Another massive earthquake could strike the Hawaiian isles at any time, but this weekend's 6.7 magnitude tremor does not signal an increase in ground-shaking activity, researchers said.
Hawaii is always vulnerable to earthquakes, and temblors above 6.0 magnitude occur about once every decade, said Cecily Wolfe, a seismologist at the University of Hawaii.
"You can't assume that just because one occurred yesterday, that we're not going to get another one later this week," Wolfe said. It's also possible that no rumblings will occur soon, she said.
The earthquake was created when a 36-square-mile plate near the west coast of the "Big Island" slipped about one yard at a depth of about 20 miles below the ocean floor, Wolfe said.
"This might have relieved stress on this one fault, but there are many other faults that are building up stresses and could rupture who knows when," she said.
Hawaii has one of the most active and shifting surfaces in the world because the island is still growing from two decades of eruption at Kilauea Volcano. That growth puts tremendous weight on the earth's crust, inevitably forcing it to move, Wolfe said.
No tsunami threat was produced by the 7:07 a.m. Sunday earthquake because it wasn't powerful enough and it was too deep to generate significant waves, said Ian Robertson, a structural engineer at the University of Hawaii and chairman of the Hawaii state Earthquake Advisory Committee.
Still, the quake should serve as a reminder that tsunamis are a possibility. "One lesson we would like people to learn is when you feel the ground is shaking, you move away from the shoreline to higher ground," he said.
If a Hawaii earthquake creates a tsunami, the island would only have a few minutes to react, and the island of Oahu's 800,000 residents would be hit within 15 to 20 minutes, Robertson said.
This time, state officials determined well within 10 minutes that there was no danger of a tsunami, he said.
"To generate a tsunami, you have to significantly deform the sea floor," Wolfe said. "The sea floor creates a bulge, and that effectively bulges the ocean above it, and the ocean doesn't like to be bulged so it tries to reach equilibrium."
Hawaii likely will continue to experience powerful earthquakes, such as Sunday's tremor, for thousands of years, Robertson said.
Hawaii's largest earthquake, a 7.9 magnitude shaker on April 2, 1868, caused 77 deaths and knocked down homes made of stone, wood or straw. Landslides buried homes, and a tsunami drowned dozens of victims.
"This was not a random or unexpected event _ these things happen in Hawaii," Wolfe said of the recent earthquake. "This is just part of what makes Hawaii special."
