CASCADIA Winter 2010 1 Oregon Department of Geology and Mineral Industries

Home , Cape Mendocino, Cascadia (bioregion), Cascadia subduction zone

CASCADIAwww.OregonGeology.org Oregon Department of Geology and Mineral Industries News & information from the Oregon Department of Geology and Mineral Industries WINTER 2010

Creating a culture of preparedness— Oregon’s earthquake risk and resiliency With the Cascadia Subduction Zone offshore, Basin and Range faults to the east, and a line of volcanoes in between, Oregon is at risk for earthquakes. Are the state’s infrastructure, your community, and your family ready? Why does the Pacific Northwest have earthquakes? In the Pacific Northwest, two of the earth’s tectonic plates collide, The effects of a great (magnitude 9.0) CSZ earthquake will reach and the boundary between them is a 600-mile-long fault called the far inland. Shaking will be strongest on the coast but also strong Cascadia Subduction Zone (CSZ). Here the Juan de Fuca Plate and in Willamette valley. We can expect up to 5 minutes of shaking. the North American plate converge at the rate of 1-2 inches per Prolonged shaking can cause structure collapse, landslides, and year (3-4 cm/yr), causing stress to accumulate on the fault (called disruption of lifeline services. If a CSZ earthquake generates a sig- a megathrust) that extends from Northern California to Vancouver nificant tsunami, Oregon can expect an estimated 5,000 fatalities Island. Earthquakes are caused by the abrupt release of this slowly and over $30 billion in damages. accumulated stress.

a e c O Do you know Oregon’s four kinds of earthquake sources?  Cascadia Subduction Zone    Example: the 1700 earthquake that caused shaking and a tsunami that inundated the  Oregon coast and reached as far as Japan.  Intraplate Example: the 2001 Nisqually, Washington, earthquake that affected Washington and

c northwestern Oregon. i f i c  Volcanic a Example: the 1980 Mount St. Helens P eruption-related earthquakes. See page 3 for explanation of  Crustal Cascadia seismic source. Example: the 1993 Scotts Mills and Klamath Falls earthquakes Crustal earthquakes also occur in southeast- IN THIS ISSUE ern Oregon where the crust is pulling apart. Notes from your State Geologist – page 2 Coming to terms with seismicity – page 3 ALSO Preparing for earthquakes – page 4 Earthquake Educational Resources Seismic safety legislative time line – page 5 DOGAMI Publications Post-earthquake lifeline damage – page 6 Places to See DOGAMI geohazards research – page 7 Visit us at TsunamiReady, TsunamiPrepared – page 8 www.OregonGeology.org Tsunami hazard zones and maps – page 9 CASCADIA Winter 2010 1 Oregon Department of Geology and Mineral Industries www.OregonGeology.org

Notes from your State O L O G G E Y F A N O D T N M I E N M E T R

R A A L Geologist P

I E

D D

— Oregon’s take away question: time or money? T

R E S by Vicki S. McConnell, Oregon State Geologist O

Earthquake and seismological science just We have accelerated our tsunami mitiga- 1937 keeps getting better and better. In-depth geo- tion program by setting forth the goal to have logic and geophysical study of seismic zones new, expanded inundation maps for the entire Cascadia is published by the Oregon combined with near real-time GPS strain Oregon coast by 2013. These will be followed Department of Geology measurements of movement along faults can by new evacuation maps designed with input and Mineral Industries provide data to pinpoint precisely where the from the Tsunami Advisory Group, whose 800 NE Oregon Street, #28, next earthquake along a fault zone may occur members represent the end users for our Suite 965, Portland, OR 97232 (971) 673-1555 fax (971) 673-1562 and even give us a probable notion of when products. Our earthquake and tsunami hazards it might occur. No predictions here, folks; we outreach and education projects are now an can only discuss likely activity over years and equal part of our hazard mitigation program. Governing Board decades, not the hours, minutes, and seconds We are focusing on grass roots projects such Larry Givens, Chair, Milton-Freewater that are preferable for human planning and as placing tsunami preparedness coordinators Stephen H. Macnab, Vice Chair, Bend response. in coastal communities to conduct education R. Charles Vars, Corvallis and outreach. It will still take several years for Lisa Phipps, Tillamook Advances in structural engineering for Douglas W. MacDougal, Portland earthquake and tsunami active areas mean us to complete the maps and to develop fully our buildings can be designed to be safer the outreach. and to be more likely to withstand a geo- With earthquake science and engineer- State Geologist – Vicki S. McConnell logic process. Contributions from scientists in ing it is a similar story. Over the past decade Assistant Director – Don Lewis these areas and others can provide informa- DOGAMI has worked with dozens of state Cascadia special contributor – Yumei Wang Cascadia design – Deb Schueller tion and tools for communities to survive an agencies, emergency responder communi- earthquake and tsunami with relatively mini- ties, two Governors’ offices, and scores of leg- mal loss of life and infrastructure IF commu- islators to implement the Oregon Emergency Mineral Land Regulation nities can or do respond to the information. Management Seismic Rehabilitation Grant Pro- and Reclamation Program In almost every case, time is of the essence. gram. This grant program awards state bond 229 Broadalbin Street, SW, Albany, OR 97321 We in the hazard characterization and mitiga- funds to public school districts and emergency (541) 967-2039 fax (541) 967-2075 Gary W. Lynch, Assistant Director tion business always feel we are struggling to response facilities that are in need of seismic catch up to Mother Nature. retrofit and that have successfully applied for Baker City Field Office The recent Haiti and Chile earthquakes are funds. Baker County Courthouse prime examples. Haiti, with virtually no build- After seeing the destruction of the 2004 1995 3rd Street, Suite 130 ing codes and only a very recent understand- Sumatra earthquake and tsunami we recog- Baker City, OR 97814 nize that infrastructure (water mains, bridges, (541) 523-3133 fax (541) 523-5992 ing of their relative earthquake risk, suffered Mark L. Ferns, Regional Geologist tremendous loss of life (>200,000) and infra- railroad lines, fuel storage, transmission lines, structure from an earthquake of magnitude etc.) is very vulnerable, is costly to repair and Coastal Field Office 7.0. Chile, on the other hand, has just weath- replace, and frequently is the reason that an 313 SW 2nd Street, Suite D ered the fifth largest earthquake recorded area remains uninhabitable long after the Newport, OR 97365 (magnitude 8.8, nearly 500 times stronger hazard has abated. How do we assess the infra- (541) 574-6642 fax (541) 265-5241 Jonathan C. Allan, Coastal Team Leader than the Haiti earthquake) with a loss of about structure vulnerability in Oregon and prioritize 500 lives and many buildings still standing. retrofits? Will it take us another 10 years to de- The Nature of the Northwest What was the difference? Awareness of the velop a plan to begin the fix? Information Center magnitude of the risk and willingness to ad- I end this message with a note from Paul 800 NE Oregon Street, #28, Suite 965 dress social issues like enforcing strict build- Mann, senior research scientist with the In- Portland, OR 97232-2162 ing codes and outreach and education of the stitute for Geophysics at University of Texas (971) 673-2331 fax (971) 673-1562 Donald J. Haines, Manager general public. at Austin. In an American Geophysical Union Internet: http://www.NatureNW.org Although at the end of the day everyone Eos magazine interview (January 26, 2010) he must take some personal responsibility to be cautioned, “Countries with faults threatening informed, be aware, and be prepared, it is our dense populations need to approach earth- For free copies of this and past mission at DOGAMI to provide everyone with quake ‘defense’ with the same energy, consis- issues of Cascadia, visit www.OregonGeology.org as much information about earthquake and tency, and level of scientific spending as devot- tsunami hazards as possible and to provide ed to their military defense.” I completely agree; mitigation tools to reduce the risk — a risk we we should be defending against hazards now, now know is nearly as high as Chile’s. not after the fact.

