Forward modeling of radio-magnetotelluric method based on Julia acceleration and study on effect of displacement current

Authors

MEI Zhuxu, Engineering Research Center of Nuclear Technology Application (East China University of Technology), Ministry of Education, Nanchang 330013, China; School of Geophysics and Measurement-Control Technology, East China University of Technology, Nanchang 330013, ChinaFollow
YUAN Yuan, Engineering Research Center of Nuclear Technology Application (East China University of Technology), Ministry of Education, Nanchang 330013, China; School of Geophysics and Measurement-Control Technology, East China University of Technology, Nanchang 330013, ChinaFollow
ZHOU Feng, Engineering Research Center of Nuclear Technology Application (East China University of Technology), Ministry of Education, Nanchang 330013, China; School of Geophysics and Measurement-Control Technology, East China University of Technology, Nanchang 330013, China
ZHOU Cong, Engineering Research Center of Nuclear Technology Application (East China University of Technology), Ministry of Education, Nanchang 330013, China; School of Geophysics and Measurement-Control Technology, East China University of Technology, Nanchang 330013, China
ZHANG Lincheng, College of Information and Electronic Engineering, Hunan City University, Yiyang 413002, China

Abstract

Radio-magnetotelluric method (RMT) is one of the important tools for shallow surface electromagnetic exploration. Since the exploration frequency band is 10‒300 kHz, the propagation of electromagnetic fields is greatly affected by the dielectric permittivity of the earth. The electromagnetic response calculated with traditional quasi-static conditions severely restricts the accuracy of RMT forward modeling and further affects the resolution of the inversion imaging. In response to this problem, a numerical simulation method of full-current RMT electromagnetic response based on Julia parallel acceleration was proposed. Then, the calculation of each frequency point was sent through the distributed computing in Julia to different processes for solving, so as to achieve the purpose of accelerating the calculation. At the same time, the influence of displacement current was considered in the calculation to improve the accuracy of forward modeling. Besides, the influence law of displacement current on the apparent resistivity and phase response of electromagnetic field in the radio frequency band was analyzed and summarized by calculating the RMT response of several typical high-resistance/high-dielectric models. The numerical simulation results show that: The calculated RMT apparent resistivity and phase response under the quasi-static conditions were relatively high in case that a high-resistance overburden is present in the shallow surface. Besides, the higher the frequency, the greater the resistivity of the overburden, and the larger the response deviation is. For the coal goaf model, the RMT method can effectively reflect the location of the abnormal body, but ignoring the displacement currents may cause a large calculation error in the goaf and its vicinity. As shown in the calculation example of rugged terrains, the RMT numerical response of underground anomalous body may be covered by the terrain, especially at the corner of terrain. Further, the parallel numerical examples at two different scales comparatively demonstrate the efficiency of the parallel algorithm herein, and the efficiency of the parallel algorithm is improved with the increasing scale of the problem to be solved. Our research improved the computational efficiency and accuracy of RMT forward modeling, laying the foundation for the realization of subsequent rapid inversion algorithm. In addition, the numerical calculation examples also indicate that the RMT method has a good application prospect in the actual exploration of coal goaf.

Keywords

radio-magnetotelluric method, displacement currents, finite element method, parallel calculation, Julia

DOI

10.12363/issn.1001-1986.22.06.0489

Recommended Citation

MEI Zhuxu, YUAN Yuan, ZHOU Feng, et al. (2023) "Forward modeling of radio-magnetotelluric method based on Julia acceleration and study on effect of displacement current," Coal Geology & Exploration: Vol. 51: Iss. 3, Article 60.
DOI: 10.12363/issn.1001-1986.22.06.0489
Available at: https://cge.researchcommons.org/journal/vol51/iss3/60

Reference

[1] TURBERG P,MULLER I,FLURY F. Hydrogeological investigation of porous environments by radio magnetotelluric–resistivity (RMT−R 12–240 kHz)[J]. Journal of Applied Geophysics,1994,31(1):133−143.

[2] ISMAIL N,SCHWARZ G,PEDERSEN L B. Investigation of groundwater resources using controlled–source radio magnetotellurics (CSRMT) in glacial deposits in Heby,Sweden[J]. Journal of Applied Geophysics,2011,73(1):74−83.

