Efficient three-dimensional inversion of magnetotelluric data using approximate sensitivities
Efficient three-dimensional inversion of magnetotelluric data using approximate sensitivities
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DOI：
10.1111/j.1365-246x.2008.03894.x
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发表时间：
2008-11
影响因子：
2.8
通讯作者：
Nuree Han;M. Nam;H. Kim;T. Lee;Yoonho Song;J. Suh
中科院分区：
文献类型：
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作者：
Nuree Han;M. Nam;H. Kim;T. Lee;Yoonho Song;J. Suh
摘要介绍了一种用于静位移大地电磁（MT）数据有效三维反演的精确近似灵敏度方法。近似的灵敏度，通过替换伴随的二次电场与那些在以前的迭代计算。这些灵敏度可以减少计算时间，而不会显着损失的精度时，构造一个完整的灵敏度矩阵的三维反演，基于高斯-牛顿法。通过修改反演方案以在并行计算平台上运行，可以进一步降低计算成本。近似灵敏度的有效性进行了测试，通过反演合成和现场数据在浦项，韩国，和Bajawa，印度尼西亚。通过对模拟数据的敏感性分析，验证了近似敏感性的准确性。为了使静偏移MT数据的反演更加稳定，在目标函数中加入静偏移参数的加权系数，并在每次迭代时更新。近似灵敏度的计算比精确灵敏度快得多，并且足够精确以驱动迭代反演算法。
SUMMARY A method for accurately approximating sensitivities is introduced for the efficient 3-D inversion of static-shifted magnetotelluric (MT) data. Approximate sensitivities are derived by replacing adjoint secondary electric fields with those computed in the previous iteration. These sensitivities can reduce the computation time, without significant loss of accuracy when constructing a full sensitivity matrix for 3-D inversion, based on the Gauss–Newton method. Additional reduction of computational cost can be attained by modifying the inversion scheme to run on a parallel computing platform. The effectiveness of approximate sensitivities is tested by inverting both synthetic and field data obtained in Pohang, Korea, and Bajawa, Indonesia. The accuracy of approximate sensitivities is validated by sensitivity analysis of synthetic data. To make the inversion of static-shifted MT data more stable, a weighting coefficient for static-shift parameters is added to the objective function and is updated at each iteration. Approximate sensitivities are calculated much faster than exact sensitivities, and are accurate enough to drive an iterative inversion algorithm.