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本文研究了1970—1979年华北地区11个中等强度地震前区域微震时-空分布图象.发现大部分地震前1—2年,在其周围70—120公里范围内(简称“震兆区”),微震活动出现活化—寂静图象.同时,震前微震活动似有一个逐渐扩散到日趋收缩直至发震的过程.利用泊松分布检验活化、寂静阶段地震次数发生的概率,其结果是活化阶段绝大多数地震的概率小于5%.而寂静阶段只有近半数地震的概率小于5%.另外,发现大多数地震前震兆区的累加频度曲线的速率有一个加速—减小的过程,而外围区的速率基本保持稳定.最后,给出典型的异常图象模式并予以初步解释.
In this paper, we study the time-space distribution of regional microseisms prior to 11 moderate-intensity earthquakes in North China from 1970 to 1979. It is found that in most of the earthquakes one to two years ago, in the range of 70-120 km around them (referred to as “earthquake zone” ), Microseismic activity appears active - quiet image.At the same time, the microseismic activity before the earthquake seems to be a process of gradual diffusion to shrinking until the onset of the earthquake.Using the Poisson distribution to test the activation and quiescence of the probability of seismic frequency, the result is activated The probability of most earthquakes in the phase is less than 5%, while the probability of only half of the earthquakes in the quiet phase is less than 5%. In addition, it is found that there is an acceleration-decrease process for the rate of the cumulative frequency curve in most earthquake precursors The rate of the peripheral area basically remained stable.Finally, a typical anomalous image pattern was given and preliminarily explained.