Seismic Fault Model for Predicting Strong Ground Motions Based on Physical Relation Between Surface and Subsurface Slip

Abstract eng:
The strong ground motions and the displacement of the surface fault trace are the results of the rupture of the subsurface fault, but they are not related physically with each other so far. Therefore, we proposed a procedure to model a subsurface fault for predicting strong ground motions under the physical constraint of the displacement of the surface fault trace estimated by the empirical relationship between the fault length and the displacement. In the procedure, given the fault length and the width, eight fault parameters of the fault area, the seismic moment, the short-period level, the average stress drop on the entire fault, the average slip on the entire fault, the area of the asperities, the stress drop on the asperities, and the S-wave velocity of the shallow layers were evaluated based on the eight theoretical and empirical equations of these fault parameters. Here, the short-period level is the flat level of the acceleration source spectrum in the short-period range. Since two unknown constants were included in the equations, they were determined by the results of a preliminary dynamic rupture simulation. We carried out the dynamic rupture simulation by the 3D finite difference method. We took an example of the fault model 25-km long and 15-km wide, consisting of two asperities. And, we obtained the areas of the asperities of 3.2 km×3.2 km and 1.9 km×1.9 km, the dynamic stress drop of the asperities of 32 MPa, and the S-wave velocity of the shallowest layer of 0.5 km/s. On the other hand, the rupture propagation velocity of the results was faster than the S-wave velocity, called super-shear, on some area of the fault. Since the super-shear rupture propagation velocity is not realistic in the earthquake of the fault size studied in this paper, we should further examine the parameters of the slip weakening model, for example, giving some random fracture energy on the fault.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket