[S-SS14] Active faults and paleoseismology

[SSS14-18] History of Coseismic Uplifts at Port of Murotsu and the Coming Nankai Trough Earthquake

Kunihiko Shimazaki¹, *Takashi Nakata², Akira Shibata³ (1.Emeritus Prof., Univ. Tokyo, 2.Emeritus Prof., Hiroshima Uinv., 3.Natl. Inst. Tech Niihama Col.)

Keywords:time-predictable model for large earthquakes, historical earthquake, coseismic uplift, Nankai trough earthquake, Port of Murotsu

Shimazaki and Nakata (1980) (hereafter referred to as SN1980) proposed a hypothesis named as time-predictable recurrence model for large earthquakes (hereafter referred to as time-predictable model) that, based on historical earthquake data at port of Murotsu in Kochi Prefecture, Holocene terraces in the southern part of the Boso Peninsula and Kikai Island, provides information on the timing of the next earthquake based on the size of the previous earthquake. SN1980 estimated the amount of uplift caused by Hoei earthquake to be 6 shaku (1.8 m) based on the depth of the port before and after Hoei earthquake by Imamura (1930). However, since the depth value could not exclude the influence of mud dredging, it became necessary to reexamine the historical earthquake data at port of Murotsu. After re-examination on hstory of coseismic uplifts at the port due to 1707 Hoei, 1854 Ansei, and 1946 Showa earthquakes are estimated to be 6 shaku 5 sun (1.97 m), 4 shaku (1.21 m), and 1.10 m, respectively. This regularity of earthquake repetition is more compatible with the time-predictable model than SN1980. This time-predictable hypothesis indicates that the next Nankai trough earthquake will occur around 2030 (Fig. ).