Introduction
Due to the large number of injured people after disasters, most hospitals and medical centers do not have enough capacity to provide services to them. In addition, in disasters such as floods and earthquakes, most hospitals and medical centers located in the affected regions are often destroyed and become impossible to use. Therefore, the establishment of mobile medical units, which are known as field hospitals, can partially solve the lack of capacity and the inability to provide local medical services. However, it should be noted that field hospitals are useful if they become available and on-site within the first days after the disaster to prevent high casualties and carry out rescue operations faster with better quality. Another important point is the location of field hospitals. The time of transferring the injured from the affected areas to these facilities increases, If they are built at a far distance from the affected areas, which can increase the casualties. Therefore, this study aims to determine the appropriate location of field hospitals. The main questions in this paper are as follows:
• How many field hospitals are needed in Amol city and where should they be established?
• How to use the available resources to provide medical services to more people?
• How much is the effect of the budget on the quality of services provided to the injured people?

Methods
This paper provides a mathematical modeling of the problem of selecting location for field hospitals and allocation of resources after the earthquake. In this regard, we used the real data of Amol City located in Mazandaran province, Iran, to evaluate the proposed model. After collecting the required data, the proposed model was implemented in GAMS 25.1 optimization software and with the GUROBI solver. 

Results
Field hospitals include different types, three of which are: tent, container, and a mix of both. The main differences between these hospitals are the cost of their construction and their capacity (number of beds). This article assumed the first, second, and third types of field hospitals had 30, 60, and 90 beds, respectively. The optimal place for constructing a field hospital was Banafsheh Park, and this field hospital should be of the second type (container).
Conclusion
Nowadays, the world is facing an increase in the number and variety of disasters due to climate, biological, and technological changes. Among the challenges that arise after a disaster, the selection of a optimal location for field hospitals and proper allocation of medical resources are of great importance. For this purpose, an integer programming model was proposed in this study with various constraints, including constraints in the budget for the construction , the capacity of hospitals to admit victims, the number of ambulances, the number of medical staff, and the amount of available medications. The results of this study can help medical centers to make the best decisions regarding how to use their limited available resources after a disaster.

Ethical Considerations

Compliance with ethical guidelines
All ethical principles were observed in this study . All participants were informed about the study objectives and methods.

Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors

Authors' contributions
All authors equally contributed to preparing this article.

Conflicts of interest
The authors declare no conflict of interest.

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