Keep in mind: a fault, especially a huge regional fault like the San Andreas or San Jacinto, is not really just one line in most parts. The fault trace - the fault as it's mapped at ground surface - frequently gets a "braided" appearance from parallel smaller faults that meet and split, and cross, and meet again, but because they are so much smaller in length and have the same direction of movement as the "main" fault, they aren't usually recognized on their own. At ground surface above such an area, there may not be the nice split where one side slid one way, and the other side slid to the opposite direction - there could just be an acre, or a few, where the dirt looks so torn up you might mistake it for human-dug dirt piles. Places like that look just like ordinary fields after a few thousand years - that's why in many areas, a mapped fault line appears to just "stop". It's under there someplace but no one has had the money or time to dig and see. Water also tends to run along faulted areas, because the rock and dirt is soft and torn up; that also hides the fault evidence. We had a whole course on how fault areas make wonderful-looking places that humans tend to move into and live in - it was an interesting book.
Just because a map has a line - well, that may be the main direction of movement, but faults often reach thousands of feet deep, and are angled out of the vertical, and may very well have one or more split-off 'faultlets' as described above - unless a map is from an agency like USGS that has set standards for how they will depict a fault, it can be really chancy relying on a fault map made by lesser-known makers. A line can be a surface trace, or the average of recorded movement in trenches or by seismometers, or based on disturbed dirt; unless there is "metadata" - background info on how, when, and by whom the data was collected, and how it was processed and/or mapped and by whom - it can be tricky to judge if one map is as good as another. Personally I'd say that an iron framed house ought to be OK unless it's on an entire slope that slides; otherwise I think it could be lifted by jacks and replanted! Really all I mean to say is, take any map with a grain of salt - they all have their limits. And I work on maps for my living.
Disclaimer: majored in geology at UCR, but never became a professional geologist; I would never claim to be an expert but we did study this stuff. And as for dates of mapping - a really amazing amount of work is done inconspicuously by grad students each year, as well as by professionals; trenching, searching out faulted areas in visible surface rock, soil sampling, study of airphotos and radar surface maps, all go on all the time, unknown to most. Just because no one has spotted a geologist lately doesn't mean they haven't been there unnoticed.
The above are all cool maps though. But there sure is a lot of moveable ground in the Wrightwood valleys.
