Data from Seismic Stations

Encoded in the data from the seismic stations are several key types of information: the arrival time of the seismic waves at the seismic station, the first motion of ground displacement (up or down, called polarity), the amount (amplitude) of displacement shown by the height of the waveforms (squiggles) on the recording, and the duration of displacement.

The origin time and location (latitude, longitude, and depth) of an earthquake are calculated from the arrival times of seismic waves at three or more stations. For example, how far away an earthquake is can be estimated by the difference in time between the arrival of the P wave and the arrival of the S wave, analogous to estimating how far away a lightning strike is by counting the seconds between the flash and the thunder.

To more robustly determine an earthquake location, seismologists use a computer program, with information about the seismic stations and the local or regional Earth structure, to calculate the location of the earthquake from a starting position of the closest seismic station.  Accurate locations require many stations and a good spatial distribution of the stations.

 

The federal government has monitored earthquakes in Canada since the late 1800s. By the 1950s (e.g. Banff station 1955 – 1966), the federal network of seismic stations was capable of detecting earthquakes of magnitude 6 and larger throughout Canada. The addition of two Alberta stations and several BC stations allowed the detection of hundreds of smaller earthquakes in southwestern Alberta (Suffield station 1966 to 1993, Edmonton station 1966 to the present, Waterton station 1993 to the present, as well as close by BC stations 1966 to the present). 

The Alberta Geological Survey began monitoring earthquakes in 2010. We monitor seismic stations in and around Alberta that are owned by us or by other agencies. Since 2010, we have installed more than a dozen seismic stations in Alberta, mostly in areas where we see increases in earthquakes. Our network of stations (a group of seismic stations that record ground movement in a region) is known as RAVEN, which comes from Regional Alberta ObserVatory for Earthquake Studies Network. The RAVEN stations send us data from local earthquakes and moderate or larger earthquakes from around the world in real time using satellite and cellular technology.