Molten sodium thorium reactors
He3 fusion using lunar regolith
Geothermal, like the Kiwis use (and they are a small island located on a major fault line too just like the Japanese)
I've seen an analysis that 1000 square km of solar in Arizona could supply the energy needs of all of America. Given that climate change over the next 100 years will likely render the current population of Arizona unsustainably large due to permanent drought, this may be a wise use of the land.
Deep ocean thermal exchangers need to be explored in more detail. I've seen some very promising papers on the technology.