File under one more thing to worry about: Parts of the Embarcadero and the man-made seawall that rings the Bayfront could present a "greater than expected risk" of failure in a major earthquake. This is according to a memo obtained by the Chronicle, in which the Port of San Francisco reveals the results of a new analysis of the seawall from Fisherman's Wharf down to Mission Creek.

The analysis, commissioned two years ago, reassuringly says that "complete failure of the seawall is unlikely" in an earthquake, but that beneath it is "a weak, saturated ... marine clay that tends to amplify earthquake shaking."

You may or may not know that North Beach is so named because the beach and coastline actually used to be a lot further inland, and much of the eastern edge of the city sits on man-made fill.

Does this mean we could lose the Ferry Building into the Bay in a significant temblor? How about Pier 5, or the Exploratorium, or could whole parts of the Embarcadero just sink?

These seem to be open questions, and a $10 million initial budget for preliminary studies is being recommended, with a "conceptual budget" of $500 million to create actual plans. The initial estimate to address the entire, enormous potential problem is $2 billion to $3 billion.

How big of an earthquake are we talking? As one Port of San Francisco project manager tells the Examiner, "We can definitely say a large earthquake, [magnitude] 7 or above, on the San Andreas fault will likely cause movement of the seawall... The Embarcadero roadway may or may not be usable after that event."

Given how long these studies take, could any work even be likely to occur before the next big one hits? Says Port Commission interim Executive Director Elaine Forbes, "With a concerted effort ... it is possible to make significant improvements in the next eight to 10 years."

Related: Cool So, This Downtown Santa Rosa Earthquake Fault Is Larger Than We Thought