Ground motions in New Zealand from Kermadec megathrust earthquakes

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Fry, B.; Gledhill, K.R.; Benites, R.A. 2018 Ground motions in New Zealand from Kermadec megathrust earthquakes. Lower Hutt, N.Z.: GNS Science. GNS Science report 2018/33. 17 p.; doi: 10.21420/7J43-G338

Abstract: We use numerical simulations of earthquake ground shaking to test the ability of natural warning to trigger self-evacuation in communities in the north-western North Island that are at risk of tsunami generated along the Kermadec Subduction Zone in the southwest Pacific. In this region, self-evacuation defined as “Long or Strong, Get Gone” is the dominant mechanism for risk mitigation. However, we conclude that many possible earthquakes will not be felt strongly in these regions, including densely populated metropolitan areas on the coast from the Bay of Plenty to Northland, such as the cities of Tauranga, Auckland and Whangarei. These earthquakes could then cause tsunami waves with maximum wave amplitudes in excess of 5m within the first hour after the earthquake. This finding suggests that reliance on self-evacuation alone must be supplemented with scientific monitoring and alerting mechanisms to protect vulnerable populations. (auth)