Two rare earthquakes struck within twelve hours of each other in the US, each of which have heightened our sense of vulnerability cross-country. Being one of the most populist cities in the US, New York may also be one of the most vulnerable. So what would happen to the different types of buildings spread throughout the city if a 5.8 quake were to hit closer to home? The short answer is “it’s complicated” – but the building science is now well understood. If you’re concerned about the building you live in, read ahead and as we give a look into the risks associated with various constructions, and offer some ideas on what you can do to mitigate these risks.
Photo by Wikicommons
As you probably guessed bricks and masonry walls are a problem. Due to the lack of flexibility brick walls tend to crack, or burst compromising the structure’s wood or steel beams holding up the floors and roof. With so many hundred-plus year old buildings ringing the city, retrofitting each one will be a huge job. One approach is to add a reinforced outer concrete shell, which is relatively simple, but can significantly change the look of a building. Many older multi-story buildings in California have steel cross bracing on either the exterior or interior to keep floors from separating. Another risk is to those outside of the buildings as façade elements fail and come crashing down to the sidewalk.
Buildings made from concrete are safer as they are reinforced with rebar. Even if the rigid concrete cracks, it remains in place by the steel. These types of buildings fail often where structural elements meet each other and cannot hold up against the sheer forces. These types of buildings also often have larger glass windows that may not survive the shaking and break apart. Beefing up the structural connections is often near the top of the list during a retrofit.