Jul 2, 2010 - Base map scanned from USGS film positive, 1979. Shaded elevation from 10 m DEM. Culture and drainage by multiplex methods from.
IDAHO GEOLOGICAL SURVEY MOSCOW-BOISE-POCATELLO
DIGITAL WEB MAP PHILLIPS, WELHAN, AND BRECKENRIDGE
WWW.IDAHOGEOLOGY.ORG
Liquefaction Susceptibility Map for the Rigby Quadrangle, Bonneville, Jefferson, and Madison Counties, Idaho William M. Phillips, John A. Welhan, and Roy M. Breckenridge 2010
WHAT IS LIQUEFACTION? Liquefaction occurs during strong earthquake ground shaking when saturated, cohesionless earth materials lose strength due to high excess pore-water pressure. The consequences of liquefaction can be catastrophic, including destruction of railways, roads, bridge abutments, and building foundations. Liquefaction susceptibility is highest in artificial fills and loose, sandy deposits that are saturated with water. Such deposits may occur adjacent to rivers, streams, and lakes, even in a semi-arid region like southern Idaho. Irrigation may also increase liquefaction susceptibility by saturating deposits. HOW THIS MAP WAS PRODUCED 15
This map was produced using a standard methodology that relates deposit age, grain size, and environment of deposition to liquefaction susceptibility (Federal Emergency Management Administration, 2009, Table 4-10, p. 4-22; Youd and Perkins, 1978). Earth materials within about 100 ft (30 m) of the surface were classified using 1:24,000-scale geologic maps (Phillips and Welhan, in preparation). The classification process was similar to that employed in Washington State (Palmer and others, 2004). Bedrock does not liquefact, so only unconsolidated units were assigned a liquefaction susceptibility. Areas of bedrock overlain by >10 feet of unconsolidated materials were identified with water well records (IDWR, 2010) and classified on the basis of the unconsolidated deposits.
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Liquefaction susceptibility is strongly increased by a shallow groundwater table. To highlight areas with high water tables, saturated (aquic) soils within 5 ft (1.5 m) of the surface are indicated using data from county soil maps (Jorgensen, 1979; Noe, 1981; Miles, 1981). These soils have redoximorphic features characteristic of transient saturation. In most of these soils, saturation occurs only during spring runoff and the irrigation season. Changes in irrigation practices and field draining alter local water tables so areas of saturation may have changed since collection of soil data. Contours showing average depth-to-water are used to further identify regions with potentially saturated conditions. The contours were created using data obtained from wells drilled into the Eastern Snake River Plain (ESRP) aquifer. This aquifer underlies the lowlands of the ESRP. The paucity of wells in upland areas required the contours to end at the ESRP boundary. In the ESRP, water tables experience large seasonal fluctuations. Multi-year droughts or wet cycles also influence water table levels. Local pumping, and irrigation practices are other important factors controlling the depth-to-water. These factors make it difficult to precisely estimate water table depths. Therefore, the depth-to-water contours should be viewed as guidelines to focus further investigation of liquefaction susceptibility rather than definitive measures of the depth-to-water. Details of how the water table contours were generated are given in Welhan (in preparation).
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HOW TO USE THIS MAP Map users should use both the susceptibility class and indicators of water table depth when evaluating liquefaction susceptibility. The highest liquefaction hazards are in areas underlain by young, sandy sediments with high water tables. Artificial fills that have not been properly compacted are especially hazardous.
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LIMITATIONS ON THE USE OF THIS MAP 35
This map is a general guide to outline areas with the potential for liquefaction. Because this map is based on regional geological and hydrological mapping, detailed geotechnical investigation is required to determine actual ground conditions for specific building sites.
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This map is intended to be used at a scale of 1:24,000. As with all maps, users should not apply this map, either digitally or on paper, at more detailed scales.
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EXPLANATION High Liquefaction Susceptibility: Holocene, sandy alluvium of meandering streams and dunes; modern artificial fill. Moderate Liquefaction Susceptibility: Holocene, coarse alluvium of meandering streams, fine alluvial fans, and coarse colluvium; younger Pleistocene sandy alluvium of meandering streams.
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Low Liquefaction Susceptibility: Younger to older Pleistocene coarse alluvium of braided streams; younger Pleistocene loess and loess >10 ft thick over bedrock. No Liquefaction Susceptibility: Bedrock 60
Water
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This explanation is standardized for this series of quadrangle-based liquefaction maps; some categories may not appear on this map.
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Base map scanned from USGS film positive, 1979. Shaded elevation from 10 m DEM. Culture and drainage by multiplex methods from aerial photographs taken 1946. Topography by plane-table methods 1948. Photorevised 1979. Projection: Idaho coordinate system, east zone (Transverse Mercator). 1927 North American Datum. 10,000-food grid ticks based on Idaho coordinate system, east zone.
SCALE 1:24,000
MN
1
GN
0o 39
16.5o
UTM Grid and 1979 Magnetic North Declination at Center of Map
0.5 1000
0
1
0 1000
2000
0.5
1 3000
4000
0
5000
6000 1
7000
FEET
1
2
MILE 3
4
6
7
8
9
10
11
12
5
KILOMETER IDAHO
Contour interval 5 feet
QUADRANGLE LOCATION
1. Menan Buttes 2. Rexburg 3. Lewisville 4. Rigby 5. Ririe 6. Idaho Falls North 7. Ucon 8. Woodville 9. Idaho Falls South 10. Ammon 11. Firth 12. Goshen
Digital cartography by Collette Gantenbein at the Idaho Geological Survey’s Digital Mapping Lab. Map version 7-2-2010. PDF (Acrobat Reader) map may be viewed online at www.idahogeology.org. A digital version of this map is available at www.idahogeology.org.
