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.