Why would an earthquake be more devastating in a country that rarely gets serious earthquakes?

Answer 1

First world countries or regions that are earthquake prone tend to have very strict building regulations so that earthquake resistant designs and construction techniques are employed in the design and construction of buildings and other infrastructure. These regulations are also strictly enforced. Countries where earthquake are rare are unlikely to require the results of seismic activity to be considered in the design and construction process (except in the most sensitive of buildings e.g. nuclear reactors) as this is more expensive and is considered to not be a significant enough risk to warrant the additional expense.

As such in the unlikely event that a large earthquake did occur in the country where they were rare, it would do significantly more damage as the structures were not designed to withstand earthquakes.

Also earthquake prone regions will have an emergency response prepared in the event of a major earthquake that will be well practised. The emergency response in a country with low earthquake risk will be less well prepared as they will concentrate their training on dealing with other more likely scenarios.