Oscillations in hydrothermal systems as a source of periodic unrest at caldera volcanoes: Multiparameter insights from Nisyros, Greece

Gottsmann, Joachim; Carniel, Roberto; Coppo, Nicolas; Wooller, Luke; Hautman, Stefanie and Rymer, Hazel (2007). Oscillations in hydrothermal systems as a source of periodic unrest at caldera volcanoes: Multiparameter insights from Nisyros, Greece. Geophysical Research Letters, 34(L07307)

DOI: https://doi.org/10.1029/2007GL029594

Abstract

Unrest at collapse calderas is generally thought to be triggered by the arrival of new magma at shallow depth. But few unrest periods at calderas over the past decades have culminated in volcanic eruptions and the role of hydrothermal processes during unrest is drawing more and more attention. Here we report joint and simultaneous continuous multi-parameter observations made at the restless Nisyros caldera (Greece), which reveal non-steady short-term oscillatory signals. The combined geodetic, gravimetric, seismic and electromagnetic records indicate that the oscillations are associated with thermohydromechanical disturbances of the hydrothermal system. The dominant period of oscillation (40–60 min) indicates short-term processes most likely associated with instabilities in the degassing process. Amplitudes of recorded geodetic and gravimetric signals are comparable to amplitudes observed at other periodically restless calderas. We conclude that shallow aqueous fluid migration can contribute significantly to periodic unrest, explaining the lack of eruptions in many cases of unrest.

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