Earthquakes cannot be eliminated. However, the injury, loss of life, and property damage associated with them can be reduced and recovery accelerated by making earthquake-loss reduction part of an on-going program, rather than a hasty response to disaster. An earthquake-loss-reduction program entails three basic elements: (1) understanding the nature and extent of the earthquake risk, (2) taking actions to reduce the risks, and (3) establishing policy to guide the development of effective risk-reduction programs. Gori (1984) presents a collection of papers that provide practical information on improving the level of earthquake hazard mitigation and preparedness. Scott (1979) describes the elements of a state seismic safety program and the state policies needed to carry it out. The U.S. Geological Survey, the Federal Emergency Management Agency, the Washington Department of Natural Resources, and the Washington Department of Community Development, Division of Emergency Management began a multi-year cooperative earthquake hazards reduction program in 1985 to investigate earthquake potential, hazards mitigation, and preparedness efforts in the Puget Sound area. Workshops to review the results of these studies will be held periodically and workshop proceedings published in U.S. Geological Survey open-file reports (for example, Hays and Gori, 1986). The program was enlarged to include the Portland, Oregon, area in 1987.
Understanding Earthquake Risk
Risk can be numerically defined as the probability of a hazardous event multiplied by the cost of damage that would result should the event happen. Using this definition, the level of risk may be very high for a low-probability event if the consequences of the event are considered to be very costly. For example, although many safeguards exist to assure safe operation of nuclear power plants and although the likelihood of a major accident at a U.S. nuclear power plant is generally considered to be low, the cost of an accident involving release of radioactivity could be extremely high. On the other hand, a magnitude 8 earthquake occurring in a remote, unpopulated area might be considered a low-risk event because the consequences would have an impact on few people. A similar event in an urban area would involve high levels of risk. Therefore, the level of effort required to reduce earthquake losses will vary depending upon the severity of the hazard, the number of people that would be affected, and the amount and kind of property exposed.
The nature and extent of the earthquake risk in Washington is determined by estimating the level of expected ground shaking, identifying the sites susceptible to ground failures and tsunamis, and by combining such hazards information with information concerning the distribution of population, type of building construction, and technological hazards in the state. The present level of development of information identifying these factors is summarized below.
Maps have been published depicting expected levels of ground shaking in the United States. Recent maps (Algermissen and Perkins, 1976; Algermissen and others, 1982) show ground accelerations and velocities expected to affect structures with lifetimes of 10, 50, and 250 years. Since these maps are based on past earthquake activity, they most accurately estimate the level of ground shaking from earthquakes similar to those already experienced, like the 1949 Olympia earthquake in Washington. A large shallow earthquake in the Puget Sound region, a large shallow earthquake in southwestem Washington, or a great subduction-style earthquake along the coast have not been considered in the development of existing maps that depict expected levels of ground shaking. Ground shaking maps may need to be revised as new information on potential earthquake sources is developed.
Only a few maps are available that show areas in Washington that are susceptible to ground failure. Tubbs (1974) mapped potential landslide sites in Seattle. The Washington Surveying and Rating Bureau (1966) published maps showing areas of fill or unstable ground in Seattle, Bellingham, Everett, and Tacoma. County soil maps exist for areas throughout the state. Rasmussen and others (1974) used soil maps of counties in the Puget Sound region and estimates of ground shaking in past earthquakes to develop a method that can be satisfactorily used to identify sites likely to show the greatest damage to structures in future earthquakes. Maps indicating areas vulnerable to earthquake-generated waves and tsunamis or seiches do not exist.
Sociological factors that should be considered in the determination of earthquake risk in Washington include the distribution of people, businesses and industries, financial institutions, hazardous waste transportation routes and permanent storage sites, and the location of critical facilities such as nuclear reactors. Most of the state's population is concentrated west of the Cascade mountains in the Puget Sound region. Major businesses and industries like the Boeing Company are also in this area. Besides having significant earthquake activity, the Puget Sound region has many sites susceptible to ground failures. The lower population of eastern Washington somewhat limits the earthquake risk in that area even though moderate levels of ground shaking are anticipated. One matter of concern, however, is the impact of an earthquake on the storage of hazardous wastes in eastern Washington.
