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John Daley reportingWhen a large earthquake hit off Indonesia, seismologists at the University of Utah immediately began monitoring it, but were surprised when it didn't spawn another killer tsunami.
The earthquake was described as a "twin" of the one on December 26th, which unleashed the tsunami and left some 280-thousand people dead. But this time, a deadly tsunami never materialized and that has scientists trying to figure out why.
At the University of Utah, a series of drums turn 24-hours a day with needles connected to sensors around Utah and at Yellowstone Park. These seismographs record movements in the earth, and when straight lines get squiggly, "it tells me there's been a big earthquake somewhere in the world," says Jim Pechmann.
When the 8.7 magnitude earthquake hit in the Indian Ocean, residents on the nearby island of Sumatra ran for their lives. At the same time, on the other side of the world at the U.S. Geological Survey Earthquake Information Center, warnings went out immediately. predicting a repeat of December's monster tsunami.
Kerry Seih. Ph.D./ California Institute of Technology: "I think it's inescapable that there will be a tsunami associated with this."
But by late this afternoon, though hundreds were killed by the quake, the tsunami never materialized even though this too--like December's 9.0 temblor--was a big quake.
Jim Pechmann/ Uni. of Utah Seismologist: "I would have expected that the bigges waves might occur in somewhat different places, but I still would have expected to see a tsunami somewhere in the Indian Ocean because of this earthquake."
Scientists believe the difference may be found in the enormous underwater landslide triggered by December's quake, which unleashed the tsunami, that didn't happen this time.
But looking at a map showing earthquake locations around the globe, the larger picture is clear--two massive continental plates are colliding in the Indian Ocean and the quakes--and sometimes tsunamis--are set off as one slides under the other.
Jim Pechmann/ Uni. of Utah Seismologist: "In last December's earthquake, there was a sudden slip of several meters along the fault like this. The same thing happened in this morning's earthquake, but presumably on an adjacent section of the fault."
The researcher I talked with today says he's confident that in time- scientists will figure out why this time the tsunami--thankfully--never arrived.