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The PEER NGA headers for acceleration files (*.AT2) always consists of 4 lines. The 4th line format has changed multiple times over the years.
The four header lines represents the following:
1.Title: “PEER STRONG MOTION DATABASE RECORD. PROCESSING BY (PACIFIC ENGINEERING or other data provider)
2.Earthquake Information: In line 2, either of the following options might be available:
•Earthquake name; date, time and time zone; magnitude; station name; channel orientation
•Latitude and Longitude of the earthquake epicenter
3.Units: Acceleration, velocity, or displacement and units. Filter points (optional)
4.Record Metadata: NPTS (number of points) and DT (time interval between them)
Line 1 should have one of the following representations below proving that the record is provided by PEER. The following titles validates PEER records:
•“PEER NGA STRONG MOTION DATABASE”
•“PACIFIC ENGINEERING AND ANALYSIS STRONG-MOTION DATA”
•“PAIFIC ENGINEERING AND ANALYSIS STRONG-MOTION DATA”
•“PEER STRONG MOTION DATABASE”
The second and third titles are provided by "Pacific Engineering" agency.
Line 2 might be represented in two different cases as follows:
Case 1: The second line components may be in the following order:
•Earthquake Name
•Earthquake Date (might contain only year), time (optional) and time zone (optional)
•Magnitude (optional)
•Station Name
•Channel Orientation
•An example of this line would be: “DENALI 11/03/02, PS10, 047”
Note that a comma is optional to separate between each component of this line
Case 2:
•Latitude
•Longitude (optional)
Line 3 may be as follows:
•It is optional to start with the word “STATIC”
•Then should have one of the following words:
1.ACCELERATION (indicating that the record data are acceleration data)
2.VELOCITY (indicating that the record data are velocity data)
3.DISPLACEMENT (indicating that the record data are displacement data)
•TIME
•Then should have one of these words
•HISTORY
•SERIES
•IN UNITS OF
•The actual unit (capitalize)
•FILTER POINTS: HP = …. Hz LP= …. Hz (optional)
An ideal example for this line would be: “ACCELERATION TIME HISTORY IN UNITS OF G”
Line 4 discussed as follows:
•NPTS to indicate the number of data points. NPTS represents the actual number of data in the file (whether acceleration, displacement or velocity)
•DT to indicate time step, i.e. the time interval between each of the data. Note that the time step is usually in seconds.
An ideal example of this line would be: “NPTS= 5106, DT= .0100 SEC”
Each file contains single time series. The data is read horizontally, line by line. The record consists of one or more columns. Additionally, 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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