THREE DIMENSIONAL GEOLOGIC MODEL OF THE NEW MADRID SEISMIC ZONE

Geologic and geophysical data including surface topography DEM data, stratigraphic tops of the Precambrian, Paleozoic, Cretaceous, and Tertiary sections, faults, plutons, and earthquake foci have been integrated into a three dimensional software model centered on the New Madrid seismic zone of the northern Mississippi Embayment. This geologic model allows a view of the data from any direction and provides the ability to “walk” through the subsurface geology. Geologic interpretation within a 3-D environment promotes better interpretations of the relationships among mapped faults, earthquake foci, the structures of the Reelfoot rift, and the tectonic/stratigraphic evolution of the Mississippi embayment. One observation made within the model is the coincidence of a major down-to-the-southwest step in the Precambrian basement beneath the seismically active Reelfoot thrust fault. Thus, it appears that the Reelfoot thrust may have formed above a basement normal fault. As additional data are put into the model we anticipate an ability to track seismogenic faults from the basement into the Holocene alluvium of the Mississippi River valley and provide a geometrically accurate geologic framework for geophysical and fault kinematic analyses.