| In engineering, Time history analysis is often applied to discuss the response of structure under seismic action. Acceleration time history of artificial is indispensable in the structure vibration analysis. Stochastic finite-fault method for simulating of high frequency ground motion has a unique advantage, is often used in engineering practice. In acceleration time history simulation, the source parameters have great influence on simulated results. For the same event, often because of the researchers focus on different point, and the source parameters will be different, which lead different results. Such as stress drop impact the ground motion amplitude, kappa factor can have influence on high frequency ground motion, the strike and the dip of fault, the position of the site, site category, also will affect the synthetic ground motion. Besides, in simulating near filed ground motion on bedrock site, the energy of simulated ground motion by stochastic finite-fault method is always on the low side in some frequency band. In this paper, stochastic finite-fault is applied to simulate the near field ground motion on bedrock site, and then the energy distribution of some frequency band is calculated. The energy distribution of frequency band of synthetic ground motion and record ground motion is compared and analyzed to find their difference. By adjusting the energy distribution of some frequency band to makes the synthetic ground motion match to the record ground motion at near field on bedrock. Embodied in the following aspects:1) Based on record near field accelerations time history on bedrock are chose from the Center for Engineering Strong Motion Data, the Fourier Transform has been applied to calculate the energy accumulation distribution curve in frequency(energy accumulation curve for short), to analyzing the law of energy distribution in frequency and law of energy to magnitude and hypocentral distance, and reveal the law of energy distribution with ground motion in horizontal and vertical direction.2) The program of stochastic finite-fault method EXSIM is used to simulate ground motion and to discuss the effect law of source parameters like stress drop, kappa factor, strike and dip on amplitude, response spectrum and energy distribution curve.3) An improved stochastic finite-fault method based on energy has proposed. This improved method mainly reflects on adjusting the energy distribution in frequency to get simulated acceleration more approach to the record ground motion at near field on bedrock. Northridge earthquake and Wenchuan earthquake, which is Rich of bedrock seismic record in near field, are taken for instance respectively. The reasonable source model and source parameters are applied to simulate the acceleration time history in near field on bedrock. By comparing and analyzing the simulated ground motion and the record motion on respects of energy distribution and acceleration amplitude to verify the reasonable and feasibility of the improved method. |
