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Aykut Barka - One of the best experts on this subject based on the ideXlab platform.
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Slip partitioning in the Sea of Marmara pull‐apart determined from GPS velocity vectors
Geophysical Journal International, 2003Co-Authors: Frédéric Flerit, Rolando Armijo, Bertrand Meyer, G. King, Aykut BarkaAbstract:SUMMARY Dislocation modelling is used to examine the GPS velocity vectors for the Marmara Sea region. First, the vectors due to the known Anatolia/Eurasia rotation are reproduced by introducing structures that approximate the large-scale tectonics. Observed features of the smaller scale fault system in the Marmara region are then progressively included with slip amplitudes and directions adjusted to fit an 80-vector subset of the GPS data. The motion in the Marmara Sea region is partitioned with the faults that bound the north of the basin carrying more strike-slip motion than predicted from the Anatolia-Eurasia plate motion and faults to the south having a greater perpendicular component. Taken together however, there is no net opening across the Marmara Sea perpendicular to the overall trend of the boundary and thus deformation in the Marmara region results only from the pull-apart geometry of the North Anatolian fault. No extension related to the Aegean system is needed to explain the observations. The GPS results are consistent with motion over the last 5 Myr that has been determined from geological reconstructions.
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Slip partitioning in the Sea of Marmara Pull-Apart determined from GPS velocity vectors
Geophysical Journal International, 2003Co-Authors: Frédéric Flerit, Rolando Armijo, Bertrand Meyer, G.c.p. King, Aykut BarkaAbstract:Dislocation modelling is used to examine the GPS velocity vectors for the Marmara Sea region. First, the vectors due to the known Anatolia/Eurasia rotation are reproduced by introducing structures that approximate the large-scale tectonics. Observed features of the smaller scale fault system in the Marmara region are then progressively included with slip amplitudes and directions adjusted to fit an 80-vector subset of the GPS data. The motion in the Marmara Sea region is partitioned with the faults that bound the north of the basin carrying more strike-slip motion than predicted from the Anatolia-Eurasia plate motion and faults to the south having a greater perpendicular component. Taken together however, there is no net opening across the Marmara Sea perpendicular to the overall trend of the boundary and thus deformation in the Marmara region results only from the pull-apart geometry of the North Anatolian fault. No extension related to the Aegean system is needed to explain the observations. The GPS results are consistent with motion over the last 5 Myr that has been determined from geological reconstructions.
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Interseismic Strain Accumulation in the Marmara Sea Region
Bulletin of the Seismological Society of America, 2002Co-Authors: Mehmet Emin Ayhan, Semih Ergintav, Aykut Barka, Coskun Demir, Onur Lenk, Ali Kılıçoğlu, Yüksel Altiner, Haluk OzenerAbstract:The Marmara Sea region is deforming along the branches of the North Anatolian Fault (NAF), which is the boundary between the Anatolian and the Eurasian plates. We evaluate Global Positioning System (GPS) measurements performed from 1992 to 1999, up to the 17 August 1999 Izmit earthquake, to quantify the interseismic strain accumulation pattern in the Marmara Sea region. We compute interseismic velocities in a frame fixed to the Eurasian plate at 136 GPS points. To compute the frame-independent strain rates, we first smooth the north-south and the east-west velocity components separately to obtain the values at grid nodes, and then we compute directional derivatives and strain rates. Shear-strain rates reveal that the Marmara Sea region is within the plate boundary deformation zone having a width of about 110 km. The largest shear-strain rate accumulation is along the northern branch of the NAF, with maximum shear-strain rate reaching 220 nstrain/yr in the Marmara Sea. We calculate clockwise rigid body rotation rates with a maximum of 10 deg/m.y. along the northern branch while the Anatolian plate rotates anticlockwise. Dilatation rates display adjacent local tensional and compressional areas in the east-west direction within the Marmara Sea. Assuming the uniform simple shear, we compute the NAF slip rates vary between 11 and 26 mm/yr, with a minimum around Izmit, and increase east and west of Izmit. Manuscript received 30 August 2000.
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The seismotectonics of the Marmara region (Turkey): results from a microseismic experiment
Tectonophysics, 2000Co-Authors: Cemil Gurbuz, Aykut Barka, Mustafa Aktar, Haluk Eyidogan, A. Cisternas, H. Haessler, Mehmet Ergin, Niyazi Türkelli, Orhan Polat, S.b. ÜçerAbstract: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.
Rolando Armijo - One of the best experts on this subject based on the ideXlab platform.
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Fault interactions in the Sea of Marmara pull-apart (North Anatolian Fault): Earthquake clustering and propagating earthquake sequences
Geophysical Journal International, 2007Co-Authors: Nicolas Pondard, Geoffrey C.p. King, Rolando Armijo, Bertrand Meyer, Frédéric FleritAbstract:Knowledge on large earthquakes (M >= 7.0), geology and fault kinematics is used to analyse conditions that favour isolated seismicity, clustered earthquakes or propagating sequences along the North Anatolian Fault (NAF) and the Sea of Marmara pull-apart. The overall NAF-Marmara fault system is one of the most appropriate on Earth to document fault interactions because reliable information covers almost completely two seismic cycles (the past similar to 500 yr). Coulomb stress analysis is used to characterize loading evolution in well-identified fault segments, including secular loading from below and lateral loading imposed by the occurrence of previous earthquakes. Earthquakes along the NAF tend to occur where previous events have increased the stress, but significant isolated events in the Sea of Marmara region (1894, 1912) have occurred, suggesting the secular loading has been the determining factor. Present-day loading appears to be particularly high along the 70-km-long segment located in the central Marmara Sea, southwest of Istanbul. For the 18th century M >= 7.0 earthquake clusters, we construct scenarios consistent with the tectonic and historical data. We find that scenarios consistent with slip deficit and secular loading distributions (from below) clearly involve a sequence that propagates westward through the Sea of Marmara, despite the structural complexity. However, the inference of a propagating sequence implies that each event has occurred in a segment previously stressed by lateral Coulomb stress interactions. The most likely scenarios for the propagating sequence are also consistent with Coulomb stress interactions between faults with significant normal slip across the Cinarcik basin. Propagating earthquake sequences do not occur every seismic cycle along the NAF. The loading has to be in a particular state of stress close to failure and uniform all along the fault segments to experience propagating earthquake sequences. Non-uniform stress relief during the 18th century sequence explains the occurrence of isolated events in Marmara in 1894 and 1912. As a consequence, the well-known 20th century sequence along the NAF has not propagated as a sequence across the Sea of Marmara. The most linear part of the NAF across northern Turkey behaves as a single fault segment, accumulating stress during hundreds of years and rupturing entirely during very short periods. The Marmara pull-apart fault system behaves as a major geometric complexity, stopping or delaying the progression of earthquake clustering and propagating sequences. Fault zones interact with each other at a very large scale.
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submarine fault scarps in the sea of Marmara pull apart north anatolian fault implications for seismic hazard in istanbul
Geochemistry Geophysics Geosystems, 2005Co-Authors: Rolando Armijo, Nicolas Pondard, Bertrand Meyer, Gulsen Ucarkus, Bernard Mercier De Lepinay, Jacques Malavieille, Stephane Dominguez, Marcandre Gustcher, Sabine Schmidt, Christian BeckAbstract: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.
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Slip partitioning in the Sea of Marmara pull‐apart determined from GPS velocity vectors
Geophysical Journal International, 2003Co-Authors: Frédéric Flerit, Rolando Armijo, Bertrand Meyer, G. King, Aykut BarkaAbstract:SUMMARY Dislocation modelling is used to examine the GPS velocity vectors for the Marmara Sea region. First, the vectors due to the known Anatolia/Eurasia rotation are reproduced by introducing structures that approximate the large-scale tectonics. Observed features of the smaller scale fault system in the Marmara region are then progressively included with slip amplitudes and directions adjusted to fit an 80-vector subset of the GPS data. The motion in the Marmara Sea region is partitioned with the faults that bound the north of the basin carrying more strike-slip motion than predicted from the Anatolia-Eurasia plate motion and faults to the south having a greater perpendicular component. Taken together however, there is no net opening across the Marmara Sea perpendicular to the overall trend of the boundary and thus deformation in the Marmara region results only from the pull-apart geometry of the North Anatolian fault. No extension related to the Aegean system is needed to explain the observations. The GPS results are consistent with motion over the last 5 Myr that has been determined from geological reconstructions.
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Slip partitioning in the Sea of Marmara Pull-Apart determined from GPS velocity vectors
Geophysical Journal International, 2003Co-Authors: Frédéric Flerit, Rolando Armijo, Bertrand Meyer, G.c.p. King, Aykut BarkaAbstract:Dislocation modelling is used to examine the GPS velocity vectors for the Marmara Sea region. First, the vectors due to the known Anatolia/Eurasia rotation are reproduced by introducing structures that approximate the large-scale tectonics. Observed features of the smaller scale fault system in the Marmara region are then progressively included with slip amplitudes and directions adjusted to fit an 80-vector subset of the GPS data. The motion in the Marmara Sea region is partitioned with the faults that bound the north of the basin carrying more strike-slip motion than predicted from the Anatolia-Eurasia plate motion and faults to the south having a greater perpendicular component. Taken together however, there is no net opening across the Marmara Sea perpendicular to the overall trend of the boundary and thus deformation in the Marmara region results only from the pull-apart geometry of the North Anatolian fault. No extension related to the Aegean system is needed to explain the observations. The GPS results are consistent with motion over the last 5 Myr that has been determined from geological reconstructions.
Bertrand Meyer - One of the best experts on this subject based on the ideXlab platform.
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Fault interactions in the Sea of Marmara pull-apart (North Anatolian Fault): Earthquake clustering and propagating earthquake sequences
Geophysical Journal International, 2007Co-Authors: Nicolas Pondard, Geoffrey C.p. King, Rolando Armijo, Bertrand Meyer, Frédéric FleritAbstract:Knowledge on large earthquakes (M >= 7.0), geology and fault kinematics is used to analyse conditions that favour isolated seismicity, clustered earthquakes or propagating sequences along the North Anatolian Fault (NAF) and the Sea of Marmara pull-apart. The overall NAF-Marmara fault system is one of the most appropriate on Earth to document fault interactions because reliable information covers almost completely two seismic cycles (the past similar to 500 yr). Coulomb stress analysis is used to characterize loading evolution in well-identified fault segments, including secular loading from below and lateral loading imposed by the occurrence of previous earthquakes. Earthquakes along the NAF tend to occur where previous events have increased the stress, but significant isolated events in the Sea of Marmara region (1894, 1912) have occurred, suggesting the secular loading has been the determining factor. Present-day loading appears to be particularly high along the 70-km-long segment located in the central Marmara Sea, southwest of Istanbul. For the 18th century M >= 7.0 earthquake clusters, we construct scenarios consistent with the tectonic and historical data. We find that scenarios consistent with slip deficit and secular loading distributions (from below) clearly involve a sequence that propagates westward through the Sea of Marmara, despite the structural complexity. However, the inference of a propagating sequence implies that each event has occurred in a segment previously stressed by lateral Coulomb stress interactions. The most likely scenarios for the propagating sequence are also consistent with Coulomb stress interactions between faults with significant normal slip across the Cinarcik basin. Propagating earthquake sequences do not occur every seismic cycle along the NAF. The loading has to be in a particular state of stress close to failure and uniform all along the fault segments to experience propagating earthquake sequences. Non-uniform stress relief during the 18th century sequence explains the occurrence of isolated events in Marmara in 1894 and 1912. As a consequence, the well-known 20th century sequence along the NAF has not propagated as a sequence across the Sea of Marmara. The most linear part of the NAF across northern Turkey behaves as a single fault segment, accumulating stress during hundreds of years and rupturing entirely during very short periods. The Marmara pull-apart fault system behaves as a major geometric complexity, stopping or delaying the progression of earthquake clustering and propagating sequences. Fault zones interact with each other at a very large scale.
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submarine fault scarps in the sea of Marmara pull apart north anatolian fault implications for seismic hazard in istanbul
Geochemistry Geophysics Geosystems, 2005Co-Authors: Rolando Armijo, Nicolas Pondard, Bertrand Meyer, Gulsen Ucarkus, Bernard Mercier De Lepinay, Jacques Malavieille, Stephane Dominguez, Marcandre Gustcher, Sabine Schmidt, Christian BeckAbstract: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.
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Slip partitioning in the Sea of Marmara pull‐apart determined from GPS velocity vectors
Geophysical Journal International, 2003Co-Authors: Frédéric Flerit, Rolando Armijo, Bertrand Meyer, G. King, Aykut BarkaAbstract:SUMMARY Dislocation modelling is used to examine the GPS velocity vectors for the Marmara Sea region. First, the vectors due to the known Anatolia/Eurasia rotation are reproduced by introducing structures that approximate the large-scale tectonics. Observed features of the smaller scale fault system in the Marmara region are then progressively included with slip amplitudes and directions adjusted to fit an 80-vector subset of the GPS data. The motion in the Marmara Sea region is partitioned with the faults that bound the north of the basin carrying more strike-slip motion than predicted from the Anatolia-Eurasia plate motion and faults to the south having a greater perpendicular component. Taken together however, there is no net opening across the Marmara Sea perpendicular to the overall trend of the boundary and thus deformation in the Marmara region results only from the pull-apart geometry of the North Anatolian fault. No extension related to the Aegean system is needed to explain the observations. The GPS results are consistent with motion over the last 5 Myr that has been determined from geological reconstructions.
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Slip partitioning in the Sea of Marmara Pull-Apart determined from GPS velocity vectors
Geophysical Journal International, 2003Co-Authors: Frédéric Flerit, Rolando Armijo, Bertrand Meyer, G.c.p. King, Aykut BarkaAbstract:Dislocation modelling is used to examine the GPS velocity vectors for the Marmara Sea region. First, the vectors due to the known Anatolia/Eurasia rotation are reproduced by introducing structures that approximate the large-scale tectonics. Observed features of the smaller scale fault system in the Marmara region are then progressively included with slip amplitudes and directions adjusted to fit an 80-vector subset of the GPS data. The motion in the Marmara Sea region is partitioned with the faults that bound the north of the basin carrying more strike-slip motion than predicted from the Anatolia-Eurasia plate motion and faults to the south having a greater perpendicular component. Taken together however, there is no net opening across the Marmara Sea perpendicular to the overall trend of the boundary and thus deformation in the Marmara region results only from the pull-apart geometry of the North Anatolian fault. No extension related to the Aegean system is needed to explain the observations. The GPS results are consistent with motion over the last 5 Myr that has been determined from geological reconstructions.
Frédéric Flerit - One of the best experts on this subject based on the ideXlab platform.
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Fault interactions in the Sea of Marmara pull-apart (North Anatolian Fault): Earthquake clustering and propagating earthquake sequences
Geophysical Journal International, 2007Co-Authors: Nicolas Pondard, Geoffrey C.p. King, Rolando Armijo, Bertrand Meyer, Frédéric FleritAbstract:Knowledge on large earthquakes (M >= 7.0), geology and fault kinematics is used to analyse conditions that favour isolated seismicity, clustered earthquakes or propagating sequences along the North Anatolian Fault (NAF) and the Sea of Marmara pull-apart. The overall NAF-Marmara fault system is one of the most appropriate on Earth to document fault interactions because reliable information covers almost completely two seismic cycles (the past similar to 500 yr). Coulomb stress analysis is used to characterize loading evolution in well-identified fault segments, including secular loading from below and lateral loading imposed by the occurrence of previous earthquakes. Earthquakes along the NAF tend to occur where previous events have increased the stress, but significant isolated events in the Sea of Marmara region (1894, 1912) have occurred, suggesting the secular loading has been the determining factor. Present-day loading appears to be particularly high along the 70-km-long segment located in the central Marmara Sea, southwest of Istanbul. For the 18th century M >= 7.0 earthquake clusters, we construct scenarios consistent with the tectonic and historical data. We find that scenarios consistent with slip deficit and secular loading distributions (from below) clearly involve a sequence that propagates westward through the Sea of Marmara, despite the structural complexity. However, the inference of a propagating sequence implies that each event has occurred in a segment previously stressed by lateral Coulomb stress interactions. The most likely scenarios for the propagating sequence are also consistent with Coulomb stress interactions between faults with significant normal slip across the Cinarcik basin. Propagating earthquake sequences do not occur every seismic cycle along the NAF. The loading has to be in a particular state of stress close to failure and uniform all along the fault segments to experience propagating earthquake sequences. Non-uniform stress relief during the 18th century sequence explains the occurrence of isolated events in Marmara in 1894 and 1912. As a consequence, the well-known 20th century sequence along the NAF has not propagated as a sequence across the Sea of Marmara. The most linear part of the NAF across northern Turkey behaves as a single fault segment, accumulating stress during hundreds of years and rupturing entirely during very short periods. The Marmara pull-apart fault system behaves as a major geometric complexity, stopping or delaying the progression of earthquake clustering and propagating sequences. Fault zones interact with each other at a very large scale.
