This is a good question and one that in light of recent events, many of us may be curious about. Thankfully, there has been ongoing research into what's called earthquake engineering, which focuses on designing and constructing structures that can withstand reasonable levels of seismic activity without failing. One thing to keep in mind however, is that no amount of "earthquake proofing" will make a structure safe or immune to an earthquake if the earthquake is big or close enough.

Naturally, there are materials that are just "stronger" and therefore more resistant to movement and seismic load such as steel. A general rule of thumb to follow in terms of what materials are stronger to seismic loading is "what material can absorb more energy without yielding". For example, certain materials are strong in compression but weak in tension – or brittle – such as masonry or inadequately reinforced concrete. Such materials have the tendency to crumble and break apart during seismic activity.

There are many characteristics to consider when analyzing materials, such as its stiffness, toughness, hardness, and elasticity. All such characteristics contribute to a material's performance both before and during an earthquake. Modern structural steel is the product of extensive research and experimentation, and taking cost into consideration, is as close as we have come to "the perfect alloy" in terms of strength in all relevant forms.

Wooden Houses walk away with the Last Laugh

I'm sure we've all heard somewhere that wooden houses were also surprisingly strong to earthquakes. While this is true, it's important that we understand just what characteristics of wooden houses made them so resistant to earthquakes. Although wood as a construction material contains ideal properties such as elasticity and reasonable strength, this alone will not do the trick if your house isn't braced adequately in shear. What makes most wooden houses famously strong to earthquakes is that they often incorporate what's called shear walls and diaphragms into their construction.

Shear walls and diaphragms must work together to form what's called a "diaphragm structure". Simply put, shear walls are walls made to counter a shear force, and are typically made with plywood – or the equivalent – nailed or otherwise secured to framing. A diaphragm is commonly the roof and/or floor of the structure and is the horizontal version of a shear wall. When constructed properly, this diaphragm structure has the ability to withstand most lateral forces, wind or earthquake, and is responsible for the strength of most wooden houses.

Base Isolation, TMD's, and the P-Delta Effect

Aside from the materials used and proper construction methods, there are various techniques used to counter seismic loads. Base isolation is considered to be one of the most effective tools at our disposal and is the essential decoupling of a structure from its substructure or foundation during seismic activity. Another common device used in taller structures such as skyscrapers are tuned mass dampers(TMD). These are typically huge masses of concrete and/or steel which sway or move in the opposite direction of that of the building, countering its lateral movement.

TMD's are beneficial not only during earthquakes, but also during periods of turbulence or winds that would cause discomfort or even motion sickness if unchecked. TMD's can also counter a phenomenon called the P-Delta effect, which is a destabilizing force that acts on taller buildings subject to large lateral displacements due to heavy wind or seismic activity. As the top end of a skyscraper for instance, sways from side to side, the gravitational force of the section of the building offset from the original vertical position creates a downward force. This is called the P-Delta effect.

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