Preparing for 'the big one'

Thursday, April 4, 2002 • Vol 8, Issue 7

---

Taking steps at work and home can reduce damage

By RON CLARK

Scarcely over a year ago, February 28, 2001 at 10:54:32 in the morning, an earthquake shook the Puget Sound Region. The quake, which measured 6.8 magnitude on the Richter Scale, was centered 30 miles deep beneath the Nisqually River Delta, approximately 36 miles southwest of Seattle. We can probably all recall where we were that exact moment and what we did. On all counts, the seismologists tell us, we were lucky. This was not the BIG ONE. Just another abrupt reminder we live in a very seismically active region. They say the BIG ONE is yet to come. To the people who study earthquakes in our region, it is not a question of IF, but WHEN the BIG ONE will occur.

Earthquake Anatomy 101

What is the nature of the hazard that Seattle faces? It is complex. Typically, each year over 1000 earthquakes with magnitude 1.0 or greater occur in Washington and Oregon. Of these, approximately two dozen are large enough to be felt. There have been about 25 damaging earthquakes since 1872. This century about 17 people lost their lives due to earthquakes in the Pacific Northwest.

Western Washington lies in the contact between two of the Earth's tectonic plates that are colliding. The Juan de Fuca plate, which forms the floor of the northeastern Pacific Ocean, moves northeastward with respect to the North American Plate at a rate of about 1.5 inches per year. As it collides with the North American Plate, the Juan de Fuca plates slides (or subducts) beneath the continent and sinks slowly into the earth's mantle. These ongoing geologic processes over the years has thrust up the beautiful Olympic and Cascade Mountain Ranges, and produced Mount Rainier, and Mount St. Helens. It also the source of the three different types of earthquakes our region experiences. All three are capable of producing the BIG ONE.

Cascadia Subduction Zone Earthquakes can occur anywhere along the 1,000km long thrust fault. It lies about 50 miles offshore and runs from British Columbia to northern California. No historic earthquakes have been recorded from this source zone, but the earthquakes generated prehistorically in this zone bare evidence of tremendous earthquakes producing magnitudes estimated to be in excess of 9.0.

The unlocking of the two plates can produce the largest type of earthquake. When the Cascadia fault ruptures it will likely cause severe ground motions along the coast, with shaking in excess of 1g. The Seattle area is likely to see 0.2 to 0.3g accelerations. Because of the very large fault area involved, slippage will produce strong motions that may last for two to four minutes. The frequency of occurrence is estimated to be every 500-600 years, with the last such earthquake occurring on January 26, 1700.

On January 26, 1700, the largest earthquake known to have occurred in the lower 48 United States rocked the region. The quake violently shook the ground for three to five minutes. It caused the entire Pacific Northwest ocean coastline to drop from three to six feet. The earthquake set off a tsunami up, to 33 feet in height that struck the Pacific Coast, and also crossed the Pacific Ocean to Japan, where it inundated the ocean coast. Written records of the damage in Japan pinpoint the earthquake to the evening of January 26, 1700.

Deep Zone Earthquakes are the most common in our region and occur as the Juan de Fuca plate subducts under North America. The plate becomes denser than the surrounding mantle rocks and breaks apart under its own weight. Beneath Puget Sound, the Juan de Fuca plate begins to bend even more steeply downward forming a "knee". It is at this knee that the largest deep zone earthquakes occur. These quakes occur between a depth of 3.5 to 70km. Since they are farther from the surface they are not felt as intensely, but are felt over a wider area. The 1949, 1965, and 2001 earthquakes occurred at the knee. The 1949 magnitude 7.1 Olympia earthquake was the largest recorded deep zone earthquake in Washington State. The rate of occurrence is two magnitude 7 events every 130 years and five events greater than magnitude 6.0 have occurred since 1909. Acceleration of 0.20-0.35g with strong shaking lasting 15-30 seconds can be expected. These type of earthquakes do not typically spawn aftershocks, though aftershocks were recorded following the February 2001 quake.

Shallow Or Crustal Quakes occur on the North American Plate as it adjusts to the build up of strain along the plate interface. Of the three source zones, this is the least understood. The depth of these quakes can vary from 0 to 30km. They are usually felt intensely near their epicenter, but their effects usually diminish quickly with distance. The largest shallow earthquake recorded in Washington State occurred in 1872 and was approximate magnitude 7.5. The largest expected is less than magnitude 8.0. The rate of occurrence of these types of quakes is uncertain. However, four known crustal quakes have occurred in the last 1,000 years. This type of earthquake is generally followed by many aftershocks that can be as large as magnitude 6.5+. The acceleration of this type of quake can be greater than 0.5g and their duration is likely to be 20-60 seconds.

