Magnitude 9.0 Sumatra-Andaman Islands Earthquake

5° Northern Sumatra Earthquake of 28 March 2005 95° 100° Satun Songkhla, ANDAMAN SEA Penis Perlis Pattani THAILAND ValaNarathiwat 105° 0° 5° 2004 2005 2005 Sumatera Utara 1861 Kedah Pulau Pinang SOUTH CHINA SEA Kelantan Terengganu- 5° Perak Sumatera Utara MALAYSIA Pahang Selangor. Negeri Sembilan Melaka Johor SINGAPORE Singapore Singapore Sumatra Sumatera Barat Sumatera Barat Sunda Trench INDIAN OCEAN Riau EXPLANATION Main Shock * 28 March 2005 Earthquakes 28 Mar - 8 Apr 2005 4.0-4.9 Ⓒ 5.0-5.9 6.0-6.9 Main Shock 26 December 2004 SUNDA PLATE Rupture Zones Jambi 1833 Sumatera Selatan 1861 Sumatera Selatan 1833 Bengkulu 2004 Aftershocks AN 2005 Aftershocks INDONESIA Lampung 5° When was the last big one? ▪How often do they occur? 95° AUSTRALIA PLATE 100° Kilometers 0 50 100 200 300 400 Jakarta Jawa Barat 105° Prior to December 26th, the largest earthquake along the subduction zone from southern Sumatra to the Andaman Islands occurred in 2000 and had a magnitude of 7.9. A magnitude 8.4 earthquake occurred in 1797, a magnitude 8.5 in 1861 and a magnitude 8.7 in 1833. All three ruptured sections of the subduction zone to the south of the recent earthquake. Interestingly, the 1797 and 1833 quakes are believed to have ruptured roughly the same area with only 36 years separating the events. Paleoseismic evidence shows that great earthquakes or earthquake UMR couplets occur about every 230 years.

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