Relative Earthquake Hazard Map for the Vancouver, Washington, Urban Region
by Matthew A. Mabey, Ian P. Madin, and Stephen P. Palmer
WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES Geologic Map GM-42 December 1994
The information provided in this map cannot be substituted for a site-specific geotechnica/ investi gation, which must be performed by qualified prac titioners and is required to assess the potential for and consequent damage from soil liquefaction, am plified ground shaking, landsliding, or any other earthquake hazard.
Location of quadrangles
WASHINGTON STATE DEPARTMENTOF ~~ Natural Resources Jennifer M. Belcher- Commissioner of Public Lands ... Kaleen Cott ingham- Supervisor Relative Earthquake Hazard Map for the Vancouver, Washington, Urban Region
by Matthew A. Mabey, Ian P. Madin, and Stephen P. Palmer
WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES Geologic Map GM-42 December 1994
The information provided in this map cannot be substituted for a site-specific geotechnical investi gation, which must be performed by qualified prac titioners and is required to assess the potential for and consequent damage from soil liquefaction, am plified ground shaking, landsliding, or any other earthquake hazard.
WASHINGTON STATE DEPARTMENTOF Natural Resources Jennifer M. Belcher- Commissioner of Public Lands Kaleen Cottingham - Supervisor Division of Geology and Earth Resources DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not neces sarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
WASHINGTON STATE DEPARTMENT OF NATURAL RESOURCES Jennifer M. Belcher-Commissioner of Public Lands Kaleen Cottingham-Supervisor
DIVISION OF GEOLOGY AND EARTH RESOURCES Raymond Lasmanis-State Geologist J. Eric Schuster-Assistant State Geologist William S. Lingley, Jr.-Assistant State Geologist
This project was supported by the Department of the Interior, U.S. Geological Survey, under award number 1434-93-G-2318, as part of the National Earthquake Hazard Reduction Program. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the offi cial policies, either expressed or implied, of the U.S. Government.
This report is available from: Publications Washington Department of Natural Resources Division of Geology and Earth Resources P.O. Box 47007 Olympia, WA 98504-7007
This publication is free. Mail orders must be prepaid. Please add $1.00 to each order for postage and handling. Make checks payable to the Department of Natural Resources.
Pamphlet and map printed 011 acid-free paper. Printed in the United States of America Relative Earthquake Hazard Map for the Vancouver, Washington, Urban Region
Matthew A. Mabey and Ian P. Madin Stephen P. Palmer Oregon Department of Geology and Mineral Industries Washington Department of Natural Resources Box 28 Division of Geology and Earth Resources Portland, OR 97232-2162 P.O. Box 47007, Olympia, WA 98502-7007
INTRODUCTION structure, and the construction details of the structure. During the late 1980s, the scientific understanding of earth At present the potential earthquake sources in the Vancou quake hazards in the Vancouver metropolitan area advanced ver area are not sufficiently well understood to permit an exact significantly. It is now widely accepted that damaging earth assessment of the size and location of future earthquakes. Our quakes much larger than any in the historical record are pos assessment of the seismic hazards is based on detailed geo sible and that it will be necessary to employ a wide variety of logic mapping of the greater Vancouver region and state-of mitigation measures to minimize economic losses and casual the-practice analyses of specialized geophysical and geotech ties resulting from these future earthquakes. These mitigation nical measurements. Plates 1 and 2 cannot be used to directly measures should be based on a thorough assessment of the ascertain either (1) which of the hazards may affect a particu likely extent and distribution of earthquake damage. lar site during an earthquake or (2) the severity of these haz The accompanying mapping is a synthesis of our assess ards and the likelihood of catastrophic consequences. Only a ment of three specific hazards associated with future earth site-specific geotechnical investigation performed by a quali quakes in the Vancouver urban area-Plate 1 covers the west fied practitioner can adequately assess the potential for and ern half, and Plate 2 covers the eastern half. They are pre consequent damage from soil liquefaction, amplified ground sented as two halves of one map product intended to provide shaking, landsliding, or any other earthquake hazard. land-use planners, emergency-response personnel, business Each of the three earthquake hazards considered in this owners, and private citizens with a qualitative assessment of study is a distinct and separate phenomenon. When they act in the relative degree of the earthquake hazard throughout the concert, the severity of the total hazard dramatically increases. Vancouver area. The mapping covers the Vancouver and Or As an example, the buildings damaged or destroyed in the Ma chards 7 .5-minute quadrangles and the portions of the Port rina District in San Francisco during the 1989 Loma Prieta land and Mount Tabor 7 .5-minute quadrangles in Washington earthquake were subject to both strongly amplified ground State (Fig. 1). Similar relative earth- quake hazard maps have been produced for the portions of the Portland and Mount Tabor 7 .5-minute quadrangles in Oregon. Three earthquake hazards were evaluated: soil liquefaction, amplifica tion of ground shaking, and earth quake-induced landsliding. Maps de lineating areas more or less susceptible CLARK COUNTY to each of these hazards were merged into a combined hazard map (presented as Plates 1 and 2) for the urban area. In this combined hazard map, we segre gated the study area into four hazard categories, ranging from the most haz ardous (category A) to the least hazard ous (category D). The rankings are relative because they can only be used to compare the combined hazard at a I ~ I given location to that at some other lo I ,._s I I cation in the study area. These rankings I ~rs I ~"',__~ I cannot be used to predict the level of L __ _._ __ .J structural damage resulting from these MAP LOCATION hazards during an earthquake. The ac tual damage will depend on the loca- tion and size (magnitude) of the earth Fl~ure 1. Location map showing the boundaries and names of the 7.5-minute quadrangles cov quake, the site-specific response of the ering the Vancouver urban area and the study area. The stippled pattern corresponds to the area soil and geologic material beneath the shown on Plate 1, and the hatched pattern corresponds to the area shown on Plate 2.
