Add Bayless and Somerville (2024) GMM for Australia

[thuanycostadelima]

Summary

Adding Bayless and Somerville (2024) ground motion model (BS24) for Australia to OpenQuake hazardlib.

New classes

• BaylessSomerville2024Cratonic — for Yilgarn, Gawler, Pilbara, Kimberley
  and Northern Australian Cratons (NSHA23 Precambrian classification)
• BaylessSomerville2024NonCratonic — for Eastern Australian Phanerozoic
  Accretionary Terranes and extended crust (NSHA23 Phanerozoic classification)

Note: Coefficients updated (May 2026) following personal communication with Jeff Bayless: revised depth scaling Z = min(Ztor-10, 5), d4=0, updated a1/d1/d2/d3 coefficients.

Reference

Bayless J. and P. Somerville (2024). An Updated Ground Motion Model for Australia Developed Using Broadband Ground Motion Simulations. Proc. AEES 2024 National Conference, Adelaide, South Australia.

[CB-quakemodel]

Hi @thuanycostadelima,

Many thanks for submitting this implementation. I have left some minor comments to address (mostly formatting, and one or two things about the class organisation), but it looks good to me.

Once you have made these small fixes, please update the changelog (https://github.com/gem/oq-engine/blob/master/debian/changelog) and the contributors list (https://github.com/gem/oq-engine/blob/master/CONTRIBUTORS.txt).

Thanks,

Christopher

[thuanycostadelima]

Hi @CB-quakemodel, thank you for the detailed review! I have addressed all your comments. Please let me know if anything else needs attention. Thanks.

[CB-quakemodel]

Hi @CB-quakemodel, thank you for the detailed review! I have addressed all your comments. Please let me know if anything else needs attention. Thanks.

Thanks for thoroughly addressing the comments @thuanycostadelima.

I think the expected results CSVs have not been updated however (at least based on a quick visual inspection of the versions in the most recent commit). Also, please not that there appears to be a merge conflict in the changelog (I think most likely you first need to pull from master for the most recent version of the changelog and then update it).

Thanks,

Christopher

[thuanycostadelima]

Hi @CB-quakemodel, thank you for the detailed review! I have addressed all your comments. Please let me know if anything else needs attention. Thanks.

Thanks for thoroughly addressing the comments @thuanycostadelima.

I think the expected results CSVs have not been updated however (at least based on a quick visual inspection of the versions in the most recent commit). Also, please not that there appears to be a merge conflict in the changelog (I think most likely you first need to pull from master for the most recent version of the changelog and then update it).

Thanks,

Christopher

Hi @CB-quakemodel, I have now also fixed the unit conversion issue: np.log(980.665) is subtracted in compute() to convert from ln(cm/s²) to ln(g). The CSVs were regenerated from the Fortran reference code using the same conversion. Thanks!

[CB-quakemodel]

Hi @CB-quakemodel, thank you for the detailed review! I have addressed all your comments. Please let me know if anything else needs attention. Thanks.

Thanks for thoroughly addressing the comments @thuanycostadelima.
I think the expected results CSVs have not been updated however (at least based on a quick visual inspection of the versions in the most recent commit). Also, please not that there appears to be a merge conflict in the changelog (I think most likely you first need to pull from master for the most recent version of the changelog and then update it).
Thanks,
Christopher

Hi @CB-quakemodel, I have now also fixed the unit conversion issue: np.log(980.665) is subtracted in compute() to convert from ln(cm/s²) to ln(g). The CSVs were regenerated from the Fortran reference code using the same conversion. Thanks!

Hi @thuanycostadelima, thanks for making these fixes. The unit tests using the latest commit still show a mismatch however. Please check the regenerated CSVs because we still see the unit tests failing on remote. I share the information here in case not visible to yourself:

Also, I forgot to mention that you will need to also add the GSIM module to https://github.com/amirxdbx/oq-engine/blob/master/doc/api-reference/openquake.hazardlib.gsim.rst

Thanks,

Christopher