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oa Effects of the Trace Interval on Surface Wave Dispersion and Inversion
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 76th EAGE Conference and Exhibition - Workshops, Jun 2014, cp-401-00047
- ISBN: 978-90-73834-90-3
Abstract
It is the trace interval that determines the spatial frequency property of one shot gather. As the trace interval increases, spatial aliasing emerges and data quality deteoriates. Aliased surface waves in the dispersion energy map have false higher-mode dispersion curves, or low velocity noise, and have missing or pronged dispersion energy trends at certain frequency ranges. Qualitatively, large spacing causes a severe aliasing that smears the dispersion plot, yielding it unusable. As long as spatial aliasing is not dominant, the surface waves can be used to invert the corresponding subsurface structure. We present a synthetic example to test the effectiveness of the high resolution linear Radon transform (HRLRT) and the least squares Radon transform (LSRT), which are used to calculate dispersion curves. Since the HRLRT typically affords a better low frequency response, we use it to map the field example. Effects caused by different spatial intervals in dispersion maps of synthetic and field examples are also shown. A genetic algorithm is used in the inversion to determine the subsurface structure, and these results are then compared with a nearby borehole test. The agreement between the test and the model shows the promising prospect of the surface wave methods.