IRIS Knowledge Base

Q. IRIS provides data from several earthquake catalogs. What are all of these catalogs and where do they come from?

A. The catalogs are publications of earthquake origins and magnitudes from a particular institution.  Many of these institutions update their catalogs on a regular basis.

Some catalogs consist of preliminary determinations, while others are considered more authoritative and the product of months of processing.

The USGS NEIC puts out a catalog called the Preliminary Determination of Events (PDE), which is actually an aggregation of quick determinations as well as better quality bulletins that come weeks after the event has occurred.  The PDEs are automatically improved over time such that quality bulletins begin to replace quick determinations.

For more information on earthquake catalogs, please consult this web page.