Using the 6.3 Richter scale, the energy released would be ~43 kilotons of TNT. I think that's a pretty good guess- they seem kind of skeptical of the 6.3, but there may be some additional energy that wasn't transferred into the quake, like heat loss/air pressure.

I plotted a 43.2 kiloton airburst bomb over LA using NUKEMAP[1], which is under heavy load right now (surprise surprise). tl;dr: 166k fatalities, 341k injuries, 270 m fireball and 100% fatalities within 1km. Almost all structures destroyed within 2.5 km, and 3rd degree burns within 3.2 km. Still far from a "real" nuke, but significantly more impressive than their last tests. It's about 1/10th the size of the biggest fission bomb the US made, the Mark 18. Our current missiles are ~475 kilotons per warhead, with 12 warheads per missile (several hundred times more destructive).

[1]: https://nuclearsecrecy.com/nukemap/?&kt=43.2&lat=34.0453902&...