Palaeoseismology of the North Anatolian Fault near the Marmara Sea: implications for fault segmentation and seismic hazard


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Rockwell T., Ragona D., Seitz G., LANGRIDGE R., Aksoy M. , Ucarkus G. , ...Daha Fazla

PALAEOSEISMOLOGY: HISTORICAL AND PREHISTORICAL RECORDS OF EARTHQUAKE GROUND EFFECTS FOR SEISMIC HAZARD ASSESSMENT, cilt.316, ss.31-54, 2009 (Diğer Kurumların Hakemli Dergileri) identifier identifier

  • Cilt numarası: 316
  • Basım Tarihi: 2009
  • Doi Numarası: 10.1144/sp316.3
  • Dergi Adı: PALAEOSEISMOLOGY: HISTORICAL AND PREHISTORICAL RECORDS OF EARTHQUAKE GROUND EFFECTS FOR SEISMIC HAZARD ASSESSMENT
  • Sayfa Sayıları: ss.31-54

Özet

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 = c. 283 +/- 113 years) for the past millennium, and a rate of c. 16 mm/a if all events experienced similar slip.