Evidence of a previously unrecorded local tsunami, 13 April 2010, Cook Islands: implications for Pacific Island countries

Abstract. Tsunami hazard assessments for Pacific Islands Countries (PICs) tend to focus on subduction zone sources. It is generally recognised that while volcanic-related tsunamigenic sources exist, they are probably only of minor relevance to the overall hazardscape of the Pacific. This paper outlines the evidence for a previously unrecorded local tsunami that struck the uninhabited south coast of Mangaia, Cook Islands, on 13 April 2010. The tsunami had a maximum inundation of 100 m inland and a runup of 12 m a.s.l. This event was most probably caused by a small submarine slope failure, the most recent of an unknown number of previous inundations. Since most PICs have a volcanic origin, it is suggested that current perceptions about the local and regional significance of such events is inaccurate. A review of volcanic-related tsunamigenic sources throughout the Pacific reveals a wealth of data concerning submarine slope failures in particular and a more general background of active volcanism. These sources are as relevant to PICs close to or far away from subduction zones. As populations grow and the coastlines of many PICs and those on the edge of the Pacific Ocean become increasing occupied, the likelihood for loss of life from these events increases.