Overview: Lessons And Recommendations From The Committee For The Symposium On Practical Lessons From The Loma Prieta Earthquake
The moderately large (7.1 on the Richter Scale) Loma Prieta earthquake of October 17, 1989, took 63 lives, cost $10 billion, and damaged more than 27,000 structures. It resulted from a slip along a 25-mile segment of the San Andreas fault where it traverses the Santa Cruz Mountains, approximately 60 miles south of San Francisco and Oakland (Figure 1). Because the fault ruptured bilaterally, propagating north and south simultaneously, the duration of shaking was surprisingly short, about 10 seconds.
Within minutes of its occurrence, it was evident that the Loma Prieta earthquake would become an important case study for all interested in earthquake hazard assessment and risk reduction. Because it presented such an obvious opportunity to learn more about earthquake hazards and ways to mitigate their effects, the U.S. Geological Survey (USGS) asked the National Research Council (NRC) to convene a Symposium on Practical Lessons from the Loma Prieta Earthquake and to issue a report on the lessons learned from the research conducted on the earthquake. The symposium, conducted in conjunction with the Earthquake Engineering Research Institute (EERI), was attended by over 400 individuals. It took place on March 22-23, 1993, in San Francisco, California. The National Science Foundation, the Federal Emergency Management Agency, and the National Institute of Standards and Technology joined the USGS as sponsoring agencies. The symposium consisted of keynote papers, panel discussions, and technical sessions.
This report is the result of the symposium. It contains the opening keynote address, six keynote papers, and highlights of the discussants' comments. This overview chapter, authored by the NRC committee, contains the principal les-
sons and recommendations drawn from the presentations made and discussions held at the symposium and the committee's collective opinions.
In emphasizing the practical lessons of the Loma Prieta earthquake, the committee does not wish to downplay the importance of long-term research efforts, which have been the principal focus of other meetings. Rather, the primary objective of this conference was to respond to the more immediate concerns of user groups such as local and state governments, in terms of measures they might take at this time to better prepare for future earthquakes.
The Loma Prieta earthquake was the first opportunity in almost two decades to assess design and construction procedures used in this country to accommodate earthquake forces generated by a moderately large earthquake with widespread structural damage. It was the most damaging and costly earthquake to strike California since 1906. However, because of its distance from major population centers and the short duration of shaking, Loma Prieta was not a rigorous test of the performance of the Bay Area's built environment.
Many lessons were learned; some lessons reinforced prior understanding of earthquake vulnerability and design. Other lessons contradicted previous understandings. For example, an earthquake of the magnitude of Loma Prieta on the San Andreas fault would have been expected to be associated with significant surface faulting that did not occur. Some lessons identified social problems that challenged the efficacy of the emergency response efforts; some helped to identify new concepts with regard to earthquake vulnerability assessment and preparedness. In some cases, old lessons were re-learned.
Loma Prieta emphasized that:
local geology and site soil conditions affect the severity of the shaking and the damage it causes to the built environment;
older residential construction is vulnerable to failure that can cause extreme personal, social, and economic consequences;
there is urgent need to improve the seismic resistance of unreinforced masonry and non-ductile reinforced concrete building and bridge structures;
many of the most successful mitigation efforts were the direct result of state legislation;
practical, problem-focused research is needed to assess the appropriate repair and retrofit procedures for restoring and improving various building types;
emergency response efforts are complicated by existing social conditions, such as homelessness; and
Why did some sections of the Cypress Street viaduct collapse and not others? What were the structural characteristics that caused some older buildings to remain undamaged while nearby newer buildings sustained damage? Why did nearby buildings of similar type and age perform differently? Was it the design
details? Was it the lack of adequate construction supervision to ensure proper construction? Was it the different site geologic and soil conditions? Was it a combination of these and other factors? How did retrofitted bridges and buildings perform? Could relief efforts have been more effective in ethnic neighborhoods? How does one manage droves of volunteers? These and other vital questions call for an urgent examination to seek explanations and solutions through multidisciplinary cooperation.
