The huge moment magnitude (Mw) 9.2 earthquake that struck Sumatra in December 2004, producing a devastating tsunami, ruptured the western end of a major plate boundary. Two subsequent earthquakes ruptured progressively eastward sections, including a Mw 8.4 earthquake in September 2004. The area to the east last ruptured in two great earthquakes in 1797 and 1833. Quakes are associated with local uplift of several meters, which expose shallow corals. Sieh et al. (p. http://www info-aaas.org/util/link.jsp?e=0-jkh8dWkT3n-qkJdT6KB-x1uZDiskeKJgcntqZQGiR0ccA..A&s=1TbJ-2Es.A&v=2dapMESvl9VSS8g..A" target="_blank">1674) have accurately dated bands in these corals to reconstruct the quake history. Major quakes occurred in the 1300s and again, about 200 years later. With the known quakes, this record implies that major quakes in this region appear in a series of events about 200 years apart.