Land subsidence pattern controlled by old alpine basement faults in the Kashmar Valley, northeast Iran: results from InSAR and levelling

SUMMARY

Fluid storage systems, such as oil, gas, magma or water reservoirs, are often controlled by the host rock structure and faulted terrain. In sedimentary basins, where no direct information about underlying structure is available, the pattern of ground deformation may allow us to assess the buried fault arrangement. We provide an example in the semi-arid area of Iran, in the Kashmar Valley, a region subject to land subsidence due to water overexploitation. Geodetically determined subsidence rates in the Kashmar Valley exceed 15–30 cm yr⁻¹. The pattern of surface deformation is strongly non-uniform and displays NE–SW elongated bowls of subsidence. The trend resembles old Cretaceous-to-Tertiary faults that evolved during early alpine tectonic deformation. Although these early alpine structures are considered tectonically inactive in the present day, the observed land subsidence pattern indicates significant structural control on the geometry of the aquifer basin and its deformation during reservoir drainage.