random variability explains apparent global clustering of large earthquakes 1 the occurrence of 5 mw 8 5 earthquakes since 2004 has created a debate over whether or not we are in a global cluster of large earthquakes temporarily raising risks above long term levels i use three classes of statistical tests to determine if the record of m 7 earthquakes since 1900 can reject a null hypothesis of independent random events with a constant rate plus localized aftershock sequences the data cannot reject this null hypothesis thus the temporal distribution of large global earthquakes is well described by a random process plus localized aftershocks and apparent clustering is due to random variability therefore the risk of future events has not increased except within ongoing aftershock sequences and should be estimated from the longest possible record of events

applying the coulomb failure function with an optimally oriented plane to the 2008 mw 7 9 wenchuan earthquake triggering the coulomb failure function cff quantitatively describes static stress changes in secondary faults near the source fault of an earthquake cff can be employed to monitor how static stress transfers and then shed some light on the probability of successive events occurring around a source fault in this paper we focus on the cff and particularly on optimally oriented planes we present a unified model to determine an optimally oriented plane and its corresponding coulomb stress then apply the model to the 2003 mw 6 6 bam iran earthquake and the 2008 mw 7 9 wenchuan china earthquake thereby checking its effectiveness our results show that spatial correlation between positive coulomb stress changes and aftershocks are for the 2003 bam earthquake 47 06 when elastic coulomb stress changes are resolved on uniform planes and 87 53 when these are resolved on optimally oriented planes at depth for the 2008 wenchuan earthquake the correlations are 45 68 and 58 20 respectively it is recommended that account be taken of optimally oriented planes when drawing a coulomb stress map for analyzing earthquake triggering effects

the 1994 sefidabeh earthquakes in eastern iran blind thrusting and bedding plane slip on a growing anticline and active tectonics of the sistan suture zone summary in 1994 a sequence of five earthquakes with mw 5 5 6 2 occurred in the sistan belt of eastern iran all of them involving motion on blind thrusts with centroid depths of 5 10 km coseismic ruptures at the surface involved bedding plane slip on a growing hanging wall anticline displaying geomorphological evidence of uplift and lateral propagation the 1994 earthquakes were associated with a nw trending thrust system that splays off the northern termination of a major n s right lateral strike slip fault elevation changes along the anticline ridge suggest that displacement on the underlying thrust dies out to the nw away from its intersection with the strike slip fault this is a common fault configuration in eastern iran and accommodates oblique ne sw shortening across the n s deforming zone probably by anticlockwise rotations about a vertical axis this style of fault kinematics may be transitional to a more evolved state that involves partitioning of the strike slip and convergent motion onto separate subparallel faults

seismic tomography of the colorado rocky mountains upper mantle from crest lithosphere asthenosphere interactions and mantle support of topography abstract the crest experiment colorado rocky mountains experiment and seismic transects integrated the earthscope usarray transportable array with portable and permanent stations to provide detailed seismic imaging of crust and mantle properties beneath the highest topography region of the rocky mountains inverting approximately 14 600 p and 3600 s wave arrival times recorded at 160 stations for upper mantle v p and v s structure we find that large v p perturbations relative to ak135 of 7 and v s variations of 8 take place over very short approaching tens of kilometers lateral distances highest heterogeneity is observed in the upper 300 km of the mantle but well resolved low velocity features extend to the top of the transition zone in portions of these images the previously noted low velocity upper mantle aspen anomaly is resolved into multiple features the lowest v p and v s velocities in the region are found beneath the san juan mountains which is clearly distinguished from other low velocity features of the northern rio grande rift taos latir region aspen region and below the never summer mountains we suggest that the san juan anomaly and a similar feature below the taos latir region of northern new mexico are related to delamination and remnant heat and melt beneath these sites of extraordinarily voluminous middle cenozoic volcanism we interpret a northeast southwest grain in velocity structure that parallels the colorado mineral belt to depths near 150 km as being reflective of control by uppermost mantle proterozoic accretionary lithospheric architecture further to the north and west the wyoming province and northern colorado plateau show high velocity features indicative of thick 150 km preserved archean and proterozoic lithosphere respectively overall we interpret the highly heterogeneous uppermost mantle velocity structure beneath the southern rocky mountains as reflecting interfingered chemical proterozoic lithosphere that has been is currently being replaced and modified by upwelling asthenosphere low velocity features resolved here indicate that this process may be sourced as deeply as the top of the mantle transition zone at 410 km one driving mechanism for this is upper mantle interaction between upwelling hydration induced partial melt and destabilized downwelling lithosphere in the deeper upper mantle tomographic imaging of mantle seismic velocity and crustal thickness results and modeling from the crest experiment indicate that the highest elevations of the colorado rocky mountains are substantially supported by the mantle and strong correlations between low velocity mantle and thin crust high topography are noted across the region this along with rich upper mantle seismic heterogeneity suggests that mantle buoyancy and dynamics are central to present day topographic support and recent geomorphic evolution of the region

combination of precise leveling and insar data to constrain source parameters of the mw 6 5 26 december 2003 bam earthquake we used new precise leveling data acquired 40 days after the bam earthquake in combination with radar interferometry observations from both ascending and descending orbits to investigate static deformation associated with the 2003 bam earthquake we invert this geodetic data set to gain insight into the fault geometry and slip distribution of the rupture the best fitting dislocation model is a steeply east dipping right lateral strike slip fault that has a size of 11 by 8 km and strikes n2 w we find that such smooth geometry fits available geodetic data better than previously proposed models for this earthquake our distributed slip model indicates a maximum strike slip of 3 m occurring about 3 to 5 km deep the slip magnitude and depth of faulting taper to the north where the fault approaches the bam city inclusion of crustal layering increases the amount of maximum slip inferred at depth by about 4

stress transfer relations among the earthquakes that occurred in kerman province southern iran since 1981 summary we explore the possible stress triggering relationship of the m 6 4 earthquakes that occurred in kerman province southern iran since 1981 we calculated stress changes due to both coseismic sudden movement in the upper crust and the time dependent viscous relaxation of the lower crust and or upper mantle following the event four events of m 6 4 occurred between 1981 and 2005 on and close to the gowk fault show a clear coulomb stress load to failure relationship the 2003 m 6 5 bam earthquake however which occurred approximately 95 km sw of the closest gowk event shows a very weak stress relation to preceding earthquakes the coseismic static stress change at the hypocentre of the bam earthquake is quite small 0 006 bars the time dependent post seismic stress change could be 26 times larger or 7 times lower than that of coseismic static stress alone depending on the choice of viscoelastic crustal model and the effective coefficient of friction given the uncertainties in the viscoelastic earth models and the effective coefficient of friction we cannot confidently conclude that the 2003 bam event was brought closer to failure through coseismic or post seismic stress loading interestingly the southern gowk segment with a similar strike to that of the bam fault experienced a stress load of up to 8 3 bars between 1981 and 2003 and is yet to have a damaging earthquake

quantitative description of induced seismic activity before and after the 2011 tohoku oki earthquake by nonstationary etas models 1 the epidemic type aftershock sequence etas model is extended for application to nonstationary seismic activity including transient swarm activity or seismicity anomalies in a seismogenic region the time dependent rates of both background seismicity and aftershock productivity in the etas model are optimally estimated from hypocenter data these rates can provide quantitative evidence for abrupt or gradual changes in shear stress and or fault strength due to aseismic transient causes such as triggering by remote earthquakes slow slips or fluid intrusions within the region this extended model is applied to data sets from several seismic events including swarms that were induced by the m9 0 tohoku oki earthquake of 2011

ground motion prediction equation for small to moderate events at short hypocentral distances with application to induced seismicity hazards abstract the evaluation of seismic hazard from induced seismicity requires the development of ground motion prediction equations gmpes that are tuned to the key magnitude distance range for such applications i use events of m 3 6 at hypocentral distances less than 40 km drawn from the next generation attenuation west 2 nga west 2 database to develop a gmpe that accounts correctly for point source scaling in both magnitude and distance space for such events the developed gmpe is in demonstrable agreement with the nga west 2 database and with the predictions of a stochastic point source simulation model the database is sparse at close distances implying epistemic uncertainty of as much as a factor of 2 in ground motion amplitudes within 10 km of the hypocenter an important conclusion from this study is that the ground motion amplitudes for moderate induced events could be much larger near the epicenter than predicted by most of the nga west 2 gmpes the potential for large motions is a consequence of the shallow depth of induced events which places the earthquake fault only a short distance beneath the epicenter

