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Geothermal Energy

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Figure 6 | Geothermal Energy

Figure 6

From: Characterization of ambient seismic noise near a deep geothermal reservoir and implications for interferometric methods: a case study in northern Alsace, France

Figure 6

Impact of the noise directivity on the CCF phase. Top left: cross-correlation functions band-pass filtered at 2-s period (0.5 Hz). The dashed lines indicate the phase speed of the Rayleigh waves averaged over the full network and measured via slant stack (2.45 km/s). Top right: time shift measured between the phase arrival time of each CCF and the time predicted by the average phase speed. A negative time shift corresponds to a phase arriving before the predicted one. Because of the chosen orientation convention, phase shifts measured on the positive (resp. negative) part of the CCFs are attributed to azimuths ranging from 180° to 360° (resp. 0° to 180°). Bottom left: synthetic distribution of the noise energy with back azimuth. Amplitudes are normalized so that the area below the curve is 1. Bottom right: synthetic time shifts predicted using the formula from Weaver et al. (2009) at 2 s in a homogeneous medium (2.45 km/s).

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