Environmental effects and ESI-07 intensity of the Mw 7.7, September 19th, 2022, Michoacán, Mexico, earthquake

Abstract

Most seismic risk assessments primarily focus on the impact of ground acceleration on infrastructure. However, in Mexico, along with numerous countries in Latin America and beyond, a significant portion of earthquake risk stems from secondary environmental effects such as tsunamis, landslides, and liquefaction processes. These secondary effects can often prove more lethal than the earthquake shaking itself. We used the Environmental Seismic Intensity scale (ESI-07) to assess the Earthquake Environmental Effects (EEEs) of the Mw 7.7 Michoacan earthquake on September 19th, 2022. This made it possible to comprehensively characterize the EEEs and their potential social consequences in the epicentral area along the Mexican subduction zone. Our study draws on data gathered from extensive field surveys, satellite imagery analysis, social media monitoring, and online resources, totalling data from over 8000 sites with EEEs. Through rigorous analysis, ESI-07 intensity values illuminate the vulnerability of coastal areas and coastal ranges to specific secondary effects triggered by large seismic events. We meticulously map the spatial distribution of these triggered EEEs, presenting A) an ESI-07 isoseismal map, and B) comparative analysis with other significant earthquakes, particularly subduction megathrust interface events. Our findings underscore the critical importance of considering environmental coseismic effects and using the ESI-07 scale in territorial planning and seismic risk preparedness. Furthermore, we highlight the unique characteristics of the Mexican Pacific coastal region and, more broadly, the distinct risks posed by coastal areas along subduction zones in terms of secondary seismic environmental hazards. This work emphasizes the urgent need to acknowledge the vulnerability of these regions to secondary effects and the imperative for resilience-building measures to safeguard human well-being and mitigate economic repercussions in the face of future seismic events.