the impact of static stress change dynamic stress change and the background stress on aftershock focal mechanisms the focal mechanisms of earthquakes in southern california before and after four m 6 7 main shocks provide insight into how fault systems respond to stress and changes in stress the main shock static stress changes have two observed impacts on the seismicity changing the focal mechanisms in a given location to favor those aligned with the static stress change and changing the spatial distribution of seismicity to favor locations where the static stress change aligns with the background stress the aftershock focal mechanisms are significantly aligned with the static stress changes for absolute stress changes of 0 02 mpa for up to 20 years following the main shock the dynamic stress changes have similar although smaller effects on the local focal mechanisms and the spatial seismicity distribution dynamic stress effects are best observed at long periods 30 60 s and for metrics based on repeated stress cycling in the same direction this implies that dynamic triggering operates at least in part through cyclic shear stress loading in the direction of fault slip the background stress also strongly controls both the preshock and aftershock mechanisms while most aftershock mechanisms are well oriented in the background stress field 10 of aftershocks are identified as poorly oriented outliers which may indicate limited heterogeneity in the postmain shock stress field the fault plane orientations of the outliers are well oriented in the background stress while their slip directions are not implying that the background stress restricts the distribution of available fault planes

some insight on why bam iran was destroyed by an earthquake of relatively moderate size 1 the bam iran earthquake of 2003 resulted in one of the worst human disaster in recent years yet the magnitude of the event mw 6 6 was relatively moderate we show that the remarkable recording of the ground motion produced in the city itself contains some clues which help explain this disaster we identify three factors whose unfortunate combination led to the strong ground shaking which destroyed the city 1 the rayleigh like speed of the rupture 2 the high slip velocity which exceeded 2m s over a large part of the fault 3 the strong directivity which focused the elastic energy released directly toward the city

fault slip distribution of two june 2000 m w 6 5 earthquakes in south iceland estimated from joint inversion of insar and gps measurements abstract we present the first detailed estimates of co seismic slip distribution on faults in the south iceland seismic zone sisz an area of bookshelf tectonics we have estimated source parameters for two m w 6 5 earthquakes in the sisz on june 17 and 21 2000 through a joint inversion of insar and gps measurements our preferred model indicates two simple 15 km long near vertical faults extending from the surface to approximately 10 km depth the geometry is in good agreement with the aftershock distribution the dislocations experienced pure right lateral strike slip reaching maxima of 2 6 m and 2 9 m for the june 17 and 21 events respectively we find that the distribution of slip with depth may be correlated to crustal layering with more than 80 of the total geometric moment release occurring in the uppermost 6 km according to the distributed slip model the middle and upper crust appears to be more apt to generate large displacements than the lower crust the geodetic estimates of seismic moments are 4 4 10 18 nm m w 6 4 and 5 0 10 18 nm m w 6 5 the total moment released by the two events equals that generated by several decades of plate motion in the area but is only a fraction of the moment accumulated in the area since the last major earthquake in 1912

co seismic deformation following the 2007 bengkulu earthquake constrained by grace and gps observations abstract gravity changes caused by giant earthquakes can be detected by gravity recovery and climate experiment grace which provide new constraints on earthquake ruptures however detailed rupture seismic moment and density displacement induced gravity changes are not clear for less than mw 8 5 earthquakes in this paper the fault parameters of the 2007 mw 8 4 bengkulu earthquake are retrieved from grace and gps data and the fault slip distribution is inverted using gps data furthermore the theoretical coseismic displacements and coseismic gravity changes from different slip models are compared with gps and grace data the results show that the significant positive and negative gravity anomalies with a peak magnitude of 2 0 to 1 3 gal are extracted from grace data the grace inverted and joint inverted seismic moment of the bengkulu earthquake are 3 27 10 21 nm and 3 30 10 21 nm with the rake angle of 108 and 114 respectively the gps inverted mw 8 4 earthquake is mainly dominated by the thrusting with slight right lateral strike slip which is consistent with the focal mechanism grace observed coseismic gravity changes agree well with the results from the fault models based on the spherically dislocation theories in spatial pattern but are larger than model estimated results in magnitude the coseismic gravity changes caused by the density change are basically same as those caused by the vertical displacement in the magnitude of order which are 0 8 to 0 2 gal and 0 2 to 1 4 gal for the caltech model 0 9 to 0 2 gal and 0 5 to 1 3 gal for the usgs model and 0 9 to 0 2 gal and 0 3 to 1 3 gal for the gps inverted layered model in addition both the near field and the far field displacements calculated from the caltech model and gps inverted layered model are in good agreement with the gps observations whereas the usgs model has good agreement in the far field and poor agreement in the near field with the gps observations especially in the pagai selatan area

refining seismic parameters in low seismicity areas by 3d trenching the alhama de murcia fault se iberia three dimensional paleoseismology in strike slip faults with slip rates less than 1 mm per year involves a great methodological challenge we adapted 3d trenching to track buried channels offset by the alhama de murcia seismogenic left lateral strike slip fault se iberia a fault net slip of 0 9 0 1 mm yr was determined using statistical analysis of piercing lines for one buried channel whose age is constrained between 15 2 1 1 ka and 21 9 22 3 cal bp this value is larger and more accurate than the previously published slip rates for this fault the minimum number of five paleo earthquakes identified since the deposition of dated layers suggests a maximum average recurrence interval of approximately 5 ka the combination of both seismic parameters yields a maximum slip per event between 5 3 and 6 3 m we show that accurately planned trenching strategies and data processing may be key to obtaining robust paleoseismic parameters in low seismicity areas

the july 20 2017 m6 6 kos earthquake seismic and geodetic evidence for an active north dipping normal fault at the western end of the gulf of gokova se aegean sea on july 20 2017 22 31 utc a strong mw 6 6 earthquake occurred at shallow depth between kos island greece and bodrum turkey we derive a co seismic fault model from joint inversion of geodetic data gnss and insar assuming that the earthquake can be modelled by the slip of a rectangular fault buried in an elastic and homogeneous half space the gnss observations constrain well most of the model parameters but do not permit to discriminate between south and north dipping planes however the interferograms produced from c band esa sentinel 1 data give a clear preference to the north dipping plane we also map surface motion away from the satellite along the turkish coast from bodrum towards the east which reached about 17 cm onshore islet karaada the best fit model is obtained with a 37 north dipping n283 e striking normal fault in agreement with the published moment tensor solutions the resolved slip vector is dominantly normal with a slight component of left lateral motion 15 the surface projection of the seismic fault outcrops in the gokova ridge area a well developed bathymetric feature inside the western gulf of gokova our geodetic model fits the pattern of the shallow north dipping aftershocks obtained from rigorous relocation of all available recordings in the region about 1120 events relocated mainshock is at 36 955 n 27 448 e depth at 9 2 km 0 5 km the relocated aftershocks also indicate clustering at both ends of the rupture and seismicity triggering mainly towards the east and the north within 2 weeks following the mainshock we also analysed regional gps data interseismic velocities and obtained an extension rate of 3 2 mm yr across the gokova rift along a direction n165 e

coseismic three dimensional displacements determined using sar data theory and an application test we present a methodology to construct three dimensional deformation maps using different parameters that can be extracted using sar data we apply the methodology using envisat sar data before and after the december 26 th 2003 mw 6 6 bam earthquake in iran to determine spatial quasi continuous three dimensional coseismic deformation maps two near vertical deformation offset components are computed using envisat asar differential interferometry dinsar while two horizontal deformation offset components are measured using sub pixel correlation techniques applied to asar amplitude images using the presented methodology we combine four unevenly precise independent projections of surface coseismic deformation to obtain the full three dimensional coseismic deformation field caused by an earthquake the full 3 d coseismic displacement vector is modeled using elastic deformation models constraining details of the fault geometry and slip distribution at depth results from the inversion are interpreted in the framework of the iranian present day tectonism full exploitation of dense 3 d coseismic surface deformation using sar data even for moderate earthquakes should facilitate distinguishing between different interpretations of the mechanical properties of seismically active areas and within the inherent ambiguity of the geophysical inversion solutions

size distribution of parkfield s microearthquakes reflects changes in surface creep rate s u m m a r y the nucleation area of the series of m6 events in parkfield has been shown to be characterized by low b values throughout the seismic cycle since low b values represent high differential stresses the asperity structure seems to be always stably stressed and even unaffected by the latest main shock in 2004 however because fault loading rates and applied shear stress vary with time some degree of temporal variability of the b value within stable blocks is to be expected we discuss in this study adequate techniques and uncertainty treatment for a detailed analysis of the temporal evolution of b values we show that the derived signal for the parkfield asperity correlates with changes in surface creep suggesting a sensitive time resolution of the b value stress meter and confirming near critical loading conditions within the parkfield asperity

