Abstract: A concept of generalized seismicity window has been suggested. Investigations have been made within various generalized seismicity - window s to stress local tectonic features. A method of dividing generalized seismicity window s has been proposed on the basis of the average value of earthquake frequency for many y ears. 45 generalized seismicity window s have been identified in the eastern China. They have obvious tectonic implications. Based on some existing seismicity parameter a relative index f has been proposed to eliminate the influences of local differences and temporal fluctuations of the seismicity, thus enhance our ability to draw more information f rom the original seismicity parameter. Using the seismicity index A(b) to form a relative index f _A(b), a method of multi-window anomaly combination plot combining the three-dimensional information of anomalies in time and space has been proposed to trace the developmental process of anomalies. The results show that migration phenomenon of anomalies exists prior to the mainshock, that is, anomalies appear successively in a number of generalized seismicity window s. Advances of strain waves are tentatively considered as the physical nature of this phenomenon.

Key words: Generalized seismicity window, Multi-window anomaly combination, Migration of anomalies, Strain waves