The 8 September 2017 Tsunami Triggered by the M w 8.2 Intraplate Earthquake, Chiapas, Mexico MARI ´ A TERESA RAMI ´ REZ-HERRERA, 1 NE ´ STOR CORONA, 2 ANGEL RUIZ-ANGULO, 3 DIEGO MELGAR, 4 and JORGE ZAVALA-HIDALGO 3 Abstract—The 8 September 2017, M w 8.2 earthquake offshore Chiapas, Mexico, is the largest earthquake in recorded history in Chiapas since 1902. It caused damage in the states of Oaxaca, Chiapas and Tabasco, including more than 100 fatalities, over 1.5 million people were affected, and 41,000 homes were damaged in the state of Chiapas alone. This earthquake, an intraplate event on a normal fault on the oceanic subducting plate, generated a tsunami recorded at several tide gauge stations in Mexico and on the Pacific Ocean. Here, we report the physical effects of the tsunami on the Chiapas coast and analyze the societal implications of this tsunami on the basis of our post-tsunami field survey. The associated tsu- nami waves were recorded first at Huatulco tide gauge station at 5:04 (GMT) 12 min after the earthquake. We covered ground observations along 41 km of the coast of Chiapas, encompassing the sites with the highest projected wave heights based on our preliminary tsunami model (maximum tsunami amplitudes between 94.5° and 93.0°W). Runup and inundation distances were measured along eight sites. The tsunami occurred at low tide. The maximum runup was * 3 m at Boca del Cielo, and maximum inundation distance was 190 m in Puerto Arista, corresponding to the coast in front of the epicenter and in the central sector of the Gulf of Tehuantepec. Tsunami scour and erosion was evident along the Chiapas coast. Tsunami deposits, mainly sand, reached up to 32 cm thickness thinning landward up to 172 m distance. Key words: Post-tsunami survey, M w 8.2 intraplate earth- quake, Mexican subduction, runup, tsunami early warning. 1. Introduction The 8 September 2017, M w 8.2 earthquake off- shore Chiapas, Mexico (Fig. 1), was the largest earthquake in the recorded history of Chiapas since 1902. Few historical tsunamis have been recorded near the coast of Chiapas, but only one event caused by a magnitude M s 7.7 on 22 March 1928 in Puerto Angel Oaxaca, having caused no reported fatalities (Nun ˜ez-Cornu and Ponce 1989; Sanchez and Farreras 1993; NGDC/WDS 2017). The 8 September 2017, M w 8.2 earthquake caused damage in the states of Oaxaca, Chiapas and Tabasco; the official estimates exceed 100 fatalities, more than 1.5 million people affected, and 41,000 homes damaged in the state of Chiapas alone. Although the epicenter of this earth- quake was close to the Mexican subduction zone where the Cocos plate subducts under the North American plate, this was not an interplate event, a megathrust earthquake, but rather a deep intraplate event within the subducting oceanic plate, near the slab bend from a shallow to steeper dip at greater depth in the slab (e.g., Hayes et al. 2012; Okuwaki and Yagi 2017; Hjorleifsdottir et al. 2017), with a focal mechanism indicating normal faulting (strike 311, dip 84.4, and rake 94.7, the plane given is the preferred plane) at 58 km depth (SSN 2017). The 8 September 2017 earthquake generated a tsunami that was recorded at several tide gauge stations in Mexico and around the Pacific Ocean (SMN 2017; PTWC 2017). Here, we report the physical effects of the tsunami (runup) on the Chiapas coast and analyze the societal implications of this tsunami on the basis of our field observations. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00024-017-1765-x) contains sup- plementary material, which is available to authorized users. 1 Laboratorio Universitario de Geofı ´sica Ambiental, Instituto de Geografı ´a, Universidad Nacional Auto ´noma de Me ´xico, Ciudad de Me ´xico, Me ´xico. E-mail: tramirez@igg.unam.mx 2 El Colegio De Michoaca ´n, La Piedad, Michoaca ´n, Mexico. 3 Centro de Ciencias de la Atmo ´sfera, Universidad Nacional Auto ´noma de Me ´xico, Ciudad de Me ´xico, Me ´xico. 4 Department of Earth Sciences, University of Oregon, Eu- gene, OR, USA. Pure Appl. Geophys. 175 (2018), 25–34 Ó 2017 Springer International Publishing AG, part of Springer Nature https://doi.org/10.1007/s00024-017-1765-x Pure and Applied Geophysics