Tectonic Evidence of the Tigris River Derived from Potential Data in Wasit and Salah Al-Din, Iraq

The Tigris River in central Iraq is closely associated with the tectonic activity. This paper combines gravity and magnetic data to explore the river path related faults. The magnetic data was processed by reduction-to-the-pole algorithm to emphasize structural edges and tectonic lineaments, and a total horizontal derivative filter. Gravity data were processed in a similar way to detect lateral density contrasts and shallow subsurface structures. The results identified four main faults. Local displacements of the river channel due to a transverse fault (Fault 1) affect the deviation of the Tigris River in Salah Al-Din city, penetrate the basement, and cause a sharp eastward shift in the river’s direction. Fault 2 is a basement fault with north-south strikes and crosses Fault 3. Fault number three runs east–west, and its location coincides with a fault previously identified in the literature as the Kut fault. This fault has a significant impact on the river’s eastward course. It intersects with fault number two in the southern part. This fault was identified using gravity and magnetic data, indicating its extension within the sedimentary cover and basement rocks. Fault number four runs parallel to fault number three, and together the two faults form two parallel strike faults that cause movement of the rock mass within the Tigris River’s course in that region. Results of the study indicate that there is a direct relationship between the sharp and significant changes in the course of Tigris River in Salah al Din and Wasit Governorates with the subsurface tectonic structure, especially faults. Combined with gravity data, magnetic data has been a valuable aid in identifying regional and local faults that influence the course of the river.