subroutine nmo1( adj, add, slow,    x, t0, dt, n,zz,  tt )
integer  it, iz, adj, add,                        n
real  xs, t , z,           slow(n), x, t0, dt, zz(n), tt(n), wt
call adjnull(    adj, add,                     zz,n,  tt,n)
do iz= 1, n {	z = t0 + dt*(iz-1)
		xs = x * slow(iz)
		t = sqrt ( z * z + xs * xs) + 1.e-20
		wt = z/t * (1./sqrt(t)) 		#  weighting function
		it = 1 + .5 + (t - t0) / dt
		if( it <= n )
			if( adj == 0 )
				tt(it) = tt(it) + zz(iz) * wt
			else
				zz(iz) = zz(iz) + tt(it) * wt
	   }
return; end