How vulnerable is your apartment to earthquake damage? Is it located near a fault, landslide or liquefaction zone?
The United States Geological Survey has published an interactive map online, (https://maps.conservation.ca.gov/cgs/EQZApp/app/) enabling the public to search by property address to determine the earthquake risks associated with specific land parcels.
Much of Central Orange County lies within liquefaction zones, where the ground reacts like Jell-O to seismic waves — jiggling, undulating and putting the structures built upon it in jeopardy.
Active earthquake faults run along the coast and mountain ranges, hitting places such as Huntington Beach and Yorba Linda.
And the hillside communities of Laguna Beach, San Clemente and Santiago Canyon are prone to landslides that can be triggered in a major earthquake, potentially undermining the foundation of a home, or sliding into one.
Determine your risks
I have been working for many years with professional organizations and communities throughout California to help educate people about the risks they face from earthquakes.
It’s important to arm yourself with the facts when assessing your options about earthquake safety.
This makes sense, not only from a business perspective, but it also helps to build resiliency within our communities — and that benefits everyone.
According to the Federal Emergency Management Agency, there are three factors to consider when determining your property’s seismic risk. They include: the level of the seismic hazard, the number of people affected by the hazard, and the vulnerability of these people and potential loss of property value to the hazards.
This article is the first of many I will be writing to help inform Apartment Association of Orange County members about earthquake resilience, financial risks and benefits of protecting one’s self from liability and damage, and importance of avoiding the type of social and economic ruin anticipated when the “Big One” strikes.
The United States Geological Survey determined that 300,000 structures would be damaged in a 7.8 San Andreas earthquake.
That’s one in every 16 buildings in our region.
The composition of your apartment is therefore another important factor to consider.
Building safety experts have determined the following building types to be most at risk of damage from an earthquake:
Soft-story structures built before 1978: This style is common among apartment buildings, characterized by open parking on the ground floor and dwelling units built above. In some instances, the ground floor may be used as retail space and enclosed by windows that do not provide any structural support. These wood-framed structures are considered extremely vulnerable to collapse in a major earthquake.
Non-ductile concrete buildings built before 1977: These structures have concrete floors and/or roofs supported by concrete walls, columns and/or frames. Due to their rigid construction and limited capacity to absorb the energy of strong ground-shaking, these structures are at risk of collapse in an earthquake.
In fact, non-ductile concrete buildings make up the majority of earthquake losses around the world. Because they are frequently used for office and retail uses that draw large numbers of people, the potential for death and injury with these structures is of particular concern.
Tilt-up construction built before the 1994s: This type of building began in the early 1900s, but didn’t really catch on until the post-World War II construction boom. This cost-effective technique of pouring a building’s walls directly at the jobsite and then raising or “tilting” the panels into position was and continues to be a popular way to meet California’s demand for new commercial buildings.
The walls of a concrete tilt-up building can weigh between 100,000 and 300,000 pounds. Steel plates with headed studs are positioned into the forms prior to pouring the concrete to establish viable connection points that secure the walls to the foundation and the roof trusses to hold them in place.
Many tilt-up structures built prior to 1994 were constructed with limited or weak connections that have been proven to fail in an earthquake, causing severe damage and/or collapse. These building defects can be easily corrected with seismic retrofitting.
Steel moment frame construction dates back to the 1880s with the very first skyscraper, the Home Insurance Building in Chicago, but this building technique was most commonly used in the 1960s to 1990s.
Steel moment frame construction is characterized by the use of a rigid steel frame of beams connected to columns to support the many floors of the structure.
These structures, when built before 1996 following The Northridge earthquake, can sustain brittle fracturing of the steel frames at the welded joints between the beams and the columns. In fact, many moment frame buildings in Southern California reveal cracks and fissures in these frames and may be susceptible to collapse in a major earthquake.
Unreinforced masonry buildings make up many of the older structures typical in downtown communities. They are characterized by walls (both load-bearing and not) and other structures such as chimneys that are made of brick, cinderblock, or other masonry materials not braced with rebar or another reinforcing material.
URM structures are vulnerable to collapse in an earthquake, due to a general failure of the mortar or when portions of the masonry such as parapets peel from the building façade and fall onto the sidewalk below.
If you own one of these types of buildings, or if your apartment is located near a fault or liquefaction or landslide zone, it is important to gather the facts you need to make an informed decision about your property.
Stop by our booth at the 2020 Trade & Conference Expo March 25 to learn more. I hope to see you there.