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The PEER NRC headers for acceleration files (*.AT2) consist always 7 lines.
To generate an NRC record, spectral matching is performed on a PEER record along with baseline correction. So, NRC headers consist of two parts:
1.Old header lines (contains information about the record before applying spectral matching to it)
2.Current header line (actual information concerning the given record).
Line 1: standard for all NRC records. It indicates that correction is applied on the data and states the correction method
Example: “TIME-DOMAIN CORRECTION USING BASE.FOR”.
Line 2: matches the start of the old header lines (old header of the record before the spectral matching is applied)
Example: “********OLD HEADERS FOLLOW:*********************”
Line 3: informs that this is an NRC record resulted from applying spectral matching on a PEER record
Line 4:
•Start with the word “OUTPUT” to indicate data
•Then should have one of these words
•ACCELERATION (should indicate that the data that follows are acceleration data)
•VELOCITY (should indicate that the data that follows are velocity data)
•DISPLACEMENT (should indicate that the data that follows are displacement data)
•TIME
Then should have one of these words
•HISTORY
•SERIES
•Data unit between parenthesis.
•NIT value
Example: “OUTPUT ACCELERATION TIME HISTORY (G'S): NIT = 2”
Line 5: gives details about the number of points and time step of the old record before applying spectral matching. In addition to AMAX value. The line should follow this format: “ 16384 DT = .0050 SEC , AMAX = .9094E-01 G”
Line 6: matches the end of the old header lines (old header of the record before the spectral matching is applied)
Line 7: discussed as follows:
•NPTS to indicate the number of data points after spectral matching
•The actual number of data of the current record
•DT to indicate time step
•Time interval between each of the data
•Time step unit.
•Scaled Factor Applied on the previous record to produce the new data
Example:
“NPTS= 15801, dt= .0050SEC, SCALED BY .100000E+01”
Each file contains one time series (single component as you noticed). The data is to be read horizontally, line by line. There could be one column or multiple columns. Also, number of data could differ between lines. The data is fully processed for engineering applications so the user has nothing to do but to read it. All the components for a given event and station are aligned in time (no need for a start time) and have the same number of points and duration.
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