Be sure to press Apply after making changes!
Event filtering determines which events from the IRIS database are shown in any given map view. Events are filtered in two ways:
The first two options, Display at most: and Prioritize:, determine the number of events that will be displayed in a map. The rest of the options determine what event parameters to use in selecting (filtering) events.
Options Display at most: and Prioritize: are always shown. To show the other options you must click on the option names.
Display at most: determines the maximum number of events that will be shown in any given view. You can choose values between 100 and 5,000.
Displaying too many events can cause some web-browsers to be slow or unresponsive. In some extreme cases the web browser may have to be restarted.
Prioritize: determines which events have priority to be displayed when the number of events for a map view is greater than the Prioritize: option. You can either prioritize Newer Events or Larger Events.
Time Range: determines the dates of events that will be shown. By default all available dates are used: Earliest Available to Latest Available.
To use your own date range, uncheck one or both of the check boxes and enter dates in the text fields. Dates are in Universal Time (UTC) and run midnight to midnight.
Magnitude Range: determines the magnitudes of events that will be shown. By default all available magnitudes are used.
To use your own magnitude range, uncheck the check box and enter values in the text fields.
Depth Range: determines the depths of events that will be shown. By default all available depths are used.
To use your own depth range, uncheck the check box and enter values in the text fields.
Advanced Event Filter: allows you to control what catalogs, contributors and magnitude types are used when selecting events. It is important to understand that the database contains a large number of duplicate events. This is mainly because the database contains multiple catalogs. Each event maybe recorded in more than one catalog. There are roughly two database entries for each actual recorded earthquake. By default Automatic Logic is used to determine which records in the database will be shown in the map. The logic attempts to show unique, non-duplicate earthquakes.
Uncheck the Automatic Logic check box to select a catalog,contributor or magnitude type. To see all events in the database, uncheck Automatic Logic and leave the other fields set to <All>. After doing this, you should see the Display Statistics field increase.
Using the Advanced Event Filter in conjunction with the Download Table link at the top of the map makes it possible to quickly understand the relationships between contributors, catalogs and events.
The Events Displayed field shows how many events are currently plotted on the map view along with the total number of events that could be shown.
If the Events Displayed field reads "500 of 38738" then 500 events will have been plotted and 38,738 - 500 = 38,238 events not plotted. Zooming into the map and pan to reveal the hidden events.
If the two displayed numbers are the same ("123 of 123") then all events are being displayed and zooming and panning will not display any more events.
The region selection control allows you to quickly select a region and zoom into. Only events in the selected region will be shown.
The region selection control is only available with the Firefox and Safari web browsers.
To start, click Select a region and drag from top-left to bottom-right of the desired region.
Only events in the selected region are now shown.
Note: occasionally the existing events will remain shown. If this happens, click the Apply button to refresh the display.
Next click Zoom to region to zoom into the selected region.
As long as a region is selected, the group of selected events is effectively frozen - even if you move the selected region off of the view!
Click Clear Selection to remove the selection rectangle.
Alternatively, you may click Select a region to select a new region.
The Download data links at the top of the page allow you to export the data shown in the current map view. These links are dynamically updated as the map is zoomed and panned.
The Table link leads to a new HTML page containing a list of earthquakes in table format. The column headers of this table can be clicked to re-order the data. Use the event table in conjunction with the Advanced Filter Control to better understand the relationships between contributors, catalogs, mag-types and events.
The NetCDF link can be used to download the events in NetCDF data format. NetCDF (Network Common Data Form) is a binary data format standard for exchanging scientific data. The NetCDF data created by the IEB can be imported into the GEON IDV and visualized three dimensionally.
Click Here to learn more about using the GEON IDV.
The XML link goes to an XML document containing the displayed earthquake information. This is is the same XML document that is used in plotting the points on the map. It is mainly useful as a diagnostic tool. If the map does not appear to be working properly, click on the XML link and see if it downloads without errors. If the XML document does not download properly, the map will not work properly either. Problems with this link are indicative of problems with IRIS' earthquake event web-service.
The WEED link goes to an WEED event file document containing the displayed earthquake information. See WEED Manual: IRIS for more information.
