[ravinson]

early 1990s office building, built on slab foundation on deep piers driven into former salt evaporater / dried out bay mud.

Keep in mind that those piers are supposed to be driven deep enough to go through the mud and into the solid rock below.

[Arthalion]

Keep in mind that those piers are supposed to be driven deep enough to go through the mud and into the solid rock below.

There is no solid rock in the Bay Area, just shattered rock that's not moving at the moment. On top of that, many areas in the south bay near the waters edge have hundreds of feet of topsoil above their rock layers, so anchoring is only done on the newer larger buildings.

Just one of the many reasons I no longer work in the Silicon Valley.