Feb 28 2010 - Tsunami alert from Chile earthquake

A tsunami was generated from a magnitude 8.8 earthquake in Chile on 27 February 2010.

Last update 1 March, 3:00 pm

Latest advice

Please visit the Ministry of Civil Defence and Emergency Management's website for the latest information and advice on what to do (and what not to do) in the event of a tsunami warning.

Latest wave recordings

View the GeoNet tsunami gauges' readings.

Arrival times of the first waves

Chatham Islands:
  • Owenga Wharf (east coast): 07:25 am (NZDT), 08:10 am (CHADT)

New Zealand mainland:
  • Gisborne (port): 08:20 am (NZDT)
  • East Cape (Lottin Point): 08:20 am (NZDT)
  • Napier (port): 08:25 am (NZDT)
  • Castlepoint (Wairarapa coast): 08:25 am (NZDT)
Observations

Waves of nearly two metres (peak to trough) were observed at Owenga Wharf on Chatham Island and at Gisborne. Higher frequency waves seen earlier at Owenga Wharf were believed to be due to seiching, where the waves continued to reverberate around the bay like water in a bathtub. The unusual sea level activity continued at all recording sites for at least 24 hours after the first arrivals.

Overview

The magnitude 8.8 earthquake that occurred off the coast of Chile resulted from the oceanic Nazca plate being thrust under the South American plate. Since the main shock, there have been numerous large aftershocks with magnitudes greater than 6.0. Historical seismicity suggests that continued aftershock activity could include events with magnitudes equal to or greater than 7.0. The earthquake occurred in a region of known stress accumulation between the hypocentres of the great (magnitude 9.5) earthquake of 1960 and the 1922 (magnitude 8.5) earthquake.

The earthquake generated a tsunami propagated west-north-westward across the Pacific Ocean. The largest waves were not expected to hit New Zealand. However, numerical simulations of effects of the tsunami on New Zealand predicted measurable waves with amplitudes of between 0.2 and 1 metre along much of the eastern coast. Variations in the bathymetry around New Zealand lead to amplification of the tsunami around the Chatham Islands and Bank's Peninsula, and in these areas maximum wave amplitudes of between one and three metres were predicted, based on numerical modelling and historical comparison with a similar earthquake on the South American coast in 1877. The historical accounts suggested that the largest waves would in many areas arrive between 6 and 12 hours after the initial arrivals, and this was also supported by the numerical modelling; this is most evident at Gisborne. These larger waves are due to reflections of the tsunami from other parts of the Pacific arriving in New Zealand later than the direct waves, and adding to the activity currently under way.

Responsible agencies

The Ministry of Civil Defence and Emergency Management is responsible for the dissemination of national official tsunami notifications in New Zealand, with technical support and advice provided by GNS Science.

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