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The San Fernando Earthquake

In the early morning hours of February 9, 1971, the San Fernando region of Southern California was shaken by a magnitude 6.6 earthquake. Three hospitals were badly damaged, several freeway interchanges collapsed, and the Lower San Fernando Dam sat perilously close to failure, threatening to unleash its 15 million tons of water on the valley below. The shaking initiated a major failure on the upstream side of the dam, leaving only a steep slide head scarp and very marginal freeboard. Had the head scarp been slightly lower, the outflow from the reservoir would have quickly eroded the dam and flooded many communities downstream. Considering the extremely precarious situation, some 80,000 people over an 11-square-mile area were evacuated while the reservoir was emptied over a period of three to four days.

The Upper and Lower San Fernando dams have become extremely important case histories for geotechnical earthquake engineering. Due to their significance, the cases have become the subject of years of research and numerous publications. In light of the importance of the San Fernando Dam case histories and their prominence in the literature, it is important to show how GeoStudio 2007 can be used to analyze cases like these.

The purpose of the study is not to replicate what has been done by others, or to necessarily adopt the exact conditions presented by others, but to more generally illustrate the features and capabilities of GeoStudio 2007 in the context of a famous case history.

Interestingly, what became evident through the modeling process was that in order to fully understand all aspects of the dams' responses, it was necessary to not only use QUAKE/W alone, but to integrate the results with a SEEP/W seepage analysis, a SIGMA/W stress-deformation analysis, and a SLOPE/W stability analysis, as seen in the analysis tree above.

Read the whole Upper San Fernando Dam story and follow along in GeoStudio 2007 using this data file:

       Upper San Fernando Dam (16.60 MB)

Then read about the Lower San Fernando Dam and follow along with this file:

       Lower San Fernando Dam (7.48 MB)

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