- © 2010 by the Seismological Society of America
We present high-resolution earthquake locations for the New Madrid seismic zone (NMSZ) using the double-difference location method. The NMSZ consists of four major arms of seismicity centered in the central United States and is one of the few places of concentrated earthquake activity far from a major plate boundary. The zone generates approximately 200 earthquakes per year. Double-difference relocation techniques prove well suited for this region because the distance between neighboring events is small and station coverage is relatively dense. The initial data set consists of 1,394 earthquakes recorded between 2000 and 2006 by 197 stations. The catalog contains approximately 67,000 P-wave and 54,000 S-wave observations, which yields 480,000 differential times. Waveform cross-correlation of P and S waves provides an additional 135,000 high-precision differential times. Relocated hypocenters align along individual segments of the seismic zone, providing a sharper image of the NMSZ faults.