ADDSTACK

SUMMARY: Add a new file to the stack file list.
SYNTAX: [A]DD[S]TACK filename [property ...]
where property is one or more of the following:
[W]EIGHT v
[DI]STANCE v
[BE]GINTIME v
[END]TIME v
[DE]LAY v [[S]ECONDS|[P]OINTS]
[I]NCREMENT v [[S]ECONDS|[P]OINTS]
[N]ORMAL
[R]EVERSE
INPUT: filename:
Name of the file to be added to the stack file list.
[W]EIGHT v:
Weighting factor for this file in the range zero to one. Each data point is multiplied by this value when the stack is summed.
[DI]STANCE v:
Station to epicenter distance in kilometers for this file. This is used to calculate dynamic time delays.
[BE]GINTIME v:
Time of the begining of the event.
[END]TIME v:
Time of the end of the event.
[DE]LAY v [[S]ECONDS|[P]OINTS]:
Static time delay to apply to file.
This delay is in either seconds or number of data points.
[I]NCREMENT v [[S]ECONDS|[P]OINTS]:
Static time delay increment for this file. This increment is in either seconds or number of data points. The static time delay is incremented by this ammount each time the incrementstack command is executed.
[N]ORMAL:
File has normal polarity.
[R]EVERSED:
File has reversed polarity. (Each data point in the signal is multiplied by -1.0 when the stack is summed.)
DEFAULT VALUE: Each file is given the global property value if no local one is entered. The default units for the DELAY and INCREMENT options is SECONDS.
DESCRIPTION: There are seven properties associated with each stack list file. They are:
  • The weighting factor.
  • The station to epicenter distance.
  • The begin time of the event.
  • The end time of the event.
  • The static time delay in either seconds or number of data points.
  • The static time delay increment in either seconds or number of data points.
  • The polarity of the file, either normal or reversed.

There is a global value associated with each of these properties. They are defined by the globalstack command. When a file is added to the stack file list, that file's properties will be set to the global value if no local value is given. The changestack command can be used to change a file's properties after it has been added to the stack file list.
EXAMPLES: The following examples illustrate several of the features of the Signal Stacking Module. Suppose you entered the following set of commands:
u: GLOBALSTACK DELAY 1.0 INCREMENT 0.03
u: ADDSTACK FILEA DELAY 2.0
u: ADDSTACK FILEB DELAY 3.0 INCREMENT 0.01 REVERSED
u: ADDSTACK FILEC
u: ADDSTACK FILED WEIGHT 0.5

The first command changes the global property values for time delay and time delay increment. The other global properties have their default values. FILEA's properties would be the global ones except for the time delay. FILEB's properties would be the global ones except for the time delay, the time delay increment, and the signal polarity. FILEC's properties would be the same as the global ones. FILED's properties would be the global ones except for the weighting factor. Now you enter:

u: SUMSTACK
 The summation is done on the four files in the stack file list: FILEA, FILEB, FILEC, and FILED. The time delays are 2.0, 3.0, 1.0, and 1.0 respectively. The polarity of FILEC is reversed. FILED's weighting in the summation is half that of the other files. Now you enter:

u: INCREMENTSTACK
u: CHANGESTACK FILEC NORMAL
u: SUMSTACK
 This stack is performed with the following delays:
2.03, 3.01, 1.03, and 1.03. The polarity of FILEC is now normal. Now you enter:
u: DELETESTACK FILED
u: INCREMENTSTACK
u: SUMSTACK
 This third stack is performed on the three files:
FILEA, FILEB, and FILEC. The delays are 2.06, 3.02, and 1.06 respectively.

ERROR MESSAGES: 5108: Maximum length of stack file list exceeded.
1306: Illegal operation on unevenly spaced file - stacking module requires evenly spaced data files. 1307: Illegal operation on spectral file 5109: Sampling intervals are not equal.
  • the sampling rates for all files in the stack file list must agree to within a given tolerance.
  • the SRCHECK command can turn this check off or change the tolerance.
  • the default check is for agreement within machine roundoff error.
WARNING MESSAGES:
HEADER CHANGES:
TYPE: Parameter-setting
FUNCTIONAL MODULE:
LIMITATIONS: The maximum number of files in the stack file list is limited to the maximum number of data files allowed by SAC.
SEE COMMANDS: GLOBALSTACK, SUMSTACK, CHANGESTACK, INCREMENTSTACK, DELETESTACK
REFERENCES:
ACKNOWLEDGMENTS:
LATEST REVISION:

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