examples of predicted PGV for the Landers and Northridge earthquakes, and can
be directly compared to the TriNet maps of slide 5. The contours are in cm/s and the red numbers show the values
recorded at local strong motion stations.
The contour maps were constructed from predicted values only at the
locations of the actual stations, although it is possible to calculate PGV at
points where there are no stations.
The lower panels compare the data (red circles) to predictions (black
squares) as a function of distance.
The model predictions are found to describe the overall attenuation
quite well however there are deviations due to unaccounted for Earth
structure such as Los Angeles Basin in the Landers comparison.
regions of strong shaking (PGV greater than 10 cm/s) compare very well
between the observed TriNet maps (slide 5) and the predicted maps
(above). The predicted map for
Landers tends to over estimate the value at LUC which is in part due to the
methodology and in part due to an artifact of our simple single plane model
for Landers in which the station is located only 200m from the fault when it
should be located approximately 3 km away in reality. This is a short coming of the method
however as we will show later in the generation of combined data/model maps
it is a problem that can be circumvented.
The Northridge map (above) is also found to agree well with the TriNet
map (slide 5) in terms of the area of the PGV greater than 10 cm/s and the
fact that the strongest ground motions are located at the northern edge of
the San Fernando Valley and to the north.