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QuakeManager provides two methods for selecting and scaling ground motion records:
•Method 1: Select and Scale Individual Records -> Use the "GM Search Panel" to perform your search.
•Method 2: Select and Scale Suites of Records -> Use the "GM Suite Selection" tool to perform your search
When selecting individual records using the "GM Search Panel" (Method 1), the records are selected, scaled and ranked to have the best match to the target design spectrum spectral shape, on an individual basis, using the selected fitting criteria. The "GM Search Panel" tool is useful because of its extensive filtering capabilities, and the individual spectral shape fitting can be useful in some cases such as for selecting seeds for spectral matching.
One disadvantage of selecting records individually is that combining the top records (say best 7 or 11) of those records does not usually result in an optimal suite (see images below for an example). The mean (average) and dispersion (standard deviation) of the resulting suite may not be very good, since the selected records may all be biased in the same direction (higher or lower) at any particular period. The "GM Suite Selection" tool (Method 2) offers the solution to this problem. It can evaluate millions of possible solutions, each consisting of a suite of records and their scale factors, in order to find the optimal solution that minimizes error for the suite as a whole.
Once QuakeManager reports scaled records, you can modify the scale factor of individual records from the "Record Properties" pane by modifying the "SF" (Scale Factor) field.
Below are samples results from the two methods.
Note that the mean and standard deviation fit is vastly superior in the second method. However, the "Search Panel" might still be useful when the user wants to explore the database or select a preliminary suite of seeds for further processing such as spectral matching.
Table: GM Selection methods
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Method 1
GM Search Panel
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Method 2
GM Suite Selection
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Magnitude Range
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6.2 - 7.6
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6.2 - 7.6
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Distance Range
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5 - 30
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5 - 30
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Pulse Records
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Any (pulse and non-pulse)
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2 records: 0 sec < Tpulse < 3 sec
3 records: 3 sec < Tpulse < 6 sec
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Scale Factor Range
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0.25 - 3
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0.25 - 3
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Generated Records
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1760
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11 (Suite)
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Results
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Figure 1 & Figure 2
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Figure 3 & Figure 4
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Figure 1: Selected records from GM Search Panel
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Figure 2: Selected records from GM Search Panel
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Figure 3: Suite of Selected Records from GM Suite Selection
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Figure 4: Selected Records from GM Suite Selection
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