The quake that caused the tsunami was three times more powerful than previously estimated, according to two US geologists.

The geologists have warned that the danger of a a local tsunami generated by large aftershock in the region still 'remains'.

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Latest analysis of seismograms from the December 26 Sumatra earthquake has resulted in a revision of its magnitude to 9.3 from the previously reported 9.0, Seth Stein and Emile A Okal of the Department of Geological Sciences at the Northwestern University have reported.

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The revised value makes it the second most powerful quake after the one in Chile in 1960. This 'explains in part why the tsunami was so destructive', the two scientists said.