Yeah, I can do a little bit of earthquake stuff, which is my main love, but we are in an earthquake drought, perhaps caused by climate change. :)
The ground velocities (pgv) are a factor of 10 stronger on the soft muck, than the stiff soil. As with Mexico City, I suspect a factor of 100 compared to the surrounding rock, but they didn't instrument that.
The pgv of about 20 cm/s is the point where the worst garbage buildings collapse and there is some structural damage to others. This is what happened. Tall buildings had no damage, and it is assumed that they are on the rock, but who knows?
Usually the pgv levels are as follows.
1 cm/s - everybody panics and runs out into the street.
10 cm/s - coffee spills, alcohol bottles act like being attacked by a crazy lady
20 cm/s - piles of bricks fall down. Really bad brickwork falls on people in the street
40 cm/s - cheap condos crack and tilt
80 cm/s - cheap condos fall over, significant damage to everything
Anything above that is Wonderland.