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Geological Impacts and Sedimentary Record of the February 27, 2010, Chile Tsunami-La Trinchera to Concepcion

June 23, 2010

The February 27, 2010, Chilean tsunami substantially altered the coastal landscape and left a permanent depositional record that may be preserved at many locales along the central coast of Chile. From April 24 to May 2, 2010, a team of U.S. Geological Survey (USGS) and Chilean scientists examined the geological impacts of the tsunami at five sites along a 200-km segment of coast centered on the earthquake epicenter. Significant observations include: (1) substantial tsunami-induced erosion and deposition (+/- 1 m) on the coastal plain; (2) erosion from return flow, inundation scour around the bases of trees, and widespread planation of the land surface; (3) tsunami sand deposits at all sites that extended to near the limit of inundation except at one site; (4) evidence of multiple strong onshore waves that arrived at different times and from different directions; (5) vegetation height and density controlled the thickness of tsunami deposits at one site, (6) the abundance of layers of plane-parallel stratification in some deposits and the presence of large bedforms at one site indicated at least some of the sediment was transported as bed load and not as suspended load; (7) shoreward transport of mud boulders and rock cobbles where they were available; and (8) the maximum tsunami inundation distance (2.35 km) was up an alluvial valley.

Most of the tsunami deposits were less than 25 cm thick, which is consistent with tsunami-deposit thicknesses found elsewhere (for example, Papua New Guinea, Peru, Sumatra, Sri Lanka). Exceptions were the thick tsunami deposits near the mouths of Rio Huenchullami (La Trinchera) and Rio Maule (Constitucion), where the sediment supply was abundant. The substantial vertical erosion of the coastal plain at Constitucion

Publication Year 2010
Title Geological Impacts and Sedimentary Record of the February 27, 2010, Chile Tsunami-La Trinchera to Concepcion
DOI 10.3133/ofr20101116
Authors Robert A. Morton, Mark L. Buckley, Guy Gelfenbaum, Bruce M. Richmond, Adriano Cecioni, Osvaldo Artal, Constanza Hoffmann, Felipe Perez
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 2010-1116
Index ID ofr20101116
Record Source USGS Publications Warehouse
USGS Organization St. Petersburg Coastal and Marine Science Center