Observations on the spatio-temporal patterns of radon along the western fault of the Dead Sea Transform, NW Dead Sea

Abstract

An extensive radon anomaly is developed along the western boundary fault of the Dead Sea Transform in the NW sector of the Dead Sea, extending 15–20 km north-south. The highest radon values occur in proximity to the fault scarp. Radon is measured, in gravel (depth 1.5–3 m) at sites located at a) on-fault positions, 1–30 meters east of the fault scarp, and b) off-fault positions located 600–800 the east. Prominent signals occur in the annual and daily periodicity bands, as well as non-periodic multi-day variations (2–20 days). Modulations occur among the annual variation and the multi-day and the daily signals, and between the multi-day and the daily signal. Dissimilar variation patterns occur at on-fault versus off-fault sites in the time domain, and in the relative amplitude of the daily periodicities. Variation patterns and their modulations are similar to those encountered in experimental simulations. It is concluded that: 1) above surface atmospheric influences can be excluded; 2) a remote above surface influence probably drives the periodic components in the annual and diurnal bands; 3) diurnal as well as the multi-day signals are modified and inter-modulated by near field geological (static) and geophysical (dynamic) influences. Systematically different influences are operating at on-fault versus off-fault positions, So far the natures of these near field influences are unidentified.