middle pleistocene bivalves of the iznik lake basin eastern marmara nw turkey and a new paleobiogeographical approach iznik lake is a tectonically originated basin mainly controlled by the e w trending middle strand of the north anatolian fault naf system pleistocene sediments occurring in front of the faults are well exposed both in the northern and in the southern shorelines of the basin in this study two endemic brackish water bivalve species didacna subpyramidata pravoslavkev 1939 and didacna nov sp were found in the oldest terrace of the northern pleistocene sequence having characterized morphology these species serve as stratigraphic indicators in the regional pleistocene stratigraphy of the ponto caspian region and thus are well correlated to the assemblages of the early khazarian subhorizon middle pleistocene hence these data demonstrate that the early khazarian brackish water sea covered the study area additionally a model for the formation of the basin is proposed the iznik lake basin was a gulf of the former marmara sea in the early khazarian connecting the marmara to the black sea and the caspian sea the subsequent regional prograding uplifts main dextral strike slip fault and many normal faults of the naf zone cut off the marine connections to the basin leading to its present location and topographic level

comparison of frequency of occurrence of earthquakes with slip rates from long term seismicity data the cases of gulf of corinth sea of marmara and dead sea fault zone summary in this article through the comparison of knowledge relating to historical earthquakes with the understanding of present day earthquake mechanics and overall gps slip rates in the eastern mediterranean region it has been possible to obtain an idea of how frequently large earthquakes may be expected in some parts of the region it has also been possible to make an assessment from these early events of slip rates over a long period of time for the gulf of corinth in greece the marmara sea in turkey and the dead sea fault system as well as deriving long term magnitude frequency relations for these same regions it has been demonstrated that slip rates calculated from historical data are in general comparable to those calculated from gps measurements and field observations while the size of historical earthquakes and their uncertainty can be quantified this permits a more reliable estimation of the long term hazard the calculation of which is the concern of the engineering seismologist it has also been shown that in most cases large earthquakes are less frequent when they are estimated from long term data sets rather than from the instrumental period making the notion of recurrence time and of hazard assessment questionable this study focuses on some of the few areas in the world for which long term macroseism information exists and which facilitate this kind of analysis

fault interactions in the sea of marmara pull apart north anatolian fault earthquake clustering and propagating earthquake sequences summary knowledge on large earthquakes m 7 0 geology and fault kinematics is used to analyse conditions that favour isolated seismicity clustered earthquakes or propagating sequences along the north anatolian fault naf and the sea of marmara pull apart the overall naf marmara fault system is one of the most appropriate on earth to document fault interactions because reliable information covers almost completely two seismic cycles the past 500 yr coulomb stress analysis is used to characterize loading evolution in well identified fault segments including secular loading from below and lateral loading imposed by the occurrence of previous earthquakes earthquakes along the naf tend to occur where previous events have increased the stress but significant isolated events in the sea of marmara region 1894 1912 have occurred suggesting the secular loading has been the determining factor present day loading appears to be particularly high along the 70 km long segment located in the central marmara sea southwest of istanbul for the 18th century m 7 0 earthquake clusters we construct scenarios consistent with the tectonic and historical data we find that scenarios consistent with slip deficit and secular loading distributions from below clearly involve a sequence that propagates westward through the sea of marmara despite the structural complexity however the inference of a propagating sequence implies that each event has occurred in a segment previously stressed by lateral coulomb stress interactions the most likely scenarios for the propagating sequence are also consistent with coulomb stress interactions between faults with significant normal slip across the cinarcik basin propagating earthquake sequences do not occur every seismic cycle along the naf the loading has to be in a particular state of stress close to failure and uniform all along the fault segments to experience propagating earthquake sequences non uniform stress relief during the 18th century sequence explains the occurrence of isolated events in marmara in 1894 and 1912 as a consequence the wellknown 20th century sequence along the naf has not propagated as a sequence across the sea of marmara the most linear part of the naf across northern turkey behaves as a single fault segment accumulating stress during hundreds of years and rupturing entirely during very short periods the marmara pull apart fault system behaves as a major geometric complexity stopping or delaying the progression of earthquake clustering and propagating sequences fault zones interact with each other at a very large scale