There is a shallow fault system running from Bremerton through the middle of Seattle. Much of the region's infrastructure is concentrated in the Seattle fault zone. History has preserved evidence of past earthquakes along this fault that should give us pause. Imagine an earthquake that causes a tsunami in Puget Sound and landslides into Lake Washington; that lifts Alki Point up 22 feet and the western tip of Queen Anne sinks 7 feet. According to the geologists, this happened approximately 1,100 years ago.

Until recently, little was known about this fault or the potential impact it could have on Seattle. It was thought to be a spectacular yet quiet fault. In June 1997, a magnitude 4.9 quake occurred near Bainbridge Island that was determined to be associated with the Seattle Fault. A study known as SHIPS, Seismic Hazards in the Puget Sound, began in 1998, further identified the risk. Now researchers believe that most shallow earthquakes west of Lake Washington are likely related to the Seattle Fault. The fault is considered a lot more active and more dangerous than previously thought. Geophysical measurements show crustal contraction across the Seattle Fault, clear evidence that strain is slowly building toward the next earthquake.

Because the Seattle Fault is shallow and runs directly underneath a dense urban area, it has the potential to do great damage. Had the February 2001 magnitude 6.8 occurred on the Seattle Fault, there would have been a lot more damage, more like what happened to Kobe Japan. There would have been billions of dollars of damage - and many casualties. The 1995 Kobe, Japan and 1994 Northridge, California earthquakes, with ground motions of 0.5 to 1.0 g, may be good analogs for a crustal earthquake in the greater Seattle area.

Secondary Events

Large earthquakes will spawn additional hazards in their wake. Fires are the principal threat. Most of the 28,0000 buildings destroyed in the 1906 San Francisco earthquake were destroyed in the conflagration that followed. It is estimated that a city the size of Seattle will generate nearly 450 ignitions. These fires will severely strain emergency resources. It is estimated that 1,400 search and rescue personnel will be required to search the more than 140 buildings likely to catastrophically collapse.

Most of Seattle's housing should perform relatively well in an earthquake. Although 51% of the housing units were built prior to the introduction of modern seismic codes in 1949, many of them (and nearly all of the single-family homes) are wood-frame, a type that performs well in earthquakes. Areas with large concentrations of older, multi-family structures may be more vulnerable because taller buildings experience more lateral force during an earthquake and more people occupy them. The most vulnerable structures are those constructed with unreinforced masonry. There are over 500 of these structures, mainly in the older cores of the city: Downtown, Ballard, Capital Hill, Columbia City, and the University District. Another vulnerable types of construction include concrete frame structures with masonry infill, and tilt-up structures. Most of these buildings are commercial and older multi-family dwellings.

One of Seattle's major vulnerabilities is its dependence upon bridges. Breaks in the street and bridge network would impair the delivery of emergency services. Most of the city's medical facilities are on First Hill and Capital Hill. These facilities would be difficult to reach if a major bridge or section of highway collapsed.

Landslides are likely in areas prone to unstable hillsides. Hazardous material spills are likely as tanks, pipes, and other containers rupture.

Some areas of new, loose deposits, e.g., Duwamish Valley, Interbay, Rainier Valley, will be subject to liquefaction, magnifying ground movement and the potential for damage.

Tsunamis are less likely, but could be highly dangerous. Generally, it is thought that a quake needs to have a magnitude of 6.5 to 7.5 to produce a dangerous tsunami or seiche, an enclosed body of water produced tsunami. Current theory holds that either a large subduction zone quake off the Washington Coast or one along the Seattle Fault could produce a tsunami. They occur with little warning, crush buildings, and flood shoreline areas. Seattle never considered itself at possible risk for tsunami, but the discovery of tsunami deposited sand on Bainbridge Island indicates it can happen here. A eight-foot seiche occurred on Lake Washington following an earthquake near Port Angeles. Both Lake Washington and Lake Union experienced seiches during a 1949 earthquake. The 1964 Alaskan earthquake also produced a seiche that damaged boats by battering them against docks and moorings on Lake Washington and Lake Union.

Prediction or Preparation

Many precursors to earthquakes have been studied in the hope that they will predict the size, location, and time of an earthquake, all of which must be accurately predicted simultaneously to be useful in preparing for and responding to earthquakes. Some of the precursors studied are small magnitude earthquakes, water levels in wells, concentrations of radon and helium in ground water, changes in natural electromagnetic radiation, lunar phases, and animal behavior. Psychics and amateur scientists frequently claim to be able to predict earthquakes. However, as yet, none of the precursors or other prediction methods have been consistent. Consequently, in the United States, more effort is directed toward understanding earthquake sources, their effects, and preparation. than toward prediction.

