EGU2020-22449
https://doi.org/10.5194/egusphere-egu2020-22449
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Magma Degassing as a Source of Long‐Term Seismicity at Volcanoes: The Ischia Island (Italy) Case

Mauro Di Vito1, Elisa Trasatti1, Valerio Acocella2, Carlo Del Gaudio1, Gregor Weber3, Ida Aquino1, Stefano Caliro1, Giovanni Chiodini1, Sandro de Vita1, Ciro Ricco1, and Luca Caricchi3
Mauro Di Vito et al.
  • 1Istituto Nazionale Geofisica e Vulcanologia, INGV, Roma, Italy
  • 2Università Roma Tre, Roma, Italy
  • 3University of Geneva, Geneva, Switzerland

Transient seismicity at active volcanoes poses a significant risk in addition to eruptive activity.
This risk is powered by the common belief that volcanic seismicity cannot be forecast, even on a long
term. Here we investigate the nature of volcanic seismicity to try to improve our forecasting capacity. To this
aim, we consider Ischia volcano (Italy), which suffered similar earthquakes along its uplifted resurgent
block. We show that this seismicity marks an acceleration of decades‐long subsidence of the resurgent block,
driven by degassing of magma that previously produced the uplift, a process not observed at other
volcanoes. Degassing will continue for hundreds to thousands of years, causing protracted seismicity and
will likely be accompanied by moderate and damaging earthquakes. The possibility to constrain the future
duration of seismicity at Ischia indicates that our capacity to forecast earthquakes might be enhanced when
seismic activity results from long‐term magmatic processes, such as degassing.

How to cite: Di Vito, M., Trasatti, E., Acocella, V., Del Gaudio, C., Weber, G., Aquino, I., Caliro, S., Chiodini, G., de Vita, S., Ricco, C., and Caricchi, L.: Magma Degassing as a Source of Long‐Term Seismicity at Volcanoes: The Ischia Island (Italy) Case, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22449, https://doi.org/10.5194/egusphere-egu2020-22449, 2020

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Presentation version 1 – uploaded on 21 Apr 2020
  • CC1: Questions and answers from the live chat during EGU2020, Michael Heap, 11 May 2020

    Q: Are your team currently monitoring gas fluxes along these faults?

    A: Yes there are periodical measurements in the area for gas fluxes. The computed deggassing rate is comparable is 12/18 kTon/year. The computed degassing rates are 12-18 kt/yr and are negligible amount w.r.t. emissions at Ischia (e.g., at Donna Rachele)

    Q: Interesting work. Your study seems suggesting that the “high” subsidence rate is at the origin of the seismicity. Is it correct? Thus the seismicity is and efects rather than the cause of the acceleration.

    A: Thank you for your question. Yes the seismicity is an effect of the deformation along the boudaries of the block