Why do earthquakes occur only above the brittle/plastic transition depth?

It occurs at the level in the crust where the downwards increasing brittle strength equals the upwards increasing ductile strength, giving a characteristic "saw-tooth" crustal strength profile. This zone is, therefore, the strongest part of the crust and the depth at which many earthquakes occur.

This country likely has a high total fertility rate (tfr).

Master planned communities outside of chicago. note: population density means people living in an area per square mile. chicago, an urban and highly populated area has a much more higher density than a desert, amish community, settlement, or nomadic region.