White Island Earthquakes

A moderately strong earthquake struck near White Island at 9:06 this morning, Friday the 13th of June 2008. The shallow quake has been followed by numerous aftershocks.

The magnitude 5.4 quake was located 10 km south-west of White Island (50 km north of Whakatane) at a depth of 5 km. By 2 o’clock this afternoon, 80 felt reports had been lodged with GeoNet, reporting shaking from Tauranga, through the Bay of Plenty to Gisborne.

There have been numerous aftershocks, but only three larger events had appeared in GeoNet’s databases by mid-afternoon. They are: a magnitude 3.8 event at 9:13 a.m., a magnitude 4.1 quake at 9:18 a.m., and a magnitude 3.5 tremor at 15 minutes after midday. All quakes were at a depth of 5 km.

Another quake of about magnitude 4 occurred at 2:07 and another 4th magnitude event at 3:34 this afternoon.

An alert bulletin for White Island was issued at 1 o’clock today, advising that this morning’s earthquake was a tectonic event (i.e. not volcanic) and these are common in the outer Bay of Plenty area. There have been numerous aftershocks, and there may have been landslides on the island following the ground shaking.

There has been no immediate response from the volcano, but the large number of aftershocks that have followed this morning’s shallow earthquake make it difficult to monitor the seismic response from the volcano itself. A monitoring flight, to check for altered volcanic gas levels, is planned.

White Island is popular with tourists, but Brad Scott, Duty Volcanologist at GNS Science, has recommended that visits to the island be suspended for the next 48 to 72 hours.

The bulletin noted, “The active crater at White Island is now occupied by a crater lake, ponding in the crater that formed during eruptions in the 1970s – 1990s. The last eruption at White Island, in 2000, occurred from a vent that is now beneath the lake. Recent volcanic seismicity has included weak volcanic tremor and low frequency volcanic earthquakes, both of which are common at White Island.”

The crater lake at White Island had almost completely evaporated by October 2007, but began to refill during December. By mid-February this year, it had risen by 6 metres and cooled from 63 ºC to 53 ºC.

The Alert Level for White Island volcano remains at 1 (signs of unrest).

A map showing the location of recent earthquakes near White Island and Matata can be found on GeoNet’s website.

[Compiled from data provided by the Geonet project and its sponsors EQC, GNS Science and FRST.]

2 Responses to “White Island Earthquakes”

  1. Darren says:

    I’d love to see the fault plaine of the BOP quake…. I Wish they posted more info on the aftershocks.

    Of which there’s been plenty.

  2. Ken says:

    I’ve crunched some of the numbers on the 80 aftershocks catalogued up to midday today – see latest posting.

    I hear on the grapevine that they did a flyby and the sniffer didn’t pick up anything significant in the way of increased gas emissions from the volcano – but I haven’t seen anything official on that yet.

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