That is definitely an option however I really don't see that it being possible.

First off Russia has detailed surveys and documentation on the exact location of these pipelines and areas that they are extremely susceptible to this kind of sabotage.

Next up is the amount of explosives needed to create a 2.3 and 2.1 Richter scale seismic reading.

It takes 320 lb of explosives to cause a 1.5 Richter scale.

320 =1.5

3200=1.6
32,000= 1.7
320,000=1.8
3,200,000=1.9
32,000,000=2.0
320,000,000=2.1
3,200,000,000=2.2

Basically looking at the energy released the world needs to consider that russia has just used nuclear devices underwater.