Difficult to tell actually who is copying whom since apparently Deep Core is dated 2000 and The Core is dated 2003.
At any rate, the similarities (but not the budgets) are compelling: 1)Laser-operated drilling gizmo for going through the Earth 2) Lots of magma around 3) People get snuffed by magma 4) Earth put in peril by misuse of something related to drilling/earthquakes 5) Nukes needed to restore balance 6) Five nukes required 7) Detachable unit(s), at least one required for success.
Draw your own conclusions.
I must admit that Wil Wheaton did a credible job.
I didn't mind him getting snuffed though.
Oz