2005 年 58 巻 3 号 p. 231-246
This paper reviews studies on the relation between the eventual earthquake size and its rupture nucleation size. Although a large number of studies have been made in order to find whether the seismic nucleation phase depends on the eventual earthquake size or not, this subject is still in controversy. Several recent papers have reported that the duration of the seismic nucleation phase scales with the final rupture size, and that the scaling relation can be explained by rupture nucleation models. These studies suggest that larger preslip occurs before a larger earthquake. On the contrary, other papers have reported that the seismic nucleation phase is independent of the earthquake size; earthquakes of all sizes initiate in a similar manner. Adding to these existing studies, we perform a numerical simulation of sliding behavior on a fault assuming two asperities of different sizes. The result shows that when the rupture of the small asperity triggers the rupture of the large asperity, short term preslip occurs at the small asperity, and the magnitude of the preslip does not depend on the eventual earthquake size. However, intermediate-term aseismic slip which occurs around the main asperity depends on the eventual earthquake size.