1 2 GEOLOGIC MAP GM-42 shaking and widespread liquefaction of the underlying soils. The distinction between each of the hazards is important to technical specialists, but it is not as useful to a nontechnical audience. We resolved that a single map expressing the total severity of the combined individual hazards would be the most effective way to present this information to nonspecialists. All of the seismic hazard analyses were compiled and re cast as a map using a Geographical Information System (GIS). Because these maps and the supporting analyses have been de ·.-:·.·. veloped as data layers in a GIS environment, they can easily be incorporated with specific earthquake source information to produce scenarios that can be used in emergency response planning, facility siting studies, lifeline vulnerability assess r\~Jan ./ ment, etc. d~fuca<2 I Rldge North SOURCES OF EARTHQUAKES America Scientific research conducted in the last decade has greatly plate increased our understanding of the sources of earthquakes that could cause major damage in western Washington. We now understand that three distinct types of earthquakes may affect the Vancouver region. Crustal earthquakes occur between 5 to IO miles (8 to 16 kilometers) below the surface along shallow faults in the Pacific Earth's crust; this is the type of earthquake that affects most plate of California. The Scotts Mills earthquake that occurred in northwest Oregon on March 25, 1993, was a shallow crustal earthquake. At magnitude 5.6, this was the largest earthquake in the Portland-Vancouver area since the 1962 magnitude 5.5 Portland earthquake, which was also a shallow crustal event that actually occurred beneath downtown Vancouver. In the past few decades, earth scientists have recognized Cascade that the outer crust of the earth is composed of a small number Range of mobile plates. The Pacific Northwest (British Columbia, Washington, Oregon, and northern California) lies on the lead ing edge of the North America plate where it overrides the Juan de Puca plate (Fig. 2). The process of plate convergence is termed subduction, and the boundary of the two plates is termed the subduction zone. Estimates of the relative move North Juan ment between the Juan de Puca and North America plates sug America de Fuca gest that they are converging at approximately 1 to 1.5 inches plate per year (3 to 4 centimeters per year). Worldwide, subduction plate zones are typically expressed as deep submarine troughs, or ' not to scale ' trenches, that lie offshore of a landmass. In Washington and ' northern Oregon, the Cascadia subduction zone starts at a sub Figure Z. (Top) Map showing the geometry of the North America and dued trench about 50 miles (80 kilometers) offshore at the base Juan de Fuca plates. Arrow indicates the motion of the Juan de Fuca of the continental slope. In the subduction zone, the Juan de plate relative to a fixed (nonmoving) North America plate. The barbed line indicates the line of convergence of the two plates and the approxi Puca plate is pushed beneath the North America plate (Fig. 2). mate location of the trench. (Bottom) A vertical slice through the earth Consequently, the Juan de Puca plate is at a depth of approxi (cross section) showing the Juan de Fuca plate thrust beneath the North mately 30 miles (50 kilometers) beneath Vancouver. America plate. lntraplate earthquakes occur as the Juan de Fuca plate breaks up beneath the North America plate. The 1949 and 1965 Puget Sound earthquakes (magnitudes 7 .1 and 6.5, respec Subduction zone earthquakes occur when two converging tively) were intraplate earthquakes. Those who lived in Van plates, such as the Juan de Fuca and North America plates, couver in 1949 may recall that Portland suffered some dam become 'stuck' together along their interface directly down aging and frightening effects during that earthquake, even dip from the trench. As the plates continue to converge, the though the epicenter was nearly 125 miles (200 kilometers) strain energy across this locked interface builds until the away. Small (magnitudes less than 3) intraplate earthquakes plates abruptly slip along the interface as the strain is re occur as far south as the Portland area, and there is some pos leased. This unlocking and slippage causes an earthquake. sibility that a large intraplate earthquake could occur closer Subduction zone earthquakes are consistently among the to Vancouver. most powerful recorded. For example, the 1964 Good Friday RELATIVE EARTHQUAKE HAZARD MAP FOR THE VANCOUVER, WASHINGTON, URBAN REGION 3 earthquake in southern Alaska caused large land-level prone to strong amplification of ground shaking. Recent stud changes and severe damage throughout southern Alaska (in ies of the Loma Prieta earthquake have shown that the majority cluding Anchorage), and the tsunami generated by the earth of the total property loss was concentrated in areas with sig quake destroyed a number of coastal villages and towns in nificantly amplified ground shaking. Alaska and the Pacific Northwest. The Good Friday earth quake had a magnitude of 9.2 and is the second largest earth Soil Liquefaction quake this century. Liquefaction is a phenomenon in which strong shaking of a Geological research initiated in the mid-1980s has demon soil causes it to rapidly lose its strength and to behave more strated that large subduction zone earthquakes have occurred like a liquid than a solid. Typically, loose sandy soils that in the Pacific Northwest, although none has occurred during have been deposited in the last few thousand years are most our historical