祁连山地震带地震活动性增强现象研究

RESEARCH ON THE SEISMICITY INCREASING BEFORE STRONG EARTHQUAKES IN QILIANSHAN SEISMIC BELT

应用能量应变释放曲线和地震频次曲线对祁连山地震带MS5.0以上的20次地震震前中小地震活动演化过程进行了研究.结果表明:70%的地震在震中附近2°×3°范围内震前有明显的地震活动增强现象;地震活动增强持续时间约为6～12个月,其演化过程大致可划分为两种类型:A:背景→增强→平静→发震;B:背景→增强→发震.增强区能量释放曲线有明显的幂指数增长趋势.

The evolution processes of middlesmall seismic activities before 20 MS≥5.0 earthquakes occurred in Qilianshan seismic belt since 1980 are studied, by using the curve of energy release and the curve of frequency. The result showes that the phenomenon of increasing middlesmall seismic activity before strong earthquakes in the range of 2°×3° near mainshockes exists obviously for 70% of events. The continues time of increasing is about 6～12 months and evolution process can be divided into two styles: A. Background level→increasing→tranquil→eruption; B. background level→increasing→eruption. There is an obviously power index increasing on curve of energy release for increasing area.