Earth Planets Space, Vol. 60 (No. 10), pp. 1059-1062, 2008LETTER
Yasuo Awata1, Shinji Toda1, Heitaro Kaneda1, Takashi Azuma1, Haruo Horikawa1, Masanobu Shishikura1, and Tomoo Echigo2
1Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Site 7, Higashi 1-1-1, Tsukuba 305-8567, Japan
2Geo-Research Institute, Itachibori 4-3-2, Osaka 550-0012, Japan
(Received June 30, 2007; Revised October 19, 2007; Accepted October 23, 2007; Online published November 7, 2008)
The March 25, 2007 Noto Hanto earthquake (Mj = 6.9, Mw = 6.7) generated vertical crustal movement along the northwestern coast of the Noto Peninsula, central Japan. Soon after the event, we estimated the pattern and amount of coseismic coastal movement based on uplifted and subsided intertidal sessile organisms. Our observations reveal a broad 20-km-wide asymmetric zone of surficial deformation above and across the south-dipping source fault, with a steep north-facing frontal limb and a gentle south-facing back limb. The maximum coseismic uplift was approximately 40 cm at the crest of the zone of deformation. The result of forward modeling suggests that the top of the south-dipping source fault is buried at a depth of approximately 2 km, and that 1.2 m of slip on the fault provides the best fit to our surface observations. Our results demonstrate that traditional field investigations should be combined with modern instrumental observations such as GPS and InSAR to obtain the most effective and reliable spatio-temporal estimates of crustal movement associated with large earthquakes.
Key words: 2007 Noto Hanto earthquake, coseismic crustal movement, coastal uplift, intertidal organisms, concealed reverse fault.