UACE: Hydroacoustic waves detected by an interferometry-based fiber optic strainmeter from a series of submarine earthquakes near Torishima Island, Japan

• Day: June 16, Monday
    Location / Time: A. TERPSIHORI at 15:10-15:30
• Last minutes changes: -
• Session: 04. Comprehensive Nuclear-Test-Ban Treaty Monitoring, and its Civil and Scientific Applications
  Organiser(s): Georgios Haralabus, Mario Zampolli, Tiago Oliveira, Mark Prior
  Chairperson(s): Georgios Haralabus, Tiago Oliveira
• Lecture: Hydroacoustic waves detected by an interferometry-based fiber optic strainmeter from a series of submarine earthquakes near Torishima Island, Japan [Invited]
  Paper ID: 2171
  Author(s): Hiroyuki Matsumoto, Mario Zampolli, Eiichiro Araki, Georgios Haralabus
  Presenter: Hiroyuki Matsumoto
  Abstract: On 08 October, 2023, a series of submarine earthquakes that took place in the Izu-Ogasawara (Izu-Bonin) Islands, Japan, excited at least 14 hydroacoustic waves (i.e., T-waves or H-waves) over a period of three hours. These waves were detected by the hydrophone triplets of the CTBT International Monitoring System (IMS) station HA11 at Wake Island. Although the amplitude among packets varied, the frequency contents were commonly broadband with short duration times, suggesting that explosive phenomena occurred during this series of episodic events. We performed cross-correlation analysis to determine the direction of arrivals (DOAs) of the hydroacoustic waves and make hypotheses about their origin. The cross-correlation analysis shows that the DOAs of hydroacoustic waves at the two triplets cross near Sofugan Island, about 100 km south from Torishima Island, where numerous seismic sources were determined by the USGS. Therefore, we interpreted that the hydroacoustic sources were likely located near Sofugan Island. The same hydroacoustic waves were also recorded by three 200-m long interferometry-based fiber optic strainmeters deployed at the seafloor in the Nankai Trough, Japan, on the opposite side from the source area compared to HA11. The fiber optic detections of hydroacoustic waves were also confirmed by a broadband seismometer and a pressure gauge of the nearby DONET seafloor observatories. The frequency contents observed by the interferometry-based fiber optic strainmeters were very similar to those at the HA11 hydrophone triplets, supporting the potential of these fiber optical interferometric technologies for detecting hydroacoustic waves.
• Corresponding author: Dr Hiroyuki Matsumoto
  Affiliation: JAMSTEC
  Country: Japan