Earthquake Risks: How Architectural Features Affect Seismic Resistance

The age-old saying, “The bigger they are the harder they fall” is believed to have originally come from boxing. But for those of us in property risk management, it’s also a fair description of how buildings of certain structural types can react to seismic events. In fact, there are a lot of architectural and logistical details that help determine just how resilient a property will be in the case of an earthquake. These fall into a category called “secondary COPE data,” where COPE stands for “Construction Occupancy Protection Exposure.” By knowing what COPE data to look for, insurance companies and underwriters can more accurately assess risk levels and calculate insurance rates.

Today, we’ll talk a little bit about which details they look for, and what details you’ll want to collect if you’re in a Seismic Zone. By gathering these details, you can help ensure your property is properly covered in the case of seismic damage and avoid “worst case scenario” insurance ratings because you have the right details on hand.

seismic zone predicting earthquake riskSo What Is a Seismic Zone?

According to the United States Geological Survey (USGS), a Seismic Zone is an area where earthquakes tend to be centered. This is not to be confused with a Seismic Hazard Zone, which is a regulatory area near a Seismic Zone that has a particular level of hazard — such as areas with water-saturated soil (a “liquefication zone”) and/or an area of slopes, where landslides may be common. High Seismic Hazard Zones would be located near a very active Seismic Zone and have a strong chance of earthquake activity. In contrast, a Low Seismic Hazard Zone would be further from a high activity Hazard Zone and offer minimal probability of threat. You can check out FEMA’s Earthquake Hazard Maps here to view Hazard Zones across the U.S. These are based on “seismic design categories” (SDCs), which predict the chance of seismic activity of various intensities. These SDCs are then used in building code specifications, to guide building design and construction in areas where earthquakes are common and the land is viewed as potentially volatile.

The Seismic Zone is just one guide for calculating risk and insurance coverage, however. Valuation specialists also take into account…

earthquake risks in the size of buildingThe Size, Shape and Layout of Buildings

When it comes to architecture, buildings with simple geometry tend to hold up best from seismic activity. Tall buildings without proportionate base support are obvious candidates for instability issues during an earthquake, but other building layouts can be problematic, too. Short but long buildings are often subject to structural earthquake damage, as are large open buildings like warehouses, where walls and columns react to the stress of horizontal shaking.

Buildings with the first few stories wider than the rest of the building may discover damage at the level the two widths meet. And building shapes with additional corners and curves — like plus signs or U-shaped and H-shaped structures — tend to be more affected by seismic activity than buildings that are more simply shaped.

But even simply-shaped structures can have structural damage due to seismic activity. Buildings with evenly-distributed support from walls and columns generally perform better than those that don’t have these features. And buildings with fewer walls or columns, wide doors and unobstructed commercial spaces on a particular floor (called “soft floors”), or buildings with inconsistent floor heights, can also be points of likely earthquake damage due to a lack of stability in those areas.

Basically, when it comes to building construction and earthquakes, consistency of design is the key to reducing damage.

earthquake risk building locationBuilding Location

Building location is another important factor when determining a building’s risk for seismic damage. If a building is situated too closely to another building, these adjacent buildings can sway and collide during an earthquake — an action called “pounding.” When the buildings are not of equal height, the roof level of the shorter building can pound the side of the taller building, causing significant damage.

Buildings located on a slope can also be affected by earthquake conditions. The unequal height of the sloped building columns, and the fact that short columns tend to be stiffer than larger columns, puts the shorter columns in peril of twisting and other damage. This is called “Short Column Condition” and it’s something to note when collecting COPE data.

earthquake risk in building exteriorBuilding Exterior

The more inflexible the exterior materials for the walls and cladding of a building, the more potential damage there is likely to be during a seismic event. Some important questions to ask about the property’s exterior to help determine seismic risk levels include:

          • Are there wall frames or shear walls in the building, and if so, what types?
          • Is the building constructed of tilt-up concrete walls? These heavy concrete panels have shown to collapse under moderate earthquake conditions, separating from what is often a plywood roof. In many areas, these structures must be retrofitted with roof-to-wall anchors, continuity ties, steel-braced frames, concrete footings, and other elements to improve their safety in high Seismic Zones.
          • Are there 50% or more open walls (this includes windows) in the exterior of the building? More open walls can mean less overall stability and greater potential for seismic damage.
          • Are there setbacks and/or overhangs in the building? These are also potential features that can fall victim to damage during a quake.
          • And are there any items attached to the building exterior, like rooftop tanks, signs, marquees, canopies and ornamentation? These are details that, depending on their materials and how they’re braced, can be of issue under seismic activity.
          • And don’t forget the parapets! Are there parapets, and, if so, have they been braced to resist earthquake loads?

By knowing more about the design and materials of your building’s exterior, you can help manage your risk and ensure a more accurate Statement of Values for your insurance coverage.

earthquakeriskfoundationBuilding Base

A building’s foundation can predict a lot about how it might handle an earthquake. Some items to look at here include:

          • Is there a basement?
          • If there is no basement, does the structure have cripple walls (short, wooden stud walls and crawlspace beneath the first floor)?
          • Are the cripple walls reinforced or unreinforced?
          • Are there flexible bearings attached to the base to reduce earthquake damage?

Knowing the materials and design elements of your foundation go a long way toward predicting its resilience during a seismic event.

Sprinkler Systems and Earthquake RisksBuilding Interior

Inside a building, an important feature to look at in terms of earthquake activity is the sprinkler systems. You’ll want to know if your building has a wet or dry sprinkler system. A wet system will always have water in the pipes, even before it’s activated. In a dry system, however, water will be pumped through the system only after the system is triggered. A wet system, therefore, becomes the greater risk for leaking (and for the water damage associated with that) should an earthquake occur.

Valuation Services for Earthquake RisksCoping with All of That COPE Data

Of course, these are just a few of the items to take into account when documenting COPE data associated with seismic activity. (You’ll find more resources on our website for COPE data related to risk events here.) But for more information directly related to your property insurance coverage, we recommend you contact your insurance provider regarding the specific details they commonly track. Also, a professional property valuation consultant can be indispensable when trying to determine accurate details of your property’s design, construction and risk levels. At AssetWorks, we help customers all the time with gathering and tracking important primary and secondary COPE data, so that though the ground may tremble, our clients’ property data will still hold firm.

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