Mixed deformation styles observed on a shallow subduction thrust, Hikurangi margin, New Zealand Academic Article uri icon

abstract

  • Abstract Geophysical observations show spatial and temporal variations in fault slip style on shallow subduction thrust faults, but geological signatures and underlying deformation processes remain poorly understood. International Ocean Discovery Program (IODP) Expeditions 372 and 375 investigated New Zealands Hikurangi margin in a region that has experienced both tsunami earthquakes and repeated slow-slip events. We report direct observations from cores that sampled the active Ppaku splay fault at 304 m below the seafloor. This fault roots into the plate interface and comprises an 18-m-thick main fault underlain by 30 m of less intensely deformed footwall and an 10-m-thick subsidiary fault above undeformed footwall. Fault zone structures include breccias, folds, and asymmetric clasts within transposed and/or dismembered, relatively homogeneous, silty hemipelagic sediments. The data demonstrate that the fault has experienced both ductile and brittle deformation. This structural variation indicates that a range of local slip speeds can occur along shallow faults, and they are controlled by temporal, potentially far-field, changes in strain rate or effective stress.

published proceedings

  • GEOLOGY

altmetric score

  • 10

author list (cited authors)

  • Fagereng, A., Savage, H. M., Morgan, J. K., Wang, M., Meneghini, F., Barnes, R. M., ... LeVay, L.

citation count

  • 30

complete list of authors

  • Fagereng, A||Savage, HM||Morgan, JK||Wang, M||Meneghini, F||Barnes, RM||Bell, R||Kitajima, H||McNamara, DD||Saffer, DM||Wallace, LM||Petronotis, K||LeVay, L

publication date

  • September 2019