HR: 1330h
AN: S12B-0386    [PDF]
TI: The last two faulting events on the southern strand of the North Anatolian Fault Zone, NW Turkey
AU: Ozalp, S
EM: ozalps@mta.gov.tr
AF: MTA, General Directorate of Mineral Research and Exploration, Ankara, 06520 Turkey
AU: Dogan, A
EM: dogan@mta.gov.tr
AF: MTA, General Directorate of Mineral Research and Exploration, Ankara, 06520 Turkey
AU: * Emre, O
EM: emre@mta.gov.tr
AF: MTA, General Directorate of Mineral Research and Exploration, Ankara, 06520 Turkey
AB: The North Anatolian Fault Zone (NAFZ) in the Eastern Marmara Region consists of two main strands, the northern and the southern. GPS data indicate 25 mm/yr slip rate along the NAFZ. The slip rate of the southern strand is approximately half of that observed on the northern strand. Relatively few historical earthquakes are associated with the southern strand. The southern strand consists of four main segments: Geyve-Iznik, Gemlik, Zeytinbagi and Bandirma that follow each other in a right stepping pattern between Dokurcun valley and Bandirma Bay. The Gemlik segment is 40 km-long, between the Gemlik and Iznik pull-apart basins. The eastern and western parts of the segment cut Holocene alluvial fans while the central part cuts basement rocks. We excavated six trenches at three different sites along the segment at Asil Celik, Terme and Tuzlaburnu, from east to west. Faulting structure was observed at the Terme site near Gemlik, but not at the other sites, despite clear active fault morphology. The Terme trench is 10m long, 2m wide and only 2.5m deep due to high ground water level. The stratigraphy of the trench consists of four units from bottom to top: 1) coarse gravel and gravel, 2) fine sand and silty clay, 3) silty mud with fine gravel and 4) soil. We identified two faulting events. Event 1 was observed between units 3 and 4. This event is younger than 180 ñ 40 years BP. Event 2 was observed between units 2 and 3. Event 2 occurred between 820 to 180 years BP. There is no detailed paleoseismological data for more than one event on the southern strand of the NAFZ. This study found two faulting events along the Gemlik segment in the last six century. Event 2 is larger than the last event based on the faulting structures. This event can be correlated with the 1419 historical earthquake in the region. Our findings confirm that it was a large earthquake probably rupturing several segments of the southern strand including the Gemlik segment. Event 1 can be correlated with the 1857 historical earthquake west of Lake Iznik which may have been triggered by the 1855 Bursa earthquake.
DE: 5475 Tectonics (8149)
DE: 7200 SEISMOLOGY
DE: 7221 Paleoseismology
SC: Seismology [S]
MN: 2003 Fall Meeting