scholarly journals Contrasting seismogenic behaviors on the North Anatolian Fault in the Sea of Marmara

2020 ◽  
Author(s):  
Pierre Henry ◽  
Céline Grall ◽  
M Sinan Özeren ◽  
Volkan Özbey ◽  
Gülsen Uçarkus ◽  
...  
Keyword(s):  
Heat Flow ◽  
Sedimentary Cover ◽  
Large Earthquake ◽  
Fault Slip ◽  
North Anatolian Fault ◽  
Fault System ◽  
Seismogenic Zone ◽  
Sea Of Marmara ◽  
The North

<p>Since the 1999 Izmit-Kocaeli earthquake, the Main Marmara Fault (MMF) of the North Anatolian Fault system in the Sea of Marmara has been considered at an imminent risk for a large earthquake. Land geodesy has difficulties characterizing the distribution of interseismic loading, and hence of slip deficit, on the offshore faults, and notably on the Istanbul-Silivri segment of the NAF. The need to clarify the status of offshore fault segments has motivated seafloor monitoring experiments and marine geophysical and sedimentological studies, notably in the framework of EMSO consortium and MARSITE and MAREGAMI projects. Results from cross-disciplinary projects have shown that aseismic creep, spatially correlated to active gas venting at the seafloor, occurs on the Western segment of the MMF. This segment is also capable to large earthquake ruptures such as the 1912 event. On the eastern part of the Sea of Marmara, the Istanbul-Silivri and Prince Island segments appear essentially locked. Moreover, the base of the seismogenic zone and locking depth appears to shallow (from 15-20 to 10-15 km) from west to east.</p><p>On one hand, we propose to further evaluate fault slip rates and distribution of locking ratio on individual fault segments using an elastic block model constrained by land geodesy data and marine observations (long-term fault slip rate estimates, local acoustic ranging results). On the other hand, we evaluate the temperature at the seismogenic depths by basin modelling. Results suggest that spatial variations of fault behavior in the Sea of Marmara may result from a combination of factors. First, thermogenic gas generation within the > 6 km thick sedimentary cover in the Western Sea of Marmara may contribute to unlock the shallow part of the fault by generating overpressures. Second, heterogeneity of the crust composition could be a factor as the North Anatolian Fault system follows the intra-pontide ophiolitic suture. For instance, long term post-seismic creep onland at Ismet Paşa has been related to the presence of serpentinite in the fault zone. Moreover, high-density magnetic bodies have been identified along the MMF. Third, varying thermal regimes between the Western and Eastern parts of the Sea of Marmara may account for variations in the seismogenic depths. Seafloor heat flow in the Sea of Marmara is strongly affected by sediment blanketing and basin modeling considering this process suggests that the crustal heat flow is about 20 mW/m<sup>2</sup> higher in the eastern part than in western part of the Sea of Marmara. This difference may be explained by a more spread out crustal extension in the western Sea of Marmara.</p>

Locking Behavior of Main Marmara Fault in Western Turkey During Interseismic Period

2020 ◽  
Author(s):  
Zeynep Yılmaz ◽  
Ali Özgün Konca ◽  
Semih Ergintav
Keyword(s):  
3D Structure ◽  
Slip Rate ◽  
Fault Slip ◽  
North Anatolian Fault ◽  
Gps Data ◽  
Strain Accumulation ◽  
Sea Of Marmara ◽  
Western Turkey ◽  
The North ◽  
Fault Slip Rate

<p>The North Anatolian Fault (NAF) produced multiple earthquakes of M>7 throughout the 20th century, while the part of NAF beneath Sea of Marmara did not rupture during this period. Analysis of the Main Marmara Fault's interseismic behavior, the most active branch of the North Anatolian Fault in this region, in terms of locking depth and fault slip rate is critical for evaluating the region's seismic risk with a population of more than 20 million, as it provides information about the seismic moment deficit that may release in a potential future earthquake.</p><p>In this study, we modeled the Main Marmara Fault's interseismic locking with realistic geometry and 3D structure including sedimentary basins, by implementing a 3D finite element approach and using interseismic GPS velocities. We have optimized the fits with GPS data by evaluating cases where each fault segment is constrained by a fault slip rate below a predefined locking depth ranging from 0 to 20 km. Preliminary models reveal that a difference in locking depth is required between the Western Marmara and the eastern end of the Ganos Segment entering the Sea of Marmara. This result, which is consistent with seismicity studies and other previous studies using 1D profiles shows that the strain accumulation under Western Marmara is less and that the locking depths or couplings are not similar in these two segments. For the Princes' Islands Segment, further analysis is required due to complexity in the GPS data. Recent earthquakes along Silivri also indicate that the strain accumulation is complex with most mechanisms showing significant thrust component. We have also calculated various possible strain accumulation patterns and compared the strain rate field around the Main Marmara Fault. Our results show that in most cases the change in the seismicity of each segment is consistent with the interseismic behavior associated with its fault locking.</p><p>(This research has been supported by Boğaziçi University Scientific Research Projects Coordination Unit. Project Number: 15022, 2019)</p>

