Tsunami Boulder Transport and Other Dramatic Effects of the 15 November 2006 Central Kuril Islands Tsunami on the Island of Matua

The 15 November 2006 central Kurils subduction-zone great earthquake (Mw 8.1–8.4) generated a mildly damaging tsunami in the far field, but no observations in the near field. We surveyed the near-field effects of this tsunami in the summers of 2007 and 2008, having previously visited several sites in summer 2006. Of the central Kurils, Matua was one of the islands most dramatically affected by the tsunami, including infrastructure left from World War II that was damaged and moved. On the Pacific-facing side, where runup ranged from 12.3 to 19.5 m, and inundation from 38 to 93 m, the tsunami caused erosion and boulder transport on steep, rocky shorelines. Many of the transported boulders had attached flora and fauna indicative of subtidal origin. Using measured profiles, boulder surveys, and before-and-after photos, we have generated a case history of boulder transport where the parameters are well known. More thorough analysis of the transport mechanisms awaits numerical modeling of tsunami runup coupled with detailed bathymetry and local topography. Given the size of the tsunami, it is surprising that available larger boulders were not moved; we suggest that roughness is an important factor in this case.