Research On The Method Of Determination Ground Motion Parameters Against Great Earthquake

Great earthquakes (M≥27.0) are the main reason of the earthquake disaster and the collapse of buildings is the direct cause of the casualties. Great earthquakes in China are frequently occurred, widely distributed, great harmful. There are many shortcomings in the current seismic fortification system of China, especially, determination design ground motion parameters for rare ground motion. This article expbres difference and relationship between "great earthquake" and rare ground motion, very ground motion, and detailed analyzed the statistical characteristics and spatial distribution of the ratio between basis ground motion(10%probability of exceedance in50years) and c(2%PE in50years), very ground motion(1×10-4PE in one year) on rocks, and defined as K2and Kl, respectively. Coupling the probability distribution for the collapse capacity with a corresponding ground motion hazard curve for the location of the structure, we proposed method of controlling collapse risk for general construction projects. We attempted to consider correlation of seismic risk for different sites, and using Monte Carb (stochastic simulation) simulate two-dimensional distribution of ground motion, to proposed aggregate seismic hazard analysis method Finally in order to achieve better urban disaster prevention and mitigation work, we suggested that only integrated defense system of soft and hard Measures for great earthquake should be established and improvedFirstly we reviewed the great earthquake disaster before and after20th century in China, using rich data of historic earthquake in China, analyzed spatial distribution and frequency feature of great earthquakes (M≥7.0); using potential seismic source zone with magnitude greater than7.0in China’s fifth generation ground motion map, analyzed the space distribution characteristics of potential source zone with high magnitude limit, final analyzed the distribution characteristics of urban in potential seismic source zone with high upper limit magnitude. The analysis shows that our country is located in an active tectonically regions, and is prone to occur great earthquakes. More cities located in potential seismic source zone with high upper limit magnitude, and the task of fortification against great earthquakes is urgent.This article stated that difference and relationship between "great earthquake" and rare ground motion, very ground motion, and taking Beichuan-Yingxiu potential seismic source zone in middle of Longmenshan seismic belt as example to reveal relationship between "great earthquake" and rare ground motion, very ground motion. And then using six of potential seismic source zone schemes of the fourth, fifth generations seismic ground motion parameter zonation, the K1and K2values on each grid point in China was obtained and analyzed the statistical characteristics and frequency distribution characteristics of the Kl and K2values in different potential seismic source zone schemes, different seismic zones, different partition of attenuation relationship and different acceleration Zoning. Finally, the space distribution characteristics of maximum and minimum value of K2and Kl values, as well as standard deviation and coefficient of variation for K2and Kl value were made clear. We can get the following understanding:Distribution of K-value was quite unevenly, which was closely linked to its earthquake environment. K2and Kl values in seismic active area were small relatively, but slightly larger overall in Stable area. Seismic hazard of sites with a maximum and minimum value of K is mainly controlled by a single potential seismic source zone. Uncertain of potential seismic source zone does not affect the spatial distribution of standard deviation and coefficient of variation of K2and Kl, only affect its area. And standard deviation and coefficient of variation increases with the level of risk. Areas with larger Standard deviation and coefficient of variation are mainly located in eastern China, mainly distributed along big active fault in western China. We suggested using acceleration values of a single probability of exceedance (50years,10%), the spatial distribution of K2values with uncertain and amplification coefficients of soil jointly determine seismic fortification parameter values of rare ground motion; very rare ground motion should be considered, in order to "anti-great earthquake "; the maximum value of deterministic method and Probability approach should be used to fortify in potential seismic source zone with high upper limit magnitude.Using data of potential seismic source zone modified after the Wenchuan earthquake, and coupling the probability distribution for the collapse capacity recommended by ATC-63with a corresponding ground motion hazard curve for the location of the structure, method of controlling collapse risk for general construction projects was proposed And accessed the probability of the collapse targeted at the MCE level PGA, PGA corresponding to the50-year probability of1%collapse and ratio for PGA of50-year1%collapse probability and PGA of MCE level,(hereinafter referred to as "risk factor") on96,189grid point. Research and analysis shown that (1) PGA of MCE level is roughly equivalent to PGA for50years the rate of1%collapse in China and risk factor in China is most concentrated in the0.8-1.2. PGA of MCE level slightly adjusted to the risk level of the collapse rate of1%in50years.(2) Though spatial distribution PGA of MCE is similar to PGA of the collapse rate of1%in50years, we proposed use of risk factor of this paper to adjust PGA of MCE level,in order to get a consistent collapse rate in China.(3) Collapse rate for PGA of MCE level was significantly higher than other regions, for example, the west coast of Taiwan, including Taipei Basin, and the southeast coast of China, and this should arouse the attention.Using Monte Carb (stochastic simulation) to simulate the two-dimensional distribution field of PGA, aggregate seismic hazard analysis method was proposed for fortification of big cities and urban agglomerations. Selecting potential seismic source zone of Changde7.0, Changsha-yiyang6.0and Xiangtan5.5to carry out seismic risk analysis for specific and aggregate site, and comparison of this two methods was made. Studies have shown that (1) site-specific seismic hazard analysis method may underestimate the impact of great earthquakes rarely occurred in the region;(2) design acceleration near more active source was controlled by site-specific seismic hazard analysis; acceleration near source with high magnitude was controlled by aggregate hazard analyses.(3) Seismic design of buildings should meet site-specific seismic risk and aggregate risk at the same time, which can to some extent control the spatial extent of the destruction and the extent of the damage under great rare earthquake.(4) Aggregate seismic hazard analysis method, which considers spatial correlation of seismic hazard among sites, can provide a theoretical basis of earthquake fortification for the big cities and urban agglomerations.Finally, we suggest that only combination of soft and hardware disaster prevention system, Consistency of urban planning and disaster planning can really provide a solid foundation for earthquake disaster reduction in future.