Near Real-Time Estimation of Spatial Distribution for Ground Motion Parameters During Recent Earthquakes in Japan

Estimation of spatial distribution for the earthquake ground motion indices plays an important role in early-stage damage assessments for rescue operations by disaster management agencies as well as for damage studies of urban structures. However, subsurface geology layers and local soil conditions lead on soil amplification that may be susceptible to distribution of estimated ground motion parameters on the surface. In this case study the applicability of the nationwide proposed GIS-based soil amplification ratios by Yamazaki et al. (2000) in the October 6, 2000 Tottori-ken Seibu (western Tottori Prefecture) and the March 24, 2001 Geiyo earthquakes in Japan have been examined. First, the ground motion parameters were converted to those at the hypothetic ground base-rock level (outcrop) using the amplification ratio for each 1 km x 1 km mesh size of geomorphological and subsurface geology classification unit. Then a Kriging method with the attenuation relationship at the base-rock as a trend component is applied.Finally the distribution of spatial ground motion parameters on the ground surface are obtained by multiplying those values with the GIS-based amplification factors for the entire region