The New Madrid seismic zone of the Central United States - Intraplate Earthquakes - page 179

Absence of a scarp along the Reelfoot South fault and absence of displacement at the
southern end of the Reelfoot North fault may indicate that the Reelfoot South fault did
not rupture during the New Madrid earthquakes of 1811-1812 (Hough and Page, 2011 ) .
Alternatively, the February 1812 earthquake may have been the only rupture that has
occurred along the full length of the Reelfoot fault during the Holocene.
7.3.4 Coseismic regional deformations
A number of landforms were formed or enhanced during the New Madrid earthquakes of
1811-1812 (Fuller, 1912 ; Mihills and Van Arsdale, 1999 ; Guccione, 2005 ; Csontos, 2007 ) .
Most obvious is the subsidence of Reelfoot Lake and uplift of the adjacent Lake County
uplift (Fuller, 1912 ; Russ, 1982 ; Stahle et al ., 1992 ) . Uplift along the Blytheville arch
in northeastern Arkansas and subsidence of the area immediately northwest of the arch
occurred in 1811 and during prehistoric faulting events ( Figure 7.2 ) . To be more specific,
uplift has been documented along the northwestern flank of the subcropping Blytheville
arch at the Manila high (Guccione et al ., 2000 ; Odum et al ., 2001 ) and the Marked Tree
high (Guccione, 2005 ) . Uplift of the Manila high partially impounded the Little River to
form the Big Lake sunkland and uplift of the Marked Tree high partially impounded the St.
Francis River to form the Lake St. Francis sunkland.
7.3.5 Seismicity and Reelfoot Rift faults
Only particular segments of the Reelfoot Rift faults are currently seismically active (Chiu
et al ., 1992 ; 1997) and/or have Holocene fault displacement. These include the Axial
fault (Guccione, 2005 ) , Reelfoot fault (Mueller and Pujol, 2001 ) , New Madrid North fault
(Baldwin et al ., 2005 ) , Commerce fault (Harrison et al ., 1999 ) , and the central segment
of the southeastern Reelfoot Rift margin ( Figure 7.2 ) (Cox et al ., 2001b ; 2006; Williams
et al ., 2001 ) . Each of these seismically active segments is truncated by basement faults.
The Reelfoot fault seismicity is truncated by the Reelfoot Rift margin faults, the Axial fault
seismicity is truncated on its north by the Grand River tectonic zone and on its south by
the Boliver Mansfield tectonic zone, the New Madrid North seismicity is truncated on its
southern end by the Grand River tectonic zone with its northern end possibly truncated by
the Charleston uplift, and there is Holocene displacement along the southeastern Reelfoot
Rift margin between the Grand River tectonic zone and the Boliver Mansfield tectonic zone
( Figure 7.2 and Table 7.1 ) . Thus, it appears that (1) the Precambrian basement faults divide
the basement into structural blocks ( Figure 7.2 ) , (2) basement fault intersections control
near-surface faulting and geomorphology (e.g., southern Crowley's Ridge, Lake County
uplift, and Joiner Ridge), and (3) active fault segment lengths are controlled by basement
fault intersections. This suggests earthquake size may be controlled by the length of fault
segments that bound the basement blocks of Figure 7.2 .
Reelfoot Rift fault segments appear to have turned on and off through geological time.
The Commerce fault segment of the Commerce Geophysical Lineament at Thebes Gap