GNGTS 2014 - Atti del 33° Convegno Nazionale

124 GNGTS 2014 S essione 3.1 In τ - Γ domain the FDS-RT code from ProMAX gives a better vertical resolution than our FDS-RT code, while the latter gives a better horizontal resolution than the former. We tested also the standard parabolic and hyperbolic Radon transform code from ProMAX. Fig. 2c shows the demultiple result by using our FDS-RT code while Fig. 2d to Fig.2f show the demultiple results by using ProMAX. From Fig. 2d we see that FDS-RT from ProMAX is less suitable for multiple attenuation because most of the multiple energy remains. The parabolic and hyperbolic Radon transform from ProMAX (Figs. 2e and 2f, respectively) can attenuate multiples quite efficiently but they create some artifacts, in particular between 2 s and 4 s, which over-impose to the primaries between 3 s and 4 s. These artifacts, which are stronger in the hyperbolic case, can cause difficulties in the seismic data interpretation. The FDS-RT code written by us (Fig. 2c) is slightly less efficient in multiple attenuation compared with the standard parabolic or hyperbolic Radon transform from ProMAX, especially at far-offset, but very few artifacts can be observed. Indeed in Fig. 2c the multiples appear well attenuated and the primaries between 3 s and 4 s can be clearly seen. Both our FDS-RT code and the standard parabolic Radon transform code are less efficient in demultiple at the end points when there is an abrupt ending of the multiples in the seismogram. Real data application. We used both our FDS-RT code and the standard parabolic Radon transform code from ProMAX to attenuate the multiples in a real marine data. Fig. 3a shows the marine data. Muting, bandpass filtering (3-12-60-95 Hz), NMO correction and spherical divergence correction have been applied to the data by using ProMAX. The data is made by 154 traces. The offset ranges from 375 m to 4200 m. The maximum time is 5500 ms. The time sampling rate is 4 ms. The water bottom is at about 1.5 s. Fig. 3 shows the seismic data in the time window [1200 ms, 5500 ms]. The data are muted at time lower than 2.8 s before forward Radon transform. Fig. 3 – a) Real marine data. Muting, bandpass filtering (3-12-60-95 Hz), NMO correction and spherical divergence correction have been applied to the data. b) Our FDS-RT code applied to the data in (a). c) The standard parabolic Radon transform from ProMAX applied to the data in (a).