Interaction between faulting and sedimentation

in the Sea of Marmara, western Turkey

J. R. Parke,1 R. S. White,1 D. McKenzie,1 T. A. Minshull,2 J. M. Bull,2 I. Kuscu,3

N. Gorur,4 and C. Sengor4

Received 13 February 2001; revised 17 August 2001; accepted 22 August 2001; published 12 November 2002.

[1] The Aegean region is one of the most rapidly deforming continental areas in theworld. In the Sea of Marmara, interaction between strike-slip and extensional faulting hasled to a complicated style of local deformation. To the east, the continental platecontaining eastern and central Turkey is moving westward with respect to Eurasia, withlittle internal deformation. Tectonic deformation is restricted to a narrow zone along thedominantly strike-slip North Anatolian fault. However, in the vicinity of the Sea ofMarmara, both surface mapping of faults and earthquake fault plane solutions indicate thatextensional motions, presumably related to back arc extension behind the Hellenicsubduction zone, create a much wider zone of deformation which reaches hundreds ofkilometers in width. We use a regional grid of high-resolution seismic reflection profiles tomap the fault systems as they cross the Sea of Marmara and show how they divide theSea of Marmara into separate deep basins with distinctive sediment sources anddepositional styles. In the southern Sea of Marmara these basins are half graben, formedon north dipping fault planes, which have trapped sediment coming into the Sea ofMarmara from the south. No evidence is found in the data set for the existence of a singlestrike-slip fault through the Sea of Marmara or for the existence of a northernboundary fault along the Tekirdag and Central Marmara basins. We conclude that a singlestrike-slip fault would be incapable of accommodating the relative motion and extensionobserved between western Turkey and Eurasia. INDEX TERMS: 3025 Marine Geology and

Geophysics: Marine seismics (0935); 8105 Tectonophysics: Continental margins and sedimentary basins; 8010

Structural Geology: Fractures and faults; KEYWORDS: faulting, tectonics, Turkey, Marmara, active, seismic

Citation: Parke, J. R., R. S. White, D. McKenzie, T. A. Minshull, J. M. Bull, I. Kuscu, N. Gorur, and C. Sengor, Interaction between

faulting and sedimentation in the Sea of Marmara, western Turkey, J. Geophys. Res., 107(B11), 2286, doi:10.1029/2001JB000450,

2002.

1. Introduction

[2] Because the Aegean region is deforming rapidly and isseismically active, it has inspired a great deal of research intoactive continental tectonics [e.g., McKenzie, 1972; Robertsand Ganas, 2000; Briole et al., 2000]. East-west striking,normal faulting earthquakes occur in central Greece andwestern Turkey, but large right-lateral strike-slip earthquakesoccur along the approximately east-west North Anatolianfault, in eastern and central Turkey, and with a northeast-southwest trend in the north Aegean. The two sets of focalmechanisms have markedly different slip vectors, whichchange direction between the eastern and western parts ofthe Sea of Marmara. McKenzie and Jackson [1986] and

Taymaz et al. [1991] describe block models which accountfor the sudden transition between strike-slip and normalfaulting across the north Aegean. They suggest that thenormal faults in central Greece accommodate the deforma-tion imposed by the strike-slip faults in the northern Aegeanby forming a right-lateral shear zone within which thenormal fault blocks rotate clockwise.[3] It is now apparent that most of the present-day

deformation in the Aegean region may be accounted forby the transfer of the westward motion of Turkey along theNorth and East Anatolian faults, with respect to stableEurasia. Central Turkey is characterized by coherent platemotion (internal deformation of <2 mm yr�1) [McClusky etal., 2000], while western Turkey is extending. The centraland southern Aegean is also characterized by coherentmotion toward the southwest. The westward motion ofTurkey is the consequence of continental collision betweenArabia and Eurasia to the east [McKenzie, 1972], which isthought to have begun during the Miocene [Morris andAnderson, 1996].[4] The North Anatolian fault is a relatively simple,

narrow, right-lateral strike-slip fault zone along most of its

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. B11, 2286, doi:10.1029/2001JB000450, 2002

1Bullard Laboratories, Cambridge, UK.2Southampton Oceanography Centre, Southampton, UK.3Maden Tetkik ve Arama Genel Mudurlugu, Ankara, Turkey.4Istanbul Technical University, Maden Fakultesi, Jeoloji Bolumu

Ayazaga, Istanbul, Turkey.

Copyright 2002 by the American Geophysical Union.0148-0227/02/2001JB000450$09.00

EPM 2 - 1

1500 km length (Figure 1). Its trend is clearly visible in thetopography, running through eastern and north centralTurkey. The deformation zone widens in western Turkey,where it enters the Sea of Marmara. Eleven earthquakes ofMw > 6.7 have ruptured 1200 km of the fault in the period1939–1999. TheMw 7.4 Kocaeli earthquake occurred on 17August 1999, �70 km from Istanbul. It highlighted the needfor detailed maps of the fault distribution in the area. Thekey question of whether the deformation in the Sea ofMarmara could be accommodated on one single fault,which could generate a Mw 7.5–8 earthquake, or on severalsmaller (Mw 6.5–7) faults is still a matter of debate.Although accurate documentation of surface rupture is arecent activity, the surface expressions of each event arerelatively well known in these cases. Rather than being onecontinuous, unbroken fault, it is apparent that the deforma-tion is concentrated in a narrow zone some 50 km wide,with the motion between Turkey and Eurasia being taken upon many faults within this zone.[5] Eastern and central Turkey can be modeled kinemati-

cally as a single rigid solid body, moving westward on theNorth and East Anatolian faults, with little internal defor-mation, and GPS data for central Turkey can be fit by asolid body rotation about a pole in the Nile Delta [Reilingeret al., 1997; McClusky et al., 2000] (Figure 2a). This fit

fails in western Turkey where the GPS velocities are nolonger consistent with such a simple rotation. This failure isdue to the onset of north-south extension, possibly becauseof the influence of the Hellenic subduction zone to thesouth. The GPS velocities in western Turkey and theAegean increase in magnitude toward the Hellenic arcand also have a radial component, responsible for thenorth-south extension (Figure 2b).[6] The regional seismicity of the area confirms the

pattern of deformation described above (Figure 3). In eastand central Turkey the seismicity is confined to the Northand East Anatolian fault zones, with central Turkey beingrelatively aseismic and undeformed. In the west, manyextensional mechanisms occur, taking up the internal defor-mation of western Turkey. Both surface mapping and earth-quake focal mechanisms indicate that the North Anatolianfault zone becomes more complex, with both strike-slip andextensional mechanisms west of 31�E [Reilinger et al.,1997]. It splits into several well-defined fault strands inthe vicinity of the Sea of Marmara so that the deformationbecomes distributed over a 130-km broad zone [Barka andKadinsky Cade, 1988]. The distributed deformation contin-ues to the west across the north Aegean [Taymaz et al.,1991]. Fault plane solutions show that the faults whichcontrol the tectonics of a region usually have either a clear

o

Figure 1. Map of the eastern Mediterranean, showing the main fault systems. The dashed line showswhere the strike-slip motion on the North Anatolian fault must be transferred through to the Hellenicsubduction zone but does not define a specific location or type of fault.