uplift and subsidence from oblique slip the ganos marmara bend of the north anatolian transform western turkey abstract bends that locally violate plate motion parallel geometry are common structural elements of continental transform faults we relate the vertical component of crustal motion in the western marmara sea region to the nnw pointing 18 bend on the northern branch of the north anatolian fault naf n between the ganos segment which ruptured in 1912 and the central marmara segment a seismic gap crustal shortening and uplift on the transpressive west side of the bend results in the ganos mountain crustal extension and subsidence on the transtensional east side produce the tekirdag basin we propose that this vertical component of deformation is controlled by oblique slip on the non vertical north dipping ganos and tekirdag segments of the north anatolian fault we compare holocene with quaternary structure across the bend using new and recently published data and conclude the following first bend related vertical motion is occurring primarily north of the naf n this suggests that this bend is fixed to the anatolian side of the fault second current deformation is consistent with an antisymmetric pattern centered at the bend up on the west and down on the east accumulated deformation is shifted to the east along the right lateral naf n however leading to locally opposite vertical components of long and short term motion uplift has started as far west as the landward extension of the saros trough current subsidence is most intense close to the bend and to the ganos mountain while the basin deepens gradually from the bend eastward for 28 km along the fault the pattern of deformation is time transgressive if referenced to the material but is stable if referenced to the bend the lag between motion and structure implies a 1 1 1 4 ma age for the basin at current dextral slip rate 2 0 2 5 cm year third the tekirdag is an asymmetric basin progressively tilted down toward the naf n which serves as the border fault progressive tilt suggests that the steep northward dip of the fault decreases with depth in a listric geometry at the scale of the upper crust and is consistent with reactivation of paleogene suture related thrust faults fourth similar thrust fault geometry west of the bend can account for the ganos mountain anticline monocline as hanging wall block folding and back tilting oblique slip on a non vertical master fault may accommodate transtension and transpression associated with other bends along the naf and other continental transforms

reassessment of probabilistic seismic hazard in the marmara region abstract in 1999 the eastern coastline of the marmara region turkey witnessed increased seismic activity on the north anatolian fault naf system with two damaging earthquakes m 7 4 kocaeli and m 7 2 duzce that occurred almost three months apart these events have reduced stress on the western segment of the naf where it continues under the marmara sea the undersea fault segments have been recently explored using bathymetric and reflection surveys these recent findings helped scientists to understand the seismotectonic environment of the marmara basin which has remained a perplexing tectonic domain on the basis of collected new data seismic hazard of the marmara region is reassessed using a probabilistic approach two different earthquake source models 1 the smoothed gridded seismicity model and 2 fault model and alternate magnitude frequency relations gutenberg richter and characteristic were used with local and imported ground motion prediction equations regional exposure is computed and quantified on a set of hazard maps that provide peak horizontal ground acceleration pga and spectral acceleration at 0 2 and 1 0 sec on uniform firm rock site condition 760 m sec average shear wave velocity in the upper 30 m these acceleration levels were computed for ground motions having 2 and 10 probabilities of exceedance in 50 yr corresponding to return periods of about 2475 and 475 yr respectively the maximum pga computed at rock site is 1 5 g along the fault segments of the naf zone extending into the marmara sea the new maps generally show 10 to 15 increase for pga 0 2 and 1 0 sec spectral acceleration values across much of marmara compared to previous regional hazard maps hazard curves and smooth design spectra for three site conditions rock soil and soft soil are provided for the istanbul metropolitan area as possible tools in future risk estimates

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

abrupt environmental changes within a late holocene lacustrine sequence south of the marmara sea lake manyas n w turkey possible links with seismic events abstract a coring campaign in lake manyas kus golu on the southern coast of the sea of marmara turkey has provided insights into basin infilling processes during the upper 11 metres of the sedimentary record combined sedimentary features between 5 and 4 m depth have been explained by a seismite a brittle mixed layer uniquely rich in seeds and ostracod valves was widely detected at 4 m downcore this has been interpreted as being the result of a seiche either through a salt inundation linked to a tsunami in the sea of marmara the large scale scenario or a local hydrothermal fluid discharge the small scale scenario ostracod valves which are usually not preserved in lake manyas sediment are either incorporated here as tsunami debris providing a spatially averaged snapshot of the regional assemblage or are locally preserved following a temporary geochemical hydrochemical change of the water of unknown duration but probably several decades the brittle mixed layer overlies cracks resulting from the direct effects of the seismic shock wave on slightly compacted sediment at around 964 cm depth palynological and particle size analyses indicate a change from backswamp to open lacustrine conditions the end of the backswamp has been correlated with a decrease in the level of the sea of marmara from 4000 to 3000 2800 yr ago uncal caused by regional tectonic movements an age depth model is presented based on two ams radiocarbon dates on the palynological detection of the end of the beysehir occupation phase 130 cm above the event and on maximal sedimentation accumulation rates obtained by radionuclide analyses the entire study sequence covers the last 4300 yr the paper examines the possibility of an early byzantine age for the seismic event this may have been the historical event at ad 460 that destroyed cyzicus the ancient erdek 20 km north of the lake and various villages in the interior and was felt widely in the then known world other possibilities include various local and regional events in that same period the early byzantine tectonic paroxysm and the large earthquake in ad 447 that affected the entire sea of marmara region

