-Appeared on San Diego County Apartment Association (SDCAA)
Southern California got hit by some monster quakes this summer, thankfully with no casualties and little destruction due to the remoteness of the epicenters’ sparsely populated desert location.
But what if the Ridgecrest temblors happened here?
San Diego’s Rose Canyon Fault runs right through the middle of the city — from the Silver Strand to La Jolla — snaking its way under lofty sky scrapers, commercial districts and apartment buildings that draw tens of thousands of people each day.
Seismologists agree that the Rose Canyon Fault, while relatively inactive, has the capacity for a 7.0-magnitude quake similar to those in Ridgecrest. And when it does strike, the damage caused would be colossal: at between $124 million and $13 billion.
In fact, the California Geological Survey ranks San Diego as one of the state’s top 10 areas for projected loss from an earthquake.
That’s one reason why the city is taking action to retrofit Balboa Park’s iconic California Tower so that it continues to stand after a major quake.
City officials have also been pushing for retrofits of unreinforced masonry buildings to prevent their historic facades from falling in a quake. So far, the work has been left up to the building owners to fix, but officials with the Development Services Department as discussing possible fines and injunctions to get the work done, city spokesman Scott Robinson told the San Diego Union-Tribune.
Is Your Building at Risk?
What are the buildings most likely to fail in a major earthquake? Seismologists and structural engineers have identified five types:
- Soft-story buildings built before 1978: These structures, with parking on the ground floor and units built above, are prone to collapse during major earthquakes.
- Unreinforced Masonry buildings built before 1975: The facades of these buildings can collapse in a quake.
- Concrete tilt-up buildings built before 1994: Weak connections can fail and cause walls to pull apart from the roof, presenting a collapse hazard.
- Non-ductile concrete buildings built before 1977: Limited lateral resisting capacity makes these structures brittle.
- Steel moment frame buildings built before 1996: These buildings can sustain brittle fracturing of the steel frames at welded joints between beams and columns.
The Cost Benefits of Retrofits
Researchers at Caltech have determined that for every dollar spent in retrofitting soft-story structures, property owners could expect to save up to seven dollars, and that study didn’t factor in loss to contents, alternate living expenses or deaths and injuries – all of which would have significantly increased the cost-to-benefit ratios.
In a separate study, the university determined that seismic retrofits are cost-effective when projected annualized loss would be reduced by 50 percent or more, at a cost that would equal no more than 10 percent of the replacement cost of a building.
The Federal Emergency Management Agency found similar cost benefits in a two-year analysis of seismic retrofit scenarios applied to a variety of building types, including a scenario of a tilt-up warehouse building in California.
Avoid Liability, Loss of Income
There are other strong economic factors to consider when weighing the benefits of a seismic retrofit. These include potential loss of income and liability associated with damage, death and injury due to earthquakes.
Loss of income can 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 not only lose their monthly rental income, but are simultaneously facing the costs of recovery coupled with ongoing monthly payments associated with their original mortgage.
Most earthquakes are small, virtually imperceptible, but scientists universally agree that — even with these recent quakes —can damage buildings over time. In addition, the Big One can happen at any time.
Let these recent quakes be your wake-up call to get prepared. It’s just a matter of time until the next one strikes, possibly in our area.
If you own a building of the type determined to be vulnerable in a quake, you would be wise to get a seismic engineering assessment of your structure to determine whether there are any risks and what can be done to correct them.