Deep Investigations of Outer-Rise Tsunami Characteristics Using Well-Mapped Normal Faults Along the Japan Trench
Authors:Baba, ToshitakaChikasada, NaotakaNakamura, YasuyukiFujie, GouObana, KoichiroMiura, SeiichiKodaira, Shuichi
Source:JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
Volume:125
Published:2020
Document Type:Article
Abstract:To assess the risk of tsunamis from outer-rise earthquakes, we carried out tsunami simulations using 33 simple rectangular fault models with 60 degrees dip angles based on marine seismic observations and surveys of the Japan Trench. The largest tsunami resulting from these models, produced by a M-w 8.7 normal-faulting event on a fault 332 km long, had a maximum height of 27.0 m. We tested variations of the predictions due to the uncertainties in the assumed parameters. Because the actual dip angles of the Japan Trench outer-rise faults range from 45 degrees to 75 degrees, we calculated tsunamis from earthquakes on fault models with 45 degrees, 60 degrees, and 75 degrees dip angles. We also tested a compound fault model with 75 degrees dip in the upper half and 45 degrees dip in the lower half. Rake angles were varied by 15 degrees. We also tested models consisting of small subfaults with dimensions of about 60 km, models using other earthquake scaling laws, models with heterogeneous slips, and models incorporating dispersive tsunami effects. Predicted tsunami heights changed by 10-15% for heterogeneous slips, up to 10% for varying dip angles, about 5-10% from considering tsunami dispersion, about 2% from varying rake angles, and about 1% from using the model with small subfaults. The use of different earthquake scaling laws changed predicted tsunami heights by about 50% on average for the 33 fault models. We emphasize that the earthquake scaling law used in tsunami predictions for outer-rise earthquakes should be chosen with great care.
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Reprint Address:Baba, T (corresponding author), Tokushima Univ, Grad Sch Sci & Technol, Tokushima, Japan.
Addresses:[Baba, Toshitaka] Tokushima Univ, Grad Sch Sci & Technol, Tokushima, Japan. [Chikasada, Naotaka] Natl Res Inst Earth Sci & Disaster Resilience, Ibaraki, Japan. [Nakamura, Yasuyuki; Fujie, Gou; Obana, Koichiro; Miura, Seiichi; Kodaira, Shuichi] Japan Agcy Marine Earth Sci & Technol, Res & Dev Ctr Earthquake & Tsunami, Yokohama, Kanagawa, Japan.
E-mail Addresses:baba.toshi@tokushima-u.ac.jp