3:45 PM - 4:00 PM
[SVC41-08] Temporal changes in the resistivity structure beneath Aso volcano during the last eruption period from November 2014 to October 2016, inferred by ACTIVE observations
Keywords:Aso, ACTIVE, controlled-source, monitoring, magma, resistivity structure
In this study, we developed a new three-dimensional (3-D) inversion code for ACTIVE responses by adopting an edge-based finite-element method (e.g. Schwartzbach and Haber, 2013) and the data-space inversion method (e.g. Siripunvaraporn et al., 2005), in order to infer a common background resistivity structure and temporal changes corresponding to ACTIVE responses between August 2014 and August 2015. A modified version of the 3-D resistivity structure obtained from AMT data in 2004 and 2005 (Kanda et al., 2015, JpGU) were used as an initial model for inversions for a common background resistivity structure. In inversions for the background structure, the inversion model space is the whole area beneath the ground surface, while the model space for inference of temporal changes is restricted to a prism located beneath the crater whose bases are squares 400m on a side. It was found from our inversions that the conductive zone is located 200m beneath the ground on the western side of the crater in the background structure. On the other hand, as temporal changes in the resistivity structure, a zone which became resistive were imaged just below the crater, while a conductive change was inferred 200 – 400 m beneath the crater. The former change is attributed to the escape of ground water due to inclement of temperature and pressure before the magmatic eruptions, while the conductive change is to upcoming fresh magma from deeper part.
In this presentation, we report and discuss temporal changes in the resistivity structure between August 2014 and August 2015, inferred by the inversions mentioned above. Furthermore, we plan to comprehensively discuss changes in the resistivity structure beneath Aso volcano and related volcanic activities during the last active period using all the ACTIVE data available including August 2017.