SUMMARY

Immediate impacts on society and civil infrastructure systems (CIS) caused by earthquake induced strong ground motions during a major seismic event often last for fractions of a minute. During this short period of time, many earthquake related casualties may occur, millions of dollars in property loss realized, and vital urban delivery systems disrupted. When left unprepared for such an event, and caught without appropriate mitigation measures in place, it is very clear that "full recovery will take years, and some losses will never be recovered." (FEMA, 1991)

On an urban and regional scale, a significant concern in this process is found in the capacity of key elements in the built environment and urban delivery systems to maintain, or regain as rapidly as possible, full operational and functional capacities during and after the seismic event. Within this setting, along with policy actions taken by local and regional government officials, the architect and urban planner have extremely important roles to play in assuming responsibility for seismic risk reduction.

As team members in the planning and design professions, architects and urban planners are directly responsible for actions and decisions taken in the planning and design of essential structures and civil infrastructure systems (CIS) in metropolitan centers located in zones of high seismicity. For communities that do not have the foresight and capability to anticipate the issues and problems associated with earthquake hazard mitigation, the consequences are predictable and opportunities to design and build more safely are lost. As part of this equation, architects and planners must take advantage of such opportunities on a professional basis in addressing the consideration of seismic risk reduction measures.

INTRODUCTION

Major investments in civil infrastructure systems (CIS) made by public agencies and private industry represent a major portion of a nation's wealth. In the U.S.A. alone, it is clearly

*) Prof. of Architecture, Emeritus, Dept. of Architecture University of California, Berkeley

estimated that $20 trillion has been invested in civil infrastructure systems (CIS) which include all installations that house, transport, transmit, and distribute people, goods, energy, resources, services, and information. Historic evidence indicates that many other nations around the world have also invested heavily in the development of their civil infrastructure systems in the last century. However, an extensive assessment of the same evidence reveals that these aging infrastructure systems are rapidly deteriorating owing to excessive demands, obsolete performance standards, and inadequate capacity levels that render many of them incapable of meeting contemporary needs. (NSF 1993)

In terms of urban and regional planning issues, the fragility of these systems and the resulting negative economic impacts on local, regional, and national programs are potentially staggering. Many have eroded to the point of threatening economic advancement and the quality of the environment. In addition they are becoming more vulnerable to catastrophic failure caused by the destructive forces of natural hazards. This is a particularly important consideration to be taken into account for those located in zones of high seismicity. The very survival of metropolitan centers is directly tied to the functional and operational capacities of key infrastructure components during damaging earthquakes.

CIS Exposure to Earthquake Hazards:

Immediate impacts on society and civil infrastructure systems (CIS) caused by earthquake induced strong ground motions during a major seismic event often last for only fractions of a minute. During this short period of time, many earthquakes related casualties occur, million dollars in property losses realized, major indirect economic losses incurred, and vital urban delivery systems disrupted. When left unprepared for such an event, and caught without appropriate mitigation measures in place, it is very clear that "full recovery will take years, and some losses will never be recovered." (FEMA, 1991)

During and following a major damaging earthquake, metropolitan centers are immediately confronted with the complexities of changing conditions, competing priorities, and unexpected demands. For communities that do not anticipate the problems and issues associated with rapid post-earthquake recovery efforts, "the consequences are predictable. Confusion is magnified, lack of interagency coordination slows the pace of recovery, and most importantly, opportunities to rebuild more safely may be lost." During the emergency post-earthquake recovery period, it is clear that key actions must be taken objectively to see that: (1) crucial problems are accurately detected, (2) priorities are quickly assigned to urgent needs, (3) critical resources are assembled and deployed, and (4) restoration of critical CIS lifeline service components and emergency public facilities is rapidly and systematically employed. (Durham, 1993)

RESTORATION OF KEY CIS LIFELINE COMPONENTS

On an urban and regional scale, as previously noted, significant concern in the post-earthquake recovery process is found in the capacity of key elements in the built environment and urban CIS delivery systems to maintain, or regain as rapidly as possible, full operational and functional capacities during and after the seismic event. Within this setting, along with policy actions taken by local and regional government officials, the architect, design engineer, and urban planner have extremely important roles to play in assuming responsibility for seismic risk reduction.

