Experts brief supervisors on likely damage if 1906-style quake struck today; estimate up to $120 billion in building losses

City-appointed and regional earthquake professionals told the Board of Supervisors that a repeat of the 1906 earthquake or a modern magnitude-7.9 San Andreas rupture would cause severe damage across the Bay Area, displace hundreds of thousands of households, and inflict tens of billions of dollars in building losses.

The presenters summarized findings from a multi-scenario analysis using HAZUS loss-estimation software and improved local building inventories. Key figures presented to the board included an estimate of about 10,000 damaged commercial buildings across the region; nearly a quarter-million displaced households; nighttime casualty estimates as many as 1,800 fatalities and daytime estimates as high as 3,400; and direct building losses across Bay Area counties totaling roughly $120 billion for a worst-case large event. Presenters also noted that accounting for secondary effects such as fires, utilities and transportation disruption would raise total losses above $150 billion.

The briefing explained which building types are most vulnerable to catastrophic collapse, including non-ductile concrete structures built before modern detailing standards and soft-story residential buildings (wood-frame buildings over an open ground level such as garages). The presenters recommended three broad action areas for the region: cultivate a culture of preparedness, invest strategically in mitigation (focusing on the most vulnerable buildings and critical infrastructure such as hospitals and fire stations), and ensure financial resources for recovery, including insurance and reinsurance strategies.

The analysis covered two scenarios: a historical reconstruction based on the 1906 event and a plausible future M7.9 event on the San Andreas Fault. Animations shown to the board illustrated rapid propagation of strong shaking across the peninsula within seconds, with the most intense shaking concentrated along the fault but with strong shaking in other basins as well. Presenters emphasized that the duration and frequency content of shaking matter for which buildings will be damaged.

Why it matters: The study frames the scale of regional exposure to a major earthquake and reinforces calls for targeted mitigation of housing and critical facilities, community preparedness (especially for elderly and non-English-speaking populations), and regional coordination for recovery.

Notable quantitative findings presented to the board (estimates provided by presenters): - Damaged commercial buildings in the scenario: ~10,000. - Displaced households (temporary shelter needs): ~250,000. - Casualties: nighttime up to ~1,800 deaths; daytime up to ~3,400 deaths. - County-level direct building losses cited: Alameda ~$15 billion; San Francisco ~$30.4 billion; San Mateo ~$20.6 billion; Santa Clara ~$20.8 billion; other counties combined ~$18 billion; total regional building losses ~ $120 billion. With fires and infrastructure damage, total losses could exceed $150 billion.

Presenters also urged attention to the region's seven major fault zones and noted the Hetch Hetchy aqueduct crossing multiple fault zones, identifying water supply disruption as a major regional risk.

Quotes "When the 1906 event reoccurs, we'd expect tremendous damage to structures around the Bay Area," a presenter said, summarizing modeling results and stressing the need for immediate preparedness.

"For the first 72 hours, many residents are going to be on their own," presenters told the board, calling for household and neighborhood-level readiness and special planning for vulnerable populations.

Ending The briefing did not require board action but served as a technical prompt for supervisors and city departments to prioritize retrofit, planning, and financing strategies. Presenters and officials noted the need for coordinated regional advocacy for state and federal resources to support mitigation and recovery planning.