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Seismogram Envelope Inversion Using a Multiple Isotropic Scattering Model: Application to Aftershocks of the 2001 Bhuj Earthquake

¹ National Geophysical Research Institute
Hyderabad 500007, India
 (S.P.)
² Department of Geophysics and Geology
University of Leipzig
D-04103 Leipzig, Germany
 (U.W., M.K.)

We apply the energy transfer theory of 3D multiple isotropic scattering to analyze seismogram envelopes of the 2001 Bhuj earthquake of India. We synthesized the S-wave coda envelopes by using a numerical Monte Carlo method. Our model is described by total scattering coefficient g, intrinsic absorption coefficient b, spectral source energy S, and site factors Z. Isotropic source radiation and acoustic wave propagation were assumed. We inverted the observed coda envelopes of 10 aftershocks (M_L 4) using the grid search for g, least-squares inversion for b, and S between 1 and 24 Hz. Parameter g does not show significant frequency dependency and averages to 0.01 1/km. This corresponds to a mean free path of 100 km. Parameter b shows weak frequency dependency, increasing with frequency. Its value ranges from 0.02 1/sec to 0.05 1/sec. Consequently, the frequency dependency of intrinsic attenuation takes the power-law form of Q_i(f) = 280f^0.72. The source energy is largely consistent with the well-known ²-source model and the seismic moment is comparable to estimates using standard empirical relations between seismic moment and local magnitude. We also inverted the envelopes for site-amplification factors Z. The values of Z range from 0.5 to 1.75 with no clear frequency dependence, which is consistent with the geology of the region, as the stations were deployed on hard- rock sites.

This article has been cited by other articles:

				S. Padhy Characteristics of Body-Wave Attenuations in the Bhuj Crust Bulletin of the Seismological Society of America, December 1, 2009; 99(6): 3300 - 3313. [Abstract] [Full Text] [PDF]

				S. Padhy Inversion of Seismogram Envelopes Using a Multiple Isotropic Scattering Model in Garhwal Himalaya Bulletin of the Seismological Society of America, April 1, 2009; 99(2A): 726 - 740. [Abstract] [Full Text] [PDF]