There are many times I have looked at seismos near the NMSZ and in STL and they look like this but there is no explanation for it. My guess is that it's from EQs elsewhere - far enough away you wouldn't think of it as the source. We've seen how super large quakes will show up on seismos in opposite parts of the world, so it makes sense something in the 2-3 range in OK, KS or TX would show up on a seismo a few hundred miles away. It's been an active week around the globe but only 4 very small quakes in the MO boot heel some days ago(see link below) so I definitely am not convinced what is seen here has anything to do with the NMSZ, nor is it likely anything to worry about.

[link to earthquake.usgs.gov (secure)]