Increasing the number and signal-to-noise ratio of OBS traces with supervirtual refraction interferometry and free-surface multiples

Handle URI:
http://hdl.handle.net/10754/554383
Title:
Increasing the number and signal-to-noise ratio of OBS traces with supervirtual refraction interferometry and free-surface multiples
Authors:
Bharadwaj, P.; Wang, X.; Schuster, Gerard T. ( 0000-0001-7532-1587 ) ; McIntosh, K.
Abstract:
The theory of supervirtual interferometry is modified so that free-surface related multiple refractions can be used to enhance the signal-to-noise ratio (SNR) of primary refraction events by a factor proportional to√Ns, where Ns is the number of post-critical sources for a specified refraction multiple. We also show that refraction multiples can be transformed into primary refraction events recorded at virtual hydrophones located between the actual hydrophones. Thus, data recorded by a coarse sampling of ocean bottom seismic (OBS) stations can be transformed, in principle, into a virtual survey with P times more OBS stations, where P is the order of the visible free-surface related multiple refractions. The key assumption is that the refraction arrivals are those of head waves, not pure diving waves. The effectiveness of this method is validated with both synthetic OBS data and an OBS data set recorded offshore from Taiwan. Results show the successful reconstruction of far-offset traces out to a source-receiver offset of 120 km. The primary supervirtual traces increase the number of pickable first arrivals from approximately 1600 to more than 3100 for a subset of the OBS data set where the source is only on one side of the recording stations. In addition, the head waves associated with the first-order free-surface refraction multiples allow for the creation of six new common receiver gathers recorded at virtual OBS station located about half way between the actual OBS stations. This doubles the number of OBS stations compared to the original survey and increases the total number of pickable traces from approximately 1600 to more than 6200. In summary, our results with the OBS data demonstrate that refraction interferometry can sometimes more than quadruple the number of usable traces, increase the source-receiver offsets, fill in the receiver line with a denser distribution of OBS stations, and provide more reliable picking of first arrivals. Apotential liability of this method is that long-offset refraction arrivals extracted by interferometry might not necessarily be head waves from deeper refraction interfaces. The extracted arrivals might be from a shallower interface, and so only supply redundant information about that portion of the subsurface. Nevertheless, our tomography example shows the value of these arrivals in reducing artefacts and increasing resolution in the tomogram. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Citation:
Increasing the number and signal-to-noise ratio of OBS traces with supervirtual refraction interferometry and free-surface multiples 2013, 192 (3):1070 Geophysical Journal International
Journal:
Geophysical Journal International
Issue Date:
10-Jan-2013
DOI:
10.1093/gji/ggs087
Type:
Article
ISSN:
0956-540X; 1365-246X
Additional Links:
http://gji.oxfordjournals.org/cgi/doi/10.1093/gji/ggs087
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Physical Sciences and Engineering (PSE) Division

Full metadata record

DC FieldValue Language
dc.contributor.authorBharadwaj, P.en
dc.contributor.authorWang, X.en
dc.contributor.authorSchuster, Gerard T.en
dc.contributor.authorMcIntosh, K.en
dc.date.accessioned2015-05-21T07:02:49Zen
dc.date.available2015-05-21T07:02:49Zen
dc.date.issued2013-01-10en
dc.identifier.citationIncreasing the number and signal-to-noise ratio of OBS traces with supervirtual refraction interferometry and free-surface multiples 2013, 192 (3):1070 Geophysical Journal Internationalen
dc.identifier.issn0956-540Xen
dc.identifier.issn1365-246Xen
dc.identifier.doi10.1093/gji/ggs087en
dc.identifier.urihttp://hdl.handle.net/10754/554383en
dc.description.abstractThe theory of supervirtual interferometry is modified so that free-surface related multiple refractions can be used to enhance the signal-to-noise ratio (SNR) of primary refraction events by a factor proportional to√Ns, where Ns is the number of post-critical sources for a specified refraction multiple. We also show that refraction multiples can be transformed into primary refraction events recorded at virtual hydrophones located between the actual hydrophones. Thus, data recorded by a coarse sampling of ocean bottom seismic (OBS) stations can be transformed, in principle, into a virtual survey with P times more OBS stations, where P is the order of the visible free-surface related multiple refractions. The key assumption is that the refraction arrivals are those of head waves, not pure diving waves. The effectiveness of this method is validated with both synthetic OBS data and an OBS data set recorded offshore from Taiwan. Results show the successful reconstruction of far-offset traces out to a source-receiver offset of 120 km. The primary supervirtual traces increase the number of pickable first arrivals from approximately 1600 to more than 3100 for a subset of the OBS data set where the source is only on one side of the recording stations. In addition, the head waves associated with the first-order free-surface refraction multiples allow for the creation of six new common receiver gathers recorded at virtual OBS station located about half way between the actual OBS stations. This doubles the number of OBS stations compared to the original survey and increases the total number of pickable traces from approximately 1600 to more than 6200. In summary, our results with the OBS data demonstrate that refraction interferometry can sometimes more than quadruple the number of usable traces, increase the source-receiver offsets, fill in the receiver line with a denser distribution of OBS stations, and provide more reliable picking of first arrivals. Apotential liability of this method is that long-offset refraction arrivals extracted by interferometry might not necessarily be head waves from deeper refraction interfaces. The extracted arrivals might be from a shallower interface, and so only supply redundant information about that portion of the subsurface. Nevertheless, our tomography example shows the value of these arrivals in reducing artefacts and increasing resolution in the tomogram. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.en
dc.relation.urlhttp://gji.oxfordjournals.org/cgi/doi/10.1093/gji/ggs087en
dc.rightsArchived with thanks to Geophysical Journal International © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.en
dc.subjectInterferometryen
dc.subjectControlled source seismologyen
dc.subjectBroad-band seismometersen
dc.subjectInterface wavesen
dc.subjectSeismic tomographyen
dc.subjectWave propagationen
dc.titleIncreasing the number and signal-to-noise ratio of OBS traces with supervirtual refraction interferometry and free-surface multiplesen
dc.typeArticleen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.identifier.journalGeophysical Journal Internationalen
dc.eprint.versionPublisher's Version/PDFen
dc.contributor.institutionDept. of Applied Geophysics, Indian School of Mines, Dhanbad, 826004, Indiaen
dc.contributor.institutionInstitute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78758-4445, USAen
kaust.authorSchuster, Gerard T.en
kaust.authorBharadwaj, Pawanen
kaust.authorWang, Xinen
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