EPM 2 - 2 PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA

normal, thrust, or strike-slip component, with only thesmaller faults exhibiting combined dip-slip motion.[7] Of the two fault strands which continue into the

eastern Sea of Marmara, the northernmost, which runsthrough the Gulf of Izmit and Cınarcık, has experiencedmost historical seismicity (Figure 4) [Ambraseys, 1988]. Inthe northwest the Ganos fault is the only major tectonicfeature which leaves the Sea of Marmara and continues intothe north Aegean. In the intervening region beneath the Sea

of Marmara, there must exist a complex transfer of thismotion.[8] There is a sparsity of data between Cınarcık and

Tekirdag (Figure 4), with respect to the locations of thefaults in the zone of deformation. Traditional methods ofhistorical earthquake analysis and location, based on dam-age assessment to population centers, work reasonably wellin populated areas because records of building damage andrepair work can be studied. However, without recorded fault

Figure 2. GPS data from McClusky et al. [2000] for the eastern Mediterranean. (a) GPS velocitiesrelative to stable Eurasia. Note the solid body rotation of eastern and central Turkey and the increase inmagnitude of velocities toward the Hellenic subduction zone. (b) The same velocity field in a centralTurkey rest frame, highlighting the extensional opening of western Turkey.

PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA EPM 2 - 3

breaks it is not yet possible to locate individual historicalearthquakes onto specific faults. For events located inunpopulated areas, or underwater, no such historical recordcan exist. This is true for the submarine events in the Sea ofMarmara, and the area has not experienced a major earth-quake since modern seismological techniques like P and SHbody wave inversion were developed [Nabelek, 1984]. Evenusing these types of methods, instrumental earthquakelocations are rarely sufficiently accurate to be located ontoa specific fault without further field study [Ambraseys andJackson, 2000].[9] Several models have been proposed to explain the

observed deformation in and around the Sea of Marmara[Smith et al., 1995; Wong et al., 1995; Barka and KadinskyCade, 1988; Okay et al., 1999, 2000; Imren et al., 2001].Here we consider the kinematic aspect of the problem. Okayet al. [2000] attempted to model the development of theeastern Sea of Marmara as a series of transform faults,meeting at an unstable triple junction. While concepts suchas these may be adequate for oceanic faulting, they aremisleading when applied on land as they fail to take accountof the distributed nature of continental deformation. Such isalso the case with Imren et al. [2001], who concluded that asingle fault crossed the Sea of Marmara. We show that such

a fault would be unstable in time and that there is noevidence in the historical seismic record of such a faultrupturing its entire length in one event [Ambraseys andJackson, 2000].[10] Here we present a detailed analysis of over 1500 km

of high-resolution seismic reflection profiles acquired inthe Sea of Marmara in September 1997 [Parke et al., 1999](Figure 4). The seismic source was a 10-gun, 23-L tunedair gun array. The hydrophone had 96 channels andextended to a maximum offset of 1500 m from the ship.Because of the relatively small offset the stacking andinterval velocities generated from data processing arepoorly constrained; hence the seismic profiles are presentedas time sections.[11] Navigation was by differential Global Positioning

System (DGPS), allowing a theoretical source locationaccuracy of 5 m. However, the position of the streamer isless well known. Magnetic data acquired from birds alongthe length of the streamer during the cruise suggested that itcould at times have been as much as 20� away from the sailline. This, along with the sparse density of reflectionprofiles in the northern Sea of Marmara, and the lack ofdepth constraints from well data prevent a realistic quanti-tive analysis of the structures and their evolution.

o

o

o

o o o o o

o

o

o

o o o o o

Figure 3. Regional seismicity of the eastern Mediterranean from the Harvard centroid moment tensor(CMT) catalogue [Dziewonski et al., 1981]. Focal mechanisms plotted areMw � 5.0. Extensional faultingin central Greece and western Turkey contrasts with the inactivity of central Turkey. Regions of strike-slip deformation in the Aegean are also clear.

EPM 2 - 4 PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA

Figure

4.

Map

oftheSea

ofMarmara,showingseismicity,andreflectionprofilesacquired.Areas

covered

inmore

detail

byFigures5,10,and15arelabeled

a,b,andc.

Faultplanesolutionsfrom

theHarvardCMTcatalogue,

exceptwhere

mechanismshavebeenP

andSH

modeled

[Taym

azet

al.,1991].Onshore

faultsarefrom

Saroglu

etal.[1992],and

offshore

faultsarefrom

Parkeetal.[1999].GPSdatafrom

McC

luskyetal.[2000]areshownin

theTurkey

restfram

e.The

relativeopeningofthewestern

Sea

ofMarmaracompared

totheeastisapparent.

PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA EPM 2 - 5

[12] The effects of normal faulting are generally easy toobserve on seismic reflection profiles. Normal faults pro-duce vertical displacements in sedimentary horizons, andthe horizons are tilted by repeated slip on the faults. Strike-slip faults are much more difficult to identify because thesense of motion is out of the plane of the reflection profile.Horizons may not be offset vertically nor tilted by slip on astrike-slip fault. In this study, attention is given to areaswhere the sediments have been deformed in some way, andthese areas are identified as zones of potential strike-slipfaulting.[13] This data set has been used to produce a detailed map

of large faults as they cross the deep basins in the Sea ofMarmara and transfer motion from the North Anatolian faultin the east to the Ganos fault which continues into the northAegean in the west. We consider differences in tectonicstyle in each of the basins and discuss implications for anyfuture model of faults in the area. Despite these data leadingto a better understanding of the deformation in the Sea ofMarmara, all the issues raised by previous work have stillnot been resolved.

