LOS ANGELES — A 4.5 magnitude earthquake on the Puente Hills fault jolted much of Los Angeles and Orange counties Friday, raising concerns about the volatility of this seismic threat to Southern California.
Considered far more deadly than the infamous San Andreas, the Puente Hills thrust fault has the capacity to kill more people and cause more damage because it lies under vulnerable older neighborhoods and dangerous concrete buildings, and produces heavy reverberations that can be felt over a wide area.
The United States Geological Survey estimates that a magnitude 7.5 earthquake along that fault could kill up to 18,000 people and cause up to $250 billion in damage – devastation that would only be experienced with an 8.0 quake along the San Andreas.
“This relatively modest September 19 Puente Hills quake is a reminder of much more serious damage that can be inflicted by lesser known earthquake faults that riddle our area,” says Optimum Seismic Chief Operating Officer Ali Sahabi, an expert in resilience and sustainability.
He encouraged concerned businesses to attend an informational series of webinars beginning in October in partnership with the Los Angeles County Business Federation, the Los Angeles Area Chamber of Commerce, and other leading businesses organizations. Visit optimumseismic.com for information.
Los Angeles County ranks as the nation’s No. 1 region for earthquake damage and loss, according to the USGS. A recent study at U.C. Berkeley performed by the CGS supported that finding, ranking potential damage in Southern California higher than that of any other part of the state, including San Francisco.
Estimates for potential damage along other Southern California earthquake faults include: $29 billion from a 6.8 event on the Whittier fault; $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; and $24 billion for a 6.7 event on the Verdugo fault.
An estimated 300,000 structures could be damaged in a 7.8 earthquake along the better-known San Andreas fault, according to the USGS. That’s as many as one in every 16 buildings in the region.
These sobering figures represent more than just widespread loss. Every dollar reflects damage to the building or structure – in many cases putting severe hardship on the building owner and its occupants.
Seismologists and structural engineers have identified specific types of buildings that are most likely to be damaged in a major earthquake. These include:
- Soft-story structures built before 1978
- Unreinforced Masonry built before 1933
- Concrete Tilt-up built before 1980
- Non-Ductile Concrete built before 1978
- Steel moment frame built before 1996
“Protecting buildings makes good economic sense for property owners,” says Sahabi. “Many of the structural deficiencies in older buildings can be corrected relatively easily and cost effectively by earthquake retrofits. Modern resilient design techniques can enable new buildings to withstand anticipated shaking.”
Not only could a major quake cause costly property damage or trigger lawsuits, loss of income can also occur when commercial property is damaged to the point where it is no longer habitable. This can create severe financial hardship for property owners who lose their monthly rental income, and simultaneously face the costs of recovery coupled with ongoing monthly payments on their original mortgage.
California’s Earthquake Risks
Los Angeles is not the only California region at risk.
More than 30 years after the devastating Loma Prieta earthquake of 1989, a USGS geologist called the Bay Area a “tectonic time bomb,” and the head of U.C. Berkeley’s Seismological Lab warned that “Loma Prieta was not the big one” — that an even more destructive quake is waiting to strike.
Southern California had major wakeup calls last year, when a whopping 7.1-magnitude earthquake in July came on the heels of a 6.4 temblor in desert area near Ridgecrest, a relatively undeveloped area. A similar quake in a more urban area could have been devastating.
Lurking just beneath the Long Beach harbor is a newly awakened giant: the Wilmington Blind-Thrust fault, which was long dormant but has recently shown new activity that could spark a destructive 6.4-magnitude quake locally, or trigger the nearby San Andreas to produce an even larger temblor reaching in the 7 magnitudes.
San Diego also faces serious earthquake risks. The Rose Canyon Fault runs right through the city — from the Silver Strand to La Jolla — snaking its way under lofty skyscrapers, commercial districts and apartment buildings that draw tens of thousands of people each day. Seismologists agree that Rose Canyon, while relatively inactive, has the capacity for a 7.0-magnitude quake – larger and more destructive than Loma Prieta and Northridge.
If such an earthquake does strike San Diego, the damage estimates range between $124 million and $13 billion because many of the area’s buildings are older and built under outdated codes.
Good News
We are all fortunate that woven into this fabric of earthquakes and fault discoveries is a growing movement to make our cities safer.
California in 2019 rolled out its early warning system, designed to save lives by giving people about 20 valuable seconds to prepare before an earthquake strikes. A newly released phone app will enable the Office of Emergency Services to broadcast warnings throughout the state, should a major quake be detected.
Optimum Seismic is taking a lead role in presenting a series of webinars using the theme “The Resilience Advantage” beginning in October to educate businesses to the many actions they can take to protect their buildings, assets and employees from earthquake risks. These webinars will be presented in cooperation with the Los Angeles County Business Federation (BizFed), the Los Angeles Area Chamber of Commerce and other leading business .
“Preparation is the key to resilience,” Sahabi said. “Educating ourselves about our earthquake risks and vulnerabilities is the first step to guarding against it.”
State and local governments continue to identify vulnerable buildings that may be significantly damaged or collapse in a major earthquake. This includes some 600 structures recently pinpointed on college campuses up and down the coast.
And in the Los Angeles region, more than 4,900 soft-story apartment buildings have been retrofitted, with another 10,000 in the process or expected to complete retrofits within the next five years. Optimum Seismic has completed many of these projects.
About Optimum Seismic: Optimum Seismic, Inc., is one of Southern California’s leading construction and engineering companies performing earthquake retrofits and renovations and a preferred supplier for regional apartment and business associations. The Optimum Seismic team has been performing retrofit engineering and construction since 1984, and has completed more than 3,500 projects throughout California. For information, visit www.optimumseismic.com.
