DRI Update: 28 Dec. 2000

1. The next High-Frequency Sediment Acoustics meeting will begin at 0830 on 16 January in the Rouchen House at the Stennis Space Center, MS. Coffee and doughnuts (or the equivalent) will be available starting at 0800. Directions to the Rouchen House (the site of a previous DRI meeting) will be available at the south gate to SSC. It is important that you notify Mike Richardson if you plan to attend. (Mike.Richardson@nrlssc.navy.mil)

2. The meeting format will be as suggested by Rob Wheatcroft during the Bangor meeting in April. No individual presentations are expected, but instead a series of topical sessions will be conducted. A set of discussion topics for the meeting is included below. Participants are encouraged to bring materials to present at the sessions. Feel free to bring interesting results even if they to do not clearly fit into any session category. The meeting will end at noon on the 18th.

3. For accommodations Mike recommends the Holiday Inn in Waveland (228-467-9261) or the Key West Inn in Bay St. Louis (228-466-0444). Mike is setting up a group dinner for Tuesday night, and either of these hotels would be conveniently located for the dinner. If you need additional information on directions, alternate hotels, etc., contact Kim Klein at NRL-SSC (228-688-4657, -5752(fax), Kim.Klein@nrlssc.navy.mil).

4. Some interest has been expressed in allowing small groups to work separately on data analysis or paper preparation. A separate room will be available for that purpose if some participants prefer to meet privately and thereby miss some of the topical sessions. In general, however, group interactions will be enhanced if all attend the full slate of topical sessions, and thus it would be preferable to hold such meetings in the evenings if that is possible.

5. Topics and moderators for meeting sessions are listed below. All discussions related to these topics should focus on SAX99 measurements. Additional suggestions, together with moderators, are welcome.

5.1. What are the results of sediment roughness measurements? What are the properties of the large-scale ripple field? Aside from the large-scale ripple, is a single power-law model appropriate? Aside from the large-scale ripple, is the roughness isotropic? [Richardson]

5.2. What evidence is there for subcritical penetration due to large-scale ripple? What evidence for other mechanisms? [Thorsos]

5.3. How do the various permeability measurements compare? What is the accuracy of measured permeability for the methods used? Is the quantity they measure the acoustically relevant one? [Bennett]

5.4. How do the various measurements of porosity compare? [Stoll]

5.5. What is the status of measuring or inferring values of other Biot parameters (including the uncertainty)? [Chotiros and Stephen]

5.6. What is the evidence (including uncertainty) for velocity dispersion? How does attenuation vary with frequency? [Richardson and Bibee]

5.7. What acoustic propagation models are consistent with velocity dispersion and attenuation data? [Jackson]

5.8. To what extent can we understand the frequency and grazing angle dependence of backscatter? [Williams]

5.9. What is the evidence that small-scale sediment heterogeneity affects acoustic processes (propagation, backscattering, and penetration)? [Tang]

5.10. What deficiencies or uncertainties are there in acoustic modeling? What additional data analyses can be carried out to further test acoustic models? [Thorsos]

5.11. What indications were observed for biological and hydrodynamic forcing of sediment properties? What evidence is there that this forcing affected acoustic processes? How much are the results of experiments influenced by our presence? [Holliday]

5.12. What spatial variability (including vertical gradients) was observed in sediment properties? [Wheatcroft]

5.13. What diurnal variations were observed in backscatter from the seabed and from the water column? Can we tell which is which? [Jumars]

5.14. What do manipulative experiments tell us about acoustic processes under natural conditions? [Williams]