2. Western (Tekirdag) Basin

[14] The evolution of the Strait of Canakkale (Figure 5)has been much disputed [Yaltırak et al., 2000; Armijo et al.,1999; Demirbag et al., 1998]. While there is still debateabout timing and development, the consensus is that the

present coastline is defined by strike-slip faulting interactingwith easily eroded Miocene-Pliocene sediments and Holo-cene deposits. Smith et al. [1995] examined the approachesto the Dardanelles using high-resolution sparker seismicreflection profiles which provide a useful complement to themore deeply penetrating air gun seismic profiles discussedhere. The sparker survey was carried out on the shallownorthern and southern shelves in the western Sea of Mar-mara and only penetrates to a two-way time (TWT) of 200ms (�150 m). The sparker data show clear offsets in theburied sediments just to the north of Marmara Island (Figure5). To the north of the Kapidag Peninsula, a north dippingseabed scarp with an apparent offset of 3 m is observed,showing that the fault has been active recently.[15] On 20 September 1999, a Mw 5.3 earthquake

occurred close to Marmara Island (40.49�N, 27.58�E,National Earthquake Information Center). The uncertaintyin its location is �10 km, which means that the event cannotbe located on the faults in the deep Tekirdag basin, and mostlikely occurred on either the Marmara Island fault or theKapidag fault.[16] The westernmost basin within the Sea of Marmara is

the simplest to describe in terms of the kinematics of itsformation. The basin floor is at �1150 m depth. The presentdepth of this depression is thought to be due to reducedQuaternary sedimentation, as no large rivers drain into thebasin from the north. Sediments brought in from the southare trapped by back tilting of fault blocks, which fault on

Figure 5. Map of the western Sea of Marmara. Reflection profiles are shown by thin solid lines, withthe sections discussed here shown by heavy dashed lines. Faults are interpreted from mappable horizonson profiles. Depths and altitudes in meters. Contour interval is 250 m.

EPM 2 - 6 PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA

north dipping planes. Until August 1999, the largest twen-tieth century earthquake in northwest Turkey had beenalong the Ganos fault on 9 August 1912. It was responsiblefor the deaths of over 2000 people and the destruction ofmore than 300 villages and towns. Right-lateral slip of over3 m was measured along this fault.[17] The south side of the basin is bounded by a steep

north dipping extensional fault at common depth point(CDP) 3850 (Figure 6). Many sedimentary packages dipand thicken into it, and these horizons can be traced ontoother lines around the basin, giving an indication of thepoint of maximum displacement of the fault and the anglethrough which the paleohorizontal has been rotated. Smallantithetic south dipping faults also cut through the sedi-mentary layers, up to the seafloor.[18] The steep slope on the northern side of this basin has

previously been attributed to a ‘‘northern boundary fault’’[Barka and Kadinsky Cade, 1988; Smith et al., 1995; Wonget al., 1995; Okay et al., 2000], but there is little evidencefor this in either the seismic profiles or the microseismicityof the area [Oncel and Wyss, 2000]. What is usually markedas the northern boundary fault is actually a paleohorizontalsurface which is now south dipping and forms the scarp of ashelf due to the much more active fault to the south. Thisslope has a maximum dip of 17� ± 5� toward the fault. Theuncertainty in this dip is due to the range of possible intervalvelocities which give acceptable stacks of the seismic data.A lower interval velocity brings the basement reflectorshallower and hence reduces the dip of the slope. No activenormal fault with a dip this shallow has been observed,either in the field or in the instrumental seismicity, so weconclude that this surface is not an active fault.[19] There is a change in depositional style in the basin

sediments at 2 s TWT in this section. At greater depths theindividual packages are thick and have been rotated anddownthrown to the south, with slight folding. The shallowsediments overlying this unit are flat lying and have notbeen tilted significantly. They also onlap up the edges of thebasin on both the northern and southern margins. While thedeeper sediments in the basin are clearly synrift, it seemsthat there has either been a change in the rate of movementon the controlling fault or a change in sediment type orsedimentation rate.[20] The horizons identified in Figure 6 are also visible

along strike of the Tekirdag fault (Figure 7). The paleohor-izontal surface which dips into the Tekirdag fault dips downto the west and is slightly deformed. It is cut by smallantithetic west dipping faults, which propagate to the sur-face. The line crosses the Tekirdag fault at CDP 6200, at anoblique angle of 20�, west and south of which is a sequenceof disturbed sediments which have some small active faultsaffecting the seafloor but little internal coherence. Weinterpret these disturbed sediments as having been shearedby strike-slip deformation. No large faults cut through thesesediments. The south side of the Tekirdag basin is moreseismically active than the north, and this region is the directoffshore extrapolation of the active Ganos fault (Figure 5),so it is unsurprising that it should be highly deformed. Theclosest available well data are from the K. Marmara I well,drilled into the shelf rock some 50 km to the west [Ergunand Ozel, 1995] (Figure 8). This well penetrates <20 m ofQuaternary marine sediment overlying >1500 m of Oligo-

cene sandstones. There are no major structures between thiswell and the Tekirdag basin, so it is likely that the dippingbasement reflector visible in both Figures 6 and 7 is the topof this Oligocene sequence.[21] As yet, insufficient data exist to explain the detailed

evolution of the Tekirdag basin. Okay et al. [1999] havemade inferences about the history of the basin based on theextrapolation of well data across major structural featuresand used this to try to explain the development of the Sea ofMarmara generally. Until more is known about the relativedates of the onset of extension in these areas, compared withthe onset of strike-slip faulting, such an extrapolation couldbe misleading, since it cannot take into account lateralmovement of material along strike of the faults. It is clear,however, that the western Sea of Marmara has developed asa series of half grabens, on north dipping fault planes, whichare still active (Figure 9). These half grabens trap sedimentfrom the Gonen and Biga rivers, both of which drain intothe Sea of Marmara to the west of the Kapidag Peninsula.The subdued expression of the active normal faults beneaththe southern shelf is partially due to the greater sedimentinflux from the south. This sediment influx exaggerates thetectonic activity of the deep northern basin, relative to thesouthern shelf, when only the bathymetry is considered.South of the Tekirdag basin, and north of Marmara Island,the sediments are highly deformed, and this area seems tobe the most likely zone of deformation associated with theeastern end of the Ganos fault.

