The hypocentre of the main earthquake was approximately off the western coast of northern Sumatra, in the Indian Ocean just north of Simeulue island at a depth of below mean sea level (initially reported as ). The northern section of the Sunda megathrust ruptured over a length of . The earthquake (followed by the tsunami) was felt in Bangladesh, India, Malaysia, Myanmar, Thailand, Sri Lanka and the Maldives. 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.