[CIG-SEISMO] Mineos problem

[Jeroen Tromp]

I think this is a known problem with the version of mineos available via 
CIG. In fact, I believe the main author of mineos, Guy Masters, advises 
against using it...

My recommendation is reaching out to Guy.

Best regards,

Jeroen

On 3/3/16 10:00 AM, Matthew Knepley wrote:
> We have a problem with the eigenfunctions calculated by Mineos at near 
> degenerate eigenvalues.
>
> Mineos works fine to calculate the eigenfrequencies of normal modes, 
> but there is a problem for the eigenfunctions. For those different 
> modes with very close eigenfrequencies in the mathematical point of 
> view(see Figure f-l), Mineos regards them as degeneracy in the 
> numerical point of view, and therefore it gets a linear combination of 
> pure R mode's and pure Stoneley mode's eigenfunctions, i.e. the 
> eigenfunctions are not orthogonalized. For example, based on Okal's 
> classification [1], 2S25  and 3S25 should be Stoneley mode and R mode, 
> respectively. But the eigenfunctions from Mineos have both surface 
> oscillations (the feature of R modes) and exponentially decaying along 
> CMB (the feature of Stoneley modes).(see Figure 2S25 and 3S25)
>
> Since the eigenfunction is not calculated properly, the group velocity 
> is also not reliable. According to Okal's paper [1], for each branch 
> of R modes or Stoneley modes, the group velocity should be continuous. 
> And we notice that there are some "bad points" in the group velocity 
> picture, which are exactly the modes we mention before. (see Figure 
> groupV_R2)
>
> What eigensolver is being used inside Mineos? The standard symmetric 
> eigensolvers in LAPACK handle this problem I believe.
>
>   Thanks,
>
>     Jingchen and Matt
>
> References:
>
> [1] Okal, Emile A. "A physical classification of the earth's 
> spheroidal modes." Journal of Physics of the Earth 26.1 (1978): 75-103.
>
>
>
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