3. Central Basin

[22] The northern Central Marmara Basin is the area ofmost sparse data coverage in this survey because of the busyshipping lane which restricted data acquisition. Data cover-age is much better farther to the south (Figure 10), where ashallow shelf dips gently (<1� slope) from the coast towardthe southern bounding edge of the basin. The shelf deepensfrom 50 m close to the shore, to 100 m at the shelf break inthe north.[23] The Marmara I well (Figure 8) in the southern shelf

penetrates Upper Cretaceous (UC) limestones at 2174 mdepth, overlain unconformably by upper Miocene-Pliocenecalcareous mudstones and sandstones. This unconformityproduces a clear reflection which can be mapped acrossmuch of the southern shelf and is the basement reflector inall the southern basins. Figure 11 shows a section of areflection profile shot over the well, and Figure 12 shows adepth-converted panel showing the fit between the well andthe profile.[24] Reflection profile Mar97-26 (Figure 11) was shot in

a north-south direction, to the east of the Kapidag Peninsula.At the southern end of the section shown (CDP 3950) is anorth dipping normal fault. The total offset on this fault isunknown, as the footwall block has been eroded down tothe characteristic 50-m shelf level found elsewhere in theSea of Marmara. The limestone basement is much shallowerin the half graben to the south of this fault, with only a thinlayer of Miocene sediments. These sediments are southdipping, probably due to block rotation on either theKapidag fault, or the Bandırma fault, to the south.[25] The UC limestone unconformity can also be traced

north of the well, onto east-west striking line Mar97-19

PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA EPM 2 - 7

Figure 6. Line Mar97-08, a N-S line across the Tekirdag basin, showing a major extensional fault. Thenorthern shelf has a depth of 50 m and is of erosional rather than tectonic origin. The change in the thebasin fill sediments is highlighted. Apparent dip scale assumes an interval velocity of 1500 m s�1.The inset shows reduced line drawing of the profile, at the same vertical exaggeration.

Figure 7. Line Mar97-02, a SW-NE line, shot obliquely to the Tekirdag fault. The basin fill terminatesagainst the basement (CDPs 5000–6000). The apparent superposition of material from both sides of thefault (CDPs 5800–6400) is due to the small angle between the reflection profile and the strike of thefault.

EPM 2 - 8 PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA

(Figure 13). The basement is clearly visible across the wholesection. Many small faults propagate through and affectsedimentary horizons, although the seafloor is not visiblyaffected at this resolution. At CDP 3700 the line obliquelycrosses a northeast dipping normal fault. The seafloor slopeinto the resulting basin has been cut into by a channel whichconnects with the offshore extrapolation of the Simav river.It is likely therefore that the largest catchment area during thelast sea level minimum drained into this channel.[26] The reflector shallows to the east of this fault and

continues into the eastern Sea of Marmara. It is also

expressed in the surface geology and geomorphology ofImralı Island. The faulted north side of this island observedduring the cruise exposes UC limestones onlapped from thesouth by Neogene strata [Ternek et al., 1964], dippinggently south at �7�.[27] On the western end of Figure 13, the reflector can

be traced onto the regional north-south line Mar97-13(Figure 14), which traverses the Central Marmara Basin.The southern shelf in the Sea of Marmara is dominated byblock faulting of UC limestone on north dipping fault planes.Marmara and Imralı Islands and the Kapidag Peninsula

Figure 8. (top) Well data from the Sea of Marmara [Ergun and Ozel, 1995] and (bottom) map showinglocations of boreholes relative to seismic data.

PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA EPM 2 - 9

have all been created in this style, and evidence has beenpresented here that some of these structures are still activetoday, despite a lack of fault-controlled bathymetry.[28] North of the shelf break on Figure 14 (at CDP 7200),

there is a gentle (3�) slope into the 1-km-deep basin bottom,12 km to the north. The slope deposits are relativelyundisturbed, with little internal deformation. They terminateabruptly at CDP 4800 where a significantly more deformedunit extends north to CDP 4000. This unit is faulted on a

very small scale, which affects the bathymetry at the bottomof the basin. Given the distance to the shelf break in thesouth and nearest sediment source, it is difficult to see howthis feature could be generated without ongoing tectonicactivity. Bearing in mind that the strike-slip motion observedon the North Anatolian fault zone must pass through the Seaof Marmara and into the Ganos fault in the west, thisdisrupted unit seems a likely candidate for the sheared zonepreviously associated with such motion.

Figure 9. Sketch showing a N-S section over the western Sea of Marmara. The change in lithologyacross the Sea of Marmara from sandstone to granite and metamorphic rocks is apparent. The zone ofhighly deformed sediments between Marmara Island and the Tekirdag basin is highlighted.

Figure 10. Map of the central Sea of Marmara. Reflection profiles are shown by the thin lines, withsections discussed here marked by heavy dashed lines. Faults are interpreted on the basis of mappablehorizons on profiles. Depths and altitudes are in meters. Contour interval is 250 m.

EPM 2 - 10 PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA

[29] Unfortunately, the feature is not mappable on otherlines because of the sparsity of data. Similar features areseen elsewhere, but whether they connect from line to line isbeyond the resolution of this data set. To the north of thissheared zone, the northern basin slope rises to the northern

shelf break at CDP 2200. There is evidence of slumping andsubsequent erosion in the shelf deposits but no clearevidence of faults cutting through the sediments. The north-ern slope is thought to be Oligocene sandstone on the basisof the findings of the K. Marmara I well, but because of the

Figure 12. Depth-migrated section of line Mar97-26, through the Marmara I well, compared to aschematic of the well data from Ergun and Ozel [1995], with an interval velocity plot from the stackingvelocities for that section.

Figure 11. Line Mar97-26, a N-S profile, intersecting the Marmara I well at CDP 2300. The position ofthe UC limestone is highlighted.

PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA EPM 2 - 11

lack of any large catchment area it is not anticipated to havea large effect on the sedimentation offshore.

4. Eastern (Cınarcık) Basin

[30] The easternmost basin in the Sea of Marmara hasrecently suffered from a large (Mw 7.4) earthquake on 17August 1999, which caused considerable damage. Over17,000 people died and more than 44,000 others wereinjured. The earthquake was caused by slip on the Cınarcıkfault strand at the western end of the North Anatolian faultzone. Surface rupture from the event was mainly confinedto Pliocene and Quaternary sedimentary basins and to valleyfill. Some of these basins appear to have been formed owingto repeated slip of the fault segments [U.S. GeologicalSurvey, 2000].[31] The shape of the Cınarcık basin is closely related to

the faulting (Figure 15). The basin has steep boundingslopes on both the north and south margins. The northdipping Cınarcık strand of the North Anatolian fault definesthe northern shore of the Cınarcık Peninsula. Its effect isalso apparent in the bathymetry of the Gulf of Izmit, wherethe hanging wall seafloor block dips slightly to the south,

into the fault. It has not been mapped farther along the coastto the west [Saroglu et al., 1992] and is not visible inseismic line Mar97-33 [Parke et al., 1999]. There is noevidence in the available data that it continues westward toform the northern coast of Imralı Island [Okay et al., 2000].[32] The UC limestone reflector observed in Figure 13 in

the south central Sea of Marmara is continued in Figure 16.It is visible in the western end of this section and shallowsto the east until it meets the seafloor at CDP 4400, just at theshelf break for the Cınarcık basin. It has been previously cutby small faults which do not disturb the overlying sediment.The unit as a whole gives the appearance of a tilted faultblock, downthrown to the west, with the crest defining thepresent shelf break. The UC limestone basement is alsovisible in the southern shelf on all the north-south lines eastof Imralı Island but is buried at shallower depths onconsecutive sections, moving east.[33] The shelf break has been interpreted as the eastern-

most limit of a deformed zone, which extends some 10 kmdown the slope and into the basin bottom (CDPs 4400–6000). The slope has a gradient of �6� and shows evidenceof small faults and active slumping. The basin sedimentsonlap onto a strong reflector on the west side, which may be

