Computing field statics with the help of seismic tomography

Journal Article · Thu Oct 01 04:00:00 EDT 1987 · Geophys. Prospect.; (United States)

DOI:https://doi.org/10.1111/j.1365-2478.1987.tb00849.x· OSTI ID:5602380

De Amorim, W N; Hubral, P; Tygel, M

Field static corrections in general need be applied to all onshore seismic reflection data to eliminate the disturbing effects a weathering layer or near-surface low velocity zone has on the continuity of deep seismic reflections. The traveltimes of waves refracted at the bottom of the low velocity zone (or intermediate refracting interfaces) can often be observed as first breaks on shot records and used to develop a laterally inhomogeneous velocity model for this layer, from which the field static corrections can then be obtained. A simple method is described for computing accurate field statics from first breaks. It is based on a linearization principal for traveltimes and leads to the algorithms that are widely and successfully applied within the framework of seismic tomography. The authors refine an initial model for the low velocity layer (estimated by a standard traveltime inversion technique) by minimizing the errors between the observed first arrivals on field records and those computed by ray theory through an initial model of the low velocity layer. Thus, one can include more lateral velocity variations within the low velocity layers, which are important to obtain good field static corrections. Traditional first break traveltime inversion methods cannot, in general, provide such refined velocity values. The technique is successfully applied to seismic data from the Amazon Basin. It is based on a simple model for the low velocity layer that consists of an undulating earth surface and one planar horizontal refractor overlain by a laterally changing velocity field.

• Research Organization: Petrobras, Cenpes/Divex/Segef, Cidade Universitaria Quadra 7, Ilha do Fundao, Rio de Janeiro
• OSTI ID: 5602380
• Journal Information: Geophys. Prospect.; (United States), Journal Name: Geophys. Prospect.; (United States) Vol. 35:8; ISSN GPPRA
• Country of Publication: United States
• Language: English

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