2 CASCADIA Winter 2010 www.OregonGeology.org Oregon Department of Geology and Mineral Industries Coming to terms with seismicity Oregon’s earthquake hazards come not only from different kinds of earthquakes coseismic subsidence Relative rises and falls Uplift and from associated tsunamis but from damage that can result from processes in land, sea floor, and sea level triggered by these events. Understanding earthquakes and how damage occurs caused by the buildup and can help you prepare your home or business. (See pages 4-5 for how to prepare.) release of stress associated SUBDUCTIN G PLAT Shortening fault A break in the earth’s crust which ruptures during an earth- with great (magnitude 9) E Locked zone quake, allowing the two sides of the fault to slip past each other. underwater earthquakes. The slippage may range from less than an inch to more than 30 (image modified from Geological Coastline feet in a severe earthquake. Survey of Canada) earthquake Seismic vibrations produced when a fault in the earth’s crust ruptures or breaks, causing movement or slippage of the liquefaction A process by which water-saturated sediment temporar- rocks along the fault. ily loses strength and acts as a fluid when exposed to strong seis- seismic waves Vibrations that travel outward from the earthquake mic shaking. The shaking causes the grains to lose grain-to-grain fault at speeds of several miles per second. Although fault slip- contact, so the sediment tends to flow. Liquefaction is most likely page directly under a structure can cause considerable damage, in loose sandy soil with a shallow water table. seismic waves cause most of the destruction during earthquakes. earthquake liquefaction hazards magnitude The amount of energy released during an earthquake. If an earthquake induces LIQUEFACTION An increase of one full point on a magnitude scale represents liquefaction, several things Before an about a 30-fold increase in the energy released. Therefore, an can happen: The liquefied earthquake earthquake measuring magnitude 6.0 is about 30 times more layer and everything lying powerful than one measuring 5.0. on top of it may move Sediment layer intensity The severity of an earthquake in terms of its effects on the downslope. Alternatively, Loosely packed grains; pore spaces lled earth’s surface and on humans and their structures. The intensity the layer may vibrate with water. Water-saturated for a particular earthquake will vary depending on the distance with displacements large granular layer from the epicenter and the type of soil and rock at the site. enough to rupture pipelines, epicenter The place on the earth’s surface directly above the point on move bridge abutments, or the fault where the earthquake rupture begins. Once the rupture rupture building founda- During an Sand injected into earthquake Sand boils begins, it expands along the fault during the earthquake and can tions. Light objects, such overlying sediment extend hundreds of miles before stopping. as underground storage foreshock An earthquake that precedes the main earthquake. tanks, can float toward the Sand dike main shock The largest magnitude earthquake in a group of earth- surface, and heavy objects, quakes. such as buildings, can sink. Grains pushed apart aftershock An earthquake of similar or lesser intensity that follows Thus, if the soil at a site by upward ow the main earthquake. liquefies, the damage result- Cascadia seismic source, locked zone, transition zone, and rupture zone ing from an earthquake can be Tightly packed grains The Cascadia subduction zone is locked where the rock is not dramatically increased over what slipping because frictional resistance on the fault is greater shaking alone might have caused. than the stress across the fault. The transition zone separates earthquake ground-shaking amplification hazards Soils and soft sedimen- the locked zone from the zone of continuous sliding to the east. tary rocks near the surface can modify bedrock ground shaking Stored energy is eventually released in an earthquake when fric- caused by an earthquake. This modification can increase (or tional resistance is overcome. The rupture zone is the area along decrease) the strength of shaking or change the frequency of the which the earthquake can occur; it is equivalent to the pink shaking. The nature of the modifications is determined by the zones shown in the diagram. thickness of the geologic materials and their physical properties, such as stiffness. Cascadia seismic source earthquake-induced landslide hazards Steep and moderate slopes can produce landslides during earthquakes. Not all landslides occur Trench in the first few minutes following an earthquake; some can occur days later. In 1949, a large landslide near Tacoma, Washington, Accretionary Prism NORTH AMERICAN PLATE slipped three days after the earthquake. The steep slopes along the edges of the Willamette Valley, often near saturated condi- Locked Transition tions because of high rainfall, are candidates for earthquake- Cross section induced failure. Road cuts and fills can also have slope failures. of the Cascadia Subduction Slip lateral spreading A kind of landslide that forms on gentle slopes and Zone and the interface between the Juan de Fuca and North American plates. The locked that has rapid fluid-like flow movement, often associated with zone (dark pink surface) and transition zone (light pink sur- liquefaction. face) can be the source of next great earthquake. The gray surface is the deeper slip zone. (image modified from Geological Survey of Canada See animations of earthquake terms and concepts: [http://gsc.nrcan.gc.ca/geodyn/casaction_e.php]) http://earthquake.usgs.gov/learn/animations/

CASCADIA Winter 2010 3 Oregon Department of Geology and Mineral Industries www.OregonGeology.org

What to do BEFORE an earthquake (from FEMA: http://www.fema.gov/hazard/earthquake/) Earthquakes strike suddenly, violently and without warning. Identifying 6. Help Your Community Get Ready potential hazards ahead of time and advance planning can reduce the • Publish a special section in your local newspaper with emer- dangers of serious injury or loss of life from an earthquake. Here are six gency information on earthquakes. Localize the information ways to plan ahead. by printing the phone numbers of local emergency services of- 1. Check for Hazards in the Home fices, the American Red Cross, and hospitals. • Conduct a week-long series on locating hazards in the home. • Fasten shelves securely to walls. • Work with local emergency services and American Red Cross • Place large or heavy objects on lower shelves. officials to prepare special reports for people with mobility im- • Store breakable items such as bottled foods, glass, and china in pairments on what to do during an earthquake. low, closed cabinets with latches. • Provide tips on conducting earthquake drills in the home. • Hang heavy items such as pictures and mirrors away from beds, • Interview representatives of the gas, electric, and water compa- couches, and anywhere people sit. nies about shutting off utilities. • Brace overhead light fixtures. • Work together in your community to apply your knowledge to • Repair defective electrical wiring and leaky gas connections. building codes, retrofitting programs, hazard hunts, and neigh- • Secure a water heater by strapping it to the wall studs and bolt- borhood and family emergency plans. ing it to the floor. • Repair any deep cracks in ceilings or foundations. Get expert advice if there are signs of structural defects. What to do DURING an earthquake • Store weed killers, pesticides, and flammable products securely Stay as safe as possible during an earthquake. Be aware that some earth- in closed cabinets with latches and on bottom shelves. 2. Identify Safe Places Indoors and Outdoors quakes are actually foreshocks and a larger earthquake might occur. Minimize your movements to a few steps to a nearby safe place and stay • Under sturdy furniture such as a heavy desk or table. indoors until the shaking has stopped and you are sure exiting is safe. • Against an inside wall. • Away from where glass could shatter around windows, mirrors, Indoors pictures, or where heavy bookcases or other heavy furniture • DROP to the ground; take COVER by getting under a sturdy could fall over. table or other piece of furniture; and HOLD ON on until the • In the open, away from buildings, trees, telephone and electri- shaking stops. If there isn’t a table or desk near you, cover your cal lines, overpasses, or elevated expressways. face and head with your arms and crouch in an inside corner 3. Educate Yourself and Family Members of the building. • Contact your local emergency management office or American • Stay away from glass, windows, outside doors and walls, and Red Cross chapter for more information on earthquakes. anything that could fall, such as lighting fixtures or furniture. • Teach children how and when to call 9-1-1, police, or fire de- • Stay in bed if you are there when the earthquake strikes. Hold partment and which radio station to tune to for emergency in- on and protect your head with a pillow, unless you are under formation. a heavy light fixture that could fall. In that case, move to the • Teach all family members how and when to turn off gas, elec- nearest safe place. tricity, and water. • Use a doorway for shelter only if it is in close by and you know 4. Have Disaster Supplies on Hand it is a strongly supported, load-bearing doorway. • Flashlight and extra batteries. • Stay inside until shaking stops and it is safe to go outside. Re- • Portable battery-operated radio and extra batteries. search has shown that most injuries occur when people inside • First aid kit and manual. Pack buildings attempt to move to a different location inside the • Emergency food and water. everything building or try to leave. • Nonelectric can opener. in backpacks • Be aware that the electricity may go out or the sprinkler sys- • Essential medicines. so you are tems or fire alarms may turn on. • Cash and credit cards. ready to go. • DO NOT use the elevators. • Sturdy shoes. Outdoors 5. Develop an Emergency Communication Plan • Stay there. • In case family members are separated from one another during • Move away from buildings, streetlights, and utility wires. an earthquake (a real possibility during the day when adults are • Once in the open, stay there until the shaking stops. The great- at work and children are at school), develop a plan for reuniting est danger exists directly outside buildings, at exits, and along- after the disaster. side exterior walls. Ground movement during an earthquake is • Ask an out-of-state relative or friend to serve as the “family seldom the direct cause of death or injury. Most earthquake- contact.” After a disaster, it’s often easier to call long distance. related casualties result from collapsing walls, flying glass, and Make sure everyone in the family knows the name, address, and falling objects. phone number of the contact person.

