Brigham Young University Geoj (3Gy

BRIGHAM YOUNG UNIVERSITY GEOJ (3GY

GEOLOGICAL SOCIETY OF AMERICA

1997 ANNUAL MEETING SALT LAKE CITY, UTAH

PART2 TWO

EDITED BY PAUL KARL LINK AND BART J. KOWALLIS

VOLUME 42 1997 MESOZOIC TO RECENT GEOLOGY OF UTAH Edited by Paul Karl Link and Bart J. Kowallis

BRIGHAM YOUNG UNIVERSITY GEOLOGY STUDIES Volume 42, Part 11, 1997

CONTENTS

Triassic and Jurassic Macroinvertebrate Faunas of Utah: Field Relationships and Paleobiologic Significance ...... Carol M. Tang and David J. Bottjer

Part 2: Trace fossils, hardgrounds and ostreoliths in the Carmel Formation (Middle Jurassic) of southwestern Utah ...... Mark A. Wilson

Part 3: Low-diversity faunas of the Middle Jurassic Carmel Formation and their paleobiological implications ...... Carol M. Tang and David J. Bottjer

Part 4: Paleoecology of Lower Triassic marine carbonates in the southwestern USA ...... David J. Bottjer and Jennifer K. Schubert

Structure and Kinematics of a Complex Impact Crater, Upheaval Dome, Southeast Utah ...... Bryan J. Kriens, Eugene M. Shoemaker, and Ken E. Herkenhoff

Stratigraphy, and structure of the Sevier thrust belt, and proximal foreland-basin system in central Utah: A transect from the Sevier Desert to the Wasatch Plateau ...... T. E Lawton, D. A. Sprinkel, F! G. DeCelles, G. Mitra, A. J. Sussman,, and M. l? Weiss

Lower to Middle Cretaceous Dinosaur Faunas of the Central Colorado Plateau: A Key to Understanding 35 Million Years of Tectonics, Sedimentology, Evolution, and Biogeography ...... James I. Kirkland, Brooks Britt, Donald L. Burge, Ken Carpenter, Richard Cifelli, Frank DeCourten, Jeffrey Eaton, Steve Hasiotis, and Tim Lawton

Sequence Architecture, and Stacking Patterns in the Cretaceous Foreland Basin, Utah: Tectonism versus Eustasy ...... l? Schwans, K. M. Campion

Fluvial-Deltaic Sedimentation, and Stratigraphy of the Ferron Sandstone ...... Paul B. Anderson, Thomas C. Chidsey, Jr., and Thomas A. Ryer

Depositional Sequence Stratigraphy and Architecture of the Cretaceous Ferron Sandstone: Implications for Coal and Coalbed Methane Resources-A Field Excursion ...... James R. Garrison Jr., C. V van den Bergh, Charles E. Barker, and David E. Tabet Extensional Faulting, Footwall Deformation and Plutonism in the Mineral Mountains, Southern Sevier Desert ...... Drew S. Coleman, John M. Bartley, J. Douglas Walker, David E. Price, and Anke M. Friedrich

Neotectonics, Fault segmentation, and seismic hazards along the Hurricane fault in Utah and Arizona: An overview of environmental factors ...... Meg E. Stewart, Wanda J. Taylor, Philip A. Pearthree, Barry J. Solomon, and Hugh A. Hurlow

Part 2: Geologic hazards in the region of the Hurricane fault ...... William R. Lund

Part 3: Field Guide to Neotectonics, fault segmentation, and seismic hazards along the Hurricane fault in southwestern Utah and northwestern Arizona ...... Meg E. Stewart, Wanda J. Taylor, Philip A. Pearthree, Barry J. Solomon, and Hugh A. Hurlow

Fault-Related Rocks of the Wasatch Normal Fault ...... James l? Evans, W. Adolph Yonkee, William T. Parry, and Ronald L. Bruhn

Geologic Hazards of the Wasatch Front, Utah ...... Michael D. Hylland, Bill D. Black, and Mike Lowe

Bedrock Geology of Snyderville Basin: Structural Geology Techniques Applied to Understanding the Hydrogeology of a Rapidly Developing Region, Summit County, Utah ...... Kelly E. Keighley, W. Adolph Yonkee, Frank X. Ashland, and James l? Evans

New explorations along the northern shores of Lake Bonneville ...... Charles G. (Jack) Oviatt, David M. Miller, Dorothy Sack, and Darrell Kaufman

Quaternary Geology and Geomorphology, Northern Henry Mountains Region ...... Benjamin L. Everitt, Andrew E Godfrey, Robert S. Anderson, and Alan D. Howard

Part 2: Wind Erosion of Mancos Shale Badlands ...... Andrew E. Godfrey

Part 3: Long-Term Measurements of Soil Creep Rates on Mancos Shale Badland Slopes ...... Andrew E. Godfrey

Part 4: Vegetation and Geomorphology on the Fremont River ...... Ben Everitt

Part 5: Gravel Deposits North of Mount Ellen, Henry Mountains, Utah ...... Andrew E. Godfrey

Part 6: Monitoring flash floods in the Upper Blue Hills badlands, southern Utah ...... Gregory S. Dick, Robert S. Anderson, and Daniel E. Sampson

Part 7: Dating the Fremont River Terraces ...... James L. Repka, Robert S. Anderson, Greg S. Dick, and Robert C. Finkel A Publication of the Department of Geology Brigham Young University Provo, Utah 84602

Editor

Bart J. Kowallis

Brigham Young University Geology Studies is published by the Department of Geology. This publication consists of graduate student and faculty research within the department as well as papers submitted by outside contributors. Each article submitted is externally reviewed by at least two qualified persons.

Cover photos taken by Paul Karl Link. Top: Upheaval Dome, southeastern Utah. Middle: Luke Bonneville shorelines west of Brigham City, Utah. Bottom: Bryce Canyon National Park, Utah.

ISSN 0068-1016 9-97 700 23870124290 Preface

Guidebooks have been part of the exploration of the American West since Oregon Trail days. Geologic guidebooks with maps and photographs are an especially graphic tool for school teachers, University classes, and visiting geologists to become familiar with the temtory, the geologic issues and the available references. It was in this spirit that we set out to compile this two-volume set of field trip descriptions for the Annual Meeting of the Geological Society of America in Salt Lake City in October 1997. We were seeking to produce a quality product, with fully peer-reviewed papers, and user-friendly field trip logs. We found we were buck- ing a tide in our profession which de-emphasizes guidebooks and paper products. If this tide continues we wish to be on record as producing "The Last Best Geologic Guidebook." We thank all the authors who met our strict deadlines and contributed this outstanding set of papers. We hope this work will stand for years to come as a lasting introduction to the complex geology of the Colorado Plateau, Basin and Range, Wasatch Front, and Snake River Plain in the vicinity of Salt Lake City. Index maps to the field trips contained in each volume are on the back covers. Part 1 "Proterozoic to Recent Stratigraphy, Tectonics and Volcanology: Utah, Nevada, Southern Idaho and Central Mexico" contains a number of papers of exceptional interest for their geologic synthesis. Part 2 "Mesozoic to Recent Geology of Utah" concentrates on the Colorado Plateau and the Wasatch Front. Paul Link read all the papers and coordinated the review process. Bart Kowallis copy edited the manu- scripts and coordinated the publication via Brigham Young University Geology Studies. We would like to thank all the reviewers, who were generally prompt and helpful in meeting our tight schedule. These included: Lee Allison, Genevieve Atwood, Gary Axen, Jim Beget, Myron Best, David Bice, Phyllis Camillen, Marjorie Chan, Nick Christie-Blick, Gary Christenson, Dan Chure, Mary Droser, Ernie Duebendorfer, Tony Ekdale, Todd Ehlers, Ben Everitt, Geoff Freethey, Hugh Hurlow, Jim Gamson, Denny Geist, Jeff Geslin, Ron Greeley, Gus Gustason, Bill Hackett, Kimm Haw, Grant Heiken, Lehi Hintze, Peter Huntoon, Peter Isaacson, Jeff Keaton, Keith Ketner, Guy King, Me1 Kuntz, Tim Lawton, Spencer Lucas, Lon McCarley, Meghan Miller, Gautarn Mitra, Kathy Nichols, Robert Q. Oaks, Susan Olig, Jack Oviatt, Bill Perry, Andy Pulharn, Dick Robison, Rube Ross, Rich Schweickert, Peter Sheehan, Norm Silberling, Dick Smith, Barry Solomon, K.O. Stanley, Kevin Stewart, Wanda Taylor, Glenn Thackray and Adolph Yonkee. In addition, we wish to thank all the dedi- cated workers at Brigham Young University Print Services and in the Department of Geology who contributed many long hours of work to these volumes.

Paul Karl Link and Bart J. Kowallis, Editors Geologic Hazards of the Wasatch Front, Utah

MICHAEL D. HYLLAND BILL D. BLACK MIKE LOWE Utah Geological Survey, PO. Box 1461 00, Salt Lake City, Utah 84114-6100

ABSTRACT The results of recent and ongoing research into six significant geologic hazards of the Wasatch Front region will be summarized on this field trip, including: (1)surface fault rupture on the Salt Lake City segment of the Wasatch fault zone; (2) seismic site response in the Salt Lake Valley, including ground shaking and liquefaction; (3) liquefaction-induced landsliding at the Farmington Siding landslide complex; (4) lake flooding along the shores of Great Salt Lake; (5) debris-flow deposition on alluvial fans at the base of the Wasatch Range; and (6) landsliding in the Ogden area. The trip will ~rovidean opportunity to discuss the scientific, engineering, and administrative aspects involved in geologic-hazard evaluation in this rapidly growing region.

INTRODUCTION and near its gently sloping shores. A seiche hazard also exists because of the regional earthquake hazard. Further- Situated at the eastern margin of the Basin and Range more, thick deposits of soft, fine-grained lacustrine sediment physiographic province, the Wasatch Front is subject to a from repeated cycles of deep-water lakes that inundated variety of geologic hazards due to a unique combination of geologic, topographic, and climatic conditions. The Wasatch the valleys could amplify earthquake ground motions, and Front occupies a series of north-trending valleys at the foot loose, saturated sands are potentially liquefiable. of the western slope of the Wasatch Range (fig. 1). The This field trip provides an opportunity to observe and mountains rise steeply as much as 7,100 feet (2,165 m) discuss six of the most significant types of geologic hazards above the valley floor, reaching elevations near 12,000 feet of the Wasatch Front. These include (1) surface fault rup- (3,660 m) above sea level. This impressive relief is the ture on the Salt Lake City segment of the Wasatch fault result of ongoing uplift along the Wasatch fault zone, a zone; (2) seismic site response in the Salt Lake Valley, in- major intraplate tectonic boundary which is the longest cluding ground shaking and liquefaction; (3) liquefaction- active normal-slip fault zone in the United States and one induced landsliding at the Farmington Siding landslide of several fault zones in the region considered capable of complex; (4) lake flooding along the shores of Great Salt producing large earthquakes that could generate strong Lake; (5) debris-flow deposition on alluvial fans at the base ground shaking, surface fault rupture, and seismically of the Wasatch Range; and (6) landsliding in the Ogden induced liquefaction and landslides. area. These topics are discussed in the following six sec- In the winter, frontal storms traveling east from the tions, which in turn are followed by a road log that describes Pacific Ocean encounter the Wasatch Range and produce the field-trip route. The route and stop locations are shown heavy snowfall in the mountains. Snow avalanches are com- on figures 25 through 27. mon and present a significant, widespread hazard. Freeze- thaw cycles in steep exposures of fractured rock produce FIELD TRIP STOP NO. 1 rock falls. Rapid melting of a lingering snowpack periodi- Bill D. Black, Leader cally results in slope failures, debris flows, and stream and Mouth of Little Cottonwood Canyon, alluvial-fan flooding. Convective storms in the spring and Wasatch Boulevard and 9800 South; see Figure 25. late summer also contribute to these hazards. Great Salt Lake, the remnant of Pleistocene Lake Bonne- pALEOSEISMIC STUDIES ON THE SALT LAKE ville, forms the western boundary of the northern Wasatch CITY SEGMENTOF THE WASATCH FAULT ZONE Front. Because the lake occupies a closed basin within the internally draining Great Basin, it is subject to climate- The Wasatch fault zone is one of the longest and most induced fluctuations that may cause flooding in areas along active normal-slip faults in the world. Situated near the 300 HYLJ (;EOLOCY STUDIE

