Transient deformation in southern Mexico in 2006 and 2007: Evidence for distinct deep-slip patches beneath Guerrero and Oaxaca

Abstract

We model three slow slip events in 2006 and 2007 recorded by continuous GPS stations in central and southern Mexico to test for overlap between their source regions along the Mexican subduction interface and whether they intrude upward into the rupture zones of previous large earthquakes. Inverse modeling yields source regions beneath central Oaxaca for two of the three slow slip events (SSE), where a previously described SSE occurred in 2004, and beneath Guerrero for the third, where slip events previously occurred in 2001-2002 and possibly 1998. Along with previously published results, our work suggests there are persistent differences between the depths and magnitudes of transient slip beneath Oaxaca and Guerrero. Transient slip beneath Oaxaca in 2004, 2006, and 2007 had a common source region downdip from the seismogenic zone and released elastic strain energy equivalent to Mw̃7.3 earthquakes, equaling most or all energy that accumulated below the seismogenic zone. Transient slip beneath Guerrero in 2006 had a larger moment magnitude (Mw̃7.3) and extended somewhat farther updip, possibly to seismogenic depths. Transient slip thus appears to relieve some elastic strain that accumulates at shallow levels in the Guerrero seismic gap. We find no evidence for spatial or temporal correlations of slow slip along these two widely separated source regions, although better data are needed to test more definitively for any interaction between them. © 2009 by the American Geophysical Union.