Time‐lapse analysis of ambient surface wave anisotropy: A three‐component array study above an underground gas storage

Abstract

[1] We perform a time-lapse analysis of Rayleigh and Love wave anisotropy above an underground gas storage facility in the Paris Basin. The data were acquired with a three-component seismic array deployed during several days in April and November 2010. Phase velocity and back azimuth of Rayleigh and Love waves are measured in the frequency range 0.2-1.1 Hz using a three-component beamforming algorithm. In both snapshots, higher-surface wave modes start dominating the signal above 0.4 Hz with a concurrent increase in back azimuth ranges. We fit anisotropy parameters to the array detections above 0.4 Hz using a bootstrap approach which also provides estimation uncertainty and enables significance testing. The isotropic phase velocity dispersion for Love and Rayleigh waves match for both snapshots. We also observe a stable fast direction of NNW-SSE for Love and Rayleigh waves which is aligned with the preferred orientation of known shallow (<300 m) and deeper ( 1000 m) fault systems in the area, as well as the maximum horizontal stress orientation. At lower frequencies corresponding to deeper parts of the basin, the anisotropic parameters exhibit higher magnitude in the November data. This may perhaps be caused by the higher pore pressure changes in the gas reservoir in that depth range.Citation: Riahi, N., G. Bokelmann, P. Sala, and E. H. Saenger (2013), Time-lapse analysis of ambient surface wave anisotropy: A three-component array study above an underground gas storage,

Azimuthal anisotropy of Rayleigh waves in the crust in southern Tohoku area, Japan

“…The anisotropic intensity is defined by the magnitude of anisotropy for the i th component normalized by v iso [Figure g; Riahi et al ., ]. In Southern California, the 2 θ anisotropic intensity is much larger than the 4 θ anisotropic intensity [ Alvizuri and Tanimoto , ; Riahi and Saenger , ] because the 2 θ anisotropy is generally dominant in Rayleigh waves [ Montagner and Nataf , ].…”

Rayleigh and Love wave anisotropy in Southern California using seismic noise

“…The raw data of each station was conservatively quality checked by analyzing the distribution of spectral amplitudes for each month of the year 2012 [ McNamara and Buland , ]: If any component of a station contained gaps, instrument failures, or narrow band spectral peaks, the station was excluded for that month. The three‐component beamforming method is a relatively straight‐forward generalization of conventional single‐component beamforming and is described in detail by Riahi et al []. We only provide a very brief summary of the processing steps here.…”

The seismic traffic footprint: Tracking trains, aircraft, and cars seismically

“…The ambient seismic wavefield has received much interest in the recent past both for its natural sources [Gerstoft et al, 2006a;Koper and de Foy, 2008;Kedar, 2011;Hillers et al, 2012] but also as a new probing signal for the solid Earth [Sabra et al, 2005;Gerstoft et al, 2006b;Moschetti et al, 2007;Riahi et al, 2013;Weemstra et al, 2013] and to predict earthquake ground motion [Denolle et al, 2014]. In comparison, anthropogenic seismic noise has received little attention so far [e.g., Groos and Ritter, 2009] or was only used indirectly for site amplification studies [Bonnefoy-Claudet et al, 2006;D'Amico et al, 2008] or subsurface imaging [Nakata et al, 2011].…”