Specfem3D_globe for PKIKP phase

Hi there,

We plan to use Specfem3D_globe to study CMB with velocity tomography models. We already installed the package, and succeeded to get synthetic waveforms with setting NPROC_XI(ETA)=8, and NEX_XI(ETA)=512 due to limit of computational power. However for PKIKP, we prefer to get precision as ~2Hz, therefore we need bigger number for NEX_XI(ETA). What else parameters should I change to make it work with limit of computational power?
Your suggestion will be appreciated in advance.



you are looking for a 2 Hz global simulation with 3D earth models using a spectral-element code? then you are probably out of luck with the SPECFEM3D_GLOBE code as there is currently no supercomputer big enough to achieve that. however, CIG also hosts the AxiSem code that might help you out with this.



Well, maybe not that big. :slight_smile:
Actually we only need 3D velocity model in small region around inner/outer core boundary, the rest is 1D earth model for PKIKP phase.
This should work, right?


the runtime of a SPECFEM3D_GLOBE simulation is independent of having a 1D or 3D model. that is, running a simulation for a 1D model is as expensive as running it for a 3D model. so it doesn’t matter if you only want a portion of the Earth to be 3D.

you could only save time by turning off some of the physics (attenuation, ocean, gravity, rotation) or by limiting the simulation to a 1-chunk, regional simulation.

concerning the maximum frequency range for global simulations, Laura went down to 2s in 2008 on Ranger (High-frequency simulations of global seismic wave propagation using SPECFEM3D_GLOBE on 62K processors - IEEE Conference Publication), Seiji went down to 1.2s in 2016 on the K computer (https://journals.sagepub.com/doi/full/10.1177/1094342016632596). having a global 2Hz simulation is not achievable yet with current HPC systems, mostly due to memory limitations.

try looking into AxiSem and AxiSEM3D (GitHub - kuangdai/AxiSEM3D) which might help you with your 2Hz setup (https://academic.oup.com/gji/article/217/3/2125/5333339).