How to Engineer Buildings That Withstand Earthquakes
Roughly, There are a few things that are generally applicable for earthquake performance.<p>1) The period fundamental period of a building is roughly .1 sec&#x2F;floor. (+-, OOM)  Earthquakes tend to have an energy peak in the 1 second range.  Houses and skyscrapers have an advantage here, 5-10 story apartment buildings, no.  (Houses move with the ground, it hits higher modes of skyscrapers, but apartment buildings resonate)<p>2) Unreinforced masonry or lightly reinforced concrete sucks in an earthquake. Very low tensile strength, which leads to crumbling under shear loads. Combine this with 5-10 story buildings and you have a death trap.  Reinforced concrete helps, but it takes a _lot_ of steel, so much that you have difficulty placing the concrete. It&#x27;s mostly for containment, so that you have this core of concrete wrapped in a steel jacket that can retain enough strength that the building doesn&#x27;t collapse. It&#x27;s still a write off after the quake, but hopefully you haven&#x27;t killed anyone.<p>3) You want relatively consistent height vs stiffness and stiffness vs orientation profiles. One weak floor (e.g, double height ground floor with columns) concentrates the motion there, and with that the forces. One of the California quakes (Maybe Northridge) showed that the typical for the time arrangement of 3 walls + one open side for parking on the ground level, + 2 stories above was a really bad idea because that one weak wall doomed the buildings. You can&#x27;t do that in California anymore.<p>4) Stiffness attracts load. This is a displacement driven regime, rather than a force driven one. If you make something stronger, it often becomes stiffer, and then attracts more load. This can go in a loop. The solution is to make things _really_ flexible, such as using base isolation.<p>(source, Masters in Civil, working EIT for a couple years in an earthquake region before switching to internet stuff)