QUATERNARY TECTONICS OF UTAH WITH EMPHASIS ON EARTHQUAKE-HAZARD CHARACTERIZATION by Suzanne Hecker Utah Geologiral Survey BULLETIN 127 1993 UTAH GEOLOGICAL SURVEY a division of UTAH DEPARTMENT OF NATURAL RESOURCES 0 STATE OF UTAH Michael 0. Leavitt, Governor DEPARTMENT OF NATURAL RESOURCES Ted Stewart, Executive Director UTAH GEOLOGICAL SURVEY M. Lee Allison, Director UGSBoard Member Representing Lynnelle G. Eckels ................................................................................................... Mineral Industry Richard R. Kennedy ................................................................................................. Civil Engineering Jo Brandt .................................................................................................................. Public-at-Large C. Williatn Berge ...................................................................................................... Mineral Industry Russell C. Babcock, Jr.............................................................................................. Mineral Industry Jerry Golden ............................................................................................................. Mineral Industry Milton E. Wadsworth ............................................................................................... Economics-Business/Scientific Scott Hirschi, Director, Division of State Lands and Forestry .................................... Ex officio member UGS Editorial Staff J. Stringfellow .......................................................................................................... Editor Patti F. MaGann, Sharon Hatnre ............................................................................... Editorial Staff Patricia H. Speranza, Jatncs W. Parker, Lori Douglas ............................................... Cartographers UTAH GEOLOGICAL SURVEY 2363 South Foothill Drive Salt Lake City, Utah 84109-1491 THE UTAH GEOLOOICAL SURVEY is organized into three geologic programs with Administration, Editorial, and Computer Resources providing necessary support to the programs. THE ECONOMIC GEOLOOY PROORAM undertakes studies to identify coal, geothermal, uranium, hydrocarbon, and industrial and metallic mineral resources; to initiate detailed studies of the above resources including mining district and field studies; to develop computerized resource data bases, to answer state, federal, and industry requests for information; and to encourage the prudent development of Utah's geologic resources. THE APPLIED GEOLOOY PROORAM responds to requests from local and state governmental entities for engineering geologic investigations; and identifies, documents, and interprets Utah's geologic hazards. THE GEOLOOIC MAPPING PROORAM maps the bedrock and surficial geology of the state at a regional scale by county and at a more detailed scale by quadrangle. Information Geologists answer inquiries from the public and provide information about Utah's geology in a non-technical format The UGS manages a library which is open to the public and contains many reference works on Utah geology and many unpublished documents on aspects of Utah geology by UGS staff and others. The UGS has begun several computer data bases with information on mineral and energy resources, geologic hazards, stratigraphic sections, and bibliographic references. Most files may be viewed by using the UGS Library. The UGS also manages a sample library which contains core, cuttings, and soil samples from mineral and petroleum drill holes and engineering geology investigations. Samples may be viewed at the Sample Library or requested as a loan for outside study. The UGS publishes the results of its investigations in the form of maps, reports, and compilations of data that are accessible to the public. For information on UGS publications, contact the UGS Sales Office, 2363 South Foothill Drive, Salt Lake City, Utah 84109-1491, (801)467-7970. The Utah Department ofNatural Resources receives federal aid and prohibits discrimination on the basis of race, color, sex, age, national origin, or handicap. For information or complaints regarding discrimination, contact Executive Director, Utah Department ofNatural Resources, 1636 West North Temple #316, Salt Lake City, UT 84116-3193 or Office of Equal Opportunity, U.S. Department of the Interior, Washington, DC 20240. 0 Printed on recycled paper CONTENTS ABS1RACT ............................................................... 1 IN1RODUCTION . 1 1ECTONIC-ACTIVITY P ARAME1ERS AND COMPILATION 1ECHNIQUES . 4 PREVIOUS WORK: REGIONAL STUDIES . 5 PHYSIOGRAPHIC AND TECTONIC SETTING . 6 EARTHQUAKE MAGNITUDES AND SURFACE FAULT-RUPTURE DIMENSIONS . 8 COMPLE1ENESS OF THE QUA1ERNARY 1ECTONIC RECORD ................................ 