Could cause the ground to shake by walking

Harold Flower’s thoughts were promptly shut up, however, by the distinct rumbling of the ground beneath his peg-like feet. The earth shook and trembled in steadily increasing beats, the intensity of each impactful shaking growing stronger and stronger. Mr. Krabs glanced around in confusion as the vibrations developed ever stronger. These weren’t simply the cause of the earth suffering some quakes, nor were they caused by Mr. Krabs himself (he wasn’t using that much power today). No, these juddering occurrences were being caused by something big and heavy moving its way near his location.