record, which extends back about 200 years. susceptible to liquefaction. However, liquefaction will only These studies indicate that around the year 1700 there was a occur if all pore space between sand grains is filled with water large earthquake on the Cascadia subduction zone along the (that is, the sand is saturated). Soil liquefaction is typically Oregon and Washington coast. Geologic evidence left by this triggered by strong ground shaking during a large earthquake. event includes indications of land-level changes similar to When soil strength is lost during liquefaction, the conse those near Anchorage in 1964, sand deposited by a large tsu quences can be catastrophic. For example, the liquefied soil nami that immediately followed the earthquake, and signs of layer, and everything lying on top of it, can move downhill, soil liquefaction occurring possibly as far inland as the Sandy even on very shallow slopes. Movement of liquefied soils can River delta and Reed Island, approximately 15 miles (25 kilo rupture pipelines, move bridge abutments, and pull apart the meters) east of Portland. Further investigation has shown that foundations and walls of buildings. Buried objects, such as un there have been several other subduction zone earthquakes off derground storage tanks, can float upward through the lique the northwest Oregon and southwest Washington coast in the fied layer, and heavy objects, such a tall buildings, can sink last few thousand years and that they occurred every 400 to into it. Liquefaction and consequent ground movement caused 600 years on average. There is every reason to believe that massive damage to highway and railway bridges throughout similar earthquakes will occur in the future. southern Alaska during the 1964 Good Friday earthquake. The Vancouver urban area faces a more significant earth quake hazard than is indicated by the historical record, even Earthquake-Induced Landsliding though there is currently significant uncertainty about the ex act location, size, and timing of future earthquakes. It is cer Landslides are a problem familiar to inhabitants of the Pacific tain, however, that damaging earthquakes will be a part of the Northwest. They occur when the soil on a slope does not have Vancouver area's future. sufficient strength to resist the downslope force due to the soil's weight. The shaking resulting from an earthquake tends to cause existing landslides to move as the shaking simply EARTHQUAKE EFFECTS adds to the downhill force driving the failure. Likewise, The relative hazard map (Plates 1 and 2) presented in this re earthquakes can create new landslides where the strength of port is based on our evaluation of three earthquake effects: the soil is exceeded by the dynamic forces caused by the amplification of ground shaking, soil liquefaction, and earth earthquake shaking. quake-induced landsliding. The steepness of a slope and thickness of soils are indica tors of the slope's landslide potential. In addition, existing Ground Shaking Amplification landslide masses can be identified and mapped. By investigat The intensity of the ground shaking caused by an earthquake ing these known landslides, criteria can be developed that will can be significantly modified by the soils and poorly consoli allow delineation of other potentially unstable slopes. Land dated sedimentary rocks near the surface. This modification slide hazard maps developed using this general approach have can increase ( or decrease) the strength of shaking or change been produced for many urban areas, including Clark County. the frequency content of the shaking. For example, the shak ing could be changed from a rapid vibration (like a jet flying RELATIVE EARTHQUAKE HAZARD MAP low overhead) to a long rolling motion (like being on a boat We evaluated three earthquake hazards (ground shaking am in a storm). The nature of these modifications is determined plification, liquefaction, and landsliding) and prepared maps by the thickness of the geologic materials and their physical delineating areas more or less susceptible to each of these properties, such as shear-wave velocity. Using measurements hazards. The resulting relative earthquake hazard map shows of these characteristics, sophisticated computer programs can which areas will have the greatest tendency to experience estimate the effects of the local geology on ground shaking damage due to any one of, or a combination of, these individ and can broadly delineate areas where the ground shaking ual hazards. will tend to be strongest. A qualitative rating scale ranging from Oto 3 was devised Mapping of the amplification resulting from near-surface as part of the mapping of each individual hazard. A O rating geology has been done in other areas, such as the San Fran was assigned to areas having the lowest likelihood of being cisco Bay region and Mexico City. For example, damage to the affected by the hazard, and areas having the greatest likelihood Nimitz Freeway during the Loma Prieta earthquake was con were assigned a rating of 3. For every point in the map area, fined to areas of the Cyprus Street Viaduct where the ground the rating for each individual seismic hazard was squared and shaking was strongly amplified by near-surface soft soils. the resulting numbers were summed. The square root of this These areas had been previously recognized and delineated as sum was then rounded to the nearest whole number. A result 4 GEOLOGIC MAP GM-42 of 4 was assigned to category A (the highest relative hazard site-specific response of the soil and geologic material be rating), a