I would venture a guess that it is a broken auto fill line or a broken circulation line. The crack in the pool indicated the ground has shifted and it may have punctured or cracked a water line.
If you would go out to your water meter and look at it, there is what is called a leak detector on most of them. Looking at it in the correct orientation, it is situated at about 4oclock (on most of them when i worked for the water dept.). The detector is a small black triangle and every time you use water, it will spin extremely fast. Watch it closely for about a minute and note if it moves (moving in one direction then back in another may sometimes be normal if water hammers have been installed in the home, we are just looking for the advancement of the triangle). Even a dripping toilet can be seen by the movement of the triangle if you look close enough.
Of course if no one is using water (make sure all toilets have filled before checking) in the home and it is still spinning indicates a leak. Shutting off the water will just require you to turn the valve in the meter box 1/4 turn either way for repairs.
If the triangle is not spinning, I would look at the possibility of a broken circulation line. In either case, i would watch very closely my water level in the pool. The water from whatever source it is has made your water table extremely high and your pool may float or crack further.
To test this, as close as practical, dig a hole in the ground near the crack to about the pool water level. Dig somewhat carefully so you do not damage water lines if you hit them with a shovel. If the water level is high from a leak, in a short time the hole will have water in it.