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

Author: William R. Lund

Publisher: Utah Geological Survey

Published: 1998

Total Pages: 28

ISBN-13: 1557916136

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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

Consensus Preferred Recurrence-interval and Vertical Slip-rate Estimates
Consensus Preferred Recurrence-interval and Vertical Slip-rate Estimates

Author: William R. Lund

Publisher: Utah Geological Survey

Published: 2005-06-30

Total Pages: 114

ISBN-13: 1557917272

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This report presents the results of the Utah Quaternary Fault Parameters Working Group (hereafter referred to as the Working Group) review and evaluation of Utah’s Quaternary fault paleoseismic-trenching data. The purpose of the review was to (1) critically evaluate the accuracy and completeness of the paleoseismictrenching data, particularly regarding earthquake timing and displacement, (2) where the data permit, assign consensus, preferred recurrence-interval (RI) and vertical slip-rate (VSR) estimates with appropriate confidence limits to the faults/fault sections under review, and (3) identify critical gaps in the paleoseismic data and recommend where and what kinds of additional paleoseismic studies should be performed to ensure that Utah’s earthquake hazard is adequately documented and understood. It is important to note that, with the exception of the Great Salt Lake fault zone, the Working Group’s review was limited to faults/fault sections having paleoseismic-trenching data. Most Quaternary faults/fault sections in Utah have not been trenched, but many have RI and VSR estimates based on tectonic geomorphology or other non-trench-derived studies. Black and others compiled the RI and VSR data for Utah’s Quaternary faults, both those with and without trenches.

Paleoseismic Investigation of the Northern Strand of the Nephi Segment of the Wasatch Fault Zone at Santaquin, Utah
Paleoseismic Investigation of the Northern Strand of the Nephi Segment of the Wasatch Fault Zone at Santaquin, Utah

Author: Christopher B. DuRoss

Publisher: Utah Geological Survey

Published: 2008

Total Pages: 39

ISBN-13: 1557917892

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This CD contains a 33 page report, appendix, and plate. This study presents the results of fault-trench excavations near Santaquin, Utah, and includes discussion of (1) previous paleoseismic investigations on the Nephi segment, (2) the geology of the Santaquin trench site and excavations (3) paleoseismic results, including the timing of the most recent surface-faulting earthquake, fault displacement and slip rate, and surface-faulting earthquake recurrence and (4) implications for the segmentation of the southern Wasatch fault zone.

Paleoseismic Investigation of the Clarkston, Junction Hills, and Wellsville Faults, West Cache Fault Zone, Cache County, Utah
Paleoseismic Investigation of the Clarkston, Junction Hills, and Wellsville Faults, West Cache Fault Zone, Cache County, Utah

Author: Bill D. Black

Publisher: Utah Geological Survey

Published: 2000

Total Pages: 29

ISBN-13: 1557916462

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Field work for this paleoseismic investigation was performed in 1997 at three sites (Winter Canyon, Roundy Farm, and Deep Canyon) on the Clarkston, Junction Hills, and Wellsville faults. These faults, along with several lesser associated faults nearby, comprise the West Cache fault zone on the west side of Cache Valley. No previous paleoseismic studies had been conducted on these faults. The information reported here on the size, timing, and recurrence of surface-faulting earthquakes on the West Cache fault zone is critical to public officials, planners, and others making decisions regarding earthquake-hazard mitigation in Cache Valley and the northern Wasatch front. 23 pages + 1 plate

History of Late Holocene Earthquakes at the Willow Creek Site and on the Nephi Segment, Wasatch Fault Zone, Utah
History of Late Holocene Earthquakes at the Willow Creek Site and on the Nephi Segment, Wasatch Fault Zone, Utah

