Seismic noise correlation imaging of the Vendenheim geothermal reservoir - implications for understanding the Nov 2019 seismic crisis
Between Nov 2019 and Jan 2021, a series of seismic events were felt by the population of Strasbourg, France. The first major event (MLv3.0) on Nov. 12, 2019 was part of a seismic swarm that began a few days earlier, lasted four months and was located under the La Robertsau area at a depth of 5 km.
Recently, Schmittbuhl et al (2021) were able to use local seismic data to provide a precise analysis of seismic activity and concluded that the temporal correlation with activity in the wells at the Vendenheim deep geothermal site (GEOVEN), the similarity in depth between the bottom of the wells and the earthquake hypocentres, the absence of local seismicity prior to recent earthquakes, known regional geological structures, including regional crustal faults, strongly support the possible triggering of events by deep geothermal activities despite the relatively large distance (4-5 km) for the November 2019 earthquakes.
An innovative way of complementing these results obtained from local seismicity monitoring, in order to improve understanding of triggering mechanisms at a distance or over long periods of time, is to seek to image progressive reservoir deformation using complementary information: the use of seismic background noise, and to calculate the temporal variations that could be linked to perturbations in the reservoir's elastic properties. Seismic interferometry using ambient noise has become a powerful seismological tool for continuously monitoring temporal variations in subsurface velocity. Quantifying in situ reservoir responses to stress transients provides a better understanding of the evolution of geothermal reservoirs. By exploiting the stress dependence of seismic velocity changes, it is possible to study the temporal evolution of the reservoir stress state of this geothermal field and shed light on the origin of the loss of control of induced seismicity.
Funded by: Eurométrople de Strasbourg in collaboration with Cercle Gutenberg
Project partner:
Prof. Hayrullah Karabulut from Bogacizi University Kandilli Observatory and Earthquake research, Turquie
ITES budget: 50 000€
Project duration: 2022-2025