Finding Possible Precursors for the 2015 Cotopaxi Volcano Eruption Using Unsupervised Machine Learning Techniques

Figure 2

(a) Sample of low frequency seismic signal; (b) power spectra. The components of the feature vector are the peaks of both the blue line (maximum spectral values in 0.2 Hz intervals) and red line (exact spectral value sampled in 0.2 Hz steps).

(a)

(b)