Nuclear explosion size required to create a Shattered Horzion scenario

[Cifyra]

I'm not sure if any of you have heard about the game, Shattered Horizon. It's story takes place in 2047 when the Moon Mining Corporation accidentally fractured a large chunk of the moon and sent fragments and debris in orbit around Earth. International Space Agency workers and MMC miners are now stranded in space, as they fight over scarce resources to survive. How big of an underground nuclear explosion is require to "break" the moon as illustrated in the following video?

 

[JesseC]

Suppose 5% of the moons mass is now moving away from the moon at its escape velocity (2.4km/s according to wikipedia). That 5% has a mass of, very roughly, 10^21 kg. So the kinetic energy of that mass is of order 10^27 Joules. That is, very roughly, 10^12 megatons. The error on this calculation is probably plus/minus several orders of magnitude.