Interplate slip rate variation between closely spaced earthquakes in
southern Mexico: The 2012 Ometepec and 2018 Pinotepa Nacional thrust
events
Abstract
On 20 March 2012, a Mw 7.5 thrust earthquake started a series of large
events up to magnitude Mw 8.2 (2017) that struck central Mexico during a
period of nine years. Before this event, the Mexican subduction zone did
not experience subduction earthquakes (Mw > 7.0) for at
least 12 years. Most of the events during this highly active period
(2012-) occurred in the plate interface, resulting in a significantly
larger interplate slip rate in the states of Oaxaca and Guerrero. In
this study, we explore how the aseismic slip transient caused by the
2012 Mw 7.5 earthquake affected the region and whether this earthquake
had a causal relationship with a nearby similar magnitude event that
occurred in 2018 (Mw 7.2). To this end, we identified and analyzed
characteristic repeating earthquakes along the Mexican subduction zone
for assessing the plate interface slip history and found a notably
increase in the aseismic slip rate inferred from repeating earthquake
activity following the 2012 mainshock, which suggests a long-standing
slip perturbation in Oaxaca near the trench that continued until the
2018 Mw 7.2 Pinotepa Nacional earthquake.