• Antelope Release 5.5 Mac OS X 10.8.5 2015-04-21

 

NAME

xcoravg - average redundant arrivals in dbxcor source array processing

SYNOPSIS

xcoravg db [-u -v -pf pffile]

SUPPORT


Contributed code: NO BRTT support.
THIS PIECE OF SOFTWARE WAS CONTRIBUTED BY THE ANTELOPE USER COMMUNITY. BRTT DISCLAIMS ALL OWNERSHIP, LIABILITY, AND SUPPORT FOR THIS PIECE OF SOFTWARE.

FOR HELP WITH THIS PIECE OF SOFTWARE, PLEASE CONTACT THE CONTRIBUTING AUTHOR.

DESCRIPTION

This program is a companion to the dbxcor (3) program when it is run in source array processing mode. Source array processing is an alternative to cluster style cross correlation of local events. Instead of correlating all pairs dbxcor allows processing of ensembles of events from a common source region. The groups, however, are rarely orthogonal so it is necessary to resolve duplicate arrival estimates when the same seismogram is correlated with two groups of events. This program uses a simple averaging method. This is not theoretically correct, but is an approximation that will work reasonably well if groups do not overlap too drastically. The exact solution is a generalization of the method commonly used for pairs of events to a form that is virtually identical to that used in seismic reflection processing in what is called surface consistent static estimates. I (GLP) have not yet implemented such a procedure, however, so for now this is the only way to resolve redundant arrival estimates. In fact, running this program is currently the only way to transfer the output of dbxcor to the master arrival table.

The program has only one required parameter of the database name db. Note, however, that the program will look for extension tables special to dbxcor when run in source array processing mode. The main required table is one called xsaa (intended to be mnemonic for xcor source array analysis).

OPTIONS

PARAMETER FILE

By default the program sets all deltim attributes in arrivals it computes to a fixed constant defined by the parameter arrival_deltim. Set the boolean set_deltim_in_arrival to false to retain the deltim of the original arrival table entry for each pick being changes.

BUGS AND CAVEATS

This is a relatively crude program that has not been extensively exercised. Proceed with caution and make sure you always retain an original arrival table before running this program. As noted in the description the algorithm used to estimate each new arrival is an approximation whose validity has not been thoroughly investigated.

AUTHOR

Prof. Gary L. Pavlis
Department of Geological Sciences
Indiana University
pavlis@indiana.edu


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