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In response to
"it's derived somehow from pga (peak ground acceleration). -- nm"
by
loosilu
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here.
Posted by
loosilu (aka loosilu2)
Jan 4 '13, 13:58
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Probabilistic ground motion maps depict earthquake hazard by showing, by contour values, the earthquake ground motions (of a particular frequency) that have a common given probability of being exceeded in 50 years (and other time periods).The ground motions being considered at a given location are those from all future possible earthquake magnitudes at all possible distances from that location. The ground motion coming from a particular magnitude and distance is assigned an annual probability equal to the annual probability of occurrence of the causative magnitude and distance.
The method assumes a reasonable future catalog of earthquakes, based upon historical earthquake locations and geological information on the recurrence rate of fault ruptures.When all the possible earthquakes and magnitudes have been considered, one can find a ground motion value such that the annual rate of its being exceeded has a certain value. Hence, on a given map, for a given probability of exceedance, PE, locations shaken more frequently, will have larger ground motions.
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