abstract

A recent study of seismicity in the New Madrid seismic zone by Stauder et al. (1976) has shown the existence of linear micro-earthquake patterns of up to 120 km in length. This study presents the results of composite microearthquake focal mechanism studies along these trends together with focal mechanisms obtained using long-period surface-wave data from larger events. Due to the present microearthquake array geometry, the composite focal mechanism studies do not indicate a complete picture of the nature of the earthquake processes for all the trends. However, the motion on the major 120-km long trend into northeastern Arkansas has significant components of right lateral fault motion. The consistency of surface-wave focal mechanisms and the composite focal mechanism along this trend indicates that it should be considered as a single tectonic unit.

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