A study on dynamic rupture process of an asperity and radiation of short-period seismic waves

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We investigate effects of stress concentration at the rim of an asperity due to surrounding aseismic sliding through numerical simulations. The stress concentration due to aseismic sliding promotes earlier occurrence of seismic rupture. This results in lower average stress drop of earthquake. This effect of stress concentration at the rim of asperity may explain the difference in average stress drop between intraplate and interplate earthquakes. The stress concentration at the edge of an asperity affects rupture process of asperity, and the average stress drop of asperity rupture increases with fracture energy or critical slip-weakening distance. A numerical simulation is conducted for dynamic rupture process of a circular asperity, where stress concentration is generated at the rim of the asperity. Seismic rupture starts from a point of the stress concentrated rim and propagates bilaterally around the rim. A significant slip pulse is generated at the end of the rupture due to rupture front focusing. We compile spatial distributions of short-period seismic energy radiation on faults estimated from the envelope inversion method to obtain the scaling law, frequency dependence of seismic energy radiation, and locality.