Greater L.A. Tops List of Regions Most Prone to Earthquake Damage
When it comes to earthquakes, Los Angeles County ranks Number One in the U.S. for estimated annualized loss, according to the Federal Emergency Management Agency. A recent study at the University of California at Berkeley performed by the California Geological Survey supported that finding, ranking potential damage in Southern California higher than that of any other part of the state, including San Francisco.
Why is the Los Angeles Area Most Vulnerable?
Projected earthquake damage is calculated based on population density, the strength or intensity of potential ground shaking and the ability of a structure to withstand it. The California Geological Survey determined that a perfect storm of anticipated ground motions, soil conditions and development in Los Angeles County, our region faces the potential of significant annualized earthquake loss. The agency found that in Southern California, a magnitude 7.1 quake along the Puente Hills fault would bring an estimated $69 billion in damages. A similar study by the University of Southern California projected total economic loss could be as high as $252 billion. Other calculations for Southern California include $49 billion from a 6.9 magnitude quake on the Newport-Inglewood fault; $30 billion from a 7.1 magnitude event along the Palos Verdes fault; $29 billion from a 6.8 event on the Whittier fault; and $24 billion for a 6.7 event on the Verdugo fault.
Major reasons the U.S. Geological Survey put Los Angeles County at the top of annualized earthquake loss has to do with the population density, the types of buildings located here and the likelihood that they may be damaged when a major quake strikes.
Is Your Building at Risk?
Every building is different and approaches to safeguarding a structure against earthquake damage are as diverse as the thousands of soft-story apartment complexes needing retrofits in the City of Los Angeles. In our public presentations at community workshops, professional conferences and in discussions with prospective clients, we inevitably get asked to provide assessments of a specific building sight-unseen.
We are often asked: What will you need to do to my building? How long will it take? How much will it cost? These are all valid and important questions, but they are impossible to answer without seeing the property, measuring it and calculating the work to be done based on engineering science. Generally speaking, seismologists and structural engineers have identified certain buildings that are more likely to sustain damage in a major earthquake. These include:
- Soft story structures built before 1978: These structures, with parking on the ground floor and units built above, are prone to collapse during major earthquakes.
- Unreinforced Masonry built before 1975: The facades of these buildings can collapse in a quake.
- Concrete Tilt-up built before 1994: Weak connections can fail and cause walls to pull apart from the roof, presenting a collapse hazard.
- Non-Ductile Concrete built before 1977: Limited lateral resisting capacity makes these structures brittle.
- Steel Moment Frame built before 1996: These buildings can sustain brittle fracturing of the steel frames at welded joints between beams and columns.
Sign up for “Retrofits Protect Investments, Improve Safety” Webinar March 17
Optimum Seismic has teamed up with a coalition of leading business organizations and government officials to launch a monthly webinar series, “The Resilience Advantage,” to help educate property owners and managers, as well business and community leaders, about the threats they face and the approaches to take to avoid social and economic disaster.
Sign-Up Today. Our next webinar series on “Retrofits Protect Investments, Improve Safety” will be held from 11:00 a.m. to 12:30 p.m. on
Wednesday, March 17, 2021. Visit https://www.optimumseismic.com/the-resilience-advantage/ to register or to view past webinars in the series.
Ali Sahabi, a licensed General Engineering Contractor (GEC), is an expert in seismic resilience and sustainability. He is Co-Founder of Optimum Seismic, Inc., which has completed more than 3,500 seismic retrofitting and adaptive reuse projects for multifamily residential, commercial, and industrial buildings throughout California. Visit OptimumSeismic.com for more information, or call (323) 978-7664.