You widen the quotes a bit... activate auto-hedge... or not and play around a bit. MM's have already idea's about what would roughly happen to IV when something might happen. You have to adjust vols quickly and hedge delta's and trade in/out of vega. Sounds easier than it is, but when you're on top of it it's not too bad.
I was MM during GFC in bank stock options... now that was fucked up. IV up and down 20, 30, 40 points. Vols of 150+...