Well, I've never seen any rainbow like what's in the video!
Even malformed, discontinuous rainbows don't look anything like what's in that video.Here's an article relating to "earthquake lights"
... such things have been observed before on numerous occasions.
Earthquake lights have been described as looking like auroral streamers diverging from a point on the horizon. Beams like those from a searchlight have been reported. Other reports describe sheets or circular glowing regions, either touching the ground or in detached clouds above ground.
The luminescence in the sky was 450km from the quake's epicenter however... which stretches that possible relationship.
The problem with topics like this (and others) is that earthquakes are unpredictable. Its thus very difficult to do real science on such posited pre-quake phenomena. The best thing to do is dismiss it because we don't know what it is; in our know-it-all arrogance, we are less than comfortable in not having a definitive answer to stuff.
I don't think its Venus. Or even marsh gas. I doubt it's a secret weapon being tested by al Qaeda.
And, btw, before Shawn et al chimes in, it's not a UFO either ..