Interplate Slip Rate Variation Between Closely Spaced Earthquakes in Southern Mexico: The 2012 Ometepec and 2018 Pinotepa Nacional Thrust Events

On 20 March 2012, a M-w 7.5 thrust earthquake started a series of seven large events (7.0 <= M-w <= 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 (M-w > 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 M-w 7.5 earthquake affected the Oaxaca region and whether this earthquake had a causal relationship with the M-w 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.