Paleoseismology Study Northwest of the New Madrid Seismic Zone
Abstract
During this paleoseismology study, we surveyed more than 400 km of river cutbank and documented liquefaction features, including sand dikes and sand blows, at over 50 sites. In addition, we studied several structures, including the Bodenschatz-Lick, Eureka-House Springs, and Ste. Genevieve fault systems and the Farmington and Valmeyer anticlines, that are spatially associated with concentrations of historical and instrumentally recorded seismicity. Although no evidence of Holocene faulting was found, possible earthquake sources responsible for liquefaction include the St. Louis, Centralia, and New Madrid faults, the Valmeyer and Waterloo-Dupo anticlines, and the Du Quoin monocline. We found liquefaction features along the Big Muddy, Cache, Marys, Meramec, and Kaskaskia Rivers and Mud, Shoal, and Silver Creeks. The age and size distributions of liquefaction features suggest that a large to very large earthquake occurred east of St. Louis about 6,500 years ago and that another significant event occurred in the same area in the past 4,000 years. We propose three possible earthquake scenarios to account for the observed pattern of liquefaction. However, additional information regarding the age and size distribution of liquefaction features is needed to estimate the timing, source area, and magnitude of large prehistoric earthquake(s) with more confidence. A large to very large earthquake centered in southwestern Illinois today would have a major impact on urban areas including St. Louis, Missouri, Davenport, Iowa, and Springfield, Peoria, and possibly Chicago, Illinois. The seismic hazard remains poorly understood due to large uncertainties pertaining to the timing, sources, and magnitudes of large prehistoric earthquakes in this region.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1999
- Accession Number
- AD1075628
Entities
People
- J. Chester
- K. Dyer-williams
- M. Tuttle
- R. Cande
- R. Lafferty
Organizations
- University of Maryland