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GMEG - Geology, Minerals, Energy, & Geophysics Science Center

Seismic Hazards in the Sacramento Delta


Issue / Impacts / Project Objectives / Staff

Project objectives:

  • Increase our understanding of the seismic sources that could affect the Delta:
    • 3-D mapping of blind faults and adjacent stratigraphic horizons in the Delta region to address parameters such as fault area (related to maximum magnitude) and slip rate.
    • Increased understanding of seismic parameters on the easternmost San Andreas System fault (Greenville, Diablo, Concord-Green Valley Faults).
  • Model scenario-based seismic shaking:
    • Develop a 3-D seismic velocity model based on a detailed 3-D geologic map and unit-depth-velocity relations.
    • Develop a suite of 3-D wave-propagation models based on realistic scenario earthquakes, similar to the models developed for the San Andreas and Hayward Faults.
    • Develop a technique to account for the unusually thick low-velocity layer near the surface related to accumulation of peat in the Delta.

Strategy and Approach:

  1. Create a 3-D geologic map of the Delta and surrounding regions. Analyze for seismic source parameters.
  2. Create a 3-D seismic velocity model of the Delta region.
  3. Paleoseismic investigation of the Greenville, Mount Diablo, Concord-Green Valley Faults.
  4. Assess the completeness of the surficial geologic maps and geotechnical characteristics of the levees in the Delta.
  5. Maintain the broadband seismic deployment in the Delta: use the seismic data to estimate velocity structure and to simulate ground motions for large regional earthquakes.
  6. Calculate synthetic ground motions in the Delta for a set of scenario earthquakes in the East Bay and Delta.

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