Comparison of geophysical investigations for detection of massive ground ice (pingo ice)

Abstract

Six different geophysical investigations, (1) ground‐penetrating radar, (2) DC resistivity sounding, (3) seismic refraction, (4) very low frequency (VHF) electromagnetic, (5) helicopter borne electromagnetic (HEM), and (6) transient electromagnetic (TEM) techniques, were employed to obtain information on the ice body properties of pingos near Fairbanks, Alaska. The surface nuclear magnetic resonance (NMR) data were also compared from similar sites near one of the study pingos. The geophysical investigations were undertaken, along with core sampling and permafrost drilling, to enable measurement of the ground temperature regime. Drilling (ground truthing) results support field geophysical investigations, and have led to the development of a technique for distinguishing massive ice and overburden material of the permafrost. The two‐dimensional DC resistivity sounding tomography and ground‐penetrating radar profiling are useful for ice detection under heterogeneous conditions. However, the DC resistivity sounding investigation required high‐quality ground contact and less area coverage. The active layer thickness and the homogeneous horizontal structure of the overburden material are important parameters influencing detection of massive ice in permafrost for most methods such as seismic, TEM, or surface NMR.