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Resources in Spanish

Geologic and Seismic Hazards

Consistent with the 2015 Ventura County Multi-Hazard Mitigation Plan, this section focuses on geologic and seismic hazards in Ventura County, which include the following areas of concern:

  • Earthquake Faults
  • Seismic Hazards -Liquefaction/Earthquake Induced Landslides
  • Landslides
  • Soil Erosion
  • Expansive Soils
  • Seiche
  • Subsidence

It is important to note that there are several earthquake faults in the county that have a status of “Active” or “Potentially Active,” according to the California Geological Survey’s Seismic Hazards (Assessment and Mapping) Program. Areas throughout the county are also susceptible to liquefaction, with the most vulnerable locations being along the Santa Clara River and the Oxnard Plain. These areas are described and illustrated on figures in Section 11.1, “Geologic and Seismic Hazards,” of the Background Report.

Goal: HAZ-4

To minimize the risk of loss of life, injury, collapse of habitable structures, and economic and social dislocations resulting from geologic and seismic hazards.

The County shall not allow development in mapped landslide/debris flow hazard areas unless a geologic and geotechnical engineering investigation is performed and appropriate and sufficient safeguards, based on this investigation, are incorporated into the project design.
RDR

The County shall consider Seiche Hazard Areas during the preparation of regional and area plans and special studies and be used to guide future investigations of the hazard.
RDR

The County should, where feasible, require that land in Earthquake Fault Zones and potentially Holocene active fault areas be designated Open Space or Agriculture on the General Land Use Diagram.
RDR

Structural design of buildings and other structures shall recognize the potential for subsidence and hydroconsolidation and provide mitigation recommendations for structures that may be affected.
RDR

The County shall require that potential ground surface subsidence be evaluated prior to approval of new oil, gas, water or other extraction well drilling permits and appropriate and sufficient safeguards are incorporated into the project design and facility operation.
RDR

The County shall not allow development in potential seiche hazard areas unless a geotechnical engineering investigation is performed and appropriate and sufficient safeguards, based on this investigation, are incorporated into the project design.
RDR

The County shall not allow habitable structures or individual sewage disposal systems to be placed on or in expansive soils unless suitable and appropriate safeguards are incorporated into the project design to prevent adverse effects.
RDR

Drainage plans that direct runoff and drainage away from slopes shall be required for construction in hillside areas.
RDR

The County shall not allow alteration of land in landslide/debris flow hazard areas, including concentration of water through drainage, irrigation or septic systems, removal of vegetative cover, and undercutting of the bases of slopes or other grading activity unless demonstrated by geologic, geotechnical, and civil engineering analysis that the project will not increase the landslide/debris flow hazard.
RDR

The County shall prohibit new structures for human occupancy and subdivisions that contemplate the eventual construction of structures for human occupancy in Earthquake Fault Zones unless a geologic investigation is performed to delineate any hazard of surface fault rupture and appropriate and sufficient safeguards, based on this investigation, are incorporated into the project design.
RDR
EJ

The County shall require geotechnical reports that demonstrate adequate slope stability and construction methods for building and road construction on slopes greater than 50 percent pursuant to the California Building Code Appendix J Section 108.6.
RDR

The County shall not allow development of habitable structures or hazardous materials storage facilities within areas prone to the effects of strong ground shaking, such as liquefaction, landslides, or other ground failures, unless a geotechnical engineering investigation is performed and appropriate and sufficient safeguards, based on this investigation, are incorporated into the project design.
RDR

The County shall require, as necessary, the use of soil stabilization methods on graded areas to reduce the potential for erosion, particularly during the construction phase.
RDR

The County shall require discretionary development to minimize the removal of vegetation to protect against soil erosion, rockslides, and landslides.
SO

The County shall require discretionary development be designed to prevent soil erosion and downstream sedimentation and pollution.
RDR

The County shall require discretionary development below rocky outcrops to evaluate and mitigate potential rockfall hazards including but not limited to by avoiding placement of structures that could be impacted by rockfall hazards, rock removal, rock anchoring, walls, fence barriers, or other similar systems.
RDR

The County shall require that all structures designed for human occupancy incorporate engineering measures to reduce the risk of and mitigate against collapse from ground shaking.
RDR

The County shall require that linear projects, including roads, streets, highways, utility conduits, water transmission facilities, and oil and gas pipelines, avoid intersecting active faults to the extent possible. When such locations are unavoidable, the project design shall include measures to minimize the effects of any fault movement.
RDR
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