Quake tsunami destroys boats on Lake Taupō
150 aftershocks rock North Island after 5.6 tremor strikes overnight
AIt’s not something we ever thought would happen — an earthquake, and a lake tsunami.
Jess Ratana Taupō Pedal Boats
tsunami in Lake Taupō sparked by a strong earthquake destroyed boats and caused damage to the town’s foreshore yesterday as more than 150 aftershocks were detected.
The 5.6 magnitude quake struck about 20km southwest of Taupō shortly before midnight on Wednesday, at a depth of 5km.
One of the larger aftershocks recorded was a 4.1 magnitude tremor at 1.53pm yesterday.
Coastguard Lake Taupō skipper Mike Hughes said the earthquake caused a surge of water to sweep up some beaches.
In Four Mile Bay at the southern end of Taupō township, the water had surged about 20-30m up the beach, destroying two boats belonging to Taupō Pedal Boats, ripping wooden bollards from a park area nearby and eroding about 2m of soil away from the foreshore.
Hughes said it was the same concept as a tsunami at sea — if it is long and strong, with an earthquake lasting more than a minute, then it was best advised to get away from the water’s edge. In this case, Four Mile Bay shelves off sharply into deep water which could have been a factor.
Niwa hydrodynamic scientist Dr Emily Lane showed in a tweet the tsunami as measured by water level gauges at Acacia Bay and Tokaanu.
Lane told the Herald it was interesting a tsunami resulted from an earthquake of this size.
“With these volcanic earthquakes, you will get deformation, it actually deforms the ground underneath the lake,” Lane explained.
She referenced the complex Kaikōura earthquake when describing to what it might look like under Lake Taupō at the moment.
During the 7.8 magnitude shake in 2016, parts of the land in Kaikōura were jolted several metres upwards due to the many fault lines activated.
Although it may not be as extreme under Lake Taupō, the ground shifting is what would have caused its wave of water.
However, Lane said, the tsunami was bigger than scientists would have guessed, given the magnitude of Wednesday night’s quake.
“One of the interesting things is that an earthquake of this size, in terms of generating tsunamis, that’s pretty small,” Lane said.
“We sort of think that maybe the amount of movement you got was more than what you would expect for an earthquake of that size.”
Lane said she and her team are very interested in talking with locals who have seen any more inundation (the very high tide line) around Taupō so they can continue to piece together the science around Wednesday night’s quake.
Taupō Pedal Boats owners Jess Ratana and Kiripiti Bowden were down at the lake’s edge pulling the two four-person pedal boats off the rocks with a 4WD ute.
Ratana said they were fortunate all of their pedal bikes were intact but the larger pedal boats were the only two they had.
“We pulled them right up last week because of the wind. It was really windy down here.
They were on the grass, they weren’t really near the water at all.
“It’s just pulled them out and the wind direction has taken them this way and they have ended up being smashed against the rocks.”
She said they were insured. “It’s not something we ever thought would happen — an earthquake, and a lake tsunami. I don’t think anyone would have expected that.”
She said their summer season kicks off in about two weeks but it would likely take at least two months to get replacement boats bought and shipped in from overseas.
The business had been going great since they started in January last year and they had also expanded the pedal bikes into Pilot Bay in Mt Maunganui.
Taupō mayor David Trewavas said it was a pretty big quake but so far they had not identified any damage to infrastructure although teams were out checking pipes yesterday morning. “It was a juicy one all right.”