Recently talking to an engineer, a natural gas line welder, and some guys on a gas leak response crew from our utility company.. regarding my earthquake preparations. I'd gone to great pains to get a non-sparking gas meter valve shut-off wrench, and was proud of myself. These guys, unanimously, suggested that I add to my kit the following:
Two or three 3/4" 3' wooden dowels, sharpened on one end. Two or three old T-shirts.
When encountering a gas leak in a ruptured pipe NOT readily controlled by a valve they suggested using the T-shirt wrapped dowel crammed into the rupture, to stop the leak temporarily.
I though they were jacking with me, but they all agreed that in fact "that's actually what we use" .. perhaps with some duct tape overwrap.. until they can safely excavate back to the nearest working valve.
Never would have thought of this.