ESP 179- Winter 2012       Geology and Soils       January 24, 2012   Instructor: Trevor Macenski
Outline Review CEQA Checklist Questions Seismic Hazards in CA Alquist-Priolo Earthquake Fault Zoning Act Seismic Hazar...
Geology and Soils Appendix G Checklist: Geology and Soils   Expose people or structures to substantial adverse effects  ...
Appendix G: Checklist Questions                  Projects that have large
Appendix G: Checklist Questions
Seismic Hazards Pose a substantial danger to property and  human safety. Seismic hazards present in California  include:...
Fault Rupture  Fault rupture is a seismic hazard that   affects structures sited above an   active fault.  The hazard fr...
Ground Shaking Ground shaking depends on several  variables:   Earthquake magnitude   Epicenter distance   Local geolo...
Richter vs. MMI Richter Scale   Measurement comparison between earthquakes   Evaluates magnitude used for scientific co...
Richter vs. MMI Modified Mercalli Intensity (MMI)   Scale provides a useful qualitative assessment   of ground shaking....
Alquist-Priolo EarthquakeFault Zoning Act Passed in 1972 Intent: to mitigate the hazard of surface  faulting to structur...
Alquist-Priolo Cont. Requires the State Geologist to establish  regulatory zones (known as Earthquake Fault  Zones) aroun...
Seismic Hazards Mapping Act Passed in 1990 Intent: Directs the Department of  Conservation, California Geological Survey...
SHMA Cont. Geologists in the Seismic Hazard Zonation  Program gather existing geological, geophysical  and geotechnical: ...
Ground Failure Ground failure includes:   Liquefaction   Liquefaction-induced phenomena:     Lateral spreading     Lu...
Liquefaction Liquefaction is a process by which sediments below the  water table temporarily lose strength during an eart...
Lateral Spreading and Lurching Lateral spreading   is lateral ground movement, with    some vertical component, as a res...
Landslide Hazard Mapping Act Produced from 1986 through 1995, as  directed by the now-repealed Landslide  Hazard Mapping ...
Landslides Categorized as either 1) rock, 2) soil, or 3)  rock and soil. Rock= refers to hard or firm bedrock that  was ...
Landslide Classification 1) Falls: Masses of soil or rock that dislodge from steep  slopes and free-fall, bounce, or roll...
Hazardous Minerals of CA Asbestos-Inhalation of asbestos fibers may  cause cancer.   Most commonly, asbestos occurrences...
Sample EIR Discussion
Significant Geology and SoilImpacts? What are a few types of projects?   Residential project close to a fault   Natural...
Questions?  Thank You
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January 24 ESP 179 GEO& Soils

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January 24 ESP 179 GEO& Soils

