alert bulletin: Jun 13 2008, 1:00 pm - White Island Volcano

Science Alert Bulletin WIZ-08/02 - Large earthquake nearby; Alert Level remains at 1

A magnitude 5.4 earthquake occurred at 9:06 am (NZST) today, 10 km south-west of White Island, and was widely felt in the Bay of Plenty. There has been no immediate response from the volcano, though the large number of aftershocks means that any seismic response may be difficult to see for several hours. As a consequence of this event we would recommend no visits to the island for the next 48 - 72 hours as the potential for eruptive activity will be higher during that period. After 48 - 72 hours the hazard level may decrease to what is usual at White Island, however, we cannot guarantee that any response at the island will occur within a 48 - 72 hour period. We are continuing to assess the activity on a regular basis.

This morning's earthquake was a tectonic-type earthquake, and these are common in the outer Bay of Plenty. We are recording many aftershocks following this event. The level of ground shaking may have produced some landslides, but we are not aware of any at this time from viewing the camera images. There has been no immediate response from the volcano though the large number of aftershocks means that any seismic response may be difficult to see for several hours.

We will continue to monitor the earthquake activity and, conditions permitting, make a monitoring flight to assess the volcanic gas output. If the volcano responds there is likely to be an increase in gas output and/or an increase in volcano seismic activity.

White Island is an active volcano and there is always a level of hazard associated with it. Moderate-sized tectonic earthquakes are also common events in the outer Bay of Plenty and historically no connection has been demonstrated between them. However as a consequence of this earthquake the eruption hazard at the island may have increased above the normal levels and we would recommend no visits to the island for the next 48 - 72 hours as a precautionary measure.

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 Alert Level for White Island remains at Alert Level 1; there is no significant change in volcanic activity on the island.

Brad Scott
Duty Volcanologist