Heron DW, Lukovic B, Wang X, Power WL. 2019. Evacuation time estimates for local source tsunami for Porirua and Kapiti suburbs. Lower Hutt (NZ): GNS Science. 192 p. (GNS Science report; 2019/79). doi:10.21420/YH6M-D367.
Abstract
Porirua and the Kapiti Coast are in an active earthquake region. Both areas sit above the Hikurangi Subduction Interface and are cut by or close to a number of major local faults (e.g. the Fisherman Fault, Manaota Fault, Mascarin Fault, Ohariu Fault, Okupe Fault, Onepoto Fault, offshore Rangitikei Fault and Wairau Fault). Modelling of the tsunami generated by these local major faults was completed as a separate piece of research and for the scenarios undertaken, two of the local faults, the offshore Rangitikei Fault and Ohariu Fault, did not to produce tsunami of a size that would create a threat to land at any Porirua and Kapiti Coast suburb. Modelled scenarios of the tsunami generated by earthquakes on the remaining local sources showed all produced land threat tsunami (greater or equal to 1.0 m above the initial sea level) and some had very short (less than 5 minutes) travel times. Timely evacuation has proven to be the most effective means of reducing loss of life from tsunami, but a local source tsunami allows limited time for evacuation. With little time available for official warnings, self-evacuation is recommended should a strongly felt (hard to stand up in) or long-duration (greater than 1 minute) earthquake occur. Prompt evacuation together with a knowledge of evacuation routes and of the nearest safe zone minimises evacuation time and increases an evacuee’s chance of reaching the safe zone before the tsunami arrives. This study provides an estimate of the time needed for people within coastal and other low-lying suburbs of the Porirua and the Kapiti Coast to move to the designated safe zones. Combined with the tsunami travel times available from previous work and with population information, it provides valuable information to inform risk-reduction and preparedness discussions and can be used to aid the development of evacuation plans. The modelling has identified a number of suburbs where immediate and efficient evacuation is necessary to avoid loss of life in a local-source tsunami. (auth)
