an active deep marine strike slip basin along the north anatolian fault in turkey the tekirdag depression within the marmara sea in the mediterranean region is an active rhomb shaped strike slip basin along the north anatolian fault with a basin floor at a water depth of 1150 m new multichannel seismic reflection data and on land geological studies indicate that the basin is forming along a releasing bend of the strike slip fault and is filled with syntransform sediments of pliocene quaternary age the basin is bounded on one side by the north anatolian fault and on the other side by a subparallel normal fault which forms the steep submarine slope in cross section the basin is strongly asymmetric with the thickness of the syntransform strata increasing from a few tens of meters on the submarine slope to over 2 5 km adjacent to the north anatolian fault seismic sections also show that the slope forming normal fault connects at depth to the north anatolian fault implying that the basin is completely detached from its substratum the whole structure can be envisaged as a huge rather flat negative flower structure the releasing bend of the north anatolian fault responsible for the formation of the basin is flanked by a constraining bend along the constraining bend the syntransform strata are being underthrust implying a recent change in the direction of the regional displacement vector this thrusting is responsible for the uplift of the submarine slope to a height of 924 m possibly by a mechanism of elastic rebound regional geology suggests that most of the syntransform strata are lacustrine with only the topmost few hundred meters consisting of deep marine clays the anomalous present depth of the tekirdag depression is due to reduced quaternary sedimentation coupled with high rates of displacement along the north anatolian fault which amounts to 20 mm yr in the marmara sea region

active thrusting and folding along the northern tien shan and late cenozoic rotation of the tarim relative to dzungaria and kazakhstan we have studied geometries and rates of late cenozoic thrust faulting and folding along the northern piedmont of the tien shan mountain belt west of urumqi where the m 8 3 manas earthquake occurred on december 23 1906 the northern range of the tien shan rising above 5000 m overthrusts a flexural foredeep filled with up to 11 000 m of sediment of the dzungarian basement our fieldwork reveals that the active thrust reaches the surface 30 km north of the range front within a 200 km long zone of neogene quaternary anticlines fault scarps are clearest across inset terraces within narrow valleys incised through the anticlines by large rivers flowing down from the range in all the valleys the scarps offset vertically the highest terrace surface by the same amount 10 2 0 7 m inferring an early holocene age 10 2 kyr for this terrace which is continuous with the largest recent fans of the piedmont yields a rate of vertical throw of 1 0 0 3mm yr on the main active thrust at the surface a quantitative morphological analysis of the degradation of terrace edges that are offset by the thrust corroborates such a rate and yields a mass diffusivity of 5 5 2 5 m 2 kyr a rather fresh surface scarp 0 8 0 15 m high that is unlikely to result from shallow earthquakes with 6 m 7 in the last 230 years is visible at the extremities of the main fold zone we associate this scarp with the 1906 manas earthquake and infer that a structure comprising a deep basement ramp under the range gently dipping flats in the foreland and shallow ramps responsible for the formation of the active fault propagation anticlines could have been activated by that earthquake if so the return period of a 1906 type event would be 850 380 years the small size of the scarp for an earthquake of this magnitude suggests that a large fraction of the slip at depth 2 3 is taken up by incremental folding near the surface comparable earthquakes might activate flat detachments and ramp anticlines at a distance from the front of other rising quaternary ranges such as the san gabriel mountains in california or the mont blanc aar massifs in the alps we estimate the finite cenozoic shortening of the folded dzungarian sediments to be of the order of 30 km and the cenozoic shortening rate to have been 3 1 5 mm yr assuming comparable shortening along the tarim piedmont and minor additional active thrusting within the mountain belt we infer the rate of shortening across the tien shan to be at least 6 3 mm yr at the longitude of manas 85 5 e a total shortening of 125 30 km is estimated from crustal thickening assuming local airy isostatic equilibrium under the same assumption serial n s sections imply that cenozoic shortening across the belt increases westwards to 203 50 km at the longitude of kashgar 76 e as reflected by the westward increase of the width of the belt this strain gradient implies a clockwise rotation of tarim relative to dzungaria and kazakhstan of 7 2 5 around a pole located near the eastern extremity of the tien shan west of hami 96 e 43 5 n comparable to that revealed by paleomagnetism between tarim and dzungaria 8 6 8 7 a 6 mm yr rate of shortening at the longitude of manas would imply a rate of rotation of 0 45 m y and would be consistent with a shortening rate of 12 mm yr north of kashgar taking such values to be representative of late cenozoic rates would place the onset of reactivation of the tien shan by the india asia collision in the early to middle miocene 16 22 9 m y in accord with the existence of particularly thick late neogene and quaternary deposits such reactivation would thus have started much later than the collision roughly at the time of the great mid miocene changes in tectonic regimes denudation and sedimentation rates observed in southeast asia the himalayas and the bay of bengal and of the correlative rapid change in seawater sr isotopic ratio 20 to 15 ma like these other changes the rise of the tien shan might be a distant consequence of the end of indochina s escape

