Abstract
A comparative study of Landsat images, SLAR image strips, and Skylab photographs was made to help develop a regional tectonic model and to evaluate the seismic hazards of the northern part of the Mississippi embayment as far south as the Ouachita front.The geomorphic character and distribution of lineaments reflects the structure and tectonics of the area. The fairly consistent trends of northwest-oriented lineaments suggest the influence of jointing, whereas the variable north- and northeast-trending groups suggest a variety of influences including jointing, faulting, and surficial factors that control stream orientation. A number of northeast-trending faults are relatively recent, or have significant surface displacements, as they disrupt slopes in equilibrium with drainage.Seismic and aeromagnetic data are available for part of the area. Well-defined trends of epicenters near New Madrid conform to a pronounced lineament pattern along the Mississippi River. Over a small area near New Madrid, a trend analysis was made of the totals of length-width ratios of magnetic anomalies grouped in 10-degree intervals. Anomaly trend distributions show some correlation with the azimuth frequency diagrams of lineaments in the embayment. These data suggest basement control along gradients of magnetic anomalies where they parallel mapped lineaments.The tectonic pattern of the area is generally revealed in the landscape, of which the lineaments seem to be a particularly important part. The Mississippi River flows along an axis of active subsidence, possibly actually controlled by tectonic events along the west edge of the embayment, including uplift of the Ozark dome. The tectonic evolution seems to be one of an episodically opening wedge, combining strike-slip movement along the north and west side of the embayment and step-faulting down to the east.
