But unlike December's quake, this latest one did not lead to a wave with anywhere near the same destructive force.
Scientists say this may be because the new quake did not release enough energy to cause slippage in the sea floor - and the quake's focus was also deeper.
Measurements show a small tsunami did result but its effects were hardly noticeable.
It is likely that we did not have nearly as large a displacement as with the December 26 event
Greg Romano, Noaa
Energy values
The epicentre of Monday's quake was about 200km (125 miles) northwest of the town of Sibolga, at the edge of a particularly high stress area on the undersea Sunda trench fault.
Major earthquakes tend to cluster at these subduction zones, where two or more plates of the Earth's outer material grind and overlap.
ANIMATED GUIDE
How an earthquake happens
The disturbance this caused in the water column above generated waves that, by the time they reached land, were up to 10m (30ft) high.
The figures quoted by agencies for the size of the quakes are on the moment magnitude scale - and although the jump from 8.7 to 9.3 may not sound like much, the way the calculations are made means there is actually a big difference between the two.
In terms of the energy released, Monday's quake was probably 5-6 times smaller than the Boxing Day event.
"That's crucial, because the bigger the energy released, the greater the chance that the sea bed will move," said John McCloskey of the University of Ulster.
Deep underground
Just 10 days ago, Professor McCloskey's team forecast in the journal Nature that the Boxing Day quake had increased stress on two nearby fault lines - the Sumatran fault and on the undersea Sunda trench.
Greg Romano, of the US National Oceanic and Atmospheric Administration (Noaa), told the BBC: "A tsunami is generally generated when you have a large displacement of water in a vertical direction and it is likely that we did not have nearly as large a displacement as with the December 26 event."
The earthquake's magnitude may yet be revised up
"We don't know what depth it nucleated at but if the earthquake did nucleate slightly deeper then the effect on the surface is much less," Professor McCloskey told the BBC.
"Tsunamis of the type we observed on Boxing Day are thankfully very, very rare."
Monday's quake was close to the magnitude range predicted by the Ulster team, which calculated that it would measure between magnitude 8 and 8.5.
It could also have added to stress on the Sumatran fault, which cuts through the Indonesian island and was, according to Professor McCloskey's team, also destabilised by the December event.
'''March 28, 2005'''
Epicenter map from NOAA
A magnitude 8.7 earthquake has been reported in northern Sumatra, Indonesia by the U.S. Geological Survey (originally an 8.2 magnitude at 2:37 ET (7:37 GMT) the USGS reclassified it to an 8.7 magnitude). 
Government spokesman Agus Mendrova reported more than 290 deaths on the island of Nias. Hundreds of others were reported trapped in collapsed buildings, including structures weakened by the December 26th earthquake.

A destructive wave was intially feared and many nations issued tsunami warnings. After the quake a USGS instrument near the Cocos Islands recorded a tsunami type wave which the USGS classified as "small." Tsunami warnings were later withdrawn.

The quake occurred at 11:09 ET (16:09 GMT), and is considered a "great" earthquake, the largest of seven grades. This earthquake is also classified as a "shallow" earthquake, occurring within the top 50 kilometres of the Earth's crust. Shallow earthquakes are more likely to cause a tsunami, because as the lower within the surface the earthquake occurs, the less warping of the ocean floor occurs.  This earthquake was a thrust quake; the December 26th Indian Ocean quake was considered a megathrust quake.

The U.S. Geological Survey originally estimated the magnitude at 8.2, but Japan's Meteorological Agency measured the quake at magnitude 8.5 and the U.S. Geological Survey later raised its estimate to 8.7.  In comparison, last December's earthquake was measured at 8.1 initially by the USGS, before finally being placed within the 9.1 to 9.3 range by scientists in February 2005. 

At 16:29 UTC, an informational Tsunami Bulletin Number 001 was released by the Pacific Tsunami Warning Center, stating that there is no threat to Pacific coastlines, but warning of the possibility of destructive tsunamis on waters near the earthquake's origin.

There have been numerous reports of persons who have felt the earthquake fleeing their homes to higher ground, and Sri Lanka was under an evacuation order. Residents of Banda Aceh, Indonesia, one of the cities most devastated by the December tsunami, also fled. Since the December 26th earthquake relatively minor tremors have been common however this was reported to be more intense and long-lasting than any aftershock.

Thailand, which was criticized for its failure to alert citizens to tsunami dangers after last December's earthquake, warned about the possibility that a tsunami might hit that nation's southern provinces.