عنوان مقاله [English]
نویسنده [English]چکیده [English]
Geomagnetic observatories are constructed to continuously record the earth’s geomagnetic field. The importance of such buildings has resulted in an increasing construction of geomagnetic observatories all over the world. Although geomagnetic observatories are sometimes unknown to most people and even some scientists, these very important data centers have been measuring the geomagnetic field for about 500 years. The number of standard observatories is now approaching 150, but there are still very few standard geomagnetic observatories in the Middle East. Despite the large area of Iran, Tehran geomagnetic observatory is the only observatory in the country. It was constructed by the Institute of Geophysics in 1961. Unfortunately, in the recent decade, due to the old instruments used in this observatory and considering the expansion of Tehran city, the data obtained at this geomagnetic observatory are subjected to many noise sources. Therefore, its data are not reliable anymore and Tehran observatory is removed from the list of world’s standard geomagnetic observatories. In this paper, which is aimed as an informative research note, the necessity of constructing new geomagnetic observatories in Iran is discussed from various aspects. The most important advantages of constructing a geomagnetic observatory include: providing a data center for the correction of magnetic exploration data, prediction of magnetic storms and providing a constant monitoring of the geomagnetic field variations as one of the probable earthquake precursors. Considering the various advantages of continuous recording of the earth’s geomagnetic field, it is completely necessary to construct new geomagnetic observatories in Iran. The first step to construct a standard geomagnetic observatory that can record highly reliable data, is to select an optimum area for the construction of the observatory. From the very early observations of the geomagnetic field, it was understood that the observatories must be far enough from natural fluctuations resulted from volcanic rocks or mineral deposits. It was also discovered that artificial noises can disturb the data recorded in a geomagnetic observatory. However, there is still no comprehensive report discussing the various criteria to be studied while selecting a site for the construction of these observatories. This paper presents different parameters that should be carefully investigated to select optimum sites for the construction of geomagnetic observatories. Considering the type of data that should be recorded in geomagnetic observatories, knowledge of the criteria affecting the geomagnetic data is critical. Various criteria such as the magnetic intensity, variations of the electrical conductivity of subsurface soils, artificial sources of geomagnetic changes, development of cities, geology, topography, access roads, and underground possible economical deposits can affect selection of the optimum sites for the construction of geomagnetic observatories. Keeping a proper distance away from magnetic anomalies and controlling the homogeneity of the electrical conductivity of subsurface soils fall among the most important factors to be considered at the first stage. Then, artificial sources of the geomagnetic disturbance and urban development patterns must be carefully considered. It should be noted that finding the areas that can fully satisfy all the criteria might be impossible, but the minimum requirements should be satisfied to construct an observatory. Closure or relocation of several geomagnetic observatories all over the world is an experience showing how carefully the site selection of these structures should be carried out. Having understood the necessity of constructing new geomagnetic observatories in Iran, Kerman Province is considered as one of the favorable areas for the construction of an observatory. A comprehensive research is being carried out by authors to carefully acquire and interpret all the required data to find the best sites for this purpose.