Abstract：
At present, the fault sliding speed functions, or source time functions that used in theoretical seismogram calculation are all theoretical results. That is, the fault speed time functions are the results of the theoretical study, and they are not proved by the measured data. The method that used to calculate fault sliding speed by using Doppler effect has been greatly improved in this paper from the following four perspectives: Firstly, the paper proves theoretically how to confirm the seismic waves that received in some frequency bands by two receivers are emitted by the same source. Secondly, the paper puts forward the method to make sure whether seismic waves received by two receivers in some frequency bands are similar by using relative change of Fourier amplitude standard deviation in some frequency bands of two receivers, and similar seismic waves are emitted by the same frequency bands. Thirdly, to eliminate the interference of reflection and refraction waves, S wave records in fault sliding time are selected for data processing. Finally, long time Fourier transform is replaced by short time Fourier transform (STFT) to enhance fault sliding time positioning accuracy. On the basis of the work above, a general method to calculate the fault sliding speed by using Doppler effect is summarized systematically. The fault sliding speed of Wenchuan earthquake is calculated by the method mentioned above. The calculations show that Wenchuan earthquake fault sliding speeds are basically consistent with the seismic moment changes. It has proved that the sliding speed of Wenchuan earthquake fault has the characteristics of abrupt change, that is, the sliding speed increases suddenly and decreases rapidly. For most of the time, the sliding speed is not large, and sometimes the fault does not slide. There are obvious differences from sliding speed functions that are applied currently, such as Haskell function, Bell shaped functions, Exponential function, Triangle function, etc. To compute fault sliding speed by using Doppler effect, instead of grasping so-far unknown crust parameters, we only need to know the earthquake records, the locations of the epicenter and the receivers. In a word, the calculation method has clear physical meaning and the parameters required are easier to be obtained.
2018, Vol. 15 
