For China Basin 7/13/09 audience:

7/16/09:  Well this is the closest thing to a blog I've ever done...

Regarding what is under the China Basin buildings, I've heard from Mark Zuffo, the Director of Leasing & Property Management for the complex, that "because the building is a leased facility, it had to receive a UC seismic rating of at least 'Fair' before being occupied. BTW, The garage was constructed in 2002."  The building sat on dirt before then; they hollowed out the area below the building to put in the garage and rebuilt the entire foundation while they were at it.

7/20/09:  I've heard from Mike Freeman at McCarthy Cook & Company.  He has a lot of very useful information that should put China Basin employees at ease, which I have reprinted here:

"With regard to China Basin, the structural systems and foundations in
both the Wharfside Building and the newer Berry St Building are in great
shape. The older Wharfside building was originally designed and built as
a warehouse with loading capacity far exceeding the current loads from
the office tenant users. Mark Zuffo is correct and the building
underwent a major renewal and upgrade to the foundation systems when the parking garage was constructed in 2000. The building has been reviewed by independent structural engineers and meets the muster for an institutional quality building and investment.

The Berry St Building is an amazing story and can be considered in the
top percentile of seismically safe buildings in San Francisco. A two
level addition was recently constructed on top of the original three
level structure. The Addition structure is mounted on base isolators.
This sophisticated base isolation technology greatly reduces earthquake
forces within the building, and is typically used in high value
structures such as data centers or mission critical centers. The Berry
Building Addition structure has received recognition and received six
awards from structural engineers and related industry associations.

Both buildings have been built on piles that reach through the bay mud layer to solid base soil. The wharfside building was built in 1922 and the Berry Bldg was built in 1991 with the two-level Addition completed in 2008."