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

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.

Hydrothermal alteration of andesitic lava domes can lead to explosive volcanic behaviour

“…We further note that hydrothermal alteration typically weakens volcanic rock 19,56–58,64 and that such weakening could reduce the stability of the dome and further increase the likelihood of unexpected dome explosions and associated hazardous pyroclastic density currents 4,19,65–67 . On the basis of our findings, mapping the extent and evolution of hydrothermal alteration at active lava domes using geophysical methods such as electrical 20,21,68,69 and muon tomography 70–72 , spectroscopic methods such as visible and infrared spectroscopy 36,73 , and gas monitoring 26 emerge as an important tools to help anticipate dome explosions at otherwise unpredictable dome-forming volcanoes.…”

Hydrothermal Alteration on Composite Volcanoes: Mineralogy, Hyperspectral Imaging, and Aeromagnetic Study of Mt Ruapehu, New Zealand

“…Complementing ground and remote sensing methods, geophysical techniques, including electromagnetic resistivity, gravity and aeromagnetic surveys (Finn et al, 2018; Miller & Williams‐Jones, 2016), magnetotelluric surveys (Abdallah et al, 2020; Bowles‐Martinez & Schultz, 2020; Jones et al, 2008; Matsunaga et al, 2020), seismicity (Pu et al, 2020), and muon imaging (le Gonidec et al, 2019), have also been used to infer internal architecture and locate hydrothermal fluids and zones of demagnetization of the host rock. These methods are often complemented with numerical methods (e.g., inversion) and spring and gas chemistry data to gain insights into the thermal and chemical evolution of shallow magmatic‐hydrothermal systems (Berlo et al, 2020; Collard et al, 2020; Gresse et al, 2018; Miller et al, 2020).…”

Imagery of internal structure and destabilization features of active volcano by 3D high resolution airborne electromagnetism

“…Water circulation also contributes to the overall complexity and instability of volcanoes. Heating of the water table by magma injections and accumulations at depth generates extensive hydrothermal systems underneath active volcanoes 5 . The induced circulation of acid hydrothermal fluids leads to intense leaching and alteration 6 .…”