Abstract: Based on abnormal characteristics of cross-fault observation in and around the mid-southern segment of the North-South Seismic Belts, and combined with the results from Earthquake cases in China, this paper qualitatively analyse temporal and spatial variation characteristics of cross-fault anormalies before typical earthquakes happened in the research zone. The results show that, for earthquakes less than M_S8.0, time variation characteristics that cross-fault anomaly increased obviously two to three years before earthquake happened, reached top value one year to a year and a half before earthquake occurred, and some anomalies disappeared before earthquake happened, may have relations to the prediction of the occurrence time of the large earthquakes which maybe happened in 1~2 years, or in several months; the epicentral distance and abnormal types of abnormal cross-fault observations are related to the prediction of the magnitude of the earthquake in the future; and all of the abnormal types, the spatial distribution characteristics and the time variations characteristics have no relationship with the place which the earthquake will happened in the future. For Wenchuan earthquake, it shows that there were more trend anomalies, little short term anomalies, more peripheral anomalies, and little in the center near the epicenter. The anomaly of Wenchuan earthquake first occurred about seven or eight years ago, and increased obviously about three years and some anomaly disappeared before the earthquake. The main types of these anomalies were trend and velocity variations, and there were no breaking yearly changes.

Key words: Cross-fault observation, Abnormal deformation characteristics, Earthquake prediction, Mid-southern segment of the north-south belt