Rapid Determination of Earthquake Size for Hazard Warning

Abstract

The 26 December 2004 M9 Sumatra–Andaman Islands earthquake caused a tsunami that devastated Indian Ocean coasts within three hours after the earthquake. Improved tsunami warning and emergency response for future great earthquakes require knowing an earthquake’s size within minutes after the event. Although the hypocenter of a distant earthquake is routinely determined from the fi rst seismic P waves within about 15 min, several hours may pass before a reliable size determination for very large earthquakes is available (e.g., for the 2004 Sumatra–Andaman earthquake see Menke and Levin [2005]).