Thermo-Hydro-Mechanical Model and Caprock Deformation Explain the Onset of an On-going Seismo-volcanic Unrest

Waheed Gbenga Akande; Quan Gan; Dave Cornwell; Luca de Siena

doi:10.1029/2020JB020449

Thermo-Hydro-Mechanical Model and Caprock Deformation Explain the Onset of an On-going Seismo-volcanic Unrest

Waheed Gbenga Akande, Quan Gan^* (Corresponding Author), Dave Cornwell, Luca de Siena

^*Corresponding author for this work

Johannes Gutenberg University Mainz

Research output: Contribution to journal › Article › peer-review

10 Citations (Scopus)

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Abstract

Modeling seismicity at volcanoes remains challenging as the processes that control seismic energy release due to fluid transport, heat flow, and rock deformation are firmly coupled in complex geological media. Here, we couple fluid‐flow and mechanical (deformation) simulators (TOUGHREACT–FLAC3D) to reproduce fluid‐induced seismicity at Campi Flegrei caldera (southern Italy) in isothermal (HM) and nonisothermal (THM) conditions. The unique ability of the Campi Flegrei caprock to withstand stress induced by hot‐water injections is included in the model parametrization. After pore pressure accumulation is guided by a combination of thermal and hydromechanical interactions, contrasting compressive and extensional forces act on the basal and top parts of the caprock, respectively. Then, pressure perturbation and caprock deformation induce fractures that allow hot fluids uprising to pressurize the overlying fault, driving it toward failure and triggering seismicity. Under similar mechanical boundary conditions, the induced thermal effects prompt seismic slip earlier but with higher seismic magnitudes when (1) thermal equilibrium is preserved and (2) the thermal contrast is enhanced due to increased fluid injection temperatures. The results indicate that numerical models of volcano seismicity must consider the influence of rock‐sealing formations to obtain more robust, accurate, and realistic seismic predictions at volcanoes. The proposed models satisfactorily reproduce the magnitude–depth distribution of the swarm (October 5, 2019), preceding the two strongest earthquakes recorded in 35 years at the caldera (3.1 and 3.3—on December 6, 2019, and April 26, 2020, respectively) using hot‐water injection from depth.

Original language	English
Article number	e2020JB020449
Number of pages	26
Journal	Journal of Geophysical Research: Solid Earth
Volume	126
Issue number	3
Early online date	24 Mar 2021
DOIs	https://doi.org/10.1029/2020JB020449
Publication status	Published - Mar 2021

Bibliographical note

Acknowledgments
The authors are grateful to the Editor, Prof. Ben‐Zion Yehuda, and the reviewers: Prof. Micol Todesco and an anonymous reviewer, whose comments and recommendations have significantly improved the quality of this work. The authors acknowledge the financial support of the Petroleum Technology Development Fund (PTDF) Nigeria for this research. The comparison of our models with monitoring data was made possible by the outstanding efforts of the staff at the INGV‐Osservatorio Vesuviano, who provide weekly information about geophysical parameters at the Campanian volcanoes (http://www.ov.ingv.it/ov/en/bollettini/272-campi-flegrei-bollettini-settimanali.html). The authors are particularly grateful to them for providing the accurate magnitude and hypocentral parameters used to create the earthquake magnitude–depth plot in this study. The authors also extend our appreciation to Prof. Derek Elsworth for his generous support in the FLAC3D software license usage.

Keywords

Campi Flegrei caldera
caprock deformation
induced seismicity
thermo‐hydro‐mechanical modeling
volcano seismicity
thermo-hydro-mechanical modeling

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Akande_etal_Thermo‐Hydro‐Mechanical_Model_VOR
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Cite this

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title = "Thermo-Hydro-Mechanical Model and Caprock Deformation Explain the Onset of an On-going Seismo-volcanic Unrest",

abstract = "Modeling seismicity at volcanoes remains challenging as the processes that control seismic energy release due to fluid transport, heat flow, and rock deformation are firmly coupled in complex geological media. Here, we couple fluid‐flow and mechanical (deformation) simulators (TOUGHREACT–FLAC3D) to reproduce fluid‐induced seismicity at Campi Flegrei caldera (southern Italy) in isothermal (HM) and nonisothermal (THM) conditions. The unique ability of the Campi Flegrei caprock to withstand stress induced by hot‐water injections is included in the model parametrization. After pore pressure accumulation is guided by a combination of thermal and hydromechanical interactions, contrasting compressive and extensional forces act on the basal and top parts of the caprock, respectively. Then, pressure perturbation and caprock deformation induce fractures that allow hot fluids uprising to pressurize the overlying fault, driving it toward failure and triggering seismicity. Under similar mechanical boundary conditions, the induced thermal effects prompt seismic slip earlier but with higher seismic magnitudes when (1) thermal equilibrium is preserved and (2) the thermal contrast is enhanced due to increased fluid injection temperatures. The results indicate that numerical models of volcano seismicity must consider the influence of rock‐sealing formations to obtain more robust, accurate, and realistic seismic predictions at volcanoes. The proposed models satisfactorily reproduce the magnitude–depth distribution of the swarm (October 5, 2019), preceding the two strongest earthquakes recorded in 35 years at the caldera (3.1 and 3.3—on December 6, 2019, and April 26, 2020, respectively) using hot‐water injection from depth.",

