On October 21, 1981, a magnitude 3.4 (ML) earthquake occurred in Long Island Sound, NY, approximately 40 km southeast of New Haven, CT. The earthquake was felt throughout most of Connecticut and Long Island, and the maximum intensity was IV (M.M.). Using two station subsets which surround the epicenter, our hypocentral solution was latitude 41.14 (41°08.1′), longitude −72.57 (−72°33.9′), depth 5.0 km at O.T. 16:49:07.1 UTC. The fault plane solution based on 27 P-wave first motions shows thrust faulting on NE-SW trending fault planes.