When a disaster occurs, professional emergency managers are responsible for implementing plans and procedures designed to lessen the impact of the disaster agent. During a disaster, information must be assimilated under conditions of stress. This stress can cause decision-makers to overlook necessary procedures or choose irrational courses of action. During this time period rapid access to data and procedures presented in an easy to understand format can help ameliorate the problem. In this respect, the complex structure of a disaster situation necessitates the use of a decision support system rather than a management information system. DSS can provide detailed models to assist the decision-maker and has three components:

• A database management system
• A model base management system
• A dialogue management system

n Additional note: As a decision aid, the system can be designed to enhance data display by representing the data in the form of representations (i.e. road maps, evacuation routes, etc.) as well as in list or tabular form. In addition, an algorithm can be developed to assist the manager in assigning response resources to demands.n

The database of the DSS will contain information about the disaster situation, for example,

• What resources are needed depending on location, weather conditions, population affected, type of damage etc.?
• What resources are available to respond? (personnel file, shelters file, food resources file, equipment file, health-care resources file)
• What is the current weather? What is the earthquake risk? (geographic file)
• What is the risk of damage in case of an earthquake? (geographic file, building file, population file)
• How many hospitals are available in the region? (facility file)
• What are our emergency personnel and their qualifications? (staff file)

The capability of the system to provide for data retrieval, data display and modelling of both the potential impacts of a disaster and "optimal" ways to respond, enables the emergency manager to obtain relevant data in a timely fashion and in formats conducive to understanding.

Data may be processed statistically to provide information useful in arriving at useful decisions, a data analysis capability, which is often used to define the earthquake risks. Making queries is possible via dialogue management system of the DSS. The modelling components are controlled by the model base management system, which utilises the data in the database of DSS. Statistical models, OR models, simulation and many other modelling tools can be used in the model base management system.

Although DSS technology is expensive, the functions it serves are of such importance that the costs of using the technology would be far outweighed by the consequences of incorrect decision or ineffective action. This is obvious from our experience of the August 17, 1999 earthquake. The main problem of not being able to coordinate the resources could possibly be solved by a DSS. If we could have known the available resources in each city, we could find the nearest cities to help the disaster area. Building files could show which buildings must have possibly been collapsed. Facility files could show the nearest hospitals and their capacities.

Most decisions in disaster management are made in a highly uncertain environment. Since uncertainty decreases our ability to structure the decision process, "what if" type analysis is crucial. The relative infrequency of disasters means that past experiences are of limited use for planning future responses. This is because of the fact that the destructiveness of an earthquake depends on many factors, like the population distribution in the area, frequency and intensity of earthquakes, building characteristics in the region, etc. Therefore, disaster management is an unstructured problem and DSS is the most suitable tool for these kinds of problems. For example, maintaining inventories of response resources is a structured task, but how to evacuate an urban area is not as structured and needs a "what if" type analysis.