At our house, the March 11th earthquake was about a 6 on the Japanese scale. We were very lucky that we didn't have any damage and no one was hurt. There are a few things sitting around that could have fallen, but they didn't. We have a few things around the house that prevent earthquake damage.
We also put these braces on tall pieces of furniture. That's Little Brother's desk that has built-in book shelves. A sliding glass door kept the books from falling out of the shelves.