Slide Image: The slide shows a round global map with Sumatra, the epicenter of the December 2004 earthquake, in the center. The locations of the Global Seismographic Network (GSN) stations are represented by small triangles and their acronyms. They are located on all the continents and on oceanic islands. The stations are connected by lines to the epicenter in Sumatra. Four circles increasing in size from the center are numbered: 40, 80, 120 and 160 followed by the symbol for degree.

Credit: IRIS Consortium