Naturally occurring earthquakes result from seismic energy released along fault lines in a planet’s crust. Powerful magic, the release of a legendary monster, or the destruction of a powerful artifact might also result in an earthquake. Earthquakes range from those that are harmless and nearly undetectable to those that are catastrophic and cause widespread destruction and loss of life.
The exact damage of an earthquake is subject to the GM’s discretion. Listed below are general guidelines to assist GMs in running earthquake events. The baseline used here assumes an earthquake of average strength. GMs should modify the values listed depending on the severity of the earthquake.
Earthquakes can have additional effects such as disrupting rivers, draining lakes and marshes, and even triggering tsunamis or volcanic events. Earthquakes might cause widespread fires in urban areas or displace wildlife in wilderness environments. The additional effects should be determined by the GM but should match the strength and severity of the earthquake.
Collapse: Creatures in an enclosed space or underground during an earthquake are at risk of having the ceiling or structure collapse on them. If a structure collapses, each creature inside takes 8d6 points of damage (Reflex DC 15 half ) from the falling rubble and becomes pinned. A creature that takes cover (under furniture, for example) gains the normal bonus for cover on its Reflex save. A creature pinned beneath rubble takes 1d6 points of nonlethal damage per minute while pinned. If a pinned creature falls unconscious, each minute thereafter until it is freed or dies, it must succeed at a DC 15 Constitution check or take 1d6 points of lethal damage.
Falling Debris: Even creatures not in a structure are still at risk of falling debris, whether from a collapsing building nearby or a natural structure such as a cliff or mountain. Any creature caught in the area of falling debris suffers the collapse effects, but it takes 4d6 points of damage at the time of collapse instead of 8d6.
Fissure: Earthquakes can open massive cracks and fissures in the ground. A creature near a fissure as it opens has a 25% chance of falling in unless it succeeds at a DC 20 Reflex save. Additionally, each creature standing in the area when a fissure opens must succeed at a DC 15 Reflex save or fall prone if it avoids falling into the fissure. Fissures are typically 1d4+1 x 10 feet deep, and creatures falling into one take the appropriate falling damage. There is also a 25% chance that surrounding debris also falls into the fissure. Creatures in the fissure when debris falls on them take additional damage from the falling debris. Surviving creatures that are not pinned can attempt to climb their way out.
Impaired Actions: The tremors of an earthquake impose a –8 penalty on Dexterity-based skill checks for creatures on the ground. Spellcasters on the ground must succeed at a concentration check (DC = 20 + the spell’s level) to cast a spell.
Structures: Most wood or masonry buildings collapse during an earthquake. Structures built of stone or reinforced masonry take 100 points of damage that is not reduced by hardness. Large structures such as castles might not collapse outright, but certain features such as towers or entire sections of a wall might. Creatures caught in a structure that is destroyed suffer collapse effects.
Pathfinder Roleplaying Game: Ultimate Wilderness © 2017, Paizo Inc.; Authors: Alexander Augunas, John Bennett, Robert Brookes, John Compton, Dan Dillon, Steven T. Helt, Thurston Hillman, Eric Hindley, Mikko Kallio, Jason Keeley, Isabelle Lee, Jason Nelson, Stephen Radney-MacFarland, Alex Riggs, David N. Ross, David Schwartz, Mark Seifter, Jeffery Swank, and Linda Zayas-Palmer.