Todd...the Santa Monica Mountains geology seems pretty continuous on the old Los Angeles sheet of the California Geologic map and so separate LA downtown from the Valley. I don't know much about these mountains east of Malibu, but if something is high-standing in this part of California, it is probably going up, and if it is going up, it is probably due to a thrust/reverse fault, or to folding above a blind thrust fault. In a paper I am working on, the western end of the Santa Monica Mountains is going up because of a restraining bend in an offshore left-lateral strike-slip fault (restraining bend means a bend that causes the blocks on either side of the fault to converge with each other).
Chris