AKIPRESS.COM - Scientists have been stumped by the 20-minute rumble of a mysterious seismic wave which was detected earlier this month, Sky News reports.
The tremor occurred on the morning of 11 November near the archipelago of Mayotte, a collection of French islands in the Indian Ocean between Madagascar and Mozambique.
It is unclear whether it was caused by volcanic activity or a meteor strike, but it was felt by seismometers across the world, from New Zealand to Canada - and even in Hawaii.
Geologists shared their discovery of the surprisingly low frequency activity on Twitter, with Jamie Gurney, the founder of the UK Earthquake Bulletin, among the first to note the event.
A number of possibilities have been suggested, inspired by the fact that - despite the monitoring stations detecting seismic waves - there was no corresponding earthquake felt that morning.
The low frequency of the waves has been particularly interesting to seismologists.
The most prominent suggestion in the seismology community has related to what they've called a "seismic swarm" - essentially an event including many earthquakes rolling together.