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

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


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 (US)
Pages (from-to)1677-1689
Number of pages13
JournalGeophysical Journal International
Issue number3
StatePublished - Jul 2 2015

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

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