the morphology of thrust faulting in the 21 september 1999 chichi taiwan earthquake abstract the 80 km long surface rupture of the chelungpu fault in the 21 september 1999 chichi taiwan mw 7 6 earthquake resulted in a surface scarp with vertical throws of 2 9 m and horizontal heaves of 4 8 m few major thrust faults have broken the surface in the past century and the chelungpu surface rupture is of interest in that it provides a morphological template for the identification of paleo surface thrusts in similar neotectonic environments such as the himalaya the toe of the thrust is found emplaced gently over underlying hanging wall materials partly by prograde hanging wall rotation and partly by simple shear leaving few overt clues as to the total amount or sense of slip despite the large surface slip near the toe of the chelungpu thrust its emplacement appears to have been relatively slow msk the medvedev sponheuer karnik 1981 revision of the seismic intensity scale msk81 supersedes the mercalli intensity scale for the description of acceleration induced damage to modern buildings intensity viii accelerations were imposed on buildings on the hanging wall and intensity vii on the footwall decaying in both directions by perhaps one intensity unit a few hundred meters from the rupture the somewhat moderate amplitude of these accelerations for a rupture with several meters of slip is attributed to non linear dissipative deformation near the toe of the rupture the partitioning of thrusting into basal slip and hillside steepening in some locations on the chelungpu fault suggests that the estimation of paleoseismic slip from the offset of piercing points crossing historic thrust faults elsewhere may result in underestimates of fault slip

long term seismicity of istanbul and of the marmara sea region we examine the long term seismicity of the marmara sea region in turkey over a period of twenty centuries to attempt to answer two questions 1 how well recorded in history is the earthquake activity of this region and 2 does seismicity over this long period of time differ from that over the present century we study this densely populated and fast developing region because it is one of the most tectonically active regions on the continents that appears today to be relatively quiescent

the seismicity in the eastern marmara sea after the 17 august 1999 izmit earthquake we used seismic stations that we deployed after the izmit earthquake along the shores and islands of the izmit bay cinarcik basin to study the seismic activity that took place after the earthquake in the eastern marmara sea the aftershock distribution indicates the existence of three clusters of activity there in the days that followed the earthquake one of the clusters shows the extension of the e w trending izmit rupture into the eastern marmara sea the seismic activity there clearly outlines the fault plane of the main rupture and shows its termination 35 km beyond the hersek peninsula two other clusters of activity are present in the region one is in the armutlu peninsula and the other one is located a few kilometers southwest of the tuzla peninsula beneath the northern slope of the cinarcik basin the focal mechanism solutions indicate strike slip faulting along the main branch of the izmit rupture and normal faulting within the two swarms the presence of the different mechanisms suggests the existence of slip partitioning in the region a remarkable feature of the aftershock data is the absence of seismicity above 4 km in the marmara sea manuscript received 30 august 2000

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

morphology displacement and slip rates along the north anatolian fault turkey 1 geological and geomorphological offsets at different scales are used to constrain the localization of deformation total displacement and slip rates over various timescales along the central and eastern north anatolian fault naf in turkey the naf total displacement is reevaluated using large rivers valleys 80 15 km and structural markers pontide suture 85 25 km tosya vezirkopru basins 80 10 km these suggest a neogene slip rate of 6 5 mm yr over 13 myr the river network morphology shows offsets at a range of scales 20 m to 14 km across the main fault trace and is also used to estimate the degree to which deformation is localized at a smaller scale the morphology associated with small rivers is offset by 200 m along the naf the age of these features can be correlated with the holocene deglaciation and a slip rate of 18 3 5 mm yr is determined this is consistent with a rate of 18 5 mm yr deduced independently from the 14c dating of stream terrace offsets over the short term gps data gives a similar rate of 22 3 mm yr all our results tend to show that most of the deformation between the anatolian and eurasian lithospheric plates has been accommodated along or very close to the active trace of the naf the difference between the neogene and the holocene slip rate may be due to the recent establishment of the current plate geometry after the creation of the naf

the active main marmara fault abstract this paper presents selections from and a synthesis of a high resolution bathymetric sparker and deep towed seismic reflection data set recently acquired by the french ifremer r v le suroit in an e w deep trough that forms the northern half of the sea of marmara in nw turkey it includes the first high resolution complete bathymetric map of this area a single throughgoing dextral strike slip fault system which is the western continuation of the northern branch of the north anatolian fault cuts this trough lengthwise and joins the 1999 8 17 kocaeli earthquake fault with the 1912 8 09 arkoy murefte earthquake fault both of which display strike slip offset in its eastern one fourth the structure follows closely the northern margin of the deep trough whereas in the west it hugs its southern margin the eastern one fourth of the structure has a minor component of its displacement distributed across the deep trough owing to a possible original bend in the course of the dextral structure the present course of the north anatolian fault in the sea of marmara originated some 2 105 a ago by cutting across the older basin fabric generated by a dominant nne ssw extension before it began taking up major motion in the pliocene

