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The continuous volcanic activity at Semeru volcano (Indonesia) from 2014 to 2023 investigated with remote sensing data (SAR, thermal and optical) and geodetic modelling.

Federico Galetto1, Diego Reale2, Eugenio Sansosti2, Diego Coppola3, Matthew Pritchard1

Abstract

Semeru (Indonesia) is erupting since 2014, but its volcanic activity remains poorly constrained. Here we used a combination of different remote sensing data to improve the understanding of Semeru. Time series of deformation, obtained with Synthetic Aperture Radar Interferometry (InSAR) from Sentinel-1 data, show a constant subsidence of the SE flank occurred from 2014 to 2023. We modelled this deformation with a Boundary Element Method. Results show that the subsidence is related with a limited (~1x106 m3) deflation of a shallow (~1 km from the surface) reservoir. Thermal data from MIROVA show peaks in the Volcanic Radiative Power and in the cumulative radiant energy (VRE) related with the main lava flow eruptions. By differencing high resolution (2m) Digital Elevation Models (DEM) derived from optical data (EarthDEMs), we found a bulk volume of ~46x106 m3 erupted from 2014 to 2020. We used this volume to calibrate the VRE and to calculate the erupted volume directly from VRE for periods not covered by EarthDEM, allowing also the near-real-time estimation of the erupted volumes from MIROVA data. The discrepancy between the erupted volume and the modelled volume suggests that the shallow reservoir of Semeru is constantly fed by new magma that balances most of the erupted magma (or that directly fed the persistent eruption). This study highlights that the combination of different remote sensing data can be used to monitor, quantify, and interpret the volcanic activity in poorly monitored and studied volcanoes, highlighting the importance of remote sensing data for volcanology.