result of 3 was assigned to category B, etc. Category neath the structure, and the construction details of the struc D was assigned to a numerical result of 1. In this ranking ture. scheme, a numeric result of O or 5 is theoretically possible, but At present the potential earthquake sources in the V ancou in practice neither value is likely to occur. In those instances ver area are not sufficiently well understood to permit an exact where a O or 5 rating did occur, they were assigned respec assessment of the size and location of future earthquakes. Our tively to the Dor A category on the relative hazard map. assessment of the seismic hazards is based on detailed geo Example: Suppose that the block that includes your logic mapping of the greater Vancouver region and state-of house had a ground shaking amplification rating of 2, the-practice analyses of specialized geophysical and geotech a liquefaction rating of 2, and a landslide rating of 0. nical measurements. This map cannot be used to directly as We would take the ground shaking amplification rat certain either (1) which of the hazards may affect a particular ing of 2 and square it to get 4. We would do the same site during an earthquake or (2) the severity of these hazards with the liquefaction rating and also get 4. Squaring and the likelihood of catastrophic consequences. Only a site the landslide rating of zero gives zero. So we add 4 + specific geotechnical investigation performed by a qualified 4 + 0 to get a sum of 8. The square root of 8 is 2.828, practitioner can adequately assess the potential for and conse which rounds to 3, placing your block in a category B quent damage from soil liquefaction, amplified ground shak relative hazard rating. Because B is the next to the ing, landsliding, or any other earthquake hazard. highest rating, your block is thus of greater concern, from an earthquake hazard standpoint, than would be ACKNOWLEDGEMENTS a block a few miles away that has a hazard rating of D. We greatly appreciate the contribution of Carl Harris, Divi Generally, areas with a high rating (3) from a single indi- sion of Geology and Earth Resources, to this study through vidual earthquake hazard (for example, liquefaction) have a his expertise in GIS manipulation of the map data and carto relative hazard rating of B (next to highest overall hazard rat graphic rendering of the GIS map files as the final printed ing) for that area. The highest relative hazard category (A) map. We thank Dan Meier, Woodward-Clyde and Associates, typically results from a high rating for two or more individual for his outstanding job managing the geotechnical drilling hazards (for example, both liquefaction and amplification). and testing phase of this study. We also thank Beth Reynosa However, a relative hazard rating of B can result from a single of the Port of Vancouver for her help in compiling the very severe hazard that may result in considerable property agency's geotechnical reports and data and the Geotechnical damage. In fact, 48 percent of the study area comprises cate Branch, Materials Laboratory, Washington Department of gory A and B hazard zones, and the remaining 52 percent falls Transportation, for allowing access to their geotechnical in category zones C and D. Thus, categories A and B represent files. a relative hazard higher than 'average' in the Vancouver area, This project was supported by the Department of the Inte and similarly categories C and D represent a relative hazard rior, U.S. Geological Survey, under award number 1434-93-G- lower than 'average'. The highest relative hazard category (A) 2318, as part of the National Earthquake Hazard Reduction covers only 10 percent of the map area and is primarily con Program. The views and conclusions contained in this docu centrated in the present flood plain of the Columbia River and ment are those of the authors and should not be interpreted as tributary creeks. necessarily representing the official policies, either expressed or implied, of the U.S. Government. SUMMARY SELECTED REFERENCES We evaluated three earthquake hazards (soil liquefaction, am plification of ground shaking, and earthquake-induced land Technical sliding) and constructed maps of the Vancouver region de Fiksdal, A. J., 1975, Slope stability of Clark County, Washington: lineating areas more or less susceptible to each of these Washington Division of Geology and Earth Resources Open-File hazards. These individual hazard maps were combined into a Report 75-10, 4 p., 1 plate, scale 1 :62,500. relative earthquake hazard map presented as Plates 1 and 2. Mabey, M. A.; Youd, T. L., 1991, Liquefaction hazard mapping for This map subdivides the Vancouver urban area into four cate the Seattle, Washington urban region utilizing LSI; Final techni gories of relative earthquake hazard ranging from the most cal report-Program element III, Geologic and seismic hazard hazardous (category A) to the least hazardous (category D). evaluation and synthesis; Objective 1(4), Studies of liquefaction Categories A and B represent a relative hazard higher than and landsliding, and other ground failure problems that affect the 'average' in the Vancouver area, and similarly categories C Seattle-Portland urban regions: Brigham Young University Tech and D represent a relative hazard lower than 'average'. Only nical Report CEG-91-01 [under contract to] U.S. Geological Sur 10 percent of the study area, mainly concentrated in the pre vey, 64 p. sent flood plain of the Columbia River, falls in the highest Madin, I. P., 1990, Earthquake-hazard geology maps of the Portland category of relative earthquake hazard. The category rankings metropolitan area, Oregon-Text and map explanation: Oregon are relative because they can only be used to compare the Department of Geology and Mineral Industries Open-File Report combined hazard at a given location to that at some other lo 0-90-2, 21 p., 8 plates. cation in the study area. These rankings cannot be used to Madin, 1. P.; Swanson, R. D., 1992, Earthquake-hazard geology maps predict the level of structural damage resulting from these of southwestern Clark County: Intergovernmental Resource Cen hazards during an earthquake. The actual damage will depend ter [Vancouver, Wash.], 5 p., 2 plates. on the location and size (magnitude) of the earthquake, the RELATIVE EARTHQUAKE HAZARD MAP FOR THE VANCOUVER, WASHINGTON, URBAN REGION 5
