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Steps toward Monitoring a Deep Geothermal Reservoir in Northern Alsace with Ambient Seismic Noise Interferometry
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 80th EAGE Conference and Exhibition 2018, Jun 2018, Volume 2018, p.1 - 5
Abstract
We apply ambient noise coda wave interferometry to almost 6 years of continuous data at two short period seismic stations located in the vicinity of a deep geothermal EGS project located in Rittershoffen (northern Alsace, France). Using a multiple reference approach, we compute the matrices of the optimal stretching coefficient and related maximum coherence for every pair of days and for the nine pairs of components and apply a weighted scheme to recover seismic velocity variations over time.
For the 3 analysed frequency bands (2–5Hz, 1–3Hz, 0.1–0.5Hz) we observe stable cross correlation functions and coherent velocity variations. We can associate most of them either to artefacts related to temporal changes in the frequency content of the ambient noise or to natural phenomena such as changes in the water table elevation. However, a sudden decrease of coherence, not related to changes in the noise sources, is observed just after an hydraulic stimulation that occurred in one of the wells.