On 19 September 2022 a Mw 7.6 earthquake occurred along the Mexican subduction zone in the Michoacán region with an onshore epicenter at a focal depth of 15 km. We document the environmental effects triggered by the earthquake by means of field surveys and remote sensing. Observed primary effects include permanent coastal uplift, while secondary effects include landslides, rock fall, liquefaction, ground cracking, lateral spreading and tsunami waves. We assign an ESI-07 (Environmental Seismic Intensity) value to each site where an environmental effect has been observed. ESI-07 is an intensity scale based only on effects on the natural environment; intensity values are based on the dimension of each effect: amount of tectonic uplift or subsidence; volume of mobilized material for slope movements; length and width of ground cracks; diameter and height of liquefaction sand boils. We investigate the spatial distribution of earthquake effects and we draw isoseismal lines; we analyze the intensity attenuation with distance, comparing the 2022 Michoacán earthquake to previous events in the same region. Additionally, the comparison of this case study with a dataset of over 150 earthquakes analyzed using the ESI-07 scale shows a good consistency. One of the challenges in documenting the environmental effects by the Michoacán earthquake is rainfall. Heavy precipitation in the days following the earthquake quickly erased or altered some of the effects, in particular the smaller ones. We argue that a methodological approach complementing a rapid acquisition of data in the field, screening of local news sources and remote data analysis (e.g., satellite images) can partially overcome such limitations. EEEs analysis provide useful information that should not be neglected in seismic hazard assessment.
Michoacan earthquake (Mw 7.6): application of the ESI-07 scale
2023
Abstract
On 19 September 2022 a Mw 7.6 earthquake occurred along the Mexican subduction zone in the Michoacán region with an onshore epicenter at a focal depth of 15 km. We document the environmental effects triggered by the earthquake by means of field surveys and remote sensing. Observed primary effects include permanent coastal uplift, while secondary effects include landslides, rock fall, liquefaction, ground cracking, lateral spreading and tsunami waves. We assign an ESI-07 (Environmental Seismic Intensity) value to each site where an environmental effect has been observed. ESI-07 is an intensity scale based only on effects on the natural environment; intensity values are based on the dimension of each effect: amount of tectonic uplift or subsidence; volume of mobilized material for slope movements; length and width of ground cracks; diameter and height of liquefaction sand boils. We investigate the spatial distribution of earthquake effects and we draw isoseismal lines; we analyze the intensity attenuation with distance, comparing the 2022 Michoacán earthquake to previous events in the same region. Additionally, the comparison of this case study with a dataset of over 150 earthquakes analyzed using the ESI-07 scale shows a good consistency. One of the challenges in documenting the environmental effects by the Michoacán earthquake is rainfall. Heavy precipitation in the days following the earthquake quickly erased or altered some of the effects, in particular the smaller ones. We argue that a methodological approach complementing a rapid acquisition of data in the field, screening of local news sources and remote data analysis (e.g., satellite images) can partially overcome such limitations. EEEs analysis provide useful information that should not be neglected in seismic hazard assessment.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
