THE NEW MADRID SEISMIC ZONE WITHIN THE CONTEXT OF SEISMIC ENERGY RELEASE IN THE CENTRAL U.S.

MIAO, Q. and LANGSTON, C. A., Center for Earthquake Research and Information, University of Memphis, Memphis, TN 38152, qingmiao@memphis.edu, clangstn@memphis.edu.

Seismic parameters for the central U.S. were collected for 5909 events occurring between 1974 and 2004. We computed elastic strain energy release (E) from event magnitude using Gutenberg's relation to investigate spatial and temporal changes of strain energy release for the New Madrid Seismic Zone (NMSZ) within the larger central U.S. area. The results show that log(E) decreased with time for the NMSZ over the past 31 years, while the central U.S. as a whole maintained a nearly constant level of log(E). This can be considered as evidence for apparent seismicity migration out of NMSZ into other parts of the central U.S. The elastic strain energy release map also shows that most events with magnitude equal to or greater than M4 occur at the edges of zones of elastic strain energy release produced by events with magnitude below M4. If this spatial observation is true, it could be helpful in identifying potential seismic sources within the NMSZ. We also show that the depth distribution of cumulative strain energy release from seismicity in the central U.S. can be used as a better physical proxy for lithospheric strength compared to numbers of earthquakes in the standard lithospheric strength model.