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本文介绍了1974年8月11日新疆乌恰7.3级地震的低烈度现象。并结合1976年龙陵等几次近期大震,对出现低烈度的原因进行分析。在印度板块向北楔入的尖角部位,这种特殊构造条件下,碰撞力直接作用,处于弱介质环境,可能是出现低烈度的重要原因。此外,存在多组方向的断裂系统,明显的三层地壳结构;以及地震过程复杂,地震能量释放和传递可能具有多个途径。这也是出现低应力降,弱破坏地震的一个原因。
This article describes the low intensity of the MS8.18 Wucun earthquake in Xinjiang on August 11, 1974. Combined with several recent large earthquakes such as Longling in 1976, the causes of low intensity were analyzed. Under the special construction conditions, the sharp force of wedges to the north of India plate, the direct impact of the collision force, in a weak medium environment may be an important reason for the low intensity. In addition, there are multiple sets of directional fault systems, obvious three-layer crustal structure, as well as complicated seismic processes and possible release and transmission of seismic energy. This is also one of the reasons for the low stress drop and the weak damage earthquake.