I live in the SF East Bay and this is earthquake country.
I’m also located by a railway with a bridge that runs through the middle of the town. When a freight train rolls through it feels like a 2-3 magnitude quake. Which is nothing by CA standards, but you feel the shaking.
My house is on a slab. The cracks were not huge but they were there for sure. The polyurethane is flexible so it shouldn’t crack. It says in the warranty that it is NOT WARRANTED AGAINST EARTHQUAKES…
I have lived through hundreds + quakes in my life. We just sit through them and guess the magnitude. You get pretty good at guessing over time…
To be honest I never really noticed the cracks but the patching accentuated them.
On a side note my car is the dirtiest it’s ever been. Sitting outside for the first time ever for a week. I’m going to have to get it washed before I put it back in the garage Monday night!
Deplorable California 2A supporter.
with envy. 
Cracks around here can get big, up to a half inch across and run for many feet. It’s just a non stop issue for her but for me it’s just normal.