A South Korean research team has used an unmanned surface vehicle to receive seismic signals and image geological structures more than 200 meters below the seafloor. The achievement is expected to extend marine geological surveys into shallow coastal waters, where large research vessels cannot easily operate their equipment.
The Korea Institute of Geoscience and Mineral Resources said on the 19th that a team led by Shin Jung-kyun of its Pohang Geo-Environment and Resources Research Center developed a coastal seismic survey technology using an unmanned surface vehicle, or USV, and completed open-sea verification off Pohang jointly with the Marine Robot Test and Evaluation Center of the Korea Institute of Ocean Science and Technology.
Marine seismic surveying identifies geological structures by analyzing waves sent into the seabed that either pass through or reflect off rock layers. It is used in resource exploration, seabed geological surveys and offshore infrastructure construction. Previous methods mounted both the seismic source and the receiving equipment on a single large survey vessel, which limited operations in shallow water or close to shore.
The team separated the manned vessel that generates the seismic waves from the unmanned surface vehicle that receives the signals. The USV, positioned at a distance, independently receives and records the seismic data. To make that possible, the researchers developed a compact, low-power data acquisition system suited to the vehicle's limited payload space and electricity supply. They integrated the seismic receiving and recording device with a wireless communication unit, allowing the equipment to be controlled remotely and the status of data collection to be checked in real time.
The demonstration was conducted along a survey line of about 4 kilometers in waters east of Hwajin Beach in Pohang. The team collected data at five receiving points, moving the USV between them, and identified refracted wave signals at distances of up to about 2 kilometers between the source and the receiving equipment.
The researchers then applied first-arrival travel-time tomography, which analyzes the time at which seismic waves first arrive, to image the P-wave velocity structure to depths of more than 200 meters below the seafloor. The P-wave velocity structure is the distribution of seismic wave speeds through rock layers and provides clues to the geological structure beneath the seabed.
KIGAM handled development of the data acquisition system, survey design, and data collection, processing and analysis. KIOST supported the work with an open-sea testbed, unmanned platform demonstration infrastructure and the operation of a surveillance vessel. The team plans to broaden the technology's applications to vertical cable seismic surveys and long-offset reflection surveys using unmanned surface vehicles. Ultimately, it aims to build a survey system operating multiple USVs at once to widen the scope of coastal exploration and to make data collection unmanned and automated.