investigation of the tectonics of the main marmara fault by means of deep towed seismic data abstract we report a study of the active principal deformation zone pdz of the main marmara fault mmf in the sub basins of the sea of marmara by means of deep towed seismic pasisar as well as multi beam bathymetry data collected by ifremer s r v le suroit in september 2000 our main objective is to investigate the active deformation within the uppermost sedimentary layers with a much higher resolution than hitherto has been available to the west of the sea of marmara the pdz is located along the southern flank of the tekirdag basin where the sediments are affected by steep reverse faults dipping toward the north e w strike slip faults are also observed in the central part of the tekirdag basin and thrusting occurs along its n50 trending margin we interpret these structures in terms of a slight clockwise rotation in the basin north of the pdz to the east the pdz enters the central basin and follows a steep scarp along the southern flank of a tectonic depression the scarp consists of an en echelon fault system with a normal component these faults are combined with small parallel anticlines and synclines that extend along the southern portion of the depression the northern scarp of the depression is made of a mixed system of faults with both normal and reverse components associated with anticlines and synclines these faults are best interpreted as right lateral strike slip faults with a vertical component that is dominantly normal these faults and the sigmoid shape of the depression are compatible with a clockwise rotation above the pdz this recent tectonic structure appears to be superimposed over a pre existing graben that is now essentially deactivated the pdz continues eastwards out of the central basin as a n50 e trending nw verging thrust system toward the kumburgaz basin that is located on a restraining bend of the pdz this shortening zone consists of two main n60 e trending branches the northern one is more pronounced and composed of two successive restraining bends the southern branch is smoother and forms a gently curved connection between the two segments of the pdz this suggests that the pdz migrates southward to cut through this restraining bend further east the pdz enters the cinarcik basin along its northern scarp active deformation observed on the pasisar profiles along the 290 trending eastern portion of this scarp consists of n110 5 trending dextral strike slip faults connecting short segments of active n130 140 normal faults that control elongated depocenters along the southern flank of the cinarcik basin the e w izmit fault enters the basin from the east pasisar data confirm the extension of the izmit strike slip fault into the cinarcik basin and the large development of normal faulting along the southern flank of the basin some of the normal faulting observed here may be related to horse tail termination of the izmit fault while most of it is the expression of strain partitioning

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

the sea of marmara a two dimensional seismic reflection profile data archive 1 in 1997 1500 km of high resolution two dimensional 2 d reflection seismic data were acquired in the sea of marmara region western turkey an archive of the 40 profiles of processed seismic data in segy format together with the differential global positioning system dgps locations and acquisition parameters for each profile are available for download from iris

slip partitioning in the sea of marmara pull apart determined from gps velocity vectors summary dislocation modelling is used to examine the gps velocity vectors for the marmara sea region first the vectors due to the known anatolia eurasia rotation are reproduced by introducing structures that approximate the large scale tectonics observed features of the smaller scale fault system in the marmara region are then progressively included with slip amplitudes and directions adjusted to fit an 80 vector subset of the gps data the motion in the marmara sea region is partitioned with the faults that bound the north of the basin carrying more strike slip motion than predicted from the anatolia eurasia plate motion and faults to the south having a greater perpendicular component taken together however there is no net opening across the marmara sea perpendicular to the overall trend of the boundary and thus deformation in the marmara region results only from the pull apart geometry of the north anatolian fault no extension related to the aegean system is needed to explain the observations the gps results are consistent with motion over the last 5 myr that has been determined from geological reconstructions

the 1999 izmit turkey earthquake a 3d dynamic stress transfer model of intraearthquake triggering before the august 1999 izmit kocaeli turkey earthquake theoretical studies of earthquake ruptures and geological observations had provided estimates of how far an earthquake might jump to get to a neighboring fault both numerical simulations and geological observations suggested that 5 km might be the upper limit if there were no transfer faults the izmit earthquake appears to have followed these expectations it did not jump across any step over wider than 5 km and was instead stopped by a narrower step over at its eastern end and possibly by a stress shadow caused by a historic large earthquake at its western end our 3d spontaneous rupture simulations of the 1999 izmit earthquake provide two new insights 1 the west to east striking fault segments of this part of the north anatolian fault are oriented so as to be low stress faults and 2 the easternmost segment involved in the august 1999 rupture may be dipping an interesting feature of the izmit earthquake is that a 5 km long gap in surface rupture and an adjacent 25 restraining bend in the fault zone did not stop the earthquake the latter observation is a warning that significant fault bends in strike slip faults may not arrest future earthquakes manuscript received 30 august 2000

