Sahara is a desert and deserts are hard to cross. Sahara is especially bad and potentially deadly: it's very dry and there is no water to be found for miles.
Therefore it was a barrier and it has isolated South Africa from European influence for a long time. (until the time of European explorations)
Earthquakes became by movement in tectonic plate majorly at ring of fire that is the primary driver of earthquakes in Japan, where many earthquakes occur.
The fact that Japan is an island nation with a large coastline is also vulnerable to tsunamis and most of the Japanese population lives close to the coast due to the mountainous interior of the country.
A very notable damage was done in Sendai that is the big city that was the epicenter of the earthquake. An earthquake in Sendai destroyed homes and other buildings.
The tide has flooded inland, damaged cars, ships and additional homes and businesses.
