1766 Marmara earthquake: Difference between revisions
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Revision as of 23:42, 29 August 2023
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| Local date | 5 August 1766 |
|---|---|
| Magnitude | 7.4–7.6 Mw |
| Epicenter | 40°36′N 27°00′E / 40.6°N 27°E |
| Fault | North Anatolian Fault |
| Areas affected | Ottoman Empire |
| Max. intensity | MMI X (Extreme) |
| Tsunami | None |
| Casualties | >5,000 fatalities |
The 1766 Marmara earthquake occurred on 5 August; the second major earthquake to strike the Sea of Marmara region of present-day Turkey that same year. Estimates of the earthquake's moment magnitude (Mw ) range between 7.4 and 7.6. The earthquake was caused by strike-slip movement along a segment of the North Anatolian Fault. There was further damage and casualties in the Sea of Marmara area which had been affected by another major earthquake in May 1766. The worst affected areas were Tekirdağ and Gelibolu.
Tectonic setting
The Sea of Marmara represents a pull-apart basin in a zone of complex strike-slip tectonic interactions associated with the North Anatolian Fault. The North Anatolian Fault is a predominantly right-lateral strike-slip fault that extends from Karliova to the Gulf of İzmit. West of the gulf, the fault splits into three branches; the northernmost strand plunges into the gulf and into the Sea of Marmara. The 230 km (140 mi) by 70 km (43 mi) basin itself hosts smaller pull-apart basins; the Tekirdağ, Central, Çınarcık, Karamürsel, and İzmit basins. These basins are bounded by short strike-slip and normal faults suggesting significant extensional tectonics in the area. Further west of the Sea of Marmara is the strike-slip Saros (Ganos) Fault which continues west into the North Aegean Sea.[1]
Earthquake
Estimates of the moment magnitude range between 7.4 and 7.6 and the epicenter location was suggested to be at 40°36′N 27°00′E / 40.6°N 27°E.[1] The same region was affected by a Ms 7.3 earthquake on 9 August 1912. Both earthquakes ruptured the Ganos Fault along Gallipoli. The 1912 event released seismic strain which had been accumulating in the 146 years since the 1766 event. Meanwhile, the 22 May 1766 earthquake was associated with rupture on the Prince's Islands Segment. Geologic trenching along the North Anatolian Fault where it plunges into the Gulf of Saros indicate evidence of rupture associated with this event.[2] In the northwestern Sea of Marmara, fresh surface ruptures in the basin floor revealing offsets of 5 m (16 ft) were associated with the 1912 event but older scarps could be associated with the 1766 event.[3]
Impact
There were more than 5,000 deaths associated with the mainshock.[2] This earthquake "completed the destruction" caused by another earthquake on 22 May 1766. It enlarged the earthquake-damage area further west of Rodosto. Destruction occurred in the area between Silivri and Tenedos with fatalities. Ganohora District in Tekirdağ was completely razed and there was heavy damage in Gelibolu. Many castles located within an area extending from the Dardanelles Strait to Evreşe were affected. Damage was reported in Istanbul, Bursa, Thrace, Edirne and Biga.[4]
The observed maximum Modified Mercalli intensity (MMI) was X (Extreme) at Hoşköy (Hora). MMI IX (Violent) was observed at Gülcük, Gelibolu, Gazikoy, Mürefte, Sarkoy, Tekirdag and Evrese. The towns of Bozcaada, Çanakkale, Kilidbahir, Malkara, Seddulbahir, Mudanya and Seddulbahir was assigned MMI VIII (Severe).[2]
The earthquake's felt area extended as far as Athos, Thessaloniki, Aydın and İzmir. It was also felt across the Balkan Peninsula and in the Carpathian Mountains. An damaging aftershock sequence continued for a year. On 29 May 1776, another earthquake struck the Sea of Marmara region; many buildings damaged by the 1766 earthquakes were damaged again. Damage from this shock was widespread but minor.[4]
See also
References
- ^ a b Ambraseys, N. (2002). "The Seismic Activity of the Marmara Sea Region over the Last 2000 Years". Bulletin of the Seismological Society of America. 92 (1): 1–18. doi:10.1785/0120000843.
- ^ a b c Parsons, T. (2004). "Recalculated probability of M ≥ 7 earthquakes beneath the Sea of Marmara, Turkey". Journal of Geophysical Research: Solid Earth. 109 (B5). doi:10.1029/2003JB002667.
- ^ Armijo, Rolando; Pondard, Nicolas; Meyer, Bertrand; Uçarkus, Gulsen; Lépinay, Bernard Mercier de; Malavieille, Jacques; Dominguez, Stéphane; Gustcher, Marc-André; Schmidt, Sabine; Beck, Christian; Çagatay, Namik; Çakir, Ziyadin; Imren, Caner; Eris, Kadir; Natalin, Boris; Özalaybey, Serdar; Tolun, Leyla; Lefèvre, Irène; Seeber, Leonardo; Gasperini, Luca; Rangin, Claude; Emre, Omer; Sarikavak, Kerim (2005). "Submarine fault scarps in the Sea of Marmara pull-apart (North Anatolian Fault): Implications for seismic hazard in Istanbul". Geochemistry, Geophysics, Geosystems. 6 (6). doi:10.1029/2004GC000896.
- ^ a b Ambraseys, N.; Finkel, C.F. (1991). "Long-term seismicity of Istanbul and of the Marmara Sea region". Terra Nova. 3 (5): 527–539. doi:10.1111/j.1365-3121.1991.tb00188.x.