Marsquake

A marsquake is a Martian version of an earthquake; similarly, it is a shaking of a planet's crust, and a possible phenomenon in Motherload. Marsquakes can only happen when you are on the surface. All marsquakes are caused by a low-chance roll that automatically occurs every time you enter any of the interactive shops. For this reason, limiting your shopping by a number of methods means you must pass a much lower amount of these low-chance rolls, giving you substantially better odds of having a marsquake-free game. Briefly, some of these shop-limiting methods are: replacing your fuel-buying entirely with fuel reserve tanks, buying more than one item at a time at the junk shop (planning your buys), and perhaps in the later game replacing repairing entirely with nano repair bots.

When a marsquake occurs, the screen shakes briefly, and a large, flashing red and white exclamation mark appears. A marsquake will almost completely reset the underground, forcing you to dig tunnels nearly from scratch. However, they are quite rare (perhaps once or twice every several hours of gameplay).

It is referred to as an "Earthquake" in one of the transmissions from another mining pod, although that is technically incorrect. Also, the transmission mentions being trapped by an "Earthquake" which damaged the drill, both of which cannot happen to you in the game.