Analysis Of Characteristics Of Duration Of Ground Motion Of Wenchuan Earthquake

As one of the three elements of ground motion,the duration has received extensive attention and deep research in the earthquake engineering field.Firstly,in the process of earthquake,the cumulative damage effect and the low cycle fatigue phenomenon caused by the duration have a serious impact on the damage of structures,which has been generally recognized by seismologists,and the importance of duration can thus be seen.But,in practical engineering applications,the duration is not widely used just as amplitude and frequency spectrum.Secondly,computing the duration is often based on point records of a component.Then,three durations of different sizes are often obtained at a point record,which is not convenient to be used and popularized in engineering application.Consequently,the further analysis and research on the duration will help to promote the theoretical research and application of engineering.Finally,existing studies of the duration are often based on actual seismic records,while the study on influencing factors and the characteristics of the duration are often restricted by the limitation of station records and the specificity of source parameters.Based on these,it is necessary to utilize the appropriate way of simulating ground motion,and to base on model parameters determined by inversion of existing seismic records.And the ground motion,which is consistent with the structural environment,seismogeology and site conditions of actual seismic region,is simulated to analyze the parameter sensitivity,spatial distribution and spatial variability of the duration.In general,in this paper,based on the stochastic finite fault method,the ground motion,which is consistent with regional characteristics of Wenchuan earthquake,is simulated,and durations of different definitions are obtained to analyze characteristics of parameter sensitivity and spatial variability of durations.The main research contents are as follows:1)Based on the recorded data of Wenchuan earthquake,two kinds of rotation-invariant mean duration are calculated and the correlation between the rotation duration and the record duration are compared and analyzed.Then,the characteristics of the spatial distribution and spatial variation of the rotation duration are discussed to prove the necessity,feasibility and rationality of using the rotation duration to replace the record duration.2)Based on the EXSIM program of stochastic finite-fault method,durations of different definitions are simulated and calculated to analyze the influence of model parameters,such as magnitude,stress drop,kappa factor,quality factor and the depth of the top of the fault,on the duration.3)Based on stochastic finite-fault method and considered the previous research on model parameters of Wenchuan earthquake,source and regional parameters of Wenchuan earthquake have been determined by inversion.Then,the rationality of those parameters was tested from four aspects,such as the waveform,the response spectrum,the geometric attenuation and the spectral error of the simulated ground motion.Finally,the ground motion of 87 stations with the fault distance of less than 300 km are simulated to analyze the spatial distribution and spatial variability of simulated durations of different definitions.And,the results are compared with characteristics of the record duration.