Earth Planets Space, Vol. 60 (No. 11), pp. 1075-1080, 2008LETTER
Yosuke Aoki1, Masato Furuya2, and Teruyuki Kato1
1Earthquake Research Institute, University of Tokyo, Tokyo 113-0032, Japan
2Department of Natural History Sciences, Hokkaido University, Kita-ku, N10W8, Sapporo 060-0810, Japan
(Received December 19, 2007; Revised June 7, 2008; Accepted June 9, 2008; Online published November 18, 2008)
Global Positioning System (GPS) and Synthetic Aperture Radar Interferometry (InSAR) detected substantial ground deformation due to the 2007 Chuetsu-oki earthquake (Mw = 6.8); GPS observation detected a horizontal deformation of up to about 170 mm and subsidence of up to 30 mm, and InSAR detected up to 290 mm of line-of-sight changes. A fault model is proposed to fit the ground deformation field as well as the aftershock distribution. Our model shows that a northwest-dipping fault to the north and a southeast-dipping fault to the south, consistent with the aftershock distribution, fits well with the observed data. However, our model also suggests that the modeled faults are likely to extend to shallower depths, where aftershocks are terminated. Combining our model with the subsurface structure suggests that the earthquake rupture initiated at depth and propagated into shallower depths that are not capable of nucleating an earthquake because of the presence of unconsolidated sediments.
Key words: Coseismic deformation, Global Positioning System, Synthetic Aperture Radar, Interferometry.