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大地震的孕育与发生,是构造变动的一部份,是受区域应力场控制的。本文正是通过对区域地震活动图象的研究,探索大震可能发生的危险地点;并通过其变化规律,探讨大震孕育的周期。笔者根据对川滇地区两千年的历史地震资料及1965年至1982年底的十八年地方台网资料的研究,初步确定了以 NW50°、NE40°的地震密集条带构成的网状图象。7级大震,90%以上发生在条带内,80%以上发生在网状结构的“结点”区。通过对1970—1976年五次7级大震的综合对比研究,初步确定,大地震的孕育周期:6—5年、4—3年为中长期阶段,2—1年为中短期阶段。而大震前,震源结点区及其相应的共轭条带上,多有中强震发生。从而可为大地震的长、中、短期预报,为中强震的中、短期以至临震预报提供趋势意见。
The birth and occurrence of a large earthquake is part of structural changes and is controlled by regional stress fields. This article is through the study of regional seismicity images to explore the possible danger of major earthquakes occurred; and through its variation, to explore the cycle of earthquake nurturing. Based on two thousand years of historical seismic data in Sichuan and Yunnan Provinces and 18 years of local network information from the end of 1965 to the end of 1982, the author initially established a network image composed of seismic-intensive bands of NW50 ° and NE40 °. For the magnitude 7 earthquake, more than 90% occurred in the stripe and more than 80% occurred in the “node” area of the network structure. Through the comprehensive comparative study of five MS7 earthquakes from 1970 to 1976, it is preliminarily determined that the gestation period of major earthquakes is 6 to 5 years, 4 to 3 years is medium to long term, and 2 to 1 year is short to medium term. Before the earthquake, the source node area and its corresponding conjugate strip, more than moderately strong earthquake occurred. Which can be long, medium and short-term forecasts for large earthquakes and provide trending suggestions for medium and short-term moderate earthquakes and medium earthquakes.