GNGTS 2017 - 36° Convegno Nazionale

562 GNGTS 2017 S essione 3.1 Kirchhoff integral solution to scalar wave equation (using both near-field and far-field terms; Berryhill, 1984) can provide a basis computation to deal in the datuming with irregular surfaces and variable velocities (Wiggins, 1984; Bevc, 1997). In the pre-stack domain, we applied WED in two steps: i) common-source and ii) common-receiver domains. Operating on a common-source gather, it has the effect of extrapolating receivers from one datum to another, and, because of reciprocity, operating on a common-receiver, gathers it changes the datum of the source. Details about this method can be found in Giustiniani et al. , (2015) and references therein. We applied WED utilizing a Seismic Unix package (SU), a free software developed at Colorado School of Mines integrated by home codes. AfterWED and the application of a gap deconvolution, we interactively performed a velocity analysis for dynamic corrections and residual statics applications. After stack, we applied fx- deconvolution and a time-variant trace mixing to enhance identified signals, Finally, a post- stack Kirchhoff time-migration, computed reducing and smoothing stack velocities and limiting the aperture (the maximum angle was restrained to 30°), and a time-variant filter completed the processing. Fig. 1 shows the migrated seismic section PN, while Fig. 2 illustrates the section PS. Thin lines overprinted on seismic data connote horizons marking structural trend. Discussion and conclusion. SIRIPRO profile has documented a major tectonic stacking operating in northern Sicily. Crustal inhomogeneity and/or fragmentation of the foreland plate appear to have strongly controlled orogeny developed with an arcuate frontal shape, i.e. the thinned crust of Central Sicily Basin and the two blocks represented by western platforms system and eastern Hyblean Plateau, each intruded by magmatic products. The application of the WED allowed improving signal to noise ratio and preserving reflections amplitudes, let us differentiate seismic facies, offering a direct image of ongoing tectonic setting and of variable lithology and ������������� ���������� �������������� ����������� petrophysical ���������� �������������� ����������� properties characterizing distinctive nature of central Sicily crust. �������� ��� ��� ������� ������ ����� �� �������������� ���� Clearly, the new seismic images allow an interpretation that differs in some points from earlier published reconstructions ( Accaino et al., 2011; Catalano et al., 2013). In the following the main results of this study: 1. Sicily belongs to the north African margin, a mosaic of structural blocks inherited from Permian, Late Triassic-Lias and Cretaceous extensional episodes, progressively disrupted during Late Cretaceous and Tertiary; 2. migrated sections underline continuity of high amplitude horizons within middle-lower Hyblean crust (Fig. 2) that we guess it should derive from re-crystallization of magmatic rocks and thermo-metamorphic phenomena with a possible layering of sub-horizontal sills fractured and filled by hydrothermal minerals. The data confirm that Hyblean crust remarkably thins towards the Caltanissetta trough; 3. post-nappe sub-thrust duplexes occurred in northern Sicily, where major tectonic stack operated on the construction of a wide anticline (Figs. 1 and 2). A southward push of Tyrrhenianmantleandasthenosphereandaprogressivenorthwardmigrationof contraction tectonics during late Pleistocene have accompanied the chain uplift. ��������� ��� Analyzing the seismic facies, the presence of shallow water carbonates platforms covering the basement in the PN section remains questionable, but possible (see �������� Basilone et al. , 2016)� ������� , whereas this presence can be very likely excluded within the deep Caltanissetta trough and over the Hyblean platform. Mostly debatable the existence of an allochthonous Hyblean platform; 4. deformation processes involvedmultiple deep detachment planes and a passive deepening of the detachment surfaces down to decoupling levels located near the crust/mantle transition, supporting a presence of high-density lenses beneath the chain, interrelated to Tyrrhenian mantle activity (Fig. 1). The correlation with offshore deep seismic profiles may help to fix markers associable to the base of the Tyrrhenian crust or to the African mantle roll-back and to lithospheric faults accommodating the lateral escape of tectonic blocks;