One attempt to estimate earthquake losses by combining the types of information described above was carried out by the U.S. Geological Survey (1975). This study focused on the potential impact of a major earthquake on six counties in the Puget Sound area. The study describes potential effects of earthquakes on buildings and other structures and estimates the impact of earthquakes on the availability of essential services, traffic patterns, communications, and other factors. Studies such as this can be used in combination with geotechnical data to develop risk reduction programs. Since the U.S. Geological Survey study was completed in 1975, the population of the Puget Sound area has increased by 25 percent, to 2.6 million in 1986. Capital investment increased 290 percent from 1975 to 1984 when assessed property valuation in the Puget Sound area reached $93.3 billion (Washington Seismic Safety Council, 1986). Social and economic changes in Washington combined with recent geologic evidence suggesting the possibility of earthquakes having magnitudes greater than 8 along the coast change the nature and extent of earthquake risk in the state. The 1975 U.S. Geological Survey report will be updated to take these changes into account.
Risk Reduction
Earthquake damage can be reduced by (a) taking account of earthquake hazards in land-use decisions, (b) using appropriate engineering and construction design to reduce the hazard, and (c) involving communities in earthquake preparedness programs.
Land-Use Decisions
Land owners, lenders, government officials, and others involved in land development need to understand the consequences of building in areas exposed to earthquake hazards. Those consequences should be carefully considered when making decisions on land use. Building in hazardous areas may necessitate a more expensive design, increased insurance coverage, or additional long-term maintenance. Individuals using property in hazardous areas may be at greater risk of injury and loss during an earthquake. Further, emergency response may be more difficult in areas developed in regions of high earthquake risk, and recovery following an earthquake may be slower and more costly.
Federal, state, and local regulatory laws can encourage some types of land use (Baker, 1976; Palm, 1981). The 1968 National Flood Insurance Act, the 1973 Flood Disaster Protection Act, the Flood Disaster Relief Act of 1973, and the Disaster Protection Act of 1975 make federally subsidized flood insurance and certain federal disaster relief funds available only to communities that control development within flood plains. Similar federal legislation providing federally subsidized earthquake insurance does not presently exist, and regions with high earthquake risk are not required to control development in order to qualify for federal disaster relief funds. However, the National Earthquake Hazard Reduction Act (PL-95-124) of 1977 established the National Earthquake Hazard Reduction Program (NEHRP) for the purpose of reducing the risks to life and property from future earthquakes. NEHRP objectives include the development and promotion of model building codes and the education of state and local officials about seismic risk. Some federal funds are provided under NEHRP to facilitate Washington state earthquake hazard mitigation and preparedness activities. Beginning in 1989, state participation, in the form of matching funds, will be required before other federal monies will be allocated. Federal regulations also guide siting of critical facilities, such as nuclear power plants, with respect to earthquake hazards and provide seismic design standards for federal hospitals and highways.
States can regulate land use by establishing policies to be followed at the state and local level. In California, state law requires that real estate agents disclose the presence of active faults (shown on state maps) prior to sale of property. The Washington State Environmental Policy Act of 1971 requires all state and local governmental agencies to consider environmental values both in undertaking their own projects and in licensing private proposals. Although the focus of this act is on the preservation and enhancement of the environment, an assessment of geologic factors affecting a proposal is required as part of the environmental impact statement. The Washington Energy Facility Site Evaluation Council considers earthquake hazards in the siting and licensing of state nuclear power plants and in the review of proposed oil pipeline routes.
Local governments can regulate land use through building permits, zoning provisions, and ordinances. The Seattle Greenbelt Ordinance is an example of a regulation that can be used to reduce earthquake hazards by limiting land use. The King County Sensitive Areas Ordinance 4365 can limit land use in certain areas, defined
by the ordinance as those subject to landslides or significant earthquake hazard. (King County has mapped areas identified as unstable during ground shaking. However, if a property is in an unstable area not so identified by the county, the property owner is still required to follow Ordinance 4365.)
Engineering and Architectural Design
Although appropriate land use management may be an effective way to reduce earthquake risk, the benefits of utilizing a site may outweigh the risk. Significant earthquake hazards exist throughout the state, and not all high-risk sites can be avoided. Therefore, engineers have developed methods to increase the resistance of land and structures to the damaging effects of strong ground shaking.
Examples of engineering methods used to reduce earthquake hazards include the stabilization of landslide areas and compaction of soft-soil sites. Many landslides that occurred in King County following the January 19, 1986, rains might have been prevented by adequate drainage of the slide-prone areas. A landslide area along Perkins Lane in the Magnolia area of Seattle was improved by the installation of drain fields to reduce the water content of the slide material. This lowers, but does not remove, the susceptibility of the material to slip. A method called vibro-flotation can be used to compact the soil before a structure is built. This technique was used to compact the abutment area of the West Seattle bridge before the pier supports were emplaced.
