Radon emanation along the Dead Sea transform (rift) in Jordan

Abstract

Radon emanations were sampled during summer and winter along the active faults of the Dead Sea Rift, which consists of three segments: the Wadi Araba in the south, the Dead Sea in the middle and the Jordan Valley in the north. In Wadi Araba, radon emanations were measured in three sites in gravel: two sites across the left lateral active strike slip fault zone and one site across the normal boundary fault. The highest values across the strike slip fault (maximum of 3,300 Bq/m3) were measured at the fault planes, while the lowest (minimum of 400 Bq/m3) were measured outside the fault zone. Across the normal boundary fault, higher concentrations (2,700 Bq/m3) were measured at the junction between the mountain front and the alluvial fan (where the eroded fault scarp is located). East of the Dead Sea, radon was measured in Quaternary evaporates and alluvial deposits. High concentrations were measured on the main topographic scarps, which formed as a result of normal faulting. In this area higher radon emanation indicates the presence of faults. In the area of the Jordan Valley, radon was sampled in highly fractured evaporates across the active strike slip fault. Higher concentrations (maximum of 1,940 Bq/m3) were measured at the fault planes, while lower concentrations (minimum of 570 Bq/m3) were measured at the non-deformed beds between the fault planes. Generally, summer readings are higher than winter readings due to the attenuation effect by pore water during the wet season.