Ground motion simulations of Hope fault earthquakes

Ethan M Thomson,Brendon A Bradley,Robin L Lee

doi:10.5459/bnzsee.52.4.152-171

Ethan M Thomson, Brendon A Bradley + Show 1 more

Open Access

https://doi.org/10.5459/bnzsee.52.4.152-171

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Abstract

This paper examines ground motions for a major potential Mw7.51 rupture of the Hope Fault using a physics based simulation methodology and a 3D crustal velocity model of New Zealand. The simulation methodology was validated for use in the region through comparison with observations for a suite of historic small magnitude earthquakes located proximal to the Hope Fault. Simulations are compared with conventionally utilised empirical ground motion models, with simulated peak ground velocities being notably higher in regions with modelled sedimentary basins. A sensitivity analysis was undertaken where the source characteristics of magnitude, stress parameter, hypocentre location and kinematic slip distribution were varied and an analysis of their effect on ground motion intensities is presented. It was found that the magnitude and stress parameter strongly influenced long and short period ground motion amplitudes, respectively. Ground motion intensities for the Hope Fault scenario are compared with the 2016 Kaik¯oura Mw7.8 earthquake, it was found that the Kaikoura earthquake produced stronger motions along the eastern South Island, while the Hope Fault scenario resulted in stronger motions immediately West of the near-fault region and similar levels of ground motion in Canterbury. The simulated ground motions for this scenario complement prior empirically-based estimates and are informative for mitigation and emergency planning purposes.

Highlights

The 2016 Kaikoura Mw7.8 earthquake resulted in significant ground motions and caused substantial damage to infrastructure throughout the Northern South Island and as far away as Wellington [1, 2], and provides motivation for further assessment of the potential impacts from significant ruptures of faults in this region of New Zealand
Leveraging physics-based ground motion simulation advancements and validation, this paper presents physics-based ground motion simulations for a Mw7.51 Hope Fault scenario
This paper examined ground motions for a major rupture of the Hope Fault using a physics-based simulation methodology and a 3D crustal velocity model of New Zealand

Summary

INTRODUCTION

The 2016 Kaikoura Mw7.8 earthquake resulted in significant ground motions and caused substantial damage to infrastructure throughout the Northern South Island and as far away as Wellington [1, 2], and provides motivation for further assessment of the potential impacts from significant ruptures of faults in this region of New Zealand. The Hope Fault is generally considered as a collection of contiguous faults in the South Island of New Zealand and can be traced from the Alpine Fault to offshore northeast of Kaikoura [3, 4]. The Conway Offshore segment has a relatively low slip rate compared with the Onshore segment, partially due to the slip transfer onto the Jordan Thrust This indicates that the Conway offshore segment is unlikely to participate in the majority of large Hope Fault earthquakes and was not included in the rupture scenario generated. The total rupture area of the modelled faults is 163323km218 yieldin2g0 a m2e2an cha2ra4cteristic magni2tu8de of 30

14 Wellington

Methodology

Method and Variables

DISCUSSION AND CONCLUSIONS