| 1976年唐山地震前后的重力变化和震区莫霍面的变形 |
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| 引用本文： | 朱岳清,吴兵,邢如英.1976年唐山地震前后的重力变化和震区莫霍面的变形[J].地震学报,1985,7(1):57-73. |
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| 作者姓名： | 朱岳清 吴兵 邢如英 |
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| 作者单位： | 国家地震局分析预报中心 |
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| 摘 要： | 本文分析了1976年唐山地震前后十年的流动重力测量资料及其观测精度,通过降噪试验和可靠性分析,证实了重力趋势性异常变化的存在;分析了引起重力变化的物理因素,采用时域带通滤波的方法对资料进行预处理,用样条函数求得了重力测值的拟合曲面和分析区域等间距网点异常变化值,借助于窗口滑动求均方法滤去浅部短波长密度扰动的重力效应,根据剩余重力异常场作约束反演,发现震前、震时和震后该区莫霍面附近岩层可能出现过变形,尤其是震前数年,变形幅度可能更大。看来,莫霍面附近岩层的变形可能是造成壳内应力集中并孕育唐山地震的重要原因。
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GRAVITY VARIATION AND MOHO SURFACE DEFORMATION BEFORE AND AFTER 1976 TANGSHAN EARTHQUAKE |
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| Affiliation: | Analysis and Prediction Center, State Seismological Bureau |
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| Abstract: | In this paper, data of mobile gravity survey and the observation precision within ten years before and after the 1976 Tangshan earthquake were investigated. It was proved that there existed a trend of anomalous change in the epicentral region before and after the earthquake through the noise-depression experiment and reliability analysis. We analysed the physical factors which caused the gravity variation. Bandpass filtering method in the time domain was adopted to preprocess the data. A fitting curved surface to the values of gravity survey was obtained. We also analysed the values of anomalous change at equally spaced points in the region with the aid of the moving window average method to filter out the gravitational effect caused by shallow short wavelength density changes. Restraint inversion was done according to the remainder of the abnormal gravity field and it was found that deformation in rock formation in the vicinity of the Moho surface in this area might have appeared before, during and after the earthquake; especially, the deformation amplitude might be rather large several years proior to the earthquake. It is shown that the deformation of the rock formation near tie Moho surface may be a significant cause of stress concentration in the crust and the seismogenesis of the Tangshan earthquake. |
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