Fig. 1

Historical sequence of Nankai Trough earthquakes (after Ishibashi 2004). Upper map shows distribution of six rupture segments along Nankai Trough. Each rupture segment has been broken or unbroken in historical Nankai Trough earthquakes. Areas surrounded by gray dashed and gray dotted lines represent maximum estimates of seismogenic sources and possible tsunamigenic sources for future Nankai Trough earthquakes, respectively (Cabinet Office 2012). Black and white stars indicate hypocenters of the 1944 Tonankai and 1946 Nankai earthquakes, respectively (Kanamori 1972). In the table below, horizontal thick lines indicate segments that ruptured during each historical event in the Japanese eras named in the left column. Thick dashed lines and thin dotted lines indicate probable and possible broken segments, respectively. Roman and italic numerals indicate earthquake occurrence years and time intervals between two successive earthquakes, respectively. Since the 1605 Keicho event (shown by a gray broken line) was obviously a tsunami earthquake, this event is excluded in counting the time intervals between successive events. Among successive earthquakes, the 1707 Ho’ei and 1361 Ko’an earthquakes are considered to be larger earthquakes than ordinary ones from the evidences of uplifts and large tsunamis at the southern tip of the Kii Peninsula (e.g., Shishikura et al. 2011)