In review of the post-earthquake recovery process over the years, six key CIS lifeline components, as listed in Table 1, which are identified as having typically experienced moderate to severe disruption because of a damaging earthquake consistently reappear on the list of records associated with historical earthquakes.

TABLE 1

KEY CIS LIFELINE COMPONENTS IDENTIFIED WITH POTENTIAL MODERATE TO SEVERE EARTHQUAKE DAMAGE LEVELS
 

Communications                     Water Supply

Transportation                        Wastewater Lines

Electric Power                        Fuel Pipelines
 

SOURCE: (1) EERI Reconnaissance Reports, NSF "Learning from Earthquakes Program"

In consideration of overall response actions to be undertaken, these six lifeline systems are clearly the most critical. Of the six listed, however, five of them warrant special consideration and top priority in past-earthquake recovery actions: 1) Communications, 2) Transportation, 3) Electric Power, 4) Water Supply, and 5) Fuel Pipelines.

Additionally, in many situations encountered, there is an intradependent nature which exists between these five CIS components that implies that the failure of one could have a serious and disruptive impact on another. For example, among others, water supply pumping stations would cease to function without the availability of electric power.

An article in the Summer 1993 edition of The CUSEC Journal makes the following observations from an urban planning point of view:

In regard to CIS renewal, one of the most important considerations that must be assessed is the tremendous expenditure of assets that must available to obtain the improvement of large scale systems seismic performance level. The resulting economic impact on urban environments can be devastating for an extended period when a substantial public debt bond measure is required to complete the anticipated program of work. Accordingly, it is quite clear that it would be prohibitively costly, disruptive and impractical to undertake a complete replacement of these complex systems in their entirety. Renewal, retrofit, and/or rehabilitation are typically the measures selected for the anticipated work. Even then, as illustrated in Table 2, in cases of certain large scale urban system renewal efforts, planners are more often than not dealing with billions of dollars and not necessarily with millions for the completion of a single rehabilitation or renewal program. Certainly, such costs are enough of a reason for the cancellation of any overly ambitious urban system renewal program and/or even result in the total postponement of a single rehabilitation project of great importance .

As an illustration of the remarkably high economic impacts that can be identified and associated with large scale urban earthquake hazards mitigation programs, the State of California is currently struggling with the problem on how to pay for the costs of a major state-wide program relating to improving the general seismic performance of seven major bridges. Work on the seven bridges is phased to start in 1997 and extend through 1999. Table 2 below indicates the estimated costs anticipated for completion of the scheduled work on the seven toll bridges. Based on these estimated costs, the State is now planning to build a new bridge for the eastern section of the SFO-Oakland Bay Bridge-rather than simply retrofit the existing eastern portion.

TABLE 2

ESTIMATED COSTS FOR SEISMIC RETROFIT OF SEVEN BRIDGES IN THE STATE OF CALIFORNIA
 

Name of Bridge:                           Estimate of Costs:*of Costs:*
 
 

SFO-Oakland Bay Bridge                          $1,216

San Diego-Coronado Bridge                           146

San Mateo-Hayward Bridge                                9

Benicia-Martinez Bridge                                    83

Richmond-San Rafael Bridge                           290

Carquinez Bridge                                               69

Vincent Thomas Bridge                                     42

Total Cost:                                                  $1,852*
 
 

*Note: In millions

SOURCE: Casciati, Lagorio, 1996
 

As indicated on an urban and regional scale, a significant concern exists in the capacity of key elements in the built environment and urban delivery systems to maintain, or regain as rapidly as possible, full operational and functional capacities during and after a seismic event. Within this setting, along with policy actions taken by local and regional government officials, the architect and urban planner have extremely important roles to play in assuming responsibility for seismic risk reduction.
 
