可移动式超音频快速电磁勘探技术研究

doi:10.19657/j.geoscience.1000-8527.2025.010

摘要/Abstract

摘要：

可控源射频大地电磁法(controlled source radio magnetotelluric method, CSRMT) 是一种新型的频率域近地表电磁测深技术。该方法基于传统的大地电磁法(magnetotelluric, MT),通过设置人工发射源,并在远距离处观测电磁场的各个分量,从而推断地下结构。本文提出的可移动式超音频快速电磁勘探技术基于可控源射频大地电磁法(CSRMT),它可以利用广播电台发射的AM信号、VLF海军电台发射的甚低频电磁信号、国家授时中心发射的电磁信号这些已有的人工场源进行电磁勘探,可通过运载车装配超音频可控源电磁接收机进行移动式勘探,不需要像传统的CSMT中那样现场布置人工场源,可使勘探效率大幅提升,节约了布置和维护发射机的勘探成本。本项技术中所研发可移动式超音频可控源电磁接收机的带宽范围达到1 Hz~600 kHz,采样率高达2.5 MHz,动态范围达到138 dB,视电阻率测量精度优于3%。

关键词: 可控源射频大地电磁法, 电磁接收机, FPGA, 视电阻率

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

中图分类号:

阮宏宇, 王猛, 林祖灿, 张袭远, 王心畅, 周珂宇, 张辉, 张魁元, 张荣薄, 汪永青, 张启升. 可移动式超音频快速电磁勘探技术研究[J]. 现代地质, 2025, 39(02): 514-522.

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.

图/表 12

图1 可移动式超音频快速电磁勘探技术示意图

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

图2 接收机整体硬件结构框图

Fig.2 Overall hardware architecture block diagram of the receive

图3 接收机硬件组装实物图

Fig.3 Physical assembly diagram of the receiver hardware

图4 模数转换电路示意图

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

图5 信号调理电路示意图

Fig.5 Schematic diagram of signal conditioning circuit

图6 FPGA程序结构框图

Fig.6 FPGA program structure block diagram

表1 超音频可控源电磁接收机频率范围测试结果

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

图7 超音频电磁接收机短接噪声时域波形

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

表2 超音频可控源电磁接收机视电阻率自测结果

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

图8 上位机软件显示频谱分析结果

Fig.8 Upper computer software displays the spectrum analysis results

图9 上位机软件显示总体结果

Fig.9 Upper computer software displays the overall results

图10 Stratagem EH4 电磁系统数据采集结果

Fig.10 Stratagem EH4 electromagnetic system data acquisition results

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