sacread.f -- subroutines to read and write SAC-format files -- adjusted to write 6-component greens functions

sacread.f

subroutines to read and write SAC-format files -- adjusted to write 6-component greens functions. The routines provided by SAC are fine, of course, but I use a hydrid file format for greens-function files. These files contain six displacement traces rather than one, one for each independent component of the seismic moment tensor. There is a flag in the SAC header that I took over for indicating that six traces need to be read instead of one.

if(chead(145).ne.' GRN'.and.chead(145).ne.' grn') then
nword=nscan+158
nrec=(nword-1)/128+1
last=nword-128*(nrec-1)
else
print *,'reading greens functions'
nword=6*nscan+158
nrec=(nword-1)/128+1
last=nword-128*(nrec-1)
endif

The subroutines are sacread, sacout, sacread_swap and sacout_swap. The last two routines swap big-endian and little-endian data. You will be happier if you never need to swap bytes, but they are there for when you are painted into that corner.