One of the first things to determine, is the type of foundational material. Do you have deep or permafrost soils or solid rock. Solid rock is the best foundation for earthquake resistant construction. In softer earth, earthquake
energy moves all the soil particles. There are three types of movement in most earthquakes, depending upon depth, strength and foundation material. P, S and Surface waves. P waves are pressure waves and generally are the first to arrive. They move forward and backward. S waves are secondary waves. They tend to move from side to side. The last form is the least common and is the Surface Wave. This is the Hollywood favorite as the ground moves similarly to
water waves and can crack open and close.
If you have certain types of soil, they may be subject to a process known as liquefaction. This is a soil that is usually solid enough, but when subjected to a sudden jolt, turns to near liquid. In 1964 several hundred feet of a cliff along the coast of Alaska failed, nearly taking a hospital with it. It also
led to massive road disruptions. If you have any potential liquefaction soil or permafrost, I would tend to discourage an underground construction method, I would opt instead for a earth bermed structure with reinforcement. Wood has great tensile strength and lasts underground for decades if not allowed to connect with the atmosphere. Constructing a net of wooden poles, especially poles with wood mortise and tendon connections is extremely strong and resilient. Connecting layers of such wood nets and covering them with
cob or rammed earth would create a very high strength system. Earth bag construction can be earthquake resistant, as noted in one of the replies, but generally, my experience has been that is only if the entire structure is placed on stone fill. It seems the stone fill under the entire structure allows the structure to move as an integral unit, dissipating the earthquake energy. In Alaska, with the high water table, a stone base might become a source for too much humidity inside. The initial design for the earth bag round homes that have the above earthquake construction method were for arid/semi-arid areas without the issue of high ground water tables. I would avoid any long, straight walls with earth bag construction.
You identify that you live in southern Yukon. It is not clear what resources you might have available. If you have a source of waste tires available, bolting tires together and ramming earth into them would provide an earth bermed structure that would be highly resistant to many hazards. The walls would be strong enough to take the weight of earth bermed against them in terraces which would allow placement of a roof with a natural grass cover. I would be cautious if the area gets too dry and would allow the grass to become readily flammable however. It may also be prohibitive from a resource/time/cost perspective to strengthen a natural earth roof to resist earthquake forces. It is probably better to consider using a metal sandwich roof. A good insulation could be made of ground foam mixed with
concrete. It is light, highly insulating and non-flammable. Just as a comment, I would strongly suggest cutting any nearby
trees if wildfire is at all possible. Also ensure no shrubs are allowed to grow under nearby trees. Those are called "ladder fuels" in wildfire parlance. Trim any lower branches to 8 to 10 feet above dry grasses.
As in any earth bermed or underground structure, please ensure you are above the 1,000 year flood. Flood is a hazard no construction can resist.
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