Editions Explained
USGS hazard models are created and updated in response to user needs. In some cases a model is updated in response to cyclic updates to the U.S. Building Code. In other cases, enough time has passed that there have been significant advancements in the science, availability of relevant data, or modeling procedures that warrant a model update. Every model the USGS produces is associated with a USGS Open-File report or refereed journal article and supporting datasets. However, layered on top of any given model release are bug-fixes and model improvements.
With the update to a new codebase, nshmp-haz, the NSHMP has adopted semantic versioning to keep track of different hazard models. For any given model region, the first number (or major version) corresponds to a particular release or update year. For example, we consider the initial 1996 conterminous U.S. NSHM to be v1.0.0. The second number (or minor version) reflects updates to a particular release that likely causes small changes to hazard values. The third number reflects non-hazard altering changes; for instance, a change to the model file format that has no consequence on computed hazard.
The USGS NSHMP is committed to supporting current and prior model releases in any given region via web services. The table below provides a summary of all NSHM releases and their corresponding version numbers.
| Region | Year | Version | Static | Dynamic | Notes |
|---|---|---|---|---|---|
| Conterminous U.S. | 2014 | v4.2.0† | 🔹 | ||
| Conterminous U.S. | 2014 | v4.1.4† | 🔹 | ||
| Conterminous U.S. | 2014 | v4.0.0 | 🔹 | ASCE7-16 | |
| Conterminous U.S. | 2008 | v3.3.3 | 🔹 | ||
| Conterminous U.S. | 2008 | v3.2.0 | 🔹 | ||
| Conterminous U.S. | 2008 | v3.1.0 | 🔹 | ASCE7-10 | |
| Conterminous U.S. | 2008 | v3.0.0 | |||
| Conterminous U.S. | 2002 | v2.0.0 | |||
| Conterminous U.S. | 1996 | v1.0.0 | |||
| Alaska | 2007 | v2.1.0 | 🔹 | ||
| Alaska | 2007 | v2.0.0 | 🔹 | ASCE7-10 | |
| Alaska | 1999 | v1.0.0 | |||
| American Samoa | 2012 | v1.0.0 | |||
| Guam | 2012 | v1.0.0 | |||
| Hawaii | 2018 | v2.0.0 | TBD | ||
| Hawaii | 1998 | v1.1.0 | TBD | ||
| Hawaii | 1998 | v1.0.0 | 🔹 | ASCE7-10 | |
| Puerto Rico & U.S. Virgin Islands |
2003 | v1.0.0 |
† Note on the 2014 Conterminous U.S. NSHM: Initial publication of the 2014 model included data to support updates to the U.S. Building Code, specifically hazard curves for peak ground acceleration (PGA), and 0.2 and 1.0 second spectral accelerations, all at a BC boundary site class with Vs30 = 760 m/s. Some time later, the model was deployed to the Unified Hazard Tool (UHT) and included support in the Wester U.S. for calculations at sites other than Vs30 = 760 m/s, consistent with dynamic calculations using the 2008 model. Subsequently, we updated the 2014 model with addional periods and site classes. Doing so required dropping several ground motion models (GMMs) and a redistribution of logic-tree weights. Specifically, the Idriss (2014) model is inappropriate for use at soft soil sites and the Atkinson & Boore (2003) model does not support long periods (see the open-file report for more information). Moving forward, we will continue to include the original dynamic version of the 2014 model (v4.1.4) in the UHT. However, we recommend that users consider the updated model (4.2.0).
Historically, the USGS NSHMP has produced static datasets of hazard curves that accompany the 'official' release or update to a model. In the context of providing interactive web services, such static datasets can be quickly retreived and provide most users with the data they seek. More complex analyses, such as deaggregations, require that a complete hazard calculation be performed on demand. Historically, USGS deaggregation services were provided for particular model years and regions, each located at a unique web address and supported by a unique codebase. However, it has proven too difficult to maintain numerous isolated services, and we therefore developed a single codebase that supports all current and prior models.
Moreover, as time goes by, there may be more customization options we want to expose to users. However, with each additional level of customization, it quickly becomes too difficult to produce and version corresponding static datasets. We therefore identify model versions that support deaggregations and other calculations as 'dynamic'. At present, only the most current versions of a particular model region and year are supported via 'dynamic' calculations.
In practice, this leads to results produced by 'dynamic' caluculations being somewhat different than those stored in static datasets of prior model minor versions, although usually not by much. The release notes for each model version detail the changes that give rise to changes in hazard between between versions. There are also differences that arise from different modeling assumptions between past and current codebases that are detailed below.
It is important for users to know which edition they should be using. For instance if one is bound to use those values adopted by the U.S. building code, one of the editions marked ASCE7-* is probably most appropriate. However, if one is bound to use the most up to date source model, one of the dynamic editions is likely better.
Dynamic editions are supported through web-services provided by the nshmp-haz-ws library (this repository). Static editions are supported via a separate set of services. Both are documented on the web services page.
Changes between editions in model regions are documented in the release notes of the individual model repositories.
U.S. Geological Survey – National Seismic Hazard Mapping Project (NSHMP)