Author: Anthony J. Crone

Publisher: Utah Geological Survey

Published: 2014-09-15

Total Pages: 65

ISBN-13: 1557918945

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This 43-page report presents new data from the Willow Creek site that provides well-defined and narrow bounds on the times of the three youngest earthquakes on the southern strand of the Nephi segment, Wasatch Fault zone, and refines the time of the youngest earthquake to about 200 years ago. This is the youngest surface rupture on the entire Wasatch fault zone, which occurred about a century or less before European settles arrived in Utah. Two trenches at the Willow Creek site exposed three scarp-derived colluvial wedges that are evidence of three paleoearthquakes. OxCal modeling of ages from Willow Creek indicate that paleoearthquake WC1 occurred at 0.2 ± 0.1 ka, WC2 occurred at 1.2 ± 0.1 ka, and WC3 occurred at 1.9 ± 0.6 ka. Stratigraphic constraints on the time of paleoearthquake WC4 are extremely poor, so OxCal modeling only yields a broadly constrained age of 4.7 ± 1.8 ka. Results from the Willow Creek site significantly refine the times of late Holocene earthquakes on the Southern strand of the Nephi segment, and this result, when combined with a reanalysis of the stratigraphic and chronologic information from previous investigations at North Creek and Red Canyon, yield a stronger basis of correlating individual earthquakes between all three sites.

Earthquake Probabilities for the Wasatch Front Region in Utah, Idaho, and Wyoming
Earthquake Probabilities for the Wasatch Front Region in Utah, Idaho, and Wyoming

Author: Working Group on Utah Earthquake Probabilities

Publisher:

Published: 2016

Total Pages: 164

ISBN-13: 9781557919236

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This publication presents probabilistic earthquake forecasts developed by the Working Group on Utah Earthquake Probabilities which developed 30,50, and 100 year forecasts that include combined time dependent probabilities of large earthquakes for the five central segments of the Wasatch Fault Zone.

The Gilbert episode in the Great Salt Lake Basin, Utah
The Gilbert episode in the Great Salt Lake Basin, Utah

Author: Charles Gifford Oviatt

Publisher: Utah Geological Survey

Published: 2014-03-12

Total Pages: 24

ISBN-13: 1557918937

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This 20-page report summarizes observations of sediments and shorelines of the Gilbert episode in the Bonneville basin of northwestern Utah. Lake Bonneville dropped to altitudes similar to those of modern Great Salt Lake by 13,000 years ago, remained low for about 1400 years, then rapidly rose about 50 ft (15 m) during the Gilbert episode (about 11,600 years ago). The Gilbert lake was probably less extensive than shown by previous mapping of the Gilbert shoreline. The lake reached altitudes of 4250-4255 ft (1295-1297 m), and its shoreline, which is not well defined anywhere in the basin, was probably not deformed by residual isostatic rebound associated with removal of the Lake Bonneville water load. Holocene Great Salt Lake has not risen as high as the Gilbert-episode lake.

Investigation of land subsidence and earth fissures in Cedar Valley, Iron County, Utah
Investigation of land subsidence and earth fissures in Cedar Valley, Iron County, Utah

Author: Paul Inkenbrandt

Publisher: Utah Geological Survey

Published: 2014-03-12

Total Pages: 122

ISBN-13: 1557918910

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This 116-page report presents the results of an investigation by the Utah Geological Survey of land subsidence and earth fissures in Cedar Valley, Iron County, Utah. Basin-fill sediments of the Cedar Valley Aquifer contain a high percentage of fine-grained material susceptible to compaction upon dewatering. Groundwater discharge in excess of recharge (groundwater mining) has lowered the potentiometric surface in Cedar Valley as much as 114 feet since 1939. Groundwater mining has caused permanent compaction of fine-grained sediments of the Cedar Valley aquifer, which has caused the land surface to subside, and a minimum of 8.3 miles of earth fissures to form. Recently acquired interferometric synthetic aperture radar imagery shows that land subsidence has affected approximately 100 mi² in Cedar Valley, but a lack of accurate historical benchmark elevation data over much of the valley prevents its detailed quantification. Continued groundwater mining and resultant subsidence will likely cause existing fissures to lengthen and new fissures to form which may eventually impact developed areas in Cedar Valley. This report also includes possible aquifer management options to help mitigate subsidence and fissure formation, and recommended guidelines for conducting subsidence-related hazard investigations prior to development.