|
Pathway 1 (shown
below in green) is the current methodology of probabilistic seismic
hazard analysis (PSHA), which combines an earthquake forecast model
with attenuation relationships to provide probabilistic estimates
of intensity measures. The latter might include the peak ground
acceleration (PGA), peak ground velocity (PGV), or the response
spectral densities at specified frequencies. The earthquake forecast
comprises a set of earthquake scenarios, each described by a magnitude,
a location, and the probability that the scenario will occur by
some future date (e.g., a Poisson distribution). The attenuation
relationship is a relatively simple analytical expression that relates
each earthquake scenario to the intensity of shaking (e.g., PGA)
at each site of interest; it usually accounts for the local geologic
conditions at each site (e.g., sediment sites tend to shake more
than rock sites). The analysis determines the intensity that will
be exceeded at some specified probability over a fixed period of
time (e.g., PGA with a10% probability of exceedance during the 50-year
life span of a building). The results are often presented as hazard
maps, and engineers use these maps to design buildings, emergency
preparedness officials use them for planning purposes, and insurance
companies use them to estimate potential losses.
SCEC/CME Computational
Pathway Diagram:
|