Figure 13. Tie line Mar97-19. The UC limestone is traceable onto the western end of this section fromthe Marmara I well. The limestone and overlying sediments have many small faults but no large offsetsuntil the normal fault at CDP 4200. The basement reflection highlighted to the east of this fault is thoughtto be UC limestone, on the basis of exposures on Imralı Island.

EPM 2 - 12 PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA

the hanging wall of the UC limestone block, but this isuncertain due to a lack of stratigraphic data in the basin.This reflector is correlatable within the Cınarcık basin, butits age and lithology are unknown. The overlying sedimentsare unconformable with the basement and are �2000 mthick on this section. The character of the deposits changessuddenly at CDP 6800, where an oblique fault is crossed.

This fault has a small but visible effect on the bathymetry,so it may have moved recently. It has brought two differentsedimentary deposits of different nature next to each other,so there is some component of motion out of the plane ofthe section.[34] Just west of the edge of the shelf break, a region-

al line crosses this section in a north-south direction

Figure 14. Regional line Mar97-13. The UC limestone highlighted in the south shows extensionalfaulting as well as some near-vertical faults. The bottom of the basin (CDPs 3800–4600) has somedipping and some near-vertical faults, which between them accommodate extensional and strike-slipdeformation.

PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA EPM 2 - 13

(Figure 17). This line shows the same UC limestone in thesouthern shelf, at a relatively shallow depth, this time withan erosional channel cut into it, which has been infilled.We interpret the shelf break and slope as a deformedsheared region, which terminates abruptly in the basinbottom (CDP 3500). The basin fill is of relatively flatlying sediments, which have started to onlap up the slope(CDPs 3400–3200). This observation is repeated on otherlines, in all areas of the Sea of Marmara. If a sedimenta-tion rate of 1 mm yr�1 in the basins is assumed, then inthe last 250 kyr, either the sedimentation rate has increasedor the rate of movement on the faults has reduced. Since itseems unlikely that the rates of movement on all theobserved basin bounding faults would have slowed atthe same time, the former explanation is preferred, giventhe climatic changes which have taken place in northwest-ern Turkey during this time.[35] The north side of the Cınarcık basin is more

complicated. There is a north dipping fault at CDP 4600,on either side of which the horizons dip in oppositedirections. This apparent change in dip may be due tothe possible strike-slip nature of the fault, juxtaposing twodifferent sedimentary units, or it may simply be due to thegeometry of the reflection with respect to the fault. Thenorthern slope of the basin is irregular and is incised anderoded in places.[36] At its western end the Cınarcık basin presents the

appearance of a full graben, bounded by normal faults,

with a potential strike-slip fault along the center of thebasin. A similar picture is seen 30 km farther east inFigure 18. Again, the UC limestone basement is visible inthe south, extending under the sediments in the basin.In this case the basement is downthrown to the north.There is a narrow region of disturbed, incoherent sedi-ments between CDPs 2200 and 2550, with flat sedimentsin the basin bottom, and a unit of more coherent reflectorsfarther up the slope. This region has a shallower gradient�10� lower than the upslope unit (20�) in the plane of thissection and also has a seismic velocity closer to that ofwater. We interpret this region as a possible zone of sheardeformation, which has affected the slope on the northernedge of the basin and deformed the sediments in this area.The horizons on the reflection profile exhibit a distinctchange in character at 2.2 s TWT, below which thereflections are widely spaced in time, upward into moreclosely spaced reflections. This change can be correlatedon other lines also (e.g., Figure 19). At the eastern end ofthe section the limestone reflector dips down to the west,beneath the basin sediments (CDPs 1009–3600). It isrelatively continuous, although there is some scatter atCDP 2000, so it may have been faulted or eroded in thepast.[37] The basin-filling sediments can again be divided

into two types. The older has more widely spaced reflec-tors, visible from 4 s up to 2.5 s TWT. The sediments areunconformable with the basement, at an angle of 25� ± 5�.

Figure 15. Map of the eastern Sea of Marmara. Reflection profiles are shown by thin solid lines, withthe sections discussed here shown by heavy dashed lines. Faults are interpreted on the basis of mappablehorizons on profiles. Depths and altitudes are in meters. Contour interval is 250 m.

EPM 2 - 14 PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA

They dip shallowly down to the east and onlap thebasement. The basement had already been tilted prior tothe onset of sedimentation; however, in this section therotated sediment filling this basin has been tilted in theopposite direction.[38] From the rotation of the basement we infer initial

activity on an east dipping normal fault, possibly lying tothe west. However, the first unit of infilling sediment hasbeen downthrown to the east, implying activity on a westdipping normal fault on the opposite side of the basin. Thechange in character from the lower to the upper layers ofsediments which occurs at 2.5 s TWT also corresponds to achange in the style of deposition. The sediments no longerterminate against the tilted basement block but instead drapeup the block and form a shallow syncline containing someoff-lapping horizons as the beds pinch out. The basinsediments also have many small antithetic faults, anddespite some local gravity slumping and folding, the basinis controlled by extensional tectonics.[39] Another feature visible at the western end of the

basin, from CDPs 7700 to 8000, is an incised channel. Thesediment has been cut into to a depth of �500 m and laterinfilled. Features like this can be misleading, as this ero-sional channel has left a 75 m scarp in the seafloor, which

from the bathymetry alone could be mistakenly misinter-preted as a tectonic feature.

