| 华北地区中等强度地震前近震中区微震活化-寂静图象 |
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| 引用本文： | 魏光兴,赵兴兰,聂振海.华北地区中等强度地震前近震中区微震活化-寂静图象[J].地震学报,1983,5(3):287-296. |
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| 作者姓名： | 魏光兴 赵兴兰 聂振海 |
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| 作者单位： | 山东省地震局 |
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| 摘 要： | 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.
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ON ACTIVE-QUIET PATTERN OF MICROEARTHQUAKES IN AND AROUND THE EPICENTERS PRIOR TO SOME MODERATE EARTHQUAKES IN NORTH CHINA |
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| Affiliation: | Seismological Bureau of Shandong Province |
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| Abstract: | In this paper, the time-space distribution patterns of microearth-quakes before 11 moderate earthquakes occurred during 1970-1979 in North China have been studied. It is found that active-quiet patterns of microearthquakes, 1-2 years before most of the moderate earthquakes prevail in areas of radii 70-120km around the epicenters (earthquake precursory areas). At the same time, these microearthquakes seem to undergo a process from gradual spreading to contraction until the occurrence of the moderate earthquakes.The probability of the microearthquake frequencies for the active-quiet stages is lested by using the Method of Poisson Distribution. As a result, the probability of the majority of microearthquake frequencies for the active stage is less than 5%. Besides, in the earthquake precursory areas, the rate of change of the curve of accumulated micro-earthquake frequencies before most moderate earthquakes showa a spreading and slowing down process; but in the areas around this rate keeps basically unchanged.Finally, a model of the typical anomalous pattern before moderate earthquakes is given and preliminarily discussed. |
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