SALT LAKE CITY, Aug. 18 (UPI) — Researchers say a deadly 2009 earthquake in the South Pacific was actually three tremors, with the largest hiding the immediate evidence of two smaller ones.
Scientists at the University of Utah say the 8.1 “great earthquake” in September 2009 that killed 192 people in Samoa, American Samoa and Tonga triggered two subsequent 7.8 temblors, a university release said Wednesday.
“At first, we thought it was one earthquake,” study co-author Keith Koper, director of the school’s seismograph stations, said.
“When we looked at the data, it turned out it wasn’t just one great earthquake, but three large earthquakes that happened within two minutes of one another.”
The quakes generated tsunami waves more than 49 feet above sea level in some places that killed at least 149 people in Samoa, 34 people in American Samoa and nine on Niuatoputapu, an island in the northern part of Tonga.
“The two quakes that were hidden by the first quake ended up being responsible for some of the damage and tsunami waves,” Koper said.
In terms of energy release, the two magnitude-7.8 quakes combined “represent the energy release of another magnitude-8 quake,” Koper, an associate professor of geology, said.
“It was essentially a great earthquake that was triggered. It was not some silly little aftershock.”
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