Seismic characterization of the Quaternary sediments at Llancanello Lake Area

CARCIONE, JOSÉ; DE LA VEGA, MATIAS; GEI, DAVIDE; OSELLA, A.,; TASSONE, ALEJANDRO; POSCOLIERI, M.

JOURNAL OF SEISMIC EXPLORATION

GEOPHYSICAL PRESS

Lugar: Benahavis; Año: 2013 vol. 22 p. 1 - 17

0963-0651

 A preliminary near-surface seismic reflection study was carried out at Llancanelo-Lake Area with the aim of mapping the quaternary layers. A petro-elastical model hasbeen obtained by interpreting the events of a common-shot gather. Expressions of thetraveltimes of the direct and refracted waves versus offset provide alternative evaluationsof the velocities of the layers and thickness of the upper layer. An interface hasbeen found approximately between 54 and 56 m depth. The P- and S-wave velocitiesof the shallow layer are 2000 and 600 m/s, according to the slopes of the direct andRayleigh waves, while the lower layer has a P-wave velocity of 2800 m/s, obtainedfrom the refracted event. A tentative interpretation of the apex of a reflection eventlocates the top of the basalt layer at 190 m depth approximately. A viscoelastic model surface 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 offull-wave pseudospectral methods. The synthetic gather resembles the real one, providingadditional 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 affected by the filtering of the direct and refracted events, which have the same slope of the medium- and far-offset reflection signals.