Optimized arrays for 2-D resistivity survey lines with a large number of electrodes
Optimized arrays for 2-D resistivity survey lines with a large number of electrodes
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DOI：
10.1016/j.jappgeo.2014.11.011
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发表时间：
2015-01-01
影响因子：
2
通讯作者：
Sorensen, J. P. R.
中科院分区：
文献类型：
--
作者：
Loke, M. H.;Wilkinson, P. S.;Sorensen, J. P. R.
以前的研究表明，使用“比较R”方法生成的优化阵列具有比传统阵列更好的分辨率。该方法通过选择那些给出最大模型分辨率的阵列来确定最佳阵列集。可能的阵列（综合数据集）的数量随着电极数量的四次方而增加。对于具有超过60个电极的2-D测量线，其中可能的阵列数量超过一百万，优化方法面临实际限制。提出了几种技术来减少这种测量线的计算时间。使用新排名函数的“Compare R”算法的单精度版本将计算时间减少了2到8倍，同时提供与双精度版本类似的结果。计算机GPU技术的最新改进可以将计算时间减少约7倍。通过使用关于线中心对称的阵列在模型分辨率值中产生相同变化的事实，计算时间减少了一半。通过计算所有可能的两电极组合的谢尔曼-莫里森更新，然后用于计算四电极阵列的模型分辨率值，它进一步减少了三十倍以上。通过使用仅由对称阵列组成的综合数据集的子集，计算时间减少了十倍以上。与合成模型和现场数据集的测试表明，优化阵列从这个子集产生的反演模型与使用完整的综合数据集的差异小于10%。在所有测试中，优化的数据集产生的模型比温纳-斯伦贝谢阵列数据集更准确。(C)2014爱思唯尔有限公司版权所有。
Previous studies show that optimized arrays generated using the 'Compare R' method have significantly better resolution than conventional arrays. This method determines the optimum set of arrays by selecting those that give the maximum model resolution. The number of possible arrays (the comprehensive data set) increases with the fourth power of the number of electrodes. The optimization method faces practical limitations for 2-D survey lines with more than 60 electrodes where the number of possible arrays exceeds a million. Several techniques are proposed to reduce the calculation time for such survey lines. A single-precision version of the 'Compare R' algorithm using a new ranking function reduces the calculation time by two to eight times while providing results similar to the double-precision version. Recent improvements in computer GPU technology can reduce the calculation time by about seven times. The calculation time is reduced by half by using the fact that arrays that are symmetrical about the center of the line produce identical changes in the model resolution values. It is further reduced by more than thirty times by calculating the Sherman-Morrison update for all the possible two-electrode combinations, which are then used to calculate the model resolution values for the four-electrode arrays. The calculation time is reduced by more then ten times by using a subset of the comprehensive data set consisting of only symmetrical arrays. Tests with a synthetic model and field data set show that optimized arrays derived from this subset produce inversion models with differences of less than 10% from those derived using the full comprehensive data set. The optimized data sets produced models that are more accurate than the Wenner-Schlumberger array data sets in all the tests. (C) 2014 Elsevier B.V. All rights reserved.