UNR Seismological Lab Combined Catalogs

J. Louie, 5/19/95

Availability

The UNRSL has available catalogs of earthquake seismicity developed by the Nevada Seismological Laboratory at the University of Nevada, Reno. Please contact Prof. John N. Louie (702-784-4219; louie@seismo.unr.edu) for more information on these data.

For more recent earthquake location and magnitude data, execute ``finger quake@seismo.unr.edu'' on an Internet-connected UNIX system. For other systems, use the Mosaic or Netscape programs to access the Uniform Resource Locator (URL) `` gopher://seismo.unr.edu:79/0quake''.

Available by anonymous FTP are catalogs resulting from the operation of UNR's Western Great Basin Seismic Network, recent operations of the Southern Great Basin Seismic Network, and combined catalogs merging these catalogs with other regional catalogs.

The FTP directory contains this description (also as a README text file) and the files:

	calnev3.cat
	calnev3.good.cat
	calnev.cat
	calnev.cat.Z
	*.hcat

The "*.hcat" files are ascii catalogs in HCAT format resulting from the operation of the Western Great Basin Seismic Network alone.

calnev.3.cat is a version of the California-Nevada Combined Catalog including only events of magnitude 3 or greater. This file has the ascii format:

yr mo da hrmin sec  lat   lon   dep   mag  qual
I4 I3 I3 I5    F8.4 F10.4 F10.4 F10.4 F7.2 A5

calnev3.good.cat includes only events having proper time field values, eliminating largely events having origin time seconds over 59.99. While these times are believed to be correct, they violate the column format.

The full California-Nevada Combined Catalog calnev.cat is about 20 megabytes in size. calnev.cat.Z is a version compressed via the UNIX "compress" command, with adaptive Lempel-Ziv coding, and is a binary file 6 megabytes in size.

Forms-capable WWW browsers such as Mosaic 2.0 and Netscape can enter parameters into the UNRSL WWW server to search these catalogs by date, magnitude, depth, and location.

Software to plot maps and cross sections including these catalogs on UNIX workstations running X-windows is available via anonymous ftp to this machine (quake.seismo.unr.edu) in the file /pub/louie/louie.tar.Z. See that directory on how to extract and compile the "xmap" application program.

Developing the Combined Catalogs

The following table shows the data we merged into this combined catalog:

Data Source	Time Period	No. of Events	Comments
_______________________________________________________________________
WGBSN		1852-6/92	 43582		All events included
SGBSN		1/31-9/92	 21678		All events included
NEIC		1897-11/88	 17618		Worldwide
Harvard-CMT	1/77-6/92	 10159		Worldwide M>=5
CIT		1/32-11/92	205252		All events included
CIT		1/92-7/14/93	 45930		All events included
WGBSN		1/92-4/93	  6477		All events included

The resulting combined catalog lists 302646 events after culling of duplicates. Events were considered duplicate if they appeared in two or more catalogs, with the listed origin times differing by 60 s or less and listed locations separated by 100 km or less. We always took the largest magnitude given by any catalog for a duplicated event. Event hypocenters, origin times, and quality were taken from the catalog listing produced by the network closest to the epicenter. We believe this combined catalog should list all events of magnitude 3 or greater occurring after 1972 and through April 1993 in western Nevada, southern Nevada, eastern California, and Southern California.

Quality ratings in the Combined Catalogs reflect the sources of the catalog listings. Here are some examples:

``ab'' - quality rating given by UNR since 1980; the first letter reflecting epicenter location quality, and the second reflecting hypocenter depth estimate quality.
``ABC'' - quality ratings given by the USGS, Golden, for SGBSN events from 1978 through 1992. The first rating is of origin time accuracy, the second of location quality, and the third is of magnitude accuracy. If one of these was not rated, a question mark is substituted, as in ``A?C''.
``GDY'' - Pre-1978 historical events in the southern Great Basin from the Gawthrop-Dewey catalog. No quality rating is given.
``CDM'', ``SRA'', ``GUT'', ``CGS'', etc. - The first three letters of the network data source given for southern Great Basin events listed on the 1991 NEIC worldwide catalog data CD-ROM. No quality rating is given.
``cmt'' - indicates an event from the Harvard CMT catalog.
``A'' - quality rating assigned by Caltech since 1932.

The combined catalogs are described and tested in the following publication:

J. G. Anderson, J. N. Brune, J. N. Louie, Y. Zeng, M. Savage, G. Yu, Q. Chen, and D. dePolo, 1994, Seismicity in the western Great Basin apparently triggered by the Landers, California Earthquake, 28 June 1992: Bull. Seismol. Soc. Amer., 84, 863-891.