[3] ISMAIL N,PEDERSEN L. The electrical conductivity distribution of the Hallandsas Horst,Sweden:A controlled source radiomagnetotelluric study[J]. Near Surface Geophysics,2011,9(1):45−54.

[4] BASTANI M,PERSSON L,BEIKI M,et al. A radio magnetotelluric study to evaluate the extents of a limestone quarry in Estonia[J]. Geophysical Prospecting,2013,61(3):678−687.

[5] 杨思朋,张丽莉. 大地电磁二维有限元正演过程和编码[J]. 地球物理学进展,2016,31(3):1010−1016.

YANG Sipeng,ZHANG Lili. Forward modeling process of magnetotelluric using finite element method and numbering[J]. Progress in Geophysics,2016,31(3):1010−1016.

[6] 张林成,汤井田,任政勇,等. 基于二次场的可控源电磁法三维有限元–无限元数值模拟[J]. 地球物理学报,2017,60(9):3655−3666.

ZHANG Lincheng,TANG Jingtian,REN Zhengyong,et al. Forward modeling of 3D CSEM with the coupled finite–infinite element method based on the second field[J]. Chinese Journal of Geophysics,2017,60(9):3655−3666.

[7] 郭家松,秦策,乃国茹,等. 基于非结构化网格的大地电磁2D自适应有限元正演模拟[J]. 物探化探计算技术,2019,41(5):616−622.

GUO Jiasong,QIN Ce,NAI Guoru,et al. MT 2D adaptive finite element forward modeling based on unstructured mesh[J]. Computing Techniques for Geophysical and Geochemical Exploration,2019,41(5):616−622.

[8] 曹晓月,殷长春,张博,等. 面向目标自适应有限元法的带地形三维大地电磁各向异性正演模拟[J]. 地球物理学报,2018,61(6):2618−2628.

CAO Xiaoyue,YIN Changchun,ZHANG Bo,et al. A goal–oriented adaptive finite−element method for 3D MT anisotropic modeling with topography[J]. Chinese Journal of Geophysics,2018,61(6):2618−2628.

[9] ÖZYILDIRIM Ö,DEMIRCI İ,GUNDOGDU N T,et al. Two dimensional joint inversion of direct current resistivity and radiomagnetotelluric data based on unstructured mesh[J]. Journal of Applied Geophysics,2020,172:103885.

[10] PEDERSEN L B,BASTANI M,DYNESIUS L. Groundwater exploration using combined controlled−source and radiomagnetotelluric techniques[J]. Geophysics,2005,70(1):G8−G15.

[11] CANDANSAYAR M E,TEZKAN B. Two–dimensional joint inversion of radiomagnetotelluric and direct current resistivity data[J]. Geophysical Prospecting,2008,56(5):737−749.

[12] KALSCHEUER T,PEDERSEN L B,SIRIPUNVARAPORN W. Radiomagnetotelluric two−dimensional forward and inverse modelling accounting for displacement currents[J]. Geophysical Journal International,2008,175(2):486−514.

[13] 原源,汤井田,任政勇,等. 基于非结构化网格的任意复杂2D RMT有限元模拟[J]. 地球物理学报,2015,58(12):4685−4695.

YUAN Yuan,TANG Jingtian,REN Zhengyong,et al. Two–dimensional complicated radio−magnetotelluric finite–element modeling using unstructured grids[J]. Chinese Journal of Geophysics,2015,58(12):4685−4695.

[14] 原源,庞成,汤井田,等. 基于非结构双网格的2D RMT双参数同步反演研究[J]. 地球物理学报,2019,62(6):2150−2164.

YUAN Yuan,PANG Cheng,TANG Jingtian,et al. Unstructured duple mesh based dual–parameters simultaneous inversion for 2D Radio–magnetotelluric data[J]. Chinese Journal of Geophysics,2019,62(6):2150−2164.

[15] BEZANSON J,EDELMAN A,KARPINSKI S,et al. Julia:A fresh approach to numerical computing[J]. SIAM Review,2017,59(1):65−98.

[16] 彭荣华,胡祥云,韩波,等. 基于拟态有限体积法的频率域可控源三维正演计算[J]. 地球物理学报,2016,59(10):3927−3939.

