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

Y Le Gonidec,D Gibert,J De Bremond D’Ars,B Kergosien,J Marteau,M Rosas-Carbajal,J.-C Ianigro,B Carlus

doi:10.1038/s41598-019-39606-3

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 events in populated areas is problematic because of their very short time of occurrence. 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 (at timescales of few hours to few days) of a hydrothermal spot located 50 to 100 m below the summit of an active volcano, the La Soufrière of Guadeloupe, in the Lesser Antilles. 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.

Highlights

Phreatic and hydrothermal eruptions frequently occur in volcanic geothermal fields[1]
To detect potential early warning signals, we use seismic and temperature data acquired with our high time-resolution (4 ms) arrays of sensors located on the summit of La Soufrière lava dome together with one of our 6 cosmic muon telescopes, located inside the 30-August fracture (Fig. 1)
We focus our analysis on this 3-day period by combining temperature, seismic and muon monitoring to relate the transient signature of the hydrothermal activity to physical properties

Summary

Introduction

Phreatic and hydrothermal eruptions frequently occur in volcanic geothermal fields[1]. Volcanoes with moderate activity and well-developed hydrothermal systems often experience decades of intense hydrothermal activity smearing out potential warning signals announcing an imminent destabilization[7,8] The detection of such transient signals, possibly very localized in time and space, together with the quantification of hydrothermal volumes and amount of energy involved, constitute new challenges for modern volcanology. The recent hydrothermal activity at the summit of the lava dome is compatible with an increasingly vapor-dominated system favorable to local destabilization as shown by at least two small explosions that occurred in 2016 in the East-Napoléon vent (Fig. 1). Such hazardous environments result from rapid phenomena occurring inside the lava dome at time scales of few hours or days

Methods

Results

Conclusion