كليدواژه :
باستان سنجي , گراني و مغناطيس سنجي , بارزسازي لبه , فيلترهاي فازي , تپه حصار
چكيده فارسي :
كاوش در آثار به جاي مانده از گذشتگان داراي اهميت ويژه اي در شناسايي تاريخ و هويت يك سرزمين دارد. پيشرفت دانش بشري روش هاي نويني در شناسايي مكان هاي باستاني ارائه داده است كه با استفاده از آن‌ها بدون نياز به حفاري يا تخريب آثار باستاني به اطلاعات مفيدي مي توان دست يافت. امروزه از روش هاي ژئوفيزيكي غيرمخربي مانند گراني سنجي (Gravimetry) و مغناطيس سنجي (Magnetometery) كه تنها از خاصيت هاي طبيعي و ذاتي مواد زيرسطحي بهره مي‌برند، در اكتشافات باستان-شناسي استفاده مي شود. در گراني سنجي از تباين چگالي بين ديواره‌ها و اتاقك ها استفاده مي شود. درحالي‌كه در روش مغناطيس-سنجي از تباين مغناطيدگي (Magnetization) موجود بين اجسام آنومال و محيط پيرامون ناشي از عوامل طبيعي و يا فعاليت هاي بشري نظير اقلام فلزي، مصالح ساختماني و حفره‌هاي پرشده استفاده مي شود. در اين مقاله سعي شده است با استفاده روش هاي گراني سنجي و مغناطيس سنجي به شناسايي ساختارهاي زيرسطحي در قسمتي از محوطه باستاني تپه حصار دامغان موسوم به پهنه سفال منقوش، پرداخته شود. به اين منظور در يك شبكه منظم مربع‌مستطيلي داده هاي ميدان گراني و مغناطيس در محدوده مورد نظر برداشت شد و پس از تصحيحات لازم روي داده هاي گراني و مغناطيس مانند رانه دستگاه، تصحيح هواي آزاد، تخته بوگه، توپوگرافي و اصلاحات روزانه، نقشه آنومالي هاي گراني و مغناطيس تهيه گرديد. بر اساس اين نقشه ها موقعيت و محدوده ديواره ها و اتاقك هاي باستاني شناسايي گرديد. سپس با استفاده از فيلترهاي روند سطح، مشتق قائم اول و فازي اثر ميدان ناشي از آثار باقيمانده از ناحيه اي تفكيك شد. نتايج حاصل از بررسي هاي انجام شده داده هاي گراني و مغناطيس در شناسايي ساختارهاي زيرسطحي مانند ديواره ها و اتاقك ها انطباق بالايي با نتايج حاصل از كاوش هاي انجام شده در دهه هاي گذشته دارد. با توجه به اينكه عمليات كاوش به روش حفاري هزينه بر، وقت گير و از همه مهم‌تر امكان آسيب رساندن به سازه هاي قديمي را در بردارد، با استفاده از نتايج بررسي‌هاي غيرمستقيم ژئوفيزيكي مي توان يك طرح كلي براي كاوش هاي باستان شناسي به‌وسيله حفاري طراحي و اجرا نمود تا آثار زيرسطحي كمتر آسيب ديده و حفريات هدفمند باشند.
چكيده لاتين :
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.