0 50 MILES 0- 50 KILOMETERS Figurc 2. Salt I,itk~ City segment (?ftJ~e1Wt~s(itchfi1~lt zon~ (WFZ) and loccztiofu of thc Lit& Cotto?zrcoocl Canyon JLCC),Sorrth Fork Figtire 1. G~rzrt-clliz~rliwc,o of the Miasatck Front (tlashct! litle). Dry Creek (SFDC), (n~dDrt~ Grilc1t (DG) tr.(vtch ,sites. WSF = Chtrcrl Jire sr~giv~lncntsof the Wisotch fault zone s1wrc.r~b!j heclrtj Ct'crnn Sp~-ingsfi~ubEBF = East Bcnchfrrzilt. linr~toifla clr*lu>ri.sindicczting srg~nenthounclarics (vnotlifi~c!fi-orn ~tf(tc1tetteei (11.. 1992). BC = Bt-ig/latn Citytll, 1%' = \%her, SLC = Salt Lake (:it!/. P = Protjt, N = h'ephi. quakes hiis been determined through h~lt-trenchingstnd- ies ;it Little Cottotlwood Ca~lyoriin 1979, South Fork Dry Creek in 1985 and 1994, and Dry Gulch in 1991. center of thc Xrrtermotmtain seismic belt (S~rrithand Sbar, Little Cottonwood Canyon (1979) 1974; Smith ant1 Arahasz, 1991), a north-trc-nding zone of historical seisniicity that extends fro111 northern Ari~onato Tlre first paleo\eismic investigaticrn of the Salt Lake City central Montana, the hi11t zone extends 213 nrilcs (343 h) segment ura5 at Little Cottonwood Canyon in 1979 (fig. 2) along the \wstrrrr base of the W7asatc.h Range kom south- by Wood\vartl-Clyde Consultant\, ~~ndcrcontract to the eastern Idaho to north-central Utah (Machettc et al., 1992) I?. S. Geological SIIIT,~~(USGS) (Swim et al., 1981).The fa11lt and comprises 10 independent, seisrnogenic segments zone at this site is defined by a pmniinent west-facing main (Sch~vartz~IICX Coppersmith, 1984; Machette et al., 1992). scarp that splays northward into three sd)-parallel scarps Results of numerous trenching studics indicate that the and :in east-facing antithetie scuaq>.Sottth of the rite, the central five segments (Brigliani City, Vi'elrer, Salt Lake City, farlit zone fonns a wide, deep gra13en ;L\ it traverses moraines Provo, Ncphi) (fig. 1) each have gc~nerattbtlthree or Inore near the nroutli ofthe canyon (fig. 3). surface-f:~ultingearthquakes in the past 6,000 years. Rour trrbnches were excavated acres\ the scalps at Little The Salt I,ake City segment of the \Vasatcli Sa111t zone Cottonwoocl Canyon, exposing evicii>~~eefir two surfacr- trends tl1roug11 the densely populated Salt Lakc Valley, faulting earthqriakex. Radiocarl~ondating of detrital char- extending 29 rnilvs (46 krn) from the lkaverse Mountain\ on coal sho~veclthe oldcr earthquake occurred \frortly before the south to the Salt Lake salient on tlre north (fig. 2). The 8,000 to 9,000 years ago. how eve^; no rriatei-id suitable for fhult segment cfisplays alr~mdlultevidence for multiple snr- radiocarl~ondating was fol~ndto eonstrai~itlie timing of the face-fiaulting earthquakes during Holocene tiirre (Sch~vartz younger event. Based on scarp profiling arid 5tratigraphic and Coppt~rsmith,1984), arid thus it poses a sigrrificarit seis- evidence in the trenches, Swan et al., (1981) calculated a mic risk to people living in the Salt Lake City nletropolitan recui-rence interval of 2,200 years and an average net slip area. The IIolocene chronology of surfhce-faulting c~arth- per event of 6 fi~t(2 111). HYLLAND, ET AL.: GEOLOGIC HAZARDS OF THE WASATCH FRONT, UTAH 301 this information, Schwartz and Lund (1988) estimated a recurrence interval of 3,000 to 5,000 years. However, they acknowledged uncertainty regarding the paleoseismic history of the Salt Lake City segment, and cautioned that a true paleoseismic history could be developed only if information is obtained for every scarp at a site.

Dry Gulch (1991-92) The incomplete nature of the Salt Lake City segment's earthquake history was demonstrated in 1991, when a non- research trench was excavated by a local consultant across the fault zone at Dry Gulch (fig. 2). Detailed geologic mapping by Personius and Scott (1992) shows the scarp at Dry Gulch extends northward to South Fork Dry Creek. How- ever, this scarp was not trenched in 1985. The UGS inspected the Dry Gulch trench and found evidence for two surface- faulting earthquakes (Lund, 1992; Black et d., 1996). Radio- carbon dating indicated the earthquakes occurred: (1)rough- ly 1,600 years ago, which coincided with timing for the most recent event at South Fork Dry Creek; and (2) shortly after 2,400 years ago, which did not correspond to any previously known event. This newly discovered event showed that at least three (rather than two) surface-faulting earthquakes have occurred in the past 6,000 years, and at least four events (rather than three) in the past 8,0004,000 years. Based on timing for the additional event, Lund (1992) calculated a surface-faulting recurrence interval of 2,150 r Figure 3. Wasatch fault zone at the mouth of Little Cottonwood 400 years for the past 6,000 years. Canyon. A. Aerial uiew, looking east, of fault scarps (arrows) cutting upper Pleistocene moraine and alluuial &posits. B. South uiew South Fork Dry Creek (1994) of fault scarps (in shadow) cutting Bells Canyon moraine (Zarge arrow on Fig. 3A). Resihntial deuelopment in foreground occupies In 1994, the UGS excavated five new trenches across a graben along the fault zone. fault scarps at South Fork Dry Creek to complete the investigation started there in 1985 (Black et al., 1996). With these additional trenches, all fault scarps at South Fork Dry Creek have now been trenched. The new trenches exposed evi- South Fork Dry Creek (1985) dence for one to four surface-faulting earthquakes, and doc- The Utah Geological Survey (UGS), in cooperation with umented a previously unrecognized earthquake (event X) the USGS, conducted a paleoseismic investigation at South which increased to four the total number of events on the Fork Dry Creek (fig. 2) in 1985 (Lund and Schwartz, 1987; Salt Lake City segment in the past 6,000 years. Radiocarbon Schwartz and Lund, 1988). The fault zone at South Fork age estimates show these earthquakes occurred: (1) shortly Dry Creek consists of six sub-parallel, west-dipping main after 1,100-1,550 years ago (event Z), (2) shortly after 2,100- fault scarps and a single east-dipping antithetic scarp (Per- 2,800 years ago (event Y), (3) shortly after 3,500-4,500 years sonius and Scott, 1992). Four trenches were excavated across ago (event X), and (4) shortly after 4,9504,750 years ago three of the main scarps, but access restrictions precluded (event W). Net slip per event could not be calculated, but trenching all of the scarps. earthquake timing combined with the age and cumulative Two trenches each exposed evidence for two surface- offset of a debris-flow levee along South Fork Dry Creek faulting earthquakes. The other two trenches each exposed suggests it is likely in the range of 5 to 8 feet (1.5-2.5 m), evidence for one surface-faulting earthquake, but no mater- which is similar to that determined by Swan et al., (1981) at ial suitable for radiocarbon dating was found in these Little Cottonwood Canyon. Events W through Z show a trenches. Radiocarbon age estimates indicated that the varying pattern of surface rupture (fig. 4), indicating that in earthquakes occurred (1)shortly after 1,100 to 1,800 years a wide fault zone containing many fault traces, subsequent ago, and (2) shortly after 5,500 to 6,000 years ago. Based on earthquakes do not always rupture every trace. 302 BYU GEOLOGY STUDIES 1997, VOL. 42, PART I1 r Based on mean elapsed times between events W through Event Z Event Y Z, Black et al., (1996) calculated a new recurrence interval for surface faulting in the past 6,000 years of 1,350 + 200 years (fig. 5). Elapsed time since event Z (about 1,300 years) is close to the new shorter recurrence interval and within the assigned range of uncertainty, suggesting risk for a future surface-faulting earthquake is higher than previously thought. However, more work is needed to character- ize the surface-faulting history of the Salt Lake City segment in early Holocene time and refine the recurrence interval.

SFDC Sm FIELD TRIP STOP NO. 2 Michael D. Hylland, Leader Salt Lake Valley overlook from Wasatch Boulevard at Pete's Rock; see Figure 25.

SEISMIC SITE RESPONSE IN t THE SALT LAKE VALLEY N The Salt Lake Valley is a deep, sediment-filled structural basin formed by basin-and-range extensional block faulting. The combined thickness of unconsolidated Quaternary and semi-consolidated Tertiary basin-fill deposits locally exceeds 3,300 feet (1,000 m) (Zoback, 1983; Mabey, 1992). Quaternary Event X Event W deposits are dominated by lacustrine sediments deposited by repeated cycles of deep-water lakes during the Pleisto- cene. Coarse-grained Lake Bonneville shore facies consisting of sand and gravel are present along the margins of the Salt Lake Valley up to an elevation of about 5,180 feet (1,580 m), whereas deep-water facies consisting of clay, silt, and fine sand predominate toward the center of the valley (fig. 6). Post-Lake Bonneville materials include alluvial, flood-plain, and flood-plain/delta deposits. The lateral and vertical variability of Quaternary deposits SFDC SllE in the Salt Lake Valley results in a wide range of earthquake-induced ground motions. Furthermore, the presence of loose, sandy soils and shallow ground water makes many areas susceptible to liquefaction.

Earthquake Ground Shaking t Historical Seismicity and Building Damage N The Salt Lake Valley occasionally experiences ground : DGSm shaking from earthquakes within and beyond the Wasatch 3,5004,mwm Igo ., 49W75fJwmlgo Not drawn to scale Figure 4. Pattern of surface rupture at the South Fork Dry Creek (SFDC) and Dry Gulch (DG) sites. Main scarps (S-1 through S-6) knoum to have been active during surjiacezfaulting earthquakes on the Salt Lake City segment in the past 6,000 years are shown by heavy solid lines; scarps possibly active are shown by heavy dushed lines. HYLLAND, ET AL.: GEOLOGIC HAZARDS OF THE WASATCH FRONT, UTAH 303

Paleoearthquake Z Y X W

2,250 yr

Maxlmum elapsed time 2,400 yr between contiguous surface-faulting events

1,700 yr

Minlmum elapsed tlme between contlguous surface-faulting events

Calculated elapsed tlme 1,150 yr 1,500 yr 1,350 yr between contlguous V V surfacefaultingevents

I I I I I 0 1,000 2,000 3,000 4,000 5,000 6,000 Tlme, in years B.P.

Figure 5. Timing of surJace-faulting earthquakes on the Salt Lake City segment in the past 6,000 years.

Front region. Oaks (1987) summarized the effects of six graded or retrofit, however, and some new structures are moderate to large earthquakes (ML 5.0 to 6.6) that pro- being built to seismic zone 4 standards. A well-known produced ground shaking in the Salt Lake City area. These ject is the seismic retrofit of the Salt Lake City and County earthquakes occurred between 1909 and 1962 and resulted Building. Several earthquakes have caused damage, primar- in damage consisting of toppled chimneys, cracked walls ily masonry cracking, to this historic landmark, which was and windows, broken gas and water mains, and seiches on originally constructed between 1892 and 1894. During the Great Salt Lake. The 1934 Hansel Valley earthquake, which 1934 Hansel Valley earthquake, 2.5 tons of mechanical produced surface rupture on the Hansel Valley fault at the clock equipment fell from the 12-story clock tower and north end of Great Salt Lake, generated the strongest ground "crashed down through the building" (Kaliser, 1971), and shaking in the Salt Lake Valley in historical times. This ground shaking from the 1983 Borah Peak, Idaho earth- earthquake had a maximum Modified Mercalli intensity of quake (Ms 7.3) caused extensive masonry cracking. Concerns VIII in the Salt Lake City area and produced several long- over the possibility of severe structural damage associated period effects. Newspaper accounts described statues that with near-field strong ground shaking prompted Salt Lake shifted on the towers of the Salt Lake City and County City to commission a study to determine the need for seis- Building and the LDS Salt Lake Temple, as well as adjacent mic strengthening of city buildings. The resulting upgrade six- and ten-story downtown buildings that swayed and bat- of the City and County Building included structural rein- tered against each other. forcement and base isolation designed for a ground acceler- The Salt Lake Valley is in Uniform Building Code (UBC) ation of 0.2 g (Prudon, 1990). The retrofit was completed in seismic zone 3. Much of the development in the valley was 1989 at a cost of $30 million, and was the world's first appli- originally constructed prior to implementation of the UBC cation of seismic base isolation in the restoration of an his- seismic provisions. Many existing structures are being up- toric structure (Bailey and Allen, 1988). BYU GEOI,OGY STPDIES 1987, VOI,. .12. PAKT 11

Figure 6: C:c~ncr-c~lizedgeologic inap of tlze Salt Lake Ftzllt.!y fivnz LII)E~1990)

Ground-Motion Levels rnotioils during future cal~hcluiikes,especially in the CVi~satch Front arca. Utali has few strong-motion accelerographs and tnean- ingful earthquake records, so clriantitative estimates of National probal~ilisticseismic-risk ]nap\ indicate that, ground shaking are made using data fro~nother arras, par- for a SO-year exposurr tirne, peak ground accc~lerations ticularly (hlifornia. However, federal, state, and private (PGA) at rock sites around the Salt Lake Valley I-tave a 10 entities preserrtly operate 20 three-component strong-motion percent probability of exceeding 0.20 to 0.30 g (illget~ni+ accelerograplrs in the Salt Lake Valley, including eight serr et id., 1990; Building Seisrnic Safety Courlcil, 1994). instru~nerits deployed iir the last two years. Although flowevel; t~nconsolidatedjudicial cieposits and basin effects statewide coverage still is relatively sparse, the new instru- could anlplifj' earthquake gro~rrrdmotions, procluc~ingeven nie~~tsit~creas~ the likelihood of ~~~easuringactilal grout~d hig11er ~lcet~lerationiat soil \itcls. Youngs et a)., (1987) indi- HYLLAND, ET AL.: GEOLOGIC HAZARDS OF THE WASATCH FRONT, UTAH 305

