A Study Of The Surface Geological Structure Model For The Seismic Amplification Site In Yuhuanguan

This paper firstly gives an introduction to the observation experiment of seismicamplification in the Yuhuangguan delta area. The area marks with variation in seismicamplification. In order to study the mechanism of seismic amplification, a surfacegeological structure model was built using comprehensive information obtained byreflection seismic exploration, refractive seismic exploration, and forward simulationtrail of earthquake data. Then the model was evaluated by2-D forward modeling, ofwhich the synthetic results are in good agreement with the data from the reflectionseismic exploration. The research results of this paper provide important informationfor studying the seismic amplification of the Yuhuanguan area.The main work and achievement in this paper are as follows:(1) Unconventional wide-angle reflection prospecting method was used to collectreflection seismic data. By muting air waves、ground surface waves, direct waves, anddeleting noisy near-shot traces, interference components were effectively removed.Then through nmo correction, refractions and multiples were suppressed. Togetherwith other processing measures, an effective flow of processing procedures was usedfor the processing of the wide angle reflection seismic data. Satisfactory stacksections and migration seismic profiles were obtained though the processing, whichprovided good images of the shallow layer interface structure and the seismic velocityinformation.(2) The processing and interpretation of refraction seismic exploration datayielded a new layering structure for P wave velocity parameters. It not only confirmedthe bedrock reflection interface observed in the reflection seismic data, but alsorevealed a new shallow interface at the depth of5metres，which was not seen in thereflection data. Combined with the velocity information from the reflection seismicdata, a3D shallow hierarchical P wave velocity structure was obtained for the area.(3) Based on the exploration data, a model was developed for forward modelingof SH wave propagation in the area. The trials of hundreds of models with randomparameters allowed us to reach a good model, of which the synthetic data is in goodagreement with the observed earthquake data at the site. This provided us a reasonableestimate of the shear wave structure and Q value structure in the S06area. (4) Base on the information obtained in chapters2,3and4, a2D seismicstructure parameter model was developed. An elastic wave equation finite differencemodeling was performed on the model to simulate the reflection seismic data. Theresults are in good agreement with the data from the reflection seismic exploration.This indicates that the model reflects the actual geologic structure well. Accordinglywe are convinced that the model can be used as a basis for the modeling analysis ofthe seismic amplification phenomena observed in the surrounding area near Site S06.