diff --git a/fortran_src_codes/qseis2025_src/qsglobal.h b/fortran_src_codes/qseis2025_src/qsglobal.h
index 38b75d0..df95adb 100644
--- a/fortran_src_codes/qseis2025_src/qsglobal.h
+++ b/fortran_src_codes/qseis2025_src/qsglobal.h
@@ -6,7 +6,7 @@ c     nrmax: max. number of traces;
 c     nfmax: max. number of frequency samples
 c
       integer*4 nzmax,lmax,nrmax,nfmax,ndtransmax
-      parameter(lmax=500)
+      parameter(lmax=2048)
       parameter(nzmax=lmax+2)
       parameter(nrmax=101,nfmax=4096)
       parameter(ndtransmax=4)
diff --git a/fortran_src_codes/qseis2025_src/qswvint.f b/fortran_src_codes/qseis2025_src/qswvint.f
index 187ef5a..95f63dd 100644
--- a/fortran_src_codes/qseis2025_src/qswvint.f
+++ b/fortran_src_codes/qseis2025_src/qswvint.f
@@ -6,6 +6,8 @@ c
       include 'qsglobal.h'
 c
       integer*4 istp,n,nrec,l,lf,lf1,i,ir,nrr,nrs
+      integer*4 lfbegin,lfend,envstat,envlen,ioerr
+      character*32 envfirst,envlast
       integer*4 ik,ik1,ik2,nk1,nk2,nbsj,idtrans
       real*8 f,fcut,k,kc,dk,slwn
       real*8 pi,pi2,rr,rs,delta,cmax,ymax,yabs
@@ -191,7 +193,25 @@ c
      &     1000.d0*kcut2(1)/(pi2*fcut),' / ',
      &     1000.d0*kcut2(4)/(pi2*fcut),' s/km'
 c
-      do lf=lf1,nf
+      call get_environment_variable('PGW_FREQ_START',envfirst,
+     &     length=envlen,status=envstat)
+      if(envstat.ne.0.or.envlen.le.0)then
+        stop 'Error: PGW_FREQ_START must be defined'
+      endif
+      read(envfirst,*,iostat=ioerr)lfbegin
+      if(ioerr.ne.0)stop 'Error: invalid PGW_FREQ_START'
+      call get_environment_variable('PGW_FREQ_STOP',envlast,
+     &     length=envlen,status=envstat)
+      if(envstat.ne.0.or.envlen.le.0)then
+        stop 'Error: PGW_FREQ_STOP must be defined'
+      endif
+      read(envlast,*,iostat=ioerr)lfend
+      if(ioerr.ne.0)stop 'Error: invalid PGW_FREQ_STOP'
+      if(lfbegin.lt.1.or.lfend.gt.nf.or.lfbegin.gt.lfend)then
+        stop 'Error: frequency shard must lie within 1..nf'
+      endif
+      write(*,*)'Frequency shard:',lfbegin,lfend,' of ',nf
+      do lf=max0(lf1,lfbegin),min0(nf,lfend)
         f=dble(lf-1)*df
         n=nno(ls)
         wvlen=vp(n)/(f+df)
diff --git a/fortran_src_codes/qseis2025_src/qsfftinv.f b/fortran_src_codes/qseis2025_src/qsfftinv.f
index a5debbc..b33e920 100644
--- a/fortran_src_codes/qseis2025_src/qsfftinv.f
+++ b/fortran_src_codes/qseis2025_src/qsfftinv.f
@@ -132,7 +132,7 @@ c
       enddo
       close(20)
 1003  format(f12.5,$)
-1004  format(E12.4,$)
-1005  format(E12.4)
+1004  format(E24.15,$)
+1005  format(E24.15)
       return
       end