First evaluation and mapping of the environmental seismic effects generated by the 2017 Mw 8.2 Chiapas Earthquake in Mexico

A Mw 8.2 intraslab earthquake hit the whole Chiapas region and the southern part of the Oaxaca state in Mexico, on September 7, 2017 at 23h49 PM local time (nucleation depth 58 km). The rupture length of this mainshock was of 200-220 km, corresponding to the coastal sector from Salina Cruz to the Pijijiapan village. The focal mechanism obtained by the Mexico National Seismological Service (MNSS) indicates a normal fault striking N311° dipping 84.4° with rake of -94.7°. We surveyed and categorized the earthquake environmental effects in the epicentral area, applying the ESI-07 scale (Environmental Seismic Intensity Scale; Michetti et al., 2007); in the following we present our preliminary results. From our observations, the total area affected by secondary effects is in the order of 18.000 km2; however, ground cracks and landslides have been reported as far as in the Vera Cruz State and Guatemala (total area in the order of 54.000 km2). Intensity of VII to IXESI-07 has been assigned in the Gulf of Tehuantepec region. In the epicentral area, displacements up to - 0.5 m by coseismic coastal subsidence (primary effects) have been documented at Salina Cruz and Playa Vicente in Juchitán Oaxaca. Oceanic tsunami propagation reached Puerto Chiapas (run-up of 3.4 m above tide level), Salina Cruz (run-up of 1.89 m), and Huatulco (run-up of 1.37 m), thirty-six minutes after the mainschock (MNSS). A maximum intensity of IXESI-07 has been assigned to this coastal area. VIIIESI-07 is...