different phases of the earthquake cycle captured by seismicity along the north anatolian fault the north anatolian fault has accommodated three major earthquakes during the last 15 years although the fault zone has substantially failed during the last century it did not completely fail in nw turkey and therefore left several segments at different physical stages in this study the seismicity rate is used as a proxy to locate the brittle fault sections with high low strain accumulation the results show that the 1999 m7 4 izmit and the 2014 m6 9 aegean earthquakes were preceded by almost a decade long period of enhanced microearthquake activity representing a brittle process preparing the failure this interpretation is supported by observed lateral migration of microearthquakes toward the main shock hypocenter within a time scale of roughly a decade the sea of marmara segments of the north anatolian fault show a rather temporally uniform seismicity trend leading to the hypothesis that those segments are still not in the preparation stage for a large earthquake the results also show that the duration of aftershock activity is not controlled only by the size of main shocks

inverse q filter for seismic resolution enhancement a principal limitation on seismic resolution is the earth attenuation or q effect including the energy dissipation of high frequency wave components and the velocity dispersion that distorts seismic wavelets an inverse q filtering procedure attempts to remove the q effect to produce high resolution seismic data but some existing methods either reduce the s n ratio which limits spatial resolution or generate an illusory high resolution wavelet that contains no more subsurface information than the original low resolution data in this paper seismic inverse q filtering is implemented in a stabilized manner to produce high quality data in terms of resolution and s n ratio stabilization is applied to only the amplitude compensation operator of a full inverse q filter because its phase operator is unconditionally stable but the scheme neither amplifies nor suppresses high frequencies at late times where the data contain mostly ambient noise the latter property makes the process invertible differ

interseismic deformation and creep along the central section of the north anatolian fault turkey insar observations and implications for rate and state friction properties 1 we present high resolution measurements of interseismic deformation along the central section of the north anatolian fault naf in turkey using interferometric synthetic aperture radar data from the advanced land observing satellite and envisat missions we generated maps of satellite line of sight velocity using five ascending advanced land observing satellite tracks and one descending envisat track covering the naf between 31 2 e and 34 3 e the line of sight velocity reveals discontinuities of up to 5 mm yr across the ismetpasa segment of the naf implying surface creep at a rate of 9 mm yr this is a large fraction of the inferred slip rate of the naf 21 25 mm yr the lateral extent of significant surface creep is about 75 km we model the inferred surface velocity and shallow fault creep using numerical simulations of spontaneous earthquake sequences that incorporate laboratory derived rate and state friction our results indicate that frictional behavior in the ismetpasa segment is velocity strengthening at shallow depths and transitions to velocity weakening at a depth of 3 6 km the inferred depth extent of shallow fault creep is 5 5 7 km suggesting that the deeper locked portion of the partially creeping segment is characterized by a higher stressing rate smaller events and shorter recurrence interval we also reproduce surface velocity in a locked segment of the naf by fault models with velocity weakening conditions at shallow depth our results imply that frictional behavior in a shallow portion of major active faults with little or no shallow creep is mostly velocity weakening

the geometry of the north anatolian transform fault in the sea of marmara and its temporal evolution implications for the development of intracontinental transform faults the north anatolian fault is a 1200 km long strike slip fault system connecting the east anatolian convergent area with the hellenic subduction zone and as such represents an intracontinental transform fault it began forming some 13 11 ma ago within a keirogen called the north anatolian shear zone which becomes wider from east to west its width is maximum at the latitude of the sea of marmara where it is 100 km the marmara basin is unique in containing part of an active strike slip fault system in a submarine environment in which there has been active sedimentation in a paratethyan context where stratigraphic resolution is higher than elsewhere in the mediterranean it is also surrounded by a long civilised rim where historical records reach well into the second half of the first millennium bce before common era in this study we have used 210 multichannel seismic reflexion profiles adding up to 6210 km profile length and high resolution bathymetry and chirp profiles reported in the literature

3 d crustal structure along the north anatolian fault zone in north central anatolia revealed by local earthquake tomography summary 3 d p wave velocity structure and vp vs variations in the crust along the north anatolian fault zone nafz in north central anatolia were investigated by the inversion of local p and s wave traveltimes to gain a better understanding of the seismological characteristics of the region the 3 d local earthquake tomography inversions included 5444 p and 3200 s wave readings obtained from 168 well located earthquakes between 2006 january and 2008 may dense ray coverage yields good resolution particularly in the central part of the study area the 3 d vp and vp vs tomographic images reveal clear correlations with both the surface geology and significant tectonic units in the region we observed the lower limit of the seismogenic zone for north central anatolia at 15 km depth final earthquake locations display a distributed pattern throughout the study area with most of the earthquakes occurring on the major splays of the nafz rather than its master strand we identify three major high velocity blocks in the mid crust separated by the izmir ankara erzincan suture and interpret these blocks to be continental basement fragments that were accreted onto the margin following the closure of neo tethyan ocean these basement blocks may have in part influenced the rupture propagations of the historical 1939 1942 and 1943 earthquakes in addition large variations in the vp vs ratio in the mid crust were observed and have been correlated with the varying fluid contents of the existing lithologies and related tectonic structures

a shallow fault zone structure illuminated by trapped waves in the karadere duzce branch of the north anatolian fault western turkey summary we discuss the subsurface structure of the karadere duzce branch of the north anatolian fault based on analysis of a large seismic data set recorded by a local passcal network in the 6 months following the mw 7 4 1999 izmit earthquake seismograms observed at stations located in the immediate vicinity of the rupture zone show motion amplification and long period oscillations in both p and s wave trains that do not exist in nearby off fault stations examination of thousands of waveforms reveals that these characteristics are commonly generated by events that are well outside the fault zone the anomalous features in fault zone seismograms produced by events not necessarily in the fault may be referred to generally as fault zone related site effects the oscillatory shear wave trains after the direct s arrival in these seismograms are analysed as trapped waves propagating in a low velocity fault zone layer the time difference between the s arrival and trapped waves group does not grow systematically with increasing source receiver separation along the fault these observations imply that the trapping of seismic energy in the karadere duzce rupture zone is generated by a shallow fault zone layer traveltime analysis and synthetic waveform modelling indicate that the depth of the trapping structure is approximately 3 4 km the synthetic waveform modelling indicates further that the shallow trapping structure has effective waveguide properties consisting of thickness of the order of 100 m a velocity decrease relative to the surrounding rock of approximately 50 per cent and an s wave quality factor of 10 15 the results are supported by large 2 d and 3 d parameter space studies and are compatible with recent analyses of trapped waves in a number of other faults and rupture zones the inferred shallow trapping structure is likely to be a common structural element of fault zones and may correspond to the top part of a flower type structure the motion amplification associated with fault zone related site effects increases the seismic shaking hazard near fault zone structures the effect may be significant since the volume of sources capable of generating motion amplification in shallow trapping structures is large

heightened odds of large earthquakes near istanbul an interaction based probability calculation we calculate the probability of strong shaking in istanbul an urban center of 10 million people from the description of earthquakes on the north anatolian fault system in the marmara sea during the past 500 years and test the resulting catalog against the frequency of damage in istanbul during the preceding millennium departing from current practice we include the time dependent effect of stress transferred by the 1999 moment magnitude m 7 4 izmit earthquake to faults nearer to istanbul we find a 62 15 probability one standard deviation of strong shaking during the next 30 years and 32 12 during the next decade

regional difference in scaling laws for large earthquakes and its tectonic implication we compiled 67 large earthquakes which occurred at and around plate boundaries for the last 140 yrs and classified them into four groups interplate strike slip events intraplate strike slip events underthrust events at island arc subduction zones and underthrust events at continental margin subduction zones for each group of earthquakes we examined relations between seismic moment m 0 fault length l fault width w and average fault slip d and found the following scaling laws in the case of interplate strike slip events the well known l cubed dependence of seismic moment breaks down when l exceeds 30 km because the extent of the seismogenic zone is limited in depth 12 km for large events l 30 km d and m 0 increase with l as d overline delta tau l mu left alpha l beta right and m 0 overline delta tau w l 2 left alpha l beta right respectively where the mean fault width bar w is 12 km and the mean stress drop overline delta tau is 1 8 mpa here and are structural parameters for intraplate strike slip events we obtained nearly the same relations except for significantly higher stress drop 3 1 mpa the difference in stress drop between interplate and intraplate events may be ascribed to the difference in stress accumulation rates and thus the recurrence time of earthquakes in the case of underthrust events at island arc subduction zones we also found the saturation of fault width bar w 120km and the breakaway from the l cubed dependence of m 0 for events larger than l 200 km if we consider the average dip angle of plate boundaries at island arc subduction zones to be 20 30 this indicates that the extent of the seismogenic zone in depth is limited to 40 60 km in the case of continental margin subduction zones on the other hand we could not find the saturation of fault width nor the breakaway from the l cubed dependence of m 0 from the analysis of the present data set w 200 km l 1000 km for sufficiently large earthquakes in general the downward rupture growth is limited to a certain depth due to the existence of a ductile unstressed region which extends under the brittle seismogenic zone since the brittle ductile transition occurs at 300 400 c the difference in the lower limit of the seismogenic zones between tectonically different regions may be attributed to the difference in thermal state there

a complex seismogenic shear zone the duzce segment of north anatolian fault turkey abstract this work highlights how surface geological data can integrate and complete a fault characterization including its seismogenic depth we investigated the area struck by the november 1999 mw 7 1 earthquake that ruptured the duzce segment of the north anatolian fault zone nafz after the august 1999 mw 7 4 izmit earthquake to explore the persistency or evolution of the active fault setting at the surface we compared detailed coseismic surface expressions with the long term morphology and structural architecture of the duzce zone we identified a simple 1999 coseismic fault trace cft and an older complex fault system rfs involving a wider zone of deformation two different parts of the duzce segment were recognized a western section presents a staircase trajectory of the coseismic fault trace that reactivated part of the older fault system an eastern section presents a straight coseismic fault trace that cross cuts the older and complex fault system the western duzce fault segment splays out from the izmit counterpart of the nafz forming a releasing fault junction by comparing a model of its coseismic surface deformation field with the long term morphology we observed that the present topography of this western section results from the nafz activity by repeating coseismic deformations like those in 1999 the mechanical interaction in the release fault junction produces local transtension across the western duzce fault and justifies its stable complexity it does not evolve into a straight trace the surface boundary between the duzce fault sections also separates at depth two fault sections one with low slip to the west and another with a big asperity to the east thus the izmit duzce interaction 1 may produce an unfavorable setting for a build up of asperities in the western duzce segment and 2 could delay the propagation of the izmit rupture along the duzce segment that nucleates mainshocks only on its eastern section in other words the arrangement of the fault junction may permanently control how the two sections of the duzce fault behave and rupture

