Yellowstone Region Earthquake Catalog
The Yellowstone region earthquake catalog is a list of instrumentally located earthquakes that have occurred in the Yellowstone region since November 1972. The Yellowstone region is defined as the area extending from 44º 0´ - 45º 10´ N latitude and from 109º 45´ - 111º 30´ West longitude. This region includes Yellowstone National Park and neighboring areas within approximately 24´ of the western park boundary, 15´ of the eastern park boundary, and 8´ of the northern and southern park boundaries. The U.S. Geological Survey (USGS) produced the original version of the catalog for the time period 1973-1981 (Pitt, 1987). The University of Utah Seismograph Stations (UUSS) produced the catalog for 1982 to the present (see Nava et al., 1996, and references therein).
2006 Revision of the 1982-2001 Catalog
In 2006, the UUSS completed a major revision of the magnitudes in the 1982-2001 Yellowstone region catalog. This revision added more than 400 magnitude determinations of the preferred type (local magnitude, ML) for the time period 1994-2001. It also corrected a systematic magnitude overestimation averaging 0.9 units in the other, more common type of magnitude determination (coda magnitude, MC) used during 1982-2001. See Summary of UUSS Magnitude Determinations: 1981-2006 for a more complete description of the magnitude revisions. Miscellaneous other problems in the catalog were corrected at the same time that the magnitude changes were implemented.
Husen and Smith (2004) produced a catalog of Yellowstone earthquakes for the time period November 1972 through December 2002 that features hypocenters computed using a three-dimensional velocity model. Their hypocenters should be more accurate than those in the UUSS catalog, which were computed using a one-dimensional velocity model (see Computation of UUSS Earthquake Locations: 1981 – Present ). However, the magnitudes in the UUSS catalog are an improvement on those in the Husen and Smith (2004) catalog. The UUSS catalog includes MLs for some earthquakes, whereas the Husen and Smith catalog does not. The MCs in the Husen and Smith catalog are mostly the same as in the UUSS catalog because they used the same methodology to compute them. However, Husen and Smith (2004) discarded as unreliable all MCs based on data from less than three stations. To avoid discarding these magnitudes, UUSS put considerable effort into adding data from more stations to these questionable MC determinations and performing various checks on all of the revised coda magnitudes (see Summary of UUSS Magnitude Determinations: 1981-2006 ).
The old Yellowstone catalog for 1981-2001 has about 18% more earthquakes than both the Husen and Smith (2004) catalog and the new UUSS catalog. The difference is primarily due to the fact that the old catalog included some earthquakes located with arrival time picks that came entirely from an automatic picking program or from seismic networks outside of the Yellowstone region (e.g., Nava et al., 1993).
The Yellowstone earthquake catalog is based primarily on data from a telemetered seismic network in the Yellowstone region. The U.S. Geological Survey operated this network from 1972 through 1981 and from 1984 until 1991 (Pitt, 1987). Until 1981, the data from this network were recorded at Yellowstone Park Headquarters at Mammoth, Wyoming (on tape recorders) and at the USGS office in Menlo Park, California (primarily on 16-mm analog film recorders), and were analyzed by the USGS. The Yellowstone network did not operate during 1982 and 1983. The locations and magnitudes for the few earthquakes in the catalog during this two-year period were determined by UUSS using data from other seismic stations in the vicinity. In November 1983, digital computer recording and analysis of the Yellowstone network data was initiated at the UUSS through the support of the USGS and the National Park Service. Operation and maintenance of the network was transferred to the UUSS in 1991.
The number of stations in the Yellowstone seismic network varied considerably from 1972 through 1981, reaching a high of 26 stations in October 1974 (Husen and Smith, 2004). From 1984 through 1991, the network consisted of 16 vertical-component stations. Three-component stations were added beginning in 1993 and broadband digital telemetry stations beginning in 1995. As of September 2006, the network consisted of 26 stations: six broadband 3-component digital telemetry stations—including two maintained by the USGS, three 3-component short-period stations, and 17 vertical-component short-period stations. Descriptions of the general seismicity and history of seismic recording in the Yellowstone National Park region can be found in Smith and Arabasz (1991) and Husen and Smith (2004).
Data Processing and Analysis, 1981-present
The data processing and analysis procedures for the 1982-present catalog are described in Nava et al. (1996) and other published catalogs referenced therein, and in the following more up-to-date documents:
- Overview of UUSS Data Processing and Analysis: 1981 – Present
- Summary of UUSS Magnitude Determinations: 1981-2006
- Computation of UUSS Earthquake Locations: 1981 – Present
- Quality and Completeness of UUSS Catalog Data: 1981 – Present
The catalog format is documented in
Husen, S., and R. B. Smith (2004). Probabilistic earthquake relocation in three-dimensional velocity models for the Yellowstone National Park region, Wyoming, Bull. Seism. Soc. Am. 94, 880-896.
Nava, S. J., R. B. Smith, L. L. Hall, E. McPherson, P. J. Oehmich, and R. A. Hutchinson (1993). Earthquake Catalog for the Yellowstone National Park Region: January 1 to December 31, 1991, Special Publication, University of Utah Seismograph Stations, Salt Lake City, Utah, 29 pp.
Nava, S. J., R. B. Smith, L. L. Hall, J. K. Whipp, E. McPherson, and R. A. Hutchinson (1996). Earthquake Catalog for the Yellowstone National Park Region: January 1, 1992 to December 31, 1994, Special Publication, University of Utah Seismograph Stations, Salt Lake City, Utah, 61 pp.
Pitt, A.M. (1987). Catalog of earthquakes in the Yellowstone National Park - Hebgen Lake Region, Wyoming, Montana, and Idaho, for the years 1973 to 1981, U.S. Geol. Surv., Open-File Rept. 87-611, 65 pp.
Smith, R. B., and W. J. Arabasz (1991). Seismicity of the Intermountain Seismic Belt, in Neotectonics of North America, D.B. Slemmons, E.R. Engdahl, M.D. Zoback, and D.D. Blackwell (Editors), Geol. Soc. Am. Decade Map Vol. 1, 185-228.