A CASE FOR THE NEW MADRID EARTH OBSERVATORY

CERI WORKING GROUP (LANGSTON, C.A.), Center for Earthquake Research and Information, University of Memphis, 3876 Central Ave., Suite 1, Memphis, TN 38152-3050, clangstn@memphis.edu.

The New Madrid Seismic Zone (NMSZ) represents one of the major unsolved mysteries in the Earth Sciences and is a primary source of hazard in the central United States. The existence of a major earthquake source zone in intraplate North America with geological evidence suggesting perhaps 4 major earthquake sequences over the past 2000 years continues to confound our ideas of how the lithosphere accumulates and releases strain energy within the plate tectonic paradigm. Physical observations of the state of the lithosphere are the primary means for constructing system level models for faulting. Conditions at the NMSZ are unique compared to west coast source zones because much of the geology and geologic structure are hidden by thick sections of coastal plain sediments. These sediments also present their own scientific problems with respect to the propagation of strong ground motions in the region. In order to even develop testable hypotheses on the workings of the NMSZ, there is a need to perform high resolution studies of crustal and mantle structure using the full spectrum of geophysical techniques to infer elastic and rheological heterogeneity to further infer stress heterogeneity. Knowledge of lithospheric thermal conditions is rudimentary at best and the state of fluids in the crust only conjecture. A New Madrid Earth Observatory would include high resolution seismic arrays for deducing velocity structure throughout the lithosphere, deep borehole observations of crustal rocks and fluids, deep borehole seismic instrumentation to learn about the physical properties of upper crustal materials and wave propagation, dense GPS array observations of secular strain, and regional scale campaigns of thermal and geophysical measurements.