Three Dimensional Level Terrain Effects

The study of the effect on ground motion about different surface topography is an important issue to seismology and earthquake engineering, and it is a urgent requirement to protect the stability and development of human society and reduce the earthquake disaster. Wealth of observations and studies has shown that surface topography have a major impact on ground motion, and surface projections and the top of the hill have more serious damage. Earthquake engineering has known that the solitary place will have more severe damage. With the rapid development of China’s economic construction, the growing industrialization and urbanization and population more and more intensive, some large projects which can’t be built in the plain all, will inevitably be built on hills and slopes. So how to know the impact of earthquake damage on different derrains, become an urgent research questions.Using the theoretical methods to simulation the earthquake ground motion and analysis seismic hazard on mountain marginal areas is one of the effective ways to reduce earthquake disaster and provide a reliable theoretical basis for Earthquake Disaster Mitigation. It can be directly used for strong ground motion parameter calibration and engineering ground motion prediction, and also provides a theoretical basis for engineering seismic design of structures and lifeline systems, seismic hazard study, that, to study the ground motion of surface topography and Insight into the development. One of the most, direct means to study the ground motion of different surface topography is observations of actual seismic data. The survey found that the building at the special terrain (ridges, valleys, steep slopes, cliffs, etc.) have Intensity anomalies. To study the ground motion by Array System, get a lot of observational data, and further confirmed the Influence of local terrain (Wei Wang, 2011), but because of the particularity of the actual terrain, as well as the Earth’s interior media complexity, we can’ t say that the effect is due to the terrain, so we need to find a theoretical approach which is Numerical Simulation Method. By analyzing the advantages and disadvantages of various methods, the paper selected spectral element method to simulate.This article simplifies the edge of the mountain to step terrain, and because the standard step terrain is very rare and more step terrain have convex, so to research the three-dimensional step terrain is more important. This paper uses spectral element method to simulate the different types of three-dimensional step terrain effects of vibration on the point source. Level terrain, as well as several different three-dimensional stepped terrains are simulated. Found that the three-dimensional stairs terrain have an important impact, on seismic waves. The effect is different on the intersecting lines of stepped slopes and the flat layer. This paper describes the characteristics of various terrain by the ground motion snapshot figure received, and finds that the waveform diagrams of three-dimensional stairs terrain have obvious secondary waves. Also found that the measuring lines of three-dimensional stairs terrain are amplified. Under measuring lines waveforms amplify from1.1to1.5, and upper measuring lines waveforms amplify from0.9to1. These studies that describe the impact of the edge of the step structure mountain in point source earthquake and calculate the respective positions’magnification of the three dimensional stepped terrains provide a basis for engineering studies. Also Select a different source positions and different frequencies to research. Considering that the source located below the vertex of the sharp convex step terrain and the sharp concave step terrain. Found that when the souce is different the waveform snapshot is similar. Also research the ground motion effects of different frequency including0.5,1, and1.5hz, found that as the frequency decreases, the sphere of influence of three dimensional step increases terrain.