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

quaternary paleoclimatic paleoceanographic and tectonic evolution of the marmara sea and environs strabo 63 bc 21 ad book 1 3 4 jones 1954 themarmarasea fig 1 hasalwaysattractedinterestasagreatgatewaylinkingtheblackseato the eastern mediterranean sea through a net work of narrow straits with shallow sills straitsof bosphorus istanbul and dardanelles c anakkale forthepast2500 3000yr informa tion about surface and bottom currents depthsoundings and sea level variation were crucialforsafenavigationacrossthesestraitsbysea far ingpeopleandexplorers thusconstitutingama jorstrategicassetandyieldingenormouseconom icandpoliticaladvantages throughoutantiquity sailors knew that the bottom waters across thestraits of dardanelles and bosphorus owednorthward and utilized this knowledge to sailintothemarmaraseaandblackseabyloweringlargebasketswithweightsintothenorth owingmediterranean water to counteract the strongsouth directed surface out ow from the blacksea systematic scienti c investigations in the mar marasearegionstartedinthelate19thcentury the rstbathymetricsurveyrevealedthepresenceof three deep basins and their intervening ridges andrussow 1901 p nar 1943 subsequentlyproposedthatasinglefaulttransectedthesethreebasins extending from the izmit bay in the eastto the gulf of saros in the west pfannensteil 1944 noted the rhombohedric shape of thedeepmarmaraseabasinsandproposedthattheridgesseparatingthebasinsrepresenthorstblocksbounded by normal faults healsosuggested inadditiontothestraitofbosphorus thepresenceofasecondchannel thesakaryabosphorus fig 1 which connected the black sea to the mar mara sea during the quaternary in 1948 ketinpublished his renowned paper revealing the truenatureofthenorthanatolianfaultasoneoftheworld slargest active intra continental strike slipfaults ketin 1948 pavoni 1961 and kopp etal 1969 proposedthataseriesofsyntheticand

the north anatolian fault within the sea of marmara a new interpretation based on multi channel seismic and multi beam bathymetry data abstract we analyze 2200 km of multi channel seismic reflection profiles that have become recently available in the sea of marmara this analysis benefits from the recent acquisition of multi beam bathymetric data covering the axial portion of the northern basins we conclude that the northern sea of marmara is at present cut by an active continuous strike slip fault system that we call the marmara fault it links the 270 izmit portion of the northern branch of the north anatolian fault to the east of the sea to the 245 ganos fault to the west the marmara fault itself consists of two main parts the western one is a single 80 km long fault it follows a 265 direction that differs by 20 from the direction of the ganos fault at its northeastern extremity it turns toward the northern margin of the cinarcik basin this western part of the fault is seismically quite active the eastern part is more complex it extends over 65 km in a 280 direction there is thus a 10 clockwise rotation with respect to the 270 izmit fault strand that should result in a slight extensional component within the eastern cinarcik basin this part of the marmara fault has two parallel branches 10 km apart the northern one near the foot of the northern slope the southern one near the foot of the southern slope a shortening zone occupies the northwestern corner of the cinarcik basin and much of the adjacent eastern central high and separates the northern branch from the western one the southern branch on the other hand may cross the eastern central high along a narrow 280 valley the data we have provide no definitive evidence on which of these two branches carries most of the motion the establishment of the present trace of the fault through the marmara basin is contemporaneous with a recent phase of deposition of deep giant ripples parallel to the bathymetric slope contours and adjacent to the turbidites basin deposits the base of these deep basins sedimentary deposits is marked by a widespread erosional unconformity below which lies a gently folded sedimentary sequence that may consist of shallow thrace basin deposits

contamination of seismicity catalogs by quarry blasts an example from istanbul and its vicinity northwestern turkey abstract scientists have proposed two fault systems of different ages in the sea of marmara the thrace eskisehir fault zone of early miocene early pliocene age and the north anatolian fault zone of late pliocene recent age different seismicity rates and extensions of these faults onto land near istanbul have been suggested one of the reasons for these differences is the contamination of seismicity catalogs by seismic events from quarries operated in istanbul and its vicinity including gaziosmanpasa cebeci and kemerburgaz catalca omerli gebze and hereke in this study we investigated waveforms of 179 seismic events 1 8