Phillips, W. M., compiler, 1987, Geologic map of the Vancouver Western Oregon's wake-up call: Oregon Geology, v. 55, no. 3, quadrangle, Washington: Washington Division of Geology and p. 51-57. Earth Resources Open File Report 87-10, 27 p., 1 plate, scale May, P. J.; Fox, Edward; Hasan, N. S., 1989, Earthquake risk reduc 1:100,000. tion profiles-Local policies and practices in the Puget Sound and Weaver, C. S.; Baker, G. E., 1988, Geometry of the Juan de Puca plate Portland areas: University of Washington Institute for Public Pol beneath Washington and northern Oregon from seismicity: Seis icy and Management, 73 p. mological Society of America Bulletin, v. 78, no. 1, p. 264-275. Noson, L. L.; Qamar, Anthony; Thorsen, G. W., 1988, Washington Weaver, C. S.; Smith, S. W., 1983, Regional tectonic and earthquake state earthquake hazards: Washington Division of Geology and hazard implications of a crustal fault zone in southwestern Wash Earth Resources Information Circular 85, 77 p. ington: Journal of Geophysical Research, v. 88, no. B12, Perkins, J. B.; Moy, K. K., 1989, Liability of local government for p. 10,371-10,383. earthquake hazards and losses-A guide to the law and its impacts Yelin, T. S.; Patton, H.J., 1991, Seismotectonics of the Portland, Ore in the States of California, Alaska, Utah, and Washington; final gon, region: Seismological Society of America Bulletin, v. 81, report: Association of Bay Area Governments [Oakland, Calif.], no. 1, p. 109-130. 52p. Seattle Planning Department, 1992, Seismic hazards in Seattle: Seat Nontechnical tle Planning Department, 53 p. Bott, J. D. J.; Wong, I. G., 1993, Historical earthquakes in and around Sunset Magazine, 1982, Sunset special report-Getting ready for a Portland, Oregon: Oregon Geology, v. 55, no. 5, p. 116-122. big quake: Lane Publishing Co., 12 p. Cope, Vern, 1994, The Washington earthquake handbook-An easy Sunset Magazine, 1990, Sunset's guide to help you prepare for the to-understand information and survival manual: Vern Cope [Port next quake: Sunset Publishing Corporation, 16 p. land, Ore.], 145 p. Wong, Ivan; Hemphill-Haley, Mark; Salah-Mars, Said, 1993, The Dehlinger, Peter; Berg, J. W., Jr., 1962, The Portland earthquake of Scotts Mills, Oregon, earthquake on March 25, 1993: Earthquakes November 5, 1962: Ore Bin, v. 24, no. 11, p. 185-192. and Volcanoes, v. 24, no. 2, p. 86-92. Gere, J.M.; Shah, H. C., 1984, Terra non firma-Understanding and Wong, I. G.; Silva, W. J.; Madin, I. P., 1990, Preliminary assessment preparing for earthquakes: W. H. Freeman and Company, 203 p. of potential strong earthquake ground shaking in the Portland, Iacopi, Robert, 1971, Earthquake country: Lane Books [Menlo Park, Oregon, metropolitan area: Oregon Geology, v. 52, no. 6, p. 131- Calif.]. 160 p. 134. Mabey, M. A.; Madin, I. P., 1993, Relative earthquake hazard map of Wong, I. G.; Silva, W. J.; Madin, I. P., 1993, Strong ground shaking the Portland, Oregon 7 1/2-minute quadrangle: Metro [Portland, in the Portland, Oregon, metropolitan area-Evaluating the ef Ore.]. 14 p., 1 pl. fects of local crustal and Cascadia subduction zone earthquakes and near-surface geology: Oregon Geology, v. 55, no. 6, p. 137- Mabey, M. A.; Madin, I. P.; Meier, D. B.; Palmer, S. P., in press, 143. Relative earthquake hazard map of the Mount Tabor quadrangle, Multnomah County, Oregon, and Clark County, Oregon: Oregon Yanev, Peter, 1974, Peace of mind in earthquake country-How to Department of Geology and Mineral Industries GMS-89. save your home and life: Chronicle Books [San Francisco, Calif.], Madin, I. P.; Priest, G. R.; Mabey, M.A.; Malone, S. D.; Yelin, T. S.; 304p. • Meier, Dan, 1993, March 25, 1993, Scotts Mills earthquake- WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES
WAS HINGTON STATE DEPARTMENTOF Raymond Lasmanis, State Geologist Natural Resources Jennifer M . BekhN • Commi,sionor of Publlr Lands GEOLOGIC MAP GM -42 Ka le<.>n Cottingham - Su p ervisor PLATE 1 - VANCOUVER AND PORTLAND 122°45' 7.5-MINUTE QUADRANGLES 4 5 " ,15' ,---,1r,:c:,a .. : .. - .. "'66
I RELATIVE EARTHQUAKE HAZARD MAP OF THE . l
j• VANCOUVER, WASHINGTON, URBAN AREA . . by ~5 ,... .. ·. . : Matthew A. Mabey and Ian P. Madin, Oregon Department of Geology and Mineral Industries, and Stephen P. Palmer,
.. •.. , .. Washington Division of Geology and Earth Resources
(fr I ,f \,,_ -.: .. 1994
760 ODO FEET ;i_. ... o; . V. ••• . (OR!'.G I ...... , -. ·. <...... •··.·. r 150000 FEET ZONE A ------Greatest relative hazard • -.-.. ' l'.\11\SH l • "63 • .N - ... .·: .. • ·. ··t· ' ZONE B ~. -:• . D 14 . ; . 1· . . . ' . . ... 29'1, . .. '•.,>I. f f. ,I - :, .... "61 -~ ...... ,a· ZONE C !.. i'.cl ·.. . : ...f .. : .• .. ·" D -i,I:': ·::: . . • . : :. Y
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T. 3 N T 3 N r,da! Fl~l T 2 N T 2 N •.
