What happened to Ephyra?

I was looking over one of the new maps for Gears 5 and learned that it is set in old Ephyra but that fact got me wondering what happened to the city to cause it to end up like that within the gap between Gears and Gears 5. I am of course aware of the massive damage to the planet and my best guess is earthquakes ravaged the area after the Cog abandoned the city but I thought it would be a good discussion for the community.

The state of the city during Gears 1

The state of the city during Gears 5


From the wiki β€œIn the months following the Lightmass Offensive, seismic activity caused by the Riftworm severely damaged the city.”