Molten Salt Thorium Reactors are earthquake safe. Thorium reactors have a very simple and compact design where gravity is the only thing needed to stop the nuclear reaction. Conventional nuclear reactors depend on external power to shut down after a SCRAM, where poison rods fall down to halt the reaction. The next figure shows the concept of a Thorium reactor.
The idea is to empty the fissile U-233 core through gravity alone. All that is needed is a melt-plug that is constantly cooled by cold air. In an earthquake or complete electric failure the cold air flow automatically shuts off, and since the fuel is already molten, it will melt the plug, and the molten fluid will run down into channels like pig-iron into heat exchangers that absorb the residual heat.
As we can see the reactor hardened structure is compact, and can be completely earthquake and tsunami proof. What can be sheared off are the steam pipes and external power, but even then the reactor shutdown will be complete safe without any additional power.
Len Bilén's blog, a blog about faith, politics and the environment. 