| 云南地区 M6.7地震前的中强地震活动/ |
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| 引用本文： | 钱兆霞.云南地区 M6.7地震前的中强地震活动/[J].地震学报,1983,5(3):313-322. |
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| 作者姓名： | 钱兆霞 |
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| 作者单位： | 云南省地震局 |
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| 摘 要： | 本文分析了云南地区(通海、永善、龙陵、宁蒗、普洱)五次 Ms6.7大震前的中强地震活动,发现:(1)大震前一年或稍长一点时间内中强地震活动明显加强,年频度达 n(MS4)20次/年,n(MS5)6次/年;(2)同时区域内 b 值相应下降;(3)大震前数月至一年内中强地震活动由原来的大范围散布状态逐渐向未来震中收缩,有的地震(如龙陵、通海地震)的前震,收缩为交叉带状.这些特征可能与云南地区的地壳构造格局和孕震过程有关,文中称这些中强地震为广义前震。
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ON THE SEISMIC ACTIVITY OF MEDIUM-SIZE EARTHQU- AKES BEFORE LARGE EARTHQUAKES OF MAGNIT- UDES GREATER THAN OR EQUAL TO 6.7 IN YUNNAN PROVINCE |
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| Abstract: | In this paper, the seismic activity of medium-size earthquakes before five large earthquakes (Tonghai, Yongshan, Longling, Ninlang, Puer) of magnitudes M 6.7 occurred in Yunnan Province has been analysed. It is revealed that (1) one year or little longer time before the large earthquakes, seismic activity of medium-size earthquakes is distinctly enhanced, reaching 20 or more earthquakes of Ms 4 and 6 or more earthquakes of Ms 5 per year respectively; (2) at the same time, b-values within the earthquake regions decrease correspondingly; (3) few months to one year before the large earthquakes, those medium-size earthquakes scattering over very broad areas begin to move toward the epicenters of the coming large earthquakes. They gathered onto intersecting belts in the case of the Longling and Tonghai earthquakes.The phenomena may be related to the crustal structure of Yunnan and the process of development of the earthquake sources. All such medium-size earthquakes are given a term general foreshocks in this paper. |
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