Use Cases

This page explains in greater detail how to obtain different types of information from the Unified Hazard Tool (UHT).

How do I get the PGA value for a specific return period (e.g. 2475 years)?

This information was formerly available via the Hazard Curve Application and various Interactive Deaggregation applications.

1. Input panel: select Edition, Location, and Site Class. You may also select Spectral Period and Time Horizon at this time but it is not necessary.
2. Hazard Curve panel: Compute Hazard Curve.

What's happening above? When Compute Hazard Curve is selected, either static hazard curves are retreived from a database or curves are computed on demand depending on the Edition selected. In either case, the curves for all supported spectral periods are retrieved. When the Hazard Curve plot is drawn, whichever Spectral Period is selected in the Input panel is now highlighted in black. You can change the selected Spectral Period by either changing the input control, or by selecting the curve or legend item in the plot. Note that when you change the spectral period, the black dot on the Reponse Spectrum plot also moves.

What is a response spectrum? The Reponse Spectrum plot shows the ground motion values of each spectral period for the currently selected Time Horizon. These values are the intercepts, computed via log-log interpolation, of the red, horizontal line in the Hazard Curve plot (KNOWN ISSUE: RED TIME HORIZON LINE IS NOT BEING DRAWN ON PLOT). If you change the Time Horizon in the Input panel, you will see the shape of the response spectrum change.

3. Hazard Curve panel: Response Spectrum plot; hover over the points to get the ground motion value for the Spectral Period and Time Horizon of interest. The first point (at x = 0.0) is always PGA. In the near future, we will be adding a label to the response spectrum plot that shows the selected spectral period and corresponding ground motion level, the information currently displayed in the pop-up.

How do I perform a deaggregation?

This information was formerly available via various Interactive Deaggregation applications.

It is important to note that many users had been using the interactive deaggregations applications to get a single value off a hazard curve. While a deaggregation does compute and report this data point as part of a result, it can also be found following the steps in the first use case above. In point of fact, a deaggregation uses that single value as a starting point to analyze the relative contributions to hazard from different sources. The value itself is not the primary result of performing the deaggregation.

1. Input panel: select a 'dynamic' Edition.
2. Input panel: select a Location, and Site Class, Spectral Period and Time Horizon.
3. Deaggregation panel: Compute Deaggregation.

KNOWN ISSUES:

• Deaggregation bars overrun plot boundaries
• Download Deaggregation Report link does not work. This is a known issue with recent versions of Internet Explorer; please use Chrome until this can be fixed.