During 1989-1990, a “Blind”
Weak-Motion Test was conducted at the Turkey Flat, USA Site
Effects Test Area as part of the long-term experiment plan. For
18 months prior to the weak-motion test, the California
Geological Survey teamed with the Lawrence Livermore National
Laboratory to record weak ground motions across the Turkey Flat
array. Weak-motion sensors were co-located at each of the
strong-motion recording sites, and provided the data necessary
to conduct the blind test. The purpose of the weak-motion test
was threefold, to provide:
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A means of setting up and
testing prediction models and procedures for readiness when a
strong-motion event occurs;
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An opportunity to compare very
low strain ground motion predictions and observations with
those at high levels of strain; and,
-
A means of validating how well
dynamic soil characteristics have been estimated throughout
the test site.
Principal findings from the
weak-motion test are:
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All predictions tend to group,
and are successful in that the observed ground motions fall
within the range of prediction uncertainties. The uncertainty,
however, is large;
-
Damping in the “standard”
geotechnical model may be too low, suggesting the accuracy of
the site characterization is more important than the method
used to calculate response; and,
-
There was a tendency to
underestimate uncertainty of predictions.
Details of the weak-motion test
results may be of value in the strong-motion test, and are
available in the following publications:
(Cramer, 1995)
(Field and Jacob, 1993)
(Turkey Flat Report 6, 1991)
(Turkey Flat Report 5, 1990)
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