This kind of shockwave happens all the time on the 101 between Camarillo and Ventura. In at least two places.

This short timelapse video shows a real life traffic shockwave, happening for no precise reason https://t.co/sDIzoEIGSF [more about this process: https://t.co/wASkaT3FeS ] pic.twitter.com/Hb0VQJPR51

— Massimo (@Rainmaker1973) March 16, 2019</blockquote>

Going to have to study the info at this link.