10:45 AM - 12:15 PM
[MIS07-P02] Development of pop-up type Ocean Bottom Turbidity Current Detector (TCD)
Keywords:Turbidity Current, Suruga bay, Typhoon origin, Fuji River
A structural survey was conducted in Suruga Bay, Shizuoka, Japan, in October 2018. 18 ocean bottom seismographs (OBSs) were installed along the survey line when Typhoon No. 24 passed near Suruga Bay from September 30 to October 1, 2018. After its passage, seven of the 18 OBSs experienced abnormal surfacing due to turbidity currents on the seafloor (Baba et.al, 2021). Suruga Bay is fed rivers of special importance and has a complex seafloor topography. Therefore, river-induced turbidity currents may occur repeatedly with a relatively high frequency, as in this case. The number of large typhoons that make landfall in Japan is increasing every year, and their force tends to increase. The probability of occurrence of turbidity currents is expected to be much higher than that of volcanic eruptions or large earthquakes. However, the observation method of turbidity currents has not yet been established, and their actual conditions are unknown.
In this study, we developed an ocean bottom turbidity current monitoring system called a turbidity current detector (TCD021) to observe turbidity currents generated by typhoons passing near Suruga Bay and have continued observations (Nakao et.al, 2022). We have developed an ocean bottom turbidity current device (TCD) to observe turbidity currents generated by typhoons passing near Suruga Bay and conducted the second observation in the field in 2022.
During the observation period of this study, from the beginning of the night of September 23 to the dawn of September 24, 2022, Typhoon No. 15 caused heavy rainfall in the central, western, and eastern parts of Shizuoka Prefecture, with record-breaking heavy rainfall with 16 record-breaking short-time heavy rainfall advisories issued (Meteorological observatory of Shizuoka Prefecture, 2022).
In 2022type TCD equipped with a camera and an inertial measurement unit (IMU) was built, and observations were conducted at observation point TCD021. The location of the observation point was selected by simulating the flow from the Fuji River. A horizontal distance of approximately 2.8 km was observed between the location surveyed at the time of installation on August 11, 2022, and the location surveyed on October 12, 2022. The details of the recovery voyage by the Kaiyo Maru ROV will be presented separately at the conference.
The recovered TCD was dismantled for data recovery, but the data could not be analyzed due to severe internal damage. In this study, a method to determine the velocity of floating objects using photographs was investigated based on the data obtained from the preliminary experiments.
In this study, we developed an ocean bottom turbidity current monitoring system called a turbidity current detector (TCD021) to observe turbidity currents generated by typhoons passing near Suruga Bay and have continued observations (Nakao et.al, 2022). We have developed an ocean bottom turbidity current device (TCD) to observe turbidity currents generated by typhoons passing near Suruga Bay and conducted the second observation in the field in 2022.
During the observation period of this study, from the beginning of the night of September 23 to the dawn of September 24, 2022, Typhoon No. 15 caused heavy rainfall in the central, western, and eastern parts of Shizuoka Prefecture, with record-breaking heavy rainfall with 16 record-breaking short-time heavy rainfall advisories issued (Meteorological observatory of Shizuoka Prefecture, 2022).
In 2022type TCD equipped with a camera and an inertial measurement unit (IMU) was built, and observations were conducted at observation point TCD021. The location of the observation point was selected by simulating the flow from the Fuji River. A horizontal distance of approximately 2.8 km was observed between the location surveyed at the time of installation on August 11, 2022, and the location surveyed on October 12, 2022. The details of the recovery voyage by the Kaiyo Maru ROV will be presented separately at the conference.
The recovered TCD was dismantled for data recovery, but the data could not be analyzed due to severe internal damage. In this study, a method to determine the velocity of floating objects using photographs was investigated based on the data obtained from the preliminary experiments.