I read the comments, but could someone more expert in seismic activity break this down for me? How does this demonstrate Wolfram Alpha knew about the nuke itse

I read the comments, but could someone more expert in seismic activity break this down for me? How does this demonstrate Wolfram Alpha knew about the nuke itself (or could ascertain there might have been a nuke)? It looks like it just indexed seismic activity. Is it because the measurements are peculiar?