 IRIS
Earthquake Browser
The IRIS DMC is pleased to announce the release of a new generation
of web based earthquake query tool - the IRIS
Earthquake Browser (IEB).
The IEB combines the DMC's large database of earthquakes with the popular
Google Maps web interface. The IEB is useful both educationally and as
a research tool. With the IEB you can quickly find earthquakes in any
region of the globe and then import this information into the GEON Integrated
Data Viewer (IDV) where the hypocenters may be visualized in three dimensions.
The GEON IDV is a powerful, free, Java based, desktop application that allows 3D visualization
of complex solid earth science data.
The IEB features a simple, yet powerful, user interface.
To start using it, you simply zoom and pan a map of the world just as
you would with any other Google map. By default, the IEB shows the most
recent 200 events in any given view. The number of events shown can be
varied from 100 to 5000 while the prioritization of events (which events
have priority to be shown) can be toggled between recent events and larger
events.
In the map, we have zoomed down to a region
on the west coast of South America.
The 1000 largest events from this region are
displayed. A distinctive line of deep (red) events are shown on the
eastern side of the selection.
Links at the top of the page allow the user to download the data plotted
on the map. The data can be viewed as an HTML table or exported as a
NetCDF (Network Common Data Form) binary. The exported NetCDF data can
then be imported into the GEON IDV.
On line help (Click
Here) gives detailed instructions on how to import data from the
IEB into the GEON IDV along with other useful information.
The next image is an animation taken from the GEON IDV using the NetCDF
data exported from the previous map. The line of deep events is clearly
seen as a straight line at depth.
Advanced Controls
Advanced controls in the IEB allow users to select events by (1) Time
Range, (2) Magnitude Range, (3) Depth Range, (4) Catalog, (5) Contributor
and (6) Magnitude Type. Using these controls can be very informative.
For example, constraining event depth ranges from 700 to 900 km shows
that majority deep events are located near the Tonga trench as shown
in the following map:
Constraining time ranges can be useful in estimating how many events
occur in a given region. For example, selecting a region roughly covering
the west coast of the United States and selecting the time range 2000-2004
and the magnitude range 3 and greater results in 2033 earthquakes being
selected. If the magnitude range is limited to 4 and greater, 124 events
are selected.
Seismo-surfing
"Seismo-surfing" around the world can be quite interesting
and fun. The following maps shows Mt.
St. Helens Vocano in Washington,
along with nicely collocated earthquake events.
How it Works
IEB is a Google Map "Mashup" composed of a Google Map, HTML
and Javascript code and an IRIS earthquake web-service. The web-service
accesses several earthquake catalogs stored
in the IRIS database. In total, the database contains around 2 million
unique events dating from the early 1960s until present. To make the
earthquake web-service fast, all events from the IRIS database are cached
in memory on an IRIS server. Every 15 minutes the cache is synchronized
with the IRIS earthquake database.
Javascript code in the IEB web page calls back to the Google web site
to retrieve map information and calls back to the IRIS earthquake web-service
to retrieve earthquake information. The earthquake information is returned
in an XML format. With the advent of modern web-browsers this type of
technology architecture is becoming increasingly common. It goes by the
acronym AJAX which stands for Asynchronous JavaScript and XML. AJAX technology
places a heavy burden on the user's web browser. Recent versions of Firefox
seem to work best. Microsoft Internet Explorer 6 and below are not supported.
The earthquake catalogs are provided by USGS/NEIC, ISC and the ANF.
Conclusion
The IEB is part of a new wave of web-service based technology being
developed at the IRIS DMC. The IEB makes a large data set quickly and
easily available. We would like to give special thanks to UNAVCO's Stuart
Weir for his help in integrating IEB data with the GEON IDV.
Go
to IRIS Earthquake Browser
Submitted by Bruce Weertman and Tim Knight, IRIS DMC |
