Effects of the source parameters on long period near-fault ground motion in the case of complex site condition

Using a 3-D structure model of Kunming basin, the effects of source parameters on long period ground motions are studied in this paper by the explicit finite element method and kinematic source model. The results show that the rupture mode, the rupture velocity, the fault depth and the distribution of the heterogeneous dislocations on the fault plane have great influence on near-fault long period ground motions. Different rupture mode can generate very different distribution of near-fault ground motion owing to the forward-directivity effect and the complex site conditions, since the areas with strong forward-directivity effect are very different in different rupture mode. As the rupture velocity increases, the forward-directivity effect become more obvious, and the long period ground motion increases. As the fault depth increases, the long period ground motions decrease rapidly. The long period ground motions will increase greatly as the asperity is located near the upper egde of the fault for very shallow earthquakes. So how to estimate these basic parameters reasonably is the most important problem for predication of near-fault strong ground motions.