The program is written by John Ebel (Ebel and Bonjer, 1990) for moment tensor inversion for very local events. The program uses instrument-corrected amplitudes of the direct (upgoing) phases of P, SV and SH phases and makes a linear inversion for the moment tensor. The program then finds the largest double couple component of the traceless moment tensor. For more details see file invrad.txt in the INF directory.
The original program has been slightly modified in input and output to be integrated with EEV in SEISAN. The steps to get the fault plane solution are:
Select the event from EEV
|Creates the model input file for INVRAD called invrad.mod. This file is created from the STATION0.HYP file, either from the current directory or DAT.
|Creates the data input file for INVRAD called invrad.inp. This file is made from the current database file (S-file) by extracting all amplitudes associated with Pg and Sg amplitudes and converts to P, SV or SH amplitudes in microns. The depth of the event is taken from the S-file header and the estimated error is fixed to 0.1 micron.
|Runs the INVRAD program which produces the invrad.out file
|Reads the invrad.out file to get the fault plane solutions which overwrite the current fault plane solution in the S-file. If you do not want to get the current solution overwritten, put a character in column 79 on the solution, see also focmec program.
The fault plane solution can then be plotted with FOCMEC.