SOURCE PARAMETERS OF JABALPUR EARTHQUAKE OF 22 MAY 1997

摘要

A moderate earthquake occurred in the morning of 22 May 1997 close to Jabalpur town in Madhya Pradesh. The earthquake records of seismological observatories maintained by India Meteorological Department were analysed to obtain source parameters. Of these, ten observatories in the Indian Peninsula have recently been upgraded with equipment of the Standard of Global Seismograph Network. The upgraded observatories recorded ground velocity in broad frequency band and also the ground acceleration in digital mode. The high quality digital data have especially been processed to obtain both kinematic and dynamic source parameters. The basic source parameters are - Origin time: 04 h 21 m 30.8 s (IST), epicentre: 23 degrees 0.8N, 80 degrees.06E, focal depth: 35 km, magnitude: 6.0. The focal depth of this earthquake could be clearly obtained using depth phase sPn in filtered waveforms. The first motions of P wave were used to obtain the focal mechanism. The first motion of P waves at the upgraded observatories were obtained through filtering and their amplitudes are also used to evaluate the focal mechanism. The focal mechanism solution was obtained as: Strike direction N90 degrees E, dip 66 degrees and slip angle 66 degrees. This is a thrust type fault with left lateral strike slip component. The study of amplitude spectra of S wave from upgraded observatories gave seismic moment (M-0) of 5.4 x 10(24) dyne.cm and radius of circular fault, 3.2 km. These results gave an average dislocation as 37 cm. [References: 17]