Resistivity mapping in the Tatun Volcano Group, Northern Taiwan, revealed by VLF-MT surveys

Abstract

In a volcanic region, unstable conditions of the surface geology result in natural hazards such as landslides. The present study aims to examine the properties of the formation near the surface in the Tatun Volcano Group (TVG), Northern Taiwan. Dense Very Low Frequency magnetotelluric (VLF-MT) surveys were conducted to obtain the near-surface resistivity. A geostatistical approach and stochastic simula­tion were used to examine the continuity of the data, and to render the spatial distri­bution of the resistivity. The results show that the estimated range is consistent with the length scale of the geological features such as the hydrothermal phenomena and volcanic edifices. The estimated distribution of the resistivity successfully identified a fresh lava (≥ 1000 Ωm), a lineament-bearing, weathered lava (≤ a few hundred Ωm), and hydrothermal areas (≤ 30 Ωm). On the basis of the present study, we expect further detailed geophysical investigations will be performed from the viewpoint of hazard mitigation in the TVG.