On the state of stress in New England as determined from earthquake focal mechanisms

Abstract

Assuming only that slip occurs in the direction of resolved shear stress on fault planes, we have found a wide range of uniform stress tensors, each of which is consistent with ten diverse focal mechanisms for recent moderate-size earthquakes in New England and vicinity. Thus, it is possible that the variations in focal mechanisms are due to the occurrence of specific pre-existing zones of weakness rather than to inhomogeneous stresses. Acceptable stresses are broadly consistent with those established for other parts of the eastern United States—namely, northeast- or east-northeast–directed maximum compression and nearly vertical minimum compression.