By Lori Dengler, Humboldt State University
I’m leading an interdisciplinary group under the auspices of the Earthquake Engineering Research Institute (EERI) of that includes an environmental scientist, an anthropologist and an emergency manger that will be working in American Samoa and Samoa over the next two weeks. We will be coordinating our efforts with a group of engineers sponsored by the American Society of Civil Engineers who will be examining the performance of port and coastal structures over the same time period as our visit.
Post tsunami field studies are important for a number of reasons. Usually the first teams to visit a tsunami-struck area are the water height specialists who measure tsunami runup (the elevation of the tsunami at the inland extent of inundation) and other water height indicators. Records of water heights such as debris lines, water marks on buildings, and debris in trees are ephemeral and these measurements are critical to calibrating numerical models of tsunami flooding such as those used to estimate California tsunami hazards. Almost as quick on the scene are scientists who study tsunami deposits – the cobbles, sands, silts and debris transported by tsunamis. The characteristics of deposits of recent tsunamis can be used to help interpret paleotsunami deposits such as those found in Crescent City and the southern parts of Humboldt Bay.
Our group is focusing on a different aspect of tsunamis – how people responded to the natural warning signs of the tsunami and how coastal structures, planning and management affected exposure. We are also going to be looking at how people responded to the natural warning of September 29 – the strong ground shaking of a magnitude 8 earthquake, and the official warning that was issued on October 7 when a large earthquake occurred in the Vanuatu Islands about 1500 miles away from Samoa.