Use of magnetic surveying in landslide analysis at the boundary between the granite

Abstract

A helicopter-borne magnetic survey is conducted at the landslide-prone area of the boundary zone between the Hida belt and the green tuff in southwestern Toyama Prefecture, and the effectiveness of the airborne magnetic survey is considered in relation to its ability to verify the magnetic structure in the slope regions. Analysis using the reduction-to-thepole (RTP) method is applied to airborne magnetic anomaly data in the survey after diurnal correction and removal of the International Geomagnetic Reference Field (IGRF)-7. In addition, the magnetic properties are measured, and x-ray powder diffraction of boring cores drilled in the region of the Funatsu granite is examined. According to the magnetic anomaly distribution using the RTP method, the area of igneous rock distribution shows high magnetic anomaly, and the hydrothermal alteration zone and colluvial deposit area of landslides show low magnetic anomaly. It has become clear through the study of boring cores that pole magnetic anomaly by airborne magnetic survey refl ects the distribution of many magnetization substances in the shallow part. Aeromagnetic surveys are an effi cient method of identifying both the distribution of collapsed soil sediments in the Neogene and areas of high landslide potential in Funatsu granitic rock.