modification of wave cut and faulting controlled landforms from a casual observation that the form of degraded fault scarps resembles the error function this investigation proceeds through an elementary diffusion equation representation of landform evolution to the application of the resulting equations to the modern topography of scarplike landforms the morphologic observations can be analyzed either in the form of one or more cross strike elevation profiles or in the form of the slope offset plot a point plot of maximum scarp slope versus scarp offset working with either or both of these data representations for nine geologic structures which range in age from 3 to 400 ka b p and in offset from 1 to 50 m we apply analytical solutions for the vertical initial value scarp the vertical continuous offset scarp and the finite slope initial value scarp the model calculations are intrinsically ambiguous yielding as the final answer only the product t in the case of the initial value problem or the product a 1 in the case of the repeated faulting problem here t is the age of a single scarp forming event 2a is the vertical slip rate and is the mass diffusivity a single profile across three sea cliffs along the santa cruz california coast is analyzed as three separate initial value problems a reasonably constrained age for the sea cliff standing above the highway 1 platform returns 11 gkg 1 gkg 1 m2 ka with this we can date the two older sea cliffs in fact we do the converse age estimates for these two older sea cliffs based on a uniform rate of uplift both yield the same as for the lower sea cliff we treat a single profile of the raymond fault in pasadena san marino in terms of the repeated faulting problem for it the uplift rate of r crook and others yields 16 gkg the very substantial preexisting offset across the raymond fault must have been buried leveled some 230 ka b p when the modern topography began to form our analysis of the lake bonneville shoreline scarps reveals a dependence of t on 2a suggestive of nonlinear modification processes this appearance is treated with the finite slope initial value scarp model to determine 1 1 gkg for the lake bonneville shoreline scarps the suggestion of m n machette that approximately 100 000 year old meter high scarps are unobservable in weakly consolidated alluvial terranes of the basin and range and rio grande rift valley provinces can be formulated as 1 gkg the coincidence between this inequality and the lake bonneville shoreline is striking and it suggests that the value of 1 gkg may be generally applicable as a good first approximation to the modification of alluvial terranes within the semiarid regions of the western united states the lake bonneville shoreline is the basis for dating four sets of fault scarps in west central utah the drum mountains fault scarps can be modeled in several different circumstances but the most likely interpretation is that these fault scarps formed as the result of a single episode of normal faulting 3 6 to 5 7 ka b p the younger age is associated with quite low initial slope angles 25 the other three sets of fault scarps show no evidence for finite initial value slopes fault scarps along the eastern base of the fish springs range are very young 3 ka b p we estimate the age of fault scarps along the western flank of the oquirrh mountains to be 32 ka b p which meets the weak geologic constraint that they be older than the lake bonneville shoreline fault scarps along the northeastern margin of the sheeprock mountains are even older 53 ka b p an intriguing consequence of our single event analysis of these scarps is that an 11 5 m offset occurred in a single earthquake

the sea of marmara a plate boundary sea in an escape tectonic regime abstract the sea of marmara is dissected by two major fault systems the first consists of two east west striking transtensional boundary faults and a number of secondary faults subparallel to them the second is made up of ne sw trending subvertical strike slips and their conjugates oriented nw se that offset the first system these fault systems segment the deep marmara sea into 5 blocks that are either rhomboidal lazy z or wedge shaped three of these blocks may be interpreted as pull apart basins characterized by transtension while the other two sill areas which separate the basins are transpressional push up structures the blocks are subjected to rapid episodic subsidence but they also undergo pervasive vertical motions and possible rotations relative to one another the sedimentary column above the acoustic basement mapped within the sea of marmara can be divided into 3 seismic units a folded and truncated pre transform unit and two syn transform units the lower thick syn transform unit exhibits 3 distinct seismic facies a well stratified basin fill facies cut by subvertical growth faults a push up facies with a contorted or chaotic internal configuration and a slump facies the observed neotectonic and sedimentary regimes result from compressional movement between eurasia and africa which has led to major dextral transform movements along the north anatolian fault zone escape tectonics and from the fact that this fault zone splinters into two overlapping right stepping oblique master faults at the eastern and western border of the sea of marmara respectively

seismic hazard in the marmara sea region following the 17 august 1999 izmit earthquake on 17 august 1999 a destructive magnitude 7 4 earthquake occurred 100 km east of istanbul near the city of izmit on the north anatolian fault this 1 600 km long plate boundary 1 2 slips at an average rate of 2 3 cm yr 1 refs 3 5 and historically has been the site of many devastating earthquakes 6 7 this century alone it has ruptured over 900 km of its length 6 models of earthquake induced stress change 8 combined with active fault maps 9 had been used to forecast that the epicentral area of the 1999 izmit event was indeed a likely location for the occurrence of a large earthquake 9 10 here we show that the 1999 event itself significantly modifies the stress distribution resulting from previous fault interactions 9 10 our new stress models take into account all events in the region with magnitudes greater than 6 having occurred since 1700 ref 7 as well as secular interseismic stress change constrained by gps data 11 these models provide a consistent picture of the long term spatio temporal behaviour of the north anatolian fault and indicate that two events of magnitude equal to or greater than the izmit earthquake are likely to occur within the next decades beneath the marmara sea south of istanbul

