nordstream video and guessing

My first naive thought was outside explosion, but I gather that internal issues can cause RUD too. Unfortunately the first publicly released video is short and doesn't show much. The top of the pipe shown is dented down, but that's not proof of an outside explosion. If you've broken a pipe you'll have seen that the last bit to fail is at the top, and the twisting around that last bit is apt to push the last contact point down into the pipe. My intuition could be wrong applied to such large pipes embedded in a trench, but it looks sort of like what's left after the previous chunk of pipe was wrenched up and away.

50 meters seems like a lot of pipe to rip away. There was a lot of gas pressure inside that thing, of course, and the sections looked about 12 meters long in the construction video (and in an estimate from the length and numbers, assuming by line they mean one of the pair). I'd guess that the pressure would blow a damaged section out of the way. One from each end, and one or more destroyed by the explosion, and we could account for the absent span.

So what would we expect to find? The continual blowing would have stirred up no end of mud (probably why we haven't seen images before now(*)), and rolled away some of the smaller debris. Unless you can find and sort-of reconstruct the pipe fragments from the point of the explosion it'd be hard to tell if it blew from the outside or the inside. They should be nearby somewhere.

The surrounding area might be partly protected from the blowing by the pipe being in a trench, which would help deflect force upward. If the water flow is largely upward, that might pull mud and debris in towards the pipe.

Let's see how well my intuition works. If the explosion were a high speed slug of hydrite ice bursting from the inside of the pipe, I'd expect the bulk of the pipe fragments to be distributed in a "cone" along the pipeline in the direction of the slug's motion, with some chunks ripped out by the initial pressure near each of the open pipe ends. Near the open pipe ends there shouldn't be much mud. (Video suggests there isn't a huge amount, but it's hard to see.) As some pointed out, there might be a secondary explosion as the hydrites evaporated on impact, which would make the debris field a little more symmetric.

If it were an external explosion (or some kind of weld failure), you'd still get chunks ripped out near each of the open pipe ends, but the main explosion point's debris would be more symmetrical, with more chunks still at the explosion site.

I wonder what they'll find.

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(*) I'd be astonished if there weren't submarines from several different navies on the spots within hours of the explosions, but whatever they were able to see is probably classified. The blowing would have stirred up too much mud for video, but I assume there are other ways to inspect, but how and with what kind of resolution would be secret. Sonar might pick out the big chunks, but the noise from the pipes would be a huge background. I'm sure private exploration was deprecated until the gas dispersed.

UPDATE: Swedes say sabotage--they detected explosive residues. So everybody's first thought was right. I really really really hope it wasn't our official doing. If it is, the disconnect between the actors and what the country as a whole wants and would benefit from is so huge that I'd worry about our stability. Best case is that it was a private party, and everybody starts looking to harden their infrastructure, and nobody starts a war.