 
 

EARTHQUAKE LOSS ESTIMATION STUDIES AND EARTHQUAKE HAZARDS MITIGATION PLANNING

In view of the major physical and economic losses generated by recent damaging earthquakes (1989 Loma Prieta earthquake: $9 billion, 1994 Northridge earthquake: $13-22 billion, 1995 Kobe earthquake: $30 billion), the development of earthquake hazards mitigation planning measures is most critical at all levels. In view of the large damage costs resulting from these three earthquakes, it is quite appropriate and legitimate to ask the question, "What levels of savings could have been realized if assigned mitigation plans had been in place and completed prior to these three earthquake events?" In the U.S., earthquake loss estimation modeling has become increasingly recognized as a useful tool in identifying, stimulating, and planning mitigation activities prior to a seismic event in order to diminish the impact of potential casualties and economic losses in the future.

A GIS-based regional earthquake loss estimation methodology has been developed in the U.S. on a national basis as a result of a coordinated four-and-a-half year project by the Federal Emergency Management Agency (FEMA) and the National Institute of Building Sciences (NIBS). The methodology incorporates state-of-the-art approaches for: (a) characterizing earthscience hazards, including ground shaking, liquefaction and landslides, (b) estimating damage and losses to buildings and CIS lifeline components, (c) estimating casualties, shelter requirements and economic losses, (d) projections of post-earthquake anticipated debris removal problems, (e) locations of hazardous materials release sites, and (f) data entry to support loss estimates. The FEMA/NIBS earthquake loss estimation methodology is intended primarily for use by state, regional, and community governments and planning officials.

On an urban planning level, it has the capacity to evaluate a wide range of losses resulting from scenario earthquakes to provide a basis for decisions concerning preparedness and disaster response planning and to stimulate and assist planning for mitigation to reduce potential future losses. It is implemented in a software package (HAZUS) which operates through MapInfo, a geographic information systems (GIS) application. (NIBS, 1997)

Users and Applications:

From an applications perspective, the FEMA/NIBS methodology through its HAZUS software has the potential of becoming a valuable integrating tool to bring together key State and local players, planners, and design professionals in a focused approach to risk assessment and mitigation. Because of its comprehensive base, it has an extraordinary range of potential applications for a wide range of users. However, it is important to recognize that while the HAZUS software program is a powerful tool for estimating potential losses from future earthquakes, the level of detail of analysis is directly related to the completeness of the existing building stock inventory and soil conditions data, and other variables. By design, HAZUS is a flexible, versatile decision-support tool that can be used by a variety of individuals and organizations for analyzing mitigation policies, programs, goals and options. (Durham, 1997)

It is quite clear that the FEMA/NIBS national earthquake loss estimation technology is intended primarily for use by state, regional, community governments and agencies in any part of the U.S. to provide a basis for decisions concerning mitigation planning, preparedness and disaster planning, and forecasting potential direct and indirect impacts on the economy as a whole. It is potentially of use to many other organizations as well. For illustrative purposes, Table 3 lists examples of some of the types of governmental agencies, departments, and other institutions that could find estimation results potentially useful in planning strategies and goals within their organizational capacities.

TABLE 3

LIST OF POTENTIAL USERS AT GOVERNMENT AGENCY AND DEPARTMENT LEVELS
 

Office of Emergency Services (OES)                                         Department of Public Works

Public Utility Commission                                                          Planning Commission

Transportation/Highway Departments                                        Housing Department

Department of Water Resources                                                Seismic Safety Commission

Building Department                                                                  Police/Fire Departments

Public Health Services                                                               Office of Public Education

Office of the Governor                                                              Community Services Dept.

Fiscal/Budget Planning Department                                           Assessors Office

Engineering/construction/Design Dept.
 

SOURCE: Earthquake Engineering Research Center (EERC) Library, UC Berkeley

At another level, earthquake loss estimates generated by the FEMA/NIBS methodology will play a significant role in the evaluation of alternate cost-effective approaches to the strengthening and retrofit of buildings identified as having a high vulnerability to seismic loads. In addition, other examples of potential applications include:

• Department of earthquake loss scenarios to illustrate the dimension and complexity of the local and regional exposure and risk to damaging earthquakes.

• Demonstration of costs and benefits, over time, of adopting and enforcing seismic building performance standards and implementation of other mitigation measures and policies.

• Provision of a basis for planning, zoning, building code regulations and policies that would reduce the risk posed by the effects of violent ground shaking ground failure.

