Frequently Asked Questions
- What is the Unified Hazard Tool (UHT)?
- How long will the UHT be supported?
- Will the URL of the tool change?
- What are the strengths and limitations of the UHT?
- Where are the earthquake rate, deaggregation, and other tools now?
- Why were the existing tools retired?
- Are the web-services underlying the UHT documented and available for use?
- I have a question or suggestion; how can I provide feedback?
- What models are supported?
- Is the 2002 Conterminous U.S. model supported?
- Are time dependent models supported?
- Why are some site classes and spectral periods disabled?
- How do I enter a custom site class or Vs30?
- How do I generate a PDF deaggregation report?
- Where is the geographic deaggregation option?
- Where is the conditional spectrum option?
- How are UCERF3 deaggregations handled?
- What are 'Recovered targets'?
The Unified Hazard Tool provides a single, streamlined interface for accessing various USGS National Seismic Hazard Models (NSHMs) and data derived therefrom. One may use the UHT to obtain probabilistic hazard curves, perform deaggregations of seismic hazard, as well as obtain earthquake rate and probability data. The UHT replaces a suite of independent tools formerly available on the USGS website.
Indefinitely.
Not anytime soon. If and when it does, a redirect will be used. We apologize that this was not done when retiring our legacy tool set.
TODO
These data and services are now provided exclusively through the UHT and its underlying web services. Please see the legacy tools page for a summary of those tools that were retired and how they are being replaced.
TODO
Yes, please see the web-service documentation.
Developers of the UHT can be reached via the "Question or comments?" link at the bottom of the UHT page. For technical problems relating to the UHT, consider submitting an issue. For problems relating to any underlying web-services and results generated by the UHT, one may alternatively submit an issue here.
Our goal is to support static datasets and dynamic calculations in the UHT using the current and prior model in any given region. For the Conterminous U.S., we therefore provide access to the 2008 and 2014 models and related data. In other regions, for example Hawaii where the last model update was in 1998, we've decided to delay support for dynamic calculations (e.g. deaggregation) until we've updated the model itself, an effort that is currently underway.
Unfortunately, no. See above. The 2002 raw data and publications are still available here. We recommend users try to use the much improved 2008 model if possible.
All USGS models and data provided by the UHT are time-independent. This may change in the future.
The UHT provides both static and dynamic data. Static data only exists at those site classes and spectral periods for which we have precomputed hazard curves. Some site classes are region specific. For example hazard for hard-rock sites (Vs30 = 2000 m/s) is only available for sites on the stable craton of the central and eastern U.S. For the 2014 Conterminous U.S. editions, we are currently reviewing datasets for additional site classes and spectral periods and will add them to the tool soon. For dynamic editions, we plan to add the ability for users to specify a site class (Vs30 value) in the near future.
The UHT provides both static and dynamic data. Static data is precomputed and retrieved from a database and only exists for those sites
Geographic deaggregation was an option in the legacy deaggregation tools. The UHT does not currently generate an aerial perspective plot as was available previously, however the Deaggregation Contributors list reports location data for those sources that significantly contribute to hazard at a site. We are considering adding a downloadable Google Earth KML to the deaggregation results, or may spend time developing a new perspective plot. We welcome any feedback on what users would prefer.
Conditional spectrum was an option in the legacy deaggregation tools. We are actively developing a replacement for this, however it will intitally only be available via the web-service results. At some later date, we'll likely add a plot to accompany the total and per-ground-motion-model deaggregations.
UCERF3 is the California component of the 2014 USGS National Seismic hazard Model (NSHM). It relaxes fault segmentation, allowing for "multi-fault ruptures", and therefore provides rates for hundreds-of-thousands of possible rupture geometries within the California fault network, where all named, mapped, 'parent' faults have been discretized into ~7 km long sections. When deaggregating, the list of contributing sources to hazard at a site is very long with no individual rupture or ruptures contributing significantly to the total hazard. To address this, the deaggregation service behind the UHT aggregates contributions on a per-fault-section basis, with rupture contributions only ever counted once. The UHT deaggregation contributor list shows those sections, identified by a 'parent' fault name and section index, which contribute most to hazard at a site. Under the hood, the total contribution of a section is also decomposed by magnitude, however we do not report these value at this time, just the mean magnitude for the section.
When deaggregating hazard, the target ground motion at which to deaggregate is selected via interpolation using the specified time horizon in the UHT. This target ground motion is rarely the same as one of the original hazard ordinates, so in performing the deaggregation, the contribution to hazard at the specified ground motion is computed for all sources, with the sum of the contributions generally coming in a few percent lower than that computed via interpolation of the total hazard curve. UHT deaggregations also do not consider the additional epistemic uncertainty applied to ground motion models used in the Western U.S.
U.S. Geological Survey – National Seismic Hazard Mapping Project (NSHMP)