4 CASCADIA Winter 2010 www.OregonGeology.org Oregon Department of Geology and Mineral Industries Oregon’s seismic safety legislative time line recent Pacific Northwest and 21st century 2001 Gujarat M 7.7 > 20,000 killed California destructive earthquakes highly destructive 2003 Bam, Iran M 6.5 > 40,000 killed Loma Prieta, Calif., earthquake, M 6.9, 1989 earthquakes 2004 Sumatra M 9.1 ~ 230,000 killed Scotts Mills, Oreg., earthquake, M 5.6, 1993 2005 Kashmir M 7.6 > 79,000 killed Klamath Falls, Oreg., earthquakes, M 6.0, 1993 2008 Chengdu M 8.0 ~ 90,000 killed Northridge, Calif., Nisqually, Wash., earthquake, M 6.8, 2001 2010 Haiti M 7.0 > 200,000 killed earthquake, M 6.7, Eureka, Calif., earthquake, M 6.5, 2010 2010 Chile M 8.8 > 500 killed 1994 1990 2000 2010 2020 2030 2040

1991 1994 2001 2002 2005 2007 2009 2022 2032 As a result of Oregon’s first Statute 455.400 Ballot Measures Senate Bills DOGAMI pub- Seismic Seismic Seismic citizen con- statewide required seismic 21 and 22 2, 3, 4, and 5, lished seismic Rehabilitation mitigation mitigation cern after the seismic “life-safety” in passed, allow- introduced report (Open-File Grant Program to be to be 1989 Loma building schools and ing for ~$1.2 by Senate Report O-07-02) provided $30 completed completed Prieta, Calif., code (Oregon emergency facili- billion of state President indicating 3,352 million in state for for public earthquake, Structural ties. Five pieces of bonds for seis- Peter Court- educational and bond funds emergency high- Oregon Senate Specialty legislation intro- mic upgrades. ney, required emergency facili- ($15 million for facilities (fire occupancy Bill 96 created Code) duced at request These seismic statewide ties buildings are public schools and police schools the Oregon adopted. of Senator Peter upgrades are for seismic needs at seismic risk. and $15 million stations, (K–12, Seismic Safety New building Courtney as public schools assessment, a SB 1 pro- for fire, police, acute care community Policy Advisory designs must part of OSSPAC: and emergency grant program, vided Oregon and hospitals hospitals, colleges Commission incorporate Senate Bills 13, facilities. (Refer and authorized Emergency [$1.2 billion and and (OSSPAC) seismic 14, 15 and Senate to Constitutional state bonds. Management authorized emergency universities). to increase provisions. Joint Resolutions Articles XI-M and First time public (OEM) funds for by voters]) to operation Oregon’s Many build- (SJRs) 21 and 22. XI-N.) universities four new staff to begin seismic centers). awareness to ings built All passed. Drills received seismic establish grant mitigation of earthquake before 1994 required of large mitigation program. schools and hazards by will not be employers (pri- funds. emergency supporting able to with- vate and public). SB 2 directed (In 2008 facilities and earthquake stand shaking SJRs created bal- DOGAMI to con- the Oregon to improve education, from earth- lot measures. Law duct statewide Department community research, quakes and (ORS 455.400) risk study. SB 3 of Education preparedness. mitigation, and are at risk of required schools directed Oregon created the legislation. collapse. and emergency Emergency The “Quake (In 2011 more facilities to be Management Safe Schools” state bond seismically safe. (OEM) to start program to share funding is slated grant program. information to be appropri- SB 4 and 5 al- on the seismic ated for addi- lowed Dept. of scores and other tional seismic Administrative earthquake upgrades.) Services (DAS) preparedness and Treasury to information with issue XI-M and the public.) XI-N bonds.

Collapse potential for all educational Relative Collapse Potential and emergency sites in DOGAMI’s seis-  Very High (100%) mic needs assessment study (O-07-02).  High (>10%) These sites occur throughout Oregon.  Moderate (>1%)  Low (<1%) Over 1,300 buildings have high to very high seismic collapse potential.

Resources: Oregon Emergency Management Seismic Rehabilitation Grant Program: http://www.oregon.gov/OMD/OEM/ Oregon Department of Education Quake Safe Schools: http://www.ode.state.or.us/go/quakesafeschools/ DOGAMI seismic needs assessment study (O-07-02): http://www.oregongeology.org/sub/projects/rvs/default.htm Oregon Seismic Safety Policy Advisory Commission (OSSPAC): http://www.oregon.gov/OMD/OEM/osspac/osspac.shtml 2007 Oregon Structural Specialty Code: http://www2.iccsafe.org/states/oregon/07_Structural/Building07_Frameset.htm

CASCADIA Winter 2010 5 Oregon Department of Geology and Mineral Industries www.OregonGeology.org Post-earthquake lifeline damage Certain infrastructure systems—for example, fuel, electrical, water, the telecommunication lines will all be down. highway—are called “lifelines” because our lives depend on them. Oregon’s lifelines were constructed to standards well below cur- While the seismic provisions in Oregon’s current building code rent seismic safety specifications. In a major earthquake, many of (Oregon Structural Specialty Code) mean new buildings will be our critical lifelines, such as major highways, fuel ports, electrical able to withstand most earthquakes, our roads, bridges, and elec- transmission, and telecommunication systems will not be able to trical and waterlines might not fare as well. Disruption to these provide their intended services. critical services could dramatically slow aid and relief efforts—as Understanding lifeline locations, their interdependencies, and happened after the February 2010 Chile earthquake. their locations in relationship to earthquake hazards is only the first Lifelines often depend on each other, so that failure of one can step toward making lifeline systems seismically resilient. After risk affect other systems. For example, the telecommunications system identification and assessment, stakeholders can be identified and requires cooling, which requires electricity, gas or liquid fuel, and engaged, and risk prioritized and mitigated. Oregon is currently fo- water. If a water pipeline is located on a bridge and the bridge col- cusing on reliable fuel supply, electricity, and gas service as part of lapses in an earthquake, then the bridge, the water services, and a state energy assurance project.

The majority of Oregon state-owned VANCOUVER bridges built between 1950 and 1980

1962, Mag 5.2 are seismically vulnerable. An Ore- gon Department of Transportation 2009 study (http://library.state.or.us/reposito- ry/2009/200911171034432/) found that Camas Oregon would face devastating damage PORTLAND to the transportation system from a large

99E 30 Cascadia Subduction Zone earthquake or a crustal earthquake located in the Wil- lamette Valley. Coastal U.S. Highway 101 Fairview 30 would have dozens of impassable loca-

Troutdale tions due to bridge failures, and all high- 405 213 ways connecting U.S. 101 and I-5 would Gresham be impassable due to bridge damage. Beaverton 205 Vulnerable bridges will need strengthen- ing or replacement to ensure that they

208 survive a large earthquake. 217 Milwaukie 5 Tigard Lifeline Systems Major water supply line, water treatment Interstate highway plant State highways, and other major roads Major sewer pipeline, treatment plant Railroad Electric transmission line, 115kV, 230kV, 500kV Major airport (map lines with thicker width are adjacent pipelines) Minor airport Natural gas pipeline Liquid fuel pipeline Regional Geology Data sources for the compilation of map and text  Close-up of Portland metro area from Earthquake Hazards and Lifelines in the Interstate 5 Urban Corridor— (See Reference section on reverse side) WoodburnBackground to geology Centralia, explanation: Washington, by E. A. Barnett and others (U.S. Geological Survey Scientific Investigations Palmer, S.P., et al, 2003 Map 3027 [http://pubs.usgs.gov/sim/3027/Consolidated sediments and rock ]). The I-5 corridor from Cottage Grove to Woodburn,Palmer, S.P., Oregon, et al 2004 has also been studied (U.S.Regions Geological considered Survey less susceptible Scientific Investigations Map 3028 [http://pubs.usgs.gov/sim/3028/]). than unconsolidated deposits to Mabey, M., et al, 1994: GM-42 liquefaction, ground amplification, and Mabey, M., et al, 1997: IMS-1 landslides during earthquakes. These I-5 Madin, I.P., et al, 2000: IMS-7 areas have been identified through Madin, I.P., et al, 2000: IMS-8 interpretation of detailed geologic Burns, R., et al, 2008: IMS-24 hazard mapping Hofmeister, R.J., et al, 2003: Unconsolidated young deposits  AerialOFR -03-10 view of collapsed Earthquake hazard regions. sectionsWalker and of McLeod, the Cypress 1991 via- Relative toconsolidated sediments and rock, these areas are more duct of Interstate Highway susceptible to liquefaction,ground 880, Oakland, California, amplification, and landslides duringearthquakes. These areas after the 1989 Loma Prieta have been identified through earthquake (H. G. Wilshire, interpretation of detailed geologic Vancouver WASHINGTON hazard mapping U.S. Geological Survey). Portland Magnitudes of earthquakes from Pacific Northwest Seismic Network, 1969-2007 Map Area OREGON 2.0- 3.0- 4.0- 5.0- 2.9 3.9 4.9 5.9 Depth 0-35 km Base map: U.S. Geological Survey National Elevation Dataset 6 CASCADIA WinterDepth greater 2010than 35 km 30-meter digital elevation model (DEM) UTM 10, NAD27 projection. www.OregonGeology.org Oregon Department of Geology and Mineral Industries DOGAMI geohazards research

Coos County multi-hazard mapping Tsunami hazard modeling and Cascadia paleoseismicity DOGAMI is conducting Digital Flood Insurance Rate Map DOGAMI coastal geologists continue revising tsunami inun- (DFIRM) flood-plain redelineation for the Federal Emergency Man- dation maps that cover the state’s entire 362-mile-long coastline agement Agency (FEMA) using lidar-based data to create the base using sophisticated computer models coupled with laser-based maps. Once the base maps are created, DOGAMI will use the new terrain mapping and field-based geologic investigations. Products base imagery to identify and map channel migration zone hazards; include tsunami inundation and evacuation maps and grass-roots 100-year and 500-year flood hazard loss estimation (using HAZUS, outreach and education to coastal communities. FEMA’s risk assessment methodology); landslide hazards; earthquake hazards including liquefaction and ground shaking amplification; tsunami inundation hazards; and coastal erosion hazards. The multi-hazards maps will be available in paper format and in digital format via an interactive web map.

Portland urban area geologic hazard assessment DOGAMI is partnering with the U.S. Geologic Survey (USGS) to make a new, state-of-the-art digital geologic map and database of the greater Portland urban area, stretching from Estacada to St. Helens, Washougal to Newberg. The map will feature highly detailed geology mapped on new lidar imagery, which allows geologists to see unprecedented detail in the shape of surface. The data from the new map will be used to make detailed landslide and earthquake hazard maps of the area in cooperation with local gov- DOGAMI geologist Rob Witter (left) and USGS geologist Brian Atwater (right) pres- ernments and the USGS. ent evidence for great Cascadia earthquakes and tsunamis to middle school science teachers participating in the Teachers on the Leading Edge program, supported by the National Science Foundation. Bob Butler, University of Portland earth science educator, Multi-hazard risk and vulnerability assessments for Mount Hood is at far right. (Photo: James Roddey, DOGAMI) The goal of this USGS-funded, 1½-year project is to assist communities within the Mount Hood, the Highway 26/Sandy River corridor, and the Highway 35/Hood River corridor study area Advanced National Seismic System, Pacific Northwest Region in understanding the risk associated with volcanic, earthquake, The Advanced National Seismic System (ANSS) is a U.S. Geo- landslide, and flooding hazards. DOGAMI is compiling existing logical Survey effort to coordi- hazard and asset data throughout the study as well as creating nate and upgrade seismic-mon- new data using lidar-based maps. itoring networks nationwide and to implement rapid dis- Pre-Disaster Mitigation (PDM) studies for mid/southern tribution of earthquake infor- Willamette Valley, mid Columbia River Gorge, mation. Under the ANSS, the and south central Oregon Pacific Northwest Seismic - Net The purpose of these studies is to help communities prepare work (PNSN) has begun install- pre-disaster mitigation plans, identify potential geologic hazards, ing a new generation of digital help communities perform earthquake damage and loss estima- earthquake sensors in urban tion, and to recommend future action items. Products include digi- areas that can accurately record tal GIS layers for each community, depicting relative earthquake ground motions. This infor- ground shaking amplification hazards, relative earthquake lique- mation will help improve the design of future buildings to faction hazards, relative earthquake-induced landslide hazards, be earthquake resilient. Information on the intensity and and identified landslide areas. Damage and loss estimates for each distribution of ground shaking can be used by emergen- community were analyzed for two earthquake scenarios. The mid/ cy managers to direct rescue service to hard-shaken areas. southern Willamette study is complete (DOGAMI IMS-24); the other This information is available on USGS and PNSN web sites. two studies will be published in 2010. Funding was provided by http://pubs.usgs.gov/fs/2004/3073/pdf/Factsheet3073.pdf FEMA with matching funds from the State of Oregon.

CASCADIA Winter 2010 7 Oregon Department of Geology and Mineral Industries www.OregonGeology.org

New multi-year tsunami mapping and outreach program Oregon coastal communities will be TsunamiReady, TsunamiPrepared Scientific research looking 10,000 years into the geologic past indicates great earth- HOW A TSUNAMI IS GENERATED quakes and tsunamis generated by a rupture of the Cascadia Subduction Zone have occurred with alarming frequency (see time line below). The last great earthquake happened just over 300 years ago, and we can INUNDATION expect another of these great earthquakes waves pile up when they hit and tsunamis at any time. An earthquake shallow water could result in a tsunami inundating the Or- FAULT PROPAGATION egon coast within 15 to 30 minutes. Before low waves spread that, ground shaking could cause liquefac- out from epicenter tion, landslides, and coastal subsidence. TsunamiReady™, TsunamiPrepared, a multi- GENERATION (epicenter of earthquake) year, multi-million dollar program funded by the National Tsunami Hazard Mitigation Pro- (image modified from Geoscience Australia [http://www.ga.gov.au/hazards/tsunami/] gram and overseen by the U.S. Department where the image appears courtesy of the Russian Academy of Sciences) of Commerce’s National Oceanic and Atmo- spheric Administration (NOAA), has the goal of reaching every resident and visitor at the TsunamiReady, TsunamiPrepared will also north coast, Yachats, Waldport, and Seal Rock on Oregon coast with a message of how to pre- accelerate the remapping of the Oregon the central coast, and Bandon on the south pare for and respond to an earthquake and coast for tsunami inundation using state of coast. State parks adjacent to these commu- tsunami generated by a rupture of the Cas- the art computer modeling and laser based nities will also participate. cadia Subduction Zone. terrain mapping (lidar). The outcome will be TsunamiReady™, TsunamiPrepared is ad- The program will build on the work coast- the creation of new, more accurate tsuna- ministered by DOGAMI in collaboration with al communities have already accomplished mi evacuation maps for the entire 362-mile Oregon Emergency Management, the Ore- or assist in work they are ready to begin by length of the Oregon coast. gon Coastal Zone Management Association, supporting a grass roots program of aware- Communities chosen for the first year of and the National Weather Service. For more ness and preparedness. TsunamiReady, Tsu- accelerated funding of the TsunamiReady, information contact James Roddey, Oregon namiPrepared will also provide much need- TsunamiPrepared program include Rockaway Department of Geology and Mineral Indus- ed resources to help these communities Beach, Manzanita, Nehalem, and Wheeler on the tries, (971) 673-1543. create or maintain a sustained effort of education and preparation.

CascadiaCascadia E Earthquakearthquake Timeline Time Line

EVENTS IN HUMAN HISTORY

rst wine made Kennewick Man cattle domesticated Mount Mazama erupts horses domesticated rst use of wheel Great PyramidStonehenge at Giza Code built of HammurabiTutankhamen bornHomer writesbirth of Iliad Buddhabirth of Jesus fall of Rome Magna Cartavoyage written of Columbus

YEARS BC 8000 7000 6000 5000 4000 3000 2000 1000 0 1000 2000 YEARS AD

KNOWN CASCADIA EARTHQUAKES ALONG THE CASCADIA SUBDUCTION ZONE IN NORTHERN CALIFORNIA, OREGON, AND WASHINGTON YOU ARE HERE! Earthquake of Magnitude 9+ (fault breaks along entire subduction zone)

Earthquake of Magnitude 8+ (fault breaks along southern half of subduction zone)

Comparison of the history of subduction zone earthquakes along the Cascadia Subduction Zone in northern California, Oregon, and Washington, with events from human history. Ages of earthquakes are derived from study and dating of submarine landslides triggered by the earthquakes. Earthquake data provided by Chris Goldfinger, Oregon State University; time line by Ian P. Madin, DOGAMI.

