alert bulletin: Nov 15 2007, 11:00 am - White Island Volcano

Science Alert Bulletin WIZ-07/04 - Earthquake swarm near White Island, Alert Level remains at 1

A vigorous earthquake swarm including dozens of small to moderate sized events occurred north-west of White Island overnight. The earthquakes began at about 20:40 New Zealand time on 21 November and have persisted to the present time. The earthquakes are not well recorded, due to sparse seismic station coverage in the Bay of Plenty, but locate about 10 km to the north-west of White Island in a depth range from 5 to 20 km. The events (largest magnitude 4.2) were too small to be felt on the mainland in the Bay of Plenty region.

Associated activity at White Island volcano is unchanged as a result of the earthquakes. Tremor levels at the volcano are similar to those recorded over the past few months and visual observations via remote cameras indicate no change in hydrothermal activity. While monitoring indicates no apparent changes to the volcanic system, local and regional earthquake activity may have perturbed the hydrothermal system. Such changes could destabilise the hydrothermal system resulting in local steam explosions with no warning.

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

Arthur Jolly
Duty Volcano Seismologist