New equipment helps monitor Tongan volcano

New detection equipment will assist Tonga's Geological Service in monitoring the Hunga Tonga-Hunga Ha'apai volcano.

Infrasound is a highly refined microphone that can detect acoustic waves including those made by an active volcano.

One of these devices has now been installed in Nuku'alofa, as a result of the efforts of the volcanic eruption detector project, a US-Tonga partnership.

Head of Tonga's Geological Service Taaniela Kula said that the project will attempt to closely monitor the volcano.

"The only equipment we have for detecting volcanic eruptions is satellite, so we heavily rely on satellite systems. The earthquake sensors or seismic sensors that we have distributed throughout Tonga, detect movement of the earth," Kula said.

Unfortunately, Kula said that seismic sensors do not accurately detect volcanic eruptions.

"So the earth does not move when the magma tries to escape the ocean crust. So we cannot rely on a seismic sensor but as soon as any eruption breaks the water in the atmosphere, then it is picked up by the infrasound, if it is large enough, it can detect," he said.

Martin LaFevers, a geophysicist with the United States Geological Survey (USGS) Volcano Disaster Assistance Program was invited to visit by the Tongan government.

Monitoring instruments from the USGS were donated to Tonga in 2022.

However, Covid-19 meant that the USGS team was unable to travel to Tonga until April of 2023.

There is also an infrasound device in Papua New Guinea's East New Britain but it is programmed to monitor global activity.

This infrasound device installed in Nuku'alofa, has been programmed to monitor a very specific area - the Kingdom of Tonga.

"The infrasound instrument is like the microphone that I am speaking into now, except that it is sensitive to a broader range of air pressures signals, when you speak generate air pressure, and the microphone picks it up, well when the earth speaks in various ways also changes pressure changes," LaFevers said.

He said that the data produced by the sensor will be connected to a computer system via a cellular telemetry

"The computer system has automated processing to determine what the direction was to the event and when it happened."

"Those results are produced within seconds and they can provide some idea of how big the explosion is, and inform scientists of next steps, whether the public needs to be informed and alerted or whether this is, just a standard activity that is familiar and not of concern," LaFevers said.

The USGS team have since returned to the US, and LaFevers said data from the new sensors has started to flow into the Tonga Geological Service.