Abstract
Shallow lakes along minor structural bends or discontinuities of strike-slip faults are not usually paleoseismological target sites. In the present study, we show that a 2-m-deep, 700-m-long lake that is cross-cut by the North Anatolian Fault contains a reliable paleoseimological record that can be obtained through coring. The North Anatolian Fault is a major strike-slip fault in Turkey, and it last ruptured across the Asagitepecik Lake in 1939, with a slip of about 6 m. Seismic lines still show remains of the fault rupture in the form of minor scarps across the lake. Collected short cores show a set of sedimentary sequences. Each sequence is composed of similar organic-rich sedimentary units. The lower unit is dark and fibrous, and is similar to the present sedimentation at the top of the core. The upper unit is disturbed and has anomalous organic matter content, grain size and mineralogy. It is interpreted as an earthquake-induced sedimentary event. The 2.5-m-long AT2007LG core comprises four sequences, and four sedimentary events. Radiogenic 210 Pb and 137 Cs data obtained previously imply that the shallowest event 1 was triggered by the 1939 M = 7.9 Erzincan earthquake. Radiocarbon dating and correlation to a reference varved record suggest that events 2 and 4 were initiated by the 1668 and 1254 historical earthquakes. Event 3 does not correspond to a large historical earthquake on the North Anatolian Fault.
Highlights
IntroductionThere is the need for a site where continuous and slow trapping of sediments occurs
Constraining the rupture history of a given strike-slip fault can be challenging
In this report we focus on the eastern North Anatolian Fault (NAF), which ruptured during the 1939 M = 7.9 Erzincan earthquake between the towns of Erzincan and Niksar (Figure 1)
Summary
There is the need for a site where continuous and slow trapping of sediments occurs. These key sites are often located along structural discontinuities, like pull-apart basins and releasing bends present at different scales along strike-slip faults. These sedimentary traps have been exploited to retrieve continuous paleoseismological records along different strike-slip fault systems throughout the world [Klinger et al 2003, Weldon et al 2004, Liu et al 2007, Kozacı et al 2011]. A paleoseismic record can still be obtained by coring, as in the present study
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