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

east west extension and holocene normal fault scarps in the hellenic arc examination of surface fault traces with spot images and in the field corroborates the inference that the active tectonics of southern peloponnesus and crete are dominated by approximately north south normal faulting and approximately east west extension the heights of holocene normal fault scarps yield first order regional estimates of fault slip rates between 0 1 and 2 3 mm yr most of the surface scarps probably ruptured during past earthquakes such as that which destroyed sparta in 464 b c on the sparta fault the holocene average slip rate and the recurrence time of large earthquakes may be 1 mm yr and 3000 yr respectively the regional pattern of quaternary faulting suggests that the east west extension near the hellenic subduction zone is fast about 5 10 m y the change from north south to east west extension in the late pliocene 2 4 ma implies that the aegean is starting to collide with the northern margin of africa

submarine fault scarps in the sea of marmara pull apart north anatolian fault implications for seismic hazard in istanbul earthquake scarps associated with recent historical events have been found on the floor of the sea of marmara along the north anatolian fault naf the marmarascarps cruise using an unmanned submersible rov provides direct observations to study the fine scale morphology and geology of those scarps their distribution and geometry the observations are consistent with the diversity of fault mechanisms and the fault segmentation within the north marmara extensional step over between the strike slip ganos and izmit faults smaller strike slip segments and pull apart basins alternate within the main step over commonly combining strike slip and extension rapid sedimentation rates of 1 3 mm yr appear to compete with normal faulting components of up to 6 mm yr at the pull apart margins in spite of the fast sedimentation rates the submarine scarps are preserved and accumulate relief sets of youthful earthquake scarps extend offshore from the ganos and izmit faults on land into the sea of marmara our observations suggest that they correspond to the submarine ruptures of the 1999 izmit mw 7 4 and the 1912 ganos ms 7 4 earthquakes while the 1999 rupture ends at the immediate eastern entrance of the extensional cinarcik basin the 1912 rupture appears to have crossed the ganos restraining bend into the sea of marmara floor for 60 km with a right lateral slip of 5 m ending in the central basin step over from the gulf of saros to marmara the total 1912 rupture length is probably about 140 km not 50 km as previously thought the direct observations of submarine scarps in marmara are critical to defining barriers that have arrested past earthquakes as well as defining a possible segmentation of the contemporary state of loading incorporating the submarine scarp evidence modifies substantially our understanding of the current state of loading along the naf next to istanbul coulomb stress modeling shows a zone of maximum loading with at least 4 5 m of slip deficit encompassing the strike slip segment 70 km long between the cinarcik and central basins that segment alone would be capable of generating a large magnitude earthquake mw 7 2 other segments in marmara appear less loaded

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

using mechanical modeling to constrain fault geometries proposed for the northern marmara sea 1 in recognition of potential seismic hazard along the north anatolian fault within the marmara sea geophysical surveys have recently been conducted to collect high resolution bathymetry and seismic reflection data despite the high quality of the data fault interpretations by different authors are varied and a conclusive fault geometry within the marmara sea remains elusive this paper presents a mechanical modeling method for constraining proposed fault geometry interpretations in the model crustal faults within the marmara sea slip in accordance with gps constrained slip rates along deep plate boundary dislocations we test three fault models proposed by others and show that an interpretation with a series of pull apart basins along a master strike slip fault best produces the observed deformation pattern within the marmara sea the locations and relative subsidence of the basins along the northern marmara trough are well matched the computed slip vectors on the faults in the best fitting model indicate that except for small faults bounding the tekirdag basin the faults have dominantly right lateral slip with rakes within 15 of horizontal on the local scale this suggests that interaction between the segmented strike slip faults is the dominant mechanism producing the observed vertical deformation in the marmara sea on the regional scale if the marmara sea faults behaved in this manner over geologic timescales then right lateral plate boundary motion without an additional component of north south extension associated with the aegean sea is sufficient to produce the marmara sea pull apart basin morphology