holocene slip rate of the north anatolian fault beneath the sea of marmara abstract the north anatolian fault naf is a major continental transform system that extends e w across turkey for over 1600 km separating the anatolian and eurasian plates a portion of its northern branch runs below the sea of marmara this portion constitutes a seismic gap because the last destructive earthquakes occurred at the western 1912 ganos earthquake m 7 4 and eastern 1999 izmit and duzce earthquakes m w 7 4 7 2 edges of the marmara basin it is likely that fault ruptures will fill this gap in the next decades this region of the north anatolian fault is critical to our understanding of fault interactions stress buildup during seismic cycle and seismic hazard in the istanbul area we obtained high resolution acoustic images of the naf in the floor of the eastern marmara sea gulf of izmit and measured fault related offsets of 14 c dated subseafloor channels and paleoshorelines the resulting average slip rate on the fault is 10 mm year for the last 10 kyr this is less than half the total anatolia eurasia relative motion estimated at 24 mm year for the last 10 years from satellite geodetic measurements we conclude that either much of the strike slip motion along this branch of the naf did not occur on the main fault segment or the slip rate increased recently or both these results affect kinematic models of the naf and assessments of seismic hazard for the city of istanbul and the surrounding region

distribution of interseismic coupling along the north and east anatolian faults inferred from insar and gps data the north anatolian fault naf has produced numerous major earthquakes after decades of quiescence the mw 6 8 elazig earthquake january 24 2020 has recently reminded us that the east anatolia

a 2000 year long paleoseismologic record of earthquakes along the central north anatolian fault from trenches at alayurt turkey paleoseismologic data from trenches excavated across the central part of the north anatolian fault at alayurt turkey reveal evidence for at least four and possibly five surface ruptures during the past 2000 years as well as one much older event these surface ruptures as recognized on the basis of upward fault terminations and colluvial gravel layers include 1 the historic 1943 m w 7 7 tosya earthquake 2 an older event that is not well dated but which we interpret as the great 1668 earthquake which historical accounts suggest ruptured this part of the fault 3 a late eighth to early thirteenth century surface rupture 4 a surface rupture that occurred between the first and third centuries a d possibly the historic a d 236 event 5 a possible surface rupture that occurred between the late fourth and early eleventh centuries a d and 6 a much older event that occurred sometime between 4600 and 3550 b c our documentation of a late eighth to early thirteenth century surface rupture at alayurt is particularly important because when taken in context with available historical and paleoseismologic data it suggests the occurrence of a brief interval during which large earthquakes ruptured most of the north anatolian fault this interval resembles two other short lived clusters of activity in the sixteenth to eighteenth and twentieth centuries these brief intervals of activity are separated by much longer periods of relative quiescence that range from 250 years to 800 years if there was not a late fourth to early eleventh century event or 600 years if there was a late fourth to early eleventh century event the factor of 2 3 variation in inter event times suggests quasiperiodic earthquake occurrence which we attribute to the structural simplicity and relative isolation of the central north anatolian fault from other earthquake producing faults

the surface rupture and slip distribution of the 17 august 1999 izmit earthquake m 7 4 north anatolian fault the 17 august 1999 izmit earthquake occurred on the northern strand of the north anatolian fault zone the earthquake is associated with a 145 km long surface rupture that extends from southwest of duzce in the east to west of hersek delta in the west detailed mapping of the surface rupture shows that it consists of five segments separated by releasing step overs herein named the hersek karamursel golcuk izmit sapanca lake sapanca akyazi and karadere segments from west to east respectively the hersek segment which cuts the tip of a large delta plain in the western end of the rupture zone has an orientation of n80 the n70 80 e trending karamursel golcuk segment extends along the linear southern coasts of the izmit gulf between karamursel and golcuk and produced the 470 cm maximum displacement in golcuk the northwest southeast striking golcuk normal fault between the karamursel golcuk and izmit sapanca segments has 2 3 m maximum vertical displacement the maximum dextral offset along the izmit sapanca lake segment was measured to be about 3 5 m and its trend varies between n80 e and east west the sapanca akyazi segment trends n75 85 w and expresses a maximum displacement of 5 2 m the karadere segment trends n65 e and produced up to 1 5 m maximum displacement the karadere and sapanca akyazi segments form fan shape or splaying ruptures near their eastern ends where the displacement also diminished

active tectonics of the north and central aegean sea summary in this paper we examine the connection between the westward motion of turkey relative to europe and the extension in and around the aegean sea the principal new data available since the last attempt to synthesize the tectonics of this region by mckenzie 1978 are much improved focal mechanisms of earthquakes constrained by p and sh body wave modelling as well as by first motions these mechanisms show that the faulting in the western part of the aegean region is mostly extensional in nature on normal faults with a nw to wnw strike and with slip vectors directed nnw to nne there is evidence from palaeomagnetism that this western region rotates clockwise relative to stable europe in the central and eastern aegean and in nw turkey distributed right lateral strike slip is more prevalent on faults trending ne to ene and with slip vectors directed ne palaeomagnetic data in this eastern region is more ambiguous but consistent with very small or no rotations in the northern part and possibly anticlockwise rotations relative to europe in the south the strike slip faulting that enters the central aegean from the east appears to end abruptly in the sw against the nw trending normal faults of greece the kinematics of the deformation is controlled by three factors the westward motion of turkey relative to europe the continental collision between nw greece albania and the apulia adriatic platform in the west and the presence of the hellenic subduction zone to the south as the right lateral slip on the north anatolian fault enters the aegean region it splays out becoming distributed on several parallel faults the continental shortening in nw greece and albania does not allow the rotation of the western margin of the region to be rapid enough to accommodate this distributed e w right lateral shear and thus leads to e w shortening in the northern aegean which is compensated by n s extension as the southern aegean margin can move easily over the hellenic subduction zone the dynamics of the system once initiated is self sustaining being driven by the high topography in eastern turkey and by the roll back of the subducted slab beneath the southern aegean the geometry of the deformation resembles the behaviour of a system of broken slats attached to margins that rotate in spite of its extreme simplicity a simple model of such broken slats is able to reproduce quantitatively most of the features of the instantaneous velocity field in the aegean region including the slip vectors and nature of the faulting in the eastern and western parts the senses and approximate rates of rotation the overall extensional velocity across the aegean and the distribution of strain rates as seen in the seismicity and topography or bathymetry and using geodetic measurements as part of this study we re examined the relation between the surface faulting and the focal parameters determined seismologically for the three large 1981 gulf of corinth earthquakes and reassessed the evidence for associating particular earthquakes in the sequence with observed surface faulting an important result is that in one of the events there is a resolvable discrepancy between the slip vector measured at the surface and that determined from the seismic body waves

a relict paleoseismic record of seven earthquakes between 2000 b c and 600 a d on the central north anatolian fault at elmacik near osmancik turkey deformation along the northern edge of the westward moving anatolian plate is concentrated along the north anatolian fault this northward arching fault extends from the karliova triple junction in the east 1500 km into the aegean sea in the west a sequence of twentieth century earthquakes ruptured the fault displaying a spatiotemporal pattern consistent with a stress triggering mechanism in 1943 the m w 7 6 tosya earthquake ruptured a 280 km long segment near the center of the fault four paleoseismic investigations have previously investigated this segment and the present study was conducted near its center in an 180 km long gap between existing studies a paleoseismic trench revealed a sequence of eight sediment packages abutting a highly developed shear zone each of the packages consists of a fine grained layer overlying a coarse grained layer based on correlation between the age of the base of the coarse grained layers and existing earthquake records we infer that the coarse grained layers were deposited in response to earthquakes because of increased erosion on an adjacent steep slope the most recent event horizon may correlate to the historical 529 a d earthquake timing of six older earthquakes is constrained to 2s 23 b c 103 a d 609 185 b c 971 814 b c 1227 968 b c 2050 1777 b c and 2556 2235 b c which correspond to a summed interevent time of 97 912 yr 2s the earthquake record is relict because the local stream network was incised ca 1000 a d isolating the trench site from its sediment source a stream near the trench was subsequently offset by 23 5 1 5 m yielding a right lateral slip rate of 21 4 25 6 mm yr and suggesting that the 1943 rupture caused an uncharacteristically small offset

aftershock activity of the 1999 izmit turkey earthquake revealed from microearthquake observations an accurate aftershock distribution of the 1999 izmit turkey earthquake was obtained by using the data from a local seismic network izinet and 10 temporary seismic stations more than 2000 aftershocks were relocated for the period of about 2 months following the mainshock from this aftershock distribution we obtained several pieces of information on the characteristics of the mainshock first the mainshock initiated fault rupture from a place adjacent to an active swarm area where many microearthquakes had been occurring for more than 20 yr prior to the mainshock second the aftershock region extended in the east west direction along the north anatolian fault zone nafz this confirms that the mainshock was caused by a slip on the nafz third the western end of the rupture caused by the mainshock is likely to have reached up to about 29 2 e in the izmit bay and hence the total length of the fault rupture caused by the mainshock amounts to about 150 km as long as the estimate of the fault rupture length is based on the aftershock distribution this information is important for the discussion on the possibility of future large earthquakes in the west of the source region of the izmit earthquake we also found a clear tendency that aftershocks occur in clusters which implies strong heterogeneity in both the rupture process and the medium along the fault zone manuscript received 7 october 2000

ground motion scaling in the marmara region turkey summary predictive relationships for the ground motion in the marmara region northwestern turkey are parametrized after regressing three component waveforms from regional earthquakes in the frequency range 0 4 15 0 hz and in the distance range 10 200 km the data set consists of 2400 three component recordings from 462 earthquakes recorded at 53 stations moment magnitudes m w range between 2 5 and 7 2 the largest event for which we have waveforms available m w 7 2 occurred in duzce on 1999 november 12 the aftershocks of that earthquake together with the aftershocks of the 1999 august 17 izmit event m w 7 4 are included in the dataset regressions are performed independently on fourier velocity spectra and on peak ground velocities for a large number of sampling frequencies a simple model is used to relate the logarithm of the measured ground motion to excitation site and propagation terms results obtained for peak velocities are used to define a piecewise continuous geometrical spreading function g r a frequency dependent q f and a distance dependent duration function the latter is used through random vibration theory rvt in order to predict time domain characteristics i e peak values of the ground motion the complete model obtained for the peak ground motion was used to match the results of the regressions on the fourier amplitudes fourier velocity spectra for the combined horizontal motion are best fit by a hinged quadrilinear geometrical spreading function for observations in the 10 200 km hypocentral distance ranges as a function of frequency f 100 f 1 0 hz r 1 0 for r 30 km r 0 6 for 30 100 km the frequency dependent crustal shearwave quality factor q f coefficient q f 180 f 0 45 the t 5 75 per cent duration window provides good agreement between observed and predicted peak values by modelling the behaviour of the small earthquakes at high frequency we also quantified a regional parameter 0 055 s spectral models with one single corner frequency brune and with two corner frequencies atkinson and silva fit the observed high frequency excitation levels equally well whereas the model by atkinson and silva fits the low frequency observations slightly better than brune s rvt is used to predict the absolute levels of ground shaking following boore s implementation of the stochastic ground motion model boore s smsim codes our regional empirical predictive relationships are compared to the ones adopted in several regions of the world from california to western united states