structural interpretation of the marmara region nw turkey from aeromagnetic seismic and gravity data abstract the seismically active marmara region located in nw turkey lies on the westward end of the north anatolian fault naf the naf is well defined on land previous investigations of its extension in the marmara sea include marine bathymetry seismological activity and seismic profiles in this study faults and their configurations identified inland are extended into the marmara sea by means of aeromagnetic anomalies as well as seismic and gravity profiles the deep structure was resolved by constructing a map of the tertiary bottom shallow curie isotherm was determined by spectral analysis indicating a thinner crust in the northern marmara depression area with respect to the continental crust a combination of the geophysical data allows us to propose the existence of subsidence and isostatic equilibrium in the northern marmara sea a less active zone identified in the central high zone dividing the marmara sea into two parts may also be deduced from the seismic data this structural arrangement may play a key role in earthquakes that will affect the surrounding regions

origin of the strait of canakkale dardanelles regional tectonics and the mediterranean marmara incursion abstract the regional tectonics and the mid to late quaternary seismic stratigraphy of the strait of canakkale dardanelles and its opening towards the aegean sea were interpreted by using shallow seismic profiles this strait is a narrow valley that resulted from regional uplift of the gelibolu and biga peninsulas in the pliocene as a consequence of compressional events generated by strike slip faulting activity of the ganos fault a northern strand of the north anatolian fault a nne ssw trending fault system between eceabat and canakkale believed to result from the left lateral displacement of the ganos fault on the gelibolu peninsula cut this valley into different segments the connection between the marmara basin and the aegean sea has been achieved after flooding of the connected valleys during the mid to late pleistocene three major sea level lowstands 130 150 m during this period 600 kyear bp interrupted the sea water connection at least twice three main seismic unconformities detected in the sediments of the strait of canakkale represent these lowstands minor sea level lowstands could have induced narrowing of the strait and erosion of depositional units the recent geological history of the strait of canakkale appears as deduced from the gelibolu peninsula and its western regions strongly related to escape tectonics influenced by the compressional forcing of the anatolian block in addition it also shows a morphological evolution which carries the effects of the global sea level variations

strain localization in the sea of marmara propagation of the north anatolian fault in a now inactive pull apart 1 the sea of marmara is presently the site of pure dextral strike slip faulting that connects the izmit fault in the east to the ganos fault in the west along a linear strike slip fault that is part of the northwestern branch of the north anatolian fault this active main marmara fault mmf cuts across a succession of depocenters and highs analysis of a large data set that includes multichannel seismic lines sparker and deep towed high definition seismics shows that most of the n120 e trending normal faults framing these depocenters are now inactive as they are sealed by an average thickness of 300 m of sediments the highs correspond to a series of ne sw trending anticlines and reverse faults blanketed by a thin cover of undeformed sediments we interpret these structures as inverted former transfer faults of the now inactive sea of marmara pull apart system depocenters and highs are the relicts of a former pull apart basins and transfer faults system that accommodated the north anatolian fault motion within the sea of marmara prior to the formation of the mmf we propose that a relatively short a few hundreds of thousands of years period of basin inversion accompanied the localization of strain along the present main marmara fault until it was fully formed 200 100 kyr ago the preexisting pull apart basin system accounts for about 30 km of motion along this fault system and thus probably appeared sometime in late pliocene or early pleistocene as a reactivated portion of the old thrace basin during the plio quaternary the sea of marmara has been the site of progressive localization of strain

tilt measurements in western canada pairs of short baselength mercury level tiltmeters mounted on shallow piers coupled to sedimentary rocks have been used to monitor ground tilting at three inland locations in western canada noise levels have been estimated over large nyquist intervals to evaluate site conditions and for comparison with results observed in crystalline rocks at other locations the results show that tilt noise patterns are similar for different locations and that noise levels are higher for unconsolidated sediments tidal estimates for the principal lunar semidiurnal constituentm2 were obtained from the least noisy sections of the tilt series uncertainties in the estimated amplitudes for the record lengths considered range from 4 to 20 depending on location and azimuth comparison of the observedm2 tide with those predicted for an elastic earth loaded by two different ocean configurations schwiderski or parke shows better agreement with the schwiderski marine tidal model differences between observaton and theory suggest a strain induced perturbation source

