South Pacific Tsunami Caused By Two Earthquakes

By Reema, Gaea News Network
Thursday, August 19, 2010

SAN FRANCISCO ( Scientists have come up with studies that have concluded that the devastating 2009 South Pacific tsunami which caused havoc on Samoa, American Samoa and Tonga was not due to one earthquake of magnitude 8.1, but two consecutive earthquakes each of magnitudes greater than 8 on Richter scale. Research conducted by two group of scientists using different techniques to study the South Pacific tsunami have concluded that it was a rare kind of one-two seismic activity within minutes that had led to the horrific tsunami. The studies have been published in the Thursday issue of Nature.

The two teams that went for the study were led by geophysicist John Beavan of the New Zealand geological agency GNS Science and Thorne Lay of the University of California, Santa Cruz. The group led by John Beavan used GPS data and deep-ocean tsunami wave observation techniques to determine the cause of the South Pacific tsunami. They have concluded that the South Pacific tsunami was actually generated by two earthquakes, one “outer rise” of magnitude 8.1 and another “megathrust” of magnitude 8 that was caused by the diving of plates into one another. Although John Beavan and group did not conclude which of the two occurred first, the group led by Thorne Lay has concluded that the first earthquake that hit the South Pacific region was the “outer rise” of magnitude 8.1. It is this earthquake that resulted to the megathurst jolt. The research also held that the ground vibrations from the first earthquake were so strong that it engulfed the energy released by the second earthquake.

The finding by the two groups has been able to shed some light on the 2009 South Pacific tsunami occurrence that had baffled scientists all over the world. The discovery according to the scientists who were not involved will help in further studies.

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