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 seven large events (7.0 ≤ Mw ≤ 8.2) that struck central Mexico during a period of 9 years (2012–2021). Before this event, the Mexican subduction zone did not experience significant subduction earthquakes (Mw > 7.0) for at least 12 years. Five of the events 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 an aseismic slip transient caused by the 2012 Mw 7.5 earthquake affected the Oaxaca region and whether this earthquake had a causal relationship with the Mw 7.2 Pinotepa Nacional event that took place six years later in a nerby zone. 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 remarkable increase in the aseismic slip rate following the 2012 mainshock, which suggests a long-standing slip perturbation near the trench in Oaxaca that continued until the Pinotepa Nacional earthquake of 2018.