ESTIMATES OF REGIONAL AND LOCAL STRONG MOTIONS DURING THE GREAT 1923 KANTO, JAPAN, EARTHQUAKE (MS-8.2) - PART 2 - FORWARD SIMULATION OF SEISMOGRAMS USING VARIABLE-SLIP RUPTURE MODELS AND ESTIMATION OF NEAR-FAULT LONG-PERIOD GROUND MOTIONS

This article addresses the forward simulation of regional and local st rong motions from the 1923 Kanto, Japan, earthquake (Ms 8.2), using tw o variable-slip rupture models: the Wald and Somerville (1995) slip mo del (WS slip model) derived from geodetic and teleseismic data and a r esampled version of the Takeo and Kanamori (1992) slip model (TK slip model) that was obtained from the forward simulation of the Ewing seis moscope record at Hongo (HNG, epicentral distance R = 60 km). Green's functions are calculated using Bat-layered velocity models for specifi c source-receiver paths, which were developed in our first article (Sa te ct al., 1998). For regional stations Sendai (R = 350 kill) and Gifu (R = 220 In), the WS slip model provides a much better match to the w aveform data than the TK slip model, For local station HNG, the first 40 sec of the N77 degrees E Imamura seismogram is successfully reprodu ced by both of the slip models, although the arrivals are delayed in t he TK slip model. The large-amplitude long-duration, long-period (13 s ec) later phases in the southwest-component Ewing seismogram are not r eproduced by either of the slip models. Our results suggest that the W S slip model gives a better representation of the overall rupture proc ess of the 1923 event than the TK slip model does. Near-fault long-per iod ground motions calculated at several stations using the WS slip mo del suggest that the motions at HNG were not the largest in the Tokyo metropolitan area during the 1923 event. in addition, we estimate that the ground motions near the southern margin of the fault plane were s ignificantly larger than the recorded near-fault motions of recent mag nitude 7 earthquakes, such as North-ridge and Kobe, for periods longer than several seconds. This suggests that design codes based on the ex perience of these recent events may not adequately describe the long-p eriod response expected during a magnitude 8 earthquake.