Dr. Gabriel R. Venegas
Assistant Professor of Ocean Engineering
UNH Department of Environmental and Civil Engineering
UNH Center for Acoustics Research and Education
UNH Center for Coastal and Ocean Mapping
Friday, September 25, 2026, 3:10pm
Chase 105
ABSTRACT
Deep-sea sediments represent one of the least directly observed environments on Earth, yet their stability has important implications for sediment transport, benthic habitat, and subsea operations. We report results from a two-week pilot study of the Longer-term Acoustic Seafloor Stability Instrument (LASSI), a free-falling autonomous lander deployed at 3320 m water depth off the coast of California—to our knowledge, the deepest deployment of its kind. LASSI is a component of a multidisciplinary university initiative supported by the Office of Naval Research to develop new approaches for understanding and quantifying deep-sea sediment stability.
LASSI carried an integrated suite of acoustic, optical, and environmental sensors, including a forward-looking stereo camera, calibrated 38–120 kHz seafloor backscatter, a forward-looking imaging sonar, and upward-looking current and echosounder measurements. Multibeam bathymetry and ROV Jason imagery show that LASSI landed atop an approximately 4 m tall seafloor mound. Push cores collected in front of the lander reveal an approximately 10 cm layer of organic-rich mud overlying consolidated clay; processing is ongoing.
Optical observations reveal a densely populated benthic environment, with abundant epifauna including sea pigs and large burrowing echiurine worms, providing context for interpreting acoustic observations of seafloor change. Sonar image decorrelation exhibited characteristic timescales of 12–24 h, indicating restructuring of the acoustic scene on diurnal timescales. Spatially distinct patches also showed episodic decorrelation in phase with the M2 tidal constituent, consistent with current-driven resuspension of the flocculent surface sediment layer or tidally modulated benthic activity. The LASSI pilot deployment demonstrates the feasibility of sustained, high-resolution observations of deep-sea sediment dynamics in this poorly characterized environment.
BIO
Dr. Gabriel R. Venegas is an Assistant Professor of Ocean Engineering in the Department of Environmental and Civil Engineering, Center for Acoustics Research and Education, and Center for Coastal and Ocean Mapping. He conducts research in the fields of underwater acoustics, acoustical oceanography, and plant and animal bioacoustics. Specific areas of interest include sediment acoustics in hydrodynamically and biologically dynamic environments, understanding the effect organic carbon sequestration has on sediment geoacoustic properties, and the acoustic scattering from underwater flora and fauna.
Dr. Venegas received his B.S. degree magna cum laude in Mechanical Engineering from Boston University, and his Ph.D. degree in Mechanical Engineering with a focus on Physical Acoustics from The University of Texas at Austin. He is a member of the Acoustical Society of America, the Coastal Estuarine Research Federation, and the American Geophysical Union.
