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usgs / nshmp-haz-fortran

National Seismic Hazard Mapping Project (NSHMP) Legacy Fortran Code
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Perform cluster calculation before combining GMM exceedance curves #60

Closed pmpowers-usgs closed 7 years ago

pmpowers-usgs commented 7 years ago

Currently, exceedance curves for each GMM are combined for each fault in a cluster before computing the conditional probability of exceedance for the cluster. The GMM models are independent logic tree branches and as such should be treated independently when computing hazard for a cluster (compute conditional probabilities of exceedance and then combine). For whatever reason, the suite of GMMs used in 2008 does not exhibit a significant difference between either order of operations, but the 2014 suite yields a higher hazard.

The attached figures show total hazard curves across all source types for Cape Girardeau, MO. The curves have been decomposed and it is the cluster sources that give rise to the discrepancy in each.

2014_hazcurves_us_bc_760_cape_girardeua_mo_1hz

2014_hazcurves_us_a_2000_cape_girardeua_mo_1hz

pmpowers-usgs commented 7 years ago

The cluster calculation is done correctly in nshnmp-haz and will not be fixed in this codebase.