Revised Historical Earthquake Catalog for the Utah Region, 1850- June 1962

Compiled by Walter J. Arabasz, 10 January 2019

This earthquake catalog is the most complete catalog of the University of Utah Seismograph Stations (UUSS) presently available for the Utah Region (UTR: lat. 36.75° to 42.50° N, long. 108.75° to 114.25° W) for the time period prior to the beginning of the UUSS instrumental earthquake catalog.  This historical catalog begins in 1850, the year of publication of the first newspaper in Utah, and extends through June 1962. A uniform moment magnitude is assigned to every earthquake for which suitable size information is available (398 of 566).

  • Note: In the Hypo71 sum format, the following letter codes are used in Column 47 to characterize the event magnitude listed in Columns 48-52
    • B = Best-estimate moment magnitude from Arabasz and others (2017).
    • F = Shock reported in U.S. Geological Survey (USGS) source catalogs as “felt:; no magnitude or other size information available.
    • X = Magnitude unknown (shock instrumentally located by U.S. Coast and Geodetic Survey).
    • N = Shock reported in USGS source catalogs with magnitude < 2.9 on Nuttli magnitude scale, MN; equivalent moment magnitude uncertain.
    • M = Observed moment magnitude from a direct instrumental measurement of seismic moment.

Background Information

This catalog augments the comprehensive, uniform moment magnitude catalog of Arabasz and others (2016), which lists 395 earthquakes in the UTR during the pre-July 1962 period.  For this region and time period, the latter catalog excluded 166 documented earthquakes of unknown size, two shocks judged to be below the magnitude threshold of interest, and three shocks inferred to be mining-related.  Adding these 171 earthquakes results in a total of 566 events in this augmented catalog, accounting for all known historical shocks in the UTR.

Significantly, the earthquake compilation of Arabasz and others (2016) unified earlier authoritative source catalogs compiled or produced directly by the UUSS and the U.S. Geological Survey (USGS).  The assignment of uniform moment magnitude with quantified magnitude uncertainty was central to the exercise. We refer the reader to that publication for details.  [For the pre-July 1962 time period, the UUSS source catalog that was integrated with USGS catalogs was the historical earthquake catalog compiled by Arabasz and McKee (1979).]  

It should be noted that the earthquake database of Arabasz and others (2017), compiled for a map of Utah earthquakes (1850‒2016) and Quaternary faults (Bowman and Arabasz, 2017), simply incorporated the historical earthquake catalog of Arabasz and others (2016) for the UTR.  The 2017 earthquake database contains 398 historical earthquakes (1850 through June 1962) in the UTR, geographically separated into an “Earthquake Catalog” and a “Coal-Mining Region Catalog.”  The total of 398 is accounted for by the addition of three mining-related shocks to the original 395 earthquakes. Note that an earthquake on June 2, 1928 (09:00) was inadvertently included in both subcatalogs.

References

Arabasz, W.J., and McKee, M.E., 1979, Utah earthquake catalog, 1850–June 1962, in Arabasz, W.J., Smith, R.B., and Richins, W.D., editors, Earthquake studies in Utah 1850 to 1978: Salt Lake City, University of Utah Seismograph Stations, Department of Geology and Geophysics, p. 119–121, 131–143.

Arabasz, W. J., Pechmann, J. C., and Burlacu, R., 2016, A uniform moment magnitude earthquake catalog and background seismicity rates for the Wasatch Front and surrounding Utah region, appendix E of Working Group on Earthquake Probabilities, Earthquake probabilities for the Wasatch Front region in Utah, Idaho, and Wyoming: Utah Geological Survey Miscellaneous Publication 16-3, p. E-1 to E-126 plus 10 electronic supplements.

Arabasz, W. J., Burlacu, R., and Pechmann, J. C., 2017, Earthquake database for Utah Geological Survey Map 277: Utah earthquakes (1850–2016) and Quaternary faults: Utah Geological Survey Open-File Report 667, 12 p. plus 4 electronic supplements.

Bowman, S. D., and Arabasz, W. J., 2017, Utah earthquakes (1850–2016) and Quaternary faults: Utah Geological Survey Map 277, 1 plate, scale 1:500,000.