Heat flow in the Sea of Marmara Central Basin: Possible implications for the tectonic evolution of the North Anatolian fault

Geology ◽  
2011 ◽  
Vol 40 (1) ◽  
pp. 3-6 ◽  
Author(s):  
C. Grall ◽  
P. Henry ◽  
D. Tezcan ◽  
B. Mercier de Lepinay ◽  
A. Becel ◽  
...  
Keyword(s):  
Heat Flow ◽  
Tectonic Evolution ◽  
North Anatolian Fault ◽  
Central Basin ◽  
Sea Of Marmara ◽  
The North

scholarly journals Active fault segments along the North Anatolian Fault system in the Sea of Marmara: implication for seismic hazard

2021 ◽  
Author(s):  
Luca Gasperini ◽  
Massimiliano Stucchi ◽  
Vincenzo Cedro ◽  
Mustapha Meghraoui ◽  
Gulsen Ucarkus ◽  
...  
Keyword(s):  
High Resolution ◽  
Seismic Hazard ◽  
Seismic Reflection ◽  
Strike Slip ◽  
North Anatolian Fault ◽  
Sediment Supply ◽  
Fault System ◽  
Sea Of Marmara ◽  
Seismic Reflection Data ◽  
The North

AbstractA new analysis of high-resolution multibeam and seismic reflection data, collected during several oceanographic expeditions starting from 1999, allowed us to compile an updated morphotectonic map of the North Anatolian Fault below the Sea of Marmara. We reconstructed kinematics and geometries of individual fault segments, active at the time scale of 10 ka, an interval which includes several earthquake cycles, taking as stratigraphic marker the base of the latest marine transgression. Given the high deformation rates relative to sediment supply, most active tectonic structures have a morphological expression at the seafloor, even in presence of composite fault geometries and/or overprinting due to mass-wasting or turbidite deposits. In the frame of the right-lateral strike-slip domain characterizing the North Anatolian fault system, three types of deformation are observed: almost pure strike-slip faults, oriented mainly E–W; NE/SW-aligned axes of transpressive structures; NW/SE-oriented trans-tensional depressions. Fault segmentation occurs at different scales, but main segments develop along three major right-lateral oversteps, which delimit main fault branches, from east to west: (i) the transtensive Cinarcik segment; (ii) the Central (East and West) segments; and (iii) the westernmost Tekirdag segment. A quantitative morphometric analysis of the shallow deformation patterns observed by seafloor morphology maps and high-resolution seismic reflection profiles along the entire basin allowed to determine nature and cumulative lengths of individual fault segments. These data were used as inputs for empirical relationships, to estimate maximum expected Moment Magnitudes, obtaining values in the range of 6.8–7.4 for the Central, and 6.9–7.1 for the Cinarcik and Tekirdag segments, respectively. We discuss these findings considering analyses of historical catalogues and available paleoseismological studies for the Sea of Marmara region to formulate reliable seismic hazard scenarios.

scholarly journals Seismic stratigraphy of the north-western Sea of Marmara shelf along the North Anatolian Fault system

2021 ◽  
Vol 64 (2) ◽  
Author(s):  
Denizhan Vardar ◽  
Hakan Alp ◽  
Sinan Demirel ◽  
Hande Vardar ◽  
Bedri Alpar
Keyword(s):  
Sea Level ◽  
North Anatolian Fault ◽  
Fault System ◽  
Sea Of Marmara ◽  
Sea Level Fluctuations ◽  
The North ◽  
Marine Terraces ◽  
Southern Side ◽  
Northern Side ◽  
The Town

The Ganos Fault, a part of the Northern strand of the North Anatolian Fault system, is an active- strike slip fault and divides the narrow NW shelf of the Sea of Marmara into two parts near the town of Gaziköy. This paper presents recently collected shallow high-resolution seismic data to discriminate the sedimentary successions, each characterized by distinctive stratigraphic patterns on both sides of the Ganos Fault. Two main units, namely U1 and U2, and three para-sequences (U1a, U1b and U1c) were identified, depending on their internal reflection patterns, accommodation depths as well as the presence of conformity and the unconformity surfaces. The thickness of Unit U1 reaches its maximum at the northern side of the Ganos Fault; it is much thinner to the south. The para-sequences of U1b and U1c have “progradation” and “aggradation to progradation” depositional characters, respectively. This probably implies fluvial deposition controlled by sea- level fluctuations. Unit U1b can only be observed at the northern side of the Ganos Fault, while Unit U1c at the southern side. Units U1a and U1b were deposited during the transgressive system tract, while Unit U1c was deposited during a sea-level fall and/or a lowstand phase marked by an erosional surface. The marine terraces in the study area are shallower than those along the northern shelf of the Sea of Marmara, possibly due to successive tectonic displacements along the Ganos Fault, which also controls the distribution and thickness of the parasequences identified in this study.

scholarly journals Monitoring aseismic creep trend in Ismetpasa and Destek segments throughout the NAF with a large scale GPS network

2019 ◽  
Author(s):  
Hasan Hakan Yavaşoğlu ◽  
Mehmet Nurullah Alkan ◽  
Serdar Bilgi ◽  
Öykü Alkan
Keyword(s):  
Large Scale ◽  
Rare Event ◽  
North Anatolian Fault ◽  
Arabian Plate ◽  
Seismogenic Zone ◽  
Eurasian Plate ◽  
The North ◽  
Fault Parameters ◽  
The World

Abstract. North Anatolian Fault Zone (NAFZ) is an intersection area between Anatolian and Eurasian plates. Also another plate is responsible for this formation, Arabian plate, which squeezes the Anatolian plate from the south between Eurasian plate and itself. Block boundaries, forming the faults, generally locked to the bottom of seismogenic layer because of the friction between blocks, and responsible for these discharges. However, there are also some unique events observed around the world, which may cause partially or fully free slipping faults. This phenomenon is called aseismic creep, and may occur through the entire seismogenic zone or at least to some depths and is a rare event in the world, with two reported segments along the North Anatolian Fault (NAF): Ismetpasa and Destek. In this study, we established GPS networks covering these segments and made three campaigns between 2014–2016. Considering the long term geodetic movements of the blocks (Anatolian and Eurasian plates), previous studies for each segment, calculated surface velocities and fault parameters; aseismic creep still continues to some rates, 13.2±3.3 mm/year at Ismetpasa and 9.6±3.1 mm/year at Destek. Results indicates that this aseismic creep behavior will not prevent a medium-large scale earthquake in the long term.

Methane-derived authigenic carbonates along the North Anatolian fault system in the Sea of Marmara (Turkey)

2012 ◽  
Vol 66 ◽  
pp. 114-130 ◽  
Author(s):  
Antoine Crémière ◽  
Catherine Pierre ◽  
Marie-Madeleine Blanc-Valleron ◽  
Tiphaine Zitter ◽  
M. Namik Çağatay ◽  
...  
Keyword(s):  
North Anatolian Fault ◽  
Fault System ◽  
Sea Of Marmara ◽  
Authigenic Carbonates ◽  
The North

The geometry of the North Anatolian transform fault in the Sea of Marmara and its temporal evolution: implications for the development of intracontinental transform faults

2014 ◽  
Vol 51 (3) ◽  
pp. 222-242 ◽  
Author(s):  
A.M. Celâl Şengör ◽  
Céline Grall ◽  
Caner İmren ◽  
Xavier Le Pichon ◽  
Naci Görür ◽  
...  
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Strike Slip ◽  
North Anatolian Fault ◽  
Strike Slip Fault ◽  
Fault System ◽  
Transform Fault ◽  
Sea Of Marmara ◽  
The North ◽  
Macro Scale

