Abstract: Based on studying the consistency of time-varying direct S wave maximum acceleration peak value and the change in tectonic environmental background stress and apparent stress before and after Xiuyan earthquake sequence (from November 1999 to January 2000) in detail using the digital seismic data from August 1999 to December 2000 recorded by Liaoning digital seismic network, we obtained the result that the seismic kinematic parameters changed differently in the evolution process of the pre-main-after shock generation and occurrence. The physical parameters can be determined rapidly and accurately, which provided physical information of change in seismic tectonic stress for identifying pre-earthquakes and predicting strong aftershocks. The contrastive analysis of time-varying process for apparent stress, shear stress value τ0 and S wave acceleration peak value at single station shows that those three physical parameters strongly depend on the stress background and they reflect the same physical process, have coincident physical meaning and their time-varying processes accord well with each other. As the methods of calculating these three parameters are simple, they can be accurately determined in the conditions that the variation for earthquakes distribution is small and the position of station is relatively fixed. Their abnormal values are much higher than the normal background values, so they has high abnormal resolution. Users can choose appropriate research method according to the observation condition and necessity for field study.

Key words: Direct pre-earthquake, Apparent stress, Environmental shear stress, Peak value of S wave acceleration, Identification of pre-earthquake