Project IDs Potential At-Risk Buildings in Orange County. Is your apartment building ready for the Big

Project IDs Potential At-Risk Buildings in Orange County Is your apartment building ready for the Big One? BY ALI SAHABI

How many unsafe, soft-story apartment units are there in Orange County?

That question and similar ones about other counties in California led Optimum Seismic, Inc. and the U.S. Resiliency Council to team up with Esri, a leading mapping company, to combine resources to develop maps showing where thousands of potential soft story buildings are located in cities large and small throughout Southern California.

The maps were then woven together to present a visual story showing where the quantities and concentrations of older, multistory apartment buildings were located. Such information could be used to help legislators and community leaders identify soft story buildings to better understand where resources might be directed to address these vulnerable structures.

There may be as many as 60,000 locations in California with these older multi-story apartment buildings in cities without retrofit ordinances., representing nearly 800,000 units. If 30% of those structures need retrofitting, that is almost 250,000 units. Assuming an average of 2.5 residents per unit based on census estimates, that represents 625,000 people potentially at risk of death, injury or homelessness when a major earthquake strikes near their homes. (Visit http://bit.ly/3GQAN7m for more information.)

Those at-risk structures also represent thousands of apartment owners whose lifelong investments may be in jeopardy. How would you manage if your income property were destroyed?

Wood-framed, soft-story buildings represent a design commonly found among apartment buildings, because they maximize space by putting parking spaces on the ground floor, with dwelling units above. In some instances, the ground floor may be used as retail space and enclosed by windows that do not provide any structural support.

But these structures, when built prior to 1978, can be extremely vulnerable to collapse in a major earthquake. Because of their design, they lack the ability to withstand lateral forces that push the building from side to side. The swaying can cause the first floor to collapse, and the upper stories to pancake on top of it. Retrofit construction for soft-story buildings usually entails the installation of a steel moment frame or frames, a sturdy foundation and drag lines to absorb seismic ground motion and prevent swaying.

We saw these structures collapse in the 6.7-magnitude Northridge earthquake of 1994. The images of the flattened multi-level soft-story Northridge Meadows apartments — and the smashed vehicles beneath them — still rattle people today.

Earthquake disasters come without warning, and their devastation can happen instantaneously. The situation requires circumspective, strategic thinking to resolve. We can’t make earthquakes go away, but we can retrofit structures to withstand them.

The California Earthquake Authority estimates that as many as 270,000 people could be displaced from their homes when the next major earthquake strikes the greater Los Angeles region. Other potential impacts, cited in the USGS ShakeOut scenario include:

• 1,800 deaths • 1,600 fires • 750 people trapped inside buildings • 50,000 ER visits • 19 days of search and rescue efforts

Seismic retrofits of vulnerable buildings stave off catastrophic social and economic consequences that would cripple the region for many years following a major earthquake. A constrained housing market resulting from red-tagged apartment buildings would drive up the cost of housing even fur-

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