wiki:ShmDocMenuLocateLocateTtfit
Last modified 14 years ago Last modified on 02/05/2009 01:52:14 PM

Menu entry Locate by TTFit

Calls external program for locating a teleseismic event. This external program is part of the distribution. It makes calls to GMT plotting utilities and a PostScript interpreter (like gv, ghostview, pageview, ...), so these software utilities must be available.

The program uses travel time differences of a reference phase (in most cases P phase) and phase difference times of other phases with the reference phase (like S-P, PP-P, ScS-P, ...) for finding an optimum source location. From a given start location, usually computed before by Locate Tele, it minimizes the residuals in travel time differences.

The default algorithm used is a downhill simplex method in 2 or 3 dimensions (dimension is depending on fixed or free source depth), evaluating the least square sums of the residuals. It is possible to change the algorithm to a grid search within a rectangular area in latitude and longitude.

After selecting this menu item an xterm window pops up, offering a parameter menu. Simply enter Return to start location process.


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