Intraplate seismic hazard: Evidence for distributed strain and implications for seismic hazard - Intraplate Earthquakes - page 307

38˚

37˚

RF

36˚

35˚

−91˚ −90˚ −89˚ −88˚

Figure 12.3 NewMadrid seismic zone, including instrumentally recorded seismicity (black dots) and
inferred traces of the Cottonwood Grove fault (gray line; CGF) and Reelfoot fault (gray line; RF).
The location of the northern limb of the NMSZ is also indicated (gray line extending northeastward
from the northern end of the RF).

among the largest - if not the largest - earthquakes to have ever occurred in a so-called
Stable Continental Region (SCR; Johnston, 1996 ) . Ground motions from the principal
events were felt by individuals as far away as Canada, New England, and at a number of
locations along the Atlantic coast (Mitchill, 1815 ; Fuller, 1912 ; Nuttli, 1973b ; Street, 1982 ,
1984; Johnston, 1996 ) . Contemporary accounts document three principal mainshocks:
approximately 2:15 a.m. local time (LT) on December 16, 1811; around 8:00 a.m. LT
on January 23, 1812, and approximately 3:45 a.m. LT on February 7, 1812 (henceforth
NM1, NM2, and NM3, respectively). Additionally, a large aftershock to NM1 (NM1-A)
occurred near dawn on December 16, 1811. There is some documentation of energetic
aftershock sequences following each mainshock (Drake, 1815 ; McMurtie, 1819 ; Hough,
2009 ) .
As noted, rupture scenarios have been developed for the four principal 1811-1812 events
based on a number of lines of evidence (e.g., Johnston and Schweig, 1996 ; Figure 12.3 ) . Of
these, the association of NM3 with the Reelfoot thrust fault is the best supported by direct