There's no doubt that when it comes to natural disasters, liquid nitrogen storage of precious samples is your best option. Provided there is sufficient liquid nitrogen, or you can access the area to add more, you can keep your samples going until the power comes back on again.
The link here offers a quick look at DMSO, asking the basic question: is this the best cryoprotectant now available?
There are some excellent reviews of cryopreservation available - also consider looking at a good cell culture textbook for more information. For one recent review see:
And for those of you who operate a repository and simply must get it right, an excellent resource for biobanks has been published by ISBER:
Via Amanda Capes-Davis