title: Long range acoustic measurements of an undersea volcano.
abstract: A seamount 8 km southeast of Sarigan Island erupted on 29 May 2010 and was visually observed. The recordings on two sets of hydrophones, operated by International Monitoring System (IMS) of the Comprehensive Test Ban Treaty Organization (CTBTO) are analyzed. Each array is a triplet of axial single hydrophones deployed as a 2 km triangle. Measurements of acoustic intensity for the path to the southern triplet are on the order of 6 dB lower than those received on the northern triplet. Temporal cross-correlation beamforming estimation is performed and the estimated arrival angles for the two arrays, 265° and 267° were consistent with the predicted geodesic arrival of 264.6° and 267.8°, respectively. Cross-correlation between single phones on the northern and southern arrays reveals a peak at 266°, with a cross-correlation of 0.1. Nx2D parabolic equation modeling predicts complete blockage due to seamount interaction along the geodesic path. Overprediction of the seamount blockage indicates that the 2D approximation is incorrect, and three-dimensional propagation must be used to explain the observations. This is demonstrated by the computation of the Adiabatic Mode Parabolic Equation Transmission Loss, which predicts a 5-10 dB lower reception at the southern site.
authors.affiliation: Ocean Acoustical Services and Instrumentation Systems, Inc., 11006 Clara Barton Drive, Fairfax Station, Virginia 22039.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Heaney
authors.forename: Richard L
authors.initials: RL
authors.lastname: Campbell
authors.forename: Mirjam
authors.initials: M
authors.lastname: Snellen
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D003198:Computer Simulation; D004867:Equipment Design; D008962:Models, Theoretical; D009038:Motion; D009716:Numerical Analysis, Computer-Assisted; D009791:Oceanography / Q000295:instrumentation / Q000379:methods*; D009792:Oceans and Seas; D012623:Seawater; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013018:Sound Spectrography; D013997:Time Factors; D014159:Transducers; D018707:Volcanic Eruptions