Well, an earthquake isn't karma, it's the movement of tectonic plates against each other to cause violent perturbation of the earth's crust and consequential damage to structures it supports.
As for the suffering: all beings suffer - I remember the Buddha's 'double pain' parable about the man struck by an arrow, the arrow causes a painful sensation but the added suffering, much worse, is the result of wanting the pain to stop. And I recall what the Buddha wanted me to know about the cause of just such suffering-in-ignorance: it's my poisoned mind.
My mind has been slowly poisoned by what has happened to me since I was conceived; some of what has happened to me is of my own brutish making, more or less choicefully and/or awarely. Some of what has happened to gradually poison my mind has been the brutishness of others towards me, more or less choicefully and/or awarely, as their own minds have been poisoned in their turn; some of what has happened to me is just stuff that happens to anyone: an earthquake, a tornado, a lightning strike, German measles while she was in her mother's womb, Thalidomide, nuclear fall-out, drought.
Most of those I've missed so far, not living across a tectonic faultline or in a tornado belt. I did once or twice live in a fever belt in tropical Africa, but I was blessed with a good education, medical training, indoor sanitation and money to buy anti-malarials and mosquito screens.
To the extent that what I described as happening to us to poison the mind, so that we suffer needlessly and in ignorance, greed and hatred, I'd agree with people who say what causes suffering amongst the people of Haiti is karma. "Just their karma" is a bit too glib for me.
From what I've seen on TV of the way the people of Haiti have responded to ferocious natural events, I'd characterise them as models of restraint, composure, dignity and resilience, which is their karma too, by the way. And I think they could show some of us Buddhists a thing or two about lived-out compassion and wisdom.
That's what I would say, if I were to say anything about the people of Haiti and karma.