*Ayaka Tagami¹, Tomomi Okada¹, Shin'ichi Sakai², Mako Ozono^2,3, Kei Katsumata³, Masahiro Kosuga⁴, Yoshiko Yamanaka⁵, Katao Hiroshi⁶, Takeshi Matsushima⁷, Hiroshi Yakiwara⁸, Takashi Nakayama¹, Satoshi Hirahara¹, Toshio Kono¹, Shu'ichiro Hori¹, Toru Matsuzawa¹, . Group for the aftershock observations of the 2011 off the Pacific coast of Tohoku Earthquake(1. Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, 2. Earthquake Research Institute, University of Tokyo, 3. Institute of Seismology and Volcanology, Graduate School of Science, Hokkaido University, 4. Graduate School of Science and Technology, Hirosaki University, 5. Graduate School of Encironmental Studies, University of NAGOYA, 6. Research Center for Earthquake Prediction, Disaster Prevention Research Institute, Kyoto University, 7. Institute of Seismology and Volcanology, Faculty of Sciences, Kyushu University, 8. Nansei-toko Observatory for Earthquakes and Volcanoes, Kagoshima University)