Magnitudes 6.7 and 6.0 Earthquakes Rattle Big Island Sunday, October 15, 2006 A strong earthquake occurred about 10 miles (15 km) north-northwest of Kailua Kona or 65 miles (100 km) west of Hilo, Hawai`i at 11:07 AM MDT, Oct 15, 2006 (7:07 AM HST in Hawaii). The earthquake epicenter was near Kiholo Bay at a depth of 24.4 miles approximately along the margin of Hualalai and Mauna Loa volcanes. At 7:14 a.m. a magnitude 6.0 earthquake located 34 miles north of Kailua-Kona rattled the island again; this quake was offshore of Kohala volcano beneath the Mahukoa Seamount, the oldest of the volcanoes comprising the Big Island. Numerous people suffered minor injuries, many buildings damaged and landslides blocked roads on Hawai`i. Power outages occurred throughout the Hawaiian Islands. Felt (VII-VIII) in northern and western Hawai`i and (V-VI) in eastern and southern Hawai`i. Also felt (VI) on Maui; (V) on Lana`i, Moloka`i and O`ahu; (IV) on Kaua`i. Multiple aftershocks accompanied these strong earthquakes. The strongest aftershock was magnitude 4.2 at 10:35 a.m. 31 miles north of Kailua-Kona.
Link to Full Text of the University of Hawaii Civil and Environmental Engineering Report:
On October 15th, 2006, two earthquakes with magnitudes of Mw6.7 and Mw6.0 struck in close succession just off the Northwest coast of the Island of Hawai`i. No deaths were attributed to ground shaking, and only minor injuries were reported, including two broken bones. Damage caused by these earthquakes had exceeded $100 million as of the writing of this report, without including damage to private residences. It is likely that the total cost of these earthquakes will exceed $200 million. This is significantly less than the $17.8 billion in damages caused by the similar magnitude 6.7 Northridge earthquake in the Los Angeles area in 1994. The low injury rate and economic loss is attributed to the relatively rural area in which the Kiholo Bay and Hawi earthquakes struck, and the relatively large 40 km (25 miles) focal depth of the M6.7 Kiholo Bay earthquake. It was also fortunate that the earthquakes struck just after sunrise on a Sunday morning. Overall, the vast majority of built infrastructure in the vicinity of the earthquake epicenters survived with little or no damage. Recorded ground accelerations show a maximum horizontal ground acceleration of 1.03g and a maximum vertical ground acceleration of 0.72g at the Waimea fire station, about 32 km (20 miles) from the Kiholo Bay earthquake epicenter. Shaking reached Intensity VIII on the Mercalli Scale as reported by residents. Strong ground motions lasted for approximately 20 seconds during the Kiloho Bay earthquake, and 15 seconds during the Hawi earthquake.  | Structural damage occurred at a number of buildings, bridges and port facilities, particularly those closest to the earthquake epicenters. Much of the damage to buildings was in the form of failure of non-structural elements such as ceilings, light fixtures, plumbing and other utility lines. Although over 1,800 individual residences were damaged to varying degrees, tens of thousands of light-framed timber homes in neighborhoods close to the epicenters survived with virtually no damage. The provision of shear walls and continuous load-path for hurricane wind design may have contributed to the superior seismic performance of many residences. Many of the homes that were destroyed or experienced severe damage were constructed on pier-and-beam foundation systems resting on small loose concrete foundation blocks. The ground shaking resulted in lateral movement of the posts off these substandard foundations resulting in moderate to complete damage to the residence. Longer duration or more intense ground shaking would likely have caused significantly more damage to residential structures elevated on pier-and-beam framing.  | Numerous rockfalls and slides occurred in road cuts, embankments and natural slopes. The extent of these failures diminished considerably toward the more populated centers of Hilo and Kailua-Kona. Because of the lack of redundancy in the highway system on Hawai`i Island, road closures due to rockfalls or landslides can have a devastating effect on emergency response and economic recovery efforts. For a number of hours after the earthquakes, the area of North Kohala, including the town of Hawi, was cut off from the rest of the island because of road closures on Highways 250 and 270, the only access roads to this region. Fortunately, the rockfalls and landslides caused by these earthquakes could be cleared relatively easily, and all roadways were open to at least one-lane traffic within a day or two of the earthquakes. It was noted that wide shoulders on Highway 19 North of Kailua-Kona were able to accommodate much of the rockfall material without encroaching on the driving lanes.Some damage occurred to dams and irrigation ditches in the Waimea-Kamuela area. Two dams experienced earth fill disturbance and cracks along their crests, while at least two others showed clear evidence of incipient slope failure on their embankments. A system of irrigation ditches feeding some of these reservoirs was interrupted due to debris blockage. Roadway embankments were affected at a series of locations, in one case resulting in the collapse of a traffic lane on the approach to a bridge. A few retaining walls collapsed, primarily poorly-built, un-reinforced and un-mortared rock walls.  | One of the two major commercial ports on the island, Kawaihae Harbor, sustained major damage from liquefaction and lateral spreading. This facility is located less than 24 km (15 miles) from both earthquake epicenters. Much of the fill material under the shipping container handling yard consists of dredged fill. As this material liquefied, the resulting lateral spreading caused significant vertical settlement of the asphalt pavement, and lateral displacement of the pile supported concrete piers. Large torsional cracks in the reinforced concrete edge beam of one of the two pile-supported piers, Pier 1 (North pier), were attributed to this lateral movement. It is unknown at the time of writing this report if any damage had been incurred by the piles supporting this pier. Pier 1 remains closed indefinitely.The lateral spreading also resulted in deformation of the pre-manufactured metal frame warehouses adjacent to the concrete piers. Although damage to these buildings is relatively minor, the potential remains for further liquefaction of the fill materials during future earthquakes. No damage was noted at Hilo Harbor on the East side of the island, however it is known that much of the harbor is constructed on fill materials that are susceptible to liquefaction.  | Because Hilo and Kawaihae Harbors are the only two ports on Hawai`i Island capable of handling the barges that transport most of the island’s supplies from Honolulu Harbor, they are an essential lifeline for the inhabitants of the island. Remedial measures should be taken to replace or stabilize any fill material with liquefaction potential in critical harbor facilities to avoid loss of function of either of these ports during future earthquakes.
eTN/AP:
Two strong earthquakes shook Hawaii residents, tourists and our eTN staff out of bed this morning and triggered a power outage in three counties.
Gov. Linda Lingle was staying at the Mauna Lani Bay Hotel and Bungalows, only a few miles from the epicenter, when the quake struck.
“The jolt we felt was intense,” Lingle said at a news conference this afternoon in the state Civil Defense conference room in a former military bunker in Diamond Head Crater. “It threw everything around the room.”
Lingle, who has experienced earthquakes in California , said she knew what to do when the earthquake struck.
“I went under the door frame,” the governor said.
Just after they straightened the room out, the aftershock struck, Lingle said, sending the television in the room crashing to the ground a second time.
After leaving the hotel, Lingle went to the Kona police station to get briefed on the damage and then took to a National Guard helicopter to see the damage from the air before returning to Honolulu .
Lingle said at Kealakekua Bay a rockslide into the ocean was continuing hours after the initial quake. She said she saw boulders falling into a brownish sea.
She also witnessed patients being evacuated from Kona Community Hospital and loaded into yellow buses, although she said there was no evidence of damage to the outside of the structure.
At the state civil defense headquarters, Lt. Gov. James “Duke” Aiona, acting on Lingle’s behalf, signed an executive order declaring a state-wide disaster and authorizing the use of the National Guard. Later Gov. Linda Lingle issued a disaster declaration for the state, saying there had been damage to buildings and roads. There were no reports of fatalities, but the state Civil Defense had several reports of minor injuries.
The quake hit at 7:07 a.m. local time, 10 miles north-northwest of Kailua Kona, a town on the west coast of Hawaii Island, also known as the Big Island, said Don Blakeman, a geophysicist at the National Earthquake Information Center, part of the U.S. Geological Survey.
The quake prompted fears of a tsunami, but forecasters quickly put those fears to rest, predicting only choppier-than-normal waves.
The Pacific Tsunami Center reported a preliminary magnitude of 6.5, while the U.S. Geological Survey gave a preliminary magnitude of 6.6. The earthquake was followed by several strong aftershocks, including one measuring a magnitude of 5.8, the Geological Survey said. Experts said aftershocks could continue for weeks.
