Monday, November 13, 2017
Iran Earthquake - Standard Blind Thrust
In this neck of the woods, mountains are there for a reason. It is a sign of compression. It gets a lot worse up in the 'stan' countries. So you have mountains and you have valleys. The mountains are the footwalls of thrust faults, and the valleys are the chewed-up hanging walls. It's the same geometry around Toronto.
This shows the pure thrust. In the hanging wall (the valley) you would get very high ground motion as measured by peak ground velocity (PGV). But I'm sure there aren't any instruments here.
You can see there is light reinforcement in the concrete columns and floor slabs. This may have saved a lot of lives. In the Armenia earthquake, no steel meant that everything went to powdered rubble. However, the only way to really tell how well the buildings did is to get a reading of the PGV. Without instruments, we learn nothing here.