Abrupt changes of hydrothermal activity in a lava dome detected by combined seismic and muon monitoring

TL;DR

This study demonstrates that combining seismic noise monitoring with muon density tomography enables high-resolution detection of rapid hydrothermal activity changes beneath a volcano, improving short-term hazard assessment.

Contribution

It introduces a novel integrated monitoring approach using seismic and muon data to detect and localize hydrothermal activity changes with high temporal and spatial resolution.

Findings

Detected hydrothermal activity increase 50-100 m below volcano summit.

Improved localization of hydrothermal focus using combined methods.

Demonstrated potential for early warning of volcanic hazards.

Abstract

The recent 2014 eruption of the Ontake volcano in Japan recalled that hydrothermal fields of moderately active volcanoes have an unpredictable and hazardous behavior that may endanger human beings. Steam blasts can expel devastating ejecta and create craters of several tens of meters. The management of such hydrothermal hazards in populated areas is problematic because of their very short time constants. At present no precursory signal is clearly identified as a potential warning of imminent danger. Here we show how the combination of seismic noise monitoring and muon density tomography allows to detect, with an unprecedented space and time resolution, the increase of activity of a hydrothermal focus located 50 to 100 m below the summit of an active volcano, the La Soufri\`ere of Guadeloupe, in the Lesser Antilles. The present study deals with hydrothermal activity events at timescales of few hours to few days. We show how the combination of those two methods improves the risk evaluation of short-term hazards and the localization of the involved volumes in the volcano. We anticipate that the deployment of networks of various sensors including temperature probes, seismic antennas and cosmic muon telescopes around such volcanoes could valuably contribute to early warning decisions.