Detection of low-frequency underwater sounds from a submarine volcano in the Western Pacific

Abstract

Underwater sound signals in the frequency band below 100 Hz were recorded at several widely spaced SOFAR depth hydrophones in the North Pacific. The signals, which typically lasted from 5 to 30 sec and were spaced about 1 min apart, continued at a high level of activity during the fall and winter of 1973–1974. SOFAR fixes obtained on discrete events in the series plot in the volcano islands near 22°N, 144°E. Some of the signals exhibited spectral banding with fundamental frequencies in the 1–2-Hz region. If one assumes the spectral banding is due to constructional interference of surface- and bottom-reflected sound in the vicinity of the source, the calculated depth of the explosions was between 375 and 750 m. The volcanic noises are therefore believed to have originated from explosive volcanic activity associated with the shallow seamount charted at 21.9°N, 143.4°E with a minimum sounding of 150 m (Navy Hydrographic Office Chart No. 970000).

The Seismo‐Acoustics of Submarine Volcanic Eruptions

“…Seven reports have described a unique subset of explosive activity from a few different seamounts, primarily in the western Pacific (NW Rota‐1 and other seamounts in the Mariana and Volcano Islands, Chadwick et al., 2008; Dziak & Fox, 2002; GVP, 1974; Northrop, 1974; Tepp, Dziak, et al., 2019; West Mata, NE Lau Basin, Dziak et al., 2015; North Su, Bismarck Sea, Crone & Bohnenstiehl, 2019). These eruptions produced eruptive signals that are characterized by repetitive broad‐band pulses of energy that increase in amplitude before abruptly stopping (Figure 6).…”

“…The hydrophone arrays at Wake Island in the central Pacific (Figure 10) seem to be especially well‐suited to detecting submarine eruptions from the Pacific basin, based on the number of eruption observations made from that site. This location also hosted SOSUS hydrophone arrays prior to the IMS (e.g., McCreery et al., 1989; Northrop, 1974; Yamasato et al., 1993).…”

The Hearing Abilities of the Prawn Palaemon Serratus

“…There are several types of anthropogenic sources used routinely that produce intense levels of noise, such as the Low Frequency Active Sonar (LFA) used by the military in antisubmarine warfare, or from the airgun arrays used during a seismic survey of the substrate beneath the seafloor by the petroleum industry. Seismic airgun arrays can generate noise levels in excess of 253 dB (re 1 µPa at 1 m) [3] and are comparable to the noise levels generated by a seafloor volcanic eruption, which can produce a source level of in excess of 255 dB (re 1 µPa at 1 m) [4]. Recent concerns regarding the impact of these anthropogenic sounds on fish and other marine animals has prompted a number of investigations into the effects of intense noise exposure on the hearing systems of marine mammals [5,6,7].…”