1.问题的由来1920年的海原大地震不仅是我国和世界历史上的著名的大地震之一,而且也是发生在大陆内部的少数大地震之一。因此,深入研究海原大地震的动力学过程,有助于对大陆内部地震成因的认识。这次地震后,于1920年12月25日发生的7级强余震,震中位置曾定在主震极震区东南端 1. The Origin of the Problem The 1920 Haiyuan earthquake was not only one of the famous earthquakes in our country and in world history, but also one of the few major earthquakes that took place in mainland China. Therefore, in-depth study of the dynamics of the Haiyuan earthquake can help to understand the causes of the earthquake in the interior of the continent. After the earthquake, the magnitude 7 aftershock occurred on December 25, 1920, and the location of the epicenter was fixed at the southeast end of the main shock polar area