We geodetically investigate the interseismic deformation along two neighboring sections of the Dead Sea Fault in Israel and present first clear evidence for shallow creep along this fault. We obtain the velocities of near‐fault GPS campaign stations across the northern section of the Jordan Valley Fault (JVF) and the Jordan Gorge Section (JGS) that were surveyed each year between 2009 and 2015. The JVF extends from the northern shore of the Dead Sea to the eastern shore of the Sea of Galilee, and the JGS extends from the Sea of Galilee to the Hula Basin. We infer a slip rate of ~4.1 mm/yr and a locking depth of ~10 km for both sections. Data analysis indicates that while the JGS is found to be fully locked above the locking depth, the northern section of the JVF is found to be creeping from a depth of 1.5 ± 1.0 km to the surface, with a creep rate of 2.5 ± 0.8 mm/yr. Our observations also suggest that the current slip rate of the fault at the western margin of the Jordan Valley is minor, less than the GPS velocities uncertainties.

[1] High time resolution monitoring of radon (= 222 Rn) in three boreholes, 4, 10 and 53 m deep, along a 0.6 km transect is carried out in massive granite in southern Israel. Three components of variation occur in the measured signal (MS) -seasonal radon (SR -periodic), multiday (MD), and daily radon (DR -periodic). Temporal variation of the components suggests an association between the overall level of the long-term variation and the amplitude of the daily variation. The daily mean level of radon and the daily standard deviation vary periodically throughout the year. Time offsets occur among time series of the MS and were investigated also for the MD and DR components, using consecutive 20-day intervals spanning +900 days. The resulting time series show that systematic time offsets occur, whereby the radon signal always occurs first at the easternmost site. The MD shows a gradually varying lag of 0-12 h, and the DR a stable 1-3 h lag. Spectral analysis shows that diurnal (24-h) and semidiurnal (12-h) periodic components characterize the DR. The amplitudes of these components exhibit regular temporal variation having a seasonal pattern. The ratios of co-occurring amplitudes of these components define a linear pattern indicating a fundamental statistical property in the frequency domain of the radon time series. The results indicate that unrecognized dynamic processes are driving the radon signal in the subsurface regime of the pluton, suggesting new prospects for radon behavior in the frame of interacting geodynamic (tectonic?) and Earth-Sun system related processes.

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S U M M A R YRadon is a naturally occurring radioactive noble gas generated within mineral grains of uranium bearing rocks by alpha decay from radium. The Amram tunnel (A. Bloch Geophysical Observatory) is a particularly suitable location for the investigation of radon variability. Located in the arid environment of the Arava desert, near Elat, the 170 m tunnel that constitutes the observatory enables radon monitoring in a desert environment and under fairly stable environmental conditions. The analysis of the temporal variability of continuous measurements of radon and environmental parameters at the Amram tunnel over a period of several years shows a complex temporal pattern characterized by non-stationary and multiscale features. Radon concentrations exhibit multiyear variability in the form of a increasing trend of ∼1000 Bq m −3 yr −1 in the mean and much larger trends up to ∼2500 Bq m −3 yr −1 in the maximum radon levels. Radon concentrations also display strong seasonal patterns, with maxima in summer and minima in winter, ranging from 2.5 kBq m −3 in winter to 35 kBq m −3 in summer. Intraseasonal variability is characterized by very large radon anomalies, with sharp increases of more than 20 kBq m −3 relative to the base level, that occur in spring and summer and last for several days. Daily periodic variability with maxima around midnight appears also in spring and summer, being absent in the cold months. Radon variability at seasonal, intraseasonal and daily timescales is associated with the air temperature outside the tunnel, specifically the temperature gradient between the external environment and the more stable environment inside the tunnel where the measurements are performed.

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