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1932年12月25日,我国甘肃省西部玉门镇以南的昌马地区发生了7.6级地震。震中区产生了规模较大的地面破裂带,其中有张性、压性和剪切等多种型式裂缝。本文根据分析各种自然破坏现象的形成条件,结合极震区地质构造特征,对震源区的应力作用和地震成因提出初步看法。 对地震破裂带的分析结果表明,这次地震起主要作用的是南北向的水平挤压作用,并与自白垩纪以来控制着本区构造断裂的区域应力场是一致的。地震破裂带出现的部位与长期活动的昌马构造断裂带一致。因此,我们认为昌马地震的发生是昌马构造断裂带继承性活动的结果。
On December 25, 1932, a magnitude-7.6 earthquake hit Changma, south of Yumen Town in the west of Gansu Province. The epicenter area produced large-scale ground rupture zone, in which there are many types of cracks such as tension, pressure and shear. Based on the analysis of formation conditions of various natural disasters and the geological structural features of the extremely shock zone, this paper presents a preliminary view on the stress effects and the causes of earthquakes in the source zone. The analysis results of the earthquake rupture zone show that the main role played by this earthquake is the north-south horizontal squeezing and consistent with the regional stress field that controlled the tectonic fracture in this area since the Cretaceous. The site of the earthquake rupture zone coincides with the Changma tectonic fault zone that has long been active. Therefore, we think that the occurrence of the Chang-Ma earthquake is the result of the succession activity of the Chang-Ma tectonic fault zone.