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Earthquake Catalog Details

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Contributors | Creation | Authoritative regions
Caveats | Documentation

ANSS Worldwide Earthquake Catalog Description:

In the early 1990s, the CNSS initiated the effort to create a composite earthquake catalog. With the replacement of the CNSS by the ANSS, this effort is ongoing, with hope of expansion and improvement in the future.

The composite catalog is a world-wide earthquake catalog which is created by merging the master earthquake catalogs from contributing ANSS member institutions and then removing duplicate events, or non-unique solutions for the same event. Please note that, like all earthquake catalogs, the ANSS composite catalog should be used with care.

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Updates and Changes

01/29/2004
The USGS NEIC has resolved the problems with their contribution to the ANSS catalog! Global events should once again be available from the catalog.
12/04/2003
We have not received any contributions from the USGS NEIC since 11/18/2003. We are working with them and hope to fix this soon. In the meantime, there are no global events in the catalog from mid November to the present.
10/15/2003
We are experiencing problems with the September submission from NEIC. The submission is truncated in mid-September, which means that it is missing events - particularly the 9/25/2003 M8.3 in Hokkaido. We have notified NEIC about this problem and hope to have it resolved soon.
02/20/2003
The formatting problem with the CI submissions has been resolved! The data from 10/01/2002-present have been resubmitted and CI events no longer appear in West Africa.
01/30/2003
The problem with submission of the US catalog from USGS Golden has been fixed! Special thanks to Ray Buland and Doug Neuhauser who worked through a number of subtle security issues to fix this problem. As of today, the NEIC catalog is current.
01/07/2003
An alert user has notified us of a problem with the CI contributions to the ANSS composite catalog. For events submitted since 10/01/2002, a formatting problem has created erroneous locations. As a result, US and NC solutions are appearing for southern California earthquakes - and the CI events are being reported at locations in West Africa. We have notified Southern California about the problem and hope to have it resolved soon.
01/01/2003
We are currently experiencing problems with transmission of the US data from the USGS Golden. No catalog submissions have been received since mid-November. We hope to resolve this soon.
12/05/2002
The Hawaii catalog is back! After an absence of several months, the HV catalog has been reinstalled in the ANSS composite catalog. Events which were previously reported by NEIC should now appear with HV solutions. The newly installed catalog also solves an earlier problem with HV data reported in local time, rather than UTC.
11/05/2002
The CI and NC polygons were modified to reflect a change in the boundaries between the northern and southern California networks. The catalog was rerun with the new boundaries. This figure illustrates the new (dotted blue) and old (solid red) boundaries. No changes to the NN boundaries were made.
02/26/1997
The catalog search was modified:
  • Default output format now has more fields and precision.
  • Added event type selection.
  • Added option to include events with no reported magnitude.

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How to Access the ANSS Earthquake Catalog

Search the ANSS catalog
You may search the ANSS catalog using an easy-to-use Web form. Help on the form is available.
Earthquake lists and maps from the ANSS catalog
You may browse the collection of earthquake lists and maps generated from the ANSS catalog.
Copying the ANSS Composite Catalog:
The current ANSS composite catalog files are available via anonymous ftp at the NCEDC. The catalog is divided into monthly files. You may copy any or all of the ANSS catalog files to your system if you wish. However, you should be aware that the ANSS catalog at the NCEDC will be updated whenever any contributing network provides updated information.
ANSS Composite Catalog Format
There is online documentation that describes the ANSS composite catalog format.
ANSS Catalog Source Code Tables
provides a list of the codes used in the ANSS catalog for contributors of location and magnitude information.

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Contributing networks

Contributions to the ANSS catalog are made on a regional basis. Regions may contain one or more seismic networks and may be monitored by one or more institutions.

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ANSS Catalog Creation:

Each seismic network that contributes catalog data to the ANSS composite catalog is assigned a geographic region where that network's solution (location and magnitude) for earthquakes is considered authoritative. This means that if that network locates an earthquake in its authoritative region, the network's solution is considered to be the "best" solution, and its solution is guaranteed to be in the catalog.

If more than one network supplies a solution for the same earthquake, only one solution for that earthquake is included in the composite catalog. The current rules for chosing a solution for duplicate events is outlined below. These rules will be updated as we get more experience with the catalog.

  1. Events from all networks are merged together, and then divided into separate catalogs for each distinct authoritative network region.
  2. Each of the regional catalogs is independently examined for duplicate events (multiple solutions to the same earthquake), and are resolved as follows:
    • If one of the solutions comes from the authoritative network for this region, that network's solution is kept, and the other solutions for the event are discarded.
    • If none of the solutions are from the authoritative network for this region, the solution with the largest magnitude is kept, and the other solutions for the event are discarded.
  3. The remaining solutions from all regions are then merged, and examined for duplicate events.
    • If duplicate events are found, the solution with the largest magnitude is kept, and the other solutions for the event are discarded.

The ANSS composite catalog is created and stored at the Northern California Earthquake Data Center (NCEDC).

Duplicate Events

Each contributing seismic network is presumed to submit only one solution for each earthquake. However, it is entirely possible for multiple seismic networks to each contribute their own solution for the same earthquake. Since no two networks will locate an earthquake at the exact same location and time, we use the following critera to decide whether any 2 solutions represent the same earthquake:

  1. The two solutions must be submitted by different networks. We assume that each network has eliminated duplicate solutions to the same event within their own catalog.
  2. The two solutions must be within 100 km and within 16 seconds of each other.

Any two solutions that satisfy the above critera are considered duplicate solutions, and only one of them will be retained in the composite catalog.

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Authoritative Regions

Each reporting network is assigned an authoritative region, represented by a closed polygon and given as latitude and longitude pairs. The following maps shows the boundaries of the authoritative regions for the contributing networks. The symbols on the maps show the seismic station locations of the respective networks. Any region not assigned to a regional network is by default assigned to NEIC.

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Documentation

Catalog Search Help
Provides help on using the catalog search form.
Raw catalog format
The raw format of the ANSS catalog is the CNSS Ver 1.0.1 format.
Source Code Tables
Tables of the source ids used in the ANSS catalog to designate contributing institutions.
Catalog caveats
Documents some of the known problems with the catalog and provides figures showing data availability.