Blind thrust earthquake

Blind thrust faults generally exist near tectonic plate margins, in the broad disturbance zone.

As shown in the diagram, a weak plate under compression generally forms thrusting sheets, or overlapping sliding sections.

After a long period of erosion the visible landscape may be flattened, with material eroded from the hills filling up the valleys and hiding the underlying hill-and-valley geology.

The valley rock is very weak and usually highly weathered, presenting deep, fertile soil; naturally, this is the area that becomes populated.

If the region is under active compression these faults are constantly rupturing, but any given valley might only experience a large earthquake every few hundred years.