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

active tectonics of the izmit gulf ne marmara sea from high resolution seismic and multi beam bathymetry data abstract several active faults were determined in the gulf of izmit using high resolution shallow seismic and multi beam bathymetry data one of them is a buried fault fault 2 following central axis of the gulf which forms the current morphology within its releasing and restraining bends releasing bends control the current morphology of the sub basins also restraining bends form folds in the central basin and a thrust in the western basin a left step over between two strike slip faults faults 2 and 11 creates a transpressional area therefore hersek and catal deltas are uplifted it is determined that fault 2 could not be related to the origination of the gulf because it cuts all basins and ridges thus present geometry of the fault 2 is not suitable for the initial formation of the gulf from this point of view the fault 2 is initiated recently compared to the whole north anatolian fault zone nafz in the marmara sea therefore fault 2 is recognised as a new rupture of the nafz probably active since the end of the last glacial ice period

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

moment tensor inversion of recent small to moderate sized earthquakes implications for seismic hazard and active tectonics beneath the sea of marmara summary we retrieve the moment tensors of 64 small to moderate sized events that occurred mostly beneath the sea of marmara using near field data recorded at strong motion and broad band seismic stations the near field displacement records are inverted to their sources utilizing kuge s method where the best fit between the synthetic and observed seismograms is achieved through searching a centroid moment tensor cmt point in a grid scheme we also analyse the stress fields acting in the eastern and western parts of the sea of marmara by inverting the p and t axes of the focal mechanisms obtained significant biases in the stress tensors are obtained the nearly horizontal maximum compressive axis 1 in the western part is rotated 16 counter clockwise compared with 1 in the eastern part the 2 axis is close to vertical shear tectonic regime in the east and the plunge of 2 axis in the west is 36 transpressive tectonic regime changes in the 3 axis are also observed that is it is close to horizontal in the east and dips 49 in the west the spatial distribution of the focal mechanisms suggests that the stress field in the eastern part of the sea of marmara is homogenous compared with the western part and we identify five distinct subsidiary faults 1 a wnw ese striking right lateral strike slip fault located a few kilometres sw of the princes islands 2 a wsw ene striking right lateral strike slip fault named the yalova hersek fault 3 an e w striking normal fault located onshore between

seismic activity triggered by the 1999 izmit earthquake and its implications for the assessment of future seismic risk summary a serious question has remained as to the location of the western end of the main rupture zone associated with the 1999 izmit turkey earthquake a clear answer to this question is extremely important for the assessment of future seismic risk in the eastern marmara sea region turkey in this paper we show an effective approach to answering this important question unifying different kinds of information such as seismic activity focal mechanism solutions and stress changes caused by the main shock into a clear image we first point out that the major moment release is 1 6r10 20 n m and covered the area between 29 7ue and 30 5ue and we then claim that the enhanced seismic activity after the main shock in the eastern marmara sea region should be regarded as activity triggered by the increase of stress rather than as aftershock activity along the ruptured zone we propose three fault segments with an average stress increase on each in the western extension of the main shock rupture zone as potential sites for future large earthquakes namely i the 50 km long yalova hersek segment 0 45 mpa ii the nw setrending right lateral strike slip fault known as the princes islands segment 0 18 mpa

quaternary time scales for the pontocaspian domain interbasinal connectivity and faunal evolution the pontocaspian black sea caspian sea region has a very dynamic history of basin development and biotic evolution the region is the remnant of a once vast paratethys sea it contains some of the best eurasian geological records of tectonic climatic and paleoenvironmental change the pliocene quaternary co evolution of the black sea caspian sea is dominated by major changes in water lake and sea levels resulting in a pulsating system of connected and isolated basins understanding the history of the region including the drivers of lake level and faunal evolution is hampered by indistinct stratigraphic nomenclature and contradicting time constraints for regional sedimentary successions in this paper we review and update the late pliocene to quaternary stratigraphic framework of the pontocaspian domain focusing on the black sea basin caspian basin marmara sea and the terrestrial environments surrounding these large mostly endorheic lake sea systems

structural framework of onshore and offshore avcilar istanbul under the influence of the north anatolian fault summary to investigate the onshore offshore structural framework of the northern shelf of the sea of marmara a multidisciplinary study was carried out including multichannel and singlechannel seismicreflection profiling multibeam bathymetry sounding side scan sonar imaging on offshore as well as land studies for s wave velocity estimation by passive and active array measurements and monitoring of block deformations by global positioning system gps based on the multidisciplinary data possible interactions between landslides and active faulting have been reviewed and their possible relation to the north anatolian fault zone nafz has been discussed it is observed that structurally the most deformed subsurface zone offshore coincides with the most undulated landform due to landslides in the area this observation leads to idea that the structural complexities of the area may also contribute to land sliding as much as other contributing mechanisms such as slope instability shallow groundwater level lithology and

