Rayleigh / Love Wave Discriminant for Events in and around Pakistan Region, using VMAX Technique

Discrimination between earthquakes and nuclear explosions is an important topic among the seismologists. Beside the famous (Ms: mb) relation, in which Rayleigh waves of 20 sec period is used, the comparison of filtered Love and Rayleigh surface wave magnitudes at variable periods (08 sec to 24 sec) is getting importance. In present study, the broadband data of NIL seismic station (located at Nilore, Islamabad, Pakistan) for the Earthquakes has been used to check the effectiveness of the discriminant involving only surface wave amplitudes (filtered Love and Rayleigh wave). The method works by taking the maximum amplitudes (VMAX) at variable periods. Earthquake data of 10 years (2014 to 2023) at NIL station has been analyzed for shallow events (depth ≤ 30 km) within five regions including Pakistan, India, Iran, Afghanistan and China. Total of 349 earthquake events with magnitude 5.0 or higher has been studied. For the earthquake cases, 86.4% to 94.4% (average 89.4%) cases are discriminated as Earthquakes. Most dominating periods in most of the regions were found to be 16 sec to 18 sec for both Love and Rayleigh waves. For explosions Chinese, North Korean, Indian and Pakistani cases have been studied at different international stations (Varying epicentral distances). From 98 cases 86.6% cases are discriminated well as explosions. For implementation of method and results, a computer code has been developed in Python using available ObsPy modules. Results authenticate our code and provide information for further regional studies.