Years after the Loma Prieta earthquake of 1989, many of the columns that hold up roads and bridges in the Bay have not been retrofitted for earthquake safety.
The state of California owns most of the columns and bridges in the Bay Area and has retrofitted virtually of them. But some bridges are locally owned by counties and cities and many of those have not been retrofitted yet. And along the BART line, many columns have been retrofitted, but some won't of it won't be done till 2019.