The purpose of this symposium was to understand how to apply the legacy of knowledge left by the Loma Prieta earthquake to reduce the impacts of future earthquakes throughout the United States. To accomplish this task, the symposium committee and participants attempted to understand and translate this knowledge into practical lessons and recommendations that can be implemented by the appropriate government agencies, designers, builders, care-givers, and others responsible for people's well-being and quality of life.
In light of the presentations and discussions at the symposium, the following lessons and recommendations are offered by the NRC committee in the hope that these short statements will stimulate the reader to read further and to take appropriate action. The committee recognizes that within earthquake-prone regions of the United States there are varying levels of seismic risk. These lessons and recommendations do not distinguish between these risk levels but are directed, in general, to areas where risk is sufficient for seismic safety to be a priority.
One of the primary purposes of the conference was to emphasize the interdisciplinary nature of seismic hazard mitigation; the lessons and recommendations demonstrate this well. The forty lessons and recommendations listed below have been ordered so that the overall flow of thought is from general observations, to the earth sciences, to geotechnical and structural engineering, and finally to planning and emergency response. Nevertheless, the committee points out the cross-cutting nature of most of the lessons and recommendations, and it urges readers to review the entire list regardless of their own individual specialties.
Lesson 1: Investments made in earthquake preparedness and hazard and risk mitigation paid off. It was apparent from the papers presented at the symposium that the Loma Prieta earthquake demonstrated that the San Francisco Bay Area has made progress toward improving the ability to minimize damage and cope with destructive earthquakes. However, Loma Prieta was a moderately large earthquake that occurred a significant distance from major population centers; therefore it was not a rigorous test.
Recommendation: Rather than creating over-confidence and complacency, the Loma Prieta earthquake must serve as a stern warning to residents of the Bay Area and other earthquake-prone areas throughout the United States
about future earthquakes, some of which will be larger, shake longer, and be closer to major population centers.
Lesson 2: Many earthquake professionals knew that the San Francisco Marina District was prone to liquefaction, that unreinforced masonry buildings were vulnerable to earthquakes, and that existing older concrete structures probably lacked adequate steel reinforcement and connection details vital to resist strong shaking. However, government and business leaders expressed great surprise that these professionals knew so much, but so little was done. The failures stemming from the Loma Prieta earthquake reinforce the need for a communication program to close the knowledge gap among researchers, practicing professionals, decision makers, and the public in a prioritized and systematic way.
Recommendation: Earthquake professionals must work harder to close the gap between what is known and what is used, between researchers and practitioners. They must increase their emphasis on integrating seismic risk concerns and their existing knowledge into the mainstream activities of both government and business. There is a strong need for advocacy; narrowing the gap by enacting new policy depends on earthquake professionals having a commitment to do so. Practicing professionals must adequately inform policy makers of the risks and the costs and benefits of various strategies; they must make strong recommendations for earthquake hazard and risk mitigation, including evaluation, assessment and enforcement measures to assure effective implementation.
The National Earthquake Hazard Reduction Program must emphasize the application of existing knowledge and the development of new knowledge and must provide incentives for risk reduction activities.
Lesson 3: In the first few hours following the Loma Prieta earthquake, uneven and in some cases inappropriate emergency responses resulted from the inability of emergency-response decision makers to know where the heaviest shaking and greatest damage actually occurred and from undue dependence on news media reports.
Recommendation: In the principal earthquake-prone areas of the country federal and state governments, in particular, should accelerate efforts to develop on-line, real-time seismic monitoring systems capable of producing generalized maps of the intensity of heavy ground shaking and the relative vulnerability of the built environment within a few minutes of a major earthquake. Such systems are achievable with currently available technology, and prototype systems are currently under development.
