The sound of the Hunga-Tonga-Hunga-Ha’apai underwater volcano eruption

Most of you will have seen the news of an underwater volcanic eruption in Tonga, and the resulting tsunami. The eruption has led to  unknown amounts of damage in Tonga at the time of writing, but our thoughts are with the people of Tonga, and anyone else in the Pacific region impacted.

To give you an idea of the power of the eruption, please have a look at the attached image. Our school seismometers in Taupo Nui A Tia College and St Mary’s Catholic Primary In Rotorua recorded a cigar-like signal between 6 and 7.30 UTC. This equates to 7pm and 8.30pm local time, and is a recording of the the sound of the eruption, travelling through the air — not through the ground! — from Tonga to Taupo and Rotorua. At ~340 m/s, this sound took almost two hours to travel the ~2000 km from Tonga to Aotearoa.

By the way, you can also see the increase in noise on the station that started at 21.00UTC; this noise in Taupo (!) is caused by ocean waves from Cyclone Cody crashing on Aotearoa’s Eastern shores, and then shaking the ground all the way to Taupo…

Finally, as an exclamation point of the powers of Ranginui, Papatūānuku, and Rūaumoko, an Earthquake in Te Araroa (Magnitude 4.7) was also recorded at 3.22 UTC.

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