In a previous post Phil Scott wrote...
In seismic zones the city will want civil or structural
engineering on the columns. If I were going to boot leg it
in Id put blocks down the center with 4 1/2" rebars then
pour the centers then brick around the outside. Id photo
graph the entire set up so if the city comes out later you
have a chance the inspector wont make you tear it out...Id
also leave the top caps removeble do the rebar install can be
seen.


I concur with Phil's assessment that engineering will be required if you
plan to get a permit (a wise choice). As for DIY, the (4) # 4 are
probably okay, but if you are in a medium or high seismic risk zone you
will need to add ties wrapping around the verticals. The size and spacing
if the ties is partially dependent on the column dimensions.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA