Analysis of Spatial Distribution and Mechanism of Formation of Fissures due to Land Subsidence in Dasht-e-Neyshabur

In many plains in Iran, including those in Dasht-e-Neyshabur in Northeast of Iran, the dangerous phenomenon of subsidence has occurred. The main source of water supply in this plain is groundwater resources. Due to over-exploitation of groundwater resources, land subsidence has occurred and tension Fissures and splits have appeared on the surface in different parts of this plain. The main purpose of this research is to analyze the distribution and mechanism of Fissures formation caused by land subsidence. Using Sentinel 1 satellite sensor data, the land subsidence range in this plain was investigated, and using Quick Board and Sentinel 2 sensor data which have high spatial resolution, the Fissures in subsidence zone were determined. Then, during field observations, the existence and position of these Fissures were verified and, using GPS, full coordinates of the Fissures including 25.5 km of continuous and discontinuous Fissure and 181 Fissures were mapped and a map from the plain’s Fissures was drawn. In addition, the possible and covered Fissures in different areas of the plain were studied and identified in the maps. Geo-electric data from the plain and the condition of bedrocks were analyzed based on conceptual models of Fissure formation. Based on the investigations and taking into account the geometric shape and condition of the plain and its subsurface, it can be said that: the mechanism of the mechanical-based model, the mechanism of aquifer materials’ heterogeneity as well as tension stretch mechanism, are the most important mechanisms in the Fissure formation in Dasht-e-Neyshabur.