Seismic characterization of the Quaternary sediments at Llancanello Lake Area

CARCIONE, J.; DE LA VEGA, M.; OSELLA, A.; TASSONE A.; POSCOLIERI, M.

JOURNAL OF SEISMIC EXPLORATION

GEOPHYSICAL PRESS

Lugar: Paris (Francia); Año: 2013 vol. 22 p. 1 - 17

0963-0651

A preliminary near-surface seismic reection study was carried out data at Llancanelo-Lake Area with the aim of mapping the quaternary layers. A petro- elastical model has been obtained by interpreting the events of a common-shot gather. Expressions of the traveltimes of the direct and refracted waves versus o_set provide alternative evaluations of the velocities of the layers and thickness of the upper layer. An interface has been found approximately between 54 and 56 m depth. The P- and S-wave velocities of the shallow layer is 2000 and 600 m/s, according to the slopes of the direct and Rayleigh waves, while the lower layer has a P-wave velocity of 2800 m/s, obtained from the refracted event. A tentative interpretation of the apex of a reection event locates the top of the basalt layer at 190 m depth approximately. A viscoelastic model is obtained by assuming Poisson layers and quality factors of typical volcaniclastic sediments. We then compute a synthetic common-shot gather and snapshots by means of full-wave pseudospectral methods. The synthetic gather resembles the real one, providing additional support of the interpretation. Furthermore, the standard processing sequence is applied to the data to obtain a stacked section. This procedure reveals the location of deeper interfaces, although the process is highly a_ected by the _ltering of the direct and refracted events, which have the same slope of the medium- and far-o_set reection signals.