Environmental effects caused by the Mw 8.2, September 8, 2017, and Mw 7.4, June 23, 2020, Chiapas-Oaxaca (Mexico) subduction events: Comparison of large intraslab and interface earthquakes

Earthquake Environmental Effects (EEEs) such as surface faulting, landslides, liquefaction and tsunamis are widely distributed following strong seismic events and may account for a significant part of the overall damage. Here, we investigate EEEs generated by two earthquakes with different source parameters, both occurring along the Mexican subduction zone: the Sept. 8, 2017, Mw 8.2, moderate depth, normal fault, intraslab event; and the June 23, 2020, Mw 7.0, shallow depth, thrust fault, interface event. We document all the EEEs for each event, assign an intensity value using the Environmental Seismic Intensity (ESI-2007) scale, and derive the macroseismic fields. Finally, we compute the attenuation of intensity with distance and we compare it with other subduction zone earthquakes worldwide, demonstrating the repeatability of EEEs. This work represents the first application of the ESI-2007 scale to an intraslab earthquake and documents its wide applicability in different seismotectonic settings. We argue that EEEs provide useful information that should not be neglected in seismic hazard assessment procedures.