The February 27, 2010, magnitude 8.8, offshore Maule, Chile, earthquake and earthquake-induced tsunami caused extensive damage to structures in cities along the Chilean coast. Field observations from this event can provide valuable data for calibration of experimental and numerical models and tsunami design guidelines being developed under current NSF-supported NEES research grants including the "Performance-Based Tsunami Engineering" project. Through support from the NSF Engineering Directorate's NEES Research Program and the NSF Office of International Science and Engineering's Americas Program, this RAPID project team will survey the structural damage and scour effects of the affected coastal areas. The field survey will be conducted by an eight-member team of faculty and students from the University of Hawaii, Manoa; University of Michigan, Ann Arbor; Princeton University; University of Tennessee, Knoxville; and Stanford University. Similar to the Samoan tsunami survey conducted in November 2009 by some of the team members, this survey for the Chilean tsunami intends to collect and preserve data to (1) compare against numerical simulations, (2) update the database for risk models, (3) develop retrofit and design recommendations, and (4) improve the understanding of the dynamics of fluid, structure and sediment interactions, which is critical to the general design and retrofit of levees, dams, and a wide range of coastal structures. In addition, the RAPID team will (5) perform a comparison of the data and analysis results obtained from the Chilean tsunami with those from the Samoan tsunami survey and document findings in conference and journal papers.
Intellectual Merit: The effects of combined earthquake and tsunami have not been examined in detail by researchers due to the complex nature of sequential loading and response. The complexities involved include structural response due to earthquake, potential liquefaction of the supporting soil foundation, and fluid impact load due to tsunami run-up and drawdown, with each of the phenomenon being highly nonlinear. To date, there is little, if any, field data available for such combined events, which are likely scenarios of the anticipated Cascadia Subduction Zone earthquake and tsunami in the U.S. Pacific Northwest.
Broader Impacts: The current design guidelines in Chile do not have provisions for tsunami effects. Chilean researchers and their students will join this RAPID survey team to collaborate to develop tsunami load modeling, simulation and design, incorporating aspects of the FEMA P646 "Guidelines for Design of Structures for Vertical Evacuation from Tsunamis" into new design guidelines for Chile. The body of scientific literature that would be impacted by the lessons learned from this survey includes tsunami run-up height and inundation prediction; tsunami impact on coastal structures including harbors, docks and naval facilities; sediment transport and scour; foundation design; and bridge engineering.
Our project team consists of two faculty members from Oregon State University, one from the University of Hawaii at Manoa, one from Princeton University, a student from Sanford University and a local student from Santa Maria University in Chile. We conducted a tsunami damage survey on buildings, bridges and lifeline infrastructure along the coast of Chile including the cities of Constitucion, Concepcion, Dichato and Talcahuano using state-of-the-art LIDAR equipment. The majority of buildings observed during this reconnaissance withstood earthquake with minimal damage. Structures damaged from earthquakes were spread throughout cities instead of being concentrated in one specific locale. Tsunami damage, however, was consistent throughout specific locales. Wood structures failed from tsunami impacts. Masonry structures better withstood the impact, although there were several masonry structures that still failed from the tsunami. In Dichato, it was observed that coastal erosion and scour were more prevalent and coincident with roadways, which channeled water. This indicates that the scouring probably happened with outgoing waves. Most tsunami damage was observed on first floor, breakaway walls would make a good structural design. Also, water moves around columns easier. Hence buildings with windows that broke had columns that better withstood the earthquake, compared to large walls that did not have break-away sections. We documented the survey in a report. Based on our survey data and subsequent analysis, we published one journal and two conference papers and have an additional journal paper in press. The knowledge gained and technologies developed from the project are transferred to undergraduate and graduate class lectures and seminar presentations.
