Sound field near hydrothermal vents on Axial Seamount, Juan de Fuca Ridge. Technical report

Technical Report · Fri Aug 10 00:00:00 EDT 1990

OSTI ID:5705468

Little, S A; Stolzenbach, K D; Purdy, G M

High-quality acoustic noise measurements were obtained by two hydrophones located 3 m and 40 m from an active hydrothermal vent on Axial Seamount, Juan de Fuca Ridge, in an effort to determine the feasibility of monitoring hydrothermal vent activity through flow noise generation. Most of the measured noise field could be attributed to ambient ocean noise sources of microseisms, distant shipping, and weather, punctuated by local ships and biological sources. Long-period, low-velocity, water/rock interface waves were detected with high amplitudes which rapidly decayed with distance from the seafloor. Detection of vent signals was hampered by unexpected spatial nonstationarity due to the shadowing effects of the calders wall. No continuous vent signals were deemed significant based on a criterion of 90% probability of detection and 5% probability of false alarm. However, a small signal near 40 Hz, with a power level of 0.0001 Pa sq/Hz was noticed on two records taken within 3 m of the Inferno black smoker. The frequency of this signal is consistent with predictions, and the power level suggests the occurrence of jet noise amplification due to convected density inhomogeneities. Keywords: Seamounts; Flow noise; Underwater acoustics; Acoustic measurement; Geothermy/noise; Ocean ridges; Underwater sound signals; Reprints; North Pacific Ocean. (EDC).

• Research Organization: Woods Hole Oceanographic Institution, MA (USA)
• OSTI ID: 5705468
• Report Number(s): AD-A-230312/1/XAB; WHOI-CONTRIB-7122; CNN: N00014-87-K-0007; NA86-AA-D-SG090
• Resource Relation: Other Information: Pub. in Jnl. of Geophysical Research, v95 nB8 p12,929-12,945, 10 Aug 90
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
HYDROTHERMAL SYSTEMS
ACOUSTIC MONITORING
ACOUSTIC MEASUREMENTS
AMPLIFICATION
BIOLOGY
DENSITY
FEASIBILITY STUDIES
INTERFACES
NOISE
PACIFIC OCEAN
ROCKS
SEA BED
SHIPS
SIGNALS
VENTS
WATER WAVES
WEATHER
ENERGY SYSTEMS
GEOTHERMAL SYSTEMS
GRAVITY WAVES
MONITORING
PHYSICAL PROPERTIES
SEAS
SURFACE WATERS
150301* - Geothermal Exploration & Exploration Technology- Geophysical Techniques & Surveys