"Are tunnels safe in an equake?” 

> Musk wrote on Twitter. He attached a brief primer on seismology and tunnel design from the Boring Company website.

> According to that blurb, tunnels are “some of the safest places to be during an earthquake.”

> Jean-Philippe Avouac, geology professor at Caltech, more or less agree.

> “Structures which are underground are less vulnerable to shaking than structures at the surface,” he says. “That’s just the effect of inertia.”

https://la.curbed.com/2019/1/16/18178979/subway-tunnels-earthquake-fault-lines