Understanding the Impact of Earthquakes on San Francisco’s Infrastructure
In a city notorious for its seismic activity, it’s no surprise that San Francisco has taken extensive measures to better handle strong earthquakes with magnitudes of 6 and above. However, geophysicists warn that this is not the whole story. While San Francisco may be more prepared, the likelihood of experiencing a major earthquake is significantly higher compared to other regions. The city’s vulnerability lies in its older buildings, which may not withstand the devastating effects of a powerful earthquake.
Geophysicist Ross Stein emphasizes that while San Francisco may be less vulnerable to earthquake damage, it is much more prone to experiencing them. He likens the situation to a ticking time bomb, where potentially catastrophic failures can occur when the inevitable earthquake strikes. Skip Walker, an ASHI certified and CREIA Master inspector of buildings in San Francisco, echoes this sentiment, having witnessed numerous structural inspections throughout his career. Civil Engineer Peter Yanev, the legendary founder of EQE Consulting, shares their concerns, particularly regarding the older buildings in the city.
The issue lies with pre-1990 buildings that lacked adequate reinforcing steel. Many buildings on Nob and Telegraph hills, for example, do not have enough steel to make them ductile, meaning they are not flexible enough to withstand seismic shocks. This lack of ductility puts these non-ductile concrete buildings at risk of collapse in the event of a strong earthquake. The devastating 1985 earthquake in Mexico City serves as a harrowing reminder of the dangers posed by such structures. Despite being 220 miles from the epicenter of a magnitude 7.5 earthquake, buildings between six and 15 stories high buckled, resulting in around 10,000 lives lost.
Peter Yanev explains that San Francisco also has city blocks filled with older, non-ductile concrete buildings, making it vulnerable to similar disasters. Brian Strong of SF City Hall confirms this, stating that there are approximately 2,700 concrete buildings in San Francisco built before 1990 that have low-ductility concrete. These structures are not up to par with modern seismic standards, making them susceptible to collapse in the event of a major earthquake.
Concerningly, the city has yet to take significant action to address this issue. Ross Stein’s apprehension is warranted, as San Francisco residents live atop one of the most urbanized fault systems on Earth. The city is surrounded by the San Andreas and Hayward-Rogers Creek faults, both of which are active and pose a constant threat. It is crucial to remember that an earthquake of significant magnitude is inevitable, and it will expose all the substandard buildings, potentially leading to their destruction.
To address this issue, it is imperative for individuals to be proactive in earthquake preparedness. Websites such as Temblor’s (https://temblor.net) and the state’s preparedness website (https://www.caloes.ca.gov/office-of-the-director/operations/planning-preparedness-prevention/seismic-hazards/earthquake-preparedness/) provide valuable information on earthquake risks and preparedness measures. Understanding the vulnerabilities and taking necessary precautions can help mitigate the potential devastation caused by earthquakes.
While San Francisco may have implemented measures to better handle strong earthquakes, the city’s vulnerability lies in its older buildings. These structures, lacking proper reinforcement, are at a higher risk of collapse during a major seismic event. The city’s geographical location atop an active fault system adds to the potential for devastation. It is crucial for both individuals and the city to address this issue proactively and prioritize earthquake preparedness to minimize the impact of future earthquakes on San Francisco’s infrastructure and residents.