Electronic Supplement to
Holocene Behavior of the Brigham City Segment: Implications for Forecasting the Next Large-Magnitude Earthquake on the Wasatch Fault Zone, Utah

by Stephen F. Personius, Christopher B. DuRoss, and Anthony J. Crone

This report contains an electronic supplement, consisting of eight parts: 1) Cross sections and estimated displacements across the Brigham City segment (BCS); 2) Table of radiocarbon and luminescence ages used in this report; 3) Evaluation of Box Elder delta earthquake chronology; 4) Code of OxCal models shown in Figure 2; 5) Reinterpretation of Bowden Canyon trench log; 6) Sources of surface offset data for Figures 4b and 8; 7) Descriptions of Calls Fort gravel pit fault exposures; and 8) List of references cited in the electronic supplement.

---

Section One. Cross sections and estimated displacements across the Brigham City segment

FigureS1a.jpg. Location map of cross section A-A'-A" across the southern BCS and cross section C-C' across the northern Weber segment; geologic base maps are Crittenden and Sorensen (North Ogden, Ogden, and Plain City quadrangles, 1985a) to south and Mantua and Willard quadrangles (1985b) to north.

FigureS1b.jpg. Cross section A-A'-A" across the southern BCS and cross section C-C' across the northern Weber segment at Pleasant View salient; from Crittenden and Sorensen (1985a). Section A'-A" interpreted from geologic contacts and bedding attitudes simplified from Crittenden and Sorensen (1985a; 1985b).

FigureS1c.jpg. Location map of cross section BC-BC' across the northern BCS; geologic base maps are Honeyville quadrangle to north (Oviatt, 1986) and Brigham City quadrangle to south (Jensen and King, 1999); both maps reprinted with permission of Utah Geological Survey. JK99, A-A' marks part of the line of cross section A-A' of Jensen and King (1999).

FigureS1d.jpg. Cross section BC-BC' across the northern BCS, from geothermal test well #1 Davis on west, to crest of Wellsville Mountains. Geologic contacts and bedding attitudes in Wellsville Mountains are simplified from Oviatt (1986) and Jensen and King (1999). Subsurface contacts are modified from cross section A-A' and discussion of relations in #1 Davis test well of Jensen and King (1999; redrawn with permission of Utah Geological Survey).

Section Two. Table of radiocarbon and luminescence ages used in this report.

Table S1. Descriptions of radiocarbon and luminescence ages used in this report.

Section Three. Evaluation of Box Elder delta earthquake chronology.

Section Four. Code for OxCal models shown in Figure 2.

Code for OxCal models shown in Figure 2, using OxCal v4.1.7 (Bronk Ramsey, 1995, 2001, 2008), and the IntCal09 calibration curve of Reimer et al. (2009).

Section Five. Reinterpretation of Bowden Canyon trench log of Personius (1991a).

FigureS2a.jpg. Original trench log of Personius (1991a, Fig. 6); reprinted with permission of Utah Geological Survey.

FigureS2b.jpg. Reinterpretation of part of Bowden Canyon trench wall (Personius, 1991a); base is oblique photo circa October, 1986 by S.F. Personius.

FigureS2c.jpg. Reinterpreted log of Personius (1991a), based on field notes and analysis of trench wall photographs (Fig. S2b). See text for discussion.

Section Six. Sources of surface offset data for Figures 4b and 8.

Table S2. Data and sources of surface offset measurements shown in Figures 4b and 8.

FigureS3.jpg. Plots of unpublished topographic profiles across the Brigham City segment used to determine surface offset measurements shown in Figures 4b and 8. Profiles with numbers beginning with "SP" were measured in the field with collapsible stadia rod and Abney level; profiles with numbers beginning with "TPBCS" were measured with Global Mapper GIS software from 5-m DEM acquired from the Utah Automated Geographic Reference Center (AGRC).

Plocations.kml. Keyhole Markup Language (KML) file of locations of topographic profiles shown in Figure S3. (KML files, developed for use with Google Earth, enable geographic annotation and visualization within internet-based, two- or three-dimensional maps.)

Section Seven. Calls Fort gravel pit fault exposures.

Description of Calls Fort gravel pit fault exposures.

FigureS4.jpg. (a) Location map of Calls Fort gravel pit exposures (see Figure 1 for location); base map from Personius (1990). Map units: af1—upper Holocene fan alluvium; aft—middle Holocene to uppermost Pleistocene fan alluvium; cd1—upper Holocene debris flows; chs—Holocene to upper Pleistocene hillslope colluvium; lbpg—upper Pleistocene (Bonneville) sand and gravel; lpg—uppermost Pleistocene sand and gravel related to Provo shoreline; MCr—Mississippian to Cambrian bedrock; uppercase "P" marks Provo shoreline. (b) View looking north of broad fault zone in late Pleistocene gravels of Bonneville lake cycle. White line marks contact between transgressive-phase gravel (Btg; 24-30 ka) unconformably overlain by silty sandy gravel reworked during regression of the lake from Provo shoreline (Prg; <15 ka). Total apparent throw across the fault zone is about 2.2 m. (c) Close-up of main fault zone (see Fig. S4b for location). Three subaerial deposits of scarp colluvium (Cw1, Cw2, Cw3) overlie the recessional gravels, indicating at least three surface ruptures have occurred at the site since the lake regressed below this elevation (~1,356 m) <15 ka. (K—burrowed sediment). (d) Offset of remnants of carbonate-cemented lacustrine gravel (Blg) deposited on Paleozoic bedrock, overlain by an undifferentiated subaerial deposit of scarp colluvium. Exposed faults form a separate trace of the fault zone about 100 m upslope from the fault zone shown in Figures S4b and S4c. Total throw is about 2.0 m, but outcrop is likely eroded so we could not determine how many surface ruptures were recorded in this exposure.

---

[ Back ]