Architects can contribute to the reduction of earthquake hazards by designing buildings with shapes that do not localize large stresses when the ground shakes and by considering ground shaking in the design of the non-structural elements of the building. Nonstructural hazards can be reduced in new or existing buildings by securely attaching ceiling panels, light fixtures, and shelving and by installing special equipment, like safety glass and automatic gas shut-off valves. Closed storage cabinets with secure latches should be used for loose objects whose movements during ground shaking might be dangerous.
The Uniform Building Code (prepared by Interational Conference of Building Officials) contains building design standards commonly used by architects and engineers in the westem United States. These standards are periodically modified through experience and research. New versions of the Uniform Building Code apply only to new construction. Therefore, the age of a building provides a guide to the design criteria used at the time of construction and to the type of risk it offers.
Before the first Uniform Building Code was developed in 1926, architects and engineers relied on design criteria that varied in different localities or with specific projects. From 1927 to 1946 the Uniform Building Code classified Washington state as an area where only minor earthquake damage was expected-the state was put in seismic zone I on a scale ranging from 0 to 3. In 1949, after the 1939 and 1946 Puget Sound earthquakes and the June 23, 1946, Canadian earthquake, Washington was reclassified and put in seismic risk zone 2. In 1952, the risk potential was upgraded again to seismic zone 3 because of the major 1949 Olympia earthquake.
Although Puget Sound is still classified as zone 3, the design requirements are much more stringent today than they were under the 1952 code. From 1952 to 1961 the recommendations for seismic design were included in an appendix to the Uniform Building Code as an optional consideration. In 1961, the seismic design section was moved from the appendix to the main text as a mandatory design requirement. Even though the Uniform Building Code was used by many jurisdictions in the state, doing so was not required by the State of Washington until January 1, 1975. At that time all jurisdictions were then required to adhere to the provisions of the most recently adopted version of the Uniform Building Code.
In 1976, the classification of seismic risk zones used in the Uniform Building Code was modified to range from 0 to 4. Seismic zone 4 includes areas expected to have major damage because of their proximity to major fault systems. In this classification, areas along the San Andreas fault and the Alaska subduction zone are in seismic zone 4. To date, no area of Washington has been proposed for inclusion in seismic zone 4.
A map of seismic zones in Washington (Uniform Building Code, 1988) is shown in Figure 44. It is a modification of the seismic zones depicted in the Uniform Building Code of 1985 and, like its predecessor, is based on Washington earthquake history. It illustrates the changes that recent studies have made in our assessment of earthquake hazards. For example, the St. Helens Seismic Zone ( Figure 15) has been placed in the higher risk zone 3; it was formerly in zone 2. More of the North Cascades is now included in seismic zone 3 because of recent studies of the severity of the 1872 North Cascades earthquake. Future revisions of the seismic risk zones in Washington could include placing part or all of the Cascadia subduction zone in seismic zone 4.
State regulations do not require structural improvement of buildings built prior to the required use of lateral resistance in building design. Strengthening older buildings is required only during extensive remodeling. However, the State of Washington has begun a program of improving the seismic safety of selected buildings. In 1979, the State of Washington spent $9.1 million strengthening the old state capitol building (now housing the Office of the Superintendent of Public Instruction). It also spent $3.4 million on the legislative office building in 1975, and $3.5 million on the insurance office building in 1973 and 1979. At the present time, however, no program exists to modify schools, hospitals, or fire stations built before 1949 so that they can resist ground shaking comparable to levels recorded during the 1949 and 1965 earthquakes.
Many older masonry buildings similar to those damaged during the 1949 and 1965 earthquakes exist throughout the Puget Sound region. Some examples are shown in Figure 45. Poor maintenance further weakens such buildings, creating significant hazards to occupants or passersby.
Earthquake Preparedness Programs
A major earthquake in Washington could occur tomorrow-or 25 years from now. Earthquake preparedness actions must be a part of routine safety and building maintenance procedures to insure protection when the next earthquake happens. Individuals must know what to do before, during, and after an earthquake where they live and work.
