Radioactivity monitoring in the vicinity of Jawalamukhi thrust NW Himalaya, India for tectonic study

Abstract

This work reports radon-thoron monitoring at two depths (60 and 90 cm) and at 82 sites around Jawalamukhi thrust of NW Himalaya, India using Solid State Nuclear Track Detectors (SSNTDs). Further, radium contents of soil samples have been measured using NaI(Tl) crystal detectors and the exhalation rates have been measured using SMART Rn Duo monitor. The average radon-thoron concentrations at two different depths are found to be 3043 $\pm$ 691 Bq m⁻³, 4969 $\pm$ 561 Bq m⁻³ & 448 $\pm$ 416 Bq m⁻³, 773 $\pm$ 117 Bq m⁻³. Average value of area exhalation rate found to be 299.9 $\times$ 10⁻³ Bq m⁻² h⁻¹ with radium contents of value 51.04 Bq kg⁻¹. The convective velocity of radon-thoron along with their flux densities has also been calculated. The average magnitudes of flux densities for radon-thoron found to be 44.96 $\times$ 10⁻² Bq m⁻² s⁻¹ and 15.57 $\times$ 10⁻² Bq m⁻² s⁻¹ whereas the convective velocities calculated to 8.38 $\times$ 10⁻⁶ m s⁻¹ and 25.69 $\times$ 10⁻³ m s⁻¹. The recorded values of thoron are lower than the recorded radon values. Moreover, the value of radon and thoron is higher at depth 90 cm than at depth 60 cm. The anomalous radon-thoron concentrations have been observed along the Jawalamukhi thrust and at some other sites suggesting secondary porosity or presence of local fault/lineament. A good correlation between area exhalation rates and radium contents, as well as between mass exhalation rates and radium has been observed. However weak correlation between porosity and area exhalation rates has been observed in this region.