. - + ' This map is a synthesis of our assessment of geologic hazards associated with ,[ ·::::· ·...... future earthquakes in the Vancouver urban area. It is intended to provide land-use • • . :;,!:', .....: ;;•:: . planners, emergency-response personnel, the business community, and private citizens ~- with a relative assessment of the overall earthquake hazard throughout the Vancouver \' A N C 0 u V B R .. ,: ...... ,.,• . ., .. ,;. area. 1· ; r::, , \ • ~...:.·-~ Three specific earthquake hazards were evaluated: soil liquefaction, ampli _:J,(• - _: '~- <,- - • fication of ground shaking, and earthquake-induced landsliding. For each of these L A B / hazards, we constructed a map that delineates areas more or less susceptible to that .Sc ' ·.,,.... -~ f.,\~. : hazard. These three hazard maps were then combined to produce this map, which -;-' ·, ..;, ...... ,. qualitatively ranks the combined hazards into four categories ranging from greatest ~ .. :·- ~·-· / .. -:~ hazard (Zone A) to least hazard (Zone D). The rankings are relative because they only ·- ...... 1. . '·r ', 11 ·-· can be used for comparison of the combined hazard among localities within the study 0 ...... -: .:1 · 111'' .. :.-:· ...... area. These rankings cannot be used to predict the actual level of damage resulting ~ ...... ~...... : ""57 from the individual hazards during an earthquake. The actual damage will depend on J '·. .. . -·· '-'.. :, ~ ·t.a 40' ... .. • ··h •• • , • , , I · , 40· the location and size (magnitude) of the earthquake as well as on the effects of strong .:.-.:., • -~.. :to>, ·- ' "! • ..•• •· . ..: : ! ; . ... • .. C,i>(\, .Ye;- - ...... - I ~ .. ... • ground shaking, liquefaction, and landsliding . . : : .: :... ; ...... ; vf ..-.~ ...... -. -:l·r•····~·.,·.s. .. r\.. ~pp .. :.·: -....::.~.r;... 1+ .. ";': -~-:. ·• :;· ~-- •..
.-.\ - .. ---1 • • ~./ :::: rn t, . :; ;· ·. : .. ~ :~1 i \ / Ll': ·: " ' " ...... I' -. "·c" ... ,.·:,',I'.• ,:,··•·•: It is not possible using this map to di rectly ascertain which of these particular 4 • •• I I (.J.. • • • ..:..•, • -9:: i •• :,,:.:,....._ ~-· ,. : - •• . ~- ;\Li I II·.·:·,... .. , !"(!1• ...... hazards may affect a site during a given earthquake. This map cannot be substituted ,1,..;.~ I - .. ·. : . :-.- .. : ·: :: .. '::r.::=•:.,1·:~-.:~~~j:. = ,. ·--·· . ' .... for a site-specific geotechnicol investigation, which must be performed by qualified
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'I· ·1cl•,1 • WASHINGTON ' Polyconic projection 1927 North Americc:m Datum I 27 1_-, l ,., .,, 1 0,000-foot grid based on Washington coordinate system, south I I • •• • - zone ·~~;r-... :,;;:, ' " and Oregon coordinate system, north zone f ' •·, I 1,000-meter Universal Tronsverse Mercator grid ticks, zone 10 1· .... , CLARK COUNTY Base mops by U.S. Geological Survey .. _.,,, 'Ii Vancouver quadrangle: mopped, edited, and published - 1961 --~ --~ Photorevised - 1978 .. ... Portland quadrangle: mapped, edited, and published - 1961 Photorevised - 1970 and 1977 4 5°37'30'' --, Additional highway information from the Washington Department of ~. ~ .., \'; ,tl\,,r• ,. - I r, ..r L-~" -l ' u5J Natural Resources, Geographic Information System - 1994 I Cartographic design and production by Corl F.T. Harris, /?0000 ~E U Washington Division of Geology and Earth Resources (OREG.) I ' --~
* SCALE 1:24,000 .5 0 f MILE MAP LOCATION
o" 13' 1000 0 1000 2000 3000 4000 5000 6000 7000 FEET 4 MILS .5 0 ======~KILOMETER ....__ __ UTl.t GRID ANO 1978 ~AGNETIC NORTH ------DECLINATION AT CENTER OF CONTOUR INTERVAL 10 FEET VANCOUVER QUADRANGLE NATIONAL GEODEOIC VERTICAL DATUt.4 OF 1929 WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES W A SHINGTON STATE DEPARTMENTOF Raymond Lasmanis, State Geologist Natural Resources Jennifer M. Be lcher - Commissioner of Public l a nd< GEOLOGIC MAP GM-42 Kalee n Cottingham - Sup ervisor PLATE 2 - ORCHARDS AND MOUNT TABOR 7.5-MINUTE QUADRANGLES
I .. M11 .. . '., . ~ ·1 f .. I .
