1.1.8. Loc2ssst - generate SSST corrections on a to 3D grid for NLLoc locations

Given a set of NLLoc locations, Loc2ssst generates station and phase specific, SSST corrections over a specified 3D grid and adds these corrections to the input travel-times used for NLLoc location to generate new, SSST travel-time grids.

1.1.8.1. Overview

For each station and phase in the input NLLoc locations (see LSLOCFILES), the Loc2ssst program accumulates over a specified SSST 3D grid (see LSGRID) a weighted sum of the residuals for the station and phase for each input NLLoc location. Each residual is weighted based on the distance D between the grid cell and the coresponding hypocenter using the relations:

weight = exp(-(D^2 / char_dist^2)) + weight_floor

where CharDist and WeightFloor are specified in LSPARAMS.

1.1.8.2. Running the program - Input

Synopsis: Loc2ssst InputControlFile

The Loc2ssst program takes a single argument InputControlFile which specifies the complete path and filename for an Input Control File with certain required and optional statements specifying program parameters and input/output file names and locations. See the Loc2ssst Statements section of the Input Control File for more details. Note that to run Loc2ssst the `Generic Statements section of the Input Control File must contain the ``CONTROL` and TRANS (Geographic Transformation) statements.

In addition, the Loc2ssst program requires a set of `Loc2ssst Statements in the Input Control File

1.1.8.3. Output

The calculated SSST values throughout the requested LSGRID grid are written to a new 3D Grid. The updated travel-time values throughout the requested LSOUTGRID grid are written to a new 3D Grid, these files can be used as travel-time files for subsequent NLLoc location. For a descrition of the naming convention for these grid files, see the `LSOUT statement in the Loc2ssst Statements section of the Input Control File.

1.1.8.4. Processing and Display of results

The 3D SSST and updated travel-time grids can be post-processed with the program Grid2GMT to produce a GMT command script for plotting with the GMT plotting package.