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

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

the yellowstone magmatic system from the mantle plume to the upper crust the yellowstone supervolcano is one of the largest active continental silicic volcanic fields in the world an understanding of its properties is key to enhancing our knowledge of volcanic mechanisms and corresponding risk using a joint local and teleseismic earthquake p wave seismic inversion we revealed a basaltic lower crustal magma body that provides a magmatic link between the yellowstone mantle plume and the previously imaged upper crustal magma reservoir this lower crustal magma body has a volume of 46 000 cubic kilometers 4 5 times that of the upper crustal magma reservoir and contains a melt fraction of 2 these estimates are critical to understanding the evolution of bimodal basaltic rhyolitic volcanism explaining the magnitude of co2 discharge and constraining dynamic models of the magmatic system for volcanic hazard assessment

3 d velocity structure of the 2003 bam earthquake area se iran existence of a low poisson s ratio layer and its relation to heavy damage abstract to understand the generation mechanism of the bam earthquake mw 6 6 we studied three dimensional v p v s and poisson s ratio structures in the bam area by using the seismic tomography method we inverted accurate arrival times of 19490 p waves and 19015 s waves from 2396 aftershocks recorded by a temporal high sensitivity seismic network the 3 d velocity structure of the seismogenic region was well resolved to a depth of 14 km with significant velocity variations of up to 5 the general pattern of aftershock distribution was relocated by using the 3 d structure to delineate a source fault for a length of approximately 20 km along a line 4 5 km west of the known geological bam fault this source fault dips steeply westward and strikes a nearly north south line the main shallow cluster of aftershocks south of the city of bam is distributed just under the minor surface ruptures in the desert the 3 d velocity structure shows a thick layer of high v s and low minimum 0 20 at a depth range of 2 6 km the deeper layer with a thickness of about 2 km appears to have a low v s and high maximum 0 28 from 6 km depth beneath bam to a depth of 9 km south of the city the inferred increase of poisson s ratio from 2 to 10 km in depth may be associated with a change from rigid and sio 2 rich rock to more mafic rock including the probable existence of fluids the main seismic gap of aftershock distribution at the depth range of 2 to 7 km coincides well with the large slip zone in the shallow thick layer of high v s and low the large slip propagating mainly in the shallow rigid layer may be one of the main reasons why the bam area suffered heavy damage

a hybrid method for simulating near source broadband seismograms application to the 2003 bam earthquake mw 6 5 the main objective of this article is to simulate the three components of near source ground shaking recorded at bam station close to the causative fault during the destructive the 2003 bam earthquake where were strongly influenced by rupture directivity effect a hybrid technique composed of the theoretical green s function finite element and finite difference method proposed by spudich et al 1987 2003 compsyn and a 2 based finite fault approach proposed by beresnev and atkinson 1998a finsim are used for generating seismograms at low and high frequencies respectively a genetic algorithm technique is developed for minimizing the differences between the recorded and simulated data incorporating parameters within a predefined upper lower bound s values previously estimated for main shock by other investigators two different faulting models consist of a straight line segment and a straight line segment followed by a slightly north eastward branch are used the simulated three component seismograms at bam station in terms of elastic response spectra are validated by comparing the simulated time series with those of the observed data moreover the pulses involved in the recorded time series due to the rupture directivity are estimated and compared with those of the observed data a sensitivity analysis is performed for recognizing the influence of model parameter changes such as focal mechanism strike dip and rake rise time rupture velocity and hypocenter location on the simulated seismograms relatively good match of the simulated and observed time series particularly the two faulting models confirm the potentiality of the proposed technique and the suitability of seismological model parameters used this technique can be used for specific site hazard analysis of the bam region and linear nonlinear dynamic analysis of structures where were damaged during the bam earthquake particularly for retrofitting the well known international adobe buildings of arg e bam

on varying b values with depth results from computer intensive tests for southern california summary the gutenberg richter b value is thought to reflect the stress conditions in the crust therefore spatial and or temporal variations of the b value can provide important information regarding crustal tectonics we investigate the variation of b value with depth in seven selected areas of southern california a previous study provided a detailed mapping of the variations of b with depth in california our study is less systematic than this study our approach is more similar to the regional one used by mori abercrombie in comparison to these previous studies our investigation indicates that the variability of b is often not statistically significant and that the decrease of b with depth should be interpreted with caution the seismic catalogues used are subsets of a set of about 100 000 seismic events recorded by the southern california seismic network scsn and relocated by richards dinger shearer we study the performance of utsu s test compared to bootstrap tests for comparison of b values the results of our investigation also raise the question of the relevancy of utsu s test when comparing b values both simulations and real cases show that the utsu s test is biased towards rejection of the null hypothesis in favour of the hypothesis that b values are significantly different

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

including foreshocks and aftershocks in time independent probabilistic seismic hazard analyses time independent probabilistic seismic hazard analysis treats each source as being temporally and spatially independent hence foreshocks and aftershocks which are both spatially and temporally dependent on the mainshock are removed from earthquake catalogs yet intuitively these earthquakes should be considered part of the seismic hazard capable of producing damaging ground motions in this study i consider the mainshock and its dependents as a time independent cluster each cluster being temporally and spatially independent from any other the cluster has a recurrence time of the mainshock and by considering the earthquakes in the cluster as a union of events dependent events have an opportunity to contribute to seismic ground motions and hazard based on the methods of the u s geological survey for a high hazard site the inclusion of dependent events causes ground motions that are exceeded at probability levels of engineering interest to increase by about 10 but could be as high as 20 if variations in aftershock productivity can be accounted for reliably

randomness of megathrust earthquakes implied by rapid stress recovery after the japan earthquake the 2011 tohoku oki earthquake released stress within a subduction zone analysis of seismic data shows that stresses returned to pre quake levels within a few years implying that large quakes could occur more often than previously thought

characterizing potentially induced earthquake rate changes in the brawley seismic zone southern california the brawley seismic zone bsz in the salton trough of southern california has a history of earthquake swarms and geothermal energy exploitation some earthquake rate changes may have been induced by fluid extraction and injection activity at local geothermal fields particularly at the north brawley geothermal field nbgf and at the salton sea geothermal field ssgf we explore this issue by examining earthquake rate changes and interevent distance distributions in these fields in oklahoma and arkansas where considerable wastewater injection occurs increases in background seismicity rate and aftershock productivity and decreases in interevent distance were indicative of fluid injection induced seismicity here we test if similar changes occur that may be associated with fluid injection and extraction in geothermal areas we use stochastic epidemic type aftershock sequence models to detect changes in the underlying seismogenic processes shown by statistically significant changes in the model parameters the most robust model changes in the ssgf roughly occur when large changes in net fluid production occur but a similar correlation is not seen in the nbgf also although both background seismicity rate and aftershock productivity increased for fluid injection induced earthquake rate changes in oklahoma and arkansas the background rate increases significantly in the bsz only roughly corresponding with net fluid production rate increases moreover in both fields the interevent spacing does not change significantly during active energy projects this suggests that although geothermal field activities in a tectonically active region may not significantly change the physics of earthquake interactions earthquake rates may still be driven by fluid injection or extraction rates particularly in the ssgf

