Seismic monitoring experiment of deep-sea driling

As human exploration and exploitation of seabed mineral resources intensify, concerns about the degradation of the ocean bottom noise environment have risen. To address this, we conducted a seismic monitoring experiment during the 78^th Chinese Dayang cruise in 2023, focusing on drilling activities at the Yuhuang seafloor massive sulfide deposits located at the Southwest Indian Ridge. Five Ocean Bottom Nodes (OBNs), each equipped with three orthogonal seismometers and one hydrophone operating at a sampling rate of 1000 Hz, were deployed around a sulfide mound by using the "Hailong IVE" ROV, which featured a real-time Ultra-Short Baseline (USBL) positioning system for precise placement. Additionally, high-sampling-rate cabled hydrophones, capable of capturing data at 32 kHz, were installed on a cable positioned 15 meters above the seabed drill site. Throughout the experiment, a seabed drilling rig capable of drilling up to 20 meters below the seafloor conducted a total of 13 drill operations. Our objectives were to identify drilling-related signals from the seawater and drill bit signals from the subseafloor, assess the impact of drilling operations on marine noise, and invert the velocity structure using ambient noise data. The initial insights gained from our experiment indicate that the maximum radius of drilling-related noise does not exceed 100 meters. The noise level produced by the drilling rig is influenced by the drilling parameters, such as revolutions per minute and weight on bit, as well as the hardness of the rock. To gain a more comprehensive understanding of the impact of drilling activities on the ocean sound field, further drilling tests with additional seismometers and hydrophones are necessary. This will provide a richer dataset, enabling more accurate assessments of noise generation and propagation patterns associated with seabed drilling operations.