Lesson 4: Even in the San Francisco Bay Area, where the seismic geology is well mapped and seemingly well understood, surprises occurred in the way in which the San Andreas fault zone ruptured and in the resulting geographic patterns of seismic shaking.
Recommendation: Federal, state, and local governments should continue to support the preparation of seismic zoning maps and emergency response plans, recognizing that geologic knowledge is necessarily limited, that local earthquakes of the historical past will not be exactly like those of the future, and that surprises will continue to occur. Continued studies by researchers on the mechanics of the earthquake rupture process and the prediction of destructive effects are essential; maps should be updated as soon as more reliable data become available.
Lesson 5: Damaging intensities of seismic shaking occurred at considerable distances from the epicenter of this moderately large earthquake. Strong crustal reflections resulting from regional geologic structure may have been of particular importance at these large distances.
Recommendation: In preparing emergency response plans, communities must recognize, and scientists must emphasize, that seismic hazard is by no means limited to local faults, nor will significant damage be caused only by ''the big one.'' Data on seismic velocity structure and regional geologic structure, including crustal thickness, are significant in assessing the potential for local damaging ground motions from distant events, and should be assessed.
Lesson 6: Surprising variations in the intensity and nature of strong ground motion were seen in the close-in epicentral area as a function of proximity to the causative fault, rupture direction, azimuth to the epicenter, frequency of ground vibration, and other factors.
Recommendation: Seismologists and geologists must increase their efforts to understand and quantify the nature of strong ground shaking very close to highly active faults, and engineers must give special attention to the placement and design of structures in these areas.
Geotechnical And Structural Engineering
Lesson 7: As has been observed in many earthquakes, and was dramatically re-emphasized by the Loma Prieta earthquake, the intensity of seismic shaking is critically dependent upon the nature of the local soils and shallow geologic structures. Major differences in intensities of shaking were observed over distances of only a few hundred feet in areas where soil conditions changed rapidly, such as near the edges of old stream channels or along the boundaries of filled
ground. Most of these features were well delineated on pre-existing maps, but the impact of the possible hazards had not been fully incorporated into land-use plans or building codes.
Recommendation: Federal, state, and local governments should make an expanded effort in mitigation planning to use current knowledge of the effects of prior shaking and local soil and geologic conditions in major earthquake-prone metropolitan areas of the country. Microzonation should be used for new construction and for rehabilitation efforts. Furthermore, agencies must address how seismic hazard maps can be used effectively in land-use planning, design, and in administrative practices.
Lesson 8: Geologic maps prepared for the purpose of identifying potential areas of liquefaction proved accurate in defining the locations of major occurrences of liquefaction and lateral spreading. Where compaction, restraining walls, piles, vibroflotation, or other remedial methods were implemented, they significantly reduced the liquefaction susceptibility, although significant liquefaction damage occurred in adjacent areas of unimproved ground.
Recommendation: In earthquake-prone areas subject to potential liquefaction, practicing professionals should use regional maps of potential areas of liquefaction as guidelines to indicate where detailed site-specific studies need to be performed to characterize accurately geologic, soil, and groundwater conditions. When facilities must be built in areas identified as being susceptible to liquefaction, measures must be taken to ensure that ground improvement techniques are used to minimize earthquake damage.
Lesson 9: Loma Prieta caused about 4,000 landslides. Throughout the affected area, large, deep-seated ancient landslides were reactivated, many of which had been specifically delineated and recognized as potentially active prior to the earthquake. Nevertheless, little effective land-use planning and few mitigation measures had been carried out. Fortunately, the extent and impact of landsliding were moderated by the effects of a four-year drought, as well as by the moderate size of the earthquake, the short duration of shaking, and the distance of the energy release from large populations.
Recommendation: Appropriate government agencies should continue to develop maps of landslide potential. These maps should become an integral part of land-use planning, and the information should be communicated to developers and building owners. Communities having high landslide potential should not be complacent when reviewing the lessons from the Loma Prieta earthquake—what appears to have been successful performance could have turned out to have unacceptable consequences if the earthquake had occurred closer to cities, the shaking had lasted longer, or the ground had been highly saturated.
