Wednesday, November 11, 2009

Disclaimer and Free Software Statement

The computer codes that I post to the JParkCodes blog are provided as free software.

You can redistribute the codes and/or modify them under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of


GNU General Public License for more details.

You may obtain a copy of the GNU General Public License

along with these program at the link above. If not active, see

Thursday, November 5, 2009

grn_propzon.f -- code to compute greensfunctions for zonally-symmetric earth models.

click title to see Google Drive directory JParkCodes

c program grn_propzon -- three-component gfcts
c for zonally-symmetric earth models
c f77 -o /Users/jjpark/bin/grn_propzon grn_propzon.f /Users/jjpark/Ritz/jlib.a
c xf77 -o /Users/jjpark/bin/grn_propzon grn_propzon.f /Users/jjpark/Plotxy/plotlib.a /Users/jjpark/Ritz/jlib.a
c the code reads a special compressed hybrid eigenvector file
c produced by program propzon.
c This routine does a coupling calculation in frequency intervals, storing all
c hybrid singlets in a central interval of the coupling bandwidth.
c the trick is to read the coupling partners for each block, calculate
c receiver and source scalars, then read the eigenvectors one by one.

As with the spherical-earth greensfunction code, this code creates waveforms for a source-receiver geometry stored in the SAC header of a common seismic data file. Unlike the sph-earth code, the output is tied to geographic coordinates (east/north), not radial/transverse. The code syndat.f takes the greensfunctions and sums with a source mechanism to form synthetic seismograms.

sample input:

0 --> # of point to compute, 0=same number as in the data file
ffc.lhz --> data file for source-receiver-station info
gzB0.05_ffc --> filename root for greenfct files, code will append ".lhz" ".lhe" ".lhn"
../Vary/ymodel10_B0.05.zon20 --> input file of hybrid singlets, computed with zonchn.f
/Users/jjpark/Mineos/Models/premiss --> earth model (isotropic PREM in this case)
/Users/jjpark/Mineos/sphnl --> N,L file of spheroidal mode parameters
/Users/jjpark/Mineos/sphe --> direct-access Fortran file of spheroidal modal eigenfunctions
/Users/jjpark/Mineos/tornl --> N,L file of toroidal mode parameters
/Users/jjpark/Mineos/tore --> direct-access Fortran file of toroidal modal eigenfunctions

zonsubs.f -- the subroutines needed to make zonchn.f work

click title to see Google Drive directory JParkCodes

This set of subroutines serves zonchn.f, see the earlier post. The first routine yread reads the parameters of the zonally symmetric model example file here

1 1 ! useless parameters for option I never implemented
0.0 0.05 0.0 0.0 0.0 A,B,C,D,E relative perts to the Backus anisotropy parameters for azim anisotropy with an axis of symmetry.
1 152 181 ! lithosphere in model premiss
10 ! k=10 wavenumber on the sphere

Some relevant passages of code are the following:

c angint is original theta integral for cos{(l+1/2)\theta} structure
c angint2 uses 3-j tricks to speed up the calculation
c angint2X uses 3-j tricks, but for either spherical cap or equatorial band
c angint2XX is s=20 expansion of equatorial band model, no discontinuites
c call angint2(l1,l2,ls(kii),angi)
call angint2X(l1,l2,ls(kii),angi)
c call angint2XX(l1,l2,ls(kii),angi)

c combine isotropic and anisotropic parts, use b,c,e & a,d
c **************************** note that code can incorporate only
c ***************************** one aspherical wavenumber, despite
c ***************************** the do loops
c NOTE: some lines have alternate versions for phi and theta as axis of sym
if(ick.eq.3) then ! tor-tor
do j=1,nom
x +angi(3,j)*(c*ysc(1,1)+e*ysc(2,1)) ! anisotropic
c x -angi(5,j)*e*ysc(3,1)-angi(6,j)*c*ysc(1,1) ! anisotropic-phi
x +angi(5,j)*e*ysc(3,1)-angi(6,j)*c*ysc(1,1) ! anisotropic-theta
x +angi(2,j)*d*ysc(3,1)+angi(3,j)*d*ysc(2,1) ! isotropic
end do

comment or uncomment the phi and theta terms as you wish, but dont comment both or uncomment both.

zonchn.f -- code to couple free oscillations for a zonally symmetric earth model

click title to see Google Drive directory JParkCodes

zonchn.f is a code to couple together free oscillations of Earth for a set of highly restricted aspherical earth models. The models are zonally symmetric, dependent only on co-latitude. The code has subroutines that integrate the modes against two types of models (1) a model that depends on a single wavenumber k, and (2) a model that is an equatorial band or a symmetric spherical cap. The first model type was used to examine the wavenumber behavior of surface-wave coupling, and the second type simulates the interaction of surface waves with a sharp boundary. The paper that describes the code's workings is

Park, J., The sensitivity of seismic free oscillations to upper mantle anisotropy I. Zonal symmetry, J. Geophys. Res., v98, 19933-19949, 1993.

