Abstract
AbstractWe estimated the source model for the foreshock of the 2004 off the Kii peninsula earthquakes by empirical Green’s function modeling. The size and the rise time of the strong motion generation area (SMGA) were estimated to be 30 × 15 km, and 0.9 sec, respectively. The stress drop of the SMGA was calculated to be 8.3 MPa. This model could reproduce long-period ground motions following the direct S-wave observed in the Osaka basin well. Using the derived source parameters, we simulated strong motions of the hypothetical Tonankai earthquake. Distribution of the seismic intensity derived here is similar to that obtained by the previous report. We could predict long-period ground motions which last for a long duration at the basin sites.
Highlights
At 19:07 on 5 September 2004, an MJMA7.1 earthquake occurred in the south east off the Kii peninsula, Japan
The 2004 off the Kii peninsula earthquakes would provide valuable information to grasp the gross characteristics of the strong motion of the Tonankai earthquake, especially its propagation effect, their source regions were not exactly the same
We considered that we could obtain a satisfactory result to the frequency band in which we were interested by characterizing only the asperities from the source model of HERP (2001b)
Summary
At 19:07 on 5 September 2004, an MJMA7.1 (magnitude determined by Japan Meteorological Agency, JMA) earthquake occurred in the south east off the Kii peninsula, Japan. A larger MJMA7.4 earthquake took place about 30 km away from the first one We call the latter large event the mainshock of the 2004 off the Kii peninsula earthquakes and take the 19:07 one as its foreshock. In order to examine the source characteristics of these earthquakes, we estimated the source model for the foreshock comparing the observed and synthetic strong-motion waveforms. The 2004 off the Kii peninsula earthquakes would provide valuable information to grasp the gross characteristics of the strong motion of the Tonankai earthquake, especially its propagation effect, their source regions were not exactly the same. Using the estimated source parameters for the foreshock analysis, we carried out an EGF simulation of the ground motion caused by the hypothetical Tonankai earthquake which showed some characteristics of the simulated strong ground motions
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