Activity at Mt. Ruapehu

A series of earthquakes were recorded near Mt Ruapehu overnight, and a volcanic earthquake at 10:30 p.m. was reported by Geonet.

An attempt to determine whether a small eruption had occurred were thwarted this morning, when bad weather prevented observation from an aircraft.

Earthquake activity commenced at 10:24 last night when the first of a series of eight earthquakes struck the volcano. Quakes recorded in Geonet’s databases are –

October 4th
10:24 p.m., mag. 2.8, 4.3 km deep
10:24 p.m., mag. 2.0, 4.9 km deep
10:25 p.m., mag 2.9, 0 km deep
10:32 p.m., mag 2.1, 0 km deep
11:08 p.m., mag 1.8, 0 km deep
October 5th
12:40 a.m., mag 2.2, 0 km deep
2:11 a.m., mag 1.5, 0 km deep
5:19 a.m., mag 2.0, 0 km deep

A magnitude 3.0 earthquake struck further north at a depth of 7 km at a location 10 km north-west of Turangi at 4:14 a.m.

In a media release, Steven Sherburn, Duty Volcanologist for GNS Science reported that a magnitude 2.8 volcanic earthquake occurred at 10:30 p.m., but it is not clear whether this is one of the tectonic earthquakes recorded by Geonet’s monitoring network.

The cold southerly conditions which caused disruption in Wellington yesterday prevented scientists from flying over Ruapehu’s crater lake this morning to determine whether a small eruption had occurred. However, the activity appears to have triggered one of the components of the lahar monitoring system installed on the volcano.

Mt Ruapehu last erupted in 1995 and 1996, and the crater lake has refilled since then.

On August 18th, the lake level was reported to be about 1.5 metres above the base of the tephra dam, with snow and ice preventing the contents spilling from the crater. The lake temperature cooled during the latter part of August at the same time as a swarm of small earthquakes was recorded between Ohakune and Turoa ski-field on the southern flank of the volcano.

The lake cooled to 13 °C during the first week of September, the coolest it has been since the 1996 eruptions, aided by ice cliffs falling into the lake on August 30th. The lake warmed to 15.5 °C during the second week of September, but seismic activity was low, with the activity near Ohakune having ceased.

The mountain has been quiet since, apart from a brief period of weak tremor on the 27th and 28th of September and the various noises emitted by happy skiers enjoying themselves on the ski-fields.

[Compiled from data supplied by GNS Science, Geonet, Hazard Watch and their contributing agencies.]

Leave a Reply