  1. 1. ESP 179- Winter 2012 Geology and Soils January 24, 2012 Instructor: Trevor Macenski
  2. 2. Outline Review CEQA Checklist Questions Seismic Hazards in CA Alquist-Priolo Earthquake Fault Zoning Act Seismic Hazards Mapping Act Common Geologic Hazards Impact Analysis Approach Sample Discussion and Analysis
  3. 3. Geology and Soils Appendix G Checklist: Geology and Soils  Expose people or structures to substantial adverse effects  Alquist-Priolo Fault Zone  Seismic ground Shaking  Ground failure/Liquefaction  Landslides  Loss of top soil  Lateral Spreading  Expansive Soils  Soils and Septic System
  4. 4. Appendix G: Checklist Questions Projects that have large
  5. 5. Appendix G: Checklist Questions
  6. 6. Seismic Hazards Pose a substantial danger to property and human safety. Seismic hazards present in California include:  Ground rupture along faults  Strong seismic shaking  Liquefaction, Lateral Spreading, Lurching  Landsliding  Slope failure  Hazardous Minerals  Tunamis
  7. 7. Fault Rupture  Fault rupture is a seismic hazard that affects structures sited above an active fault.  The hazard from fault rupture is the movement of the ground surface along a fault during an earthquake.  Creep= Slower moving fault action  Earthquakes-  Strike-slip  Normal  ThrustInfrastructure often can’t handle Creep or Earthquakes
  8. 8. Ground Shaking Ground shaking depends on several variables:  Earthquake magnitude  Epicenter distance  Local geology and Soils Thickness  Seismic wave-propagation properties of unconsolidated  Materials  Groundwater conditions  Topographic setting Sample Modeling
  9. 9. Richter vs. MMI Richter Scale  Measurement comparison between earthquakes  Evaluates magnitude used for scientific comparison  Only accounts for the actual slip that is generated Actual damage= Propagation of seismic or ground waves as a result of initial failure Loose materials tend to amplify ground waves, while hard rock can quickly attenuate them, causing little damage to overlying structures.
  10. 10. Richter vs. MMI Modified Mercalli Intensity (MMI)  Scale provides a useful qualitative assessment of ground shaking. The MMI Scale is a 12-point scale of earthquake intensity:  Local effects experienced by people  Structures  Earth materials. Each succeeding step on the scale describes a progressively greater amount of damage at a given point of observation.
  11. 11. Alquist-Priolo EarthquakeFault Zoning Act Passed in 1972 Intent: to mitigate the hazard of surface faulting to structures for human occupancy Purpose: Direct result of the 1971 San Fernando Earthquake  Extensive surface fault ruptures that damaged numerous homes, commercial buildings, and other structures.
  12. 12. Alquist-Priolo Cont. Requires the State Geologist to establish regulatory zones (known as Earthquake Fault Zones) around the surface traces of active faults and to issue appropriate maps. The maps are distributed to all affected cities, counties, and state agencies for their use in planning and controlling new or renewed construction. If an active fault is found, a structure for human occupancy cannot be placed over the trace of the fault and must be set back from the fault (generally 50 feet). Project will require site specific geotech mitigation
  13. 13. Seismic Hazards Mapping Act Passed in 1990 Intent: Directs the Department of Conservation, California Geological Survey to identify and map areas prone to liquefaction, earthquake-induced landslides and amplified ground shaking. Purpose: The SHMA was passed by the legislature following the 1989 Loma Prieta earthquake.
  14. 14. SHMA Cont. Geologists in the Seismic Hazard Zonation Program gather existing geological, geophysical and geotechnical:  Produce the Seismic Hazard Zone Maps.  Designate as Zones of Required Investigation (ZORI)  Prone to liquefaction and earthquake–induced landslides. The SHMA requires site-specific geotechnical investigations within ZORI’s  To identify and evaluate seismic hazards and formulate mitigation measures prior to permitting
  15. 15. Ground Failure Ground failure includes:  Liquefaction  Liquefaction-induced phenomena: Lateral spreading Lurching
  16. 16. Liquefaction Liquefaction is a process by which sediments below the water table temporarily lose strength during an earthquake and behave as a viscous liquid rather than a solid. Liquefaction is restricted to certain geologic and hydrologic environments, primarily recently deposited sand and silt in areas with high groundwater levels. The process of liquefaction involves seismic waves passing through saturated granular layers, distorting the granular structure and causing the particles to collapse. This causes the granular layer to behave temporarily as a viscous liquid rather than a solid, resulting in liquefaction. USGS has maps to identify areas: MAP
  17. 17. Lateral Spreading and Lurching Lateral spreading  is lateral ground movement, with some vertical component, as a result of liquefaction.  The soil rides on top of the liquefied layer Lurching  is the movement of the ground surface toward an open face when the soil liquefies. An open face could be a graded slope, stream bank, canal face, gully, or other similar feature.
  18. 18. Landslide Hazard Mapping Act Produced from 1986 through 1995, as directed by the now-repealed Landslide Hazard Mapping Act. Online Resource: MAPs
  19. 19. Landslides Categorized as either 1) rock, 2) soil, or 3) rock and soil. Rock= refers to hard or firm bedrock that was intact and in place prior to slope movement. Soil=means unconsolidated particles or poorly cemented rock or aggregates.  Soil is also distinguished further on the basis of texture: Debris (coarse fragments) Earth (fine fragments)
  20. 20. Landslide Classification 1) Falls: Masses of soil or rock that dislodge from steep slopes and free-fall, bounce, or roll downslope. 2) Topples: Move by the forward pivoting of a mass around an axis below the displaced mass. 3) Spreads: Commonly induced by liquefaction of material in an earthquake, move by horizontal extension and shear or tensile fractures. 4) Slides: Displace masses of material along one or more discrete planes.  Rotational: Sliding the slide plane is curved and the mass rotates backwards around an axis parallel to the slope  Translational: Sliding the failure surface is more or less planar and the mass moves parallel to the ground surface 5) Flows : mobilize as a deforming, viscous mass without a discrete failure plane.
  21. 21. Hazardous Minerals of CA Asbestos-Inhalation of asbestos fibers may cause cancer.  Most commonly, asbestos occurrences are associated with serpentinite and partially serpentinized ultramafic rocks. Mercury- Mercury from historic mercury mines or gold mines has entered a number of watersheds in California. Radon- Gas is a naturally-occurring, radioactive gas that is invisible and odorless. It forms from the radioactive decay of small amounts of uranium and thorium naturally present in rocks and soils.
  22. 22. Sample EIR Discussion
  23. 23. Significant Geology and SoilImpacts? What are a few types of projects?  Residential project close to a fault  Natural Gas Pipeline close to fault  Oceanfront Development  Other?
  24. 24. Questions? Thank You

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