DAEJEON — Researchers have developed technology that can survey geological structures more than 200 meters beneath the seabed without a crew on board.
The Korea Institute of Geoscience and Mineral Resources (KIGAM) said on the 19th that a team led by Shin Jung-kyun at its Pohang Geo-Environment and Resources Demonstration Research Center developed a coastal seismic survey technology using an unmanned surface vehicle (USV), and verified it in open waters off Pohang in a joint demonstration with the Marine Robot Demonstration Center of the Korea Institute of Ocean Science and Technology (KIOST). The technology is designed to overcome the spatial limits of conventional survey-ship-based methods.
Seismic surveying, which identifies geological structures below the seabed, is a core technology for marine resource exploration, seabed geological studies and offshore infrastructure construction. Conventional marine seismic surveys, however, have mostly placed the seismic source and the receiving equipment together on a single large survey vessel, which limited both ship access and equipment operation in shallow waters and in coastal zones where land meets sea.
The team built a marine refraction survey system that separates the two functions: a crewed source vessel that generates the seismic waves and an unmanned surface vehicle that receives the signals. Rather than loading both the source and the receiving system onto one vessel, the USV acquires seismic data independently from a distant position, laying the groundwork for extending survey coverage into coastal areas.
The researchers developed a compact, low-power seismic data acquisition system suited to the limited payload space and power environment of a USV, integrating the seismic receiving and recording unit with a wireless communication device. A nearby monitoring system allows the equipment to be controlled remotely and the data acquisition status to be checked in real time.
For the open-water performance verification, KIGAM handled development of the data acquisition system, the design and acquisition for the marine refraction survey, seismic data processing and first-arrival traveltime tomography analysis. KIOST supported the work with its open-water testbed, unmanned platform demonstration infrastructure and the operation of a guard vessel.
The team acquired seismic data at five receiving points along a survey line of about 4 kilometers in waters east of Hwajin Beach in Pohang, moving the USV between positions. Refracted wave signals were identified at source-receiver distances of up to about 2 kilometers, and first-arrival traveltime tomography imaged a long-wavelength P-wave velocity structure to depths of more than 200 meters below the seabed.
In a shallow section in the western part of the survey area, the team found a P-wave velocity structure relatively faster than the surrounding area, confirming that seismic data acquired from a distant USV can image actual geological structures beneath the seabed.
Starting from this refraction survey demonstration, the team plans to widen the technology's scope to vertical cable seismic surveys and long-offset reflection surveys using USVs, and to build a multi-USV seismic survey system that operates several vehicles at once. The goal is to broaden the range of coastal surveys and advance unmanned, automated data acquisition.
"This goes beyond simply mounting survey equipment on an unmanned surface vehicle," Shin said. "The significance is that we verified a new marine seismic survey system based on an unmanned platform in shallow coastal waters that were difficult to reach with conventional technologies built around large survey vessels." Shin added, "We will link various seismic survey techniques with multi-USV operating technology to expand unmanned and automated marine seismic surveying step by step."