Shallow M6.3 earthquake hits off the west coast of northern Sumatra, Indonesia

A strong and shallow earthquake registered by the BMKG as M6.3 hit off the west coast of northern Sumatra, Indonesia at 05:19 UTC (12:19 local time) on December 30, 2023, at a depth of 12 km (7.4 miles). USGS and EMSC report this quake as M5.6 at a depth of 10 km (6.2 miles).

The epicenter was located about 368.4 km (228.9 miles) W of Sinabang and 386.5 km (240.2 miles) WSW of Meulaboh, Aceh, Indonesia.

The location of the epicenter is about 280 km (173 miles) E of the epicenter of December 26, 2004 M9.1 Sumatra-Andaman Earthquake. The tsunami caused by that quake left an estimated 230 000 fatalities in 14 countries across 2 continents. Sumatra was the hardest hit, with more than 160 000 fatalities — or nearly 5% of the local population.

Based on pre-run model scenarios, there is no tsunami threat to countries in the Indian Ocean, InaTEWS-BMKG said at 05:43 UTC. “No further bulletins will be issued unless the situation changes.”

The USGS issued a Green alert for shaking-related fatalities and economic losses. There is a low likelihood of casualties and damage.

There are likely to be no affected structures in this region.

Recent earthquakes in this area have caused secondary hazards such as landslides that might have contributed to losses.

BMKG initially reported the quake as M6.6 and later downgraded it to M6.3.

“BMKG analysis results show that this earthquake had updated parameters with a magnitude of M6.3. The epicenter of the earthquake was located at coordinates 2.50° N; 93.00° East Longitude, or precisely located in the sea at a distance of 372 km (231 miles) southwest of Calang City, Aceh at a depth of 12 km (7.4 miles)… The results of the source mechanism analysis show that the earthquake has a strike-slip movement mechanism.”

According to BMKG, the earthquake was felt in South Aceh and Simeulue at an intensity of IV MMI, noticeable indoors by many during the day. Southwest Aceh experienced it as III MMI, with vibrations akin to a passing truck. In Aceh Besar and Banda Aceh, it was felt at a lighter intensity of II MMI, causing light objects to sway.

Regional seismicity

Featured image credit: TW/SAM, Google