response of the san andreas fault to the 1983 coalinga nunez earthquakes an application of interaction based probabilities for parkfield 1 the parkfield cholame section of the san andreas fault site of an unfulfilled earthquake forecast in 1985 is the best monitored section of the world s most closely watched fault in 1983 the m 6 5 coalinga and m 6 0 nunez events struck 25 km northeast of parkfield seismicity rates climbed for 18 months along the creeping section of the san andreas north of parkfield and dropped for 6 years along the locked section to the south right lateral creep also slowed or reversed from parkfield south here we calculate that the coalinga sequence increased the shear and coulomb stress on the creeping section causing the rate of small shocks to rise until the added stress was shed by additional slip however the 1983 events decreased the shear and coulomb stress on the parkfield segment causing surface creep and seismicity rates to drop we use these observations to cast the likelihood of a parkfield earthquake into an interaction based probability which includes both the renewal of stress following the 1966 parkfield earthquake and the stress transfer from the 1983 coalinga events we calculate that the 1983 shocks dropped the 10 year probability of a m 6 parkfield earthquake by 22 from 54 22 to 42 23 and that the probability did not recover until about 1991 when seismicity and creep resumed our analysis may thus explain why the parkfield earthquake did not strike in the 1980s but not why it was absent in the 1990s we calculate a 58 17 probability of a m 6 parkfield earthquake during 2001 2011 index terms 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics 7260 seismology theory and modeling keywords coalinga earthquake parkfield stress change earthquake probability seismicity rate

analysis of the north anatolian shear zone in central pontides northern turkey insight for geometries and kinematics of deformation structures in a transpressional zone abstract the western part of the north anatolian shear zone at the southern boundary of the central pontides in turkey was investigated in the kursunlu arac area by means of a geological structural field study in this area the north anatolian shear zone results in a transpressional deformation zone that extends between two master faults striking parallel to the main shear direction the main systems of structures identified in the deformation zone appear to be oriented parallel to the directions predicted by riedel theoretical model nevertheless the strain partitioning is more complicated than predicted by theory the structural analysis suggests a polyphase deformation characterized by a steady component of transcurrence associated with alternance of compression and extension along each of theoretical directions the combination of double verging structures can be observed with folds and thrust surfaces root into high angle shear zones according to flower type geometries the discrepancies of directions kinematics and geometries from theoretical models are due to transpressive and or transtensive nature of the deformation according to the observed outcropping structures we propose a conceptual model for the north anatolian shear zone interpreting it as a crustal scale positive flower structure

the off fault deformation on the north anatolian fault zone and assessment of slip rate from carbonate veins abstract discrepancies in earthquake characteristics between geodetically determined and geologically observed slip rates are prominent for the eastern part of the north anatolian fault naf zone we investigated the spatial distribution of deformation across a naf fault segment near erzincan ne turkey through field observations of physiographic features along the principle fault and a carbonate filled fissure system we propose that distributed deformation across the principal fault in a stretching zone caused sigmoidal simple shear rotation of the carbonate filled fissure system displacement data of that sigmoidal fissure using isotopic age data of the carbonate fill indicates an off fault deformation rate of 15 90 3 19 mm per year for the holocene which corresponds to at least 50 of the geodetically estimated annual slip across the fault it is critical to take the distributed deformation into account for determining earthquake characteristics of active fault systems

a 3000 year record of ground rupturing earthquakes along the central north anatolian fault near lake ladik turkey the north anatolian fault naf is a similar to 1500 km long arcuate dextral strike slip fault zone in northern turkey that extends from the karliova triple junction to the aegean sea east of bolu the fault zone exhibits evidence of a sequence of large m w 7 earthquakes that occurred during the twentieth century that displayed a migrating earthquake sequence from east to west prolonged human occupation in this region provides an extensive but not exhaustive historical record of large earthquakes prior to the twentieth century that covers much of the last 2000 yr in this study we extend our knowledge of rupture events in the region by evaluating the stratigraphy and chronology of sediments exposed in a paleoseismic trench across a splay of the naf at destek similar to 6 5 km east of lake ladik 40 868 degrees n 36 121 degrees e the trenched fault strand forms an uphill facing scarp and associated sediment trap below a small catchment area the trench exposed a narrow fault zone that has juxtaposed a sequence of weakly defined paleosols interbedded with colluvium against highly fractured bedrock we mapped magnetic susceptibility variations on the trench walls and found evidence for multiple visually unrecognized colluvial wedges this technique was also used to constrain a predominantly dip slip style of displacement on this fault splay sediments exposed in the trench were dated using both charcoal and terrestrial gastropod shells to constrain the timing of the earthquake events while the gastropod shells consistently yielded 14 c ages that were too old by similar to 900 yr we obtained highly reliable 14 c ages from the charcoal by dating multiple components of the sample material our radiocarbon chronology constrains the timing of seven large earthquakes over the past 3000 yr prior to the 1943 tosya earthquake including event ages of 2 sigma error a d 1437 1788 a d 1034 1321 a d 549 719 a d 17 585 1 3 events 35 b c a d 28 700 392 b c 912 596 b c our results indicate an average interevent time of 385 166 degrees yr 1 sigma

earthquake recurrence and magnitude and seismic deformation of the northwestern okhotsk plate northeast russia 1 recorded seismicity from the northwestern okhotsk plate northeast asia is currently insufficient to account for the predicted slip rates along its boundaries due to plate tectonics however the magnitude frequency relationship for earthquakes from the region suggests that larger earthquakes are possible in the future and that events of mw 7 5 which should occur every 100 350 years would account for almost all the slip of the plate along its boundaries due to eurasia north america convergence we use models for seismic slip distribution along the bounding faults of okhotsk to conclude that relatively little aseismic strain release is occurring and that larger future earthquakes are likely in the region our models broadly support the idea of a single okhotsk plate with the large majority of tectonic strain released along its boundaries

slip accumulation and lateral propagation of active normal faults in afar we investigate fault growth in afar where normal fault systems are known to be currently growing fast and most are propagating to the northwest using digital elevation models we have examined the cumulative slip distribution along 255 faults with lengths ranging from 0 3 to 60 km faults exhibiting the elliptical or bell shaped slip profiles predicted by simple linear elastic fracture mechanics or elastic plastic theories are rare most slip profiles are roughly linear for more than half of their length with overall slopes always 0 035 for the dominant population of nw striking faults and fault systems longer than 2 km the slip profiles are asymmetric with slip being maximum near the eastern ends of the profiles where it drops abruptly to zero whereas slip decreases roughly linearly and tapers in the direction of overall aden rift propagation at a more detailed level most faults appear to be composed of distinct shorter subfaults or segments whose slip profiles while different from one to the next combine to produce the roughly linear overall slip decrease along the entire fault on a larger scale faults cluster into kinematically coupled systems along which the slip on any scale individual fault or fault system complements that of its neighbors so that the total slip of the whole system is roughly linearly related to its length with an average slope again 0 035 we discuss the origin of these quasilinear asymmetric profiles in terms of initiation points where slip starts and barriers where fault propagation is arrested in the absence of a barrier slip apparently extends with a roughly linear profile tapered in the direction of fault propagation

the seismotectonics of the marmara region turkey results from a microseismic experiment the marmara region is an active tectonic zone characterised by the transition between the dextral strike slip regime of the north anatolian fault naf and the extension regime of the aegean sea strong historical earthquakes m 7 and the presence of known seismic gaps imply a high level of seismic hazard a synthesis of recent studies of active tectonics in the region is presented including inland and underwater observations the branching of the naf is explained in terms of increasing influence of the extension historical information and instrumental seismicity are reinterpreted in order to have a critical appraisal of the existence of large seismic gaps in the central and eastern marmara sea focal mechanisms of strong earthquakes are used to obtain orientation and shape factor of the deviator of the stress tensor the resulting tensor is in shear regime s 2 vertical but close to extension r 0 93 with s 1 oriented n145 0 a microseismic experiment with 48 stations distributed around the marmara sea was carried out in october december 1995 a total of 137 microearthquakes were located and 23 of those were selected to obtain focal mechanism solutions the epicentral distribution indicates activity along the system of pull apart basins north of the marmara sea the segment between marmara sea and the saros bay activated in 1912 and the gulf of izmit site of the 1754 earthquake are now silent seismic activity is very linear along the northern branch of the naf but it is more divused on the bursa and iznik branches southeast of the marmara sea the stress tensor obtained from the focal mechanisms of the micro earthquakes is compared to the one inverted from teleseismic data the microseismic stress is compatible with a shear intermediate regime like the one obtained from strong earthquakes though not as well constrained one of the acceptable solutions having the same orientation but diverent shape r 0 5 2000 elsevier science b v all rights reserved

a late holocene slip rate for the central north anatolian fault at tahtakopru turkey from cosmogenic 10be geochronology implications for fault loading and strain release rates 1 measurement of a stream offset and cosmogenic dating 10be of the alluvial surface into which the stream incised yield a preferred late holocene slip rate of 18 6 3 5 3 3 mm a 1 for the central part of the north anatolian fault naf at tahtakopru turkey use of variable cosmogenic production rate vpr models yields a slightly slower rate of 16 4 6 4 4 5 mm a 1 the offset drainage karanlik dere which flows southward almost perpendicular to the east west trace of the naf at the site is displaced right laterally by 55 10 m with no vertical displacement a 10be age of 3 ka 3 5 ka vpr from the top of a boulder on the best preserved part of the incised alluvial surface provides the most reliable maximum age for the onset of incision 11 10be ages from cobbles collected from the cultivated surface to the south yield younger ages consistent with exhumation erosion and mechanical mixing during plowing our 18 6 3 5 3 3 mm a 1 rate is similar to other geologic slip rates measured along the naf all of which cluster between 15 and 20 mm a 1 over a wide range of 103 105 timescales all of these geological rates however are slower than the 25 2 mm a 1 short term rate of elastic strain accumulation measured geodetically this disparity suggests the possibility that the naf is experiencing a strain transient in which the lower crust beneath the fault is deforming faster than its long term rate

slip distribution along the north anatolian fault associated with the large earthquakes of the period 1939 to 1967 abstract between 1939 and 1967 six large fault ruptures formed a westward migrating sequence of events along a 900 km long nearly continuous portion of the north anatolian fault for these events the 1939 erzincan 1942 niksar erbaa 1943 tosya 1944 bolu gerede 1957 abant and 1967 mudurnu valley earthquakes i have compiled a record of dextral slip which contains nearly 100 points these data indicate that the amount of slip is irregularly distributed along the 1939 to 1967 rupture zone the maximum slip 7 5 m occurred during the 1939 earthquake in the eastern 150 km of the 900 km long rupture zone dextral offsets diminish very abruptly eastward but very gradually westward the rate of westward decrease in the 1939 to 1967 offsets is only slightly greater than the rate of westward decrease of post miocene displacement along the north anatolian fault this suggests that westward decrease in slip can be expected to be a general characteristic of earthquake ruptures along the north anatolian fault in the future nevertheless within the 1939 to 1967 slip distribution there are three regions that had less slip than the neighboring regions these i interpret as possible sites of large future earthquakes one of these seismic gaps has already experienced another earthquake in 1951 and subsequent creep

