Global Catalog of Calibrated Earthquake Locations (GCCEL)
This section describes a repository of calibrated earthquake locations (referred to as the Global Catalog of Calibrated Earthquake Locations, GCCEL or “the Catalog”) that have been determined using the Hypocentroidal Decomposition algorithm for multiple event relocation (Jordan and Sverdrup, 1981), as implemented and developed in the program mloc by Eric Bergman since 1989. The source code, supporting data files and documentation for mloc are posted elsewhere on this website.
Since the late 1990s, mloc’s development has emphasized its use for obtaining calibrated locations, meaning hypocenters with minimal location bias from unknown Earth structure and with reliable estimates of uncertainty. Calibrated hypocenters are determined for clusters of earthquakes (up to about 200 events), typically in source regions up to about 150 km in size in order to minimize the biasing effects of lateral heterogeneity. For GCCEL emphasis is given to events that have been well-recorded at far-regional and teleseismic distances and for which focal depth can be constrained.
The Catalog contains the hypocenters and associated phase data for a globally-distributed set of calibrated earthquake clusters, as well as the regional velocity model, station coordinates, summary plots of the results and a commentary for each cluster. The official website also carries documentation on the standard approach used in these studies and the data file format. The Catalog does not carry the input files used for the relocation analysis with mloc, or most of the standard output files from a calibrated relocation analysis, but those files are all available on this website (see below). A large inventory of previously-analyzed clusters has been reprocessed for inclusion in the GCCEL, and new clusters will be added to the Catalog as they become available.
GCCEL is permanently archived by the U.S. Geological Survey’s National Earthquake Information Center, as an official USGS data product in a collaborative research environment called ScienceBase. The URL for GCCEL is:
https://doi.org/10.5066/P95R8K8G
Harley Benz manages the publication of GCCEL on ScienceBase. At this time the ScienceBase-hosted website is the official website for GCCEL, from which all currently-available data can be downloaded.
A paper summarizing the GCCEL project and data set has been published:
Bergman, E. A., H. M. Benz, W. L. Yeck, E. Karasözen, E. R. Engdahl, A. Ghods, G. P. Hayes, and P. S. Earle (2022). A Global Catalog of Calibrated Earthquake Locations, Seismol. Res. Lett. 94(1), 485-495, doi: 10.1785/0220220217
As of August 9, 2023, the GCCEL database contains 323 calibrated clusters.
GCCEL at the ISC
A recent version (July 22, 2023) of the GCCEL dataset has been published in the Data Repository of the International Seismological Centre (ISC), with the link https://doi.org/10.31905/MFDY4QHD. The ISC distribution is expected to be updated periodically, but not with each new calibrated cluster, as are the GCCEL dataset at USGS/ScienceBase and the MLOC data for GCCEL page of this website. With that caveat, the basic GCCEL dataset, contained in the file all_gccel.dat, is identical to what is offered on the ScienceBase website, but the ISC distribution contains additional data files for each cluster in the directory byCountry/ as well as the gccel.kmz file discussed below.
GCCEL in Google Earth
A KMZ file has been created for the GCCEL dataset to facilitate exploration by viewing in Google Earth (or any program that can display a KMZ file). It displays the hypocentroids of all calibrated clusters and the individual event epicenters. Display of the hypocentroids and the entire set of epicenters can be toggled on and off separately. If a hypocentroid icon (red) is clicked it displays detailed information about the cluster. The icons for individual events display the hypocenter, calibration level and magnitude when clicked.
Download the file gccel.kmz, release date August 9, 2023, 850 KB
MLOC data for GCCEL
The folders containing all files used for the calibrated relocation analysis (with the program mloc) of every cluster in GCCEL are available for download. Researchers who have installed mloc can use these files to investigate the calibrated relocation analysis of any GCCEL cluster, or to modify the analysis to suit their own needs.
There is one caveat: Each run of mloc uses certain output data from the previous run to set starting location parameters and certain statistical parameters that change slightly from run to run. Therefore, in order to attempt to reproduce the exact output of a cluster posted in GCCEL, it would be necessary to have access to some output files of the previous run. Because of the way the files are stored it would have been a substantial amount of extra work to include those files in the posted archives. A run of mloc started from the data files of the run posted in GCCEL will not, in general, be identical to the posted output. The differences will be minor (relative to uncertainties) in most cases, but could occasionally be significant. If you wish to reproduce any GCCEL results exactly, contact Eric Bergman.