Investigation of Offshore Fault Modeling for a Source Region Related to the Shakotan-Oki Earthquake
Tsuneo Ohsumi† and Hiroyuki Fujiwara
National Research Institute for Earth Science and Disaster Resilience (NIED)
3-1 Tennodai, Tsukuba, Japan
The purpose of this study is to verify fault modeling in the source region of the 1940 Shakotan-Oki earthquake using active faults offshore of Japan. Tsunami heights simulated in previous studies are found to be lower than observed levels, which makes it difficult to explain historical tsunami records of this earthquake. However, the application of appropriate slip magnitudes in the fault models may explain these differences. In the “Project for the Comprehensive Analysis and Evaluation of Offshore Fault Informatics (the Project),” a new fault model is constructed using marine seismic data and geological and geophysical data compiled by the Offshore Fault Evaluation Group, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) as part of the Project for Fault Evaluation in the Seas around Japan (Ministry of Education, Culture, Sports, Science and Technology, MEXT). Single-channel and multichannel reflection seismic data were used that includes information from a new fault identified in previous surveys. We investigated fault geometries and their parameters using the above data. Here, we show that the geometric continuity of these faults is adjusted by increasing the magnitude of fault slip. Standard scaling laws are applied on the basis of strong ground motion of the fault parameters, and the validity of the fault model is examined by comparing tsunami heights along the Japanese coastline from historically observed records with tsunami height from simulation analysis. This verification quantitatively uses Aida’s K and κ scale and variance parameters. We determine that the simulated tsunami height determined using the new model approach the heights observed historically, which indicates that the model is valid and accurate for the source region.
-  Headquarters for Earthquake Research Promotion, “Strong ground motion prediction method (“Recipe”) for earthquakes with specified source faults,” 2009 (in Japanese).
-  “An Approach to Tsunami Hazard Assessment along the Northeastern Coastal Area in Japan – Method and Preliminary Results –,” Technical Note of the National Research Institute for Earth Science and Disaster Prevention, No.400, p. 54, 2015 (in Japanese).
-  Y. Okamura, K. Satake, K. Ikehara, A. Takeuchi, and K. Arai, “Paleoseismology of deep-sea faults based on marine surveys of northern Okushiri ridge in the Japan Sea,” J. Geophys. Res., Vol.110, B09105, 2005.
-  K. Satake, “Re-examination of the 1940 Shakotan-oki earthquake and the fault parameters of the earthquakes along the eastern margin of the Japan Sea,” Phys. Earth and Planetary Int, pp. 137-147, 1986.
-  The Headquarters for Earthquake Research Promotion, “Project for the Comprehensive Analysis and Evaluation of Offshore Fault Informatics,” 2015 (in Japanese).
-  I. Aida, “Reliability of a tsunami source model derived from fault parameters,” Journal of Physics of Earth, Vol.26, pp. 57-73, 1978.
-  “Tsunami Assessment Method for Nuclear Power Plants in Japan,” The Tsunami Evaluation Subcommittee, The Nuclear Civil Engineering Committee, JSCE, Japan Society of Civil Engineers, pp. 321, 2006.
-  Japan Tsunami Trace database, Tsunami trace height information, Int. Research Institute of Disaster Science (IRIDeS), Tohoku University, http://tsunami-db.irides.tohoku.ac.jp/tsunami/mainframe.php [accessed Sep. 21, 2017]
-  Y. Okada, “Internal Deformation due to Shear and Tensile in a half-space,” Bull. Seismol. Soc. Am., Vol.85, pp. 1018-1040, 1992.
-  Y. Tanioka and K. Satake, “Tsunami generation by horizontal displacement of ocean bottom,” Geophys. Res. Letters, Vol.23, pp. 861-864, 1996.
-  Geospatial Information Authority of Japan, Measurement of the sea level at a tide station, http://www.gsi.go.jp/kanshi/tide_furnish.html [in Japanese, Sep. 21, 2017]
-  N. Miyabe, “Tunami associated with the Earthquake of August 2,” Bull. Earthq. Res. Inst., pp. 104-114, 1941 (in Japanese).
-  K. Irikura and H. Miyake, “Prediction of Strong Ground Motions for Scenario Earthquakes,” J., of Geography, Vol.110, No.6, pp. 849-875, 2001.
This article is published under a Creative Commons Attribution-NoDerivatives 4.0 Internationa License.