Detection of pre-eruption warning signals at Whakaari White Island

Context

Though, it is believed that volcano has its own “personality”, it has been found that volcanoes share behaviour traits — and this could form the basis for an eruption warning system.

About

About Whakaari Island:

Whakaari/White Island is currently New Zealand’s most active cone volcano.
It is located in the Bay of Plenty sitting 48 kilometres offshore.
The cone has been built up by continuous volcanic activity over the past 150,000 years.
The island covers an area of around 325 hectares and this is only about 30 per cent of the volcanos mass - the rest is under the sea.
Even so, it is only about half the size of other cone volcanoes like Mount Ruapehu, Tongariro or Taranaki.
It is a tourist magnet, with its alien landscape and spectacular hydrothermal features.

2019 Explosive Eruption

A fatal explosive volcanic eruption occurred in December 2019.
Tragically some visitors and guides on the island at the time were killed, and many injured.
The eruption removed the Crater Lake, formed new vents and generated landslides into the active crater area.

Deciphering volcanic language

Every volcano behaves differently: some have crater lakes while others are “dry”, they have diverse magmas and rise to different elevations.
Despite these differences, we think volcanoes such as Whakaari, Ruapehu and Tongariro in New Zealand could be driven to eruption by common processes in the shallow sub-surface below their craters.
The new study noted that one pattern repeatedly in the days before all the known Whakaari eruptions over the past decade, and most Ruapehu and Tongariro ones.
This pattern is a slow strengthening of a quantity called Displacement Seismic Amplitude Ratio (DSAR), which peaks a few days before each event.
DSAR is a ratio that compares the “activity” of fluids (gas, hot water, steam) at the volcano’s surface to those several hundred metres deep.
When DSAR increases, surface fluids are quiet, but deep ones are still actively moving and circulating vigorously below ground.
This indicates a blockage or seal has formed, preventing gas escape. Like a pressure-cooker, if the gas can’t escape a volcano, it explodes.