The analysis of the spatial structure of Qom metropolis with emphasis on the formation of sub-cores

Among the patterns of building a city, a , polycentric cities pattern of larger cities is true, as experience has shown that smaller cities, especially historic cities, often have a metropolitan core, usually located in the central geometric and historical boundaries of the city. This is due to the physical development of large cities towards the periphery, urban sub-centers, and the city’s multi-core spatial structure gradually emerges. The present paper aims to identify the evolution of the spatial structure of the metropolis of Qom from the viewpoint of the nuclei and urban centers, especially in the last three decades. The idea of this research was that the specific characteristics and functions of the city prevented the city from becoming a part of the city’s central depopulation, as compared to other similar cities. For analyzing data, quantitative methods including general G and LISA statistics, standard deviation and kernel density functions have been used in Arc Gis 10.3 software. The results of the research show that the metropolis of Qom despite its special religious features and its second rank in the religious cities of the country after the holy Mashhad, like many other major Iranian-Islamic cities, have been shown to accelerate urbanization and the physical and diffuse development of urban texture during the year. From 1986 to 2016. During this process, the central part of the city still retains many of its functions, and despite the relative burnout and physical barriers and constraints, it is now considered to be the most important urban core in the metropolis’s spatial structure. Consequently, the metropolis of Qom is rapidly increasing due to the rapid increase in population and extent (horizontal expansion), as well as the formation of some urban centers, nodes and sub-centers, although it is changing to several cities, but because of specific religious features and Its extensive functions in the central part of the city are still known as a Single-core city dominated by the city’s historical core.