Yet, it's likely that a colony on Mars would be built underground to avoid surface radiation: http://www.newscientist.com/article/dn22520-mars-is-safe-from-radiation--but-the-trip-there-isnt.html
Dartnell suggests that a base or colony on Mars could be built underground to avoid surface radiation. Or, with enough advance warning, astronauts could retreat to protective shelters during a flare.
"Could be". Or... use "protective shelters" instead.
Nobody is arguing that underground bases can't protect against radiation. I just don't see them as being pratical
on a large scale. If anyone is digging on Mars, you'll dig your own with a shovel. It'll be a rabbit-size
bunker hole where you can hide from solar flares.
And it'll just be a hole in the ground. You'll still be in your spacesuit. So if a blackout knocks
out all of the power, you'll be safe from radiation, but with little oxygen left. But no problem,
you've already dug your own grave. Nothing else left to do except die.