The Southern Ontario Seismic Network (SOSN) consists of 11 three component short period seismic stations located mainly in the Toronto-Hamilton-Niagara area of Ontario, Canada. The network is operated by the University of Western Ontario for Ontario Power Generation and has been in operation since 1991. Its purpose is to obtain information on the seismicity and seismic hazards of a region of Southern Ontario in which a number of nuclear power stations are located. Although the region covered by the network is not as active as other areas of Canada such as the St. Lawrence Valley, it has still experienced a number of small earthquakes in the past. Larger earthquakes have occurred in adjacent areas of New York State (Attica, 1929, M=5.7), Northern Ontario (Temiscaming 1935, M=6.2), Eastern Ontario (Cornwall, 1944, M=5.7), Leroy, Ohio (near Cleveland, 1986, M=5.0), Pennsylvania-Ohio border (1998, M=5.4), and Northern Ontario (70 km NE of North Bay, Jan. 1 2000, M=5.2).
The first 4 stations (WLVO, ACTO, TYNO and STCO) were completed late in 1991. The next 2 stations (BRCO and PKRO) were added in 1996 to provide an improvement of the coverage of the ground motion within 20 km of the Bruce and Pickering nuclear power stations. Four remote call-up stations (RD01, RD02, RD03, and RD04) were added in 1999 to obtain more information concerning the nature of the cluster of earthquakes in the Hamilton-Burlington area. In 1999 one of the former UWO network stations (LDN) near London Ontario was upgraded and also added to the SOSN network. The University of Western Ontario has been operating a small 3 station FM network (LDN, ELF and DLA) near London, Ontario since 1976. The stations of the SOSN are also being augmented with 2 Geological Survey of Canada (GSC) stations (EFO in the Niagara Peninsula and SADO on the Canadian Shield east of Georgian Bay).
Over the past 9 years the network has been in operation more than a 100 local earthquakes have been detected and more than half of these have been located in the western Lake Ontario area. The largest earthquake (M = 3.8) in western Lake Ontario region happened on Nov. 26, 1999 in Lake Ontario at a distance of 16 km SE from the town of Pickering.