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

Figure 3

Typical events (top) from family 1, filtered signals between 0.3 and 1 Hz (mid), and spectral density vectors (bottom). The signals frequency content is varied, yet low frequency content is important as depicted above. Horizontal axis is time and vertical axis is counts.