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Title: Seismic hazards of the upper Mississippi embayment
Authors: University of Memphis.
Van Arsdale, Roy Burbank, 1950-
Keywords: Earthquakes
Mississippi River Valley
New Madrid
Publisher: Geotechnical Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Contract report (U.S. Army Engineer Waterways Experiment Station) ; GL-98-1.
Description: Contract Report
Abstract: Earthquakes are a major hazard in the middle Mississippi River valley of the upper Mississippi embayment. Microseismicity along the New Madrid seismic zone is illuminating faults that are believed responsible for the great New Madrid earthquakes of 1811-1812. These faults are right-lateral strike-slip faults within the Blytheville arch and western margin of the Reelfoot rift that are linked by the southwest-dipping Reelfoot reverse fault The Bootheel lineament and back thrusts of the Reelfoot fault may also have slipped in 1811-12. Geomorphic effects of the 1811-12 sequence include displacement of the Mississippi River; uplift of the Lake County uplift, Tiptonville dome, Blytheville arch; subsidence of Reelfoot Lake, Big Lake, and Lake St Francis; landslides on the eastern bluffs of the Mississippi River valley; and extensive liquefaction. In addition there is evidence for 1811-12 landsliding on the eastern margin of Crowley's Ridge, formation of a lake on the Obion River, and formation of seismic craters on the loess-covered eastern Mississippi Valley bluffs. Peripheral to the New Madrid seismic zone; the Big Creek, Commerce, and Crittenden County faults have Holocene displacement and faults along the margins of Crowley's Ridge have Pleistocene displacement. The margins of Sikeston Ridge are underlain by faults that apparently lifted the ridge in Quaternary time. Similarly, the eastern Mississippi Valley bluffs are underlain by faults that appear to have affected the current position of the Mississippi River. Thus, there is evidence for widespread Quaternary faulting within the upper Mississippi embayment Paleoliquefaction and trench excavations across the Reelfoot fault reveal a minimum of 3 prehistoric earthquakes and an estimated recurrence interval of 450 years. This very high strain rate may be transitory and/or deformation may move around the upper Mississippi embayment through time. Since the Plio-Pleistocene Lafayette Formation and subsequent Quaternary section is incised into the Eocene section, it appears that the northern Mississippi embayment has been rising during Quaternary time. Thus, the widespread faulting may be a consequence of Quaternary uplift of the northern Mississippi embayment. Future earthquakes would cause widespread and potentially catastrophic effects on the built environment of the Mississippi River. Of particular concern is the Reelfoot reverse fault that trends from near Dyersburg, Tennessee, to New Madrid, Missouri. Displacement, like that which occurred on February 1, 1812 on the Reelfoot fault and its associated back thrusts, would displace the Mississippi River bed at a minimum of 5 locations resulting in breaking of river levees, warping the river profile, and fonning temporary ponding and rapids/waterfalls. Liquefaction was dramatic in 1811-12 and is also a major concern in future earthquakes. Although the water table is generally lower today in the Mississippi River valley due to drainage ditches, it remains high below the river levees. The levees may be vulnerable to liquefaction effects.
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