Local Subsidence of active volcanoes measured by Synthetic Aperture Radar
Abstract
An active volcano deforms even during its dormant period, as well as its active period, although the deformation during its dormant period has paid less attention than its active period. Here we investigated the deformation of Asama and Usu volcanoes, Japan, during their dormant periods by Synthetic Aperture Radar Interferometry.
In Usu volcano, we found subsidence at lava domes intruded during previous eruptions in 1943--1945, 1977--1982, and 2000. SAR images in the last 25 years indicate that the subsidence at the 1977--1982 and 2000 lava intrusion sites decays over time, while the subsidence at the 1943--1945 lava intrusion site is constant in the last 25 years. We modeled the observed deformation as the thermal contraction of the intruded lava dome. However, the apparent thermal diffusivity of the 1977--1982, and 2000 lavas is on order larger than lab-derived values. We interpret this discrepancy that abundant groundwater, which is present beneath the volcano, effectively releases the heat in the lava dome, especially in the early periods after the intrusion. In Asama volcano, Sentinel-1 images indicate Line-of-sight (LOS) extension and shortening up to 7 mm/yr in the northern and southeastern flank. While the subsidence in the northern flanks coincides with the 1783 lava flow, the observed deformation cannot be due to thermal contraction but could be interpreted as hydrothermal activity and flank instability. The LOS shortening in the southeastern flank is likely due to flank instability.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMV028.0001A
- Keywords:
-
- 4314 Mathematical and computer modeling;
- NATURAL HAZARDS;
- 4336 Economic impacts of disasters;
- NATURAL HAZARDS;
- 8485 Remote sensing of volcanoes;
- VOLCANOLOGY;
- 8488 Volcanic hazards and risks;
- VOLCANOLOGY