Empirical scaling relationships between earthquake magnitudes, epicentral distances and amplitudes of radon anomalies in N-W Himalaya

Radon data accumulated during the time-window (1992-1999) in the grid (30-34°N, 74-78°E) in N-W Himalaya has been analysed vis-a-vis seismic data recorded in the same area, supplied by Indian Meteorological Department (IMD) network. In general, there is a positive correlation between total radon emission and the micro-seismicity in the area under investigation. The earthquake magnitude has moderate positive correlation with epicentral distance and low positive correlation with amplitude of radon precursory signal, whereas, both show low negative correlation between them. Empirical scaling relations are proposed using the best-fit straight line from the log-linear graphs between magnitude of the events (M) and log of the product of amplitude of radon anomaly (A) and epicentral distance (D). The error between recorded and the calculated magnitude is also taken into account. The number of points lying within ′ 25 % limit is 74 out of the total 142 cases, on which the test is applied. The error range is higher at lower epicentral distances and magnitudes, which shows that, the local geology and tectonics have predominant influence on radon signals.