diff --git a/docs/pages/Code-Versions.md b/docs/pages/Code-Versions.md new file mode 100644 index 0000000000000000000000000000000000000000..1f23c218c2bc3b191e34281e0ed484b4f61c5f16 --- /dev/null +++ b/docs/pages/Code-Versions.md @@ -0,0 +1,41 @@ +# Hazard Calculation Code Versions + +The static datasets of USGS NSHMs prior to 2014 were computed using Fortran (see +(nshmp-haz-fortran)[https://github.com/usgs/nshmp-haz-fortran]). The static datasets for the +2014 Conterminous U.S. NSHM were computed using the Fortran codes and +(OpenSHA)[https://opensha.org/] for the California portion of the model. The dynamic versions +of the 2008 and 2014 Conterminous U.S. models were then implemented in the 1st version of +(nshmp-haz)[https://github.com/usgs/nshmp-haz] (on GitHub). This updated Java codebase uses XML +source models and supports the web services behind the dynamic calculations of the (Unified Hazard +Hazard Tool)[https://earthquake.usgs.gov/hazards/interactive/] (UHT). + +The 2nd version of nshmp-haz (this repository) supercedes prior codebases. The development of this +version involved a significant refactoring of both the computational code and source model format. +The source models are now defined using JSON, GeoJSON, and CSV files to better reflect the +underlying logic trees and support uncertainty analysis. + +## Transitioning from _nshmp-haz_ v1 to v2 + +NSHMs are very detailed and migrating from one format to another is not trivial and prone to error. +Moreover, approximations (e.g. using 3.1415 for Pi rather than the the value built into most +languages) can yield different results. When multiple such small changes exist, deciphering what +si giving rise to differences in results can be challenging. + +To document the transition from nshmp-haz v1 to v2, we here attach comparison maps at four return +periods (475, 975, 2475, and 10,000 year) for the 2018 Conterminous U.S. model. Maps are included +for PGA and 3 spectral periods ( 0.2 s, 1 s, and 5 s). There are no differences in the Central & +Eastern U.S. and differences in the WUS are <<1%. The difference in hazard in the vicinity of +Salt Lake City arises from the cluster models in nshmp-haz v1 not being able to consider the +additional epistemic uncertainty added to the the NGA-West2 ground motion models. + +We continue to investigate the cause of other differences but they are small enough that we are +comfortable moving forward deploying nshmp-haz v2 codes and models to our public web services and +applications. + +## Example map + + + +--- + [U.S. Geological Survey](https://www.usgs.gov) +National Seismic Hazard Mapping Project ([NSHMP](https://earthquake.usgs.gov/hazards/)) diff --git a/docs/pages/images/comp_JSON_vs_XML_0p2-grid-20220216-BC.pdf b/docs/pages/images/comp_JSON_vs_XML_0p2-grid-20220216-BC.pdf new file mode 100644 index 0000000000000000000000000000000000000000..ad3bce8c30c86f53ce637f925e44ed243dc40c96 Binary files /dev/null and b/docs/pages/images/comp_JSON_vs_XML_0p2-grid-20220216-BC.pdf differ