5. Discussion

[40] The character and nature of the three main basins inthe Sea of Marmara have been examined from the point ofview of evolution and current tectonic activity. We observethat the large sediment input from the south can skew theapparent effect of faulting on the bathymetry and that thedevelopment of the western Tekirdag basin is relatively easyto explain compared to that of the central Sea of Marmara. Itis also important to consider the implications of faultlocation, linkage, and growth from a seismic risk perspec-tive. A key question to have arisen in recent work [Okay etal., 2000; Imren et al., 2001] is whether or not there is asingle fault crossing the Sea of Marmara and connecting theIzmit fault to the Ganos fault.[41] We see little evidence of a single fault either in our

data or in the seismic record. The greatest damage inIstanbul was caused by earthquakes in 1509, 1754, and1766 [Ambraseys and Jackson, 2000], and estimates of theirrupture lengths based on macroseismic effects indicatebreaks on relatively short faults �70 km or less offshore,

Figure 16. Line Mar97-40, a continuation of the W-E tie line Mar97-19 from the central Sea ofMarmara into the Cınarcık basin. The extensional nature of the ridge is apparent from the dippinglimestone basement (CDPs 1200–4000).

PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA EPM 2 - 15

compared to rupture lengths of >100 km observed onshore.Whether a single fault is likely to exist and to be stable overtime can be assessed by considering the geometry requiredto maintain its existence.[42] If a situation exists as in Figure 20a, where a single

strike-slip fault forms the boundary between two plates,one of which is stable and the other is undergoing somelocal deformation in places, then the configuration isstable in time. As the fault system develops, the singlestrike-slip fault can maintain its position along the plateboundary irrespective of the deformation taking place tothe south of it.[43] Consider the configuration presented in Figure 20b,

with a single strike-slip fault cutting through a region ofdeformation, bounded to the north by a stable plate boun-dary. As the system evolves and extension occurs, the faultcan no longer maintain the same strike along its length orthe same distance from the stable boundary in the deform-ing region (Figure 20c). Indeed, the fault must by necessityrotate in order to accommodate the motion. Rotations mustinvolve some component of extension or compression inthe area, so the strike-slip fault would have to ‘‘step’’ across

an area of smaller faults, of various nature, which move inresponse to the larger controlling faults in the region(Figure 20d). This situation has been observed elsewhere[Jackson et al., 1982].[44] Recent publications concerning the North Anatolian

fault [Parsons et al., 2000; Okay et al. 1999, 2000;Ambraseys and Jackson, 2000] have all acknowledged thateast of the Sea of Marmara, the strike-slip deformation isrelatively well confined to a zone some 50 km wide. Northof this is the Black Sea, which is currently shortening at arate which is small compared to the rates of motion in theAegean and western Turkey [McClusky et al., 2000]. It istherefore safe to assume that in this area the location of theNorth Anatolian fault would not change relative to stableEurasia because of movement along its length. It has alsobeen acknowledged that the seismic activity in the westernSea of Marmara is concentrated on the south side of theTekirdag basin, where the strike-slip motion links up withthe Ganos fault. Figure 6 shows a north-south section of theTekirdag basin, in which the basement reflector has beentilted and downthrown to the south. Even if it is assumedthat there has only been a small amount of deformation on

Figure 17. Line Mar97-29, a N-S line shot across the Cınarcık basin. The limestone horizon in thesouthern shelf is visible beneath a thin covering of sediment. Basin fill sediments show a change in dip atCDP 4600, as a fault is crossed.

EPM 2 - 16 PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA

Figure 18. Line Mar97-31, a N-S line across the eastern end of the Cınarcık basin. The change in basinfill is marked, as is the change in the north slope, associated with deformed sediments and lower intervalvelocity.

Figure 19. Line Mar97-32, showing dipping basement from CDPs 1000–3600, with unconformabledeposits above. An infilled, incisional canyon is highlighted at CDP 7600.

PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA EPM 2 - 17

land to the north of this basin, a situation still exists wherethe single strike-slip fault must migrate southward relativeto stable Eurasia because of the opening of the Tekirdagbasin. A single fault running from east of the Sea ofMarmara to the Ganos fault could not be stable in time,assuming it could even form initially.[45] Extension of continental lithosphere is commonly

distributed over regions that are broad in the direction ofextension, whereas strike-slip motion is generally restrictedto relatively narrow zones [England and Jackson, 1989].This fits well with the observed distribution of faults withinthe North Anatolian fault zone. The zone of deformation iswell confined in eastern and central Turkey, but becomesmuch more diffuse with the onset of extension tectonics inthe west.[46] The North Anatolian fault is occasionally referred to

as a transform fault, a term usually reserved for oceanicplate boundaries. While the analogy between continentaland oceanic faulting may be useful in eastern and centralTurkey, it fails in the west because of the distributed natureof extensional and compressional deformation on the con-tinents. It is this finer-scale deformation that allows faults topropagate past each other without linking up. Indeed, in the

North Sea, where faults had previously been mapped withtwo-dimensional (2-D) seismic reflection profiles, thesefaults were later found to be discontinuous when the areawas remapped in three dimensions with higher resolution[Demyttenaere et al., 1993]. Many smaller accommodatingfaults were found in the area. It is for this reason that themodel proposed by Okay et al. [2000] is unlikely incontinental deformation. A three transform triple junctionis always unstable, both in oceanic and continental tecton-ics, and the style of deformation seen in western Turkey issimilar to that seen in the Aegean, i.e., that of distributedcontinental extension.[47] At no location in the Sea of Marmara does strike-slip

deformation appear to run along a stable boundary on thenorth shelf. Strike-slip motion enters the Sea of Marmara onthe Cınarcık fault, which bounds the south side of theCınarcık basin. Deformation observed on the north andsouth sides of the Cınarcık basin, the central Sea ofMarmara, and south of the Tekirdag basin has all beenidentified as relating to strike-slip motion. These are zonesof differing strike and, as such, cannot be connected by asingle fault. Strike-slip motion is observed leaving the Seaof Marmara and connecting to the North Aegean Trough on

Figure 20. Schematic diagrams showing possible configurations of a strike-slip fault in an extensionalregime. (a) The only stable configuration, in which the strike-slip fault is confined to the stable plateboundary. (b)–(d) The evolution of the system if the strike-slip motion is not confined in this manner.

