Government or official record
Progress Toward a Safer Future Since the 1989 Loma Prieta Earthquake
U.S. Geological Survey
Cross-File evidence ledger
Where this source supports the record
Each entry separates the File’s editorial relevance note from its exact, section-level claims. A bibliography link without a direct claim is labeled plainly.
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Engineering failures · 17 October 1989Open File evidence →
The Cypress Street Viaduct Collapse
Cypress Street Viaduct collapse zone and memorial park · United States
Why editors use it hereUSGS explanation and map of how soft sediment amplified shaking under the collapsed portion.
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Quick read
When the magnitude 6.9 Loma Prieta earthquake struck on 17 October 1989, a 0.7-mile section of Oakland's double-deck Cypress Street Viaduct collapsed.
Reviewed 24 July 2026 -
Trigger and conditions
At 5:04 p.m., shaking from the Santa Cruz Mountains reached the Bay margins.
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Uncertainty
Official sources sometimes report 41 rather than 42 Cypress deaths because of differences in attribution.
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Why it matters
The failure was not produced by shaking alone.
Reviewed 24 July 2026
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Quick read