Investigating the land subsidence in the Semnan province Plains using Differential SAR Interferometry (Case study: Damghan plain)

In this research a Differential SAR Interferometry method was used to investigate
land subsidence in the Damghan plain of the Semnan Province. Deformation maps
of the study area were generated and the subsidence rate was determined over a 3-
year period. The high risk of subsidence was observed at twenty locations in the
Damghan plain. This shows the distribution of threat level in the aquifers of the area
in which water supply wells are located. The subsidence zones are associated with
the center and the north of the study area (Damghan plain and Chardeh plain) where
the density of the Qanat systems and water supply wells are very high in
comparison to other areas. From geodynamical point of view, the study area is
highly susceptible to subsidence due to the presence of unconsolidated deposits and
the Quaternary alluvial deposits. The results further show that the water extraction
in significant quantities in the limestone rocks from the outer boundary of the
Damghan city to Solh Abad caused a reduction in pore-water pressure and an
increase in the effective stress in this formation. This caused an increase in
lithostatic pressure to the aquifer matrix, causing the aquifer matrix to compact.
Consequently, this resulted in a considerable subsidence in these zones. Most
probably, low rainfall in the province, especially in recent years and excessive and
sometimes illegal extraction of groundwater resources are the main cause of
subsidence in the study area. The results show that the Differential SAR
Interferometry can be used as an effective tool in predicting the subsidence
phenomenon at various plains in Iran.

Investigating the land subsidence in the Semnan province Plains using Differential SAR Interferometry (Case study: Damghan plain) Keywords:

Subsidence , Interferometry , Remote Sensing , Groundwater , Damghan plain , Differential interferometric SAR