Abstract
In order to simulate near-field ground motions accurately, it is necessary to use a physically reasonable time function of the slip velocity on a fault. Although the analytical expression of slip velocity is preferred for the simulation, the slip velocity on a fault is currently estimated numerically for each set of dynamic parameters of source process. In this study, an approximate expression of slip velocity is proposed on the basis of the numerical solution of 2D and 3D crack simulations including a slip-weakening friction law. For the time of slip onset to the time of maximum slip velocity, the slip velocity is approximated by a quadratic function based on a solution of a 2D steady state crack with a slip-weakening friction law. For a latter part of the slip history, the slip velocity is approximated on the basis of results of 3D crack simulation using the staggered grid finite difference method with the slip-weakening friction law. The important parameters for describing the slip velocity are maximum amplitude of the slip velocity, the time of the maximum slip velocity, and the rise time.