EXPLANATION nesses of soft clay having shear-wave velocities lower than average soft-soil shear-wave velocities in the San Francisco Bay area (Rollins and Gerber, 1995). Theoretical studies of DESCRIPTION OF MAP UNITS stronger motions have also indicated the for significant amplifications, particularly of short-period motions, Quaternary and Recent Deposits: in areas around the edge of the valley having characteristics Alluvial DepoaiEs - Stream alluvium, exIsUng and abandoned similar to where amplification was observed in the 1994 Ilbodplol118, alluvie/ fans, end local mwmowS Northridge earthquake in California (Rollins and Adan, 1994). Flood-plain and Delta Complex - Chie@finegrainedendpoody These amplifications are associated with shallow, stiff soil drained sedimenIs; includes depnsits hwn Ute Jordan River and Great Selt Lake. conditions (Adan and Rollins, 1993; Wong and Silva, 1993). Glacial Moraines and Talus - Moraines, ti14 and outwasl, Three-dimensional elastic-wave-propagation modeling in&- daposa consisthg d unsmw mlr(wes d cky, sil~sand, cates basin effects could produce significant amplification gravel, and bouIders; telus accumulatims el the bese d steep skpes LY CI~. of low-frequency ground motions at sites over the deepest Provo-level and Younger Lake Bottom Sediments - Clays, siB, parts of the basin (Olsen et al., 1995). sends, Pndlocdy o&hw# send bets Site-specific studies are helping to refine ground-shak- Prwo-level and Younger Shore Facie8 - Chiefly send md ing estimates in various parts of the Salt Lake Valley rela- gravel in booch d.posils, barn, spHs, and &+I&. tive to estimates based on the existing regional maps. These Bonnevllle-Level Shore Facles - Ch* sand and gravel ~n beach -Its, bars. spns. addeRa studies include probabilistic ground-motion modeling for Kennecott Utah Copper Corp.'s Magna tailings impound- Horkem Alluvlum - Umsdkiatedand~~bouMers, gravel, send sill. and clay dwoshd in pre-Lake Bonnevllk, ment (Wong et al., 1995) and the Interstate 15 reconstruc- al1uvi.l hns. tion project (Dames & Moore, 1996). Also, a cooperative

Tertiary Sedimentary Rock Units, undi&uenLYated. study by the UGS and Brigham Young University begin- ning in 1997 will result in a site-response map of the Salt Tertluy Volcanic Rock Units, unMorentYated. Lake Valley that can be used in future probabilistic ground- Terliary Plutonic Rock Units, und&renbioled. shaking estimates.

Mesozoic Rock Units, undMerentYaW The issue of appropriate ground-motion design levels for structures in the Wasatch Front region is complicated by Paleozoic Rock Units, WrdiVemtiated. long recurrence intervals (102 to 103 yr) for large earth- Precambrien Rock Units, und&mntiat& quakes (see Machette et al., 1991). In other seismically active areas such as California, the probabilistic PGA does not continue to increase appreciably at long exposure times MAP SYMBOLS because crustal strain is dissipated by relatively frequent large earthquakes (fig. 8). In contrast, the infrequency of large earthquakes in the Wasatch Front region allows crustal Conla* Between Unlts. strain to continue building over long periods of time, resulting in probabilistic PGAs associated with long exposure times being significantly greater than those associated Suspador Known Quatemery Faults - Dashed whereapprox- with shorter exposure times. Imately located, dotted where concealed, queried where sus- pcted; Bar and Ball on downthrown side. Liquefaction Much of the Salt Lake Valley is underlain at shallow cate the PGA with a 10 percent probability of being ex- depths by unconsolidated lacustrine and alluvial sand, silt, ceeded in 50 years could be as high as 0.35 g at soil sites in and clay, and has shallow ground water. The combination of the northern part of the Salt Lake Valley (fig. 7). soil gradation and density and shallow ground water results Ground-motion monitoring of Nevada Test Site nuclear in extensive areas that are susceptible to liquefaction- tests confirmed amplifications of weak motions in the fre- induced ground failure (Anderson et al., 1986). quency range of engineering significance (0.2- to 0.7-sec- Anderson et al., (1986) mapped much of the Salt Lake ond periods) in the Salt Lake Valley (Hays and King, 1984; Valley as having a moderate to high liquefaction potential Tinsley et al., 1991).The largest amplifications (in some cases (fig. 9) based on soil liquefaction susceptibility as deter- greater than lox) were in central valley areas and were mined from geotechnical parameters, calculated critical attributed to deep, soft soil conditions. Recent studies along accelerations, and earthquake magnitude exceedance prob- Interstate 15 identified areas underlain by significant thick- ability. Although prehistoric liquefaction-induced ground 306 BYU GEOLOGY STUDIES 1997, VOL. 42, PART I1

10% Probability of Excdance in 10 Yoarr 10% Probability of Excwdanco in 50 Ywrs 10% Probability of Exceedanca in 250 Years

Figure 7. Contours of peak ground acceleration on soil sites with 10 percent probability of being exceeded in 10 years, 50 years, and 250 years (after Youngs et al., 1987). failure has been verified in numerous excavations through- FIELD TRIP STOP NO. 3 out the valley (Gill, 1987), many studies in areas mapped as Michael D. Hylland, Leader having a high liquefaction potential have demonstrated moderate to very low liquefaction susceptibility based on Corner of 1525 West and 675 North, an absence of sandy sediments, the presence of dense west of Fannington; see Figure 26. deposits, or the presence of undeformed Lake Bonneville THE LIQUEFACTION-INDUCED FARMINGTON sediments older than 10,000 years (Keaton and Anderson, SIDING LANDSLIDE COMPLEX 1995). More site-specific engineering-geologic information is needed to refine and update the existing liquefaction- The prehistoric Farmington Siding landslide complex, potential maps. about 15 miles (25 km) north of Salt Lake City, comprises 10% probabili of being exceeded in %O ears 70% probability of OR 2.F probabity being exceeded in of bem exceeded 4 507ea- in #O years

I 0 10 50 100 150 200 250 Exposure Time (years)

1;igriw 8 l'lot ~f~~'ct~kl;(ltiorts072 rock rtidt ii 10 pc~rcrntprobc~hili- t(j ofhcittg tsccc~cl~~rlcjtjring r~irioti~stifnr ~)PI~oc/.~(fi-ottt Olig, 1991). Drrslteti eztrcrs ore fi-o~rrAlg(v-tnissc11 (l9881 crnrl solid c,rcn.f>crccw c.rrlcrrlritc~d-fr-stigators a~s possible liquef:ltction-i~lclllcedlateral sprcacts (\.'a11 Hont, 1975; Miller, 1980; Artdcbrson ct al., 1982; Nelson iu~tlPcrsorrius, 1993). Dctailetl clisct~ssionsa11c1 rcsrtlts of rcccnt investiga- tio~trof the la~tdslicit~eon~plex tire> prcsentetl it1 Ilarty ct al., (1993), W>lland and 1,owc. (1995), I,owca cst al., (1993), at an clcvatiotl of aljnut 4,400 feet (1,342 111) in tlrc cicinity i-lyllanci (1996), and liyllarrd and Lowc (in press). of the city of F~tnt~iilgtor~.'Cllcb toe rnay 11,1\ c ltcelr ericoun- tcsret1 Ileneatli C;re,;it Salt L,ake daring a clrilling project in (:c~)lo~r;!~ancl C:eon~orpIlolo~gy F:irn-ringto~~Bay to test for~r~clationcontlitiolr5 for a pro- The H1rmingtor-r Sitling landslide cornplcx is it1 a gcntly ~~oiecfM ;lt~~r-storaige rc~st~rvoir (Everitt, 1991). sloping archa rtrrclrrlt~irrtit s11:illow tIcpths primarily 1)y fine- Thc Iimtlslide deposit\ can he grotlpctl rn hvo age cate- grained, \tratifiecj, late Plci\toecne to Iioloct~nthI,tcu\trine gosit,\ rt.l,rli\ c* to the ;igr, of tlrc C:ill)t,rt \horc.li~r~corrrplr~x, rlepclsits of Lakc 13onncvillr and (:reat Salt I,ake (fig. 10). whicli fbr-rtrctl ltctwc~cn10,900 ;u~cl10,300 ) cxrs itgo (Clo~cy, Crouncl slopes within the lantfslitlt colnp1e.c ~-;u~gc~fronr 1990). l'lrch tirtrt-ltrrn p'trt of thc l,ii~c'lslirlecorrrplex trrinc,ltcs alwrtt 0.4 to 0.8 percerrt. U~rfail~cti1opt.s adi,ic,ent to thck the C;ill~o.t sfiorelirrc~(Mi11 I lont, /975), indicating nraior complex ratrgc korri ailtol~t1 to 2 pi~rcentalorrg tltch t1atliks lx'st-<:ilbcrt IIIO.~e-.~~ic.trt. Xlov evcr. tlrch C:ill,t,rt \l-torc~lint,can and fS to I I percent in tht. c-row 'trca. 'The tleposit\ he tracc~cl'tcross the 5o11thentpat of tht' landslitle cort~plc\ ix~volvcclin lanclslidirlg conaist of intel-l>etldc~cl,laterally clis- (A11c1ersortt't '11.. 1982; lI,lrt! c.t ,I]., 101-)3),itrtfic,~tirtg LXC- co~itinltoitsIityt~s of c1,tjt.y to siatd? silt, well-\ortee1 fittr~ (;ill,crt ii~ovemctltin this part of the corrrp1c.c. sand to silty sand, and minor clay and gravel. The crowr1 is C:c~ornorI)liic katrrres ix~clt~clescarl15, humr-rlocks, closecl untlcrlaitl by L'ike Uorineville sand arlcl silt deposits and i\ cleprcssions, ancl tr,ulsvt.rscx lincaxncnts. \2.icll-prcsc~rvccI Map Units Qmy Younger mass-movement (lateral spread and flow) deposits Qmo Qlder mass-movement (lateral spread and flaw) deposits Qaf Alluvial-fan and debris-flow deposits Qsrn Marsh deposits Qly Younger lacustrine (Great Salt Lake) deposits Qlo Older lacustrine (Lake Bonneville) deposits

Map Symbols Landslide scarp Normal fault; ball on downthrown side ---- Lineament

---G-G- Gilberl shoreline

-- X----X~ Other shorelines of Great Salt Lake

lutcbr,~l,urcl rmin \carp\ ir-r the, northrrn part of tllc' c~)~~lpl('\~l(~Ilo5it\ 111 ti%<,\l~'~IlO\% \lll>,~~~f~~~~~ 1)c~llt~'kkflt!W l'~t~(~\Ilrrrchlrolt.\in ,tn f lurntl~ock\ctrrcl clijsccl clcpres\lorl\ 'ire pre\ent c,\rxr rnoit attcsrrlpt to cot-rcl,itt% lx>d\!)c~lxc>,ith OCZLI)II"~LI l(i\l It(6 rlt) of~v~ltcf rir-c ~orrt*tJl,tt itcalrs \trtllrrl ~t r1eptE-r rang<,oi 14 to -60 fc1c.t ,uid lcttt~r,~ldir~rt~rl\ion\ loe,dl> c~\oecrlit~g1,000 tetxt tiutn- (-k-I2 ilk). '~I>I$XOIlt~ h><~'#lliiOli(~\[>08itlc, \,txht ct>n'1 r(~l,iti\el\tlt~zws tt;trr\vc%\\ri cb ~,IC\~I"~Ei1l~vt~(li1t-'11~'(~ gcncr.ill> h'tvirlg less tlr'ttl ,tl>ont 6 fchcxt (2 111) of rr'lrcf. con\r\tirrg of tlcatsho~c,\,itltl ,rnrl c;r,t\c~l cIt~i~oc~t-t~tltlrrr~rtr?, Sui,tle trilns\cr.se I~nranrc'ntiarc prt'\cnt ill the cthtrtrdl pxt tlrc ('drl? pdrt of the !~OIIII{T111~ p,iicolCiht' C'\C~C oi ~)oi\if>l\ of tllc cornplt'\. Sub\urf,~cc.dcfonir,itioll of lac~istrirrcxtic,- pre-f3011ric\1lledltn rrrrtr, ,inti 0%c~r-l\lng loow ir-r-ft, i,fls'rrolI\ occurrctl ail ,I corr~l,rlr,itlorrof I'iter- (fig. 12) ,il \lxvad ',~rrcl flo\\ ( i l\ ll,tncl ,tilt1 I.(>\\ c,, I 9935) 'f'rrc~tt an\- \cr\e Iine,untwt\ ric,u tlrc- rnrtltll(, of thcb cot>lpks\ rtla\ r cp- rc\vrrt rt-grc\sl\ e Icllir. \llor clrnt>\\Lo\\ c. c.1 ,ti lW5,1.1~1t So11 gr<~i~i-\~zcdiitril)l~ti~~i. stdt~ddrd-~~(~~it~tr~xtt~)~r r~ji\- ll\ lll,iti\c* ts~ecl,.uld groutrd-\t,tter.tlcptl1 noted otr logs of gr~)tt~cl-rni-,igc. of the* 111~c~at~rent\rriclii ,ttc tlic\ I t,pr-c>sitrrtri1fil1t.d (;I onxltl c,il Itorc.holc\ (Antlerstjrl t.r dl.. 1982) trlctlcatc Itcl~it~fi,tl~Iccr;u.hs as~ocr,tte~ci\ildj l,tt

