Madagascar field survey after the December 2004 Indian Ocean tsunami

The effects of the 26 December 2004 Indian Ocean tsunami on the island of Madagascar were surveyed in July and August of 2005. Runup and inundation were obtained at 52 sites, covering most of the eastern coast of the country, ranging from a maximum runup of 5.4 m in the south to locations where the tsunami was not observed by eyewitnesses present on the day of the event. The data set is characterized by significant heterogeneity, suggesting the importance of local factors in controlling runup. The report of a 50-m vessel breaking its moorings in the port of Toamasina several hours after the maximum visible activity of the wave underscores the complexity of harbor responses and the need to re-evaluate civil defense policies in port environments. Important factors are how the Malagasy population responded to the warning issued during the Nias earthquake, on 28 March 2005, and the hazard posed to Madagascar by possible future mega-earthquakes in south Sumatra.