ARTICLE

Seismic characterization of the Quaternary sediments at Llancanelo-Lake area, Argentina

JOSÉ M. CARCIONE1 MATÍAS DE LA VEGA2 DAVIDE GEI1 ANA OSELLA2 STEFANO PICOTTI1 ALEJRO TASSONE3 MAURIZIO POSCOLIERI4
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1 Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Borgo Grotta Gigante 42c, 34010 Sgonico, Trieste, Italy. jcarcione@inogs.it,
2 Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires - IFIBA Conicet, Ciudad Universitaria, Pab. 1, 1428 Buenos Aires, Argentina. osella@df.uba.ar,
3 INGEODAV, Departamento de Ciencias Geologicas, FCEyN, Universidad de Buenos Aires , Argentina.,
4 IDASC, Institute of Acoustics and Sensors “Orso Mario Corbino”, Research Area of Rome Tor Vergata, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.,
JSE 2013, 22(1), 1–17;
Submitted: 16 July 2012 | Accepted: 5 November 2012 | Published: 1 February 2013
© 2013 by the Authors. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution -Noncommercial 4.0 International License (CC-by the license) ( https://creativecommons.org/licenses/by-nc/4.0/ )
Abstract

Carcione, J.M., de la Vega, M., Gei, D., Osella, A., Picotti, S., Tassone, A. and Poscolieri, M., 2013. Seismic characterization of the Quaternary sediments at Llancanelo-Lake area, Argentina. Journal of Seismic Exploration, 22: 1-18. A preliminary near-surface seismic survey was carried out at Llancanelo Lake (Argentina) with the aim of mapping the quaternary layers, composed of sedimentary layers overlying basalt. A geological model has been obtained by interpreting the events of a common-shot gather. Expressions of the traveltimes of the direct and refracted waves versus offset provide means to evaluate the velocities of the layers and thickness of the upper layer. Moreover, the standard processing sequence is applied to the data to obtain a stacked section. This procedure reveals the location of deeper interfaces, although it 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. The fact that the direct arrival has not a zero intercept time indicates the presence of a very thin layer at the surface(shallow salt deposits), Further evidence of the near-surface layer is that the refracted and reflection events are ringing and there are strongly dispersive Rayleigh waves. An interface has been found approximately between 54 and 57 m depth. The P- and S-wave velocities of the shallow layer are 2000 and 550 m/s, according to the slopes of the direct and Rayleigh waves, 0963-0651/13/$5.00 © 2013 Geophysical Press Ltd. 2 CARCIONE ET AL., respectively, and rock-physics empirical relations, 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 reflection event locates the top of the basalt layer at 190 m depth approximately. A viscoelastic model has been defined, with 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 to the interpretation.

Keywords
processing
modeling
waves
interpretation
References
  1. Carcione, J.M., 1992. Modeling anelastic singular surface waves in the Earth. Geophysics, 57:781-792.
  2. Carcione, J.M., 2007. Wave Fields in Real Media. Theory and numerical simulation of wavepropagation in anisotropic, anelastic, porous and electromagnetic media, 2nd ed. ElsevierScience Publishers, Amsterdam.
  3. Carcione, J.M., Helle, H.B., Seriani, G. and Plasencia, M.P., 2005. On the simulation ofseismograms in a viscoelastic Earth by pseudospectral methods. Geophys. Internat., 44:123-142.de la Vega, M., Lopez, E., Osella, A., Rovere, E.J. and Violante, R.A., 2011. Quaternarystratigraphy and evolution of the Llancanelo lake region (Southern Mendoza, Argentina)evidenced from geoelectric methods. Submitted to Quatern. Res.
  4. Dziewonski, A.M. and Hales, A.L., 1972. Numerical analysis of dispersed surface waves. In: Bolt,
  5. B.A. (ed.), Methods in Computational Physics, Vol. 11. Academic Press, New York.
  6. Gil, A., Zarate, M. and Neme, G., 2005. Mid-Holocene paleoenvironments and the archeologicalrecord of southern Mendoza, Argentina. Quatern. Internat., 132: 81-94.
  7. Greenhalgh, S.A. and King, D.W., 1981. Curved raypath interpretation of seismic refraction data.Geophys. Prosp., 29: 853-882.
  8. Hunter, J.A., Burns, R.A., Aylsworth, J.M. and Pullan, S.E., 2000. Near-surface seismic-reflectionstudies to outline a buried bedrock basin in eastern Ontario. Geological Survey of Canada,Ottawa.
  9. Mavko, G., Mukerji, T. and Dvorkin, J., 1998. The Rock Physics Handbook: Tools for Seismic
  10. Analysis in Porous Media. Cambridge Univ. Press, Cambridge.
  11. Petrosino, S., Cusano, P., Saccorotti, G., Del Pezzo, E., 2002. Seismic attenuation and shallowvelocity structures at Stromboli Volcano, Italy. Bull. Seismol. Soc. Am., 92: 1102-1116.
  12. Picotti, S. and Carcione, J.M., 2006. Estimating seismic attenuation (Q) in the presence of randomnoise. J. Seismic Explor., 15: 165-181.
  13. Pilant, W.L., 1979. Elastic Waves in the Earth. Elsevier Science Publishers, Amsterdam.
  14. Ramos, V.A. and Folguera, A., 2011. Payenia volcanic province in the Southern Andes: Anappraisal of an exceptional Quaternary tectonic setting. J. Volcanol. Geotherm. Res., 201:53-64.
  15. Risso, C., Németh, K., Combina, A.M., Nullo, F. and Drosina, M., 2008. The role ofphreatomagmatism in a PlioPleistocene high-density scoria cone field: Llancanelo Volcanic
  16. Field (Mendoza, Argentina). J. Volcanol. Geotherm. Res., 169: 61-86.
  17. Sheriff, R.E. and Geldart, L.P., 1995. Exploration Seismology. Cambridge University Press,Cambridge.
  18. Steeples, D.W. and Miller, R.D., 1998. Avoiding pitfalls in shallow seismic reflection surveys.Geophysics, 63: 1213-1224.
  19. Violante, R., Osella, A., de la Vega, M., Rovere, E. and Osterrieth, M., 2010. Paleoenvironmentalreconstruction In the Western Lacustrine Plain of Llancanelo Lake, Mendoza, Argentina.J. South Am. Earth Sci., 29: 650-664.
  20. Yilmaz, O., 1989. Seismic Data Processing. SEG, Tulsa, OK.CHARACTERIZATION OF QUATERNARY SEDIMENTS 17
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Journal of Seismic Exploration, Electronic ISSN: 0963-0651 Print ISSN: 0963-0651, Published by AccScience Publishing