Location:

M 7.2 off the west coast of northern Sumatra

Magnitude:

7.2

Time:

10 Jan 2012 18:36:59

Depth:

19.0

M 7.0+:

M 8.6; 2012 Wharton Basin Earthquake; (11 Apr 2012) (20km from the earthquake)

There is one swarm found nearby.

2012

PS20120411.3(26.5km)

11 Apr

1 day 4 hours

10 earthquakes

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Seismic Activity Off Northern Sumatra: The January 2012 M7.2 Earthquake

The region off the west coast of northern Sumatra forms part of the tectonically active Sunda subduction zone, where the Indo-Australian plate converges with the Eurasian plate. This setting produces frequent seismic events ranging from shallow crustal earthquakes to deeper intraslab activity. The January 2012 event occurred within this framework at a focal depth of 19 km. On 10 January 2012 at 18:36 UTC, a magnitude 7.2 earthquake struck off the west coast of northern Sumatra. The event was followed months later by the 11 April 2012 M8.6 Wharton Basin earthquake approximately 20 km distant, highlighting the clustered nature of seismicity in the area.

Strong Earthquakes Since 2000

Seismic records document two notable events in close proximity since the start of 2000:

M8.6 Wharton Basin earthquake on 11 April 2012, located about 20 km from the January event.
M7.2 earthquake off the west coast of northern Sumatra on 10 January 2012. These occurrences reflect ongoing deformation along fracture zones and the subducting slab in the eastern Indian Ocean.

Regional Geological Setting and History

Northern Sumatra sits at the boundary between the Sunda Trench to the west and the Sumatran Fault system onshore. Subduction has generated major historical earthquakes, including the 2004 M9.1 event that produced a devastating tsunami across the Indian Ocean basin. Post-2004 aftershock sequences and subsequent intraplate ruptures, such as the 2012 sequence, demonstrate the continued release of stored strain in both the megathrust and adjacent oceanic lithosphere. The Wharton Basin, east of the Ninetyeast Ridge, hosts diffuse strike-slip faulting that accommodates regional plate motion complexities. Updated monitoring by global networks confirms persistent moderate-to-large events in this corridor, underscoring the need for continued hazard assessment in coastal communities of northern Sumatra.

References

USGS Earthquake Catalog Global CMT Catalog NOAA Significant Earthquake Database