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Ambient seismic noise eikonal tomography for near-surface imaging at Valhall

Sjoerd de Ridder and Joe Dellinger


Abstract:

We demonstrate that in three passive seismic datasets recorded by an ocean-bottom-cable array at the Valhall field in the Norwegian North Sea, virtual-source interferometry over the frequency range 0.35-1.75 Hz produces strong omnidirectional Scholte-wave sources. We then use these virtual-sources gathers to image the shallow structure in high resolution using eikonal traveltime tomography. Unlike conventional tomography, which determines velocities between source and receiver using an inversion scheme, eikonal tomography computes the local traveltime gradient at each receiver, and thus directly estimates the local velocity in the neighborhood of each receiver. The Scholte-wave images produced from imaging the passive noise reveal many of the same features visible in the active P-wave data. These results suggest that a permanent recording system using passive seismic noise might be useful for real-time surveillance of shallow shear-wave velocity anomalies.




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Next: Introduction Up: Reproducible Documents

2011-05-24