Distinguishing cryoseisms from earthquakes in Alberta, Canada

Characterizing the ground-motion signature of various event types is important for event discrimination and for the development of reliable earthquake catalogues. Small-magnitude seismic events are often enigmatic and determining their cause can be challenging. This is because there are various sources of energy (e.g., rock bursts, construction blasts, cultural noise, etc.) that generate seismic waves similar to those from small-magnitude earthquakes. A sequence of eight unusual small-magnitude (local magnitude, ML, of -0.17 to 1.39) seismic signals were detected in the area surrounding the Brazeau Reservoir and river (Alberta), beginning in mid-2014. Detailed analyses of the waveforms and spectra for these events, as well as their timing, strongly suggest that at least seven of these events are cryoseismic signals associated with freeze-up on the reservoir and Brazeau River.