strong motion and teleseismic waveform inversions for the source process of the 2003 bam iran earthquake the bam earthquake m w 6 5 occurred on 26 december 2003 in southeastern iran causing a major disaster in the city of bam a remarkable vertical peak ground acceleration value of 988 cm s2 and two horizontal pulses were recorded inside the damaged city previous analyses showed that the earthquake was caused by a subsurface rupture on an unknown strike slip fault in this study we attempt to determine the precise fault location and source process of the 2003 bam earthquake by performing a multiple time window linear waveform inversion of teleseismic and strong motion data both individually and jointly we examined the general features of the fault location and the source process by analyzing the teleseismic displacement waveforms and determined the precise features and fault geometry by inverting the three components of strong motion velocity records the final estimate of the source process of the 2003 bam earthquake was determined by joint inversion of the datasets our results show that a single fault model characterized by the appropriate location of the hypocenter rake angle variations and the rayleigh like speed of the rupture front can satisfactorily explain the three components of the strong motion records at bam station

some thoughts on measuring earthquake deformation using optical imagery optical imagery has been proven to be an effective tool for measuring earthquake deformation in continental regions since its first application in the 1999 izmit earthquake in this article we compile and analyze all the earthquakes that have been investigated with optical image matching by 2019 based on which we comment on various issues regarding measuring earthquake deformation with optical imagery new generations of very high resolution vhr data are effective for earthquake studies but orthorectification of the vhr images is the major source of error which is often ignored we found that the displacements derived from the worldview images strongly correlate with the errors in the shuttle radar topography mission srtm digital elevation model dem that was used in orthorectification based on the observed correlation between displacements and topography we propose a new dem based method using the advanced land observing satellite alos world 3 d dem to reduce the orthorectification errors combining the published optical data of earthquake deformation we re analyze the coseismic slip distribution and shallow slip deficit ssd the ssd model states that the coseismic slip in many strike slip earthquakes decreases in magnitude toward the surface but this model remains arguable because the interferometric synthetic aperture radar insar derived slip is usually not well constrained at shallow depths due to decorrelation because optical matching directly measures the surface slip we re examine the slip distribution of 11 strike slip earthquakes and find that the ssd model may primarily be artifacts in the insar measurements it is therefore of great importance to include the optical data in earthquake studies to constrain coseismic slip inversions

the 2003 december 26 bam earthquake iran mw 6 6 aftershock sequence summary from 2003 december 29 to 2004 january 30 a dense seismological network of 23 stations was installed in the epicentral area of the 2003 december 26 bam earthquake to study the aftershock seismicity we select the 331 earthquakes recorded at a minimum of 10 stations with rms less than 0 1 s and uncertainties less than 1 km to infer the precise geometry of the seismicity in the fault region we also process the data with the double difference technique to confirm the results the aftershock cluster is 25 km long trends north south and is located 5 km west of the bam baravat escarpment exactly beneath the observed surface breaks at depth aftershocks are concentrated between 6 and 20 km beneath the upper layer of relatively low velocity that experienced the maximum slip and they dip slightly westward the southernmost part of the aftershock cluster is narrow and defines the rupture zone that is likely the bam baravat fault at depth however it is unlikely that it is connected at surface to the bam baravat escarpment but more likely to the co seismic ruptures south of bam on the contrary the distribution of the northernmost aftershocks spread into a more complex pattern which is consistent with a northward propagation of the rupture along the fault plane the focal mechanisms are consistent with right lateral strike slip faulting on n s trending faults parallel to the bam baravat escarpment

tomography of southern california via bayesian joint inversion of rayleigh wave ellipticity and phase velocity from ambient noise cross correlations the data used in this work are archived and distributed by the southern california earthquake data center scedc http scedc caltech edu research tools waveform html and the iris earthquake data center https ds iris edu ds nodes dmc both the scec community velocity models used in this work cvms 4 26 and cvmh 15 1 0 are available from the southern california earthquake center https github com sceccode ucvmc this study was supported by the southern california earthquake center award 17195 the national science foundation grants cybersees 1442665 and ear 162061 and the king abdullah university of science and technology award ocrf 2014 crg3 2300 we also thank the reviewers of this paper an anonymous individual and jan dettmer for their valuable insight and constructive reviews of the manuscript the 3 d shear wave velocity model will be available from iris data services products earth model collaboration https ds iris edu ds products emc

the 2003 bam se iran earthquake precise source parameters from satellite radar interferometry summary differential radar interferometry provided high quality near field deformation data for the 2003 bam earthquake and therefore strong constraints on its source parameters the ruptured fault segments could be clearly detected by using a sobel edge filter on the phase unwrapped deformation field the estimated total rupture length is about 24 km more than 80 per cent of the seismic moment was released from its southern segment of about 13 km where the slip reached a maximum of up to 270 cm resulting in a stress drop of at least 6 mpa in addition optical remote sensing data show that the bam fault is not a single fault but consists of a 4 5 km wide fault system with the known main branch running between the city of bam and baravat the fault ruptured by the bam earthquake appears to continue the nw branch of this fault system from bam city southwards based on these results we suggest that the bam earthquake ruptured a hidden or new fault and that in this process an unusually strong asperity was involved

variations in earthquake size distribution across different stress regimes the earthquake size distribution follows in most instances a power law1 2 with the slope of this power law the b value commonly used to describe the relative occurrence of large and small events a high b value indicates a larger proportion of small earthquakes and vice versa statistically significant variations of b values have been measured in laboratory experiments mines and various tectonic regimes such as subducting slabs near magma chambers along fault zones and in aftershock zones3 however it has remained uncertain whether these differences are due to differing stress regimes as it was questionable that samples in small volumes such as in laboratory specimens mines and the shallow earth s crust are representative of earthquakes in general given the lack of physical understanding of these differences the observation that b values approach the constant 1 if large volumes are sampled4 was interpreted to indicate that b 1 is a universal constant for earthquakes in general5 here we show that the b value varies systematically for different styles of faulting we find that normal faulting events have the highest b values thrust events the lowest and strike slip events intermediate values given that thrust faults tend to be under higher stress than normal faults we infer that the b value acts as a stress meter that depends inversely on differential stress

patterns of historical earthquake rupture in the iranian plateau the iranian plateau accommodates the 35 mrn yr convergence rate be tween the eurasian and arabian plates by strike slip and reverse faults with relatively low slip rates in a zone 1000 km across although these faults have only locally been the subject of paleoseismological studies a rich historical and archeological record spans several thousand years long enough to establish recurrence intervals of 1000 to 5000 yr on individual fault segments several clusters of earthquakes provide evidence of interaction among reverse and strike slip faults probably due to adjacent faults being loaded by individual earthquakes the dasht e bayaz sequence of 1936 to 1997 includes earthquakes on left lateral right lateral and reverse faults the neyshabur sequence of four earthquakes between 1209 and 1405 respected the seg ment boundary between the neyshabur and binalud reverse fault systems the two pairs of earthquakes may have ruptured different faults in each segment similar to the 1971 and 1994 san fernando california earthquakes the 1978 tabas reverse fault earthquake was preceded by the 1968 ferdows earthquake part of the dasht e bayaz sequence the north tabriz fault system ruptured from southeast to north west in three earthquakes from 1721 to 1786 a previous cluster may have struck this region in 855 to 958 the mosha fault north of tehran ruptured in three earthquakes in 958 1665 and 1830 five large earthquakes struck the tehran region from 743 to 1177 but only two that large have struck the area since 1177 other earthquakes occurred in pairs in the talesh mountains near the caspian sea 1863 1896 the iran turkey border 1840 1843 and the nayband gowk fault system both 1981 other historical events did not occur as parts of sequences the historic seismic moment release in iran accounts for only a small part of the plate convergence rate which may be due to aseismic slip or to the iranian historical record long as it is being too short to sample long term deformation across the plateau no historic earthquakes of m 8 have struck iran however several long straight strike slip faults doruneh west neh east neh and nayband have not sustained large historical earthquakes raising the possibility that these long faults could produce earthquakes of m 8 thereby removing at least part of the apparent slip deficit an increased understanding of iran s seismic hazard could be obtained by an extensive paleoseismology program and space geodetic arrays supplementing the abundant historical and archaeological record

