USGS Studying New Madrid Seismic Zone Today in Poinsett County

MAY 16, 2006 - Posted at 11:16 a.m. CST

LEPANTO, AR - The U.S. Geological Survey, in collaboration with the University of Memphis and the University of Texas, is imaging the sediment beneath the Mississippi River valley near Lepanto today.

By vibrating the ground and listening to the echoes, the high-resolution seismic-imaging study will investigate the layering, stiffness, and faulting of the sediments to improve the understanding of earthquake hazards.  Today's work is part of a pilot for a multi-year effort to acquire a continuous seismic cross section to examine past earthquake history in the New Madrid seismic zone.

A small, rubber-tired vibroseis truck will generate vibrations to create small waves that will travel into the earth, will be reflected by layered sediment and then recorded by a 720-meter long string of seismometers spread out along the survey line.  The vibroseis truck is preferred over explosions as an energy source near cities and towns because the vibrations are spread out over ten to 20 seconds, rather than being suddenly released, and because no drilling of shot holes is needed.  The truck shakes the ground slightly, then moves on and leaves nothing behind.  Scientists say you can feel a slight shaking in the bottom of your feed, if you stand close to the truck.