a possible normal fault rupture for the 464 bc sparta earthquake surface ruptures have been identified for some normal faulting earthquakes in the aegean region1 3 but for most historical earthquakes the associated faults are unknown this hampers the evaluation of the rates and styles of present day deformation and the assessment of seismic hazard in the region4 here we examine the famous earthquake that destroyed sparta in 464 bc using spot satellite images and fieldwork we have mapped a 20 km long normal fault scarp trending approximately north south a few kilometres east of the ancient city our observations combined with an examination of historical descriptions of the earthquake damage suggest that the sparta earthquake ruptured this fault scarp in an event of magnitude ms 7 2 the holocene slip rate and the recurrence time for such large events on the sparta fault would be 1 mm yr 1 and 3 000 yr respectively

late holocene expansion of a south swedish peatland and its impact on marginal ecosystems evidence from dendrochronology peat stratigraphy and palaeobotanical data in this study a reconstruction of the long term development and lateral expansion of a south swedish peat bog was performed using a multi proxy approach including dendrochronology peat stratigraphy and macrofossil and pollen analyses by combining mapping of cross dated subfossil trees with radiocarbon dated peat sequences an improved approach to reconstruction of lateral peat expansion was applied apart from providing approximate ages of tree burial episodes the ring width records offer information on hydrological variations prior to the bog expansion new bog oak pine and alder chronologies are presented and their potential as a dating tool for peatland expansion as well as for local to regional environmental interpretations is examined our tree replication records show that increased amounts of bog trees in the central parts can be linked to drier bog surface conditions whereas an increase in wood remains in the marginal zone is related to enhanced preservation due to lateral bog expansion our reconstructions of the development of the peat deposit and associated changes in the distribution of vegetation communities provide new insight into peatland responses to climate change at the end of the holocene thermal maximum 5000 4000 cal yr bp less

characteristics of the 1912 co seismic rupture along the north anatolian fault zone turkey implications for the expected marmara earthquake evidence of right lateral offsets associated with the 1912 earthquake mw 7 4 along the north anatolian fault gazikoy saros segment allow us to survey using dgps the co seismic and cumulative slip distribution the damage distribution and surface breaks related with the earthquake show an elongated zone of maximum intensity x msk parallel to the fault rupture on land but this may extend offshore to the north east and south west detailed mapping of the fault using topographic maps and aerial photographs indicates the existence of pull apart basins and pressure ridges at several localities the average 1912 offset along strike is 3 5 4 m and cumulative slip is 2 6 times that of individual movement the fault rupture geometry and slip distribution suggest the existence of three subsegments with a combined total length of 110 120 km a fault length and maximum slip similar to those of the 1999 izmit earthquake the amount of slip at the north easternmost section and in the coastal region of the sea of marmara reaches an average 4 m thereby implying the offshore exten sion of the 1912 rupture the results suggest that the 1912 event generated up to 150 km of surface faulting which would imply a mw 7 2 7 4 earthquake and which added with rupture lengths of the 1999 earthquakes help to constrain the remaining seismic gap in the sea of marmara

triggered slip observations of the 17 august 1999 izmit turkey earthquake using radar interferometry we use synthetic aperture radar interferometry insar to map the displacement field of the 17 august 1999 izmit earthquake which largely conforms to that predicted for an elastic upper crust we determine the earthquake source parameters and show that slip continues farther west than the mapped fault ruptures we also show that additional sub surface displacements occurred on parallel strands of the north anatolian fault zone we argue that this was caused by changes in static stress accompanying the mainshock or by the dynamic release of regional stresses

westward propagation of the north anatolian fault into the northern aegean timing and kinematics we present new evidence for the propagation processes of the north anatolian fault folding in the dardanelles straits region allows us to document the timing of the deformation preceding and the finite displacement after the passage of the propagating tip of the fault the accuracy of the observations is due to interplay between deformation and the sea level changes in the mediterranean the well known messinian regression followed by the pliocene transgression the long term kinematics around the sea of marmara pull apart total displacement of about 85 km over the past 5 m y is similar to the present day kinematics deduced from space geodesy at a larger scale westward propagation of the north anatolian fault over nearly 2000 km in the past 10 m y appears to be associated with strain recovery suggesting that the continental lithosphere retains long term elasticity

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

asymmetric slip partitioning in the sea of marmara pull apart a clue to propagation processes of the north anatolian fault between 1939 and 1999 the north anatolian fault naf experienced a westward progression of eight large earthquakes over 800 km of its morphological trace the 2000 km long north anatolian transform fault has also grown by westward propagation through continental lithosphere over a much longer timescale 10 myr the sea of marmara is a large pull apart that appears to have been a geometrical mechanical obstacle encountered by the naf during its propagation the present paper focuses on new high resolution data on the submarine fault system that forms a smaller pull apart beneath the northern sea of marmara between two well known strike slip faults on land izmit and ganos faults the outstandingly clear submarine morphology reveals a segmented fault system including pull apart features at a range of scales which indicate a dominant transtensional tectonic regime there is no evidence for a single continuous purely strike slip fault this result is critical to understanding of the seismic behaviour of this region of the naf close to istanbul additionally morphological and geological evidence is found for a stable kinematics consistent both with the long term displacement field determined for the past 5 myr and with present day anatolia eurasia motion determined with gps however within the sea of marmara region the fault kinematics involves asymmetric slip partitioning that appears to have extended throughout the evolution of the pull apart the loading associated with the westward propagation process of the naf may have provided a favourable initial geometry for such a slip separation

