Short-Term Interaction between Silent and Devastating Earthquakes in Mexico

Abstract

Triggering of large earthquakes on a fault that hosts aseismic slip or, conversely, triggering of slow slip events (SSE) by passing seismic waves involves seismological questions with major hazard implications. Just a few observations plausibly suggest that such interactions actually happen in nature. In this study we show that three recent devastating earthquakes in Mexico are likely related to SSEs, describing a cascade of events interacting with each other on a regional scale via quasi-static and/or dynamic perturbations. Such interaction seems to be conditioned by the transient memory of Earth materials subject to the “traumatic” stressing produced by the seismic waves of the great Mw8.2 Tehuantepec earthquake, which strongly disturbed the aseismic beating over a 650 km long segment of the subduction plate interface. Our results imply that seismic hazard in large populated areas is a short-term evolving function of seismotectonic processes that are often observable.

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

“…This intense RE activity strongly suggests the widespread aseismic slip occurring in the plate interface during the years following the 2012 Ometepec earthquake, which certainly reached shallow interface portions (i.e., above 10 km depth and probably next to the trench) and a large part of the 2018 earthquake rupture zone (both onshore and offshore, including the vicinity of the nucleation point) as previously noticed around the hypocentral region in an increase of foreshock seismicity (Cruz‐Atienza et al., 2021).…”

“…Black dashed lines show the slab isodepth as shown by Cruz‐Atienza et al. (2021). Black closed contours represent rupture areas of large earthquakes (Kostoglodov & Pacheco, 1999).…”

“…In both cases, significantly larger slip rate and RE activation were reported after the main shock, but in the case of Mexico this may have a significant contribution in the nucleation of the 2018 Pinotepa earthquake. Furthermore, sustained seismic and RE activity continued until 2021, this could certainly be explained by the regional plate interface softening produced by seismic waves of the great M w 8.2 (2017) Tehuantepec earthquake (Melgar, Pérez‐Campos, et al., 2018; Meng et al., 2019; Suárez et al., 2019), which strongly disturbed the SSE cycles in Guerrero and Oaxaca (Cruz‐Atienza et al., 2021).…”

“…During the 4 years of postseismic relaxation, the site steadily moved seawards (southward), indicating interplate slip rates larger than the plate convergence velocity. After the relaxation, the displacement partially recovered its interseismic regime to the north until the great 2017 M w 8.2 Tehuantepec earthquake perturbed the entire region, most likely leading the 2018 M w 7.2 Pinotepa earthquake (Cruz‐Atienza et al., 2021). In other words, during 2016 and until the Tehuantepec rupture on 8 September 2017, the upper plate at PNIG moved northward with speed smaller than the long‐term expected velocity, which suggests a large creeping rate at the interface.…”

“…Colored contours show the rupture areas of the reported slow slip events (SSEs) and the afterslip of the 2018 Pinotepa earthquake determined by Cruz‐Atienza et al. (2021) (blue, Guerrero SSE 2017; red, Oaxaca SSE 2017–2018; green, Guerrero–Oaxaca SSE 2018; pink, Oaxaca SSE 2018; purple, Oaxaca SSE 2018; brown, Guerrero SSE 2019). Inset indicates known estimated hypocenters of large events ( M $$\ge $$ 6.9) since 1901 (Sawires et al., 2019).…”