In Operation Swordbreaker you'll have to clear out the LZ for the helicopter. Eventually you'll get to a turret on a vehicle. Carefully clear the area around your vehicle of all enemies. After some time, you'll no longer have to shoot the additional approaching enemies, as both you and the enemies will be stunned by an earthquake. You'll successfully reach the helicopter in the next mission Uprising. At the beginning of this mission the earthquake continues. During the cutscene, you'll pass out; but you'll wake up in a very short amount of time. Once you wake up and are ready to proceed on a longer trip to the new LZ, you'll get the achievement, since you've survived the big earthquake.