Hypocenter migration and crustal seismic velocity distribution observed for the inland earthquake swarms induced by the 2011 Tohoku-Oki earthquake in NE Japan: implications for crustal fluid distribution and crustal permeability
T. Okada, T. Matsuzawa, N. Umino, K. Yoshida, A. Hasegawa, H. Takahashi, T. Yamada, M. Kosuga, T. Takeda, A. Kato, T. Igarashi, K. Obara, S. Sakai, A. Saiga, T. Iidaka, T. Iwasaki, N. Hirata, N. Tsumura, Y. Yamanaka, T. Terakawa, H. Nakamichi, T. Okuda, S. Horikawa, H. Katao, T. Miura, A. Kubo, T. Matsushima, K. Goto and H. Miyamachi
Article first published online: 30 SEP 2014 | DOI: 10.1111/gfl.12112
Temporal expansion of the focal area in some earthquake swarms near Sendai (Nagamachi-Rifu fault), Moriyoshi-zan volcano, Senya fault, and the Yamagata-Fukushima border (Aizu-Kitakata area, west of Azuma volcano) induced by the 2011 Tohoku-Oki earthquake was observed. This temporal expansion can be explained by fluid diffusion. We found seismic low-velocity areas, which is the possible areas with fluid, beneath the swarms. From the results, the induced earthquakes are thought to be affected by the possible fluid pressure change.