Magnitudes and locations of the 1811-1812 New Madrid, Missouri, and the 1886 Charleston, South Carolina, earthquakes
We estimate locations and moment magnitudes M and their uncertainties for the three largest events in the 1811–1812 sequence near New Madrid, Missouri, and for the 1 September 1886 event near Charleston, South Carolina. The intensity magnitude M I , our preferred estimate of M , is 7.6 for the 16 December 1811 event that occurred in the New Madrid seismic zone (NMSZ) on the Bootheel lineament or on the Blytheville seismic zone. M I is 7.5 for the 23 January 1812 event for a location on the New Madrid north zone of the NMSZ and 7.8 for the 7 February 1812 event that occurred on the Reelfoot blind thrust of the NMSZ. Our preferred locations for these events are located on those NMSZ segments preferred by Johnston and Schweig ( 1996 ). Our estimates of M are 0.1–0.4 M units less than those of Johnston ( 1996b ) and 0.3–0.5 M units greater than those of Hough et al. ( 2000 ). M I is 6.9 for the 1 September 1886 event for a location at the Summerville–Middleton Place cluster of recent small earthquakes located about 30 km northwest of Charleston.