HR: 09:45h
AN: S11C-08    [Abstracts]
TI: Quasi-static Slips Around the Source Areas of the 2003 Tokachi-oki (M8.0) and 2005 Miyagi-oki (M7.2) Earthquakes, Japan Estimated From Small Repeating Earthquakes
AU: * Uchida, N
EM: uchida@aob.geophys.tohoku.ac.jp
AF: Research Center for Prediction of Earthquakes and Volcanic Eruptions, Tohoku University, Aramaki Aza Aoba Aoba-ku, Sendai, 980-8578 Japan
AU: Matsuzawa, T
EM: matuzawa@aob.geophys.tohoku.ac.jp
AF: Research Center for Prediction of Earthquakes and Volcanic Eruptions, Tohoku University, Aramaki Aza Aoba Aoba-ku, Sendai, 980-8578 Japan
AU: Hirahara, S
EM: hirahara@aob.geophys.tohoku.ac.jp
AF: Research Center for Prediction of Earthquakes and Volcanic Eruptions, Tohoku University, Aramaki Aza Aoba Aoba-ku, Sendai, 980-8578 Japan
AU: Igarashi, T
EM: igarashi@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-Ku, Tokyo, 113-0032 Japan
AU: Hasegawa, A
EM: hasegawa@aob.geophys.tohoku.ac.jp
AF: Research Center for Prediction of Earthquakes and Volcanic Eruptions, Tohoku University, Aramaki Aza Aoba Aoba-ku, Sendai, 980-8578 Japan
AU: Kasahara, M
EM: mkasa@eos.hokudai.ac.jp
AF: Institute of Seismology and Volcanology, Hokkaido University, Kita10 Nishi8, Sapporo, 060-0810 Japan
AB: We have estimated spatio-temporal distribution of interplate quasi-static slips around the source areas of the 2003 Tokachi-oki (M8.0) and 2005 Miyagi-oki (M7.2) earthquakes by using small repeating earthquakes. The small repeating earthquakes are thought to be caused by repeated rupture of small asperities surrounded by stable sliding areas on the fault. Here we estimated cumulative slips for small repeating earthquakes assuming that they were equal to the quasi-static slip histories in the surrounding areas on the plate boundaries (Igarashi et al., 2003; Uchida et al., 2003). The 2003 Tokachi-oki earthquake occurred on September 26, 2003 off the southeast of Hokkaido, Japan. The present analyses show that the slips in the areas around and to the east of the asperity of the earthquake were slow before the earthquake but that it was significantly accelerated after the earthquake. The slip rate acceleration to the east of the asperity probably triggered a M7.1 event which occurred on November 29, 2004 at the eastern edge of the accelerated area (about 100km east from the hypocenter of the Tokachi-oki earthquake). It seems that the quasi-static slip released the slip deficit in the locked area between the asperities of the 2003 Tokachi-oki and 1973 Nemuro-oki (M7.4) earthquakes. The 2005 Miyagi-oki earthquake occurred on August 16, 2005 in the anticipated source area for the recurrent _eMiyagi-oki earthquake_f. However, it was estimated that the earthquake did not destroyed the whole area of the asperity which caused the previous Miyagi-oki earthquake in 1978 (The Headquarters for Earthquake Research Promotion, 2005). Our result shows the quasi-static slips for the period of 20 years before the earthquake was almost constant to the west of the source area of the 2005 earthquake. The slips after the earthquake were not significant for the period of 15 days which suggests the plate boundary around the asperity for the earthquake is still locking.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 7200 SEISMOLOGY
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Seismology [S]
MN: Fall Meeting 2005