The Preliminary Study On Characteristics Of Subduction-zone Ground Motion And Its Attenuation Relationship

As a result of the continuing development and construction about the South China Sea, marine engineering anti-seismic problem is becoming more and more attention. There are numerous earthquakes activities in subduction zones near the South China Sea. The ground motion parameters estimation of subduction zone earthquakes need to understand its’ characteristics. In this paper, we study ground motion of subduction zone earthquakes and its attenuation relationships.Just work is as follows:1. We provide the domestic research present products, situation and problems of the subduction zone regional seismic problems, as well as international scholar. Summarizing the basic information, subduction zone position, focal depth characteristics and seismicity of the South China Sea, there are many six to eight magnitude subduction interface earthquakes, at the same time, mainly less than six magnitude earthquakes in subduction intraslab zone. The effects of subduction earthquakes should be considered for engineering of the South China Sea.2. Collecting the Chile magnitude 8.2 subduction earthquakes, and subduction zone interface and intraslab earthquakes in Japan, We compare and analyze the ground motion parameters. Statistics indicate: For the two subduction zone earthquakes, there are obvious differences in Fourier spectrum, predominant frequency in Japan is less than Chile, and Japan’s earthquake response spectrum amplitude is larger than the result of Chile especially long period.Comparing the peak ground acceleration(PGA) attenuation trendency with distance relationship under similar magnitude subduction zone earthquake including interface and intraslab and shallow crustal earthquakes, the result is: under similar magnitude earthquakes, the PGA attenuation relationship of subduction interface is the slowest, however, intraslab fastest. When close the source, PGA of the subduction zone interface earthquakes slightly smaller than shallow crustal style, more small the subduction intraslab earthquakes. Subudction zone earthquakes have regional difference.3. We simulate the subduction zone intraslab ground motion in the South China Sea and the different seawater depth influence on the undersea ground motion using the point model. The paper thinks that the seawater will have little impact on the level of the horizontal gound motion and can be ignored in the engineering. Accordiong to the characteristics of the South China Sea sunbuction zone seismicity, we simulate larger magnitude interface gound motion records in rock sites using the finite fault method and have a simple comparison. Simulation results and the actual data have certain similarity on the changing trends, so the simulation can be used as a reference.4. We try to build South China Sea subduction zone intraslab and interface peak ground acceleration and absolute acceleration response spectrum attenuation relationship in rock site based on ground motion simulated by the point model and the finite fault method respectly. Through the PGA decay comparison of earthquakes in our land zone, subduction zone about southeast of Taiwan and simulation results, the paper thinks the effects of numerical simulation and fiting is meaningful.