Aftershocks and Intensity of the Managua Earthquake of 23 December 1972

Two portable seismic stations and a fixed array of five seismometers were used to record aftershocks in the vicinity of Managua, Nicaragua, after the earthquake of 23 December 1972. Approximately 3000 aftershocks were recorded during a 20-day period in January 1973. Left lateral motion along at least two faults, both trending N40 degrees E, is inferred from the seismic data. This is in good agreement with dislocations mapped at the surface in Managua. The data suggest that the shallow earthquakes of the Managua region are a consequence of north-south compressional stresses and east-west tensional stresses. This is consistent with regional plate movements deduced in other investigations.