simulation of selected strong motion records of the 2003 mw 6 6 bam earthquake se iran the modal summation ray tracing methods in the wkbj approximation

coulomb stress changes and secondary stress triggering during the 2003 mw 6 6 bam iran earthquake abstract the 26 december 2003 mw 6 6 bam earthquake is one of the most destructive events in the recorded history of iran good variable slip fault models and precise aftershock data enabled us to calculate coulomb stress changes on the surrounding faults optimally oriented faults and the aftershock nodal planes to learn whether they were brought closer to failure we also test the role of secondary stress on the aftershocks triggering calculated stress on the surrounding faults showed that the southern part of the gowk fault and middle part of the dalfard and bam faults received positive stress changes stress also increases at the ends of the ruptured fault plane to expand it our calculations showed that deeper part of the bam fault planes received positive stress changes due to slipping on the shallow depth it can lead to the occurrence of aftershocks and enhance the probability of large events in the future that represent a substantial remaining seismic hazard to the reconstructed city of bam by imparting stress on optimally oriented faults the correlation between coulomb stress changes and aftershock distribution is investigated obtained results showed good correlation between coulomb stress change and seismicity from 331 well located aftershock hypocenters about 270 events 81 are located in the positive stress changes area the imparted stress due to the main shock and secondary aftershocks on the nodal planes of the 158 aftershocks is calculated the results show that the imparted stress due to main shock encouraged about 60 1 of nodal planes and 77 8 of the chosen nodal planes of aftershocks and added secondary aftershock encouraged about 81 6 of chosen nodal planes in other word by adding secondary triggering stress coulomb index for chosen nodal planes increased from 0 778 to 0 816 and about 80 of aftershocks receive greater positive stress changes

historical eruptions of merapi volcano central java indonesia 1768 1998 abstract information on merapi eruptive activity is scattered and much is remotely located a concise and well documented summary of this activity has been long needed to assist researchers and hazard mitigation efforts and the aim of this paper is to synthesize information from the mid 1700s to the present a descriptive chronology is given with an abbreviated chronology in a table that summarizes events by year assigns preliminary volcanic explosivity index vei ratings and hartmann classifications and provides key references the history of volcano monitoring is also outlined the study reveals that a major difference in eruption style exists between the twentieth and nineteenth centuries although the periodicity between larger events seems about the same during the twentieth century activity has comprised mainly the effusive growth of viscous lava domes and lava tongues with occasional gravitational collapses of parts of oversteepened domes to produce the nuees ardentes commonly defined as merapi type in the 1800s however explosive eruptions of relatively large size occurred to vei 4 and some associated fountain collapse nuees ardentes were larger and farther reaching than any produced in the twentieth century these events may also be regarded as typical eruptions for merapi the nineteenth century activity is consistent with the long term pattern of one relatively large event every one or two centuries based on the long term eruptive record deduced by others from volcanic stratigraphy it is uncertain whether or not a recurrence time model continues to apply to merapi but if so merapi could soon be due for another large event and its occurrence with only modest or inadequately appreciated precursors could lead to a disaster unprecedented in merapi s history because the area around the volcano is now much more densely populated

temporal trends in lava dome extrusion at santiaguito 1922 2000 we present a means of extracting lava dome extrusion rates from data provided by the thematic mapper and enhanced thematic mapper plus instruments flown on the landsat satellites extrusion rates derived from the landsat data for santiaguito dome complex guatemala during november 1987 and january 2000 of 0 72 0 08 and 0 48 0 09 m3 s 1 compare favorably with ground based estimates of 0 63 0 28 and 0 48 0 17 m3 s 1 a satellite data derived set of 18 extrusion rate estimates between 1987 and 2000 along with ground based volume estimates prior to 1987 allow us to infer volumes of magma erupted since 1922 these data reveal cyclic extrusion at santiaguito each cycle begins with a 3 6 year long phase of high extrusion rate 0 5 2 1 m3 s 1 followed by a longer 3 11 years phase of low extrusion rate 0 2 m3 s 1 the 8th cycle began in 1996 and was still in its high extrusion rate phase during january 2000 with time however the durations of the low extrusion rate phases have increased peak extrusion and time averaged extrusion rates for each cycle have decreased and the difference between extrusion rates during the high and low extrusion rate phases of each cycle has decreased these trends may be the result of depressurization and exhaustion of the source in this case the current eruption may be expected to end around 2020 alternatively santiaguito may be entering a period of persistent activity maintained by a stable magma supply in this case we may expect extrusion to become less cyclic and to stabilize at 0 2 0 4 m3 s 1 however a 2 wt decrease in sio2 content of erupted products since 1970 appears to be consistent with chamber exhaustion as well as an increase in block lava flow lengths during 1970 2000

s wave anisotropy in the aftershock region of the 2003 bam iran earthquake mw 6 5 abstract the 2003 bam earthquake mw 6 5 occurred in the southeastern iran on december 26 2003 we studied s wave anisotropy using the aftershock data observed at 5 stations in and around the aftershock region the fast polarization direction of shear wave splitting at the stations near the aftershock region is almost ne sw which corresponds to the maximum compressive stress trend the p axis of the main shock it is suggested that the inferred anisotropy might be caused by a systematic alignment of cracks resulting from the present day stress field the fast direction at the station just above the fault zone shows ew direction normal to the fault strike the fault normal alignment of cracks introduces a significant reduction of shear stress of the fault which suggests a high stress drop and large slip asperity another possible explanation for different result at the station from that of other stations is the effect of inhomogeneous velocity structure in and around the fault damaged zone the delay time of the split s waves ranges between 20 and 100 ms large delay time area is found in the shallower part of the fault zone with high aftershock activity assuming a uniform distribution of anisotropy inside and outside the aftershock region we estimated that the crack densities are 0 013 inside and 0 004 outside the aftershock region it may show more intense cracks within the high active region of aftershocks

comparison of etas parameter estimates across different global tectonic zones abstract branching point process models such as the epidemic type aftershock sequence etas models introduced by ogata 1988 1998 are often used in the description characterization simulation and declustering of modern earthquake catalogs the present work investigates how the parameters in these models vary across different tectonic zones after considering divisions of the surface of the earth into several zones based on the plate boundary model of bird 2003 etas models are fit to the occurrence times and locations of shallow earthquakes within each zone computationally the expectation maximization em type algorithm of veen and schoenberg 2008 is employed for the purpose of model fitting the fits and variations in parameter estimates for distinct zones are compared and seismological implications are discussed in particular we find that estimated background seismicity rates range by a factor of nearly 500 for interplate and trench events respectively the estimated productivity parameter governing the relationship between the magnitude of an earthquake and its expected number of direct aftershocks ranges by a factor of more than five from events in the slow moving zone to events in active continental areas suggesting a much higher rate of swarming in the ridges than in the trenches and active continental zones despite the pronounced differences between the seismicity patterns and parameter estimates in the different zones the etas model with few parameters and with the same functional form seems to fit reasonably well to the seismicity in each zone

a long term earthquake rate model for the central and eastern united states from smoothed seismicity abstract i present a long term earthquake rate model for the central and eastern united states from adaptive smoothed seismicity by employing pseudoprospective likelihood testing l test i examined the effects of fixed and adaptive smoothing methods and the effects of catalog duration and composition on the ability of the models to forecast the spatial distribution of recent earthquakes to stabilize the adaptive smoothing method for regions of low seismicity i introduced minor modifications to the way that the adaptive smoothing distances are calculated across all smoothed seismicity models the use of adaptive smoothing and the use of earthquakes from the recent part of the catalog optimizes the likelihood for tests with m 2 7 and m 4 0 earthquake catalogs the smoothed seismicity models optimized by likelihood testing with m 2 7 catalogs also produce the highest likelihood values for m 4 0 likelihood testing thus substantiating the hypothesis that the locations of moderate size earthquakes can be forecast by the locations of smaller earthquakes the likelihood test does not however maximize the fraction of earthquakes that are better forecast than a seismicity rate model with uniform rates in all cells in this regard fixed smoothing models perform better than adaptive smoothing models the preferred model of this study is the adaptive smoothed seismicity model based on its ability to maximize the joint likelihood of predicting the locations of recent small to moderate size earthquakes across eastern north america the preferred rate model delineates 12 regions where the annual rate of m 5 earthquakes exceeds 2 10 3 although these seismic regions have been previously recognized the preferred forecasts are more spatially concentrated than the rates from fixed smoothed seismicity models with rate increases of up to a factor of 10 near clusters of high seismic activity online material figures of minimum magnitude determination b value estimation and maps of earthquake rate and forecasts and tables of optimized neighbor numbers and smoothing distances

