Hey, Super Monkey, this is a matter of straight astrophysics.
To actually blow-up the Earth means overcoming the Gravitational binding energy of the planet. (The electromagnetic binding energies at this scale cancel out themselves so much that gravity is actually the more dominant, powerful force at this level. Even so, EM binding energy to overcome is on the order of 65,066 sun-power seconds or 17.8 hours of its energy output.)
Gravitational binding energy in the Earth is given by the formula:
B = m**2*G/r
Where B is the binding energy in ergs
and m is the mass in grams
and G is the Gravitational Constant (6.672x10e-8Nm)
and r is the radius in centimeters.
Earth mass = 5.977 x 10e27 grams
Earth radius = 6.378 x 10e8 centimeters
Plug in the values and you get 3.73 x 10e39 ergs
which translates into 3.73 x 10e32 joules or watt/seconds.
The Sun emits 3.846 x 10e26 watts per second.
Divide the binding energy figure above by the Sun figure below and we get over 971,692 sun-power seconds -- or a bit shy of a million of them as I posted earlier. That's the energy the Sun emits over a period of 11.25 days, FYI -- And Superman can easily generate this in less than a second.
It's like I was going to say on an older thread, just haven't got around to it. The best writers actually know more about science and the real world than the mediocre ones. Certainly Stanley Schmidt, editor of Analog magazine, subscribes to this, as does Jack London (author of Call of the Wild), Michael Crichton, Isaac Asimov, Larry Pournelle, and Ray Bradbury.
Some misguided people think writing is just about making stuff up and to heck with any kind of realistic grounding esp. in comics and SF. The reality is the better writers actually are better educated than the ones trying to evade education by being writers.
Or to put it as the Dalai Lama puts it:
"Know what the rules are so you know how to break them properly."
Also, FYI, there's a reason it takes a supernova blast to blow-up a star. The energy levels are galaxy-level which is what the grav binding energy for a star is.