8 CASCADIA Winter 2010 www.OregonGeology.org Oregon Department of Geology and Mineral Industries

Tsunami evacuation maps and information available online Tsunami vertical refuges Will you know where to go if a tsunami hits? A tsunami caused by an undersea earth- ground stops shaking, evacuate on foot, if quake near the Oregon coast is called a lo- possible. Follow evacuation signs and ar- cal tsunami. An undersea earthquake in the rows. Pacific Ocean far away from the coast may Coastal residents and cause a distant tsunami. visitors can prepare for the A distant tsunami will take 4 hours or possibility of a tsunami by more to come ashore. No earthquake will becoming familiar with the be felt at the coast, and the tsunami will tsunami hazard zones and generally be smaller than that from a local evacuation routes in their earthquake. Typically, there is time for an communities. Oregon tsunami Conceptual illustration by Jay Raskin, president official warning and evacuation to safety. evacuation zone maps for some commu- of Ecola Architects and former mayor of Cannon A local tsunami can come onshore nities are online, and more are planned. Beach, of a proposed new Cannon Beach City Hall. The elevated building could double as a within 15 to 20 minutes after the earth- See your local emergency preparedness tsunami evacuation shelter for people who do quake—before there is time for an official agency for specific information on tsunami not have time to reach higher ground as well as warning from the national warning system. shelters and other specific evacuation in- ensure that city government services continue Ground shaking from the earthquake may structions for your community. to function during all but the largest tsunamis. be the only warning you have. After the On September 28-29, 2009, the Cascadia Region Earthquake Workgroup (CREW) Oregon Coast Local Emergency Preparedness Agencies held the Pacific Northwest region’s first workshop on tsunami vertical evacua- Clatsop County Sheriff’s Office, Emergency Services:http://www.co.clatsop.or.us/default. tion buildings (TEBs) as a way to protect asp?pageid=391&deptid=5 people and to improve community recov- Coos County Emergency Services: http://www.cooscountysheriff.com/tsunami.htm ery in the event of a tsunami. Curry County Emergency Services: http://www.co.curry.or.us/Emergency%20Services/emergency_Services.htm TEBs, reinforced concrete buildings on Douglas County Emergency Services: http://www.dcso.com/tsunami_maps.asp robust deep foundations that allow water Lane County Emergency Management: http://www.lanecounty.org/EmerMgmt/default.htm to flow through the first floor, could be stra- Lincoln County Emergency Services: http://www.lincolncoemergencyservices.us/home.cfm?dir_cat=34589 tegically located in low-lying coastal com- Tillamook County Emergency Management: http://www.co.tillamook.or.us/gov/EMGMGNT/ munities. Elevated platforms designed to NOAA West Coast and Alaska Tsunami Warning Center: http://wcatwc.arh.noaa.gov/ withstand earthquake and tsunami forces could be erected in state parks. American Red Cross, Oregon Chapters: http://www.oregonredcross.org/index.asp?IDCapitulo=663B0ID44V Cannon Beach, Oregon, may become Oregon State Police: http://www.oregon.gov/OSP/ the first community in the United States Oregon Emergency Management: http://www.oregon.gov/OMD/OEM/ to erect a TEB. Several designs for a new city hall building were showcased and discussed at the CREW workshop. The designs feature wave-dissipation structures in the front and back, and refuge for about a 1,000 people. With about 50% of residents and 75% of businesses in the tsunami zone, the City of Cannon Beach is exploring options on how to fund a new state-of-the art, sustainable TEB. Depend- ing on the features, a TEB structure would add $1-2 million to the cost of a new city hall. The CREW workshop minutes are available as DOGAMI Open-File Report O-10- 02. For more information on TEBs, contact Online interactive maps and evacuation brochure maps show tsunami inundation zones for Oregon coastal communities such as the Cannon Beach area shown above. Yumei Wang, DOGAMI Geotechnical En- • Online interactive evacuation maps: http://www.nanoos.org/data/products/oregon_tsunami_ gineer, at (971) 673-1551 or email yumei. evacuation_zones/index.php. [email protected]. • Evacuation brochures: http://www.oregongeology.org/sub/earthquakes/Coastal/Tsumaps.htm

CASCADIA Winter 2010 9 Oregon Department of Geology and Mineral Industries www.OregonGeology.org Earthquake educational resources Earthquake Preparedness DOGAMI Earthquake and Tsunami Publications

ISSN 0270-952X

STATE OF OREGON OPEN-FILE REPORT 03-02 DEPARTMENT OF GEOLOGY AND MINERAL INDUSTRIES Map of Selected Earthquakes for Oregon, VICKI S. McCONNELL, ACTING STATE GEOLOGIST Map of Selected Earthquakes for Oregon, 1841 through 2002 1841 through 2002 By Clark A. Niewendorp and Mark E. Neuhaus American Red Cross DOGAMI earthquake hazard maps (IMS series) Map of selected 2003 Astoria

WASHINGTON IDAHO

COLUMBIA 46° CLATSOP

Saint Helens

Pendleton Hood River WASHINGTON WALLOWA The Dalles UMATILLA TILLAMOOK Portland Hillsboro MULTNOMAH Moro HOOD GILLIAM Enterprise Tillamook RIVER Oregon City Heppner La Grande YAMHILL SHERMAN MORROW UNION McMinnville CLACKAMAS Condon WASCO

Fossil 45° http://www.redcross.org/ Dallas Salem MARION POLK WHEELER online earthquakes for Oregon, Baker Newport Albany BAKER JEFFERSON Madras LINCOLN Corvallis GRANT LINN

BENTON Canyon City

Prineville

CROOK

Eugene Bend

Vale 44°

LANE

DESCHUTES http://www.oregongeology.org/sub/publications/IMS/ Burns

Magnitude 7 and higher HARNEY Coquille Roseburg 1841-2002 (Open-File Magnitude 6.0 - 6.9 COOS DOUGLAS Magnitude 5.0 - 5.9 MALHEUR Magnitude 4.0 - 4.9 LAKE Magnitude 3.0 - 3.9

Magnitude 1.0 - 2.9 KLAMATH Magnitude 0.0 - 0.9

Fault - Holocene JACKSON Federal Emergency Management Agency (FEMA) CURRY Fault - Late quaternary Grants Pass Gold Beach State line

