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What Are Base Isolation Systems?

In 2010, more than 230,000 people died in Haiti after a Magnitude 7 earthquake; in that same year, only a few thousand died in Chile after it suffered a much more massive 8.8 Magnitude earthquake. The reason for the much lower death toll in Chile was more extensive and stringent building codes that emphasized the use of base isolation systems. These antiearthquake protection measures help prevent buildings from collapsing in the event of an earthquake.

Earthquakes
- Earthquakes occur when areas of the earth, typically around the borders of tectonic plates, release large amounts of energy. This energy comes from the earth in the form of energetic shock waves. As these waves interact with buildings, the waves shake the buildings like a whip. Buildings which remain fully rooted to the ground have no way of absorbing this energy wave and, as a result, often shake so hard they collapse. It is this collapse that creates death tolls like the one seen in Haiti in 2010.
Base Isolation Technology
- Base isolation systems detach the building from its foundation in a way that allows the building to separate itself from an earthquakes shock wave. While the building still rests firmly over its foundation, it is separated from it by a distinct layer of material that acts as a shock absorber. When an earthquake occurs, the building can rely on this layer of shock absorption to counteract and dampen any movement as a result of the earthquake's shock waves and therefore maintain its structural integrity.
Ancient
- Some ancient structures, particularly in earthquake-prone areas of the world like Persia, have early base isolation systems. The tomb of Cyrus the Great is considered to have one of the earliest base isolation systems. In this tomb, the stone blocks above the foundation were built without mortar, which allows the blocks to shift in response to an earthquake. Each block, while supporting the weight of the blocks above it, also is independent of others around it, enabling flexible freedom of movement.
Modern
- Modern buildings use a variety of materials for base isolation. Buildings often have a combination of different devices that act in conjunction with one another to absorb an earthquake's energy. Modern buildings, even enormous skyscrapers, may rest on springs, padding or even ball bearings. These simple devices separate the building from its foundation and allow the building to maintain its structural integrity in the face of an earthquake.

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