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November 29, 1975 Kalapana Earthquake

Residents and visitors on the Big Island of Hawaiʻi were sharply awakened during the early morning hours of November 29, 1975. At 3:35, a magnitude 5.7 shock registered on the seismic recording instruments at the Hawaiian Volcano Observatory. Although there were no reports of severe damages, many were frightened. This, however, was merely a foreshock. By 4:47, everyone had just about calmed down and returned to slumber, only to be awakened once more by a larger, even more frightening magnitude 7.7 shock.

The M7.7 earthquake is the largest event since the devastating magnitude 7.9 of 1868. It is also the largest local earthquake ever to be instrumentally recorded by the Hawaiian Volcano Observatory. The November 29th earthquakes were located west of Kalapana, along Hawaiʻi's southeastern coast, at a depth of about 8.5 km. An intense period of aftershocks continued for several months during which thousands of earthquakes were recorded. Most of these earthquakes were too small to be felt.

During and immediately after the main shock, 'earthquake lights' of white to bluish flashes or glows lasting several seconds were reported by a number of observers. Earthquake lights are associated with major earthquakes and have been observed in Japan and California. The lights are believed to be results of earthquake-induced distortions of the atmosphere.

The earthquake was closely followed by a tsunami that reached as much as 14.6 m in wave height and caused the death of two campers. Downward and seaward ground movement resulted in widespread subsidence along the southeast coast of Hawaiʻi Island.

5:32, a little over a half hour after the main shock, marked the onset of an eruption apparently triggered by the vigorous ground shaking. The outbreak of lava at Kilauea's summit was preceeded by shallow, high-amplitude harmonic tremor typically associated with magma movement. The visible eruptive activity ended by 10:00 pm. During eruptive repose periods roaring, jetlike degassing was observed and continued until 2:00 on the morning of November 30.

An estimated $4 million (worth approximately $13 million in 1999 dollars) of damages is attributed to the earthquake and its related catastrophic events. The maximum intensity of VIII occurred in the southeastern part of Hawaiʻi Island, in Hilo, Puna and Volcano. The shock was strong enough to be felt as far away as Kauaʻi, more than 500 km from the epicenter.

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Updated: 07 Dec 1998 (pnf)