Multi-Trace Rupture Behaviour of Reverse Faults: New Paleoseismic Insights from the Dunstan Fault, Otago, New Zealand

Alex Travers, Mark Stirling, Kathleen Rodrigues, Jonathan Griffin, & Dan Clark

Submitted August 30, 2026, SCEC Contribution #15360, 2026 SCEC Annual Meeting Poster #115

The Dunstan Fault is a slow slip rate reverse fault within the Otago Range and Basin Province, South Island, New Zealand. It is expressed at the surface by multiple parallel to sub-parallel traces spanning a ≤2.5km fault zone width. On the Devonshire Alluvial Fan, the Dunstan Fault is expressed along four major fault traces: D1, M2, D2 and D3 (Van Dissen et al., 2007). Paleoseismic trenches, excavated as part of this study, across D1, M2 and D3 provide evidence for 3, 2 and 1 earthquakes, respectively. Previous paleoseismic work on the D2 trace provides evidence for 4-6 earthquakes (Van Dissen et al., 2007). If all earthquakes are assumed to have ruptured independently, there is evidence for at least 10-12 earthquakes on the Devonshire Fan. Optically stimulated luminescence dating of key stratigraphic horizons was used to confine earthquake timing. Timings of earthquakes are as follows: D1-E1: <1.90ka, D1-E2: 1.65ka – 2.35ka, D1-E3: >7.57ka, M2-E1: 7.67ka – 11.51ka, M2-E2: 9.57ka – 12.61ka, D3-E1: 3.37ka – 8.33ka. Analysis of these ages, along with the earthquake chronology from the D2 trace (Van Dissen et al., 2007), yield some interesting results: (1) The most recent earthquake on the Dunstan Fault occurred within the past 1,900 years, far earlier than previously estimated (8,830 – 14,400 yrs; Van Dissen et al., 2007); (2) There have been at least 5 ground rupturing earthquakes within the past 12,600 years; (3) The three most recent earthquakes on the Dunstan Fault appear to have ruptured individual fault traces only, providing evidence to suggest that traces on the Dunstan Fault do not rupture together; (4) The two most recent earthquakes ruptured the antithetic trace only, providing insights into the possible subsurface fault geometries which could kinematically allow such rupture. These findings have not only enhanced our understanding of the multi-trace behaviour of the Dunstan Fault, but contribute to our understanding of reverse fault displacement more generally.

Key Words
Paleoseismology, Tectonic Geomorphology, Reverse Fault, Fault Displacement

Citation
Travers, A., Stirling, M., Rodrigues, K., Griffin, J., & Clark, D. (2026, 08). Multi-Trace Rupture Behaviour of Reverse Faults: New Paleoseismic Insights from the Dunstan Fault, Otago, New Zealand. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology