COMPARISON OF METHODS TO DETERMINE <i>Q</i> IN SHALLOW MARINE SEDIMENTS FROM VERTICAL REFLECTION SEISMOGRAMS*

Jannsen, D.; Voss, J.; Theilen, F.

doi:10.1111/j.1365-2478.1985.tb00762.x

Cited by 106 publications

(55 citation statements)

References 10 publications

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“…The differential decay of different frequencies depends upon the Q of a medium. Jannsen et al (1985) discuss the application of the SR method to estimate Q from seismic data. Amplitude spectrums (A 1 ðωÞ and A 2 ðωÞ) of two reflections from different depths (Z 1 and Z 2 ), can be written as…”

Section: Spectral Ratio Methodsmentioning

confidence: 99%

“…The data converted to the frequency domain are used to study seismic attenuation. We use the centroid frequency shift (Quan and Harris, 1997) and the SR method (Jannsen et al, 1985) to estimate Q in gas-hydrate-and free-gas-saturated sediments.…”

Section: Methodsmentioning

confidence: 99%

“…The quality (Q) factor has been estimated from P-cable seismic data using the SR method (Jannsen et al, 1985) and the centroid frequency shift method (Quan and Harris, 1997). The centroid frequency shift method establishes a relationship between the change in the centroid frequency of an amplitude spectrum and the Q value of a medium (Quan and Harris, 1997).…”

Section: Introductionmentioning

confidence: 99%

“…The seismic quality factor (Q), the inverse of seismic attenuation, can be estimated from the seismic data set using different methods, which include the amplitude decay method (Badri and Mooney, 1987), the rise time method (Gladwin and Stacey, 1974), the centroid frequency shift method (Quan and Harris, 1997), wavelet modeling (Jannsen et al, 1985), the pulse broadening method (Hatherly, 1986), the spectral ratio (SR) method (Båth, 1982;Jannsen et al, 1985), and the inversion method (Amundsen and Mittet, 1994). Tonn (1991) compares 10 methods of attenuation estimation using VSP seismograms and concludes that no single method is suitable for all situations.…”

Section: Introductionmentioning

confidence: 99%

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Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data

et al. 2016

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We have estimated the seismic attenuation in gas hydrate and free-gas-bearing sediments from high-resolution P-cable 3D seismic data from the Vestnesa Ridge on the Arctic continental margin of Svalbard. P-cable data have a broad bandwidth (20-300 Hz), which is extremely advantageous in estimating seismic attenuation in a medium. The seismic quality factor (Q), the inverse of seismic attenuation, is estimated from the seismic data set using the centroid frequency shift and spectral ratio (SR) methods. The centroid frequency shift method establishes a relationship between the change in the centroid frequency of an amplitude spectrum and the Q value of a medium. The SR method estimates the Q value of a medium by studying the differential decay of different frequencies. The broad bandwidth and short offset characteristics of the P-cable data set are useful to continuously map the Q for different layers throughout the 3D seismic volume. The centroid frequency shift method is found to be relatively more stable than the SR method. Q values estimated using these two methods are in concordance with each other. The Q data document attenuation anomalies in the layers in the gas hydrate stability zone above the bottom-simulating reflection (BSR) and in the free gas zone below. Changes in the attenuation anomalies correlate with small-scale fault systems in the Vestnesa Ridge suggesting a strong structural control on the distribution of free gas and gas hydrates in the region. We argued that high and spatially limited Q anomalies in the layer above the BSR indicate the presence of gas hydrates in marine sediments in this setting. Hence, our workflow to analyze Q using high-resolution P-cable 3D seismic data with a large bandwidth could be a potential technique to detect and directly map the distribution of gas hydrates in marine sediments.

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Section: Spectral Ratio Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data

et al. 2016

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“…Methods to calculate the frequency dependence of attenuation have been given by several authors to suit low-and high-frequency applications (O' Connell and Budianski, 1978;Kjartansson, 1979). However, in nearly every experimental geometry attenuation is di⁄cult to measure (Jannsen et al, 1985;Tonn, 1989;Bromirski et al, 1995;Bowles, 1997;Richardson and Briggs, 1997). The processing technique by Frazer et al (1999), which we applied to our data, combines the standard spectral ratio method (e.g., Tonn, 1989) and Bayesian inverse theory (e.g., Tarantola, 1987).…”

Section: Calculation Of In Situ Acoustic Compressional Wave Attenuationmentioning

confidence: 99%

In situ acoustic and laboratory ultrasonic sound speed and attenuation measured in heterogeneous soft seabed sediments: Eel River shelf, California

Gorgas

Wilkens

et al. 2002

Marine Geology

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We compared in situ and laboratory velocity and attenuation values measured in seafloor sediments from the shallow water delta of the Eel River, California. This region receives a substantial volume of fluvial sediment that is discharged annually onto the shelf. Additionally, a high input of fluvial sediments during storms generates flood deposits that are characterized by thin beds of variable grain-sizes between the 40-and 90-m isobaths. The main objectives of this study were (1) to investigate signatures of seafloor processes on geoacoustic and physical properties, and (2) to evaluate differences between geoacoustic parameters measured in situ at acoustic (7.5 kHz) and in the laboratory at ultrasonic (400 kHz) frequencies. The in situ acoustic measurements were conducted between 60 and 100 m of water depth. Wet-bulk density and porosity profiles were obtained to 1.15 m below seafloor (m bsf) using gravity cores of the mostly cohesive fine-grained sediments across-and along-shelf. Physical and geoacoustic properties from six selected sites obtained on the Eel margin revealed the following. (1) Sound speed and wet-bulk density strongly correlated in most cases. (2) Sediment compaction with depth generally led to increased sound speed and density, while porosity and in situ attenuation values decreased. (3) Sound speed was higher in coarser-than in finer-grained sediments, on a maximum average by 80 m s 31 . (4) In coarse-grained sediments sound speed was higher in the laboratory (1560 m s 31 ) than in situ (1520 m s 31 ). In contrast, average ultrasonic and in situ sound speed in finegrained sediments showed only little differences (both approximately 1480 m s 31 ). (5) Greater attenuation was commonly measured in the laboratory (0.4 and 0.8 dB m 31 kHz 31 ) than in situ (0.02 and 0.65 dB m 31 kHz 31 ), and remained almost constant below 0.4 m bsf. We attributed discrepancies between laboratory ultrasonic and in situ acoustic measurements to a frequency dependence of velocity and attenuation. In addition, laboratory attenuation was most likely enhanced due to scattering of sound waves at heterogeneities that were on the scale of

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On the Method of Adaptive Waveform Inversion with Zero‐Offset VSP Data

Gao

Wang

Zhao

2009

Chinese J of Geophysics

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In this paper, we develop a waveform inversion method to estimate the interval velocity and quality factor Q with zero‐offset VSP data. The inversion is done in the time domain and the objective function is constructed using the undisturbed segment of the direct downgoing wave. According to the signal‐to‐noise ratio and the interference of upgoing wave, our method can adaptively choose the undisturbed segment of the direct downgoing wave as long as possible, so it can make use of the most of the data. A new data weighting scheme is proposed to make the objective function more sensitive to Q. To deal with the ill‐posed nature of waveform inversion, the recently developed multiplicative regularization approach is adopted, which can adaptively determine the regularization parameter as the iterations proceed. In addition, a nonlinear transform is applied to the unknown model parameters to constrain them within their upper and lower bounds. For reducing computational cost, the analytic expressions of the elements of the Jacobian matrix are given. The application of this method on the synthetic VSP data and real data demonstrates the effectiveness of this method, and indicates this method is less sensitive to random noise and upgoing waves.

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COMPARISON OF METHODS TO DETERMINE Q IN SHALLOW MARINE SEDIMENTS FROM VERTICAL REFLECTION SEISMOGRAMS*

Cited by 106 publications

References 10 publications

Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data

Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data

In situ acoustic and laboratory ultrasonic sound speed and attenuation measured in heterogeneous soft seabed sediments: Eel River shelf, California

On the Method of Adaptive Waveform Inversion with Zero‐Offset VSP Data

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