Year: 2024
Type: article
Abstract: Inversion tectonics, in which old normal faults act as reverse faults in current stress fields, are frequently observed in northeastern Japan (Tohoku District); however, the conditions that control these fault activities remain unclear. To improve the identification of faults that are more favorable to slip under current stress conditions, the regional fault mechanisms in the Tohoku District must be better understood. The stress field in the Tohoku District and the likelihood of fault activities were thus estimated using slip tendency (ST) analysis. The results show that in the eastern margin of the Japan Sea (EMJS), the reverse fault type is dominant in the stress field. The maximum horizontal direction changes clockwise from E–W to NW–SE from the northern to the southern regions and counterclockwise from NW–SE to E–W from the Japan Sea to the inland area. In the Tohoku inland area, the estimated direction of the maximum horizontal axis changed after the 2011 Tohoku-Oki earthquake, from E–W to WNW–ESE. ST values were calculated for seven events in the EMJS area. To avoid the influence of the Tohoku-Oki earthquake, only stress field data prior to the 2011 Tohoku-Oki earthquake were used to determine ST values for four of the events in the Tohoku inland area. The results showed eastward-dipping fault planes with low dip angles (approximately 30°–45°) and large ST values (approximately > 0.7). The large ST values indicate that the stress field fault is favorable to slip and the results were consistent with the actual fault plane in the EMJS area. However, in the Tohoku inland area and the southern part of fault model of the 1993 Hokkaido Nansei-Oki earthquake, fault planes with large ST values were found to be inconsistent with the slipped fault plane, thus indicating that slipping was unfavorable. The regional differences are consistent with the volcano distribution and thus, the fluid supply from volcanic activity may have helped the fault slip under difficult stress conditions. Graphical Abstract
Source: Earth Planets and Space
Authors: Ayaka Tagami, Miu Matsuno, Tomomi Okada, Shin’ichi Sakai, Mako Ohzono, Kei Katsumata, Masahiro Kosuga, Yoshiko Yamanaka, Hiroshi Katao, Takeshi Matsushima, Hiroshi Yakiwara, Satoshi Hirahara, Toshio Kono, Shu’ichiro Hori, Toru Matsuzawa, Shuutoku Kimura, Takashi Nakayama, Group for the aftershock observations of the 2011 off the Pacific coast of Tohoku Earthquake
Institutions: Tohoku University, Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, Earthquake Research Institute, University of Tokyo, The University of Tokyo, Hokkaido University, Hirosaki University, Nagoya University, Kyoto University, Disaster Prevention Research Institute, Kyoto University, Kyushu University, Kagoshima University
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,590
Funder: Tohoku University
OpenAlex ID: W4392558232