recalculated probability of m 7 earthquakes beneath the sea of marmara turkey 1 new earthquake probability calculations are made for the sea of marmara region and the city of istanbul providing a revised forecast and an evaluation of time dependent interaction techniques calculations incorporate newly obtained bathymetric images of the north anatolian fault beneath the sea of marmara le pichon et al 2001 armijo et al 2002 newly interpreted fault segmentation enables an improved regional a d 1500 2000 earthquake catalog and interevent model which form the basis for time dependent probability estimates calculations presented here also employ detailed models of coseismic and postseismic slip associated with the 17 august 1999 m 7 4 izmit earthquake to investigate effects of stress transfer on seismic hazard probability changes caused by the 1999 shock depend on marmara sea fault stressing rates which are calculated with a new finite element model the combined 2004 2034 regional poisson probability of m 7 earthquakes is 38 the regional time dependent probability is 44 18 and incorporation of stress transfer raises it to 53 18 the most important effect of adding time dependence and stress transfer to the calculations is an increase in the 30 year probability of a m 7 earthquake affecting istanbul the 30 year poisson probability at istanbul is 21 and the addition of time dependence and stress transfer raises it to 41 14 the ranges given on probability values are sensitivities of the calculations to input parameters determined by monte carlo analysis 1000 calculations are made using parameters drawn at random from distributions sensitivities are large relative to mean probability values and enhancements caused by stress transfer reflecting a poor understanding of large earthquake aperiodicity index terms 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics 8150 tectonophysics plate boundary general 3040 keywords earthquake probability sea of marmara seismic hazard turkey stress interaction north anatolian fault

moho topography beneath the corinth rift area greece from inversion of gravity data summary our aim is to understand better the rifting process by imaging the moho depth variation beneath corinth and evvia we present here the results of a gravity inversion analysis in the region of the corinth and evvia rift system and compare them to those obtained independently from teleseismic tomography and receiver function analyses the results of these different studies appear to be consistent and show 1 a 10 km crustal thickening in the western part of the area beneath the hellenides mountains 2 nw se trending periodic crustal thinning and 3 a maximum crustal thinning north of the gulf of corinth this 4 km thinning is unlikely to be the result of the rifting alone which seems to have been reactivated since only 1 ma we propose here a geodynamical scenario in two major steps to explain the evolution of corinth area aegean miocene extension involving boudinage resulted in periodic crustal thinning consistent with observations these lithospheric instabilities could have favoured rupture initiation in particular areas especially near the city of corinth then the reactivation of the corinth rift extension 1 myr ago led to westward rift propagation the offset observed between the maximum crustal thinning and the gulf of corinth could be accommodated by a lowangle normal fault at about 10 15 km depth the corinth rift is thus asymmetrical and was initiated in places of crustal weakness due to miocene lithospheric instabilities

susehri basin an active fault wedge basin on the north anatolian fault zone turkey abstract the susehri section of the north anatolian fault zone nafz is dominated by an active fault wedge basin its recent configuration is a quaternary strike slip depression superimposed on a larger fault controlled fluvial to lacustrine setting inherited from the pliocene in and around the susehri fault wedge basin the nafz is characterized by the north anatolian master fault namf or principal displacement zone pdz and four second order fault sets namely the kelkit akcaa il beyde irmeni and ekenek fault sets the namf cuts through the basin the fault sets border the margins of the basin and impart a double divergence character to the namf which is proposed as an evolutionary model for the susehri fault wedge basin the susehri basin fill deposits of pliocene age rest on the quiet and shallow marine limestones of burdigalian age with a sharp angular unconformity besides the upper half of the pliocene basin fill deposits is dominated by the well developed syndepositional mesofractures which reveal the existence of a right lateral shearing at the time of deposition these observations also imply the emergence of a new tectonic regime after the burdigalian by which time the susehri basin had experienced a subsidence of about 660 m to 1150 m during its evolution on the other hand at the south easternmost end of the susehri basin the lutetian volcano sedimentary sequence of the yesilyayla group is cut and displaced right laterally by about 35 km which is the detectable minimum offset on the nafz finally during the 1939 12 27 erzincan earthquake the erzincan erbaa segment of the nafz was reactivated and several modern faults were produced along these modern faults some natural and man made features were displaced right laterally these offsets vary in decreasing order from 7 5 m near the epicenter at the southeastern end to 3 7 m away from it at the northwestern end of the erzincan erbaa segment of the nafz

extent and distribution of aseismic slip on the ismetpasa segment of the north anatolian fault turkey from persistent scatterer insar we use the persistent scatterer insar psi technique with elastic dislocation models and geology along the creeping section of the north anatolian fault naf at ismetpasa to map and deduce the velocity field and the aseismic slip distribution revealing the spatiotemporal nature of the creep helped us associate the creep with potential lithological controls hence providing a new perspective to better understand the underlying causes and mechanisms the psi analysis of envisat asar images between 2003 and 2010 reveals a clear picture of surface creep along the fault and a new interseismic velocity field transitioning gradually between the creeping and the locked fault sections the creep rate is found to fluctuate along a 100 km long section of the fault in a manner similar to that along the hayward fault reaching a maximum of 20 2 mm yr close to the far field plate velocity 25 1 5 mm yr at ismetpasa it is in the range of 8 2 mm yr consistent with the previous geodetic observations the creeping section appears to extend 30 km further east than those previously reported modeling of the psi data reveals a heterogeneous creep distribution at depth with two main patches confined mostly to the uppermost 5 km portion of the seismogenic crust releasing annually 6 2 1016 nm mw 5 1 geodetic moment our analysis combined with previous studies suggests that creep might have commenced as postseismic deformation following the 1944 earthquake and has evolved to stable fault creep with time there is a correlation between aseismic surface creep and the geology along the fault as it is in major part associated to rocks with low frictional strength such as the andesitic basaltic limestone and serpentine bodies within the fault zone

continental transforms a view from the alpine fault abstract continental transform faults are dominantly highly localized strike slip shear zones hundreds of kilometers long that accumulate tens to hundreds of kilometers of displacement from work on the alpine fault we pose the questions what is the deep structure of a continental transform and how does the displacement become localized we review research on the alpine fault and propose a model in which the fault partitions at depth into a steep zone extending into the mantle with largely fault parallel motion and a flat ductile decollement in the lower crust the fault localizes around two thirds of the plate motion within a 100 km wide zone of distributed deformation a review of other active continental fault systems suggests that variation between them may reflect their tectonic origins the nature of the crust in which they develop the presence of a significant oblique component of motion and the displacement rate all however have evidence for the development of a single principal fault zone that carries 50 of the total displacement and extends as a localized zone of shear into the upper mantle we review mechanisms of strain weakening and suggest that localization of a principal fault may be initiated in the seismogenic crust and through a series of positive feedbacks eventually extend through the lower crust into the upper mantle

geodetic observations of postseismic creep in the decade after the 1999 izmit earthquake turkey implications for a shallow slip deficit the relationship between aseismic slip and tectonic loading is important for understanding both the pattern of strain accumulation along a fault and its ability to generate large earthquakes we investigate the spatial distribution and temporal evolution of aseismic creep on the western north anatolian fault naf using time series analysis of envisat interferometric synthetic aperture radar insar data covering the full extent of the 1999 izmit and duzce earthquake ruptures and spanning 2002 2010 discontinuities in the line of sight velocity across the fault imply that fault creep reaches the earth s surface at an average fault parallel rate of 5 mm yr along an 80 km section of the naf by combining insar and published gps velocities we are able to extract the vertical and east west components of motion and show that the adapazari basin is subsiding at a rate of 6 mm yr vertical motions have biased previous estimates of creep in this region the displacement time series close to the fault is consistent with an afterslip model based on rate and state friction which predicts a rapid deceleration in fault creep rate after the izmit earthquake to a near steady state 5 mm yr after 5 years projecting our model 200 years into the future we find that the cumulative displacement of 1 1 3 m is insufficient to account for the shallow coseismic slip deficit observed in previous studies distributed off fault deformation in the shallow crust or transient episodes of faster slip are likely required to release some of the long term strain during the earthquake cycle

geological and geomorphologic asymmetry across the rupture zones of the 1943 and 1944 earthquakes on the north anatolian fault possible signals for preferred earthquake propagation direction summary the east and west rupture directions of the 1943 and 1944 earthquakes on the north anatolian fault naf are hypothesized to represent respectively long term preferred propagation directions on the corresponding sections of the naf fault sections with preferred rupture direction are expected to have an asymmetric damage structure with respect to the slipping zone to test the above hypothesis we study geological and geomorphologic manifestations of structural asymmetry with respect to the active trace of the naf along the 1943 and 1944 sections the following fault zone elements are mapped gouge fabric in the cm scale fault core structure in a metre scale and secondary faults and fault rocks in tens of metres scale mapping results at three sites on the 1943 rupture and one site on the 1944 rupture are consistent with accumulation of more rock damage on the south side of the 1943 section and on the north side of the 1944 section erosion patterns adjacent to the fault that are not correlated with the distribution of intrinsic and extrinsic erosion controlling variables e g rock type are interpreted as morphologic responses to the damage content of rocks and its impact on rock erodibility the valleys of 11 rivers are parallel to the studied fault sections about 75 per cent of the total river valleys length along the 1943 rupture is on the south side of the fault and about 89 per cent of the total river valleys length along the 1944 rupture is on the north side of the fault morphometric analysis of watersheds in two correlative terrains displaced along the 1944 rupture section shows that stream erosion is considerably more intense in the terrain north of the fault with drainage density values almost double in the north compare to the south badland topography at two sites along the 1943 rupture section is substantially more developed at the 100 m scale on the south side of fault our observations along the 1943 1944 rupture sections including various types of signals that span a large range of scales are systematically compatible with an opposite sense of damage asymmetry between the two fault sections these observations are consistent with opposite preferred direction of ruptures for the two sections similar to the propagation directions of the two recent earthquakes if those rupture directions are dictated by the velocity structure at depth we infer that the south side of the 1943 rupture has faster seismic velocity at seismogenic depth than the north side and that the sense of velocity contrast is reversed along the 1944 rupture zone

paleoseismic evidence of characteristic slip on the western segment of the north anatolian fault turkey we have conducted a paleoseismic investigation of serial fault rupture at one site along the 110 km rupture of the north anatolian fault that produced the mw 7 4 earthquake of 17 august 1999 the benefit of using a recent rupture to compare serial ruptures lies in the fact that the location magnitude and slip vector of the most recent event are all very well documented we wished to determine whether or not the previous few ruptures of the fault were similar to the recent one we chose a site at a step over between two major strike slip traces where the principal fault is a normal fault our two excavations across the 1999 rupture reveal fluvial sands and gravels with two colluvial wedges related to previous earthquakes each wedge is about 0 8 m thick considering the processes of collapse and subsequent diffusion that are responsible for the formation of a colluvial wedge we suggest that the two paleoscarps were similar in height to the 1999 scarp this similarity supports the concept of characteristic slip at least for this location along the fault accelerator mass spectrometry ams radiocarbon dates of 16 charcoal samples are consistent with the interpretation that these two paleoscarps formed during large historical events in 1509 and 1719 if this is correct the most recent three ruptures at the site have occurred at 210 and 280 year intervals

late holocene slip rate for the north anatolian fault turkey from cosmogenic 36cl geochronology implications for the constancy of fault loading and strain release rates geomorphologic mapping and cosmogenic radionuclide 36cl dating of an offset fluvial terrace yield a preferred late holocene slip rate of 20 5 5 5 mm yr for the central part of the north anatolian fault turkey an independent slip rate constrained by 14c ages is 20 5 8 5 mm yr these rates are generally similar to but possibly slightly slower than the short term rate of elastic strain storage of 25 1 measured geodetically across this major strike slip fault reilinger et al 2006 1 suggesting that loading and strain release on this part of the north anatolian fault have been relatively constant when averaged over the past 2 2 5 k y we attribute this consistency to the relatively simple structure of the anatolia eurasia plate boundary in north central turkey where almost all plate boundary strain is accommodated along the north anatolian fault the absence of other moderate to high slip rate faults and the earthquakes they produce leads to a relatively simple stress evolution for the fault dominated by steady tectonic loading 1 ref 10

