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Subduction, Faulting and Earthquake Interaction Across the Cook Strait of New Zealand

Description: 

The Southern Hikurangi Subduction margin in New Zealand intersects the Cook Strait and the surrounding Wellington and Marlborough regions. Together, these regions form a tectonically diverse and active part of New Zealand monitored by a relatively dense seismic network. The study area has hosted several large earthquakes in recorded history and acted as the termination of the 2016 Kaikoura earthquake. Despite these earthquakes and the availability of good long-duration seismic data, there remains significant uncertainty in our understanding of the drivers of seismicity in the region, in particular, the mechanisms of earthquake triggering and nucleation. Studies in other regions around the world have shown that small, previously undetected earthquakes can provide key insights into understanding fault geometry at depth, foreshock and swarm processes as well as triggering and earthquake nucleation.

We have extended a nationwide machine learning earthquake catalogue to detect and locate earthquakes in the Southern Hikurangi Margin between 2011 and 2018. Our catalogue contains 69,152 earthquakes, 32,620 of these being newly detected events, as well as high quality locations with reduced uncertainties and an improved magnitude of completeness. Our self-consistent cataloguing methods allow us to investigate spatial and temporal variability in earthquake occurrence in the region. We first present the key structural features illuminated by this catalogue including subduction interface geometry, upper plate faulting and the presence of a double Wadatti-Benioff Zone. We then investigate fault reactivation between the 2013 Cook Strait and 2016 Kaikoura Sequences, as well as other key temporal features of seismicity. Finally, we discuss the results of our dynamic triggering study in the region, identifying triggering from local, national and global events and the discussing implications this has on the temporal variations in seismicity.

Session: Linking Subduction Zone Processes and Cascading Hazards in Alaska, Cascadia, Chile and Beyond [Poster]

Type: Poster

Date: 4/16/2026

Presentation Time: 08:00 AM (local time)

Presenting Author: Codee-Leigh Williams

Student Presenter: Yes

Invited Presentation: 

Poster Number: 137

Authors