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Slip partitioning in the Sea of Marmara pull‐apart determined from GPS velocity vectors
Geophysical Journal International, 2003Co-Authors: Frédéric Flerit, Rolando Armijo, Bertrand Meyer, G. King, Aykut BarkaAbstract:SUMMARY Dislocation modelling is used to examine the GPS velocity vectors for the Marmara Sea region. First, the vectors due to the known Anatolia/Eurasia rotation are reproduced by introducing structures that approximate the large-scale tectonics. Observed features of the smaller scale fault system in the Marmara region are then progressively included with slip amplitudes and directions adjusted to fit an 80-vector subset of the GPS data. The motion in the Marmara Sea region is partitioned with the faults that bound the north of the basin carrying more strike-slip motion than predicted from the Anatolia-Eurasia plate motion and faults to the south having a greater perpendicular component. Taken together however, there is no net opening across the Marmara Sea perpendicular to the overall trend of the boundary and thus deformation in the Marmara region results only from the pull-apart geometry of the North Anatolian fault. No extension related to the Aegean system is needed to explain the observations. The GPS results are consistent with motion over the last 5 Myr that has been determined from geological reconstructions.
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Slip partitioning in the Sea of Marmara Pull-Apart determined from GPS velocity vectors
Geophysical Journal International, 2003Co-Authors: Frédéric Flerit, Rolando Armijo, Bertrand Meyer, G.c.p. King, Aykut BarkaAbstract:Dislocation modelling is used to examine the GPS velocity vectors for the Marmara Sea region. First, the vectors due to the known Anatolia/Eurasia rotation are reproduced by introducing structures that approximate the large-scale tectonics. Observed features of the smaller scale fault system in the Marmara region are then progressively included with slip amplitudes and directions adjusted to fit an 80-vector subset of the GPS data. The motion in the Marmara Sea region is partitioned with the faults that bound the north of the basin carrying more strike-slip motion than predicted from the Anatolia-Eurasia plate motion and faults to the south having a greater perpendicular component. Taken together however, there is no net opening across the Marmara Sea perpendicular to the overall trend of the boundary and thus deformation in the Marmara region results only from the pull-apart geometry of the North Anatolian fault. No extension related to the Aegean system is needed to explain the observations. The GPS results are consistent with motion over the last 5 Myr that has been determined from geological reconstructions.
Bedri Alpar - One of the best experts on this subject based on the ideXlab platform.
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Marmara Island earthquakes, of 1265 and 1935; Turkey
Natural Hazards and Earth System Sciences, 2006Co-Authors: Yildiz Altinok, Bedri AlparAbstract:Abstract. The long-term seismicity of the Marmara Sea region in northwestern Turkey is relatively well-recorded. Some large and some of the smaller events are clearly associated with fault zones known to be seismically active, which have distinct morphological expressions and have generated damaging earthquakes before and later. Some less common and moderate size earthquakes have occurred in the vicinity of the Marmara Islands in the west Marmara Sea. This paper presents an extended summary of the most important earthquakes that have occurred in 1265 and 1935 and have since been known as the Marmara Island earthquakes. The informative data and the approaches used have therefore the potential of documenting earthquake ruptures of fault segments and may extend the records kept on earthquakes far before known history, rock falls and abnormal sea waves observed during these events, thus improving hazard evaluations and the fundamental understanding of the process of an earthquake.
