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TitleUnconsolidated sediment mapping using multi-component seismic reflection data in the Richelieu (QC) area
AuthorPugin, A J M; Pullan, S E
Alt SeriesEarth Sciences Sector, Contribution Series 20090424
Meeting44th Annual CMOS Congress, 36th Annual Scientific Meeting of CGU 3rd Joint CMOS-CGU Congress; May 31 - June 4, 2010
ProgramGroundwater Geoscience, Aquifer Assessment & support to mapping
AbstractOver the past 2 years we have tested a vibroseis system towing a landstreamer consisting of 3-component geophones mounted on 48 sleds at 0.75 m spacing. Two types of shear waves are observed: SV reflections primarily in in-line (H1) and vertical (V) components, and SH in the cross-line component (H2). SV waves have been observed to reach frequencies up to 200 Hz or more, significantly higher than the frequency content in the SH mode recorded in the cross-line component. The high frequencies correspond to sub-metric wavelengths in areas where shear wave velocities are very low (e.g. Holocene marine clays from the St Lawrence valley lowlands) allowing very high resolution ultra-shallow seismic reflection observations. On processed SV wave reflection sections from these environments we can observe data quality on land with resolutions comparable to data acquired with high resolution water-borne systems. Moreover, significant P-wave reflection signals are also present in the V component with inline horizontal source orientation.
The sequential stratigraphy can be thoroughly analysed in the Richelieu area using more than 50 km seismic lines of such high resolution data. The sedimentary sequences are usually delimited by erosion surfaces. Detailed seismic facies observation allow the characterisation of till, gravel, sand and mud deposited in systems related with eskers and large subsea fans and are being used for hydrogeological investigations. In the next stage of this research, the calibration of seismic facies using borehole data will allow the recognition of typical aquifer and aquitard lithologies.