Why does the end of the fracture have a branch? (Fracking)

[miraboreasu]

Hello, I have seen some pictures about hydraulic fracturing, which is injecting water into the ground under high pressure, and when people draw the schematic, it looks like this
I am wondering why the fracture will be branched. Thanks!

 

[Baluncore]

I am wondering why the fracture will be branched. Thanks!

It is probably just an artist's impression of what running cracks might look like, based erroneously on lightning in the atmosphere.
A branched tree pattern, similar to lightning, connects the greatest volume of material, through the minimum total volume of channel. River systems follow similar rules.

Horizontal sheet jointing, due to regional unloading, is common. Vertical joints are due to tension. Because the joints in rocks form a connected network, the fracking pressure widens the joints into connected cracks. The rock will yield to a limit at some pressure, then as the pressure continues to rise, some other joint will open and yield, and so the pattern will spread.

 

[Lnewqban]

Please, see:
https://en.wikipedia.org/wiki/Fracking