The SAC (Seismic Analysis Code) files are named using the following convention:
YYYYJJJHHMMSS.SS.STAT.CHA, where the fields have the following meanings:
| YYYY | Year |
| JJJ | Julian Day |
| HH | Hour |
| MM | Minute |
| SS.SS | Seconds.Fractional-Seconds |
| STAT | Station (three or four characters) |
| CHA | Channel |
The time (YYYYJJJHHMMSS.SS) is referred to the time when the recording starts. For example the file 2007335070000.00.ACOM.HHZ refers to station ACOM, channel HHZ and the record begins on December 12, 2007 at 07:00:00.
The SAC software (see the SAC User's Guide) has functions for reading
and processing these waveforms.
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The miniSEED (Standard for the Exchange of Earthquake Data) file names are named using the following convention:
STAT.CHA.YYYY.JJJ.HH.MM.SS, where the fields have the following meanings:
| STAT | Station (three or four characters) |
| CHA | Channel |
| YYYY | Year |
| JJJ | Julian Day |
| HH | Hour |
| MM | Minute |
| SS | Seconds |
| STAT | Station (three or four characters) |
The time YYYY.JJJ.HH.MM.SS refers to the time when the recording starts. For example the file ACOM.HHZ.2007.335.07.00.00 refers to station ACOM, channel HHZ and the record starts December 12, 2007 at 07:00:00.
The miniSEED files can be read, decompressed and converted in other formats (SAC, AH, CSS, ...) using the IRIS software rdseed. After installation, the software runs on your terminal and you must use d option and choose the output format; you can also select other preferences, the default is typed in brackets:
>rdseedRdseed reads miniseed file named 'inputfile' and convert it to other formats (SAC, AH, ...) with the options for selecting
channel, station, start time and end time.
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In folder 'dataless' you can find the instrumental corrections in dataless format. More details can be found at the IRIS web site These files can be converted in other formats (RESP, Poles and Zeros, ...) using rdseed with the apposite options:
>rdseedThe response files ('.RESP') contains the whole history of the station with the corrections related to all instruments that recorded in the selected site from the starting date of the station to nowadays; the response files are divided for channel. The file names are named using the following convention:
RESP.NT.STAT..CHA
where the fields have the following meanings:
| NT | Network |
| STAT | Station (three or four characters) |
| CHA | Channel |
The PZ (Poles and Zeros) files are divided for channel and different instrument generates different PZ files. The file names are named using the following convention:
SAC_PZs_NT_STAT_CHA__YYYY.JJJ.HH.MM.SS.SSSS__ YYYY.JJJ.HH.MM.SS.SSSS
where the fields have the following meanings:
| NT | Network |
| STAT | Station (three or four characters) |
| CHA | Channel |
| YYYY | Year |
| JJJ | Julian Day |
| HH | Hour |
| MM | Minute |
| SS.SSSS | Seconds.Fractional-Seconds |
The first time refers to starting time for instrument, the second time refers to end time for the same instrument;
if the instrument is operative end time is 99999.999.99.99.99.99999.
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In this paragraph we describe the procedure to remove the instrumental response using SAC software and SAC formats; it is worth to evidence that the correction with the PZ files gives the results in displacement so you must differentiate the seismograms if you want velocity or acceleration. The procedure is:
| >sac | ... open the SAC software |
| SAC>read filesac | ... read the recording file |
| SAC>rmean | ... remove the mean |
| SAC>rtrend | ... remove the trend |
| SAC>transfer from polezero S pzfile | ... remove the instrumental response |
| SAC>dif differentiates | ... if you want velocity |
| SAC>dif differentiates | ... if you want acceleration |
| SAC>bandpass butter corner fmin fmax npoles n passes p | ... filter the signal |
| SAC>write newfilesac | ... save new corrected file |
| SAC>quit | ... quit the SAC software |