Figure 11. Aerial view of hummocky landslide terrain on the northern part of the Farmington Siding lanrlslide complex. H~~mmocks appear as light-colored patches. across hummock flanks and adjacent ground in the north- em part of the complex, Harty et al., (1993) determined the hummocks are relatively intact "islands" of lacustrine strata surrounded by liquefied sand which resulted from flow failure. Other evidence for flow failure includes the existence Figure 12. Liquefied sand (arrow) injected along fault plane in of a landslide main scarp up to 40 feet (12 m) high; the trench exposure of thin-bedded lacustrine rleposits. Trowel for overall negative relief in the head region of the complex, scale. indicating evacuation of a large volume of material; and the overall positive relief in the distal region of the complex, indicating deposition of landslide material. studies with the timing of landslide events indicates a close correspondence between landsliding and certain earth- Landslide Timing and Seismic Considerations quakes (fig. 14). Within uncertainty limits, surface-faulting earthquakes on the Brigham City segment coincide with all Relative timing information and limiting radiocarbon soil four possible landslide events. Surface-faulting earthquakes ages indicate at least three, and possibly four, landslide on the Weber, Salt Lake City, and Provo segments also events (fig. 13). Hylland and Lowe (1995) considered the timing of these landslide events within the context of paleo- coincide with the more recent landslide events. Earthquake climatic and lacustral fluctuations, and observed that lands- chronologies for these segments generally do not extend liding was associated with climate-induced highstands of beyond 7,000 years ago, so unrecognized and/or undated Great Salt Lake. The apparent correspondence between earthquakes on these segments may also correspond to the landslide events and lacustral highstands suggests that earlier landslide events. landsliding may have occurred under conditions of relative- Hylland and Lowe (in press) used a variety of determin- ly high soil pore-water pressures, and possibly increased istic analyses to evaluate the relative likelihood of large- artesian pressures, associated with rising lake and ground- scale liquefaction-induced landsliding being triggered by water levels. earthquakes on various source zones, including: (1) empiri- Many features (for example, evidence of lateral spread, cal earthquake magnitude-distance relations, (2) compari- flow failure of gentle slopes, sand dikes, deposits susceptible son of expected peak horizontal ground accelerations with to liquefaction, and proximity to faults with recurrent Holo- calculated critical accelerations, (3) liquefaction severity cene activity) indicate landsliding was likely triggered by index, and (4) estimated Newmark landslide displacements. strong earthquake ground shaking. Numerous fault studies All of these analyses indicate that widespread liquefaction- (Machette et al., 1987; Schwartz et al., 1988; Personius, 1990; induced ground failure involving significant lateral dis- Forman et al., 1991; Lund et al., 1991; McCalpin and For- placements is most likely associated with large earthquakes man, 1994; Black et a].; 1996) constrain the timing of pre- on the nearby Weber segment of the Wasatch fault zone. historic surface-faulting earthquakes on the active segments At least two large earthquakes have occurred on the of the Wasatch fault zone; comparison of the results of these Weber segment that apparently do not coincide with land- AGE (loJcrrt yr B.P.)

Between 14,Wand 10.900 "C yr B.P.

Figtrrc. 14 ('o~~ymit,orcoj tlit trr/trrr:: trl lont!s/iik r i ( tits tr c/!ilr, fht I+[itrs~zttrgtorcStdtrrc /rirri/s/tr(c~( orrii~lr z (\/rtirk>ti(11~ rict 11 rtll \irritifcIi filrrlf :ottc, j,cr/(>o\c>~\rrr~r111j 110jr1 (itid C;i(>rit Smli I,cilir fJirctrtntrotri

Ot(ti I 1 1 1 l'i(j)i) Iki\frc c.! /iff( \ f-i'pti2>1~ltf/ifttltiiig (igt 5 P(il('O%($\?!it(

11(r1 /ii~ffc~~f (I/ ,151t57~~ lttt {~ttz( t u/ I 1055J i siijiltis i 19901 fij~-rrtiiii 1 t (11, (I991 httid P! ((1 f1901l C"cil/~ltt({)it/ f i~~~tt~~ta ( 2')O-C) N/ctt c2f nl (1906) cortl Zlc ('riij~trrcirirf I idii 13Xo 11996' (:I it S(df I,trl\i /ii/tbogr trj)/r trjtr I Jlzii r litririr i9h9

slicte i1\cnt\ 1'tthr.r gc~ologicntld I~\droiogic.cim(litio1rs ,kt tlrc. ttriicA of t11c.ii. e,irtl~clrr,ikt~swtArc sue11 th,tt Irttfo or 110 slop<' rrrovcxs~rcutocc~ri*cd, irr t~vrtlctlct~for I,it~d\lrtlir~glid\ not >ct.l)t~>lr ot)ser.ccltl. Iic,c,trrsta prrx5clrtI,ll\t> ,urd qroiitld- water lt%\,c4s

FIELD TRIP STOP NO. 1 Bonneville 7 Little Valley lake cycle Cutler Dam lake cycle

I60 130 TIME BEFORE PRESENT, IN THOUSANDS OF MARS

E'lgrrre 16 I-l[/tlrogrc~y,hrf /~rc)f~nblr.InXp liar rlr it, the Ct-cttrt Snlt Lake bmirt fi)r the 150,O(W) r/cJnr\ (rnorl~fic)tl/i~11,t C:tirrcrl (z~d Ot inn; 1985, nlnr.hrttc7 ei (11. 1087) Ss = Stur~sbt~t~~thorc~ltncz, Bc = Bont~evill~shorc~lit~e. PA = PIYXi) ~ltorelivt~~.C5 = G~111et-tc1101 e- lirte

tation, inflo\v, :and c.v;ul,oration v:uiatiom. I,ong-tern1 climatic trends play a major role in rleterinining lake levels, as do diversion and consrtnrptive use of water sources 1)y man. Fluctuations iir Crc:.ct Salt have a proforrntl efkct on the ~~~t*fitccarea of thc 1:;ke beciuise of tlic flatness of tli~ lake basin. Extretnc lo\v or high lake levels are likely to per- sist evcw after tt~eEtctors which cclust~dthe111 have changeil.

Lakes liiiw oceupiecl tlre Uonncvillc basin sekeral tirneil over tlre past sevcr:tl rtlilliotl rars. \.V:tter levels in lakes srtch as Lakc Roi1ne.r ille and (kcat Salt Lakc have oscillatccl witlr great clevatiori ditri.rences brt\veen highstands a11d lowstands (fig. 16). I,ake Ronneville reached a masimun~ elnation (Borlneville shorclinc~)of 5,092 feet 11,552 rn)

ar-ountl 15,000 years ago, and rceedecl to C* port-Botlneville lowstand after Ltbct~it13,000 years 'igo (Currey ant1 C)\?i,ttt, 1985). In the S~lt1,tkr V;llley, the elevation of the Bonnc- ville ~horelincvarier fi-orn 5,161 tit 5,216 feet (1,573 to 1,590 ni) (\:III I-torrt, 1972; Currey, 19821, due to a combination of isost,ltic rel>ound as the. 1,lIc. lo\\ ered ,inel port-lake f'ttllting (14iller, 15180). Isostatic re1)ortntI was generally greater near tlre ctlritcr of thc' Uorrnc\ ilk. basin t11,trl at the etlgcs of the basin wlirre w,tter dtpths were shallo\vt,c Creat S:dt I,akel reac4li~cl.I tioloct~ni~highstanti of approui- nr,itel) 4,221 ftxct (1,287 rn) I>chvccrt,d,out 2,500 anti 1,300 ) cx,trs ago (Cr~rrchy d., 1988, tZ~tr~'hi~o~l,1989). A late prc- hsstoric highstanti of C:rt%at Salt Lakc \\7,1r at 4,215 feet rthrnoved by evaporation, like levels drop lo xvintcr ~nirtimn. (1,286 nr) sorrrctiirlt- during the I6005 (\lurchison, 1989; Creat Salt L,i&ca levels fluctrlatc on iivcbragcb2 feet (0.6 rn) C:tlrrey, 1990). betwi>enwinter low ant1 sulnlner high. 1,ong-tern1 fluctua- Although no sigrific'urt di11ni;il tides occur 011 Cre.t'dt Sidt tions result from persistent lo\v or high \v~tter-s~tpplycoltdi- Lake, mint1 seiches ,Ire corirliron. Sirch seichc~sdevelop on tions, and lake levels arc highly scnsiti\e to mirror precipi- the itmiri Itocly of thtb Iiike in respotisc to st,u)rrg \\i11ds frorrl 312 BYU GEOLOGY STUDIES 1997, VOL. 42, PART I1

25 - 7.5 PROMONTORY - 20. #)INT .6.0 =- ,. 15- > w w 10-

...

?- 10- d IS- > Y w 10.

5. - 1.5

0 0 Figure 18. Hydrograph of Great Salt Lake. Elevations before 1875 SLC AIRPORT 60 - are estimated from traditional accounts (fi-omAtwood et al., 1990). 40 { f 20 torical high of Great Salt Lake was 4,211.5 feet (1,283.6 m) (Arnow and Stephens, 1990), which was reached in the n 24 12 14 12 24 12 34 12 24 12 24 early 1870s (Gilbert, 1890). The lake dropped slowly from JAN 25 26 27 28 29 30 its high in the 1870s, reaching an historical low of 4,191.35 feet (1,277.46 m) in 1963. Above-average precipitation in Figure 17. Great Salt Lake seiche hydrographs for Promontory the 1980s caused Great Salt Lake to attain a new historical Point (north) and Silver Sands (south), and wind speed at the Salt high of 4,211.85 feet (1,283.71 m) in June 1986 (Arnow and Lake City International Airport, showing wind seiches over afive- day period grom Lin and Wang, 1978). Stephens, 1990) and April 1987 (USGS records). This lake- level rise caused damage to structures and other property along the shoreline and within the lake. The cost to Salt the south or west. A major wind seiche commonly needs Lake County for flooding at lake elevations greater than wind velocities in excess of 10 knots (18.5 kmhr) (Lin and 4,212 feet (1,284 m) is believed to be in the millions of dol- Wang, 1978). Sustained, strong south winds cause the water lars (Atwood et al., 1990). If the lake rises to 4,217 feet level to decline in the south and increase in the north (wind (1,285 m), potential additional costs could exceed $3 billion (Steffen, 1986). setup). When the wind velocity drops, water levels try to reach equilibrium. These wind-induced oscillations have a Flood Mitigation fundamental period of about 6 hours and seiching lasts about 2 days (fig. 17; Atwood et al., 1990). During this time, The rapid rise of Great Salt Lake between 1982 and up to 2 feet (0.6 m) of flooding may occur along the south 1986 doubled the lake volume and increased its surface shore. area by nearly 500,000 acres (Atwood et al., 1990). Flooding Great Salt Lake levels go through a seasonal cycle, wax- associated with the lake rise caused more than $240 million ing in spring or early summer in response to spring runoff, damage to facilities within and adjacent to the lake (Austin, and waning in the fall at the end of the period of high evap- 1988). The Southern Pacific Railroad causeway divided the oration (fig. 18). The maximum seasonal lake rise (measured lake into two unequal areas of different elevations: the in 1983) is 5 feet (1.5 m), and the maximum seasonal lake north arm and the main Great Salt Lake. Most of the inflow decline (measured in 1988) is 3 feet (0.9 m) (Atwood et al., was to the main Great Salt Lake. The causeway was breached 1990; Atwood and Mabey, 1995). Seasonal fluctuations are in 1984, reducing the elevation of the main Great Salt Lake largely controlled by weather and are difficult to predict, by about 8 inches (20 cm) and increasing the elevation of but generally do not present a direct threat to life due to the north arm by about 16 inches (40 cm). However, the their slow rate of rise (maximum of about 1 inch per day lake continued to rise and peaked (at its historical high) two [2.5 cmlday]). years later. Historical water levels in Great Salt Lake have also fluc- In response to flooding, the Utah State Legislature tuated over the long term (fig. 18). Until mid-1986, the his- authorized a study of potential lake-level control measures HYLLAND, ET AL.: GEOLOGIC HAZARDS OF THE WASATCH FRONT, UTAH 313 (Utah Division of Water Resources, 1984). Pumping excess 7 water into the shallow desert basin west of Great Salt Lake was the only measure that could be implemented quickly t enough to provide flood-damage relief. Thus, construction I began in 1986 on the West Desert Pumping Project (Atwood et al., 1990). By the end of 1988 2.05 million acre-feet (2.52 billion m3) of water had been pumped from Great Salt Lake (James Palmer, written communication, 1989). The lake dropped 5.4 feet (1.6 m) by the end of 1988 due to a combination of pumping, evaporation, and decreased inflow from *cc- - two drier than average years. The pumps are kept in reserve for future lake rises. 1-*

