Focal mechanisms determined using surface wave techniques. The mechanisms with the red compressional quadrants have been obtained recently.

Focal mechanisms determined using surface wave techniques. The mechanisms with the red compressional quadrants have been obtained recently. The following two figures focus on New Madrid and on the surrounding region.

Focal mechanisms determined using surface wave techniques. The mechanisms with the red compressional quadrants have been obtained recently. The small red dots represent the earthquake locations from 1975 - 1990 in the region from the Saint Louis University catalog.

Focal mechanisms determined using surface wave techniques. The mechanisms with the red compressional quadrants have been obtained recently. The small red dots represent the earthquake locations from 1975 - 1990 in the region from the Saint Louis University catalog.