多数瞬变电磁仪器可以同时采集三个分量的响应，但目前瞬变电磁的解释方法却主要以中心回线垂直分量为主。为了充分利用瞬变电磁三分量的信息，介绍一种大定源瞬变电磁三分量约束反演方法。基本思想是利用瞬变电磁三个分量的场分别求取全区视电阻率，并以此为基础建立初始模型，利用阻尼最小二乘法进行三分量反演。首先，将回线源看成是多个电偶极子产生的场的叠加，利用偶极子叠加的原理求取回线的三分量电磁响应，并推导视电阻率的全区与全期定义（即全域视电阻率定义）；然后，利用烟圈理论求取视深度，并以此建立反演的初始地电模型。最后，利用阻尼最小二乘法实现三分量约束反演。利用文中视电阻率定义方法对已知模型数据进行处理，视电阻率曲线与模型的电性参数变化一致；以视电阻率结果为依据建立初始模型，利用三分量约束反演方法对层状模型数据进行反演，结果与模型吻合较好。%Most instruments of transient electromagnetic method ( TEM) can survey three-component field at the same time;neverthe-less, the current interpretation technique is only based on the vertical component. In order to use the information of three-components, the authors introduced a constrained inversion method with the three-component field data. The basic idea is to get the full-zone appar-ent resistivity from the three components of TEM and, on such a basis, to establish the initial model and use the conjugate gradient method to realize three-component inversion. The first step is to take the loop as the superposition of many electric dipoles so as to get the three-component responses of the loop on the basis of electric dipole superposition. Besides, the definition of the full region and all time apparent resistivity can be deduced. After that, the smoking ring theory is adopted to get the apparent depth, which is finally taken as the initial model in inversion. Lastly, the conjugate gradient method is used to realize three-component constrained inversion. Some models were used to test the apparent resistivity definition, and the results show that the apparent resistivity curves match well with the given models. Then based on the apparent resistivity results, the authors established an initial model and used three-component con-strained inversion to conduct the inversion of layered models. The final results match well with the given models.
展开▼
