• journal_title：Bulletin of the Seismological Society of America
• Contributor：John E. Ebel ; Megan Dupuy ; William H. Bakun
• Publisher：Seismological Society of America
• Date：2013-02-01
• Format：text/html
• Language：en
• Identifier：10.1785/0120110063
• journal_abbrev：Bulletin of the Seismological Society of America
• issn：0037-1106
• volume：103
• issue：1
• firstpage：588
• section：Short Notes

The Charlevoix, Quebec, earthquake of 20 October 1870 caused damage to several towns in Quebec and was felt throughout much of southeastern Canada and along the U.S. Atlantic seaboard from Maine to Maryland. Site‐specific damage and felt reports from Canadian and U.S. cities and towns were used in analyses of the location and magnitude of the earthquake. The macroseismic center of the earthquake was very close to Baie‐St‐Paul, where the greatest damage was reported, and the intensity magnitude M_I was found to be 5.8, with a 95% probability range of 5.5–6.0. After corrections for epicentral‐distance differences are applied, the modified Mercalli intensity (MMI) data for the 1870 earthquake and for the moment magnitude M 6.2 Charlevoix earthquake of 1925 at common sites show that on average, the MMI readings are about 0.8 intensity units smaller for the 1870 earthquake than for the 1925 earthquake, suggesting that the 1870 earthquake was M_I 5.7. A similar comparison of the MMI data for the 1870 earthquake with the corresponding data for the M 5.9 1988 Saguenay event suggests that the 1870 earthquake was M_I 6.0. These analyses all suggest that the magnitude of the 1870 Charlevoix earthquake is between M_I 5.5 and M_I 6.0, with a best estimate of M_I 5.8.

Online Material: Earthquake catalogs with distance to assignment epicenter and modified Mercalli intensity estimates.