Abstract
Paleoseismological trenching was performed along the Düzce fault providing some preliminary insight about its seismogenic behavior. Dating was based on radiocarbon analysis of peat samples collected from the trenches and suggested seven earthquakes have occurred since 1740 BC. Integrating date constraints of events exposed in the trenches suggests a periodical earthquake recurrence model. According to a linear sequential event serial that has minimum misfit determined by considering the probability curve limits of the sample dates, the earthquake recurrence interval is between 384 and 460 years (or possibly between AD 394 and 400). A probability curve was also calculated for the date of the last earthquake (1999 Düzce earthquake) considering the probability distributions of sample dates based on the same event serial. This probability-distribution-based method, similarly, predicted that the 1999 Düzce earthquake occurred between 1933 and 2005 (±36 years) with a 68% probability. After this verification, using this method, it was estimated that the next earthquake along the Düzce fault has a 68% probability of occurring between 2328 and 2392. According to this calculation, the earthquake recurrence interval is about 391 ± 34 years with a 68% probability and the AD 967 historical earthquake likely ruptured the Düzce fault. Assuming an average slip of 350 cm (the average slip of the 1999 earthquake), the slip rate was estimated to be between 8.7 and 11.2 mm/a.
Highlights
On November 12, 1999, a destructive earthquake struck the town of Düzce (Turkey), resulting in tragic deaths and considerable structural damage to buildings
A probability curve was calculated for the date of the last earthquake (1999 Düzce earthquake) considering the probability distributions of sample dates based on the same event serial
According to the predating fitted linear line (Fig. 14) based on this sequential serial set using the data determined in the current study, the lower bound of the range of the recurrence interval zone is about 394 years based on 68.2 % probability curves of the samples used
Summary
On November 12, 1999, a destructive earthquake struck the town of Düzce (Turkey), resulting in tragic deaths and considerable structural damage to buildings. The earthquake produced about 42-km of dextral rupture with 350-cm average slip (Fig. 2). This right lateral fault is likely composed of four segments (Efteni, Aydınpınar, Mengencik and Kaynaşlı), each having similar length, and are separated by left-stepping structural discontinuities (stepovers) that result in pressure ridges (Fig. 3a). The object of the current paleoseismic trenching study is to provide constraints for the dates of past earthquakes that ruptured the Düzce fault. Seven 14C accelerator mass spectrometry (AMS) dates were used to obtain preliminary information about the recurrence intervals for large earthquakes originating from the Düzce fault. According to a sequential earthquake serial set suggested in this study, the recurrence interval is between 394 and 400 years based on the limit values of pre- and post-dating samples, respectively. The results here will be helpful for addressing questions such as: 1) Is it the character of Düzce fault that typically results in a rupture as a single segment? or are there multiple segments along the Düzce fault that can fail individually? 2) If the Düzce fault is a single segment, does it produce characteristic earthquakes? and 3) Did the surface ruptures of the 1719, 1509, and 967 historical earthquakes occur along the Düzce fault?
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