Estimation of velocity perturbations using amplitude and phase fluctuations for earthquakes recorded at Gauribidanur Seismic Array in southern India

Abstract

The Chernov medium approach has been applied for analysie of 24 earthquakes recorded at Gauribidanur Seismic Array (GBA) in southern India. Correlation coefficients of log-amplitude and phase fluctuations between every possible pair of seismometers are used to determine the correlation length of the medium. The Chernov theory can be well applied for the observed P-wave velocity perturbations at 0.5 Hz. Thus, the average correlation length for the Gaussian correlation function is determined to be about 18 km. The estimated velocity perturbations for GBA are around 1.4 % - 2.3 %, which is slightly greater than the corresponding estimates by previous workers for the array while the extension of the medium is around 660 km. The scattering coefficient under GBA at 0.5 Hz is 9.0 - 22.7 × 10-4 km-1. The Born approximation condition is violated for frequencies higher than 0.5 Hz due to the strong scattering coefficient for the region under GBA.