"There is a certain type of cosmic explosion that becomes, in a flash, the brightest thing in the universe, emitting for a few seconds as much radiation as a million galaxies. Don't bother looking for one in the sky, though, since most of the light is in the gamma-ray part of the spectrum, a realm we can't see." As taken from, http://www.msnbc.msn.com/id/18398244/

Question is, do these occur near Earth and if they did what would the affects be?

Upon reflection, IMHO, the effect of a near Earth gamma ray burst such as is described could be to literally sterilize the surface of the Earth and the oceans to a considerable depth. Might account for some mass extinctions. Any animals exposed to the Gamma ray flux would be in serious hurts. We use gamma rays to sterilize foods and labware.

Excellent point Rose II, I have heard of a theory which attributes mass extinctions to Gamma Ray bursts, as oppossed to celestial body impacts. Question is, what can we do to protect against such events?

Sincerely,

Live in mine shafts? I don't know. But it's theoretically possible that one day the people working in mines (shaft type, not open pit) might somehow be the only survivors of such an event. I sense a good science fiction story lies in that scenario. Maybe I'd best go write it down.