澜沧、耿马大震前的地震活动特征

CHARACTERISTICS OF SEISMIC ACTIVITIES BEFORE LANCANG-GENGMA LARGE EARTHQUAKES

本文按远震源区、近震源区、震源区三个不同层次,分析了澜沧、耿马大震之前的地震活动图象,结论是: 1.大震之前,在上述不同的范围内均出现了地震活动性的异常,其表现形式为小震频度上升、应变释放加速、条带及空区形成等。 2.震前四年,近震源区出现的异常较其它两区远远超前,震前一年震源区出现异常,震前半年远震源区出现异常,表现出孕震发展的阶段性。 3.异常图象特征具有普遍性、异常发展迅速,大震发生在异常之中,震前两个多月发生5级前震序列是其特殊性。

This paper analyzes the seismic activity patterns before the Lanchang earthquake with Ms 7.6 and Gengma earthquake of MS 7.2 November 6,1988 in three diffirent space range of far-source region, near-source region and source region. The results are: 1. Before the large earthquakes, there had occurred seismicity anomalies in the above various ranges, there had expressed as the increment of the frequencies of small shocks, acceleraton of strain release, the formation of seismic bands and gaps. 2. There had appeared anomalies in near-source region four years before, in the source region one year before, and in the far-source region half a year before the main earthquakes. They show stages of earthquake-preparedness development. 3. Abnormal pattern characteristics are of universality, the extremely quick development and large earthquakes occurred during anomalies. It is the particularity for the foreshock series of Ms= 5.0 to occur more than two months prior to the large earthquakes.