Fig. 4
From: Integration of distributed acoustic sensing for real-time seismic monitoring of a geothermal field
Spectral content of the DAS recordings at the study site. Panel a: Evolution with depth of the frequency content of the strain-rate data acquired on two consecutive days. The probabilistic power spectral density (PPSD) is computed from each time-series, using 192 data segments of 30 min. The color scale indicates the median PPSD at the sensor depth. The frequency band from 5 to 40 Hz is bounded by the dashed lines. Panel b Evolution with depth of the spectral energy (the integral of the PPSD) in the 5–40 Hz frequency range (black curve and bottom black abscissa) in parallel with the amplitude of TH3 cement bond log (CBL) (red curve and top red abscissa). The colored background represents the lithological units defined in Fig. 1 (c). The spectral energy curve and the CBL amplitude have been filtered with a moving average filter of 10 m. Panel c: Same as panel b, but considering the energy below 0.1 Hz (black curve)