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Evidence of NW extension of the North Anatolian Fault Zone in the Marmara Sea: a new interpretation of the Marmara
2002Co-Authors: Bedri Alpar, Zeki Yaşar YücelAbstract:Active faults aligning in NW–SE direction and forming flower structures of strike-slip faults were observed in shallow seismic data from the shelf offshore of Avcilar in the northern Marmara Sea. By following the parallel drainage pattern and scarps, these faults were traced as NW–SE-directed lineaments in the morphology of the northern onshore sector of the Marmara Sea (eastern Thrace Peninsula). Right-lateral displacements in two watersheds of drainage and on the coast of the Marmara Sea and Black Sea are associated with these lineaments. This right-lateral displacement along the course of these faults suggests a new, active strike-slip fault zone located at the NW extension of the northern boundary fault of the Cinarcik Basin in the Marmara Sea. This new fault zone is interpreted as the NW extension of the northern branch of the North Anatolian Fault Zone (NAFZ), extending from the Cinarcik Basin of the Marmara Sea to the Black Sea coast of the Thrace Peninsula, and passing through Buyukcekmece and Kucukcekmece lagoons. These data suggest that the rupture of the 17 August 1999 earthquake in the NAFZ may have extended through Avcilar. Indeed, Avcilar and _ Izmit, both located on the Marmara Sea coast along the rupture route, were strongly struck by the earthquake whereas the settlements between Avcilar and _ Izmit were much less affected. Therefore, this interpretation can explain the extraordinary damage in Avcilar, based on the newly discovered rupture of the NAFZ in the Marmara Sea. However, this suggestion needs to be confirmed by further seismological studies.
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Evidence of NW extension of the North Anatolian Fault Zone in the Marmara Sea: a new interpretation of the Marmara Sea (İzmit) earthquake on 17 August 1999
Geo-Marine Letters, 2001Co-Authors: Erkan Gökaşan, Bedri Alpar, Cem Gazioğlu, Zeki Yaşar Yücel, Şükrü Ersoy, Oguz Gundogdu, Cenk Yaltırak, Buser TokAbstract:Active faults aligning in NW–SE direction and forming flower structures of strike-slip faults were observed in shallow seismic data from the shelf offshore of Avcilar in the northern Marmara Sea. By following the parallel drainage pattern and scarps, these faults were traced as NW–SE-directed lineaments in the morphology of the northern onshore sector of the Marmara Sea (eastern Thrace Peninsula). Right-lateral displacements in two watersheds of drainage and on the coast of the Marmara Sea and Black Sea are associated with these lineaments. This right-lateral displacement along the course of these faults suggests a new, active strike-slip fault zone located at the NW extension of the northern boundary fault of the Cinarcik Basin in the Marmara Sea. This new fault zone is interpreted as the NW extension of the northern branch of the North Anatolian Fault Zone (NAFZ), extending from the Cinarcik Basin of the Marmara Sea to the Black Sea coast of the Thrace Peninsula, and passing through B uy uk cekmece and K u c uk cekmece lagoons. These data suggest that the rupture of the 17 August 1999 earthquake in the NAFZ may have extended through Avcilar. Indeed, Avcilar and Izmit, both located on the Marmara Sea coast along the rupture route, were strongly struck by the earthquake whereas the settlements between Avcilar and Izmit were much less affected. Therefore, this interpretation can explain the extraordinary damage in Avcilar, based on the newly discovered rupture of the NAFZ in the Marmara Sea. However, this suggestion needs to be confirmed by further seismological studies.
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Subtidal Sea-level Variations in the Sea of Marmara, Their Interactions with Neighboring Seas and Relations to Wind Forcing
Journal of Coastal Research, 1997Co-Authors: Huseyin Yuce, Bedri AlparAbstract:Subtidal sea level fluctuations in the Sea of Marmara, their interactions with neighbouring seas (Black Sea and Aegean) and relations to wind forcing were examined over a three-year (1992-1994) period. Although the dominant sea level fluctuations occurred at time scales greater than 10 days, there are shorter period fluctuations occurring between 3-8 days. Subtidal sea levels for Sea of Marmara are highly coherent for all subtidal frequencies. There is no cross coherency for periods greater than 2.5 days between Sea of Marmara and Black Sea, while there are some coherent fluctuations in subtidal band between Sea of Marmara and the Aegean Sea. Local wind forcing is important for the Sea of Marmara and most of the sea level change is driven by NE-SW wind for Erdek and Fenerbahce. However, at longer time scales, nonlocal contribution is important.
