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本文从理论上讨论了两种预位移终止相。一种是预位移在震源断层面上局部地区发生,简称为局域预位移;另一种是预位移在整个断层面上展开,称为全域预位移。这两种预位移的终止条件有重大差异,这种差异导致预位移终止相的差异,从而使预位移引起的长周期波,以及由长周期波产生的突跳型前兆也产生差异。得到的初步研究结果如下: 1.大多数大地震发生前的预位移属局域预位移,而中强震大多属全域预位移。2.局域预位移的震源过程为有限源传播,全域预位移为有限源与瞬时面源。前者仅有一个长周期P波,后者产生两个不同到时的长周期P波。3.局域预位移和全域预位移所引起的长周期波与它们各自的源时间函数相近。前者产生单峰型突跳前兆,后者产生双峰型突跳前兆。由这两种前兆异常类型可粗略判断未来地震的强度。4.由于大震局域预位移区的尺度与中强地震全域预位移区尺度相当,因而它们的预位移幅度相近,从而大震和中强震前大多数前兆异常幅度相近。这样从理论上解释了前兆异常幅度与震级无关这一观测事实。
This paper theoretically discusses two kinds of pre-displacement termination phase. One is that the pre-displacement occurs in a local area on the focal plane of the source, referred to as the local pre-displacement for short, and the other is that the pre-displacement spreads over the entire fault plane and is called global pre-displacement. These two pre-displacement termination conditions have significant differences, this difference leads to the termination of pre-displacement phase difference, so that pre-displacement caused by long-period waves, as well as by the long-period waves produced by sudden jump precursors also produce differences. The preliminary results obtained are as follows: 1. The pre-displacement before most large earthquakes is localized pre-displacement, while the moderate-strong earthquakes mostly belong to global pre-displacement. 2. Local pre-displacement source process is limited source propagation, global pre-displacement is limited source and instantaneous surface source. The former has only one long-period P wave, which produces two different long-period P waves. 3. Long-period waves caused by local pre-displacement and global pre-displacement are similar to their respective source-time functions. The former produces a unimodal kyphosis and the latter produces a bimodal kyphosis. From these two types of precursory anomalies, the strength of future earthquakes can be roughly judged. 4. Since the scale of the pre-displacement area in the large earthquake area is similar to the global pre-displacement area scale of the moderate-strong earthquake, their pre-displacement amplitudes are similar, and the magnitude of most precursor anomalies before and after the strong earthquake is similar. This theoretically explains the observed fact that amplitude of precursor anomaly is not related to magnitude.