时变重力场球面模型反演算法和模拟实验

时变重力场是研究地球内部介质物性变化的重要手段。本文提出了一种适用于地面流动重力测量获得的时变重力信号的场源反演方法,该方法采用球坐标系下的六面体单元来模拟场源介质,适合大尺度地震流动重力测量数据的等效源模型构建。通过引入重力时变信号的一阶光滑先验条件,压制了时变重力信号中的短周期高频分量,可用于提取与地震孕育相关的长周期信号。通过理论和模型实验证明了本文算法的可靠性和稳定性,并使用南北地震带南段2014—2017年的流动重力实测数据进行了反演解释,获得了地壳内部等效场源的视密度时变信号,变化量级在正常地壳密度的±0.7‰之间,其空间形态受川滇菱形块体边界控制。研究成果可用于时变重力场模型解释和深部场源特征提取,可为地震重力前兆信号分析和相关研究提供完备的方法保障。

Time-varying Gravity Inversion using Spherical Model and Synthetic Test

Time-varying gravity field is an important means to study the physical properties of the earth.In this paper,a field source inversion method which is suitable for the time-varying gravity signals obtained from ground flow gravity measurements is proposed.The method uses hexahedral elements in spherical coordinate system to simulate the field source media and is suitable for constructing equivalent source models of large-scale seismic flow gravity measurements.In this method,the high-frequency components of time-varying gravity signals are suppressed by introducing a first-order smoothing priori,which can be used to extract long-period signals related to earthquake preparation.The theory and model experiments prove that the algorithm is reliable and stable.We also used the campaign gravity survey of the southern section of the north-south seismic zone from 2014 to 2017 for inversion.And the time-varying apparent density signal of the equivalent field source in the crust was obtained,which was within±0.7‰of the normal crust density,and its spatial morphology was controlled by the boundary of the Sichuan-Yunnan block.The results of this paper can be applied to the interpretation of time-varying gravity field model and the extraction of deep field source characteristics,which can provide a complete method for seismic gravity precursor signal analysis and related research.