FIELD TRIP STOP NO. 5 Mike Lowe, Leader Turn-out along North Ogden Canyon Road east of North Ogden; see Figure 27. CAMERON COVE DEBRIS FLOW, NORTH OGDEN A debris flow from an unnamed canyon deposited material on an alluvial fan in North Ogden (fig. 19) on Septem- ber 7, 1991, damaging seven houses in the Cameron Cove subdivision (Mulvey and Lowe, 1991, 1994; Lowe et al., 1992). Over the %-hour period prior to the debris-flow event, rainfall in the North Ogden area ranged from 2.5 to 8.4 inches (6.4 to 21.3 cm) (Brenda Graham, National Figure 19. Aerial view, looking northeast, of the September 7, 1991 Weather Service, verbal communication, 1991). This rain- Cameron Cove deln-is flow in North Ogden (photo taken in August storm set a new state record for a 24-hour period, and was 1996). estimated to be equivalent to a 1,000-year storm. Runoff from the storm was concentrated in channels on Tintic Quartzite cliffs at the head of the canyon and formed water- noticeably contributed sediment to the debris flow. Mulvey falls which cascaded several hundred feet to talus slopes at and Lowe (1991) concluded that sediment contribution from the base of the cliffs. The runoff mobilized talus and other the burned area was low because of rapid revegetation of debris in and near tributary channels at the base of the oakbrush, woody plants, and grasses. cliffs, initiating debris flows. As the tributary flows moved Muhey and Lowe (1991, 1994) observed that much downstream and combined with the main channel, addi- debris remained in and along the main and tributary chan- tional channel material was incorporated into the debris nels after the debris-flow event. Considerable debris was flow. The flow exited the canyon mouth and traveled down trapped behind several natural dams composed of large an alluvial fan for a distance of about 1,300 feet (400 m), boulders. In many places along the channel, side slopes had damaging the houses (Mulvey and Lowe, 1991). been destabilized by scour and undercutting of channel An examination of the main and tributary channels indi- banks. Mulvey and Lowe (1991) were not able to accurately cated that channel material, from the base of the cliffs to estimate the volume of debris still in the channel, but they the mouth of the canyon, had been incorporated into the believed that enough debris remained in the channel that debris flow (Mulvey and Lowe, 1991). Depth of scour in another large debris-flow event from the drainage basin the main channel averaged 5 to 6 feet (1.5 to 1.8 m), and was possible. was as much as 17 feet (5 m) locally. Soils on drainage-basin The volume of the debris-flow deposit was about 25,728 slopes did not appear to have contributed much material to cubic yards (19,553 m3) (Mulvey and Lowe, 1991). Using the flow except from an area of limited extent near the base the Pacific Southwest Inter-Agency Committee (PSIAC) of the cliffs where grasses were absent, cobbles were left (1968) Sediment Yield Rating Model, Lowe et a]., (1990) standing on soil pedestals, and small rills were present. estimated an average annual post-fire sediment yield of This was the only place damaged by a wildfire in 1990 that approximately 387 cubic yards (294 m3) per year from 314 HYU GEOLOGY STUDIES 1997, VOL. 32. PART I1

aged by the 1991 debris flow (Dennis Shupe, North Ogden City Manager, verbal communication, 1992). The lawsuit alleged that North Ogden City wa\ negligent for not miti- gating the debris-flow hazard on tlie alluvial fiin after thc hazard was identified by geologic studies (Mulvey and Lowe, 1994). The case judge ruled that the city could not be sued due to governmental immunity. The homeowner has subse- quently erected a debris wall that can be seen along the eastern edge of the subdivision. Because 110 ~najorsedi~nent deposition has occu~redon the ,illuvial f'ln rince 1991, stream channels in the canyon above still contain debris that could be n1ol)ilizcd iu~dincorporated into another lawc' c1el)ris flow. Del~rirflows will likely be clepo\itecl again on the alluvial fan, ant1 houses within tlie Cameron Cove sub- Figure 20. View, looking sotrtl~west,from nenr the apex ofthe allu- division remain at risk until a long-terni, permanent solu- cia1 fan above the Cameron Cove subclivision slzowing brevs from tion to the problcni is implemented. past dellm',sflotus(~nodif;erl from M~tlveynnrl Lowe, 1994). FIELD TRIP STOP NO. 6 slopes within the drainage basin. The large difference be- Mike Lowe, Leader tween the PSIAC estimate and the actual volume of the Rninhow Gart1r.n.s pnrking lot, Ogclen; set> Figt~re27 debris flow supports Mulvey and Lowe's (1991) field obser- RAINBOW IMPORTS LANDSLIDE, OGDEN vation that a small percentage of the total volume of debris was derived from the slopes and that the 1990 fire was not The Rainbow Iinports landslide, near the mouth of a significant cause of the debris flow. The majority of Ogden Canyon in Weber County is part of the Ogden debris-flow material in the 1991 event was derived from River landslide complex of Pashley and \Viggins (1972). scour of stream channels and talus on slopes imniediately Vandre and Lowe (1995) delineated four tloniains within below the cliffs. this landslide complex (fig. 21), each characterized I)!, unique combinations of topography, ground-water contli- Relative Hazard tions, soil properties,- - and movement mechanisms. Thev named the easte~nmostdomain the frontage trough. After Future debris flows from the unnamed canyon are inevi- Pashley and Wiggins (1972), XLII~~Pand hwe (1995) refemcl table. Levees from prehistoric debris flows are present on to two other landslidc domains, which include topographic the steep, active alluvial fan at the mouth of the canyon (fig. reentrants, as the eastern amphitheater and westen1 amphi- 20), indicating the 1991 debris flow was not a geologically theater. The fourth domain, the Rainbow Imports landslide, unusual event for this canyon, but instead is part of the allu- is along the eastern margin of the eastern amphitheater vial-fan-l>uilding process (Mulvey and Lowe, 1991). Ridd (figs. 21 and 22) and is the most active of the IaildslitIc and Kaliser (1978) recognized that tlie alluvial fan is active, domains. The landslide was nanied after the Rainbow and mapped relative flood-hazard zones on the fin. Lowe Imports (now Rainl~owGarclens) commerci:d development (Weber County Planning Commission, 1988; Lowe, 1990) north of the landslide. mapped- - debris-flow hazards as part of a comprehensive evaluation of geologic hazards in Weber County and placed Geology the alluvial fan in a dehris-flow-hazard special-stucly zone. The Cameron Cove su1)division was approved prior to com- The Wasatch Range east of the Ogden Rivcr landslidt, pletion of these geologic-hazard studies. The Ricld and complex is chariicterized by a lower section of near-~ertical Kaliser (1978) study led to enactment of a hazard ordinance cliffs, consisting predominantly of Precam1)rinn Farmington regulating development on alluvial hns in the City of North Canyon Complex granitic gneiss and Cambrian Tintic quart- Ogden where the Cameron Cove subdivision is located. zite, and an upper section of more gently s1oping mountain- In spite of the existence of these geologic-hazard studies ous terrain consisting predominantly of Paleozoic setlinien- and ordinance, homeowners and North Ogden City officials tary rocks (Crittenden and Sorensen, 1985; Yonkee ant1 were apparently unaware that flooding and debris-flow Lowe, in preparation). Below 5,200 feet (1,585 m) in eleva- hazards existed in the Cameron Cove subdivision (Mulvey tion, bedrock is generally covered hy Lake Bonneville and Lowe, 1994). North Ogden City was named in a law- lacustrine sediments, or by post-Lake Bonneville alluvial- suit brought by the owner of the home l no st severely clam- fan deposits. The hench area south of the lantlslitle comples HYLLAND, ET AL.: GEOLOGIC HAZARDS OF THE WASATCH FRONT, UTAH 315

0 0.5 Kilometers

~i~~~~21. ~~~hlid~domains witlzin 0den~i~~~ lanhlide Figure 22. Aerial view, looking south, of the emfern amplzitheater complex, and location of the ~~~~b~~ imports landslide lfrom of the Og&n River lanrlslide coinplex. Rainbow Imports landslirle Vandre and Lowe, 1995). indicated by avow. Photo taken Athgz~~t1996.

The Ogden River incised and eroded laterally into the is the Provo-level delta of the Ogden and Weber Rivers and deltaic and lacustrine deposits at the mouth of Ogden Can- consists of gravel, sand, and silt deposited as Lake Bonne- yon as Lake Bonneville regressed from the Provo shoreline, ville occupied and then regressed from the Provo shoreline leaving steep bluffs (Lowe et al., 1992) and depositing flu- after about 14,000 years ago (Oviatt et al., 1992). The delta- vial sand and gravel between the bluffs. The Ogden River ic deposits overlie fine-grained, cyclically bedded sand, silt, landslide complex is along the erosional bluffs south of the and clay deposited during the earlier transgressional phase Ogden River. All landslides in the complex are below about of Lake Bonneville. 4,710 feet (1,435 m) in elevation (Vandre and Lowe, 1995). Several ephemeral streams flow westward from the Wasatch Range and have deposited various ages of alluvial Movement History fans onto the delta. The four drainages between the Ogden River and Taylor Canyon, about 1.5 miles (2.4 km) south of The Rainbow Imports landslide initiated on March 9, the landslide complex, are ephemeral with catchment areas 1987, damaging a steel transmission tower (fig. 24) causing of less than 0.5 square mile (1.3 kmz). Taylor Canyon Creek a loss of power to much of Ogden's east bench area (Kaliser, has a much larger catchment area of about 2 square miles 1987). Additional movement occurred on either the night of (5.2 km2) and may be a significant source of recharge to March 9 or early in the morning of March 10. Kaliser (1987) ground water in the Lake Bonneville deposits at the land- attributed the movement to soil saturation from melting slide (Vandre and Lowe, 1995). snow and ice. Landsliding occurred again during April 1988 The Weber segment of the Wasatch fault zone offsets and February 1992. These landslide events involved mostly Lake Bonneville and alluvial-fan deposits along the eastern earth flows, and landslide activity generally stopped within margin of the deltaic bench. Paleoseismic trenching studies a week or two. of the Weber segment on the deltaic bench just north of the The landslide moved again in early March 1994 (fig. 24) Ogden River show evidence of three to four surface-fault- (Delta Geotechnical Consultants, 1994). Movement again ing events during the past 6,000 to 7,000 years (Nelson and involved mostly earth flows; however, the main scarp con- Personius, 1993). Most of the fault scarps in the vicinity of tinuously retreated after the earth flows ceased. The main the Ogden River landslide complex are west-facing, valley- scarp of the landslide retreated an additional 50 feet (15 m) side-down scarps. An antithetic, east-facing, mountain-side- southward between April and August 1994, and two homes down scarp is also present on the delta south of the Ogden south of the landslide were removed in October 1994 due River landslide complex, and this fault terminates along the to concerns caused by the retreating main scarp (Vandre eastern margin of the Rainbow Imports landslide (Yonkee and Lowe, 1995). The main scarp had retreated southward and Lowe, in preparation). Two large conical depressions, an additional 15 to 20 feet (4 to 6 m) by April 1995. The probably sinkholes, along the base of the westernmost west- overall slope of the main scarp during April 1995 was facing fault scarp (fig. 23) may be evidence of northward approximately 80 percent, with the top 15 to 20 feet (4 to 6 ground-water flow along the Wasatch fault zone. m) nearly vertical (Vandre and Lowe, 1995). 316 BYU GEOLOGY STUDIES 1997, VOL. 42, PART I1

IT.dll,"UW U~IU~II: vnrcial Devc I +. Sinkl \

Figure 23. Sinkholes almg a normal fault crossing tlze frontage trough, Ogclen River Zudlicle complex.

Vandre and Lowe (1995) estimated the width of historical landsliding to be approximately 50 yards (45 m). From 1987 to 1990, most of the movement involved sandy landslide debris. From 1990 to 1994, movement involved mostly deltaic and lacustrine deposits that had not previously been disturbed by landsliding (Vandre and Lowe, 1995). The volume of landslide material was about 25,000 cubic yards (19,000 m3) between 1987 and 1990 and about 50,000 cubic yards (38,000 m3) between 1990 and 1994. Vandre and Lowe (1995) noted two springs discharging in the landslide area near the contact between the regres- Figure 24. Rainbow Iinports lanclslide in 1987 (A) and 1994 (B). sive deltaic and transgressive lacustrine deposits. They pro- jected the top of the 1990 main scarp to he slightly below runoff from springs discharging at the top of the zone, and the elevation of the springs. A fault trace was noted in the earth flows. 1994 main-scarp area; water moving northward along the The deposition zone is below the erosion zone. The Wasatch fault zone may have contributed to the spring flow. ground slope at the top of this zone is 25 to 30 percent, but lower in the zone is 20 percent or less (Vandre and Lowe, Movement Mechanisms 1995). Soil deposition is caused by decreases in slope and SHB AGRA (1994) noted different soil movement mech- spreading out of flowing water due to lack of confinement. anisms in different areas of the Rainbow Imports landslide. Vandre and Lowe (1995) refer to these areas as the under- Potential for Additional Movement cut, erosion, and deposition zones. Conditions contributing to slope failure at the Rainbow The approximately 90-foot- (27 m) high main scarp is the Imports landslide include the presence of: (1) slopes steep- undercut zone. The overall slope of this area was very steep er than 60 to 70 percent which are sul~jectto undercutting with the finer grained soil layers generating near-vertical and raveling, (2) soils prone to erosion by wind and water, faces and the granular soils raveling to their angle of repose (3) ground water in close proximity to the contact between (Vandre and Lowe, 1995). The main soil movement mecha- the deltaic and lacustrine deposits, and (4) saturated sandy nism in this area is collapse due to undercutting of fine- soils which have the potential to undergo liquefaction. Due grained layers in response to wind and water erosion, and to these conditions, a high potential for future movement raveling of granular soils. exists (Vandre and Lowe, 1995). The most significant land- The erosion zone is the area immediately downslope from slide hazard is to homes south of the present main scarp. the undercut zone. The erosion zone's vertical extent was The Rainbow Imports landslide will continue to retreat approximately 50 feet (15 m) with side scarps on the order southward into the delta as the main scarp is undermined of 20 to 30 feet (6-9 m) high (Vandre and Lowe, 1995). Soil by erosion, flow slides, and/or raveling of the sand and gravel movement in this zone was primarily erosion caused by in the scarp. The rate of main-scarp retreat cannot he pre- IIYI,IANU, ET AL,.. (:EOI,OCIC HAZARDS OF TIIE WJASATCII FRONT, L'1'AfI 317 dieted. 'IIle time needed to reach stability may be 10,50, or 100 years or more, and Vmdre and Lowe (1995) expect the rate of muin-scarp retreat to decrease as its slope decrensrs. Major earthc~uakeswill likely accelerate the raveling of the nlin scarp, possibly calisillg liquefaction of the saturated sands deposited in the erosion zone, tlrerelty causing lique- fictiorr-induced slope failures and more erosion meld runtlcr- cutting. Nniioff over the milin scarp may accelerate thc ntte of retreat (Va~idreand L,o\ve, 1995).

