HR: 0800h
AN: T31A-0486    [Abstracts]
TI: The Acoustic Signature of High-Temperature Deep Sea Hydrothermal Vents
AU: * Crone, T J
EM: tjc@ocean.washington.edu
AF: School of Oceanography University of Washington, Box 357940, Seattle, WA 98195-7940 United States
AU: Wilcock, W S
EM: wilcock@ocean.washington.edu
AF: School of Oceanography University of Washington, Box 357940, Seattle, WA 98195-7940 United States
AU: Parsons, J D
EM: parsons@ocean.washington.edu
AF: School of Oceanography University of Washington, Box 357940, Seattle, WA 98195-7940 United States
AU: Barclay, A H
EM: andrew@ocean.washington.edu
AF: School of Oceanography University of Washington, Box 357940, Seattle, WA 98195-7940 United States
AB: Motivated by a desire to find new measurements that might be sensitive to flow rate variations within mid-ocean ridge hydrothermal systems, we have conducted field studies to collect passive acoustic measurements at black smoker hydrothermal vents using two versions of a simple dual-hydrophone recording device capable of collecting continuous acoustic data for about one week at sampling rates of 1000--2000 Hz. We deployed the first-generation instrument on the Sully sulfide structure in the Main Endeavour Field of the Juan de Fuca Ridge during September of 2004. We were able to collect approximately 48 hours of data before the instrument was partially destroyed by venting fluid. We are in the process of obtaining additional measurements in the same vent field with a second-generation instrument. For the 2004 deployment, the venting fluid produced an acoustic signal that was far above the background level at all measured frequencies. The acoustic spectrum contains a broadband signal that is weighted toward the low frequencies and extends to the Nyquist frequency at 500 Hz. The spectrum also contains several sharp peaks below 150 Hz. The signal is variable in time, with the broadband and peak amplitudes fluctuating by ~20 dB, and the frequencies of the sharp spectral peaks fluctuating by ~1--3 Hz. The complex nature of the acoustic signal suggests that more than one sound production mechanism is operating within the vent. The sharp peaks suggest the presence of a resonant mechanism such as pipe resonance excited by turbulent flow. The high level of the broadband signal is not predicted by theoretical investigations of low Mach number jet acoustics. It is likely that another broadband sound source is present, which could be related to phase separation or to the mixing of different density fluids. More observations will be required to fully understand the basic mechanisms of sound production within black smoker chimneys.
DE: 3017 Hydrothermal systems (0450, 1034, 3616, 4832, 8135, 8424)
DE: 3021 Marine hydrogeology
DE: 3035 Midocean ridge processes
DE: 3094 Instruments and techniques
DE: 4259 Ocean acoustics
SC: Tectonophysics [T]
MN: Fall Meeting 2005