Field Survey of the 2015 Chile Tsunami with Emphasis on Coastal Wetland and Conservation Areas

Abstract

The September 16th 2015 Illapel M8.3 earthquake, Chile, generated a tsunami that affected a sparsely populated region, causing 15 casualties and destroying 1069 houses (USGS 2015). A maximum surface elevation of +4.5 m was observed in Coquimbo's tide gauge while in other sites of the tide network, the tsunami did not exceed +2.0 m. A post-tsunami survey team comprised by local researchers was deployed from September 17th to November 14th 2015. The survey covered approximately 80 sites along 500 km of the primary impact zone, from the northernmost site where damage was reported, Bahía Carrizalillo (29.11{\textdegree}S; 71.46{\textdegree}W), southward to El Yali National Reserve (33.75{\textdegree}S; 71.73{\textdegree}W) beyond which no tsunami damage occurred. The results of the survey in coastal towns with evident damage and isolated sites where the tsunami signature remained almost intact are summarized in this paper. A large amount of quantitative material is presented; including (1) inundation lines in five coastal sites, (2) 157 profiles including wave runup and flow depths and (3) 47 interviews to eyewitness, generally 2--3 per site. About two-thirds of the data were collected in isolated areas to guarantee spatial homogeneity along the impact zone. The type of damage in specific areas of biological interest and in coastal cities such as Concón, Tongoy and Coquimbo is also reported. A maximum runup of 13.6 m was recorded in La Cebada (30.97{\textdegree}S; 71.65{\textdegree}W). The information presented herein provides spatial completeness in places that may have not been surveyed by other teams, and redundancy in areas surveyed by others.