Anisotropic Seismic Noise Gradiometry with Finite Difference Stencil Correction

Sjoerd De Ridder, Andrew Curtis

Research output: Contribution to conferenceAbstractpeer-review

Abstract

We introduce an anisotropic wavefield gradiometry technique to estimate phase velocities from seismic surface wave noise. The method inverts a two-dimensional wave equation, equating the spatial and temporal derivatives of the wavefield amplitudes
with elliptically anisotropic medium parameters. The derivatives are evaluated using finite differences which causes anisotropic velocity errors. A two step approach corrects this error. Finite difference stencils are first calibrated, then the output of the wave-equation inversion is corrected using the linearized impulse response to the inverted velocity anomaly. We test the procedure on ambient seismic noise recorded in a large and dense array installed over Ekofisk field. The azimuthal anisotropy forms a circular geometry around the production induced subsidence bowl which is confirmed by results from controlled source and noise-correlation studies. The methodology is a promising technique for studying changes in the subsurface geomechanical stress-state resulting from timedependent phenomena operating over short time-scales.
Original languageEnglish
DOIs
Publication statusPublished - 1 Sep 2016

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