Abstract: In this paper the authors discussed the pattern, time and space evolutional characteristics before two deep source earthquakes, occurred in Wangqing and Hunchun County, Jilin Province. There are such features as phasic and assorted development and concentration, showing that the anomaly is distributed non-uniformly and discontinuously, and is closely related to the epicentral distance and the distance between the well and epicenter. Its time and space evolution is of migration feature, the short- and medium-term phasic anomaly migrated from the periphery to the epicentral direction and contracted. During the imminent stage the anomaly migrated from the epicenter to the periphery. The paper discussed the similarities and differences of underground fluid and anomaly mechanism before the deep source and shallow earthquakes. The authors conclude that the anomaly curve, frequency band, change rate and repeatedness of single well as well as anomaly time distribution of multiple well group are same, however, the direction, amplitude, pattern, macroscopic phenomenon and anomaly stage of single well are different from the time characteristics and time-space evolution of the multiple well group. The anomaly of underground fluid before the deep source earthquakes is resulted from joint action of three kinds of mechanism, i.e. equivalent extensional stress, change of pore pressure for aquifer and hydrodynamics.

Key words: Deep source earthquake, Anomaly of underground fluid, Time-space evolution, Anomaly blind area, Anomaly mechanism