pacific EQ.
The 2004 Indian Ocean earthquake was initially documented as having a moment magnitude of 8.8. In February 2005, scientists revised the estimate of the magnitude to 9.0.[17] Although the Pacific Tsunami Warning Center has accepted these new numbers, the United States Geological Survey has, as of 2022, so far not changed its estimate of 9.1.[18] A 2006 study estimated a magnitude of Mw 9.1–9.3; Hiroo Kanamori of the California Institute of Technology estimates that Mw 9.2 is representative of the earthquake's size.[19]
The hypocentre of the main earthquake was approximately 160 km (100 mi) off the western coast of northern Sumatra, in the Indian Ocean just north of Simeulue island at a depth of 30 km (19 mi) below mean sea level (initially reported as 10 km or 6.2 mi). The northern section of the Sunda megathrust ruptured over a length of 1,300 km (810 mi).[15] The earthquake (followed by the tsunami) was felt in Bangladesh, India, Malaysia, Myanmar, Thailand, Sri Lanka and the Maldives.[20] Splay faults, or secondary "pop up faults", caused long, narrow parts of the seafloor to pop up in seconds. This quickly elevated the height and increased the speed of waves, destroying the nearby Indonesian town of Lhoknga.[21]
Indonesia lies between the Pacific Ring of Fire along the north-eastern islands adjacent to New Guinea, and the Alpide belt that runs along the south and west from Sumatra, Java, Bali, Flores to Timor. The 2002 Sumatra earthquake is believed to have been a foreshock, preceding the main event by over two years