No one can predict earthquakes or tsunamis. That's why building an underground city is not a very bright idea.
I just want to remind you that at least we can classify the regions based on seismic risk. However, I am definitely opposing any plans for an underground city. Extremely expensive, and pretty much unrealistic with current technology (considering the depth of international waters).
OK... now let's move forward and finalize the location for our artificial island.
My choice is Saya de Malha. Any objections?