EPM 2 - 18 PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA

the Ganos and Tekirdag faults, which bound the south sideof the Tekirdag basin. In both cases, there is extension to thenorth of the main areas of deformation.[48] Thin sheet viscous models of continental deforma-

tion [England et al., 1985] suggest that systems withextensional boundaries have aspect ratios of �1–2, whileaspect ratios for strike-slip boundaries are �5–10. Thisimplies that faults which produce earthquakes from a depthof �10 km would be roughly 10–20 km in length if theywere extensional and of the order of 100 km in length ifthey were strike slip. Again, this correlates well with fieldobservations. Normal faults to the south of the Sea ofMarmara and in Greece show typical lengths of 10–20km [Jackson, 1994], whereas in the eastern North Anatolianfault zone, segments of faults over 100 km in length havebeen mapped.[49] Sand box experiments [Dooley and McClay, 1997]

have been used to model the development of two offsetstrike-slip faults and their effect on developing basins.Results from these models suggest that as displacementincreases on the strike-slip faults, oblique extensional faultsform on smaller and smaller scales to accommodate thedeformation. The material between the initial faults alsobecomes rotated. The initial faults anastomose into the basinand never link together.[50] In an area such as the Sea of Marmara, the deforma-

tion is being taken up on a series of faults that transfer themotion on the Izmit strand of the North Anatolian fault zoneacross the Sea of Marmara and onto the Ganos fault. This isa distance of �300 km, and since nowhere else in the NorthAnatolian fault zone is a continuous fault segment of thislength observed, it is even less likely that it should beobserved in western Turkey, where the onset of extensionalfaulting would be expected to reduce considerably thelengths of individual faults.[51] This pattern is clear in the western basin of the Sea of

Marmara. The three north dipping faults with evidence ofrecent seismicity on them, Tekirdag Marmara, and Kapidagare all tilting and trapping sediment from the south. Thefault relationships in north central Marmara are less clear.There are no large normal fault-like structures visible in thebathymetry, or in the subsurface. The major tectonic struc-tures in this region are buried beneath at least 7 km ofsediment. The Simav river drains into this basin and has acatchment area of 23,530 km2, larger than the combinedareas of all the other rivers draining into the Sea ofMarmara, so it is unsurprising that no basement reflectoris visible in the basin. The south central Marmara region hasnot subsided much and has been drilled. The well helps toconstrain the stratigraphy in the south and because of the tielines gives some control to the east and west of the Sea ofMarmara as well.[52] The defining feature of the southern shelf is the Upper

Cretaceous limestone basement, which has undergone atleast two episodes of deformation. Prior to deposition ofthe Miocene-Pliocene sediments the basement was down-thrown to the west. The limestone is found at a depth of �2km in the Marmara I well, yet in the Cınarcık basin, 20 kmaway, it is at the surface and defines the shelf break. From theseismic data in the east (Figure 19) it appears that the initialdeposition of the sediments onto the basement was postrift.They are all flat lying and terminate unconformably against

the basement limestone. There is no indication of synriftsedimentation in the Cınarcık basin. More recently, the onsetof ESE-WNW normal faulting in the area has cut, rotated,and back tilted the limestone blocks, forming Imralı Islandand the small half graben just to the east.

6. Conclusions

[53] 1. The existence of the Sea of Marmara on a longstrike-slip fault requires the right-lateral strike-slip motionto be offset to the north. GPS observations are consistentwith such an offset being present in the region. A substantialamount of the total strike-slip motion must be taken up onthe Ganos fault. Large tectonic features on land at both theeastern and western ends of the Sea of Marmara can be seenextending into the sea before dying out in the middle.Unfortunately, the basement reflector in the central andeastern basins is not imaged in this survey. With the sedi-ment interval velocities used in this survey (1.8–4 km s�1),the estimated minimum sediment thickness in these basinsis �6 km.[54] 2. Previous work [Smith et al., 1995] and the

catalogue of seismic events indicate that at least two normalfaults are active in the western Marmara. How the motion isdistributed between these active faults is unclear from thestratigraphic record, but the western end of the Sea ofMarmara is experiencing extensional tectonics which arevisible to a much greater extent than in the east. This fitswith GPS data for the area [McClusky et al., 2000] whichshow a larger north-south component of extension in thewestern Sea of Marmara than in the east.[55] 3. Areas where the bottom of the basins have become

disturbed can be seen over the seafloor, and these have beeninterpreted as possible strike-slip faults. They are mostdominant in the Central Marmara Basin, where they have adistinct effect onwhat would otherwise be a flat basin bottom,causing changes in bathymetry and deforming the surround-ing sediments. It is not easy to see if and how they link upbecause of the large distances between the seismic lines.[56] 4. Sediment sources are different in each basin and

appear to be controlled by sea level changes, as well as byuplift due to ongoing faulting. During a drop in eustatic sealevel the southern shelf down to a depth of 65 m would havebeen subaerially exposed. This would have moved the south-ern shoreline to just north of the present-day Marmara andImralı Islands. The 65 m contour fits well with the presentshelf break just north of these features, where it is tectonic innature, but not in between, where the Simav river has beendepositing sediment and prograding the shelf to the north.This highlights the importance of the interaction betweentectonics, sedimentation, and erosion in the Sea of Marmara.[57] 5. With the observed distribution and type of faults

seen in the area, it is difficult to see how a single strike-slipfault could account for the different styles of tectonicdeformation observed in the Sea of Marmara. A morerealistic model has that motion stepping across the Sea ofMarmara, on a set of en echelon faults.

[58] Acknowledgments. We thank the captain, officers, crew, andscientific party of the R/V MTA Sismik 1 for their assistance during theMarmara cruise in September 1997 and the Royal Society for funding thisresearch. Earth Sciences contribution 6299 (University of Cambridge).

PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA EPM 2 - 19

ReferencesAmbraseys, N., Engineering seismology (historical seismicity of Turkey),Earthquake Eng. Struct., 17, 1–105, 1988.

Ambraseys, N., and J. Jackson, Seismicity and strain in the Sea of Marmara(Turkey) since 1500, Geophys. J. Int., 141, F1–F6, 2000.

Armijo, R., B. Meyer, A. Hubert, and A. Barka, Westward propagation ofthe North Anatolian fault into the northern Aegean: Timing and kine-matics, Geology, 27, 267–270, 1999.

Barka, A. A., and K. Kadinsky-Cade, Strike-slip fault geometry in Turkeyand its influence on earthquake activity, Tectonics, 7, 663–684, 1988.

Briole, P., A. Rigo, H. Lyon-Caen, J. C. Ruegg, K. Papazissi, C. Mitsakaki,A. Balodimou, G. Veis, D. Hatzfeld, and A. Deschamps, Active deforma-tion of the Corinth rift, Greece: Results from repeated Global PositioningSystem surveys between 1990 and 1995, J. Geophys. Res., 105, 25605–25625, 2000.

Demirbag, E., E. Gokasan, H. Kurt, and C. Tepe, On the formation of thenorth eastern Dardanelles, Mar. Geol., 145, 31–38, 1998.

Demyttenaere, R., A. Sluijk, and M. Bentley, A fundamental reappraisal ofthe structure of the Cormorant Field and its impact on field developmentstrategy, in Petroleum Geology of Northwest Europe: Proceedings of the4th Conference, edited by J. Parker, pp. 1151–1157, Geol. Soc., London,1993.

