How to seismically retrofit a doublewide
Quake Safe Products
[...] QuakeSafe® foundation systems are specially designed to protect manufactured homes in the event of an earthquake. Standard manufactured home foundations are simply stacked cinder blocks that offer no stability in an earthquake. QuakeSafe bracing is engineered to fully support your home even if the cinder blocks fail. QuakeSafe foundations are engineered and certified to meet state earthquake resistance codes. [...]The site has a slide show of an installation.
Manufactured Housing Disaster-Resistant Pier Systems
[...] A good foundation gives homeowners peace of mind. For manufactured homes, one option is a disaster-resistant pier system -- stout members rigidly connecting the home's chassis to a slab, grade beam, or array of pads. Some systems incorporate lateral or diagonal bracing for greater resistance. Although often referred to as "earthquake resistant bracing" (ERB) systems, many also resist high winds, frost heaves, and floods. Not only are these systems cost-effective in reducing structural movement (compared to conventional manufactured housing foundations), they can save lives and property. [...]Most of the articles I've been able to find talk about doing the install while the double wide is being installed. I've yet to see one about retro-fitting, doing the install after the home is build without the bracing.