The property owner is responsible to maintain the sidewalk. California's Streets and Highways Code states, "The owners of lots or portions of lots fronting on any portion of a public street shall maintain any sidewalk in such condition that the sidewalk will not endanger persons or property and maintain it in a condition that will not interfere with the public convenience."
If the sidewalk fronting private property becomes a hazard, the City will either require the sidewalk to be repaired by the owner, or it will be repaired at the owner's expense.