The New Madrid seismic zone of the Central United States - Intraplate Earthquakes - page 184

(b)

Figure 7.11 (b) The strain ellipse illustrates the nature and orientation of structures that form within
an area undergoing right-lateral simple shear (map view). Local east-west compression results in
north-striking folds and reverse faults and local north-south extension results in east-striking normal
faults as seen in (a) (from Keller and Pinter, 2002 ) .

et al ., 1995 ) . Neogene movement has been documented on the Crittenden County fault
(Luzetti et al ., 1995 ) , the Reelfoot fault (Kelson et al ., 1996 ; Van Arsdale, 2000 ) , Axial
Fault (Guccione, 2005 ) , Bootheel Fault (Guccione et al ., 2005 ) , New Madrid North fault
(Baldwin et al ., 2005 ; Pryne et al ., 2013 ) , bounding faults of Crowley's Ridge (Van Arsdale
et al ., 1995 ) , the Commerce fault (Harrison et al ., 1999 ) , and the southeastern Reelfoot
Rift margin faults (Cox et al ., 2006 ) ( Figure 7.2 and Table 7.1 ) . Thus, the Reelfoot Rift is
unique among its neighboring rifts in that although the total amount of displacement on
individual Reelfoot Rift faults has been small (e.g., 70 m on the Reelfoot fault since the
Cretaceous) many of the rift faults (perhaps all) have experienced Cenozoic movement.
The fifth reason, which is also unique to the Reelfoot Rift, is that the very large Missis-
sippi River passes directly over the NMSZ and most of the rift. Van Arsdale et al . ( 2007 )
have discussed the late Pliocene through Holocene erosional history of the central Missis-
sippi River valley that they believe may be tied to the late Holocene onset of the NMSZ,
which is discussed below.

7.3.7 Earthquake recurrence

Paleoseismologic investigations have revealed a recurrence interval of approximately
500 years for large NMSZ earthquakes over the past

1,700 years (Kelson et al ., 1996 ;