. . ' . ' . I , RELATIVE EARTHQUAKE HAZARD MAP OF THE l C • l •• \ • VANCOUVER, WASHINGTON, URBAN AREA •·' .• I ·.: by 1:, .. ' ' Matthew A. Mabey and Ian P. Madi n, I•. - • • '-~ : Oregon Department of Geology and Mineral Industries, 0. .. .,,. .: - -:,,\---+ I 1···. --- - .. ~ .. -... ---...- ·1 " and i" . ·• ·- ', I" ... " = •' ' ., ' Stephen P. Palmer, -1 : • .-:J' J .. "/ : .. .., ••• ' 'v .•); . •, Washington Division of Geology and Earth Resources ..... -:'- - ' ; I . ·vi.,._,·;,.·, ii1}11.~l1.Proiiri 1994 ., J : ·.1. aufi''""'"" 1 •• "'/ • ••·• ...... • ,J: • • • .., • ·,· / . ... • ?4 ,•, ./' . ,· _, ,/' ·. . •'' I :l .. 150 lJOO , •' HE! ,.. 1•• ~·· , .. -- . .r ._.. ''' A Greatest relative hazard • ,J' 1·. = • ·•• ZONE . I , r ;I " "· . .) ... 1 ·., ·r·· ,' ...... ) ,.. ' • •, ~. . ... •. ·: ...... :1: •' . I ':r . · ...... ::'.!1' . " ,053 I ''"'""'" He,,:h• '' ' . I I ·: 1 ·.·,· ui. .. ZONE B j ") • D ... • .. I I• " ' ' 1.. ·1, ' . ·, ,, d I ,0 • I ...... • ' t-' ·. I . •, .. , C I'· .. ·, .I ! " ZONE .. '. . '' •61 D , I ' I I' " i ·, .: •. . . " . .. 42']0" ·~··.:...:..• • 1 ... --.-.------:-. - - - 42'3(1" -.--.,.:...... - >---, '' ZONE D Least relative hazard a D
\ ' Ll R T H ,., ! l ''161 :·lfomar\ ''.- I D OPEN WATER
TH, __ (''·-., · 1· .' .:-:1 •. '''/! : T ZN T 2N ·~· ... • ,•• \ .. • • I .i :: .. \. .. :: . . ." .. , ' 0 "\. , I ;,i // I ·.,, ... • • ,,_(f • :.1:: J -·~ ·I . ;;· ':I : " • ' ' .; '• ::~•: ... ';, .-,,._·. ·r . •' ,. ·V I I p .[. 5 ' A N- s ;g . / . .• ··'' 1.- This map is a synthesis of our assessment of geologic hazards associated with ~~ : .'·/ __i--,-, . : . ..•. 1 ;;,- - '{ .... 2'. ·., •• • ,,..... ,, >/·. future earthquakes in the Vancouver urban area. It is intended to provide land-use '.1· •••• ...... ;1 •. '. . . . ' . . . . . : :: :: ;,, l planners, emergency-response personnel, the business community. and private citizens ." , ...... I :, ·.: :: ·. : .. <: ,, with a relative assessment of the overall earthquake hazard throughout the Vancouver I . t - . ,: area. : :'...... :: l:; /.. ··: ...... :-...... "\ . I : . : ·.: ,,, . /· ' 0 .. . : : C '' ...... ·:. : . ; .. : / . ., . .. ' ... . • . . : ... .. -.. --:' ·• :L ---,., . . :~ -~- _._.. _·.. ·:~ Three specific earthquake hazards were evaluated: soil liquefaction, ampli r· •. - - .,!',:.. ,'.,-, .. ,-;..., = - - . ,- ) ,I,~- . . .. " .. " . I fication of ground shaking, and earthquake-induced landsliding. For each of these : ...... : . , hazards, we c onstructed a map that delineates areas more or less susceptible to that • • I -1.: i:?: ' .; : : " '. ' -:. .. : : : I .-· hazard. These three hazard maps were then combined to produce this map, w hich ,...... ' :::: -;:,,. :.:~ 1 qualitatively ranks the combine d hazards into four categories ranging from greatest ...... , . . ;,.,. ·11 .:.. :·;:·=' ~·:: _,. -4,. - t/ '' hazard (Zone A) to least hazard (Zone D). The rankings are relative because they only ..._ : :· . ' ' ...... ~- can be used for comparison of the combined hazard among localities within the study •:: .:·. --~--- . ·-· . \ ...... : : I area. These rankings cannot be used to predict the actual level of damage resultin g ·: --:,:--··· .,...... "' . .I I from the individual hazard s during an earthquake. The actual damage will depend on .: ··.:..: :; : . : .. :·: .... : ; I- the loc ation and size (ma gnitude) of the earthquake as well as on the effects of strong •' 4CT' . ::::::·;s ::;,, I ground shaking, liquefaction, and landsliding . ·:. _::: ::: •. ··; :: :+...... ,. ' " I 1 • ..... '•, :::~:::::·: ; ·. '·,. I ', --- I ·.: . ,: ·: : ... ······ .. · I It is not possible using thi s map to directly ascertain which of these particular ... r ,-.. -~- . ' :.,• hazards may affect a site during a given earthquake. This map cannot be substit uted .. I : : : : ' • ·, ~----' ..... ·: · ... I ---·-:: -- for a site- specific geotechnical investigation, which must be performed by qualifi~d lOS6 : Ill • -- j practitioners a nd is required t o assess the potential for and consequent damage • S: ••• . . : " . ' : ~.