California’s devastating wildfires and the recent quake in Alaska may distract us from our own vulnerability to natural disaster.
But did you know that Southern California’s deadliest earthquake occurred right here in the Apartment Association of California Southern Cities region? That 6.4-magnitude quake, occurring on March 10, 1933, led to the adoption of laws regulating earthquake safety at all public school campuses in our state.
Some 120 deaths, 500 injuries and $50 million in damage – $921 million in today’s dollars – was reported in Long Beach, Huntington Park, Compton and surrounding areas.
Untold numbers of children were spared from death or injury that day because the quake happened around dinner time. Had it struck just a few hours earlier, the more than 120 schools that were destroyed or severely damaged in the quake – facades crumbed, entire floors pancaked on top of each other – would have certainly harmed many hundreds more than the lives it did take that day.
Legislation Enacted to Save Lives
The widespread destruction – and realization that many of Southern California’s children could have easily been killed – prompted the state of California just one month later to adopt the Field Act, which authorized a thorough architectural review of all new public schools built. The Garrison Act of 1939 required reviews of existing schools built prior to the Long Beach Quake.
Today, because of these and other laws put in place to improve building regulations, the damage caused from earthquakes is much less than what it was in the past. However, Southern California has yet to see seismic activity significantly larger than the Long Beach temblor. The 1994 Northridge quake – the nation’s most expensive earthquake in terms of damage – measured 6.7 on the Richter scale compared to Long Beach’s 6.4.
Seismologists predict that we are long overdue for an earthquake of epic proportions – larger than Northridge and Long Beach. In fact, they estimate that “The Big One” could be up to 45 times larger than Northridge.
A Quake 45 Times Larger than Northridge
According to the U.S. Geological Survey, “California has more than a 99 percent chance of having a magnitude 6.7 or larger earthquake within the next 30 years.” The likelihood of an earthquake greater than magnitude 7.5 occurring is 46 percent over the next 30 years.”
The closer you are to the convergence of two tectonic plates, the more likely you are to be impacted by seismic activity. Buildings in the Greater Los Angeles area have up to a 5 percent chance of being damaged by an earthquake this year, according to the United States Geological Service.
In fact, Los Angeles County ranks as No. 1 in the nation for estimated annualized earthquake loss, the USGS reported. A U.C. Berkeley study performed recently 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. One of the major reasons the USGS put L.A. 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?
Seismologists and structural engineers have identified certain buildings that are most likely to sustain damage in a major earthquake. These include:
- Soft-story built before 1978: These structures, with parking on the ground floor and units built above, are prone to collapse during major earthquakes.
- 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.
A detailed USGS scientific assessment of potential damage from a magnitude-7.8 San Andreas earthquake in Southern California estimated that 300,000 structures would be damaged. That’s one in every 16 buildings in the region.
Will yours be among them? Most earthquakes are small, virtually imperceptible, but scientists universally agree that we are long overdue for “The Big One.” It’s just a matter of time.