Kinematic analysis and palaeoseismology of the Edremit Fault Zone: evidence for past earthquakes in the southern branch of the North Anatolian Fault Zone, Biga Peninsula, NW Turkey (original) (raw)
Related papers
2011
Th e 26 December 1939 Erzincan (M s = 7.8) and 20 December 1942 Erbaa-Niksar (M s = 7.1) earthquakes created a total surface rupture more than 400 km between Erzincan and Erbaa on the middle to eastern sections of the North Anatolian Fault. Th ese two faulting events are separated by a 10-km-wide releasing stepover, which acted like a seismic barrier in the 20 th century. To understand the rupture behaviour in this structurally complex section of the North Anatolian Fault, we undertook palaeoseismological trench investigations on the Kelkit Valley segment where there is little or no palaeoseismic information. We found evidence for three surface faulting earthquakes predating the 1939 event during the past millennium in trenches excavated in Reşadiye and Umurca.
2010
The North Anatolian Fault Zone is one of the Earth's most important active dextral strike-slip structures, which is extending more than 1500 km from the eastern Turkey to the northern Aegean Sea. This deformation zone is the northern boundary of the westward moving Anatolian block and connects Aegean extensional regime with East Anatolian high plateau. 26 December 1939 Erzincan (Ms=7.8) and 20 December 1942 Erbaa-Niksar (Ms=7.1) earthquakes created a total surface rupture more than 400 km between Erzincan and Erbaa on the middle to eastern sections of the North Anatolian Fault. These two faulting events are separated by a 10-km-wide releasing step-over, acted like a seismic barrier in the 20th century. In contrast, the historical Anatolian Earthquake of 17 August 1668 is thought to have a probable rupture length of more than 400 km, starts from east of Gerede, crossing the 10-km-wide releasing step-over at Niksar, and stops somewhere close to Koyulhisar. However, some other historical earthquake catalogues do not share the idea of a single very large earthquake and mention a series of events between July and September 1668 at various places. In the framework of T.C. D.P.T. Project to 2006K.120220 we undertook paleoseismological trench investigations on the Kelkit Valley segment to test the multi-cycle earthquake behavior of the North Anatolian Fault at this structural complex section. We found evidences for three surface faulting earthquakes predating the 1939 event during the past millennium in trenches, excavated at Reşadiye (40.38N, 37.35E) and Umurca (40.33N, 37.35E). While Reşadiye trench is excavated on alluvial fan deposits at the east of the Reşadiye town, where sedimentation is modified by a man-made artificial channel after a certain period of time, Umurca trench is located at the distal part of an alluvial fan at 23 km east of Reşadiye trench. In addition to the 1939 Erzincan earthquake, prior earthquake surface ruptures are interpreted as: (a) 17 August 1668, (b) A.D. 1254, and (c) A.D. 1045 events. The 17 August 1668 Anatolia earthquake surface rupture is reported in previous paleoseismological studies on different segments of the North Anatolian Fault, which have created individual earthquakes at 1942, 1943, and 1944 in the 20th century. Taking into account previous studies and our results, we suggest very large 17 August 1668 historical strike-slip earthquake surface rupture jumped the 10-km-wide releasing step-over at Niksar and continued towards east until somewhere close to Koyulhisar. The existence of different magnitude offsets of field boundaries (sets of 4 m, 6.5 m, and 10.8 m) shows the effect of multiple events, in which 1939, 1668, and 1254 surface ruptures have around 4, 2.5, and 4 meters of coseismic horizontal slip on the Kelkit Valley segment, respectively.
Paleoseismology of the western Sürgü–Misis fault system: East Anatolian Fault, Turkey
Mediterranean Geoscience Reviews
The East Anatolian fault bifurcates into a north strand and a south strand near the City of Çelikhan, Turkey. The northern strand is referred to as the Sürgü-Misis fault (SMF) system, which is divided into a number of distinct fault segments based on geological and geomorphological characteristics. However, no paleoseismological data regarding the movement history of the SMF system previously have been reported. We excavated seven trenches across four segments of the SMF system to evaluate the paleoseismological history of these fault zones. These trenches exposed structural and sedimentological evidence of paleoseismic events that had primarily strike-slip displacements with secondary normal and reverse components of motion. Geochronological dating of the trench stratigraphy and event horizons provide the time elapsed since the last event and confirmed the Holocene activity of the faults. These fault segments are individually capable of producing surfacerupturing earthquakes, but may also rupture together generating large, complex, multi-segment ruptures. However, the SMF system has not produced surface-rupturing earthquakes in the last millennia, and therefore is accumulating strain. In light of our findings, we suggest that about 1.7 m of strain has accumulated across the Karataş and Yumurtalık fault segments, which is sufficient to produce moderate to large earthquakes when released seismically. The surrounding Gulf of İskenderun is a highly industrialized district in the Eastern Mediterranean. Therefore, the data obtained from this paleoseismological investigation will contribute to a better understanding of the earthquake hazards in the region.
