A strong earthquake rattled Hawai'i at 7:07 a.m. local time on Sunday morning, damaging buildings, disrupting power and telephone service, and startling athletes preparing for this weekend's Ironman triathlon World Championships.
Nobody was killed by the magnitude 6.7 temblor, although there were numerous reports of minor injuries.
The quake was centered offshore from the Big Island's Kona Coast, 10 miles (16 kilometers) from the town of Kailua Kona (Hawai'i map).
The main quake, which was felt on all seven of the state's inhabited islands, was followed minutes later by an aftershock of magnitude 6.0.
Earthquakes aren't rare in Hawai'i, but the vast majority are smaller than the most recent quake and are associated with the underground movement of magma during volcanic activity.
Yesterday's earthquake was not only larger than average but deeper—centered 24 miles (39 kilometers) beneath the surface, according to data reported on the U.S. Geological Survey (USGS) Web site.
In addition, the quake's location on the opposite side of the island from current volcanic activity suggests that magma movements were not the cause, says Paul Okubo, a seismologist at the USGS Hawaii Volcano Observatory.
Such earthquakes are probably caused by stresses in Earth's crust created by the weight of the growing volcanoes.
"In general terms," Okubo said, "it's a lithospheric flexure process where the mass of the island has deformed the underlying earth." The earthquake resulted when Earth's crust readjusted to the pressure.
Land Rolled Like a Ship
Yesterday's temblor is by no means the largest quake ever recorded in Hawai'i. That honor goes to a quake on April 3, 1868, now estimated to have been a magnitude 7.9.
Because that earthquake predated modern instruments, its cause is not well understood.
