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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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| Ambient seismic noise eikonal tomography for near-surface imaging at Valhall | |
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Next: Introduction
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2011-05-24