Earthquake Source Fault Beneath Tokyo
Hiroshi Sato,1
Naoshi Hirata,1
Kazuki Koketsu,1
David Okaya,2
Susumu Abe,3
Reiji Kobayashi,1
Makoto Matsubara,4
Takaya Iwasaki,1
Tanio Ito,5
Takeshi Ikawa,3
Taku Kawanaka,3
Keiji Kasahara,4
Steven Harder6
Devastating earthquakes occur on a megathrust fault that underlies the Tokyo metropolitan region. We identify this fault with use of deep seismic reflection profiling to be the upper surface of the Philippine Sea plate. The depth to the top of this plate, 4 to 26 kilometers, is much shallower than previous estimates based on the distribution of seismicity. This shallower plate geometry changes the location of maximum finite slip of the 1923 Kanto earthquake and will affect estimations of strong ground motion for seismic hazards analysis within the Tokyo region.
1 Earthquake Research Institute (ERI), University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113–0032, Japan.
2 Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089–0740, USA.
3 JGI Incorporated, 1-5-21 Otsuka, Bunkyo-ku, Tokyo 112–0012, Japan.
4 National Research Institute for Earth Science and Disaster Prevention, 3-1 Tennodai, Tsukuba 305–0006, Japan.
5 Department of Earth Science, Chiba University, Chiba 263–8522, Japan.
6 Department of Geological Sciences, University of Texas El Paso, El Paso, TX 79968–0555, USA.
