Just a side point that I think is relevant to this discussion: It's almost impossible to accurately measure the massive amounts of GHGs from any single source, much less from ALL of them. This is not to say that they shouldn't be approximated and they could end up being pretty accurate percentage-wise, but the exact measurements are assuredly wrong just because the system we are trying to measure is so HUGE and dynamic. Science is never settled, but this is currently the best guess based on other observed principles.

It's also important to note that the energy epicenter is below ground. So the release of energy (the equivalent of the volcanic "explosion" you speak of) is actually below ground at the point of greatest elastic rebound (or friction overcome). That "explosion" has to then travel through thousands of feet of rock (depending on how deep the epicenter is, which is controlled by what kind of plate margin it is), so it is greatly dissipated.

Edit: has to travel through *miles of rock ("thousands of feet of rock" wasn't wrong, but doesn't put the reader in the right frame of magnitude)