Rainfall-induced Gravity Movement of the Unzen-Fugendake Volcanic Dome Analysis combining Ground-Radar Interferometry and XRAIN Rainfall radar system

Abstract

Lava domes created by volcanoes often cause pyroclastic and debris flows, which have a significant impact on the surrounding infrastructure and population and have been the subject of much research. However, because volcanic domes tend not to survive the eruptions that form them, the instability of domes that survive eruptions such as Unzen Fugendake in Japan is both a poorly understood process and a danger. Therefore, the present contribution aims to (1) Displacement and precipitation from 2018 to 2020 for lava domes at Unzen volcano and their relationship to earthquakes, and (2) Haar wavelet analysis to understand the response of displacement to precipitation. The method is based on dome displacement from the Unzen Ground Based Synthetic Aperture Radar system and 48-hour rainfall from the MP radar rain gauge system. As a result, the authors confirmed the following: (1) precipitation of 150 mm or more in 48 hours tends to increase the vertical fluctuation of the dome, and even rainfall of less than 100 mm per 48 hours has a similar effect when it is repeated in an intensive manner; (2) After precipitation, major dome displacement can take days or weeks to occur, and is not instantaneous like the dome collapses in Soufriere and Merapi.