A city (or county) is not an accident but the result of coherent visions and aims

C H A P T E R   4 :   R E Q U I R E D   E L E M E N T S
   |   148
4
Useful Definitions
Alquist-Priolo Earthquake Fault Zone: A regulatory zone, delineated by the State Geologist, within which site-specific 
geologic studies are required to identify and avoid fault rupture hazards prior to subdivision of land and/or construction of most 
structures for human occupancy.
Climate Adaptation: Adjustment or preparation of natural or human systems to a new or changing environment that 
moderates harm or exploits beneficial opportunities.
Climate Mitigation (Greenhouse Gas Emissions Reductions): A human intervention to reduce the human impact 
on the climate system; it includes strategies to reduce greenhouse gas sources and emissions and enhancing greenhouse gas 
sinks. Refer to Chapter 7, Climate Change, for more information.
Critical Facility: Facilities that either (1) provide emergency services or (2) house or serve many people who would be 
injured or killed in case of disaster damage to the facility. Examples include hospitals, fire stations, police and emergency 
services facilities, utility facilities, and communications facilities.
Extreme Weather Event: In most cases, extreme weather events are defined as lying in the outermost (“most unusual”) ten 
percent of a place’s history. Analyses are available at the national and regional levels.
Fault:  A fracture or zone of closely associated fractures along which rocks on one side have been displaced with respect to those 
on the other side. A fault zone is a zone of related faults which commonly are braided, but which may be branching. A fault 
trace is the line formed by the intersection of a fault and the earth’s surface.
Active Fault: A fault that has exhibited surface displacement within Holocene time (approximately the past 11,000 years).
Potentially Active Fault: A fault that shows evidence of surface displacement during Quaternary time (the last 2 million years).
Flooding: A rise in the level of a water body or the rapid accumulation of runoff, including related mudslides and land 
subsidence, that results in the temporary inundation of land that is usually dry. Riverine flooding, coastal flooding, mud flows, 
lake flooding, alluvial fan flooding, flash flooding, levee failures, tsunamis, and fluvial stream flooding are among the many 
forms that flooding takes.
Ground Failure: Mudslide, landslide, liquefaction or soil compaction.
Hazardous Building: A building that may be hazardous to life in the event of an earthquake because of partial or complete 
collapse. Hazardous buildings may include:
(1)  Those constructed prior to the adoption and enforcement of local codes requiring earthquake resistant building design.
(2)  Those constructed of unreinforced masonry.
(3)  Those which exhibit any of the following characteristics:

---

C H A P T E R   4 :   R E Q U I R E D   E L E M E N T S
   |   149
4
•  exterior parapets or ornamentation which may fall on passersby
•  exterior walls that are not anchored to the floors, roof, or foundation 
•  sheeting on roofs or floors incapable of withstanding lateral loads
•  large openings in walls that may cause damage from torsional forces
•  lack of an effective system to resist lateral forces
•  non-ductile concrete frame construction
Hazardous Material: An injurious substance, including pesticides, herbicides, toxic metals and chemicals, liquefied natural 
gas, explosives, volatile chemicals, and nuclear fuels.
Hazard Mitigation: Sustained action taken to reduce or eliminate long-term risk to people and their property from hazards 
and their effects.
Landslide: A general term for a falling, sliding, or flowing mass of soil, rocks, water, and debris. Includes mudslides, debris 
flows, and debris torrents.
Liquefaction: A process by which water-saturated granular soils transform from a solid to a liquid state during strong 
ground shaking.
Maladaptation: Any changes in natural or human systems that inadvertently increase vulnerability to climatic stimuli; an 
adaptation that does not succeed in reducing vulnerability but increases it instead.
Natural Infrastructure: The preservation or restoration of ecological systems, or utilization of engineered systems that use 
ecological processes, to increase resiliency to climate change, manage other environmental hazards, or both. This may include, 
but is not limited to, floodplain and wetlands restoration or preservation, combining levees with restored natural systems to 
reduce flood risk, and urban tree planting to mitigate high heat days.
Peakload Water Supply: The supply of water available to meet both domestic water and fire fighting needs during the 
particular season and time of day when domestic water demand on a water system is at its peak.
Resilience: The ability of a social or ecological system to absorb disturbances while retaining the same basic structure and 
ways of functioning, the capacity for self-organization, and the capacity to adapt to stress and change.
Seiche: An earthquake-induced wave in a lake, reservoir, or harbor.
Seismic Hazard Zone: A regulatory zone, delineated by the State Geologist, within which site-specific geologic, soils, and 
foundation engineering studies are required to identify and avoid earthquake-caused ground-failure hazards, or selected other 
earthquake hazards, prior to subdivision of land and for construction of most structures for human occupancy.
Storm surge: An abnormal rise of water generated by a storm, over and above the predicted astronomical tides.

---