Geoslicer survey across the 1999 Nov. Duzce earthquake fault, Turkey A prompt report

概要

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At the southwest margin of the Lake Efteni, we extracted Geoslicer samples with the interval of 5-10 m in order to reveal the recurrence of the past large earthquakes produced by the 1999 Duzce earthquake (M7.1)segment. The geologic section across the earthquake rupture zone indicates that the mud flow deposits (Unit 2)drop toward the north more than 15 m, and that Unit 2 is covered by younger fine sediments with several angular unconformities. These unconformities, which are probably associated with surface faulting events, indicate two probable and two possible faulting events after the deposition of Unit 2. Considering that the radiocarbon dates of the peat layer just above Unit 2 are about 2 ka, we can estimate that the average recurrence interval of faulting events is about 400 to 500 years and that the vertical offset of each individual faulting event is 2.5 to 3 m. Moreover, we can point out the possibility that the timing of the penultimate faulting event is younger than AD 1500. The Duzce fault shows very high activity during the past 2000 years.