Zonal symmetry in the model allows the coupling to vanish for all free-oscillation singlets with differing azimuthal numbers m, m'. In this manner, if there are two modes nSl and n'Sl' with a total of 2l'+1+2l+1 = 2(l+l'+1) singlets, the coupling problem splits apart into (for l'>l) 2l+1 2x2 coupling matrices, and l'-l uncoupled singlets. As a result of this symmetry, zonchn can readily accept a large number of modes in a narrow frequency band without breaking the computer memory or the CPU. The general scheme is to march up in frequency in steps of df and Df: All modes in a half-bandwidth Df about some fiducial frequency fo are coupled, but only those hybrid modes in a narrower bandwidth df about fo are saved. The code increases fo by 2*df and iterates up to some cutoff frequency. The user specifies how many overtones n are included. The uploaded version of zonchn.f has been tested with 0.2.le.f.le.20 mHz and df=0.1 mHz, Df=0.5 mHz and n-max=5.

The code depends on a set of subroutines in the file zonsubs.f, which are posted next in this blog.

The code reads from an input file "phzonchn" that contains

print *,'open(15,file=phzonchn,form=formatted)'
call yread
print *,'output chain file '
print *,namchn
102 format(80a)
print *,'initial open of output file in append mode (0=no) '
read(15,*) iappend
print *,'iappend= ',iappend
print *,'enter inner freq halfwidth, outer freq halfwidth (mHz)'
c outer band is modes that couple, inner band contains modes that are saved
read(15,*) hfin,hfout
print *,hfin,hfout
print *,'enter freq band for hybrid modes (mHz)'
read(15,*) fb1,fb2
print *,fb1,fb2
print *,'enter max overtone branch to consider'
read(15,*) nbrmax

The option of writing the output file in "append" mode is an artifact of slow computers of the 1990s, in which one might need to stop and restart a long computation. I doubt that the user will need this option in 2009, though my test calculation required the greater part of an hour to complete.

example for phzonchn:

ymodel10_B0.05 --> aspherical model file
ymodel10_B0.05.zon20 --> output file of hybrid modes (linear comb of sph-earth modes, new frequencies)
0 --> dont open output file in append mode (usual case)
0.1 0.5 --> inner band contains modes that are saved, outer band is modes that couple (mHz)
0.2 20 --> frequency band to compute (mHz)
5 --> max number of overtones
/Users/jjpark/Mineos/Models/premiss --> earth model (isotropic PREM in this case)
/Users/jjpark/Mineos/sphnl --> N,L file of spheroidal mode parameters
/Users/jjpark/Mineos/sphe --> direct-access Fortran file of spheroidal modal eigenfunctions
/Users/jjpark/Mineos/tornl --> N,L file of toroidal mode parameters
/Users/jjpark/Mineos/tore --> direct-access Fortran file of toroidal modal eigenfunctions

The model file is based on the A,B,C,D,E Backus parameterization of hexagonally-symmetric anisotropy. A and D are isotropic P and S wavespeed perturbations (peak2peak variation: A=0.05 implies 5%). B is the 2\phi azimuthal Vp term, C is the 4\phi azimuthal Vp term, and E is the 2\phi azimuthal Vs term. The input, as explained in the post for zonsubs.f iare the values of the ABCDE and the wavenumber k of a corrugation in colatitude. The code does not allow the user to choose the equatorial band model on input. You must change a subroutine call and recompile the code. I may fix this soon, as it is cumbersome. Similarly, there is a slight alteration in the coupling formulas that switches the cases for an anisotropic symmetry axis w-hat aligned with theta-hat, or with phi-hat, that is, with colatitude and longitude, respectively. Due to symmetry restrictions, only w-hat parallel to theta-hat or phi-hat is allowed by this code. No tilted axes of symmetry, no general azimuthal angle.