For some events magnitude was not calculated either because the reporting seismic stations were too distant or response files were not available for the reporting stations. In this situation a magnitude of -999 was assigned.
The points represent a unique seismic event determined by date, time, lat, long, and depth.
The data points represent earthquakes that were capable of being located due to their size, proximity to seismic stations, and signal to noise ratio of the seismic stations. Events whose phase arrivals were not detected and picked on more than two seismic stations were not located and included in the database. Events that were judged to be surface mining blasts due to location and time of day or to blast reports from industry were not included in the earthquake database. The dataset is considered generally complete for events above a 2.5 magnitude for most of Alberta, although it approaches a 3.0 magnitude threshold for the northern Albera, and is lower than 2.0 magnitude threshold for the foothills and southern Alberta.
Blasts from mining activities such as known surface coal mines or limestone quarries were not included in the dataset. The criteria for determining that an event was a blast include: location at a known mine, time of event during mine operations, spectral content of event. Locations of events north of latitude 55 N and in the Peace River Arch region were more poorly constrained and therefore time of day was used as a descriminator. Some of these events labeled as blasts could have been mislabeled.
Data acquisition: Raw seismic waveforms were acquired, using BRTT's Antelope real-time seismic acquisition software, from three sources: near-real time data from Earthquake Canada (EC) for the Canadian National Seismograph Network (CNSN) and the Alberta Telemetered Seismograph Network (ATSN) part of POLARIS consortium using the Antelope program orb2orb; near-real time data transfers from Incorporated Research Institutes for Seismology (IRIS) for the Montana Regional Seismograph Network (MRSN) and the American Advanced National Seismic System (ANSS) using the Antelope program slink2orb; and offline raw data collection from the Canadian Rockies and Alberta Network (CRANE) biannually from compact flash cards in station dataloggers. The CRANE data was converted to the Standard for the Exchange of Earthquake Data (SEED) format and merged with the real-time data.
Data processing: batch processing of the waveform data was performed with the Antelope dbdetect module to detect seismic signals in the raw data, dbgrassoc module to associate detections into seismic events with phase arrivals flagged, and the dbpick or smartpick modules were used to perform visual scans and manually pick phase arrivals for missed events.
Data analysis: The phase arrivals were imported into the dbloc2 module . The placement of picks were refined, then using the GENLOC hypocentre inversion algorithm to produce earthquake locations giving the latitude, longitude, depth, date, and time in Universal Co-ordinated Time (UTC). The dbevproc module was used to measure and calculate magnitudes.
GIS shapefile creation: The solutions containing the latitude, longitude, depth, date and time of origin, and magnitude of each earthquke was stored in an Antelope relational database. The database of earthquake locations was transferred to a comma separated spreadsheet using the db2xml program. The csv spreadsheets were converted to shapefiles using ArcGIS.