The Need for Structural Health Monitoring in the San Francisco Bay Area

The San Francisco Bay Area is one of the most seismically active and densely urbanized regions in the United States. Sitting along the San Andreas and Hayward faults, it faces a well-documented likelihood of future major earthquakes. The 2023 United States National Seismic Hazard Model (NSHM) places the Bay Area among the highest-probability regions nationwide for damaging ground shaking within the next century [3]. That hazard, combined with rapid urban densification and an aging building stock, is why systematic Structural Health Monitoring (SHM) matters here — to safeguard lives, infrastructure, and economic activity.

Structural Health Monitoring is critical for resilient infrastructure in the Bay Area.

Seismic hazard in the Bay Area

The region’s hazard profile is shaped by a complex tectonic environment and a history of large earthquakes, including the 1906 San Francisco event and the 1989 Loma Prieta earthquake. The 2023 NSHM integrates new data on earthquake rupture forecasts, ground-motion models, and site amplification, and shows particularly high hazard in California’s coastal urban centers, including San Francisco and Los Angeles [3]. Geotechnical conditions add further risk: much of the Bay shoreline consists of artificial fill, mud, and clay with high liquefaction potential, where earthquake shaking can lead to severe ground failure [1].

Vulnerabilities in the built environment

California has strengthened critical lifelines such as hospitals, bridges, and transportation corridors — but the broader building stock remains vulnerable. Current building codes are designed primarily to prevent collapse, giving structures roughly a 90% probability of avoiding total failure during severe shaking. Crucially, codes do not require that a building remain functional afterward. So even where collapse risk is limited, large numbers of structures may be rendered unusable by nonstructural damage to plumbing, elevators, or internal systems [1].

Historical lessons also expose weaknesses in certain construction practices. Welded steel moment-frame buildings erected before the mid-1990s were later found to contain a critical connection flaw that can substantially raise their risk of fracture during extreme shaking — a lesson learned from the 1994 Northridge earthquake. A U.S. Geological Survey study identified dozens of such structures in downtown San Francisco, many of them high-rise commercial or residential towers built between the 1960s and early 1990s [2]. Retrofitting has begun in some jurisdictions, but the scale of the problem remains considerable.

The role of Structural Health Monitoring

SHM offers a pathway to mitigate these vulnerabilities. The systems continuously sense structural response — through accelerometers, strain gauges, or distributed networks of low-cost devices — to track changes in stiffness, frequency content, and other dynamic properties. In plain terms: a structure’s natural vibration is its fingerprint, and a shift in that fingerprint signals damage.

The benefits of SHM in the Bay Area context include:

1. Rapid post-event assessment — real-time identification of damaged or compromised structures after an earthquake, supporting emergency response and prioritization.
2. Enhanced resilience planning — long-term monitoring to detect gradual degradation from repeated minor events or environmental factors, informing retrofit strategies.
3. Economic risk reduction — better distinction between safe and unsafe buildings, reducing unnecessary evacuations, downtime, and economic disruption.
4. Public safety and confidence — transparent monitoring and reporting that build trust in the safety of urban infrastructure.

Conclusion

The Bay Area’s combination of high seismic hazard, concentrated urban development, and an aging building inventory makes it especially vulnerable to future earthquakes. Current codes and preparedness measures, while essential, cannot guarantee post-event functionality. Integrating SHM across the region’s built environment is a critical step toward seismic resilience — enabling both immediate safety assurance and long-term risk reduction.

Recap

Without scrolling up — the argument in one breath:

• The Bay Area stacks high hazard, dense exposure, and an aging, code-minimum building stock.
• Codes deliver life safety, not functional recovery — a survived building can still be unusable.
• SHM watches a structure’s stiffness and vibration fingerprint to flag damage, delivering rapid post-event assessment, resilience planning, economic risk reduction, and public confidence.

Where to go next

Related posts here: Structural Health Monitoring Using Low-Cost Sensors and Wireless Networks and Understanding MEMS Accelerometers.

References

1. San Francisco's Big Seismic Gamble — Fuller, Singhvi & Williams, 2018, The New York Times.
2. At Risk in a Big Quake: 39 of San Francisco's Top High Rises — Fuller, 2018, The New York Times.
3. The 2023 US 50-State National Seismic Hazard Model: Overview and Implications — Petersen et al., 2024, Earthquake Spectra, 40(1), 5–88.