- ...... resulting from soil liquefaction, amplified ground shaking, landsliding, or any other -.... : ...... Lsl. •, ..... ( : :. : . '. ..: : . : ; 15 --, potential earthquake hazard. :... r~:::;-J;...... :, .. ··. ; -I .: ·1-- -:·~- .,,._,_,_,, ., ': ...... ,...... : . , ...... ',·' . · t··...... '..: ::·.: : 1-· ··, • .J-· -~ .. . . . : . . . • ,; I This project was supported by the Department of the Interior, U.S. Geological ' . . I o . .... ;{:· ·:·. ·. I· / ' ' Survey under award number 1434-93-G- 2318. The v iews and conclusions contained in L , -·~· I ,: : : " A • ' • . -· this d o cument are those of the authors and should n ot be interpreted as necessarily . ~- .·,; • ...... \··:·--·:::·.: ' ' .. J ' ' ,• ·1··· . : :IT-:(~ ·_.:--· .. ; =-·:.:· .. -· 'J representing the official policies, either expressed or implied, of the U.S. Government. ; i ;:-.-- .. • .... , . . : I ' ,• .. ' . . ,..... I··. "• I ._...... :,,\' "J · . ::-· - '·. ' ... ;;. ·.- :" :· .·: .I :... ···'·' j . ... . ; : . : .... . ·21. : ·:,.:;:_;:..::_: ·-:...:. ,, - ...... ·- ...... -- -;--.. :, .-:-; ...... I ·,,. ::· :·:. -. - -. --;·. -- ;:i.1'' .. rn 1 _-r: _. .,.. .•.. -:=< -;- .. ;1.,,, ' ffFT ,. ' ... _, :- .-.i . •• -- :; ·-··· - . \ -·.... .• J - __ ..,,..;--;- - -_ .c- ' :·· '.( •:, =. . .I!' . ~-:':· :: .. ( ! ·J-"' ' --- , ,L ' . : . ' . . ' --- I • I ,.,,.'. :,_: :.·.:··.·: ::-..·. ·.:/_., I ,ill ../ . " .. - <:. I. - .I[•,., ..... --,. ' • I .- :;; ''l ··. . .· '. ""i • lll.i' ' ., I ./+' ,, ...- I .: '·I:- .. ·-----._/ . . . : : :- ..... ·. :_,:.:\.'.··- SCALE 1:24,000 - - --- ....:· .:.. :··..:;:.··...:· ··,; ..: - •:...: L :, ' • 1= --.· ~\: - '1: .5 0 1 MILE "'.: .... ( . !. • ~ - -_~,- "\\ . . . . ' 1-- . .-T'- • ' : ' I ' 1000 0 1000 2000 3000 4000 5000 6000 7000 FEET ..... : " • I I . ' :.;..,,,: ·-:: . ' " .. : ·-::.\; ... I , , .. , ..... - i I' • . ' : . '" ' i ,.I ; --, .5 0 KILOMETER 'I ,, . 'M:'I: : I. :L. I L p I L A N :irt' 'I0 53"""'" N • I : : {: : /,;: • '. • i : : .. ) · . - . I ... -- -". I ,'jl' <(• ':/ ::: :·:.: f ..... I CONTOUR INTERVAL 10 FEET ...... \. •"' .... : : . -:;7 ·· ····,\"· .· ,I' NATIONAL GEODEDIC VERTICAL DATUM Of" 1929 "'".'.."".," . .. ·: ·-- ·~ ·.. / I '' ,:, :.•.• ·~- l, ·:: \{;./' ' • -1 45°37'30" . :..... 4:5" 37'30" I' :'.•.:.;' :..,, .'". I • '·' ''·' FCC • .l!:. ,'1. I F[ , I =I·.. - .. L L p L A I N ' ...... -·~- - ... -, ...-.. . : ...... " . I' J ,+ ::: I .. !I ·r··· .. :. - - ; '.•· .. .. - - -.':- ... .:.... "'·::... :t1.,: · - - ...... ~ -.: "· .. -·1 .... L: "I ,. - -·. ... -- . . . : -:a.. .-. · . ' I' . >·' '- I I I;• - ' -. ":",-=---.. ',-c:;l" _ _;;;;....,..;;;:--I l .-,- '• .. r 42 -'!! ...... , .· ' ' . -..\ 3b ·51' -- ' ...... " ..... WASHINGTON I . ,_' ... •' ··-· .~ ~ .. •• < .1 . •, '• .. •. ~- . I ------_f'J.,11,J .- : '• .j, --..!_:I.... I '/) T 2 N CLARK COUNTY _-.. .. - "" .. -· - I J: . Po lyconic projection - "--..._ . 7 I I --- --.... 1927 North American Datum .I 10,000- foot grid based on Woshington coordinotti system, south zone 1,000-meler Universal Transve rse Me rcator g rid ticks, zone 10 Bose maps by U.S. Geotoglcol Survey Orchards quadrangle: m opped, edited, and p ublished - 1961 ..... 1• " Photorevised - 1970 and 1975 J, Mou nt Tabor quadrangle: mopped, edited, a nd publlshed - 1961 * Photorevised - 1970 and 1978 . ·i' .... I .
Additional highway Informatio n from the Washington Department of 0° 19' 120'11 Natural Resou rces, Geographic In formation System - 1994 6 tr.11LS 364 MI LS MAP LOCATION Cartographic design a nd production by Carl F.T. Harris, .... Washington Divis ion of Geo logy and Earth Resourc es --.... __ " i· , 1, .ll(' l .;;-..._ ,1,\·ri 11"-- UTM GRID AND 1975 MAGNETIC NORTH ,: . DECLI NATION AT CENTER OF MAP . A/1 --, .,, - .. --...... _ -- --- ,o4s