Abstract: Using the nonlinear relations and the time-frame coefficient of earthquake sequence, the four earthquake sequences (1975, M_S 7. 3; 1978, M_S 5. 9; 1988 M_L 3. 7 swarm; 1999, M_S 5. 6) occurred in the Haicheng-Xiuyan region of Liaoning Province since 1975 are studied. The result indicates that there are evident differences among the foreshocks sequence, aftershock sequence and small normal swarms in the time-frame characteristics and the time-frame variation coefficient (δ) . δ≈1 for a foreshocks sequence,and δ 1 for an aftershock. A new state, a stage of large energy release with a main earthquake and many aftershocks co me about when the behavior of the earthquake generation system of a region is of enough randomness, which is the special frame and foundational nonlinear features of a complex system with the irreversible process. A time-frame variation coefficient method to diagnose the forerunner earthquake sequence is consequently proposed. A similar study of different types of seismic activity states and nonlinear time-frame relation earthquake sequences that occurred in other regions are also presented.

Key words: Time frame variation coefficient, Nonlinearity, Earthquake sequence and situation diagnosis, Earthquake prediction