A small lake that forms in a depression, or sag, where active or recent movement along a fault has impounded a stream.

an area between two parallel fault zones that has dropped, or sagged, down creating a depression that can fill with water

A pond occupying depression along a geological fault; the depression is normally due to uneven settling of the ground or other causes.

a small body of water occupying an enclosed depression or sag formed where active or recent fault movement has impounded drainage. AGI

A sag pond is a body of water, which forms as water collects in the lowest parts of the depression that forms between two strands of an active strike-slip fault . The relative motion of the two fault strands results in a stretching of the land between them, causing the land between them to sink.