THE EARTHQUAKE OF OCTOBER 15, 2006 IN HAWAII
George Pararas-Carayannis
Introduction
In the morning of October 15, 2006, two strong earthquakes occurred on the underwater segment of the major rift zone
of the Hualalai volcano on the Northwest side of the Island of Hawaii. The earthquakes affected mostly the North Kona
and the Kohala areas of the island but extensive damage occurred also in the islands of Maui and Oahu. There were
many injuries but no deaths were reported. No tsunami of significance was generated.
Earthquake Origin Time, Epicenter, Magnitude, Focal Depth and Aftershocks
Two earthquakes occurred in Kiholo Bay on the northwest side of Hawaii Island, early on Sunday morning, October 15,
2006.
First Earthquake
Origin date and time: Sunday, October 15, 2006 at 17:07: 48 (UTC) (7:07: 48 AM local time).
Epicenter: 19.878°N. 155.935°W about 6 miles NNW of Pauanahulu off the northwest coast of Hawaii and about 20 km
northeast of the Kona airport.
Magnitude: The original magnitude was given as 6.5 but later revised to 6.7.
Focal depth: Estimated at 29 km (18.0 miles) (according to the U.S. Geological Survey's Hawaiian Volcano Observatory).
Distances (NEIC data):
11 km (7 miles) NNW (348°) from Kalaoa, HI
20 km (13 miles) N (351°) from Kailua, HI
21 km (13 miles) SW (234°) from Puako, HI
99 km (62 miles) W (278°) from Hilo, HI
250 km (155 miles) SE (131°) from Honolulu, HI
The quake was felt as a steady, rumbling shudder that shook houses, cracked buildings and swayed high-rises. It was
the largest recorded in the island of Hawaii since the November 16, 1983, earthquake, which had M6.7 and occurred
under the east flank of Mauna Loa.
Second Earthquake - The second earthquake occurred seven minutes later. Its magnitude was 6.0. Its epicenter was
about 44 km north of the Kona airport. Its focal depth was shallower at 20 km.
Earthquake Intensities - The earthquakes were felt most strongly in the North Kona and Kohala areas. The shaking was
strong enough to cause power generators to trip offline in Hawaii, Maui, and Oahu counties.
Distribution of aftershocks in the first 24 hours after the main earthquake (Hawaii Volcano Observatory data)
Aftershocks
About 80 aftershocks with magnitudes greater than 1.7 were recorded in the first 24 hours. The largest with a magnitude
of 4.2 and occurred at 10:35:21 AM HST on October 15. It was located at sea at 20.09 N, 155.97 W. Most of the
subsequent aftershocks had focal depths of less 20 km and were concentrated under the Hualalai volcano.
The Aftershock of 23 November 2006 - A strong (magnitude 5.0) aftershock occurred at 19:20:10 (UTC)
on November 23, 2006 along the Hulalai volcano's Northwest rift zone. The epicenter of the aftershock was at sea
(19.890°N, 155.979) in the same general area as the main quake of October 15, 2006°W. Its focal depth was also deep
- 37.7 km (23.4 miles)
Major aftershock of the Hualalai earthquake on November 23, 2006 (U.S. Geological Survey, Hawaii Volcano
Observatory map)
Damages
Most of the damage occurred on the west side of the island of Hawaii but there was also damage on Maui and Oahu.
There were no reported fatalities. The earthquake disrupted air traffic on all major islands and knocked out power on
parts of the Big Island, Maui and all of Oahu.
On the island of Hawaii, there was major structural damage at Kona Hospital, the Royal Kona Resort and the Honokaa
Long-term Care Facility. There was also some damage to the ceiling at Kohala Hospital. There were reports of boulders
crashed onto the highways. The state Department of Transportation estimated the damage to state roads and bridges
at about $20 million. Total damage estimates are expected to increase to over $200 million.
On the island of Oahu there was major power outages that forced the disruption of flights at the Honolulu International
Airport. Several flights out of Maui, and the island of Hawaii Island were disrupted or cancelled.
Hawaii Volcano Observatory Map of Intensities associated with the 15 October 2006 Earthquake