not arguing Calif being a bear on building codes, but I think in your estimation of stickbuilts withstanding a “10” you neglected to consider earth movement.
Yesterday’s 5.1 caused foundation slab cracks significant enough to red-tag some apartments. In 94, the 6.7 Northridge quake cracked foundations of stickbuilts in Woodland Hills and Thousand Oaks (and probably more areas-these are just two people I knew). The 6.9 Loma Prieta quake in the Bay Area damaged 12,000 homes. Even a modular home can twist and warp from earth movement, and they’re built better than stickbuilts. That stickbuilt house may stand, but it’s not going to be much use when the bedroom is 2 feet higher than the front door, which is now 6 inches wider at the base post-earthquake.
Earthquakes aren’t just about shaking a structure, they’re about how far and which way the earth moves underneath a structure and how well that structure’s foundation bounces, and that’s something they can’t show you on Mythbusters :)
I didn't say the house would necessarily end up in good condition, but it will not fall in on itself. Most new home construction is wood frame stucco. The frame is wrapped in chicken wire and then covered in stucco and it may twist and crack a lot, but bringing it down is almost impossible.
The roof tiles will likely come flying off, which means you shouldn't run outside while the house is shaking but as long as you aren't standing under a chandelier or a loose bookcase, you are probably going to walk out of the house after it is over. You can't say the same thing about a tornado.