Aftershocks of the Managua, Nicaragua, earthquake of December 23, 1972

Abstract
Epicenters determined from 164 of the Managua aftershocks define two seismic zones. The primary zone, which is 15 to 20 km in length and strikes northeast along the Tiscapa-Ciudad Jardin fault system, contains 80 per cent of the aftershock locations. A subsidiary zone, northwest of Managua, suggests strain release possibly related to the north-south striking San Judas fault. Depth of foci are principally in the upper 7 km for both zones. Composite fault-plane solutions indicate a predominate left-lateral strike-slip displacement; the preferred planes for each zone agree with the strike of surface fractures or previously mapped faults.