Forgive my uninformed question but I remember seeing a video many years ago where a (Samsung?) hard-drive had built-in protection from being dropped. The disk will stop spinning within a millisecond when it detects movement. They could survive a sudden drop onto a floor. I assumed this was a common feature of modern disk based hard-drives.

Could built-in protections like this in harddrives be a sufficient protection in an earthquake? What other moving parts are that at risk here? Assuming the servers themselves are locked in cages, I wouldn't expect them to crash to the floor.

Although the big difference here is it's not a sudden drop but a prolonged forceful shaking.