I'm not going to call BS on LA blowing up, but it seems a bit extreme. IF all the gas in that region could move about freely then wouldn't they just need to drill one big ass well to extract it all? I can see some movement of some gas, but not at all like it is being described.

I could imagine significant doom over time. It could create a cascading effect where the initial blast destablizes surrounding geology. Then water washes out more salt domes, and another explosion occurs, and the process continues. I'd envision that to occur over time, not all at once in a single cataclysmic event.