The North Anatolian Fault is a 1200 km long strike-slip fault system connecting the East Anatolian convergent area with the Hellenic subduction zone and, as such, represents an intracontinental transform fault. It began forming some 13–11 Ma ago within a keirogen, called the North Anatolian Shear Zone, which becomes wider from east to west. Its width is maximum at the latitude of the Sea of Marmara, where it is 100 km. The Marmara Basin is unique in containing part of an active strike-slip fault system in a submarine environment in which there has been active sedimentation in a Paratethyan context where stratigraphic resolution is higher than elsewhere in the Mediterranean. It is also surrounded by a long-civilised rim where historical records reach well into the second half of the first millennium BCE (before common era). In this study, we have used 210 multichannel seismic reflexion profiles, adding up to 6210 km profile length and high-resolution bathymetry and chirp profiles reported in the literature to map all the faults that are younger than the Oligocene. Within these faults, we have distinguished those that cut the surface and those that do not. Among the ones that do not cut the surface, we have further created a timetable of fault generation based on seismic sequence recognition. The results are surprising in that faults of all orientations contain subsets that are active and others that are inactive. This suggests that as the shear zone evolves, faults of all orientations become activated and deactivated in a manner that now seems almost haphazard, but a tendency is noticed to confine the overall movement to a zone that becomes narrower with time since the inception of the shear zone, i.e., the whole keirogen, at its full width. In basins, basin margins move outward with time, whereas highs maintain their faults free of sediment cover, making their dating difficult, but small perched basins on top of them in places make relative dating possible. In addition, these basins permit comparison of geological history of the highs with those of the neighbouring basins. The two westerly deeps within the Sea of Marmara seem inherited structures from the earlier Rhodope–Pontide fragment/Sakarya continent collision, but were much accentuated by the rise of the intervening highs during the shear evolution. When it is assumed that below 10 km depth the faults that now constitute the Marmara fault family might have widths approaching 4 km, the resulting picture resembles a large version of an amphibolite-grade shear zone fabric, an inference in agreement with the scale-independent structure of shear zones. We think that the North Anatolian Fault at depth has such a fabric not only on a meso, but also on a macro scale. Detection of such broad, vertical shear zones in Precambrian terrains may be one way to get a handle on relative plate motion directions during those remote times.

Recent and active deformation in the North Evia domain, a diffuse plate boundary between Eurasia and Aegean plates in the Western termination of the North Anatolian Fault. 

2021 ◽  
Author(s):  
Fabien Caroir ◽  
Frank Chanier ◽  
Virginie Gaullier ◽  
Julien Bailleul ◽  
Agnès Maillard-Lenoir ◽  
...  
Keyword(s):  
Fault Zone ◽  
Plate Boundary ◽  
Fault Zones ◽  
North Anatolian Fault ◽  
Fault System ◽  
Eurasian Plate ◽  
Slip Rates ◽  
The North ◽  
South West ◽  
North Aegean

<p>The Anatolia-Aegean microplate is currently extruding toward the South and the South-West. This extrusion is classically attributed to the southward retreat of the Aegean subduction zone together with the northward displacement of the Arabian plate. The displacement of Aegean-Anatolian block relative to Eurasia is accommodated by dextral motion along the North Anatolian Fault (NAF), with current slip rates of about 20 mm/yr. The NAF is propagating westward within the North Aegean domain where it gets separated into two main branches, one of them bordering the North Aegean Trough (NAT). This particular context is responsible for dextral and normal stress regimes between the Aegean plate and the Eurasian plate. South-West of the NAT, there is no identified major faults in the continuity of the NAF major branch and the plate boundary deformation is apparently distributed within a wide domain. This area is characterised by slip rates of 20 to 25 mm/yr relative to Eurasian plate but also by clockwise rotation of about 10° since ca 4 Myr. It constitutes a major extensional area involving three large rift basins: the Corinth Gulf, the Almiros Basin and the Sperchios-North Evia Gulf. The latter develops in the axis of the western termination of the NAT, and is therefore a key area to understand the present-day dynamics and the evolution of deformation within this diffuse plate boundary area.</p><p>Our study is mainly based on new structural data from field analysis and from very high resolution seismic reflexion profiles (Sparker 50-300 Joules) acquired during the WATER survey in July-August 2017 onboard the R/V “Téthys II”, but also on existing data on recent to active tectonics (i.e. earthquakes distribution, focal mechanisms, GPS data, etc.). The results from our new marine data emphasize the structural organisation and the evolution of the deformation within the North Evia region, SW of the NAT.</p><p>The combination of our structural analysis (offshore and onshore data) with available data on active/recent deformation led us to define several structural domains within the North Evia region, at the western termination of the North Anatolian Fault. The North Evia Gulf shows four main fault zones, among them the Central Basin Fault Zone (CBFZ) which is obliquely cross-cutting the rift basin and represents the continuity of the onshore Kamena Vourla - Arkitsa Fault System (KVAFS). Other major fault zones, such as the Aedipsos Politika Fault System (APFS) and the Melouna Fault Zone (MFZ) played an important role in the rift initiation but evolved recently with a left-lateral strike-slip motion. Moreover, our seismic dataset allowed to identify several faults in the Skopelos Basin including a large NW-dipping fault which affects the bathymetry and shows an important total vertical offset (>300m). Finally, we propose an update of the deformation pattern in the North Evia region including two lineaments with dextral motion that extend southwestward the North Anatolian Fault system into the Oreoi Channel and the Skopelos Basin. Moreover, the North Evia Gulf domain is dominated by active N-S extension and sinistral reactivation of former large normal faults.</p>

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