SOME STATISTIC CHARACTERISTICS OF UNDERGROUND HOT VORTEX IN CHINA DURING 1980-1993 .1. SPATIAL-TEMPORAL DISTRIBUTION OF UNDERGROUND HOT VORTEX

Using ground temperature data from meteorological stations as well as earthquake, ground tilt and precipitation data, the spatial-temporal d istribution of ''Underground Hot Vortex'' (UHV) in China was analyzed in derail. The results show that concerning an ''Underground Hot Vorte x'' cell, its life-span is 3-8 seasons, 1.5 years on average; the mean horizontal scale is 600 km and its characteristic velocity is about 4 00 km/a; UHV is likely to appear in some areas where the crustal movem ent is intense and the absolute value of vertical deformation rate is relatively high; its activity could hardly be detected in the area whe re the crust is stable and the vertical deformation is weak; most of ' 'Underground Hot Vortex Groups'' originate; from the edge of Indian Pl ate, then migrate eastwards with a leaping-frog style. 5-10 years are needed for their arrival in the eastern border of China. Their horizon tal migrating velocity is 200-500 km/a which is nearly equal to the ch aracteristic velocity of a single UHV.