云南地区近期强震重复发生时地震学的动态演化特征

通过地强震重复发生的滇西北、滇东北、滇西南澜沧江以西３个地震区多项地震活动性和地震波参数的动态追踪，发现在同一地震区重复发生的强震，震前的异常形态可以具有相惟性，反向变化的特征。如滇东北地区中小地震在１９８５年禄劝强震前的活跃和１９９５年武定强震前的平静；澜沧地震叶波速比月均值在１９８８年澜沧－－耿马大震前的低值异常和１９９５年孟连西中缅边境大震前的高值异常。本同时以ｂ值和波速比为例，讨论了强震

CHARACTERISTICS OF SEISMOLOGICAL DYNAMIC EVOLUTION IN THE RECENT RECURRENCE OF STRONG EARTHQUAKES IN YUNNAN AREA

Through dynamic tracing of multi-seismic activities and seismic wave parameters in the three areas of north-west Yunnan, north-east Yunnan and west of Lancang River of south-west Yunnan where strong earthquakes occurred, it is found out that the anomalous forms could be similar, or opposite before the strong earthquakes reoccurred in the same seismic area. For instance, small earthquakes in north-east Yunnan area were active before Luquan earthquake in 1985 and quiescent before Wuding earthquake in 1995; the monthly mean values of ratio of velocity at Lancang station anomaly appeared anomalies with low values before Lancang-Gengma earthquake in 1988, and anomalies with high values before Menglian earthquake in 1995. Taking b value and ratio of velocity as examples, different variation features, such as seismic area where strong earthquake occurred and where without strong earthquake, have been discussed in this paper. The results show that in the seismic area where strong earthquake had occurred, mutation anomaly of b value as high as 1.80 appeared 2-8 years before strong earthquake; and it the area of west Yunnan where without strong earthquake, the maximum value of b was 1.50, which has put forward a problem of source precursors with long-medium term. Similarly, mutation amplitude of high value for ratio of velocity at single station near the epicenter of strong earthquake is 20-60% bigger than that where far away from the epicenter.