Inferring Interseismic Coupling along the Lesser Antilles Arc: a Bayesian Approach

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Authors

Elenora van Rijsingen , Eric Calais, Romain Jolivet, Jean Bernard de Chabalier, Jorge Jara, Steeve Symithe, Richard Robertson, Graham A. Ryan

Abstract

The Lesser Antilles subduction zone is a challenging region when it comes to unraveling its seismogenic behavior. Over the last century, the subduction megathrust has been seismically quiet, with no large thrust event recorded, which raises the question whether this subduction zone is able to produce large interplate earthquakes or not. However, two historical earthquakes in the 19th century, a M 7-8 in 1839 and M 7.5-8.5 in 1843, are proposed to have occurred along the subduction megathrust, although no direct evidence exists. Here we provide a new assessment of interseismic coupling for the Lesser Antilles subduction zone, based on updated GPS velocities and the latest models of the slab geometry and elastic crustal structure. We use a Bayesian approach, allowing us to explore the entire range of plausible models and to provide realistic estimates of interseismic coupling and associated uncertainties. We find low to very low coupling along the entire plate interface, including in the proposed rupture areas of the 1839 and 1843 events, where the sensitivity of our model is high. While a further understanding of temporal variations in interseismic coupling needs to be addressed in future studies, our results indicate that the Lesser Antilles subduction zone is uncoupled, which challenges the idea that the 1839 and 1843 earthquakes were thrust events. The updated GPS velocities of this work now also reveal a small, but detectable amount of along-arc extension, consistent with geological observations of active normal faulting within the arc.

DOI

https://doi.org/10.31223/osf.io/kn7hq

Subjects

Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Keywords

Bayesian inversion, Caribbean, GPS, Interseismic coupling, Lesser Antilles, Megathrust, Seismotectonics, Subduction earthquakes, Subduction interface, Subduction zone

Dates

Published: 2020-07-31 15:12

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License

GNU Lesser General Public License (LGPL) 2.1

Additional Metadata

Data Availability (Reason not available):
All data used in this work are openly available from the IGS (igscb.jpl.nasa.gov), UNAVCO (www.unavco.org), and IPGP data center (http://volobsis.ipgp.fr/) archives. Ancillary information necessary to process GPS data, such as precise satellite orbits and antenna phase center models, is openly available from the IGS (http://www.igs.org). Global SINEX files used here are publicly available at MIT (acc.igs.org/reprocess.html). The software used to process the GPS data (GAMIT-GLOBK) is openly available at MIT (http://geoweb.mit.edu/gg/). Geodetic coupling models were obtained using a combination of the CSI (https://github.com/jolivetr/csi) and AlTar (https://github.com/AlTarFramework/altar) softwares. Figures were produced using the Generic Mapping Tools software package (Wessel & Smith, 1998).

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