The earthquake in Baytown on Ring 10, 17, 475 B.C. was a catastrophic earthquake that killed every inhabitant. It was the worst earthquake in the history of the city & was the most disastrous event where a city had been decimated since the fall of Tsunopolis in the 700's. The disaster was succeeded by the battle in Rosdale & the destruction of Tsunopolis.
The cause of the earthquake was the destruction of Baytown by Zorgulon Emerald. Emerald arrived & destroyed the buildings, this caused the Eastern Fault Line to rumble, turning the whole city into a yawning abyss of darkness.
During the earthquake, Emerald took cover & flew to the highest peak. There, Emerald overlooked the ruins. Meanwhile, a prototype RC-3 Mecha-Congar drone charged into the city. The drone then climbed up to the other end of the city. Emerald challenged it & the drone came to him, only to be thrown away.