Today at around ~13:36:00 ET Nasdaq stopped reporting to the SIP. After they came back online, we noticed this interesting "fishbone" pattern in our one second chart.
Upon closer inspection, you can see the "spikes" in trades actually occured as trades through EDGX.
Click Start/Stop to run a slide show, or Prev/Next to step through one at a time.
It turns out these trades were delayed from the inital trading that occured after the outage, they were just 10-15 min behind.
Only showing trades from EDGX
Here are the trades from all the exchanges zoomed in.
And again, only trades from EDGX