Hypocentre of the 1925 Charlevoix-Kamouraska earthquake
The main shock was recorded by 29 seismograph stations worldwide. The evening of the main shock, seismologist E.A. Hodgson located the epicentre at about 70 km downstream from Quebec City using the horizontal component records from the station at Ottawa. He first deduced the azimuth from the relative amplitudes on the North-South and East-West components; then he calculated the epicentral distance from the difference in arrival times between the P and the S waves. The same evening, he was able to tell the press about the epicentre!
The epicentre location in Charlevoix-Kamouraska was confirmed by the analysis of seismograms recorded on numerous seismograph stations. In Canada, five stations recorded this earthquake: Ottawa, Halifax, Toronto, Saskatoon and Victoria. Field trips, conducted by E.A. Hodgson during the next two years confirmed the location of the epicentre (see scientific work).
According to more recent work (Stevens, 1980), the earthquake occurred near Île aux Lièvres, an area where numerous earthquakes with magnitudes larger than 4.0 have occurred during the XXth century. Another study has established the focal depth at about 10 km beneath the surface (Bent, 1993), a depth similar to the average for Charlevoix earthquakes.