Sight Response and Cypress Structure Collapse, Oakland, CA 1989

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Detailed Description

Retrospective interview with USGS Geophysicist Susan Hough about her early earthquake work during the 1989 Loma Prieta earthquake. The interview covers how the Cypress Structure collapse in Oakland, CA, served as a site response study for seismic research.
 

Details

Image Dimensions: 763 x 512

Date Taken:

Length: 00:01:47

Location Taken: Pasadena, CA, US

Video Credits

Susan Hough USGS Geophysicist hough@usgs.gov

Transcript

Yeah. I think there were some important lessons that came out for ground motion. So. Yeah. The “Moho [Mohorovicic discontinuity] Bounce,” the importance of that. My response. I ended up deploying portable instruments around the Nimitz Freeway and was looking to understand the ground motions where it collapsed. And the story that came  out there was that part of the double-deck freeway that collapsed had been built over bay mud, whereas another part of the double-deck freeway that had been built over older alluvial sediments had not collapsed. And so it had turned into -- I had seismometers -- I had one on the alluvial sediments where it hadn’t collapsed [and] one on the bay muds where it had and one up in the hills. And it turned into a classic site response study that just illustrated...it was known but it was early on...it was just such a clear and powerful illustration of what site response could do. We’ve known for a long time -- even early observers going back to 1906 and even before that noticed -- that shaking and damage tended to be worse where you had softer sediments like the bay muds or if you’re close to a river valley. Things tend to shake more. And we use the analogy of a bowl of Jello compared to a bowl of rocks. If you shake the Jello it will just shake more. So, we’ve known about that.