The Research On Site Amplification Factors For Shakemaps Used In Fujian Province

In this paper, the engineering geological conditions are utilized to infer thedistribution of equivalent shear wave velocity in Fujian province and comparativeanalysis of relationships between site categories of China and the US is made inthis study. Also, we calculate the site amplification factors applicable for Fujianprovince by using the computing methods of the American ShakeMaps system forreference. The site amplification factors are corresponded to the site categorystandard provided by “Code for Seismic Design of Buildings” of China(GB50011-2001). Combined those factors with topography and others, sitecorrections to the ShakeMap system running-time in Fujian province areaccomplished. The main work of this study have been summarized as follows:1. According to the statistical analysis of the data provided by EarthquakeGeology Engineering Investigation Institute, the reason why the equivalent shearwave velocity varies in calculation value is found. That because the value of thecalculation depth has been altered in the “Code for Seismic Design of Buildings”.In response to this situation, we find the fitting relationship of the differentequivalent shear wave velocity values belonging to different periods in this paper.Thereby, all the equivalent shear wave velocity values are geared to the codecurrently in effect.2. On the basis of comparing the differences of engineering site categoryclassification standards between Chinese and American, the relationship ofdifferent equivalent shear wave velocities obtained from the different codes isfitted and the relation between the two countries’ site categories is also achieved.3. We compartmentalize the engineering geology conditions of Fujian to threeengineering geology categories according to the engineering investigation data.The distribution of the equivalent shear wave velocity in the Fujian meshed regionis speculated in virtue of ArcGIS Geostatistical Analyst and empirical formula provided by “Code for seismic design of special structures”(GB50191-93). Andaccording to the seismic activity in history of Fujian, we synthesize artificialseismic waves with reasonable peak values by software: Earthquake SafetyEvaluation (ESE), and together with the shear wave velocity value of the selectedreference site, we calculate the site amplification factors.4. Mountain topography has significant impact on ground motion. Thescientific achievements of domestic and foreign scholars are summarized in thisstudy. As a result, the site correction formulas are given considered the factors ofsite amplification and topography comprehensively. And also, the distributionmaps of site amplification factors are drawn in this paper, referred to theconditions of the topography and geology categories in Fujian.5. In virtue of the ground motion attenuation relation for small to moderateearthquake in Fujian region(JinXing, OuYiping,2007), the author draw theShakeMaps on the bedrock and the modified by the site amplification factorsseparately, including the distribution maps of the seismic peak groundacceleration (PGA) and the seismic peak ground velocity in the directions ofhorizon and vertical. The earthquakes chosen in this paper are YongchunEarthquake (August29,2007), Gutian Earthquake (March6,2008) andShunchang Earthquake (March13,2007).