可控源电磁磁场频率梯度一维Occam反演
One-Dimensional Occam Inversion of Controlled-Source Electromagnetic Magnetic Field Frequency Gradient

Occam反演作为一种地球物理正则化反演方法，被广泛使用于求取光滑的反演结果。传统的场值单分量一维Occam反演虽然能够对层状模型有着较好的恢复效果，但是反演结果严重依赖于收发距，通常收发距需要达到数千公里才可获得满意的反演结果。当偏移距过小时反演结果几乎是直线，对模型的电性变化无任何反映。本文对水平电偶极源产生的磁场求取频率梯度，层状模型的梯度值采用高精度差分值进行代替。将磁场频率梯度应用于Occam反演中，大量的反演结果表明，磁场三分量频率梯度的反演结果不会随着收发距而改变，均可以在近场源下很好地恢复模型真实情况，对电阻率的恢复效果优于层厚度。与其他电磁方法一样，反演结果对低阻层更为灵敏，对复杂模型的高阻层的恢复效果不如低阻体。
As a geophysical regularization inversion method, Occam inversion is widely used to obtain smooth inversion results. Although the traditional single-component one-dimensional Occam inversion of field values can have a good recovery effect on the layered model, the inversion results are heavily dependent on the transmitter-receiver distance, which usually needs to reach thousands of kilometers to obtain satisfactory inversion results. When the offset is too small, the inversion results are almost straight lines, and there is no reflection on the electrical changes of the model. In this paper, the frequency gradient of the magnetic field generated by the horizontal electric dipole source is obtained. The gradient value of the layered model is replaced by the high-precision difference value. The magnetic field frequency gradient is applied to Occam inversion. A large number of inversion results show that the inversion results of the three-component magnetic field frequency gradient will not change with the transmission distance, and the real condition of the model can be well restored under near-field sources, and the resistivity recovery effect is better than that of layer thickness . As with other electromagnetic methods, the inversion results are more sensitive to the low-resistivity layer, and the recovery effect of the high-resistivity layer of complex models is not as good as that of the low-resistivity layer.