Welcome JR.
Seismologist eh? Nice to have another sphere of knowledge added to our eccletic know-how. The Med. is of course seismically active; we get 300 tremors a day here in Cyprus (most of them detectable only by seismometers/-graphs). Colorado, too, in its own way. I hope in neither place are you called on for garden advice in the event of an earthquake, but you never know.
Your beach-side garden seems to pose interesting challenges (I would guess more than just the sand ingress). Perhaps, in considering doors and suchlike as barriers/impedances to the sand-laden winds, you should ponder something partly perforated. Solid structures can need more anchoring and in some ways be less effective. They can also cause scouring by the wind - the opposite of the original problem. In the north of Scotland, my sister has used 'paraweb' as a windbreak to good effect; it is intended for that purpose. Beware: there are various products using that name;
this is the one I refer to. It is sold as 'the world’s toughest lightweight fencing', and supposedly gives '58% shade and wind reduction'.
If you do use doors/similar, perhaps you could consider arranging them in ranks and angling them so the wind shoots up the side and where it comes back to ground level it encounters the next door, similarly arranged; and so on. That way, you may be able to create protected avenues at right angles to the prevailing wind. You would be creating a structure similar to a field of sand dunes, with plants in the swales. You might achieve the same thing by creating rows of boulders/'soil', which would look a lot nicer. But if your wind direction is variable, that's more of a problem.
Some plants cope with blown sand and inundation - marram grass being the obvious one. But there are many others, such as Pancratium maritimum (sea daffodil) and Eryngium maritimum (sea holly). In planting some of these, consideration should be given to the microclimatic/ecological zones in which they occur naturally. But in a broad sense, perhaps you could consider creating a shelter-belt, with the most salt-tolerant and inundation-tolerant plants on the seaward side, grading to more garden-worthy plants on the garden side. Get that right, and in time you might be able to do away with the doors.
Keep us posted on how things go!
