Moderate Rotorua Quake Rocks North Island

At 1:14pm NZDT on the 11th January 2016 a local magnitude 4.6 (moment magnitude 4.8) earthquake struck 25 kilometres east of Rotorua in the north of the North Island, just south of the Bay of Plenty. The earthquake was given a focal depth of 150 kilometres, consistent with subduction related earthquakes beneath the Taupo Volcanic Zone. This earthquake was likely near the plate interface as the Pacific Plate subducts beneath the Indo-Australian Plate below the North Island. The earthquake was very well felt, with over 750 felt reports received by GeoNet, from Te Kaha in the north to Blenheim on the South Island. The highest intensities were received from eastern locations on the North Island, namely Te Aro & Tawa (Wellington area), Hastings and Mangapapa (Gisborne area), all at MM5 (moderate) intensity.

This is the first moderate felt earthquake in New Zealand since the local magnitude 4.7 earthquake near Opotiki on the 5th January. As with that earthquake, this earthquake occurred at an intermediate depth, although owing to the fact it was further west than the Opotiki event it struck at a greater depth. This is because the Pacific Plate is sinking beneath the North Island from off the east coast at the Hikurangi Trench.This it the second most felt earthquake so far this year after the local magnitude 5.1 Akitio earthquake on the 4th January (which received over 1100 felt reports).

Yesterday's Rotorua earthquake was a result of oblique reverse faulting on a vertical fault plane at a depth of 150 kilometres. Whether this puts it within the Pacific or Indo-Australian plates is impossible to say with certainty. Nevertheless, with a moment magnitude of 4.8 this is the largest New Zealand earthquake so far this year.

Written by J H Gurney, 12:05am NZDT, 12th January 2016.
From Devon, United Kingdom.