Complex Spatial-Temporal Rupture Patterns of Reverse Faults: The Dunstan Fault, Otago, New Zealand

Alex Travers, Mark Stirling, Andrew Gorman, Jonathan Griffin, & Dan Clark

Submitted September 7, 2025, SCEC Contribution #14345, 2025 SCEC Annual Meeting Poster #TBD

Tectonic geomorphology resulting from active reverse faulting is highly variable and often complex (E.g. 1988 Spitak earthquake rupture, 2016 Kaikoura rupture). Surface expressions can range from single, well-defined fault scarps to multiple parallel scarps, to zones of deformation dominated by folding. Furthermore, reverse faults are frequently blind, meaning that they have no surface expression (E.g. 1994 Northridge earthquake rupture occurred on a fault previously unknown). With increased infrastructural development directly over active faults (E.g. Franz Josef on the Alpine Fault) it is necessary to better understand the complex behaviours of reverse fault surface displacement.

The Dunstan Fault in Central Otago, New Zealand, exemplifies this complexity. Like many active reverse faults in the region, it is expressed at the surface by multiple parallel fault traces, sometimes spanning a zone up to 2.5 km wide. A key question is whether all traces within this fault zone rupture during a single surface-rupturing earthquake, or if individual traces rupture independently. If the latter, is there a temporal or spatial pattern to these ruptures that could inform future rupture forecasting? Alternatively, what is the likelihood of new surface traces forming in future seismic events?

We present new paleoseismic data from three of the four major traces preserved on the Devonshire fan section of the Dunstan Fault to constrain the timing of past surface-rupturing events on individual traces. This is complemented by high-resolution active and passive seismic reflection data, which contextualises the multi-trace reverse fault system with its subsurface tectonic structure.

These results have implications for our understanding of fault displacement hazard of reverse faults. Current New Zealand Ministry for Environment guidelines recommend a 20-meter fault avoidance zone on either side of an active fault trace, irrespective of fault type. In this study we explore the potential to refine fault avoidance zones for multi-trace reverse faults.

Key Words
Paleoseismology, Tectonic Geomorphology

Citation
Travers, A., Stirling, M., Gorman , A., Griffin, J., & Clark, D. (2025, 09). Complex Spatial-Temporal Rupture Patterns of Reverse Faults: The Dunstan Fault, Otago, New Zealand. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology