A discussion of 2D induced polarization effects in airborne electromagnetic and inversion with a robust 1D laterally constrained inversion scheme
A discussion of 2D induced polarization effects in airborne electromagnetic and inversion with a robust 1D laterally constrained inversion scheme
复制标题
使用鲁棒的一维横向约束反演方案讨论机载电磁和反演中的二维诱发极化效应
DOI：
10.1190/geo2018-0102.1
复制
发表时间：
2019-03-01
期刊：
影响因子：
3.3
通讯作者：
Christiansen, Anders Vest
中科院分区：
文献类型：
--
作者：
Lin, Changhong;Fiandaca, Gianluca;Christiansen, Anders Vest
近年来，航空时域电磁（ATEM）数据中的激发极化（IP）现象引起了人们极大的兴趣。IP可能会影响ATEM数据显着和掩盖下伏的地质结构。为了模拟二维机载激电数据，已经开发了一种二维有限元正演模拟算法，其中色散电导率由著名的Cole-Cole模型描述。我们验证了我们的算法与一维解决方案的AarhusInv代码的比较。模拟原型二维导电和带电异常，在六个合成模型上的二维正演响应已经产生，结果表明，二维IP影响数据显着。2D IP响应和1D IP响应之间的差异在2D异常上方及其边缘处是明显的。这些差异类似于在不考虑IP的情况下比较导电2D异常的2D和1D正演响应时发现的差异。我们评估了一种有效的鲁棒反演方案，使用一维横向约束反演（LCI）方案来恢复2D IP参数。使用鲁棒方案的合成数据的反演表明，不仅可以恢复IP参数，而且IP反演可以提供比仅反演电阻率值和异常厚度/深度更准确的电阻率剖面。考虑到剖面的一部分仅由负数据组成，不能用仅重性方案进行反演，来自加拿大Hope Bay地区的现场实例甚至更有价值。此外，在异常边界的边缘效应是不太明显的IP参数比在电阻率参数的合成模型具有更多的导电背景。
Recently, the interest in the induced polarization (IP) phenomenon in airborne time-domain electromagnetic (ATEM) data has increased considerably. IP may affect the ATEM data significantly and mask underlying geologic structures. To simulate 2D airborne IP data, a 2D finite-element forward-modeling algorithm has been developed with the dispersive conductivity described by the well-known Cole-Cole model. We verify our algorithm by comparison with the 1D solution of the AarhusInv code. Two-dimensional forward responses on six synthetic models, mimicking archetypal 2D conductive and chargeable anomalies, have been generated, and the results indicate that 2D IP affects the data significantly. Differences between the 2D IP responses and the 1D IP responses are evident above the 2D anomalies and at their edges. These differences are similar to what is found when comparing 2D and 1D forward responses over conductive 2D anomalies without considering IP. We evaluate an effective robust inversion scheme to recover the 2D IP parameters using the 1D laterally constrained inversion (LCI) scheme. The inversion of the synthetic data using the robust scheme indicates that not only can the IP parameters be recovered, but also the IP inversions can provide more accurate resistivity sections than a resistivity-only inversion, in terms of resistivity values and anomaly thickness/depth. The field example from Hope Bay area in Canada is even more valuable, considering that part of the profile consists of only negative data, which cannot be inverted with a resistivity-only scheme. Furthermore, the edge effects at the anomaly boundaries are less pronounced in the IP parameters than in the resistivity parameter on the synthetic models with more conductive backgrounds.