宁夏中强地震前重力变化原因探讨
A DISCUSSION ON THE CAUSE OF GRAVITY VARIATIONS BEFORE MODERATELY STRONG EARTHQUAKES OCCURRED IN NINGXIA REGION
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摘要: 依据八十年代以来宁夏境内中强地震前观测到的重力异常变化,结合地下水、垂直形变、区域应力场以及地质构造资料进行了综合分析。其结果认为,重力变化原因与地下水位的变化关系不大。也不是由于地壳垂直形变引起的。其主要原因可能是在强大NE向水平挤压应力场作用下,活动断裂带及其附近某种特殊部位有物质密度变化所致。同时进行了海原大断裂走滑摸拟计算,其结果支持上述看法。Abstract: This paper comprehensively analyzed the anomalous variation in gravity measured before moderately strong earthquakes occurred in Ningxia region since 1980 based on the data of groundwater, vertical deformation, regional stress field and geological structure. The results show that the variation in gravity has no clear relation with the variation in ground-water level and is not due to vertical crustal deformation either Its main cause may be that it was caused by the variation in material densisy in the active fault zone and a special position near it under a strong action of the NE horizontal compressive stress field. Meanwhile a simulative calculation was made for the strlke-slip of Haiyuan large fault and the result supports the above idea.
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