• journal_title：Bulletin of the Seismological Society of America
• Contributor：W. H. Bakun ; M. C. Stickney ; G. C. Rogers
• Publisher：Seismological Society of America
• Date：2011-
• Format：text/html
• Language：en
• Identifier：10.1785/0120110054
• journal_abbrev：Bulletin of the Seismological Society of America
• issn：0037-1106
• volume：101
• issue：6
• firstpage：3065
• section：Short Notes

The largest historical earthquake in the northern Great Plains occurred on 16 May 1909. Our analysis of intensity assignments places the earthquake location (48.81° N, 105.38° W) close to the Montana–Saskatchewan border with an intensity magnitude M_I of 5.3–5.4. Observations from two seismic observatories in Europe give an average M_s value of 5.3. The 1909 earthquake is near an alignment of epicenters of small earthquakes in Montana and Saskatchewan and on strike with the mapped Hinsdale fault in Montana. Thus, the 1909 earthquake may have occurred on a 300-km-long seismically active fault, which could have seismic-hazard implications for the region, particularly for the hydraulically emplaced earth-filled Fort Peck Dam, constructed in the 1930s on the Missouri River in northeast Montana.