华北地区中等强度地震前近震中区微震活化-寂静图象
ON ACTIVE-QUIET PATTERN OF MICROEARTHQUAKES IN AND AROUND THE EPICENTERS PRIOR TO SOME MODERATE EARTHQUAKES IN NORTH CHINA
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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.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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[2] 魏光兴等,华北地区地震前大地震的围空区特征,地球物理学报,21,3,213——217,1978.
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[4] Mizuho Ishido & Hiroo Kanamori. The foreshock activity of the flan Ferando earthquake Califor——nia, B. S. S. A., 68 5, 1265——1279, 1978.
[5] Wei Guangxiug(魏光兴),Zhao Xinglan(赵兴兰)and Gu Zheuqing(顾贞庆),An example of seismic gape prior to two moderate iutraplate, earthquakes, Keaue Tongbao, 26, 12, 1113——1115,1981.
[6] 冯德益,1974年5月云南省永善一大关7.1级强震前波速比的异常变化,地球物理学报,18,4,1975.
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[8] 冯德益等,我国西部地区一些强震及中强震前后波速异常的初步研究(二)——波速异常区及其特性,地球物理学报,20,2, 1977.
[9] 牛志仁,我国西部地区某些强震及中强震前后的异常地震活动,地震学报,2,3,1980.
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[11] K. Magi, Laboratory study of elastic shocks prior to rock failuye, Eos, Trams. dmer., Geo——phys., 50, 5, 401, 1969.[1] S. A. Fedotov, DolbilkW a, N. A. et al., Investigation ou earthguake Prediction in kamchatka, Tectonphysics, 9, 249——258, 1970.
[2] 魏光兴等,华北地区地震前大地震的围空区特征,地球物理学报,21,3,213——217,1978.
[3] F. F. Evison, Precursory seismic seguenees认New Zealand, Neiv 7ealand J. Geol. Geophy.,20,1, 129——141, 1977.
[4] Mizuho Ishido & Hiroo Kanamori. The foreshock activity of the flan Ferando earthquake Califor——nia, B. S. S. A., 68 5, 1265——1279, 1978.
[5] Wei Guangxiug(魏光兴),Zhao Xinglan(赵兴兰)and Gu Zheuqing(顾贞庆),An example of seismic gape prior to two moderate iutraplate, earthquakes, Keaue Tongbao, 26, 12, 1113——1115,1981.
[6] 冯德益,1974年5月云南省永善一大关7.1级强震前波速比的异常变化,地球物理学报,18,4,1975.
[7] 力武常次,地震预报(冯锐、周新华译),地震出版社,1978.
[8] 冯德益等,我国西部地区一些强震及中强震前后波速异常的初步研究(二)——波速异常区及其特性,地球物理学报,20,2, 1977.
[9] 牛志仁,我国西部地区某些强震及中强震前后的异常地震活动,地震学报,2,3,1980.
[10] 地球物理研究所三室,单轴压力下岩石破裂的初步研究,地球物理学报,19,4,1976.
[11] K. Magi, Laboratory study of elastic shocks prior to rock failuye, Eos, Trams. dmer., Geo——phys., 50, 5, 401, 1969.
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