Short-Term Interaction between Silent and Devastating Earthquakes in Mexico
Abstract
Inferred effects of slow slip events (SSE) on large and devastating earthquakes have led to critical questions closely related to seismic hazard. The role of SSEs in the seismic cycle has been identified as preponderant in the initiation of some megathrust earthquakes. Recently, three major earthquakes took place in southcentral Mexico causing more than 480 deaths and losses for 1,6 billion dollars. The earthquake sequence initiated with the great Mw8.2 Tehuantepec event on September 8, 2017, the largest earthquake ever recorded in Mexico, which may have broken the whole subducted Cocos lithosphere. Eleven days later and 480 km northwest, on September 19, the intraslab Mw7.1 Puebla-Morelos normal faulting (57 km depth) event delivered a deadly shock to Mexico City. The sequence ended five months later on February 16, 2018, with a Mw7.2 thrust event below Pinotepa Nacional, Oaxaca more than 250 km away from both previous earthquakes. At the time of the Tehuantepec and Puebla-Morelos events, two separate SSEs were taking place in Guerrero and Oaxaca. Other SSEs also happened in both states in an unusual way during and after the five-month earthquake sequence. Three of them in Guerrero (Mw 6.9-7.0), and other two in Oaxaca (Mw 6.9) interspersed by the Pinotepa earthquake post-seismic slip, all in only two years. In this work we investigate possible interactions between such SSEs and the three devastating earthquakes and found that most of our observations can be explained as a regional cascade of causally related events through short-term, quasi static and dynamic interactions that have strongly perturbed the regional plate-interface aseismic beating. Unlike the last 20 years, during which all SSEs occurred every ~4 years in Guerrero, the last two events reported here had much smaller recurrence periods, of 0.25 and 0.5 years. In Oaxaca the plate interface unusually slipped (aseismically) continuously for the whole two years period with at least two reactivations, one during the post-seismic relaxation of the Mw7.2 Pinotepa earthquake, and the other one with the second Oaxaca SSE. Such unprecedented behavior and the interaction between these events seem 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.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMT003.0019V
- Keywords:
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- 7215 Earthquake source observations;
- SEISMOLOGY;
- 7230 Seismicity and tectonics;
- SEISMOLOGY;
- 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICS;
- 8164 Stresses: crust and lithosphere;
- TECTONOPHYSICS