I live in SoCal, so while hurricanes and tornados are not considered a normal consideration (albeit I was within a few miles of that tornado that ripped through some vacant areas and a freeway a few years back), wildfires and earthquakes are the primary disasters that can and have severely impacted whole regions. I’ll leave wildfires aside for now, but for an earthquake, the important things to remember is that the ground and anything attached to it or in the way of it is going to move back and forth (or up and down depending on the type of wave) violently, and it will happen without any appreciable warning (I did on one occasion hear one coming when all else was quiet or and a friend once saw street lights go out in a rolling wave, but neither gave any real reaction time). Unlike a hurricane or tornado, there is no warning (studies have actually found that even trying to take shelter beyond a simple duck and cover during an earthquake increases your odds of injury), and unlike a tornado, there is no sanctuary from an earthquake under ground. Anything that would collapse an earthquake coded house will covert a storm bunker into coffin even if you happen to be there already, or if you were able to get to it. That means, your earthquake shelter needs to be whatever shelter you happen to be in when the earthquake hits.
The ideal building to be in during an earthquake is pretty much any commercial building built to current earthquake codes. That covers most people that have office or warehouse type jobs – at least during work hours. But finding or building a house to commercial earthquake standards probably isn’t an option for most people.
That all said, the way houses have historically been damaged is by sliding off the foundation (hence the permanent foundation for the previously mentioned manufactured house) or secondary fire. When I was researching earthquake risks, I could not find a single instance of well built residence that was damaged by an earthquake from anything other than sliding off the foundation, or being burnt in a secondary fire. Simply put, unless the magnitude is such that your foundation rips down the middle and half your house disappears into a trench, your house is either going to slide off its foundation and shed in the process, burn in a secondary fire (possibly in addition to having slid off the foundation and shredding), or it is going to be structurally fine.
So that brings us to building or upgrading a house to function as an earthquake shelter. If I were to postulate an ideal "earthquake bunker", it would be a modern manufactured house on a permanent foundation or a site built house properly bolted to an earthquake coded foundation. There is a theoretical benefit in vibration and flex tolerance to the manufactured house, but I’ve yet to see any indication that there is a functional difference. Second to the foundation and structure of the house, there is the concern with gas appliances. Simply put, they need to be secured such that they won’t start walking during an earthquake. Added piece of mind can be had by installing an automatic gas shutoff valve that turns gas off at the meter if an earthquake is sensed.
Those two things cover the big losses seen in disasters like the
That brings us to that last thing that people often consider for earthquakes (in terms of their homes at least). Earthquake insurance. I’m not familiar with any earthquake insurance other than the insurance offered directly from the state of