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Surface motion map for a hypothetical earthquake on the northern portion of the Hayward Fault Zone and its presumed northern extension, the Rodgers Creek Fault Zone. A seismic hazard is the probability that an earthquake will occur in a given geographic area, within a given window of time, and with ground motion intensity exceeding a given threshold.
Ground motion hazard map for Hawaii, based on a 2% probability of exceeding 0.2 second spectral acceleration at 5 Hz in 50 years. Spectral acceleration (SA) is a unit measured in g (the acceleration due to Earth's gravity, equivalent to g-force) that describes the maximum acceleration in an earthquake on an object – specifically a damped, harmonic oscillator moving in one physical dimension.
Global components will provide preliminary data on a global scale, but on a local scale, regional and national programmes will provide more detailed and reliable data. One Global component was the Global GMPEs project that proposed a set of ground motion prediction equations for use when calculating seismic hazard. [4]
It is often used within earthquake engineering (including seismic building codes) and it is commonly plotted on seismic hazard maps. [6] In an earthquake, damage to buildings and infrastructure is related more closely to ground motion, of which PGA is a measure, rather than the magnitude of the earthquake itself.
Ground motion is typically measured in three components: west-to-east, south-to-north, and vertical. Recordings from multiple seismometers can be combined to form a detailed model of the ground motion. This is known as a seismograph, and it can be used to study the spatial and temporal characteristics of the ground motion.
Different hazard maps have different uses. For instance, the hazard map created by the Rizal Geological Survey is used by Rizalian insurance agencies in order to properly adjust insurance for people living in hazardous areas. [2] Hazard maps created for flooding are also used in insurance rate adjustments. [3] Hazard maps can also be useful in ...
According to the USGS, "ShakeMaps provide near-real-time maps of ground motion and shaking intensity following significant earthquakes. These maps are used by federal, state, and local organizations, both public and private, for post-earthquake response and recovery, public and scientific information, as well as for preparedness exercises and ...
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 ...