It is necessary to identify the role and limitation of a tsunami protection facility in installing the hardware elements and performing damage-reduction activities necessary to mitigate aftermath of the calamity. This paper examines the probabilities of occurrence of earthquakes of various magnitudes based on the earthquake occurrence frequency, estimates the corresponding tsunami damage, and proposes a method to determine the expected damage reduction, B(H), and expected damage, D(H), when a tsunami protection facility of a given scale, H, is built. With the goal of facilitating an agreement with the local government regarding the scale of the tsunami protection facility, promoting damage reduction measures, and reducing the overall social cost, it also proposes a scheme built on the results of the aforementioned method and the cost, C(H). The present method can also be used to identify residual risks, which will allow concerned parties to set concrete damage reduction targets.

1. [1] Japan Society of Civil Engineers (JSCE), “2011 Great East Japan Earthquake – JSCE Information Forum,” 2011, http://committees.jsce.or.jp/2011quake/node/79 (in Japanese) [accessed February 1, 2019]
2. [2] Central Disaster Management Council, “Report of the Committee for Technical Investigation on Countermeasures for Earthquakes andTsunamis Based on the Lessons Learned from the ‘2011 off the Pacific coast of Tohoku Earthquake’,” 2011, http://www.bousai.go.jp/kaigirep/chousakai/tohokukyokun/pdf/Report.pdf [accessed February 1, 2019]
3. [3] Ministry of Land, Infrastructure, Transport and Tourism (MILT), “Guide to Determining the Potential Tsunami Inundation,” 2012, http://www.nilim.go.jp/english/disaster/tsunami.pdf [accessed February 1, 2019]
4. [4] K. Kobayashi and E. Hideshima, “Social norms of disaster prevention facility,” H. Tatano and A. Takagi (Eds.), Economics of Disaster Prevention, pp. 334-342, Keiso Shobo, 2005 (in Japanese).
5. [5] Ministry of Agriculture, Forestry and Fisheries (MAFF), Rural Development Bureau, MAFF Fisheries Agency, MLIT River Bureau, and MLIT Coast Bureau, “Guideline for Cost-Benefit Analysis for Coastal Businesses (Revised Edition),” 2004, http://www.mlit.go.jp/kowan/beneki/index.html (in Japanese) [accessed February 1, 2019]
6. [6] The Headquarters for Earthquake Research Promotion, “List of long-term evaluation,” 2012, https://www.jishin.go.jp/evaluation/long_term_evaluation/lte_summary/ (in Japanese) [accessed February 1, 2019]
7. [7] Ministry of Land, Infrastructure, Transport and Tourism (MLIT), “Manual for Economic Evaluation of Flood Control Investment (Draft),” 2005, http://www.mlit.go.jp/river/mizubousaivision/toushin_e/1805_manual_e.pdf [accessed February 1, 2019]
8. [8] Shizuoka Prefecture Disaster Prevention Center, “The third series of earthquake damage estimation,” 2001, http://www.pref.shizuoka.jp/bousai/e-quakes/shiraberu/higai/soutei/index.html (in Japanese) [accessed February 1, 2019]
9. [9] Izu City, “Izu city statistical report,” 2011, http://www.city.izu.shizuoka.jp/gyousei/gyousei_category_main0701.html (in Japanese) [accessed February 1, 2019]
10. [10] T. Seno, “Great Earthquakes along the Nankai Trough –A New Idea for Their Rupture Mode and Time Series– ,” J. of the Seismological Society of Japan. 2nd ser., Vol.64, No.2, pp. 97-116, 2012 (in Japanese).
11. [11] T. Utsu, “A Method for Determining the Value of b in a Formula logn=a-bM showing the Magnitude-Frequency Relation for Earthquakes,” Geophysical Bulletin of the Hokkaido University, Vol.13, pp.99-103, 1965 (in Japanese).
12. [12] Cabinet Office, Government of Japan, “Great Earthquakes Model along the Nankai Trough (second report),” 2012, http://www.bousai.go.jp/jishin/nankai/model/index.html (in Japanese) [accessed February 1, 2019]
13. [13] Ministry of Land, Infrastructure, Transport and Tourism (MLIT), “Restoration method of coastal dikes and seawalls,” 2011, http://www.mlit.go.jp/river/shinngikai_blog/kaigantsunamitaisaku/dai02kai/dai02kai_siryou5.pdf (in Japanese) [accessed February 1, 2019]
14. [14] National Institute of Population and Social Security Research, “Population & Household Projection,” http://www.ipss.go.jp/site-ad/index_english/population-e.html [accessed February 1, 2019]
15. [15] Google, “GoogleEarth,” http://www.google.co.jp/earth/index.html [accessed February 1, 2019]
16. [16] Non-Life Insurance Rating Organization of Japan, “Statistics Compiled by Non-Life Insurance Rating Organization of Japan,” 2012, https://www.giroj.or.jp/publication/statistics/ (in Japanese) [accessed February 1, 2019]
17. [17] Y. Hayashi, “A note for the probabilistic tsunami source assessment,” private massage, 2012.