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Non-characteristic slip behavior on the Kekerengu fault throughout the past four to five earthquakes at Bluff Station, New Zealand

Judith Gauriau, James F. Dolan, Russ J. Van Dissen, Tim Little, Ed J. Rhodes, & Andrew Ivester

Submitted September 10, 2023, SCEC Contribution #13212, 2023 SCEC Annual Meeting Poster #075

The 2016 rupture of the Kekerengu fault, one of the fastest-slipping faults onshore New Zealand, generated much of the seismic moment of the Mw=7.8 Kaikōura earthquake. We use field- and lidar-based geomorphological mapping to study the Kekerengu fault at the Bluff Station site, where the fault exhibited ~10 m of right-lateral displacement during the 2016 earthquake, and document two additional cumulative displacements of 20 m and 29 m, recorded by offset fluvial terrace risers. We use radiocarbon and InfraRed-stimulated luminescence dates to constrain the ages of these offsets. By combining these offset data together with published paleo-earthquake ages from a nearby trench site (Morris et al. 2022), we determine the potential range of displacements of the past four to five earthquakes at this site, including the Kaikōura earthquake. We show that the past slip-per-event behavior of the Kekerengu fault is unlikely to be consistent with the slip observed during the Kaikōura earthquake, and that the average slip per event prior to the 2016 event was 4.8 m for the previous four earthquakes, or, alternatively, 6.4 m for the previous three earthquakes. This result reinforces the singular nature of slip during the 2016 Kaikōura earthquake on the Kekerengu fault, and has key implications for earthquake fault behavior and seismic hazard analyses in New Zealand, and, more generally, for earthquake recurrence in other complex strike-slip fault systems around the world.

Key Words
characteristic displacement, Kaikoura earthquake

Gauriau, J., Dolan, J. F., Van Dissen, R. J., Little, T., Rhodes, E. J., & Ivester, A. (2023, 09). Non-characteristic slip behavior on the Kekerengu fault throughout the past four to five earthquakes at Bluff Station, New Zealand. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology