3D surface deformation in the 2016 MW 7.8 Kaikōura, New Zealand earthquake from optical image correlation: Implications for strain localization and tectonic evolution of the Pacific-Australian plate boundary

Robert Zinke, James Hollingsworth, James F. Dolan, & Russ J. Van Dissen

Published August 13, 2018, SCEC Contribution #8415, 2018 SCEC Annual Meeting Poster #123

We measure high-resolution, 3D surface deformation patterns resulting from the 2016 MW 7.8 Kaikoura, New Zealand earthquake using stereo WorldView satellite imagery, with an advanced workflow based on COSI-Corr subpixel optical image correlation. This workflow triangulates 3D displacement vectors directly from different combinations of stereo pre- and post-earthquake image correlations, providing highly detailed maps of 3D surface deformation without the need to combine multiple sensors, or generate separate DEMs to orthorectify imagery. From these high-resolution correlation maps, we extract measurements of horizontal and vertical fault slip at 500 m intervals along 19 mapped fault strands. We use these measurements to refine interpretations of fault rupture kinematics in the Kaikoura earthquake, which in turn provide new insights into the role of the 2016 earthquake in accommodating relative tectonic plate motions. Comparison of our correlation measurements with published field measurements along the Kekerengu fault indicates a significant amount of coseismic surface deformation was expressed as distributed, off-fault deformation (OFD), which occurs over zones of variable width (typically within ~100 m of the primary fault). Specifically, comparison of traditional, short-aperture (< 5 m) field offsets shows that ~35% of surface deformation is expressed as OFD. In contrast, comparison of our correlation measurements with field offsets for which previously linear features (e.g., fence lines) are projected into the fault demonstrates that field measurements capture nearly all (~90 %) surface deformation when projected > 5-100 m from the fault.

Key Words
Kaikoura earthquake, off-fault deformation, optical image correlation

Citation
Zinke, R., Hollingsworth, J., Dolan, J. F., & Van Dissen, R. J. (2018, 08). 3D surface deformation in the 2016 MW 7.8 Kaikōura, New Zealand earthquake from optical image correlation: Implications for strain localization and tectonic evolution of the Pacific-Australian plate boundary. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy