I happened to be teaching about earthquakes in April 2006. I hadn't given it much thought, but I was watching the Today show on the morning of April 18, and there was a segment on the 100th anniversary of the San Francisco Earthquake and Fire.
Well, the timing couldn't have been better (well... I could have planned a bit further ahead and been a bit more prepared...) so when I got to school that morning I went searching for something to share with my students to mark the date.
I came across The Virtual Museum of the City of San Francisco. There, I found a whole collection of eyewitness accounts as well as lots of other information.
I printed out a few accounts and shared parts of them with my students that day. These do tend to be longer narratives, so you won't be able to read several whole accounts, unless your students are much more patient than mine.
Since this was a plan that was hatched about an hour before school started, I read the accounts and left it at that. You may want to take it further...
Assign each student a different eyewitness account to read as homework. Then, have them summarize their story for the rest of the class the next day.
Perhaps you could have your students write their own account of what it would have been like to survive the San Francisco Earthquake of 1906. Or maybe you'd like them to research another earthquake and write an account of that experience in the first person. If you live in a place that experiences earthquakes, you could have your students write of their own experiences. (Talk to the language arts teacher, maybe it'll work out that your students are working on writing first person narratives or memoirs and you could team up).
You could adapt this exercise to other natural disasters: hurricanes, tornadoes, volcanoes, etc.