Structural variability along the submarine south flank of Kilauea volcano, Hawai'i, from a multichannel seismic reflection survey

Abstract

Recent analysis of marine multichannel seismic reflection data collected across the south flank of Kilauea volcano, Hawaii has confirmed that the distal flank records significant accretion and deformation of volcaniclastic strata, building a broad and laterally extensive midslope bench [Morgan et al., 2000]. Further examination of adjacent reflection lines across the mobile flank of Kilauea demonstrates along-strike continuity in styles of deformation within the bench, as well as significant variability, which is commonly reflected in flank morphology. Correlation of reflections on 14 seismic lines allow us to identify at least 4 continuous thrust faults, several of which are traceable as far as ∼60 km from the south-western margin of the mobile flank to the subaerial to submarine transition of the East Rift Zone in the northeast. A landward thrust fault rises from the top of the Cretaceous oceanic crust, and displaces the primary volcanic edifice seaward onto folded and faulted bedded strata. The more seaward faults originate at a horizon slightly above the oceanic crust that appears to define a regional decollement at the base of the flank. To the southeast, imbrication of seaward thrust sheets builds a broad bench which ponds sediments behind it in a deep midslope basin. A lateral fault locally disrupts these structures, marking a transition in structural style to the northeast, where thrust sheets are stacked vertically defining an antiformal stack. The basin is absent in this region, and the primary volcanic edifice is overthrust directly upon accreted and recently deposited sediments building a narrow bench. A seaward change in decollement level from the top of oceanic crust beneath the volcanic edifice to a horizon within bedded strata beneath the bench, and the lateral change in thrust sheet geometries, suggest variations in sliding resistance beneath the mobile south flank of Kilauea, contributing to the complicated morphology evident in the offshore region.