keywords = "Campi Flegrei caldera, caprock deformation, induced seismicity, thermo‐hydro‐mechanical modeling, volcano seismicity, thermo-hydro-mechanical modeling",

author = "Akande, {Waheed Gbenga} and Quan Gan and Dave Cornwell and {de Siena}, Luca",

note = "Acknowledgments The authors are grateful to the Editor, Prof. Ben‐Zion Yehuda, and the reviewers: Prof. Micol Todesco and an anonymous reviewer, whose comments and recommendations have significantly improved the quality of this work. The authors acknowledge the financial support of the Petroleum Technology Development Fund (PTDF) Nigeria for this research. The comparison of our models with monitoring data was made possible by the outstanding efforts of the staff at the INGV‐Osservatorio Vesuviano, who provide weekly information about geophysical parameters at the Campanian volcanoes (http://www.ov.ingv.it/ov/en/bollettini/272-campi-flegrei-bollettini-settimanali.html). The authors are particularly grateful to them for providing the accurate magnitude and hypocentral parameters used to create the earthquake magnitude–depth plot in this study. The authors also extend our appreciation to Prof. Derek Elsworth for his generous support in the FLAC3D software license usage.",

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AU - Gan, Quan

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AU - de Siena, Luca

N1 - Acknowledgments The authors are grateful to the Editor, Prof. Ben‐Zion Yehuda, and the reviewers: Prof. Micol Todesco and an anonymous reviewer, whose comments and recommendations have significantly improved the quality of this work. The authors acknowledge the financial support of the Petroleum Technology Development Fund (PTDF) Nigeria for this research. The comparison of our models with monitoring data was made possible by the outstanding efforts of the staff at the INGV‐Osservatorio Vesuviano, who provide weekly information about geophysical parameters at the Campanian volcanoes (http://www.ov.ingv.it/ov/en/bollettini/272-campi-flegrei-bollettini-settimanali.html). The authors are particularly grateful to them for providing the accurate magnitude and hypocentral parameters used to create the earthquake magnitude–depth plot in this study. The authors also extend our appreciation to Prof. Derek Elsworth for his generous support in the FLAC3D software license usage.

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N2 - Modeling seismicity at volcanoes remains challenging as the processes that control seismic energy release due to fluid transport, heat flow, and rock deformation are firmly coupled in complex geological media. Here, we couple fluid‐flow and mechanical (deformation) simulators (TOUGHREACT–FLAC3D) to reproduce fluid‐induced seismicity at Campi Flegrei caldera (southern Italy) in isothermal (HM) and nonisothermal (THM) conditions. The unique ability of the Campi Flegrei caprock to withstand stress induced by hot‐water injections is included in the model parametrization. After pore pressure accumulation is guided by a combination of thermal and hydromechanical interactions, contrasting compressive and extensional forces act on the basal and top parts of the caprock, respectively. Then, pressure perturbation and caprock deformation induce fractures that allow hot fluids uprising to pressurize the overlying fault, driving it toward failure and triggering seismicity. Under similar mechanical boundary conditions, the induced thermal effects prompt seismic slip earlier but with higher seismic magnitudes when (1) thermal equilibrium is preserved and (2) the thermal contrast is enhanced due to increased fluid injection temperatures. The results indicate that numerical models of volcano seismicity must consider the influence of rock‐sealing formations to obtain more robust, accurate, and realistic seismic predictions at volcanoes. The proposed models satisfactorily reproduce the magnitude–depth distribution of the swarm (October 5, 2019), preceding the two strongest earthquakes recorded in 35 years at the caldera (3.1 and 3.3—on December 6, 2019, and April 26, 2020, respectively) using hot‐water injection from depth.

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Thermo-Hydro-Mechanical Model and Caprock Deformation Explain the Onset of an On-going Seismo-volcanic Unrest

Abstract

Bibliographical note

Keywords

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