Abstract

Two earthquakes occurred on the island of Hawaii on November 29, 1975, a magnitude (Ms) 5.7 event at 0335 (local time) and a magnitude (Ms) 7.2 event at 0447. During the larger event, a maximum acceleration of 0.22 g was recorded in the southern part of Hilo, 43 km north of the epicenter. A 0.05 g threshold duration of 13.7 sec was measured for the same component. Smaller amplitude accelerograph records were obtained at two other locations on the island along with four seismoscope records.

During or subsequent to the larger event, a large sector of the southeastern coastline subsided by as much as 3.5 meters. A tsunami generated by the larger event caused at least one death (one person also missing), injury to 28 persons, and significant structural and nonstructural damage.

Only scattered evidence of strong ground shaking was observed in the epicentral area, and most of the several dozen nearby structures sustained little or no structural damage from ground shaking. In Hilo, 45 km north of the Ms = 7.2 epicenter, structural and nonstructural damage was slight to moderate but more extensive than elsewhere on the island.

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