1996 Interactive Deaggregation Documentation

This application computes the deaggregation of the values displayed on the 1996 USGS NSHMP Hazard Maps for the conterminous U.S. and the 1998 USGS NSHMP Hazard Maps for Alaska and Hawaii. The published hazard maps consider a range of earthquakes that might occur over a given time frame and aggregates the results into an overall hazard value to display on the map for a particular location. This application considers the component earthquakes that may occur near a given location, contrasts each earthquake with its likelihood of occuring and displays the contribution of each earthquake to the location's overall hazard.

To use this application, start by filling out the input form fields. If you need more information about any of the input fields, please see the corresponding section below. After filling out the input fields, examine the red location marker on the map. If you want, you can drag the location marker to a new location if it is not quite where you wanted it to be. Wherever the red location marker is pointing on the map is where the application will compute its output files for.

When you are satisfied with your input choices and location, click on the, “Compute” button below the map. Depending on your input choices, two or three output files are generated. Just below the map and above the buttons you will see a new section appear that displays the input parameters you selected and links to the generated output files. The output files always open in a new window, and you can save them to your computed by right–clicking on the link and selecting “Save File As…”.

If you run more than one location in a single session, new locations will be added to the bottom of this new output area. If your list of output is getting too long you can clear it by clicking on the “Clear” button.

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The site name can be whatever you like and can even be left blank. This value (if specified) is only used for labeling purposes and if left blank, the application automatically names the site, “Unknown”.

Site names can be between 0 and 16 characters. Spaces are allowable, however the lables on the generated image files will have the spaces replaced by undercores (“_”). Other special characters should be avoided if at all possible. If the application is failing to return the expected output files it is a common problem that the site name is too long or contains invalid characters.

The location input field is fairly flexible and accepts full or partial street addresses or latitude and longitude values. The application does its best to find the closest match to the input location and ithe arrow on the map will automatically update to identify where it thinks the desired location is.

Input addresses can be full addresses with a number, street, city, state, and zip code, or any valid partial combination thereof. The more specific you are, the closer the application will be to your desired location. If your input location is not found, the location marker arrow on the map will not update and a warning message to that effect will be displayed.

If specifying latitude and longitude coordinates you should do so using decimal degrees. You can either use negative numbers for southern/western values, or you can use the “S”/“W” label suffix. Feel free to try other input formats, and always watch the red location marker arrow on the map to see where the application is interpretting your location to be.

If you are not using Javascript, instead of seeing a single “Location” input field, you will see an individual input field for each of the latitude and longitude coordinates. These input fields are less flexible and values must be specified in deimal degrees with negative values indicating southern/western locations.

This application is only defined for locations within the conterminous U.S., Alaska, and Hawaii. For your general reference, this inlcludes the following ranges of valid longitude and latitude values:

• Conterminous U.S. [ Latitude: 24.6°N – 50.0°N ] [ Longitude: 65.0°W – 125.0°W ]
• Alaska [ Latitude: 48.0°N – 72.0°N ] [ Longitude: 125.0°W – 200.0°W ]
• Hawaii [ Latitude: 18.0°N – 23.0°N ] [ Longitude: 154.0°W – 161.0°W ]

This option allows you to specify the time span over which to consider the hazard for deaggregation. Values are listed as both a probability in time (X% in Y years) and as in a corresponding number of years (Z years). Generally design maps consider the “2% in 50 years” option, and so we have made that option the default value.

Clearly, if you select a fairly short return period, large earthquakes will contribute a smaller portion of the overall hazard for your location since they are less likely to occur in this shortened time frame. The opposite is also true with respect to both return period and relative strength of the earthquake.

This options allows you to specify the spectral acceleration you the application to consider while computing the deaggregation. For a more thorough discussion, see our FAQ pages regarding Peak Ground Acceleration (PGA) and spectral acceleration (SA).

In addition to the standard deaggregation chart that gets produced by this application, for certain choices of spectral acceleration we can also generate a geographically deaggregated hazard map centered on your input location. Check this checkbox if you wish to produce these maps as well. Performing this operation can add a few seconds to the processing time, so please be patient while the application is generating your output.

Geographic deaggregations are only suppored for the following selections of spectral acceleration.

• Peak Ground Acceleration (PGA)
• 1.0Hz (1.0 Second)
• 5.0Hz (0.2 Second)
• 3.33Hz (0.3 Second)

Attempting to run geographic deaggregations for other values of spectral acceleration could cause unknown errors and we ask you please try to refrain from doing so.

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