While wearing these steel-toed boots, the earth itself shakes when you walk, causing harmless, but unsettling, tremors. If you move at least 15 feet in a single turn, all creatures within 10 feet of you at any point during your movement must make a DC 16 Strength saving throw or take 1d6 force damage and fall prone. In addition, while wearing these boots, you can cast earthquake, requiring no concentration, by speaking a command word and jumping on a point on the ground. The spell is centered on that point. Once you cast earthquake in this way, you can't do so again until the next dawn.