Northridge earthquake: A look back 25 years later
This month marks the 25th anniversary of the Northridge Earthquake that struck in the early morning hours on Jan. 17, 1994. The magnitude-6.7 blind thrust earthquake struck Northridge, Calif., causing chaos and leaving much of the city in ruins with buildings and freeways collapsed. When the dust settled, 57 people had died, including 33 from fallen buildings. Of those, 16 were killed when the 164-unit Northridge Meadows apartments collapsed. An emblem of urban catastrophe, the quake was one of the worst and most costly natural disasters in U.S. history — causing $20 billion in damage with collapsed buildings and freeway overpasses, snapped water and gas lines, rampant fires and landslides.
While the Northridge Earthquake was bad, in some respects, Los Angeles got lucky with Northridge. It occurred early in the morning at 4:31 a.m. on a relatively short, unknown 10-mile-long fault, and the brunt of its 6.7-magnitude force was concentrated in the outlying suburban areas that were less densely populated. The next “big one” could be much worse.
According to an predictive analysis report by the United States Geological Survey, there’s a 60-percent chance an earthquake measuring in at magnitude 6.7 or higher will strike the Los Angeles area in the next 30 years; there’s also a nearly one-in-three chance that the earthquake will measure in at 7.5 on the Richter scale.
In 2016, a Los Angeles Times report found more than 1,000 old concrete buildings at risk of collapse, and 50 that could be destroyed, exposing thousands to injury or death; though new rules requiring seismic retrofits for some of the most vulnerable structures should help mitigate the destruction.
Thousands of Southern California buildings remain vulnerable to earthquakes and are at risk of collapse. These “soft story” structures — with open-air parking on the ground floor and dwellings above, supported by narrow columns and considered one of the most vulnerable construction types (along with brick and concrete) — remain scattered around the region. Many steel-frame buildings also cracked during Northridge, surprising engineers who thought steel to be earthquake-resistant. To date, no one knows exactly how many of those damaged buildings remain. And numerous concrete buildings built pre-1970, including some of the city’s tallest structures, lack steel reinforcement bars that could keep them from collapsing in the next large seismic event.
These findings demonstrate the importance of regular updates to the building codes and strong code enforcement in order to mitigate damage from natural disasters such as earthquakes. The National Institute of Building Sciences (NIBS) recently released the Natural Hazard Mitigation Saves: 2018 Interim Report, which found that adopting the 2018 International Codes — the most widely used and adopted set of building safety codes in the world — generates a national benefit of $11 for every $1 invested — the national mitigation benefit-cost ratio associated with code adoption is $12 to $1 for earthquakes — with benefits coming through avoided casualties, post-traumatic stress, property damage, business interruptions and insurance premiums. The results show that all building stakeholders benefit from regularly updated codes — from developers, titleholders and lenders, to tenants and communities.