I've been wondering too... Got like 6 in a row today about 5 minutes apart each, same thing for 1000s miles away. I tried within messages app but no dice despite there being settings available.
I did just try blocking that number those all came from to see what happens there if anything.
The odd thing also is, when one comes through it changes my notification vibration intensity to far less in my settings. And for whatever reason, my keyboard vibration seems attached to that setting too. So to type after getting these alerts I was missing most of that haptic feedback that I enjoy - though most don't. Finally figured it out
I don't understand the many in a row with the same info. Thankfully I was awake at the time, this time.
I wouldn't mind at all if they pop up, with no sound and no vibration. But no such luck so far.
I'm not even sure as a rooted user what I could do to stop them. My last device didn't support them. This is new to me! I would keep this device in wcdma mode and avoid completely, but for whatever reason texts take SO long to send on anything except LTE...