ROAD LOG The following road log describes the route of the field Mp iu~dindicates selected geologic features and other points of interest. Space litrritations preclude reference to many sites and features along the route, however, and the reader is encor~rag~dto consult guiclebooks for previous geologic field trips along the Wasatcli Front (for example, Utall Geo- logical Association, 1971; Gurgel, 1983; Machette, 1988; Lowe et al., 1992; Horns ct al., 1995) for additional information.

Mileage 0.0 Tlic field trip departs from the Salt Palace Convention Center at 100 South West Temple in Salt Lake City (fig 25); pro- ceed SOUTH on WEST TEMPLE. 0.4 (0,4) Turn LEFT (EAST) 011 400 SOUTFI. 0.7 (0.3) Turn RIGHT (SOUTfl) on Srl'ATE STREET 3.5 (2.8) Tuln LEFT (EAST) onto 1-80 eastbound: follow signs for 1-215, SOUTH BELT ROUTE, at the lnouth of Parleys Canyon. Rocks exposed in thc vicinity of Parleys Canyon consist of folded Mesozoic strata. 10.0 (6.5) On the left (east) side of the freeway, resi- dences :ilong the upper nlargins of Olyrrl- pus Cove are periodically affected by rock falls. The prominent peak rising above the soutltern part of Olympus Cove is Mt. Olympus, the north hce of which is ;t dip slope of Cambrian Tintic Quartzite (Crit- tenden, 19Ea). 13.0 (3.0) Tike EXIT 6 (6200 SOUTH), turn LEFT (SOUTITEAST) under freeway, proccxtd rtp hill and contirurt. SOUTH on WASA'TC t 1 BOULEVARD. 14.0 (1.0) Active sand and gravel mining operations on the left (east) side of the road in out- Figztre 25. Route of8fi~ldtrip ~Itot~iizgsf011~ 1 (111d 2 Bnse frarrr wsh-faa/delta-co~nplexsediments (Scott, IrSCS Snlt L,akc. Cit!y 30 X 60 rniutltr~c/llc~~lrrntgle 1981; Personius and Scott, 1992). 14.9 (0.9) h4outh of Big Cottctnwood Canyon. IZocks exposecl at the rrlouth of the canyon con- BYU GEOLOGY STUDIES 1997, VOL. 42, PART I1 sist of quartzite, shale, and siltstone of the 32.7 (0.7) Robert L. Rice Stadium on the right Precambrian Big Cottonwood Formation (south) will be the locale for the opening locally intruded by quartz monzonite of and closing ceremonies of the 2002 Winter the Tertiary Little Cottonwood stock (Crit- Olympics. Foundation excavations for the tenden, 1965b). stadium, as well as the George S. Eccles 17.0 (2.1) Turn RIGHT (SOUTH) and continue on Tennis Center on the south side of 500 WASATCH BOULEVARD; the road is South, revealed evidence of faulting in in a graben bounded by scarps of the pre-Bonneville alluvial-fan deposits. main trace of the Wasatch fault zone on 33.2 (0.5) 500 SOUTH turns to the RIGHT the left (east) and an antithetic fault on (NORTH) to descend a hill formed by the the right (west) (Scott and Shroba, 1985; scarp of the East Bench fault. At the base Personius and Scott, 1992). of the scarp, the road turns to the LEFT 18.1 (1.1) Turn RIGHT (WEST) on 9800 SOUTH, (WEST) and becomes 400 SOUTH. then RIGHT (SOUTH) into large vacant 34.5 (1.3) At the intersection of 400 SOUTH and lot near the mouth of Little Cottonwood 200 EAST, the Salt Lake City and County Canyon for STOP 1 (fig. 25) and discus- Building is on the left. The seismic retrofit sion of PALEOSEISMIC STUDIES ON of this historic building is summarized THE SALT LAKE CITY SEGMENT above in the discussion for field-trip stop 2. OF THE WASATCH FAULT ZONE. 35.2 (0.7) Turn RIGHT (NORTH) on 300 WEST. From here, Wasatch fault zone scarps can 37.0 (1.8) 300 WEST becomes BECK STREET. be seen to the southeast cutting the Pine- Several hot springs occur in this area dale-aged Bells Canyon moraine. along the Warm Springs fault at the base Retrace route to NORTH on WA- of the slope to the right (east). SATCH BOULEVARD. 38.5 (1.5) Active quarry operations on the right 22.6 (4.5) Turn RIGHT (EAST) at traffic light (east) side of the road in Paleozoic car- and continue NORTH on WASATCH bonates. Crushed stone is produced here BOULEVARD. for use in aggregate and other engineer- 23.3 (0.7) New golf course on the left (west) side of ing applications. A faulted Holocene allu- the road is in a reclaimed sand and gravel vial fan observed here by G.K. Gilbert pit in Lake Bonneville regressive-phase (1890) has been removed by quarrying; deltaic deposits (Personius and Scott, striated bedrock in the footwall of the 1992). fault is now exposed at the base of the 24.1 (0.8) Park at Pete's Rock, an outcrop of Pre- slope. cambrian Mutual Formation quartzite 39.4 (0.9) Continue NORTH on 1-15. The Bonne- (Crittenden, 1965a) and local climbing ville and Provo shorelines of Lake Bonne- area, for STOP 2 (fig. 25) and discussion ville are well exposed near the base of the of SEISMIC SITE RESPONSE IN Wasatch Range on the right (east). The THE SALT LAKE VALLEY. This stop Bonneville shoreline marks the highest provides an overlook of the Salt Lake level reached by Lake Bonneville around Valley with views from left (south) to right 15,000 years ago (Currey and Oviatt, 1985); (north) of the Traverse Mountains, Oquirrh the Provo shoreline is a regressive shore- Mountains and Bingham open-pit mine, line about 350 feet (107 m) below the Great Salt Lake and Antelope Island, Bonneville shoreline. Several of the can- downtown Salt Lake City, and the Salt yons on the west slope of the Wasatch Lake salient. Range between Bountiful and Farming- Continue NORTH on WASATCH ton have produced damaging and, in BOULEVARD. some cases, fatal debris flows and floods. 27.5 (3.4) At 3300 SOUTH, continue NORTH on I- Notable debris flows occurred in the 215 and follow signs for FOOTHILL 1920s, 1930s, and 1983. Debris flows dur- DRIVE. ing the 1920s and 1930s were primarily 32.0 (4.5) University of Utah campus. FOOTHILL generated by overland erosion during DRIVE turns to the LEFT (WEST) and summer cloudburst storms (Woolley, 1946; becomes 500 SOUTH. Butler and Marsell, 1972; Keaton, 1988), 11YL,LrliVD, ET AL.. GEC)I,OCIC EII1ZARDS OF TIIE WASATCI1 FRONT, UTAH 319 wl~ereasdebris flows during the spring of INDUCED FARMINGTON SIDING 1983 were mobilized from landslides LANDSLIDE COMPLEX. caused by l-apid melting of an unilsually Continue WEST on 675 NORTIf. thick snowpack (kvieczorek et al., 1983, 53.7 (1.0) 'R~rri RICIIT (EAST) on SHEPARD 1989). LANE and cross over freeway. The golf 49.7 (103) Take EXIT 325 (LAGOON DRIVE- course was constructed on naturallj hum- FARMINCTON) and bear RIGHT to rnocbky landslide terrain; tile clrtbho~tse continue NORTII on 200 WEST and parking lot (on the left [north]) arc at 50.6 (0.9) Turn LE??T (\'VrEST)on STATE STREET the top of the landslide main scarp. (US, 227). Cross over freeway, pass rrew 54.9 (1.2) Xirrr RlGIlT (SOUTH) on U.S. 89. Davis County Crirninal Justice Conrplex 55.2 (0.3) nun RIGHT (WEST) onto 1-15 N0K'I'I-I- on the left (south), which is near the ten- BOUND. ter of the prehistoric Rinnington Siding fi3.5 (8.3) Take EXIT 335 (SYRACUSE). landslide comples. 63.8 (0.3) Ttlrrt LEFT (WEST) on ANTELOPE 52.1 (1.5) Turn RIGIIT (NORTH) on 1525 WEST I2RIVE (U'TAH 108). Proceecl WEST Note hummocky landslide temin in this following signs for Syracuse and Antt~lope area. Island. 52.7 (0.6) Park near the intersection of 1525 WEST 70.6 (6.8) Antelope Island State Park fee station. and 675 NORTH irt hrxrnn~ockylartdslide The causeway that provides vehicle asccss terrain for STOP 3 (fig. 26) and discus- to Antelope Island was cclmpletely sub- sion of THE LIQUEFACTION- merged by high lake levels in 1985. The

Figur~?26. R~lte(!fjel(l trip shotcing top^ 3 cirill 4. B(ise from ClSGS Salt Lake Cit!y, Bc~ele,Pro?n(>ntory Point, (irul Og(1etz 30 X (iO minute cluotlrcingles. islarid was maccc~\sr't~l~~to thrl 1>uX)licuiitil Ihvis Coutlty rc*l,uilt tl~rcausernay In 1993. Hear LEFT (S(JL1'TFIWEST) arid f(~llo\v pa\ ed road to BulF;do Poixrf. Stop at NnfE~loPoi1 rt fbr STOP 4 (fig. 26), discuseion of FI,OOD HAZARD FROM CKEAT SALT LAKE, Lt~idlunch. Ante- lopi%Iilnncl tr;~cexcrllerit exposures of hke Bor~ncvilleant1 (:reat Salt I ake ihorelines. Because of icoct;it~crc>bourld, the clevd- tion of the Uonrrcvillc sl~orelinc.is as muclr ,is 150 fit.t (45 rn) h~glteron Antc- lope l~l,irldtl~tn at tl.tt3 rrl:rrgins of the Borrnrville basin (Doelling txt,d., 1988). Kctrace rorltt3 to 1-15. 'lii11r LEFT (NOtiTI1) mto 1-1,; NOKI'II- BOU N D. 'Ihke ESTT 352 il'l,iifN CITY-NONTII OCDEN) a11c1tun1 RIC:I-IT (EAST) on 2700 NoKI21. Viccv to rhi, left (north) of Hen Lomontf Y"t.,rk.Ilijcks expo\td on the south fl,uik of tlte rnount,iirr consist of quart/: rt~onzor~itcgnei$s of the 1,owc.r Vrotero~otcEtrrriinqtor~ C'tlryon C:o~nplc.x overl,~in by ,I thrurt-L~rrlt-reI>eett~~ci:ce- tluence of Carrrl)riii~~rrrnrir~c strata (Crit- tt~rrtlenant1 Sol.rr~serz,1985). 'nre pmrni- nent cccarprnent orr the alllrlial fan at the bare of the mountain triarki the Uolme- villc sl~orelrnc. lilrr~RIGFIT (SC)IIPTkI)orl US.89. Turn LEFT (EAST) oil UTAII 205 32550 NOE$T11). 7'lre road l)eh\ctxrrthe fieewCty exit and FVasl3irigton I'toulevard crosses FLOW Vrtw to the v,e\t crf tllc 1991 landslicle depo\its of tire prehistoric liq- tlel)ni-flot\ itilc.po.;~ton tlte ,iIlrrct,rl f,ln ~refactictrr-irrduct~clNortlr Ogdthrl la-tid- Hc%trdce t oirtt* to \IZ-\SIII\C;TOY slide compl(~(Millel; 1980: Vt~rsonir~c, B01'IdiI:\'=\KI2. 1990; IIarty ct dl., 1993). 119.9 (2.61 'li~rrl LEFT (SOL ?'I-1) or, ?? -iSI11\(:- Turn LEFT (NCIKTI-1) on MrASI31NC- T( )h BOI;I,E\'ARD TON BOLJI,E\'L41ZIl. 124 0 (4 1) 'Ilrrn lAI?F1'(EAS'n on 127'El STI.IEF:T T~imNICEIT (EAST) on 2600 NC)RTII, 125.2 11 2) C:tn?tir~ticb \iraigltt ,rt the t~,i-llrc Irgllt Tii1-n 1,EFT (NOKI'IT)on 1050 EAST. \\ X~r~rtlIS'TFT STREET bt~c~t>rt~c~\1 '1'ttII Xrni RTGII'T (ELISFT)on 3100 NORTH 3-1 (NOKTI-X OCDEN C:AYYON IiOAD). 126.2 (1 0) 'litittl KICiFI'T (\'\'EST) on iAI,X,EY Debri\ flo\zr Irr 1901 eritcxil c~trlyonrncrutfr lIKI\'E: ,inti thchrr LEFT 'SOU'1'1I) into or1 the left (north), cros~ckcltht. ro,td, ,trrcl tllc li,til-rt,ctw (;articns pdrk~i-rglot, iocatcd deposited mntt.ncll rn the resrtlentral snb- ltl tilt‘ ed\t1'171 ctfllph1tht'clt~'l.of tht' ogdl~ll dl\ icion

