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Segmentation of shallow slow slip events at the Hikurangi subduction zone explained by along-strike changes in the fault geometry and plate convergence rates
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  • Andrea Perez-Silva,
  • Yoshihiro Kaneko,
  • Martha Kane Savage,
  • Laura Wallace,
  • Duo Li,
  • Charles A. Williams
Andrea Perez-Silva
Victoria University of Wellington

Corresponding Author:[email protected]

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Yoshihiro Kaneko
Kyoto University
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Martha Kane Savage
Victoria University of Wellington
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Laura Wallace
GNS Science
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Duo Li
LMU Munich
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Charles A. Williams
GNS Science
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Abstract

Over the last two decades, geodetic and seismic observations have revealed a spectrum of slow earthquakes along the Hikurangi subduction zone in New Zealand. Of those, shallow slow slip events (SSEs) that occur at depths of less than 15 km along the plate interface show a strong along-strike segmentation in their recurrence intervals, which vary from ~1 year from offshore Tolaga Bay in the northeast to ~5 years offshore Cape Turnagain ~300 km to the southeast. To understand the factors that control this segmentation, we conduct numerical simulations of SSEs incorporating laboratory-derived rate-and-state friction laws with both planar and non-planar fault geometries. We find that a relatively simple model assuming a realistic non-planar fault geometry can reproduce the characteristics of shallow SSEs as constrained by geodetic observations. Our preferred model captures the magnitudes and durations of SSEs, as well as the northward decrease of their recurrence intervals. Our results indicate that the segmentation of SSEs’ recurrence intervals is favored by along-strike changes in both the plate convergence rate and the downdip width of the SSE source region. Modeled SSEs with longer recurrence interval concentrate in the southern part of the fault (offshore Cape Turnagain), where the plate convergence rate is lowest and the source region of SSEs is widest due to the shallower slab dip angle. Notably, the observed segmentation of shallow SSEs cannot be reproduced with a simple planar fault model, which indicates that a realistic plate interface is an important factor to account for in modeling SSEs.
Jan 2022Published in Journal of Geophysical Research: Solid Earth volume 127 issue 1. 10.1029/2021JB022913