Regional probabilistic tsunami hazard assessment associated with active faults along the eastern margin of the Sea of Ja
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Regional probabilistic tsunami hazard assessment associated with active faults along the eastern margin of the Sea of Japan Iyan E. Mulia1* , Takeo Ishibe2, Kenji Satake1, Aditya Riadi Gusman3 and Satoko Murotani4
Abstract We analyze the regional tsunami hazard along the Sea of Japan coast associated with 60 active faults beneath the eastern margin of the Sea of Japan. We generate stochastic slip distribution using a Monte Carlo approach at each fault, and the total number of required earthquake samples is determined based on convergence analysis of maximum coastal tsunami heights. The earthquake recurrence interval on each fault is estimated from observed seismicity. The variance parameter representing aleatory uncertainty for probabilistic tsunami hazard analysis is determined from comparison with the four historical tsunamis, and a logic-tree is used for the choice of the values. Using nearshore tsunami heights at the 50 m isobath and an amplification factor by the Green’s law, hazard curves are constructed at 154 locations for coastal municipalities along the Sea of Japan coast. The highest maximum coastal tsunamis are expected to be approximately 3.7, 7.7, and 11.5 m for the return periods of 100-, 400-, and 1000-year, respectively. The results indicate that the hazard level generally increases from southwest to northeast, which is consistent with the number and type of the identified fault systems. Furthermore, the deaggregation of hazard suggests that tsunamis in the northeast are predominated by local sources, while the southwest parts are likely affected by several regional sources. Keywords: Probabilistic Tsunami Hazard Assessment, Active faults, Sea of Japan Introduction While our attention is drawn to the Pacific coast of Japan due to the past occurrences of damaging tsunamis in major subduction zones such as the Japan Trench and the Nankai Trough, its counterpart on the Sea of Japan coast poses non-negligible tsunami hazards. The Sea of Japan is known to host large tsunamis generated by submarine earthquakes (M > 7) on several active fault systems along its eastern margin. The most recent damaging tsunami was generated by the 1993 Hokkaido Nansei-oki earthquake of magnitude assigned by Japan Meteorological Agency (JMA) (MJMA) 7.8, causing a maximum run-up height of more than 30 m on Okushiri Island in Hokkaido (Shuto and Matsutomi 1995). In 1983, an earthquake of MJMA 7.7 (known as the 1983 Sea of Japan earthquake) *Correspondence: [email protected]‑tokyo.ac.jp 1 Earthquake Research Institute, The University of Tokyo, Tokyo, Japan Full list of author information is available at the end of the article
occurred off the Sea of Japan coast of Tohoku (Satake 1989). The highest recorded tsunami run-up of this event was approximately 15 m in the northern part of Akita prefecture (Shuto 1983). The 1964 Niigata earthquake (Abe 1978) with magnitude (MJMA) 7.5 induced a tsunami with maximum measured inundation height of ~ 6 m. The 1940 Shakotan-oki earthquake with MJMA of 7.5 (Satake 1986)
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