Earthquake Monitoring

Earthquake Monitoring

The federal government has monitored earthquakes in Canada since the late 1800s and by 1950 had the capacity to detect earthquakes of magnitude 6 and larger throughout Canada. While there has been no recorded evidence of any major destructive earthquake occurring in Alberta to date, hundreds of micro to moderate earthquakes have occurred since 1950.
Although there appears to be little threat from major earthquakes, it is important to understand the seismicity patterns within Alberta. Amongst other reasons, there is evidence that in some cases earthquakes worldwide have been related to hydrocarbon production, such as fluid extraction, enhanced recovery methods, or wastewater injection.

The Alberta Earthquake Studies Project

The Alberta Earthquake Studies Project (AESP) was launched by the AGS in 2009 to locate and characterize earthquakes in Alberta. It began with a collaborative effort with the University of Calgary to investigate potential locations for six of their telemetered seismic stations, creating the Alberta Telemetered Seismic Network (ATSN). In 2010, the project acquired Boulder Real Time Technologies (BRTT) Antelope seismic acquisition software and began collecting and analyzing seismic waveforms in near real time. Since then, the AGS has forged partnerships with other organizations to create a robust seismic monitoring network for the province.



Figure 1. Seismic station with seismometer, digitizer, and electronics buried in a polypropylene vault. On the surface are the solar panel and satellite dish.

The data from this network from 2006 to present (updated annually) are compiled into a comprehensive earthquake catalogue. The earthquake catalogue establishes a baseline of seismic activity to help understand the pattern of natural seismicity as well as detect any unusual patterns caused by human activity, including any linkages to hydrocarbon production or waste disposal.

Seismic Stations in and around Alberta

The density of the seismic stations is critical to effective earthquake monitoring. Building a dense network of both telemetered and offline stations increases the sensitivity and scope of detection. The greater the density of seismic stations, the smaller the earthquake that can be detected and located.

For this reason, the AESP has been working with the University of Alberta, the University of Calgary, Western University (WO), and Natural Resources Canada (NRCan) to install and maintain additional seismic stations. AESP installed seven seismic monitoring stations in 2014 and two additional stations in 2015.
We are currently acquiring data from eight seismic monitoring networks:

The CRANE (PER), RAVEN, ATSN, TD, MRSN, and USArray waveform data are available in near real time from the Incorporated Research Institutions for Seismology (IRIS), which allows us to detect and locate earthquakes in Alberta.



Figure 2. Seismic stations in and around Alberta.

Earthquakes in Alberta

Alberta is a prairie province bordering the eastern flank of the Rocky Mountains. Its geographic location is characterized by a transition from a relatively low-seismicity intraplate regime to a more active foreland belt. It is also an area of active energy resource development, including coal, natural gas, conventional oil, and unconventional hydrocarbon resources.
Seismic events in Alberta tend to be between micro (0 on the Richter, or local magnitude [ML] scale) and minor (3 ML) in size. Moderate earthquakes with a magnitude greater than 4 ML are rarer (see table below for a classification of earthquake sizes based on magnitude).

Table 1. Magnitudes of Earthquakes

Magnitude (ML) Earthquake Class Effects of Earthquakes Recording of Earthquakes
4 to 6 Moderate or Medium Often felt, may cause minor damage Readily recorded on distant near-surface seismographs
2 to 4 Small or minor May be felt above 2.5 ML Readily recorded on regional near-surface
Less than 2 Micro Usually not felt Events above 1 ML recorded on local near-surface seismographs.
Less than 0 Micro Not felt Not recorded at the surface, but readily recorded on downhole geophones used for microseismic monitoring.

Alberta is not well known for its earthquakes, and most Albertans may be surprised to discover that the province experienced 605 earthquakes between 1985 and 2011. Although these earthquakes were very small, it is a significant figure when compared with just 41 recorded earthquakes in Saskatchewan during the same time. However, comparing Alberta with B.C. is also revealing; in southwestern B.C., there are approximately 400 earthquakes recorded each year.