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本文在考虑各种干扰因素(如温度、气压、地下水和台站高程变化等)的同时,详细分析了唐山地震的后区域重力场变化的几个特征。分析结果表明,唐山地震前发生了明显的区域重力场异常。异常有四个特点:(1)重力变化围绕着震中,最大变化值恰好在震中;(2)重力随时间的变化是非线性的;(3)变化最大值出现在1975年年中,而不是在1976年7月份;(4)1977年区域重力场基本恢复到震前水平。不能用台站高程变化和地下水位变化来解释这些异常。作者用扩容模式计算了区域重力变化理论值,计算结果同观测值相符。此外,作者用相应地区的垂直形变资料和地下水观测资料讨论了该模式的合理性。
In this paper, several characteristics of post-region gravitational field changes of Tangshan earthquake are analyzed in detail while considering various disturbing factors (such as temperature, pressure, groundwater and station elevation changes). The results show that obvious regional gravity anomalies occurred before the Tangshan earthquake. Abnormalities have four characteristics: (1) gravity changes around the epicenter, the maximum change is just in the epicenter; (2) the change of gravity with time is nonlinear; (3) the maximum change occurs in mid-1975, not in July 1976; (4) In 1977, the regional gravity field basically returned to the level before the earthquake. These anomalies can not be explained by station elevation changes and groundwater level changes. The author calculated the theoretical value of regional gravity change with the expansion mode, and the calculated result is consistent with the observed value. In addition, the authors discuss the rationality of the model using vertical deformation data and groundwater observations from the corresponding areas.