seismicity declustering and hazard analysis of the oklahoma kansas regionseismicity declustering and hazard analysis of the oklahoma kansas region

crust and upper mantle structure of the new madrid seismic zone insight into intraplate earthquakes we determine a 3 d p wave velocity model of the crust and upper mantle down to 400 km depth to investigate structural heterogeneity and its influences on the generation of intraplate earthquakes in the new madrid seismic zone we used 4871 high quality arrival times from 187 local earthquakes and 30 846 precise travel time residuals from 1041 teleseismic events recorded by the earthscope usarray transportable array our results show that beneath the reelfoot rift a significant low velocity low v zone exists in the upper mantle down to 200 km depth with a large volume of 200 x 200 x 150 km 3 the origin of the low v zone may be related to the passage of the bermuda hotspot and the stalled ancient farallon slab materials foundering in the mantle transition zone this low v zone may have relatively low shear strength and act as a viscously weak zone embedded in the lithosphere being apt to concentrate tectonic stress and transfer stress to the seismogenic faults in the upper crust leading to the large intraplate earthquakes in the new madrid seismic zone c 2014 elsevier b v all rights reserved

core concept seismic tomography uses earthquake waves to probe the inner earth computerized tomography ct scans revolutionized medicine by giving doctors and diagnosticians the ability to visualize tissues deep within the body in three dimensions in recent years a different sort of imaging technique has done the same for geophysicists seismic tomography allows them to detect and depict subterranean features data gathered by a network of seismic instruments red have enabled researchers to discern a region of relatively cold stiff rock shades of green and blue beneath eastern north america this is likely to be the remnants of an ancient tectonic plate image credit suzan van der lee northwestern university evanston il the advent of the approach has proven to be a boon for researchers looking to better understand what s going on beneath our feet results have offered myriad insights into environmental conditions within the earth sometimes hundreds or even thousands of kilometers below the surface and in some cases the technique offers evidence that bolsters models of geophysical processes long suspected but previously only theorized researchers say seismic tomography lets us image earth s structures at all sorts of scales says jeffrey freymueller a geophysicist at michigan state university in east lansing and director of the national office of the national science foundation s earthscope that 15 year program among other things operates an array of seismometers some permanent some temporary that has collected data across north america among its more impressive finds the remnants of an ancient tectonic plate sitting deep below north america and a plume of buoyant material fueling a well known geothermal hot spot tomography roughly translated from greek means writing by slices researchers relish this ability to take digital models of three dimensional 3d objects and slice through them to create cross sections to virtually dissect them from any angle both medical tomography and seismic tomography use large arrays of sensors to collect energy that

remote monitoring of the earthquake cycle using satellite radar interferometry the earthquake cycle is poorly understood earthquakes continue to occur on previously unrecognized faults earthquake prediction seems impossible these remain the facts despite nearly 100 years of intensive study since the earthquake cycle was first conceptualized using data acquired from satellites in orbit 800 km above the earth a new technique radar interferometry insar has the potential to solve these problems for the first time detailed maps of the warping of the earth s surface during the earthquake cycle can be obtained with a spatial resolution of a few tens of metres and a precision of a few millimetres insar does not need equipment on the ground or expensive field campaigns so it can gather crucial data on earthquakes and the seismic cycle from some of the remotest areas of the planet in this article i review some of the remarkable observations of the earthquake cycle already made using radar interferometry and speculate on breakthroughs that are tantalizingly close

seismicity anomalies of the 2003 bam iran earthquake abstract the bam earthquake occurred in an area without any historically recorded major earthquake based on active tectonics and cmt solutions the area is under the influence of shortening and right lateral strike slip faulting seismicity is of a shallow crustal type which is mainly distributed within the koohbanan golbaf lakarkooh shahdad gowk fault systems and the terminal sections of zagros in order to detect temporal seismicity anomalies before this earthquake we compiled a catalog from the isc events and then analyzed it for the magnitude of completeness after declustering this catalog changes in seismicity were assessed by the z value test the temporal variations indicate a relative decrease in z value before the bam earthquake additional to seismic quiescence and decrease in b value before the main shock there are pieces of evidence corresponding to increase in triggered background seismicity after this earthquake

gps constraints on africa nubia and arabia plate motions summary we use continuously recording gps cgps and survey mode gps sgps observations to determine euler vectors for relative motion of the african nubian arabian and eurasian plates we present a well constrained eurasia nubia euler vector derived from 23 igs sites in europe and four cgps and three sgps sites on the nubian plate 0 95 4 8 n 21 8 4 3 e 0 06 0 005 myr 1 we see no significant 1m m yr 1 internal deformation of the nubian plate the gps nubian eurasian euler vector differs significantly from nuvel 1a 21 0 4 2 n 20 6 0 6 e 0 12 0 015 myr 1 implying more westward motion of africa relative to eurasia and slower convergence in the eastern mediterranean the arabia eurasia and arabia nubia gps euler vectors are less well determined based on only one cgps and three sgps sites on the arabian plate the preliminary arabia eurasia and arabia nubia euler vectors are 27 4 1 0 n 18 4 2 5 e 0 40 0 04 myr 1 and 30 5 1 0 n 25 7 2 3 e 0 37 0 04 myr 1 respectively the gps arabia nubia euler vector differs significantly from nuvel 1a 24 1 1 7 n 24 0 3 5 e 0 40 0 05 myr 1 but is statistically consistent at the 95 per cent confidence level with the revised euler vector reported by chu gordon based on a re evaluation of magnetic anomalies in the red sea 31 5 1 2 n 23 0 2 7 e 0 40 0 05 myr 1 the motion implied in the gulf of aqaba and on the dead sea fault dsf by the new gps nubia arabia euler vector i e ignoring possible sinai block motion and possible internal plate deformation grades from pure left lateral strike slip in the gulf and on the southern dsf with increasing compression on the central and northern dsf with relative motion increasing from 5 6 to 7 5 mm yr 1 1m m yr 1 from south to north along the northern dsf i e north of the lebanon restraining bend motion is partitioned between 6 1m m yr 1 left lateral motion parallel to the fault trace and 4 1m m yr 1 faultnormal compression relative motions on other plate boundaries including the anatolian and aegean microplates derived from the gps euler vectors agree qualitatively with the sense of motion indicated by focal mechanisms for large crustal earthquakes m 6 where data are available on fault slip rates on plate bounding faults north anatolian fault east anatolian fault dead sea fault red sea rift they are generally lower than but not significantly different from the full plate motion estimates suggesting that the majority of relative plate motion is accommodated on these structures

offset and evolution of the gowk fault s e iran a major intra continental strike slip system abstract we use drainage reconstructions to estimate long term offsets on the gowk fault an oblique right lateral strike slip fault in eastern iran on which there have been a number of recent large earthquakes a 3 km horizontal offset is inferred from well preserved geomorphology we further identify a total cumulative offset of 12 km which produces a simple reconstruction of geomorphology across the fault filling in pull apart basins restoring rivers to linear courses across the fault trace and aligning structural and bed rock features the probable age of the gowk fault and k ar dating of offset basalts north of the study region suggest an overall slip rate of 1 5 2 4 mm year this is small compared with the overall 10 20 mm year of shear expected between central iran and afghanistan and the deficit is likely to have been accommodated on other faults east of the gowk fault drainage displaced by dextral movement leads to the development of a series of basins along the fault and a longitudinal topographic profile that resembles an asymmetric saw tooth the geomorphic evolution of the fault zone at the surface includes both normal and reverse faulting components reflecting a probable ramp and flat structure in cross section this interpretation is consistent with evidence from the analysis of seismological radar and surface rupture data in recent earthquakes

