航空电磁技术在冻土调查中的探测能力分析  

Capabilities of airborne electromagnetic methods to detect permafrost

作　　者：孙思源 余学中 谢汝宽 何怡原 单希鹏 李诗珺 SUN Si-Yuan;YU Xue-Zhong;XIE Ru-Kuan;HE Yi-Yuan;SHAN Xi-Peng;LI Shi-Jun(China Aero Geophysical Survey&Remote Sensing Center for Natural Resources,Beijing 100083,China)

机构地区：[1]中国自然资源航空物探遥感中心,北京100083

出　　处：《物探与化探》2022年第1期104-113,共10页Geophysical and Geochemical Exploration

基　　金：中国地质调查局项目“青藏高原典型区冻土与地下水分布航空物探调查”(DD20211396)。

摘　　要：准确评估冻土三维分布和阶段性变化对我国气候、水资源、生态、工程建设等方面具有重要意义。我国多年冻土大多分布在高海拔地区,利用地面物探确定多年冻土厚度具有效率低、成本高、交通不便等问题,而依据电阻率差异的航空电磁技术具有较大优势。根据青海祁连地区冻土厚度、电阻率等信息构建地电模型,并针对AeroTEM时间域航空电磁系统和Impulse频率域航空电磁系统,通过模拟冻土电阻率、厚度、冻土下低阻层、飞行高度和线圈角度变化,分析不同条件下时间域和频率域航空系统一维正演电磁响应差异,进而确定航空电磁技术对冻土顶、底界面的探测能力。模拟结果表明,在较低噪声水平下,Impulse频率域航空电磁系统可以根据融化冻土厚度确定沼泽、湿地及湿润草甸覆盖下的冻土顶界面;AeroTEM时间域系统可以确定冻土底界面,且当冻土下存在低阻层时,确定的底界面准确性将大幅提高。因此,在调查冻土厚度时,可综合利用频率域和时间域航空电磁数据,共同确定多年冻土的顶、底界面。本文研究成果将为航空电磁技术服务于我国冻土调查提供理论支撑。It is critical for climate,water resources,ecology,and engineering construction in China to accurately assess the three-dimensional distribution and periodic change of permafrost.Permafrost is mainly distributed in high-elevation regions in China.Therefore,the surface geophysical prospecting suffers from low efficiency,high cost,and poor transportation in determining the thickness of permafrost in China.In contrast,the airborne electromagnetic methods using resistivity difference enjoy great advantages.This study established a geoelectric model based on the thickness and resistivity of permafrost in Qilian area,Qinghai Province.Then,by simulating the thickness and resistivity of permafrost,low resistance layer under permafrost,flight height,and changes in the angles of receiver coils,this study analyzed the differences in electromagnetic responses under different conditions obtained from one-dimensional forward modeling using time-domain and frequency-domain airborne electromagnetic systems AeroTEM and Impulse.Based on this,this study assessed the capability of airborne electromagnetic methods to detect the top and bottom interfaces of permafrost.According to the simulation results,frequency-domain airborne electromagnetic system Impulse can determine the top interface of the permafrost covered by a marsh,wetland,or moist meadow according to the thickness of melted permafrost under a low noise level.In comparison,time-domain airborne electromagnetic system AeroTEM can determine the bottom interface of the permafrost,with the determination accuracy significantly improving when low-resistivity layers occur beneath the permafrost.Therefore,the top and bottom interfaces of permafrost can be jointly determined using frequency and time-domain airborne electromagnetic data.The results of this study will provide theoretical support for the future application of airborne electromagnetic methods to permafrost surveys in China.

关 键 词：冻土 航空电磁 一维正演 厚度 探测能力 

分 类 号：P631[天文地球—地质矿产勘探]