Continue WEST on VALLEY DRIVE. Building Seismic Safety Council, 1994, NEHRP recommended provisions Landslides within the Ogden hver land- for seismic regulations for new buildings: Washington, D.C., Federal slide complex are on the left (south). At Emergency Management Agency Publications 222A (Part 1-Pro- visions, 290 p.) and 223A (Part 2--Commentary, 335 p.). the golf course, the road crosses landslide Butler, E., and Marsell, R.E., 1972, Cloudburst floods in Utah, 1939-69: toe deposits. Utah Department of Natural Resources, Division of Water Resources, 127.3 (1.1) Cross HARRISON BOULEVARD and Cooperative Investigations Report No. 11, 103 p. continue WEST on 20TH STREET. Crittenden, Jr., M.D., 1965a, Geology of the Sugar House quadrangle, Salt Lake County, Utah: U.S. Geologcal Survey Geologc Quadrangle Map Follow signs for 1-15. 64-380, scale 1:24,000. 130.7 (3.4) Turn LEFT (SOUTH) onto 1-15 SOUTH- Crittenden, Jr., M.D., 1965b, Geology of the Draper quadrangle, Utah: US. BOUND and return to Salt Palace Con- Geological Survey Geologic Quadrangle Map 64-377, scale 1:24,000. vention Center. Crittenden, Jr., M.D., and Sorensen, M.L., 1985, Geologic map of the North Ogden quadrangle and part of the Ogden and Plain City quad- rangles, Box Elder and Weber Counties, Utah: U.S. Geological Survey REFERENCES CITED Miscellaneous Investigations Series Map 1-1606, scale 1:24,000. Currey, D.R., 1982, Lake Bonneville-Selected features of relevance to Adan, S.M., and Rollins, K.M., 1993, Damage potential index mapping for neotectonic analysis. U.S. Geological Survey Open-File Report 82- Salt Lake Valley, Utah: Utah Geological Survey Miscellaneous Publica- 1070,30 p. tion 93-4,64 p. Currey, D.R., 1990, Quaternary paleolakes in the evolution of semidesert Algermissen, S.T., 1988, Earthquake hazard and risk assessment-Some basins, with special emphasis on Lake Bonneville and the Great Basin, applications to problems of earthquake insurance, in Hays, W.W., ed., U.S.A.: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 76, p. Workshop on "Earthquake Risk-Needs of the Insurance Industry": 18S214. U.S. Geological Survey Open-File Report 88-669, p. W9. Currey, D.R., Atwood, G., and Mabey, D.R., 1984, Major levels of Great Algermissen, S.T., Perkins, D.M., Thenhaus, FC., Hanson, S.L., and Bender, Salt Lake and Lake Bonneville: Utah Geological and Mineral Survey B.L., 1990, Probabilistic earthquake acceleration and velocity maps for Map 73, scale 1:750,000. the United States and Puerto Rico: U.S. Geological Survey Miscellan- Currey, D.R., Berry, M.S., Douglass, G.E., Merola, J.A., Murchison, S.B., eous Field Studies Map MF-2120, scale 1:7,500,000. and Ridd, M.K., 1988, The highest Holocene stage of Great Salt Lake, Anderson, L.R., Keaton, J.R., Aubrey, K., and Ellis, S.J., 1982, Liquefaction Utah [abs.]: Geological Society of Amenca Abstracts \nth Programs, v. potential map for Davis County, Utah: Logan, Utah State University 20, no. 6, p. 411. Department of Civil and Environmental Engineering and Dames & Currey, D.R., and Oviatt, C.G., 1985, Durations, average rates, and proba- Moore Consulting Engineers, final technical report for the U.S. Geo- ble causes of Lake Bonneville expansions, still-stands, and contractions logical Survey, 50 p. (published as Utah Geological Survey Contract during the last deep-lake cycle, 32,000 to 10,000 years ago, in Kay, FA., Report 94-7). and Diaz, H.E, eds., Problems of and prospects for predicting Great Anderson, L.R., Keaton, J.R., Spitzley, J.E., and Allen, A.C., 1986, Lique- Salt Lake levels-Proceedings of a NOAA Conference, March 2628, faction potential map for Salt Lake County, Utah. Logan, Utah State 1985: Salt Lake City, University of Utah, Center for Pubhc Affairs and Administrabon, p. $24. University Department of Civil and Environmental Engineering and Dames & Moore, 1996, Final report, seismic hazard analysis of the 1-15 Dames & Moore Consulting Engmeers, final technical report for the conidor, 10600 South to 500 North, Salt Lake County, Utah: Seattle and U.S. Geological Survey, 48 p. (published as Utah Geolog~calSurvey Salt Lake City, unpublished consultant's report, variously paginated. Contract Report 94-9). Delta Geotechnlcal Consultants, 1994, Preliminary assessment, Ogden Can- Arnow, T., and Stephens, D., 1990, Hydrological characteristics of the yon landslide, Ogden, Utah: Salt Lake City, unpublished consultant's Great Salt Lake, Utah-1847-1986. U.S. Geological Survey Water- report, 3 p. Supply Paper 2332,32 p. Doelling, H.H., Willis, G.C., Jensen, M.E., Hecker, S., Case, W.E, and Atwood, G., and Mabey, D.R., 1995, Flooding hazards associated with Hand, J.S., 1988, Geology of Antelope Island, Davis County, Utah: Great Salt Lake, in Lund, W.R., ed., Environmental and engineering Utah Geological and Mineral Survey Open-File Release 144,82 p. geology of the Wasatch Front region. Utah Geological Association Everitt, B., 1991, Stratigraphy of eastern Farmington Bay: Utah Geologcal Publication 24, p. 483-493. and Mineral Survey, Survey Notes, v. 24, no. 3, p. 27-29. Atwood, G., Mabey, D.R., and Lund, W.R., 1990, The Great Salt Lake-A Federal Emergency Management Agency, 1985, Reducing losses in high hazardous neighbor, in Lund, W.R., ed., Engineering geology of the risk flood hazard areas-A guidebook for local officials: Federal Emer- Salt Lake City metropolitan area, Utah: Utah Geological and Mineral gency Management Agency Publication No. 116,225 p. Survey Bulletin 126, p. 5458. Forman, S.L., Nelson, A.R., and McCalpin, J.P, 1991, Thermolumines- Austin, L.H., 1988, Problems and management alternatives related to the cence dating of fault-scarp-derived colluvium4eciphering the timing rising level of Great Salt Lake, in Proceedings 6th International Water of paleoearthquakes on the Weber segment of the Wasatch fault zone, Resources Association World Congress on Water Resources: Ottawa, north central Utah: Journal of Geophysical Research, v. 96, no. B1, p. Canada, International Water Resources Association. 595-605. Bailey, J.S., and Allen, E.W., 1988, Massive resistance: Civil Engineering, Gilbert, G.K., 1890, Lake Bonnewlle: U.S. Geological Survey Monograph v. 58, no. 9, p. 5255. 1,438 p. Black, B.D., Lund, W.R., Schwartz, D.F, Gill, H.E., and Mayes, B.H., Gill, H.E., 1987, Utah Geological and Mineral Survey excavation inspec- 1996, Paleoseismic investigation on the Salt Lake City segment of the tion program-A tool for earthquake hazard recognition in Utah, in Wasatch fault zone at the South Fork Dry Creek and Dry Gulch sites, Gori, EL., and Hays, W.W., eds., Assessment of regional earthquake Salt Lake County, Utah, in Lund, W.R., ed., Paleoseismology of Utah, hazards and rlsk along the Wasatch Front, Utah, Volume 11: U.S. Volume 7: Utah Geological Survey Special Study 92,22 p. Geological Survey Open-File Report 87-585, p. U1-U19. 322 BYU GEOLOGY STUDIE S 1997, VOL. 42, PART I1

Gurgel, K D., ed., 1983, Geologlc excursions In neotectonics and engineer- memorandum to Dennls R. Shupe, North Ogden C~tyAdministrator, ing geology in Utah, Geologcal Society of Arnenca Guidebook-Part 5 P. IV. Utah Geologcal and Mineral Survey Special Studies 62,109 p Lund, WR., ed., 1990, Engineenng geology of the Salt Lake Clty metro- Harty, K M , Lowe, Mike, and Christenson, G E., 1993, Hazard potentla1 polltan area, Utah Utah Geologcal and Mineral Survey (m conjunction and paleose~smicimplications of hquefactlon-lnduced landslides along wth the Association of Engneering Geologists) Bullet~n126,66 p the Wasatch Front, Utah Utah Geologcal Survey, unpubl~shedFlnal Lund, WR , 1992, New ~nformationon the t~mingof earthquakes on the Technical Report for the U.S Geological Survey, 57 p. Salt Lake City segment of the Wasatch fault zone-Implicat~ons for Hays, WW., and King, K.W., 1984, The ground-shaking hazard along the Increased earthquake hazard along the central Wasatch Front: Utah Wasatch fault zone, Utah, in Hays, WW, and Gori, EL., eds., A work- Geological Survey, Wasatch Front Forum, v 8, no 3, p 12-13. shop on "Evaluat~onof regional and urban earthquake hazards and rlsk Lund, W.R., and Schwartz, D.tl, 1987, Fault behav~orand earthquake in Utah". U.S. Geolog~cal Survey Open-File Report 84-763, p. recurrence at the Dry Creek site, Salt Lake C~tysegment, Wasatch 13S147. fault zone, Utah [abs.]: Geological Soc~etyof Amenca Abstracts \nth Horns, D., Evenstad, N., Amodt, L., Atwood, G, Black, B.D., Hylland, M., Programs, v. 19, no. 5, p 317. Keaton, J.R., Lund, WR, Rolllns, K., and Vandre, B., 1995, Envlron- Lund, W.R., Schwartz, D P, Mulvey, WE , Budd~ngK.E., and Black, mental and eng~neeringgeology of the Wasatch Front region, 1995 B.D , 1991, Fault behavlor and earthquake recurrence on the Provo Utah Geological Assoc~ationField Conference, September 23, 1995, segment of the Wasatch fault zone at Mapleton, Utah County, Utah road log, in Lund, W.R., ed., Envlronmental and engneenng geology Utah Geological and Mmeral Survey Special Stud~es75,41 p. of the Wasatch Front reglon: Utah Geologcal Assoc~ationPubllcation Mabey, D R , 1992, Subsurface geology along the Wasatch Front, in Gon, 24, p. 533541 EL., and Hays, W.W., eds., Assessment of regional earthquake hazards Hylland, M.D., 1996, Paleoseism~canalysls of the hquefaction-induced and nsk along the Wasatch Front, Utah U.S. Geologcal Survey Pro- Farmington Siding landsl~decomplex, Wasatch Front, Utah [abs.]. fesslonal Paper 1500-A-J,p. C1416. Geological Society of America Abstracts with Programs, v. 28, no. 7, p Machette, M.N., ed., 1988, In the footsteps of G.K. Gllbert-Lake Bonne- A-157. ville and neotectonlcs of the eastern Bas~nand Range Province, Hylland, M.D, and Lowe, M., 1995, Hazard potential, falure type, and Geological Soclety of America Guidebook for Fleld Trip Twelve. Utah tim~ngof I~~uefaction-lnducedlandslldlng In the Farmlngton Siding Geological and Mlneral Survey Miscellaneous Publ~cat~on88-1, 120 p. Machette, M.N., Personlus, S.F, and Nelson, A.R., 1987, Quaternary geol- landslide complex, Wasatch Front, Utah Utah Geological Survey ogy along the Wasatch fault zone-Segmentation, recent invest~ga- Open-File Report 332,47 p. t~ons,and prel~m~naryconclusions, in Gon, PL , and Hays, W.W., eds , Hylland, M.D, and Lowe, M., in press, Characteristics, timmg, and haz- Assessment of reglonal earthquake hazards and risk along the Wasatch ard potential of hquefaction-mduced landsliding In the Farmington Front, Utah. U.S. Geologlcal Survey Open-File Report 87-585, p Siding landsl~decomplex, Wasatch Front, Utah. Utah Geologlcal A1-A72. Survey Special Study. Machette, M.N., Personms, S.E, and Nelson, A R, 1992, Paleose~smology Kaliser, B.N , 1971, Engineering geology of the C~tyand County Buildmg, of the Wasatch fault zone-A summary of recent mvestlgations, Inter- Salt Lake City, Utah. Utah Geological and Mineralogical Survey pretations, and conclusions, m Gon, PL , and Hays, W.W, eds., Assess- Spec~alStudies 38, 10 p. ment of regional earthquake hazards and risk along the Wasatch Front, Kallser, B N., 1987, Ranbow Gardens landslide of March 9, 1987, Weber Utah: U.S Geolog~calSurvey Professional Paper 1500, p A1-A71. County: Utah Geological Survey, unpublished memorandum, 2 p. Machette, M.N., Pe~son~us,S.E, Nelson, A R., Schwartz, D I?, and Lund, Keaton, J R , 1988, A probabilistic model for hazards related to sedimenta- W.R., 1991, The Wasatch fault zone, Utah-Segmentahon and history tlon processes on alluvial fans in Davis County, Utah: College Station, of Holocene earthquakes Journal of Structural Geology, v 13, no 2, p Texas A&M University, 441 p 137-149. Keaton, J.R., and Anderson, L.R., 1995, Mapp~ngliquefaction hazards in McCalpin, J, and Forman, S.L., 1994, Assess~ngthe paleoseismic act~v~ty the Wasatch Front reglon-Opportun~t~es and limitations, tn Lund, of the Brigham C~tysegment, Wasatch fault zone, Utah-S~te of the WR , ed., Environmental and englneerlng geology of the Wasatch next major earthquake on the Wasatch Front? Utah State Un~vers~ty Front reaon. Utah Geological Association Publlcation 24, p 45M68. and Byrd Polar Research Institute, unpubl~shedFinal Technical Report Lin, A,, and Wang, E, 1978, Wind tides of the Great Salt Lake Utah for the U S Geological Survey, 19 p Geolog~caland Mineral Survey, Utah Geology, v. 5, no 1, p 17-25. McCalpln, J E, and N~shenko,S.E, 1996, Holocene paleose~sm~clty,tem- Lowe, M., 1990, Geolog~chazards and land-use planning-Background, poral clustering, and probab~lltlesof future large (M>7) earthquakes explanat~on,and guidelines for development m Weber County in des- on the Wasatch fanlt zone, Utah Journal of Geophysical Research, v. ignated specla1 study areas. Utah Geolog~caland Mineral Survey 101, no B3, p. 62334253. Open-File Report 197,70 p. Miller, R D , 1980, Surficial geologc map along part of the Wasatch Front, Lowe, M., Black, B D., Harty, K M , Keaton, J.R., Mulvey, WE., Pashley, Salt Lake Valley, Utah. U.S. Geological Survey Miscellaneous Field Jr., E.E, and Williams, S.R., 1992, Geologc hazards of the Ogden area, Studles Map MF-1198, scale 1:100,000, 13 p. pamphlet. Utah, in Wilson, J.R., ed., Fleld gulde to geolog~cexcursions in Utah Miller, R.D., Olsen, H.W, Enckson, G S, M~ller,C.H., and Odum, J.K., and adjacent areas of Nevada, Idaho, and Wyommg: Utah Geological 1981, Bas~cdata report of selected samples collected from SIX test Survey Miscellaneous Publication 92-3, p 231-285. holes at five sltes In the Great Salt Lake and Utah Lake valleys, Utah. Lowe, M., Harty, K M , and Hylland, M.D., 1995, Geomorphology and U.S. Geologcal Srlrvey Open-File Report 81-179,49 p falure h~storyof the earthquake-mduced Farmington Sid~nglandsl~de Mulvey, W.E., and Lowe, M , 1991, Cameron Cove subdlv~s~ondebr~s complex, Dav~sCounty, Utah, in Lund, W.R., ed., Envlronmental and flow, North Ogden, Utah, tn Mayes, B.H , compiler, Techn~calreports englneerlng geology of the Wasatch Front region. Utah Geolog~cal for 1990-1991, Applled Geology Program Utah Geologlcal Survey Association Publication 24, p. 20.5219. Report of Investigation 222, p. 186191 Lowe, M., Harty, K.M., and Rasely, R.C., 1990, Reconnaissance of area Mulvey, WE., and Lowe, M , 1994,1991Cameron Cove subdivision debris burned by wild fire northeast of North Ogden and evaluation of poten- flow, North Ogden, Utah, U.S.A.. Proceedings of the 1992 And West t~alsed~ment yield. Utah Geological and Mineral Survey, unpubl~shed Flood Plain Managers Conference, p. 117-123 HYLLAND, ET AL.: GEOLOGIC HAZARDS OF THE WASATCH FRONT, UTAH 323

