[S-CG52] Ocean Floor Geoscience

[SCG52-P07] Hydrothermal plume survey at Higashi-Aogashima Knoll Caldera in the Izu-Bonin arc by shipboard multi-beam echo sounder

*Junji Kaneko¹, Takafumi Kasaya¹, Tatsuo Nozaki¹, Kazuhide Mimura², Youhei Sugimoto³, Hidenori Kumagai¹, Kentaro Nakamura⁴ (1.Japan Agency for Marine-Earth Science and Technology, 2.Chiba Institute of Technology, 3.NIPPON MARINE ENTERPRISES, 4.The University of Tokyo)

Keywords:Hydrothermal activity, Izu-Ogasawara arc, Higashi-Aogashima knoll caldera, Water column data, Voxel Model, Multi-beam echo sounder

During the cruise KM18-02C, a preliminary acoustic survey on hydrothermal plume using a high-frequency shipboard multi-beam echo sounder (MBES) was conducted to observe water column acoustic scattering anomalies at the Central Cone Site, Higashi-Aogashima Knoll Caldera hydrothermal field in the Izu-Bonin arc. The water column data were visualized/quantified based on a voxel model and acoustic scattering anomalies detected from the water column were attributable to the occurrence of hydrothermal plumes (Kaneko & Kasaya, 2022). Although the shipboard hydrothermal plume survey has been considered to be not effective so far in the Izu-Bonin arc, our result is the first report of the hydrothermal plume successfully observed by shipboard MBES.
During cruises YK21-10, KM22-11C, KM23-01, and KM23-02, we conducted detailed plume surveys within the entire Higashi-Aogashima Knoll Caldera hydrothermal field using a shipboard MBES. In addition, we changed settings and parameters of the transmit frequency and pulse length of the low-frequency MBES (12 kHz) and high-frequency MBES (40 - 100 kHz) equipped with the R/V Kaimei and observed changes in the acoustic scattering value and plume shape. In this presentation, we report the preliminary results of the plume survey using shipboard MEBS conducted during a series of research cruises at the Higashi-Aogashima Knoll Caldera hydrothermal field.