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Tsunami research 2011-12

NZ tsunami gauges 2011 v2

In 2011, the most significant tsunami to affect New Zealand was caused by the Tohoku earthquake in Japan. This magnitude 9.0 earthquake occurred on the 11th of March, and the subsequent tsunami had devastating effects on the northeast coast of Honshu island. In places the tsunami run-up reached 40 metres above sea level. The tsunami caused the majority of the nearly 20,000 casualties as well as a very serious nuclear accident at Fukushima.

The effects on New Zealand were much less serious, though they still represented by far the most major tsunami to affect this country in 2011. Initial waves reached New Zealand approximately 13 hours after the earthquake, and the maximum recorded amplitudes were up to around one meter (and trough to crest wave-heights nearly twice that). Particularly noteworthy was the long duration of the tsunami, which continued for several days; in some locations the largest waves occurred nearly two days after the first arrivals, such a long delay has important implications for how we should respond to future distant-source tsunami.

The tsunami was widely observed around the country. An online survey conducted by Geonet received 52 reports nationwide, though these tended to be concentrated around the northeast coast of the North Island. Notable observations include one from Orewa where the “water level varied between the low tide and high tide marks over a period of about 8 minutes” corresponding to a surge height of about 2.2 meters, and from Baddeleys Beach in Millons Bay where the water’s edge was estimated to have moved back and forth by approximately 650m in response to the tsunami. There was minor damage caused to small boats and marine facilities in various locations, and inundation damage to houses in Port Charles at the northern tip of the Coromandel Peninsula.

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 Last updated 2 October 2013