Abstract

In order to retrieve a 2D background velocity model and to retrieve the geometry and depth of shallow crustal reflectors in Southern Apennines thrust belt a separate inversion of first arrival travel times and reflected waveforms was performed.
Data were collected during an active seismic experiment in 1999 by Enterprise Oil Italiana and Eni-Agip using a global offset acquisition geometry. A total of 284 on-land shots were recorded by 201 receivers deployed on a 18 km long line oriented SW-NE in the Val D’Agri region (Southern Apennines, Italy).
The two steps procedure allows for retrieval of a reliable velocity model by a non-linear tomographic inversion and reflected waveform semblance data inversion.
The tomographic model shows that the P wave velocity field varies vertically from about 3 km/s to 6 km/s in less than 4 km from the earth surface. Moreover at distance of about 11 km along the profile, there is an abrupt increase in the velocity field. In this zone, indeed, a rise up of the 5.2 km/s iso-velocity contour can be noted from 2 km depth to 0 km above the sea level. The retrieved velocity can be associated with Plio-Pleistocene clastic deposits outcropping in the basin zone and with Mesozoic limestone deposits. The inversion of waveform semblance data shows that a P-to-P reflector is retrieved at depth of about 2 km. This interface is deeper in the north eastern part of the profile, where it reaches 3 km depth and can be associated with a limestone horizon.

 

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