Abstract: As the most basic geophysical field, the earth gravity field has achieved wide attention, and its spatial anomaly characteristics and dynamic variation can provide important scientific basis for studying the internal structure and dynamics of the Earth. Based on the mobile gravity observation data of the southeastern Tibetan plateau from 2013 to 2016, the dynamic variation tendency and anomaly characteristics of the regional gravity field in different temporal resolutions are obtained before and after the Ludian and Jinggu earthquakes in the study area respectively. The method of wavelet multi-scale decomposition is used to analyze the relationships of gravity field variation with the earth movement, material density change, and strong earthquake preparation. The deep material variation, dynamic process and the mechanism of earthquake inoculation in the southeastern Tibetan plateau are further discussed. Results indicate that the gravity field variation in the source region before the Ludian and Jinggu earthquake respectively is characterized by obvious positive and negative anomalous transition zone and gradient zone that are consistent with the direction of fault tectonics, suggesting the strong crustal movement and mass migration during the earthquake incubation period. The result of wavelet multi-scale decomposition of the gravity field during the period from September 2013 to April 2014 shows that the gravity field variation at different depth and space scale in the crust and upper mantle of the southeastern Tibetan plateau is significantly correlated with seismic distribution and the location of active fault zone. This indicates that the earthquake inoculation in the study area is closely related to the fault movement and the distribution of material density in the crust and upper mantle, which may be affected by the complex deep dynamic process of the material migration in the crust and mantle. The characteristic that strong earthquakes always occur near positive and negative anomaly transition zones and gradient zones of gravity field change is preliminarily explained, based on the dynamic process of material migration in the crust and upper mantle of the southeastern Tibetan plateau. The research results of this paper have some reference value to the study on the earth movement and seismogenic mechanism.

Key words: mobile gravity, gravity field variation, southeastern Tibetan plateau, North-south seismic belt, seismogenic mechanism

摘要： 文中基于青藏高原东南缘2013-2016年的流动重力观测资料，获得了鲁甸和景谷地震前后不同时间尺度下区域重力场的动态演化趋势和异常特征，利用小波多尺度分解分析重力场变化与构造运动、物质密度变迁和强震孕育的关系和规律，对青藏高原东南缘深部物质变化、动力学过程及地震孕育机理进行了探讨。结果表明：1）鲁甸、景谷震前震源区重力场变化呈现与断裂构造走向一致的剧烈正、负异常过渡带和梯度带特征，显示了孕震期间震源区强烈的地壳运动和深部物质变化过程；2）2013年9月-2014年4月重力场变化的小波多尺度分解结果显示，青藏高原东南缘地壳、上地幔不同深度和尺度的重力场变化与地震分布及活动断裂带位置相关性显著，表明研究区地震孕育与断裂运动以及地壳、上地幔内物质密度分布变化关系密切，可能受地壳、上地幔物质运移的复杂深部动力学过程影响；3）基于青藏高原东南缘地壳、上地幔物质运移的动力学过程，对强震多发生在重力场变化的正、负异常过渡带和梯度带附近的特征进行了初步的解释。文中的研究结果对地球构造运动、地震机理研究具有一定的参考价值。

关键词: 流动重力, 重力场变化, 青藏高原东南缘, 南北地震带, 孕震机理