Early History of the Canadian Seismograph Network
The earliest reference to the use of seismological instruments in Canada occurs in a paper by Dawson (1870), where he says,
Note: A slight shock of earthquake was felt at Hawkesbury on the Ottawa on the 3rd January (1871). Dr. Smallwood states that though not appreciable in Montreal, it was indicated by the seismometer.
No further information about this instrument could be found.
McLeod and Callendar (1897), of McGill University, were apparently unaware of Dr. Smallwood's "seismometer". They reproduced a record of a magnitude 5 earthquake that occured near Montreal on March 23, 1897, made on a 3-component Ewing seismograph and stated, "This earthquake is the first of which a record was obtained in Canada." Their Ewing seismograph was configured to start automatically by the force of a shock, and it only operated on occasion.
At the suggestion of the British Association for the Advancement of Science, the Government of Canada decided to get involved in earthquake monitoring with the establishment of seismograph stations in eastern and western Canada. Two Milne seismographs were purchased by the Dominion Government Meteorological Service. The first seismograph, installed at Toronto in September 1897, became the first instrument to record continuously in Canada. It was later replaced by a pair of 'Milne-Shaw instruments]eqcani cnsn milneshaw eng in May, 1923.
The second instrument, a Milne horizontal-type seismograph, began operations in Victoria, B.C. on January 1, 1899. It was serial number ten of the original group of seismographs of this design. The paper speed of this instrument was 250 mm per hour, the static magnification was quoted as six, and the period was approximately 19 seconds. The instrument was operated by the Meteorological Service under the supervision of Mr. Baynes Reid, and later, of Mr. F. Napier Denison. In 1907, Mr. Denison designed and put into operation a second similar seismograph, and, in 1914, a Wiechert, 80 kg, vertical seismograph was added.
In 1905, responsibility for seismological observations was taken over by the newly-created Dominion Observatory, part of the Department of the Interior. In January 1906, a pair of Bosch-Omori photographic seismographs (one East-West and one North-South) began operation in Ottawa. The seismographs were able to capture the April 18, 1906 great San Francisco earthquake. In March 1912, an 80 kg vertical Wiechert was added. In 1915, a "Deformation Instrument" with a free period of about 30 seconds was set up at Ottawa. The Ottawa instruments were further augmented by two Milne-Shaw seismographs in 1922.
In January 1910, a station was opened at Saint-Boniface, near Winnipeg, Manitoba, as part of the North American Jesuit seismological network. It was then the fourth seismograph station in Canada. The station operated for more than 10 years before a fire destroyed the college and its seismograms in 1922.
In 1915, Mainka bifilar horizontal seismographs were installed at Dalhousie University in Halifax and at the University of Saskatchewan in Saskatoon.
During that time in British Columbia, the Gonzales observatory was built in 1916 by the Meteorological Service near Ross Bay along the Strait of Juan de Fuca. The three instruments mentioned above were then installed on piers in the basement of the observatory and orientated to record east-west, north-south, and vertical motion. It is told in Victoria that Mr. Denison would amaze visitors to the observatory by showing them that the building moved up and down with the rise and fall of the tides. Certainly the location was not ideal for a tiltmeter-type seismograph. In January 1923, two Milne-Shaw seismographs replaced the original Milne instrument.
Back east, from April 1925 until June 9, 1927, a Milne-Shaw instrument was operated at Ste-Anne-de-la-Pocatiere, Que., near the source of the February 28, 1925, Charlevoix-Kamouraska earthquake.
Unfortunately, none of these early instruments were very well adapted to recording local tremors, and hence their records could contribute little to the understanding of small local earthquakes. Indeed, until 1927, Canadian stations were only able to detect large, distant earthquakes (teleseisms). They were insensitive to earthquakes of magnitude less than 5 1/2. More sensitive, short-period seismographs only began regular operations in the beginning of 1928.
References:
- Hodgson, J.H., 1989. The Heavens Above and the Earth Beneath, a History of the Dominion Observatories: Part 1, To 1946; Geological Survey of Canada, Open File 1945, 193 pages
- Milne, W.G., 1955. Seismic activity in Canada, West of the 113th Meridian, 1841-1951. Publications of the Dominion Observatory, Ottawa, Vol. 18, 119-146.
- Smith, W.E.T., 1962. Earthquakes of eastern Canada and Adjacent areas 1534-1927; Publications of the Dominion Observatory vol. 26, no. 5.
- Stevens, A.E. 1980. A history of some Canadian and adjacent American seismograph stations. Bulletin of the Seismological Society of America, 70, 1381-1393.