Study Of The Long Period Acceleration Response Spectrum For Sichuan Area Basing On The Wenchuan Earthquake Ground-motion Attenuation

The goal of this paper is to study the long period attenuation relationship ofhorizontal acceleration response spectrum for Sichuan basing on the strongground-motion records from the Wenchuan earthquake. This work is very importantfor the seismic design of increasing number of high-rise buildings and long-spanbridges with a long natural period. Because there are few strong-motion recordsobtained in China, the less are the long period data, the long period attenuationmodels is much more difficult to be developed. The ground motion attenuationrelationship used in the past design code are modified attenuation models for thewestern part of the United States based on the relationships between the seismicintensity attenuations in the two regions. During the2008Wenchuan earthquake andits aftershocks, a large number of strong-motion records were obtained. It is possibleto develop a long period attenuation relationship for horizontal acceleration responsespectrum in Sichuan province.Firstly, with collecting the base data of the Wenchuan earthquake, this paperclear the earthquake magnitude, distance from source to site, local average shear-wavevelocity, and fault type for every event. Secondly, Study the long period attenuationrelationship for horizontal acceleration response spectrum based on strongground-motion records from the Wenchuan earthquake by comparing it with the NGAmodels and the Zhao2006model; Thirdly, we analyse the affects of the geologicstructure on the attenuation of the wave using the seismic modeling method. Finally,we make some suggestions for Sichuan long period ground motion attenuationrelationship in the analysis of seismic hazard by the result of the seismic modelingand the Sichuan historical earthquake intensity and ground motion attenuationrelationships.(1) Two formula are obtained, The One reveals the relationship between Mwdetermined by China and the United States, the other reveals the relationship betweenMs and Mw of the Wenchuan earthquake and its aftershocks. We get the filterparameters for the strong ground motion records by the displacement Fourierspectrum. The focal mechanism of the wenchuan earthquake aftershocks and theVS30of every stations based on the NGA document were shown here.(2) Comparing the ground motion of Wenchuan earthquake and its aftershockswith the results from the four NGA models and the Zhao2006model of Japan forshallow crustal earthquakes in active tectonic regions, We find that the CY2008model is the best similar to the ground motion records of Wenchuan earthquake;The aftershocks data is much smaller than the resulats of these models; The Zhao2006model is the best similar to the relationship of the data, but the results is larger thanthe records.(3)We find that the evaluate result of the attenuation relationship used in Sichuan nowadays is larger than the data of Wenchuan earthquake and its aftershocks,especially in the long period term. It is increasing the hazard of this areas in the longperiod.The major innovations of the paper are manifested by the following works:(1)A long period attenuation function of the horizontal acceleration responsespectrum for Sichuan area basing on the fault model of Wenchuan earthquake were setup.(2)The affects of the geologic structure on the attenuation of the wave wereanalysed by the seismic modeling method(3)Comparing the characteristics of the long period ground motion attenuationrelationship for Wenchuan earthquake and its aftershocks with the attenuationrelationgship used nowadays in sichuan area, we find that the hazard of this area inthe long period were increased by the attenuationship used at present.