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The left column
compares histograms of the log of predicted-to-observed PGV ratios for the
Northridge earthquake. The predicted
ground motions were computed using rock Green’s functions and site
corrections derived empirically. In
this case we used the QTM site corrections employed by the southern
California TriNet ShakeMap. The histograms compare the performance for
quaternary, tertiary and Mesozoic sites.
The red bars show that stations located in the Los Angeles basin are
systematically under predicted by factors of 2-3. Slide 14 illustrates the predicted-to-observed amplitude ratios
in map view.
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