Research on Mobile Ultrasonic Rapid Electromagnetic Exploration Technology

doi:10.19657/j.geoscience.1000-8527.2025.010

Abstract

Abstract:

The controlled source radio magnetotelluric method (CSRMT) is an innovative frequency-domain electromagnetic sounding technique designed for near-surface exploration.Building upon the traditional Magnetotelluric (MT) method, CSRMT employs an artificial transmitter source and measures various components of the electromagnetic field at a distance to infer subsurface structures.This paper introduces a mobile ultra-high-frequency rapid electromagnetic exploration technology based on CSRMT.This technology leverages existing artificial field sources, such as AM signals from radio broadcast stations, very low frequency (VLF) electromagnetic signals from naval communication stations, and electromagnetic signals from national time service centers, to conduct electromagnetic surveys.By equipping a vehicle with an ultra-high-frequency controlled-source electromagnetic receiver, mobile exploration can be achieved without on-site deployment of artificial field sources, as required in traditional Controlled Source Magnetotellurics (CSMT).This significantly enhances exploration efficiency and reduces the costs associated with deploying and maintaining transmitters.The mobile ultra-high-frequency controlled-source electromagnetic receiver developed for this technology features a bandwidth range of 1 Hz to 600 kHz, a sampling rate of up to 2.5 MHz, a dynamic range of 138 dB, and an apparent resistivity measurement accuracy better than 3%.

Key words: CSRMT, electromagnetic receiver, FPGA, apparent resistivity

CLC Number:

RUAN Hongyu, WANG Meng, LIN Zucan, ZHANG Xiyuan, WANG Xinchang, ZHOU Keyu, ZHANG Hui, ZHANG Kuiyuan, ZHANG Rongbo, WANG Yongqing, ZHANG Qisheng. Research on Mobile Ultrasonic Rapid Electromagnetic Exploration Technology[J]. Geoscience, 2025, 39(02): 514-522.

Figures/Tables 12

Fig.1 Diagram of mobile ultrahigh frequency rapid electromagnetic exploration technology

Fig.2 Overall hardware architecture block diagram of the receive

Fig.3 Physical assembly diagram of the receiver hardware

Fig.4 Schematic diagram of analog-to-digital conversion circuit

Fig.5 Schematic diagram of signal conditioning circuit

Fig.6 FPGA program structure block diagram

Table 1 Test results of frequency range for supersonic controllable source electromagnetic receiver

信号频率(Hz)	电压幅度(V)	衰减倍数(dB)
1	1.00076	0.0066
10	1.00044	0.0038
100	1.00078	0.0068
1000	0.99885	-0.0100
10000	0.99947	-0.0460
100000	0.99617	-0.0330
600000	0.96660	-0.3000

Fig.7 Time-domain waveform of short-circuit noise in supersonic electromagnetic receiver

Table 2 Self-test results of apparent resistivity for supersonic controllable source electromagnetic receiver

信号频率 (Hz)	电场输入电压 (V)	磁场输入电压 (V)	电场测量电压 (V)	磁场测量电压 (V)	理论视电阻率 (Ω∙m)	测得视电阻率 (Ω∙m)	相对误差ε (%)
1	0.50	0.50	0.503	0.502	1266.5	1270.400000	0.304
10	0.50	0.50	0.503	0.502	126.65	127.050000	0.316
100	0.50	0.50	0.503	0.502	12.665	12.707000	0.327
1000	0.50	0.50	0.504	0.503	1.2665	1.271400	0.389
10000	0.50	0.50	0.503	0.502	0.12665	0.127010	0.287
100000	0.50	0.50	0.502	0.501	0.012665	0.012705	0.311
600000	0.50	0.50	0.494	0.493	0.0021194	0.002119	0.403

Fig.8 Upper computer software displays the spectrum analysis results

Fig.9 Upper computer software displays the overall results

Fig.10 Stratagem EH4 electromagnetic system data acquisition results

References 16

[1]	CAGNIARD L. Basic theory of the magneto-telluric method of geophysical prospecting[J]. Geophysics, 1953, 18(3): 605-635.
[2]	GOLDSTEIN M A, STRANGWAY D W. Audio-frequency magnetotellurics with a grounded electric dipole source[J]. Geophysics, 1975, 40(4): 669-683.
[3]	汤井田, 何继善. 可控源音频大地电磁法及其应用[M]. 长沙: 中南大学出版社, 2005: 39-40.
[4]	王胜涛, 林昌洪, 王旭东. 发射电流波形对瞬变电磁一维正反演的影响[J]. 现代地质, 2023, 37(1):99-106.DOI:10.19657/j.geoscience.1000-8527.2022.059.
[5]	刘庆斌. 串联谐振式人工源射频大地电磁发射机的研制[D]. 长沙: 中南大学, 2023.
[6]	张荣薄, 王猛, 张魁元, 等. 超音频可控源大地电磁发射系统关键技术研发[C]// 中国地球物理学会地球物理技术委员会第十届学术会议——“探索地学仪器原始创新致力地球物理技术突破” 研讨会论文集.成都, 2023: 84-85.
[7]	刘钟尹, 陈小斌, 王培杰, 等. 可控射频大地电磁法的野外观测实验和数据处理新技术 C]// 2021年中国地球科学联合学术年会论文集(七)—专题十九环境与灾害地球物理检测和监测的前沿技术与先进装备研究进展、专题二十城市地下介质成像和探测、专题二十一现代工程地球物理技术进展与应用. 2021: 45-46.
[8]	陈兴朋, 王亮, 龙霞, 等. CSRMT正交水平发射源电磁场分布规律研究[J]. 物探与化探, 2024, 48(3): 721-735.
[9]	BASTANI M, PERSSON L, MEHTA S, et al. Boat-towed radio-magnetotellurics: A new technique and case study from the city of Stockholm[J]. Geophysics, 2015, 80(6): B193-BB10.
[10]	BASTANI M, SAVVAIDIS A, PEDERSEN L B, et al. CSRMT measurements in the frequency range of 1-250 kHz to map a normal fault in the Volvi basin, Greece[J]. Journal of Applied Geophysics, 2011, 75(2): 180-195.
[11]	MUTTAQIEN I. Controlled source radiomagnetotelluric method applications in near surface geophysics[D]. Köln: Universitaet zu Koeln, 2018.
[12]	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. DOI
[13]	徐永锋. 可控源射频大地电磁(CSRMT)系统发射机技术研究[D]. 北京: 中国科学院大学, 2014.
[14]	PEDERSEN L B, PERSSON L, BASTANI M, et al. Airborne VLF measurements and mapping of ground conductivity in Sweden[J]. Journal of Applied Geophysics, 2009, 67(3): 250-258.
[15]	SPIES B R, EGGERS D E. The use and misuse of apparent resistivity in electromagnetic methods[J]. Geophysics, 1986, 51(7): 1462-1471.
[16]	YUAN Z Z, WANG Y Q, LIU S H, et al. Research and development of ADS 1271 based distributed engineering seismic acquisition unit[C]// 2016 Third International Conference on Digital Information Processing, Data Mining, and Wireless Communications (DIPDMWC).July 6-8, 2016. Moscow, Russia.IEEE, 2016: 302-306.