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研究地震活动图象而引入的地壳屈曲,从地壳为一层状结构物的基本事实出发,对很多地震前兆现象可做出自己的解释。本文对屈曲的特点、大陆地壳是否具备产生屈曲的条件、地壳屈曲与地震的关系等讨论后得到,当地块加强运动时,由于地壳中薄岩层屈曲的临界应小,将首先屈曲并出现小震活动和异常,它们是区域运动加强的反映,称为“区域前兆”。相当部分的中长期前兆似属此例。与较大地震相应的厚岩层临界应力大,对前兆场明显影响较晚(扩容除外),故来自大震震源的突出前兆主要将为短临。联系场源关系,地壳屈曲给出大震前区域地震活动有一由小变大的增强过程,这与唐山7.8级震前区域小震活动的R—t图吻合。 地壳屈曲对前兆的意义主要有两点:①失稳性,为前兆场变化、失稳破裂提供了重要背景。②突变性,屈曲的发生、发展将强烈地反映于前兆观测中,突跳现象,外因调制,触发等与此有关。故地壳屈曲是地震前兆的力学基础之一。
The crustal buckling introduced by the study of seismicity images, starting from the basic fact that the earth’s crust is a layered structure, can make its own interpretation of many earthquake precursors. In this paper, the characteristics of buckling, whether the continental crust has buckling conditions, and the relationship between crustal buckling and earthquakes are discussed. When the block strengthens, the buckling of thin and thin layers in the crust should be small and the first buckling and the emergence of small earthquakes Activities and anomalies, which are a reflection of the intensification of regional movements, are called “regional precursors.” A considerable part of the long-term precursor seems to be this case. The critical stress of thick rocks corresponding to large earthquakes is large, and the effect on the precursor field is obviously delayed (except for expansion). Therefore, the prominent precursors from the epicenter of the major earthquakes will mainly come in short term. In connection with the field-source relationship, the crustal buckling gives a small-to-large enhancement of regional seismic activity before the earthquake, which is in agreement with the R-t diagram of the small earthquakes in the region before the MS7.8 Tangshan earthquake. The significance of crustal buckling on precursors is twofold: (1) Instability, which provides an important background for the change of precursor field and instability and rupture. ② mutation, the occurrence of flexion, development will be strongly reflected in the precursory observation, sudden jump phenomenon, external modulation, trigger and so on. Therefore, crustal buckling is one of the mechanics of earthquake precursors.