Ascertainment Of Design Ground Motion Parameters Basing On Seismic Microzonation In Downtown Areas Of Chongqing

Seismic microzonation is defined as dividing seismic security circumstances on some location and predicting distribution of influence from earthquake on the location. Seismic microzonation is becoming the focal point research of disaster prevention and reduction. Chongqing is locating in the zone with moderately strong earthquake and seismic microzonation in Chongqing is recognized make great significance on making reasonable seismic fortify criterion and earthquake resistance.Primary study on seismic microzonation in downtown areas in Chongqing will be researched basing on technology of seismic microzonation. The details including:①Seismic risk analysis and the indeterminacyThe major factors and processing methods of indeterminacy of seismic risk analysis are analyzed. The downtown areas of Chongqing is divided into two multiply two gridding points and six hundred and sixty six reference points are gained. Two kinds of latent hypocenter and attenuation relation of earthquake motion are composed as four analysis models and a series of seismic parameters are obtained by the seismic risk analysis. Then the median value is selected from the result of seismic risk computing. Moreover, the distribution of peak acceleration and the maximums of acceleration spectrum along warp and woof are statistical analyzed. And finally chorograms of peak and the maximum acceleration and acceleration spectrum of different transcendental possibility in Chongqing are gained.②Seismic response analysisExplored data of engineer sites in downtown areas of Chongqing is collected and analyzed, and the three hundred and ninety six computing solid models are built with double exponential method and solid exponential method. Then the solid models are analyzed with the method of 1-D equivalent linear analysis and the corresponding horizontal peak acceleration on site and the acceleration magnification coefficient from rock to solid of three kinds of transcendental possibility in four different sites. Four normalizedβspectrums corresponding to four kinds of site are obtained from acceleration magnification coefficient spectrum. Finally influence from solid thickness and solid natural vibration period on horizontal peak acceleration is statistical analyzed.③Preliminary achievement of seismic microzonation in downtown areas of Chongqing.Curve and formula of solid natural vibration period and horizontal acceleration magnification coefficient are fitted by least squares method, according to the statistics result from solid earthquake response computation. The fitting model with five controlling parameter is used that four standardizedβspectrums correspond to different sites is fitted from normalβspectrums. Finally the horizontal peak acceleration and standardizedβspectrums from seismic microzonation are compared with present code.