tectonically induced quaternary drainage diversion in the northeastern aegean the maritsa river in the balkans over 500 km long flows at present into the northern aegean sea geological and geomorphological data indicate that it was flowing into the marmara sea until about 1 5 ma and was diverted into the aegean sea following coseismic uplift along the north anatolian fault seismic reflection sections in the marmara sea indicate the presence of up to 2 5 km thick fluviatile to limnic upper miocene quaternary sediments probably supplied by a palaeo maritsa river the drainage diversion cut off the sediment supply with the result that the terrigeneous sediments of the marmara sea were depressed to a water depth of 1150 m

a statistical approach to relationships between fluid emissions and faults the sea of marmara case the sea of marmara is traversed by the north anatolian fault system and also presents abundant emission sites of methane gas into the water column in order to assess the spatial relationship between gas emissions and active faults the distribution of distances between gas emission sites and the nearest fault is calculated and compared with the distribution of distances between a uniform random distribution of points poisson process representing the null hypothesis of an absence of relationship between gas emissions and faults and the nearest fault interestingly the distance distribution for the poisson process is nearly exponential indicating that the fault map does not have a characteristic scale other than that representing the intensity of the fault network the distance distribution for the observed gas emissions is significantly narrower than that arising from the poisson process with a kolmogorov distance of 0 25 0 02 the crossing point between the two distributions defines the characteristic half width of the swath of gas emission sites around the mapped active faults for the whole sea of marmara data set a characteristic half width of 900 1000 m is found which matches the half width of the seafloor deformation zone observed around the main active fault when the same analysis is applied to zones covering the western high and the central high it is found that the swath of gas emissions is wider on the central high 2 km half width and not clearly related to the seafloor deformation zone there this difference is put in perspective with recent work showing that creep is occurring on the western segment of the main marmara fault this also causing microseismicity while the central istanbul silivri segment may have remained locked since the 1766 magnitude 7 earthquake this suggests that aseismic slip and not only earthquake occurrence effectively maintains high permeability conduits in fault zones in sediments

the earthquake of 1509 in the sea of marmara turkey revisited this article is interdisciplinary in nature relevant to the fields of both earth sciences and historiography which come together in the investigation of long term earthquake hazard taking here as an example the earthquake of 10 september 1509 which was associated with an inferred 70 30 km long offshore fault break in the sea of marmara m w 7 2 0 3 and with widespread damage in istanbul and the adjacent region this article emphasizes the need for systematic and consistent analysis of historical earthquake data and sets an example for such a task the re examination of this earthquake in the context of the long term seismicity of the region over the last 2000 yr and in comparison with larger historic and modern events in the region shows no macroseismic and to some extent no tectonic evidence that the 1509 earthquake was a catastrophic event it is one of the damaging shocks in the 17 century long history of istanbul of a magnitude that was smaller than the large events that can occur further east in the anatolian fault zone this is consistent with the evidence from seismic reflection surveys in the sea of marmara which shows that faults are generally less continuous offshore than onshore as well as from the long term seismicity of the region which is an implication of the opening up of the sea of marmara earthquakes and its association with relatively short faults compared with ruptures of great lengths in the anatolian fault zone further east which is dominated by strike slip

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

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

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

imaging the basin and fault geometry from the multichannel seismic reflection data in the tekirda g basin marmara sea turkey summary determination of the fault geometry in the marmara sea has been a major problem for the researchers after the occurrence of the 1999 august 17 golcuk m 7 4 earthquake to shed a light to the problem we applied the pre stack kirchhoff depth migration technique to the multichannel seismic reflection data of three profiles to investigate the basin and fault geometry in the tekirda g basin in the western marmara sea the boundary of the basin and its sediments were revealed in n s and ne sw directions in depth sections we identify major fault types involving these structures at different locations in tekirdag basin showing that the basin is developed under their movement the north anatolian fault is imaged and interpreted as transtensional character at the centre of the tekirda g basin that is symmetrically divided with a large distributed zone the fault plane is imaged through the depth of 2 km dipping to the north with 90 in the upper 350 m and 82 in the lower part the basin thickness reaches about 2 5 km at that point syn transform sediments of the basin are disturbed by some normal faults dipping to the north these faults are represented by notable displacements of the reflections which prompted us to consider them as a potential tsunami source if they move during a large earthquake along the major fault another major fault is identified at the westernmost of the basin because it shows the same character as ganos fault it might be submarine part of it it has reverse component with the dip angle of 65 to the north and trending along the western flank of the basin a reverse fault is identified appearing in low angle 20 surrounding the edge of the submarine slide at southwest of the basin from its geometry it is interpreted as a local fault formed between two main faults from the sketch of the basin and the fault geometry obtained from the images we suggest that the basin should be formed by a pull apart system

