Structure of the Managua graben, Nicaragua, from remote sensing images

Abstract

From remote sensing interpretations, combined with seismological data of the 1972 earthquake, the Managua Fault Zone is seen as a N-S - trending, composite structure of regional importance. The eastern margin of the Managua Fault Zone is formed by lower-order, N-S - trending graben structures such as the Managua graben or the Airport graben, which are bordered by oblique faults. The intensity of lateral movements on these N-S trending faults seems to decrease to the east as normal faulting increases. Lateral components on N-S trending faults are mainly dextral in recent times. In combination with the NW - trending marginal faults of the Nicaragua depression this represents a transpressional regime for the Managua Fault Zone. Components of left lateral movements on NNE- to NE - trending structures are clearly indicated from seismological data for the 1972 Managua earthquake (extension within substructures like the Managua graben, Airport graben). N-, NW- and NE - trending planes should be regarded as recently active in the region. These kinematic relations must be taken into account for seismic hazard assessment: NE - trending planes are emphasized because of their extensional regime.
It is postulated that during the 1972 event only the western part of the Managua graben was activated. Higher recent stress concentration along the eastern margin of the graben may be a consequence, among others.