William R. Lund

Bill D. Black

David P. Schwartz

Harold E. Gill

Bea H. Mayes

The South Fork Dry Creek and Dry Gulch sites lie within a few hundred meters of each other in the southeastern part of the Salt Lake Valley, and together provide the only location on the heavily urbanized Salt Lake City segment of the Wasatch fault zone where it is possible to develop a complete surface-faulting chronology for the segment since middle Holocene time (the past 6,000 years). Investigations at the two sites took place intermittently between 1985 and 1995 as permission was obtained to trench more and more of the scarps within the broad fault zone. The new information reported here on the size, timing, and especially recurrence of surface-faulting earthquakes on the Salt Lake City segment shows that the earthquake hazard presented by this segment of the Wasatch fault is greater than previously thought. Such information is vital to public officials, planners, and others making decisions regarding earthquake-hazard mitigation. 22 pages + 1 plate

Paleoseismic Investigation on the Salt Lake City Segment of the Wasatch Fault Zone at the South Fork Dry Creek and Dry Gulch Sites, Salt Lake County, Utah

Field work for this paleoseismic investigation at Rock Canyon was performed in 1988. It was one of three studies conducted in the late 1980s and early 1990s to determine if the Provo segment of the Wasatch fault zone should be subdivided into three smaller segments as tentatively proposed by Machette and others on the basis of their geologic mapping. This investigation was the last of the three studies performed. Those results, combined with the results of paleoseismic investigations at American Fork Canyon and Mapleton, showed that the Wasatch fault where it passes through Utah Valley probably consists of a single, almost 70-kilometer-Iong fault segment (Machette and others, 1992). Publication of the details of the Rock Canyon study has been delayed for several years, chiefly due to the press of new job duties on the part of the investigators. The information remains important and is presented here for the use of those individuals interested in earthquake hazards and seismic-source characteristics of the Wasatch fault in Utah Valley. 21 pages + 2 plates

Paleoseismic Investigation at Rock Canyon, Provo Segment, Wasatch Fault Zone, Utah County, Utah

Barry J. Solomon

Kimm M. Harty

The petrographic database consists of 705 maceral analyses, reflectance measurements, and density and porosity determinations from Utah coal samples. These data were collected by the Utah Geological Survey from 1982 to 1995. Samples were collected from seven of Utah's 22 coal fields. Coal fields sampled are the Book Cliffs (182 samples), Wasatch Plateau (262 samples), Emery (41 samples), Sego (27 samples), Henry Mountains (173 samples), Kaiparowits Plateau (12 samples), and Coalville (four samples). The data are sorted by coal-field names; within each field the analyses are arranged alphabetically by coal-bed name to facilitate comparison. The aim of the database is to provide the industry with information on petrographic properties of Utah coals. In addition, it should help the coal operators and purchasers to determine the best uses for Utah coals.

Bill D. Black

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