Question

Discuss the relationship of hydrogeology with fault and fold. Sketch the possible drilling location (14 marks)

Answer 1

HYDROGEOLOGY

Groundwater is the main source of water supplies in the study area. The occurrences, distributions, and
quality of groundwater aquifers controlling by different factors such as structures, geomorphology,
climate changes, type of rocks and minerals. Groundwater occurs under semi-confined to confined
conditions in fractured crystalline gneisses and charnockites in the study area.

the interaction between the
water resources and faults with the intention of identifying faults based on the effects of this inter-relation and their impacts on water resources. The research was conducted in the Lar valley located in the northeast of Tehran, the capital of Iran. The results indicate the influence of faults on 60% of Lar valley’s rivers as well as on the quality of Sefidab River. The location of 57.5% of the springs was also influenced by the fault’s actions and the change in the height of wellspring from 2500 to 3800 was attributed to the fault’s impact. 32.5% of the springs were of karstic, while 54% were of contact and 46% of overflow type, originating from the limestone (karstic), sandstones, siltstones, shale, tuff and volcanic rocks as well as he quaternary sedimentations. The water quality of most springs is thought to be influenced by faults. The results of this research complement the previous methods and they can be applied in addition to other procedures in similar cases to identify faults having an impact on surface or ground water resources.

Tectonics and the two important parameters of faults and folds affect the surface and ground water resources. The study of the evidence of tectonic impact on water resources can lead to the identification of the factors and their characteristics

Mountain Mountain Old Fan Fault Young Fan Fault Old Fan Young Fan A Figure 2- The alluvial fans impacted by fault. A is alluvial fan deposited adjustment to Mountain (active fault with rapid deformation). B is alluvial fan that deposited in Mountains down (Normal case) (After Keller 1986) It is also said that the action of overthrust or reverse faults on river slope is such that in active faults the height of basin increases with the rapid deformation and the main river