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Abstract
This article addresses the forward simulation of regional
and local strong motions from the 1923 Kanto, Japan, earthquake
(Ms 8.2), using two variable-slip rupture models: the Wald and
Somerville (1995) slip model (WS slip model) derived from geodetic and
teleseismic data and a resampled version of the Takeo and Kanamori
(1992) slip model (TK slip model) that was obtained from the forward
simulation of the Ewing seismoscope record at Hongo (HNG, epicentral
distance R = 60 km). Green's functions are calculated using
flat-layered velocity models for specific source-receiver paths, which
were developed in our first article (Sato et al., 1998). For
regional stations Sendai (R = 350 km) and Gifu (R = 220
km), the WS slip model provides a much better match to the waveform data
than the TK slip model. For local station HNG, the first 40 sec of the
N77oE Imamura seismogram is successfully reproduced by both
of the slip models, although the arrivals are delayed in the TK slip
model. The large-amplitude long-duration, long-period (13 sec) later
phases in the southwest-component Ewing seismogram are not reproduced by
either of the slip models. Our results suggest that the WS slip model
gives a better representation of the overall rupture process of the 1923
event than the TK slip model does. Near-fault long-period ground motions
calculated at several stations using the WS slip model 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 significantly larger
than the recorded near-fault motions of recent magnitude 7 earthquakes,
such as Northridge and Kobe, for periods longer than several seconds.
This suggests that design codes based on the experience of these recent
events may not adequately describe the long-period response expected
during a magnitude 8 earthquake.
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