Abstract

Shadowing methods were used on raised plastic relief maps of New England to produce pseudo-radar photo maps. These were then analyzed for regional linear components by the methods of Wise (1969). The most pervasive of the fracture systems striking N20E, N25W, and N70E, extend at least from Lake Ontario to Pennsylvania to Maine. These topographic linears, ranging from 20 to 200 km in length, are ubiquitous, independent of rock type, local geologic provinces or curvatures of the mountain systems, and do not change patterns near the coastlines. In one detailed area in NW Massachusetts they were compared with all ground measured brittle fracture elements and with ERTS linears. There, a striking correlation in azimuth pattern exists between relief map linears, ERTS linears, and small fault systems of 1-5 meters displacement. Traditional photo linears show little correlation in azimuth with any of the fracture sets at other scales. The system of regional linears is interpreted as the result of sub-continental sized stress trajectories, probably of several ages, acting on vast crustal plates as proposed by Wise (1967, Trans. AGU). The name Hobbs Linears is proposed for these features.