PENG Ronghua,HU Xiangyun,HAN Bo,et al. 3D frequency–domain CSEM forward modeling based on the mimetic finite–volume method[J]. Chinese Journal of Geophysics,2016,59(10):3927−3939.

[17] HAN Bo,LI Yuguo,LI Gang. 3D forward modeling of magnetotelluric fields in general anisotropic media and its numerical implementation in Julia[J]. Geophysics,2018,83(4):F29−F40.

[18] SHAN Chunling,BASTANI M,MALEHMIR A,et al. Integration of controlled–source and radio magnetotellurics,electric resistivity tomography,and reflection seismics to delineate 3D structures of a quick−clay landslide site in Southwest of Sweden[J]. Geophysics,2016,81(1):B13−B29.

[19] MEHTA S,BASTANI M,MALEHMIR A,et al. Resolution and sensitivity of boat–towed RMT data to delineate fracture zones:Example of the Stockholm bypass multi–lane tunnel[J]. Journal of Applied Geophysics,2017,139:131−143.

[20] WANG Shunguo，MALEHMIR A，BASTANI M. Geophysical characterization of areas prone to quick–clay landslides using radio−magnetotelluric and seismic methods[J]. Tectonophysics，2016，677–678(5)：248–260.

[21] SARAEV A,SIMAKOV A,SHLYKOV A,et al. Controlled source radiomagnetotellurics:A tool for near surface investigations in remote regions[J]. Journal of Applied Geophysics,2017,146:228−237.

[22] 汤井田,任政勇,周聪,等. 浅部频率域电磁勘探方法综述[J]. 地球物理学报,2015,58(8):2681−2705.

TANG Jingtian,REN Zhengyong,ZHOU Cong,et al. Frequency–domain electromagnetic methods for exploration of the shallow subsurface:A review[J]. Chinese Journal of Geophysics,2015,58(8):2681−2705.

[23] 何继善. 可控源音频大地电磁法[M]. 长沙：中南工业大学出版社，1990.

[24] ÖZYILDIRIM Ö,CANDANSAYAR M E,DEMIRCI İ,et al. Two–dimensional inversion of magnetotelluric/radiomagnetotelluric data by using unstructured mesh[J]. Geophysics,2017,82(4):E197−E210.

[25] 肖晓,付弘流,汤井田,等. 斜入射平面电磁波的视电阻率及其影响[J]. 地球物理学报,2015,58(12):4661−4674.

XIAO Xiao,FU Hongliu,TANG Jingtian,et al. Research on apparent resistivity and its influence of obliquely incident plane electromagnetic waves[J]. Chinese Journal of Geophysics,2015,58(12):4661−4674.

[26] 徐世浙. 地球物理中的有限单元法[M]. 北京：科学出版社，1994.

[27] MAZA M M. Parallel and distributed computing with Julia[EB/OL]. (2014-10-16) [2022-06-14]. https://www.csd.uwo.ca/~mmorenom/cs2101a_moreno/Parallel_computing_with_Julia. pdf.

[28] MIKUCKI J A,AUKEN E,TULACZYK S,et al. Deep groundwater and potential subsurface habitats beneath an Antarctic dry valley[J]. Nature Communications,2015,6:6831.

[29] 沈华,吴跃东,金世恒,等. 安徽霍山石英岩玉矿床地质特征与地球物理找矿方法研究[J]. 华东地质,2017,38(1):51−57.

SHEN Hua,WU Yuedong,JIN Shiheng,et al. Geological features of the Huoshan quartzite jade ore deposit in Anhui Province and study of geophysical prospecting methods[J]. East China Geology,2017,38(1):51−57.

[30] 杨建军,吴汉宁,冯兵,等. 煤矿采空区探测效果研究[J]. 煤田地质与勘探,2006,34(1):67−70.

YANG Jianjun,WU Hanning,FENG Bing,et al. Research on prospecting effect for gob area of coal mines[J]. Coal Geology & Exploration,2006,34(1):67−70.

[31] 姜国庆,贾春梅,谭强,等. 频率域电磁法在煤矿采空区调查中的应用[J]. 物探与化探,2015,39(3):646−650.

JIANG Guoqing,JIA Chunmei,TAN Qiang,et al. Application of fdem in detecting coal mined–out areas[J]. Geophysical and Geochemical Exploration,2015,39(3):646−650.