m 7 earthquake rupture forecast and time dependent probability for the sea of marmara region turkey we forecast time independent and time dependent earthquake ruptures in the marmara region of turkey for the next 30 years using a new fault segmentation model we also augment time dependent brownian passage time bpt probability with static coulomb stress changes cff from interacting faults we calculate mw 6 5 probability from 26 individual fault sources in the marmara region we also consider a multisegment rupture model that allows higher magnitude ruptures over some segments of the northern branch of the north anatolian fault zone beneath the marmara sea a total of 10 different mw 7 0 to mw 8 0 multisegment ruptures are combined with the other regional faults at rates that balance the overall moment accumulation we use gaussian random distributions to treat parameter uncertainties e g aperiodicity maximum expected magnitude slip rate and consequently mean recurrence time of the statistical distributions associated with each fault source we then estimate uncertainties of the 30 year probability values for the next characteristic event obtained from three different models poisson bpt and bpt cff using a monte carlo procedure the gerede fault segment located at the eastern end of the marmara region shows the highest 30 year probability with a poisson value of 29 and a time dependent interaction probability of 48 we find an aggregated 30 year poisson probability of m 7 3 earthquakes at istanbul of 35 which increases to 47 if time dependence and stress transfer are considered we calculate a twofold probability gain ratio time dependent to time independent on the southern strands of the north anatolian fault zone

seismicity of the sea of marmara turkey since 1500 summary we use the earthquake history of the last 500 years to help evaluate the tectonic and hazard contexts of the1999 earthquakes at izmit and dzce in westernturkey the 20th century has been unusually active but over the 500 year period the seismic moment release can account for the known right lateral shear velocity across the marmara region observed by gps two areas of known late quaternary faulting stand out as unusually quiet over this period the northwest shore of the sea of marmara and the southern branch of the north anatolian fault system between bursa and mudurnu

polyphased block tectonics along the north anatolian fault in the tosya basin area turkey abstract the tosya basin is located in the bending segment of the north anatolian fault naf in turkey we have obtained original observations on the neotectonics from sar ers images digital elevation model dem and field structural analysis regional neogene deformation is characterised by the occurrence of several basins that are superimposed in time and space they result from differently oriented movements since 12 ma including southwestward motion along a fault subparallel to the naf we propose a model of polyphased tectonics related to the displacement of several individualised blocks in the first stage tortonian the north tosya block has moved toward the n250 azimuth parallel to the dextral n70 striking segment of the naf as a consequence a triple junction related compatibility basin was opened at the intersection with a n60 to n30 striking fault this pattern is similar to the karliova corner where the naf and the east anatolian fault meet in the second stage early pliocene middle pleistocene a segment of the former n70 naf was abandoned and the naf propagated eastward to form a n90 striking segment n90 naf cutting the former tosya block and basin into two parts the north tosya block has moved again and this new geometry has permitted a south tosya block to move parallel to the naf but with a higher rate which has induced compression in the tosya basin in the third stage holocene the south tosya block moved toward n240 obliquely to any of the naf segments this has resulted in the formation of two holocene pull apart type basins along the previous n60 to n30 striking fault while extensional faults were formed in the south tosya block estimated dextral displacement along the naf is 5 9 to 8 5 km at this stage this model of blocks moving in different directions including holocene local movements toward n240 means that the naf can be considered not to be a simple transform fault our model implies that the n90 naf was non existent before the early pliocene

influence of releasing step overs on surface fault rupture and fault segmentation examples from the 17 august 1999 izmit earthquake on the north anatolian fault turkey the 17 august 1999 izmit earthquake broke four distinct structural segments of the north anatolian fault from east to west the karadere sakarya sapanca and golcuk fault segments these segments are separated from one another and the adjoining yalova and duzce fault segments to the west and east respectively by distinct right releasing step over and or gaps in the fault trace these include from east to west the eften lake step over 2 4 km wide akyazi gap 6 13 km long sapanca step over 1 2 km wide golcuk step over 1 2 km wide and karamursel step over 4 5 km wide the earthquake nucleated within or near the golcuk step over with bilateral rupture propagation to the west and east to the west about 4 5 5 m of surface rupture up to 7 m of subsurface rupture on the golcuk segment was mostly if not entirely arrested by the 4 to 5 km wide karamursel step over to the east about 3 4 m of surface rupture about 4 m of subsurface rupture propagated through the 1 to 2 km wide sapanca step over triggering up to 4 5 5 5 m of surface rupture up to 5 6 m of subsurface rupture on the sakarya segment rupture on the sakarya segment stepped across the akyazi gap triggering 1 1 5 m of rupture on the karadere segment rupture on the karadere segment was arrested by the 2 to 4 km wide eften lake step over modeling of the transient stress field associated with the rupture propagation agrees well with the field observations the modeled fault rupture of 5 m on the golcuk segment appears to decrease the transient stress on the eastern tip of the adjoining yalova segment across the 4 to 5 km wide karamursel step over even if we allow rupture on the golcuk segment to extend along the entire southern margin of the step over our model shows that regardless of the amount of slip in a generic sense it is difficult to increase stress on the tip of an adjoining fault segment across a 5 km wide step over on the other hand fault rupture of 3 m on the western tip of the sapanca fault segment significantly increases the transient stress on the adjoining sakarya segment across the 1 to 2 km wide sapanca step over allowing rupture propagation across the basin an evaluation of 30 historical strike slip earthquakes involving 59 step over basins supports our field observations and stress modeling of the izmit fault rupture historical strike slip events with small to large displacements usually propagate through step overs less than 1 2 km wide with increasing displacement larger and larger step overs can be ruptured through the empirical data generally show a ratio ranging from 2 1 to 1 1 between step over width in kilometers and strike slip displacement in meters for a through going rupture however step overs of 4 to 5 km width appear to always arrest fault rupture regardless of the amount of displacement these results therefore provide important constraints for evaluating the probability of multisegment ruptures on segmented strike slip faults manuscript received 20 august 2000

the izmit kocaeli turkey earthquake of 17 august 1999 previous seismicity aftershocks and seismotectonics a field experiment carried out from 17 july to 2 november 1999 with a dense seismic network surrounding the marmara sea region and including the rupture zone of the izmit kocaeli destructive earthquake of 17 august 1999 m w 7 6 harvard centroid moment tensor delouis et al 2002 permitted the collection of precise seismic data and the quantitative evaluation of the associated set of surface ruptures a previous experiment conducted in 1995 had already given reliable information about the distribution of seismicity in space focal mechanisms and the regional stress regime aftershock distribution and clustering together with the variations of slip amplitude along the fault allow the identification of at least five segments a maximum horizontal displacement of about 5 m is observed in golcuk and east of sapanca lake the rupture is extremely linear but its complexity increases toward the western end including the bifurcation the stress field associated with the aftershocks is compared with the one obtained in 1995 showing the invariance of the smallest principal axis lack of definition of the other principal axes suggests a transition from shear to extension a clear quiescence period of 18 days preceded the izmit earthquake a precursor which occurred 100 sec before had the same epicenter as the mainshock manuscript received 30 august 2000

paleoseismological evidence of recent earthquakes on the 1967 mudurnu valley earthquake segment of the north anatolian fault zone this study contributes paleoseismological data on the recent history of surface rupturing earthquakes on the southern main branch of the north anatolian fault zone nafz turkey west of the bolu basin we focused on the fault segment that ruptured during the 1967 mudurnu valley earthquake m s 7 1 which preceded the devastating earthquakes of 1999 in the sequence of westward migrating nafz earthquakes since 1939 geomorphological mapping was carried out in a search for trenching sites on the central part of the 22 july 1967 earthquake segment in the absence of locations in sedimentary environments best suited for paleoseismological interpretation of faulted holocene deposits we trenched fluvial channel deposits at a terrace of the gravel dominated mudurnu river the most conservative interpretation of the trench stratigraphy and faulting evidence suggests that at least one paleoearthquake most probably two occurred after a d 1693 the 1967 earthquake segment has ruptured at least once since the historical earthquake of a d 1668 which was previously considered to be a likely candidate for the penultimate event and before 1967 it is not possible to confidently assign the penultimate event to one of the post a d 1693 historical earthquakes in the broader area around the mudurnu valley e g the earthquake of a d 1719 because the historical data published so far do not provide conclusive information about when past ruptures of the mudurnu valley branch of the nafz a secluded area did or did not take place

measurement of interseismic strain accumulation across the north anatolian fault by satellite radar interferometry in recent years interseismic crustal velocities and strains have been determined for a number of tectonically active areas through repeated measurements using the global positioning system the terrain in such areas is often remote and difficult and the density of gps measurements relatively sparse in principle satellite radar interferometry can be used to make millimetric precision measurements of surface displacement over large surface areas in practice the small crustal deformation signal is dominated over short time intervals by errors due to atmospheric topographic and orbital effects here we show that these effects can be overcome by stacking multiple interferograms after screening for atmospheric anomalies effectively creating a new interferogram that covers a longer time interval in this way we have isolated a 70 km wide region of crustal deformation across the eastern end of the north anatolian fault turkey the distribution of deformation is consistent with slip of 17 32 mm yr below 5 33 km on the extension of the surface fault at depth if the gps determined slip rate of 24 1 mm yr is accepted the locking depth is constrained to 18 6 km

the 2020 mw 6 8 elazig turkey earthquake reveals rupture behavior of the east anatolian fault the 2020 mw 6 8 elazig earthquake was the largest along the eastern anatolian fault eaf in over a century and so provides valuable insights into its rupture behavior because the eaf is of low to

displacement and geometrical characteristics of earthquake surface ruptures issues and implications for seismic hazard analysis and the process of earthquake rupture there now exist about three dozen historical earthquakes for which in vestigators have constructed maps of earthquake rupture traces accompanied by de scriptions of the coseismic slip observed along the fault strike the maps and slip distributions are compiled here to place observational bounds on aspects of seismic hazard analysis and fault mechanics analysis leads to an initial statistical basis to predict the end points of rupture and the amount of surface slip expected at sites along the strike during earthquakes on mapped faults the observations also give support to the ideas that there exists a process zone or volume of about 3 4 km in dimension at the fronts of large laterally propagating earthquake ruptures within which stress changes may be sufficient to trigger slip on adjacent faults and that the ultimate length of earthquake ruptures is controlled primarily by the geometrical complexity of fault traces and variations in accumulated stress levels along faults that arise due to the location of past earthquakes to this may be added the observation that the form of earthquake surface slip distributions is better described by asymmetric rather than symmetric curve forms and that earthquake epicenters do not appear to correlate in any systematic manner to regions of maximum surface slip observed along strike online material maps of surface ruptures digitized values and curve fits to surface slip distributions and notes and references for tables 1 and 2