Scientists and emergency planners are busy trying to inform and persuade the public to prepare. There is a lot that can be done. Not to prevent earthquakes, but to limit the death, injury, damage, and disruption earthquakes cause. Here are some things you can do to prepare:

At Home

Create A Family Disaster Plan

Where will your family be when a disaster strikes? How will you find each other? Will you know if your children are safe? Disaster strikes quickly and without warning. It can force you to evacuate your neighborhood or confine you to your home. While the buildings you occupy are likely to survive, the infrastructure that got you to work or to school may not do as well. What would you do if you could not get home right away? What if basic services, water, gas, electricity or telephones were cut off? Emergency agencies will be on the scene of a disaster, but they may not be able to reach everyone right away. The guidance fire departments and other emergency organizations are providing is to prepare to be self sufficient for at least 72 hours. Do you have a plan to survive for 72 hours?

How should your family cope with disaster? By preparing in advance and working together as a team.

• Find out about the disaster plans at work, your children's school or day care center and other places where your family spends time.
• Meet with your family and discuss why you need to prepare for disaster. Explain the dangers of fire, severe weather, and earthquakes to children. Plan to share responsibilities and work together as a team.
• Discuss the types of disasters that are most likely to happen. Explain what to do in each case.
• Pick two places to meet:
• Right outside your home in case of a sudden emergency, like a fire.
• Outside your neighborhood in case you can't return home. Everyone must know the address and phone number.
• Ask an out-of-state friend to be your "family contact". After a disaster it is often easier to call long distance. Other family members should call this person and tell them where they are. Everyone must know your contact's phone number.
• Discuss what to do in an evacuation.
• Post emergency telephone numbers by phones (fire, police, ambulance, etc). ? Teach children how and when to call 911 or your local emergency medical services number for emergency help.

Emergency Supplies

Keep enough supplies in your home to meet your needs for at least three days. Assemble a disaster supplies kit with items you may need in an evacuation. Store these supplies in sturdy, easy-to-carry containers such as back-packs, duffle bags, or covered trash containers. Include:

• A three-day supply of water (one gallon per person per day) and food that won't spoil.
• One change of clothes and foot-wear per person, and one blanket or sleeping bag per person.
• A first aid kit that includes your family's prescription medications.
• Emergency tools including a battery-powered radio, flashlight, and plenty of extra batteries.
• An extra set of car keys and a credit card, cash, or traveler's checks.
• Sanitation supplies
• Special items for infant, elderly or disabled family members.
• An extra pair of glasses.

Keep a smaller kit in the trunk of your car.

Conduct a Home Hazard Hunt

During an earthquake, ordinary objects in your home can cause injury or damage. Anything that can move, fall, break, or cause a fire is a home hazard, e.g., a hot water heater or bookshelf can fall. Inspect your home at least once a year and fix potential hazards.

Locate the main electric panel, water service main and natural gas main. Learn how and when to turn these utilities off. Teach all responsible family members. Keep necessary tools near gas and water main valves.

Turn off the utilities only if you suspect the lines are damaged or if you are instructed to do so. If you turn the gas main off, you will need a professional to turn it back on.

In Your Community

Working with neighbors can save lives and property. Meet with your neighbors to plan how the neighborhood could work together after a disaster until help arrives.

Do you live in the City of Seattle? Checkout SDART! One of the shining stars in the recent earthquake, SDART (Seattle Disaster Aid & Response Teams) is the City of Seattle's all-hazard personal and neighborhood preparedness program. Its primary goal is to help people prepare to be self-sufficient for the three days following a serious disaster, when 911 emergency responders - police, fire, and medical personnel - may not be available.

When a serious disaster hits, neighbors who are trained and organized to implement a coordinated response: save lives, reduce injuries and protect property. Ninety-two percent of SDART neighborhoods reported activating at least a minimal neighborhood response, and expressed gratitude in knowing what to do to minimize the consequences of the disaster to people and property.

SDART establishes seven Disaster Response Teams comprised of neighbors who can respond to basic needs following a major disaster:

• Communications - monitors emergency radio broadcasts, keeps the neighborhood informed of relevant information, and relays information to the City about the damage the neighborhood has sustained via amateur radio operators.
• Damage Assessment - assesses the damage the block has sustained, and assists neighbors with documenting damage.
• First Aid - establishes a neighborhood First Aid Station, and treats those who have been injured
• Safety & Security - provides safety to the neighborhood by turning off natural gas as necessary, roping off downed electrical lines, and clearing debris.
• Light Search & Rescue - performs simple searches of homes, and rescues neighbors who may be trapped.
• Sheltering & Special Needs - establishes a care center for children whose parents may not be home, and for anyone who may need extra care or comfort.
• Block Coordinators - coordinate the activities of the neighborhood Response Teams both before and during a disaster.

