Journal
GEOPHYSICAL PROSPECTING
Volume 62, Issue 1, Pages 97-116Publisher
WILEY-BLACKWELL
DOI: 10.1111/1365-2478.12079
Keywords
P-waves; Velocity; Attenuation; Marine sediments
Categories
Funding
- former Defence Research Agency of the United Kingdom
- Natural Environment Research Council [noc010011, NE/H022260/1, NE/J020753/1] Funding Source: researchfish
- NERC [NE/H022260/1, NE/J020753/1, noc010011] Funding Source: UKRI
Ask authors/readers for more resources
We describe a new laboratory technique for measuring the compressional wave velocity and attenuation of jacketed samples of unconsolidated marine sediments within the acoustic (sonic) frequency range 1-10 kHz and at elevated differential (confining- pore) pressures up to 2.413 MPa (350 psi). The method is particularly well suited to attenuation studies because the large sample length (up to 0.6 m long, diameter 0.069 m) is equivalent to about one wavelength, thus giving representative bulk values for heterogeneous samples. Placing a sediment sample in a water-filled, thick-walled, stainless steel Pulse Tube causes the spectrum of a broadband acoustic pulse to be modified into a decaying series of maxima and minima, from which the Stoneley and compressional wave, velocity and attenuation of the sample can be determined. Experiments show that PVC and copper jackets have a negligible effect on the measured values of sediment velocity and attenuation, which are accurate to better than +/- 1.5% for velocity and up to +/- 5% for attenuation. Pulse Tube velocity and attenuation values for sand and silty-clay samples agree well with published data for similar sediments, adjusted for pressure, temperature, salinity and frequency using standard equations. Attenuation in sand decreases with pressure to small values below Q(-1)= 0.01 (Q greater than 100) for differential pressures over 1.5 MPa, equivalent to sub-seafloor depths of about 150 m. By contrast, attenuation in silty clay shows little pressure dependence and intermediate Q(-1) values between 0.0206-0.0235 (Q= 49-43). The attenuation results fill a notable gap in the grain size range of published data sets. Overall, we show that the Pulse Tube method gives reliable acoustic velocity and attenuation results for typical marine sediments.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available