a more precise chronology of earthquakes produced by the san andreas fault in southern california improved methods of radiocarbon analysis have enabled us to date more precisely the earthquake ruptures of the san andreas fault that are recorded in the sediments at pallett creek previous dates of these events had 95 confidence errors of 50 100 calendar years new error limits are less than 23 calendar years for all but two of the dated events this greater precision is due to larger sample size longer counting time lower background noise levels more precise conversion of radiocarbon ages to calendric dates and better stratigraphic constraints and statistical techniques the new date ranges with one exception fall within the broader ranges estimated previously but our estimate of the average interval between the latest 10 episodes of faulting is now about 132 years variability about the mean interval is much greater than was suspected previously five of the nine intervals are shorter than a century three of the remaining four intervals are about two to three centuries long despite the wide range of these intervals a pattern in the occurrence of large earthquakes at pallett creek is apparent in the new data the past 10 earthquakes occur in four clusters each of which consists of two or three events earthquakes within the clusters are separated by periods of several decades but the clusters are separated by dormant periods of two to three centuries this pattern may reflect important mechanical aspects of the fault s behavior if this pattern continues into the future the current period of dormancy will probably be greater than two centuries this would mean that the section of the fault represented by the pallett creek site is currently in the middle of one of its longer periods of repose between clusters and sections of the fault farther to the southeast are much more likely to produce the next great earthquake in california the greater precision of dates now available for large earthquakes recorded at the pallett creek site enables speculative correlation of events between paleoseismic sites along the southern half of the san andreas fault a history of great earthquakes with overlapping rupture zones along the mojave section of the fault remains one of the more attractive possibilities

geomorphic evidence for tilting at a continental transform the karamursel basin along the north anatolian fault turkey abstract continental transform boundaries are characterised by regional transcurrent faults that locally slip obliquely and spawn rapidly subsiding and tilting basins a type example is the north anatolian fault naf that accounts for the westward motion of the anatolian platelet relative to asia at about 25 mm yr many of the basins along the naf are asymmetric half grabens that border a strand of the naf on the extensional side of a fault bend and tilt obliquely toward the fault a prominent example is the 17 km long karamursel half graben south of the naf in izmit gulf one of the starved basins flooded by the marmara sea a tilt rate of 3 10 kyr has been proposed for the submerged part of the basin within 2 km south of the naf on the basis of a tilted early holocene paleo shoreline very rapid tilt and subsidence have been reported for similar basins along the naf but the locus of tilt shifts relative to the basin and is short lived at any one place we find evidence of recent tilting from surface flow patterns on the steep flank of the basin above the southern coastline up to 6 8 km from the naf drainage divides between 13 rivers mark a northward 8 10 tilted sub planar surface that extrapolates down into the basement below the progressively tilted sediments of the basin river profiles are only slightly concave below this surface we interpret this as the bevelled surface that preceded tilting and the immature comb like drainage to be symptomatic of recent tilt on the north flank of the basin the drainage is equally steep but markedly different it suggests a backward eroding fault scarp northward drainage into the black sea suggests a subtle but regional northward tilt of the kocaeli plateau possibly a flexural response to unloading along the fault along the western naf rapid progressive tilting of sediments is typical of submarine transform basins they provide ground truth for investigating the geomorphic effects of rapid tilting on land

present day strain distribution across a segment of the central bend of the north anatolian fault zone from a persistent scatterers insar analysis of the ers and envisat archives

effect of seismic source model parameters on the probabilistic seismic hazard assessment results a case study for the north anatolian fault zone the inputs to the probabilistic seismic hazard analysis psha contain large uncertainties regarding the seismic source model parameters therefore results may vary significantly due to subjective judgment and interpretation of the limited data the objective of this study is to show the effect of seismic source models on the hazard results by quantifying the differences in the design ground motions for different hazard levels at different locations around the north anatolian fault analysis showed the variances in the hazard results obtained by different seismic source models are closely correlated with the location of the site and hazard level additionally sensitivity of the hazard results to the uncertainties involved in each source parameter especially the source zone boundaries annual slip rate maximum and minimum magnitudes fault width b value and scenario weights are analyzed and presented to provide insight on the relative contribution of source or fault parameters to the psha results

stress history controls the spatial pattern of aftershocks case studies from strike slip earthquakes earthquake ruptures perturb stress within the surrounding crustal volume and as it is widely accepted now these stress perturbations strongly correlates with the following seismicity here we have documented five cases of the mainshock aftershock sequences generated by the strike slip faults from different tectonic environments of world in order to demonstrate that the stress changes resulting from large preceding earthquakes decades before effect spatial distribution of the aftershocks of the current mainshocks the studied mainshock aftershock sequences are the 15 october 1979 imperial valley earthquake mw 6 4 in southern california the 27 november 1979 khuli boniabad mw 7 1 the 10 may 1997 qa enat mw 7 2 and the 31 march 2006 silakhor mw 6 1 earthquakes in iran and the 13 march 1992 erzincan earthquake mw 6 7 in turkey in the literature we have been able to find only these mainshocks that are mainly characterized by dense and strong aftershock activities along and beyond the one end of their ruptures while rare aftershock occurrences with relatively lower magnitude reported for the other end of their ruptures it is shown that the stress changes resulted from earlier mainshock s that are close in both time and space might be the reason behind the observed aftershock patterns the largest aftershocks of the mainshocks studied tend to occur inside the stress increased lobes that were also stressed by the background earthquakes and not to occur inside the stress increased lobes that fall into the stress shadow of the background earthquakes we suggest that the stress shadows of the previous mainshocks may persist in the crust for decades to suppress aftershock distribution of the current mainshocks considering active researches about use of the coulomb stress change maps as a practical tool to forecast spatial distribution of the upcoming aftershocks for earthquake risk mitigation purposes in near real time it is further suggested that the background mainshocks along the neighbouring faults should be taken into account in producing the stress change maps for commenting on aftershock occurrences

north anatolian fault in the gulf of izmit turkey rapid vertical motion in response to minor bends of a nonvertical continental transform 1 the catastrophic rupture of the north anatolian fault east of the marmara sea on 17 august 1999 highlighted a need for mapping the underwater extension of that continental transform a new bathymetric map of izmit gulf indicates that the fault follows the axis of the gulf with a few minor bends submerged shorelines and shelf breaks that formed during the last glacial maximum provide markers to quantify vertical deformation variable tilting of these horizons reveals that vertical deformation is highest just south of the fault a correlation between vertical deformation of the southern fault block and distance to fault bends can be accounted for by a fault dipping steeply to the south hence subsidence uplift of the southern hanging wall block would be expected where the fault strikes at a slightly transtensional transpressional orientation to relative plate motion subsidence reaches about 8 mm yr west of the town of golcuk and might be accommodated in 1 2 m subsidence events during large earthquakes that scenario is compatible with the tsunami runups and the coseismic subsidence of the southern shore that occurred in 1999 seafloor morphology also suggests that earthquakes are accompanied by widespread gas and fluid release the periphery of the deepest basin displays a hummocky texture diagnostic of sediment fluidization and mud volcanoes occur west of hersek peninsula that might be activated by earthquakes finally the backscatter imagery reveals a series of lineaments midway through the gulf that are interpreted as products of the 1999 surface rupture the seafloor is undisturbed farther west suggesting that surface slip decreased to an insignificant level beyond hersek possibly the stress shadow from the 10 july 1894 earthquake which was felt strongly along the western izmit gulf contributed to arrest the 1999 surface rupture

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

slip along the san andreas fault associated with the great 1857 earthquake historical records indicate that several meters of lateral slip along the san andreas fault accompanied the great 1857 earthquake in central and southern california these records together with dendrochronological evidence suggest that the rupture occurred along 360 to 400 km of the fault including several tens of kilometers of the currently creeping reach in central california geomorphic expressions of late holocene right lateral offsets are abundant along the 1857 rupture along 300 kilometers of the 1857 rupture between cholame and wrightwood the youngest discernible offset ranges from 3 to 9 1 2 meters dormancy of the fault since 1857 almost certainly indicates that this latest offset was created in 1857 fault slip apparently associated with the 1857 earthquake varies in a broadly systematic way along the trace of the fault it is relatively uniform along each of several long segments but changes rather abruptly in value between these segments this nonuniform displacement pattern may imply that some segments of the fault rupture more frequently or experience a slower long term slip rate than others the 1857 offsets indicate a seismic moment m o between 5 3 and 8 7 10 27 dyne cm assuming a 10 to 15 km depth of rupture and relatively uniform slip as a function of depth a comparison with the rupture length average slip value and tectonic setting of the california earthquake of 1906 m s 8 1 4 indicates a value of m 8 1 4 for the 1857 event

a new multilayered visco elasto plastic experimental model to study strike slip fault seismic cycle nowadays technological advances in satellite imagery measurements as well as the development of dense geodetic and seismologic networks allow for a detailed analysis of surface deformation associated with active fault seismic cycle however the study of earthquake dynamics faces several limiting factors related to the difficulty to access the deep source of earthquake and to integrate the characteristic time scales of deformation processes that extend from seconds to thousands of years to overcome part of these limitations and better constrain the role and couplings between kinematic and mechanical parameters we have developed a new experimental approach allowing for the simulation of strike slip fault earthquakes and analyze in detail hundreds of successive seismic cycle model rheology is made of multilayered visco elasto plastic analog materials to account for the mechanical behavior of the upper and lower crust and to allow simulating brittle ductile coupling postseismic deformation phase and far field stress transfers the kinematic evolution of the model surface is monitored using an optical system based on subpixel spectral correlation of high resolution digital images first results show that the model succeed in reproducing the deformation mechanisms and surface kinematics associated to the main phases of the seismic cycle indicating that model scaling is satisfactory these results are comforted by using numerical algorithms to study the strain and stress distribution at the surface and at depth along the fault plane our analog modeling approach appears then as an efficient complementary approach to investigate earthquake dynamics

late quaternary co seismic sedimentation in the sea of marmara s deep basins the deep northern part of the sea of marmara northwestern turkey is composed of several aligned actively subsiding basins which are the direct structural and morphological expression of the north anatolian fault s northern branch the last 20 kyr of their sedimentary fill lacustrine before 12 kyr bp have been investigated through giant piston coring onboard r v marion dufresne marmacore cruise 2001 and chirp subbottom profiler onboard r v atalante during marmarascarps cruise 2002 especially during the lacustrine stage the infilling of the deep basins tekirda central kumburgaz and cinarcic basins up to 1250 m depth was dominated by turbidites with coarse mixed siliciclastic and bioclastic basal part intercalated in hemipelagic type finegrained calcareous and slightly siliceous clays often especially in the thickest ones the turbidites show strong segregation and a sharp boundary between coarse part and suspendedload part in the central basin 8 m of a unique sedimentary event include a 5 to 8m thick homogenite well imaged on seismic profiles the latter is interpreted as related to a major possibly triggered tsunami effect as described in the eastern mediterranean by kastens and cita 1981 in the marine holocene upper part of the sedimentary fill repeated to and from structures affecting silt or fine sand are evidencing seiche like effects and thus earthquake triggering detailed correlations between two deep coring sites 1250 and 1200 m indicate more than 100 overthickening in the deepest one this implies specific processes of distribution of terrigenous input by dense hyperpycnal currents high kinetic energy seiche effect complex reflections on steep slopes the peculiar sedimentary infilling of the sea of marmara s central basin and by extrapolation of the whole set is tentatively interpreted as a direct consequence of the strong seismic activity the imprint of the latter is more obvious prior to the base of the holocene as environmental conditions favoured marginal accumulation especially on the southern shelf of large amounts of erosion products available for mass wasting

