时移可控源音频大地电磁法三维反演研究

时移地球物理监测是观测地下物性参数随时间动态变化的有效方法。地球物理反演结果会受到测量误差、测量环境的噪声污染以及地球物理反演多解性等系统性因素的影响。如果对时移地球物理数据进行不同时刻数据的单独反演，可能会导致不同时刻的反演结果可对比性差，从而影响时移地球物理的监测效果。针对可控源音频大地电磁法在监测领域的实际需求，将不同时刻的观测数据放在一起反演，不同时刻的电阻率模型相互约束，实现了时移可控源音频大地电磁法三维反演。设计三种类型模型进行合成数据的单独反演和时移反演对比试算，验证了时移反演算法的有效性。反演结果表明：通过加入相邻时刻模型约束，时移反演可以更好地聚焦异常体的位置，降低噪声以及测量环境变化对反演结果的影响，防止反演伪影掩盖真实的地下变化。研究成果为时移可控源音频大地电磁法的实际应用奠定了良好基础。

3D Inversion of Time-lapse Controlled Source Audio-frequency Magnetotellurics

Time-lapse monitoring is an effective way to observe underground dynamic changes. Geophysical inversion results could be affected by systemic factors, including measurement errors, noise pollution in the studied environment, and the inversion ambiguity. If time-lapse geophysical data is inverted separately at different times, the results may have poor comparability, which would affect the monitoring of time-lapse geophysics. For the actual needs of the controlled-source audio frequency magnetotelluric (CSAMT) in the monitoring field, we integrated the observation data at different moments for inversion, and constructed resistivity models at different moments (mutually constrained) for three-dimensional inversion of the time-lapse CSAMT. Three types of models were designed to perform without time-lapse constraint inversion and time-lapse inversion comparison trial calculations of synthetic data, which verified the inversion algorithm and its effectiveness. The inversion results show that by adding adjacent time model constraints, the time-lapse controllable source inversion can better focus on the anomaly locations, reduce the noise impact and local environment changes, and minimize the impact of inversion artifacts. Our findings have laid a good foundation for the application of time-lapse CSAMT.