sea level changes and depositional environments in the izmit gulf eastern marmara sea during the late glacial holocene period abstract offshore and onshore stratigraphic studies together with high resolution shallow seismic reflection profiling and multibeam bathymetric mapping were carried out in the western and central part of the izmit gulf these studies indicate that the izmit gulf was a lacustrine environment as part of the marmara lake during the late glaciation and early deglaciation until 12 kyr bp when the marmara basin was inundated by the mediterranean waters correlation of 14 c dated onshore and offshore stratigraphic units in the western izmit gulf indicates that generally coarse late glacial sediments overlie a marked erosional surface formed during the low water level of the marmara lake these coarse sediments are succeeded by 10 4 7 kyr bp old transgressive and by late holocene post transgression mud units the bathymetry and sub bottom chirp profiles clearly show that the paleoshoreline of the gulf was located at 85 m having been controlled by the bedrock sill depth of the canakkale strait another paleoshoreline observed at 65 m on the northern margin of the western izmit and karamursel basins was probably formed during the younger dryas sea level stillstand the shelf areas during this time were colonized by bioherms which were subsequently drowned and disappeared after a further rise of the sea level the presence of a 65 m marine paleoshoreline in the karamursel basin indicates that the sill restricting this basin to the west was much deeper than its present 55 m level and was located further south the golcuk basin restricted by a 38 m sill to its west was probably not flooded by marine waters until 9 kyr bp

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

stress coupling between earthquakes in northwest turkey and the north aegean sea we have investigated the coulomb stress interactions of 29 earthquakes m s greater than or equal to 6 0 that have occurred in the region of northwest turkey and north aegean sea since 1912 of these events 23 may be related to earlier events and 16 are clearly related to earlier events all events after 1967 are related to previous events events in the early part of our time interval that show no correlation could be related to historical events as yet unidentified in some cases faults that have received a stress reduction from earlier events are prepared for an event by an earthquake occurring a few years before that creates a local coulomb stress rise thus regions of coulomb stress shadow can become regions where a damaging earthquake may occur the relation between smaller events and the coulomb stress distribution is less clear but may be related to poor data quality and practical limitations of our modeling technique nonetheless there are 4 times as many events per unit area in regions of enhanced stress than where stress is reduced we discuss the contemporary distribution of coulomb stress and argue that it is possible to identify the likely locations of future damaging earthquakes including identifying the most likely candidate faults

oblique slip slip partitioning spatial and temporal changes in the regional stress field and the relative strength of active faults in the basin and range western united states when viewed with stress transformation laws and an idealized physical model observations of oblique slip and slip partitioning in the basin and range western united states are interpreted to show that 1 separate regions with the same net extension direction are not necessarily characterized by the same regional stress field 2 fault systems exhibiting partitioning where one of the faults is near vertical generally do not require temporal changes in the stress field to explain the disparate slip vectors on the adjacent faults and 3 the relative strengths of active fault zones may vary by more than an order of magnitude

rapid slip along the central altyn tagh fault morphochronologic evidence from cherchen he and sulamu tagh consistent with the d 18 o record from the guliya ice cap in the west kunlun the features of interest were all formed by glacial and fluvial processes subsequent to marine isotope stage 5e with the youngest features having formed during the early holocene optimum this near field morphochronological slip rate is averaged over many earthquake cycles and is hence little affected by interseismic strain it is kinematically consistent with other somewhat lower geomorphic slip rate measurements to the east the average rate and lower bounds obtained from alternate interpretational models 18 4 mm yr cannot be reconciled with the most rece geodetic measurements 7 mm yr suggesting that interseismic strain and interactions with adjacent faults may lead to disparate geologic and geodetic rate estimates this late pleistocene holocene morphochronologic rate would imply that at this longitude the altyn tagh fault on the north edge of tibet might absorb almost as much of india s convergence relative to siberia as the himalayan main frontal thrust does on the southern edge of the plateau index terms 1035 geochemistry geochronology 1208 geodesy and gravity crustal movements intraplate 8110 8102 tectonophysics continental contractional orogenic belts 8107 tectonophysics continental neotectonics keywords slip rates cosmogenic dating indo asian collision

