujarat in their perspective bilham et al warn that major earthquakes may be expected in another part of india the himalayan arc an analysis of historic earthquakes suggests that several major earthquakes are overdue in this region but that recent low activity has focused attention away from the himalayan arc projections from earlier earthquakes suggest that just one of the possibly overdue himalayan earthquakes may lead to 200 000 predictable fatalities

insights into the 1968 1997 dasht e bayaz and zirkuh earthquake sequences eastern iran from calibrated relocations insar and high resolution satellite imagery summary the sequence of seismicity in the dasht e bayaz and zirkuh region of northeastern iran which includes 11 destructive earthquakes within a period of only 30 years forms one of the most outstanding examples of clustered large and intermediate magnitude seismic activity in the world we perform a multiple event relocation analysis with procedures to remove systematic location bias of 169 earthquakes most of which occurred in the period 1968 2008 to better image the distribution of seismicity within this highly active part of iran the geographic locations of the clustered earthquakes were calibrated by the inclusion of phase arrivals from seismic stations at short epicentral distances and also by matching the relative locations of the three largest events in the study to their mapped surface ruptures the two independent calibration methods provide similar results that increase our confidence in the accuracy of the distribution of relocated epicentres these calibrated epicentres combined with the mapping of faults from high resolution satellite imagery and from an insar derived constraint on fault location in one case allow us to associate individual events with specific faults and even with specific segments of faults to better understand the nature of the active tectonics in this region during the past four decades several previous assumptions about the seismicity in this region are confirmed 1 that the 1968 august 30 mw 7 1 dasht e bayaz earthquake nucleated at a prominent segment boundary and left step in the fault trace 2 that the 1968 september 11 mw 5 6 aftershock occurred on the dasht e bayaz fault at the eastern end of the 1968 rupture and 3 that the 1976 november 7 mw 6 0 qayen earthquake probably occurred on the e w left lateral avash fault we show in addition that several significant events including the 1968 september 1 and 4 mw 6 3 and 5 5 ferdows earthquakes the 1979 january 16 mw 6 5 and 1997 june 25 mw 5 9 boznabad events and the 1979 december 7 mw 5 9 kalat e shur earthquake are likely to have ruptured previously unknown faults our improved description of the faulting involved in the 1968 1997 earthquake sequence highlights the importance of rupturing of conjugate left and right lateral faults in closely spaced events or potentially even within a single earthquake as was likely the case at the eastern end of the 1979 november 27 mw 7 1 khuli buniabad main shock the high level of clustered seismic activity probably results from the simultaneous activity on left and right lateral faults an inherently unstable arrangement that must evolve rapidly the combination of high resolution satellite imagery and calibrated earthquake locations is a useful tool for investigating active tectonics even in the absence of detailed field observations

short term patterns and processes of coastal cliff erosion in santa barbara california abstract sequential terrestrial lidar scans and 3d volumetric change were used to document coastal cliff erosion at several sites along the coast of santa barbara california retreat rates along the base middle and cliff top were calculated for six different scans throughout the el nino of 2015 16 to quantitatively link wave action to cliff base erosion and two seasonal scans were taken during 2017 to investigate patterns in erosion and retreat rates retreat rates along the cliff base middle and top converged over the course of the study period and observations and patterns in erosion help characterize the fundamental mechanisms that govern the retreat of soft shale cliffs the base and middle of the cliff preferentially eroded during high energy swell events and are strongly coupled whereas cliff top erosion is temporally variable and retreat rates increased with higher seasonal rainfall totals we observe that the cliff base experiences erosion from both abrasion and mechanical wave action but the dominant processes is segregated by elevation above the cliff toe abrasion was found to be the dominant processes at elevations up to 0 8 m above the cliff toe whereas block removal from mechanical wave action was dominant at elevations above 0 8 m threshold behavior was observed for cliff base retreat rates and spearman correlation coefficients suggest strong relationships with the sum of the wave energy flux imparted to the cliff base r2 0 84 the sum of the wave energy flux 35 000 w m r2 0 82 and the average total water level above the cliff toe r2 0 85 threshold behavior and maximum retreat rates occurred when average total water levels were 0 8 m above the cliff toe seasonal schmidt hammer measurements suggest that energy thresholds are modulated by weathering rates which remain poorly understood these thresholds when exceeded produced the highest cliff base retreat rates during the study period and reinforce the expectation that coastal cliff retreat rates will increase with rising sea levels

slip history and dynamic implications of the 1999 chi chi taiwan earthquake we investigate the rupture process of the 1999 chi chi taiwan earthquake using extensive near source observations including three component velocity waveforms at 36 strong motion stations and 119 gps measurements a three plane fault geometry derived from our previous inversion using only static data ji et al 2001 is applied the slip amplitude rake angle rupture initiation time and risetime function are inverted simultaneously with a recently developed finite fault inverse method that combines a wavelet transform approach with a simulated annealing algorithm ji et al 2002b the inversion results are validated by the forward prediction of an independent data set the teleseismic p and sh ground velocities with notable agreement the results show that the total seismic moment release of this earthquake is 2 7 10 20 n m and that most of the slip occurred in a triangular shaped asperity involving two fault segments which is consistent with our previous static inversion the rupture front propagates with an average rupture velocity of 2 0 km s 1 and the average slip duration risetime is 7 2 s several interesting observations related to the temporal evolution of the chi chi earthquake are also investigated including 1 the strong effect of the sinuous fault plane of the chelungpu fault on spatial and temporal variations in slip history 2 the intersection of fault 1 and fault 2 not being a strong impediment to the rupture propagation and 3 the observation that the peak slip velocity near the surface is in general higher than on the deeper portion of the fault plane as predicted by dynamic modeling

crustal scale cross sections across the nw zagros belt implications for the arabian margin reconstruction quantified balanced and restored crustal cross sections across the nw zagros mountains are presented in this work integrating geological and geophysical local and global datasets the balanced crustal cross section reproduces the surficial folding and thrusting of the thick cover succession including the near top of the sarvak formation 90 ma that forms the top of the restored crustal cross section the base of the arabian crust in the balanced cross section is constrained by recently published seismic receiver function results showing a deepening of the moho from 42 2 km in the undeformed foreland basin to 56 2 km beneath the high zagros the internal parts of the deformed crustal cross section are constrained by new seismic tomographic sections imaging a 50 ne dipping sharp contact between the arabian and iranian crusts these surfaces bound an area of 10800 km 2 that should be kept constant during the zagros orogeny the arabian crustal cross section is restored using six different tectonosedimentary domains according to their sedimentary facies and palaeobathymetries and assuming airy isostasy and area conservation while the two southwestern domains were directly determined from well constrained surface data the reconstruction of the distal domains to the ne was made using the recent margin model of wrobel daveau et al 2010 and fitting the total area calculated in the balanced cross section the arabian continental oceanic boundary at the time corresponding to the near top of the sarvak formation is located 169 km to the ne of the trace of the main recent fault shortening is estimated at 180 km for the cover rocks and 149 km for the arabian basement including all compressional events from late cretaceous to recent time with an average shortening rate of 2 mm yr 1 for the last 90 ma