A regional microearthquake network has been established in the New Madrid seismic zone to study better the seismic characteristics of this region. The network consists of 16 stations distributed on the borders of and within the head of the Mississippi embayment. The network has a location sensitivity for all earthquakes of mb ≧ 1 occurring within the network. A total of 330 earthquakes has been located within a 1.5° by 1.5° area inside the array during the first 21 months of operation. The spatial distribution of these hypocenters has identified for the first time in this region the existence of linear seismically active zones, corresponding presumably to seismically active faults. Several of these trend N40°E, parallel to the axis of the embayment. Others trend NW; these latter are parallel to and possibly are related to the crest of the Pascola arch which joins the Ozark uplift to the Nashville dome. The linear dimensions of the features identified thus far vary in length from about 25 km to about 100 km. The b value as determined by the number of earthquakes located thus far is about 0.8.

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