tectonic and sedimentary controls on widespread gas emissions in the sea of marmara results from systematic shipborne multibeam echo sounder water column imaging understanding of the evolution of fluid fault interactions during earthquake cycles is a challenge that acoustic gas emission studies can contribute a survey of the sea of marmara using a shipborne multibeam echo sounder with water column records provided an accurate spatial distribution of offshore seeps gas emissions are spatially controlled by a combination of factors including fault and fracture networks in connection to the main marmara fault system and inherited faults the nature and thickness of sediments e g occurrence of impermeable or gas bearing sediments and landslides and the connectivity between the seafloor and gas sources particularly in relation to the eocene thrace basin the relationship between seepage and fault activity is not linear as active faults do not necessarily conduct gas and scarps corresponding to deactivated fault strands may continue to channel fluids within sedimentary basins gas is not expelled at the seafloor unless faulting deformation or erosional processes affect the sediments on topographic highs gas flares occur along the main fault scarps but are also associated with sediment deformation the occurrence of gas emissions appears to be correlated with the distribution of microseismicity the relative absence of earthquake induced ground shaking along parts of the istanbul silivri and princes islands segments is likely the primary factor responsible for the comparative lack of gas emissions along these fault segments the spatiotemporal distribution of gas seeps may thus provide a complementary way to constrain earthquake geohazards by focusing the study on some key fault segments e g the northern part of the locked princes islands segment

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

active faults in the sea of marmara western turkey imaged by seismic reflection profiles turkey is moving westward relative to eurasia thereby accommodating the collision between arabia and eurasia this motion is mostly taken up by strike slip deformation along the north and east anatolian faults the sea of marmara lies over the direct westward continuation of the north anatolian fault zone just east of the sea of marmara the north anatolian fault splits into three strands two of which continue into the sea while the locations of the faults are well constrained on land it has not yet been determined how the deformation is transferred across the sea of marmara onto the faults on the west coast of turkey we present results from a seismic reflection survey undertaken to map the faults as they continue through the three deep marmara sea basins of clnarclk central marmara and tekirdag in order to determine how the deformation is distributed across the sea of marmara and how it is taken up on the western side of the sea the data show active dipping faults with associated tilting of sedimentary layers connecting the north anatolian fault to strike slip faults that cut the biga and gallipoli peninsulas

clay mineral distribution in last glacial holocene sediment cores from the eastern marmara sea cinarcik basin izmit gulf transition nw turkey multisources and transport paths in a two way flow system abstract the regional variations in grain size xrd bulk and clay mineral distribution in 97 sediment samples from 6 gravity cores obtained from 20 to 300 m water depths have been investigated to reveal source and transportation patterns as well as the effects of climatic and sea level changes during the last 25 000 14 c bp in the eastern marmara sea ems nw turkey the major proportions of sediments in the ems consist of silt 20 83 and clay 17 90 whereas sand and gravel abundances rarely exceed 10 of the bulk minerals 10 a micas 23 55 and feldspars 17 55 dominate over quartz 10 21 and calcite 10 26 smectites 23 62 illite 18 36 chlorites 6 21 kaolinite 2 20 and 14s 14c mixed layer minerals 0 27 constitute the principal clay mineral assemblages both bulk and clay mineral assemblages in the ems are similar to those found in the izmit gulf on the southern marmara shelf at the marmara aegean approaches and the southern black sea this would suggest that there is no distinct source for mineral assemblages of the study area outside the marmara basin the concentrations of clay fractions and clay mineral assemblages tend to increase or decrease with depth in the cores but this is limited to some intervals and not to entire sections in the cores this distribution pattern therefore represents rather local sources of provenance and surrounding fluvial drainage basins together with dilution and distribution effects by current transport processes rather than the expected paleoclimatic features and sedimentary input by inflowing black sea and aegean sea water masses throughout the last glacial to holocene