1975 Nov 29 14:47:40.1 UTC
The largest earthquake in more than a century (since April 2, 1868) struck Hawaii on the morning of November 29, killing two people, injuring several, and inflicting property damage estimated at $4.1 million in Hawaii (including damage caused by the tsunami). It was accompanied by a damaging tsunami, massive ground movements, hundreds of aftershocks, and a brief, small-volume volcanic eruption. The earthquake was felt throughout Hawaii Island, and on Lanai, Molokai, and Oahu.
Most of the buildings in the epicentral area sustained little or no structural damage from ground shaking. Structural and nonstructural damage in Hilo, 45 kilometers north of the epicenter, was slight to moderate but was more extensive than elsewhere on the island.
Structural damage on the southeast part of the island included minor cracks, floor-to-wall separations a few millimeters wide, and bowing of walls in Hilo at a hospital, schools, and libraries. Floor sections dropped 5 to 10 millimeters in some of the buildings; hotel, apartment, and commercial buildings sustained structural and equipment damage. A damage survey of the area revealed that slight to moderate structural damage was sustained by five churches (Hilo, 4; Opihikao, 1), 11 commercial buildings (Hilo, 10; Mountain View, 1), and 80 private dwellings (Hilo, 51; Puna, 23; Hamakua, 2; Kau, 3; and Kona, 1). Five poorly constructed or old houses were demolished (Hilo, 4; Kau, 1). Houses shifted on their foundations at Kalapana, Kurtistown, Pahoa, and Hawaiian Paradise Park. Water tanks were destroyed at Opihikao, Pahoa, and Volcano.
The summit and south flank areas of Kilauea Volcano were displaced by vertical and horizontal movements of several meters, forming many ground cracks and faults. Roads in Hawaii Volcanoes National Park were damaged by extensive ground cracking. Landslides occurred on Coast Road.
Fault displacements resulted in widespread subsidence (locally as much as 3.5 meters near Halape), leaving coconut palms stranded in the sea and almost submerging a small nearby island. Inland, an almost continuous zone of ground cracking and faulting, having vertical offsets as much as 1.5 meters, occurred along the Hilina fault system over a 25 square kilometer area. To the south and southwest of this zone of maximum faulting, vertical displacements of as much as 0.5-1.0 meters were common along other faults.
A large part of the coastal area between Cape Kumukahi and Punaluu subsided during or soon after the earthquake. A leveling survey of the bench marks near the Keauhou tide gauge (2 kilometers east of Halape) indicated that the coast subsided about 3.5 meters.
The tsunami generated by this major earthquake consisted of five of more distinct waves in some places. The only locally generated tsunami in Hawaii this century to be destructive, it killed two people at Halape, where it was about 7.9 meter high, and caused property damage estimated at $1.2 million at Punaluu, Honuapo, Kaalualu Bay, Hilo, and Kailua-Kona. At Punaluu (7.6 meters), 30 kilometers southwest of Halape, several wood-frame houses were flattened or washed off their foundations; nearby county park facilities were damaged severely, and buildings at the Seamountain Resort sustained heavy nonstructural damage. Tsunami damage also was severe at Honuapo (6.6 meters), 6 kilometers southwest of Punaluu. The highest wave reached a maximum height of 14.6 meters above the post-submergence shoreline, 1.5 kilometers east of Halape. The tsunami was recorded in Alaska, California, Japan, Okinawa, Samoa, and on Johnston and Wake Islands.
Abridged from Seismicity of the United States, 1568-1989 (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993.
See also: 1975 Hawaiian Tsunami