MODELING OF SUBSURFACE FAULT FOR STRONG MOTION PREDICTION INFERRED FROM SHORT ACTIVE FAULT OBSERVED ON GROUND SURFACE

Short active faults observed on the ground surface have been supposed to indicate longer subsurface faults in the seismogenic layer. However, no concrete procedures have been proposed so far for modeling the subsurface faults for predicting strong ground motions. Hence, we surveyed several important research papers, and proposed a procedure for modeling the subsurface faults. Here, the seismic moment M0 of 7.5×1025 dyne•cm was assumed as the minimum size of the source for the case that any short active faults were observed on the surface. The modeling procedure was based on the asperity model, that was adopted by the Headquaters of Earthquake Research Promotion (2005) in Japan. Five main fault parameters of the area of the entire fault S, the averaged stress drop Δσ, the area of the asperities Sasp, the stress drop on the asperities Δσasp, and the short-period level A were determined by the two theoretical relationships and the three empirical relationships among the six main fault parameters including the seismic moment M0.