Abstract 7 events of crust deformation anomaly with great magnitude are given, and, these events always were followed by strong earthquake near the abnormal area in a mediumshort period. The reason why such kind of important phenomena has not drawn more attention to yet is analyzed. Furthermore some new understandings of the relationship between crust deformation anomalies and disturbances are presented, and some conclusions and suggestions are given as follows. 1)As concerning crustal deformation event of great magnitude, “great magnitude” means that the event has a big difference from the varied magnitude in normal time. The index has be given here that during a half year to one year, if the varied magnitude is more than 4 times of that for 3 years before the event, the event can be looked as crustal deformation event of great magnitude. 2) Crust deformation anomaly is coexistent with disturbances. 3) It is difficult to distinggaish between crust deformation and disturbance in most of situation. But crustal deformation of great magnitude has special value for strong earthquake prediction, because this kind of deformation can not be induced commonly by disturbance alone. When the crustal deformation of great magnitude appears, we should look it as the precursory anomaly first for near strong earthquake in a mediumshort time period. 4) Before strong earthquake, crustal deformation of great magnitude should appear at some key points in the mediumshort period. Monitoring such great deformation has important significance for effective prediction of strong earthquake.