estimation of an earthquake focal mechanism from a satellite radar interferogram application to the december 4 1992 landers aftershock using the interferometric fringes generated by the phase difference between a pair of synthetic aperture radar sar images acquired by the ers 1 satellite we estimate the focal mechanism of a small shallow thrust earthquake the inversion procedure is an iterative linearized least squares algorithm based on a standard elastic dislocation formulation for coseismic displacements our preferred estimate is a thrust focal mechanism with its hypocenter at n34 35 0 4 km w116 91 0 2 km 2 6 0 3 km depth on a plane dipping southward beneath the san bernardino mountains with a moment magnitude mw of 5 4 the strike dip and rake are n106 e 7 28 4 and 93 4 respectively on a fault 3 1 0 5 km wide and 2 9 0 4 km long the precision of these estimates is competitive with seismological determinations

seismotectonic rupture process and earthquake hazard aspects of the 2003 december 26 bam iran earthquake summary the catastrophic 2003 m w 6 6 bam earthquake in southern iran attracted much attention and has been studied with an abundance of observations from synthetic aperture radar teleseismic seismology aftershock studies strong ground motion geomorphology remote sensing and surface field work many reports have focused on the details of one or other data type producing interpretations that either conflict with other data or leave questions unanswered this paper is an attempt to look at all the available data types together to produce a coherent picture of the coseismic faulting in 2003 and to examine its consequences for active tectonics and continuing seismic hazard in the region we conclude that more than 80 per cent of the moment release in the main shock occurred on a near vertical right lateral strike slip fault extending from the city of bam southwards for about 15 km with slip of up t o2mb utmostly restricted to the depth range 2 7 km analysis of the strong ground motion record at bam is consistent with this view and indicates that the extreme damage in the city can be attributed at least in part to the enhancement of ground motion in bam because of its position at the end of the northward propagating rupture little of the slip in the main shock reached the earth s surface and more importantly aftershocks reveal that 12 km vertical extent of a deeper part of the fault system remained unruptured beneath the coseismic rupture plane at depths of 8 20 km this may represent a substantial remaining seismic hazard to the reconstructed city of bam we believe that some oblique reverse slip up to 2 m and less than 20 per cent of the released seismic moment occurred at a restricted depth of 5 7 km on a blind west dipping fault that projects to the surface at the bam baravat escarpment an asymmetric anticline ridge that is the most prominent geomorphological feature in the area this fault did not rupture significantly at shallow levels in 2003 and it may also represent a continuing seismic hazard widespread distributed surface ruptures north of the city are apparently unrelated to substantial slip at depth and may be the result of enhanced ground motion related to northward propagation of the rupture the faulting at bam may be in the early stages of a spatial separation partitioning between the reverse and strike slip components of an oblique convergence across the zone such a separation is common on the continents though in this case the slip vectors between the two faults differ only by 20 as a substantial strike slip component remains on the obliquereverse fault the bam earthquake is one in a series of large earthquakes involving faulting along the western edge of the lut desert in addition to the unruptured parts of the faults near bam itself continuing and substantial hazard is represented by unruptured neighbouring faults particularly blind thrusts along the jebel barez mountains to the south and strike slip faulting at sarvestan to the west

a geodetic study of the 23 october 2011 van turkey earthquake abstract the van eastern anatolia turkey earthquake occurred on sunday october 23 2011 with a moment magnitude of 7 2 the tectonics of this region is characterized by strike slip faulting on the bitlis suture zone and thrusting in the zagros fold and thrust belt using high rate 1 second gps data from permanent gnss stations from the cors tr network co seismic displacements of eleven stations were determined using precise point positioning during this earthquake we used the time series of coordinate changes for fourteen cors tr stations and calculated the crust movements before and after the earthquake according to the ppp solutions computed using high frequency gps data to determine the co seismic motions of stations we conclude for the van earthquake an occurrence time of 10 41 22 utc no pre seismic horizontal movement of stations at the level more than 5 mm before the earthquake could be observed that means that no kinematic warning or prediction before the earthquake exists along an east west horizontal line north of the van sea with a length of about 100 km the northern part of this line experienced extension of 0 2 1 ppm in a nw se direction the southern part experienced n s shortening of 0 5 1 5 ppm the n s shortening we estimated geodetically matches well with the n s shortening and thrust focal mechanism derived independently using seismic data by the usgs co seismic surface displacements derived from the gps data are consistent with the teleseismic source model given by the usgs the geodetic source model derived from the gps data reproduces the same moment magnitude and centroid as the teleseismic model but shows a higher spatial resolution of the slip distribution we also analyzed the post seismic surface displacements derived from the gps data within the first two weeks after the mainshock no reasonable slip distribution on the co seismic fault plane could be found indicating that the sources for the early post seismic deformation might come from the widely scattered aftershocks

second order moment of central california seismicity 1969 1982 the second order moment cross correlation function of earthquakes in the u s geological survey central california catalog between 1969 and 1982 was calculated with respect to a magnitude threshold m 4 0 over interevent distances up to 80 km and interevent times up to 320 days the statistical procedure results in a representation of the spatial temporal structure of the catalog associated with m 4 0 earthquakes and is capable of revealing patterns too weak to be detected in the space time distribution of seismicity for individual earthquake sequences a method is introduced for identifying aftershocks based on a physical two parameter model of the earthquake interaction process the results show that the aftershock process dominates the second order moment and may even obscure the statistical expression of a precursory process a concentration of foreshocks within 15 km and 3 days of m 4 0 main shocks exhibits an apparent migration toward the main shock loci with velocity 2 6 5 3 km d this concentration may be related to an observed tendency for m 4 0 events to cluster auto correlate over this interevent range with the identified aftershocks removed the residual catalog is poissonion in space and time when two m 4 0 earthquakes occur within 80 km and 40 days of each other aftershock productivity appears to be relatively enhanced in the earlier sequence this suggests that aftershock populations are not solely dependent on their main shocks and that unusually productive aftershock sequences may be predictors of future moderate earthquakes

a comparison between the forecast by the united states national seismic hazard maps with recent ground motion records confidence in scientific models accumulates by continuously validating the model s predictions by observations we compared the seismic hazard forecasts of the four published versions of the u s geological survey national seismic hazard maps with observed ground motions a large dataset is necessary for a statistically meaningful comparison and so our comparison was based on an aggregated approach such that the observations and the forecast in a region california and the central and eastern united states ceus were combined and compared as a whole we used instrumental records in california and macroseismic intensity in the ceus since 2000 as the observation which was largely prospective to the hazard maps we verified that the observed seismic hazard based on macroseismic intensity was consistent with that based on instrumental records making model evaluation in the ceus for which instrumental records were almost nonexistent viable the observed hazard was found to be generally consistent with the forecasted one for peak ground acceleration pga in california and for both pga and spectral acceleration at 1 s sa1 in the ceus forecasted hazard for sa1 for california appeared to be conservative recent versions of the hazard map were in better agreement with observations in california small earthquakes as expected were found to have insignificant impact on sa1 induced earthquakes in the ceus have increased the observed seismic hazard but did not invalidate the hazard model as a whole we examined the resolving power of the test by computing its statistical power

present day crustal deformation and plate kinematics in the middle east constrained by gps measurements in iran and northern oman summary a network of 27 gps sites was implemented in iran and northern oman to measure displacements in this part of the alpine himalayan mountain belt we present and interpret the results of two surveys performed in 1999 september and 2001 october gps sites in oman show northward motion of the arabian plate relative to eurasia slower than the nuvel 1a estimates e g 22 2m m yr 1 at n8 5 e instead of 30 5 mm yr 1 at n6 e at bahrain longitude we define a gps arabia eurasia euler vector of 27 9 0 5 n 19 5 1 4 e 0 41 0 1 myr 1 the arabia eurasia convergence is accommodated differently in eastern and western iran east of 58 e most of the shortening is accommodated by the makran subduction zone 19 5 2m m yr 1 and less by the kopet dag 6 5 2m m yr 1 west of 58 e the deformation is distributed in separate fold and thrust belts at the longitude of tehran the zagros and the alborz mountain ranges accommodate 6 5 2m m yr 1 and 8 2m m yr 1 respectively the right lateral displacement along the main recent fault in the northern zagros is about 3 2m m yr 1 smaller than what was generally expected by contrast large rightlateral displacement takes place in northwestern iran up to 8 mm yr 1 the central iranian block is characterized by coherent plate motion internal deformation 2m m yr 1 sites east of 61 e show very low displacements relative to eurasia the kinematic contrast between eastern and western iran is accommodated by strike slip motions along the lut block to the south the transition zone between zagros and makran is under transpression with right lateral displacements of 11 2m m yr 1

