You know that earhquake level 1 only damaging 24% to walls, but 4 spells of level 1 could destroy walls, which is 4 spells of level 1 have 96% total damage into walls.
If we calculate, total damage of 3 earthquake spells would be 96% too. So if 96% total damage of 4 earthquake spells could destroy walls, why 96% total damage of 3 earthquake spells couldn't destroy walls?

