Researchers: Andria Ellis, Chuck DeMets, Beatriz Cosenza Muralles, Neal Lord, and Basil Tikoff, University of Wisconsin; Robert McCaffrey, Portland State University; Peter Briole and Hélène Lyon-Caen, CNRS, Paris; Omar Flores, Universidad San Carlos, Guatemala; Marco Guzma ́n-Speziale and Vladimir Kostoglodov, Universidad Autonoma de Mexico; Douglas Herna ́ndez, Ministerio de Medio Ambiente y Recursos Naturales, El Salvador; Peter LaFemina, Pennsylvania State University; Ce ́cile Lasserre, CNRS, Grenoble; Manuel Rodriguez Maradiaga, Universidad Nacional Autonoma de Honduras; Enrique Molina and Jeffrey Rivera, Universidad Mariano Galvez; Robert Rogers, California State University Stanislas; and Alejandra Staller, Universidad Politecnica de Madrid.
Written by Linda Rowan
30 December 2019
Data collected between 1999 and 2017 from over 200 GPS sites in southern Mexico and northern Central America are utilized to constrain plate motion and fault characteristics in the region. A new elastic-kinematic model fit to the geodetic observations and other constraints provides the angular velocities for eight blocks and shows that three of the blocks are deforming internally. The velocity and direction of motion determined for each block describe the geodynamic complexity of the region. The model suggests little locking of the Middle America subduction zone, a rheologically weak volcanic arc, and a Central America forearc sliver that moves slowly.
The tectonics of multiple small plates in Central America and their interactions with the large North America plate are complex. The main tectonic components in Central America are the subduction of the Cocos Plate beneath the Caribbean Plate. The subduction zone has formed an offshore forearc and an onshore volcanic arc along the west coasts of Guatemala, El Salvador, Honduras, and Nicaragua. The subduction zone extends into Costa Rica, but this study only considers northern Central America.
GPS observations have been used to measure the surface motion over decades to try to decipher some of the geodynamic complexity over time and with depth. Interseismic velocities for 201 GPS sites in southern Mexico and northern Central America were determined and used to model the elastic-kinematic characteristics of eight different elastic blocks that are bounded by faults and plate boundaries. A previous study used the 200 GPS sites to determine the coseismic and postseismic motions for major earthquakes in the region (Ellis et al., 2018) and these earthquake affects have been removed from the interseismic velocity estimates. Seismic and geologic observations are included to define fault and boundary characteristics in the model.
The elastic-kinematic model based on the geodetic data shows that the Middle America subduction zone is not locked or is weakly locked. This suggests that subduction zone earthquakes are less likely to occur and represent a less likely hazard for the region. The Central America forearc sliver, which runs the length of the Cocos Plate and is situated offshore, moves slowly and is seismically quiet. The volcanic arc that parallels the forearc as a line of volcanoes along the coast is weak and pliable, so it can absorb some of the deformation from the collisions and interactions of the tectonic plates.
Andria Ellis, Chuck DeMets, Robert McCaffrey, Peter Briole, Beatriz Cosenza Muralles, Omar Flores, Marco Guzmán-Speziale, Douglas Hernández, Vladimir Kostoglodov, Peter LaFemina, Neal Lord, Cécile Lasserre, Hélène Lyon-Caen, Manuel Rodriguez Maradiaga, Enrique Molina, Jeffrey Rivera, Robert Rogers, Alejandra Staller, Basil Tikoff, GPS constraints on deformation in northern Central America from 1999 to 2017, Part 2: Block rotations and fault slip rates, fault locking and distributed deformation, Geophysical Journal International, Volume 218, Issue 2, 1 August 2019, Pages 729–754, doi: 10.1093/gji/ggz173 .
plate tectonics, subduction zone, volcanic arc, forearc, elastic-kinematic model
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