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本文分析了华北地区(30°—42°N,105°—124°E)自16世纪以来8次7.5级以上大地震发生之前的地震活动图象.发现在这些大地震发生之前的若干年(绝大多数不超过20年),都表现出一个M≥4(3/4)地震在某一范围內相对较集中活动的区域,然后在该区中部或边缘发生大地震。 唐山7.8级地震前,随着大地震发生时间的逼近,M_s≥4.0地震的震中分布,在大范围活动的基础上,分阶段地逐步自外围向主震震中收缩,然后发生大地震。这种地震活动图象的演变过程可分成若干阶段的现象,对于研究震源性质、地震孕育过程和中长期地震预报等,可能具有一定意义。
This paper analyzes the seismic activity images of eight pre-earthquake earthquakes of magnitude 7.5 in North China (30 ° -42 ° N, 105 ° -124 ° E) since the 16th century, and found that in the years prior to these major earthquakes ( Most of them less than 20 years) showed a relatively concentrated area of M ≥ 4 (3/4) earthquakes within a certain range, and then a large earthquake occurred in the middle or the periphery of the area. Before the Tangshan earthquake with magnitude 7.8, with the approaching of the occurrence time of the large earthquake, the epicenter distribution of M_s≥4.0 earthquakes gradually shrank from the periphery to the epicenter of the main shock on a large scale, and then a large earthquake occurred. The evolution of this seismic activity image can be divided into several phases, which may be of great significance to the study of the source nature, the earthquake breeding process, and the long-term earthquake prediction.