Detection Threshold and Location Resolution of the Alberta Geological Survey Earthquake Catalogue

Abstract

The Western Canada Sedimentary Basin (WCSB) is a low seismicity area, with fewer than fifteen cataloged M L>3.5 events since 1985 (Earthquakes Canada, 2013b). Since 1918, there have been more than 800 earthquakes reported in this region (Earthquakes Canada, 2013b), mainly clustered near the town of Rocky Mountain House (Rebollar et al. , 1982, 1984; Wetmiller, 1986), the Brazeau River (Schultz et al. , 2014), Fort St. John (Horner et al. , 1994), Turner Valley, Kinbasket Lake (Ellis and Chandra, 1981), and the Horn River Basin (BC Oil and Gas Commission, 2012); a single event larger than M L 4.5 was also reported near Snipe Lake (8 March 1970, 18:52:18 UTC; see Milne, 1970). The most active of these clusters is in the Strachan D‐3A gas field near Rocky Mountain House, where 146 events were recorded over a span of 23 days in 1980 (Wetmiller, 1986). Many of these aforementioned clusters have been conjectured as induced by gas extraction (Baranova et al. , 1999), waste water disposal (Horner et al. , 1994; Schultz et al. , 2014), or hydraulic fracturing operations (BC Oil and Gas Commission, 2012; Farahbod et al. , 2014). Historically, the compilation of the Earthquakes Canada Catalogue (EqCC) has been the responsibility of Natural Resources Canada (NRCan). More recently, a new initiative was taken by the Alberta Geological Survey (AGS) to improve the earthquake catalog in an effort to better understand the tectonics and seismicity of Alberta (AB). Interested readers are referred to Stern et al. (2013) for specific details on the methodology, station parameters, and earthquake locations of the AGS catalog. Overall, the quality and density of documented earthquakes is subject to the performance of the recording array (Fig. 1). Similar to the EqCC, the AGS catalog includes continuous waveform data from the Canadian National Seismic Network (CNSN); …