"We were rocking and rolling," said Anne LaVasseur, who was on the second floor of a two-story, wood-framed house on the east side of the Big Island when the temblor struck. "I was pretty scared. We were swaying back and forth, like King Kong's pushing your house back and forth."
Mayor Harry Kim estimated that as many as 3,000 people were evacuated from three hotels on the Big Island. Brad Kurokawa, Hawaii County deputy planning director, confirmed the hotels were damaged, but could not say how many people had left. They were being taken to a gymnasium until alternate accommodations could be found, he said.
The earthquake caused water pipes to explode at Aston Kona By The Sea, a condominium resort, creating a dramatic waterfall down the front of the hotel from the fourth floor, said Kenneth Piper, who runs the front desk.
"You could almost see the cars bouncing up and down in the parking garage," Piper said.
The quake caused statewide power outages, and phone communication was possible, but difficult. The outages were caused because power plants turned off automatically when built-in seismic monitors were triggered by the earthquake, Lingle said.
Some power had been restored late Sunday in Maui, parts of Honolulu and other places, but many remained in the dark. All electricity systems needed to be rebooted, which was expected to take several hours in more populated areas like Honolulu.
A FEMA computer simulation of the quake estimated that as many as 170 bridges on the Big Island could have suffered damage in the temblor, said Bob Fenton, FEMA director of response for the region. More than 50 federal officials were en route to the Big Island to assess damage and begin recovery work, he said.
Lingle told radio station KSSK that she toured the Kona area by helicopter to view the damage, including earth falling into Kealakekua Bay.
"You could see the water was turning brown," said Lingle.
On Hawaii Island, there was some damage in Kailua-Kona and a landslide along a major highway, said Gerard Fryer, a geophysicist at the Pacific Tsunami Center. Officials also said there were reports of people trapped in elevators in Oahu.
In Waikiki, one of the state's primary tourism areas on Oahu, worried visitors began lining up outside convenience stores to purchase food, water and other supplies. Managers were letting tourists into the darkened stores one at a time.
Karie and Bryan Croes waited an hour to buy bottles of water, chips and bread.
"It's quite a honeymoon story," said Karie, as she and her husband sat in lounge chairs surrounded by grocery bags beside a pool at ResortQuest Waikiki Beach Hotel.
Kona Community Hospital on the western side of Big Island was evacuated after ceilings collapsed and power was cut off, according to a hospital spokeswoman.
At least 10 acute care patients were being evacuated across the island to a medical center in Hilo, said Terry Lewis, spokeswoman for the hospital. About 30 nursing care patients were being moved temporarily to a nearby conference center, she said.
"We were very lucky that no one got hurt," said Lewis.
The quake affected travel plans for many visitors, though the state was in its low period of the tourism season. Airports were functioning despite the power outages, though travel was difficult and some flights were being canceled, officials said.
Federal Aviation Administration spokesman Les Dorr said planes were arriving at Honolulu International Airport, but there were few departures. Dorr said the Transportation Security Administration security checkpoints were without power, so screeners were screening passengers and baggage manually.
Resorts in Kona were asked to keep people close to hotels, Kim told television station KITV. Cruise ships were told to keep tourists on board, and ships that were due to dock were asked to move on to their next location, he said.
"We are dealing with a lot of scared people," he said.
The quake hit roughly 150 miles southwest of Honolulu's Oahu Island, near a much less populated area. The Big Island has about 167,000 people, according to a 2005 Census estimate, and many of them live in and around Hilo, on the opposite site from where the quake was centered.
Earthquakes in the 6.0 magnitude range are rare in the region, though they have happened before. The region more commonly sees temblors in the 3- and 4-magnitude range caused by volcanic activity.
"We think this is a buildup from many volcanic earthquakes that they've had on the island," Waverly Person, a geophysicist with the U.S. Geological Survey's National Earthquake Information Center.
The last Hawaiian earthquake this strong struck more than 20 years ago. The magnitude 6.7 caused heavy property damage on Hawaii Island and collapsed trails into a volcano in Hawaiian Volcanoes National Park on Nov. 16, 1983. A 6.1-magnitude quake also hit in 1989, according to the Earthquake Information Center.
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