Science Center Objects

The USGS Coastal/Marine Hazards and Resources Program is a leader in the acquisition, processing, and interpretation of high-resolution seismic data collected in the open ocean, on the continental shelf, and in estuaries, lakes, canals, and rivers. Depending on the scientific target of a survey, the CMHRP uses a variety of acoustic sources (chirp, sparker, boomer, or airguns) to image sediment and rock at depths of meters to kilometers below the seafloor. The CMHRP also maintains state-of-the-art instrumentation to record the reflected acoustic signals. For example, the CMHRP deploys multichannel streamers with 8, 16, or more than 100 receiving elements that allow for enhanced data processing and better constraints on the properties of Earth’s subsurface. 

Image: Multichannel Seismic Airgun Sled being Deployed off CCGS Louis S. St-Laurent

The airgun sled is painted orange and suspended from the A-frame.  The three airguns are suspended beneath the sled. The multichannel digital streamer (yellow cable going into the water from the sled) is towed from the the weighted sled to keep it under the ice. This photo shows the number of crew required to safely deploy the airgun sled. This photo also shows USCGC Healy circling behind Louis in preparation for taking the lead and breaking a path through the ice for Louis.

(Credit: Debbie Hutchinson, USGS. Public domain.)

Image: Night Recovery of the Multichannel Seismic System Aboard CCGS Louis S. St-Laurent

Looking astern, the airgun sled is in its cradle in the center of the photo.  The crew are manually recovering the multichannel streamer and beginning the large figure-8 shape of coiling it on deck. Work at sea occurs 24 hours a day.  In late September, there is ~12 hours of night, resulting in gear recovery at night. This was final recovery of gear at the end of the cruise.  The streamer is manually recovered by hand because it is faster than winch recovery and therefore less likely to get tangled in ice floes. It is transferred to the large winch drum for storage after recovery.  A large red tent with a heater covers the second airgun sled and keeps hose and gun temperatures above freezing and ready for deployment when needed.

(Credit: Debbie Hutchinson, USGS. Public domain.)

The CMHRP has acquired thousands of kilometers of airgun seismic data to support the U.S. Extended Continental Shelf (ECS) project  and the characterization of gas hydrate deposits on the U.S. Atlantic margin and in the northern Gulf of Mexico.  For half of the ECS surveys, the USGS used a specialized Federal fleet vessel to collect data with large airguns and a multichannel streamer up to 8 km long. For the gas hydrates research cruises, the CMHRP used general purpose Federal fleet vessels, deployed smaller airguns, and managed all parts of the acquisition during projects jointly supported by the USGS, U.S. Department of Energy, and the Bureau of Ocean Energy Management. These airgun seismic activities extend the ~45 year legacy of USGS marine seismic acquisition, producing data that will be used by the USGS, Federal partners, and academic collaborators for decades into the future. The data also support USGS studies on submarine landslides. the distribution of seafloor faults and shallow sub-bottom gas, the history of sea level rise, and sedimentary and erosional processes. The CMHRP maintains an environmental compliance program to ensure that airgun seismic research is conducted in consultation with the appropriate regulators and in a manner that minimizes its environmental impact.

The CMHRP also collects thousands of kilometers of sparker, boomer, and chirp seismic data each year. Recent surveys have mapped seafloor faults offshore Southeast Alaska and California, tectonic structures in subduction zones offshore the Pacific Northwest and Puerto Rico, erosional features on the New England margin, gas hydrate in the U.S. Arctic Ocean, and inner shelf structures in mid-Atlantic areas affected by Hurricane Sandy and in areas offshore Maine, New York, Massachusetts, North Carolina, South Carolina, Florida, Louisiana, and California. Sub-bottom profiling is also a key component in the CMHRP’s lacustrine studies. For example, seismic data are used to map the distribution of mine tailings in Lake Superior in cooperation with the U.S. Army Corps of Engineers and to characterize sediment thickness in Lake Powell in cooperation with the U.S. Bureau of Reclamation. 

CMHRP scientists design seismic experiments and adopt new approaches to ensure appropriate imaging of the targets while maximizing image clarity and resolution. The USGS mission is also served by new approaches to seismic data processing and interpretation. For example, a recent CMHRP innovation greatly increases the resolution and coherence of data obtained from sparker seismic surveys. CMHRP scientists have also advanced the use of seismic attributes and neural networks for data interpretation and developed expertise in the processing and interpretation of three-dimensional data. Recent 3D applications offshore central California include imaging complex fault structures and fluid flow pathways near a nuclear power plant and in regions of slope failure. These 3D approaches are also being used to map and interpret the structure of the karstic aquifer systems in southeastern Florida for wastewater management purposes.

The CMHRP is a partner in the National Science Foundation-supported Ocean Bottom Seismograph (OBS) Instrumentation Center at the Woods Hole Oceanographic Institution. This facility provides the U.S. research community with passive seafloor sensors for detection of earthquake motions, refracted waves from airgun experiments, and ambient noise that constrains seafloor geotechnical properties. The CMHRP also contributes OBS instruments to the facility and provides technical staff to assist with OBS deployment for some U.S. community projects. The CMHRP has also taken on a leadership role in the development of small, rapid-response OBSs that can be deployed soon after major earthquakes, volcanic eruptions, or other events. 

 
Computer model output looking at an angle, at seismic data represented by lines and swirls, with streams of color going upward.

Three-dimensional view of the Hosgri fault 45 meters below the seafloor, revealing fault strands (black), and potential paths along the fault that fluid could follow (green/blue). The other colors represent different geologic layers.

(Credit: Jared Kluesner, USGS Pacific Coastal and Marine Science Center. Public domain.)