September 8, 2017 Tsunami: S. Mexico

A small- to moderate-size tsunami was generated by the September 7th earthquake, and detected along the Pacific coast in the region of the earthquake. According to initial water-level measurements by Stuart Weinstein of the Pacific Tsunami Warning Center (PTWC) (via the International Tsunami Bulletin Board), the tsunami was recorded on several tide gauges in southern Mexico and El Salvador. Based on this information, the largest tsunami amplitudes occurred during the first five hours of the observed arrival times at each tide gauge except for the El Salvador location, where the peak occurred 14 hours after first arrival. Videos posted on Youtube indicate that there was minor flooding along the waterfront of the harbor at Puerto Chiapas. In the far field, the maximum tsunami amplitudes from this event were all less than 0.35m, which was the measured amplitude in Owenga, Chatham Islands, in New Zealand (PTWC). (reference #11912)

The associated tsunami 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 93.0W). 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. (reference #11983)