RAPID: Tsunami deposits and coastal uplift near Concepcion, Chile before and after the major earthquake of February 27, 2010

Central Washington University, Ellensburg WA

Investigators

Abstract

On February 27, 2010 a catastrophic magnitude 9 earthquake and accompanying tsunami struck the coast of central Chile. The effects of this event were particularly devastating in the area surrounding Concepción, the second largest city in Chile. This project will precisely document the geomorphic and tectonic signatures of this earthquake and tsunami at several previously described study sites in the Concepción region. In 2009 and early 2010 the author and Chilean collaborators described and surveyed tsunami deposits and uplifted coastal marine platforms at 10 sites between 36.5°S to 38.5°S. Lat. The objectives of this project are twofold: 1) Investigate deposits and impacts of the 2010 tsunami at existing study sites containing geological and historical evidence of previous tsunamis in the Concepción area; and 2) Assess co-seismic and post-seismic land-level changes at existing study sites that underwent significant uplift in previous earthquakes. Field work will be conducted in two separate field excursions between May, 2010 and January, 2011. Field investigations will include mapping and surveying the erosional and depositional effects of the 2010 tsunami at the previously documented sites to compare the deposits from the 2010 tsunami with those from previous events; calibrate the sedimentary deposits with the observational data; assess the preservation potential of tsunami deposits in this environment; and use the 2010 deposits to guide the search for additional repositories where stratigraphic records of multiple paleotsunami deposits are likely to be preserved. At the locations of land-level changes the field objectives will be to resurvey heights of marine platforms that were uplifted during previous earthquakes and surveyed by our team in January, 2010; determine the amount of additional uplift in the 2010 earthquake; establish a baseline elevation for subsequent monitoring of post-seismic land-level changes; and compare locations and amount of uplift in the 2010 earthquake with that measured after the 1835 earthquake. This research has the potential to advance knowledge of the impacts, recurrence, and geological signatures of catastrophic events on the scale of the 2010 Chilean earthquake, which could lead to better preparation, education and decreased loss of life in similar coastal areas. The project will occasion U.S.-Chile collaboration that fosters mutual exchanges of knowledge and expertise. An accurate measurement of the effects of the recent tsunami and coastal uplift from the earthquake, together with the prior measurements, will enable a complete documentation of recurrence intervals of these events and the areas that are most affected. These data will be of great value in the rebuilding process for the communities devastated by the most recent event, and the investigation will have a sustainable presence where it will be most needed and useful.