extension of the north anatolian fault into the north aegean trough evidence for transtension strain partitioning and analogues for sea of marmara basin models 1 the north aegean trough is tectonically controlled by the projection of the north anatolian fault from western turkey and the sea of marmara into the aegean where deformation is distributed in contrast to the simple strike slip fault model for central eastern turkey this region accommodates extensional and dextral displacement new side scan sonar data coupled with new subbottom profiler and published seismic data reveal evidence for dextral displacement within the eastern trough and gulf of saros in the form of oblique en echelon and riedel r r and p fractures and displaced geomorphic features strain partitioning in the shallow crust allows the following two styles of faulting to coexist supported by earthquake focal mechanisms 1 transtensional basin bounding faults controlling the significant vertical topography of the basin and 2 dextral faulting within the central basin these styles of faulting merge at greater depths into a single fault a possible sinistral nw striking fault separates two subbasins and may indicate crustal block rotation with deformation focused in block corners such evidence and models from the north aegean are similar to models of transtension and pull apart basins within the sea of marmara

late cenozoic right lateral strike slip faulting in southern tibet field observations collected during the sino french himalaya tibet cooperation project 1980 1982 show that right lateral faulting between southern and northern tibet roughly along the chord joining the eastern and western syntaxes of the himalayan arc is a major component of the active tectonics north of the himalayas just north of the well developed rifts of southern tibet we studied three right lateral 100 200 km long strike slip faults forming an en echelon array along that chord evidence for earthquake surface breaks was found on each of these faults for the m 8 beng co or damxung strike slip earthquake of november 18 1951 rupture parameters could be constrained to be 8 2 m and l 90 km offset glacial and postglacial morphological markers 105 years and 104 years b p imply displacement rates of the order of 1 2 cm yr on the three faults the en echelon fault zone appears to extend westward 2000 km across the plateau to the karakorum fault and is thus referred to as the karakorum jiali fault zone kjfz fast rates of slip on it and on faults along the northern rim of tibet appear to contrast with the slower rates of deformations in the interior of the plateau our estimates of slip rates on the strike slip and normal faults of southeastern tibet suggest that eastward extrusion of north tibet between the right lateral kjfz and the left lateral altyn tagh and kun lun faults absorbs at least 30 of the present convergence between india and asia we propose an instantaneous velocity model of the active tectonics of asia compatible with such faulting rates and geometries evidence for tertiary right lateral strike slip movements in southern tibet and around the eastern syntaxis of the himalayas is also found in the structural record offsets of various large scale geological features imply that these movements have been large

linear elastic fracture mechanics explains the past and present evolution of the aegean abstract geologically the deformation in the anatolian aegean region has been dominated by two processes the propagation of the north anatolian fault associated with the extrusion of the anatolian plateau and the north south stretching of the aegean we model gps data in the context of this understanding localised deformation zones are represented by dislocation elements which extend from the base of the lithosphere to the locking depth at the base of the seismogenic layer unlike other gps interpretations our models incorporate geological and seismological constraints to provide a robust description of the present day deformation of the anatolian aegean region we then show that the present day deformation observed by gps today is consistent with the continuation of the geological processes that started in the tertiary our approach is also consistent with the lithosphere preserving long term elastic strength and with the concepts of linear elastic fracture mechanics applying at a large scale

characteristics and evolution of ore forming fluids associated with yanshanian magmatic activity in dongguashan copper deposit anhui province china based on petrography microthermometry and lrm analysis of fluid inclusions in garnet diopside quartz and calcite this paper has discussed characteristics and evolution of ore forming fluids in the dongguashan copper deposit the ore forming fluids of yanshanian magmatism evolved from high temperature high salinity and k rich fluids via moderate high temperature and co2 ch4 rich fluids to moderate low temperature and low salinity fluids the analytical results suggest that the dominant volatiles in the ore forming fluids are h2o co2 and ch4 with minor c2h6 h2s n2 etc na k as well as ca2 mg2 are dominant cations whereas cl and so42 are major anions high k and co2 ch4 constitute the main feature of the ore forming fluids related to yanshanian magmatism

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

active faults and evolving strike slip basins in the marmara sea northwest turkey a multichannel seismic reflection study abstract the north anatolian fault is a 1200 km long transform fault forming the boundary between the anatolian and eurasian plates near its western end it strikes through the marmara sea and is responsible for the creation of three deep marine depressions the north anatolian fault system and the linked basins in the eastern marmara sea were studied using newly acquired multi channel seismic reflection data in the marmara sea the north anatolian fault consists of a main strand and a few subsidiary branches the main strand is made up of the ganos 15 km long central marmara 105 km and north boundary 45 km fault segments the north boundary fault joins in the east to the izmit segment which was ruptured during the m s 7 4 earthquake on 17 8 1999 the north boundary fault is highly oblique to the regional displacement vector which results in the generation of a symmetrical fault wedge basin this cinarcik basin is a wedge shaped deep marine depression south of istanbul it is about 50 km long up to 20 km wide and 1250 m deep and is filled with pliocene to quaternary sediments over 3 km thick the north boundary fault joins in the west to the transpressional central marmara fault around the restraining segment boundary the syntransform sediments are being deformed into a large anticlinorium the cinarcik basin started to form when the westward propagating north anatolian fault intersected a northwest trending pre existing fault zone during the pliocene and bifurcated into nw and sw trending segments forming a transform transform transform type triple junction dextral strike slip movement along the arms of the triple junction led to the development of the cinarcik basin the present fault geometry in the marmara region was achieved later during the mid pliocene following the termination of the triple junction geometry south of the main north anatolian fault system there is a second active strike slip fault in the marmara sea made up of several segments a highly asymmetrical fault bend basin comprising pliocene quaternary sediments over 2 5 km thick is forming along a releasing fault segment of this south boundary fault system

