The Taupo earthquake increased in magnitude, nearly 700 aftershocks, and triggered landslides

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Aerial view of Tobu. photo/NZME

The earthquake that shook Taupo residents on November 30 has been upgraded to 5.7, GeoNet said today, while producing nearly 700 aftershocks, tsunamis and more than 30 landslides.

The increase in size is due to “the greater resolution we’ve been able to provide earthquake analysis since the earthquake.”

“We have identified over 680 aftershocks (as of this story being published), with the most recent being M3.4 on Dec. 12. The aftershock sequence (magnitude of events and numbers) is as we would expect for a mainshock of M5.7,” GeoNet said in a statement. statement.

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More than 30 landslides resulted from the 5.7-magnitude quake.

“This is not unexpected, given the intensity of the shaking and the timing of the earthquake, which followed several weeks of particularly wet weather. The landslides were identified through a combination of contact with Taupo District Council, public reports provided to GeoNet through our online survey, and mapping field by GNS staff, and analysis of satellite images obtained in the days following the earthquake.

“Most of the landslides were small slides on steep slopes near roads, particularly in the northern regions, near Acacia Bay, while large rockslides possibly up to the size of a bus, were identified near the epicenter in the vicinity of Hatepe.

“Most of it originated on the white cliffs along the lake’s eastern shore north of Hatepe, just 7 kilometers from the epicenter,” GeoNet said.

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A section of cliffs several hundred meters long collapsed into the lake creating a large white column of sediment that could still be seen running north along the coast several days after the earthquake.

“On land, a number of large rockslides in the vicinity of Hatepe appear to have occurred from slopes within river valleys close to the lake. These are areas that we know are vulnerable to long-term erosion, and rockfall may be considered earthquake-induced, although not Incredibly popular, a natural landscape process.”

Our experts have been busy collecting and analyzing data to understand the M5.7 earthquake at Lake Taupo on November 30, including ground shaking, landslides, volcanic activity, and tsunamis. This is an update on what we know so far: https://t.co/4BfXqYtzcp pic.twitter.com/6g67i9SmQT

– GeoNet (@geonet) December 13, 2022

Aside from the rockslides on the white cliffs, the most notable overland movement caused by the earthquake was 15 kilometers north of the epicenter, at Wariwaka Point.

An underwater landslide likely occurred at the site of the popular swimming beach, causing 170 meters of shoreline into the lagoon to subside, with a maximum retreat of 20 metres. While still under investigation, a beach slide into the lagoon likely caused It pulled water in from behind it, creating a local tsunami that swept through the picnic area behind,” GeoNet said.

Underwater landslides are known to be some of the largest landslides on Earth and can trigger tsunamis, however, there is currently no evidence to suggest that the Wharewaka Point landslide triggered the largest lake level tsunami ever observed after this earthquake.

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GeoNet said the recent earthquake activity was consistent with minor volcanic disturbances and did not warrant a move to a higher volcanic alert level.

“Taupō has experienced 18 episodes of unrest in the past 150 years, lasting from months to years. None of them led to an eruption. Depending on this history, the current period of unrest could last for several weeks to months, with varying rates or intensity.”

The Taupō Volcanic Alert Level is currently at Level 1.

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