September 11, 2012
The Alberta Microseismicity Project is part of the Geohazards Program. The project started in 2009 with the goal to monitor natural and induced seismicity to compile a comprehensive earthquake catalogue of Alberta. An earthquake catalogue (seismic database) will help us understand the natural seismicity patterns and recognize unusual patterns from anthropogenic activities. We will also produce a baseline of natural seismicity to detect unusual seismic activity in the future.
Historically, Alberta has been a seismically quiet part of North America. The federal government began serious monitoring of Alberta seismic activity in the mid-1960s. Prior to that, less than two dozen earthquakes had been recorded. From 1985 to 2010, Earthquakes Canada recorded 471 earthquakes in Alberta. The vast majority of these are natural earthquakes that occurred in a southeast trend along the Rocky Mountain Foothills.
In 1980, the Geological Survey of Canada and the University of Alberta studied a cluster of earthquakes southwest of Rocky Mountain House because of suspected links to gas production. These events are the only suspected cases of induced seismicity in Alberta studied in detail.
We are working with Alberta universities to install seismic stations, develop regional and site-specific seismic velocity models and monitor stations in near-real time.
Alberta uses seismic stations from five networks:
The number of CNSN stations changed very little from the mid-1960s to the 1990s. With the two Alberta stations (EDM near Edmonton and SES near Suffield) and the B.C. station (MCE near Mica Creek), the federal government could detect and locate earthquakes as small as 2 ML (local magnitude on the Richter scale) in southwestern Alberta. Since the 1990s, the number of B.C. stations increased and the Suffield station was replaced with one station near Waterton (WALA), allowing the federal government to detect earthquakes as small as 1 ML for southwestern Alberta. However, the minimum detectable magnitude for the northern and eastern regions was around 3 ML because of the distribution and number of stations.
In 2006, the University of Alberta installed six offline CRANE stations in central Alberta, increasing the number of offline stations to 13 by 2010. Offline stations store the data instead of transmitting in near-real time. These data are collected every six months.
In 2009 and 2010, we worked with the University of Calgary to install eight ATSN stations, five in northern Alberta and three in southern Alberta. The data from these stations are available in near-real time and allow us to detect and locate earthquakes in northwestern Alberta as small as 2 ML.
In 2011, we collaborated with the University of Alberta to replace the seismic monitoring equipment in six pre-existing sites (HON, HLO, RW3, NOR, LYA and CZA) and to install equipment at two new sites (RDR replacing a station near Red Deer and CLK near Cold Lake), bringing the total number of CRANE stations to 16. The data from these stations are manually downloaded twice a year and merged with the real-time data to increase the coverage. The data are used for structural analysis and microseismic monitoring.
We use Boulder Real Time Technologies' Antelope Seismic software package to acquire near-real time data from the CNSN and ATSN stations via the Pacific Geoscience Centre (western branch of the Geological Survey of Canada), and from the MRSN and USArray stations via IRIS DMC, to automatically process and archive the data.
We review all Alberta events to determine their nature and to refine the locations, depths and times prior to saving in the seismic database.