Retrofitting masonry chimneys with bracing or strapping is not an effective safety measure because many braced or strapped masonry chimneys typically will still fall when exposed to violent shaking.
In the 1994 Northridge earthquake, approximately 60,000 masonry chimneys were destroyed or damaged beyond repair. Quite a few of these were braced.
Don’t use the area outside next to your chimney as a play area for your children and don’t use the area inside next to your chimney as a sleeping area! The one fatality in the 1992 Landers earthquake was a child sleeping next to a fireplace and the one near fatality in the 2000 Napa earthquake was a child that was having a birthday party sleep-over next to the fireplace.
You can put sheets of plywood above the ceiling framing to reduce the chance of bricks falling through a sheetrock ceiling. If you are more concerned, you can consider replacing your masonry chimney with a modern stud-framed one around a metal flue, not simply bracing or strapping it. Generally, the cost of replacing an existing brick chimney with a lightweight one is comparable to the cost of repairing or replacing a damaged chimney after an earthquake.
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