Just south of Lake Rotorua, Horohoro mountain, a rhyolite dome, has very high cliffs[4] in an apparent fault scarp that defines the western edge of the lower lying Paeroa Garben and its northern Kapenga Caldera.

This fault area of the Taupō Rift is controversial as the components of historic tectonic and volcanic contribution have led to debate.

What is known is that the fault has displaced historically at a much higher rate before the last Taupō Hatepe eruption.

It has also been speculated that the northern part of the fault is actually the western edge of the Kapenga Caldera with the Horohoro dome in its rim.

[3] This intra-rift fault has been estimated to have single event earthquakes in its northern portion up to about 6.5 Mw[2] every 5000 to 7000 years.