How does a complex crater form after the initial excavation stage?

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four impact craters — Meteorite crater Four impact craters of the same size (30 km [20 miles] in diameter) imaged by spacecraft on different solid bodies of the solar system and reproduced at the same scale. They are (clockwise from upper left) Golubkhina crater on Venus, Kepler crater on the Moon, an unnamed crater on Jupiter's moon Ganymede, and an unnamed crater on Mars. The images are oriented such that the craters appear illuminated from the left; the Venusian crater is imaged in radar wavelengths, the others in visible light.

After the initial excavation stage, large meteorite craters undergo a process known as the modification stage because the resulting parabolic cavity is too large to remain stable. While this stage is conceptually considered to occur after excavation, it may begin before the excavation process is fully complete.1

During this phase, material moves back toward the point of impact, creating several distinct geological features:1

Central Peaks and Rings: In smaller complex craters, the floor flattens due to the rebound of material from beneath the crater. In larger craters, this same rebound creates a central peak, while even larger structures may develop a raised circular ring.1
Terracing: Downward faulting occurs along the inner rim of the initial cavity, resulting in terraces composed of large blocks of material.1
Impact Basins: In the case of extremely large craters, the process can form discrete, widely spaced, inward-facing faults known as megaterraces, which extend well outside the original excavation cavity.1

These features are often compared to the backsplash and ripples observed when an object is dropped into water.1