Paleoearthquakes of the Düzce fault (North Anatolian Fault Zone): insights for earthquake recurrence

摘要

The November 12, 1999, Mw 7.1 earthquake, ruptured the Düzce segment of theNorth Anatolian Fault Zone and produced a ca. 40 km-long surface rupture. To improveknowledge about earthquake recurrence on this fault, we undertook paleoseismologicaltrench investigations. We found evidence for repeated surface faulting paleoearthquakespre-dating the 1999 event during the past millennium. Dating was based on radiocarbon,210Pb analyses, and archaeological considerations. In addition to the 1999 earthquake, priorsurface faulting earthquakes are dated as follows: AD1685-1900 (possibly end of 19thcentury); AD1495-1700; AD685-1020 (possibly AD890-1020). The AD967 and AD1878historical earthquakes are good candidates to have ruptured the Düzce fault correlatingwith the oldest and penultimate paleoearthquakes. No obvious correlation for the thirdpaleoearthquake (AD1495-1700) exists. These results shows that the Düzce faultconsiderably participates, along with the parallel Mudurnu fault sections, in theseismogenic deformation taking place along this part of the North Anatolian Fault.Four events since AD 685-1020 (possibly AD890-1020), would yield an averagerecurrence time for the Düzce fault of 330-430 yr (possibly 330-370 yr). The three mostrecent earthquakes, including 1999, occurred within 500 yr. Merging results from otherpaleoseismological studies along the Düzce fault show a consistency of results and yieldsaverage recurrence times for the past 2000 yr of 320-390 yr. Assuming that the 1999 slip(2.7 m average, 5 m maximum) is representative of the behavior of this fault, the aboverecurrence times yield a reference figure of fault slip rate in the range 6.9-15.6 mm/yr.