Earthquake preparations that can be taken now are easy to identify. Learning and practicing what to do during an earthquake is an important first step toward earthquake preparedness. Preparations at home or work might initially include identifying areas that are safe from falling objects, practicing what to do during the shaking and when the shaking stops, and obtaining essential emergency supplies like a first aid kit. Some preparations, like securing water heaters and bookshelves, may require a longer time to complete ( Figure 46). Earthquake preparedness is an on-going activity, not something to do once and forget.
During an earthquake, individuals, no matter where they are, must be able to respond quickly to reduce loss of life and injury. Strong ground shaking often lasts only 30 to 60 seconds. One should expect considerable noise and confusion. Power failures may plunge a room into darkness. Sprinkler and alarm systems may be activated. One must immediately find a nearby protected place to take shelter until the shaking stops. The drop and cover position ( Figure 47) should be taken under a sturdy desk or table, inside a doorway, along a wall entirely inside a building, or within the inside corner of a room. Table 4 lists actions to take during an earthquake if one is inside a building, outside, or in a vehicle.
After a major earthquake, individuals must be able to perform a number of actions to prevent additional injury and loss of life (Table 5). Usually a building should be evacuated because of the possibility of further damage during aftershocks or secondary hazards like fire or gas leaks. All building occupants should be accounted for and given medical attention if needed. People may need to be self-sufficient for as long as 72 hours after an earthquake because emergency response personnel will likely be handicapped by impaired communications, damaged and blocked transportation routes, damaged equipment, and injured personnel.
Besides protecting personnel from injury, schools, hospitals, governments, and certain businesses need to be concerned about maintaining and continuing operations after an earthquake. Nearly two-thirds of all businesses fail following a major disaster for which they were unprepared (Bay Area Regional Earthquake Preparedness Project, 1986).
In 1983, FEMA established a comprehensive Earthquake Education Program under the authority of the National Earthquake Hazards Reduction Act of 1977. The goals of this program include increasing public awareness of earthquake hazards and promoting public involvement in earthquake preparedness and hazard reduction. Three pilot projects of the Earthquake Education Program were funded to develop methods to provide information on earthquake safety to specific audiences, such as school personnel and hospital administrators, and to encourage the development of local earthquake safety programs. Strong response to these pilot projects indicates a keen interest in earthquake preparedness and a need for guidance to develop earthquake preparedness programs. Information developed by the pilot projects is available from the national FEMA office in Washington, D.C.
The following lists summarize some recommendations about additional earthquake preparedness actions for work, school, and the home that have been suggested in FEMA publications and by participants in the pilot projects:
School:
Home:
Risk Reduction Policy
Many of the actions necessary to reduce earthquake risks can be carried out by any interested individual. Often, however, risk reduction efforts require the cooperation of many people. The establishment of policies to guide earthquake loss reduction programs provides needed coordination and provides program standards. Preparation for future Washington earthquakes must be an on-going process, not a momentary effort inspired by events like the recent earthquake disasters in Mexico or California. Such tragedies may motivate the hasty development of earthquake safety programs, but that action does not substitute for thoughtful program development and implementation during less stressful and emotional times.
In 1985, the Governor of Washington instructed the Director of the Department of Emergency Management to form a Washington State Seismic Safety Council to make policy recommendations for dealing with Washington state earthquake risks. This action followed the Governor's veto of a bill that would have established a Washington State Seismic Safety Commission. Activities of the council, including the final report to the Governor, were funded by the Federal Emergency Management Agency out of the Washington State National Earthquake Hazard Reduction Program allocation for fiscal year 1986. Although the state legislature has made significant contributions to the modemization of building codes, the Seismic Safety Council identified several additional areas that require attention. The final report of the council to the Governor (Washington Seismic Safety Council, 1986) includes an assessment of the state role in reducing earthquake losses and suggests priorities for state action. The council concluded that the key policy issue for the state is definition of the state role in both fulfilling its responsibilities and inducing others to fulfill theirs. The council suggested that those two sets of obligations could be carried out through the following actions at a statewide level:
The long-term agenda for the state was outlined as an on-going seismic risk reduction program that fulfills the obligations listed above. The Council proposed the following legislative priorities:
Following the release of the council report in September of 1986, the House of Representatives passed a resolution in the 1987 session recognizing the potential for serious damage, loss of life, and injury in Washington from earthquakes. This was an important first step in developing public policy that will improve our ability to reduce the risk of earthquakes in Washington.
Meanwhile, individuals, both at home and in the work
place, should not wait until earthquake safety actions become required by law. Rather, for their physical, emotional, and financial protection, earthquake preparedness
should be included in routine training and building
safety programs as soon as possible.