Abstract

Between 1939 and 1967, six large fault ruptures formed a westward-migrating sequence of events along a 900-km-long nearly continuous portion of the North Anatolian fault. For these events—the 1939 Erzincan, 1942 Niksar-Erbaa, 1943 Tosya, 1944 Bolu-Gerede, 1957 Abant, and 1967 Mudurnu Valley earthquakes—I have compiled a record of dextral slip, which contains nearly 100 points. These data indicate that the amount of slip is irregularly distributed along the 1939 to 1967 rupture zone. The maximum slip, 7.5 m, occurred during the 1939 earthquake in the eastern 150 km of the 900-km-long rupture zone. Dextral offsets diminish very abruptly eastward but very gradually westward. The rate of westward decrease in the 1939 to 1967 offsets is only slightly greater than the rate of westward decrease of post-Miocene displacement along the North Anatolian fault. This suggests that westward decrease in slip can be expected to be a general characteristic of earthquake ruptures along the North Anatolian fault in the future. Nevertheless, within the 1939 to 1967 slip distribution, there are three regions that had less slip than the neighboring regions. These I interpret as possible sites of large future earthquakes. One of these seismic gaps has already experienced another earthquake (in 1951) and subsequent creep.

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