system
A chat on subreddit /r/wallstreetbets
human
The main problem a lot of people had was that PG&amp;E had no way to quickly shut off the gas. It took them over 2 hours to dig into the street and clamp it off manually. 
  
 In an earthquake prone area there really needs to be a fast way to shut off the gas.

gpt
In the event of an earthquake they just shut off the entire transmission line. That cuts off the gas to everybody. In this event it didn't make sense to do that and the remaining gas in the entire system would have fuelled the fire longer than digging a hole and blanking off the pipe. I've read a bunch of articles on it and that was stated in one of them I'll try and go back through to find the exact one.