Spatial patterns of initiation ages of active faulting in the Japanese Islands

Doke, Ryosuke; Tanikawa, Shinichi; Yasue, Kenichi; Nakayasu, Akio; Niizato, Tadafumi  ; Umeda, Koji; Tanaka, Takenobu*

Based on the collection and analysis of existing information, we clarified a spatial distribution of started age of present faulting pattern on active fault in Japanese Islands. The number of active faults which started its activities are gradually increased from about 3 Ma, dramatically increased after 1.5 Ma, and peaked at around 0.5 Ma. After 1.5 Ma, active faults which types of activity or trends are different from previously started active faults are developed. Therefore, there are plural types of active faults in the present tectonic field in Japan. After the peak around 0.5 Ma, newly developed active faults are decreased. It is possibly that newly developed active faults are undetectable; therefore, it is needed to develop new technics for detecting and assessing non-distinguishing active faults.