Lesson 10: Earth and rockfill dams within the epicentral region built to California's modern standards of construction performed well. Some old dams suffered significant damage. Fortunately, because of the drought that had plagued California for several years, very little water was retained in most of the reservoirs at the time of the earthquake.
Recommendation: Responsible government agencies should ensure that all dams are designed and built to a high standard. Older dams should be reexamined and retrofitted to improve stability and safety where deficiencies are found.
Lesson 11: Where specific geotechnical engineering measures had been taken to compact major artificial fills throughout the Bay Area, these fills performed well.
Recommendation: Placement and compaction using appropriate geotechnical engineering should be mandatory wherever filled ground is to be used in earthquake-prone areas. Communities having existing fills should evaluate the ability of the fills to withstand stronger shaking than that caused by the Loma Prieta earthquake, and should take remediation steps, if necessary.
Lesson 12: With the appropriate application of existing knowledge and with more attention to detail, practicing professionals licensed to site, design, and retrofit buildings and lifelines could have significantly reduced the loss of life and the damage resulting in loss of function.
Recommendation: Professional and trade organizations should place a priority on improving the knowledge of practicing designers, engineers, geotechnical professionals, and building contractors. These organizations should develop training programs for practicing professionals who should be provided incentives to upgrade their knowledge. Frequent training is needed to keep their skills and methods up to date so they can effectively apply the knowledge learned from past earthquakes. Building owners need to be encouraged to hire professionals who have demonstrated competence in addressing earthquake hazards.
Lesson 13: In some cases, bridges and buildings that had been retrofitted to resist earthquakes sustained structural damage. In other cases, many bridges and buildings that had not been retrofitted sustained little or no damage. (See "Note on Supporting Sources" at the end of this chapter.)
Recommendation: To assess the appropriate retrofit procedures for improving various bridge and building types, practicing professionals need to know more about bridge and building performance during earthquakes. Professionals and researchers need to focus efforts to correlate actual re-
sponse with predicted response using realistic earthquake scenarios. This requires studies of the expected earthquake response of specific bridges and buildings. Both retrofitted and non-retrofitted structures should be thoroughly instrumented to allow direct measurements of their actual response. Appropriate state and local government agencies should take the lead in encouraging the instrumentation of critical bridges and buildings in metropolitan areas that are close to sources of likely future large earthquakes, such as Seattle, Portland, San Francisco, Los Angeles, San Diego, Charleston (South Carolina), the Wasatch front region in Utah, and the New Madrid seismic zone in Missouri.
Lesson 14: The good performance of "hinge restrainers" is testimony that highway bridge structures can be economically retrofitted to enhance seismic performance. This simple, relatively inexpensive, interim retrofit technique provided displacement control across expansion joints.
Recommendation: Transportation departments can obtain a significant improvement in seismic resistance in most simple span bridges or bridges having hinge seats by installing cable restrainers. Although not a complete solution, they are an interim "quick fix" that can provide a measure of protection at minimal cost.
Lesson 15: Many owners and managers of buildings that were built to the Uniform Building Code or had been seismically upgraded were surprised when their buildings experienced significant damage. In some cases, the owners were not able to reoccupy their buildings for some time after the earthquake and could not understand why.
Recommendation: Earthquake professionals must educate owners of buildings to understand that building code compliance will not and was never intended to make buildings earthquake proof. The codes and most seismic strengthening of buildings are intended to protect life and to minimize catastrophic damage. A modern building that meets current codes or an older one that has undergone retrofitting can experience damage that could cause it to be closed for what may be an unacceptable period of time. Owners can make informed decisions on investments in greater earthquake resistance to achieve a superior level of building performance during earthquakes and of post-earthquake integrity. Engineering estimates can indicate what level of performance owners can expect at what cost. Practicing professionals need to develop refined techniques, consistent with the historical behavior of structures, to make such estimates.
