Earthquakes in Alberta (Microseismicity)

Project Goal

Alberta Geological Survey is creating a seismic database to understand the locations of earthquakes in Alberta. 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. This database will help us understand the natural background seismicity in Alberta, which will allow us to contribute to making probabilistic seismic-hazard calculations and recognize events that may be caused by human activities.

Project Background

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.

Seismic Stations

Alberta has seismic stations from three networks: Canadian National Seismograph Network (CNSN), owned and operated by the Geological Survey of Canada; Alberta Telemetered Seismograph Network (ATSN), owned and operated by the University of Calgary; and Canadian Rockies and Alberta Network (CRANE), owned and operated by the University of Alberta.

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.

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). 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.

Seismic Data Acquisition and Analysis

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), to automatically process and archive the data.

For Alberta events, we review the data to determine the nature of the events and refine their locations, depths and times.