rapid active thrusting along the northwestern range front of the tanghe nan shan western gansu china the western part of the tanghe nan shan range southwest of subei western gansu china is presently growing on thrust ramps splaying from the left lateral altyn tagh fault late cenozoic thrusting has folded and sliced oligocene miocence red beds into an imbricate wedge capped by warped and uplifted quaternary terraces that form a 2 to 5 km wide ledge north of the steeply faceted range front seismic scarps 1 5 to 4 5 m high cut young fans along the outer thrusts carbon 14 dating of organic remains collected on strath terraces constrains the chronology of deposition and incision by the streams most of the fans and terraces in the southern part of the subei basin appear to have been emplaced after the last glacial maximum particularly during the early holocene optimum 9 5 ka measurements of the shapes of the warped terraces constrain minimum and maximum throws on the outer thrusts the minimum vertical throw of 34 2 m of a surface dated at 8411 530 years b p at one site provides a minimum vertical uplift rate of 4 1 0 5 mm yr the maximum possible uplift 115 15 m of the oldest terrace surface whose probable age is 15 to 18 ka places an upper bound on the uplift rate of 7 2 mm yr the thrust geometry at depth and the cumulative shortening 10 20 km deduced from balancing sections logged across the imbricate thrust wedge are consistent with a shortening rate of about 5 mm yr and an onset of thrusting at about 4 2 ma such a shortening rate implies a significant northward decrease in slip rate along the altyn tagh fault the recent growth of the western qilian mountain ranges thus appears to be intimately coupled with sinistral motion on the altyn tagh fault and the extrusion of tibet

gps and geologic estimates of the tectonic activity in the marmara sea region nw anatolia a dense network of 52 global positioning system gps sites is used to determine the velocity field and strain rate pattern at the western end of the north anatolian fault zone nafz in the marmara sea region nw anatolia based on four gps campaigns carried out biannually between 1990 and 1996 the detailed kinematic field of crustal motion is calculated the southernmost station shows an average rate of 22 3 mm yr oriented westward relative to istanbul eurasia this value is indicative of the dextral strike slip motion of nw anatolia relative to the black sea the gps velocity field reveals that the sites located on the thrace black sea block show negligible motion relative to istanbul the gps based deformation pattern of three sections crossing the westward prolongation of the nafz is compared with neotectonic data both the gps and the neotectonic data give clear evidence that most of the deformation occurs along a relatively narrow e w oriented zone this belt extends from the single fault trace of the nafz through the gulf of izmit the marmara sea the arkoy region and the gulf of saros into the north aegean trough nat in addition the cross sections show the increasing influence of the n s oriented extension in the aegean sea region from the comparison of the directions and rates of shear and normal strain deduced from gps data with geologic and seismic observations we conclude that the most active zone of dextral shear follows a line along mudurnu valley the northern marmara sea and the saros trough where it joins the nat

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

interaction between faulting and sedimentation in the sea of marmara western turkey 1 the aegean region is one of the most rapidly deforming continental areas in the world in the sea of marmara interaction between strike slip and extensional faulting has led to a complicated style of local deformation to the east the continental plate containing eastern and central turkey is moving westward with respect to eurasia with little internal deformation tectonic deformation is restricted to a narrow zone along the dominantly strike slip north anatolian fault however in the vicinity of the sea of marmara both surface mapping of faults and earthquake fault plane solutions indicate that extensional motions presumably related to back arc extension behind the hellenic subduction zone create a much wider zone of deformation which reaches hundreds of kilometers in width we use a regional grid of high resolution seismic reflection profiles to map the fault systems as they cross the sea of marmara and show how they divide the sea of marmara into separate deep basins with distinctive sediment sources and depositional styles in the southern sea of marmara these basins are half graben formed on north dipping fault planes which have trapped sediment coming into the sea of marmara from the south no evidence is found in the data set for the existence of a single strike slip fault through the sea of marmara or for the existence of a northern boundary fault along the tekirdag and central marmara basins we conclude that a single strike slip fault would be incapable of accommodating the relative motion and extension observed between western turkey and eurasia