Fig. 5
From: Long-duration seismicity and their relation to Copahue volcano unrest
The NB tremor occurred at 01:20:00 UTC on 01 January 2015. a Energy in the range 0.5–10 Hz. b Spectral peaks with energy above 95% of the maximum. c Averaged rectilinearity (R) of each sample in the range ±0.05 Hz when σR⩽0.1 . The normalized PDF of averaged horizontal azimuth ΘH\(\Theta _H\)(d), and vertical incidence ΘV\(\Theta _H\) (e) in the range ±0.1 \(\pm 0.1\) Hz around the characteristic peaks. Black rectangular boxes in b and c show the 1.6-Hz secondary peak that is filtered in the statistical analysis in d