Lesson 16: There were numerous structures, ranging from residential buildings to multistory facilities, that were seriously damaged in the Loma Prieta earthquake because of design or construction errors that should have been found
during the building inspection process. Local building departments rarely have the necessary resources to accomplish this fundamental step in the construction process, and design professionals often shy away from providing the needed oversight. (See "Note on Supporting Sources" at the end of this chapter.)
Recommendation: In regions of the United States where seismic safety must be a priority, local governments should insist on adequate inspection and enforcement of construction regulations and standards. Similarly, regulators need to demand attention to detail, as well as procedures that result in construction quality. Design professionals should be required to inspect and accept the work. Educational courses should be mandatory to provide building inspectors with up-to-date principles of seismic design that cover the majority of structures. Local governments should provide qualified and properly trained building inspectors who have adequate resources to confirm that all the seismic elements are properly installed.
Lesson 17: Unreinforced masonry buildings are not only dangerous to building occupants but can be equally dangerous to adjacent buildings and people on sidewalks and in the streets, due to falling debris.
Recommendation: Local governments should create mandatory procedures or programs to reduce the seismic hazards associated with unreinforced masonry buildings in all cities that may be exposed to damaging earthquakes.
Lesson 18: For residential structures, simple retrofits made prior to the earthquake greatly reduced losses. The simple and inexpensive procedures of strengthening cripple-walls, bolting residences to their foundations, and anchoring water heaters have a very high benefit/cost ratio.
Recommendation: Homeowners should be encouraged to perform simple retrofits. Earthquake-prone communities desiring guidance for establishing formal procedures or recommendations for homeowners should review the California Seismic Safety Commission's publication, The Homeowner's Guide to Earthquake Safety. State law requires home sellers to disclose to buyers all earthquake weaknesses; real estate agents are required to distribute the publication.
Lesson 19: Loma Prieta re-emphasized the need to understand and deal effectively with "adjacency hazards." These include debris or building components falling from one building and damaging the adjacent building, adjacent buildings pounding each other, and the interaction of differing heights of adjacent buildings. All of these adjacency hazards were observed throughout the area affected by the Loma Prieta earthquake. There are currently no codes or ordinances that deal with these hazards.
Recommendation: Local governments should encourage cooperation between adjacent building owners when adjacency hazards are identified, so that life-threatening hazards and economic impacts can be minimized.
Lesson 20: Experience during the Loma Prieta earthquake confirmed the inherent ruggedness of modern steel natural gas transmission pipelines and distribution mains. Damage to gas mains was generally limited to old cast iron pipe in areas that experienced ground failure due to liquefaction, landslides, and extreme settlement of natural and man-made fills. This behavior is consistent with observations from past earthquakes worldwide.
Recommendation: Gas pipeline vulnerability studies must include the assessment of areas of potential ground failure, including liquefaction, differential settlement, and surface faulting. These hazards should be mitigated by replacing cast iron pipes with modern steel ones and by designing plans for rerouting or rapid repair.
Lesson 21: Well-designed water and wastewater-treatment facilities experienced little structural damage; however, non-structural components were prone to damage due to sloshing effects.
Recommendation: Non-structural components of water and wastewater-treatment facilities should be designed using the same principles as those for water storage tanks.
Lesson 22: As a moderately large earthquake of short duration, Loma Prieta resulted in only a few cycles of strong shaking and demonstrated that older bridges on soft soil are vulnerable to even this limited level of ground motion. Extensive damage to similar transportation structures elsewhere in the United States must be expected.
Recommendation: Earthquake-prone communities throughout the United States should examine the vulnerabilities of their bridges. Screening procedures to set priorities, and retrofit methods are available that have immediate application in other areas. These are the result of extensive research funded by the California Department of Transportation, the Federal Highway Administration, and the National Science Foundation. They are applicable throughout the United States without the need to "reinvent the wheel."
