Cracks were visible yesterday on the exterior walls above the side entrance of the Hulihee Palace, in Kailua-Kona. The palace, which was built in 1838, as well as many of the items in the museum inside, were damaged in yesterday's earthquake. "On a scale of 1 to 10, this is a 10 in terms of disaster," said docent Kahea Beckley. "It really hurts even to look at." CLICK FOR LARGE
Mystery surrounds temblors' origins
Vertical pressure on the ocean floor is likely, but finding answers will take time
Hawaii geophysicists described the dramatic seismic activity off the Big Island yesterday as a relatively rare series of events that will be studied for weeks, if not months, to come.
The first two quakes, measuring 6.6 and 5.8 in magnitude, came seven minutes apart and had different epicenters under the sea floor west of Waikoloa.
The bigger quake occurred at a depth of 24.2 miles, while the second was much shallower at 11.7 miles, according to the U.S. Geological Survey.
Just what caused them -- and dozens of small aftershocks throughout the morning -- is the "$64,000 question," said Mike Poland, a geophysicist at the Hawaiian Volcano Observatory on the Big Island.
While the exact mechanism will take a thorough study of seismic data, a likely trigger was the release of vertical pressure exerted by the weight of the Big Island on the ocean floor, or lithosphere, Poland said.
"The earth's crust is flexing under the Big Island, and that flexing will occasionally cause breakage," he said.
That scenario also was mentioned yesterday by Stuart Koyanagi, a geophysicist at the Pacific Tsunami Warning Center in Ewa Beach.
Huge chunks of the interior ceiling and museum items lay on the floor of an upstairs bedroom of the palace. CLICK FOR LARGE
"The problem," said Poland, "is that there have been no real big historical earthquakes in that area." The last one was a 4.8-magnitude quake in 1982, he said.
Yesterday's 6.6-magnitude quake was the largest in any area of the Big Island since a quake registering 6.6 on Nov. 16, 1983, but that one was centered on land in the Kaoiki area between Kilauea and Mauna Loa.
Since yesterday's initial quakes came back to back, it is possible that they are somehow related, Poland said.
"It is possible that the first event triggered the second, but it is difficult to say," he said.
Over the next four hours, 28 aftershocks ranging in magnitude from 2.5 to 4.4 shook the Big Island and the sea floor between the Big Island and Maui.
The contents of kitchen cabinets and a refrigerator were spilled across a floor in a Kailua-Kona kitchen following yesterday's earthquake. Similar damage was reported in many homes on the Big Island. The state Civil Defense had unconfirmed reports of injuries, but communication problems prevented more definite reports. Gov. Linda Lingle issued a disaster declaration for the entire state, saying there had been damage to buildings and roads. There were no reports of fatalities. CLICK FOR LARGE
The Big Island is one of the most active seismic regions in the world, with many small quakes typically occurring each week. Most so-called "microquakes" are too small to be felt.
Kilauea, which has been erupting since January 1983, and Loihi, a submarine volcano southeast of the Big Island, are common causes of those tremors.
The other major source of quakes in Hawaii is the Molokai Fracture Zone, an offshoot of the San Andreas Fault. That was the apparent source of a 3.7-magnitude quake centered 27 miles east of Kailua, Oahu, and felt over much of the island on Aug. 28.
Yesterday's initial quake was topped on Nov. 29, 1975, by a 7.2-magnitude temblor on the south flank of Kilauea. That quake caused a tsunami that washed out a Boy Scout camp at Halape, Big Island, killing two.
The quake yesterday generated a small seismic wave about 8 centimeters, or 3 inches, high at Kawaihae Harbor, said Gerard Fryer, a geophysicist at the tsunami warning center.