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.
well a earthquake mile is split up into 60 min wch is split up into 60 sec so it will take about 30 to 60 min for it to cover 1 degree longitude. hope this helps a little bit.
