A 5- to 6-kilometer-deep scientific drill hole is the ultimate goal of Fault Observatory for the Central U.S. (FOCUS), a new multidisciplinary, multi-institutional working group that formed at a workshop held at the University of Memphis, in Tennessee. Beneficial shortand intermediate-term science goals are also part of establishing this borehole geo-observatory in the most prominent, widely known intraplate earthquake zone in the world.
The midcontinent has a long, complex history of tectonism. Precambrian basement rocks record intense tectonic deformations that preceded the accumulation of thick sedimentary sequences of sediments that constitute the present-day Mississippi Embayment. Despite its location far from the active North American plate margins, the New Madrid seismic zone of the central United States exhibits a persistent pattern of seismicity. What causes this intraplate seismicity? How does the intraplate lithosphere support the forces that maintain earthquake productivity in this supposedly stable tectonic setting? Is there evidence for spatial or temporal migration of seismicity in the continental interior?