Geo-INQUIRE installation: BedrettoLab testbed (TA3-82-1)

Hosting team: Liliana Vargas Meleza, Marian Hertrich, Antonio Rinaldi, Frederick Massin, Pascal Edme and Mathilde Wimez (ETHZ)

Transnational access principal investigator: Prof. Dr. Gregor Hillers (Karlsruhe Institute of Technology, Germany)

ORCID: 

Homepage: 

LinkedIn: 

Transnational access team: Dr. Emmanuel Gaucher (Karlsruhe Institute of Technology, Germany)

Project title: Fault Zone Coda Wave Imaging

Project acronym: FZCOWI

Project report ID: C4_TA3-82-1_1

Date of visit: Aug-Sep 2025 Remote planning sessions; 13-24 October 2025 Data acquisition; Feb – May 2026 Remote access.

Geo-INQUIRE Virtual Access: 

Data/Products: 

We aim to reconstruct cross-correlation functions between all receiver pairs using multiply-scattered waveforms excited by the energetic sweeps. Details of the sweeps are not important as long as they generate a sufficiently scattered broadband wavefield that supports the convergence of the correlations. The repeated sweep activities along the hot-water injection (Figure 1) allows us to construct stable correlation functions at different times. We are not interested in the ballistic arrivals reconstructed by the correlation but analyze the coda part of the converged correlation functions for signatures of arrival time or waveform changes. The coda waves travel longer in the medium, including the water injected fault, compared to the direct or ballistic waves, and are thus more sensitive to small changes. The correlation coda wave sensitivity to medium changes has been established in numerous environments across a range of scales. Here, the controlled experiment in the Bedretto underground lab facilities allows us to systematically investigate possible relationships between the injected water in a fault and the waveform changes in the correlation coda waves. We plan to apply a newly developed coda wave change inversion approach to the obtained observations. This would be a first, because we plan to employ newly developed probabilistic sensitivity distributions (kernels) that are specifically designed for the narrow fault zone structures, and that have been only applied in synthetic experiments. The active seismic data collected for the FZCOWI project is available at https://doi.org/10.3929/ethz-c-000802239.

The FZCOWI experiment facilitated knowledge transfer between the Bedretto team and the KIT. The KIT is a key consortium partner for the development of a new underground laboratory in Germany, the GeoLaB (https://geolab.helmholtz.de/en/). The goal of GeoLaB is the development of economically plausible geothermal systems in naturally fractured and faulted reservoirs. The KIT team has a strong interest to benefit and learn from the BedrettoLab infrastructure in order to support the development of the GeoLaB scientifically, technically, and logistically. This project is therefore a training opportunity for KIT scientists that will be involved in the GeoLaB development.

Project report: FZCOWI by Gregor Hill