Objectives

The objectives of this project are:

  1. To complete the installation of our remote telemetered seismograph station just outside Calgary by constructing a vault for our three-component broadband and short-period vertical seismometers, by upgrading the present data-transmission system, and by establishing an appropriate data-management system.
  2. To monitor the seismicity, both locally (the Calgary area) and regionally (S Alberta, SE British Columbia, NW Montana, N Idaho), in collaboration with the Geological Surveys of both Canada and the USA (the GSC and the USGS) and other agencies, with a view to assessing seismic risk, both natural (of tectonic origin) and induced (due to oilfield, mining, or dam-construction activity).
  3. To provide an educational and informational resource for students, as well as the public, and to provide data for graduate-student research into such topics as earthquake risk, oilfield seismicity, deep-Earth structure, etc.
  4. To contribute in a continuing way to the mutual exchange of teleseismic data with the GSC and the USGS.

Background

The Department of Geology and Geophysics at the University of Calgary (U of C) owns a short-period Kinemetrics Ranger earthquake seismometer and Kinemetrics direct-write recording drum. This system has been provisionally installed for the last few years at the Rothney Astrophysical Observatory (RAO) run by the Department of Physics and Astronomy (U of C), just south of Calgary near Priddis, about 30 km from the campus. This location, on the concrete basement floor of the RAO, has turned out to be quite sensitive and fairly quiet. It is also located close enough to the campus with a virtual line of sight, so that a UHF radio link between the RAO and the U of C, which has been in operation for about four years, is functioning very successfully. The telemetered data are recorded on the visual drum which is displayed in the window of the Gallagher Library, near the main entrance of the Earth Sciences building (U of C).

In order to outfit our station properly, we have purchased three broadband Kinemetrics seismometers. These will be installed in an orthogonal three-component configuration and, together with the short-period vertical, will constitute a so-called four-component station. There is a Kinemetrics chronometer at the RAO owned by Physics and Astronomy that will be available to us for accurate timing of the seismograms after necessary repairs to the chronometer are carried out. These repairs will make up a part of the costs we will have in acquiring and setting up the electronic components needed to upgrade the data telemetering from one to four seismic channels and the computerized management of the data at the U of C. The funds we have available at this point are just sufficient to cover this instrumentation, provided that Physics and Astronomy can contribute to the data-link upgrade as expected.

Rationale

The four earthquake stations of the GSC that are closest to the Priddis site are those at Waterton, Alberta, (~200 km south), Edmonton (~300 km north), Mount Dainard, B.C. (~350 km northwest), and Penticton, B.C. (~425 km west-southwest). There is therefore a large area around Calgary with no seismograph station (particularly to the southeast since the station formerly at Suffield was last year moved to Waterton in 1993).

There are several reasons why there should be an earthquake station near Calgary.

The area is relatively quiet seismically but just barely makes it into Zone 1 on the seismic zoning map (based on peak-horizontal-velocity) of the National Building Code of Canada. [Zones range from 0 (least active) to 6 (most active).] Calgary has been shaken twice in the last 11 years, once by the Borah Peak (central Idaho) shock of 1983 and again by the Milk River (southern Alberta) quake of 1984. These events, particularly the former, alarmed many Calgarians on upper floors of tall buildings but were also felt near ground level. There is low-level seismicity - of uncertain origin - associated with some areas where there has been significant removal of hydrocarbons from the subsurface, such as near Turner Valley, within 20 km of our station, Rocky Mountain House, about 150 km north of Calgary, and the Fort St. John area of B.C.

There is low to moderate seismicity in the Rocky Mountain Trench, about 125 km from Calgary at its closest approach. Roughly where the Trench intersects the US border, there is some activity in the Waterton-Glacier area, as well as to the north in the Blairmore-Fernie coal-mining district and to the south near Flathead Lake, Montana. In the mountains of the Blairmore-Fernie-Waterton region, there are geologically well documented instabilities, such as led to the Frank slide. We have received requests for information and collaboration from coal-mining companies in the Blairmore-Fernie area who have experienced collapses of large rockmasses in their mines. In an environmental-impact study (including seismicity) preceding construction of the Oldman River dam, just north of Waterton, there was a regrettably inadequate catalogue of earthquake activity for the area. Changes in rock-pore pressure after dam impoundment is widely believed to have induced many earthquakes worldwide. And an explosives company in Calgary has approached us regarding collaborative monitoring and analysis of the vibrational effects of their blasting. We have not to date been equipped to contribute very much to such undertakings.

Project Description

The RAO is constructed on top of a hill or ridge. There are a number of areas on the slope up to the RAO building where a vault could be excavated into the hillside to take advantage of the noise suppression of a buried structure without the expense of a full excavation from surface. Sites are available that are sufficiently removed from the telescopes that their noise will not be a problem, yet close enough to the RAO for electric power and antenna connection. We require a concrete floor that is mechanically isolated from the vault walls, in contact with consolidated rock, and with some form of drainage. Local geologists and the contractor who built the RAO tell us that such rock is accessible close to the surface. Some trenching to the RAO building will likely be necessary and the vault will need to be insulated. The Design Office of the U of C Physical Plant had sketched out a vault design incorporating our ideas. However, their vault-construction estimate exceeded $20,000. We are therefore searching for other construction alternatives.