Vertical deformation measurements on the submerged south flank of Kīlauea volcano, Hawai'i reveal seafloor motion associated with volcanic collapse

Abstract

A four‐year seafloor geodetic study was conducted to measure vertical deformation of the submerged south flank of Kīlauea volcano on the active Hilina slump. The Hilina slump is a site of significant deformation, major earthquakes with ground cracking and associated tsunami. A new technique was developed to measure vertical deformation on the seafloor using pressure sensors in campaign‐style surveys. The data revealed the midslope bench of the offshore slump is uplifting at 9.0 ± 2.4 cm/a, but transitions to no significant deformation on the outer bench and slump toe. Elastic half‐space inverse modeling of these data show that the observed deformation can be fit by seaward slip of 28.1 ± 7.3 cm/a extending from the East rift zone 27.0 ± 0.5 km on a gently island‐dipping decollement fault plane at a depth of approximately 7 km. Modeling suggests that the outer bench is not currently deforming. Because the majority of Kīlauea is submerged, these offshore measurements are necessary to constrain the seaward extent of fault slip and the motion of the outer bench.