The 2016 Mw 7.8 Kaikōura, New Zealand, Earthquake Triggers Slow Slip Events and Delays Megathrust Earthquakes in Rate-and-State Friction Simulations of the Hikurangi Subduction Zone

Jeena Yun, Jeremy Wing Ching Wong, Yuri Fialko, Alice-Agnes Gabriel, Dave A. May, Laura M. Wallace, & Charles A. Williams

Submitted September 7, 2025, SCEC Contribution #14499, 2025 SCEC Annual Meeting Poster #TBD

The 2016 Mw 7.8 Kaikōura earthquake triggered slow slip events (SSEs) along the nearby Hikurangi subduction zone (HSZ), which is characterized by quasi-periodic SSEs spanning the entire margin. While large earthquakes have been observed to influence SSE occurrence, and vice versa, the underlying mechanisms driving such interactions remain poorly understood.
We use data-informed physics-based numerical simulations to investigate the impact of the Kaikōura earthquake on the spatiotemporal evolution of sequences of earthquakes and aseismic slip (SEAS) in the HSZ. We simulate 2D quasi-dynamic HSZ SEAS using the open-source volumetric software Tandem, incorporating realistic slab geometry, plate convergence rate, velocity structure, and spatially variable pore fluid pressure, together with a loading scheme tailored to volumetric SEAS simulations. These models reproduce observed spatial distributions and recurrence intervals of SSEs and earthquakes across different sections of the HSZ and are validated against GNSS data and interseismic locking models.
To explore the influence of upper plate earthquakes on megathrust slip behavior, we perturb the SEAS models using dynamic and static stress changes derived from 3D dynamic rupture or kinematic slip models of the Kaikōura earthquake using SeisSol. We explore multiple source models and perturbation timings, with and without ongoing SSEs.
Our results show that the Kaikōura earthquake can trigger SSEs along the northern HSZ and delay subsequent large megathrust earthquakes by months to years. Dynamic triggering dominates the immediate SSE response, while static stress changes trigger delayed SSEs occurring several years after the perturbation. These findings are consistent with observations of dynamically triggered SSEs after the Kaikōura earthquake and the absence of large megathrust earthquakes on the northern HSZ. Our framework illustrates the complex interactions between megathrust slow slip events and earthquakes in the upper plates: upper plate rupture modulates megathrust SSE activity, in turn influencing megathrust earthquake timing. Our Tandem and SeisSol simulations will be publicly accessible via the Quakeworx Science Gateway.

Key Words
Slow slip events, SSE, Kaikoura, Hikurangi, megathrust

Citation
Yun, J., Wong, J., Fialko, Y., Gabriel, A., May, D. A., Wallace, L. M., & Williams, C. A. (2025, 09). The 2016 Mw 7.8 Kaikōura, New Zealand, Earthquake Triggers Slow Slip Events and Delays Megathrust Earthquakes in Rate-and-State Friction Simulations of the Hikurangi Subduction Zone. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)