I was told by a contractor that it's extremely common for houses to have shifted considerably, sometimes by several feet. Mine certainly has, though not nearly that bad.
Most of the houses are built on concrete foundation walls that go about 3 feet into the sand. Despite being unreinforced and using water-permeable cement, they've seemed to hold up reasonably well. It's usually the whole house that shifts and racks. Yet looking from the street you wouldn't expect that because all the houses abut each other, with only a few inches or none of space in-between. (Perhaps this has mitigated the problem somewhat, though.)
Despite being built entirely on giant sand dunes, the Richmond district is only "moderately" prone to liquefaction. And there wasn't much notable damage during the 1989 earthquake, AFAIK. I think (though cannot confirm) that similar foundation techniques were used as far back as 1905 and earlier, in the Richmond, Sunset, and elsewhere, and judging by their survival and continued use of the foundation techniques I'm not particularly worried. (While widespread building in the western half of the city didn't begin in earnest until about 1910'ish, there are hundreds of buildings many decades older randomly distributed, especially closer to the beaches.)
The bigger problem is that almost all houses in the western half of the city were built with so-called soft stories as the first floor--basically a giant open space supported almost entirely by the external walls. Interestingly, AFAIK this design came before the widespread introduction of cars. These days nearly all houses use that space as a garage, but I believe they were built as unfinished first floors intended to be finished as desired--e.g. workshop, additional family rooms, in-law apartments, etc--while keeping the initial purchase price low.