As I pointed out before, there is some disagreement on this issue.  Will Wilkinson at The Economist helps us out by reviewing some of the evidence himself. And here we go:

By far the boldest claim… is that some disasters can boost GDP by forcing upgrades in technology and infrastructure, and offering the opportunity for critical reappraisal of ingrained modes of economic activity, leading to a higher level of productivity and, eventually, to net gains in growth. They find that this holds for some weather-related disasters, but not for geological disasters. They find persistent, long-run negative effects for geological catastrophe, suggesting any upside from Japan’s earthquake and tsunami is unlikely. The argument of this paper, which is as strong as the disaster-bonus case gets, is a touchstone for a good deal of later research.

Wilkinson also directs us to a review from Binyamin Applebaum in the New York Times.

And there is a rather extensive piece from Ilan Noy over at Econbrowser with this surprising conclusion:

Given the findings described above, one can conclude that the likely indirect impacts of this horrific earthquake/tsunami event on growth in the Japanese economy will be quite minimal. The Japanese government and the Japanese people have access to large amounts of human and financial resources that can be directed toward a rapid and robust reconstruction and rebuilding of the affected region. Neither do we have any evidence to suggest that the earthquake is likely to have any enduring monetary effects.

After reviewing some potential regional impacts, he gets to the elephant in the room:

We still do not know what will be the impact of the enfolding crisis in the various nuclear reactors that have been affected. The analysis above ignored this danger, though the still present devastation in Chernobyl attests to its potentially destructive powers.