Integrated Probabilistic Tsunami Hazard Assessment against possible tsunamis along the Pacific coast of Honshu and Shikoku islands, Japan
Abstract
Since 2014, we have presented regional Probabilistic Tsunami Hazard Assessments (PTHAs) for the pacific coasts of major Japanese islands, along Nankai Trough (Hirata et al., 2015, 2016, AGU), Sagami Trough (Hirata et al., 2017, AGU), and Japan Trench (Hirata et al., 2014, AGU).
In this study, we integrate three of the regional PTHAs to get a nationwide PTHA. For the nationwide PTHA, we consider two kinds of probabilistic tsunami hazards; "present-time hazard" and "long-term mean hazard". The former is a tsunami hazard appropriate for assessment of short-term tsunami potential within several hundred years. It is assessed under an assumption that for major events, earthquake occurrence follows a renewal process based on a set of BPT probability distribution that the Earthquake Research Committee, the Headquarters for Earthquake Research Promotion of Japanese Government already estimated. The latter is a tsunami hazard showing tsunami potential averaged for more than a few thousand years, which is effective to make social/infrastructural preparations. It is assessed under an assumption that earthquake occurrence follows a stationary Poisson process, that is the earthquake occurrence is random. A "present-time hazard", showing the excess probability that the tsunami height will exceed 3 meters at coastal points in next 30 years (starting at 1st January, 2016), suggests that (1) very high excess possibility over 60% in several coastal regions along the southern coasts of Shikoku to Tokai region along Nankai Trough, perhaps due to contribution from the next Nankai earthquake, (2) mediate high excess possibility between 30% to 60% in many coastal regions along Japan Trench, and (3) a low excess possibility less than 10% in most of coastal regions around Sagami bay but over 20% in a some regions. On the other hand, a "long-term mean hazard", showing the probability that the tsunami height will exceed 3 meters at coastal points in next 30 years, suggests that (4) a not so high excess possibility less than 10-20% in most of coastal regions along Nankai Trough, and (5) very high excess possibility over 40% in most of coastal regions along Japan Trench. These implies that the Pacific coast of northeast Honshu is subjected to relatively high tsunami potential than the Pacific coast of southwest Honshu in periods over a few thousand years.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMNH41C1003H
- Keywords:
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- 4315 Monitoring;
- forecasting;
- prediction;
- NATURAL HAZARDSDE: 4333 Disaster risk analysis and assessment;
- NATURAL HAZARDSDE: 4341 Early warning systems;
- NATURAL HAZARDSDE: 4564 Tsunamis and storm surges;
- OCEANOGRAPHY: PHYSICAL