The gods have access to many dimensions. Yet in any calculation, from any perspective, the source of the quake is DOWN.
Something this powerful would have to span the multiverse, the metaverse, the Diamond of Existence itself.
Campaign worlds rarely produce such events, though sometimes they do - as Thrash pointed out earlier, the Forgotten Realms Facet is undergoing a great event known as the Sundering.
In the annals of the Precedent, in the Icy Wastes and Plane of the Mountain, you find reference to powerful deities whose potency extends to the heart of the universe. Hundred Handed Ones, Titans, Protogenoi...The Abrominae, Sessile Tartarus, and once-captive Steep Loki and Steep Fenris...these monsters and primordials would have the strength to shake the universe to its core. This quake is nothing compared to the events that ravaged the Icy Wastes and made even the Steepest flee (some coming through a portal much like the one in the Hamlet of Heroes, no less).
Yerkan bends to notice trilobites fleeing from chasms in the earth. His perceptions of the land below become steadily less cloudy.