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Lessons learned from the 2006 Kiholo Bay earthquakes

Updated: 
October 11, 2015 - 1:30am

Thursday is the third annual Great Hawaii ShakeOut. That day also marks the ninth anniversary of Hawaii’s two most recent damaging earthquakes.

On Sunday, Oct. 15, 2006, at 7:07 a.m., a magnitude-6.7 earthquake, centered deep beneath Kiholo Bay off the northwest coast of the island, shook many Hawaii Island residents awake. It was followed seven minutes later by a magnitude-6.0 earthquake centered 5.6 miles off the island’s North Kohala coast.

Damage from these earthquakes was heaviest in the North Kona and Kohala districts, but impacts were felt across the state, notably with an extended power outage on Oahu.

Fortunately, no lives were lost as a result of these earthquakes. Had the earthquakes occurred on a different day of the week, when many people would have been on their way to — or already at — work or school, the outcome might have been much different.

From a financial viewpoint, estimated damages from post-earthquake assessments amounted to at least $200 million. Though the October 2006 earthquakes were not the largest ever experienced in Hawaii, they resulted in the greatest earthquake-related financial losses in Hawaii’s history by far. With continued development and population growth, we can expect future earthquake losses to escalate.

As we learned in 2006, moderately large earthquakes can be very costly and seriously impact much, if not all, of the state.

At a societal level, we brace against damaging earthquakes with zoning, building codes and building practices. We use experiences and observations from historical events, combined with the best available technical tools and capabilities, to avoid catastrophic structural failures resulting from earthquakes. Over the years, building codes in the United States have been modernized and upgraded to the point that the likelihood of structural collapse is now considered quite low.

The collective experiences from 2006 highlighted the particular vulnerability of the post-and-pier type construction that is quite common in Hawaii’s communities. Inspections that were conducted to determine if homes were safe to reoccupy after the earthquakes led to a series of projects that focused on the seismic performance of post-and-pier construction.

After an inventory was compiled, a structural engineering team developed retrofit strategies and specifications for strengthening post-and-pier homes. With this engineering information, a software team created a “Retrofit Expert System” (http://www.hilo.hawaii.edu/~nathazexpert/expertsystem/flash_path_fix.php) for homeowners to develop appropriate retrofit designs and procure materials and hardware for their home seismic retrofits.

Home retrofits are an example of what can be done at an individual level, well in advance of an earthquake, to protect our families during strong earthquakes. It is also important to know exactly what to do when the shaking starts.

Emergency managers, planners and researchers now largely agree that “Drop! Cover! Hold On!” is the appropriate strategy to reduce injury, or prevent death, during large, damaging earthquakes. This was borne out in 2006 by the extent of nonstructural damage, like fallen ceiling panels and fixtures and toppled cabinets and shelves, noted in the post-Kiholo Bay earthquake damage surveys.

Because we cannot know how strong an earthquake will be at its onset, drop to the ground any time you feel shaking. Cover your head and neck, and take shelter under a sturdy object, like a desk or table. Then hold on to your shelter until the shaking stops. If there is no nearby sturdy shelter, drop to the floor and protect your head and neck. If possible, crawl to an inside corner of the room and be ready to move, if necessary.

ShakeOut, first conducted in California in 2008, is now a global earthquake awareness and preparedness exercise. As of this week, almost 40 million participants are registered in worldwide events.

There’s still time to join the more than 240,000 Hawaii residents now registered for the Great Hawaii ShakeOut that takes place at 10:15 a.m. Thursday. In your home and workplace, identify sturdy objects that you can shelter under and then practice “Drop! Cover! and Hold on!” This will speed up your reaction time when the need to protect yourself during an earthquake is real.

For more detailed information about earthquake preparedness, visit the Great Hawaii ShakeOut website (http://shakeout.org/hawaii/). A University of Hawaii report produced from post-Kiholo Bay earthquake studies is available at http://www.hilo.hawaii.edu/~nathazexpert/expertsystem/report_forPost_and....

Volcano activity updates

Kilauea continues to erupt at its summit and East Rift Zone with no significant changes this past week. The summit lava lake level varied between 180 and 218 feet below the vent rim within Halemaumau Crater. On the East Rift Zone, scattered lava flow activity remained within 4.3 miles of Puu Oo.

Mauna Loa is not erupting. During the past week, earthquake rates continued to be elevated, though at a lower weekly rate than recorded in late summer. Deformation data remain consistent with inflation of magma reservoirs within the volcano.

One earthquake was reported felt on Hawaii Island this past week. On Oct. 3 at 12:24 p.m., a magnitude-2.9 earthquake occurred 3.1 miles southeast of Kawaihae at a depth of 18.1 miles.

Visit the HVO website at hvo.wr.usgs.gov for Kilauea daily eruption updates, Mauna Loa weekly updates, volcano photos and recent earthquakes information; call for summary updates at 967-8862 (Kilauea) or 967-8866 (Mauna Loa); email questions to askHVO@usgs.gov.

Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.

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