The aim of this research was to find information about the wides and percentage of coral reef after earthquake and tsunami that happened on December 26th 2006 and March 28th 2005 at North Beach Waters in Nias Island, and for mapping the ecosystem by using Landsat-7 ETM+ data with Lyzenga algorithm. This research divided into three phase, consist of: 1. The calculation of wides coral reef by usi…