Study On Source Rupture Mode Effects Of Near-field Long Period Strong Ground Motion And Its Applications In Yunnan Area

Study on long period seismic ground motion plays an important role in the analysis of the damage of buildings and structures. Some damage data in major earthquakes shows that damage of high-level structure, large-span structures and storage tanks are mainly caused by long period ground motion. Currently, the study of the effect of long period ground motion on near fault areas has important theoretical reference and application value on the analysis of distribution characteristics of earthquake damage, seismic hazard, and earthquake disaster mitigation.The source rupture mode has two meanings. First is, source rupture mode can be divided into one-side mode, two-side mode and disc-shaped mode according to different rupture propagation modes. Second is, there are many kinds of real source rupture modes such as conjugate fault mode and cascade fault mode according to different source fault forms. This dissertation is focused on seismic source, and its effect on ground motion from the aspects of theoretical source model and inversion source model.To explain the matter briefly and effectively, this dissertation constructed virtual fault model to study near fault strong ground motion characteristics of different rupture propagation modes, made a comparison between different models, and revealed important effect of rupture propagation direction to near fault strong ground motion.To illustrate the complex source rupture modes has important impact on the long-period ground motion, this dissertation select areas around Ludian, and use preliminary kinematic source inversion model and finite difference method to simulate wave field propagation of three kinds of fault models of Ludian Earthquake. Simulation results showed that conjugate fault modes is more similar to strong ground motion observations than single fault modes, and verify conjugate fault has effect on the complexity of ground motion distribution. Consequently, long-period ground motion simulation should pay more attention on the complexity of source rupture modes.To illustrate the complex source rupture modes has impact on the near fault long-period ground motion of very rare earthquake and major earthquake and use to the disaster prevention and emergency preparedness, this dissertation sets different schemes of different fault and different source rupture process on Xiaojiang Fault, to study the ground motion distribution with 16 source model. These probable results of setting earthquake can provide reference to the construction of disaster scenarios in such area.Based on the studies above, this dissertation achieved some progress and advances:(1) Based on kinematic source model, this dissertation constructed the seismic source rupture process of one-side rupture, two-side rupture and disc-shaped rupture, and use finite difference method to study distribution of ground motion of different rupture process.(2) This dissertation use conjugate source model to simulate Ludian Earthquake, and made comparison between simulation result and real damage distribution, and explored the explanation of complex damage distribution of Ludian earthquake from the aspect of source rupture form. The study showed that setting source rupture modes reasonably has important impact on ground motion simulation results, even an earthquake of Ms 6.5.(3) This dissertation use the method of setting earthquake on Xiaojiang Fault to study the probable damage distribution if major earthquake happened. Constructed different scheme of source rupture modes, analyzed near source ground motion of every scheme, and assessed cities with high risk in the cascade fault rupture. This research provided reference to disaster prevention and emergency preparedness in areas near Xiaojiang Fault.