https://github.com/seismology/mc_kernel/blob/master/src/kernel.f90#L435-L460
I noticed when compiling mc_kernel on my local machine, the following warning for kernel.f90:
'Extension: Unary operator following arithmetic operator (use parentheses) at (1)
Warning: ‘normalization_term’ may be used uninitialized in this function [-Wmaybe-uninitialized]'.
By placing brackets around each of the four -1.d0 terms in the above lines (e.g. calc_misfit_kernel(itrace) = this%integrate_parseval( timeseries_cut, this%seis_velo_cut_fd) &
* this%normalization * (-1.d0)) , this warning goes away.