• Generation of disaster response planning, post-earthquake recovery measures, and targets for long-term post-earthquake reconstruction goals and priorities.

ARCHITECTURE AND URBAN PLANNING RESPONSIBILITIES IN EARTHQUAKE HAZARD MITIGATION

As team members in the planning and design professions, architects and urban planners are directly responsible for actions and decisions taken in the planning and design of essential structures and civil infrastructure systems (CIS) in metropolitan centers located in zones of high seismically. For communities that do not have the foresight and capability to anticipate the issues and problems associated with earthquake hazard mitigation, the consequences are predictable and opportunities to design and build more safely are lost. As part of the equation, architects and planners must take advantage of such opportunities on a professional basis in addressing the consideration of seismic risk reduction measures.

There are several areas in the adoption of hazard mitigation efforts which require active participation of architects and planners, all of which are very important to activities related to either: (a) pre-earthquake preparedness planning initiatives, or (b) post-earthquake recovery and reconstruction projects. As indicated previously, the application and use of earthquake loss estimation modeling represent effective ways to identify, project, test, and prioritize specific mitigation policies and programs for their cost-effectiveness. Design professionals can use this methodology for analyzing potential programs and goals, and investigating options open to them during all planning and design phases. These specific areas of interest include, among others: (a) a full range of seismic programs in the strengthening and rehabilitation of existing buildings, (b) open urban space utilization objectives, (c) post-earthquake reconstruction goals, (d) physical land development planning provisions, and (e) disaster response and recovery measures. Details on the first three areas are analyzed and presented below. In the long run, as successful programs in these five critical areas have a potential of great benefit to society at large, the public itself will be the ultimate beneficiary.

Seismic Rehabilitation of Older, Existing Buildings:

Of the many earthquake hazard mitigation measures in existence, this one still remains the most elusive even today and requires constant attention as it is well known that any updated changes and adjustments to current building code performance requirements are not retroactive. In fact, after the 1994 Northridge earthquake, steel moment frame buildings were added to the list of potentially hazardous structures. Accordingly, the majority of older structures constructed over the years are still recognized as not meeting the seismic standards promulgated by current code levels of performance, which makes them quite vulnerable to earthquake risk.

Over the years, it has become clear that most of the casualties resulting from seismic activity around the world are, in fact, a result of the failure of older classes of buildings with unreinforced masonry, pre-1970 non-ductile concrete frame, and late 1960's pre-cast, prestressed structures being among the most vulnerable. It has only been during the last two decades that the problem associated with the seismic safety of older, existing buildings has been seriously addressed and codified. It is only recently in the U.S. that NEHRP provisions for the earthquake performance of existing buildings have been published on a national basis.

Currently, the rehabilitation and seismic upgrading of older, existing buildings is clearly recognized as one of the most critical areas of study in which the architect and design engineer have an important responsibility of joint interest. The economic feasibility of these retrofit programs is based on the assumption that it is possible to produce dramatic improvements in a structure's seismic performance on several levels.

In typical urban environments today, a basic rehabilitation problem confronted by design professionals is that many older, existing buildings are represented by structures of high architectural value. Many have a highly prized architectural heritage which can not be duplicated. The rehabilitation and renewal process also means dealing with the complexities of structural systems and the modeling of the mechanical behavior of materials of construction. An acute problem occurs when the historical and architectural value of these buildings is incompatible with strengthening interventions which can not be appropriately masked. Fortunately in the late 1980's, a new concept dealing with "structural control" systems was introduced.

Structural control systems are designed to dissipate energy in which a considerable reduction of spectral acceleration can be achieved. Various technological devices, passive and active, have been developed which allows the architect greater freedom in design options when dealing with retrofit strategies. Passive devices include base isolators and/or dampers as energy absorption or dissipation elements which can be used without destroying the architectural values of a building. More advanced techniques related to active and semi-active control systems are currently being investigated and tested wherein the external load acting on the structure would be balanced by the excitation of suitable external forces. An active control system would contain three elements: (1) sensors which measure the responses of the structure to external forces, (2) controllers to compute the necessary control forces from the information received from the sensors based on a control algorithm, and (3) actuators to generate the required forces. Hybrid systems combine active control with passive systems such as base-isolators. One of the main limitations of active control systems for large buildings currently under investigation is that the actuators need a large amount of reliable energy to move massive structures effectively. Studies are currently underway to determine the viability of such a system for use in the rehabilitation of existing buildings. (Casciati, Lagorio, 1996)