Medford JOSEPHINE County line

Klamath Falls County seat Lakeview

IDAHO 42° ims.htm NEVADA

Report 03-02), by C. A. CALIFORNIA NEVADA http://www.fema.gov/ 126° 125° 124° 123° 122° 121° 120° 119° 118° 117° 116° WHAT DOES THE MAP SHOW? faults are defined as those that moved in the last 780,000 years. Faults active in the last 1993, Scotts Mills (near Silverton and Woodburn in Marion County, Oregon) earthquake Dougherty, M.L., and Trehu, A.M., 2002, Neogene deformation of the Mt. Angel/Gales Creek Fault Zone: 20,000 years are color-coded red. Faults that moved between 20,000 and 780,000 years are with an epicenter near Mount Angel, in Marion County, Oregon, may be associated with this Constraints from high-resolution seismic reflection imaging: USGS Earthquake Hazards Reduction Program fault zone (Madin and others, 1993). Other active faults in the Willamette Valley, no less sig- Annual Summaries of Technical Reports, Vol. 37. This map shows over 14,000 known earthquakes from 1841 to 2002. The Table to the right is color-coded blue. A less-than-straightforward connection between earthquakes and active Geomatrix Consultants, Inc., 1995, Final Report, Seismic Design Mapping, State of Oregon: January, ODOT a summary of major quakes that have affected Oregon, causing ground shaking and damage faults exist in Oregon. The uncertainties in earthquake locations can be large and not all nificant, can produce future earthquakes as well. Project No. 2442, 5 sections, 4 appendices, 5 plates. (Wang and Clark, 1999). It shows that Oregonians face injury and property damage from faults are known. Often this uncertainty makes it difficult to associate an earthquake with a earthquakes originating throughout the Pacific Northwest. For this reason, the Oregon De- particular fault. South-Central Oregon Goldfinger, C., McCaffrey, R., Murray, M., Zwick, P., Nabelek, J., Smith, C.L., and Johnson, C., 1999, GPS partment of Geology and Mineral Resources produced this map of the epicenters of historic The dense cluster of earthquakes in south-central Oregon is associated with the September constraints on plate coupling in central western Oregon [abs.]: Seismological Research Letters, v. 70, p. 244-245. earthquakes in Oregon, off the coast, and along Oregon's border with southern Washington Seismicity Patterns 20, 1993, earthquakes of 5.9 and 6.0 magnitude (Wiley and others, 1993). Aftershocks as large and northern California. Historic patterns show areas in Oregon that are especially vulnera- We can make some general observations regarding the seismicity patterns shown on this as magnitude 5.1 continued to disturb residents for six months (Sherrod and others, 1997). Johnson, A.G., Scofield, D.H., Madin, I.P., 1994, Earthquake database for Oregon, 1833 through October 25, 1993: ble to earthquakes. map. Overall, earthquakes in Oregon are associated with four zones of seismicity: the Cas- Epicenters for these earthquakes are near north- to northwest-trending faults about 19 miles Oregon Department of Geology and Mineral Industries Open-File Report O-94-4, 1 diskette. cade seismic zone, Portland Hills (Portland-Vancouver metropolitan area), south-central northwest of Klamath Falls. Quakes in this area are related to the northernmost part of the The earthquake dataset for this map was compiled from two sources: the Oregon Depart- (Klamath Falls), and northeastern Oregon. Basin and Range geologic province, a vast area extending from south-central Oregon to Ari- Madin, I.P., Priest, G.P., Mabey, M.A., Malone, S., Yelin, T.S., and Meier, D., 1993, March 25, 1993, Scotts Mills earthquake--western Oregon's wake-up call: Oregon Department of Geology and Mineral Industries, Oregon ment of Geology and Mineral Resources' Earthquake Database for Oregon (Johnson and zona and encompassing most of Nevada. The Basin and Range in south-central Oregon is Geology, Vol. 55, no. 3, May 1993. others, 1994) and data from the Pacific Northwest Seismograph Network (PNSN) at the Uni- Cascade stretching in an east-west direction causing the crust to break into blocks along steeply dip- versity of Washington Geophysics Department. You can view and retrieve earthquake data The earthquakes in the Cascade seismic zone are part of the Cascade Range of Washington, ping faults (Wong and Bott, 1995; Wells and others, 1998). Earthquakes such as those near Shedlock, K.M., and Weaver, C.S., 1991, Program for earthquake hazards assessment in the Pacific Northwest: in PNSN's earthquake catalog from the following website: Oregon, and California, an active volcanic mountain chain where magma ascends into the Klamath Falls and the earthquake swarm near the town of Adel (magnitude 5.1) to the east of U.S. Geological Survey Circular 1067, 29 pgs. crust because of the underlying subduction processes. The portion of the Cascade seismic Lakeview were probably triggered as the crust broke along existing faults. Sherrod, D.R., Mastin, L.G., Scott, W.E., and Schilling, S.P., 1997, Volcano Hazards at Newberry Volcano, http://www.geophys.washington.edu/SEIS/PNSN/CATDAT/welcome.html. zone in southwestern Washington contains the earthquake (magnitude 5.1) triggering the Oregon: USGS Open-File Report 97-513. major lateral blast that ripped away the northern side of the Mount St. Helens volcano. The Northeastern Oregon Johnson and others' (1994) dataset covered the area shown on this map. However, PNSN's blast probably happened 20 to 30 seconds after the earthquake began. Approximately 440 In northeastern Oregon, several diffuse areas of seismicity fall on the Oregon-Washington Wang, Y., and Clark, J.L., 1999, Earthquake damage in Oregon: Preliminary estimates of future earthquakes current earthquake catalog contains records for earthquakes located between -125° and -117° earthquakes were associated with the 1980 eruption of Mount St. Helens. border. The area near Milton-Freewater was the site of the 1936 magnitude 6.4 earthquake. losses: Oregon Department of Oregon and Mineral Industries Special Paper 29, p. 13. longitude and 42° and 49° latitude. Earthquakes outside PNSN's coverage are recorders old- This earthquake and the scattered seismicity in the region are related to the Olympic-Wallo- Wells, R.E., Weaver, C.S., and Blakely, R.J., 1998, Fore-arc migration in Cascadia and its neotectonic significance: er than October of 1993. A remaining task in preparing a comprehensive earthquake map for In a typical year, one to several, short-lived swarms of small earthquakes are recorded on wa lineament. The lineament is a broad zone of northwest-trending faults and intervening Geology, 26, p. 759-762. Oregon is to incorporate data from other earthquake catalogs, particularly those that cover the south flake and below the summit of Mount Hood volcano in Oregon. These swarms basins and uplifts stretching from the Olympic Mountains of western Washington across the Niewendorp and M. E. Cascades and Columbia Basin into the northeast side of the Wallowa Mountains in northeast- Wiley, T.J., Sherrod, D.R., Keefer, D.K., Qamar, A., Schuster, R.L., Dewey, J.W., Mabey, M.A., Black, G.L., and extreme eastern and southeastern Oregon. Also, the magnitudes of some earthquakes before probably represents a reaction to regional tectonic stresses, not pre-eruption volcanic 1962, roughly 250 events, were determined using intensity data (Jacobson, 1986). Data of this activity. ern Oregon. Wells, R.E., 1993, Klamath Falls earthquakes, September 20, 1993--including the strongest quake ever kind are not always precisely accurate. The data reflects poorly determined locations or measured in Oregon: Oregon Department of Geology and Mineral Industries, Oregon Geology, Vol. 55, no. 6, p. 127-136. magnitudes, and are often incomplete. Portland Hills REFERENCES A scattered, northwest-trending cluster of earthquakes, called the Portland Hills seismicity Wong, I.G., and Bott, J.D.J, 1995, A look back at Oregon's earthquake history, 1841-1994: Oregon Department of Earthquake epicenters are displayed on this map as diamonds and circles. These symbols zone, lies in the Portland-Vancouver metropolitan area (Blakely and others, 1995). Notable Atwater, B.F., Nelson, A.R., Clague, J.J., Carver, G.A., Yamaguchi, D.K., Bobrowsky, P.T., Bourgeois, J., Geology and Mineral Industries, Oregon Geology, Vol. 57, no. 6, p. 125-139. are plotted at different sizes so as to provide a scale. Filled diamonds correspond to an earthquakes in this zone included the 4.7 magnitude earthquake on November 7, 1961 and Darienzo, M.E., Grant, W.C., Hemphill-Haley, E., Kelsey, H.M. Jacoby, G.C., Nishenko, S.P., Palmer, S.P., Peterson, C.D., and Reinhart, M.A., 1995, Summary of coastal geologic evidence for past great earthquakes at Wong, I.G., 2002, Intraplate earthquake potential in the Cascadia Subduction Zone beneath western Oregon earthquake with a magnitude between 0 and 0.9. Open diamonds represent earthquakes the November 5, 1962, earthquake of 5.5 magnitude. The Portland Hills seismicity zone is in the Cascadia subduction zone: Earthquake Spectra, Vol. 11, no. 1, p. 1-18. [abs]: Geological Society of America Abstract with Programs. with magnitudes between 0.9 and 3.9. The colored circles represent larger magnitude earth- a portion of northwestern Oregon sheared into a series of juxataposed blocks moving in dif- quakes, those over 3.9. A legend explaining these symbols is shown in the lower right mar- ferent directions. Atwater, B.F., and Hemphill-Halley, E., 1997, Recurrence intervals for great earthquakes of the past 3,500 years at northeastern Willapa Bay: U.S. Geological Survey Professional Paper, 108. gin of the map. Historical Earthquakes affecting Oregon Movement of the blocks induces earthquakes along northwest- and northeast-trending fault Geologic hazards, earthquake and landslide haz- Blakely, R.J., Wells, R.E., Yelin, T.S., Madin, I.P., and Beeson, M.H., 1995, Tectonic setting of the Date Location Magnitude Comments The blackened areas on the map are the concentration of many symbols. This clustering is a zones. Two have particular significance: the north northwest-trending Portland Hills and Portland-Vancouver area, Oregon and Washington: Constraints from low-altitude aeromagnetic data: Approximate years Offshore, Cascadia Probably Researchers Brian Atwater and result of earthquake activity that occurs in swarms. The largest earthquake in a swarm is the the Mount Angel-Gales Creek fault zones. The Portland Hills fault can be traced through Geological Society of America, Vol. 107, no. 9, p. 1051-1062. 1400 BCE subduction zone1 8-9 Eileen Hemphill-Haley have dated mainshock, sometimes preceded by foreshocks, and almost always followed by aftershocks. downtown Portland and the fault may be a reason for the unusually steep scarp of Port- 1050 BCE earthquakes and tsunamis at Willapa Also, within one cluster, there could be many earthquake swarms. land's West Hills. To the west, the Mount Angel-Gales Creek fault zone is a single, potential- Brantley and Topinka, 1984, Volcanic Studies at the U. S. Geological Survey's David A. Johnston Cascades 600 BCE Bay, Washington; these are the Volcano Observatory, Vancouver, Washington: Earthquake Information Bulletin, Vol.16, no. 2, March-April 400, 750, 900 midpoints of the age range for these ly active fault system that has been mapped from the Cascades into the Willamette Valley 1984. six events.

Geologically active faults are shown on this map (Geomatrix Consultants, 1995). Active through to the Coast Range (Dougherty and Trehu, 2002). The 5.6 magnitude March 25, January 26, 1700 Offshore, Cascadia Approx- Generated a tsunami that struck

subduction zone1 imately 9 Oregon, Washington and Japan; destroyed Native American villages along the coast.

November 23, Oregon/Califormia 6.8 Felt as far away as Portland and San 1873 border, near Francisco; may have been an Brookings intraplate event because of lack of aftershocks. NOAA West Coast and Alaska Tsunami Warning July 15, 1936 Milton-Freewater 6.4 Two foreshocks and many aftershocks felt; $100,000 damage (in 1936 dollars). EARTHQUAKE TERMS ground shaking can accompany a magnitude 5 or 6 event, and major damage com- SOURCE OF EARTHQUAKES to creep and undoubtedly western Oregon will again experience the affects of a April 13, 1949 Olympia, 7.1 Eight deaths and $25 million damage monly occurs from earthquakes of magnitude 7 and greater. The Richter scale has subduction-zone earthquake (Shedlock and Weaver, 1991). Washington1 (in 1949 dollars); cracked plaster, An earthquake is defined as the "perceptible trembling to violent shaking of the no upper limit. Recently, another scale called the moment magnitude scale has been other minor damage in northwest Three sources cause earthquakes in Oregon (Mabey and others, 1993). First, shal- Oregon. ground, produced by the sudden displacement of rocks below the Earth's surface." devised for more precise study of seismic activity. Moment magnitude is generally low earthquakes (depths of 0-10 miles) occur on active faults in the crust. Second, The earthquakes shown on the above map were triggered within the Earth's crust November 5, Portland/Vancouver 5.5 Shaking lasted up to 30 seconds; Rocks respond to stress (being squeezed or pulled apart) near the Earth's surface by used now to describe earthquakes, but the categories are about the same. deeper earthquakes (depths of 10-31 miles) are associated with the subducting Juan at depths less than 25 miles (Jacobson, 1986). The largest of these earthquakes breaking. Where the rocks break and move, we call it a fault. The buildup of tecton- 1962 chimneys cracked, windows broke, de Fuca plate. Third, deep earthquakes (depths of 31-62 miles) happen where the struck the coastline of Oregon and California near Brookings, Oregon, on Novem- furniture moved. ic forces and release of stress on individual faults is what causes quakes. Higher Earthquake intensity is not the same as Richter's earthquake magnitude. They are continental crust and ocean floor plates are locked against each other and periodi- ber 23, 1873, with an estimated 6.8 magnitude. Wong (2002) suspects that this stresses lead to larger earthquakes. frequently confused in media reports. Earthquake intensity describes the strength cally snap loose. earthquake could be an exception and the quake was deeper within the descending 1968 Adel 5.1 Swarm lasted May through July, Neuhaus, 2003. of shaking at a particular place, based on observations made of building damage. Juan de Fuca plate. decreasing in intensity; increased flow at a hot spring was reported. The earthquake's epicenter is the position on the Earth's surface directly above the The intensity of an earthquake is expressed today as the Modified Mercalli Scale, The Juan de Fuca plate is a slab of ocean floor moving eastward from the Juan de focus of the earthquake. The focus is the location within the Earth where under- devised in 1902 by Giuseppe Mercalli. The scale provides a series of idealized de- Fuca Ridge, which is about 300 miles off the coastline of Oregon and Washington. April 12, 1976 Near Maupin 4.8 Sounds described as distant thunder, ground rock moves and sends out earthquake energy waves. We feel these waves scriptions of the effects of an earthquake. Intensity 1 is imperceptible shaking. In- The term Cascadia subduction zone was given to the part of the plate that has de- sonic booms, and strong wind. as ground shaking. Earthquakes produce three main types of energy waves: P- tensity increases by steps to 10, which is total destruction. The intensity scale re- scended beneath the westbound continental crust of western Oregon. Earthquakes waves (push-pull waves), S-waves (side-to-side waves), and L-waves (surface quires no instrumentation because any observer can make a classification. It April 25, 1992 Cape Mendocino, 7.0 Subduction earthquake at the triple- can be very large in the subduction zone and often produce damaging tsunamis. 1 waves). Each radiates from the earthquake focus through the Earth at different provides a basis to estimate the size of historic earthquakes. Also, it is useful be- California junction of the Cascadia subduction The last great Cascadia subduction zone earthquake happened off the coast of Ore- zone and the San Andreas and rates. The distribution of earthquakes over time is known as seismicity. cause an earthquake has only a single magnitude, but different intensities can be gon and Washington in 1700, with an estimated magnitude of 9.0. Geological evi- Mendocino faults. distributed throughout the affected area. dence indicates that huge subduction zone earthquakes have struck Oregon's coast March 25, 1993 Scotts Mill 5.6 On Mount Ange l-Gales Creek fault; The energy released from the earthquake is a basic quantity scientists have meas- every 300-800 years, with a record that extends back at least 11,000 years (Atwater ured for more than fifty years. This energy release, or magnitude, is measured on $30 million damage, including and others, 1995; Atwater and Hemphill-Haley, 1997; Goldfinger, 1999). These Molalla High School and Mount the familiar Richter scale, invented by Charles F. Richter in 1934. Scientists calculate earthquakes are not evenly spaced in time, and the calculated average intervals be- Angel church. the magnitude of the earthquake from the largest seismic wave or vibration, and a tween events can be less or more. The Cascadia subduction zone is still continuing seismograph records the vibrations (seismogram) that an earthquake makes. Earth- September 20, Klamath Falls 5.9 and 6.0 Two deaths, $10 million damage, quakes with a magnitude of about 2 or less are usually called microquakes. They 1993 including county courthouse; ard maps, and future earthquake damage esti- are not usually felt and are generally recorded only on local seismographs. Magni- rockfalls induced by ground motion. tude 3 and 4 earthquakes are commonly felt, but rarely cause damage. Damaging February 28, Near Olympia 6.8 About 400 injuries, $2 to 3.9 billion 1 2001 Washington damage in the Seattle/Tacoma area. Felt area: Vancouver BC, Northwest Oregon, Salt Lake City UT.

1 not shown on the map

The Nature of the Northwest Information Center is map 800 NE Oregon Street #5 This m: le fro Portland, OR 97232 vailab a 503/872-2750 www.naturenw.org and the Baker City (541-523-3133) and Grants Pass (541-476-2496), Field Offices of the Oregon Center http://www.oregongeology. Department of Geology and Mineral Industries http://wcatwc.arh.noaa.gov/ mates for six org/sub/earthquakes/images/ counties in the EpicenterMap.pdf Are You Ready? An In-depth Guide to Citizen Mid/Southern Preparedness by FEMA Willamette Earthquake damage in Oregon: Preliminary http://www.fema.gov/areyouready/ Valley includ- estimates of future earthquake losses, (Special Quake Safe Schools (Oregon Department of ing Yamhill, Marion, Polk, Benton, Linn, and Lane Paper 29), by Y. Wang, and J. L. Clark, 1999, 59 p. Education) Counties, and the City of Albany, Oregon (Interpre- Tsunami hazard zone and evacuation maps online http://www.ode.state.or.us/go/quakesafeschools/ tive Map 24), by W. J. Burns, R. J. Hofmeister, and Y. Wang, http://www.oregongeology.org/sub/earthquakes/Coastal/ 2008, 121 p., map scale 1:422,400. FEMA 395, Incremental Seismic Rehabilitation of Tsumaps.HTM School Buildings (K-12) Oregon Public Utilities Commission--Oregon Tsunami hazard assessment of the northern http://www.fema.gov/library/viewRecord.do?id=1980 Department of Geology and Mineral Industries Oregon coast: A multi-deterministic approach Oregon Emergency Management (OEM) Seismic Leadership Forum and Seismic Critical Energy tested at Cannon Beach, Clatsop County, Oregon Rehabilitation Grant Program Infrastructures Workshop, April 2, 2008 (Open-File (Special Paper 41), by G. R. Priest, C. Goldfinger, K. http://www.oregon.gov/OMD/OEM/plans_train/SRGP. Report 08-10), by Y. Wang and J. R. Gonzalez, 2008, 13 p. Wang, R. C. Witter, Y. Zhang, and A. M. Baptista, 2009, 87 shtml p. plus app., GIS data files, time histories, and animations. Statewide seismic needs assessment: Oregon Building Codes Division Implementation of Oregon 2005 Senate Bill Tsunami Evacuation Building Workshop, http://www.cbs.state.or.us/bcd/ 2 relating to public safety, earthquakes, and September 28-29, 2009, Cannon Beach, Seaside, seismic rehabilitation of public buildings (Open- and Portland, Oregon (Open-File Report 10-02), Y. Earthquake Science File Report 07-02), by D. Lewis, 2007, 140 p. plus app. Wang, complier, 2010, 35 p. Pacific Northwest Seismic Network (PNSN) http://www.oregongeology.org/sub/projects/rvs/default. Prehistoric Cascadia tsunami inundation and http://www.pnsn.org/ htm runup at Cannon Beach, Clatsop County, Oregon U.S. Geological Survey Oregon Earthquake Enhanced rapid visual screening (E-RVS) for (Open-File Report 08-12), by R. C. Witter, 2008, 36 p. and Information prioritization of seismic retrofits in Oregon, 3 app. http://earthquake.usgs.gov/earthquakes/ (Special Paper 39), by Y. Wang and K. A. Goettel, 2007, states/?region=Oregon 27 p. Oregon Geology Fact Sheet Tsunami Hazards in Oregon

What is a tsunami? A tsunami is a series of ocean waves most often generated by disturbances of the sea floor during shallow, undersea earthquakes. Less commonly, landslides and volcanic eruptions can trigger a tsunami. In the deep water of the open ocean, tsunami Fact Sheet: Tsunami hazards waves can travel at speeds up to 800 km (500 miles) per hour and are imperceptible to ships because the wave height is typically less than a few feet. As a tsunami approaches the coast it slows dramatically, but its height may multiply by a factor of 10 or more and have cata- strophic consequences to people living at the coast. As a result, The December 26, 2004, Indian Ocean tsunami strikes Khao Lak, Thailand. A wall of water people on the beach, in low-lying areas of the coast, and near dwarfs a tourist and boats on the beach. (Photo source: John Jackie Knill – family photo/AP) National Earthquake Hazards Reduction Program bay mouths or tidal flats face the greatest danger from tsunamis. A tsunami can be triggered by earthquakes around the Pacific Ocean including undersea earthquakes with epicenters located Portland State University Ondine Residence Hall only tens of miles offshore the Oregon coast. Over the last century, wave heights of tsunamis in the Pacific Ocean have reached up to 13.5 m (45 ft) above the shoreline near the earthquake in Oregon, 2008, 4 p. source. In a few rare cases, local conditions amplified the height of a tsunami to over 30 m (100 ft). What is the difference between a Cascadia (local) tsunami and a distant tsunami? An earthquake on the Cascadia Subduction Zone, a 960-km- long (600 mile) earthquake fault zone that sits off the Pacific (NEHRP) Northwest coast, can create a Cascadia tsunami that will reach the Oregon coast within 15 to 20 minutes. Massive earthquakes of magnitude 9 or greater that can last for several minutes have seismic rehabilitation demonstration project been generated on the fault zone. A destructive tsunami can fol- http://www.oregongeology.org/pubs/ low moments later. A distant tsunami produced by an earthquake far from Or- egon will take 4 or more hours to travel cross the Pacific Ocean, Destruction at Seaside, Oregon, due to the March 28, 1964, Alaska tsunami. Water lifted the usually allowing time for an official warning and evacuation, if car against the house, uprooted the tree, and washed in driftwood logs. Beach grass hanging necessary. A distant tsunami will be smaller in size and much in the tree branches indicates the maximum water depth at this location was 3.5 m (12 ft). less destructive, but it can still be very dangerous. This house was 1200 m (4000 ft) from the shore. (Photo source: Herb Schlappi) http://www.nehrp.gov/ (Special Paper 38), by Y. Wang and C. J. Heathman, 2007, Tsunami Generation fs/tsunami-factsheet_onscreen.pdf

Vertical Slice Through a Subduction Zone Between Earthq uakes During an Earthq uake Minutes Later One of the many tectonic plates that make up Stuck to the subd ucti ng plate, the overriding An earthquake along a subduction zone happ ens Part of the tsunami races toward nearby land, Earth’s outer shell descends, or “subducts,” under plate gets squeezed. Its leading edge is dragged when the leading edge of the overriding plate growing taller as it comes in to shore. Ano the r an adjacent plate. This kind of boundary between down, while an area behind bulges upward. This breaks free and springs seaward, raisi ng the sea part heads across the ocean toward distant plates is called a “subduction zone.” When the movement goes on for decades or cent ur ies, oor and the water above it. This uplift starts a shores. plates move suddenly in an area where they are slowly building up stress. tsunami. Meanwhile, the bulge behind the leading usually stuck, an earthquake happens. edge collapses, thinning the plate and lowering coastal areas.

G E O L O G Y F A N O D (Source: U.S. Geological Survey Circular 1187) T N M I E N M E T R

R A A L

I E

R E S Oregon Department of Geology and Mineral Industries 800 NE Oregon St., Suite 965 Portland, OR 97232 971-673-1555 www.OregonGeology.org O 23 p. LAST UPDATED 04-03-2009 PRINTED ON RECYCLED PAPER 1937 Earthquake Organizations Portland State University Montgomery Court Oregon Seismic Safety Policy Advisory seismic rehabilitation project (Open-File Report 07- Fact Sheet: TsunamiReady, Commission (OSSPAC) 04), by Y. Wang, and C. J. Heathman, 2007, 16 p. TsunamiPrepared: Oregon http://www.oregon.gov/OMD/OEM/osspac/osspac.shtml Coast-Wide National Tsunami Cascadia Subduction Zone earthquakes: A Western States Seismic Policy Council (WSSPC) Hazard Mitigation Program, magnitude 9.0 earthquake scenario (Open- http://www.wsspc.org/ 2010, 2 p. File Report 05-05), by Cascadia Region Earthquake http://www.oregongeology.org/pubs/fs/ Oregon Partnership for Disaster Resilience Workgroup, J. Roddey, and L. Clark, 2005, 21 p. TsunamiPreparedFactSheetAlt-12-28-09.pdf http://opdr.uoregon.edu/ http://www.crew.org/PDFs/CREWSubductionZoneSmall. pdf Cascadia Region Earthquake Workgroup (CREW) http://www.crew.org/index.html

10 CASCADIA Winter 2010 www.OregonGeology.org Oregon Department of Geology and Mineral Industries

Publications available now from

The Orphan Tsunami of 1700—Japanese Clues to a Parent Earthquake in North America, U.S. Geological Survey Professional Paper 1707, by Brian Atwater and others, 2005, 144 p., 325 illus, paperback, $24.95. Nature of the Northwest Information Center Suite 965, 800 NE Oregon Street Tells the scientific detective story of the tsunami through Portland, OR 97232-2162 clues from both sides of the Pacific. Also available as a phone (971) 673-2331, fax (971) 673-1562 PDF file: http://pubs.usgs.gov/pp/pp1707/pp1707.pdf

Volcanoes and Earthquakes, by Ken Rubin, Preparedness Now! An Emergency Simon and Schuster, New York, Survival Guide, revised ed., by 2007, 64 p., $16.95. Aton Edwards, Process Media, Self- Reliance Series, Port Townsend, Brings volcanoes and earthquakes to life, Wash., 2009, 343 p., $16.95. with the most up-to-date information and state-of-the-art 3-D illustrations that Guide for those who want to live more practically leap off every page, stimulating self-sufficiently and learn how to minds and imaginations in a whole new way. prepare for emergencies and disasters.

Living With Earthquakes in the Oregon’s Greatest Natural Pacific Northwest: A Survivor’s Disasters, by William L. Sullivan, Guide, 2nd ed., by Robert S. Navillus Press, Eugene, Oregon, Yeats, Oregon State University 2008, 263 p., $18.95. Press, Corvallis, 2004, 390 p., The cycles behind the state’s historic $22.95. earthquakes, tsunamis, eruptions, Describes the threat posed by the floods, and fires — and how they Cascadia Subduction Zone fault. are changing.

A complete list of DOGAMI publications can be found online at www.OregonGeology.org. Use the order form below or log on to www.NatureNW.org to order.

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CASCADIA Winter 2010 11 Oregon Department of Geology and Mineral Industries www.OregonGeology.org Places to see: University building seismic mitigation

Cross-bracing (far left) and, steel plate wall floor-to-floor connections (left) are some visible results of the PSU Ondine residence hall seismic mitigation effort. Portland area places to see: Ondine Residence Hall, PSU; TriMet Washington Park/Zoo station

Oregon is at risk for a major earthquake. In duct similar seismic retrofit projects. other university buildings have serious addition to the Cascadia Subduction Zone As part of a long-term, 7-campus-wide, seismic deficiencies and are slated to be threat, many communities have active seismic mitigation plan, DOGAMI devel- seismically strengthened via the long-term crustal faults nearby. One major success of oped a 6-step method for evaluating build- comprehensive mitigation plan. The plan is the 2001 laws to better prepare and protect ings for seismic risk. Out of about 1,000 driven by the seismic life-safety risk index Oregonians from future earthquake losses buildings evaluated using this method, coupled with deferred maintenance needs (see p. 5) is requiring life-safety in public the Oregon University System (OUS) and and energy efficiency improvements. university buildings. DOGAMI identified five demonstration Related DOGAMI publications: SP-39, Enhanced The state’s goal is to increase aware- projects as part of the initial Seismic Risk rapid visual screening (E-RVS) for prioritization of ness and promote preparedness through Management Program, which began in seismic retrofits in Oregon; SP-38, Portland State demonstration projects such as the one at 2005: Montgomery Court and Ondine Resi- University Ondine Residence Hall seismic reha- Ondine Hall, Portland State University (PSU). dence Hall, Portland State University; Snell bilitation demonstration project; O-07-04, Port- Demonstration projects create momentum Hall Administration Building, Oregon Insti- land State University Montgomery Court seismic in earthquake preparedness throughout tute of Technology; Humanities and Social rehabilitation project. the state by providing an impetus for in- Sciences, Western Oregon University; and dividual owners and communities to con- Nash Hall, Oregon State University. Many

Places to see: Geologic time line at Portland TriMet station

Portland’s TriMet Washington Park/Zoo light-rail (MAX) station (Red/Blue lines) is the deepest tunnel station in North Ameri- ca at 260 feet. The public art on the station platform includes a geologic time line and drill core from one of the many geotechnical borings made along the tunnel route. This is the most accessible and complete “exposure” of Portland geology in exis- tence. Visitors can walk along the core as it traverses Columbia River Basalt, Boring Lava, and loess. To learn more about Portland’s geology, including faults, see the field trip guide “Portland, Oregon, geology by tram, train, and foot” by Ian P. Madin (http://www. oregongeology.org/pubs/og/OGv69n01- PDXtram.pdf).

12 CASCADIA Winter 2010 Learn more about Oregon’s geology at www.OregonGeology.org.