Timeline
National Oceanic and Atmospheric Administration (NOAA) Tsunami Warning Center: Timeline of events for the Dec. 25, 2004, Indian Ocean Tsunami. This version contains additional information—based on phone records, etc.—from the preliminary timeline posted Dec. 29, 2004. The items in brackets are awaiting further verification. 2:59 p.m. The rupture of the great earthquake begins in the Indian Ocean off NW Sumatra, Indonesia. 3:07 p.m. Initial seismic signals from the earthquake trigger alarms at the NOAA Pacific Tsunami Warning Center (PTWC) in Hawaii. 3:10 p.m. PTWC issues a message to other observatories in the Pacific with preliminary earthquake parameters. Several geophysical observatories, including PTWC, initially under-estimated the size as around a magnitude 8.0. 3:14 p.m. PTWC issues a Tsunami Information Bulletin providing information on the earthquake and stating there is no tsunami threat to Pacific coasts. It is a text message distributed by multiple means to participants of the Tsunami Warning System in the Pacific. PTWC also advises the following offices by telephone as part of its standard operating procedure: 1) Hawaii Civil Defense, 2) Pacific Command (PACOM) of U.S. Military Forces, 3) U.S. Navy-Hawaii Region, and 4) International Tsunami Information Center. [3:15 p.m.] Tsunami waves begin striking the coasts of northern Sumatra and the Nicobar Islands. 4:04 p.m. PTWC issues a second Tsunami Information Bulletin to the Pacific revising the earthquake magnitude to 8.5 based on later seismic energy. The bulletin again indicates no tsunami threat to the Pacific, but language is added to advise the possibility of a tsunami near the epicenter. [4:30 p.m.] PTWC attempts to contact the Australian Bureau of Meteorology to verify they received the bulletin. As their main line was busy, they called Emergency Management Australia instead. EMA indicated Australia was aware of the earthquake. [4:45 p.m.] Tsunami waves begin striking the coasts of Sri Lanka, India and Thailand. 6:21 p.m. A magnitude 7.1 aftershock occurs. PTWC staff evaluate the earthquake with some difficulty due to its signal being mixed with large seismic waves still active from the main event. No bulletin is issued for this event due to its much smaller size compared to the main shock. [6:30 p.m.] Tsunami waves begin striking the Maldive Islands. 7:12 p.m. Reuters Internet wire service posts its first story indicating a tsunami has hit Sri Lanka causing 150 casualties. It also reports 100 tsunami injuries in Thailand. 7:25 p.m. The first data from the Australian National Tidal Center gauge at Cocos Island gives a reading of 0.5m crest-to-trough. This was the only sea level data in the Indian Ocean available to PTWC. Also at 7:25 p.m. the Harvard University Seismology Department reports its preliminary Centroid Moment Tensor solution that indicates a magnitude of 8.9. (This was adjusted by Harvard the following day to 9.0.) 7:32 p.m. PTWC issues a message to the Tsunami Bulletin Board that goes by e-mail to international tsunami scientists and organizations. The message reports that based on the Reuters news wire article, a destructive tele-tsunami was generated by the Sumatra earthquake. 7:55 p.m. PTWC re-contacts the Australia Bureau of Meteorology and advises it of the increased earthquake magnitude and the 0.5 m reading at Cocos Island. They indicate that while they can't make any kind of forecast there is the possibility of destructive tsunami waves on Australia's western coasts. [8:00 p.m.] PTWC re-contacts PACOM to advise of the increased earthquake magnitude and potential tsunami impacts in the western Indian Ocean. [8:15 p.m.] The Australia Bureau of Meteorology calls PTWC to advise they have issued an alert to their western coasts. [9:00 p.m.] PTWC receives a call from a Sri Lanka Navy Commander inquiring about the potential for further tsunami waves from aftershocks. [9:15 p.m.] The U.S. Ambassador in Sri Lanka calls PTWC to set up a notification point in case of aftershocks with tsunamigenic potential. [9:30 p.m.] The NOAA National Weather Service Pacific Region director reports to PTWC that PACOM has informed him they did not observe a destructive tsunami at Diego Garcia. [10:00 p.m.] The U.S. State Department Operations Center calls PTWC and is advised of the potential threat to the western Indian Ocean and eastern Africa. They agree to set up a conference call with U.S. embassies in the region. 10:15 p.m. The U.S. State Department Operations Center sets up a conference call with the U.S. embassies at Madagascar and Mauritius. PTWC advises that based on the size of the earthquake and there being reports of tele-tsunami impacts in the Bay of Bengal, there is the potential threat of a damaging tsunami in the western Indian Ocean. [10:15 p.m.] Tsunami waves have crossed Mauritius and are close to reaching Madagascar. They are also starting to impact the northernmost part of the east coast of Africa. Dec. 26, 2004 5:36 a.m. PTWC issues a third tsunami information bulletin indicating small sea level fluctuations from the Indian Ocean tsunami are being observed in the Pacific Ocean, probably from tsunami energy that passed south of Australia. Source: National Oceanic and Atmospheric Administration (NOAA) Tsunami Warning Center |