Magnitude 6.4 quake off Indonesia's Sumatra
"The epicenter is in the sea and there is no tsunami warning because at less than 7.0 magnitude it is still considered moderate," said Arif Nurahim, an official at
The quake hit 640 kilometers (400 miles) southwest of Aceh province, which was shaken Wednesday by two massive earthquakes that triggered a tsunami alert.
At a magnitude of 8.6, the first of the two quakes was the strongest to hit since the 2004
Sunday's aftershock was not felt in Aceh, unlike the quakes last week which sent panicky residents pouring out of their homes.