I am just a layman when it comes to this kind of thing, but I notice that many articles online claim that variable bedrock depth explains why Manhattan's skyscrapers come in two distinct clumps. If this is true, then it seems strange to me that NYC professionals would ignore bedrock depth in SF out of pure ignorance.
I just found a blog where the author explains that its actually a myth and mostly coincidental. The reason the skyscrapers are in midtown and downtown was due to historical and economic reasons. Those were the dense wealthy business areas where people wanted and needed to build taller buildings and it turned out they also had the shallowest bedrock.
They also said the shallow bedrock didn't force them to stay there. It isn't much of a problem to drill deeper and a number of early skyscrapers were built elsewhere... It's just that people wanted their skyscrapers to be in midtown and downtown.
