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:

TRUST ON|OFF
[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.
TRUST ON|OFF:	This option is used to resolve an ambiguity in converting files from SAC to CSS format. When converting the data, matching event IDs could mean the files have identical event information, or they could be an artifact of the merging of these two very different formats. When TRUST is ON, SAC is more likely to accept matching event IDs as identical event information than when TRUST is OFF, depending on the history of READ commands associated with the current data files in memory.
[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.)

DEFAULTS VALUES

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.

All commands which load data into memory have are now monitored to maintain a level of confidence in the event information when moved from the SAC data buffer to the CSS data buffer. For ADDSTACK, when the confidence is HIGH that all the data files are cosistent in the numbering of event IDs, matching event IDs are treated as having identical event information. When the confidence is LOW in ADDSTACK, matching event IDs are understood as an artifact, and new event IDs are generated for the incoming file. For more details use HELP READ.

EXAMPLES

The following examples illustrate several of the features of the Signal Stacking Module. Suppose you entered the following set of commands:

SAC> GLOBALSTACK DELAY 1.0 INCREMENT 0.03
SAC> ADDSTACK FILEA DELAY 2.0
SAC> ADDSTACK FILEB DELAY 3.0 INCREMENT 0.01 REVERSED
SAC> ADDSTACK FILEC
SAC> 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:

SAC> 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:

SAC> INCREMENTSTACK
SAC> CHANGESTACK FILEC NORMAL
SAC> 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:

SAC> DELETESTACK FILED
SAC> INCREMENTSTACK
SAC> 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.

ERRORS 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.

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