Discrimination of Earthquake and Blast Seismicity in Western Alberta

Abstract:

Recorded seismicity in western Alberta is caused by natural and induced earthquakes or blast events from

mining and quarry operations. Accurate discrimination of earthquakes from blast events is crucial for evaluating

recent seismicity with respect to the historical catalog and for assessing seismic hazards associated with

naturally occurring or induced seismicity. In general, blast events are discriminated from earthquakes based on

their proximity to active mines and quarries in addition to day-of-week and time-of-day timing patterns. In some

parts of western Alberta, however, seismicity originates in regions with active mines, historical earthquake

seismicity, and hydraulic fracturing operations. Based on timing patterns or event locations alone, natural or

induced seismicity may be misidentified as mining activity. Several studies report that relative differences in

Fourier or response spectra can be used to discriminate blast and earthquake events. Other studies report that

the relative timing and amplitude of seismic phases may provide useful metrics for classifying blast events.

Here we propose an alternative method that accounts for both differences in phase spectra and phase timing

and amplitude. In particular, we evaluate the normalized time integral for characteristic functions of particle

motion from confirmed blast and earthquake events recorded by regional Alberta seismic networks. We

then use these time-integral profiles to re-classify events that are initially categorized as suspected blasts

based on timing pattern and event location indicators.