The 10 April 2014 Earthquake in Central Nicaragua: Evidence of Complex Crustal Deformation in Central America

Abstract:

On 10 April 2014 a magnitude M_w 6.1 struck central Nicaragua. The main event and the aftershocks were clearly recorded by the Nicaraguan seismic network. These crustal earthquakes were strongly felt but caused relatively little damage to the city of Managua and to the surrounding cities and towns. This is in sharp contrast to the destructive effects of the 1972 earthquake in the capital city of Managua. The differences in damage stem from the fact that in 1972, the earthquake occurred on a fault beneath the city; in contrast, the 2014 event lies offshore, under Lake Managua. The distribution of aftershocks shows two clusters of seismic activity. In the northwestern part of Lake Managua, an alignment of aftershocks suggests a southeast trending fault. The reported source mechanism suggests right-lateral strike slip motion on a plane with the same azimuth as the aftershock sequence. A second cluster of seismic activity occurred simultaneously, but spatially separated, beneath Apoyeque volcano. There is no clear alignment of the epicenters in this cluster. Seismic scaling relations between magnitude and the fault length predict a length of approximately 10 km for an earthquake of this magnitude. This is in agreement with the extent of the fault defined by the aftershock sequence. The northeast - southwest trending Tiscapa and Ciudad Jardín faults that broke during the 1972 and 1931 Managua earthquakes are orthogonal to the fault where the 10 April earthquake occurred. This set of conjugate faults confirms that Central Nicaragua is being deformed in a complex tectonic style of deformation. The forearc sliver between the trench and the volcanic arc moves to the northwest relative to the Caribbean plate. This deformation, however, does not take place on a single set of faults. The motion is apparently accommodated by a system of conjugate faults: right lateral, strike-slip faults oriented parallel to the volcanic arc and another set of faults trending northeast - southwest, on which the slip is left lateral. The presence of this complex geometry of conjugate faults highlights the seismic hazard not only in the capital city of Managua, but also to the major Nicaraguan cities, all lying close to the volcanic arc.