Estimation of earthquake source parameters in the Kachchh seismic zone, Gujarat, India, using three component S-wave spectra

Abstract

Earthquake source parameters and crustal $$Q_{0}$$ values for the 138 selected local events of ( $$\hbox {M}_{\mathrm{w}}{:}2.5{-}4.4$$ ) the 2001 Bhuj earthquake sequence have been computed through inversion modelling of S-waves from three-component broadband seismometer data. SEISAN software has been used to locate the identified local earthquakes, which were recorded at least three or more stations of the Kachchh seismological network. Three component spectra of S-wave are being inverted by using the Levenberg–Marquardt non-linear inversion technique, wherein the inversion scheme is formulated based on $$\omega ^{2}$$ source model. SAC Software (seismic analysis code) is being utilized for calculating three-component displacement and velocity spectra of S-wave. The displacement spectra are used for estimating corner frequency (in Hz) and long period spectral level (in nm-s). These two parameters play a key role in estimating earthquake source parameters. The crustal $${Q}_{0}$$ values have been computed simultaneously for each component of three-component broadband seismograph. The estimated seismic moment ( $$M_{0}$$ ) and source radius (r) using S-wave spectra range from 7.03E+12 to 5.36E+15 N-m and 178.56 to 565.21 m, respectively. The corner frequencies for S-wave vary from 3.025 to 7.425 Hz. We also estimated the radiated energy ( $$E_{S}$$ ) using velocity spectra, which is varying from 2.76E+06 to 4.07E+11 Joules. The estimated apparent stress drop and static stress drop values range from 0.01 to 2.56 and 0.53 to 36.79 MPa, respectively. Our study also reveals that estimated $$Q_{0}$$ values vary from 119.0 to 7229.5, with an average $$Q_{0}$$ value of 701. Another important parameter, by which the earthquake rupture process can be recognized, is Zuniga parameter. It suggests that most of the Kachchh events follow the frictional overshoot model. Our estimated static stress drop values are higher than the apparent stress drop values. And the stress drop values are quite larger for intraplate earthquakes than the interplate earthquakes.