Each team has a simple task description that provides step-by-step directions for how to be an effective team member. With the exception of First Aid, no team requires extra training or advanced skills.

Just think how safe you would feel living in a neighborhood that practices SDART. E-mail Seattle Emergency Management at sem@ci.seattle.wa.us for more information.

At Work

State-of-the-art structural design and a thorough seismic program keep Hutch buildings steady and occupants safe.

Phase I - the Weintraub and Hutchinson buildings - was designed for life safety' for an earthquake with a size predicted to occur once every 500 years. Life safety means damage resulting from the 500-year event is moderate, life safety is protected, and while the structure may be damaged, it and any falling hazards remain stable.

Seattle's earthquake-risk rating was upgraded to a classification of 3 on a scale from 0 to 4, after the major 1949 quake centered near Olympia. Seattle code requires that buildings meet zone 3 seismic requirements, but the design of Phases II and III (the Thomas building and the Seattle Cancer Care Alliance) were upgraded to exceed the current code. Those buildings are designed to meet zone 4 requirements. Phase IV structures, including New Yale and Public Health Sciences Division buildings, also will be constructed to meet zone 4 requirements.

In addition to the building structure, all of the buildings' infrastructure systems have been braced to prevent damage. Pipe racks, pumps, chillers, boilers, emergency generators and electrical gear have been bolted to the floor or walls to prevent movement from seismic forces. In laboratories, casework has been designed with special seismic accommodations that include bracing and lips on shelves. Additionally, the Center has implemented a "non-structural" seismic program over the past five years. Equipment such as biosafety cabinets, freezers, incubators and other large equipment are braced to walls. Contact Facilities Engineering if you have a piece of equipment that needs to be secured.

• Check your work area for hazards that may fall on you and get these secured.
• Identify "Safety Spots" that can provide you with immediate cover.
• Maintain a three-day supply of essential medications.
• Maintain a list of emergency contact numbers.
• Each Department should prepare and organize. Maintain a supply of flashlights, batteries, portable battery operated radio and first aid kits.
• Following a major earthquake an Emergency Operations Center will be established to prioritize and coordinate recovery actions.

In an Earthquake remain calm and patient. Put your plan into action.

Indoors

• When you feel and earthquake, DROP and COVER under a desk or sturdy table. Stay away from windows, bookcases, file cabinets, heavy mirrors, hanging plants, and other objects that could fall. HOLD onto the desk or table. If it moves, move with it. DO NOT RUN! Stay where you are and, "DROP, COVER, and HOLD."
• If you do not have anything to take cover under, DROP against an inside wall and COVER your head and neck with your arms.

Outdoors

• If you are outdoors, move to a clear area away from trees, signs, buildings, or downed electrical wires and poles.

Downtown Area

• If you are on a sidewalk near a tall building, get into the building's doorway or into the building's lobby to protect yourself from falling bricks, glass, and other debris.

Crowded Store or Public Place

• DO NOT rush for the exits. Move away from display shelves holding objects that could fall on you and DROP, COVER, and HOLD.

Driving

• If you are driving, slowly pull over to the side of the road and stop. Avoid overpasses, power lines, and other hazards. Stay inside the vehicle until the shaking stops.

Theater or Stadium

• If you are in a theater or stadium, stay in your seat, protect your head with your arms or get under the seat if possible. Do not attempt to leave until the shaking stops.

After the Earthquake

• Check yourself and those around you for injuries.
• Evaluate your area for safety. Stay inside unless hazards are present.
• Be prepared for aftershocks
• Use the phone only to report a life threatening emergency
• If you smell gas or hear a hissing sound, open a window or leave the building. Shut off the main gas valve outside.
• Try to make contact with your out-of-area phone contact and continue to monitor your radio.

Earthquake Drill

Emergency management agencies throughout the state are working together to promote awareness and emergency preparedness. Urging all citizens to join him in this effort, Governor Gary Locke proclaimed April, 2002 as Washington State Disaster Preparedness Month. Activities include a statewide earthquake "DROP COVER and HOLD" drill will be conducted April 18th, between 9:45 A.M. and 10:00 A.M. to remind Washingtonians what to do when the ground starts shaking.

Fred Hutchinson Cancer Research Center and Seattle Cancer Care Alliance will be participating. When you hear the drill announcement, imagine that an earthquake is occurring. DROP under a sturdy desk or table; COVER your head; and HOLD on to the desk or table until the drill message is complete (about 30 seconds). We hope you participate and that the drill will act as a springboard to discuss other essential earthquake safety actions with family, friends, and coworkers.

Back to Table of Contents