Hydrogeological Studies to Identify the Trend of Concealed Section of the North Tabriz Fault (Iran)

Abstract

The North Tabriz Fault (NTF) is the predominant regional-scale tectonic structure in the northwest of Iran. In the east side of the city of Tabriz, a portion of the fault trend has been completely concealed by recent sediments and urbanization. In this paper, some hydrogeological methods are used to locate the concealed sector. As is clear from the pumping tests results, despite the fact that the northern observation wells were closer to the pumping wells than the southern ones, they have not been affected by pumping. Conversely, all southern wells were affected by pumping and displayed decline of the water table. In addition, obvious differences in groundwater levels combined with clear differences in groundwater quality within a short distance across the probable fault trend are sufficient reasons for the presence of the fault that behaves as a barrier to groundwater lateral flows. Significant change in the elevation of the bedrock base of the aquifer over less than 200 m suggests that the fault has near vertical dip. These results indicate that the inferred trend of the NTF closely conforms to its actual trend. Therefore, the hydrogeological studies can be complementary tools to determine the position and trend of concealed faults.

Conjoint use of hydraulic head and groundwater age data to detect hydrogeologic barriers

“…One represents a barrier that fully penetrates the entire depth of the aquifer, and the other a fault or dyke that has been overlain by younger, undeformed (or unintruded), sediment (e.g. Rajabpour and Vaezihir 2017). Two alternative spatial patterns of recharge were applied and the simulations with a barrier were compared to those for the baseline case.…”

“…Smerdon and Turnadge (2015) used numerical modelling to demonstrate that a difference in hydraulic head of up to 50 m could be attributed to the presence of hydrogeologic barriers. Some examples of the observed change in hydraulic head across barriers include: approximately 5-10 m in Iran (Rajabpour and Vaezihir 2017); approximately 20-60 m in Germany (Gumm et al 2016); and over 80 m in California, USA (Mayer et al 2007).…”

“…Analytical and numerical methods have illustrated discrete barrier features that displace and widen solute plumes (Sebben and Werner 2016). Field studies demonstrate the relevance of geochemical data, such as ratios of magnesium to calcium in groundwater (Valdes et al 2007), and discontinuities in total dissolved solids (Rajabpour and Vaezihir 2017), to map fault properties. Geochemistry can also infer connectivity between aquifers separated by horizontal flow barriers (Apaydin 2010); however, most previous studies are conducted with knowledge of the approximate location of the fault, with geochemistry refining fault properties.…”

The Effect of Undetected Barriers on Groundwater Drawdown and Recovery

“…Where the effect of a barrier during pumping is insignificant, other methods are required to detect its presence. These might include surface or aerial geophysics (Ball et al 2010;Vittecoq et al 2015), geochemistry and environmental tracers (Toutain and Baubron 1999;Umeda and Ninomiya 2009;Pereira et al 2010;Rajabpour and Vaezihir 2016;Sun et al 2018), and lineament analysis (Sander et al 1997;Tam et al 2004). Analysis of the prepumping potentiometric surface might also provide information on the existence of barriers to flow (Bense et al 2003;Seaton and Burbey 2005), although often bore networks are sparse in areas that are not affected by groundwater pumping.…”