THE CHARACTERISTICS OF ATMOSPHERIC PRESSURE FIELD BEFORE STRONG AND MODERATE EARTHQUAKES OCCURRED IN YUNNAN PROVINCE

In order to seek for short-range precursory phenomena of earthquakes, time space changes of the atmospheric pressure field before strong and moderate earthquakes (M_s5.0) occurred during 1960—1974 in Yunnan province have been investigated.Some correlative regions (or stations) of the atmospheric pressure related to three seismic active belts in Yunnan province were selected by the statistical method of optimal two-way classification.Finally, the results of prediction test within the period 1975—1977 indicate that the anomaly of atmospheric pressure may possibly be an indication of short-range precursor of the occurrence of earthquakes.