“Most landslides were small slips on steep cut slopes close to roads, particularly in northern regions, close to Acacia Bay, while larger rockfalls perhaps up to the size of a bus, were identified closer to the epicentre in the vicinity of Hatepe.
“Most were generated on the White Cliffs along the eastern lake shore north of Hatepe, just 7km from the earthquake epicentre,” GeoNet said.
A several-hundred-metre-long section of the cliffs collapsed into the lake generating a large white plume of sediment that could still be seen stretching north along the coastline several days after the earthquake.
“Further onshore, a number of larger rockfalls in the vicinity of Hatepe appear to have occurred from cliffs within river valleys close to the lake. These are areas that we know are prone to long-term erosion, and earthquake-induced rockfalls, though not incredibly common, can be considered a normal landscape process.”
Aside from the rockfalls on the White Cliffs, the most notable single earthquake-triggered land movement was located over 15km north of the epicentre, at Wharewaka Point.
“It is possible an underwater landslide occurred at the location of the popular swimming beach, causing 170m of the shoreline to subside into the lake, with a maximum retreat of up to 20m. Whilst still under investigation it is possible that the collapse of the beach into the lake drew water in behind it, generating the local tsunami that washed up onto the picnic area behind it,” 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 the Wharewaka Point landslide generated the larger lake-wide tsunami observed following this earthquake.
GeoNet said the recent earthquake activity was consistent with minor volcanic unrest and did not warrant a move to a higher volcanic alert level.
“Taupō has had 18 episodes of unrest in the past 150 years, lasting for months to years. None of them led to an eruption. Based on this history, the current unrest period could continue for many weeks to months, at varying rates or intensities.”
Taupō Volcanic Alert Level is currently at one.