reconstructing the deformation of the north anatolian fault zone through restoring the oligo miocene exhumation pattern of the almacik block northwestern turkey based on the apatite u th he ages the almacik block is an approximately 73 km long and 21 km wide tectonic sliver formed by the north anatolian fault zone in northwestern turkey morphologically it is one of the most pronounced st

viscoelastic deformation from north anatolian fault zone earthquakes and the eastern mediterranean gps velocity field 1 we have modeled linear viscoelastic relaxation of a uniform viscosity asthenosphere following large earthquakes in the aegean anatolian region during the 20th century to evaluate whether this process contributes significantly to the regional velocity field we address in particular whether southward motion of the aegean sea region relative to central anatolia and thus extension of western turkey can be attributed to a postseismic strain pulse our models show that postseismic relaxation of a thick 250 km viscoelastic substrate cannot generate the observed extension in western turkey regardless of the choice of viscosity we also find that the asthenosphere viscosity must exceed about 5 1020 pa s at least north of the north anatolian fault zone nafz to be consistent with low gps site velocities in the black sea region and highly localized strain around the fault

bay of bengal coupling of pre monsoon tropical cyclones with the monsoon onset in myanmar the pre monsoon tropical cyclone tc activity and the monsoon evolution in the bay of bengal bob are both influenced by the madden julian oscillation mjo but the two do not always occur in unison this study examines the conditions that allow the mjo to modulate the monsoon onset in myanmar and tc activity concurrently using the aphrodite gridded precipitation and the era interim reanalysis datasets composite evolutions of monsoon rainfall and tc genesis are constructed for the period of 1979 2010 it is found that the mjo exhibits a strong interannual variability in terms of phase and intensity which in some years modulate the conditions for bob tcs to shortly precede or form concurrently with the monsoon onset in myanmar such a modulation is absent in years of weaker mjo events further understanding of the interannual variability of mjo activity could facilitate the prediction of the monsoon onset and tc formation in the bob

are u th dates correlated with historical records of earthquakes constraints from coseismic carbonate veins within the north anatolian fault zone u th dating of carbonate veins in connection with active tectonics has recently been used as an attractive tool for constraining the absolute timing of late quaternary crustal deformations in this study for the first time we correlate u th ages of travertine deposits in coseismic fissures along the north anatolian fault zone with records of paleoseismological studies supported by historical earthquake catalogued data u th ages are assessed in relation to the recurrence interval and the size and epicenter distance of major holocene earthquakes our statistical evaluations on age correlations indicate that the carbonate vein precipitation is concentrated in eight different periods along the north anatolian fault zone the periods are well correlated with historical earthquake records and with previous dating results of the nearby trench studies at least six of the periods correspond to the earthquakes reported in the historical catalogues the age correlations of carbonate precipitation intervals for the last millennium show a recurrence along the eastern north anatolian fault zone with a mode at 130 330 years that is consistent with a previously proposed paleoseismic recurrence interval of the fault recorded events in carbonate veins indicate a close epicenter d vi paleoearthquakes our results suggest that coseismic carbonate veins could be used to determine paleoseismic records as a supplementary tool to augment paleoseismological techniques this tool has advantages over traditional paleoseismological methods for the understanding of long term earthquake behavior particularly for prehistoric late pleistocene events which cannot be dated easily by traditional paleoseismological methods

the effects of the north anatolian fault zone on the latest connection between black sea and sea of marmara abstract the development of the strait of istanbul is also one of the principal results of the tectonics which led to the evolution of the north anatolian fault zone nafz in the marmara region 3 7 ma ago high resolution seismic profiles from the marmara entrance of the strait of istanbul show a folding which occurred after the deposition of the parallel reflected tyrrhenian sediments over the tyrrhenian strata a fondoform zone of a deltaic sequence and marine sediments of the latest sea level rising are present these sediments also display syn depositional folding this situation implies that a local compressional stress field was created over the area probably since the wurm glacial age this recent variation of the tectonic regime in the northern shelf of the sea of marmara may indicate a significant change in the development of the nafz through the sea of marmara this variation of evolution of the nafz affected the latest development of the strait of istanbul via clockwise rotation of the istanbul and kocaeli peninsulas by right lateral shearing between two zone bounding faults this rotation has led to the development of nne ssw left lateral faults in the strait of istanbul and local compressional and tensional areas explaining the compressional structures seen in the southern entrance of the strait of istanbul therefore the latest mediterranean black sea connection was established by means of the sufficient deepening of the bosphorus channel by a variation in the evolution of nafz through the sea of marmara

3d mechanical modeling of the gps velocity field along the north anatolian fault the north anatolian fault naf extends over 1500 km in a complex tectonic setting in this region of the eastern mediterranean collision of the arabian african and eurasian plates resulted in creation of mountain ranges i e zagros caucasus and the westward extrusion of the anatolian block in this study we investigate the effects of crustal rheology on the long term displacement rate along the naf heat flow and geodetic data are used to constrain our mechanical model built with the three dimensional finite element code adeli the fault motion occurs on a material discontinuity of the model which is controlled by a coulomb type friction the rheology of the lithosphere is composed of a frictional upper crust and a viscoelastic lower crust the lithosphere is supported by a hydrostatic pressure at its base representing the asthenospheric mantle we model the long term deformation of the surroundings of the naf by adjusting the effective fault friction and also the geometry of the surface fault trace to do so we used a frictional range of 0 0 0 2 for the fault and a viscosity varying between 10 19 and 10 21 pa s one of the most striking results of our rheological tests is that the upper part of the fault is locked if the friction exceeds 0 2 by comparing our results with geodetic measurements mcclusky et al j geophys res b 105 2000 5695 5719 and tectonic observations we have defined a realistic model in which the displacement rate on the naf reaches v17 mm yr for a viscosity of 10 19 pa s and a fault friction of 0 05 this strongly suggests that the naf is a weak fault like the san andreas fault in california adding topography with its corresponding crustal root does not induce gravity flow of anatolia rather it has the counter intuitive effect of decreasing the westward anatolian escape we find a poor agreement between our calculated velocity field and what is observed with gps in the marmara and the aegean regions we suspect that the simple lithosphere model is responsible for this discrepancy taking into account the weaknesses of these deforming regions should allow us to build a more realistic model that would match ground observations more appropriately on the other hand our results fit well gps measurements in central anatolia setting the basis of modeling crustal strain in turkey b 2003 elsevier science b v all rights reserved

tsunami hazard in the marmara sea turkey a numerical approach to discuss active faulting and impact on the istanbul coastal areas abstract the westward propagation of the seismic ruptures along the north anatolian fault naf during the 20th century has increased the probability that the next rupture will be located offshore in the marmara sea in the prolongation of the 1999 izmit earthquake faulting historical tsunamis have been evidenced in the marmara sea e g those associated with the 1509 may 1766 strong earthquakes that broke submarine parts of the naf in the vicinity of istanbul and future submarine events are expected to produce tsunamis as well that could be triggered either by submarine coseismic displacements or by landsliding the assessment of their amplitude and extent of their effects is discussed in this paper through numerical modeling based on both earthquake and landsliding sources we use a finite difference method that yields the maximum water levels reached in the marmara sea and the effects run up values around the coasts of istanbul using a set of three nested bathymetric grids with a decreasing cell size to focus on istanbul first we consider probable earthquake sources along the northern branch of the emerged naf namely in the eastern cinarcik basin magnitude mw 7 2 in the western tekirdag and central basins magnitude mw 7 5 and along the whole branch magnitude mw 7 6 the impact obtained in istanbul is all the more important as a normal component in the eastern basin is present and maximum water levels can reach 2 m along the shoreline provoking locally significant inundations these results show that the historical tsunami observations around istanbul 1509 may 1766 provided they are directly due to earthquake sources imply a significant normal component in the eastern basin whatever the extent of the rupture westward conversely a source located in the western and or central basin does not provoke large waves in istanbul e g august 1766 most probably finally we test three landslide sources in the southern vicinity of istanbul and show that the damage is expected to be larger than in the case of earthquake sources for moderate to large volumes involved this kind of source in addition to the coseismic deformation could therefore be a good candidate to explain the historical waves in istanbul especially in 1509 where run up values as high as 6 m have been reported provided we are confident in the historical documents available

the 17 august 1999 izmit earthquake on 17 august 1999 an earthquake of magnitude 7 4 shook northwestern turkey details on the earthquake9s characteristics and effects across northwestern turkey are provided and are put in the historical context of previous earthquakes in the region the earthquake was the seventh in a series of earthquakes migrating westwards along the north anatolian fault since 1939 information on historical earthquakes modeling and estimates of the slip rate along the fault indicate that the location and severity of the earthquake should not have come as a surprise

strike slip fault geometry in turkey and its influence on earthquake activity the geometry of turkish strike slip faults has been reviewed and described from this data set it appears that fault geometry the distribution of discontinuities such as bends and stepovers along the main fault trace plays an important role in controlling the location of large earthquake rupture segments along the fault zones large earthquake ruptures generally do not propagate past individual stepovers that are wider than 5 km or bends that have angles greater than about 30 more important than the size of each discontinuity however is the total geometric pattern i e the distribution of adjacent bends and stepovers based not only on distance from one another but also on relative discontinuity size certain geometric patterns restraining single or double bends are particularly common and can be viewed as responsible for strain accumulation along portions of the fault zone fault geometry not only plays a role in the extent of earthquake rupture but also in characteristics of earthquake behavior for example large earthquake epicenters often occur near restraining bends or double bends furthermore aftershocks and swarm activity can often be associated with releasing areas areas along the strike slip fault that are undergoing a relatively large amount of extension

analysis of izmit aftershocks 25 days before the november 12th 1999 duzce earthquake turkey abstract we investigate spatial clustering of 2414 aftershocks along the izmit mw 7 4 august 17 1999 earthquake rupture zone 25 days prior to the duzce earthquake mw 7 2 november 12 1999 we analyze two spatial clusters namely sakarya sc and karadere duzce kdc we determine the earthquake frequency magnitude distribution b value for both clusters we find two high b value zones in sc and one high b value zone in kdc which are in agreement with large coseismic surface displacements along the izmit rupture the b values are significantly lower at the eastern end of the izmit rupture where the duzce mainshock occurred these low b values at depth are correlated with low postseismic slip rate and positive coloumb stress change along kdc since low b values are hypothesized with high stress levels we propose that at the depth of the duzce hypocenter 12 5 km earthquakes are triggered at higher stresses compared to shallower crustal earthquake the decrease in b value from the karadere segment towards the duzce basin supports this low b value high stress hypothesis at the eastern end of the izmit rupture consequently we detect three asperity regions which are correlated with high b value zones along the izmit rupture according to aftershock distribution the half of the duzce fault segment was active before the 12 november 1999 duzce mainshock this part is correlated with low b values which mean high stress concentration in the duzce basin this high density aftershock activity presumably helped to trigger the duzce event mw 7 2 after the izmit mw 7 4 mainshock