Contours showing average depth to water below ground surface. Seasonally saturated soils within 5 ft (1.5 m) of the surface.
REFERENCES CITED Federal Emergency Management Agency, 2009, Multi-Hazard Loss Estimation Methodology Earthquake Model, HAZUS-MH MR4, Technical Manual (Available at http://www.fema.gov/ library/viewRecord.do?id=3731). IDWR, 2010, Water well logs: Idaho Department of Water Resources, Boise. (Available at http://www.idwr.idaho.gov/ GeographicInfo/GISdata/wells.htm). Jorgensen, W., 1979, Soil survey of Jefferson County, Idaho: U.S. Department of Agriculture, Soil Conservation Service, 219 p. 66 map plates, scale, 1:20,000. Noe, H.R., 1981, Soil survey of Madison County area, Idaho: U.S. Department of Agriculture, Soil Conservation Service, 128 p., 29 map plates, scale 1:24,000.
PROJECT AREA QUADRANGLE INDEX
Miles, R.L., 1981, Soil survey of Bonneville County area, Idaho: U.S. Department of Agriculture, Soil Conversation Service, 108 p., 58 plates, scale 1:24,000. Depositional Environment
Palmer, S.P. and others, 2004, Liquefaction susceptibility and site class maps of Washington State by county: Washington Department of Natural Resources, Division of Geology and Earth Resources Open File Report 2004-20 (Available at fftp://198.187.344/geology/pubs/ofr04-20/).
Age
Label
Unit
Environment
Description
Label
Age
Description
fill
m
artificial fill
landfill and/or road, levee, canal fills
T
older than Quaternary
al
Qas
alluvial
side stream alluvium meandering
J
al
Qaw
alluvial
side stream alluvium, meandering, Willow Creek
P
al
Qa
alluvial
main-stream alluvium, meandering
oP
af
Qaf
alluvial
alluvial fan
yP
Holocene anthropogenic deposits
mw
Qc
mass wasting
hillslope colluvium
H
>2.6 Ma >2.6 Ma 2.6 Ma - 11 ka 2.6 Ma - 25 ka 25 ka - 11 ka 11 ka - 0 ka
es
Qes
eolian
sand dunes and sand sheets
m
modern
el
Qel
eolian
loess
older than Quaternary Quaternary undivided older Pleistocene younger Pleistocene
Table 1. Classification of liquefaction susceptibility of geologic units in the Rigby quadrangle. Unit1
Name1
Age2
Texture3
Environment4
Class
Qa
alluvium of Snake River
H
c
alm
Moderate
Qas
alluvium of side streams
H
s
alm
High
Qes
sand dunes and sheets
H
s
es
High
mw
Qls
mass wasting
landslide deposits, mostly rotational
Qt
Fill-cut terrace of Snake River
yP
c
alb
Low
al
Qt
alluvial
stream terraces, fill-cut
Qg
glacial outwash of Snake River
yP
c
alb
Low
al
Qsvl
alluvial
sandy outwash streams
Qtln
tuff of Little North Annis Butte
oP
b
v
Bedrock
al
Qg
allluvial
gravel outwash streams, braided
Qtls
tuff of Little South Annis Butte
oP
b
v
Bedrock
al
Qgh
alluvial
gravel outwash streams, braided
Qes/Qtl
Qes over tuffs of Little Annis Butte
yP,oP
s, b
es,v
Bedrock
al
Qgo
alluvial
outwash streams, braided
v
Qb1
volcanic
basalt lava flow
v
Qyh
volcanic
rhyolite ash flow tuff
Label
Description
v
Th2
volcanic
rhyolite ash flow or lava flow
c
coarse, predominantly gravel and sand
la
Ts
alluvial/lake
sediments
s
sandy, predominantly sand and silt
Texture
m
Jp
marine
Preuss Formation
f
fine, predominantly silt and clay
m
Jtc
marine
Twin Creek Limestone
u
unknown or texturually diverse
m
Js
marine
Stump Formation
b
bedrock
1. Unit and Name from geologic maps (Phillips and Welhan in preparation). 2. See Age table for explanation of symbols. 3. See Texture table for explanation of symbols. 4. See Depositional Environment table for explanation of symbols.
Phillips, W.M. and J.A. Welhan, in preparation, Geologic map of the Rigby quadrangle, Bonneville, Jefferson and Madison Counties, Idaho: Idaho Geological Survey Digital Web Map, scale 1:24,000. Welhan, J.A., in preparation, Water table model for use in liquefaction susceptibility mapping in the Idaho Falls-Rexburg area: Idaho Geological Survey Staff Report. Youd, T.L. and M. Perkins, 1978, Mapping liquefaction-induced ground failure potential: Journal of the Geotechnical Engineering Division-ASCE, v. 104(4), pp. 433-446.
ACKNOWLEDGMENTS Funded under Task Orders 001-FY-2009 and 003-FY-2009 from the Idaho Bureau of Homeland Security.
1. Qb refers to Qba, Qbbr, Qbhc, Qbhh, Qbib, Qblg, Qblk, Qbrr, Qbsb, Qbsh, and Qbst. 2. Th refers to Thk, Thr, Thu, and Thw.
Published and sold by the Idaho Geological Survey University of Idaho, Moscow, Idaho 83844-3014
