Earth Planets Space, Vol. 60 (No. 2), pp. 139-144, 2008LETTER
Manabu Hashimoto1, Hiroaki Takahashi2, Ryosuke Doke3, Minoru Kasahara2, Akira Takeuchi3, Kenusuke Onoue1, Yoshinobu Hoso1, Yo Fukushima1, Kajuro Nakamura1, Fumio Ohya1, Ryo Honda2, Masayoshi Ichiyanagi2, Teruhiro Yamaguchi2, Takahiro Maeda2, and Yoshihiro Hiramatsu4
1Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
2Institute of Seismology and Volcanology, Graduate School, Hokkaido University, Sapporo 060-0810, Japan
3Graduate School of Science and Engineering, University of Toyama, Gofuku 3190, Toyama, Toyama 930-8555, Japan
4Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
(Received June 29, 2007; Revised November 3, 2007; Accepted November 13, 2007; Online published February 19, 2008)
We have been conducting dense GPS observation in and around the epicentral region of the 2007 Noto peninsula earthquake since March 25, 2007, in order to detect postseismic displacements. Continuous observation has been underway at 12 sites to fill the gap of GEONET. Preliminary analysis of data up to early May shows that initial postseismic displacement rapidly decayed within 20 days after the occurrence of the mainshock. Horizontal displacements do not exceed 20 mm even at sites above the aftershock zone for this period. We also found a maximum uplift of about 20 mm there. Inversion of postseismic displacements with the variable slip model suggests a nearly right-lateral afterslip of less than 5 cm on the shallow portion of the source fault. Fitting a theoretical function to a time series of coordinate changes also suggests that the observed postseismic displacements might have been generated by afterslip.
Key words: Noto peninsula earthquake, GPS, crustal deformation, postseismic deformation, afterslip.