anchor.diff:      call read_srcmod_fsp(fsp_file,fsp_data,ierr)
       if (ierr.eq.0) then
           areFaultsRead = .true.
  +    else
  +        call usage('read_faults: error reading fault file in SRCMOD FSP format')
       endif
       nfaults = nfaults + fsp_data%nflt
   endif
  
positive.code:     call read_flt(flt_file,flt_data,ierr)
      if (ierr.eq.0) then
          areFaultsRead = .true.
      endif
      nfaults = nfaults + flt_data%nflt
  endif
  
negative.code:     call read_mag(mag_file,mag_data,ierr)
      if (ierr.eq.0) then
          areFaultsRead = .true.
      else
          call usage('read_faults: error reading fault file in GMT psmeca -Sa format')
      endif
  
      ! Calculate fault slip, width, and length
  