The most powerful of the series had a magnitude of 8.4, which makes it in the top 20 of the largest earthquakes ever recorded on a seismograph.

After further aftershocks above magnitude 5, a third large earthquake, 7.0 Mw, occurred at 03:35:28 UTC (10:35:28 local time) on 13 September.

Tidal buoys[6] positioned in the Indian Ocean and other seismic tools have led scientists to issue a series of tsunami bulletins.

[10][11] In Singapore, which is about 670 km (416.3 mi) from the epicenter, the tremor was felt at around 11:10 UTC (19:10 local time).

[13] In Peninsular Malaysia, tremors were reported after 19:15 local time, including Kuala Lumpur, Putrajaya, Johor Bahru, Malacca and Penang.

The Government of India asked the states of Tamil Nadu, Kerala, Andhra Pradesh and the union territories of Andaman and Nicobar Islands and Puducherry to be on high alert.

However, Malaysian authorities had detected a 1–3 m (3.3–9.8 ft) high tsunami heading away from the epicenter of the earthquake.

The component of plate motion perpendicular to the boundary produces thrust faulting on the offshore plate-boundary.

It occurred about 225 km northwest of the magnitude 8.4 earthquake, at the northern end of the aftershock zone.

This article incorporates public domain material from websites or documents of the United States Geological Survey.