"Weaken walls and buildings with crippling earthquakes! Earthquake Spells cause structures to lose a portion of their remaining hitpoints. Walls are especially vulnerable to this effect. Earthquake Spells can also cause structures that are almost destroyed to collapse instantly!"


Summary
The Earthquake Spell is a spell added in the July 1, 2015 update. It deals a percentage of damage to all buildings within its area of effect, except for Gold Storages, Elixir Storages, and the Dark Elixir Storage.

Offensive Strategy 
It is best used on buildings with high hitpoints, as the amount of HP it takes away will be higher due to the percentage being constant. It will not be as effective on buildings with lower HP, such as the Builder's Hut. They are great pseudo-Wall Breakers, unlike their counterpart the Lightning Spell. A single maxed Earthquake Spell can damage up to 48% of any Wall, meaning that 2 maxed Earthquake Spells will severely weaken it. Any buildings or Walls that are severely damaged can be destroyed instantly by this spell; try to get as many of them as you can with one Spell!


Trivia 
Earthquake Spells have bonus percentage damage when walls are in its radius. Earthquake Spells cannot damage Storages, but can damage collectors, mines, and drills.