Spatial distribution of scatterers in the crust by inversion analysis of coda envelopes: A case study of Gauribidanur seismic array (Southern India)

Abstract

The 3-D spatial distribution of relative scattering coefficients in southern India was estimated by means of an inversion technique applied to coda wave envelopes. The inversion analysis was performed for the first time in this kind of seismological research by means of the simultaneous iterative reconstruction technique and filtered backprojection method. Whereas the first one allows to obtain more exact solutions, the second one is a much faster non-iterative algorithm that has proved to provide very accurate reconstructions. Data used consisted of selected 636 vertical-component, short-period recordings of microearthquake codas from shallow earthquakes with magnitudes ranging from 0.7 to 3.7 and epicentral distances up to 120 km recorded by the Gauribidanur seismic array (GBA). Results are almost independent of the inversion method used and they are frequency dependent. They show a remarkably uniform distribution of the scattering strength in the crust around GBA. However, a shallow (0-24 km) strong scattering structure, which is only visible at low frequencies, seems to coincide with the Closepet granitic batholith which is the boundary between the eastern and western parts of the Dharwar craton. © 2006 The Authors Journal compilation © 2006 RAS.