利用小波变换研究民乐M6.1地震前区域重力场变化特征

Wavelet analysis of the gravity field variation before Minle M6.1 earthquake

对民乐M 6.1地震前4年河西地区重力场变化进行小波分解,结果表明:重力异常变化一阶小波分体呈现随机性与局部性,反映浅层和局部质量变化引起重力变化;二阶小波分解与地质结构一致,反映断层活动引起的重力变化;三阶小波分解结果表明,在民乐M 6.1地震前,重力显著改变,显示深部物质状态发生变化是引起此次地震发生的重要因素;四阶小波分解反映深部物质状态引起重力变化,对此次民乐M 6.1地震反应不明显。地震发生后,震区构造活动减弱,各阶小波分解对地震反应不明显。

In this paper, the gravity field variation in Hexi area four years before Minle M6.1 earthquake was decomposed by wavelet method, and the results show that： The locality and randomness do exist in the first-order wavelet decomposition of the gravity field variation in Hexi Corridor, which mainly reflects that the gravity field variation was caused by mass change of the shallow layers and local areas; The second wavelet transformation is consistent with the geological structure, which mainly reflects the gravity field variation caused by fault movements in Hexi Corridor; The third wavelet transformation shows significant gravity variation in Minle area before the M6.1 earthquake, which indicates that the middle-deep layer material density change is closely related to the earthquake; The fourth wavelet transformation which reflects the deep layer material density variation of the earth has no obvious variations during the earthquake. After the earthquake, the geological structure movements in Minle area relatively decreased, and every order of wavelet decomposition results have no obvious variations.