Preprints
https://doi.org/10.5194/egusphere-2024-586
https://doi.org/10.5194/egusphere-2024-586
01 Mar 2024
 | 01 Mar 2024
Status: this preprint is open for discussion.

Selection and Characterisation of the Target Fault for Fluid-Induced Activation and Earthquake Rupture Experiments

Peter Achtziger-Zupančič, Alberto Ceccato, Alba Simona Zappone, Giacomo Pozzi, Alexis Shakas, Florian Amann, Whitney Maria Behr, Daniel Escallon Botero, Domenico Giardini, Marian Hertrich, Mohammadreza Jalali, Xiaodong Ma, Men-Andrin Meier, Julian Osten, Stefan Wiemer, and Massimo Cocco

Abstract. Performing stimulation experiments at approximately 1 km depth in the Bedretto Underground Laboratory for Geosciences and Geoenergies necessitates identifying and characterizing the target fault zone for on-fault monitoring of induced fault-slip and seismicity, a current challenge in understanding seismogenic processes. We discuss the multidisciplinary approach for selecting the target fault zone for the experiments planned within the Fault Activation and Earthquake Ruptures (FEAR) project, aiming to induce fault-slip and seismicity up to a magnitude 1.0 earthquake while enhancing monitoring and control of fluid-injection experiments.

Structural geological mapping, remote sensing, exploration drilling and borehole logging, ground-penetration radar, and laboratory investigations were employed to identify and characterize the target fault – a ductile-brittle shear zone several meters wide with intensely fractured volume persisting over 100 m. Its orientation in the in-situ stress field favors reactivation in normal to strike-slip regimes. Laboratory tests showed slight velocity strengthening of the fault gouge. The fault's architecture, typical for crystalline environments, poses challenges for fluid flow, necessitating detailed hydraulic and stress characterization before each of the FEAR experiments. This multidisciplinary approach was crucial for managing rock volume heterogeneity and understand implications for the dense monitoring network. Successfully identifying the fault sets the stage for seismic activation experiments commencing in spring 2024.

Peter Achtziger-Zupančič, Alberto Ceccato, Alba Simona Zappone, Giacomo Pozzi, Alexis Shakas, Florian Amann, Whitney Maria Behr, Daniel Escallon Botero, Domenico Giardini, Marian Hertrich, Mohammadreza Jalali, Xiaodong Ma, Men-Andrin Meier, Julian Osten, Stefan Wiemer, and Massimo Cocco

Status: open (until 18 Apr 2024)

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  • RC1: 'Comment on egusphere-2024-586', Richard Haslam, 12 Apr 2024 reply
Peter Achtziger-Zupančič, Alberto Ceccato, Alba Simona Zappone, Giacomo Pozzi, Alexis Shakas, Florian Amann, Whitney Maria Behr, Daniel Escallon Botero, Domenico Giardini, Marian Hertrich, Mohammadreza Jalali, Xiaodong Ma, Men-Andrin Meier, Julian Osten, Stefan Wiemer, and Massimo Cocco
Peter Achtziger-Zupančič, Alberto Ceccato, Alba Simona Zappone, Giacomo Pozzi, Alexis Shakas, Florian Amann, Whitney Maria Behr, Daniel Escallon Botero, Domenico Giardini, Marian Hertrich, Mohammadreza Jalali, Xiaodong Ma, Men-Andrin Meier, Julian Osten, Stefan Wiemer, and Massimo Cocco

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Short summary
We detail the selection and characterization of a fault zone for earthquake experiments within the FEAR project at the Bedretto Lab. Overcoming challenges of data collection near faults, FEAR conducts experiments to study earthquakes. We selected the fault from the structural inventory at the Rotondo granite based on geometry, monitorability, and hydro-mechanical properties, employing remote sensing, borehole logging, and geological mapping to yield a 3D model.