near fault strong motion complexity of the 2003 bam earthquake iran and low frequency ground motion simulation summary the 2003 december 26 bam earthquake was an intermediate size strike slip event that occurred beneath the bam city causing more than 26000 fatalities the record of the only near fault station bam station shows a clear long period pulse in almost fault normal direction suggesting a near fault forward directivity effect contributing to the heavy damage observed in bam city in this study the long period 0 1 1 5hz strong ground motions were simulated to answer some ambiguities in source parameters for fully description of the observed motion in different components at bam station to this end the hisada s kinematic model accounting for both heterogeneous source characteristics and underground geology is applied to simulate the long period ground motion different source scenarios suggested by previous studies are examined and the optimum scenario that could provide the best fitting between the simulated and observed motions for different components was introduced the slip model and asperities as well as velocity structure parameters are optimized in order to have the best possible fit between the simulated and observed velocity time histories and spectra the good agreements between the simulated and observed low frequency motions indicate a successful identification of source and slip parameters of the bam earthquake and provide a good test for the simulation technique furthermore the uniqueness of the identified source parameters and the slip model is further checked against the observed near and far field recordings of the bam earthquake a good agreement between the simulated and the observed waveforms provides a base for model verification and results confirmation

control of magma flow in dykes on cyclic lava dome extrusion 1 lava dome eruptions are commonly characterized by large fluctuations in discharge rate with cyclic behaviour on time scalesranging from hours to decades examples include bezymianny volcano russia merapi java santiaguito guatemala mt st helens usa mt unzen japan and soufriere hills volcano montserrat previous models have assumed simple cylindrical conduits for magma transport but extrusions are mainly fed by dykes with cylindrical geometries developing only at shallow levels the widths of dykes embedded in an elastic medium are influenced by local magma pressure affecting flow rates and system dynamics strongly we develop a model for magma flow in dykes which predicts intense pulsations of magma extrusion for the case of a constant source pressure the period time scale is determined by the elastic deformation of the dyke walls and the length to width ratio of the dyke the dyke acts like a volumetric capacitor storing magma as pressure increases and then releasing magma in a pulse of extrusion for the soufriere hills volcano cyclic extrusions with time scales of a few weeks are predicted for dykes 300 500 m long and 3 6 m wide matching observations the model explains the sharp onset of tilt pulsations and seismic swarms citation costa a o melnik r s j sparks and b voight 2007 control of magma flow in dykes on cyclic lava dome extrusion geophys res lett 34 l02303 doi 10 1029 2006gl027466

descent of the ancient farallon slab drives localized mantle flow below the new madrid seismic zone 1 the great earthquake sequence that occurred in the central mississippi river valley during the winter of 1811 1812 is unprecedented in the historical record of seismicity within stable continental plate interiors we show using viscous flow models based on high resolution seismic tomography that the descent of the ancient farallon slab into the deep mantle beneath central north america induces a highly localized flow directly below the new madrid seismic zone nmsz this localization arises because of structural variability in the farallon slab and the low viscosity of the sub lithospheric upper mantle and it represents a heretofore unrecognized and possibly significant driving mechanism for the enigmatic intraplate seismicity

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

slip distribution aftershocks and co seismic fault of some large persian earthquakes this investigation concentrates on slip distribution aftershocks mainshock location and related co seismic faults for seven continental large earthquakes in the persian plateau most of the earthquakes m s 5 7 7 7 1981 2005 with both measurable surface slip along a mature rupture and a precisely aftershock surveying with a local seismological network in iran are evaluated in most of the case studies we observe an acceptable correlation between maximum surface slip along the fault trace and the asperity an area which is recognized as an obvious gap or an area with lack of aftershocks on a fault plane on the other hand we conclude that the aftershocks which are associated with immeasurable or smaller surface slips mainly concentrate at the outside of the asperities also the mainshocks in most of the earthquakes are in neighboring with the big asperities and segment the co seismic faults we could see a gradual increase in the co seismic slip when the magnitude of the earthquake increases but examples with defuse aftershocks and with no specific pattern are also found

the 2003 bam iran earthquake rupture of a blind strike slip fault a magnitude 6 5 earthquake devastated the town of bam in southeast iran on 26 december 2003 surface displacements and decorrelation effects mapped using envisat radar data reveal that over 2 m of slip occurred at depth on a fault that had not previously been identified it is common for earthquakes to occur on blind faults which despite their name usually produce long term surface effects by which their existence may be recognised however in this case there is a complete absence of morphological features associated with the seismogenic fault that destroyed bam

source process and slip model of 2005 dahuiyeh zarand earthquake iran using inversion of near field strong motion data summary on 2005 february 22 the dahuiyeh zarand earthquake mw 6 5 struck one of the most seismically active regions in south central iran east of zarand city in kerman province causing more than 500 fatalities the causative fault of the 2005 dahuiyeh zarand earthquake a reverse fault striking nearly ew and dipping to the north was located within a mountainous region and therefore more difficult to identify compared to the range bounded faults its identification after the 2005 event is very important for both the estimation of seismic hazard as well as for the damage and fatality functions we have inverted six three component near field strong motion waveforms to obtain the complete earthquake rupture history and slip distribution accelerograms are bandpass filtered with 0 2 1 0 hz and a length of 15 17 s of the waveforms is inverted the lack of absolute timing has been successfully overcome by estimating from the velocity model of the region the propagation of p and s waves from the epicentre to the stations the final fault slip model and the estimated source parameters are able to explain the observed waveforms the rupture is found to be bilateral with a maximum slip of 2 4 m concentrated on two asperities in the west and east sides of the nucleation point at depths of 6 12 km the western asperity is located to the east of zarand city and beneath the dahuiyeh village which might explain why the dahuiyeh village was totally destroyed by this earthquake

joint estimation of afterslip rate and postseismic relaxation following the 1989 loma prieta earthquake global positioning system gps data from campaigns carried out over the 5 years following the 1989 loma prieta earthquake and leveling data measured in 1990 and 1992 define the postseismic velocity field around the loma prieta rupture zone subtraction of a background velocity field yields a residual velocity pattern which we interpret as the product of two physical processes 1 slow afterslip along distinct planes in the upper cru st and 2 viscoelastic relaxation of the lower crust and upper mantle biirgmann et al 1997 previously derived an afterslip model involving uniform afterslip on two optimally determined planes in cluding oblique reverse slip on the coseismic rupture and reverse slip on a shallow thrust fault to the northeast of the san andreas fault we further consider models of distributed slip on these two fault planes plus a viscoelastic relaxation pattern which depends on a suitable cose ismic rupture model and crust and mantle viscosities several fault models from the literature were considered for the 1989 coseismic rupture with nearly identical impact on the results simultaneous maximum likelihood inversion of the gps and leveling data for afterslip distri bution and viscosity yields the following results 1 a good fit to the data is obtained by smooth afterslip distributions without any viscoelastic relaxation being required 2 tangible broad scale viscoelastic relaxation of the lower crust and upper mantle are present in this data set at 97 confidence and a lower crustal viscosity of 1029 pa s is obtained however the viscosity of both the lower crust and upper mantle are poorly constrained 3 for a given misfit 20 less integrated afterslip and smoother afterslip distributions result when viscoelas tic relaxation is included 4 maximum slip rates on the slip distributed models are 3 5 crn yr the dominant patches estimated on the two planes fill in the entire depth range 4 13 km without significant overlap and deeper afterslip is not required the afterslip distribution on the coseismic rupture plane is strongly dominated by reverse slip immediately southeast of the main center of coseismic reverse slip