TThe 2012 August 27 Mw7.3 El Salvador earthquake: Expression of weak coupling on the Middle America subduction zone

Halldor Geirsson*, Peter C. Lafemina, Charles Demets, Douglas Antonio Hernandez, Glen S. Mattioli, Robert Rogers, Manuel Rodriguez, Griselda Marroquin, Virginia Tenorio

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


Subduction zones exhibit variable degrees of interseismic coupling as resolved by inversions of geodetic data and analyses of seismic energy release. The degree to which a plate boundary fault is coupled can have profound effects on its seismogenic behaviour. Here we use GPS measurements to estimate co- and post-seismic deformation from the 2012 August 27, Mw7.3 megathrust earthquake offshore El Salvador, which was a tsunami earthquake. Inversions of estimated coseismic displacements are in agreement with published seismically derived source models, which indicate shallow (<20 km depth) rupture of the plate interface. Measured post-seismic deformation in the first year following the earthquake exceeds the coseismic deformation. Our analysis indicates that the post-seismic deformation is dominated by afterslip, as opposed to viscous relaxation, and we estimate a post-seismic moment release one to eight times greater than the coseismic moment during the first 500 d, depending on the relative location of coseismic versus post-seismic slip on the plate interface. We suggest that the excessive post-seismic motion is characteristic for the El Salvador-Nicaragua segment of the Central American margin and may be a characteristic of margins hosting tsunami earthquakes.

Original languageEnglish
Pages (from-to)1677-1689
Number of pages13
JournalGeophysical Journal International
Issue number3
Publication statusPublished - 2 Jul 2015

Bibliographical note

Publisher Copyright:
© The Authors 2015. Published by Oxford University Press on behalf of The Royal Astronomical Society. All rights reserved.

Other keywords

  • Creep and deformation
  • Friction
  • Seismic cycle
  • Transient deformation
  • Tsunamis


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