Focal mechanisms of aftershocks of the 1979 Carlisle earthquake: a re-interpretation

Summary. A composite fault plane solution of aftershocks of the 4.8 ML Carlisle earthquake of 1979 December 26, and the geographic distribution of their epicentres, indicate the predominance of right-lateral strike-slip focal mechanisms, with a significant component of dip-slip faulting, on a NW–SE trending fault zone. Data presented here, combined with an alternative interpretation of the published results of King, closely constrain the possible fit of nodal planes. The strike of the NW–SE nodal plane is in excellent agreement with a trend in aftershock epicentres. The aftershock zone is close to the edge of a long positive NW–SE trending gravity anomaly.