Archaeological investigations at Tepe Hissar-Damghan using Gravity and Magnetics methods

Research and exploration of the remaining relics from the past has special importance in identifying the date, history and the identity of a country. Development and the advancement of human knowledge have offered new methods for the detection archaeological sites that by using them without the need for excavation and destruction of antiquities can be found useful information. Today, the non-destructive geophysical methods such as gravimetry and Magnetometry used to detect the archaeological discoveries without harmful environmental effects that only use natural properties of the subsurface material. For archeology studying, the target is detection of sub-surface structures which was made in the enceint. But here it’s posible was coverd by some overburden such as alluvium.The gravity method is based on density contrast between the anomalous body (walls and chambers) and the host deposites and environments of them. While, in magnetic survey we use contrast of magnetization in between the environment and anomalous bodies, which is caused by natural factors or human activities such as metal products, building materials and cavities are filled. In this paper; to investigate the subsurface structures of walls and rooms in a part of the Teppe-Hissar archaeological site in Damghan, the gravity and magnetic data were used. In order to this work, the gravity and magnetic data measured in a regular grid in the desired area and then after do corrections such as instrument drift correction, free air and slab Bougure, latitude and terrain corrections on gravity data and the daily correction and Reduction to pole (RTP) correction on the magnetic data, the gravity and magnetic anomalies map were obtained. When the data quality permits, a range of highpass filters, such as downward continuation or vertical derivatives, can be applied to bring out fine detail. Also, In order to separate the residual anomaliy from regional we used trend surface method. Local phase filters provide an alternative approach but conventional phase functions need to be unwrapped to remove phase ambiguity. Therefore, detection of the boundary of chambers or walls and the horizontal location of sources can be obtained from derivative based filters such as the horizontal gradient magnitude, tilt-angle, theta-map, Laplacian and tangent hyperbolic. since the tilt angle is based on a ratio of derivatives, it enhances large and small amplitude anomalies well. The results show that the tilt angle is effective in balancing the amplitudes of the different anomalies, but it is not primarily an edge-detection filter. The theta map uses the analytic signal amplitude to normalize the total horizontal derivative. The amplitude of the response of this filter from the deeper and shallow source bodies is similar, although the response from the deeper bodies is rather diffuse. The hyperbolic tilt angle (HTA) filter uses of the real part of the hyperbolic tangent function in the tilt angle calculation achieved better delineation of the edges of the anomalous body than the other filters we use here. The maximum value of the HTA gives location of the body edges. Normalized Derivatives Ratio (NDR), a new edge-detection filter, is based on ratios of the derivatives orthogonal to the horizontal of the field. The NDR is demonstrated using synthetic and real gravity and magnetic data from an archaeology site, Tepe-Hissar. Compared with other filters, the NDR filter produces more detailed results as can see that the separation and detection walls and chambers have a high compliance with the results of excavations carried out. The results of these methods with the results of excavations carried out in the last few decades are highly adaptable, as it can be, according to the results of drilling, subsurface structures such as streets, walls or houses on the data obtained by gravity and magnetic survey. The information and data from these methods in an ancient area can be used as a basic plan by archaeologists for the archaeological exploration and excavation depth of field.