This is my first post on any forum anywhere so forgive any faux pas I may make.

I am planning an ocean-front cabin for the Pacific northwest coast and need suggestions for a problem I have with the design of a pier foundation. The particulars that affect the design are as follows:

The area has a significant seismic history. This is the root of all my difficulties.

The site where the cabin will go has about 7 or 8 feet of VERY low density soil overburden on good bedrock. The soil above the bedrock is so insubstantial that a stick of rebar can be driven down through the soil 8 feet with just your hands – no tools – just push it on down till it hits rock.

The property is very remote and boat-access-only so all materials must be barged in and then carried to the building site by hand. Clearly, this limits the amount of material that can reasonably be thrown at the foundation, as well it means that all excavation occurs by hand.

It rains 10 feet per year at the site (almost all in winter) so any material that can’t stand constant moisture is a non-starter.

So, the choice of a pier foundation is good at limiting the amount of hand digging required as well as the amount of concrete. Concrete was chosen since it is more moisture resistant than any treated wood. The problem is that with any seismic event the pier can just overturn and down comes the cabin (2-storey). It would be very difficult to crossbrace below grade because of the amount of required excavation and the fact that any cross bracing below grade would either rot or corrode, depending on material. The backfilled soil will be useless for keeping the piers upright because it is so insubstantial. The cabin is post-and beam with posts going from the top of the concrete piers all the way to the top of the second storey. Because of site slope the floor plate is well above grade on the downhill side. These posts are cross braced easily as they are above grade. Any suggestions that would solve this problem would be greatly appreciated.