Paleoseismology of Utah, Volume 14 PALEOSEISMIC INVESTIGATION AND LONG-TERM SLIP HISTORY OF THE HURRICANE FAULT IN SOUTHWESTERN UTAH by William R. Lund1, Michael J. Hozik2, and Stanley C. Hatfield3 1Utah Geological Survey 88 Fiddler Canyon Road, Suite C Cedar City, UT 84720 2The Richard Stockton College of New Jersey P.O. Box 195, Pomona, NJ 08240-0195 3Southwestern Illinois College 2500 Carlyle Ave., Belleville, IL 62221 Cover Photo: Scarp formed on the Hurricane fault at Shurtz Creek about 8 km south of Cedar City. ISBN 1-55791-760-4 SPECIAL STUDY 119 UTAH GEOLOGICAL SURVEY a division of Utah Department of Natural Resources 2006 STATE OF UTAH Jon Huntsman, Jr., Governor DEPARTMENT OF NATURAL RESOURCES Michael Styler, Executive Director UTAH GEOLOGICAL SURVEY Richard G. Allis, Director PUBLICATIONS contact Natural Resources Map/Bookstore 1594 W. North Temple Salt Lake City, Utah 84116 telephone: 801-537-3320 toll-free: 1-888-UTAH MAP Web site: http://mapstore.utah.gov email: [email protected] THE UTAH GEOLOGICAL SURVEY contact 1594 W. North Temple, Suite 3110 Salt Lake City, Utah 84116 telephone: 801-537-3300 fax: 801-537-3400 Web site: http://geology.utah.gov Although this product represents the work of professional scientists, the Utah Department of Natural Resources, Utah Geological Survey, makes no warranty, expressed or implied, regarding its suitability for any particular use. The Utah Department of Natural Resources, Utah Geological Sur- vey, shall not be liable under any circumstances for any direct, indirect, special, incidental, or consequential damages with respect to claims by users of this product. The Utah Department of Natural Resources receives federal aid and prohibits discrimination on the basis of race, color, sex, age, national origin, or disability. For information or complaints regarding discrimination, contact Executive Director, Utah Department of Natural Resources, 1594 West North Temple #3710, Box 145610, Salt Lake City, UT 84116-5610 or Equal Employment Opportunity Commission, 1801 L. Street, NW, Washing- ton DC 20507. FOREWORD This Utah Geological Survey Special Study, Paleoseismic Investigation and Long-Term Slip History of the Hurricane Fault in Southwestern Utah, is the fourteenth report in the Paleoseismology of Utah series. This series makes the results of paleoseis- mic investigations in Utah available to geoscientists, engineers, planners, public officials, and the general public. These studies provide critical information regarding paleoearthquake parameters such as earthquake timing, recurrence, displacement, slip rate, and fault geometry, which can be used to characterize potential seismic sources and evaluate the long-term seismic hazard pre- sented by Utah’s Quaternary faults. This report presents the results of a study of the Hurricane fault in Utah, and is part of a more extensive National Earthquake Hazards Reduction Program-funded cooperative study by the Utah Geological Survey (UGS) and Arizona Geological Survey (AZGS) of the Hurricane fault in Utah and Arizona. The Hurricane fault is one of the longest and most active of several large, late Cenozoic, west-dipping normal faults within the structural and seismic transition between the Colorado Plateau and Basin and Range physiographic provinces. Assessing the seismic hazard of the Hurricane fault is important because southwestern Utah is experiencing a now decades-long construction and population boom. Results of the AZGS study of the Hurricane fault in Ari- zona are reported elsewhere. This study shows that (1) the rate of slip on the Hurricane fault has slowed in more recent geologic time, (2) a previously identified structural segment boundary near Anderson Junction is likely a seismogenic segment boundary as well, (3) a third, previously unrecognized seismogenic segment likely exists at the north end of the fault, and (4) two of the three seismogenic segments recognized in Utah have experienced Holocene surface faulting. Based on these study results, the Hurricane fault in Utah is considered active and capable of generating earthquakes in excess of M 7.0. William R. Lund, Editor Paleoseismology of Utah Series CONTENTS ABSTRACT . .1 INTRODUCTION AND OVERVIEW . .2 THE HURRICANE FAULT IN SOUTHWESTERN UTAH . .5 Previous Investigations . .5 Physiography and General Geology . .6 PALEOSEISMIC INVESTIGATIONS . .7 Field Reconnaissance . .8 Fault Section 1: Utah–Arizona Border to Large Unnamed Drainage . .8 Fault Section 2: Large Unnamed Drainage to Frog Hollow . .8 Fault Section 3: Frog Hollow to Anderson Junction . .9 Fault Section 4: Anderson Junction to Locust Creek . .9 Fault Section 5: Locust Creek to Murie Creek . .10 Fault Section 6: Murie Creek to Cedar City . .10 Discussion . .11 Age of young faulting . .11 Variations in slip rate along the fault . .11 Scarcity of fault scarps . .12 Sites Identified for Possible Detailed Paleoseismic Study . .12 Shurtz Creek Site . .12 Site geology . .12 Surface age estimates from soil development . .13 Surface age estimates from cosmogenic isotopes . .13 Net vertical displacement and vertical slip-rate estimate . .14 Coyote Gulch Site . .14 Site geology . .14 Surface age estimates from soil development . .15 Net vertical displacement and vertical slip-rate estimate . .16 Middleton Site . .16 Bauer Site . .16 Kanarraville Site . .16 Water Tank Site . .17 Trenching . .17 Dating Stream and Alluvial-Fan Deposits . .17 Middleton Site . .17 Bauer Site . .19 Coyote Gulch Site . .19 Discussion . .24 Long-Term Slip Rates from Displaced Basalt Flows . .24 Basalt Correlation . .26 Basalt Age Estimates . .26 Evaluating Near-Fault Deformation . ..