Application of data fusion methods of index overlay, Dempster Shafer and fuzzy AHP in geothermal resources potential mapping and their prioritization in Zanjan Province

In spite of the occurrence many evidences that indicate several rich regions of the geothermal resource in Iran, very few exploration studies have been carried out so far specially in Zanjan province that have a lot of hot springs and other relevant evidences. Geothermal heat flux is one of the main parameters to be investigated in geothermal exploration programs but few direct heat flux measurements are available in Iran. We can get reliable and better result by using all exploration criteria related to the geothermal resources such as lithological, remote sensing, structural and geophysical information layers, if we use a suitable method to overlaying and fusion these layers. In this study we firstly use index overlay and fuzzy methods for overlaying these data and the DS-fuzzy AHP technique is then used for data fusion and prioritizing of the results.

 Methodology and Approaches:

 In the first step, relevant digital information layers were prepared. They comprised of lithology layer, alteration layer obtained from ASTER data, structural layer acquired from lithology, ASTER and airborne magnetic data. Then, Curie depth, thermal gradient and thermal flow maps were obtained using a set of high resolution airborne magnetic data. All of these layers were then integrated by fuzzy logic and index overlay methods to determine the promise regions of geothermal resources. Finally, the favorable geothermal areas, obtained in the previous stage, were prioritized using DS-FAHP fusion method. 

Results and Conclusions

By examining and evaluating the results and considering the existing evidences such as hot water springs, it is found that the data fusion DS-fuzzy AHP methods can provide an acceptable and reliable results. Moreover, the prioritization of the results using these data fusion methods indicates that high potential geothermal regions are related to all the evidences of geothermal resources. The obtained results also show that by applying fuzzy AHP for weighting exploration layers, one can consider uncertainty in decision making, and then, by using DS method for data fusion more reliable results can be acquired.