HR: 12:05h
AN: T22A-08    [Abstracts]
TI: A 3000 Year Geologic Slip Rate From the Central North Anatolian fault, Turkey, Using 10Be Cosmogenic Nuclide Dating
AU: * KOZACI, O
EM: kozaci@usc.edu
AF: USC Department of Earth Sciences, 3651 Trousdale Parkway ZHS117, LOS ANGELES, CA 90089, United States
AU: Dolan, J
EM: dolan@usc.edu
AF: USC Department of Earth Sciences, 3651 Trousdale Parkway ZHS117, LOS ANGELES, CA 90089, United States
AU: Finkel, R
EM: finkel1@llnl.gov
AF: LLNL Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory,Post Office Box 808 (L-232), LIVERMORE, CA 94550, United States
AB: Understanding whether strain loading and release rates on major faults are constant or not in time is one of the major, unresolved questions in active tectonics. As part of our ongoing studies of the North Anatolian fault (NAF) in Turkey, we mapped the offset of a drainage that has incised into a mid-late Holocene alluvial fan along the NAF in north central Turkey, near the villiage of Tahtakopru. The drainage (Karanlik Dere), which is displaced ~60 meters right-laterally with little vertical displacement, flows southward almost perpendicular to the east-west trace of the NAF at the site. We used cosmogenic ¹⁰Be to determine the age of the fluvial fan surface. The combination of the measured offset and ~3-3.5 ka fan surface yielded an average slip rate of 20 mm/yr. The Karanlik Dere slip rate is indistinguishable from the slightly shorter-term (~2-2.5 ka) rate we measured at our Eksik slip rate site, which is located ~200 kilometers to the west. Three different dating methods (¹⁴C, ³⁶Cl and ¹⁰Be) revealed the same slip rate from two different sites within 200 kilometers. Our geological slip rates are indistinguishable from the geodetically measured 25±1 mm/yr rate of elastic strain accumulation across the NAF (Reilinger et al., 2006), suggesting that the rates of strain storage and release along the central NAF have been relatively constant over the past 3500 years. We attribute this constancy to the geometrical simplicity and mechanical efficiency of the North Anatolian fault where there are no other major faults that can produce large earthquakes and affect the timing of these earthquakes. We note however, that the geodetic rates fall near the high end of our longer-term geological rate ranges, leaving open the possibility that the lower crust beneath the NAF is deforming slightly faster than its long-term rate, possibly in response to some long-lived effects of the 20th century sequence of large NAF earthquakes.
DE: 1150 Cosmogenic-nuclide exposure dating (4918)
DE: 1209 Tectonic deformation (6924)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8111 Continental tectonics: strike-slip and transform
SC: Tectonophysics [T]
MN: 2007 Fall Meeting