INTERNATIONAL SYMPOSIUM ON INFORMATION TECHNOLOGY IN OCEANOGRAPHY (ITO-98)

GOA, INDIA 12-16 OCTOBER 1998

Seismic tomography of oceanic crust: data acquisition processing and modelling

Yu.P.Neprochnov, B.N. Grinko
Shirshov Institute of Oceanography,
Moscow, Russia

2D and 3D Seismic Tomography (STOM) techniques using Ocean Bottom Seismometers (OBS) spacing 10 to 20 km and 30 L airgun shots spacing 150 or 300 m was developed and applied for detailed study of the oceanic crust. More than 500 OBS installations were executed from 1976 for 2D STOM in ocean basins, mid-oceanic and aseismic ridges, fracture zones, marginal seas. 3D STOM experiments were,made initially 1988-1.989 in the Bering Sea Murray F.Z.,East Mariana Basin and Central Indian Basin 40x40 Km grids by geophysical survey at 2OOx200 Km area gridercom by passing the area of interest . Array of OBS was used for acquisition refraction and wide-angle reflection data along done grid of profiles. Near-vertical reflections were collected simultaneously by hydrodrophone streamer and digital tape recorder.

Main procedures of data analysis include processing of near-vertical reflection data, digitising of OBS analogue records, correction of airgun OBS distances using water-wave OBS digital processing of records resulted in seismic record sections, travel time plots and preliminary ID velocity models and 2D cross-sections. Trial-and-error computer modelling was applied to construct final 2D and 3D images of the crust. Results from Central Indian Basin and East Basin are presented to illustrate the processing and modelling of STOM data, which have revealed the detailed inhomogeneity of the oceanic crust. The work is Partly supported by Russian Science Foundation (Grant 97-05-64304).

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