Tsunami Runup in the Middle Kuril Islands from the Great Earthquake of 15 Nov 2006 (abstract)

Document Type

Article

Department or Administrative Unit

Geological Sciences

Publication Date

2007

Abstract

Two expeditions to the middle Kuril Islands [IMGG FED RAS, NSF Kurils Biocomplexity Project] in the summer of 2007 yielded tsunami runup and inundation measurements from the 15 Nov 2006 Mw 8.3 subduction-zone earthquake, and possibly from the 13 Jan 2007 Mw 8.1 earthquake seaward of the subduction zone. Both earthquakes produced measurable tsunamis in the far field, the 13 Jan tsunami significantly smaller; the 15 Nov tsunami did some damage in the harbor of Crescent City, CA. Ours are the first near-source measurements because no one lives in the middle Kurils. Moreover, because KBP visited many of the same sites in summer of 2006, we have numerous before-and-after comparisons, including quantified erosion. We measured 120 profiles and made more than 300 runup measurements. We found dramatic tsunami effects of erosion and deposition, with widespread runup of 8-12 m, up to about 20 m, between and including Simushir and Matua islands. In most cases, we measured runup with a transit and surveying rod, producing a topographic profile from sea level to the slope above runup indicators; in some cases, we used a hand level and tape. Runup/inundation criteria were generally subhorizontal lines of floatable debris, typically wood, plastic, glass floats, and styrofoam. Single occurrences, e.g., of a plastic bottle were not considered adequate. Corroborative evidence, not used independently, included limits of consistently oriented stems of tall grasses and flowers, limit of sand and gravel deposits above turf and dead vegetation, and elevation of fresh erosion of turf from slopes landward of the beach plain. Currently we are compiling, correcting and vetting our measurements, which will be submitted to online databases. Topographic profiles obviously had an effect on the data, with short, steep profiles generating high runup and short inundation; most beach-ridge profiles had longer inundation and shorter runup. However, at Ainu Bay on Matua Island, we found as much as 18-20 m of runup at the landward limit of inundation 350-400 m inland. Our survey did not include islands north of Matua; the next major island, Shiashkotan, is almost 100 km away, so it is hard to predict effects there. Some preliminary results [m runup height at landward limit, m inundation distance]: Matua, Pacific coast [6-17, 50-100]; Matua, South Bay [6-8, 100-220]; Matua, Ainu Bay [12-20, 70-400]; Rasshua, Okhotsk coast, [5-10; 50-65]; Ryponkicha, Pacific coast [10-11, 45-55]; Ketoi south coast [6-9; 45-65]; NE Simushir [7-19; 50-150]; SE Simushir [5-7; 80-140].

This abstract is available in Eos.

Journal

Eos (Transactions, American Geophysical Union)

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