basically splash drops off really sharply initially... sampling his graph...
at impact, damage is the same
.1 distance away, damage is a little under 1/2
.25 max distance, damage is around 1/3 of the damage you'd take in q3
halway away from the explosion, q2 damage is a little less 1/3 of q3s damage...
.9, it's still about 1/4 the damage.
that's just rough figuring, the noticable result will be a bunch less splash damage