coseismic and early post seismic slip associated with the 1999 izmit earthquake turkey from sar interferometry and tectonic field observations summary we use combined tectonic field observations and sar data to determine an improved model of the slip associated with the 1999 izmit earthquake which ruptured the north anatolian fault at the eastern end of the sea of marmara the leading goal is to understand the main features of the coseismic and post seismic deformation which are captured together in the sar data to achieve this we make a critical analysis of the ers1 2 sar data which allows atmospheric effects to be identified and removed we also use detailed field mapping and measurements of the earthquake surface rupture dislocations in elastic half space and a forward modelling strategy allow us to obtain a slip model by steps a trial and error approach is combined with conventional inversion techniques to determine the slip in the different regions of the fault the sar data are well explained with three main zones of high slip along the fault releasing a total moment of 2 3 10 20 nm mw 7 6 which is higher than the seismological estimates 1 7 2 0 10 20 n m the inhomogeneous slip distribution correlates with fault segments identified at the surface the izmit rupture appears to have extended 30 km west of the hersek peninsula into the sea of marmara with slip tapering fro m2mt ozero the western end of the rupture is located 40 km sse from istanbul we show that some features seen near to mudurnu and gevye and previously interpreted as slip on secondary faults are explained mostly as atmospheric effects correlated with the topography using our approach and the available gps data we obtain a slip model that represents the coseismic slip alone which suggests that the moment release during the main shock was 1 9 10 20 nm mw 7 5 consistent with the seismological estimates we conclude that the sar data include the effects of 2 m of fast after slip during the month following the main shock within a zone of the fault located 12 24 km below the epicentral region near the hypocentre at a depth of 18 km the fault appears to have experienced dynamic slip of 1 m associated with the main shock followed by 2 m of rapidly decelerating post seismic shear during the following month we suggest that the distribution of heterogeneous slip and loading along the different fault segments may be important factors controlling the propagation of large earthquake ruptures along the north anatolian fault

seismic hazard in istanbul following the 17 august 1999 izmit and 12 november 1999 duzce earthquakes two recent destructive earthquakes that occurred along the western part of the north anatolian fault zone nafz the 17 august 1999 m w 7 4 izmit and 12 november 1999 duzce m w 7 2 earthquakes have caused major concern about future earthquake occurrences and their possible consequences in the istanbul area probabilistic seismic hazard analyses are performed for the larger istanbul area including the gulf of izmit and the marmara sea region hazard computations were done assuming different combinations of four attenuation relations and three alternative source models the three models used are 1 standard poissonian earthquake occurrence with area sources 2 renewal model assuming characteristic earthquakes with area and fault sources and 3 renewal model assuming characteristic earthquakes with refined area and fault sources results are presented in twelve different maps of peak ground acceleration pga with a 10 chance of exceedance in 50 yr among the earthquake recurrence models the results assuming model 3 yield the highest pga values reaching greater than 0 3 g at the western end of the gulf of izmit in general pga values decrease toward north and are reduced down to less than 0 2 g in central istanbul in the bosphorous area the four attenuation relations examined display significant variations and their effects become especially critical for distances less than 50 km in addition spectral hazard levels corresponding to 475 yr return period are computed and presented as uniform hazard response spectra for 5 damping two sites are selected one in hard rock and the other in soft sediments in general these results correlate well with the turkish seismic design code tsdc recommendations for the two site conditions the estimates of the future earthquake hazard potential of the istanbul area are sensitive to our present day understanding of the behavior of the fault segments in the marmara sea region

strong ground motions generated by earthquakes on creeping faults a tenet of earthquake science is that faults are locked in position until they abruptly slip during the sudden strain relieving events that are earthquakes whereas it is expected that locked faults when they finally do slip will produce noticeable ground shaking what is uncertain is how the ground shakes during earthquakes on creeping faults creeping faults are rare throughout much of the earth s continental crust but there is a group of them in the san andreas fault system here we evaluate the strongest ground motions from the largest well recorded earthquakes on creeping faults we find that the peak ground motions generated by the creeping fault earthquakes are similar to the peak ground motions generated by earthquakes on locked faults our findings imply that buildings near creeping faults need to be designed to withstand the same level of shaking as those constructed near locked faults

late holocene rupture behavior and earthquake chronology on the hope fault new zealand the hope fault is the most active and southernmost splay of the marlborough fault system in the northern south island of new zealand the fault consists of five geometrically defined segments we used trenching to acquire paleoseismic data and radiocarbon dating of faulted late holocene sediments on the hurunui segment of the hope fault to derive an earthquake chronology that extends from the historic 1888 mw 7 1 amuri earthquake to ca 300 c e thereby providing the longest chronologic record of earthquakes on the hope fault to date earthquake event horizons were identified by upward fault terminations colluvial wedges unconformities and or progressive folding of shutter basin deposits six earthquakes identified at c e 1888 1740 1840 1479 1623 819 1092 439 551 and 373 419 indicate a mean recurrence interval of 298 88 yr with successive median interevent times ranging from 98 to 595 yr the large variance in interevent times with respect to mean recurrence interval is explained by 1 possible coalescence of rupture overlap from the adjacent hope river segment onto the hurunui segment at our study site including the 1888 mw 7 1 amuri earthquake sourced primarily from the hope river segment which results in apparently shorter interevent times at the study site compared to mean recurrence intervals from adjacent fault segments 2 possible earthquake temporal clustering on the hurunui segment which could result in interevent times that are significantly shorter or longer than interevent times and mean recurrence intervals predicted by a periodic earthquake rupture model and or 3 missing events which could result in interevent times and mean recurrence intervals at the study site that are longer than the actual mean recurrence interval while we cannot exclude option 3 as a possibility we prefer options 1 and 2 to explain earthquake chronologies and rupture behavior on the hurunui segment of the hope fault given the detailed nature of our geologic and chronologic investigations by demonstrating that the 1888 amuri earthquake propagated through a proposed segment boundary we provide the first evidence for coseismic multisegment ruptures on the hope fault in contrast the penultimate earthquake ruptured the hurunui segment at 1740 1840 c e with no known rupture of the hope river segment paleoearthquake records near geometrically complex segment structural boundaries on major strike slip faults may show temporal recurrence distributions resulting from earthquake ruptures that variably arrest or propagate through proposed segment boundaries we note that earthquake recurrence along major strike slip plate boundary faults may vary between more periodic and more episodic end members even on adjacent geometrically defined segments

geotechnical assessment of the 2005 kuzulu landslide turkey in this study a complex landslide which occurred on 17 march 2005 near koyulhisar town of sivas province of turkey is presented the landslide resulted in 15 deaths and the destruction of about thirty houses at kuzulu village the main aims of this study are to assess the landslide in terms of engineering geology and geotechnics to back analyze the landslide in the source area and to estimate its motion and destructive forces on structures furthermore the effect of a future earthquake on stability condition of the mobilized but not completely failed mass adjacent to the right flank of the landslide is also investigated field observations eyewitnesses geomechanical laboratory tests interpretations on pre event aerial photographs and analyses using different approaches have been fundamentals of this study site observations indicate that the initial landslide in the source area occurred in highly weathered volcanics along a failure surface passing through the volcanics and along the interface between the volcanics and underlying limestone then the movement transformed into an earth flow and moved down through a v shaped channel in the underlying limestone about 2 km until it stopped at a small settlement which is called kuzulu site observations and back analysis of the initial slide suggest that the most likely cause should be water pressure increase as it is the season of snow melting and thawing of the groundwater interpretations on pre event aerial photographs and the information obtained from eyewitnesses indicated that slope movements in the study area where old landslide topography is evident were continuing for many years the simulation of the landslide with consideration of bingham type yielding criterion together with water pressure variation suggested that the maximum velocity of the earth flow was 14 4 m s and 13 6 m s when it reached kuzulu furthermore this evaluation showed that the earth flow reached kuzulu after 300 s which is consistent with the information obtained from local people the impact of the earth flow on the structures could be about 170 kpa against which only reinforced concrete structures may resist dynamic analyses suggested that a future earthquake which may occur in the region may result in a complete failure of the unstable mass remaining at the source area

the landslides threatening tasova town central anatolia turkey and their environmental impacts there exist a number of landslides along the north anatolian fault zone nafz between tasova and alparslan in amasya province in turkey these landslides extending over an area of 2 5 6 0 km are triggered by steepening of slopes due to undercutting by the yesilirmak river and groundwater fluctuations the landslides have affected 30 buildings in the western part of tasova in this study in order to investigate the engineering geological characteristics of the landslides and their environmental impacts representative samples from geological units were collected and a total of six boreholes were drilled plastic pipes were installed into the boreholes to measure the groundwater fluctuations and to determine the position of the sliding surface for a two year monitoring period using a gps linked to a fixed station system the magnitude of the movements ranged between 11 7 and 17 6 cm at the toe of landslide the landslides that occurred in the study area were in the form of retrogressive circular and multiple circular failures the factor of safety along a number of cross sections calculated by the limit equilibrium method of analysis is 0 96 in static condition after further analyses construction of a toe buttress with surface drainage may be suggested as a remedial measure to minimize the effects of these landslides

lateral offsets and revised dates of large prehistoric earthquakes at pallett creek southern california recent excavation and new radiocarbon dates of sediments at pallett creek are the basis for new conclusions regarding the late holocene history of the san andreas fault systematic dissection of a 50 m long 15 m wide 5 m deep volume of earth centered on the fault enables documentation in three dimensions of fault patterns lateral offsets and vertical deformation associated with large earthquakes of the past the excavations expose evidence for 12 earthquakes that occurred between about 260 and 1857 a d with an average recurrence interval of about 145 years prehistoric slip events that occurred in 1720 50 1550 70 1350 50 1080 65 and 845 75 a d have lateral offsets that are comparable to those of the most recent great earthquake of 1857 thus all of these events represent earthquakes of large magnitude the lateral offsets of two other events in 935 85 and 1015 100 a d are an order of magnitude smaller and may be interpreted in several ways with regard to the size of these events the new data constrain the average recurrence interval for large earthquakes at this site to between 145 and 200 years but suggest a monotonic decrease in individual intervals to below this range during the past 900 years on the basis of these data the probability of a large earthquake with surficial fault rupture at this site is between 0 2 and 5 during 1984 and 7 and 60 by the year 2000

dendroseismology on the central north anatolian fault turkey documenting three centuries of surface rupture history using tree rings 1 tree ring analysis provides a precise dating source for characterizing the timing of natural hazards specifically seismogenic disturbances on trees have been successfully documented on major faults such as the san andreas fault in california and denali fault in alaska in this study dendroseismology was employed along a 15 km long stretch of the central north anatolian fault naf between ilgaz and tosya turkey where the most recent surface rupturing event was the mw 7 6 1943 a d earthquake morphologic documentation and dendrochronologic analyses of 28pinus sylvestristrees demonstrates the effects of proximal surface rupture and secondary earthquake deformation fourteen trees show similar abrupt growth suppression and accelerated recovery trends following the 1943 a d tosya earthquake the number of trees yielding similar results the linear spatial distribution of the traumatized trees along the naf similarity in the trend of annual ring growth response and synchronity of these anomalies with the 1943 a d earthquake provide robust evidence for the correlation of the observed anomalies and the earthquake in addition four trees going back to early 18th century provide evidence for the lack of another surface rupturing large magnitude earthquake along this stretch of the fault this finding corroborates that the historical 1668 a d earthquake is most likely the penultimate event for the ilgaz tosya segment of the naf