Fault Determination Due to Sinkhole Array on the Kabudar-Ahang Plain of Hamedan, Iran

Tectonic structures, especially faults, play an important role in the formation and spread of sinkholes and Karst. The main aim of this paper is to identify active faults in the north region of Hamedan province of Iran (Kabouda-Aahang, Razan and Famenine) through sinkhole array and chemical analysis of water. A lot of sinkholes have been created in the north of Hamedan. Most of these sinkholes are located in underground discharge areas near limestone of Oligo-Miocene age. The analysis of hydrogeological and hydrological conditions in the recent years showed that the conditions were suitable for sinkhole to form and develop. The presence of CO 2 and H 2 S gases with a lot of amount in underground water, due to the rise of gases from hydrothermal and pneumatolytic resources, resulted in acidity of underground water and finally the acidic water rises to the enclosed aquifer through underground faults and fracture systems, leading to dissolution of limestones, and provide the ground for sinkhole formation. The sinkhole array in the region of the study showed that their formation and location are influenced by active faults in the region. As a result, a number of karst features such as sinkholes, caves, gully and karst spring have been formed in the north of Hamedan due to performance of active faults. Based on field visits, the review of aerial photo, chemical analysis of region water and dispersion of sinkholes, two faults with NW-SE, NE-SW trend were identified. Based on the evidence, it is assumed that formation and spread of sinkhole in the study area are controlled by active faults and vice versa the activity of faults may be determined by the formation and array of sinkholes and karst gully.