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Studies of liquefaction features left by prehistoric earthquakes, called paleoliquefaction or paleoseismology, can reveal information about earthquakes that occurred before records were kept or accurate measurements could be taken. [21] Soil liquefaction induced by earthquake shaking is a major contributor to urban seismic risk.
Seismic microzonation is defined as the process of subdividing a potential seismic or earthquake prone area into zones with respect to some geological and geophysical characteristics of the sites such as ground shaking, liquefaction susceptibility, landslide and rock fall hazard, earthquake-related flooding, so that seismic hazards at different locations within the area can correctly be ...
Some maps released by the USGS are shown with peak ground acceleration with a 10% probability of exceedance in 50 years, measured in Metre per second squared.For parts of the US, the National Seismic Hazard Mapping Project in 2008 resulted in seismic hazard maps showing peak acceleration (as a percentage of gravity) with a 2% probability of exceedance in 50 years.
The determination of seismic risk is the foundation for risk mitigation decision-making, a key step in risk management. Large corporations and other enterprises (e.g., local governments) analyze their 'portfolio' of properties, to determine how to best allocate limited funds for structural strengthening of buildings, or other risk reduction measures such as emergency planning.
The Seismic Hazard Mapping Act ("The Act") was enacted by the California legislature in 1990 following the Loma Prieta earthquake of 1989. The Act requires the California State Geologist to create maps delineating zones where data suggest amplified ground shaking, liquefaction, or earthquake-induced landsliding may occur ("seismic hazard zones").
The New Madrid seismic zone (NMSZ), sometimes called the New Madrid fault line (or fault zone or fault system), is a major seismic zone and a prolific source of intraplate earthquakes (earthquakes within a tectonic plate) in the Southern and Midwestern United States, stretching to the southwest from New Madrid, Missouri.
A strong earthquake on the Wasatch Fault could trigger landslides, cause mass liquefaction, and flooding of low-lying areas forming near lakes due to subsidence and tilting. The quake may also rupture the surface causing displacement of up to 20 feet (6.1 m), and severely damage gas, electric, water, communication, and transportation lifelines ...
Simplified fault map of southern California The faults of Southern California viewed to the southeast, as modeled by the Southern California Earthquake Center. Highlighted in purple are the San Andreas Fault (left) and Santa Monica Bay complex (right). The foreground is in the Santa Barbara Channel, the east-trending zone marks the Transverse Range