Explosion Measurements of Crustal Structure in Maine and the Gulf of Maine

A series of 61 explosions were fired in the Gulf of Maine during June and July, 1961, by the U. S. Navy and the U. S. Coast Guard, forming a detailed line of shot points along an azimuth 129° true from Thomaston, Maine. These shots were recorded by a line of portable seismic stations 70 km long on the landward extension of the shot line. Shots were continued to the edge of the continental shelf. Additional recordings were made on Matinicus Rock and Texas Tower number 2. The research vessel Bear recorded some of the shots at the edge of the continental shelf. The principal advantages of this technique are that a reverse profile may be obtained from one set of shots and that the effects of large scale crustal inhomogeneities may be separated from the average picture of crustal structure. A preliminary analysis based only on first arrivals shows that the M discontinuity dips flown from the edge of the shelf at about 4° and that the crustal thickness near the coast of Maine is about 35 km.