Historical tsunami database for New Zealand

Abstract

New Zealand has suffered relatively few tsunamis compared to many countries around or within the Pacific rim, but has experienced over 30 tsunamis during the last 177 years. The larger events occurred prior to the time when coastal settlements became highly populated. The New Zealand Ministry of Civil Defence is responsible for managing such extreme events, and for this function it is advantageous to have a comprehensive database for rapid appraisal of tsunami warnings. This project therefor aims to extend the existing tsunami events data and to present it in an operational database for The New Zealand Ministry of Civil Defence. In addition from the tsunami database, tsunami runup risk and expected tsunami runup heights for several New Zealand coastal sectors were calculated.

Using existing dates of tsunami events, new reports of tsunami waves were researched from South Island newspaper archives. Additional extra information about the tsunami waves, for example wave height and wave period, was also obtained from the newspapers for existing reports.

The tsunami data, including source mechanism data, was entered into a database spreadsheet in the form of a lookup table using Microsoft Excel. Event sources are divided into key regions as defined by The National Geophysical Data Centre of the National Oceanic and Atmospheric Administration. Tsunami events are divided up into key regions defined by Regional Council authorities. The database will enable The Ministry of Civil Defence to predict tsunami heights around New Zealand by interpolating data from past events.

Tsunami return periods and expected runup calculations were made for various sites around New Zealand. It was found that destructive tsunami waves are most likely to originate from local sources. The most common and largest far-field tsunami waves are from the West Coast of South America