The 1860 magnitude 6.1 Charlevoix, Quebec, earthquake: macroseismic information and interpretation

Abstract

The Moment Magnitude (M) 6.1 Charlevoix earthquake occurred on October 17, 1860, at around 6:15 am local time. The epicentre was located in the Charlevoix Seismic Zone (CSZ), probably in the surroundings of the towns of La Malbaie, Baie-St-Paul and Rivière-Ouelle. The main shock was felt from New Brunswick to the east to Southern Ontario to the west and as far south as New Jersey, more than 800 km from the epicentre. Newspapers in Quebec City reported the damage caused by this earthquake in the regions of Charlevoix and Kamouraska, Quebec. There, damage was reported to many houses, and the intensity was greatest in the communities of Rivière-Ouelle, (south shore of the St. Lawrence River) and La Malbaie (north shore). Some damage to masonry was also reported in Quebec City, about 110 km from the epicentre. The Moment Magnitude is approximated to be 6.1 from a direct conversion from the assumed Local Magnitude (ML) 6.0. Based on the impact of other Charlevoix earthquakes, the region affected by the 1860 event is in general agreement with this magnitude. This Open File Report presents the macroseismic information and its ratings on the Modified Mercalli Intensity (MMI) Scale for a total of 91 locations in Canada (69) and the United States (22). For each locality, the felt information is rated on the MMI scale and tabulated in a Microsoft Excel spreadsheet. The original text of many of the newspaper accounts was copied and when possible, images of the newspaper clipping are added. The Open File also provides a GoogleEarth kmz file that allows the felt information reports to be viewed in a spatial tool.