Lesson 23: High-voltage (500-kilovolt) substations were the least seismically resistant element in the electric utility bulk power transmission system. Power system failures were largely due to older-vintage, live-tank circuit breakers; no dead-tank circuit breakers failed.
Recommendation: Utilities should replace older-vintage, live-tank circuit breakers with dead-tank circuit breakers or new live-tank breakers that have been shake-table tested.
Lesson 24: The results of earthquake research have not been effectively translated to many potential users of the research findings in the Bay Area. Earthquake research often is viewed as too narrowly focused, not particularly useful, or inadequately communicated to practitioners.
Recommendation: There must be a balance between basic research and problem-focused research. To improve the transfer of research technology to the research-user community, strong partnerships should be formed among researchers, design professionals, industry, and federal, state and local government agencies. One of the most effective ways to initiate these partnerships is to involve the practicing professionals and the end-users of research in problem-focused earthquake research programs. This involvement should include the research users in the planning and scoping activities, as well as in decision-making activities during implementation of the research.
Lesson 25: The disruption of water pipelines resulted in the rapid loss of water supplies stored in elevated water tanks, depleting water vital for fire fighting.
Recommendation: Local agencies and the appropriate public utilities should install "smart" valves in the system to shut off the loss of water and protect the water supply when a break in the system has occurred. These shut-off valves should be sited on the upstream side of potential ground failure areas. Automatic shut-off valves that are activated by strong shaking are not recommended, because they often shut off the water supply to pipeline systems that have not experienced damage and the water may be needed to fight fires.
PLANNING AND EMERGENCY RESPONSE
Lesson 26: During the response period, there was an urgent need for better coordination among the various levels of government and private sector businesses. Those organizations that had developed and tested realistic earthquake planning scenarios prior to the Loma Prieta earthquake were better prepared than those that had not. Good emergency response and recovery plans are essential to facilitate coordination and to enable quick response and full recovery following even a moderate earthquake.
Recommendation: Local governments, with assistance from state or federal agencies, utilities, or other organizations, should develop realistic earthquake scenarios to evaluate the vulnerability of their communities (including lifeline systems, businesses, neighborhoods, and other community investments), to test emergency response plans and communication links,
and to gain insight for recovery plans. Large organizations, businesses, and utility companies should conduct earthquake exercises periodically, to practice emergency response and communications. These organizations should use the resulting understanding of earthquake vulnerabilities to implement realistic, priority-driven earthquake risk reduction and risk management programs.
Lesson 27: Power outages in downtown San Francisco lasted several days following the earthquake due to the need for time-consuming inspections of major buildings for gas leaks and ignition sources prior to energizing the downtown power grid. This was the largest single source of business interruption resulting from the Loma Prieta earthquake.
Recommendation: Local agencies and the appropriate public utilities should. develop building inspection procedures and train personnel to facilitate the building inspections for gas leaks.
Lesson 28: Existing federal disaster recovery policy is written in a way that inhibits upgrading of hazardous structures. Disaster recovery laws are biased toward returning to pre-earthquake conditions, even when those conditions represent high earthquake risk.
Recommendation: The federal government should maintain flexibility in recovery policy to react to changed conditions and to reflect the need for seismic hazard mitigation. "Exact replacement" is unsound public policy. With such flexibility, future opportunities to improve seismic safety are enhanced, and damaged or collapsed facilities can be replaced with improved seismic resistance. Appropriate government agencies and professional and trade organizations should develop guidelines and standards to guide earthquake repair in a way that provides for a variety of performance levels that are based on the facilities' intended function and the level of safety desired. Federal procedures for awarding earthquake recovery funds to state and local governments should require that the federal contribution be used to restore the stricken community to a functioning, viable community that has improved seismic safety.
Lesson 29: Pre-existing social problems such as homelessness, housing shortages, tight government budgets, land-use disputes, and inadequate lifelines will be made worse immediately after a destructive earthquake.