Dooley, T., and K. McClay, Analog modelling of pull-apart basins, AAPGBull., 81, 1804–1826, 1997.

Dziewonski, A. M., T.-A. Chou, and J. H. Woodhouse, Determination ofearthquake source parameters from waveform data for studies of globaland regional seismicity, J. Geophys. Res., 86, 2825–2852, 1981.

England, P., and J. Jackson, Active deformation of the continents, Annu.Rev. Earth Planet. Sci., 17, 197–226, 1989.

England, P., G. Houseman, and L. Sonder, Length scales for continentaldeformation in convergent, divergent, and strike-slip environments: Ana-lytical and approximate solutions for a thin viscous sheet model, J. Geo-phys. Res., 90, 3551–3557, 1985.

Ergun, M., and E. Ozel, Structural relationship between the Sea of Marmarabasin and the North Anatolian fault zone, Terra Nova, 7, 278–288, 1995.

Imren, C., X. Le Pichon, C. Rangin, E. Demirbag, B. Ecevitoglu, and N.Gorur, The North Anatolian fault within the Sea of Marmara: A newinterpretation based on multi-channel seismic and multi-beam bathymetrydata, Earth Planet. Sci. Lett., 186, 143–158, 2001.

Jackson, J., Active tectonics of the Aegean region, Annu. Rev. Earth Planet.Sci., 22, 239–271, 1994.

Jackson, J., J. Gagnepain, G. Houseman, G. King, P. Papadimitriou, C.Soufleris, and J. Virieux, Seismicity, normal faulting, and the geomor-phological development of the Gulf of Corinth (Greece)—The Corinthearthquakes of February and March 1981, Earth Planet. Sci. Lett., 57,377–397, 1982.

McClusky, S., et al., Global Positioning System constraints on plate kine-matics and dynamics in the eastern Mediterranean and Caucasus, J. Geo-phys. Res., 105, 5695–5719, 2000.

McKenzie, D., Active tectonics of the Mediterranean region, Geophys. J. R.Astron. Soc., 30, 109–185, 1972.

McKenzie, D., and J. Jackson, A block model of distributed deformation byfaulting, J. Geol. Soc., 143, 349–353, 1986.

Morris, A., and M. Anderson, First palaeomagnetic results from the Cycla-dic Massif, Greece, and their implications for Miocene extension direc-tions and tectonic models in the Aegean, Earth Planet. Sci. Lett., 142,397–408, 1996.

Nabelek, J., Determination of earthquake source parameters from inver-sion of body waves, Ph.D. thesis, Mass. Inst. Technol., Cambridge,1984.

Okay, A. I., E. Demirbag, H. Kurt, N. Okay, and I:. Kuscu, An active, deep

marine strike-slip basin along the North Anatolian fault in Turkey, Tec-tonics, 18, 129–147, 1999.

Okay, A., A. Kaslılar-Ozcan, C. I:mren, A. Boztepe-Guney, E. Demirbag,

and I:. Kuscu, Active faults end evolving strike-slip basins in the Mar-

mara Sea, northwest Turkey: A multichannel seismic reflection study,Tectonophysics, 321, 189–218, 2000.

Oncel, A., and M. Wyss, The major asperities 1999 Mw = 7.4 Izmit earth-quake defined by the microseismicity two decades before it, Geophys. J.Int., 143, 501–506, 2000.

Parke, J., T. Minshull, G. Anderson, R. White, D. McKenzie, I. Kuscu, J.Bull, N. Gorur, and C. Sengor, Active faults in the Sea of Marmara,western Turkey, imaged by seismic reflection profiles, Terra Nova, 11,223–227, 1999.

Parsons, T., S. Toda, R. Stein, A. Barka, and J. Dieterich, Heightened oddsof large earthquakes near Istanbul: An interaction-based probability cal-culation, Science, 288, 661–665, 2000.

Reilinger, R., S. McClusky, M. Oral, R. King, and M. Toksoz, GlobalPositioning System measurements of present-day crustal movements inthe Arabia-Eurasia plate collision zone, J. Geophys. Res., 102, 9983–9999, 1997.

Roberts, G., and A. Ganas, Fault-slip directions in central and southernGreece measured from striated and corrugated fault planes: Comparisonwith focal mechanism and geodetic data, J. Geophys. Res., 105, 23443–23462, 2000.

Saroglu, F., O. Emer, and I. Kuscu, Active fault map of Turkey, report, Gen.Dir. of Miner. Res. and Explor., Ankara, Turkey, 1992.

Smith, A., T. Taymaz, F. Oktay, H. Yuce, B. Alpar, H. Basaran, J. Jackson,S. Kara, and M. Simsek, High-resolution seismic profiling in the Sea ofMarmara (northwest Turkey): Late Quaternary sedimentation and sea-level changes, Geol. Soc. Am. Bull., 107, 923–936, 1995.

Taymaz, T., J. Jackson, and D. McKenzie, Active tectonics of the north andcentral Aegean Sea, Geophys. J. Int., 106, 433–490, 1991.

Ternek, Z., et al., Geological map of Turkey, Istanbul sheet, scale1:100,000, Inst. of Miner. Res. and Explor., Ankara, Turkey, 1964.

U.S. Geological Survey, Implications for earthquake risk reduction in theUnited States from the Kocaeli, Turkey, earthquake of August 17, 1999,U.S. Geol. Surv. Tech. Rep., 1193, 2000.

Wong, H., T. Ludmann, A. Ulug, and N. Gorur, The Sea of Marmara: Aplate boundary sea in an escape tectonic regime, Tectonophysics, 244,231–250, 1995.

Yaltırak, C., B. Alpar, M. Sakınc, and H. Yuce, Origin of the Strait ofCanakkale (Dardanelles): Regional tectonics and the Mediterranean-Mar-mara incursion, Mar. Geol., 164, 139–156, 2000.

�����������������������J. M. Bull and T. A. Minshull, Southampton Oceanography Centre,

Southampton, SO14 32H, UK.N. Gorur and C. Sengor, ITU, Maden Fakultesi, Jeoloji Bolumu, Ayazaga

80626, Istanbul, Turkey.I. Kuscu, Maden Tetkik ve Arama Genel Mudurlugu, Ankara, Turkey.D. McKenzie, J. R. Parke, and R. S. White, Bullard Laboratories,

Madingley Road, Cambridge CB3 0EZ, UK. (mckenzie@esc.cam.ac.uk;parke@esc.cam.ac.uk; rwhite@esc.cam.ac.uk)

EPM 2 - 20 PARKE ET AL.: FAULTING AND SEDIMENTATION IN THE SEA OF MARMARA