The sensitivity of the intraplate Kachchh Rift Basin, NW India to the direction of incoming seismic waves of teleseismic earthquakes

The dynamic stresses generated during the passage of surface waves perturb most major plate boundaries and active volcanic/geothermal regions. The present investigation aims to understand and find evidence for dynamic triggering in the intraplate Kachchh Rift Basin, northwestern India. We analysed the local earthquake catalogues and waveforms of 36 teleseismic earthquakes with M-w >= 7.5, which occurred between 2007 and 2017 and generated peak dynamic stresses of at least 1 kPa. The study manually examines the waveforms 24 hr before and after the teleseismic P wave and detects missing earthquakes by applying the matched filter technique. Notably, the analysis reveals that 6 out of 36 earthquakes (17 per cent of the analysed earthquakes) are responsible for triggering non-volcanic tremors or microearthquakes during the passage of surface waves and later. Although the triggering potential in the region seems insensitive to the amplitude of dynamic stresses imparted by the teleseismic surface waves, the direction of the incoming waves appears critical. The surface waves of events whose backazimuths are parallel to the strike of the active faults are capable of triggering. The triggered earthquakes lie along the Kachchh Mainland Fault, North Wagad Fault and South Wagad Fault, in the vicinity of the epicentre of the 2001 January 26, M-w 7.7 Bhuj earthquake. The largest triggered event of magnitude 3.2 occurred similar to 7 hr after the 2009 October 7, M-w 7.7 Vanuatu event.