The ESHM20 logic tree of the seismogenic source model is described by source model end-branches with correlated values of the activity parameters. Each end-branch is a complete model consisting of different source typologies: area sources for shallow crust, deep seismicity, subduction inslab and volcanic regimes; point sources for the smoothed seismicity model, simple faults for shallow crust faults and complex faults for subduction interface.
The OpenQuake implementation of the complete suite of ground motion model logic trees for the different tectonic regions requires a change of approach in comparison to the ESHM13 and other models that adopt a “weights-on-multiple-models” approach to developing the GMM logic tree.
The fundamental difference here is that in the present version we are considering a small number of core backbone GMMs to which we then apply a set of adjustments. The concept of a user adjustable GMM, one in which arguments can be passed by the user from the GMM logic tree configuration file that modify the operation of the GMM, has been supported in OpenQuake for several years. The new GMMs required for the ESHM20 have been implemented around this framework, with the adjustments needed to construct the full scaled backbone logic tree supported as configurable parameters.
The input files for OpenQuake were created from the data files of the single source models and the proposed logic-tree for the ground motion prediction equations defining the respective weights. The input files reflect the seismogenic source model and the ground motion logic tree as described in Danciu et al., 2021.
Danciu L., Nandan S., Reyes C., Basili R., Weatherill G., Beauval C., Rovida A., Vilanova S., Sesetyan K., Bard P-Y., Cotton F., Wiemer S., Giardini D. (2021) - The 2020 update of the European Seismic Hazard Model: Model Overview. EFEHR Technical Report 001, v1.0.0, https://doi.org/10.12686/a15
Pagani M., Monelli D., Weatherill G., Danciu L., Crowley H., Silva V., Henshaw P., Butler L., et al. (2014) OpenQuake Engine: An Open Hazard (and Risk) Software for the Global Earthquake Model, SRL 85 (3), https://doi.org/10.1785/0220130087
Weatherill, G., Kotha, S., Cotton, F. (2020a): A Regionally-Adaptable "Scaled Backbone'" Ground Motion Logic Tree for Shallow Seismicity in Europe: Application to the 2020 European Seismic Hazard Model. - Bulletin of Earthquake Engineering, 18, 5087-5117, https://doi.org/10.1007/s10518-020-00899-9
Weatherill G., and Cotton F. (2020b) A ground motion logic tree for seismic hazard analysis in the stable cratonic region of Europe: regionalization, model selection and development of a scaled backbone approach. Bulletin of Earthquake Engineering. 18: 6119 – 6148, https://doi.org/10.1007/s10518-020-00940-x
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