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USGS CMG InfoBank: Liquefaction

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Comment: 16:20 - 17:47 (01:27)
Source: Annenberg/CPB Resources - Earth Revealed - 25. Living With Earth, Part I
Keywords: "William Bakun", "James Buika", liquefaction, epicenter, earthquake, "Loma Prieta Earthquake", "San Francisco Bay", soil, "ground motion", Embarcadero

Our transcription: Those very soft surface deposits shook very violently, and, in fact, they failed.
You had what we call a "liquefaction" where the ground simply loses the ability to support loads, and so that buildings that are sitting on that material sunk into the ground and shifted, the foundations of the building shifted.
And the reason for that is that because as the earthquake wave moved away from the epicenter, when it hit this geology, this loose unconsolidated soil, the ground motion actually was amplified or increased five times what it was maybe a mile up on solid bedrock up here.
So geologists have understood in the last ten years where to build, not only where to build, but how to build.
And we have maps showing where areas of loosely consolidated ground, and this is one of them here.
If we look all around the edge of the San Francisco Bay: downtown, the Embarcadero, the Embarcadero Freeway, south of Market -- these are small packets of liquefiable soils, and these are where we have the most documented damage in the entire San Francisco area.

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