Plio-Quaternary kinematic development and paleostress pattern of the Edremit Basin, western Turkey
Tectonophysics, 2016
The Edremit Basin and Kazdağ High are the most prominent morphological features of the Biga Peninsula in northwest Anatolia. There is still no consensus on the formation of Edremit Basin and debates are on whether the basin evolved through a normal, a right-lateral or a left-lateral strike-slip faulting. In this study, the geometric, structural and kinematic characteristics of the Edremit Basin are investigated to make an analytical approach to this problem. The structural and kinematic features of the faults in the region are described according to field observations. These fault-slip data derived from the fault planes were analyzed to determine the paleostress pattern of faulting in the region. According to the performed analysis, the southern end of the Biga Peninsula is under the influence of the ENE-WSW-trending faults of the region, such as the Yenice-Gönen, the Edremit, the Pazarköy and the Havran-Balıkesir Fault Zones. The right step-over geometry and related extension caused to the development of the Edremit Basin as a transtensional pull-apart basin between the Havran-Balıkesir Fault Zone and the Edremit Fault Zone. Field observations showed that the Plio-Quaternary faults at the Edremit Gulf and adjacent areas are prominently right-lateral strike-slip faults. Our paleostress analyses suggest a dominant NE-SW extension in the study area, as well as NW-SE direction. This pattern indicates the major effects of the North Anatolian Fault System and the component of Aegean Extensional System in the region. However, our kinematic analysis represents the dominant signature of the North Anatolian Fault System in basin bounding faults. The field observations and kinematic findings of this study are also consistent with the regional GPS, paleomagnetic and seismological data. This study concludes that the North Anatolian Fault System is the prominent structure in the current morphotectonic framework of the Edremit Gulf and adjacent areas.
Journal of Seismology - J SEISMOL, 2001
We excavated five trenches across the North Anatolia fault zone (NAFZ)along the Ganos fault (Gazikoy-Saros segment), which last produced surfacerupture in 1912, near Kavakkoy where the fault enters the Gulf of Saros. The trenches exposed faulted sediments in a flood-plain environment withabundant detrital charcoal and scattered land-snail shells. Twenty-tworadiocarbon dates place constraints on the ages of the exposed sediments,which range from less than a few hundred years to about 6000 years inage. In two closely spaced trenches, we identified five discrete earthquakeevent horizons in the upper 2.5 m of stratigraphy based on abruptupward termination of shear zones, folding, fissuring, and abruptstratigraphic thickening, four of which may corresponded to historicallyrecorded large regional earthquakes. The earliest of the identified eventsoccurs below an unconformity and dates to about 4 ka B.P. The morerecent four events all occurred within the past 1000–1200 years and maycorrespo...
Tectonic evolution of the central part of the East Anatolian Fault Zone, Eastern Turkey
TURKISH JOURNAL OF EARTH SCIENCES, 2021
The Eastern Anatolian Fault Zone (EAFZ), having a prominent place in the tectonic evolution of the Eastern Mediterranean, is a structural element of tectonic indentor due to the convergence between the African-Arabian plates and the Eurasian Plate. This study investigates the central part of EAFZ between Doğanyol (Malatya) and Çelikhan (Adıyaman). The geometry of the fault and the morphotectonic structures were determined by the field studies. Moreover, fault-slip data are measured according to the fault planes along the deformation zone for paleostress analysis. The paleostress analysis revealed three deformation phases that developed from the Late Eocene to the present due to the convergence between the Arabian Plate and the Anatolian Block. The first deformation phase is characterized by NW-SE compressional stress between Late Eocene and Late Oligocene periods. The second deformation phase is related to N-S compressional stress from the Middle Miocene to Pliocene. The most recent deformation phase shows the strike-slip faulting under the NNE-SSW compressional stress from the Late Pliocene to the present. The EAFZ developed during the last phase of these deformation stages. In addition, elongated ridges parallel to the fault, sinistral offsets of drainage networks, linear valleys, and fault terraces observed along the segment show that the study area exhibits active tectonic morphology of the EAFZ. The distribution of seismic activity that occurred during and after the recent mainshock (24 January 2020, Sivrice-Doğanyol earthquake) is compatible with the geometry of the segment and confirms strongly the active tectonics of the segment.
Geological Society, …, 2009
We conducted palaeoseismic studies along the North Anatolian fault both east and west of the Marmara Sea to evaluate its recent surface rupture history in relation to the well-documented historical record of earthquakes in the region, and to assess the hazard of this major fault to the city of Istanbul, one of the largest cities in the Middle East. Across the 1912 rupture of the Ganos strand of the North Anatolian fault west of the Marmara Sea, we excavated 26 trenches to resolve slip and constrain the earthquake history on a channel-fan complex that crosses the fault at a high angle. A distinctive, well-sorted fine sand channel that served as a marker unit was exposed in 21 trenches totaling over 300 m in length. Isopach mapping shows that the sand is channelized north of the fault, and flowed as an overflow fan complex across a broad fault scarp to the south. Realignment of the feeder channel thalweg to the fan apex required about 9+1 m of reconstruction. Study of the rupture history in several exposures demonstrates that this displacement occurred as two large events. Analysis of radiocarbon dates places the age of the sand channel as post AD 1655, so we attribute the two surface ruptures to the large regional earthquakes of 1766 and 1912. If each was similar in size, then about 4 -5 m of slip can be attributed to each event, consistent with that reported for 1912 farther east. We also found evidence for two additional surface ruptures after about AD 900, which probably correspond to the large regional earthquakes of 1063 and 1344 (or 1354). These observations suggest fairly periodic occurrence of large earthquakes (RI ¼ c. 283+113 years) for the past millennium, and a rate of c. 16 mm/a if all events experienced similar slip.
Bulletin of the Seismological Society of America, 2003
Paleoseismologic data from trenches excavated across the central part of the North Anatolian fault at Alayurt, Turkey, reveal evidence for at least four, and possibly five, surface ruptures during the past 2000 years, as well as one much older event. These surface ruptures, as recognized on the basis of upward fault terminations and colluvial gravel layers, include (1) the historic 1943 M w 7.7 Tosya earthquake;