Recommendation: Community leaders should incorporate the social problems that currently exist in their communities into their emergency planning. The leaders should consider how such social problems are likely to be exacerbated during the emergency response and recovery period. Community agencies need to develop policies to address these issues and to develop the capacity to innovate. For example, volunteers can be trained to provide
a support service to police and fire units as is done by the Los Angeles Fire Department.
Lesson 30: There was an outpouring of unselfish concern for the welfare of others, even though the massive response often created widespread confusion and coordination problems. People were adaptive and flexible. Destructive earthquakes invariably produce unexpected challenges for responders whose effective action is dependent on their education and training and on their willingness to develop and help implement innovative solutions on the spot. When well informed about earthquake hazards, people significantly improve their chances of safety. For example, the Oakland Fire Department has 5,000 citizen volunteers who have completed training modules and are now a support service to police and fire units. These individuals can lead the emergent volunteers and help to manage them so they are a resource and not a liability.
Recommendation: Local governments must show a commitment to earthquake hazard mitigation and preparedness efforts so that the populace's resiliency and ability to function in response to the earthquake is improved.
Lesson 31: Rushed post-earthquake inspections of damaged buildings resulted in some inaccurate and emotional assessments that led to inappropriate actions (for example, demolition) in the spirit of protecting public safety, which caused extreme financial impact to owners and renters.
Recommendation: Local governments should develop and implement strategies, procedures, and training for post-earthquake inspections. These should be communicated prior to the event to avoid costly mistakes. New, realistic guidelines for emergency demolition are needed.
Lesson 32: Within the Bay Area's communication systems, sufficient slack in fiber-optic cable assisted in minimizing failure and service disruptions, even in areas where large differential displacements occurred. For example, the fiber-optic cable attached to the Bay Bridge was not disrupted, even though one of the upper spans of the bridge collapsed during the earthquake. Although the cable stretched, there was sufficient slack to accommodate the damage to the bridge.
Recommendation: Appropriate utilities should incorporate cable slack as a design requirement in order to minimize failure of the fiber-optic communication systems.
Lesson 33: In many culturally diverse communities in the Bay Area, the languages and customs were not understood by relief workers after the Loma Prieta earthquake. As a consequence, actions by relief workers were not as effective as they might otherwise have been.
Recommendation: Relief agencies must be knowledgeable about the ethnic composition of at-risk areas and must be prepared to train relief workers in
the language and customs of diverse populations, so that organized efforts to provide assistance to earthquake victims will be effective.
Lesson 34: The demolition or preservation of damaged historic buildings was and remains a bitterly fought issue in many Bay Area communities. Historic buildings can be a community asset, but they carry with them certain costly responsibilities for the owner.
Recommendation: Communities need to address the issue of historic buildings through a well-considered, long-term plan, prior to a destructive earthquake. Government entities and private historic preservation organizations should consider providing incentives to strengthen chosen historic buildings and repair them after damaging earthquakes.
Lesson 35: More-effective education of the public is needed about risks that are related to natural gas leakage following earthquakes. Despite efforts by California natural gas companies to educate the public, almost all of the 156,000 customer gas shut-offs following the Loma Prieta earthquake were unnecessary. They were mostly initiated by poor advice from the media immediately after the earthquake.
Recommendation: Public education needs to be repeated whenever there is an opportunity. Pre-recorded audio and video tapes should be furnished to the media by natural gas companies, and notices should be inserted in utility bills periodically. Emergency response training for all media reporters should be encouraged.
Lesson 36: Disagreements over damage estimates, the cost of repairs, and the level of expected performance were frustrating and caused restoration delays. For example, a peer-review panel was selected by the California Department of Transportation immediately after the earthquake; however, this panel did not convene until March 1990. Following its review, some of the repairs to transportation structures, which had already begun, had to be halted or abandoned and much of the design redone, resulting in considerable delay and wasted effort and money.
