Ground deformation associated with the 1975 magnitude-7.2 earthquake and resulting changes in activity of Kilauea Volcano, Hawaii

Abstract

A magnitude-7.2 earthquake on November 29, 1975, the largest in Hawaii in over a century, was associated with large-scale deformation of the entire south flank of Kilauea Volcano. Surface ground breakage occurred along a 25-km-long sector of the Hilina fault system, with vertical displacements of as much as 1.5 m along individual preexisting fault scarps. Reoccupation of extensive horizontal and vertical geodetic networks on Kilauea demonstrated that the entire volcanic edifice and adjacent lower slopes of Mauna Loa were displaced downward and seaward. Maximum horizontal and vertical displacements, about 8 and 3.5 m respectively, occurred along the coastline south of Kilauea's summit area, about 30 km southwest of the earthquake hypocenter.