Paleoseismicity of the Nukumi Fault Ruptured during the 1891 Nobi Earthquake, Central Japan, Revealed by a Trenching Study

Discovery, Controls, and Hazards of Widespread Deep‐Seated Gravitational Slope Deformation in the Etsumi Mountains, Central Japan

“…Dynamic ground motion is calculated as peak ground acceleration (PGA; in gal or cm/s 2 ) using a distance attenuation equation for shallow Japanese earthquakes (Kanno et al, ) with a calibration of site effects evaluated from geomorphic classification and bedrock geology (Matsuoka et al, ). Scenario earthquakes are based on the active fault model in and around the Etsumi Mountains that is established modified from available information of active fault locations (Suzuki & Sugito, ) and slip rates (Kaneda & Okada, ; Kaneda & Sago, ; Okada et al, ; Yoshioka et al, ). We calculate the earthquake size using the empirical relationship among magnitude, fault length, and fault slip rate (Anderson et al, ) because widely used global empirical relationships (Wells & Coppersmith, ) do not take into account the dependency of earthquake size on earthquake repeat times (Kanamori & Allen, ) and thus substantially underestimate earthquake magnitudes for Japanese low slip‐rate faults with long rupture intervals.…”

“…The Nukumi, Neodani, Kurozu, and Umehara faults are known to have ruptured simultaneously in 1891 in the destructive moment magnitude ( M w ) 7.5 Nobi earthquake (Fukuyama et al, ; Kaneda & Okada, ; Koto, ; Matsuda, ). Tectonic geomorphic and paleoseismic studies suggest that recurrence times of large earthquakes on these active faults are on the order of a few to tens of thousands years (e.g., Kaneda & Okada, ; Okada & Matsuda, ; Okada et al, ; Yoshioka et al, ). In contrast to the northeastern half of the study area where the Nobi fault system runs through, the southcentral part has almost no active faults (Figure d) (Suzuki & Sugito, ).…”