Velocity/interface model building in a thrust belt by tomographic inversion of global offset seismic data

Abstract

Between September and November 1999, two test seismic lines were recorded in the southern Apennine region of southern Italy using the global offset technique, which involves the acquisition of a wide offset range using two simultaneously active seismic spreads. One consisted of a symmetrical spread moving along the line, with geophone arrays every 30 m and a maximum offset of 3.6 km. The other one consisted of fixed geophone arrays every 90 m with a maximum offset of 18 km. This experimental acquisition project was carried out as part of the enhanced seismic in thrust belt (ESIT) research project, funded by the European Union, Enterprise Oil and Eni‐Agip. An iterative and interactive tomographic inversion of refraction/reflection arrivals was carried out on the data from line ESIT700 to produce a velocity/interface model in depth, which used all the available offsets. The tomographic models allowed the reconstruction of layer interface geometries and interval velocities for the target carbonate platform (Apula) and the overburden sequence. The value of this technique is highlighted by the fact that the standard approach, based on near‐vertical reflection seismic and a conventional processing flow, produced poor seismic images in both stack and migrated sections.