10 DISTRIBUTION AND PAT1ERNS OF QUATERNARY 1ECTONICFEATURES ........................ 11 Wasatch Front Region ...................................................... 12 Southwestern Utah . 17 West-Central Utah ........................................................ 18 Eastern Utah ........................................................... 19 Areas of Folding and Distributive Faulting ........................................... 19 Areas of Volcanism . 20 STYLES OF FAULTING AND 1ECTONIC PROCESSES: IMPLICATIONS FOR EARTHQUAKE- HAZARD CHARACTERIZATION . 20 Basin and Range - Middle Rocky Mountains Transition Zone . 22 Basin and Range of West-Central Utah ............................................. 23 Basin and Range - Colorado Plateau Transition Zone . 27 Colorado Plateau . 29 SUMMARY ............................................................... 29 ACKNOWLEDGMENTS ........................................................ 31 REFERENCES ............................................................. 32 APPENDICES Appendix A. Tectonic-activity information for Quaternary faults and folds in Utah . 39 Appendix B. Age data for Quaternary volcanic rocks in Utah ................................ 121 Appendix C . 137 Alphabetical listing of Quaternary faults and folds in Utah . 137 Alphabetical listing of Quaternary volcanic rocks in Utah . 144 References used to compile plates 1 and 2 . 146 Index maps for plates 1 and 2 showing location numbers of faults, folds, and volcanic rocks listed in appendices A and B . in pocket ILLUSTRATIONS Plate 1. Quaternary faults and folds, Utah . in pocket Plate 2. Quaternary volcanic rocks and vents, Utah . in pocket FIGURE CAPTIONS Figure 1. A) Major physiographic boundaries with respect to the transition zone between provinces, Utah. B) Quaternary tectonic features and seismicity of Utah with respect to the Basin and Range- - Colorado Plateau - Middle Rocky Mountains transition zone. 3 Figure 2. Landsat image showing an example of basin-and-range topography. 6 Figure 3. Index map of the Intermountain seismic belt and historical earthquakes of magnitude 6.0 and greater. 7 Figure 4. Landsat image of the Basin and Range - Middle Rocky Mountains transition zone in Utah. 9 Figure 5. Landsat image of the northern High Plateaus in the Basin and Range - Colorado Plateau transition zone. 9 Figure 6. Landsat image of the Paradox Basin in the Colorado Plateau. 9 Figure 7. Fault scarp formed during the 1934 Hansel Valley earthquake. ............................. 10 Figure 8. Quaternary tectonic map showing regions used to organize discussion on the distribution and patterns of Quaternary tectonism. 13 Figure 9. Oblique aerial views of the Wasatch fault zone. A) Salt Lake City segment . .14 B) Nephi segment ............................................. .14 Figure 10. Cumulative frequency- magnitude plot for independent main shocks in the Wasatch Front region and recurrence-interval estimates for large-magnitude earthquakes. .. 16 Figure 11. Timing of surface-faulting events on segments of the Wasatch fault zone during the past 6,000 years. 16 Figure 12. View of the Hurricane fault at the base of the Hurricane Cliffs near Pintura. .. 18 Figure 13. Timing of some latest Pleistocene and Holocene tectonic events in west-central Utah. .. 19 Figure 14. Oblique aerial view of the Redmond Hills diapiric salt anticline. .. 21 Figure 15. Oblique aerial view of Fumarole Butte at the northern end of the Drum Mountains fault zone. .. 21 Figure 16. Oblique aerial view of Tabernacle Hill basalt flow and tuff ring. .. 21 Figure 17. Generalized cross section showing fault geometry on the west side of the Crawford Mountains. 23 Figure 18. Region of west-central and southwestern Utah where detachment geometries have been identified within the upper crust . 23 Figure 19. Cross sections showing interpretations of regional crustal structure, western Utah. ..... 24 Figure 20. A) Clear Lake fault zone superimposed on depth contour map of the Sevier Desert detachment. 25 B) Geologic cross section of the Sevier Desert basin. 25 Figure 21. Oblique aerial view along the Drum Mountains fault zone ... 26 Figure 22. Oblique aerial view of the Joes Valley graben. ....... .. 28 TABLE Table 1. Surface-faulting earthquakes in the past 15,000 years in the Wasatch Front region .................... 15 QUATERNARY TECTONICS OF UTAH WITH EMPHASIS ON EARTHQUAKE-HAZARD CHARACTERIZATION by Suzanne Heckel Utah Geological Survey ABSTRACT years for the middle to late Holocene, but only 220 years for the past 1,500 years. Other patterns of spatially and temporally This report consolidates and synthesizes information on clustered tectonic activity in northern and west-central Utah Quaternary faulting, folding, and volcanism in Utah and charac­