Open Urban Space Utilization:

This is a critical area in the disaster mitigation process that still requires intensive study by urban planners and architects. Immediately following a major damaging earthquake, confusion reigns as the forces of the immediate post-earthquake recovery process are called into action. During the emergency recovery period six days after the January 17, 1995 Kobe earthquake, a large number of families still continued to experience major disruptions to their life styles owing to the loss of their homes, their possessions, and their neighborhood. Up to 300 thousand people required temporary and/or emergency housing during this period. During the 1985 Mexico earthquake, in Mexico City itself, approximately 76,000 housing units were lost or seriously damage and left unoccupied. Under such conditions, open urban space as a refuge area commands a premium particularly if the seismic event is followed by conflagration as occurred in Kobe.

Within such earthquake recovery scenarios as described above, careful consideration must be given to the planning, design, and provision of emergency shelter, temporary housing, and neighborhood needs by city officials, architects, urban planners, and social scientists. In appropriate earthquake preparedness planning efforts, existing open urban spaces, including facilities such as public parks, large scale public parking lots, high school campuses, etc., must be targeted and made available for use. The pre-planned use of such spaces in high-density metropolitan centers has often been discussed, but except for the use of high school campuses, actual pre-event preparedness efforts in this direction have yet to take place objectively as far as actual implementation and action plans are concerned. Today more than ever because of our constantly growing populations in metropolitan centers, attention must be given to this oversight --- it is desperately needed as a part of any viable earthquake hazard mitigation effort. A clear-cut interdisciplinary investigation focusing on this problem must be given top-priority for fiscal support as an essential element of any earthquake preparedness planning endeavor proposed.

Post-earthquake Reconstruction Goals:

The immediate recovery period following a seismic event must be carried out as a short-term operation, but the reconstruction period after a major damaging earthquake should be given careful consideration as a constructive long-term process. The entire scope of urban planning and design goals and objectives requires attention at this point and short cuts avoided. Housing patterns, civil infrastructure systems renewals (transportation, lifeline utilities, communication components, etc.), land development upgrades, open urban space needs, local and regional government facilities, social centers, --- in short, to be successful as a long-term earthquake mitigation act, all the elements that are essential to the societal and living aspects of a sustainable urban environment must be examined as part of a conscious effort by the public, government officials, private industry, and all planning and design professionals. Architects and urban planners must be expected to play an important role in this aspect

Because local and regional planning must include consideration of natural disasters and prescribe physical, economic, social, and administrative strategies and programs for their mitigation, the events following a major earthquake (e.g., such as the 1994 Northridge earthquake) are a measure of the effectiveness of existing plans and policies. Important considerations for future plans and policies are the activities during and after the event, including; the impact on the lives of the area's inhabitants; the informal responses as well as those that were planned; and finally, the long-term consequences for commerce and culture. The soundness and relevance of the planning that follows an earthquake will be measured by its capacity to minimize future human tragedies, reduce property damage, and lower the obstacles to recovery. (Kreditor, 1990) The most important post-earthquake reconstruction goal to achieve is to provide a more earthquake resistant environment rather than continue the vulnerability aspects of a status quo position.

CONCLUSION

This technical paper was developed with the purpose of allowing a wider group of individuals to participate as part of an interdisciplinary team of planning and design professionals in the effective results of earthquake mitigation efforts at international levels. It is sincerely hoped that the ability of the individual to use the information presented in this report will accommodate incentives to explore alternatives, examine the effectiveness of new initiatives in earthquake hazard reduction plans and policies, and undertake innovative studies to reduce the damage caused by major seismic events.

ACKNOWLEDGEMENTS

The author acknowledges the support and assistance given by Dr. Shih Chi Liu, Program Director, Earthquake Hazard Mitigation Program, National Science Foundation.

References: