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A New View on Interseismic Locking of the Hikurangi Megathrust Along the North Island of New Zealand

Description: 

The largest earthquakes in subduction zones occur where significant interseismic slip deficit has accumulated on the plate interface. Slip deficit accumulates most quickly in mechanically locked regions, and these also cause the regions around them to accumulate slip deficit; therefore, large earthquakes are typically expected to rupture in and around locked areas. Resolving the locations and dimensions of these mechanically locked zones from kinematic geodesy (leveling, GNSS and/or InSAR time series) has been difficult, particularly when the overriding plate is subject to multiple drivers of active deformation at significant rates, like the Pacific Northwest and Alaska.

We focus on the North Island of New Zealand, where GNSS velocities show the superposition of locking of the Hikurangi megathrust and backarc extension in the Taupo system. To be able to use both horizontal and vertical time series data we develop a mechanical model with the 3D geometry of the Hikurangi slab from Slab2 (Hayes et al., 2018). The slab and shallow overriding plate are taken to be elastic, and the mantle wedge and sub-slab asthenosphere have linear viscoelastic properties. We discuss the relevance of including major trench-parallel faults that bound forearc blocks, like the Wairarapa fault. We show results of assuming the megathrust locking pattern found in previous studies, and the corresponding backarc extension imprint on the North Island. We discuss how prior information may help improve the reliability of locking estimates, and Bayesian inference methods that aim to constrain the uncertainties of future megathrust locking estimates.

Session: Learning Across Geological, Geophysical & Model-Derived Observations to Constrain Earthquake Behavior [Poster Session]

Type: Poster

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Rob

Student Presenter: No

Invited Presentation: 

Authors