GeoActa Special Publication 1
2008
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GeoActa
an international Journal of Earth Sciences
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Alessandro Amorosi1, Silvia Castellaro2 and Francesco Mulargia2
1Dipartimento di Scienze della Terra e Geologico-Ambientali, University of Bologna, Via Zamboni 67, 40127 Bologna, Italy. E-mail: alessandro.amorosi@unibo.it
2Dipartimento di Fisica, Settore Geofisica, University of Bologna, Viale Berti Pichat 8, 40127 Bologna, Italy. E-mail: silvia.castellaro@unibo.it, francesco.mulargia@unibo.it
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Single-Station Passive Seismic Stratigraphy: an inexpensive tool for quick subsurface investigations
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PDF (1,4 MB)
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Abstract
Single-Station Passive Seismic Stratigraphy (S-SPSS) is a geophysical method able to retrieve subsurface information from seismic tremor spectra recorded at a single station. It is an non-invasive, fast and inexpensive technique that can find applications in subsurface stratigraphy. Tests on a hierarchy of stratigraphic units from the Po River Basin, in northern Italy, show that S-SPSS can represent a powerful tool on a variety of scales.
A critical comparison with well data available from oil exploration shows that S-SPSS can identify deep unconformities, such as the sediment/bedrock interface, down to depths higher than 1000 m. At shallower depths (100-300 m), accurate calibration with sedimentological data from continuous cores documents how S-SPSS can resolve thick sand intervals, thus providing the basis for the three-dimensional reconstruction of sedimentary bodies, and for aquifer management. In contrast, S-SPSS fails to identify the key surfaces for high-resolution sequence-stratigraphic interpretation.
The easy of use and speed of S-SPSS (a tremor acquisition for passive stratigraphy requires typically 15-20 minutes) suggest that an extensive use of this technique for subsurface mapping of sedimentary bodies can be an attractive alternative to the classical methods, which are economically less convenient. If properly calibrated with accurate facies analysis from cores, S-SPSS can be used as an independent method for subsurface stratigraphic correlations, and may help in the prediction of the geometry, proportion and spatial distribution of coarse-grained (sand, gravel) vs. fine-grained deposits. Eventually, this may lead to 3-D stratigraphic models providing a link between geometrical reservoir characterization and variation in geophysical parameters.
Keywords: Passive seismic stratigraphy, H/V, Microtremor, Facies analysis, Quaternary, Po Plain
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