Holocene right-lateral slip-rate revealed by sediment core analyses and ground penetrating radar profiling, the Sagiriko fault, Izu Peninsula, Japan, at the northern tip of the Izu–Bonin–Mariana arc

Abstract

On the Izu Peninsula of Japan, the Sagiriko fault group is located to the south of the Kita-Izu fault zone, which ruptured during the 1930 Kita-Izu earthquake (Mjma = 7.3). A NS-trending strand of the Sagiriko fault group was ruptured during the 1930 earthquake, but conjugate EW-trending strands were not ruptured, and no Holocene activity on them has been documented. We surveyed the near-surface structure across the Sagiriko-b fault, one of the EW-trending strands, by ground penetrating radar profiling and radiocarbon dating of sediments obtained from two drilling cores. The results revealed a right-lateral displacement of 5.5 m of fluvial terraces around the survey site that formed after about 10 ka. The right-lateral slip-rate was calculated to be more than 0.55 mm/yr. This rate, which is significantly smaller than the crustal contraction rate in this area, suggests that the crustal contraction was probably spread across several EW-trending active faults parallel to the Sagiriko-b fault.