Earth Planets Space, Vol. 57 (No. 4), pp. 261-270, 2005
Reiji Kobayashi and Kazuki Koketsu
Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
(Received July 20, 2004; Revised February 22, 2005; Accepted March 1, 2005)
The historical geodetic and teleseismic data are jointly inverted for the rupture process of the 1923 Kanto earthquake together with the strong motion data recently discovered. The resultant slip distribution shows two asperities (areas of large slips) on the fault plane with a total seismic moment of 1.1 × 1021 Nm (Mw 8.0). The asperity in the shallow central portion of the fault is larger with maximum slip of approximately 10 m than the one in the hypocentral region. The recovered slip functions indicate that the initial slip was abrupt in the hypocentral asperity, though it was gradual in the larger asperity. The major discrepancies between the observations and synthetics are attributed to volcanic activities and the 3-D structure of the Kanto Basin. We compare the slip and aftershock distributions and also discuss the relation of the asperities to silent earthquakes.
Key words: The 1923 Kanto earthquake, source process, asperity.