Abstract

The 135-km-long Bootheel lineament is a zone of en echelon, narrow, linear bands of sand blows, oriented N24°E in southeast Missouri and northeast Arkansas within the epicentral area of the 1811–1812 New Madrid earthquakes. Holocene faulting along the central part of the lineament vertically displaced a <10.2-ka-old Pleistocene braid-stream sand ∼3 m and dextrally displaced a ca. 2.4-ka-old Holocene paleochannel at least 13 m. The fault zone is less than 8 m wide where studied in detail. These observations suggest that the Bootheel lineament is a fault, and we therefore suggest that it be renamed the Bootheel fault.

The area east of the Bootheel fault in our study area may have been uplifted ∼3 m during at least three Holocene events, perhaps by a compressional pop up at a 1.5-km-wide left-step restraining offset south of the study site. The very low level of instrumental seismicity recorded near the Bootheel fault suggests that it is either locked because of structural complexity, or it is currently inactive. Though the source zones are poorly known, great earthquake sequences in A.D. 1811–1812, A.D. 1450, and A.D. 900 have been identified in the New Madrid seismic zone using the historical record and paleoseismology (Tuttle et al., 2002). Based on the estimated 13 m of horizontal paleochannel displacement, an approximate 2.4 ka paleochannel age, and a mean great earthquake recurrence interval of ∼500 yr (Cramer, 2001; Tuttle et al., 2002), the local mean horizontal slip rate is estimated to be ∼3.5 m per event. When displacement does occur on the Bootheel fault, it may subsequently load other faults, accounting for past earthquake sequences in the New Madrid region.

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