Recommendation: State and local governments and departments of transportation should select and contract with seismic peer-review panels in anticipation of future earthquakes. The panels should be charged with the review of designs for new facilities, as well as retrofit concepts and implementation methods for mitigation measures for old facilities. A clear set of instructions should be established for these panels ahead of time so that both the panels and the owners know what to expect and know the limitations on each party.
Lesson 37: Many of the most successful mitigation efforts were the direct result of state legislation, such as the California Field Act to protect schools and the California Hospital Act to protect hospitals. Nevertheless, it appears that many local governments in California and elsewhere do not adopt seismic safety requirements to protect the local population.
Recommendation: State governments should provide legislative incentives for local governments to adopt ordinances and to work cooperatively with adjacent and regional governments and with state and federal agencies to implement seismic safety improvements.
Lesson 38: The low-income population of the Bay Area was most seriously impacted, because these individuals typically occupy old, seismically weak buildings that have not been adequately maintained. Many of these buildings were so badly damaged that they had to be evacuated. This increased the homeless population during the response phase, thus adding an increased burden to already over-burdened local governments, as well as to mass-care and shelter providers such as the Red Cross. In 1993, some of these buildings still stand empty, waiting for decisions and actions. Many are in no worse condition than they were before the earthquake. Advocates for the homeless believe that seismic upgrades will increase rents and make the buildings unavailable to the poor. Regulators responsible for seismic safety require the buildings to be upgraded. Some building owners simply choose to demolish their buildings rather than do the upgrade.
Recommendation: Communities must identify seismically weak buildings, especially in poor neighborhoods, and solutions should be developed prior to a destructive earthquake. Guidelines for evacuation and re-use are needed. Realistic social and economic incentives are necessary to motivate owners to bring older buildings up to acceptable standards. Earthquake professionals must take note of the factors that motivate building owners and business leaders: improving return on investments, lowering expenses, curtailing losses, and avoiding liability.
Lesson 39: The fact that the Loma Prieta earthquake occurred as the third World Series game between San Francisco and Oakland was starting resulted in extensive international media coverage and increased earthquake awareness.
Recommendation: Local governments and other public and private entities should be prepared to capitalize on the greater awareness of earthquakes that occurs immediately after an event. If agencies have well thought out plans prior to an earthquake, such plans are more likely to be adopted following the event. Communities respond more readily to preparedness and mitigation advice when the citizens understand that they are also at risk.
Lesson 40: Recovery from destructive earthquakes is expensive for everyone. Federal disaster aid pays for only a small portion of the recovery expenses. The damage losses from the Loma Prieta earthquake are estimated at about $10 billion. The federal contribution, through a variety of federal programs, will amount to approximately $2.5 billion. The state of California levied a 1/4-cent sales tax increase for 13 months and raised about $800 million. Insurance payments totaled about $1 billion. The remaining $5.7 billion—more than 50 percent of the losses—must be accommodated by local governments, businesses, and private individuals.
Recommendation: Earthquake hazard and risk mitigation and education efforts must be accelerated in earthquake-prone areas. The Loma Prieta earthquake dramatically demonstrated that an investment of a few percent of the $10 billion would have paid off many-fold in reducing the earthquake losses (death, injury, and economic impact). Citizens must do everything possible to convince decision makers of the value of investing in pre-earthquake mitigative measures.
NOTE ON SUPPORTING SOURCES
See the 1989 Hearings on the Loma Prieta Earthquake conducted by the California Seismic Safety Council in which numerous examples are described to support Lessons 13 and 16. Other references include: California Seismic Safety Commission, 1991, Loma Prieta's Call to Action, 97 pp., Sacramento; Lew, H.S. (Ed), 1989, Performance of Structures During the Loma Prieta Earthquake of October 17, 1989, U.S. Department of Commerce, National Institute of Standards and Technology, Special Publications #778, 175 pp.