The Lumbridge Earthquake was a significant geological event that occurred recently, in the Year 169 of the Fifth Age. The earthquake's epicenter is believed to have been near Lumbridge, possibly in the Lumbridge Swamps to the south. Although the event did not occur in-game, it was described in a newspost by Jagex.
The earthquake did not cause significant damage to any structures on or below the surface, but within the swamps significant subterannean events took place. The Lumbridge Swamp Caves were partly re-exposed to the surface as a result; caves that may have been hidden since the mid Third Age, when the deity Bandos smote the region.
The re-exposure of the caves ultimately resulted in the rediscovery of the Dorgeshuun cave goblins, who had established Dorgesh-Kaan beneath Lumbridge millennia ago. The quake was responsible for the re-discovery of much of the southern Misthalanian cave network, which is now being explored, mapped, and studied.