Murchison, S.B., 1989, Fluctuabon history of Great Salt Lake, Utah, dur- Scott, W.E., 1981, Field-trip gu~deto the Quaternary stratigraphy and mg the last 13,000 years. Salt Lake City, University of Utah, Ph.D. thesis, faulting In the area north of the mouth of Big Cottonwood Canyon, 137 p. Salt Lake County, Utah. U.S. Geological Survey Open-File Report 81- Nelson, A.R., and Personius, S.E, 1993, Surficial geologic map of the 773,12 p. Weber segment, Wasatch fault zone, Weber and Davis Counties, Utah. Scott, W.E., and Shroba, R.R., 1985, Surficial geologic map of an area US. Geological Survey Miscellaneous Invest~gat~onsSeries Map I- along the Wasatch fault zone in the Salt Lake Valley, Utah. U.S. Geo- 2199,22 p. pamphlet, scale 1.50,000. logical Survey Open-File Report 85-448, scale 1.24,000. Oaks, S.D., 1987, Effects of six damaging earthquakes in Salt Lake City, SHB AGRA, 1994, Report, geotechnical evaluation, effect of proposed Utah, in Gori, PL., and Hays, WW., eds., Assessment of regional earth- demolition of res~dencesat 1846 and 1850 East and 1950 South Street quake hazards and risk along the Wasatch Front, Utah, Volume 11. U.S. on stab~l~tyof active landslide in the Ogden River landslide complex, Geological Survey Open-File Report 87-585, p P1-P95. Ogden, Utah: Salt Lake City, unpublished consultant's report, 8 p Olig, S.S., 1991, Earthquake ground shaking in Utah. Utah Geological and Smith, R B., and Arabasz, WJ., 1991, Seismic~tyof the Intermountain seis- Mineral Survey, Survey Notes, v. 24, no. 3, p. 20-25 mic belt, in Slemmons, D B., Engdahl, I.R., Zoback, M.L., and Black- Olsen, K.B., Pechmann, J.C., and Schuster, G.T., 1995, Sirnulabon of 3D well, D.D., eds., Neotectonics of North Amenca. Geological Society of elastic wave propagation in the Salt Lake basin: Bulletin of the Sels- America Decade Map Volume 1, p. 185-228. mological Society of America, v. 85, no. 6, p. 1688-1710. Smith, R.B., and Shar, M L., 1974, Contemporary tectonics and seismlclty Oviatt, C.G., Cuny, D.R., and Sack, D., 1992, Radiocarbon chronology of of the western United States \nth emphasis on the Intermountain seis- Lake Bonneville, eastern Great Basin, U.S.A.: Palaeogeography, Palaeo- mlc belt. Bullet~nof the Geological Society of Amenca, v. 85, p. climatology, Palaeoecology, v. 99, p. 225-241. 1205-1218. Pacific Southwest Inter-Agency Committee, 1968, Report on factors affect- Steffen, C.C., 1986, Economic impact of flooding on the Great Salt Lake. ing sediment yield in the Pacific Southwest area and selection and Speech presented to the Natural Resources Law Forum, J. Reuben evaluat~onof measures for reduction of erosion and sediment yield: Clark Law School, Brigham Young University, Provo, Utah, October 3, Report of the Water Management Subcommittee, 10 p. 1986.14 p. Pashley, E.E, Jr., and Wiggms, R.A., 1972, Landslides of the northern Swan, EH., 111, Hanson, K.L., Schwartz, D.P, and Black, J.H., 1981, Study Wasatch Front, in Env~ronmentalgeology of the Wasatch Front, 1971: of earthquake recurrence intervals on the Wasatch fault at the Little Utah Geological Association Publication 1, p. K1-K16. Cottonwood Canyon site, Utah. U.S. Geological Survey Open-File Personius, S.E, 1990, Surficial geologic map of the Brigham City segment Report 81-450,30 p. and adjacent parts of the Weber and Coll~nstonsegments, Wasatch T~nsley,J C , King K.W., Trumm, D.A., Carver, DL., and Williams, Robert, fault zone, Box Elder and Weber Counties, Utah. U.S. Geolog~calSurvey 1991, Geologic aspects of shear-wave velocity and relat~veground M~scellaneousInvestigabons Map 1-1979, scale 1:50,000. response m Salt Lake Valley, Utah, in McCalpin, J P, ed , Proceedings Personius, S.E, and Scott, W.E., 1992, Surficial geologic map of the Salt of the 27th Symposium on Engmeenng Geology and Geotechn~cal Lake City segment and parts of adjacent segments of the Wasatch fault Engineenng. Logan, Utah State University, p 25-1 to 25-9. zone, Davis, Salt Lake, and Utah Counties, Utah. U.S. Geolog~cdSurvey Utah Division of Water Resources, 1984, Great Salt Lake-Summary of Miscellaneous Investigation Senes Map 1-2106, scale 1.50,000. technical ~nvestigations for water level control alterations. Utah Prudon, TH.M., 1990, The seismic retrofit of the City & County Building Department of Natural Resources unpublished report, variously pa@- In Salt Lake City-A case study of the application of base isolation to a nated. h~storicbuilding, in The City and County Building, Salt Lake C~ty, Utah Geological Associabon, 1971, Environmental Geology of the Wasatch Utah-Earthquake risks and the architectural landmark. Salt Lake City Front, 1971. Utah Geological Association Publication 1, variously pagi- Corporation, Proceedings from the Internat~onalSeismic Isolation1 nated. Histonc Preservation Sympos~um,May 11-14.1988, variously paginated. Van Horn, Richard, 1972, Surficial geologic map of the Sugar House quad- Ridd, M.K., and Kal~ser,B.N., 1978, North Ogden sensitive area study. rangle, Salt Lake County, Utah. U.S. Geological Survey Miscellaneous Salt Lake City, unpublished report to North Ogden Planning Com- Geologic Investigations Map I-766-A, scale 1.24,000 mission, 124 p. Van Horn, R., 1975, Largest known landslide of its type m the United Rollms, K.M., and Adan, S.M., 1994, Soil response m the Salt Lake Basin States-A failure by lateral spreading in Davis County, Utah. Utah Salt Lake City, EERI Wasatch Front Seismic Risk Regional Seminar, Geology, v. 2, no. 1, p. 8-3-87. Seminar %Earthquake Research and Mitigation, p. 3-1 to 3-22. Vandre, B.C., and Lowe, M., 1995, The Rambow Imports landshde-A Rollins, K.M., and Gerber, T.M., 1995, Seism~cground response at two window for looking at landslide mechanisms wth~nthe Ogden R~ver br~dgesites on soft-deep soils along Interstate 15 in the Salt Lake landslide complex, Weber County, Utah, in Lund, W.R., ed , Environ- Valley, Utah. Provo, Brigham Young University, unpublished Intenm mental and engineering geology of the Wasatch Front region: Utah Report for the Utah Department of Transportat~on,116 p. Geological Association Publicat~on24, p 137-156 Schwartz, D.P, and Coppersmith, K.J., 1984, Fault behavior and character- Weber County Planning Commission, 1988, Geologic hazards and land-use isbc earthquakes-Examples from the Wasatch and San Andreas fault planning-Background, explanation, and guidelines for development zones: Journal of Geophys~calResearch, v 89, no. B7, p. 5681-5698. in designated geologic hazards special study areas as requ~redm Schwartz, D.P, and Lund, W.R., 1988, Paleoseismicity and earthquake Weber County ordmances. Ogden, unpublished Weher County Plan- recurrence at Little Cottonwood Canyon, Wasatch fault zone, Utah, in nmg Commiss~onreport and maps, 69 p., scale 1.24,000 Machette, M.N., ed , In the footsteps of G K. Gilbert-Lake Bonne- W~eczorek,G E, Ellen, S., Lips, E.W., Cannon, S.H., and Short, D.N., 1983, ville and neotectonics of the eastern Basin and Range Provmce. Utah Potential for debr~sflow and debns flood along the Wasatch Front Geological and M~neralSurvey M~scellaneousPublication 88-1, p. between Salt Lake City and Willard, Utah, and measures for their mit- 82-85. igation: US Geolog~calSurvey Open-File Report 83-635,45 p. Schwartz, D.P, Lund, WR, Mulvey, W.E., and Budding, K.E., 1988, New Wieczorek, G.E, Lips, E.W, and Ellen, S.D., 1989, Debris flows and hyper- paleoseism~citydata and implications for space-time clustering of large concentrated floods along the Wasatch Front, Utah, 1983 and 1984: earthquakes on the Wasatch fault zone, Utah [abs.]. Seismological Bulletin of the Assoc~at~onof Engineering Geologists, v 26, no. 2, p. Research Letters, v. 59, no. 1, p. 15. 191-208. 324 BYU GEOLOGY STUDIES 1997, VOL. 42, PART I1

Wong, I., Olig, S , Green, R., Monwala, Y., Abrahamson, N., Baures, D., Youngs, R.R., Swan, EH., Power, M.S., Schwartz, D.P, and Green, R.K., Sdva, W, Somerville, E, Dandson, D., Pilz, J., and Dunne, B., 1995, 1987, Probabilisbc analysls of earthquake ground shaking hazard along Seism~chazard evaluation of the Magna tailings impoundment, in the Wasatch Front, Utah, in Gon, EL., and Hays, WW, eds., Assess- Lund, WR., ed., Environmental and engineering geology of the Wasatch ment of regtonal earthquake hazards and nsk along the Wasatch Front, Front region: Utah Geological Association Publication 24, p. 95-110 Utah, Volume 11. U.S. Geological Survey Open-File Report 87-585, p. Wong, I G , and Silva, W.J., 1993, Slte-specific strong ground motlon estl- M1-M110. mates for Salt Lake Valley, Utah: Utah Geologtcal Survey Miscellaneous Zoback, M L , 1983, Structure and Cenozolc tectonism along the Wasatch Publ~cation93-9,34 p. fault zone, Utah, in Miller, D.M , Todd, VR., and Howard, K A., eds., Woolley, R.R., 1946, Cloudburst floods In Utah, 185Ck1938. U.S. Geologcal Tectomc and strabgraph~cstudies in the eastern Great Baslrr: Geological Survey Water-Supply Paper 994,128 p. Soc~etyof America Memo~r157, p S28 Yonkee, W.A., and Lowe, M., in preparation, Geologic map of the Ogden quadrangle, Utah. Utah Geologcal Survey Map, scale 1:24,000.