Seismic Hazard

Title 24 of the California Code of Regulations, also known as the California Building Standards Code, sets forth the minimum requirements for the design and construction of buildings and structures in the state. Additionally, the Humboldt County Code (HCC) Chapter 6 Geologic Hazards regulations ensure that risks to life and property in moderate and high geologic hazard areas shall be minimized. These standards are intended to ensure the safety and welfare of the public by regulating the construction of buildings to be more resilient in the face of seismic events.

Here's a brief overview of how Title 24 and related regulations address seismic hazards:

  1. Seismic Design Categories: Based on the geographic location, soil type, structure type, and the seismic risk of an area, buildings are assigned to a Seismic Design Category (SDC). Each category has specific requirements for the structural design and construction of the building to ensure that it can withstand the anticipated ground motions from an earthquake.
  2. Structural Requirements: Title 24 includes various provisions for the structural design and construction of buildings, such as detailing the required strength and ductility of building materials, as well as specific reinforcement requirements for elements like walls, columns, and foundations. These requirements help to ensure that buildings are more likely to remain standing and minimize the risk of collapse during an earthquake. Depending on the buildings assigned SDC and the complexity of the proposed structure you may be required to submit Structural Calculations from a California licensed engineer (see Construction Documents).
  3. Nonstructural Components:In addition to the structural requirements, Title 24 addresses the design and installation of nonstructural building components, such as plumbing, electrical, and mechanical systems, as well as architectural elements like ceilings and partitions. Proper installation of these components can help prevent damage and reduce hazards during an earthquake. See below.
    • Anchorage of Appliances CMC §303.4 – Appliances designed to be fixed in position shall be securely fastened in place in accordance with the manufacturer's installation instructions. Supports for appliances shall be designed and constructed to sustain vertical and horizontal loads within the stress limitations specified in the building code.
    • Water Heater Seismic Provisions CPC §507.2 – Water heaters shall be anchored or strapped to resist horizontal displacement due to earthquake motion. Strapping shall be at points within the upper one third (1/3) and lower one-third (1/3) of its vertical dimensions. At the lower point, a minimum distance of four (4) inches (102 mm) shall be maintained above the controls with the strapping.
    • Masonry Chimneys Seismic Reinforcing CRC §R1003.3 – Masonry or concrete chimneys shall be anchored, supported, and reinforced.
  4. Geotechnical Investigation: For certain types of developments, a geotechnical soils report may be required (see Soils Report Calculator and HCC 336-5). Whether or not a geotechnical soils report is required will ultimately be at the discretion of your inspector at the presite inspection (see Inspections). A soils report will assess the soil conditions and potential for liquefaction or landslides, which can significantly impact a building during an earthquake. The findings of this investigation will inform the building's design and construction.