GNGTS 2014 - Atti del 33° Convegno Nazionale

20 GNGTS 2014 S essione 3.1 been obtained which is of about 60% with the same results of a careful manual cleaning of the spikes. The main sequences of seismic data elaboration, applied in the multichannel seismic data processing are here also described. There are three main phases, i.e. the deconvolution, the stacking and the migration. A set of auxiliary processes has been added to these phases in order to improve the seismic signal. While for the main phases it is important to maintain a specific processing sequence, for the auxiliary processes the commutative property is valid, such as the order of phases is not important. The seismic signal is recorded in a digital format and then is subject to a discrete sampling during the time. The format is convenient for the recording, but not for the data elaboration. It is necessary to order another time the points of sampling in a trace-sequence way (demultiplexing). All the points of sampling related to each single trace are grouped. The format in which the data are converted is the SEG standard format (Society of Exploration Geophysicists). The most used versions are the SEG-Y and the SEG-D formats. The SEG-D is characterized by a greater flexibility of use. It allows to order the data both in a multiplexed and in a demultiplexed modality and has been projected in such a way to satisfy the increase of the quantity of data for record. Once upon a time the data have been demultiplexed, they must be elaborated in such a way to remove the kill traces. The kill traces eliminated are those ones including no information or that ones with monocyclic waveforms caused by electronic interferences (a sinusoidal wave shape with a constant amplitude and wavelength) or that ones with an excessive noise. The editing consists of the cleaning of the dataset to improve the quality of the remaining data. The data, such as they are recorded, may include a certain quantity of noise, due both to instrumental and environmental factors. In our specific case, the bad quality may be linked to a set of causes mainly due to problems related to the energization or to the seismic cable or to noises due to the instruments of recording. For what concerns the problems of energization it must be verified the possibility that some shots are lacking in energy or that some replies having a low intensity (autopop) have been produced, which are added to the main pulse. The phenomenon of the autopop must be eliminated during the phase of elaboration with techniques similar to that ones used during the removal of the multiple reflections. The Salerno Valley, bounding the southern sector of the Sorrento Peninsula, represents an useful laboratory for the study of submarine instabilities related to tectonically-controlled slopes. The individuation of the valley and the activity along the rocky slope bounding it are related to the regional normal or strike-slip fault (Capri-Sorrento fault) bounding southwards the Meso-Cenozoic structural high Capri-Sorrento Peninsula. The Salerno Valley is represented by a deep WSW-ENE trending depression, limited northwards by the normal faults down throwing the Mesozoic carbonates of the Sorrento Peninsula and filled by a Plio-Quaternary sequence thick up to 3300 m (Mina 1 well; Agip, 1977). Multibeam bathymetric survey has evidenced the high steepness of the slope and the occurrence of strong erosional processes, partly active, where a dense network of channellised erosional morphologies has been detected. The analysis of seismic reflection profiles has evidenced the tectonic activity of the fault slope as a triggering cause for gravity instability processes during the Late Pleistocene – Holocene. This has been evidenced also by slumping deposits, characterized by a chaotic seismic facies, interstratified in the distal filling of the Salerno Basin. On the contrary in the distal areas of the valley, where the deposition prevails, the shallower sector appears in intense erosion (Salerno canyon) and shows recent tectonic deformations, as antiformal structures and high angle normal faults, interpreted in the regional geological framework as hints of a strong extensional tectonics, lasted up to recent times. A three-dimensional restitution DTM (Digital Terrain Model) covering an area of 1600 square kilometers extending from north-west to the southern slope of the Capri island to south-east to the Sele river mouth has been produced (Fig. 1). The geologic interpretation of Multibeam bathymetry has evidenced a pronounced asymmetry of the continental shelf proceeding from north to south, reflecting the different structural domains