A phrase in this article jumped out at me.

https://www.outerplaces.com/science/item/19109-seismic-wave-earth-november-11

>National Geographic points out that slow earthquakes are often linked to volcanic activity, which tracks with the theory that the mystery event was linked to the Mayotte quakes because Mayotte was formed by a volcano. There hasn't been an eruption in 4,000 years,

but that doesn't mean that things aren't happening beneath the surface.